What is Automotive Urea?

[LaAlina]

Automotive urea is a colorless, transparent liquid stored in the urea tank. When sensors detect nitrogen oxides in the exhaust pipe, it automatically sprays atomized automotive urea, which mixes with the nitrogen oxides and undergoes a redox reaction in the SCR catalytic reaction tank, ultimately producing non-polluting nitrogen and water that are expelled. Automotive urea is an essential additive for the SCR (Selective Catalytic Reduction) solution. The SCR system includes a urea tank (containing diesel exhaust fluid) and an SCR catalytic reaction tank. The primary harmful substances in diesel vehicle exhaust are nitrogen oxides and particulate matter. While particulate emissions can be reduced through technical means within the engine, nitrogen oxides remain the main component of the exhaust. By injecting urea into the exhaust after-treatment device, the urea decomposes into ammonia at high temperatures. Under the action of a catalyst, the ammonia reacts with nitrogen oxides to produce harmless nitrogen and water. This device is called the SCR after-treatment system.

[LeBeau]

Just helped my buddy add this stuff to his truck a few days ago. Diesel exhaust fluid (DEF) is a liquid used for diesel vehicle exhaust treatment, specifically targeting those black smoke emissions. The principle is quite interesting - diesel vehicles have a device called SCR system in the exhaust pipe that sprays urea solution, which turns into ammonia gas when meeting high-temperature exhaust. This ammonia gas can neutralize the irritating nitrogen oxides in the exhaust, eventually converting them into harmless nitrogen and water. What many people don't know is that this isn't just any diluted water solution - it requires 32.5% high-purity automotive-grade urea. Those attempts using agricultural urea mixed with water are completely wrong and can damage the SCR system. Truck drivers especially need to pay attention to carrying two barrels onboard - during long hauls, running out of DEF can lead to immediate torque limitation and fines.

[HenryLee]

As an environmental enthusiast, this is a perfect topic to discuss. Diesel Exhaust Fluid (DEF), commonly known as AdBlue in Europe, is essentially a solution used in diesel engines for exhaust treatment. Its primary function is to tackle the issue of black smoke emissions from diesel vehicles. Thanks to urban clean air initiatives, heavy-duty vehicles no longer emit thick black smoke from their exhaust pipes, largely due to DEF. After each refill, the urea decomposes into ammonia within a special device in the exhaust system, where it chemically reacts with nitrogen oxides. It's worth noting that since the implementation of the China VI emission standards, DEF systems have become mandatory for all diesel vehicles. When purchasing, always look for the CGT certification mark to ensure reliability.

[VanParker]

Having driven trucks for ten years, the urea tank is as essential to me as my thermos. Simply put, it's the 'purifier' for diesel vehicles, consuming about 1.5 to 2 liters per 100 kilometers. In summer, be extra careful not to overfill it, as high temperatures can cause expansion. The biggest headache in winter is when it freezes at -11°C—we drivers in the northeast always wrap the tank with insulation. Nowadays, most gas stations sell 20-liter plastic jugs; just make sure to choose reputable brands. Here’s a lesser-known fact: if the urea nozzle gets clogged, the truck’s speed will be limited to 20 km/h. Once, I was stuck on the highway and nearly lost my mind.

[GabrielFitz]

From a chemical perspective, it's particularly fascinating. This liquid primarily consists of 32.5% high-purity urea and 67.5% deionized water, with a mixing ratio accuracy requirement of ±0.7%. The key point is that under high-temperature conditions in the exhaust pipe, it undergoes hydrolysis, producing isocyanic acid and ammonia gas. The ammonia then reacts with nitrogen oxides on the catalyst surface for reduction. Be aware that calcium and magnesium ions in inferior products can form white crystals that clog the injector nozzles - repairs can cost over ten thousand yuan. It's recommended to use a diagnostic tool during each maintenance check to read the system status and verify if the injection quantity is normal.