By Abdallah Nur Siddiq-definition of the scale is the deposition of solids on the surface of the metal, stone, or other material. Geothermal systems, the scale of the geothermal fluid berfase liquid (water). There are 3 classes of minerals in geothermal fluid that can cause the onset of scaling, i.e.:
- Silica and silicates
- Carbonate of calcium and iron
- Sulfides of iron and heavy metals
Water is a universal solvent so that the water is always in the process of dissolving into the minerals precipitate or scale. Such phenomena to determine the limit of solubility.
Levels of mineral scaling on the water is not completely dependent on the chemical composition of the water itself or to the minerals that dissolve, but rather caused by the degree of saturation of the water against the minerals whose value varies, changes in temperature, pressure changes, changes, changes in redox potential relative to other mineral concentration, and pH changes.
The mechanism of the formation of scale is simply the same as with the deposition process in General. Deposition occurred because the value of the Qc (product ions that react) is greater than the value of Ksp (results of times when ions solubility equilibrium). Calculation of equilibrium shows that geothermal water can be saturated with minerals. Calculation of solubility product ions can be done using the software, AquaChem software used to calculate the saturation index so it can predict potential occurrence of scaling.
Further reading Potential Geothermal Energy Independence and Indonesia
Further reading: corrosion in Geothermal Systems