NO Abatement Using Microwave Micro Plasma Generated With Granular Activated Carbon

Abstract

Abatement of NO using microwave micro-plasma is presented in this paper. The micro-plasma is generated using granular activated carbon (GAC) particles of size (2–3 mm) in loosely fluidized bed in a microwave cavity operated at 2.45 GHz. A single-mode microwave cavity reactor (SMMCR) was constructed and microwave was injected through another slotted single-mode waveguide in a sandwiched manner. COMSOL Multiphysics software was used to investigate the microwave electric field and the power density within the SMMCR. Gas mixture of air and 500 ppm NO (in N2) at the flow rate of 2 l/min was passed through a quartz tube centered within the SMMCR, while the supplied microwave power was very low 10–80 W and corresponding NO reduction was greater than 98%. The mass of GAC used for generating the plasma was 5g. The efficiency of NO reduction is found to be 24.84 g(NO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text{2}}$</tex-math></inline-formula> )/kWh. When air is mixed with NO (in N <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{\text{2}}$</tex-math></inline-formula> ), the efficiency of NOx reduction achieved vary greatly with respect to the supplied microwave energy, and behavior has become complex and is not predictable, which needs further investigation. A gas analyzer (testo 350) was used to measure the gas (NO, NO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{\text{2}}$</tex-math></inline-formula> , CO, and O <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text{2}}$</tex-math></inline-formula> ) concentration and temperature.