Come 2010, engine manufacturers will have to meet the U.S. Environmental Protection Agency’s more stringent diesel emission standards. These regulations will dramatically reduce discharges of both particulate matter (soot and ash), hydrocarbons and nitrogen oxide (NOx).
To do this, manufacturers are making engine modifications for cleaner combustion and adding exhaust aftertreatment devices. The exhaust aftertreatment devices remove pollutants from exhaust gases after they leave the engine’s combustion chamber.
Meeting the reduced pollutants standards has required a change in diesel fuel to ultra-low sulfur diesel fuel (ULSD) and a reformulation of engine oils. ULSD is a cleaner-burning fuel that inherently produces less particulate emissions from combustion.
Engine oils had to be developed for lubrication oil compatible with the new low-emissions solutions. Designated CJ-4 oils, also called low-ash oils because they are formulated with a lower sulfated ash level, have been designed with better wear protection, higher oxidation protection and better soot handling characteristics.
Beyond this, engine manufacturers are using two types of technology â€” selective catalytic reduction (SCR) and exhaust gas recirculation (EGR) â€” to comply with the 2010 diesel emissions regulations. These technologies control nitrogen oxide emissions. To handle particulate matter emissions, diesel particulate filter (DPF) technology is required.
In essence, SCR is a system that works by a chemical reaction triggered by heat. It treats the downstream exhaust by injecting a fine mist of diesel exhaust fluid (DEF) into the exhaust gas. The high temperature converts nitrogen oxide levels into harmless levels of nitrogen and water vapor, and eliminates the diesel smell.
Diesel exhaust fluid, also known as urea, is an organic compound that is harmless to the environment. Urea is already widely distributed for many other industrial and agricultural needs.
Urea consumption varies with duty cycle and other factors. A rule of thumb is that 1 gallon of urea will take a truck about 250 miles.
SCR systems require a separate container for urea, along with extra wiring, hoses and sensors to manage the injection flow of urea into the truck’s exhaust stream. In simple terms, exhaust gas recirculation, also referred to as cooled EGR, captures a small proportion of exhaust gas and injects it into the engine’s combustion cycle, along with fresh air and fuel. This slows down the violence of the combustion itself, resulting in a lower level of nitrogen oxide emissions. Unlike SCR, EGR does not require an additive.
Both EGR and SCR are proven technologies that have been used in a wide range of applications around the world to meet emission requirements for diesel-powered commercial vehicles.
Diesel particulate filters, installed in place of mufflers, typically contain a porous substance to “strain” and “catch” the particulate matter from the exhaust stream and prevent the particles from reaching the atmosphere.
Over time, these traps “fill up” and need to be periodically cleaned by means of a regeneration process. Otherwise, the filter can plug up and adversely affect the engine’s performance and fuel economy.
This regeneration process is typically achieved by burning off the trapped particulate matter.
There are two types of regeneration: passive and active. With passive regeneration, particulate matter is continually burned off while a vehicle is driven. Active regeneration refers to a periodic burning off of particulate matter by adding a small amount of diesel fuel into the exhaust gas.
Active regeneration typically won’t be necessary for those applications where truck engines work hard enough to generate the heat necessary to continually burn off the trapped particulate matter. They may, however, be required for those applications where vehicles do a lot of stop-and-go operation or prolonged idling.
Drivers will not notice passive regeneration, as the engine continues to operate normally. The only sign of the regeneration is an indicator light on the dashboard.
A major concern about the adoption of SCR is whether an infrastructure for urea will be in place by 2010. To that end, a number of companies in the refining, packaging and distribution segments of the nation’s fuel market are preparing to provide diesel exhaust fluid availability.
Most recently, Accuride Corp., a manufacturer of commercial vehicle components, has entered into a joint venture with Benecor, a company that designs and develops dispensers for urea. The two are working together to expedite the manufacturing and installation of urea storage and dispensing units at truck stops, diesel fueling stations and fleets throughout North America.
Brenntag, the world’s largest distributor of automotive-grade urea, has launched its Urea 2010 initiative. It is a national program to provide diesel exhaust fluid availability by coordinating the necessary supply of urea, blending capabilities and flexible packaging options.
The company, which has extensive experience with diesel exhaust fluid, already has more than 120 locations throughout the United States and Canada and currently is distributing some 150,000 gallons of DEF every day.