Simultaneous removal of NO and SO2 through a new wet recycling oxidation–reduction process utilizing micro-nano bubble gas–liquid dispersion system based on Na2SO3

Abstract

Wet desulfurization and denitrification technologies are one of the main research directions in the future air pollution control. Compared with the traditional macro-bubbles, the MNBs can spontaneously generate ·OH with high oxidizing ability, and also improve the gas solubility. Na2SO3 is a strong reducing agent and can react with NO, NO2, NO2– and NO3– to convert ionic N to non-toxic and harmless N2. In the study, based on the principle of wet desulfurization and denitrification, a new recycling oxidation–reduction process was firstly proposed for simultaneous removal of NO and SO2 by using the MNBGLS which was generated with a MNBG through recycling Na2SO3 aqueous solution at a given concentration from a column reactor and the simulated flue gas composed of NO, SO2, N2 and/or other gases such as O2 and CO2. The MNBGLS was recycled continuously from the MNBG to the reactor. The effects of various experimental parameters, such as operation time, initial pH and temperature of absorbent, Na2SO3 concentration, NO concentration, SO2 concentration, the presence of O2 and CO2, on the removal of NO and SO2, were investigated. All the investigated parameters affected the removal of NO, whereas only initial solution pH influenced the removal of SO2. This new process can not only achieve high NO and SO2 removal efficiencies but also treat NO2– and NO3– so as to reduce the cost of subsequent wastewater treatment. Moreover, the main removal product, SO42−, can be recycled. Thus it is an economical, environmentally friendly and efficient desulfurization and denitrification process.