The promotion of SCR denitration technology in cement industry can be expected in the future
时间: 2021-07-24 14:27
In recent years, with the tightening of national environmental protection policies and the strengthening of management and control, local requirements for nitrogen oxide (NOx) emission in cement industry have become more stringent. It is st
In recent years, with the tightening of national environmental protection policies and the strengthening of management and control, local requirements for nitrogen oxide (NOx) emission in cement industry have become more stringent. It is still an urgent task for the cement industry to strengthen the control of air pollutants, protect the ecological environment, reduce pollutant emissions and achieve green development.
On December 18, 2020, China Building Materials News published the news that the SCR denitration project of medium and low temperature flue gas of the first set of cement kiln at home and abroad passed the expert review. The project passing the review means that China's cement industry has achieved the transcendence and leadership of flue gas denitration technology, and provided solid and powerful technical support for air pollutant treatment, energy conservation and emission reduction and green development of cement industry. Once the news was released, it was concerned by many aspects of the cement industry. Many cement manufacturers called to inquire about the details of this technology.
China's annual production of cement clinker is about 1.3 billion tons. According to the NOx emission coefficient of 1.5kg/t clinker to 1.8kg/t clinker, the NOx emission from China's cement industrial kilns will be about 2 million tons in 2020, accounting for 10% of the country's total NOx emission. It is also the third largest emission source after thermal power plants and motor vehicles. At present, the emission standard implemented by the domestic cement industry is the emission standard of air pollutants for cement industry (gb4915-2013). Some places have also issued stricter emission standards. For example, the local standards issued by Zhejiang Province require that the NOx emission concentration of cement kiln flue gas should be less than 50mg / Nm3 by 2025. In addition, the technical guide for emergency emission reduction of key industries in heavily polluted weather issued by the Ministry of environmental protection requires that only when SNCR, SCR and other technologies are adopted in cement production to achieve ultra-low emission, and the ammonia consumption per ton of cement clinker is less than 4kg, can it be recognized as A-level enterprise and enjoy corresponding policy support.
China's cement industry has been comprehensively promoting non catalytic reduction technology (SNCR) since 2007. The denitration efficiency of SNCR technology can be as high as 60%. During this period, the staged combustion technology was also studied, that is, by controlling the combustion conditions in the calciner and pipeline, the CO produced by incomplete combustion was used to reduce NOx. The denitration efficiency of staged combustion technology is about 30%. SNCR injects ammonia into the decomposition furnace and connecting pipes. In the high temperature area above 800 ℃, NH3 molecules collide with NOx molecules directly to form N2 and H2O. SCR technology is to arrange denitration reactor in the area where the kiln flue gas is less than 320 ℃, and install multi-layer catalyst materials in the reactor. Such catalyst materials have strong adsorption capacity for NH3 molecules and NOx molecules, so that NH3 molecules and NOx molecules in flue gas can effectively contact and collide on the catalyst surface, which greatly speeds up the reaction. The denitration efficiency of SCR technology can be greater than 95%, and ammonia escape can be greatly reduced.