What Is A Diesel Selective Catalytic Reduction (SCR) System?

truck parts

Selective Catalytic Reduction (SCR) is an advanced active emissions control technology system. SCR injects a liquid-reductant agent through a specialized catalyst and into the exhaust stream of a diesel engine. Automotive-grade urea, also known as Diesel Exhaust Fluid (DEF), is usually the reductant source.


The DEF creates a chemical reaction to convert nitrogen oxide into nitrogen, water, and small amounts of carbon dioxide. These components are then expelled through the vehicle tailpipe.


What are SCR systems designed to do?


SCR systems are designed to allow nitrogen oxide (NOx) reduction reactions to happen in an oxidizing atmosphere. SCR systems reduce levels of NOx using ammonia as a reductant in a catalyst system.


The chemical reaction that happens when the DEF enters the exhaust stream is known as reduction. The DEF is the reducing agent that reacts with the NOx to convert the pollutants in the system into nitrogen, water, and carbon dioxide (natural components of the air we breathe).


DEF is capable of being rapidly broken down to produce the oxidizing ammonia in the exhaust system, allowing SCR systems to achieve NOx reductions by 90%.


Why are SCR systems important for semi-trucks?


Carbon emissions are a major threat to the environment and our air. SCR technology is not only effective in helping heavy-duty diesel truck engines meet EPA emissions standards to reduce carbon emissions but it's also effective in helping those same trucks meet maximum efficiency.


Heavy-duty commercial trucks are the largest sector for using SCR technology. SCR is capable of reducing NOx emissions by 90% and reducing hydrocarbon (HC) and CO emissions by 50% to 90%. SCR can also reduce exhaust particulate matter (PM) by 30% to 50%.


SCR technology enables semi-trucks and other large vehicles to operate efficiently and effectively while minimizing their impact on air quality and the climate crisis.


Looking for an SCR system or other semi truck parts?


It's no secret that truck replacement parts as a vital part of the automotive industry. In fact, the global automotive aftermarket industry is expected to reach up to $722.8 billion by 2020.


If you're looking for big truck replacement parts and big truck accessories, BIG Machine Parts is the place for you. For more information on SCR systems and other big semi truck parts, contact BIG Machine Parts today.

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