In-situ FTIR And Raman Spectroscopic Studies On The Pyrolysis Of Low-Rank Lignite

As an important primary energy of China, coal has played an important role in promoting the development of national economy of our country. However, the mass consumption of coal has also led to serious environmental problems, such as haze and acid rain. In order to coordinate economic development and environmental protection, the development of more efficient and environmentally friendly coal utilization technology is imperative. Coal pyrolysis is the basis of a variety of coal utilization technology. The deep understanding of coal pyrolysis process is an important basis of further developing modern coal chemical industry. At present, because of lack of in situ analysis method, numerous information of coal pyrolysis is only ‘schematic’. In order to get more accurate and in situ information of coal pyrolysis and provide effective information for further study coal pyrolysis mechanism, this paper studied on coal pyrolysis using in situ infrared spectroscopy and in situ Raman spectroscopy, and mainly focused on the effect of temperature, reaction atmosphere and minerals on the pyrolysis process of coal.This paper studied the decomposition of some typical functional groups of coal during pyrolysis using in situ pyrolysis coupled with FT-IR and multiple peak fitting technique. The effects of temperature, atmosphere and mineral matter on coal pyrolysis were analyzed. The results show that temperature is the main factor influencing coal pyrolysis. The OH-π hydrogen bond can be easily formed by OH and aromatic ring with increasing the temperature. The methyl, methylene, ester and acid anhydride can decompose obviously at above 400℃. H₂ atmosphere improve the decomposition of aliphatic, aromatic ethers and esters structure, but it can inhibit the further decomposition of acid anhydride at higher temperature. It can also be found that H₂ has no significant effect on the decomposition of carboxyl. At below 400℃, the minerals in coal can promote the formation of anhydride via carboxyl crosslinking reaction. Minerals can inhibit the decomposition of aliphatics significantly since Na₂CO₃ has stronger inhibition. At above 400℃, the minerals can promote the decomposition of esters and anhydride to form CO₂. The promotion of Na₂CO₃ is higher than that of NaCl.The in-situ Raman results show that the degree of the structural order of the samples increases after 400℃. The carbon content is one of the important influence factors of the aromatic degree. Na₂CO₃ can inhibit the removal of aliphatics and improve the cyclization of aliphatic free radicals. It also causes the position of G peak to be shifted to the lower wavenumber side.