Novel Coal Gasification Process: Improvement of Syngas Yield and Reduction of Emissions

Abstract

This article is intended to propose and model an innovative process layout for coal gasification that improves the production of syngas and also reduces the sulfur and CO₂ emissions. The typical coal gasification process uses Sulfur Recovery Units to convert H₂S to sulfur, but these have some disadvantage, e.g low sulfur price, coal charge with low sulfur flow rate, use of Tail Gas Treatment unit. Compared to the Claus process, this solution converts H₂S and CO₂ into syngas (economically appealing), reduces emission of H₂S and CO₂ and allows the use of coal charge with high sulfur flow rate, e.g. 9.5% mol/mol. The novel process takes advantage of a double amine wash, a thermal regenerative furnace and considers the recycle of the acid gases coming from the catalytic reactor to further promote the H₂S conversion. In particular, the double amine wash is useful to purify the H₂S stream to be sent to the thermal furnace from the syngas and CO₂, in order to reduce the reactor inlet flow rate. The regenerative furnace is simulated using a large detailed kinetic scheme to appropriately describe the minor species (among them, pollutants like CS₂ and COS). As a result, the recycle appears to substantially reduce the pollutant emissions. In addition, the conversion of the Claus process into the novel process doesn’t require any change in the main equipment, just needing for a variation in the layout and the operating conditions.