The Experimental Research On Leaching Properties Of Fly Ash In Dry Disposal Site Of Power Plant

With the development of electric power industry in our country, the scale of the power plant is continuously extended and the discharge capacity of fly ash sharply increases. The fly ash is solid waste produced by coal fired power plants. The main of fly ash will be stored in disposal site, except to utilize. Because wet disposal technique has lots of shortcoming and brings some environmental problems, dry disposal technique develops rapidly. Dry disposal technique needs little water and the pollution is slashed. But during the long-term storing of fly ash, the rain may penetrate through to fly ash and brings on pollution to the groundwater.Many dry disposal sites have been constructed recent years. However, they have affected the local groundwater to different extent because the leaching properties at different sites are quite different for the different geological conditions. Therefore different measures should be taken to prevent the possible water pollution based on the different geological conditions. The environment effect of dry disposal sites has been explored both at home and abroad; however, most of the researches are just aimed at a certain area and are not of universality. So it is rather significant to research the leaching properties of fly ash from dry disposal sites under different geological conditions in general.Fly ash samples were collected from the dry disposal site of the first thermal power plant of Taiyuan. The paper researched the leaching properties of fly ash through lixiviation test and leaching test of F~-. Thus measures on how to store the fly ash on the strata with different leaching capacities are advanced.The research findings are as follows:1. The lixiviation time of fly ash has little effect on the pH and the concentration of F~-. The pH has an effect on lixiviation of F~- and alkalinity is adverse to lixiviation of F~-.2. The variation rule of the concentration of F~- in the leachate accords with the logarithmic curve.3. When fly ash is stored on different strata, the smaller the permeability coefficient is, the smaller the F~- concentration in the leachate is and the greater the F~- adsorption amount of the strata is. Even the F~-adsorption amount of the same kind of strata with different thickness is different and the F~- concentration in the strata decreases with the increase of the distance to the fly ash layer. 4. When Fly ash is stored in the strata with a permeability coefficient greater than 9.6 m / day, the F- concentration of the leachate is great and has a greater impact on the environment, so impervious measures must be taken. When Fly ash is stored in the strata with a permeability coefficient less than 0.13 m / day, the setting up of an effective drainage can solve the problems. When Fly ash is stored in the strata with a permeability coefficient less than 0.006 m / day, there is no need to take measures basically.