CA(OH)2/FLY ASH SORBENTS FOR SO2 REMOVAL

The reactivity of Ca(OH)2/fly ash sorbent with SO2 has been studied by using a fixed-bed differential reactor under the conditions simulating the bag filters of the spray-drying flue gas desulfurization. The source of fly ash and the sorbent preparation conditions affect the reactivity of the sorbent. The reactivity of the sorbent was found to be closely related to the content of the calcium silicate hydrate formed in the sorbent preparation. The sorbent has a much higher utilization of Ca(OH)2 than that of pure Ca(OH)2 sorbent, and in some range of Ca(OH)2 content the sorbent also has a higher SO2 capture capacity per unit weight of sorbent than that of pure lime. The fly ash from the Shin-Da plant of the Taiwan Power Company produced the best sorbent of all fly ashes in this study. The higher ratio of fly ash/Ca(OH)2, the higher slurrying temperature, the longer slurrying time, and the smaller particles of fly ash enhance the utilization of Ca(OH)2, but the water/solid ratio has an optimal value. The relative humidity in the reactor has a significant effect on the reactivity of Ca(OH)2/fly ash sorbents, but the effect of the sulfation temperature is subtle.