US2623815A - Apparatus for gasifying carbonaceous fuel - Google Patents

Description

Dec. 30, 1952 E. ROETHELI ETAL APPARATUS FOR GASIFYING CARBONACEOUS FUEL 4 Sheets-Sheet 1 F206 GIJ' Original Filed Nov. 23, 1945 4027407 70 (ii/V5616 a. E. ROETHELI ETAL APPARATUS FOR GASIFYING CARBCNACEOUS FUEL Dec. 30, 1952 4 Sheets-Sheet 4 Original Filed Nov. 23, 1945 mo l M Q\ Q 8 .WQ 5' 6 HA t 3w 1 www ob v8 1- m mm x 3% \mv 6& ne 2% NmJv r H 8* 4 q u A a WW ww ,V w Q/ kmhwfio k6 LQaGKUkWU fifim. MW WOW N w T m6 \I\NV 4 U @RON fi w k nx \w v ko uwwxvmw MLO w a 93 Q A T Q 9% \QO a. mo 99v 93 b Tr A J a m NYUNK AWE wb Patented Dec. 30, 1952 UNITED STATES RATENT OFFICE APPARATUS FOR GASIFYING CARBONACEOUS FUEL Delaware Original application November 23, 1945, Serial No. 630,518. Divided and this application May It, 1948, Serial No. 27,054

1 Claim. 1

The present invention relates to the art of producing valuable fuels. More particularly, the present invention relates to a novel process and apparatus for the conversion of non-volatile carbonaceous materials, such as coal, coke, peat, tar sands, oil shales, heavy oil residues, and the like, into volatile fuels, such as combustible gases, motor fuels, heating and fuel oils.

This application is a division of our copending application Serial No. 630,518 filed November 23, 1945, now abandoned.

Heretofore, non-volatile carbonaceous materials of the type mentioned above have been converted into liquid and gaseous fuels by various fixed bed operations, such as coal gas, producer gas and water gas processes. However, these processes either require frequent cleaning periods resulting in discontinuous operation or they involve inefficient conversion of the available carbon into heat and volatile fuels. The operation of these processes may be made fully continuous by employing the fluid solids technique in which the reactions take place in a dense fluidized bed of finely-divided solids maintained in a turbulent ebullient state by means of fluidizing gases. This technique has highly desirable additional advantages including greatly improved heat distribution and ease of solids handling. It has also been found that a greatly improved utilization of the carbon available in the starting material may be accomplished when the coking and/or gasification reactions are carried out in so-called fluid reactors and the heat required to support these endothermic processes is supplied by the combustion of carbon, for instance, in the form of sensible heat of solid combustion residues circulated to the heat-consuming reaction from a zone wherein solid coking or gasification residue is subjected to combustion. This procedure constitutes a considerable improvement over fixed bed and conventional fluid operation. However, even this improved procedure falls short of a full utilization of the available carbon in the conversion process itself since large quantities of high-temperature heat are Wasted as sensible heat of the volatile products, such as coal gas, Water gas or flue gases. In addition, multiple and complicated gas-solids separation equipment is required to prevent loss of carbonaceous fines entrained in the product vapors and gases and to obtain gases free of entrained solids.

The present invention overcomes the aforementioned drawbacks and affords various addi tional advantages. These advantages, the nature of the invention and the manner in which it is Cit carried out will be fully understood from the fol lowing description thereof read with reference to the drawing which shows semi-diagrammatic views of apparatus particularly adapted to carry out the invention.

It is an important object of our present invention toprovide means by which the heat generated in the conversion of non-volatile carbonaceous materials into volatile fuels in fluidized solids reactors may be substantially completely utilized for the conversion itself.

Another object of our invention is to provide a process and apparatus by which the sensible heat of the volatile products obtained by the conversion of non-volatile carbonaceous materials in fluidized solids reactors may be utilized in said conversion.

Still another object of our invention is to simplify the gas-solids separation equipment required in the conversion of non-volatile carbonaceous material into volatile fuels by means of the fluid solids technique.

Other objects and advantages of our invention will appear hereinafter.

We have found that these objects may be accomplished quite generally by recycling volatile products, particularly fuel gases and flue gases, in a system comprising two or more fluidized solids treating zones exhibiting substantial temperature gradients, from one or more treating zones to one or more other treating zones of different temperature.

In accordance with one embodiment of our invention, we subject the non-volatile starting materials to at least two successive endothermic reactions operating normally at different temperature levels and pass volatile products together with entrained solids fines from a high-tempe'rature reaction to a reaction of lower temperature without intermediate separation of solids fines. For example, carbonizable non-volatile fuels, such as carbonization coal, oil shale, heavy oil residues or the like are subjected in a fluidized reaction zone to a carbonization treatment at a temperature level of, say, 800-l20il F. to produce volatile carbonization products and coke. The coke is passed to a fluidized gasiflcation zone wherein a substantial portion of the available carbon is converted by means of steam into a fuel gas containing CO and H2 at a temperature level of, say, 14G0-l800 F. The fuel preferably together with entrained solids fines, is passed to the carbonization zone to supply a portion of the heat required therein. The volatile products issuing from the carbonization zone now represent the total volatiles produced and contain all entrainable solids fines formed in the process. The fuel gas from the gasiflcation zone may also be contacted with the fresh fuel charge outside the carbonization zone for the purpose of drying and/or preheating the charge. In cases involving a separate carbon combustion zone or heater in combination with carbonization and/ or gasifica-tion zones, we feed the flue gases leaving the heater normally at the highest temperature level of, say, 1800-2500 F., preferably without intermediate separation of entrained solids to the gasification and/or carbonization zones in series or in parallel or to the fuel charge of these zones to supply heat for drying, preheating, coking and/or gasification. Our invention also comprises the circulation of volatile products and entrained solids from a reaction zone of relatively low temperature, for instance a carbonization zone to a reaction zone of relatively high temperature, such as a gasiflcation zone. In most cases it is feasible and desirable to circulate hot solids from a zone of relatively high temperature to a zone of relatively low temperature in order to accomplish full recovery of the heat generated and to facilitate the heat supply for the heatconsuming operations. it will be appreciated, however, that in all the cases indicated above our invention affords a greatly improved heat economy and eliminates a substantial proportion of the separation equipment normally required. As a further result of our new process, we may substantially consolidate the necessary reactor equipment with attending great savings in construotion, maintenance and operation cost, as will appear more clearly hereinafter.

' Having set forth the general nature and objects, the invention will be best understood from the subsequent more detailed description in which reference will be made to the accompanying drawing wherein Fig. 1 is a partly schematic and partly diagrammatic illustration of an apparatus for carrying out one embodiment of our invention; Fig. 2 illustrates in a similar manner suitable apparatus for carrying out the carbonization and gasiflcation of carbonaceous material in accordance with our invention;

Fig. 3 is a partly schematic and partly diagrammatic illustration of an apparatus for carrying out our invention in a single reactor; and

Fig. 4 is a similar illustration of another embodiment oi. our invention involving circulation of volatile and solid conversion products through a number of reaction zones in series.

Referring now in detail to Fig. 1, finely-divided carbonaceous solids which may be carbonization coal, tar sands, oil shale or the like and which for purposes of illustration will be hereinafter referred to as oil shale to be distilled in accordance with our invention, are supplied by any conventional means (not shown) to line i. Pressure hoppers, standpipes, both of which may be fluidized, mechanical conveyors or the like may be used for the purpose. The particle size of the solids may vary from less than 100 mesh up to A; or inch. The solids are preferably fluidized with a gas to facilitate the transport through line I. While air, steam or any inert gases may be used, flue gases recovered from the process and supplied through line 2 by means of blower 3 are preferred for this purpose. The finely-divided fresh shale passes from line i to the preheating zone 4 of an essentially cylindrical combined preheating and combustion vessel 5 which is divided into an upper preheating zone a and a lower combustion zone 8 by a horizontal foraminous member such as a grid or perforated plate I. The shale entering preheating zone 4 above grid '5' is maintained in zone 4 in the form of a dense turbulent suspension resembling a boiling liquid and having a well-defined upper level 9. Flue gases passing from combustion zone 3 upwardly through grid "1 and zone t, as will appear more clearly hereinafter, and, if desired, supplementary gas admitted through line 5, simultaneously fluidize and preheat the shale in zone 4 to the desired temperatures which for the present purpose may be controlled between the approximate limits of 300 and 700 F. Flue gases of considerably reduced temperature leave zone 3 through a conventional gas-solids separator is and line it which may be provided with cooler or waste heat boiler I la, either to be returned to the process through line 2 or to be withdrawn through line 52 for any other desired purpose. Separator H] may be of the centrifugal and/or electrical type. Solids separated therein may be returned through pipe I4 to the fluidized mass in zone i.

Preheated fluidized shale is withdrawn from zone A downwardly through an overflow pipe, such as a slotted well or standpipe l5, and passed to distillation chamber l7. If desired, the flow of the shale through pipe :5 may be facilitated by the addition of small amounts of fiuidizing gas, such as air, steam, flue gas or the like, through line I6. Chamber ll, which is essentially of cylindrical shape, is preferably provided with a conical bottom portion is separated from the cylindrical main section by a grid or other foraminous member is. The shale supplied by pipe I 5 forms above grid I 9 a dense fluidized mass of solids having a well defined upper level 20. A suitable fiuidizing gas may be supplied through line 2| and distributing grid is. The additional heat required to raise the temperature of the shale to the desired distillation temperature of, say, 800-1200 F. is preferably supplied in the form of sensible heat of solid combustion residues recirculated from zone 8 of vessel 6, as will appear hereinafter. A mixture of volatile distillation products and small amounts of fiuidizing gas is withdrawn from chamber I"! through conventional gas-solids separator 22 and line ,23 to a conventional shale oil processing plant (not shown). Solids separated in separator 22 may be returned through pipe 24 to the fluidized mass in chamber l7.

Solid fluidized carbonaceous distillation residue is withdrawn from a point above grid l9 downwardly through pipe 26 and passed to a dispersing chamber 28. If desired, the contents of pipe 2e, which may be designed as a standpipe, may be further fluidized by the addition of fiuidizing gas through line 21. An oxidizing gas, such as air, which may be preheated to any desired temperature, e. g., above the ignition temperature of the shale coke, preferably about 1000" F., in suitable heat exchange with highly heated spent or burned shale withdrawn from the system, as shown below, is supplied through line 29 to dispersing chamber 28. The suspension of coked shale in air thus formed having a lower density than that in standpipe 26 ispassed under the pseudo-hydrostatic pressure of the fluidized column in pipe 2% back to the lower zone 8 of vessel 6 via line 36. The suspension enters zone 8 through a distributing grid 3| above which it forms a dense fluidized mass of solids having an upper level 32. In

zone ii the carbonaceous constituents of the coked shale are subjected to combustion by means of the oxidizing gas in order to generate the heat required for the distillation of the-shale. By a proper adjustment of the oxygen supply to zone 8, the combustion may be so controlled as to establish any desired temperature from about 1000 to above 2000" F. in this combustion zone. Temperatures between 1000 and 1500 F. are sufiicient for the purpose of shale distillation. Higher temperatures may be used for other starting materials but are less desirable in the case of oil shale distillation because it is advisable to keep the temperature of the preheating zone t (which is a function of the combustion temperature in zone 8) below the temperature of beginning shale distillation in order to prevent desired volatile distillation products from leaving the system with the flue gases through lines H and I2.

Hot flue gases, together with any entrained solid combustion residues, .pass overhead from zone 8 through distributing grid 1 into preheating zone a. The flue gases maintain the fresh. shale in zone s in the desired turbulent fluidized state. A substantial portion of the sensible heat of the hot flue gases and entrain-ed hot solids is transferred in zone 4 to the fresh oil shale which is thus rapidly preheated to the desired sub-distillation temperature of about -3(l9-5G0 F. Low-temperature ilue gases leave zone 5 through separator It, as described above.

Solid fluidized combustion residue is withdrawn from zone 8 at a point above grid 3| through pipe 33 and passed substantially at the temperature of combustion zone 8, to distillation. chamber ll either directly or via pipe l'5, as shown in the drawing. The amount of burnt shale flowing through pipe 33 is so controlled that its sensible heat is sufficient to raise the temperature of the shale in chamber ill to the desired distillation temperature. While this amount depends, of course, on the temperature difierence between zone 8 and chamber H and on the oil content of the shale, it. may be said that operative circulating rates for many shales may vary in general between 0.5 and 2 lbs. of burnt shale supplied through pipe 33 per lb. of fresh shale supplied through pipe 15. A minor portion of burnt shale may be branched oif from pipe 31-; through draw-off pipe 34, passed through air preheater 35, and then withdrawn from the system through line 35. Air or any other suitable oxidizing gas may be fed through line 33 to preheater 35 and from there through line 38 into air feed line 29. If desired, further amounts of spent shale may be withdrawn from chamber ill through draw-on" line All and either directly discarded or used in a manner similar to that explained in connection with the burnt withdrawn through line 34.

The superficial velocity of the gases passed through the dense fluidized beds in zones 4 and d and chamber H is controlled to establish the desired bed density in cooperation with the gaseous reaction products formedin these zones. While this velocity depends largely on the particle size and density of the solids to be fluidized, it may vary in general between the approximate limits of 0.5 and ft. per second.

From the foregoing, it will be readily appreciated that the embodiment of our invention illustrated by Fig. 1 permits complete conversion of available carbonaceous material into volatile fuels and heat which is substantially completely utilized in the process itself. Only two gas-solids separators need be provided for three fluidized-solids treating zones. The number of separators may be reduced to one without detriment to the operation by eliminating separator H] in case the due gases are recycled through line 2 so that any entrained solids are continuously recirculated to vessel 6. Since the temperature in the preheating zone 4% depends entirely on the relative mass and specific heats of combustion gases and the mass and. specific heat of the solids, no heat exchange facilities are required in which the .efiiciency would be reduced due to the temperature difference between hot and cool materials required for satisfactory rates of heat exchange. The system of Fig. 1 permits of numerous modifications. For example, additional heat may be supplied to distillation chamber I! by feeding an oxidizing gas through line 2| to cause a partial combustion of carbonaceous substances within chamber ll. Also, chamber i! may be operated as a water gas or producer gas generator by supplying steam or a mixture of steam with oxygen and/or air through line 21 and adjusting the temperature in combustion zone 8 to a higher level which may range from about 14:00 to about 2580 Likewise, zone B of vessel '6 may be operated as a gas-generating zone of the type mentioned by supplying steam and oxidizing gas, either'simultaneou'sly or alternately through line 29 to zone 8 and maintaining a gasification temperature of about l600-2000 F. in zone 8. All these modiiications permit the realization of the operational advantages mentioned above. Additional ad vantages of operation and design will appear from the following description of the embodiments of our invention illustrated in Figs. 2 and 3.

Referring now in detail to Fig. 2, the system shown therein essentially comprises two superimposed substantially cylindrical vessels 2ti2 and 2 M which may be operated as carbonization and gas generation zones respectively, as will be presently explained. Finely-divided carbonizable solid material, such as a carbonization coal, of a particle size suitable for fiuidization is supplied by any conventional means, such asa standpipe, pressurized hopper, screw feeder or the like to carbonization vessel M2 by way of feed pipe 25H. The coal forms in vessel are above a horizontal grid 203 a dense, turbulent, ebullient mass with an upper level 2535 and is fluidized and heated 'to the desired carbonization temperature of about 800-1400 F. by means of flue gases and entrained solid gasification residue entering vessel 262 from gas generator 2M through pipe 2% and grid 203. A mixture of fuel gas, volatile carbonization products and entrained solids fines is withdrawn overhead and passed through line 2% to a conventional gas-solids separator 20?. Volatile products and gases substantially free of solids fines are passed from separator 23! through line 2% to conventional separation, purification and recovery systems (not shown). Solids fines separated in separator may be returned through lines 2% and 2th to the fluidized mass in carbonizer 2% or withdrawn and discarded through line 2 ll.

Solid fluidized carbonization residue, such coke, is withdrawn downwardly from carbonizer 202 at a point above grid 2% through a standpipe 212 and passed to the lower vessel 2 M which is equipped with a horizontal grid 2E5. Steam and an oxidizing gas, such as oxygen or air, is

admitted through line M at a point below grid 2! 5 at a superficial velocity sufficient to maintain the finely-divided coke in vessel 2H4 in the form of a dense, turbulent, ebullient mass having an upper level 2l ia. The absolute and relative proportions of steam and oxygen supplied are so controlled that sufiicient heat is generated by combustion of coke to support the conversion of a substantial portion of the available carbonaceous material into CO and H2 by means of the steam. While these amounts may vary within wide limits, depending on the type of solid fuels charged, good results may in general be obtained when 8 to 12 cu. ft. of oxygen and .4 to .7 lb. of dry steam are supplied per lb. of carbonizable solid material charged. Gasification temperatures may vary between the approximate limits of 1500 and 2000 F. and are preferably maintained between about 1600" and 1800 F. Oxygen or air enriched with oxygen is preferably used for production of water gas or feed gas for the synthesis of hydrocarbons from C0 and H2, while air may be used for the production of producer gas. Steam and oxidizing gas may be supplied simultaneously or alternately in a make and blow fashion. Particularly during the starting period, the steam and/or oxidizing gas may be preheated in any desired manner.

Fuel gases and entrained solid gasification residue pass overhead through pipe 204 into carbonizer 202, as outlined above. Solid gasification residue which may be substantially free of carbon is withdrawn from gas generator 2M at a point above grid 295 through line 2|"! and passed to heater 213 where it may be used to preheat steam and/or oxidizing gas supplied through line 213 and passed through lines 229 and 2l6 to gas generator 214. Solid gasification residue of considerably reduced temperature is withdrawn from the system through line 22!.

Aside from full utilization of the high-temperature heat generated in the system for the desired conversion in the form of sensible heat of solids and product gases, the system illustrated in Fig. 2 makes it possible to conduct three conversion reactions, that is, carbonization, gas generation and combustion in two fluidized reaction zones equipped with only one gas-solids separation system. A further advantage resides in the fact that the fuel gases produced in zone 2 [4 are enriched in zone 202 with high B. t. u. hydrocarbon gases. The operation of the system may be further improved by branching off part of the hot gas-solids mixture from pipe 204 and bypassing it through line 222 to line 206 ahead of separator 20?. In this manner sensible heat of the gas-solids mixture is utilized to prevent undesired condensation of tar in the separator .207 and subsequent recovery equipment. If desired, the ash content of the fluidized mass in gas generator 2|4 may be considerably reduced by withdrawing solids through line 223 and passing the same admixed with steam or product gases from the process from line 224 to elutriator 225 where the small ash particles having a relatively high specific gravity may be separated by elutriation from the expanded and relatively light coke particles. Ash may be discarded through line 220 and coke returned to gas generator 2i4 through line 227. It may also be advisable to add a fluidizing gas, such as air, steam, etc., to standpipes 2l2 and 2H through lines 2l2a and Mia, respectively, to facilitate the flow of solids through the pipes.

The operation of the system shown in Fig. 2 may be further modified by circulating volatile carbonization products from zone 202 through line 230 provided with blower 232 and line 2l6 to the bottom of generator 2M so that the normally liquid hydrocarbons produced in zone 202 are cracked and converted into additional amounts of CO, H2 and gaseous hydrocarbons in generator 2 M. In this case zone 202 may be operated at a temperature of about 1200 to 1800 F. and generator 214 at about 1400" to 2200 F. If desired, valve 23! in pipe 204 may be closed and product gas withdrawn from generator 2l4 through line 233; an oxidizing gas, such as air and/or oxygen, if desired, together with steam may be supplied to zone 202 through line 234 in order to generate the heat required for carbonization by partial combustion and to provide proper fluidization in zone 202. No gas-solids separator is required to separate fines entrained in the hydrocarbon vapors leaving zone 202 through line 230 and the heat generated in zone 202 is fully recovered by circulating vaporous and solid products from zone 202 substantially at the temperature of said zone to generator 2l4.

A further embodiment of our invention affording still greater economies of design and operation is illustrated in Fig. 3. The apparatus of Fig. 3 consists essentially of a single substantially cylindrical vessel 30l which is subdivided by a horizontal plate 302 and a horizontal grid 303 into an upper preheating zone 304, a lower reaction zone 305 and. an intermediate reaction zone 305. When used for the carbonization of carbonizable material, such as oil shale or the like, finely-divided solid starting material of fluidizable particle size is fed through line 301 to the upper preheating zone 304. Standpipes, hoppers, screw feeders, redlers or the like may be used to pass the solids feed through line 301. The finely-divided material forms above grid 303 a dense, turbulent, ebullient mass having an upper level L4, maintained in this state of fiuidization and preheated to temperatures of about 300-500 F. by hot gases and entrained solids fines passing upwardly from zone 306 through grid 303, as will appear hereinafter. Gases and entrained solids fines are withdrawn overhead and separated in conventional separator 300. Separated solids fines are returned through pipe 3 I 0 or 3 l 011 to the fluidized mass. Pipe 3 l 0a leads directly into solids draw-off pipe 3M to prevent undesired accumulation of fines in zone 304. Low-temperature gases substantially free of solids are withdrawn through line 3!! to be used either for further heat recovery or fluidization in the system by way of lines 3I2 and 3|3 provided with blowers 3l2a and 3l3a, respectively; or for any other purpose.

Preheated fluidized shale is withdrawn downwardly from zone 304 at a point above grid 303 through standpipe 3l4 which is preferably provided with a vertical slot 3| 5 extending over a substantial portion of the depth of the fluidized mass in zone 304 and with a control valve 3H5. The lower portion of standpipe 3; extending deep into the lower reaction zone 305 is provided with a vertical perforated section or grid 3!! through which the preheated shale may enter zone 305. A fluidizing gas, preferably flue gas from lines 3| 1 and 3E2, may be admitted through line 3I8 and/or 3 [9 to aid in the fiow of the shale into zone 305 and establish a dense mass of fluidized shale therein having an upper level L5. Any other desired fluidizing gas, for example steam, may be admitted to zone 305 through line 320.

The shale is subjectedin zone 305 to carbonization conditions of temperature and residence time. The heat required'to establish thetemperature level of about 300-1200 F. required-for carbonization is supplied in the form of sensible heat ofhighly'heated solids circulated from zone 395, as will be explained hereinafter. Volatile carbonizationproducts and entrained solidsfines are withdrawn overheadland passed through a conventionalgas-solids separator 32! from which volatile products pass through pipe 322 to' a conventional recovery plant (not shown). Separated solids fines are returned to zone 335 through pipe 323 which preferably leads directly into solids draw-off pipe 324 to prevent accumulation of solids fines in zone 305.

Fluidized shale coke is withdrawn downwardly from carbonization or retorting zone 305 preferably at a point above. grid 3|! through standpipe 324, which may be further fluidized through line 325 with steam, air, flue gas-orthe like. The fluidized coke passes to dispersing chamber 326 in which it is suspended in an oxidizing gas, preferably air, supplied through line 321. The air may be preheated in heater 329 to any desired temperature between 800 and 1200" F. by spent shale branched off from pipe 324 through pipe 323. Fresh air may be supplied through lines 333 and 331. Spent shale is withdrawn from the system through line 332. Steam or any other diluting gas may be added to the air, if desired.

The suspension of shale coke in air is passed underthe pressure of the fluidized solidscolumn in pipe 323 through 1ine333 to the intermediate reaction zone 336 preferably by way of a perforated bottom plate 334. A dense fluidized mass of shale coke is formed in zone 306 having an upper lovel L6. The shale coke is subjected in zone 306 to combustion to establisha temperature level in the combustion zone of from about 1000 to about 1500" F. The desired temperature level may be adjusted by a suitablecontrol of the air supply as outlined in connection with combustion zone 8 of Fig. 1. Hot flue gases with entrained solids pass overhead through grid 333 into preheatin zone 304 as described above.

Solid fluidized combustion residue is withdrawn downwardly'from zone 356 through standpipe 335 which may be substantially of the same design as standpipe 3l4, having an upper vertical slot 333, a control valve 33'! and a lower'vertical grid 333. r The lowerend of'standpipe 335 extends deep into-retorting zone-305. Hot combustion residue substantially at the temperature of zone 333 flows from standpipe 335 through grid 333 into the fluidized shale in zone 305 in amounts sufiicient to supply the heat required for carbonization. lhe flow of the solids through standpipe 335 and grid 330 may be facilitated by a fluidizing gas such as flue gas from lines 3H and 313 or any other fluidizing gas supplied through lines 339 and 340.

The embodiment of our invention last described permits the consolidation of three different fluidized reaction zones into one integral reaction vessel with attending considerable savings in construction materials. Aside from the fact that only one reaction vessel is required, the number of standpipes and gas-solids separation zones is kept at a minimum. While two separators are shown in the drawing, separator 309 may be of any inexpensive low-'efficiency design or be entirely omitted when the-off-gases are recirculated to the system through lines 3|2 this case.

through lines 3 l9 and 339.

-communicating through standpipes.

1 M6, as will appear hereinafter.

and/or3 1 3, so that onlyione separator is required for the "three'reaction zones. Full recovery of the heatgenerated for the purposes of'the process is accomplished without special heat-exchanging "means by utilization of the sensible heat of both solid and gaseous reaction products in the process. The system permits of numerous variations and modifications. Solid carbonization residue from line 333 and/or spent shale from line3i-8 may be circulated to the reto'rting zone 305 and/or preheating zone 304. Other 'carboni'zable materials, such as coal, tar sands, peator the like, may be used. Fuel gases comprising CO and H2, such as water gas "or producer gas, may beproduced by raising the temperaturein combustion zone 306 aboveabout 1600 1. by' means of an increased air supply, operating zone 3'34 as a retorting zone heated by thehotter flue gases and fines from combustion zone/306 and supplying steam and an oxi- 'dizinggas to zone 3B5 toconvert the coke therein-into the desired fuel gas. For the same purpose coke maybe fed to zone 304 which is then operated asazpreheating 'zone for a gas generation\zone=335. The r-elativeposition of the reaction zoneswithinvessel 33! may also be altered so as to reverse oi otherwise change the temperature gradients between the superimposed zones by a suitable change in the flow of solid and gaseous reaction products. For example,

zone 366 maybe operated as agasgeneration zone'zone 304 as acarbonization zone and zone 4335 as a combustion' zone by supplying steam and oxidizinggas to zone/ 306, air to zone 305 and .fuel

:gasfromzone3t3to zone 304 to supply 'heat for retorting while solids :are circulated from zone 304 to zone 305, from zone 306 to zone 305 and from there'back to'zone 303 and/or 304 for'heat supply. Fuel gases enriched with gaseous hydrocarbons may be recovered from line 3!! in On the other hand, .zone 306 may be operated as a combustion zone, zone 334 as a carbonization or retorting zone and zone 335 as a gas-generating zone by supplying steam In this case volatile carbonization products and entrained fines may bereturned through lines-312 and/or3l3 to zone 335and normally'liquid'hydrocarbons may be cracked and converted therein to additional amounts offuel. gas. The proportion of gaseous and solid reactants, gas velocities and circulation rates of solids and gases are similar to'thosc indicated in connection with Figs. 1 and 2.

A still further modification of our invention which permits utilization of heat generated in our processfor metallurgical or other preferably exothermic chemical processes, particularly reduction processes, is illustrated in Fig. 4 which shows a system consisting essentially of a coal zones 434 fluidized and preheated by hot fuel gas supplied from gas generator 432 through line Fluidized coal flows downwardly through preheater 332 from zone to zone in countercurrent with hot fuel gas .and .is thus gradually dried and preheated to temperatures of about 400-700 F. Low-tem- 11 perature fuel gas which may be producer or water gas is withdrawn overhead through separator it? and line 408 for any desired use.

Coal preheated to temperatures of about 400- 700 F. is withdrawn from the lowest zone through standpipe 4H1, passed to dispersing chamber M2 where it is taken up by a fluidizing gas such as steam, fiue gas or the like from line ill and passed through line 454 into the lower section of carbonizer M6 which it enters through a horizontal grid M5 to form a dense, fluidized mass therein. Heat for carbonization is supplied as sensible heat of solid gasification residue circulated from gas generator 432 through line All to line ll l or, if desired, directly to carbonizer H6, as will appear hereinafter. Additional heat may be supplied by hot reduction zone off-gases or fuel gases from gas generator 432 branched off from line s06 through line H9. The temperature in carbonizer M6 may vary between about 900 nd 1400 F., depending on the carbonizable material used. Volatile carbonization products and gases pass overhead through separator 122s and line 42! and may flow through either line 422 to a conventional recovery system (not shown) or through line s23 to line 398 to enrich the fuel gas therein.

Hot fluidized coke is withdrawn downwardly through standpipe 425 taken up in dispersing chamber 526 by an oxidizing gas and steam supplied through GZSa, and passed through lines 421 and 328 into the lower portion of gas generator M2 by way of grid iBI. Additional steam and/ or oxidizing gas may be supplied through line 439. The coke in gas generator 432 is subjected, in the form of a dense fluidized mass, to a gasgenerating reaction with steam, sufficient heat being supplied from a partial combustion with oxygen to establish a temperature level of between about l500 and 2000 F. Solid fluidized gasification residue is withdrawn downwardly through standpipe Q33 and returned through dispersing chamber 535 and line 457 to carbonizer M8. A fiuidizing gas, such as steam or flue gas, may be added to chamber 435 through line :iB'l to facilitate the circulation of the solids.

Fuel gases comprising CO and H2 are withdrawn overhead, if desired through separator 38, to deposit and return solids fines, and then passed through line 339 to the bottom portion of the vertical ore reduction zone 449 which is of a similar design as preheating zone M2, having subdividing horizontal grids 4M and connecting standpipes M2. A side stream of hot fuel gas may be returned vthrough lines 439a, 4% and M9 to preheating zone 4632 and/or carbonizer M6. Finely-divided metal ore of fiuidizable particle size and reducible by hot reducing gases, such as iron ores and other oxidic metal ores, is supplied through line 443 to form dense, turbulent beds above grids Mil, fluidized by the upwardly flowing stream of hot fuel gas. The ore flowing downwardly through standpipes M2 in countercurrent to the reducing fuel gas is gradually and increasingly reduced to metal or metal concentrate which is withdrawn through pipe M5 for further processing. It will be appreciated that the solids fines entrained in the fuel gases leaving the fluidized bed of gas generator 432 may still contain considerable proportions of coke which may assist in the reduction of ore in zone are. Separator s38 may therefore be omitted in many cases.

' Reduction zone off-gases containing steam, CO2, unreacted H2, as well as unreacted and newly formed CO together with impurities and entrained ore fines, pass overhead through gassolids separator 441 and lines 448 and 449 to be returned through line 496 to preheater 402 and/or carbonizer 4H5 substantially at the temperature of the top of the ore preheating zone Ml, which may vary within the wide limits of 300 and 800 F., depending on the ore treated. If desired, portion of the gases in line 443 may be combined via line 450 with the fuel gases in line 408.

It will be understood that the system illustrated in Fig. 4 may be readily modified by incorporating many of the specific features described in connection with Figs. 1, 2 and 3. For example, a separate combustion zone or heater may be provided to supply the heat required in the process in the form of sensible heat of solid combustion residues or hot flue gases. Zones 482, M6 and 632 may be combined in one or two reaction vessels similar to the systems of Figs. 1, 2 and 3. Also, an oxidizing gas may be supplied to carbonizer M5 to supply additional heat by partial combustion therein. Hot fuel gases, coke, and/or volatile carbonization products recovered from the process may be used to fire steam boilers or the like to produce steam useful in the process or for other purposes such as distillation of liquid and liquefiable products of the process. Feed rates of gaseous and solid reactants, circulation rates of heat-carrying gases and solids and gas velocities are similar to those indicated in connection with Figs. 1, 2 and 3. Preheating means may be provided for solids and gaseous feed materials,.l articularly for the purpose of starting up the process.

It will be appreciated that all embodiments of our invention described above accomplish the desired full recovery of heat generated for purposes of the process which thus becomes selfsupporting with respect to heat balance and which may be made fully continuous by sup-plying the reactants and withdrawing the reaction products in a continuous manner. The process may be readily adapted to the conversion of heavy oilv residues as carbonaceous starting material by injecting the heavy residues in any of the systems illustrated into the carbonization or retorting zone, which for this purpose may be supplied with a dense fluidized bed of finely-divided inert solid material on which the coke formed is deposited to be thereafter treated as described above. The apparatus of the present process is all constructed for operation at relatively low pressures which may range from slightly subatmospheric pressures to about 150 lbs. per sq. in., pressures ranging from 25 to 125 lbs. per sq. in. being preferred for the carbon conversion zones. However, high temperatures are required especially in the combustion and gas generating zones and in the associated pipes. The equipment should be lined with high-temperature tile or brick and it is found that there need be little wear if the velocity of the fluidized stream is kept down in the range of 25 to ft. per second.

Ourinvention will be further illustrated by the following specific example.

Example A typical Pittsburgh seam coal ground so that about 2% of the coal remains on a 50 mesh sieve is continuously fed to a system of the type illus- 'trated by Fig. 2 and treated therein to produce water gas and coal tar at operating conditions as follows:

Coal feed rate 15-20 lbs/sq. ft. of

reactor space/hr. Pressure 30 lbs/sq. in. gauge. Oxygen feed rate 8 cu. ft./lb. of coal. Steam feed rate 15 lbs/lb. of coal. Temperatures Carbonization zone 1000 F. Gasification zone 1500 F.

Solids circulation rate from carbonization zone to gasification zone. 2 lbs/lb. of coal fed.

At these conditions the product yields per ton of coal amount to about 30 gal. of coal tar and 54,000 cu. ft. of water gas, the latter having a composition as follows:

Per cent CO2 4.0

CO 62.0 111. 1.0 CH4 2.0

C'zHs 1.0 Hz 29.0 N2 1.0

into at least three treating zones, at least one of said horizontal plates being perforate and at least one of said horizontal plates being imperforate, one of said imperforate plates separating the lowermost treating zone from an intermediate treating zone a conduit for introducing finely divided solids into the uppermost treating zone, a conduit for withdrawing finely divided fluidized solids disposed in the lowermost of said treating zones, a conduit disposed in a lower portion of the lowermost treating zone for introducing thereto gasiform material, a standpipe for conveying finely divided solids from the uppermost treating zone into the lowermost treating zone, a second standpipe for conveying solids from the intermediate treating zone to the lowermost treating zone, conduit means for conveying solids from the lowermost treating zone to said intermediate treating zone, means for injecting gas into said last-named conduit means in the direction of solids flow therein means for withdrawing volatile material from the uppermost treating zone, conduit means for recycling a portion of the withdrawn volatile material to the lowermost zone and conduit means for withdrawing volatile material from said lowermost zone.

BRUNO E. ROETHELI. CHARLES E. HEMMINTGER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,414,883 Martin Jan. 28, 1947 2,425,849 Voorhees Aug. 19, 1947 2,429,721 Jahnig Oct. :28, 1947

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