Improvement of $hbox{NO}_{rm x}$ Reduction Efficiency in Diesel Emission Control Using Nonthermal Plasma Combined Exhaust Gas Recirculation Process

摘要

Atmospheric-pressure nonequilibrium nonthermal plasma hybrid exhaust gas aftertreatment systems that do not utilize precious metal catalysts, harmful ammonia, etc., have been developed by the authors. Two types of new environmental protection systems (a dry system and a wet system), which enable the production of ultralow $hbox{CO}_{2}$, particulate matter and $hbox{NO}_{rm x}$ emissions as well as reduced fuel consumption and low cost, are investigated for diesel engines, marine engines, and combustion boiler applications. This paper reports the principles of the dry system and some recent experimental results of laboratory tests. The $hbox{NO}_{rm x}$ reduction comprises three flow processes: 1) adsorption, 2) heating, and 3) cooling processes. The heating process corresponds to the regeneration process. These processes are repeated in the following order: 1), 2), and 3). This dry system demonstrates excellent energy efficiencies that meet the most recent Japanese national regulations regarding automobile diesel engine exhaust gas. In this study, approximately 60% of the $hbox{NO}_{rm x}$ of the exhaust ($hbox{NO}_{rm x}$: 240 $sim$ 325 ppm, $hbox{flow rate} = 300 hbox{NL/min}$, N: standard state) can be treated for 35 h. An improved system energy efficiency of 143 $hbox{g} (hbox{NO}_{2})/hbox{kWh}$, which is the highest yet, is achieved for $hbox{NO}_{rm x}$ red-n-nuction.