Treatment of Rare Earth Concentrates by High Temperature Chlorination
High temperature chlorination (HTC) is one of the most common ways to process rare earth concentrate. It has been used for many years and is still widely used because of its low cost and high efficiency. HTC involves heating rare earth concentrate in an organic solvent, such as sulfuric acid, and bubbling chlorine gas through it to form a dense caliche layer on the particles. This caliche layer then prevents the rare earth concentrate from leaching out into the solution during digestion.
The process of HTC is relatively simple and consists of a few main steps. First, the rare earth concentrate is mixed with the organic solvent and heated. The temperature is dependent on the amount of rare earths present and may range from 350-450°C. Once the rare earth concentrate has been dissolved, a stoichiometric amount of chlorine gas is bubbled through the mixture. The chlorine gas then reacts with the rare earths to form oxides.
After the reaction is complete, the solids are separated from the solution and the oxides are then dissolved in acid. The resulting solution is then cooled and the rare earths are precipitated out as pure oxides. These oxides are washed and dried before they can be used in further downstream applications.
One of the main advantages of HTC is that it can produce a higher quality rare earth concentrate than other methods. It is more efficient than other leaching techniques and creates less waste. Additionally, since chlorine gas is used in a self-contained system, there is no need to handle hazardous and corrosive acids, which can be dangerous.
The major drawbacks of HTC are that it produces a caliche layer, which can cause difficulties during the separating and washing processes. Additionally, since chlorine gas is a toxic substance, special safety measures must be taken when dealing with it. Finally, a large amount of energy is needed for this process, making it an expensive operation.
Despite its drawbacks, HTC is still one of the most popular methods of rare earth concentrate processing. The process is relatively simple and can produce a high quality product with minimal effort. Although other methods may be more efficient, the cost savings associated with HTC make it an attractive option for many customers.
