Molten Carbonate Fuel Cells (MCFCs) are commercially employed in MW-scale power production, and recently are being developed also for carbon capture. Past experiments showed that MCFC performance with wet cathode feeding was higher than with dry cathode feeds at otherwise similar conditions. This was ascribed to a mechanism that predicted the water increasing the apparent CO 2 diffusion rate. However, recent tests performed at low CO 2 cathode feed concentrations, as in carbon capture service, showed the emergence of a different water effect. Namely, there seems to be an electrochemical reaction path attributable to water, involving hydroxide ions that runs parallel with the main path involving CO 2 . This results in lower CO 2 transfer from the cathode to the anode than what can be calculated from the electrical current. For the first time, here, a theoretical analysis will be presented to introduce a kinetic expression for MCFCs working under this dual-ion regime. Focus will be given to the expression of CO 2 and water polarization to assess the ratio between the current due to the two anions. Simulation and experimental results will be discussed providing a reliable and effective basis for the performance optimization of the MCFCs both in power and in carbon capture applications.

No abstract

No abstract

Molten Carbonate Fuel Cells (MCFCs) are used in MW-scale power plants. Recently, they have also been explored for carbon capture. A recent MCFC experimental campaign for carbon capture applications has shown interesting results. It revealed that at carbon capture conditions a secondary reaction mechanism involving hydroxide ions starts to affect cell performance. This is important since part of the electricity produced will be used to transfer water instead of CO 2 , decreasing capture efficiency. Previously, the authors developed a dual-ion model for MCFCs to account for the observed loss of carbon capture efficiency at low-CO 2 cathode gas conditions. A more recent, deeper exploration of MCFC control parameters found that the split between the competing reaction paths depends not only on the cathode gas composition, but also on cathode diffusion resistance. Thus, in this work we increase the applicability range and reliability of the dual-ion electrochemical model by including the diffusion of reactants in the porous cathode along the axis perpendicular to the cell plane. This transport component can account for the shifting of carbonate and hydroxide contributions to the overall cell current as a function of cathode feed properties and for different current collector designs that determine the diffusion resistance term.

Solid Oxide Cells (SOCs) can work efficiently in reversible operation, allowing the energy storage as hydrogen in power to gas application and providing requested electricity in gas to power application. They can easily switch from fuel cell to electrolyzer mode in order to guarantee the production of electricity, heat or directly hydrogen as fuel depending on energy demand and utilization. The proposed modeling is able to calculate effectively SOC performance in both operating modes, basing on the same electrochemical equations and system parameters, just setting the current density direction. The identified kinetic core is implemented in different simulation tools as a function of the scale under study. When the analysis mainly focuses on the kinetics affecting the global performance of small-sized single cells, a 0D code written in Fortran and then executed in Aspen Plus is used. When larger-scale single or stacked cells are considered and local maps of the main physicochemical properties on the cell plane are of interest, a detailed in-home 2D Fortran code is carried out. The presented modeling is validated on experimental data collected on laboratory SOCs of different scales and electrode materials, showing a good agreement between calculated and measured values and so confirming its applicability for multiscale approach studies.