| Nowadays,the pollution of particulate matter is still severe in China,especially in submicron particles(PM1.0).Besides that,submicron particles are di:ff-icult to be removed by conventional electrostatic precipitators(ESPs)due to the extremely low charge.Therefore,in the face of ultra-tow emission standards for particulate matter in coal burning,steel and other industries,it is urgent to develop some technologies to improve the collection efficiency of submicron particles.Particle agglomeration,a most simple and effective way to increase mean particle size through physical and chemical methods,is drawing interest in increasing the collection efficiency of submicron particles in ESPs.Alternating electric coagulation,considered to be one of the most effective coagulation techniques,is widely studied at home and abroad.However,the researchs about Alternating Electric Coagulation have been carried out not in actual and complex smoke,strongly affect the electric field and coagulation,but mainly in air or nitroge.Therefore,in this paper,based on the two-zone alternating electro-coagulation platform,the corona characteristics and particle condensation law of particles under different conditions were explored.Firstly,exploreing the effect of pre-charge voltage,condensation voltage and residence time on condensation law of particles.The results of the experiments are as follows.With the increasing of pre-charge voltage,charge amount of particles is improved,but too hi'gh voltage will change the distribution of particle concentration due to part of the particles are trapped by grounded platem,which has a centrian degree of interference to the detection of coagulation efficiency.With the AC voltages going up from 0 to 25 kV,the collision between particles intensified,the mass average particle diameter of the particles is increased by 1.57 times,and the mass of the particles with particle size below 1 ?m and from 1 ?m to 2.5 ?m decreased by 16.3%and 22.8%,respectively,Besides that,For particles with diameters less than 1?m,the particle mass change rate of 0.5 ?m-1 ?m was-29.2%,the tendency on particle mass change of 0.15?m-0.5 ?m was disordered,and the mass of the particles below 0.15 ?m hardly varies with the voltages.With the residence time growing up from 0.5 s to 1.5 s,the total removal efficiency maximum increased by 11%and the mass of the particles with particle size below 1 ?m and from 1?m to 2.5 ?m decreased by 33.7%and 40.6%,respectively.In addition,the particle mass variation rates of 0.5?m-1?m,0.15?m-0.5?m,and less than 0.15 ?m were-43.9%,-18.2%,and-35.7%,respectively.Secondly,exploreing the effect of air humidity and SO3 concentration on condensation law of particles.The results of the experiments are as follows With the air relative humidity increasing from 20%to 80%,the average charge of per particle increases by 20%?120%,and the mass average particle diameter of the particles is increased by 1.93 times.Besides that,the mass of the particles with particle size below 1 pm and from 1?m to 2.5 ?m decreased by 80.1%and 54.5%,respectively.The particle mass variation rates of 0.5?m-1 ?m,0.15 ?m-0.5 ?m,and less than 0.15?m were-83.2%,-64.5%,and-66.6%,respectively.With the SO3 concentration going up from 0 ppm to 30.8 ppm,the average charge of per particle increases by 20%?270%,and the total removal efficiency maximum increased by 39.1%.Besides that,the mass of the particles with particle size below 1?m and from 1 ?m to 2.5 ?m decreased by 91.3%and 67.7%,respectively.The particle mass variation rates of 0.5?m-1 ?m,0.15?m-0.5 ?m,and less than 0.15 ?m were-92.7%,-67.9%,and-61.5%,respectively.In addition to that all,compared with the particle with a aerodynamic diameter from 1 ?m to 2.5 ?m,the increase of air humidity and SO3 concentration is more conducive to the coagulation of particles below 1?m. |
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