A new AdBlue additive has been launched by Liqui Moly to help protect the SCR system for exhaust gas treatment against damage.
Anyone who drives a modern series-production diesel has to fill up not only with fuel, but also with urea. Dissolved in water, it is sold under the name AdBlue. Only with this reducing agent can vehicle manufacturers comply with the standards for nitrogen oxide emissions that apply in Europe. No technology without pitfalls: Damage to the exhaust system is possible without appropriate care. This is where DEF anti crystal additive concentrate, newly developed by Liqui Moly, comes in.
Tackling residue
Diesel fuel is required to keep the vehicle moving. AdBlue creates the prerequisites allowing the diesel engine to comply with the legally prescribed nitrogen oxide levels. The reducing agent AdBlue, also known as diesel exhaust fluid (DEF), is injected into the hot exhaust tract in the appropriate doses via a separate tank. “The solution evaporates there. Residues can form because a liquid film forms on the exhaust pipe surface, where the water evaporates faster than the urea can decompose,” says David Kaiser, head of research and development at Liqui Moly. He is responsible for the development of DEF Anti Crystal Additive Concentrate. “The additive lowers the temperature to achieve the so-called Leidenfrost effect. This phenomenon promotes residue-free decomposition of the AdBlue solution. The Leidenfrost effect reduces the formation of a liquid film on the exhaust surface,” continues David Kaiser.
The additive’s sphere of influence is the exhaust gas treatment system, or SCR system for short. SCR stands for selective catalytic reduction. With the help of this technology, the nitrogen oxides produced during the combustion process in the diesel engine are converted into elemental nitrogen and water in a catalytic converter. The central component of SCR treatment technology is the dosing system and the pump is at its heart.
Residues can be formed because AdBlue consists of around two thirds demineralized water and about one third urea. When this substance is heated, the organic compounds biuret and triuret are formed by the separation of ammonia. “Urea crystals form in lines or in dosing valves. This happens when the water in the lines evaporates or vaporises,” explains the head of development. In extreme cases, this leads to a blockage in the AdBlue system. This in turn can cause damage to the pump and injection nozzles or trigger an error message in the engine control unit. “The surfactant contained in the additive reduces the surface tension in AdBlue. It hinders the formation of drops. This prevents the development of unwanted crystals and deposits on the injection nozzle,” says David Kaiser.
Freezing problem solved
Cold sensitivity is the second weak point of the aqueous solution. To protect the SCR system from freezing, the vehicle manufacturers use heaters. However, they are only activated when the engine is started. “AdBlue freezes at temperatures below – 11.5°C. With our additive, you can lower the freezing point to around -16°C,” David Kaiser explains. Because construction vehicles are often unprotected from the cold on building sites, the risk of breakdown increases in winter. Various construction companies and also workshops had turned to Liqui Moly with the question of a product that would solve the problem. The result is DEF anti crystal additive concentrate.
However, the additive only has a preventive effect. Existing crystallisation can only be removed mechanically. In most cases, this is put into practice by the expensive replacement of parts. “That’s why providing information is so important here,” the expert underlines.
The new product is available in a plastic container with a capacity of 2.5 litres and in a plastic dispensing bottle with 250 millilitres of capacity.
