SELECTIVE CATALYTIC REDUCTION (SCR) OF NO BY AMMONIA OVER V2O5/TiO2 CATALYST IN A CATALYTIC FILTER MEDIUM AND HONEYCOMB REACTOR: A KINETIC MODELING STUDY

M Nahavandi

doi:10.1590/0104-6632.20150324s00003584

M Nahavandi

Open Access

https://doi.org/10.1590/0104-6632.20150324s00003584

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Abstract

The present study addresses a numerical modeling and simulation based on the available knowledge of SCR kinetics for prediction of NO conversion over a V2O3/TiO3 catalyst through a catalytic filter medium and honeycomb reactor. After introducing the NH3-SCR system with specific operational criteria, a reactor model was developed to evaluate the effect of various operating parameters such as flue gas temperature, velocity, NH3/NO molar ratio, etc., on the SCR process. Computational investigations were performed based on the proposed model and optimum operational conditions were identified. Simulation results indicate that SCR performance is substantially under the effects of reactant concentration and operating temperature, so that the concentration of unreacted ammonia emitted from reactor discharge (ammonia slip) increases significantly at NH3/NO ratios of more than 1.14 and operating temperatures less than 360 oC and 300 oC, respectively, in the catalytic filter medium and honeycomb reactor. The results also show that there are three sections in NO conversion variation versus changing temperature and the required conversion with a maximum of almost 87% and low level of ammonia slip can be achieved at the NH3/NO ratio of 1 and temperature range of 240–360 oC in both reactors.

Highlights

The concentration of anthropogenic and toxic pollutants in the atmosphere has increased rapidly throughout the last decades, which is basically due to the combustion of fossil fuels and biomass
Nitrogen oxides (NOx) are a group of air pollutants, including nitrogen oxide, nitrogen dioxide and nitrous oxide, considered as very dangerous, since they contribute to the greenhouse effect and participate in photochemical reactions that lead to acid rain
selective catalytic reduction (SCR) performance depends on the temperature and reactant concentration of the flue gas mixture that flows into the SCR reactor

Summary

Introduction

The concentration of anthropogenic and toxic pollutants in the atmosphere has increased rapidly throughout the last decades, which is basically due to the combustion of fossil fuels and biomass. The control of NOx emissions from stationary sources includes techniques of modification of the combustion stage (primary measures) and treatment of the effluent gases (secondary measures). A well-established technology is represented by the ammonia selective catalytic reduction process (NH3-SCR). This method, which was established in the 1970s, has been used mainly for stationary sources and still is the major strategy for the reduction of NO, industrially, due to its high efficiency and the ability of ammonia to react selectively with NOx to form nitrogen (N2) and water (H2O), together with the resistance to poisoning and aging of the applied catalysts (Vega et al, 2011)

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