Process for absorption of sulfur dioxide and nitric oxide from flue gas
First Claim
1. A process for abating nitric oxide and sulfur dioxide from a flue gas, comprising the steps of;
- (a) contacting flue gas with an absorbent solution, in an absorption stream comprising a reduced metal chelate and a sulfite to absorb sulfur dioxide and nitric oxide from said flue gas to form an oxidized chelate absorbent solution;
(b) directing said oxidized chelate absorbent solution to a cathode compartment in an electrochemical cell having a corrosion resistant nickel or stainless steel anode in an anolyte solution having a pH greater than 12 in an anode compartment separated by a cationic membrane from a cathode in said cathode compartment and imposing an electrical potential across said anode and said cathode to reduce said oxidized chelates in said cathode compartment to obtain a regenerated absorbent solution; and
(c) recycling said regenerated absorbent solution to said contacting step.
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Accused Products
Abstract
The simultaneous abatement of NO and SO2 in flue gas is provided by an absorption process and apparatus utilizing an absorbent composition comprising an aqueous solution of chelates and sulfite salts. Metal chelates oxidized to an inactive state are electrochemically reduced. In the electrochemical cell, nickel or stainless steel anode materials are stable and may be used in the place of platinum coated anode materials when the anolyte pH is maintained greater than 12. At these conditions, the anode is corrosion resistant with a long operating time between replacement. Ultrafiltration or Donnan dialysis may be used to separate the chelate sorbents from the waste salts to reduce the loss of expensive chelate sorbents. Alternatively, an anionic exchange membrane can be used to electrodialytically separate waste sulfur/nitrogen salts from the absorbent solution.
54 Citations
14 Claims
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1. A process for abating nitric oxide and sulfur dioxide from a flue gas, comprising the steps of;
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(a) contacting flue gas with an absorbent solution, in an absorption stream comprising a reduced metal chelate and a sulfite to absorb sulfur dioxide and nitric oxide from said flue gas to form an oxidized chelate absorbent solution; (b) directing said oxidized chelate absorbent solution to a cathode compartment in an electrochemical cell having a corrosion resistant nickel or stainless steel anode in an anolyte solution having a pH greater than 12 in an anode compartment separated by a cationic membrane from a cathode in said cathode compartment and imposing an electrical potential across said anode and said cathode to reduce said oxidized chelates in said cathode compartment to obtain a regenerated absorbent solution; and (c) recycling said regenerated absorbent solution to said contacting step. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An apparatus for the absorption of SO2 and NO from flue gases comprising;
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(a) an absorber column; (b) an absorbent solution comprising a metal chelate and sulfites; and (c) an electrochemical cell comprising a nickel or stainless steel anode, an anolyte solution having a pH greater than 12 and a cationic exchange membrane. - View Dependent Claims (12, 13)
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14. A process for abating nitric oxide and sulfur dioxide from a flue gas, comprising the steps of;
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(a) contacting flue gas with an absorbent solution, in an absorption stream comprising a reduced metal chelate and a sulfite to absorb sulfur dioxide and nitric oxide from said flue gas to form an oxidized chelate absorbent solution; (b) directing said oxidized chelate absorbent solution to a chathode compartment in an electrochemical cell having a corrosion resistant anode in an anolyte solution in an anode compartment separated by a non-ionic membrane from a cathode in said cathode compartment; (c) imposing an electrical potential across said anode and said cathode to reduce said oxidized chelates in said cathode compartment to obtain a regenerated absorbent solution; and (d) recycling said regenerated absorbent solution to said contacting step.
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Specification