Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~q3 8545
The increasing scarcity of fluid fossil fuels,
such as oil and natural gas is causing much attention
to be directed towards converting solid carbonaceous
materials such as coal, oil shale, and solid waste to
liquid and gaseous hydrocarbons by pyrolyzing the solid
carbonaceous material. Typically, pyrolysis occurs
under non-oxidizing conditions in the presence of a
particulate source of heat.
In the past, pyrolysis has been carried out in
tubular reactors. While effective, the yield of middle
boiling hydrocarbons, i.e. C5 hydrocarbons to hydrocarbons
having a boiling end point of about 950F(510 C.) has
been less than desired. Their loss has been attributed
to protracted effective pyrolysis times which result in
thermal cracking of such hydrocarbons. A need exists
therefore for a more efficient pyrolysis process which
maximizes the yield of the middle boiling hydrocarbons
which are useful for the production of gasoline, diesel
; fuel, heating oil, and the like.
In one aspect the invention provides a process for
the pyrolysis of carbonaceous materials wherein the
carbonaceous material is primarily pyrolyzed by heat
transferred thereto from a high temperature, particulate
solid source of heat to yield as products of pyrolysis,
a pyrolytic vapor including condensible and noncondensible
hydrocarbons and a particulate carbon-containing solid
residue, characterised by tangentially introducing to
and passing along a curved path in a cyclone reaction-
separation zone a stream of carbonaceous material, while
introducing to said cyclone reaction-separation zone a
-- 2
~13545
high temperature stream of the particulate solid source
of heat, contained in a carrier gas which is non-
deleteriously reactive with respect -to the products of
pyrolysis , at an angle inclined to the path of travel
of carbonaceous material so as to penetrate and
initiate pyrolysis of said carbonaceous material, the
introduced quantity of particulate source of heat being
sufficient to raise the carbonaceous material to a
pyrolysis temperature of at least about 315C, while
simultaneously separating a gaseous mixture of the
carrier gas and pyrolytic vapor from a solids mixture
including the particulate solid source of heat and the
carbon-containing solid residue by the action of
centrifugal forces induced, at least in part by the
introduction velocities of each feed stream.
Preferably the introduction velocity of each
said stream is from about 100 ft (30m) to about 250 ft
(76m) per second so that the stream mix and rapidity
exchange heat within a suitably short contact time.
However, as will be explained, in certain embodiments
; of the invention it may be desirable to introduce the
said streams at velocities nearer to the lower end of
this velocity range while another stream of particulate
solid heat source is introduced at a higher velocity
for a purpose to be described.
The pyrolysis temperature is preferab]y within
the range 315C. to 1095 C. but desirably does not
exceed about 760C. while being at least about 480 C.
The operating parameters are preferably so
selected that the pyrolysis occurs in a contact time
S4S
ranging from about 0.1 to abQut 3 seconds, more preferably
in a contact time of no* more than about 1 second.
Desirably the weight ratio of the particulate
solid source of heat to carbonaceous material is from
about 2 to about 10. Depending upon the selected value
for this ratio and other operating parameters, the
particulate solid source of heat may conveniently have
a temperature ranging from 55 to about 280C. above the
pyrolysis temperature.
In preferred embodiments, the separated solids
mixture obtained from the cyclone reaction-separation
zone is passed to a cyclone combustion zone into which
a stream of a gaseous source of oxygen is introduced,
the solids mixture being introduced at an angle to this
stream so as to heat the solids mixture, the heated
solids mixture then being separated and recycled to the
cyclone reaction-separation zone to serve as the
~` particulate source of heat.
In preferred practice, the particulate solids
mixture obtained from the cyclone reaction-separation
zone is transferred to a first solids collection zone
wherein the particles are maintained at least partly
fluidized, being withdrawn from this collection zone
and passed through a first fluidizing conduit to the
said cyclone combustion zone~, the heated particles
obtained from this zone being fed to a second solids
collection zone from which they are transported
through a second, vertically oriented, fluidized
conduit to the cyclone reaction-separation zone.
The separated gaseous mixture is preferably
385~5
withdrawn ~rom the cyclone reaction-separation zone,
the condensible hydrocarbons in that gaseous mixture
being condensed and a light hydrocarbon fraction
obtained from the condensate.
: In this case, the process is advantageously
further characterised by passing the said separated
gaseous mixture to a venturi quench zone where by in-
troduction of a quench fluid, the condensible hydro-
carbons are condensed to yield agaseous residue; passing
the quench fluid, condensed hydrocarbons and gaseous
residue to a fractional separation zone wherein the
gaseous residue is separated from the condensed hydro-
carbons and the condensed hydrocarbons are separated into
a middle distillate light hydrocarbon fraction and a
heavy hydrocarbon fraction; and recovering the light
hydrocarbon fraction as product and recycling at
least a portion of the heavy hydrocarbon fraction to
the venturi quench zone as the said quench fluid.
When the process is to be applied to carbonaceous
materials such as agglomerative coals that pass through
a tacky state on being heated to the pyrolysis temp-
erature and have a tendency, therefore, to agglomerate
or adhere to any surfaces that they contact, such as
a wall defining the cyclone reaction-separation zone,
preferably an additional high temperature stream of
particulate solid source of heat is introduced
tangentially into the cyclone reaction-separation
zone and caused to follow a curved path therein
at a higher velocity than the said stream of carbonaceous
material thereby to form a layer of source
~ 5L~5
of heat between said stream of carbonaceous material and a wall
defining said zone.
In such embodiments of the invention, conveniently the
said stream of carbonaceous material and the first said stream of
particulate solid source of heat are introduced into the cyclone
reaction-separation zone at velocities not greater than about 61 m
per second, whereas said additional stream is introduced into said
zone at a velocity in the range 61 to about 76 m per second.
The said additional stream may comprise from about 10 to
about 50% by weight of the total amount of particulate solid
source of heat introduced into said cyclone reaction-separation
zone. However, preferably, said additional stream comprises 20 to
30~ by weight of the total particulate solid source of heat
introduced into said zone.
Especially when an additional stream of the particulate
solid source of heat is introduced into the cyclone reaction-
separat,ion zone for the aforesaid purpose, the (first) said stream
of the said source of heat is preferably introduced at an angle in
the range 15 to 40 relative to the path of the stream of carbon-
aceous material. The most preferred values for such an angle arewithin the range 15 to 25.
In another aspect, the invention also provides an
apparatus for pyrolysis of a carbonaceous material in the presence
of a particulate source of heat which comprises a high temperature
cyclone separator-reactor having a tangential first feed inlet for
a low velocity stream of carbonaceous material, and a second feed
inlet for a low velocity stream of the particulate source of heat
at an angle inclined to the tangential feed inlet, a vapor exhaust
at one end of the cyclone separator-reactor for removal of
vaporized products of pyrolysis and a solids outlet at the opposed
end thereoI for removal of the particulate solid source of heat
and carbon-containing solid products of pyrolysis.
~i85~5
The invention also provides apparatus for carrying
out the process. Thus in another aspect the invention provides
apparatus for pyrolysis of carbonaceous material in the presence
of a particulate source of heat, characterised by a high temper-
ature cyclone separator-
- 6a -
~8545
: reactor having a tangential feed inlet for the
carbonaceous material and a second feed inlet for
the particulate source of heat at an angle inclined
to the tangential feed inlet, a vapor exhaust at one
end thereof for removal of vaporized products of
pyrolysis and a solids outlet at the opposed end thereof
for removal of the particulate solid source of heat and
carbon containing solid product of pyrolysis; quench
means coupled in open receiving relation to said vapor
exhaust outlet and including means for introduction
of a hydrocarbon quench fluid for condensing at least
a portion of the high temperature vapors received from
the vapor exhaust outlet; means connected to the quench
means for fractional separation of condensate from the
quench means; means for receiving the particulate solid
source of heat and carbon-containing solid products of
pyrolysis, said means including means to at least partly
to fluidize the collected particles; means to transport
the particulate solid source of heat and carbon-containing
solid product of pyrolysis to said combustion means;
means to combust carbon contained in particulate solid
source of heat and carbon-containing solid residue of
pyrolysis; receiving means to receive the particulate
solid source of heat from said cyclone burner; and
means to transport particulate solid source of heat from
said receiving means to the second feed inlet of said
cyclone separator reactor.
The said means for fractional separation of the
condensate from the quench means includes means to
cycle a portion of a fractionally separated condensate
s~s
as quench fluid to said quench means.
In another aspect the invention provides an apparatus for pyrolysis
of a carbonaceous material in the presence of a particulate source of heat,
characterised by a high temperature cyclone separation-reactor having a first
tangential feed inlet for a high velocity stream of the particulate source
of heat, a second tangential feed inlet defining a flow path substantially
parallel to the flow path defined by the first inlet for a low velocity
stream of carbonaceous material, and a third feed inlet for a low velocity
stream of the particulate source of heat at an angle inclined to the first and
second feed inlets, a vapor exhaust at one end of the cyclone separation-
reactor for removal of vaporized products of pyrolysis and a solids outlet
at the opposed end thereof for removal of the particulate solid source of
heat and carbon containing solid products of pyrolysis.
Preferably, the third feed inlet is inclined at an angle from about
15 to about 40 degrees to the first and second inlets.
More preferably, the third feed inlet is inclined at an angle from
about 15 to about 25 degrees to the first and second inlets.
Preferably the second and third feed inlets are adjacent.
The invention is further explained with reference to the accompanying
drawings, in which:
Figure 1 illustrates apparatus suitable for carrying out the process
of this invention;
Figure 2 is a diagrammatic top view of the cyclone reactor-separator
of the apparatus of Figure l;
Figure 3 is a diagrammatic top view of a cyclone burner;
Figure 4 is a diagrammatic elevation of a modified cyclone ~eactor~
separator that may be utilised in certain embodiments of the invention;
Figure 5 is a sectional view on line 5-5 of Figure 4;
'~
:L~.r.38545
and
FIGURE 6 is a sectional view on line 6-6 of
Figure 4.
According to the present invention, there is
provided a process for the pyrolysis of liquid and
solid carbonaeeous materials which may be used to
maximize the yield-of middle distillate hydrocarbons
by extremely short pyrolysis contact times and apparatus
therefore.
The carbonaceous materials which my be pyrolyzed
in accordance with the present invention include solids
such as agglomerative coals, nonagglomerative coals, tar
sands, shale, oil shale, the organic portion of solid
wastes and the like and liquids such as shale oils,
tar sands oils, heavy refinery hydrocarbons and the
heavy hydrocarbons which result from the pyrolysis
operations as well as mixtures thereof. For ~lids, it
is desirable to limit particle size to about 1000 microns,
and to about 250 mierons for the instanee of agglomer-
ative eoals.
Referring first to Figures 1 and 2, earbonaeeous
material enters a feedline 10 along with, if neeessary,
a earrier gas 12 and, if desired steam, to a venturi
mixer 14. If desired, the heavy hydrocarbon pyrolysis
produets may be eombined with the feed and added by line
15. The carrier gas, if employed, is nondeleteriously
reaetive with respeet to the produets of pyrolysis. By
the term "nondeleteriously reaetive" as applied to the
carrier gas or gas stream, there is meant a gas
substantially free of free oxygen but which may contain
cj4s
constituents which react with the pyrolysis products to
upgrade their value. The gas should not, however,
have constituents which by reaction degrade the
pyrolysis products. The gas can serve as a diluent
to minimize pyrolysis contact time and in the instance
of solid carbonaceous materials it can serve as a
transport gas. The carrier gas may, for instance, be
the inert off-gas product of pyrolysis, steam which will
react under suitable condi-t:ions with the char or coke
formed from pyrolysis to yield hydrogen, by a water-gas
shift reaction, which serves to react with and stabilize
unsaturated products of pyrolysis, or any desired inert
gas or mixtures thereof.
As best shown in Figure 2, the carbonaceous feed
and the carrier gas, if present, are injected as a
stream into a cyclone reactor-separator 16, tangentially
to the walls thereof. Venturi mixer 14 serves to
intimately mix the carbona~eous feed with -the carrier
gas to enhance dilution of the feed and so promote
short reaction pyrolysis times.
Simultaneously, there is introduced a particulate
solid source of heat, through a line 18, at an angle
inclined to the path of travel of the stream of
carbonaceous materia]. The solid particulate source of
heat is transported into the pyrolysis reactor by a
carrier gas which may be the same or different from the
gas carrying the carbonaceous feed into the pyrolysis
reactor, although it will be at a temperature approx-
imately equal to the temperature of the particulate
solid source of heat.
-- 10 --
545
The hot particulate solids are supplied at a
rate and at a temperature consonant with maintaining
a temperature along the walls of the cyclone reactor
separator 16 suitable for pyrolysis. Pyrolysis will
initiate at about 600F. (315C.) but -the pyrolysis
temperature may range up to the softening temperature
of the inorganic constituents of the particulate source
of heat or the carbonaceous feed, higher temperatures
leading to slagging or fusion. Preferably the pyrolysis
temperature ranges from 600 to about 2000F. (1095 C.).
More typically, however, pyrolysis is conducted at a
temperature from about 600 to about 1400 F. (760 C.)
and preferably in the range 900 to about 1400F. (480-
760C.) to maximize the yield of middle boiling hydro-
carbons and olefins. Higher temperatures may be
employed with equal ease to facilitate, where desired,
gasification reactions.
Depending upon pyrolysis temperature, normally
- - from about 2 to about 20 parts by weight of particulate
solid source of heat are fed per part of carbonaceous
material entering the reactor 16. The solids employed
may be solids from a source external to the process,
such as sand, ormay be the solid product resulting from
pyrolysis of the carbonaceous material such as char or
coke or, in the instance of municipal solid waste, the
glass-like inorganic residue resulting from the decarbon-
ization of the solid residue of pyrolysis. The
particulate source of heat is generally at a temperature
from about 100 to about 500F. (55-280C.) above the
desired pyrolysis temperature.
3545
The streams of particulate solid source of heat,
and of carbonaceous material, respectively, preferably
both have a velocity within the range 100 to 250 feet
(30-76m) per second.
The amount of gas employed to transport the solid
carbonaceous material and the particulate source of heat
is sufficient to maintain transport of the materials
and avoid plugging and normally in excess of that amount
to dilute materials and minimize pyrolysis contact time.
Normally, the solids content will range from about 0.1
to about 10% by volume based on the total volume of the
stream.
The particulate solid source of heat penetrates and
enters the stream of carbonaceous material. This
penetration initiates the rate of heat transfer from
the particulate solid source of heat to the carbonaceous
material, instantaneously causing pyrolysis which is a
combination of vaporization and cracking reactions.
As the vaporization and cracking reactions occur,
condensible and non-condensible hydrocarbons are
generated from the carbonaceous material with an
attendant production of a carbon containing solid
residue such as coke or char. The carbon containing
solid residue and the particulate source of heat being
the heaviest materials present are retained and pass
spirally along the walls of the cyclone reactor
separator 16 and settle to reservoir 17 at the base
thereof. The carrier gas as well as the pyrolytic
vapors separate in spiral vortex flow towards the
centre of the cyclone reactor separator 16 and rapidly
~g i8545
terminate the primary pyrolysis reactions due to the
absence o~ solids. Effective pyrolysis contact time
will be less than 3 seconds, preferably from about
0.1 to 1 second, more preferably from 0.2 to about
o.6 secDnd.
"Pyrolysis contact time" or "contact time" as
referenced to pyrolysis, as used herein, means the
time from when the carbonaceous material first contacts
the particulate source of heat until the vaporized
products separate from the particulate source of heat.
A convenient measure of contact time is the average
residence time of the carrier gas in the cyclone
reactor-separator. The lower limit is that required
to heat the carbonaceous material to the desired
pyrolysis temperature. This is a function of particle
size and concentration of solid particulate source of
heat. For example, under average feed conditions,
contact time to achieve about 1000F.(5L~0C.) is about
1.5 seconds for particles of about 250 microns in
diameter and 0.5 seconds for particles of 75 microns
in diameter.
The carrier gas along with the pyrolytic vapor
exit reactor 16 and enter a venturi mixer 20 where they
are contacted with a quench fluid to reduce gas
temperature at least below pyrolysis and cracking
temperatures to prevent further cracking reactions from
occurring. Preferably, the quench fluid reduces
temperatures below the dew point of the condensible
hydrocarbons. Typically a portion of the condensed
heavier hydrocarbons formed from the pyrolysis reactor
8545
is employed as a quench fluid and fed to the venturi
mixer 20 by line 24. Immiscible quench oils may also
be used and when used are separated from the products
and recycled to venturi mixer 20.
The quench effluent, normally a mixture of gas and
liquids, is fed to a fractionating tower 22. In the
fractionating tower 2Z, the carrier gas and lighter
hydrocarbons are separated from the middle distillate
hydrocarbons which are, in turn, separated from heavy
hydrocarbons. Normally, the gaseous cut, containing
about C4 hydrocarbons and less, exit the top of the
fractionating tower 22 by line 26. The cut of about
C5 to hydrocarbons having an end boiling point of about
950 F. (510C.) which constitutes gasoline, diesel and
heating fuel components, is separated as middle
distillate hydrocarbon products in line 28. A portion
may be cooled and recycled as reflux.
The hea~y hydrocarbon residue exits the base of
fractionator 22 and is cooled. One portion is recycled
as reflux, another as quench and the balance, if not
recovered, as a product returned to cyclone reactor
separator 16 to be pyrolyzed to extinction.
Because of short residence time and at pyrolysis
temperatures below about 1400F. (760C.) the amount
of C4 hydrocarbons plus the carbon-containing solid
residue of pyrolysis will be a minimum while the C5
to 950 F- (510 C.) boiling end point fraction will be
maximized. The C4 and lower hydrocarbons will tend
to be rich in olefins if hydrogen is not added to or
generated in the cylone reactor-separator 16. The
amount of C4 or less hydrocarbons
- 14 -
~i8545
generated will increase with pyrolysis temperature
and pyrolysis contact time.
The presence of hydrogen during pyrolysis,
whether internally generated or externally supplied,
is desired to enhance stabilization of the hydrocarbons
formed, particularly the heavier hydrocarbon to prevent
their polymerization to tars.
The particulate carbon-containing solid residue
of pyrolysis and the particulate solid source of heat
exit the reservoir 17 and pass by a line 30 and
collected in a fluidized stripper 32. A flow of a
carrier gas which is also non-deleteriously reactive
with respect to the products of pyrolysis enters the
base of stripper 32 to maintain the solids in a mixed
condition and in at least a semi-fluidized state. A
flap 34 on the leg 30 prevents backflow of the gas into
the cyclone. Rather, the gas is bypassed around cyclone
reactor-separator 16 through a conduit 36 for combin-
ation with the feed. The gas serves to remove any of
the hydrocarbon oils which result from pyrolysis from
the surface of the particles and return them to the
system for further pyrolysis.
The cooled particulate source of heat and the
carbon-containing solid residue of pyrolysis are passed
through a slide valve 38 and transported along an angle
riser 40 and a vertical riser 42 to a combustion zone,
preferably a cyclone burner 44, the cross section of
which is depicted in ~igure 3. The cyclone burner may
be operated in conjunction with an identical cyclone
burner 46 or simply a cyclone separator for fines. If
1~8545
other combustion apparatus are used, a cyclone separator
is employed to separate flue gases from the particulate
source of heat.
Combustion cyclone 44 operates in a manner
substantially identical to cyclone reactor-separator 16.
The transport gas used to carry the particles to cyclone
burner 44 may be air or flue gas, with the balance of
the combustion air injected tangentially through a line
48. As shown in Figure 3, the solids penetrate the
air stream at an angle and rapidly undergo oxidative
combustion. The heavier particles rapidly pass through
the air stream, so that effective combustion residence
time is short, ranging from abou-t 0.1 to about o.6 second.
As a consequence, even despite the fact that excess air
is supplied, the effective residence time for combustion
is short. As a result the amount of carbon dioxide
generated will be maximized, as the faster carbon
dioxide reaction rate is favoured as compared to the
slower carbon monoxide reaction rate. As a consequence,
the amount of heat generated per unit of carbon consumed
is maximized. In general, partial combustion will yield
a flue gas having a C02 to C0 ratio of about 2 to 1.
The gases and fine solids which elude recovery
from cyclone 44 enter cyclone 46 where additional
air may be added, the cyclone 46 also preferably having
the form depicted in Figure 3 for short contact time
combustion. Alternatively, a simple cyclone separator
may be employed. The high temperature particulate source
of heat collected in cyclones 44 and 46 passes by
standpipes 48 and 50 to a surge hopper 52. Surge hopper
- 16 -
38545
52 is maintained at a temperature consonant with the
operating temperature of the pyrolysis reactor 16 and
generally from about 300 to about 500 ~. (165-280 c)
above the pyrolysis temperature.
As required, the particulate source of heat is
passed through a standpipe 54, slide valve 56, angle
riser 58 to the vertical riser 18 for feed to cyclone
reactor-separator 16. Excess particles are withdrawn
from surge hopper 52 through a screen siphon tube 60
as product char.
A gas which may be steam that becomes superheated
by contact with the contained particulate source of
heat and forms hydrogen by a water gas shift reaction,
enters the surge hopper 52 and passes through a pass
line 62 for feed to the cyclone 44 and cyclone 46 as
part of the carrier gas. The use of the gas, however,
is contingent on complete consumption of oxygen in
cyclone 44 and 46 as the gas entering pyrolysis cyclone
reactor-separator 16 must be substantially free of oxygen.
The transfer gas in the vertical riser 18 serves
to aceelerate the partieulate souree of heat to the
veloeity required for feed to eyelone reaetor separator
16.
As has been mentioned, eertain earbonaceous
materials, especially agglomerative coals, pass through
a tacky state upon being heated to pyrolysis temperatures
so that particles thereof at temperatures within a
certain range tend to adhere to and build up on any
surfaces with which such particles may come into contact.
Such a surface is the curved wall of a cyclone reactor-
- 17 -
~8545
separator such as shown at 16 in Figures 1 and 2.
Although a system such as described with reference to
Figures 1 to 3 can accomplish satisfactory pyrolysis
of agglomerative coals, the system is preferably
modified to incorporate a cyclone reactor-separator
of the construction illustrated in Fi~ures 4 to 6 when
such coals constitute the feed so as to ensure avoidance
of the problems involved in the pyrolysis of such
coals.
Thus, Figures 4 to 6 illustrate a cyclone reactor-
separator 110 consisting of a vertically oriented
cyclindrical body 112 merging into a conical section
114 below and axially aligned with the main body 112.
Below the conical section there is a reservoir 116,
which feeds a dipleg 118 serving as a solids outlet.
A vapor exhaust conduit 120, which preferably is coaxial
with the main body, extends from the bottom 122 out
through the top 124 of the cylindrical main body section.
There are three side-by-side inlets 126, 128 and
130 communicating with the top portion of the main body
section. The first feed inlet 126 is tangential to the
cyclone reactor-separator wall 117 and is intended
for a relatively high velocity stream of a particulate
source of heat, whereas the adjacent second feed inlet
128, also tangential to the cyclone reactor-separator
wall is intended for a lower velocity stream of
carbonaceous material. The second feed inlet 128
defines a flow path parallel to the flow path defined
by the first inlet 126. The third feed inlet 130 is
intended for a relatively low velocity stream of the
i~85~5
particulate source of heat. This inlet is inclined
at an angle so as to direct this stream toward the
streams entering through the first and second
tangential feed inlets.
In the operation of this cyclone re~ tor-
separator, a particulate solid source of heat is
injected as a stream 132 into the cyclone reaction-
separation zone tangentially to the walls thereof
through the first inlet 126. The velocity of the
stream 132 is preferably greater than about 200 feet
(61m) per second so that the hot particles have
sufficient momentum to travel along the inner wall
of the cyclone reactor-separator along the path marked
by the arrows 133 in Figure 5. The velocity of this
stream preferably is less than about 250 feet (76m)
per second so that the particles do not erode the
inner wall 136 of the cyclone reactor-separator.
Simultaneously with the introduction of the
relatively high velocity stream, there is introduced
a Lower velocity stream 134 containing the carbonaceous
material, and if necessary a carrier gas. The carrier
gas, if employed, is non-deleteriously reactive with
respect to the products of pyrolysis, and serves as a
diluent to minimize pyrolysis contact time and to dilute
the carbonaceous material to prevent self-agglomeration.
The carbonaceous material is introduced so as to
follow a path substantially parallel to the path followed
by the high velocity stream 132 of the particulate source
of heat when it is introduced into the cyclone. The
velocity of the carbonaceous material stream is less than
-- 19 --
35~5
the velocity of the stream 132 preferably being less
than about 200 fee-t (61m) per second. This ensures
that the carbonaceous material is separated from the
inner surface of the wall 136 by a layer of the
higher velocity stream of the particulate source of
heat. Thus, the higher velocity stream has greater
momentum and thereby preferentially travels along the
inner wall 136 of the cyclone reactor-separator. The
carbonaceous material p~eferably has a velocity of at
least 100 feet (30m) per second so that sufficient
centrifugal forces are induced in the particles in this
stream to effect a separation of the gaseous products
of pyrolysis and the carrier gas from the solid
products of pyrolysis and the particulate source of heat.
The carbonaceous material travels along the flow
path 138 marked by "~" signs 39 shown in Figure 5. This
path is closer to the central vertical axis than of the
flow path 133 of the higher veloeity stream 132 of the
particulate source of heat.
The earbonaeeous material may be treated before
it is fed to the eyelone reaetion separation zone by
proeesses such as removal of inorganie fraetions by
magnetie separation and elassifieation, partieularly in
the ease of munieipal solid waste. The earbonaeeous
material also ean be dried to reduee its moisture eontent.
The solid carbonaceous material usually is comminuted to
increase the surface area available for the pyrolysis
reaction.
Simultaneously with the introduction of the
carbonaceous material and the higher velocity stream of
- 20 -
854S
the particulate source of heat, a lower velocity stream
140 of the high temperature particulate source of heat
is introduced into the cyclone reactor-separator 110
through the third inlet 130 which is adjacent to the
inlet 128 for the carbonaceous material and inclined at
an angle to the path of travel 138 of the carbonaceous
material.
Both the lower velocity and the higher velocity
streams of the particulate source of heat may be
transported into the pyrolysis reactor by a carrier gas
nondeleteriously reactive with respect to pyrolysis
product. The gas may be the same as or different from
the gas carrying the carbonaceous feed into the
pyrolysis reactor, although this carrier gas would
preferably be at a temperature approximately equal to
the temperature of the particulate solid source of heat.
Because the lower velocity particulate solid source
of heat enters the pyrolysis reactor 110 at an angle
inclined to the path 138 of travel of the carbonaceous
material, it penetrates the path of the carbonaceous
material, as shown by dotted line 142 in ~igure 5. This
penetration initiates heat transfer from the particulate
solid source of heat to the carbonaceous material,
causing pyrolysis which is a combination of vaporization
and cracking reactions. As the vaporization and
cracking reactions occur, condensible and noncondensible
hydrocarbons are generated from the carbonaceous material
with an attendant production of a carbon-containing solid
residue such as coke or char. The carbon-containing
solid residue and the particulate source of heat being the
8545
heaviest materials present are retained and pass spirally
along the walls of the cylindrical main body 112 and
cone section 114 of the cyclone reactor-separator 110,
pass through the reservoir 116, and are discharged
through the dipleg outlet 118. The carrier gas as well
as the pyrolytic vapors separate in spiral vortex flow
towards the centre of the cyclone reactor-separator 110
as shown by line 119 in Figure 5, and rapidly terminate
the primary pyrolysis reactions due to the absence of
solids.
The lower velocity stream of the particulate source
of heat preferably has a velocity approximately the same
as that of the carbonaceous material, i.e. from about
100 to about 200 feet (30-61m) per second. If its
velocity is greater than about 200 feet (61m) per
second, the lower velocity particulate source of heat
tends to carry a portion of the carbonaceous material
up against the walls of the cyclone reactor-separator,
and this may lead to caking. At velocities less than
about 100 feet (30m) per second, there may be in-
sufficient momentum to effect a good separation of
vapors from solids in the cyclone reactor-separator.
Although the streams of carbonaceous material
134 and the particulate source of heat 140 introduced
through the second inlet 128 and third inlet 130
respectively, have been described as "low velocity"~
what is meant is that their velocity is low as compared
to the higher velocity stream 132 of the particulate
source of heat introduced through the first inlet 126.
The preferred minimum speed for streams 134 and 140 is
~98545
about 100 feet (30m) per second.
The distribution of the particulate source of heat
between the high and low velocity streams 132 and 140
is a balance between two competing considerations. First,
if less than about 10% of the particulate source of heat
is used in the higher velocity stream, an inadequate
layer of hot nonagglomerative particles is formed along
the reactor inner wall 136 and thus carbonaceous material
can agglomerate along the walls. Therefore it is
preferred that at least 10% of the particulate source of
heat be contained in the higher velocity stream 132.
; The second consideration is the necessity of
providing a sufficient amount of the particulate source
of heat in the lower velocity stream 132 to rai8e the
temperature of the carbonaceous material to the desired
pyrolysis temperature. Only a limited amount of heat is
transferred from the higher velocity stream to the
carbonaceous material, and this is primarily due to heat
transfer by eonveetion and radiation.~Therefore,
preferably at least 50% of the partieulate souree of
heat is included in the lower velocity stream, and more
preferably from about 70 to about 80% ~ that is, the
higher velocity stream 132 amounts to 20-30% of the
total particulate solid source of heat introduced into
the cyclone reactor-separator.
The solids mixture 148 discharged from the bottom
outlet 118 of the cyclone reactor-separator 110 contains
particulate solid source of heat and the carbon-
containing solids residue. The solids residue may be
used as the particulate source of heat by at least
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3545
partially oxidizing it in the presence of a source of
oxygen such as air and recycling it back to the
pyrolysis reactor 110, using for instance an arrangement
as described in connection with Figure 1.
The gas stream 150 exiting the top outlet 112 from
the pyrolysis reactor 110 contains pyrolytic vapors
comprising hydrocarbons, carrier gases, and undesirable
components such as hydrogen sulfide which may be
generated in the pyrolysis reaction. The volati:Lized
hydrocarbons produced by pyrolysis consist of
condensible hydrocarbons which may be recovered by
simply contacting the volatilized hydrocarbons with
condensation means, and noncondensible hydrocarbons
such as methane and other hydrocarbon gases which
are not recoverable by ordinary condensation means.
Condensible volatilized hydrocarbons can be separated
and re¢overed by suitable recovery means for instance
as described in connection with Figure 1. The un-
desirable gaseous products can be removed from the
uncondensible hydrocarbons by conventional means such
as chemical scrubbing. Remaining uncondensed hydro-
carbons can be sold as a product gas stream and can be
utilized as the carrier gas for carrying the carbonaceous
material and the particulate source of heat to the pyrolysis
reaction-separation zone.
Although the higher velocity stream 132 of the
particulate source of heat has been described as being
introduced tangentially into the cyclone reactor-separator,
this stream may be inclined at a small angle relative
to the wall of the cyclone. However, if the higher
- 24 -
8545
velocity stream 132 is inclined toward the cyclone
walls, increased erosion of these walls results, whereas
if it is introduced inclined away from the cyclone walls,
it tends to do a poorer job of keep carbonaceous
material away from the walls of the cyclone. Similarly,
the stream 134 of carbonaceous material does not have
to be introduced strictly parallel to stream 132. However,
it is undesirable to introduce the carbonaceous material
in a path inclined towards the walls ofthe cyclone since
this increases the chance of carbonaceous material
; caking on the wall. On the other hand, if the carbon-
aceous material is inclined towards the centre of the
cyclone, this results in greater penetration of the
carbonaceous material by the lower velocity stream of
the particulate source of heat with potentially
better heat transfer between these two streams, at the
expense of increased pyrolysis time by reducin~ the
` effectiveness of solids/~ases separation.
; .
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