ANL-7t

10,

5-3 ANL-76-3

CASIFICATION OF CHARS PRODUCED UNDERSIMU.ATED in situ PROCESSING CONDITIONS

Quartoriy Report for the Period

October-December 1975

by

J. Fiscbor, R. Lo,

J. Young, and A. Jonke

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The facilities of Argonne National Laboratory are owned by the United States Govern-rnent. Under the terms of a contract (W-31-109-Eng-38)between the U. S. Energy Besearch andDevelopment Administration, Argonne 'Jnivc -sities Association and The University of Chicago,thr University employs the staff and operates the Laboratory in accordance with policies andprograms formulated, approved and reviewed by the Association.

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-N---OTICE-

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This report was prepared as an account of work sponsoredby the United States Governmcnt. Neither the United Statennor the United States Energy Research nnd Development Ad-ministration, nor any of their employees. nor any of theircontractors, subcontractors, or their employees, makes anywarranty. express or implied, or assumes any legal liabil-ityor responsibility for the accuracy, completeness or use-fulness of any information. apparatus, product or processdisclosed, or represents that its use would not iWfringeprivately-owned rights. Mention of commercial products,their manmiacturars, or their surptiers in this publicationdoes not imply or come approval or disapproval of theproduct by Argonne National Laboratory or the U. S. energyResearch and Development Administration.

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Distribution Category:(.oal Conversion and Ut i iizat i on- -

(. oal Gai i icat ion (LC-90c)

ANI.-76-3

ARJONNE NATIONAL LABORATORY9700 South Cass Avente

Argonne, Illinois 60439

GASIFICATION OF CHARS PRODUCED LEADERSIMUI.ATED in situ PROc:ESSING CONDITIONS

Quarterly Report for the PeriodOctober-December 1975

by

J. Fischer, R. 1.4)0J. Young, and A. Jonke

Chemical Engineering Division

all.

Previous reports in this series

ANL-8151 July-December 1974ANL-75-39ANL-75-77

January-June 1975July-September 1975

TABI.E OF t.NTENTS

ABSTRACT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I

SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

I.ABORATORY-SCALE CHAR-GAS I F I CATION SYSTEM . . . . . . . . . . . . . . . I

COORDINATION OF ANL EXPERIMENTS WITH FIELD TESTS. . . . . . . . . . . . . I

EXPERIMENTAL STUDIES. . . . . . . . . . . . . . . . . . . . . . . . . . 4

REVISED MILESTONES FOR COAL. AND CHAR GASIFICATION WORK. . . . . . . . . .

REFERENCES. . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

FIGURE

No. Tit 1."P.'ge

1. Schemat it Flow Diagram of Laboratory-ScaIl* Char Gasit irat ionSystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

TABLE

No. Title Pgge

1. Chemical Quality of Groundwater at Western .'s .'''4

GaNification Sites........ . . . . . . . . . . . . .7

iii

I

GASIFI ATION OF CHARS PRODUCED UNDERSIMUL.ATED r'/ . 'I"'' PROCESSING CONDITIONSS

Quarterly Report for the PeriodOctober 1 - December 31, 1975

by

.1. Fischer, R. Lo.1. Young, and A. Jonke

ABSTRACT

This effort, which is part of the Argonne National Laboratoryenergy program for ERDA, is being directed toward support studiesfor the national endeavor on :P ;tu coal gasification. This taskinvolves the investigation of reaction-controlling variables andproduct distributions for the gasification of both coals and charsutilizing steam and oxygen. Included in this task is the investi-gation of the effects of using brackish water as the water supply.The high-pressure char gasification system has been received fromthe manufacturer and is currently undergoing testing. The typesof experiments that would he most useful in their studies havebeen discussed with two of the three laboratories carrying outfIeld tests of ':-.':'. gasification.

SE'MMARY

This task has the object ives of providinug engineering data and analysesfor the char gasification by steam and oxygen under simulated Fn hit process-ing conditions. The coal samples will be representative of coal at sitesbeing considered for in situ gasification field tests. Chars for gasificationwill be made by pyrolyzing the coals at the low heating rates characteristicof :'i ut gasification processes. The results will be interpreted in termsof field design and resource recovery; thus this work will support the majorfield projects in the ERDA Pi atu coal program.

A laboratory-scale unit to study the reaction of steam and oxygen withcoal and char was completed, installed, and tested in December 1975. Thissystem will be operated at 850 C and 450 psig pressure. At a future date,after replacement of the reactor vessel, its upper operating limit will be1000*C and 2000 psig. The gasification unit and analytical system are currentlyundergoing shakedown tests. Experimental work is scheduled to begin in January1976.

A number of studies will be carried out pertaining to gasification ofcoals and chars. We will determine the variation of the product distribute ionas a function of (1) coal devolitilization conditions, (2) reaction temperature,and (3) total pressure. Several of the individual gasification reactions willbe studied. These reactions are:

CO + H. 3 1 Co + H.

H2O + C ; CO + H

(;0; + C 2CO

INTROI)UCT I ON

The objective of thi3 pro ject is to determine the reaction-controllingvariables and reaction kinetics for the gasification of coals and charsresulting from the pyrolysis of coal in underground gasification. This workis relevant to all underground gasification projects being funded by ERDA.The data obtained from this work will be used in modeling i 'n tu gasificationsystems, in order to understand and interpret field experimental data, andwill be used in the design of future field experiments.

In the gasification of coal and char in a laboratory-scale gasifier usingsteam and oxygen, a number of variables will be investigated that are repre-sentative of actual tn situ gasification conditions. These variables includetotal pressure, reaction temperature, coal devolatilization conditions, andpartial pressure of steam. Quantitative information about gaseous productssuch as hydrogen, methane, higher hydrocarbons, carbon monoxide, and carbon

dioxide will be measured in order to establish the Btu value of gas obtainedby gasification of the coal or (,ar.

3

The water supply for :i rt: gasification projects will frequently bebrackish, containing dissolved or suspended minerals such as carbonates,bicarbo1iates, halides, and hydroxides of alkali and alkaline earth metals.The catalytic effects of these materials on char gasif .cation will he investi-gated under conditions likely to be encountered in underground gasification.

In this report, the laboratory-scale reactor system is described. Also,planned studies of the reaction kinetics and the possible effects of brackishwater components on the reaction rates are describe-l in detail.

l.ABORATORY-SCALE CHAR-GASIFICATION SYSTEM

The laboratory-scale reactor system was received from the constructor inlate November 1975. It is now undergoing testing an- minor modification bythe constructor and is expected to be operational in e.rly January, 1976. Aschematic diagram of the system is sh" i^ Fig. 1.

The water for steam generation is supplied by a high-pressure (2000 psig)positive-displacement meteri.ig pump. This pump provides a variable feed rate(whi jh can he set to a ininimunr of > cm'/hr). The water flows into a coiled-tube high-pressure steam generator which Is encased in a split-type furnace.The steam is then blended wish an additional reactant or carrier gas (N. CO,(O. , I) prior to entering the reactor. The gas flow is monitored by meansof .j differential pressure unit, the output of which is connected to a massflow controller, located or the remote-control console. This mass flow con-troller drives a pneumat.ically actu; ted high-pressure needle valve, whichcontrols the flow of gis. Both the steam and the react ion gas flows can beremotely switched to bypass the reactor, either for flow calibration purposesor for standby conditions.

The reac.or vessel (1.6 cm 11) x 91 cm long) is constructed of type 316stainless steel and 1s rated for a pressure of 450 psig at 8500C.* The reactoris heated using a three-zone split-type tube furnace with 15.25, 30.5, and15.25 cm long heater sections. Reactor temperatures are monitored by meansof a cluster of three thermocouples situated at the center axis of the reactor.

The product stream is cooled in a high-pressure, water-cooled condenser,with the steam and hydrocarbon condensate being collected in a high-pressureseparator. The product gas is then dried, let down to atmospheric pressurethrough a remotely controlled back-pressure regulator, and passed to theanalytical sect ion. At this point, the gas is fed to an on-line gas chromato-graph and then to a wet-test meter for measurement of total product gas flow.The chromatograph analyzes for H., CO, CO; , and CHi 1 in the gas stream. In thefuture, a sulfur analyzer will be added in order to analyze for H:S in theproduct gas.

COORDINATION OF ANI. EXPERIMFNTS WITH FIELD TESTS

In order to coordinate our experimental efforts with those of laboratoriesconduct in,- underground field tests, Lawrence Livermore Laboratories (LII) and

At a future date, after replacement of the reactor vessel, its upper opera-tin- limit will be 1000 C and 2000 psig.

4

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Fig. 1. Schematic Flow Diagram of Laboratory-ScaleChar Gasification System

Laramie Energy Research Center were visited. Following these dissua.lons,an experimental plan (dircussed below) has been drawn up to further definethe studies to be carried out during approximately the next nine months.

EXPERIMENTAL STUDIES

Three materials will be studied, each being characteristic of the coalbeing utilized in one of the ERDA-supported field tests. Thes coals arePittsburgh Seam, Hanna No. I Seam, and a Wyodak-Anderson Seam. The last-mentioned coal has been studied in laboratory tests conduced at 1.1.1.. It issimilar to the Felix No. 2 coal which will he used in the field tests carriedout by LLL. As more core samples of the Felix No. 2 coal become available,this material will be studied in our reactor system, but for the present, theWyodak coal will be used. The Hanna and Wyodak coals are subbituminous; thePittsburgh Seam coal is a high-volatile bituminous coal. The last-mentionedcoal is also a strongly caking coal and hence will present problems during thedevolatilization stage of our studies. This problem will be discussed furtherin later sections.

*In .Ianuary, ai similar trip will be made to Morgantown Energv Research Center.

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5

The reactor system will be operated at differential conversion rates,... conversion of less than 17 of the input reactant. This has several

advantages over an integral reactor. Temperature control is much easierwith a dif ferential reactor. At a high conversion rate, a strongly exothermicor endothermic reaction would produce a temperature profile in the reactionbed, making def inition of the reaction temperature extremely difficult. Atd i t t ervnt Lia I convers ion rates, tnemperat ure uniformity throughout the bed is

s ri1r d.

Use of the differential reactor permits reaction rates to be calculateddirectly from experimental conversion data. The concentrations of reactantsand products are essentially uniform throughout the reaction bed; hence, there.ict ion order can easily be determined by studying the variation of productdistribution as a function of initial reactant gas partial pressures. Thekinet ic informat ion to be obtained for each of the reactions studied includesratt constants, react ion orders with respect to "ach of the reactants andproduct s, and apparent act ivat ion energies.

The chars will be prepared in the reactor in order to prevent exposureto oxygen between the devolatil ization reaction and the gasification reaction..\ standard set. of pyrolysis conditions will be used for the initial experimentsof these studies. These conditions will consist of a heating rate of 3 C/minup ito the gasificat ion react ion temperature, with pyrolysis carried out in aflow of approximately five liters per hour nitrogen, at atmospheric pressure.

For two subbituminous coals to be studied, the initial particle size ofthe coal should have little effect on the nature of the resulting char. Thesecoals fragment and form fissures as they pyrolyze. The size of the final char

part icles is apparently independent of the size of the initial coal particle;this fact must be confirmed, and experiments will he carried out utilizingtwo differing coal particle sizes, .:. , 1 mm diameter and 5-10 mm diameter.If this variation in starting particle size has little effect on the kineticsof the gasification reactions, the use of an arbitrary standard particle sizewi l l be Just if ied.

In the care of the Pittsburgh Seam coal, the starting material swellsand forms a coke during pyrolysis. For this coal, a series of particle sizeswill be studied in order to find the necessary conditions that will minimizethe effects of bulk diffusion limitations upon the gasification kinetics.

It is expected that differing pyrolysis conditions will have an effect onthe kinetics of the subsequent gasification reactions. These conditions includerate of heating, the nature of the atmosphere present during pyrolysis, andthe total pressure during pyrolysis. Under expected in situ gasification con-ditions, the coal is heated to the final reaction temperature at a rate ofapproximately 3 C/min. However, experiments will be carried out with heatingrates of l"C/min and 10*C/min in order to determine the effect of pyrolysisrate on the gasification kinetics.

Studies carried out at Lawrence Livermore Laboratory) indicate thatvarying the composition of gas present during pyrolysis of subbituminouscoal results ini a change in the amount of volatile matter pyrolyzed from

6

the coal. It is unknown yet whether th is eof tec t a lso ext ends to t he react i v i t vof the resulting char. S ince the yrotvs is gas is exptc ted t contain .It, cand CO; as well as nitrogen under ' :"''-cond i t ions, experiment s w it I hecarried out utilizing each of t hest component s as the at mosphlre present during Wpreparat ion of the chars. These experiments wi lhe carr led out .it pressuresof 1, 15, and 30 atm of hydrogen, carbon dioxide and carbon minox idi, us i nthe Wyodak coal as starting material. It an effect is observed on the kin.t ic';of the steam-char react ion, these experiments will a Is, te ;.ide wit h t he ianiand Pittsburgh Seam coals.

As is true for pyrolysis gas composit ion, the et cots on char re.lct ivit v

of variations in overall pressure during pvrolvsis is unknown. lvro l vs is wilhe carried out at pressures of 1, 15, and 3O atm of nit rogen .nd Cdrhon iein-

oxide, easing the Wyodak coal as starting material. If .in et tect is observedon the kinetics of the steam-char react ion, these exper imelnt s wil l . lso hemade with the Hanna and Pittsburgh Seam coals.

The primary reactions to he studied are t he clhar-steam rle t ion, clt- treaction, and the water gas shift reaction. The temperat urt range for;tochar-steam and char-CO2 kineties study will he 400-90'C. O . Thret ov ra I I tit am

pressures will be u'-d--I, 5, and 15 atm. The ef fect on t ht. ki net ies cau:redby varying each of thi. char preparation conditions ment ioned above wit I hbdeter tined.

The water-gas shift react ion may he strongiv cat a lvred by chars .inl b,ashes from the chars of the coals expected to he used in field tests. I ngzI esobserved that in the case of 'lhars and ashes prepared from .I number ofAust ral ian brown coals, the react ion approaches t herrmodvnam i e 'qu i l i hr i um atvery short contact times.' Sintering of this coal ash suhstant I alItv reducedits activity. He believes that the reaction was catalyzed b the mineralmatter present in the coal char, since the rates for this react ion were verylow when the reaction was carried out over a relat ivelv pure Tter prepare Ifrom sugar. 3

The water-gas shift reaction will be stud ied over chars or coke preparedfrom each of the three coals proposed for field tests. The devolat itizat ionconditions for these coals will be standardized, most closely simulating thoseexpected in actual underground gasification. Except possibly at very high

temperatures, variation in the devolat it izat ion conditions would not he expect td

to aave a great effect on the properties of the mineral matter in these mat erisls.

Therefore, no full study of the range of devolat ilization conditions is planned.The shift reaction will be studied in the temperature range of 400-900"(:, attotal pressures of one to fifteen atmospheres.

Ingles2 also observed that with some ashes prepared from Austral ian brown

coals, the disproportionntion reaction:

2C " CO + C

is catalyzed at temperatures in the range, 600-1000"C. Tihis react ion will he

studied in the temperature and pressure range of interest (400-900"C, I- 1 atmpressure) for each of the three carbons of interest In these experiments. Asin the case of the water-gas shift react ion, a standard set of devolat iI1izat ionconditions will be chosen; the full range of variables will not be studied.

7

*The ground water at the Western field gasification sites is brackish.

Analvse"s of these waters are shown in Table 1. The high levels of sodium,potassium, and calcium indicate that use of these waters as a water sourcefor steam generate ion might result in an advantageous catalvt it effect on thegasificat ion kinetics. On the other hand, the chloride levels migl.t inhibitthe primary gasification react ions.

Table 1. Chemical Quality of Groundwater atWestern .'-: : Gas if icat ion Sites

Hoc Creek Site ,r :' g Hanna, Wyoming

i)vt rhurden Felix No. . Underhurden Hanna No. 2 Scam

8 75 60(00N,K

I CO, +C(eSO

nn1 r

(oflient rait

30 25 60 71075 96 0 22

9. 0.47 0.12 --280 480 448 Hl00!00 174 162 400

12.5 12.5 18 4()

7. 7.8 9.3 8.:2718 976 1236 1750

i ons in mg/liter.

lotl disso I v-d sol ids.

Simulated groundwaters will be prepared incorporating appropriate levelsof Na, K, Ca, UCO.-, Sg,,-~, and Cl". Coal will he impregnated with solut ionfor an extended period of time prior to devolatilization. Also, attemptswill be made to form an aerosol of simulated groundwater in a hot gas streamjust prior to introduction into the reactor. The latter technique would:dImulate ondit ions encountered if this brackish water is flash-vapor izedon contact with hot char or ash underground. The effects of the presence ofthese salts on the char-steam and char-CO, reactions will be investigated.

Hanna basin and Hoe Creek site.

8

REVISED MILESTONES FOR COAL AND CHAR GASIFICATION WORK

1. Gasifier apparatus was received late in November 1975.

2. Installation and functional testing of gasifier in December; preliminarytesting of the gasifier and analytical techniques to be completed inJanuary 1976.

3. Preliminary data on kinetic and product distribution from gasificationof subbituminous and cther coal and char, made at low heating rates,delivered May 1976.

4. Final data on kinetics and product distribution from gasification ofcoal delivered August, 1976.

5. Data on effects of brackish water constituents on gasification ofcoal and on the effect of minerals in coal and in surrounding strataon gasification will be delivered December 1976.

6. Semiannual reports will be prepared. In addition, the ERDA contractofficer will be provided with informal summary quarterly reports onthe status of the work, including data. An annual report will besubmitted.

REFERENCES

1. J. Campbell, Lawrence Livermore Laboratories, unpublished information

(1975).

2. 0. G. Ingles, "The Water-Gas Shift Reaction in Fuel Systems II. TheReaction on Some Coal Chars and Coal Ashes," Australian J. Appl.Sci. 4, 451-461 (1953).

3. 0. G. Ingles, "The Water-Gas Shift Reaction in Fuel Systems I. TheWater-Gas Shift on Carbon," Trans. Faraday Soc. 48, 706-712 (1952).

4. R. Rozsa, Lawrence Livermore Laboratories, private communication (1975).

5. D. Fischer, Laramie Energy Research Center, private communication (1975).