Novel Membrane Systems for Off-Road Diesel Engine NOx Reduction

The Bush Administration recently proposed a 90 percent reduction of air pollution emissions from off-road diesel equipment. The Administration indicated that diesel emissions are responsible for large amounts of particulate and NOx emissions from off-road construction, farm, mining, and locomotive and marine engines. A primary approach used to reduce NOx emissions is exhaust gas recirculation (EGR). In EGR, the exhaust gas from the engine is recycled to the engine, thereby lowering the oxygen level and engine temperature, which reduces NOx emissions. With EGR, there are questions concerning wear implications of recirculated soot particles as well as problems associated with the need for heat exchangers to cool EGR systems. These concerns related to EGR (wear and heat load for diesel engines), although significant for on-road engines, are even more severe for off-road engines. Off-road vehicles traditionally run at a higher power and lower ram-speed than on-road vehicles. Off-road vehicles also run at a high power for a disproportionately high percentage of time. This leads to very high exhaust gas temperature, and if EGR is used to reduce NOx emissions, there would be very high heat loads placed on the engine. Furthermore, the mechanism to cool exhaust gas involves flowing gas across a heat exchange surface that utilizes the ram-velocity of the engine to assist in cooling. This is more difficult with slow moving off-road vehicles. The net effect takes place in off-road vehicles; the conventional EGR treatment for reduced NOx emissions has major limitations. The goal of this Phase I research project is to introduce a retrofittable membrane system to supply nitrogen-enriched air to diesel engines for reduced NOx emissions instead of EGR. This system would be driven by a turbocharger that feeds high-pressure air into engines. The high productivity of the membrane device will lead to a modest loss in engine power and reduce NOx emissions by 50 percent. Compact Membrane Systems, Inc.¿s (CMS) membranes are not negatively effected by the higher exhaust temperature associated with off-road vehicles because they use ambient air as feed. CMS membranes work best at peak load because turbo pressure is highest at peak load and CMS membranes work best at a high turbo pressure. CMS has strong working relationships with major diesel companies and industrial gas companies. These relationships will be of significant value in Phases I and II, as well as in subsequent commercialization. In Phase I, CMS will demonstrate feasibility related to reductions in off-road diesel NOx emissions, while maintaining fuel efficiency and particulate emissions and industry cost requirements.