Clean Technology 2008
T. Gerdes, M. Willert-Porada
University of Bayreuth, DE
bio mass, steel, microwave, CO2
The paper presents a process to strongly increase the efficiency of bio mass as energy source in steel production by direct use of wood chips instead of charcoal combined with a new microwave based heating concept. For the lab scale a dual zone fixed bed reactor has been used, with a bottom zone containing the wood chips and an upper zone with the iron ore concentrate. In the first stage the hematite is selectively heated within less than a minute to a temperature level of about 1000°C by 2.45 GHz microwave radiation. The dielectric losses of the hematite are more than 10 times higher than the losses of the beech chips. Accordingly the wood chips are mainly heated indirectly by heat radiation and convection from the hematite. The wood chips undergo a flash pyrolysis and react in multiple steps mainly to the gaseous products. The CO and H2 reduce the ore to metal. At the end of reduction a oxygen containing atmospheric plasma is ignited on top of the melt, that enables removal of excess carbon as well as impurities. In the presented paper the detailed process, the energy balance as well as the scale up concept will be discussed.