A Process and System for Extracting Rare Earth Elements Using High Pulp Density Cracking

Abstract

The present application provides a process and system for extraction of rare earth elements from a solid feed that employs a high solid to liquid pulp density during cracking. In particular, the present application provides a high pulp density cracking water leaching process for extracting rare earth elements, which comprises: combining a ground solid feed with a strong acid and water to form a slurry or mud having a solid to liquid pulp density of at least 33%; cracking the slurry or mud in a reactor, with or without agitation; and leaching the slurry with an aqueous leaching solution to obtain a leachate comprising the rare earth elements. Also provided is a system for extraction of rare earth elements, which includes a grinding and/or milling device, a cracking reactor and a leaching device C configured to perform the high pulp density cracking water leaching process.

1 . A process for extracting one or more rare earth element (REE) from an ore, said process comprising:
 a) grinding the ore to produce a ground ore;   b) combining the ground ore with a strong acid in an amount from 100 g-1000 g of the strong acid per 1000 g of the ground ore to form a slurry or a mud;   c) optionally adding water;   d) cracking the slurry or mud at a reaction temperature or over a range of reaction temperatures of from about 30° C. to less than 100° C. for a period of time from about 30 minutes to about 6 hours in a reactor; and   e) leaching a product of step (d) with an aqueous leaching solution to obtain a leachate comprising the one or more rare earth element.   
     
     
         2 . The process according to  claim 1 , wherein in step (d) the cracking of the slurry or mud is a static step, or wherein in step (d) during cracking the slurry or mud is agitated in the reactor. 
     
     
         3 . The process according to  claim 1 , wherein the strong acid comprises HNO 3 , HCl or H 2 SO 4 . 
     
     
         4 . The process according to  claim 3 , wherein the strong acid comprises HNO 3  or H 2 SO 4 . 
     
     
         5 . The process according to  claim 1 , wherein the solid to liquid pulp density in step (d) is from about 33% to about 90%. 
     
     
         6 . The process according to  claim 1 , wherein the reaction temperature for step (d) is between about 40° C. and about 99° C. 
     
     
         7 . The process according to  claim 6 , wherein the temperature in step (d) is between about 85° C. and less than 100° C. 
     
     
         8 . The process according to  claim 1 , wherein the aqueous leaching solution comprises water or an REE-barren acidic solution. 
     
     
         9 . The process according to  claim 1 , wherein the leaching is performed for a period time from about 1 hour to about 10 hours. 
     
     
         10 . The process according to  claim 1 , wherein the leaching is performed at a temperature, or over a range of temperatures, of from about 20° C. to about 100° C. 
     
     
         11 . The process according to  claim 1 , wherein water is added in step (c) in an amount from about 10 g of water per 1000 g of ore to about 5000 g of water per 1000 g of ore. 
     
     
         12 . The process according to  claim 1 , wherein the strong acid is mixed with the ground ore in an amount from 100 g-500 g of strong acid per 1000 g of ground ore. 
     
     
         13 . A system for extracting one or more rare earth element (REE) from a rare earth-containing ore, said system comprising:
 f) a grinding and/or milling device for grinding the ore to produce a ground ore;   g) a cracking reactor having ground ore inlet, a strong acid inlet, optionally a water inlet, and a mixed mud or slurry outlet, wherein the cracking reactor is configured to receive the ground ore for mixing with a strong acid in an amount from 100 g-1000 g of the strong acid per 1000 g of the ground ore and optionally with added water to form a slurry or mud by means of an agitator arranged in the cracking reactor;   h) means for heating the slurry or mud to a reaction temperature of from about 30° C. to less than 100° C. to crack the slurry or mud for a period of time from about 30 minutes to about 6 hours to produce a cracked slurry or mud; and   i) a leaching device configured to accept the cracked slurry or mud and comprising a leaching chamber, having an aqueous leaching solution inlet and a leached slurry or mud outlet.   
     
     
         14 . The system according to  claim 13 , wherein the strong acid comprises HNO 3 , HCl or H 2 SO 4 . 
     
     
         15 . The system according to  claim 14 , wherein the strong acid comprises HNO 3  or H 2 SO 4 . 
     
     
         16 . The system according to  claim 13 , wherein a solid to liquid pulp density of the mud or slurry in the cracking reactor is from about 33% to about 90%. 
     
     
         17 . The system according to  claim 13 , wherein the cracking reactor is configured to heat the mud or slurry to a reaction temperature or a range of reaction temperatures between about 40° C. and about 99° C. 
     
     
         18 . The system according to  claim 13 , wherein the aqueous leaching solution inlet provides water or an REE-barren acidic solution into the leaching chamber. 
     
     
         19 . The system according to  claim 13 , wherein the system additionally comprises means for heating the leaching chamber to a temperature from about 20° C. to about 100° C. 
     
     
         20 . The system according to  claim 13 , wherein the ground solid ore inlet is fluidly connected to the grinding and/or milling device, and/or wherein the leaching device comprises a cracked mud or slurry inlet fluidly connected to the mixed slurry outlet of the reactor. 
     
     
         21 . The system according to  claim 13 , wherein the cracking reactor is configured to introduce added water in an amount from about 10 g of water per 1000 g of ore up to about 5000 g of water per 1000 g of ore. 
     
     
         22 . The system according to  claim 13 , wherein the cracking reactor is configured to combine the strong acid with the ground ore in an amount from 100 g-500 g of strong acid per 1000 g of ground ore.