Use of limestone for SO_2 removal from flue gas in the semidry FGD process with a powder-powder-particle spouted bed

摘要

Hydrated lime is normally used as SO_2 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 SO_2 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 S0_2 removal were investigated, such as Ca/S molar ratio, particle size of SO_2 sorbent. apparent residence time of gas in the bed and approach to saturation temperature. The comparison of reactivity with SO_2, between limestone and hydrated lime was also made based on their structural properties. The experimental results showed that SO_2 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 S0_2 sorbent may be an attractive alternative to other FGD technologies in terms of removal efficiency, price and availability of sorbent.