Method for controlling compounds and conditions in a wet flue gas desulfurization (WFGD) unit
View Patent ↗The present invention relates generally to the field of emissions control and, in particular to a new and useful method and/or system by which to control various types of corrosion and/or precipitation issues in at least a portion of a wet flue gas desulfurization (WFGD) scrubber system. In one embodiment, the method and/or system of the present invention relies on the supply of at least one reducing agent to the slurry of a wet flue gas desulfurization scrubber to lower the oxidation reduction potential in the absorber slurry contained within the wet flue gas desulfurization scrubber. In still another embodiment, the method and/or system of the present invention control the oxidation-reduction potential in at least one bleed stream of an absorber slurry, filtrate, and/or solution from a wet flue gas desulfurization scrubber.
1. A method for controlling the oxidation-reduction potential in a recirculation tank, or an absorber recirculation tank, of a wet flue gas desulfurization unit, the method comprising the steps of:
(i) supplying at least one reducing agent to a slurry, or a solution, portion of the recirculation tank, or the absorber recirculation tank, or at least one recirculation pump thereto so that the at least one reducing agent is supplied to the wet flue gas desulfurization unit recirculation tank or absorber recirculation tank; and
(ii) permitting the at least one reducing agent to react with one or more oxidizing compounds and/or ions present in the slurry, or the solution, portion of the recirculation tank, or the absorber recirculation tank or the at least one recirculation pump thereto, so as to achieve a reduction in the oxidation-reduction potential of the slurry, or the solution, in the recirculation tank, or the absorber recirculation tank, or in the at least one recirculation pump thereto, or in a combination of the recirculation tank, or the absorber recirculation tank, and the at least one recirculation pump thereto so that an amount of at least one insoluble precipitate compound in the recirculation tank, or the absorber recirculation tank, is controlled, prevented, or eliminated by the addition of the at least one reducing agent,
wherein the at least one reducing agent is selected from iron (II) sulfate (FeSO 4 ), phosphorous acid (H 3 PO 3 ), iron (II) ammonium sulfate ((NH 4 ) 2 Fe(SO 4 ) 2 ), hydroxylamine hydrochloride (HONH 2 .HCl), hypophosphorous acid (H 3 PO 2 ), or a combination of any two or more thereof.
2. The method of claim 1 , wherein the at least one reducing agent is hydroxylamine hydrochloride (HONH 2 .HCl).
3. The method of claim 1 , wherein the at least one reducing agent further permits control, prevention, or elimination of the precipitation of manganese from soluble manganese present in the slurry, or the solution, of the recirculation tank, or the absorber recirculation tank, of the wet flue gas desulfurization unit.
4. The method of claim 3 , wherein the at least one reducing agent is hydroxylamine hydrochloride (HONH 2 .HCl).
5. The method of claim 1 , wherein the at least one reducing agent further permits control of the type of selenium species present in the slurry, or the solution, of the recirculation tank, or the absorber recirculation tank, of the wet flue gas desulfurization unit via an oxidation-reduction reaction.
6. The method of claim 5 , wherein the at least one reducing agent is hydroxylamine hydrochloride (HONH 2 .HCl).
7. The method of claim 5 , wherein the at least one reducing agent permits an oxidation-reduction potential to exist in the slurry, or the solution, of the recirculation tank, or the absorber recirculation tank, of the wet flue gas desulfurization unit so as to favor the formation of Se(IV)O 3 2− species.
8. The method of claim 1 , wherein the at least one reducing agent further permits control of mercury re-emission in the wet flue gas desulfurization unit.
9. The method of claim 8 , wherein the at least one reducing agent is hydroxylamine hydrochloride (HONH 2 .HCl).
10. The method of claim 1 , wherein mercury re-emission is controlled by a combination of the at least one reducing agent in combination with sodium hydrosulfide (NaHS).
11. The method of claim 1 , wherein the oxidizing compound and/or ion is a persulfate and the at least one reducing agent is utilized in a concentration range of about 0.5 moles of the at least one reducing agent to every one mole of persulfate ions to 3 moles of the at least one reducing agent to every one mole of persulfate ions.
12. The method of claim 1 , wherein the oxidizing compound and/or ion is a persulfate and the at least one reducing agent is utilized in a concentration range of about 0.75 moles of the at least one reducing agent to every one mole of persulfate ions to 2.5 moles of the at least one reducing agent to every one mole of persulfate ions.
13. The method of claim 1 , wherein the oxidizing compound and/or ion is a persulfate and the at least one reducing agent is utilized in a concentration range of about 1 mole of the at least one reducing agent to every one mole of persulfate ions to 2.25 moles of the at least one reducing agent to every one mole of persulfate ions.
14. A method for controlling the oxidation-reduction potential in a recirculation tank, or an absorber recirculation tank, of a wet flue gas desulfurization unit, the method comprising the steps of:
(a) supplying at least one reducing agent to a slurry, or a solution, portion of the recirculation tank, or the absorber recirculation tank or at least one recirculation pump thereto so that the at least one reducing agent is supplied to the wet flue gas desulfurization unit recirculation tank or absorber recirculation tank;
(b) permitting the at least one reducing agent to react with one or more oxidizing compounds and/or ions present in the slurry, or the solution, portion of the recirculation tank, or the absorber recirculation tank or the at least one recirculation pump thereto, so as to achieve a reduction in the oxidation-reduction potential of the slurry, or the solution, in the recirculation tank, or the absorber recirculation tank, or in the at least one recirculation pump thereto, or in a combination of the recirculation tank, or the absorber recirculation tank, and the at least one recirculation pump thereto; and
(c) permitting the at least one reducing agent to further control, prevent, or eliminate the precipitation of manganese from soluble manganese present in the slurry, or the solution, of the recirculation tank, or the absorber recirculation tank, or in the at least one recirculation pump thereto, or in a combination of the recirculation tank, or the absorber recirculation tank, and the at least one recirculation pump thereto, of the wet flue gas desulfurization unit via control of the oxidation-reduction potential of the slurry, or the solution, in the recirculation tank, or the absorber recirculation tank, and/or in the at least one recirculation pump thereto of the wet flue gas desulfurization unit,
wherein the at least one reducing agent is selected from iron (II) sulfate (FeSO 4 ), phosphorous acid (H 3 PO 3 ), iron (II) ammonium sulfate ((NH 4 ) 2 Fe(SO 4 ) 2 ), hydroxylamine hydrochloride (HONH 2 .HCl), hypophosphorous acid (H 3 PO 2 ), or a combination of any two or more thereof.
15. The method of claim 14 , wherein the at least one reducing agent is hydroxylamine hydrochloride (HONH 2 .HCl).
16. The method of claim 14 , wherein the at least one reducing agent further permits control of the type of selenium species present in the slurry, or the solution, of the recirculation tank, or the absorber recirculation tank, of the wet flue gas desulfurization unit via an oxidation-reduction reaction.
17. The method of claim 16 , wherein the at least one reducing agent is hydroxylamine hydrochloride (HONH 2 .HCl).
18. The method of claim 14 , wherein the at least one reducing agent permits an oxidation-reduction potential to exist in the slurry, or the solution, of the recirculation tank, or the absorber recirculation tank, of the wet flue gas desulfurization unit so as to favor the formation of Se(IV)O 3 2− species.
19. The method of claim 14 , wherein the at least one reducing agent further permits control of mercury re-emission in the wet flue gas desulfurization unit.
20. The method of claim 19 , wherein the at least one reducing agent is hydroxylamine hydrochloride (HONH 2 .HCl).
21. The method of claim 14 , wherein mercury re-emission is controlled by a combination of the at least one reducing agent in combination with sodium hydrosulfide (NaHS).
22. The method of claim 14 , wherein the oxidizing compound and/or ion is a persulfate and the at least one reducing agent is utilized in a concentration range of about 0.5 moles of the at least one reducing agent to every one mole of persulfate ions to 3 moles of the at least one reducing agent to every one mole of persulfate ions.
23. The method of claim 14 , wherein the oxidizing compound and/or ion is a persulfate and the at least one reducing agent is utilized in a concentration range of about 0.75 moles of the at least one reducing agent to every one mole of persulfate ions to 2.5 moles of the at least one reducing agent to every one mole of persulfate ions.
24. The method of claim 14 , wherein the oxidizing compound and/or ion is a persulfate and the at least one reducing agent is utilized in a concentration range of about 1 mole of the at least one reducing agent to every one mole of persulfate ions to 2.25 moles of the at least one reducing agent to every one mole of persulfate ions.
25. A method for controlling the oxidation-reduction potential in a recirculation tank, or absorber recirculation tank, of a wet flue gas desulfurization unit, the method comprising the steps of:
(I) supplying at least one reducing agent to a slurry, or a solution, portion of the recirculation tank, or the absorber recirculation tank or at least one recirculation pump thereto;
(II) permitting the at least one reducing agent to react with one or more oxidizing compounds and/or ions present in the slurry, or the solution, portion of the recirculation tank, or the absorber recirculation tank or the at least one recirculation pump thereto, so as to achieve a reduction in the oxidation-reduction potential of the slurry, or the solution, in the recirculation tank, or the absorber recirculation tank, in the at least one recirculation pump thereto, or in a combination of the recirculation tank, or the absorber recirculation tank, and the at least one recirculation pump thereto;
(III) permitting the at least one reducing agent to further control, prevent, or eliminate the precipitation of manganese from soluble manganese present in the slurry, or the solution, of the recirculation tank, or the absorber recirculation tank, or in the at least one recirculation pump thereto, or in a combination of the recirculation tank, or the absorber recirculation tank, and the at least one recirculation pump thereto, of the wet flue gas desulfurization unit via control of the oxidation-reduction potential of the slurry, or the solution, in the recirculation tank, or the absorber recirculation tank, and/or in the at least one recirculation pump thereto of the wet flue gas desulfurization unit; and
(IV) permitting the at least one reducing agent to control mercury re-emission in the wet flue gas desulfurization unit via control of the oxidation-reduction potential in the slurry, or the solution, of the recirculation tank, or the absorber recirculation tank, of the wet flue gas desulfurization unit,
wherein the at least one reducing agent is selected from iron (II) sulfate (FeSO 4 ), phosphorous acid (H 3 PO 3 ), iron (II) ammonium sulfate ((NH 4 ) 2 Fe(SO 4 ) 2 ), hydroxylamine hydrochloride (HONH 2 .HCl), hypophosphorous acid (H 3 PO 2 ), or a combination of any two or more thereof.
26. The method of claim 25 , wherein the at least one reducing agent is hydroxylamine hydrochloride (HONH 2 .HCl).
27. The method of claim 25 , wherein the at least one reducing agent further permits control of the type of selenium species present in the slurry, or the solution, of the recirculation tank, or the absorber recirculation tank, of the wet flue gas desulfurization unit via an oxidation-reduction reaction.
28. The method of claim 27 , wherein the at least one reducing agent is hydroxylamine hydrochloride (HONH 2 .HCl).
29. The method of claim 25 , wherein the at least one reducing agent permits an oxidation-reduction potential to exist in the slurry, or the solution, of the recirculation tank, or the absorber recirculation tank, of the wet flue gas desulfurization unit so as to favor the formation of Se(IV)O 3 2− species.
30. The method of claim 25 , wherein mercury re-emission is controlled by a combination of the at least one reducing agent in combination with sodium hydrosulfide (NaHS).
31. The method of claim 25 , wherein the oxidizing compound and/or ion is a persulfate and the at least one reducing agent is utilized in a concentration range of about 0.5 moles of the at least one reducing agent to every one mole of persulfate ions to 3 moles of the at least one reducing agent to every one mole of persulfate ions.
32. The method of claim 25 , wherein the oxidizing compound and/or ion is a persulfate and the at least one reducing agent is utilized in a concentration range of about 0.75 moles of the at least one reducing agent to every one mole of persulfate ions to 2.5 moles of the at least one reducing agent to every one mole of persulfate ions.
33. The method of claim 25 , wherein the oxidizing compound and/or ion is a persulfate and the at least one reducing agent is utilized in a concentration range of about 1 mole of the at least one reducing agent to every one mole of persulfate ions to 2.25 moles of the at least one reducing agent to every one mole of persulfate ions.