Influence of Nitrogen Monoxide on the Complex Phase and Chemical Equilibria in Wet Flue Gas Cleaning Processes

The present paper reports the absorption behavior of sulfur dioxide in the presence of nitrogen oxides (NO and NO2). The absorption process has been studied at 298.65 and 318.45 K and ambient pressure. The results show that after a few hours NO2 vanishes from the gas phase. This leads to a reproducible frozen (stable) state in which tetravalent sulfur exists in phase and chemical equilibrium. The gas phase contains SO2, N2O, and NO. The liquid phase contains a number of nitrogen−sulfur compounds besides tetravalent and hexavalent sulfur and nitrate. The absorption of NO2 is accelerated by the presence of NO, and the solubility of SO2 increases with the increasing amount of NO. The results of model calculations that give the concentration profile of the species produced in this system as a function of time are presented. The effects of temperature and the initial concentration of the gas mixture on the absorption behavior of SO2 are discussed.