Systems and methods for recovering nitric acid from pickling solutions

摘要

An embodiment of a method for recovering nitric acid from acid pickling solution includes introducing a treating material comprising at least one chemical into a pickling solution comprising free nitric acid. The treating material reacts with at least a portion of the free nitric acid in the pickling solution and produces NOx. A gas stream comprising at least a portion of the NOx is contacted with ozone, thereby forming oxidation products including nitrogen sesquioxide and nitrogen pentoxide. At least a portion of the nitrogen sesquioxide and nitrogen pentoxide is contacted with water, thereby forming nitric acid, and at least a portion of the nitric acid is collected.

主权项

1. A method for recovering nitric acid from a used or spent acid pickling solution generated by treating one of titanium and a titanium alloy, the method comprising:
introducing a treating material comprising a reducing agent into the used or spent acid pickling solution comprising free nitric acid, wherein the treating material reacts with at least a portion of the free nitric acid in the used or spent acid pickling solution, thereby producing NOx; directly following the preceding step, contacting a gas stream comprising at least a portion of the NOx with ozone, thereby forming oxidation products including nitrogen sesquioxide and nitrogen pentoxide; directly following the preceding step, reacting at least a portion of the nitrogen sesquioxide and nitrogen pentoxide with water, thereby forming nitric acid; and collecting at least a portion of the nitric acid; wherein the NOx is not treated with a caustic scrubbing solution in a scrubber between the step of producing the NOx and the step of collecting at least a portion of the nitric acid.