NOx removal from a flue gas in a corona discharge-catalyst hybrid system

The objective of this work was to investigate NOx removal with a hybrid system consisting of a dc corona discharge and a catalyst at a room temperature (22 °C) in the presence of ammonia. The experimental procedure was as follows. A positive dc corona discharge was generated between a stainless steel hollow needle and a flat mesh made of brass. The needle was placed perpendicularly to the mesh maintaining the interelectrode distance of 40 mm. The outer and inner diameters of the hollow needle were 2 and 1.6 mm, respectively. The catalyst used in this investigation was a layer of V2O5 and TiO2 deposited on Al2O3 globules of 5–6 mm in diameter. They were placed on the mesh so that the distance between the tube and the globules was 30 mm. The catalyst was either saturated with NH3 or free of NH3. A gas mixture of N2 (80%):O2 (5%):CO2 (15%):NO (200 ppm) flowed through the tube with a flow rate of 1 l/min. Ammonia was added to the gas mixture through a hollow needle in a concentration of either 400 ppm when NH3-free catalyst was used or 30 ppm when catalyst saturated with NH3 was used. Results of the investigation showed that the hybrid system (with NH3-saturated catalyst) removes up to 96% of NOx with an energy efficiency of 3.4 g NO/kWh. Without the catalyst, NOx removal in the “pure” corona discharge in the gas mixture with ammonia was lower (up to 66%). Also the energy efficiency was lower (about 1.8 g NO/kWh). The obtained results showed that the investigated corona discharge-catalyst hybrid system is attractive for NOx removal because of relatively high efficiency both in NOx decomposition and energy consumption.