Use of limestone for SO2 removal from flue gas in the semidry FGD process with a powder-particle spouted bed

Hydrated lime is normally used as SO2 sorbent in spray dry scrubbers, whereas limestone is considered unreactive under conditions prevailing in such a system. However, limestone is more easily available and several times cheaper than hydrated lime. We tried to use limestone to remove SO2 from flue gas in the semidry FGD process with a powder-particle spouted bed. If limestone can be utilized in the process it would be of particular advantage. In the present study, the effects of operating parameters on SO2 removal were investigated, such as Ca/S molar ratio, particle size of SO2 sorbent, apparent residence time of gas in the bed and approach to saturation temperature. The comparison of reactivity with SO2 between limestone and hydrated lime was also made based on their structural properties. The experimental results showed that SO2 removal efficiency of limestone was considerably enhanced in the present process by increasing Ca/S molar ratio and decreasing the approach to saturation temperature and sorbent size. Thus, the present process with limestone as SO2 sorbent may be an attractive alternative to other FGD technologies in terms of removal efficiency, price and availability of sorbent. (C) 2000 Elsevier Science Ltd. All rights reserved.