Study On Characteristics And Stabilization Of Heavy Metals In Fly Ash From Refuse Incineration Power Plan

With the improvement of living conditions and the increase of the consumption level of urban residents,the output of municipal solid waste?MSW?in China is increasing by 10%per year.The amount of garbage disposal has increased with the rising amount of garbage generated.MSW disposal technology includes landfill,incineration and composting,and the incineration is the mainly method.Garbage incineration will produce the residues-fly ash which contains a large number of easy leaching of heavy metals are listed as hazardous waste.There are numerous ways to deal with fly ash,which are summarized as follows:landfill,cement solidification,chemical stability and high temperature melt stabilization.The cement curing and high temperature melting processing technology in China has been quite mature,but there are drawbacks which can not be ignored and is not a permanent solution for the disposal of fly ash.The chemical stabilization method has the characteristics such as small capacity,low cost and strong pertinence.It is widely used in the treatment of MSW fly ash.Due to the large difference in the composition of domestic waste,coupled with the external environmental factors,the fly ash characteristics and heavy metal component content of different areas of waste incineration power plant generated are divergent.Therefore,according to the properties of fly ash in different regions,it is necessary to study the stabilization of fly ash with the corresponding chemical stabilizer.This study focused on the expansion of Kaifeng city waste incineration fly ash in different seasons,analysis fly ash samples composition,particle size distribution,heavy metal content,speciation and leaching toxicity of heavy metals and other physicochemical properties.According to the property of the heavy metals in various aspects,the experiment choosed different inorganic and organic reagents and laboratory reagents for stabilization,screened effective reagents for complex experiments and explored the addition of different proportions of pharmaceutical stabilization effect,ultimately found the adding amount that fly ash heavy metals leaching toxicity can reach the standard.Through the analysis of the content,morphological distribution and leaching characteristics of heavy metals in garbage fly ash from Kaifeng City,the waste incineration fly ash of Kaifeng City were determined as hazardous waste.The leaching concentration of two elements Cd and Pb in fly ash were higher than the national standard value,so the chemical stabilization experiment will be mainly aimed at the two kinds of heavy metals.The experiment selected inorganic chemicals?FeSO₄,NaH₂PO₄?,organic reagent?two methyl two sodium dithiocarbamate,referred to as DTC?and laboratory reagents with thiourea and formaldehyde chelating agent?NQ?,amino thiourea formaldehyde chelating agent?AJNQ?on the heavy metal stabilization treatment in waste incineration fly ash of Kaifeng city.The results showed that two kinds of inorganic pesticides?FeSO₄ and NaH₂PO₄?could not make the heavy metal leaching standards,organic reagent DTC on heavy metal stabilization effect was stronger than that of FeSO₄ and NaH₂PO₄;When the DTC and FeSO₄ composite chemical compound proportion was 1:5,the stabilization extent of Cd and Pb was the highest,and the stabilization effect was better than the single use of two pesticides.For the Cd element,the 1:3 ratio of NQ was better than that of DTC alone,and the stabilization effect of NQ and DTC were the same as that of Pb.The stabilization effect under different pH conditions on Cd and Pb of AJNQ were divergent,and under the acidic condition,the chelating agent had the highest degree of Cd stabilization when the 1:3 ratio was 4%and 1:2 ratio of 5%addition,Pb leaching concentration reached the lowest.Under the neutral condition,AJNQ had no obvious effect on the stability of the Cd element in fly ash and 1:1:1:2 and 1:3 ratio could make Pb leaching concentration standards.Under the alkaline condition,the best ratio of AJNQ to stabilize Cd was 1:3,1:4 and 2:1,and the ratio of AJNQ which has higher degree to stabilize Pb was 1:2 and 1:3,which was the same as that under acidic conditions.