Integrated Diesel Engine Emission Control Using Plasma-Combined Hybrid System

Innovative diesel particulate (PM) collection and NO_x reduction technology were developed using plasma-combined systems over the years. As for PM control, the electrohydrodynamically assisted electrostatic precipitator (EHD ESP) to collect low resistive diesel PM and the plasma ESP to collect and incinerate PM were developed. As for NO_x reduction systems, NO_x concentration, followed by nitrogen plasma, was developed without using catalysts or ammonia used for selective catalytic reduction. The integrated diesel engine emission component reduction system consists of EHD ESP, plasma ESP, NO_x concentration followed by nitrogen plasma, reactive species injection for NO_x and PM reduction and regeneration, and a NO_x recirculation (EGR) system. Each component technology was evaluated and optimized to establish the state-of-the-art integrated diesel emission control. The integrated plasma-combined hybrid system is extremely economical and practical and leads to zero emission systems.

I. Introduction

Post-Flue gas treatment is essential to meet the stringent requirement from the diesel engine emission regulations. However, the conventional process such as the use of diesel particulate filter (DPF) for PM collection was excellent but not cost-effective. The selective catalytic reduction (SCR) system for removal has practical limitations such as low exhaust gas temperature operation for engine start-up period due to the usage of catalysts, sulfur poisoning, and ammonia. The laboratory- and pilot-scale nonthermal plasma-chemical hybrid processes for removal have been investigated over the years and have demonstrated to achieve an economical and high removal efficiency for boiler applications [1]–[3]. The radical injection (often referred to as indirect plasma or remote plasma) means that air radicals are externally produced at ambient temperature and pressure and are injected into the hot flue gas. It is extremely effective for NO oxidation especially when the flue gas temperature exceeds 300 °C, where is rather generated when the plasma is applied at this temperature. The radical injection methods for the purpose of NO oxidization and reduction have been investigated using ozone , ammonia , nitrogen , and methane and mixture in both laboratory-scale and pilot-scale experiments [4]–[10].