Alumina dry purification for roasting flue gas purification

Alumina dry purification is to use alumina as an adsorbent to wash the flue gas generated during the roasting process. Without the need for water or other liquids, the alumina has a large active surface area to absorb the flue gas in the roasting flue gas. Tar, dust and fluoride, this method is currently used in aluminum and carbon enterprises such as Tianshan Aluminum, Xinjiang Jiarun, Shanxi Huaze, etc.

1. Main equipment and process principle

The main equipment for dry purification includes: main exhaust flue gas machine, bag filter, total evaporation cooling tower, etc. Take the roasting flue gas purification system with an annual output of 80,000 tons of pre-baked anodes as an example. A square vertical flue is mixed with the Al2O3 ejected from the vertical radial injector (VRI for short) to complete the adsorption process, and then enters the dust collector at the pulse bag of four groups and eight chambers. After the particles are separated by the bag, the exhaust gas passes through Three temperature-resistant main fans are sent into the chimney with a height of 18m for discharge. Except for a part of the reacted Al2O3 which is recycled, the rest enters the post-reaction silo as the electrolysis raw material, and the bypass is used when the equipment fails.

2. Purification effect

Alumina dry purification is a method to treat the flue gas containing tar and fluorine and other pollutants discharged from the open anode roaster, which can ensure that the flue gas is discharged stably up to the standard. At present, most aluminum and carbon enterprises use this method to purify hydrogen fluoride in flue gas. When the amount of alumina is continuous and uniform, a good adsorption effect can be obtained, which can improve the purification effect of flue gas and is suitable for supporting construction of electrolytic aluminum enterprises. carbon production line.

Relevant studies have shown that after the flue gas is purified by the alumina dry purification system, the emission concentration of fluoride in the flue gas is lower than 2 mg/Nm. This value is lower than the emission standard of air pollutants stipulated in my country, indicating that the purification effect of alumina dry purification method for fluoride meets the requirements of relevant standards in my country.

3. Combination of electrostatic capture method and alumina adsorption dry purification

With the advancement of roasting flue gas purification technology, electrostatic capture and alumina dry purification are well combined. The combination of these two methods significantly reduces the emission concentrations of particulate matter, asphalt smoke, fluoride and SO in the flue gas during the purification process. This combination allows the electric tar catcher or the alumina dry purification system to operate independently. For example, when the bag filter or the electric tar catcher fails, one of the purification methods can be used alone to keep the equipment running stably .

The article is reproduced from: China Business Carbon Research Institute