Loading...
Sulfation roasting and leaching of samarium-cobalt magnet swarf for samarium recovery
Stanton, Caleb William
Stanton, Caleb William
Citations
Altmetric:
Advisor
Editor
Date
Date Issued
2016
Date Submitted
Collections
Research Projects
Organizational Units
Journal Issue
Embargo Expires
2017-02-15
Abstract
During production of samarium cobalt magnets, a large amount of magnetic swarf is generated due to milling and cutting. This can accrue up to 30% of input materials. Recycling end-of-life magnets is equally important as these materials are critical components of aging green energy systems and a variety of electronic components. Samarium is currently listed as one of the semi-critical materials by the Critical Materials Institute and the Department of Energy. This report describes a novel sulfation, roast and leaching process for the recycling and reuse of samarium from samarium-cobalt magnet waste. Three stages are necessary for this process. The steps begin with sulfate conversion during acid roasting, selective thermal decomposition at higher temperatures, and leaching in demineralized water. This process is capable of separating samarium from cobalt, iron, and copper into a greater than 95% purity samarium sulfate leach solution. Several factors were tested to identify the parameters that exert the highest effect on samarium sulfate grade and overall recovery in the leach solution. These include acid addition, temperature, residence time, mixing, gas flow rate, and gas composition. Preliminary muffle furnace tests produce a samarium sulfate product with over 99% purity. Rotary kiln experiments were conducted to better control mixing and atmospheric conditions within the reactor vessel. Complete sulfate conversion was achieved with 40% excess sulfuric acid at 400°C and a 15 minute residence time. Several stages of acid-roasting, residue recycling, and leaching may increase the final leach solution samarium sulfate grade and recovery. Better control of sulfur dioxide partial pressure in the reactor may also enable more selective roasting conditions. This process is only viable if built with or alongside an existing sulfur recovery system such as an acid plant. Net present value after five-years with an acid plant is $2.2 million whereas the project is unfeasible without sulfur recovery. This is based on a two stage roasting process and treatment of 1000 tonnes per year of samarium-cobalt magnet waste. Based on the success of the results from this study, this process is highly recommended for immediate pilot-scale testing.
Associated Publications
Rights
Copyright of the original work is retained by the author.