COMBINED PYROLYSIS COMBUSTION CYCLE - EFFECTS OF OPERATING-CONDITIONS ON SULFUR AND CALORIFIC VALUE DISTRIBUTION IN COAL PYROLYSIS

The pyrolysis of subbituminous coal was studied in a 6.5 cm i.d. fluidized bed reactor to achieve particle heating rates estimated to approach 200 K min-1. A three-variable composite factorial experimental design was used to investigate the effects of reaction temperature, pressure and char residence time over the ranges 500-750-degrees-C, 0.1-1.1 MPa and 5-30 min respectively. Quadratic response surface models were used to analyse the distribution of sulfur and calorific value from the coal into the product char and gas. Temperature was generally the most important variable; all the responses exhibited temperature-dependence. Char residence time influenced most of the responses but its effects were smaller than those of temperature. Only one response, the fraction of calorific value transferred into the gas, exhibited a small pressure-dependence. These statistically substantiated experimental trends provide a database for validating the predictive capabilities of more comprehensive models.