JPS59126730A - Manufacture of aluminum or aluminum alloy by refining - Google Patents

Abstract

PURPOSE:To lower advantageously the temp. of a reducing environment when alumina is refined by a blast furnace method, by diluting generated CO with H2 or an inert gas to accelerate reduction. CONSTITUTION:Al2O3 or natural and/or artificial minerals contg. Al2O3 are used as a starting material, and the starting material and a solid carbon-base reducing agent are heated to 1,400-2,000 deg.C in a furnace. CO generated by the reduction of the starting material is diluted with H2 or an inert gas to reduce the partial pressure of CO in the furnace. The temp. at which the reduction of Al2O3 with C begins can be lowered under the reduced partial pressure of CO, so Al or an Al alloy such as Al-Fe or Al-Si can be obtd. by advantageous reduction at a relatively low temp.

Description

[Detailed description of the invention]

(Technical Field) The present invention relates to a method for smelting aluminum or an aluminum alloy, in particular, using aluminum oxide or a natural or/and artificial mineral containing the same as a raw material, particularly by an advantageous reduction at a relatively low temperature. Developments in obtaining aluminum or aluminum alloys such as aluminum-iron, aluminum-silicon and aluminum-silicon-iron are disclosed. The objects of smelting according to the present invention include those that have independent uses or applications, such as aluminum and aluminum-silicon alloys, as metal materials as they are, and as deoxidizing agents in iron uA refining, and Naturally, the term also includes so-called crude metals or crude alloys that are refined and used. (Conventional technology) Up until now, aluminum has been produced exclusively by the Hall-Herou method, that is, by molten salt electrolysis, in which alumina is dissolved in molten cryolite and electrolysis is carried out at approximately 950°C using this as an electrolytic bath. This is the mainstream, but it has a crucial flaw in that it consumes a huge amount of electricity. Therefore, recently, as international competitiveness in aluminum production has been lost, it has been forced to stop using electrical energy.
The development of aluminum smelting technology has been progressing in various fields, and proposals have been made, for example, as in Japanese Patent Application Laid-open No. 150142/1983. However, in this so-called blast furnace method, the aluminum-silicon alloy obtained through reduction smelting is absorbed into molten lead immediately after its formation, and the molten lead is absorbed into the molten lead during cooling.
Although the volatilization and re-oxidation of aluminum can be cleverly avoided by recovering aluminum from the molten bath through phase separation, carbon is originally used as a reducing agent in the reduction smelting process, especially for aluminum nitride. In order to avoid the formation of CO, oxygen is blown into the furnace through the tuyere instead of air as in the case of iron smelting, so CO is generated at a pressure of about 1 atm or more in the furnace, so the following As such, the reaction temperature environment C1 is difficult in actual operation. In other words, under the above conditions, an extremely high temperature of approximately 2030"C or higher is required for the reduction reaction of alumina to proceed as shown in the following formula % formula % (1). Under such #Ei high temperatures, mineral Alternatively, various oxides in the gangue contained in coke, such as 3i 02, and even 5iO1Aρ20 and A
Suboxides such as βO are generated and volatilized, carried along with the reducing gas in the furnace to the upper part of the furnace, and reach the furnace loss reduction section where they are reoxidized and condensed. Such aggregates block the voids in the charged charging layer due to the carbon used as the reducing agent, coke, raw material minerals, solvent, etc., and obstruct the smooth flow of gas into the furnace. It is clear that this is extremely disadvantageous in terms of operational life, as the smooth operation of the refractories is not possible, and the wear and tear caused by the erosion of large furnace wall materials at extremely high temperatures is significant. The use of zirconium carbide, titanium carbide, etc. is expensive and increases equipment costs.Therefore, in the temperature range of 2000℃ or less, which has already been used in ordinary metal smelting, excessive power consumption is required. The technical significance of realizing aluminum melting and smelting without aluminum is extremely important.

[You have to pull it. (Purpose of the invention) This invention discloses the results of development research aimed at advantageously meeting such demands, and the basis of the idea is the establishment of a method for advantageously lowering the reducing environment temperature. It is based on (Structure of the Invention) That is, the present invention uses aluminum oxide or a natural or/and artificial mineral containing aluminum as a raw material, and heats the raw material together with a solid carbon-based reducing agent to a temperature range of 1400 to 2000°C or less. This is a method for smelting aluminum or aluminum alloys, which comprises diluting carbon monoxide generated by reduction with hydrogen or/and an inert gas to promote reduction at the temperature. In addition, the reduction according to the present invention is carried out in an externally heated shaft furnace as the most practical mode, and furthermore, the raw material contains or is blended with iron oxide.
This is particularly suitable for implementation. In accordance with the above configuration, the details of the smelting behavior that can advantageously achieve the intended purpose of the present invention will be explained in detail below. Granular minerals mainly composed of alumina,
Various bauxites 1 - Man-made materials such as refractory materials of aluminous and mullite porcelain compositions and brick shavings, as well as other clays, especially frog's-eye clay, Honbushi clay, and even pavilion and especially clay shale. Like crushed minerals,
Regarding the AJ2 raw ore that can be used indiscriminately and is subjected to the conventional whole-el method, diasboer (α-AJ2z03t120) of bauxite, followed by boehmite (γ-Abu20:1H20) are used. It's an advantage in a way that has nothing to do with what was difficult. In general, aluminum oxide and natural and/or artificial minerals containing aluminum are mostly in powder form, except in cases where they are granular, such as corundum or crushed brick chips, so the above-mentioned information is not applicable. It is desirable to make appropriate selections or mix them before agglomerating. Here, the blending ratio is adjusted according to the composition of the object to be smelted and the composition of the slag produced during the smelting process, and if necessary, silica, limestone, quicklime, slaked lime, or cement, etc. In order to further support the reduction reaction, a solid carbon-based reducing agent is added to the grains, and the mixture is kneaded with an appropriate amount of water and an appropriate binder, and then pressure-molded into a shape of Briquella. After being formed into pellets using a polling drum, they are cured, solidified to the required strength, and made into briquettes. At this time, curing can be promoted using high-temperature and/or high-pressure steam, air containing steam, or the like. The briquette thus obtained is originally the same as the granular raw material mentioned above, but hereafter it will be simply referred to as the raw material, and it will be treated with a solid carbon-based reducing agent such as coke, coal, graphite, etc. Charging is carried out sequentially from the top of an externally heated shaft furnace, and although the furnace is omitted for simplicity of illustration, the furnace top charging device is connected to outside air using a double sealing means. The inside of the furnace is sealed and sealed. Figure 1 shows a skeleton diagram of the cross section of an external heating type shaft furnace, where 1 is the main body of the shaft furnace, 2 is a combustion chamber surrounding the main body, 3 is a heat-resistant partition wall, 4 is a slag layer, and 5 is a metal 6 is a heat-resistant, slag-resistant grate, A is a raw material charging port, and a port is a spout, and a is a dilution gas inlet.
b is an exhaust gas outlet, C is a combustion gas and combustion supporting gas inlet, and d is a combustion exhaust gas outlet. On the other hand, in the blast furnace method mentioned earlier, pure oxygen is blown into the blast tuyere, which is similar to the blast furnace used in the smelting of pig iron, and coke, a reducing agent, is charged together with alumina at the top of the furnace. Alternatively, the heat of combustion reaction between coke of red-hot nodules made from a mixture of raw ore and powdered coal is used to reduce alumina, and pure oxygen is used here because the aluminum produced when air is used. This is to prevent nitriding. In such an internal heating method, the partial pressure of CO generated by the reaction between oxygen and carbon is, even when operating at a pressure close to atmospheric pressure,
In order for the pressure to reach approximately 1 atm and for the reaction shown in equation (1) above to proceed to the right, ΔG6=316900-137.
Since 39T=0, T=2307 requires =2034°C, which means that the temperature must be higher than this. However, if it is possible to control ilI'tJ to about 10-8 atmospheres using this 00 partial pressure, ΔG' = 316900-137.39T+(-a)X
Since a RTJ2n 10 =0, it becomes possible to generate oil from a temperature of T=1775=1502°C. In other words, by using a reducing furnace type that can lower the 00 partial pressure, it is possible to be freed from the constraints caused by extremely high temperatures. It is conceivable to dilute the CO'a content within the tank, but in this case, the flow rate of the diluent gas becomes excessive, resulting in an increase in cost. However, an externally heated shaft furnace has a
Atmosphere adjustment is much easier without zero partial pressure problems and independent of constraints associated with internal heat. In other words, specifically: ■ exhausting and depressurizing the inside of the furnace, ■ circulating an inert gas such as argon or helium inside the furnace, ■ circulating hydrogen inside the furnace, and ■ circulating inert gas and hydrogen inside the furnace. In addition, (1) circulating hydrocarbon gas in the furnace may be mentioned. Among these, regarding C, it is difficult to maintain the reduced pressure in the furnace.
Therefore, especially in the case of ■, ■, and ■, as the raw material charged into the furnace, as mentioned above, it is necessary to include a solid carbon-based reducing agent in the briquette, or to add a solid carbon-based reducing agent together with the raw materials including the briquette. Needless to say, it is necessary to simultaneously charge the reducing agent (2), and in the case of (2), the reducing action of hydrocarbons is produced without necessarily using a solid carbon-based reducing agent, but the When using hydrogen as a diluent gas to promote the reduction of raw materials, it is of course necessary to simultaneously charge a solid carbon-based reducing agent with the raw materials. Among the above items, in this invention, ■, ■, and ■, that is, for example, in a shaft furnace, are listed in formula (1)! The concentration of carbon monoxide generated by the reaction is diluted with hydrogen and/or an inert gas to lower the partial pressure in the furnace. As the partial pressure in the furnace decreases, the temperature at which reaction (1) starts can be lowered rapidly. Considering AA203.0 and A℃ as pure substances among the substances involved in the reaction in equation (1), from the theory of chemical thermodynamics -RTJ2n K-ΔG°...(2) Here: equilibrium constant R : Gas constant king: Since absolute temperature holds, -RTJ2n K=-RTJ2n Pco8-ΔG. is the standard free energy change of reaction (1). Using the value of ΔG°, equation (3) becomes 316900− (137,39−13,731ogP
co) T-〇...(4) Now, in equation (4), if we set 00 partial pressure, Pco as 1°1 10.10-2 and 10 atm, the reaction initiation temperature of equation (1) becomes as shown in the table below. co partial pressure (atmospheric pressure) 1 10-110-210-8 formula (
1) Reaction initiation temperature (°C) 2034 1824 1649
1502 That is, if the 00 partial pressure in the reduction furnace can be controlled to less than 0.1 atm, the temperature at which AJ2 is produced by reduction of Al2O2 can be easily reduced to about 1800° C. or lower. As mentioned above, incorporating a solid carbon-based reducing agent into the briquette as a raw material or charging it into a reduction furnace together with the briquette or raw materials is a method using raw materials containing iron such as clay and bauxite. , Fe-AJ2 or Fe-
It is also suitable for producing AA-8i alloys. That is, in a high-temperature furnace, alumina is reduced by carbon to produce AJ2 and to generate β20 gas as shown in the following equation (5). AA203+2C,=Aβ20+2GO (5) On the other hand, iron contained in the raw material is in the form of iron oxide, and this iron oxide is more easily reduced than alumina to become metallic iron. In this case, if solid carbon is present in the furnace, the metal iron will immediately absorb carbon and become saturated with forurine, but due to the carbon in the metal iron, gaseous A1120 will be converted to AJ220+ (C )=2 (AJri+GO・ (6)
It is reduced and 8λ dissolves into the iron. This reduction and dissolution reaction (6) of aluminum proceeds more easily because the activity of aluminum becomes 1 or less by forming an iron alloy. Now, regarding the temperature inside the shaft furnace, in this invention where hydrogen and inert gas are circulated, reaction (1) occurs. Temperature range 1400 in which (5) and (6) readily proceed
The temperature is adjusted to ~2000°C. This temperature adjustment is performed by controlling the combustion state in the combustion chamber shown in FIG. The fuel in the combustion chamber 2 shown in FIG. The combustion state is controlled by mixing gas containing oxygen and gases containing oxygen. 6. This combustion chamber 2 has a structure in which a solid carbon fuel such as coke, coal, charcoal, char, etc. is charged from the top, or the above fuel is blown into fine powder, and a gas containing oxygen is blown into the combustion chamber 2. The heat generated in the combustion chamber 2, which can also obtain heat by burning these fuels, is transferred into the shaft furnace body 1 by the partition wall 3 shown in FIG. In this invention, the dilution gas is flowed into the furnace as follows. Aluminum may be flowed from the lower part of the furnace to the upper part, but the aluminum produced as a result of reduction smelting in the furnace is easily volatilized because the temperature inside the reduction furnace is adjusted to a range of 1400 to 2000°C. (If the gas flow in the furnace is from the bottom to the top, it may move to the top of the furnace and condense there, interfering with the operation. Therefore, the flow of diluent gas is at least It is preferable to condense the volatilized aluminum in the molten pool 5 in the lower part of the furnace by pouring the aluminum from the top to the bottom in the zone. Aluminum-based alloys, as well as iron-silicon-aluminum alloys, accumulate in the hot-spot area of the reduction furnace and are intermittently discharged outside the furnace. By the way, hydrogen or inert gas used as diluting gases are both expensive. Therefore, in this invention, the exhaust gas from the shaft furnace, which mainly consists of CO and diluent gas, is treated by PSA (pressure swing adsorption method). After separating CO and diluent gas using an adsorption separation method, the diluent gas is recycled to the shaft furnace, and GO is used as a fuel for heating the reduction furnace or as a raw material for C1 chemistry. Figure 2 shows the adsorption/separation state (breakthrough curve) of hydrogen, argon, and carbon oxide mixed gas when using zeolite 5A, and it can be seen that this method is effective. In order to be efficient, the basic type of shaft furnace is shown in FIG. 1, and modified examples for more effective heat utilization are shown in FIGS. 3 and 4. Both devices in both figures adopt a furnace structure in which combustion chambers 2 and shaft furnace bodies 1 are alternately arranged in parallel, similar to a coke oven, in order to suppress heat dissipation from the combustion chamber walls to the outside air.Parallel furnace chambers The number of combustion chambers can be arbitrarily selected depending on the production volume.As shown in the front view of the furnace in each figure, the furnace has a depth like a coke oven.Therefore, the type shown in Figure 1 Compared to a furnace, the heat loss from the side surface of the combustion chamber 2 can be reduced by 1].In this case, if the shaft furnace body 1 is provided with a taper, it is possible to make the descent of the charge easier. Needless to say, the exhaust gas emitted from the shaft furnace consists of carbon oxide and inert gas when an inert gas is used as the diluent gas, and consists of carbon oxide and hydrogen when hydrogen is used as the diluent gas. It consists of In addition, since the exhaust gas discharged from the shaft furnace has a high temperature, especially in the case of exhaust gas consisting of carbon oxide and inert gas, if it is immediately introduced into the combustion chamber 2 as fuel gas after being discharged from the reduction furnace, the sensible heat of the exhaust gas can be increased. can be used effectively. Figure 13 shows a device that takes this point into consideration. In this case, the oxygen-containing gas as a combustion improver is supplied from the system <f>, and if there is a problem with combustion, such as a low monoxide concentration in the shaft l~furnace exhaust gas, the oxygen-containing gas is supplied from the system (e).
) can also be supplied with fuel. In the reactor shown in FIG. 3, the combustion chamber exhaust gas discharged from the upper end (d) of the combustion chamber contains two or three of carbon dioxide, water vapor, and inert gas, and is therefore dehydrated in the carbon sludge separator 7. Or/and after decarboxylation, the inert gas can be returned to the shaft furnace main body 1 through the dilution gas inlet (a) and used for circulation. In this case, it is advantageous to provide a heat exchanger using combustion chamber exhaust gas in the upper part of the furnace 8 to preheat the inert gas sent between the shaft furnace main body 1 from the dilution gas inlet <a>. In addition, Q in the figure is combustion chamber 2.
This is a ventilation hole from the upper part of the furnace to the upper part 8 of the furnace. In contrast to the above, in the reactor shown in FIG. 4, the exhaust gas from the shaft furnace is discharged from the outlet, but is first led to the heat exchange chamber 9, where it is sent to the combustion chamber 2 through the system ( The same system (e) as the fuel supplied and sent from [)
A combustion improver such as an oxygen-containing gas supplied from a combustion chamber is preheated, and then sent to an exhaust gas separation device 10 that exits the heat exchange chamber 9, where it is separated into a diluent gas (hydrogen or active gas) and CO. The dilution gas is sent to the shaft furnace main body 1 for circulation and reuse.The combustion exhaust gas is led from Q to the heat exchange chamber 8, and the dilution gas is sent into the shaft furnace main body 1 for circulation. After preheating, it is discharged from the furnace through the discharge port (d).As described above, if a furnace of the type shown in Fig. 3 or 4 is adopted, sufficient preheating and circulation of expensive diluent gas can be achieved. Example: Two types of bauxite mixtures with the following compositions were used as powdered raw materials.Component Al2O8SiO□ Fe2O8Ti
02 (wt%) 45.2 10.3 20.
7 4.4 Add 8 parts by weight of Portland cement to 100 parts by weight of this bauxite raw material, add 7 parts by weight of water to the colander, mix well, and then form into pellets of 5 to 13 cm using a polling disk. The mixture was left at room temperature for 27 days to fully solidify. The strength of this pellet was 107 kg/piece. These assimilated pellets are combined with 6 to 8 graphite grains at 1760
It was charged into a reduction furnace heated to 14° C. with an inner diameter of 9.6 ann and a height of 80 marks so that the bed height was 14 cn+. The mixing ratio of pellets and graphite particles at this time is 1=1
And so. Under these conditions, argon was used as dilution gas at 14NJ2/
The mixture was allowed to flow for 1 to 20 minutes at min. to reduce bauxite. In this case, the dilution gas was flowed downward from the top of the furnace. Further, a graphite container was placed in a temperature region of about 1300° C. in the lower part of the furnace to receive dripping of the produced molten metal. After the practical training, the amount of produced metal taken out was 23.6 parts by weight based on 1.00 parts by weight of bauxite pellets, and its chemical composition was as follows. Ingredients AI Si Fe Ti weight%
54.2 12.9 31.5 1.4 (Effects of the invention) According to the present invention, aluminum oxide or natural and/or artificial minerals containing the same can be used almost indiscriminately as a raw material, Effective reductive smelting can be advantageously achieved without the disadvantage of ultra-high temperatures required in the blast furnace method, without dependence on electric power, and without any particular deterioration in the heat source unit consumption.

[Brief explanation of the drawing]

Figure 1 is a sprue diagram of the shaft furnace used in the examples of this invention. Figure 2 shows hydrogen, argon, and
- A breakthrough curve diagram showing an example of the separation state of carbon oxide. Figures 3 and 4 are skeleton diagrams showing modified examples of the reaction apparatus. Figure 1 A Figure 2 Clear space (Screen Figure 3

Claims (1)

[Scope of Claims] 1. Generated by reducing the raw material by heating aluminum oxide or a natural or/and artificial mineral containing it to a temperature range of 1400 to 2000°C together with a solid carbon-based reducing agent. A method for smelting aluminum or an aluminum alloy, which comprises diluting carbon monoxide with hydrogen or an inert gas to promote reduction at the temperature. 2.-The method according to 1, wherein the promotion of reduction by dilution of the carbon oxide takes place in an externally heated shaft furnace. 3. The method according to 1 or 2, wherein the promotion of the reduction by dilution of the carbon oxide is by means of a downward flow of a diluting gas in the externally heated shaft furnace, at least in its reduction reaction zone. 4. The raw material contains or contains iron oxide.1
The method described in any one of ~4.