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# OAR Box 1784 Prepped by Ollie Stewart

Document

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' . 1 . TECHNOLOGIE S INC . Octobe r

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Mr . Larr y Elmor e U.S . Environmenta l Protectio nAgenc y MD-1 3 Researc hTriangl e Park , Nort hCarolin a2771 1 Dea r Mr . Elmore : Pleas e excus e th e dela y i nsendin g yo u th e preferre dflo w diagra mfo r

th e LO-CAT® Hydroge nSulfid e Oxidatio nproces s f o r refiner y fue l ga s treating . Th e flo w diagra mwa s correct , bu t th e attache dproces s descriptio nha da nerro r i nit , an di t

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i t would . Your s ver y truly ,

AR I TECHNOLOGIES INC .
L . C . Hardiso n Presiden t LCH.n n Attachment s

60 0 N . Firs t Ban k Drive • Palatine , Illinois 6006 7 (312 ) 359-781 0 • TW

X 310-693-159 1 

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PROCES S DESCRIPTION CONVENTIONA

L LO-CAT

® HYDROGE NSULFID E OXIDATIONPROCES S

FLO W DESCRIPTION Sour ga s passe s throug h a n inle t ga s scrubbe r t o remov e entraine d liquid s an

d enter s the absorbe r a t lin e pressur e through a speciall y designe d ventur i prescrubber . The ga s passe s upwar d through a low liquid-fille d vesse l i n whic h i t contact s the LO-CA T catalys t solu
tio n flowing downward . The H2 S i s absorbe d i n the solutio n an d converte d immediatel yt o soli d sulfur . Swee t ga s wit h les s than 10 0 pp mH2 S leave s the absorbe r vesse l an d passe s through a swee t ga s scrubbe r t o guard agains t mis t carryove r befor e entering the fue l system . The following chemica l reaction s tak e plac e i n the absorbe r vessel :

(1 ) H2 S Absorptio n

H 2 S + H 2 0 -*

• H2 S (aqueous ) + H2 O (2 ) Firs t Ionizatio n

H2 S (aqueous ) •*• H + + HS " (3 ) Secon

d Ionizatio n HS" + H + + S = (4 ) Oxidatio n o f Sulfid e

2Fe ++ + + S = •*• 2Fe + + + S° l Activ e LO-CA

T solutio n enter s the absorbe r colum n a t the to

p an d flow s downwar d through the vesse l counter-curren t t o the ga s flow . The spen t solutio n leave s the vesse l through an interna l con e bottom . Partiall yreduce d solutio n run s b ygravit yo r pressur e differenc e through a solutio n cooler.and int o the oxidize r vessel , i n whic h i t i s regenerate d b ydirec t contac t wit h compresse d air . Regeneratio n o f the LO-CA T solutio n i n the oxidize r involve s the following reactions :


# v_ . . M /P. 4

(5 ) (6 ) 

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TEOWXOQtSf C Oxyge n Absorptio n O 2 + H2 O -»

• 2 0 aqueous ) + H2 O Regeneratio n o f Iron 2F e + + + 0 (aqueous ) + H2 O + 2Fe ++ + + 2 (OH) " Overall , the reactio n i s

(7 ) H 2 S + 1/ 2 O 2 -» • H 2 0 + S ° + The spen t air , wit h a smal l fractio n o f the oxyge n removed , leave s the to p o f th e oxidize r vesse l an d discharge s t o the atmosphere . Sulfu r forme d i n the Absorbe r vesse l circulate s wit h th e solutio n an d the particle s gro wt o the 10-2 0 micromete r range . Th e large r particle s settl e ou t o f the bul k solutio n flowi n the bottom o f the Oxidize r vesse l an

d ar e flushe d ou t o f the cone-bottome d settling are a a s a slurrya t 1 0 t o 2 0 wt % sulfur . The sulfu r slurr

yi s pumpe d a t approximatel y10 0 psi g through a specia l non-pluggin g hea t exchange r o r melter , wher e i t i s heate d t o 270° F b

y5 0 psi g steam . The solutio n an d molte n sulfu r phas e forme d i n the melte r flowthrough stea m jackete d piping t o a stea m jackete d separato r vessel , wher e a liquid-liqui d interfac e i s main
tained . Molte n sulfu r i s withdraw n fro mth e separato r vesse l o n leve l contro l t o a molte n sulfu r storag e tan k o r a sulfu r pi t wher e i t i s store d fo r ultimat e shipmen t b ytruc k o r rai l car . The solutio n retur n leave s the sulfu r settle r through a bac k pressur e contro l valv e se t a t abou t 7 5 psig . Th e bul k o f the solutio n i s re turne d t o the settle r vesse l an d the n t o the absorber/oxidize r cir
cuit . CHEMICA L REQUIREMENT S I n the oxidatio n o f H2 S t o sulfur , some sid e reactio n take s plac e whic h mayb e represente d b ythe equation : (8 ) 2HS " + 1-1/20 2 + H 2 S 2 0 3 Thi s reactio n reduce s the p H o f the scrubbing solution , an d Na2C03 , KOH o r othe r alkalin e sal t mus t b e adde d t o maintai n the p H o f the solutio n i n the 8-8. 5 p H range . Thi s lead s t o a gradua l buildu p o f Na2S20 3 o r simila r water-solubl e sulfur-containin g salt s i n the solution . Thes e hav e no deleteriou s effec t a t concentration s belo w 3 0 wt % o r so . The solutio n compositio n i s maintaine d a t a stabl e leve l b ycontinu
ou s addition s o f the following chemicals :P. 5

ARI-31 0 Concentrat e i s adde d t o replac e an ysolutio n whic h ma yb e los t wit h th e sulfu r cake . ARI-310 M Chelate-ric h Makeu p solutio n i s adde d t o replac e Typ e Aan d Typ e B chelat e compound s los t fro mthe solutio n b

yslo woxidatio n reactions . AR I provide s a complet e analytica l servic e an d catalys t sample s o n a weekl yo r semiweekl ybasi s whic h ar e sufficien t t o maintai n economical'additio n rates . N____2____(__ 3 Buffering Solutio n i s adde d t o replac e losse s wit h the sulfu r cok e an d t o neutraliz e thiosulfat e ion s forme d i n the process . Adjustment s i n th e additio n rat e ar e base d o n dail ymeasurement s o f the solutio n pH . ARI-40 0 BiochemBiosta t i s adde d a t abou t 1 0 pp mb yweigh t pe r day . Thi s prevent s biologica l damag e t o th e chelat e system . Wettin g Agen t an

d Anti-FoamAdditive s ma yb e adde d continuousl yi n smal l amount s i f the ga s strea mcontain s oil ymaterial s whic h inter
fer e wit h sulfu r settling , o r surfac e activ e material s whic h ca n otherwis e caus e foaming .SOU R GA S VEiNITUR l LIQUI D FILLE D

SCRUBBE R PRE-CO.NTACTO R ABSORBE R OXIDIZE R AI R COMPRESSO R 

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SOU R GA S l*M = CWM6 J

. 1 SULFU R LOADOU T STATIO N MOLTE N SULFU R STORAG E SULFU R SEPARATO R SWEE TGA S OU T

SOLUTIO N CIRCULATIO N PUM P

NOT E : CHEMICA L ADDITIO N EQUIPMEN TNO TSHOWN . 

# a n TBOHN0L0G6 S HC ANAEROBI C LO-CAT*'* * HYDROGE N SULFID E OXIDATIO N PROCES S A