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Session: Poster session
Session starts: Tuesday 13 October, 13:30

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Valdimarsson Pall (Atlas Copco Energas GmbH)
Markus Sauerborn (Atlas Copco Energas GmbH)

Abstract:
The fluid in a high enthalpy geothermal field is saturated liquid with dissolved minerals and gases. The wells produce a mixture of mineralized brine, non-condensable gas and steam. The well fluid cannot be cooled below the silica saturation in the plant. The non-condensable gas has to be separated from the fluid at some stage and disposed of. This will all influence the power plant design. The heat of the geothermal fluid is transferred to a working fluid in heat exchangers in an ORC plant. All heat transfer over a finite temperature difference will cause exergy loss, which will be less, the smaller the temperature difference is. But the cost of the heat exchanger will be higher the smaller this difference is, so an optimization has to be made. The temperature profiles both for the geothermal fluid and the ORC working fluid are determined from the thermodynamic properties of the fluids. The selection of the working fluid has thus to be made with the thermodynamic properties of the complex geothermal mixture in mind. Atlas Copco is proposing a novel way of fitting an ORC power plant to geothermal fluid from high enthalpy resources. This plant is described, and temperature-heat duty and Carnot efficiency-heat duty diagrams are used to describe how the ORC plant is optimized for each geothermal fluid mixture and enthalpy.