Method for the treatment of iron-containing sludge

Patent metadata

Field	Value
Publication number	US-11519053-B2
Application number	US-201615572077-A
Country	US
Kind code	B2
Filing date	May 4, 2016
Priority date	May 5, 2015
Publication date	Dec 6, 2022
Grant date	Dec 6, 2022

Abstract

The present invention provides a method for the treatment of sludge containing iron and between 4.5% to 12% by weight of zinc. This method includes a leaching step wherein leaching agents include hydrochloric acid and chlorate, and wherein the pH of the leachate directly resulting from this leaching step is set at a value below 1.5. A recycling method and treatment installation are also provided.

First claim

The invention claimed is:

1. A method for the treatment of sludge, the method comprising the step of
providing sludge, the sludge including iron and between 4.5% to 12% by weight of zinc;
providing leaching agents, the leaching agents consisting of hydrochloric acid and chlorate;
leaching the sludge with the leaching agents to form a leachate, a pH of leachate directly resulting from this leaching step being less than 1.5.

2. The method of claim 1 , wherein the leaching agents are provided in a solution.

3. The method of claim 2 , wherein the solution is a solution of hydrochloric acid and chlorates.

4. The method of claim 3 , wherein the chlorates are selected from the group consisting of an aqueous solution of NaClO 3 a powder of NaClO 3 , and a solution of KClO 3 .

5. The method according to claim 1 , wherein the leachate has a pH of at least 0.8.

6. A method for the treatment of sludge, the method comprising the step of
providing sludge, the sludge including iron and between 4.5% to 12% by weight of zinc;
providing leaching agents, the leaching agents consisting of hydrochloric acid and chlorate;
leaching the sludge with the leaching agents to form a leachate, a pH of leachate directly resulting from this leaching step being greater than or equal to 0.8 and less than 1.5.

7. The method according to claim 6 , wherein the leachate has a pH between 0.8 and 1.2.

8. The method according to claim 6 , wherein the chlorate is a sodium chlorate compound.

9. The method according to claim 6 , wherein the leaching step is performed at a temperature between 50 and 65° C.

10. The method according to claim 6 , wherein the sludge initially contains 7%<Zn≤12%, by weight.

11. The method according to claim 6 , wherein the sludge initially contains between 1 and 2% by weight of lead.

12. The method according to claim 6 , further comprising:
performing at least one separation step after the leaching step, in order to separate a leached sludge from a residual liquid in the leachate.

13. The method according to claim 12 , further comprising:
performing an iron precipitation step after the at least one separation step to precipitate goethite.

14. The method according to claim 13 , further comprising:
performing a zinc and lead precipitation step after the iron precipitation step to obtain zinc and lead hydroxides.

15. The method according to claim 13 , wherein the iron precipitation step includes lime addition.

16. The method according to claim 12 , further comprising:
performing a single precipitation step after the at least one separation step to obtain a concentrate of zinc, lead and iron hydroxides.

17. The method according to claim 16 , wherein the single precipitation step includes lime addition.

18. The method according to claim 16 , wherein the zinc and lead precipitation step includes lime addition.

19. The method according to claim 6 , wherein the sludge has an initial composition comprising, with contents being expressed by weight:
15%<Fe<30%;
30%<C<60%;
1%<Pb≤2%;
2%<Al 2 O 3 <30%;
2%<CaO<5%;
0.5%<MgO<2%;
0.1%<Mn<0.2%;
0.05%<P<0.1%;
0.1%<TiO 2 ≤0.3%;
0.02%<Cr 2 O3<0.08%;
0.01%<ZrO 2 <0.05%;
0%<V 2 O 5 <0.03%;
0.05%<Ti≤0.2%;
22%<Fe2O3<38%;
0%<V≤0.007%;
4.5%<Zn<12%; and
1%<S<4%.

20. The method according to claim 6 , wherein the sludge is blast furnace sludge.

21. A recycling method comprising the steps of:
treating blast furnace sludge with the method according to claim 6 ; and
sending the treated blast furnace sludge to a sintering plant.

22. A method for the treatment of sludge, the method comprising the step of
providing sludge, the sludge including iron and between 4.5% to 12% by weight of zinc;
providing leaching agents, the leaching agents consisting of hydrochloric acid and chlorate;
leaching the sludge with the leaching agents to form a leachate, a pH of leachate directly resulting from this leaching step being greater than or equal to 0.8 and less than 1.5,
wherein a final product is a sludge containing less than 0.40% by weight in zinc and less than 0.10% by weight in lead.

Assignees

• Arcelormittal

Inventors

• Giordana Severine

Classifications

• C22B13/00

  Obtaining lead · CPC title

• C22B3/06 Primary

  in inorganic acid solutions {, e.g. with acids generated in situ; in inorganic salt solutions other than ammonium salt solutions} · CPC title

• C22B7/007 Primary

  by acid leaching · CPC title

• C22B7/008

  by an alkaline or ammoniacal leaching · CPC title

• C22B7/02

  Working-up flue dust · CPC title