A production control method for a fully graphitized cathode aluminum electrolytic cell

Abstract

The present invention relates to the technical field of electrolytic aluminum, and provides a production control method for an aluminum electrolytic cell with a fully graphitized cathode. The present invention adopts an electrolytic production energy balance management mode based on the characteristics of low resistance and high heat dissipation of the fully graphitized cathode, determines the process technology standards based on the electricity income and heat energy expenditure, and maintains the energy balance relationship of the electrolytic production; during the normal production period of the electrolytic cell, the present invention adopts the "five lows and one high" control standard of "low voltage, low aluminum level, low molecular ratio, low alumina concentration, low furnace bottom pressure drop, and high electrolyte level", which can stabilize the electrolytic production and reduce the DC power consumption. Industrial experimental verification shows that by using the method of the present invention to control the production process of the fully graphitized cathode aluminum electrolytic cell, the current efficiency can reach 93.5%, and the DC power consumption is below 12300kWh / t.Al, which can achieve better economic and technical indicators, achieve the goals of reducing energy consumption and reducing carbon emissions, and has good promotion value and application value.

Description

Technical Field

[0001] The present invention relates to the technical field of electrolytic aluminum, and in particular to a production control method for a fully graphitized cathode aluminum electrolytic cell. Background Art

[0002] The aluminum electrolysis production process is molten salt electrolysis. In the early stage of the development of the aluminum industry, small self-baking electrolytic cells were used. With the continuous advancement of electrolysis technology, self-baking cells were eliminated and small pre-baked electrolytic cells such as 80KA and 180KA were established. Later, they gradually developed into large pre-baked electrolytic cells such as 200KA, 240KA, 280KA, 300KA, 350KA, 400KA, 500KA, and 600KA. However, the cathode structure of the electrolytic cell has always been made of GS-3 or GS-5 material. Problems such as high cathode voltage drop and weak conductivity restrict the reduction of production voltage and the power consumption level is relatively high.

[0003] At present, the domestic electrolytic aluminum industry is facing the challenge of developing low-energy consumption electrolytic cathode technology under the background of energy conservation and carbon reduction. In recent years, in the electrolytic cell technology revolution, graphitized cathodes have stood out. Graphitized cathodes have low resistance and high conductivity. When applied to electrolytic cells, they have the advantages of low resistivity, strong corrosion resistance, and good thermal shock resistance. However, due to the high thermal conductivity and good heat transfer of graphitized cathodes, the electrolytic cell has large heat dissipation and is difficult to control the process. The parameters are prone to fluctuations during the operation of the electrolytic cell, insufficient heat input, increased heat dissipation, and increased cold stroke of the electrolytic cell. These factors make it difficult to play the advantages of the fully graphitized cathode and the energy consumption indicators cannot be improved. Summary of the invention

[0004] In view of this, the present invention provides a production control method for a fully graphitized cathode aluminum electrolytic cell. The present invention standardizes the process of the fully graphitized cathode aluminum electrolytic cell throughout its life cycle, so that the fully graphitized cathode aluminum electrolytic cell can achieve stable production, reduce energy consumption, and extend its life.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] A production control method for a fully graphitized cathode aluminum electrolytic cell, wherein the fully graphitized cathode aluminum electrolytic cell is used to produce electrolytic aluminum, wherein the production process is divided into a startup late stage and a normal production stage which are performed in sequence;

[0007] During the normal production period, the electrolyte level of the electrolytic cell is 180-200 mm, the aluminum level is 190-230 mm, the molecular ratio is 2.35-2.45, the electrolysis temperature is 935-945°C, the aluminum oxide concentration is 1.5-2.5wt%, and the set voltage is 3.80V.

[0008] Preferably, the late startup period starts from the startup of the fully graphitized cathode aluminum electrolytic cell until it runs for 120 days; and the normal production period starts from the 120th day after the fully graphitized cathode aluminum electrolytic cell runs for.

[0009] Preferably, the normal production period is divided into three stages according to the tank age, which are respectively recorded as the first stage, the second stage and the third stage. The first stage is from 121 days to 5 years, the second stage is from the 6th year to the 8th year, and the third stage is more than 8 years.

[0010] The electrolyte levels of the first stage, the second stage and the third stage are independently 180 to 200 mm;

[0011] The aluminum levels of the first stage, the second stage, and the third stage increase successively by 10 to 20 mm, and the aluminum level of the first stage is 190 to 210 mm;

[0012] The molecular ratios of the first stage, the second stage and the third stage are independently 2.30 to 2.45;

[0013] The electrolysis temperatures of the first stage, the second stage and the third stage are independently 935-945°C;

[0014] The alumina concentrations of the first stage, the second stage and the third stage are independently 1.5-2.5 wt %.

[0015] Preferably, the late start-up period is divided into a furnace building period and an adjustment period, which are carried out in sequence. The furnace building period lasts for 90 days, and the adjustment period lasts for 30 days.

[0016] The voltage management standard of the electrolytic cell during the furnace construction period is: the voltage is maintained at 6.0-7.0V on the first day after startup, reduced by 0.5V every day on the 2nd to 4th days, reduced by 0.1V every day on the 5th to 9th days, kept unchanged on the 10th to 31st days, and reduced to 3.80V in proportion on the 32nd to 90th days. During the 32nd to 90th days, the voltage is reduced by 3-4mV every day.

[0017] Preferably, during the furnace wall construction period, the electrolyte level of the electrolytic cell is 250-350 mm on the 1st to 30th day, and the electrolyte level is 180-210 mm on the 31st to 90th day.

[0018] Preferably, during the furnace wall construction period, the aluminum level of the electrolytic cell is 170-190 mm, the molecular ratio is greater than 3.0, and the aluminum oxide concentration is 1.5-2.5 wt%.

[0019] Preferably, during the furnace building period, the electrolysis temperature of the electrolytic cell is reduced successively on the 1st to 30th day, the 31st to 60th day and the 61st to 90th day, with a reduction range of 10°C, and the electrolysis temperature on the 1st to 30th day is 965-980°C.

[0020] Preferably, during the furnace building period, the current efficiency of the electrolytic cell is 85-90%.

[0021] Preferably, the iron content of the aluminum liquid in the electrolytic cell during the normal production period is less than 0.05wt%, and the silicon content is less than 0.03wt%.

[0022] Preferably, the capacity of the fully graphitized cathode aluminum electrolytic cell is 500KA.

[0023] The invention provides a production control method for a fully graphitized cathode aluminum electrolytic cell. The fully graphitized cathode aluminum electrolytic cell is used to produce electrolytic aluminum. The production process is divided into a startup late stage and a normal production stage which are performed in sequence. During the normal production stage, the electrolyte level of the electrolytic cell is 180-200 mm, the aluminum level is 190-230 mm, the molecular ratio is 2.35-2.45, the electrolysis temperature is 935-945° C., the aluminum oxide concentration is 1.5-2.5 wt %, the set voltage is 3.80 V, and the average voltage is 3.85 V. According to the characteristics of small resistance and large heat dissipation of the fully graphitized cathode, the invention adopts an electrolytic production energy balance management mode, determines the process technology standard according to the electricity income and heat energy expenditure, and maintains the energy balance relationship of the electrolytic production. Specifically, during the normal production period of the electrolytic cell, the invention adopts a "five lows and one high" process technology control idea of ​​"low voltage, low aluminum level, low molecular ratio, low aluminum oxide concentration, low furnace bottom pressure drop, and high electrolyte level", which can stabilize the electrolytic production and reduce the DC power consumption. The method of the present invention is used to control the normal production period of the fully graphitized cathode aluminum electrolytic cell, the furnace bottom pressure drop is controlled below 200 mV, the current efficiency reaches 93.5%, the effect coefficient is as low as 0.05 times / cell day, which is conducive to the reduction of carbon tetrafluoride, and the DC power consumption per ton of aluminum is lower than 12300 kWh / t.Al, which creates conditions for energy saving and carbon reduction, and the impurity content of the aluminum liquid is low during the normal production period, the iron content is below 0.05%, and the silicon content is below 0.03%, which is conducive to the preparation of high-quality products.

[0024] Furthermore, in the later stage of electrolytic cell startup, the present invention adopts the "3+1" management standard, implements the "three highs and three lows" process standard of high voltage, high electrolysis temperature, high molecular ratio, low aluminum level, low alumina concentration, and low effect coefficient, and establishes a solid furnace side under high electrolysis temperature and high molecular conditions. DETAILED DESCRIPTION

[0025] The present invention provides a production control method for a fully graphitized cathode aluminum electrolytic cell, characterized in that the fully graphitized cathode aluminum electrolytic cell is used to electrolyze aluminum, and the production process is divided into a startup late stage and a normal production stage which are carried out in sequence;

[0026] During the normal production period, the electrolyte level of the electrolytic cell is 180-200 mm, the aluminum level is 190-230 mm, the molecular ratio is 2.35-2.45, the electrolysis temperature is 935-945°C, the alumina concentration is 1.5-2.5wt%, the set voltage is 3.80V, and the average voltage is 3.85V.

[0027] In the present invention, the use of the fully graphitized cathode aluminum electrolytic cell for aluminum electrolysis specifically refers to the use of alumina molten salt electrolysis, and the raw materials used for aluminum electrolysis, such as alumina, aluminum fluoride, cryolite, carbon anode, etc., are all controlled in accordance with relevant national or industry standards.

[0028] In the present invention, the capacity of the fully graphitized cathode aluminum electrolytic cell is preferably 500KA, specifically a 500KA series prebaked anode electrolytic cell.

[0029] In the present invention, the fully graphitized cathode aluminum electrolytic cell is first roasted and started, and then enters the production process. The production process is divided into a late startup period and a normal production period which are carried out in sequence. The present invention has no special requirements on the operating conditions of the roasting startup, and the electrolytic cell can be started by a method familiar to those skilled in the art.

[0030] In the present invention, the post-startup period refers to the period from the start-up of the fully graphitized cathode electrolytic cell to 120 days of operation; the normal production period refers to the period starting from 120 days after the fully graphitized cathode aluminum electrolytic cell has been in operation. In a specific embodiment of the present invention, the total operating time of the fully graphitized cathode aluminum electrolytic cell is 10 years, of which the normal production period is the period after the 121st day.

[0031] In the present invention, the later stage of startup is divided into a furnace building period and an adjustment period which are carried out in sequence. The duration of the furnace building period is preferably 90 days, and the duration of the adjustment period is preferably 30 days.

[0032] In the present invention, the voltage management standard of the electrolytic cell during the furnace construction period is: the voltage is maintained at 6.0-7.0V on the first day after startup, reduced by 0.5V every day on the 2nd to 4th days, reduced by 0.1V every day on the 5th to 9th days, kept unchanged on the 10th to 31st days, and reduced to 3.80V in proportion on the 32nd to 90th days. During the 32nd to 90th days, the voltage reduction is 3-4mV per day. Specifically, the voltage is maintained at 5.5-6.5V on the second day, 5.0-6.0V on the third day, 4.5-5.5V on the fourth day, 4.4-5.4V on the fifth day, 4.3-5.3V on the sixth day, 4.2-5.2V on the seventh day, 4.1-5.1V on the eighth day, 4.0-5.0V on the ninth day, and 4.0-5.0V on the tenth to 31st days; the voltage is reduced to 3.80V in proportion (3-4mV reduction per day) in the second and third months. The present invention manages the voltage of the electrolytic cell during the furnace wall construction period according to the above method, can establish a strong and stable furnace wall at high temperature and high molecular ratio, is conducive to preventing the furnace wall from being damaged under the process control standard in the normal production stage, improves production stability, improves current efficiency, and reduces power consumption.

[0033] In the present invention, during the furnace wall construction period, the electrolyte level of the electrolytic cell on the 1st to 30th day is preferably 250-350 mm, more preferably 260-320 mm, and the electrolyte level on the 31st to 90th day is preferably 180-210 mm, more preferably 190-200 mm.

[0034] In the present invention, during the furnace building period, the aluminum level of the electrolytic cell is preferably 170-190 mm, more preferably 180-185 mm, the molecular ratio is preferably >3.0, more preferably greater than 3.0V and less than 3.5V, and the alumina concentration is preferably 1.5-2.5wt%, more preferably 1.8-2.0wt%.

[0035] In the present invention, during the furnace construction period, the electrolysis temperature (i.e., the tank temperature) of the electrolytic cell on the 1st to 30th day, the 31st to 60th day, and the 61st to 90th day is successively reduced with a reduction range of 10°C. The electrolysis temperature on the 1st to 30th day is preferably 965-980°C, the electrolysis temperature on the 31st to 60th day is preferably 955-970°C, and the electrolysis temperature on the 61st to 90th day is preferably 945-960°C.

[0036] In the present invention, during the furnace building period, the electrolytic cell is controlled by the above method, the current efficiency of the electrolytic cell is 85-90%, the effect coefficient is 0.05 times / day, and the furnace bottom pressure drop is below 200mV.

[0037] In the later stage of electrolytic cell startup, the present invention adopts a "3+1" control mode and proposes a "three highs and three lows" process standard, namely, high voltage, high electrolysis temperature, high molecular ratio, low aluminum level, low alumina concentration, and low effect coefficient, which can establish a solid furnace side under high electrolysis temperature and high molecular conditions.

[0038] In the present invention, the adjustment period specifically refers to the transition from the process technology standards of the furnace construction period to the normal production process standards, which takes 30 days. It is implemented in an average of 30 days according to the difference between the process standards of the normal production stage and the process standards of the furnace construction period to achieve the conversion of the production stage. After the adjustment period ends, the normal production period begins.

[0039] In the present invention, the normal production period is divided into three stages according to the age of the tank, namely the first stage, the second stage and the third stage. The first stage is from 121 days to 5 years, the second stage is from the 6th year to the 8th year, and the third stage is more than 8 years, specifically the 8th to 10th year.

[0040] In the present invention, the electrolyte level of the first stage, the second stage and the third stage is preferably 180-200mm, more preferably 185-195mm; the aluminum level of the first stage, the second stage and the third stage increases successively, the increase is 10-20mm, the aluminum level of the first stage is preferably 190-210mm, the aluminum level of the second stage is preferably 200-220mm, and the aluminum level of the third stage is preferably 220-230mm; the molecular ratio of the first stage, the second stage and the third stage is preferably 2.30-2.45; the electrolysis temperature of the first stage, the second stage and the third stage is preferably 935-945℃; the aluminum oxide concentration of the first stage, the second stage and the third stage is preferably 1.5-2.5wt%. In the present invention, the set voltage of the entire normal production period is 3.80V, and the average voltage is 3.85V.

[0041] During the normal production period, the present invention adopts the control concept of low voltage, low aluminum level, low molecular ratio, low alumina concentration, low furnace bottom pressure drop, and high electrolyte level (i.e. "five lows and one high"), wherein: operating under low aluminum level conditions can reduce heat dissipation in the aluminum horizontal area; operating under low voltage conditions lays the foundation for reducing energy consumption and carbon emissions; operating under low molecular ratio conditions lays the foundation for improving current efficiency; operating under low alumina concentration conditions lays the foundation for improving current efficiency and increasing output; operating under high electrolyte level conditions lays the foundation for stable production.

[0042] In the present invention, the iron content of the aluminum liquid in the electrolytic cell during the normal production period is less than 0.05wt%, and the silicon content is less than 0.03wt%. The present invention adopts the above-mentioned process parameters to control the electrolytic cell, which can reduce the impurity content in the aluminum liquid and is conducive to the production of high-quality products.

[0043] In the present invention, the process parameters of the electrolytic cell are controlled within the above range during normal production, the pressure drop at the furnace bottom can be controlled below 200 mV, the effect coefficient of the electrolytic cell can be as low as 0.05 times / day, the current efficiency reaches 93.5%, and the DC power consumption per ton of aluminum is less than 12300 kWh / t.Al, creating conditions for energy saving and carbon reduction.

[0044] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] Example 1

[0046] Aluminum electrolysis is carried out in a 500KA fully graphitized cathode aluminum electrolytic cell. The raw materials used for aluminum electrolysis, such as alumina, aluminum fluoride, cryolite, carbon anode, etc., are all controlled in accordance with relevant national standards or industry standards.

[0047] The 120 days after the electrolytic cell is turned on are the late start-up period, of which the first 90 days are the furnace construction period, and the 91st to 120th days are the adjustment period. The voltage control standards for the furnace construction period are shown in Table 1, the electrolyte level, aluminum level, molecular ratio, electrolysis temperature and alumina concentration control standards are shown in Table 2, and the effect coefficient and current efficiency during the operation of the electrolytic cell are shown in Table 2.

[0048] Table 1 Voltage control standards during furnace construction period

[0049]

[0050] Table 2 Control standards for electrolyte level, aluminum level, molecular ratio, electrolysis temperature and alumina concentration during the furnace construction period

[0051]

[0052]

[0053] It can be seen from Table 2 that by controlling the furnace wall construction period of the electrolytic cell according to the above scheme, the effect coefficient of the electrolytic cell is as low as 0.05 times / day, and the current efficiency is 85-90%. In addition, the experimental results show that by adopting the above method for control, the furnace wall thickness of the electrolytic cell reaches 14 cm and the furnace bottom pressure drop is below 200 mV.

[0054] During the adjustment period, the process technology standards of the furnace construction period will be transitioned to normal production process standards, which will take 30 days and will be transitioned on average based on the difference in indicators.

[0055] The electrolytic cell entered the normal production period after the 121st day of operation. The set voltage during the normal production period was 3.8 V, and the average voltage was 3.85 V. The control standards for electrolyte level, aluminum level, molecular ratio, electrolysis temperature and alumina concentration are shown in Table 3. The effect coefficient and current efficiency during the operation of the electrolytic cell are shown in Table 3.

[0056] Table 3 Process parameter control standards during normal production of electrolytic cell

[0057]

[0058] It can be seen from Table 3 that the normal production period of the electrolytic cell is controlled according to the standard of the present invention, the effect coefficient of the electrolytic cell is as low as 0.05 times / cell day, the current efficiency reaches 93.5%, and after repeated tests and analyses, the cell condition is stable, the furnace bottom is clean, the side steel windows of the electrolytic cell, the cathode steel rod, and the furnace bottom temperature all meet the design requirements, the DC power consumption per ton of aluminum is less than 12300 kWh / t.Al, and the economic and technical indicators are stable.

[0059] In addition, the impurity content of the aluminum liquid in the electrolytic cell during normal production was analyzed. The results showed that the iron content in the aluminum liquid was below 0.05% and the silicon steel content was below 0.03%.

[0060] It can be seen from the above embodiments that the present invention adopts an electrolytic production energy balance management mode, determines the process technology standards according to the electricity income and heat energy expenditure, maintains the energy balance relationship of the electrolytic production, and specifically adopts the "3+1" management mode in the later stage of startup to implement the "three highs and three lows" process standards, namely high voltage, high electrolysis temperature, high molecular ratio, low aluminum level, low alumina concentration, and low effect coefficient, to establish a solid furnace side under high electrolysis temperature and high molecular conditions; adopts the "low aluminum level management mode" in the normal production period to implement the "five lows and one high" process technology control concept, namely low aluminum level, low voltage, low molecular ratio, low alumina depth, low effect coefficient, and high electrolyte level, to stabilize the electrolytic production, reduce energy consumption, and extend the service life of the electrolytic cell.

[0061] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A production control method for a fully graphitized cathode aluminum electrolytic cell, characterized in that: The fully graphitized cathode aluminum electrolytic cell is used to produce electrolytic aluminum, and the production process is divided into a late start-up period and a normal production period which are carried out in sequence; During the normal production period, the electrolyte level of the electrolytic cell is 180-200 mm, the aluminum level is 190-230 mm, the molecular ratio is 2.35-2.45, the electrolysis temperature is 935-945°C, the aluminum oxide concentration is 1.5-2.5 wt%, and the set voltage is 3.80 V; The start-up period starts from the start-up of the fully graphitized cathode aluminum electrolytic cell until it runs for 120 days; the normal production period starts from the 120th day after the fully graphitized cathode aluminum electrolytic cell runs; The normal production period is divided into three stages according to the tank age, namely the first stage, the second stage and the third stage. The first stage is from 121 days to 5 years, the second stage is from the 6th year to the 8th year, and the third stage is more than 8 years. The aluminum levels of the first stage, the second stage, and the third stage increase successively by 10 to 20 mm, and the aluminum level of the first stage is 190 to 210 mm; The post-startup period is divided into a furnace construction period and an adjustment period, which are carried out in sequence. The furnace construction period lasts for 90 days, and the adjustment period lasts for 30 days. The voltage management standard of the electrolytic cell during the furnace construction period is: the voltage is maintained at 6.0-7.0V on the first day after startup, reduced by 0.5V every day on the 2nd to 4th days, reduced by 0.1V every day on the 5th to 9th days, kept unchanged on the 10th to 31st days, and reduced to 3.80V in proportion on the 32nd to 90th days. During the 32nd to 90th days, the voltage is reduced by 3-4mV every day.

2. The production control method according to claim 1, characterized in that: The electrolyte levels of the first stage, the second stage and the third stage are independently 180 to 200 mm; The molecular ratios of the first stage, the second stage and the third stage are independently 2.30 to 2.45; The electrolysis temperatures of the first stage, the second stage and the third stage are independently 935-945°C; The alumina concentrations of the first stage, the second stage and the third stage are independently 1.5-2.5 wt %.

3. The production control method according to claim 1, characterized in that: During the furnace side building period, the electrolyte level of the electrolytic cell is 250-350 mm from the 1st to the 30th day, and the electrolyte level is 180-210 mm from the 31st to the 90th day.

4. The production control method according to claim 1, characterized in that: During the furnace building period, the aluminum level of the electrolytic cell is 170-190 mm, the molecular ratio is greater than 3.0, and the aluminum oxide concentration is 1.5-2.5 wt%.

5. The production control method according to claim 1, characterized in that: During the furnace building period, the electrolysis temperature of the electrolytic cell is reduced successively from the 1st to the 30th day, from the 31st to the 60th day and from the 61st to the 90th day, with a reduction range of 10°C. The electrolysis temperature from the 1st to the 30th day is 965 to 980°C.

6. The production control method according to claim 1, characterized in that: During the furnace building period, the current efficiency of the electrolytic cell is 85-90%.

7. The production control method according to claim 1, characterized in that: During the normal production period, the iron content of the aluminum liquid in the electrolytic cell is less than 0.05wt%, and the silicon content is less than 0.03wt%.

8. The production control method according to claim 1, characterized in that: The capacity of the fully graphitized cathode aluminum electrolytic cell is 500KA.

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