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Combined Heat, Power and Metal extraction from ultra-deep ore bodies

Periodic Reporting for period 3 - CHPM2030 (Combined Heat, Power and Metal extraction from ultra-deep ore bodies)

Reporting period: 2018-07-01 to 2019-06-30

The strategic objective of the CHPM2030 project is to develop a novel technology that can help satisfy the needs of Europe for both energy and strategic metals in a single interlinked process. In the CHPM technology vision, an enhanced geothermal system (EGS) will be established in a deep-seated (‘ultra-deep’, 4 km or more) metal-bearing geological formation where temperatures are above 150 oC. By leaching metals from the mineralised rock and recovering them at surface, the co-production of energy and metals will be possible, with sales of the latter providing an additional revenue stream to supplement that of the geothermal plant. It may even be possible to optimise metal recovery according to market demands.

The project’s specific objectives were:
- Deliver proof of concept for the technological and economic feasibility of mobilisation of metals from ultra-deep mineral deposits using a combination of different geo-engineering techniques enhancing interconnected fractures at depths;
- Develop innovative technologies for leaching strategic metals from the geological formation and corresponding electrochemical methods for metal recovery within equipment at the surface;
- Develop solutions for the co-generation of electricity using salt-gradient power reverse electrodialysis;
- Conceptual design of a new type of future facility that is operated from the very beginning as a combined heat, power and mineral extraction system;
- Develop an integrated feasibility assessment framework for the environmental and socio-economic impacts of the proposed new technology;
- Combine metallogenic models with geothermal datasets to develop a database of suitable sites in selected areas in Europe where the CHPM technique could be feasible;
- Create a roadmap in support of the pilot implementation of such system by 2030, and of the full-scale commercial operation by 2050.

During the project implementation, all specific objectives were achieved.
The project work started with the formulation of the conceptual framework. The objective of this work phase was to synthesise our knowledge about ultra-deep (> 4 km) metallic mineralisation that could be suitable for the CHPM technology, and to reveal data gaps.

The results from laboratory experiments showed evidence that relatively ‘mild’ leaching agents are capable of liberating metals into the recirculating fluid within an EGS. Surface modification of carbon-based nano-particles allowed metals to be adsorbed, both in acid and alkaline pH regions.

High-pressure, high-temperature metal recovery experiments proved that metals can be successfully electrodeposited at pressures up to 5 MPa and temperatures up to 150 °C. At lower temperatures (20-60 °C), gas-diffusion electroprecipitation and electrocrystallisation experiments (GDEx) resulted in different metallic products at different temperatures, with a broader variety of compounds at higher temperatures. Experiments investigating salinity-gradient power generation by reverse electrodialysis (SGP-RE) using pre-treated geothermal brines, proved that the presence of multivalent ions in geothermal fluids does not eliminate the potential for SGP-RE. Furthermore, the extraction of electrical energy was enhanced by increasing brine temperature.

Seven main technological components were identified as important in a CHPPM system. Based on a conceptual framework, a mathematical model was developed that linked the different components into a single overall system. The model was applied to several scenarios and it can be used to simulate and optimise a CHPM plant. The potential application of the technology included assessing environmental, economic, social, policy and ethical aspects.

Within the framework of the project, the future implementation of CHPM plants was also examined. Two time horizons were considered: 2030 for pilot-scale operation and 2050 for full-scale operation. Efforts were undertaken looking forward in three interlinked areas: mapping convergent technologies, studying pilot areas, and developing research roadmaps for the two identified time horizons.

Due to the extensive dissemination activities by the partners and the linked third parties of the European Federation of Geologists, the project concepts and results have reached about 50 000 scientists and professionals in Europe.

Reports on the research work and outcomes of the project are available on the project website: http://www.chpm2030.eu/outreach.
The potential impacts of the CHPM2030 project are as follows:

- The creation of the scientific basis for the future development of the CHPM technology will serve as background for a new generation of geothermal systems in Europe;
- The merging of the two, so far unconnected technologies (renewable energy and mineral extraction) will change the landscape for geothermal development in Europe and beyond, and will also have a substantial contribution in Europe’s need for critical metals;
- The results will support the objectives of the EU Raw Materials Initiative (in particular to the pillars “Foster sustainable supply from European sources” and “Boost resource efficiency and recycling”) and its Strategic Implementation Plan;
- The project results will help decision makers in Europe to frame future energy strategies and technologies and to integrate them in roadmapping. When combined with economic feasibility modelling, this will help in the identification of critical pathways;
- The number of economically-viable geothermal resources will be increased, not only in Europe, but globally, with the leverage of the co-production of valuable metals;
- The economic performance of the geothermal sector in Europe will be improved through the combined extraction of metallic raw materials and the enhanced capacity to attract private investments;
- Alternative pathways to hydraulic fracturing will be offered through the development of the “leaching” method;
- The results support “Europe 2020”, the European Union’s growth strategy for the coming decade and its flagship initiative for a “resource-efficient Europe”, with the shift towards an energy-efficient, low carbon economy.
- The development of the CHPM technology will challenge other techniques, e.g. improving drilling operations, lowering their costs, and further developing hydraulic stimulation of the bedrock at larger depths.
Custom built flow-through leaching device developed at University of Szeged
Schematic diagram of the gas-diffusion electroprecipitation and electrocrystallisation (GDEx) techno
Project team members studying one of the potential pilot sites in Romania, Bihor Mountains
Schematic diagram of the overall CHPM system showing the surface technological components.
Visualisation of a future CHPM plant.
1.5 kW laser beam applied on andesite sample during indirect tensile strength measurement by Brasil
Schematic overview of the envisioned CHPM Facility
Semi-pilot setup for salt gradient power generation by reverse electrodialysis (SGP-RE) experiments
Titanium batch reactors for leaching granulated material, designed at the British Geological Survey