Extraction of Silica and Other Minerals from Geothermal Brine in New Zealand

Abstract

Geo40 is a New Zealand technology company which was established in 2010 to develop technologies for the extraction of minerals from geothermal brines. The challenge with extracting minerals from the brine is dealing with the high temperatures and silica concentrations. Silica scaling in geothermal power generation is a significant issue. Work carried out for Geo40 by Jacobs Engineering Group (internationally recognised geothermal consultant) has shown that silica management costs can be as high as 20% of a power plants operating cost. Jacobs have also shown that up to 30% more power could be produced from reinjection fluids if silica levels were able to be reduced. This paper will take the audience through the Geo40 eight-year journey in developing a process for extracting the silica in the form of colloidal silica for sales in the specialty silica markets globally. At the time of writing this abstract Geo40 has successfully completed the construction and commissioning of a commercial demonstration plant processing geothermal brine from Contact Energy’s Ohaaki Geothermal Power station situated in the central north island of New Zealand. The processed brine has been used to restore the natural beauty of a local Maori hot spring (ngawha, see here for the video) and has demonstrated how the geothermal power industry and local indigenous people can work together to achieve a successful outcome. Following this success Geo40 has agreement form Contact Energy to proceed with a larger plant processing geothermal brine being reinjected on the field. This paper will take the audience through the construction and commissioning of the Northern Plant which will produce around 1,600 tonnes per annum of high value silica products and the first lithium extraction trials.