The production of urea for automobile mainly includes 3 stages: urea purification, water treatment and disposition. The whole process is mainly involved in the process of purification, production barriers are not too high.. Urea equipment for vehicle urea technical formula urea plant
1, urea purification
Because of the higher requirement to the purity of urea, urea (commonly used industrial impurity content less than carbamide) stop purification, at 70-75 DEG C urea attack in aqueous solution hydrolysis, 30 C urea re crystallized from aqueous solution, the crystallization time can significantly improve the hydrolysis of urea purity, general industrial grade urea a hydrolysis crystallization can reach the standard car with urea.
2, water treatment
The car with urea on strict control of impurities, ordinary tap water generation process due to reasons such as disinfectant containing chloride, difficult to handle, so the general use of deep groundwater and reduce the water hardness removal of calcium and magnesium ions lose soft water, as a vehicle for the preparation of urea solution.
3, the configuration of urea solution
Urea solution in the car urea content is generally 31.8% ~ 33.2%, the last step in the production of urea is to use soft water and purified urea to dissolve and then stop filling.
The main pollutant emissions of diesel engine is NOx (nitrogen oxides) and PM (particle), increase the two emissions required task condition is just the opposite, therefore, this paper presents EGR (EGR) and SCR (selective catalytic recovery) requires two schemes to achieve four emissions.
The engine in the process of taking out SCR Road, has been through technical means to fully extinguish so as to achieve effective control of diesel PM emissions, while NOx needs in the exhaust process of its recovery of nitrogen (N2) and water (H2O), restoration agent of this process is the car with urea solution. From the exhaust turbocharger after it enters into the exhaust pipe, the exhaust pipe is installed on the urea dosing emitting device, reach 300 degrees Celsius over the temperature of -500 DEG C when injected into the urea solution and urea in the presence of catalyst (nh2conh2) hydrolysis NH3 and CO2, NH3 and NOx reaction, the formation of nitrogen and water discharge. Urea equipment for vehicle urea technical formula urea plant
The car with urea solution recovery control in catalytic reaction process is a very precise, spray volume of urea concentration and NOx must match the amount of urea injected into the small, is not up to the proper disposal level of urea injection quantity is excessive, the excess ammonia will into the atmosphere, cause new pollution.
The car with urea is machine manufacturers international standards for heavy truck diesel essential products to more stringent national emission standards for motor vehicles, from the beginning of IV, in addition to the improvement of fuel injection system, optimization of process machine out pollution measures, but also increased the machine outside the office device. At present, the international mainstream technology road meet the state IV emission standards mainly has 2 kinds: one is the machine optimization out + selective catalytic recovery (SCR); two is the exhaust gas recirculation (EGR) and diesel particulate filter / oxidation catalytic converter (DPF / DOC) road. Because of the IV diesel engine using SCR technology with small changes and fuel requirements is relatively high, more adapt to the status of current international oil quality is poor, mow phase high sulphur content, and fuel economy than the EGR technology, has the advantage of continuity in technological upgrading; in addition, the SCR system of the catalytic converter with good durability and there is no infarction risk, therefore, the international heavy truck manufacturer IV emission standard to deal with the country, mostly using SCR after disposal technology. But after using SCR disposal technology of diesel vehicles must add urea solution as catalyst recovery agent to stop the disposal of nitrogen oxides in the exhaust gas, by car with interaction of urea solution and SCR technology, the optimization of diesel engine performance and fuel consumption increase at the same time, but also can significantly reduce the cost of the car (usually with uniform consumption of urea the solution was about 5% of the total consumption of diesel oil).