阅读说明：本技术 一种500ka铝电解槽启动控制方法 (Starting control method for 500KA aluminum electrolytic cell ) 是由 李震 杨成亮 刘进县 杨珅 蔡龙 李扬 韩启超 杨国伟 于 2020-07-08 设计创作，主要内容包括：本发明涉及电解铝技术领域,具体涉及一种500KA铝电解槽启动控制方法,包括启动阶段和控制阶段,启动步骤包括步骤1、装炉；步骤2、焙烧；步骤3、启动；步骤4、灌铝；所述的控制阶段在启动后包括以下阶段：第一阶段,27天内将电压从4.8 v降至4.11v；第二阶段,一个月内将电压从4.11v降至3.98 v；第三阶段,一个月内将电压从3.98 v降至3.92 v；第五个月将电压降至3.880 v,降低电解槽启动成本,缩短启动时间,提升电解槽使用寿命。(The invention relates to the technical field of electrolytic aluminum, in particular to a starting control method of a 500KA aluminum electrolytic cell, which comprises a starting stage and a control stage, wherein the starting step comprises the steps of 1, charging; step 2, roasting; step 3, starting; step 4, pouring aluminum; the control phase comprises the following phases after starting: first stage, voltage was reduced from 4.8v to 4.11v within 27 days; a second stage, reducing the voltage from 4.11v to 3.98 v within one month; a third stage, in which the voltage is reduced from 3.98 v to 3.92 v within one month; and in the fifth month, the voltage is reduced to 3.880 v, the starting cost of the electrolytic cell is reduced, the starting time is shortened, and the service life of the electrolytic cell is prolonged.)

1. A starting control method for a 500KA aluminum electrolytic cell comprises a starting stage and a control stage, and is characterized in that the starting stage comprises the following steps:

step 1, charging:

paving coke, hanging an anode, filling electrolyte powder and soda, embedding a thermocouple, respectively placing 8 temperature measuring sleeves on the aluminum outlet surface, the flue end and the A, B surface of the electrolytic furnace, wherein the center seams of the aluminum outlet end and the flue end of the electrolytic cell are channels built by electrolyte blocks, uniformly paving electrolyte powder with the height of 300mm around the chamber of the electrolytic cell, uniformly and sequentially paving 1.5t of calcium fluoride and 1t of sodium carbonate on the electrolyte powder, and then uniformly covering 25t of electrolyte powder on the surface of the anode and around the chamber of the electrolytic cell;

step 2, roasting:

the current is adopted to supply power in a step-by-step charging mode, and the instantaneous impact low voltage does not exceed 5v in the power supply process;

step 3, starting:

when the roasting time reaches 84h and the average roasting temperature of the middle seam is higher than 920 ℃, starting, continuously and quickly filling 25t of liquid electrolyte into the electrolytic tank, raising the voltage while filling, wherein the speed of raising the anode is matched with the speed of filling the electrolyte, the depth of the anode immersed into the electrolyte is 4-5cm, after the electrolyte is filled, keeping the voltage at 6.5-7.5v, fishing out carbon slag after materials in the electrolytic tank are completely melted, controlling the temperature of the electrolyte below 1000 ℃, controlling the voltage within 7v, and controlling the level of the electrolyte to reach 50 cm.

2. The start-up control method for the 500KA aluminum electrolytic cell according to claim 1, wherein:

further comprises the following steps of 4, aluminum pouring:

and after the electrolytic cell is started for 24 hours, pouring 28t of aluminum liquid, keeping the voltage at 6v before aluminum pouring, keeping the voltage at 5.5v after aluminum pouring, adding 5t of sodium carbonate after the surface of electrolyte forms a crust, taking an original aluminum sample every day after 3 hours after aluminum pouring, and discharging aluminum when the aluminum level reaches 21 cm.

3. The start-up control method for the 500KA aluminum electrolytic cell according to claim 1, wherein: in the step 3, the upward movement of the anode rod is measured once before starting, and whether bias current exists is checked.

4. The start-up control method for the 500KA aluminum electrolytic cell according to claim 1, wherein: in the step 1, the coke laying is to lay coke particles with the granularity of 2-4 mm and the thickness of 26mm on the projection area of the anode.

5. The start-up control method of the 500KA aluminum electrolytic cell according to claim 2, wherein: before the step 4, if the effect is generated, the effect voltage does not exceed 20V, and the time does not exceed 10 min.

6. The start-up control method of the 500KA aluminum electrolytic cell according to claim 4, wherein: cleaning the middle seam coke particles in the coke laying process, and then adding 5-10cm electrolyte powder into the middle seam.

7. The start-up control method for the 500KA aluminum electrolytic cell according to any one of claims 1 to 6, wherein: the control phase comprises the following phases after starting:

first stage

The voltage was reduced from 4.8v to 4.11v within 27 days;

second stage

The voltage is reduced from 4.11v to 3.98 v within one month;

the third stage

The voltage is reduced from 3.98 v to 3.92 v within one month; the voltage was reduced to 3.880 v in the fifth month.

8. The start-up control method for the 500KA aluminum electrolytic cell according to claim 7, wherein: the first-stage pressure reduction process comprises the following steps: the first day down to 4.8 v; the second day is reduced to 4.6v, the fourth day is reduced to 4.4v, and the third day and the fourth day are reduced by 100mv each day; the reduction is 4.31v on the seventh day, and 30mv is reduced every day from the fifth day to the seventh day; the volume is reduced to 4.21v from the twelfth day and is reduced by 20mv from the eighth day to the twelfth day; a reduction of 4.11v on the twenty-second day and a reduction of 10mv per day from the thirteenth to twenty-second day; 4.11v was maintained on the twenty-third to twenty-seventh days.

9. The start-up control method for the 500KA aluminum electrolytic cell according to claim 7, wherein: in the second stage, 30 days after the start-up procedure, 10kg of aluminum fluoride was added.

10. The start-up control method for the 500KA aluminum electrolytic cell according to claim 7, wherein: in the third stage, 60 days after the start-up procedure, 20kg of aluminum fluoride was added.

Technical Field

The invention relates to the technical field of electrolytic aluminum, in particular to a starting control method for a 500KA aluminum electrolytic cell.

Background

At present, the electrolytic cell needs to be roasted and started after the lining of the electrolytic cell is built, normal production operation can be carried out, the roasting starting quality is one of important factors influencing the service life of the electrolytic cell, and although the roasting starting process is carried out for only a few days, the working state of the electrolytic cell after the starting is greatly influenced, particularly the service life of the electrolytic cell is critically influenced. The start-up is to melt a sufficient amount of liquid electrolyte in the cell to accommodate the electrolysis production needs. In the existing starting control technology, magnesium fluoride is required to be uniformly added between an anode and an electrolyte block, cryolite is required to be uniformly added, then Caodan and the cryolite are uniformly stirred and then added to the periphery of the anode, and finally the cryolite is added on the anode and the periphery of the anode.

The electrolysis temperature for normal operation of aluminum electrolysis is generally between 930 ℃ and 970 ℃. The process by which the cell must be heated from room temperature to normal electrolysis temperatures and allowed to produce normally is referred to as the start-up and post-management of the firing of the cell. The preconditions for the conventional start-up of the roasting are established on the assumption that the cell is perfectly normal. In the recovery production process of the electrolytic cell, when the traditional roasting starting method cannot be adopted or needs a long time to start the electrolytic cell, countermeasures and methods are lacked, and simultaneously, the starting cost is high.

Disclosure of Invention

In order to overcome the problems in the prior art, the invention aims to provide a starting control method of a 500KA aluminum electrolytic cell, which reduces the starting cost of the electrolytic cell, shortens the starting time, prolongs the service life of the electrolytic cell and solves the problems in the prior art.

The technical scheme adopted by the invention is as follows:

a starting control method for a 500KA aluminum electrolytic cell comprises a starting stage and a control stage, wherein the starting stage comprises the following steps:

step 1, charging:

paving coke, hanging an anode, filling electrolyte powder and soda, embedding a thermocouple, respectively placing 8 temperature measuring sleeves on the aluminum outlet surface, the flue end and the A, B surface of the electrolytic furnace, wherein the center seams of the aluminum outlet end and the flue end of the electrolytic cell are channels built by electrolyte blocks, uniformly paving electrolyte powder with the height of 300mm around the chamber of the electrolytic cell, uniformly and sequentially paving 1.5t of calcium fluoride and 1t of sodium carbonate on the electrolyte powder, and then uniformly covering 25t of electrolyte powder on the surface of the anode and around the chamber of the electrolytic cell;

step 2, roasting:

the current is adopted to supply power in a step-by-step charging mode, and the instantaneous impact low voltage does not exceed 5v in the power supply process;

step 3, starting:

when the roasting time reaches 84h and the average roasting temperature of the middle seam is higher than 920 ℃, starting, continuously and quickly filling 25t of liquid electrolyte into the electrolytic tank, raising the voltage while filling, wherein the speed of raising the anode is matched with the speed of filling the electrolyte, the depth of the anode immersed into the electrolyte is 4-5cm, after the electrolyte is filled, keeping the voltage at 6.5-7.5v, fishing out carbon slag after materials in the electrolytic tank are completely melted, controlling the temperature of the electrolyte below 1000 ℃, controlling the voltage within 7v, and controlling the level of the electrolyte to reach 50 cm.

Further comprises the following steps of 4, pouring aluminum:

and after the electrolytic cell is started for 24 hours, pouring 28t of aluminum liquid, keeping the voltage at 6v before aluminum pouring, keeping the voltage at 5.5v after aluminum pouring, adding 5t of sodium carbonate after the surface of electrolyte forms a crust, taking an original aluminum sample every day after 3 hours after aluminum pouring, and discharging aluminum when the aluminum level reaches 21 cm.

In step 3, the anode rod up-flow is measured once before starting, and whether a bias current exists is checked.

In the step 1, the step of laying coke is to lay coke particles with the granularity of 2-4 mm and the thickness of 26mm on the projection area of the anode.

Before step 4, if effect is generated, the effect voltage does not exceed 20V and the time does not exceed 10 min.

And cleaning the middle seam coke particles in the further coke paving process, and then adding electrolyte powder of 5-10cm into the middle seam.

The control phase further comprises the following phases after start-up:

first stage

The voltage was reduced from 4.8v to 4.11v within 27 days;

second stage

The voltage is reduced from 4.11v to 3.98 v within one month;

the third stage

The voltage is reduced from 3.98 v to 3.92 v within one month; the voltage was reduced to 3.880 v in the fifth month.

The first-stage pressure reduction process comprises the following steps: the first day down to 4.8 v; the second day is reduced to 4.6v, the fourth day is reduced to 4.4v, and the third day and the fourth day are reduced by 100mv each day; the reduction is 4.31v on the seventh day, and 30mv is reduced every day from the fifth day to the seventh day; the volume is reduced to 4.21v from the twelfth day and is reduced by 20mv from the eighth day to the twelfth day; a reduction of 4.11v on the twenty-second day and a reduction of 10mv per day from the thirteenth to twenty-second day; 4.11v on the twenty-third to twenty-seventh days;

further in the second stage, 30 days after the start-up step, 10kg of aluminum fluoride was added.

Further in the third stage, 60 days after the start-up step, 20kg of aluminum fluoride was added.

The invention has the beneficial effects that:

1. compared with the traditional starting process, the starting process is simple and easy to implement;

2. the consumption of raw materials and energy is low, and the cost is reduced;

3. the starting time is shortened, and the production capacity is improved;

4. the service life of the electrolytic cell is prolonged, and the economic benefit is increased.

Detailed Description

The present invention is described in terms of particular embodiments, other advantages and features of the invention will become apparent to those skilled in the art from the following disclosure, and it is to be understood that the described embodiments are merely exemplary of the invention and that it is not intended to limit the invention to the particular embodiments disclosed. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the embodiment of the invention, NaF/AIF in the ice stone electrolyte₃The ratio can be a molecular ratio (abbreviated as MR) or a molecular ratioIn terms of weight ratio. The molecular ratio is very close to twice the weight ratio. The weight Ratio is also commonly referred to as Bath Ratio (BR for short) and Cryolite Ratio (CR for short). NaF/AIF from the acid-base point of view of the electrolyte₃The molecular ratio is greater than 3.0, i.e. according to the cryolite formula Na₃AIF₆Calculating, and the NaF is excessive, namely the NaF is called as alkaline electrolyte; those equal to 3.0, namely pure cryolite, are neutral; less than 3.0, according to cryolite formula Na₃AF₆Calculate its AIF₃The excess is acidic.

The embodiment of the invention provides a starting control method of a 500kA large-scale aluminum electrolytic cell, which comprises the following steps:

step one, furnace charging:

when the furnace is charged, the cathode adopts a full graphite electrode, the size of a graphite cathode electrolytic tank steel bar of the electrolytic tank is 170 x 210mm, the full graphite cathode is soft, the wear-resisting property of the graphitized cathode is poor, and in order to prevent the cathode from being damaged during hoisting, a rubber sheet with the thickness of 10cm is additionally arranged at the position of a hoisting tool close to a cathode carbon block to protect the hoisting process, and after the furnace charging operation is finished, the operation area protects the electrolytic tank which is charged completely. The cathode of the electrolytic cell provided by the embodiment of the invention adopts the all-graphite cathode, and has the advantages of reduced resistivity, reduced furnace bottom pressure, increased thermal conductivity and increased heat dissipation performance.

The material dosage used in the embodiment of the invention is shown in table 1, the material dosage is recommended for the material for the roasting starting of the electrolytic cell, and the subsequent electrolytic cell judges the material dosage according to the analysis result of the material component of each batch.

Spreading coke, hanging anode, filling electrolyte powder and soda, cleaning the middle seam coke particles when spreading coke, and adding the electrolyte powder with the thickness of 5-10cm to prevent the cathode from being oxidized due to heating in the roasting process. Thermocouple is pre-buried, 8 temperature measuring sleeves are respectively arranged at the aluminum outlet, flue end and A, B surface of the electrolytic bath to measure roasting temperature, and the temperature measuring sleeves can not contact with the anode carbon block. The middle seams of the aluminum outlet end and the flue end of the electrolytic cell are built with electrolyte blocks, and are covered with shell surface blocks.

Uniformly filling broken electrolyte powder with the height of 300mm into the periphery of the chamber of the electrolytic cell, uniformly filling 1.5t of calcium fluoride and 1t of sodium carbonate into the broken electrolyte powder, uniformly covering 25t of electrolyte powder on the surface of the anode and the periphery of the chamber of the electrolytic cell after filling the sodium carbonate, and keeping the charging thickness at the lower edge of a steel claw by 3 cm.

Step two, roasting:

the roasting time is 84 hours, the shunt is not needed to be installed in the first batch of electrolytic tanks, and the shunt is needed to be installed in the subsequent electrolytic tanks; the second batch of electrolytic cell shunting device is dismantled according to the following principle: the voltage of the electrolytic cell is lower than 3.5v, and the shunt is started to be dismantled, wherein the dismantling sequence is 1# and 6 #; 2#, 5 #; 3#, 4#, if the cell voltage rises more than 0.5V during the removal, the removal should be stopped. The anode current distribution was measured 1 hour after the energization, and then every 4 hours.

The cathode lining needs to be preheated and roasted before the electrolytic cell starts electrolytic production, wherein the purpose of preheating is to roast the asphalt of the lining connecting paste and raise the temperature of the cathode carbon block to the electrolytic temperature so as to keep the reasonable and uniform temperature distribution on the surface and inside of the cathode lining.

Step three, starting:

the electrolytic cell measures the upward movement of the primary anode guide rod before starting, checks whether bias current exists, prepares liquid electrolyte for 25t before starting, erects an electrolyte chute, and takes away a temperature measuring sleeve before filling the electrolyte. When the roasting time reaches 84h, the average roasting temperature of the middle seam reaches above 920 ℃, and then the electrolytic cell can be started. Before starting, the smooth middle seam is ensured. Continuously and rapidly filling 25t of electrolyte into an electrolytic tank, raising voltage while filling, wherein the speed of raising the anode is matched with the speed of filling the electrolyte to ensure that the anode is immersed in the electrolyte for 4-5cm, and the phenomena of anode gliding or steel claw redness and electrolyte seepage at a cathode window are avoided in the process of filling the electrolyte. After the 25t of electrolyte is filled, the voltage is controlled to be about 6.5-7.5V according to the actual situation on site. And (3) fishing out the carbon residue after the materials in the electrolytic cell are completely melted, controlling the temperature of the liquid electrolyte to be below 1000 ℃, controlling the voltage to be within 7V, and controlling the level of the electrolyte to reach 50 cm. Meanwhile, timing 50% NB control is carried out on line, and after the start is finished, the analysis components of the electrolyte sample are obtained. The embodiment of the invention adopts the reasonable matching of the electrolyte powder and the soda ash, reduces the use of the cryolite and better controls the molecular ratio.

Step four, pouring aluminum:

and 24h after the electrolytic cell is started, pouring 28t of aluminum liquid, keeping the voltage at 6V before aluminum pouring, keeping the voltage at 5.5V after aluminum pouring, and subsequently supplementing the aluminum yield. After the aluminum pouring is finished, after a crust is formed on the surface of the electrolyte, 5t of sodium carbonate is added, a heat preservation material is covered, and the site is cleaned. And (3) taking a raw aluminum sample for analysis after 3h after aluminum filling, and taking the raw aluminum sample once a day after the analysis. Normally analyzing that the iron content is less than 0.2 percent and the silicon content is less than 0.08 percent. And after aluminum pouring, aluminum begins to be produced when the aluminum level reaches 21cm, generally, the aluminum begins to be produced when the aluminum level reaches 21cm, and the aluminum level is controlled to be below 23 cm at the early stage.

Effect control before aluminum pouring, if effect is generated after starting, the effect voltage does not exceed 20V, the time is not more than 10min, carbon slag is thoroughly cleaned immediately after the effect is extinguished, and the side wall of the shell is ready for air cooling and heat dissipation after starting.

And (3) a control stage: voltage adjustment after starting, the voltage adjustment is three stages:

the first stage is as follows: the voltage was reduced from 4.8v to 4.11v within 27 days; the first day down to 4.8 v; the second day is reduced to 4.6v, the fourth day is reduced to 4.4v, and the third day and the fourth day are reduced by 100mv each day; the reduction is 4.31v on the seventh day, and 30mv is reduced every day from the fifth day to the seventh day; the volume is reduced to 4.21v from the twelfth day and is reduced by 20mv from the eighth day to the twelfth day; a reduction of 4.11v on the twenty-second day and a reduction of 10mv per day from the thirteenth to twenty-second day; 4.11v was maintained on the twenty-third to twenty-seventh days.

And a second stage: the voltage was reduced from 4.11v to 3.98 v within one month.

And a third stage: the voltage is reduced from 3.98 v to 3.92 v within one month; the voltage was reduced to 3.880 v in the fifth month.

Specifically, the table of voltage adjustment stages is shown in table 2.

After the electrolytic cell is started for 30 days, 10kg of aluminum fluoride is added for the first time, 10kg of aluminum fluoride is added every month, and the aluminum fluoride is adjusted according to the actual running condition of the electrolytic cell and the change of the molecular ratio in the third month. The molecular ratio was adjusted after start-up of the cell as shown in table 3.

After the electrolytic cell is started, AlF3 is not added within two months, and the molecular ratio is naturally adjusted by the electrolytic cell. The molecular ratio can be adjusted according to the target molecular ratio of the subsequent production after the fourth month. The following day of electrolyte filling, the molarity ratio was once per day for one week, and then twice per week. When the electrolytic cell provided by the embodiment of the invention is started, the molecular ratio is controlled to be 2.9-3.2, and the furnace side can be quickly formed, so that the voltage of the good furnace side can be quickly reduced to 3.8 v. Two levels of retention are shown in table 4.

In the embodiment of the invention, in the starting process of the electrolytic furnace, the charging cost is low by utilizing the electrolyte powder and the soda ash, and meanwhile, a good furnace side is easier to form by better controlling the molecular ratio, and the voltage can be quickly reduced.

Although the invention has been described in detail above with reference to a general description and specific examples, it will be apparent to one skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.