Investigation on the thermal behavior characteristics and products composition of four pulverized coals: Its potential applications in coal cleaning

Abstract

Although the thermochemical conversion of coal has dominated the research concerning the primary chemical production in the coal chemical industry utilization field, obtaining higher tar yield and lighter tar quality remain as challenges. The pyrolysis and its product distribution were studied using a thermogravimetric analyzer and a fixed bed reactor. A gas chromatograph (GC) and a gas chromatograph−mass spectrometer (GC-MS) were employed to test the properties and composition of the pyrolytic products. Here, we demonstrated that the tar yield only fluctuates when the carbon content is approximately 80%. The ratios of aliphatic hydrogen to all the functional groups (Ib1) are the largest in HM2 coal, while the change of the ratios of aromatic hydrogen to all of the functional groups (Ib2) is the same as that of the tar yield. With the increase of coalification, the ratio of CH2 to CH3 in the aliphatic structure (Ic1) decreases. The oxygen containing functional groups in YL coal were mostly converted into tar products, but the corresponding functional groups in ZC3 coal decompose to form more water. When the final pyrolysis temperature is below 550 °C, there was a higher yield of gaseous products containing carbon and oxygen than of gaseous products containing hydrogen. With the decrease of the H/C ratio, the relative content of the aliphatic hydrocarbon and phenolic compounds in tar increased, while the benzene series and polycyclic aromatic hydrocarbons decreased.