The role of calcination in lithium extraction from spodumene

In the complex production process required to convert spodumene concentrate into lithium compounds, calcination plays a key role in not just one but two processes, making it an increasingly important component in the development of this An essential technology for lithium mines.

While extracting lithium from brine has been the main focus of commercial efforts, spodumene is becoming increasingly popular due to its high lithium content and surging demand for lithium-ion batteries.

Application of spodumene and graphite in calcination

Calcination, often referred to as roasting in this context, is one of the most commonly used processing techniques throughout the extraction of lithium from spodumene.

What is calcination?

Calcination is a heat treatment technique widely used in a variety of industries to induce chemical reactions or physical changes in materials. Most commonly, it refers to the chemical dissociation of components in a material, such as the separation of calcium carbonate into calcium oxide and carbon dioxide. Calcination usually occurs in an inert environment. However, it is important to realize that the term is widely used to describe a variety of thermal processes.

When producing lithium compounds from spodumene concentrate, calcination is used to perform two separate steps in the process: explosion and acid roasting.

burst

Spodumene ore naturally has a monoclinic α-type crystal structure. However, in order to extract lithium from an ore through a leaching process, the crystal structure of the ore must be tetragonal beta. This transformation occurs through bursting, or the fragmentation of the crystal structure.

Facilitated by calcination, the explosion expands the crystal structure of spodumene by about 30 percent, ultimately allowing the chemically inert ore to react with sulfuric acid.

When processing spodumene concentrate, calcination can cause bursting at temperatures of 1075 – 1100 C. Temperature control during calcination is critical to the success of the process; if temperatures are allowed to approach 1400 degrees Celsius, undesirable structures may form between alpha spodumene and other silicates.

Sour roast

Once the material explodes or transforms into beta phase spodumene, an additional calcination step is required. The concentrate, now in beta form, is first mixed with sulfuric acid and then fed into a separate rotary kiln. This acid roasting step uses a kiln that operates at a much lower temperature—usually around 250 degrees Celsius. ¹

The purpose of the acid roasting step is to extract the lithium from the mixture in the form of water-soluble lithium sulfate, which is easily leached. Through leaching, lithium sulfate can be converted into the marketable compounds lithium carbonate or lithium hydroxide.

Calcination is an important tool in converting spodumene concentrate into lithium compounds and has two key roles in the process. Through calcination, explosion and acid baking can be achieved to produce lithium carbonate and lithium hydroxide for use in lithium-ion batteries or other applications.