Absorption of NO with Fe~II EDTA Solution Enhanced by Na_2SO_3 and Lean SO_2 in FGD Effluent

The emission of NO causes acid rain,photochemical smog and respiratory diseases to mankind.Experiments of NO absorption by FeⅡEDTA were carried out and the results confirmed that it was an effective method which could meet stringent waste gas emission regulations.The results also showed that the NO removal efficiency decreased with the increase of temperature.Equilibrium constants K at 303,313 and 323K were 1.69×106,1.38×106 and 1.20×106,respectively.pH value of the absorption solution affected NO absorption obviously.The optimum NO absorption occurred under the weak alkaline condition.By employing buffer capacity theory it was found that the theoretically permitted maximum pH value for NO absorption by FeⅡEDTA was 10.5.The addition of Na2SO3 demonstrated that Na2SO3 not only played an important role as a reducing agent but also improved buffer capacity.The presence of 0.01% SO2 greatly prolonged the period of NO absorption by 1.57 times and increased the absorption capacity of NO by 35.39% within 495 min as well.SO2 provided SO32-to compensate for the consumption of Na2SO3.This suggested that the existence of low concentration of SO2 enhanced the performance of Na2SO3 and promoted NO absorption.