Haruhiko Hirata

Gas-flow uniformity and cell performance in a molten carbonate fuel cell stack

Abstract An examination is made of the relationships between the gas-flow uniformity in the planar direction, the gas-flow uniformity in the stacking direction, and the cell performance in a co-flow type molten carbonate fuel cell stack. A simulation code that accounts fair the effects of electrochemical reactions, heat transfer, and gas flow is used to calculate the cell performance (i.e. cell temperature, current density and cell voltage) for various gas-flow uniformity levels in both the planar and the stacking directions. A comparison is made of the effects of the two kinds of gas flow uniformity on the cell performance.

Development of Chemically Recuperated Micro Gas Turbine

Micro gas turbines (MGTs) are subject to certain problems, notably low thermal efficiency of the system and high emission including NO x . The chemically recuperated gas turbine (CRGT) system introduced in this paper is one of the most promising solutions to these problems. The CRGT system we propose uses an endothermic reaction of methane steam reforming for heat recovery. It is usually thought that the reaction of methane steam reforming does not occur sufficiently to recover heat at the temperature of turbine exhaust, but we confirmed sufficient reaction occurred at such low temperature and that applications of the chemical recuperation system to some commercial MGTs are effective for increasing the efficiency.

Effect of gas channel height on gas flow and gas diffusion in a molten carbonate fuel cell stack

An investigation is made of the relationships between the gas channel height, the gas-flow characteristics, and the gas-diffusion characteristics in a plate heat-exchanger type molten carbonate fuel cell stack. Effects of the gas channel height on the uniformity and pressure loss of the gas flow are evaluated by numerical analysis using a computational fluid dynamics code. The effects of the gas channel height on the distribution of the reactive gas concentration in the direction perpendicular to the channel flow are evaluated by an analytical solution of the two-dimensional concentration transport equation. Considering the results for uniformity and pressure loss of the gas flow, and for distribution of the reactive gas concentration, the appropriate gas channel height in the molten carbonate fuel cell stack is investigated.

Pressure losses at dividing and combining junctions in a molten carbonate fuel cell stack

The pressure losses at manifold junctions in a molten carbonate fuel cell (MCFC) stack depend on the stacking positions of the cells and the flow rate in the manifold. These pressure losses affect the uniformity of gas flow rate in each stacked cell and consequently also affect the cell performance. In this study, the pressure losses at dividing and combining junctions in a plate heat-exchanger type MCFC stack were examined by numerical analysis. A stack consisting of 100 cells was assumed, and the junction pressure losses at various stacking positions of cells were calculated under various flow rate conditions ranging from the minimum possible flow rate (80% utilization of fuel gas) to the maximum possible flow rate (10% utilization of oxidant gas). The results were arranged according to the equations for loss coefficients, and were compared with the experimental results of previous studies.

溶融炭酸塩型燃料電池用ガスシール構造に関する研究 : 第2報,ガスシール構造の実験的検討(熱工学,内燃機関,動力など)

A reactant gas seal is one of critical issues to achieve the reliability of the MCFC stack which is a key equipment in MCFC power plant. The wet-gas seal with carbonate melted at operating temperature (650°C) is generally expected to be suitable for such a seal. We develop the wet seal configuration composed of thin sheet metal parts to be cost-competitive with other power plants. In this report, the proposed configuration of wet-gas seal using thin sheet metal parts is produced for trial, which is assembled in single cells. The leak rates from wet seals were examined under the condition of MCFC operating temperature. Then, the superior seal performance was found and it is confirmed that the wet seal configuration composed of thin sheet is reliable.

溶融炭酸塩型燃料電池用ガスシール構造に関する研究〔熱工学, 内燃機関, 動力など〕

Molten carbonate fuel cells (MCFCs) are expected to be large-scale, highly efficient energy sources in the future. A reactant gas seal is one of the critical issues in achievement of reliability of the MCFC stack, which is a key piece of equipment in an MCFC power plant. At present, the wet gas seal with carbonate molten at the operating temperature (650°C) is generally considered to be suitable as such a seal. On the other hand, to be cost-competitive with existing power plants, the MCFC stack must consist almost entirely of thin sheet metal parts. In this report, a wet gas seal configuration composed of thin sheet metal parts is proposed. Then, the long-term performance of the wet gas seal in an actual MCFC is evaluated.