DE1583920B1 - METAL RECOVERY PROCESS BY REDUCING THEIR HALOGENIDE - Google Patents

Description

The invention relates to a process for the production of metals by reducing their halides with Reducing metals at a temperature above the melting point of the metal to be recovered in a reactor with a closed vapor space in which at least one pressure corresponding to the vapor pressure of the reducing metal halide that is formed prevails, the metal to be recovered and form the reducing metal halide in the reactor as a melt.

Here, a reduction metal is to be understood as a metal that has a has greater affinity than the metal to be recovered.

In many known processes for the reduction of metal halides !! with reducing metals Metal sponge obtained, producing halide melts or vapors. The reaction temperatures are always lower than the melting temperatures of the metals to be extracted. The gas pressure in the reactors is 1 atm or less. After the reduction, the metal sponge is melted down or sintered.

These methods have major disadvantages. The metal sponge, which is usually stuck in the reactor, must be removed The main part of the halide melt can be freed, separated with tools and removed. Because of the hygroscopicity of the halides, the atmosphere must be kept completely dry. The sponge is then cleaned of halides and subhalides with acids, alkalis and water, whereby hydrogen is often formed, which bonds with the metal to form hydrides. Since the Metals become brittle as a result, the hydrogen must be withdrawn when the metal sponge melts will.

The cleaned metal sponge is placed in crucibles made of high-temperature resistant oxides or graphite melted or sintered under noble gases or in a vacuum. In vacuum melting, the Metal deprived of the last remnants of halides, subhalides and the hydrogen. Great difficulties This is also caused by the fact that the molten metals attack the crucible material. They take oxygen and foreign metals from the oxide crucibles or carbon from the graphite crucibles so that oxides, sub-oxides, carbides and foreign metals damage the quality of the metal obtained or render them unusable.

In the industrial production of titanium, the titanium sludge is ground and possibly mixed with other metal powders for the production of alloys, pressed into rods and in melted down in a high vacuum arc furnace with a water-cooled copper mold. Gives way the arc down to the mold wall, there is a risk of a furnace explosion, which is the use required by protective walls and a remote control device.

In order for the metal to be homogeneous, the melting process - especially with alloys - be carried out several times (Ulimanns Encyklopadie der technischen Chemie, Vol. 17, 1966, p. 420 to 424).

For the production of ferro-alloys, a process has been proposed in which, under normal pressure of 1 atm, liquid iron with a halide, ζ. B. of Ti, Zr and V, and a reducing metal, e.g. B. Mg, is treated, whereby the halide is reduced to the metal (e.g. Ti) and this is dissolved in the iron, while gaseous waste chloride (e.g. MgCl ₂ ) is formed, which is heavily contaminated by subchloride and iron chloride (German Patent 1,168,461). According to another known process, alloys are produced by treating a melt consisting of a metal and a reducing metal with a metal halide at normal pressure of 1 atm (German patent 843 165). These processes are only used for the production of alloys and are of course useless for the extraction of pure metals.

It has also already been proposed to introduce TiCl ₄ and Mg, Na or K into an inert molten salt which does not evaporate at the reduction temperature above the melting point of titanium. Liquid titanium should settle under the molten salt, while the resulting Mg, Na or K chloride escapes in gaseous form through the molten salt, since the reduction is carried out at normal pressure of 1 atm (US Pat. No. 2,667,413). This method is so uneconomical compared to the others that it could not find its way into practice. Around 80% of the TiCl _{4 is converted into gaseous TiCl 2} at temperatures above the melting point of titanium at atmospheric pressure (1 at), which leaves the reactor with the vapors of MgCl, Mg, TiCl _{4 and TiCl.}

Generally applies to processes in which refractory metals or alloys above their Melting points at a pressure of 1 at or less can be obtained from halides that vapors arise which, in addition to the halides of the reducing metals, very large proportions of the halides and subhalides of the metals to be recovered when the evaporation points of the reducing metal halides lie below the melting point of the metals to be extracted. As a result, the chemical sales uneconomically small. In addition, you have to add a lot of heat to the reactors, since the reactions are endothermic due to evaporation of the halides. The cooling and Condensation and cleaning of the condensates for the purpose of recovering the reducing metals technically extremely difficult and very expensive. For these reasons, these procedural proposals have not been implemented.

It has also been proposed to use titanium from titanium halide, e.g. B. TiCl ₄ , by means of an alkali metal, preferably sodium, to be obtained in that a reaction mass composed of a mixture of the components mentioned is caused to react in a high-pressure-resistant closed vessel (bomb) in which, by applying heat, ζ. Β. an arc to initiate the reaction such that the reaction proceeds outward from the starting point towards the walls; the reaction rate is controlled by cooling the walls of the reaction chamber (German Auslegeschrift 1067 222). This so-called bomb reduction was also known for several other metals; it was first carried out by Hunter in 1910 and is only suitable for obtaining small metal samples in a laboratory (MN Hunt er, The reduction of titanium tetrachloride with sodium. J. Am. Chem. Soc., 32 [1910], pp. 333 to 336 [Burau of mines, Report 6374, Reducing Vanadium Compounds in Bomb Reactors, 1964]).

wisely, a Bcmben reactor would have to have an interior space of around 4 m ³ so that only 240 liters = 11 titanium can be produced in it. The NaCl melt requires around 3.5 m ³ , and there is also a steam space of at least 200 1.

In addition, filling, emptying, and repairing a bomb reactor requires batch operation a lot of time and manual labor. The solidified titanium block is with the oxide ceramic or

removed, thereby destroying the lining. The encrusted surface layer must be removed from the block knocked off and twisted off, losing 15 titanium.

When the reaction is over, the contents have to be left to cool for a few hours, the reactor open, tear out the titanium and salt block, repair or replace the lining, dry for a few days

In this process, after the
Reaction container, the resulting mass of metal, reducing metal, subhalides and solid alkali halide broken out of the container, excess alkali separated, the
Metal-salt mixture leached with water and that
gravel and gravel-like titanium product washed and
dried. It consists of small and large sintered and partly due to local overheating

fused lumps. This process also inextricably fused with the graphitic lining. In-

wefsen have the disadvantage that the processing of the consequent must be very expensive by force from the reactor bomb contents, that they require a lot of manual work and that the resulting
Metal product still melted in a vacuum
must become.

All known processes in which salt and
Metal can be separated by leaching with water,
are also afflicted with the further defect that

to recover the reducing metal the salt _ ^ _w

the solution evaporated and the salt completely de-aoed, then slowly warmed up, heated and then watered. This is a particularly difficult inconvenience (to remove all, including chemically bound, major disadvantage, as it is known to remove the water during the re-watering process), and then one can only produce halides of the reduction _with the Na-TiCl _{4 mixture} re-charge, metals, mostly alkali metals or magnesium, in summary, the following results are obtained by melting electrolytic regeneration, whereby one assumes that with the proposed impurities and especially even a low bomb reduction process and the process, moisture content is very disturbing. according to USA patent 2,667,413 actually titanium in a well-known special bomb reduction process, more compact and technically usable form ren represents the other bomb reduction methods can be produced, so the production and are an improvement compared to the fact that by 30 the further necessary processing costs are a fine distribution of sodium in titanium tetrachloride eighty higher than the conventional titanium ore a higher yield of molten titanization costs of the process via the tintan sponge. Lump is achieved with attenuation of the explosive. A bomb reduction process force of the reaction, lowering of the necessary known (USA.-Patent 2787 537), with which the ignition temperature, faster union of the total 3 5 standing metal does not solidify in the bomb , but amount of reactants as well as avoiding j _n molten state is drained. The Gevon pressure and temperature peaks. mixture of metal halide and reducing metal The objective of this known invention in _w j _r d is achieved for a whole batch at a time in the that an intimate mixture of from 0.005 to 5 mm filled bomb and then initially ignited. Thick sodium particles take place, which with a passivating 40 an explosive reduction in which as a result of the oxide or salt skin are provided, and cold high temperatures of 2000 to 3000 ° C extra liquid TiCl by igniting in a bomb - quite high pressures occur, the 100 until the reactor is reacted at 200 at. Here are the amounts. The main proportion of these high pressures is particle size of the sodium and they enveloping _V on the vapor pressures of the reducing metals Ge passivation layer is of decisive importance 45 forms, while the Halogenidschmelzen tung only pressures (USA. Patent 2,843,477). cause from 10 to 20 at. This procedure involves

This proposed method has no condition, therefore, a high expenditure on equipment,

found in practice, because of the following - Since the reduction

The disadvantages: The Na- _{TiCl 4} mixture is highly explosive and completely uncontrollable, react

plosive and flammable, and if you wanted it from 50 many metals that have a strong affinity for oxygen

outside during the reduction in the bomb reactor, at the high temperatures that occur

enter continuously, the charging _and pressures with the oxide-ceramic lining would have to

speed of the propagation speed of the being caused by the oxides and sub-oxides of Mg,

Reaction exactly correspond to what is practically impossible Ca, Li, Al and the like. Are heavily contaminated before

there is even a small change in the reaction to a solid protective layer on the lining

temperature and change in reactivity of the form. The brick lining must therefore after each

Na-TiCL mixture can result in the batch being renewed.

Reaction is faster and in the entry device. For these reasons, according to the knowledge with catastrophic consequences from the reactor th process only such metals jump out in pure form. At a faster charging rate, the liquid would be obtained, but with the heat-insulating oxide resistance, the reactor with the unreacted ceramic lining of the reduction bomb would not be filled with mass and cooled. react. These are metals whose melting points The batchwise implementation of this process are below 1200 ° C and which the proposal and the other bomb reactions do not have a great affinity _for oxygen. Refractory metals, as used on an industrial scale, require non-beryllium, chromium, titanium, hafnium, molybdenum, relatively large bombs, since the volume of the niobium and tantalum, at temperatures above the NaCl melt, can be fourteen times as large as half its melting point Process like that of the extracted titanium melt. Example- cannot be obtained in a pure state. When loading

Using this bombing process, the metals obtained have to be reduced and purified and melt in a high vacuum.

In a further known method (US Pat. No. 2,825,624) is first of all in the lower part of a Reaction chamber metal formed in sponge shape, made from molten salt of the reducing metal is interspersed. The metal sludge then pushes upwards and is illuminated by means of an electric light

Molten metal and salt are to be collected in the collecting container, in two layers separate and then freeze.

According to US Pat. No. 3,085,871, a tubular body made of salt and metal sponge is obtained with a dense inner surface, which is technically worthless in this form. It would have to be crushed, freed from the salt and like a metal sponge in a high vacuum light

increased pressure in the flame the reducing metal halide no longer gaseous, but liquid, and the flame temperature rises to the melting point of the metal to be extracted.

The lining can now no longer grow, as both the salt and the metal flow off in layers in molten form with the slightest increase in temperature. If this is actually done, then the reverse of the arc described above applies in an argon atmosphere with a low layer structure, the dismantling of the lining. Pressure melted into a metal sump. This increases its thermal conductivity, so that the temperature disadvantages of the metal temperature and pressure occurring in the first phase decrease. The production of sponges from the reactors has already been explained above. The flowing melts always have only one temperature in the second process stage (melting of the temperature, which is the melting point temperature of the metal sponge obtained), the resulting vapors contain 15 metal is the same, since the lining was built up with the metal, which is very much recoverable in addition to the halides of the reducing metals, large proportions of the halides and subhalides of
metals to be mined; the chemical sales
are consequently uneconomically small. One must
also supply a lot of heat from outside.

A reference (Chemisches Zentralblatt, 1965,
Referat 2338) also contains a note that it
The ideal would be the direct reduction of uranium hexafluoride to uranium metal with sodium, the liquid
Metal constantly down and the liquid slag 25 arc furnace melted down to compact metal to pull off to the side. The reference to be answered in the negative. However, due to the excessive cost of this method, the feasibility of this process. preparation of this tubular body has the

Finally, no practical application has been found for three known methods. the pointed out, according to which a halide of the two other process proposals are not realinenden Metal (e.g. Ti) and a liquid reducible, as will be explained below, tion metal (e.g. Na) in one of a steam according to USA patents 3,085,872 and 2,941,867

mixed-filled space from a double nozzle - molten salt and metal flow together into one each other, taking a reaction-cooled sump where they are from each other flame arises. The double nozzle is intended to separate at the top and then solidify. As was already the case vertical cylindrical reaction space, it is in the nature of this process axially so placed that the flame suggests itself downward that the molten salt and the is directed. The reactor consists of a liquid metal with exactly the melting point temperature-water cooled, relatively closely built, good temperature of the metal leaves the reactor and not conductive, pressure-resistant cylinder, the downward if with a temperature above the melting point and with a cooled collecting container gas- 40 point of the resulting metal. But it follows from this is tightly connected. In the first two procedures- that the metal drops or metal jets immediately Proposals (United States patents 3,085,871, 3,085,872) have to freeze when it persists from the reactor the collecting tank inert gas with a pressure, gen. As a result of the very large radiation and Abder The vapor pressure in the reaction space at least it seems impossible in a water-cooled line should be. According to the third proposal (U.S.A.- 45th container molten salt and metal in liquid Patent 2,941,867) is said to be able to collect the collecting container as well and remain liquid for so long Inert gas, but at a pressure of only 1 atm, is contained until they are cleanly separated from each other keep. to have. This also seems impossible because

When starting up, the flame temperature is below the temperature exiting the reaction chamber far less than the melting point of the high pressure condensed (superheated) molten salt the metal. In the flame, gaseous substances are produced which evaporate spontaneously in an inert gas atmosphere (be-reducing metal halide and a smoke of solid special at an inert gas pressure of only 1 at; USA.particle of the metal to be extracted. The Reduk patent 2,941,867) and as a result of the related tion metal halide condenses on the cold wall cooling the metal to be extracted to solidify of the reaction space to solid salt, which brings the same 55 before it reaches the collecting tank, early the solid particles of the metal to be extracted In addition, it is doubtful whether the flame emps

grow into the salt layer, so that a warm temperature at all exceeds the melting point of the insulating material to be obtained Lining made of metal sponge and the metal achieved: As a result of the concentration of the solid salt is formed. Since the layer thickness of this reduction metal halide on the inner surface of the As clothing increases, its thermal conductivity becomes less and less hot ringer, and consequently the temperature of its is rises than the reaction flame, can that of the flaming one Flame facing inner surface. temperature required higher condensation pressure According to the first two proposals, the inert- this halide acts in the flame and around the gas pressure on the reaction flame, while after flame around cannot be reached. Consequently In the third proposal, the open end of the reaction arises in the hotter flame, the reduction space grows so far that the flame under metal halide is only gaseous, and it condenses a dynamic pressure. only at the less hot lining that becomes liquid. In both cases, it is now supposedly due to the salt. This makes the heat of condensation this

Halides are not released in the flame, but on the lining through which they are attached to the cooling water of the reactor jacket is derived. The flame temperature remains below the melting point of the resulting metal, so that only metal sponge is formed, and there is a risk that the lower reactor opening grows.

Certainly these methods are very prone to failure and their practical feasibility is very questionable. According to US Pat. No. 2,941,867, this is best obtained under the reactor in the collecting space just a conglomerate of salt and metal particles that has yet to be worked up in the same way as the more salty ones Metal sponge.

The cause of the deficiency of this method is that, as a result of the less hot environment, the reduction cannot actually be carried out at the vapor pressure of the molten salt, which is thought to be liquid in the flame, but only at its lower condensation vapor pressure; it is in fact taken any measure to ensure that the temperature of the environment of the reacting mixture is not f lower than the reaction temperature. The two methods of U.S. Patents 3,085,872 and 2,941,867 also found no practical application.

The invention is therefore based on the problem of the disadvantages of the known methods of extraction of metals by reducing their halides. By the method according to the invention the aim is to ensure that the metals are created directly in liquid form by means of exothermic reactions that in a reactor kept the entire amount of metal at a temperature well above its melting point and the liquid metal can be drained from the reactor without the risk of freezing, that Solid protective layers form on the reactor walls from the molten metal and thus impurities reactor materials prevent the formation of only traces of subhalides and the chemical conversion is practically complete if you have molten alloys directly in the reactor State can produce and that you can also the resulting halide of the reducing metal in pure and molten form from the Can drain reactor.

The invention is based on a method for extracting metals by reducing them Halides with reducing metals at a temperature above the melting point of the one to be recovered Metal in a reactor with a closed vapor space in which at least one pressure corresponding to the vapor pressure of the reducing metal halide that is formed, whereby the to be recovered metal and the reducing metal halide form in the reactor as a melt.

In this method, the above-mentioned object is achieved according to the invention in that after Formation of the melt, the reducing metal and / or the metal halide while maintaining the desired Reaction temperature are fed further from the outside and introduced below the melt level.

Since the reactants are introduced according to the invention below the melt level and the reaction takes place in the melt, the temperature of the melt is equal to the reaction temperature. To this In this way it is avoided that the environment of the reacting substances has a temperature which is lower than the reaction temperature. As a result, can

the reducing metal halide does not arise as vapor and condense in less hot places, rather, it is formed directly in the liquid state within the melt.

Under these conditions, one of the heat of vaporization of the reducing metal halide which forms in liquid form equivalent amount of heat released with appropriate thermal insulation of the reactor without additional heating allows the reaction temperature to be above the melting point of the To hold metal.

Since the vapor space of the reactor is also closed during start-up, this can be far beyond its Evaporation point heated halide of the reducing metal arise only as long as gaseous until his Vapor pressure has reached the condensation pressure corresponding to the reaction temperature. Of this At the moment, the halide of the reducing metal is only formed directly in the liquid state.

The further addition of the reactants after the initial formation of the melt takes place in the Process according to the invention so that the desired reaction temperature is maintained. Preferably for this purpose the amount and / or the temperature of the imported substances is regulated.

Since the resulting metal and salt melt at a temperature above the melting point of the metal to be recovered is a permanent clean separation of the reduction resulting metal and salt droplets guaranteed. Because the toughness increases with increasing temperature is greatly reduced by molten metals, the molten metal and molten salt separate very much quickly from each other. The table below shows, for example, the reduction in toughness of some molten metals when the temperature is increased above the melting point by, for example 63 ° C (graphic evaluation of the information in "Thermochemistry for Steelmaking" by J. F. Elliot and M. Gleiser, 1960, pp. 7 to 12).

metal

Al 659.0 * 722.0 50 mg 650.0 * Zn 713.0 ⁵⁵ Sn 419.5 * 482.5 231.9 * 294.9

temperature

Dynamic

toughness

η cP

4,600

2,700
1,320

1.055
5.860

3,850
2.710

1.690

reduction
of toughness
Δη cP [° / o

1,900

0.265

2.010

1.020

41.30

25.10

34.30

37.65

* Melting point temperature.

From this list it can be seen that the metal melts with a temperature increase by only 63 ° C (see following example) quickly become "more fluid"; the decrease in toughness lies on the order of 20 to 40% of the toughness at the melting point.

The pure, liquid metal obtained by the process according to the invention can be used without the risk of freezing can be removed and fed to further use without any processing. Special

109538/19?

It is also advantageous that the liquid reducing metal halide as a result of its purity immediately afterwards without any preparation by means of melt electrolysis or in any other way can be regenerated to the elemental reduction metal.

The reactants can be introduced continuously into the reactor and the reaction products continuously be drained from the reactor. So you can, for example, one continuously at the reactor Connect working continuous caster directly. However, you can also use the molten metal Discontinuously drain into cooled molds or molds and in this way castings Manufacture of any shape and size.

As a result of the great affinity of the reducing metals for the halogens and the prevailing vapor pressure the partial pressure of subhalides in the vapor space above the melt is very small. Consequently the halide melt consists practically only of the halide of the reducing metal. Subhalides are only formed in traces. So the metal halide introduced into the reactor becomes quantitatively (practically completely) converted into metal.

According to an expedient embodiment of the method according to the invention, external Cooling of the reactor jacket on the inside of the reactor lining a solid protective layer from the produced metal to be extracted. In this way the lining is protected from chemical attack and protected from high temperatures; As a result, metal and reducing metal halide remain pure, and it also eliminates the need for frequent renewal of the lining.

The process according to the invention is of particular importance for the production of high-melting points Metals, for example beryllium, chromium, hafnium, iridium, manganese, molybdenum, niobium, tantalum, thorium, Titanium and zirconium.

To produce an alloy, the halides of the desired alloy partners are in the same Reactor with reduced or metallic alloy partners introduced in elemental form. It must the metal is not first ground, mixed with the powders of the alloying partners and melted several times but you can directly in the reactor during the formation of the metal alloys in the Produce molten state, also with partners (e.g. Mg, Ca), whose evaporation points go far lie below the melting point of the alloys, which was previously impossible.

An embodiment of the method according to the invention is explained in more detail with reference to the drawing:

example

100 kg / h of titanium are to be produced from TiCl _{4 using Mg as the reduction metal.}

The reactor illustrated in the drawing is a closed, upright cylinder with a clear width of 200 mm and a height of 600 mm. Its capacity is around 201. It has a double wall 1 made of steel. The lower part is up to a height of 300 mm with a mm thick magnesium spinel layer 2 lined.

First the reactor is degassed a few times and flushed with argon and finally evacuated. In the lower part of the reactor through two tangentially attached graphite tubes 3 and 4 hot liquid magnesium with an amount of. 102 kg / h and a temperature of 700 ° C and hot TiCl ₄ vapor with an amount of 46 Nm ³ / h and a temperature of 220 ° C entered. A reaction temperature of 1500 ° C. is established during this process. The titanium initially produced (melting point 1667 ⁰ C) in solid form, while the MgCl ₂ which forms evaporated (evaporating temperature 1412 ° C). Since the MgClo vapor cannot escape, the pressure in the reactor rises until it finally reaches about 5 atm.

Now only liquid MgCl _{3 is formed} and the reaction temperature rises rapidly to 1730 ° C. The titanium that was initially formed melts, while now only liquid titanium is formed directly. The liquid MgCl ₂ forms a layer overlying the liquid Ti.

Cold water flows through the double-walled steel jacket, bottom and cover of the reactor. While the liquid MgCl _{2 forms} a solid layer 5 of 7 to 8 mm thick on the cooled steel wall, a 4 to 5 mm thick layer of solid titanium 6 is formed on the cooled spinel lining 2.

The liquid MgCl ₂ (400 kg / h) is drained from the bottom of the reactor just above the spinel lining through a graphite tube 7 and the liquid titanium (100 kg / h) through a cooled graphite tube 8. The developed heat of reaction of around 80,000 kcal / h is transferred _{to the cooling water through the solid MgCl 2} and Ti layers, the magnesium spinel lining and the steel wall. The cooling water (about 1.5 m ³ / h) leaves the reactor at a temperature of 80 ° C.

To maintain the desired reaction temperature of 1730 ⁰ C, the temperature of the TiCl ₄ is controlled -Dampfes, the heater (not shown) from a TiCl ₄ evaporators by a is supplied to the reactor. A temperature increase of the _{TiCl 4} vapor from 220 to 320 ° C corresponds to an additional heat supply of 5000 kcal / h.

The liquid titanium can be continuously withdrawn as a strand from the reactor. One can Filling it into water-cooled copper molds under argon and then receiving titanium blocks of any shape and size.

Claims (9)

Patent claims: 1. Process for the production of metals by reducing their halides with reducing metals at a temperature above the melting point of the metal to be extracted in a reactor with a closed vapor space, in which at least one pressure corresponding to the vapor pressure of the reducing metal halide being formed prevails, the metal to be recovered and the reducing metal halide being formed in the reactor as a melt, thereby characterized in that after the formation of the melt, the reduction metal and / or the Metal halide supplied from outside while maintaining the desired reaction temperature and inserted below the level of the enamel. 2. The method according to claim 1, characterized in that to comply with the desired Reaction temperature, the amount and / or temperature of the substances introduced is regulated will. 3. The method according to claim 1, characterized in that by external cooling of the Reactor jacket on the inner surface of the reactor lining a solid protective layer from the recovering metal is produced. 4. The method according to claim 1, characterized in that the metal halide to be reduced and introducing the reducing metal into the reactor in a tangential direction. 5. The method according to claim 1, characterized in that the reactants are continuous are introduced into the reactor. 6. The method according to claim 1, characterized in that the reaction products are continuous be drained from the reactor. 7. The method according to claim 1, characterized by its application to the extraction of refractory metals, for example beryllium, Chromium, hafnium, iridium manganese, molybdenum, niobium, tantalum, thorium, titanium and zirconium. 8. The method according to claim 1, characterized in that titanium tetrachloride and magnesium are introduced into the lower part of the reactor containing the melt, the temperature of the melt is kept at about 1730 ° C and MgCl ₂ - and Ti melt separately from each other Reactor to be drained. 9. The method according to claim 1, characterized in that for the production of an alloy the halides of the desired alloy partners in the same reactor with reduced or metallic Alloy partners are introduced in elemental form. For this 1 sheet of drawings Copy