JPS5980786A - Manufacture of anode for aluminum electrolytic cell - Google Patents

Abstract

PURPOSE:To obtain a carbonaceous anode with a low rate of consumption due to electrolysis for a prebaking type Al electrolytic cell by specifying the specific gravity of aggregate coke as a starting material. CONSTITUTION:Aggregate coke is kneaded with a carbonaceous binder and molded, and the molded body is calcined at 1,100-1,300 deg.C to obtain an anode. Coke having 1.75-1.95g/cm<3> true specific gravity is used as the aggregate coke. Raw coke such as pitch coke or petroleum coke is calcined at about 800- 1,300 deg.C for about 10-15hr, and calcined coke having said true specific gravity is selected from the resulting calcined coke. The quality of aggregate coke is generally controlled in accordance with the calcining temp., and the true specific gravity depends on the calcining temp. The specific gravity depends somewhat on the kind and composition of raw coke as a starting material and conditions during calcination other than temp.

Description

[Detailed description of the invention] The present invention relates to a method for manufacturing an anode for an aluminum electrolytic cell.

More specifically, the present invention relates to a method for manufacturing an anode for a P1J bake (rθ-bakθ) type aluminum electrolytic cell.

Generally, aluminum is produced by electrolyzing a molten salt made of cryolite, aluminum fluoride, fluorite, alumina, etc. using an electrolytic cell based on the Hall:L method.

The carbonaceous anode used in the pre-baked aluminum electrolytic cell is manufactured using aggregate coke (hereinafter referred to as "aggregate") and carbonaceous binder (hereinafter referred to as "binder") as the main raw materials. . Specifically, the anode is manufactured through the steps (1) to (2) shown in the first step.

■ Knead aggregate with appropriate particle size and binder, and mold the kneaded material into the required size using a molding device.

■ Fill the molded product into a firing furnace and fire it at a predetermined temperature.

■ Attach a conductive rod to the fired product and use it as the final anode for use in the electrolytic cell.

The anode manufactured through the above steps is installed in an aluminum electrolytic cell and used for molten salt electrolysis.

As the anode gradually wears out during the process of molten salt electrolysis, it is necessary to supply a new anode, and it is also necessary to take out the exhausted anode and replace it with a new anode, which is a complicated process. It is desirable to use an anode that improves the quality of the electrolyte and is less likely to be consumed during the electrolysis process, and manufacturing such an anode has been a challenge for many engineers.

Generally, the aggregate that is the raw material for the anode is raw coke at 100θ.
It is fired at a high temperature of ~/1100°C, and the quality of the aggregate is controlled at this firing temperature. True specific gravity tends to increase as the simulated firing temperature increases. Usually, as an aggregate, for example, petroleum coke has a true specific gravity of 2.0.2 to 2.
/Ill shoulder, pitch coke has a true specific gravity of 1. r~2-
Oj g/cr& is used.

The present inventor focused on the correlation between the true specific gravity of the aggregate and the consumption of the anode manufactured using the aggregate, and as a result of repeated studies in order to obtain an anode that is less likely to be consumed during the electrolysis process, the inventor developed five invention has been achieved.

The purpose of the present invention is to provide a pre-baked aluminum electrolytic cell with
The purpose is to provide a method for manufacturing an anode with a low electrolytic consumption rate, which is used in a carbonaceous binder and a bone material with a true specific gravity of The molded product obtained by molding the mixed material with material coke is fired at a temperature of
This can be easily achieved by a method for producing an anode for an aluminum electrolytic cell characterized by firing at Q~/300°C.

The method of the present invention will be explained in detail below. In the method of the present invention, a kneaded product of a carbonaceous binder and aggregate coke is molded and then fired to form an anode. Manufacture.

As the carbonaceous binder, coal tar pitch, petroleum binder pitch, etc. are used. Pitch coke is also used as aggregate coke.

Raw coke such as petroleum coke is heated to ♂00~/300℃
Of those obtained by baking for about 10~/j hours, those with true specific gravity of /, 7j-/, and 11/cr& are used. The quality of aggregate is generally controlled by the smoking temperature;
The true specific gravity varies depending on the firing temperature, but it also depends to some extent on the type and composition of the raw coke, the simulated firing conditions other than the temperature, etc.

First, mix the carbonaceous binder at a mixing rate of l-
After kneading with aggregate to a concentration of about 2 to 20%, it is molded using a method such as press molding. However, the crosstalk rate is not necessarily limited to this range, and it depends on the aggregate and binder used. Selected by characteristics. Next, the molded product is fired in a firing furnace such as a ring furnace, usually at a temperature increase rate of t-10°C/hr. The firing temperature is 1100 to 300°C, preferably //QQ, /OO°C.

Further, the firing temperature is preferably higher than the firing temperature of raw coke for obtaining aggregate. Furthermore, a conductive rod is attached to the fired product to form the final anode used for electrolysis.

According to the method of the present invention, it is possible to obtain an anode that exhibits excellent wear characteristics in the aluminum electrolysis process. Therefore, it is possible to reduce the supply amount of new anodes, and also to reduce the complicated work required for anode replacement, which has extremely great industrial value.

Hereinafter, the present invention will be explained in more detail with reference to Examples.
Non-invention unless the gist of the invention is exceeded.

The following examples are not intended to be limiting.

Example First, pitch coke was baked at various temperatures in the range of 0 to 1210°C to obtain various aggregates.

Next, for each aggregate, its true specific gravity
It was determined in accordance with the true specific gravity test method stipulated by . However, the aggregate must be pulverized into a fine powder of λ00 mesh or less, and the degassing method during the operation related to calculating true specific gravity must be depressurized in addition to the ``boiling the sample in water'' method of the 11th standard method. The accuracy of the true specific gravity measurement was further improved by performing various operations. Sara K, press-formed ridges by cross-mixing the various aggregates mentioned above and a binder pitch with a cross-mixing ratio of /7 to /♂chi, up to a maximum firing temperature of 1ioo°C in an experimental electric firing furnace //Q
After baking for a period of time, a conductive rod was attached to produce the final anode. The various produced anodes were attached to an experimental electrolytic cell and electrolysis was carried out under the operating conditions shown in Table 1.

The electrolytic consumption rates of various anodes were measured. The results are shown in FIG. FIG. 1 is a graph showing the relationship between the true specific gravity of aggregate and the electrolytic consumption rate of anodes manufactured using each aggregate.

The electrolytic consumption rate was determined by the following formula.

Table 7 From Figure 1, it can be seen that the electrolytic consumption rate increases as the true specific gravity of aggregate increases, and that the tendency of electrolytic consumption changes significantly around the true specific gravity of aggregate 1.779/i. 73. T-ri!
It can be seen that in the range of 9/(yrl), the electrolytic consumption rate is low and almost constant, whereas in the range of 2.0 yr or more, the electrolytic consumption rate increases markedly.

From the above, the true specific gravity value is 1.7! ~t,qsE//
crl, especially /, t o -t, y o g/cr! ,
It is clear that the anode manufactured using the aggregate v has excellent wear characteristics.

[Brief explanation of the drawing]

Figure 1 is a graph showing the correlation between the true specific gravity of aggregate and the electrolytic consumption rate of the anode.

Claims (1)

[Claims] (1) Carbonaceous binder and true specific gravity /, 71-/, r9/
A method for producing an anode for an aluminum electrolytic cell, characterized in that a molded product obtained by molding the kneaded product with bone phase coke of d is fired at a firing temperature of 100 to 1300°C.