Waste to Wealth: From New Zealand's Geothermal Fluid

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dc.contributor.advisor Gao, W en
dc.contributor.advisor Cao, P en
dc.contributor.author Li, Ying en
dc.date.accessioned 2015-07-17T01:36:09Z en
dc.date.issued 2015 en
dc.identifier.citation 2015 en
dc.identifier.uri http://hdl.handle.net/2292/26287 en
dc.description Full text is available to authenticated members of The University of Auckland only. en
dc.description.abstract Bearing in mind the overall goal of the project is to convert the post-flash “waste” geothermal fluid into wealth, a technology review was conducted to investigate the contemporary and potential geothermal fluid treatment techniques which are either applicable to extract valuables from New Zealand’s geothermal fluid or treat the “problematic” components which limits the recovery efficiency of valuables. Specifically, this study aims to find the bestfitting industry technologies for silica removal and hydrogen sulfide abatement, as well as common methods for extraction of lithium and boron. The performance of each competing silica removal technique was evaluated in terms of their economic and environmental impact, sustainability and feasibility. Eventually, the optimum silica removal methods were proposed to be the lime softening and ultrafiltration. On the other hand, the appropriate H2S abatement process for different geothermal plants would vary depending on the type of condenser used in the plant, ammonia to hydrogen sulfide ratio in the off gas and whether condensate needs to be treated. The lime softening method mainly utilises calcium hydroxide to remove silica. To verify the effectiveness of lime softening method for silica removal, calcium chloride and sodium hydroxide were doped to geothermal brines with various initial silica concentrations as the removing agent. As a result, the level of silica within brine was dramatically reduced with increased amount of calcium nitrate and sodium hydroxide; and silica can be perfectly removed with appropriate dosage. Moreover, arsenic and boron can be co-precipitated by this method but boron cannot be reduced significantly. In addition, one of the boron extraction methods called electrocoagulation was tested on laboratory basis. The influence of operating parameters such as current density, electrode material (iron / aluminium), and initial boron concentration were examined. At the optimised state, the boron removal efficiency from synthetic solution with initial boron concentration of 200 and 1000 ppm reached 96% under 5 minutes operation with Al electrode and current density of 20 mAcm-2. When brine was applied, electrocoagulation also worked well for silica and arsenic removal. Finally, energy consumption for the optimum operating conditions was calculated and the results proved to be economical. en
dc.publisher ResearchSpace@Auckland en
dc.relation.ispartof Masters Thesis - University of Auckland en
dc.relation.isreferencedby UoA99264788314102091 en
dc.rights Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. Previously published items are made available in accordance with the copyright policy of the publisher. en
dc.rights Restricted Item. Available to authenticated members of The University of Auckland. en
dc.rights.uri https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm en
dc.rights.uri http://creativecommons.org/licenses/by-nc-sa/3.0/nz/ en
dc.title Waste to Wealth: From New Zealand's Geothermal Fluid en
dc.type Thesis en
thesis.degree.discipline Chemical and Materials Engineering en
thesis.degree.grantor The University of Auckland en
thesis.degree.level Masters en
dc.rights.holder Copyright: The Author en
pubs.elements-id 491812 en
pubs.record-created-at-source-date 2015-07-17 en

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