JPH0689418B2 - Continuous magnesium dissolution evaporator - Google Patents

Description

TECHNICAL FIELD The present invention relates to an apparatus for producing fine powder metal oxides. More specifically, it relates to an apparatus for continuously dissolving and evaporating magnesium in the production of magnesium oxide by a vapor phase method.

[Prior Art] It is common practice to dissolve and evaporate magnesium in one pot. For example, in the production of magnesia oxide, a method of melting and evaporating in a single pot has been reported (Japanese Patent Application No. 59-15758).

[Problems to be Solved by the Invention] However, in the conventional method of melting and evaporating in one pot, it is difficult to generate stable and continuous steam, which causes a problem on an industrial production scale.

In other words, the conventional one-pot method is a batch method, which is inferior in productivity and has to be charged with magnesium lumps in a high-temperature portion heated above the boiling point, so that it burns easily like magnesium (oxidizes. (Easy) metal may partially burn in the pot when thrown.

Also, since the temperature is raised and melted in the same pot, when the magnesium lump is charged, the molten metal temperature falls, the magnesium evaporation rate decreases, and fluctuations occur, so a stable magnesium evaporation amount cannot be obtained, and in the subsequent process This may cause problems such as variations in product quality.

Further, conventionally, the state of the inside of the evaporation pan filled with magnesium vapor has been judged by the heating temperature and the state of the vapor coming out from the magnesium vapor blowing nozzle. If the internal pressure can be measured, the state can be grasped, but the measurement is impossible due to blockage due to magnesium coagulation / adhesion to the pressure detection end.

Therefore, it is a technical object of the present invention to continuously and stably supply magnesium vapor and to measure the pressure in the pan.

[Means for Solving the Problems] In order to solve the above technical problems, first, in the first invention, a melting pot for melting magnesium and an evaporation pot for magnesium evaporation are disposed below a holding surface of the molten magnesium. In the portion of, the connection is made by connecting pipes through which molten magnesium metal can pass.

Further, in the second aspect of the invention, the lid equipped with the magnesium vapor blowing nozzle and the inert gas blowing nozzle that also serves as the pressure detecting end is attached to the evaporation pot for evaporation.

Further, in the third invention, the cross-sectional area ratio of the melting pot and the evaporating pot (melting pot cross-sectional area / evaporation pot cross-sectional area) is 1 or more.

Further, in the fourth invention, the cross-sectional area of the connecting pipe is 1/10 to 1/25 of the cross-sectional area of the evaporation pan.

Further, in the fifth invention, the magnesium vapor blowing nozzle attached to the lid of the evaporation pot has a cross-sectional area of 3 cm ² or more.

[Operation] When magnesium is melted and evaporated by the device having the above-mentioned technical means, the magnesium lump is put into the melting pot, but the melting pot is in a state in which the molten metal is held at a temperature of not less than melting temperature and not more than 850 ° C. since the turned on, SF ₆ gas, CO ₂ gas,
Oxidation of magnesium can be prevented by the known flameproofing method using a molten metal surface cover with an inert gas or the like. Also, when the magnesium lump is charged into the melting pot, the molten metal at the same temperature as before charging is sent to the evaporation pan, so the steady state inside the evaporation pan does not change, there is no temperature drop inside the evaporation pan, and it is constant. The evaporation rate of is maintained.

The flow of magnesium melt from the melting pan to the evaporating pan is natural and continuous except when the magnesium lump is put into the melting pan, due to the difference in head volume between the melting pan and the evaporating pan. To be done.

In order to prevent the temperature of the molten metal from dropping due to the sensible heat and the heat of dissolution of the lump of magnesium and the sudden inflow of the molten metal into the evaporating pan as much as possible, the amount of magnesium lump according to the evaporation rate of the evaporating pan should be set continuously. It is desirable to add it to a melting pot.

However, such an operation is extremely difficult in terms of work, so make the cross-sectional area ratio (melting pan cross-sectional area / evaporation pan cross-sectional area) between the melting pot and the evaporation pan as large as possible to make the difference in molten metal holding amount. Prevents the rapid inflow of molten metal from the melting pot to the evaporation pot when the magnesium mass is put into the melting pot. Considering the evaporation rate of the evaporating pan and the magnesium lump introduction interval, etc., if the cross-sectional area ratio is 1 or more, the magnesium lump can be injected without affecting the evaporation rate in the evaporating pan.

In addition, if the cross-sectional area of the connecting pipe that connects the melting pot and the evaporation pot is smaller than 1/25 of the cross-sectional area of the evaporation pot, it causes blockage, and if it is larger than 1/10, the factor of heat diffusion from the evaporation pot to the melting pot. Therefore, an appropriate cross sectional area is required.

Therefore, the cross-sectional area of the connecting pipe is 1/10 of the cross-sectional area of the evaporation pot.
It is preferably within the range of to 1/25.

Measurement of the internal pressure of the evaporation pan is necessary for the operation of this device. There is no problem in low pressure operation, but when the pressure becomes high, the surface of the liquid inside the evaporation pan goes down and the surface of the liquid inside the melting pan rises. When the surface of the water in the evaporation pot comes below the connection pipe, magnesium vapor blows into the melting pot. In order to prevent this dangerous condition, the pressure inside the evaporation pan must be measured so that the surface of the liquid inside the evaporation pan does not go down too much.

For pressure measurement, the inert gas blowing nozzle attached to the lid of the evaporation pan is used as the detection end, the pressure is detected in the cold part of the inert gas pipe, and the pressure in the evaporation pan is estimated in consideration of the pipe pressure loss. If an inert gas is flown and the pipe of the nozzle for blowing the inert gas is heated to a temperature at which magnesium vapor does not solidify, the pressure detection end can be prevented from being blocked.

Also, the evaporative vapor blowing nozzle may be clogged due to the adhesion of oxides and nitrides, but if the cross-sectional area is 3 cm ² or more, there will be almost no adhesion due to sufficient heating, and the evaporating pot internal pressure due to the clog will be sharp. There is no rise and stable operation is possible.

[Embodiment] FIG. 1 shows an embodiment of the present invention. Magnesium is dissolved and evaporated in the apparatus shown in this figure.

Dissolve the magnesium metal in the melting pan 1 beforehand,
Molten magnesium is filled in the evaporation pan 3 through the connection pipe 2, and then the melting pan 1 part is heated to 850 ° C., the connection pipe 2 part is heated to 900 ° C., and the evaporation pan 3 part is heated to 1200 ° C. The heating by heating is performed in the heating furnace 7.

From the inert gas blowing nozzle 5, an argon gas of 0.
2Nm ³ / H Always flow. At a steady state, magnesium vapor is blown out from the magnesium vapor blowing nozzle 4 and burned by oxygen in the air.

As the evaporation proceeds, the amount of magnesium in the system decreases and the molten metal level of the melting pot 1 drops. The evaporation rate of magnesium vapor can be confirmed by measuring the amount of magnesium oxide blown out from the magnesium vapor blowing nozzle 4 and oxidized and burned. It is possible to keep the evaporation rate constant by periodically charging the melting pot 1 with a magnesium metal mass corresponding to this evaporation amount.

The pressure in the evaporation pot 3 is kept constant, and the phenomenon that magnesium vapor blows through the melting pot 1 does not occur.

A small amount of SF ₆ gas is continuously flowed on the surface of the melting pot 1 as an antioxidant. After the operation, there is almost no sludge (magnesium oxide) sinking at the bottom of the melting pot 1.

[Advantages of the Invention] The present invention has the advantages described below.

When melting and evaporating magnesium, the functions are divided into two parts, a melting part and an evaporating part, so that there is no loss of oxidative combustion and continuous melting and evaporation is possible.

Also, make the melting pot larger than the evaporation pot, and change the cross-sectional area of the connecting pipe between the melting pot and the evaporation pot to the cross-sectional area of the evaporation pot.
By setting it to 1/10 to 1/25, it is possible to prevent the temperature drop when charging the magnesium lump into the melting pot from having a large effect on the evaporation rate in the evaporation pot, and to ensure continuous and stable magnesium vapor. Occurrence is obtained.

Furthermore, since the pressure inside the evaporation pan can be detected, the state of boiling magnesium can be grasped.

Further, by setting the cross-sectional area of the steam blowing nozzle to 3 m ² or more, the clogging of the blowing nozzle is prevented, the rise of the internal pressure of the evaporation pot is suppressed, and the blowout of magnesium vapor to the melting pot part can be prevented.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an embodiment of a continuous magnesium melting / evaporating apparatus of the present invention. DESCRIPTION OF SYMBOLS 1 ... Melting pan, 2 ... Connection pipe, 3 ... Evaporating pan, 4 ... Magnesium vapor blowing nozzle, 5 ... Inert gas blowing nozzle, 6 ... Magnesium lump injection port, 7 ... Heating furnace.

Claims (5)

[Claims] 1. A continuous magnesium characterized in that a melting pot for melting magnesium and an evaporation pot for vaporizing magnesium are connected to each other by a connecting pipe through which molten magnesium metal can pass at a portion below a holding surface of the molten magnesium. Dissolution evaporation device. 2. A continuous magnesium dissolving / evaporating apparatus according to claim 1, wherein a lid equipped with a magnesium vapor blowing nozzle and an inert gas blowing nozzle which also serves as a pressure detecting end is attached to the evaporation pot. 3. The continuous magnesium dissolution / evaporation apparatus according to claim 1, wherein the sectional area ratio (dissolving pan cross-sectional area / evaporating pan cross-sectional area) of the melting pan and the evaporation pan is 1 or more. 4. The continuous magnesium dissolution evaporation according to claim 1, wherein the cross-sectional area of the connecting pipe is 1/10 to 1/25 of the cross-sectional area of the evaporation pan. apparatus. 5. The continuous magnesium dissolving / evaporating apparatus according to claim 1, wherein the magnesium vapor blowing nozzle attached to the lid of the evaporation pot has a cross-sectional area of 3 cm ² or more. .