METHOD FOR REMOVING CONTAMINANTS FROM EXHAUST GASES

摘要

A method for removing contaminants from the effluent from metal pickling operations by oxidizing the contaminants in the effluent, passing the oxidized effluent to a first scrubber thereby removing mixed acid vapors and some nitrogen oxides and passing these scrubbed gases to a second scrubbing system while injecting ozone into a duct between the first and the second scrubbing systems thereby to oxidize nitrogen oxides to higher oxides and scrubbing the oxidized nitrogen oxides gas stream in the second scrubbing system.

主权项

1. A method for removing contaminants from an effluent stream from a metal pickling operation comprising the steps:
a) injecting a measured amount of gaseous oxygen into a pickling solution in the metal pickling operation wherein the oxygen will oxidize the reaction products of nitric acid and metal in the pickling solution forming nitrogen oxides and regenerate the nitric acid; b) adding additional oxygen into the pickling solution to further reduce the depletion of nitric acid in the pickling solution; c) adding gaseous oxygen to the effluent stream which comprises pickling acid vapors and the nitrogen oxides formed in step a) wherein the gaseous oxygen is added in a controlled manner; d) collecting and conveying the effluent stream to a first scrubbing system wherein acid gas and nitrogen oxides are removed from the effluent stream; e) conveying the effluent stream by way of a duct to a second scrubbing system; f) injecting ozone into the duct between the first scrubbing system and the second scrubbing system, thereby mixing with the effluent stream to oxidize the remaining nitrogen oxides; and g) scrubbing the oxidized nitrogen oxides in the effluent stream in the second scrubbing system.