Study on Main Factors Influencing Acetylene Formation During Coal Pyrolysis in Arc Plasma

Abstract

Acetylene from coal pyrolysis in arc plasma jet is simple and environmentally friendly with promising applications. A set of rank-ordered coal samples were selected in this study, in order to study the effects of volatile matter yield and the content of carbon, hydrogen and oxygen in raw coal on the yield of acetylene from arc plasma pyrolysis. The influence of feeding rate on the conversion of coal and acetylene yield was also investigated. The results showed that acetylene and carbon monoxide were the main gaseous products during coal pyrolysis under plasma conditions. A higher acetylene yield of 17–22% could be obtained from coal with volatile matter yield of 25–40%. A high C/H mole ratio and low O/C mole ratio were favorable to the formation of acetylene. The percent conversion of coal, the yield of acetylene and the specific energy consumption (SEC) decreased as the feeding rate increased, but the trends in their changes were not identical. The relative volume fractions (RVF) in gaseous products of acetylene and carbon monoxide increased with increasing coal feeding rate until 5 g s−1, while the RVFs of light hydrocarbons such as CH4, C2H4 and C3H6 gradually increased. The change in the selectivity for acetylene was not obvious when the feeding rate was less than 4 g s−1. However, the portion of acetylene in the total gaseous products decreased rapidly when the coal feeding rate was further increased.