A physical and mathematical modeling study has been carried out to investigate mixing in a gas stirred ladle fitted with dual plugs, located diametrically opposite at Ϯ1/2 R positions. While conductivity measurement technique was applied to record 95 % mixing times, mathematical modeling was carried out via the commercial CFD package FLUENT ® wherein, a two phase flow calculation procedure based on discrete phase approach was adapted. It was demonstrated that numerically predicted flow and mixing times in general agree reasonably well with the corresponding experimental measurements.In addition to the above, a relatively simple, quasi single phase flow calculation procedure, developed inhouse, was also applied to predict mixing times and thereby, assess an earlier work. It is shown that the quasi single phase model, despite its simplicity, is reasonably effective in simulating mixing phenomena in such system. A comparison between different modeling approaches vis a vis experimental measurements is also illustrated in the text.KEY WORDS: dual plug stirred ladles; flow; mixing; discrete phase modeling; quasi single phase modeling; experimental measurements; comparison.ladle are reported in the subsequent sections.
Present WorkIn the present study, mathematical modeling was carried out adopting two conceptually different approaches namely, the discrete phase and the quasi single phase procedures; the former via the commercial CFD package FLUENT ® and the later via a three dimensional, turbulent flow calculation procedure developed in house. Parallel to these, experiments were carried out on a 0.20 scale water model of a 210 T industrial lade and 95 % mixing times were measured over a wide range of operating conditions (viz., liquid depth, gas flow rate etc.). In this section, a summary of the computational and experimental procedures is presented.
ExperimentalMixing times were measured in a cylindrical vessels (I.D.ϭ0.60 m) in which, water was agitated by injecting air or N 2 , in 1 : 1 proportion, through a pair of nozzles located at the bottom of the vessel at the mid bath radius position. Prior to monitoring mixing, air/N 2 was bubbled into the water bath at the desired flow rate for a few minutes to ensure the stability of the flow in the vessel as well as to remove any inhomogeneities present in the bath. The gas flow rates were so chosen to ensure gentle stirring condition as are typically encountered in actual ladle metallurgy steelmaking operations 1) (viz., ϳ0.001 to 0.015 Nm 3 /t · min). While lower end flow rates are typically used for bath homogenization (i.e., of thermal and/or material), relatively large gas flow rates are used to achieve enhanced slag-metal reactions. However, as the primary objective of this study was to ascertain the general adequacy of mixing models, consequently it was deliberately decided to employ only a small fraction of the above mentioned range of gas flow rates, such that some meaningful experimental data, required for validation of the mathematical models can be derived.A ...