C₁∼C₂ hydrocarbons generation and mutual conversion behavior in coal pyrolysis process

Different hydrocarbon species in coal pyrolysis gases have the NOx reduction potential. To investigate hydrocarbons CxHy mutual conversion in the coal pyrolysis gases, four typical coals were pyrolyzed under slow and fast heating rate conditions below 1200 °C. Results show that the yield of the hydrocarbon species has positive relation to coal volatiles. In fast heating condition CH₄ is the major pyrolysis products. In addition, the alkanes generation behavior is quite different from that of olefins and alkynes. In the range of 600–1200 °C, as the pyrolysis temperature increases, the yield of C₂H₄ and C₂H₂ increases while CH₄ and C₂H₆ decreases. The yield of C₂H₂ is significant at the temperature above than 1000 °C. Fourier transform infrared (FTIR) analysis show a close relationship between the coal functional group from 2800 to 3000 cm⁻¹ and the alkanes yield. In the slow heating condition, five CH₄ and two C₂H₆ evolution paths are proposed by the mathematic fitting method. The ethylene in the high temperature produced from the decomposition of C₂H₆. When the heating rate is low, no C₂H₂ is detected which illustrates that the formation of acetylene is closely related with the heating rate.