Effects of oxygen on the structure and reactivity of char during steam gasification of Shengli brown coal

Abstract

The effects of oxygen on changes in char structure and reactivity during steam gasification of Shengli brown coal were examined. A stainless steel simulated entrained-flow reactor was employed to carry out gasification at 800 and 900°C in 8 atmospheres: pure N2, 15%H2O, 25%H2O and 35%H2O balanced with N2; and 1%O2, 15%H2O+1%O2, 25%H2O+1%O2 and 35%H2O+1%O2 balanced with N2. The structure of chars was measured by Raman spectrum, and the intrinsic reactivity of chars with air was measured using a thermogravimetric analyzer (TGA) at low temperature (300°C). The results show that the effects of oxygen on char structure are different at high temperature (900°C) and low temperature (800°C) in brown coal steam gasification. The volatilization of alkali and alkaline earth metallic (AAEM) is strongly influenced by char structure. The presence of O2 during steam gasification has a similar effect on the volatilization of Na to the evolution of structure at different temperatures. Experimental data provided evidence that a mixed H2O/O2 atmosphere could promote a decrease in subsequent char reactivity in air at 300°C, and that char reactivity could correlate well with the band area ratio, I(GR+VL+VR)/ID.