US2579398A

US2579398A - Method for handling fuels

Info

Publication number: US2579398A
Application number: US609662A
Authority: US
Inventors: Bruno E Roetheli
Original assignee: Standard Oil Development Co
Current assignee: Standard Oil Development Co
Priority date: 1945-08-08
Filing date: 1945-08-08
Publication date: 1951-12-18
Anticipated expiration: 1968-12-18

Description

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OurLET Asn Brano E. Roetlzelz.' 51m/enter bgg@- Obborneq Patented Dec. 18, 19.51

METHOD FOR HANDLING FUELS Bruno E. Roetheli, Cranford, N. JL, assigner to -Standard Oil `ration of Delaware' 'Development Company, a corpo- `Applicxlition August 8, 1945, Serial No. 609,662

TheA present invention relates to an improved process: for the efficient utilization of carbonaceous solid material, such as coal, coke, peat, tar sands, oil shales, and the like, and more specifically to a process for converting such materials into more valuable products including fuel gases.

It has beenlong known and appreciated that solid fuel materials, suchl as.coke,.coal, and the like, could beconverted into more valuable gaseons fuels which can be more elciently used in vthis form. vProducer' and water gas processes are familiar to. all, but neither of these processes is entirely satisfactory because the first mentioned produces. a, low caloric fuel, and because the second has heretofore required a discontinuous type of operation. Low temperature carbonization is also known to,4 have many advantages, but it is diflicult to carry out mechanically. The present process may be .used for producing in a contin- Vruous manner valuable fuel gas of high caloriiic valueincluding gas mixiiiiresl useful in the production of synthetic hydrcarbons by the catalytic conversion of carbon monoxide with hydrogen,

. and it. can be-v employed for carrying out the carsame timein a mechanision zones.

It is an object of my present invention to provide means by which the heat required in the carbonization and/or gasification zones is generated by 'the combustion of portions of the carbonaceous materials and supplied to these zones eitherl by the circulation of iluidized solids highly heated by the heat of combustion or directly by partial combustion in the zones to be heated, or

both.

f My new process affords substantial savings in capital investment and operating cost, as well as full and easy adaptability to changes in the character of the starting materials and/or the properties of the desired products. These and other advantages will be fully understood from the following description and the drawing.

The drawingin Fig. 1 is a semi-diagrammatic view in sectional elevation of an apparatus for carrying out the present process and indicates the flow of the materials.

Fig. 2 is a semi-diagrammatic view in sectional elevation of an apparatus for carrying outthe present process when applied tothe production of fuel gas only.

Fig. 3 is a diagrammatic lflow plan showing a modification of the plan of Fig. 1.

Fig. 4 is a semi-diagrammatic view in sectional elevation of an apparatus for carrying out the present process in separate carbonization, gasification and combustion zones.

Fig. 5 is a diagrammatic ow plan showing a modification of the plan of Fig. 4. y

Referring to Fig. 1, numeral i denotes the crusher or pulverizer which is employed to reduce a solid carbonaceous fuel to a finely divided form, for example, preferably of the order of below 50 mesh, or even less than 100 mesh, although even small lumps, say 1A to 1/2 size, may be used. For the purposes of the following description, the material will be referred to as carbonization coal,`

but it will be understood that other materials can beused. The finely ground coal drops from the crusher into a dispersing chamber 2, wherein it is thoroughly dispersed in a stream of an aeration gas. such as superheated steam, nitrogen, combustion gases, etc., which is added by pipe 3. The coal in the dispersion is said to be in a fluidized" form because in thisform it is capable of flowing through pipes, valves, ducts and such equipment much like a liquid, showing both static and dynamic heads. The uidized stream is passed through pipe 4 into the lower portion of a carbonization chamber 5 which is in the form of a cylinder fitted at its lower end with a conical base 6 torwhich an oxidizing gas, such as air and/or oxygen, may be admitted through line 6'. A grid or screen is located in the lower portion of the chamber conveniently at the place where the cone and cylinder unite.

An elongated vertical pipe "l, preferably opening above the grid or screen, is provided to carry a iluidized stream of solids from the carbonization chamber 5 and the stream is then conducted by the vertical pipe 8 into a gasification chamber 9, whichis similar to chamber 5. An oxidizing gas, such as air and/or oxygen. is added to the withdrawn stream of the fluidized solid at l0 and causes the flow of the stream, as will be explained below. up into the chamber 9 where steam is added through line 9' and rapid gasification takes place to form carbon oxides and hydrogen. The

heat required for the endothermic gasification re- 3 action with steam is supplied by the combustion of a portion of the carbonaceous solids in chamber I by the oxidizing gas admitted through line Il. Additional air and/or owgen may be added to the chamber through pipe I' asindicatedin the drawing. The total supply of oxidizing gas is care--V highly heated material from the gasification chamber l, which is at a temperature of.`say, 14:00 to 2500 F., is continuously recycled 'to the carbonization chamber i. This chamber is at the usual carbonizing temperature of,'say, 1000 to 2200' F. and the preheat and heat of carbonization may thus be substantially completely furnished by heat supplied from the gasiilcation chamber. f

Vapors are withdrawn from the carbonization chamber i by a pipe l2 through cooler Il and than to any suitable means for recovery of the coal distillation products. Cooler I3 may be o f the indirect type shown or the direct type. as desired. The recovery system (not shown) need not be described in detail because such systems are well known in the art, but should provide means for segregating the dust, ammonia and fuel gas.

Fuel gases, such as water gas, are taken from the chamber I by a pipe Il which leads to a dust separator I5 and to a waste heat boiler I0 for steam generation. The separated dust may be returned to the chamber l by'a pipe l1. The gas nay be treated in any usual manner for the removal of sulfur or other impurities, in equipment not shown, making it suitable for use as city gas or otherwise. If desired, the whole or a portion of admixed with the water gas. y

A iluidized stream of solids which is now largely free from carbon is withdrawn by pipe I I' from the sas generator v9 'and can be discharged into tar, light oils.`

. 4 ization chamber l, with the supplied by the recirculated result that the heat solids is insuillcient to satisfy completely the heat requirements of the carbonization zone, an oxidizing sas, such vas and/or oxygen. may be introduced line t' into the lower cone l of carbonization chamber i. The amount of oxidizing ses tlills introduced is carefully controlled tc supply lust suillcient heat by combustion of carbonaceous material to supplement the heat supplied by the recirculated solids so as to maintain the desired carbonization temperature. Ifcoalisusedasthe'rawmateriahitism'eferably fed directly to the carbonization chamber and heat for the carbonization is supplied by a ,stream of highly heated solids flowing continf the gas resulting from coal carbonization may be v u desired amount of inert solid.

uously fromthe gasification chamber through the pipe Il anddlscharglngintothechamber I. The temperature is capable of very careful regulation and control, and ls distributed rapidly through the fiuidized mass in the carbonization chamber because of the high degree of agitation maintained therein. Chamber l is sufllciently large to permit complete carbonization and the solids removed by pipe 1 are substantially free of volatile materials and are capable of rapid gasification with steam and air in the gas generation chamber l. If desired. an inert materialsuch as sand may be added to the coal and circulated through the chambers l and l and the associated pipes 1. l and Il, so as to provide-a larger volume of heat-Carrying solid material, but this is ordinarily Vnot required as the ash content of the coal may be allowed to accumulate andthus furnish any High ash coals may thus be employed in the process.

It is important in this operation not to reach a temperature such that the solid is caused to sinter or melt, and if the ash content of the coal employed has a tendency in this direction. other materials such as alumina, lime, coal having an ash of higher fusion point, and

t the like, may be added to raise the melting point the 24 which is blown with steam ady mlttedby' pipefzs.- steam is then withdrawn by pipe-l' ina` highly'leatedf'conditlon useful for the generation'bf the'watergaa A .portion of the iluidi'zedsolid;is`- from the superheating chamber 24 by a pipe 2i and may be returnedto pipe 4 to add preheat to the charge of chamberr i. Another portion is discharged through 26 at 21 to prevent accumulation of non-carbonaceous materials in the system.

'Ihe system described above is a very flexible one. capable of many modes of operation. lnfit there are two main chambers or zones; the rst for carbonization, and the second for combustion and water gas generation. The gasification zone is operated at the most elevated temperature and high temperature heat is generated therein by combustion which is utilized for the carbonization and gas generation, which processes require lower temperatures. Excess heat generated in the gas generation chamber is carried from this chamber to -the carbonization chamber by the continuously owing streams of uidized solid. I'hus the process is made fully continuous.

If it is desired to conduct the gas generation reaction at lower temperatures, for instance in order to modify the composition of the fuel gases produced, or if it is desired to reduce the amounts of hot solids recirculated from the sas generation chamber 9 through lines Il and/or y20 to carbonofthe ash so that the operation may befcon.-

ducted eillciently, even where the ash is of relatively low melting point. The choice and quantity of these ash-modifying materials depend on the character of the low fusion point ash.

It is desirable in most cases to operate the -water gas generator along with the carbonizer asdescribed; In most cases there is heat available in the combustion of the solid involatile Dortion of the coal in excess of that required for the carbonization reaction and the gas produced with the excess carbon in this manner is therefore of low cost. y

If it is desired to convert the carbonaceous starting material` predominantly into fuel gas,y `my process may be operated in a cycle comprising' a combustion zone and a gasification zone with the feed of vthe starting material tothe gasicatlon zone. as willbe more clearly understood from the following description in connection with Fig. 2 of the drawing,

According to this modification, as shown in Fig. vil, solid carbonaceous material, lsuch as coal. shale, tar sands, and the like, or solid carbonization products thereof in finely divided form, is fed from hopper 20| into line 202 where it is iluidized with steam or a similar aerating gas as outlined before. The uidized material is introduced into line 2l I wherein it is mixed with hot residue having a temperature of about 1600 F. or higher, withdrawn from combustion zone 209 and iluidized with steam and/or an oxidizthrough line 220 and further treated as A ing gas, such as air or oxygen, as will appear more clearly hereinafter. .The mixture Inow having a somewhatl reduced temperature enters gasification zone 2|8 wherein it is maintained in a uidized state at temperatures of about 1400 to 2200 F. tocause reaction between the carbonaceous material and steam to form water gas. The heat required for the reaction is furnished substantially by the heat of the hot residue'recycled from combustion zone 209. Any additional heat required may be supplied by partial combustion of carboneous material with the aid of an oxidizing gas, such as air or oxygen, supplied as carrier gas through line 2|| or separately through line 225. If desired, additional steam may be added through line 225; this steam and/or oxidizing gas may the aid of waste heat recovered from products from zone 209 or 2|8 in a manner known per se. Fuel gas, such as water gas, is withdrawn outlined in connection with line |4 of Fig. 1.

Fluidized carbonaceous residue is Withdrawn through line 226 further fluidized with an oxidizing gas, preferably air, introduced through lines 221 and 221-a and carried under the pressure of standpipe 225 and the gas pressure in 221 into combustion zone 209 wherein it is maintained in aiiuidized condition and subjected to at least partial combustion at temperatures of about 1600 to 2400 F. Additional air or'other oxidizing gas may be supplied for this purpose through line k209'. Solid combustion residue, which may be practically carbonfree ashes, is withdrawn through standpipe 2|| aerated through lines 203 and 203-a withsteam and/or an oxidizing gas and fed to the gasification chamber 2|8, as outlined above. 4

Where carbonizable starting materials, such as coal, are used in this embodiment of my invention, the reaction in chamber 2|8 may be conducted alternatively or alternately as a carbonie zation reaction as outlined in connection with chamber 5 of Fig. l. In this case solid fluidized carbonization residue from chamber 2|8 may be fed to the combustion zone 209 and the process further carriedl out as described above.

In Fig. 3 there is a flow plan illustrating a method which is particularly applicable to the working up of solid carbonaceousl materials, such as are disclosed in Fig. l, particularly coal, peat, shale, tar sands and the'like. The apparatus employedvis closely similar to that shown inl Fig. 1, but the flow plan herein contained is more complete in some respects.

The raw material in finely divided form enters at 330, passing directly to the low temperature carbonization step indicated at 33|. Distillation products are removed from 33| and are separated into gaseous and liquid products in the separation equipment indicated generally at 332.

The coky residue produced as a result of the carbonization is conducted to the gas generation stage of the process indicated at 331 where steam and air are also introduced. The'gases are taken oi at 340 and the hot residue at 335. A portion of this residue is returned to the carbonization stage 33| as indicated by the line 336 in order to carry heat for carbonization, as explained previously. Ash constituents of the original fuel are collected and drawn oil at 339. The gas, which is largely CO and hydrogen is taken off at 340 and a portion of this may be drawn 0E for heating or other purposes at 34|. To

from chamber 209 be superheated with the 'Il through a catalytic remainder of the gas an additional quantity of steam is added at 342 and the mixture is passed conversion step 343 wherein carbon monoxide is converted with steam 'to carbon dioxide.

The gas which remains is compressed at 344 and carbon dioxide is separated at 345. ,The remaining gas, which is substantially pure hydrogen, is then employed for the hydrogenation of the liquid distillation products lproduced from the original carbonization. This is accomplished in the hydrogenation step indicated at 346. e

It will be understood ythat the carbonization and the water-gas generation stages are conducted just as indicated in the previous description of Fig. 1, that is to say while the solid material is in a. fluidized condition. The conversion of the CO toCOz and hydrogen by means of steam is preferably effected catalytically, using as a catalyst iron oxide or iron oxide promoted with chromium and similar materials which are well known in the art. The conversion is effected at a temperature of the order of 850 F. and low pressure is lordinarily employed.

The hydrogenation step may be any one of a number of dierent types which are well known in the art. For example, it may be carried out under mild hydrogenation conditions. that is to say at relatively low temperatures and pressures so that the hydrogen does little more than to effect a, purication by removal of sulfur, nitrogen and similar elements. On the other hand, the hydrogenation may be carried out under destructive conditions, that is to say at pressures above 20 atmospheres andpreferably at about 200 atmospheres and at temperatures say from '100 to 1100" F. In this way the tarry materials are converted fully into lower boiling liquids rich in hydrogen. In these various hydrogenation procedures, the preferred catalysts are of the sulfur immune type, especially those containing metals, oxides or suldes of the 6th group of the periodic table, either alone or in admixture with each other or with diicultly reducible oxides, such as alumina, zirconia, magnesia or lime. More readily reducible oxides, such as zinc oxide, can also be added to the catalyst mixtures.

In the modification of my process illustrated in Fig. 4 the heat required in the carbonization and gasification zones, described in connection with Fig. 1, may be generated in a separate combustion zone. Referring now to Fig. 4, numeral 40| denotes the crusher or pulverizer forA the solid carbonaceous fuel. The finely ground coal drops from the crusher into dispersing chamber 402, wherein itis thoroughly dispersed in a stream of steam, which is added by pipe 403. The coal in the dispersion is in a fluidizedform and is passed through pipe 404 into the lower portion of a carbonization chamber 405 which is similar in construction and operation to chamber 5 of Fig. 1;

An elongated vertical pipe 401, preferably opening above the grid or screen, is provided to carry a uidi'zed stream of solids from the carbonization chamber 405 and the stream is then conducted by the vertical pipe 408 into a combustion chamber 409, which is similar to chamber 405. Air is added to the withdrawn stream of the uidized solid at 4l0 and causes the flow of the stream, as will be explained below, up in the chamber 409 where rapid combustion takes place. Additional air may be added to the chamber by pipe 409'.

A discharge pipe 4|| takes a stream of the atrasos chamber 400 and discharges it into chamber 400 so that the highly heated material from the combustion chamber 400, having a temperature of say 1600 to 2400" F., is continuously recycled to the carbonization chamber 40|, maintained at about 1000 to 2200 F. The preheat and heat of carbonization is thus substantially completely furnished by heat supplied from the combustion chamber.

Product vaporsare withdrawn from the car- 4|! and thence passed to any suitable system for the recovery of coal distillation products.

Pipe 4| l', which is shown as a branch of pipe 4| l, is provided to draw oft a portion of the bonization chamber 400 by a pipe. 4|2 cooled at highly heated fluidized contents of chamber 40! and to conduct it to a gas generator 4|.. This generator is shown as a vertical cylindrical vessel with a conical base, similar to chambers 400 and 400 described above, and it is preferably provided with a screen at its lower portion to act as a distributor. The iluidized solid stream is discharged into the chamber, preferably below the screen as described above, and steam preferably superheated is added by a pipe 4|9. The

generator is maintained at a temperature be' tween about 1400 and 2500 F., suitable for the rapid reaction of carbon and steam to produce water gas.

Gas is withdrawn continuously by a pipe,420 to a dust separator 42| and to a cooler 422. Thereafter the gas may be treated as indicated in connection with Fig. l.

A iluidized stream of solids which is now largely free from carbon is withdrawn by pipe 423 from the gasv generator 4|8 and can be discharged into the chamber 424 which is blown with steam admitted by pipe 425 and is then withdrawn by pipe 4I9 in a highly heated condition desirable for the generation o f the water gas. A portion of the iuidized solid is taken from the superheating chamber 424 by a pipe 426 and may be returned to pipe 408 for recirculation to the combustion chamber v409. lA small portion is discharged at 421 to prevent accumulation of inert solids in the system. v

In the system last described there are three main chambers or zones: the iirst for carbon'- ization, the second for combustion and the third for water gas generation, but all three need notA be used simultaneously. In any case. the combustion zone is operated at the most elevated temperature and is used to generate high temperature heat which is utilized for iluid fuel production either by the carbonization of carbonaceous materials or by gas generation, which processes are operated at lower temperatures. Heat is carried from the combustion chamber to the carbonization and/or gas generation chambers by the continuously flowing streams of fiuidized solid. 'Thus the process is made fully continuous.

I! coal is used as the raw material, it is preferably fedy directly to the carbonization chamber and heat for the carbonization is supplied by a stream of highly heated carbon flowing continuously from the combustion chamber through the pipe 4|| and discharging into the chamber 400. The solids removed by pipe 401 are substanvthe associated pipes 401, 400 and 4| I, so as to provide a larger volume of heat-carrying solid material. but instead the ash content of the coal may be allowed to accumulate and thus furnish any desired amount of inert solid.

If the process is operated using coke instead of a carbonization coal as the raw material, there is no carbonization and the coke dust is fed directly into pipe 400 and the valves in pipes 404 and 4|| willbe closed. Inthis casethei'iuidized stream of coke is supplied to pipe 400 through the pipe 400' into chamber 400, thence by ypipe 4| I into chambers 4I! and 424. The same modiilcation may be applied to the direct gasication of suitable coals or the like. The addition of an inert heat carrier is of particular value in this operation, especially in starting up. At such time oil is introduced and burned in 400 until the ignition temperature of the coke is reached.

According to a further embodiment of my invention, the process described in connection with Fig. 4 may be modiiled by introducing an oxidizing gas, such as air or oxygen, into either or both of chambers 40| and 4|! in carefully controlled amounts to supply any additional or supplemental heatv desired in these chambers by combustion of a portion of the carbonaceous material contained therein. By this means temperature variations due to varying conditions iny Amay take place through 406' and 4|0 in a manner similar to that described in connection with lines 8' and 9' inFig. 1. y

When an oxidizing gas is thus supplied to gasification zone 4|8 solid carbonization residue from` coklngf zone 405 may be fed through line 401a`directly into gasification zone 4|8 and gasiliedl therein until the solids contain onlya low percentage'ofl carbonaceous constituents. Low carbon residue from gasiiication zone 4Il may then be fed to combustion zone 409 and from there to coking zone 405 and gasification zone 4I8 in parallel to supply heat as described above in connection with Fig. 4. In this case, it is ordinarily necessary to return a major proportion, for instance about of the residue from combustion zone 409 to the gasification zone 4|! and a minor proportion, for instance about 10%, to the carbonization zone 405.

An optional alternative of this modification provides for series flow of the combustion residue from combustion zone 409 through gasification zone 4|8 and fromthere through lines 408, 40811 and 4I| to the carbonization zone 405 as it may be easily accomplished by a suitable manipulationA of the valves indicated in Fig. 4.

In Fig. 5 there is a ow plan similar to that of Fig. 3, illustrating a method which is particularly applicable to the Working up of solid carbonaceous fuel materials such as are disclosed in Fig. 4, particularly coal, peat, shale, tar sands, and the like. The apparatus is similar to that shown in Fig. 4, supplemented by some details.

The raw material in nely divided form enters at 530, passing directly to the low temperature caibonization` step indicated at 53|. Distillation products are removed from 53| and are separated into gaseous yand liquid products in the separation equipment indicated generally at 532.

The coky oarbonization residue is conducted to the combustion stage 533 where air is also introduced. The stack gases are taken off at 534 and the hot residue at 535. A portion of this residue is returned to the carbonization stage 53| through line 536 to supply4 heat for carbonization, and the second portion of this carbonaceous residue is conducted to the water gas generation stage 531. Steam is added at 538 and ash constituents of the original fuel are drawn on at 539. The gas, which is largely CO and hydrogen, is taken off at 540 and a portion of this may be drawn off for heating or other purposes at 54|. To the remainder of the gas an additional quantity of steam is added at 542 and the mixture is passed through a catalyticconversion step 543 wherein carbon monoxide is converted with steam to carbon dioxide.

The remaining gas is compressed at 544 and carbon dioxide is separated at 545. Substantially pure hydrogen remains which is then employed for the hydrogenation of the liquid distillation products produced from the original carbonization. 'Ihis is accomplished in the hydrogenation stage 546.

The combustion and the water gas generation stages are conducted .just as indicated in the previous description of Fig. 4, that is to say while the solid material is in a fluidized condition. The conversion of the CO to CO2 and hydrogen by means of steam and the hydrogenation step may be effected as outlined in connection with Fig. 3.

The apparatus of the present process is all constructed for operation at relatively low pressure, but high temperatures are required, especially in the gas generation zone 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 thel range of 25 to 75 feet per second. The operation of the reaction zones is smooth and proceeds without difficulty. The upward gas velocity should be of the order of 0.5 to 6 feet per second, where the solid is say 50 to 200 mesh, and progressively higher with larger sizes say 10 to 20 feet per second with lumps of A to 1/2. sufdcient to prevent the settling of the solid into compact masses and the reactions occur very rapidly while carried out when the solid is in a fluidized condition. Moreover, as indicated before, temperature control is extremely accurate. The velocity of the gas required for maintaining the fluidized condition varies somewhat with the nature and size of the solid particles and on the particular iiuidizing gas, but in general the variation is not wide and the minimum amount is of the order of 0.02-0.07 cubic feetl per pound. When fiuidizing with such a small amount of gas, a very dense suspension or stream results and the only effect of adding additional gas to the iiuidized stream is the reduction of the density and the suspension. Advantage is taken of this property of the uidized stream in order to effect the flow of the material from zone to zone. Thus, in Fig. l the stream is caused to flow down the pipe 1 and up the pipe B by the addition of These velocities are y stream in thev pipe 1 is much greater 10 l air at the point I0. The density of the fluidized than in the pipe 8 and a pressure differential is thus generated, which is equal to the product of the height of the column'in pipe 1 multiplied by the density therein, minus the product height ofthe column 8 multiplied by the density of the stream ilowing therein. The equipment must be carefully designed throughout so that the pressure differential is sumcient to overcome the loss due to friction. Small amounts of gas should be added to pipes and'chambers at various points so as to maintain the uidization. This is particularly important where a uidized stream is iiowing downwardly' through a pipe or chamber.

It should be understood that whenever the use of an oxidizing gas, such as air or oxygen, is suggested in the above description of my process oxygen will be preferred when it is desired to reduce the amount of inert gases, such as nitrogen, in the reaction zones and/or the conversion products of my process. For instance, when it is desired to produce a fuel gas suitable for the synthesis of liquid and solid hydrocarbons by the catalytic conversion of CO and Hz the gas generators 9, 2|8 and 4|8 may be so operated as to produce the desired ratio of H2100, for instance by a proper adjustment of the temperature, and oxygen is preferably used as the oxidizing gas supplied to the gas generator.

In all the embodiments of my invention described above, the finely divided solid carbonaceous starting material may be fed from the hoppers l, 20| and 40| in the form of a dense aerated mass without further dispersion downwardly into the first conversion zone or, instead of being fluidized prior to its introduction into the rst conversion zone, be directly fed into the first conversion zone without the preliminary addition of any iluidizing gas, for instance by means of a screw conveyor or the like and converted within the first conversion zone into a fluidized masswith the aid of the gaseous and vaporous reactants and/or reaction products present therein.

The present process is thus capable of carbonizing coal and producing a high quality fuel gas continuously. The advantages will be fully understood by those skilled in the art.

I claim:

1. An improved process for producing valuable liquid and gaseous products from solid carbonaceous materials which comprises passing a stream of finely divided carbonaceous solid material into a carbonization zone to form a. fluidized mass of solids therein maintained at a carbonization temperature, whereby distillable portions of the material are removed, leaving a coky residue in naly powdered iiuidized form, withdrawing said iluidized residue and passing the same into a gasiiication zone to form a iiuidized mass of solids therein, reacting said mass with steam at a gasification temperature, withdrawing a fuel gas and withdrawing a fluidized residue of low carbon content from the gasication zone, feeding said latter residue to a combustion zone to form a fluidized mass of solids, therein, generating heat in said combustion zone by burning the carbonaceous constituents of said latter residue, withdrawing hot fluidized solid combustion residue from said combustion zone and feeding said hot combustion residue to said carbonization zone and to said gasification zone to supply heat required therein.

2. A process according to claim 1 in which l l inert mineral matter is charged to the circulating solid material as ay heat carrier.

3.Aprocessaccordingtoclaim iinwhicha material which raises the melting point oi' the ash of the solid carbonacoous material is added to said solid material.

4. A process according to claim 1 wherein a portion of the heat required in the carbonization zone is supplied by burning a portion of the carbonaceous material in the carbonization zone with an oxidizing gas supplied to the carbonization zone.

5. The process as claimed in claim 1 wherein an oxidizing gas is supplied to said gasiilcation zone to generate heat by combustion therein.

6. The process of converting solid carbonaceous material into valuable volatile fuels which comprises passing finely divided solid carbonaceous material through a circuit comprising a carbonization zone, a gasification zone and a combustion zone, maintaining said material as a uidized mass of solids in said zones, feeding fresh solid carbonaceous material to said carbonization zone, (carbonized solid material to said gasification zone and solid gasification residue to said combustion zone) and controlling thetemperature in said carbonization and gasication zones by recycling solid residue highly heated in said combustion zone to said gasication zone and returning solid gasification residue to said carbonization zone.

7. A process according to claim 6 in which inert mineral matter Vis charged to said circuit as a heat carrier.

8.Aprocessaeeordingtoclaim6inwhicha bonization zone.

BRUNO E. ROE'IHELI.

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

UNITED STATES PATENTS .Number Name Date 1,379,038 Odell May 24, 192i 1,687,118 Winkler Oct. 9, i928 1,924,856 Heuer Aug. 29, 193s 1,984,380 Odell Dec. 18, 1934 2,420,145 McAfee May 6, 1947 2,451,803 Campbell et al. Oct. 19, 1948 2,462,366 Davies Jr. et al Feb. 22, 1949 2,482,187 Johnson Sept. 20, i949 FOREIGN PATENTS Number Country f Date 413,130 Great Britain July l2, 1934 632.466 France a Oct. 10, 1927 Germany Nov. 24, 1932 OTHER REFERENCES Meade: Modern Gasworks Practice, (2nd edition) pgs. 406 and 407.