Experimental investigation of a triplet ash valve for circulating fluidized bed

Abstract

In a circulating fluidized bed (CFB), the ash discharge process is challenging due to poor reliability of the solid or mechanical valve at high temperatures and pressures, particularly for a CFB gasifier. This work proposed a novel triplet ash valve for solids discharge in CFB. It resembles a loop seal. The ash valve is comprised of three supply chambers and one discharge chamber. The hydrodynamics and operation characteristics of the ash valve were investigated using Geldart B particles in a cold flow model. The effects of chamber aeration, pressure drop of the standpipe and back pressure on the performance of the ash valve were analyzed. A wide linear operation range of solids flow rate can be achieved by adjusting the aeration of the three supply chambers and the discharge chamber. The specific feasible operation scheme of the ash valve was discussed. An increase of pressure drop in the standpipe promoted the solids flow rate of the ash valve, whereas a higher back pressure of the ash valve decreased the solids flow rate. Finally, a correlation was presented to predict the solids flow rate of the ash valve.