Humidification Processes in Gas Turbine Cycles

University dissertation from Division of Thermal Power Engineering Department of Energy Sciences Faculty of Engineering Lund University

Abstract: The global climate change caused by emissions of greenhouse gases from combustion processes has been recognized as a continuously growing problem and much research focuses on improving the environmental performance of gas turbines. The potential of improving gas turbine component efficiencies has become smaller each decade and therefore, thermodynamic cycles have become more interesting for power producing units. One of these cycles is the evaporative gas turbine cycle, also known as the humid air turbine. This thesis presents a theoretical model developed for the humidification tower in an evaporative gas turbine. The developed theoretical model has been validated with measurements from experiments conducted in a 600 kWe pilot plant. This thesis presents the installation of a plate heat exchanger in the pilot plant. The experience from the pilot plant is used in a comparative study. This study evaluates the influence of the aftercooler on the performance of the evaporative gas turbine. A test facility for evaporation processes at elevated pressures and temperatures have been built. Evaporation of binary mixtures into a compressed air stream has been performed. Experimental studies with the pilot plant have revealed that it is possible to use a plate heat exchanger as aftercooler in the evaporative gas turbine. The pressure drop on the air side in the aftercooler has been experimentally determined to 1.6% and the pinch-point to 0.1°C. The reconstruction of the pilot plant from a simple cycle to an evaporative cycle has resulted in an increase in thermal efficiency from 21% to 35%. A theoretical model has been developed for the humidification process that predicts the height of the humidification column with an error of 10?15%. Thermodynamic analysis of the bio-EvGT has been performed which have showed that the bio-EvGT cycle has an optimum efficiency of 34%. Further thermodynamics analysis has indicated that the bio-EvGT is a viable alternative to the biomass fueled steam turbine cycle.

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