Flue gas desulfurization process and apparatus for removing nitrogen oxides

A flue gas scrubbing apparatus for removing nitric oxide gas and acidic gases from a flue gas, the flue gas scrubbing apparatus comprising:

• means for contacting the flue gas with an ammonium sulfate-containing scrubbing solution so that the scrubbing solution absorbs acidic gases from the flue gas to produce an acidic gas-containing solution and an intermediate flue gas;
• a vessel containing the ammonium sulfate-containing scrubbing solution and in which the acidic gas-containing solution is accumulated;
• means for reducing the temperature of the intermediate flue gas to convert nitric oxide within the intermediate flue gas to nitrogen dioxide;
• means for contacting the intermediate flue gas with a water-containing scrubbing solution so that the water-containing scrubbing solution absorbs the nitrogen dioxide from the intermediate flue gas to produce a nitrogen dioxide-containing solution and a scrubbed flue gas;
• means for releasing the scrubbed flue gas to atmosphere;
• means for accumulating the nitrogen dioxide-containing solution in the vessel containing the ammonium sulfate-containing scrubbing solution;
• and
• means for introducing ammonia and oxygen into the vessel to react the acidic gases in the acidic gas-containing solution to produce ammonium sulfate and to react the nitrogen dioxide in the nitrogen dioxide-containing solution to produce ammonium nitrate.