Southwest Research Institute (SwRI) is helping a client develop a simple post-refinery treatment process that reduces exhaust emissions from diesel engines by overcoming the soot/nitrogen oxides (NOx) reduction trade-off that has plagued engine researchers for decades. The result is a modified fuel that potentially could replace today’s ultra-low sulfur diesel, biodiesel and other renewable diesel fuels.
Internal combustion engines, when burning a fuel-air mixture, produce harmful pollutants such as soot and NOx. To decrease emissions, engineers design and calibrate engines to adjust combustion temperatures, but have been stymied by the soot/NOx trade-off. Attempts to reduce soot with increased temperatures results in higher NOx, and lowering the temperature has the opposite effect. The modified fuel reduces soot production without increasing NOx and without requiring engine design or calibration changes.
Although engine manufacturers routinely develop cleaner engines for new vehicles, older model vehicles continue to contribute heavily to pollution levels. This new modified fuel could potentially lower exhaust NOx and particulates for both older and newer model diesel engine vehicles.
“While fossil fuels eventually may be replaced by electric powertrains or noncarbon fuels in our lifetime, the process developed with our client could be implemented immediately,” said project manager James Wood, a principal scientist in SwRI’s Chemistry and Chemical Engineering Division. Reducing soot and NOx could potentially protect human health and the environment from harmful emissions.
SwRI designed, built and operated a bench-scale processing plant to produce modified fuel samples for laboratory testing. This internationally patented breakthrough technology introduces a unique low concentration chemical treatment that is combined with a specialized mechanical mixing system that produces a treated diesel fuel that is stable for long periods of time. This establishes a blend-in process that easily modifies the fuel. The specimens demonstrated conformance to ASTM physical, mechanical, rheological, thermal and chemical fuel requirements.
SwRI’s Powertrain Engineering Division evaluated the fuels during steady-state and transient engine emissions testing according to Environmental Protection Agency test procedures. “The modified fuel resulted in a substantial reduction in soot mass emissions compared to the baseline ultra-low sulfur diesel,” said Dr. Imad Khalek, a senior program manager who operates SwRI’s particulate laboratory.
Based on the bench-scale plant, SwRI helped design a production-scale facility that meets ASTM International and ANSI (American National Standards Institute) standards and is capable of processing 12,000 barrels per day (150 million gallons per year).
Work on this project began about eight years ago with initial proof-of-concept and then the development of a pilot plant. More recently, SwRI has led a fuel formulation investigation project and fuel production procedures development for the client. The modified fuel has undergone evaluation in real-scale heavy-duty certification engines and is available for commercial development.