Theoretical and Experimental Evaluation of the EvGT-Process

Abstract

Abstract In recent years the interest for new advanced thermodynamical gas turbine cycles has increased. One of the new designs is the evaporative gas turbine cycle. A lot of effort worldwide has been put into predicting the possible efficiency, pollutants, and dynamic behaviour of the evaporative gas turbine cycle, but all results so far have been affected by uncertain assumptions. Until now this cycle has not been demonstrated in a pilot plant. The purpose of this work has been to identify the potential of this cycle, by erecting a pilot plant at the Lund Institute of Technology. The project was financed on a 50/50 basis from the Swedish National Energy Administration and the industrial partners. Three different thermodynamical cycles have been tested in the pilot plant: the simple, the recuperative, and the evaporative cycles. The final pilot plant roughly consists of a 600 kW gas turbine, a hydraulic brake, a recuperator, a humidification tower, an economiser, and a flue gas condenser. All layout and functional analysis were made within the project. The pilot plant is, however, optimized neither for best efficiency nor for best emissions. It has only been built for demonstration purpose. It has been shown from the performance tests that the efficiency for the simple, recuperative, and evaporative cycles are 22, 27, and 35%, respectively, at rated power output. The NOx emissions were reduced by 90% to under 10 ppm, and the UHC and CO were not measurable when running the evaporative cycle at rated power output. The performance of the humidification tower was better than expected. The humidified air out from the humidification tower is always saturated. The pinch point, i.e. the temperature difference between the outcoming water from the humidification tower and the saturation temperature of the incoming air, is around 3°C. The water circuit was closed, i.e. there was no need for additional water, when the flue gases after the flue gas condenser reached a temperature of 35° C. The inhouse heat balance program, used for both cycle optimization and evaluation, has been verified. The evaporative gas turbine cycle has, when optimized, at least the same efficiency as the best combined cycle today, based on the same gas turbine. The evaporative cycle will also show very good performance when used in small scale power plants.