Rectisol is a physical acid gas removal process using an organic solvent (typically methanol) at subzero temperatures. Rectisol can purify synthesis gas down to 0,1 vppm total sulphur (including COS) and CO2 in ppm range. The main advantages of the process are the rather low utility consumption figures, the use of a cheap and easily available solvent and the flexibility in process configuration.
Commercial scale Rectisol wash units are operated world wide for the purification of hydrogen, ammonia-, methanol syngas and the production of pure carbon monoxide and oxogases. Due to the physical nature of the process high pressure and high sour gas concentrations are particularly favourable. Rectisol is therefore frequently used to purify shifted, partially shifted or unshifted gas downstream residue oil-, coal- or lignite gasification. Due to the low operation temperature Rectisol is also favourable for cryogenic downstream processes, like liquid nitrogen wash, cryogenic recovery of carbon monoxide and oxogas.
A simplified flow scheme of the Rectisol process is shown above. CO2 and sulphur compounds are removed in separate fractions, resulting in a pure CO2 product (for example for urea production) and an H2S/COS enriched Claus gas fraction. Due to the application of Rectisol in connection with various upstream and downstream processes, a large design and operational experience is available also regarding handling of trace components.
A special feature of the process are the spiral wound heat exchangers supporting energy efficiency and plant economics.
References:
H. Weiss, Rectisol wash for purification of partial oxidation gases, Gas Separation & Purification, 1988 Vol 2
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