Combustion behavior of CWPs in a fluidized bed combustor

Combustion behavior of CWP (Coal Water Paste) fuels made of 15 types of coals was observed by using a small atmospheric bubbling fluidized bed combustor made with a quartz tube. Ignition delay, flame combustion time and char combustion time were measured and compared with those of dry coal. From these observation, the combustion behavior of CWPs was classified into three different modes. Some CWP aggregate broke up already during drying and their coal particles burned separately as in the case of dry coal combustion (mode 1). Combustion aggregates that maintained their size during the flame combustion period were classified as mode 2. Some CWP aggregates bursted into small pieces during the flame combustion period (mode 3). Burn out times of mode 2 and mode 3 CWPs were much longer than those of the dry coal combustion. It was found that the factor governing the combustion behavior of CWPs is the crucible swelling number of coal. The relation between the combustion modes and the prescription for CWPs was also studied.