Abstract

A flue-gas scrubbing arrangement removes sulfur oxides and nitrogen oxides from stack gases at low energy costs and converts these into non-noxious ammonium sulfate-nitrate, which is utilizable as an agricultural fertilizer. The flue gases, cleaned of fly ash, pass through a spray dryer, where water is spray-injected to cool and humidify the gas. Then the humidified gas passes through an e-beam reactor where high energy electrons bombard water and oxygen to create strong reagents that react with the SO2 and NOX to form sulfuric and nitric acids. These react with ammonia gas that is injected into the flue gas stream to form sulfate and nitrate salts of ammonia. The ammonia should be present in near stoichiometric amounts relative to the sulfur and nitrogen oxides. The flue gas with the moisture and entrained salts pass to a wet precipitator, where the salts are removed in aqueous solution, and the remaining, scrubbed flue gases pass to the stack. The aqueous solution is then fed back to the spray dryer, where the incoming flue gases pick up the water and precipitate the ammonium sulfate-nitrate as particles of about 100 μm. Cooling water from the electron beam generation equipment can be used as make-up water for the spray dryer.