The adhesion and the deposition behavior of coal ash on the gasifier wall were studies by the laboratory scale apparatus equipped with the wall temperature (T_w) control device. The ash melting temperature (T_M) and the sintering temperature (T_s) seemed to influence the adhesion force and the deposit form considerably. When T_w was below T_s, the deposit was "powder-ash" with very week adhesion. Between T_M and T_s, the deposit was "sintered-lump" with strong adhesion. Nealy T_M, "solid-slag" was formed. It could be detached by mechanical action.
