GB2198509A - Multiple hearth reactor and process for thermal treatment of carbonaceous materials - Google Patents

Description

MULTIPLE HEARTH REACTOR AND PROCESS FOR THERMAL TREATMENT OF CARBONACEOUS MATERIALS BACKGROUND OF THE INVENTION The multiple hearth reactor and process of the present invention is broadly applicable for the processing of organic carbonaceous materials containing residual moisture under controlled pressure and elevated temperatures to effect a desired physical and/or chemical modification thereof to produoe a reaction product suitable for use as a fuel.More particularly, the present invention is directed to a reactor and process by which carbonaceous materials containing appreciable quantities of moisture in the raw feed state are subjected to elevated temperature and pressure conditions wfiereby a substantial reduction in the residual moisture oontent of the solid reaction product is effected in addition to a desired thermal chemical restructuring of the organic material to impart improved physical properties thereto including an increased heating value on a dry moisture-free basis.

Shortages and increasing oosts of conventional energy sources including petroleum and natural gas have occasioned investigations of alternative energy sources which are in plentiful supply such as lignitic-ype coals, sub-bituminous coals, oellulosic materials such as peat, waste cullulosic materials such as sawdust, bark, wood scrap, branches and chips derived from lumbering and sawmill operations, various agricultural waste materials such as ootton plant stalks, nut shells, corn husks or the like and municipal solid waste pulp.

Such alternative materials, unfortunately, in their naturally occurring state are deficient for a nutter of reasons for use directly as high energy fuels. Because of this, a variety of processes have heretofore been proposed for converting such materials into a form more suitable for use as a fuel by increasing their heating value on a Disture-free basis while at the sane time increasing their stability to thering, shipment and storage.

Typical of such prior art apparatuses and processes are those as described in United States Patent Nb. 4,052,168 by which lignitic-type coals are chemically restructured by a controlled thermal treatment praviding an upgraded solid carbonaoeous product which is stable and resistant to weathering as well as being of increased heating value approaching that of biturincus coal; United States Patent No. 4,127,391 in which waste bituminous fines derived from conventional coal washing and cleaning operations is thermally treated to provide solid agglomerated coke-like products suitable for direct use as a solid fuel; and United States Patent No. 4,129,420 in which naturally occurrng oellulosic materials such as peat as well as waste cellulosic materials are upgraded by a controlled thermal restructuring press to provide solid carbonaceous or coke-like products suitable for use as a solid fuel or in admixture with other conventional Is such as fuel oil slurries.A reactor and process for effecting an upgrading of such carbonaceous feed materials of the types described in the aforementioned United States patents is disclosed in United States Patent No. 4,126,519 by which a liquid slurry of the feed material is introduced into an inclined reactor and is progressively heated to form a substantially dry solid reaction product of enhanced heating value.The reaction is performed under a controlled elevated pressure and temperature in further consideration of the residence time to attain the desired thermal treatment which rtay include the vaporization of substantially all of the moisture in the feed material as well as at least a portion of the volatile organic constituents while simultaneously undergoing a controlled partial chemical restructuring or pyrolysis thereof. m e reaction is carried out in a monoxidizing environment and the solid reaction product is subsequently cooled to a temperature at which it can be discharged in contact with the atmosphere without combustion or degradation.

While the processes and apparatuses as described in the aforementioned United States patents have been found to provide satisfactory treatment of a variety of raw carbonaceous feed materials to produce an upgraded solid reaction product, there is a continuing need for a reactor and process which provides for still further efficiency, versatility, simplicity and ease of control in the continuous thermal treatment of a variety of such moist raw carbonaceous feed materials providing thereby still further economies in the conversion and production of high-energy solid fuels as a replacement and alternative to conventional energy souses.

SUMARY OF THE INVENTION The benefits and advantages of the present invention in accordance with one of the apparatus embodiments thereof are achieved by a miltiple hearth reactor comprising a pressure vessel defining a chamber containing a plurality of superimposed annular hearths including a series of upper hearths which are angularly inclined downwardly toward the periphery of the * defining a drying or preheating zone in which moisture md clinically combined water in the feed material is extracted.Disposed below the upper hearths, is a series of lower hearths defining a reaction zone including heating arans for effecting a e heating of the feed material to an elevated temperature under a contraolled super atrospheric pressure for a period of time sufficient to vaporize at least a portion of the volatile substances therein and to form reaction gases and a solid reaction product of enhanced heating value on a rtoisture-free basis. the hot reaction gases formed in the reaction zone pass upwardly in heat eacchange relationship with the feed material in the drying zone in a countercurrent manner effecting at least a partial nsation of the condensible portions thereof an the inning feed material effecting a preheating thereof by a liberation of the latent heat of vaporization and further effecting a liberation of chemically combined water in the feed material which is extracted from the angularly inclined hearths under pressure to a sition exterior of the reactor.

The reaction vessel is provided with a centrally extending rotatable shaft having a plurality of rabble arms thereon disposed adjacent to the upper surface of each of the hearths and are operative upon rotation thereof to effect a progressive transfer of the feed material radially along each hearth in an alternating inward and outward direction to to effect a downward cascading travel of the feed material from one hearth to the next hearth therebelow.Annular baffles are preferably employed in the drying zone of the reactor disposed above the hearths and rabble arms thereabove to confine the flow of countercurrent hot reaction gases in a region immediately adjacent to the feed material an such hearths in order to enhance contract and heat transfer between the feed material and gases.

The solid reaction prodct is srtracted from the bottan portion of the reactor and is transferred to a suitable cooling clamber in which it is cooled to a temperature at which it can be discharged in contact with the atmosphere without adverse effects.

The reactor is provided with an outlet in the portion thereof for withdrawing the reaction gases under pressure as a product gas which can be employed, if desired, for combustion and heating of the reaction zone of the reactor. The upper portion of the reactor is also provided with an inlet by which the raw carbonaceous feed material or mixtures thereof are introduced through a suitable pressure lock into the reaction chamber and on to the uppermost hearth in the drying zone.

In accordance with an alternative satisfactory embodiment of the apparatus of the present invention, a drying and preheating of the feed material is effected in a first stage reactor disposed exteriorly of the multiple hearth reactor and the resultant preheated and partially dewatered feed material is thereafter discharged into the multiple hearth reactor defining the reaction zone similar to the reaction zone comprising the lower portion of the composite multiple hearth reactor as hereinbefore described.It is further contemplated in accordance with both apparatus embodiments that suitable cleaning devices such as wire brushes can be employed for removing any accumulation of encrustations fran the exterior surfaces of the annular baffles to maintain optimum operating efficiency of the apparatus. It is further contemplated that the tubular heat exchange elements or electrical heating elements can be enclosed within conductive shields and which similarly are subjected to cleaning to maintain optimum heat transfer characteristics.

In accordance with the process aspects of the present invention, the moist organic carbonaceous feed materials are introduced into a preheating zone rate from or integrally combined with the reactor in which the feed material is preheated by the countercurrent flow of reaction gases to a temperature of fran about 300 to about 5000F. Simultaneously, moisture condensing on the cool incoming feed material as well as moisture liberated in response to the heating thereof is drained from the feed material and is extracted fram pressure through a drain system.The feed material in a partially dewatered state passes fran the preheating zone downwardly through the reaction zone and is heated to a temperature of from about 4000 to about 1200 F or higher under a pressure ranging from about 300 to about 3000 psi or higher for a period of time generally ranging fan as little as about 1 minute up to about 1 hour or longer to effect a vaporization of at least a portion of the volatile substances therein forming a gaseous phase and a solid reaction product.

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 drawings and the specific examples provided.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a vertical transverse aectional view through a multiple hearth reactor constructed in accordance with the preferred entodiments of the present invention; Figure 2 is a transverse horizontal sectional view through the reactor shown in Figure 1 and taken through the reactor section illustrating the disposition of the transverse heat exchanger tubes; Figure 3 is a fragmentary plan view partially in section of the discharge ports in an inclined annular hearth positioned within the upper preheating zone of the reactor shown in Figure 1;; Figure 4 is a schematic flow diagram of the reactor and the several process streams associated in the thermal treatment of carbonaceous feed materials; and Figure 5 is a fragmentary side elevational view partly in section of a multiple hearth reactor provided with a separate preheating and drying stage separate from the reactor in accordance with an alternative invention.

DESCRIPTION OF THE PROVIDED EMBODIMENTS Referring now in detail to the drawings, and as may be best seen in Figures 1 through 3, a multiple hearth reactor in accordance with one of the embodiments of the present invention comprises a pressure vessel 10 comprising a dbme-shaped upper ' portion 12, a circular cylindrical enter section 14 and a dore-shaped lower portion 16 secured together in gas-tight relationship by means of annular flanges 18. he reactor is supported in a substantially upright position by means of a series of legs 20 secured to abutments 22 connected to the lower flange 18 of the center section of the vessel. The upper domed portion 12 is provided with a flanged inlet 24 for introducing a particulated moist carbonaceous feed material into the interior of the reactor. An angular baffle 26 is provided adjacent to the inlet 24 for directionally guiding the entering feed material toward the periphery of the reaction chamber. A flanged cutlet 28 is provided at the opposite side of the upper portion 12 for withdrawing reaction gases under pressure from the reaction charter in a manner subsequently to be described in further detail.A downwardly depending annular boss 30 is formed on the inner oentral portion of the upper portion 12 in which a bearing 32 is disposed for rotatably supporting the upper end of a rotary shaft 34.

The rotary shaft 34 extends centrally of the interior of the reactor and is rotatably journaled at its lower end in an annular boss 36 formed in the lower portion 16 by neans of a bearing 38 and a fluid-tight seal assembly 40. The outward projecting end of the rotary shaft 34 is formed with a stepped stub shaft portion 42 which is seated in supported relationship within a thrust bearing 44 mounted in a bearing carrier 46.

A plurality of radially extending rabble arms 48 are affixed to and project radially fran the rotary shaft 34 at vertically spaced intervals therealong. Generally, two, three or four rabble arms can be employed in the preheating or drying zone and up to six rabble arms can be employed in the reaction zone.

Typically, four rabble arms disposed at approximstely 90 degree increments are affixed at each level to the rotary shaft. A plurality of angularly disposed rabble teeth 50 are affixed to the lower sides of the rabble arms 48 and are angularly oriented so as to effect a radial inward and outward transfer of feed material along the multiple hearths in response to rotation of the shaft.

Rotation of the shaft 34 and the rabble arm assemblies thereon is achieved bj means of a reactor 52 sported on an adjustable base 54 having a bevel drive gear 56 affixed to the output shaft thereof which is disposed in constant meshing relationship with a driven bevel gear 58 affixed to the lower end portion of the shaft. The motor 52 is preferably of the variable speed type to provide controlled variations in the speed of rotation of the shaft.

In order to provide for longitudinal expansion and contraction of the shaft and variations in the vertical disposition of the rabble arms projecting from in response to variations in the tertperature within the multiple hearth reactor, the base 54 and the outward projecting end of Ehe shaft 34 are disposed on adjustable jacks 60 assisted by a fluid actuated cylinder 62 for selectively varying the height of the base 54 to assure appropriate disposition of the rabble teeth 50 relative to the upper surfaces of the hearths within the reactor.

In accordance with the specific angement shown in Figure 1, the interior of the reactor is divided into an upper preheat or dewatering zone and a lower cation zone. The preheating zone is comprised of a plurality of superimposed angularly inclined annular hearths 64 which slope downwardly, toward the periphery of the reaction preheating zone is provided with a circular cylindrical liner 66 which is radially spaced inwardly of the wall 14 of the Center section and to which the angularly inc earths 64 are affixed. The uppermost end of the liner 66 is formed with an outwardly inclined section 68 to prevent entry of tny carbonaceous feed material between the annular space between the liner and wall 14 of the center section. The rmOst hearth 64 as viewed in Figure 1 is connected at its periphery to the liner 66 and extends upwardly and inwardly toward the rotary shaft 34.The hearth 64 terminates in a downwardly disposed circular baffle 70 which defines an annular chute through which the feed material cascades downwardly on the inner portion of the annular hearth therebelow.

The downwardly inclined annular hearth 64 disposed below the uppermost hearth 64 is affixed to and supported by means of brackets 72 to the liner 66 at angularly spaced intervals therealong. The second annular hearth 64 as best seen in Figure 3 is formed with a plurality of ports or apertes 73 around the periphery thereof through which the feed material is discharged in e cascading manner to the next hearth therebelow.In accordance with the foregoing arrangnent, a moist carbonaceous feed rnaterial introduced through the inlet 24 is diverted by the baffle 26 to the outer periphery of the uppermost hearth 64 and is theThfter transferred upwardly and inwardly by weans of the rabble teeth 50 to a position above the circular baffle 70 whereby it drops downwardly to the hearth spaced therebelow. Similarly, the rabble teeth 50 on the second uppermost hearth are effective to transfer the feed material downwardly and outwardly along the upper surface of the hearth for ultimate discharge through the ports 73 around the periphery thereof.The feed material oontinues to pass downwardly in an alternating inward and outward cascading fashion as indicated by the arrows in Figure 1 and is ultimately discharged into the lower reaction zone.

During its downward cascading travel, the feed material is subjected to oontact with the countercurrent outward flaw of heated reaction gases effecting a preheating thereof to a

temperature generally between about 200 to about 5000F/. In order to assure intimate contact of the feed material with the upwardly traveling reaction gases, annular baffles 72 are disposed iddddiately above the rabble arrrs 48 over at St sate of the angularly inclined hearths 64 to confine the flow of such hot reaction gases to a vicinity immediately adjacent to the upper surface of the annular hearths and in heat exchange relationship with the feed material thereon. A preheating of the feed material is achieved in part by the condensation of the reaction gas such as steam on the surfaces of the cool incoming feed material as well as by direct heat exchange.

condensed liquids as well as the liberated chemically ocobined water in the incoming feed material ins downwardly and outwardly along the angularly inclined hearths end is withdrawn at the periphery of those hearths connected at their outermost ends to the circular liner through an annular gutter 74 provided with a screen 76 such as a Johnson Screen over its inlet end which is adapted to be continuously wiped by a scraper element or wire brush 77 on the outermost rabble tooth on the adjacent rabble arm.

The annular gutters 74 are disposed in communication with downcomers 78 disposed within the annular space tween the liner 66 and wall 14 of the center section and the liquid is withdrawn fran the reaction vessel through a condensate outlet 80 as shown in Figure 1.

The e cooled reaction gases passing upwardly through the preheat zone are ultimately withdrawn fran the upper portion 12 of the pressure vessel through the flanged outlet 28.

The preheated and partially dewatered feed material passes fran the 1ermOst hearth in the preheat zone to the uppermost annular hearth 82 within the reaction zone under content controlled elevated Pressure and is subjected to - further

heating to temperotures generally ranging fran about 4000 up to

about 1200 F/or higher. The annular hearths 82 in the reaction zone are disposed in a substantially horizontal position and alternating ones thereof are disposed with the periphery thereof in substantial sealing relationship against a circular cylindrical refractory lining 84 on the inside wall 14 of the center section.

The rabble teeth 50 on the rattle arms 48 in the reaction zone similarly effect an alternating radial inward and radial outward movement of the feed material through the reaction zone in a cascading maner as indicated by the arrows in Figure 1. The substantially moisture free and thermally upgraded solid reaction product is discharged at the center of the lowermost hearth 82 into a conical chute 86 and is extracted from the pressure vessel through a flanged product outlet 88.

In order to further reduce loss of heat from the pressure vessel, the cylindrical eectian as well as the lower portion 16 is provided with an outer layer of insulation 90 of any of the types wellknown in the art. The center section is preferably further provided with an outer shell 92 to protect the insulation therebelow.

A heating of the feed rraterial within the reaction zone can be achieved by electrical heating elements disposed therein, by a jacket encircling the periphery of the wall 14 of the oenter section through which a heat exchange fluid is circulated, or alternatively in accordance with the arrangement as shown in Figure 1, by a circumferential tubular heat exchange comprising a helical tube bundle 94 disposed adjacent to the inner surface of the refractory lining 84 as well as a transverse heat exchanger comprising a plurality of U-shaped tubes 96 projecting horizontally across the pressure vessel at a position immediately below the annular hearths 82 therein.The tube bundle 94 of the circumferential heat exchanger is connected by means of a flanged inlet 98 and a flanged outlet 100 to an external supply of a heat transfer fluid such as compressed carbon dioxide or like transfer fluids. The U-shaped tubes 96 of the transverse heat exchanger as best seen in Figures 1 and 2 are connected to an inlet header and an outlet header 102 and 104 respectively, which are in turn connected to a flanged inlet 106 and flanged outlet 108 extending through the wall of the pressure vessel.The circumferential and transverse heat exchanger systems can be ccnnected to the same source of heat exchange fluid or alternatively, in accordance with a preferred embodiment as further Figure 4, are connected to separate heating sources enabling irependant control of each system to achieve the desired heating and thermal restructuring of the feed material in the reaction zone.

In operation and with particular reference to the flow diagram comprising Figure 4 of the drawings, a suitable moist = aceaus feed material is introduced from a storage hopper 110 through a suitable pressure lock 111 under pressure into the inlet 24 of the pressure vessel 10.The moist raw feed material is transferred downwardly through the upper preheat zone 112 in a manner as previously described and in heat exchange oontact with the upwardly moving reaction gases to effect a preheating of the feed material within a temperature generally ranging from about

200 / up to about 500 Fkin a manner as previously described in connection with Figure 1.Thereafter, the preheated and partially dewatered feed material passes downwardly into the lower reaction zone 114 of the multiple hearth reactor in which it is heated to

an elevated temperature generally ranging from about 400O up to

about 1200 F to effect a controlled thermal resttucturing or partial pyrolysis thereof accompanied by a vaporization of substantially all of the residual moisture therein as well as organic volatile constituents and paralysis reaction products.

The pressure within the reactor is generally controlled within a

range of about 300 & p to about 3000 psilor higher depending upon the type of feed material employed and the desired thermal restructuring thereof desired to product the desired final solid reaction product. The number of annular hearths in the preheat zone and in the reaction zone of the reactor is controlled depending upon the duration of treatment desired so as to provide a residence time of the material in the reaction zone which generally ranges fram as little as about 1 minute up to about 1 hour or longer. m e resultant thermally upgraded solid reaction product is dischareed from, the product outlet 88 in the lower section of the reactor and is further cooled in a cooler 116 to a temperature at which the solid reaction product can be discharged into contact with the atmosphere without effects.Generallv, a cooling of the solid reaction product to a

temperature less than about 500 F/, and more usually temperatures

below about 300 F/ is adeuate. She discharge conduit from the product outlet 88 is also provided with a pressure lock 118 through which the reaction product passes eo prevent loss of pressure fran the reactor.

The cooled reaction gases are withdrawn fran the upper end of the reactor thrtugh the flanged outlet 28 and pass through a pressure letdown valve 120 to a condenser 122. In the condenser 122, the organic and condensible portions of the reaction gas are condensed and extracted as by-pruuuct noncondensible portion of the gas comprising product gas is withdrawn and can be recovered and used to supplement the heating requirements of the reactor. Similarly, the liquid portion extracted from the reactor in the preheating zone is withdrawn through a suitable pressure letdown valve 124 and is extracted as waste water.The waste water frequently contains valuable dissolved organic constituents and can be further prooessed to effect an extraction thereof or in the alternative, the waste water including the dissolved organic constituents can be directly employed for forming an aqueous slurry containing portions of the comminuted solid reaction product therein to facilitate a transportation thereof to a point remote from the reactor.

Additionally, the flow diagram of Figure 4 schematically depicts auxiliary heating systems for recirculating the fluid heat transfer medium through the circumferential and transverse heat exchanger sections of the reaction zone 114. As shown, the circumferential heat exchange system includes a pump 126 for circulating the heat transfer fluid through a heat exchanger or furnace 128 to effect a reheating thereof and for discharge into the tube bundle in the reaction zone. Similarly, the transverse heat exchanger system is provided with a recirculating pump 130 and furnace 132 for circulating and reheating the heat transfer fluid for discharge into the U;shaped tubes in reaction zone 114.

The e multiple hearth reactor and process as hereinbefore shown and described is eminently adapted for processing carbonaceous materials or mixtures of such materials of the general types hereinbefore described which are generally characterized by having relatively high moisture contents in their raw feed state. AL e term "carbonaceous" as employed in this specification is defined as materials which are rich in carbon and may comprise naturally occurring deposits as well as waste materials generated in agricultural and forestry operations.

Typically, such materials include sub-bituminous coals, lignitic-type coals, peat, waste cellulosic materials such as sawdust, bark, wood scrap, branches and chips from lumbering and sawmill operations, agricultural waste materials such as cotton plant stalks, nut shells, corn husks, rice hulls, or the like, and municipal solid waste pulp fran which metallic contaminants have been removed containing less than about 50 percent by weight moisture, and typically, about 25 percent by weight moisture.

The multiple heart reactor and process as herein described is eminently suitable for processing and upgrading such cellulosic materials under the conditions and prooessing parameters as described in United States Patents Nb. 4,052,168; 4,126,519; 4,129,420; 4,127,391; and 4,477,257,########################## ################################.

A typical example of the operation of the multiple hearth reactor in accordance with the embodiment of Figure 1 for upgrading a sub-bituminous coal containing approximately 30 percent by weight moisture in the raw feed state will now be described. be raw feed coal is introduced from the feed hopper 110 as illustrated in Figure 4 through the Pressure lock 111 at a

temperature of about 60 F/ and at atmospheric pressure into the

reactor which is maintained at a pressure of about 830 The The feed coal is heated in the preheat zone 112 of the reactor from

about 6O0Fiduring the course of its sward travel therethrough

and enters the reaction zone 114 at a temperature of about 5000F.

The waste water extracted from the preheat zone is removed at a temperature of about 3230F (1620C) and a pressure of 830 psig (57.2 bar) while product gas is also removed from the upper portion of the preheat zone at a temperature of about 323 F (162 C) at a pressure of 830 psig (57.2 bar).

The reaction gas from the reaction zone enters the lower portion of the preheat zone at a temperature of 5000F (2600C) and at a pressure of 830 psig (57.2 bar). The resultant solid reaction product is extracted from the bottom of the reaction zone at a temperature of about 7180F (3810C) at a pressure of 830 psig (57.2 bar) whereafter it is subsequently cooled to a temperature of about 2000F (930C) and is discharged at atmospheric pressure.

A typical mass flow rate of the feed material and various product streams in terms of pounds (kilos) per hour comprises 51 470 pounds (23 370 kilo) per hour of feed material containing 15 956 pounds (7 244 kilo) per hour water. The waste water recovered is 20 326 pounds (9 228 kilo) per hour while the product gas comprises 5 548 pounds (2 519 kilo) per hour in addition to 328 pounds (149 kilo) per hour of steam. The solid reaction product discharged from the reactor comprises 25 368 pounds (11 517 kilo) per hour and the net product gas after extraction of the condensible portions comprises 5 548 pounds (2 519 kilo) per hour in addition to 328 pounds (149 kilo) per hour water.

A heat balance of the foregoing process comprises the raw moist coal feed containing 745 085 Btu/hour (218.4 KW) charged to the reactor with the solid reaction product cooled to 2000F (93 0C) containing 1 278 547 Btu/hour (374 KW). The product gas recovered has a sensible heating value of 1 071 872 Btu/hour (314.2 KW) while the hot waste water extracted contains 5 955 518 Btu/hour (1745.6 KW).

The foregoing process sequence and conditions is typical for processing sub-bituminous coals and it will be understood that the particular temperatures in the various zones of the reactor, the pressure employed and the residence time of the feed material within the several zones can be carried to achieve the requisite thermal upgrading and/or chemical restructuring of the cellulosic feed material depending upon its initial moisture content, the general chemical construction and carbon content thereof, as well as the desired characteristics of the solid reaction product recovered.Accordingly, the preheat zone of the reactor can be controlled so as to effect a preheating of the incoming feed material at room temperature to an elevated temperature generally ranging from about 2000F (93 0C) up to about 5000F (2600C) whereafter upon entering the reaction zone in further heated to a temperature up to about 1200 F (649 C) or higher. The pressure within the reactor can also be varied with a range of about 300 psig (20.7 bar) to about 3000 psig (207 bar) with pressures of from about 600 psig (41.3 bar) to about 1500 psig (103.4 bar) being typical.

An embodiment of apparatus comprising the present invention is best seen in Figure 5, in which the preheat zone is defined by an inclined chamber 134 which is disposed with the upper outlet end thereof connected via a flange 136 to a flanged inlet 138 of a multiple hearth reactor 140 defining the reaction zone. The chamber 134 is provided at its lower end portion with an inlet 142 through which the moist caronaceous feed material enters and is transferred through a screw-type feeder or lock hopper 144 under pressure into the lower end of the chamber. The carbonaceous feed material is transferred under pressure upwardly through the chamber 134 by means of a screw conveyor 146 extending the length thereof.The upper end of the screw conveyor is journaled by an end cap 148 bolted to the end end of the charter and at its lower end by means of a seal and bearing assembly 150 mounted on a flange bolted to the lower end of the chamber. The projecting end shaft of the screw conveyor 146 is connected by means of a coupling 152 to a variable speed electric motor 154.

The upper end of the chamber 134 is provided with a flanged outlet 156 adapted to be equipped with a rupture disk or other suitable pressure relief valve for releasing pressure fran the reactor system at a present excessive pressure level. The lower portion of the inclined chamber is provided with a second flanged outlet 158 connected by rreans of a suitable foraminous screen such as a Johnson-type screen in the wall of the chamber 134 through which the nonoonnsible gases are exhausted fran the system. The flanged outlet 158 is connected in an arrangement as illustrated in Figure 4 to a valve 120 to a product gas treatment and recovery system.

A preheating and partial dewatering of the carbcnaceous material canveyed upwardly through the inclined chamber 134 is effected in response to the contercurrent flow of reaction gases discharged outwardly of the multiple hearth reactor 140 through the flanged inlet 138. As in the case of the embodiment described in connection with Figure 1, a preheating of the feed material is achieved in part by the condensation of condensible portions of the reaction gas such as steam on the surfaces of the cool incoming feed material as well as by direct heat exchange.A preheating of the feed material is generally effected to a temperature of from about 2000 up to about 500 F. condensed liquids and the chemically wtined water liberated during the preheating and carpaction of the carbonaceous material in the chamber 134 drains downwardly and is extracted from the lower portion of the charter through a port 160 in a manner as previously described in connection with Figure 4 equipped with a suitable valve 124 for waste water treatment and recovery. The wall of the chamber 134 adjacent to the port 160 is provided with a suitable foraminous screen such as a Johnson-type screen to minimize escape of the solid portion of the feed material.

The multiple hearth reactor 140 as shown in Figure 5 is of a structure similar to the reactor illustrated in Figure 1 with the exceptino that the interior of the reactor defines a reaction zone and does not employ the angularly inclined hearths 64 as shown in Figure 1 in the upper preheat section thereof. The reactor 140 is of similar construction and includes a dome-shaped upper portion 162 which is connected to a circular cylindrical center section 164 in gas-tight sealing relationship by means of annular flanges 166.An annular boss 168 is formed an the inner central portion of the dome-shaped portion 162 for receiving a bearing 170 in which the upper end of a rotary shaft 172 is journaled carrying a plurality of rabble arms 174 in accordance with the arrangement previously described in connection with Figure 1. Each rabble arm is provided with a plurality of angularly disposed rabble teeth 176 for radially transferring the feed material radially inwardly and outwardly across a plurality of vertically spaced hearths 178.

In accordance with the foregoing arrangeent, the preheated and partially dewatered feed material dischaced fran the upper end of the angularly inclined chamber 134 enters the reactor through the flanged inlet 138 equipped with a chute 180 for distributing the feed material across the uppermost hearth 178. In response to rotation of the rabble arrrrs, the feed material passes downwardly in a cascading alternating manner as previously described and as indicated in the arrows of Figure 5.

Since the lower portion of the reactor 140 is substantially identical to that as shown in Figure 1, no specific illustration is prwided. The drive arrangement and supporting arrangement as illustrated in Figure 1 can be satisfactorily employed for supporting the reactor 140.

As in the case of the arrangement of Figure 1, the reactor 140 of Figure 5 is provided with a cylindrical liner 182 defining the interior wall of the reaction zone which is provided with an exterior layer of insulation 184 between the wall 164.

Similarly, the otter surface of the wall and dome-shaped upper portion can be provided with an insulating layer 186 to minimize heat loss.

In the embodiment illustrated in Figure 5, the feed material on the upper surface of each of the hearths 178 is heated t an electrical heating device schematically indicated at 188 which is substantially completely enclosed within an annular conducting shield 190 affixed to the underside of the hearth. The shield 190 reverts deposition of tars and other thermal degradation products on the heating elements which would otherwise reduce the efficiency of heat transfer. The use of such shields 19C is equally applicable in connectoin with the embodiment illustrated in Figure 1 for enclosing the tubes 94 and 96 to correspondingly prevent deposition of carbon and other extraneaous natter thereon.

In accordance with the arrangement of Figure 5, at least the lower surfaces of the annular shields 190 are cleaned by means of suitable scraping elements, preferably wire brushes indicated at 192 affixed to and extending radially along the upper edge of the rabble arms 174. Accordingly, rotation of the shaft 172 and the rabble arms thereon effects a continuous cleaning of the underside of the shields maintaining efflcient heat transfer for the heating elements encased therein.

It is further contemplated that after prolonged operatin@ ar undesirable accumulation of tars and other matter may occur on the interior surfaces of the reactors illustrated in @@@@e@ and @@ such event the interior of the reactor can be cleaned by halting the further introduction of feed material and after the last product passes through the outlet thereof, air can be introduced into the interior of the reactor effecting oxidation and removal of the accumulated carbonaceous deposits.

In accordance with the arrangement il illustrated in Figure 5, the reactor 140 is also preferably provided with a flanged outlet 194 in the dcme-shaped upper section thereof which is adapted to be connected to a suitable rupture disk or pressure relief system in a manner similar to the outlet 156 on the chamber 134.

The operating conditions for the reactor arrangarent illustrated in Figure 5 are substantially similar to those as previously described in connection with the reactor of Figure 1 to produce an upgraded, chemically restructured partially pyrolyzed product.

While it will be apparent that the preferred embodiments of the invention disclosed are well calculated to fulfill the objects above stated, it will be appreciated that the invention is susoeptible to modification, variation and change without departing frar the proper scope or fair weaning of the subjoined claims.

Claims (9)

CLAIMS 1. A multiple hearth reactor for thermal treatment of organic caronaceous materials under pressure comprising a pressure vessel defining a chamber containing a plurality of suparinposed annular hearths including a series of upper hearths angularly inclined downwardly toward the periphery of said chamber and a series of Tower hearths spaced therebelow, inlet means in the upper portion of said vessel for introducing a moist carbonaceous feed material under pressure onto the uppermost hearth, rabble means disposed above each hearth for transferring the feed material radially along each hearth in an alternating inward and outward direction to effect a downward cascading of the feed material fran one hearth to the next hearth therebelow, outlet means in the upper portion of said vessel for withdrawing reaction gases under pressure from said overlying the upper hearths and rabble oceans for directing the upward countercurrent flow of reaction gases adjacent to the feed material and in heat transfer relationship disposed in communication with said upper heaths for withdrawing any liquid thereon under pressure from said in said chamber disposed in the region of the lower hearths for heating the feed material thereon to an elevated temperature for a period of time sufficient to vaporize at least a portion of the volatile substances therein to form reaction gases and a reaction product and discharge means in the lower portion of said vessel for withdrawing the reaction product under pressure from said chamber. 2. The reactor as defined in claim 1 further including cleaning means associated with said rabble means for cl v said drain means. 3. Ihe reactor as defined in claim 1 in which said heating means are disposed circumferentially around the interior of said * r. 4. The reactor as defined in claim l in which said heating neans are disposed transversely at spaced Intervals within the interior of said chamber and adjacent to the underside of each of said lower 6 s. 5. qhe reactor as defined in claim 1 in which said heating means are disposed within a protective conductive shield snd further includiny scraping means on said rabble means for dislodging deposits from at least a portion of the exterior surfaces of said shield. 6. be reactor as defined in claim 1 further including means of adjustably supporting said rabble means for vertical sent relative to the upper surfaces of said upper and said lower hearths. 7. A process for the thermal treatment of moist organic carbonaceous materials under pressure which comprises the steps of: (a) Introducing a supply of moist carbonaceous material to be prooessed under pressure into a multiple hearth reactor comprising a pressure vessel containing a plurality of superimposed annular hearths including a series of upper hearths angularly inclined downwardly toward the periphery of the vessel and a series of lower hearths spaced therebelow, (b) depositing the feed material onto the uppermost hearth and transferring the feed material radially along each hearth in an alternating inward and outward direction to effect a downward cascading of the feed material fran one hearth to the next hearth therebelow, (c) contacting the feed material with a countercurrent flow of reaction gases to effect a preheating of the feed material on the upper hearths to a temperature of fran about 2000 up to about 5000F, (d) draining liquid fran the upper hearths derived from the moisture liberated in the feed material and condensible liquids in the reaction gases under pressure fran the interior of said vessel, (e) heating the preheated feed material on the lower hearths to an elevated temperature for a period of time sufficient to vaporize at least a portion of the volatile substances therein to form reaction gases and a solid reaction product, (f) withdrawing the residual reaction gases from the upper portion of said vessel and discharging the solid reaction product under pressure from the lower portion of said vessel. A A process for the thermal treatment of of moist organic carbonaceous materials substantially as hereinbefore described with reference tolthe accompanying drawings. . A multiple hearth reactor for thermal treatment of organic carbonaceousmaterials under pressure constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in/the accompanying drawings. Amendments to the claims have been filed as follows CLAIMS

1. A multiple hearth apparatus for thermal treatment of organic carbonaceous materials under pressure comprising a pressure vessel defining a chamber containing a plurality of superimposed annular hearths including a series of upper hearths angularly inclined downwardly toward the periphery of said chamber and a series of lower hearths spaced therebelow, inlet means in the upper portion of said vessel for introducing a moist carbonaceous feed material under pressure onto the uppermost hearth, rabble means disposed above each hearth for transferring the material radially along each hearth in an alternating inward and outward direction to effect a downward cascading of the feed material from one hearth to the next hearth therebelow, outlet means in the upper portion of said vessel for withdrawing volatile gases under pressure from said chamber, baffle means overlying the upper hearths and rabble means for directing the upward countercurrent flow of volatile gases adjacent to the feed material and in heat transfer relationship therewith, drain means disposed in communication with said upper hearths for withdrawing any liquid thereon under pressure from said chamber, heating means in said chamber disposed in the region of each of the lower hearths for independently heating the feed material thereon to a controlled elevated temperature for a period of time sufficient to vaporise at least a portion of the volatile substances therein to form volatile gases and a thermally restructured product and discharge means in the lower portion of said vessel for withdrawing the thermally restructured product under pressure from said chamber.

2. Apparatus as claimed in claim 1, further including cleaning means associated with said rabble means for cleaning said drain means.

3. Apparatus as claimed in claim 1 or 2, in which said heating means are disposed circumferentially around the interior of said chamber.

4. Apparatus as claimed in claim 1, 2 or 3, in which said heating means are disposed transversely at spaced intervals within the interior of said chamber and adjacent to the underside of each of said lower hearths.

5. Apparatus as claimed in claim 1, 2, 3 or 4, in which said heating means are disposed within a protective conductive shield and wherein scraping means are provided on said rabble means for dislodging deposits from at least a portion of the exterior surfaces of said shield.

6. Apparatus as claimed in any preceding claim, further including means for adjustably supporting said rabble means for vertical movement relative to the upper surfaces of said upper and said lower hearths.

7. A process for the thermal treatment of moist organic carbonaceous materials under pressure which comprises the steps of: (a) introducing a supply of moist carbonaceous material to be processed under pressure into a multiple hearth reactor comprising a pressure vessel containing a plurality of superimposed annular hearths including a series of upper hearths angularly inclined downwardly toward the periphery of the vessel and a series of lower hearths spaced therebelow, (b) depositing the feed material onto the uppermost hearth and transferring the feed material radially along each hearth in an alternating inward and outward direction to effect a downward cascading of the feed material from one hearth to the next hearth therebelow, (c) contacting the feed material with a countercurrent flow of reaction gases to effect a preheating of the feed material on the upper hearths to a temperature of from about 2000 up to about 5000F, (d) draining liquid from the upper hearths derived from the moisture liberated in the feed material and condensible liquids in the reaction gases under pressure from the interior of said vessel, (e) heating the preheated feed material on the lower hearths to an elevated temperature for a period of time sufficient to vaporise at least a portion of the volatile substances therein to form reaction gases and a solid reaction product, (f) withdrawing the residual reaction gases from the upper portion of said vessel and discharging the solid reaction product under pressure from the lower portion of said vessel.

8. A process for the thermal treatment of moist organic carbonaceous materials substantially as hereinbefore described with reference to Figures 1 to 4 of the accompanying drawings.

9. A multip]e hearth reactor for thermal treatment of organic carbonaceous materials under pressure constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 4 of the accompanying drawings.