EMILI Project: responsible water management, from ore concentration to conversion into lithium

Although water is regularly used in extractive activities, it does not play a major role in the first phase of the industrial process, meaning extraction of the rock. This is notably the case for the current kaolin mining or lithium mining as proposed in the EMILI project. 

Separation of minerals by flotation before transport by hydraulic pipeline

On the other hand, water does play a role in the various processing steps:

• separation of minerals to isolate the lithium-bearing mineral known as mica (concentration),
• transportation of the mica from the concentration plant to the conversion plant,
• conversion of mica into lithium.

First, the minerals are separated by flotation, which takes place in an aqueous medium. "This type of process, which we already use on many Imerys sites, will be used for the future operation of the lithium mine," explains Fabrice Frébourg. After crushing the granite, flotation consists in recovering the mica by selectively raising these minerals via the injection of fine air bubbles. "At this stage, most of the unused waste rock will be placed back underground in the mined galleries, after the addition of a binder to preserve the geotechnical characteristics of the massif.”

The lithium-bearing micas and other minerals (feldspar and quartz) are transported by underground pipes of small diameter (approx. 15 cm) to a loading facility close to the railroad line. "We chose to transport the micas hydraulically to avoid the CO2 emissions and nuisances (noise, dust, etc.) that would have been caused by truck transport". The water-mica mixture is then pressed to recover as much water as possible. "At the end of these first steps, we are able to recycle a large portion of the water used, since it is returned by a parallel pipe from the loading area to the concentration plant for reuse," comments Fabrice Frébourg. "This is a closed circuit, similar to that of domestic radiator heating systems, which Imerys intends to favor as much as possible in order to preserve natural resources.”

Minerals are then loaded onto trains and transported to the conversion plant.

However, partial loss cannot be avoided, as a certain amount of water remains trapped in the form of moisture both in the unused waste rock that will be backfilled underground and in the lithium-bearing micas or feldspar/quartz shipped by train. "Water loss is essentially linked to the moisture content of all the products coming out of the concentration stage, which we estimate to be between 15 and 22%," says Fabrice Frébourg. "For this reason, we will need a water supply source to make up for this loss. In terms of quantity, initial laboratory work has given us a preliminary estimate, which we will refine during the various stages of the pilot plants. For these first stages of concentration and transport, the annual requirement is estimated at 600,000m3.”

Identifying adequate supplementary water sources for the Echassières site

The studies conducted since winter 2022 by Antea notably aim to locate the waterways or water tables where it may be possible to find the necessary resources. “To make sure we can find an adequate water source and not disrupt the natural environment's ability to adapt, we conducted our research over a wide area, extending well beyond the Massif de la Bosse,” notes Fabrice Frébourg.

The Sioule, a river located about twenty kilometers from the site, would meet these criteria. "Studies based on information provided by the Commission Locale de l'Eau (CLE) indicate that our supplementary needs represent one thousandth of the average flow of the Sioule," explains Fabrice Frébourg. He adds: "We are also studying optimization solutions to plan for the driest periods of the year. One possibility is to use the reserves created by kaolin mining activities.”

Studies underway to use wastewater from the lithium conversion site

The final step in the process is to convert the lithium-containing mica concentrate into lithium hydroxide powder for use by electric battery manufacturers. This involves a series of pyro- and hydrometallurgical processes carried out in a conversion plant.

Since water is also essential to the conversion process, Imerys is looking into all supply solutions compatible with a rational use of natural resources. "According to initial estimates based on laboratory tests, net water consumption should be around 50m3 per hour, or around 400,000m3 per year," says Fabrice Frébourg. "One of the avenues we are currently exploring is to recycle greywater from wastewater treatment plants. This would avoid additional extraction from the natural environment. Furthermore, after treatment, the wastewater would be returned to the waterways in compliance with the strict standards in force. For all these reasons, the reuse of treated wastewater is both an innovative and promising solution, and one that is destined to become increasingly widespread in France's industrial sector."

These comments confirm Imerys' determination to carry out a project that addresses the crucial issues of water management as fully as possible. The initial conclusions of the studies currently underway on this subject should be finalized by the end of 2023.

The EMILI lithium conversion site may be supplied with wastewater from a water treatment plant to avoid extraction from the natural environment

What is the total water consumption of the EMILI lithium project?

In all, water consumption for the entire process remains comparable to that of many other industrial activities in France. As a reminder, industrial water consumption represents less than 5% of total water consumption in France. Assuming that the production of one metric ton of lithium hydroxide requires a gross consumption of 65m3 of water (taking into account wastewater treatment at a treatment plant for conversion), producing a battery for an electric vehicle would consume the equivalent of a four-person household for four days. Not to mention that this battery will be used for 10 years, or even longer if recycled. This level of water consumption is also 5-15 times lower than the water needed for lithium production in South American salars (natural expanse of salts – mainly sodium chloride that may be fully or partially covered by a small layer of water).