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Method of removing sulfur dioxide and nitrogen oxides from a gaseous stream

  • US 5,785,841 A
  • Filed: 04/19/1996
  • Issued: 07/28/1998
  • Est. Priority Date: 05/04/1995
  • Status: Expired due to Fees
First Claim
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1. In a method of removing sulfur dioxide and nitrogen oxides from a gaseous stream wherein said gaseous stream is contacted with an aqueous scrubbing medium containing sulfites which react with and remove sulfur dioxide therefrom and ferrous chelates which react with and remove nitrogen oxides therefrom to form a spent aqueous scrubbing medium containing solids and a solution of ferric chelates, the improvement comprising:

  • separating the solids from said spent aqueous scrubbing medium to provide the aqueous solution of ferric chelates;

    passing said aqueous solution of ferric chelates as a catholyte, at an acidic pH of 4.0-6.5, to a cathode compartment of an electrochemical cell containing said cathode compartment and an anode compartment separated from said cathode compartment by a separator, said electrochemical cell having a corrosion resistant anode, and an anolyte feed solution in said anode compartment having an acidic pH of 1.5 to 6.5 and containing magnesium sulfate;

    passing an electrical current from said cathode compartment to said anode compartment to reduce ferric chelates in said catholyte to ferrous chelates and form a regenerated ferrous chelate solution; and

    recycling said regenerated ferrous chelate solution to said contacting step for use as said ferrous chelates.

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