Fly ash is extremely toxic and contains the most toxic inorganic substances “heavy metals” and the most toxic organic substances “dioxins”. It contains five common heavy metals that are most harmful to the human body: lead, chromium, mercury, arsenic, and cadmium. These heavy metals cannot be decomposed in water, and combine with other toxins in water to generate more toxic organic matter, which is classified as hazardous waste (HW18).

Once the fly ash is discharged into the environment, it will cause serious pollution and damage to water, air and soil, and also cause great harm to organisms. Therefore, how to rationally utilize fly ash and realize the reuse of waste resources is imminent.

Through physical or chemical reactions, one or several substances such as heavy metals, dioxins, and chloride salts in the fly ash are removed to a certain extent, or their leachability is inhibited, so that the treated fly ash can meet the requirements of subsequent utilization or The process of disposing of the request.

1. Low temperature thermal decomposition: The process of dechlorination and detoxification of dioxins in fly ash through low temperature thermal decomposition reaction below 500 ℃ in an oxygen-deficient or oxygen-free atmosphere.

2. High-temperature sintering: the process of mixing fly ash or its processed product with other silicon-alumina components and fluxes, partially melting it at high temperature, and cooling to form a sintered body product.

3. High temperature melting: After mixing fly ash or its processed product with other silicon-alumina components and fluxes, it is completely melted by high temperature, and then subjected to rapid cooling such as water quenching to form a dense glass product.

4. Solidification and stabilization technology: This treatment method can make all the polluted components involved in the hazardous waste to show chemical inertness, or contain them, so as to facilitate their disposal, utilization or transportation.

(1) Asphalt curing technology

Asphalt has good chemical stability, and at the same time has certain adhesiveness, elasticity and plasticity, and can resist the corrosion of many acids and alkalis. Asphalt curing is to stir the asphalt curing agent and fly ash together, and at a specific ratio, alkalinity and temperature, it will produce a saponification reaction, so that the harmful substances can be uniformly attached to the asphalt, thereby producing a solidified body. There are mainly two specific methods for asphalt curing. One is to heat the asphalt. Under the action of high temperature, the asphalt is turned into a molten adhesive liquid, mixed with fly ash, and the hazardous waste is wrapped with the help of the bonding effect of the asphalt. After cooling. A solidified body can be obtained. Second, through the use of emulsifiers, the asphalt is emulsified, and then the emulsified asphalt and fly ash are mixed, and then a series of operations such as demulsification and dehydration are performed to obtain a solidified asphalt body. This method is at room temperature. will be completed.

(2) Cement curing technology

The technology is to mix the curing agent and fly ash to produce a new substance – a solidified body, so that the harmful components in the hazardous waste are blocked in the solidified body. The most commonly used hazardous waste solidifying agent is cement, the cementitious material. Therefore, in the treatment of fly ash from incineration, cement solidification technology is a common treatment method. Pour the fly ash into the cement matrix, and after brewing under the established conditions, some tiny metal oxides can be produced under the action of chemistry and physics, so that the migration of pollutants can be controlled. In this process, in order to improve the effect of curing and ensure the performance of the cured body, during the curing process, it is necessary to select the appropriate type and dosage of additives according to the nature of the hazardous waste and its requirements for product quality.

(3) Chemical stabilization technology

This technology uses the chemical reaction of chemical agents to reduce the poisoning level of toxic and harmful substances, and gradually transform them into substances with low toxicity and low solubility. In the treatment and disposal of fly ash, the use of chemical stabilization technology can not only meet the requirements of harmlessness, but also ensure little or no compatibilization, so that the efficiency of treatment can be improved, thereby improving the economic benefits of fly ash treatment. . The application of chemical stabilization technology must be established within a specific range, and it is mainly used in the treatment of heavy metal waste. At this stage, metal stabilization technology has been very rich, such as pH control technology, ion exchange technology, precipitation technology and so on.

5. Water demineralization pretreatment (FWD) + cement kiln co-processing technology: use three-stage or multi-stage countercurrent rinsing technology to wash fly ash, kiln dust or similar powder materials to remove soluble substances in the materials, and then achieve two The purpose of secondary utilization or detoxification. To achieve efficient desalination of fly ash, and then to achieve full resource utilization. The fly ash or kiln ash treated by FWD technology has a chlorine removal rate of ≧ 95% and a moisture content of less than 2%.