Apparatus for removing SO.sub.2 from flue gases and for producing ammonium sulfate solution

An apparatus for removing SO.sub.2 from a flue gas and for producing an ammonium sulfate solution from which ammonium sulfate can be recovered, said apparatus comprising:

• a scrubber having at least one scrubbing zone traversed upwardly by the flue gas, a distributor above the scrubbing zone for distributing a scrubbing liquid in the upwardly traveling flue gas and for absorption of SO.sub.2 therefrom, and a gas-permeable liquid-collecting bottom below said scrubbing zone;
• means for feeding ammonia-containing water to said scrubbing zone to form part of the scrubbing liquid therein;
• an oxidation unit receiving scrubbing liquid from said liquid-collecting bottom and containing ammonium sulfite and ammonium hydrogen sulfite and oxidizing said ammonium sulfite and ammonium hydrogen sulfite to ammonium sulfate;
• means for forming an absorption-liquid circulation path connecting said liquid-collecting bottom with said oxidation unit and said oxidation unit with said distributor;
• a flue gas duct opening above a sump in said scrubber;
• a flue gas quench comprising a spray device opening into said duct and supplied with a water-containing quenching liquid to saturate said flue gas with water vapor and form droplets therein which are collected in said sump;
• means for recirculating liquid collecting in said sump to said spray device;
• means connecting said oxidation unit with said sump to supply ammonium sulfate solution thereto for concentration of said ammonium sulfate therein;
• a slurry duct connected to said sump for discharging an ammonium sulfate solution from said sump suitable for fertilizer production;
• and
• means connected with said oxidation unit for discharging a solution containing substantially uncontaminated ammonium sulfate.