Final Report: Cost-Effective Rare Earth Element Recycling Process from Industrial Scrap and Discarded Electronic Products to Valuable Magnetic Alloys and Permanent MagnetsEPA Contract Number: EPD12030
Title: Cost-Effective Rare Earth Element Recycling Process from Industrial Scrap and Discarded Electronic Products to Valuable Magnetic Alloys and Permanent Magnets
Investigators: Liu, Jinfang
Small Business: Electron Energy Corporation
EPA Contact: Manager, SBIR Program
Project Period: March 1, 2012 through August 31, 2012
Project Amount: $80,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2012) RFA Text | Recipients Lists
Research Category: Small Business Innovation Research (SBIR) , SBIR - Innovation in Manufacturing
The overall objective of this program was to develop a scalable, low-cost manufacturing method to recycle rare earth-based magnets from industrial sites or discarded electronic products into valuable magnetic alloys and high performance magnets. The Chinese monopoly in the rare earth element market creates a strategic vulnerability for the United States and undermines our national security and competitiveness in the defense and clean-energy sectors. Rare earth elements shortages also could cause huge supply-chain problems for U.S. green energy and technology companies. In a typical neodymium-iron-boron (Nd-Fe-B) magnet manufacturing facility, about 20-30 percent of the magnets are wasted as scrap in order to machine them into desired shapes. The scrap is estimated to be about 1,500-2,500 tons/year. In the case of Sm-Co magnets, about 15-30 percent of the raw materials are wasted as scrap at typical Sm-Co manufacturing sites. Hence, rare earth element recovery appears to be gaining importance in the recycling industry. To date, only very small quantities of rare earth elements (estimated at 1 percent) have been recycled from pre-consumer scrap.
During the Phase I research effort, Electron Energy Corporation (EEC) has successfully recycled rare earth (RE)-based scrap permanent magnets into useful magnets with good magnetic properties. EECs approach comprised of recovering the magnets, cleaning, induction melting and optimizing the composition by the addition of a small percentage (less than 5 wt. percent) of virgin elements to achieve the required magnetic properties. The research encompassed hard disk drive Nd-Fe-B scrap magnets, industrial Sm (Co, Fe, Cu, Zr)z and Nd-Fe-B scrap magnets.
A scalable, environmentally friendly, low-cost method was developed to remove the Ni/Cu plating from the Nd-Fe-B hard drive scrap magnets.
- The surface-cleaned hard drive Nd-Fe-B scrap magnets were separated by size and shape, after which elemental analysis was completed for each magnet. The elemental analyses showed that even hard drive magnets of the same size and shape had a wide range of compositions.
- About 5 lbs. of the surface-cleaned computer hard drive Nd-Fe-B scrap magnets were induction-melted, compensated with virgin elements and hydrogenated. The hydrogenated powders were milled and isopressed to make Nd-Fe-B sintered magnets. The resulting magnetic properties were: remanent magnetization (Br) = 10.74 kG; intrinsic coercivity (Hci) = 12.08 kOe and the energy product (BH)max = 26 MGOe.
- About 50 lbs. of Sm2 Co17 magnetic scrap were collected from the industrial site, and the sinter skin was removed. The magnets were baked at 300o C for 2 hours to remove the moisture. The surface-cleaned Sm-Co scrap magnets were melted using an industrial scale induction furnace and composition analysis was carried out on the melted alloy. Based on the elemental analysis, the alloy was compensated with the virgin elements of Sm, Co, Fe, Cu and Zr to make the stoichiometric Sm2 Co17 alloy composition, and induction melted again. The stoichiometric Sm2 Co17 alloy was ball milled to make a powder with a particle size in the range of 3-4 µm. Test magnet parts were made and processed with standard sintering and machining procedures. These recycled magnets show almost equivalent properties compared to commercial magnets of the same grade. The magnetic properties were: remanent magnetization (Br) = 10.67 kG; intrinsic coercivity (Hci) > 24.5 kG, Hk = 11.9 kOe and the energy product (BH)max = 27.1 MGOe.
- About 10 lbs. of N38H-grade Nd-Fe-B scrap magnets were collected from the manufacturing facility, and the magnets were induction melted, compensated and hydrogenated to make sintered magnets. The hydrogenated powders were milled and isopressed to make Nd-Fe-B-sintered magnets. The magnetic properties were: remanent magnetization (Br) = 9.74 kG; intrinsic coercivity (Hci) = 16.29 kOe; the energy product (BH)max = 21 MGOe.
EEC is developing a low-cost manufacturing method to recycle RE magnet scrap. EEC's approach involves the conversion of Sm-Co (samarium-cobalt) and Nd-Fe-B (neodymium) chipped and broken magnets, as well as scrap from the machining slag, swarf and excess material left over from machining into useful, compositionally controlled RE magnet alloys. The process will produce specialty and master alloys of sufficient quality to be blended with other magnet alloys or to be used as virgin alloy for the production of RE permanent magnets. Alloys will be produced to meet customer-specified properties and can be crushed and milled to desired particle sizes. Preserving the material value by developing a process that does not adversely affect the structural properties will increase the value of EEC's recycling system. Also, the recovery of heavy RE elements should be considered as part of the overall project.