US2579397A

US2579397A - Method for handling fuels

Info

Publication number: US2579397A
Application number: US487187A
Authority: US
Inventors: Bruno E Roetheli
Original assignee: Standard Oil Development Co
Current assignee: Standard Oil Development Co
Priority date: 1943-05-15
Filing date: 1943-05-15
Publication date: 1951-12-18
Anticipated expiration: 1968-12-18
Also published as: BE460668A

Description

Dec. 18, 1951 B. E. ROETHELI 2,579,397

METHOD Fo HANDLING FUELS Filed May 15, 194s 2 SHEETS- SHEET 1 Patented Dee. 1s, 1951 UNITED STATE METHOD FOR FUELS Bruno liknoethcli,- Cranford, N. J., assigner to Standard Gil Development ration of Delaware Company, a corro'- Appneanon May 15, 194s, semi No. 481,131

, is claims. (c1. .ia-2oz) The present invention relates tofan improved process' for the efllcient utilization of carbonaceous solid fuels such es coal, coke.' peat andthe like, and more specifically verting such `materials in more valuable pr'oducts including fuel gases. The-invention will be fully understood from the following description and the drawing- The drawing in Fig. 1 is a. semi-diagrammatic view insectional elevation of an apparatus `for carrying out the present .process and indicates the ilow ofthe materials.

Fig. 2 is a mmatic ilow plan showing a modification of the plan of Fig. 1.

It has been long known and appreciated that solid fuel materials such as coke, coal and the like could be converted into more valuable gaseous fuels which can be more efilciently used in this form. Producer and water gas processes are familiar to all, 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 it is difficult to carry out mechanically. The present process may be used for producing valuable fuel gas of high caloric value in a continuous manner and can be employed for carrying out the carbonization of coal at the same time in a mechanically, efficient manner.

Referring to the drawing, numeral I denotes the crusher or pulverizer which is employed to reduce a solid carbonaceous fuel to a nely divided form, for example, preferably of the order of below 50 mesh, or even less than 100 mesh although even small lumps say $4; to V2 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 be used. The finely ground coal drops from the crusher into a dispersing chamber 2, wherein it is thoroughly dispersed in a stream of superheated steam, which is added by pipe 3. The coal in the dispersion is said to be in a uidized" form because capable of flowing through pipes, valves, ducts and such equipment much like -a liquid, showing both static and dynamic heads: The liuidized 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. A grid orl screen is located in the lower portion of the chamber conveniently at'the place where the cone Iand cylinder unite.

to a process for con-` but neither of these processes is to have many advantages, but

in this form it isv the withdrawn stream of 'tion chamber An elongated vertical pipe fl, preferably opening abovev the grid or screen, is provided to carry a fluidized stream of solids from the carbonization chamber 5 and the stream is then conducted by the vertical pipe 8 into a combustion chamber 9, which is similar to chamber 5. Air is added to the fluidized solid at I0 and'causes the flow of the stream, as will be explained below,` up into the chamber 9 where rapid combustion takes place. Additional air may be added to the chamber by pipe 8'.

A discharge pipe I I is provided to take a stream of the nuidlzed solid material from the combus- 9 and discharges it into chamber B so that the highly heated material from the combustion chamber 9, which is at a temperature of say 1800 to 2400" F., is continuously recycled to the carbonization chamber 5. This chamber is at the usual carbonizing temperature of say 500 to 1200`F. and the preheat and heat of carbonization is thus substantially completely furnished by heat supplied from the combustion chamber.

vapors are withdrawn from the carbonization chamber 6 by a pipe I! through cooler I3 and thence to any suitable means for recovery of the coal distillation products. Cooler I3 may be of 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 f means for segregating the dust. tar, light oils,

ammonia and fuel gas.

Combustion gases are taken from the chamber 9 by a pipe Ilwhich leads to a dust separator I6 and to a waste heat boiler I6 for the Vsteam generation. The separated dust may the chambers by a pipe I1. l

Pipe II', which is shown as branch-of pipe II, is provided to draw off a portion of the highly heated fluidized contents of chamber 9 and t0 conduct it to a gas generator I8. This generator is shown as a vertical cylindrical vessel with a conical base, similar to chambers 6 and 8 de`- scribed above, and it is preferably provided with a screen at its lower portion to act as a distributor. The fluidized solid stream is discharged into the chamber, preferably' below the screen as de scribed above and super-heated steam is added by a pipe I9. The generator is maintained at a temperature between about 1400 and 2000 F., suitable for the rapid reaction of carbon and steam to produce water gas by the well known reaction.

' Gas is withdrawn continuously by a pipe 20 to a dust separator 2I and to a cooler 22. Therebe'returned to 'rst for carbonization,

i y chamber because of after the gas may be treated in any usual manner i'or the removal oi sulfur or other impurities, in equipment not shown, making it suitable for use as city gas or otherwise. It desired, the whole or a portion of the gas resulting from coal carbonization may be admixed with the water gas.

A iluidized stream of solids which is now largely free from carbon is withdrawn by pipe 23 from the gas generator I8 and a portion of this ash may be returned to carbonization chamber 5 in any suitable manner, for example through line Il. The solids can be discharged into the chamber 24 which is blown with steam admitted by pipe 25 and is then withdrawn by pipe I9 in la highly superheated condition required for the generation of the water gas. A portion oi. the nuidized solid is taken from the superheating chamber 24 by a pipe 26 and may be returned to pipe 8 for recirculation to the combustion chamber 9. A small portion is discharged at 21 to prevent accumulation in the system.

f 'I'he system described above ls a very exible one, capable of many modes of operation. In'it there are three main chambers or zones; the

the second for combustion and the third for water gas generation'. but

all three need not 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 gas generationeither by the carbonization of the charge orby water gas generation, which processes are operated at lower temperatures. Heat is carried from the combustion chamber to the gas generation chambers by the continuously owing streams of fluidized solid. 'I'hus the process is made fully continuous.

Ii.' coal is used as the raw material, it is preferably fed directly to the carbonizaton chamber and heat for the carbonization is supplied by i a stream of highly heated carbon flowing continuously from the combustion chamber through the pipe Il and discharging into the chamber 5. The temperature is capable of very careful, regulation and control and is distributed rapidly through the iluidized mass in the carbonization the high degree of agitation maintained therein. Chamber 5 is suillciently large to permit the complete carbonization very rapidly and the solids removed by pipe 1 are substantially free of volatile materials and are capable of rapid combustion with air in the combustin chamber 9. 'I'he process may be operated without the water gas generation step by closing a valve in pipe Il'. It desired. an inert material such as sand maybe added to the coal and circulated through the chambers i and 9 and the associated pipes 1, l and Il, so as to provide alarger volume of heat carrying solid material, but it is not required as the ash content of the coal may be allowed 'to accumulate and thus furnish any desired amount oi.' inert solid. High ash coals may thus be employed in the process.

It is important in this voperation 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, additional materials such as lime, magnesia and the like may be added to raise the melting point of the ash so that the operation may be conducted emciently, even where the ash is ot relatively low melting point.

It is desirable in most cases to operate the water gas generatoralong with the carbonizer as described. In most cases there is heat available need be little wear it the velocity of the 4 Y in the combustion of the solid involatile portion oi the coal in excess of that' required for thescarbonization reaction and the sas produced 'with the excess carbon in this manner is therefore of low cost.

lt will be understood that the present process `may be operated using coke instead ot a carbonization coal as the raw material. In this instance, of course. there is no carbonization. The coke dust will be fed directly into pipe land thevaives in pipes 4 and Il will be closed. In this case the iiuidized stream oi coke is supplied to pipe 8 through the pipe l' into chamb'er l. thence by pipe Il' into chambers Il and 2l.v The addition of an inert heat carrier is o! particular value in this operation, especially in starting up. At such time oil is introduced and burned in l until the ignition temperature of the coke is reached.

The apparatus of the present process is all constructed for operation at low pressure. but high temperatures arerequired. especially in the combustion zone and in the associated pipes. 'I'he equipment should be lined with high temperature tile or brick and it is found that there uidized streams is kept down in the range of 25 to 75 i'eet per second. 'Ihe operation of the reaction zones is smooth and proceeds without dimculty. The upward gas velocity should be of the order of 0.5 to 6 feet per second. where the solid is say to 200 mesh. and progressively higher with larger sizes say 10 to 20 i'eet per second with lumps of V4 to l/g". 'I'hese velocities are sumcient to prevent the settling of the v:solid into compact masses and the reactions occur very rapidly while carried out when the solid is in a iluidized condition. Moreover, as indicated before, temperature control is extremely accurate. The velocity of the gas required for maintaining the iluidized condition varies somewhat with the nature and size of the solid particles and on the particular iluidizingrgas. but in generaljth'e variation is not wide and the minimum amount is of the order o! 0.020 .07 cubic feet peiI pound. When iluidizing with such a small amount of gas, a very dense suspension or stream results and the only eilect of adding additional gas to the iluidized stream is the reduction of the density and the suspension. Advantage is taken of this property of the iiuidized stream in order to eilect the now of the material from zone to zone. Thus the stream is caused to ilow down the pipe l and up the pipe l by the addition oi air at the point I0. I'he density of the iluidized stream in the pipe 1 is much greater than in the erated. which is equal to the product of the height of the column in pipe 1 multiplied by the l such as are disclosed in Fig.

density therein, minus the product height of the column 8 multiplied by the density of the'stream ilowing therein. The equipment must be carefully designed throughout so that the pressure diilerential is suillcient to overcome the loss due to friction. Small amounts of gas should be added to pipes and chambers at various points so as tomaintain the fluidization. This is particularly important where'a uidized stream is ilowing downwardly through a pipe or chamber.

In Fig. 2 there is a now plan illustrating a method which is particularly applicable to the working up of solid carbonaceous fuel materials l, particularly coal. peat, shale, tar sands and the like. The apparatus employed is closely similar to that shown in stage Il drogen by means of l understood by those Fig. l; but the flow plan herein contained is soliewhat more complete.

The raw material in finely divided form enters at 3l, passing directly to the low temperature carbonization step indicated at 3i. Distillation products are removed from 3| and are separated into gaseous and liquid products in the separationv equipment indicated generally at 32.

The coky residue produced as a result of the carbonization is conducted to the combustion stage of the process indicated at 33 where air is also introduced. The stack gases are taken olf at Il and thehot residue at 36. A portion o! this residue is returned to the carbonization as indicated by the line 38 in order to carry heat for carbonization, as explained pre- `viouxsly, andthe second portion of this carbonaceous residue is conducted to the water-gas .generation stage indicated at 31. Steam is added at 3B and ash constituents of the original fuel are collected and drawn on at 39. The gas,

l which is largely C0 and hydrogen, is taken ofi.' at 4| and a portion ofv this may be drawn of! for heating purposes at 4I. To the remainder of the gas an additional quantity ofsteam is added at 42 and the mixture is passed through a catalytic conversion step wherein carbon monoxide is converted with steam to carbon dioxide.

Thegas which remains is compressed at 44 and carbon dioxide is separated at 45. The remaining gas, which is substantially pure hydrogen, is then employed for the hydrogenation of the liquid distillation products produced from the original carbonization. This is accomplished in thehydrogenation step indicated at 46.

It will be understood that the carbonization.

the combustion and the water-gas generationV stages are conducted just as indicated in the previous description of Fig. 1, that is to say while the solid material is in a iluidized condition. The conversion of the CO to CO2 and hysteam is preferably effected catalytically, using asy a catalyst iron oxide or iron oxide promoted with chromium and similar materials which are well lmown in the art. The conversion is effected at a temperature of the order of 850 F. and low pressure is ordinarily employed. v

The hydrogenation step may be any one of a number of different 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 purification by removal of sulfur, nitrogen and similar elements. On the other hand, the hydrogenation may be carried out under destructive conditions, above atmospheres and preferably at about 200 atmospheres and at temperature say from v '70o to 11o0 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 dimcultly 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.

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

Reference is made to the copending ltoetheli application Serial No. 609,662, filed August 8, 1945, and the now abandoned Roetheli and Hemminger application Serial No. 630,518, filed November 23, 1945, which applications disclose and claim specific embodiments of the invention disclosed herein. l

I claim:

1. The continuous process of carbonizing and gasifying finely divided solidcarbonaceous material while said material is in a uidized state, which comprises continuously charging a nely divided fuel and steam into a fluidizedmass of previously carbonized finely divided solids at a solids in the said combustion fuel in a gas generating that is to say, at pressures carbonization temperature in a carbonizing zone thus-mixed solids are in a uidized state therein, thereby carbonizing said fuel, continuously circulating the hot carbonized solids from said zone to a separate combustion zone in which they are iluidized along with previously carbonized fuel. burning some of the fiuidized zone by blasting them continuously with a combustion supporting fluid thereby heating them to a gas making temperature, continuously withdrawing hot solids from said combustion zone, charging them while at a gas making temperature into a separate gas generating zone in which they are also iluidized, blasting them in the latter zone with steam to generate combustible gas, continuously withdrawing a solid residue from said gas generating zone and returning at least a portion of it continuously to said combustion zone to be reheated. recirculating a portion of the said hot carbonized fuel from said combustion zone to said carbonizing zone, removing the volatile products of carso that the bonization from said carbonizing zone, and separately removing the said combustible gas from said gas generating zone.

2. The process of claim 1 in which at least a portion of said residue is returned to said carbonizing zone.

3. The continuous process'of carbonizing and .gasifying finely'divided solid carbonaceous materials, which comprises. continuously charging a stream of finely divided fuel dispersed in steam into a fluidized bed of hot previously carbonized fuel in a carbonizing zone thereby carbonizing said finely divided fuel in said iluidized bed. heating a separately fluidized mass of carbonized, finely divided fuel in a separate heating zone to a gas making temperature by blasting it with a combustion supporting fluid and discharging gaseous products of combustion, generating combustible gas by passing steam through a. separate, fluidized mass of nely divided carbonized zone while it is at a gas making temperature, withdrawing and recovering the gas thus made, separately withdrawing the volatile products of carbonization from said carbonizing zone and withdrawing solid residue from said gas generating zone, substantially continuously circulating hot carbonized fuel from said heating zone to said carbonizing zone, circulating carbonized fuel from said carbonizing' zone to said heating zone and circulating hot carbonized fuel from said heating zone to said gas generating zone whereby the heat for carbonization and gasification is largely generated in said separate heating zone.

4, The process of claim 3 in which at least a portion of said residue' is circulated to said carbonizing zone.

5. An improved process for utilizing solid carbonaceous materials which comprises continuaardse? 7 ously feeding fiuidizable, finely divided. carbonizable solids into a carbonization zone and forming a fiuidized mass of solids therein, withdrawing therefrom vaporous carbonization products and a fiuidized stream of finely divided, solid, carbon-containing carbonization residue, gasifying a portion of the carbon of said residue while the latter is in the form of a fiuidized mass of solids by a water gas reaction with steam in a gas generation zone, burning another portion of the carbon of said residue while the latter is in the form of a iiuidized mass of solids by a reaction with a combustion-supporting gas in a separate combustion zone to generate heat, heating fiuidized solids in said combustion zone, contacting solids so heated with said solids undergoing said water gas reaction to supply heat required by said water gas reaction, returning solids highly heated in said combustion zone to said carbonizationzone to supply heat required therein, and returning solid residue from said gas generation zone to said combustion zone.

6. An improved process for utilizing solid carbonaceous materials comprising continuously feeding fiuidizable finely powdered carbonaceous solids containing volatile constituents into a carbonization zone and forming a fluidized mass of solids therein, withdrawing therefrom vaporous carbonization products and a fiuidized stream of finely divided carbonization residue, subjecting a portion of said residue while in the form of a fluidized mass of solidsI to a water gas reaction with steam in a separate gasification zone, subjecting a portion of said residue while in the form of a fluidized mass of solids to combustion in a separate gasification zone with a combustion-supporting gas to generate heat, heating fiuidized solids by said heat of combustion, oontacting solids so heated with said solids undergoing said water gas reaction to supply heat required by said water gas reaction, and returning solid powdered residue highly heated by the heat of said combustion to the carbonization zone to supply at least a portion of the heat required in said carbonization zone. f

7. An improved process for utilizing solid carbonizable fuel materials comprising continuously feeding fluidizable, finely divided carbonaceous solids containing volatile constituents into a carbonization zone and forming a fiuidized mass of solids therein, withdrawing vaporous carbonization products therefrom, separately withdrawing a iiuidized stream of finely divided carbonization residue, passing the same into a combustion zone and forming a fiuidized mass of solids therein, burning a portion of the carbon therein 9. Aprocessaceordingtoclaim'linwhichinert mineral matter is charged to the combustion zone as a heat carrier.

10.Aprocess accordingtoclaim'linwhlnh material capable of raising the melting point of the ash is charged to the process.

11. An improved process for utilizing solid carbonaceous materials which comprises, continuously feeding fiuidizable finely divided carbonizable solids intn a carbonization zone and forming a fluidized mass of solids therein, withdrawing therefrom vaporous carbonization products and a iiuidized stream of finely divided solid carbon-containing carbonization residue, gasifying a portion of the carbon of said residue while the latter is in the form of a fiuidized mass of solids by an endothermicgasiiication reaction with a fluid gasifying medium in a gas generation zone. -burning another portion of the carbon of said residue while the latter is in the form of a uidized mass of solids by a reaction with a combustion supporting gas in a separate combustion zone to generate heat. heating iiuidized solids in said combustion zone, contacting solids so heated with said solids undergoing said gasification reaction to supply heat required by said gasification reaction, returning solids highly heated in said combustion zone to said carbonization zone to supply heat required therein, and returning solid residue from said gas generation zone to said combustion zone.

12. An improved process for utilizing solid carbonizable fuel materials, comprising continuously feeding iiuidizable finely divided carbonaceous solids containing volatile constituents into a carbonization zone and forming a fiuidized mass of solids therein, withdrawing vaporous carbonization products therefrom, separately withdrawing a uidized stream of finely divided carbonization residueppassing the same into a combustion zone and forming a `uidized mass of solids therein, burning a portion of the carbon therein while in the form of a fiuidized mass of solids whereby the remainder is raised to a high temperature.

while in the form of a fluidized mass of solids whereby the remainder is raised to a high temperature, passing a stream of the highly heated solid from the combustion zone to the carbonization zone whereby heat for carbonization is supplied, passing a second stream from the combustion zone to a gas-producing zone and forming a mass of fiuidized solids therein, adding steam to the gas producing zone whereby water gas is generated from the hot fiuidized carbonaceous material while in a uidized form, withdrawing the gas so produced, withdrawing a solid residue from said gas producing zone, and returning at least a portion of it to said combustion zone to be reheated.

8. A process according to claim 7 in which a portion of the solids withdrawn from said 'gas producing zone is returned to the carbonization zone. z

passing a stream of the highly heated solid from the combustion zone to the carbonization zone whereby heat for carbonization is supplied, passing a second stream from the combustion zone to a gas producing zone and forming a mass of fiuidized solids therein, adding superheated steam to the gas producing zone whereby water gas is generated from the h ot iiuidized carbonaceous material while in a fiuidized form, withdrawing the gas so produced. and withdrawing a solid residue from said gas producing zone.

13. .An improved process for utilizing solid fuel materials. comprising continuously feeding fluidizable finely divided carbonaceous solids containing volatile constituents into a carbonization zone and forming a fluidized mass of solids therein,

withdrawing vaporous carbonization products therefrom, separately withdrawing a fiuidized stream of flnely divided carbonization residue, passing thesame into a combustion zone and forming a fiuidized mass of solids therein, burning a portion of the carbon therein while in the form of a uidized mass of solids whereby the remainder is raised to a high temperature, passing a stream of the highly heated solid from the combustion zone to the carbonization zonewhereby heat for carbonization is supplied, passing a second stream from the combustion zone .to a gas producing zone and forming a mass of uuidized solids therein, adding a fluid gasifying medium to the gas producing zone whereby a fuel gas is generated from` the hot iiuidized carbo- 9 naceous material while in a uidized form, withdrawing the gas so produced and withdrawing a solid residue from said gas producing zone.

14. The process of claim 13 wherein said gasifying medium is superheated steam.

15. The process of claim 13 wherein at least a portion of said solid residue withdrawn from said gas producing zone is returned to said combustion zone to be reheated.

16. The process for recovering vaporizable products from finely divided carbonaceous solids and for producing mixtures of hydrogen and carbon monoxide which process comprises introducing incandescent finely divided carbonaceous solids into a confined contacting zone, introducing a gas comprising steam into said zone and passing said gas upwardly through said zone at a rate suflicient to maintain said solids in suspended turbulent dense phase condition, maintaining said zone under conditions for effecting conversion of a substantial amount of said steam with carbon in the carbonaceous solids for producing hydrogen and carbon monoxide, continuously separating reaction products from solids in the upper part of said zone and withdrawing gasiform reaction products from the upper part of said zone, separately removing a portion of the solids from the dense turbulent suspended phase at a point below the upper level thereof, transferring at least a portion of said removed solids to a coking zone, introducing raw finely divided carbonaceous solids into said coking zone, maintaining the solids within the coking zone in a iluidized dense turbulent phase by passing a gasiform fluid upwardly therethrough, continuously separating gasiform products from solids in the upper part of said coking zone and withdrawing said gasiform products from the upper part of said coking zone, separately withdrawing coked solids from the dense phase in said coking zone below the upper level thereof, introducing the coked solids thus removed into a heating zone, introducing a gas comprising free oxygen at a low point in said heating zone and passing it upwardly therethrough at a rate sumcient to maintain the solids in dense turbulent suspended phase in said heating zone and for heating said solids in said zone to incandescence, separating combustion products from solids in the upper part of the heating zone and removing 10 said combustion products, continuously removing a portion of the incandescent solids from said heating zone at a point below the dense phase level therein and transferring said incandescent solids to said contacting zone.

17. A method for converting coal which comprises establishing first, second and third beds of finely divided coke, passing a gas through each of said beds to maintain said finely divided coke in a fluidized state. the gas fed to the second bed being a combustion supporting gas and that to the third bed comprising a gasifying medium for said coke, continuously feeding coal in finely divided form to said first bed, maintaining said first bed at a carbonizing temperature, continuously feeding coke from said first bed to said second bed, subjecting said coke in said second bed to a combustion reaction in which the finely divided coke is highly heated and continuously feeding hot finely divided coke from said second bed to said first bed and said third bied.

18. A method according to claim 17 in which the coke gasifying medium is steam.

BRUNO E. ROETHELI.

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

UNITED STATES PATENTS Number Name Date 1,687,118 Winkler Oct. 9, 1928 1,899,887 Thiele Feb. 28, 1933 1,983,943 Odell Dec. 11. 1934 1,984,380 Odell Dec. 18, 1934 2,361,978 Swearingen Nov. 7, 1944 2,451,804 Campbell et al. Oct. 19, 1948 2,480,670 Peck Aug. 30, 1949 FOREIGN PATENTS Number Country Date 214,544 Great Britain Apr. 24,'1924 301,975 Great Britain Dec. 13, 1928 611,924 Great Britain Nov. 5, 1948 632,466 France Oct. 10, 1927 564,870 Germany Nov. 24, 1932 OTHER REFERENCES Haslam and Russell: Fuels and Their Combustion, pages 140. 546, 547. 600 and 801.