Molten Carbonate Fuel Cell Stack Research Articles

Analysis of the assembly pressure of a high-power molten carbonate fuel cell stack during initial roasting

This study investigated the effect of the assembly pressure during the initial roasting of a 15 kW molten carbonate fuel cell (MCFC) stack on its performance, with the aim of enhancing the success rate of large-area, high-power stacks. The corresponding assembly scheme was designed to possess an intermediate intake structure for ensuring a uniform intake distribution along the vertical axis of the MCFC stack. Monitoring the correlation between the settling distance of the MCFC stack and roasting temperature revealed the crucial stage of diaphragm roasting and identified the appropriate compensation period for pressure loss, thereby enhancing the success rate of the initial roasting process. At an assembly pressure of 4.35 MPa, the MCFC stack exhibited a constant voltage of 84 V, achieving a maximum output power of 16.51 kW and discharge current density exceeding 95 mA/cm2, thereby confirming the effectiveness of the assembly scheme and initial roasting process.

Novel integration of molten carbonate fuel cell stacks in a biomass-based Rankine cycle power plant with CO2 separation: A techno-economic and environmental study

A novel integration of molten carbonate fuel cell (MCFC) stacks in a biomass-based Rankine cycle power plant with CO2 separation has been proposed, and techno-economic and environmental analyses have been performed for the plant configuration. Both a biomass gasifier and a biomass combustion fluidized boiler (CFB) have been considered for the proposed plant, which has a unique configuration of MCFC stacks placed in the back-pass of the CFB to achieve an efficient plant configuration. Parametric variations of the key performance parameters with varying input variables have been observed, and a best-case operating condition has been identified from the parametric study. It is observed that the proposed plant can produce 12.645 MW of power with 60.22 % electrical efficiency at a unit electricity cost of 0.09497 $/kWh at best-case operating condition. Moreover, 137701 tons/year of CO2 cutting is observed at the best-case condition, which results in 20.66 million $/year of total environmental benefit. Cost sensitivity suggests that the plant can yield a unit electricity cost of 0.03314 $/kWh at the best economic conditions, and the payback analysis outlines that the plant can recover its initial investment in 3.467 years when there is a 50 % capital subsidy.

Performance and Stability of Molten Carbonate Fuel Cell Cathode Electrode Under Carbon Capture Endurance Tests

Introduction The molten carbonate fuel cell (MCFC) has emerged as one of the promising alternatives for carbon capture from industrial and power generation CO2 sources. MCFC technology is less energy-intensive compared to conventional amine scrubbing that requires a significant amount of energy (steam) for solvent regeneration process.MCFC has been commercially used for distributed power generation, however its use in carbon capture applications has been limited to development activities and a few demonstrations during the past decades. The electrochemical reactions taking place during cell operation involve the CO2 transfer from cathode to anode in the form of carbonate ions resulting in a gas stream with high CO2 concentration on the anode exhaust. Therefore, MCFC stack systems can be combined with conventional combustion-powered generators (coal and/or natural gas-based power plants) for simultaneous CO2 separation, power and hydrogen generation.CO2 capture applications will typically take in flue gas from industrial furnaces, coal and gas fired combined cycle plants as the cathode inlet gas stream having low CO2 concentrations ranging from 4% to 10% by volume and high CO2 utilization (>90%). These CO2-lean conditions may pose a challenge for attaining good mass-transfer performance and life stability, therefore innovative approaches are needed in terms of hardware design and cathode structure to achieve long-term stability.FCE has tested numerous single cells (250 cm2) and technology stacks (30 kW) under carbon capture operating conditions (4-8% CO2 in the cathode inlet as opposed to >12% in baseline MCFC systems) to understand impact of design parameters on performance, life, and to investigate design solutions for further enhancement. Figure 1 highlights the effect of cathode water content on CO2 utilization. It appears that differences exist between the ideal and measured CO2 utilizations, indicating that less CO2 is transferring from the cathode to anode than expected. This CO2 transference reduction becomes more pronounced with higher water concentration, suggesting that a species other than CO3 2- ion, likely hydroxide (OH- ion), may be generated and transported through the electrolyte matrix.This paper will review the cathode material stability and electrochemical performance under long-term carbon-capture operation. The effect of parameters such as water content, gas composition, utilization, and electrolyte chemistry, as well as approaches to enhance the CO2 capture efficiency and life, will be discussed. Figure 1

Development and investigation of a pollutants emission reduction process from a coal-gasification power plant integrated with fuel cell and solar energy

Abstract Even though coal resources are the most abundant among fossil fuels, coal-fired plants release large amounts of greenhouse gases into the atmosphere. In this regard, reducing environmental challenges and crises caused by coal burning can be a promising option to reduce today's crises in the energy field. The integration of coal-fired plants with renewable-driven energy systems can simultaneously improve thermodynamic performance and reduce pollutants emission rates. This article presents the thermodynamic and pollutant emission investigations of a new coal-fired plant coupled with a linear Fresnel solar collector (LFSC)-driven solar unit, a parabolic trough solar collector (PTSC)-driven solar unit, a high-temperature fuel cell stack (molten carbonate fuel cell stack [MCFCS]) and a heat recovery system (based on the steam turbine and gas turbine-based power cycles). The plant is able to produce electricity and hot water (HW). The main structure of the offered plant is based on coal, whereas, is coupled with renewables-based cycles to mitigate environmental impacts. The plant could generate ~ 207 MW of power and 3728 m3/h of HW. In such conditions, the energy efficiency of 73.1% and exergy efficiency of 44.18% could be achievable. Further, the emitted gas rates of the plant were nearly 403 tons/h. A comprehensive comparison is also presented for the plant's behavior under different types of coal (petcoke and anthracite). In addition, a two-function optimization is developed to determine the maximum value of exergy efficiency and the minimum value of total pollutants emission rate.

Evaluation of carbon dioxide emission reduction in an energy cycle based on biomass gasification and molten carbonate fuel cell: exergoeconomic and environmental analyses

Abstract A competitive advantage for the molten carbonate fuel cell (MCFC)-driven energy processes is their fuel versatility. On the other hand, since MCFC consumes carbon dioxide, it can reduce the amount of carbon dioxide emissions compared with other fuel cells. Accordingly, the current paper develops and evaluates the thermodynamic, exergoeconomic and environmental analyses of a new hybrid energy process (HEP) based on a reformer MCFC stack and a biomass gasification process. A homogeneous ignition engine (HIE) and a heat recovery system are two other main units embedded in the developed HEP. In the developed cycle, MCFC and HIE produce electric energy, for which the required fuel is supplied through the obtained syngas from the biomass gasification process and the anode off-gas, respectively. The heat recovery system also leads to the establishment of the thermal balance of the energy cycle by recovering the thermal energies of the MCFC and HIE. The aim of the present work is to develop the multi-aspect evaluation of the proposed energy system toward a fruitful implementation feasibility analysis. The outcomes indicated that the rates of electrical and thermal powers obtained from the planned HEP were equal to nearly 1112 and 367 kW, respectively. Further, the calculated efficiencies for electric, gross power and total energy terms were equal to 51.5%, 55.7% and 69.9%, respectively. The developed HEP had 48% less carbon dioxide emissions compared with a petroleum-fired power plant, 15.8% less compared with a natural gas-fired plant and approximately 63% lower compared with a coal-fired power plant.

Thermoeconomic comparison of a molten carbonate fuel cell and a solid oxide fuel cell system coupled with a micro gas turbine as hybrid plants

This study presents a comparative evaluation of Molten Carbonate Fuel Cell (MCFC) and Solid Oxide Fuel cell (SOFC) stacks coupled with a micro gas turbine (MGT). For the analysis, it is assumed that the fuel supply to the stacks is constant in all the analyzed conditions. The components of the system have been sized using the first law of thermodynamics to meet the thermal conditions required to maintain fuel cell stack operation, while an exergetic analysis has been implemented in order to assess the components in terms of irreversibilities. Furthermore, an economic analysis to estimate the Levelized Cost of Electricity (LCOE) has been carried out to indicate the most feasible option between the two analyzed systems. The capacity of the fuel cell stacks is 500kWdc operating at 350 kPa and 600 °C/650 °C. The results indicate that MCFC stacks are more efficient than SOFC stacks, but are considerably more expensive. Nevertheless, the SOFC/MGT system has a global efficiency higher than that of the MCFC/MGT; also its Total Capital Investment (TCI) is 2.5–3.5 times lower, thus making the SOFC/MGT coupling more attractive. The only product considered coming out from the systems to determine the LCOE is electricity. The LCOE for the SOFC/MGT system is 0.339–0.402$/kWh and for the MCFC/MGT is 0.875–0.897$/kWh, which for both configurations is still higher than the current electricity prices. One aspect that increases the investment and consequently the LCOE is the high cost of the stacks and their replacements which is around 19 % and 10 % of the total Purchased Equipment Cost (PEC) for MCFC and SOFC stacks, respectively.

Thermodynamic and Economic Analysis of State-of-the-Art Reversible SOFC-SOEC Systems Using Stable Rare-Earth Nickelate Oxygen Electrodes

Gaia Energy Research Institute (Gaia) will present a preliminary thermodynamic and techno-economic analysis of a state-of-the-art (SOA) reversible solid oxide electrolyzer (SOE) using stable rare-earth nickelate oxygen electrodes. Part of the significance of this work is that it quantifies the potential future cost of producing extremely pure hydrogen and oxygen using SOA reversible SOEs in dollars per kilogram of hydrogen ($/kg H2) and oxygen ($/kg O2). This work also analyzes the impact of thermal storage on increasing reversible SOE round-trip efficiency, and the value of electrochemically-compressing the H2 and O2.Primary cost drivers of solid oxide fuel cells (SOFC) systems tend to include the power density of the SOFC stack. Primary cost drivers of SOE systems tend to include (1) system capital costs and (2) the electricity consumed per unit of hydrogen / oxygen produced. In SOEs, electricity consumption can be displaced by heat consumption. In a combined reversible SOE system, heat produced by the SOFC can be stored and reused to provide heat to the SOE. The extent of this heat reuse is estimated to be a primary cost driver, because for every unit of electricity input displaced by reused heat as an input, the SOE produces more hydrogen and oxygen per unit of electricity input. Heat reuse by the reversible SOE can increase the hydrogen and oxygen output per unit of electricity by up to ~30%. Efficient design of this heat reuse subsystem is crucial to the reversible SOE achieving round-trip efficiencies of >70%, a necessity for viability in the long-duration energy storage market. The work examines the primary cost drivers for the reversible SOE system, including the heat storage and reuse subsystem. This research effort considers valid heat storage media including, but not limited to, (1) the ceramic materials of the reversible SOE stack, (2) steam exhausted from the SOE stack (in the same stream as the hydrogen but with the hydrogen potentially electrochemically separated at high temperature via proton-conducting ceramics), and (3) phase change materials, such as molten salts.The reversible SOE stack being evaluated is a unique, all-ceramic stack, and therefore, the materials of the stack have the potential to maintain greater stability as a thermal storage media compared with stacks composed of multiple material types each with potentially quite different thermal expansion coefficients. A primary failure mechanism of high temperature electrochemical systems is a mismatch in thermal expansion coefficients of electrochemical stack materials. For example, historically, the FuelCell Energy Inc. stationary, commercial Molten Carbonate Fuel Cell (MCFC) system has been limited to a turn down ratio of only 12% of maximum rated power over the course of one (1) hour, primarily due to mismatches in the thermal expansion coefficients of its MCFC stack materials.The all-ceramic reversible SOE stack evaluated here is also unique in that it has the capacity to supply hydrogen and oxygen at pressure. This analysis also quantifies the value of this electrochemically-compressed hydrogen and oxygen, compared with hydrogen and oxygen produced by mechanical compression. Based on techno-economic analyses of electrochemical and mechanical compression, electrochemical compression has the most compelling cost advantage over mechanical compression in the lower pressure range (i.e., for example, 1 to 100 bar). Electrochemical compression appears to have the highest theoretical efficiency advantage over mechanical compression across a larger pressure range going up to very high pressures (1 bar to 900 bar). When practical, measured, in-use efficiencies are considered, electrochemical compression appears to have a substantial potential advantage over mechanical compression in part because mechanical compression systems are often not designed to maintain high efficiencies at lower throughputs and are limited in their turn-down ratio (in some cases, their turn-down ratio is limited to only 25% of maximum flow rate.) Electrochemical compression with an all-ceramic stack is estimated to be less limited in response time and less limited in turn-down ratio due to more uniform thermal expansion coefficients, compared with some mechanical compressor systems built today.Model results indicate that the reversible SOE is expected to produce hydrogen at less than $2/kg H2, which is the DOE Fuel Cell Technologies Office (FCTO) H2 production cost target. Model results further indicate that, between near-term and far-term cases, the estimated energy storage costs are expected to decline due to decreases in (1) the reversible SOE system capital costs (mainly at the stack), (2) net system-wide energy consumption, (3) the extent of waste heat dissipated by the system, and (4) operations and maintenance costs. Energy storage costs are also analyzed using single-variable sensitivity studies and Tornado charts.

Gibbs energy minimization using Lagrange method of undetermined multipliers for electrochemical and thermodynamic modeling of a MCFC with internal steam reforming

Precise determination of the chemical equilibrium state is important for electrochemical and thermodynamic modeling of a molten carbonate fuel cell (MCFC). One method for determining the equilibrium state of a MCFC with internal reforming is to compute the total Gibbs free energy of the system (G) and minimize it by adjusting the molar amounts of each substance. Multi-dimensional optimization algorithms can be used for this purpose. The Lagrange method of undetermined multipliers as a powerful analytical solution is used in the present work to estimate chemical equilibrium state. Under this condition, the effects on voltage losses, output voltage, stack power, efficiency and molar portions of the exhaust chemical species at the anode and cathode are investigated, separately of such parameters as current density, reaction temperature, stack pressure as well as fuel and carbon dioxide utilization ratios. A simulation of a MCFC stack performance by the Lagrange method at a specified state, results in an efficiency of 50.3% and output power of 554.3 kW.

Numerical Analysis of a Molten Carbonate Fuel Cell Stack in Emergency Scenarios

Abstract Molten carbonate fuel cells (MCFCs) offer several advantages that are attracting an increasingly intense research and development effort. Recent advances include improved materials and fabrication techniques as well as new designs, flow configurations, and applications. Several factors are holding back large-scale implementation of fuel cells, though, especially in distributed energy generation, a major one being their long response time to changing parameters. Alternative mathematical models of the molten carbonate fuel cell stack have been developed over the last decade. This study investigates a generic molten carbonate fuel cell stack with a nominal power output of 1 kWel. As daily, weekly, and monthly variations in the electrical power load are expected, there is a need to develop numerical tools to predict the unit’s performance with high accuracy. Hence, a fully physical dynamic model of an MCFC stack was developed and implemented in aspen hysys 10 modeling software to enable a predictive analysis of the dynamic response. The presented model exhibits high accuracy and accounts for thermal and electrochemical processes and parameters. The authors present a numerical analysis of an MCFC stack in emergency scenarios. Further functionality of the model, which was validated using real operational data, is discussed.

Effect of Carbon Capture Endurance Conditions on Performance and Stability of Molten Carbonate Fuel Cell Cathode Electrode

IntroductionThe molten carbonate fuel cell (MCFC) is one of the most advanced high-temperature and clean power generating devices. To date >8 billion kWh of electricity has been produced commercially using this new technology. The high operating temperature of MCFC (550-650 °C) dramatically improves the reaction kinetics and eliminates the need for a noble metal catalyst. The electrochemical reactions taking place during cell operation involve the CO2 transfer from cathode to anode in the form of carbonate ions (Figure 1). Therefore, MCFC stack technology can be used for power generation and simultaneously, as an effective CO2 separator. MCFC systems can be combined with conventional combustion-powered generators (coal and/or natural gas based power plants) to efficiently separate CO2 in the exhaust gas and produce additional electricity.The state of the art MCFC cathode is porous lithiated nickel oxide. The cathode stability and performance are affected by several factors such as gas composition, temperature, electrode structure and electrolyte chemistry. To ensure long-term performance and material stability against NiO dissolution, polarization loss, and carbon capture efficiency, major considerations need to be taken into account in material selection, operating conditions, and electrode structure design.FCE has tested many single cells (250 cm2) and technology stacks (30 kW) under carbon capture operating conditions (4-5% CO2 in the cathode inlet as opposed to >15% in baseline MCFC systems) to understand parameters affecting performance, life, and to investigate design solutions for further enhancement. Figure 2 highlights the effect of CO2 concentration on the cathode lithiation. These measurements were conducted using an out-of-cell test (OCT) where cathode samples were exposed to different oxidizing environments. It appears that lean-CO2 gas atmospheres (<5%CO2) lead to increased lithium content in the NiO cathode. This may impact the electrolyte distribution and the cathode microstructure. Therefore, the electrolyte inventory (fill level), the lithium content and the basicity need to be considered to achieving optimal operating conditions.This paper will review the cathode material stability, microstructure, and durability under long-term carbon-capture operations. The effect of parameters such as electrolyte fill, gas composition, and electrolyte chemistry, as well as approaches to enhance the CO2 capture efficiency and life, will be discussed. Figure 1

Dynamic model of a molten carbonate fuel cell 1 kW stack

Molten Carbonate Fuel Cells (MCFC) offer several advantages that are accelerating the research and development effort. Recent advances include improved materials, new fabrication techniques and new designs, flow configurations and applications. Nevertheless, several factors are holding back large scale implementation of fuel cells, especially in distributed energy generation, a major one being their long response time to changing parameters.Whereas alternative mathematical models of the molten carbonate fuel cell stack have been developed over the last decade, there are no reported analyses of regarding the application of models for emergency scenarios such as fuel cell malfunctions. This paper presents the 0D model of MCFC, calibrated to the appropriate available experimental data. This study investigates a generic molten fuel cell stack with nominal power output of 1 kWel. As daily, weekly and monthly variations in the electrical power load are expected, there is a need to develop numerical tools to predict the unit’s performance with high accuracy. Hence, a fully physical dynamic model of an MCFC stack was developed and implemented in Aspen HYSYS 10 modeling software to enable predictive analysis of the dynamic response. The model is used to simulate a number of few malfunctions with 5 . 66% broken cells in the stack. Losses of performance are obtained, manifested by rising operating temperature and falling power output. Moreover, a number of emergency operation scenarios were investigated, such as sudden loss of electric load, fuel and oxidiant supply. The presented model exhibits high accuracy and accounts for thermal and electrochemical processes and parameters. The paper presents the methodology used in the study to analyze the sensitivity of key scenarios such as load changes and emergencies. Further functionality of the model, which was validated using real operating data, is discussed.

Performance and Stability of Cathode Electrode Under Carbon Capture Operating Conditions

Introduction The high-temperature molten carbonate fuel cell (MCFC) is one of the most advanced clean power generating devices. To date >8 billion kWh of clean electricity has been produced commercially using this new technology. The high operating temperature of MCFC (550-650°C) dramatically improves the reaction kinetics and eliminates the need for a noble metal catalyst. The electrochemical reactions taking place during cell operation involve CO2 transfer from cathode to anode through electrolyte matrix in the form of carbonate ions (Figure 1). The transport of CO3 = is equivalent to that of O= and CO2 (CO3 = ⇔ O= + CO2). Therefore, MCFC stack technology can be utilized for efficient simultaneous power generation and CO2 separation/capture by integrating with conventional combustion-based coal and/or natural-gas power plants. The state of the art MCFC cathode is porous lithiated NiO. The cathode performance and stability are affected by several factors such as gas composition, temperature, electrode structure, and electrolyte chemistry. To ensure long-term performance and material stability (such as NiO cathode dissolution, polarization loss and CO2 capture efficiency), material selection, operating characteristics, and electrode design need to be carefully considered. FCE has operated numerous bench-scale single cells (100 W) and technology stacks (30 kW) under carbon capture operating conditions (4-5% CO2 in the cathode inlet as opposed to >15% in baseline MCFC systems) to understand parameters affecting performance, life, and to investigate design solutions for further enhancement. Figure 2 shows similar NiO cathode stability under standard as well as carbon capture conditions, projecting to useful life of >7-years under both operation conditions. More endurance carbon capture tests are being conducted for further verification. This paper will review the cathode material stability, microstructure, and durability under long-term carbon-capture operations. The effect of parameters such as electrolyte fill, gas composition and electrolyte chemistry, as well as approaches to enhance the CO2 capture efficiency and life, will be discussed. Figure 1

Safety integrity level (SIL) determination for a maritime fuel cell system as electric propulsion in accordance with IEC 61511

This study investigates the safety integrity levels for an electric propulsion system based on a molten carbonate fuel cell in a liquefied hydrogen tanker. The electric propulsion system necessitates multiple electronic and electric elements; thus, the functional safety of the system should be considered. Additionally, a maritime fuel cell system is nonconventional propulsion machinery. This system should follow a risk-based ship design framework, and IEC 61511 is a suitable standard for evaluating the functional safety of the system. Hazardous operability studies provide basic information for determining the safety integrity. In this work, a safety layer matrix and calibrated risk graph are generated, and a layer of protection analysis is conducted for a molten carbonate fuel cell stack. Eight guidewords are used to describe accidental scenarios and compare the results of the three methods in an unbiased manner. The most severe consequences are fire and explosion caused by overflows or a control failure in the stack, and the safety integrity levels are mutually different.

Exergetic, environmental and economic sustainability assessment of stationary Molten Carbonate Fuel Cells

In this study, exergetic, environmental and economic (3E) analyses have been performed in order to provide sustainability indicators from resource extraction to the final product of stationary power Molten Carbonate Fuel Cells (MCFC) systems (500 kW). Two environmental life cycle impact assessment methods have been selected: the ReCiPe 2016 hierarchical midpoint and endpoint, and the Cumulative Exergy Extraction from the Natural Environment (CEENE). The levelized cost of electricity (LCOE) under technology cost and performance parameters was calculated to analyze the system from the economic point of view. The global warming potential (GWP) is estimated to be 0.549 kg CO2-eq/kWh while acidification (5.06e−4 kg SO2-eq/kWh), eutrophication (9.81e−4 kg P-eq. freshwater/kWh), ozone layer depletion (4.11e−6 kg CFC-11-eq/kWh) and human toxicity (1.07 kg 1,4-DB-eq/kWh). Aggregated CEENE was estimated to be about 8.55 MJex/kWh. Results show that majority of impacts are dominated by fuel supply, while some others are dominated by manufacturing of system. GWP is the only impact category dominated by system operation. Due to potentially high electrical efficiency, MCFC energy systems can lead to lower CEENE and improvements of global warming, fossil fuel and resource scarcity, and photochemical oxidant formation potential with respect to other conventional energy conversion systems. Advances in longer lifetimes of the MCFC stack can help trigger innovation in manufacturing processes and will lead to less resource use of electricity, metal, and minerals, thus less resource scarcity and toxicity related burdens. The baseline LCOE is calculated 0.1265 €/kWh being comparable with the Italian grid (0.15–0.16 €/kWh). The costing results indicate that the unit decreasing the system capital cost could potentially reduce the LCOE by around 25%. Advancing the use of life-cycle thinking in MCFC industry with site-specific data raise systems credibility and enables clarifying the trade-offs between the sustainability pillars, thus designing more sustainable products.

Dynamic wetting of dense Ni foil by molten carbonate

Wetting is an important factor that affects the active reaction area inside the porous Ni anode in molten carbonate fuel cell stacks. To provide a relatively simple base case, the dynamic wetting of the dense Ni foil was investigated under different atmospheres, including reducing atmosphere (80%H2 + 20%CO2 humidified at 45 °C), pure CO2 atmosphere and, oxidizing atmosphere (1%O2 + 99%N2). It was demonstrated that the water-gas shift reaction occurs at the interface of dense Ni foil and the molten carbonate under reducing atmosphere but not under CO2 atmosphere and oxidizing atmosphere. The contact angle was affected by the mass of the carbonate pellet under reducing atmosphere but not under CO2 atmosphere. The contact angle decreased rapidly under oxidizing atmosphere due to the formation of nickel oxides on the surface.

Electrochemical Carbon Separation in a SOFC–MCFC Polygeneration Plant With Near-Zero Emissions

The modularity and high efficiency at small-scale make high temperature (HT) fuel cells an interesting solution for carbon capture and utilization at the distributed generation (DG) scale when coupled to appropriate use of CO2 (i.e., for industrial uses, local production of chemicals, etc.). The present work explores fully electrochemical power systems capable of producing a highly pure CO2 stream and hydrogen. In particular, the proposed system is based upon integrating a solid oxide fuel cell (SOFC) with a molten carbonate fuel cell (MCFC). The use of these HT fuel cells has already been separately applied in the past for carbon capture and storage (CCS) applications. However, their combined use is yet unexplored. The reference configuration proposed envisions the direct supply of the SOFC anode outlet to a burner which, using the cathode depleted air outlet, completes the oxidation of the unconverted species. The outlet of the burner is then fed to the MCFC cathode inlet, which separates the CO2 from the stream. This layout has the significant advantage of achieving the required CO2 purity for liquefaction and long-range transportation without requiring the need of cryogenic or distillation plants. Furthermore, different configurations are considered with the final aim of increasing the carbon capture ratio (CCR) and maximizing the electrical efficiency. Moreover, the optimal power ratio between SOFC and MCFC stacks is also explored. Complete simulation results are presented, discussing the proposed plant mass and energy balances and showing the most attractive configurations from the point of view of total efficiency and CCR.

Multi-objective optimization of molten carbonate fuel cell system for reducing CO2 emission from exhaust gases

The aim of this paper is to investigate the implementation of a molten carbonate fuel cell (MCFC) as a CO2 separator. By applying multi-objective optimization (MOO) using the genetic algorithm, the optimal values of operating load and the corresponding values of objective functions are obtained. Objective functions are minimization of the cost of electricity (COE) and minimization of CO2 emission rate. CO2 tax that is accounted as the pollution-related cost, transforming the environmental objective to the cost function. The results show that the MCFC stack which is fed by the syngas and gas turbine exhaust, not only reduces CO2 emission rate, but also produces electricity and reduces environmental cost of the system.

Experimental and numerical analysis of gas distribution in molten carbonate fuel cells

Flow maldistribution through the cell package affects the efficiency of the fuel cells, thus limiting the reliability and the diffusion of such a technology. This subject is a key-point in the progress of the fuel cells, so deserving the greatest attention and the most thorough research. This paper faces the issue by evidencing the possibility to improve the quality of flow distribution through an appropriate design based on the use of numerical methods. In particular, this research deals with the gas flow rate distribution in a Molten Carbonate Fuel Cell (MCFC) and with the effect on maldistribution of baffles inserted into the inlet manifolds. To this extent, an experimental set-up was built to analyze the flow field inside the cell: the test section reproduces full-scale inlet manifolds for the anodic and cathodic supply of a MCFC stack of 150 cells. Experimental runs covered start-up as well as loading conditions. Air was used to simulate actual flow conditions inside the fuel cell package, basing similarity on inlet Reynolds numbers equivalence. Gas flow rate distribution has been evaluated by measuring the exit velocity at the outlet of the experimental set-up, operating at different working conditions for both cathode and anode, with and without the presence of baffles inside the inlet manifolds. Uneven distributions were observed for high mass flow rates at the cathode manifold without baffle. For the anode, manifold flow distribution resulted acceptably uniform for all working conditions. The baffle improved the distribution for both cathode and anode manifold; particularly, sharp peaks of velocity observed for cathode in the absence of the baffle disappeared at all. Then, velocity and flow rate distributions were modelled by means of a 3D computer code. In order to validate the accuracy of the model, calculated results were compared with experimental data; as a result, their agreement was very good and suggested the opportunity of a manifold design based on a numerical approach. The numerical model was finally utilized to predict flow rate distributions for all working conditions, by taking into account the detailed actual geometry of the manifolds. Numerical analysis of flow rate distribution by means of specific indexes permitted to better understand critical conditions and the reasons of maldistribution. The model was finally used to analyze various design solutions and get a more uniform gas distribution of flow rates. Thus, the numerical modelling can be effectively used during FC plants’ design to analyze the flow distribution, by taking into account devices and systems in order to improve the uniformity of the distribution. In this way, the numerical modelling permits to avoid expensive and time-consuming experiments, and to optimize, with a limited effort, the manifolds according to the cell package characteristics and mass flow rates.

Study of Gas-steam Combined Cycle Power Plants Integrated with MCFC for Carbon Dioxide Capture

In the field of fossil-fuel based technologies, natural gas combined cycle (NGCC) power plants are currently the best option for electricity generation, having an efficiency close to 60%. However, they produce significant CO2 emissions, amounting to around 0.4 tonne/MWh for new installations. Among the carbon capture and sequestration (CCS) technologies, the process based on chemical absorption is a well-established technology, but markedly reduces the NGCC performances. On the other side, the integration of molten carbonate fuel cells (MCFCs) is recognized as an attractive option to overcome the main drawbacks of traditional CCS technologies. If the cathode side is fed by NGCC exhaust gases, the MCFC operates as a CO2 concentrator, beside providing an additional generating capacity.In this paper the integration of MCFC into a two pressure levels combined cycle is investigated through an energy analysis. To improve the efficiency of MCFC and its integration within the NGCC, plant configurations based on two different gas recirculation options are analyzed. The first is a traditional recirculation of exhaust gases at the compressor inlet; the second, mainly involving the MCFC stack, is based on recirculating a fraction of anode exhaust gases at the cathode inlet. Effects of MCFC operating conditions on energy and environmental performances of the integrated system are evaluated.

A Cylindrical Molten Carbonate Fuel Cell Supplied with Landfill Biogas

A small size cylindrical Molten Carbonate Fuel Cell stack was installed at Giugliano landfill in Italy. The stack was constituted by 16-cells with a 300 W nominal power. Preliminary tests were performed in order to verify the possibility to supply the stack by the landfill biogas, characterized by low methane content (32%). Results showed that the proposed plant is able to correctly operate also when supplied with low methane content biogas.