Fluid Flow and Mixing Phenomena in Mechanically Agitated and Gas Stirred Ladle Systems and Their Comparisons

Abstract

A sliding mesh-based LES (large eddy simulation) mathematical model has been developed to investigate fluid flow and mixing phenomena in a mechanically agitated (MA) water model ladle (D = 0.30 m) fitted with an impeller/paddle. Parallel to such, liquid velocity and 95% bulk mixing times were experimentally measured as a function of rotational speed of the impeller. These were applied to validate mathematical model predictions. On the basis of results derived from the present physical and mathematical modelling investigation and already published data on gas stirred (GS) ladle systems, a performance comparison between mechanical and gas agitated systems has been presented. It is shown that at specific stirring power, similar to those practised in ladle refining (~10 −3 W/kg), while intensity of motion is more pronounced and mixing is considerably faster, corresponding flow establishment periods are relatively longer in the mechanically agitated system. Furthermore, while relationship between mixing time -specific stirring power in both the systems are found to be very similar e.g.,, markedly different and contrasting dependence of mixing time on liquid depths i.e., τ mix,95%,MA ∞H 1.8 vs. τ mix,95%,GS ∞H −1.0 in the two systems have been observed. In addition to such, dynamic similarity criterion for mechanically agitated systems has been investigated and it is demonstrated that similar to gas stirred ladle systems, a Froude based modelling criteria suffices. KEY WORDS: mechanically agitated system; mathematical modelling; fluid flow and mixing phenomena; comparison with inert gas stirred ladle systems.

Influence of Electromagnetic Field on Stirring Energy in Selected Metallurgical Equipment

“…Moreover, in the case of the commonly known gas stirring, the flow behavior is characterized mainly by laminar flow with extensive areas of stagnant flow. Additionally, the authors [8,[16][17][18] focus on the evaluation of the stirring energy based on the flow rate of the gas via plugs, which is not included in the EMS-stirred cases. The lack of a formula valid for EMS cases motivated authors to propose a new approach.…”

“…The stirring energy as an indicator is well known in the gasstirred systems, [5,[16][17][18] but for relatively new solutions, like EMS, it is difficult to properly estimate its value inside the equipment. The lack of literature on that topic, due to the limitations of measurement methods of the effectiveness of stirring in the past, motivated authors to develop the formula for the evaluation of stirring energy in EMS-stirred devices.…”

Development and Validation of Computational Fluid Dynamics Model of Ladle Furnace with Electromagnetic Stirring System

“…Different methods such as gas stirring [3], mechanical stirring [4] and electromagnetic stirring [5,6] can realize an increase in the mixing process in the ladle furnace. As EMS (electromagnetic stirring) systems seem to have great potential in increasing mixing efficiency, a proper design of a ladle furnace with EMS was tackled in the current paper.…”