Efficient Denox using an Intermittent DBD with One Cycle Sinusoidal Power Source

Summary form only given. Nitric oxide (NOx) gases are emitted from sources such as thermoelectric power plants and diesel automobiles. It is important to reduce them to preserve air environment. There are needs for the removal of NO gases, where a high efficient and maintenance-free NO/NOx removal system is demanded. The efficient NOx removal (DeNOx) system is expected to use plasma reactors, because plasma species have a high average energy enough to easily decompose NO/NOx species. We have already developed a radical injection system using an intermittent dielectric barrier discharge (DBD) produced by a power source with a one-cycle sinusoidal output. Ammonia radicals are produced in a separate plasma chamber from the reaction zone for DeNOx. An energy efficiency of 250 g/kWh was obtained. The system developed in this paper is based on the previously developed one. However, the different point is that NO is directly decomposed in the DBD plasma. By this, the system can be compact. This paper concerns a direct decomposition of NO gas, which flows through an intermittent DBD plasma generated by the same power source as the radical injection system. An energy efficiency of 100 g/kWh is attained, where the duty cycle of the power output is optimized. The power source with an intermittent output voltage is advantageous to easily control the consumed power. A parametric survey for the optimization of DeNOx is carried out for DeNOx. Several parameters are varied: applied voltage and its duty cycle, gas temperature, gas flow rate, NO concentration, concentrations of additive gases as ammonia, argon, and methane. In the case of direct decomposition of NO gas, oxygen contained in the NO/N₂ gas flow significantly influences the DeNOx characteristics. In the previously-developed radical injection method, oxygen does not significantly influence the DeNOx characteristics, because oxygen is not activated. In the direct DeNOx system, in which oxygen-contained NO gas fl- ows through the DBD plasma, oxygen is activated. The byproduct of DeNOx is mainly NO₂. NO₂ is hardly produced in the absence of oxygen, where NO may be decomposed to be N₂ and O₂. The excess of oxygen contained in the NO gas flow field contributes to prepare NO₂ from N₂ and O₂. NO₂ formation from N₂ and O₂ is confirmed by decomposition test of a simulated air (N₂/O₂ = 80/20%). By optimizing the parameters for DeNOx, energy efficiencies of 100 g/KWh and 50 g/kWh are obtained in the absence and in the presence of oxygen, respectively.