Analysis Of Mixed Combustion Characteristics And Pollutant Emissions Of Lignite And Oil Shale

Coal,as one of the most important material foundations for human survival and development,plays an important role in the development of social productivity.Mixed combustion technology is a relatively important clean coal utilization technology at present.The state has given great support to the graded utilization of coal and the coupling of other fuels.At present,more research has been done on the combustion of single coal,while oil shale is rich in combustible organics,which is a solid fossil fuel.According to the basic characteristics of lignite and oil shale,this paper analyzes their co combustion characteristics and pollutant emission characteristics,and provides some references for the rational utilization of resources.Firstly,the combustion characteristics of the two are analyzed by thermogravimetric analyzer.The TG-DTG curve shows that the combustion process of oil shale is divided into three stages,and the combustion process of lignite has two stages.As the heating rate increases,the overall reaction moves towards the high-temperature zone,and the ignition temperature and burnout temperature also increase,resulting in an increase in the comprehensive combustion characteristic index of each sample.With the increase of the mixing ratio of oil shale,the weight loss peak gradually increases,the ignition temperature Ti and the later burnout rate f₂ of each sample decrease,and the ignition characteristics and burnout characteristics of the mixed fuel are improved compared with those of the sample burned alone.The kinetic parameters of each sample were calculated by Coats-Redfern method,and the activation energy of each sample increased with the increase of heating rate and oil shale mixing ratio.The weighted average method is used to analyze the synergistic characteristics and calculate the dimensionless performance influence degree coefficient.The results also show that mixed oil shale is conducive to improving the combustion characteristics of lignite.Then the ignition characteristics and volatile combustion time characteristics of oil shale and lignite were studied on a small fluidized bed test rig.As the furnace temperature increases,the sample preheating time tp decreases.The combustion time of volatile matter of oil shale and lignite and the particle size of the feed sample conform to the allometric model,and the relationship between the average particle size of the feed and the combustion time of volatile matter is obtained under different variables.Overall,the feeding quality,fluidized air flow rate,and feeding particle size all have an impact on the combustion time of fuel volatile matter.Established an improved volatile combustion time prediction model,completed the mathematical model verification work,and more accurately predicted the volatile combustion time of high-temperature fuel.When changing the blending ratio of lignite,as the proportion of lignite increases,the combustion preheating time and volatile combustion time also increase.Finally,pollutant gas release tests of oil shale,lignite and mixed samples were conducted in a small fluidized bed to analyze the release characteristics of NO_x and SO₂ under different furnace temperatures,particle sizes and mixing ratios.The results show that the instantaneous emissions of NO_x and SO₂in the combustion of oil shale and lignite show a single peak trend.With the increase of furnace temperature,the peak time of NO_x instantaneous release from oil shale and lignite is earlier and lower;When the particle size increases,the peak emission trend of SO₂ is opposite to that of NO_x;When changing the blending ratio of lignite,as the blending ratio of lignite increases,the instantaneous NO_xemissions show an increasing trend,while on the contrary,the instantaneous SO₂ emissions show a decreasing trend.