Pyrolysis Mechanism And Gasification Characteristics In Fluidized Bed Of Hailar Lignite

The feature of our country's energy source is“rich in coal,poor in oil,less in gas”.As environmental problems become more and more serious,it is very important to develop clean coal utilization technology.Lignite fluidized bed gasification has gradually become the research focus of both domestic and foreign scholars in the case of a substantial reduction of high-quality coal reserves.The author provided an overview of the present researches on coal pyrolysis and gasification,revealed the key factors of the coal gasification process.Taking Hailar lignite as raw material,the research was carried out from the aspects of pyrolysis characteristics,fluidized bed gasification experiment and simulation optimization.To lay a foundation for the future development of lignite gasification technology and mixed fuel utilization.Firstly,Combining TG-FTIR and Py-GC/MS detection techniques to analyze the thermal conversion mechanism of lignite.The TG/DTG curve showed that the pyrolysis process of lignite can be divided into four stages.The intense pyrolysis stage of lignite occurred in the range of 430⁶20^oC,the maximum weight loss peak appeared at 500^oC.According to the infrared spectrum obtained by FTIR,the evolution process of CH₄?CO?CO₂ and functional groups were analyzed.It was confirmed that the functional groups in the lignite matrix had a great impact on the precipitated gas.Combined with Py-GC/MS,the variation trends of hydrocarbons and heteroatoms compounds were analyzed,and three kinds of conversion paths of PAHs during pyrolysis were deduced.The experimental investigation of lignite gasification was carried out on a self-designed fluidized bed.The effects of bed temperature,air equivalent ratio?ER?and steam to fuel mass ratio?S/F?on syngas composition,gasification efficiency and carbon conversion were investigated.The results showed that as the temperature increases,the content of H₂ and CO increases,the CO₂ content decreases,and the LHV,gasification efficiency and carbon conversion rate increase.With the increase of air volume,the content of H₂ and CH₄ decrease,CO content increases first and then decreases.The gasification efficiency decreases and the carbon conversion increases with the increase of ER.With the increase of steam,the content of H₂ and CO₂ increases significantly,while CO content decreases.Both gas yield and carbon conversion show an upward trend.Based on the experimental data of lignite fluidized bed gasification,the ASPEN PLUS was applied to establish and simulate a gasification model.The simulation values were basically consistent with the experimental values.Through the inside optimization module,a high syngas LHV?6.47MJ/Nm³?can be obtained when the temperature reached900?,ER=0.24 and S/F=0.14.