CN104313642B - A kind of method for reducing aluminium electrolysis anode air film voltage drop - Google Patents

Abstract

The present invention proposes a method for reducing the voltage drop of the anode gas film of aluminum electrolysis, which is characterized in that by adding graphite intercalation compound, aluminum powder in the anode, and adding NaCl, NaF, carbonate in the electrolyte to reduce the anode-electrolyte The interfacial tension improves the wettability of the electrolyte to the anode and promotes the discharge of anode bubbles, thereby reducing the voltage drop of the anode gas film in aluminum electrolysis. At the same time, due to the good conductivity of graphite intercalation compounds, adding graphite intercalation compounds to the anode can significantly improve the conductivity of the anode and reduce the voltage drop of the anode body.

Description

A method for reducing the voltage drop of the anode gas film in aluminum electrolysis

technical field

The invention belongs to the technical field of aluminum electrolysis, in particular to a method for reducing the voltage drop of an anode gas film of aluminum electrolysis.

Background technique

During the electrolysis process, under the action of direct current, the anode undergoes the following reactions:

2Al ₂ O ₃ +3C＝4Al+3CO ₂ (1)

Al ₂ O ₃ +3C＝2Al+3CO (2)

During the electrolysis process, air bubbles are generated under the palm of the anode. Due to the poor wettability of the electrolyte to the anode, some air bubbles are adsorbed under the palm of the anode. Fortin ^[1] et al. found that the coverage of air bubbles under the bottom of the anode is as high as 50%-60%. The behavior of the bubbles has a great influence on the electrolysis process. Since the bubbles are not conductive, the adsorption of the bubbles under the palm of the anode will increase the cell resistance, thereby increasing the cell voltage. Haupin ^[2] and others found that the voltage caused by the air bubbles is about 0.15-0.35V. When the air bubbles cover too much area under the palm of the anode, an air film will be formed, and even cause the anode effect, resulting in a cell voltage as high as 20-30V. Therefore, how to promote the discharge of air bubbles under the palm of the anode is an important aspect to reduce the pressure drop of the anode gas film and save energy.

At present, the research on promoting air bubble discharge and reducing film voltage drop mainly focuses on slotting and ultrasonic. In the early stage of electrolysis, although slotting is beneficial to the discharge of air bubbles under the palm of the anode, as the anode is consumed, the depth of slotting decreases, and the effect of slotting on promoting bubble discharge is weakened, and the depth of slotting is limited, so it is impossible to accompany the entire anode. use process. However, the use of ultrasonic waves to promote the discharge of air bubbles at the bottom of the anode is still in the laboratory research, and there are technical problems such as the transmission of ultrasonic waves and the connection of ultrasonic transmitters, which are currently difficult to solve.

Contents of the invention

The invention proposes a method for reducing the voltage drop of the anode gas film of aluminum electrolysis, aiming at the problem that the anode bubbles cover the bottom palm of the anode to increase the voltage drop.

The purpose of the present invention is achieved through the following technical solutions.

A method for reducing the voltage drop of the anode gas film of aluminum electrolysis. At the same time, different additives are added to the anode and the electrolyte, and one or more of aluminum powder and graphite intercalation compounds are added to the anode; NaCl and NaF are added to the electrolyte , one or more of carbonates; or only add one or more of aluminum powder and graphite intercalation compounds to the anode, or only add one or more of NaCl, NaF, and carbonates to the electrolyte or more.

The mass percentage of the additive in the anode is 1-10%, and the mass percentage of the additive in the electrolyte is 1-15%.

The graphite intercalation compound includes: one or more of Br-GIC, C-Na intercalation compound, C-K intercalation compound, and C-Li intercalation compound.

The carbonate includes: one or more of Na ₂ CO ₃ , CaCO ₃ , Li ₂ CO ₃ , K ₂ CO ₃ .

In the invention, different additives are respectively added to the anode and the electrolyte to reduce the anode-electrolyte interfacial tension, improve the wettability of the electrolyte to the anode, and thereby promote the discharge of the anode bubbles. And the additive can improve the conductivity of the anode and reduce the voltage drop of the anode body.

detailed description

The following examples are intended to further illustrate the present invention, rather than limit the present invention.

A method for reducing the voltage drop of the anode gas film of aluminum electrolysis, adding one or more of graphite intercalation compound and aluminum powder during the anode preparation process, or adding one of NaCl, NaF, and carbonate to the electrolyte or more, or add the above-mentioned different additives in the anode and the electrolyte at the same time.

Example 1

In this example, 5 wt% of C—Na intercalation compound was added during the preparation of the anode to improve the surface properties of the anode and promote the discharge of bubbles from the anode, and a test was carried out.

In this experiment, the cell voltage is used to study the anode bubbles. The experimental principle: in a short period of time, it can be considered that the alumina concentration, pole distance, and electrolyte composition have not changed. For short periods of time, the cell voltage is only related to the anode bubbles.

In this experiment, the concentration of alumina is 2.5%, the immersion height is 2cm, the degree of superheat is 15°C, and the current density is 0.8A/cm ² . The resulting gas film voltage drop in two different cases of Na intercalation compounds.

The experimental results show that the addition of C-Na intercalation compound is beneficial to promote the discharge of anode bubbles, and the voltage drop of the anode gas film in aluminum electrolysis is reduced by 50-70mV.

Example 2

In this example, 5wt% aluminum powder was added during the preparation of the anode to promote the discharge of the anode bubbles, and a test was carried out.

In this experiment, the cell voltage is used to study the anode bubbles. The experimental principle: in a short period of time, it can be considered that the alumina concentration, pole distance, and electrolyte composition have not changed. For short periods of time, the cell voltage is only related to the anode bubbles.

In this experiment, the concentration of alumina is controlled at 2.5%, the immersion height is 2cm, the degree of superheat is 15°C, and the current density is 0.8A/cm ² . case, the resulting film voltage drop.

The experimental results show that the addition of aluminum powder is beneficial to promote the discharge of anode bubbles, and the voltage drop of the anode gas film of aluminum electrolysis is reduced by 40-60mV.

Example 3

In this example, 10wt% NaCl was added to the electrolyte to promote the discharge of anode air bubbles, and a test was carried out.

In this experiment, the anode bubbles are studied by analyzing the cell voltage. The principle of the experiment is that in a relatively short period of time, it can be considered that the alumina concentration, pole distance, and electrolyte composition have not changed. For short periods of time, the cell voltage is only related to the anode bubbles.

In this experiment, the concentration of alumina is controlled at 2.5%, the immersion height is 2cm, the degree of superheat is 15°C, and the current density is 0.8A/cm ² . The resulting film voltage drop.

The experimental results show that the addition of NaCl is beneficial to promote the discharge of anode bubbles, and the voltage drop of the anode gas film of aluminum electrolysis is reduced by 50-70mV.

Example 4

In this example, 10wt% Na ₂ CO ₃ was added to the electrolyte to promote the discharge of anode bubbles, and a test was carried out.

In this experiment, the anode bubbles are studied by analyzing the cell voltage. The principle of the experiment is that in a relatively short period of time, it can be considered that the alumina concentration, pole distance, and electrolyte composition have not changed. For short periods of time, the cell voltage is only related to the anode bubbles.

In this experiment, the concentration of alumina is controlled at _2.5 %, the immersion height is _2cm , the degree of superheat is ₁₅ °C, and the current density is _0.8A /cm ² . The resulting film voltage drop in two different cases.

The experimental results show that the addition of Na ₂ CO ₃ is beneficial to promote the discharge of anode bubbles, and the voltage drop of the anode gas film in aluminum electrolysis is reduced by 40-60mV.

Example 5

In this example, 5wt% of C—Na intercalation compound was added during the preparation of the anode, and 10wt% of NaCl was added to the electrolyte to promote the discharge of anode bubbles, and a test was carried out.

In this experiment, the anode bubbles are studied by analyzing the cell voltage. The principle of the experiment is that in a relatively short period of time, it can be considered that the alumina concentration, pole distance, and electrolyte composition have not changed. For short periods of time, the cell voltage is only related to the anode bubbles.

In this experiment, the concentration of alumina is controlled at 2.5%, the immersion height is 2cm, the degree of superheat is 15°C, and the current density is 0.8A/cm ² . The gas film voltage drop when 10wt% NaCl is added to the electrolyte and no additive is added to the anode and electrolyte.

The experimental results show that adding C-Na intercalation compound to the anode and adding NaCl to the electrolyte at the same time is beneficial to promote the discharge of anode bubbles, and the voltage drop of the anode gas film in aluminum electrolysis is reduced by 70-90mV.

Claims (1)

1. a kind of method for reducing aluminium electrolysis anode air film voltage drop, it is characterised in that add 5wt% in anode preparation process C-Na intercalation compounds, and addition 10wt% NaCl, to promote the discharge of anode gas bubble, controls aluminum oxide in the electrolyte Concentration is 2.5%, immersion height be 2cm, the degree of superheat be 15 DEG C, current density be 0.8A/cm²。