Effect of Wall Temperature on Ash Deposition in an Entrained-bed Gasifier

Abstract

The adhesion and the deposition behavior of coal ash on an entrained-bed gasifier wall were studied with a laboratory scale apparatus equipped with a wall temperature (T_W) control device. The ash melting temperature (T_M) and the sintering temperature (T_S) seemed to influence the adhesive force and deposit form considerably. When T_W was below T_S, the deposit was a “powder-ash”. Between T_M and T_S, the deposit was a “sintered-ash”. Near T_M, a “solid slag” was formed. The wall temperature also affected the detachment behavior between the wall and deposit. The sticking temperature (T_ST) was below T_S and the deposit could be detached by gravity from the wall when T_W was below T_ST.
Experiments indicated wall cooling may significantly reduce both particle-wall and particle-particle adhesive forces.
A modest numerical simulation model for ash growth was developed. When grow-ing the deposits formed triple layers, powder-ash / sintered-ash / slag. Easy removal, such as by a soot blower, is possible by not allowing the deposit to become “sintered-ash”.