Study On Flame Propagation And Thermodynamic Properties Of Non-stick Coal Pulverized Coal

Most of the large-scale enterprises in China's cement,power generation,metallurgy,and chemical industries require pulverized fuel.Under normal circumstances,the above-mentioned enterprises basically use outsourced raw coal and adopt the vertical coal grinding system to process and produce the required pulverized coal.The pulverized coal explosion is a major safety hazard in the process of production,transportation,and storage of the pulverized coal system.In this paper,the STA 449 F3 type synchronous thermal analyzer is used to analyze the characteristics of thermal weight loss,combustion characteristics and thermodynamics during the combustion of pulverized coal.The pulverized coal cloud explosion test device in vertical pipeline is used to reveal the flame propagation characteristics.The numerical simulation software simulates the flame propagation process under experimental conditions and studies the flame propagation characteristics of pulverized coal clouds under ideal conditions.The main conclusions are as follows:(1)The combustion process of pulverized coal includes pulverized coal loss weight loss stage,weight gain oxidation stage,thermal decomposition stage,combustion stage and burnout stage;the heating rate and oxygen concentration affect the combustion characteristics of pulverized coal mainly in the combustion process and combustion.The characteristic index,as the heating rate increases,the temperature range of the five stages shifts to the high temperature area,the characteristic temperature increases,the TG,DTG and DSC curves appear hysteresis;the combustion characteristics of the coal sample and the heating rate and oxygen The concentrations are all positively correlated,and the effect of oxygen concentration on the combustion characteristics index is more pronounced than the heating rate.(2)Both the heating rate and the oxygen concentration can affect the activation energy required for the combustion of pulverized coal.Both have a negative correlation with the activation energy,the oxygen concentration is 5%,and the maximum activation energy is at a heating rate of 5?/min.The value is 108.12 kJ/mol,that is,the low heating rate and low oxygen concentration increase the activation energy required for pulverized coal combustion,and pulverized coal is not easy to burn.(3)The pulverized coal flame is affected by the turbulent flow in the pipeline.At three mass concentrations,the flame morphology is quite different.With the continuous development of the flame propagation process,the front surface of the flame front is irregular to a large extent;the flame propagation speed is basically.The process of "fast increase-peak value-rapid decrease-slowly increase-slowly decrease" oscillation occurs at about 20 ms;the pulverized coal cloud concentration is positively correlated with the flame propagation velocity,and the particle size is negatively correlated with the flame propagation velocity.When the average particle size is 45?m and the concentration is 0.5 kg/m3,the flame propagation speed reaches its maximum value,which is 17.1 m/s;the explosion pressure shows the process of "slow increase-rapid increase-peak reach-slight decrease" At about 95ms,the explosion pressure peak appeared.The value was 0.948 MPa.(4)For the pulverized coal explosion flame propagation process,the numerical simulation and experimental results are consistent;numerical simulation and experimental results show that the pulverized coal cloud flame propagation speed characteristics show a tendency of increasing first and then decreasing,and oscillation propagation phenomenon occurs after 60 ms.The numerical simulation of the pulverized coal cloud flame propagation process has a positive correlation between the explosion pressure and the flame propagation time.The numerical simulation agrees well with the experimental results.(5)The preheating and drying of pulverized coal has a great influence on the flame propagation process.The main influencing factor is the moisture content in pulverized coal.At the same time,the main reason for the irregular pulverized coal flame propagation is the release of volatiles from the pulverized coal combustion process.Rate differences and regional distribution of concentrations.