| Title | PROGRESS IN THE CALCIUM SILICATE TECHNOLOGY DEVELOPMENT TO PREVENT SILICA DEPOSITION AND FACILITATE ENHANCED ENERGY RECOVERY FROM A GEOTHERMAL RESOURCE |
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| Authors | J.H. Johnston, T. Borrmann, M. Schweig, M.J. Cairns and H.P. Fraser |
| Year | 2019 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Geothermal, separated water, nanostructured calcium silicate, silica sinter, binary, heat exchanger, enhanced energy recovery, fertilizer, building, paper |
| Abstract | We are continuing to successfully develop and implement our proprietary nanostructured calcium silicate, CaSil, technology at pilot plant scale to demonstrate how we can prevent the polymerisation and precipitation of silica from separated geothermal brine supersaturated in dissolved silica, which undesirably results in the formation of intractable silica sinter deposits in pipes, heat exchangers and reinjection wells. Our objective is to provide an attractive alternative approach and new technology to obviate the silica deposition problem and at the same time enhance the amount of heat energy recoverable and electricity generated in binary cycle plants, as well as reducing maintenance costs. Our approach captures the silica entities dissolved at supersaturated levels in geothermal brine following steam/water separation by precipitating a proprietary nanostructured calcium silicate material, before these entities can polymerise, precipitate and deposit as an intractable sinter. The calcium silicate particles remain suspended in the brine flow and do not form such a sinter. Silica deposition is avoided. This enables binary plant heat exchange temperatures, considerably below those currently determined by the silica saturation index, to be used without the risk of silica deposition. The recoverable heat energy and electricity generated can be enhanced accordingly. The calcium silicate particles are recovered continuously in a proprietary separator to provide CaSil products as a concentrated slurry, or with further processing as a filter cake or dry powder, depending on the application. Following efficient CaSil particle separation, the resulting cooled geothermal brine exiting the binary plant heat exchangers can be reinjected without risk of silica deposition. By controlling the chemistry, different CaSil products can be produced. We are progressing CaSil applications in the building, paper, coatings, absorbent, mining and environmental remediation industries. The presentation will provide an overview of our pilot scale implementation of the CaSil technology and calcium silicate applications development work. |