From December 2016 to July 2017, the pilot plant was moved from the Norske Skog pulp and paper mill site to Mercury NZ Limited’s site on the Kawerau (NZ) geothermal field where they operate a 100MW geothermal power station. The geothermal fluid used for this power station comes from deep down in the field and is hotter than the fluid drawn for Norske Skog. The separated geothermal fluid (SGW) from this power station entered the pilot plant at a temperature of 140 degrees C and a silica concentration of 950 ppm. The fluid is acidified by the power station to suppress silica scaling in the reinjection pipework and reinjection well.
Though the geochemistry of this fluid was different, operating results at the pilot plant showed that colloidal silica can be extracted using the same process. This has further demonstrated that the process is very robust and able to produce good quality silica products.