Incineration experiments are carried out to investigate the agglomeration characteristics of bed materials during fluidized bed incineration of dye sludge in a lab-scale system. With several criteria, the agglomeration potential is assessed during a 26 hr-operation, Silica sand and alumina sand are used as a bed material in the experiment, Above a temperature of 800 degreesC, the fluidized bed of silica sand shows agglomeration behavior instantaneously resulting in serious channeling and defluidization during fluidized bed incineration of dye sludge. In the case of an alumina bed material, steady-combustion can be achieved during a 26 hr-operation.