Follow-up research for integrative process of pre-oxidation and post-absorption cleaning flue gas: Absorption of NO2, NO and SO2

Abstract

A method for simultaneous removal of SO2, NO2 and NO from coal-fired flue gas by sodium humate (HA–Na) solution was proposed. The effects of various influencing factors on the simultaneous removal were investigated systematically, such as the concentration of HA–Na, the reaction temperature, the pH of HA–Na solution and the coexistence gases in the simulated flue gas. The experimental results indicated that the desulfurization efficiency was constant at 100% in almost all tests, whereas the removal of NO2 and NO was significantly affected by the reaction temperature, the pH of HA–Na solution and the coexistence gases. SO2 was characterized as either promotion or inhibition on NOx removal, depending on the concentration. NO2 and O2 as two gas oxidants can promote NO removal. However, the introduced CO2 will compete with SO2 and NOx for HA–Na, which results in a decrease of simultaneous removal. Under the established optimal reaction conditions, the simultaneous removal efficiencies of 100% for SO2, 99.6% for NO2 and 65% for NO were obtained. The main products were identified as humic acid (HA), sulfate, nitrite and nitrate based on the characterizations by FT-IR, XRD, IC and EDX.