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Introduction to the technology of hazardous waste treatment industry

Hazardous waste belongs to the resource development and utilization waste, which has great utilization value. Besides storage and disposal, it also includes comprehensive recovery and utilization after treatment. At present, the comprehensive utilization of hazardous waste treatment is the main. In 2016, the comprehensive utilization of hazardous wastes in China reached 28.237 million tons, accounting for 50.53%.

The treatment of hazardous waste should follow the principle of "three chemical", namely, reduction, resource and harmlessness. First, the reduction treatment of hazardous waste should be controlled from the source, such as secondary separation of metal from tailings, or separation of steel slag from smelting slag. Secondly, many things such as circuit board and sludge can be treated by resource. These solid wastes contain a lot of heavy metals such as copper and silver, which can be recycled to make it resource-oriented and increase benefits. Finally, the hazardous waste should be treated with acid-base neutralization and other chemical treatment before incineration or landfill.

In addition to the general process in the conventional technical route, some new technologies have emerged, such as cement kiln co-treatment, plasma technology, pyrolysis incineration technology, supercritical water oxidation technology, electrolytic oxidation method, etc. Two new technologies for hazardous waste treatment are introduced here

——Cement kiln co-operation

In developed countries, the cement kiln co-treatment of hazardous waste has been more than 30 years old, which plays a great role in the treatment and disposal of hazardous waste. Compared with landfill and incineration, the collaborative treatment of cement kiln has obvious economic and environmental benefits.

Compared with the special incinerator, the use of new dry cement kiln to dispose hazardous waste with synergetic treatment has significant environmental and economic effects. On the one hand, the combustion process of cement kiln is sufficient to reduce the emission of dioxin and other pollutants; the heavy metal ions in waste are solidified, which greatly reduces the production of fly ash. On the other hand, the reconstruction of cement kiln can reduce the investment scale, and the cost of disposal is significantly lower than that of incineration. From the perspective of social influence, cement production enterprises are usually more remote and have less neighborhood avoidance effect.

In a comprehensive way, the collaborative treatment of cement kiln, as a new circular economy, has a high promotion value.

——Plasma technology

Plasma treatment of hazardous waste is to decompose and destroy hazardous waste quickly by using high temperature hot plasma produced by plasma torch. Organic matter is decomposed into small combustible molecular substance, and inorganic matter is melted at high temperature to generate glass like residue. The technology has the characteristics of fast reaction, small secondary pollution and wide application range. It overcomes the disadvantages of traditional treatment technology such as incineration and chemical treatment, such as large secondary pollution, complex process and selectivity to waste, especially suitable for the environmental protection of solid hazardous wastes such as medical waste, asbestos, incineration fly ash, battery, tire and radiation pollution.

Compared with conventional incineration technology, plasma treatment technology is an environmentally friendly technology, which is completely treated without secondary pollution and less carbon emission. Plasma is usually a large number of ionizing gases with electrons, ions, molecules, atoms and free radicals, but they are electrically neutral and have high chemical activity. The center temperature of hot plasma can reach 20000 ℃ and the temperature of torch edge can reach 3000 ℃. Plasma technology can destroy all kinds of toxic and harmful substances completely, and it is a new technology which can effectively eliminate pollution and has wide application. The core technology of plasma treatment waste technology is plasma generator (plasma torch), and the most widely used technology is DC arc plasma. The unique treatment method of plasma treatment of hazardous waste shows safety, efficiency, no secondary pollution and wide applicability. It provides a scientific and effective method for harmless, reducing capacity and recycling of hazardous wastes and urban solid wastes.