Assessing silica precipitation using calcium hydroxide addition on Dieng's geothermal brine

Abstract

Geothermal is one of the most reliable energy sources in Indonesia. The utilization of geothermal energy in the electricity generation provides green energy, as it can slow down the global warming and help control the climate change. However, the development of its capacity is still considerably slow. One of the most common problems encountered in geothermal power plants is silica scaling. This limits energy production by inhibiting the mass flow of the geothermal fluid and also adding resistance to the heat transfer. This study focuses on the silica precipitation of geothermal fluid using the addition of calcium hydroxide (Ca(OH)2) in a continuous reactor. The experiment was conducted by varying the reaction times of 5.00 and 8.33 minutes; reaction temperatures of 30 and 70°C; and pH levels of 7 and 9. The silica concentration of the initial and processed fluids was analyzed using UV-Vis Spectrophotometry. The observed silica concentration of the initial fluid was 600 ppm, with the best concentration at 150 ppm (25%) under 5 minutes reaction time, 70°C of reaction temperature, and pH of 9. Significance analysis showed that the silica concentration in the fluid is decreased when pH is increased, but with a shorter time of reaction. In addition, pH has a significant effect on the silica precipitation, while temperature and reaction time are much less significant.