Diesel Exhaust Fluid (DEF) is a nontoxic and safe-to-handle solution of urea in water - around one-third urea to two-thirds water - that is required by many new diesel trucks and buses equipped with selective catalytic reduction exhaust emissions control equipment (SCR). DEF is injected in small volumes into the exhaust upstream of a catalyst, where it vaporises and decomposes to create ammonia and carbon dioxide. The desired product is ammonia (NH3), which, in conjunction with the SCR catalyst, transforms NOx to harmless nitrogen (N2) and water (H2O).
Diesels have EGR as well, but because they combust so hot, EGR alone is insufficient. After passing through several different pollution control devices, the exhaust is sprayed with DEF fluid. The remaining pollution is handled by a chemical reaction, which converts it into harmless compounds. As a result, DEF is used up during the procedure. But, after the DEF is filled, it consumes relatively little fuel. As a result, you won't have to fill it up as frequently.
Diesel Exhaust Fluid objective is to minimise the concentration of nitrogen oxide (NOx) in diesel engine exhaust emissions. DEF is often carried in a separate storage container or tank in diesel-powered vehicles before being injected into an engine's hot exhaust stream. This process aids in the breakdown of NOx gases in exhaust, converting them to nitrogen gas and water vapour, both of which are harmless to the environment.
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