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WSA Process
(Wet gas Sulphuric Acid)

The WSA process is one out of many gas desulfurization processes on the market today. Since its introduction in the 1980s, it has been recognised as an efficient process for recovering sulphur from various process gasses in the form of commercial quality sulphuric acid. The WSA process is applied in all industries where removal of sulphur is an issue.

Wet catalysis processes differ from other contact sulphuric acid processes in that the feed gas still contains moisture when it comes into contact with the catalyst. The sulphur trioxide formed by catalytic oxidation of the sulphur dioxide reacts instantly with the moisture to produce sulphuric acid in the vapour phase to an extent determined by the temperature. Liquid acid is subsequently formed by condensation of the H2SO4 (sulphuric acid) vapour and not by absorption of the sulphur trioxide in concentrated sulphuric acid, as is the case in contact processes based on dry gases. The concentration of the product acid depends on the H2O/SO3 ration in the catalytically converted gases and on the condensation temperature.

The wet catalysis process is especially suitable for processing the wet gasses obtained by the combustion of H2S (hydrogen sulphide)-containing off-gasses. The combustion gasses are merely cooled to the converter inlet temperature of about 420-440°C. To process these wet gasses in a conventional cold-gas Contact process (DCDA) plant would necessitate cooling the gas to an economically unacceptable extent to remove the large excess of moisture. Therefore in many cases Wet catalysis processes is a more cost-efficient way of treating H2S containing off-gases.



The technology is able to treat one or more sulphur containing streams such as:

H2S gas from amine gas treating unit

SWS gas

Spent acid

Claus process tail gas

Heavy residue or petcoke-fired utility boiler off-gas

FCC regenerator

Bolier flue gas