Scale can be a major problem for geothermal power plants.
It clogs surface equipment, reduces output, and requires costly maintenance that may also take the plant offline. Understanding the causes and developing strategies for prevention can make a significant difference to a plant’s performance.
Scale precipitation is the main issue in water-dominated geothermal systems. The hot geothermal fluid interacts with the rocks at depth, under high temperature and pressure conditions, influencing its chemical composition. The dissolved minerals eventually build up as scale on equipment such as heat exchangers and preheating systems, impairing their performance.
But not all scaling is the same. Calcite and silica are common while stibnite scaling (where geothermal fluids are instead enriched in sulphide and sulphosalt minerals) is generally rare.
Unfortunately, not in Turkey…
Across the country’s 65 geothermal power units, most of them in the volcanically active Western Anatolia region, it’s been regularly observed and has become a complex issue to address. Building a fuller understanding of this lesser-encountered form of scaling has therefore become a key part of Turkey’s drive towards greener energy.
However, solving this challenge extends beyond knowing the nature of the minerals at play.
Stibnite scaling can also be a feature of the type of power plant in use. So how to understand where the main problems lie, and what to do about it?
With the help of 3D models created by Leapfrog Energy, this independent case study by geoscientists at Turkey’s Izmir Institute of Technology sets out to improve understanding of these complex cause and effect interplays, while also establishing the appropriate reinjection temperature for stibnite scaling.
- Investigating stibnite scaling in the surface equipment system in comprehensive detail and determining why ORC-Binary systems can be more susceptible to it
- Evaluating the hydrogeological and geochemical properties of the geothermal waters in the studied Germencik Geothermal Field
- Exploring the types of scale that can occur in geothermal wells, and the behaviour of Sb in the geothermal fluid.
Read the full academic study to see how a 3D conceptual model of the research area was created in Leapfrog Energy software, using well logs from 25 plants in the study area. Plus, what was learned from geothermal water sampling, the evaluation of rock and scale samples at a variety of depths, and the inhibitors judged most effective for the future prevention of stibnite scaling.
Example extract: According to the 3D conceptual model, the geothermal waters in the study area are recharged from the high-altitude regions. The Gümüşdağı horst constitutes the main recharge area of the geothermal waters. Geothermal waters move up to the surface thanks to the tectonic lines after heating at depth. In this way, a favourable environment is created for the geothermal systems in the region.
Serhat Tonkul is a dedicated researcher specializing in environmental science and engineering. Currently pursuing his Ph.D. at the Izmir Institute of Technology, Serhat’s research interests include mathematical modeling, groundwater contamination, geothermal energy, and hydrology. He holds an M.Sc. in Energy Engineering and a B.Sc. in Geological Engineering.
