Abstract: The glass and cement industries are important basic materials industries in China with industrial scale more than half of the world total. Compared with the advanced level, China's glass, cement kiln NOx emission levels were significantly higher, and its reduction of nitrogen oxides in furnace kiln for improving the environmental quality of our country is of great significance. On the glass, cement kiln emissions of nitrogen oxides, emission reduction technologies and application status were analyzed, in order to further reduce the industrial furnace emissions provide a reference. 0 Preface According to China's "National Economic and Social Development Twelfth Five-Year Plan" requirement, "the 12th Five-Year" period of the chemical oxygen demand, ammonia nitrogen, sulfur dioxide, nitrogen oxides, the implementation of the four major pollutants emission control. Nitrogen oxides is one of the new emission reduction targets in China during the "12th Five-Year Plan" period, with a target of 10% reduction in 5 years. However, according to the verification data of the Ministry of Environmental Protection on the emission of pollutants in 2011, the total nitrogen oxide emissions in the current year were 240.43 million tons, an increase of 5.74% over 2010. In addition, About 2.5% of PM2.5, which has been the subject of public concern recently, contributes to the oxidation of nitrogen oxides to nitrate. China's nitrogen oxide emissions are mainly concentrated in thermal power, cement industry and motor vehicles. As one of the binding indexes, the index of nitrogen oxides rises and falls, which shows the difficulty of reducing nitrogen oxides. 2011 is the "Twelfth Five-Year" the first year, the state vigorously promote energy-saving emission reduction policies, the emission of nitrogen oxides did not even fall, so the reduction of nitrogen oxides has become a national energy-saving emission reduction work Top priority. 1 glass industry denitrification 1.1 glass industry production status Flat glass industry belongs to the basic raw material industry, and has very close ties with the national economy. Flat glass and its processed products are widely used in construction, transportation, decoration, electronic information, solar energy utilization and other emerging industries. They are indispensable important material industries for the development of national economy and improvement of people's living standards. In 2011, the output of flat glass in our country reached 738 million cases, accounting for about half of the total output of flat glass in the world, up 15.84% over the same period of previous year, ranking first in the world for more than 20 consecutive years. The top three cities of plate glass production are Hebei, Shandong and Guangdong, accounting for 39.02% of the total output of the three provinces. As of May 2012, the country has a total of 278 production lines with a daily production capacity of 152,400 t. Flat glass, including ordinary flat glass and float glass, as ordinary flat glass production process is lagging behind, with the upgrading of the industry and structural adjustment, more and more production lines using float glass production technology. As of the end of 2010, the proportion of float glass nationwide rose to 87%, of which high-quality float capacity rose to 35%. At present, there are more than 200 flat glass production lines adopting float process in our country, and nearly 170 production lines which use all or mainly Chinese float technology. Float production line has been built, single line melting capacity of <450t / d accounted for 38.9%, ≥ 600t / d accounted for 30%, ≥ 700t / d accounted for 11.1%. With the upgrading of the structure, the production of float glass is gradually being studied and developed in energy saving (oxygen-rich combustion, oxygen injection, pure oxygen combustion) and environmental protection (control of SO2 and NOx). 1.2 glass industry nitrogen oxide pollution status quo Flat glass industry belongs to high energy consumption, high emissions industry, is one of China's key industrial pollution control industries. The main pollutants in the glass furnace flue gas are soot, SO2, NOx, HCl, HF and a few heavy metals. China's flat glass industry annual emissions of particulate matter about 12,000 t, SO2 about 160,000 t, NOx about 140,000 t, HCl and HF were 4000t and 1200t. Sources of flat glass soot mainly include that a small portion of the raw materials are brought into the flue gas during the charging process. Volatiles (some metal oxides, such as Na2O, etc.) in the furnace are volatilized at high temperature and then condense to form soot; flue dust generated after fossil fuels. As more than 90% of flat glass enterprises in our country use heavy oil as fuel, the sulfur content of heavy oil is between 0.5% and 3%, resulting in a large amount of SO2 in flue gas. In addition, Glauber's salt (Na2SO4) in the glass raw material is decomposed and a large amount of SO2 is also produced. In the use of heavy oil as a fuel, flue gas desulfurization is not the case, the glass furnace SO2 emission concentration is generally about 1800mg / m3. Nitrogen oxides in glass furnaces are produced by the combustion of air and the decomposition of small amounts of nitrate in the glass starting material. As flat glass furnace flame temperature up to 1650 ~ 2000 ℃, nitrogen in the air will react with oxygen to generate a large amount of NOx. The nitrate (KNO3) contained in the raw material also decomposes to generate partial NOx at a high temperature. Therefore, the emission of flat glass flue gas contains a lot of NOx, the concentration can be as high as 2000mg / m3. According to the statistics, the amount of NOx produced by the plate glass furnace with the daily capacity of more than 600 tons using heavy oil as fuel is 4.37 kg / t. SO2 emissions of 5.613kg / t. The kiln NOx and SO2 emissions below the daily melting point of 400t were 6.05 and 8.638kg / t, respectively. 1.3 glass industry nitrogen oxide control In recent years, in order to promote the structural adjustment and sustainable development of the glass industry, the state has made the flat glass industry one of the key macro-control measures and formulated and promulgated a series of policies, regulations and standards. In the layout of manufacturing enterprises, the glass industry, energy consumption, environmental protection and other aspects of the strict rules, by continuously improving the access threshold of the glass industry, and promote the industrial upgrading of the glass industry. In order to promote clean production in the glass industry, the state encourages the use of natural gas as fuel for flat glass and strictly limits producer gas as fuel. Existing production line "furnace overhaul" should be combined with "flat glass industry access conditions," technological transformation and upgrading, out of gas furnace device, the use of other clean energy, optimization and improvement of combustion control system, the use of new energy-saving technologies to ensure a reasonable combustion , Energy saving, and promote energy-saving technologies such as glass furnace low temperature waste heat power generation technology. New or modified (expanded) construction of flat glass production lines should be used dust removal, desulfurization facilities, should also be set aside denitration pollution control facilities site. By August 2012, the Ministry of Industry and Information Technology announced a total of 97 production lines in line with the "access conditions for the flat glass industry" with a capacity of 56,650 tons per day. According to the newly released GB26453-2011 "Standard for Emission of Industrial Air Pollutants for Flat Glass Industry" issued by the Ministry of Environmental Protection of China, before the end of 2013, the SO2 emission level of the existing flat glass enterprises should be controlled below 600mg / m3. The new enterprises need to control NOx at 700mg / m3, since 2014, all glass furnace kiln NOx emissions must meet the 700mg / m3 ceiling requirements, SO2 emission levels should be controlled below 400mg / m3. Under the existing technical conditions, the glass furnace kiln using terminal denitration technology (SCR and wet reduction absorption), NOx emission control effect can reach about 700mg / m3. If China's flat glass industry is fully implemented nitrogen oxide emissions standards, annual reduction of at least 100,000 tons of nitrogen oxide emissions (reduction rate of 70%). China's 12th Five-Year Plan on Energy Conservation and Emission Reduction proposed to strengthen desulfurization and denitrification in non-electric industry, to implement flue gas desulphurization or switch to natural gas production in the float glass production line, to promote the reduction of nitrogen oxides such as oxy-fuel and oxygen-enriched combustion in glass furnaces Row technology. China's first 600t / d glass furnace denitrification project with SCR denitration process was put into operation in January 2012. Under the condition of flue gas flow rate of 68000m3 / h and NOx concentration of imported NOx system of 1950 ~ 2200mg / m3, the system can be maintained The denitrification efficiency is stable at about 70%, NOx concentration at exit is less than 700mg / m3. The first 900t / d glass production line SCR flue gas denitration system was also implemented in April 2012 to run in the import of nitrogen oxide concentrations of 2300 ~ 2450mg / m3 conditions, the export of nitrogen oxides stable at 700mg / m3 or less, denitrification efficiency reached 70%, the highest denitrification efficiency of the system up to 85.7%, the export of nitrogen oxide concentration can be controlled below 350mg / m3. 2 cement industry denitrification 2.1 cement industry production status Cement industry is an important basic raw material industry, China has nearly 5,000 cement companies. In recent years, the annual new cement output in the country accounts for more than 80% of the new output in the world. In 2011, the total output of cement reached 2.085 billion tons, accounting for more than 56% of the world's cement output, ranking first in the world for nearly 30 consecutive years. Among them, The proportion of new dry-process cement is about 80%. As of the end of 2010, China's Nissan 4000, 5000t new dry-process cement production line a total of more than 800. 2.2 cement industry nitrogen oxide pollution status quo Cement industry as a basic material for the development of the national economy has made an important contribution, but the development process is also facing more and more serious environmental problems, reducing air pollution will be one of the major problems facing the industry. According to statistics, from 2006 to 2008, China's cement industry nitrogen oxide emissions of about 5% of the total industrial emissions. With the rapid growth of the cement industry, China's nitrogen oxide emissions from the cement industry have soared from 764600 tons in 2008 to more than 2.2 million tons in 2010, accounting for 10% of the industrial emissions from 5%. Cement industry has become the third largest emission of nitrogen oxides after electricity and motor vehicles. According to the survey data in 2009, China's cement kiln average total nitrogen oxide emissions of about 700mg / m3, tons of clinker nitrogen oxide emissions 1.12 ~ 1.40kg. The new type of dry-process cement kiln with an annual output of 5000t / d or above has an average emission of nitrogen oxides of 600mg / m3 and a new-type dry-process cement kiln with an average emission of more than 1100mg / m3 and 1500t / d Dry cement kiln nitrogen oxide emissions average 1600mg / m3. Rotary kiln is the key technology and equipment of the new dry process cement material firing, but also the main source of nitrogen oxide emissions in the cement industry. In the rotary kiln exhaust gas, nitrogen dioxide generally accounts for less than 5% of the total nitrogen oxides, nitrogen oxides accounted for more than 95% of the total. As the nitrogen oxide in the cement industry has not been effectively controlled for a long time, it has directly exerted pressure on China to achieve the "12th Five-Year" pollution reduction targets. According to a survey of more than 150 cement companies in 2010, nitrogen oxides from cement plants have become the major source of emissions. Taking the 5000t / d clinker new dry process cement production line as an example, enterprises need to pay about 85% of the pollutant discharge fee each year, and nitrogen oxides emission reduction has become the only way for the cement industry to develop in the future. 2.3 Cement industry restructuring and pollution control 2.3.1 China's nitrogen oxide emissions reduction plan of the cement industry In 2010, the Ministry of Industry and Information Technology promulgated the "Access Conditions for Cement Industry", requiring new expansion projects to be installed with NOx reduction efficiency of not less than 60%. During the "Eleventh Five-year Plan" period, a total of 340 million tons of backward production capacity of cement in our country was eliminated. While promoting industrial upgrading, NOx emissions in the cement industry were reduced. NOx emissions control of the existing cement production line transformation is also an important way to achieve emission reduction of NOx. Nitrogen oxide control techniques commonly used on new dry-process cement rotary kilns include optimizing the firing of kilns and calciners, changing batching schemes, using low nitrogen burners, and staged combustion techniques. At present, except for some cement kilns with low-nitrogen burner designs and some new dry-process kilns that generate reducing gases to reduce nitrogen oxide emissions by controlling the calciner, China's cement industry has basically taken no control measures. The GB4915-2004 promulgated in 2004, "Cement Industry Air Pollutant Emission Standards" still maintain 800mg / m3 of nitrogen oxide emissions standards, that GB4915-1996 standard. With the development of the national environmental protection situation, during the "12th Five-Year Plan" period, the state reduced the emission of nitrogen oxides as a binding target. The current emission standard of nitrogen oxides for thermal power plants has been raised to 100mg / m3. The nitrogen oxide Emissions standards will also be more stringent. The new NOx emission standard for the cement industry under study included both 300 mg / m3 and 400 mg / m3. According to the experience of foreign countries in the prevention and control of nitrogen oxides pollution in the cement industry, comprehensive measures including SNCR technology can reduce the nitrogen oxide emission concentration in the cement industry by 70% -80% and achieve the maximum NOx emission level of 100mg / m3. China's 12th Five-Year Plan on Energy Conservation and Emission Reduction requires the cement industry to implement a new dry-process kiln to reduce nitrogen and denitrification. The comprehensive denitrification efficiency of newly built and re-expanded cement production lines should not be lower than 60%. Currently more feasible approach is to take a discriminatory approach to gradually improve the cement industry NOx emission standards. Production lines operating for more than 3 years should reach the current national standard of 800mg / m3; the operating time is less than 3 years and the new production line can be transitioned to the new national standard of 600mg / m3 by 2015, and then 2017 or 2018 Achieve 400mg / m3 of the international advanced level. During the "12th Five-Year Plan" period, a new type of dry-process cement kiln larger than 2000t / d clinker will be the key point of the "12th Five-Year Plan", achieving a comprehensive denitrification efficiency of 70%. Generally, the main parameters are determined according to the requirements of the material handling system, the conditions of the loading and unloading sites, the relevant production process and the characteristics of the materials. Conveyor System,Conveyor Belt Systems,Mini Conveyor System,Motorized Conveyor System Shandong Sinolion Machinery Corp., Ltd. , https://www.sinolion.cc
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