| Title | ELIMINATION OF THE PROBLEMATIC DEPOSITION OF SILICA FROM SEPARATED GEOTHERMAL BRINE |
|---|---|
| Authors | J.H. Johnston, T. Borrmann, M. Schweig, M.J. Cairns |
| Year | 2018 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Silica, silica deposition, sinter, nanostructured calcium silicate, calcium silicate, geothermal, enhanced energy recovery, building, phosphate, environmental |
| Abstract | The precipitation of silica from separated geothermal brine supersaturated in dissolved silica and the consequent formation of silica sinter deposits in pipes, heat exchangers and reinjection wells is a major problem in geothermal resource utilisation worldwide. This sinter compromises heat energy recoverable in binary cycle electricity generation and increases maintenance. Current approaches to address the problem include using higher steam/water separation temperatures to reduce silica saturation, acid dosing and additives to retard silica polymerisation. However these are not wholly satisfactory and silica still precipitates. We are turning this problem into an attractive operational and business opportunity though the development and demonstration of a new technology that captures the dissolved silica species as a novel nanostructured calcium silicate material, thereby reducing the silica level below that from which silica can precipitate and the sinter forms. The nanostructured calcium silicate material has a unique 3D framework structure, providing it with high liquid absorbent and surface area properties. The particle surface is different from that of silica and desirably the calcium silicate particles do not deposit on metal surfaces, thus eliminating silica sinter formation. It has the potential to enable lower steam/water separation temperatures and lower exit temperatures in binary plant heat exchangers to be used, thereby enabling more heat energy to be recovered from a geothermal resource. There is no further propensity for silica to deposit in process equipment or in reinjection wells. We control the calcium silicate chemistry and composition, and hence its properties, to provide products which have multiple potential applications in the building, paper, paint, polymer, absorbent, mining and environmental remediation industries. We have progressed the development to pilot scale operation at a New Zealand geothermal field and are evaluating commercial opportunities for the calcium silicate products. An overview of the technology and product applications is presented here. |