Numerical simulation analysis of rotary cup centrifugal blast furnace slag

In the process of centrifugal dry granulation of blast furnace slag, the thickness of the liquid film at the outlet of the rotor will have a significant impact on the degree of crushing of the slag after leaving the rotor and the size of the solid particles formed. Therefore, this paper uses the VOF method to analyse the flow of molten slag inside the cup. The results have shown that the slag flow has a significant effect on the thickness of the liquid film and the linear relationship is obvious; the thickness of the liquid film decreases with the increase of the diameter of the rotary cup and the rotation speed, and the negative correlation with the diameter of the cup is more obvious; Secondly, as the depth of the cup increases, the thickness of the liquid film decreases first and then increases. The inclination angle of the cup wall has little effect on the thickness of the liquid film.

Kinetic study on the reaction between Incoloy 825 alloy and low-fluoride slag for electroslag remelting

A kinetic model for the reactions between the low-fluoride slag CaF2–CaO–Al2O3–MgO–Li2O–TiO2 and Incoloy 825 alloy was proposed based on the two-film theory. The applicability of the model was verified to predict the variation of components in the slag–metal reaction process. The results show that the controlling step of the reaction 4[Al] + 3(TiO2) = 3[Ti] + 2(Al2O3) is the mass transfer of Al and Ti in the liquid alloy and the controlling step of the reactions 4[Al] + 3(SiO2) = 3[Si] + 2(Al2O3) and [Si] + (TiO2) = [Ti] + (SiO2) is the mass transfer of SiO2 in the molten slag. With increasing TiO2 content in the slag from 3.57% to 11.27%, the Al content in the alloy decreased whereas the Ti content increased gradually. The Si content continued to decrease during the slag–metal reaction. Soluble oxygen in the alloy reacts with Al, Ti, and Si, resulting in a decrease of the oxygen content in the alloy. The variations of TiO2 content were in good agreement with the calculated results by the kinetic model whereas the measured results of Al2O3 and SiO2 in the slag were lower than the calculated results, which is mainly due to the volatilization of fluoride.

Study on the corrosion of refractory materials by coal blended with the extraction residue of direct coal liquefaction in a simulated gasification atmosphere

Utilizing the extraction residue (ER) of direct coal liquefaction residue as a gasification feedstock has significant economic value. But the characteristic of high ash and iron in the ER would increase the risk of corrosion of the refractory materials and affect the long-term operation of the gasifier. In this work, corrosion experiments of molten slag derived from a mixture of 20 wt% ER and 80 wt% coal on a high-chromia refractory brick and SiC brick were carried out using a rotary-drum furnace in a simulated gasification atmosphere. The experimental results show that the viscosity of the poured slag is larger as compared to the initial ash sample at the same temperature, which suggests that the viscosity–temperature relationship of the poured slag should be used as the reference for the operation temperature of the gasifier to ensure that the slag can flow during operation. For a high-chromia refractory brick, iron oxides in molten slag could react with Cr2O3 in the refractory matrix but, because the aggregate was not found to be damaged, the damage to the matrix structure was the key factor for causing the corrosion of the high-chromia refractory brick. Metallic iron was observed in the exposed SiC brick, which indicated that the reaction between the iron oxides in the slag and SiC occurred, forming metallic iron and SiO2. The corrosion of a SiC brick by molten slag depended mainly on the dissolution of Al2O3 particles and the reaction between iron oxides in the molten slag and SiC particles. Therefore, the high iron content in coal ash had a serious influence on the corrosion of refractory materials. More efforts need to be made on coal blended with ER as a gasification feedstock in the future.

Effect of Basicity on the Sulfur Precipitation and Occurrence State in Kambara Reactor Desulfurization Slag

Kambara Reactor (KR) desulfurization slag used as slag-making material for converter smelting can promote early slag melting in the initial stage and improve the efficiency of dephosphorization. However, its direct utilization as a slagging material can increase the sulfur content in molten steel since KR desulfurization slag contains 1~2.5% sulfur. Therefore, this research focuses on the effect of basicity on the precipitation behavior and occurrence state of sulfur in KR desulfurization slag in order to provide an academic reference for the subsequent removal of sulfur from slag through an oxidizing atmosphere. The solidification process of slag was simulated by the Factsage8.0. The slag samples were analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM), and the amount of CaS grains was analyzed using Image-ProPlus6.0 software. The thermodynamic calculation showed that the crystallization temperature of CaS in the molten slag gradually decreased with the increase in basicity, and the CaS crystals in the molten slag mainly existed in the matrix phase and at the silicate grain boundaries. A large number of CaS grains were precipitated along the silicate grain boundary in low-basicity (R = 2.5 and 3.0) slags and fewer CaS grains were precipitated along the silicate grain boundary, while the CaS grain density in the matrix phase was higher in the high-basicity (R = 3.5, 4.0, 4.5) slag. With the increase in basicity, the number of CaS grains gradually decreased, and the CaS grain sizes in slag sample increased gradually. The sulfur in the synthetic slag was in the form of CaS crystals and the amorphous phase, and the content of amorphous sulfur gradually increased with increasing basicity.

Effect of Erosion Behavior of FeO-CaO-SiO2-MgO-Al2O3 Blast Furnace Primary Slag on Al2O3 Substrate

Al2O3 substrate is widely used as a lining refractory material throughout the blast furnace (BF) process. Accordingly, the erosion of Al2O3 refractory by molten slag has a negative influence on the running cost and smooth operation of BFs. The effect of the erosion behavior of BF primary slag containing FeO-CaO-SiO2-MgO-Al2O3 on Al2O3 substrate refractory was fundamentally investigated using the high-temperature contact angle method and FactSage thermodynamic software based on the composition of BF primary slag in a typical iron and steel enterprise of China. The results showed that the primary slag mentioned above was easily wetted with Al2O3 substrate, and the observed contact angles were 24.5° and 22.0°, when the FeO mass fraction (w(FeO)) was maintained at 10% and 15% of the primary slag, respectively. Moreover, the starting melting temperature of the primary slag with high FeO content, of 1263 °C, was lower. The erosion thickness between the slag and Al2O3 substrate increased from 19.23 to 23.17 μm as the added w(FeO) increased from 10% to 15%. In addition, it was observed via SEM-EDS analysis that the interface layer was formed, and high-melting-point compounds were generated during the wetting process. This was attributed to the interaction between the molten slag and Al2O3 existing in the substrate, which may have inhibited the continuous dissolution of the Al2O3 in the substrate into slag. Good surface wettability and the dissolution of the Al2O3 substrate refractory into the primary slag of the BF are two dominant factors leading to the erosion of the refractory.