Research on removal of NOX, SO2 and PM from flue gas of coal-fired boilers and engineering application

Removal of NOX and SO2 from flue gas by Ozone (O3) oxidation and NaOH absorption was carried out in practical engineering. The effects of the liquid to gas ratio (L/G), the molar ratio of O3 dosage and initial content of NOX (O3/NOX), pH and NaOH concentrations on the removal efficiencies of NOx and SO2 were investigated. In addition, the influences of O3/NOX and voltage on the removal of PM were analyzed. The results show that the NOX removal efficiency increases with the increasing of O3/NOX (0∼2.0), solution pH (4∼7) and L/G (2∼8), while is slightly affected by NaOH concentration (0.05∼1%). The SO2 removal efficiency increases with the increase of L/G from 2 to 8 L/Nm3, but is hardly changed by O3/NOX (0∼2.0), NaOH concentration (0.05∼1%) and solution pH (4∼10). It was found that the outlet concentration of PM (CPM) decreased with the rise of voltage ranging from 0 to 40 kV, however, slightly increases with the increment of O3/NOX at a range from 1.6 to 2.0. The optimal operating conditions can be established when taking running costs and rigorous ultra-low emission standards into consideration. Under the optimal conditions, the removal efficiencies of NOX and SO2 reached more than 75% and 98% respectively, and CPM could be also controlled within 5 mg/Nm3.