Research On Aggregation Of Ultrafine Particle In Flue Gas By Population Balance Model

In most of China's major urban airborne particulate matter now more than sulfur dioxide and nitrogen oxides become the main urban pollutants.Coal-fired power plant emissions of fly ash particles is one of the main sources of PM2.5 in the air.Fly ash particles can cause problems,especially environmental and health problems.Due to the serious harm caused by the fine particulate matter of coal flue gas,how to effectively capture its current hot spot and focus.The influence of different particle aggregation mechanism models on the particle aggregation process of turbulence aggregation device was studied.Aggregation kernel was defined based on the UDF function of FLUENT;the influence of inter-particle repulsive potential energy barrier Umax and hydromechanics on the aggregation rate was considered and capture efficiency f(?)was introduced for the correction of aggregation kernel;then corrected turbulence aggregation model was obtained and compared with the traditional turbulence aggregation model.The process of ultrafine particulate matter agglomeration in the cyclone separator was studied.In order to get the particle agglomeration effect on the separation performanceof Cyclone separator under different inlet particle concentration to speed research on its impact on efficiency.Based on the Reynolds stress model(RSM)calculation of turbulent flow through the population balance model(PBM)coupled CFD numerical calculation of particle phase.Results showed that: at the time of 2s,aggregation role within the cyclone has stabilised,the particle size in the range of 1.5?m to 3?m basic set cannot be arrested within the particles in cyclone separator and particle size greater than 5?m the separation efficiency is close to 100%;with increasing inlet mass concentration,the overall separation efficiency increase,and increase the inlet gas velocity,the impact on the separation efficiency is not great.The mechanism of ultrafine particle agglomeration of new turbulence aggregation device was studied.One way to increase their capture efficiency is to increase the size of the fly ash particles,that is,to improve submicron particle aggregation by physical or chemical action prior to passing through an electrostatic precipitator or bag filter.Turbulence aggregation due to its simple operation,low investment,low operating costs,have better prospects for development of new technologies.The turbulence aggregation increases the particle collision process by the turbulence between the particles in the flow,and the turbulence causes the difference in velocity between the particles and improves the physical collision between the particles to form the aggregation of ultrafine particles.Numerical simulation of particle aggregation was carried out through population balance model(PBM)coupled with CFD.According to the results,the comparison between ideal turbulence aggregation model,corrected turbulence aggregation model and the experimental results show that the ideal turbulence aggregation model has an error of approximately 8% and the corrected turbulence aggregation model has an error of only 3% and coincides with the experimental results.Brownian aggregation obviously reduces the particles less than 2?m in diameter and cannot be ignored in turbulence aggregation.The coupled corrected turbulence aggregation and Brownian aggregation model basically coincide with the experimental results.