On December 29, 2011, the Ministry of Environmental Protection released the Announcement on Implementing the Fourth Stage Compression Standard for Vehicle Compression Engines and Vehicles in China. The Notice requires the official implementation of China's heavy-duty diesel vehicles on July 1, 2013 National Ⅳ emission standards. The emission standard of China Ⅳ refers to the emission standard of motor vehicles in the fourth stage of the country. The pollutants emitted by vehicles mainly include HC (hydrocarbon), NOx (nitrogen oxide), CO (carbon monoxide) and PM (particulates) Through better catalytic converter active layer, secondary air injection and cooling with the exhaust gas recirculation system and other technology applications, control and reduce emissions of pollutants to the vehicle below the standard value.
Diesel vehicles, especially heavy-duty diesel vehicles, are the most urgent targets for remediation under the State IV emission standards. Although only 17% of the vehicle ownership, diesel vehicles account for 67.4% of the total NOX emissions of vehicles. Among them, heavy-duty diesel vehicles account for only 4% of the total vehicle ownership, but occupy about 56% of the total emissions of nitrogen oxides Therefore, the emission requirements of heavy-duty diesel vehicle pollutants should be more stringent. In order to meet the emission standards of the country Ⅳ for heavy trucks, buses and other diesel vehicles, the most realistic choice for exhaust gas treatment is SCR (Selective Catalytic Reduction) technology, which must treat the nitrogen oxides in the exhaust gas with urea solution. Therefore, automotive urea solution has become an essential product for heavy trucks and buses to meet the emission standards of the country IV.
European countries demand for car urea, has formed a large-scale industrial scale. Vehicle urea Specifically, vehicle urea production mainly includes urea purification, water treatment and solution configuration of the three stages. The whole production process is mainly involved in the purification process, production barriers are not too high.
1) Purification of urea: As automotive urea requires high purity, it is generally used to purify industrial urea (impurity content is lower than that of agricultural urea), urea is hydrolyzed in aqueous solution at 70-75 ° C, and urea Crystallization out of aqueous solution, hydrolysis and crystallization time can greatly improve the purity of urea, the general industrial grade urea hydrolysis and crystallization can reach the car with urea standards.
2) Water Treatment Vehicle urea has strict control over impurities. Ordinary tap water contains chloride because of disinfection and other reasons, so it is difficult to handle with deep groundwater. Therefore, deep groundwater is used to remove calcium and magnesium ions to reduce the hardness of water to obtain soft water. As a vehicle urea solution Preparation of the use.
3) The urea content of urea solution for vehicle urea vehicle is generally 31.8% -33.2%. The final step of vehicle urea production is to mix and dissolve the soft water and purified urea and then fill the urea solution.
Car urea reaction principle
Since ammonia and NOx need to be reacted under the catalyst, whether or not the catalyst is effective is closely related to the metal content. If the metal and other impurities are large, the catalyst will be deactivated, resulting in failure of the entire device. Therefore, car urea production barriers are mainly reflected in the purity of urea
