Fe-Si particles on the surface of blast furnace coke

This study investigates the surface of unpolished samples of blast furnace （BF） coke drilled from the tuyere zone, which hosts Fe-Si particles （mostly Fe3Si） that vary in size, shape, depth of submersion （penetration） into the coke matrix, and contact features with the surface. Based on the shape of the particles and the extent of their contact with the coke matrix, they have been grouped into three major types： （I） sphere-like droplets with limited contact area, （II） semi-spheres with a larger contact area, and （III） irregular segregations with a spherical surface, which exhibit the largest contact area among the three types of particles. Considering the ratio between the height （h） of the particles and half of their length at the surface level （/） along the cross-section, these three types can be characterized as follows： （I） h 〉/, （II） h ~/, and （1II） h 〈/. All the three types of particles can be found near each other. The shape and the extent of the contact depend on the de- gree of penetration of the material into the matrix, which is a function of the composition of the particles. Type （I） particles were initially saturated with Si at an earlier stage and, for that reason, they can react less with carbon in the coke matrix than type （II） and （III）, thereby moving faster through the coke cone. Thermodynamic calculations have shown that the temperature interval of 1250-1300~C can be consid- ered the starting point for Si entering into molten iron under quartz-dominated coke ash. Accordingly, the initial pick-up of Si by molten iron can be assumed to be mineral-related. In terms of BF practice, better conditions for sliding Fe-Si droplets through the coke cone are available when they come into contact with free SiO2 concentrated into small grains, and when the SiO2/∑MexOy mass ratio in the coke ash is high.

Textural changes in metallurgical coke prepared with polyethylene

The effect of high-density polyethylene （HDPE） on the textural features of experimental coke was investigated using polar- ized-light optical microscopy and wavelet-based image analysis. Metallurgical coke samples were prepared in a laboratory-scale furnace with 2.5%, 5.0%, 7.5%, 10.0%, and 12.5% HDPE by mass, and one sample was prepared by 100% coal. The amounts and distribution of textures （isotropic, mosaic and banded） and por^s were obtained. The calculations reveal that the addition of HDPE results in a decrease of mosaic texture and an increase of isotropic texture. Ethylene formed from the decomposition of HDPE is considered as a probable reason for the texture modifications. The approach used in this study can be applied to indirect evaluation for the reactivity and strength of coke.

Fe-Si droplets associated with graphite on blast furnace coke

Fe-Si droplets on the surface of blast furnace （BF） coke from 25 to 50 cm at the tuyere level are mostly composed of Fe3Si, which has various shapes （round, elongated, and irregular） and penetration degrees into the BF coke matrix. The shapes and penetration degrees may depend on the saturation of molten iron by silicon during interaction with the coke matrix. The droplets are covered by a tiny shell of carbon. Graphite observed inside the droplets can be divided into two categories： well-formed tabular crystals with relatively large size and flakes with structures similar as those in cast iron. The textures of the droplets reflect composition, interaction with the coke matrix, and cooling conditions.