Mixing time and correlation for ladles stirred with dual porous plugs
- PDF / 134,785 Bytes
- 9 Pages / 612 x 792 pts (letter) Page_size
- 45 Downloads / 186 Views
I. INTRODUCTION
THE efficiency of many chemical processing operations carried out in the present day steelmaking ladles is intricately related to mixing phenomena. Mixing enhances chemical reactions by bringing in reactants together and removing products from reaction sites. In addition, it also influences the extent of thermal and particulate inhomogeneities within the ladle. It is therefore desirable to ascertain the extent of mixing in order to evaluate the process performance of argonor nitrogen-stirred ladles. Mixing phenomena, by and large, have been investigated in aqueous models of gas-stirred ladle systems in which a centrally or an asymmetrically placed single porous plug/nozzle is used to stir the contents of the ladle. A great deal of information on these is already available in the literature and summarized by Mazumdar and Guthrie[1] in a review. While fluid model studies on gas-stirred systems using a single, axisymmetric/asymmetric plug/nozzle have been relatively common, not much information on ladles fitted with dual plugs/nozzles is available in the literature. It is to be noted that occasionally it might be necessary to bubble an industrial ladle with two or more porous plugs, in order to achieve gentle but rapid JAYANTA MANDAL, Engineer, is with Ispat Industries, Dolvi, Maharastra, 402107, India. SUJOY PATIL, Graduate Student, M. MADAN, Senior Project Associate, and DIPAK MAZUMDAR, Professor, are with the Department of Materials and Metallurgical Engineering, Indian Institute of Technology, Kanpur, 208016, India. Contact e-mail: [email protected] Manuscript submitted September 18, 2003. METALLURGICAL AND MATERIALS TRANSACTIONS B
mixing, as well as to promote better slag/metal intermixing and to avoid explosive degassing effects under vacuum. Given such, the relevance of the present study to industrial steelmaking practice is readily apparent. Joo and Guthrie[2] were among the first to investigate mixing phenomena in a ladle fitted with twin porous plugs both experimentally and computationally. Their study indicated that shorter mixing times (relative to conventional axisymmetrical/ asymmetrical gas bubbling) can be achieved by injecting gases through two porous plugs, located diametrically opposite at midbath radius position (i.e., at 1/2R). Reconstructed from Reference 2, this is shown in Figure 1, in which mixing times for an axisymmetrically placed single porous plug/nozzle is shown vis รก vis the same for twin plug bubbling as a function of net gas flow rates. There, it is at once evident that the twin plug configuration ensures relatively faster mixing only at moderately higher gas flow rates. The figure also appears to suggest that such advantages associated with twin plug bubbling are likely to fade away at lower operating gas flow rates. This aspect, however, was not given sufficient attention by Joo and Guthrie in their work and has not since been confirmed through any subsequent investigation. In a later work, Zhu et al.[3] carried out similar investigations on ladles fitted with one
Data Loading...
