Note: Descriptions are shown in the official language in which they were submitted.
48
PROCESS FOR THE CONVERSION OF CARBONACEOUS MATERIALS
The present invention relates to conversion of carbonaceous
materials in a molten mass reaction medium. More particularly,
the invention relates to a process and apparatus for conversion
of carbonaceous materials in a molten mass medium wherein at least
a portion of the reactants is in the gaseous phase to facilitate
intimate and uniform contact between the reactants and the molten
mass medium, short reaction times and independent control of the
ratio of molten mass flow rates to feed flow rates through the
reaction zone. The invention may be used to simultaneously
conduct more than one continuous chemical reaction in a common
molten mass medium with continuous transfer of molten mass medium
between several reaction zones in series or in parallel operation
without the aid of a mechanical pump, and the reaction zones may
be operated at differing pressures,
~4~4t3
Over the past many years, variGus investigators have recorded
the conversion of hydrocarbonaceous materials employing a molten
mass medium for such conversions. The predominant category of
molten mass used as the medium for conversion processes and/or
equipment has been various molten salts. For example, some of
the more recent U. S. Patents include No. 3,252,773; 3,252,774;
3,567,412; 3,619,144; 3,708,270; 3,170,737; 3,740,193; 3,758,673
3,916,617; 3,941,681; and 4,017,271. These enumerated patents
suggest the use of a molten alkali metal salt as the reaction
medium in the gasification of hydrocarbon feed materials. Similarly,
U. S. Patents No. 3,553,279; 3,081,256; 3,745,109; 3,582,188;
3,862,025; 3,871,992; and 3,876,527 disclose the use of a molten
alkali metal salt as a reactant medium in the cracking of hydro-
carbon feedstocks to produce ethylene. As a further example of
the prior art, molten salts have also been suggested for use in
the dehydrogenation of hydrocarbon feedstocks in U. SO Patents
No. 3,270,086; 3,309,419; 3,449,458; 3,586,733; 3,637,895; and
3,697,614. As an additional example, U. S. Patents No. 3,387,941
and 3,440,164 disclose the use of alkali metal salts as the reac-
tion medium in the desulfurization of hydrocarbon materials.
Heretofore, the reported use of a molten mass as a reactionor conversion medium has been limited to process and mechanical
designs which are restricted to relatively low capacity as opposed
to design systems which lend themself to commercial use. Moreover,
the necessity of maintaining feed rates at low levels in the prior
art molten mass methods becomes particularly disadvantageous in
those types of conversion reactions wherein yields are disadvantage-
~ 144~8
ously affected by long contact times between the molten mass andthe hydrocarbon reactants.
U. S. Patents No. 2,031,987; 3,852,188; 3,862,025; 3,871,992
and 3,876,527 also suggest that the hydrocarbon feed may be con-
currently contacted with the molten mass. However, in order toachieve sufficient separation between the molten mass and the
gaseous hydrocarbonaceous materials to permit product recovery,
the feed rates must again be restricted to undesirably low levels,
which limit processing capacities and adversely affect product
yields. It has also been suggested in U. S. Patent No. 2,055,313
that the hydrocarbon feed may be used to hydraulically transport
a molten mass reaction medium. However, in the method of this
reference, the actual conversion of hydrocarbonaceous feed occurs
by contacting the molten mass in a countercurrent flow therebe-
tween. Again, the capacity of the largest practical size equip-
ment built in accordance with this teaching would be limited to
the rate at which gaseous reactants could disengage from the molten
mass at the interfacial level.
The present invention has as its object the provision of a
process and apparatus for converting carbonaceous materials in a
molten mass reaction medium which overcome the deficiencies of the
prior art in that it has a high capacity, produces improved product
yields, and facilitates short contactitimes between the carbonaceous
reactants and the molten mass medium.
It is also the object of the present invention to provide a
process and apparatus wherein several different reactions may be
carried out in separate reaction zones at differing pressures
1~44g48
utilizing a common molten mass reaction medium which is circulated
without the aid of a pump.
The object of the invention also includes a process and
apparatus in which there is an intimate and uniform contact between
reactants and the molten mass, and wherein the ratio of reactants
to molten mass in each reaction zone may be independently controlled.
In accomplishing the foregoing and other objects, there has
been provided in accordance with the present invention, a process
for the conversion of carbonaceous feed materials into more valuable
products which accrues substantial savings in capital investment
costs and improved product yields as compared with the prior art
molten mass hydrocarbon conversion methods. This process comprises
contacting a carbonaceous feed material, with a molten mass medium
maintained at a temperature above the melting point of the molten
mass medium in a substantially vertical, elongated hydrocarbon
conversion zone(s), with a substantially upward co-current flow
of feed and molten mass medium, and with a velocity sufficient to
establish preferably at least a froth flow transport condition
hereinafter defined through the reaction zone; and then separating
the co-current flow of feed and molten mass medium into a stream
of more valuable products and a stream of a molten mass medium at
the upper portion of the reaction zone. A flow of lower turbulence
(or flow rate) may be designed and operated, but the economic
benefits would be greatly reduced. By employing a co-current froth
flow of reactants and molten mass, applicant has found that flow
rates as great as ten times those possible with the prior art
molten mass processes may be successfully utilized, As a result
4~
of the much higher feed rates possible with the process of the
instant invention, commercially significant quantities of hydro-
carbon feed material may be efficaciously prGcessed with a much
smaller equipment size requirement than that of the prior art
molten mass processes and equipment. Moreover, through the use
of a co-current froth flow contacting of the molten mass and
carbonaceous reactants, the present invention enables the contact
time between the molten mass and carbonaceous feed (or reactants)
to be adjusted to very low levels, on the order of 1 second or
less, accruing thereby a significant improvement in product yield.
In other words, by enabling the use of greater feed velocities, the
present invention enables the use of a time-temperature profile
which is more optimum for hydrocarbon conversion reactions.
Broadly, the process of the present invention may be utilized
in any molten mass medium hydrocarbon conversion reaction. The
molten mass medium and the hydrocarbon feed must be contacted with
a co-current flow in a vertically elongated reaction zone wherein
the gaseous feed and/or reactant and/or diluting gas form a hydrau-
lic flow pattern of sufficient turbulence to represent preferably
the froth or more turbulent type of hydraulic transport flow as
hereinafter defined. Any suitable transport velocity above this
typical value may be successfully, and in certain situations
preferably, utilized in the practice of the present invention. It
is advantageous to select a hydraulic flow pattern and a ratio of
molten mass to gaseous feed and/or gaseous reactants and/or gaseous
diluting materials for an economical balance between operating
costs and intimate contact. For example, the hydraulic transport
of molten mass and hydrocarbon feed and/or reactants through the
reaction zone may occur such that an annular mode of hydraulic
transport condition as hereinafter defined, or a mist hydraulic
transport condition, or any hydraulic transport condition inter-
mediate therebetween is produced in the reaction zone.
As used herein, the term "froth flow" transport conditionrefers to that hydraulic condition, or degree of turbulence, within
the mixed phase reaction zone or zones which is necessary to esta-
blish and maintain the circulation of molten mass reaction medium
by the phenomenon known in the art as air lift or gas lift. The
optimum design is achieved by a turbulence greater than the minimum.
The optimum degree of turbulence for each molten mass reaction
zone will need to be determined separately, but the applicant has
found the most logicai design in several molten medium systems
to be in the "froth flow" pattern such as is described and set
forth in Anderson, R.J., and Russell, T.W.F., "Chemical Engineering"
December 6, 1965. Certain flow conditions characterized by those
authors as "slug flow" may meet the definition of "froth flow"
according to the present invention because the requisite gas lift
effect is produced. It is intended that such conditions also fall
within the scope of the term "froth flow" as used in this applica-
tion and therefore within the scope of the present invention.
The process of the instant invention is particularly suit-
able for use in the cracking of a high sulfur content hydrocarbon
feed material into more valuable products, and is simultaneously
suitable for partial oxidation of the carbonaceous product from
the cracking reaction. The molten mass medium may be selected
9~8
so as to readily retain essentially all of the sulfurous compounds
which are liberated during the cracking and during the partial
oxidation reactions, and such a molten mass medium is readily re-
generated to remove the retained sulfur therefrom without the
necessity of prior costly desulfurization treatment of the feed.
Moreover, a further advantage of the instant invention is that
a single supply of molten mass medium may be employed to sustain
a plurality of chemical reactions by recycling the molten mass
medium therebetween. The hydrocarbon conversion reaction may
occur in conjunction with an exothermic reaction, such as, for
example, a partial oxidation reaction, whereby the heat released
in the exothermic (oxidation) reaction zone is utilized to furnish
the necessary heat of reaction for other reactions or conversions
which are endothermic. This transfer of heat from exothermic reac-
tion zones is facilitated by the circulation of molten mass betweenthe respective zones, thus allowing the molten mass to carry heat
in the form of sensible heat of the molten mass medium. The cir-
culation rate required to transfer the necessary heat is dependent
upon temperature differences between the respective reaction zones,
and the heat capacities of the molten mass utilized, Independent
of the heat transfer requirements being satisfied by the circulation
of molten mass between the respective exothermic and endothermic
reactions, recirculation of molten mass from a separation device
and back to the respective lower section of a vertically elongated
froth flow hydraulic transport reaction zone(s) enables the designer
to control the ratio of molten mass to feed and/or reactants andtor
diluting gas within each transport reaction zone.
4~8
BRIEF DESCRIPTION OF THE FIGURES OF DRAWINGS
Figure 1 is a schematic flow diagram of a closed-cycle
gasification process employing the inventive concepts of the
present invention;
Figure 2 is a schematic flow diagram of a continuous gasi-
fication process for a sulfur-containing carbonaceous feed
material according to the invention;
Figure 3 is a schematic flow diagram of a two reaction zone
system according to the invention utilizing a common moltem medium;
Figure 5 is a schematic flow diagram illustrating a three
reaction zone system according to the invention employing a common
molten medium.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Applicant has found that through the use of the co-current
froth flow hydraulic transport concept of the instant invention,
feed velocities as great as ten times those possible with the prior
art molten mass processes may be utilized through single train
equipment, a range of feed rates which enables molten mass techno-
logy to be commercially utilized for the first time in the conver-
sion of tonnage quantity carbonaceous feed materials.
Broadly, the process of the instant invention is highly
suitable for use in any type of hydrocarbon conversion reaction
well known to those skilled in the art, as well as in any other
type of chemical reaction capable of being conducted in a molten
reaction medium. By way of illustration, but not of limitation,
suitable reactions which may be conducted in accordance with the
instant invention include cracking, oxidation, partial oxidation,
gasification, methanization, polymerization, dealkylation, desul-
furization, reforming, isomerization, dehydrogenation, oxidative
dehydrogenation, the catalyzed versions thereof, combinations
thereof, or any of the processes described in U. S. Patents No.
3,252,773j 3,252,774; 3,449,458; 3,081,256; 3,708,270; 3,710,737;
3,745,109j 3,916,617; 4,017,271; 3,871,992; 3,862,025; 3,852,118.
2,031,987, 2,055,313; 3,387,941; 3,440,164; 3,270,086i 3,309,419-
3,587,733; 3,637,895; 3,697,614; 3,553,279; 3,567,412; 3,619,144;
3,740,193; 3,758,673; 3,941,681; 3,948,759; 2,053,211; 2,334,583
2,354,355; 2,100,823; 2,074,529;.3,449,458; and 2,682,459. The
only limit upon the particular type of reaction process and equip~
ment to which the principle of the instant invention can be applied
48
is that the particular reaction be capable of being carried out in
a molten reaction medium and must have a gas reactant or gas di-
luent in sufficient amount to create a froth flow as herein defined
in a vertically elongated reaction zone. A detailed listing of
other types of organic reactions which can be conducted in molten
medium is set forth in Advances ln Molten Salt Che!nistry, Vol. 3,
Plenum Press (New York 1975), Library of Congress Catalog No.
78-131884. Each of the aforementioned types of reactions is well
known to those skilled in the art, and the molten mass techniques
of the instant invention are highly suitable for use therein.
The molten medium may comprise any molten material suitable
for use as a reaction medium in reactions of the above-discussed
type. A requirement for successful practice of the instant inven-
tion is that the molten medium be sufficiently fluid to permit
hydraulic mixing followed by separation and be stable at the
reaction temperatures and pressures employed to allow the reaction
to proceed. Typically, the molten medium with which the hydro-
carbon feed is brought into contact will comprise a molten metal
selected from Groups I-VIII of the Periodic Chart of the Elements
or a molten metal salt which is molten within the temperature
range between about 50C and about 2500C, and which is of suffi-
ciently low volatility that loss of the molten medium with product
gas is minimized. Preferred materials for use as the molten
medium comprise alkali metal melts, mixtures of alkali metal melts
molten alkali metal salts, mixtures of molten alkali metal salts,
and mixtures of molten alkali metals and alkali metal salts. Suit-
able alkali m-!tal salts are the alkali metal carbonates, hydroxides,
~ 4~348
11
nitrat:es, sulfides, chlorides and oxides, of which the carbonates,
sulfides, chlorides, and hydroxides are preferred. Use of the car-
bonate is particularly advantageous when removal of sulfur from
the product is desired, as the carbonate has the ability to react
with sulfurous compounds which are liberated from the feedstock
at elevated temperatures during the overall reaction,
While it is possible to employ a single alkali metal salt
as the reaction medium, it is often preferred to employ a eutectic
or near eutectic mixture, e.g., binary, ternary, quaternary, etc.
Particularly preferred for use as the molten medium in the instant
invention are mixtures of alkali metal salts, such as alkali metal
carbonates, examples of which include sodium carbonate-potassium
carbonate-lithium carbonate; sodium carbonate-lithium carbonate;
potassium carbonate-lithium carbonate and sodium carbonate-potas-
sium carbonate, as well as any other salts thereof. Mixtures ofthe alkali metal salts comprise ideal candidates for use as the
molten medium in the instant invention since these materials tie
up sulfur very readily and can be easily regenerated, When the
process of the instant invention is being utilized for the gasifi-
cation of carbonaceous feed materials, a single alkali metal saltmay be utilized with advantage since the higher temperatures
employed therein allow the use of a molten medium with a higher
melting point.
Particularly preferred in this regard is sodium carbonate since
this material is readily available in the typical refining or petro-
chemical complex, and can be supplied from otherwise waste caustic.
The present invention also contemplates that the molten
144~
12
medium may also contain an additional catalytic material admixed
therewith in order to enhance and promote the carbonaceous materials
conversion reaction. When a promoter or catalyst material is
utilized, the molten medium will usually contain from about 0 to
50% by weight of the promoter or catalyst materials and preferably
will contain about 25% by weight of the promoter or catalyst
material or less.
The carbonaceous material utilized as the feed material
in the instant process may comprise any carbon-containing material
well known to those skilled in the art, Suitable carbonaceous
feed materials include vegetable and mineral oils, other naturally
occuring carbonaceous materials, asphalts, hydrocarbon residiums
produced by distillation or distillation and solvent extraction of
crude oil, fuel oils, cycle oil, gas oil, rubbers, heavy crude oils
pitch, coal tar, coal, natural tars, hydrocarbon-containing polymers,
tar sand oil, naphtha, shale oil, natural gas, refinery gas, light
hydrocarbons, e.g,, ethane, propane, and butane, kerosene, shredded
automobile tires, automobile crank case oil drainage, etc.~ and
mixtures or products thereof.
The carbonaceous feed material may comprise a high sulfur
content carbonaceous feed material. Examples of feed materials of
this type include the heavy hydrocarbon feed stocks, such as, crude
oils, heavy residiums, the asphalts, hydrocarbon residiums produced
by distillation or distillation and solvent extraction1~ crude bottoms,
pitch, other heavy hydrocarbon pitch-forming residua, coal, coal
tar or distillates, natural tars, cycle oil, slurry oil, tar sand,
and oil shale. Of particular interest are high sulfur content, low
948
13
ash materials such as asphalts, cycle oil, tar sand oil, shale oil,
slurry oil, and the hydrocarbon residiums and aromatic tars.
The carbonaceous feed and the molten medium are contacted
with a co-current flow through the reaction zone and with veloci-
S ties sufficient to establish preferably at least a "froth flow"
transport condition in the reaction zone, as defined above. The
exact feed rate necessary to establish this type of transport
phenomenon will vary, e.g., with the particular molten medium
utilized, the particular carbonaceous feed stock and the necessity
to maintain contact times within certain limits, and this feed
rate can be readily determined by those skilled in the art. The
particular transport velocity actually employed can vary over
wide ranges, provided that the transport conditions are sufficient
to establish at a minimum the gas lift effect transport condition
as above defined through the reaction zone, and in practice the
velocity will frequently be greater than the minimum level which
is necessary to produce this gas lift effect, For example in
those types of hydrocarbon conversion reactions such as cracking
and partial oxidation or gasification, wherein the hydrocarbon
conversion reaction is favored by minimal contact times, very high
transport velocities will generally be employed in order to reduce
the contact time to a minimum. In addition, the use of multi-phase
froth flow transport eliminates the necessity for pumps in order
to circulate the molten mass throughout the process equipment.
In the cracking of asphalt to product ethylene, for example~
using a molten medium comprising a mixture of potassium and lithium
carbonates containing approximately 1% by weight alkali metal
3Li~4~
14
sulfide under steady-state operating conditions, typical feed
rates will include a carbonaceous feed rate corresponding to a
reaction zone superficial velocity of about 10 to 100 ft/second,
and preferably about 20 to 35 ft/second; and a molten mass to
carbonaceous feed weight ratio of about 2 to 20, and preferably
about 4 to 8 depending on heats of reaction, heat capacity of
molten mass, and temperature differences between reaction zones.
With reaction zone conditions in this range, contact times of
from about 0.5 to 10 or more seconds are readily obtainable.
Similarly, in the gasification of carbonaceous materials
to produce low or medium BTU gas, using a sodium carbonate molten
medium containing from about 0 to 25 percent by weight alkaline
metal sulfide under steady state operating conditions, air and
steam are typically fed in a ratio to control the overall heat
generation such that said total heat is (1) removed in the form
of sensible heat of the exiting product gas, and (2) lost through
the walls of the container. Temperature is therefore controllable
by the adjustment of the ratio of air to steam. Typical air rate
is from 3 to 7 pounds of air per pound of carbonaceous feed and
typical feed rate of steam is from about 0 2 to 0.5 pounds of water
vapod per pound of carbonaceous feed, The transport reactor is
sized such that the gaseous and liquid mixture typically rises
upwardly at a velocity which corresponds to the superficial velo-
city of from about 25 to 100, preferably 10 to 80 and typically
10 to 40 feet per second.
While not essential to the reaction, an inert diluent can
be employed in order to regulate or control the partial pressure of
4~48
reactants in the molten medium reaction zone, and/or to assist in
the gas lift of the multi-phase hydrocarbon-molten medium mixture.
Diluents which may be employed include helium, carbon dioxide,
nitrogen, steam, methane, and the like. In those types of carbon-
aceous material conversion reactions in which the presence ofhydrogen is necessary or desirable, such as in reforming, hydro-
desulfurization, or hydrocracking, suitable quantities of hydrogen
gas may also be injected into the reaction zone. The inert
diluent would typically be employed in a mole ratio of from about
0.1 to 50 mols of diluent per mol of carbonaceous feed or reactant,
and more preferably from about 0,1 to 1.
The present invention is particularly suitable for use in
the cracking and partial oxidation or gasification of heavy carbon-
aceous feedstocks of high sulfur content, the conversion of which
has heretofore not been as economically beneficial by conventional
methods as is desired due to the product states achievable and/or
the excessive coking in the reaction zones, and the necessity for
extensive desulfurization treatments to reduce the high sulfur
content thereof. The present process and equipment are suited
for those high sulfur content hydrocarbon conversion reactions
which are favored by minimal contact times~ such as, for example~
the cracking of heavy carbonaceous feedstocks to ethylene and other
products. Accordingly, the instant process will be described with
reference to preferred embodiments involving the cracking and
partial oxidation or gasification of heavy hydrocarbon feedstocks
to produce ethylene and other products and a low or medium BTU gas,
respectively, although it is to be emphasized that the present
16
invention provides a broad reaction technique which is suitable
for use in any type of chemical conversion reaction capable of
being conducted in a molten reaction medium.
Generally, in the cracking of asphalts and other heavy
hydrocarbon feedstocks to produce ethylene, the hydrocarbon feed
will be contacted with a mixture of alkali metal carbonates or a
mixture of alkali metal carbonates and alkali metal sulfides at a
temperature of from about 600 to 850C, and a pressure of from
about 0.5 to 10 atmospheres, preferably approximately 1 atmosphere
absolute. The feed rates of the hydrocarbon feedstock and the
molten medium are adjusted such that a froth flow transport condi-
tion is established in the reaction zone~ with a contact time of
a maximum of about 25 seconds. Preferably, the feed rates will
be adjusted to provide a contact time of less than about 5 seconds
and most preferably, of about 1 second or less, since ethylene
production is favored by a minimum contact time-high temperature
reaction profile, Optionally, a suitable diluent gas, such as
steam or hydrogen, may be admixed with the multi-phase mixture of
molten salt and hydrocarbon feed, with a steam and/or hydrogen to
reactants mole ratio in the range of from about 0.1 to 1 0 and
preferably with a steam and/or hydrogen to reactants mole ratio
of about 0.3.
In the partial oxidation or gasification of heavy hydro-
carbonaceous feedstocks or the carbonaceous product of for example
cracking to produce a low or medium BTU gas comprising predomi-
nantly carbon monoxide and hydrogen, the hydrocarbon feed will
typically be contacted with an alkali metal carbonate molten medium,
4~8
17
or a mixture of alkali metal carbonates and sulfides, at a
temperature of from about 800 to 1200C, preferably at a temperature
of approximately 1000C, and with a pressure of from about 1 to
20 atmospheres absolute. A suitable molten medium may comprise
sodium carbonate or an admixture of sodium carbonate and sulfide
since at the temperatures employed, the sodium metal salt is
molten and very fluid. The use of sodium metal salt as the molten
medium is also desirable since this material is lower in cost than
most other media and also has a very high affinity for retaining
sulfur oxides. The gasification reaction proceeds almost
instantaneously, and the contact time will generally be less than
about 10 seconds, preferably less than about 5 seconds, and most
preferably less than about 2.0 seconds. The specific oxygen feed
rates will vary depending upon whether air, pure oxygen. or some
other oxygen-containing gas is utilized, The ratio is oxygen-
containing gas to carbonaceous feed material is controlled so that
the production of carbon monoxide and hydrogen from the feedstock
is preferred. In order to control the temperature by the amount
of water gas reaction, steam will usually be injected into the
reaction zone, the specific amount necessary increasing with
increasing temperature. Where the partial oxidation is operated
in conjunction with an endothermic reaction to supply the heat
therefor, it may be necessary to control the heat evoluation by
a means such as injecting steam to promote a water-gas reaction.
Where it is desirable to obtain complete oxidation of the feedstock,
the same reaction conditions will usually be employed, with the
exception that the amount of oxygen or oxygen-containing gas addition
- ~4~
18
will be increased sufficiently to provide complete oxidation
If the oxidization is employed in conjunction with a cracking
reaction to supply heat, and the carbonaceous material formed in
the cracking reaction is not sufficient to sustain the heat
requirement, additional feed (same as or different from that
supplied to cracking reaction zone) may be added directly into
the oxidation zone.
In a further embodiment of the instant invention, a
hydrocarbon conversion reaction in accordance with the present
invention is combined with a second reaction or reactions in order
to take advantage of the heat transfer capacity of the molten
reaction medium to sustain a plurality of different reactions.
For example, in the cracking of heavy carbonaceous feeds, it is
desirable to conduct the cracking reaction in conjunction with an
exothermic coke oxidation or partial oxidation reaction whereby
the coke contained in the molten medium as a result of the cracking
reaction may be utilized as an energy source to maintain the
temperature in the endothermic cracking reaction zone in a closed
cycle type operation. Additionally, a sulfur removal reaction
may be conducted in conjunction with the cracking reaction and/or
the carbon oxidation reaction to convert the sulfide contained
in the molten medium as a result of the cracking and/or oxidation
reaction into valuable hydrogen sulfide gas A significant advan-
tage of the use of molten mass technology in the conversion of
carbonaceous material is thus that it readily lends itself to use
in multiple reaction processing operations.
Referring now to the drawings, Figure 1 illustrates a
` 11~4~8
19
continuous gasification process according to the instant invent;on
in its simplest form. In this Figure, a single reaction zone is
employed, wherein the molten mass is circulated in a closed cycle
system. Carbonaceous feed is introduced through line 2 into the
lower section of a mixed phase gasification reaction zone 1. An
oxygen containing gas, and steam if desired, and optionally a di-
luting gas, enter the lower section of said zone through line 3.
Molten mass medium enters the lower section of said mixed phase
gasification zone 1 through line (or conduit) 4. The feed may be
admixed with oxygen containing gas and/or steam, if any and/or
diluting gas, if any, prior to entering the lower section of said
zone. Upon mixing of feed, steam, oxygen containing gas, and diluting
gas with hot molten medium in said lower section of said zone~ the
mixed phase mixture flows in a co-current~ turbulent flow pattern
to the upper section of said vertical, elongated gasification zone
1, and during this transport the chemical reactions proceed. From
the upper section of said gasification zone, the mixed phase
consisting of gaseous products and a liquid containing molten mass
and any unreacted liquid or solid reactants flow through conduit
5 to a separation device, herein shown as a cyclone 6. In the
cyclone 6, the gaseous products exit from the upper section of
said cycline through line 7 for use or separation elsewhere. The
liquid portion of the mixed phase fluid entering cyclone 6 is
directed to the lower section of said cyclone by the action of the
cyclone and exits said lower section through line 9. The accumu-
lation of liquid in the system causes an interfacial level 8,
which may be maintained in the lower section of cyclone 6 or in
line 9. As shown in Figure 1, line 9 becomes line 4 which directs
the return of molten medium back to the lower section of the said
gasification zone 1 to complete the closed cycle of molten medium
in this reaction system. The circulation rate of molten medium
and unreacted liquid or solid reactants may be adjusted in operation
by increasing or decreasing the inventory of molten medium so as
to raise or lower the interfacial level 8 within line 9 and/or
cyclone 6 (a higher level resulting in an increased flow rate for
the molten medium). With some types of feedstock there will be
an accumulation of heavy metals in the form of elemental metal, or
oxides, or compounds thereof, and/or ash which can be controlled
by continuously or intermittently withdrawing molten medium from
the system and replacing same by makeup.
Reference is now made to Figure 2, which is a schematic
flow diagram of a continuous gasification process for a sulfur-
containing carbonaceous feed materials. In this figure. molten
medium flows in a continuous cycle through the gasification zone
and associated cyclone and back to the gasification zone, although
separately, but simultaneously the fungible or common molten medium
also flows in a continuous cycle between the mixed phase carbona-
tion zone, the associated cyclone, and the heat exchanger. Also
simultaneously, but independently, the molten mass flows between
the two closed circuits in a separately controlled cycle. High
sulfur carbonaceous feed enters the mixed phase gasification
reaction zone 200 through line 201 in the lower section of said
zone. Oxygen-containing gas, steam, if any, and/or diluting gas~
if any, enter the lower section of said gasification zone 200
21
through line 202. In this lower zone of the gasification reactor,
molten medium enters through line 203 and mixes with said feed
of line 201 and said oxygen-containing gas and steam, if any, and/
or cliluting gas, if any, to form a multi-phase mixture in the lower
5 section of said gasification zone. The mixed-phase mixture rises
through the vertically elongated gasification zone to the upper
section of said zone wherein said mixture is transferred to cyclone
208 through line 207. Feed may be introduced into the mixed phase
gasification zone either separately in admixture with steam and/or
10 diluting gas, if any. While a cyclone is shown in this preferred
example, other separation type devices can also be utilized. In
cyclone 208 the gaseous reactants are separated from the liquid
consisting of molten medium and the non-gaseous portion of the
reactants. The gaseous reactants exit cyclone 208 through line 209
15 and are directed to downstream separation equipment (not shown) or
are used as such, The liquid separated in cyclone 208 settles to
the lower portion of the cyclone and is withdrawn through 211 -forming
an interfacial level 210 which may be maintained in line 211 or
the lower portion of cyclone 208. The liquid in line 211 is
20 separated into two portions, with one portion flowing by way of
line 204 back to line 203 to complete one of the continuous cycles
referred to above. Circulation within this closed loop system
of molten mass is dependent upon the location of the interfacial
level of liquid 210 and other physical factors of the reactants
25 and equipment. The second portion of liquid contained in line 211
flows through line 206 to combine with molten medium of line 223
to form a mixture contained in line 212, which then flows to exchanger
3l~L~ 3 4 8
22
213. In exchanger 213 the molten medium is cooled by a fluid such
as steam, which enters heat exchanger 213 through line 225 and
exits through line 224. The cooled molten medium from heat ex-
changer 213 flows through line 214 into the lower section of a
mixed phase carbonation zone 217. A C02 rich gas enters the lower
section of the carbonation zone 217 through line 215. Steam, and/
or a diluting gas, if any, enters the lower section of said car-
bonation zone to form a mixed phase mixture which flows upwardly
and co-currently through said carbonation zone to the upper portion
thereof. The carbonation zone is sized such that the multi-phase
mixture of gases and liquid will create a flow which is sufficiently
turbulent that the average density is sufficiently low to create
a gas lift effect within the vertically elongated carbonation
zone 217. The multi-phase mixture from the upper portion of car-
bonation zone 217 exits through line 218 and enters the associated
cyclone 219. Said multi-phase mixture is separated in cyclone
219 into a hydrogen sulfide-rich product gas and a liquid consisting
of desulfurized molten medium and liquid or solid reactants. The
hydrogen sulfide-rich gas product exits cyclone 219 through line
220 to an external recovery system, such as a Claus type sulfur
plant, not shown. The molten medium separated in cyclone 219
settles to the lower section of said cyclone and exits through
line 222 and is divided into two portions. The first portion of
the desulfurized medium in line 222 passes through line 223 and
combines with liquid molten medium of line 206 to form an admixture
molten medium in line 212, as previously mentioned, Molten medium
is thereby circulated in the continuous cycle through heat exchanger
213, carbonation zone 217, and cyclone 219 back to heat exchanger
213 to complete that cycle.
~1~4~
23
In addition to the two continuous cycle circulation systems
of molten medium referred to above, in Figure 2 molten medium from
line 222 flows by way of line 205 to combine with molten medium in
line 204 which forms the molten medium of line 203 referred to
above. Therefore, the molten medium flows back and forth between
the two reaction systems, whereby a portion of the molten medium
from the gasification system flows by way of line 206 to the car-
bonation reaction system, while an equal quantity of molten medium
flows in the opposite direction through line 205 to complete the
cycle.
In Figure 2, the pressure maintained in the carbonation
reaction zone 217 and associated cyclone 219 is a lower pressure
than the pressure maintained in the gasification zone 200 and
associated cyclone 208. This is achieved by locating the carbona-
tion zone 217 and its associated cyclone 219 such that the inter-
facial level 221 between hydrogensulfide gaseous product and
molten medium is at a greater elevation than the interfacial level
210 between the gaseous product of the gasification zone and
molten medium. The difference in pressure between these two
reaction zones is a function of the difference in interfacial level
elevation and other physical factors. In actual operation, the
absolute pressure difference may be varied somewhat by adjusting
the relative elevation between interfacial level 221 and inter-
facial level 210. Likewise, the molten medium circulation rate
within the gasification zone 200 and associated cyclone 208 may
be varied within design limits by raising or lowering the inter
facial level 210 (a higher level creating a greater circulation
4~8
24
and a lower level causing a lower circulation rate). Likewise,
the circulation rate of molten medium in the cycle between carbon-
ation zone 217, cyclone 219, and heat exchanger 213 is adjusted
within design limits by raising or lowering the interfacial level
221.
In order to control the flow of molten medium back and
forth between the two respective reaction zone closed systems
through line 206 and line 205, this line is sized so as to limit
the flow due to differential static pressure, or alternatively,
a restricting line or orifice or a valve may be incorporated therein.
Restrictions or control valves also may be desirable to control
flow of molten medium, such as restriction 226 shown in line 205
or restriction 227, shown in line 206. Other flow controlling or
restricting equipment will be helpful, particularly if a variety
of carbonaceous feeds are to be processed at frequent time intervals.
Referring now to Figure 3, there is described a two reaction
zone system utilizing the fungible or common molten medium for
different reactions in each of the two zones. A carbonaceous feed
material enters the lower section of mixed phase cracking reaction
zone 10 through line (or conduit) 11. Steam, if any, and/or dilu-
ting gas, if any, enters said lower section of the cracking zone
10 through line 12. Feed may be admixed with steam, if any, and/or
diluting gas, if any, prior to entering the lower section of said
cracking zone 10. Molten medium enters the lower section of said
cracking zone 10 through line 13, wherein it mixes with carbonaceous
feed and steam if any, and diluting gas, if any, to form a turbu-
lent mixed-phase mixture which flows co-currently upwardly through
~1~4~4~
the vertically elongated cracking reaction zone 10 to the upper
section of said zone. In the upper section of said cracking zone,
the mixed-phase consists of gaseous reactants and a liquid com-
posed of molten medium and/or liquid or solid reactants. Said
5 mixed-phase mixture is transferred from the upper section of said
vertically elongated cracking reaction zone 10, through line 14,
to a separation device herein identified as a cyclone 15. The
gaseous products of the cracking reaction exit from the upper
section of cyclone 15 through line 16 for separation and/or use
10 of external equipment, not shown. The liquid portion of material
entering cyclone 15 settles to the lower section of said cyclone
and exits through line 18 to form an interfacial level 17, which
may be maintained in line 18 or in the lower section of cyclone 15.
The liquid of line 18 consisting of molten medium and liquid or
15 solid reactants from the cracking reaction zone, flows into line
19 which enters the lower section of the mixed phase oxidation
zone 22, An oxygen-containing gas enters the lower section of
said mixed phase oxidation zone 22 through line 20. Steam, if any~
and/or diluting gas, if any, enter the lower section of said
20 mixed phase oxidation zone 22 through line 21. The oxygen-con-
taining gas may be admixPd with steam, if any, and/or diluting
gas, if any, prior to introduction to the lower section of said
oxidation zone 22. Additional carbonaceous feed material may
also be introduced into the lower section of said oxidation zone
25 22 to supplement any deficiency of liquid or solid reaction
products to sustain and heat balance the desired overall system
operation. The feed, steam9 if any, and diluting gas, if any,
4~8
26
mix with the liquid consisting of the molten medium and liquid or
solid carbonaceous reactants to form a multi-phase mixture which
passes in turbulent flow upwardly through the vertically elongated
oxidation reaction zone 22 to the upper portion of said zone.
From the upper section of said oxidation zone 22, the mixed-phase
mixture is transported by way of line 23 to a separation device,
herein ident;fied as cyclone 24, for the separation of vapor
phase from liquid phase. The vapor phase consisting of gaseous
products of the oxidation reaction exits cyclone 24 through line
25 for use or separation externally. The liquid separated in
cyclone 24, consisting of molten medium and any liquid or solid
reactants, collects in the lower section of said cyclone 24 and
exits through line 27 to form an interfacial level 26 The inter-
facial level 26 may be maintained in line 27 or in the lower section
of cyclone 24. Line 27 flows into line 13, through which molten
medium completes the cycle by returning to the lower section of
cracking zone 10. The pressure of the oxidation zone 22 and asso-
ciated cyclone 24 may be maintained at a pressure different from
the cracking zone 10 and its associated cyclone 15 by designing
the equipment so that interfacial level 26 is different from
interfacial level 17. By increasing or decreasing the inventory
of molten medium, this raising or lowering both interfacial levels
simultaneously, one may increase or decrease the circulation rate
of molten medium throughout the system (raising both interfacial
levels causing an increase in circulation rate - lowering both
interfacial levels creating decreased circulation rate of molten
medium).
4~4~
27
Reference is now made to Figure 4, which differs from
Figure 3 only in that line 28 and valve or restriction 29 have
been added. The addition of these two items is to facilitate
some independent control of the circulation rate of molten medium
through one or more reaction zones independent of the overall
circulation rate between respective reaction zones. In Figure 4,
the liquid from cyclone 24, consisting of molten medium and any
unreacted liquid or solid reactants, is separated into two
portions as follows: one portion flows through line 28 and re-
striction 29 to combine with the molten medium and liquid or solidreactants in line 18, after which the two streams admix in line
19, from said line 19 the admixture flows into the lower section
of the oxidation zone 22; the second portion flows to line 13, as
described in connection with Figure 3, The two independent molten
streams meeting and mixing in line 19 could alternately be intro-
duced into the lower section of said oxidation zone 22 independently.
Restriction 29 can consist of a line sized so as to not permit a
flow greater than that desired~ or it may be a fixed restriction
such as an orifice, or a control valve. The addition of line 28
and restriction 29 permits control of the circulation rate of
molten medium through oxidation zone 22 and its associated cyclone
24 somewhat independently of the circulation rate in the cracking
zone 10 and its associated cyclone 15.
Referring to Figure 5 there is disclosed a system having
three separate reaction zones for independently conducting three
separate chemical reactions simultaneously, utilizing a fungible
or common molten mass medium. This specific example differs from
~4~
28
that illustrated in Figure 3, in that a portion of the molten
medium is withdrawn after the oxidation reaction and is used as
the reaction medium for conducting the third chemical reaction,
and the molten medium, after being used as the medium in the
third chemical reaction, is returned to the oxidation zone from
which it came. Alternatively, the molten medium from the third
chemical reaction, e.g., carbonation, could be returned instead
to the cracking reaction zone. Referring to Figure 5, a carbona-
ceous feed material such as, but not limited to, asphalt enters the
lower section of the mixed phase cracking zone 100 through line
101. Steam, if any, and/or diluting gas, if any, enters the lower
section of said cracking reaction zone 100 through line 102.
Molten medium enters the lower section of the cracking reaction
zone 100 by way of line 103, and it mixes with feed and steam, if
any, and/or diluting gas if any, in the lower section of said
cracking zone 100. The mixed phase fluid rises through the
vertically elongated cracking zone 100 to the upper portion thereof.
From the upper section of cracking zone 100 the multi-phase mix-
ture of gas and liquid flows by way of line 104 to a separation
device identified as cyclone 105. In cyclone 105, the gaseous
products of the cracking reaction exit through line 106 to external
recovery and/or use equipment, not shown. The liquid of cyclone
105, consisting of molten medium and liquid or solid reactants~
is separated and settles to the lower section of cyclone 105 from
which it exits through line 108 to form an interfacial level 107,
which may be maintained in line 108 or in the lower section of
cyclone 105. The molten liquid of line 108 combines with molten
29
medium from line 131 (to be described later) to form an admixture
in line 109 which enters the lower section of the mixed phase
oxidation zone 112. An oxygen-containing stream is introduced
into the lower section of the oxidation reaction zone 112 through
line 110. Steam, if any, and/or diluting gas, if any, enters the
lower section of the oxidation reaction zone 112 through line 111.
The molten medium of line 109 combines and mixes with the oxygen
containing gas of line 110 and steam, if any, and/or diluting gas.
if any, entering through line 111 to form a multi-phase mixture
in the lower section of said oxidation zone 112. This multi-phase
mixture rises in turbulent co-current flow to the upper section
of said oxidation zone 112, From the upper section of said oxi-
dation zone 112, the multi-phase mixture flows by way of line 113
to an associated separation device identified as cyclone 114,
wherein the gaseous reaction products of the oxidation reaction
separate from liquid consisting of molten medium and liquid or
solid reactants. The gaseous reaction products of the oxidation
reaction exit cyclone 114 through line 115 for sçparation and/or
use externally. The liquid, consisting of molten medium and liquid
or solid reactants, settles to the lower section of cyclone 114
from which it exits said cyclone through line 117 to form an inter-
facial level 116, which may be maintained in line 117 or in the
lower section of cyclone 114. The liquid of line 117 is divided
into two portions, whereupon one portion flows by way of line 103
back to the lower section of the cracking zone 100. The second
portion of the liquid in line 117 flows by way of line 118 to a
heat exchanger 119, wherein the temperature of the molten medium
4~3
is reduced by heating a fluid, such as a circulated oil which flows
into heat exchanger 119 through line 120 and exits said heat ex-
changer by way of line 121. The thus-cooled molten medium of
line 118, after passing through heat exchanger 119. flows to the
lower section of the carbonation reaction zone 125 by way of line
124. A carbon dioxide-rich gas enters the carbonation reaction
zone 125 by way of line 123 Steam and diluting gas~ if any~ enter
the lower section of the mixed-phase carbonation zone 125 by way
of line 122. Alternatively, it is possible to introduce the carbon
dioxide-rich gas and/or steam and/or diluting gas into the molten
medium in line 118 before said molten medium enters heat exchanger
119. The molten medium mixes with carbon dioxide-rich gas and
steam and diluting gas, if any, in the lower section of the carbon-
ation zone 125 to form a multi-phase mixture which rises through
the vertically elongated carbonation reaction zone 125 to the upper
section of said zone. From the upper section of said carbonation
zone, the-multi-phase mixture of gaseous reactants and liquid flows
by way of line 126 to a separation device identified as cyclone
127. From cyclone 127, the gaseous products, consisting of a
hydrogen sulfide-rich gas, exit cyclone 127 through line 128 for
further processing such as in a Claus type plant (not shown) to
form elemental sulfur or to be used externally. The liquid
entering cyclone 127, consisting of molten medium and unreacted
liquid or solid reactantsl settles to the lower section of said
cyclone 127 and exits by way of line 130 to form an interfacial
level 129, which may be maintained in line 130 or in the lower
section of cyclone 127. The liquid in line 130, which in Figure
31
5 becomes line 131, returns to mix with the liquid of line 108
to flow through line 108 back to the lower section of the oxida-
tion zone 112 as previously mentioned.
While still referring to Figure 5 but as was shown in
Figure 4, the liquid line 130 could alternatively be divided into
two portions, with one portion flowing as shown through line 131
back to the oxidation zone, and the second portion flowing by the
way of a line (not shown) back to line 118 to recycle through the
carbonation zone 125 with an appropriate restriction or valve. if
desired, as described in connection with Figure 4.
In each of the embodiments illustrated in Figures 1-5, the
mixed phase reaction zones are designed so that the multi-phase
mixtures will create a co-current flow with such a velocity that
the average density within said zones will create a gas lift effect
and cause circulation of the molten medium. It will be appreciated,
however, that the second and/or third stage reaction zones need
not be designed and/or operated in this manner in order for each
of the illustrated embodiments, as a whole~ to fall within the
scope of the present invention,
Optionally, in each of the illustrated embodiments the
stream of molten mass medium exiting from the separation device
(cyclones) for recirculation may be subjected to a second or sub-
sequent separation treatment in order to further separate any gases
dissolved therein. Such a second separation step may take the
form of a second separation device, such as a cyclone, or alter-
natively, the molten mass medium may be contacted with a stripping
agent, such as a stripping gas. Such a stripping gas can also be
.
-
used concurrently with a second cyclone.Example 1
A high sulfur-content asphalt is cracked to produce ethylene
by the process described with reference to Figure 3. The molten
mass comprises a eutectic mixture of lithium, potassium, and sodium
carbonates, in which an alkali metal sulfide concentration of about
5% by weight is maintained. The asphalt feed is first preheated
to a temperature of about 250C, and is then contacted with the
molten mass in the lower portion of the reaction zone such that
the upward velocity is in the range of 10 to 100 ft/second pre-
ferably 20 to 40 ft/second, Steam and/or diluting gas may also
be introduced into the lower portion of the cracking zone, and
is taken into consideration in determining the upward velocity.
The circulation rate of the molten mass is maintained at between
1 and 15 pounds of mass per pound of total feed including steam
and diluting gas in addition to asphalt to establish, under steady-
state operating conditions, a froth flow transport condition in
the cracking reaction zone, and a total contact time between reac~
tants and molten salt of about 1 to 10, perferably about 2 seconds.
The processing capacity and ethylene yields of the instant process
are then compared with the conventional prior art molten mass
cracking process, such as that described in U.S. Patent No. 3,745,109.
All other reaction conditions are maintained at similar values in
each process, with the temperature being maintained at about 850C~
and the pressure being maintained at about 1.3 atmospheres absolute
in each cracking zone. In contradistinction to the instant inven-
tion, the prior art countercurrent flow cracking process possesses
9~ 8
33
feed rates approximately l/lO that utilized in the instant inven-
tion, and contact times approximately 3 to 5 times longer than
those utilized in the instant invention.
Example 2
Similarly to Example l, a heavy hydrocarbon residium pro-
duced by distillation is satisfied according to the process des-
cribed with reference to Figure l, and the results are compared
with those obtained from a conventional countercurrent flow gasi-
fication reaction. Each reaction zone is maintained with a tempera-
ture of about lO00C and a pressure of about l.5 to l5,0 atmos-
pheres. Oxygen-containing gas (air) and steam are introduced into
the reaction zone with a steam to oxygen weight ratio of about 0.3
to 5.0 pounds H20 vapor to each pound of oxygen depending on heat
losses and oxygen purity. The feed rate of the hydrocarbon residium
and oxygen-containing gas, and steam in the process of the present
invention is adjusted to establish under steady-state operating
conditions a froth flow transport condition within the reaction
zone, and comprises about lO to lOO ft/second, preferably 20 to
40 ft/second. In contrast, in order to maintain a countercurrent
flow between molten medium and hydrocarbon residium in the process
of the prior art, the feed rate of hydrocarbon residium feed and
oxygen-containing gas, and steam is maintained at about 2 0 feet
per second therein. The aforementioned feed rates are sufficient
to establish contact times of about 0.5 seconds in the process
of the instant invention, and contact times of about 3 to 5 seconds
in the prior art gasification process. Comparison of the two
processes reveals that much greater amounts of hydrocarbon residium,
~1~4~48
34
on the order of about 10 times as much, can be processed by the
process of the instant invention than can be processed by the
countercurrent flow process of the prior art, and due to the larger
size of equipment required by prior art, the percentages of total
heat lost through vessel walls is about 4 times greater.
It is thus seen from the foregoing examples that by
contacting a hydrocarbonaceous feed material with the molten medium
with a multi-phase co-current froth flow transport, a significant
increase in processing capacity is accrued, a processing capacity
which for the first time enables competitive, commercial use of
molten mass technology in the conversion of hydrocarbonaceous
feed materials. Moreover, due to the much lower contact times
possible therein improved product yields are possible in many
reactions. Accordingly, the present invention provides an improved
and highly efficacious method for the conversion of carbonaceous
feed materials.
While the invention has been described in terms of pre-
ferred embodiments, and illustrated by examples, various modifica-
tions, substitutions, omissions, and changes may be made without
departing from the spirit thereof. Accordingly, it is intended
that the scope of the present invention be defined solely by the
scope of the following claims.
