Removal of Hydrogen Sulfide from a Steam-Hydrogasifier Product Gas by Zinc Oxide Sorbent

Removal of H 2 S by a commercially available zinc oxide sorbent was studied using a packed-bed reactor for desulfurizing the gas produced from steam-hydrogasification of carbonaceous materials. Experimental runs were conducted to monitor sulfur removal efficiency and H 2 S breakthrough time for the operation variables such as reaction temperature, steam content, space velocity, inlet H 2 S concentration, and sorbent particle size. For the inlet gas with 45 vol % steam content, the initial sulfur removal efficiency exhibited a maximum around 636 K. Varying the steam content of inlet gas affected the equilibrium of sorbent sulfidation in a reversible way, leading to the decrease of sulfur capture capacity of the sorbent as the steam content increased. Increasing the space velocity from 8 000 to 24000 h -1 decreased sulfur capture capacity significantly, indicating the deterioration of gas−solid contact in the reactor at the increased gas flow rates. Inlet H 2 S concentration was varied from 100 to 800 ppmv to reflect the diversity of steam-hydrogasifier feedstocks, which affected sulfur capture capacity of the sorbent in such a way that the extent of sorbent utilization was limited by the increased H 2 S concentration. Sorbent particle size was varied from 150−250 to 425−1000 μm to look into the effect of intraparticle mass transfer limitation. The particles greater than 425 μm exhibited the sulfur capture capacity that was limited by the reduced extent of sorbent utilization.