company news about Maintenance of SCR post-treatment of automotive urea equipment

Maintenance of SCR post-treatment of automotive urea equipment

With the national emission upgrade, the exhaust emissions of domestic heavy trucks have also improved. Since National Emission Standard for Quatri-fourth-generation Motor Vehicles period, urea has become one of the important issues that the majority of truck drivers care about in their daily lives. Although every truck driver knows that the vehicle needs to be filled with urea solution, most drivers still do not know enough about automotive urea, which has led to many people's subsequent preference for shielding urea, purchasing inferior urea, and even causing damage to the vehicle's post-treatment system.

Below, Lanchi will start with the SCR post-treatment system and talk about the possible cognitive misunderstandings and the use of urea solution and the routine maintenance of the SCR post-treatment system. What is the SCR post-treatment system?

The SCR system is a catalyst that sprays ammonia or urea as a reducing agent to reduce nitrogen oxides (NOx) in the exhaust gas into gas (N2) and water (H20), thereby achieving both energy saving and emission reduction. The structure of SCR technology is very simple. It only needs to build a system of adding urea reduction agent on the basis of the engine, and then regularly add automotive urea water solution. This technology can not only improve the fuel economy of the vehicle, but also help it to extend the maintenance cycle.

The SCR system includes urea pump, urea nozzle, urea tank and other components. Its normal engineering process is: the exhaust gas enters the exhaust mixing pipe after coming out of the turbine, and a urea metering and injection device is installed on the mixing pipe. Urea aqueous solution is sprayed in. Urea undergoes hydrolysis and pyrolysis reactions at high temperature to generate re-gas NH3). NH3 is used on the surface of the SCR system catalyst to reduce NOX and discharge N2. In fact, automotive urea solution can also be said to be a consumable of the SCR post-treatment system, because even if the vehicle is equipped with an SCR post-treatment system, it cannot achieve the effect of cleaning the exhaust gas without adding urea solution.

Although automotive urea is also urea, the main components are the same, but it is very different from agricultural urea. There are strict ratio requirements for automotive urea. It is basically composed of high-purity urea and deionized water. The ratio is strictly controlled. One of the most important quality standards is the control level of impurities. However, agricultural urea has a lot of impurities such as particulate matter, metal ions, and minerals, which are extremely easy to clog the nozzle, damage the SCR system, and cause the vehicle to be unable to use normally.

Engine torque limit shielding urea is definitely not possible

Since the National IV era, when card friends buy new cars with SCR post-treatment systems, the sales staff of the car sales company will inform the vehicle that urea needs to be added on demand. If urea is not added, the torque output of some vehicles will be limited when they start, because the engine ECU will send a limit signal when it receives the signal of excessive exhaust gas. Some card friends will find a way to shield the signal, so as to achieve the purpose of not using urea and not being limited by the engine torque. I have heard many old drivers say that the practice of shielding signals is basically not to use urea solution, and the shielding equipment can be removed when the vehicle is inspected. So is it possible to shield urea radiation? Lanchi tells you that the answer is definitely not! It is definitely not cost-effective. Cheap urea is not worth buying. Long-term use is very harmful.

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