Note: Descriptions are shown in the official language in which they were submitted.
109~8Z0
Background of the Invention
A variety of apparatuses and processes have
heretofore been used or proposed for use in the thermal
pyrolysis and/or gasification of carbonaceous materials for
producing gaseous fuels, activated chars, extraction of
valu~able hydrocarbon constituents and the like.
Conventionally, the carbonaceous material in a particulated
form is introduced into a retort or reaction chamber in
which it is heated to an elevated temperature while in a
controlled atmosphere for a period of time sufficient to
effect a thermal degradation or pyrolysis of the feed
material accompanied by a liberation of volatile gaseous
constituents and gaseous pyrolysis by-products. The
carbonaceous feed material can comprise materials of vegetable
origin including, for example, tree bark, wood chips, sawdust,
rice hulls, nutshells, corn husks, as well as vegetable
derivatives, such as peat, lignite, coal, and materials
containing such carbonaceous substances, such as oil shale
and tar sands.
A continuing problem associated with processes of
the foregoing`type has been the tendency of the gaseous
pyrolysis products produced to deposit on the surfaces of
the carbonized product produced, as well as on the surfaces
of the equipment, reducing the efficiency of the pyrolysis
reaction and also necessitating frequent shut-downs to
remove the carbonaceous deposit from the walls of the
retort and associated gas passages. In the manufacture of
activated char or carbon employing thermal pyrolysis reactors
of the foregoing type, the redeposition of the carbonaceous
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residues on the surfaces of the char produced substantially
reduces the activity of the activated carbon product normally
necessitating supplemental activation treatments. The
deposition of carbonaceous residues on the equipment surfaces
in the form of tars and coke obstructs the uniform flow of
the feed material and an efficient removal of the gaseous
by-products frequently causing localized hot spots, causing
an overcracking or excessive thermal degradation of the
gaseous by-products, which still further aggravates the
formation and deposition of carbonaceous residues~
In our U.S. Patent No. 4,069,107, a process and
apparatus is disclosed which overcomes many of the problems
associated with prior art apparatuses and techniques by
providing a pyrolysis reactor system in which improved
control of the uniformity of heating of the carbonaceous
feed material is achieved and wherein the deposition of
carbonaceous residue on equipment surfaces and on the
carbonized product itself is substantially reduced. In the
adaptation of the apparatus and process for making activated
carbon, a continuous production of activated carbon having
high adsorptive capacity is provided without requiring
further activation treatments as is required in accordance
with prior art techniques. The apparatus of the present
inyention provides similar benefits as are achieved in accor-
dance with the prior invention and further provide for an
improved reactor apparatus which is more compact, more
efficient and of increased versatility.
Summary of the Invention
The benefits and advantages of the present invention
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`~re achieved by a thermal reactor comprising a reactor
vessel defining an elongated upright reaction chamber including
upper and lower end portions, a rotary distributor in the
upper portion of said chamber for introducing a particulated
carbonaceous feed material and preheated pebbles into said
chamber and a residue outlet in the lower portion of said
chamber for withdrawing the pyrolyzed residue therefrom, a
separator in the lower portion of said chamber for separating
the pyrolized residue from the pebbles, a pebble lift conduit
having upper and lower end portions and extending longitudinally
of said chamber having a pebble inlet in the lower end
thereof and a pebble outlet in the upper end portion thereof,
conveying means in said lift conduit for conveying separated
pebbles from said pebble inlet upwardly for discharge from
said pebble outlet into said rotary distributor, gas supply
means disposed in communication with said lift conduit for
introducing an oxidizing gas for combustion of the carbonaceous
residue on the pebbles and to provide a preheating of said
pebbles during their ascending movement, vent means disposed
in communication with the upper portion of said lift conduit
for withdrawing said oxidizing gas and combustion products
exteriorly of said chamber, supply means for supplying feed
material to said rotary distributor, drlve means for rotating
said rotary distributor for mixing a portion of the preheated
pebbles with the feed material in the form of a downwardly
moving columnar reaction mass and for distributing the
remaining portion of the pebbles substantially devoid of any
feed material in the form of a downwardly moving upstream
layer and a downwardly moving downstream layer overlying and
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surround sad reaction mass, and a gas inlet for introducinga gas into said reaction chamber along a region intermediate
of said rotary distributor and said separator for passage
substantially transversely through said upstream layer, said
reaction mass and said downstream layer; and a gas outlet
for withdrawing the gas and gaseous pyrolysis products from
said reaction chamber along a region disposed adjacent the
said downstream layer and transversely spaced from said gas
inlet.
Additional benefits and advantages of the present
invention will become apparent upon a reading of the description
of the preferred embodiments taken in conjunction with the
accompanying drawings.
Brief Description of the Drawings
Figure 1 is a schematic layout of a continuous reactor
apparatus arranged in accordance with a preferred embodiment
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of the present invention;
Figure 2 is a magnified vertical longitudinal sec-
tional view of the reactor apparatus section of the arrange-
ment shown in Figure l;
Figure 3 is a fragmentary transverse sectional view
of the rotary distributor of the reactor shown in Figure 2
as viewed substantially along the line 3-3 thereof;
Figure 4 is a horizontal plan view looking down-
wardly of the reactor shown in Figure 2 substantially along
the line 4-4 thereof and;
Figure 5 is a fragmentary longitudianl sectional
view of the upper portion of the reactor as shown in Figure
4 and as taken substantially along the line 5-5 thereof.
Description of the Preferred Embodiments
The schematic arrangement of the apparatus as shown
in Figure 1 is particularly adapted but not necessarily
limited to the continuous pyrolysis of vegetable matter,
such as tree bark, wood chips, sawdust, rice hulls, nutshells,
corn husks, as well as vegetable derivitives, such as peat,
lignite, coal, and materials containing such carbonaceous
substances, such as pulverized oil shale and tar sands, for
example. When the feed material comprises a particulated
vegetable origin substance, such as wood chips, for example,
an activated carbon or char product is produced of a type
suitable for use as an adsorbent and upon further comminution
as a filler in a variety of elastomeric and resinous compos-
itions.
As shown in Figure 1 a particulated carbonaceous
feed material of any of the types as hereinabove set forth
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is loaded into a hopper 10 and transferred through an air
lift conduit 12 to a storage hopper 14 disposed at an
elevated position above the upper end of a reaction vessel
16. A high capacity blower 18 is connected to the inlet
of the airlift conduit for effecting an entrainment and
lifting of the particulated feed material through the air
lift conduit, which in accordance with the specific arrange-
ment illustrated can also effect a partial drying and/or
preheating of the feed material during the course of its
conveyance and storage. The inlet of the blower 18 is
connected to the outlet of a waste heat steam generator 20
by means of a conduit 22 wherein the sensible heat remaining
in the hot effluent gases of the reactor are utilized to
effect a partial drying and/or preheating of the feed
material. The storage hopper 14 is constructed in the form
of a cyclone-type separator, whereby the particulate matter
is retained and the conveying gas is harmlessly discharged
to the atmosphere through a stack 2~.
Referring now to Figure 2 of the drawings, the
interior of the reaction vessel or reactor 16 is substantially
completely filled with a solid heat transfer media or pebbles
indicated generally at 26 which during the operation of the
apparatus are preheated to an elevated temperature and are
simultaneously cleansed of any carbonaceous residues or
coke deposits thereon prior to being admixed with the feed
material in the upper end of the reactor vessel. The heat
transfer media or pebbles may comprise any substance which is
possessed of a high heat capacity, which is resistant to
attrition, which is capable of withstanding the elevated
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temperatures to which they are subjected and which are of
relatively low cost. While various te ~ ature~resistant
metals and metal alloys, including cast iron, can be employed
for this purpose, refractory ceramic compositions are
usually preferred and of which alumina constitutes a par-
t~cularly satisfactory substance. The configuration of the
heat transfer bodies or pebbles preferably is of a generally
spheroidal shape and of substantially uniform size in order
to provide a reaction mass of substantially uniform porosity
and which will move downwardly through the reaction zone of
the reactor under the influence of gravity. The size of the
pebbles may range from a diameter of about 1/4 inch up to
about 3/4 inch, while sizes of from about 3/8 inch to about
1/2 inch diameter are usually preferred. The particular
size of the pebbles employed is selected in consideration
of the type and particle size of the carbonaceous containing
feed material processed and wherein the pebbles are of a
size generally greater than the feed material particle size.
The upper end portion of the reactor 16 as best seen
in ~igures 2-5 is provided with a rotary distributor assembly
28 which is àdapted to rotate about a vertical axis extending
centrally through the reactor. The rotary distributor com-
prises an inner pebble distributor nozzle 30, an outer pebble
distributor nozzle 32 and a feed distributor nozzle 34
affixed at their inner ends and projecting substantially
radially of a tubular shaft 36. The tubular shaft 36 is
rotatably supported by an upper bearing 38 mounted in the
center of the dome shaped top wall 40 of the reactor and a
lower bearing assembly ~2 mounted in a transversely extending
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wall 44 positioned in spaced relationship below the domed
top wall and joined around its periphery to form a gas tight
seal. Both the upper and the lower bearings 38, 42
incorporate suitable gas tight seals which in combination
with a portion of the top wall 40 and transverse wall 44
define a gas tight chamber 46. The lower portion of the
tubular shaft 36 as best seen in Figure 5 is formed with an
enlarged bell shaped section 48 having the lower end thereof
disposed in a gas tight slip fit bearing 50 mounted on the
upper end of a stationary pebble lift tube 52 extending
centrally of the reactor and terminating at a point spaced
from the lower portion thereof. The pebble lift tube 52 is
supported by triangular brackets 54 as indicated in phantom
in Figure 2.
The tubular shaft 36 is closed at a point above the
bell shaped section 48 by an angularly extending wall or
partition 56 defining a portion of the feed material
distributor nozzle 34 whereby feed material from the hopper
14 (Figure 1~ passes downwardly by gravity through a feed
conduit 58 which is connected through a suitable slip joint
connection as shown in Figure 2 to the upper open end of
the tubular shaft 36. Accordingly feed material is contin-
uously discharged downwardly from the hopper 14 through the
feed conduit and tubular shaft through the feed material
distributor nozzle 34 into the interior of the reactor
chamber in response to the rotation of the rotary
distributor.
Rotation of the rotary distributor is effected by
means of a bevel gear 60 affixed to the upper end of the
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tubular shaft 36 which is disposed in constant meshing
relationship with a drive bevel gear 62 affixed to the
output shaft of a variable speed electric motor 64 as best
seen in Figures 1 and 2.
The tubular shaft 36 is formed with an aperture
or port 66 as best seen in ~igures 2 and 5 located at a
position below the angular partition 56 and in communication
with the upper chamber 46 through which flue gasses are dis-
charged from the pebble lift tube 52 and bell shaped section
48 in a manner and for the purposes subsequently to be
described. A screw type conveyor or auger 68 including a
tubular shaft 70 is connected to the center of the angular
partition 56 and is drivingly connected to the rotary
distributor 28. The lower portion of the tubular shaft 70
is rotatingly supported in a rotating gas seal assembly 72
of an inlet conduit 74 through which air or a combustible
air fuel mixture is adapted to be introduced into the
interior of the tubular shaft. The lower portion of the
tubular shaft 70 is imperforate to prevent escape of the
air or fuel air mixture into the reaction zone of the
reactor. The tubular shaft 70 is provided with a plurality
of perforations at a point indicated at 76 spaced from the
bottom thereof or lower end thereof for permitting the air
or fuel air mixture to escape and come in contact with the
pebbles being moved upwardly in the pebble lift tube 52 to
effect a combustion of the carbonaceous residue thereon
effecting a simultaneous cleansing of the pebbles as well as
a preheating thereof in response to the rotation of the screw
conveyor. The gaseous combustion products or flue gas pass
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upwardly through the pebble lift tube 52 and through the
bell shaped section 48 of the rotor assembly whereafter they
pass through the port 66 into the chamber 46 at the upper
end of the reactor and are removed through a flue gas outlet
conduit 78 as shown in Figures 2 and 4 through which they are
passed through the waste heat steam generator 20 as shown
in Figure 1. As shown in Figures 2, 3, and 4, the inlet ends
of the inner and outer pebble distributor nozzles 30, 32 are
disposed in communication with the bell shaped section 48 of
the rotor assembly by means of appropriately sized ports
through which the cleansed and the preheated pebbles are
transferred by gravity as they attain the elevated position
in the pebble lift tube in response to rotation of the screw
conveyor.
In the specific embodiment illustrated in Figure 2,
the interior of the reactor 16 is defined by the dome shaped
top wall 40 connected by suitable flanges to a generally
circular cylindrical side wall 80 which in turn is connected
at its lower end to a generally conical shaped bottom wall 82.
An inner annular wall 84 is mounted within the reaction
chamber in substantially spaced concentric relationship with
respect to the inner surface of the side wall 80 and is closed
at its upper end by an annular wall 86 and at its lower end
by an annular wall 88. The annular walls 86, 88 are imper-
forate while the inner annular wall 84 is perforate such as by
incorporating a plurality of perforations therethrough along
the lower portion thereof. The inner annular wall in
combination with the upper and lower annular walls 86, 88
define in combination an annular gas chamber or chest 90
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which is disposed in communication with a gas inlet conduit
92 by which a gas, such as steam, carbon dioxide, air,
oxygen as well as mixtures thereof ean be introduced into
the interior reaction chamber through the perforated wall
section 94 of the inner annular wall 84.
A gas outlet conduit 96 extends downwardly in spaced
substantially concentric relationship around the pebble lift
tube 52 as best seen in Figure 2 and is of a porous or
perforate strueture along the lower portion thereof along a
region corresponding substantially to the perforated section
94 of the inner annular wall 84. The upper end of the gas
outlet conduit 9~ is imperforate and is sealed by means of a
sealing ring 98 forming an annular chamber to which a produet
gas outlet conduit 100 is eonneeted as best seen in Figure 4
and extends radially out through the side wall of the
reaetor.
In the speeifie arrangement as illustrated in
Figure 2, the foraminous or perforated seetion 94 of the
inner annular wall and of the gas outlet conduit 96 extends
vertieally along a region of the reaetion ehamber in whieh
the pyrolysis or gasifieation reaetion of the feed material
oeeurs. Aeeordingly, the transverse passage of gas
eontinuously or on an intermittent basis from the gas ehamber
90 through the reaetion bed into and through the foraminous
portion or perforated section of the gas outlet conduit 96
effeets a eontinuous sweeping or purging of the volatile
eonstituents and pyrolysis produets formed from the reaction
bed. It is also contemplated in accordanee with an
alternative embodiment of the present invention, that only
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109~8~30
the lower portion oE the inner annular wall 84 and gas
outlet conduit 96 is formed with a foraminous or perforated
structure at a position below the normal pyrolysis zone,
such that in the case of the operation of the reactor for
producing an activated char product, the carbonaceous char
produced is contacted at substantially the conclusion of the
pyrolysis reaction with a gas such as steam to effect an
activation thereof in the lower region of the reaction zone
by removing any deposited constituents from the active
sites thereof.
As shown in Figure 2, the lower portion of the
reactor is provided with a generally conically shaped screen
102 formed with a horizontal center section 104 for
separating the pebbles from the pyrolyzed carbonaceous
product or the residual ash in the case of a gasification
operation. Alternatively in the case of finely comminuted
oil shale or tar sands, the pebbles are separated from the
residual strip sand or shale which passes through the holes
in the screen and are discharged from the base of the reactor
through an outlet or discharge conduit 106.
The~lower inlet end of the pebble lift tube 52 is
spaced upwardly of the center section 104 of the ~creen
forming therebetween an annular inlet nozzle for the pebbles.
The screw type conveyor extends downwardly to a position
adjacent to the upper surface of the screen. Accordingly
the pebbles and carbonized feed material or residue move
downwardly and radially inwardly along the conical section
of the screen and thence substantially horizontally inwardly
toward the inlet of the pebble lift tube whereby they are
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lifted in response to rotation of the screw conveyor
upwardly through the lift tube for recycling through the
pebble inner and outer discharge nozzles. In this regard,
the lower outer portion of the pebble lift tube is formed
with a radially downwardly projecting annular flange 108
which serves to support the lower end of the gas outlet
conduit 96 and also serves to maintain the integrity of the
pebbles surrounding the periphery of the gas outlet conduit
by restricting downward movement of the inner portion of
the pebbles thereby assuring continuity of the pebble layer
o~er the length of the foraminous section of the gas outlet
conduit.
The upper portion of the reaction chamber as best
seen in Figures 2 and 4 is provided with an inner circular
baffle or shroud 110 and an outer circular baffle or shroud
112 which are disposed substantially concentrically to each
other and to the inner surface of the inner annular wall 84
and the outer surface o~ the gas outlet conduit 96. The
upper edges of the inner and outer baffles 110, 112 are
disposed adjacent to the lower edges of the distributor
nozzles of the rotary distributor. The inner baffle 110 in
combination with the periphery of the gas outlet conduit
96 define an inner annular distribution chamber 114 while
the outer circular baffle 112 in combination with the inner
surface of the inner annular wall 84 define an outer annular
distribution chamber 116 for feeding the heated pebbles
into the upper end of the annular reaction chamber in the
form of two concentric annular layers. The lower ends of
the inner and outer circular baffles terminate at a point
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spaced above the foraminous sections of the annular wall 84
and gas outlet conduit 96. As shown in Figures 2 and 4,
the outlet of the inner pebble distributor nozzle 30 is
disposed at a radial distance in alignment with the inner
annular distribution chamber 114 while the outlet of the
outer pebble distributor nozzle 32 is disposed in vertical
alignment above the outer annual distribution chamber 116.
On the other hand, the outlet of the feed material distributor
nozzle 34 is disposed in vertical alignment above an annular
feed distribution chamber 118 as defined by the annular
space between the inner and outer circular baffles.
In accordance with the foregoing arrangement, the
preheated pebbles are introduced into the upper ends of the
inner and outer annular distribution chambers and move
downwardly through the action of gravity and thereafter
move in a converging fashion upon passing beyond the lower
edges of the circular baffles for admixture with the
particulated feed material introduced into the annular
feed distribution chamber 118. The particulated feed
material becomes uniformly admixed with the preheated pebbles
as they tumble in converging relationship upon passing
beyond the lower edges of the circular baffles.
As will be apparent in accordance with the arrange-
ment illustrated in Figure 2, the pebble heat transfer
media is in the form of stratified layers comprising an
outer layer or stratum disposed adjacent to the inner
annular wall 84 and an inner layer or stratum disposed
around the periphery of the gas outlet conduit 96 indicated
at 120 and 122 respectively. The outer stratum 120 and
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inner stratum or layer 122 are substantially devoid of any
carbonaceous feed material. Disposed between the outer and
inner layer of pebbles is an annular-shaped reaction mass or
stratum indicated at 124 comprising a uniform mixture of
the particulated feed material and pebbles which moves down-
wardly in the form of an annular columnar mass. During the
downward movement of the reaction mass, a suitable gas or
gaseous mixture is continuously or intermittently introduced
into the gas chamber 90 for passage in a substantially
transyerse and radial inward direction through the outer
annular layer, the annular reaction mass and the inner
annular layer to effect a sweeping of the volatile
constituents and gaseous pyrolysis decomposition products
through the porous reaction bed and out through the gas
outlet conduit 96. The annular layer of pebbles or upstream
layer disposed adjacent to the foraminous section 94 of the
inner annular wall serves to heat the entering gas to a
temperature approaching that of the reaction mass. When the
gas comprises steam, the saturated steam is super heated
while any super heated steam employed becomes further super
he~ted upon passage through the outer annular layer of pebbles
and in heat transfer relationship therewith. The inner
annular layer or downstream layer of pebbles serves as a
depository for the tarry carbonaceous reaction products,
coke and carbon deposits, preventing any appreciable
deposition of such residues on the surfaces of the gas
outlet conduit and associated equipment. The inner annular
or downstream layer of pebbles also effects a further
thermal decomposition and/or cracking of the volatilized
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constituents during the pyrolysis or yasification process.
It will be understood, that the transverse flow of
gas through the reaction mass can be reversed, if desired,
whereby gas is introduced into the product gas outlet
conduit 100 and passes substantially transversely and
radially outwardly through the reaction mass and passes
through the foraminous section 94 into the chamber 90 and
is withdrawn through the gas inlet conduit 92. In such
event, the inner pebble layer 122 becomes the upstream
layer while the outer pebble layer 120 becomes the downstream
layer. In accordance with the preferred operation of the
apparatus, gas flow passes radially inwardly from the
chamber 90 through the foraminous section of the gas outlet
conduit in a manner as previously described.
In operation, the variable speed drive motor 64
is energized to effect a rotation of the rotor assembly at
a controlled speed. Feed material is introduced from the
storage hopper 14 through the feed conduit 58 into the upper
end of the tubular shaft for discharge in a circular pattern
through the feed material distributor nozzle. It will be
appreciated that the feed conduit 58 can be provided with
a suitable feeder mechanism ~not shown) such as a paddle or
star type feeder for controlliny the rate of feed of
material to the reactor. Simultaneously, the preheated and
cleansed pebbles passing upwardly beyond the pebble lift
tube are discharged into the inner and outer annular
distribution chambers by the inner and outer pebble
distributor nozzles forming a downwardly moving annular
reaction mass comprised of the inner and outer pebble layers
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devoid of any feed material and an intervening pebble layer
incorporating the feed material in admixture therewith.
The reaction mass moves downwardly and a suitable gas is
transferred from the gas chamber 90 transversely and
radially inwardly for sweeping the pyrolysis and reaction
products as well as the volatile constituents from the
reaction mass which pass through the porous section of the
gas outlet conduit 96 and are withdrawn from the reactor
through the product gas outlet conduit.
A progressive cooling of the pebbles occurs on
moving downwardly through the reaction zone as a result of
the loss of heat by direct heat exchange contact with the
particulated feed material, the exchange of heat between
the pebbles and the gas sweep passing through the reaction
mass during the pyrolysis reaction, as well as a result of
the heating of the volatilized gaseous pyrolysis products
produced in addition to the loss of heat during their ~-
separation from the char product or residue in the base of
the reactor. The pebbles in the base of the reactor after
separation of the product or residue are picked up by the
screw conyeyor and lifted through the pebble lift tube. The
separated pyrolyæed product is withdrawn from the base of the
reactor through the discharge conduit 106 which as illustrated
in Figure 1 is provided with a heat exchanger 126 to effect a
cooling of the pyrolyzed product to a temperature usually
below about 400F in order that it can harmlessly be
discharged to product storage in contact with the atmosphere.
The cooling air introduced into the heat exchanger 126 and
the sensible heat recovered thereby can be advantageously
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employed to form a combustion mixture by directly connecting
the outlet of the heat exchanger to the inlet conduit 74 as
schematically illustrated in Figure 1 which in turn is
introduced into the interior of the pebble lift tube in a
manner to burn the carbonaceous residue from the surfaces
of the pebbles as well as to effect a preheating thereof to
an elevated temperature. In this regard and as schematically
illustrated in Figure 1 a portion of the combustible product
gas withdrawn through the gas outlet conduit 100 can be
diverted through a conduit 128 for admixture with air
introduced via a conduit 130 into the inlet of the heat
exchanger 126. The quantity of combustible product gas
empl~yed ~an be varied to effect the desired degree of
reheating of the recycled pebbles in accordance with the
particular type of feed material and the desired reactibn
to be performed.
As the pebbles are lifted through the pebble lift
tube by the screw conveyor, their contact with the air or
air gas mixture causes combustion to occur as a result of
the presence, if any, of the combustible gas and the combus-
tion of the carbonaceous residue or coke deposited on the
surfaces of the pebbles. The combustion process is performed
50 as to reheat the pebbles at a temperature normally ranging
from about 800F up to about 1700F, which will vary
depending upon the specific pyrolysis or gasification process
being performed in the reactor. Normally the pebbles are
preheated to a temperature ranging from about 1000F to about
1400F in the process for producing activated char or carbon
from carbonaceous vegetable matter, such as wood chips or the
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like. On the other hand, when the reactor is employed for
the gasification of the carbonaceous feed material into a
gaseous fuel of high heating value leaving only a residual
ash, pebble preheat temperatures ~rom about 1400F to
about 1700F are preferred.
The gaseous combustion products or flue gas formed
in the pebble lift tube are withdrawn through the port in
the upper portion of the rotor and are discharged through
the flue gas outlet conduit 78. In accordance with the
preferred practice as schematically illustrated in Figure 1,
the hot flue gases are introduced through the conduit 78
into the waste heat steam generator 20 to extract a portion
of the sensible heat therefrom and the cooled flue gas is
subsequently employed for conveying the feed material from
the hopper 10 to the upper storage hopper 14. The steam
produced in the steam generator 20 can be advantageously
used as all or a portion of the gas introduced into the
reactor for sweeping the volatiles and other gaseous pyrolysis
products from the reaction mass. In such event as shown in
Figure 1, the outlet of the steam generator 20 is connected
by means of a conduit 132 for transferring the saturated or
super heated steam to the gas inlet conduit 92 which in
turn is disposed in communication with the gas chamber 90
~Fig. 2).
The preheated and cleansed pebbles are reintroduced
into the upper portion of the reactor for admixture with
fresh particulated feed material in a continuous recirculating
manner. The walls of the reactor are suitably provided with
removable ports or manholes (not shown) for introducing
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additional pebbles or for replacement with different size
pebbles to provide for optimum operation consistent with
the feed material being processed. Suitable temperature
monitoring devices such as thermocouples (not shown) are
also provided at selected locations in the reaction mass and
pebble lift tube to enable proper control of the reaction
temperature and pebble preheat temperature.
The reaction zone of the reactor is isolated from
the oxidizing gas within the interior of the pebble lift
tube at both the upper and lower portions of the lift tube.
The seal at the lower end is provided by a sufficient depth
of pebbles in the lower portion of the lift tube extending
to a depth along the imperforate portion of the tubular
shaft 70. The seal at the upper end of the lift tube is
achieved by maintaining a depth of preheated pebbles in
the inner and outer pebble distributor nozzles. The
pressure in the reaction zone and in the pebble lift tube
is kept substantially the same to prevent mixing of the
product gas generated in the reaction zone with the flue
gas generated in the pebble lift tube. The pressure in the
pebble lift tu~e preferably is kept slightly below that
within the reaction zone to assure that no leakage of
oxidizing gas into the reaction zone occurs.
While it will be apparent that the invention herein
described is well calculated to achieve the benefits and
advantages hereinabove set forth, it will be appreciated
that the invention is susceptible to modification, variation
and change without departing from the spirit thereof.
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