Research Of Alkali-activated Material Dual Solidification Heavy Metals In MSWI Fly Ash

MSWI fly ash is city life garbage after incineration,collected in the flue gas purification plant powder residue,which contain a variety of high leaching concentration of heavy metals and high toxicity of dioxin,belong to the hazardous solid waste.The current production of fly ash is increasingly large,environmental protection standards in the processing and utilization must ensure the harmless to the environment.By means of the blast furnace slag has a high temperature molten state,adding fly ash in the process of slag discharge,through high temperature under the action of slag and fly ash content should be to the contrary,the slag in the condition of high temperature melting solidification of heavy metals in fly ash.Molten slag after the solidified fly ash(in this paper,referred to as the solid solution)after water quenching will still be able to form a certain activity of water quench solid solution.Compared with the ordinary slag,the solid solution are similar to ordinary slag in chemical composition and mineral composition,only mineral content changed and added a small amount of heavy metals and salts.Accordingly it believed that solid solution combined fly ash still has good gelling activity.This not only reduces energy costs that simply melted by heating solidification treatment of fly ash and can be more thorough removal of dioxins of fly ash.Explore achieve the disposal technologies of MSWI fly ash of low cost,simple process,technically feasible,safe and reliable that solidification effect of heavy metals.To simulate the slag under the molten state during discharge solid fusion fly ash,this paper intends to calcine slag and fly ash after pressing under different calcination temperatures and fly ash content solid,test the heavy metals leaching law in solid solution at different temperatures and fly ash content,and the cementitious property and securityof solid solution for the mineral admixtures;Analysis of the basic characteristics of solid solution is used for preparation of alkali-active material,and its mechanism of heavy metals action for alkali-active material and the effect of solidification heavy metals.The experimental results showed that,in the process of solid solution formation,fly ash and slag occured a series of reaction and formed some new materials.In the reaction process,the heavy metals will be involved,solidification heavy metals of fly ash in the form of chemical;In the calcination temperature is 1200? and ash content of40%,the solid solution has the highest gelling activity.Hardened cement paste solidification of heavy metals in solid solution is better,at the same time the main performance index of the cement paste with solid solution are within the scope of the qualified,the solid solution as a kind of mineral admixture is feasible;Solid solution used for the preparation of alkali-active material has good mechanical properties,when the dosage of fly ash is 40% in solid solution and NaOH dosage is 4%,the 3d strength of block is 38.4MPa and has good late development rule,and and the mixed solid solution can reduce the shrinkage rate of block.Cu not only can delay and to a certain extent hinder the early hydration of material.High leaching concentration of heavy metal of MSWI fly ash after high-temperature volatilization and dual solidification effect of slag and alkali-active material,its leaching quantity is little,will not cause harm to the environment;Alkali-active material mixed solid solution have poor resistance to acid,120 d strength loss is 62%,and the mass loss is 20%,but has the strong ability of resistance to alkali,chlorine salt and sulphate.In the natural environment,block strength decrease but still maintain a high strength,leaching amount of heavy metal is added but has no effect on the ecological,it is visible that solid solution used for the preparation of alkali-active material has good durability and solidification heavy metal with long-term stability.