PROCESS FOR THE PRODUCTION OF GROUP IVB TRANSITION METAL-ALKALI METAL-FLUORIDE SALTS AND PURIFICATION THEREOF

Abstract: Group IVb transition metal oxide ores are fluorinated with an alkali metal fluosilicate in fluorination zone (10). The fluorinated ore (16) is leached with hydrochloric acid in leach zone (18). The group IVb transition metal - alkali metal fluoride - containing solution (20) is then cooled in a crystallization zone (22). Silicon tetrafluoride (30) produced in the fluorination zone (10) is scrubbed with water in the fluosilicic acid production zone (32) and the fluosilicic acid (34) is then reacted with alkali metal chloride (38) to form alkali metal fluosilicate, which is used in fluorination zone (10) and, hydrochloric acid which is used in leach zone (18).

Description: PROCESS FOR THE PRODUCTION OF GROUP IVB TRANSITION METAL- LKALI METAL-FLUORIDE SALTS AND PURIFICATION THEREOF Field of the Invention The present invention is directed to a method for th preparation and purification of Group IVb transitio metal-alkalimetal-fluoride salts, such as sodium fluotitanat and sodium fluozirconate, from Group IVb transition meta oxide ores, such as ilmenite and zircon, by fluorinatin the ore with an alkali metal fluoride salt, such as sodiu silicofluoride and the like, in a kiln reactor at elevate temperature between about 650°C and 1000°C. Background of the Invention Titanium metal has been essential to the aerospac industry since the early 1950's because it combines a hig strength-to-weight ratio with the ability to perform a much higher temperatures than aluminum or magnesium Titanium also has experienced growing usage in the chemica processing industry because of its excellent resistance t chloride corrosion. In the United States, primary titanium is imported fro Japan, Europe and the USSR. The bulk of titanium metal i made by the "Kroll" Process, which involves the magnesiu reduction of titanium tetrachloride, which is made fro rutile (Ti0 2 ) or synthetic rutile. Titanium metal is als made from titanium tetrachloride by sodium reduction an electrowinning. The product of the Kroll Process is metalli sponge, which is consolidated by a high temperature ar melting process. The most important consideration in titanium productio is the prevention of contamination of the titanium wit metallic and non-metallic impurities because the presenc of impurities, even in very small amounts, can make th product brittle and unworkable. Typically, steps are take to prevent the contamination of the titanium metal wit oxygen, nitrogen, alkali metals, alkaline earth metals iron, manganese, halides, carbon, silica and the like However, controlled amounts of oxygen, nitrogen and carbo can be added to titanium to yield strengthened titaniu alloys. U.S. PatentNo.2,550, 47 teaches aprocess forpreparin titanium metal from titanium oxide ores, such as rutile anatase and ilmenite, which comprises reduction of the or by aluminum metal followed by iodination of the produc obtained from such reduction. The iodinated product i then reacted with potassium iodine to yield titaniu tetraiodide. The titanium tetraiodide, after removal o the potassium iodide, is converted to titanium metal b either heat decomposition or reduction. This is a ver expensive method for preparing titanium metal. U.S. Patent No. 2,781,261 discloses the process fo converting titanium dioxide to titanium by fluorinatin the titanium dioxide, neutralizing the fluotitanic aci product and reducing the neutralized fluotitanic aci product with aluminum. U.S. Patent No. 2,837,426 discloses a process fo converting ilmenite to an alkali metal fluotitanate b reacting ilmenite with sulphuric acid to form titaniu sul ate, removing a portion of the iron included with th titanium sulfate by reduction and precipitation of th reduced iron compound, and converting the titanic suirat filtrate to an insoluble fluotitanate with ammonium and/o alkali fluoride solution. U.S. No. Patent 2,857,264 teaches a process forpreparin an alkali metal chlorotitanate by digesting ilmenite or in a mixture of sulphuric acid and hydrochloric acid. Th iron present is precipitated out as ferrous sulfate an then further recovered by the addition of hydrochlori acid to -precipitate a ferrous chloride. After removal o the solid ferrous chloride, potassium chloride is added t the titanium-containing liquor tc salt out potassiu chlorotitanate, which may be reduced with a Group I meta to titanium. U.S. PatentNo.3,012,878 discloses aprocess forreducin titanium halides to titanium metal by the use of sodium metal. U.S. Patent No. 3,825,415 discloses a process simila to the process disclosed in U.S. Patent No. 3,012,878, except that the process is carried out in the vapor phase. U.S. Patent Nos.. 4,127,409 and 4,072,506 are relate to the recovery of zirconium and hafnium by the reduction of the correspondingpotassium chlorozirconates andhafniates by means of an alloy of aluminum and zinc. U.S. Patent No. 4,390,365 is directed to a process for making titanium metal from ilmenite ore by fluorinating the ore' with an alkali metal fluosilicate at a temperature of from about 600"C to about 1000°C to form titanium fluorides optionally in the presence of carbon and/or silica tetrafluoride; leaching the titanium fluoride to provide an aqueous solution of titanium fluoride, crystallizing the titanium fluoride out of solution and reducing titanium fluoride to titanium metal with a reducing alloy of aluminum and zinc. The leach solution optionally contains hydrogen fluoride and, optionally, the leach solution is oxidized and hydrolyzed to form insoluble iron hydroxide, which is separated from the leach solution before crystallizatio of the titanium fluoride. U.S. Patent No. 4,468,248 is directed to a process fo reducing titanium halides to titanium metal by reducing th titanium halides with a molten alloy of aluminum and zin at elevated temperatures to produce a titanium and zin alloy. The titanium metal is recovered by distilling of the zinc. U.S. Patent No. 4,470,847 is directed to a process fo making titanium, zirconium and hafnium metal and allo particles suitable forpowdermetallurgy fromthecorrespondin Group IVb transition metal-zinc alloy by distilling of the zinc to form a corresponding sponge, sintering th sponge, hydriding the sponge, comminuting the hydride sponge, dehydriding the resulting hydrided particles an pacifying the dehydrided particles. Summary of the Invention The present invention is directed to a process for t preparation of +4 valent Group IVb transition metal-alka metal-fluoride salt (also referred to as "+4 valent salt" from a Group IVb transition metal oxide ore which compris the steps of fluorinating a Group IVb transition met oxide ore by contacting said ore in an unsealed react with an alkali metal fluosilicate (also known as "alka * Sιetal silicofluoride") and alkali metal fluoride salt at temperature of from about 600°C to about 1000°C to conve the Group IVb transition metal oxides in the ore to +3 a +4 valent Group IVb transition metal-alkali metal-fluori values (also referred to as "+3 and +4 valent values") For each mole of Group IVb transition metal oxide presen in said ore, the ore is contacted with at least about 0. molar equivalent of an alkali metal fluosilicate and wit at least about 1.6 molar equivalents of an alkali meta fluoride salt to minimize the loss of fluorine as silico tetrafluoride gas from the reactor. It has been ' found that, in a kiln reactor operation one mole of silicon tetrafluoride gas escapes in th exhaust gases for each two moles of alkali metal fluosilicat introduced into the kiln. This gas, which has a residenc time of less than 30 seconds in the kiln, is exited wit the exhaust gas from the kiln and very little reacts wit the ore. Stoichiometrically, one mole of a Group IV transition metal oxide should react with one mole of a alkali metal fluosilicate to form one mole of +4 valen Group IVb transition metal-alkali metal-fluoride salt an one mole of silicon dioxide. In practice, however, if on mole of a Group IVb transition metal oxide is introduce " with one mole of an alkali metal fluosilicate into a kil reactor, only one-half of the silicon tetrafluoride generate from the decomposition of the fluosilicate reacts to for Group IVb transition metal fluoride salts. One-third o the fluorine in the alkali metal fluosilicate escapes fro the kiln as silicon tetrafluoride. The loss of fluorine i an economic detriment to the process, since the fluoride containing reagents are the most expensive reagents employe in the process. Theoretically, in view .of the silico tetrafluoride loss, 1.5 moles of alkali metal fluosilicat are required to fluorinate the metal oxide in the ore, bu for most ores an excess is needed to react with impurities such as lime, carbonates and the like in the ore. Unexpectedly, it has been found that if at least 0. mole of an alkali metal fluosilicate, at least 1.6 mole of an alkali metal fluoride salt, and 1 mole of a Grou IVb transition metal oxide are introduced into the kiln essentially all the Group IVb transition metal oxide i convertedto +3 and+4valentGroupIVbtransitionmetal-alkal metal-fluoridevalues andlittle, ifany, silicontetrafluorid is liberated in the process which can escape with th exhaust gases from the kiln (see Reaction (6) below) . Thi method of converting metal oxides to metal fluoride salt is a great improvement over the prior-art processes. Moreover, ithasbeenfoundthatalkalimetalnon-fluorid salts (alkali metal basic salts) may be employed in plac of alkalimetalfluoridesaltsto obtainsubstantiallycomplet conversion of the metal oxide to the corresponding meta fluoride salt with little, if any, production of silico tetrafluoride gas. However, if an alkali metal basic sal is present, an additional amount of an alkali metal silico fluoride salt sufficient to convert the alkali meta non-fluoride salt to an alkali metal fluoride salt i required. This improved process for the preparation o Group IVb transition metal-alkali metal-fluoride values fro Group IVb transition metal oxide ores comprises fluorinatin a Group IVb transition metal oxide ore by contacting th ore in an unsealed fluorination zone with an alkali meta fluosilicate at a temperature of from about 600 α C.to abou 1000°C to convert the metal oxide to +3 and +4 valen Group IVb transition metal-alkali metal-fluoride values For each mole of metal oxide present in the ore, the or is contacted with at least 1.07 molar equivalents of a alkali metal fluosilicate and with at least 1.07 mola equivalents of an alkali metal in the form of an alkali meta basic salt. Preferably, the alkali metal basic salt is carbonate salt, a bicarbonate salt, or oxide salt, such a sodium hydroxide. This process has the added advantage that alkali meta basic salts may be employed rather than the more costly alkal metal fluoride salts. In this embodiment, the alkali meta basic salts are converted to alkali metal fluoride salts which may react with the metal oxide in the ore to fluorinat the metal oxide. Alternatively, for each mole of Group IVb transitio metal oxide in an ore, the ore can be fluorinated with a least 1.6 molar equivalents of an alkali metal fluosilicat to fluorinate substantially all the ore and produc approximately 0.8 molar equivalent of silicon tetrafluorid gas. The gas exits from the kiln with the exhaust gas. Th exhaust gas can be scrubbed with water to capture th silicon tetrafluoride and convert it to fluosilicic aci and silicon dioxide. It is difficult to use fluosilici acid as an additional fluorinating agent for the or fluorinationbecause fluosilicic acid at elevated temperatur decomposes to silicon tetrafluoride and hydrofluoric acid. However, the fluosilicic acid can be contacted with an alkal metal halide salt, such as sodium chloride, to produce a alkali metal fluosilicate and a hydrogen halide, such a sodium fluosilicate and hydrochloric acid. The alkal metal fluosilicate is separated from the acid and employe in the ore fluorination reaction. This alternative process for preparation of +3 and +4 valentGroup IVb transitionmetal-alkalimetal-fluoridevalues from a Group IVb transition metal oxide ore comprises th steps of: a) fluorinating a Group IVb transition -metal oxid ore by contacting the ore in an unsealed fluorination zon with an alkali metal fluosilicate at a temperature .of fro about 600"C to about 1000"C to produce a fluorinated or containing +3 and +4 valent Group IVb transition metal-alkal metal-fluoride values, the ore is contacted with at leas 1.6 molar equivalents of the alkali metal fluosilicate fo each mole of Group IVb transition metal oxide present i said ore, 0.5 mole of silicon tetrafluoride gas bein formed and liberated foreachmoleof alkalimetal fluosilicat introduced into the fluorination zone. Plus 4 (+4) valent Group IVb metal-alkalimetal-fluorid values can be recovered by the additional steps of: b) removing the fluorinated ore from the fluorinatio zone and introducing it into a leaching zone wherein th fluorinated ore is leached with an aqueous hydrochlori acid solution to convert the +3 and +4 valent Group IV transition metal-alkali metal-fluoride values to +4 valen Group IVb transition metal-alkali metal-fluoride salt an to solubilize in the leachate at least 95% by weight o the Group IVb transition metal-alkali metal-fluoride salt σ) separating the leachate from the insolubl solids to produce a leachate free of solids; d) introducing the separated leachate into crystallization zone wherein the leachate is cooled to temperature of at least 60°C to drop out at least 99% b weight of the silicon impurities, such as Na 2 SiF 6 , and portion of the +4 valent Group IVb transition metal-alkal metal-fluoride salt from the leachate as solids; and e) separatingthe solids formed in the crystallizatio zone from the leachate to yield an aqueous solution containin +4 Group IVb transition metal-alkali metal-fluoride sal substantially free of silica. Optionally, the silicon tetrafluoride gas formed an liberated in the fluorination zone can be recovered t produce alkali metal fluosilicate and hydrochloric acid which can be recycled, by the additional steps of: f) introducing the silicon tetrafluoride gas from th fluorination zone into a hydrolysis zone wherein the silico tetrafluoride is contacted with water to convert the silico tetrafluoride to fluosilicic acid and silicon dioxide; g) introducing the fluosilicic acid into an alkali meta fluosilicate production zone wherein the fluosilicic aci is contactedwith an alkali metal chloride to produce an alkal metal fluosilicate and aqueous hydrochloric acid; h) separating the aqueous hydrochloric acid solutio from the alkali metal fluosilicate; i) introducingthe separatedhydrochloricacidsolutio into the leaching zone; and j) introducing the separated alkali fluosilicat into the fluorination zone. This process has the advantage that it does no require the use of alkali metal fluoride salts or alkal metal basic salts in the fluorination step, and it avoid the loss of fluoride from the overall reaction scheme a silicon tetrafluoride. The +3 and +4 valent Group IVb transition metal-alkal metal-fluoride values produced from the above-describe fluorination processes are a mixture comprising +3 transitio metal fluoride value and +4 transition metal fluorid value, such as Na3Ti g and Na2TiOF - These values can b converted to a +4 valent Group IVb transition metal-alkal metal-fluoride salt, such as sodium fluotitanate or sodiu fluozirconate. This conversion is carried out in the leaching ste in the presence of aqueous hydrochloric acid. This conversio requires the presence of ferric iron, which is converte to ferrous chloride. The conversion requires at leas about 1.75 moles of hydrogen chloride per mole of Grou IVb metal present as +3 and +4 valent values. Under th proper leaching conditions, time, temperature and agitation at least 95% by weight of the +3 and +4 valent values ar solubilized. The leachant is separated from the insolubl component of the leaching step and cooled to a-temperatur of at least about 60"C to precipitate out silicon impurities Silicon impurities have a very low solubility in th leachant at temperatures of 60 β C or lower, and substantiall all of the silicon impurities drop out. Unavoidably, som of the +4 valent salt, depending on the HC1 concentratio and generally less than 10% by weight, also drops out wit the silicon impurities. Generally stronger hydrochlori acid concentrations favor a better split by maximizing th leaching of the +4 valent salt. However, strong aci concentrations favor a back reaction between silica an the +4 valent salt. These solids are separated from th cooled leachant and can be recycled into the leaching zon to recover the +4 valent salt. The leachant in the leachin zoneis saturatedwithrespectto dissolvedsiliconimpurities Thus, the recycled solid silicon impurities cannot cause build-up of silicon impurities in the leachant. The +4 valent salt is dropped out of the leachant b cooling the leachant to a temperature no greater tha 30°C. Preferably, sodium chloride (solid) and/or hydroge fluoride is added to the leachant to help salt out the + valent salt. The +4 valent salt crystallizes out in sub stantially pure form; however, it does contain mino amounts of dissolved iron andmanganesevalues. Unexpectedly the iron and manganese values or impurities can be easil removed from the product crystals by washing the crystal one or more time(s) with dilute aqueous hydrochloric acid This is an important consideration when the +4 valen Group IVb transition metal-alkali metal-fluoride salt i to be used to produce a Group IVb transition metal b reducing the +4 valent salt as described herein. Th preferred means of reducing the +4 valent salt is b adding the salt to a molten aluminum-zinc alloy and agitatin the same to obtain intimate contact between the alloy an the salt. The +4 valent salt is reduced to a Group IVb meta which is soluble in the zinc and the aluminum is oxidize to an aluminum fluoride salt. This type of reduction can also be utilized to purif the Group IVb transition metal. Impurities that are " -no soluble in the molten zinc or the molten Group IVb transitio metal-zinc alloy report to the top of the molten alloy o ' drop to the bottom of the molten alloy depending upo respective densities of the alloy and the impurities. I is very difficult to purify Group IVb metal scrap, such a titanium metal scrap, containing insoluble impurities suc as halide salts, alkali metal salts, alkaline earth meta salts, tungsten carbide and nitrides. Such metal scrap ca be purified by adding it to molten zinc, which will dissolv the Group IVb transition metal but not the insolubl impurities. The insoluble impurities, that is, for example, halide salts, alkali metal salts, alkaline earth meta salts, and nitrides, will report because of their insolubilit and density to the top of the molten Group IVb transitio metal-zinc alloy (referred to as the "molten alloy") t form a separate phase and/or slag. Other insoluble impuritie which are denser than the molten alloy, such as tungste carbide, will drop to the bottom of the molten alloy. I theGroup IVb transitionmetal-zincalloycontainsunacceptable amounts of impurities that are soluble in the molten allo ("soluble impurities"), a high purity Group IVb transition metal can be added to the molten alloy to dilute the soluble impurities concentration to yield a Group IVb transition metal-zinc alloy which has an acceptable impurity level. Alternatively, a +4 valent Group IVb transition metal-alkali metal-fluoride salt and a molar equivalent of aluminum can be added to the molten alloywherein the +4 valen salt will be reduced to a Group IVb transition metal to dilut the soluble impurity content. The insoluble impurities o the top of the molten alloy are skimmed off, and th molten alloy is removed from the heavier insoluble impuritie that drop to the bottom of the molten alloy to yield molten alloy substantially free of insoluble impurities. The zinc is removed by sublimation either under a vacuu or with the aid of an inert gas purge to yield a Group IV transition metal sponge that can be converted to a Grou IVb transitionmetal powder suitable for powdermetallurgica usage as described in U.S. Patent No. 4,470,847. Description of the Drawings FIG. 1 is a schematic illustration of the process o the present invention for the production of sodiu fluotitanate; FIG. 2 is a schematic representation of the purificatio steps of the present invention for the removal of silicon iron and magnesium impurities from a sodium fluotitanat produc ; FIG. 3 is a schematic illustration of a purificatio process for the present invention for purifying Group IV transition metal scrap to produce a metal sponge; and FIG. 4 is a graph showing the effect of washing sodiu fluotitanate crystals with 1% by weight of HC1 washes. Detailed Description of the Invention Referring to Fig. 1, the process is illustrated fo the production of. sodium fluotitanate employing ilmenit ore. However, the process can be utilized with other ore containing titanium dioxide or zirconium oxide to produc alkali metal fluotitanate or alkali metal fluozirconate, respectively. The fluorination zone 10 is in an unseale kiln wherein the ore and, optionally, additives are adde into the feed end 12. Hot gas is introduced into th product end 14 counter-current to the flow of the ore. Preferably the kiln is heated by indirect means, such a kiln wall heaters. Preferably, the ore is ground, mixe with the other feed materials and formed into agglomerate of less than 2-inch diameter. It has been found that th addition of " carbon in conjunction with either the iro present in the ore or iron, such as ferrous oxide, adde to a low iron-containing ore, has a synergistic effect o the subsequent recovery of the Group IVb transition metal. From about 1 to about 10, and preferably from about 1.2 t about 4, weight-percent carbon may be admixed with th iron-containing ore to enhance the recovery of titanium. It has been found that ores that are low in iron, o substantially free of iron, benefit from the addition o iron, such as ferric oxide, to the ore. The ore shoul contain at least 14% by weight iron. Preferably the or contains from about 14% to about 36% by weight iron an from about 25% to about 50% by weight Group IVb transitio metal. In the embodiment of the present invention wherei the ore is fluorinated in the presence of an alkali meta fluoride salt or an alkali metal basic salt, the salt carbon and iron are compounded with the ore to form a integral component of the feed agglomerates. In thi embodiment, the ore is compounded with at least 1.6 mola equivalents of alkali metal fluoride, such as sodiu fluoride, or alkali metal basic salt, such as sodiu carbonate, for each mole of Group IVb transition metal i the ore. The feed agglomerates are also compounded with th fluorination agent, an alkali metal fluosilicate, preferabl sodium fluosilicate. If the fluosilicate is the sol fluorinating agent, at least 1.6 molar equivalents o fluosilicate are compounded with the ore for each mole o Group IVb transition metal in the ore. If the feed is als compounded with an alkali metal fluoride salt, the fee ■ agglomerates are compoundedwith at least 0.8 molar equivalen of an alkali metal fluosilicate and at least 1.6 mola equivalents of an alkali metal fluoride salt for each mol of Group IVb transition metal in the ore. If the fee agglomerates are compounded with an alkali metal basi salt, the feed agglomerates are compounded with at leas about 1.07 molar equivalents of an alkali metal fluosilicat and with at least 1.07 molar equivalents of an alkal metal as an alkali metal basic salt for each mole of Grou IVb transition metal in the ore. The additional alkal metal fluosilicate is required to fluorinate the akali meta basic salt. The ore, iron (if any) , carbon, fluorination agent an alkali metal basic salt or fluoride salt (if any) ar ground to a particle size from about 30 to about 400 mesh, preferably from 100 to 400 mesh, and thoroughly mixed an then formed into agglomerates for feeding into the fluorinatio zone kiln. The feed agglomerates are heated in the fluorinatio zone to a temperature between about 600°C and about 1000°C, preferably from about 750°C to about 950°C to convert th Group IVb transition metal oxide to +3 and +4 valent Grou IVb transition metal-alkali metal-fluoride values. Th fluorination is believed to proceed by the series o reactions which are set forth below. The reactions ar illustrated employing sodium salts and Group IVb transitio metal values (M "3' and M "1"4 ) . However, the same reactions occu with other alkali metal salts. (1) Na 2 SiF 6 — > 2NaF + SiF 4 (2) SiF + 2Na 2 C0 3 > 4NaF + 2C0 2 + Si0 2 (3) SiF 4 + 4NaHC0 3 > 4NaF + 4C0 2 + Si0 2 + 2H 2 (4) SiF 4 + 4NaOH > 4NaF + Si0 2 + 2H 2 0 (5) M0 2 + Na 2 SiF 6 + Na 2 C0 3 — > Na 2 MOF 4 + 2NaF + Si0 2 + C0 2 (6) 2M0 2 + Na 2 SiF 6 ÷ 2NaF > 2Na 2 M0F 4 + Si0 2 (7) Fe 2 0 3 + C > 2FeO + CO (8) 2FeO + Na 2 SiF 6 > 2NaFeF 3 + Si0 2 (9) NaFeF 3 + Na 2 SiF 6 + M0 2 — > Na 3 MF 6 + 1/2 Fe 2 0 + 3/4 SiF + 1/4 Si0 (10) Na 2 SiF 6 + M0 2 > 2Na 2 M0F + 1/2 Si0 2 + 1/2 SiF (11) Fe 2 0 3 + 3Na 2 SiF 6 > 2Na 3 FeF 6 + 1 1/2 Si0 + 1 1/2 SiF 4 (12) 1.6 Na 2 SiF 6 + M0 2 + .48 FeO —> .48 Na 3 MF 6 + .52 Na 2 MOF 4 + .18 Si0 2 + .44 SiF 4 + .24 Na 3 FeF 6 + .12 Fe 2 0 3 - (13) .48 Na 3 MF 6 + .52 Na 2 MOF + .12 Fe 2 0 3 + .24 Na 3 FeF 6 + 1.76 HCl > Na 2 MF 6 + .48 FeCl 2 + 0.40 NaF + 0.80 NaCl + .88 H 2 0 (14) 3SiF + 2H 2 0 > 2H 2 SiF 6 + Si0 2 (15) H 2 SiF β + 2NaCl > Na 2 SiF 6 + 2HC1 Reaction (1) occurs at elevated temperatures, such a 600°C or more, wherein the alkali metal fluosilicat breaks down to form 2 moles of an alkali metal fluorid and silicon tetrafluoride gas. Reactions (2) through (4 are reactions between silicon tetrafluoride with alkal metal basic salts, . which yield an alkali metal fluorid salt, carbon dioxide, silicon dioxide and water as th case may be. Reaction (5) is the reaction between a Grou IVb transition metal oxide (M0 2 ) with 1 molar equivalen of an alkali metal fluosilicate and 2 molar equivalent o an alkali metal as an alkali metal basic salt, such a sodium carbonate. In this fluorination reaction, the Grou IVb transition metal oxide is fluorinated to form a + valentGroup IVbtransitionmetal-alkalimetal-oxide-fluorid value Na M0F . Reaction (6) shows that if Reaction (5) is conducte in the presence of at least 2 molar equivalents of a alkali metal fluoride salt rather than a basic salt, 2 mola equivalents of the metal oxide are fluorinated. Reactio (7) is a reaction that occurs between the carbon source and iron oxide in the ore to produce ferrous oxide and carbon monoxide. The ferrous oxide reacts with the alkali metal fluosilicate to yield an alkali metal ferrous fluoride as shown in Reaction (8) . The alkali metal ferrous fluoride reacts with the alkali metal fluosilicate and the Group IVb transition metal oxide M0 2 to form a +3 valent Group IVb transition metal-alkali metal-fluoride value, ferric oxide, silica tetrafluoride and silica as shown in Reaction (9). If an alkali metal basic salt is present, the silicon tetrafluoride will react with the salt to form an alkali metal fluoride salt [see Reactions (2) and (4)]. Some of the Group IVb transition metal oxide (M0 2 ) reacts directly with the alkaline metal fluosilicate as shown in Reaction (10) to form a +4 valent Group IVb transition metal-alkali metal-oxide-fluoride value, silicon tetrafluoride and silica. If an alkali metal basic salt is present, the silicon tetrafluoride will react with the salt to form an alkali metal fluoride salt. As shown in Reaction (11) , a portion of the ferri oxide in the ore reacts directly with the alkali meta fluosilicate to form an alkali metal ferric fluoride salt, silicon tetrafluoride and silica. The silicon tetrafluorid can react within the alkali metal basic salt to form a alkali metal fluoride salt. Reaction (12) is a compilatio of Reactions (8) through (11) wherein, for each mole o Group IVb transition metal oxide in the ore, the ore i contacted'^ i h 1.6 molar equivalents of an- alkali meta fluosilicate and 0.48 molar equivalents of ferrous oxide. The carbon and the ferric oxide compounded in the fee agglomerates react to form ferrous oxide and carbon monoxide. The +3 and +4 valent Group " IVb transition metal-alkal metal-fluoride values comprise a mixture of a +3 valen Group IVb transition metal-alkali metal-fluoride valu (Na 3 MFg) and a +4 valent Group IVb transition metal-alkal metal-oxide-fluoride value (Na 2 M0F 4 ) . A portion of th errous oxideis convertedtoanalkalimetal-ferrous-fluorid salt (Na 3 FeF 6 ) . Approximately 1 molar equivalent o silicon tetrafluoride is produced for each mole of alkal metal fluosilicate present in the feed agglomerates. A explained above, the addition of 2 molar equivalents of a alkali metal fluoride salt or the addition of a mola equivalent of an alkali metal as an alkali metal basi salt per mole of alkaline metal fluosilicate will eliminat the production of free silicon tetrafluoride gas in Reactio (12). The +3 and +4 valent Group IVb transition metal-alkal metal-fluoridevalueproducts (Na MF 6 andNa 2 MOF 4 ) ofReactio (12) are converted to the desired +4 valent Group IV transition metal-alkali metal-fluoride salt, namely alkal metal fluotitanates and alkali metal fluozirconates. Th conversion is accomplished- by contacting the +3 and + valent Group IVb transition metal-alkali metal-fluorid values with an aqueous hydrogen chloride solution in th presence of ferric oxide and an alkali metal ferric fluorid salt as shown. The feed mixture should contain ' at least 0.24 mola equivalent of iron per mole of Group IVb transition meta oxide, preferably as iron oxide, to supply sufficien fluoride as an alkali metal ferric fluoride salt (Na 3 FeF 6 to form Na 2 MFg during the leach step. The feed mixture ca also contain more than 1.6 molar equivalents of alkal metal fluosilicate per mole of Group IVb transition meta oxide. However, only 1.6 molar equivalents of th fluosilicates are necessary when at least 0.24 mola equivalent of iron is present. Referring back to Fig. 1, fluorinated ore 16 comprisin the solid products of Reaction (12) and other solid impuritie is passed from the product end 14 of the kiln to a leach zon 18 , wherein the fluorinated ore is leached with aqueou hydrochloric acid. The leach solutionhas anHC1 concentratio of less than 10% HC1 by weight, preferably from about 1 to about 3% by weight. Conventional leaching equipment ca be employed in the leached zone to solubilize the +3 an +4 valent Group IVb transition metal-alkali metal-fluorid values (Na 3 MF 6 and Na 2 MF 4 ) identified in Reaction (12) . The solubilized salts are converted to the desired +4 valent Group IVb transition metal-alkali metal-fluorid salt (Na 2 MF 6 ) , namely, alkali metal fluotitanates an alkali metal fluozirconates. It is believed that the chemical reactions responsible for this conversion are those set forth in Reaction (13) . Reactions (12) and (13) illustrate the importance of iron values to the fluorination and conversion reactions to produce the desired +4 valent Group IVb transition metal-alkali metal-fluoride salt. The Group IVb transition metal values of Reaction (12) report to the aqueous leachant in the leach zone. The leachant is separated from the insoluble solids, following the leaching ' , which comprise iron-containing solids, silicon impurities (primaril silicon dioxide) , clays and the like. The leaching operatio is normally conducted at a temperature between about 60° to the boiling point temperature of the leach solution, preferably between about 100°C and 110"C. The leaching i normally done in a continuous mode, rather than a batc mode, with a residence time between about 1 minute an about 3 hours, preferably for about 4 to about 10 minutes. The hot leachant solution 20 containing the desired + valent Group- IVb transition metal-alkali metal-fluorid salt is passed to a crystallization zone 22 wherein th leachant is cooled to a temperature from about 60°C to abou 25°C, preferably between about 27 β C and 33 β C, wherein portion, generally less than 10% by weight, of the desire +4 valent Group IVb transition metal-alkali metalfluorid salt is crystallized out and substantially all of th silicon impurities are precipitated out. Conventiona crystallization equipment, such as that described in Th Chemical Engineer's Handbook, 5th Edition; " R.H. Perry an CH. Chilton, McGraw-Hill Book Co., New York, N.Y. (1973), can be used in the crystallization zone. The solids ar removed from the cooled leachant to yield a substantiall pure dissolved +4 valent Group IVb transition metal-alkal metal-fluoride salt (Na 2 TiFg) . In the embodiment of the invention wherein the alkal metal fluosilicate is the sole fluorinating agent used i the fluorination zone, silicon tetrafluoride is produce and exits the fluorination zone with the exhaust gases 30. The exhaust gases are passed through a conventional ga scrubber (H 2 SiFg Production Zone) 32 wherein the gases ar washed with water to capture the silicon tetrafluoride t produce fluosilicic acid and silicon dioxide as shown i Reaction (14) . Silicon dioxide solids are separated fro the fluosilicic acid. The fluosilicic acid 34 is passed t a sodium fluosilicate production zone 36, wherein th fluosilicic acid is reacted with sodium chloride 38 o other alkali metal chloride to form sodium or other alkal metal fluosilicate and an aqueous hydrochloric acid solution as shown in Reaction (15) . In the fluosilicic acid production zone, the hot exhaus gas containing the silicon tetrafluoride is rapidly coole by the scrubber water, thus eliminating the need to coo the exhaust gas before scrubbing. However, the exhaust ga can be preσooled before scrubbing, if desired. The amoun of fluosilicic acid produced in the fluosilicic aci production zone is insufficient to produce the require amount of alkali metal fluosilicate needed in the fluorinatio zone. Accordingly, and preferably, additional fluosilici acid 40 is added to the alkali metal fluosilicate productio zone to produce at least 1.6 moles of alkali metal fluosilicat for each mole of Group IVb transition metal oxide introduce into the fluorination zone. The alkali metal fluosilicat produced in the alkali fluosilicate production zone, whic is sparingly soluble in the aqueous hydrochloric aci solution, is separated from the hydrochloric acid solution, preferably after the entire mixture is cooled to a temperatur of at least 30°C. The separated alkali metal fluosilicat is dried and mixed with the ore and additives as describe above, to form the feed mixture for the fluorination zone. The hydrochloric acid solution 42, after separation, i introduced into the leach zone to leach and convert the +3 and +4 valent Group IVb transitionmetal-alkalimetal-fluorid values as described above. In the preferred embodiment o the present invention, the leached solution contains less than 10% by weight HCl, preferably from about 1% to about 3% by weight HCl. Fig. 2 shows a preferred embodiment of the presen process to yield a +4 valent Group IVb transitionmetal-alkal metal-fluoride salt of enhanced purity with a very hig salt recovery. The leached zone 18 illustrated in Fig. is operated in the samemanner as the leached zone illustrate in Fig. 1. The leachant 20 is passed to a firs crystallization zone 50 wherein the leachant is cooled t a temperature between about 25"C and about 60 β C, preferabl between about 27°C and about 33 β C. A portion of the sal product and substantially all the silicon impuritie (primarily alkali metal fluosilicate) are dropped out a insoluble solids 52 and separated ' from the cooled leachant. The separated solids are recycled back to the leach zon to recover the +4 valent Group IVb transition metal-alkal metal-fluoride salt, which is solubilized in the leachant. Some of the silicon impurities are also solubilize by the leachant; however, since the leachant in the leac zone is substantially saturated with silicon impurities, most of the silicon impurities from the first crystallizatio zone drop out with the other insolubles 54 in the leac zone. Thus, recycling of the silicon impurities from th first crystallization zone back to the leach zone does no result in a concentration or build-up of silicon impuritie in the leachant. The leachant 54 from the first crystal lization zone is passed to a second crystallization zon 56 where the leachant is cooled to a temperature of betwee about -10 " C and about 30 β C, preferably from about -10°C t about 0°C, to substantially drop out all the +4 valen Group IVb transition metal-alkali metal-fluoride salt. The rate of crystallization can be enhanced by saltin the mother liquor in the second crystallization zone wit sodium chloride 58. Small amounts of hydrofluoric acid ca also be added to improve yields. However, hydrofluori acid is relatively expensive and quite corrosive. Its us can be minimized or omitted by operating the leach ste under optimum conditions. The salting σu-c is carπeα O by adding between about 50 and about 150 grams of sodi chloride per liter of leachant. From 0 to about 10 gra of hydrofluoric acid (49% solution) per liter of leacha can be added to improve titanium yield. The crystallize solids 58, containing the desired fluoride salt product an substantially free of silicon impurities, are separate from the leachant of the second crystallization zone an passed to multi-stage counter-current wash zone 60. Th spent leachant 62 can be disposed of in an environmentall acceptable manner or can be recycled as the salting-ou medium for the sodium silicofluoride crystallization zone In the wash zone 60, the +4 valent Group IVb transitio metal-alkali metal-fluoride salts are washed in counter-current manner in one or more stage(s) with dilut hydrogen chloride solution to remove substantially all th iron and manganese and other minor impurities soluble i dilute hydrochloric acid. In each washing, the crystal are washed with at least an equal weight amount of dilut HCl. The dilute hydrochloric acid contains less than 5% b weight HCl, preferably less than 2% by weight. The washin is done at a temperature of less than 30°C, preferably a ambient temperature. A single washing of the salt with th dilute hydrochloric acid solution reduces the iron conten and manganese content in the salt product to less than 10 parts per million (pp ) . The wash liquid with the solubl impurities is disposed of by conventional environmentall sound procedures. Afterthe Group IVb transitionmetal-alkalimetal-fluorid is washed, the salt is dried to remove moisture. The sal can then be reducedby conventional methods toproduce titaniu metal or advantageously reduced with an aluminum and zin molten alloy, as taught in U.S. Patent Nos. 4,390,365 an 4,468,248, to produce a Group IVb metal-zinc molten alloy. The molten alloy, after the separation of the insolubl impurities, can be converted to a pure Group IVb metal by subliming off the zinc, preferably under a vacuum or with the-sweep of an inert gas stream, such as an argon gas stream. The dried crystals of the fluorides of the Group IVb metal can be reduced in a reducing zone where they are contacted in a molten state with a molten zinc-aluminum alloy. The alloy may comprise from 1:99 to 20:80 parts by weight of aluminum to zinc. The molten salt and the alloy are mutually immiscible; therefore, agitation of the molten salt and molten alloy to insure intimate contact is preferred. Reduction takes place at a temperature from at least 650"C to about 1000°C, preferably from about 850"C to about 950°C. The time of contacting the molten alloy and the molten salt can be varied to assure that the Group IVb metal present in the salt is converted into a Group IVb metal-zinc alloy. The aluminum present in the aluminum- zinc alloy during the course of the reduction is converted into the corresponding fluoride salt and may be isolated as the pseudocryolite. After agitation of the mixture is stopped, the reduced mixture separates with the molten salt rising to the top, where itmaybe decanted fromthemolten alloy. Alternatively, the molten Group IVb metal-zinc allo . may be separated from the bottom of the vessel and passed to a reducing zone wherein the zinc is separated from the Group IVb metal. The removal or reduction of the zinc must take place under inert conditions because of the Group IVb metal's propensity to pick up oxygen and nitrogen. * Suitably, an argon atmosphere is present during the sublimation step or the sublimation is carried out under a vacuum. A suitable vessel for carrying out the sublimation, as well as othe of the various high temperature operations describe herein, is a graphite-lined reactor. It has been found tha during the salt reduction step, it is advisable that bot the salt and alloy phases be maintained above the licruidous temperature to avoid solids formation, which can be abrasive to both the agitator and the reactor walls. It is desirable to have the molten zinc nearly saturated with dissolved Group IVb metal, if possible, to minimize the amount of zinc to be distilled in the subsequent sublimation step. Advantageously, the salt reduction step can take place under an elevated pressure to raise the boiling point temperature of the Group IVb metal-zinc molten alloy, which enhances the solubility of the Group IVb metal into molten zinc. For example, at atmospheric pressure, a titanium-zinc alloy boils at approximately 915 β C. At that temperature, only about 15% by weight titanium metal can be dissolved into molten zinc before solids formation. However, if reduction is carried outunder an elevatedpressure (about 1.5 atmospheres), then the molten titanium-zinc alloy boils at about 950"C and approximately 25% by weight titanium metal can be dissolved in the zinc before the onset of solids formation. At elevated pressures, the principal limitation of the reduction temperature is dictated by the materials of construction of the reactant vessel. For example, at temperatures approaching 1000 β C, there is a substantial increase in contamination of the Group IVb metal by carbon from the graphite reactor wall. The degree of carbon contamination becomes severe above 1100°C. In the sublimation step, the sublimation is carried out under vacuum or inert gas atmosphere, such as argon gas . atmosphere, to prevent oxygen and nitrogen contamination of the Group ' IVb metal. The zinc is distilled off at a temperature from about 800°C to about 1000°C to leave a- Group IVb metal sponge. When the distillation is conducted under a vacuum, distillation can take place at a somewhat lower temperature. The Group IVb metal sponge may be sintered to reduce its surface area. After sintering and cooling, the sponge can be pacified by exposure to a controlled amount of oxygen-containing gas to give a thin (monomolecular) protective coating of the Group IVb transition metal oxide thereon before the sponge is exposed to the air or other non-inert atmosphere. . The sublimed zinc can be recovered and recycled for use in subsequent salt reduction steps. Referring to Fig. 3, Group IVb metal scrap contaminated with impurities soluble in molten Group IVb metal and molten zinc is added to a molten aluminum-zinc alloy in a zinc alloy zone 70 to dissolve the metal scrap. A Group IVb transition metal fluoride salt is added to the zinc alloy zone 70, which is reduced by the molten aluminum metal to a Group IVb metal which reports to the zinc to dilute the soluble impurities in the molten Group IVb metal-zinc alloy. The aluminum is reduced to form an aluminum fluoride salt insoluble in the molten Group IVb metal-zinc alloy. The reduction is preferably conducted with agitation to insure intimate contact between the molten metal salt and the molten aluminum-zinc alloy. Optionally, the zinc and aluminum separately, or as an aluminum-zinc alloy, and the metal salt may be co-melted in the zinc alloying zone. By the above methods, the purity of the scrap metal can be increased by diluting the soluble impurities in the metal with pure Group IVb transition metal produced from the metal fluoride in the presence of the scrap so that the resulting metal can meet industrial and/or military speci ications» In an alternative embodiment of the present invention, Group IVb metal scrap can be added to the zinc alloying zone, wherein the zinc is not alloyed with aluminum, to remove insoluble contaminants, such as carbon, halide salts, alkali metal salts, alkaline earth metal salts, aluminum salts, silica and nitrogen, which are insoluble in molten zinc and molten Group IVb transition metal. These latter contaminants will float to the surface of the Group IVb metal-zinc molten alloy and can be decanted off. If th metal scrap contains dense insoluble contaminants, such a tungsten carbide, tungsten molybdenum or the like, thes contaminants will drop to the bottom of the zinc alloyin zone after agitation is complete, and the molten Group IV metal-zinc molten alloy can be decanted from such dens insoluble contaminants. If the metal scrap contain undesirable amounts of soluble impurities, high purit Group IVb transition metal can be added to the zinc alloyin zone to dilute the soluble contaminants in the metal scrap to yield Group IVb transition metal in the metal-zinc molten alloy which will pass industrial and/or military specifications. In a further embodiment of the present invention, the Group IVb metal-zinc alloy produced in the zinc alloying zone can be alloyed with alloying agents, such as vanadium, aluminum, nickel and the like, to form a Group IVb transition metal alloy after the removal of the zinc. Alternatively, the metal scrap, the alloying agents, the high purity metal and/or the metal salt, can be co-melted with zinc and/or aluminum and zinc. After the formation of the molten Group IVb transition metal-zinc alloy optionally containing alloying agents, the molten alloy is passed to a sublimation zone wherein the zinc is removed by sublimation to yield a Group IVb transition metal sponge. The sublimation, if conducted under an inert gas atmosphere, can be conducted at a temperature between about 800"C and about 1000°C. If the sublimation is carried out in a vacuum, sublimation can be conducted at a temperature of less than 800°C. To prevent oxygen and nitrogen contami¬ nation of the Group IVb metal during sublimation, the sublimation is conducted under an inert gas atmosphere unless it is conducted in a vacuum. The metal sponge may be sintered to reduce its surface area and then passified with an oxygen-containing gas in order that the sintered Group IVb metal sponge can be further treated to produce Group IVb metal powder usable for metallurgical powder purposes in accordance with the procedures taught in U.S. Patent Nos. 4,470,847 and 4,595,413. The present invention will be further described with reference to the following examples, which are presented for the purposes of illustrating the invention. These examples are not intended as a limitation of the invention. EXAMPLE 1 Referring to Fig. 1, 1.5 moles of fluosilicic acid 40 (as a 23 weight percent aqueous solution) is reacted with 3 moles of sodium chloride 38 to form 1.5 moles of sodium silicofluoride crystals 39 and 3 moles of hydrochloric acid 42 (approximately a 10 wt% aqueous solution) . Sodium silicofluoride is combined with ilmenite ore containing 1 mole of titanium dioxide and heated in a fluorination zone, opened in kiln 10 to a temperature between about 700"C and 800"C. The sodium silicofluoride decomposes in the kiln to form sodium fluoride and silicon tetrafluoride. One-half of the silicon tetrafluoride, 0.75 mole, reacts with the titanium dioxide in the ore to form +3 and +4 valent titanium fluoride salts and silicon dioxide. The remaining half of the silicon tetrafluoride exits the reactor as silicon tetrafluoride gas in the exhaust gases 30. The silicon tetrafluoride in the exhaust gas is passed to the silicon tetrafluoride production zone, where it is scrubbed with water to form 0.25 mole of silicon dioxide and 0.5 mole of fluosilicic acid 34 (approximately a 23% by weight aqueous solution) . The fluosilicic acid is ' recycled to the sodium fluosilicate production zone. The fluorinated ore 16 is ground and then passed to leach zone 18, wherein the fluorinated ore is leached with aqueous hydrochloric acid to convert the +3 and +4 valent titanium fluoride salts to titanium fluoride which is solubilized by the leachate. The leachate is separated from the insoluble solids and passed to the crystallization zone 22. In the crystallization zone, the leachate is cooled to form crystals of titanium fluoride and a spent leachate containing soluble impurities of iron, hydrochloric acid, sodium fluoride and the like. EXAMPLE 2 The process of Example 1 can be conducted in a manner to eliminate the .loss of silicon tetrafluoride gas in the exhaust gas. The ore containing 1 mole of titanium dioxide is compounded with 1.6 moles of sodium fluoride and 0.8 mole of sodium silicofluoride and introduced into the fluorination zone to produce fluorinated ore containing the +3 and +4 valent titanium fluoride salts, sodium fluoride, silicon dioxide impurities, iron oxide and iron salts, and unreacted gangue. The fluorinated ore is passed to a leach zone where it is leached with a hydrochloric acid solution obtained from an external source to produce a leachate containingthe desired+4 valent sodium fluotitanate to solubilize in the leachate and in the soluble solids which are separated from the leachate. The leachate is passed to the crystallization zone to crystallize out the desired sodium fluotitanate product, leaving a spent leachate containing soluble sodium chloride, soluble iron salts, other impurities and excess hydrochloric acid. EXAMPLE 3 The process of Example 1 can be conducted in such a manner as to prevent the loss of silicon tetrafluoride in the exhaust gases by compounding the ilmenite ore which contains 1 mole of titanium dioxide with 1.07 moles of sodium silico¬ fluoride and 1.07 moles of a basic sodium salt, such as sodium carbonate, sodium bicarbonate or sodium hydroxide. The feed material is passed through fluorination zone 10, wherein the feed material is heated to form +3 and +4 valent titanium fluoride salts, sodium fluoride, silicon dioxide impurities, iron salts and carbon dioxide or water. Fluorinated ore is passed to leach zone 18, wherein the fluorinated ore is leached with hydrochloric acid solution obtained from an external source to solubilize titanium fluoride salts and produce the soluble sodium fluotitanate. The leachate is separated from the insoluble solids and passed to a crystallization zone 22, wherein it is cooled to crystallize outthe desired sodium fluotitanate. Although processes of Examples 1-3 have been illustrated employing sodium salts, other alkali metal salts, such as potassium salts or lithium salts, can also be used. However, the sodium salts are less expensive than the corresponding potassium salts and lithium salts, and thus offer economic advantages. EXAMPLE 4 A mixture of finely ground ilmenite ore (36.8 parts by weight) , sodium silicofluoride (61.5 parts by weight) and calcined petroleum coke (1.7 parts by weight) was intimately mixed dry. The mixture contained 1.36 molar equivalents of sodium fluosilicate per mole of titanium dioxide. Water (9.4% by weight) was blended into the mixture, and balls having a diameter between +3/8 and -5/8 inch prepared from the mixture in a balling pan. The balls were dried in a tray drier. The dried balls (2501.5 grams) were placed in a po , heated by an indirect heater to a ' temperature between 750 " C and 788 ° C for a total of 4 hours to insure that the charge was fully reactedwith silicon tetrafluoride, and 256 grams of silicon tetrafluoride were metered into the pot over the last two hours of the reaction after the evolution of silicon tetrafluoride from the reaction had essentially ceased. Only a small amount (about 35 grams) of this later-added silicon tetrafluoride was consumed oy the charge. During the reaction, a total of 10.8 grams of carbon, 28.8 grams of oxygen and 646 grams of silicon tetrafluoride was swept out of the pot with the nitrogen purge gas (200 cc per minute) , which was continued for the duration of the reaction. In addition, 126 grams of water were trapped in a dry ice-cooled trap from the off gas. The fluorinated ore from the reaction was in its original shape, that is, in the shape of balls, but the fluorinated ore had less bulk density because of the weight loss occurring during the reaction. The balls were fryable and were ground in a hammer mill to 90% -60 mesh. A small sample of the ground fluorinated ore was leached in two stages with hydrochloric acid (3.6 wt%) . Seventy percent of the titanium in the ore was solubilized. The remainder of the fluorinated ore was leached in a single stage with an aqueous hydrogen fluoride-hydrogen chloride solution (3 wt% HF and 7 wt% HCl) in a ratio of 1 part by weight fluorinated ore to 5.1 parts by weight of a leaching solution. The titanium was solubilized and sodium fluotitanate crystals were recovered from the leachate (63.8 wt%) . This Example showed that about one-half of the silicon tetrafluoride that was formed during the heating from the sodium fluosilicate formulated in the balls reacts with the ilmenite ore. The other one-half of the silicon tetrafluoride did not react with the ore and exited the reaction zone with the purge gas. The amount of titanium recovered was not high due to the loss of fluorine. Of the 1.1 moles of Na 2 SiF 6 per mole of titanium in the balls, only about 0.53 mole of Na 2 SiFg reacted with the ore, the remainder passing into the gas phase and being removed from the system by the nitrogen purge-. EXAMPLE 5 A new ball formulation comprising 33.1 parts by weight ilmenite ore, 65.3 parts by weight sodium fluosilicate and 1.6 parts by weight calcined petroleum coke was prepared in the same manner as in Example 4. The mixture was finely ground and formed into balls and heated in accordance with the process of Example 4. The fluorinated ore, after being ground, was leached with a hydrochloric acid-hydrofluoric acid solution (6 wt% HCl and 5 wt% HF) . In this experiment, one-half of the silicon tetrafluoride formed from the sodium fluosilicate in the balls passed into the gas phase and did not react with the ore. In a larger scale leach of the fluorinated ore, 87 wt% of the titaniumwas solubilized when the fluorinated ore was leached with a hydrogen fluoride-hydrogen chloride solution (2.9 wt% HF and 6.9 wt% HCl) . EXAMPLE 6 Another ball formulation ' was prepared comprising 28.7 parts by weight ilmenite ore, 69.9 parts by weight sodium fluosilicate and 1.4 parts by weight calcined petroleum coke. The mixture was finely ground and formed into balls as described in Example 4, and then heated in accordance with the process of Example 4. The fluorinated ore was ground and leached with an aqueous hydrochloric acid solution (9.5 wt% HCl) and 95% of the titaniumwas solubilized in the leachate.. Nearly 96% of the titanium in the leachate was recovered as sodium fluotitanate crystals by cooling the leachate to -7°C and adding 100 grams of sodium chloride per liter of leachate to salt out the sodium fluotitanate. EXAMPLE 7 Wetsodium fluotitanatecrystals recoveredfrσmleachates, such as the leachate inExample 6, were washed with successive batches of a 1% by weight hydrochloric acid solution. The iron and magnesium impurities in the sodium fluotitanate crystals were reduced to low levels in the first few washings. The residual level of iron and manganese in the sodium fluotitanate crystals is dependent upon the quality and size of crystals grown which, in turn, depends on the quality of the crystallizer design and operating parameters. To aid in the removal of these impurities, the crystals are preferably grown in small size, which is accomplished by cooling the leachate down quickly to a temperature below 0°C. Silicon impurities are not reduced by washing. Since some of the sodium fluotitanate crystals are dissolved during the ' washing operation, the silicon impurity level increases because the sodium silicofluoride is not dissolved by the wash liquor. The effectiveness of washing the sodium fluotitanate crystals crystallized from leachates, containing about 7% to about 10% by weight hydrogen chloride, with a 1% by weight aqueous hydrochloric acid wash, is shown in Fig. 4. The first wash effectively lowers the concentration of iron to below 100 parts per million (Curve A) . However, each washing with the 1% by weight aqueous hydrogen chloride wash gradually increases the concentration of sodium silicofluoride impurities in the crystals (Curve B) . EXAMPLE 8 The leachate obtained from leached fluorinated balls of Example 6 was cooled from the leach temperature of 95 β C to 35°C in a crystallizer. The titanium content in the leachate was reduced from 20.8 to 15.0 grams per liter. The silicon content in the leachate was reduced from 0.23 to 0.001 gram per liter. The leachate was filtered to remove the precipitated solids containing silicon and titanium. The filtered leachate was then cooled to -7°C in a crystallizer, while slowly adding 100 grams of sodium chloride for each liter of leachate and 5.0 grams of hydrofluoric acid (49 wt%) for each liter of leachate. Sodium fluotitanate crystals dropped out and the titanium content of the leachate was reduced to 0.3 gram titanium per liter of leachate. The sodium fluotitanate crystals were separated from the leachate by filtration and washed with 1% by weight aqueous hydrochloric acid wash as disclosed in Example 7 to remove iron, manganese andotherminor impurities soluble in the leachate. EXAMPLE 9 The solids recovered from the leachate in Example 8, where the leachate is cooled to 35°C, can be recycled to the initial step of leachingthe ore. The sodium fluotitanate is solubilized in the leachate with some of the silicon impurities. However, the bulk of the silicon impurities are not solubilized and are removed from the leachate by filtration. Since the leachate, at this stage, is relatively saturated with respect to silicon impurities, this recycling step does not result in a build-up of silicon impurity concentration in the leachate.

Claims: WHAT IS CLAIMED IS: 1. Aprocess forthepreparation of Group IVb transitio metal-alkali metal-fluoridevalues froma Group IVb transitio metal oxide-containing ore which comprises the step of: fluorinating a Group IVb transition meta oxide-containing ore by contacting said ore in an unseale reactor with an alkali metal fluosilicate and alkali metal fluoride salt at a temperature of from about 600°C to about 1000°C to convert the Group IVb transition metal oxides to +3 and +4 valent Group IVb transition metal-alkali metal-fluoride values, for each mole of Group IVb transition metal oxide present in said ore, the ore is contacted with at least 0.8 mole of an alkali metal fluosilicate and with at least 1.6 molar equivalents of an alkali metal fluoride salt to minimize the loss of fluorine as silicon tetrafluoride gas from the reactor. 2. The process according to claim 1 wherein the ore is selected from the group consisting of ilmenite and zircon. 3. The process according to claim 1 wherein the alkali metal fluosilicate is sodium fluosilicate, and the alkali metal fluoride is sodium fluoride. 4. The process according to claim 3 wherein the Group IVb transition metal oxide is titanium dioxide, and the +3 and +4 valent Group IVb transition metal-alkali metal-fluoride values are Na 3 TiFg and Na 2 Ti0F 4 . 5. The process according to claim 3 wherein the Group IVb transition metal oxide is zirconium dioxide, and the Group IVb transition metal-alkali fluoride values are Na 3 ZrF β and Na 2 ZrOF . 6. A process for the production of a Group IVb transition metal-alkali metal-fluoride salt from a Group IVb transition metal oxide ore which comprises the step of: fluorinating a Group IVb transition metal oxide-containing ore by contacting- said ore in an unsealed reactor with an alkali metal fluosilicate in the presence of an alkali metal basic salt at a temperature of from about 600"C to about 1000 β C to convert the Group IVb transition metal oxides to +3 and +4 valent Group IVb transition metal-alkali metal-fluoride values, for each mole of Group IVb transition metal oxide present in said ore, the ore is contactedwith at least 1.07 molar equivalents of an alkali metal fluosilicate and at least 1.07 molar equivalents of an alkali metal in the form of said alkali metal basic salt. 7. The process according to claim 6 wherein the alkali metal basic salt is selected from the group consisting of an alkali metal carbonate, an alkali metal oxide, an alkali metal bicarbonate or mixtures thereof. 8. The process according to claim 7 wherein the alkali metal fluosilicate is sodium fluosilicate, and the alkali metal basic salt is selected from the group consisting of sodium carbonate, sodium hydroxide, sodium bicarbonate and mixtures thereof. 9. The process according to claim 8 wherein the Group IVb transition metal oxide ore is ilmenite, and the +3 and +4 valent Group IVb transition metal-alkali metal-fluoride values are Na 3 TiF 6 and Na 2 Ti0F . 10. The process according to claim 8 wherein th Group IVb transition metal oxide ore is zircon, and the + and +4valent Group IVb transitionmetal-alkalimetal-fluorid values are Na 3 ZrF 6 and Na 2 ZrOF 4 . 11. The process for the preparation of a Group IV transition metal-alkali metal-fluoride salt substantiall free of silica from a Group IVb transition metal oxide or comprising the steps of: (a) fluorinatinga Group IVb transitionmetal oxid ore by contacting the ore in an unsealed fluorination zon with an alkali metal fluosilicate at a temperature of fro about 600"C to about 1000"C to obtain a fluorinated ore, forming gaseous silicon tetrafluoride and converting- the Group IVb transition metal oxide to +3 and +4 valent Group IVb transition metal-alkali metal-fluoride values, for each mole of Group IVb transition metal oxide present in said ore, the ore being contacted with at least about 1.6 molar equivalents of the alkali metal fluosilicate; (b) removing the fluorinated ore from the fluorination zone and introducing it into a leaching zone wherein the fluorinated ore is leached with an aqueous hydrochloric acid solution to solubilize the +3 and +4 valent Group IVb transition metal-alkali metal-fluoride values and a portion of the iron salts and silica and to convert the +3 and +4 valent Group IVb transitionmetal-alkali metal-fluoride values to a +4 valent Group IVb transition metal-alkali metal-fluoride salt soluble in the leachate; (c) separatingthe leachate from insoluble solids; (d) introducing the separated leachate into a crystallization zone wherein the leachate is cooled to a temperature of at least 60°C to drop out solids containing silicon impurities and +4 valent Group IVb transition metal-alkali metal-fluoride salt; and Claim 11, continued. . . (e) separating the solids formed in the crystallization zone from the leachate to yield an aqueous solution containing the +4 Group IVb transition metal-alkali metal-fluoride salt product substantially free of silicon impurities. 12. The process according to claim 11 including the steps of: (a) introducingthe gaseous silicon tetrafluoride from the fluorination zone into a hydrolysis zone wherein the silicon tetrafluoride is contacted with water to convert the silicon tetrafluoride to fluosilicic acid; (b) introducingthe fluosilicicacid into analkali metal fluosilicate production zone wherein the fluosilicic acid is contacted with an alkali metal chloride to produce an aqueous hydrochloric acid solution and a solid alkali metal fluosilicate; (c) separatingthe solidalkalimetal fluosilicate from the aqueous hydrochloric acid; and (d) introducing the separated hydrochloric acid solution into the leaching zone. 13. The process according to claim 12 wherein about 2.0 molar equivalents of alkali metal chloride are introduced into the alkali metal fluosilicate production zone for each mole of fluosilicic acid introduced. 14. Theprocess according to claim 13 wherein the alkali metal fluosilicate produced in the alkali metal fluosilicate production zone is introduced into the fluorination zone. 15. The process according to claim 13 wherein at least 1.0 molar equivalent of fluosilicic acid is introduced from an external source into the alkali metal fluosilicate Claim 15, continued. . . production zone for each mole of Group IVb transitio metal oxide in the ore introduced into the fluorination zone. 16. The process according to claim 15 wherein the alkal metal chloride introduced into the alkali metal fluosilicat production zone is sodium chloride, and the alkali metal fluosilicate produced in the alkali metal fluosilicat production zone and introduced into the fluorination zone is sodium fluosilicate. 17. The process according to claim 11 wherein the Group IVb transition metal oxide ore is ilmenite, and the +4 valent Group IVb transitionmetal-alkalimetal-fluoride salt is sodiu fluotitanate. 18. The process according to claim 11 wherein the Group IVb transition metal oxide ore is zircon, and the +4 valent Group IVb transitionmetal-alkalimetal-fluoride salt is sodium fluσzirconate. 19. The process according to claim 11 wherein at least 3 molar equivalents of hydrogen chloride in the form of the aqueous hydrochloric acid solution are introduced into the leaching zone for each mole of Group IVb transition metal oxide in the ore introduced into the fluorination zone. 20. The process according to claim 11 wherein the leaching of the fluorinated ore with an aqueous hydrochloric acid solution is conducted at a temperature of between about 60°C and the boiling point temperature of the leachate. 21. The process according to claim wnerεm ine leachate is crystallized in the crystallization zone at a temperature between about 27°C and about 33"C. 22. The process according to claim 12 wherein the fluosilicic acid is contacted with the alkali metal chloride in the alkali metal fluosilicate production zone at a temperaturebetweenaboutambienttemperatureandabout1000"C. 23. The process according to claim 11 wherein the Group IVb transition metal oxide ore is mixed with a carbon source, and the resulting ore-carbon source mixture is introduced into the fluorination zone, the mixture containing from about 1 percent to about 10 percent by weight carbon source. 24. Theprocess accordingto claim 23 whereinthe carbon source is selected from the group consisting of coal coke, petroleum coke, charcoal, carbon black and activated carbon. 25. The process according to claim 11 wherein the Group IVb transitionmetal oxide-containingore comprises fromabout 14 percent to about 36 percent by weight iron and from about 25 percent to about 50 percent by weight titanium. 26. The process according to claim 11 wherein the Group IVb transition metal oxide-containing ore contains at least 14.percent by weight iron as iron oxide. 27. The process according to claim 11whereinthe Group IVb transition metal oxide-containing ore is admixed with a carbon source, and the resulting ore-carbon source mixture is introduced into the fluorination zone, the mixture containing from about 1.2 weight-percent to about 4 weight-percent carbon source. 28. The process according to claim 11 wherein the Grou IVb transition metal oxide-containing ore is contacte with the alkali metal fluosilicate at a temperature fro about 750°C to about 950°C. 29. A process for the preparation of a purified Grou IVb transition metal-alkali metal-fluoride salt from fluorinated Group IVb transition metal oxide-containin ore comprising the steps of: (a) leaching a fluorinated Group IVb transition metal oxide-containing ore containing +3 and +4 valent Group IVb transition metal-alkali metal-fluoride values in a leaching zone with an aqueous hydrochloric acid solution under conditions to solubilize +3 and +4 valent Group IVb transition metal-alkali metal-fluoride values, to convert the +3 and +4 valent Group IVb transition metal-alkali metal-fluoride values to a +4 valent Group .IVb transition metal-alkali metal-fluoride salt soluble in said leachate; (b) separatingthe leachate from insoluble solids; (c) cooling the separated leachate in a crystallization zone at a temperature between about 30°C and about 60"C to precipitate out solids containing silicon impurities, the silicon impurities concentration in the leachate being reduced to a concentration no greater than about 0.001 gram of silicon impurities per liter of leachate; (d) separating the precipitated solids from the leachate and recycling the separated solids into the leaching zone; and (e) introducing the leachate into a second crystallization zone wherein the leachate is cooled to a temperature no greater than 30"C to crystallize out +4 valent Group IVb transition metal-alkali metal-fluoride salt substantially free of silicon impurities. 30. The process according to claim 29 wherein the crystallized salt from the second crystallization zone is separated from the leachate and washed at least once with dilute aqueous hydrochloric acid to remove substantially all the iron and magnesium impurities from the salt to yield a +4 valent Group IVb transition metal-alkali metal-fluoride salt containing less than 100 ppm of iron, less than 100 ppm of manganese and less than 0.001 percent silicon. 31. The process according to claim 29 wherein the fluorinated ore is leached with an aqueous hydrochloric acid solution having a hydrogen chloride concentration of less than about 23 percent by weight. 32. The process according to claim 29 wherein the fluorinated ore is leached with an aqueous hydrochloric acid solution having a concentration of from about 1 percent to about 3 percent by weight hydrogen chloride. 33. The process accordingto claim 29 wherein from about 50 grams to about 150 grams of alkali metal chloride and from about zero to about 1 gram of a 49 percent solution of hydrogen fluoride are introduced into the second crystallization zone with each liter of leachate introduced. 34. The process according to claim 29 wherein about 100 grams of alkali metal chloride and about 1.25 grams of hydrogen fluoride are introduced into the second crystallization zone with each liter of leachate introduced. 35. Theprocess accordingto claim 34 whereinthe alkali metal chloride is sodium chloride. 36. Theprocess accordingto claim29 wneremπuormateα ore is fluorinate ilmenite ore, and the +4 valent Group IVb transition metal-alkali metal-fluoride salt is sodium fluotitanate. 37. Theprocess accordingto claim29 whereinfluorinated ore is fluorinated zircon ore, and the +4 valent Group IVb transition metal-alkali metal-fluoride salt is sodium fluozirconate. 38. The process according to claim 30 wherein the dilute aqueous hydrochloric acid solution employed in the washing step has a hydrogen chloride concentration of less than 2 percent by weight. 39. The process according to claim 28 wherein the fluorinated ore is contacted with at least about 1.7 molar equivalents of hydrogen chloride per each mole of +3 and +4 valent Group IVb transition metal-alkali metal-fluoride values contained in the fluorinated ore. 40. A process for the preparation of a purified Group IVb transition metal di-alkali metal hexafluoride salt from a fluorinated Group IVb transition metal oxide ore comprising the steps of: (a) contacting a fluorinated ore containing +3 and +4 valent Group IVb transitionmetal-alkalimetal-fluoride values with an aqueous hydrochloric acid solution under conditions to convert said values to a salt of the formula A 2 MF 6 and to solubilize the A 2 MFg salt to form a leachate, wherein A is an alkali metal, M is a Group IVb transition metal and F is fluorine; (b) separating the leachate from insoluble salts; (c) cooling - the separated leachate in a crystallization zone at a temperature between about 27°C and Claim 40, continued. . . about 33 ° C to precipitate out solids containing silicon impurities, the silicon impurities concentration in the leachate being reduced to a concentration no greater than about 0.001 gram of silicon impurities per liter of leachate; (d) separating the precipitated solids from the leachate; (e) introducing the leachate into a second crystallization zone, together with an alkali metal chloride salt and hydrofluoric acid wherein the resulting mixture is cooled to a temperature no greater than 0°C to crystallize out the A 2 MF 6 salt; (f) separating the A 2 MF 6 salt from the leachate; and (g) washing the A 2 MF 6 salt in a washing zone at least once with dilute aqueous hydrochloric acid to remove iron and magnesium impurities from the salt to yield an A 2 MF 6 salt containing less than 100 ppm of iron, less than 100 ppm of manganese and less than 0.001 percent silicon. 41. Aprocess for the preparation of a highpurity Group IVb transition metal-zinc alloy from Group IVb transition metal scrap containing impurities insoluble in molten Group IVb transition metal and molten zinc comprising the steps of: (a) dissolvinginmolten zinc aGroup IVbtransition metal scrap containing impurities insoluble in molten Group IVb transition metal and molten zinc in molten zinc at a temperature between about 650°C and about 1000 a C to form a molten Group IVb transition metal-zinc alloy phase and a separate phase containing said insoluble impurities; and (b) separating said molten alloy -phase fro said phase containing insoluble impurities. 42. The process according to claim wnerem c impurities insoluble in molten Group IVb transition met and molten zinc are halide salts, alkali metal salt alkaline earth metal salts, nitrides, nitrogen and refracto carbides. 43. The process according to claim 41 wherein t impurities insoluble in molten Group IVb transition met and molten zinc have a density less than the density o said molten alloy phase, and said separate phase containin said insoluble impurities floats on top of said molte alloy phase. 44. The process according to claim 41 wherein th impurities insoluble in molten Group IVb transition meta and molten zinc have a density greater than . said molte alloy phase, and said separate phase containing sai insoluble impurities sinks to the bottom of said molte alloy phase. 45. The process according to claim 41 including th additional step of subliming the zinc off the separate molten alloy phase to produce a Group IVb transition meta substantially free of said insoluble impurities. 46. A process for the preparation of a highpurity Grou IVb transition metal from. Group IVb transition metal scra containing impurities insoluble inmolten Group IVb transitio metal and molten zinc comprising the steps of: (a) dissolving inmolten zinc aGroup IVbtransitio metal scrap containing impurities insoluble in molte Group IVb transition metal and molten zinc at a temperatur between about 650°C and about 1000°C to form a molte Group IVb transition metal-zinc alloy phase and a separat phase containing said insoluble impurities; Claim 46, continued. . . (b) separating said molten alloy phase fro said phase containing insoluble impurities; and (c)- subliming the zinc from said separate molten alloy phase at a temperature of at least 1000°C t yield a Group IVb " transition -metal sponge substantiall free of zinc metal and said insoluble impurities. 47. The process according to claim 46 wherein th impurities insoluble in molten Group IVb transition metal and -molten zinc are halide salts, alkali metal salts, alkaline earthmetal salts, nitrides, nitrogenandheat-stable carbides. 48. The process according to claim 46 wherein th impurities insoluble in molten Group IVb transition metal and molten zinc have a density less than the density of said molten alloy phase, and said separate phase containin said insoluble impurities floats on top of said molten alloy phase. 49. The process according to claim 46 wherein the impurities insoluble in molten Group IVb transition metal and molten zinc have a density greater than said molte alloy phase, and said separate phase containing sai insoluble impurities sinks to the bottom of said molte alloy phase. 50. Aprocess for the preparation of ahighpurity Grou IVb transition metal-zinc alloy from Group IVb transitio metal scrap containing impurities soluble in molten Grou IVb transition metal and molten zinc comprising the step of: (a) dissolvinginmoltenzinc aGroup IVbtransitio metal scrap containing impurities soluble in molten Grou Claim 50, continued. . . IVb transition metal and molten zinc in molten zinc at temperature between about 650"C and about 1000°C to form molten Group IVb transition metal-zinc alloy containin said soluble impurities; and (b) dissolving additional Group IVb transitio metal having a low content of said, soluble impurities int saidmolten alloy, sufficient Group IVb transitionmetal havin a low content of soluble impurities into said molten allo to produce a second Group IVb transition metal-zinc molte alloy having a soluble impurity content not exceeding predetermined value. 51. The process according to claim 50 including th additional step of subliming the zinc from said secon molten alloy at a temperature of at least 1000°C to yiel a Group IVb transition metal sponge substantially free o zinc and having a soluble impurity content not exceeding predetermined value. 52. A process for the preparation of a high purity Grou IVb transition metal-zinc alloy from Group IVb transitio metal scrap containing impurities soluble in molten Grou IVb transition metal and molten zinc comprising the steps of: (a) dissolving inmolten zinc aGroup IVbtransitio metal scrap containing impurities soluble in molten Group IVb transition metal and molten zinc at a temperature between about 650°C and about 1000"C to form a molten Group IVb transition metal-zinc alloy containing said soluble impurities; and (b) dissolving additional Group IVb transition metal having a low soluble impurity content by reducing a predetermined amount of a Group IVb transition metal salt of the following formula: Claim 52, continued. . . A 2 MF 6 wherein A is an alkali metal, M is a Group IVb transitio metal and F is fluorine, with a molar equivalent of aluminu metal dissolved in said molten zinc, sufficient Group IV transition metal salt being introduced to obtain a secon molten alloy having a soluble impurity content not exceedin a predetermined value. 53. The process according to claim 50 wherein th zinc is sublimed fromsaid secondmolten alloyat a temperatur of at least 1000°C to yield aGroup IVb transitionmetal spong substantially free of zinc metal and havinga soluble impurit content not exceeding a predetermined concentration. 54. The process according to claim 41 whereinthe Grou IVb transition metal scrap is titanium metal scrap. 55. The process according to claim 41 wherein the Grou IVb transition metal sponge is a zirconium metal scrap. 56. The process according to claim 46 wherein the Grou IVb transition metal scrap is titanium metal scrap. 57. The process according to claim 46 wherein the Grou IVb transition metal sponge is a zirconium metal scrap. 58. The process according to claim 50 wherein the Grou IVb transition metal is titanium metal scrap. 59. The process according to claim 50 wherein the Grou IVb transition metal is a zirconium metal scrap. 60. The process according to claim 52 wherein the Grou IVb transition metal scrap is titanium metal scrap. 61. The process according to claim 52 wherein the Grou IVb transition metal sponge is a zirconium metal scrap.

Inventors: MEGY JOSEPH A, MEGY, JOSEPH, A.
Applicants: ALBANY TITANIUM INC, ALBANY TITANIUM, INC.
Application year: 1988
Main classification: G01N23
IPC codes: C01G23, C22B1, C22B34