Pyrolysis Characteristics And Products Distribution Of Low-rank Coal

Developing poly-genenration technologies on low-rank coal coversion is one of the best ways to realize the clean and efficient utilization of low-rank coal.The pyrolysis is the basic process during coal chemical engineering and thermal conversions,and the studies of pyrolytic product distributions can lay a firm foundation for increasing the products'additional value.To investigate the thermal pyrolytic characteristics of different coalification degree and heating rate,the TG analyzer was adopted in the experiment.Through the analysis,the pyrolytic parameters such as the initial temperature,the temperature corresponding to the maximum rate of weight-loss,ending pyrolytic temperature and so like were examined with the help of thermal analysis.And the C-R model and DAEM model were carried out to study the kinetics from 180°C to 650°C.To explore the pyrolytic products distribution of low-rank coals at different temperature,the Py-GC/MS method was adopted in this study.Identified by NIST mass spectral database,more than 200 compounds were detected,The major products were categorized into six parts,including aliphatic hydrocarbons?alkanes,cycloalkanes,olefins,cyclenes and dienes?,aromatic hydrocarbons?benzene,toluene,naphthalene,PAHs and their derivatives?,oxygen-containing products?phenols,alcohols,ketones,esters,ethers and oxy-heterocycle compounds?,nitrogen-containing compounds,sulfur-containing compounds and others.Due to the latter three kinds were present modicum,they will not be analyzed any further in this work.The total peak area of pyrolysates which can be detected increased with increasing temperature range of 400⁶00°C,but decreased from 600⁷00°C.The aliphatics and oxygen-containing compounds are the major product,which reflects the feature of low-rank coals'structure.Benzenes,naphathenes and indenes increased with the increasing pyrolytic temperature,which has the same tendency as the relative intensity of the aromatic compounds.However,the increasing temperature contributes to the generation of PAHs below 600°C,after 600°C the yield of PAHs significantly changed to be decreased.The content of the oxygen-containing compounds increased with the increasing temperature from 400 to 600°C,then decreased above 600°C.By the fixing-bed experiments,the effects of different temperature on pyrolytic product yields and components were studied.With the increasing temperature,the yield of char is decreased,the yield of gas is inceased;however,the tar yield firstly increased then decreased,the mixmum is at 550°C.To study the distribution of pyrolytic gas,the GC method we used in this research.By the means of FT-IR and ¹³C NMR analysis,effects of temperature on the structure of char were investigated.For coal tar,we treat it with pickling and alkanine washing coupling with the column chromatogram for separating five components,then detected and analyzed these components by GC/MS.