Note: Descriptions are shown in the official language in which they were submitted.
~077~4
FLUID-WALL REACTORS ~ND TII~IR UTILIZATION IN
HI~,H TEMPERATURE C~IEMICAL REACTION PROCESSES
The present invention relates to fluid-wall reactors
for high temperature chemical reaction processes, as well as to the
various processes which may be conducted in such reactors, many of
which processes previously have been impractical or only theoret-
ically possible. Both the fluid-wall reactor and the processes
employed in such reactors utilize radiation coupling as a heat
source, and maintain the contemplated chemical reactions in isolation
within a protective fluid blanket or envelope out of contact with
the containing surfaces of the reactor.
BACKGROUND OF TIIE INVENTION
. _ _ .. _ _
High temperature reactors are presently employed to
carry out pyrolysis, thermolysis, dissociation, decomposition
and combustion reactions of both organic and inorganic compounds.
Substantially all such reactors transfer heat to the reactants
by convection and/or conduction, but this characteristic inherently
produces two major problems which limit the nature and scope of
the reactions which may be carried out. Both problems result
from the fact that in a conventional reactor which transfers
heat to the reactants by convection, the highest temperature in
I1 10776~4
1 ¦the system is necessarily at the interface between the inside
2 ¦wall of the reactor and the reactant stream.
3 ¦ The first problem involves the limitations on available
4 ¦temperatures of reaction which are imposed by the strength at
5 ¦elevated temperatures of known reactor wall materials. The
6 ¦decreasing capability of such materials to maintain their
71 integrity under conditions of increasing temperature is, of
81 course, well known. However, since it is necessary that such
9¦ materials be heated in order that thermal energy may be trans-
lO¦ ferred to the reactant stream, available reaction temperatures
11¦ have been limited by the temperature to which the reactor wall
12¦ could be safely heated. This factor is particularly critical
13¦ in cases where the contemplated reaction either must take place
14¦ at or produces high pressures.
15¦ The second problem inherently results both because the
16¦ wall of a conventional reactor is at the highest temperature in
17¦ the system and because convective/conductive heat transfer re-
~8¦ quires contact between the wall and the reactant stream. Being
19¦ at such elevated temperature, the reactor wall is an ideal if not
20¦ the most desirable reaction site in the system and, in many in-
21¦ stances, reaction products will accumulate and build up on the
22¦ wall. Such build-up impairs the ability of the system to transfer
231 heat to the reactants and this eve~ increasing thermal impedance
241 requires the~l'source temperature to be raised progressively just
25 to maintain the initial rate of heat transfer into the reactant -
26 stream. Obviously, as the build-up increases, the required source
27 temperature will eventually exceed the capabilities of the reactor
28 wall material. ~loreover, as additional energy is required to sus-
29 tain the reaction, the process becomes less efficient in both the
30 technical and economic sense. Thus, at the point where the con-
1~776~A ~ ¦
1 templated reaction can no lonyer be sustained on the basis of
2 either heat transfer, strength of materials, or economic considera
3 tions, the system must be shut down and cleaned.
4 Usually, cleaning is performed mechanically by scraping
5 the reactor wall or chemically by burning off the deposits. In
6 some continuous processes, it has been attempted to scrape the
7 reactor wall while the reaction proceeds. However, the scraping
8 tool itself necessarily gets hot, becomes a reaction site and,
9 thereafter, must be cleaned. In any event, this down time
10 represents a substantial economic loss. In many instances, a
11 second system will be installed in order to minimize lost pro-
12 duction time. However, such additional equipment generally
13 represents a substantial capital investment. Some high
14 temperature chemical reactors include a tube which is heated
15 to a temperature at which its inner walls emit sufficient
16 radiant energy to initiate and sustain the reaction. However,
17 as in the case of conductive and convective reactors, for
~8 reactions yielding solid products there is frequently an
19 undesirable build-up of product on the tube walls which
20 leads to reduced heat transfer and even clogging of the tube.
21 The reactor disclosed in U.S. patent No. 2,926,073
22 is designed to produce carbon black and hydrogen by the pyrolysis ~
23 of natural gas. The process is stated to be continuous but, in ~-
24 practice, the convective heat transfer principle under which the
25 reactoe operates causes serious problems both in sustaining and
26 controlling the reaction. Since the heated tubes of the reactor
27 are ideal reaction sites, carbon invariably builds up and eventu- ¦ `
28 ally clogs the system. More serious, however, is the problem of
29 thermal runaway which can result in explosions. With respect to
30 this condition, it has been determined that during pyrolysis of
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I . ,
1 ¦natural gas, thermal conductivity of the gas phase suddenly in-
2 ¦creases from about five to thirty times, depending upon the
3 ¦composition of the gas. Because the temperatures in a conven-
4 ¦tional convective reactor cannot be regulated with sufficient
5 ¦speed and accuracy to compensate for this phenomenon, in some
6 ¦instances the system would become unstable and explosions would
7 ¦result. Such conditions are inherent in conventional reactors
8 ¦and, as yet, no way has been found to overcome this problem.
9 ¦ U.S. patent No. 3,565,766 represents a recent attempt
lO Ito upgrade coal by pyrolysis. The disclosed system comprises
11¦ a series of hollow steel vessels which act as a multi-stage
12¦ fluidized beds at successively increasing temperatures up to
13 ¦about 1600F. Fluidization at lower temperatures is achieved
14 ¦by an inert gas which may itself supply heat although external
15¦ heating is contemplated. At higher temperatures, fluidization
16¦ is achieved by the overhead gas obtained in the final stage;
17¦ and, in the final stage, temperature is maintained by internal
18 ¦combustion of the char in air or oxygen. Because it relies
19¦ primarily upon heat transfer by convection, this system is
20¦ subject to many of the defects and disadvantages which have
21¦ previously been discussed.
22¦ The apparatus for the manufacture of carbon black
231 disclosed in U.S. patent No. 2,062,358 includes a porous tube
241 disposed within a heating chamber. Hot gas is directed from a
251 remote furnace into the chamber, and thereafter forced through -
26¦ the wall of the porous tube to mix with the reactants. Thus,
271 only convective transfer of heat from a fluid to reactants is
28¦ employed. This, together with the absence of a "black body
291 cavity" necessitates the flow of a large volume of fluid through
301 the heating chamber in order to make up for heat losses.
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1 ¦ U. S. patent No. 2,769,772 discloses a reactor for heat-
2 ¦treating fluid materials such as hydrocarbons which includes two
3 Iconcentric tubes disposed in a flame heated furnace. Reactants
4 ¦flow axially through the pervious inner concentric tube. A heat-
6 ¦carrier gas flowing in the annular chamber between the concentric
6 ¦tubes is heated by contact with the outer wall. Fluids in the
7 ¦inner tube are heated by convection when the heat-carrier gas
8 ¦passes through the pervious wall and mixes with them. Radiant
¦ heat transfer is expressly avoided. ~n fact, it is impossible to
lO¦ heat the inner tube without simultaneously heating the outer tube
11¦ to at least as high a temperature.
12¦ The surface-combustion cracking furnace of U.S. patent
13¦ No. 2,436,282 employs the convective heat carrier gas principle
14¦ similar to that of U. S. patent No. 2,769,772. The furnace inclu-
15¦ des a porous, refractory tube enclosed by a jacket. A combustible ~;
16¦ fluid from an annular chamber is forced through the porous wall
17¦ to the inside of the tube where it is ignited. It is evident,
18¦ however, that the combustible fluid in the annular chamber will
19¦ explode unless it is forced through porous wall at a rate faster
2~1 than the rate of flame propagation back through the wall. Like-
21¦ wise, the temperature in the annular chamber must be maintained
22¦ below the ignition temperature of the gas/air mixture. Combustion
231 products from the surface flame mix with reactants in the furnace
241 diluting and possibly reacting with them. Heat is imparted to the
251 reactants by convective mixing of the combustion products and the
26¦ reactants.
271 U. S. patents Nos. 2,670,272; 2,670,275; 2,750,260;
28¦ 2,915,367; 2,957,753; and 3,499,730 disclose combustion chambers -~
291 for producing pigmentary titanium dioxide by burning titanium
301 tetrachloride in oxygen. In the '275 patent which is representa-
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~ 11)~7684
tive of this group, titanium tetrachloride is hurned in a porous,
refractorv tube. An inert gas is continuously diffused through
the porous tube into a combustion cham~er where it forms a pro-
tective blanket on the inner surface of tube. This gaseous blan-
ket substantially reduces the tendency of the titanium dioxide
particles to adhere to the walls of the reactor. Since the
combustion of titanium tetrachloride is an exothermic reaction,
no provision is made to supply heat to the reaction mi~ture as
it passes through tube. In fact, the '275 patent teaches that
it is advantageous to remove heat from reactor chamber either by
exposing the porous tube assembly to the atmosphere or hy circu-
lating a cooling fluid through a coil disposed about the porous
tube.
SUM~IARY OF THE Il`~VENT ION
..... . __ .. _ .. __ :
In the present high temperature chemical reaction
process, an annular envelope of an inert fluid which is sub- -~
stantially transparent to radiation is generated; the envelope
has a substantial axial length. Next, at least one reactant
is passed through the core of the envelope along a predetermined
path which is substantially coincident with the envelope axis,
the reactants being confined within the envelope. After the
reactant flow has started, high intensity radiant energy is
generated at a point external to the envelope and is collected
and focussed through the envelope to coincide with at least a
portion of the path of the reactants. Sufficient radiant energy
is absorhed in the core to raise the temperature of the reac-
tants to a level required to initiate the desired chemical re-
action.
In the event that the reactants are themselves trans-
parent to radiant energy, an absorptive target is introduced
into the reactant stream. The target will absorb sufficient
radiant energy to raise the temperature in the core to the desired
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level. In some instances, however, while the reactants are
transparent to radiation, one or more of the reaction products
will be an absorber. In such event, once the reaction has been
initiated the target may be withdrawn and the reaction will
continue. An example of such reaction is the pyrolysis of
methane to carbon and hydrogen.
Some reactions will reverse either partially or comple- -
tely if the reaction products are not cooled Lmmediately and
rapidly. In such cases, it is further contemplated that cooling
of reaction products and any remaining targets to prevent such
undesired chemical reactions be carried out immediately upon
completion of the desired reaction.
The high temperature fluid-wall reactors of the present
invention transfer substantially all of the required heat to the
reactants by radiation coupling. The reactor comprises a tube
having an inlet and an outlet end, the interior of the tube
defining a reactor chamber. A diffuser for introducing an inert
fluid into the reactor chamber provides a protective blanket for
the radially inward surface of the reactor tube. Means for in-
troducing at least one reactant into the reactor chamber through
the inlet end cause such reactants to be directed in a predeter-
mined path axially of the reactor tube. The inert fluid blanketconfines the reactants suhstantially centrally within the reac-
tor chamber and out of contact with the reactor tube. High in-
tensity radiant energy is generated by a radiant energy source
disposed within a reflector which is located externally of the
reactor tube, the radiant energy being collected and focussed by
the reflector and being directed into the reactor chamber to
coincide with at least a portion of the path of the reactants,
sufficient radiant energy heing absorbed to raise the temperature
of the reactants to a level required to initiate the desired chem-
ical reaction.
1077684
In contrast to the conventional convective reactors,the present invention relies upon radiation coupling to transfer
heat to the reactant stream. The amount of heat transferred is
independent both of physical contact between the reactor wall and
the stream and of the degree of turbulent mixing in the stream.
The primary consideration for heat transfer in the present system
is the radiation absorption coefficient (a) of the reactants. The
inert fluid blanket which protects the reactor wall is desirably
substantially transparent to radiation and thus exhibits a very -
low value of (). This enables radiant energy to be transferred
through the blanket to the reactant stream with little or no
energy lossesO Ideally, either the reactants themselves or a
target medium will exhibit high () values and will thus absorb
large amounts of energy, or alternatively, the reactants may be
finely divided ~as in a fog) such that the radiation is absorbed
by being trapped between the particles. Since materials which
are good absorbers are generally good emitters of radiation, when
the reactants or targets are raised to a sufficiently high temper-
ature, they become secondary radiators which re-radiate energy
throughout the entire reactin~ volume and further enhance the heat
transfer characteristics of the system. This occurs almost
instantaneously and is subject to precise and rapid control.
Moreover, the re-radiation phenomenon which ensures rapid and
uniform heating of the reactants is completely independent of the
degree of turbulent mixing which may exist in the reactant stream.
The present high temperature chemical process and appar-
atus provide a solution to proble~s which have plagued the art
and thus permit the carrying out of reactions which heretofore
10776<~4
have been impractical or only theoretically possible. Because
heat is supplied by radiation coupling rather than by convection
and/or conduction, the temperature of the reactant stream may be
independent of both the temperature of the reactor wall and of
the condition of the reactant stream, and the serious strength of
materials problem is overcome. Two embodiments of the present
reactor contemplate that the reactor wall in fact be cooled; third
and fourth types of reactor which are the subject of co-pending
parent Canadian Application No. 236,325 filed September 25, 1975,
althouqh providinq a heated wall as a source of radiant energy,
are not subjected to the high pressures which are normally atten-
dant to many kinds of reactions. For this reason, refractory mat-
erials such as carbon or thorium oxide, which are not suitable for
use as a wall material in a conventional reactor, may be success-
fully employed. As compared to the most temperature-resistant
alloys which melt at about 2900F., thorium oxide, for example, is
servicable at temperatures greater than 5400F. This feature per-
mits reaction temperatures far in excess of those presently achiev-
able and reactions which had been only theoretically feasible may
he carried out.
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The provision of the protective inert fluid blan-
ket, which is made possible largely by the use of radiation
coupling, isolates the reactor wall from the reactant
stream and makes it impossible under normal operating con-
ditions for any precipitates or other deposits to accumulate
and clog the system.
The use of radiation coupling further enables the
accurate and almost instantaneous control of heat transfer
rates which is impossible to achieve in a conventional
convectiv~ reactor. Furthermore, the present reactor may
provide a power flux at the reaction site in excess of
10,000 watts/cm . This figure represents a great improve-
ment over the 2-3 watts/cm which is ordinarily obtained
in conventional reactors.
The reactions which may be carried out by the pro-
cess of this invention as implemented by the present reac-
tor are many and varied. For example, organic compounds,
particularly hydrocarbons, may be pyrolized to produce
carbon and hydrogen without the attendant build-up and ther-
mal runaway problems which were encountered in the prior
art. Saturated h~drocarbons may be partially pyrolized
to obtain unsaturated hydrocarbons; thus, for example,
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propane and ethane may be dehydrogenated to propylene
and ethylene, respectively. Vnsaturated hydrocarbons may
he partially pyrolized in the presence of hydrogen to
form saturated hydrocarbons and, more specifically, pet-
roleum products may be thermally cracked. Thus, gas oil
may be readily converted into diesel oil, kerosene, gaso
line fractions or even methane. Halogen intermediates
may be added to partially pyrolized hydrocarbons to produce
higher molecular weight compounds. Hydrocarbons may be
completely or incompletely pyrolized in the presence of
steam to form carbon monoxide and hydrogen; additional hy-
drogen may then be added and the reaction carried out to
form alkane series hydrocarbons which are high BTU-value
fuel gases.
Inorganic compounds may likewise be pyrolized. For
example, salts or oxides of iron, mercury, silver, tungsten
and tantalum, among others, may be dissociated to obtain
pure metals. Oxides of iron, nickel, cobalt, copper and
silver, to name a few, may be directly reduced in the
presence of hydrogen with the same result. This list is
by no means intended to be exhaustive.
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1 Novel composite products may also be produced by the
2 present process. For example, carbon or talc particles coated
3 with silicon carbide may be obtained. This product serves as an
4 excellent abrasive because as it is used, it continually breaks
5 up and forms fresh new sharp surfaces. Particles of certain
6 elements such as U 5 may also be encapsulated in a chemically-
7 tight envelope of another material such as carbon; this
81 articular product is useful as a nuclear reactor fuel element.
9 It is further contemplated that the present invention
10 may provide the terminal step in conventional aerobic incinera-
11 tion of waste such as garbage and sewage. The relatively low
12 temperatures encountered in current incineration processing
13 techniques permit the formation of organic peroxides and oxides
14 of nitrogen which are major contributors to photochemical smog
15 and other forms of air pollution. Because such compounds are
16 not stable at the higher processing temperatures afforded by
17 the present invention, a waste incineration effluent which is
18 very low in pollutants may be obtained.
19 Further, the present invention contemplates the high
20 temperature anaerobic destructive distillation and/or disassocia-
21 tion of waste to yield useful products such as carbon black,
22¦ ctivated charcoal, hydrogen, and glass cullet, to name a few.
23 he addition of steam to such waste will produce carbon monoxide
241 nd hydrogen which may then be processed in the conventional
25 anner to obtain fuel gases. Finally, the addition of hydrogen ~ -
26¦ o such waste will produce petroleum-e~uivalent heavy oils and
27 ther petroleum products. Thus, substantial reductions in air
28 ollution as well as significant economic gains may be realized
29 hrough such contemplated applications of the present invention.
The present invention represents a major breakthrough
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in the art. Because it makes available for the first time a
source of thermal energy which has never been harnessed in this
manner, its potential applications are numerous and varied. More-
over, in surmounting the strength of materials probl~m which has
shackled the art for many years, this invention makes possible
in the practical sense many useful chemical reactions which have
long been known but which could not be performed because of
temperature limitations inherent in reactors which depended upon
convective and/or conductive heat transfer.
BRIEF DESCRIPTION OF T~E DRAWI~JGS
FIG. 1 is an elevation in partial section of one embod-
iment of the reactor of the present invention;
FIG. 2A is an elevation in section of the inlet end of
a second embodiment of the aforesaid co-pending parent Application
No. 236,325.
FIG. 2B is an elevation in section of the outlet end
of the second embodiment of the reactor; FIGS. 2A and 2B represent
halves of an integral structure which has been divided along line
A-A in order to provide an illustration of sufficient size to show
clearly certain structural detailss
FIG . 2C is a perspective in partial section of the
second embodiment of the reactor wherein certain elements have
either been removed or illustrated diagrammatically to illustrate
more clearly the operation of the reactor;
FIG. 3 is a section taken substantially along line 3-3
of FIG. 2A;
FIG. 4 is a section taken substantially along line 4-4
of FIG. 2B;
FIG. 5 is a section taken suhstantially alon~ line 5-5
30 of FIG. 2A;
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FIG. 6 is a perspective of a portion of the reactor
tube heating means of the second embodiment;
FIGS. 7A, 7B, 7C, and 7D together constitute a composite
elevation in partial section of the reactor of the aforesaid parent
Application 236,325; the integral structure of the reactor has been
divided along lines A-A, B-B and C-C, respectively, in order to
provide an illustration of sufficient size to show clearly certain
structural details;
FIG. 8 is a section taken substantially along line 8-8
of FIG. 7A
FIG. 9 is a section taken substantially along line 9-9
of FIG. 7B;
FIG. 10 is a section taken substantially along line 10-10
of FIG. 7B;
FIG. 11 is a section taken substantially along line 11-11
of FIG. 7C;
FIG. 12 is a section taken substantially along line 12-12
of FIG. 7C;
FIG. 13 is an elevation in section of a post-reaction
treatment assembly of an alternate embodiment of the reactor of
the present invention;
FIGS. 14A and 14B together constitute a composite eleva-
tion in partial section of an inlet assembly of an alternate em- - :
bodiment of reactor; the integral structure of the inlet assembly
has been divided along line D-D in order to provide an illustra-
tion of sufficient size to show clearly certain structural de-
tails,
FIG. 15 is an elevation/schematic view of a reactor
in combination with apparatus for pre-processing and introducing
solid reactants into an inlet assembly of the reactor of the ~: ~
present inventions ~.
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FIG. 16 is a schematic representation illustrating the
refractory coating and etching systems of the reactor;
FIG~ 17 is a schematic diagram of the temperature
regulation circuit of the reactor;
FIG. lB is a graphical representation of the electrical
resistance of a heating element of the reactor as a function of
temperature and the number of layers of refractory fabric which
constitute such element; and
FIG. 19 is a schematic representation illustrating the
operation of the several control systems of the reactor.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring specifically to FIG. 1, a first embodiment
of the present high-temperature chemical reactor 10 according to
the invention comprises a reactor tube 11 which has an inlet end 12
and an outlet end 14. The reactor tu~e 11 includes an inner wall
15 and an outer wall 16 which define an annular channel therebetween
and the interior of the tube 11 constitutes a reactor chamber 17.
The tube 11 is made of a material which is substantially trans-
parent to radiation. Suita~le materials of this nature which exhi-
bit a very low absorption coefficient (~) include glass, quartz,hot sintered aluminium oxide, hot sintered yttrium oxide, Pyrex*
(a borosilicate glass), Vycor* (a silicate glass) and sapphire;
organic polymers 14 such as Plexiglass* (acrylic), Lucite* (acrylic),
polyethylene, polypropylene and polystyrene; and, inorganic salts
such as the halides of sodium, potassium, cesium, lithium or lead.
As used herein, the terms "radiant energy" and
"radiation" are intended to encompass all forms of radiation
including high-energy or impacting nuclear particles. However,
* Trade Marks
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1 1077~i84
1 because the practical use of such radiation is not possible
2 ¦under the present state of the art, black body or other el.ectro-
3 ¦magnetic radiation, particularly of wavelengths ranging from
4 ¦about 100 microns to 0.01 microns, is considered to be the
5 ¦primary energy source upon which design considerations are to
6 ¦be based.
7 ¦ During operation of the reactor 10 a fluid medium which
8 ¦is substantially transparent to radiation is introduced through
9¦ inlet 18, circulates throughout the annular channel to cool the
lO¦ reactor tube 11 and exits through outlet 19. Such fluid medium
11¦ may be a gas or a liquid; representative suitable fluids which
12¦ have low coefficients of absorption (a ) include li~uid or .:
13¦ gaseous water, heavy water, nitrogen, oxygen and air. :
14¦ Means for introducing an inert fluid into the reactor
15¦ chamber 17 through an inlet 20 comprises first and second laminar
16¦ diffusers 21 and 22, respectively, which are disposed adjacent .
17¦ the inlet end 12 of the tube 11. Such diffusers 21, 22 may be in
18¦ the form of honeycomb cores or any other suitable configuration
19¦ which causes a fluid directed under pressure therethrough to flow
2~1 in a substantially laminar fashion. The inert fluid is thus
21¦ introduced substantially axially into the reactor chamber 17 to
22¦ provide a protective blanket for the radially inward surface of
231 the reactor tube 11 and is collected for recirculation as it
241 exits through outlet 23. The inert fluid is substantially :~ ~
251 transparent to radiation in that it has a low (a~ value. Fluids ~-
26¦ hich are suitable for this purpose include simple gases such as
271 helium, neon, argon, krypton and xenon; complex gases which do
28¦ not decompose to form a solid product such as hydrogen, nitrogen,
291 xygen and ammonia; and, liquid or gaseous water. The term
30~ "inert" as used herein, involves two factors: the ability of
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107768~ 1
1 ¦the fluid to react chemically with the material of the reactor
2 ¦tube 11 and the ability of the fluid to react chemically with
3 ¦the materials which are being processed. Thus, the selection of
4 ¦an "inert" blanket fluid depends in each instance upon the
5 ¦particular environment. Except as otherwise specifically
6 ¦provided, it is desirable that the fluid be inert with respect
7 Ito the reactor tube and it is usually desirable that the fluid
81 be inert with respect to the reaction which is carried out.
9¦ However, it is contemplated that in some instances the "inert"
10¦ fluid of the protective blanket shall also participate in the
11¦ reaction as, for example, where iron or carbon particles are
12¦ reacted in the presence of a steam blanket to produce iron
13¦ oxide and hydrogen or carbon monoxide and hydrogen, respectively.-
14¦ Reactants are introduced into the reactor chamber 17
15¦ through an inlet 24 at the inlet end 12 of the reactor tube 11.
16¦ The reactants are directed along a predetermined path 25 axially
17¦ of the reactor tube 11 and are confined by the protective inert
18¦ fluid blanket substantially centrally within the reactor chamber
19¦ 17 out of contact with the reactor tube 11.
20¦ A high-intensity radiant energy source (not shown) is
21¦ isposed within a polished reflector 31 which is mounted on a
221 frame 32 externally of the reactor tube 11. The radiant energy
23¦ source may be a plasma arc, a heated filament, a seeded flame,
2i¦ pulsed flashlamp or other suitable means; a laser may also
251 erve as the source but, at present, laser technology has not
26¦ een sufficiently developed to the extent where it is economi-
271 ally practical for the purposes contemplated by the present
28¦ invention. The radiant energy generatd by the source is col-
291 ected by the reflector 31 and is directed through the tube 11
301 into the reactor~hamber 17 to coincide with at least a portion
1(~77684
1 ¦of the path 25 of the reactants. Sufficient radiant energy
2 ¦will thus be absorbed to raise the temperature of the reactants
3 Ito a level required to initiate and carry out the desired chemi-
4 ¦cal reaction. As previously stated, the tube 11, the cooling
51 fluid and the inert blanket are all substantially transparent
6 Ito radiant energy. Accordingly, they do not interfere to any
I gFeat extent with the transmission of energy to the reactant
81 steam and remain relatively cool. Thus, the reactor tube
91 11 is not subjected to appreciable thermal stress and remains
10¦ free from precipitates and other deposits which would normally
11¦ accumulaté.
12¦ The above discussion presumes that the reactants
13¦ themselves exhibit a relatively high radiation absorption
14¦ coefficient (~). However, if such is not the case, a radiant
15¦ energy absorptive target must be introduced into the reactor
16¦ chamber 17 coincident with at least one point along the path
17¦ 25 of the reactants. In the embodiment of FIG. 1, the target
l8¦ medium is a finely divided solid such as carbon powder or other
19¦ suitable material which enters the reactor chamber 17 together
20¦ with the reactants through inlet 24 and absorbs sufficient
21¦ radiant energy to raise the temperature of the reactants to
22¦ the required level.
231 Alternatively, the target may be a liquid such as tar,
241 asphalt, linseed oil or diesel oil, and may include solutions,
25¦ dispersions, gels and suspensions of varied make-up which may
26¦ be readily selected from available materials to suit particular
27¦ requirements. The target may be a gas which preferably exhibits
28 absorption in the electromagnetic spectrum from about 100 microns
29 to about 0.01 microns; such gases include ethylene, propylene,
30 oxides of nitrogen, bromine, chlorine, iodine, and ethyl bromide.
' .
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1 ¦The target may also be a solid element made of a material such
2 ¦as carbon which is disposed in the reactor chamber 17 along at
3 ¦least a ~ortion of the path 25 of the reactants.
4 ¦ Other means for raising the temperature of the
5 ¦reaction to the required level may include an electrically
6 ¦heated element, an electric arc or a flame disposed within the
7 ¦reactor chamber 17 coincident with at least a portion of the
8 ¦path 25 of the reactants. In such instances, the initiating
9¦ heat source is self-contained and is not derived from the
10¦ radiant energy generating means. Such means are particularly
11¦ useful where the reactants themselves are transparent to ~ -
12¦ radiation but at least one of the reaction products is an
13¦ absorber. Thus, once the contemplated reaction has been
14¦ initiated, the temperature raising means may be deactivated
15¦ because the reaction products will absorb sufficient radiant
16¦ energy to sustain the reaction. Likewise, if a target medium
17¦ is used, it may be discontinued or withdrawn once the reaction
18¦ has begun as by operation of a control means 35. An example of
191 a reaction where a target or other initiating means is required
201 only at the outset is the pyrolysis of methane to produce carbon
21¦ and hydrogen.
22¦ As previously stated, some reactions will reverse
231 either partially or completely if the reaction products are not
241 cooled immediately and rapidly. For this purpose, reaction
251 product cooling means 40 may be provided within the reactor
26¦ chamber 17 adjacent the outlet end 14 of the reactor tube 11.
271 One embodiment of such means 40 is disposed substantially
28¦ centrally within the reactor chamber 17 and includes a tubular
291 ember 41 having an internal channel 42 through which is cir-
301 culated a coolant such as water~ The radially inward surface of
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the tube ~1 is designed to constitute an absorber of radiant
energy. As the reaction products, remaining reactants and tar-
gets, if any, pass within the cooled tube 41, heat is transfer-
red rapidly by radiation coupling and the system is effectively
quenched to prevent any further undesired chemical reactions.
FIGS. 2A-6, inclusive, and particularly to FIGS~ 2A-
2C, show an embodiment of reactor which is claimed in the afore-
said parent application No. 236,325 but which is described herein
for completeness. This reactor 60 comprises a reactor tu~e 61 hav-
ing an inlet end 62 and an outlet end 63; the interior of the tube61 defines a reactor chamber 65. The reactor tube 61 is made of a
porous material which is capable of emitting radiant energy; pre-
ferably the pore diameter is in the range of ahout 0.001 to 0.020
inch to permit uniform flow of sufficient inert fluid through the `
tube wall to provide an ade~uate protective blanket. Other wall
constructions such as mesh, screening or various types of perfor-
ations may also be used to provide the desired result. The reactor
tube 61 may be made from materials such as qraphite, carbon, sin-
tered stainless steel, sintered tungsten, or sintered molybdenum,
and, inorganic materials such as oxides of thorium, magnesium, zinc,
aluminum or zirconium, anong others. Tungsten, nickel and molyb-
denum are also suitable for use as mesh or screening.
A fluid-tight, tubular pressure vessel 70 which
is preferably made of stainless steel encloses the reactor
tube 61. The integrity of the vessel 70 is maintained hy a
series of sealing flanges 71, 72; 73, 74; and 75, 76 which
join the several sections of the reactor 60. Flanges 72, 73
and 76 further are grooves to receive stainless steel O-rings
77, 78 and 79, respectively, which act as pressure seals.
The reactor tube 6~ is slidably mounted at one end within
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l~a raphite sleeve 81 which allows for any elon~ation of the
2 ¦tube 61 which may occur during operation at elevated
3 Itemperatures.
4 ¦ The pressure vessel 70 further includes an inlet
5 ¦83 for admitting an inert fluid, which as in the case of the
6 ¦FIG 1 embodiment, is substantially transparent to radiant
7 ¦energy. The inert fluid is first directed under pressure
8 ¦into a plenum 85 which is defined between the reactor tube
9 ¦61 and the pressure vessel wall 70. Thereafter, such fluid is
10 ¦directed through the porous wall of the tube 61 into the reactor
11 ¦chamber 65 to constitute a protective blanket for the radially
12 ¦inward surface of th~ reactor tube 61.
13¦ Means for cooling the pressure vessel 70 comprises
14 ¦cooling coils 87 which are disposed about the radially outward
15¦ surface of the pressure vessel 70. The coils 87 are preferably
161 covered with a flame-sprayed aluminum coating which enhances the
171 thermal contact between the vessel 70 and the coils 87 to increase
18¦ cooling efficiency. Such coils 87 are also disposed about a view-
19¦ port 88 which is provided in the pressure vessel wall.
2a¦ As shown best in FIGS. 2A and 3, the reactants are
21¦ introduced into the reactor chamber 65 throu~h the inlet end 62
22¦ of the reactor tube 61. Means for introducing the reactants
231 comprises an inlet section 90 which is mounted in fluid-tight
241 relationship by flanges 71, 72 adjacent the inlet end 62 of the
251 tube 61. The reactants are carried in a gaseous stream through
26 inlet 91, past a tangential baffle 92 and into a plenum 93 which
27 is defined between an outer wall 94 and a diffuser 95. Suitable
28 materials for the diffuser 95, whose function is to minimize
29 turbulence in the stream, include porous carbon, steel wool and
30 mesh screening. As in the case of the FIG. 1 embodiment, the
~077~84
reactants are directed in a predetermined path axially of the
reactor tube 61 and are confined by the protective blanket
substantially centrally within the reactor chamber 65 and out of
contact with the inner wall of the reactor tube.
In this reactor, the reactor tube 61 itself
generates the high-intensity radiant energy which is directed
centrally therewithin substantially coincident with at least a
portion of the path of the reactants, Heating is provided by a
plurality of carbon electrodes lOOa-lOOf which are disposèd
radially outwardly of and spaced circumferentially about the tube
61; the heat generated by the electrodes 100 is transferred to
the tube 61 by radiation. In this reactor, as best shown in
FIGS. 2A, 5 and 6, electrodes lOOa and lOOb, for example, are
embedded at one end in an arcuate carbon cross-over element
lOla; electrodes lOOc and lOOd are e~bedded in cross-over lOlb;
and, electrodes lOOe and 100~ are likewise embedded in cross-
over lOlc. Tubular alumina spacers 102a-102c have the dual
function of centering the porous reactor tube 61 and of dividing
the three circuits. Referring specifically to FIG~. 2B and 4,
each carbon electrode lOOa-lOOf is mounted at its other end in
a copper bus bar electrode 104. Although there are six such
electrodes 104, only one is actually shown in FIG. 4 as a matter
of convenience. Each copper bus bar electrode 104 includes a
phenolic flange 105 and a ceramic insulator 106. The electrode
104 is cooled by water which circulates in an internal channel
107, entering through inlet 108 and exiting through outlet 109.
A high current electrical connection is illustrated at 110. A
polytetrafluoroethylene seal 111 assists in preventing any
leakage from the pressure vessel 70. The electrical system
illustrated herein is particularly suitable for use with a
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~o776~
three-phase power source. Howe~er, other systems may be used
where circumstances warrant. It is further contemplated that
the porous tube 61 may itself be heated directly by elec~rical
resistance; in such event the electrodes 100 may be eliminated.
The thermal efficiency of the tube heating means is
further improved by the provision of a molybdent~ heat shield
120 which constitutes the containing surface of the "black body
cavity", reflecting electromagnetic radiation from the carbon
electrodes 100 toward the porous tube 61. In that the heat
shield 120 reflects rather than transfers heat, it functions
as an insulator and may thus be made of any material which
exhibits this characteristic and which can withstand the temper-
atures generated by the electrodes 100. The heat shield 120
is disposed within the pressure vessel 70 radially outwardly
of the electrodes 100 and preferably comprises a flat strip
of rectangular cross-section which is wound in a series of
helical turns. Such construction allows the inert blanket
gas to enter through the inlet 83 and to circulate freely
throughout the plenum 85.
As in the case of FIG. 1 embodiment, a target medium
or other initiating means may be provided if required. Target
media are introduced into the reactor chamber 65 through an
inlet 121. Also, reaction product cooling means 125 of a con-
struction, as previously described, or of any other suitable
construction, may be provided to prevent any undesired chemical
reactions which might occur if the reaction produc~s were not
cooled immediately after formation.
The primary advantage of this reactor over the first
embodiment is that in the former, the inert fluid blanket is
introduced into the chamber 65 in a radially inward
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.
. : , - : . :
- - - -
1077684
direction whereas in the latter, the ~lanket is introduced
axially into the chamber 17. It will be appreciated that laminar
flow can be maintained for only relatively short distances
before turbulence causes intermixing and destroys the integrity
of the protective blanket. Because radial blanket introduction
does not require laminar flow of the blanket fluid, much greater
axial reactor chamber lengths may be obtained. All that need
be done in the second reactor is to maintain the absolute
level of the inert fluid pressure greater than the absolute
level of the pressure in the reactant stream in order to prevent
any reactants and/or reaction products from impin~inq upon the
reactor tube 61. This feature aids in making the second
reactor more suitable for large scale commercial operation.
A further distinction between the respective embodi-
ments is that the reactor tube 11 of FIG. 1 is positively cooled
whereas the tube 61 of FIG. 2 must be heated and may operate at
temperatures in excess of 54000F, as in the case where porous
thorium oxide is the base material. Although the cool wall is
better able to withstand pressuxe because it is not subject to
thermal stress, the hot wall 61 is not subject to a pressure
gradient, except perhaps the relatively small differential
between the fluid blanket and the reactive stream. The pressure
is borne by the stainless steel pressure vessel wall 70 which, of
course, is cooled by the coils 87 and thus is not subject to
thermal stress. Accordingly, a refractory material, such as
carbon or thorium oxide, which can withstand temperatures far
in excess of those tolerable by conventional reactor wall
materials but which are unsuitable for use in a conventional
convective reactor, may now be employed for the first time to
provide a practical, ultra-high-temperature system.
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77~8~
The present invention further includes a third
embodiment which combines features of the first two. Accordingly,
the reactor tube may be constructed of a porous material which
is suhstantially transparent to radiation. Suitable wall mat-
erials include for example porous quartz, porous ~lass frit,
and porous sapphire. An inert fluid which is substantially
transparent to radiation may thus be introduced into the reactor
chamber radially inwardly through the porous reactor wall rather
than axially in a laminar fashion as described with respect to
the first embodiment. P~adiant energy is generated, collected
and directed into the reactor chamber also as described with
respect to the first embodiment.
The third embodiment provides the higher power density
of the first embodiment and the radially injected fluid blanket
of the second embodiment. However, at the present stage of de-
velopment, the second embodiment is the most suitable for large
scale commercial applications since its radiant energy source is
derived from ordinary electrical resistance heating. The second
embodiment is therefore more readily capable of being serviced
and maintained. Moreover, the second embodiment may be made to
carry out all of the processes and reactions contemplated by the
present invention merely by adjusting the residence time of the
reactants within the reactor chamber to compensate for the lower
power density. -
Referring to FIGS. 7A throu~h 15, inclusive, a fourth
chemical reactor which represents an improvement of the second
reactor an~ which likewise is claimed in parent Application 236,325
generally comprises an inlet assembly 200 and electrode assembly
300, a main assembly 400, and a post-reaction treatment assembly
500. The principal elements of this reactor include:
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10'776~ ~
1 (A) A reactor tube 401 which has an inlet end 402 and
2 an outlet end 403; at least a portion of the interior of the tube
3 401 defining a reaction zone 404. The reactor tube 401 is made of
4 a fabric of a fibrous refractory material capable of emitting
5 sufficient radiant energy to raise the temperature of reactants
6 within the reaction zone 404 to a level required to initiate and
7 sustain the desired chemical reaction. The fabric has a multipli-
8 city of pores of such diameter as to permit a uniform flow of suf-
9 ficient inert fluid which is substantially transparent to radiant .
lO energy through the tube wall to constitute a protective- blanket
11 for the radially inward surface of the reactor tube 401.
12 (B) A fluid-tight, tubular pressure vessel (which has :
13 an inlet assembly section 201, an electrode assembly section 301,.
14 a main assembly section 405, and a post-reaction treatment assem-
15 bly section 501) encloses the reactor tube 401 to define an inert
16 fluid plenum 406 between the reactor tube 401 and the pressure
17 vessel. The inlet and outlet ends, 402 and 403, respectively, of
18 he reactor tube 401 are sealed from the plenum 406. The pressure
19 vessel has a first inlet 408 and a second inlet 409 for admitting
20. the inert fluid which is directed under pressure into the plenum
21 406 and through the porous tube wall 401 into the reaction zone 404 .
22 (C) Means for introducing reactants, either gaseous,
23 liquid, or solid, into the reaction zone 404 through the inlet e~nd
24 402 of the reactor tube 401. The reactants are directed in a pre-
2~ determined path axially of the reactor tube 401 and are confined by
26 the protective blanket substantially centrally within the reaction
27 zone 404 and out of contact with the inner wall of the reactor tube
28 401.
29 (D) Electrical means including heating elements 302a,
30 302b, and 302c which are disposed within the plenum 406 and spaced
~0776~4 ``
1 Iradially outwardly of ~he reactor tube 401 for heating the reactor
2 ¦tube to the temperature level at which it emits sufficient radiant
3 ¦energy to initiate and sustain the desired chemical reaction. The
4 ¦radiant energy is directed into the reaction zone 404 substantially
5 ¦coincident with at least a portion of the path of the reactants.
6 ¦ (E) A heat shield 410 which is disposed within the pres-
7 ¦sure vessel substantially enclosing the heating elements 302a,
8 ¦302b, and 302c and the reaction zone 404 to define a black body
9¦ cavity. The heat shield 410 reflects radiant energy inwardly
lO¦ toward the reaction zone 404.
11 ¦ A. INLET ASSEMBLY .
12¦ Referring particularly to FIGS. 7A and 8, the pressure
13¦ vessel inlet assembly section 201 is a tubular member having -
14¦ first and second flanges, 202 and 203, at its respective ends.
15¦ An annular nozzle block 204 is secured to an annular sealing
161 flange 205 which, in turn, is secured in fluid-tight relationship
17¦ to the first flange 202 of the inlet assembly pressure vessel
18 section 201. A principal atomizing gas inlet tube 206 extends
19¦ through the annular nozzle block 204 and is fixedly secured
20¦ thereto by a support flange 207. An O-ring 209 in the support
21¦ flange 207 assures a fluid-tight seal between the principal -
22¦ atomizing gas inlet tube 206 and the flange 207. An inlet
231 fitting 210 is secured to an end of the principal atomizing -
241 gas inlet tube 206 as shown in FIG. 7A. Atomizing gas enters
251 a plenum 211 through inlet 212.
26¦ A principal liquid reactant inlet tube 214 is disposed 5
271 within the principal atomizing gas inlet tube 206 and extends//
28 substantially coextensively therewith. A principal liquid
29 reactant enters the tube 214 through inlet 215 in fitting 210.
As best shown in FIG. 7B, a fogging nozzle 216 is
~o77~84
secured to the outlet end of both the principal atomizing gas
inlet tube 2n6 and the principal li~uid reactant inlet tube
214. The fogging nozzle 216 includes a tubular shroud 217 which
is secured to and disposed radially outwardly of the nozzle as
shown. The axis of the shroud 217 is substantially parallel
to the axis of the reactor tube 401. In operation, the liquid
reactant and the atomizing gas are directed under pressure
through tubes 214 and 206, respectively, and, under pressure, are
mixed within the nozzle 216. The liquid reactant is thus dis-
persed from the nozzle outlet as a fog which absorbs radiantenergy. The shroud 217 serves to assist in containing the
liquid reactant fog centrally within a pre-reaction zone 411
of the reactor tube 401.
As shown best in FIGS. 7A a~d 8, the inlet assembly
of this fourth reactor may further include a plurality of secon-
dary inlet tubes 218a, 218b, and 218c which enable the introduc- -
tion of additional liquid reactants. The means for introducing
the secondary liquid reactant are structurally and functionally
similar to the means for introducing the prinicpal liquid reactant,
previously described, and thus further embodv secondarv atomizing
gas inlet tubes 219a, 219b, and 219c and fogging nozzles ~uch
as 220a (the additional fogging nozzles are not shown~. A repre-
sentative inlet for a secondar~y liquid reactant and a represen-
tative inlet for a secondary atomizing gas are designated bv
reference numerals 221 and 222, respectively.
The above discussion presumes that the reactants
themselves either exhibit a relatively high radiation absorp-
tion coefficient (~) or can be converted into a fog which
absorbs radiant energv However, if such is not the case, a
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li 'i
1~)77684
1 ¦radiant energy absorptive target, such as previously described,
2 ¦must be introduced into the reactor zone 404 coincident with at
3 ¦least one point al~ng the path of the reactants.
4 ¦ Referring particularly to FIG. 7A, a sweep gas assists
5 ¦in directing the liquid reactant fog toward the reaction zone 404.
6 ¦The sweep gas enters nozzle block 204 through sweep gas inlet ~ -
71 fitting 225, passes through channel 227 and is directed axially
81 of the reactor tube 401 toward the pre-reaction zone 411.
9¦ As shown in FIGS. 7A and 8,-a reaction viewport 226
lO¦ provides an axial view into the reaction zone 404.
111 B. ELECTRODE ASSEM8LY
I ~ .
12¦ Referring particularly to FIGS. 7B, 9, 10 and 11, the
13¦ tubular electrode assembly pressure vessel section 301 has first
14¦ and second flange portions 303 (shown in FIG. 7A) and 304, respec-
15¦ tively. Electrode assembly pressure vessel section 301 is secured
16¦ at its first flange 303 to the second flange 203 of the inlet -
17¦ assembly pressure vessel section 201 in fluid-tight relationship.
18 A coolant channel 305 is defined between the electrode assembly
19¦ pressure vessel section 301 and an electrode assembly cooling
?¦ jacket 306. Coolant enters the channel 305 through inlet 307 and
21¦ exits through outlet 308.
221 As shown best in FIGS. 7B and 9, copper bus bar
231 electrodes 309a-309f are mounted on and extend through the second
241 flange 304 of the tubular electrode assembly pressure vessel
251 section 301. Although there are six such electrodes 309, as a
26¦ matter of convenience only one is actually shown in detail in FIG .
271 7B. Each copper bus bar electrode 309 includes a phenolic
28¦ flange 310 and a ceramic insulator 311. Each such electrode 309
291 is cooled by a fluid, preferably ethylene glycol, which circulates
in an in rnal ~ha~el 312~ ;nter n~ through inlc~ ~13 a~d exiting~
.. ,
1077684
1 ~t r oug h o u t le t 314. An electrical connec~ion is illustra t ed at
2 ¦315. A polytetrafluoroethylene seal 316 assists in preventing any
3 ¦leakage from inside the inert fluid plenum 406. Although, as
4 ¦illustrated in FIG. 17, the electrical system employed in connec-
5 ¦tion with the present reactor is of the 3-phase "Y" connection
6 ¦type, other systems may be used where circumstances warrant.
7 ¦ Referring particularly to FIGS. 7B and 7C, each copper
81 electrode 309 is secured by a tongue and groove connection to a
9¦ first extremity of a rigid carbon electrode extension 317. The
lO¦ electrode extensions 317 project through but do not contact a
11¦ first end section 412 of the heat shield 410 and are secured at a
12¦ second extremity to an arcuate heating element support 318. As
13¦ shown best in FIG. 10, heating elements 302a-302c are secured at a
14¦ first end to one of the arcuate heating element supports 318 and
15¦ are spaced circumferentially about the reactor tube 401 within
16¦ the inert fluid plenum 406. The heating elements are secured at
17¦ a second end to a 3-phase center connection ring 319 as shown in
18 FIGS. 7C and 11. Preferably, each electrically resistive heating
19¦ element 302 is made of a fabric of a fibrous refractory material
201 such as graphite or carbon. Heating element supports 318 and
21¦ center connecting ring 319 may be made of an electrically-con-
22¦ ductive, refractory material such as carbon.
231 C. MAIN ASSEMBLY
241 Referring to FIGS. 7B, 7C and 10, the tubular main
251 assembly pressure vessel section 405 has first and second flange
261 portions 414 and 415, respectively. Section 405 is secured at
271 its first flange 414 in fluid-tight relatiGnship to the second
28¦ flange 304 of the electrode assembly pressure vessel section 301.
291 A main assembly coolant channel 416 is defined between the main
301 assembly pressure vessel section 405 and a main assembly cooling
- . ~
I 1~7768~ ~
1 ¦jacket 417. The channel 416 is further defined by a spiral baffle
2 ¦418. Coolant enters the spiral channel 416 through inlet 419 and
31 exits through outlet 420.
4 ¦ The reactor tube 401 includes three zones: the pre-
~¦ reaction zone 411, the reaction zone 404, and a post-reaction
61 zone 422. As previously stated, the reactor tube 401 is made of
71 a fabric of fibrous refractory material such as carbon or graphite.
81 The fabric may be knitted, woven, or non-woven. The reaction
91 tube 401 is secured at its outlet end-403 to a reactor tube
lO¦ outlet support ring 424 which, in turn, is secured in place by
111 a reactor tube anchor block 425. The reactor tube 401 is
12¦ secured at its inlet end 402 to a reactor tube inlet support
~31 ring 426 which, in turn, is joined in fluid-tight relationship
14¦ to a tubular bellows 427 disposed within the pressure vessel
15¦ inlet assembly section 201. An inlet end of the bellows 427
16¦ is secured in a fluid-tight manner between the first flange
17¦ 202 of the pressure vessel inlet assembly section 201 and the
18 annular sealing flange 205 to insure that the inlet end of the
19 reactor tube 401 remains sealed from the plenum 406. The
20 bellows 427 is deformable to accomodate axial expansion and
21 contraction of the reactor tube 401.
22 Means for applying an axial tensile force to the
23 reactor tube 401 comprises three identical assemblies spaced
24 equidistant about the circumferential surface of the pressure
25 vessel inlet assembly section 201. For convenience, the assembly
26 428 which is illustrated in FIG. 7A shall be described. Each -
27 assembly 428 includes a translatable push rod 429 secured at one
28 end to the reactor tube inlet support ring 426 and at an opposite
29 end to an annular plate 430. Each push rod 429 is supported in
30 a bearing 431 which is sealed in a fluid-tight manner by O~ring -
. .
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,~ . . . . . . . .
'' '. ' : . . " - ' . ~ .
Il 1C377684
1~4 2. Eye-bolt 433 which is secured to the annular plate 430
2 ¦anchors a cable 434 which extends generally parallel to the
3 ¦longitudinal axis of the reactor and over a pulley assembly 435.
4 ¦A wei~ht 436 secured to an opposite end of the cable 434 applies
S la force which maintains the reactor tube 401 in axial tension.
61 Referring particularly to FIGS. 7B and 7C, the heat
71 shield 410 includes a first circumferential section 438 which is
81 disposed within the pressure vessel main assembly section 405,
9¦ radially outwardly of the heating elements 302a, 302b and 302c
10¦ and between the first end section 412 and a second end section 439
11¦ of the heat shield 410. As shown in FIG. 7C, the first circum-
12¦ ferential section 438 of heat shield 410 rests in a seating ring
13¦ 437 which is preferably made of carbon. If desired, the first
14¦ circumferential portion of the heat shield 410 may be extended
15¦ in a direction toward the electrode assembly 300 to include a
16¦ second circumferential portion 440 as shown in FIG. 7B.
17¦ Although molybdenum was the initial choice and had been found to b~
18 a satisfactory material for a heat shield of the type re~uired in
19¦ the present high temperature chemical reactor, it is preferred
?l that the heat shield 410 of the present embodiment be made of a
21¦ graphitic material such as pyrolytic graphite or a material
22¦ manufactured by Union Carbide Corporation and sold under the
23¦ tradename "Grafoil".
241 Radiometer viewports 441 and 442 are provided in the
251 main assembly section 400. Viewport 442 enables observation and
26 measurement of the temperature of the reaction zone 404 of the
27 reactor tube 401 and viewport 441 enables observation and measure-
28 ment of the temperature of heating element 302c.
29 D. POST-REACTION TREATMENT ASSEMBLY
As shown in FIG. 7C, a first flange portion 302 of the
1077f~84
1 ¦post-reaction treatment assembly pressure vessel section 501 is
2 ¦secured in a fluid-tight manner to a fluid-cooled interface
3 ¦flange 503 which, in turn, is secured in a fluid-tight manner
4 Ito the second pressure vessel main assembly section flange 415.
5 ¦A coolant channel 504 is defined between post-reaction treatment
6 ¦assembly cooling jacket 505 and the post-reaction treatment as-
7 ¦sembly pressure vessel section 501. Coolant flows into the channel
8 1504 through inlet 506 and exits through outlet 507. Radiometer
9¦ viewport 509 is provided to enable observation and temperature
lO¦ measurement within the post-reaction zone 422 of the reactor
11¦ tube 401.
~21 Reaction products exiting the outlet end 403 of the
13¦ reactor tube 401 of the embodiment of FIG. 7 pass into a first
14¦ section 510 of heat sink 511. As shown in FIGS. 7C and 7D, the
; 15¦ first section 510 of the heat sink 511 includes an inner tubular
16¦ wall 512 and an outer tubular wall 513 which define therebetween
171 a coolant channel 514. Spiral coolant baffle 515 directs the
18 coolant which enters through inlet 516 and exits through outlet
19¦ 517. A first thermocouple probe 518 which extends into the first
201 section 510 of the heat sink 511 enables the measurement of
21¦ temperature of the entering reaction products. A second thermo-
22¦ couple probe 519 which extends into the first sectio~ 510 of the ~ -
2~¦ heat sink 511 measures the temperature of the reaction products
241 about to exit.
251 Referring particularly to FIG. 7D, the first section 510
26¦ of the heat sink 511 is joined to a second section 520 by flanges
27 521 and 522, respectively. The second section 520 includes an inne r
28 wall 524 and an outer wall 525 which define therebetween a coolant
29 channel 526. Coolant enters the channel 526 through inlet 527
30 and exits through outlet 528. Thermocouple probes 530 and 531
~. ' : . , . ' .
I! `;
1 1077684
1 ¦enable measurement of the temperature of reaction products enter-
2 ¦ing the second section 520 and exiting the second section 520,
3 ¦respectively.
4 ¦ In the embodiment of FIG. 13, a post-reaction treatment
5 ¦assembly 500a includes a post-reaction treatment assembly pressure
6 ¦vessel section 501a having a flange portion 502a which is secured
7 ¦in a fluid-tight manner to a fluid-cooled, interface flange such ac
8 ¦flange 503 illustrated in Fig. 7C. A coolant channel 504a is de-
9¦ fined between a post-reaction treatment assembly cooling jacket
lO¦ 505a and the post-reaction treatment assembly pressure vessel
7 1 ¦ section 501a. Coolant flows into the channel 504a through inlet
12¦ 506a and exits through outlet 507a. Radiometer viewport 509a
13¦ enables observation and temperature measurement in the post-
14¦ reaction zone 422 of the reactor tube 401.
15¦ Reaction products exiting the outlet end 403 of the
16¦ reactor tube 401 of the embodiment of FIG. 13 at high temperature
17¦ pass into a variable profile, counter-flow heat exchanger 532
18¦ which abuts the reactor outlet 403 at its inlet end 533. The
,9l heat exchanger 532 includes an inner tubular wall of refractory
2~1 material 534, an outer tubular wall of refractory material 535
21¦ spaced concentrically outwardly from the inner wall 534, and a
22¦ spiral baffle of refractory material 536 disposed between the
23¦ walls 534 and 535 to define a spiral, annular coolant channel
241 537. The inner tubular wall 534, outer tubular wall 535 and
251 spiral baffle 536 together constitute a high temperature spiral
261 heat exchanger assembly 544 which rests on a resilient carbon
271 felt cushion 545 disposed on~end plate 546 of heat exchanger
28¦ pressure vessel section 547. Coolant inlets 538, 539 and 540
291 extend through the outer tubular wall 535 in communication with
301 the spiral coolant channel 537. -
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1077G84 ``
1 In the specific embodiment illustrated in FIG. 13,
2 after circulating throughout the spiral coolant channel 537 in a -
3 pre-selectable, variable, and controllable manner, the coolant is
4 discharged at an outlet 541 of the spiral annular channel 537
5 adjacent the inlet end 533 of the heat exchanger 532. Thereafter,
6 the coolant circulates through inlet port 542 in reactor tube
7 anchor block 425a into the inert fluid plenum 406. In such case,
8 it is apparent that the coolant employed should be a fluid which
9 is the same as or, at least, compatible with the inert fluid which
10 is present in the plenum 406. However, since the operation of the
11 heat exchanger 532 does not require that the coolant be circulated
12 into the plenum 406, alternative circulation patterns and exped-
13 ients are feasible. In such instances, the choice of coolant
14 fluid is not limited by the criteria set forth above. Circum-
15 ferential heat exchanger cooling jacket 548 is spaced radially ~ :
16 outwardly of the heat exchanger pressure vessel section 547,
17 defining therebetween an annular channel 549. Coolant is intro-
18 duced into channel 549 through inlet 550 and exits throu~h outlet
19 551.
20 E. INLET ASSEMBLY FOR SOLID REACTANTS
. ~ .
21 Inlet assembly 200a of the embodiment of FIGS. 14A and
22 14B is substantially identical to the inlet assembly 200 of FIGS.
23 7A and 7B except that means for introducing a principal solid
24 reactant of inlet assembly 200a replaces the means for introducing
25 a principal liquid reactant of inlet assembly 200. For convenience
26 only the features of the embodiment of FIGS. 14A and 14B which
27 differ from correspondin~ features of the embodiment of FIGS. 7A
28 and 7B shall be described.
29 A solid reactant inlet tube 232 extends through the
30 annular nozzle block 204 and is fixedly secured thereto by a
1` 1(177684
1 support flange 235 A principal solid reactant, prefe{ably
2 finely divided, enters inlet tube 232 through inlet 233 in suppor~
3 flange 235 and exits within reactor tube 401 adjacent the pre-
4 reaction zone 411. Secured to and disposed radially outwardly of
5 outlet 234 is a tubular shroud 217, the axis of which is sub-
6 stantially parallel to the axis of the reactor tube 401. Shroud
7 217 assists in containing finely divided solid reactants centrally
8 within the prereaction zone 411 of reactor tube 401.
9 Referring to FIG. 15, a solid reactant feed system 238
10 is shown in combination with a high-temperature reactor having an
11 inlet assembly 200a of the type depicted in FIGS. 14A and 14B. A
12 supply bin 240 for holding the solid reactant feeds a crusher 241,
13 which, in turn, feeds a sieve 242, Coarse product output 245
14 of the sieve 242 is recycled to the crusher 241 and fine pro-
15 duct output 243 is fed to a hopper 244 which is secured to
16 an elongated tubular housing 246. Helical feed screw 247 is ~ -
17 rotatably mounted within the housing 246 and is driven by motor
18 248. A pressure-sealing fluid may be introduced into the housing
9 246 through an inlet nozzle 249 located at a point downstream
20 from the hopper 244; the interior of reactor tube 401 is thus
21 sealed from the atmosphere. The solid reactant and the sealing
22 fluid are discharged from housing 246 into the reactor through an
23 outlet 250.
24 F. REFRACTORY COATING AND ETCHING SYSTEMS
For reasons set forth below, it is contemplated that
26 a refractory coating may be deposited on surfaces of reactor
27 tube 401, heating elements 302, and heat shield 410 which are
28 xposed to the blanket gas and to high temperatures during -~
29 operation of the reactor. Such refractory coating may be,
30 for example, pyrolytic carbon or a refractory oxide such as
107768~ 1
1 thorium oxide, magnesium oxide, zinc oxide, aluminum oxide, or
2 zirconium oxide. It is further contemplated that portions of
3 the surface of the reactor tube 401 may be selectively etched
4 ~r eroded.
Referring to FIG. 16, a refractory coating and etching
6 system 600 is schematically represented and comprises a first
7 refractory deposition agent metering system 601 having a carbon-
8 aceous gas supply 602 connected to a carbonaceous gas metering
9¦ line 603. The metering line 603 has an on/off valve 604 connected
lO¦ to a needle valve 605 and a flow meter 606. A first feeder line
11¦ 608 connects the carbonaceous gas metering line 603 to an admixture
12¦ gas supply line 607.
13¦ A second refractory deposition agent metering system
14¦ 610 includes a carrier gas supply 611 connected to a carrier gas
15¦ metering line 612 which has an on/off valve 613, a needle valve
16¦ 614, and a flow meter 615. The carrier gas metering line 612 is
17¦ connected to a bubble tube 616 disposed within a tank 617 which
18 contains a solution of a volatile metal-containing compound.
19¦ The temperature of the tank 617 is regulated by a temperature
201 controller 618 which senses the temperature of the tank by a
21 thermocouple 619 and supplies heat to the tank, as reguired, by
22 an electric heating mantle 620. An outlet end 621 of bubble tube
23 616 is submerged in the solution contained in the tank 617. An
24 outlet 622 of the tank 617 connects a second feeder line 623 to
25 the tank 617 at a point above the solution surface. The
26 second feeder line 623 is also connected to the admixture gas
27 supply line 607.
28 In an etching agent metering system 625, an etching
29 agent supply 626 is connected to an etching agent metering line
30 627 which includes, in series, an on/off valve 6~8, a needle valve
l ` i
1 1C~77684
1 ¦629, and a flow meter 630, Connected to the etching agent meterin~
2 ¦line 627 is a third feeder line 631, which is connected to the
3 ¦admixture gas supply line 607.
4 ¦ The three lines 608, 623, and 631, all feed into the
5 ¦admixture gas supply line 607, which branches at a T-joint 632.
61 A first branch line 633 includes a firs~ branch line valve 634
71 and is connected to a first inlet of an inert fluid mixing
81 manifold 635. A second branch line 636 includes a second
9¦ branch line valve 637 and is connected to a first inlet of a
lO¦ sweep gas mixing manifold 638.
11¦ An inert fluid supply 640 is connected to an inert fluid
12¦ metering line 641 which includes an on/off valve 642, a needle
13¦ valve 643 and a flow meter 644 which is connected to a second inlet
14¦ of inert fluid mixing manifold 635. An outlet of mixing manifold
15¦ 635 is connected to an inert fluid supply line 645 which, in turn,
16¦ is connected to the pressure vessel inlets 408 and 409 for direct-
17¦ ing the inert fluid into the inert fluid plenum 406. A plenum
18¦ pressure sènsor 646 is connècted to the inert fluid supply line
19¦ 645 and is in communication with the plenum 406 for measuring the
20.¦ pressure of the inert fluid within the plenum. A plenum exhaust
2~1 valve 647 is also connected to the inert fluid supply line 645
22¦ and provides an outlet for discharging fluid from the plenum.
231 A sweep gas supply 648 is connected to a metering line
24 649 which includes an on/off supply valve 650, a needle valve 651,
25 and a flow meter 652 which is connected to a second inlet of the
26 sweep gas mixing manifold 638. An outlet of mixing manifold 638 ¦ :
27 is connected to a sweep gas supply line 653 which, in turn, is
28 connected to the sweep gas inlet fitting 225 for introducing the ¦ -
29 sweep gas into the interior of the reaction tube 401. A reaction
30 zone pressure sensor 654 which connects to the sweep gas supply
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1 ~77684
1 ¦line 653 and which communicates with the interior of the reactor
2 ¦tube 401, measures the pressure in the reaction zone of the reac-
3 ¦tor.
41 As shown best in FIG. 7D, a reactor tube outlet closure
51 valve 655 is secured to the second section 520 of the heat sink :
511 by flanges 555 and 656.
71 - When the reactor is in operation, a pressure differential
81 must be maintained between the inert fluid in plenum 406 and
9¦ gas in the reactor tube 401 to cause a uniform flow of inert
lO¦ fluid radially inward through the porous wall of the tube 401. It
11¦ is thus advantageous that the fabric of tube 401 be sufficiently : -
12¦ stiff that the pressure differential may be maintained without : .
13¦ inward collapse of the tube 401. Accordingly, it is contemplated ~ :
141 that a refractory coating such as pyrolytic carbon be deposited
15¦ upon portions of the fibrous refractory material of the reactor
16¦ tube 401 which are disposed within the black body cavity to ;~
17¦ increase the stiffness or dimensional stability of the fabric.
~.81 To deposit such coating, reactor tube outlet closure
lg¦ valve 655 is closed and the reactor tube 401 is heated to about
201 3450F. Next, the on/off valve 650 in the sweep gas metering line
21¦ 649 is opened, the on/off valve 642 in the inert fluid metering
22¦ line 641 is closed, and the plenum exhaust valve 647 is opened,
231 permitting sweep gas to flow into the interior of the reactor
241 tube 401, then radially outwardly through the porous wall of the
251 tube 401 into the plenum 406, and, finally through the pressure
26¦ vessel inlets 408 and 409 and the plenum exhaust valve 647. This
271 tends to expand the tube 401 to its maximum diameter. Thereafter,
28 the on/off valve 604 in the carbonaceous gas metering line 603 -~
29 is opened. The needle valves 605 and 651 are adjusted to set the
30 flow rates of the carbonaceous gas and the sweep gas, respectively~
~o77684
l~t suitable values as registereù on elow meters 606 and 65~. The
2 ¦first branch line valve 634 is closed and the second branch line
3 ¦valve 637 is opened so that the carbonaceous gas flows through
4 ¦the first feeder line 608, the admixture gas supply line 607, the
5 ¦T- joint 632, the second branch line 636, and into the sweep gas
6 ¦mixing manifold 638 where it mixes with the sweep gas and flows
71 i-nto the interior of the reactor tube 401 through sweep ~as supply
81 line 653 and sweep gas inlet fitting 225.
9¦ The carbonaceous gas dissociates on the heated surfaces
lO¦ which it contacts, depositing a pyrolytic graphite coating. Thus,
11¦ pyrolytic graphite is generally deposited on ~he portions of the
i2¦ reactor tube 401, the heating elements 302, and the heat shield -
13¦ 410 which are within the black body cavity.
14¦ Since the portion of the reactor tube 401 which lies
15¦ within the pre-reaction zone 411 is outside of the black body
16¦ cavity and, thus, may not be heated conveniently to temperatures
17¦ above the decomposition temperature of the carbonaceous gas, it
~81 is contemplated that a stainless steel screen 450, shown in FIGS.
19¦ 7A and 7B, be provided to prevent the flexible reactor tube 401
2p1 from collapsing inwardly under the pressure differential of the
21¦ inert fluid, although it has been found that increased tension on
22¦ the porous fabric accomplishes substantially the same result.
231 To control the rate of flow of inert fluid through the
24 walls of the reactor tube 401, the diameter of the pores in the
25 tube wall may be reduced or enlarged while the reactor is in
26 operation by mixing a refractory deposition agent or an etching
27 agent with the inert fluid. The pressure differential between the
28 plenum and the reaction zone may be monitored by the pressure
29 sensors 646 and 654 and the rate of flow of inert fluid throuqh
30 the wall may be monitored by the flow meter 644.
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1 ~077684
I
l¦ When the pressure differential becomes too low for the
21 desired rate of flow of inert blanket gas, the diameter of the
3 ¦ pores in the tube of the reactor wall may be reduced by opening th~
41 on/off valve 604 and adjusting the needle valve 605 to allow a
51 carbonaceous gas from the carbonaceous gas supply 602 to flow
61 through carbonaceous gas metering line 603. The second branch
1 line valve 637 is closed and the first branch line valve 634 is
81 opened to direct the carbonaceous gas into the inert fluid mixing
9¦ manifold 635 and thence into the plenum 406 through the inert
lO¦ fluid supply line 645 and the pressure vessel inlets 408 and 409.
ll¦ The plenum exhaust valve 647 remains closed and ~he reactor tube
12¦ outlet closure valve 655 remains open during normal operation of
13 ¦ the reactor. The carbonaceous gas dissociates on the heated
l4¦ surfaces within the reactor which it contacts. Accordingly,
lS¦ carbonaceous gas which flows into the pores of the fabric of the
16¦ walI of reactor tube 401 dissociates, depositing a coating of
l7¦ pyrolytic graphite which reduces pore diameter. Since the pres-
18 sure differential across the reactor tube wall will increase for -
l9¦ a fixed flow of inert fluid, the decrease in porosity of the tube
201 may be monitored with pressure sensors 654 and 646 and flow meter
21¦ 644 as the graphite is deposited. When the pressure differential
22¦ exceeds a predetermined value, the growth of the graphite coating
231 may be halted by closing the on/off valve 604 in the carbonaceous
241 gas metering line 603. The entire process of reducing the diamete
251 of the pores in the reactor tube wall may be carried out without
26¦ interrupting the operation of the reactor.
271 Conversely, it may be necessary to increase the diameter
28¦ of the pores of the reactor tube 401. In this case, an etching
291 agent such as steam or molecular oxygen from the etching agent
301 supply 626 is mixed with the inert fluid by opening valve 628,
l ~.C1776S4
1~ adjusting needle valve 629 in the etching agent metering line
21 627, closing the second branch line valve 637, and opening the
31 first branch line valve 634. The etching agent mixes with the
~¦ inert fluid in inert fluid mixing manifold 635 and flows into
51 the plenum 406 through the pressure vessel inlets 408 and 409.
61 The etching agent attacks heated surfaces which it contacts,
7 ¦ thereby increasing the diameter of the pores of the heated
8¦ portion of the reactor tube 401. The flow of etching agent may
gI be continued until pressure sensors 654 and 646 indicate a
lO¦ sufficiently low pressure differential across the reactor tube
11¦ 401 for the desired rate of flow of inert fluid as monitored by
12¦ flow meter 644. As with reducing the pore diameter with the
13¦ carbonaceous gas, this process may be carried out while the
14¦ reactor is in operation.
15¦ It may be advantageous in some applications to use
16¦ steam or another medium which reacts chemically with the materials
17 ¦ being processed as the inert fluid. To prevent or, at least, to
~81 retard the corrosion of materials of which the reactor is
~9¦ constructed, it is contemplated that a coating of a refractory
201 oxide such as thorium oxide, magnesium oxide, zinc oxide,
21¦ aluminum oxide, or zirconium oxide be deposited on the portions
22¦ of the reactor tube 401, heating elements 302, and heat shield
231 410 which come into contact with the inert fluid and operate at
24¦ high temperatures. To deposit a coating of refractory oxide,
251 a refractory deposition agent which is a volatile metal-containing
26 ¦compound such as methylmagnesium chloride, magnesium ethoxide,
27 Ior zirconium-n-amyloxide may be employed. Methylmagnesium
28¦ chloride, for example, decomposes on a surface heated to about
29 ¦1100F. to deposit a coating of magnesium metal. The hot magnesiu~
30 ¦metal is subsequently oxidized by introducing steam or molecular
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77684 ' I
~ .
1 ¦oxygen into the plenum 406. Zirconium-n-amyloxide and magnesium
2 ¦ethoxide both generally decompose on heated surfaces to form
3 ¦zirconium oxide or magnesium oxide respectively.
4 I Referring to FIG. 16, the volatile metal-containing
5 ¦compound may be introduced into the plenum 406 by causing a ~-
6 ¦carrier gas from the supply 611 to flow through the metering
7 ¦line 612 by opening the on/off valve 613. The needle valve 614,
81 adjusts carrier gas flow rate to a suitable value as measured by
9¦ flow meter 615. The tank 617 contains, for example, a solution of
lO¦ the volatile metal containing compound such as methylmagnesium
11¦ chloride dissolved in diethyl ether or zirconium-n-amyloxide
12¦ dissolved in tetrahydrofuran. The carrier gas flows through the
13¦ bubble tube 616 and into the solution of tank 617. The second
14¦ branch line valve 637 remains closed and the first branch line
15¦ valve 634 remains open in order that the carrier gas, solvent
16¦ vapor, and metal-containing compound vapor are directed sequen-
17¦ tially through the outlet 622 of the tank 617, the second feeder
18¦ line 623, the admixture gas supply line 607, and the first branch
19¦ line 633, and into the inert fluid mixing manifold 635 where they
201 are mixed with the inert fluid and then carried to the plenum 406
21¦ over the inert fluid supply line 645 and through the pressure
22¦ vessel inlets 408 and 409. The volatile, metal-containing com-
231 pound decomposes on hot surfaces which it contacts within the
24 reactor. If it decomposes into a pure metal, oxygen or steam is
25 subsequently introduced into the plenum 406 to cause formation of
26 the oxide.
27 G. PROCESS VARIABLE CONTROL SYSTEMS
28 FIG. 17 illustrates a reactor temperature control system
29 700. There, heating elements 302a, 302b and 302c are depicted in
30 schematic form connected in a "Y" configuration circuit, one end
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~077684
1 ¦of each heating element being connected to a tie point 701 and
2 Ithe other end being connected to a branch 702a, 702b, or 702c of
3 la three-phase power line 702. The tie point 701 corresponds to
4 ¦the three-phase connecting ring 319 of FIG. 7C. The power line
5 1702 connects to a heater power output 703 of a power controller
6 1704, which, in turn, connects to a principal three-phase power
71 l-ine 705 and a firing circuit 706. The principal three-phase
81 power line 705 supplies current, preferably at 440 volts, for
9¦ heating the reactor. A radiometer 708 disposed within the view-
iO¦ port 441 of FIG, 7B is focussed on the heating element 302c and
11¦ produces a signal, generally in the millivolt range, which corres-
12¦ ponds to the temperature of the heating element. An "MV/I" con-
13¦ verter 709 amplifies the radiometer signal and converts it to an
14¦ electric current. A setpoint controller 707, an output siqnal
15¦ line 712 for connection to a computer (not shown), and a recorder
16¦ 710 which makes a permanent log of the temperature measured by the
17¦ radiometer 708 are all connected to the converter 709. An input
18¦ signal line 713 connects a control signal input 711 of the set-
79 ¦ point controller 707 to a computer (not shown). Current meters
201 750a, 750b, and 750c are inserted in the three branches 702a, 702b
21¦ and 702c, respectively, to measure the current supplied to heating
22I elements 302a-c; and, voltmeters 751a, 751b, and 751c are tied to
23I the branches 702a-c to measure the voltages across the heating
241 elements. The power dissipated in the heating elements and the
251 electrical resistance of the heating elements can be calculated
26¦ from such voltage and current measurements. Knowledge of the
27¦ electrical resistance of each heating element Provides informa-
28¦ tion as to its physical integrity since, as a heating element
291 erodes, its electrical resistance increases.
50j ~IG. 18 is a ~raph of the electrical sheet resistance o~
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1o77684
1 a sample of graphite cloth (sold under the trade name of "WCA
2 Graphite Cloth" by Union Carbide Corporation) as a function of th~
3 temperature of the cloth. The cloth has been stiffened with
4 pyrolytic graphite by heating and exposing it to an atmosphere of a
5 carbonaceous gas, generally according to the procedure described
6 above. The vertical axis of the FIG. 18 graph gives the sheet
7 resistance in units of "ohms per square" since, as is known, the
8 resistance measured between opposing edges of squares of a
9 resistive material of a given thickness is independent of the
lO dimensions of the square. Thus, the resistance at a particular
11 temperature of a heating element formed from a single rectangular
12 strip of "WCA Graphite Cloth" may be found by considering the
13 strip to be made up of squares of the cloth connected in series.
14 For example, the resistance of a strip 6 inches by 51 inches at
15 2500F. measured between the two six-inch sides is found by
16 multiplying (51/6) times 0.123 ohms, the sheet resistance at
17 2500F. given on FIG. 18. The resistance of a heating element
18 made up of more than one layer of fabric, each layer having the
19 same dimensions and therefore the same resistance, is found by
20 dividing the resistance of a single layer by the number of layers.
21 For convenience, the calculated sheet resistances in "ohms per
22 square" for samples of stiffened "WCA Graphite Cloth" made up
23 of 2, 3, and 4 layers have also been graphed on FIG. 18.
24 In operation, after the setpoint controller 707 is set tc '
25 a specified temperature either manually or by a computer, it com-
26 pares such temperature with the measured temperature of the elec-
27 trode 302c and produces an error signal which depends upon the
28 algebraic difference between the measured temperature and the spec-
29 ified temperature. The setpoint controller 707 controls the
30 firing circuit 706, which, in response to the error signal,
!
~ ~077684
1 auses the power controller 704 to increase or decrease the power
2 supplied to the heating elements to reduce, as necessary, the
3 agnitude of the error signal, causing the temperature of the
heating element 302c to approach the specified temperature.
5 Because the heating element 302c is within the black body cavity
6 enclosed by the heat shield 410, its temperature is generally
7 represen.ative of the temperature of surfaces throughout the
8 cavity. However, radiometers focussed on other surfaces within
9 the black body cavity may also be used for temperature control.
As shown in FIG. 19, process variables in addition to
11 temperature may be regulated by feedback control systems as, for
12 example,a principal liquid reactant feed rate regulation system
13 714 which includes a supply 715 communicating with a metering
14 system 716 over a feed line 717. The metering system 716 con-
15 trols the flow rate of the principal reactant and may include,
16 for example, a variable speed pump and pump controller or a
17 variable orifice valve and valve controller. An output 718 of the
18 rincipal reactant metering system 716 is connected to a flow rate
19 transducer 719 which produces an electrical signal output 720
20 corresponding to the rate of flow of the principal reactant. An
21 output 721 of the principal reactant flow rate transducer 719
22 is connected to the principal liquid reactant inlet pipe 215. A
23 signal output 722 of the reaction zone pressure sensor 654 and the
24 signal output 720 of the flow rate transducer 719 are connected
25 to the first and second signal inputs, respectively, of the princi-
26 pal reactant metering system 716. An output of a computer system ¦
27 723 is connected to a third input of the metering system 716.
2 In one mode of operation of the principal liguid reactant
2 feed rate regulation system 714, the computer system 723 communica-
3 tes both a pre-selected value for the principal reactant flow rate
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1 1~77684
1 and an upper limit for the reaction zone pressure to the principal¦
2 reactant metering system 716 which compares the pre-selected flow
3 rate with that measured by the transducer 719 and adjusts the flow
4 rate to approach the selected value, provided, however, that the
5 reaction zone pressure is below the prescribed upper limit. Should
6 the reaction zone pressure exceed this upper limit, the metering
7 system 716 will lower the pressure by reducing the flow rate of the
8 principal reactant.
9 A secondary liquid reactant flow rate regulation s~stem
10 724 is another feedback control system which includes a supply 725
11 communicating with a metering system 726 over a feed line 727.
i2 The secondary reactant metering system 726 may be of the same type
13 as the principal reactant metering system 716. An output 728 of
14 the secondary reactant metering system 726 is connected to a flow -
15 rate transducer 729 which produces a signal corresponding to the
16 rate of flow of the secondary reactant. An output 731 of the tranC _
17 ducer 729 is connected to the secondary reactant inlet 221, A
~8 signal output 722 of the reaction zone pressure sensor 654 and a
.9 signal output 730 of the secondary reactant flow rate transducer
20 729 are connected to separate signal inputs of the secondary reac-
21 tant metering system 726, and an output of the computer system 723
22 is connected to a third input. The secondary liquid reactant flow
23 rate regulation system 724 may be operated in a mode analagous to
24- that described above for the principal li~uid reactant regulation
25 system 714.
26 In an inert fluid flow rate regulation system 734, an
27 output of the inert fluid supply 640 is connected to the needle
28 valve 643, which, in turn, is connected ~o the onjoff valve 642.
29 Valve 642 is connected to an inert fluid flow rate transducer 735.
30 A signal output 736 of the transducer 735 is connected to a first
. -43-
107768~
1 input of an inert fluid needle valve controller 737. A second inpult
2 of the needle valve controller 737 is connected to the computer
3 system 723 and a third input is connected to the plenum pressure
4 sensor 646. The opening of the needle valve 643 may be set by the
5 controller 737. An inert fluid output of transducer 735 is con-
6 nected to the pressure vessel inlets 408 and 409 of the reactor.
7 For convenience, the plenum exhaust valve 647, flow meter 644 and
8 inert fluid mixing manifold 635, of FIG. 16 are not shown in FIG.
9 19, and the inert fluid flow rate transducer 735 of FIG. 19 is not
lO shown in FIG. 16.
11 In operation, the on/off valve 642 is opened, allowing
12 the inert fluid to flow through transducer 735 and into the inlets - :
13 408 and 409. The needle valve controller 737 compares a flow-rate
14 signal from the transducer 735, to a flow rate specified by the
15 computer system 723 and adjusts needle valve 643 accordingly, pro-
16 vided, however, that the plenum pressure as sensed by pressure
17 sensor 646 does not exceed an upper limit also specified the by ~:
18 omputer system 723 n If the pressure is excessive, the needle
,9 valve controller 737 reduces the flow rate to lower the pressure. :
20. A reactor temperature control system 700, shown in detai:
21 in FIG. 17 and depicted schematically in FIG. 19, comprises a
22 reactor temperature controller 738 which includes the power contro: _ .
23 ler 704, firing circuit 706, set point controller 707, converter
24 709, recorder 710, and meters 750 and 751 shown in FIG. 17. The
25 radiometer 708 (not shown in FIG. 19) is housed within the view-
26 port 441 and connected to the controller 738. The three-phase
27 power line 702 connects the heater power output 703 of the reactor
28 temperature controller 738 to the heating elements 302 (not shown
29 in FIG. 19) through the electrodes 309. Thus, the level of elec-
30 trical power supplied at the heater power output 703 determines th
1~77684
1 ~temperat re o e the reactor tube 401. Tlle contr~l signa1 inpu~` l~ll
2 land an output of the reactor temperature controller 738 are con- '
3 ¦nected to the computer system 723 by the input signal line 713 and
4 ¦the output signal line 712, respectively.
5 ¦ A reactor product sampler 740, connected to an outlet 741
61 located adjacent the reactor outlet closure valve 655, transfers at
7 ¦preselected time intervals samples of reaction product into a
81 sample inlet 742 of a gas chromatograph 743. An electrical signal
9¦ at an output 744 of the chromatograph 743 responds to changes in
10¦ the chemical composition of the samples. For example, the gas
11¦ chromatograph 743 in conjunction with the reaction product sampler
12¦ 740 may produce a signal which corresponds to the concentration of
13¦ ethylene in a process for the partial pyrolysis of a hydrocarbon.
14¦ Outputs of the gas chromatograph 743 are connected to a
15¦ recorder 749 and the computer system 723. An input 745 of the
16¦ computer system 723 is connected to transducers for the process
17¦ variables by a data bus 746, which includes signal lines connected
~8 to the flow rate transducers 719, 729 and 735, pressure sensors
19¦ 646 and 654, temperature controller 738, and gas chromatograph
20¦ 743. Other transducers may be tied to the data bus 746 as desired.
21¦ An output 747 of the computer system 723 is connected to a command
22¦ bus 748 which includes signal lines tied to the principal reactant
231 metering system 716, secondary reactant metering system 726,
241 reactor temperature controller 738, and inert fluid needle valve
25¦ controller 737. The computer system 723 may include a digital
26¦ computer, an analog-to-digital converter for converting analog
271 signals of the transducers to digital data for the computer, a
28¦ digital-to-analog converter for converting digital signals from th~
291 computer to analog control signals, and a multiplexer for switch-
30¦ ing among signal lines in the data bus 746 and the command ~us 748
1(~77684
1 It is contemp~ated that during a process run the
~ ¦computer system 723 may specify and monitor process variables by
3 ¦signals communicated over the command bus 748 and the data bus ,46.
4 ¦Thus, the computer system 723 may supervise the operation of the -
5 ¦reactor to ensure that process variables remain within specified
6 ¦ranges. Moreover, the computer may be programmed to search for
71 optimum operating conditions for a particular process by making
81 systematic variations in the process variables while monitoring
¦ the output of the reactor with the chr-omatograph 743. For example,
~¦ the computer may be programmed to search for reactor temperatures
11¦ and feedstock flow rates which maximize the ethylene concentration
~21 in the output for a particular hydrocarbon feedstock. The computer
13¦ system 723 may also be incorporated in feedback control systems;
14¦ such as a reaction product control system which includes in additic n
15¦ to the computer system 723 the reaction product sampler 740, the
16¦ gas chromatograph 743, the reactor temperature controller 738, and
17¦ the three-phase power line 702 connected to th-e heating elements
~8¦ 302. In this reaction product control system, the computer system
.9l compares the chemical composition of samples of reaction product
201 withdrawn from the reactor to a preselected composition and gene-
21¦ rates an electrical signal at its output 747 corresponding to
22¦ deviations in the chemical composition of the samples. The out-
231 put 747 of the computer system 723 is connected to the input 711
241 of the reactor temperature controller to enable variation of the
25¦ temperature of the reactor tube in response to changes in the
26¦ signal from the computer system, reducing the deviations in the
271 chemical composition of the reaction products. Other process
28¦ variables such as the feedrates of selected reactants and the
291 pressure in the reaction zone may also be controlled by similar
301 feedback control systems.
: - :
' 1~77~4
PR~CES~ P~RAM~TER~
-
High temperature chemical reaction processes conducted
in accordance with the present invention necessitate the use of
an annular envelope or blanket of an inert fluid which is suhstan-
tially transparent to radiation. The envelope has a substantial
axial length. The annular envelope may he generated in a direc-
tion generally parallel to its axis or in a direction generally
perpendicular to its axis and radially inwardly of its outer cir
cumferential surface.
In the former instance, as previously described with
respect to the first emhodiment of the present reactor, the
envelope fluid must be maintained in laminar flow to prevent
intermixing with the reactant stream. This requirement imposes
certain limitations upon the axial length of the envelope because
such laminar flow, and thus blan~et integrity cannot be main-
tained for indefinite lengths downstream, especially if a particu-
larly violent reaction is contemplated. ~ccordingly, this manner
of generating the envelope is most suitable for smaller-scale and
laboratorv applications.
In the latter instance, as previously descrihed with
respect to the second, and third and fourth emhodiments of the
reactor, the integritv of the fluid envelope is independent of
any flow considerations andmay be maintained for an axial dis-
tance much greater than that ohtainahle in the case of the axially
injected laminar envelope. The primary re~uirement is to main-
tain the flow of the inert fluid under a greater pressure than
that of the reactant stream to prevent the reactants from "pun-
ching through" or otherwise hreaking out of confinement within
the envelope.
After the envelope has heen generated, at least one
reactant is passed through its core along a predetermined path
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1 ~776~4
1 ¦which is substantially coincident with the envelope axis. ihe
2 ¦envelope confines the reactants therewithin and out of contact
3 ¦with the containing surfaces of the reactor chamber.
4 ¦ Finally, high intensity radiant energy is directed into
5 ¦the envelope core to coincide with at least a portion of the pre-
6 ¦determined path of the reactants. Such radiant energy may be
7 ¦dïrected to at least one point along the path of the reactants as
81 in the first and third embodiments, or it may be directed along a
9¦ finite length of the path as contemplated by the second and fourth
10¦ embodiments. In either case, sufficient radiant energy is absorbed
11¦ in the core to raise the temperature of the reactants to a level
12¦ required to initiate the desired chemical reaction.
13¦ In the event that the reactants will not themselves
14¦ absorb radiant energy, an absorptive target may be introduced
15¦ along the path of the reactants, preferably before the radiant
16¦ energy is directed into the core. The target will then absorb
17¦ sufficient radiant energy to raise the temperature in the core to
18 ¦the level required to initiate the desired chemical reaction. As
19¦ previously stated, if the contemplated reaction is such that the
20¦ transparent reactants produce at least one product which absorbs
21¦ radiant energy, the target may be deactivated after the reaction
22¦ has been initiated.
231 The contemplated process may further include the step
241 of cooling the reaction products and any remaining reactants and/
251 or targets immediately after the desired reaction has been com-
26¦ pleted. The purpose of this procedure is to terminate the desired
271 reaction and to prevent the occurence of any further undesired
28¦ reaction. The products, targets and remaining reactants may be
291 cooled conveniently and effectively by radiation heat transfer
301 to a cool, radiant energy absorbing surface.
Il , i
1077~
1 UTILIZATION OF THE FLUID-WALL REACTORS
A _ _.. _ .. ' - - - '- - ! ,
2 The fluid-wall reactors of the invention may be used in
3 virtually any high temperature chemical reaction, many of which
4 reactions have been previously regarded as either impractical or
5 only theoretically possible. The most important criterion for
6 utilizing these fluid-wall reactors in a particular high tempera-
7 ture chemical reaction is whether such reaction is themodynamic-
8 ally possible under the reaction conditions. Utilizing these
9 fluid-wall reactors, such high temperature chemical reaction
lO processes can be conducted at temperatures up to about 6000F.
11 by (1) generating within the interior of the porous reactor tube
12 an annular envelope consituting an inert fluid which is substan-
13 tially transparent to radiant energy to form a protective blanket
14 for the radially inward surface of the reactor tube, the annular
15 envelope having substantial axial length and the interior of the
16 envelope defining a reaction chamber; (2~ passing at least one
17 reactant (which may be either in solid, liquid or gaseous state)
18 through the reaction chamber along a predetermined path substan-
19 tially coincident with the longitudinal axis of the envelope, the
20 reactants being confined within the reaction chamber; and (3)
21 directing high intensity radiant energy into the reaction chamber :
22 to coincide with at least a portion of the predetermined path of
23 the reactants, sufficient radiant energy being absorbed within :
24 the reaction chamber to raise the temperature of the reactants
25 to a level required to initiate and sustain the desired chemical
26 reaction~
27 Among the reactions which may be carried out in the
28 fluid-wall reactors of the invention are the dissociation of
29 hydrocarbons and hydrocarbonaceous materials, such as coal and
30 various petroleum fractions, into hydrogen and carbon black;
-54-
377~i84
l I
1 the steam reforming of coal, petroleum fractions, oil shale, tar
2 ¦sands, lignite, and any other carbonaceous or hydrocarbonaceous
3 ¦feedstock into synthesis gas mixtures, which processes may also
4 ¦include the optional use of one or more inorganic carbonates (such
5 ¦as limestone or dolomite) or inorganic oxides to chemically react
6 ~ith any sulfur-containing contaminants such that they may be
7 ¦removed from the resultant synthesis gas mixtures; the partial
8 ¦dissociation of hydrocarbons and hydrocarbonaceous materials into
9 ¦lower molecular weight compounds; the partial pyrolysis of satur-
10¦ ated hydrocarbons into unsaturated hydrocarbons, such as ethylene,
11¦ propylene and acetylene; the conversion of organic waste materials,
12¦ such as sewage sludge or lignin-containing by-products, into a fuel
13¦ gas; the complete or partial desulfurization of sulfur-containing
14¦ hydrocarbonaceous feedstocks; the reduction of mineral ores or
15¦ inorganic compounds to a lower valence state with hydrogen, carbon,
16¦ synthesis gas, or other reducing agent; and the partial or complete
17¦ reaction of an inorganic element or compound with a carbonaceous
~8I material to form the corresponding inorganic carbide.
19¦ If desired, one or more catalysts may be used in such
20¦ high temperature chemical reaction processes to accelerate the
21¦ reaction or to change its course to a desired reaction sequence.
221 Where such processes involve carbonaceous or hydrocarbonaceous
231 reactants, the addition of an an appropriate catalyst to the sys-
241 tem may be used to promote the formation of free radicals, carbo-
251 nium ions or carbanions to influence the course of the reaction.
26¦ Of course, no one set of operating conditions is optimum I -
271 or appropriate for all reactions which may be carried out in the
28¦ fluid-wall reactor. Operating conditions, such as temperatures,
29I pressures, rates of feed, residence time in the reactor tube, and
30I rates of cooling, may be varied to match the requirements for the
10776~4
particular reaction conducted. By wav of illustration, among the
factors which influence the products of the pyrolysis of a hydro-
carbon are the temperature to which the hvdrocarbon is heated and
the length of time it is maintained at that temperature. It is
known, for example, that methane must be heated to about 2250F.
in order to produce acetylene. Ethylene formation from ethane
begins at a lower temperature, about 1525F. In a tvpical pro-
cess for pyrolyzin~ hydrocarbons, acetylene, ethylene, h~drogen,
carbon black, and hydrocarbon oils are produced. Reaction times
on the order of a millisecond generallv maximize the yield of acet-
ylene, since reaction times of greater than a millisecond generally
favor the production of ethylene and other products at the expense
of acetylene, while reaction times of less than a millisecond gen-
erall~ reduce the yields of both ethylene and acetylene. Very high
temperatures, for example in excess of 3000F., generally favor
the production of carbon black and hydrogen at the expense of
acetylene and ethylene. Reaction times in the fluid-wall
reactors of the invention may be shortened by shortening the
reactor tube and by increasing the rate of flow of reactants
introduced into the reactor tube. For verv short reaction times,
it may be advantageous to mix a radiation-absorbing target, such
as carbon black, with the reactants in order to promote efficient
coupling between the reactant stream and the thermal radiation
from the tube wall and thereby facilitate heating the reactants
~uickly.
F~AMPLES
The following examples are illustrative o the ease
with which various high temperature chemical reaction processes
may be carried out in 1uid-wall reactors in accordance with the
3~ invention and in accordance with the invention of parent Applica-
tion 236,325. In each of these examples, the high temperature fluid- --
-56-
,ll ` I
1~77684
1 ¦wall reactor previously illustrated by FIGS. 2A through 6 was uti-
2 ¦lized to carry out the particular high temperature reaction. The
3 ¦reactor tube 61 was a porous graphite tube 36 inches in length
4 ¦which had an inside diameter of 3 inches and an outside diameter of
5 14 inches, the average pore radius being 20 microns. The porous
6 ¦tube was encased in a steel pressure vessel 70, which was 10 inche
¦in diameter. Reactor tube 61 was heated by carbon electrodes lOOa
8¦ through lOOf, which were disposed within plenum 85. The heat
9 ¦shield 120, also located within plenum 85, was made of molybdenum.
10¦ A water-cooled collar 125 was located adjacent to the outlet end
11¦ of reactor tube 61 to cool the reaction products formed by radia-
12¦ tion coupling. After each example had run continuously for vari-
13¦ ous periods of time, the reactor tube 61 was inspected for build-
14¦ up of carbon black or other material. None was found.
15¦ EXAMPLE I -
161 THERMAL DISSOCIATION OF METHANE
l . . .. __ .
17¦ A series of tests was conducted to determine the effec-
18¦ tiveness of the fluid-wall reactor in thermally dissociating
19¦ natural gas at various feedrates and reaction temperatures.
20¦ In each of these tests, hydrogen was introduced into plenum 85
21¦ through inlet 83 and forced through porous reactor tube 61 into
22¦ the reactor chamber at a constant rate of 5 scfm. The current
231 through carbon electrodes lOOa-lOOf was adjusted to set the tem-
241 perature of the reactor tube from 2300 to 3400 F., as measured
251 with an optical pyrometer. Natural gas, consisting of greater
26¦ than 95% methane with the balance being ethane and propane, was ~-
271 introduced into the reactor through inlet 91 at various flow-rates
28 ranging from 1 to 5 scfm. A small amount of carbon black was
29 introduced into the reactor at the same time through inlet 121
30 to serve as an absorbent target for the purpose of initiating the
;
.11 , I
1(~77684
1 pyrolytic dissociation. Once the dissociation had begun, it was
2 not necessary to add additional carbon black to s~stain the reac-
3 ¦ tion. A dense black smoke streamed from the outlet end of the
41 reactor tube and was found to consist of carbon black and hydrogen.
51 The carbon black particles were extremely fine and difficult to
61 filter. By spraying water into the effluent stream just below
71 the outlet end of the reactor tube 61, it was possible to agglome-
¦ rate the carbon black particles and collect them on a cloth dust
9¦ filter. Table I sets forth the percent dissociation at various
lO¦ flow-rates ranging from 1 to 5 scfm and at dissociation tempera-
11¦ tures ranging from 2300 to 3400F., the fraction of methane
12¦ dissociated being determined by measuring the thermal conductivity
~3 ¦ of the effluent gas after filtering the carbon black particles
14¦ from the sample.
15¦ TABLE I
161 PERCENT DISSOCIATION AT VARIOUS FLOW-RATES AND TEMPERATURES
171 ...._ ... _ . ,, ,.,_
l Dissociation Flow-Rate
18l Tem~erature(F.) (scfm)
. .~_ _
191 1 2 3 4 5
201 2300 86 74 66 60 54
~ 2500 89 79 72 68 63
211 2700 91.5 83 78 74.5 70.5
l 2900 94 88 84.5 82.0 79
221 3000 95.5 91 88.5 86 83.5
l 3100 97 94 92.5 91.0 89.5
231 3200 98.5 98.5 98.5 98.5 98.5
l 3300 100 100 100 100 100
241 3400 100 100 100 100 100
251 EXAMPLE II
26l THERMAL DISSOCIATION OF LIQUID HYDROCARBONS
I _ . , , . , _ .
271 A series of tests were performed to determine the
28¦ effectiveness of the fluid-wall reactor in thermally dissociating
291 liquid hydrocarbons. Hydrogen was used as the blanket gas at a
30~ constant flow rate of 5 scfm. The liquid hydrocarbons selected
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Il 1077684
1 ¦for the test series were typical distillates obtained from crude
21 etroleum and included naphtha (b.p. 100 to 200 F.); kerosene-
31 iesel (b.p. 220 to 350 F.); gas oil (b.p. 350 to 600 F.);
41 and residual oil and asphalt (b.p. > 600 F.~ The results of
¦ these tests were as follows:
6¦ A. NAPHTHA. A stream of naphtha at approximately 80F.
71 as fed into reactor tube 61 at a rate of 0.05 gallon per minute
8¦ through inlet 121. The temperature of the reactor tube was held
I at 3400F. The pure naphtha passed through the reactor unaffected,
lO¦ apparently being transparent to the thermal radiation emanating
11¦ from the incandescent reactor tube. The naphtha was then made
12¦ opaque by mixing it with 0.1% by weight of finely divided carbon
13¦ black. When this opaque mixture was introduced into the reactor
14¦ as before, there was an excellent coupling with the thermal --~
15¦ radiation. Carbon black and hydrogen streamed from the outlet of
16¦ the reactor tube. An analysis of the product gas with a thermal
17¦ conductivity cell showed it to be greater than 98 mole % hydrogen,
)8 indicating that the dissociation was nearly complete.
191 B. KEROSENE-DIESEL. Kerosene-diesel was mixed with
20¦ 0.1% by weight carbon black and then fed into the fluid-wall
21¦ reactor at a rate of 0.05 gallon per minute. The reactor tube was
22¦ held at 3400F. The kerosene-diesel dissociated into carbon black
231 and hydrogen. Thermal conductivity measurements indicated that
241 the effluent gas consisted of greater than 98 mole % hydrogen.
251 C. GAS OIL. Gas oil mixed with carbon black was
26¦ introduced into the fluid-wall reactor at a flow rate of 0.05
27¦ gallon per minute. When the reactor tube was held at 3400F., the
28¦ gas oil dissociated into carbon black and hydrogen, which, when
291 separated from the carbon black, was found to consist of 98 mole
301 pure hydrogen, based on thermal conductivity measurements. When
~C177684
1 ¦the temperature of the reactor tube was decreased to 2800~., the
2 ¦effluent from the reactor changed from a dense black smoke to a
3 ¦light gray fog, indicating that at the lower reaction temperature
4 ¦the gas oil was only partially dissociated, probably into lighter
5 ¦hydrocarbon fractions and a small amount of carbon.
6 ¦ D. RESIDUAL OIL AND ASPHALT. Residual oil containing
7 ¦asphalt, introduced into the fluid-wall reactor at 0.05 gallon
81 per minute, completely dissociated into carbon black and hydrogen
9¦ when the reactor tube was held at 3400F. Thermal conductivity
lO¦ analysis of the gaseous component of the effluent stream showed
11¦ that it was greater than 98 mole % hydrogen.
12¦ EXAMPLE III .
13¦ THERMAL DISSOCIATION OF COAL
14¦ A sample of Utah soft coal was analy~ed and found to
15¦ contain 0.58% by weight of sulfur and 8.55% by weight of ash. ~ -
16¦ The coal was pulverized to -50 mesh and fed into the reactor at ~ -
17¦ approximately 35 pounds per hour. Reactor tube 61 was held at
18 3000F. and was protected by a blanket of nitrogen, which was
19¦ forced through the porous wall at a rate of 5 scfm. The coal
20¦ dissociated into carbon black, gaseous products, and a light coke.
21¦ The carbon black differed from that produced in Example
2Z¦ I in that the particles were sufficiently large to filter without
23 the addition of water. The carbon black was found to contain 8,63
24 weight % ash and 0.54 weight % sulfur. The gaseous product was a
25 mixture of hydrogen and nitrogen (the latter from the blanket gas)
26 containing only 0.02 mole % sulfur, which was present as hydrogen
27 sulfide.
28 Approximately 62~ by weight of the starting material was
29 converted into coke. This coke was extremely light and open; its
30 densîty was only 35% of the density of the coal from which such
'' 10776t~4
1 coke was ~ade. When freshly prepared, the coke spontaneously
2 oxidized in air to an ash in less than 12 hours, indicating that
3 it had high surface activity. When the coke was allowed to remain
4 at room temperature in a nitrogen atmosphere overnight, it did
5 not show evidence of surface activity and did not spontaneously
6 oxidize when subsequently exposed to air. Microscopic examination
7 of the coke showed that it consisted of small, hollow, spherical
8 globules of a glass-like substance. Chemical analysis showed that
9 the coke contained 8.27 weight % ash~and 0.70 weight % sulfur.
EXAMPLE IV
.
11STEAM REFORMING AND GASIFICATION OF COAL
.
i2A sample of coal from Carbon County, Utah, which con-
~3 tained an ash with a high limestone content, was analyzed and founc
14 to contain 0.60% by weight of sulfur. The coal was pulverized
15 to -50 mesh and fed into the reactor at approximately 10.45 pounds
16 per hour. Steam at a temperature of 250F. was simultaneously
17 introduced into the reactor at a rate of 20 pounds per hour.
18 Reactor tube 61 was held at 3400F. and was protected by a blanket
19 of hydrogen which was forced through the porous wall at a rate
20 of 5 scfm. A dense white vapor was observed to emanate from the
21 outlet of the reactor. There was no evidence of any carbon
22 black or heavy residue having been produced. No ash or other
23 solid material was found in the hopper located directly beneath
the reactor tube outlet, indicating that all of the solid residue
25 in the coal was entrained in the gaseous product.
26 The solid products were filtered from the effluent
27 stream and the remaining gas was dried prior to analysis with
28 a mass spectrometer. The results of the analysis, neglecting
29 air, are as follows (concentrations being given in mole percent):
30 nitrogen (0.051%); carbon monoxide (7.563%); hydrogen sulfide
10~7684
(none observed); car~on disulfide (none observed) carbon dioxide
(0.277%); hydrogen (89.320%); methane (1.537%); other hydro-
carbons, such as benzene, acetylene, etc. (1.25396).
The gaseous product from this reaction is suitable as
a fuel. Moreover, no sulfur-containing components were observed
in the analysis, although the mass spectrometer was capable of
detecting sulfur cc~npounds in concentrations as low as 10 ppm.
This indicated that essentially all of the sulfur initially
present in the coal had been entrained in the solid particles
10 which were filtered from the ef1uent stream.
EXAMPLE V
STE~M REFORMING AND GASIFICATION OF OIL SH~LE
A sample of Green River oil shale, obtained from a source
near Rifle, Colorado, was pulverized to a -100 mesh size. The
sample was analyzed for the various carbonaceous materials present
in oil shale. Methylene chloride at room temperature extracted
0.93 weight ~ of the shale. The sample was further analyzed by
heating a portion of it in air and observing the weight loss as
a function of temperature. The results of such further analysis
were as follows:
TEMPERATURE ~NGE WEIGHT LOSS ~ REMARKS
.... _
68- 932F. 11.60 distillation of volatiles
932-1436F. 2.50 oxidation of carbon
1436-2192F. 12.00 decarboxylation of CaCO3
From these measurements it was estimated that the oil shale was
composed of 15 weight % of organic material and 27.3 weight ~ of
limestone as CaCO3. The remaining 57.7% by weight was assumed to
be siliceous material.
The pulverized sample was introduced into the reactor
at a rate of 38 pounds per hour. Simultaneously, steam was fed
30 into the reactor at approximately 20 pounds per hour. The steam
--62--
- : . ..
10776~4
was at a temperature of 250F~ at the inlet to the reactor. The
tube was maintained at a temperature of 3100F.~ and hydrogen,
injected through the porous wall at a rate of 5 scfm, served
as the blanket gas. A water-white vapor streamed from the
outlet end of the tube. The temperature of this vapor stream
was measured to be 970F. just below the outlet of the reactor.
A solid ash material was also produced and dropped in
the hopper beneaththe reactor tube. The ash consisted predomi-
nately of fused glass heads of various colors. This material
was analyzed for residual carbonaceous material hv ~ulverizing
it and carrying Ollt the same heating verses weight loss analysis
performed on the original oil shale. No weight loss was observed
upon heating from 932 to 1436F., indicating that none of the
organic material present in the original shale was left in the
ash material. A 14% weight loss was observed upon heating the
solid ash from 1436F. to 2192F., which indicated that most of
the calcium carbonate present in the original sample remained in
the ash and that some of this calcium carbonate had undergone
decarboxylation during the reaction. Treating the ash with 0.1
N HCl resulted in the evolution of hydrogen sulfide and carbon
dioxide, which indicated that whatever sulfur had been present
in the original sample was at least in part found also in the ash.
The gaseous component of the effluent from the reactor
was dried and then analyzed with a mass spectrometer. The results,
reported in mole percent, were as follows: hydrogen ~87.86%);
methane (0.74%); acetylene (0 07%); ethylene (0.39~); nitrogen
(1.24%); carbon monoxide (8.70%); mixed hydrocarbons (0.04~);
carbon dio~ide (0.016%); ben~ene (0.016~); toluene (0.002%); and
hydrogen sulfide (C0.~005~), This gas is suitable for use as
a low-sulfur fuel.
-63-
.
Il 1077~;84 ~
l! EXAMPLE Vl
2 I STEAM REFORMING AND GASIFICATION OF SEWAGE SLU~GE
I ~
3 ¦ A sample of activated sewage sludge, consisting of
¦dried human waste admixed with siliceous clay binder and prilled
5 Ito a particle size of approximately 2mm, was analyzed and found
61 to have the following composition (concentrations being expressed
71 in weight percent): organic carbon (33.21%); organic hydrogen
81 (4.38%); organic nitrogen (6.04%); organic sulfur (0.23%); water
9¦ 6.14%); and inorganic residue (50%).
10¦ The sludge was introduced into the reactor at a rate
11¦ of 54 pounds per hour. A total of 25 pounds was added. Steam
12¦ at 250F. was simultaneously fed into the reactor at 55 pounds per
13¦ hour, which was about twice the stoichiometric rate for the -
14¦ water-gas reaction. Hydrogen was injected through the porous
15¦ wall at a rate of 5 scfm. The temperature of the reactor was
16¦ maintained at 3750F
17¦ The products of the reaction were a dense, white fog
~81 and a solid residue. The residue, which collected in a trap
191 below the reactor tube, weighed 15 pounds and corresponded to 60%
20¦ by weisht of the activated sludge. The residue had the following
21¦ composition (concentrations being expressed in weight percent):
22¦ organic carbon (12.88%); organic hydrogen (1.69~); organic
231 nitrogen (2.34%); organic sulfur (0.37%); water (trace); and
241 inorganic residue (83%).
251 A portion of the vapor effluent from the reactor was
26~ condensed in a liquid nitrogen trap. The sample collected in the ~¦~
27 trap was brought to room temperature and found to have liquid and
28 gaseous components. The boiling point of the liquid was 212F.,
29 indicating that it was water. The gaseous component, which was
30 suitable for use as a low-sulfur fuel, was analyzed with a mass
.
.
Il ` 1077684
l .
1 ¦spectrometer and gas chromato~raph and found to have the following
2 ¦composition (concentrations being expressed as mole percent):
3 ¦hydrogen (60.933%); ammonia (0~0005%); methane (1.320%); water
4 1(o.083%); acetylene (0.463%); ethylene (0.304%); ethane (0.102%);
51 hydrogen cyanide (0.281%); nitrogen (0.990~); carbon monoxide
6¦ (34.122~); oxygen (0.0005%); argon (0.0078%); butene (0.175%);
71 butane (0,026%); carbon dioxide (0.996~); benzene (0.100~);
81 toluene (0.019%); hydrogen sulfide (0.0005%); and dicyanogen
91 (0.008%).
10 ¦ EXAMPLE VII
11 ¦ PARTIAL PYROLYSIS OF GAS OIL
12¦ To demonstrate the use of the fluid-wall reactor in the
13¦ partial pyrolysis of petroleum distillates, a light lube stock or -
14¦ "gas oil" was partially pyrolyzed. This particular petroleum dis-
15¦ tillate was characterized by the following distillation analysis:
16¦ TEMPERATU~E (F. ? % DISTILLED ~-
171 174 0
I 392 10
18l 428 20
446 30
19l 482 40
518 50
20l 532 60
l 532 70
21l 536 80
221 536 90
231 The gas oil was introduced into the reactor tube in the form of
241 a fog by atomizing it through a fogging nozzle. Hydrogen was
251 employed as the atomizing gas as well as to form the fluid-wall. Ir
26¦ addition, hydrogen was introduced into the inlet end of the reactor
271 tube through a sweep gas inlet to sweep the gas oil fog through th~ -
28¦ tube.
291 The reactor tube was initially heated to 3400F., with
~o¦abou~ ~ cfm of bydrogel~ being introduced i~to th- l~lenulr t-
``" ` 1~776~4
form the fluid-wall and about 5 scfm of hydrogen being introduced
into the sweep gas inlet. The gas oil was then introduced into
the reactor tube at about 0.25 gallon per minute, using about 5
scfm hydrogen for the atomizing gas. The temperature of the
effluent stream just below the outlet of the reactor was set to
about 820F. by lowering the temperature of the reactor tube to
2600F. Before samples were taken, the reactor was given time to
stabilize at these operating conditions.
Samples of the effluent stream were collected by three
methods, namely (1) by passing a portion of the effluent stream
through a liquid nitrogen trap and collecting a sample by freezing
it; ~2) by collecting gaseous samples from the stream at a position
downstream from the liquid nitrogen trap; and (3) by passing a
portion of the stream through a water-cooled condenser and col-
lecting a liquid fraction. The material collected in the liquid
nitrogen trap was allowed to warm to about 50F. and samples of
the liquid and vapor phases of this material at this temperature
were then collected.
The liquid collected below water-cooled condenser was
20 characterized by the following distillation analysis:
TEMPERATURE (F.) ~ DISTILLED
257 0
491 10
5430 19
590O 29
617 38
619 48
648 58
666 67
691 77
702 87
734O 95
The liquid-phase sample collected from the liquid nitrogen trap was
dried to remove water and was tnen analyzed and found to contain
xylene, styrene, toluene, benzene, pentane, pentadiene, cyclopenta- ~
diene, butene, butadiene, propylene, methyl acetylene, methyl -
.
Il 1077684
1 ~naphthalene, napthalene, and higher molecular weight hydrocarbons.
2 ¦The gaseous component of the material collected in the liquid
3 ¦nitrogen trap was dried and analyzed with a mass spectrometer and
4 ¦gas chromatograph. After correcting for the presence of air, two
5 ¦samples of this gaseous component were found to have the following
6 ¦average composition (concentrations being expressed as mole per-
7 ¦cent): hydrogen t88.23%); methane (4.62%); ethylene (3.09%); pro-
8 ¦pylene (1.22~); acetylene (0.55%) ethane (0.41~); butene (0.36%);
9 ¦benzene (0.35%); butadiene (0O31~); carbon dioxide (0.14%); penta-
lO¦ diene (0.13%); pentene (0.13%); propane (0.12~); carbon monoxide
11¦ (0.12%); cyclopentadiene (0.10%); methyl pentadiene (0.06%);
12¦ cyclohexane (0.03%); butane (0.03%); methyl acetylene (0.02%); and
13¦ toluene (0.02~). -~
14¦ EXAMPLE VIII
161PARTIAL STEAM REFORMING OF GAS OIL
. ... .._ ... . _
16¦ Gas oil identical to that used in Example VII was
17¦ partially reformed with steam in the fluid-wall reactor in two
18¦ substantially identical runs. In each of these runs, the gas oil
I was introduced into the reactor in the form of a fog by atomizing
20¦ it through a fogging nozzle. Hydrogen was used for the fluid
21¦ blanket, sweep gas, and atomizing gas at a rate of about 5 scfm
22¦ for each purpose.
231 In both runs, the reactor tube was initially heated to
241 3300F., with hydrogen being introduced into the sweep gas inlet ar Id
251 the plenum at approximately the rates to be used in the run. The
26¦ gas oil was then introduced into the reactor at approximately 0.25
271 gallon per minute together with steam at about 4 pounds per minute
28¦ which corresponded to a carbon-to-steam molar ratio of about
291 1.0:1.6. Under the thermal load of the gas oil and steam, the
301 temperature of the reactor fell to 2900~F. The temperature of the
1077684
effluent stream just below the outlet was about 850F. Samples
2 were collected and treated in the same manner as in Example VII.
3 The liguid collected below the water-cooled condenser in
4 the first run was characterized by the following distillation
5 analysis:
6 TEMPERATURE (F.) % DISTILLED
7 482 0 .
8 581 10
9 66355O 430
651 60 ~ :
11 684 80 `:
12 716 9O
13 In the second run, a sample of the li~uid component collected from ; ::
14 the liquid nitrogen trap was warmed to 50F., then dried to remove
ater, and then analyzed qualitatively. The resultant sample was ~:
16¦ ound to contain toluene, benzene, pentene, pentadiene, cyclopenta-
17 iene, butene, butadiene, naphthalene, xylene, styrene, and higher
18 olecular weight hydrocarbons. That portion of the original sample19¦ rom the liquid nitrogen trap which was volatile at 50F. was dried
nd analyzed with a gas chromatograph and mass spectrometer and was :~
21¦ ound to have the following composition after correcting for the
22 resence of air (concentrations being expressed in mole percent): :
23 thylene (36.85%); propylene (23.22%); acetylene (8.56~); ethane
24 (7.99~); hydrogen (4.41%); butene (4.41~); butadiene (3.50%);
25 ropane (2.47%); methane (2.10%); methyl acetylene (1.98%); benzene : .
26¦ 1.56%); pentadiene (0.62%); pentene (0.62%); cyclopentadiene
27 0.49%); carbon dioxide (0,37~); butane (0.25%); methyl pentadiene
28 0.25%); cyclohexane (0.13%); and toluene (0.04%). -
320
-6~-
. . .
'1077~8~
EXAMPLE IX
THERMAL DISSOCIATION OF SAWDUST
Sawdust, a typical lignin-containing by-product, was
thermally dissociated in the reactor tube 61 at a temperature of
3400F. while hydrogen was forced through the porous wall of the
tube at a rate of 5 scfm. The sawdust was fed into the reactor
at a rate of about 50 pounds per hour. The pyrolysis products -
consisted of finely divided carbon black sLmilar to that produced
by the dissociation of methane, gaseous products from the disso-
ciation of volatile compounds, and an open-weave char in which the
fibrous structure of the original wood was essentially intact.
EXAMPLE X
SILICON CARBIDE ABRASIVES FROM SILICA
Silica sand, having a particle size distribution in the
range from -50 to +100 mesh, was introduced into the reactor tube
61 through inlet 121 at a rate of 10 pounds per hour. Methane
was simultaneously added t~ the reactor tube through inlet 91
at a rate of 1 scfm. The temperature of the reactor tube was held
at 3400F. Nitrogen was injected into the reactor tube through
the porous wall at a rate of 5 scfm to form the fluid-wall. A
powdered material dropped from the reactor tube and was collected
in a hopper below.
The powdered product was sufficiently abrasive to
scratch glass easily, indicating that it contained silicon car-
bide. Microscopic examination of the powder showed that it con-
sisted of spheres of silicon dioxide covered with a shell composed
of amorphous carbon and thin platelets of crvstalline silicon
carbide.
EXAMPLE XI
PRODUCTION OF ALUMINUM CARBIDE
A stoichiometric mixture of aluminum powder and elemental
-69-
' . . . - .. '
1(:~776~4
1 ¦carbon was prepared for the anticipated reaction:
2 ¦ 4Al + 3C ~ A14C3 (1)
3 ¦This mixture was introduced into the reactor at a rate of approxi-
4 ¦mately 10 pounds per hour. Reactor tube 61 was maintained at
5 ¦3400F., and hydrogen was forced through the porous wall of the
6 ¦reactor tube at a rate of 5 scfm. The reaction yielded an amorph-
7 ¦ous, gray-brown material, which was collected in a trap below the
8 ¦reactor tube. A sample of the gray-brown product was mixed with
9 ¦0.1 N HCl. A gas evolved which burned with the characteristic
lO ¦yellow flame of methane, which indicated that the following reac-
11 ¦tion had occured between the product and the hydrochloric acid:
12 ¦ A14C3(s) + 12 HCl(aq) ~ 3CH4(g) + 4 AlC13(aq) (2)
13¦ The sample dissolved completely in the hydrochloric acid, yielding
14 la clear solution. Since the elemental carbon used as a starting
lS¦ material is insoluble in 0.1 N HCl, this indicated that the
16¦ aluminum and carbon reacted quantitatively in the fluid-wall reac-
17¦ tor to form aluminum carbide. -
18 ¦ To test the feasibility of producing aluminum carbide
19¦ in the fluid-wall reactor from aluminum chloride and carbon,
201 anhydrous AlC13 was placed in a carbon crucible and heated
21¦ until it sublimed. The aluminum chloride vapor was mixed into
22¦ a stream of hydrogen and the resultant stream was then passed
231 over a bed of carbon black. An arc-image lamp was focused on
2~1 the surface of the carbon bed and heated an area of the bed to
251 1830F., as measured by an optical pyrometer. Small orange
261 crystals formed just downstream from the heated zone, indicating
271 that the aluminum chloride had reacted with carbon and hydrogen
28¦ to produce aluminum carbide and hydrogen chloride in accordance
291 with the following reaction:
30~ 4AlC13 + 3C + 6H2 ~ Al4c3 + 12HCl ~3)
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.
, I ..
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1 hen the orange crystals were added to O.1 N HCl, the crystals
2 issolved and a gas was evolved which burned with the character-
3 istic yellow flame of methane.
4 Since this procedure simulated what could accomplished
5 in the fluid-wall reactor by reacting aluminum chloride with
6 arbon and hydrogen (produced by thermal dissociation of a gas
7 r liquid hydrocarbon), this suggests a new approach to manu-
8 acturing methane by (1) reacting aluminum chloride with an in-
9 xpensive hydrocarbonaceous material to form aluminum carbide
nd hydrogen chloride, and (2) quenching the reaction product
11 n water such that the resultant aqueous hydrochloric acid
12 ydroyzes the aluminum carbide to produce methane and aluminum
13 hloride which, in turn, can be recycled through the process.
14 ¦ EXAMPLE XII
. _ .
15 I REDUCTION OF FERRIC OXIDE WITH HYDROGEN
i --~
16¦ To demonstrate the utility of the fluid-wall reactor for
17¦ educing metal ores, pure ferric oxide (-100 mesh) was fed into the
18¦ eactor at a rate of 35.1 pounds per hour at the same time as
~9l ydrogen was forced through the porous wall at a rate of 5 scfm.
20¦ he hydrogen thus served both to form the fluid-wall and as the
21¦ educing agent for the iron oxide. The reactor tube was maintained
22¦ t a temperature of 3400F., as measured by focusing an optical
231 yrometer on the incadescent inner wall of the tube. The tempera-
241 ure of the reactants in the reactor tube was determined to be
251 750F., as measured with the optical pyrometer. A gray powder
26 as produced which collected in the hopper beneath the reactor
271 ube. The temperature of the effluent stream just below the outlet
28¦ f the reactor was measured at 600F.
291 The product was pure iron powder, which tended to be
~0 ~yrophori at temperat~res oE about 300~. when freshly prepare~.
I
~
I .~ .,
- ,. .
- , . . .
11 ) ) I
1~77f~4
1~ i wing the po~lder with a microsc~pe showed that it consisted
2 of small, spherical particles, which indicated that the iron had
3 been in a molten state during its passage through the reactor tube.
4 EXAMPLE XIII
_
THERMAL DISSOCIATION OF HYDROGEN SULFIDE AND METHANE
.~ .
6 Using the fluid-wall reactor, hydrogen sulfide was reac-
7 ted with the in situ carbon formed by the thermal dissociation of
8 ethane, thereby forming carbon disulfide and hydrogen. Runs were
9 erformed at two different temperatures, namely at 2975F. and
lO at 3200F. In both instances, temperatures were measured by
11 focusing an optical pyrometer on the incandescent reactants
12 in the reactor tube, the carbon particles from the dissociating
13 ethane being the primary incandescent constituents of the
14 reaction mixture. Hydrogen was forced through the porous wall
15¦ f the reactor tube at a rate of 5 scfm to serve as the blanket
16 as. Hydrogen sulfide at a rate of 0.32 scfm and methane at
17 a rate of 1 scfm were mixed together and introduced into the
18 reactor tube. The gas mixture was at room temperature at the
19 inlet to the reactor tube. A target of carbon black was added
201 o initiate the reaction, although once the reaction was initiated
21 it was self-sustaining and no further carbon black was needed.
22 Samples of the gaseous component of the products for
23 he two runs were analyzed with a mass spectrometer. The results
24 f the analysis are given in the following table, the concentra-
ions being reported in mole percent:
2~ COMPO~ND REACTION TEMPERAT~RE
27 2975F. 3200F. ~-
28 Hydrogen 83.974 88.560
Methane 11.379 6.230
29 Acetylene 1.681 2.281
Ethylene 1.397 1.519
Hydrogen sulfide 1.021 0.813
31 Carbon dioxide 0.296 0.160
32 Carbon disulfide 0.216 0.403
33 Benzene 0.036 0.034
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Il )
I 1077t;84
1 ¦ Although each of the foregoing examples was conducted
2 ¦in the fluid-wall reactor shown in FIGS 2A-2B, even better
3 ¦results can be achieved by using the fluid-wall reactor of
4 ¦FIGS 7A-7D, with suitable modifications (where necessary) to
5 ¦handle solid feedstocks. The use of process variable control
6 ¦systems should permit the optimum operating conditions to be
7 ¦located and maintained accurately. If such control systems
81 incorporate a digital computer, the search for the optimum
~ perating onditions can be carried out automati~ally.
.
18
221 .
231 ~:
~
261 ''': '
27
281 :-
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