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How does the incineration plant treat fly ash from the incinerator?
Hits: 129 Times Added: 2019-11-14 [ Print ] [ Return ] [ Favorite ]

With the vigorous development of waste incinerator power generation projects and the requirements of relevant national standards, "Pollution Control Standards for Domestic Waste Incineration" and "GB16889-2008 Standard for Pollution Control of Domestic Waste Landfill Sites", pollutant emissions from all aspects of waste incineration There are clear regulations, such as: The "dust pollution control standards for domestic waste incineration" for dioxin emission limits from strict to 0.1 ng toxic equivalent per cubic meter, consistent with the world's most stringent EU standards. With the improvement of the national production level, the classification of waste sources has been gradually improved, the calorific value of waste has increased year by year, and the incineration profit of waste incineration power plants has also increased.

1.How does the waste incineration plant treat the fly ash from the waste incinerator?

It is reported that the fly ash of the waste incineration plant has three destinations: construction materials after high temperature melting treatment; co-processing in cement kilns; solidification and stabilization and detection into the landfill. The third one is the international mainstream fly ash treatment method. After solidification and stabilization of the fly ash produced after the waste is incinerated, the volume can be reduced to 2-10% of the original waste, and it has excellent resistance to leaching, resistance to wet and dry, penetration resistance, and freeze resistance. The mechanical strength meets the entry requirements for zoning landfills.

2. Status of fly ash treatment technology

The structure of the research on the characteristics of heavy metals in fly ash at home and abroad shows that heavy metals with high boiling points are easy to condense uniformly during the combustion process, thereby forming the core of fly ash, and the volatile heavy metals at high temperature will condense on the surface of fly ash as the temperature decreases. The heavy metals in fly ash increase as the particle size of fly ash decreases. The leaching toxicity of heavy metals in fly ash is related to the particle size, surface area, and pH of fly ash, which mainly depend on the morphology of heavy metals in fly ash. Ca (OH) 2 has a strong inhibitory effect on the dissolution of Cd, Zn, and Cr, but it has a solubilizing effect on Pb. It is considered that adding CaCl2 to melt fly ash for more than 3 hours at 1000 ℃ can reduce the content of heavy metals in fly ash and reduce the dissolution rate of heavy metals in fly ash. However, the leaching of Al will increase after heat treatment of Al and Cr, mainly because After heat treatment of fly ash, the morphology changes from aluminosilicate state to soluble aluminum iron oxide, and the same is true for Cr. Studies have shown that when using activated carbon powder for dust removal in waste incineration, the dioxin concentration in the exhaust gas from incineration is reduced by 54% compared to when no activated carbon is added, which indicates that a large amount of dioxin was transferred to fly ash. Therefore, with the strict implementation of national atmospheric emission standards, the dioxins generated from waste incineration will mainly enter fly ash, making the pollution control of fly ash even more important. Depending on the composition of the waste, the current domestic and foreign treatment methods for incineration fly ash are: ① Landfill as hazardous waste after proper treatment. But the processing cost is higher; ② solidification and stabilization. There are mainly cement solidification, asphalt solidification, melt solidification, and chemical agent solidification and stabilization. The solidified fly ash can be disposed of as ordinary waste if it meets the requirements for leaching toxicity standards. Its main role is to make the heavy metals and their polluting components in fly ash chemically inert or to be contained for transportation and processing, and to reduce the toxicity of pollutants and their migration to the ecosystem; The ash is separated, and the resources are processed separately, such as acid extraction, alkali extraction, biological extraction, etc. This article mainly analyzes curing and stabilization.

3.Fly ash stabilization (solidification) treatment process

Waste incineration can not only provide waste treatment methods, but also use incineration thermal energy to generate electricity and heat energy, which can be said to meet the requirements of a circular economy. According to relevant data, the current domestic incineration power generation technology can generate electricity of about 250-350kw.h / t, and each ton of domestic waste incineration can save 81-114kg of standard coal and 202-283kg of carbon dioxide. The discharge and generation of pollutants during the waste incineration process have a greater relationship with the technical design of the waste incinerator. Therefore, it is important to choose a good manufacturer of fly ash solidification and stabilization equipment.