Shanxi Huasheng Aluminum Co., Ltd. uses the SY300KA electrolytic cell designed by the Shenyang Aluminum Magnesium Design and Research Institute for the electrolytic aluminum project, and the designed annual production capacity is 220,000 tons. The company has a total of 276 electrolyzers of 300KA, divided into 6 zones with 46 slots in each zone. In November 24th, 2003, six electrolyzers in electrolyzers 1 and 4 were electrified for roasting until the power failure occurred on December 31 of the same year. During the period, the electrolyzer was not started, and then started on October 16, 2004. In the fourth zone, the second power was put into operation, and 92 electrolyzers were all started. After that, due to the alumina and electricity problems, all were stopped on November 30. The current situation facing the start-up of the second batch of electrolyzers is: 92 electrolyzers that have been shut down since they were started, of which 61 anodes have been inserted into the liquid aluminum, and 31 anodes have been pulled up when the troughs have stopped. Basic draining; the upper part of the anode of the 92 electrolyzers is covered with more than 20 tons of cryogenic insulation; most of the electrolyzers have poor insulation in all parts, and there are many problems in the upper part of the tank and other ancillary equipment. In view of the actual situation of the electrolytic cell, we have established a reasonable clearance, replenishment and roasting start-up plan. In the overall idea, the premise of successful startup is the premise of safety, energy saving and environmental protection. Combined with the long-term storage time, and most of the tanks have 20 tons of solid aluminum, protective clearing furnaces, low-cost replacement tanks, and low-voltage coke are adopted. Granulation roasting start-up method and low-efficiency, low alumina concentration control strategy. Cleaning the electrolyzer In the determination of clearing tank plan, to protect the principle of the cathode and the upper structure, the use of core technology to separate the aluminum block after removal, and take the cathode surface oxidation protection measures to protect the cathode. The main points to consider are the following: 1. When the tank is covered with cryolite, there is a certain amount of alumina on the anode. Therefore, when cleaning the pole, the cryolite should be separated from the alumina as much as possible for future use. 2. When cleaning the crust around the trough, avoid touching the side carbon block. 3. The aluminum block in the slot is a large whole, with a thickness of more than 10cm and a weight of more than 10 tons. The edge of the aluminum block is close to the side of the electrolytic tank. When cleaning, various tools are difficult to display, so when cleaning Must be careful not to damage the side, pulling the cathode carbon block. Repair electrolyzer After the electrolytic cell covering materials, crusts, anodes and aluminum blocks were cleared, the damages to the side and cathode parts of the electrolytic cell were more serious. The main manifestations were: breakage of the artificial legs, formation of layers, and severe aluminizing; carbon blocks on the side were broken and damaged. Etching oxidation, loss of block; cathode carbon block weathering, fracture, from the layer, falling block; cathode carbon block cracks, aluminizing and so on. In view of the prevalence of the above situations, in order to ensure the smooth start of the electrolyzer, electrolyzers must be repaired before the tank can be put into production. In determining the repair plan, mainly to prevent the formation of the aluminum liquid channel principle, the use of hot paste to solidify the need for repair between the carbon seam and artificial stretch leg, when the solid paste temperature control at 90 °C -120 °C, the cathode surface temperature heating To 80 °C -100 °C, the side block basically does not change. For the different damage conditions of the electrolytic cell, we have taken targeted repair methods: 1. For the phenomenon of cracks, delamination, exfoliation, and aluminizing of artificial stretch legs, it is required to remove 2-4 layers of artificial stretch legs and refix them. 2. For the phenomenon of cracking and aluminizing between cathode carbon blocks, it is required that the paste between carbon blocks should be dug 10cm, and the aluminizing part should be more 20cm. 3, the cathode carbon block from the layer, the place where the block, after the clean-up with paste to fill the solid. 4. For all visible gaps in the body of the cathode carbon block, it is required to drill about 1cm to 2cm wide from the gap and fill it with paste. 5. For cracked side blocks, it is required to use a grinding wheel to expand the gap and then fill it with a paste. Secondary firing of electrolytic cell 1, the choice of firing start method. Taking into account the short start-up time of the second batch tank, the bottom surface of the furnace is relatively flat. We adopt the coke roasting method, which can block the cracks and channels formed by roasting with the polymer electrolyte liquid before pouring the aluminum liquid. The low voltage and low anode effect coefficient are adopted at startup, and the macromolecule is more environmentally friendly than the start-up method to achieve the purpose of protecting the cathode, prolonging the service life of the tank, and reducing environmental pollution. In order to prevent strong thermal shocks to the edge and corners of the tank, resulting in cracks in the edges and corners of the tank, wet-effect start-up was used. The roasting time we determined was 96 hours. The second firing is critical, the current gradient is 120KA, 180KA, 240KA, and 300KA. The current is sent to 240KA to measure the current distribution. After confirming that there is no abnormality and the impulse voltage is not greater than 5V, it is sent to the next level and the power is stopped. The time is controlled within 30 minutes. 2, installed furnace operation and soft connection installation. Since the electrolyzer requires the electrolyte ratio to be more than 2.8 after start-up, if an ordinary acid cryolite is used during the tank installation, a large amount of soda ash is required to increase the molecular ratio. Therefore, a macromolecule ratio of cryolite is selected when loading the furnace, so that soda ash can be used. The amount of use is greatly reduced. A certain amount of magnesium fluoride is added to protect the legs when the furnace is installed. In order to enhance the thermal convection in the middle of the tank during the roasting of the electrolyzer, the roasting temperature is evenly distributed, the surface of the cathode cathode is prevented from being oxidized, and at the same time, a small amount of liquid electrolyte is contained in the tank before starting, and we adopt the hollow furnace method. Before the power is applied, install the flexible strap connection bus between the anode lead and the anode bus. All parts of the soft connection that are in contact with the anode guide bar and the anode bus bar must be ground and cleaned before installation. The bolts on the various parts should be fastened to ensure that the soft connection has sufficient curvature to prevent ignition failure due to poor contact or anode rise during firing. Pull the flexible connection bus off. 3, installed dismantling splitter. Due to the increase in cathode irregularities and coke thickness in the electrolyzers of the 1st and 4th regions, the surge voltage at the time of the electrolyzer being powered on will increase, and the thermal shock to the electrolyzer will increase. In order to reduce this disadvantage, we adopted the method of adding shunts on the basis of the original shunt to increase the split flow. The original electrolyzer diverter was 5 sets/slot, each set was divided into 2 groups, each with 8 pieces. Add 1 to 9 pieces on the basis of 8 pieces per group. After the full current is applied for 6 hours, the voltage at 3V is removed firstly from the front and the fifth sub-compartment. After 12 hours, the remaining shunt is removed. If the voltage suddenly rises, the dismantling work shall be stopped, and the voltage shall be stabilized before continuing to dismantle. 4, start and start late management. After 96 hours of calcination, when the start conditions are confirmed, the electrolysis cell can be started; the following conditions must be met before start-up: (1) Seam cryolite is mostly opened and the temperature is higher than 900°C. (2) The melting began around the groove, and the temperature at the TAP end and the DE end was above 750°C. (3) The liquid electrolyte in the seam should not be less than 15cm. The voltage within 24 hours after the electrolyzer was started to aluminize was evenly reduced from 4.8V to below 4.5V by the computer; within 48 hours, the voltage was uniformly controlled by the computer and fell below 4.3V; the voltage was evenly reduced to below 4.2V by the computer within 72 hours. In 96 hours, the voltage is controlled by the computer to fall evenly below 4.18V. After 120 hours, the voltage is kept below 4.16V to enter the later stage of management. At the beginning of the electrolyzer start-up, the addition of alumina is automatically processed at regular intervals. After half a month, it is automatically transferred to fuzzy control feeding, that is, normal production and feeding. Therefore, the NB processing interval at the initial start-up period is 110 to 130 seconds, and the NB interval is gradually shortened along with the normal process conditions such as the bath temperature. At the beginning of the secondary start-up of the electrolyzer, the trimming of the man-made stretched leg is not fully coked, and the edge temperature is required in order to make the edges of the mandrel sticky, coherent and sintered together, and to prevent the peeling of the layer after the repair. The rise should not be too fast. At the beginning of the electrolyzer start-up, the tank temperature drops more after the aluminum pouring, the melting of the edge material slows down, and the liquid electrolyte solidifies at the edges to form a reversible process. In this process, all the technical conditions are controlled to reduce the melting of the electrolyte at the edge, so that the edge heats up slowly, so that the edges can be glued and coke well, so as not to cause the layered peeling of the artificial extension and the early cracking of the side carbon. , damage, and help form a regular furnace interior type. 5, the implementation of results. At present, these electrolytic tanks have been started for more than seven months, with good operating conditions, stable technical conditions, stable tank voltage at 4.12V, effect coefficient of 0.3 times/day, current efficiency of 93%, and no difference from other normal tanks. 6. Conclusion. Through the protective low-cost clearing and replenishing work, the low-voltage and environmentally-friendly roasting start-up method and the low-alumina concentration and low-effect management measures in the late start-up period have not only saved 50% of the roasting start-up power, but also solved the problem. The 300K large pre-baking tank side with 75mm thick silicon carbide red area of ​​the technical problems, greatly reducing the environmental pollution during start-up and the labor intensity of workers, after the start of various economic and technical indicators have achieved a good start effect , Save roasting start power consumption 100,000 degrees / tank; aluminum liquid quality reached AL99.70 or more average time is 16 tank days; in the same industry in the country a large area of ​​the second time to start the electrolytic tank history can be said to be a miracle, for the Chinese aluminum industry The secondary start-up of large prebaking tanks has explored valuable experience and has practical guidance and application value. Performance advantages: VTM Tube,Tube VTM,VTM Tube Price,VTM Test,VTM Test Tube,Lab Test Tube,Small Test Tube,VTM Sampling Tube Yong Yue Medical Technology(Kunshan) Co.,Ltd , https://www.yymeds.com
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