Effects Of Thermal Field Temperature And Dust On Secondary Reaction And Coking Of Tar

The high-efficiency dust removal of high-temperature pyrolysis gas plays a vital role in the stable operation of the pyrolysis system,but the gas-phase tar will continue to undergo secondary reaction in the thermal field of the dust removal system and produce coke.Tar composition,thermal field conditions and dust have a significant effect on the stable operation of the high-temperature dust removal system,the secondary reaction of the tar and coking.Therefore,the author selects an oil-rich long-flame coal and uses the small fluidized bed pyrolysis reaction device designed and built by myself to investigate the influence of pyrolysis temperature and volatile'reaction temperature on the secondary reaction of tar and coking and to discuss the effect of dust on the process of secondary reaction of tar and coking.The specific research conclusions are as follows:(1)The volatile components produced by pyrolysis of coal particles at different temperatures are different and they have significantly different reaction behaviors when passing through the same thermal field.Pyrolysis temperature determines the degree of covalent bond breakage during coal pyrolysis,and has a significant effect on pyrolysis product yield,the secondary reaction of gas-phase tar and coking.When the pyrolysis temperature increases,the yield of char decreases,and the yield of tar increases first and then decreases to a maximum of13.24%at 600 ~oC,and the pyrolysis gas yield increases.The increase of pyrolysis temperature will aggravate the secondary reaction of gas-phase tar,which can increase the relative content of components with a boiling point lower than 420~oC and reduce the relative content of asphalt,but at the same time,more coke will also be formed.As for the composition of tar,with the increase of pyrolysis temperature,the content of aliphatic hydrocarbons in tar decreases significantly,and the content of polycyclic aromatic hydrocarbons increases significantly.(2)The reaction degree of volatile determines the final distribution of pyrolysis product and tar composition.The increase of reaction temperature of volatile will aggravate the reaction between volatile,which obviously affects the yield of pyrolysis products,secondary reaction of gas-phase tar and coke.As the reaction temperature of volatiles increases,the yield of tar continues to decrease,the yield of pyrolysis gas continues to increase,the content of aliphatic hydrocarbons in tar decreases,and the content of polycyclic aromatic hydrocarbons increases,but the changes are not particularly obvious.When the reaction temperature of volatile is?450 ~oC,as the temperature increases,the relative content of light oil continuously decreases,the relative content of asphalt and anthracene oil increases,the coke content changes little.Light oil cracking generates small molecular gas,and large molecular organic matter polycondensation generates asphalt,anthracene oil,etc.,soluble in tetrahydrofuran.When the reaction temperature of volatile was>450 ~oC,the relative content of light oil and coke increased significantly,while the relative content of anthracene oil and asphalt decreased.With the temperature increased,the cracking reaction intensified to generate more light oil and pyrolysis gas,and at the same time the polycondensation reaction also becomes violent to generate more coke.(3)The dust has a significant effect on the secondary reaction and coking of tar:after adding char,no matter how the thermal field temperature changes,the pyrolysis tar yield is lower than without,the pyrolysis gas yield is higher.The char and coal ash have a certain catalytic cracking effect on the gas-phase tar in the thermal field,so that the relative content of light components in tar is significantly increased,the asphalt content is significantly reduced,and it has a certain upgrading effect.When the temperature of the thermal flow field is lower than 450 ~oC,the catalytic effect of char and coal ash is more obvious on the secondary reaction of tar,and the component of tar changes significantly.As the thermal field temperature increases,the catalytic effect continues to weaken.The presence of dust will promote the formation of more coke,and compared with coal ash,the effect of char is more obvious.