Effect of Silica Scaling Inhibitor in Geothermal Brine

Abstract

Silica scaling is among the major limiting factors in increased energy extraction from geothermal fluids in the geothermal industry. Commonly, reinjection of brine is conducted at high temperature to overcome potential silica scale formation which can occur due to cooling. Silica and silicates have prograde solubility (i.e. decreasing solubility with decreasing temperature) and are anticipated to scale for example in heat exchangers at temperatures below 80-150°C depending on aqueous silica concentration. The aim of this study was to explore the optimal conditions to minimise or avoid scaling from the geothermal brine upon cooling. A series of laboratory experiments with and without commercial silica inhibitors were conducted as a function of temperature and pH, and silica concentration/scaling was monitored in the solution over time. The rates of initial silica scaling due to aqueous silica polymerisation may be delayed in order to reduce silica scaling using such inhibitors in geothermal equipment. Recent achievements have demonstrated that silica scaling can be controlled during geothermal fluid production at lower temperatures, thereby increasing energy output from geothermal power plants. This work was conducted in the GeoSmart project. The overall aims of the project are: 1) reduced geothermal energy cost, 2) reduced carbon footprint, 3) competitiveness in smart and flexible operation.