An efficient and durable solid oxide fuel cell integrated with coal gasification system

The synergetic effects of carbon and hydrogen metabolism on the exergy destruction and loss in a coal-to-SNG process

Modelling and energy analysis of an integrated coal gasification and pyrolysis system for synthetic natural gas

Performance analysis of methanol-fueled solid oxide fuel cell system incorporated with palladium membrane reactor

ABSTRACT: It is expected that fuel cells and particularly solid oxide fuel cells (SOFC) as direct converters of chemical energy into electrical energy will gain an important position in future stationary electric power generation. SOFCs of present development state operate in a temperature range of around 900 °C. Their efficiency is considerably higher and their operation less burdened by wastes and environmental problems compared to presently applied systems. Therefore, there exists great interest to make such SOFC units available in a technical scale. A main precondition for a wide spread application of SOFCs is particularly a considerable reduction of the production costs. Besides the improvement of presently used methods mainly basing on sintering techniques, also new technologies have been under consideration and development. In this connection DC and RF plasma deposition processes became attractive for producing components or even entire cells. But further process improvements are needed to meet the special quality and economic demands of the SOFCs.

This work proposes a novel yet practical dragonfly optimization algorithm that addresses four competing objectives simultaneously. The proposed algorithm is applied to a hybrid system driven by the solid oxide fuel cell (SOFC) integrated with waste heat recovery units. A function-fitting neural network is developed to combine the thermodynamic model of the system with the dragonfly algorithm to mitigate the calculation time. According to the optimization outcomes, the optimum parameters create significantly more power and have a greater exergy efficiency and reduced product costs and CO2 emissions compared to the design condition. The sensitivity analysis reveals that while the turbine inlet temperatures of power cycles are ineffective, the fuel utilization factor and the current density significantly impact performance indicators. The scatter distribution indicates that the fuel cell temperature and steam-to-carbon ratio should be kept at their lowest bound. The Sankey graph shows that the fuel cell and afterburner are the main sources of irreversibility. According to the chord diagram, the SOFC unit with a cost rate of 13.2 $/h accounts for more than 29% of the overall cost. Finally, under ideal conditions, the flue gas condensation process produces an additional 94.22 kW of power and 760,056 L/day of drinkable water.

Coal to SNG: Technical progress, modeling and system optimization through exergy analysis

Fabrication and characterization of low-temperature SOFC stack based on GDC electrolyte membrane

Solid oxide fuel cells (SOFCs) stand out in sustainable energy systems for their unique ability to efficiently utilize hydrocarbon fuels, particularly those from carbon-neutral sources. CeO2-δ (ceria) based oxides embedded in SOFCs are recognized for their critical role in managing hydrocarbon activation and carbon coking. However, even for the simplest hydrocarbon molecule, CH4, the mechanism of electrochemical oxidation at the ceria/gas interface is not well understood and the capability of ceria to electrochemically oxidize methane remains a topic of debate. This lack of clarity stems from the intricate design of standard metal/oxide composite electrodes and the complex nature of electrode reactions involving multiple chemical and electrochemical steps. This study presents a Sm-doped ceria thin-film model cell that selectively monitors CH4 direct-electro-oxidation on the ceria surface. Using impedance spectroscopy, operando X-ray photoelectron spectroscopy, and density functional theory, it is unveiled that ceria surfaces facilitate C─H bond cleavage and that H2O formation is key in determining the overall reaction rate at the electrode. These insights effectively address the longstanding debate regarding the direct utilization of CH4 in SOFCs. Moreover, these findings pave the way for an optimized electrode design strategy, essential for developing high-performance, environmentally sustainable fuel cells.

Energy and exergy analyses of an integrated SOFC and coal gasification system

A planar anode-supported electrolyte was fabricated using a tape casting method that involved a single step cofiring process. A standard NiO∕8YSZ cermet anode, 8mol% YSZ electrolyte, and a lanthanum strontium manganite cathode were used for the solid oxide fuel cell unit cell. A pressurized cofiring technique allows the creation of a thin layer of dense electrolyte about 10μm without warpage. The open circuit voltage of the unit cell indicated negligible fuel leakage through the electrolyte film due to the dense and crack-free electrolyte layer. An electrochemical test of the unit cell showed a maximum power density up to 0.173W∕cm2 at 900°C. Approximated electrochemical properties, e.g., activation energy, Ohmic resistance, and exchange current density, indicated that the cell performance was significantly influenced by the electrode properties of the unit cell.

Enhancing hydrogen production from propane partial oxidation via CO preferential oxidation and CO2 sorption towards solid oxide fuel cell (SOFC) applications

The nickel(Ni)-patterned electrode enables researchers to quantify the triple-phase boundary (TPB) length and Ni surface area, exclude the influence of bulk gas diffusion and clearly separate the active regions of the chemical/electrochemical reactions. This tool has been studied for identifying the reaction mechanism in SOFC but rarely in SOEC. In this study, the Ni-patterned electrodes with the stripe width of 100 μm were tested in both the solid oxide fuel cell (SOFC) and solid oxide electrolysis cell (SOEC) modes at the atmosphere of H2O/H2 and further H2O/CO2/H2/CO. The experimental test shows the stability of the Ni-patterned electrode in the H2O/H2 atmosphere was much poorer than that in the CO/CO2 atmosphere due to the nickel reacting with steam. Thus, the Ni-patterned electrode needed to operate at a temperature of ≤700oC with the inlet H2/H2O molar ratio of >7 and the current-applied time shouldn’t be over 5 h to keep the accuracy of the TPB length and Ni surface area. The effects of the temperature, partial pressure of H2O and H2 are investigated. The activation energy of the Ni-patterned electrodes was 0.386 eV. The electrochemical performance had a positive correlation with both the partial pressure of H2 and H2O, especially showed higher sensitivity to the partial pressure of H2O. Further, a possible mechanism of the H2O/H2 electrochemical conversion was proposed according to the experimental data and existing literature, which contains two-step charge-transfer reaction: H(Ni)+O2-(YSZ)OH-(YSZ)+(Ni)+e- and H(Ni)+OH-(YSZ)H2O(YSZ)+(Ni)+e-. Based on the experiments, an analytical calculation was performed to investigate the rate-determining steps in the Ni-patterned electrodes by bridging the connection between the kinetic parameters and operating conditions. The results indicate the rate-limiting steps may be different for the SOFC and SOEC modes. In SOFC mode, the H2 electrochemical oxidation could depend more on the charge-transfer reaction H(Ni)+O2-(YSZ)→OH-(YSZ)+(Ni)+e-, however in SOEC mode, the rate-determining step of the H2O electrochemical reduction should be H2O(YSZ)+(Ni)+e-→OH-(YSZ)+H(Ni). In this way, a reversible mechanism could be applied for reversible SOFC (RSOFC) to describe the conversion between hydrogen and steam by different charge-transfer-reaction domination in the SOFC and SOEC mode. Figure 1

Navigating the future of solid oxide fuel cell: Comprehensive insights into fuel electrode related degradation mechanisms and mitigation strategies

The solid oxide fuel cell (SOFC) is recognized as one of high efficiency plants of electricity generation for a sustainable future system with low environmental impact. In term of fuel flexibility, SOFC is suitable for direct use of syngas from a coal gasification plant. The application of integrated SOFC in coal gasification based power plant, such as a light integrated gasification fuel cell (L-IGFC) power plant, could be one of the most promising coal energy conversions system providing high electrical efficiency with low CO2 emitted to the atmosphere. The system consists of a coal gasifier and SOFC module on the top of a steam turbine. The sensitivity analyses of major operating parameters were performed using the developed model. The results indicated that the L-IGFC plant could achieve electrical efficiency in the range of 46.35- 60.32% in lower heating value.

Solid oxide fuel cells (SOFC) are highly efficient electrical cogeneration systems that operate at temperatures of 850 to 1000degC. This attribute allows for the steam reforming of gaseous hydrocarbon fuels into hydrogen and carbon monoxide constituents without the need for extensive gas clean-up processes. Natural gas and propane are the more common conventional fuels used in SOFC systems. Coal methane gas, biogases, and waste derived gases have also been investigated as potential fuels for use in SOFCs. In recent years, Volatile Organic Compounds (VOCs) from industrial paint and coating processes have been explored as a new fuel source for SOFCs. Fuel Cell Technologies Ltd., in conjunction with Ford Motor Company, successfully demonstrated an SOFC-based, proof of concept VOC abatement system at Ford's Rouge River Plant in July 2003. This proof of concept system utilized a reformer system to convert the VOCs into a H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and CO rich gas that was subsequently used to fuel a 5 kW SOFC. Feasibility studies have shown that an SOFC-based abatement system can provide reasonable financial payback periods. This type of system also benefits from significantly reduced GHG emissions in comparison to conventional VOC abatement technologies.