Thermodynamic Study on Reduction of Iron Oxides by H2 + CO + CH4 + N2 Mixture at 900 °C

Abstract

The reduction gas used in the gas-based direct reduction iron-making process contains CH4 in different concentrations, which has an important effect on the gas and heat needed for the reduction of iron oxide. To investigate the influence of CH4 on gas utilization rate and heat needed at 900 °C, the initial conditions are set as H2% + CO% = 90, CH4% + N2% = 10, gas pressure 1–9 atm, and 0.5 mol Fe2O3, and the equilibrium state composition is calculated using the minimum free energy method. The utilization rate of total gas can be improved, and gas demand can be decreased by increasing CH4 concentration or H2 concentration or reducing gas pressure. For the production of per ton of Fe from 25 °C to 900 °C, 6.08–7.29 m3 of reduction gas, and 7.338–8.952 MJ of gas sensible heat can be saved by increasing 1 m3 CH4, while 10.959–11.189 MJ of reaction heat is increased. Compared with 3390.828–3865.760 MJ of the total heat of per ton of Fe for the reduction by H2 + CO, 2.174–3.703 MJ of total heat is increased by increasing 1 m3 CH4, and the increase ratio is 0.065–0.096%. This study is helpful to improve the gas efficiency and lower the pursuit of higher concentration of H2 + CO in reduction gas.

CO2 utilization in chemical looping gasification and co-gasification of lignocellulosic biomass components over iron-based oxygen carriers: Thermogravimetric behavior, synergistic effect, and reduction characteristics

“…2-4). When blended materials are considered (i.e., O/B=0.5 and O/B=1), the possible reactions typically taking place during the chemical looping gasification process can be classified by the indirect and direct reduction reactions of iron oxide [21]. The former is known as the gas-solid reduction reaction, triggered by biomass volatiles (i.e., H 2 , CO, CH 4 ), which are generated from the pyrolysis and tar cracking processes [22], while the latter is regarded as the solid-solid reduction reaction caused by fixed carbon [23].…”

“…Main chemical reactions occurring during the biomass chemical looping gasification with iron oxide carriers[21][22][23].…”

Some Aspects of the Thermochemical Route for the Valorization of Plastic Wastes, Part I: Reduction of Iron Oxides by Polyvinyl Chloride (PVC)

“…The values of standard entropy (∆rH • ) and free energy (∆rG • ) changes at 1000 • C computed using the HSC thermochemical database [36] are provided below (Table 5) for a set of reactions (Equations ( 4)-( 20)) likely to take place during the thermal treatment and considering simple reducing agents such as C (s) , CO (g) , and H 2(g) . Several scientific findings devoted to the thermodynamic and kinetics aspects as well as the modeling of iron oxide reductions with various reducing agents were summarized recently [44][45][46][47][48]; most of their developed approaches were based on selected reactions being analogous to those described by Equations ( 4)- (20). Reactions of the direct reduction of iron oxides by solid carbon are of endothermic nature (Equations ( 4)-( 6)), hence they should be favored at high temperatures.…”

A Kinetic Study on the Reduction of Single Magnetite Particle with Melting Products at High Temperature Based on Visual and Surface Analytical Techniques

“…Among these gases, H 2 is a highly reactive gas reductant for the reduction of iron ores. However, the disadvantage of this reduction is that it needs an extra external energy supply, which is commonly supplied from the combustion of CO, H 2 , and CH 4 with O 2 or the reduction of CO with Fe 2 O 3 [8,13,14]. When the iron ore is reduced by the gas mixtures of H 2 and CO, the reduction rate of iron ore with H 2 is higher than the value in CO [10].…”

“…Then, the reduction of iron ore with H 2 at lower temperature affects the total reduction rate of the iron ore. Thus, the following issue is the low reduction reactivity of CO with iron in the H 2 /CO atmosphere [8,14]. The novel flash ironmaking technology operates at a high temperature around 1300 • C and even close to 1400 • C [8], and hence the reduction characteristics of iron ore in the mixing gases of H 2 and CO at high temperature are key to ensure both a sufficient heat supply for the reduction of H 2 with iron ore and to improve the overall reduction degree.…”