Reaction characteristics of Shenmu coal pyrolysis volatiles with an iron-based oxygen carrier in a two-stage fixed-bed reactor

The reaction of volatiles with oxygen carriers (OCs) is a common issue in the chemical looping combustion of coal or chemical looping reforming of hot pyrolysis gas. A two-stage fixed-bed reactor was used to determine the characteristics of the reaction of pyrolysis volatiles of Shenmu coal with an Fe-based OC. The effects of the oxygen/carbon ratio (O/C, phi, 0-1.31) and temperature (750-900 C) on the three-phase products (carbon deposition, tar, and gas) were systematically studied. The results showed that an increase in phi caused a decrease in the carbon content in tar, whereas carbon deposition and the gaseous carbon content increased. Moreover, the amount of reducing gases slowly decreased while CO(2 )significantly increased, indicating that the increase in CO(2 )mainly originates from the carbon in tar. Additionally, phenols decreased fast, but naphthalene decreased rapidly at phi > 0.63. Rise in temperature decreased carbon deposition, and tar substances, whereas increased the CO content, notably, naphthalene significantly decreased only when the temperature exceeded 800 C. The reaction of volatiles with OCs consisted of volatiles complete oxidation, tar catalytic cracking, and carbon deposition oxidation, for which the effects of the O/C ratio and temperature were evaluated.