SU548662A1 - The method of obtaining graphitized anodes - Google Patents

Description

from which it is clear that a part of carbon in the form of its oxide leaves the volume of the material, leading to the formation of additional porosity, which, in turn, leads to a decrease in the purity of the aiode and its consumption expendables.

Whole isotopes are a result of the physicomechanical and operational characteristics of graphitized anodes for metal extraction, for example, zirconium, by the electrolysis of molten salts.

The essence of the invention is that the metal oxide, an example of zirconium dioxide, is mixed with coke powder with a crux of no more than 100 microns, and this mixture is subjected to preliminary heat treatment at a temperature of 1700-1900 ° C for 1-2 hours in a vacuum 10 mm Hg Art. Then granulated coke is added to this mixture and a coal-tar nexus (binder) is added, blending, molding, firing, and graphitization are carried out.

Introduction to carbon anodes by pre-precursor dioxides and zirconium provides anodes with enhanced physicomechanical and operating properties.

A distinctive feature of the invention is that, prior to the introduction of the inoculation, the coke powder with zirconium oxide is thermally treated at 1700-1900 ° C in vacuum - mm Hg. Art. within 1-2 teas and granulated coke is added.

The selected treatment modes are optimal, since KaiK anodes manufactured in modes that are beyond the recommended values (pyaz 1700 ° C and higher than 1900 ° C) have lower strength and durability.

Carrying out and preliminary heat treatment at 1600 ° C, even for 3 teas, does not provide sufficient reduction of Zr02. This leads to the fact that in the process of grafting ZrO2 occurs in the process of grafting already in the volume of the anode, reducing its strength by 1.5 times, and durability - almost 3 times. Increasing the treatment temperature higher than 1900 ° C leads to the complete reduction of ZrO2. In this case, at the burning stage, oxidation of the formed zirconium carbide takes place, which leads to anode cracking, a decrease in its icidity by more than 3 times and the anode resistance of the anode - by 4 times.

Heat treatment is carried out in a vacuum of 10 mm Hg. Art. within 1-2 hours in order to quickly remove the reduction products from the reaction space, which leads to an increase in the reduction rate of ZrO2. Deviation from the indicated treatment regimes can lead to nitriding (in vacuum conditions, menene lO mmHg), and a further increase in vacuum is not advisable.

The method is carried out as follows.

Circoium dioxide Zr02 is mixed in a ratio of 1: 1 and weight to coke powder at a comedian temperature for 25-30 minutes. The mixture obtained is subjected to preliminary heat treatment in order to partially restore ZrO2 to a temperature of 1700–1900 ° C for 1-2 teas. Heat treatment to temperature 1700-1900 ° C is carried out at a speed of 800-2000 degrees / tea in vacuum mm RT. Art. Then granular coke (with a granule size of 0.3-1.2 mm) is added to the mixture on a bond (coal tar pitch) and blending is carried out for 1 hour at a temperature of 100-120 ° C until a homogeneous mass is obtained. From received

the masses molded anodes under pressure of 250-300 kgf / cm2 with a holding at this pressure for 3 minutes. Molded anodes are burned at a speed of 8-10 degrees / hour for 100-150 hours before temperature 1000-1200 ° C and then graphitize at a temperature of 2000-2200 ° C. Acelium, the partial reduction of zirconium dioxide outside the volume of the anode makes it possible to obtain less porous and more durable anodes with less consumable and more indicative ones. Partially reduced dioxide, in contrast to metal zirconium and zirconium carbide, is not oxidized during the firing process of the anodes, which makes it possible to manufacture higher-quality anodes.

Example 1. A mixture of 10 kg of zirconium dioxide and 10 kg of calcined coke powder (particle size 100 µm), after stirring in a mixing machine for 30 minutes at room temperature, is placed in graphite crucibles and heat treated in a vacuum oven at a vacuum of mm Hg. Art., the temperature of 1700 ° C for 2 hours. Then, 60 kg of granulated coke (0.3–1.2 mm in size) and 20–1 kg of medium-temperature coal tar pitch (softening temperature 65–70 ° C) are added to this mixture. The zirconia content in the mixture is 10%. The resulting mixture is unmixed at 110 ° C for 1 hour. Mass is formed into blanks

200X100X100 mm at a pressure of 300 kgf / s, which are then fired at 1100 ° C and graphitized at a temperature of 2200 ° C.

Example 2. The procedures described in example 1 are repeated, only a mixture of zirkopy dioxide and coke powder is heat treated.

at a temperature of 1800 ° C for 1.5 hours

vacuum W mm RT. Art. Dioxide content

zirconium in a mixture of 10%.

Example 3. The procedures of Example 1 are repeated.

Only laugh thermoablative at a temperature of 1900 ° C for 1 hour in a vacuum of 10 mm Hg. Art. The content of zirconium dioxide in the mixture is 10%. Example 4. The procedures of Example 1 are repeated.

only laugh treated at a temperature of 1800 ° C for 1.5 hours in a vacuum of 10 mm Hg. Art. and 8 kg of granulated coke and 5 kg of carbonaceous coal are added to the mixture. Zirconia content in

a mixture of 30%.

The table shows the physicomechanical and operational characteristics of the anodes obtained in accordance with the present method {examples 1-4) and on the modes outside the present method (examples 5-6), as well as anodes manufactured in accordance with by known methods (examples 7-8).

Samples were tested under the same conditions, namely; the temperature of the electrolyte (a mixture of potassium fluorocirconate, potassium fluoride and sodium chloride) was 750-800 ° C, the concentration of fluorine in the electrolyte was 28-30%. The anode under investigation was immersed into the prepared electrolyte and a direct current was passed through the electrolyte, creating an initial current density of 0.1 a / cm at the anode. With an interval of 1 min, the current density was gradually increased until an anodic effect appeared. The occurrence of this phenomenon is determined by a sharp increase in voltage and current drop, as well as the appearance of glowing points around the anode.

The anode was vented before and after the test. About the resistance of the anode was judged by the loss of its weight (B g), the arrival of the masters at 1 a / hour.

From the table it can be seen that at odioiac values of anodic current density, which is determined by practically chemical composition (0.75-

5 0.8 a / cm2 - 10% ZrOa and 1.0-1.05 A / cm - for 30% ZrOa) the strength of the anodes obtained by the proposed method (Example 1--4) is 2-4 times higher, and the consumption of anodes is 3 times less than that of anodes obtained by known methods.

Claims (1)

Invention Formula A method for producing graphite-coated anodes, which includes mixing coke powder with a metal oxide, such as zirconium oxide, introducing coal tar pitch into a mixture, forming blanks, and pressing roasting and graphitizing the blanks, characterized in that, in order to improve the physical-mechanical and strength characteristics, With the introduction of pitch, a mixture of iKOKca powder with zirconium oxide is treated at 1700–1900 ° C under vacuum, mm Hg. Art. within 1-2 hours and add granular coke.