Design, Optimization and Economic Analysis of a Molten Carbonate FC System for Biogas Valorisation

There is worldwide effort to develop cleaner and renewable energy sources in order to address challenges posed by climate change and dwindling fossil fuel sources. In this context, the EU Energy and Security Action Plan agreed on a 20-20-20 initiative in 2008 for the European Union countries, with the goal of reducing emissions of greenhouse gases by 20%, and producing 20% of energy from renewable sources by 2020. The present thesis deals with the design and economical assessment of a Molten Carbonate Fuel Cell (MCFC) system within a multi-partner project-WAGNER MCFC. The major focus is the design of a process for the cleanup of a biogas produced by a waste water treatment plant and its use in MCFC. After an analysis of the possible cleanup techniques, a combination of two different devices was chosen. A biotrickling filter is designed and analyzed for the objective of filtering over 90% of H2S, followed by an adsorption bed system for the adsorption of siloxanes and the remaining H2S. The goal of the complete cleanup system was to reduce H2S from 1000 ppm to less than 1 ppm and siloxanes from 50 ppb to less than 1 ppb. The MCFC system was then simulated using the Aspen Plus V8.8 software. An electrochemical model from the work of Baranak and Atakul was used in the simulation. Several possible models were simulated, and based on simulations, two optimum systems were analyzed. These two systems provided 58% electrical efficiency and 28% thermal efficiency. The electrical power production is 258 kW and heat production is 148 kW, using a biogas flow of 100 Nm3/h containing 59% methane, 40% carbon dioxide, 1% Oxygen. The economical analysis showed that the system may not be economically feasible at the current state, with break even in the eight year after installation and starting. Considering instead a long term scenario where the costs of the components would be lower, the system would be economically acceptable. The thesis represents a part of the effort for a dual-degree program between the Politecnico di Torino (Italy) and the University of Illinois at Chicago. A similar thesis- Innovative solution for the valorisation of biogas in a CHP MCFC system: design, optimization and economic analysis -was defended at Politecnico di Torino in July 2016.