JPH046780B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a heating furnace. Specifically, the present invention relates to a heating furnace suitable for reductive distillation of metal compounds or distillative purification of metals, and particularly suitable for producing metal elements by heating a mixture of a metal oxide or halide and a reducing agent in vacuum.

(Prior Art) Metal metallurgy is generally carried out in the atmosphere, but in this case, the inherent properties of the metal are often inhibited by various gases such as oxygen and nitrogen in the atmosphere. Vacuum metallurgy is one of the methods to obtain highly pure metals.
Among them, the reductive distillation method or the distillation purification method in which reduction reaction and distillation are performed simultaneously has been practiced for a long time. This method is mainly used for producing active metals having high vapor pressure at relatively low temperatures, such as magnesium, calcium, barium, and rare earth elements.

A heating furnace that performs reductive distillation under vacuum consists of a heating device and a retort. The retort has a heating section for raw materials at the bottom and a condensing section for metal vapor at the top so that reduction reaction and distillation can be carried out simultaneously.
It has a structure as shown in FIG. That is, the heating part is located below the baffle plate 3, and the condensing part is located above the baffle plate 3.

In Figure 2, raw material 1 charged into retort 1
5 is heated by a heating source in the furnace to cause a reduction reaction and generate metal vapor. The metal vapor passes through the gap between the baffle plates 3 and is removed with heat by the cooler 9, and is condensed and solidified. After the reductive distillation is completed, the condensed and solidified metal is obtained by cooling the entire retort and taking it out of the heating furnace, and then opening the upper cooler 9.

Also, in the retort shown in FIG. 3, the metal vapor generated in the same manner as in FIG. 2 is condensed and solidified inside the sleeve 7. The condensed metal 16 is taken out by cooling the entire retort and taking it out from the heating furnace in the same manner as described above, and then opening the upper lid 14 and taking out the sleeve 7 from the retort 1.

Distillation and purification of metals is carried out in the same manner as above, except for the raw materials charged (for example, Satoshi Nakajima, "Vacuum Engineering Handbook" (1965), Asakura Shoten Co., Ltd.).
Chikara Hayashi, Koji Muramatsu “Vacuum Metallurgy” Vacuum Technology Lecture 9
(1965) Nikkan Kogyo Shimbun. (See Jiro Shiokawa, New Experimental Chemistry Course, 8, 61 (1976) Maruzen Co., Ltd.).

(Problems to be solved by the invention) When using a retort as shown in Figure 2,
The metal vapor condenses and solidifies not only on the surface of the cooler 9 but also between the cooler 9 and the retort 1. Therefore, there is a problem that the cooler 9 and the retort 1 are integrated by the condensed metal 16, making it difficult to separate and open them.
Sometimes it was necessary to cut the top of the retort 1 and take out the metal. Another problem was that metal vapor condensed and solidified at the exhaust port 12, making it difficult to maintain the degree of vacuum inside the retort 1 at a predetermined value.

The retort 1 must be taken out from the heating furnace after it has been sufficiently cooled because the temperature of reductive distillation is as high as 750 to 2000°C. However, from 750
Since it takes a long time to cool the product from a high temperature of 2000°C to around room temperature, there was also the problem that the operating cycle for each batch was lengthened, resulting in poor production efficiency.

In FIG. 3 as well, there was a problem in that the metal vapor condensed and solidified across the sleeve 7 and retort 1, and the two became integrated, making it difficult to remove the sleeve.

Further, since reductive distillation is performed at a high temperature of 750 to 2000° C., the retort 1 and sleeve 7 undergo distortion (expansion, contraction) due to heat. When the retort 1 and sleeve 7 are repeatedly exposed to high temperatures,
There was also a problem in that it became difficult to insert the sleeve 7 into the retort 1 because strain accumulated over time and the deformation became large. When the retort is removed from the heating furnace, it takes a long time to cool down, similar to the apparatus shown in FIG. 2, and there is also the problem of poor production efficiency.

It is also possible to divide the retort into a heating section and a condensing section and connect them with a flange type, but in a retort operated at high temperatures of 750 to 2000 degrees C There is a problem that distortion occurs due to heat, resulting in poor bonding. Leakage of metal vapor can be prevented by tightening the bolts and nuts, but due to the high temperature required for repeated use,
There are drawbacks that cannot be tolerated such as distortion.

(Means for Solving the Problems) As a result of intensive study on a vacuum heating furnace that overcomes the above problems and has good production efficiency, the present inventors have found that a heating method for heating metals and/or metal compounds in a vacuum state In a heating furnace consisting of a heating device and a retort having a heating section and a condensing section for condensing metal vapor generated by the heating, the retort is configured to be able to be divided into a heating section and a condensing section, and It has been discovered that the above problems can be solved by sealing the joint with a packed layer of powder, and the present invention has been completed based on this knowledge.

Next, the present invention will be explained in detail using the drawings.

FIG. 1 is a longitudinal sectional view of a retort showing an embodiment of the present invention.

The retort is composed of a heating section A and a condensing section B. The heating section A consists of a crucible 2 that stores raw materials and a powder filling groove 4 that holds a sealing powder 17.
The crucible 2 usually has a baffle plate 3. On the other hand, the condensing section B consists of a cooler 9 provided above the skirt 5 and the crucible 2 with a cladding plate 8 in between. The cooler 9 has an inlet 10 and an outlet 11 for the refrigerant flowing therein.
has.

The most significant feature of the present invention is that the heating section A and the condensing section B are configured to be separable, and their joints are sealed with a packed layer of powder.

In order to create a packed layer, it is preferable to provide a groove and put the powder into the groove, but if the width of the groove is too wide, it will require a lot of powder to be filled, and if it is narrow, it will be difficult to join the skirt 5. Undesirable. Although it depends on the size of the heating furnace and retort, it is usually selected from the range of 5 to 100 mm, preferably 10 to 50 mm, and more preferably 20 to 40 mm.

The higher the depth of the groove, that is, the filling height of the powder, the greater the sealing effect, but if it is too high, the heating furnace in which the retort is installed will also become large, which is undesirable, and if it is too low, the sealing effect will not be sufficient. Its height is usually selected from the range of 5 to 200 mm, preferably 10 to 100 mm.

Since there is a risk that the powder-filled bed will melt if directly heated, the powder-filled groove 4 is provided at the upper tip of the crucible 2 and at a position that is not directly heated by the heating device 18 .

If the particle size of the powder is too large, the metal vapor may pass between the particles filled with it and flow out of the retort, or it may condense between the powder particles and cause the crucible 2.
If the condensing part B and the condensing part B are integrated, it may become difficult to separate them.

On the other hand, even if the powder is quite fine, there is no particular problem, so the powder particle size of the present invention is usually 0.1 to 500 μm,
Preferably 0.5 to 100 μm, more preferably 1 to 50 μm
selected from a range of m.

The powder that can be used is selected from substances that can withstand the high temperature atmosphere of reductive distillation and do not react with the metal vapor generated. Preferably, if the powder to be filled is the same as the oxide or halide of the raw metal, there is less risk of contamination with impurities and repeated use is possible. Moreover, after use, it can be used as a raw material for reductive distillation, which is preferable. For example, samarium oxide, calcium oxide, barium oxide,
Powders such as yttrium chloride and dysprosium fluoride are used.

A plurality of baffle plates 3 are normally provided above the crucible 2 in order to prevent the heat inside the crucible 2 from radiating to the condensing part B and to rectify rising metal vapor. One to four pores 6 are provided in the upper part of the skirt 5 so as to maintain equal pressure between the inside of the crucible 2 and the skirt 5 (inside the retort) and the outside. The size of the pores is about 1 to 5 mm.

Cladding plate 8 is connected to cooler 9 to facilitate rapid separation of condensed metal 16 from cooler 9.
provided on the condensation surface of the

The case of performing reductive distillation and distillation purification using the heating furnace of the present invention will be specifically described below.

(1) In the case of reductive distillation, metal oxides or halides are inserted as raw materials. Examples include calcium oxide, barium oxide, calcined dolomite (CaO/MgO), samarium oxide, yttrium chloride, dysprosium fluoride, and europium fluoride.

These metal oxides or halides are reduced to simple metals by a reducing agent.
Reducing agents include calcium, calcium hydride, silicon, lithium, lanthanum, cerium,
Mitsushi Metal (lanthanum, cerium mixture)
etc. are used. These raw materials and reducing agents are used in combination, for example, samarium oxide and Mitsushi metal, calcined dolomite and silicon, neodymium fluoride and calcium, and the like.

If the amount of the reducing agent is too small relative to the raw material metal compound, the metal yield will decrease, and if the amount is too large, the metal yield will improve.

However, if there is too much, the capacity of the crucible will also increase, so the amount of reducing agent is usually 0.9 to 1.5
Selected from a double equivalent range.

The temperature of reductive distillation is usually a high temperature of 1000 to 2000℃, for example, calcium oxide is heated to a temperature of 1100 to 1300℃.
℃, samarium oxide at 1400-1700℃, dysprosium fluoride at 1000-1400℃.

(2) In the case of distillation refining of phase metals Crude metals containing impurities that are charged as raw materials include crude materials such as calcium, barium, magnesium, samarium, and Mitsushi metal.

Although the temperature for distillation purification cannot be determined unconditionally because it varies depending on the vapor pressure of the metal to be separated, it is usually carried out at a temperature 50 to 500°C higher than the melting point of the metal.

Purification by distillation can be divided into two types: One method is to evaporate and condense the main component to obtain the desired product; for example, it is used to purify calcium from calcium containing a trace amount of calcium oxide. The other method is to evaporate the volatile impurities contained in the crude product and obtain the main components remaining in the crucible as the target product, such as removing magnesium from Mitsushi metal and removing calcium from rare earth metals. It will be done.

The crucible 2 is made of a material that can withstand the high temperatures of reductive distillation and is stable against raw metals and metal compounds and reducing agents, such as alumina, graphite, tantalum, molybdenum, and stainless steel. The clad plate 8 is selected from those that can withstand the high temperatures of reductive distillation and are stable against metal vapor. Preferably, metals are excellent in terms of heat conduction (cooling) and workability. For example, tantalum, stainless steel, molybdenum, alumina, etc. are often used.

As the heating device, devices such as high frequency induction heating, low frequency induction heating, and indirect low resistance heating are used.
High frequency induction heating equipment and low frequency induction heating equipment are
Since heat is induced directly into the substance, the heating rate is fast and has the advantage of being easy to control. Among these, high-frequency induction heating devices are excellent in that they can efficiently utilize current for heating.

Note that the preferred degree of vacuum when performing operations such as distillation in a vacuum heating furnace varies depending on the target metal and the type of impurity, but is usually 10 ^-4 ~
It is about 10 ^-2 Torr. Although FIG. 1 shows an example in which the entire heating furnace is evacuated by an exhaust means (not shown), it is also possible to evacuate only the inside of the retort. However, it is even more preferable in the present invention to make the entire heating furnace a vacuum.

(Function) The retort of the present invention is divided into a heating section and a condensing section, and each joint has a seal structure that prevents leakage of metal vapor by inserting a skirt into the packed layer of powder. .

The powder in the packed bed also acts as a buffer and can absorb distortion of the crucible and skirt.

The two can be easily joined by simply inserting, for example, a skirt into the powder from above, as described above. Therefore, each process such as installation, joining, separation, replacement, and removal inside the vacuum furnace can be performed by remote control.

Therefore, after the distillation is finished, the condensing section B and the crucible 2 can be divided and taken out and the next batch can be started immediately without waiting for the retort to cool down.

(effect) The effects obtained by the present invention will be listed below.

(1) It can absorb distortion caused by heat in the joint.

(2) Metal does not condense and solidify at the joint.

(3) Metal vapor does not leak out of the system.

(4) Loading raw materials, taking out products, installing equipment,
Each process such as joining, separating, and replacing can be performed remotely.

(5) Similarly, each of the above steps can be carried out in a short time.

As a result of the above-mentioned effects, it is possible to work at high temperatures, thereby shortening the operating cycle and improving the operating efficiency of the vacuum and heating equipment, which in turn improves production efficiency.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a retort representing one embodiment of the present invention, and FIGS. 2 and 3 are examples of longitudinal sectional views of a conventionally used retort. A... Heating section, B... Condensing section, 1... Retort, 2... Crucible, 3... Baffle plate, 4... Powder filling groove, 5... Skirt, 6... Pore, 7... Sleeve, 8... Cladding plate, 9... Cooler, 10...
... Refrigerant inlet, 11 ... Refrigerant outlet, 12 ... Exhaust port, 13 ... Blocking plate, 14 ... Upper lid, 15 ... Raw material, 16 ... Condensation metal, 17 ... Seal powder,
18...Induction heater.

Claims (1)

[Scope of Claims] 1. A heating furnace consisting of a heating device and a retort that has a heating section that heats metals and/or metal compounds in a vacuum and a condensation section that condenses metal vapor generated by the heating. A heating furnace characterized in that a retort is configured to be freely divisible into a heating section and a condensing section, and a joint section between the two is sealed with a packed bed of powder. 2. The heating furnace according to claim 1, wherein the powder is a powder of a metal, a metal oxide, or a metal halide. 3. The heating furnace according to claim 1 or 2, wherein the particle size of the powder is 0.1 to 500 μm. 4. The heating furnace according to claim 1, wherein the heating device is a high frequency induction heating device. 5. The heating furnace according to claim 1, wherein the crucible is provided with a plurality of baffle plates. 6. The heating furnace according to claim 1, wherein the metal vapor is produced by reductive distillation from a mixture of a metal oxide or halide and a reducing agent. 7. The heating furnace according to claim 1, wherein the metal vapor is produced by distillation from crude metal containing impurities.