Reduction of nitrogen oxide in N2 by NH3 using intermittent dielectric barrier discharge

Abstract

NO in N2 gas was removed by injecting ammonia radicals, which were externally generated by flowing the NH3 gas diluted with Ar gas through dielectric barrier discharge with a one-cycle sinusoidal-wave power source. The NO reduction for changes in both the applied voltage and the repetition rate was well correlated with the discharge power, which was proportional to the total discharge time per unit time. There was an optimum NH3 concentration in the narrow concentration window for the energy efficiency of NO reduction at a fixed discharge power. The maximum energy efficiency was obtained at small values of the NH3 concentration and the discharge power. The low NH3 concentration effectively increased the energy efficiency by drastically decreasing the discharge-firing voltage.

Plasma Chemistry in an Atmospheric Pressure Ar/NH3 Dielectric Barrier Discharge

“…In the last decade, alternative methods have been developed to improve the efficiency of the NO x reduction by the application of plasma directly to the exhaust gases or even by a combination of direct plasma treatment and SCR 4. Experiments with the so‐called “radical injection method” have also been conducted,5 in which (as assumed by many authors) NH x radicals produced in an atmospheric pressure plasma (DBD or corona) are injected into the exhaust stream and, e.g., initiate the reaction shown in Equation (2). Electronically excited NH* and NH 2 * radicals can be efficiently produced in an Ar/NH 3 DBD by collisions of ammonia molecules with metastable argon atoms, Ar( 3 P 2 , 3 P 0 ): or …”

“…However, the lifetimes of NH and NH 2 radicals are short (a few microseconds) which make their transportation into the main exhaust gas stream difficult at moderate gas flow rates through the DBD system. Nevertheless, this method was just recently efficiently applied to remove NO in an N 2 /NO mixture 5. A mixture of Ar/NH 3 passing through a DBD was mixed with N 2 /NO(1 000 ppmv: 1 ppmv of gas is one part of gas per 1 million parts of a carrier gas in volume units) in a heated chamber, and the dependence of the NO reduction efficiency on the temperature of the exhaust gas was measured.…”

Continuous operation of commercial-scale plasma–chemical aftertreatment system of smoke tube boiler emission with oxidation reduction potential and pH control

“…However, the direct application of nonthermal plasma to treat NO x is not effective because the temperature of flue gas exceeds 300°C and the gas volume is extremely large. As alternative methods for the oxidization and reduction of NO, radical injection methods have been investigated using ozone (O 3 ), ammonia (NH 3 ), nitrogen (N 2 ), and a methane (CH 4 ) and N 2 mixture; these are generated by the indirect plasma (often referred to as remote plasma) in both laboratory-scale and pilot-scale experiments [7][8][9][10][11][12][13][14][15][16][17]. An advantage of the indirect plasma technique is that radicals can be externally produced at ambient temperature and pressure, and injected into the hot flue gas.…”

Molar ratio and energy efficiency of DeNO/sub x/ using an intermittent DBD ammonia radical injection system

“…As the plasma reactors for NO removal, dielectric barrier discharge [1], [2] and corona discharge [1], [3] are typical sources to supply energy to NO gases and/or gases to assist decomposition of NO . Manuscript We have developed a radical injection NO removal system, in which ammonia radicals are generated by dielectric barrier discharge (DBD) in a separate chamber called radical injector, and then injected into a reaction chamber [4], [5]. This system has an advantage to easily control the consumed power to produce ammonia radicals because the power source is an intermittent source because the duty cycle of the power source can easily control the power with no changing the amplitude of the output voltage of the power source.…”