US2925335A - Process for the gasification of carbonaceous solid fuel at constant volume - Google Patents

Description

Feb. 16, 1960 E. E. DONATH 2,925,335

PROCESS FOR THE GASIFICATION OF CARBONACEOUS SOLID FUEL AT CONSTANT VOLUME Filed Dec. 21, 1955 FINELY uzvmm sauo wa es-5am.

-cAnIuuz GAS 4 6 YNTHlS1$ GA$ TO srozmz INVENTOR. EZA/EST .5. DON/8TH ."FI'njtheknown processtor' the gasification ,.Of carbo- H uaceon'smaterials such as, for enamplefinel divlided' coal, the'jc al isinjected together WithLoxygen" nd st'eamroflr fiswam I r r r 2,925,335. PROCESS FOR THE VGASIFICATION F CARBO- NACEQUS sO n FUELAT CQNVSTANT VOLUME E. Donath, Pittsburgh,'Pa., 'assignor to 'Koppers Company, Inc., a corporation of Delaware I Application December 21 1955 :10 Claims. c1. 48-206) Ernest T "f-This invention relates, in generaljto a {process or'the ff o'r example, coal; in suspensionwithokygenicontaining gas to produce gases containing primarily'fcarbon "monpanama, hydrogen, wherein the volume of the product 'ga'ses is maintained constant during the concomitant pressure "increase as a result of the'jgasification reaction;

carbon dioxide into the gasifier and reacted? t ubstam tially constant tpressureamDue to; theivoluineincrease I occurring during the 'reaction,}the produced" gas supplies work which reduces the reaction; temperature.

*ca'rbonimonoxide and hydrogenh'as beencai-r-i to' .f decrease as. aresult ,of a the 2cyli nder aw rom the piston head decrea n process is of geo veryt: undesirable beusedgto replacethe heat lost to the gas making process, inasmuch as the gasification of carbonaceous material such as Ecoal to CO and H requ'ires high temperatures tova'chieve a" rapid reaction between carbon and antendo- .thermically reacting gasJsuch as steam. l.

It has been found .by the present -1nventor' that' improved yieldsiof synthesis gas (-CO-l-H fromqcoalacan be obtained with the heat available and heretoforelost to theCO an d- H gasmaking process by conducting .the reaction at constant volume. When the gasification of coal to synthesis gas is-conducted in an apparatus at constant volume, the gases cannot expandand higher reaction'temperaturesare obtained, since the specific heat of the reaction'productsat constant y olume issmaller than. at constant pressure and thus: higher temperatures can berobtained at -constant volume withbetter and more rapid utilization ot the carbon y reactionjwith steam; Consequently, the-same, carbonutilization as-iob-f tained :in ;gasification; at constant'pressure ,can beob-t' a nt with; me a'mo nt f qbx gc p if e i qat qn reaction 1 is carried out at constant -volume,

provide anaimproved process, particularlyrfrom an eco- :rnqmic. -,a ln im n o he. g fic ti ns tot sc da rbonace ous'rnat erial such as, for examplocoaljtoi produce '15 ification of carbonaceous solidfuelat constantvolum'el 1:;

, f ore specificallylit is directe'dj't'o a processto'r thegasiification offinely-divided carbonaceous 'solidfuel-such as e product gases in moving "the his temperature 7 .7 a 45 sine" t 1s:1ost to lithe synthesis .ga making process and so increasesthe eostar making -the;g'as,as more fuel must r ivs t n t I 2,925,335 lia en ed rea 1 6,. 1 .69

gases comprising iprimarily carbonmonoxide and hydro- I P a a Additional objects and advantages will be apparent as the invention is hereinafter described in more detail.

The instantprocess, in its broader aspects, comprises reactingfinely-divided solid carbonaceous fuel in suspenl:

sion withlfree oxygen-containing .gas to produce gases containing primarily carbon monoxide and hydrogen,

while maintaining the volumeot the product gasesconstant during the concomitant pressure 1 increase as a reu .Q heirsact nt e The. terminology 'egiii a'e'd'i or: fexploding iused herein tofdesignatethe rapid and sometimes violent in- Vcorn plete "combustion of "the jfinelyidivide'di carbonaceous solid fue be'pun' od as, synonymous in 'soffar'as they indicate tion. e

fuelisin suspension in free oxygen-containing gas which is in admiziture with; an endothe'rmically reacting gas se I and mixtures thereof. a

utilized, herein are bituminous coal, anthracite, Q brown ox n; s m i adv ne a a within,the-scope'of 'this I be utilijzed in some instances, if de- Calculations show that less oxygen'in relation .to coal is,required-torgasification ata constant volume. rather than constant pressure, g inaccordance ,with: this invention, [to

obtain the same tem'peraturejas at essentially constant a pressure )in iaccordance'fwithr prior; art, processes, since the specifie heatof gases at cons'tantvolumeis. smaller than at constant pressurei,Therefore, theendothermic fsteam carhon action proceeds further-at constant volume in cs rdan. V veriti onal constant, pressuresprocessgbefore. the system reaches the temperature at: as sufficient .rate.

Theaccompanying drawing is 'llustrative of one arrangement of apparatus for. carrying out the instant invention.

Referringrnow to. the,dr'awing, the gasifierfi comprises a rigid,,non expansible, pressure'vessel and reaction chamber Z and .a .jacket 16 surrounding orrencompassing the wallsgot this reaction chamber and spaced therefrom liquid suchIas water is fed. througlrline 10into the annular zone located between this jacket, 16 and the wallsiof theareaction chamber where a-SubstantiaLp rtion of this liouidjs converted by the heat of reaction :into

ly femployed as the cooling liquidinasmuch; as thegsteam; it un es d; an a ter ardsbe ut e m t ific ioncre c- Th mpreventsioverheating 6f) e gasifier' V wallsj and i naintainstits walls F atxasufliciently low ternperatureto prevent attack by oxygen ras well'as sulfur t he sms ,tfexpl o ngl sm y a combustion. generally, butdiffering inrate or speed with a I fexploding? designating the more rapid orfaster reac-- Advantageously the finely-divided: carbonaceous lected iron the group consistingofsteam, carbon dio iide,

25 1 :Finely-divided, carhonaceous solid;

coal,"-ligni te or ligniticvcoal,vpeat, coke,' charcoal wood;

contarnlng gasjadvantageous. oxygen,}oxygenenriched ,ontainin'g} a higher. cona i o'ntained; in atmospheric with the instantninventionthan-ihthe con-- for-cooling thetjwallsOf the.reactionchamber. Cooling ,a gaseous medium suchas steam. Water is advantageous- V 3 compounds formed by the reaction. Temperatures between about 200 and 500 F; or higher are advantageous. At such temperatures the steam used as reactant does not condense and in the. cooling jacket steam can be generated under sufiicient pressure for use in the reaction, as conveying gas, etc. The gasifier 3 is also provided with means 8 for feeding coal, oxygen, and steam into the reaction chamber 2,fwith means-9 for exploding the suspension in the reaction chamber, and with means 15 for the removal of product gases and unreacted solid carbonaceous material and ash fromv the reaction chamber as hereinafter described.

: 7 Prior to starting the gasification reaction, the rigid, nonexpansible, pressure vessel and reaction chamber 2 is advantageously heated to an elevated temperature, e.g., 410 F., by passing steam through line 10 into the an nular zone located betweenthe jacket 16 and the wall of'the reaction chamber 2, or by any other suitable heatoxygen-containing gas. steam, etc., into'the reaction chamber 2 through valved line 8. This feed vessel 5 had been previously charged with a weighed amount of finely-divided carbonaceous solidfuel through valved line 4, and with carrier gas through valved line 6 to pressurize the carbonaceous solid fuel therein to the desired extent.

As soon as the desired pressure, is reached in thereac t on'chamber 2. which pressure:

1s advantageously within the range of approximately 2 to 20 atmospheresor higher, desirably approximately 3-10 atmospheres pressure, valve 7 in line 8 is closed. The reactionjmixture suspension within the reaction chamber is then ignited by means of a spark plug 9 operatively connected with a source of electric current to start the reaction that produces gas consisting primarily of carbon monoxide and hydrogen. Any suitable igniting or exploding means such as an electric resistance heater, injection of self igniting chemicals such as metal alkyls, etc., a torch device, or any other suitable igniting or exploding means could be. employed for exploding the suspension instead of'this spark plug. The reaction begins before the suspension of finely-divided carbonaceous solid'fuel such as-coal has had time to settle to the'bottorn of the reaction chamber 2. Usually after 0.1-5 seconds, and in mostcases after0.5-2 seconds, the reaction is terminated, that is, the temperature drops to a point where further reaction occurs very slowly.

At the high temperature resulting from the initial reac tion, viz., the incomplete combustion of carbonaceous solid fuel such as coal with oxygen, a very rapid reaction of endothermically reacting gas. such as steam with the coal is observed. As a result of the reaction, the pressure maybe as much as. ten times or more higher than the initial pressure in the reaction chamber. 'As the cooling proceeds, the pressure decreases. After a suitable. time for instance, 5 seconds'to' 5 minutes, especially 10 to 60 seconds, the gas mixture is cooled sufiiciently to be -depressured through valve 14 into'the synthesis gas.

main 15- without danger of corroding valves. Advantageously the synthesis gas pressure-is above atmospheric pressure, for instance, between 5 to 50 atmospheres or reaction chamber 2 by additional-steam'supplied to this reaction-chamber. When-large"gasifiers are employed, displacement of the synthesis gas can be aehievedby thesis gas from the gasifier into the gas main. After closing valve 14, excess steam can be vented through valved line 17 and the entire gasification cycle is advantageously repeated.

Instead of simultaneous addition of finely-divided car-1 bonaceous solid fueL'such as coal, and oxygen-containing gas, such as oxygen, into the steam filled reaction chamber, the reactants can be added in different sequences. For instance, the reaction chamber of the gasifier can be filled with oxygen under pressure and the heated coal dust blown into the reaction chamber with steam, or other suitable carrier gas under pressure; or the coal can be blownwith a suitable inert gas into the reaction chamber containing steam and oxygen; or the gasifier can be charged with fine coal and oxygen; or oxygen and steam can be blown into the gasifier preferably at high velocity and thereby bring the coal in the gasifier into suspension. Further the exploding of the reactionmixture suspension neednot be done at the end of the.

charging cycle. For example, the coal can be passed into the reaction chamber of the gasifier that is filled with oxygen and, if desired, steam. Igniting or exploding can be initiated as soon as only small amounts of coal have entered the reaction'vessel. In this case,a relatively higher charging pressure is'requiredfor the carrier gas that feeds the coal into the reactionchamber than is necessary in those instances previously described.

In accordance with this invention, the gasification of a finely-divided carbonaceous solid fuel such as coal to produce synthesis gas may be represented stoichiomet'rical ly by the following reaction:

Inasmuch as'the above reaction is endothermic, as is the reaction of carbon dioxide with hot carbon to produce more carbon-monoxide, suflicient oxygen and coal are spraying watersinto reaction chamber -2. The-water is 7 converted into steam which pushes 'or 'for'ces'the synadded to the reaction chamberlto result in the following reaction?- 7 2C+O 2C0 This latter exothermic reaction liberates sufiicient heat to maintain the endothermic reactions. I

Advantageously about 5-14 cubic feet of 0 especially about 7-10 cubic feet, is utilized in the gasification reaction of this invention per pound of carbonaceous solid fuel such as bituminous coal. j

The synthesis gas yield per unit fuel fromthe first reaction is higher than from the second reaction. Thecontribution of the first reaction isincreased as heat'loss'es from the gasifier decrease. The heat loss decreases as the size of the gasifier vessel decreases. While satisfactory reaction is obtained in experimental gasifier'units with a volume as small as 0.1-0.2 cubic foot, the oxygen consumption in such units may exceed 350 cubic feet per 1000 cubic feet of synthesis gas. For commercial operation therefore larger gasifier vessels of a volume advantageously greater than 50 cubic feet, desirably greater than 200 cubic feet, are employed. Two or more of such units can be used in parallel with a staggered reaction cycle to obtain a more uniform synthesis gas stream for further continuous processing and purification steps.

A smaller limited amountof a gaseous material selected from the group consisting of oxygen'and cornbustible'gas such as, for example, synthesis gas, methane, natural gas, producer gas, water gas, or materials known as combustion catalysts, etc., can be advantageously admixed with the suspension in the reaction chamber, advantageously at high velocity, immediately prior to exploding the suspension to effect gasification. It has been found that'thead'dition of this gaseous material will chamber will be determinedby experience and judgment and Willdepend on: the compositionofthdcoal; the

ployed, if desired. 7

estates oxygen-coal ratio, the amount "of steam; employed, "the pressure and, if needed, this amount can be determined by preliminary experiments The solid carbonaceous fuel that is utilized herein is finely'divided so that it can readily. be suspended and distributed in the gasifier. Advantageously a size is used such that 70% thereof will pass through a 200 mesh U.S. standard sieve, and desirably a size such that 100% will pass through a 200 mesh U.S. standard sieve. 1

Although the gasification reactionl'is advantageously carried out within the reaction' chamber at superatmospheric pressure, it is to be understood that this gasification reaction could be initiated,"if desired,j under atmospheric pressure. 'The essentialfeatureof this ir ive:ntion is that the volumeof the productgasesiy'vithin the re-- action chamber is maintained constant while the gasification reaction is being efiected therein, with the'co'ncomitant pressure increase resulting from this reaction.

The wall of the rigid, 'non expansiblegasifier vessel or.

reaction chamber of this invention .are advantageously constructed of a material which exhibits excellent strength and durability so as to enable this material to withstand the relatively high. and alternating pr'essure and .the3attack of reactants and. reaction products'produced within the chamber during therapid andsor'netimes violent gasification reaction. Steelsuch as stainless steel, and other suitable metals are emin ntly adapted and can be em- The obtained synthesisgasf'can bereadily-p Fischer-Tropschtype reactibns hydrogenation reactions,

etc. 1

The following specific examples are giv'n illustration only and without limitation. y

The coal utilized in these following examples is bituminous coal from the Sewickley Seam, Bunker Mine, Morgantown, West vVirginia and'shows in its ultimate analysis the following percentages of the indicated ele- Example 1 Finely-divided bituminous coal of the analysis set forth above and of a size such that 90% passes through'a 200 mesh U.S. standard sieve is blown at high velocity .with oxygen into a rigid, non-expansible steel pressure vessel or reaction chamber of 50 cubic feet volume at a temperature of 410 F. The gasifier, constructed as shown in the accompanying drawing and 'as hereinbefore described, contains steam which has been, previously introduced therein. The pressure within the gasifier vessel or reaction chamber is raised to 3 atmospheres pressure. Approximately 9 cubic feet of oxygen and 0.2 pound of steam are utilized per pound of coal. This suspension of finely-divided coal in oxygen and steam is then ex- "ploded in the sealed pressure vessel by means of a spark plug 9 inserted through the wall of the gasifier vessel. After product gases within the reaction chamber have been permitted to cool down,, the considerable"pressure within the reaction chamber is released and the. product gases are withdrawn.

25 analysis is obtainedzi" I urifiedand 1 used in the synthesisfof ammonia, methanol,' and' in Analysis of the. synthesis gas obtained showed the fol- V "Per thousand cubic feet of-Cd plusH produced, 213 .poundsof coal and 300cubic feet of oxygen' are consumed, and 6.6 pounds of steam are employed.

Good results'are also obtained when finely-divided anthracite coal, brown .coaLlignitic coal or lignite, peat,

' place of the bituminous coal.

' Qli t t coke, charcoal or wood are utilized wholly or partly in 'A finely-divided bituminous coal of the type utilized Example 1 and of-a sizesuch that 95% passes through a -200 mesh U.S.'standard sieve is suspended in oxygenenriched 'air containing 48% by volume oxygen, and steam and is gasifiedby vbeing exploded utilizing the procedure and the rigidnon-expansible gasifying apparatus "of Exa'mple'l. The pressure within the. reaction chamber is 5 atmospherespressure prior to exploding the sus'pensidnQ-AT small amount I of productsynthesis g'asj and bxygen is-admixed therewith-through line 18 at a rela 20 tively high velocity immediately prior to the exploding nearthe ignition pjoint -9. 9.3 cubic feet of oxygenand OAS-pound of steamperpound of coal are utilized in the 1 gasification and there is'about 85% carbon utilizationin this gasification reaction. Synthesis gas of the following Percent-by volume 9. 1 .m z s, n 'Hi-H "with 'ste'amby the" catalytic shift 'i'eactio'n,"and CO and synthetic ammonia.

Example v3 The'finely-divided coal of Example 1 is suspended in oxygen and steam and is gasified by exploding, utilizing 40 the procedure and the rigid, non-expansible gasifying .apparatussubstantially identical to that of Example 1 except that the gasifier vessel or reaction chamber has a volume of 200 cubic feet. This gasifier vessel is at a temperature of 435 at the time of the introduction of the reactants therein. The pressure within the reaction a chamber 2 is 4 atmospheres pressure prior to exploding the suspension. Only 8 cubic feet of oxygen and 0.2 pound of steam per pound of coal are used in the gasification and there is about 90% carbon utilization in the gasification reaction. Synthesis gas of the following analysis is obtained:

Per thousands cubic feet of CO plus H produced, 31

pounds of coal and 250 cubic feet of oxygen are consumed and 6.2 pounds of steam is employed.

. Similar results are also obtained in this example when most of the steam is replaced by carbon dioxide as the endothermically reacting material; A synthesis gas with '65 a higher content of'CO'and CO is obtained.

Obviously many modifications and variations of the invention as above set forth may be made without departing from the spirit and scope thereof, and'therefore only f such limitations shouldbe imposed'as are indicated in the appendedclaims.

What I claim is:

' I. In a process of gasification of solid carbonaceous fuel in suspension with free oxygen and steam'toform synthesis gas comprising primarily CO and .Hg, which comprises reacting a suspension of said solid carbonaeeous H S removal, the gas is suitable for the production of fuel in finely divided form in free oxygen in the presence of steam with the free oxygen in amount suflicient for combustion of only that part of the fuel required for supplying the heat for reaction .of the remaining part of the fuel with the steam to form the vsynthesis gas comprising primarily CO and H the improvement comprising igniting said suspension at an elevated temperature in a closed zone of constant volume so that an explosive combustion of said fuel takes place in said closed constant volume zone,.and maintaining the volume of theexploded products constant insaid closed zone during said explosion and thereafter .to produce the synthesis gas comprising primarily 'CO and H until completion of the synthesis gas reaction whereby the gases cannot expand and cool during .the reaction and gas ;a :result the heat thereof is consumed-in furthering'theendothennic reactionof the steam and carbon.

2. The process of claim 1 whereinsaid carbonaceous .fuel is so finely divided @that at .least 7.0% passes through a 200 mesh U.S. standard sieve.

'3. The .process of claim 1 wherejinthe .free oxygen of said oxygen-containing gas is present :to the extent of 5 to 14 cubic feet of-oxygen per pound of coal.

4. The process :of claim 1 wherein the initial elevated temperature is between 200 and 500 '5. A process in accordance with claim 1 wherein said carbonaceous fuel is coal.

6. A process-inaccordance with .claimS wherein the "coal is in suspension in.freeoxygemcontaining. gas .whichis in admixture with-an endothermically-reacting gas selected from the group consisting of steam, .carbon dioxide and mixtures thereof. v

7. A processin rv'cordance .with claim .6 wherein-the endothermically reacting gas is steam in the ratio of .15 to .20 pound of steam per pound .of coal.

'8. A process in accordance with claim 1 wherein the pressure is increased ,within the closed zone prior to exploding the suspension therein to approximately 2-20 atmospheres pressure.

9. A process in accordance with claim 8 wherein the pressure is increased within the closed zone prior to exploding the suspension therein to approximately 3-10 atmospheres pressure.

10. A process in accordance with claim 9 wherein a small amount of at least one member of the group consisting of oxygen and combustible gas is added to the suspension within the closed zone, in the vicinity of the igniting means, immediate y prior to explodingsaid suspension't'o facilitate exploding the suspension. 7

References Cited in the fileof this patent UNITED .STATES PATENTS 4..6.9.5."-Car on- B acks Form d .by De ompos tion of ixt res of Ace yl n -w tm Hyd o arbo or Other Gas at El vat diRressur s. May 19 0,;9 pages Melvin-Nord: Chemical Engineering, March 1955,

.pages 226 and 228.

Claims (1)

1. IN A PROCESS OF GASIFICATION OF SOLID CARBONACEOUS FUEL IN SUSPENSION WITH FREE OXYGEN AND STEAM TO FORM SYNTHESIS GAS COMPRISING PRIMARILY CO AND H2, WHICH COMPRISES REACTING A SUSPENSION OF SAID SOLID CARBONACEOUS FUEL IN FINELY DIVIDED FORM IN FREE OXYGEN IN THE PRESENCE OF STEAM WITH THE FREE OXYGEN IN AMOUNT SUFFICIENT FOR COMBUSTION OF ONLY THAT PART OF THE FUEL REQUIRED FOR SUPPLYING THE HEAT FOR REACTION OF THE REMAINING PART OF THE FUEL WITH THE STEAM TO FORM THE SYNTHESIS GAS COMPRISING PRIMARILY CO AND H2, THE IMPROVEMENT COMPRISING IGNITING SAID SUSPENSION AT AN ELEVATED TEMPERATURE IN A CLOSED ZONE OF CONSTANT VOLUME SO THAT AN EXPLOSIVE COMBUSTION OF SAID FUEL TAKES PLACE IN SAID CLOSED CONSTANT VOLUME ZONE, AND MAINTAINING THE VOLUME OF THE EXPLODED PRODUCTS CONSTANT IN SAID CLOSED ZONE DURING SAID EXPLOSION AND THEREAFTER TO PRODUCE THE SYNTHESIS GAS COMPRISING PRIMARILY CO AND H2 UNTIL COMPLETION OF THE SYNTHESIS GAS REACTION WHEREBY THE GASES CANNOT EXPAND AND COOL DURING THE REACTION AND AS A RESULT THE HEAT THEREOF IS CONSUMED IN FURTHERING THE ENDOTHERMIC REACTION OF THE STEAM AND CARBON.

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