CA1084275A - Method of reducing zirconium - Google Patents
Method of reducing zirconiumInfo
- Publication number
- CA1084275A CA1084275A CA262,580A CA262580A CA1084275A CA 1084275 A CA1084275 A CA 1084275A CA 262580 A CA262580 A CA 262580A CA 1084275 A CA1084275 A CA 1084275A
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- zirconium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
- C22B9/10—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals with refining or fluxing agents; Use of materials therefor, e.g. slagging or scorifying agents
- C22B9/106—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals with refining or fluxing agents; Use of materials therefor, e.g. slagging or scorifying agents the refining being obtained by intimately mixing the molten metal with a molten salt or slag
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B34/00—Obtaining refractory metals
- C22B34/10—Obtaining titanium, zirconium or hafnium
- C22B34/14—Obtaining zirconium or hafnium
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- Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Manufacture And Refinement Of Metals (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A method for reducing zirconium is disclosed in which a reductant metal, preferably aluminum, is dissolved in the molten state in a solvent metal, preferably zinc. This molten metal phase is contacted with a fused salt phase which includes a zirconium salt to be reduced as one of its components. The desired reduction is effected by mutual dis-placement, with aluminum being transported from the molten metal phase to the fused salt phase, replacing zirconium in the salt, while zirconium is transported from the fused salt phase to the molten metal phase. The fused salt phase and the molten metal phase are then separated, and the solvent metal and zirconium are separated, such as by distillation.
A method for reducing zirconium is disclosed in which a reductant metal, preferably aluminum, is dissolved in the molten state in a solvent metal, preferably zinc. This molten metal phase is contacted with a fused salt phase which includes a zirconium salt to be reduced as one of its components. The desired reduction is effected by mutual dis-placement, with aluminum being transported from the molten metal phase to the fused salt phase, replacing zirconium in the salt, while zirconium is transported from the fused salt phase to the molten metal phase. The fused salt phase and the molten metal phase are then separated, and the solvent metal and zirconium are separated, such as by distillation.
Description
Tlle present invention relates to methods for reducin~ zirconium by a reductant metal such as aluminunl which is more economical than the prior art methods.
The usual naturally occurring mineral from which zirconium is obtained is zircon, which is Zr02.Si02 (usually also containing about 2%
Hf02.Si02 by weight). In the usual process for obtaining zirconium in its metallic form, the zircon ore is first chlorinated to obtain ZrC14, for example, by ~he following reaction:
(1) ZrO2-SiO2 + 3C * 4C12 ~ ZrC14 + SiC14 + 2C0 + C02 The zirconium tetrachloride is then reduced by a reductant metal, usually magnesium. A typical reduction reaction is as follows:
The usual naturally occurring mineral from which zirconium is obtained is zircon, which is Zr02.Si02 (usually also containing about 2%
Hf02.Si02 by weight). In the usual process for obtaining zirconium in its metallic form, the zircon ore is first chlorinated to obtain ZrC14, for example, by ~he following reaction:
(1) ZrO2-SiO2 + 3C * 4C12 ~ ZrC14 + SiC14 + 2C0 + C02 The zirconium tetrachloride is then reduced by a reductant metal, usually magnesium. A typical reduction reaction is as follows:
(2) ZrC14 + 2Mg 7~ C Zr + 2Mg C12 This reduction reaction is usually effected in a Kroll furnace, in which an excess of magnesium, typical~ly about 80% more than is needed to complete the reduction, must be provided, and in which the reaction products (zirconium, magnesium, chloride, and the excess magnesium) are mixed after the reaction, and must then be separated.
This is obviously a rather expensive method of reducing zirconium from its ore, and those skilled in the art have frequently searched for an alternate method which is both practical and less expensive. For example, since magnesium is a relatively expensive metal, the use of other less expensive reductant metals have been proposed.
One inexpensive reductant metal which has been considered is aluminum. ~lowever, if aluminum is used in the Kroll process described above, the following reaction occurs ! (3~ ZrC14 * (4/3 + x) Al --~ 4/3 AlC13 * ZrAlx ; where ZrAl is a series of intermetallic compounds ranging from ZrA13 to '~
'' ' ,'; '' .: . : . :
:L~8~75 Zr3AI~ all of which have strong intermetalLic bonds. The rcsu:Ltant product is thus unllsabIe for one of the primary applications of zirconium, cladding for fuel rods in nuclear reactors, because of this high aluminum contaminat-ion. A typical specification for such zirconium allows no more than 75 parts per million aluminum.
Another metallic reduction process for reducing oxides using ~-~
aluminum as the reductant metal is the thermite processO Such a process is used, for example~ in reducing niobium by the following reaction:
(4) 3Nb205 + lOAl -;~ 5A1203 + 6Nb The thermite process is particularly attractive for many applications because, once the reaction is started, it generates a sufficient amount of heat to be self-sustaining. However, if the thermite process is used with zirconium, the following reaction occurs:
(5) (4 ~ 3x)Al + 3Zro2 -~ 2A1203 + 3ZrAlx Again, the zirconium-aluminum intermetallic reaction product results in this process being unusable for zirconium. Because of the ;
known reactions described in equations (3) and (5) above, it has been .
widely accepted in the art that aluminum cannot be used as a reductant metal to recover zirconium. See, for example, Warren Bo Blumenthal, The Chemical Behavior of Zirconi=, which is the leading general reEerence on zirconium and its properties.
It is accordingly an object of the present invention to provide an improved method of reducing zirconium.
It is another object of the present invention to provide an improved method of reducing zirconium which can utilize a reductant metal such as aluminumO
It is still another object of the present invention to provide an improved method for reducing zirconium using aluminum as the reductant metal and in which the resultant zirconium is not contaminated by aluminum.
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~ ri~1y stated, and in accordance with the pres~nt invention, a method ~f producing nuclear grade zirconium from a zirconium compound is provided, comprising the steps of preparing a fused salt phase including the - 7irconiuD~ con~ound to be reduced, and contacting the fused salt phase with a molten metal phase which comprises alumlnum and zinc. The desired reduction is effected by mutual displacement, with aluminum ~eing transported rom the molten metal phase to the fused salt phase, replacing zirconium in the salt, while zirconium is transported from the fused salt phase to the molten metal phase. The fused salt phase and the molten metal phase are then separated, and the solvent metal and zirconiwn are separated, such as by distillation.
For a co~plete understanding of the invention, together with an appreciation of its other objects and advantages, see the following detailed description of the invention and o the attached drawings~ in which:
Figure 1 is a block diagram of one embodiment of the invention, and illustrates the principles of the invention;
Figure 2 is a block diagram of a second embodiment of the invention;
Figure 3 is a block diagram of a third, and the presently preferred embodiment of the invention; and Figure 4 is a block diagram of a modification of a portion of the embodiment of Pigure 3.
Th~ present invention achieves reduction o zirconium by a reductant metal such as aluminum by mutual displacement, without the above-described problems by first dissol~ing the reductant metal in a suitable metal solvent prior to contacting it with the molten or fused salt which contains the zirconium ions to be reduced. The molten metal phase is then stirred vigorously with the fused salt phase to entrain the f~sed salt phase in the molten metal phase. I~ has been found that this causes the , . . .
~ 3 ,,"~0 27~j .
mLY~ure to approach equili~rium in less than five minutes with suf~icient a~itation, and somet~les in less than one minuteO The mixture is then allowed to settle~ and the fused s~lt phase rises essentially entirely to the top of the mi~ture~ while the molten metal phase :ls beneath the fused salt phase. The fused salt phase can then be poured off or siphoned off, or the molten metal phase can be removed through a suitable tap or like in the bottom of the container in which the reaction has then occurred.
If desired~ the molten metal phase may again be subjected to the same process a second time to remove more of the reductant metal from the molten metal phase, and the entire process may be repeated in as many cycles as desired to achieve the desired purity of zirconium. The solvent metal is then separated from the zirconium in any suitable manner, such as , , .
by distillation or sublimation.
The solvent metal is a metal which has the following characteristics.
First, of course, it must be a metal in which both zirconium and the ;I reductant metal are soluble to at least a significant extent. The boiling temperature of the solvent metal must be such that, in the range of operat-ing temperatures of the reaction, both the solvent metal and the fused salt `;
phases are in their liquid phases. The solvent metal should be a metal which is relatively easy to separate from zirconium once the reaction is complete. The solvent metal must be less electropositive than zirconium and hafnium, so that it does not replace zirconium and hafnium in the salt phase. Final b, it is preferable that the metal have the greater affinity for zirconium than it does for aluminum, so that the aluminum atoms in the metal phase are more available for reaction with the zirconium ions ;
in the salt phase to enter into the mutual displacement reaction~ In practice it has been found that the best metal for use as a solvent metal -~
~ ~, is zinc, although other metals, such as cadmium~ lead, bismuth, copper, and tin may also be used as the solrent metal.
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~ pI` in~ary characteristic of the reductant metal is that it is more electropositi-ve than zirconiwn, so that it can replace zirconium in the salts, thereby reducing it to its metallic stage. Another important characteristic of the reductant metal is that it has less affinity for solvent metal, which is preferably zinc, than zirconium has for zinc, so that no alloy of the reductant metal and zirconium is formed; instead, zinc forms an alloy with zirconium and rejects the reductant metal. Also, of course, it is important that the reductant metal and the salts which it subsequently forms after the reduction reaction be liquid at the temperatures at which the reaction is occurring. The preferred reductant metal is aluminum, since, as is shown in the equations below, the objection-able aluminum-zirconium reactions described above do not occur in the method of the present invention, and thus the economies of using aluminum as a reductant metal can be realizedO However, those skilled in the art will readily recognize that other reductant metals, such as magnesium sodium and calcium could also be used in a similar methodO
The characteristics of the salt are as follows: First, the cation in those portions of the salt which are not a zirconium salt should be more electropositive than zirconium so that it will not be reduced by the reductant in the metal phase. Preferred cations are the alkali elements~
preferably sodium and potassium~ the alkaline earth elements~ the rare earth elements and aluminum. The anions in the salt are preferably halides or complexes of halides and the cations given above~ so that the salts are halide salts As is explained in more detail below, the preferred halides are chlorides and fluorides, with the advantages of each being set forth oelow.
As is set forth below, the zirconium salt which is present in the process is usually ZrC14 or ZrF4~ and by providing chloride or fluoride salts, this allows the formation of ZrCl or ZrF anions, whose va]ence - S -' is a function o~ ~. The usual such anions formed is ZrF7 ~ ZrC16 ~ or ZrF6 . These compl~xed anions reduce the vapor pressure of the zirconium salt to an acceptable :Level at the temperatures at which reduction is effected.
The melting point of the salt must be below the boiling point of the metal used as a solvent for the zirconium, in order that both the salt and the metal may be in the liquid phase at the same ti~e. As is well ` known to those skilled in the art, the melting temperature of the salt, ; -` as well as the viscosity of the salt~ can be changed by mi-xing various salts. Thus, it is frequently useful to add an additional salt such as sodium ; chloride to the salt phase to reduce the melting temperature of the salt and lower the viscosity of the salt.
; ., .
-~ As was noted above, it has been found that the best salts to use are either an all-chloride salt system, a chloride-fluoride mixed salt system, or an all-fluoride salt system. The all-chloride salt system has the advantage of being easier to contain. As is well known to those skilled in the art, if a fluoride is present in the fused salt phase, this can lead to difficulties in containment, since the molten fluoride tends to enter into many undesired reactions with either the container material or any other materials present in the system. The disadvantages of the all-chloride salt system is its tendency to form lower valence chlorides such as ZrC12, the tendency of ZrC14 to volatize from the salt, and also the tendency of the zinc metal to interact with the zirconium and ....
hafnium salts and enter into the salt phase.
In contrast to this, the chloride-fluoride salt system has a low vapor pressure~ very slight interaction of zinc with the salt phase, - and a much reduced tendency to form lower valent zirconium compounds in the salt phase. The all-fluoride salt phase has the advantages of the chloride-fluoride salt syste~ and can be used if a zirconium fluoride salt ., ~ .
.. , . . . , . ~
~8~Z'75 is made from th~ ore. However, ;n an aLl ~luoride salt phase system, carc must be tal~cn in selecting -the concentration of the salt. Aluminum-~luoride compounds are present as reaction products after the reduction reaction, and these con~po~Lnds tend to be either very volatile or do not melt at the reaction temperature unless the salt system is carefully chosen.
The container in which the reaction is carried out must be carefully chosen so that it will contain the materials of the reaction at the temperatures at which the reaction is occurring, while not itself entering into the reaction. A number of different material have been tried for the container, and it has been found that the preferred containers are formed from graphite or carbon.
~ aving described the general parameters of the present invention, let us now consider a specific example of the use of the process to effect reduction of zirconium.
Figure 1 shows a block diagram of a process for reducing zirconium in accordance with one embodiment of the invention. In Figure 1, a reductant metal input lOg a salt input 12 and a solvent metal input 14 are provided to a suitable container in which the desired reduction is to be effected. The reductant metal input, of course~ is preferably aluminu~.
This metal is provided to a reduction stage 16, along with a salt component ; which might be a mixture of zirconium tetrachloride, which is the zirconium compound to be reduced, and potassi~l chlorideO Approximately ten moles of potassium chloride are used for each three moles of zirconium tetra~
; chloride. A portion of the potassium chloride and the zirconium tetra- ;
chloride, when melted, undergoes the following reaction~
(6) ZrC14 -~ 2KCl = K2ZrC16 Typically, a sufficient amount of solvent metal, preferably ~ zinc, is provided to the reduction stage 16 to provide approximately i twelve weight percent zirconium at the conclusion of the operation. As is ., ' ~:.
:; . . . , - . . . :. .
~L~8~ 5 ~escribed below, this zinc input need only be supplied on the initial run, SillCe thereafter it is recovered and returned to the reduction stage 16 for subsequent runs.
typical charge to the red~ction stage 16 is as follows:
Input ~omponent Weight ~rC14 100 lb.
KCl 96 lb.
Al 13.9 lb.
Zn 334 lb.
The mixture is then heated to about 900C and is stirred ` vigorously to cause the now molten metal phase to entrain the now fused or molten salt phase. At this time, in accordance with the present invent-.:
ion, the aluminum in the metal phase reduces the zirconium in the salt ; phase by the following reaction:
(7) 4KCl -~ 3K2 ZrC]6 ~ 4Al ~O 4KAlC14 ~ 6KCl -~ 3Zr l As was noted in the description of the desired characteristic ; of the salt above, the excess KCl is provided to reduce the vapor pressure of the ZrC14 at the temperatures at which the reaction occurs ~ . .
This vigorous mixing is continued for five minutes to one-half hour, and the mixture is then allowed to separate by settling~ with the molten salt phase~ now containing the aluminum salt~ rising to the top and the molten metal phase~ now containing the zirconium metal, settling to the bottom. After separation by any desired manner, the salt phase is taken to the stage 18 to recover the salt for subsequent use, if so deslred.
The metal phase component is taken to a distillation stage 20 at which the zinc metal is distilled from the zirconium and is again available to be returned to the reduction stage 16 for a future Feduction reaction such as is described above~ Prior to such distillation~ the metal ~ . - . - . . ... .
%~5 pha~e cont ins th~ following components:
Component Weight 334 lb.
Zr 35.2 lb.
Al .035 lb.
The zirconium metal is now available at the zirconium output stage 22, and again consists of sponge metal.
Figure 2 shows a block diagram of a second embodiment of the present invention. The process sho~m in Figure 2 is essentially the same as that shown in Figure l~ except now, at the reduction stage 16, after the initial heating and mixing described above is completed~ and after the salt phase is remo~ed from the container in which the reduction ; stage 16 is effected, the metal phase is retained in the reduction stage 16 and approximately sixteen pounds of potassium chloride is added to the container. This salt-metal mixture is then again heated to approximately 900 C, and an oxidizing gas 24, such as two pounds of Cl2 is passed into the metal~ reacting with the zirconium and aluminum in the metal phase to form zirconium and aluminum chloride salts which are absorbed into the salt phase. The two phases are then again well mixed, and the process is completed in the manner described above. It has been found that this two-stage process results in a zirconium metal output having an alumin~m content of less than 40 parts per million.
In the embodiment of Figure 2, rather than using chloride gas as the oxidizing agent~ any suitable material can be injected directly into the mixture to form a zirconium salt to provide a second stage of ; the desired displacement reaction to separate the aluminum from the metal `~
phase into the salt phase. For example, zinc chloride has been successfully :,:, ~
used, and in some instances, it is desirable to inject a zirconium salt such ~-~
~ 9 -:' 27 ~ !
as ~irconium -tetrachloride directly into the mixture for the second stage of separation.
The for~going description of the parameters of the present invention and the description of Figures 1 and 2 have illustrated the principals upon ~hich the present invention is based. The presently preferred embodiment of the invention is a somewhat more complex process than the relatively simple processes of Figures 1 and 2, and comprises a complete process for obtaining zirconium in which the input material is a raw zircon ore and finished~ high purity zirconium is obtained as the OlltpUt product. Figure 3 is a block diagram of that complete process/ and discloses the presently preferred embodiment of the invention.
In Figure 3, the input materials to be processed are zircon ore, which is ZrO2.SiO2 containing relatively low levels of HfO2.SiO2, and sodium silicof]uoride (Na2SiF6). These inputs are represented by the blocks 30 and 32 respectively in Figure 3. These materials are supplied . . .
to an ore cracking stage 34, in which the following reactions occur: ;
(8) Na2siF6 + Zr2-Si2~i~ Na2ZrF6 ~ 2SiO2 : , :
) 2siF6 + Hf2-Si2 ~ Na2HfF6 + 2SiO
Typically, the ore cracking stage 34 is effected in an indirectly fired kiln at a temperature of approximately 700 a for appro~imately one hour.
The output product is removed from the klln, and the Na2ZrF6 and Na2HfF6 are leached from the SiO2 and crystalized from the leach liquor.
This is in itself a good purification step for the zirconium, and removes the zirconium from most of the other împurities which may be present in the ore other than hafniumO
The Na2ZrF6 and Na2HfF6 are then supplied to a reduction and ~ -sepsration stage 36, in which they are dissolved in a solvent metal such '.
. .. . . . . .
'7~
as zinc, as was described above in conne~tion with Pigu~es 1 and 2. An aluminum reductant l~al input 38 is also supplied to the reduction and separation stage 36. In the reductant and separation stage 36, the zinc, aluminum and Na2ZrF6 and Na2HtP6 ar~ heated to a ten~erature of approximately 900C, at which the entire mixture is molten, and the molten liquids are s~irred vigorously, ~s in ~igures 1 and 2 above. A* this time, the following reactions occur:
Zn (10~ ~ F6 1 4Al --~ 4[(Nar:)l 5-AlF3] ~ 3Zr and Zn (11) 3Na2H~F6 ~ 4Al --~ 4~(NaP~1 5.AlF3] + 3Hf . :
In the preferred embodiment of the invention, approximately 85%
to 95% enough aluminum to complete the above reactions is supplied to the reduction and separation stage 36, so that practically all of the aluminum present enters the salt phase and some Na2ZrP6 is left in the mixture.
It has been previously discovered that any hafnium metal which was formed in accordance with equation ~1) above displaces a zirconium ion in the salt by the following reaction:
(12~ Na ZrF ~ Hf ~ Na HF6 + Zr After vigorous stirring, the mixture is allowed to settle, and the salt phase is removed from the metal phase, in the manners described ; above. The now separated metal phase is then again ~aken to a distillation phase 40, at which the z.inc is distilled from the zirconium. The zinc can then be returned for reuse in the reductlon and separation stage 36.
Virtually pure zirconium is now available at the zirconium output 42.
The following Table 3 shows the input materials, ancl output product (zirconium sponge) achieved in five typical runs in accordance , ~ with the process just described.
." v 2~Si Tl~BLE 3 INPUT ~IATE RIAL ZIRCONIUM OUTPUT
Na2ZrF6 ~ ~5 lb-Na2Hf~6 - o7 lb Zn -230 lbo 24~2 lbo Al - 9.6 lb.
Na2ZrF6 - 85 lb-Na2HfF6 ~ 0-7 lb.
Zn -231 lb. 24 ~ 3 lb~
Al - 9.6 lb.
-. 10 ,, ,_ . ,", ,_ _ , . _ ~ . . _ . . , _ Na2ZrF6 - 85 lb~
Na2HfF6 ~ -7 lb-Zn -236 lb. 24.9 lb.
Al - 9.8 lb.
._ . _ .. . . . ~ ., .
Na2ZrF6 - 85 lb-Na2HfF6 ~ 0-7 lb-Zn -235 lb. 2407 lbo Al - 9.8 lb.
~ . _ . _ _ Na2ZrF6 - 85 lb-Na2HfF6 ~ 0-7 lb.
20 Zn -235 lb. 24.7 lb.
Al - 9.8 lb.
In accordance with another of the features of the present invention, when the salt phase is removed from the reduction and separation ~;~
stage 36 after completion of the reactions described above, it is taken `~
to a salt processing stage 44. At this time, the salt phase is again a mixture of (NaF)l 5-AlF3, Na2ZrF6 and Na2HfF6, but is considerably richer in hafnium than was the input salt to the reduction and separation stage 360 At the salt processing stage 44, these salts are again melted and , ~8~2~i mL~ed ~ith a molten ~inc bath, and a reductant met~l such as al~inum is ~g~in provided to the bath. Now, however, in contrast with the reduction and separation stage 36 described above, a sufficient amount of aluminum is provided to complete the reactions of equations (10) and (11) above for the entire salt phase. After this reaction is completed7 the now virtu~lly pure molten (NaF)l 5-~1F3 is removed from the molten metal phase, and these materials are provided at the outputs 46 and 48 respectively of Figure 30 The salt (NaF)l 5AlF3, which may be termed a pseudocryolite, is itself a desirable product which can be sold to the aluminum industry, ' and thus the only salt by-product of the process of Figure 3 is itself usefulg and not a waste product. Similarly, in the metals output 48, the zinc can again be distilled off and reused in the process~ leaving ' only the hafnium, zirconium and slight amounts of aluminum as output metals from this part of the process. If desired, these metals may be returned to the reduction and separation stage 36 to further extract any zirconium ` in this metal. In any event, in a typical such process, the amount of output metal left at the stage 48 is only approximately 5% of the available metals which was in the zircon ore at the input stage 30.
If even higher separation factors of zirconium from alumin~
and hafnium are desired, in the embodiment of Figure 3, the reduction and separation stage 36 may also be "fluxed" in the manner descri'bed in Figure 2 above. If this is desired, the presently preferred manner to do this is to inject a quantity of ZnF2 into the zinc-zirconium molten metal after the salt phase has been removed from the metal phase. At this time, the following reaction occurs~
(13) 2ZnF2 + Zr ~ ZrF4 + 2Zn The zirconium tetrafluoride so formed then reacts with any remaining alumin~ and hafnium in the metallic phase in accordance with the following eqnatio~l:
~143 ZrF -~ ~If-` HfF -~ Zr If ~his second stage of separation is desired, it is the presently preferred practice to provide enough zinc fluoride to oxidize - about 2% of the 3irconium in the metal phase. Thus~ in the quantities .
given in the examples of Table 3 above, it is preferred to use about 1.1 lbs of ZnF2 for this fluxmg operation, if it is to be effected. If an excess of ZnF2 is provided, it results in a higher aluminum and hafnium removal, but a~ the expense of a loss of a greater amount of zirconium.
Similarly, if less ZnF2 is used~ a lower hafnium removal is achieved, but a greater quantity of zirconium remains in the metallic phaseO
It is noted that, in contrast to the processes described in - Figures 1 and 2 above, in the presently preferred embodiment described in , .
Figure 3, no excess salt such as potassium chloride, or sodium fluoride is provided into the reaction at the separation stage. As was described above~ the embodiment of Figure 3 results in the formation of the pseudo cryolite salt (NaF)l 5-AlF3. If an excess of sodium fluoride were provided in thisphase of the reaction, the resultant salt would be ordinary cryolite, or ~NaF)3 AlF3, which does not melt until a temperature of 1000 a, which ,- .
~ 20 is above the boiling temperature of the zinc-zirconium metal mixture.
; Those skilled in the art will further recognize that the ; embodiment of Figure 3 also reduces ha~nium metal from a hafnium compound in the same manner as zlrconium is reduced. Thus~ the method can be used to reduce hafnium, and is a superior reduction method than the prior art methods of reducing hafnium.
Figure 4 is a block diagram of a modification of the method of Figure 3, and shows a two stage counter-current reduction process to ~
' reduce the levels of aluminum and hafnium even lower in the zirconiumO
In Figure 4, the reduction and separation stage 36 is divided ~:~ , : . . , .- .
into two stages, designatcd 36a and 36b. In an initial run, first stage 36~ is supp]ied an initial charge of Na2ZrF6, also containing Na2HfF6, aluminum and zinc, and the reaction occurs as described in ~igure 3 above.
After the reaction is completed, the salt output is taken to the salt pro-cessing stage 44, described above, and the metal phase is taken to the second stage 36b of the reduction and separation stage.
The metal phase at this point might typically contain about 1000 to 1500 parts per million aluminum and 500 parts per million hafnium (both expressed as a function of zirconium only). These levels are too high for nuclear grade zirconium. In second stage 36b, the metal phase is mixed with the salt input from ore cracking stage 34, and the mixture is again heated to about 900C and stirred vigorously. At this time, the following reactions again occur:
(15) Na2ZrF6 ~ Hf ~ Na2HfF6 ~~ Zr and ~16) 3Na2zrF6 ~ 4A1 ~ 4[ (NaF) 1 50AlF3~ ~ 3Zr These reactions at this time reduce the levels of both hafnium and aluminum in the metal phase to less than 100 parts per million, again expressed as a function of zirconium only. Now, the ~xture is allowed to settle and is separated, as before. The metal phase is taken to the dis-tillation stage 40, where the zinc is distil]ed off and returned to the first stage 36a of the reduction and separation stage, and the new high purity zirconium is taken to the zirconium output stage 42. The salt phase (which was hardly changed in second stage 36b, since only low levels of hafnium and aluminum were available there to react with the Na2ZrF6) is taken to the first stage 36a of the reduction and separation stage, where new aluminum and zinc from the distillation stage are again provided.
Thus this modification of the process, which may now be termed a two stage counter-current reduction and separation process, provides . . . , , . - .,, : . ~: . :, high purity z:ircon:ium without the use of the fluxing step described in Fi~lre 2 above.
While the invention is thus disclosed and several embodiments are described in detail, it is not intended that the invention be limited to these shown embodiments. Ins~ead, many modifications will occur to those skilled in the art which lie within the spirit and scope of the in-vention. It is thus intended that the invention be limited in scope only by the appended claims.
. , .
''~ . : '.' ,. .
This is obviously a rather expensive method of reducing zirconium from its ore, and those skilled in the art have frequently searched for an alternate method which is both practical and less expensive. For example, since magnesium is a relatively expensive metal, the use of other less expensive reductant metals have been proposed.
One inexpensive reductant metal which has been considered is aluminum. ~lowever, if aluminum is used in the Kroll process described above, the following reaction occurs ! (3~ ZrC14 * (4/3 + x) Al --~ 4/3 AlC13 * ZrAlx ; where ZrAl is a series of intermetallic compounds ranging from ZrA13 to '~
'' ' ,'; '' .: . : . :
:L~8~75 Zr3AI~ all of which have strong intermetalLic bonds. The rcsu:Ltant product is thus unllsabIe for one of the primary applications of zirconium, cladding for fuel rods in nuclear reactors, because of this high aluminum contaminat-ion. A typical specification for such zirconium allows no more than 75 parts per million aluminum.
Another metallic reduction process for reducing oxides using ~-~
aluminum as the reductant metal is the thermite processO Such a process is used, for example~ in reducing niobium by the following reaction:
(4) 3Nb205 + lOAl -;~ 5A1203 + 6Nb The thermite process is particularly attractive for many applications because, once the reaction is started, it generates a sufficient amount of heat to be self-sustaining. However, if the thermite process is used with zirconium, the following reaction occurs:
(5) (4 ~ 3x)Al + 3Zro2 -~ 2A1203 + 3ZrAlx Again, the zirconium-aluminum intermetallic reaction product results in this process being unusable for zirconium. Because of the ;
known reactions described in equations (3) and (5) above, it has been .
widely accepted in the art that aluminum cannot be used as a reductant metal to recover zirconium. See, for example, Warren Bo Blumenthal, The Chemical Behavior of Zirconi=, which is the leading general reEerence on zirconium and its properties.
It is accordingly an object of the present invention to provide an improved method of reducing zirconium.
It is another object of the present invention to provide an improved method of reducing zirconium which can utilize a reductant metal such as aluminumO
It is still another object of the present invention to provide an improved method for reducing zirconium using aluminum as the reductant metal and in which the resultant zirconium is not contaminated by aluminum.
: :
. ~.~, -,~ - - . . . . . - - , :
z~
~ ri~1y stated, and in accordance with the pres~nt invention, a method ~f producing nuclear grade zirconium from a zirconium compound is provided, comprising the steps of preparing a fused salt phase including the - 7irconiuD~ con~ound to be reduced, and contacting the fused salt phase with a molten metal phase which comprises alumlnum and zinc. The desired reduction is effected by mutual displacement, with aluminum ~eing transported rom the molten metal phase to the fused salt phase, replacing zirconium in the salt, while zirconium is transported from the fused salt phase to the molten metal phase. The fused salt phase and the molten metal phase are then separated, and the solvent metal and zirconiwn are separated, such as by distillation.
For a co~plete understanding of the invention, together with an appreciation of its other objects and advantages, see the following detailed description of the invention and o the attached drawings~ in which:
Figure 1 is a block diagram of one embodiment of the invention, and illustrates the principles of the invention;
Figure 2 is a block diagram of a second embodiment of the invention;
Figure 3 is a block diagram of a third, and the presently preferred embodiment of the invention; and Figure 4 is a block diagram of a modification of a portion of the embodiment of Pigure 3.
Th~ present invention achieves reduction o zirconium by a reductant metal such as aluminum by mutual displacement, without the above-described problems by first dissol~ing the reductant metal in a suitable metal solvent prior to contacting it with the molten or fused salt which contains the zirconium ions to be reduced. The molten metal phase is then stirred vigorously with the fused salt phase to entrain the f~sed salt phase in the molten metal phase. I~ has been found that this causes the , . . .
~ 3 ,,"~0 27~j .
mLY~ure to approach equili~rium in less than five minutes with suf~icient a~itation, and somet~les in less than one minuteO The mixture is then allowed to settle~ and the fused s~lt phase rises essentially entirely to the top of the mi~ture~ while the molten metal phase :ls beneath the fused salt phase. The fused salt phase can then be poured off or siphoned off, or the molten metal phase can be removed through a suitable tap or like in the bottom of the container in which the reaction has then occurred.
If desired~ the molten metal phase may again be subjected to the same process a second time to remove more of the reductant metal from the molten metal phase, and the entire process may be repeated in as many cycles as desired to achieve the desired purity of zirconium. The solvent metal is then separated from the zirconium in any suitable manner, such as , , .
by distillation or sublimation.
The solvent metal is a metal which has the following characteristics.
First, of course, it must be a metal in which both zirconium and the ;I reductant metal are soluble to at least a significant extent. The boiling temperature of the solvent metal must be such that, in the range of operat-ing temperatures of the reaction, both the solvent metal and the fused salt `;
phases are in their liquid phases. The solvent metal should be a metal which is relatively easy to separate from zirconium once the reaction is complete. The solvent metal must be less electropositive than zirconium and hafnium, so that it does not replace zirconium and hafnium in the salt phase. Final b, it is preferable that the metal have the greater affinity for zirconium than it does for aluminum, so that the aluminum atoms in the metal phase are more available for reaction with the zirconium ions ;
in the salt phase to enter into the mutual displacement reaction~ In practice it has been found that the best metal for use as a solvent metal -~
~ ~, is zinc, although other metals, such as cadmium~ lead, bismuth, copper, and tin may also be used as the solrent metal.
,.
.
~B~2~7~
~ pI` in~ary characteristic of the reductant metal is that it is more electropositi-ve than zirconiwn, so that it can replace zirconium in the salts, thereby reducing it to its metallic stage. Another important characteristic of the reductant metal is that it has less affinity for solvent metal, which is preferably zinc, than zirconium has for zinc, so that no alloy of the reductant metal and zirconium is formed; instead, zinc forms an alloy with zirconium and rejects the reductant metal. Also, of course, it is important that the reductant metal and the salts which it subsequently forms after the reduction reaction be liquid at the temperatures at which the reaction is occurring. The preferred reductant metal is aluminum, since, as is shown in the equations below, the objection-able aluminum-zirconium reactions described above do not occur in the method of the present invention, and thus the economies of using aluminum as a reductant metal can be realizedO However, those skilled in the art will readily recognize that other reductant metals, such as magnesium sodium and calcium could also be used in a similar methodO
The characteristics of the salt are as follows: First, the cation in those portions of the salt which are not a zirconium salt should be more electropositive than zirconium so that it will not be reduced by the reductant in the metal phase. Preferred cations are the alkali elements~
preferably sodium and potassium~ the alkaline earth elements~ the rare earth elements and aluminum. The anions in the salt are preferably halides or complexes of halides and the cations given above~ so that the salts are halide salts As is explained in more detail below, the preferred halides are chlorides and fluorides, with the advantages of each being set forth oelow.
As is set forth below, the zirconium salt which is present in the process is usually ZrC14 or ZrF4~ and by providing chloride or fluoride salts, this allows the formation of ZrCl or ZrF anions, whose va]ence - S -' is a function o~ ~. The usual such anions formed is ZrF7 ~ ZrC16 ~ or ZrF6 . These compl~xed anions reduce the vapor pressure of the zirconium salt to an acceptable :Level at the temperatures at which reduction is effected.
The melting point of the salt must be below the boiling point of the metal used as a solvent for the zirconium, in order that both the salt and the metal may be in the liquid phase at the same ti~e. As is well ` known to those skilled in the art, the melting temperature of the salt, ; -` as well as the viscosity of the salt~ can be changed by mi-xing various salts. Thus, it is frequently useful to add an additional salt such as sodium ; chloride to the salt phase to reduce the melting temperature of the salt and lower the viscosity of the salt.
; ., .
-~ As was noted above, it has been found that the best salts to use are either an all-chloride salt system, a chloride-fluoride mixed salt system, or an all-fluoride salt system. The all-chloride salt system has the advantage of being easier to contain. As is well known to those skilled in the art, if a fluoride is present in the fused salt phase, this can lead to difficulties in containment, since the molten fluoride tends to enter into many undesired reactions with either the container material or any other materials present in the system. The disadvantages of the all-chloride salt system is its tendency to form lower valence chlorides such as ZrC12, the tendency of ZrC14 to volatize from the salt, and also the tendency of the zinc metal to interact with the zirconium and ....
hafnium salts and enter into the salt phase.
In contrast to this, the chloride-fluoride salt system has a low vapor pressure~ very slight interaction of zinc with the salt phase, - and a much reduced tendency to form lower valent zirconium compounds in the salt phase. The all-fluoride salt phase has the advantages of the chloride-fluoride salt syste~ and can be used if a zirconium fluoride salt ., ~ .
.. , . . . , . ~
~8~Z'75 is made from th~ ore. However, ;n an aLl ~luoride salt phase system, carc must be tal~cn in selecting -the concentration of the salt. Aluminum-~luoride compounds are present as reaction products after the reduction reaction, and these con~po~Lnds tend to be either very volatile or do not melt at the reaction temperature unless the salt system is carefully chosen.
The container in which the reaction is carried out must be carefully chosen so that it will contain the materials of the reaction at the temperatures at which the reaction is occurring, while not itself entering into the reaction. A number of different material have been tried for the container, and it has been found that the preferred containers are formed from graphite or carbon.
~ aving described the general parameters of the present invention, let us now consider a specific example of the use of the process to effect reduction of zirconium.
Figure 1 shows a block diagram of a process for reducing zirconium in accordance with one embodiment of the invention. In Figure 1, a reductant metal input lOg a salt input 12 and a solvent metal input 14 are provided to a suitable container in which the desired reduction is to be effected. The reductant metal input, of course~ is preferably aluminu~.
This metal is provided to a reduction stage 16, along with a salt component ; which might be a mixture of zirconium tetrachloride, which is the zirconium compound to be reduced, and potassi~l chlorideO Approximately ten moles of potassium chloride are used for each three moles of zirconium tetra~
; chloride. A portion of the potassium chloride and the zirconium tetra- ;
chloride, when melted, undergoes the following reaction~
(6) ZrC14 -~ 2KCl = K2ZrC16 Typically, a sufficient amount of solvent metal, preferably ~ zinc, is provided to the reduction stage 16 to provide approximately i twelve weight percent zirconium at the conclusion of the operation. As is ., ' ~:.
:; . . . , - . . . :. .
~L~8~ 5 ~escribed below, this zinc input need only be supplied on the initial run, SillCe thereafter it is recovered and returned to the reduction stage 16 for subsequent runs.
typical charge to the red~ction stage 16 is as follows:
Input ~omponent Weight ~rC14 100 lb.
KCl 96 lb.
Al 13.9 lb.
Zn 334 lb.
The mixture is then heated to about 900C and is stirred ` vigorously to cause the now molten metal phase to entrain the now fused or molten salt phase. At this time, in accordance with the present invent-.:
ion, the aluminum in the metal phase reduces the zirconium in the salt ; phase by the following reaction:
(7) 4KCl -~ 3K2 ZrC]6 ~ 4Al ~O 4KAlC14 ~ 6KCl -~ 3Zr l As was noted in the description of the desired characteristic ; of the salt above, the excess KCl is provided to reduce the vapor pressure of the ZrC14 at the temperatures at which the reaction occurs ~ . .
This vigorous mixing is continued for five minutes to one-half hour, and the mixture is then allowed to separate by settling~ with the molten salt phase~ now containing the aluminum salt~ rising to the top and the molten metal phase~ now containing the zirconium metal, settling to the bottom. After separation by any desired manner, the salt phase is taken to the stage 18 to recover the salt for subsequent use, if so deslred.
The metal phase component is taken to a distillation stage 20 at which the zinc metal is distilled from the zirconium and is again available to be returned to the reduction stage 16 for a future Feduction reaction such as is described above~ Prior to such distillation~ the metal ~ . - . - . . ... .
%~5 pha~e cont ins th~ following components:
Component Weight 334 lb.
Zr 35.2 lb.
Al .035 lb.
The zirconium metal is now available at the zirconium output stage 22, and again consists of sponge metal.
Figure 2 shows a block diagram of a second embodiment of the present invention. The process sho~m in Figure 2 is essentially the same as that shown in Figure l~ except now, at the reduction stage 16, after the initial heating and mixing described above is completed~ and after the salt phase is remo~ed from the container in which the reduction ; stage 16 is effected, the metal phase is retained in the reduction stage 16 and approximately sixteen pounds of potassium chloride is added to the container. This salt-metal mixture is then again heated to approximately 900 C, and an oxidizing gas 24, such as two pounds of Cl2 is passed into the metal~ reacting with the zirconium and aluminum in the metal phase to form zirconium and aluminum chloride salts which are absorbed into the salt phase. The two phases are then again well mixed, and the process is completed in the manner described above. It has been found that this two-stage process results in a zirconium metal output having an alumin~m content of less than 40 parts per million.
In the embodiment of Figure 2, rather than using chloride gas as the oxidizing agent~ any suitable material can be injected directly into the mixture to form a zirconium salt to provide a second stage of ; the desired displacement reaction to separate the aluminum from the metal `~
phase into the salt phase. For example, zinc chloride has been successfully :,:, ~
used, and in some instances, it is desirable to inject a zirconium salt such ~-~
~ 9 -:' 27 ~ !
as ~irconium -tetrachloride directly into the mixture for the second stage of separation.
The for~going description of the parameters of the present invention and the description of Figures 1 and 2 have illustrated the principals upon ~hich the present invention is based. The presently preferred embodiment of the invention is a somewhat more complex process than the relatively simple processes of Figures 1 and 2, and comprises a complete process for obtaining zirconium in which the input material is a raw zircon ore and finished~ high purity zirconium is obtained as the OlltpUt product. Figure 3 is a block diagram of that complete process/ and discloses the presently preferred embodiment of the invention.
In Figure 3, the input materials to be processed are zircon ore, which is ZrO2.SiO2 containing relatively low levels of HfO2.SiO2, and sodium silicof]uoride (Na2SiF6). These inputs are represented by the blocks 30 and 32 respectively in Figure 3. These materials are supplied . . .
to an ore cracking stage 34, in which the following reactions occur: ;
(8) Na2siF6 + Zr2-Si2~i~ Na2ZrF6 ~ 2SiO2 : , :
) 2siF6 + Hf2-Si2 ~ Na2HfF6 + 2SiO
Typically, the ore cracking stage 34 is effected in an indirectly fired kiln at a temperature of approximately 700 a for appro~imately one hour.
The output product is removed from the klln, and the Na2ZrF6 and Na2HfF6 are leached from the SiO2 and crystalized from the leach liquor.
This is in itself a good purification step for the zirconium, and removes the zirconium from most of the other împurities which may be present in the ore other than hafniumO
The Na2ZrF6 and Na2HfF6 are then supplied to a reduction and ~ -sepsration stage 36, in which they are dissolved in a solvent metal such '.
. .. . . . . .
'7~
as zinc, as was described above in conne~tion with Pigu~es 1 and 2. An aluminum reductant l~al input 38 is also supplied to the reduction and separation stage 36. In the reductant and separation stage 36, the zinc, aluminum and Na2ZrF6 and Na2HtP6 ar~ heated to a ten~erature of approximately 900C, at which the entire mixture is molten, and the molten liquids are s~irred vigorously, ~s in ~igures 1 and 2 above. A* this time, the following reactions occur:
Zn (10~ ~ F6 1 4Al --~ 4[(Nar:)l 5-AlF3] ~ 3Zr and Zn (11) 3Na2H~F6 ~ 4Al --~ 4~(NaP~1 5.AlF3] + 3Hf . :
In the preferred embodiment of the invention, approximately 85%
to 95% enough aluminum to complete the above reactions is supplied to the reduction and separation stage 36, so that practically all of the aluminum present enters the salt phase and some Na2ZrP6 is left in the mixture.
It has been previously discovered that any hafnium metal which was formed in accordance with equation ~1) above displaces a zirconium ion in the salt by the following reaction:
(12~ Na ZrF ~ Hf ~ Na HF6 + Zr After vigorous stirring, the mixture is allowed to settle, and the salt phase is removed from the metal phase, in the manners described ; above. The now separated metal phase is then again ~aken to a distillation phase 40, at which the z.inc is distilled from the zirconium. The zinc can then be returned for reuse in the reductlon and separation stage 36.
Virtually pure zirconium is now available at the zirconium output 42.
The following Table 3 shows the input materials, ancl output product (zirconium sponge) achieved in five typical runs in accordance , ~ with the process just described.
." v 2~Si Tl~BLE 3 INPUT ~IATE RIAL ZIRCONIUM OUTPUT
Na2ZrF6 ~ ~5 lb-Na2Hf~6 - o7 lb Zn -230 lbo 24~2 lbo Al - 9.6 lb.
Na2ZrF6 - 85 lb-Na2HfF6 ~ 0-7 lb.
Zn -231 lb. 24 ~ 3 lb~
Al - 9.6 lb.
-. 10 ,, ,_ . ,", ,_ _ , . _ ~ . . _ . . , _ Na2ZrF6 - 85 lb~
Na2HfF6 ~ -7 lb-Zn -236 lb. 24.9 lb.
Al - 9.8 lb.
._ . _ .. . . . ~ ., .
Na2ZrF6 - 85 lb-Na2HfF6 ~ 0-7 lb-Zn -235 lb. 2407 lbo Al - 9.8 lb.
~ . _ . _ _ Na2ZrF6 - 85 lb-Na2HfF6 ~ 0-7 lb.
20 Zn -235 lb. 24.7 lb.
Al - 9.8 lb.
In accordance with another of the features of the present invention, when the salt phase is removed from the reduction and separation ~;~
stage 36 after completion of the reactions described above, it is taken `~
to a salt processing stage 44. At this time, the salt phase is again a mixture of (NaF)l 5-AlF3, Na2ZrF6 and Na2HfF6, but is considerably richer in hafnium than was the input salt to the reduction and separation stage 360 At the salt processing stage 44, these salts are again melted and , ~8~2~i mL~ed ~ith a molten ~inc bath, and a reductant met~l such as al~inum is ~g~in provided to the bath. Now, however, in contrast with the reduction and separation stage 36 described above, a sufficient amount of aluminum is provided to complete the reactions of equations (10) and (11) above for the entire salt phase. After this reaction is completed7 the now virtu~lly pure molten (NaF)l 5-~1F3 is removed from the molten metal phase, and these materials are provided at the outputs 46 and 48 respectively of Figure 30 The salt (NaF)l 5AlF3, which may be termed a pseudocryolite, is itself a desirable product which can be sold to the aluminum industry, ' and thus the only salt by-product of the process of Figure 3 is itself usefulg and not a waste product. Similarly, in the metals output 48, the zinc can again be distilled off and reused in the process~ leaving ' only the hafnium, zirconium and slight amounts of aluminum as output metals from this part of the process. If desired, these metals may be returned to the reduction and separation stage 36 to further extract any zirconium ` in this metal. In any event, in a typical such process, the amount of output metal left at the stage 48 is only approximately 5% of the available metals which was in the zircon ore at the input stage 30.
If even higher separation factors of zirconium from alumin~
and hafnium are desired, in the embodiment of Figure 3, the reduction and separation stage 36 may also be "fluxed" in the manner descri'bed in Figure 2 above. If this is desired, the presently preferred manner to do this is to inject a quantity of ZnF2 into the zinc-zirconium molten metal after the salt phase has been removed from the metal phase. At this time, the following reaction occurs~
(13) 2ZnF2 + Zr ~ ZrF4 + 2Zn The zirconium tetrafluoride so formed then reacts with any remaining alumin~ and hafnium in the metallic phase in accordance with the following eqnatio~l:
~143 ZrF -~ ~If-` HfF -~ Zr If ~his second stage of separation is desired, it is the presently preferred practice to provide enough zinc fluoride to oxidize - about 2% of the 3irconium in the metal phase. Thus~ in the quantities .
given in the examples of Table 3 above, it is preferred to use about 1.1 lbs of ZnF2 for this fluxmg operation, if it is to be effected. If an excess of ZnF2 is provided, it results in a higher aluminum and hafnium removal, but a~ the expense of a loss of a greater amount of zirconium.
Similarly, if less ZnF2 is used~ a lower hafnium removal is achieved, but a greater quantity of zirconium remains in the metallic phaseO
It is noted that, in contrast to the processes described in - Figures 1 and 2 above, in the presently preferred embodiment described in , .
Figure 3, no excess salt such as potassium chloride, or sodium fluoride is provided into the reaction at the separation stage. As was described above~ the embodiment of Figure 3 results in the formation of the pseudo cryolite salt (NaF)l 5-AlF3. If an excess of sodium fluoride were provided in thisphase of the reaction, the resultant salt would be ordinary cryolite, or ~NaF)3 AlF3, which does not melt until a temperature of 1000 a, which ,- .
~ 20 is above the boiling temperature of the zinc-zirconium metal mixture.
; Those skilled in the art will further recognize that the ; embodiment of Figure 3 also reduces ha~nium metal from a hafnium compound in the same manner as zlrconium is reduced. Thus~ the method can be used to reduce hafnium, and is a superior reduction method than the prior art methods of reducing hafnium.
Figure 4 is a block diagram of a modification of the method of Figure 3, and shows a two stage counter-current reduction process to ~
' reduce the levels of aluminum and hafnium even lower in the zirconiumO
In Figure 4, the reduction and separation stage 36 is divided ~:~ , : . . , .- .
into two stages, designatcd 36a and 36b. In an initial run, first stage 36~ is supp]ied an initial charge of Na2ZrF6, also containing Na2HfF6, aluminum and zinc, and the reaction occurs as described in ~igure 3 above.
After the reaction is completed, the salt output is taken to the salt pro-cessing stage 44, described above, and the metal phase is taken to the second stage 36b of the reduction and separation stage.
The metal phase at this point might typically contain about 1000 to 1500 parts per million aluminum and 500 parts per million hafnium (both expressed as a function of zirconium only). These levels are too high for nuclear grade zirconium. In second stage 36b, the metal phase is mixed with the salt input from ore cracking stage 34, and the mixture is again heated to about 900C and stirred vigorously. At this time, the following reactions again occur:
(15) Na2ZrF6 ~ Hf ~ Na2HfF6 ~~ Zr and ~16) 3Na2zrF6 ~ 4A1 ~ 4[ (NaF) 1 50AlF3~ ~ 3Zr These reactions at this time reduce the levels of both hafnium and aluminum in the metal phase to less than 100 parts per million, again expressed as a function of zirconium only. Now, the ~xture is allowed to settle and is separated, as before. The metal phase is taken to the dis-tillation stage 40, where the zinc is distil]ed off and returned to the first stage 36a of the reduction and separation stage, and the new high purity zirconium is taken to the zirconium output stage 42. The salt phase (which was hardly changed in second stage 36b, since only low levels of hafnium and aluminum were available there to react with the Na2ZrF6) is taken to the first stage 36a of the reduction and separation stage, where new aluminum and zinc from the distillation stage are again provided.
Thus this modification of the process, which may now be termed a two stage counter-current reduction and separation process, provides . . . , , . - .,, : . ~: . :, high purity z:ircon:ium without the use of the fluxing step described in Fi~lre 2 above.
While the invention is thus disclosed and several embodiments are described in detail, it is not intended that the invention be limited to these shown embodiments. Ins~ead, many modifications will occur to those skilled in the art which lie within the spirit and scope of the in-vention. It is thus intended that the invention be limited in scope only by the appended claims.
. , .
''~ . : '.' ,. .
Claims (9)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. The method of producing nuclear grade zirconium from a zirconium compound, comprising the steps of: preparing a fused salt phase including the zirconium compound to be reduced, and contacting the fused salt phase with a molten metal phase which comprises aluminum and zinc, whereby the zirconium compound is reduced by the aluminum, with the aluminum being transported from the molten metal phase to the fused salt phase while zircon-ium is transported from the fused salt phase to the molten metal phase.
2. The method of claim 1 which further comprises the steps of separat-ing the molten metal phase from the fused salt phase and then separating the zinc from the zirconium.
3. The method of claim 1 in which the zirconium compound is Na2ZrF6.
4. The method of claim 3 in which a sufficient quantity of aluminum is used to reduce the zirconium in from 85% to 95% of the Na2ZrF6.
5. The method of claim 4 which further comprises the steps of again placing the fused salt phase after it is separated from the molten metal phase into a second molten metal phase which comprises aluminum and zinc, and which contains enough aluminum to reduce all of the zirconium in the Na2ZrF6 to obtain virtually pure (NaF)1.5.AlF3 and then separating the (NaF)1.5.AlF3 from the second molten metal phase.
6. The method of claim 1 in which the fused salt phase contains salts other than the zirconium compound whose cations are alkali elements.
7. The method of claim 1 in which the fused salt phase contains salts other than the zirconium compound which are halide salts.
8. The method of claim 1 which further comprises the steps of separating the molten metal phase from the fused salt phase, contacting the molten metal phase with a second fused salt phase including the zir-conium compound to be reduced, separating the molten metal phase from the second fused salt phase, and then separating the zinc from the zirconium
9. The method of claim 8 further comprises the steps of contacting the second fused salt phase, after it has been separated from the molten metal phase, with a second molten metal phase which comprises aluminum and zinc.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US623,325 | 1975-10-17 | ||
| US05/623,325 US4072506A (en) | 1975-10-17 | 1975-10-17 | Method of separating hafnium from zirconium |
| US05/684,096 US4127409A (en) | 1975-10-17 | 1976-05-07 | Method of reducing zirconium |
| US684,096 | 1976-05-07 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1084275A true CA1084275A (en) | 1980-08-26 |
Family
ID=27089424
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA262,580A Expired CA1084275A (en) | 1975-10-17 | 1976-10-01 | Method of reducing zirconium |
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| Country | Link |
|---|---|
| JP (1) | JPS5944377B2 (en) |
| AT (1) | AT359291B (en) |
| BR (1) | BR7606910A (en) |
| CA (1) | CA1084275A (en) |
| FR (1) | FR2328052A1 (en) |
| GB (1) | GB1539959A (en) |
| IT (1) | IT1069267B (en) |
| MX (1) | MX143963A (en) |
| SE (1) | SE425670B (en) |
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| CN102676852A (en) * | 2012-05-30 | 2012-09-19 | 深圳市新星轻合金材料股份有限公司 | Method for industrially producing zirconium metal and synchronously producing low-temperature aluminum electrolyte |
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|---|---|---|---|---|
| BE541741A (en) * | ||||
| DE609501C (en) * | 1933-11-24 | 1935-02-16 | Philips Nv | Process for the production of zirconium |
| US2797160A (en) * | 1951-09-07 | 1957-06-25 | Frank H Spedding | Production of zirconium |
| FR1165945A (en) * | 1955-11-29 | 1958-10-30 | Nat Lead Co | Process and device for the continuous production of zirconium and product obtained by this process |
| IT649745A (en) * | 1961-05-18 | |||
| FR1321508A (en) * | 1962-02-06 | 1963-03-22 | Pechiney Prod Chimiques Sa | Manufacturing process of metals and alloys by metallo-thermal reduction |
| DE1231438B (en) * | 1962-08-16 | 1966-12-29 | Helmut V Zeppelin Dr Ing | Process for the production of difficult-to-melt metals, in particular zirconium and beryllium, and their alloys |
| FR1353163A (en) * | 1963-02-22 | 1964-02-21 | Degussa | Process for manufacturing metals in the very pure state such as zirconium and device for its implementation |
-
1976
- 1976-09-10 MX MX16625076A patent/MX143963A/en unknown
- 1976-09-28 GB GB4028976A patent/GB1539959A/en not_active Expired
- 1976-10-01 CA CA262,580A patent/CA1084275A/en not_active Expired
- 1976-10-12 FR FR7630619A patent/FR2328052A1/en active Granted
- 1976-10-15 SE SE7611500A patent/SE425670B/en not_active IP Right Cessation
- 1976-10-15 AT AT770476A patent/AT359291B/en not_active IP Right Cessation
- 1976-10-15 BR BR7606910A patent/BR7606910A/en unknown
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| Publication number | Publication date |
|---|---|
| SE425670B (en) | 1982-10-25 |
| ATA770476A (en) | 1980-03-15 |
| JPS5250915A (en) | 1977-04-23 |
| IT1069267B (en) | 1985-03-25 |
| BR7606910A (en) | 1977-08-30 |
| SE7611500L (en) | 1977-11-08 |
| JPS5944377B2 (en) | 1984-10-29 |
| MX143963A (en) | 1981-08-11 |
| FR2328052A1 (en) | 1977-05-13 |
| FR2328052B1 (en) | 1980-05-23 |
| AT359291B (en) | 1980-10-27 |
| GB1539959A (en) | 1979-02-07 |
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