Influence of the coal-derived synthesis gas composition on the thermal stability of ZnO sorbents in the desulfurization process

Abstract

Abstract The priority direction of thermal energy on solid fuels is to increase efficiency and environmental safety, approaching zero emissions of harmful substances. To achieve these goals, they are currently creating new schemes for combined cycle gas turbine units with intra-cycle gasification (IGCC). To improve the efficiency of the IGCC cycle, hot dry desulfurization (HGC) technologies are being developed. HGC uses regenerable sorbents that allow the repeated adsorption of hydrogen sulfide from synthesis gas, among which the most acceptable thermodynamic and operational characteristics are based on ZnO sorbents. The article uses the method of thermogravimetric analysis (TGA) to investigate the development of target reaction capture hydrogen sulfide ZnO-containing sorbent and sorbent reactions with components of synthesis gas in the temperature range up to 1000°C. The sorbent calcined at 900°C shows thermal stability in an inert atmosphere over the entire temperature range studied. Uncalcined sorbents at temperatures of 200 and 600°C emit carbon dioxide in an amount of 1.5-4.5% by weight of the sorbent. At temperatures up to 550°C, the target reaction is basic, and side reactions practically do not develop. The maximum rate of absorption of hydrogen sulfide by the sorbent is observed at a temperature of 600°C. At 500-550°C reactions of a sorbent begin with H2 and CO, at 750-800°C – with carbon, at 850°C – with CH4. The intensity of effect of reagents is defined on degradation of a sorbent by reactionary ability of gases more than temperature.