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

The fly ash is the main solid waste produced by coal fired power plants. The main of fly ash will be stored in disposal site, except to utilize. At present, although the storing of fly ash mainly uses dry disposal technique, but during the long-term storing of fly ash, the rain may penetrate through to fly ash and the toxic elements in leaching water may cause pollution of local 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. Setting up one-dimensional numerical simulation model, we study the vertical transport regularity of leachate in unsaturated layer before F- of coal ash leaches into groundwater and the effect of factors such as lithology, thickness, osmosis of unsaturated layer on the regularity by the Visual MODFLOW software.The results of lixiviation test indicate that 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~-.The results of leaching test offer the variation rule of the concentration of F~-in the leachate conforms to the exponential curve along with the time variation rule and conforms to the multinomial curve along with the void volume number change rule.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. 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.The results of numerical simulation show that the bigger the soil osmotic coefficient is, the worse osmotic prevention is, the shorter the time when F~-leaches into aquifer, the higher the concentration of contaminant which leaches into aquifer after the several years is. The thicker the unsaturated layer is, the longer the time when F~- leaches into aquifer is, the lower the concentration of F~-which leaches into aquifer after several years is.