Simulation Study On Gasification Reaction Characteristics Of Double Coal Char Particles

The reaction characteristics of coal char particles under the high temperature flame conditions are difficult to obtain in the experiment because of the complex environment of entrained flow gasifier,while the gasification characteristics of coal char particles can be observed from the microscopic scale by simulation.CFD simulation was used to study the gasification reaction characteristics of double reacting porous spherical carbon particles under H2O/O2/CO2 atmosphere,including four heterogeneous reactions,carbon monoxide oxidation reaction and water-gas shift reaction The reaction process of coal char particles in gasifier was investigated at the particle scale,and we can know the particle characteristics from temperature,reaction rate,carbon consumption rate,and so on.The research of this thesis is divided into two parts.In the first part,the effects of double particles'distance,ambient temperature and atmosphere concentration on particle gasification reaction characteristics are studied.The distance L varies in the range of 2.2 R-5 R.The results show that with the gradual increasing of L,the temperature between the two particles rises rapidly due to the migration of the reaction area,and the characteristics of the double coal char particles gradually approach that of the single coal char particle.The ambient temperature ranges from 1200 K to 1800 K.The results show that with the increasing of ambient temperature,the highest temperature of particles gradually increases and the flame layer gradually merges in the middle of the two particles.The endothermic and exothermic reactions are the key factors which affect the flame layer.The reaction rate of exothermic reaction and carbon consumption rate decrease when the concentration of CO2 and H2O/O2 increase,because O2 is the reactant of main exothermic reaction.The change of atmosphere concentration affects the chemical reaction equilibrium and reaction rate.In the second part,the influence of particle size and different distance on gasification characteristics of double coal char particles was studied.The particle size varies from 0.1 mm to 1 mm.The results show that the high temperature reaction area of particle decreases relative to the particle due to the increase of particle size,and finally attach to the particle surface,while the high-temperature flame layer expands at an objective scale.The increase of particle size also enhances the reaction rate and carbon consumption rate almost linearly.The reaction characteristics of coal char particles with different sizes are affected by particle distance to varying degrees.The reaction rate trend of double coal char particles at the same particle distance of 0.5 mm and 1 mm is basically the same,while the change degree of reaction rate is different.The carbon consumption rate of coal char particles with particle size of 1 mm increases with distance,which is less than that of coal char particles with particle size of 0.5 mm.