Anode Structure Degradation Model for Planar-SOFC Configuration Under Fuel Gas Contaminants

Abstract

Solid Oxide Fuel Cells (SOFCs) is one of the enabling technologies that are being extensively researched for clean power generation from coal-derived syngas. Anode structural degradation is one of the problems that limit the SOFCs operation lifetime and it is further aggravated by some common contaminants found in coal syngas such as phosphine. An accurate model for predicting the degradation patterns inside an SOFC anode operating under different conditions will be an effective tool for advancement of this technology. In this study, a structural durability model developed earlier for button SOFC anodes is extended to simulate the planar-SOFC anodes. The model accounts for thermo-mechanical and fuel gas contaminants effects on the anode material properties to predict evolution, in space and time, of degradation patterns inside the anode and consequently its lifetime. The temperature field and contaminant concentration distribution inside the SOFC anode are the required inputs for the degradation model which are obtained from DREAM-SOFC: a multi-physics code for SOFC modeling. Due to larger active areas compared to button cell, planar-SOFCs bear greater spatial and temporal temperature gradients which lead to higher thermo-mechanical degradation. Moreover, fuel contaminants are distributed on the anode surface which leads to non-uniform microstructure degradation along the fuel flow. For the case of co-flow configuration, anode thermo-mechanical degradation is severe at the anode-electrolyte interface at the fuel outlet. Whereas the fuel gas contaminants effects on the anode microstructure begin at the fuel inlet and propagate through the anode thickness and along the fuel flow. This research will be useful to establish control parameters to achieve desired service life of SOFC stacks working under coal syngas.

Failure Modes, Mechanisms, Effects, and Criticality Analysis of Ceramic Anodes of Solid Oxide Fuel Cells

“…For anode-supported SOFCs, the stress field in the anode may arise due to thermal expansion mismatch between the anode and other components, residual stresses, and stresses resulting from thermal cycles. These stresses can cause delamination and micro-cracking in the anode/electrolyte interface and lead to performance degradation and eventual failure [53]. Another factor leading to degradation is the generation of thermal gradients due to uneven thermodynamic reactions that occur in the triple-phase boundary of the cells [16].…”