Syngas cleaning for coal to methanol demo plant – H2S and COS removal

Syngas cleaning, especially the removal of COS and H2S, is a crucial step in the production of valuable chemicals from coal. As a part of the Tuncbilek Coal to Methanol project, a gas cleaning demo plant has been built. The aim of this paper is to disseminate the experience gained from these demo plant experiments concerning the performance of the gasifier and syngas cleaning demo-plant, especially about the removal of sulfur compounds. Additionally, some practical recommendations regarding the design and operation of such demo plants are given. The design-basis for the demo plant was a gas stream of 450 m3/h (at STP) containing 4,000 ppmv H2S and 2,000 ppmv COS. The performance target was to reduce H2S and COS concentrations to less than one ppmv each. The gas cleaning process consisted of a particulate filter, COS hydrolysis reactors, caustic scrubbers, H2S guard beds and heat exchangers. Two demo plant runs were conducted, and Tuncbilek lignite was gasified in the 6 ton/day (coal feeding capacity) entrained flow gasifier. The gasifier produced syngases with lower heating values of 7.64 and 8.86 MJ/m3 (at STP), and cold gas efficiencies of 71 and 81% were achieved. The H2S and COS content of the successful run were 3,300 ppmv and 550 ppmv, respectively. At the exit of the gas cleaning demo plant, a concentration of 0.12 ppmv for H2S and 0.72 ppmv for COS were measured. Consequently, it was concluded that the performance of the gas cleaning demo plant was satisfactory for methanol production.