| Coal is the main energy of China, but coal combustion causes serious environmental pollution. The exhausted dust emission is the major source of the inhalablc particle in atmosphere. In particular, PM2.5 has become the main atmosphere pollutant in China. The small particles with hazardous substances have adverse impact on environment and human health. The efficiencies of current conventional dust removal equipment, such as ESP and cyclone are very low for PM2.5.External field acting on agglomeration is an effective method in removing inhalable particle. Through the external field, fine particles are able to collide with each other and agglomerate together. The mean diameters of large-scale aggregates will increase and the total number will decrease. By conventional devices, it is easy to remove these big particles from the exhausted gas and the control of the fine particle release can be obtained.The gas-solid turbulent jet experimental results show that many fly ash inhaiable particles agglomerate and settle out in the chamber, which causes that the mass of particles collected in the aerosol cascade decreases and correspondingly the particle removal efficiency increases. The experiments also indicated that, adding solid particles in the introduced jet flow can raise the removal efficiency. The addition of coarse solid particles leads to a higher removal efficiency of inhalablc particles than that of adding fine particles. It is found that the removal efficiency can be increased significantly by raising the jet flow velocity, and the introduced direction of the jet flow affects the removal efficiency obviously. When the jet flow is introduced in the agglomeration chamber with an angle 6 (angle between vectors of jet flow and main gas flow in the chamber) in the range of 90°<#<180°(thc jet flow inclines towards the inlet of the main gas flow), the removal efficiency of inhaiable particles is higher than that when 0 is in the range of 0°<0<9O°(the jet flow inclines towards the outlet of the main gas flow); and there exists a maximum removal efficiency of inhaiable particles when the jet flow is introduced perpendicularly (0 = 90°).Acoustic waves exert on agglomeration chamber to intensify the collision among particles and promote their agglomeration by air, CO2, and gas mixture of CO2 and N2. Acoustic wave has different entrainment effect on the same fly ash particles generated in coal combustion, which causes different agglomeration effect. Under the air atmosphere, the particle removal efficiency is the maximum among the three experimental atmospheres, about 37%. As the gas flow rate increases, the removal efficiency increases; at the gas velocity of 10 nrs" , the particle removal efficiency achieves the maximum; while at high gas velocity, the gas velocity has negligible effect on particle removal. Relative humidity influences the moisture content between particles, so that the capillary forces between particles increases. When the relative humidity reaches 42%, the removal efficiency approaches the highest level.The removal efficiency reaches 45.4% by combining acoustic wave and gas-solid jet. The given inhaiable particies arrive at optiimun agglomeration effect at 1416 Hz of sound frequency. In gas-solid jet flow, gas turbulence energy strengthens particies colliding in acoustic wave, thus combined process is beneficial for commercial industrial applications. With jet velocity increasing, the removal efficiency initially increases, and then a reduction occurs. When velocity is 25 nrs" , there exists a maximum removal efficiency occurs. Because agglomerating forces mechanism among inhaiable particles under different relative humidity (RH), there exist higher mass removal efficiency for size particle less than 2μm and size particles exceeding 9μm... |
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