Analysis of product distribution and quality for continuous pyrolysis of coal in different atomspheres

The continuous coal pyrolysis at 850 ℃ in a fluidized bed reactor under atmospheres containing O2, H2,CO,CH4,N2 and CO2 were carried out. The char product was characterized using Raman,BET and TGA( for evaluating reactivity). The results showthat without O2 in the atmosphere,adding H2 and CO2 lowers the pyrolysis tar yield which is conversely higher with raising the CO and CH4 contents in the atmosphere. The introduction of O2 promotes the formation of CO and CO2,and thus the yields of tar and char decrease. The char yield increases with the addition of CH4 into the pure N2 atmosphere,which is ascribed to the cracking of CH4. PAHs content decreases with the addition of O2 into N2 atmosphere. CH4 promotes the production of alkyl- substituted naphthalenes and benzenes. CO inhibits the cracking of phenols to form benzenes. CO2 facilitates the formation of newmicropores or opening of the closed pores,producing the chars with high surface area and the corresponding highest oxidation reactivity. The carbon deposition via CO disproportionation and CH4 cracking in the presence of CO / CH4 blocks some pores and thus lowers the surface area and reactivity of the char. The char produced with the inclusion of H2 and CH4 results in a more condensed crystallite structure via hydrogen radicals penetration and thus lowers the oxidation reactivity.