Simultaneous Control of Unburned NH3 And Nox Emissions From High Load Dual-Fuel Ammonia Operation On A High Speed Diesel Engine Using A Cu-SCR System

Abstract

Dual-fuel ammonia (NH3) strategies are being investigated as a promising way to utilize NH3 as an alternative fuel for internal combustion engines in the maritime sector. One of the remaining barriers to implementing dual-fuel NH3 combustion strategies is understanding ways to minimize unburned NH3 and nitrogen oxide (Nox) emissions from these engines, both of which are elevated relative to a conventional diesel baseline. Selective catalytic reduction (SCR) systems are widely used for lean Nox emissions controls for engines across transportation and stationary energy applications. SCR systems use a reducing agent, such as NH3, to react with Nox in the exhaust, converting it into nitrogen and water. The presented work evaluates a commercial copper-zeolite SCR and ammonia slip catalyst system, designed for on-road diesel engine applications, for controlling unburned NH3 and Nox emissions from a dual-fuel NH3 combustion engine. The emissions were characterized by using a Fourier transform infrared spectrometer for both late- and early-injection diesel pilot strategies over three air-fuel equivalence ratios spanning from 1.6 to 1.0 at 1,200 rpm and 12.6 bar IMEPg condition (with greater than 95% ammonia energy fraction). Initial findings indicate that the SCR achieves more than 99% Nox conversion with less than 50 ppm NH3 slip at air-fuel equivalence ratios greater than 1.4 at the operating conditions investigated. However, these benefits are accompanied by additional N2O emissions that are formed over the Cu-SCR.