A mathematical model of in-bed char combustion of Australian coals in PFBC

The combustion efficiency of Australian coals in PFBC is being studied in a batch-fed rig. Elutriation of unburnt char is the main source of combustion inefficiency and is proportional to the char loading in the bed. Hence, in-bed char combustion is being studied to identify those coal-related factors which significantly affect the in-bed char loading and thereby combustion efficiency. This paper describes a mathematical model designed to simulate in-bed char combustion specifically in the PFBC rig, with the aim of identifying those aspects which need to be studied further experimentally. Through a sensitivity analysis of in-bed char loading to model input parameters, coal-related parameters were ranked in priority order as follows: char reactivity, the C/O2 molar ratio consumed on the surface of a burning char particle in the bed and secondary fragmentation. In further work, these significant parameters will be chosen for experimental study and the model will be used to extract coal-specific values from PFBC experiments.