Studying The Pyrolysis Of Honghe Lignite Under Nitrogen And Methanol-Nitrogen Atmosphere

The direct liquefaction, in-direct liquefaction and coal pyrolysis were three methods for oil producing from coal. And, coal pyrolysis was a process which separated the carbon-rich and hydrogen-rich part of coal into different parts on wild conditions by carbonization, and the high quality transformation and utilization of coal were realized. While the coal tar yields of the traditional pyrolysis processed were low, so the methanol was injected in pyrolysis in this work. The pyrolysis of honghe lignite under nitrogen and methanol-nitrogen atmosphere was studied, and the reaction mechanism of methanol during pyrolysis was investigated too.The pyrolysis of honghe lignite under nitrogen and methanol-nitrogen atmosphere was studied systemically in experiments. And, the effects of temperature (440～560℃), pressure (0.1～1.2MPa), flow rate of carrier gas (50～200ml/min), holding time (0～30min), methanol flow rate (0.06-0.14ml/min) on products yields and components during pyrolysis were investigated. And, the pyrolysis reaction parameters with the maximum coal tar yields were found out on laboratory fixed-bed facility under corresponding atmosphere. The proper conditions for honghe lignite pyrolysis under nitrogen atmosphere are:temperature520℃, pressure0.5MPa, carrier gas flow rate50ml/min and holding time20min. And, the yields of char, coal tar and water were71.15%,9.61%and7.99%for dry coal, respectively. And, the proper conditions for honghe lignite pyrolysis under methanol-nitrogen atmosphere were temperature520℃, pressure0.5MPa, carrier gas flow rate50ml/min, holding time20min, methanol flow rate0.1ml/min and the injection time of methanol20min. The corresponding yields of the char, coal tar and water were72.26%,12.01%and12.35%on proper pyrolysis conditions.The pyrolysis of honghe lignite in two different atmospheres were comparatively studied under the same conditions on fixed-bed facilities, the results showed that the yields of coal tar, water and gas increased significantly with the presence of methanol for the unit mass of dry coal. And, the char yields increased slightly.In order to understand the role of methanol in pyrolysis, the char and gas were detected and analyzed by IR and GC respectively; the coal tar on proper conditions were pre-treated and separated into five group components, such as the acidic, alkaline, aliphatic, aromatic and polar fractions, and then these group components were analyzed by GC-MS. And, with the comparison and analysis we insisted that the methanol attend in the reactions during pyrolysis, it supplied hydro, methyl or other free radicals to the reaction system. These radicals stabilized the fragments radicals and inhibited the condensation reactions among the fragments, so the yield and quality of coal tar were improved. Took the acidic fractions in coal tar under proper pyrolysis conditions as example, the total yields (dry and ash free basis) of phenol, cresol and xylenol (short for PCX) increased form1.15%to1.93%, the yields increased nearly70%on proper conditions.