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Recycling Aluminum Salt Cake

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Presentation on theme: "Recycling Aluminum Salt Cake"— Presentation transcript:

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

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