Combustion characteristics of demineralized coal pyrolysis char

摘要

In the oxy-coal combustion steam system (OCCSS), the demineralized coal combusts with gaseous O_2 and steam being recycled from condenser and injected stage by stage in order to produce a flue gas consisting predominantly of steam and CO_2. The flue gas is then expanded through an advanced turbine, and then separated in a condenser to produce high-purity CO_2. Stable demineralized coal combustion at high steam concentrations is crucial to the development of the OCCSS technique. In this study, Zhundong coal was used to prepare demineralized coal. Pyrolysis chars were prepared from the raw coal and the demineralized coal in a high-temperature drop tube furnace at 1200°C. The effects of the reaction atmosphere (O_2/H_2O and O_2/N_2) and temperature (1100-1400°C) on the combustion characteristics of the two chars were investigated. The results show that at 1200°C, steam gasification of the demineralized coal pyrolysis char was slow because of alkali metal removal, which cannot compete with char O_2 combustion. The effects of steam on char combustion are mainly physical. Demineralized coal pyrolysis char combustion in an O_2/H_2O atmosphere accelerated significantly with increasing temperature. Steam gasification of demineralized coal pyrolysis char significantly promotes char conversion at 1300°C. The effect of O_2 concentration on the demineralized coal pyrolysis char combustion was mild. When the O_2 concentration was higher than 40%, the combustion rate of the demineralized coal pyrolysis char increased significantly.