1993 Volume 33 Issue 6 Pages 640-645
To achieve a pulverized coal rate of more than 200 kg/t, a technology is needed by which the combustion zone in front of tuyeres can be properly controlled in terms of the combustibility of pulverized coal. It is, especially, necessary to quantify the combustion behavior inside the tuyeres and raceway. Experiments were conducted on off-line models with and without coke to investigate the pyrolysis and combustion behavior of pulverized coal in order to analyze the influence of blast conditions and coal properties on their combustibility.
(1) The final volatile yield of pulverized coal increases with the rise in blast temperature, and rise in O2 content accelerates the devolatilization rate.
(2) With the progress of pyrolysis, the pulverized coal became spherical and a large number of pores formed in the particles. Thus the reactivity of char is estimated to be higher than that of coke.
(3) Rising blast temperature is effective to improve the combustion efficiency of pulverized coal in the raceway, presumably a little effective to improve with the addition of steam. O2 enrichment at constant air ratio requires enhancement of the gas and particle mixture.
(4) Q-factor that determined the final volatile yield can be shown by the blast temperature and C content in coal, and devolatilization rate parameters can also be learned by C content in coal. A practical equation representing the devolatilization rate inside tuyeres with various kinds of coal are presented.