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

NOx removal from an actual boiler flue gas is investigated using an indirect plasma and chemical hybrid system comprising a commercial ozonizer and an Na2SO3 chemical scrubber. A high NOx removal efficiency in the continuous operation of a commercial-scale apparatus is achieved by controlling pH and oxidation reduction potential (ORP) and injecting additional Na2SO3 and NaOH aqueous solutions into the scrubber sump when required. Ozone injection is demonstrated to be extremely effective for NO oxidation. The relation between the ORP and NOx removal efficiency, which is essential for the optimal operation of this system, is obtained.