Development of a Solid Oxide Fuel Cell for the utilization of coal mine gas

Abstract

Apart from natural gas there is another important natural source of methane. The so-called coal mine gas is a by-product of the geochemical process of the carbonization of sediments from marsh woods of the Earth's Carboniferous Period. Methane evaporates from the coal and has to be removed out of the active mines where it represents one of the main safety risks. Methane also evaporates in abandoned coal mines. In the federal state Saarland in Germany exists above ground a more than 110 km pipeline for the drained coal mine gas from 12 different sources. The content of methane varies between 25 and 90%, the oxygen content (from air) is in the range up to 10%. This wide range or variation, respectively, of fuel and oxygen content, causes a lot of problems for the use in conventional engines. Therefore the company Evonik New Energies GmbH is interested in using SOFC with coal mine gas as efficient as possible to produce electric power. For that purpose at Forschungszentrum Jülich the available SOFC technology was adapted to the use with coal mine gas and a test facility was designed to operate an SOFC stack (approximately 2 kW electrical power output) together with a pre-reformer. This paper presents the results of the coal mine gas analysis and the effect on the pre-reformer and the fuel cell. The composition of the coal mine gas was determined by means of micro-gas chromatography. The results obtained from preliminary tests using synthetic and real coal mine gas on the pre-reformer and on the fuel cell are discussed.