Releasing Characteristics Of Volatiles During Low Temperature Thermal Treatment Of Pulverized Coal

Before the coal is processed and utilized,it is usually subjected to a low-temperature thermal treatment process such as preheating and drying process.However,people have always focused on improving the efficiency of utilization,and overlooked the potential pollution problems.The potential danger of low-temperature heat treatment for coal such as preheating and drying attracts less attention.Due to the consideration of clean utilization of coal,it is necessary to control the content of pollutants in the exhaust gas after low temperature thermal treatment.The result is carried out on a thermogravimetric analyzer,PY-EGA-MS combined device,pyrolysis-meteorology chromatography/mass spectrometry device and vertical fixed bed-quantitative detector etc.And three representative coal samples?HM,YM,WYM?was chosen to study and conduct a low-temperature heat treatment experiment.Through the qualitative and quantitative analysis of volatile emissions,the releasing characteristics of contaminant volatiles including alkanes,olefins,aromatic hydrocarbons,carbon dioxide,formaldehyde and other substances of three coal samples under different low-temperature thermal treatment conditions were investigated during low temperature thermal treatment process.At the same time,the data of volatiles releasing under different conditions were obtained,and the releasing characteristics of typical volatiles were summarized to some extent.The results of the study show that:In the temperature range of 100³50°C,under the inert atmosphere,some volatiles will be released after the coal sample is heated.The released volatile species include aliphatic hydrocarbons,aromatic hydrocarbons,oxygen-containing,nitrogen-containing sulphur-containing organic compounds,as well as some small molecule inorganic compounds.It has been determined that the detected components are:C1-C7paraffins,ethylene,cyclohexane,benzene,toluene,xylene,ethylbenzene,CO₂,NH₃,HF,HCl,COCl₂,HCN,NO,H₂,H₂S and NO₂.In the experimental temperature range,the content of CO₂ is the highest among the volatiles released;the volatile organic compounds will produce a certain release,with the highest alkane content,followed by aromatics.Inorganic components other than CO₂ have a extremely low release.With the increase of thermal treatment temperature,the composition of volatiles is more complicated and the content gradually increases.When the temperature exceeds 300°C,the increasing trend in HM and YM is more obvious.The degree of coalification has different effects on the releasing characteristics of different volatiles.The organics,H₂,and CO₂ of the three samples are significantly affected by the degree of coalification,and there are significant differences in the release of the three samples;the release of constituents such as NH₃,HF,HCl,COCl₂,HCN,NO,H₂S and NO₂ was less affected by the degree of coalification and was not evident in the three samples.