An SDBD plasma-catalytic system for on-demand air purification

Surface-dielectric-barrier discharges (SDBDs) can be applied for a wide range of applications, such as ozone generation, surface treatments, and air-pollutants removal. An important advantage of the SDBD plasma is that relatively low high-voltage (HV) pulses (<10 kV) are needed to generate the plasma. They are effective in removing a wide range of pollutants. Despite their high energy efficiency, plasma decomposition generally results in the reaction by-products and the formation of ozone and nitrogen oxides. This drawback can be overcome by combining the SDBD plasma with catalysis. In this paper, a novel plasma-catalytic topology is proposed for the purpose of on-demand air purification. The main idea of the plasma-catalytic reactor is that both the plasma and the catalytic function are configured as planar structures which are positioned in parallel to each other. The plasma is generated along a planar dielectric structure. We use an SDBD for this purpose. Plates coated with the catalytic material are positioned in parallel to the SDBD plates. The air to be treated is flushed along the plates. There are no restrictions to the type or combination of catalysts used; the catalysts and their specifications can be chosen freely. We have developed a modular plasma-catalytic SDBD reactor to handle large flows, which can be scaled up and scaled down easily. To energize the plasma, an SDBD power modulator was developed. The modulator is able to generate a HV output pulse over an SDBD plasma load with a magnitude adjustable from 4.78 to 6.95 kV. The pulse rise time is about 1μs and its ramp is about 6 kV/μs. The energy per pulse then ranges from 1.1 to 17.4 mJ. The output power can be adjusted up to 48 W at a repetition rate of 5.5 kHz. The maximum possible pulse repetition rate is 22 kHz, but it is limited to 5.5 kHz due to the limited current rating of the available dc power supply. The total energy efficiency of the power modulator is 68%. A single modulator unit can power up to two SDBD reactor plates of 100× 150 mm size, having plasma at both sides of the plate. The operational efficiency of the developed SDBD catalytic reactor has been investigated by studying the removal of NO _x and ethylene. The removal efficiency of NO _x and ethylene is determined as a function of energy density and operational parameters, such as their initial concentrations and the gas flow rate.