IN STEAM GENERATION. Rosain and James D. Mavis CH2M HILL. dictate that developers practice maximum. water recovery, recycle, and reuse at their

Transcription

1 WATER REUSE IN STEAM GENERATION SYSTEMS FOR OIL SHALE PLANTS By Robert M. Rosin Jmes D. Mv CH2M HILL ABSTRACT All oil shle plnts require certin qun dictte tht developers prctice mximum wter recovery, recycle, reuse t ir tities low mediumpressure, fcilities. Although most developers hve eir for rerting process itself, for n upgrding fcility, or for mcellneous proposed zero dchrge wter mngement schemes, most such schemes re still plnt services. Bsed on direct experience untested. in use tretment produced wters in enhnced oil recovery field ( A potentilly significnt wter/wstewter flooding), cse mde for judicious reuse opportunity tht ten overlooked use rw or pretreted oil shle plnt genertion for use in wstewters (mine wter, rert wter, round oil shle plnt. Experience process condenstes) s mkeup with generr systems in sourn generr systems. Th wter reuse option Cliforni norrn Albert hevy oil cn effectively reduce requirements for fields hs shown tht wter does not hve fresh wter, in some cses, provide be completely deminerlized be used mens concentrting wstewter orgnics in se systems. In fct, feedwters with slts in generr blowdown. tl dsolved solids (TDS) concentrtions Th lower volume, concentrted wste strem up 23,000 mg/l hve been used, use my be more menble ultimte tretment feedwters with up 60,000 mg/l TDS or dposl in overll wter mngement concentrtions hs been suggested (1, 2). pln. Recommendtions on generr Certin pretretments re required, but feedwter qulity tretment re mde. Options for blowdown tretment /or reuse wstewters in th mnner my represent costeffective lterntive ultimte dposl re lso provided. The or tretments under considertion. types generr systems vilble re described s re dt on operting The trnsfer genertion technology systems in enhnced oil recovery field. from hevy oil industry oil Opportunities for furr reserch development re explored. shle industry subject th pper. INTRODUCTION The syntic fuels industry hs developed STEAM AND WATER MANAGEMENT Stem Use Opportunities CONSIDERATIONS in response diminhing resource oil. Most mjor oil shle rerting Ironiclly, successful development processes under design use, or cn use, syntic fuels hinges on vilbility certin quntity within nor limited resource wter. The sitution on oilshlerich Colordo process. purposes, The serves vriety perhps most importnt being western slope typicl in tht it contins significnt energy resource, but mrginl quntities wter. improvement heting vlue fgs obtined through rerting process. In Equity BX process, primry mechnm for Regulry resource lloction pres extrction shle oil. sures, s well s simple economics, will 347

2 In ddition rerting process, shle oil upgrding fcilities might lso require purposes th dcussion, high qulity will be clssified s tht resulting significnt quntities. These from generr system using 100 per fcilities cn include heter treters, hydrogention fcilities, delyed or cent deminerlized feedwter, producing 100 percent sturted or superheted. fluid coking opertions. Generl plnt Low qulity will be clssified s tht opertions will lso require for such things s heting Wter Reuse Opportunities het trcing. resulting from generr system using less thn 100 percent deminerlized feedwter producing 90 percent or less sturted (i.e., 10 percent or greter Three bsic sources wter re vilble liquid wter content). for reuse in n oilshle fcility: mine wter, process condenstes, rert Depending on process, qulity wter. Of se, mine wter process requirements my or my not be specified, condenstes re most pplicble for however, high qulity ten reuse in generr system. The mine specified where lower qulity my wter generlly uncontminted by orgn suffice. In ttempts use low qulity ics, refore more menble generted from reuse process deslintion /or deminerliztion oper tions. Although process condenstes contin some dsolved orgnics, y cn be effec wstewters, ll consuming processes should be criticlly evluted determine dequcy qulity require tively treted remove orgnics ments wher those requirements cn in require miniml deminerliztion becuse fct be lowered. ir low TDS content. STEAM GENERATOR SYSTEMS Rert wter lest effectively treted for generr feedwter becuse its Both high qulity low qulity generr systems re dcussed below. high dsolved solids orgnic content, Becuse low qulity systems re more however, it should not be completely over menble reuse wstewters s looked s wter source. Little known bout chrctertics behvior feedwter, y detil. re ddressed in more rert wter in generr systems. It possible though, bsed on oil field experience, tht some rert wters could be High Qulity High qulity Stem Generr Systems generr systems use used or blended with or sources used conventionl technology found throughout s generr feedwter. industril utility secrs. These STEAM QUALITY CONSIDERATIONS Stem qulity function feedwter systems re chrcterized by low highpressure, wter tube, multicircuit, drum boiler designs cpble producing 100 qulity, type opertion percent qulity t sturtion or t generr system in question,, some superheted tempertures. Th technology degree, piping dtribution well undersod hs been used for system. Stem cn contin impurities such mny yers. s liquid wter, voltile components, solid prticles precipitted slts from Low Qulity Stem Generr Systems feedwter. Certin criticl systems my The technology vilble for production low qulity hs been developed require extremely pure, such s highpressure, driven, turbine drives. Or systems my not; for exmple, low primrily in oil fields, where it used in flooding opertions for pressure heting systems. For enhnced oil recovery (EOR). These 348

3 cn generrs wter, with or use from generlly wter, tions flood Produced 30,000 long tubes. Th tends r condensed 5) continully formed during The concentr systems produced using ccepted follows. wter OnceThrough The mjority be systems cn through th As type oil termed preheted shown, (3) An. feedwter through integrl het exchngers, routed through n flue, generr rdint section, These generted. units drum for phse seprtion; generte on through leves s silic enters stripper flows subjected not use leving ctully column sodium stening be hs p lso drum. Th from gses if n internl n flow it s stripper strip effect countercurrent bility dded downwrd flling orgnics within Feedwter removed. column, crbonte s oil feedwter unit, rection chloride t unit entering with quntities voltile feedwter. through" pss generr system inter 100percent qulity Mgnesium system. insted, y "once injected chemicl in do trce industry feedwter A System. widely 2) field oil sten cn Before section n where enters system economizer, exmple remove 7). (6, once in Figure 1. depicted conditions clled system (Figure system generte s well. generr conventionl generrs system Stem Generrs field trnsient generr within it becuse nlly Conventionl pre ny removing lso gener Stem Generr Thermosludge Thermosludge low qulity mjor frction. ptented ends generr fresh TDS mg/l. A description liquid percent wipe tubing, (4, 10 Th leves tht wter cipitnts wter thn tl pproch my opertion lower qulity well. combintion groundwter. nturl tht liquid brckh or "produced" from producing oil wter produced fresh eir wter Stem tubes. 90percent or FEEDWATER less SOFTENING CHEMICALS qulity rnge t sturtion. up 170 kgm/sq System pressures cm (2,400 OXYGEN SCAVENGERS CORROSION INHIBITORS psig). BLOWDOWN TO DISPOSAL FLUE STACK 4 ECONOMIZER TUBES FEED WATER HEAT EXCHANGER STEAM CHEST FIGURE 2 PROCESS FLOW SCHEMATIC STEAM GENERATOR SYSTEM FUEL OIL HEAT EXCHANGER THERMOSLUDGE FEED WATER PUMP COMBUSTION AIR BLOWER The ctul tke plce clcium FIGURE 1 CONVENTIONAL ONCETHROUGH SYSTEMS Silic unusully high generrs concentrtions feedwter becuse TDS in 10percent or cn remins greter lerte TDS floe. in fst, resulting content hydroxide. mgnesium rections in n drum, precipitting mgnesium on At stening mgnesium 349 rections stening dsorbed tempertures dsolved frction in crbonte hydroxide Oncethrough chemicl pressures drum, re soluble pproching kinetics extremely clcium zero.

4 ._J A downcomer from drum routes ir high het fluxes, y lso sludge/slurry chest. The tubes in chest crry slurry through molten slt bth tht provides het cn burn solid fuel. The superhet/ desuperhet system (Figure 3) hs dvntges conventionl generr trnsfer medium for heting solution. system lso permits reuse pro Th molten slt circulted heted, duced wter (wstewter). In th system, in tubes, in seprte furnce, fired with feedwter deminerlized run through nturl gs or oil. Thermosiphon ction conventionl, multicircuit, utilitytype cuses slurry leve chest return drum, where physicl seprtion sludge boiler, exits s superheted. Th superheted n desuperheted with produced wter, resulting in working occurs. The exits through stripper fluid 90percent or less qulity. wer goes point use. Th system requires blowdown from SALINE WATER HEATER PRODUCED WATER PRETREATMENT PRODUCED WATER FEED drum since 100 percent being produced. Th blowdown must be ccounted for in overll wter mngement /or wste dposl pln. ~80% QUALITY STEAM 2000 psig DESUPERHEATER SUPERHEATED STEAM 2000 psig 1000F H.P. DRUM, COAL BOILER I 1 I DESALINATION I The Thermosludge system most useful for FRESH WATER FEED., FRESH WATER ^ DEMINERALIZATION wter tht requires significnt pretretment before use. The lrgest single Thermosludge 9 unit in opertion 6.3 x 10 gm cl/hr (25 MMBtu/hr). A system t 1.26 x 10 gm FIGURE 3 SUPERHEAT / DESUPERHEAT SCHEME cl/hr (50 MMBtu/hr) hs been proposed, however, th current upper limit on th type generr system. Th Wet Air Oxidtion Boiler Stem Generr. limit dictted primrily by bility Wet ir oxidtion (WAO) systems re used in het circulte molten slt mixture. mny instlltions throughout world for destruction wstewter sludges orgnic lden industril wstes by high Superhet/Desuperhet System. Lrge, util pressure oxidtion (8). In se systems, ity type, multicircuit generr orgnic wstewters re pumped, t pressures systems producing high qulity re not commonly used in oil field industry for up 140 kgm/sq cm (2,000 psig), in recr tht contins ir or pure oxygen t severl resons : high tempertures, up 320C (600F). Under se conditions, orgnics in o They require complete deminerli ztion feedwter. wter re oxidized crbon dioxide wter. If concentrtion orgnics in wstewter high enough, oxidtion o They re cpitlintensive. rection will become selfsustining exormic, het /or o They fer minimum operting flexibility. generted. Cpitlizing on th technology, WAO o They re not portble. generr system hs been developed for flood pplictions in oil field They re, however, reltively economicl operte once instlled becuse ir size industry. In th system, n ctul liquid or solid fuel combined with wter 350

5 injected in recr so tht it ctully becomes generr producing by exormic, selfsustining, ir oxid tion rections. The WAO system depicted in Figure 4. Development th concept in pilot plnt stge; lrger systems re being proposed. cpcity in conventionl flood opertion. At present, solr gener rs re not cost competitive with conven tionl systems. As price fuel con tinues re cost solr powered equipment decreses s result mss production, proponents believe tht solr generrs cn become competitive with conventionl equipment. LIQUID OR SOLID SLURRY FUEL PRODUCED WATER HIGH PRESSURE PUMPING STATION WAO REACTOR DownHole Stem Generrs. The genertion systems tht re probbly gr nering most ttention in oil field TO NEUTRALIZATION + AND DISPOSAL * 1 FLASH TANK BLOW!>OWN AIR OR OXYGEN V Sr^ Y industry dy, tht show gretest degree prome, re "downhole" generrs (10). In se systems, ir, fuel, wter re pumped downhole combustion device locted in well shft immeditely djcent fce reservoir. There re severl different FIGURE 4 WET AIR OXIDATION STEAM GENERATOR types systems vilble, most which produce highpressure, low qulity, stur ted pply it directly in Fluidized Bed, OnceThrough Stem Generrs oil bering strt. These systems re most In conventionl systems, pproximtely one pplicble for deep (greter thn 5,000 out every three brrels oil extrcted feet) reservoirs, or where conventionl from ground in flood opertion returned in generr system s fuel. As price liquid fuels generr system would hve be locted o fr from point injection. continues re, investigtion oil Reboilers. Reboilers re not used in hevy field generrs tht cn use solid oil fields becuse y cnnot develop fuel becoming more intense. higher pressures required. Reboilers re commonly used, however, in refining One compny hs begun mrket conven industry generte low qulity in tionl oncethroughtype generr strippers dtilltion columns. As system tht uses fluidized bed combustion such, y my lso find ppliction t n process, thus llowing operr use oil shle plnt. Reboilers re bsiclly eir col or petroleum coke s solid heted generrs, con fuel (9). sequently would require creful integrtion in both plnt wter mngement pln Solr Powered, OnceThrough Stem Generrs. Severl compnies re investigting use overll plnt het blnces. solrpowered generrs for producn in hevy oil fields. WATER TREATMENT REQUIREMENTS Although conventionl, bckup gener The following dcussion ddresses wter r systems must be vilble for use since sun not out continuously, some devel tretment requirements for feedwters used in high lowqulity genertion opers re predicting tht solrpowered systems. Agin, low qulity systems re generr systems could soon ccount emphsized becuse ir potentil in for percent genertion reuse process wstewters. The wter 351

6 tretment requirements constituent two exceptions, re generlly sme. The concentrtion levels given below re primr ily oriented wrd mintining integ two exceptions, WAO Thermosludge systems, will be dcussed lter. rity opertion generr system. Any specific requirements over As dcussed bove, low qulity, once bove those necessry mintin prticu through type generrs rely on min lr process qulity ted on csebycse bs. need be evlu tining thin film liquid (condenste) t exit generr tubes High Qulity Stem Systems continully wet or wipe ends The generl feedwter tretment requirement for high qulity systems complete tubes. Th permits TDS in feedwter remin dsolved in liquid frction fluid s it leves deminerliztion. The degree demin generr system. Thus, upon concentrtion erliztion somewht dependent on in generr system, TDS operting pressure temperture cnnot form precipitting slts tht will system. For exmple, higher pressure led scling tube surfces. systems require greter degree demin erliztion thn lower pressure systems. The requirements for feedwter tretment boiler drum chemtry hve been out Mjor components concern some lim iting prmeters s y pply oncethrough generrs re dcussed lined by Americn Society Mechnicl below, however, some specific oper Engineers for industril boiler pplic tions, re well documented (11). ting prmeters proposed below re greter thn those recommended by generr mnufcturers. These prmeters re eir A deminerlizer system removes hrdness scleforming components (ctions) from feedwter so tht y do not precip bcked by ctul operting dt or re specificlly stted be proposed lim ittions (2, 3, 12, 13). itte in boiler system itself. In ddition, predominnt nions Oil Dsolved Orgnics. Feedwters feedwter, if not removed, my become voltile or shift gseous form, should not contin ny free or emulsified oil. Oil generlly removed by ir flo crete n cid condition in subsequently ttion /or medi filtrtion. Although condensed s it returns boiler not concern in oil field industry, circuit. Th prticulrly true in effect dsolved orgnics (or truly cse crbontes bicrbontes (lkl inity). As temperture in boiler circuit increses, crbontes bicr bontes brek down form CO, which crried, with, in lines. As condenses, CO., dsolved oil) on generr opertion remins question when technology pplied oil shle industry. If tempertures pressures oper tion re high enough, dsolved orgnics redsolves in condenste. The con could ctully be coked on tube wlls. denste essentilly n unbuffered solu tion, dsolved C02 cid, creting very condenste return piping. forms crbonic corrosive condition in However, y could lso become voltile exit with or remin dsolved in condenste film. Specific chrcter iztion orgnics present s well s pilot work on ir behvior in Low Qulity Stem Systems generr system would be required for Despite diversity low qulity definitive nswer. Preliminry indictions genertion systems tht re vilble, wter tretment requirements, with only re tht dsolved orgnics in oil shle plnt wstewters might not cuse serious 352

7 2, ,000 50,000 fouling problem in genertion systems (14). Th would require csebycse nlys for confirmtion. 40,000 mg/l. Th function mjor solute species, however, n nlys pproprite phse digrms Hrdness. Hrdnessrelted slts, primrily suggested before contemplting operting in high TDS regions. clcium mgnesium, re min scle cusing gents in generr feed Iron. Becuse iron in solution will ttck wters. Consequently, feedwter hrdness protective mgnetite iron oxide lyer in should be zero. obtined in hevy Th level routinely oil field opertions with generr tubes, iron content feedwters should generlly be less thn wek cid ction, ion exchnge systems. Hot 0.05 mg/l. lime steners re sometimes used s well. Hrdness sequestering gents my lso be Mcellneous. Turbidity (suspended solids), dded feedwter. oxygen, H_S ( or dsolved cid ph. Feedwter ph should be pproximtely gses) should be removed from feedwter. Dsolved gses cn be removed by physicl minimize feedwter line cor or chemicl deertion. rosion (see "iron" below) my need be even higher mintin ny silic in solu Becuse Thermosludge generr tion. The resultnt ph condenste uses n internl stening/tretment pro film in generr my be between becuse brekdown cess, feedwter qulity requirements re different thn those for more conventionl crbontes resultnt shift in systems. The mnufcturers' recommendtions lklinity. re: Alklinity. As previously dcussed, high Hrdness 100 mg/l lklinity in high qulity system Silic 10 mg/l serious problem. In low qulity system, Suspended Solids 10 mg/l when CO tht generted from brek Oil 50 mg/l down lklinity in feedwter red TDS 1,000 mg/l solves in condenste, it doing so in highly buffered, likely high TDS, Chemicl oxygen scvengers, corrosion wter. Consequently, it hs little effect inhibirs, ntifom gents re lso on system ph. routinely dded. Silic. The llowble SiO in feedwter A mjor dvntge WAO gener function SiO_ solubility t ph r tht little, if ny, feedwter temperture condenste film. At pretretment required. A smll system ph's between , tempertures blowdown required, however, mintin bove 300F, SiO_ solubility well beyond system chemtry. At recr operting 1,500 mg/l, in fct concentrtions tempertures, pressures, ph (pproxi 1,625 mg/l hve been reported (15). Assum mtely 1.0), in solution. dsolved species tend sty The recr consequently ing 80 percent qulity, feedwter SiOconcentrtions 325 mg/l could be lerted. constructed highstrength, corrosionrestnt lloys. Totl Dsolved Solids. Oil field STEAM GENERATOR BLOWDOWN TREATMENT generrs hve operted on TDS concen High Qulity Stem Systems trtions s high s 2 3,000 mg/l, with prcticl limit proposed t pproximtely All high qulity generr systems require periodic or continuous blowdown 353

8 mintin boiler wter qulity. from liquid portion. Th blowdown will Depending on system pressure, th definitely contin significnt orgnic blowdown normlly sufficient qulity frction must be reused or dposed permit its direct reuse elsewhere in with dcretion. Reuse or dposl options plnt, for exmple, cooling system mkeup or generl plnt service wter. The tl quntity blowdown smll, however, gin include spent shle moturizing, dust control, deepwell injection, evportion, or incinertion. it must be flshed generlly cooled before reuse. RESEARCH OPPORTUNITIES Reserch opportunities for generr Low Qulity Stem Systems systems s y pply oilshle plnts The 10 percent or greter liquid frction fluid leving oncethrough generr serves s system blowdown. would fll primrily in re low qulity generr systems. Much work remins be done on ppliction Unless seprr used, liquid novel low qulity generr frction fluid crried end systems such s downhole systems, wet use process with. If ir oxidtion systems, solr systems, seprr used, or if seprte blowdown hightemperture/highpressure must be mintined for some reson, reboilers. Bsic reserch on potentil resultnt liquid must be reused or dposed. Although it function tl system opertion, blowdown will likely be high ph, sline solution with scling /or fouling chrctertics oilshle plnt generted wstewters in generr systems so needs be done. little, if ny, direct reuse potentil. It might be used for moturizing spent shle Every or or solid wstes, rod dust control, or effort should be mc.e use low mediumheting vlue fgs produced t perhps dposed by deepwell injection or n oil shle fcility. Consequently, use evportion. If th blowdown were th fuel in n oilfield type, low qulity, contin significnt frction orgnics, wet ir oxidtion destruction or inciner generr system might llow reuse significnt mount wstewter in tion might be considered. production. Reserch on burner The Thermosludge, WAO, reboiler, designs modified generr con figurtions refore necessry. generrs re only low qulity systems tht must operte with seprte, SUMMARY defined blowdown. The Thermosludge system In summry, th dcussion hs described blowdown slurry precipitted slts methods for reuse process gen tht must first be seprted if wter erted wstewters in production be reused. The seprted slts could be t n oilshle plnt. Low qulity generr systems normlly used in mixed with or solid wstes lfilled, lthough se slts re slightly wter soluble. Options for reuse /or dposl wter frction re sme s those dcussed bove for conventionl, oncethrough generrs. Tretment/ oil field industry my find direct pplic tion in oil shle industry. The tech nology oil fieldtype, oncethrough generrs well known, if feedwter qulity limits for se gener dposl options for reboiler system rs operting on oilshle plnt generted blowdown would lso be sme. wstewters cn be estblhed, tech nologies should be redily trnsferrble. Blowdown from WAO generr must be Or low qulity generr systems flshed resultnt solids seprted under development, such s downhole 354

9 REFERENCES 1. Elis, R., Jr., J. R. Johnsne, J. D. Kruse, J. C. Scnln, W. W. Young, "Stem Genertion with High TDS Feedwter," generrs, wet ir oxidtion systems, Fifth Interntionl Symposium on Freshwter From Se, 1976, solr systems, might be useful in oilshle industry for vriety resons. Volume 1, pge Stem genertion from oilshle plnt wste wters might present vible lterntive for reuse those wters before or with dditionl tretment. Hull, R. J., "The Thermosludge Wter Process," Treting Stem Genertion Journl Petroleum Technology, December 1967, pge Stem use opportunities must be ssessed in detil ctegorized s qulity required for ech unit opertion. At Rinul, Bill, "Stem from Wstewter," Pcific Oil World, JulyAugust tht point, decion cn be mde s which generr system cn be utilized s well s wter or wstewter tht cn be used s generr feedwter. Wstewter reuse in genertion systems Blog, S. E., R. K. Kerr, L. A. Prdt, "The WAO Boiler for Enhnced Oil Recovery," Albert, unpublhed. ZimproAEC, Ltd., Clgry, cn effectively reduce requirements for fresh wter t n oil shle plnt. Fnrit, J. P., C. J. Lyons, H. Nck, "Appliction Bttelle Society Petroleum Engineers AIME, 50th Annul Cliforni Region MultiSolid Fluidized Bed Combustion System Oil Field Stem Generrs," Proceedings Sixth Interntionl Conference on Fluidized Bed Combustion, Atlnt, Georgi, April 9 through 11, l Meeting, Los Angeles, Cliforni, April 9 through 11, 1980, Pper 10 Bder, B. E., et l., "Potentil No. SPE8819. Down Hole Stem Genertion Recovery Hevy Oils," UNITAR Conference on 2. "Suggested Guidelines for ThermDrive Feedwter," Tuls, Oklhom, Report, CE/Ntco, Inc., Future Hevy Crude Tr Ss, Edmonn, Albert, Cnd, June 4 through 12, Fnrit, J. P. J. D. Kimmel, 11. "Consensus on Operting Prctices for "Review Once Through Stem Gener Control Feed Wter Boiler rs, " Journl Petroleum Technology, Wter Qulity in Modern Industril April 1965, pge 409. Boilers," The Feed Wter Qulity Tsk Group, Industril Boiler Subcommittee, Mnn, G. M. W., "Dtribution Sodium ASME Reserch Committee on Wter in Chloride Sodium Hydroxide Between Stem Wter t Dryout in n Experi Therml Power Systems, Americn Society Mechnicl Engineers, mentl Once Through Boiler," Chemicl Engineering Science, 1975, Volume 30, pges Wheeler, Dougls W., "EOR Project Uses Produced Wter," The Oil Gs Journl, Mrch 26, 1979, pge 170. Yusufov, V. D., G. P. Ugrekelidze, A. I. Bronshtein, "The Intensity 13. "Wter Conditioning for Oil Field Stem Het Trnsfer Sewter NCl Generrs," Report, StrursBruner, Solutions under Conditions One Winfield, Knss. Phse Two Phse Flow in Tubes," 355

10 Prt 14. Mercer, B. W., Bttelle Pcific North west Lborry, personl communiction, 15. Kunin, Robert, "The Role Silic in Wter Tretment 1," Rohm & Hs Co., Amberhilites Bulletin #164, Summer