SIMULTANEOUS PYROLYSIS AND CHAR COMBUSTION

Simultaneous pyrolysis and char combustion of < 500 mum coal and peat particles in an entrained-flow reactor was studied experimentally and theoretically at 700-1100-degrees-C and at oxygen contents < 21 vol %. A method based on near infrared radiation was developed to measure th e particle temperatures. Simultaneous pyrolysis and char oxidation occ urs when oxygen reaches the char particle surface during the devolatil ization stage. The overlap of homogeneous and heterogeneous combustion is favoured by low temperature and high oxygen content, as well as by a decrease in particle size. A simplified method of calculating simul taneous pyrolysis and char oxidation is presented. Model calculations show that under some conditions a maximum combustion rate may be achie ved with a specific particle size, since the contribution of faster ho mogeneous combustion is increased relative to slower heterogeneous com bustion.