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Efficient, Environmentally-Compatible Recovery Technologies for Rhenium and Other Strategic Critical Materials


OBJECTIVE: The objective of this research is to demonstrate advanced, environmentally sound approaches to one or more of the following challenges associated with the recovery of rhenium: (1) economically sound methods to comminute superalloy scrap for subsequent selective treatment; (2) selective oxidation and volatilization to extract and recover rhenium; and (3) pyrometallurgical techniques to isolate and recover other valuable metals present in the superalloys. This solicitation focuses on rhenium only, but processes that show promise for other critical materials in addition to rhenium will be evaluated. DESCRIPTION: Due to the limited amount of rhenium present in the earth"s crust (approximately 1-2 part per billion) there is a significant benefit to be realized in recovering for reuse the rhenium from scrap material, spent catalysts, or end-of-life superalloys. Rhenium is found in molybdenum-copper porphyry deposits. If rhenium is present in ore that is processed, it will show up in the resulting molybdenum concentrate and will be retrieved in the molybdenum roasting process. Since there are no primary deposits of rhenium, the method in which it is processed is directly related to method in which molybdenum is produced. Very little rhenium is actually processed and isolated each year as compared to the millions of tons of copper and millions of pounds of molybdenum that are extracted from the same copper deposits. Opportunities exist for enhancing rhenium yield through technological improvements in discrete steps in the recovery process. Due to rhenium"s excellent high temperature properties (high creep resistance, high melting point, etc.) it is widely used as an alloying agent for high temperature applications including: Pt-Re petroleum reforming catalysts (20% current market use) Super alloys in high temperature turbine engines (70% current market use) Electromagnets, thermocouples, x-ray tube targets, and various others (10% current market use) As of 2010, the USGS reports that all platinum-rhenium petroleum reforming catalysts are recycled [1]. Information on the recycling rates of the remaining 80% of rhenium products is quite limited, although it is postulated to be sufficiently lower than the Pt-Re catalyst industry. Thus, the largest area for potential research may be the recovery and subsequent reuse of the rhenium in superalloys and various rhenium containing products. PHASE I: In the phase I effort, the investigators should assemble and evaluate thermodynamic data for rhenium recovery in a superalloy containing 3 wt% Re and 6 wt%. If thermodynamic data is available for all species of interest in a system, then equilibrium modeling can be performed to simulate the behavior of the system under conditions of interest, with the goal of evaluating new process approaches or optimizing existing approaches. This thermodynamic data consists of enthalpy, entropy, specific heat, and Gibbs energy, as well as Gibbs free energy of formation. The investigators will show the ability to model each processing step using existing or new models and software to predict optimal processing parameters for the Rhenium recovery. Full success in Phase I will produce a documented processing pathway for extraction of rhenium for superalloys or other rhenium-containing materials. PHASE II: In the phase II effort, the investigators shall evaluate and validate the process models, acquire missing thermodynamic data if needed, modify the process models and analyze and characterize the efficiency and the environmental impact of the proposed recovery methodology. The investigators should work with a potential industrial partner interested in recovery of rhenium. The process should evaluated and be able to show the selectivity and effectiveness of the optimized process. PHASE III: The immediate application is for secondary metals suppliers. The investigators should connect with various users of rhenium-containing alloys and materials to provide either support services for process optimization, to license the process (processes) to allow the users to recover rhenium. PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The modeling of extractive / recycling pathways should lead to an optimized recovery methodology for industry. This is of considerable interest to the aerospace, energy, and automotive industries
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