Effect Of Gas Components On The Nucleation And Growth Of Fine Particles By Heterogeneous Condensation Of Water Vapor

Particulate pollution is one of the most serious atmospheric environmental problems in China and fine particles（PM2.5）pollution is particularly serious of which.Due to the small particle size of fine particles,they are difficult to be removed by traditional dust removal equipment.One of the research directions is using pretreatment measures to increase the particle size of PM2.5,thus traditional dust removal equipment can be used to remove fine particles.The heterogeneous condensation of water vapor is a promising dust removal pretreatment technology as its uncomplicated process and high obvious superiority in efficiency.There have been many studies on the heterogeneous condensation of water vapor,but in the past studies,air was usually used as the background gas,and the influence on the composition of the flue gas was rarely considered.Firstly,in order to determine the research object,the types and contents of the components contained in the flue gas emitted from the actual combustion source are summarized and analyzed,and the similarities and differences of the physical properties of the flue gas components are compared.Finally,three flue gases of CO₂,SO₂ and O₂are selected as research objects.To study the effect of flue gas composition on the thermal and mass diffusion coefficient,a calculation model of thermal and mass diffusion coefficient of mixed flue gas is established.The results show that Increasing the concentration of CO₂and SO₂in the flue gas composition will reduce the value of the thermal and mass diffusion coefficient,while increasing the concentration of O₂will cause the value of the thermal and mass diffusion coefficient increase slightly;The values show an increasing trend as the flue gas temperature increases;meanwhile,as the relative humidity of the mixed flue gas increases,the thermal and mass diffusion coefficient also increases slightly.Then,for further exploring the influence of flue gas composition on the supersaturation in the growth tube,a heat and mass transfer calculation model in the growth tube is established,the influence of the flue gas composition,oversaturated environment construction method,the tube wall temperature on the supersaturation value was summarized.The results show that in mode 1（high temperature hot water and low temperature saturated flue gas contact）,the higher the CO₂ and SO₂ content,the greater the supersaturation value,and the higher the hot water temperature of the pipe wall,as the CO₂ and SO₂ content increases,the greater the increase in the saturation value;in Mode 2（low temperature cold water and high temperature hot gas contact）,as the CO₂ content and SO₂content increase,the supersaturation decreases;the concentration of O₂ has little effect on the value of supersaturation;the higher the hot water temperature of the pipe wall,the larger the value of supersaturation in the growth tube.Finally,an experimental platform of heterogeneous condensation of water vapor is built so as to experimentally analyze the effect of flu gas concentration,the tube wall temperature on the growth of fine particles in condensation chamber.The experimental results show that the growth efficiency of particles in the simulated flue gas atmosphere is better than the growth effect of particles in the air atmosphere;The higher the CO₂ and SO₂concentration,the better the particle growth;The O₂ concentration will hardly affect the efficiency of particle growth;the temperature of the pipe wall will have a greater impact on the efficiency of particle growth.The higher the temperature of the pipe wall,the better the particle growth.