Study On Pyrolysis Removal Process Of Trace Coal Tar In Syngas

Pyrolysis is the main step of the coal gasification process,the conditions and processes of pyrolysis in different gasification technologies are different.Among them,Fixed bed gasification and Two-stage entrained flow gasification process will produce tar due to low pyrolysis temperature,which has been the key to restrict the further utilization of syngas and energy.Effective removal of tar is an important measure to promote the further development of gasification technology.This paper designs and builds a tar pyrolysis experiment device.The effects of temperature on tar pyrolysis process were investigated,the choice of toluene as a tar model compound was carried out to study of compositional changes during tar pyrolysis.The results show that the pyrolysis temperature have a great influence on tar and toluene conversion.Between 800-1100℃,the conversion of tar and toluene and gas yield increase with temperature,and the highest conversion under N2 atmosphere is 70.29%and 90.11%respectively.The increase of temperature also will promote the formation of carbon black.The study found that H2 will inhibit the conversion of toluene,but it has a significant inhibitory effect on the formation of carbon black.When the temperature is raised,the thermal cracking product type of toluene is reduced,the branched chain compound is substantially disappeared,and a more stable polycyclic aromatic hydrocarbon compound is formed,the elevated temperature promotes the polycondensation of toluene.Two kinds of dolomite catalysts with wide source and low price were selected to study their catalytic performance for toluene cracking.The results show that the catalytic activity of the two dolomites is significantly improved after calcination,and the catalytic activity of Liaoning dolomite after calcination is higher than that of Hebei dolomite.Between 600-900℃,the conversion of toluene increases with temperature;H2 also inhibited the catalytic cracking process of toluene,and with the increase of H2 concentration,the conversion of toluene in Liaoning dolomite decreases more,and the higher of the H2 concentration,the conversion of toluene decrease more obvious.The pyrolysis model of tar model compound,which was a mixture of naphthalene and toluene and phenol,was developed based on the pyrolysis reaction and kinetic parameters of toluene etc.in Aspen Plus.Then the effects of temperature,pressure,residence time and different atmosphere on tar pyrolysis process were investigated.The results indicated that with the increase of temperature,pressure and residence time,the conversion of tar increases to varying degrees.Between 900-1100℃,the conversion increment of tar increase is basically constant.When the residence time reaches 6s or the pressure increases to 1MPa,the tar conversion increment gradually decreases.In addition,different reaction atmospheres also have different effects on the pyrolysis process of tar.CO2 and steam have an enhanced effect on the pyrolysis of tar,and the promotion of steam is more significant,steam has a remarkable inhibitory effect on the formation of carbon black;CO has little effect on tar pyrolysis.H2 has an inhibitory effect on tar conversion and the formation of carbon black.