Method for the treatment of wastewaters

Patent metadata

Field	Value
Publication number	US-11713264-B2
Application number	US-201816757345-A
Country	US
Kind code	B2
Filing date	Dec 13, 2018
Priority date	Dec 14, 2017
Publication date	Aug 1, 2023
Grant date	Aug 1, 2023

Abstract

A method for the treatment of wastewaters including a cyanide compound and a metallic compound, wherein the wastewaters are subjected to a single oxidation step during which cyanides compounds are converted into carbon dioxide and nitrogen, this oxidation step including the mixing of wastewaters with a chlorine solution and an alkaline agent so as to obtain a mixture, the alkaline agent being added in such a quantity so as to maintain the pH of said mixture between 8.8 and 9.5 and the chlorine solution being added in such a quantity so as to maintain the oxydo-reduction potential of the mixture between 150 and 450 mV.

First claim

What is claimed is:

1. A method for the treatment of wastewaters including a cyanide compound and a metallic compound, the method comprising:
subjecting the wastewaters to a single oxidation step during which cyanides compounds are converted into carbon dioxide and nitrogen, the oxidation step including mixing of the wastewaters with a chlorine solution and an alkaline agent so as to obtain a mixture, the alkaline agent being added in such a quantity so as to maintain a pH of the mixture between 8.8 and 9.5 and the chlorine solution being added in such a quantity so as to maintain one value of an oxydo-reduction potential of the mixture while the cyanides compounds are converted into carbon dioxide and nitrogen, the one value being between 150 and 450 mV.

2. The method as recited in claim 1 wherein the chlorine solution is a sodium hypochlorite solution.

3. The method as recited in claim 1 wherein the alkaline agent is lime.

4. The method as recited in claim 1 wherein the pH of the mixture is maintained between 8.9 and 9.1.

5. The method as recited in claim 1 wherein the wastewaters initially contain:
between 1.5 ppm and 15 ppm in weight of cyanides, including between 1 and 10 ppm in weight of weak acid dissociable cyanides,
between 0.8 and 3 ppm in weight of zinc,
up to 8 ppm in weight of iron, and
between 0.05 and 0.5 ppm in weight of lead.

6. The method as recited in claim 1 wherein the wastewaters are derived from blast furnace gas cleaning.

7. The method as recited in claim 1 further comprising, after the oxidation step, subjecting the mixture to a clarification step where the mixture is separated into clarified water and sludge.

8. The method as recited in claim 1 wherein the alkaline agent is sodium hydroxide.

9. The method as recited in claim 1 wherein the pH is continuously measured.

10. The method as recited in claim 1 wherein a continuous inlet flow of the wastewaters and a continuous outlet flow of treated wastewaters are provided.

11. The method as recited in claim 10 wherein the continuous inlet flow is around 1.5-5 m 3 /hour.

12. The method as recited in claim 1 wherein the wastewaters, after the treatment, comprise <0.002 m 3 sludge/m 3 .

13. The method as recited in claim 1 wherein the wastewaters after treatment comprise less than 0.4 mg/l of cyanides, less than 2 mg/L of zinc, less than 5 mg/L of iron, less than 0.5 mg/L of lead and less than 30 mg/L of ammonia nitrogen.

14. The method as recited in claim 1 wherein 6 liters, or less, of the chlorine solution is used for treating 1 m 3 of the wastewaters.

15. The method as recited in claim 1 wherein 10 liters, or less, of alkaline agent is used for treating 1 m 3 of the wastewaters.

16. The method as recited in claim 1 wherein one tank is utilized for the single oxidation step.

17. The method of claim 1 wherein the alkaline agent is milk of lime or sodium hydroxide.

18. A method for the treatment of wastewaters including a cyanide compound and a metallic compound, the method comprising:
subjecting the wastewaters to a single oxidation step during which cyanides compounds are converted into carbon dioxide and nitrogen, the oxidation step including mixing of the wastewaters with a chlorine solution and an alkaline agent so as to obtain a mixture, the alkaline agent being added in such a quantity so as to maintain a pH of the mixture between 8.8 and 9.5 and the chlorine solution being added in such a quantity so as to maintain an oxydo-reduction potential of the mixture at one value while the cyanides compounds are converted into carbon dioxide and nitrogen, the one value being between 350 mV and 400 mV.

19. The method of claim 18 wherein the alkaline agent is milk of lime or sodium hydroxide.

20. A method for the treatment of wastewaters including a cyanide compound and a metallic compound, the method comprising:
subjecting the wastewaters to a single oxidation step during which cyanides compounds are converted into carbon dioxide and nitrogen, the oxidation step including mixing of the wastewaters with a chlorine solution and an alkaline agent so as to obtain a mixture, the alkaline agent being added in such a quantity so as to maintain a pH of the mixture between 8.8 and 9.5 and the chlorine solution being added in such a quantity so as to maintain an oxydo-reduction potential of the mixture between 180 mV and 230 mV while the cyanides compounds are converted into carbon dioxide and nitrogen.

21. A method for the treatment of wastewaters including a cyanide compound and a metallic compound, the method comprising:
subjecting the wastewaters to a single oxidation step during which cyanides compounds are converted into carbon dioxide and nitrogen, the oxidation step including mixing of the wastewaters with a chlorine solution and an alkaline agent so as to obtain a mixture, the alkaline agent being added in such a quantity so as to maintain a pH of the mixture between 8.8 and 9.5 and the chlorine solution being added in such a quantity so as to maintain a set value of an oxydo-reduction potential of the mixture while the cyanides compounds are converted into carbon dioxide and nitrogen, the set value being between 180 mV and 200 mV.

Assignees

• Arcelormittal

Inventors

• Gomez Leiva Patricia
• Menendez Delmiro Vanesa
• Padilla Vivas Beatriz

Classifications

• C02F1/76 Primary

  with halogens or compounds of halogens {(C02F1/4674 takes precedence)} · CPC title

• C02F1/66 Primary

  by neutralisation; pH adjustment (for degassing C02F1/20; using ion-exchange C02F1/42; for flocculation or precipitation of suspended impurities C02F1/52; for removing dissolved compounds C02F1/58) · CPC title

• C02F2101/18

  Cyanides · CPC title

• C02F2101/20

  Heavy metals or heavy metal compounds · CPC title

• C02F2103/18

  from the purification of gaseous effluents · CPC title