US2657987A - Production of water gas - Google Patents

Description

1953 F. r. BARR PRODUCTION OF WATER GAS Filed Qct. 12, 1946 mm om atenec Nov 3, 11953 UNITED PEODUCTION OF WATER GAS Frank T. Barr, Summit, N. J. assignor to Standard il Development Company, a corporation of Delaware Application Oetober 12, 1946, Serie! Nu. 702;992

4 C'1aims. 1

The present invention relates-to the production of volatile combustibles from non-gaseous carbo naceous materials and, more partioularly, tothe production of gas mixtures containing carbon monoxide and hydrogen, such as water gas, from suchsolid carbonaceous materials as coke, various coa1s, lignites, brown coa1s, peat, oi1 shale, 0i1 coke, tar sands, cellulosi-c materials ncludng lignin, and the 1ike.

In the copending joint Barr andNelson applicaton Serial No. 690,816 fi1ed August 15, 1946, a process for the production of water gas is described wherein the water gas reaction of carbonaceous solids with steam in a system employ ing the fluid solids technique is greatly improVed by the use of a solid carbonaceous charging material of relatively high chemical reactivity. In this manner, the steam conversion at a given temperature and. under otherwise equa1 conditions may be considerably increased and the gas generator operated at temperatures considerably below the gas generation temperatures required for other feed material under similar conditions of pressure, steam concentration, contact time, carbon concentration, etc. without detrimentally affecting the steam conversion.

The preferred highly reactive carbonaceous starting material of this process is .1ow temperature coke obtained by carbonizing coa1 at temperatures not substantially higher 1than 1000 F. and preferably within the range of 600 to950 F. to an oxidation reactivity of about T=200210 C. ancl T7s=250-260 C. When 1ow temperature coke of this type is charged to a fiuid gas generator the gasification temperature may be lo-wered as much as about 100200 F. beneath the leve] required for conventional charging materials such as coa1 or high temperature coke without affecting steam conversion.

Substantially complete steam conversion may be achieved at temperatures in the neighborhood of about 1900 F. whi1e at 1700 F. the steam conversion sti1l amounts to about 80%. Gas generator plugging which may be a danger when Other highly reactive carbonaceous materials such as lignites or the like are charged is avoded. Thus, the gas generaton reaction may be eficiently conducted below the upper temperature 1imits drawn by the heat resistance of economie construction materials and the ash fusion or softening point.

1 Sebastian and Mayers, Ind. Eng. Chem. 129 :1118 (1937). '11; and 'l75 are the temperatures at which the rata of heat release by oxidaton of a sized sample becomes great enough to raise its temperature at rates of 15 C. per minuteand 70 0. per mmute respectively.

The preparation of highly reactive coke by carbonization of carbonizable materials at the 10W temperatures specified. is accompanied by the production of considerable quantities of 011 and tar of a wide boiling range. This by-product, particularly the raction boiling above the motor fuel boiling range, say above about 400 F can rare1y be eompletely anol profitably disposed of under normal market conditions. Dumping of so considerable and intrinsicaliy valuable 2, pertion of the process products not only is uneconomieal but :frequently highly inconvenient "as requiring considerable dumping space. Other means of disposal, such as burning 01 flushing away Present we1l recognzed difilculties, e. g. atmospheric and stream polluton.

The present invention in its more specific as pects is concerned with steps for utilizing this by-product tar in an efiicient and profitable manner and in this respect the present application is a continuation-in-part of the copending application identified above.

It is the principa object of the present inven tien to provide improved means -for the utilizatien of tar produced in the carbonization of carbonizable materials.

Another object of the invention is to provide an improved process for producing -10w temperature coke without the product0n of undesired quantities of tar.

A more specific object of my invention is to provide an improved. process for producing water gas rom hghly reactive 1ow temperature coke without the production of undesired quantities of tal.

Other objects and advantages of my invention will appear hereinafter.

In aecordance with the present invention, undesired tar ractions obtained in the low tempera ture carbonization of carbonizable materials are returned to the carbonization zone and represessed theren at carbonization conditions to be converted therein into additional amounts of desirable products such as gases, motor fuels, light oils and 10W temperature coke of high reactivity ior the water gas reaotion.

I have found that the conditions prevaiing in the low temperature oaroonization zone are. conducive to the cracking of tar fractions boiling above the motor fuel range, say above about 40)" F., especially those boiling above about 700 F., into more volatile fluids and coke, particularly when the fiuici solids technique is ernployed for earb0nization. In this manner, the primary :fluidized =coke pr0c-uced the carben- 3 ization zone serves as carrier for the 1iquid tar removing the neeessity for providing inert fluidized solids upon which the tar may be ooked The undesired tar fractons, preferably those boiling above the approximate range of 600- 900 F. may be separated from the 1ow temperature carbonization product by suitable condensation and/or fractionation and introduced into the preferably fiuidized. carbonization bed through suitable atomizing sprays. In this manner, the desirable lighter oi1s may be reeovered and the large quantities of product gas do not interfere with the conditions of gas flow and contact time desirable or tar coking. Since the tota1 tar consttutes only a minor proportion of the volatile carbonization products on a volume basis, recirculation of the tar requires no significant change in the design of the coker.

Recycling of tar in accordance with my invention might be expected to increase the gross tar yie1d per pass, which wou1d counteract the principal purpose of my process. I-Iowever, I have found that at a W temperature carbonization range of about 8001400 F. and in the presence of fiuidized primary 1ow temperature carbonization coke, the tar wi11 coke at a rate sufiicient to avoid bui1d-up of recycle tar to undesirable proportions. The ratio of circulating tar can be decreased by increasin the coker temperature, an increase of about 100 F. being usually sufficient.

In addition to increasing the yields of desirab1e gases, light oi1s and coke the process of my invention yields a final coke product enriched in tar coke of avorable reactivity for the water gas reaction, as compared wth conventional 1ow temperature coke.

Having set forth its general nature and objects, my invention will be best understood from the subsequent more detailed description in which reference will be made to the accompanying drawing which illustrates a system suitable for carrying out the preferred embodiment of the invention.

Referring now in detail to the drawing, a solid carbonizable uel is crushed or pulverized in crusher to a finely dvided form, for example, of the order of 50% having a size of less than 100 mesh, though small lumps of up to or inch size may be used. For the purposes of the following description, the carbonaceous material will be referred to as a bituminous carbonization coal containing 3035% volatile matter, but other materials can be used.

The properly sized carbonization coa1 is hoisted or conveyed in any manner known per se through line 3 to eed hopper 5. From here it is fed. through line 10 provided wth screw eeder I into pipe l8 provided wth control va1ve 19 and then into a dispersing chamber 20. The finely dvided coal is dispersed in dispersing chamber 20 in a stream of fluidizing gas, such as superheated steam, nitrogen, fiue gases, carbonization gases or vapors, or the 1ike, supplied through line 22 by compressor 24. The solids in the dispersion are now in the so-called fiuidized state in which 'they are capable of fiowing through pipes, valves, etc. similar to a liquid and. exhibiting static and dynamic heads.

The fluidized coa1 enters the conical lower portion of the enlarged oylindrical carbonization chamber 26 and passes-through a distributing grid 21 into the carbonization zone 28 wherein the carbonization coal is subjected in the form of a dense ebullient fluidize d mass orming a we11 defined upper level 29 to coking temperatu'reS of between about 800 and 1400 F. preferably around 1000 F. The heat required for the carbonization reaotion is preferably supplied by highly heatecl solids recireulated from combustion chamber 60 through line 65 as will appear more clearly hereinafter. Volatle carbonzation products containing small amounts of solids fines are passed through a gas-solids separator 30 which may be a centrifugal or electric type precipitator provided wth a solids return line 3I, and. through line 32 to a separating drum 33 maintained at a temperature suitable to condense undesired tar fractions depending on market demands. In general, condensation temperatures such as w1l condense materials boilin above 400 F., preierably above a temperature in the range of 400-700 F., will be used. Volatile overhead from separator drum 33 is passed through line 34 to any conventional system (not shown) for the recovery of such carbonization products as eoal gas, 1ight oils, chemicals, etc.

Condensed tar bottoms rom drum 33 are passed through line 35 and returned to the fuidized oarbonization zone 28 by means of spraying device 31. The amount of tar returned to zone 28 in this manner may range vvithin the approximate limits of 20 to 500 lbs. per ton of coa1 charged through line l8 without detrimentally aieoting the carbonization treatment.

Fluidized 1ow temperature carbonization coke containing about 1 to 15% by weight of tar coke is withdrawn rom carbonization chamber 26 at a point above grid 27 through pipe 30, and passed through control valve 41 to dispersng chamber 38 where t is taken up by highly heated steam supplied rom steam preheater 50 through line 40. From dispersing chamber 38 the fluidzed coke is passed through line 39 into the lower conica1 portion of the cylindrical gas generator 42 provided wth distributing grid 33 in an arrangement simlar to that of carbonization chamber 26.

The gas generator is maintained at a temperature of between about 1600 and 1900 F., preferably about 17001800 F. and a pressure of about 40-60 1bs. per sq. in. gauge to permit the water gas reaction to take place between the steam and the coke maintained in a dense ebullient mass 4 2 orming a level 45 in generator 42. The heat required for the water gas reaction is supplied by highly heated solid residues recircu- 1ated from combustion zone 60 through line 69 at the desired temperature, as will appear more clearly hereinafter. At these conditions, the conversion of steam to carbon monoxide and hydrogen amounts to about to of the theoretica1 as compared wth about 30 to 60% when a conventional gasification charge such as high temperature coke is used. The relative amounts and. the contact time of coke and steam supplied to generator 42 are so controlled that about 80 to 90% of the steam is converted to H2 and C0 and about 80 to 98% of the coke is ef:ciently utiiized in the combined heat and water gas generation.

A gas consisting mainly of carbon monoxde and. hydrogen is taken overhead from generator 42 and. freed in gas-solids separator 46 from entrained fines which may be returned through pipe 28 to the dense phase 44. The gas leaves separator 46 through line 49 and passes through steam preheater 50 in heat exchange wth steam admi tted through line 51, to a cooling system 52 from' which it may be withdrawn for any desired use as a fuel gas, for hydrocarbon synthesis, and 1 others. To wer 52 may also be a scrubber for re- 5 mova1 of any tracs of Susperided so1ids n t separated in 45. The steam preheated in 50 passes through line 40 to dispersing chambi 38, as out= ined above.

501101 carbonaceous gasification resdue is withcrawn through vertica1 pipe 53 from a point abve grid 03 and passed through control va1ve 55 to dispersing chamber 56 where it is taken up by hot air, oxygen, or other oxidizing gas suppl ied through 1ine 51, as Wi1l appear more clearly beiow. The mixture of solid gasification rsidue and oxidizng gas passes at about the temperature of the gasification zone through 1ine 59 to the conical lower portion of the cyiindricai combustion chamber 50 which has a construction similar to that of chambers 26 and 12 and serves as a heater for zones 26 and 42. The solids-gas mixture eriters the cylindrical portioh of heater 60 through a distributing grid 61 an forms theeabove a fluidized dense ebullent phase 62 having a weli defined upper level 53. The temperature of zone 82 is maintained btiveen 1700 and 2000 F. preferabiy at about 1800 to 1900 F. Solid cornbustion resic1ue cohsisting essentialiy of ooa1 ash is returned from a point above grid 6l at about the temperature of the combuston zone 62 through vertical pipe 65 provided with contro1 va1ve to the ower portion of carbonization ehamber 20 in amounts suificient to supply the heat required for carbonization. This amount may vary between about 100% and 200% by vreght of the soiids charged through line 20, depending on the temperature difference between combustion zone 62 and carbonization zone 28, good resu1ts being, in general, obtained at a solid reeycle ratio of about 150% to 200%. This ratio of heating solids a1so suffices to supply the heat required for coking the recycleol tars. A fiuidizing gas may be suppled by compressor 24 through 1ne 58 to facilitate the transport of the solid rom line 65.

Another consderably iarger amount of so1d combustion resdue is withdrawn trom above grid 51 through vertical pipe 69 provicled with control valve 71 to be returned through line 39 to gas generator 42 to supply the heat required in gasifieation zone 10. In accordance with the consderably higher temperature and the normaliy larger c1mensons of gas generator 42, the amount of solids recycled to 02 is a high multiple of that reoycled to carbonization chamber '25 and. may vary between the approximate limits of 30 to 300 times the carbon content of the solids charged through line 36 or may be about 20 to 100 times the amount of solids returned through line 65.

Flue gases are withdravvn overhead from heater 00 through gas-solds separator '12 where they are freed from solids fines. The fines may be returned through vertica1 pipe '13 to the dense phase 52 or withdrawn from the system. I-Iot fiue gas substantially free of solids is passed through line 15 to air preheater 15 where it preheats the air sup-plied by compressor '18 through line '19. The preheated air passes through line 51 nto dispersing chamber 55 as shown above. Flue gas, if desired after further dust removal in 00, may then be appiied to any desired use, such as the operation of a flue gas turbine 02, or heat recovery, or discarded.

The superficial gas velocity in reactors 26, 42, and 60 are those commonly used for the fluidization of dense beds of solids of the particle size indicated and may range from about 0.3 to ft. per second, preferably between about 0.5 to 3 ft. per second. The pressure of the system may he within the ap roximate 1imits of 40 to 200 1bs. per sq. in. gauge to save compresson on the gas manufacturecl. Highr pressures ma3 be used as feasibility and eoonomy of construction techmques alloW, particularly if water gas of high B. t. u va1ue is desired; The invention is par ticulail we11 adapted to high pressure operation sif1 high steam cnverson can be abtained at reasnab1e temprature even at the highest pressures desirable for gas'ifiation.

Means may be prvided to Withdraw ash from suita=ble pomts of the system in any manner liioiivii per se, for iiistance from pipes 65 and/or 69 in order to avoid a build 111) of ash in the systii; If desiied, an oiidizing gas such as air and/or oxygen may be supplied to chamber 25 and/or 42 to generate heat bycombustionthere" in, in order to supplement or replace the heat stiplid froinheater 60; Other modificatiohs of my hvention w11 appear to those skilled in the art.

My invention will be further illustrated by the following specific example.

The superority of the process of the inventon over conventional operation and operaton in accordance with patent application Seriai No. 690,816 with respect to 1ight oi1 and coke yields, coke reactivity and steam conversion is illustrated by the data given below.

Raw coal inspection (dry):

Ash, percent 8.0

V o1ati1e matter, percent...- 37, 5

F1xed carbon, percent 54. 5

Heating value, B. t. u. per 1b 13, 710

Fusion temperature, F 2, 150

Applica- Present Convent1on Ser Invennnal #690,816 tien Carbom'zation Temperature "F. 1, 700 900 1, 000 Coke Reactvity:

Ylelds per T011 of Goal:

Gas, Liquor, and Loss.lbs 340 220 280 L1ght 01'1 s.- 40 20 60 Ter (Net). i lbs 120 220 Coke (to gaslfcatlon) lbs 1, 500 1, 540 1, 660

Toto] Tar Recycled to Carbonizer .1bs 450 Gasgficatron Temperature, F. 1, 800 1, 800 1, 800 Gaslficatzon Pressure p. s. i. g 45 45 45 Steam Conversion in Gas Generator, wt. percent 50 92 and the preparation of a highly reactve charge for the water gas reacton. It should be understood, however, that the invention is not limited to this specific process but may be applied to any carbonization process yielding excessive amounts of undesired condensible products.

The foregoing description and exemplary operations have served to illustrate specific applications and results of my invention. I-Iowever, other modifications obvious to those sklled in the art are wthin the scope of my invention. On1y such limitations should be imposed on the invention as are indicated in the appended claims.

I claim:

1. The process of producing gas mixtures containing carbon monoxide and hydrogen which comprises subjecting carbonizable materials to a 1ow temperature carbonization in the form of a dense turbulent bed of finely divided carbonaceous solids fiuidized by an upwardly fiowing gas in a carbonization zone at temperatures around i000 F. coriducive to substantial crackng of carbonzation products bolng above about 700 F. to produce volatle carbonzaton products and high1y reactve coke havng an actvty of about T15=200 C. and about T2s=245 C., separating tar fractons boilng above about 7 F. from the V0- 1at1e products, returnng said fractions te said carbonizaton zone substantially completely in the 1qud state to 'be converted therein nto lower bolng volatle products and highly reactive coke of said aetvty, and contacting said. hghly reactve coke drect1y With a gasifyng medium conssting essentally of steam in a separate gasificatien zone at gasfication condtions adapted to produce said gas mixtures.

2. The process of claim 1 wherein said. steam and coke a1e contacted in a dense turbulent bed of finely dvded earbonaceous material fluidized by an upwardly flowng gas.

3. The process of claim 1 wheren the heat requred by said carbonzation and gasificaton is generated by the eombuston of so1d carbonaceous consttuents of sad carbonzable material in a separate combuston zone, and sad heat is suppled to sad carbonzation and gasfication zones in the form of sensible heat of hot solid residue from sad combustion zone.

8 4. The proess of claim 1 wheren said returned fractons are sprayed trom above on the top of said bed.

FRANK T. BARR.

References Cited in the fi1e of this patent UNITED STATES PATENTS Number Name Date 1676675 Trumble July 10, 1928 2,379,734 Martin July 3, 1945 2414,586 Egloff Jan. 21 1947 2482,187 Johnson Sept. 20, 1949 2579398 Roethel Dec. 18, 1951 FOREIGN PATENTS Number Country Date 214,544 Great Brtain Apr. 24, 1924 31,975 Great Britain Dec. 13, 1928 310,686 Great Brtan May 2, 1929 OTI-IER REFERENCES Morgen: A Textbook of American Gas Practice, vol. I, pp. 874-875.

Riegel: Industrial Chemstry, 3rd edtion, page 399.

Claims (1)

1. THE PROECESS OF PRODUCING GAS MIXTURES CONTANING CARBON MONOXIDE AND HYDRGEN WHICH COMPRIESE SUBJECTING CARBONIZABLE MATERIALS TO A LOW TEMPERATURE CARBONIZATION IN THE FORM OF A LDENSE TURBULENT BED OF FINELY DIVEIDED CARBONACEOUS SOLIDS FLUIDIZED BY AN UPWARDLY FLOWING GAS IN A CARBONIZATION ZONE AT TEMPERATURE AROUND 1000* F. CONDUCIVE TO SUBSTANTIAL CRACKING OF CARBONIZATION PRODUCTS BOILING ABOVE ABOUT 700* F. TO PRODUCE VOLATILE CARBONIZATION PRODUCTS AND HIGHLY REACTIVE COKE HAVING AN ACTIVITY OF ABOUT T15=200* C. AND ABOUT 125=245* C., SEPARATING TAR FRACTIONS BOILING ABOVE ABOUT 700* F. FROM THE VOLATILE PRODUCTS, RETURNING SAID FRACTIONS TO SAID CARBONIZATION ZONE SUBSTANTIALLY COMPLETELY IN THE LIQUID STATE TO BE CONVERTED THEREIN INTO LOWER BOILING VOLATILE PRODUCTS AND HIGHLY REACTIVE COKE OF SAID ACTIVITY, AND CONTACTING SAID HIGHLY REACTIVE COKE DIRECTLY WITH A GASIFYING MEDIUM CONSISTING ESSENTIALLY OF STEAM IN A SEPARATE GASIFICATION ZONE AT GASIFICATION CONDITIONS ADAPTED TO PRODUCE SAID GAS MIXTURES.

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