51313-02544-Prediction and Monitoring of Scaling and Corrosion In pH Adjusted Geothermal Brine Solutions

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Product Number: 51313-02544-SG

ISBN: 02544 2013 CP

Author: Keith Lichti

Publication Date: 2013

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The risk of voluminous silica scaling limits many geothermal energy plants to steam and brine separation temperatures above the saturation limit for silica in the separated brine. The impact of these limits are compounded in the face of demand for secondary heat extraction using binary plant that can significantly increase energy efficiency from geothermal fluids. Options for additional energy extraction include increase in pH to increase the solubility limit for silica and decrease in pH to delay the time for onset of polymerisation reactions for colloidal silica sufficient to allow reinjection to a reservoir where elevated temperature will lower the silica saturation index. These two scale control methods can have significant impact on localised corrosion in chloride rich brines. The scaling and corrosion risks can be modelled theoretically to predict ideal conditions for enhanced energy production with minimal risk of corrosion however prudent operators can benefit from confirmation testing of scaling and corrosion risks in pilot plant that mimic planned operating conditions. This paper will outline the processes for theoretical predictions of the risk of scaling and corrosion under pH adjusted conditions in typical New Zealand geothermal brines and describe test results for an example pilot plant.