Heavy Metal Detoxification Of Waste Incineration Fly Ash And High Value Utilization

As the waste incineration technology has the advantages of capacity reduction and heat recovery,which promote the rapid development of waste incineration industry in our country.Incineration of waste reached 61.755 million tons in 2015,accounting for 34.3 percent of the amount of garbage harmless,while generating electrical energy reached 25.2 billion kWh.But the fly ash produced by waste incineration enrich heavy metal,dioxins and other pollutants,harmful to the environment,the safe disposal and comprehensive utilization of fly ash has become a new challenge for urban sustainable development.Efficient detoxification non-hazardous disposal and high value use of fly ash increasingly attention.This article take "hydrothermal method coupled chemical additive technology to realize deep stabilization of heavy metals" as the kernel,orthogonal experiment was used to study the effects of different parameters on heavy metal leaching toxicity,and try to synthesize the polymer under hydrothermal condition,then apply the soil heavy metal safety assessment method to fly ash to evaluate the environmental threat of stabilized fly ash and analyze the feasibility of hydrothermal treatment.Finally it elaborates several high-value utilization methods,in order to provide data support for the comprehensive utilization of fly ash.The main contents and conclusions of this work are as follows:(1)Selecting six typical fly ash,and their properties in element composition,grain size,microstructure and other physical and chemical properties,heavy metal content and leaching toxicity were studied.The results show that the type,area and incinerator of the incineration plant will affect the characteristics and toxicity of fly ash.The fly ash particle size is generally concentrated in the range of 0.1 to 100 micron,PM10 is at least 70%,if disordered management will cause harm to environment and residents health.The leaching toxicity of acetic acid leaching method is more serious,and the sanitary landfill standard is stricter;The Pb of fly ash is most likely to exceed the standard,to focus on stabilizing treatment.(2)The effects of hydrothermal temperature,maintenance time,additive type and hydrothermal atmosphere to solidify heavy metal were investigated with orthogonal experiment,and the better conditions were put forward,also the change pattern of heavy metal was analyzed.Innovative use hydrothermal to synthesis polymer for solidification,analyze leaching toxicity improvements.Under the conditions of L/S=10:1 and adding 10% of fly ash by sodium carbonate,the optimal working condition was carried out at 300 ℃ for 1 h.Simultaneous hydrothermal method achieved the dechlorination,the proportion of heavy metal exchange decreased significantly,which will reduce the migration of fly ash to achieve the stability.Hydrothermal synthesis of polymer curing effect is better,the heavy metal ions involved in the formation of polymer structure,can more effectively fix in the system.(3)The adsorption performance and adsorption kinetics of fly ash as wastewater adsorbent were studied.Several new ways of high value of fly ash were introduced to provide basic data for comprehensive utilization.The results show that the adsorption of methylene blue by fly ash is related to the specific surface area and ash species,and the adsorption value is mainly used to characterize the cuhk distributed volume,and the adsorption rate is first fast and slow in the adsorption process.The adsorption at room temperature is closer to the Langmuir adsorption model,and the pseudo two order kinetic model can accurately describe the adsorption mechanism of methylthionine chloride.Hydrothermal synthesis of zeolite minerals,the adsorption method is no longer confined to the surface of the monolayer adsorption process,improved pore structure.The use of fly ash to remove heavy metals in wastewater by hydrothermal has obvious effect,and solid heavy metal becomes more stable,soluble potassium salt and sodium salt dissolved to achieve K,Na directional extraction,has great potential.Hydrothermal treatment is a promising method.The heavy metal leaching concentration is significantly reduced after it.Hydrothermal product has high value on resource reuse,which realized the harmless treatment and high value utilization of MSWI fly ash.