Electrochemical Study on MgO as an Additive in Molten Li2CO3-Na2CO3 for Molten Carbonate Fuel Cells

This study investigates the effect of MgO as an additive in molten Li2CO3-Na2CO3 electrolyte for molten carbonate fuel cells through electrochemical analyses. Addition of MgO (1~5 mol%) increased the electrochemical response in cyclic voltammogram of peroxide in molten Li2CO3-Na2CO3. The diffusion coefficient of peroxide in molten Li2CO3-Na2CO3 containing MgO was determined via the comparison between the peak currents of cyclic voltammograms from microwire electrode and macrowire electrode. The addition of MgO did not impact the diffusion coefficient, indicating that the increase in the electrochemical response with the addition of MgO might be attributed to the increase in the peroxide concentration. The change in peroxide concentration was also confirmed by electrochemical impedance analyses, which exhibited a decrease in the exchange current density. The increase in the concentration of peroxide with the addition of MgO might be associated with the high thermal decomposition constant of MgCO3, implying the high concentration of oxide ion in the molten Li2CO3-Na2CO3. This study suggests that MgO might be an effective additive for increasing the oxygen solubility in the molten Li2CO3-Na2CO3, and subsequently for enhancing the performance of molten carbonate fuel cells.

Exploring the Possibility of Using Molten Carbonate Fuel Cell for the Flexible Coproduction of Hydrogen and Power

Fuel cells are electrochemical devices that are conventionally used to convert the chemical energy of fuels into electricity while producing heat as a byproduct. High temperature fuel cells such as molten carbonate fuel cells and solid oxide fuel cells produce significant amounts of heat that can be used for internal reforming of fuels such as natural gas to produce gas mixtures which are rich in hydrogen, while also producing electricity. This opens up the possibility of using high temperature fuel cells in systems designed for flexible coproduction of hydrogen and power at very high system efficiency. In a previous study, the flowsheet software Cycle-Tempo has been used to determine the technical feasibility of a solid oxide fuel cell system for flexible coproduction of hydrogen and power by running the system at different fuel utilization factors (between 60 and 95%). Lower utilization factors correspond to higher hydrogen production while at a higher fuel utilization, standard fuel cell operation is achieved. This study uses the same basis to investigate how a system with molten carbonate fuel cells performs in identical conditions also using Cycle-Tempo. A comparison is made with the results from the solid oxide fuel cell study.

Molten Carbonate Fuel Cells for 90% Post Combustion CO2 Capture From a New Build CCGT

This paper presents the findings of the techno-economic assessment undertaken by Wood for the UK Government Department for Business, Energy and Industrial Strategy on the large-scale deployment of Molten Carbonate Fuel Cells (MCFCs) for post-combustion CO2 capture integrated with a new build combined cycle gas turbine power plant for the generation of low carbon electricity. The findings are compared with a state of the art proprietary amine scrubbing technology. Based on a new build power plant to be installed in the North East of England, with a power train comprising two trains of H-class gas turbines each with a dedicated steam turbine, the configuration presented utilises MCFCs between the gas turbine exhausts and their heat recovery steam generators and cryogenic separation for unconverted fuel recycle and CO2 purification. It was found that the proposed configuration could achieve 92% CO2 capture from the overall power plant with MCFCs while achieving 42% of additional new power production with only 2.6 %-points of thermal efficiency penalty compared to a conventional proprietary amine benchmark. While the total project capital cost increased by 65%, the high overall thermal efficiency and additional power generated resulted in a Levelised Cost of Electricity almost identical to the benchmark at £70/MWh (US$97/MWh). A number of areas are identified for potential further improvement in this scheme. It is concluded that use of MCFC technology, which also has the capability to be tailored for hydrogen production and combined heat and power services, shows significant potential to be competitive with, or exceed, the cost and technical performance of current state of the art technologies for post-combustion CO2 capture.

Current status of national integrated gasification fuel cell projects in China

Coal has been the main energy source in China for a long period. Therefore, the energy industry must improve coal power generation efficiency and achieve near-zero CO2 emissions. Integrated gasification fuel cell (IGFC) systems that combine coal gasification and high-temperature fuel cells, such as solid oxide fuel cells or molten carbonate fuel cells (MCFCs), are proving to be promising for efficient and clean power generation, compared with traditional coal-fired power plants. In 2017, with the support of National Key R&D Program of China, a consortium led by the China Energy Group and including 12 institutions was formed to develop the advanced IGFC technology with near-zero CO2 emissions. The objectives of this project include understanding the performance of an IGFC power generation system under different operating conditions, designing master system principles for engineering optimization, developing key technologies and intellectual property portfolios, setting up supply chains for key materials and equipment, and operating the first megawatt IGFC demonstration system with near-zero CO2 emission, in early 2022. In this paper, the main developments and projections pertaining to the IGFC project are highlighted.

Significance of Molten Hydroxides With or Without Molten Carbonates in High-Temperature Electrochemical Devices

Due to their low melting point and high conductivity molten hydroxides are interesting electrolytes, or additive to other molten electrolytes for high-temperature electrochemical devices. There is nowadays a revival of such reactive media, first of all for their significant role in the electrode mechanisms in molten carbonate fuel cells (MCFCs) and the reverse co-electrolysis of water and carbon dioxide process, but also in different applications, among which direct carbon fuel cells (DCFCs), hybrid carbonate/oxide fuel cells. This overview shows the properties and interest of molten hydroxides and their use in relevant energy devices, pointing out their direct use as electrolytic media or as key species in complex kinetic processes. A thorough understanding of their behavior should allow improving and optimizing significantly fuel cells, electrolyzers, and probably also CO2 capture and valorization.