Sustainable method for recycling smelting works dusts and sludges to produce iron-containing, heavy-metal-depleted reclaimed materials with recovery of lead and zinc

Abstract

The present invention relates to a sustainable regeneration process for metallurgical plant dusts and sludges for producing iron-containing, heavy metal-depleted secondary raw materials and recovering lead and zinc, by providing a first starting material which comprises at least one iron, zinc, lead and further heavy metal components containing metallurgical plant dust and/or sludge, and a second starting material containing at least one chlorine component, mixing the starting materials and drying the mixture, pyrolyzing the mixture for expelling zinc, lead and further heavy metal components, capturing the gas phase of the pyrolysis in sulfuric acid, and providing the residue which remains as an iron-containing secondary raw material depleted in zinc, lead and further heavy metal components.

Claims

1. A regeneration process for producing iron-containing heavy metal-depleted secondary raw materials and recovering lead components and zinc components from at least one of metallurgical plant dust and sludge, comprising the steps of: I) providing a first starting material which comprises at least one of iron, zinc, and lead, and a second starting material containing at least one chlorine component, II) mixing the first starting material with the second starting material, transferring the mixture to an oven unit, and subsequently pelletizing it, III) drying the mixture with expulsion of steam, and subsequently pelletizing it, IV) reacting zinc, lead and further heavy metal components and chlorine components by pyrolysis, V) capturing the gas phase from the pyrolysis from step IV) in sulfuric acid, with cooling, V-a1) subsequent to step V) the sulfuric acid solution containing Zn in the form of ions is transferred to a further vessel and heated for removing residual chloride until the sulfuric acid fumes off, V-a2) the sulfuric acid solution containing Zn in the form of ions from step V-a1) is cooled and transferred to a container with water, sulfuric acid and metallic zinc, V-c1) PbSO4 from step V) is taken off as a solid, VI) providing the pyrolysis residue which remains as an iron-containing secondary raw material depleted in zinc, lead and further heavy metal components.

2. The process of claim 1, wherein SO3 is formed and expelled in step V-a1) and is one of captured and returned to step V) or into a corresponding vessel.

3. The process of claim 2 wherein in step V-a2) heavy metals selected from the group containing As, Cd, Pb and Sn are deposited on the Zn surface by electrolytic cementation.

4. The process of claim 3 wherein pure zinc is produced by electrolytic reduction in a step V-a3) from the sulfuric acid solution containing Zn in the form of ions from step V-a2).

5. The process of claim 3, wherein the sulfuric acid solution containing Zn in the form of ions in step V-a2), after deposition of the heavy metals, is used as an electrolyte in a zinc coating plant.

6. The process of claim 5 wherein hydrogen chloride is expelled in step V and subsequent to step V) the hydrogen chloride expelled is introduced into water in a step V-b1) to form hydrochloric acid.

7. The process of claim 6 wherein the PbSO4 taken off as a solid in step V-c1) is filtered.

8. The process of claim 7 wherein the metallurgical plant dust and/or sludge used comprises at least one substance selected from the group containing converter dust, coke dust, blast furnace dust, blast furnace sludge, dust from secondary metallurgy, sintering dust, mill scale, mill scale sludge, zinc slags, copper industry slags, oil-containing sludges, electric arc furnace dust (EAF dust), hall dusts from electric steelworks, filter dusts, oxygen furnace dust and blast furnace throat sludge.

9. The process of claim 8 wherein as chlorine component at least one substance selected from the group containing hydrogen chloride, hydrochloric acid, Cl2, PVC, PCB, PCT, oils containing PCB or PCT, preferably hydrochloric acid, more preferably hydrochloric acid pickle is used.

10. The process of claim 9 wherein the steam expelled in step III) is condensed and the water is captured.

11. The process of claim 10, wherein the hydrogen chloride expelled is introduced into the water condensed from the steam, and is used as regenerated hydrochloric acid.

12. The process of claim 11 wherein the process is carried out one of continuously or discontinuously.

13. The process of claim 11 wherein the basicity of the iron-enriched, heavy metal-depleted secondary raw material is adjusted by admixing CaO to at least one of the starting materials or mixture thereof.

14. The process of claim 13 wherein the secondary raw material from step VI) is iron-enriched.

15. The process of claim 14 wherein at least one starting material comprises alkali metal components and the secondary raw material is alkali metal component-depleted in comparison to the starting material, with the alkali metal components passing through the process together with the zinc and further heavy metal components.

16. The process of claim 8 wherein the metallurgical plant dust and/or sludge used comprises at least one substance selected from the group containing metallurgical plant dust and/or sludge from secondary iron/steel production.

17. The process of claim 8 wherein the metallurgical plant dust and/or sludge used comprises at least one substance selected from the group containing blast furnace throat sludge and/or oxygen furnace dust.

18. The process of claim 9 wherein the chlorine component includes hydrochloric acid pickle.

19. The process of claim 1 wherein the first starting material further comprises heavy metal components containing metallurgical plant dust and/or sludge.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The invention is elucidated in more detail below with reference to FIG. 1. Represented schematically in detail is the process of the invention; the steps in accordance with the description, and the containers in which the respective steps are carried out, are identified using the same symbols.

(2) As step I, the first starting material I-1 and the second starting material I-2 are provided from the respective container. In step II the starting materials are mixed in the corresponding container II. An oven unit is symbolized by III and IV. This unit may consist of two different or of one single container or oven, etc. Carried out therein are the drying step III and also the pyrolysis step IV.

(3) During drying, steam D is expelled. It is subsequently condensed in a steam condenser K and collected as water in the container with the identification V-b1.

(4) The gas phase G of the pyrolysis IV is captured in step V in sulfuric acid S, optionally with cooling K. In this operation, PbSO4 is precipitated as precipitate N. Precipitate is taken off in step V-c1, and optionally filtered.

(5) In step V-a1 the sulfuric acid solution containing zinc in the form of ions is heated until the sulfuric acid fumes off R. In this way the residues of chlorine components are also expelled. These sulfur oxides and optionally further gases are passed back into step or container V.

(6) Additionally, expelled in step V is hydrogen chloride, which is mixed together with the water condensed from steam in step or container V-b1 to give an aqueous hydrochloric acid solution. This solution can be used further as a pickle B in the working of steel.

(7) Sulfuric acid solution containing zinc in the form of ions from step V-a1 is transferred, optionally with cooling K, to a further container V-a2. Located therein is zinc as solid Z and also water, and optionally there is also addition of further sulfuric acid. Here, optionally with cooling K, heavy metals selected from the group containing As, Cd, Pb and Sn are deposited on the Zn surface by electrolytic cementation E.

(8) The resulting aqueous zinc sulfate solution, containing sulfuric acid and depleted in heavy metal and/or in chloride (substantially heavy metal-free and/or chloride-free), can be used as an electrolyte in an electrolytic coil galvanizing plant ECP.

(9) Alternatively pure zinc is produced by electrolytic reduction in a step V-a3). The secondary raw material SR, as the pyrolysis residue which remains, is used further in a sintering plant or in the blast furnace.

(10) In the sense of the invention, it is also possible to use combinations of the above-described embodiments and alternatives.