Tord Torisson

Experimental and Theoretical Results of a Humidification Tower in an Evaporative Gas Turbine Cycle Pilot Plant

The Evaporative Gas Turbine Pilot Plant has been in operation at Lund Institute of Technology in Sweden since 1997. In this cycle low-grade heat in the flue gases is utilized for water evaporation into the compressed air in the humidification tower. This result in, amongst others, power augmentation, efficiency increase and lower emissions. This article presents the experimental and theoretical results of the humidification tower, in which simultaneous heat and mass transfer occurs. A theoretical model has been established for the simultaneous heat and mass transfer occurring in the humidification tower and it has been validated with experiments. The humidification tower in the pilot plant can be operated at several operating conditions. An after-cooler makes it possible to chill the compressor discharge air before entering the humidification tower. The saturation temperature of the incoming compressed air can thereby be varied from 62 to 105°C at the operating pressure of 8 bar(a). It has been shown that the air and water can be calculated throughout the column in a satisfactory way. The height of the column can be estimated with an error of 10% compared with measurements. The results from the model are most sensitive of the properties of the diffusion coefficient, viscosity and thermal conductivity due to the complexity of the polar gas mixture of water and air.

Comparison of Gas Turbine Cooling With Dry Air, Humidified Air and Steam

In order to study the impact of using a gas turbine coolant other than compressed air, a comparison is made among various gas-turbine based power cycles: the simple-cycle gas turbine, the steam injected gas turbine, the combined cycle and the Humid Air Turbine (HAT) cycle. Depending on the cycle configuration, the coolant, which is compared to the air extracted from the compressor, is either steam or humidified air. The study is based on a modern, medium-sized industrial gas turbine (net power output in base configuration: 40 MW), in order to evaluate the possibilities of different redesign options of the cooling system.It is found that steam cooling is a very efficient method of cooling; whereas, the possible benefits of humid air cooling are mainly obtained through the temperature decrease that is a result of the humidification process. Hence, for the intercooled HAT cycle, the benefit of cooling with humid air is smaller (∼0.2 percentage points increase in thermal efficiency) than for the HAT cycle without intercooler (∼0.5 percentage points increase in thermal efficiency). For the simple cycle, there is an increase in thermal efficiency of 0.8 percentage points when it is cooled with humid air.A parameter variation shows that with more advanced cooling technologies and heat resistant materials, the benefit of cooling with steam or humid air, instead of with compressed air, is reduced for the HAT and combined cycles.Copyright

Optimization with Genetic Algorithms of a Gas Turbine Cycle with H2-Separating Membrane Reactor for CO2 Capture

A gas turbine power process with CO2 capture through precombustion decarbonization, which employs a H2-separating membrane reactor is presented. Optimization with the process thermal efficiency as objective function is made through the use of genetic algorithms. The use of genetic algorithms enabled a division of the optimization parameters into two groups; one group where the values are at their optimum at the limit of the investigated parameter range, and one group where there actually is an optimum within the investigated range. It was found that the process has a severe efficiency penalty caused by the use of heat from hydrogen combustion for the reforming process. The process is a zero CO2 emission power process and also NOx emissions should be low, due to the inherent mixing of hydrogen with steam.

A Unique Correction Technique for Evaporative Gas Turbine (EVGT) Parameters

Modelling and data-normalization of a gas turbine process, called Evaporative Gas Turbine (EvGT) is studied here. The most important factor to achieve a high level of accuracy during the data normalization, is the consideration of changes in thermodynamic properties of the working medium at different environmental conditions. Performance of the EvGT, which is working with a mixture of air and steam, is strongly affected by the changes in the environmental conditions. When the properties of the working fluid such as the water content are continuously changing, the normalization process using conventional techniques becomes very difficult if not impossible. In this study, measured data from the worlds’ first Evaporative Gas Turbine at Lund University in Sweden have been used for generation of an empirical model by a single Artificial Neural Network system. Performance maps generated by ANN have been successfully used for data normalization and performance prediction of the Evaporative Gas Turbine. ANN predicted values are compared with experimental results, not used during the training, where very good correlation was observed.Copyright

A Novel Correction Technique for Simple Gas Turbine Parameters

Data normalization for gas turbines is necessary for comparison of test data collected at various environmental conditions. The normalization procedure is regulated by the ISO-standard. In this study, a single Artificial Neural Network is used to model the performance of a simple gas turbine (VT600) using measured data at various environmental and operational conditions. Consequently, engine performance maps covering a wide range of operational and environmental conditions have been generated. Comparison of the normalized/experimental data, results provided by thermodynamic models using heat and mass balance programs and results generated by the Artificial Neural Network (ANN) model shows a high level of consistency. The study presented here was performed as a pilot study, to investigate the applicability of an ANN model for data normalization applied to an Evaporative Gas Turbine (EvGT), since the ISO-standard normalization procedure is not applicable to the EvGT plant. Results of this work show that Artificial Neural Networks are powerful tools for performance prediction as well as generation of accurate power plant model of an specific simple gas turbine, and that data normalization can easily and accurately be carried out by using these performance maps.Copyright

Theoretical and experimental evaluation of a plate heat exchanger aftercooler in an evaporative gas turbine cycle

The evaporative gas turbine pilot plant (EvGT) has been in operation at Lund Institute of Technology in Sweden since 1997. This article presents the experimental and theoretical results of the latest process modifications made, i.e. the effect of the installation of an aftercooler. The purpose of the aftercooler is to increase the performance of the cycle by utilizing more low-level heat in the humidification tower. The chosen aftercooler is of plate heat exchanger type, which, is very compact, has high thermal efficiency and low pressure drop. The installation of an aftercooler lowers the temperature of the air entering the humidification tower. This also lowers the temperature of the circulating humidification water, which facilitates the extraction of more low-level heat from the economizer. This low-level heat can be utilized to evaporate more water in the humidification tower and thus increase the gas flow in the expander. The pilot plant has been operated at different loads and the measured results has been evaluated and compared with theoretical models. The performance of a plate heat exchanger in power plant applications has also been evaluated. Experience from the measurements has then been used for the potential cycle calculations. It has been shown that the aftercooler lowers the flue gas temperature in the pilot plant to 93 (Less)

Thermo-economic evaluation of bio-ethanol humidification EvGT cycle

The evaporative gas turbine pilot plant (EvGT) has been in operation at Lund Institute of Technology in Sweden since 1997. This article presents the latest development in the evaporative technology, the evaporation of bio-ethanol in a gas turbine power plant as a means to reduce the emission of greenhouse gases. Bio-ethanol is produced from a feedstock consisting of corn-stover, and the bio-ethanol is here considered to be a renewable fuel with zero impact regarding CO2 in the exhaust gases. This concept is evaluated and compared to a direct-fired Rankine cycle in the size range of 3-5 MW el and 15-30 MWel concerning plant efficiency and investment cost. The proposed bio-ethanol evaporation technology provides fuel for a Humid Air Turbine by evaporating bio-ethanol into the compressor discharge air. This evaporation process creates a combustible gas that is led to the combustor as the primary fuel. The bio-ethanol used in the process has not been distilled. The bio-ethanol is supplied to the process as a mash, i.e. a mix of water and ethanol with low concentration of ethanol. To extract the ethanol from the mash, energy is required. In this process, low-level heat from the gas turbine cycle is used for the separation process. All power cycles studied have been modeled in IPSEpro [trademark] , a heat and mass balance software, using advanced component models developed by the authors. An equilibrium model is used to model the behavior of the evaporation of ethanol and water into an air stream. A correction parameter has been introduced into the equilibrium model to account for the deviation from equilibrium. This parameter has been validated through experimental work on the Evaporative Gas Turbine pilot plant. The evaporation technology can be used with different types of cycle configurations attaining electrical efficiencies of 29% for a simple version of a Humid Air Turbine. The Humid Air Turbine can sustain a combustor outlet temperature of 1100 (Less)

The Ethanol-Water Humidification Process in EvGT Cycles

Ethanol from bio-products has become an important fuel for future power production. However, the present production technology is rather expensive. This paper focuses on how to lower the production cost of ethanol extraction from mash, and to use the ethanol as a primary fuel in gas turbines for heat and power production. Today, ethanol is produced during distillation by supplying energy to extract the ethanol from the mash. Using the evaporation process in the evaporative gas turbine to extract the ethanol from the mash before the distillation step, a lot of energy can be saved. In the evaporation process, the ethanol is extracted directly from the mash using energy from low-level energy sources. The evaporation technology is therefore expected to reduce the cost for the ethanol production. Simultaneous heat and mass transfer inside the ethanol humidification tower drives a mixture of ethanol and water into the compressor discharge air. To investigate the evaporation of a binary mixture into air at elevated pressures and temperatures, a test facility was constructed and integrated into the evaporative gas turbine pilot-plant. The concentration of ethanol in the mash is not constant but depends on the sugar content in the feedstock used in the fermentation process. Tests were therefore conducted at different concentrations of ethanol in the ethanol-water mixture. Tests were also performed at different temperature and flow conditions to establish the influence of these parameters on the lower heating value of the produced low calorific gas. It has been shown that this technology extracts about 80% of the ethanol from the mash. It has also been shown that the composition of the resulting gas depends on the temperatures, flow rates and composition of the incoming streams. The tests have shown that the produced gas has a lower heating value between of 1.8 to 3.8 MJ/kg. The produced gas with heating values in the upper range is possible to use as fuel in the gas turbine without any pilot flame. Initial models of the ethanol humidification process have been established and the initial test results have been used for validating developed models. (Less)

A Novel Gas Turbine Concept for Combined Power, Heat and Cooling Generation

An attractive and innovative technology for gas turbines for obtaining power, heat and cooling simultaneously has been developed and studied in Lund.The basic idea behind this technology, called the TRIGENERATION™, is to interrupt the expansion in the gas turbine expander at an elevated pressure level, at which the heat rejection is carried out in a heat exchanger. After that, the expansion of the flue gas continues until ambient pressure, but the temperature is below the ambient temperature. This “negative” temperature difference allows the use of the exhaust for cooling purposes. The performance coefficient, defined as the ratio between all the benefits (power, heat and cooling) and the fuel heat, can reach values higher than 100% (HHV). This technology has its major potential when integrated with “wet” cycles, e.g. HAT and STIG. In such cycles, an easier extraction of the latent heat of vaporization within the humid flue gas is allowed, due to the higher water dew point at higher pressures. In this work, this technology is evaluated through simulations in a heat and mass balance program for the simple cycle gas turbine.Copyright

A Review of Gas Turbine Flow Path Analysis: From Paper Calculation to Artificial Neural Networks

Today many methods are available for gas turbine flow path analysis. Some of them are very simple but yet very useful, since they give an indication of the compressor capacity with almost no calculation effort. The state of the art today is the heat and mass balance models (HMB), which are more sophisticated. This paper presents a general overview of these methods, including the most recent trend, Artificial Neural Networks (ANN). In the future, the ANN-based flow path analysis system will probably, to some extent, replace the HMB-based systems, or become a complementary tool for monitoring and performance analysis of power production units. This paper will give a comprehensive explanation of how to build a flow path analysis system in an equation-solving package (e.g. spreadsheet program), by using relationships presented here. This may give a system that is well within the capabilities of most commercially available systems, used and developed by consultant companies (third party companies). (Less)