What does AdBlue contain?

What does AdBlue contain?

Most modern diesel engines are equipped with additional systems to reduce carbon dioxide emissions - these technologies became mainstream in 2017 and are built on the same principle. To reduce the environmental impact of burning "heavy fuel", a special urea (or AdBlue) injection mechanism is built into the exhaust systems of vehicles to neutralise CO2 and reduce its concentration in the exhaust.

What is AdBlue and what does it contain?

This fluid is a special consumable that is used in vehicles with diesel engines and is filled in a separate tank. Through special nozzles, AdBlue is fed into the catalyst of the SCR system, where it interacts with the exhaust gases and significantly reduces their level of harmfulness.
The composition of this fluid includes deionised water and urea, more commonly known as urea. In this composition, the ratio of the components is of great importance, since the solution containing 67.5% water and 32.5% urea has the lowest freezing point (-11 C). The AdBlue liquid is not toxic, but a number of precautions must be observed when pouring it into the SCR system of the vehicle. In particular, it should be avoided on metal surfaces - individual metals, when in contact with aqueous urea solution, begin to actively rust. If the composition gets on the skin, simply wash it off with water.
A special tank is used to store AdBlue stocks in the vehicle. Its neck is located next to the fuel tank neck. The lid of the reagent tank is painted blue and often has markings on the substance itself. The name AdBlue itself is purely a marketing name and does not reflect any of its properties.

What is AdBlue for?

The working principle of the AdBlue-based system is quite simple:

• when the diesel engine is running, AdBlue is injected through special nozzles into the exhaust system;
• on the way from the nozzle to the exhaust catalyst, when exposed to high temperature, a thermolysis reaction is triggered and ammonia and isocyanic acid are formed from urea;
• a hydrolytic reaction then takes place during which isocyanic acid reacts with water to form carbon dioxide and ammonia;
• in the reduction catalyst unit, the ammonia reacts with nitrogen oxides, resulting in oxygen atoms being separated from them to form water and pure nitrogen, which do not pose a danger to living organisms;
• in order for the neutralisation reaction of dangerous nitrogen compounds to proceed with the necessary efficiency, it is necessary to supply the system with a strictly defined concentration of urea depending on the nitrogen dioxide content of the exhaust gases. This process is controlled by the vehicle computer.

Another important condition for the proper functioning of this entire system is the purity of the reagent. If the AdBlue contains foreign compounds or the concentration of urea and water differs from the standards set by the regulations, then neutralization will not be complete. Dirt can also clog the catalyst, leading to expensive maintenance.