Abstract: Incineration is an effective method to solve the increasing domestic waste. Fly ash from waste incineration is a hazardous waste because it contains a lot of pollutants such as heavy metals. In this paper, the methods of disposal and disposal of fly ash from incinerated refuse at home and abroad are introduced, and the research progress is also introduced. Finally, the future development of disposal of fly ash by waste incineration is also forecasted. Key words: Environmental Engineering; Waste Incineration; Fly Ash; Stabilization Technology Mankind is facing the challenges of environment and development. At present, the world's MSW reaches more than 27 million tons per day [1]. The problem of rubbish has become a major environmental issue that has attracted worldwide attention. At present, China's waste disposal uses mainly landfill, compost, and incineration as a supplement, which will occupy a large amount of land resources. With the development of waste treatment technology, incineration technology with the advantages of fast processing speed, small footprint, high reduction and decontamination efficiency, energy recovery and other advantages has been applied in some industries with high economic level, high heat value of garbage , Cities with limited land resources will gradually be applied. However, the fly ash produced by waste incineration will have an impact on the environment. This paper mainly introduces the domestic and international methods for handling and disposing of such fly ash and its stabilization technology. 1 waste incineration fly ash characteristics Solid waste incineration generated solid residue accounts for about 30% -35% of the weight of the garbage, which accounted for 25% -30% of the bottom ash, the rest is fly ash, accounting for about 5% [2]. Fly ash is incinerated in the heat recovery system, flue gas purification system to collect the material. Fly ash production and waste types, incineration conditions, incinerator type and flue gas treatment process. The heavy metal content in the bottom ash generated by waste incineration is relatively low, especially for volatile metals such as Pb, Zn, Hg, and Cd, which are mainly some lithophile metals such as Ni, Cr and Cu, which are generally considered as Not poisonous, can be recycled as raw materials. For example, more than 90% of the bottom ash of MSW in Denmark and the Netherlands is used as filling materials for parking lots, dams and embankments, aggregates of concrete and asphalt, with 60% and 45% respectively of bottom ash in Germany and France for subgrade and municipal services Engineering [3] Materials. Analysis shows that: incineration fly ash is not chemically inert, which contains a lot of harmful heavy metals and salts such as Cd, Pb, Zn and Cr that can be leached by water. If the incineration fly ash is directly buried or handled improperly, heavy metals in the acidic environment will gradually leachate out of the environment due to acid rain and other factors to re-enter the environment and pollute the underground water and endanger human beings [4]. Dioxins in fly ash are also potential environmental pollutants. As the heavy metals and dioxins in fly ash from waste incineration are difficult to be naturally degraded, their environmental impact is very serious. The results of domestic and foreign research on the characteristics of heavy metals in fly ash show that heavy metals with high boiling point are easily coagulated uniformly during the combustion process to form the core of fly ash. However, heavy metals which volatilize at high temperature will condense in the fly ash Surface, fly ash in the heavy metal with the fly ash to reduce the particle size increases. The leaching toxicity of heavy metals in fly ash is related to the particle size, surface area and pH value of fly ash, and mainly depends on the existing forms of heavy metals in fly ash [5]. Table 1 lists the hazardous waste leaching toxicity identification standards. Table 1 hazardous waste leaching of heavy metals toxicity identification criteria [6] 2 waste incineration fly ash treatment Currently at home and abroad for the treatment of fly ash incineration commonly used methods are: (1) curing and stabilization. Mainly cement curing, asphalt curing, melt curing, chemical curing stability. Cured fly ash, if leaching toxicity criteria are met, can be landfilled as normal waste with the primary role of chemically inertizing or containing heavy metals and other contaminants in the fly ash for transport and disposal and Reduce the toxicity of pollutants and reduce their migration to the ecosystem. (2) The heavy metals and fly ash separation, respectively, resource treatment, such as acid extraction, alkali extraction, biological extraction. (3) According to the appropriate disposal of hazardous waste landfill, but the high cost of processing. Most of the above fly ash treatment methods have been actually applied to domestic waste incineration plants and achieved some results. This article focuses on the analysis of curing and stabilization. 2.1 cement curing method Solidification is the use of curing agent and waste incineration fly ash to form a solidified body, usually by mixing the fly ash, cement by a certain percentage, adding the right amount of water, so that curing, thereby reducing the dissolution of heavy metals [7]. The method is a traditional fly ash treatment method, which has the advantages of low cost and simple processing. Fixtures used in foreign fly ash curing, in addition to different hydraulic binders (cement, lime, blast furnace slag), but also with phosphate, ferrous sulfate, etc. as a stabilizer, they can react with heavy metals to produce stable , Water-insoluble compounds, the heavy metals fixed. Cement is the most commonly used hazardous waste curing agent, so cement is often used to cure incineration fly ash. Cement curing mechanism: During the cement hydration process, the metal reacts with the cement in a variety of ways such as adsorption, chemical absorption, sedimentation, ion exchange, passivation and finally stays in the form of a hydroxide or a complex Hydration of hydrated silicate colloidal CSH surface, while the addition of cement also provides an alkaline environment for heavy metals, inhibiting the percolation of heavy metals. Cement curing method in a certain proportion of fly ash is feasible, with a certain degree of compressive strength, low metal infiltration. However, due to the side effects of fly ash, affecting the normal hydration process of cement, in order to achieve a certain degree of strength, the blending amount of fly ash is limited, generally between 20% and 30%, and the consumption of cement is large. In order to reduce the consumption of cement and reduce the cost of fly ash cement curing, many foreign researchers from different angles, carried out in-depth study of cement solidification of waste incineration fly ash. Polettini [8] studied the addition of Na2SiO3 or CaCl2 additive in cement curing process to reduce the impact of fly ash on the hardening of cement. The experiment shows that for the fly ash with high content of Si and Al and low content of Na and K, At 30%, the initial and final setting time of the resulting mixture is almost similar to that of cement (372 min, 472 min); when the fly ash content is as high as 50%, the hardening process of the cement is delayed to the extent allowed. QianJueshi [9] and KraiwoodKiattikomol [10] studied the impact of fly ash fineness and additives on the strength of the mixture, the use of fine fly ash and adding additives significantly improve the hardness of the mixture. Yuan Ling et al [11] found in the compounding of waste incineration fly ash and mineral admixtures that the composite gelation macroscopically shows not only the improvement of the mechanical properties of the cured body, but also the solidification of heavy metals. T.Mangialardi [12] pointed out that most alkaline materials, soluble sulfate and chloride are removed from the fly ash after the fly ash has been washed. When the cement is fixed with cement, the cementitious hardening process can be greatly shortened, and the fly Ash blending amount to 75% -90%, the minimum hardness of the resulting mixture between 0.6MPa-1.4MPa, to meet the requirements of engineering landfill. Some scholars pointed out that coal-fired fluidized bed fly ash (FCA) can be used to fix waste incineration fly ash. MasashiKamon [13] studied the use of coal-fired fluidized bed fly ash (FCA) combined with cement to fix salt content Higher MSW fly ash, because FCA contains a large amount of unburned carbon, lime, gypsum, and lime, gypsum just in the fly ash curing process to promote the hardness of the composition, with fly ash, cement, FCA and a small amount of additives Al2 (SO4) 3 and Ca (OH) 2 were studied under different blending ratios. The results show that when cement is fixed, the infiltration of heavy metals is only inhibited in an alkaline environment. However, due to the impact of the addition of fly ash on the hardening of cement, the fly ash content is very low. FCA is used as a fixed The strength and anti-soaking ability of the mixture are enhanced, but can not inhibit the early stage of Cd percolation; the use of composite fixative (FCA + cement), from the heavy metal leaching to the hardness of the mixture to meet the requirements. However, when Iretskaya et al. [14] studied the leaching of heavy metals in fly ash, it was found that due to the chloride ion in the fly ash, the iron, copper and zinc ions in the solidified block were easily leached, leading to excessive pollutants. Therefore, although cement-cured fly ash has the advantages of mature technology, simple operation and low processing cost, it has to be pre-treated by cement curing method to reduce the chloride ion pair due to the high chloride ion in fly ash The mechanical properties of the block after curing and the impact of the subsequent heavy metal ions leaching and other issues. Silicone Usb Flash Drive Cover About Silicone usb flash drive cover:
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