Patent ID: 8871166
Filing Date: 2014-10-28
Classification: B01D,C23G,Y02C

Abstract:
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.