Method for imitating scale formation in the Takigami binary power plant in Oita, Japan: Establishment of primary synthesis conditions

Abstract

The advantage of suitable anti-scaling technologies for individual geothermal plants would benefit from shorter development periods, making it necessary to improve the precision in evaluating a scaling technology through laboratory testing. This study focuses on developing a technology to replicate the scale formed in the Takigami binary geothermal plant. The artificial scale obtained was compared with an actual scale collected during jet washing that followed the chemical washing process in the evaporator of the Takigami binary power plant. The artificial scale was synthesized in controlled environments by removing dissolved oxygen and introducing carbon dioxide (CO₂) to simulate geothermal conditions. The artificial scale resembled the natural scale, predominantly comprising silica and metal silicates. Although the scale formed in the Takigami binary geothermal plant differed from the artificial scale in terms of particle size, the size of the dispersion particles in the geothermal brine was similar to that of the dispersion particles in the synthesized solution. In addition, the amounts of enriched elements differed from those in the natural scale, with higher aluminum and lower calcium concentrations. These discrepancies highlight the need for additional adjustments in synthesis conditions to more precisely replicate the natural scaling environment. We illustrate how laboratory-scale synthesis can help successfully imitate the intricate natural scaling processes, providing valuable insights for enhancing scaling management in geothermal facilities. Optimizing the gas and chemical inputs may help further improve the precision of these simulations. The interactions between the material and solution particles need careful consideration.