Heliyon (Feb 2025)
Exhaust gas after treatment using air preheating and selective catalytic reduction by urea to reduce NOx in diesel engine
Abstract
The oxides of nitrogen (NOx) emitted from diesel engines are perilous pollutants, contributing to environmental and health hazards. Selective Catalytic Reduction (SCR) using urea is a proven technology for reducing NOx emissions, while air preheating has been utilized to enhance NOx reduction efficiency. From the studies, a sole focus on urea-SCR with air preheating remains noticeably unexplored. This study presents an integrated approach using urea-SCR and air preheating in a four-stroke, single-cylinder, water-cooled diesel engine for a comparative study in decreasing NOx emissions. The experimental setup involved a mechanical urea injection system, a platinum-rhodium catalyst, and an air-preheating mechanism utilizing exhaust gas heat. Tests were conducted at varying engine speeds and loads to evaluate the combined system's performance. Results indicate that the combined air preheating and urea-SCR system achieved a NOx reduction of up to 55 % under low engine load conditions, with a corresponding CO emission reduction of 19 % for preheated set-up. The system enhanced brake thermal efficiency (BTE) and reduced brake-specific fuel consumption (BSFC) compared to baseline configurations, with no significant backpressure observed. A significant noise level reduction (21–27 %) was also achieved, highlighting the dual benefits of emissions and noise control. The findings demonstrate that combining urea-SCR with air preheating is an effective strategy for reducing NOx emissions while maintaining or improving engine performance. This approach offers a promising pathway for enhancing diesel engine emission control systems. Further studies are recommended to explore the scalability of this method for larger engines and to assess long-term system stability.
