In binary (ORC) plants, heat from the geothermal fluid is transferred to the organic working fluid through heat exchangers. Even a thin layer of scale on the exchanger surface lowers heat transfer and reduces the plant’s net output.
How does fouling form?
As the fluid is cooled in the exchanger, silica saturation rises and silica and metal silicate layers form at the cold end. Calcite can appear in the preheater and vaporiser, and in some fields antimony or iron sulphide deposits occur. Corrosion products and suspended solids also stick to surfaces and make the scale heavier.
Spotting efficiency loss early
- Approach temperature (difference between brine outlet and working fluid) rising over time
- Increasing pressure drop across the exchanger
- Lower net power at the same brine flow
- Reinjection temperature rising above target
Prevention approach
Exchanger fouling needs a programme rather than a single product: scale inhibitor for calcite, inhibitor/dispersant for silica, a composition-specific solution for sulphide deposits and corrosion control. Setting the cold-end temperature against the silica saturation limit directly affects the success of the chemical programme. Biyopol proposes a programme together with exchanger performance data and scale analysis.
Cleaning or prevention?
Chemical or mechanical exchanger cleaning means a partial or full plant outage. A continuous prevention programme extends cleaning intervals; when cleaning is needed, a cleaning chemical matched to the scale composition gets it done quickly without damaging equipment.
| Indicator | Why track it? |
|---|---|
| Approach temperature | Earliest sign of falling heat transfer |
| Overall heat transfer coefficient (U) | Calculating fouling resistance |
| Pressure drop | Narrowing and plugging |
| Net power / brine flow | Impact of fouling on output |
Frequently asked questions
Which scale is most common in exchangers?
It depends on the field; silica and metal silicates are common at the cold end of binary plants and calcite in hotter sections. A scale sample should be analysed for a firm diagnosis.
Is the programme different for plate and shell-and-tube exchangers?
The chemistry is the same, but narrow channels in plate exchangers raise the plugging risk, so monitoring should be more frequent.
Do you also supply cleaning chemicals?
Yes; we offer a cleaning chemical and application advice matched to the scale composition.
Related guides
- Geothermal power plant chemicals (overview)
- Calcite scaling in geothermal wells
- Silica and metal silicate scaling
- Corrosion in geothermal systems
- Downhole dosing via capillary tubing
- Scaling in reinjection lines and wells
- Geothermal heating and greenhouse systems
- Sulphide scales (stibnite, iron sulphide)
Request an assessment for your field
Share your fluid analysis and operating data; our technical team will propose a suitable programme and trial plan.