Study On The Transformation Characteristics Of Fine Particles During The Ultra-low Emission Of WFDG Process

Limestone gypsum wet desulfurization,as the mainstream flue gas desulfurization technology in coal-fired power plants,can effectively reduce the emission concentration of sulfur dioxide,nitrogen oxides and other particles.At the same time,the evaporative entrainment of the desulphurization slurry makes the desulphurized flue gas contain many soluble salts and gypsum particles,making the concentration of fine particles after wet desulphurization.It is possible to increase and change the physical property.At the same time,the ultra-low emission process of wet desulphurization has an important effect on the fine particle property and emission concentration in the process of WGFD,and its contribution to the haze is confronted with many disputes.n order to study the transfer and transformation characteristics of fine particles in the process of ultra-low emission of wet desulphurization.This paper is based on the simulated wet desulfurization atomization entrainment test system and the actual coal-fired wet desulfurization system.Around the atomization characteristics of desulphurization nozzles-evaporation entrainment of desulphurization slurry droplets and emission of particulates from desulfurization tower?taking into account the mainstream ultra-low emission desulphurization transformation process?,the main research contents include the following aspects:?1?The atomization characteristics of the common desulphurization spiral nozzles were measured by PDA using a self built wet desulfurization and atomized entrainment test system.The results show that the formation of atomized droplet number concentration and particle size distribution range is 0-460?m,the distribution of dense peak in about 10?m,while surface droplet diameter decreases with increase of axial and radial distance increases,while decreasing the liquid pressure and improve the slurry concentration,increase the number of spraying layer were to increase the average droplet diameter of atomization.Finally,the relationship between droplet diameter Dm and We?Re is determined by dimensional analysis,and the experimental data fit the standard relationship of droplet size D₅₀,which has good correlation.The droplet size will vary correspondingly during droplet droplet spray and high temperature flue gas wet heat exchange process.On the fine foundation,the particle size and its influencing factors of the droplet in desulfurization flue gas will be explored.On the basis of this,the change of the droplet size and its influencing factors in the net flue gas of desulphurization are investigated and analyzed.The results show that The particle size of 90 percentage entrainment droplet in the flue gas of desulphurization flue gas is less than 30?m,showing a single peak distribution.The evaporation entrainment of droplet is closely related to the flue gas temperature and the air velocity of the empty tower.With the decrease of inlet flue gas temperature and the increase of air velocity of the empty tower,the average particle size of the droplet in the desulfurization flue gas has increased.?2?In order to study the relationship between the evaporation entrainment of desulfurization grout and the emission of fine particles from the outlet of the tower,the emission concentration of droplets and solid particles in the flue gas was qualitatively tested by means of PDA,ELPI+and droplet trap.The results show that the desulfurization flue gas in the droplet size are micron,the smaller the particle size of the escape rate is high,the net amount of solid droplets in flue gas desulfurization slurry solid content is about 15%⁴0%,fine particle concentration increases with droplet entrainment in flue gas desulfurization net increase,the size of solid the solid particles in the liquid droplets was significantly less than that of desulfurization slurry.Meanwhile,optimization of spray layout,selection of coarse-grained gypsum to prepare desulphurization slurry and optimization of desulfurization operation parameters can reduce entrainment and emission of fine particles to a certain extent.?3?Based on the actual coal-fired wet flue gas desulfurization system and the field test of power plant,the influence of several mainstream ultra-low emission desulfurization and upgrading processes on the removal of fine particulates in limestone gypsum wet flue gas desulfurization system is explored.The results show that under the premise of achieving high desulfurization efficiency,the removal of fine particles can be helped by decreasing the flue gas temperature at the inlet of the tower,increasing the number of spray layers,or adding clear water spray.At the same time,tray tower system and double circulation system can effectively reduce the emission concentration of fine particles.Based on the measured double loop desulphurization technology of Twin Towers,it shows that the removal efficiency of fine particles can reach 65%,which can effectively meet the ultra-low emission standard.