Bio mass for CO{sub}2 neutral steel production

摘要

A process to increase the efficiency of bio mass as energy source by direct use of wood chips instead of coke in steel production is presented. Full utilisation of the bio mass constituents and excellent process control is enabled by utilisation of microwave heating for ignition of the reduction reaction and simultaneous pyrolysis of the bio mass. The process is applicable for pig iron production as well as for iron sponge production. The paper presents a comparison of both process variants, with respect to energy consumption, product quality and integration into existing technology. The process is run in a dual zone fixed bed reactor, with a bottom zone containing wood chips and an upper zone filled with iron ore concentrate. In the first zone the hematite is selectively absorbing 2.45 GHz microwave radiation and heated up to the desired temperature with a heating rate of >100 K/min. The wood chips undergo a flash pyrolysis and react in multiple steps mainly to gaseous products, e.g., CO and H{sub}2, which are immediately consumed by the reduction reaction. At the end of reduction an atmospheric plasma is ignited due to the presence of the microwave field. This enables removal of excess carbon in case of iron sponge or slag formation for purification of iron melt. The process yields, depending upon the conditions, iron sponge or raw steel for direct use in electrical arc furnaces.