The Study On The Combustion Characteristics Of The Single Coal Slime Particle

The research on the combustion characteristics of the single solid fuel particles is the basis for realizing the clean combustion of the solid fuel.This article adopts the combined method including experimental study and theory analysis to study the combustion characteristics and kinetics parameters of different ash content coal slime at different heating rates,the ignition and combustion processes of single particles slime in N2/O2 and CO2/O2 atmospheres,and the emission of pollutants from single particle coal slime combustion.The main contents are as follows:Firstly,at different heating rates,the heat release and mass loss processes of four coal slime types with different ash contents have been studied by means of the thermal gravimetric analysis.The TG and DTG curves of coal slime are used to solve the combustion characteristics parameters and combined the Coats-Redfen integration method to solve the kinetic parameters.The results show that at the same heating rate,with the increase of ash content,the TG and DTG curves of the coal slime move to high temperature region,the peak value of DTG curve gradually decreases,the ignition temperature decreases first and then increase,the ignition delay time decreases slightly,the flammability index decreases,the ignition stabilization of combustion characteristics increase first and then decrease,the burnout characteristics index decreases first and then increase,and the activation energy gradually increases.Designing and building a experimental platform for studying the combustion characteristics of the single particle coal slime particles,which is mainly composed of cylinders,mass flow controllers,gas mixing chamber,electrically vertical heated tube furnace,temperature control device,fuel particle transmission device,image and data acquisition system.The experimental facility can realize the setting of variety operating parameters,such as the composition of the combustion atmosphere,oxygen concentration,gas temperature and flow rate.,And it can collect the data,such as ignition phenomenon,ignition delay time,ignition temperature,combustion process and component concentration of the exhaust gas,to study the combustion characteristics of the single particle coal slime particles.In the electrically vertical heated tube furnace,an experimental study on the ignition mechanism and combustion process of a single coal slime particle have been carried out in N2/O2 under different gas flow rate,gas temperature and oxygen concentration.The experimental results show that with a constant flow rate,the heterogeneous ignition of char was primarily observed at low gas temperatures,while the heterogeneous ignition of coal was primarily observed at high oxygen concentrations.Additionally,the homogeneous ignition of volatiles was primarily observed at high gas temperatures and low oxygen concentrations.As gas temperature and oxygen concentration increase,the ignition temperature and ignition delay decrease gradually.In the electrically vertical heated tube furnace,an experimental study on the ignition mechanism and combustion process of a single coal slime particle have been carried out in CO2/O2 under different gas flow rate,gas temperature and oxygen concentration,and make a comparative analysis with the combustion in N2/O2.The experimental results show that under the same gas temperature and oxygen concentration,ignition delay time increases,ignition temperature increases and combustion intensity decreases in CO2/O2 atmosphere compared with N2/O2 atmosphere,for the higher specific heat capacity of CO2/O2 and the lower diffusion rate of oxygen molecules in CO2/O2 atmosphere.Finally,in the electrically vertical heated tube furnace,in N2/O2 and CO2/O2 atmosphere study the effect of oxygen concentration and gas temperature on the emission of flue gas from single coal slime particle combustion and the morphology and elements distribution of the residue surface.The experimental results show that the CO2/O2 atmosphere weakens the process of carbon oxidizing to carbon dioxide,while strengthens the gasification reaction of coke.The increase of oxygen concentration and gas temperature promote the formation of NOx.Under the same gas temperature,the higher the reducibility of hot atmosphere around the coal slime particle,the lower the ash viscosity.However,in the CO2/O2 atmosphere,the reducibility of the atmosphere surrounding the combustion slime particles is higher than the N2/O2 atmosphere.It leads to a higher degree of melting and sintering of the residue surface of coal slime particle in the CO2/O2 atmosphere.