From October 2015 to May 2016, the pilot plant was moved to the Norske Skog pulp and paper mill site on the Kawerau (NZ) geothermal field. Unlike Wairakei, where the geothermal fluid treated entered the pilot plant at a temperature of 126 degrees C and a silica concentration of 550 ppm, the geothermal fluid available for treatment at Kawerau varies in temperature from 85 – 185 degrees C while silica concentrations vary from 450 – 820 ppm silica. Initial trials concentrated on geothermal fluids presently being discharged into the Tarawera River which have a temperature of 85-95 degrees C and a silica concentration of 700 ppm.
Though the geochemistry of the fluids at Kawerau is significantly different from that at Wairakei, operating results at the pilot plant show that colloidal silica can be extracted using the same process that was developed at Wairakei. This has demonstrated that the process is very robust and able to be used on compositionally very different types of geothermal fluid.
At the completion of the work on the Norske Skog site the pilot plant was relocated to Mercury NZ Limited site on the Kawerau field. Testing work commenced in December 2016.