Study On Combustion And Bursting Characteristics Of Single Particle Coal Slime

With our increasing emphasis on the environment and stricter emission requirements in recent years,the proportion of coal washing companies in coal mining companies is increasing year by year,and the output of coal slime as a by-product of the coal washing process is also increasing year by year.The use of slime has become an urgent problem to be solved,and it is one of the best utilization methods to mix coal with slime in the boiler to generate electricity.The ignition and bursting characteristics of coal slime combustion process will seriously affect the combustion characteristics of coal slime in the boiler combustion chamber,in order to provide experimental data and theoretical basis for the combustion arranging in engineering applications,this study will take single particle slime as the research object,and explore its combustion and bursting rules and reveal its combustion mechanism,thus providing a basis for further research on the clean combustion of new fuel technology.The main purpose of this article is to conduct single particle slime heating experiment through building s a single particle fuel combustion test bench and establish a complete single particle fuel combustion ignition and observation system,and use video analysis,Image-Pro Plus image processing or software analysis methods and other means to analyze experimental data.The combustion characteristics of different 3～6mm coal slime particles under different heating modes and the bursting characteristics of 3～6mm coal slime particles under the 20% moisture were investigated,thereby obtaining reference results.The study found that the ignition mechanism and combustion process of various slime particles are different under different heating conditions.The heating rate is very high under laser heating conditions.For the slime with a higher volatile content,it will experience the ignition of the particle surface while the volatiles are precipitated,the volatiles are ignited and the carbon is burned,characterized by homogeneous and heterogeneous combined ignition.For the slime with low volatile content,only the particle surface was ignited and the combustion stage of volatile precipitated,characterized by heterogeneous ignition.However,the butane flame heating rate is slow,and the particle surface is not easy to ignition.The slime with high volatile content shows homogeneous ignition,and the slime with low volatile content shows slow homogeneous ignition.The ignition mechanism and combustion phenomena are different due to different volatile and ash contents and different heating conditions.After processing with software color threshold division method,the normalized flame area change of different slimes during combustion is obtained.The maximum normalized flame area and the average normalized flame area of the three types of coal slime burning under the conditions of laser heating and butane heating showed an increasing trend with the increase of particle size.Through high-speed camera video,it can be seen that when the slime bursts,the surface debris falls off the outer layer of the slime layer by layer in an intermittent manner.The external heating makes the outer layer of the particles dry and has a certain strength.The drying layer will prevent the internal water from leaching out and thus generate internal stress.When this internal stress reaches a certain level,the dry layer of coal slime will break under the action of stress and burst.The initial burst time and burst duration of the three types of slime increased with the particle size under the two heating conditions.However,due to the high laser heating rate,the initial burst time of the three types of slime under the laser heating was very close and varies little with the particle size.Using software program to process the slime burst images under the condition of butane heating,the normalized flame area change curves of different slime burst processes can be obtained,and it is found that the flame area and the burst frequency in the slime burst process have opposite trends.