Study On Low-rank Coal Pyrolysis And Characterization Of Coal Tar

The pyrolysis behavior of low-rank coal was carried out in the fixed bed. The influence of temperature and holding times on free radical changes was investigated by Electron spin resonance spectroscopy. The results showed different origin coal samples has different primeval free radical concentration. The consistency changes performance is that free radicals concentration increase with the pyrolysis temperature rise, the free radical concentration was the biggest during400℃-500℃, and free radical concentration tends to be stable when the more than30mins at the pyrolysis temperature.The influence of coal samples pretreated by solvent on coal pyrolysis behavior was investigated by tube furnace, TG, fixed bed pyrolysis device and ESR. Huainan coal and Shengli coal was pretreated by CS2、pyridine、THF and some other solvents under ambient conditions. The different influence of N2and CO2to coal pyrolysis behavior was compared also. The results showed the polycondensation of Shengli coal starts when the pyrolysis time is5min, earlier than Huainan coal. Different kinds of solvents has different swelling effect, mixed solvent of pyridine and THF has the highest swelling degree of1.84; the pyrolysis temperature range of pretreated coal become wider; the tar yield and the hydrogen content in pyrolysis gas were increased after solvent pretreatment, up to6%(daf) and5%respectively. The pretreat performance of strongly polar solvents is better than the performance of weakly polar solvent and non-polar solvent. The weight loss of coal pyrolysis under N2is larger than that of CO2.Coal tar was seperated into three different group component by using chromatography column and their composition were determined by GC-MS. The preservation conditions of coal tar was examined by NMR and ESR. The influence of different pyrolysis process on coal tar characterization was compared. The results showed coal tar can be seperated by chromatography column and aromatic hydrocarbons contents is49.92%. The free radical concentration in coal tar is increasing with time under ambient conditions, high temperatures promote its growth while low temperatures inhibit its growth, and remain unchanged at minus40℃. The change of free radical is mainly caused by coal tar produced from during400℃-500℃; It is no significant difference that composition of the pyrolyzed coal tar was produced from different heating rate.