Method and production of nitric acid

In a process for producing nitric acid by oxidizing ammonia gas with air to form gaseous nitric oxide and water vapor, oxidizing the nitric oxide with air to form nitrogen dioxide gas, dimerizing the nitrogen dioxide gas to form dinitrogen tetroxide gas, reacting the dinitrogen tetroxide with water in an absorption zone to form aqueous nitric acid and nitric oxide gas, removing a nitric acid/nitric oxide stream from the absorption zone and feeding the stream into a nitric acid bleaching zone, removing impurities from the nitric acid in the bleaching zone to form nitric acid product and adding supplemental oxygen gas to one or more of the reaction streams to increase nitric acid production and/or strength,

• the improvement which comprises injecting the supplemental oxygen into the nitric acid-containing process stream removed from the absorption zone and fed into the bleaching zone to form a gas bubble/liquid mixture therein, accelerating a substantial proportion of the gas bubble/liquid mixture to a supersonic velocity and decelerating the gas bubble/liquid mixture to a subsonic velocity to create a sonic shock wave forming a fine dispersion of gas bubbles having diameters of less than 0.1 mm and providing increased interfacial surface between the gas bubbles and the nitric acid in the process stream to facilitate increased mass transfer between the gas and liquid phases of the process stream.