P. 1


# OAR Box 

# 1784 Prepped byOllie Stewart



### Document

Number: ^/ 

# 79 ) ll-l-< Docket Number: 

# A-84-4 4

Printed 10/31/2008 8:05:41 AM Sheet 79 of 143p-i .

MINIMIZIN

G GA S TREATIN

G COST S WIT H LO-CAT

®FO R H 2 S REMOVAL

by L . C . Hardiso n Presiden t AR I Technologies , Inc . 60 0 Nort hFirs t Bank Driv e Palatine , Illinoi s 6006 7

Fo r Presentatio n a t th e Panhandl e Plain s Regiona l Meetin g

o f th e Ga s Processor s Associatio n Amarillo , Texa s Octobe r 11 , 198 4P. 3

Abstrac t Th e LO-CAT ®Hydroge n Sulfid e Oxidatio n Proces s use s dilut e aqueou s solution s o f chelate d iro n t o scru bH2 S from

ga s stream s an

d conver t i t directl yt o elementa l sulfur . Th e mai n feature s o f th e LO-CA T proces s whic hse t i t apar t fro mothe r direc t conversio n processe s include :

- Extremel yhig hcatalys t activit y

- Complet e non-toxicit yo f th e catalys t solutio n

- Grea t flexibilit yo f applicatio n 

### Ove r th epas t

tw o years , anumbe r o f application s i nth enatura l ga s processin g industr y hav edemonstrate dth ereliabilit y an deconom y o f t h eLO-CA Tprocess . Thi s pape r describe s th emos t recen t application s t o natura l ga s processing , an dreview s th etechnica l an deconomi c incentive s fo r ga s processor s t o utiliz ethi s technology
.

- 1

-P. 4

MINIMIZIN

G GA S TREATIN

G COST S WIT H LO-CAT

® FOR H? S REMOVAL Introductio n Th e LO-CAT ®

Hydroge n Sulfid e Oxidatio n Proces s wa s develope d i n th e earl y1970' s and firs t applie d commerciall yi n 1978 . Th e initia l applciation s wer e i n oi l refinin g an d miscellaneou s chemica l processin g plants , and ther e wer e n o installation s o f th e LO-CA T proces s i n natura l ga s treating unti l earl y198 3 whe n th e firs t uni t starte d up a t th e Seve n Sister s Ga s Fiel d nea r Freer , Texas . Sinc e then , ther e ha s bee n a secon d installatio n a t Seve n Sisters . Additiona l unit s hav e bee n furnishe d t o Teja s Ga s Corp . fo r thei r India n Rock , Texa s Plant , t o Albert a Natura l Ga s Compan yfo r th e Corchra n Ga s Treatin g Plant , t o Wes t Ba yExploration s an d JE M Petroleu mfo r Michiga n installations , an d t o Geokinetics , Vernal , Uta h(i n sit u shal e retorting) . Wit hth e exceptio n o f th e Wes t Bay unit , whic hha s no t bee n installed , al l o f thes e ar e functioning wel l and verifyin g th e representation s mad e b yAR I fo r catalys t consumption , efficiency , etc . I n almos t everycase , th e unit s whic h hav e bee n place d i n servic e ar e "firsts " wit hrespec t t o th e mechanica l arrangemen t o r th e proces s flow . Thi s i s n o longe r th e cas e an d w e ar e no wabl e t o approac hmos t job s wit ha background o f wel l demonstrate d performanc e an d wel l define d economics . I n addition , unit s ar e unde r desig n and/o r constructio n fo r ARC O Petroleu mCompany' s Sabl e Plan t a t Plains , Texa s (fo r CO 2 EOR) , Grac e Petroleum , Leonard , Michigan , Coal-Tec , Gillette , Wyomin g (coa l gasification) , an d Texaco' s Sa n Ardo , Californi a fir e floo d project . Th e mos t significan t additio n t o thi s lis t i s th e Oi l an d Ga s Commissio n o f Indi a (ONGC ) wh o hav e selecte d LO-CA T fo r th e Hazir a Plan t t o trea t aci d ga s derive d fro mth e Bomba yOffshor e Project . Thi s installatio n wil l trea t ove r 1 MMMSCF D o f ga s i n seve n LO-CA T unit s wit h12. 5 metri c ton/da yo f sulfu r productio n capacit yeach . Plan s cal l fo r immediat e installatio n o f th e firs t thre e trains , wit htw o additiona l train s i n si xmonth s an d th e remaining tw o withi n tw o years . Thi s pape r describe s th e technica l basi s o f th e process , som e recen t desig n and operatin g experience , an d outline s th e economi c factor s involve d i n th e selectio n o f a LO-CAT unit .

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-P. 5

Technica l Basi s Asimplifie d flowscheme fo r a conventiona l LO-CAT ®Hydroge n Sulfid e Oxidatio n Proces s i s show n i n Figur e 1 . Th e ga s t o b e treate d i s contacte d wit ha n aqueou s scrubbing solutio n i n a n absorbe r an d th e H2 S i s absorbe d an

d converte d immediatel yt o elementa l sulfur . N o othe r chemica l reaction s tak e plac e i n th e absorber . I f CO 2 i s present , i t ma yb e absorbe d t o a limite d extent , bu t th e oxidatio n reactio n i s strictl ylimite d t o hydroge n sulfide . Th e scrubbin g solutio n i s regenerate d b ycontac t wit hatmospheri c ai r i n a n oxidize r vessel . Th e sulfu r form s a s smal l soli d particle s suspende d i n th e aqueou s catalys t solution . The ycirculat e around unti l th e siz e ha s grow n larg e enoug htha t the yca n b e separate d b ysettling . Thi s i s usuall ydon e i n th e botto mo f th e oxidize r vessel , althoug han y vesse l designe d wit hlowvelocit yan d a suitabl e cone-bottomca n b e use d fo r separatio n o f th e sulfur . Fo r plant s whic htrea t onl ya smal l amoun t o f H2 S - 0 t o 0. 5 LT/ D - ther e i s verylittl e mor e t o th e proces s tha n i s show n o n th e left-han d sid e o f Figur e 1 . Settle d sulfu r slurryha s abou t 15 % sulfu r b yweigh t an

d 85 % o f th e dilut e catalys t solutio n i n it . Thi s materia l i s ordinaril ytreate d a s a wast e produc t becaus e o f th e ver ysmal l quantit yo f sulfu r available , an

d becaus e th e valu e o f th e catalys t solutio n i s to o low t o warran t th e installatio n o f separatio n equipmen t t o recove r i t an d retur n i t t o th e process . Alarge r plant , i n th e 0. 5 t o 5 LT/ D rang e o f sulfu r productio n rate , ca n pa yof f dewatering o f th e sulfu r bymean s o f a centrifug e o r filte r i n orde r t o recove r th e catalys t solutio n whic hwoul d otherwis e b e discarded . Large r plant s wit hcapacitie s o f 2 ton s pe r da yupwar d ca n ofte n justif yth e adde d expens e o f a sulfu r melter , molte n sulfu r storag e facilit yan d truckloadin g station . I n thes e units , n o catalys t solutio n i s discarded , an d th e sulfu r ca n ordinaril yb e sol d fo r us e i n sulfuri c aci d manufactur e o r fo r othe r industria l uses . Th e uni t describe d i n Figur e 1 woul d b e quit e suitabl e fo r a low pressur e ga s treating applicatio n a t pressure s up t o abou t 5 0 psig . Ther e i s n o proble mmeetin g th e usua l quarte r grai n H2 S specification , and ordinaril yn o CO 2 o r mercapta n sulfu r compound s ar e remove d fromth e ga s stream . * 

### Hig hpressur eunits , o r unit s wit hver y larg e ga s volumes , requir e modifie dadsorbe r

design s i norde r

t o satisf y th e performanc e requirement s wit hareasonabl efirs t cost . Ventur i scrubbers , packe dscrubbers , stati c mixer s an dothe r conventiona l contactin g device s ar eal l suitable , an dar eal l bein g use dfo r thi s service
. However , grea t

car emus t

b eexercise di nth e desig no f th e contactin g device s t o mak e sur e soli dsulfu r

particle s do no t

caus e pluggin g problems
. W ehav e unit s i noperatio nwit hawid evariet y o f contactin g devices
. - 3

-P. 6

Th e oxidize r vessel s ar e generall yliquid-fille d tank s int o whic h oxidatio n ai r i s introduce d throughai r spreader s o r sparger s a t th e botto mo f th e vessel . Non e o f th e oxidizer s i n servic e hav e mechanical mixin g device s o r packing i n th e oxidize r vesse l excep t fo r thos e whic hhav e ai r i n th e proces s ga s stream . Th e presenc e o f carbo n dioxid e i n th e ga s strea mbein g treate d require s bufferin g o f th e solutio n wit ha n alkal i sal t suc ha s sodiu mhydroxide , soda ash , KOH , o r ammonia . Th e highe r CO 2 partia l pressure , th e mor e bufferin g i s required , an d th e greate r wil l b e th e chang e i n p H o f th e operating solutio n a s th e liqui d circulate s betwee n th e absorbe r wit ha hig hCO 2 partia l pressur e i n th e oxidize r wit ha greatl yreduce d CO 2 partia l pressure . I n chelate d iro n solution s usin g EDT Ao r Typ e Achelate s alone , thi s p H variatio n ofte n lead s t o precipitatio n o f th e iro n fro mth e solution , an

d a nearl ycomplet e los s o f catalys t activity . Thi s doe s no t happe n i n th e LO-CAT ®proces s becaus e o f th e unique , patente d dua l chelat e systemwhic hstabilize s th e iro n an d prevent s precipitatio n a t al l p H levels . Thi s ver ydesirabl e characteristi c o f th e solutio n permit s LO-CA T operation s o n pur e CO 2 streams , an d o n CO 2 a t elevate d pressure s up t o an d including a supercritica l operation . Veryhig hCO 2 pressure s requir e specia l bufferin g techniques , bu t d o no t presen t any fundamenta l proces s problem s fo r LO-CAT . I n case s wher e th e ga s volum e rat e o f flo wi s low , liquid-ful l absorber s hav e prove n t o b e bot hver yefficien t an d fre e o f mechanica l problems . I n situation s wher e th e ga s flowi s lowan d ca n als o b e treate d a s a wast e ga s - tha t i s discarde d int o th e atmospher e afte r cleanu p - a verysimpl e autocirculatio n desig n ca n b e applied . Th e patente d autocirculatio n systemi s a natura l fo r treatmen t o f amin e offgase s an d Figur e 2 i s a proces s flo wdiagram fo r a n autocirculatio n LO-CA T unit . Thi s i s th e desig n whic hi s currentl yi n operatio n a t th e Teja s Ga s India n Roc k Plan t nea r Longview , Texas . Th e autocirculatio n desig n incorporate s a numbe r o f advantage s i n additio n t o thos e liste d fo r th e LO-CA T process . Thes e include :

- Extreme simplicity . Ther e ar e n o solutio n circulating pumps , leve l controls , etc .

- Lo woperating cost . Th e catalys t concentratio n ca n b e hel d t o lo wlevel s (les s tha n 1 l bo f catalys t concen trat e fo r 5 0 t o 10 0 lb s o f water) , whic hminimize s catalys t losse s wit hth e sulfu r product ; lo wcir

culating pum

p horsepower . Electrica l load s ar e limite d t o slightl ymor e tha n th e ai r blowe r horsepowe r requirement . -4
-P. 7

- Verygoo d efficiency . W e wil l guarante e thes e unit s a t 99.95 % efficienc yfo r an yordinaryamin e effluen t treating operation .

- Ver yhighreliability . Operatin g Experienc e Wit hAutocirculatio n Unit s Th e firs t full-size d autocirculatio n proces s plan t starte d u p a t th e Teja s India n Roc k Plan t a t Gilmer , Texa s o n May28 , 1984 . Figur e 3 i s a photograp ho f thi s plant . Thi s plan t wa s constructe d byTeja s t o trea t an d transpor t 5 0 MMSCF D o f ga s unde r contrac t t o Exxon . Teja s contacte d severa l majo r engineering/contractin g companie s fo r proposal s fo r th e treating plan t an d als o contacte d AR I Technologie s directly . Th e initia l proposa l wa s fo r a LO-CAT ®uni t t o trea t 2 0 MMSCF D a t lin e pressur e a s indicate d i n Figur e 1 , wit ha n alternativ e proposa l t o trea t onl y th e aci d ga s produce d bya conventiona l DE Ascrubbing system . Becaus e o f th e hig hCO 2 concentratio n o f th e gas , DE Ascrubbin g woul d b e require d downstrea mo f th e LO-CA T uni t fo r th e hig h pressur e case . Bot hcapita l and operatin g cos t appea r t o b e lowe r fo r th e cas e i n whic hth e LO-CAT uni t woul d b e treate d fo r atmospheri c pressur e an d thi s approac hwa s selected . Th e siz e o f th e plan t wa s upgrade d from 2 0 millio n cubi c fee t a da yt o 5 0 millio n cubi c fee t a day , an d contract s fo r th e equipmen t wer e le t i n 1984 . AR I wa s awarde d a contrac t fo r th e LO-CAT plan t o n a skid-mounte d basis , including th e interconnectin g pipin g betwe n skids , an d th e absorber/oxidize r vesse l a s a stand-alon e unit . Th e amin e plan t wa s furnishe d by EHR-Emro n Engineering , Inc . an d BS& B Engineers , Inc . wa s awarde d th e contrac t fo r installatio n o f al l o f th e equipment . Adeadlin e dat e o f Jun e 1 , 198 4 wa s establishe d fo r commercia l ga s processin g wit hsubstantia l penaltie s fo r failur e t o complet e th e projec t o n time . Operatio n bega n o n schedul e wit hcu t i n o f ga s t o th e LO-CA T uni t o n Ma y28 , 1984 . Initia l operatio n o f th e plan t wa s uneventful . Th e startu p consist s o f simpl yturnin g o n th e ai r blowers , chemica l injectio n pump s an d centrifug e and slurr yhandlin g pumps . Th e initia l ga s processin g rat e wa s i n th e 1 4 MMSCF D t o 2 8 MMSCF D rang e wit hvariabl e H 2 S loadings . Unde r reduce d loa d conditions , th e flow s an d catalys t concentration s i n th e LO-CA T uni t ar e ordinaril ylef t a t desig n rate s an

d 100 % turndow

n i s expecte d durin g a routin e operation . Th e flo wvariation s durin g earl yoperatio n showe d n o advers e effec t o n th e plan t operation , an d n o H2 S residua l wa s foun d i n th e ga s strea

m a t all . Durin g th e firs t mont ho f operation , chemica l additiv e -5
-P. 8



### rate s wer ese t

a t th edesig nlevels , bu t sulfu r productio naverage d les s tha none-hal f

th enorma l desig nrate . Ordinarily , whenauni t i s operate da t

belo w pea k

capacitie s i t

i s possibl et o reduc eth e concentratio no f

activ echemical s i nth esolution , an dth echemica l consumptio ni s furthe r reduce dautomaticall y b y an y decreas ei nth e amoun t o f we t sulfu r discarde dfro mth esystem . Thi s combinatio no f circumstance s le dt o a naccumulatio no f activ ecatalys t

i nth e solution , an dconcentration s ros efro mth e50 0 pp mo f activ eiro no n whic hth edesig nwa s base dt o ove r 65 0 pp mdurin g Jun ean dJuly
. Ther ei s n o advers eeffec t o f suc hchemica l overabundanc ei nth e system , excep t

tha t th ecos t

o f th e chemical s bein g supplie dis , o f course , highe r

whenth eadditio nrate s ar ese t highe r tha nthe y nee d be
. Durin g th einitia l operatin g period , th eplan t wa s attende daroun d t h eclock
. Operator s wer einstructe dt o sampl eth ecatalys t solutio nan drecor dth ep Han dredo x potentia l reading s onc epe r shift
. Alkal i level s abov e7. 5 an dredo x potentia l reading s abov e -20 0 ensur etha t

th eH2 S scrubbin g efficienc y wil l b eadequat ean d tha t th econcentratio no f catalys t

i nth esyste mi s sufficientl y hig ht o handl eth emaximu mH2 S loa do nth eunit
. Chemica l analyse s fo r chelat ecompositio nan dth econcentratio nar eno t ordinaril y recommende di nth efield , an donce-monthl y sample s o f solutio nar e returne dt o ARI' s laboratorie s fo r chec k analyses
. Afte r 3 0 day s o f

operation , th ep

Hredo x potential s indicate d satisfactor y operatio nan dth elaborator y analysi s suggeste dtha t th ecatalys t

additio nrat ecoul db ereduce dsubstantiall y withou t interferin g wit hth eplan t operation
. Subsequen t reduction s i n chemica l additio nrat ebrough t th echemica l consumptio npe r l b o f sulfu r int o lin ewit hth edesig ncondition s whil eaddition s t o th e plan t ar ea t considerabl y belo w desig nadditio nrates . Fro mth estandpoin t o f performanc ean dproces s chemistry , th eTeja s Plan t ha s performe dextremel y well
. Tw o mino r mechanica l problem s hav eoccurre dan dbee ncorrected
. Th efirs t o f thes einvolve dth e los s o f abearin g o nth esingl esulfu r dewaterin g centrifuge
. Thi s apparentl y resulte dfro minitia l misalignmen t o f th ecentrifug e shaft , an dafte r

correctio nther eshoul db en o reoccurrences . Durin g repai r

o f th ecentrifuge , th eaci dga s wa s bypasse daroun d t h eLO-CAT® uni t

t o th eflare
. Th eLO-CA Tuni t coul dfunctio n normall y withou t

th ecentrifug ea t

th eexpens eo f

ahighe r

chemica l consumptio nbecaus eo f th ecatalys t

solutio ndiscarde dwit hth ewe t slurry , an dals o wit hth eproductio no f amuc hlarge r

volum eo f wast ematerial
. Ha dproductio no f alimite damoun t

o f sulfu r dioxid ebee ncritica l fro ma nai r pollutio ncontro l standpoint , th e plan t coul dhav ebee nkep t i nservic ethroug hth eperio do f centrifug eoutage . Alternatively , aplan t o f thi s sor t

coul demplo y dua l centrifuge s (al l othe r rotatin g equipmen t i nth eplan t

i s spared) , o r

a t thi s siz eo r

slightl y larger , acontinuou s melte r coul db eemployed
. - 6
-P. 9

Th e secon

d mechanica l problemoccurre d during September , 198 4 a s th e resul t o f a boilove r o f th e amin e still . Thi s discharge d approximatel y100 0 gallon s o f MDE Asolutio n int o th e LO-CAT ®plant , probabl ya substantia l quantit yo f liqui d hydrocarbons . Th e resul t o f thi s upse t wa s continue d operatio n o f th e LO-CA T uni t withou t diminishe d efficiency , bu t som e foamin g an d carryove r o f LO-CAT solutio n fromth e uni t wit hth e oxidize r air . Ordinarily , w e d o no t expec t t o se e anynegativ e effec t o n th e proces s whe n th e solutio n i s contaminate d wit hamines . Th e same i s tru e fo r glycol , alcohol s an

d othe r completel ywate r miscibl e solvents . Hydrocarbons , o n th e othe r hand , d o hav e a negativ e effec t o n th e mechanica l separatio n o f th e sulfur . Liqui d hydrocarbon s we t th e sulfu r particle s preferentiall yan d caus e themt o agglomerat e int o sponge-lik e masse s tha t entra p ai r bubbles . This , again, woul d ordinaril yb e counteracte d b yth e additio n o f a larger-than-norma l dosag e o f wettin g agen t supplie d t o ensur e wettin g o f th e sulfu r particle s unde r norma l conditions . Thi s inciden t di d no t resul t i n anydowntim e o r discharg e o f anyH2 S o r sulfu r dioxid e fro mth e plant . However , i t di d resul t i n solutio n carryove r fro mth e oxidize r fo r a perio d o f tw o o r thre e day s whil e wettin g agent s wer e bein g adde d a t a highe r tha n norma l rate . Overall , operatio n o f th e LO-CA T uni t ha s bee n troubl e fre e an d performanc e ha s bee n nearl yperfec t wit hrespec t t o eliminatin g emission s o f SO 2 an d H2 S fromth e atmosphere . Chemica l consumptio n fo r th e uni t a t desig n condition s consist s o f addition s o f eac ho f th e following materials :

- ARI-31 0 Catalys t Concentrat e

- ARI-310 M Chelate-ric hMakeu p Solutio n

- ARI-40 0 Biosta t

- Wettin g Agen t

- KO H
Th e additio n rate s fo r thes e material s ar e lowe r tha n th e design rate , becaus e th e sulfu r productio n rat e i s lowe r an d th e chemica l consumption s ten

d t o b e proportiona l t o th e sulfu r discar d rate . Gal/h r 0.3 8 1.0 4 0.01 5 0.013 5 3.87 3 $/Da

y 86.1 8 160.7 4 4.5 7 2.1 9 163.5 9 417.2 7

-7
-P.1 0

Th e sulfu r produc t wa s represente d byAR I t o b e o f goo d chemica l quality , bu t o f littl e valu e becaus e o f th e relativel ylo w productio n rat e involved . A t 1. 5 LT/D , th e valu e o f th e recovere d sulfu r i s no t sufficien t t o payfo r th e capita l cos t o f th e melting storag e an

d truckloading facilitie s require d fo r produc t sales . Th e sulfu r produc t emitte d b yth e India n Roc k Plan t appear s t o averag e 5 0 t o 65 % sulfu r b yweight , wit himpuritie s consistin g o f th e catalys t solutio n ingredients . Achemica l assayo f thi s materia l i s show n i n Tabl e 1 . I n orde r t o evaluat e th e sulfu r whic hcoul d b e mad e b ycontinuou s melting , sample s o f th e India n Roc k Plan t produc t wer e melte d i n a laborator yautoclave . Th e molte n produc t solidifie d t o a nea r brigh t yello wcolor , an d wa s remarkabl yfre e o f impurities . Experienc e a t Albert a Natura l Ga s Th e Corchra n natura l ga s liquid s plan t operate d b yAlbert a Natura l Ga s Compan ya t Corchran , Alberta , Canad a wa s constructe d i n 1981- 2 wit ha desig n capacit yo f ove r on e billio n cubi c fee t pe r dayo f natura l gas . Th e plan t consist s primaril yo f a n expande r typ e refrigeratio n uni t followe d b ya cryogeni c ga s separatio n system whic hproduce s severa l hundre d thousand barrel s pe r dayo f natura l ga s liquids . Th e ga s enterin g th e plan t i s o f pipelin e quality , wit hles s tha n 1/ 4 grai n H2 S pe r 10 0 SCF . Carbo n dioxid e concentratio n i s als o quit e lo wan

d average s o n th e orde r o f 1.3% . Th e Corchra n plan t wa s designe d a s a "swee t gas " plan t throughout . However , provisio n wa s mad e fo r th e separatio n o f CO 2 fromth e ethan e t o liqui d produc t b y mean s o f a liquid-liqui d amin e extractio n system . Whe n thi s plan t wa s pu t o n strea mi n 1982 , i t becam e apparen t tha t alon g wit hth e CO 2 condense d fro m th e ga s b yrefrigeration , sufficien t hydroge n sulfid e wa s remove d t o rende r th e C02~ric haci d ga s fromth e amin e extractio n uni t odorless , an d capabl e o f creating a loca l nuisance . Th e Albert a Natura l Ga s personne l becam e awar e o f th e LO-CAT ® process , an d wer e encourage d byth e successfu l operation s o n hig h CO 2 stream s a t th e Seve n Sister s Ga s Field . I n October , 1983 , Albert a Natura l Ga s ordere d a LO-CAT H2 S scrubbing systemfromARI . Th e plan t wa s designe d b yAR I an

d fabricate d i n Canada . Startu p wa s i n August , 1984 , an d ha d man

yfeature s i n commo n wit hth e operation s a t India n Rock .

-8
-P.1 1

Th eH2 S loadin g t o th e plan t ha s t o dat ebee nconsiderabl y belo w th e desig nrate . Thi s doe s no t caus ean y operatin g problems , an dha s resulte di nsubstantiall y complet eremova l o f th e hydroge nsulfid e rathe r tha nth e 99 % remova l efficienc y fo r whic hth e plan t wa s designed
. Th eflo w schem ei s significantl y differen t tha ntha t

utilize da t India nRock , becaus eo f th e potentia l futur eus e o f th e CO 2 fo r beverag epurposes . I norde r t o avoi dcontaminatio no f th e ai r strea mo f

th e CO 2 'strea mwit hoxygen , separat eabsorber/oxidize r vessel s wer einstalled
. Th e basi c flo w schem eappear s nearl y identica l wit htha t utilize dearlie r wit hth e Seve nSister s operation , bu t

th e contacto r

vesse l i s markedl y different
. Wherea s t h eSeve nSister s unit s utiliz elo w pressur edro p packe dabsorbe r vessels , th e Corchra nha s alarg eliquid-ful l vesse l instead
. Th e liquid-ful l absorbe r i s muc hlarge r

i ndiameter , mor ecostl y tha n t h epacke dcolumn , an dha s ahighe r pressur edrop
. However , thi s typ eo f

contacto r

ha s almos t

n o potentia l fo r pluggin g wit h elementa l sulfur , an di s inherentl y aver y hig hefficienc y device
. T h eeconomi c consideration s involve dth e us e o f asingle , mor e expensiv eliquid-fille dabsorbe r o r alternativel y tw o packe d columns , on e o f

whic hwoul dserv ea s aspar eshoul dsulfu r pluggin g o f th e operatin g vesse l occur . Th eCorchra nplan t produce s arelativel y trivia l amoun t o f sulfu r

a s compare dwit hIndia nRock , bu t accomplishe s aver y importan t ai r pollutio nfunction
. Becaus eo f th e .lo w sulfu r

productio nrate , chemica l consumptio ni s extremel y smal l an dha s bee ndifficul t t o ascertain
. Th edesig nrate s o f eac ho f

th e chemica l constituent s are :

ARI-31 0 ARI-310 M ARI-40 0 Wettin g Agen t KO H Gal/h r 0.19 5 0.09 6 0.01 4 0.01 2 0.9 7 $/da

y 44.2 2 14.8 3 4.2 6 1.9 4 1.7 0 62.6 9

- 9

-P.1 2

Economi c Consideration s Th e tw o plant s describe d previousl yrepresen t typica l auto circulatio n and conventiona l LO-CAT ®units . Th e cost s fo r bot h type s o f unit s ar e strongl ydependen t upo n th e sulfu r productio n rate , an d relativel yles s dependen t upo n th e ga s flowrate , s o lon g a s th e ga s compositio n i s withi n th e "norma l rang e o f compositions " fo r eac htyp e o f unit . Figur e 4 i s a plo t o f estimate d capita l cost s fo r th e skid-mounte d equipmen t packag e fo r smal l (les s tha n 5 LT/D ) LO-CAT unit s o f bot h types . Thes e cost s ar e relativel yaccurat e (+10% ) and represen t currentl yquote d plant s fabricate d b yARI , les s installatio n cost . Installatio n ordinaril yinclude s th e installatio n o f foundations , th e vessel s an d equipmen t skid s i n plac e an d securin g them , installin g inter-ski d pipin g an d electrica l connections , bringin g utilitie s suc ha s electri c power , instrumen t air , an d th e ga s piping t o th e unit , an d checkou t o f equipmen t fo r prope r mechanica l operation . Mos t o f th e LO-CA T unit s i n operatio n ar e i n geographi c area s wit h moderat e climates , and n o provisio n i s mad e fo r freez e protection . Thes e unit s d o ordinaril yhav e a smal l tri mheate r installe d i n thes e circulatin g solutio n stream s o r i n th e absorber/oxidize r vesse l t o provid e fo r keepin g th e solutio n temperatur e abov e th e temperatur e o f th e incoming ga s i n orde r t o preven t condensatio n o f hydrocarbon s o r wate r i n th e unit . I n cas e o f brie f excursion s belo w32°F , thes e unit s shoul d continu e t o functio n properl ybecaus e o f th e hea t liberatio n b yth e oxidatio n o f hydroge n sulfide , an d b y us e o f th e tri m

heater s t o maintai n th e solutio n temperatur e abov e freezing . However , i n colde r climate s eithe r provision s fo r hea t tracing o r enclosur e o f portion s o f th e uni t i n a heate d buildin g i s ordinaril yrequired . Th e Teja s uni t wa s installe d withou t provision s fo r freez e protection , and i s basicl ya n outdoo r unit . Som e hea t tracin g wil l b e installe d fo r protectio n o f th e smalle r lines , an d th e us e o f ethylen e glyco l a s a n antifreez e i s contemplate d i f th e weathe r become s unusuall ycold . Inclusion s o f severa l percen t ethylen e glyco l i n th e circulating solutio n d o no t hav e a deleteriou s effec t o n th e operatio n o f th e proces s an d ca n depres s th e freezing poin t o f th e solutio n substantially . Th e Albert a Natura l Ga s uni t i s full yenclose d i n a heate d building . Th e uni t unde r constructio n fo r ARC O Oi l an d Ga s Compan

yi n Plaines , Texa s wil l b e partiall yenclose d i n a heate d building , wit hth e absorptio n column s extending beyond th e roo f line . Th e cost s fo r equipmen t package s indicate d i n Figur e 4 ar e base d o n "normal " range s o f concentratio n o f H2S . Outsid e thes e range s some additiona l capita l and/o r operating cost s ma yb e required .

-10
-"Normal " fo r a n autocirculatio n uni t o n a n amin e effluen t strea m cover s th e rang e fromabou t 1 0 vol % H2 S upward s t o 100 % H2S . Lowe r concentration s ca n b e handle d withou t difficulty , an d d o no t involv e an yincreas e i n th e operating cost . However , belo w1 0 vol % H2 S ga s stream s requir e absorbe r volume s an d add significantl yt o th e firs t cost . Unit s o f thi s basi c desig n hav e bee n buil t fo r operation s a s lo wa s 1 vol % H2S . "Normal " concentration s fo r conventiona l unit s usuall yinvolv e H2 S concentration s belo w2 vol% . A s i n th e cas e fo r autocirculatio n units , thi s rang e ca n b e extende d considerabl yabov e th e 2 % level , bu t usuall yrequire s a capita l cos t somewha t highe r tha n indicated . Th e principl e differenc e betwee n conventiona l an d autocirculatio n unit s fro m

a functiona l standpoin t lie s i n th e greate r eas e o f separatin g th e proces s ga s fro moxidize r ai r i n a conventiona l design . I n som e cases , conventional desig n i s use d eve n thoug h ther e i s n o requiremen t fo r recoveryo f th e sweetene d gas . Thi s i s usuall ybecaus e th e ga s volum e i s verylarg e an d th e concentratio n o f H2 S i s s o lo wtha t a n inordinatel yexpensiv e absorbe r woul d b e require d fo r th e autocirculatio n design . Also , th e autocirculatio n approac hi s sometime s use d eve n thoughi t i s necessar yt o separat e th e proces s ga s fro m th e oxidize r air . Thi s i s don e byth e inclusio n o f a "cap " ove r th e uppe r en d o f th e absorbe r whic hplace s a positiv e liqui d sea l betwee n th e sweetene d ga s an d th e spen t oxidize r air . Operatin g cost s fo r LO-CAT ®unit s ca n b e divide d int o utilit ycost s an d chemica l costs . Th e utilit ycost s consist s o f electri c powe r t o driv e th e solutio n circulating pump s (fo r th e conventiona l design) , th e oxidize r ai r blowers , sulfu r slurrypump s an d clarifie d solutio n retur n pump s an

d th e centrifug e i f on e i s included , o r stea m fo r th e sulfu r melte r o n large r units . Usually , ther e i s a smal l tri m heate r include d i n th e circulatin g solutio n lin e o r withi n th e oxidize r vesse l t o maintai n th e solutio n temperatur e i f insufficien t hea t i s bein g generate d b yth e reactio n o f hydroge n sulfid e an d oxyge n t o kee p th e solutio n temperatur e a t leas t a s war ma s th e incomin g ga s temperature . Th e requiremen t her e i s quit e nominal , an d o n unit s o f on e hal f to n pe r da yo r greate r capacity , ther e i s usuall yn o requiremen t fo r externa l heat . Operatin g utilit y requirement s ar e ordinaril yfixe d a t th e desig n rat e coinciding wit h maximu msulfu r handlin g capacity , an d remai n fixe d regardles s o f actua l load o f th e unit . Chemical cost s consist s o f catalys t and makeup solution , alkalin e bufferin g materia l fo r p H contro l an d trac e additive s t o contro l we t abilit yo f th e sulfu r particle s an d t o preven t biologica l attack . Thes e chemical s ar e al l use d a t rate s tha t ar e proportiona l t o th e actua l sulfu r productio n rate . Tha t is , a plan t designe d fo r 5 to n
-11
-P. M



### pe r da y sulfu r

productio ncapacit y bu t actuall y runnin g a t 0. 5 to n p e r da y wil l us eonl y on etent ho f th echemical s specifie dfo r operatio na t

desig nconditions
. Fo r prolonge doperatio na t ver y lo w loads , eve ngreate r saving s ca nb erealize db y takin g advantag eo f th ehighe r

circulatio nrat ebuil t int o th eproces s t o reduc eth e catalys t

strengt ht o aleve l adequat efo r th elowe r

loadings
. Th e discar do f

catalys t

solutio nwit hth esulfu r produc t

decrease s i n proportio nt o th edecreas ei nsulfu r production
. I f

th e concentratio no f

catalys t

i nth esolutio ni s reduce dbelo w th e desig nconcentration , eve ngreate r saving s ar erealized
. Fo r example , th e5 to nuni t operatin g a t

0. 5 to npe r

da y an ddesigne d fo r 50 0 ppmiro nconcentratio ni nth esolutio nwoul ddiscar don e tent ho f

th enorma l amoun t o f th esolution , an dth eiro n concentratio ncoul db eallowe dt o decreas et o onl y 5 0 ppm , reducin g th ediscar drat et o 1/10 0 o f th edesig nrate . Fo r autocirculatio nunits , th eai r blowe r

comprise s mos t

o f th e utilit y costs . I nsmal l unit s th eai r blowe r i s size dt o provid e adequat ecoolin g a s wel l a s oxidation , an dlowe r capacitie s typicall y requir e3 0 horsepowe r pe r to npe r

da y o f sulfu r productio n capacity
. Fo r

larg eunit s i t

i s uneconomica l t o provid ecoolin g wit hth eai r

blower , an dth ebrak ehorsepowe r pe r to no f sulfu r pe r da y i s reduce dt o 1 5 an dothe r mean s o f

coolin g ar eprovided
. Th eonl y othe r

significan t

utilit y cos t

fo r LO-CAT ® unit s i s th e circulatin g pum

p fo r conventiona l designs
. Optimumdesig ninvolve s a nabsorbe r

whic hoperate s a t abou t 2 0 psi g an da natmospheri c pressur eoxidize r

vessel
. I nthi s cas ether ear ethre elevel s o f powe r requiremen t

base do nth emetho do f disposa l o f

th esulfur
. Fo r unit s wit hmelters , th ecatalys t iro nconcentratio ni s ordinaril y maintaine da t 150 0 ppm , an dth ehorsepowe r pe r to npe r da y o f sulfu r fo r th ecirculatin g pum p i s approximatel y 25
. Unit s wit hcentrifuge s instea do f melter s ordinaril y operat ewit habou t 100 0 ppmiro nconcentratio nan dabrak ehorsepowe r pe r to npe r

da y o f 37.5
. Smal l unit s wher eth esulfu r i s discarde dwithou t dewatering , generall y operat ea t 50 0 pp man dus e7 5 horsepowe r pe r to no f sulfu r pe r day
. O f course , o nautocirculatio nunit s ther ei s n o circulatin g pum p horsepowe r

a t all
. Th ecost s consis t

principall y o f

catalys t

concentrat ean dmakeup solutio nusag ean dKO Hconsumption
. Unit s operatin g a t atmospheri c pressure , th ecatalys t consumptio nusuall y i s o f greate r

concer n tha nbufferin g agen t losses
.

-12

-ARI-31 0 catalys t i s no t consume d i n th e proces s an d nee d b e adde d onl yt o replac e solutio n whic hi s los t b yspillag e o r withdraw n wit h th e sulfu r o r i n a separat e blowdow n stream . Catalys t cost s fo r autocirculatio n unit s wit hcatalys t concentratio n o f 20 0 ppm fo r th e thre e differen t method s o f sulfu r disposal , give n i n dollar s pe r to n o f sulfur , ar e tabulate d below : Discar d o f 1 5 wt % slurry$141.20/pe r to n Fo r 50 % cak e discar d from centrifug e $ 21.20/pe r to n N o discar d wit hsulfur ; thiosulfat e withdrawn base d o n 2 % thiosulfat e productio n $ 1.23/pe r to n I n th e cas e o f unit s wit hmelters , ther e i s n o wa yfo r solubl e sulfu r compound s suc ha s thiosulfat e o r sulfat e t o leav e th e LO-CAT ® unit , an d th e laborator yoperation s hav e suggeste d tha t th e thiosulfat e concentratio n wil l i n time buil d up t o sufficientl yhig h level s t o requir e a purg e strea m t o preven t condensatio n o f sulfat e o r thiosulfat e salts . Fo r thi s reason , a calculate d los s o f catalys t wit ha purg e strea mbase d o n maintainin g n o mor e tha n 30 % tota l solubl e sulfu r compound salt s i n solutio n ha s bee n included . Actua l operatin g result s ove r 3-1/ 2 year s wit htw o larg e unit s wit h melter s hav e indicate d tha t th e thiosulfat e ha s no t buil t up t o a sufficientl yhig hconcentratio n t o requir e purging o f an ysolution . I t i s reasonabl e t o expec t tha t thi s catalys t los s ma yno t b e incurre d i n futur e units , bu t ther e i s no t sufficien t evidenc e b y wa yo f a thiosulfat e decompositio n mechanis m t o b e sur e tha t ther e wil l no t b e some catalys t los s vi a thi s route . ARI-310 M i s a chelate-ric hadditiv e whic hi s pu t i n th e uni t t o replac e th e chelate s whic hdegrad e wit htime . Bot hlaborator yan d fiel d tes t result s indicat e tha t thi s rat e fo r ARI-31 0 i s approximatel y.0 7 lb s pe r l bo f sulfu r produced . Th e cos t o f thi s materia l varie s wit hquantity , an d ma yb e roughl y characterize d a s give n below : Smal l unit s (0- 1 LT/D ) $ 94.00/pe r to n Mediu munit s (1- 5 LT/D ) $ 78.50/pe r to n Larg e unit s (greate r tha n 5 LT/D ) § 62.75/pe r to n

-13
-I t i s apparen t tha t man yfactor s ente r int o th e operating cos t o f

individua l units . However , on e ma ygeneraliz e cost s pe r to n o f sulfu r a s a functio n o f plan t siz e a s follows : P.1 6

Typica l siz e LT/ D Smal l Plant s 0. 5 Mediu

m Plant s Larg e

Plant s 1 0 Typica l cos t $/annua l to n sulfu r production : Autocirculatio n Plan t (equipmen t only ) Conventiona l Plan t (equipmen t only ) Operatin g cost s fo r Autocirculatio n Uni t Catalys t cost s $/Ton Utilit ycos t Tota l operating cost , $/Ton Conventiona l Uni t Catalys t cost s $/Ton Utilit ycos t $/Ton Tota l operating cost , $/Ton $1,000.0 0 $ 700.0 0 $ 500.0 0 2,000.0 0 1,000.0 0 680.0 0

235.2 0 1.5 0 236.7 0
450.0 0 5.2 5 455.2 5 99.7 0

1.5 0 100.7 0
184.5 0 3.3 5 187.8 5 64.0 0

0.7 5 64.7 5
81.2 0 2.0 0 83.2 0

Agrea t dea l o f car e mus t b e use d i n applying thes e figure s t o unit s tha t ar e unusual , o r whic hinvolv e operatio n a t hig hpressure s o r wit hgaseou s constituent s othe r tha n ligh t hydrocarbons , CO2 , an d H 2 S .

-14
-Summary

Th e LO-CAT ®

proces s offer s a simpl e an d cost-effectiv e metho d fo r remova l o f hydroge n sulfid e fromeithe r natura l ga s stream s o r fro m amin e aci d gas . Severa l unit s hav e come o n strea mduring th e pas t yea r and hav e generall yworke d wel l an d withi n th e representation s o f chemica l consumptio n an d operating utilitie s represented . Plan t cost s pe r to n o f sulfu r varyconsiderabl ywit hplan t size , and i n th e large r size s ar e competitiv e wit hClau s plants , althoughth e efficienc yo f th e LO-CA T proces s i s muc hhighe r and turndow n capabilit ysubstantiall yunlimited . Fo r smalle r plants , th e capita l cost s ar e no t competitiv e wit hth e Clau s process , bu t LO-CAT work s well , wherea s verysmal l Clau s unit s d o not . Chemica l cost s fo r smal l LO-CAT unit s ar e hig hi n term s o f th e cos t pe r to n o f sulfu r produced , bu t lo wi n tota l cost , an d usuall y insignifican t i n th e evaluatio n o f alternativ e processes . Larg e plant s requir e muc hles s chemica l cos t pe r to n o f sulfur , bu t th e cost s ar e larg e i n th e aggregat e an d likel yt o b e a significan t facto r i n th e proces s evaluation . Fo r larg e plant s wit hsulfu r meltin g equipment , th e minimu mchemica l cos t i s o n th e orde r o f $5 0 pe r long to n o f sulfu r produce d unde r th e mos t favorabl e conditions . Th e LO-CA T proces s i s th e onl yviabl e alternativ e fo r treating some smal l ga s stream s whic hcanno t b e adequatel yhandle d b yth e Clau s process , ye t ar e to o larg e fo r economical applicatio n o f iro n sponge . However , plant s o f substantia l capacit yar e bein g license d wher e th e outstandin g advantage s o f th e LO-CA T uni t outweighth e chemica l cos t disadvantage . Th e mos t recen t o f these , a 37. 5 LT/ D syste mfo r th e Oi l an d Natura l Ga s Commissio n o f India' s Gujara t offshor e plan t i s an example .

-15
-P.1 8



### TABL E 1 

## CHEMICA L ASSA YO F TEJA S SULFU R PRODUC T SULFUR . WT % 57.5 6 IRON.WT % 0.043 1 P H 7.2 8 MELTE D SULFU R APPEARANC E SEM I BRIGH TYELLO W MELTE D SULFU R F E ASSA Y4 5 PP M WT . REACTIVIT Y REACTIVIT YSULFID E <0.2 5 PP M WT . REACTIVITY , CYANID E <.02 5 PP M WT .P.1 9



### TABL E 2 

## RCR A HAZARDOU S WAST E DETERMINATIO N

E.P. TOXICITY 

### ARSENI C BARIU M CADMIU M CHROMIUM , TOT . LEA D MERCUR Y SELENIU M SILVE R DETERMINED VALUE PPM WT. 

### 0.00 3 <0.0 1 <0.00 1 0.00 6 <0.0 1 <0.00 1 <0.0 1 0.00 4 MAXIMUM PERh PPM WT. 

### 5. 0 100. 0 1. 0 5. 0 5. 0 0. 2 1. 0 5. 0>> S uiJ : -)U vy*! o

SOU R GA S SCRUBBE R VENTUR I PACKE D

PRECQNTAGTO R ABSORBE R OXIDIZE R AI R COMPRESSO R CENTRIFUG E 

# I

GAS* 1 I N *!«>» * J SWEE TGA S OU T 1 1 

### £** T O ATMOS
. 1 1


# T —0 - SOLUTIO N COOLE R xt n -y— vv

v>

/ |

. • - •

• * ••• o * 1

*.
.. -.

i_j / AI R SPARGE R 

# J Q^TVWN ]

FIGUR E 1 

# B e ^

NOTE : CHEMICA L 

## FLO WSCHEM E FO R CONVENTIONA L LO-CAT ®

UNI T ADDITIO N EQUIPMEN TNO TSHOW N SOLUTIO N CIRCULATIO N PUM P S 3 CLARIFIE D SOLUTIO N RETUR N TAN K SULFU R CAK E RECEPTACL E
SILENCE R



# i

* ^ T CLARIFIE D SOLUTIO N RETUR N PUM P 

# a n TECHMXOGE S N C ANAEROBI C LO'CAT^IHYDROGE N SULFID E OXIDATIO N PROCES S ASOU R GA S

SCRUBBE R

t \ SOU R GA S K ^vxx

x

NOTE : AUTOCIRCULATIO N AI R

ABSORBE R /

OXIDIZE R BLOWE R CENTRIFUG E FEE D TAN K CENTRIFUG E

VEN T T O ATMO S 

# 1

^ 

# 1

•" * •" * k ' •-»'«•• ' -• •• ' * * J V 

# ? HI— * SULFU R CAK E RECEPTACL E CLARIFIE D

SOLUTIO N RETUR N TAN K FIGUR E 2

J - v



### rr-FWN r SLURR Y PUM P 

# Ld i FLO WSCHEM E FO R TAI L GA S AUTOCIRCULATIO N LO-CAT TM

< .

SLURR Y

PUM P

CHEMICA LADDITIO N EQUIPMEN TNO TSHOWN
. f-\ NOTE : CENTRIFUG E NO TREQUIRE D

CLARIFIE D SOLUTIO N RETUR N PUM P 

# a n TECHNOLOGIE S N C PROCES S FLO WSKETC H FO R AUTOCIRCULATIO N LO-CATi»HYDROGE N / SULFID E OXIDATIO N PROCES S —"W.ASJ" ' r— = =P.2 2

*»"OI«-' | mi.-'fmm'—*...-• - *?•.'-* " ^1.1 . " r' 'CO



## c r <

. j

- i 

## o a H CO 

## o o FIGUR E 4 

## PLO TO F EQUIPMEN TCOS T V S SULFU R CAPACITY" ' 10,000,00 0

1,000,00 0

100,00 0

1 1 0 10 0 100 0

SULFU R CAPACITY , LB/H R (1 ) SULFU R CONCENTRATION , FREEZ E PROTECTIO N NO TINCLUDED .