Characteristics of in situ pyrolysis products of tar-rich coal in Yushen area under different pressures
The gas pressure environment of in situ pyrolysis of tar-rich coal under different pressures was simulated by means of pressure reaction apparatus and molecular dynamics.In the laboratory,tar-rich coal with particle size of 1mm was selected as raw material,pressurized thermogravimeter and high pressurized reactor were used to simulate the in situ pyrolysis of tar-rich coal,and the pyrolysis activation energy of tar-rich coal under different pressures was calculated by sectioning method.ReaxFF numerical simulation was used to analyze the pyrolysis process of tar-rich coal molecules under different pressures.The relationships among different pressure,temperature,tar yield and tar composition characteristics were discussed.It is found that the change of pyrolysis pressure has a limited effect on the pyrolysis activation energy,but has a significant effect on the product characteristics.The activation energy of tar-rich coal pyrolysis to form semi-coke is slightly lower with the increase of pyrolysis pressure at first stage of pyrolysis,and at second stage of pyrolysis the activation energy modestly increases with the increase of pressure.The maximum oil yield is 9.54％at 600℃ under simulated in situ pyrolysis conditions of tar-rich coal.At 2MPa,the maximum oil yield decreases to 5.42％with the increase of pressure,and the content of PAHs in tar increases with the increase of pressure.Through molecular dynamics simulation of tar-rich coal under different temperature and pressure,the pyrolysis trend similar to the experiment is obtained.In the molecular dynamics simulation,the total amount of tar increases with the increase of temperature within 2000K,and the tar production at each temperature point shows a downward trend with the increase of pressure.The tar production reaches a maximum of 23.67％at 2000K and 3MPa,corresponding to the maximum tar output at 600℃ and atmospheric pressure under experimental conditions.ReaxFF numerical simulation results show that higher temperature leads more obvious influence of pressure.At 2300K,the amount of gas produced is inversely proportional to the pressure,and the amount of tar begins to decline compared with that at 2000K.In this study,experiments related to pyrolysis of tar-rich coal under pressure were completed,and the results of pyrolysis of tar-rich coal under pressure were supported by molecular dynamics simulation,which can provide data support for the research on in situ pyrolysis of tar-rich coal.
tar-rich coalin situ pyrolysispressurized pyrolysissectioning method for activating energyreaction force field
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