The technology of selective catalytic reduction of NOx
Selective catalytic reduction (SCR) is an advanced technology to control the emissions of nitrogen oxides as well as other pollutants like particulate matter, hydrocarbons, carbon monoxide and volatile organic compounds from the exhaust stream. A liquid redundant agent is injected through a special catalyst into the exhaust system of the diesel engine to set off a chemical reaction that will convert nitrogen oxide into nitrogen, water and little amounts of carbon dioxide. These elements are present in the air the humans breathe and when they are expelled from the exhaust system, the quality of air is not compromised. The redundant source is usually diesel exhaust fuel (DEF) which is automotive-grade urea.
DEF as an integral component of SCR for the reduction of nitrogen oxides
DEF is a non-hazardous and non-toxic fluid composed of purified water and automotive-grade urea that is available in a wide range of storage and dispensing methods. Consumers have different options from the various sizes of containers that include bulk, totes, bottles and jugs. This ensures that there is no reason why DEF will not be present in the tank at all times. A consistent supply of DEF will ensure a continued operation of the vehicle or stationary equipment. Low levels of DEF supply trigger escalating audible and visible warnings to the driver or equipment operator. It is important not to allow the tank to reach near empty levels and DEF must be replenished immediately otherwise, it can prevent the vehicle from being started. There are various suggestions on the intervals with which DEF replenishment is made which must be strictly followed.
Benefits of using SCR technology
Selective catalytic reduction of NOx is the clear choice of the trucking industry in complying with the emission standards of EPA 2010. The following are the benefits of SCR technology:
- Engine changes are minimized while efficiency is maximized when SCR is used as an after-treatment technology
- SCR technology is simple and easy to use. It only requires a glance at the dashboard to check whether there is an ample supply of DEF
- It eliminates the need for driver fill ups because DEF replenishment can be done during regular servicing.
- SCR technology is cost effective. The investment is offset over the lifetime of the truck
In the consumer car industry, SCR technology is the choice. At present SCR systems can be found in Mercedes Benz, BMW, Jeep, Kia, Hyundai, Volkswagen and many other car manufacturers in North America.