Experimental Study Of Agglomeration Of Submicron Particle In Pulverized Coal Combustion

Submicrometer particles (PM2.5) are main pollutants to atmosphere in current China. According new standard of pollutions emission of China, submicrometer particles need to be controlled effectively. Although the efficiency of existing equipment (such as ESP, bag house) can reach so much as 99%, a mass of submicrometer particles are emitted into atmosphere. Spray agglomeration is a novel method to improve the efficiency of existing equipment. Some innovative research of spray agglomeration has been made in this paper. An experiment platform of spray agglomeration has been designed and built according to parameter of the factual power station. Abundant experimental studies are performed in the paper to investigate the factors that influence the effect of agglomeration, such as pH value of the agglomeration solution, the flux of agglomeration solution, the concentration of agglomeration solution, the concentration of fly ash and the temperature of the agglomeration chamber. The application of spray agglomeration in factual power station is evaluated and the foreground of this technology is prospected. A model of submicron particle agglomeration during the spray process was developed combining droplet evaporation theory and analysis of the interaction of droplets and particulates. Basing on the model, the influences of different original parameters (original droplet diameter, spray solution flux) on ultimate parameters (droplet evaporation time, agglomeration efficiency,etc) were calculated. With increasing the average original diameter of droplet, the diameter of agglomerates increases and the agglomeration efficiency of spray process decreases. When the average original diameter of droplet is about 10~20μm, the optimal agglomeration effect can be achieved. Increasing the spray solution flux can get better agglomeration effect and decreasing the original droplet diameter can spare the spray solution. Flocculation theory is presented to explain the agglomeration mechanism of particles in the spray process. The mechanism can be farther divided into compression of the double electric-layer, charge neutralization and bridging. Factors (kind of charge on the macromolecule, molecular weight of the macromolecule, structure of the macromolecule, extendibility of macromolecule chain) that might influence the effect of agglomeration are discussed.