Experimental and Modeling Investigation of CO3=/OH– Equilibrium Effects on Molten Carbonate Fuel Cell Performance in Carbon Capture Applications

Timothy A Barckholtz,Patricia H Kalamaras,Heather Elsen,Gabor Kiss,Emilio Audasso,Dario Bove,Jon Rosen,Barbara Bosio

doi:10.3389/fenrg.2021.669761

Timothy A Barckholtz, Patricia H Kalamaras + Show 6 more

Open Access

https://doi.org/10.3389/fenrg.2021.669761

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Abstract

Molten Carbonate Fuel Cells (MCFCs) are used today commercially for power production. More recently they have also been considered for carbon capture from industrial and power generation CO2 sources. In this newer application context, our recent studies have shown that at low CO2/H2O cathode gas ratios, water supplements CO2 in the electrochemical process to generate power but not capture CO2. We now report the direct Raman observation of the underlying carbonate-hydroxide equilibrium in an alkali carbonate eutectic near MCFC operating conditions. Our improved electrochemical model built on the experimental equilibrium data adjusts the internal resistance terms and has improved the representation of the MCFC performance. This fundamentally improved model now also includes the temperature dependence of cell performance. It has been validated on experimental data collected in single cell tests. The average error in the simulated voltage is less than 4% even when extreme operating conditions of low CO2 concentration and high current density data are included. With the improvements, this electrochemical model is suitable for simulating industrial cells and stacks employed in a wide variety of carbon capture applications.

Highlights

Molten Carbonate Fuel Cells (MCFCs) are electrochemical devices developed for electricity generation
Compared to conventional amine-based technologies, in addition to the capture of CO2 from flue gases, MCFCs allow the simultaneous production of additional electricity, H2 and heat (Rosen et al, 2020)
The deployment of MCFCs for CO2 Capture and Storage (CCS) requires the assessment of their performance with dilute CO2 cathode feeds that are rather different from the ones usually encountered when MCFCs are used for electricity generation

Summary

INTRODUCTION

Molten Carbonate Fuel Cells (MCFCs) are electrochemical devices developed for electricity generation. For the development of the dual-anion model, different experimental campaigns were conducted to gain a proper understanding of the mechanisms and dependences involved in the dual-anion mechanism (Rosen et al, 2020) In these campaigns, data were collected in different operating conditions of anode and cathode total flow rates and compositions, operating temperature, fuel (H2) and oxidant (CO2 and H2O) utilization factors. The graph shows that at different operating temperatures the measured utilization factors nearly overlap indicating that temperature has a negligible effect on the ratio of ionic conduction between the carbonate and the hydroxide paths This is consistent with our previous results (Audasso et al, 2020b) showing that the contribution of one path over the other is mainly dependent on the cathode-side diffusion process and only slightly affected by the temperature in the studied range.

K-1 A cm-2 atm-1

Findings

CONCLUSIONS