Long Run Polymerization Experiments at the Kawerau Geothermal Limited Power Plant

Abstract

Silica scaling is a key consideration in the operation of geothermal power plants. The silica saturation index (SSI) through different stages of process is an important factor in the overall design and operation of a plant, especially in the design of separation pressures and the disposal scheme of separated brine from the plant. Processes such as pH modification are applied to balance energy extraction from the fluid whilst preventing silica scaling in the plant and reinjection fluids.
Silica polymerization testing on a plant is normally the final proof that the process adequately prevents detrimental silica scaling from occurring.
There is a large amount of literature available that compares silica polymerization characteristics under varying temperature or pH settings, however there is a noticeable lack of polymerization curves available under conditions close to the pH, temperature and SSI conditions that Mercury’s geothermal plants operate. This paper describes a set of long run polymerization experiments conducted at the Kawerau Geothermal Limited (KGL) power plant located on the Kawerau geothermal field. Results are compared against existing silica polymerization knowledge in the industry.