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

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. (C) 2014 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.