Elimination of stagnant particles from a N-valve with side aeration in circulating fluidized bed

Abstract

The existence of stagnant particle layer in the conventional non-mechanical valves limits their utilization in CFB with the feedstock of caking particles. A new N-valve consisted of a fluidized weir chamber with bottom aeration and a moving-bed angled standpipe with side aeration was developed to eliminate the stagnant particle layer and reach high solids circulation rate G s in CFBs. The particle flow behavior and its control in the N-valve were studied experimentally. By combining the bottom aeration for weir chamber and the side aeration for angled standpipe the G s over 270 kg/(m 2 s) was achieved, and the stagnant particle layer completely disappeared. The G s increased with increasing the side aeration gas flow rate Q sa , and this loosing gas flow was optimally injected from the bend between the downcomer and the angled standpipe. At a constant but enough high Q sa , the increase in the bottom aeration gas flow rate Q ba elevated G s linearly. © 2014 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder.