Improvement of Electrical Efficiency of Solid Oxide Fuel Cells by Anode Gas Recycle

Abstract

Anode gas recycle (AGR) is one of the methods to enhance fuel utilization. In this paper, electrochemical performance of a single planar solid oxide fuel cell (SOFC) was investigated with/without AGR. Cell performance at AGR was successfully evaluated by our simulated-reformate generator without carrying out AGR actually. It was clarified that cell voltage more than 0.8 V could be obtained with AGR at utilization of 90% methane fuel and 45% air, 700ºC and 400 mA cm-2. The cell voltage was by 20 mV higher than one without AGR at the same utilizations. DC electrical efficiency more than 69%-LHV can be expected at AGR-SOFC which is by 2 percent points higher than one without AGR. Furthermore, it was found that deviation of cell voltage against change in current at a constant flow-rate and time constant for gas conversion in anode would be twice smaller with AGR than without AGR.

Addressing fuel recycling in solid oxide fuel cell systems fed by alternative fuels

“…Their study showed that anode recycle increases stack efficiency by about 10% when anode recycle is used. It was reported in [18] that cell voltage could be improved by anode off-fuel recycle in solid oxide fuel cell fed by pure methane. The study was on a cell level (not system level) with distinguished conclusion.…”

Numerical Simulation of SOFC System Performance at 90% Fuel Utilization with or without Anode Off-Gas Recycle for Enhancing Efficiency

“…We developed a cell-performance testing method by synthesizing reformate gases in SR and AGR conditions without real off-gas recycle (3)(4)(5). Then, commercial disc-typed anode-supported cell performances were measured in a seal-less condition (3)(4)(5).…”

“…We developed a cell-performance testing method by synthesizing reformate gases in SR and AGR conditions without real off-gas recycle (3)(4)(5). Then, commercial disc-typed anode-supported cell performances were measured in a seal-less condition (3)(4)(5). It was also clarified that reformate gases (H 2, H 2 O, CO, CO 2 , CH 4 ) can be replaced in experimental with H 2 -H 2 O mixtures in an anode-supported cell, giving identical cell voltage-current density (V-J) characteristics (6).…”

Electronic Structure Measurements of Heteroepitaxial Solid Oxide Fuel Cell Cathode Thin Films

“…The electrochemical performance of the device would be degraded not only because of the electrically insulating nature of SrO and SrCO 3 , but also because the formation of these surface secondary phases reduces the effective LSCF surface area for oxygen reduction reaction (ORR) process. The anode exhaust gas in SOFCs undergoing an anode gas recycle process can contain as much as 30% CO 2 produced by hydrocarbon fuels (6). Any gas leakage from the anode side due to crack formation in the seals, electrolyte or interconnects will expose the cathode to this high CO 2 concentration.…”