Heat recovery from low emission steel production through electrolysis and hydrogen reduction

Sammanfattning: The steel industry is a large emitter of carbon dioxide and uses a lot of energy. Because of an increased awareness of the detrimental effects of climate change, research in alternative ways to operate steel plants have been made. It is now possible to build plants with far less emissions by using electrolysis and hydrogen reduction. Electrolysis is a technology with a long historical background that can be used to produce hydrogen gas by splitting water molecules with the input of electricity. The electricity can be renewably produced, and the gas can then be used instead of carbon to reduce iron ore. Even though the emissions of carbon dioxide can be lowered (up to 95 %!) heat losses from furnaces and other processes remain high. The steel and hydrogen plant which is planned to be built in Boden in Sweden by H2 Green Steel (H2GS) is studied in this report. Heat sources are identified and quantified as well as different usage areas of heat. A cost analysis is carried out to determine the profitability of different usages. Four main sources of heat have been found: cooling water, electrical arc furnace (EAF) off-gases, a tail gas from the direct reduction of iron ore and off-gases from the EAF slag handling. Concerning the usage areas, it has been found to be technically possible and economically justifiable to deliver district heating from H2GS to Luleå municipality, and that a condensing turbine can be part of this solution. However, the demand of heat from Luleå municipality must be clarified. Moreover, it has been found useful to further study how waste heat can be used to heat the facilities at site. This seems viable from an economic and technical perspective and is more circular than purchasing heat. On the other hand, using heat to produce electricity through low temperature ORC is not motivated economically for H2GS.