The Kinetics of Water Removal From an Iron Ore Pellet Prior to Hydrogen Reduction

Sammanfattning: Humanity is facing one of the biggest challenges ever presented in fighting climate change. To counter global warming, industries and scientists across the world are shifting manufacturing towards fossil independence in order to decrease emissions. The steel industry in Sweden is responsible for 10% of the country’s CO2 emissions almost solely due to the use of coke as an iron ore reductant. By implementation of more scrap based steel production emissions have decreased. However, due to an increasing need for steel, ore based steel production cannot be excluded from future steel industries. Direct reduction of iron ore using hydrogen is an alternative process, to fossil based reduction, that is utilised in the Hydrogen Breakthrough Ironmaking Technology initiative (HYBRIT). When the porous iron ore pellet used in the hydrogen reduction process is transported and stored, water may be absorbed in the pores. From thermodynamic calculations it is evident that water evaporation is an endothermic reaction. How and if the water evaporation has an effect on the reduction of the pellets inside an shaft furnace is not widely studied and therefore, this bachelor's thesis examines the kinetics of water evaporation from a single pellet and presents temperature profiles from the pellet centre and surface. This study include the evaporation of water from a single pellet with different water contents. The goal is to contribute to the development and optimization of a full-scale hydrogen based reduction process. The pellet was prepared with a drilled hole for thermocouple fitment, submerged in water, weighed and placed in an oven until a target temperature was reached. Afterwards, the pellet was weighed once more to confirm evaporation of the entire water content. The results showed that the water content affects the heating rate of the pellet. Increasing heating times was seen with increased water contents. Full evaporation of the water was achieved after less than three and a half minutes and it was shown that all water had evaporated once the pellet reached a temperature above 100℃. After all water had evaporated, only the pellet was heated. Furthermore, the conditions for evaporation are more favourable in a full-scale shaft furnace than in the oven used during the experiments. This combined with the time for evaporation led to the conclusion that the water evaporation most likely has an insignificant effect on the large-scale reduction process.