Methods for recovery of rare earth elements from coal

Patent metadata

Field	Value
Publication number	US-2020002785-A1
Application number	US-201916541444-A
Country	US
Kind code	A1
Filing date	Aug 15, 2019
Priority date	Jun 8, 2016
Publication date	Jan 2, 2020
Grant date	—

Abstract

Methods of recovering rare earth elements, vanadium, cobalt, or lithium from coal are described. The coal is dissolved in a first solvent to dissolve organic material in the coal and create a slurry containing coal ash enriched with rare earth elements, vanadium, cobalt, or lithium. The enriched coal ash is separated from the first solvent. Residual organic material is removed from the coal ash. The rare earth elements, vanadium, cobalt, or lithium can then be recovered from the coal ash. The coal ash is mixed with an acid stream that dissolves the rare earth elements, thereby creating (i) a leachate containing the rare earth elements and (ii) leached ash. The leachate is heated to obtain acid vapor and an acid-soluble rare earth concentrate. The acid-soluble rare earth concentrate can be fed to a hydrometallurgical process to separate and purify the rare earth elements.

First claim

1 . A method of recovering rare earth elements from coal, comprising:
dissolving coal in a first solvent to dissolve organic material in the coal and create a slurry containing coal ash enriched with rare earth elements; separating the coal ash from the first solvent; removing residual organic material from the coal ash; and recovering the rare earth elements from the coal ash.

2 . The method of claim 1 , wherein the first solvent is a bio-based hydrogen transfer solvent.

3 . The method of claim 1 , wherein the first solvent is soybean oil.

4 . The method of claim 1 , wherein the residual organic material is removed from the coal ash by washing the coal ash with a second solvent that is different from the first solvent.

5 . The method of claim 4 , wherein the second solvent is tetrahydrofuran.

6 . The method of claim 1 , wherein the residual organic material is removed from the coal ash by burning the coal ash at a temperature of about 300° C. to about 600° C.; or
wherein the residual organic material is removed from the coal ash by comminution, froth flotation, or gravimetric separation.

7 . The method of claim 1 , further comprising separating the coal ash into fractions containing the rare earth elements before recovering the rare earth elements from the coal ash;
wherein the fractions are separated by density using a sink/float analysis, or by particle size by successively screening the coal ash, or by particle size by air classifiers or cyclones, or by chemical leaching.

8 . The method of claim 7 , wherein the chemical leaching uses a mineral base, an inorganic salt, or a mineral acid, or wherein the chemical leaching is performed by acid digestion.

9 . The method of claim 7 , further comprising a calcination step before the chemical leaching.

10 . The method of claim 1 , further comprising purifying the rare earth elements in a solvent extraction circuit to separate individual elements after recovering the rare earth elements from the coal ash.

11 . The method of claim 1 , wherein the rare earth elements are recovered from the coal ash by:
mixing the coal ash with an acid stream such that the rare earth elements present in the coal ash are dissolved in the acid stream, thereby creating (i) a leachate containing the rare earth elements, and (ii) leached ash; and heating the leachate to obtain acid vapor and a concentrate containing the rare earth elements.

12 . The method of claim 11 , wherein the acid stream comprises nitric acid, hydrochloric acid, sulfuric acid, or hydrofluoric acid.

13 . The method of claim 11 , further comprising treating the coal ash with a basic solution prior to mixing the coal ash with the acid stream.

14 . The method of claim 13 , further comprising milling the coal ash while the coal ash is treated with the basic solution.

15 . The method of claim 11 , further comprising separating the leachate and the leached ash before heating the leachate.

16 . The method of claim 15 , further comprising drying the leached ash.

17 . The method of claim 16 , wherein residual acid in the leached ash is recovered as acid vapor that is condensed and recycled to the acid stream.

18 . The method of claim 11 , wherein the acid vapor obtained from heating the leachate is condensed and recycled to the acid stream.

19 . The method of claim 11 , wherein the leachate is heated to a temperature of about 150° C. to about 200° C.

20 . The method of claim 11 , further comprising feeding the concentrate to a hydrometallurgical process to separate and purify the rare earth elements.

Assignees

• Battelle Memorial Institute

Inventors

• Peterson Rick
• Heinrichs Michael
• Gadkari Vinay V
• Taha Rachid
• Winecki Slawomir
• Argumendo Darwin

Classifications

• C22B7/02

  Working-up flue dust · CPC title

• C22B1/005

  Preliminary treatment of scrap (C22B1/02 - C22B1/26 take precedence) · CPC title

• C22B3/02

  Apparatus therefor · CPC title

• C22B59/00 Primary

  Obtaining rare earth metals · CPC title

• C22B7/007

  by acid leaching · CPC title