LONDON, UK, May 31, 2017 (ENS) - An industry-first technology developed by researchers at Loughborough University has the potential to slash nitrogen oxide (NOx) emissions from diesel engines by extending catalytic reduction systems to operate efficiently at lower temperatures.
More than half the European passenger fleet is diesel-powered, and diesel vehicles contribute about 80 percent of traffic-related NOx emissions, states a January 2016 article in the U.S. government publication "Environmental Health Perspectives."
Although the European Union has been tightening vehicle emissions for decades, new diesel cars still produce on-road NOx emissions that far exceed the current standard.
NOx emissions are also the primary cause of smog in major cities around the world and are a growing public health concern.
In 2015 the UK government estimated that exposure to NOx and particulate matter emissions from diesel engines leads to 52,000 additional deaths in the UK each year.
These facts have increased the pressure on vehicle manufacturers to reduce engine emissions, with new European NOx reduction targets for on-highway and heavy-duty diesel vehicles now so low they are difficult to meet.
The Ammonia Creation and Conversion Technology (ACCT) is the only technology of its kind in the world. Created by scientists at Loughborough University’s School of Mechanical, Electrical and Manufacturing Engineering, it increases the capacity of existing on-engine after-treatment systems.
Currently, almost all new diesel vehicles are fitted with a Selective Catalytic Reduction (SCR) system that works to remove the NOx produced by combustion.
This system uses AdBlue™ to safely provide the ammonia required to transform NOx into harmless nitrogen and water.
AdBlue is the registered trademark for AUS32, or Aqueous Urea Solution 32.5 percent that is used with the Selective Catalytic Reduction system to reduce emissions of oxides of nitrogen from the exhaust of UK diesel vehicles.
The drawback is that AdBlue only functions well at high exhaust temperatures, typically in excess of 250ºC. Selective Catalytic Reduction systems do not necessarily operate at all engine conditions.
SCR systems may not function well during short, stop-start commutes, particularly in urban areas or on construction sites.
Use of AdBlue at these problematic lower temperatures can result in severe exhaust blockages and possible engine damage, the Loughborough scientists warn.
Their discovery, ACCT, is an AdBlue conversion technology that uses waste energy to modify AdBlue so it will work effectively at these lower exhaust temperatures.
By extending the temperature range at which SCR systems can operate, the new technology enhances existing NOx reduction systems.
Loughborough Professor Graham Hargrave, an internationally acclaimed expert on the optimization of combustion engines, developed the technology with research associate Dr. Jonathan Wilson.
“We are all familiar with the cold start, where diesel vehicles spew out plumes of toxic emissions before their catalytic systems are up to temperature and able to work effectively,” said Professor Hargrave.
“Unfortunately with many vehicles doing short stop/start journeys, such as buses and construction vehicles, many engines never reach the optimal temperature required for the SCR systems to operate efficiently," he said. "The result is excessive NOx being released into the urban environment, especially in large cities."
"Our system enables the SCR systems to work at much lower temperatures - as low as 60oC. This means that the NOx reduction system remains active through the whole real world driving cycle, leading to significant reductions in tailpipe emissions,” Hargrave said.
“No viable alternative to the diesel engine currently exists for the heavy duty market and it is going to be in use for many more years,” said Wilson.
“Systems are needed now that tackle NOx emissions, to help reduce the number of air pollution related deaths and enable vehicle manufactures to meet the ever-reducing emissions targets set by the government. ACCT is the answer.”
Currently, the Loughborough technology has been tailored for heavy goods vehicles, but the researchers say the same system is fully scalable for use in all diesel vehicles.
The Energy Technology Institute's Chief Technology Officer for Heavy Duty Vehicles, Chris Thorne said, “Based upon a brief review, the ACCT technology recently developed by Loughborough has the potential to viably produce gaseous ammonia at temperatures significantly below 190°C, thus enabling increased conversion efficiency and lower NOx emissions."
“It is likely that emissions legislation will become even tighter and vehicle manufacturers will need to develop technologies to address this," said Thorne. "It is our belief that the ACCT technology should be further developed as it could help address this challenge in the real world.”
PHOTO: Dr. Jonathan Wilson tests the ACCT system at Loughborough University's Energy Technology Institute 2017 (Screengrab from video courtesy Loughborough University)