Abstract: In recent years, China advocates the concept of green development and sustainable development. While developing economy, China pays attention to the protection of ecological environment. As one of the most important industries in China, the steel industry is directly related to the development of all walks of life in our country. At the same time, the steel industry is also one of the major industries that discharges sintering gas. Sinter exhaust emissions from iron and steel enterprises are relatively low in temperature, with a large amount of exhaust gas, complex components and high pollutant content, causing serious environmental pollution and severely restricting people's health and long-term economic development. The article first analyzes the status quo of comprehensive management of sintering flue gas in China's iron and steel enterprises and explores the optimization of sintering flue gas synthesis theory.
Iron and steel enterprises sintering flue gas Iron and steel industry emissions, mainly the emissions of sintered exhaust gas, due to its large amount of exhaust gas, high levels of pollutants, the composition is very complex features, become the steel industry emissions control difficulties and priorities. Sinter emissions SO2 emissions accounted for about 50% of total emissions, nitrogen oxides emissions accounted for about 40%, dust emissions accounted for about 10%. Sintering flue gas to achieve the comprehensive management of the most important is the desulfurization and denitrification technology applications. Sintering flue gas desulfurization is the most critical assessment index of energy saving and emission reduction capacity of the national steel enterprises, which has become the key factor restricting the development of the steel industry. Shougang relocated to Caofeidian as a whole, Hangzhou Iron and Steel moved to Ningbo as a whole, and Wuhu Xinxing Ductile Iron Pipes move out of the main city of Wuhu to Sanshan District and so on.
1 steel sinter flue gas comprehensive management of the status quo
At present, there are more than 1,200 sintering machines in our country, of which the key steel companies account for nearly one half. Currently, the steel industry in China will face the predicament of overcapacity for quite a long period of time because of serious overcapacity and serious competition. , And will face severe pressure on debt, employment, environment and ecology. The Ministry of Environmental Protection has made tighter control over the emission of pollutants during the 12th Five-Year Plan, requiring the total emission of air pollutants to be continuously reduced, requiring that the total amount of SO2 emission in the country be reduced by 10% over 2010, and the emission of SO2 , On the basis of controlling the total amount of emissions of the whole country, shifting from focusing on the reduction of the total amount of key industries to the emission reduction of the entire industry.
In particular, with the promulgation and implementation of the new "Environmental Protection Law" in 2015, higher requirements have been placed on the control of various emission indexes such as dust, sulfur dioxide and nitrogen oxides in sintering flue gas. At present, the iron and steel enterprises in our country have not yet fully realized the desulfurization facilities. Even if the enterprises with desulfurization facilities are installed, the desulfurization efficiency of sulfur-containing compounds is less than 70% because of the process or management issues. In addition, most of the steel enterprises use wet desulfurization. Due to the lack of a cost-effective removal process, only a very small number of steel companies adopting activated carbon processes have met the emission standards and most of them are hard to meet the standard requirements.
2 steel sinter flue gas comprehensive management technology
Due to the need of ecological environment protection, the steel enterprises only have to use desulfurization technology and equipment to realize the need of modern production and development. Enterprises should continuously strengthen the comprehensive treatment technology of sintering flue gas. These include desulphurization, denitrification, dedusting and VAI technology to help save energy and protect the environment.
2.1 sintering flue gas desulfurization technology
As a major emission of sinter flue gas, SO2 itself is corrosive and undergoes chemical reactions in the event of rainfall to form sulfuric acid, corrode buildings, pollute the water stream and soil. Therefore, the use of flue gas desulfurization technology for emissions of exhaust pollution is of great significance. Sintering flue gas desulfurization technology there are three main types were dry, semi-dry and wet method. One dry method mainly uses LJS circulating fluidized bed method, ENS method, NID flue circulation method. Dry desulfurization technology which desulfurization efficiency is low, the production of by-products, and its chemical properties are not stable, can not be directly recycled.
Semi-dry method is often used in dense phase tower method, circulating fluidization method and SDA rotary spray method. Wet mainly refers to the double base method, lime gypsum method, magnesium oxide method, ionic liquid method. Compared with dry and semi-dry desulfurization methods, wet desulfurization technology is more efficient, but it is easy to produce chimney rain and low temperature corrosion, and it is difficult to realize the synergistic treatment and control of various pollution sources. Three-quarters of China's iron and steel enterprises to adopt wet desulfurization technology. Lime - gypsum desulfurization technology, the technology is relatively mature, desulfurization efficiency of 90% or more, but there are shortcomings of equipment corrosion and structural problems, accompanied by the occurrence of chimney rain. The key of desulphurization technology is to control the PH value in the absorption tower. Because of the fluctuating phenomenon in the operation of the sintering machine, the content of sulfide and flue gas in the absorption tower keeps changing, making it difficult to control the pH. At the same time due to the lower temperature during the smoke exhaust, the environment around the factory has a great impact. Magnesium oxide method has the advantages of not easy to scale relative to the lime gypsum method, but the resulting waste water is difficult to handle, and the resulting magnesium sulfate, the investment income, use value is not high if the direct disposal of secondary pollution problems. In summary, the desulfurization by lime gypsum method is relatively economical and applicable, and the desulfurization of flue gas without consideration of by-products is considered.
2.2 sintering furnace flue gas two VA British governance
VA VA is polychlorinated biphenyls aggregates, the chemical properties are more stable, if absorbed by humans or animals easily lead to cancer. Therefore, the two VA British governance, to prevent harm to people or animals. Two VA British largest harm is carcinogenic, teratogenic, mutagenic. Iron and steel enterprises generally adopt the method of intensified dedusting to reduce the content of chlorine in sinter flue gas. Heat treatment, decomposition treatment or rapid cooling of two VA vale gas can be used to adsorb the chlorine by the strong adsorption of activated carbon, Solvent to dissolve. At the same time in the exhaust gas to add urea particles or sodium hydroxide, calcium hydroxide and other alkaline substances, you can quickly reduce the temperature of the flue gas in order to achieve the reduction of two VA British production. So far, however, the management of two VA English is still based on theory and has not yet been widely promoted.
2.3 sintering flue gas denitration technology
Sintering flue gas denitrification technology has the gas phase reaction method, adsorption method, microbial method, liquid absorption method, selective catalytic reduction method, the selective catalytic reduction method, denitrification efficiency is the highest, the technology is relatively mature, the general use of vanadium titanium catalyst SCR , The reaction temperature is about 250 ~ 400 ℃, because dust and other impurities will reduce the service life of the catalyst, the reactor is generally installed before the precipitator arrangement. Reduction absorption method has the characteristics of low equipment cost and simple process, which can reduce nitrogen oxides to nitrogen. However, most of the iron and steel enterprises currently use flue gas desulfurization limestone wet flue gas desulfurization technology, if the desulfurization system to increase denitrification, heating requires a lot of energy consumption, and if the increase in denitrification before desulfurization, the venue is a big problem .
3 Conclusion
Sintering process, as the first important process of steel production, is the most important cost and environmental protection of steel enterprises, which directly relates to the survival and development of enterprises. However, the governance of sintering flue gas is an important factor that affects the long-term and healthy development of enterprises. The co-treatment technology of multi-pollutants activated by activated carbon flue gas jointly developed by China Metallurgical Changtian International Engineering Co., Ltd., Tsinghua University and Baoshan Iron and Steel Co., Ltd. In the application of 2 × 550m2 sintering machine flue gas purification project of Zhanjiang Baosteel, all kinds of emission indexes are better than National standards, for the comprehensive management of flue gas proposed a more optimized process. At present, China advocates green development, sustainable development and building an environment-friendly and resource-saving society. However, the current nitrogen and nitrogen oxides in flue gas from steel and sulfur
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