Silica Scale Prevention Method Using Seed Made from Geothermal Brine

Abstract

Silica scale formation from geothermal brine causes various problems. We have proposed a silica scale prevention method: the seeding method using silica gels. In this work, the seeds are made from silica scale or geothermal brine and evaluated on the silica removal performance. Tests were conducted at the Onuma geothermal field. The experiments were conducted using three kinds of seeds: (1) colloidal silica solution, (2) silica scale and (3) colloidal amorphous silica precipitate. The colloidal silica solution and the silica scale seeds could not remove the excess silica in the geothermal brine. On the other hand, the colloidal amorphous silica seeds showed silica removal-ability and could decrease the silica concentration in the brine close to the amorphous silica solubility. The silica precipitation rate on the colloidal amorphous silica seeds is correlated with the excess silica above pre-equilibrium silica concentrations. Since the colloidal amorphous silica obtained in this work has high silica purity of 98 wt%, there are good possibilities to have a good resource of silica.