Experimental Research On The Characteristics Of Growth By Vapor Condensation Of Coal Ash Particles

Particulate air pollution in our country is in serious condition which brought a lot damage to human beings. Particle emission from coal is one of the important source of air particles. Most of our coal-fired plants power had installed electric precipitator to remove particle from the ash while the electric precipitator has a small efficiency to remove the fine particles. The technology of particle enlargement by vapor condensation can make the fine particle be so larger to remove by traditional dust removal way. Nowdays there are a lot reseacher about the techonoly of application while there is nothing about the characteristics of enlargement of coal ash particle by vapor condensation.This paper had built an experiment platform to enlarge fine particle by vapor condensation. The key part of the platform is the growth tube whose insides is the supersaturated area which was generated by a liquid film flowing on the tube internal walls.This paper had calculate the distribution of degree of supersaturation and the results shows that the S is between 1 and 2. The experimental research had been done to prove that there is no homogeneous condensation.For clearing up the influence of physical and chemical properties of coal ash to the particle enlargement,XRF had been used to analyze element component of coal ash particles and the contact angle pressing method had been took to measure the wettability. The results show that:most of the coal ash particles are silicon and aluminum compounds whose oxide proportion can be above70% and is middle wettability with the contact angle about 40°.The wettability of chemical components of coal ash are different. Mullite and quartz is middle wettability whose contact angle is close to coal ash particles. Iron oxide contact angle is 55°and calcium sulphate is 17°.The contact angle of coal ash and it’s oxide component proportion is not linear relationship.The tween-20 can promote the water wettabillity to coal ash particles.This particle had done research which includes different particle growthcharacteristics and the influence of particle size and process parameters on the enlargement of mullite, quartz, ferric oxide and calcium sulfate particle by measuring particle size distribution before and after growth. Results show that the particle of good wettability can grow up obviously and can grow up more obviously with the increase of hot water temperature. The smaller the number concentration and the longer of growth time is advantageous for the particles of coal ash component to grow up. The effects of low concentration of wetting agent tween-20 solution is small while high concentration of wetting wetting agent tween-20 solution can promote the growing up to the iron oxide particles.The particle had done the study on the growth characteristics of coal ash particles from three or four electric field of coal-fired power plants which are Nanjing plant, Mongolia plant, biomass plant and the Jiaxing plant.Results show that when there are to much bold particles in the cold ash particles the fine particles can not grow up for the bold particles wasting most vapor of growth tube. When the number of particle of 2μm above of Nanjing and Mongolia ash particles are more than 20% the fine particles of them can’t grow up after vaper condensation experiment. The mixture of nanjing ash of 70% and fine quartz of 30% can’t grow up while grinded particles of jiaxing, biomass particle with a few bold particle, Nangjing and Mongolia ash particle after cyclone can grow up.The mean size of all these particles can grow 2μm above at 323K of hot water and the mean size is larger with the lower number concentration and longer growth time. Addition of wetting agent can significantly promote the ash particles to grew up and the mean size can grow up to more than 3μm.