The Leaching Behavior Of Heavy Metals From MSWI Fly Ash And Exprimental Study On Solidification Of MSWI Fly Ash

Having the advantages of remarkable volume-reduction, weight-reduction and Energy-recovery, disposing of Municipal Solid Waste (MSW) by incinerations have been widely used abroad, especially by those developed countries which are facing the insufficiency of land and energy. This technology is also being popularized in our country in recent years. The heavy metals in municipal solid waste will be distributed and transformed in the course of incineration without being destroyed. The total amount will be sent out of the furnace as much as that is contained in raw waste. Municipal Solid Waste Incineration (MSWI) fly ash contains harmful heavy metals. Since the metals are water leachable, the MSW fly ash must be properly treated.Fluidized bed combustion coal fly ash (FCA) is a byproduct of coal power plant, the use of FCA should be encouraged. In this paper, the stabilization method using fluidized bed combustion coal fly ash, and the mixture of cement and FCA, is proposed to study the control of heavy metal leachate. Furthermore, the effect of adding additives to the mixtures has been taken into account.The physical and mechanical property, heavy metals content and the distribution of particle size of three types of fly ash are studied at first. One of them is fluidized bed MSWI fly ash, the other two are grate MSWI fly ash, Then, the leaching characteristics of fly ash are studied. The stabilization method using fluidized bed combustion coal fly ash is proposed to study the control of heavy metal leachate. The effect of single variable leachate situation is also considered. The experimental results indicate that fluidized bed combustion coal fly ash can restrain the leachate of Cu, Zn, Pb, Cr, Ni on a certain extent, but can barely restrain the leachate of Cd. And the mass percentage of heavy mteals leached from original MSW fly ash decrease with the reduction of bending percentage of MSW fly ash and the increase of solidification mixture curing time, especially for Ni, Cr, Cu.Based on the grate fly ash, the stabilization method using the mixture of fluidized bed coal fly ash and cement is taken to study the control of heavy metal leachate, and compared with method of only using fluidized bed coal fly ash. The results show that the use of the mixture will receive more acceptable effect on the leachate of havey metals than the use of fluidized bed coal fly ash simply, especially for Ni, Cr, Cu and Zn. But the effect on Pbis not as good as Ni, Cr, Cu and Zn, the effect on Cd is worse. After 7 days of curing time, the predominance is more obvious. At last, the effect of the addition of additives on the leachate of heavy metals is studied, the results show that the joining of four kinds of additives can reduce the leaching of heavy metals, especially for Cd, Pband Zn.