Types and hazards of AdBlue Crystallization

2. Crystallization inside the urea pump and pipeline: easy to clean, it is not easy to find that the inside of the urea pump causes the urea pump to work poorly, and causes the Adblue post-processing system to fail to work normally.

3. Crystals on the outside of the Adblue pipe or exhaust pipe: easy to clean and easy to find.

Crystallization can greatly reduce the service life and performance of the SCR system and generate back pressure and corrode materials, which greatly reduces the performance of the SCR system and it can lead to increased vehicle emissions and damage the environment.

Causes of crystallization

An important factor that affects Adblue crystallization is the temperature of the contact point between the sprayed Adblue and the tube wall. Only when the Adblue is sprayed out, the contact point with the tube wall has a sufficiently high temperature to make the Adblue fully evaporate. Preventing the generation of crystallization on the pipe wall can increase the evaporation and pyrolysis rate of the Adblue (most of them are high-temperature hydrolysis processes), promote the full mixing of the exhaust gas and the Adblue and improve the catalytic conversion rate of the entire system.

Improper use leads to crystallization and results

1. Using inferior diesel fuel, more colloids will be adsorbed on the surface of the SCR box filter screen after the inferior fuel oil is burned, resulting in a decrease in the efficiency of the Adblue reaction, and the spray cannot fully react.

2. Shielding of Adblue or long-term non-burning of Adblue will cause blockage or damage in the SCR catalytic box. What is overlooked is that insufficient injection of Adblue will also cause blockage or damage in the SCR catalytic box.

3. Improper maintenance and use of SCR system: All urea pumps have filters or filter elements. The technical requirements must be cleaned or replaced regularly. Otherwise, it will cause blockage or damage over time and lose the filtering effect, which will inevitably cause system malfunction.

The urea pump is not completely emptied if the main power is turned off directly after the vehicle is extinguished

The alkalinity, impurities and metal ions in inferior Adblue are not up to standard. For long-term use of inferior Adblueor so-called "renovated" National IV diesel vehicles, although it can save some of the cost of purchasing Adblue, inferior Adblue will cause SCR post-processing .The urea pump and nozzle of the urea pump were damaged, the plug of the urea pump was severely corroded, the pins fell off, and the Adblue crystal state appeared in the exhaust pipe. The SCR catalytic box is poisoned and invalid. In severe cases, it will affect the vehicle's fatigue, reduce the exhaust gas conversion effect, or even lose its effect. So we must to choose high quality Adblue ,The poor quality will also affect the crystallization.

Insoluble content of Adblue

Phosphate: Phosphorus and phosphate can poison and deactivate the catalyst of the SCR system and block the nozzles and then lead to crystallization, so they need to be strictly controlled.Metal ions (calcium, iron, copper, zinc, chromium, nickel, magnesium, sodium, potassium, aluminum) as impurities in Adblue have toxic effects on the catalyst of the SCR system and affect the conversion efficiency of SCR reduction, which should be strictly controlled These indicators.

Treatment of different types of crystallization causes

The reason for the crystallization of the inside of the urea pump and the pipeline: a simple understanding is that the Adblue automatically precipitates out of crystals after the water volatilizes. Solution: Use warm water for flushing or use the cleaning function in the increasingly new testing equipment to clean the urea pump.

The reason for the crystallization of the outside of the exhaust pipe and the outside of the pipe: Adblue leakage, the solution: do a good job of sealing, clean up the crystallization, use warm water or external force to clear, according to the situation to determine whether to re-repair the exhaust pipe or directly replace.

The main reasons and solutions for crystallization inside the exhaust pipe and nozzles:

1.: The control strategy of urea injection and the urea crystallization caused by the injection volume control
2.: Performance of urea injection system
3.: Structural design defects, unreasonable SCR installation and application design

Control strategy for Adblue crystallization caused by injection volume control

Reasons:

1. The control module calculates accurately the Adblue injection rate and the Adblue mixed air volume in the vehicle compressed air system under various engine conditions. The injection rate of the data link command is converted into the input of the Adblue supply module. Control the amount of Adblue injection required. Problems with the Adblue injection control strategy will increase the risk of Adblue crystallization. But when the data is wrong, the SCR control strategy is directly related to the precise utilization of the Adblue and the NOX conversion rate.

2. Frequent operation in the project with low exhaust temperature, the proportion of SCR Adblue crystallization is larger.

Structural design defects

1. The exhaust pipe arrangement is unreasonable. After the Adblue injection point, there is a local vortex or an area with a low gas flow rate. The spray gathers here to form a wet wall. The hot water evaporates and forms crystals. The crystals gradually grow and block in the exhaust pipe. In this case, the exhaust pipe layout and direction need to be changed.

2. The nozzle connecting seat is long, which is easy to form a dead zone for gas flow. The Adblue nozzle seat crystallizes uniformly, and the middle nozzle hole is not blocked and can be ventilated. The reason is that the Adblue nozzle seat has a local swirling flow, causing a thin layer of Adblue crystals

3. Exhaust pipe material or unqualified welding leads to inadequate sealing of the exhaust pipe, which in turn causes gas vortexes inside the exhaust pipe.

As an experienced Adblue manufacturer, EverBlue Chem always puts quality first ,all of our products got the SGS & ISO & VDA certificates and we will keep the samples of each shipment for quality tracking. What's more ,we do the test with random sample each 1-2 month in international authority such as SGS ,Intertek. We provide AdBlue more than 13 knids of packing,please feel free to contact us to know more!