Pengembangan Model Prediksi Scaling Silika Pada Pipa Aliran Air Dari Separator
Long distances from separator or pond to the injection well will affect to brine flow in the pipe. In the geothermal field that has high silica content, construction and insulator of pipe will change the temperature of brine. This condition has impact to changes solubility of silica contained in the brine. Changes of pressure and heat loss causes change in enthalpy and brine flow rate and decrease in the inner diameter of the pipe caused by deposition of silica. Currently attempting to build a prediction model of silica scaling based on physical changes of brine flow in pipe. Model development of silica scaling prediction based on physical changes can be a method to determine the effects of silica deposition on brine flow in the pipe, so that it can be known that the flow pipe cleaning time effectively and efficiently.
Case studies in the Dieng geothermal field is done by modeling the effect of amorphous silica deposition in pipelines from the vertical pumps (VA) on pad 7 to pad 29. Models were analyzed with Microsoft Macro Excel software. Deposition of amorphous silica in the pipeline occurs radially. Validation result for the thickness of the silica was found that silica precipitates at 9.85% of the amount of silica formed on the pipe segments. Amorphous silica in the pipe segment that is not entirely settled will accumulate in the next pipe segment which then increases the amount of silica deposited on the pipe farther. Correlation between changes in diameter and flow rate of brine as a function of time can be simplified in the form of equations D_2=√(〖D_1〗^2-(4F_p)/(π.ρ_sa ) (m ̇_sa/L).t) and m_2=k_m.(D_2/D_1 )^(5⁄2).m_1. Deposition rate of amorphous silica at first hour is 6.38 x 10-4 gr/cm2.min. The higher pressure pump, the faster flow rate of brine. For similar deposition fraction, the higher the flow pressure causes the higher rate of precipitation of silica. Simulation results show that the insulator and the cladding will slow the rate of deposition of amorphous silica in the pipeline. The thicker the insulation, the smaller the rate of precipitation of amorphous silica.