Manufacturing High-purity Aluminum Fluoride Products Via Fluidized-bed reactor by AHF & Aluminum Hydroxide.

Aluminum fluoride is widely used in various industries.

In the electrolytic aluminum production process, it serves as a supplementary component of the electrolyte to lower the melting point and improve conductivity.

In alcohol production, it acts as a fermentation inhibitor. It also functions as a flux for ceramic outer glaze and enamel glaze, and as a flux for non-ferrous metals. In metal welding, it is used as a welding fluid. It is also utilized in the manufacture of optical lenses, as a catalyst in organic synthesis, and as a raw material for artificial cryolite.

The production of anhydrous aluminum fluoride products utilizes hydrogen fluoride and aluminum hydroxide as the primary raw materials.

The process technology used is "refined acid-wet aluminum hydroxide" for dry production.

Sulfuric acid, along with fuming sulfuric acid and fluorite powder, is measured and introduced into the pre-reactor under slight negative pressure.

Then, it enters the indirectly heated rotary reaction furnace, where it continuously generates HF gas.

The generated HF gas is directed into the pre-washing tower and washing tower to remove impurities such as dust, moisture, and high boiling point compounds such as H2SO4 and HSO3F.

The cooled and condensed HF gas is liquefied and enters the rectifying tower, where heavy components like H2SO4 and water are separated.

The HF liquid further proceeds to the degassing tower, where SO2-, SiF4-, and inert gas are removed. Finally, it enters the intermediate storage tank as an anhydrous hydrogen fluoride product, which is sent to the product storage tank after undergoing inspection and is available for sale.

Gas that cannot be condensed and contains a small amount of HF and SiF4 is directed from the condenser and rectification tower to the sulfuric acid washing tower.

The SiF4 gas is absorbed through three stages of sulfuric acid washing, resulting in the formation of a solution of fluorosilicic acid (H2SiF6), which is then transferred to a storage tank after reaching the desired concentration.

This fluorosilicic acid can be sold directly, or it can be used to manufacture other fluorite products, such as cryolite, ammonium hydrogen fluoride, potassium fluoride, and potassium fluosilicate.

It can also be further processed into AHF and SiO2 (refer to the "Introduction of Technology to Producing Anhydrous Hydrogen Fluoride by Fluorosilicic Acid" for more information).

The remaining gas is discharged into the alkali absorption tower.

Anhydrous gypsum (calcium sulfate) produced by the rotary reaction furnace is degassed, neutralized with lime, and cooled before being stored in the gypsum storage bin as a by-product of the reaction.

The anhydrous gypsum is primarily used as a mixture in cement production.

The slag gas, which is entrained in the gypsum, is absorbed, filtered, and then transferred to the fluorosilicic acid absorption tank.

AHF is pumped from the storage tank into the HF evaporator and transformed into high-temperature hydrogen fluoride gas.

A gas burner produces hot air which is mixed with the HF gas in a gas mixing chamber. The resulting mixed gas then enters the aluminum fluoride reactor (fluidized bed) via the gas distribution plate.

Wet Al(OH)3 is conveyed through a weighing system, rotary valve, and screw conveyor into the multistage dryer where the surface and crystal water are removed at medium and high temperatures, respectively. The dried Al(OH)3 is converted to alumina and then fed into the aluminum fluoride reactor where it reacts with the gaseous hydrogen fluoride in a fluidized bed at a high temperature of 560℃ ~ 650℃, producing aluminum fluoride.

The process of removing the water from the Al(OH)3 is achieved through the use of waste heat from the reactor tail gas, resulting in energy savings.

The aluminum fluoride is uniformly discharged from the fluidized bed reactor and transported via a screw conveyor and air seal valve adjustment to a cooling device. Once cooled, the aluminum fluoride is collected in a silo and packaged as the final product.

The exhaust gas and dust discharged from the reactor are treated by the tail gas washing absorption system to ensure that the amount of fluorine released into the atmosphere is below the national emission standard of 5mg/M3.

The wastewater and materials resulting from the absorption and washing process are separated and can be utilized to produce cryolite products (Investment in the Technology and Device for Producing Cryolite from Fluorine-Containing Wastewater is required).

Diagram 1 illustrates the block diagram of the process for producing hydrogen fluoride.

For further details, please refer to the "Introduction of Technology for Producing Anhydrous Hydrogen Fluoride Products by Fluorite Powder and Sulfuric Acid".