Systems for acid digestion processes

Patent metadata

Field	Value
Publication number	US-2020002784-A1
Application number	US-201916541355-A
Country	US
Kind code	A1
Filing date	Aug 15, 2019
Priority date	Jun 8, 2016
Publication date	Jan 2, 2020
Grant date	—

Abstract

A system for recovering rare earth elements from coal ash includes a leaching reactor, an ash dryer downstream of the leaching reactor, and a roaster downstream of the ash dryer that is cooperatively connected to both the leaching reactor and the ash dryer. Coal ash is mixed with an acid stream such that 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. The leachate is heated to obtain acid vapor and an acid-soluble rare earth concentrate. Mixing of the coal ash with the acid stream can occur in a leaching reactor and heating of the leachate can occur in a roaster. 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 system for recovering rare earth elements, vanadium, cobalt, or lithium from coal ash, the system comprising:
a leaching reactor for creating (i) a leachate containing the rare earth elements, vanadium, cobalt, or lithium, and (ii) leached ash; an ash dryer downstream of the leaching reactor for receiving the leached ash; and a roaster downstream of the leaching reactor for receiving the leachate.

2 . The system of claim 1 , further comprising a solid-liquid separation device downstream of the leaching reactor for separating the leached ash and the leachate from each other, wherein the ash dryer and the roaster are downstream of the solid-liquid separation device.

3 . The system of claim 2 , further comprising an evaporator downstream of the solid-liquid separation device and upstream of the roaster.

4 . The system of claim 1 , further comprising a heat recovery exchanger between the solid-liquid separation device and the roaster, the heat exchanger receiving the leachate from the leaching reactor and acid vapor recovered from the roaster.

5 . The system of claim 1 , further comprising a condenser downstream of the roaster, the condenser receiving acid vapor from the roaster.

6 . The system of claim 5 , further comprising an absorption column downstream of the condenser, the absorption column receiving (A) an acid solution from the condenser, and (B) acid vapor from the condenser or the ash dryer or the leaching reactor.

7 . The system of claim 6 , wherein the leaching reactor receives a recovered acid feed from the absorption column.

8 . The system of claim 1 , further comprising a caustic tank upstream of the leaching reactor for pretreating the coal ash before the coal ash enters the leaching reactor.

9 . The system of claim 8 , further comprising a ball mill upstream of the leaching reactor or the caustic tank for reducing the particle size of the coal ash before the coal ash enters the leaching reactor.

10 . The system of claim 8 , wherein the caustic tank further includes a ball mill for reducing the particle size of the coal ash during pretreatment before the coal ash enters the leaching reactor.

11 . The system of claim 8 , further comprising a caustic solid-liquid separator between the caustic tank and the leaching reactor, which creates a basic solution and an ash slurry, the ash slurry traveling to the leaching reactor.

12 . The system of claim 1 , further comprising a particle separation device downstream of the ash dryer, the particle separation device receiving acid vapor from the ash dryer.

13 . The system of claim 1 , wherein heated air used in the ash dryer is recovered and fed to the roaster.

14 . The system of claim 1 , further comprising a reactor heater upstream of the leaching reactor, for preheating coal ash and acid fed to the leaching reactor.

Assignees

• Battelle Memorial Institute

Inventors

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

• C01B39/02

  Crystalline aluminosilicate zeolites; Isomorphous compounds thereof; Direct preparation thereof; Preparation thereof starting from a reaction mixture containing a crystalline zeolite of another type, or from preformed reactants; After-treatment thereof · CPC title