Research Of Growth Chara Cteris Tics For Fine Coal-fired Particles In The High-humidity Environment

Nowadays,the conventional dust devices of coal-fired power plants fails to remove the fine particles in the flue gas effectively,and a large number of fine particles enter the atmosphere causing serious pollution.In this paper,the heterogeneous condensation and turbulent agglomeration preconditioning technologies are adopted to promote the growth of fine particles to achieve the efficient removal of fly ash fine particles in the flue gas.Firstly,according to the characteristics of high relative humidity of wet desulfurization flue gas,the saturated water vapor was added to it to form the oversaturated water vapor environment,in which,the heterogeneous nucleation and condensation processes were happened for fine particles.Moreover,the effects of parameters of water vapor and wet desulfurated flue gas on supersaturated vapor environment were numerically investigated.The results show that the higher the relative humidity and the lower the temperature of the desulfurated flue gas,the higher the degree of saturation of water vapor environment.Secondly,a kinetic model of heterogeneous nuclcation of supersaturated water vapor on the surface of coal-fired particles was established based on kinetic heterogeneous nucleation theory.The influences of vapor temperature,degree of saturation of vapor and macroscopic contact angle on the nucleation parameters were numerically predicted.The prediction results show that the kinetics model with the consideration of various factors is more consistent with the experimental data.The heterogeneous nucleation is more likely to occur when the particle with a better wettability and the supersaturation and temperature of the vapor is higher.Thirdly,a dynamic model was established for condensation of water vapor on the fine particle surface,the effects of operational parameters including growth time,supersaturation,temperature of vapor and number concentration of particle on particle growth were numerically investigated.The results show that particle can grow very rapidly,nearly all the particles can growth up within 50 milliseconds,and the distribution of grown particles become narrow.Finally,a novel particle aggregator device was designed,the distribution of velocity pressure,turbulence intensity and characteristics of particle trajectory of gas-solid two-phase flow field in the device were numerically simulated.The Euler-Euler model coupled Population Balance Model(PBM)was adopted with the consideration of Brownian agglomeration,turbulent agglomeration for particles.The effects of flue gas velocity and temperature,particle concentration and added vapor on particle agglomeration efficiency were numerically simulated.The results show that the novel agglomeration device can effectively promote the agglomeration of submicron particles(PM1)and fine particles(PM2.5),and the coalescence efficiency of submicron particles is higher than that of fine particles under the same condition.