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Session: Parallel Session: Heat exchangers
Session starts: Friday 23 September, 16:00
Presentation starts: 16:40
Room: Auditorium

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Carsten Trapp ()
Piero Colonna ()

Abstract:
In the transition period leading to electricity generation fully based on renewable energy resources, fossil fuel power plants need to be equipped with CO2 removal units. An ongoing research project involving Nuon-Vattenfall, TU Delft, and ECN, is aimed at the development of pre-combustion CO2 removal technology from an integrated coal gasification combined cycle (IGCC) plant in the Netherlands [1]. A fully instrumented pilot plant of the CO2 capture unit has been built at the Buggenum IGCC power station and is being commissioned for further studies and experiments. The removal of CO2 from the syngas is very energy demanding and therefore technical solutions to reduce the efficiency penalty in thermal power plants must be investigated. This study concerns the feasibility of recovering low-grade thermal energy from the CO2-capture process by means of an Organic Rankine Cycle power plant. In comparison to geothermal applications, which are widely documented in the literature [2,3], the heat source in this case is a syngas water mixture which is cooled from a temperature of 130-140 °C and condenses due to the heat transfer to the ORC evaporator. First, the application of commercially available ORC units is explored by means of steady-state simulations. The plant composed of commercially available ORC units is simulated and taken as a benchmark for a tailor-made ORC power plant. The working fluid has an important influence on system performance and therefore the effect of selecting a fluid from the hydrocarbons and refrigerants families are investigated, targeting the maximum net power output. In addition to pure fluids, also two component mixtures are investigated in a subcritical ORC cycle configuration. The use of mixtures as working fluids in ORC systems allows for a better match of the temperature profiles in the evaporator and the condenser [4], due to the temperature glide associated with phase-transition, leading to lower irreversibilities within the heat exchanging equipment. In order to further improve the thermal coupling of the cooling heat source to the heating of the working fluid, a supercritical ORC configuration is also studied. The three ORC configurations (commercial ORC, customized subcritical & supercritical ORC) are analyzed in terms of net power output, second law efficiency and component based exergy destruction.