Browsing by Author "Balku, Saziye"
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Article Citation Count: 20Analysis of combined cycle efficiency by simulation and optimization(Pergamon-elsevier Science Ltd, 2017) Balku, Şaziye; Energy Systems EngineeringNatural gas has been regarded as the cleanest fuel when compared to the other fossil fuels because of its low emission of greenhouse gases and no particulate matter after combustion. Around 22% of the world's power production is based on natural gas. Combined gas-steam power plants operating with natural gas are preferred in recent years due to their high efficiency and less emission. To meet the world's increasing energy demand, natural gas will continue to be used in the future in increasing amounts. For this reason, it is very, important to design and operate such systems in optimal conditions. Energy conversion systems can be analyzed in terms of energetic, exergetic, economic, and environmental aspects for a good management. When the overall efficiency is increased, it can be said that these four aspects will also improve. In the present study, the modeling, simulation and optimization studies on the combined gas-steam power plants are performed. The most important parameters which influence the efficiency of such plants are determined. The simulation results indicate that the crucial unit is the combustion chamber. The optimization results show that the most effective parameters in the power production are air/fuel ratio, gas/steam ratio and the pressure ratio for the compressor and, thus, the gas turbine. The thermal efficiency of the plant increases by 22.55% and the exergy destroyed decreases by 22.65% using optimal design variables determined by the optimization algorithm in which the objective function is the thermal efficiency. The study demonstrates that the modeling, simulation and optimization can be used for the optimal design of the plants before invested, for operating the present plants at optimal conditions and for analyzing the systems. The minimum detrimental effect on the environment can be provided by optimal design and operation under optimal conditions. The originality of the study is to use an objective function by defining a new efficiency term for the maximum power production with the minimum exergy destruction which results 23.49% increase in the thermal efficiency and, in the meantime, 23.61% decrease in the exergy destruction. This new efficiency term can be used as an objective function in the solution of the optimization problems related with the efficiency of power generating in order to achieve better results. (C) 2017 Elsevier Ltd. All rights reserved.Article Citation Count: 31Comparison between alternating aerobic-anoxic and conventional activated sludge systems(Pergamon-elsevier Science Ltd, 2007) Balku, Şaziye; Energy Systems EngineeringConventional activated sludge systems ensure removal of colloidal and dissolved carbonaceous organic matter whereas alternating aerobic-anoxic systems, in addition, satisfy a further reduction in nitrogen content of wastewater. Main difference between them is that the alternating system should also include an anoxic operation mode which satisfies denitrification. In other words conventional systems are operated under aerobic conditions whereas alternating systems require a periodical change from aerobic conditions to anoxic conditions. So the most important problem in alternating systems is to find the appropriate durations for both sequences. In this study a comparison between conventional and alternating systems is considered in terms of nitrogen removal and aeration time by simulation under the same conditions together with an optimization algorithm. The results show that an activated sludge system can be operated as an alternating aerobic-anoxic system so that nitrogen removal is also possible during treatment without any additional investment or operational cost. (C) 2007 Elsevier Ltd. All rights reserved.Article Citation Count: 17Control vector parameterization approach in optimization of alternating aerobic-anoxic systems(Wiley, 2009) Balku, Şaziye; Yuceer, Mehmet; Berber, Ridvan; Energy Systems EngineeringDetermination of the optimal aeration profile for an activated sludge system in which nitrification and denitrification take place sequentially in a single reactor (alternating aerobic-anoxic) is an attractive optimization problem because of complexities involved in, and high computational times required for solution. The rigorous dynamic modeling and start-up simulation of such a system, together with aeration profile optimization by an evolutionary algorithm (EA), were tackled in a previous study. In this paper an easy-to-implement dynamic optimization technique based on sequential quadratic programming method and control vector parameterization approach is provided. In comparison with EA, the proposed algorithm gives better results in shorter computation times. Copyright (C) 2009 John Wiley & Sons, Ltd.Article Citation Count: 1Heavy metal inhibition on an alternating activated sludge system and its comparison to conventional methods: case study of Cu2+(Iwa Publishing, 2021) Balku, Şaziye; Balku, Saziye; Özalp Yaman, Şeniz; Energy Systems Engineering; Chemical EngineeringIn order to understand the behaviour of wastewater treatment plants (WWTPs) with heavy metal presence, the present study evaluates the treatment process in the presence of heavy metals (Cu2+ as a case study) and compares it with the absence of heavy metals. An activated sludge model is improved by means of incorporating other novel inhibitory kinetic and settler models for this evaluation. To achieve this goal, a simulation algorithm is developed using the MATLAB code to detect any heavy metal influence on the aerobic and anoxic growth of heterotrophic and autotrophic biomass. The code also allows for a comparison of treatment plant performance with and without Cu2+ in both conventional and alternating systems. The results reveal that the presence of heavy metals, in case of the present study for Cu2+ at 0.5 mg/L, in a biological treatment system, has an inhibitory effect on the heterotrophic bacteria but more so on the autotrophic bacteria growth and it prevents nitrification and denitrification, thus negatively effecting on the nitrogen removal in the alternating systems.Article Citation Count: 152Heavy Metal Removal Investigation in Conventional Activated Sludge Systems(C Ej Publishing Group, 2020) Balku, Şaziye; Balku, Saziye; Özalp Yaman, Şeniz; Energy Systems Engineering; Chemical EngineeringThe combination of industrial and domestic wastewater in municipal WWTPs (waste water treatment plants) may be economically profitable, but it increases the difficulty of treatment, and also has some detrimental effects on the biomass and causes a low-quality final effluent. The present study evaluates the treatment process both in the presence and absence of heavy metals using ASM3 (activated sludge model no.3) so as to improve the model by means of incorporating other novel inhibitory kinetic and settler models. The results reveal that the presence of heavy metal, a case study for copper and cadmium at a concentration of 0.7 mgL(-1) in a biological treatment system has a negative effect on heterotrophic bacteria concentration by 25.00 %, and 8.76 % respectively. Meanwhile, there are no important changes in COD (chemical oxygen demand), SS (total suspended solids) and TN (total nitrogen) in the final effluent in the conventional system. However, all these parameters are acceptable and consistent with EU Commission Directives. The results indicate that ASM3 can predict and provide an opportunity of the operation for an activated sludge wastewater treatment plant that receives the effluent from an industrial plant.