Spectroscopic Study On Thermal Decomposition Of The Huolinhe Brown Coal

Coal is an important primary energy in our country, the pollutant discharge and CO2emission which caused an increasing pollution problem are greatly larger than other fossil energy. The highly efficient and clean low-carbon utilization of coal is the predominating direction of research and development in our country. Coal pyrolysis is the first step of gasification, liquefaction and other thermal-chemical conversion. So, clear understanding of coal pyrolysis is the basis of clean utilization of coal resources in our country.After the acid treatment, the Huolinhe(HLH) brown coal was studied by in situ diffuse-reflectance infrared and Raman spectroscopies during pyrolysis. In order to investigate the thermal stability of chemical bonds clearly, the FT-IR and Raman spectra were studied by curve-fitting analysis using PeakFit (v4.12) program.Curve-fitted analysis of in situ FT-IR and Raman spectra during pyrolysis are an effective method to investigate the thermal stability of the weak covalent bonds in coal.Pyrolysis reaction occurred after250℃, the carboxyl group, alkyl group, alkyl ether group and carbonyl group began to decompose during the early stage of pyrolysis. Substituent groups which directly attached to the aromatic rings gradually decompose, resulting in stronger absorption peaks of aromatic C-H stretch vibration. The aromatic ether bond is stable from100℃to400℃.The release of CO2, CH4came from the decomposition of carboxyl group and alkyl group, and that of CO may come from the decomposition of alkyl ether group and carbonyl group. Above350℃the decomposition of CH3-group, which directly attached to the aromatic rings, may be the main reason for CH4production. The pyrolysis of methylene and methyl groups is gradually completed from450℃to550℃.As the temperature increases, carbon content of HLH brown coal is gradually increased. The degree of graphitization is markedly increased above350℃, which stabilizes interlamellar spacing.