Urea is hydrolyzed to produce ammonia, which reacts with nitrogen oxides in the exhaust gas to form nitrates.
Reducing the generated NOX to N2, thereby removing NOX in the flue gas. According to the treatment process, it can be divided into wet denitrification and dry denitrification;
Mainly include: acid Absorption method, alkali absorption method, selective catalytic reduction method, non-selective catalytic reduction method, adsorption method, ion activation method, etc.; some domestic and foreign researchers have also developed methods to use microorganisms to treat NOX exhaust gas;
Urea is an organic compound composed of carbon, nitrogen, oxygen and hydrogen, also known as urea (the same as urine). Its chemical formula is CON2H4, (NH2)2CO or CN2H4O, its molecular mass is 60, and its international generic drug name is Carbamide. The appearance is white crystal or powder. It is a product of animal protein metabolism and is commonly used as nitrogen fertilizer for plants.
Urea is synthesized in the liver and is a nitrogen-containing metabolite excreted by mammals. This metabolic process is called the urea cycle. Urea is the first organic compound obtained by artificially synthesizing inorganic substances. Vitalism has since been overturned.
Extended information:
1. System engineering of denitrification
The adoption of the "SNCR" method for denitrification by cement companies is not a matter for one cement company alone. It is subject to many constraints. It not only involves production, circulation, distribution and consumption, but also involves multiple government departments such as industry, agriculture, commerce, transportation, public security, energy, prices, environmental protection, safety supervision and quality inspection.
When using the SNCR method to denitrify, the reducing agent is the largest consumable (but for SCR denitrification, the catalyst consumption is more). Cement denitration generally uses urea or ammonia (not liquid ammonia - dangerous goods) as the reducing agent. However, urea and ammonia are produced through the conversion of synthetic ammonia, but the comprehensive energy consumption per unit product of synthetic ammonia is quite high.
2. According to the formation mechanism of nitrogen oxides in cement kilns, there are two major categories of technical measures to reduce nitrogen emissions in cement kilns:
One is to control it from the source. Control the generation of NOx during calcination. Its technical measures:
① Use low-nitrogen burners;
② Segmented combustion in the decomposition furnace and pipelines to control the combustion temperature; ③ Change the batching plan and use mineralizing agents. Reduce clinker firing temperature.
The other type is management from the end. Technical measures to control NOx emitted in flue gas:
① "Staged combustion SNCR", which has been piloted in China;
② Selective non-catalytic reduction (SNCR), which has been piloted in China There are already pilot projects;
③ Selective catalytic reduction (SCR), there are only three lines of experiments in Europe;
③ SNCR/SCR combined denitrification technology, there is no successful experience in domestic cement denitrification; ④ Biological denitrification technology (under development stage).
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