(449bv) Study of Copper-Based Commercial Sorbent for Desulfurization of Syngas at Warm Temperature

Gasification is a reaction process that converts carbonaceous solid fuel, such as coal, biomass and mixture of them, into gaseous fuel which is called synthesis gas or syngas. The temperature of syngas is in the range of 800 °C to 1,800 °C, and it is decreased to room temperature for removing the pollutants with traditional gas cleaning processes. Then, syngas is needed to be heated up to the operating temperature, based on the requirement from applications. In order to increase the overall efficiency of syngas application, the desulfurization process development trends to higher temperature. However, because of material limitations in dry desulfurization technologies, the optimum temperature for copper-based sorbent has been estimated to be in warm-temperature (300-600^oC) range that is currently of industrial interest. The characteristics of selecting appropriate sorbents according to materialâ??s physical and chemical properties, such as sulfur capacity, attainable sulfur concentration in gas, possibility of regeneration, mechanical stability over multiple sorption-regeneration cycles, etc., are the parameters to design the reactors and to affect the energy consumption in the processes. The sulfur capacity is influenced by the reacting temperature, space velocity, gas composition and cycles of sorption-regeneration.

In this study, a commercial sorbent with particle size of 30~50 mesh is used for removing hydrogen sulfide from syngas (containing 1% vol. H₂S) down to ppm levels in a fixed-bed reactor. The effect of regeneration temperature and cycles of sorption-regeneration on the sulfur capacity were studied as reference to build an operation strategy. The XRD analysis indicates that sulfidation process occurs in partial reduction under reducing atmospheres, i.e., CuO â?? Cu/Cu₂O â?? Cu_xS (x â?¤ 2). The copper-based sorbent maintains excellent sulfur removal efficiency (above 90% of initial content) during ten adsorption-regeneration cycles at higher regeneration temperature. The results show that the amount of sulfate decreases as regeneration temperature increases. Considering the trend that energy consumption increases as regeneration temperature increases, a big gap between sulfidation and regeneration temperature results in efficiency decrease. The study shows that the performances of the copper-based commercial sorbent seem to be promising for application in syngas desulfurization. It is necessary to decrease regeneration temperature and minimize sulfate formation by introducing a suitable additive in future work.