Alumina dry purification of anode roasting flue gas purification
Alumina dry purification uses alumina as adsorbent to wash the flue gas generated in the roasting process. Without water or other liquids, alumina has the characteristics of large active surface area to adsorb tar, dust and fluoride in the roasting flue gas. At present, this method is applied in aluminum and carbon enterprises such as Tianshan aluminum industry, Xinjiang Jiarun and Shanxi Huaze.
1、Main equipment and process principle
The main equipment of dry purification includes: main flue gas exhauster, bag filter, full steam cooling tower, etc. Taking the roasting flue gas purification system with an annual output of 80000 tons of pre baked anode as an example, the flue gas from the roasting furnace passes through a water spray cooling tower with a diameter of 5m and a height of 30m to reduce the flue gas temperature to 83 ℃, then enters four square vertical flue gas channels, mixes with Al2O3 ejected from the vertical radial ejector (VRI) to complete the adsorption process, and then enters the pulse bag dust collector with four groups and eight rooms, After the particles are separated by cloth bags, the waste gas is sent to the chimney with a height of 18m through three high-efficiency temperature resistant main fans for discharge. In addition to some recycled Al2O3 after the reaction, the rest enters the post reaction silo as electrolytic raw materials. Bypass is used in case of equipment failure.
2、Purification effect
Alumina dry purification is the best method to treat the flue gas containing tar, fluorine and other pollutants discharged from open anode baking furnace, which can ensure the stable and up to standard emission of flue gas. At present, aluminum and carbon enterprises mostly use this method to purify hydrogen fluoride in flue gas. When the feeding amount of alumina is continuous and uniform, it can obtain good adsorption effect and improve the purification effect of flue gas. It is suitable for the carbon production line built by electrolytic aluminum enterprises.
Relevant research shows that after the alumina dry purification system purifies the flue gas, the emission concentration of fluoride in the flue gas is less than 2mg / nm ³。 This value is lower than the emission standard of air pollutants stipulated in China, indicating that the purification effect of alumina dry purification method for fluoride meets the requirements of relevant standards in China.
3、Electrostatic trapping and alumina
Adsorption dry purification combination
With the progress of roasting flue gas purification technology, electrostatic capture and alumina dry purification are well combined. The combination of the two methods can significantly reduce the emission concentration of particulate matter, asphalt smoke, fluoride and so ν in the flue gas during the purification process. This combination allows the electric tar precipitator or alumina dry purification system to operate separately. For example, when the bag filter or electric tar precipitator fails, one of the purification methods can be used separately to maintain the stable operation of the equipment.