The chemical behaviors of nitrogen dioxide absorption in sulfite solution

The simultaneous removal of nitrogen oxides (NO_x) and sulfur dioxide (SO₂) by absorption is considered to be one of the most promising technologies for flue gas treatment, and sulfite is the main component of the absorption solution. To understand the chemical behaviors of the NO₂ absorption in sulfite solution, the absorption time dependences of concentrations of nitrogen and sulfur compositions in both gas phase and liquid phases were investigated by flue gas analyzer, Ion chromatography (IC), Gas chromatography (GC), and Fourier transform infrared spectrometry (FTIR) methods using a bubbling reactor. The mass equilibrium of the N and S compositions were also studied. The results indicate that sulfite concentration plays a vital role in NO₂ absorption. The main absorption products are NO₃ ^- and NO₂ ^-, and NO₂ ^- can be converted into NO₃ ^- in the presence of oxygen. Besides, about 4% to 9% by-products of S compositions are formed, and 4% to 11% by-products of N compositions such as NO, N₂, N₂O₅, N₂O, and HNO₃ in the gas phase were detected in the emissions from the bubbling reactor. On the basis of N and S compositions, a possible pathway of NO₂ absorption in sulfite solution was proposed.