The shift towards renewable energy has steered the focus of power plant operation towards flexibility and fast response which are more attainable through the use of combined-cycle power plants. These aspects are required to account for the fluctuation of the supply as well as the demand of power that is associated with renewable energy. Combined-cycle power plants consist of a gas turbine as the topping cycle, forming the core of the plant, and a Rankine cycle with a steam turbine as the bottoming cycle. A component called the Heat Recovery Steam Generator (HRSG) forms a connection point between the two cycles. It uses the heat released from the gas turbine to produce high pressure and temperature steam to be sent to the steam turbine. The objective of this project is to develop a model of a combined-cycle power plant in Flownex which can be solved in off-design conditions in order to compare it to plant data. The verification of this model will show that Flownex can be used to effectively and efficiently model a combined-cycle power plant. The process of development of the final Flownex model was achieved using various additional software. Initially, an analytical model was developed in Mathcad (software used for engineering calculations). This software provides a tool for understanding knowns, unknowns and what is being calculated in the system. Manual calculations of the Heat Recovery Steam Generator (HRSG) were done using heat balance equations. A temperature profile of the gas and water/steam in the HRSG was developed so that the duties of each component (economiser, evaporator, superheater) could be calculated. The overall conductance (UA) of each component was calculated in the design mode for the system to be evaluated in off-design mode. The development of an analytical model provided detailed understanding of the process of mathematical modelling used in commercial tools. Thereafter, a model was built in Virtual Plant, a thermodynamic modelling software for assessing plant performance. Virtual Plant uses plant design information and first engineering principles to predict plant performance. Finally, the Flownex model was designed. Flownex uses endpoint values (initial pressure and temperature and outgoing mass flow) and the UA of each component to calculate the characteristics of the flow at each intermediate point. For the single-, double-, and triple-pressure combined-cycle power plant systems, the analytical, Virtual Plant and Flownex models were compared. The results of all the models agreed closely with one another. The triple-pressure design and off-design Virtual Plant and Flownex models were also compared to plant data and it was concluded that Flownex was successful in modelling the design and off-design conditions of a combined-cycle power plant.

A combined cycle gas/steam power plant combines a gas turbine (topping cycle) with a steam power plant (bottoming cycle) through the use of a heat recovery steam generator. It uses the hot exhaust of the gas turbine to produce steam which is used to generate additional power in the steam power plant. The aim of this study is to establish the different bottoming cycle performances in terms of the main parameters of heat recovery steam generator and steam cycle for a chosen gas turbine cycle. First of all / for a single steam power cycle, effect of main cycle parameters on cycle performance are analyzed based on first law of thermodynamics. Also, case of existence of a reheater section in a steam cycle is evaluated. For a given gas turbine cycle, three different bottoming cycle configurations are chosen and parametric analysis are carried out based on energy analysis to see the effects of main cycle parameters on cycle performance. These are single pressure cycle, single pressure cycle with supplementary firing and dual pressure cycle. Also, effect of adding a single reheat to single pressure HRSG is evaluated. In single pressure cycle, HRSG generates steam at one pressure level. In dual pressure cycle, HRSG generates steam at two different pressure levels. i.e. high pressure and low pressure. In single pressure cycle with supplementary firing excess oxygen in exhaust gas is fired before entering HRSG by additional fuel input. So, temperature of exhaust gas entering the HRSG rises. Second law analysis is performed to able to see exergy distribution throughout the bottoming plant / furthermore second law efficiency values are obtained for single and dual pressure bottoming cycle configurations as well as basic steam power cycle with and without reheat. It is shown that maximum lost work due to irreversibility is in HRSG for a bottoming cycle in a single pressure gas / steam combined power plant and in boiler for a steam cycle alone. Comparing this with the single pressure cycle shows how the dual pressure cycle makes better use of the exhaust gas in the HRSG that dual pressure combined cycle has highest efficiency values and lost work due to irreversibility in -most significant component- HRSG can be lowered. And also it is shown that by extending the idea of reheat the moisture content is reduced and improvement in the performance is possible for high main steam pressures. Another observation is that supplementary firing increases the steam turbine output compared to the cycle without supplementary firing. The efficiency rises slightly for HP steam pressures higher than 14 MPa at HRSG exit, because the increased steam production also results in increased mass flows removing more energy from the exhaust gas.

This master’s thesis deals with the possibility of increasing efficiency of energy blocks with combustion engines by the combination of the Sabat and Clausius-Rankine cycle into the combined cycle. In the thesis is briefly described the principle of the function of the auxiliary device, which can increase the efficiency of the combustion engine. This device, which consists of a waste heat boiler and two turbine modules, is designed using calculations. Both turbine modules are prepared with drawing documentation and there are described important structural elements. Each key part of the thesis is given by a brief theory, so the basic theory of combustion engines, waste heat boilers and steam turbine are described.

abstract: ABSTRACT The heat recovery steam generator (HRSG) is a key component of Combined Cycle Power Plants (CCPP). The exhaust (flue gas) from the CCPP gas turbine flows through the HRSG − this gas typically contains a high concentration of NO and cannot be discharged directly to the atmosphere because of environmental restrictions. In the HRSG, one method of reducing the flue gas NO concentration is to inject ammonia into the gas at a plane upstream of the Selective Catalytic Reduction (SCR) unit through an injection grid (AIG); the SCR is where the NO is reduced to N2 and H2O. The amount and spatial distribution of the injected ammonia are key considerations for NO reduction while using the minimum possible amount of ammonia. This work had three objectives. First, a flow network model of the Ammonia Flow Control Unit (AFCU) was to be developed to calculate the quantity of ammonia released into the flue gas from each AIG perforation. Second, CFD simulation of the flue gas flow was to be performed to obtain the velocity, temperature, and species concentration fields in the gas upstream and downstream of the SCR. Finally, performance characteristics of the ammonia injection system were to be evaluated. All three objectives were reached. The AFCU was modeled using JAVA - with a graphical user interface provided for the user. The commercial software Fluent was used for CFD simulation. To evaluate the efficacy of the ammonia injection system in reducing the flue gas NO concentration, the twelve butterfly valves in the AFCU ammonia delivery piping (risers) were throttled by various degrees in the model and the NO concentration distribution computed for each operational scenario. When the valves were kept fully open, it was found that it led to a more uniform reduction in NO concentration compared to throttling the valves such that the riser flows were equal. Additionally, the SCR catalyst was consumed somewhat more uniformly, and ammonia slip (ammonia not consumed in reaction) was found lower. The ammonia use could be decreased by 10 percent while maintaining the NO concentration limit in the flue gas exhausting into the atmosphere. / Dissertation/Thesis / M.S. Mechanical Engineering 2011

The topic of thesis is condensing turbine in gas-steam cycle, which can be divided into four basic parts. A history of gas-steam cycle is described in the beginning. Second part is all about calculation of heat recovery steam generator. Penultimate section deals with calculations of steam turbine parameters and reaction blading type. Last part contains electric power and steam turbine efficiency.

This master’s thesis deals with the design of a heat recovery steam generator. The introductory part of the thesis is dedicated to waste heat boilers, their division and their utilization in combined cycles gas turbine. In the following chapter, an analysis of the existing combined heat and power plant operation is performed. In the next part of the thesis, the conceptual layout of the new source is designed. Subsequently, the thermal calculation of the boiler is carried out as well as the design of individual heat exchanging surfaces. The sixth chapter deals with the strength calculation of the boiler and the outer piping, chambers and drum are designed here. At the end of the thesis there are described off-design states of the new combined cycle gas turbine.

This thesis deals with the design of a Heat Recovery Steam Generator (HRSG). Theintroductory part is devoted to a brief description of the boiler, the specified parametersand the compilation of the temperature profile. The main computational part of thiswork is divided into 6 parts. The first contains preparatory calculations, including thecalculation of boiler eiciency. In the second part, a flue gas duct is designed. This isfollowed by a thermal calculation of the boiler for all heat exchange surfaces. The last 3parts deal with the design of the drum, piping and the loss of boiler draft calculation.

Master thesis on topic steam generator deal with about improving the efficiency due to the use of combined cycle while producing electrical energy. The first part includes the possibility of using combustion engines in the energy sector and describes their advantages and disadvantages in the production of electricity. Further described is the use of the concept of a combustion engine in a combined cycle, and improving the efficiency of electricity through the use of waste heat boilers and steam turbines. The second part is design of the steam generator, which is connected behind the chosen combustion engine with power exceeding 10 MW. Whether this concept is profitable and competitive is in mentioned in the last chapter dealing with the return entry investment. In this chapter is compared several variants use and a demonstration of the impact of fuel prices on the profitability of this concept.

An investigation into the performance of several combined gas-steam power generating plants’ cycles was undertaken at the School of Engineering and Technology at the University of Hertfordshire and it is predominantly analytical in nature. The investigation covered in principle the aspect of the fundamentals and the performance parameters of the following cycles: gas turbine, steam turbine, ammonia-water, partial oxidation and the absorption chiller. Complete thermal analysis of the individual cycles was undertaken initially. Subsequently, these were linked to generate a comprehensive computer model which was employed to predict the performance and characteristics of the optimized combination. The developed model was run using various input parameters to test the performance of the cycle’s combination with respect to the combined cycle’s efficiency, power output, specific fuel consumption and the temperature of the stack gases. In addition, the impact of the optimized cycles on the generation of CO2 and NOX was also investigated. This research goes over the thermal power stations of which most of the world electrical energy is currently generated by. Through which, to meet the increase in the electricity consumption and the environmental pollution associated with its production as well as the limitation of the natural hydrocarbon resources necessitated. By making use of the progressive increase of high temperature gases in recent decades, the advent of high temperature material and the use of large compression ratios and generating electricity from high temperature of gas turbine discharge, which is otherwise lost to the environment, a better electrical power is generated by such plant, which depends on a variety of influencing factors. This thesis deals with an investigation undertaken to optimize the performance of the combined Brayton-Rankine power cycles' performance. This work includes a comprehensive review of the previous work reported in the literature on the combined cycles is presented. An evaluation of the performance of combined cycle power plant and its enhancements is detailed to provide: A full understanding of the operational behaviour of the combined power plants, and demonstration of the relevance between power generations and environmental impact. A basic analytical model was constructed for the combined gas (Brayton) and the steam (Rankine) and used in a parametric study to reveal the optimization parameters, and its results were discussed. The role of the parameters of each cycle on the overall performance of the combined power cycle is revealed by assessing the effect of the operating parameters in each individual cycle on the performance of the CCPP. P impacts on the environment were assessed through changes in the fuel consumption and the temperature of stack gases. A comprehensive and detailed analytical model was created for the operation of hypothetical combined cycle power and power plant. Details of the operation of each component in the cycle was modelled and integrated in the overall all combined cycle/plant operation. The cycle/plant simulation and matching as well as the modelling results and their analysis were presented. Two advanced configurations of gas turbine cycle for the combined cycle power plants are selected, investigated, modelled and optimized as a part of combined cycle power plant. Both configurations work on fuel rich combustion, therefore, the combustor model for rich fuel atmosphere was established. Additionally, models were created for the other components of the turbine which work on the same gases. Another model was created for the components of two configurations of ammonia water mixture (kalina) cycle. As integrated to the combined cycle power plant, the optimization strategy considered for these configurations is for them to be powered by the exhaust gases from either the gas turbine or the gases leaving the Rankine boiler (HRSG). This included ChGT regarding its performance and its environmental characteristics. The previously considered combined configuration is integrated by as single and double effect configurations of an ammonia water absorption cooling system (AWACS) for compressor inlet air cooling. Both were investigated and designed for optimizing the triple combination power cycle described above. During this research, tens of functions were constructed using VBA to look up tables linked to either estimating fluids' thermodynamic properties, or to determine a number of parameters regarding the performance of several components. New and very interesting results were obtained, which show the impact of the input parameters of the individual cycles on the performance parameters of a certain combined plant’s cycle. The optimized parameters are of a great practical influence on the application and running condition of the real combined plants. Such influence manifested itself in higher rate of heat recovery, higher combined plant thermal efficiency from those of the individual plants, less harmful emission, better fuel economy and higher power output. Lastly, it could be claimed that various concluding remarks drawn from the current study could help to improve the understanding of the behaviour of the combined cycle and help power plant designers to reduce the time, effort and cost of prototyping.

Nowadays, European power production has to meet requirements than ever before. Environmentally oriented efforts end of coal mining and burning of coal, on which economies of a great number of countries depend. The main objective of these efforts is primarily the production of green energy from renewable energy sources and reduction of dependence on fossil fuels. However, the disadvantage of renewable sources (photovoltaics, wind farms) is their dependence on the weather conditions. As a result, there might be delays in supply of electricity, which must be compensated. One of the solutions is the launch of a combi cycle plant, which has the possibility of almost prompt start-up and electricity production. The combustion of gas and liquid fuels also ensures almost emission-free operation. In addition, thanks to the use of waste heat energy from the gas turbine, it is possible to operate the combi cycle unit with the character of a power plant and as a heating plant. The aim of this thesis is to search for combi cycles and balance calculation of the combi cycle heating plant under given conditions. In the last point, the approximate dimensions of the calculated heating plant are given.