The Nucleation And Growth Characteristics Of Fine Particles In The Process Of Vapor Heterogeneous Condensation

This study is based on the background of the high efficient removal of fine particles,and the enhanced removal of fine particles by vapor heterogeneous condensation is taken as the research object.The spherical glass beads with different surface modification are selected as the experimental medium,and the growth characteristics of fine particles in the process of vapor phase transformation condensation are studied with the help of a self-designed experimental platform of fine particle growth tube.The main contents and conclusions are as follows:The thermodynamic calculation of the supersaturated field in the growth tube is calculated out by using the laws of conservation of energy and mass.From the point of view of constructing supersaturated environment,avoiding in-phase condensation of vapor,enhancing the condensation effect of steam on the surface of fine particles and reducing energy consumption,and according to the analysis of the thermodynamic calculation curve analysis,the suitable experimental conditions are obtained.The surface of glass beads is modified by sol-gel method.The results show that the contact angle of the modified glass beads increased with the increase of the concentration of three methyl chloride(TMCS).The growth characteristics of fine particles with different wettability during vapor phase transformation are studied.The results show that the growth rate of fine particles increases with the increase of supersaturation and the prolongation of growth time;compared with the initial particle size distribution of fine particles,when the supersaturation is 1.14,the growth rate is only 18.72%.When the supersaturation is 1.49,the growth rate increases to 85.03%;in addition,the effect of supersaturation is more significant than that of growth time,and the decrease of the initial concentration and particle size of fine particles in the inlet gas is beneficial to the growth of fine particles;the better the wettability of the fine particles,the better the effect,when the supersaturation is 1.49,the growth time is 0.6s,1s and 2 s,the growth rate of hydrophobic particles was 2.44%,3.43%and 5.01%,respectively,which is much smaller than that of hydrophilic particles;the soluble components in fine particles has a significant promoting effect on the growth of hydrophobic particles.The numerical simulation of temperature distribution,mixed gas velocity and vapor condensation in the growth tube is carried out by computational fluid dynamics software.The results show that with the increase of supersaturation,the vapor condensation volume fraction in the growth tube increases,and increases along the growth tube axis first and then decreases.At a suitable gas velocity,the condensation volume fraction in the tube can be increased to about 80%.When the gas velocity is 2m/s,the peak value of the vapor condensation curve appears at the near exit of the growth tube,showing the phenomenon of condensation peak shifting.With the increase of steam addition,the vapor condensation volume fraction in the growth tube is obviously increased,and the distribution is more evenly.