Opportunities and Challenges in Using SOFCs in Waste to Energy Systems

Abstract

Opportunities and Challenges in using SOFCs in Waste to Energy Systems An overview of the research activities and on-going multiple projects at Delft University of Technology aimed at the development of Solid Oxide Fuel Cell (SOFC) integrated waste to energy systems are presented in this paper. Resource and energy recovery from waste streams is becoming increasingly attractive. Pyrolysis, gasification, biomethanation, landfill etc lead to the production of combustible gases from waste feedstocks. However, the fuel gas produced is often contaminated when derived from waste- especially with some of the process routes mentioned above. If energy production is attempted, the use of efficient systems, when not expensive, will result in better financial returns on investment. As SOFCs are efficient and SOFC prices are expected to come down in the future, they might become an attractive option for power production from waste streams. Gasification is often considered for waste processing and results in the production of syngas rich in hydrogen and carbon monoxide. Plasma gasification is an emerging choice for municipal solid waste management and supercritical water gasification for wet waste streams. Pyrolysis systems operate at lower temperatures and hydrocarbon rich streams are produced. Biomethenation and landfill results in methane rich gas streams. Lower temperatures lead to incomplete carbon conversion in these systems thus lowering the achievable efficiencies. Different waste process routes result in different fuel mixes. High levels of contaminants in the fuel gases are expected in most of the waste to fuel gas systems. This makes it necessary to develop contaminant resistant fuel cells or complicated fuel processing and cleaning systems. Waste streams are often difficult to handle and hence system integration and heat integration becomes challenging. The research challenges hence vary from understanding the complex electrochemistry of fuel oxidation, understanding contaminant tolerance limits, developing contaminant tolerant cells, stacks and systems. Influence of waste-derived syngas compositions and contaminants on SOFCs will be presented and the removal of a variety of potential contaminants including higher hydrocarbons, particulates, H2S, HCl, alkali compounds, heavy metals etc will be discussed. A wide range of research activities ranging from pattern cell impedance analysis to integrated system development will be presented. Complex approaches required in cleaning the gas to meet the requirements of SOFCs will be explained. Additionally, a brief discussion on the achievable system efficiencies with SOFC integrated waste to energy systems and novel concepts such as gasifier- Reversible SOFC integrated power production cum energy storage systems will be presented. Finally, an overview of a wide range of national, European and international projects that helped or currently helping us to carry out the above mentioned research activities will be presented. These projects include, among others, Bill and Melinda Gates foundation funded reinvent the toilet project, a Dutch National Award winning wastewater to fertilizer and power project, an industry initiated project on Supercritical Water Gasifier-SOFC integration, an Indo-Dutch jointly funded project with activities also on biogas production from waste streams for SOFC applications and European projects on gasifier SOFC integration and reversible SOFCs.