JPS6187832A - Refining method of aluminum by blast furnace method - Google Patents

Abstract

PURPOSE:To produce an Al-Fe-Si alloy having a high Al content by charging an alumina-contg. raw material and calcia raw material into a blast furnace forming a combustion region and reduction region and dropping the same as the liquefied material co-contg. calcic material and alumina in the reduction region at a specific temp. or above. CONSTITUTION:Coke having 10-15mm grain size is supplied into the vertical type blast furnace and oxygen is blown through plural feed pipes to form plural high-temp. combustion regions at intervals and to form the high-temp. reduction zone of 2,000-2,100 deg.C above the combustion zones or at the intermediate thereof. The alumina raw material such as bauxite and CaO, CaCO3, etc. are briquetted to attain 0.2-0.6 CaO/Al2O3 molar ratio and are charged into the furnace or the coke, CaO, Al2O3 raw materials are charged in the laminar state into the furnace. The CaO and Al2O3 co-melt and liquefy and pass through the reduction region at the high temp. The Fe and Si are also reduced simultaneously. The Al-Fe-Si alloy having a high Al content is thus produced in the blast furnace.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an aluminum smelting method using a blast furnace method.

[Prior art]

Aluminum is a basic metal material second only to iron, and its demand is increasing at a high rate every year. However, in recent years, the rise in energy costs on a global scale has made it extremely difficult to manufacture aluminum in areas with high electricity costs, such as Japan, and this is causing extremely serious obstacles to the industrial structure. In addition, the area in which low-cost hydroelectric power sources can be located is expected to become narrower around the world in the future for aluminum smelting, which is an important industrial material. The development of energy-saving, low-cost manufacturing methods is becoming an urgent issue.

In recent years, as a way to overcome problems in traditional electric power-based aluminum smelting methods.

BACKGROUND ART An aluminum smelting method using a blast furnace method, in which raw material alumina is reduced with a carbon material using a countercurrent moving bed blast furnace, has been studied. In this method, a packed bed containing raw material alumina and a carbon material acting as a fuel and a reducing agent is formed in a blast furnace, and the following combustion reaction (1') and reduction reaction (2' ) at the same time.

C+1/202→2CO(1') A Q 203 + 3 C→2 A Q + 3 C
The reduction of O(2'), that is, aluminum oxide (alumina) shown by the equation (2') is carried out using the heat of oxygen combustion of the carbon material shown by the equation (1') as a heat source.

In addition, the blast furnace is a countercurrent moving bed type, in which oxygen gas is blown from the bottom, reduction products are taken out from the bottom of the blast furnace, and feedstock is charged from the top accordingly, and the entire packed bed is placed at the bottom. It moves downward while coming into countercurrent contact with the combustion gas generated in the

The above-mentioned reactions (1') and (2) can be carried out using such a blast furnace method.
’) When performing aluminum smelting at the same time, there are various technical problems that need to be solved in terms of economy and operability.
Its practical application is extremely difficult.

Conventionally, it has been thermodynamically impossible to produce pure aluminum by reducing pure alumina as described above, so there are two practically possible smelting methods using alumina as a raw material.
Either a mixture of aluminum/aluminum carbide is produced at a high temperature of 400°C or higher and the aluminum is separated by distillation, or a crude alloy of aluminum/silicon or iron is produced at a high temperature of 1900°C or higher, and the crude alloy is separated from the mixture by distillation. Research is being conducted on methods of refining aluminum into aluminum products.

By the way, in the smelting method in which alumina is made into an aluminum alloy with silicon or iron, the activity of aluminum decreases because aluminum is alloyed with silicon or iron.
It has the advantage of relaxing the thermodynamic conditions for metal formation and at the same time suppressing volatile components such as aluminum vapor, AQ 20, and SiO. This can be said to be the most expensive method. This method can be carried out using an electric furnace such as an arc furnace, but
In this case, since a large amount of electricity is required, economic benefits cannot be obtained, and economic benefits can only be obtained by implementing the blast furnace method. Many difficulties arise compared to implementation by law. In the case of implementation using the blast furnace method, the following five-order basic reactions are adopted.

C+1/202→CO(1) AQ 203+Ladle+4C-+12-M+4CO(2)(
Reaction (1) is an exothermic reaction due to combustion of the carbon material, and provides reaction heat for reduction reaction (2), which is an endothermic reaction. In this case, reaction (2) requires a temperature of 1900°C or higher, preferably 1950°C or higher to increase the production rate and reaction rate, and 1 reaction (1) is required for reaction (2) to proceed smoothly. The amount of carbon to be fed is required to be at least about 30 moles per mole of alumina since a large amount of combustion heat is generated.

In addition, when reaction (2) is allowed to proceed, it is necessary to suppress the progress of the following reactions (3) to (6), which are problematic in the blast furnace method, and to
This provides the advantage of preventing the formation and volatilization of 2O and SiO.

An 203 +2C-+ AQ 20+2CO(3)
2AQ+GO-) AQ 20+C(4)Si02+
C-+ SiO+GO(5) Si+co-*
S io+c (6) The difficulty in making the reaction (2) proceed smoothly using the blast furnace method is that the amount of CO gas produced is This is several times higher than when using an electric furnace, and as a result, volatile components such as AQ zo and SiO that are scattered with the CO gas increase, making it difficult to obtain a stable aluminum alloy.

In addition to the silicon component, this aluminum alloy is stabilized by
Further improvements can be made by adding iron components, but in this case the addition of iron components increases the technical difficulties in the process of refining the crude alloy. In addition, when refining an aluminum alloy, it is clear that the higher the aluminum content in the alloy, the more advantageous it is. Therefore, the content of silicon and iron in the alloy obtained in 1 reaction (2) should be kept as small as possible. Such technological development is required.

〔the purpose〕

The present invention provides aluminum smelting using a blast furnace method,
An object of the present invention is to provide a method for efficiently producing an aluminum alloy with a high aluminum content.

〔composition〕

That is, according to the present invention, a combustion zone and a reduction zone are formed in a blast furnace, and an alumina-containing material is caused to flow down into the reduction zone as a calcia/alumina eutectic liquefied product, and the reduction zone is Aluminum produced by a blast furnace process, characterized in that the calcia/alumina eutectic liquefied product is maintained at a temperature of ℃ or higher and in the presence of an iron component in the reduction zone to form an aluminum alloy containing iron and silicon. A smelting method is provided.

The blast furnace referred to in this specification refers to a high-temperature heat source and a high-temperature heat source in the packed bed by blowing oxygen into the lower part of a packed bed of coke or a carbon fuel material similar to coke (hereinafter simply referred to as coke), such as coal, and burning the coke with oxygen. The reactor is set up at high temperature, with combustion gases, mainly CO, flowing upwards, feedstock and coke moving downwards, and product being collected from the bottom. That is, the blast furnace used in the present invention can be said to be a countercurrent movement type reactor.

The main raw material used in the present invention is an alumina-containing material, and examples of the alumina-containing material include minerals such as clay and bauxite. Such aluminum-containing materials are generally
It contains an iron component and a silicon component, and the addition of an iron component is often not particularly required. However, if the amount of iron component is insufficient, it is necessary to add it, and by adding this iron component, the reaction (2) can proceed smoothly. In this case, the iron component includes iron such as scrap iron, iron ore, and the like. The weight ratio Fe/A Q of iron and aluminum in the feedstock is 115 or more,
Preferably, it is adjusted to 173 or more.

In the present invention, the alumina-containing material is usually used in the form of a briquette made of bauxite, but in the case of this briquette, it can be mixed with coke in advance and used as a briquette whose surface is coated with coke. As will be described later, it is advantageous to add a calcium compound to the alumina-containing material, and therefore, a calcium compound can also be added to the briquette.

When processing the alumina-containing raw material using a blast furnace,
In the conventional general operation method, the high temperature region of the packed bed, which has a temperature of 1900°C or more necessary for carbon reduction of alumina-containing materials, is the region where the coke combustion reaction is progressing (combustion region) and its extreme temperature. It is only seen in the surrounding areas. The main cause of this is heat loss from combustion heat from the furnace walls, etc., especially oxygen blowing,
The heat loss through the cooling water of pipe making is large, and the heat conduction of combustion heat to the filling layer mainly depends on the convection of the combustion gas, so the combustion gas passage (mainly above the combustion zone) The only problem is that the temperature increases. For this reason, in conventional methods, the reduction of alumina-containing materials effectively proceeds in a region of high combustion gas flow velocity within and above the combustion zone. Therefore, in such a blast furnace method, it is unreasonable that the reduction reaction must be carried out in the combustion zone where a large amount of oxygen exists, that is, in an oxidizing atmosphere, and that aluminum and AQ, which are highly volatile, are unreasonable. An absurdity arises in that the reduction reaction has to be carried out under high-speed gas flow, where SiO tends to fly off with the combustion gas, and only alloys with low aluminum content can be obtained.

The present invention aims to eliminate the above-mentioned unreasonableness and produce an alloy with increased aluminum content by a blast furnace method.A reduction zone is formed in the furnace along with the combustion zone, and alumina-containing materials are removed. In the presence of an iron component, the calcia/alumina molten liquefied product is allowed to flow down into a reduction zone maintained at a temperature of 2000°C or higher to carry out the reaction (2), thereby forming an aluminum alloy containing iron and silicon. It is characterized by this.

In the present invention, a high-temperature reduction zone is formed in the blast furnace in addition to the combustion zone. This reducing zone can be obtained by blowing oxygen into the blast furnace from multiple oxygen blast pipes to form multiple high-temperature combustion zones at intervals, and the reducing zone is between and between these combustion zones. formed upwards. In this case, the temperature of the reduction zone depends on the temperature of the combustion zone and the heat transfer from the combustion zone to the reduction zone. The temperature of the combustion zone is
It depends on the surface temperature (maximum flash point temperature) of the combustion coke, and this surface temperature can be increased by increasing the coke particle size, but in the case of the present invention, the coke particle size is 1
It has been found that it is preferable to set the diameter to 0 mm or more and usually about 15 to 501. In addition, as the coke particle size increases, the upward flow or convection of the combustion gas expands to the periphery, so the flow rate of the combustion gas per m-crystal area in the furnace decreases.

Correspondingly, the proportion of combustion gas flowing through the reduction zone can be reduced. That is, due to the above-mentioned increase in coke particle size, the combustion temperature increases, the flow rate of combustion gas to the reduction zone is reduced, and the rate of heat conduction and radiation heat transfer to the reduction zone increases. A reduction zone suitable for alumina reduction at high temperature and with a reduced combustion gas flow rate, which is the objective of the invention, is formed.6According to the research of the present inventors, in addition to implementing the above-mentioned measures, combustion heat is removed from the furnace. By suppressing heat loss to 2000℃ or higher, especially 2
It has been found that it is possible to form a reduction zone as high as 050-2200°C.

In the present invention, the alumina-containing material flows down the reduction zone in the form of a eutectic liquefaction product with calcia. Since the alumina-containing material has a high melting temperature, it exists in a solid state until it is reduced and converted into metal.

Therefore, this alumina content generally tends to accompany the coke down the furnace and be transported to the combustion zone.

As mentioned above, transport of the alumina-containing material to the combustion zone is not preferred since no advantageous reduction of the alumina-containing material is achieved in the combustion zone, and selective transport to the reduction zone is preferred. Therefore, it is preferable that the alumina-containing material is melted in advance before reaching the reduction zone and transported in the reduction zone in a liquefied state.When transporting the alumina-containing material in a liquefied state, unlike transportation in a solid state, Because of its good fluidity, it is not transported along with coke,
Its own weight allows it to flow almost evenly through the coke packed bed in the furnace, significantly reducing the proportion of transport to the combustion zone and increasing the transport to the reduction zone. In the conventional case,
Since the alumina-containing material exists as a solid until just before the reduction reaction temperature, it has the drawback of being transported to the combustion zone along with the coke, but in the case of the present invention, such a drawback is overcome.

Due to its high melting point, alumina-containing materials are difficult to melt on their own and require the use of a eutectic agent to melt them at reduced temperatures. However, the eutectic alumina-containing material has poor reducibility compared to alumina alone. The present inventor has conducted various studies on the reduction of the eutectic alumina-containing material, and found that the alumina-containing material eutecticized with a calcium compound can be heated to a high temperature of 2000°C or higher, particularly 2050°C, preferably 2100°C or higher. It has been found that reduction can be achieved by circulating a reduction zone maintained at a high temperature.

According to the invention, therefore, the alumina-containing material is reduced in the form of a eutectic liquefied product with calcium compounds by flowing down a reduction zone maintained at a temperature of at least 2000°C.

In the present invention, the eutectic agent is a calcium compound such as calcia (Cab) or calcium carbonate (Cab).
CaC03) etc. are used, but in the case of the present invention, in particular,
The use of hard calcined calcia is advantageous. This calcium compound is eutectic with the alumina-containing material in the form of calcia in the furnace. Calcium compounds can be loaded into the furnace in the form of a mixture with alumina-containing materials, or, when loading, separately from alumina-containing materials, for example, coke, calcium compounds, and alumina-containing materials can be loaded in a sequential layer. Good results can also be obtained by doing this.

When loading each JM family in layers into the furnace, volatile substances such as AQ20 and SjO generated in the reduction zone and combustion zone are
It is collected by these layered loads and promotes eutectic liquefaction of calcia and alumina-containing materials. Further, in order to facilitate eutectic liquefaction of calcia and the alumina-containing material, a part of the calcium compound can be mixed with the alumina-containing material in advance to form a briquette. The general ratio of calcium compound and alumina-containing material is CaO/A Q2
0.03 molar ratio is 0.2 or more, preferably 0.4 or more, and usually ranges from 0.4 to 2.0. When a calcium compound is used as a briquette with an alumina-containing material, the ratio of the calcium compound and alumina-containing material in the briquette is C
aO/A Q 203 molar ratio of 1 or less, preferably 0
．． 6 or less, usually in the range of 0.2 to 0.6.

When reducing an alumina-containing material according to the present invention, the loaded alumina-containing material is eutectically liquefied with a calcium compound in a temperature range of 1600 to 1800°C lower than the reduction temperature above the reduction zone, resulting in liquid calcia/alumina. It flows down the furnace as a eutectic and reaches the reduction zone.

At the same time as it is reduced, it reacts with the coexisting iron and silicon components to form an aluminum/iron/silicon/alloy. In this case, the alumina-containing material is only partially reduced, and the alumina/calcia eutectic remains in the product passing through the reduction zone, and the aluminum/iron/silicon alloy is protected by this residual alumina/calcia eutectic. The aluminum/iron/silicon alloy thus formed is rapidly flowed down the furnace in the form of a carbon dioxide gas, thereby preventing re-oxidation by oxygen of the aluminum/iron/silicon alloy formed. Therefore, in the case of the present invention, the product obtained from the bottom of the furnace includes an alumina/calcia eutectic and an aluminum/iron/silicon alloy, but both are separated, the aluminum/iron alloy is recovered as a product, and the calcia /Alumina eutectic can be reused as feedstock.

When carrying out the present invention, as described above, the alumina-containing material is caused to flow down the reduction zone in the form of a eutectic with calcia, and the temperature of the reduction zone is set at about 2000°C or higher, preferably 2100°C or higher. It is important to keep aluminum/iron/iron with high aluminum content
Silicon/alloys can be formed. In this case, in order to maintain the reduction zone at the above temperature, the maximum flash point temperature of the coke in the combustion zone is generally maintained at 2700C or higher, preferably 29008C or higher.

In the present invention, the reduction of the calcia/alumina eutectic liquefaction is carried out in the presence of an iron component, as described above.
In this case, it is advantageous to carry out the reaction in the presence of aluminum or calcium oxycarbide. Inside the furnace there is a flow of AQ 2o vapor upwards from the bottom of the furnace, which reacts with the carbon to form oxycarbide. Therefore,
The calcia/alumina eutectic liquefied material flowing down the furnace contains a small amount of aluminum oxycarbide. Also, in the reduction region, carbon is present here as well.

Aluminum oxycarbide and calcium oxycarbide are produced by the reaction of the calcia/alumina eutectic liquefied product with carbon. Such oxycarbide is
This shows the effect of increasing the reduction reaction rate of calcia/alumina eutectic liquefied product. Therefore, in the present invention, it is also effective to add aluminum oxycarbide or calcium oxycarbide to the alumina-containing material in advance. In this case, the amount of oxycarbide added is 0.1 to 1 Scenery%, preferably 1-5 Scenery%
It is best to keep it to a certain level. In addition, the slag obtained by the present invention (
Since such oxycarbide is contained in the calcia/alumina eutectic, it is very effective to add it to the alumina-containing material and reuse it.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.

Comparative Example I Using an experimental furnace with an inner diameter of 36 cm and an internal furnace height of 100 cm,
A water-cooled oxygen blast tube (tuyer diameter: 5 mm) was attached to three water bags at a circumferential angle of 120'. In this case, the angle of the blast pipe with respect to the horizontal was 12''. A graphite grate was placed approximately 5 cm below the tuyeres to facilitate the flow of the produced crude alloy.

A hopper was installed at the top of the furnace, and coke and raw material briquette were loaded. Loaded with only coke for 8 hours (166 kg) L
After preheating and stabilizing the furnace temperature, coke (130 kg) and coke-coated briquette (consisting of 1000 parts of bauxite, 250 parts of coke powder for mixing, and 770 parts of coke powder for coating, with an outer diameter of about 30 to 35 mm) were heated for 3 hours. diameter)
(40 kg) were added alternately to each. Note that the weight ratio Fe/AQ of iron and aluminum in the bauxite was 0.31. After testing, dismantle the furnace.

12 kg of unreacted briquette and 64 kg of crude alloy were collected under the grate. The composition of the crude alloy is AQ 11.7, Fe
51.2, Si 21.8. Carbon 1O63, Ti 2.
It is 8%. That is, Fe/A Q in the raw material = 0.31
On the other hand, Fe/A Q in the crude alloy increased to 4.35, which indicates that the generation of AQ20 and the reoxidation of the alloy are significant.

In addition, in the above experiment, the coke particle size used was 4 to 4.
7mm, oxygen flow rate 210Q/win x 3, combustion temperature 2200-2400℃, furnace center,
On the grate】The packed bed temperature at 0cII+ is l640°
It is C. After the test, the furnace was dismantled and the combustion zone was investigated. It was confirmed that the combustion zone formed by the three oxygen blast pipes merged into a dome shape, and that there was no reduction zone independent of the combustion zone. It was done. Therefore, in this experiment, it is clear that the reduction reaction must proceed within the combustion zone.

Comparative Example 2 Six oxygen blast pipes (tuyere diameter 7non) were installed at a circumferential angle of 60° in an experimental furnace having an inner diameter of 60 cm and an inner height of 240 cm.

In this case, the angle of the blast pipe with respect to the horizontal was 20°.

A space of about 20 cm between the hearth bottom and the tuyere was filled with coke of 30 to 50 m+n size, and care was taken so that the crude alloy would accumulate in the gap, and a tapping hole was provided in the hearth bottom. Coke and the same raw material briquette as in Comparative Example 1 were charged from the top hopper. The coke consumed during the preheating period (29 hours) was 470 kg.
790 kg of coke and 260 kg of briquette were added from the time the briquette started to the stop (20 hours). At the end of preheating, 10 hours after adding the briquette, and just before stopping, take out the hot water.
Samples weighing 6.5 kg, 7.3 kg, and 6.1 kg were collected, respectively. The previous two samplings yielded coke and re-solidified raw material as solids, as did most of the final sample, of which 2 kg was liquid, with a composition of ferrosilicon and aluminum. It was confirmed that it does not exist. In addition, the coke particle size used in this experiment was 1 to 4 mm, and the combustion temperature was 2000 mm.
~2600°C. 20cm above the tuyere, 10cm from the furnace wall
m, the temperature of the packed bed at the 306 corner position from the tuyere of the oxygen blast pipe is 1
It is 840°C. The combustion gas composition at the same position is 85% oxygen and 15% CO.

As a result of the furnace dismantling, the area from the bottom of the furnace to 30 cm above the tuyere was filled with slag material mixed with coke, and above it was found a dome-shaped coalesced combustion zone and a coke layer.

Almost no metallic aluminum was found in the slag material, and it existed as alumina. Therefore, like Comparative Example 1, this experiment also shows that reduction progresses within the combustion zone and one reactant remains in the combustion zone due to the high melting point of slag and the like.

Comparative Example 3 Using the same experimental furnace as Comparative Example 2, the coke particle size was
The diameter of each wing was increased to 14 mm instead of 25 mm. Oxygen flow rate 180 Q/min
cm, the temperature of the packed bed at a 30° angle position from the oxygen blast pipe is 1680°C. Oxygen at the same position is 4.3%,
CO□0.9%, the rest is CO.

In this experiment, 1 coke consumed during 2 hours of preheating
In addition to 40 kg of briquette, 50 kg of briquette (same as Comparative Example 1), and 200 kg of coke, 20 kg of hard-burned calcia were alternately charged over a period of 6 hours. The test taken by tapping and the sample obtained as the bottom residue of the furnace were all oxides, and the aluminum component existed only as a CaOAQ203 eutectic, and no metallic aluminum was observed. This experimental result shows that even if an alumina/calcia eutectic is formed by simply mixing calcia, an aluminum alloy cannot be obtained if the reduction temperature is low.

Example 1 In Comparative Example 3, the number of blower pipes was reduced to three, the oxygen flow rate per blower pipe was increased to 50 On/min, and the heat transfer of cooling water was reduced. The other conditions were almost the same as those in Comparative Example 3, and the preheating consumption coke was 300 kg. In addition, in this experiment, 120 kg of briquette, 360 kg of coke,
60kg of hard-burned calcia is added alternately to make 13kg of union whole leopard.
I got g. Its composition is A1132.2, Fe 40.3
, Si 20.4, Ca 1.74, C2,88, Ti
It is 2.27. In addition, approximately 26 kg of slag was generated and separated from the crude alloy, the composition of which was CaO-ΔQ
203 eutectic and a part partially containing eutectic aluminum, and the typical composition of the latter is AQ 30.4.
, Fe 5.2, Si 2.4, Ca 20.1. C
13.5, TiO, 7%.

The maximum combustion temperature at the tuyere tip in this experiment was 3200'C, and the packed bed temperature was 2000-2100C. The combustion gas composition at the same position is Co 99.7%, O2
0.3%.

Example 2 The same experimental furnace as in Example 1 was lined with graphite and had an inner diameter of 4
8cnf was used, other conditions were the same as in Example 1, and the raw material briquette was changed. That is, only bauxite was molded into an almond shape of 12 x 18 x 26 mm, and sintered at 1200 to 1300°C in a rotary kiln to produce a raw material briquette. Raw material briquette 78 kg, hard-burned calcia 50 kg, coke 605 made in this way
As a result of conducting an experiment in the same manner as in Example 1 using ε (305 kg for inner core heating), 26 kg of crude alloy and 15 kg of slag were used.
I got kg. This crude alloy composition AQ 24.8, Fe
42.4.5121.6. C3,58, Ti 3.
87, Ca 1.38. The composition of the slag obtained in this case was AQ7.6, Fe 3.62.
Si O,67, C23,3, Ti O,12, Ca
It was 51.3.

〔effect〕

By referring to the results of the comparative examples and examples shown above, it is clear that in the case of the present invention, an aluminum/iron alloy with a high aluminum content can be produced.

Claims (1)

[Claims] (1) Forming a combustion zone and a reduction zone in the blast furnace,
It consists of flowing down the alumina-containing material as a calcia/alumina eutectic liquefied product into the reduction zone, and the reduction zone is
A blast furnace method characterized in that the calcia/alumina eutectic liquefied product is maintained at a temperature of 000°C or higher and in the presence of an iron component in the reduction zone to form an aluminum alloy containing iron and silicon. Aluminum smelting method.