Alleviating the thermal aging of three-way catalyst applied to natural gas engine based on organic Rankine cycle

Abstract

Natural gas (NG) is a possible pathway for developing countries to reduce transportation carbon footprint. However, its high exhaust temperature decreases the thermal efficiency of NG engines and accelerates the thermal aging of three-way catalyst (TWC). This study proposes to place an organic Rankine cycle waste heat recovery (ORC-WHR) system between an NG engine and its TWC to recover exhaust energy and extend the useful life of TWC. The feasibility of this design concept is confirmed by the simulation results of an experimentally validated 1D NG engine model combined with an ORC-WHR model at three TWC working temperatures representing field-average, modern, and future TWC technologies. Results show that the decrease in the outlet temperature of the ORC-WHR system benefits the availability of exhaust energy, improving the overall efficiency of the engine plus ORC-WHR system and extending the useful life of the TWC. Hence, more advanced catalyst technologies, which can achieve high conversion efficiency at lower temperatures, are deemed more favorable for ORC-WHR coupling. The cost-effectiveness of such combinations is better due to more exhaust energy recovered and less noble metal catalyst needed to be added.