Zhengliang Xue

Three-dimensional structure and micro-mechanical properties of iron ore sinter

A new analysis method based on serial sectioning and three-dimensional (3D) reconstruction was developed to characterize the mineral microstructure of iron ore sinter. Through the 3D reconstruction of two types of iron ore sinters, the morphology and distribution of minerals in three-dimensional space were analyzed, and the volume fraction of minerals in a 3D image was calculated based on their pixel points. In addition, the microhardness of minerals was measured with a Vickers hardness tester. Notably, different mineral compositions and distributions are obtained in these two sinters. The calcium ferrite in Sinter 1 is dendritic with many interconnected pores, and these grains are crisscrossed and interwoven; the calcium ferrite in Sinter 2 is strip shaped and interweaves with magnetite, silicate and columnar pores. The calculated mineral contents based on a two-dimensional region are clearly different among various layers. Quantitative analysis shows that Sinter 1 contains a greater amount of calcium ferrite and hematite, whereas Sinter 2 contains more magnetite and silicate. The microhardness of minerals from highest to lowest is hematite, calcium ferrite, magnetite and silicate. Thus, Sinter 1 has a greater tumbler strength than Sinter 2.

The effect of hydrogen addition on the carbon-deposition behaviour during the reduction of pellets for the blast furnace process

With the application of large amount of pulverised coal injection into the blast furnace, the hydrogen content in the gas will increase, which accelerates the reduction of iron ore in lump zone of the blast furnace as well as carbon-deposition reaction. This study has investigated the effect of hydrogen addition on carbon-deposition reaction during the reduction of pellets through thermodynamic calculation and experiment. The results show that H2 can promote the carbon-deposition reaction, while the increase of temperature and CO2 can significantly inhibit it. The preference region of temperature for C formation is about 600°C. Moreover, the promotion effect of H2 on the carbon-deposition reaction at 700°C is better than that at 600°C. The SEM observation results show that the generated carbon is mainly distributed on the surface of the pellet, and only a little carbon is located inside the pellet. The agglomerated carbon could be more easily formed due to the dramatic carbon-deposition reaction caused by the lower temperature or higher H2 content. But, most of the carbon just exists as an individual particle at the lower carbon-deposition reaction rate. The results of SEM–EDS reveal that carbon deposited is primarily in the form of elemental carbon rather than in the form of cementite. The study also shows that with increasing reduction time, the rate of carbon-deposition increases, mainly due to the promotion effect of reduced iron during the reduction process of pellets.

Evolution of Metallurgical Properties and Microstructures of Lump Coal During the Descending Process in COREX Gasifier

The operating performance and cost efficient of the COREX ironmaking process strongly depend on the quality of lump coal. In order to investigate the degradation behavior of lump coal in COREX gasi...

Factors Influencing Gas Generation Behaviours of Lump Coal Used in COREX Gasifier

Abstract The influences of coal rank, particle size, temperature and gasifier atmosphere on the gas generation of lump coals used in COREX gasifier were investigated. The results showed that an increase in gasifier temperature and a decrease in particle size hardly affected the final mass loss of lump coals but strongly enhanced the gas generation rate. When the temperature was greater than 1000 °C, a decrease in coal rank increased the gas yield but had little effect on the gas generation rate. Moreover, the promotion ability of the atmosphere for the gas generation rate of lump coal from low to high was as follows: N2, CO2, CO and H2. Considering energy conservation, to improve the gas generation rate of the gasifier, the coal rank and particle size should be decreased first, and afterwards, an increase in reduction potential of the atmosphere in gasifier is also encouraged.