Purifying SO2- and NOx-containing flue gases

摘要

Flue gas purification processes which bind the pollutants SO2 and NOx to ammonia generate as by-products ammonium sulphate, ammonium nitrate and mixed crystals of both. In the process to which the present invention relates, SO2 and NOx are converted with the aid of ionising radiation in the presence of steam to sulphuric acid and nitric acid. During the reaction with ammonia, ammonium nitrate and ammonium sulphate nitrate, particularly useful as fertiliser, are formed in particles which are too small. The particle size can be positively influenced according to the invention by additionally adding, instead of ammonia and water separately alone, ammonia water into the reaction space, by spraying a highly concentrated ammonium sulphate nitrate solution there as collector, by recirculating fine grains from the downstream filter into the irradiation chamber and/or by irradiating in several stages at relatively low intensity.