Selective Catalyst Reduction
Next-generation SCR technology offers refined diesel performance and lower emissions
Sometimes science isn’t enough.
A process called Selective Catalyst Reduction (SCR), removes harmful nitrogen oxide NOx emissions by converting them into water and harmless nitrogen, while allowing the engine to be calibrated or tuned for maximum efficiency to lower CO2 emissions.
However, the mere existence of the solution doesn’t make it viable for mass production diesel engines. It must be robust – SCR components are required to operate under harsh environments; flexible – it has to fit in the space made available by the vehicle manufacturer and last but not least, it has to be cost-effective.
Delphi’s extensive expertise and capabilities in fuel injection, electronics and software allows it to offer key elements of this system, such as the doser or dosing injector and software and electronics to control the process. This second-generation SCR production offers more refined performance, while consuming less urea.
Delphi has won business with three major global customers. With production beginning in 2018, the company will produce more than one million injectors per year by 2020.
Delphi projects that more than 11 million SCR dosers will be sold annually by 2020 compared to less than 500,000 in 2013-2014. This is a significant volume increase and one of diesel’s most important solutions to stem the tide of negative perceptions seen in recent years.
Here’s the science behind it . . .
In an SCR system, key components include not only the catalyst, but also the urea dosing and injection system.
At the heart of an SCR dosing system is an injector that sprays a liquid-reductant agent, an automotive-grade urea also known as Diesel Exhaust Fluid (DEF), through a special catalyst in the exhaust stream of a diesel engine. For the interest of simplification and since it’s a primary component, we will call this reductant, urea. The urea injected into the exhaust is converted into ammonia and starts the chemical reaction that reduces the NOx into water and nitrogen. Ensuring the injection of the precise amount of urea is critical for the SCR reactions.
Better atomization and smaller droplet size of injected urea allow a more complete conversion to ammonia. As a result, NOx are reduced by up to 80 percent in real world driving conditions.
Delphi’s core dosing injector is derived from our gasoline PFI (Port Fuel Injection) technology that has been in production for over 30 years. Thanks to an extensive material design and research, this injector withstands the properties of the automotive-grade urea whose composition is more corrosive than water.
The system is made with 32.5 percent urea and 67.5 percent deionized water and, like water, it can both freeze and boil - states which can create havoc to the durability of the doser. By re-using our gasoline PFI existing design and manufacturing capabilities to build the SCR core injector down the same line, we are able to offer not only a cost-effective but also a customized solution to fit just right into OEMs’ applications. Delphi also is flexible in providing vehicle manufacturer either a component approach like the doser only or can partner with tank system providers when a complete dosing system is required.
Did you know?
Most people think of SCR as one of these new technologies when in fact SCR is a technology that was invented back in the 1950s and was deployed on a large scale for coal-fired power plants back in the 1970s.