Kinetics of molten iron oxides reduction using hydrogen

INTRODUCTION The use of coal, coke, and natural gas in ironand steel-making processes has led to the generation of the greenhouse gas CO2. The quantity of CO2 emitted depends on the ironand steel-making route. The integrated HyL3-electric arc furnace process route, which produces 1125 kg/ton of hot metal, is the best steel-making route in terms of greenhouse gas emissions [1]. The iron and steel industries produce 7% of the total anthropogenic CO2 emissions [2]. Hydrogen plasma smelting reduction (HPSR) uses hydrogen to reduce iron oxides to directly produce crude steel products, thus eliminating the use of carbon. Therefore, HPSR is considered a next-generation steel-making process. Hence, understanding the kinetics of this method is important for controlling the process. HPSR provides good reducing conditions by the application of hydrogen and high plasma temperature to intensify the reduction processes; thus, it not only facilitates the production of iron in a onestage process but also prevents the introduction of carbon in the product, which in turn makes the metallurgical equipment compact [3]. It has been reported that reducing iron ores by hydrogen is 20% cheaper than conventional steel-making processes; moreover, steel produced in this manner is of higher quality and has greater flexibility [4]. In HPSR, plasma is generated by creating an electric arc between a hollow graphite electrode as the cathode and molten iron oxide bath as the anode, with continual input of a mixed gas containing argon and hydrogen. The basic flowsheet of the HPSR process has been presented in our previous study [5]. In the process, argon or nitrogen is used to conduct the current in the plasma arc; argon is preferred due to its low ionization energy and high conductivity. Hydrogen operates as the reducing agent; hence, a mixture of hydrogen and argon is injected into the arc zone in the reactor through the hollow graphite electrode. Collision of electrons with hydrogen molecules at high temperatures leads to the activation of the hydrogen molecules. The injection of gases through the electrode directly to the arc zone guarantees optimal conditions for atomization and ionization. Excited hydrogen molecules provide a potentially very useful Kinetics of molten iron oxides reduction using hydrogen