NOx Reduction and Desorption Studies Under Electric Discharge Plasma Using a Simulated Gas Mixture:A Case Study on the Effect of Corona Electrodes

In this study, reduction and desorption of oxides of nitrogen （NOx） were conducted using an electrical discharge plasma technique. The study was carried out using a simulated gas mixture to explore the possibility of re-generation of used adsorbents by a nonthermal plasma desorption technique. Three different types of corona electrodes, namely, pipe, helical wire, and straight wire, were used for analyzing their effectiveness in NOx reduction/desorption. The pipe- type corona electrode exhibited a nitric oxide （NO） conversion of 50%, which is 1.5 times that of the straight-wire-type electrode at an energy density of 175 J/L. The helical-wire-type corona electrode exhibited a NOx desorption efficiency almost 4 times that of the pipe-type electrode, indicating the possibility that corona-generated species play a crucial role in desorption.

Catalyst-Packed Non-Thermal Plasma Reactor for Removal of Nitrogen Oxides

A single-stage plasma-catalytic reactor in which catalytic materials werepacked was used to remove nitrogen oxides. The packing material was scoria being made of variousmetal oxides including Al_2O_3, MgO, TiO_2, etc. Scoria was able to act not only as dielectricpellets but also as a catalyst in the presence of reducing agent such as ethylene and ammonia.Without plasma discharge, scoria did not work well as a catalyst in the temperature range of 100 ℃to 200 ℃, showing less than 10% of NOx removal efficiency. When plasma is produced inside thereactor, the NOx removal efficiency could be increased to 60% in this temperature range.

Discharge Plasma Assisted Adsorbents for Exhaust Treatment: A Comparative Analysis on Enhancing NO_x Removal

An analysis has been made on the discharge plasma coupled with an adsorbent system for NOx removal. The cascaded plasma-adsorbent system may be perceived as a better alternative for the existing adsorbent-based abatement system in the industry. In this study the exhaust is sourced from a diesel generator set. It was observed that better NO removal in a plasma reactor can be made possible by achieving higher average fields and subsequent NO2 removal can be improved using an adsorbent system connected in cascade with the plasma system. The paper describes various findings pertaining to these comparative analyses.

DeNOx Study in Diesel Engine Exhaust Using Barrier Discharge Corona Assisted by V_2O_5/TiO_2 Catalyst

A plasma-assisted catalytic reactor was used to remove nitrogen oxides (NOx)from diesel engine exhaust operated under different load conditions. Initial studies were focused onplasma reactor (a dielectric barrier discharge reactor) treatment of diesel exhaust at varioustemperatures. The nitric oxide (NO) removal efficiency was lowered when high temperature exhaust wastreated using plasma reactor. Also, NO removal efficiency decreased when 45% load exhaust wastreated. Studies were then made with plasma reactor combined with a catalytic reactor consisting ofa selective catalytic reduction (SCR) catalyst, V_2O_5/TiO_2. Ammonia was used as a reducing agentfor SCR process in a ratio of 1:1 to NOx. The studies were focused on temperatures of the SCRcatalytic reactor below 200℃. The plasma-assisted catalytic reactor was operated well to remove NOxunder no-load and load conditions. For an energy input of 96 J/l, the NOx removal efficienciesobtained under no-load and load conditions were 90% and 72% respectively at an exhaust temperatureof 100 ℃.

Unfiltered Diesel Engine Exhaust Treatment by Discharge Plasma: Effect of Soot Oxidation

A cascaded system of electrical discharges (Non-thermal plasma), catalyst andadsorption process was investigated for the removal of oxides of nitrogen (NO_x) and carbonmonoxide (CO) from a Diesel engine raw exhaust. The three processes were separately studied first,and then the cascaded processes, namely plasma-catalyst and plasma-adsorbent, were investigated. Inthis paper main emphasis was laid on the effect of carbonaceous soot oxidation on the plasmatreatment process. While the cascaded plasma-catalyst process exhibits a higher CO removal, thecascaded plasma-adsorbent process exhibits a higher NO_x removal. The experiments were conductedunder no-load. The plasma and adsorbent reactors were kept at room temperature throughout theexperiment while the catalyst reactor was kept at 200℃ / 300℃.

Studies on Nitrogen Oxides Removal Using Plasma Assisted Catalytic Reactor

An electric discharge plasma reactor combined with a catalytic reactor wasstudied for removing nitrogen oxides. To understand the combined process thoroughly, dischargeplasma and catalytic process were separately studied first, and then the two processes were combinedfor the study. The plasma reactor was able to oxidize NO to NO_2 well although the oxidation ratedecreased with temperature. The plasma reactor alone did not reduce the NO_x (NO+NO_2) leveleffectively, but the increase in the ratio of NO_2 to NO as a result of plasma discharge led to theenhancement of NO_x removal efficiency even at lower temperatures over the catalyst surface(V_2O_5-WO_3/TiO_2). At a gas temperature of 100℃, the NO_x removal efficiency obtained using thecombined plasma catalytic process was 88% for an energy input of 36 eV/molecule or 30 J/l.

Study of Pulsed Plasma in a Crossed Flow Dielectric Barrier Discharge Reactor for Improvement of NO_x Removal in Raw Diesel Engine Exhaust

Improved performance of plasma in raw engine exhaust treatment is reported. A new type of reactor referred to as of cross-flow dielectric barrier discharge （DBD） was used, in which the gas flow is perpendicular to the corona electrode. In raw exhaust environment, the cross-flow （radial-flow） reactor exhibits a superior performance with regard to NOx removal when compared to that with axial flow of gas. Experiments were conducted at different flow rates ranging from 2 L/min to 25 L/min. The plasma assisted barrier discharge reactor has shown encouraging results in NOx removal at high flow rates.

Achieving Better NO_x Removal in Discharge Plasma Reactor by Field Enhancement

Application of plasma chemistry for gas cleaning is gaining prominence in recent years, mainly from an energy efficiency point of view. In this paper we conducted a comparative study of NO/NOx removal using two different types of dielectric barrier discharge electrodes, wire- cylinder reactor, pipe-cylinder reactor. Investigations were first carried out with synthetic gases to obtain the baseline information on the NO/NOx removal with respect to the two geometries studied. Further, experiments were carried out with raw diesel exhaust under loaded condition. A high NOx removal efficiency of 90% was observed for the pipe-cylinder reactor as compared to that of 53.4% for the wire-cylinder reactor. Furthermore, for the same energy consumed per NO molecule （about 73 eV/NO molecule）, the removal efficiency increased from 67% for the wire- cylinder to about 98% for the pipe-cylinder which was quite appreciable.