Electrolysis: processes – compositions used therein – and methods – Electrolytic synthesis – Preparing alloy
Reexamination Certificate
1999-06-21
2001-06-12
Valentine, Donald R. (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic synthesis
Preparing alloy
C205S560000, C075S589000, C075S594000, C075S614000, C075S615000, C075S623000
Reexamination Certificate
active
06245211
ABSTRACT:
The present invention relates to an improved process for obtaining metals like titanium, zironium, chromium, molybdenum, tungsten, cobalt and tantalum from metal oxides using shuttle alloys. More particularly the present invention relates to a process for obtaining alloys and compounds of metals wherein the metal is very sensitive to oxygen and nitrogen, such as titanium, zirconium, magnesium, tantalum, lithium, beryllium, sodium and potassium by the use of a shuttle alloys.
Although the present invention will be described with particular reference to the isolation of titanium and complexes of titanium in the form of ingots, it is to be noted that the scope of the present invention is not so limited but rather the scope of the present invention is broader so as to include other metals. Furthermore the process of the present invention may be used to provide metals and metal complexes in forms other than ingots and may be used to supply metals or metal complexes in directly to other processes.
There are many different processes used in industry for isolating or purifying metals in their elemental form or in the form of a metal complex. Many industrial processes act directly on metal ore where the relevant metal is present as a metal oxide or a metal oxide complex. For example titanium and zirconium are commonly obtained from ores ouch as rutile, ilmenite and zircon using the Kroll process. In steelworks, ferro-titanium is routinely obtained by direct aluminothermia.
The Kroll process is based on the transformation of titanium or zirconium ore to titanium or zirconium chloride followed by reduction of the metal chloride in a bath of magnesium to create a porous mass of titanium or zirconium which is referred to as a “sponge”. The magnesium in evaporated from the sponge, and the titanium or zirconium melted and poured into ingots. Where an alloy is to be cast, the titanium or zirconium from the sponge is combined with the other alloy components during casting. The ingots are often remelted and recast in a further refinement step. Refinement of the sponge must be carried out in a vacuum oven due to the extreme sensitivity of the sponge to oxygen and nitrogen. Furthermore measures must be taken to avoid any contamination of the final finished products.
Aluminothermia is based on reacting powdered aluminium with titanium dioxide, usually derived from ilmenite. In practice this reaction is endothermic and measures must be taken to avoid producing a mere mixture of aluminium and titanium—a mixture which is particularly difficult to separate because aluminium and titanium have similar densities. In order to avoid forming a mere admixture, the titanium ore/melting agent combination and the ferro-aluminium are separately preheated in an electric oven then mixed and puddled to produce a floating slag and ferro-titanium for use by the steelworks.
These processes of the prior art suffer from many drawbacks including the difficulty of handling and processing oxygen and nitrogen sensitive intermediates such sponges, and difficulties in separating individual products of the process. Furthermore the Kroll process, aluminothermia and the like can only be carried out as batch processes, not continuous processes.
It has now been found that many of the disadvantages of the prior art can be overcome by the use of a shuttle alloy (which can also be called a “taxi alloy”). The shuttle material may for example, facilitate reduction of a metal oxide by carrying a reducing agent to the metal oxide and subsequently, form a shuttle alloy which comprises the reduced metal derived from reduction of the metal oxide. In particular the present invention does not require the production of intermediate sponges, but rather uses the continuous production of shuttle alloy comprising metal derived from reduction of metal oxide. Furthermore the reduced metal of the shuttle alloy is far less fragile and less sensitive to oxygen and nitrogen than intermediates such as sponges formed by processes the prior art. Furthermore the formation of a shuttle alloy makes it easier to isolate pure metal at a later step.
The process of the present invention also does not require an intermediate ingot refining phase as is common in many of the processes of the prior art. In the present invention, the reduced metal may be separated from the shuttle alloy in the form of a pure metal or alloy, and is sufficiently resistant to oxidation that it can be stored, or alternatively used to directly and continuously supply different types of seconds production processes such as the production of bars, tubes or sheets. The process of the present invention does not consume large amounts of chemicals such as chlorine or hydrochloric acid and the components of the shuttle alloy may be recycled. The process of the present invention is also far more economical and more environmentally friendly than the processes of the prior art.
The present invention therefore provides a process for producing a metal or alloy from metal oxide characterised by a first stage in which a metal oxide is reduced in the presence of a primary shuttle material, which forms a shuttle alloy with the reduced metal, and a second stage wherein the reduced metal is separated from the shuttle alloy as a pure metal or alloy.
As stated above, the first stage of the process comprises reduction of a metal oxide in the presence of primary shuttle material which forms a shuttle alloy with the reduced metal. The reduced metal may be in the form of metal or metal oxide or the like and may dissolve in, react with, or otherwise combine with the primary shuttle material to form the shuttle alloy. In the second stage of the process, the reduced metal may be removed from the shuttle alloy by physical means such as vacuum distillation or magnetic separation or by chemical reaction. The reduced metal removed from the shuttle alloy may be in the form of pure metal, or in the form of an alloy/bimetallic compound. Where the reduced metal is removed from the shuttle alloy by physical means, it may be cast into ingots or supplied directly to downstream processes. Where the reduced metal is in the form of an alloy, an ingot of the alloy may be further processed to produce the reduced metal in pure form.
Typically the metal oxide reactant in the first stage in a simple metal oxide such as TiO
2
, Li
2
O, MgO, CaO, CoO, Ta
2
O
5
or ZrO
2
, or a complex metal oxide such as FeTiO
3
, FeCr
2
O
4
, MnCr
2
O
4
, FeWO
4
or ZrSiO
4
. The metal oxide may be in the form of, or in combination with an ore such as rutile, illmenite, chromite, wolframite, zircon and the like.
Typically the process of the present invention will be used for the production of pure metal such as pure titanium, but it will be apparent to the person skilled in the relevant technology that the process can be used for production of many metals other than titanium. Typical the process of the present application is used to produce refined metal or metal alloy of titanium, zirconium, lithium, magnesium, chromium, molybdenum, tungsten or cobalt.
Typically the primary shuttle material comprises bismuth or antimony or a combination of the two. The bismuth or antimony be in the form of elemental metal, metal compounds or as mixtures of elemental metal and metal compounds. Optionally the primary shuttle material also comprises elemental lead or a lead compound, which may remain neutral but form eutectics with the bismuth and antimony. Lead has a greater density than antimony or bismuth, and provides much greater vapour tension, which is advantageous if in the second stage of the process, the shuttle alloy is separated from the reduced metal by heat and/or vacuum treatment. The primary shuttle material may also comprise shuttle alloy recycled from the second stage of the process.
Typically, in the first stage of the process the primary shuttle material is in the liquid state.
Typically the primary shuttle material comprises bismuth and antimony in a molar ratio of between 3:1 and 1:3. Typically, where the primary shuttle material comprises lead, th
Jenkens & Gilchrist P.C.
Valentine Donald R.
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