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# OAR Box 1784 Prepped by Ollie Stewart



### Document

Number: 

# 27 ) ll-B- 1
Docket Number: 

# A-84-4 4

Printed 10/31/2008 8:05:39 AM Sheet 27 of 143P. 2

• ; f J* ^ ' i UNITE D STATE S ENVIRONMENTA L PROTECTIO N AGENC Y i*

-r\- 1
"* " I SS2 Z * Office o f Ai rQualit

yPlannin g an d Standard s _/ 6 '- ^ x \*<Art Research Triangl e Park , Nort h Carolin a 2771 1 

### bit 

### A 1983

MEMORANDU

M SUBJECT: Tri p Repor t - Inspectio n o f LO-CA T Proces s a t Fletche rOil , Carson , Californi a FROM : Charle s B

. Sedma n Standard s Documentatio n Section , ISB/ESE D (MD-13 ) TO : Ke n Durkee , Chie f

Standard s Documentatio n Section , ISB/ESE D (MD-13 ) Th e LO-CA

T proces s a t Fletche rOi l & Refinin g Company , Carson , California , wa

s inspecte d b

yEP A personne l o n Septembe r27 , 1983

. Attendee s included :

Charle s Sedma

n U

. S

. EP A "Gai l Lac

yU

. S

. EP A Wilso n Chapma

n ' AR I Technologie s Conni e Rutte rSout h Coas t APC D Davi d Zeige rSout h Coas t APC D Th e purpos e o f th e visi t wa s t o gathe rinformatio n o n processe s whic h remov

e an d recove rsulfu rfro m refiner ysou rgase s fo ra forth

comin g NSP

S review

. Backgroun d I n 1972 a ne

w sourc e performanc e standar d wa s promulgate d whic h limit s hydroge n sulfid e (H2S ) concentration s i n refiner yfue l ga s t o 1 0 grai n pe r10 0 standar d cubi c fee t ga s o rabou t 160 ppmv
. Refinerie s havin g larg e amounts o f recoverabl e H2 S have traditionall ychose n t o scru b sou rfue l ga

s wit h a n amin e solution , eventuall yrecoverin g th e sulfu rvi a th e Clau s proces s (wit h additiona l clean-u p b ytai l ga

s treater s wher e required)

. Smalle rquantitie s o f fue l H2 S (perhap s up
. t o 1 0 lon g ton s pe rday ) ma yb e mor

e economica l t o recove rb yother , processes , including :

0 direc t conversio n o f fue l H2 S t o elementa l sulfu rb yth e Stretfor d proces s
0 direc t scrubbin g o f fue l gas whic h convert s H2 S t o salabl e sodiu m hydrosulfid e (NaSH )P. 3

° direc t scrubbin g o f fue l ga s an d conversio nt o salabl e ammoniu m thiosulfate , (NH3)2S203 .
0 us e o f th e LO-CA T proces s
A s par t o f th e revie w o f th e fue l ga s NSPS , a s require db y th e Clea n Ai r Act , th e abov e option s ar e t o b e evaluate dt o determin e th e per formanc e an

d cos t o f fue l ga s H2 S control . Result s woul dthe nb e use d t o determin e i f a revisio nt o the-NSP. S i s warranted . Th e LO-CA T Proces s Th e LO-CA T proces s consist s o f absorbers , a n oxidizer , an

d sulfu r separatio nan

d storage . Th e LO-CA T catalys t consist s o f an aqueou s solutio no f chelate diron , whic hi s circulate di n a close dloo pbetwee n absorber s an

d th e oxidize r vessel . I nth e absorbers , th e H2 S i s absorbe d int o th e catalys t solutio nan d oxidize dt o elementa l sulfur : 2Fe + 3 + S- 2 — > 2Fe+ 2 + S Th e reduce d(FE + 2 ) iro ni s the nrecirculate d t o th e oxidize r vesse l wher e th e ironi s oxidize dt o Fe + 3 b y aereatio nan

d recirculate dt o th e absorbers . Contaminate dai r exitin g th e oxidize r i s route dt o an incinerator . Elementa l sulfur , i n a slurrie dform , i s firs t coole d an d the n coalesce di

n th e oxidize r an

d settle s t o th e bottom . Sulfu r i s continuall y withdrawnfro

m th e oxidize r an

d pumpe dt o a sulfu r melter . Th e aqueou s catalys t solution/molte nsulfu r mixtur e i s the nseparate db y gravit y wher e th e sulfu r i s withdrawnt o storag e an d th e catalys t solutio nreturne dt o th e oxidizer . Normall y a slipstream

o f th e clarifie dsolutio ni s withdraw n a s by-produc t ammoniu m thiosulfat e solution , onc e th e thiosulfat e concentratio n ha s increase dt o a predetermine dmaximum , usuall y 2 0 percen t b

y weight . Figur e 1 show s th e LO-CA T proces s a s designe da t Fletche r Oil . A t Fletche r severa l additiona l feature s ar e incorporate dwhic hinclud e (1 ) two-stag e absorptio no f highpressur e proces s gas , an d (2 ) ventur i expansio nchamber s on absorbe r vessel s (no t show nin Figur e 1 ) t o flas h of f hydrocarbo nliquid s enterin g th e absorbers . Fletche r Experienc e
A t Fletche r Oi l severa l operatin g problem s wer e experienced , including : (1 ) highe r tha ndesig nlevel s o f H2 S in sou r ga s (2 ) su l fu r floatin g (3 ) solutio nfoamin g (4 ) corrosion , erosio n (5 ) pluggin g (6 ) biologica l growt h (weakenin g o f catalyst )P. 4

Th e highe r concentration s o f H2 S i nth e sou r ga s resulte di n highe r level s o f H2 S i nth e produc t fue l gas . Sinc e i t wa s determine d tha t th e existin g system woul d accommodat e th e increase dcatalys t recirculatio nan

dsulfu r meltin g demands , additio no f a secon dabsorbe r (preabsorber ) i nserie s wit hth e origina l absorbe r solve dth e problem . Sulfu r floatin g i s cause db y contaminatio no f sulfu r particle s wit h liqui dhydrocarbo ncarryove r fro m proces s units . Thi s als o result s i n a lowe r purit y

sulfu r product . Thi s problem wa s partiall y

solve db

y th e additio no f ventur i expander s t o flas hof f hydrocarbon s i nth e absorbe r liquo r andpartiall y b y th e judiciou s us e o f wettin g agent s i nth e catalys t solutio nt o sin k sulfu r i nth e separator . Solutio nfoamin g i nbot habsorber s an doxidize r vesse l wa s alleviate d b y th e continuou s additio no f smal l amount s o f anti-foamin g agen t t o th e fres hcatalys t solution . Corrosio nan

derosio nproblem s i npipin g an dvalve s wer e mitigate da t Fletche r b

y replacin g al l carbo nstee l valve s an dpipe s wit hstainles s steel . Pluggin g o r bridgin g o f th e oxidize r con e wit hsulfu r wa s solve db y additio no f a

nintermitten t ai r spargin g system . Pluggin g i nth e smal l diamete r slurr y

pipe s ha s bee ncontrolle d b y additio no f a straine r t o remove compacte dsulfu r slugs . Inth e molte nsulfu r circuit , stea m jackete d pipin g replace d stea m trace dan

dinsulate d piping . Finally , catalys t degredatio ndu e t o biologica l growt hha s bee ncon trolle db

y th e additio no f biocide s t o th e fres hcatalys t charge . Th e us e o f biocide s ha s bee nlessene db y operatin g th e system a t highe r temperature s - 125° F versu s 110° E originally . Proces s Control s Th e Fletche r LO-CA T i s operate doutdoor s wit hno centra l contro l panel . Inadditio nt o safet y alarm s fo r hightemperatures , pressures , o r mechanica l failures , proces s contro l i s als o maintaine db y intermittent-samp l in g o f th e catalys t solution . O na 2-hou r basis , redoxpotential , an dp H ar e sample dan

dmeasure db

y Fletcher' s laboratories . P H i s generall y maintaine d betwee n6. 9 an

d7.5 . Onc e a wee k a sampl e o f catalys t solutio ni s take n andsen t t o th e LO-CA T licensor , AR I Technologies , fo r determinatio n o f chelate dFe + 3
. Also , H 2 S inth e produc t fue l ga s i s sample dan danalyze d ewery 2 hours . Successfu l operatio nis , therefore , dependen t oncatalys t iro nan d chelat e concentration , pH , an dcatalys t circulatio nrates , controlle d withi n narro w range . Also , th e additio no f smal l amount s o f additive s i s critica l i nth e contro l o f advers e chemica l an dbiologica l phenomena . Also , a s discusse dearlier , th e temperatur e o f th e solutio ni s importan t i ncontrollin g biologica l activity .P. 5



### Emissio nReductio n Th e LO-CA T proces s a t Fletche r handle s u pt o 2- 3 volum e percen t o f H2 S (20,000-30,00 0 ppmv ) i nenterin g sou r gas . Durin g m y visit , I observe dproces s an

danalytica l lo g book s showin g outle t H2 S concentration s rangin g fro

m 0-3 0 ppm

v H2 S i nproduc t ga s fo r a 99.9 + percen t remova l • efficiency . Th e desig nguarante e give ni s 15 0 ppm v H2S . Othe r Discussio n- I aske drefiner y

operator s abou t th e reliabilit y o f th e LO-CA T process . Th e genera l consensu s wa s tha t i t wa s on e o f th e les s trouble some proces s unit s i nth e refinery . Th e attendin g inspector s fro m th e Sout hCoas t APC D adde dtha t th e Fletche r LO-CA T uni t hadneve r presente da complianc e problem du e t o highreliabilit y an dcomplet e emissio ncontro l redundanc y i nth e NaSH.unit . [I ncas e o f failure , the NaS H proces s ca nhandl e th e entir e proces s ga s H2 S loadin g normall y route d t o th e LO-CAT. ] Als o wort hmentionin g i s tha t th e ammoniu m thiosulfat e (ATS ) purg e ha s neve r bee nuse da t Fletcher , indicatin g tha t oxidatio no f the solutio n i s no t a problem . Summar y an dConclusion s 1 . Th e LO-CA T proces s a t Fletche r ha s experienced , an dapparentl y solved , a numbe r o f proces s problem s an dno w operate s reliabl y

an dwit h high(99.9%+ ) H2 S remova l efficiencies . 2 . Time permitting , follow-u pwit hAR I Technologie s i s recommende d t o study th e economic s o f th e LO-CA T a s compare dt o othe r alternativ e processes , a s a functio no f H2 S amount s removed .P. 6

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