Sponge iron: economic, ecological, technical and process-specific aspects

The process cycle sponge iron/hydrogen/iron oxide offers a simple possibility to store the energy of synthesis gases in the form of sponge iron, and at the same time to reform and to condition these synthesis gases. As ‘product’ of this energy storage one receives pure hydrogen which is intended for the running of fuel cells. The process cycle is investigated on two levels: (i) on a general level, economic, ecological and technical conditions are investigated and established, and (ii) on the process-specific level industrially produced iron ore pellets are tested for their suitability for employment in cyclic operation with synthesis gases. Mechanical strength, porosity, speed of reaction, additives and attendant materials (gangue) determine the properties of the pellets. The reaction degree of the iron contained in the pellets should be large and will remain constant. Negative influences such as sintering and carbonization should be avoided as far as possible in order to achieve a high number of cycles.