According to data, as of 2018, the daily processing volume of solid waste incineration is 6.247×105t, and the annual incineration volume is 2.28×108t. After incineration, the incineration fly ash equivalent to 2-5% of the original waste mass will be produced. The processing capacity is 4.36~10.9×106t. There are 152 waste incineration power generation companies nationwide. Currently, listed companies in the waste power generation industry mainly include three categories: one is state-owned enterprises; the other is private enterprises; and the third is foreign-funded enterprises.
Fly ash pollution treatment method:
The treatment methods of fly ash from solid waste incineration mainly include cement solidification, fly ash chelating agent stabilization, melting heat treatment, fly ash sintering lightweight aggregate technology, and fly ash cement kiln co-processing technology.
The advantages of cement curing are mature curing technology, simple system, easy operation, and low curing cost. However, the strength of the cured body after treatment is low, the long-term stability of heavy metals is relatively poor, and there is a risk of leaching, and the compatibilization ratio is 1.5 to 2.0.
Co-processing technology of fly ash cement kiln:
The fly ash cement kiln co-processing technology is to use fly ash to replace the raw materials of the cement kiln rotary kiln and use it as a resource. However, the fly ash must be properly pretreated to reduce the content of soluble chloride and sulfate to meet the requirements of cement production and avoid heavy metal volatilization, but it will produce a large amount of high-salt wastewater.
Stabilization of fly ash chelating agent:
Drug stabilization technology has become the mainstream technology due to its advantages of low compatibilization, low cost, high heavy metal stabilization efficiency, and strong acid leaching ability. The key to drug stabilization technology is the selection of stabilizers. At present, the commonly used fly ash stabilizers can be divided into inorganic agents and organic agents. Compared with cement curing technology, inorganic chelating agent stabilization treatment technology has a small increase in waste volume after treatment, but when the environmental pH conditions change, the heavy metals in fly ash will be leached twice, which is more difficult to meet the requirements of hazardous waste treatment. Long-term safety requirements. The current HJ/T 300-2007 solid waste leaching toxicity leaching method acetic acid buffer solution method requires an acetic acid buffer solution with a pH of 2.64 as the extractant to perform a leaching toxicity test on fly ash. This puts forward higher requirements for the selection of fly ash chelating agents, so organic agents have become a hot spot in fly ash stabilization treatment.
Fly ash melting heat treatment:
Regarding the fly ash melting treatment technology, although the process is complicated, the energy consumption is large, and the processing cost is high, the advantage of the fly ash melting treatment technology is the high volume reduction rate, which can generally be reduced to 1/2 to 1/3 (volume). Stable quality, no heavy metal leaching, recyclable, can completely decompose dioxins and other organic pollutants. Everbright (Environmental Protection) Energy Co., Ltd. is expected to operate a set of fly ash melting treatment equipment in the first phase of the Xiongan Waste Comprehensive Treatment Facility in the south of Mawutou Village, Xiong County, Xiong’an New District on August 31, 2021. The amount is not less than 4500 tons. At the same time, the second phase 1×25 tons/day fly ash melting system layout position is reserved, which can realize the harmless treatment of fly ash.
It can be seen that Everbright has invested a lot of resources in fly ash melting treatment to achieve harmlessness and resource utilization of fly ash, so as to find more outlets for the increasing amount of fly ash beyond landfill.
In addition, a new type of inorganic amorphous polymer material is used to form a polymer with a three-dimensional network gel structure. The ability of this polymer to seal heavy metal ions is related to its gel structure. The cage structure can seal heavy metal ions in the In its structural framework, studies have shown that inorganic polymers not only have a physical encapsulation effect on the curing mechanism of heavy metals, but also a chemical bonding effect. In addition, studies have shown that heavy metal ions participate in the formation process of inorganic polymers. The structure of inorganic polymers is formed by tetrahedrons linked by oxygen, and positive charges are filled in the structural pores to balance the unsaturation caused by coordinated elements. The negative charge of the valence state. Once the heavy metals are fixed in the inorganic polymer, they will not be leached out, so as to achieve the goal of thorough resource utilization and harmlessness. This harmless treatment method is also paid more and more attention.
At present, with the continuous acceleration of the development of urbanization in my country, the amount of various garbage generated within the city is also increasing. Many cities in my country cannot effectively deal with a large amount of garbage, which has caused a serious impact on the quality of people’s lives. Therefore, waste incineration and disposal have received widespread attention and attention. The disposal of fly ash from waste incineration through landfill is only a short-term method, and the technical means of resource utilization and harmlessness are the way out for fly ash from waste incineration in the future.