Effect of temperature and reaction path interaction on fluidization reduction kinetics of iron ore powder

Due to the instability of FeO at temperatures below 843 K,the fuidization reduction pathway of iron ore powder changes with the reduction temperature.Thus,the effect of temperature and reaction pathway interaction on the kinetics of fuidization reduction of iron ore powder under low-temperature conditions ranging from 783 to 903 K was investigated to describe the fluidization reduction rate of iron ore powder from three aspects:microstructure change,reaction limiting link,and apparent activation energy of the reaction,exploring their internal correlation.The experimental results revealed that in a temperature range of 783-813 K,the formation of a dense iron layer hindered the internal diffusion of reducing gas,resulting in relatively high gas diffusion resistance.In addition,due to the differences in limiting links and reaction pathways in the intermediate stage of reduction,the apparent activation energy of the reaction varied.The apparent activation energy of the reaction ranged from 23.36 to 89.13 kJ/mol at temperature ranging from 783 to 813 K,while it ranged from 14.30 to 68.34 kJ/mol at temperature ranging from 873 to 903 K.

A novel approach to enhance decrepitation temperature and reducibility of ultrafine iron ore concentrate pellets

Utilizing ultrafine iron ore concentrate for pellet production can expand domestic iron ore resources in China and promote the utilization of low-grade ores.However,a challenge arises with the low decrepitation temperature and reducibility in the preparation process of ultrafine iron ore concentrate pellets.To address the challenge,a novel approach was proposed,which incorporated straw powder as an additive to enhance pellet porosity,thereby improving the decrepitation temper-ature and reducibility of ultrafine iron ore concentrate pellets.The effect of varying proportions of straw powder(0.0-2.0%)on the characteristics of ultrafine iron ore concentrate pellets was examined.Results indicate that at a 2.0%straw powder ratio,pellet decrepitation temperature notably rises from 380 to 540℃,while the reducibility index escalates from 25.7%to 48.1%.Nevertheless,the addition of straw powder results in diminished drop strength,compressive strength of green pellets,and cold crushing strength of fired pellets.In addition,enhanced pellet reducibility leads to exacerbated reduction swelling index and reduction degradation index.Despite these effects,all parameters remain within an acceptable range.

Optimization of iron ore blending based on replacing Australian low alumina limonite

Mauritanian iron ore powder(OM)has advantages of high iron grade,low aluminum content,and low loss on ignition,which can be used as a new mineral to replace low alumina limonite that has been exhausted in Australia.However,it will have a certain negative impact on sintering because of its high SiO_(2) content.The mechanism of SiO_(2) content affecting the sintering behavior was first studied through FactSage 7.2.Then,the liquid fluidity,penetration,and high-temperature performance of different iron ore powders were compared.Finally,the optimization of ore blending structure was studied by the micro-sintering method and the sinter pot test.The results show that the increase in SiO_(2) content can reduce the assimilation temperature.The low penetration of OM can lead to an increase in the amount of liquid,and the high SiO_(2) content of OM increases the viscosity of the liquid phase.What is more,the increase in SiO_(2) also increases the formation of silicate and fayalite phase and inhibits the formation of silico-ferrite of calcium and aluminum(SFCA).To optimize ore blending structure,OM and the low SiO_(2) powder OD from Australia were used together,which improves the content of SFCA by 2.04%and decreases the contents of calcium silicate and fayalite by 0.63%and 4.99%,respectively.The results of the sinter pot test indicated that the properties of sinter have been improved.

Reduction Kinetics of Fine Iron Ore Powder in Mixtures of H_2-N_2 and H_2-H_2O-N_2 of Fluidized Bed

Reduction kinetics of fine iron ore powder in different gas mixtures were investigated in high-temperature fluidized bed at a scale of kilograms. Influence of processing parameters, such as particle size, gas flow velocity, height of charge, temperature, compositions of gas mixture, and percentage of inert components, on reduction ki- netics was experimentally determined under the condition of fluidization. The equations for calculating instantaneous and average oxidation rates were deduced. It was found that an increasing H2 O percentage in the gas mixture could obviously decrease the reduction rate because the equilibrium partial pressure of H2 decreased with increasing content of Hz O in the gas mixture and then the driving force of reduction reaction was reduced. When the H2 content was high, .the apparent reaction rate was so rapid when the average size of iron ore fines was less than 1 mm that the re- action temperature can be as low as 750 ℃ ; when the average size of iron ore fines was more than 1 mm, a high re- action temperature of 800 ℃ was required. In addition, it was also found that the content of H2O should be less than 10% for efficient reduction.