1. Recycling Aluminum Salt Cake
J.N. Hryn and E.J. Daniels
Process Engineering Section
Energy Systems Division
Argonne National Laboratory

2. About U.S. Department of Energy (DOE)
Maintains 5 major National Laboratories
Argonne, Oak Ridge, Sandia, Livermore, Brookhaven
19 smaller laboratories and technology centers
Mission includes:
Advance the national, economic, and energy security of the United States
Promote scientific and technological innovation

3. About Argonne National Laboratory
3/25/2017
About Argonne National Laboratory
Founded in 1943, designated
a national laboratory in 1946
Managed by The University of Chicago for the Department of Energy
~4000 employees and 4000 facility users
~$500M budget
1500-acre site in Illinois
800-acre site in Idaho
Use version from Feb 26. Divide into two slides, one with first two bullets as is.
The second with last three bullets but first to read “A World Leader in energy
Research with two subheads: -- nuclear fuel cycle and fuel cells/Hydrogen
Broad R&D portfolio
Argonne partners with DOE, other federal labs, academia, and the private sector
Test

4. About Process Engineering Section
Part of Energy Systems Division
Interdisciplinary, focus on applied research
Three R&D areas:
Recycling and separation process development
Aluminum and Magnesium
Automotive Shredder Residue
Plastics (recycled appliances and automotive)
Glass
Process modeling and simulation
Glass and aluminum melting furnaces
New materials applications
Diamond coatings
Thin films (atomic layer deposition)

5. Recycling Aluminum Salt Cake
Opportunity:
Aluminum recycling generates salt cake by-product
Aluminum metal
Sodium chloride and potassium chloride salt
Non-metallic product (mainly aluminum oxide)
Salt cake is disposed in landfills
Only a few companies use responsible disposal methods
Environmental concern
Project Objective:
to develop a cost-effective salt cake recycling technology
recover aluminum, salts, and non-metallic product (NMP)
NMP is converted to value-added oxide products

6. Recycling Aluminum Salt Cake – Overview
Refractory Feedstock
Recovery of
Salt Cake
Constituents
Salt
Conversion to
Value-Added
Products
Ironmaking Feedstock
Salt Cake
Non-Metallic Product
Steelmaking Feedstock

7. Project Summary History: 1990: US DOE-sponsored assessment study
1994: bench-scale work begins at Argonne
1996: Argonne & Alumitech begin collaboration
1998: Argonne begins pilot-scale tests
2001: Experimental work suspended
Preliminary conclusions:
Many technical solutions possible
No economical solutions yet for salt cake recycling
Best option is maximize aluminum recovery and disposal of residues in controlled landfill
Economic and environmental analysis suggested that recycling salt cake is not desirable

8. Average Salt Cake Composition
Non-Metallic Product 66%
Salt 28%
Aluminum 6%

9. Suggested Approach to Recycling Salt Cake
digester
screen
filter
evaporator
aluminum (to smelters)
NMP (to market)
salt (to smelters)
crusher
condenser
water
steam
salt cake

10. Salt Cake Recycling Barriers in U.S.
salt recovery by evaporation is too expensive
high energy and capital costs, low product value

11. Salt Cake Recycling Barriers in U.S.
no market for recovered NMP
high levels of impurities, variable composition

12. NMP Composition 40 to 80% up to 40% up to 10% up to 5% up to 8%
alumina (a-Al2O3)
spinel (MgAl2O4)
magnesia (MgO)
aluminum hydroxide (Al(OH)3)
aluminum
impurities (silicates, iron oxides, calcium fluoride, aluminum nitride)
In addition, “washed” NMP can contain up to 2% salt
Detrimental to many potential products

13. Best Practice – Recycling Aluminum Salt Cake
Recycling in US is driven by business opportunities
U.S. best practice is to maximize Al recovery and dispose of residues (salt and NMP) in controlled landfills
Recycling salt cake in Europe is driven by legislation
No economically viable solution yet
Best practice is to maximize Al recovery with minimum salt flux, and dispose residues in controlled landfills

14. Environmental Impact of Salt Cake Recycling
In all cases:
Salt recovery consumes more energy than can be recovered from the energy value of the recycled salt
Salt recovery generates more waste than would normally be generated if it was disposed in controlled landfills
NMP recovery becomes an environmental hazard when washed
Entrained aluminum becomes excessively reactive
Excessive energy and water consumption if dilute salt solutions are generated
Best environmental solution:
Do not recover salt, NMP
Maximize aluminum recovery
Use controlled landfills (RCRA C)

15. Project Conclusions
Many technical solutions possible for recycling salt cake
None economical yet ($35/t landfill)
Best economic option is to maximize aluminum recovery and disposal of residue in controlled landfill
Use best process technology
TTRF furnace, quality flux, energy efficient process
Keep salt cake dry
Crush and recover metallic aluminum by screens and/or eddy-current magnetic separators
Best environmental option is to minimize salt cake generation
Maximize Al recovery, minimize salt use, minimize aluminum nitride, and dispose residue in controlled landfill