Design and cost optimization of a hot fuel gas desulfurization process

Abstract

A high temperature gas desulfurization process is proposed that effectively uses the iron oxides in the waste ashes from coal gasifiers to react with and sorb the H 2S, COS, and CS 2, in coal-derived fuels. The process is carried out at 1033 K and 2.22 MPa in packed bed reactors. Sulfided ash sorbents may be repeatedly regenerated to produce a 30/70 molar mixture of S 2 and SO 2, suitable for complete reduction to elemental sulfur or sulfuric acid manufacture. An optimization theory predicts the use of very shallow bed reactors, packed to 0.61 meters, operating in a cyclic sequence where the onstream time is only 0.37 hours. This markedly reduces the capital and operating costs. A plant treating 1.22 MM SCMH of 0.63 mole percent H 2S ladened fuel gas is estimated to have a 1981 cost of $7.638 million and an annual operating cost of $5.229 million. A modular plant for recovery of byproduct SO 2, as H 2SO 4 is estimated to cost an additional $11.38 million but shows an annual before-tax profit of $10.46 million based upon a selling price of $80/Ton for the acid. This large profit reflects the value of the by-product SO 2.