Sour Gas Removal in Partial Oxidation Processes

The Rectisol process [667], [707], [711]-[715] seems to be the prime choice in partial oxidation plants. The process, invented by Lurgi and developed further by Linde, operates with chilled methanol, a cheap and readily available solvent, in which carbon dioxide, hydrogen sulfide and carbonyl sulfide (COS) are readily soluble at low operating temperatures of below - 30 °C. The Henry absorption coefficient for H2S is about six times higher than for C02- 

The Lurgi Purisol process [663], [717], [718], [726] uses AT-methylpyrrolidone (NMP) as solvent and can be operated at ambient temperature or, with inclusion of a refrigeration unit, at temperatures down to -15 °C. The bbS/CO-, selectivity is superior to Selexol, permitting the production of a rich Claus gas with about 50% H2S even at relatively low concentration of hydrogen sulfide in the raw gas. The solubility of COS is only 20% of that of H2S, but it is largely hydrolyzed by the NMP. Preferred operating pressure is 45 to 85 bar. The process can, of course, be 

The Sulfinol process [719]-[722] cannot strictly be classified as a physical solvent process, as the solvent is a mixture of sulfolane (tetrahydrothiophene 1,1-dioxide), DIPA (diisopropanolamine), and water in a ratio of about 45 40 10. Sulfolane is a true physical solvent, whereas the DIPA is a chemically acting component. To achieve a higher C02/H2S selectivity, DIPA may be substituted by MDEA (methyldiethanola-mine) in the M-Sulfinol process. In partial oxidation process a concept with two separate Sulfinol units is preferred the first ahead of the shift conversion (gas composition for example C02 5.4 vol%, H2S 0.5 vol%), and the second one for recovery of sulfur-free C02affer the shift conversion (feed gas for example C02 33vol%, H2S 0 vol %). 

Surveys and additonal literature on the C02-removal processes are found in [723]-[734] a theoretical analysis is given in [734]. 

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