TY - THES

T1 - Preparation of Al2O3-SiO2-SiC Castable for KR Stirring Head and Multiphase Flow Numerical Simulation of Desulfurization Process

AU - Li, Zhonghui

N1 - no embargo

PY - 2023

Y1 - 2023

N2 - With the rapid development of national economic construction, the demand for high-quality steel is increasing day by day. However, the high sulfur content in steel will reduce its mechanical properties such as toughness, plasticity and fatigue life. Due to the high efficiency and low cost of Reactor desulfurization, KR(Kanbara Reactor) process is widely used in hot metal desulfurization pretreatment process. During operation, KR stirring head needs to bear the abrasion and erosion of liquid iron and slag at high temperatures and the harsh thermal and thermomechanical conditions of intermittent operation, such as quenching and heating. Therefore, the refractory castable used for KR agitator should have good thermal shock resistance and high temperature strength. At the same time, in the actual production, KR desulfurization involves complex processes such as free surface fluctuation and desulfurizer mixing with high temperature hot metal. The exploration of flow velocity field in hot metal tank is an important basis for analyzing many complex processes. In view of the performance requirements of KR mixing desulfurization process on refractory lining of mixing head, the purpose was to prepare Al2O3-SiO2-SiC refractory castables with excellent thermal shock resistance and high temperature strength for KR mixing head. The effects of the addition of Al-Si metal powder, roasting temperature and aggregate type on the properties of Al2O3-SiO2-SiC refractory castables were systematically studied. The commercial CFD software FLUENT and GAMBIT were used to conduct numerical simulation of KR desulfurization process, and the feasibility of the model was verified by water model experiment. The effects of rotational speed, immersion depth, number of blades and other factors on desulfurization efficiency of KR mixing were studied through simulation experiment system of multiphase flow in KR mixing tank. The main research conclusions are as follows:(1)The properties of Al2O3-SiO2-SiC at room temperature and high temperatures are significantly enhanced with the addition of Al-Si metal powder. The best comprehensive performance of castable is at the amount of alloy powder 4%. The mechanical properties of Al2O3-SiO2-SiC enhanced by Al-Si alloy powder are enhanced by promoting the mass generation of mullite rod and acicular whiskers inside the castable, thus increasing the strength of castable at room temperature and high temperatures.(2) The Al2O3-SiO2-SiC castable can have better properties with a higher sintering temperature. The best comprehensive performance of castable when the sintering temperature is 1400℃. The high temperature stability of Al2O3-SiO2-SiC castable made from brown corundum is better when no Al-Si metal powder is added. When the alloy powder (4%) is added, the comprehensive performance of sintered mullite castable Al2O3-SiO2-SiC is the best. In the castable with brown corundum as aggregate, network and flocculent whiskers are mainly formed.(3) According to the similarity theory, the water model experiment and numerical simulation were carried out for the mixing process of the mixing head in KR mixing tank. The depth and height of free-liquid vortex at different mixing head speeds were measured. The flow velocity obtained from the water model experiment is basically consistent with the numerical calculation results. The feasibility of this modeling method is thus verified. Based on Euler-Euler method, a VOF numerical model was established, which took into account the mixing of air, cold water and desulfurizer three-phase flow. The desulfurizer particles were regarded as pseudo fluid, and laid on the top of liquid iron at the initial time for simulation analysis. Considering the swirl height, flow field distribution, desulfurizer distribution and the force exerted on the stirring head, the best effect occurs when the rotational speed is 267r/min and the immersion depth is 380mm. When the number of mixing head blades is 3, it is relatively more conducive to desulfurization of liquid iron in KR mixing considering the production and maintenance cost of mixing head.

AB - With the rapid development of national economic construction, the demand for high-quality steel is increasing day by day. However, the high sulfur content in steel will reduce its mechanical properties such as toughness, plasticity and fatigue life. Due to the high efficiency and low cost of Reactor desulfurization, KR(Kanbara Reactor) process is widely used in hot metal desulfurization pretreatment process. During operation, KR stirring head needs to bear the abrasion and erosion of liquid iron and slag at high temperatures and the harsh thermal and thermomechanical conditions of intermittent operation, such as quenching and heating. Therefore, the refractory castable used for KR agitator should have good thermal shock resistance and high temperature strength. At the same time, in the actual production, KR desulfurization involves complex processes such as free surface fluctuation and desulfurizer mixing with high temperature hot metal. The exploration of flow velocity field in hot metal tank is an important basis for analyzing many complex processes. In view of the performance requirements of KR mixing desulfurization process on refractory lining of mixing head, the purpose was to prepare Al2O3-SiO2-SiC refractory castables with excellent thermal shock resistance and high temperature strength for KR mixing head. The effects of the addition of Al-Si metal powder, roasting temperature and aggregate type on the properties of Al2O3-SiO2-SiC refractory castables were systematically studied. The commercial CFD software FLUENT and GAMBIT were used to conduct numerical simulation of KR desulfurization process, and the feasibility of the model was verified by water model experiment. The effects of rotational speed, immersion depth, number of blades and other factors on desulfurization efficiency of KR mixing were studied through simulation experiment system of multiphase flow in KR mixing tank. The main research conclusions are as follows:(1)The properties of Al2O3-SiO2-SiC at room temperature and high temperatures are significantly enhanced with the addition of Al-Si metal powder. The best comprehensive performance of castable is at the amount of alloy powder 4%. The mechanical properties of Al2O3-SiO2-SiC enhanced by Al-Si alloy powder are enhanced by promoting the mass generation of mullite rod and acicular whiskers inside the castable, thus increasing the strength of castable at room temperature and high temperatures.(2) The Al2O3-SiO2-SiC castable can have better properties with a higher sintering temperature. The best comprehensive performance of castable when the sintering temperature is 1400℃. The high temperature stability of Al2O3-SiO2-SiC castable made from brown corundum is better when no Al-Si metal powder is added. When the alloy powder (4%) is added, the comprehensive performance of sintered mullite castable Al2O3-SiO2-SiC is the best. In the castable with brown corundum as aggregate, network and flocculent whiskers are mainly formed.(3) According to the similarity theory, the water model experiment and numerical simulation were carried out for the mixing process of the mixing head in KR mixing tank. The depth and height of free-liquid vortex at different mixing head speeds were measured. The flow velocity obtained from the water model experiment is basically consistent with the numerical calculation results. The feasibility of this modeling method is thus verified. Based on Euler-Euler method, a VOF numerical model was established, which took into account the mixing of air, cold water and desulfurizer three-phase flow. The desulfurizer particles were regarded as pseudo fluid, and laid on the top of liquid iron at the initial time for simulation analysis. Considering the swirl height, flow field distribution, desulfurizer distribution and the force exerted on the stirring head, the best effect occurs when the rotational speed is 267r/min and the immersion depth is 380mm. When the number of mixing head blades is 3, it is relatively more conducive to desulfurization of liquid iron in KR mixing considering the production and maintenance cost of mixing head.

KW - KR-Entschwefelung

KW - feuerfeste Al2O3-SiO2-SiC-Gussstücke

KW - hohe Temperaturfestigkeit

KW - Verteilung des Strömungsfeldes

KW - Mehrphasen-Strömungsmischung

KW - KR desulfurization

KW - Al2O3-SiO2-SiC refractory castable

KW - High temperature strength

KW - Flow field distribution

KW - Multiphase flow mixing

M3 - Master's Thesis

ER -