The Influence Of Water Magnetization On The Growth Of Coal-fired PM_2.5 In The Supersaturated Water Vapor Environment

Coal is an important support for China’s energy structure,which is related to the steady development of the national economy and people’s life.In recent years,the atmospheric pollutant PM_2.5 has caused serious harm to people’s lives and the ecological environment of China,whose one of the main sources is coal combustion.To solve the problem of low removal efficiency of fine particles by conventional dust removal equipment in coal-fired power plants,the particle pretreatment technology of water vapor phase transition combined with the traditional dust removal technology has become one of the main research directions to effectively improve the removal efficiency of coal-fired PM_2.5.In order to solve the problem that fine particles is difficult to grow to the size of micron in the low supersaturation environment,based on the characteristics that the wettability of particles can be improved after magnetization of water,the growth tube experiment platform was established with magnetized water to create vapor supersaturation environment.Experimental and theoretical methods are used to study the characteristics of the growth of coal-fired PM_2.5 in the vapor supersaturated environment under water magnetization from the influence on wettability and growth of SiO₂、Al₂O₃、CaSO₄、Fe₂O₃.To explore the effect of magnetized water on the wettability of coal PM_2.5,firstly,the ring method was used to measure surface tension of tap water、deionized water、acidic water and salt water under different magnetic conditions.Then the contact Angle of magnetized water on the surface of particles was measured after tableting.The critical surface tension of PM_2.5.was calculated based on the theory of Zisman.The results show that the surface tension of water and its contact angle to fine particles can be reduced by magnetization within the experimental conditions,which varies with magnetic intensity in multi-extreme value and is negatively correlated with magnetization time;the effect of magnetized water on fine particle wettability is best When the magnetic intensity is 700 m T and the magnetization time is 60 min;the range of critical surface tension of four coal-fired PM_2.5 is 52.7⁵6.3 48.5⁵5.7 42.2⁴8.4 and49.3⁵4.2 m N/m,respectively.The growth tube experiment was carried out to study the growth characteristics of coalfired PM_2.5 in vapor supersaturated environment under different magnetic field conditions and process parameters with magnetized tap water.The experimental results indicated that the magnetized water was more advantageous to promote the enlargement of particles with smaller size;The ultimate growth effect was closely related to the wettability of particles;In the low supersaturated vapor environment,magnetized water obviously improved the growth effect of heterogeneous nucleation of fine particles,among which the growth effect of Fe₂O₃ with poor wettability was the most significant.The influence of magnetic field intensity on particle growth was mainly reducing the peak value of small particles and the increasing the peak value of large particles size or expanding its distribution range.The increase of magnetization time promoted the peak value of fine particles moving towards the larger and increased the geometric mean particle diameter.The final particle growth effect was inhibited by the increase of Initial quantity concentration.The rise of hot water temperature is more conducive to the activation and growth of Fe₂O₃.The growth time has positive effect on particle growth in high concentration and high supersaturation environment.According to the classical heterogeneous nucleation theory,the nucleation rate and critical saturation required for the growth of fine particles under magnetized water were calculated for theoretical analysis of water magnetization mechanism on particles growth,which revealed that compared with tap water,magnetized water can effectively increase the nucleation rate of vapor on the surface of the fine particles and reduce the critical saturation,which helped to promote the fine particles growing up better and faster.