JPS62130233A - Manufacture of metallic magnesium - Google Patents

Abstract

PURPOSE:To inhibit the lowering of the internal temp. of a reducing furnace and the crushing of briquettes as starting material by preheating the briquettes with heat transferred from the furnace to a feed tube when the briquettes are fed into the furnace through the tube. CONSTITUTION:Magnesium oxide is mixed with starting material contg. carbon, the mixture is briquetted and the resulting briquettes 6 are charged into a feed tube 7 communicating with a reducing furnace 1. The tube 7 has the 1st feed inlet 13 at a part heated to 700-1,350 deg.C with heat transferred from the furnace 1 to the tube 7. A nonoxidizing gas is fed to the inlet 13 and allowed to flow in the vertical direction so as to prevent evaporated steam from entering the high temp. part. The briquettes 6 charged into the tube 7 are continuously fed into the reducing chamber 4 of the furnace 1 in a mutual contact state. During passing through the tube 7, the briquettes 6 are preheated with heat transferred from the chamber 4. The preheated briquettes 6 are heated in the chamber 4 under reduced pressure to generate magnesium vapor.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing magnesium metal, and more particularly to an improvement in the method for producing magnesium metal by a carbon reduction method.

[Prior Art] As a method for producing metallic magnesium using a carbon reduction method, for example, a method is disclosed in JP-A-57-185938. This method will be described with reference to FIG. 2. Nodular briquettes 101 made of magnesium oxide and carbon are charged from a hopper 102 into a reduction furnace 100 made of a heat-resistant material such as Graphi 1-.

Here, a cooling chamber 104 is connected to the reduction furnace 100 via a wide-spread nozzle 103, and the cooling chamber 104 is connected to a vacuum pump 1.
05, the pressure is reduced. In addition, a heater 106 is provided in the reduction furnace 100, and the temperature in the reduction furnace 100 is 5 to 200.
The pressure is TOrr and the temperature is 1600°C or more. The briquettes 101 react under these conditions, and a reduction reaction occurs in the magnesium oxide to produce magnesium vapor and carbon monoxide gas. Due to the pressure difference between the inside of the reduction furnace 100 and the cooling chamber 104, the mixed gas is ejected from the wide divergent nozzle 103 into the cooling chamber 104 while expanding adiabatically.
Cools quickly. As a result, the magnesium vapor becomes a crown-shaped metal magnesium 108, and the collection plate 10
Collected on 7. Also, the carbon oxide gas is supplied by a vacuum pump 10.
5 and is discharged to the outside.

[Problems to be Solved by the Invention] In the example of the conventional method described above, cold briquettes at room temperature are suddenly supplied to a high-temperature reduction furnace. For this reason, the briquettes are rapidly heated, the moisture or volatile components contained within the briquettes are rapidly evaporated, and the briquettes expand explosively in volume due to their expansion force. The briquettes may not be able to withstand the force and break down into powder. In addition, Brichella I. sometimes fell and collided with the bottom of the reduction furnace, causing it to break into powder.

By the way, solid phase reactions (in some cases liquid-solid phase reactions) are
The reaction rate is highest when each reaction raw material is in close contact with each other. Therefore, when the briquettes become powdered, it becomes difficult for the reaction to occur, and there is a problem in that the reaction raw materials move unreacted from the wide-spread nozzle to the cooling chamber, and dust accumulates in the cooling chamber.

Additionally, the furnace walls and wide-end nozzles of reduction furnaces are generally made of graphite, which suffers from oxidative corrosion caused by moisture that has entered the reduction furnace, causing them to gradually lose weight and eventually cease to function. Ta.

Then, since the cold briquettes at room temperature are put into the reduction furnace, the temperature inside the furnace drops and the reaction stops momentarily, and the generated magnesium vapor and carbon monoxide gas cause a reverse reaction near the surface of the cold briquettes. Another problem was that magnesium oxide was produced.

Further, between the raw material input hopper 102 and the reduction furnace 100, the hopper 102 and the reduction furnace 100 are arranged in order to keep the pressure inside the reduction furnace constant and to prevent magnesium vapor from being deposited in the cold part.
A gate valve 108 is required to shield the air, and this gate valve 108 has the problem of shortening its lifespan because it slides at high temperatures.

The present invention was made in view of these problems.
It prevents the reverse reaction between magnesium vapor and carbon monoxide, prevents the briquettes from turning into powder and moving to the cooling room unreacted, and prevents moisture from entering the high-temperature supply cylinder and reduction furnace. The purpose of the present invention is to provide manufacturing capabilities and methods for magnesium metal that prevent corrosion of furnace materials.

[Means for Solving the Problems] The method for producing metallic magnesium of the present invention includes a mixing step of mixing raw materials containing at least magnesium oxide and carbon to form briquettes, and supplying the briquettes to a reduction furnace. a reduction step in which the briquettes are heated under reduced pressure in the reduction furnace to generate magnesium vapor, and a cooling step in which the magnesium vapor is cooled to metal magnesium by cooling the magnesium vapor using adiabatic expansion. In the method for producing metallic magnesium, a supply cylinder communicating with the reduction furnace is used in the supply step, and the adjacent briquettes are moved within the supply cylinder while maintaining contact with each other and continuously supplied to the reduction furnace. The non-oxidizing gas is supplied in a contact state, and the supply tube is provided with a first supply port through which non-oxidizing gas is supplied to a portion where the temperature is 700 to 1350°C, and a direction away from the reduction furnace from the first supply port and a direction away from the reduction furnace. It is characterized in that the non-oxidizing gas flows in both directions toward the reduction furnace.

The raw materials used in the production method of the present invention include magnesium oxide and carbon used in conventional carbon reduction methods, or magnesium oxide, oxide, and carbon as disclosed in JP-A-57-185938. A material containing at least magnesium and carbon is used. The blending ratio of each component may be exactly the same as conventional ones.

In the mixing step, the raw materials are made into briquettes formed into nodules by a conventionally known method.

In this way, each component is brought into close contact with each other in the briquettes, solid phase or solid-liquid phase reactions occur efficiently, and scattering of raw material particles is prevented. The size of the briquettes is not particularly limited as long as they do not scatter and conduct heat efficiently, but they are generally granular with a diameter of 10 to 2 Qmm.

The greatest feature of the present invention lies in the supply process. In this supply step, a supply cylinder communicating with the reduction furnace is used, and the briquettes are moved within the supply cylinder with adjacent briquettes in contact with each other, and are continuously supplied into the reduction furnace in a contact state.

As a result, unless the briquettes become fine and scattered due to a small explosion of moisture, there are 3+1 briquettes in the reduction furnace from the supply tube except at the beginning of supply! Then it will be in a filled state.

Therefore, when the reduction reaction occurs and the briquettes are consumed and voids are created, the briquettes are gradually dropped due to their own weight and are supplied to fill the voids, and no breakage occurs due to the collision of the falling briquettes.

In the feeding process, the briquettes are continuously fed in this way, so the heat in the reduction furnace is transferred to the briquettes in the supply cylinder by thermal radiation, convection, etc., and as the briquettes in the supply cylinder move, they gradually heated. As a result, the water inside the briquettes gradually evaporates, and the briquettes are prevented from being crushed due to an explosive increase in volume. Moreover, this avoids problems such as a drop in the temperature inside the reduction furnace and a reverse reaction occurring inside the reduction furnace.

By the way, the reaction products in the reduction furnace are gaseous and diffuse into the supply cylinder through the gaps between the briquettes due to concentration diffusion, thermal diffusion, convection, and the like. The inside of the supply cylinder becomes lower in temperature as the distance from the reduction furnace increases, and a reverse reaction in which magnesium vapor and carbon monoxide react may occur at a temperature of 1500 to 1200°C.

The produced magnesium oxide may adhere to the wall surface of the supply cylinder, causing clogging of the supply cylinder. Further, the magnesium vapor may turn into metallic magnesium at a temperature of 800° C. or lower, and similarly adhere to the wall surface of the supply cylinder. Furthermore, if the supply cylinder is made of graphite, etc., approximately 1
In areas where the temperature is 000°C or higher, the wall surface may be 518 eclipsed by moisture.

Therefore, in the present invention, in order to prevent such problems,
Supplying non-oxidizing gas from a first supply port for non-oxidizing gas provided at a temperature of 700 to 1350 ° C. in the supply cylinder,
A flow of non-oxidizing gas is formed in both the direction away from the reduction furnace from the first supply port and the direction toward the reduction furnace. As a result, water vapor generated in the low temperature area above the first supply port is prevented from flowing into the N wet area due to the gas flow in the direction away from the reduction furnace.
Further, the magnesium vapor generated in the reduction furnace is prevented from diffusing to the low temperature section by the gas flow in the direction toward the reduction furnace. Note that the gas flow in the direction toward the reduction furnace can be formed by suction from a vacuum pump connected to cooling air communicating with the reduction furnace. Further, the gas flow in the direction away from the reduction furnace can be formed by suctioning from the first supply port to the first exhaust port provided on the opposite side of the reduction furnace using a vacuum pump.

In the above case, water vapor may remain at the end of the supply cylinder. Therefore, a second
It is desirable to provide a supply port and supply the non-oxidizing gas from there. In this way, water vapor can be prevented from condensing at the end of the supply cylinder, and the generated water vapor can be reliably discharged to the outside of the system.

This non-oxidizing gas is generally an inert gas such as argon, but carbon monoxide gas or carbon dioxide gas can also be used in the present invention. In addition, the non-oxidizing gas is supplied so that the pressure at the first supply port and the pressure at the second supply port are slightly higher than the pressure at the first discharge port, and the pressure at the first supply port is set to the pressure in the reduction furnace. It is sufficient to supply it so that it is slightly higher than the pressure. If the amount of non-oxidizing gas supplied is too large, the non-oxidizing gas will just be wasted.
This is not preferable because the pressure inside the reduction furnace increases and the reaction amount decreases.

The reduction step is a step in which magnesium oxide is reduced to magnesium vapor and carbon monoxide gas, and can be carried out under the same temperature and pressure conditions as conventional methods. Further, as the heating method, either heater heating or arc heating can be used.

The cooling step generally takes place in a cooling chamber that communicates with the reduction furnace through a diverging nozzle. The pressure in this cooling chamber is reduced by a vacuum pump, and the pressure is lower than that in the reduction furnace. Therefore, the generated reaction gas easily moves from inside the reduction furnace to the cooling chamber side. At this time, the reaction gas is ejected through the diverging nozzle while expanding adiabatically, and is cooled to the speed of breathing. As a result, no reverse reaction occurs, and the magnesium vapor becomes metallic magnesium and is collected on a collection plate or the like.

[Operations and Effects of the Invention] In the manufacturing method of the present invention, briquettes are supplied from the supply section to the reduction furnace in a continuous contact state. The heat of the reduction furnace is thus transferred to the feed section and the briquettes are preheated. As a result, the briquettes supplied into the reduction furnace are sufficiently heated, preventing reverse reactions and preventing the temperature inside the furnace from decreasing. Then, rapid evaporation of water and the like does not occur, and the volume of the briquettes is prevented from increasing explosively and being crushed, thereby preventing the briquettes from turning into powder. Therefore, raw materials and thermal energy are used effectively, and almost no dust is generated in the cooling chamber.

Furthermore, the gas flow supplied from the first supply port in the direction away from the reduction furnace prevents water vapor from entering the high temperature section, so corrosion of the graphite wall surface can be reliably prevented. In addition, the gas flow in the direction toward the reduction furnace reliably prevents magnesium vapor from diffusing into the low-temperature region, preventing the formation of magnesium oxide and metal magnesium due to reverse reactions within the supply cylinder, making effective use of energy. This also prevents clogging of the supply cylinder.

Furthermore, if the briquettes are configured to fall by their own weight, the apparatus becomes extremely simple. Moreover, when the volume of the briquettes decreases due to the reduction reaction, the briquettes are continuously supplied by their own weight, and it is possible to avoid crushing the briquettes due to collision with the bottom surface of the reduction furnace.

Furthermore, since sliding parts such as gate valves are removed before they are needed, the life of the device is extended.

[Example] A more detailed explanation will be given below based on specific examples.

FIG. 1 is a partially cutaway front view of a metal magnesium manufacturing apparatus used in an embodiment of the present invention. The reduction furnace 1 is configured such that the inside of the furnace chamber 4 is heated by the heater 3 while being insulated from the outside of the furnace by a heat insulating material 2 .

A hopper 5 for supplying briquettes is arranged above the reduction furnace 1, and the hopper 5 for supplying briquettes is connected to the supply cylinder 7.
It communicates with the furnace chamber 4 by. The furnace chamber 4 communicates with a cooling chamber 9 through a widening nozzle 8 provided on the side wall of the reduction furnace 1, and the cooling chamber 9 is maintained at a predetermined reduced pressure state by a vacuum pump 10.

A metal magnesium collection plate 11 is provided in the cold fJI chamber 9 in alignment with the wide-end nozzle 8, so that the furnace chamber 4
The vapor of metallic magnesium generated inside is cooled by ejection while expanding adiabatically by the wide-spreading nozzle 8, collides with the collecting plate 11 at high speed, and is collected on the collecting plate 11 as a crown-shaped metallic magnesium 12. It looks like this.

The temperature distribution in the vertical direction of the supply cylinder 7 is determined by the temperature (1
An argon gas cylinder 14 is connected to a first supply port 13 provided at a portion where the temperature is 700 to 1350°C. Further, an argon gas cylinder 16 is also connected to a second supply port 15 provided in the room temperature section above the hopper 5 . A vacuum pump 18 is connected to the first discharge port 17 provided in a portion where the temperature is 500 to 700'C. Here, the pressure P1 of the first supply port 13 is 51 Torr.
r, and the pressure P2 at the second supply port is 51 Torr. In addition, the pressure P3 at the first outlet is set to 50 by the vacuum pump.
T orr, and the pressure P4 in the furnace chamber 4 is 50 T.
It is orr. That is, Pl>P3, P2>P3, Pl
>Condition P4 is satisfied.

A method for producing metal magnesium using the apparatus configured as described above will be explained.

First, assume that one briquette 6 is continuously filled into the furnace chamber 4 from the supply tube 7 as shown in FIG. The briquettes 6 are a mixture of magnesium oxide and carbon in an appropriate mixing ratio, and the inside of the furnace chamber 4 is 1800~
The temperature was 2000° C. and the pressure was 5° Torr, and the pressure in the cooling chamber 9 was 1 Torr.

In the furnace chamber 4, the briquettes 6 undergo a reduction reaction to generate a reaction gas consisting of magnesium vapor and carbon monoxide. Then, due to the pressure difference between the furnace chamber 4 and the cooling chamber 9, the reaction If gas is ejected from the wide-spread nozzle 8, expands adiabatically, and is rapidly cooled, whereby metallic magnesium is collected on the (+II collecting plate 11).

Then, the briquettes 6 are successively supplied by their own weight to the areas where the briquettes 6 react and their volume decreases. In addition,
In the case of this example, the inner diameter of the supply cylinder 7 was 50φ, and the supply (falling) speed of the briquettes 6 was 40 cm/hr.

Therefore, the falling distance of each briquette 6 is small, and the briquettes 6 are hardly affected by the impact caused by falling, so that crushing is prevented.

Furthermore, since the heat in the furnace chamber 4 is transmitted into the supply cylinder 7, the briquettes 6 in the supply cylinder 7 are heated from the top to the bottom, and components such as moisture are gradually evaporated. Therefore, the briquettes 6 do not break due to rapid expansion, and can be prevented from becoming powdery.

As a result, steam can be effectively utilized, and problems such as accumulation of dust in the cooling chamber 9 can be prevented.

Furthermore, the briquettes 6 supplied into the furnace chamber 4 are sufficiently heated, the temperature of the furnace chamber 4 hardly decreases, and there is no problem such as a reverse reaction. Therefore, the reduction reaction can proceed smoothly and energy can be used effectively.

Further, the argon gas supplied from the first supply port 13 causes a first flow from the first supply port 13 to the first discharge port 17 and a second flow from the first supply port 13 to the inside of the furnace chamber 4.
A flow is formed. Further, the argon gas supplied from the second supply port 15 forms a third flow from the second supply port 15 toward the first discharge port 17 . Due to this first flow, the water vapor generated in the area below 700 to 1350°C is discharged from the first outlet 17, preventing contact between graphite and water vapor in the area above 700°C, and preventing the wall material from coming into contact with the water vapor. Corrosion can be reliably prevented. In addition, the magnesium vapor that diffuses inside the supply tube 7 due to the second flow flows into the furnace chamber 4.
This suppresses the production of magnesium oxide and metal magnesium due to the reverse reaction in the low temperature range, thereby preventing clogging of the supply cylinder 7. The third flow also eliminates the problem of water vapor remaining in the hopper 5.

[Brief explanation of drawings]

FIG. 1 is a partially sectional front view of a metal magnesium YJ manufacturing apparatus used in one embodiment of the present invention. FIG. 2 is a partially sectional front view of a conventionally used metal magnesium VJ manufacturing apparatus. 1.100... Reduction furnace 4... Furnace chamber 5.10
2... Briquette supply hopper 6.101... Briquettes 7... Supply tube 8.103... Wide end nozzle 9.104... Cooling chamber 10.18... Vacuum pump 11.107...・Collection plate] 2.108...Metal magnesium special v1 applicant Toyota Motor Corporation agent
Patent Attorney Hirodo Okawa Patent Attorney Akio Maruyama

Claims (4)

[Claims] (1) A mixing step of mixing raw materials containing at least magnesium oxide and carbon to form briquettes, a supply step of supplying the briquettes to a reduction furnace, and heating the briquettes under reduced pressure in the reduction furnace. A method for producing metallic magnesium, which comprises: a reduction step of producing magnesium vapor using adiabatic expansion, and a cooling step of producing metallic magnesium by cooling the magnesium vapor using adiabatic expansion. Using a communicating supply cylinder, the adjacent briquettes move within the supply cylinder while maintaining contact with each other and are continuously supplied to the reduction furnace, and the supply cylinder has a portion with a temperature of 700 to 1350°C. A first supply port through which non-oxidizing gas is supplied is provided, and a flow of the non-oxidizing gas is formed from the first supply port in both a direction away from the reduction furnace and a direction toward the reduction furnace. A method for manufacturing magnesium metal, characterized by: (2) A second supply port for non-oxidizing gas is provided in the upper part of the supply cylinder where the temperature is 200°C or less, and the first supply port and the second supply port
A first outlet is provided between the supply ports at a temperature of 500°C or less, and the flow of the non-oxidizing gas is from the second supply port to the first discharge port and from the first supply port to the first discharge port. 2. The method for producing metallic magnesium according to claim 1, wherein the first supply port is connected to the first discharge port and the first supply port is connected to the reduction furnace. (3) The method for manufacturing magnesium metal according to claim 1, wherein the briquettes fall down due to their own weight in the supply cylinder and are supplied into the reduction furnace. (4) The manufacturing method according to claim 1, wherein the reduction furnace is continuously filled with briquettes from the supply tube.