Generic Methods for Coke Oven Gas Desulphurisation by Wilfried ...

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200THE COKE OVEN MANAGERS’ASSOCIATIONThe process sequence of the Perox Process is similar to theStretford Process.The chemical reaction steps are similar, too. The sulphur forming isperformed by catalyst directly, however.The Perox process needs ammonia bearing coke oven gas. Ammoniais utilized as absorbent for hydrogen sulphide and the catalysthydrochinone (parabenzolchinone) is used for sulphur forming. Sidereactions with hydrogen cyanite also lead to the formation ofthiocyanate and thiosulfate.The other wet oxidative processes (Fig. 3) such as Takahax,Thylox, Fumaks and LoCat are comparable with the Stretford andPerox processes, but using other absorbents and catalysts.All of these wet oxidative processes produce a high contaminatedwaste water, which make the addition of an elaborate treatmentfacilities necessary.Now, an overview of the third group of desulphurisation processes,the neutralization processes or also called absorption and strippingprocesses is given (Fig. 3).Neutralization ProcessesThese processes are characterised by absorption and stripping(desorption) of hydrogen sulphide and conversion into elementalsulphur or sulphuric acid as in a subsequently installed plants.The simplified flow sheet of the Sulfiban Process shows a typicalabsorption/desorption process with H 2 S scrubber, H 2 S stripper andheating equipment.In the reclaimer continuous removal of heat-stable salts isperformed. The removed hydrogen sulphide leaves the process as acomponent of the sour gas and can be processed either to elementalsulphur or sulphuric acid.
COKE OVEN GAS DESULPHURISATION 201As scrubbing agent for the Sulfiban Process a MEA-solution(monoethanolamine) is utilised. With the H 2 S also partial removal ofCO 2 , HCN and S ORG is achieved. In addition to the MEA-solutionchemicals are necessary as anti-foaming and anti-corrosion agents.At low temperatures (approx. 25 to 35 °C) the equilibrium is on theright side of the equation (absorption/scrubbing) and at highertemperatures like 110 to 130 °C the equilibrium is on the left side of theequation (desorption/stripping).In the waste water of the Sulfiban Process organic sulphurcompounds will be found.The standard process for the desulphurisation of ammonia-bearingcoke oven gas is the CYCLASULF Process. By this process hydrogensulphide and ammonia is removed simultaneously.The CYCLASULF Process mainly consists of the H 2 S and NH 3scrubbers and the deacidifier/NH 3 stripper. Most of the ammonia isremoved in the NH 3 scrubber using stripped water and most of thehydrogen sulphide is removed in the H 2 S scrubber by means ofdeacidified water.The removed hydrogen sulphide and ammonia are recovered asvapours in the deacidifier/ammonia stripper column.The stripping steam for the deacidifier/NH 3 stripper is fed directlyinto the column.The H 2 S/NH 3 rich vapours can be fed either to a COMBICLAUSplant where the ammonia is destructed and the hydrogen sulphide isprocessed to elemental sulphur or to an “indirect” ammonium sulphateproduction and sulphuric acid plant.Soda lye used for removing fixed ammonia compounds from the gasliquor, can be used first to reduce the residual hydrogen sulphide in thecoke oven gas.
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Generic Methods for Coke Oven Gas Desulphurisation by Wilfried ...

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