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REACTIONS (Hot K 2CO3 system)

CO2 partial pressures in the range o 3!"#! psi are ne$essary

or ei$ient operation%

The reactions takes place in the carbonate process are:

  K 2CO3 + CO2 + H2O 2KHCO3 --------- 1

  K 2CO3 + H2S KHS + KHCO3 -------- 2

Reactions (1) (K 2CO3 + CO2 + H2O 2KHCO3)   proceeds

in to steps:

! The "irst step is h#drol#sis o" the potassi$% carbonate:

  K 2CO3 + H2O KOH + KHCO3 -------------- 3

! &otassi$% h#dro'ide th$s "or%ed reacts ith CO2 to "or%

 potassi$% bicarbonate:

  KOH + CO2  KHCO3 -------------------------

Reactions (2) (K 2CO3 + H2S KHS + KHCO3) proceed

in to steps:

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  K 2CO3 + H2O KOH + KHCO3 ------- *

Potassium hydroxide formed also reacts with H2S

to forms potassium bisulde

KOH + H2S KHS (Potassium Bisulde) + H2O

------

Th$s KOH "or%ed d$rin, reactions reacts ith CO2 and H2S

to "or% KHCO3 and KHS

KHS h#drol#.es to "or% H2S and KOH

KHS + H2O H2S + KOH -------------------------/

0n brie"

KOH is prod$ced d$rin, reaction o" K 2CO3 and H2OKOH reacts ith CO2 and H2S to prod$ce KHCO3 and KHS

KHS H#drol#.es to "or% H2S ad KOH

 !he abo"e cycle #oes o to react with CO2 ad H2S

COS $ar&onyl suli'e

0t can be re%oed itho$t si,ni"icant sol$tion de,radation

Carbonate process has the adanta,e that both PotassiumBisulde (KHS) and carbon#l s$l"ide (COS) can be re%oeditho$t si,ni"icant sol$tion de,radation

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Carbon#l s$l"ide ill h#drol#.e as "ollos:

 COS + H2O CO2 + H2S --------------------------

K 2CO3 + H2S KHS + KHCO3 --------------------

KHS + H2O H2S + KOH -----------------------14

KOH reacts ith CO2 and H2S to prod$ce KHCO3 and KHS

KHS H#drol#.es to "or% H2S ad KOH

 !he abo"e cycle #oes o to react with CO2 ad H2S

Car&on 'isuli'e

Carbo disulde hydroly$es to form COS ad H2S

  CS2 + H2O COS + H2S ------------------------------- 11

  H2S reacts as per reaction 2

  COS h#drol#.es as per reaction

er$aptans

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%ercaptas react with potassium carboate

solutio to form mercaptides

K 2 CO3 + RSH RSK + KHCO3 + -------------- 12