| Title | Update on the CaSil technology: economically solving global silica scaling, enabling low temperature direct heat extraction and electricity generation |
|---|---|
| Authors | M. Schweig, J.H. Johnston, T. Borrmann, H.P. Fraser |
| Year | 2023 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Geothermal, silica scaling, calcium silicate hydrate, direct heat utilisation, process heat, enhanced energy extraction |
| Abstract | Silica scaling remains the world-wide largest unsolved problem in the full utilisation of geothermal resources. Dissolved silica becomes supersaturated during cooling and steam production leading to intractable scale that blocks pipework, heat exchangers and reinjection wells. This blockage can significantly lower the efficiency of heat exchangers which causes a direct decline in electricity production and sales over time. Regular and costly maintenance is required which necessitates plant downtime. Conventional silica scale mitigation methods are not wholly successful and come with drawbacks such as high cost or corrosion concerns. The proprietary CaSil Technology utilises a disruptive approach of transforming dissolved silica entities into a novel calcium silicate (CaSil) product, forming discrete particles that remainsuspended and do not adhere to metal surfaces. Within seconds, the technology achieves a significant reduction in the silica saturation index to well below 1. The robust process is compatible with a wide range of brine compositions, irrespective of the initial silica concentration, ensuring reliable prevention of silica scaling. Furthermore, the CaSil Technology enables safe lowering of brine temperatures beyond current limits without inducing any silica scaling. This opens new business opportunities for additional process heat utilisation in for example greenhouses, aquaculture or milk powder production, thus supporting the decarbonisation of industry. Successful trials on development plant scale across three different geothermal resources in New Zealand have been undertaken. The technology seamlessly integrates into existing geothermal operations or greenfield plants, offering a versatile solution. This paper presents data from the trials and highlights the effectiveness of the technology to prevent silica scaling while unlocking the full potential of geothermal resources for enhanced heat extraction. By addressing the silica scaling challenge in a novel and disruptive way, CaSil Technologies paves the way for the sustainable and efficient utilisation of geothermal energy resources on a global scale. |