Researchers from the German GeoForschungsZentrum (GFZ) in Potsdam have reached a project milestone concerning the efficient extraction of helium from geothermal fluids through membrane-based gas-water separation technology.
Generally, natural gas with a helium concentration of more than 0.3 Vol% presents an economically viable resource, if helium extraction can be integrated into existing processes, instead of disrupting them (Halford et al., 2022; Hamedi et al., 2019). The implementation of robust and durable tubular membrane material in existing geothermal production streams is therefore envisaged as an economically viable solution for the gas extraction and Helium production from geothermal brines during production cycles.
A laboratory test rig was developed to evaluate membrane performance across various media. In first tests, two types of tubular polymers, polydimethylsiloxane (PDMS) and polytetrafluoroethylene (PTFE), were identified as the most reliable and cost-effective solutions.
In lab settings, batch-type experiments demonstrated the efficiency of PDMS and PTFE membranes in separating helium from artificial nitrogen-dominated gaseous feed compositions. A gas mass spectrometer was used for continuous gas analysis and forms the basis for further experiments.
Fig. 1: (a) Various tubular membrane materials were prepared with supportive filler material and standardized end fittings for batch-type tests in (b) the autoclave. (c) Two membrane tubes were connected to the lid for parallel assessments. (d) The autoclave was flushed with helium-enriched feed gas, the composition of the feed gas, and the permeate was continuously monitored with the gas mass spectrometer to evaluate the membrane performance.
During a pump test of geothermal water, conducted at the Cornish Lithium Site in Cornwall, UK, the suitability of PDMS and PTFE for gas separation from production brine under ambient field conditions could be confirmed. Notably, PTFE exhibits rapid responsiveness to changes in gas composition and concentration.
Next, the long-time performance in saline and high temperature liquid environments will be evaluated. The focus will be on the two above-mentioned polymer types.
The results of the first field test are currently being prepared for publication. Stay tuned for more information!