Aluminum products are very common in our lives. Airplanes, mobile phones, cans and even cosmetics all have aluminum. But how is aluminum extracted from bauxite? In addition to steel, aluminum is the most commonly used metal. Aluminum is everywhere in our lives. Aluminum has many advantages, such as light weight, corrosion resistance, rust resistance, UV resistance, and soft texture. It is very easy to process and can be made into various parts and crafts. Aluminum is also an environmentally friendly material that can be recycled infinitely. Even aluminum products from decades ago can be melted and processed again.

Bauxite is widely distributed on the earth. It is the most distributed metal element in the earth's crust, second only to silicon and oxygen. It is mainly distributed in countries near the equator such as Africa and South America. The aluminum ore reserves in these countries account for more than 50% of the world's total. The reason why bauxite is bright red is mainly because it contains iron red. After smelting, bauxite will change from red to white alumina.

Currently, 95% of the world's companies are using Germany's Bayer refining method to produce alumina. First, put the bauxite into the kiln and calcine it into clinker, and then soak it in a high concentration of sodium cyanide solution. Since aluminum can dissolve in strong alkali, the remaining iron red will slowly precipitate out and become waste red mud. The purified aluminum solution will become white powder after separation, but the powder at this time is not alumina, but a kind of hydrated alumina also called boehmite. Boehmite is a very important material in the lithium battery of new energy vehicles. It can be coated on a layer of PET film to separate the positive and negative electrodes, and allow lithium ions to pass through it freely to ensure the safety of the battery. After boehmite is calcined again in the kiln, white alumina powder will be obtained.

From red bauxite to white alumina powder, a large amount of waste red mud will be generated. It is very troublesome to handle it today when environmental protection is becoming more and more important. Most of it is temporarily stored in the treatment pool and cannot be effectively treated. Therefore, pretreatment before front-end smelting is particularly important. More and more mining companies use photoelectric sorting technology to pre-treat bauxite, discard miscellaneous stone waste in advance, and reduce the subsequent process processing volume and waste mud. Reduced later energy consumption and reagent costs.

How to smelt alumina into metallic aluminum?

Electrolysis is an effective extraction method

Before electrolysis, alumina must be baked to remove the water inside. Electrolysis of aluminum is to separate aluminum from alumina. To achieve electrolysis, two conditions must be met.

First, alumina must be dissolved into a conductive solution. The melting point of alumina is 2100 degrees Celsius. For electrolysis, the temperature is extremely high. It is very difficult to find equipment and electrode materials that can withstand this temperature, and the energy consumption at this temperature is also very high. In 1885, Hall, after repeated experiments, finally invented cryolite to dissolve alumina and reduce the electrolysis temperature to an acceptable 950 degrees Celsius. In this way, metallic aluminum can be obtained by electrolysis with electrodes.

Second, the electrolytic aluminum workshop requires a very large current, and the current value must reach 185 amperes. Due to the very large current used and the high demand for electricity, it must be equipped with its own substation to ensure a sufficiently stable power supply. Because during the electrolysis process, once there is a power outage, the molten aluminum slurry will solidify, and the power consumption for re-dissolving will be 2 to 3 times that of before. Electrolysis is completed at a high temperature of 950 degrees Celsius, and the electrolyzed aluminum will settle to the bottom of the furnace, and then the liquid aluminum will be collected in a crucible. Before pouring, the impurities floating on the electrolytic aluminum water are removed and cast into aluminum ingots.