Number 17 in the Clean Air Technologies Series.
Using technology to knock out NOx (nitrogen oxide) levels in diesel exhaust with the aid of what’s called Diesel Exhaust Fluid (DEF), isn’t something new. In fact, DEF has been available from one supplier since 2003.
Available in liquid form, the DEF additive effectively is composed of two parts deionized water and one part high-purity urea, according to Wikipedia.
Added Reed Fujii in a Mar. 13, 2013 Stockton (Calif.) Record article, “When sprayed into diesel exhaust in the presence of a catalyst, it breaks down oxides of nitrogen – a major component of smog – into nitrogen and water.”
Interesting to note is how the process works.
With regard to attaining near-zero NOx emission release levels from 2010 and newer on-highway diesel engines as per a United States Environmental Protection Agency (EPA) requirement, as explained in a Cummins Filtration press release, “The SCR [Selective Catalytic Reduction] systems work by injecting DEF into the engine exhaust, creating ammonia which then flows through a SCR catalyst and reacts to form harmless nitrogen and water vapor.”
In a second Cummins Filtration press release “Cummins Filtration to Support SCR Equipped 2010 Engines with Diesel Exhaust Fluid,” meanwhile, the company stated, “Availability of DEF is an important industry focus since current pre-production estimates of DEF consumption suggest new trucks will burn approximately two gallons of DEF for every 100 gallons of diesel fuel. New trucks will be equipped with DEF tanks ranging in capacity from 10 gallons, depending on the application. It is expected that DEF refills will be required on a bi-weekly basis depending on tank capacity and mileage.”
Having to do with diesel retrofits, in “National Clean Diesel Campaign (NCDC)” subhead, “Technologies: Diesel Retrofit Devices” as it pertains to SCR, the EPA notes reductions of up to an estimated 75 percent of NOx emissions are typical, further emphasizing: “Selective Catalytic Reduction (SCR) Systems inject a reductant, also known as diesel exhaust fluid (DEF), into the exhaust stream where it reacts with a catalyst to convert NOx emissions to N2 (nitrogen gas) and oxygen.” Moreover, “Because of new NOx standards, most 2010 and newer on-highway diesel engines come equipped with an SCR system. A DEF refueling infrastructure is in place, facilitating the use of SCRs.”
In addition, the EPA also specified that nationwide, roughly 7.3 million tons of nitrogen oxides are emitted from diesel engines yearly.
Keep the NOx emissions levels reductions coming.
– Alan Kandel