‘Cold-start’ technology could reduce diesel NOx emissions

Researchers at Loughborough University have developed a device which they claim has the potential to ‘significantly’ reduce nitrogen oxide (NOx) emissions in diesel engines.

The ‘Ammonia Creation and Conversion Technology’ (ACCT), developed by the University’s School of Mechanical, Electrical and Manufacturing Engineering, would enhance the capability of existing NOx reduction technology, the researchers claim.

Jonathan Wilson (left) and Professor Graham Hargrave with ACCT

Loughborough’s Professor Graham Hargrave developed the technology with research associate Jonathan Wilson.

ACCT is designed to extend the temperature range at which selective catalytic reduction (SCR) systems can operate.

SCR systems are fitted to most new diesel vehicles to remove NOx emissions, using a fluid known as AdBlue, which at high temperatures turns to ammonia and carbon dioxide, which helps to convert NOx into nitrogen and water.

However, according to Loughborough University, AdBlue only functions well at high exhaust temperatures, typically in excess of 250ºC. The researchers added that as a result of this the SCR does not necessarily operate well at all engine conditions, for example, during short, stop-start commutes, particularly in urban areas or on construction sites.

According to the researchers ACCT is an AdBlue conversion technology that uses waste energy to modify the fluid to work effectively at lower exhaust temperatures. By greatly extending the temperature range at which SCR systems can operate the new technology significantly enhances existing NOx reduction systems.

‘Cold-start’

Commenting, Professor Hargrave said: “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.

“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. 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.”

Technology

Currently the Loughborough technology has been tailored for HGV’s, but the developers claim that the same system is fully scalable for use in all diesel vehicles.

Mr Wilson added: “No viable alternative to the diesel engine currently exists for the heavy duty market and is going to be in use for many more years.

“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.”

The Energy Technology Institute’s (ETI) 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, and it is our belief that the ACCT technology should be further developed as it could help address this challenge in the real world.”