Study On Characteristics Of Fluid Flow In Stirring Vessel Of KR Mechanical Desulfurization

Desulphurization in the molten iron is an important process to reduce the sulphur content in the modern iron and steel making processes for producing high quality steel. The representative approaches for the molten iron pretreatment are the KR mechanical stirring and gas injection desulphurization. The common feature for them is to make the molten iron to circulate through the vessel, which reinforces the mixing between molten iron and desulphurizer and realizes the purpose of desulphurization.In this dissertation, the multiple reference frame (MRF) approach and the Eulerian multi-fluid model as well as the standard k-ε turbulence model are used to simulate the characteristics for the fluid flow in the stirring vessel of KR mechanical desulfurization by using the FLUENT software. The optimum for stirring process parameters is carried out as well.For the water model of KR mechanical stirring method, the effects of centric and eccentric stirrings, impeller speed, immersion depth of impeller, and type of impeller on the stirring are investigated by changing there parameters. The results show that the fluid velocity and its turbulence kinetic energy are raised obviously as the impeller speed is increased, and the distributions of flow pattern and turbulence kinetic energy vary largely when the immersion depth and the impeller type are changed, while the stirring effect of the eccentric stirring is better than that of centric stirring. The optimum conditions for the water model of KR mechanical stirring method can be obtained when the rotating speed, immersion depth, and impeller shape are taken to be2.0s-1,0.15m, and220mm×50mm×50mm, respectively under the eccentric stirring.A new approach of gas injection desulphurization has been developed by combining the KR mechanical stirring method and gas injection method based on the above works. The effects of center and eccentric stirrings, injection speed, rotating speed, immersion depth of nozzle on the gas holdup in the liquid phase are studied. The results indicate that gas distributes evenly in the large rotating speed. Increasing the injection speed and immersion depth of nozzle can raise obviously gas holdup in the stirring vessel, and the distribution of the gas holdup in the eccentric stirring case is better than that in the centric stirring case.In order to get closely to the actual process of production, the high temperature model of the KR mechanical stirring method for the molten iron is developed as well. The effects of center and eccentric stirrings, rotating speed, immersion depth, and impeller type on the fluid flow in the stirring vessel are studied. The results illustrate that large rotating speed and long blade can induce high fluid velocity, and the immersion depth of the impeller has large influence on the distribution of fluid flow, while the distribution of fluid flow and turbulence kinetic energy in the eccentric stirring case is better than those in the centric stirring case. The optimum conditions for the high temperature model of the molten iron can be obtained when the rotating speed, immersion depth, and impeller shape are taken to be3.5s-1,0.15m, and220mm×50mm×50mm, respectively under the eccentric stirring.In this dissertation, the platform of numerical simulation for the characteristics of fluid flow in stirring vessel has been developed successfully, and the results obtained from this dissertation are of guidance importance to the optimization of desulphurization technique in molten iron pretreatment.