Oxidative Scrubber for NOx Emission Control Using NaClO2 Aqueous Solutions

Abstract

Oxidative scrubbing using different oxidizing chemicals (e.g. sodium chlorite, NaClO₂) has been proposed since several years for gas emissions control. Although higher performances than conventional after-treatment process currently in use can be reached, these technologies have not yet found a consolidated application in the power generation and other industrial fields, due to excessive chemical consumption and the formation of some harmful contaminants in the wash water that must be removed with specific treatment systems.
This work reports an experimental investigation of an oxidative wet scrubber for NO_x removal from a simulated flue-gas containing 1030 ppm_v of nitrogen oxides, using a scrubbing liquid doped with sodium chlorite (NaClO₂) as oxidizing chemical. The experiments are performed in a packed column operating in counter-current flow with a constant gas velocity of 1.15 m/s at 60 °C and a liquid-to-gas ratio variable from 1.25 to 4.06 L/m³. The packed column with a DN 100 is equipped with 892 mm of Mellapak 250.X packing.
The experimental removal efficiencies of NO_x are evaluated in function of the liquid flow rate and NaClO₂ loading. These data allow to determine the specific NaClO₂ dosage required to achieve a fixed NO_x removal. Finally, a predictive correlation for wet oxidative scrubbing is also developed.