Binary Plant Caustic Dosing Test Rig Development

Abstract

This paper is a case study of the design and development of a test rig to assess separated geothermal brine for power production at the Lihir geothermal field in Papua New Guinea. The test rig was constructed to gain an understanding of the brine chemistry from the field and how it might behave in a binary power plant. The outcomes of the testing will give Newcrest Mining Limited additional design criteria to better manage and control mineral scaling and corrosion. The test rig incorporates two independent test lines for delivery of geothermal brine: one allows for pH-modification by dosing the brine with sodium hydroxide (caustic), and the other is an undosed control line. The two test lines are fully instrumented and controlled via a Programmable Logic Controller (PLC) on the test rig. The detailed design for the rig is discussed in this paper, with particular focus on the implementation of a heat exchanger to simulate a binary plant, as well as pH control methodology, equipment packaging within the confines of a shipping container, caustic delivery, brine flashing problems and operating philosophy.