JPS58193329A - Method for operating aluminum refining blast furnace - Google Patents

Abstract

PURPOSE:To prepare Al in excellent productivity, in preparing molten Al by reacting an alumina-containing stock material with a carbonaceous reducing agent in a blast furnace, by controlling the temp. in the uppermost part of the stock material packing layer in the blast furnace to a specific temp. range to prevent the blocking accident of the furnace. CONSTITUTION:An Al2O3-containing stock material such as bauxite and a carbonaceous reducing agent such as coke or coal are mixed to be charged into a blast furnace while oxygen is blown thereinto from the lower part thereof and Al2O3 is reduced with carbon by using the combustion heat of the carbon materials to prepare molten Al. At this time, the temp. in the uppermost part of a stock material packing layer is measured by a thermocouple 7 and the supply amount of an oxygen gas, the ratio of the Al2O3 stock material and the reducing agent and the height of the stock material packing layer are adjusted so as to adjust the temp. within a range of a critical operation temp. or more generating the clogging of the blast furnace by volatile Al2O, Al and SiO or more - 300 deg.C. The lowering of the yield of the stock material resulting from the clogging of the blast furnace or volatilization loss due to a high temp. is not generated and stable operation can be carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of operating an aluminum smelting blast furnace. 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, due to the rise in energy costs on a global scale, it has become extremely difficult to manufacture aluminum in regions like Japan where electricity costs are high, causing extremely serious obstacles to the industrial structure. In addition, the Bayer-Hall L. method, which is a conventional smelting method expected to be used worldwide in the future,
■The process of extracting alumina from bokehsite requires a long extraction and crystallization process, resulting in low productivity and high equipment costs.
■The whole-el process, which is an electrolytic process, has industrial disadvantages such as no scale merging and low productivity1, high equipment costs, and the need for a large amount of electricity. The level of technological improvement is already near its limit, and the emergence of radically innovative smelting methods is required.

Conventionally, many types of alternative smelting methods, including the electric furnace reduction method, have been studied to address these drawbacks inherent in the Bayer-Hall-L method. However, these methods have not succeeded in achieving energy saving effects or cost reductions sufficient to replace conventional methods. The disadvantages of these alternative methods include:

In recent years, as a method to overcome the problems of the above-mentioned aluminum smelting method using electric power, a smelt furnace method has been developed in which a countercurrent moving bed smelt furnace is used to reduce raw material alumina with a carbon material. Aluminum smelting methods using In this method, a packed bed containing raw material alumina and a carbon material that acts as a fuel and a reducing agent is formed in a blast furnace, and in the furnace,
The following combustion reaction (1) and reduction reaction (2) are performed simultaneously.

C10%02→200 (1) A/203+ 30→2AI! +300 (2) That is, the reduction of aluminum oxide (alumina) shown by equation (2) is performed using the oxygen combustion heat of the carbon material shown by equation (1) as a heat source. In addition, the smelt furnace is a countercurrent moving bed type, and when performing aluminum smelting by simultaneously performing the above reactions (]) and (2) in such a smelt furnace system, the economic efficiency and operational efficiency are reduced. There are various technical problems to be solved in terms of performance, but in particular, volatile aluminum components (A/20 and AI) and volatile silicon components (S
occurrence of in) ] 1 and its condensation causes blockage of the smelt furnace. During the operation of the melting furnace, if the conditions inside the furnace change or the composition of the feedstock changes,
Blockage of the smelt furnace is likely to occur, and in the event of furnace blockage, operations must be shut down, resulting in significant economic losses.

The inventors of the present invention have conducted extensive research to solve the problem of furnace blockage, and have found that the temperature at the top of the packed bed containing alumina-containing raw materials and carbon materials in the furnace has a critical temperature that is correlated with furnace blockage. The operating temperature reached a certain temperature.

That is, according to the present invention, a packed bed containing an alumina-containing raw material and a carbon material is formed in a blast furnace, and in the furnace, a combustion reaction of the carbon material with oxygen gas and the combustion heat are used to burn the carbon material. In an aluminum smelting and blasting furnace in which a reaction to reduce sialumina is simultaneously carried out, the temperature at the top of the packed bed is detected as operational information, and based on this information, (a) the amount of oxygen gas supplied; (b) Ratio of alumina-containing raw material to carbon material, (C)
A method of operating an aluminum smelting blast furnace, which comprises changing one or more of the heights of the packed bed to maintain the temperature at the top of the packed bed so as not to fall below the critical operating temperature. provided.

Thermocouples such as lumerule chromel, copper-constantan platinum-platinum rosium, and tungsten-tungsten rhenium are used. These thermocouples are usually inserted into the periphery of the furnace wall at regular intervals up and down, and if necessary, inserted into the center of the furnace.

The present invention is based on temperature information at the top of the filling detected in this way, and determines (a) oxygen supply amount, (b) ratio of alumina-containing raw material to carbon material, (C)
The height of the packed bed is maintained so that the temperature at the top of the packed bed does not fall below the critical operating temperature by changing one or more of the following:

In this case, the amount of oxygen supplied can be controlled by adjusting the flow rate or concentration of oxygen gas. In this case, this can be done by adjusting the supply amount of the oxygen gas such as heavy oil or pulverized coal and the carbon material.

The critical operating temperature varies depending on the scale and shape of the furnace, the alumina content in the feedstock, etc., and cannot be determined unambiguously, but it can be determined in advance through simple operating experiments at the start of operation. That is, at least one of the items (a), (b), and (c) as described above.
While varying the species, the top of the packed bed is observed to measure the temperature at which the clogging phenomenon begins, and this temperature is taken as the critical temperature for operation. Therefore, the critical operating temperature in the present invention is the minimum temperature at which the top of the packed bed of feedstock formed in the furnace does not cause blockage when performing an aluminum smelting operation using a predetermined melting furnace. is defined as In the present invention, while automatically detecting the temperature at the top of the packed bed, the temperature at the top of the packed bed cannot be constantly manipulated to its critical value during operation of the furnace. If the temperature at the top of the packed bed becomes too high, although the problem of furnace clogging is solved, the ratio of required carbon material to aluminum yield becomes high, which is undesirable because economic efficiency decreases.

Therefore, in the case of the present invention, the temperature at the top of the packed bed is above the critical operating temperature and below the critical operating temperature +300°C, i
In particular, it is preferable to maintain the temperature within a range of 200°C or lower. Generally, this critical operating temperature is in the range of 650-80°C.

Next, the present invention will be explained with reference to the drawings.

In the drawing, reference numeral 1 indicates a countercurrent type blast furnace, and to this melt furnace, briquette containing alumina-containing raw material and carbon material mixed in a predetermined ratio is supplied from line 2 to a supply amount adjusting device 1.
1 (e.g., a bell-shaped hopper or pulp), and from line 3 a feed rate regulating device (e.g., a bell-shaped hopper or a thermocouple placed at intervals). , oxygen gas flow regulating device (e.g. pulp)
6. The alumina reduction product is withdrawn as a melt through line 9, while the combustion gases are
It is extracted from the top of the furnace through line 8. Reference numeral 10 denotes a supply amount control device for carbon material as a fuel, briquette containing alumina, and oxygen gas, including a thermocouple 7, a briquette supply amount adjustment device 11, a fuel supply amount adjustment device 4, and an oxygen gas flow rate adjustment device. The temperature at the top of the packed bed should be controlled by the amount of briquette and/or carbon material loaded and the amount of oxygen gas so that the temperature at the top of the packed bed does not exceed the critical operating temperature +3 (10°C). The amount of supply is controlled.

When the blast furnace is operated as described above to reduce alumina-containing raw materials at high temperatures, the problem of furnace blockage does not occur, and the packed bed F is smoothly moved downward. The part of the packed bed that is within 50 m, measured downward from the position of the surface of the packed bed of feedstock in contact with the wall.

Unlike the electrolytic method, the alumina-containing raw material used in the present invention can be from a wide range of raw materials, including clay minerals such as bauxite with high alumina content and banded shale with low alumina content, fly ash, and bottom ash. Can be used. The reduction reaction of alumina in reaction (2) requires a high temperature of 2100°C, but this reduction temperature can be lowered to about 1900°C by adding iron and silicon components to the raw materials. It becomes possible. The present inventors conducted various studies on the iron content in the raw materials, and found that increasing the iron content in the raw materials, together with lowering the reduction temperature, is represented by the following reaction formulas (3) and (4). SiO2+
0-+SiO+OO (4) In order to effectively suppress the generation of volatile components, it is desirable that the ratio of the iron component be at least a certain ratio with respect to the aluminum and silicon components in the raw material, and the atomic ratio is Fe/ At! is 1/7 or more, Fe/S
It has been found that i is 1 or more, more preferably l''e/Af is 1/4 or more, and Fe/Si is 2 or more.

In the present invention, a carbon material is used as a reducing agent for alumina, and this carbon material may include carbon itself such as coal or coke, or A, 1403+8iC! ,
Carbide such as FeC can also be applied.

This carbon material is usually supplied into the furnace in the form of a mixture with an alumina-containing raw material, but in this case, its shape can be any shape such as powder, pellet, or briquette. .

In the carbon material used as a fuel in the present invention, the material and the carbon material for reduction can be made into one briquette, and this and the carbon material for fuel can be filled alternately or in the form of a mixture.

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

Example 1) Thermocouples for temperature measurement were installed on the furnace wall at intervals of 10 crn above and below,
Three water-cooled oxygen lances are installed at the bottom of the furnace wall (at a position 206n from the bottom).1. A reactor with a runner near the bottom of the furnace (
1 (diameter: 40crn x height: 100crn) is first filled with charcoal and ignited, and after this ignition, oxygen gas is supplied from the oxygen lance at a flow rate of 1804/min (total oxygen gas amount) to preheat the inside of the furnace. . Next, blast furnace coke is fed into the furnace by a hopper, burned, and heated to a high temperature.

Next, in this furnace, bauxite 70 (weight) ~ 7 r
trm). In addition, in the reduction of bauxite, the temperature at the top of the packed bed was adjusted by the amount of briquette coke supplied. As a result, when the temperature at the top of the packed bed becomes 750° C. or less, a soft condensed layer is formed at the top, and when the temperature becomes 650° C. or less, the growth of this condensed layer becomes rapid. This condensed layer becomes extremely hard if left to stand, but it was observed that when the temperature at the top exceeded 800° C., the phenomenon of formation of such a condensed layer was no longer observed. Therefore, in the case of this melt furnace, its critical operating temperature was confirmed to be approximately Boo°C.

As described above, the melting furnace is operated by intermittent feeding of coke and bauxite briquette for fuel and adjusting the amount of feed at that time to maintain the temperature at the top of the packed bed at about 800°C. and about c+oKg with the odor briquette
By supplying the blast furnace coke into the furnace for 10 hours, crude alloy 6V4 could be obtained.

[Brief explanation of drawings]

FIG. 2 is an explanatory diagram of a blast furnace system when implementing the present invention. 1... Molten smelt furnace, 2... Alumina briquette supply line, 3
...Carbon material supply line, 4r 6.11...Supply amount adjustment device line, 6...Oxygen gas supply line, 7...
Heating body pair, 8... Combustion gas discharge line, 9... Aluminum alloy discharge line. Patent applicant Makoto Ishizaka, Director of the Agency of Industrial Science and Technology - Figure
surface

Claims (1)

[Claims] (1) A packed bed containing an alumina-containing raw material and a carbon material is formed in a blast furnace, and in the furnace, alumina is reduced by the carbon material using a combustion reaction of the carbon material with oxygen gas and the combustion heat. (b) The ratio of the alumina-containing raw material to the carbon material, and (C) the height of the packed bed, by changing one or more of the following: A method of operating an aluminum smelting blast furnace, characterized by maintaining the temperature at the top so that it does not fall below a critical operating temperature defined in the text.