JPS59159945A - Method for producing metallic magnesium and calcium ferrite from dolomite - Google Patents

Abstract

PURPOSE:To produce metallic Mg at a low cost by heating and reducing the compounded material of dolomite clinker and CaC2 in a vacuum, recovering Mg vapor, and recycling the CaC2 produced from the residue. CONSTITUTION:CaC2 is compounded as a reducing agent with dolomite clinker, and the compounded material is heated and reduced in a vacuum in a reducing furnace, then metallic Mg is separated and recovered as a gaseous phase. On the other hand, a carbon material is compounded with a part of the residue in the reducing furnace contg. CaO and carbon and the residue is subjected to arc heating in a carbide furnace, by which CaC2 is produced. The CaC2 is recycled as the reducing agent for said dolomite clinker. The remaining part of the residue of the reducing furnace is charged, if necessary, into a combustion furnace to burn the carbon-contg. material in the residue, thereby making the residue consisting essentially of CaO. Iron oxide is compounded with such residue and the residue is melted in a melting furnace, by which calcium ferrite is produced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing polymetallic magnesium and calcium ferrite from dolomite.

Magnesium is the lightest practical metal, has the highest specific strength and yield strength, has good workability, and has a wide range of uses such as titanium production, alloys, and die-casting. Its use is discouraged due to its high cost compared to aluminum due to the high energy cost of production.

In recent years, reduction smelting methods have been used to produce magnesium by thermally reducing magnesium oxide-containing substances such as dolomite clinker and magshea clinker at high temperatures to recover metallic magnesium. 7-step silicon reduction method to reduce, calcium carbide reduction method to reduce magnesium oxide with calcium carbide,
Various methods have been devised depending on the reducing agent used, such as a carbon reduction method in which magnesium oxide is reduced with a carbon material (coke). However, at present, the ferrosilicon reduction method is often adopted due to the cost of producing metallic magnesium.

In the ferrosilicon reduction method, the reduction reaction is shown by the following formula 2, where the calcium component in the raw material is fixed as calcium silicate, and this by-product is mainly sold as a soil conditioner. There is. This method is still not said to be sufficient in terms of effective utilization of overall production energy, and has problems such as the value of the by-products is not very high.

The present invention solves the above-mentioned problems of the conventional metal magnesium production method, and improves the utilization of thermal energy in the production process, the effective use of raw materials, and the production of high-value by-products. It is an object of the present invention to provide a method for manufacturing magnesium metal that enables reduction of manufacturing costs, that is, a method for manufacturing magnesium metal and calcium ferrite from dolomite.

The method of producing dolomite-metallic magnesium and calcium ferrite according to the present invention involves blending calcium carbide into dolomite clinker as a reducing agent, reducing the mixture by heating under vacuum in a reduction furnace to remove metallic magnesium. Calcium carbide is produced by separating and recovering the phase, blending a carbon material with a part of the residue of the reduction furnace containing calcium oxide and carbon, and heating the mixture with an arc in a carbide furnace. It is characterized by being reused as a reducing agent for clinker, and furthermore, as mentioned above, the mixture of dolomite clinker and reducing agent calcium carbide is heated and reduced under vacuum in a reducing furnace to separate and recover metallic magnesium. At the same time, the residue of the reduction furnace after subtracting the amount to be recycled as calcium carbide as a reducing agent is charged into a combustion furnace, and the carbon-containing substances in the residue are combusted to convert calcium oxide into a main component. This method is characterized by producing a sintered residue, blending it with iron oxide, and melting it in a melting furnace to produce calcium ferrite. The details will be explained below with reference to process diagrams based on examples.

FIG. 1 is a process flow chart showing an outline of the manufacturing process according to the present invention.

The raw material dolomite is used as pre-fired dolomite clinker. Dolomite clinker is 50 in crusher 1
It is crushed to ~100μ, weighed and sent to mixer 2,
Here, calcium carbide produced in a carbide furnace 16 (described later) is blended. The amount of calcium carbide blended is approximately equimolar to the amount of magnesium oxide in the dolomite clinker. The thoroughly stirred and mixed blend is sent to a granulator 6, where less than 10% of a hydrocarbon-based material, preferably a high-carbon material such as tar or pitch, is added as a binder.
It is said to be briquettes with a length of 0 to 20 m.

The briquettes are sent to a drying/preheating device 4, where moisture and volatile matter are removed, preheated to about 6°C (10°C), and charged into a reduction furnace 5.The reduction furnace may be an externally heated vertical continuous reduction furnace, etc. The reduction furnace has a preheating section at the top, a reaction section at the middle, and a cooling section at the bottom.
0°C, preferably 1100-1200°C in the reaction section
The temperature is maintained at 150° C. for at least 2 hours, and the magnesium oxide is reduced according to the following formula and separated as a gas phase.

Ca O@Mg o1c a Cx-+Mg↑+2ca
In the o+2C cooling section, reaction residues containing calcium oxide, carbon, and unreacted substances are removed from the outside by air at a temperature of 00 to 500.
cooled to ℃. The air heated to high temperature is passed through the gas combustion furnace 1.
8 (described later) is used as combustion air.

The amount of heat required in the reduction furnace 5 is the same as that in the carbide furnace 16.
(described later) and some fuel oil (heavy oil, etc.) to make up for the lack of heat in the gas combustion furnace 18.
(described later), approximately 1,600 to 16
It is supplied as a heating heat source that blows hot air at 50°C.

The metal magnesium vapor separated as a gas phase in the reduction furnace 5 as described above is led to the cooler 6 and sent there to 5'oO~9 by gas or electric heating under vacuum again.
It is heated to 50 tons, becomes high purity metal magnesium vapor, and enters the retort cooler 8 to 200 to 30,011 tons.
．． It is cooled to a temperature and recovered as liquid magnesium metal. After a certain amount of the residue containing magnesium oxide, calcium oxide, carbon, etc. deposited in the lower part of the retort distillation furnace 7 is accumulated, it is taken out and sent to the pulverizer 1, where it is repeatedly added to the raw material.

The liquid metal magnet stored in the funnel cooler 8. When the amount of ium reaches a certain level, it is transported to the casting machine 9 and cast, and is manufactured into a metal magnesium ingot.

The above-mentioned reduction furnace 5 and cooler 6 are operated by a vacuum generation equipment 10, and the retort distillation furnace 7 and retort cooler 8 are operated by a vacuum generation equipment 11 at a pressure of 1 to 5 Torr and 10 to 10 Torr, respectively.
It is maintained in a vacuum state of 20 Torr.

The reaction residue containing calcium oxide, carbon, unreacted substances, etc. discharged from the reduction furnace 5 is stored in a storage tank, and a portion (approximately half) of it is blended with carbon material such as coke in a mixer 12. The amount of coke to be blended is adjusted so that the amount of carbon after blending is in a molar ratio of 6 to 3.3:1 to calcium oxide. The mixture containing calcium oxide and carbon as main components that comes out of the mixer 12 is passed through the crusher 13 to a powder of 200 to 500 ml.
The briquettes 9' are pulverized to 20 to 401 m in the granulator 14.

The water is then sent to the dryer/preheater 15 via the storage tank. In the drying/preheating device 15, high-temperature air or exhaust gas generated during the manufacturing process is used to remove some of the moisture and volatile matter in the coke and dry it, as well as preheating the coke to about 600 to 400°C.

The above dry preheated briquettes are then sent to a carbide furnace 16 where they are heated to 1800 to 20
The mixture is heated to a high temperature of 00°C to produce calcium carbonate according to the following formula.

CaO+3C-+ CaC2+ Co ↑The molten calcium carbide discharged from the carbide furnace 16 is transferred to a container such as a ladle, cooled in the atmosphere and solidified, and then crushed to a size of 50 to 100 μ by the crusher 17, and then sent to the mixer described above. returned to 2,
Carbon monoxide gas produced as a by-product in the carbide furnace 16, which is recycled and used as a reducing agent for dolomite clinker, is recovered, dust removed and washed, and then led to the gas combustion furnace 18 for combustion, and the high-temperature combustion gas is sent to the reduction furnace 5. Used as a heat source for heating and other purposes.

As mentioned above, heavy oil and the like are used to replenish the insufficient amount of heat.

Next, among the residues discharged from the reduction furnace 5, the remainder after subtracting the amount to be recycled as the reducing agent calcium carbide as described above is sent to the residue combustion furnace 19, where the carbon and carbon produced in the reduction furnace 15 are removed. Unreacted carbon-containing substances such as calcium carbide are combusted with air to form a residue (clarified) whose main component is calcium oxide.

The residue combustion furnace 19 is equipped with a waste heat boiler, which has a heating capacity of 0 to 4 CI K depending on the calorific value of the high-temperature gas and air recovered by the boiler.
f/,, G water vapor is generated and recovered, most of which is used for power generation.

The fining from the residue combustion furnace 19 is sent to a mixer 20 where it is stirred and mixed with iron oxide.

As the iron oxide, mill scale produced as a by-product in the rolling process of a steel plant can be used, and either ferrous oxide, ferric oxide, or a mixture thereof may be used. The amount of iron oxide to be blended needs to be adjusted depending on its composition, but it is generally desirable to blend it in an equimolar amount to the amount of calcium oxide in the clarifier to be blended.

The weighed iron oxide is sent to the dryer/preheater 21, where it is dried with high-temperature exhaust gas from the residual liquid combustion furnace 19), and after removing moisture and preheating, it is sent to the mixer 20 as described above to be clarified. It is blended with.

The clarified and iron oxide mixture containing calcium oxide as a main component is sent to the melting furnace 22 and heated by electric heating or the like.
~1250°C (ferric oxide in iron oxide is heated to produce calcium ferrite according to the following formula.

CaO+nFe0 −+ CIL*nF60CaO+n
Fe, 93-+ Ca@nFe2O3 Calcium oxide (
Since the fining) and iron oxide are supplied at high temperatures from the residue combustion furnace 19 and the drying/preheater 21, respectively, the amount of heat supplied to the melting reservoir is small.

The calcium ferrite melt produced above is cooled to about 100 to 200°C in a cooler 26, passes through a crusher 24 and a granulator 25, and is manufactured into calcium ferrite briquettes. Calcium-grained ferrite is a highly valuable product as a steelmaking slag agent.

As described above, the method of the present invention uses a novel combination of raw material dolomite and reducing agent calcium carbide to produce metallic magnesium, and also produces by-products using cheap iron oxide generated in steel mills as an auxiliary raw material. We manufacture calcium ferrite with high value as
The effective use of thermal energy in the manufacturing process makes it possible to reduce the production cost of magnesium metal.The method of utilizing thermal energy explained above is just one example, and there are other methods depending on the type of fuel, etc. It goes without saying that combinations of these are possible.

Next, examples of the method of the present invention will be described.

(1) In a tube furnace with an inner diameter of 28 mm and a length of 600 m, a mixture of dolomite clinker and calcium carbide is placed in a briquette with an inner diameter of 10 mm and a length of 15 mm (MgO in the dolomite clinker and CaC7 in the calcium carbide). molar ratio 1:1
) was charged, heated to a temperature of 1100 to 1200° C. under a pressure of 4 to 5 Torr, and reacted for 2 to 3 hours to reduce and recover metallic magnesium. At that time, the balance of raw materials, recovered metal magnesium (powder), and residue was as shown in Table 1.

(2) Using a tube furnace with an inner diameter of 120 mm and a length of 100 mm, the raw material used in Example (1) was heated to a pressure of 5 Torr.
260 g of iron oxide recovered from the steelmaking rolling process was added to 166 g of clarified magnesium, which was oxidized by burning the residue and thoroughly mixed, and then 100 g of magnesium was recovered. It was collected, placed in an alumina crucible, and melted in an electric furnace.

The compositions of refined iron oxide and iron oxide are shown in Tables 2 and 6, respectively. Melting started at 1160°C and almost all of the iron oxide melted at 1255°C.

After cooling the melt, X-ray diffraction analysis revealed that CaO@
Peaks containing FeO and CBOsFezOs as main components were detected, confirming the production of calcium ferrite.

[Brief explanation of the drawing]

FIG. 1 is a process diagram of a method for producing polymetallic magnesium and calcium ferrite from dolomite according to the present invention. Agent Patent Attorney Sanro Kimura

Claims (2)

[Claims] (1) Calcium carbide is blended into dolomite clinker as a reducing agent, and the blend is reduced by heating under vacuum in a reduction furnace to separate and recover metallic magnesium as a gas phase;
In addition, a carbon material is blended with a portion of the residue from the reducing furnace containing calcium oxide and carbon, and the mixture is arc-heated in a carbide furnace to produce calcium carbide, which is recycled as a reducing agent for the dolomite clinker. A method for producing metallic magnesium from dolomite, characterized by: (2) In a reduction furnace, a mixture of dolomite clinker and reducing agent calcium carbide is heated and reduced under vacuum to separate and recover metallic magnesium, and the residue from the reduction furnace is recycled and used as reducing agent calcium carbide. The remaining material after subtracting the carbon content is charged into a combustion furnace, the carbon-containing substances in the residue are burned, and a sintered residue containing calcium oxide as the main component is produced. A method for producing polymetallic magnesium and calcium ferrite from dolomite, which comprises melting dolomite to produce calcium ferrite.