Published May 1989
A hybrid process for recovering both sulfur and hydrogen from hydrogen sulfide has been jointly developed in Japan by the National Chemical Laboratory for Industry, and ldemitsu Kosan. The process involves absorption of hydrogen sulfide into a solution containing ferric chloride, ferrous chloride, and hydrochloric acid. During the absorption, elemental sulfur is produced, and ferric chloride is reduced to ferrous chloride and hydrochloric acid. After separation of sulfur, the solution is subjected to electrolysis, during which ferrous chloride and hydrochloric acid are converted back to ferric chloride in the anodic chamber of the electrolysis cell with hydrogen generated in the cathodic chamber.
At present, sulfur can be commercially recovered from hydrogen sulfide by catalytic oxidation without recovery of hydrogen. In this review, we present a technoeconomic evaluation of the new hybrid process, and we compare its economics with the commercial Claus process.
SRI concludes that the new hybrid process is competitive with the Claus process if the coproduced hydrogen can be given a chemical value. The new process requires about less in capital investment than the Claus process. However, the product value of sulfur produced by the hybrid process will be higher than that produced by the Claus process if the hydrogen by-product cannot be credited at its chemical value, but only at fuel value. In such a case, the savings in the capital related production costs are less than the increase caused by the relatively high raw material and utilities costs required for the hybrid process.