NUMERICAL SIMULATION OF STEEL DESULFURIZATION PROCESS IN THE GAS-STIRRED LADLE

A three-dimensional isothermal multiphase flow transient CFD model simulation of the comprehensive chemical processes, including desulfurization and reoxidation in a gas-stirred ladle during the secondary refinement process, has been investigated. The multiphase interactions and turbulence flow among steel, slag, and gas inside a ladle are simulated based VOF multiphase model and discrete model (DPM) in Fluent commercial software. A widely used theory describing the desulfurization and reoxidation processes, (Al2O3) -[O] equilibrium theory, is introduced into the model. The compositions of both steel and slag are monitored, and the mass fractions of each species in steel and slag are compared with the industrial data. There are two main stages for this study.

In the first stage, the CFD model of an 80-ton ladle is developed to simulate both the flow field and reaction rates based on literature work. Then the predicated species contents are validated with industrial measurement, which proves the accuracy of the CFD model.

The validated CFD model is applied to a Nucor Decatur two plugs bottom injection ladle in the second stage. There are two different plug separation angle scenarios: 90° and 180°, investigated in this part. Three argon gas flow rate combinations ((5/5 SCFM, 5/20 SCFM, and 20/20 SCFM) were employed. The slag eye size was validated with plant measurement. The results show that the desulfurization rate and reoxidation rate are promoted with a higher argon injection rate. When the argon injection rate is fixed, a larger separation angle improves the reaction rates.