Methods and systems for recovering products from iron and steel slag

Patent metadata

Field	Value
Publication number	US-2018245182-A1
Application number	US-201615759938-A
Country	US
Kind code	A1
Filing date	Sep 19, 2016
Priority date	Sep 18, 2015
Publication date	Aug 30, 2018
Grant date	—

Abstract

Systems and methods for processing slag produced by iron and steel making processes are disclosed. The slag is treated produce a series of valued industrial products, such as metal oxides, metal carbonates, rare-earth metals, and water glass. The systems and methods also integrate slag processing with CO 2 sequestration and flue gas desulphurization. Processing slag minimizes the land use for stockpiling or landfilling wastes produced from iron and steel making processes and protects the ground water underneath. Overall, the solid and gaseous emissions of an energy-intensive and highly polluted industrial process have been largely reduced, recycled and valorized in order to achieve a near zero-emission goal.

First claim

What is claimed is:

1 . A method of recovering products from slag generated from an iron or steel making process comprising:
collecting an amount of slag generated from an iron or steel making process; isolating a non-magnetic-material-enriched portion from said slag; collecting a leachate from said non-magnetic-material-enriched portion comprising metal oxides, metal carbonates, and rare-earth elements; precipitating at least one of said metal oxides and said metal carbonates from said leachate; and collecting waste water and rare-earth elements from said leachate.

2 . The method of recovering products from slag generated from an iron or steel making process according to claim 1 , wherein isolating a non-magnetic-material-enriched portion from said slag comprises:
fracturing said slag into particles comprising magnetic and non-magnetic material; and applying a magnetic separation force to said slag particles to produce a magnetic-material enriched portion and a non-magnetic-material enriched portion.

3 . The method of recovering products from slag generated from an iron or steel making process according to claim 1 , wherein collecting a leachate from said non-magnetic-material-enriched portion comprising metal oxides, metal carbonates, and rare-earth elements comprises:
separating said leachate and a slag residue.

4 . The method of recovering products from slag generated from an iron or steel making process according to claim 3 , wherein collecting a leachate from said non-magnetic-material-enriched portion comprising metal oxides, metal carbonates, and rare-earth elements comprises:
washing said non-magnetic-material enriched portion with water, saline, or waste acids to produce a slurry having a basic pH; and dissolving a washed slurry of non-magnetic-material enriched portion in a solution comprising an acid and a chelating agent to produce said leachate and said slag residue.

5 . The method of recovering products from slag generated from an iron or steel making process according to claim 3 , further comprising dissolving said slag residue in NaOH in a conversion reactor to produce water glass and a residue comprising metal-silicates.

6 . The method of recovering products from slag generated from an iron or steel making process according to claim 5 , further comprising:
cooling the slag; recovering the heat from the slag in the form of steam; and feeding said steam to said conversion reactor.

7 . The method of recovering products from slag generated from an iron or steel making process according to claim 1 , further comprising:
fracturing said slag into particles having a diameter less than about 200 μm and an average diameter of about 20-25 μm.

8 . The method of recovering products from slag generated from an iron or steel making process according to claim 4 , wherein washing said non-magnetic-material enriched portion with water, saline, or waste acids further comprises:
bubbling CO 2 through said slurry; collecting a filtrate from said slurry; heating said filtrate to approximately 80° C.; and precipitating at least one metal carbonate.

9 . The method of recovering products from slag generated from an iron or steel making process according to claim 4 , wherein washing said non-magnetic-material enriched portion with acids further comprises:
collecting a filtrate from said slurry; providing a metal hydroxide solution; bubbling CO 2 through said metal hydroxide solution; collecting precipitated product; and recycling remaining fluid for use in the washing of said non-magnetic-material enriched portion.

10 . The method of recovering products from slag generated from an iron or steel making process according to claim 4 , wherein said acid is approximately 0.1M HCl or HNO 3 .

11 . The method of recovering products from slag generated from an iron or steel making process according to claim 4 , wherein said chelating agent is an approximately 0.01M solution selected from the group consisting of: sodium acetate, oxalate, citrate, picolinate, gluconate, glutamate, and combinations thereof.

12 . The method of recovering products from slag generated from an iron or steel making process according to claim 4 , further comprising maintaining said non-magnetic-material-enriched portion at approximately 15% by weight non-magnetic-material during at least one of:
washing said non-magnetic-material enriched portion with water to produce a slurry having a basic pH; and dissolving a washed slurry of non-magnetic-material enriched portion in a solution comprising an acid and a chelating agent.

13 . The method of recovering products from slag generated from an iron or steel making process according to claim 1 , wherein precipitating metal oxides and metal carbonates from said leachate comprises a pH swing process.

14 . The method of recovering products from slag generated from an iron or steel making process according to claim 1 , further comprising electrolyzing said leachate waste water to produce HCl and NaOH.

15 . The method of recovering products from slag generated from an iron or steel making process according to claim 2 , wherein said magnetic separation force is a magnetically assisted fluidized bed.

16 . The method of recovering products from slag generated from an iron or steel making process according to claim 1 , further comprising desulfinating a flue gas stream utilizing said non-magnetic-material-enriched portion prior to isolating said non-magnetic-material-enriched portion from said slag.

17 . A system for recovering products from slag generated from an iron or steel making process comprising:
a first source of iron or steel slag; a milling module configured to mill said first source of iron or steel slag to a predetermined size; a magnetically assisted fluidized bed configured to produce a non-magnetic-material-enriched portion from said iron or steel slag; a slag treatment module comprising a fluid stream including at least one of water, saline, acids, and flue gas, configured to contact said non-magnetic-material-enriched portion with said fluid stream; a first precipitation module in fluid communication with said slag treatment module; an acid leaching module comprising an acid and a chelating agent; a separator producing a slag residue stream and at least one leachate stream comprising metal oxides, metal carbonates, and rare-earth elements; a second precipitation module configured to produce at least one of a metal carbonate product, a metal oxide product, and a rare-earth element product; and a conversion reactor in fluid communication with said acid leaching module and configured to produce water glass from said slag residue stream.

18 . The system for recovering products from slag generated from an iron or steel making process according to claim 17 , wherein said slag treatment module is further configured to contact a non-magnetic-material-enriched portion from said iron or steel slag with a CO2 stream.

19 . The system for recovering products from slag generated from an iron or steel making process according to claim 17 , further comprising:
a first recycled fluid stream comprising fluid from said first precipitation and in fluid communication with said slag treatment module; and a second recycled fluid stream in fluid communication with said acid leaching module.

20 . The system for recovering products from slag generated from an iron or steel making process according to claim 17 , wherein said second precip

Assignees

• Univ Columbia

Inventors

• Park Ah-Hyung Alissa
• Zhou Xiaozhou

Classifications

• B03C2201/20

  Magnetic separation of bulk or dry particles in mixtures · CPC title

• C22B59/00 Primary

  Obtaining rare earth metals · CPC title

• C22B7/04 Primary

  Working-up slag · CPC title

• C21B3/08

  Cooling slag · CPC title

• C25B1/26

  Chlorine; Compounds thereof (by simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine C25B1/34) · CPC title