Abstract
The purpose of this study was to comprehensively analyze the effects of the carbon powder coating mass fraction, pressure, reduction temperature, reduction time, gas linear velocity, and particle size on fluidization reduction. Brazilian fine iron ore particles were the experimental object, and reduction experiments were performed under added carbon powder coating and pressure conditions. A six-factor, three-level orthogonal experiment method was used to obtain the optimal operating conditions and investigate the adhesion and inhibition mechanisms of fine iron ore during reduction. The experimental results show that with the addition of a carbon powder coating, an appropriate increase in pressure can increase the metallization rate, improve the fluidization state, and reduce the sticking ratio. The optimal operating conditions for pure hydrogen to reduce Brazilian fine iron ore was found to be a reduction temperature of 923–1023 K, the linear velocity of the reducing gas was 0.6 m/s, the reducing time was 30–50 min, the reducing pressure was 0.25 MPa, the mass content of the coated carbon powder was 2–6% (accounting for the mass of the mineral powder), and the particle size of the carbon powder was 4–7 µm. Iron whiskers cohesion and agglomeration were the main reasons for the adhesion of ore powder particles. It was found that carbon powder coating can effectively change the morphology of metal iron, as metal iron generates spherical particles around the carbon powder to improve the fluidization state.
Highlights
Blast furnace iron-making currently occupies a dominant position in the smelting of iron and steel, its reliance on metallurgical coke and emissions of pollutants, such as those generated during sintering and pelletizing, cause harm to humans and the environment [1,2,3]
By comparing Scheme 4 compared Scheme 3, it is evident that, after the addition of carbon powder with a particle size range of 48–75 of a mass fraction of 4% and at atmospheric pressure, the sticking ratio was reduced by 8.91%, the fluidization effect was improved, and the metallization rate was reduced by 3.93%
4 with Scheme 2, it can be seen that by adding carbon powder with a particle size range of 48–75 μm at a mass fraction of 4%, the reduction pressure was increased from 0.1 to 0.4 MPa, the metallization rate was increased by 2.5%, and the sticking ratio was increased by 0.87%
Summary
Blast furnace iron-making currently occupies a dominant position in the smelting of iron and steel, its reliance on metallurgical coke and emissions of pollutants, such as those generated during sintering and pelletizing, cause harm to humans and the environment [1,2,3]. The fluidized direct reduction process has the advantages of a large gas-solid interfacial contact area, uniform temperature and concentration, good heat and mass transfer conditions, and high operating efficiency, and meets both the metallurgical and environmental protection requirements. Problems such as sticking or flow loss are prone to occur during the high temperature fluidization reduction process, reducing the reduction efficiency and hindering the continuous operation of the process. Four sets of preliminary experiments were conducted to analyze the effects of pressure and coated carbon powder on the fluidized reduction of Brazilian iron ore powder. The mechanism of iron ore powder particle adhesion and the mechanism of coating carbon powder to inhibit iron ore powder adhesion are analyzed, which provide data and theoretical support for improving the fluidized ironmaking process
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