Method for Measuring Chromium Evaporation from SOFC Balance-of-Plant Components

Abstract

Chromium poisoning is a well-identified performance degradation process in solid oxide fuel cells (SOFC). While stainless steel interconnects have been identified to be a significant source of chromium, the contribution of the chromium from balance-of-plant (BoP) components located upstream of the cathode still needs to be ascertained. The aim of this work was to develop and validate a method to quantify the amount of chromium evaporating from hot BoP components. An austenitic stainless steel (253MA) pipe was exposed to humidified air at high temperatures. The volatile chromium species were then collected by sampling through a quartz tube coated with sodium carbonate. The chromium evaporation rate was reduced by a factor of 4 when a varying temperature history between 650 and 750oC was followed by 100 h operation at 800oC. Scanning electron microscopy was performed on pipe cross sections to show the relationship between the microstructure of the oxide layer and chromium evaporation. The method developed can be used to measure chromium concentration levels at different locations in a complete SOFC system.