2. The apparatus main electrolytic production of aluminum - an aluminum reduction cell Profile Evolution (1) an aluminum reduction cell in aluminum electrolysis industry, the size of the electrolytic cell, generally known as cell capacity, which begin magnitude of the current intensity. The current intensity of the aluminum electrolysis cell has also undergone a process of increasing from small to large. Before the Second World War, the current intensity of a series of electrolyzers in aluminum factories around the world was between 20,000 and 50,000 amps, and after the war it was developed to 50,000-80,000 amps in 1952. It developed to 150,000-200,000 amps in the early 1980s and has now reached more than 300,000 amps. It has begun research and development of larger-capacity cells.
1 The first stage (initial pre-baked tank) In the initial stage of industrial production of aluminum electrolysis, the electrolysis cell is small, the current intensity is low, the anode used is made of pre-baked graphite or carbon, and the anode current density is as high as 6- 7A/cm 2 , the power consumption is increased to 90000 kW.h/t aluminum, the production cost is high, and the aluminum price is expensive. For example, in 1888, it was used to produce a 4000A electrolytic cell. The electrolytic cell has a square anode with an anode current density of 6.4 A/cm 2 , a cell voltage of 10 V, and a power consumption of 42,000 kW·h/t aluminum. However, in 1933, the current intensity of the electrolytic cell has reached 55000A, and there are 22 prebaked anodes. The anode current density is reduced to 1.01A/cm 2 and the power consumption is reduced to 20,000 kW.h/t aluminum.
2nd stage (side slot) As early as 1923, Norway began to use the 8000A side slot. In 1927, the United States began to use a circular insert anode with a diameter of 2.lm and a height of 1.5-1.6m, and its current intensity was 25000-30000A. Later, the side slot is gradually developed until the initial prebaked tank is replaced. The side slot at the time had the following characteristics:
a. The number of anodes is small, the operation is simple, and it can adapt to a larger current intensity;
b. The anode does not need to be prefabricated, the molding and roasting process is omitted, no residual pole, and the anode cost is reduced;
c. The electrolytic cell is equipped with a closed device, which improves environmental protection and working conditions.
Figure 2 is a schematic illustration of a side slot.
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3 The third stage (upper slot) The upper slot was tested in the 1940s and expanded to some aluminum producing countries in the early 1960s. Its advantages over the side slot are:
a. The conductive system is further simplified;
b. The operation of the electrolytic cell and the anode is convenient for mechanization and automation;
c. The gas collecting hood has good airtightness, and the amount of gas extracted is small, which is beneficial to purification treatment;
d. Can adapt to a larger current intensity.
There are also serious shortcomings in the upper slot:
a. The upper structure of the electrolytic cell, the anode hoist and other mechanical equipment are complicated;
b. The quality of the secondary anode sintering is not good, affecting the production efficiency, the power consumption is large, and the anode accident is relatively more;
c. The anode side in the gas collecting hood is easily oxidized, and cracks and cracks are easily generated.
Figure 3 is a schematic illustration of the upper slot.
4 The fourth stage (modern prebaked trough) There are two types of prebaked troughs, one is the side feeding type (as shown in Figure 5-7), and the other is the intermediate feeding type (as shown in Figure 5-8). The initial prebake cell has undergone many improvements and is equipped with modern science and technology. Modern prebaked cells have emerged. At present, almost all new aluminum plants in the world use modern prebake cells. Its advantage is that it can adapt to greater current intensity, lower power consumption, simple upper structure, high degree of mechanization automation and good environmental protection. The disadvantage is that 15%-20% of the residual pole needs to be processed, and the anode is pre-prepared, which greatly increases the cost of the anode. 4 and 5 are schematic views of the side feed prebake tank and the intermediate feed prebake tank, respectively. [next]
(2) Introduction to the structure of aluminum electrolysis cell There are currently four types of electrolyzers in the world, except for the continuous prebaked anode electrolysis cell (currently only one electrolytic aluminum plant in France), and now the other three types of four types of electrolyzers Give a brief introduction.
1 Anode structure The anode of the self-baked anode cell is inserted outside the anode for anode forming and protecting the anode. The aluminum casing is usually made of an aluminum plate having a thickness of about 1 mm, and is formed in a bottomless box shape having a height of about 1 m around the periphery of the anode. In the production process, the aluminum shell and the anode carbon are consumed together, and the aluminum rivet is used to join the new aluminum shell to be supplemented, and the anode paste is added in the aluminum shell. The anode is baked while being operated by its own resistance heat and heat transferred from the electrolyte melt. The anode side of the anode side is nailed with a steel anode rod, and at the same time, the anode and the anode are supported, and the anode rod is lowered with the anode consumption. Therefore, it is necessary to periodically pull and nail the rod. The lowermost row of the head portion of the anode rod engages in a special U-shaped bail, by welding with the anode frame and into the channel of pulleys suspended from the anode hoist lifting device and is supported by four pillars of gold metal anode comprising The quality of the entire superstructure within.
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