Energy and exergy analysis and optimal design of the hybrid molten carbonate fuel cell power plant and carbon dioxide capturing process Javad Yazdanfar a , Mehdi Mehrpooya a,⇑ , Hossein Yousefi a , Ali Palizdar b a Renewable Energies and Environmental Department, Faculty of New Science and Technologies, University of Tehran, Tehran, Iran b School of Chemical Engineering, University College of Engineering, University of Tehran, P.O. Box: 11365-4563, Tehran, Iran article info Article history: Received 15 December 2014 Accepted 21 March 2015 Keywords: MCFC Separation CO 2 capturing Optimization Exergy abstract A hybrid molten carbonate fuel cell power plant and carbon dioxide capturing process is investigated through the exergy and advanced exergy analysis. The results show that the greatest exergy destruction (181 MW) occurs in the combustion chamber. It is because of irreversibility of the chemical reactions in the combustion process. Also the lowest exergy efficiency is related to the fuel cell. Advanced exergy analysis shows that the most portion of the exergy destruction is avoidable (more than 65%). Optimal design of the process is done by adjusting the effective operating conditions for reducing the power con- sumption and carbon dioxide emission of the process. Results of the optimization shows that the power consumption in the compressors can be reduced up to 33%. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction Molten carbonate fuel cells (MCFC) produce power by a feed consists of carbon dioxide (CO 2 ) and oxygen. Also outlet stream from the anode electrode contains high percent of the carbon diox- ide (40 volume%) which can result environmental problems. Nowadays, reducing the amount of CO 2 in the atmosphere is one of the most important challenges in different societies because of the air pollution and increasing the earth temperature. So design- ing a MCFC process with low CO 2 emission seems to be useful. A new process integrated to MCFC for separation and liquefaction of the anode outlet carbon dioxide is introduced [1]. In this process greenhouse gas emission is reduced and also a by-product is pro- duced. Also it was concluded that in this process post-combustion capture offers higher availability in power generation [2]. There are several researches about the molten carbonate fuel cells. Specifications of a MCFC such as cell polarization, surface area, pri- mary particle size, and crystallization index for nine particulate carbon samples derived from the fuel oil is reported [3]. Dynamics behavior of the MCFC systems operating in a load-fol- lowing mode is investigated [4]. A 1 MW molten carbonate fuel cell system (MCFCS) pilot plant was developed and investigated [5]. In [6] research and development of molten carbonate fuel cells is studied. Rashidi et al. [7] investigated the performance of a combined industrial MCFC system, including a turbo expander, which was recently installed by Enbridge Inc. in Toronto, Canada. Sciacovelli and Verda [8] investigated sensitivity analysis applied to the multi-objective optimization of a MCFC hybrid plant. Operating pressure and temperature of the MCFC, turbine inlet temperature and fuel mass flow rate were considered as design variables. Also exergy analysis of a PEM fuel cell at variable operat- ing conditions is carried out in [9]. Braun et al. [10] studied about performance improvement of a molten carbonate fuel cell power plant via exergy analysis. Rashidi et al. [11] also studied the energy and exergy analysis of a molten carbonate fuel cell hybrid system to determine the efficiencies, irreversibilities and performance of the system. The analysis includes the operation of each component of the system by mass, energy and exergy balance equations. More detail about the thermodynamic analysis and process specifica- tions can be found in [12]. Energy and exergy analysis of a com- bined molten carbonate fuel cell and gas turbine system is investigated [13]. In the literature there is not a comprehensive study about exergy analysis and splitting the exergy destruction of the process introduced in [1]. In this paper, a new process is designed and analyzed by the exergy analysis method. Sensitivity analysis is carried out to inves- tigate effect of the operating parameters on the exergy analysis indexes. Effective operating conditions are adjusted to reduce the power consumption of the compressors. Then an optimization problem is defined for finding the global optimum point. Optimization of the process is done by genetic algorithm in Matlab software. http://dx.doi.org/10.1016/j.enconman.2015.03.076 0196-8904/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +98 21 61118564; fax: +98 21 88617087. E-mail addresses: mehrpoya@ut.ac.ir, mehdiemp@gmail.com (M. Mehrpooya). Energy Conversion and Management 98 (2015) 15–27 Contents lists available at ScienceDirect Energy Conversion and Management journal homepage: www.elsevier.com/locate/enconman