Extractive Metallurgy of Rhenium: A Review Caelen D. Anderson, MCSM Dr. Patrick R. Taylor Dr. Corby G. Anderson Kroll Institute For Extractive Metallurgy George S. Ansell Department of Metallurgical and Materials Engineering
Introduction A variety of processing technologies exist for recovery from both primary and secondary sources of rhenium Currently, there are no known primary rhenium deposits, thus, the method in which primary rhenium is produced is dependent on the commodity of which it is a byproduct, e.g., copper, molybdenum, uranium, etc In addition, focus on the recovery of rhenium from secondary sources, such as alloy scraps and catalysts, is continually growing This presentation presents a review of both primary and secondary processing technologies for the recovery of rhenium
Why is rhenium so special? Extraordinarily high melting point: (3,180 C) exceeded only by W and C A refractory metal (chemically and physically stable at high temperatures), but the only such metal not to form carbides Extremely dense: (21.02 g/cm 3 ) A density exceeded only by iridium, osmium and platinum No ductile-to-brittle transition temperature: (It remains ductile) malleable or being able to be deformed plastically without fracturing from Absolute Zero to its melting point High modulus of elasticity: (Extremely stable and rigid under stress) great tensile strength rhenium has the third-highest modulus of elasticity of any metal High resistance to creep: i.e., the tendency to move slowly or deform permanently when under stress Exceptionally resistant to chemical poisoning: Rhenium is particularly resistant to poisoning from nitrogen, sulfur and phosphorus Great attribute for use in catalysts
Crustal Abundance The concentration of rhenium in the earth s crust is rather small 0.7-10 parts per billion The only documented occurrence of rhenium as a mineral, Rheniite (ReS 2 ), was found near the Russian Kudryavyi volcano (Kuril Islands) Typically associated with molybdenum-copper porphyry deposits in concentrations of up to 0.2% Currently, there are no producers of primary rhenium Byproduct of Cu and Mo industries
Worldwide Rhenium Reserves and Production by Country (Polyak 2011)
Historical Rhenium Metal Powder Price from 1952-2012 1970: Use of rhenium in petrochemical catalysts begins 1980 2006 1980: Amount of rhenium used in petrochemical catalysts doubles 1970 1991 2003 1991: Dissolution of USSR leads to an increased supply of rhenium in the market 1999, 2003, 2006: Appearance of new generation turbine blades containing rhenium (Metal Pages 2012 Year 2012; Polyak 2011 Years 2007-2011; Naumov 2007 Years 1999-2006; Blossom 1998 Years 1952-1998)
Rhenium Production as a Byproduct of Molybdenum Processing The principal molybdenum end product is molybdenum tri-oxide (MoO 3 ) the basic raw material for most commercially used products of molybdenum The method in which rhenium is produced is dependent on the production method of MoO 3 Pyrometallurgical Roasting Hydrometallurgical Pressure Oxidation
Rhenium Recovery from Pyrometallurgical Effluent Streams During molybdenum roasting rhenium present in the molybdenum concentrate is oxidized to rhenium heptoxide (Re 2 O 7 ) 2ReS 2 +7.5O 2(g) = Re 2 O 7(g) + 4SO 2(g) (ΔG 298K = -406.5 kcal) This volatile rhenium exits in the flue gas stream and is scrubbed to make perrhenic acid Re 2 O 7(g) + H 2 O = 2HReO 4(aq) (ΔG 298K = -15.16 kcal) After which the rhenium is recovered using Ion Exchange Solvent Extraction Carbon Adsorption
Overview of Primary Processing Selective Precipitation The Melaven Process IX Processes Former Kennecott KGHM SX Processes Kazakhstan USBM SX-EW Unique Processes Kennecott MAP Freeport Autoclave Process MoReLeach Process Russian Volcano Mining Uranium Leaching
The Melaven Process (1947) US Patent #: 2,414,965 Neither IX or SX Selective precipitation Rhenium scrubbed with water Precipitated using potassium chloride Reduced using H 2(g) to produce metallic rhenium at T=350 C (Melaven and Bacon 1947)
IX Processes: The Original Kennecott Process Perrhenic Acid produced ph brought to 10 to remove Fe Aqueous rhenium adsorbs on anionic exchange resin Stripped using HCl Perchloric acid and hydrogen sulfide are then added to this solution to precipitate rhenium as Re 2 S 7 Re 2 S 7 is redissolved in ammonia and hydrogen peroxide Crystallized as ammonium perrhenate (NH 4 ReO 4 ) (Sutulov 1965)
IX Processes: KGHM Ecoren Process Re from copper concentrate smelter flue gas Adsorbed on weakly basic anionic exchange resin Eluted using ammonia solution Crystallized as APR using vacuum recrystallization Capacity to produce 4-5 tonnes/year (Chmielarz and Litwinionek 2010)
SX Processes: Kazakhstan In the Zhezkhazgan deposit, copper concentrates produced can contain up to 30g/t of rhenium Re recovered from Cu Electro-smelting Volatile Re 2 O 7 is scrubbed with water Sent to SX circuit using TAA extractant Stripped using ammonium hydroxide Up to 98.5% pure APR product produced (Abisheva et al. 2011)
SX-EW: USBM Pilot Plant Alternative to precipitation/crystallization Re 2 O 7 scrubbed with water Oxidized w/ Sodium chlorate Sent to 6-stage SX circuit Loaded solution sent to EW Current Density ~ 360 Amps/ft 2 Electro-won Metallic Rhenium produced (Churchward and Rosenbaum 1963)
Kennecott: Molybdenum Autoclave Process US Patent #: 6,149,883 Molybdenite flotation concentrate is leached with either sodium or potassium hydroxide elevated temperature (150-200 C) elevated pressure (75-200 psig) Rhenium present is primarily recovered in the SX step Followed by IX quaternary amine functional groups www.utahmining.org
Freeport McMoRan Process Patent App US #0263490A1 That the rhenium rich PLS can originate from an active copper leach, stockpile copper leach, acid blowdown stream, or a leach of molybdenite roaster flue fumes and dusts. loaded stream is sent to an activated carbon column circuit for adsorption of the aqueous rhenium. Stripped using Na/NH3 solution and T = 80-110 C (Waterman et al. 2009)
MoReLeach Process Aus Patent #: 2011229125 Molybdenum/rhenium concentrate in closed reactor vessel atmospheric temperature and pressure ReS2+ 9.5NaClO + 2.5H2O = ReO4-(aq) + 9.5NaCl + 2SO42-(aq) + 5H+ Re Rich solution is separated from the undissolved residue Sent for a metal separation stage such as solvent extraction, ion exchange, etc (Sutcliffe et al. 2012)
Volcano Mining: Kudriavy, Russia In the mid-1990 s, Rheniite (ReS2) discovered that the Kudriavy Volcano Russian researchers found that gases exiting the volcano contained considerable amount of rhenium 0.5-2.5 g/t Re as ReCl5 and ReF5 Currently, working on using zeolites as the adsorption medium for the rhenium rich fumarole gases Operational on pilot scale Inherent Danger of Worksite Environment
Recovery from Uranium Hydrometallurgy Rhenium is soluble in carbonate leach liquors Found adsorbed on IX columns in Palanga, Texas Stripped from columns using ammonium nitrate Precipitated as Re2S7 using H2S (Goddard 1996)
Rhenium Recycling Super Alloys Production scrap Secondary sources Spent Pt-Re Catalysts Complete Dissolution Selective Leaching
Recycling from Superalloys and alloy scrap W-Re scrap may be recycled via an oxidative pyrometallurgical roasting technique Roasted at 1000 C oxidizing atmosphere produce Re2O7 condensed in the cooler part of the tube furnace & digested in H2O ReO4- is subsequently precipitated as potassium perrhenate using KCl (Heshmatpour and McDonald 1982) Potassium perrhenate is filtered and reduced with H2(g) at 350 C 93.1% of the rhenium was recovered 99.98% pure Reo product
HC Starck Elevated Temperature Digestion Process Patent Application (US # 0255372 A1) Superalloys are digested in a molten salt melt (rotary kiln) NaOH, Na2CO3, and Na2SO4 T = 850-1100 C Material quenched, comminuted, leached w/water Re recovered using IX (Olbrich et al. 2009)
Electrochemical Method for Recycling of Superalloys US Patent #: 0110767 Ti Basket electrodes filled with superalloy scrap Electrolytically dissolved 18 wt% HCl electrolyte frequency = 0.5Hz I = 50 Amps V = 3-4 Volts Temp = 70 C Residence Time = 25 hours IX used to recover Re (Stoller et al. 2008)
Pt-Re Catalysts: Complete Dissolution of Alumina Substrate Sulfuric Acid Lixiviant Rhenium Alumina Partially Pt Re separated using IX Elution with HCl Neutralize with NH4OH Evaporative Crystallization Produce APR (El Guindy 1997)
Pt-Re Catalysts: Selective Leaching Re and Pt Calcination or Pressure Leaching Calcination Calcine (T 1150 C) the γ-al2o3 α-al2o3 lowering the dissolution of the alumina catalyst Pt and Re leached in 5M H2SO4 w/ K-persulfate & NaCl Re Recovery 95% Pt Recovery 97% Pressure Leaching Dilute solution of sulfuric acid (0.001-1.0 Mol/L) is used in the presence of ammonium iodide or bromide and oxygen to selectively leach Pt and Re Leaving alumina substrate behind At 160 C and ano2 overpressure of 116 psig Rhenium recovery of 98%
Production of Metallic Rhenium Generally reduced from ammonium perrhenate (APR) KReO4 can be precursor With a reductant such as CO(g) or H2(g) Temp range from 175 1000 C 2NH4ReO4(s) + 7H2 = 2Re + 2NH3 + 8H2O (ΔG 298K = -37.16 kcal) 2KReO4 + 7H2 = 2Re + 2KOH + 6H2O (ΔG 298K = -16.07 kcal) (Millensifer 2010)
Future Research Opportunities Most of the processes involved in the production of primary and secondary rhenium, involve the use of elevated temperatures elevated pressures large amounts of reagents combination of the three Opportunities for improvement exist
Future Research Opportunities Roasting is an elevated Through innovation in the temperature, exothermic scrubbing equipment used process which requires (Fluidized Bed Reactor) temperatures of 630-650 C recoveries have now increased Tight temperature control Early scrubbing attempts of flues gases were relatively inefficient to approximately 80% 90% reported capturing roughly 25% of the rhenium present
Future Research Opportunities Pressure Oxidation Involves the use of elevated temperatures, pressures, and additional reagents Re in aqueous form Recovery may be higher Low Temp processes being investigated MoReLeach Increased Separation Capabilities Higher Selectivity Reagents Solvent Extraction Ion Exchange Molecular Recognition Tech (MRT) SuperLig Cu, PGM s, Co, etc. Use of Au Industry Technology Activated carbon
Future Research Opportunities Rhenium Recycling Rhenium Applications Relatively new industry Vast opportunities Due to the limited amount of rhenium present in the earth s crust (~1ppb) any scrap material, spent catalyst, or end-of-life super alloy needs to be recycled for reuse Minimization of waste generation Primary and secondary scrap recycling Improved End-of-Life Recycling Utilizing new and existing techniques
Conclusion This presentation has presented a review of both the current and former technologies used in the extractive metallurgy of rhenium Provided areas for potential technological development Special recognition is due to Tom Millensifer for his assistance with this paper Additionally, to the Office of Naval Research for the financial support which allowed this research to occur
References Anderson, C.D., Taylor, P.R., and Anderson, C.G., Extractive metallurgy of rhenium: a review, Minerals and Metallurgical Processing, Vol. 30, No. 1, pp. 59-73. If you would like a copy of our paper please give me your business card