Cement dust as an absorbent for so2 removal from stack gases

Abstract

“The limestone-wet scrubbing process for SO2 removal from stack gases has undergone much study which has resulted in construction of at least three full scale operating plants. The process used in these plants is based on calcining the limestone, by injection into the boiler, which is subsequently absorbed from the flue gases in a wet scrubber where reaction with the SO2 takes place (injection­ scrubbing process). A variation of this process, whereby 11mAstone is added directly to the scrubber slurry has also been investigated (scrubber addition process). However, this process has not been utilized because it requires more limestone than the injection process to achieve the same SO2 removal. It therefore has higher operating cost. Lime is known to be a more effective absorbent in this process, but it is much too costly. It was postulated that waste cement dust, having a calcium content comparable to limestone, might be a lower cost absorbent; but, it was not known how cement dust compares with limestone or lime for removal of SO2 in the scrubber addition process. Therefore, a bench scale scrubber system was built and this experimental investigation was conducted in an effort to obtain a preliminary comparison of cement dust with lime and limestone as a scrubber addition absorbent for re­moval of SO2. The results of these experiments indicate that the cement dust is a better absorbent than limestone and its effectiveness ap­proaches that of lime. It has been recommended that further testing be conducted in a pilot scale system.”--Summary.