US009631259B2

(12) United States Patent (10) Patent No.: US 9,631,259 B2 Sumida et al. (45) Date of Patent: Apr. 25, 2017

(54) METHOD FOR PRODUCING AOUEOUS JP 50-21998 B1 7/1975 SOLUTION OF PERRHENIC ACID FROM JP 62-124240 * 6, 1987 JP 62-148327 A 7, 1987 JP 2-20575 B2 5, 1990 JP 2011-117080 A 6, 2011 (71) Applicant: PAN PACIFIC COPPER CO., LTD., JP 2011-178573 A 9, 2011 Tokyo (JP) JP 2012-149285. A 8, 2012 WO WO 2011 115660 A2 9, 2011 (72) Inventors: Ikunobu Sumida, Oita (JP); Yuji Kawano, Oita (JP); Makoto OTHER PUBLICATIONS Hamamoto, Oita (JP) Peimin et al., “Highly effective use of metallurgical material” (73) Assignee: PAN PACIFIC COPPER CO., LTD., Metallurgical Industry Press, Sep. 30, 2012, p. 144.* Tokyo (JP) Translatioin of Guo, “Efficient Use of Resources by Metallurgy’ Metallurgical Industry Publisher, vol. 2, Section 5.6.3, Sep. 2012, p. (*) Notice: Subject to any disclaimer, the term of this 145* patent is extended or adjusted under 35 Translation of Zhang, "Tungsten-Molybdenum Metallurgy' Metal lurgical Industry Publisher, Sep. 2005, pp. 210-216.* U.S.C. 154(b) by 0 days. International Preliminary Report on Patentability and English trans lation of the Written Opinion of the International Searching Author (21) Appl. No.: 14/400,122 ity (forms PCT/IB/373, PCT/ISA/237 and PCT/IB/338), issued Jul. 9, 2015, for International Application No. PCT/JP2013/064517. (22) PCT Filed: May 24, 2013 Chinese Office Action and Search Report, dated Nov. 11, 2015, for Chinese Application No. 201380023732.6, with a partial English (86). PCT No.: PCT/UP2013/064517 translation. Guo, “Efficient Use of Resources by Metallurgy.” Metallurgical S 371 (c)(1), Industry Publisher, vol. 2, Section 5.6.3, Sep. 2012, p. 145 (pp. (2) Date: Nov. 10, 2014 142-145 provided). Zhang, "Tungsten-Molybdenum Metallurgy.” Metallurgical Indus (87) PCT Pub. No.: WO2014/103398 try Publisher, Sep. 2005, pp. 210-216. U.S. Appl. No. 14/400,028, filed Nov. 10, 2014. PCT Pub. Date: Jul. 3, 2014 Chinese Office Action and Search Report, dated Dec. 11, 2015, for Chinese Application No. 201380023747.2, with a partial English (65) Prior Publication Data translation. US 2015/0107414A1 Apr. 23, 2015 (Continued) Primary Examiner — Steven Bos (30) Foreign Application Priority Data (74) Attorney, Agent, or Firm — Birch, Stewart, Kolasch & Birch, LLP Dec. 28, 2012 (JP) ...... 2012-288828 (57) ABSTRACT (51) Int. Cl. A method allowing production of high-purity perrhenic acid COIG 47/00 (2006.01) from rhenium sulfide by applying pyrometallurgical process C22B 6L/00 (2006.01) C22B I/02 (2006.01) is provided. A method for producing an aqueous solution of (52) U.S. Cl. perrhenic acid, comprising: 1) a step for performing a first CPC ...... C22B 61/00 (2013.01); COIG 47/00 roasting process of rhenium Sulfide under an oxygen-con (2013.01); C22B I/02 (2013.01); COIP 2006/80 (2013.01); Y02P 10/214 (2015.11); taining gas to generate rhenium and Sulfur oxide, the Y02P 10/234 (2015.11) Sulfur oxide being gasified for discharge and the rhenium (58) Field of Classification Search None oxide being obtained as a roasted residue; 2) a step for See application file for complete search history. performing a second roasting process of the roasted residue under an oxygen-containing gas to collect gasified rhenium (56) References Cited oxide; 3) a step for cooling and Solidifying the gasified U.S. PATENT DOCUMENTS rhenium oxide, or a step for dissolving the gasified rhenium oxide into while water-cooling to obtain the aqueous 2,876,065. A 3/1959 Zimmerley et al. 2.967,757 A 1/1961 Zimmerley et al. Solution of perrhenic acid; and 4) in case where the rhenium 2,972,531 A 2, 1961 Zimmerley et al. 3,770414. A 11/1973 Lake et al. oxide is solidified, a step for dissolving the solidified rhe 4.321,089 A 3, 1982 Kruesi et al. nium oxide into water, or heating and gasifying the Solidified 2011 0126673 A1 6/2011 Dasan et al. 2011/0229366 A1 9/2011 Luederitz et al. rhenium oxide and then dissolving the gasified rhenium oxide into water, to obtain the aqueous solution of perrhenic FOREIGN PATENT DOCUMENTS acid. GB 1282 116 A 7/1972 JP 47-21323 10, 1972 20 Claims, 1 Drawing Sheet US 9,631,259 B2 Page 2

(56) References Cited

OTHER PUBLICATIONS Chinese Office Action with a partial English translation, dated Jun. 1, 2015, for Chinese Application No. 201380023747.2. International Preliminary Report on Patentability and English trans lation of the Written Opinion of the International Searching Author ity (Forms PCT/IB/338, PCT/IB/373, PCT/ISA/237), dated Jul. 9, 2015, for International Application No. PCT/JP2013/064516. International Search Report, issued in PCT/JP2013/064517, dated Aug. 13, 2013. Japanese Office Action, dated Aug. 25, 2015, for Japanese Appli cation No. 2012-288826, with an English translation. Metallurgy and Metal Material

6 Y. US 9,631,259 B2 1. 2 METHOD FOR PRODUCING AOUEOUS CITATION LIST SOLUTION OF PERRHENIC ACID FROM RHENIUM SULFIDE Patent Literature

5 Patent Literature 1: JP-A-S62-148327 TECHNICAL FIELD Patent Literature 2: JP-A-H2-20575 Patent Literature 3: JP-A-S47-21323 The present invention relates to a method for producing an aqueous Solution of perrhenic acid from rhenium sulfide. SUMMARY OF INVENTION In particular, the present invention relates to a method for 10 producing from rhenium Sulfide Technical Problem through perrhenic acid. As described in Patent Literature 1, a method for produc ing perrhenic acid from crude rhenium sulfide by hydromet BACKGROUND ART 15 allurgical process is known, but provision of a method for producing the perrhenic acid from the crude rhenium sulfide Rhenium is rare metal slightly entrained in molybdenite, by pyrometallurgical process is also desired. In this regard, which is molybdenum raw ore, or copper ore. It is important while Patent Literature 3 discloses that rhenium sulfide is metal used as an element to be added to a catalyst, an oxidized and converted into rhenium oxide by roasting, and element to be added to a thermocouple or a Super heat that the rhenium oxide is vaporized at a temperature of 150° resisting alloy, a high-vacuum electron tube material or the C. or higher, and accumulated in flue dust, room for like. improvement has been left for removal of an impurity. As one of promising raw materials for industrially col Therefore, an object of the present invention is to provide lecting rhenium, crude rhenium sulfide is exemplified. Zinc, 25 a method allowing production of high-purity perrhenic acid bismuth or the like are typical impurities in the crude from rhenium sulfide by applying pyrometallurgical process. rhenium sulfide. Hitherto, as described in JP-A-S62-148327 (Patent Lit Solution to Problem erature 1), a method for producing potassium perrhenate 30 The present inventors have diligently continued study in from crude rhenium sulfide has been known. In the Litera order to attain the object described above, and as a result, ture, the crude rhenium sulfide is oxidized and leached using have found that a method for performing a two-step roasting an oxidizing agent Such as peroxide, and hydrogen process of rhenium sulfide is effective. More specifically, in Sulfide is added to post-leaching Solution, thereby obtaining a first-step roasting process, impurities such as Sulfur is perrhenic acid with high purity in the solution. Then, the 35 gasified and discharged, and rhenium, Zinc, bismuth and so potassium perrhenate is produced by adding potassium forth are remained on a residue side as a non-volatile thereto. As described in JP-A-H2-20575 (Patent component. In a second-step roasting process, while the Literature 2), ammonium perrhenate can be produced from non-volatile components such as Zinc and bismuth are potassium perrhenate by a method of bringing the potassium separated as a residue, rhenium is extracted as gasified perrhenate into contact with a cation exchange resin and 40 rhenium oxide. Thus, purity of the rhenium oxide to be then neutralizing the resultant material with aqueous ammo collected rises. When the rhenium oxide obtained is dis nia and performing filtration, or the like. The ammonium Solved into water, an aqueous Solution of high-purity per perrhenate is marketable as a valuable material, and in a high rhenic acid is obtained. value-added form. It can be understood that the present invention can target 45 rhenium Sulfide containing impurities, and also high-purity Also, JP-A-S47-21323 (Patent Literature 3) describes a rhenium Sulfide Substantially containing no impurity. More method for producing rhenium, characterized by roasting specifically, in the first-step roasting process, Sulfur oxide is rhenium-containing molybdenum raw ore, extracting the generated from the rhenium sulfide, but in case where a resulting material with water, adding potassium chloride to roasting process is performed only in one step, the Sulfur this extract, dissolving a thus obtained precipitate into 50 oxide becomes the impurity and is mixed into the rhenium concentrated , adjusting Sulfuric acid concen oxide. However, the second-step roasting process is per tration to 1 to 3 mol/l and then conducting extraction using formed to allow further removal of the impurity, and there an organic Solvent containing a high-molecular-weight fore high-purity rhenium oxide having only a smaller organic tertiary amine in a concentration of 0.02 mol/l or amount of Sulfur is obtained in comparison with a case more, Subsequently applying back extraction to this extract 55 where the roasting process is performed only in one step. with an aqueous Solution of caustic potash, and applying Accordingly, in one aspect, the present invention concentrated reduction treatment to this extract. includes: Further, Patent Literature 3 discloses that rhenium is a method for producing an aqueous solution of perrhenic contained in a form of rhenium sulfide, the rhenium sulfide acid, comprising: is oxidized by roasting, and converted into rhenium oxide 60 1) a step for performing a first roasting process of rhenium (ReO2), the rhenium oxide is vaporized at a temperature of Sulfide under an oxygen-containing gas to generate rhenium 150° C. or higher, and accumulated in flue dust. The oxide and sulfur oxide, the sulfur oxide being gasified for Literature also discloses that, if the flue dust is subjected to discharge and the rhenium oxide being obtained as a roasted extraction with water, the rhenium oxide (Re-O,) is residue; absorbed into an aqueous Solution, and that the aqueous 65 2) a step for performing a second roasting process of the Solution contains a large amount of Sulfur dioxide or Sulfur roasted residue under an oxygen-containing gas to collect trioxide, and therefore shows strong acidity. gasified rhenium oxide; US 9,631,259 B2 3 4 3) a step for cooling and Solidifying the gasified rhenium using as a raw material the aqueous solution of perrhenic oxide, or a step for dissolving the gasified rhenium oxide acid obtained by the method for producing the aqueous into water while water-cooling to obtain the aqueous solu Solution of perrhenic acid as related to the present invention. tion of perrhenic acid; and In still another aspect, the present invention includes a 4) in case where the rhenium oxide is solidified, a step for 5 method for producing rhenium metal, comprising using as a dissolving the Solidified rhenium oxide into water, or heating raw material the aqueous solution of perrhenic acid as and gasifying the Solidified rhenium oxide and then dissolv obtained by the method for producing the aqueous solution ing the gasified rhenium oxide into water, to obtain the aqueous solution of perrhenic acid. of perrhenic acid as related to the present invention. In another aspect, the present invention includes: 10 Advantageous Effects of Invention a method for producing an aqueous solution of perrhenic acid, comprising: The present invention provides a pyrometallurgical pro 1) a step for performing a first roasting process of rhenium cess according to which high-purity perrhenic acid can be Sulfide containing at least one of Zinc and bismuth under an produced from rhenium sulfide. The present invention can oxygen-containing gas to generate rhenium oxide and Sulfur 15 oxide, the Sulfur oxide being gasified for discharge and the be incorporated into a method for producing ammonium rhenium oxide being obtained as a roasted residue along perrhenate from rhenium sulfide. with the at least one of zinc and bismuth; 2) a step for performing a second roasting process of the BRIEF DESCRIPTION OF DRAWINGS roasted residue under an oxygen-containing gas to separate the at least one of Zinc and bismuth as a roasted residue and FIG. 1 is a schematic diagram of roasting equipment used to collect gasified rhenium oxide; for a second-step roasting process in Examples. 3) a step for cooling and Solidifying the gasified rhenium oxide, or a step for dissolving the gasified rhenium oxide DESCRIPTION OF EMBODIMENTS into water while water-cooling to obtain the aqueous solu 25 tion of perrhenic acid; and In one embodiment of a method for producing an aqueous 4) in case where the rhenium oxide is solidified, a step for Solution of perrhenic acid as related to the present invention, dissolving the Solidified rhenium oxide into water, or heating the method comprises: and gasifying the Solidified rhenium oxide and then dissolv 1) a step for performing a first roasting process of rhenium ing the gasified rhenium oxide into water, to obtain the 30 Sulfide under an oxygen-containing gas to generate rhenium aqueous solution of perrhenic acid. oxide and sulfur oxide, the sulfur oxide being gasified for In one embodiment of the method for producing the discharge and the rhenium oxide being obtained as a roasted aqueous solution of perrhenic acid as related to the present residue; invention, the first roasting process is finished when a 2) a step for performing a second roasting process of the content of S in the roasted residue is within a range of 0.5 35 roasted residue under an oxygen-containing gas to collect to 20 mass %. gasified rhenium oxide; In another embodiment of the method for producing the 3) a step for cooling and solidifying the gasified rhenium aqueous solution of perrhenic acid as related to the present oxide, or a step for dissolving the gasified rhenium oxide invention, the first roasting process is performed at an into water while water-cooling to obtain the aqueous solu in-furnace temperature of 100 to 350° C. 40 tion of perrhenic acid; and In still another embodiment of the method for producing 4) in case where the rhenium oxide is solidified, a step for the aqueous solution of perrhenic acid as related to the dissolving the Solidified rhenium oxide into water, or heating present invention, the second roasting process is performed and gasifying the Solidified rhenium oxide and then dissolv at an in-furnace temperature of 200 to 600° C. ing the gasified rhenium oxide into water, to obtain the In still another embodiment of the method for producing 45 aqueous solution of perrhenic acid. the aqueous solution of perrhenic acid as related to the In another embodiment of a method for producing an present invention, the oxygen-containing gas is preheated at aqueous solution of perrhenic acid as related to the present 100° C. or higher in the first roasting process and the second invention, the method comprises: roasting process. 1) a step for performing a first roasting process of rhenium In still another embodiment of the method for producing 50 Sulfide containing at least one of Zinc and bismuth under an the aqueous solution of perrhenic acid as related to the oxygen-containing gas to generate rhenium oxide and Sulfur present invention, the step for cooling and solidifying the oxide, the Sulfur oxide being gasified for discharge and the gasified rhenium oxide is performed while keeping entrained rhenium oxide being obtained as a roasted residue along Sulfur oxide in a gaseous state for Solid-gas separation of the with the at least one of zinc and bismuth; sulfur oxide. 55 2) a step for performing a second roasting process of the In still another embodiment of the method for producing roasted residue under an oxygen-containing gas to separate the aqueous solution of perrhenic acid as related to the the at least one of Zinc and bismuth as a roasted residue and present invention, the solidified rhenium oxide is collected to collect gasified rhenium oxide; on a material insoluble in rhenic acid in the step for cooling 3) a step for cooling and solidifying the gasified rhenium and Solidifying the gasified rhenium oxide. 60 oxide, or a step for dissolving the gasified rhenium oxide In still another aspect, the present invention includes a into water while water-cooling to obtain the aqueous solu method for producing potassium perrhenate, comprising tion of perrhenic acid; and using as a raw material the aqueous Solution of perrhenic 4) in case where the rhenium oxide is solidified, a step for acid obtained by the method for producing the aqueous dissolving the Solidified rhenium oxide into water, or heating Solution of perrhenic acid as related to the present invention. 65 and gasifying the Solidified rhenium oxide and then dissolv In still another aspect, the present invention includes a ing the gasified rhenium oxide into water, to obtain the method for producing ammonium perrhenate, comprising aqueous solution of perrhenic acid. US 9,631,259 B2 5 6 (Rhenium Sulfide) In the first roasting process, the rhenium Sulfide is con Rhenium sulfide to be treated in the present invention may sidered to be converted into the rhenium oxide according to be rhenium Sulfide containing no impurity or crude rhenium the following reaction formulas. Sulfide containing impurities. It is typically crude rhenium Sulfide containing at least one of Zinc and bismuth, and more typically, crude rhenium Sulfide containing both. In the SO(g)+/3O2(g)->SO(g) (Formula 1) present invention, "rhenium sulfide” means both the crude rhenium Sulfide containing impurities and the rhenium Sul In the first roasting process, generated Sulfur oxide is fide containing Substantially no impurity. An origin of the intended to be gasified and separated from the rhenium 10 oxide. Therefore, from viewpoints of efficiency of removal crude rhenium sulfide is not restricted, but typical examples of the impurities and efficiency of collection of rhenium, the include crude rhenium sulfide originating from the follow roasting process is preferably carried out under conditions of ing. retaining the rhenium oxide in the furnace without gasifi In waste acid obtained by performing water-wash of a cation while the Sulfur oxide is gasified and discharged Sulfurous acid gas generated from a step for Smelting 15 outside the furnace through gas piping or the like. More non-ferrous metal Such as copper, rhenium which was specifically, if heating temperature becomes excessively contained in raw ore is mixed with impurities. Rhenium, high, a ratio of rhenium oxide lost by gasification increases, bismuth, Zinc, mercury, arsenic, iron, copper and so forth are and on the other hand, if the heating temperature is exces generally contained in Such waste acid. The rhenium in the sively low, a ratio of removal of by-produced sulfur oxide waste acid exists in a form of rhenic acid (HReO). When decreases. Incidentally, in case where mercury or arsenic is the rhenium in the waste acid is allowed to react with contained as the impurity in the rhenium sulfide, removal , rhenium sulfide is formed and can be treatment of the materials can also be made in the first collected in a form of powder by solid-liquid separation. At roasting process in a similar manner. this time, Zinc and bismuth do not react with the hydrogen Results of study by the present inventors show that the Sulfide, and therefore can be separated on a liquid phase. 25 first roasting process is finished when the content of S in the In order to provide rhenium sulfide containing only a roasted residue is preferably in a range of 0.5 to 20 mass %, Small amount of impurities, the impurities can also be more preferably, in a range of 0.5 to 10 mass %, and still removed by the following methods. For example, the waste more preferably, in a range of 0.5 to 5 mass %, thereby acid is passed through a resin having strong adsorbability to achieving a high rhenium recovery while the impurities are 30 effectively removed. mercury, Such as a chelate resin and a strongly basic anion In order to achieve S content in the roasted residue in the exchange resin, thereby allowing removal of mercury. More range described above, the first roasting process is per over, the waste acid after removal of mercury is passed formed by adjusting in-furnace temperature in a roasting through an anion exchange resin to selectively adsorb furnace preferably to 100 to 350° C., and more preferably, included rhenium and bismuth onto the resin, thereby allow 35 to 200 to 350° C. Moreover, although roasting time depends ing removal of arsenic, iron and copper that do not adsorb on a scale or structure of the roasting furnace, if the time is on the resin. An eluent such as is passed too long, gasification of rhenium proceeds, and on the other through the anion exchange resin on which rhenium and hand, if the time is too short, an oxidation reaction does not bismuth are adsorbed, thereby stripping of rhenium and sufficiently take place. Therefore, the time can be adjusted to bismuth from the anion exchange resin is achieved. Bismuth 40 30 to 240 minutes, for example, and preferably, to 120 to 180 can be separated from rhenium by chromatography. minutes. In a typical embodiment, according to a chemical analysis In order to Suppress the reaction in case where in-furnace (elements other than mercury are determined by ICP-OES temperature rapidly rises, provision for Supplying an inert and mercury is determined by reducing vaporization absorp gas such as nitrogen and argon into the furnace is also tiometry), the crude rhenium sulfide contains rhenium: 30 to 45 desired. 62 mass %, sulfur: 20 to 38 mass %, zinc: 0.01 to 1.0 mass Specific examples of the oxygen-containing gas include %, bismuth: 0.01 to 1.0 mass % and mercury: 0.01 to 1.0 oxygen, air and a mixture of oxygen and inert gas, but use mass %, and in a further typical embodiment, the crude of air is preferred in view of avoiding an increase the cost. rhenium sulfide contains rhenium: 35 to 50 mass %, sulfur: The oxygen-containing gas referred to herein includes an 25 to 32 mass %, zinc: 0.01 to 0.5 mass %, bismuth: 0.01 to 50 oxygen-containing gas existing in a form of gas from the 0.7 mass % and mercury: 0.01 to 0.7 mass %. Rhenium may beginning and also an oxygen-containing gas produced by partially exist in a form of rhenium oxide in several cases. using Solid or liquid (for example, potassium chlorate, (Step 1) ammonium perchlorate) which generates oxygen by heating. In step 1, a first roasting process of rhenium sulfide is The oxygen-containing gas, from a viewpoint of reaction performed under an oxygen-containing gas to generate rhe 55 efficiency, preferably Supplies oxygen in an amount equal to nium oxide and Sulfur oxide, the Sulfur oxide being gasified or more than a theoretical equivalent to be required in the for discharge and the rhenium oxide being obtained as a above (formula 1). For example, it can be adjusted to 1.2 roasted residue. In case where at least one of Zinc and times or more, and more preferably, 1.8 times or more as bismuth is contained in the rhenium sulfide, they are pref much as the theoretical equivalent. erably collected in the roasted residue along with the rhe 60 The oxygen-containing gas is desirably preheated prior to nium oxide. Supply to the roasting furnace. Preheating of the oxygen Types of furnaces for carrying out the first roasting containing gas allows setup of low inner wall temperature in process are not particularly restricted, and specific examples the roasting furnace, and a decrease in a ratio of gasification include a kiln furnace, a fluidized bed furnace and a tubular of rhenium oxide. More specifically, in case where the furnace, but the kiln furnace is further preferred due to 65 oxygen-containing gas is not preheated, in terms of heat presence of agitation action by rotation and high reaction transfer, a high setup value of the inner wall temperature in efficiency with oxygen. the roasting furnace is required in order to reach temperature US 9,631,259 B2 7 8 at which the oxidation reaction at an interface between the be imperfect, and therefore the oxygen-containing gas is to oxygen-containing gas and the rhenium sulfide Sufficiently be used also in the second roasting process in the present progresses. The above means that the inner wall temperature invention. in the roasting furnace reaches or goes beyond the tempera Also in the second roasting process, the oxygen-contain ture essentially needed for the oxidation reaction, resulting ing gas is desirably preheated prior to Supply to the roasting in progress of gasification of the rhenium oxide near the furnace. Preheating of the oxygen-containing gas gives an inner wall. On the other hand, preheating of the oxygen advantage of uniformization of an in-furnace reaction. containing gas eliminates necessity of increasing the inner For transporting the gasified rhenium oxide, gas piping wall temperature in the roasting furnace beyond necessity, may be used. Moreover, in case where the identical roasting 10 furnace is used, the gasified rhenium oxide is preferably and therefore gasification of the rhenium oxide can be collected using gas piping different from the gas piping used Suppressed. during the first roasting process from a viewpoint of pre From the viewpoint described above, the oxygen-contain venting impurities from being mixed. ing gas is preferably preheated to the temperature identical The gas piping is preferably heat-insulated to prevent the with in-furnace temperature. However, excessive preheating 15 rhenium oxide from Sticking onto a piping inner wall during beyond necessity causes energy loss. transportation. If in-piping temperature during heat insula (Step 2) tion is too low, the rhenium oxide might be solidified, and In step 2, the second roasting process is performed to the therefore the temperature is preferably adjusted to 300° C. or roasted residue obtained in step 1 under the oxygen-con higher. And, from a viewpoint of energy consumption, an taining gas to collect the gasified rhenium oxide. In case increase in temperature beyond necessity is unnecessary, where at least one of Zinc and bismuth is contained in the and therefore the temperature is typically 500° C. or lower, roasted residue, they are preferably separated from the and more typically, 400° C. or lower. rhenium oxide as the roasted residue. (Step 3) Types of furnaces for carrying out the second roasting Then, the gasified rhenium oxide can be cooled and process are not particularly restricted as is the case with the 25 solidified. On the occasion, the sulfur oxide is preferably first roasting process, and specific examples include a kiln Subjected to solid-gas separation by cooling and solidifying furnace, a fluidized bed furnace and a tubular furnace, but the gasified rhenium oxide while keeping the sulfur oxide the tubular furnace is preferred for the reason of reduction of entrained in the gasified rhenium oxide a gaseous state for contamination due to a scattered residue during collection, improving the purity of the rhenium oxide. The rhenium and cost. 30 oxide is desirably cooled and solidified at a predetermined The roasted residue can be once removed from the cooling part (may be inside the piping or in a container furnace used in the first roasting process and can be sub having an inlet and an outlet) in view of an improvement in jected to the second roasting process in another roasting working efficiency. At this time, the sulfur oxide entrained furnace, or a roasting furnace identical with the furnace in therein directly passes through the cooling part as gas due to the first roasting process can be used. Another roasting 35 a difference in boiling points, and therefore the purity of furnace is preferably used from a viewpoint of Suppressing rhenium oxide is improved by the Solid-gas separation. contamination. In case where the identical roasting furnace From a viewpoint of contamination prevention, the Solidi is used, it is desirable to prevent contamination for obtaining fied rhenium oxide is preferably collected on a material high-purity rhenium oxide by the following steps. A reaction insoluble in rhenic acid, for example, quartz or glass, and vessel Such as a reaction tube is introduced into the furnace. 40 can be collected into the piping or container using these After the first roasting process, the residue was cooled to materials for an inner wall material. Upon the Solid-gas room temperature, taken out and transferred to another separation, a filter may be installed in order to enhance the reaction vessel, and then the vessel is returned to the furnace rhenium recovery. Specific examples of cooling include to carry out the second roasting process. methods using spontaneous cooling and heat exchange, but The second roasting process has a purpose of positively 45 for the reason of simplification of a device, the method using gasifying the rhenium oxide, and therefore is ordinarily spontaneous cooling is preferably applied. carried out by setting up the in-furnace temperature in the The rhenium oxide is cooled to 100° C. or lower, and roasting furnace to a temperature higher than that in the first preferably, 80° C. or lower, thereby allowing complete roasting process. However, if excessively high temperature Solidification. If temperature is lower than necessary, even is set up, Zinc or bismuth might also be gasified, and 50 the sulfur oxide flowing together with the rhenium oxide therefore the second roasting process is carried out by from the roasting furnace is liquefied or solidified and then adjusting the in-furnace temperature in the roasting furnace co-collected. Therefore, the rhenium oxide is preferably preferably to 200 to 600° C., more preferably, to 300 to 550° cooled to a temperature of 50° C. or higher, which is a C., and still more preferably, to 350 to 500° C. Moreover, boiling point of SO, or higher, in order to completely although roasting time depends on a scale or structure of the 55 exclude the sulfur oxide. However, generated sulfur oxide is roasting furnace, if the time is too long, energy loss ordinarily in a form of SO, and therefore the rhenium oxide increases, and on the other hand, if the time is too short, may be cooled to room temperature (e.g.: 5 to 30° C.), which volatilization does not sufficiently proceed, and therefore the is a boiling point of SO or higher. time is adjusted preferably to 30 to 240 minutes, for Alternatively, dissolving the gasified rhenium oxide into example, and further preferably, to 120 to 180 minutes. 60 water while water-cooling also allows direct obtaining of the If the oxidation reaction of the rhenium sulfide and aqueous solution of perrhenic acid. A reaction formula at this removal of the sulfur oxide are sufficiently completed in the time is identical with the formula described in step 4. first roasting process, an atmospheric gas required in the Specific examples of the methods for allowing dissolution second roasting process only needs to play a role of a carrier into water while water-cooling include a method of collect gas for transporting the gasified rhenium oxide. However, 65 ing gasified rhenium oxide discharged from a roasting the oxidation reaction of the rhenium sulfide and the furnace using a wet scrubber, a wet filtration method or a wet removal of the Sulfur oxide in the first roasting process may electrostatic precipitator. When the wet scrubber is used, a US 9,631,259 B2 9 10 pellet-shaped, cylinder-shaped or honeycomb-shaped pack EXAMPLES ing material or the like is preferably charged thereinto in order to increase a gas-liquid contact area. The method does Examples of the present invention will be described not pass through the step for Solidifying the rhenium oxide, below, but the Examples are for illustrative purpose and the and therefore is highly simple. However, even the sulfur present invention is not intended to be limited thereby. oxide dissolves into water together with the rhenium oxide, and therefore this method is inferior to the method of (Verification of Effect by a First Roasting Process) solidifying the rhenium oxide from a viewpoint of purity. To Crude rhenium sulfide having analytical values described give an illustrative example, according to the method for in Table 1 was prepared. A content of each component was dissolving the rhenium oxide into water, a content of S in the 10 determined by a chemical analysis (determined by ICP aqueous solution of perrhenic acid is increased by about 5 to OES). 10 times in comparison with the method of solidifying the rhenium oxide. TABLE 1. (Step 4) 15 Re S B Zn In step 4, in case where the rhenium oxide is solidified, the solidified rhenium oxide is dissolved into water, or heated Content (mass %) About 48% About 28% About 0.1 About 0.5 and gasified and then dissolved into water to obtain the aqueous Solution of perrhenic acid. The rhenium oxide is Then, 500 g of the crude rhenium sulfide was subjected a considered to be converted into the perrhenic acid according first roasting process for 120 to 140 minutes under various to the reaction formula described below. in-furnace conditions of the kiln furnace, and then the resultant product was cooled to room temperature. As a Re-O,(s org)+HO(l)->2HReO(l) (Formula 2) roasting furnace, a kiln furnace was used, and as an oxygen The rhenium oxide is easily soluble in water, but if the containing gas, air was used. In all examples, an oxygen concentration in the aqueous Solution is too high, the reac 25 equivalent was adjusted to the range of 1.9 to 2.2. Moreover, tion efficiency is considered to decrease. On the other hand, it was found that supply of air to the kiln furnace after if the concentration is too low, an amount of use of water preheating the air to predetermined temperature (140° C. increases and handling properties during operation are dete herein) tended to stabilize in-furnace temperature, and a riorated, and a concentration step is required thereafter. 30 ratio of volatilization of sulfur rose. The weight of a residue Therefore, an amount of charge of the rhenium oxide into after testing was measured and a chemical analysis of the water is preferably 50 to 500 g/L, and more preferably, 150 residue was conducted. A content (g) of each element was to 250 g/L. determined from the weight of the residue and the results of A method of bringing the solidified rhenium oxide into elemental analysis of each element, and a ratio of gasifica solid-liquid contact to dissolve the rhenium oxide into water 35 tion was determined from a difference in the content (g) is simple, but it is also an applicable method that the before and after testing. Solidified rhenium oxide is heated and gasified again, and then bringing the resulting gas into gas-liquid contact by a Roasting time means a period of time from time at which scrubber or the like to dissolve the rhenium oxide into water. the in-furnace temperature in the kiln furnace reaches pre However, the latter method causes loss due to uncollection, 40 determined temperature to time at which cooling is started. and therefore the former method is further preferred. The oxygen equivalent was calculated on the assumption From the aqueous solution of perrhenic acid, potassium that rhenium and sulfur contained in the crude rhenium perrhenate and also ammonium perrhenate can be produced sulfide exist in a form of ReS, or in the form other than by any publicly known method. For example, potassium oxide, and a theoretical oxygen equivalent in which all of hydroxide is added to the aqueous solution of perrhenic acid 45 rhenium reacts to Re-O, and all of sulfur reacts to SO is 1. to control pH to about 11 to 13, thereby allowing precipi As a result, when the in-furnace temperature of the kiln tation of the potassium perrhenate, which can be collected furnace was 100° C. or higher and lower than 200°C., a ratio according to the Solid-liquid separation. Moreover, the of gasification of Re was 10% or more and less than 20%, potassium perrhenate is heavy and easy to settle, and there when the in-furnace temperature of the kiln furnace was fore is preferably subjected to the solid-liquid separation 50 200° C. or higher, the ratio increased to 20% or more, and after a floatable impurity is separated. Moreover, the purity when the in-furnace temperature of the kiln furnace can also be improved by elutriation or the like. The potas exceeded 350° C., the ratio exceeded 40%. A ratio of sium perrhenate is reduced with hydrogen or the like, gasification of S was 10% or more at an in-furnace tem thereby allowing production of rhenium metal (for example, perature of the kiln furnace of 100° C. or higher, and the see JP-A-S62-124240). 55 ratio was 80% or more at an in-furnace temperature of the Moreover, controlling perrhenic acid solution pH to about kiln furnace of 300° C. or higher. In addition, ratios of 7 to 12 by adding aqueous , the ammonium per gasification of Zn and Bi were substantially 0% at an rhenate can be precipitated and be recovered by the solid in-furnace temperature of the kiln furnace of lower than liquid separation Purification can be repeated for purity 600° C. enhancement. Specific examples of the purification methods 60 include a method of performing redissolution into pure (Verification of Effect by a Two-Step Roasting Process: A water and crystallization. After neutralization, prior to per Case of Solidifying Gasified Rhenium Oxide and then forming the solid-liquid separation, the resultant mixture is Producing an Aqueous Solution of Perrhenic Acid) preferably heated to 90 to 105° C., and concentrated. Rhe Crude rhenium sulfide having analytical values described nium metal can be produced by reducing the ammonium 65 in Table 3 was prepared. A content of each component was perrhenate with hydrogen or the like (for example, see determined by a chemical analysis (determined by ICP JP-A-S62-146227). OES). US 9,631,259 B2

TABLE 2 TABLE 4-2

Re S B Zn Ratio of collec- Ratio of collec- Ratio of collec- Ratio of collec tion of S tion of Re tion of Zn tion of Bi Content (mass %) 39.5 29.4 O48 O.18 1.6% 80.4% O.3% O% Then, 150 g of the crude rhenium sulfide was subjected to a first roasting process under conditions described in Table TABLE 4-3 3-1, and then cooled to room temperature. A tubular furnace 10 was used as a roasting furnace and air was used as an Analytical values oxygen-containing gas. In the same manners the example described above, a ratio of gasification of S, a content of S Unit Re S Bi, Zn in a roasted residue, a ratio of gasification of Re, a ratio of Mass mg/L 132,000 0.1% or less in 0.005% or less in total concentration based concentration of both gasification ratio of Zn and a ratio of gasification of Bi were 15 determined. The results are shown in Table 3-2. on Re concentration based on Re concentration

TABLE 3-1 Aqueous ammonium was added to the resulting aqueous In-furnace temperature Roasting Preheating Oxygen solution of perrhenic acid until pH became 9 for neutraliza of tubular furnace time of air equivalent tion, and then solid-liquid separation was performed to obtain powder of ammonium perrhenate (APR). The results 300° C. 120 minutes None 1.5 to 2.0 of analysis of the ammonium perrhenate are shown in Table 5. The analysis was conducted by GDMS. High-purity ammonium perrhenate was found to be obtained. TABLE 3-2 25 Ratio of gasifi- Ratio of gasifi- Ratio of gasifi- Ratio of gasifi TABLE 5 cation of S cation of Re cation of Zn cation of Bi Analytical values 80% or more 30 to 40% O% O% 30 Unit Re S Bi, Zn <10 <1 in total concentration of both Next, 133 g of the residue obtained in the first roasting Mass ppm about 70 (mass %) process was subjected to a second roasting process using roasting equipment described in FIG. 1 under conditions described in Table 4-1. As a roasting furnace, tubular furnace 35 Comparative Example 10 different from the furnace in the first roasting process was used, and air 16 was supplied at a flow rate of 1.5 L/min. A Crude rhenium sulfide having analytical values described component containing the gasified rhenium oxide was trans in Table 6 was prepared. A content of each component was ported in a gasified State at a predetermined distance in determined by a chemical analysis (determined by ICP tubular furnace external reaction tube insulation part 14 kept 40 at 300° C., and then cooled in a non-heat-insulated part in OES). reaction tube 13 having an inner wall made of quartz, and precipitated as solid-state rhenium oxide 18. Incidentally, TABLE 6 Re S B Zn gas temperature was in a state in which the gas was cooled 45 to room temperature (about 30° C.) on the way from the Content (mass %) about 50 about 20 O.O1 O.O1 insulation part to a scrubber. Sulfur oxide in the gas out of the reaction tube was absorbed in scrubber 15, and the gas was made harmless and discharged. Reaction tube 13 in Then, 531 g of the crude rhenium sulfide was subjected to which rhenium oxide 18 precipitated was removed, water at 50 a roasting process using roasting equipment described in room temperature was passed into reaction tube 13 to FIG. 1 under conditions described in Table 7-1. Then, the dissolve the rhenium oxide and to obtain an aqueous solu resultant product was cooled to room temperature. As a tion of perrhenic acid. Each component concentration in the roasting furnace, tubular furnace 10 was used, and as an aqueous solution of perrhenic acid obtained was determined oxygen-containing gas, air 16 was Supplied at a flow rate of by a chemical analysis (determined by ICP-OES), and a ratio 55 1.5 L/min. In the same manner as the example described of collection of each component when the residue prior to above, a ratio of gasification of S, a content of S in a roasted the second roasting process was taken as a standard (100%) residue, a ratio of gasification of Re, a ratio of gasification was determined. The results are shown in Table 4-2 and of Zn and a ratio of gasification of Bi were determined. The Table 4-3. results are shown in Table 7-2. 60 TABLE 4-1 TABLE 7-1 In-furnace temperature Roasting Preheating In-furnace temperature Roasting Preheating Oxygen of tubular furnace time of air of tubular furnace time of air equivalent

450 to SOO C. 180 minutes Ole 65 450 to SOO C. 180 minutes None 1.5 to 2.0 US 9,631,259 B2 14 TABLE 7-2 13 Reaction tube 14 Reaction tube insulation part Ratio of gasifi- Ratio of gasifi- Ratio of gasifi- Ratio of gasifi 15 Scrubber cation of S cation of Re cation of Zn cation of Bi 16 Air 80% or more 90% or more O% O% 5 17 Exhaust 18 Rhenium oxide What is claimed is: Subsequently, a component containing the gasified rhe 1. A method for producing an aqueous solution of per nium oxide was transported in a gasified State at a prede rhenic acid, comprising: termined distance in tubular furnace external reaction tube 10 1) performing a first roasting of rhenium sulfide under an insulation part 14 kept at 300° C., and then cooled in a oxygen-containing gas to generate rhenium oxide and non-heat-insulated part of reaction tube 13 having an inner sulfur oxide, the sulfur oxide being gasified for dis wall made of quartz, and precipitated as solid-state rhenium charge and the rhenium oxide being obtained as a oxide 18. Incidentally, gas temperature was in a state in roasted residue, which the gas was cooled to room temperature (about 30° 15 2) performing a second roasting of the roasted residue C.) on the way from the insulation part to a scrubber. Sulfur under an oxygen-containing gas to collect gasified oxide in the gas out of the reaction tube was absorbed in rhenium oxide; scrubber 15, and the gas was made harmless and discharged. 3) cooling and Solidifying the gasified rhenium oxide; and Reaction tube 13 in which rhenium oxide 18 precipitated 4) dissolving the solidified rhenium oxide into water, or was removed, water at room temperature was passed into heating and gasifying the Solidified rhenium oxide and reaction tube 13 to dissolve the rhenium oxide and to obtain then dissolving the gasified rhenium oxide into water, an aqueous solution of perrhenic acid. Each component to obtain the aqueous Solution of perrhenic acid. concentration in the aqueous solution of perrhenic acid 2. The method for producing the aqueous Solution of obtained was determined by a chemical analysis (determined perrhenic acid according to claim 1, wherein the first roast by ICP-OES), and the recovery of each component when 25 ing process is finished when a content of S in the roasted concentration in the crude rhenium Sulfide was taken as a residue is within a range of 0.5 to 20 mass %. standard (100%) was determined. The results are shown in 3. The method for producing the aqueous Solution of Table 8-1 and Table 8-2. perrhenic acid according to claim 1, wherein the first roast ing process is performed at an in-furnace temperature of 100 TABLE 8-1 30 to 350° C. 4. The method for producing the aqueous Solution of Ratio of collection of S Ratio of collection of Re perrhenic acid according to claim 1, wherein the second Less than 1% 70% or more roasting process is performed at an in-furnace temperature of 200 to 600° C. 35 5. The method for producing the aqueous solution of perrhenic acid according to claim 1, wherein the oxygen TABLE 8-2 containing gas is preheated at 100° C. or higher in the first roasting process and the second roasting process. Analytical values 6. The method for producing the aqueous Solution of Unit Re S Bi, Zn 40 perrhenic acid according to claim 1, wherein the step for cooling and solidifying the gasified rhenium oxide is per Mass mg/L 170,000 0.2% in concentration 0.005% or less in of based on Re total concentration formed while keeping entrained Sulfur oxide in a gaseous concentration of both based on state for Solid-gas separation of the Sulfur oxide. Re concentration 7. The method for producing the aqueous solution of 45 perrhenic acid according to claim 1, wherein the Solidified Powder of ammonium perrhenate (APR) was obtained by rhenium oxide is collected on a material insoluble in rhenic adding aqueous ammonium to the resulting aqueous solution acid in the step for cooling and Solidifying the gasified of perrhenic acid until pH became 9 for neutralization, and rhenium oxide. then performing Solid-liquid separation. The results of 8. A method for producing potassium perrhenate, com analysis of the ammonium perrhenate are shown in Table 9. 50 prising adding potassium hydroxide to the aqueous Solution The analysis was conducted by GDMS. of perrhenic acid obtained by the method for producing an aqueous solution of perrhenic acid according to claim 1 so as to precipitate potassium perrhenate. TABLE 9 9. A method for producing ammonium perrhenate, com Analytical values 55 prising controlling a pH of the aqueous solution of perrhenic acid obtained by the method for producing an aqueous Unit Re S Bi, Zn Solution of perrhenic acid according to claim 1, Such that the Mass mg/L. About 70 (mass %) About 100 <1 in total concentration pH is from 7 to 12, by adding aqueous ammonia to the of both based on Re aqueous Solution of perrhenic acid so as to precipitate concentration 60 ammonium perrhenate. 10. A method for producing rhenium metal, comprising adding potassium hydroxide to or controlling a pH of the REFERENCE SIGNS LIST aqueous solution of perrhenic acid obtained by the method for producing an aqueous solution of perrhenic acid accord 10 Tubular furnace 65 ing to claim 1, wherein the step of adding potassium 11 Sample hydroxide results in precipitation of potassium perrhenate, 12 Sample place and wherein the step of controlling the pH comprises US 9,631,259 B2 15 16 controlling the pH to 7 to 12 by adding aqueous ammonia to 15. The method for producing the aqueous solution of the aqueous solution of perrhenic acid so as to precipitate perrhenic acid according to claim 11, wherein the oxygen ammonium perrhenate, and containing gas is preheated at 100° C. or higher in the first reducing the potassium perrhenate or ammonium perrhe roasting process and the second roasting process. 5 16. The method for producing the aqueous solution of nate. perrhenic acid according to claim 11, wherein the step for 11. A method for producing an aqueous solution of cooling and solidifying the gasified rhenium oxide is per perrhenic acid, comprising: formed while keeping entrained sulfur oxide in a gaseous 1) performing a first roasting of rhenium sulfide contain state for solid-gas separation of the sulfur oxide. ing at least one of Zinc and bismuth under an oxygen 17. The method for producing the aqueous solution of containing gas to generate rhenium oxide and sulfur 10 perrhenic acid according to claim 11, wherein the solidified oxide, the sulfur oxide being gasified for discharge and rhenium oxide is collected on a material insoluble in rhenic the rhenium oxide being obtained as a roasted residue acid in the step for cooling and solidifying the gasified along with the at least one of zinc and bismuth; rhenium oxide. 2) performing a second roasting of the roasted residue 18. A method for producing potassium perrhenate, com 15 prising adding potassium hydroxide to the aqueous solution under an oxygen-containing gas to separate the at least of perrhenic acid obtained by the method for producing an one of Zinc and bismuth as a roasted residue and to aqueous solution of perrhenic acid according to claim 11 so collect gasified rhenium oxide: as to precipitate potassium perrhenate. 3) cooling and solidifying the gasified rhenium oxide, or 19. A method for producing ammonium perrhenate, com dissolving the gasified rhenium oxide into water while prising controlling a pH of the aqueous solution of perrhenic water-cooling to obtain the aqueous solution of perrhe acid obtained by the method for producing an aqueous nic acid; and Solution of perrhenic acid according to claim 11, such that 4) where the rhenium oxide is solidified, dissolving the the pH is from 7 to 12, by adding aqueous ammonia to the solidified rhenium oxide into water, or heating and aqueous solution of perrhenic acid so as to precipitate gasifying the solidified rhenium oxide and then dis 25 ammonium perrhenate. Solving the gasified rhenium oxide into water, to obtain 20. A method for producing rhenium metal, comprising the aqueous solution of perrhenic acid. adding potassium hydroxide to or controlling a pH of the 12. The method for producing the aqueous solution of aqueous solution of perrhenic acid obtained by the method perrhenic acid according to claim 11, wherein the first for producing an aqueous solution of perrhenic acid accord roasting process is finished when a content of S in the 30 roasted residue is within a range of 0.5 to 20 mass %. ing to claim 11, wherein the step of adding potassium 13. The method for producing the aqueous solution of hydroxide results in precipitation of potassium perrhenate, perrhenic acid according to claim 11, wherein the first and wherein the step of controlling the comprises controlling roasting process is performed at an in-furnace temperature the pH to 7 to 12 by adding aqueous ammonia to the aqueous of 100 to 350° C. Solution of perrhenic acid so as to precipitate ammonium 14. The method for producing the aqueous solution of 35 perrhenate, and perrhenic acid according to claim 11, wherein the second reducing the potassium perrhenate or ammonium perrhe roasting process is performed at an in-furnace temperature nate. of 200 to 600° C. CE: ck ck c i: