热解预处理对昭通褐煤润湿性的影响机制OACSTPCD

The significant hydrophilicity of lignite has caused many adverse effects on its processing and utilization.Pyrolysis pretreatment is one of the effective methods to regulate the wettability of lignite.The influential mechanism of pyrolysis pretreatment on the wettability of lignite was investigated using proximate analysis,Fourier transform infrared spectroscopy(FT-IR),X-ray diffraction(XRD),and contact angle measurement.The temperatures of pyrolysis pretreatment were set as 200℃,300℃,400℃,and 500℃,and the times were 30 min,60 min,90 min,and 120 min,respectively.The results show that pyrolysis pretreatment alters the chemical structure and composition of the lignite,significantly affecting its wettability.The car-boxyl group of lignite starts to decompose and volatilize at 200℃,and basically disappears at 300℃.The ester group starts to break down and volatilize at 300℃,and basically disappears at 400℃.C—O(ether bonds,phenols,and alcohols)exhibits high thermal stability,with a slight increase in relative content.The aromatic-carbon ratio of lignite increases with temperature and time,and the size of aromatic core begins to expand at 300℃.If pyrolysis pretreatment is adopt-ed to attenuate the hydrophilicity of lignite,it is essential to ensure sufficient pyrolysis time to remove oxygen-containing functional groups effectively at lower temperatures.Conversely,a shorter pyrolysis time should be available to prevent excessive loss of organic matter at higher temperatures.At the pyrolysis conditions of 300℃(120 min)or 400℃(30 min),hydrophilic oxygen-containing functional groups(carboxyl or ester groups)are decomposed and volatilized,and the size of hydrophobic aromatic core increases,resulting in a significant decrease in hydro-philicity.The contact angle increases from 44.00 ° of raw coal to 87.50 ° and 85.75 °,respective-ly.However,at 400℃(pyrolysis time greater than 30 min)and 500℃,excessive loss of organ-ic matter leads to an increase in the relative content of minerals or inorganic matter,resulting in still strong hydrophilicity.