A method has been developed at KIT with which lithium can be extracted in a geothermal plant using a sorption process.
Geothermal plants in the Upper Rhine region are already extracting lithium today, but it remains unused because the thermal brine is returned to the depths unchanged after the heat has been extracted. The new method could change this and cover a considerable part of the current lithium demand of the German automotive industry.
The brine is passed through a reactor filled with a lithium-selective sorbent, where the lithium is bound. The sorption rate depends on various framework conditions: Composition of the thermal water, pH value, lithium concentration and flow rate. If the sorbent is saturated, the flow direction is changed and a desorption solution releases the lithium from the adsorber. In order to achieve efficient and economical lithium extraction, the time at which the flow direction is changed must be specifically controlled. The criterion for the changeover time is the saturation of the adsorber. This can be read from the lithium concentration in the reactor outflow. Until now, complex laboratory measurements have been necessary to determine this.
A team at Fraunhofer IPM is developing a new method based on LIBS (Laser Induced Breakdown Spectroscopy) that will monitor the lithium concentration in the reactor effluent inline, making it possible to control the sorption and desorption process for the first time. LIBS is an established material analysis method in which a tiny part of a material is transferred into a plasma and spectrally analyzed using a short-pulse laser. As part of LiMo, the process is being further developed so that it works under harsh conditions in liquid at 20 bar and 90 °C. The LIBS system is to be tested in real operation in a pilot plant at a geothermal site.
The potential is considerable: in addition to lithium extraction in geothermal plants, the process is also suitable for lithium recycling from used batteries, which is also to be tested as part of the project.
