Desulfurization kinetics of ZnO sorbent loaded on semi-coke support for hot coal gas

Abstract

Zn-based sorbent (Z20SC) prepared through semi-coke support in 20 wt% zinc nitrate solution by high-pressure impregnation presents an excellent desulfurization capacity in hot coal gas, in which H₂S can not be nearly detected in the outlet gas before 20 h breakthrough time. The effects of the main operational conditions and the particle size of Z20SC sorbent on its desulfurization performances sorbent were investigated in a fixed-bed reactor and the desulfurization kinetics of Z20SC sorbent removing H₂S from hot coal gas was calculated based on experimental data. Results showed that the conversion of Z20SC sorbent desulfurization reaction increased with the decrease of the particle size of the sorbent and the increases of gas volumetric flow rate, reaction temperature and H₂S content in inlet gas. Z20SC sorbent obtained from hydrothermal synthesis by high-pressure impregnation possessed much larger surface area and pore volume than semi-coke support, and they were significantly reduced after the desulfurization reaction. The equivalent grain model was reasonably used to analyze experimental data, in which k_s = 4.382×10⁻³ exp(−8.270×10³/R_gT) and D_ep = 1.262×10⁻⁴exp(−1.522×10⁴/R_gT). It suggests that the desulfurization reaction of the Z20SC sorbent is mainly controlled by the chemical reaction in the initial stage and later by the diffusion through the reacted sorbent layer.