Sebastian Lepszy

Technical and Economic Analysis of the Gas Turbine Air Bottoming Cycle

The gas turbine engine has many advantages such as low investment costs, low emissions and a low water consumption. This fact allows its application in many power engineering systems, for example as parts of gas and oil transport systems. It is possible to increase the efficiency of gas turbines through the use of combined cycles. For this purpose, the steam cycle is used most frequently. These systems are highly efficient in terms of energy, but they are very complex and have a high water consumption. An alternative to steam cycles are gas-air systems, referred to as the ABC’s (Air Bottoming Cycles), which use hot combustion gases as a heat source for the air cycle. ABC’s are composed of a gas turbine powered by natural gas, an air compressor and an air turbine coupled to the system by means of a heat exchanger, referred to as the AHX (Air Heat Exchanger).The paper presents an application of gas-air systems with example configurations, together with thermodynamic characteristics. Two technological structures are taken into consideration — a simple system of the ABC and an ABC with air intercooling. A parametric analysis of these systems is performed using a special computer program with real gas properties for enthalpy and entropy calculations. A basic comparative analysis of gas turbine air bottoming cycle and combined gas-steam cycle has been also done. Other important calculations are related to the heat exchanger, which is one of the most important components in this system because it couples the gas and air parts. The efficiency of the whole cycle depends on a rationally designed heat exchanger. The calculations are performed for a shell-and-tube exchanger, as well as for a plate heat exchanger. For all investigations an purchase cost of machines and devices is also determined.Copyright

Analysis of the Biomass Integrated Combined Cycles With Two Different Structures of Gas Turbines

Biomass integrated gasification combined cycles (BIGCC) are an interesting solution for electricity production. In relation to other biomass conversion technologies, BIGCC is characterized by relative high energy efficiency. For the sake of high complexity of such systems, one of crucial tasks is evaluation and comparison of the different technological structures of BIGCC. The article shows models and results of simulations of gas steam cycles integrated with biomass gasification. All models and simulations are preformed with Aspen Plus computer program. In the paper the main comparison is made between systems with simple gas turbine and gas turbine with regeneration. Simple gas turbine model based on LM2500 gas turbine parameters, Mercury 50 gas turbine parameters are used for model of gas turbine with regeneration. The model of gas generator consists of two equilibrium reactors. The use of two reactors led to more precise simulations of the flue gas composition, than the model with one reactor. Systems used for study include low-temperature gas cleaning system. Steam cycle consists of 1-pressure heat recovery steam generator (HRSG) and a condensing steam turbine. The main results of the work are: comparison of energy efficiency between system with gas turbine with regeneration and simple gas turbine, sensitive analysis of the impact of pressure in HRSG on energy efficiency, comparison of energy efficiency and heat and mass streams for different configurations of heat exchangers.Copyright

Technical and Economic Analysis of Biomass Integrated Gasification Combined Cycle

Biomass integrated gasification combined cycles (BIGCC) are an interesting solution for electricity production. In relation to other biomass conversion technologies, BIGCC is characterized by relatively high energy efficiency. This article presents models and results of simulations of the gas steam cycles integrated with pressurized gasification using biomass as a feedstock. The model and simulations are preformed with Aspen Plus® computer program. The gas generator model consists of two equilibrium reactors. The use of two reactors led to more precise simulations of the flue gas composition, than the model with one reactor. The systems used for study include high-temperature gas cleaning system and a simple gas turbine. The steam cycle consists of 1-pressure heat recovery steam generator (HRSG) and a condensing steam turbine. The main results of the work are: comparison of energy efficiency for a system with different pressure ratio in a gas turbine, sensitive analysis of the impact of steam temperature and pressure in HRSG on energy efficiency. The economic analysis includes determination of the electricity price in Polish economic conditions.Copyright

Effectiveness of the Hydrogen Production, Storage and Utilization Chain

The paper evaluates the effectiveness of a power-to-gas hydrogen chain, comprising the production, storage and utilization sections. The production section is based on alkaline electrolyzers producing about 18.6 kg hydrogen per MWh supplied electric energy derived from renewable (wind) sources. Next, hydrogen is transported to an underground storage facility (UGF), assuming that the pressure of the produced hydrogen is sufficient to provide its transportation to the storage site. Energy demand required for hydrogen compression to the UGF is accounted for, and the maximum level of hydrogen losses is evaluated. Finally, three options for hydrogen utilization are considered: (1) hydrogen is co-fired in a gas turbine, (2) it is supplied to hydrogen vehicles, (3) it is used for process purposes replacing the existing production based on steam methane reforming. Moreover, energy effects related to the replaced oxygen production are optionally taken into account. It has been shown that the choice of a scenario (co-firing//vehicles/process application) and, to a lesser degree, the possibility of using the generated oxygen strongly affects the overall process performance which may vary between low values of 20% (energy generation), 70–80% for process application (replacement of steam methane reforming) and more than 90% for vehicle application (replacement of diesel fuel). In conclusion, the process may provide excellent energy performance for dedicated hydrogen users, and a less favorable yet still considerable option for energy storage for renewable sources.