What is the formula for preventing crystallization in automotive urea?
2 Answers
It is composed of 32.5% high-purity urea and 67.5% deionized water. Below is relevant information about automotive urea: 1. Instructions for use: Automotive urea must use ultra-pure water of electronic grade. Since the SCR catalyst carrier is highly susceptible to metal ion poisoning, which leads to loss of catalytic effectiveness, the urea solution for vehicles must use ultra-pure water of electronic grade (resistivity ≥18MΩ·cm). The urea solution begins to freeze at -11°C, and in practical use, it completely freezes at -20°C. Current technology involves adding modifiers to lower the freezing point of the solution and external heating devices to prevent the solution from freezing. 2. Advantages of automotive urea solution: The urea solution for vehicles is prepared by mixing high-purity urea without any additives with pure water, with a urea content of 32.5% (mass fraction). Most domestic and international heavy-duty diesel engine manufacturers adopt SCR (Selective Catalytic Reduction) technology to meet the Euro IV and Euro V vehicle emission standards. Vehicles using SCR technology must add urea solution as a catalytic reductant to meet emission standards.
As an enthusiast who frequently delves into automotive technology, I have conducted in-depth research on the issue of urea crystallization in vehicles. Urea solution tends to crystallize at low temperatures primarily because its 32.5% concentration freezes below zero degrees, leading to SCR system blockages. The standard formulation consists of pure urea and deionized water, but the anti-crystallization method does not involve adding chemical agents—such as ethylene glycol, which may damage the catalyst. Instead, I recommend external solutions: installing heating elements in the vehicle to keep the lines warm or using an insulated container to store urea barrels during winter. Another key factor is selecting high-quality DEF products certified under ISO 22241, as they are more resistant to low temperatures. I’ve found that regularly checking system temperature and refill levels is crucial to avoid crystallization-induced emission exceedances or engine failures—an essential part of routine maintenance.
