CN112176364B - Method for controlling lithium and potassium content in aluminum electrolyte - Google Patents
Method for controlling lithium and potassium content in aluminum electrolyte Download PDFInfo
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- CN112176364B CN112176364B CN202010826745.9A CN202010826745A CN112176364B CN 112176364 B CN112176364 B CN 112176364B CN 202010826745 A CN202010826745 A CN 202010826745A CN 112176364 B CN112176364 B CN 112176364B
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Abstract
The invention relates to a method for controlling the content of lithium and potassium in an aluminum electrolyte, which comprises the following steps: when the content of lithium fluoride in the aluminum electrolyte is more than 3 wt% or the content of potassium fluoride is more than 2 wt%, a solid volatile substance filter is additionally arranged on the flue gas pipeline, and the electrolytic flue gas is discharged into the solid volatile substance filter to obtain solid volatile substances and electrolytic flue gas after primary filtration; discharging the preliminarily filtered electrolysis flue gas into a dry purification system, and inputting the obtained fluorine-carrying aluminum oxide into an aluminum electrolytic cell needing to reduce the lithium and potassium content in aluminum electrolyte; when the content of lithium fluoride in the aluminum electrolyte is less than 2 wt% or the content of potassium fluoride is less than 1 wt%, adding the solid volatile matter into an aluminum electrolytic cell needing to improve the content of lithium and potassium in the aluminum electrolyte, or preparing an anode protection ring from the solid volatile matter and then wrapping the anode steel claw. The invention can stably adjust the lithium and potassium content in the aluminum electrolyte.
Description
Technical Field
The invention belongs to the field of non-ferrous metal aluminum smelting, and particularly relates to a method for controlling the content of lithium and potassium in an aluminum electrolyte.
Background
Until now in 1886, the cryolite-alumina fused salt electrolysis method of Hall-Heroult has been the mainstream method of the aluminium smelting industry. The cryolite-alumina fused salt is also called as aluminum electrolyte, and dissolves alumina in the aluminum electrolysis process and reduces the alumina into a reaction medium of metallic aluminum through electrolysis.
Due to the mineral sources, the preparation process and the like of the industrial alumina produced in China, the domestic industrial alumina contains lithium oxide or potassium oxide to different degrees. These lithium or potassium oxides form fluorides (generally referred to simply as lithium or potassium fluorides) with the alumina entering the aluminum electrolyte, and are continuously enriched to eventually reach an equilibrium concentration. The content of lithium oxide and potassium oxide in the alumina generally determines the equilibrium concentration of lithium fluoride and potassium fluoride in the aluminum electrolyte. The higher the content of lithium oxide or potassium oxide in the alumina, the higher the equilibrium concentration of lithium fluoride and potassium fluoride in the aluminum electrolyte.
Lithium fluoride and potassium fluoride have great influence on the physical and chemical properties of the aluminum electrolyte, such as primary crystal temperature, saturated solubility and dissolution speed of aluminum oxide, conductivity, viscosity, surface tension and the like. The physicochemical property of the aluminum electrolyte also determines the temperature of the electrolytic process and whether the electrolytic process is smooth, and the energy consumption, the product quality and the service life of the cell of the aluminum electrolyte are influenced to a great extent, so that the aluminum electrolyte is very important for the electrolytic process.
Lithium fluoride and potassium fluoride are beneficial to the aluminum electrolysis process when present in appropriate amounts in the aluminum electrolyte. In particular to lithium fluoride which can improve the conductivity of the aluminum electrolyte and is beneficial to reducing the voltage of the electrolytic cell, thereby achieving the effect of energy saving. The optimum lithium fluoride content is generally considered to be 3 wt%. Potassium fluoride can increase the saturation concentration of alumina in the aluminum electrolyte, although it can slightly reduce the conductivity of the aluminum electrolyte, but at lower levels (less than 2 wt%) it does not have a significant effect. However, both lithium fluoride and potassium fluoride are detrimental when the content in the aluminum electrolyte is too high. It is generally believed that when the lithium fluoride content exceeds 5 wt%, potassium fluoride in excess of 3 wt% will have a significant effect on the electrolysis process. For example: the primary crystal temperature is greatly reduced, the dissolution speed of alumina is greatly reduced, the electrolytic temperature is too low, a large amount of alumina is precipitated, the pressure drop of the furnace bottom is increased, the voltage swing is realized, the current efficiency is reduced, the energy consumption is increased, and the service life of the cell is even reduced.
Therefore, controlling the lithium potassium content in the aluminum electrolyte is very important for aluminum electrolysis enterprises. Because different industrial aluminas and different cell ages are adopted by electrolytic aluminum enterprises in China, the content difference of lithium fluoride and potassium fluoride in electrolyte components of different enterprises is large, some enterprises need to reduce the content of lithium and potassium, and some enterprises need to improve the content of lithium and potassium.
For enterprises needing to reduce the lithium and potassium content, the following measures are generally taken: 1) the industrial alumina with low content of lithium oxide and potassium oxide is used instead, or the industrial alumina with low content of lithium oxide and potassium oxide is mixed according to a certain proportion on the basis of the original alumina, so that the balance concentration of lithium and potassium in the aluminum electrolyte is reduced; 2) purchasing or replacing the aluminum electrolyte with low lithium fluoride and potassium fluoride content from other enterprises, adding the aluminum electrolyte into the aluminum electrolytic cell of the enterprise, and diluting the lithium potassium content of the aluminum electrolyte.
For enterprises needing to increase the lithium and potassium content, the following measures are generally taken: 1) adding lithium carbonate or potassium fluoroaluminate into the aluminum electrolytic cell; 2) the aluminum electrolyte with high lithium fluoride and potassium fluoride content is purchased or replaced from other enterprises and added into the aluminum electrolytic cell of the enterprise to improve the lithium potassium content of the aluminum electrolyte.
At present, the lithium and potassium content in the aluminum electrolyte can be effectively adjusted and controlled by the adjusting measures, but the related materials need to be purchased or transported in a large amount, and the economic cost of an enterprise can be obviously improved. Therefore, there is still a need for an effective and low-cost method or means for controlling and adjusting the lithium and potassium content of aluminum electrolytes.
Disclosure of Invention
The invention aims to provide an effective and relatively low-cost method for controlling the lithium and potassium content of an aluminum electrolyte aiming at the problem of high economic cost of the current measures for adjusting and controlling the lithium and potassium content of the aluminum electrolyte by enterprises.
The invention adopts the following technical scheme:
a method for controlling the content of lithium and potassium in an aluminum electrolyte is characterized by comprising the following steps:
(1) a solid volatile matter filter is additionally arranged between the aluminum electrolytic cell and the dry purification system, and the electrolytic flue gas in the aluminum electrolytic cell is discharged into the solid volatile matter filter to obtain solid volatile matters and the electrolytic flue gas after preliminary filtration;
(2) when the mass percentage of lithium fluoride in the aluminum electrolyte in the aluminum electrolytic cell is more than 3% or the mass percentage of potassium fluoride is more than 2%, discharging the preliminarily filtered electrolytic flue gas into a dry purification system to obtain fluorine-carrying aluminum oxide, and inputting the fluorine-carrying aluminum oxide into the aluminum electrolytic cell needing to reduce the lithium and potassium content in the aluminum electrolyte;
(3) and (3) when the mass percent of lithium fluoride in the aluminum electrolyte in the aluminum electrolytic cell is less than 2% or the mass percent of potassium fluoride in the aluminum electrolyte is less than 1%, adding the solid volatile matter obtained in the step (1) into the aluminum electrolytic cell needing to improve the lithium potassium content in the aluminum electrolyte.
The method for controlling the lithium and potassium content in the aluminum electrolyte is characterized in that the solid volatile substance filter in the step (1) is arranged on a main pipe or a branch pipe of a flue gas pipeline between an aluminum electrolysis cell and a dry purification system; the dry purification system is filled with industrial alumina.
The method for controlling the lithium and potassium content in the aluminum electrolyte is characterized in that the solid volatile matter filter in the step (1) is one or more of cyclone dust collection equipment, orifice plate dust collection equipment, cloth bag dust collection equipment and electrostatic dust collection equipment.
According to the method for controlling the content of lithium and potassium in the aluminum electrolyte, the method is characterized in that in the step (3), when the mass percentage of lithium fluoride in the aluminum electrolyte in the aluminum electrolytic cell is less than 2% or the mass percentage of potassium fluoride in the aluminum electrolyte in the aluminum electrolytic cell is less than 1%, the anode protective ring is prepared from the solid volatile matter obtained in the step (1), and then the anode protective ring is wrapped on an anode steel claw of the aluminum electrolytic cell which needs to improve the content of lithium and potassium in the aluminum electrolyte.
The method for controlling the content of lithium and potassium in the aluminum electrolyte is characterized in that the anode protection ring is an amorphous product, and the anode protection ring is wrapped on an anode steel claw of an aluminum electrolytic cell needing to improve the content of lithium and potassium in the aluminum electrolyte by adopting a mould through ramming molding.
The method for controlling the lithium and potassium content in the aluminum electrolyte is characterized in that the anode protection ring is a shaped product, the anode protection ring is formed by pressure or without pressure, and the tonnage of a press machine used when the anode protection ring is formed by pressure is 20-100 tons; when the anode protection ring is formed without pressure, the anode protection ring is formed in a die by ramming or vibration; the formed anode protection ring is wrapped on an anode steel claw of an aluminum electrolytic cell which needs to improve the lithium and potassium content in aluminum electrolyte.
The method for controlling the content of lithium and potassium in the aluminum electrolyte is characterized in that the anode protection ring comprises the following components in percentage by mass: 50-90% of solid volatile, 0.5-5% of adhesive and the balance of additive.
The method for controlling the lithium and potassium content in the aluminum electrolyte is characterized in that the additive is one or more of fluorine-carrying alumina, cryolite and electrolyte powder.
The method for controlling the content of lithium and potassium in the aluminum electrolyte is characterized in that the binder is one or two of polyvinyl alcohol and methyl cellulose.
The invention has the beneficial technical effects that: the method can stably adjust the lithium and potassium content in the aluminum electrolyte under the conditions of not changing the quality, the variety, the proportion and the like of the industrial alumina used by an aluminum electrolysis enterprise, thereby greatly reducing the purchasing cost or the transportation cost of the enterprise. In addition, the collected solid volatile matter is made into an anode protection ring or used as a raw material for extracting lithium and fluorine, and certain economic benefit can be created for enterprises. For enterprises needing to improve the lithium and potassium content in the aluminum electrolyte, the anode protection ring is adopted, so that the lithium and potassium content in the aluminum electrolyte can be adjusted, the corrosion speed of the anode steel claw can be reduced, and the influence on the quality of the original aluminum is avoided.
Drawings
FIG. 1 is a schematic process flow diagram of the present invention.
Detailed Description
Referring to fig. 1, the method for controlling the content of lithium and potassium in the aluminum electrolyte of the invention comprises the following steps:
(1) and a solid volatile filter is additionally arranged between the aluminum electrolysis cell and the dry purification system and is arranged on a main pipe or a branch pipe of a flue gas pipeline between the aluminum electrolysis cell and the dry purification system. The solid volatile substance filter is one or more of cyclone dust collection equipment, orifice plate dust collection equipment, cloth bag dust collection equipment and electrostatic dust collection equipment. Discharging the electrolysis flue gas in the aluminum electrolysis cell into a solid volatile substance filter through a flue gas pipeline to obtain solid volatile substances and electrolysis flue gas after primary filtration;
(2) when the mass percentage of lithium fluoride in the aluminum electrolyte in the aluminum electrolytic cell is more than 3% or the mass percentage of potassium fluoride is more than 2%, reducing the lithium potassium content in the aluminum electrolyte in the aluminum electrolytic cell, discharging the preliminarily filtered electrolysis flue gas into a dry purification system to obtain fluorine-carrying aluminum oxide, and inputting the fluorine-carrying aluminum oxide into the aluminum electrolytic cell needing to reduce the lithium potassium content in the aluminum electrolyte through a conveying system; the dry purification system is filled with industrial alumina, and the industrial alumina adsorbs hydrogen fluoride gas in the electrolytic flue gas and a small amount of residual solid volatile matters in the dry purification system.
(3) When the mass percentage of lithium fluoride in the aluminum electrolyte in the aluminum electrolytic cell is less than 2% or the mass percentage of potassium fluoride in the aluminum electrolyte in the aluminum electrolytic cell is less than 1%, the lithium potassium content in the aluminum electrolyte in the aluminum electrolytic cell needs to be improved, and the solid volatile matter obtained in the step (1) is added into the aluminum electrolytic cell in which the lithium potassium content in the aluminum electrolyte needs to be improved; or preparing an anode protection ring from the solid volatile matter obtained in the step (1), and then wrapping the anode protection ring on an anode steel claw of the aluminum electrolytic cell needing to improve the lithium and potassium content in the aluminum electrolyte.
The anode guard ring is an amorphous product or a shaped product.
When the anode protection ring is an amorphous product, the anode protection ring is wrapped on an anode steel claw of an aluminum electrolytic cell needing to improve the lithium and potassium content in aluminum electrolyte by adopting a mould through ramming molding. When the anode protection ring is a shaped product, the anode protection ring is formed by pressure or without pressure, and when the anode protection ring is formed by pressure, the tonnage of a used press is 20-100 tons; when the anode protection ring is formed without pressure, the anode protection ring is formed in a die by ramming or vibration, and the formed anode protection ring is wrapped on an anode steel claw of an aluminum electrolytic cell which needs to improve the lithium and potassium content in aluminum electrolyte. The anode guard ring comprises the following components in percentage by mass: 50-90% of solid volatile, 0.5-5% of adhesive and the balance of additive. The additive is one or more of fluorine-carrying alumina, cryolite and electrolyte powder. The binder is one or two of polyvinyl alcohol and methyl cellulose.
The solid volatiles comprise Na5Al3F14、AlF3、Na2AlF5、K2NaAl3F12、K2NaAlF6、KAlF4、Li2NaAl3F12、Li2NaAlF6、Al2O3. The solid volatiles can also be used as raw materials for extracting lithium and fluorine, and when lithium is extracted, the extracted lithium is mainly lithium carbonate; when extracting fluorine, the extracted fluorine is mainly composed of hydrofluoric acid and aluminum fluoride.
The technical principle of the invention is as follows:
during the aluminum electrolysis process, a large amount of volatile matters are generated in the aluminum electrolyte and enter a dry purification system. If lithium potassium is not present in the aluminum electrolyte, the volatile matter will be NaAlF as the major component when it leaves the electrolyte melt in gaseous form4HF; if the aluminum electrolyte contains lithium and potassium in relatively high concentrations, the volatile matter will leave the electrolyte melt in gaseous form and will be composed primarily of NaAlF4、HF、KAlF4、LiAlF4And the like. Due to KAlF4、LiAlF4Is lower than NaAlF4And thus more volatile. Lithium potassium in aluminum electrolyte, easy to be KAlF4、LiAlF4The form of (c) is volatilized.
Wherein NaAlF4、KAlF4、LiAlF4These substances will be decomposed and combined in the cooling process to become solid volatile matters. The final solid volatile matter in the aluminum electrolysis flue gas is relatively complex in composition, and the solid volatile matter mainly contains Na5Al3F14、AlF3、Na2AlF5、K2NaAl3F12、K2NaAlF6、KAlF4、Li2NaAl3F12、Li2NaAlF6Etc., in addition to a portion of flying Al2O3. However, it can be seen that lithium and potassium are mainly present in the aluminium electrolysis flue gas in the form of solid volatiles.
If the aluminum electrolyte contains lithium potassium in a high concentration, the content of lithium potassium in the solid volatile matters in the aluminum electrolysis flue gas is relatively high. However, if no solid volatile matter collecting device is arranged on the flue gas pipeline, the solid volatile matters are adsorbed by the industrial alumina again together with HF gas in the alumina adsorption process, enter the fluorine-carrying alumina and return to the electrolytic cell again, and the lithium and potassium concentration in the electrolytic cell cannot be reduced.
If the solid volatile matters in the aluminum electrolysis flue gas are filtered and collected before entering the alumina adsorption process, the volatilized lithium and potassium can not enter the aluminum electrolysis cell. Therefore, the equilibrium concentration of potassium fluoride and lithium fluoride in the aluminum electrolyte is greatly reduced due to volatilization.
When the lithium and potassium content in the aluminum electrolyte in the aluminum electrolytic cell needs to be improved, the collected solid volatile matter with high lithium and potassium content is added into the aluminum electrolytic cell with the lithium and potassium content in the aluminum electrolyte needing to be improved, or the anode protection ring is prepared from the collected solid volatile matter with high lithium and potassium content and then wrapped on an anode steel claw of the aluminum electrolytic cell with the lithium and potassium content in the aluminum electrolyte needing to be improved. Not only can adjust the lithium and potassium content in the aluminum electrolyte, but also can reduce the corrosion speed of the anode steel claw, and does not worry about influencing the quality of the original aluminum.
The present invention is further illustrated by the following examples, which are not intended to limit the scope of the present invention.
Example 1
The state before implementation:
k in industrial alumina in dry purification system of certain 1# electrolytic aluminum enterprise2O content of 0.041 wt%, Li2The O content is 0.012 wt%; k in fluorine-carrying alumina formed after volatile matters in aluminum electrolysis flue gas are adsorbed by industrial alumina2O content 0.094 wt%, Li2The O content is 0.028 wt%; the mass percent of lithium fluoride and the mass percent of potassium fluoride in the aluminum electrolyte in the aluminum electrolytic cell are respectively 1.72 wt% and 4.8 wt%; the enterprise needs to reduce the content of potassium fluoride in the aluminum electrolyte in the aluminum electrolysis cell.
The implementation measures are as follows:
the method comprises the following steps that a combined device of a two-stage cyclone dust collector and an electrostatic dust collector is additionally arranged on a main pipe of an aluminum electrolysis flue gas pipeline between two rows of plants of the enterprise and in front of a dry purification system, and is used for collecting solid volatile matters in the aluminum electrolysis flue gas to obtain the solid volatile matters and the preliminarily filtered electrolysis flue gas; the total aluminum production of the two trains is 211.5 tons/day, and the solid volatiles collected per day is about 2.6 tons.
And discharging the preliminarily filtered electrolytic flue gas into a dry purification system to obtain the fluorine-carrying alumina. The dry purification system is filled with industrial alumina, and the industrial alumina adsorbs hydrogen fluoride gas in the electrolytic flue gas and a small amount of residual solid volatile matters in the dry purification system. After the solid volatiles were collected, the lithium and potassium content of the fluorine-loaded alumina was significantly reduced compared to that before the application. The sampling analysis results show that: fluorine-carrying alumina medium K20.056 percent of O and Li2The mass percentage of O is 0.017 percent. And (3) conveying the fluorine-carrying alumina into the aluminum electrolysis cells of the two rows of the factory buildings through a conveying system.
After the implementation:
after three months of operation, sampling and measuring the lithium and potassium content in the two lines of factory building aluminum electrolytes, and the result shows that: the mass percent of lithium fluoride and the mass percent of potassium fluoride in the aluminum electrolyte in the aluminum electrolytic cell are respectively 0.98% and 2.9%. And, because the KF content is reduced, the current efficiency of the aluminum cell is improved by about 1.5 percent.
The collected solid volatile matters are used as raw materials for extracting fluorine, and the extracted fluorine mainly comprises hydrofluoric acid and aluminum fluoride.
The content of the industrial alumina, the content of the fluorine-containing alumina before and after the implementation, and the content of lithium and potassium in the aluminum electrolyte in example 1 are shown in Table 1.
Example 2
The state before implementation:
one 240kA electrolytic cell series factory building in certain 2# electrolytic aluminum enterprise, and industrial alumina K in dry purification system2O content 0.013 wt%, Li2The O content is 0.050 wt%; k in fluorine-carrying alumina formed after volatile matters in aluminum electrolysis flue gas are adsorbed by industrial alumina2O content of 0.031 wt%, Li2The O content is 0108 wt%; the mass percent of lithium fluoride and the mass percent of potassium fluoride in the aluminum electrolyte in the aluminum electrolytic cell are respectively 5.6% and 1.75%; the 240kA series of plants of the enterprise need to reduce the content of lithium fluoride in the aluminum electrolyte in the aluminum electrolysis cell.
One 400kA electrolytic cell series factory building in certain 2# electrolytic aluminum enterprise, and industrial alumina K in dry purification system2O content 0.008 wt% and Li2The O content is 0.009 wt%; k in fluorine-carrying alumina formed after volatile matters in aluminum electrolysis flue gas are adsorbed by industrial alumina2O content 0.009 wt%, Li2The O content is 0.011 wt%; the mass percent of lithium fluoride and the mass percent of potassium fluoride in the aluminum electrolyte in the aluminum electrolytic cell are respectively 1.28 wt% and 1.03 wt%; the 400kA series of factory buildings of the enterprise need to improve the content of lithium fluoride in the aluminum electrolyte in the aluminum electrolytic cell.
The implementation measures are as follows:
1) for the enterprise 240kA series of plants (need to reduce the content of lithium fluoride in the electrolyte)
A combined device of a perforated plate dust collector and a cloth bag dust collector is additionally arranged on a main pipe of an aluminum electrolysis flue gas pipeline between two rows of factory buildings of 240kA series factory buildings of the enterprise and in front of a dry purification system, and is used for collecting solid volatile matters in aluminum electrolysis flue gas to obtain solid volatile matters and preliminarily filtered electrolysis flue gas; the total aluminum production of the two trains is 110.3 tons/day, and the solid volatiles collected per day is about 1.4 tons.
And discharging the preliminarily filtered electrolytic flue gas into a dry purification system to obtain the fluorine-carrying alumina. The dry purification system is filled with industrial alumina, and the industrial alumina adsorbs hydrogen fluoride gas in the electrolytic flue gas and a small amount of residual solid volatile matters in the dry purification system. To volatilize solidAfter collection, the lithium and potassium content in the fluorine-carrying alumina is obviously reduced compared with that before implementation. The sampling analysis results show that: fluorine-carrying alumina medium K20.056 percent of O and Li2The mass percentage of O is 0.017 percent. The fluorine-carrying alumina is conveyed into aluminum electrolytic cells of two rows of factories of the 240kA series of factories through a conveying system.
The solid volatiles collected were divided into three fractions: one part of the lithium is used as a raw material for extracting lithium, and the extracted lithium is mainly lithium carbonate; one part is used for manufacturing an anode protection ring; and a part of the electrolyte is directly used as a high-lithium electrolyte raw material for storage.
2) For the 400kA series of plants (need to increase the content of lithium fluoride in electrolyte)
In the 400kA series factory building of the enterprise, a part of solid volatile matters collected in the 240kA series are directly used as electrolyte raw materials and added into an aluminum electrolysis cell of the 400kA series factory building. A portion of the solid volatiles collected in the 240kA series was made into an anode guard ring for use on the anode steel claw of the cell of the 400kA series plant.
The manufacturing and using processes of the anode protection ring adopt the following methods in sequence:
(1) the anode guard ring is an indefinite-shaped product
The anode guard ring comprises the following components in percentage by mass: 65% of solid volatile, 30% of fluorine-carrying alumina, 4% of polyvinyl alcohol and 1% of methyl cellulose. Uniformly mixing the solid volatile matter, the fluorine-carrying aluminum oxide, the polyvinyl alcohol and the methyl cellulose to obtain an unshaped anode protection ring material, adding water into the unshaped anode protection ring material, stirring the mixture into a mud shape to obtain a mixture, wherein the adding amount of the water is 5% of the mass percentage of the unshaped anode protection ring material, wrapping the mixture on an anode steel claw of an aluminum electrolytic cell needing to improve the content of lithium fluoride in the aluminum electrolyte by adopting a mould through ramming molding, and demoulding after the mixture is solidified.
(2) The anode protection ring is a shaped product
The anode protection ring is formed by adopting pressure, and the tonnage of the used pressure is 50 tons. The anode guard ring comprises the following components in percentage by mass: 57% of solid volatile, 40% of electrolyte powder, 3% of polyvinyl alcohol and 1% of methyl cellulose. And uniformly mixing the solid volatile matter, electrolyte powder, polyvinyl alcohol and methyl cellulose, and performing compression molding by using a 50-ton press machine to obtain the anode protection ring. Each anode protection ring is semi-annular, and when the anode protection ring is used, the two anode protection rings are spliced into an annular shape and wrapped on the anode steel claw.
(3) The anode guard ring is an indefinite-shaped product
The anode guard ring comprises the following components in percentage by mass: 65% of solid volatile, 20% of fluorine-carrying alumina, 10% of cryolite, 4% of polyvinyl alcohol and 1% of methyl cellulose. Uniformly mixing solid volatile matters, fluorine-carrying aluminum oxide, cryolite, polyvinyl alcohol and methyl cellulose to obtain an amorphous anode protection ring material, adding water into the amorphous anode protection ring material, stirring the amorphous anode protection ring material into mud to obtain a mixture, wherein the adding amount of the water is 6% of the mass percentage of the amorphous anode protection ring material, wrapping the mixture on an anode steel claw of an aluminum electrolysis cell needing to improve the content of lithium fluoride in aluminum electrolyte by adopting a mould through ramming, and demoulding after the mixture is solidified.
(4) The anode guard ring is an indefinite-shaped product
The anode guard ring comprises the following components in percentage by mass: 50% of solid volatile, 30% of electrolyte powder, 15% of fluorine-carrying alumina, 4% of polyvinyl alcohol and 1% of methyl cellulose. Uniformly mixing solid volatile matters, electrolyte powder, fluorine-carrying aluminum oxide, polyvinyl alcohol and methyl cellulose to obtain an unshaped anode protection ring material, adding water into the unshaped anode protection ring material, stirring the mixture into a mud shape to obtain a mixture, wherein the adding amount of the water is 5% of the mass percentage of the unshaped anode protection ring material, wrapping the mixture on an anode steel claw of an aluminum electrolytic cell needing to improve the content of lithium fluoride in the aluminum electrolyte by adopting a mold through ramming and vibration molding, and demolding after the mixture is solidified.
After the implementation:
1) for the 240kA series of plants of the enterprise
After three months of operation, sampling and measuring the lithium and potassium content in the aluminum electrolytes of two columns of plants of the 240kA series of plants, and the results show that: the mass percent of lithium fluoride and the mass percent of potassium fluoride in the aluminum electrolyte in the aluminum electrolytic cell are respectively 3.2% and 0.92%. And because the LiF content is reduced, the average temperature of the electrolytic cell is increased from 925 ℃ to 938 ℃ averagely, the solubility of aluminum oxide is improved, the precipitation at the bottom of the electrolytic cell is reduced, the stability of the electrolytic cell is improved, and the current efficiency is improved by about 1.2%.
2) For the 400kA series of plants of the enterprise
After three months of operation, sampling and measuring the lithium and potassium content in the aluminum electrolytes of two columns of plants of the 400kA series of plants, and the results show that: the LiF content in the aluminum electrolyte is increased to 2.8 wt%. And, because the LiF content is increased, the cell voltage of the average aluminum cell is reduced by about 10mV, and the current efficiency is improved by about 0.6%.
The content of the industrial alumina, the content of the fluorine-containing alumina before and after the implementation, and the content of lithium and potassium in the aluminum electrolyte in example 2 are shown in Table 1.
The above examples are some examples of the present invention in two electrolytic aluminum plants, and are only for the purpose of more clearly illustrating the application of the present invention, but not for the purpose of limitation. For example: the solid volatile substance filter is mainly used for filtering and collecting solid volatile substances, and the type and the number of the solid volatile substance filter do not influence the essential characteristics of the invention; the solid volatile matter is made into an anode protection ring which is mainly applied to an anode steel claw, and the manufacturing mode of the anode protection ring does not influence the essential characteristics of the invention; the embodiments are within the scope of the present invention, consistent with the features set forth herein.
Table 1 shows the content of commercial alumina, the content of fluorine-containing alumina before and after the implementation, and the content of lithium and potassium in the aluminum electrolyte
Claims (9)
1. A method for controlling the content of lithium and potassium in an aluminum electrolyte is characterized by comprising the following steps:
(1) a solid volatile matter filter is additionally arranged between the aluminum electrolytic cell and the dry purification system, and the electrolytic flue gas in the aluminum electrolytic cell is discharged into the solid volatile matter filter to obtain solid volatile matters and the electrolytic flue gas after preliminary filtration;
(2) when the mass percentage of lithium fluoride in the aluminum electrolyte in the aluminum electrolytic cell is more than 3% or the mass percentage of potassium fluoride is more than 2%, discharging the preliminarily filtered electrolytic flue gas into a dry purification system to obtain fluorine-carrying aluminum oxide, and inputting the fluorine-carrying aluminum oxide into the aluminum electrolytic cell needing to reduce the lithium and potassium content in the aluminum electrolyte;
(3) and (3) when the mass percent of lithium fluoride in the aluminum electrolyte in the aluminum electrolytic cell is less than 2% or the mass percent of potassium fluoride in the aluminum electrolyte is less than 1%, adding the solid volatile matter obtained in the step (1) into the aluminum electrolytic cell needing to improve the lithium potassium content in the aluminum electrolyte.
2. The method for controlling the content of lithium and potassium in the aluminum electrolyte according to claim 1, wherein the solid volatile substance filter in the step (1) is arranged on a main pipe or a branch pipe of a flue gas pipeline between the aluminum electrolysis cell and the dry purification system; the dry purification system is filled with industrial alumina.
3. The method for controlling the lithium and potassium content in the aluminum electrolyte according to claim 1, wherein the solid volatile substance filter in the step (1) is one or more of cyclone dust collection equipment, orifice plate dust collection equipment, cloth bag dust collection equipment and electrostatic dust collection equipment.
4. The method for controlling the content of lithium and potassium in the aluminum electrolyte according to claim 1, wherein in the step (3), when the mass percentage of lithium fluoride in the aluminum electrolyte in the aluminum electrolytic cell is less than 2% or the mass percentage of potassium fluoride in the aluminum electrolyte in the aluminum electrolytic cell is less than 1%, the anode protective ring is prepared from the solid volatile matter obtained in the step (1), and then the anode protective ring is wrapped on an anode steel claw of the aluminum electrolytic cell which needs to increase the content of lithium and potassium in the aluminum electrolyte.
5. The method for controlling the content of lithium and potassium in the aluminum electrolyte according to claim 4, wherein the anode protection ring is an amorphous product, and the anode protection ring is formed by stamping and wrapped on an anode steel claw of an aluminum electrolytic cell needing to increase the content of lithium and potassium in the aluminum electrolyte.
6. The method for controlling the lithium potassium content in the aluminum electrolyte according to claim 4, wherein the anode protection ring is a shaped product, the anode protection ring is formed by pressure molding or no pressure molding, and when the anode protection ring is formed by pressure molding, the tonnage of a press used is 20-100 tons; when the anode protection ring is formed without pressure, the anode protection ring is formed in a mould through vibration; the formed anode protection ring is wrapped on an anode steel claw of an aluminum electrolytic cell which needs to improve the lithium and potassium content in aluminum electrolyte.
7. The method for controlling the lithium potassium content in the aluminum electrolyte according to claim 4, wherein the anode guard ring comprises the following components in percentage by mass: 50-90% of solid volatile, 0.5-5% of adhesive and the balance of additive.
8. The method for controlling the lithium potassium content in the aluminum electrolyte according to claim 7, wherein the additive is one or more of fluorine-carrying alumina, cryolite and electrolyte powder.
9. The method for controlling lithium and potassium content in aluminum electrolyte according to claim 7, wherein the binder is one or both of polyvinyl alcohol and methyl cellulose.
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