Method of pyrolysis for waste light-emitting electronic components and recovery for rare-earth element

Patent metadata

Field	Value
Publication number	US-2023067876-A1
Application number	US-202217978931-A
Country	US
Kind code	A1
Filing date	Nov 1, 2022
Priority date	Jul 10, 2020
Publication date	Mar 2, 2023
Grant date	—

Abstract

The invention disclosed a method for recycling rare earth elements from waste light-emitting electronic components by pyrolysis and alkaline melting-acid leaching. Based on the pyrolysis properties of the organic polymer, through catalytic pyrolysis of the organic polymer material in electronic components and convert the carbon in the residue into water gas, realize high-efficient dismantling of waste electronic component packaging materials. The traditional problems that the compositions of waste light-emitting electronic components are difficult to disassemble are solved, the generated pyrolysis gas and water gas can continuously supply energy for the pyrolysis system and recover the heat in the flue gas to save energy. Meanwhile, based on the chemical dissolution reaction mechanism of phosphors, the combination process of alkali melting, and acid leaching is used to efficiently recover rare earth elements from the waste light-emitting electronic components, and the step leaching of rare earth elements is realized. The rare earth oxalate can be recovered by precipitation, which greatly reduces the difficulty of late separation and purification.

First claim

We claim:

1 . A method of pyrolysis for waste light-emitting electronic components and recovery for rare-earth element, comprising:
step 1: using a steel belt continuous pyrolysis furnace to pyrolyze waste light-emitting electronic components, N 2 is introduced into the furnace as a protective gas, oil-gas mixture and residue are obtained by heating and pyrolysis; initial temperature of the pyrolysis is 300-400° C., end temperature is 500-650° C.; 3-stage zone temperature control heating is adopted, temperature of zone 1 is 300-400° C., temperature of zone 2 is 400-550° C., temperature of zone 3 is 500-650° C., and pyrolysis time is 90-150 min; step 2: the residue with residual heat is sent to a gas generator in N 2 atmosphere, and high-temperature water vapor is introduced to convert carbon in the residue into water gas to obtain pyrolysis residue; temperature of the water vapor is 750-900° C., reaction pressure is 2.3-3.2 MPa, and reaction time is 3-5 min; step 3: the oil and gas mixture are sent to the spray condensing tower, HBr is removed by lye spray and the oil and gas are separated, pyrolysis Oil, pyrolysis gas and NaBr are obtained; step 4: phosphor powder and metals are separated from pyrolysis slag by eddy current separation, and acid leaching solvent and acid leaching auxiliary solvent are added to the phosphor powder; filtrate 1 and filter residue 1 are obtained by filtration; step 5: adding alkali melting agent to filter residue 1, performing high temperature alkali melting and obtaining an alkali melting product; then adding acid leaching solvent and acid leaching auxiliary solvent to the alkali melting product to carry out acid leaching treatment, phosphor powder of nitrogen oxide system and garnet system are leached, and filtrate 2 containing Eu 3+ , Tb 3+ and Ce 3+ is obtained by filtration; the mass ratio of high temperature alkali slag to alkali is 1:2-1:6, the calcination temperature is 600-1000° C., and the calcination time is 30-60 min; step 6: mix filtrate 1 and filtrate 2, add a dispersant to the mixed solution, stir and mix well; after adding the oxalic acid solution, the pH of the solution is adjusted to 1.8-2.0 with ammonia water, and the solution is settled at 23-28° C. for 4-6 hours; after the precipitation is complete, the precipitation is filtered, washed, and dried by the heat of the flue gas boiler to obtain rare earth oxalate.

2 . The method of pyrolysis for waste light-emitting electronic components and recovery for rare-earth element according to claim 1 , wherein:
in step 3, the lye is NaOH solution and the mass percentage concentration of NaOH solution is 5-10%.

3 . The method of pyrolysis for waste light-emitting electronic components and recovery for rare-earth element according to claim 1 , wherein:
in step 4, the temperature of acid leaching reaction is 30-50° C., the reaction time is 40-80 min, the acid leaching solvent addition amount is: every kilogram of alkali melting product adds 3-8 L acid leaching solvent, and 2-4 L/kg acid leaching auxiliary solvent;

4 . The method of pyrolysis for waste light-emitting electronic components and recovery for rare-earth element according to claim 1 , wherein:
in step 5, the acid leaching reaction temperature is 70-90° C., the reaction time is 20-25 min, the acid leaching solvent addition amount is: every kilogram of alkali melting product adds 3-8 L acid leaching solvent, and 2-4 L/kg acid leaching auxiliary solvent.

5 . The method of pyrolysis for waste light-emitting electronic components and recovery for rare-earth element according to claim 1 , wherein:
in step 6, the dispersing agent is PEG 20000 or PEI, and the added amount is 3-5% of the mass of the mixed solution, and the added amount of the oxalic acid solution is 20-33% of the mass of the mixed solution.

Assignees

• Univ Beijing Technology

Inventors

• Wu Yufeng
• Zhang Shuhao

Classifications

• C22B59/00

  Obtaining rare earth metals · CPC title

• C22B7/001

  Dry processes · CPC title

• B09B3/70

  Chemical treatment, e.g. pH adjustment or oxidation (involving an extraction step B09B3/80) · CPC title

• B09B2101/15

  Electronic waste · CPC title

• B09B3/80

  involving an extraction step · CPC title