Impact of Biomass-Derived Contaminants on SOFCs with Ni/Gadolinia-Doped Ceria Anodes

Abstract

The impact of biomass-derived contaminants on solid-oxide fuel cells ͑SOFCs͒ with Ni/gadolinia-doped ceria ͑GDC͒ anodes was investigated using electrochemical impedance analysis. Measurements were carried out with symmetric test cells under a singlegas atmosphere. The impact of H 2 S, HCl, and naphthalene in the gas stream on the performance of Ni/GDC anodes are presented. No significant impact has been observed up to 9 ppm H 2 S and HCl and 110 ppm naphthalene. © 2007 The Electrochemical Society. ͓DOI: 10.1149/1.2820452͔ All rights reserved. Gasification is the conversion of biomass to a gaseous fuel by heating in a gasification medium such as air, oxygen, or steam. Biosyngas from gasification consists of a mixture of carbon monoxide, carbon dioxide, methane, hydrogen, water vapor, and impurities. These impurities are mainly ͑i͒ particulate matter, ͑ii͒ tar, ͑iii͒ alkali metal compounds and other halides, ͑iv͒ sulfur compounds, and ͑v͒ nitrogen-containing compounds, especially ammonia. Once the biosyngas is cleaned to remove the contaminants to a level sufficient for solid oxide fuel cells ͑SOFCs͒, it can probably be used as an SOFC fuel.1,2 As the biomass is a sustainable primary energy source and is essentially CO 2 neutral, such systems offer the potential for sustainable high-efficiency energy systems for the future.Feeding SOFCs with biosyngas draws attention to many important issues. Because the fuel gets oxidized at the SOFC anode, chemical and physical interactions between the anode and the gas components are of critical significance. Different types of anodes have different kinds of interactions with these contaminants, and hence their tolerance levels for these contaminants may vary considerably. This, in turn, alters the choices for the required gascleaning devices when SOFCs with such anodes are connected to biomass gasifiers. Because these different types of anodes may have varying effectiveness in the conversion of the fuel, proper selection of the SOFCs with suitable anodes and gas-cleaning systems and appropriate operation parameters for them is of critical significance in the development of feasible and efficient designs of biomass gasifier-SOFC systems.Conventional SOFC anodes contain substantial amounts of nickel. Nickel is widely considered as an attractive material for SOFC anodes because it is a good electronic conductor and catalytically active for the electrochemical oxidation of hydrogen. In order to increase the mechanical properties, nickel is mixed with an ionconducting material, most commonly yttria-stabilized zirconia ͑YSZ͒. Doped ceria, such as gadolinia-or samaria-doped ceria, is a mixed conductor under reducing conditions. It offers increased surface area for electrochemical reactions, unlike materials offering mainly ionic conductivity and low electronic conductivity, which limit the reactions to fuel/electrode/electrolyte boundaries. They are also expected to give better performance with fuels containing hydrocarbons.3 For this reason, anodes comprising gadolinia-doped ceria ͑...

Low-temperature H2S removal for solid oxide fuel cell application with metal oxide adsorbents

“…In order to use biogas as a fuel for a SOFC, several of its components have to be reduced to a certain degree. Among those components are, apart from H 2 S, particulate matter, tar, hydrogen chloride, alkali metal species and nitrogen containing compounds such as ammonia (Aravind, 2007;Aravind et al, 2008). The influence of H 2 S on the performance of SOFCs has been analysed in depth.…”

Biomass Gasifier–SOFC Systems: From Electrode Studies to the Development of Integrated Systems and New Applications

“…Experiments of several hours of duration were carried out with clean tar free biosyngas (after tar reforming) as well as with tar rich biosyngas (tar reformer bypassed). The tar load in the gas with no tar reforming was few thousand mg/Nm 3 . No significant degradation in the SOFC performance was observed during this operation period.…”

Reporting Degradation from Different Fuel Contaminants in Ni‐anode SOFCs

“…The issue of tars feeding SOFC has been studied by Aravind et al [10]. Carbon depositions issues have long been investigated for Ni/YSZ anodes of SOFCs operating with CH 4 and other hydrocarbon fuels [11][12][13][14][15][16].…”