JP4195278B2 - Metallic magnesium melt evaporation apparatus and method for producing high-purity magnesium oxide fine powder using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a metal magnesium melting and evaporating apparatus that can be advantageously used for producing high-purity magnesium oxide fine powder.
[0002]
[Prior art]
A gas phase synthesis method is known as a method for producing a high-purity magnesium oxide fine powder. This vapor phase synthesis method is a method in which magnesium metal is heated to generate magnesium vapor, and this magnesium vapor and an oxygen-containing gas are brought into contact with each other to oxidize magnesium to produce magnesium oxide fine powder. .
[0003]
In order to produce magnesium oxide fine powder industrially by a gas phase synthesis method, an apparatus capable of continuously generating magnesium vapor over a long period of time is required.
[0004]
The equipment for continuously generating magnesium vapor includes a metal magnesium melting pot (also called a melting pot) for heating and melting metal magnesium, and magnesium evaporation for heating and evaporating molten magnesium. 2. Description of the Related Art A metal magnesium melting / evaporating apparatus having a structure in which a pan is connected with a heat-resistant pipe (also called a connection pipe) is known (see Patent Document 1). In this metal magnesium fusion evaporator, metal magnesium is supplied to the evaporation pan as molten magnesium, so that the temperature of the molten magnesium in the evaporation pan can be maintained at a high temperature, so that magnesium vapor can be generated efficiently and continuously. Become.
[0005]
[Patent Document 1]
JP-A-2-307822 [0006]
[Problems to be solved by the invention]
The above-mentioned metal magnesium melting and evaporating apparatus can be said to be a useful apparatus for efficiently and continuously generating magnesium vapor. However, it has been found that there are some problems when the magnesium oxide fine powder is produced by actually using the above-mentioned metal magnesium melt evaporation apparatus. One of them is that the amount of heavy metals, especially heavy metals with higher boiling point than magnesium (eg, iron, nickel, chromium) tend to increase with the progress of production time, especially in magnesium oxide fine powder produced. There is a problem.
[0007]
Therefore, as a result of the research conducted by the present inventor to determine the cause of the increase in the amount of heavy metal, the main cause is the high boiling point heavy metal in the magnesium metal, which is a raw material for producing magnesium oxide fine powder. It was found that the high boiling point heavy metal is likely to be mixed into the magnesium vapor as the accumulated amount gradually accumulates in the evaporation pan of the metal magnesium melting evaporator. Therefore, the object of the present invention is to develop a metal magnesium melting and evaporating apparatus that can generate magnesium vapor with a small amount of heavy metal mixed over a long period of time, and continuously produce high-purity magnesium oxide fine powder over a long period of time. It is to provide a technology that can do this.
[0008]
[Means for Solving the Problems]
The present invention relates to a metal magnesium melting pan having a metal magnesium inlet at the top and a molten magnesium outlet at the bottom of the side, a heat resistant pipe connected to the molten magnesium outlet of the melting pan, and the heat resistant pipe The molten magnesium inlet connected to the other end of the bottom is provided at the lower part of the side, and the upper part is a magnesium evaporation pot provided with a magnesium vapor outlet, and the distance from the molten magnesium inlet to the bottom of the evaporation pot Is longer than the distance from the molten magnesium take-out port to the bottom of the melting pan.
[0009]
In the metal magnesium melting and evaporating apparatus of the present invention, it is preferable that an opening for opening and closing the molten magnesium is provided at the bottom of the evaporating pan.
[0010]
The present invention further uses the above-described metal magnesium melting and evaporation apparatus, throwing metal magnesium into the metal magnesium inlet of the melting pan, injecting magnesium vapor from the magnesium vapor outlet of the evaporation pan, and then containing the magnesium vapor and oxygen There is also a method for producing high-purity magnesium oxide fine powder in which magnesium is oxidized to produce magnesium oxide fine powder by contacting with gas.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
The metal magnesium melting / evaporating apparatus of the present invention and a method for producing high-purity magnesium oxide fine powder using the apparatus will be described with reference to the accompanying drawings.
[0012]
FIG. 1 is a diagram showing an example of a metallic magnesium melting and evaporating apparatus according to the present invention. A metal magnesium melting and evaporating apparatus 10 in FIG. 1 includes a lid 13 having an inlet 11 for metal magnesium and an inlet 12 for an antioxidant gas for preventing oxidation of the metal magnesium, and taking out molten magnesium at the lower part of the side surface. Introduction of molten magnesium connected to the other end of the heat resistant pipe 17, and a heat resistant pipe 17 connected to the molten magnesium outlet 14 of the molten pot It consists of a pan portion 19 having a mouth 18 at the lower side of the side, and a magnesium evaporating pan 23 comprising a lid portion 22 having a magnesium vapor outlet 20 and an inert gas inlet 21, and introducing molten magnesium into the evaporating pan 23. distance from the mouth to the bottom (L _2), rather than the distance to the bottom of the molten magnesium outlet of the melting pot 16 (L ₁₎ Kuna' to have. Here, the distance (L ₂ ) from the molten magnesium inlet of the evaporating pot to the bottom means the distance between the broken line A extending horizontally from the center of the molten magnesium inlet and the deepest part of the evaporating pot. . Further, the distance (L ₁ ) from the molten magnesium outlet to the bottom of the melting pot 16 means the distance between the broken line B extending in the horizontal direction from the center of the molten magnesium outlet and the deepest part of the melting pot. .
[0013]
The high boiling point heavy metal accumulated in the evaporating pan 23 generally has a specific gravity greater than that of magnesium. For this reason, high boiling point heavy metals tend to mainly stay on the bottom side of the evaporation pot 23. Accordingly, by making the distance (L ₁ ) from the molten magnesium inlet 18 to the bottom of the evaporating pot 23 longer than the distance (L ₂ ) from the molten magnesium outlet 14 to the bottom of the melting pot 16, the evaporating pot 23 The amount of high-boiling heavy metals that can be retained on the bottom side of the steel increases, and the amount of heavy metals mixed into the magnesium vapor can be reduced over a long period of time.
[0014]
The distance (L ₂ ) from the molten magnesium inlet of the evaporating pot 23 to the bottom is in the range of 1.2 to 1.8 times the distance (L ₁ ) from the molten magnesium outlet of the melting pot 16 to the bottom. It is preferable.
[0015]
Although there is no restriction | limiting in particular in the shape of the melting pot 16 and the evaporation pot 23, It is preferable that the melting pot 16 is a flat bottom, and it is preferable that the evaporation pot 23 is a round bottom. The cross-sectional shape of the melting pot 16 is preferably rectangular, and the cross-sectional shape of the evaporation pot 23 is preferably round.
[0016]
The size of the melting pot 16 and the evaporating pot 23 is preferably such that the cross-sectional area ratio (melting pot cross-sectional area / evaporating pot cross-sectional area) of the melting pot and the evaporating pot is 1 or more, particularly 2-8. The size of the heat-resistant pipe 17 is preferably in the range of 1/10 to 1/25 of the cross-sectional area of the evaporating pot 23.
[0017]
Figure 2 is a diagram showing another example of a metallic magnesium melt evaporator. The metal magnesium melting and evaporating apparatus 30 in FIG. 2 includes a lid 33 having an inlet 31 for metallic magnesium and an inlet 32 for an antioxidant gas for preventing oxidation of metallic magnesium, and taking out molten magnesium at the lower side of the side. Introduction of molten magnesium connected to the other end of the heat-resistant pipe 37, a heat-resistant pipe 37 connected to the molten magnesium take-out port 34 of the metal pot, and a molten magnesium 36 consisting of a pot portion 35 having a mouth 34. It consists of a pan portion 39 provided with a mouth 38 at the bottom of the side surface, and a magnesium evaporating pan 43 comprising a lid portion 42 provided with a magnesium vapor outlet 40 and an inert gas inlet 41, and at the bottom of the evaporating pan 43, A molten magnesium outlet 45 that can be opened and closed by a valve 44 is provided.
[0018]
In the metal magnesium melting and evaporating apparatus of FIG. 2, the high boiling point heavy metal staying at the bottom side of the evaporating pan 43 can be extracted to the outside intermittently or continuously together with the molten magnesium. Can be reduced.
[0019]
Next, the manufacturing method of the magnesium oxide fine powder of this invention is demonstrated.
FIG. 3 is a view showing an example of an apparatus for producing fine magnesium oxide powder using the metallic magnesium melting and evaporating apparatus according to the present invention.
In FIG. 3, the magnesium oxide fine powder manufacturing apparatus includes the metal magnesium melting / evaporating apparatus 10, the magnesium oxidizing apparatus 50, the heat exchanger 51, the bag filter 52, and the hopper 53 shown in FIG. 1.
[0020]
Metal magnesium 54 as a raw material is charged from the metal magnesium inlet 11 of the melting pot of the metal magnesium melting evaporator 10 and heated to the magnesium melting temperature in the melting pot 16 to become molten magnesium 55. Molten magnesium 55 is stored in the evaporating pan 23 through the heat-resistant pipe 17, and further heated to a temperature equal to or higher than the boiling point of magnesium in the evaporating pan to generate magnesium vapor.
[0021]
When producing magnesium vapor, an antioxidant gas is supplied into the melting pot 16 from the antioxidant gas inlet 12, and an inert gas is supplied into the evaporation pot 23 from the inert gas inlet 21.
[0022]
As the antioxidant gas, sulfur hexafluoride gas, carbon dioxide gas, neon gas, argon gas, krypton gas, xenon gas, and radon gas can be used. Among these gases, sulfur hexafluoride gas is particularly preferable.
[0023]
As the inert gas, helium gas, neon gas, argon gas, krypton gas, xenon gas, and radon gas can be used. Among these gases, argon gas is particularly preferable.
[0024]
Magnesium vapor, together with the inert gas introduced from the inert gas inlet 21 of the evaporating pan, passes through the magnesium vapor outlet 20 of the evaporating pan and is sent to the magnesium vapor outlet 61 of the magnesium oxidizer 50. An oxygen-containing gas whose partial pressure is adjusted with an inert gas such as argon gas is introduced into the magnesium oxidizer 50 from an oxygen-containing gas introduction pipe 62. By bringing the magnesium vapor and the oxygen-containing gas into contact with each other, the magnesium is oxidized into a magnesium oxide fine powder 56.
[0025]
In the magnesium oxidizer 50, the magnesium vapor injection port 61 is disposed at the bottom and the oxygen-containing gas introduction pipe 62 is disposed at the side so that the magnesium vapor and the oxygen-containing gas are in contact with each other substantially vertically. The magnesium oxide fine powder take-out port 63 is provided vertically above the magnesium vapor injection port 61 so that the magnesium oxide fine powder 56 can be taken out on the flow of an inert gas introduced together with the magnesium vapor.
[0026]
The internal temperature of the magnesium oxidizer 50 (that is, the oxidation temperature of magnesium) is preferably 1200 to 2000 ° C. However, since the oxidation reaction of magnesium is an exothermic reaction, the magnesium oxidation is accompanied with the production of the magnesium oxide fine powder. The internal temperature of the device tends to increase. For this reason, in the magnesium oxidizer 50 of FIG. 3, it is partially covered by a cooling outer pipe 66 having a cooling air inlet 64 and a cooling air exhaust 65, and the cooling air inlet 64 By introducing cooling air, the internal temperature of the magnesium oxidizer 50 can be adjusted.
[0027]
The particle diameter of the magnesium oxide fine powder produced by the magnesium oxidizer 50 is the ratio of the magnesium vapor and the inert gas introduced into the magnesium oxidizer and the introduction rate thereof, or the oxygen content introduced into the magnesium oxidizer. It can be adjusted by the oxygen concentration of the gas and its introduction rate.
[0028]
In the magnesium oxidation apparatus in which the magnesium vapor injection port 61 is arranged at the bottom like the magnesium oxidation apparatus 50 in FIG. 3, metal magnesium or a magnesium compound (eg, magnesium oxide) is deposited around the magnesium vapor injection port 61. Thus, the amount of magnesium vapor introduced may vary. For this reason, the magnesium oxidizer 50 is provided with an internal observation window 67 on the side and a grinding device 68 for scraping the magnesium oxide deposited on the magnesium vapor injection port 61 in parallel with the bottom.
[0029]
The grinding device 68 includes an arm 70 provided with a grinding plate 69 at the tip, and a cylinder 71 for extending and retracting the arm in parallel with the bottom of the magnesium oxidation device. In magnesium oxide device of Figure 3, the internal observation window 67 and the grinding device 68, in their respective hollow housing 72 are disposed integrally incorporated in a window and grinding for internal observation There is no restriction | limiting in particular in arrangement | positioning of an apparatus. The operating speed of the arm 70 of the grinding device 68 is appropriately adjusted in consideration of the deposition state of metallic magnesium or magnesium compound observed in the internal observation window 67. Metal magnesium and magnesium compound scraped by the grinding device 68 can be taken out to the outside through an opening (cleaning window) 73 provided on the side of the magnesium oxidation device.
[0030]
The magnesium oxide fine powder produced by the magnesium oxidizer 50 is sent to the heat exchanger 51 through the magnesium oxide fine powder take-out port 63. The magnesium oxide fine powder cooled by the heat exchanger 51 is collected by the bag filter 52 and temporarily stored in the hopper 53.
[0031]
Magnesium oxide fine powder produced by gas phase synthesis has high activity, and thus may adsorb carbon dioxide and water vapor in the air when in contact with air. For this reason, it is preferable to re-fire the magnesium oxide fine powder stored in the hopper at a temperature of 500 to 1100 ° C. before shipment.
[0032]
【The invention's effect】
In the metal magnesium melt evaporation apparatus of the present invention, it is possible to generate magnesium vapor with a small amount of mixed metal over a long period of time. Therefore, by using the metal magnesium melting / evaporating apparatus of the present invention for production of magnesium oxide fine powder, high-purity magnesium oxide fine powder can be continuously produced over a long period of time.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of the configuration of a metallic magnesium melting and evaporating apparatus according to the present invention.
FIG. 2 is a diagram showing another example of the configuration of the metal magnesium melting and evaporating apparatus.
FIG. 3 is a diagram showing an example of the configuration of an apparatus for producing magnesium oxide fine powder using a metal magnesium melting and evaporating apparatus.
[Explanation of symbols]
10, 30 Metal Magnesium Melting Evaporator 11, 31 Metal Magnesium Inlet 12, 32 Antioxidant Gas Inlet 13, 33 Lid Part 14, 34 Molten Magnesium Outlet 15, 35 Pan Part 16, 36 Melting Pan 17, 37 Heat Resistance Pipes 18, 38 Molten magnesium inlet 19, 39 Pot part 20, 40 Magnesium vapor outlet 21, 41 Inert gas inlet 22, 42 Lid part 23, 43 Evaporation pot 44 Valve 45 Molten magnesium outlet 50 Magnesium oxidation device 51 heat exchanger 52 bag filter 53 the hopper 54 metal magnesium 55 molten magnesium 56 magnesium oxide magnesium oxide powder 61 magnesium steam injection ports 62 oxygen-containing gas introduction pipe 63 a fine powder outlet 64 the cooling air inlet port 65 cold却用air outlet 6 Cooling outer tube 67 inside the observation window 68 grinding apparatus 69 grinding plate 70 the arm 71 cylinder 72 housing 73 opening (cleaning window)

Claims (3)

  A metal magnesium melting pot having a metal magnesium inlet at the top and a molten magnesium outlet at the bottom of the side, a heat resistant pipe connected to the molten magnesium outlet of the melting pot, and the other end of the heat resistant pipe The lower part of the side is provided with a molten magnesium inlet connected to the section, and the upper part is a magnesium evaporating pot equipped with a magnesium vapor outlet, and the distance from the molten magnesium inlet to the bottom of the evaporating pot is A metal magnesium melting and evaporating apparatus characterized in that it is longer than the distance from the molten magnesium outlet of the pan to the bottom.   2. The molten metal magnesium evaporation apparatus according to claim 1, wherein a molten magnesium discharge port that can be opened and closed is provided at the bottom of the evaporation pot. Using the metal magnesium melting and evaporation apparatus according to claim 1 or 2, metal magnesium is introduced into a metal magnesium introduction port of a melting pot, magnesium vapor is injected from a magnesium vapor outlet of the evaporation pot, and then the magnesium vapor and oxygen A method for producing a high-purity magnesium oxide fine powder in which magnesium is oxidized to produce a magnesium oxide fine powder by contacting with a contained gas.

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