화학공학소재연구정보센터
Energy & Fuels, Vol.12, No.2, 409-415, 1998
Effect of pore-modifier graphite on the performance of a zinc titanate sorbent in hot coal gas desulfurization
The reactivity and performance of different zinc-titanium-based sorbent extrudates for desulfurization of coal gas at high temperature in successive sulfidation-regeneration cycles were studied in both a thermobalance and a fixed-bed reactor. The study showed that the sulfidation and the regeneration of these sorbents as cylindrical extrudates was mostly a diffusion-controlled process. In order to change the degree of dispersion of the active phase and porosity of the sorbent extrudates, some of them were prepared by coprecipitation and others by using graphite as a high-temperature pore-modifier additive. The study showed that the high degree of dispersion of the active phase achieved in the first stages of the coprecipitation process is practically destroyed during sorbent calcination at high temperature. Additionally, coprecipitation enhanced thermal sintering during preparation and the porosity of these fresh sorbents was low. Consequently, the reactivity in thermobalance tests was also low and performance in the reactor was very poor. On the contrary, graphite increased substantially the porosity of the fresh sorbent extrudates and, because it is eliminated at high temperature, this effect prevailed during calcination and successive sulfidation-regeneration cycles. Consequently, graphite notably improved the performance of zinc titanate extrudates as hot temperature sorbents which under the operation conditions used was clearly evidenced by an increase of the sorbent efficiency.