||||||||||||III USOO517549A United States Patent (19) 11 Patent Number: 5,171,549 Walsh, Jr. et al. (45) Date of Patent: Dec. 15, 1992

54 PROCESS FOR DECREASING THE LEVEL 56) References Cited OF MPURITIES IN ZIRCONUM CHLORIDE, TITANIUM CHLORIDE AND U.S. PATENT DOCUMENTS HAFNIUM CHILORIDE 2,184,884 12/1939 Muskat et al...... 423A75 3,989,510 1 1/1976 Othner ...... 42.3/84 75) Inventors: Ronald E. Walsh, Jr., Corvallis; Peter 4,840,774 6/1989 Campbell et al. ... 42.3/75 W. Krag, Albany; Roy E. Blackstone, 4,979,967 12/1990 Walter et al...... 55/259 ter, Duane L. Hug, Albany, all of FOREIGN PATENT DOCUMENTS reg. 3320641 12/1984 Fed. Rep. of Germany . 73) Assignee: Teledyne Wah Chang Albany, Albany, Oreg. Primary Examiner-Theodore Morris Assistant Examiner-Edward Squillante 21 Appl. No.: 704,120 Attorney, Agent, or Firm-Shoemaker and Mattare Ltd. 22 Filed: May 22, 1991 (57) ABSTRACT An improved halogenator process and system is pro 51 Int. Cl...... C01G 23/00; C01G 25/00; vided which significantly and economically decreases COG 27/00 the level of impurities in the processing of various re 52 U.S.C...... 423/79; 423/69; fractory metals and their halides and particularly haf 423/72; 42.3/75; 423/76; 423/81; 423/147; nium tetrachloride which is condensed from gases pro 423/149; 423/324; 423/341; 423/492; 423/210 duced by the chlorination of Zircon. 58) Field of Search ...... 423/69, 75, 76, 77, 423/79, 81, 83, 492, 210, 72, 147, 149,324, 341 5 Claims, 2 Drawing Sheets

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Cl2 U.S. Patent Dec. 15, 1992 Sheet 1 of 2 5,171,549

U.S. Patent Dec. 15, 1992 Sheet 2 of 2 5,171,549

\ S U 5,171,549 1. 2 particulate matter and then condensed. Major by-pro PROCESS FOR DECREASING THE LEVEL OF duct SiCl4 (b.p. 57 C.) is recovered downstream in a IMPURITIES IN ZIRCONIUM CHLORIDE, condenser. TITANIUM CHILORIDE AND HAFNUM There are a number of impurities in the ZrCl4/HfCl4 CHLORIDE product condensed from chlorinator off-gas. The pres ence of excess chlorine and phosgene create problems, BACKGROUND OF THE INVENTION aside from representing wasted chlorine, in that they Conventional zircon sand (ZrSiO4) halogenators, must be neutralized and the resultant hypochlorite re such as chlorinators, produce a product stream of major duced. Further, they are extremely corrosive to materi components, namely zirconium tetrachloride, hafnium 10 als of construction and represent a potential health ha tetrachloride and silicon tetrachloride and contaminat zard. It is difficult to continuously run a chlorinator ing minor components. Among the contaminating without some means of escapement of chlorine/phos minor components are volatile chloride compounds gene to product. Ferric chloride and aluminum chloride which contain iron, aluminum, uranium, phosphorus, tend to co-condense with ZrCl4/HfCl4 and coat equip titanium, and vanadium. Some finely divided solids, 15 ment with deposits which impede heat transfer. Ura carbon and oxides, are also minor impurities in the prod nium, phosphorus, silicon, titanium and compounds uct stream. The product stream then contacts a first may contaminate the product. Traces of carbon and condenser where ZrCl4/HfCl4 is largely condensed and oxide particulate matter also contaminate the product. most SiCl4 goes further downstream to another con These contaminating materials, in addition to other denser. Some of the minor impurities, however, con 20 contaminating impurities, must also be subsequently dense with ZrC14/HfCl4, These impurities, such as removed, and considerable cost and effort is required in chlorides of iron, uranium, and phosphorus, must be the process. removed at some cost in subsequent operations, see for Conventionally, many impurities are removed from instance those disclosed in German Patent 1,082,240. crude chloride by a liquid-liquid counter current sol One principal object of the invention is to decrease 25 vent extraction process (LLCCSE) for separating Zr the level of impurities in zirconium/hafnium tetrachlo and Hf. One alternative to a LLCCSE is to sublime ride (ZrO4/HfCl4) condensed from gas produced by crude chloride one or more times in a stream of H, in N,. carbochlorination of zircon. Because certain of these This removes Cl, P, U, Fe, Al, Ti, Si, Cr, V, C and impurities require removal in further processing of oxides to an acceptable level for feed to any process ZrCl4/HfCl4, their removal at this earlier stage may be 30 stream-chemical grade, non-nuclear grade metal and advantageous. A reducing gas mixture can be effec nuclear grade metal. In our experience, the sublimation tively used to react with certain of the impurities form process is expensive in terms of energy consumed, the ing condensible species which can then be filtered from need for large scale equipment, and substantial expenses the gas stream prior to condensation of ZrCl4/HfCl4 to maintain the equipment. (1). These impurities include phosphorus, (1) iron, and 35 James H. McClain and Stephen Shelton, Ch. 4, Zr/Hf Separation, in uranium. Certain other impurities react to form gaseous Reactor Handbook, Vol. 1. Materials, Ed. by C.R. Tipton, Jr., Intersci products which are more volatile than the ZrCl4/HfCl4 ence Publ, Inc., N.Y., pp. 64-73. and are non-condensible condensible chlorides. Other attempts to purify ZrCl4 and/or HfCl4 by subli A still further object of this invention is to provide mation have been made in the past. In one process, new processes for decreasing impurity level in the chlo ZrCl4 was soaked in H2 at 250 C. prior to sublimation.2 rination process for zircon which processes are cost Fe, Cr, U, Th, Si, Ti, and most Al was removed, par effective, safe, and easily reproducible. tially due to reduction of hydrogen reducible elements Zirconium occurs naturally together with hafnium, and simple distillation of impurities that boil or sublime typically such that (100) (Hf/(Zr-i-Hf)) 2.0. The combi below the s.p. of ZrCl4. A hydrogen soak is not industri 45 ally practical. nation of unseparated zirconium and hafnium has a 2W. J. Kroll and W.W. Stephens, Production of Malleable Zirconium, number of uses as chemicals, e.g., for paper, ceramics Industrial and Engineering Chemistry, Vol. 42, 1950, pp. 395-398. and metal matrix composites, or as metal in corrosive In still another process, zinc, cadmium and manga environments, e.g., Zircadyne 702 for acetic acid plants. nese have been used to reduce contaminating iron lev Nuclear grade zirconium metal (Hf/(Hf--Zr) < 100 els. It was noted that the system should be free of chlo ppm) alloys, e.g., Zircaloy 4, find application for inter 50 rine. Hydrogen sublimation is more industrially practi nal construction materials in nuclear reactors, due to the cable. property of zirconium having a low thermal neutron British 660,397, Nov. 7, 1951, Method of Producing Pure Zirconium capture cross section. Hafnium metal finds application Halides. as a control rod in nuclear reactors owing to its high Still numerous other processes are reported. ZrCl4 thermal neutron capture cross section. Hafnium is also 55 was contacted with alkali or alkaline earth chlorides 1. used in superalloys where high temperature strength is where Fe, Al, Si, Ti, Mg, Ca, Cu, Ba, Na, K, ZrOCl2 needed. and C were claimed to have been removed. HfCl4 was Traditionally, where zirconium/hafnium is destined contacted with a NaCl/KCl/HfCl4 molten salt bath for use in nuclear applications, its processing begins where Al, Fe, Si, Ti, Mn, Pb and B were largely remo with the carbochlorination of an ore, typically zircon ved. ZrCl4 was contacted with CaCl, at 200-450° C. sand. Zirconium ore may also be opened by a fluoride where Al and Fe were removed.6ZrCl4 was contacted process. Processing of zirconium and hafnium for non with a fused salt where Al, Fe, Ti, V, Si and Th were nuclear applications may also begin with carbochlorina largely removed.7 Contact with KCl, NaCl or tion of an ore. The carbochlorination process for zircon NaCl/KCl in a plate column removes Fe and Al and (Zr(Hf)SiO4) sand is based on the process of chlorinat 65 supposedly V, U, Ti and Si. The mechanism of removal ing a finely divided zircon sand mixed with coke at is the formation of compounds, e.g., NaCl --Fecly, temperature near 1000 C. The gaseous product stream NaFeCl4 which are stable and relatively non-volatile. ZrCl4/HfCl4 (sp. -331° C) is filtered to be free of They require large pieces of equipment and are subject 5,171,549 3 4. to high maintenance costs. They do not address elimi 1000 C. Chlorine gas 2 is piped into the bottom of nating chlorine in the off-gas. “British 771. 144, Mar. 27, 1957.improvements in or Relating tothe chlorinator 1 where the zircon is chlorinated. Purification of Zirconium Tetrachloride. Zr/HfCl4, SiCl4, CO, CO2, COCl2, Cl2 and other vola D. S. Fairgrieve and J. W. Fortner. Production and Purification of tile impurity chlorides 4, as well as some solids from the HighHarry Purity Greenberg Hafnium and Metal, Hyman J. Metals,R. Lubowitz, 12, Jan. purification 1960, pp. 25-26. Method for 5 reaction zone, leave the reaction zone and contact a Metal Halides, U.S. Pat. No. 3,053,620, Sep. 11, 1962. primary filter section 5 where most solids are captured "D. R. Spink. Fused Salt Scrubbing of Zirconium Tetrachloride, Trans and through which chlorinator off-gas passes on to actions,Ernest AIME,D. Lee Vol.and 224,David 1962, F. McLaughlin.pp. 965-970. Molte Salt Scrubbing of transfer line 6. Hydrogen/nitrogen gas is injected into finium or Hafnium tetrachloride, U.S. Pat. No. 4,913,778, Apr. 3, the hot reactor off-gas at tee 7. Impurities in the reactor Sublimation in the presence of carbonaceous material 10 off-gas are reduced in transfer line 8 and filter chamber has been attempted. Fe, Al, V, and Cr impurity levels 9. The solids are captured on the filter media and fall to were reduced when ZrCl4 was sublimed from an inti the bottom of the bag house where they are removed mate mix of ZrCl4 and e.g., motor oil.9 Poor ZrCl4 through valve 10. The Zr/HfCl4 scrubbed of hydrogen recovery and a mixing operation are problems with that reducible chloride impurities and solid impurities, but approach. Sublimation in the presence of a volatile 15 still containing volatile impurities, leaves settling cham hydrocarbon, such as pure or mixtures of ethane, ethyl ber/bag house 9 through transfer line 11. It is then ene, propane, propylene or butane lowered Fe, Al, Ti, condensed in primary condenser 12 and is removed as a and Silevels. 10 Addition of steam and a catalytic surface solid through valve 13. Gas exhausted from this pri area enhanced this approach. 1112 Chlorinated hydro mary condenser 12 through transfer line 14 still contains carbons produced in this process are problematic due to 20 some small amount of (Zr-i-Hf)Cl4, and so it is desirable environmental concerns and potentially costly cleanup to employ a secondary condenser 15, similar to said efforts. Walter Frey, Process fro the Production of Purified Anhydrous Zirco primary condenser. SiCl and other non-condensible nium Tetrahaide, U.S. Pat. No. 2,682,445, Jun. 28, 1954. gases pass through this secondary condenser 15 through Herman Renner, Method for the Production of Pure Zirconium Tetrachloride by Sublimation, German 1,068,683, Nov. 12, 1959. 25 transfer line 16 and go on for further treatment. The Process for the Production of Pure Zirconium Tetrachloride and Zr/HfCl4 product from primary condenser 12 is thus Hafnium/Zirconium Tetrachloride by Sublimation, British 910,289, remarkably pure and substantially free of impurities, the Nov. 4, 1962. Hans Herzog and Herman Renner, Method for the Production of same as if the material had been sublimed in the conven Pure Zirconium Tetrachloride by Sublimation, German 1,082,240, May tional manner. 24, 1960. While hydrogen sulfide or metallic sulfides in contact 30 Purifying Zr/HfCl4 of deleterious impurities has been with ZrCl4 during sublimation reduce Fe and V impu accomplished in a safe, economical and unexpected rity levels, the other impurity levels are not addressed. manner thus avoiding the need for a separate facility The formation of other sulfides necessarily means that where Zr/HfCl4(s) is fed to a substantial sublimer they will have to be rendered innocuous and subse which requires high energy input, initial high capital quently disposed of; but this would also require costly 35 costs, substantial maintenance costs, and devoted labor. rocessing. In fact, the product ZrHfCl4, produced according to James Thompson Richmond and Howard Artner Stanley Bristow, the present invention, is already a gas and the only Process for the Purification of Titanium Tetrachloride or Zirconium additional energy input required is that which is needed Tetrachoride, Brit. 866,771, May 3, 1961. to heat hydrogen/nitrogen gas and that which is neces The objects of this invention are dramatically accom sary to heat the additional transfer lines and dropout plished by the processes disclosed herein. chamber/bag house assembly. This is a substantial ad SUMMARY OF THE INVENTION vantage. No additional labor is necessary. Maintenance The present invention encompasses injecting a stream costs on the additional transfer lines and dropout cham of a reducing gas, such as a mixture of 20 Vol.% H2 in ber/bag house assembly is minimal and substantially less nitrogen, into the gas generated by carbochlorinating 45 than in a conventional sublimer. zircon sand, prior to the stream's contacting the pri Certain impurities that would normally be removed mary condenser. The products formed by reaction of in subsequent treatment of Zr/HfCl4, depending on its said reducing gas with sand chlorinator off-gas may be intended use-chemical, non-nuclear metallurgical or condensed phases (with boiling and/or melting points nuclear metallurgical-are largely eliminated. This re greater than the temperature at which said transfer line 50 sults in increased downstream yields as well as simplifi is maintained), or gases which will not condense with cation of the process. The separate iron, uranium and ZrCl4, except for minor amounts by adsorption. Means phosphorus removal operations required in prior art are to collect said condensed phases separately from no longer necessary. ZrCl4/HfCl4 product in a settling chamber, or bag filter EXAMPLE 1. condenser, is needed. 55 The apparatus sketch in FIG. 2 was made from the BRIEF DESCRIPTION OF THE DRAWINGS apparatus as actually constructed. A two inch diameter FIG. 1 is a schematic depiction of the chlorination quartz chlorinator tube 20 fitted at one end with a po and how the various starting materials and impurities rous quartz gas distributor by a resistance furnace 21. are processed and recovered; and Gas produced in this tube is conducted through a nickel FIG. 2 is a schematic depiction of the actual appara expansion chamber 22 and mineral wool filter into stain tus constructed for example 1. less steel transfer line 23. A 4:1 mixture of nitrogen and hydrogen is injected into this transfer line through stain DETAILED DESCRIPTION OF THE less steel tubing and a modified union tee fitting 25. The DRAWINGS 65 mixed and reacted gas stream is filtered through porous A preferred embodiment of the present invention is stainless steel filter 26 and introduced to a passively illustrated in FIG. 1. Zircon sand and coke 3, mixed air-cooled conical condenser 27. Condensed product together, are fed to a chlorinator 1 maintained at about ZrCl4 is collected at the bottom of this vessel at 28, and 5,171,549 5 6 exhaust gas 29 is scrubbed with sulfuric acid at 30 before are tantalum pentachloride, titanium tetrachloride, sili leaving the system. con tetrachloride and the like. Five hundred grams of finely ground zircon and pe It has been found that the disclosed process for reduc troleum coke (in 4:1 ratio) were placed in the chlorina ing impurities is effective involving metals from Group tor tube and heated to about 1000 C. in a stream of 5 IV and V and those having atomic weights of from nitrogen. After reaching this temperature, the nitrogen between 14 and 73. In particular these include tantalum, stream was replaced with 2 1/min chlorine, and reac niobium, titanium, silicon, hafnium and zirconium as tion between zircon, coke and chlorine began. Ni they exist in the form of their gaseous halides and partic trogen/hydrogen mixture was provided to the transfer ularly their chlorides. line. Zirconium chloride collected below the condenser 10 The invention has been described with respect to appeared white; it was also found to be virtually free of specific embodiments thereof. It will be readily under uranium and to have substantially lower amounts of stood that the scope of the claims appended hereto is iron and phosphorus. Specifically, analyses of chloride limited only by the applicable prior art and that a condensed from untreated and hydrogen-reduced chlo breadth of equivalents is possible where the described rinator off-gas are given below. parameters for properties are produced. TABLE 1. We claim: Fe (ppm) P (ppm) U (ppm) 1. A process for decreasing the level of impurities in intreated 3100 560 200 zirconium chloride, titanium chloride, hafnium chloride H-reduced 74 34 O or silicon chloride wherein a mixture of ziron sand and petroleum coke are fed together to a chlorinator reac tion means, including a chlorinator reactor having inlet EXAMPLE 2 means for the introduction of chlorine gas, outlet means The apparatus of Example 1 was provided with a for the removal of gaseous metal chlorides, a bottom screw feeder in order to provide for continuous addi- 25 communicating with said inlet means, a top in commu tion of zircon:coke feed mix. With this equipment, the nication with said outlet means, a reaction zone between chlorination reactor was operated for periods of time up said bottom and aid top and filter means in said top to to six hours. A five hundred gram charge of feed mix prevent solids from the top of the reactor vessel from was placed in the reactor and heated to about 1000 C. entering said outlet and further comprising condensor under a stream of nitrogen. Upon reaching this tempera- 30 means located downstream of said outlet to recover ture, nitrogen was replaced by chlorine, and nitrogen/- metal chloride product, the improvement comprising: hydrogen mixture was provided to the transfer line as (1) maintaining said reaction zone at a temperature of described in Example 1. In addition, the screw feeder from about 400° C. to about 1000 C.; was started, having been adjusted to provide roughly (2) introducing chlorine gas into the bottom of said five hundred grams of feed mix per hour. Zirconium is chlorinator reactor; chloride was collected below the condenser; the collec (3) maintaining the top of said reactor at a tempera tion bottle was replaced each hour. During the five ture high enough to maintain the metal chlorides hour experiment, 1600 g chloride was collected in four formed in the gaseous state; samples, three of which appeared white. Chemical anal (4) introducing a hydrogen-containing gas into the ysis (tabulated below) indicates that iron, uranium and 40 gaseous metal chloride stream only after it has left phosphorus have been substantially removed from zir the top of the reactor and before reaching the pri conium chloride by the described practice. mary condensor means at a temperature above the TABLE 2 condensation temperature of the gaseous metal chloride temperature; Time of Sample Fe (ppm) U (ppm) P (ppm) (5) removing from the gaseous metal chloride the 030-130 380 1.0 <50 30-1230 300 3.0 <50 condensed reduction products produced by the 1230-1330 2300 54 80 introduction into the gaseous metal chloride of a 1430-1530 450 10 60 reducing amount of a hydrogen-containing gas; and (6) subsequent to the removal of the reduction prod EXAMPLE 3 ucts, recovery by condensation of the substantially In order to confirm the discovery on a larger scale, pure metal chloride product in the condenser 4% H2 in N2 was introduced into a stream of niobium aS pentachloride from a chlorinator at approximately 400' 2. The process of claim 1 wherein the metal chloride C. that contained contaminant iron and phosphorus 55 is zirconium/hafnium tetrachloride, the chlorinator species. An additional dropout chamber was placed reactor is maintained at about 1000 C.; between the hydrogen tee and the bag house chamber. 3. The process of claim 1 wherein the reducing gas is By examining iron and phosphorus content in starting hydrogen. material, and iron and phosphorus/major metal ratios 4. The process of claim 1 where the solid impurity is before hydrogen injection and in product, plus residues 60 an iron compound produced by the reducing gas and is in the drop out chamber and bag house before filtration, vaporized at a temperature above the temperature of it was clearly obvious that substantial amounts of both the gaseous stream of the chlorides Si, Hfor Zr suffi iron and phosphorus were removed, substantially im cient to provide gas solid separation. proving the quality of the product. 5. The process of claim 1 wherein the reactor is The disclosure of the invention herein is applicable to 65 heated up to about 1000 C. in the presence of a stream cleaning reducible impurities other than those specifi of nitrogen and said nitrogen is replaced with chlorine cally disclosed herein in product gases from a chlorina thereafter. tor or halogenation system. Examples of such impurities s k