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The oxidation behaviour and the phase and microstructure evolution of VTM (vanadium titano-magnetite) pellets were studied during thermal processing in order to optimise the production method for p...

In this study, the optimisation model of fuel distribution base on numerical simulation was proposed to reduce the fuel consumption of sintering process. The simulation model of sintering p...

Flue gas circulation is an important method for energy conservation and pollutant emission reduction in iron ore sintering. In this paper the effects of flue gas recirculation ratio on sintering of different iron ores including haematite, magnetite and limonite were studied by illustrating the variation of sinter bed temperature, atmosphere and mineralisation characteristics of different types of iron ores induced by the circulation. It shows that the proper flue gas circulation ratios for haematite, magnetite and limonite are 37, 30 and 25%, respectively. For magnetite ore, preheating and high consumption of oxygen in combustion zone caused more silicate minerals and less acicular calcium ferrite, thereby lowering sinter tumbler strength. As for haematite ore, the rapid change of temperatures of combustion, melting and solidification zones leads to elevated combustion efficiency and increased formation of acicular calcium ferrite, which enhances the sinter strength. When using limonite ore as the...

Patterns of trace elements participating in PM2.5 (aerosol dynamic diameter ≤2.5 μm) formation during iron ore sintering process were investigated. For elucidating this property, PM2.5 collected from before and after the flue-gas-temperature-rising point (stage-1 and stage-2) was examined. The results show that trace elements including Pb, K, Na, Cl and S presented an enriched tendency in PM2.5 from stage-2, while characterised lower contents in PM2.5 from stage-1. Owing to the tiny size of PM2.5, trace elements participated in the formation of Fe-rich and Fe–Al–Si-rich particles in heterogeneous manner. Moreover, S participated in the formation of CaSO4 particles from stage-1 and stage-2 in the form of homogeneous pattern, while Pb, K, Na and Cl participated homogeneously in the form of hybrid PbCl2–KCl, KCl and NaCl particles only from stage-2. The finding results clearly showed the relationship between the formation mechanisms of PM2.5 and the contribution of trace elements, which can serve as the guid...

Flue gas recirculation has been introduced into iron ore sintering process to reduce pollutant emissions. Compared with the conventional process, the sintering indices reduce gradually with decreasing O2 content in the recirculating gas. With sufficient O2, the principle on the use of flue gas recirculation is proposed. The heat loss caused by the decrease in O2 content is compensated by 250°C gas and 0.5%CO. The flame and heat transfer fronts of the sintering bed coincide using mixed gases of no more than 6%CO2 and 8%H2O (g). A novel technology of 35.5% flue gas recirculation ratio is proposed with qualified sintering indices.

Implementing flue gas recirculation brings changes to gas conditions across the sintering bed, significantly influencing the mineralisation behaviours. Compared with the conventional process, the O2 partial pressure of the sintering bed decreased while COx partial pressure increased, whereas the contents of bonding phases reduced, leading to an increase in porosity and the magnetite content in the product. Simultaneously, the reduction disintegration index of sinter products decreased owing to an increased in porosity. The phase development in roasted products showed that hematite and calcium ferrite were formed in the condensation and cooling processes while more magnetite and silicate were presented in the combustion and melting processes. Consequently, the sinter products with 30% flue gas recirculation ratio were qualified as conventional sinter.

The catalytic reduction behaviours between NOx and CO in sinter zone were studied as using flue gas recirculation (FGR). Minerals in sinter can act as catalysts during NOx reduction. The catalytic activity of minerals has the order of calcium ferrite > kirschsteinite > fayalite. The catalytic procedure includes two steps: iron-bearing minerals are reduced to lower valence oxides by CO, and then NO is reduced to N2 by lower valence oxides. Improving the generation amount of calcium ferrite, especially acicular-type silico-ferrite of calcium and aluminium (SFCA), contributes to significantly reinforcing the catalytic performance between NO and CO. As the basicity of sinter increases to 2.2, it enables to generate maximum amount of acicular-type SFCA which has larger specific surface areas, therefore facilitates decreasing NOx emission during FGR sintering.

This study was carried out to determine the influence of using charcoal as a supplementary fuel on the microstructure and reduction properties of sinter. The primary fuel was coke breeze with 0, 20, 30 and 40% replacement of weight input with charcoal to produce sinter. Experimental results indicate that when the replacement percentage of charcoal to coke breeze increased from 0 to 40%, the porosity and FeO content of sinter also rose. These changes result in an enhancement from 79.8 to 84.3% for the reducibility index due to the increased reducing surface area. In addition, the reduction degradation of sinter also improves since degradation during crystalline transformation is restricted. Therefore, replacing coke breeze with charcoal is able to improve the reducing properties of sinter, which is beneficial to small and large blast furnace operation.

Based on the characteristics of the sintering process, a long and short term control strategy of sintering burn through point was put forward, with the burn through point optimised with a fuzzy controller. Long term control was realised by adjusting bed height or density according to the state of preignition permeability and vertical sintering speed. The rising position of gas temperature was stabilised by adjustment of pallet speed, enabling short term control to be carried out. By using vertical sintering speed to represent bed permeability a prediction model of vertical sintering speed was established. The predicted results are in accordance with calculated values and accuracy of the model is >95%. The application of system shows that the accuracy of guidance is >95% and this system can be used to industry production.

A predictive model of sinter chemical composition was developed to predict R (CaO/SiO2), TFe and SiO2 (CaO is calculated from R and SiO2). Based on the backpropagation neural network algorithm, it used the predictive result as a precondition. An expert system was designed to assist in controlling the sinter chemical composition by estimating the change of all the relative chemical components and providing the necessary adjustment. After the system commenced, the hit ratio of the predictive model was consistently over 90% and the goal of controlling chemical composition was achieved.