JPH0641654A - Method for smelting magnesium - Google Patents

Abstract

PURPOSE:To efficiently smelt metallic Mg by mixing aluminum dross produced in the melting of A1 with dolomite, heating, reducing the dolomite, vaporizing the metallic Mg, cooling and recovering. CONSTITUTION:The aluminum dross 1 (5mm or smaller grain diameter) produced by melting the A1 is mixed in the dolomite 2 and filled in a retort 3. This retort 3 is charged into a heating furnace 9 and the pressure in the retort 3 is reduced and the filling part 10 of the mixed raw material is heated at abut 1100 deg.C from the outer part. Then, the dolomite 2 is reduced by the A1 component, and the vaporized metallic Mg 4 is introduced to a cooling part 5 and solidified. CaO-Al2O3 produced through the reaction remains in an inserting part 10 partitioned with a shield plate 6. By this method, the high quality of the metallic Mg is recovered and also, the chemically stable CaO.Al2O3 is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for smelting magnesium with aluminum ash generated in refining aluminum.

[0002]

2. Description of the Related Art As a conventional magnesium smelting method,
There are a molten salt electrowinning method and a thermal reduction method.The molten salt electrowinning method is IG method using anhydrous MgCl ₂ and Alcan (Alca
The n) method and the Dow method using MgCl ₂ 1.25H ₂ O are available. The thermal reduction method includes an external thermal reduction method (Pigeon / Pidgeon method) and an internal thermal reduction method. Of the above-mentioned methods, the Pigeon method, which is a discontinuous operation but has simple processes, low equipment cost, and high magnesium ingot quality, will be described as an example.

The Pigeon method uses a special steel retort,
The reaction formula is shown below by the method of reducing calcined dolomite (MgO.CaO) with ferrosilicon. 2MgO · CaO + Si (xFe) = 2Mg (g) + 2CaO · SiO ₂ + xFe Magnesium evaporates by high temperature heating, moves to the cooling side of the retort and solidifies, and is separated from (CaO · SiO ₂ ) by slag and taken out. The slag (CaO ・ SiO ₂ ) is discarded, but (CaO) decomposes and collapses when water is added, so not only is disposal as industrial waste extremely limited, but it is also refined by refining. There is a problem that a large amount occurs.

On the other hand, when aluminum is melted, a large amount of aluminum dross is generated. Armidoros is a mixture of aluminum metal mass, aluminum powder and aluminum oxide. Generally, an aluminum dross is crushed by a hammer mill or a ball mill, and sieved to recover a large amount of aluminum metal lumps and a portion containing a large amount of aluminum powder, and remelting to recover aluminum.

On the other hand, if the particle size is small, there is a problem that the metal recovery rate is low because it burns during the temperature rise during the recovery of metallic aluminum due to melting, so it is usually used as a slag composition modifier in the steelmaking process. Is consumed. The rest that is not consumed is disposed of as a deposit, but when the deposited fine aluminum powder hits the rain, hydrogen gas is generated, and there is a risk of explosion if there is an ignition source nearby.
Further, there is a problem that the aluminum nitride in the aluminum dross decomposes to generate an ammonia odor. Therefore,
Prior to the dumping and depositing, aluminum dross was soaked in water to remove the generated gas, and then the landfill disposal was carried out, but this was not enough.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks of the conventional example. By using aluminum dross as a reducing agent for dolomite, high quality metallic magnesium is recovered and slag generated is generated. It is to provide a magnesium smelting method that can add utility value to slag by changing it to one with good stability.

[0007]

[Means for Solving the Problems] The magnesium smelting method of the present invention comprises: mixing dolomite (2) with aluminum dross (1) produced by dissolution of aluminum and heating the dolomite (2) to an aluminum component. And reduce it to evaporate the metallic magnesium (4), and guide the evaporated metallic magnesium (4) to the cooling part (5) to solidify the metallic magnesium (4).
Characterize things. As a result, not only MgO can be efficiently reduced to obtain metallic Mg, but also Ca produced simultaneously
O.Al ₂ O ₃ is chemically very stable unlike conventional examples and can be used as a building material. Further, since a large amount of Al ₂ O ₃ is contained in aluminum dross, the melting point of the raw material can be lowered and the reduction temperature can be lowered. or,
Since the surface of almidross is covered with a thin film of aluminum oxide, unlike aluminum fine metal powder,
There is an advantage that the explosive reaction rate that occurs when metal powder is used is moderated to become a gradual reaction, the reaction is easily controlled, and the magnesium yield can be increased.

A second aspect of the present invention defines the grain size of aluminum dross, which is characterized in that "the grain size of aluminum dross (1) is 5 mm or less in diameter". This made it possible to effectively utilize the aluminum dross, which was not suitable for recovering metallic aluminum and was consumed in the steelmaking process.

[0009]

The present invention will be described in detail below with reference to the illustrated embodiments. Figure 1 is a cross-sectional view showing the reduction process of magnesium by the Pigeon method. Dolomite (2) is mixed with aluminum dross (1) produced by melting aluminum, and retort
Enclose in (3). Almidross (1) is crushed by a hammer mill or a ball mill and then sieved. In the present embodiment, the particle size of sieving may be 5 mm in diameter {of course, finer than this, for example, 30 mesh (0.5 mm)} is the standard, and diameter of 5 mm {30 mesh is 30 mesh} or more It is sent to redissolution and used to recover metallic aluminum. If the diameter is 5 mm or less, the particle size is usually too small and if it is used for remelting metallic aluminum, it burns during the temperature rise, and the metal recovery rate deteriorates, making it difficult to use. Therefore, the aluminum dross (1) mixed in the dolomite (2) usually has a diameter of 5 mm or less. However,
It is possible to use even those with 30 mesh or less depending on the case.

Typical components of aluminum dross (1) are as follows. The main component is metallic aluminum, followed by Al ₂ O ₃ . Other than metal Si and Si
Contains oxides and contains C, Na, K, Cl, N, M as impurities
It contains g, Fe, Cu, Zn, etc., and the larger the particle size, the higher the metallic aluminum content. Composition table of Almidross (Table 1) Component analysis value Unit AB Al-Au metal% 65.7 61.6 Al-Oxide% 15.7 21.5 Si-Au metal% 6.1 5.9 Si-Oxide% 3.5 2.2 C% ---- - Na% 0.4 0.3 K% 0.2 0.1 Cl% 0.6 0.6 N% 1.1 1.2 Mg% 3.0 3.0 Fe% 1.3 1.3 Cu% 1.4 1.4 Zn% 0.4 0.4

The retort (3) is made of, for example, (25Ni15Cr) heat-resistant steel, and is an expensive one manufactured by a centrifugal casting method. The filling amount of the mixed raw material of dolomite (2) and aluminum dross (1) is usually several hundred kg weight, and the retort (3) filled with the mixed raw material is inserted into the heating furnace (9) to fill the raw material.
Heat (10) from outside. An example of heating temperature is 1,100 ℃
It is a degree. The retort (3) is used repeatedly. Dolomite (2) is reduced in the retort (3) by the following reaction. 3MgO ・ CaO ＋ 2Al ＝ 3Mg (g) ＋ 3CaO ・ Al ₂ O ₃ ……… (1) Metallic magnesium reduced by aluminum component (4)
Evaporates, and the evaporated metal magnesium (4) is guided to the cooling part (5) of the retort located outside the furnace, and this cooling part (5)
At this point, metallic magnesium (4) is cooled and solidified. (6) is a shielding plate, (7) is an exhaust port for removing air in the retort (3), and (8) is a water cooling jacket wound around the outer periphery of the cooling part.

[0012] A mixed raw material of dolomite (2) and aluminum dross (1) is filled in a retort (3), the retort (3) is inserted into a heating furnace (9), and while reducing the pressure in the retort (3), The raw material filling part (10) is externally heated at 1,100 ° C. The reaction proceeds according to the above reaction formula (1), and the reduced metal Mg is vaporized at an intrinsic vapor pressure and introduced into the cooling part (5) to be cooled and solidified. The (CaO.Al ₂ O ₃ ) produced by the reaction remains in the insertion part (10) of the retort (3) partitioned by the shielding plate (6). When a certain period of time has passed and the reaction has progressed to a certain extent and the yield has dropped, the work is terminated, the retort (3) is withdrawn from the furnace (9), metal Mg is recovered, and new raw materials are recharged to perform the work. To resume.

FIG. 2 is a comparison table of equilibrium vapor pressures when dolomite (2) is reduced by ferrosilicon (Fe-Si) and when dolomite (2) is reduced by aluminum dross (1). It can be seen that the equilibrium vapor pressure is higher in the reduction by (1) than in the reduction by ferrosilicon (Fe-Si). As a result, the temperature can be lower than the reduction temperature of ferrosilicon (Fe-Si), which can reduce energy cost and wear of the retort (3). Also, aluminum dross (1)
The fact that the equilibrium vapor pressure is higher in the reduction by the method than in the reduction by ferrosilicon (Fe-Si), on the contrary, the reduction can be performed at a low vacuum degree.

By the way, compared with the reduction by ferrosilicon (Fe-Si), the reduction by aluminum dross (1) is 100 to 100%.
The reaction temperature can be kept low at about 150 ℃. Therefore, the wear of the retort (3) is also reduced, and the life can be extended.

FIG. 3 shows ferrosilicon (Fe) at 1,200 ° C.
-Si) and aluminum dross (1) Mg yield comparison table, the horizontal axis is the reduction time (min), the vertical axis is the Mg yield (percentage). For example, comparing the reduction time of 30 minutes in Fig. 3, ferrosilicon (Fe-S
While i) is about 62%, aluminum dross (1) shows a high yield of almost 90%. In other words, the reduction rate of aluminum dross (1) is faster. This is because the melting point of the raw material is lowered due to the presence of Al ₂ O ₃ .

Below, the reaction equilibrium vapor pressure (mmHg) of Al and Si
The comparison table of is shown. From the above, it is understood that when aluminum dross containing a large amount of Al is used as the reducing agent, a large amount of Mg can be reduced at a lower temperature than when Si is used as the reducing agent. From actual experiments, aluminum dross was used so that the amount of aluminum was 1.1 times the equivalent amount of MgO in reaction formula (1). Incidentally, since the surface of the aluminum powder in the aluminum dross (1) used for the reduction is oxidized, the reaction rate is conveniently controlled,
It is possible to increase the yield of Mg.

[0017]

INDUSTRIAL APPLICABILITY The present invention uses aluminum dross as a reducing agent for dolomite. Since aluminum dross contains a large amount of Al ₂ O ₃ , it is necessary to lower the melting point of the raw material. Has the advantage that the reduction temperature can be lowered, and the vapor pressure of Mg is higher than that of Si by using aluminum as a reducing agent, which effectively reduces MgO and reduces the metal content. You can get Mg.
Since the surface of the aluminum powder in the aluminum dross used for the reduction is oxidized, the reaction rate can be conveniently controlled and the yield of Mg can be increased. Further, CaO.Al ₂ O ₃ produced at the same time is chemically very different from the conventional example and has an advantage that it can be used as a building material.
Also, if the grain size of aluminum dross is 5 mm mesh or less,
It is not suitable for the recovery of metallic aluminum, and has the advantage that the aluminum dross consumed in the steelmaking process can be effectively utilized.

[Brief description of drawings]

FIG. 1 is a sectional view of a retort and a furnace used in the present invention.

FIG. 2 is a comparative graph of equilibrium vapor pressures of the present invention and a conventional example.

FIG. 3 is a comparison graph of changes in reduction time and yield between the present invention and a conventional example.

[Explanation of symbols]

 (1)… Aluminum dross (2)… Dolomite (4)… Magnesium metal (5)… Cooling part

Claims (2)

[Claims] 1. Dolomite is mixed with aluminum dross generated by dissolution of aluminum and heated, and dolomite is reduced by an aluminum component to evaporate metallic magnesium, and the evaporated metallic magnesium is guided to a cooling portion to produce metallic magnesium. A magnesium smelting method characterized by solidifying. 2. The magnesium smelting method according to claim 1, wherein the grain size of the almidross is 5 mm or less.