The importance of preventing environmental pollution has been sharply raised as a global issue. With the development of modern industrial production and the improvement of living standards, air pollution has become a major concern for people.

Sulfur dioxide is one of the important sources of atmospheric pollution, and its pollution hazards are significant. Therefore, in the mid-1970s, research on flue gas desulfurization technology was listed as a means of preventing and controlling atmospheric pollution, and practical industrial scale treatment devices were successively built. At the same time, people also began to study and develop prevention and control technologies for another major problem in atmospheric pollution, namely nitrogen oxide NOX pollution. NOX can cause photochemical reactions under the action of sunlight, forming photochemical smog and causing serious air pollution. Since the 1970s, the issue of atmospheric pollution caused by NOX has been increasingly recognized. People have found that the harm to human health, high levels of nitric acid rain, photochemical smog, ozone depletion, and other problems are all related to low concentrations of NOX, and their harmfulness is much greater than people originally thought.

The issue of NOX emissions has been given more consideration by Japan. Japan has already established strict NOX emission standards worldwide. Japan is adding technical measures to eliminate NOX equipment on boilers fueled by coal and oil, and is still striving to obtain this technology.

The flue gas of thermal power plants contains a large amount of nitrogen oxides. If not treated, these exhaust gases will be discharged into the atmosphere, causing pollution and forming acid rain. In order to further reduce the emission of nitrogen oxides, the flue gas after combustion is subjected to denitrification treatment. The flue gas denitrification equipment in thermal power plants is a device used to treat nitrogen oxides.

Flue gas denitrification refers to the reduction of generated NOx to N2, thereby removing NOx from flue gas. According to the treatment process, it can be divided into wet denitrification and dry denitrification. Some researchers have also developed methods for treating NOX emissions using microorganisms.

Due to the fact that over 90% of the NOx emitted from the combustion system is NO, which is difficult to dissolve in water, wet treatment of NOx cannot be achieved through simple washing methods. The principle of flue gas denitrification is to use oxidants to oxidize NO into NO2, and the generated NO2 is then absorbed by water or alkaline solution to achieve denitrification. The O3 oxidation absorption method uses O3 to oxidize NO to NO2, and then absorbs it with water. The product of this method, HNO3 liquid, requires concentration treatment, and O3 needs to be produced at high voltage, resulting in high initial investment and operating costs. ClO2 oxidation-reduction method: ClO2 oxidizes NO to NO2, and then Na2SO3 aqueous solution is used to reduce NO2 to N2. This method can be combined with wet desulfurization technology using NaOH as a desulfurizer, and the reaction product Na2SO3 of desulfurization can also be used as a reducing agent for NO2. The denitrification rate of ClO2 method can reach 95%, and it can simultaneously desulfurize, but the prices of ClO2 and NaOH are relatively high, resulting in increased operating costs.

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