An improved lance design for hot metal de-sulphurisation

Abstract

Hot metal de-sulphurisation is a dip-lance process involving the pneumatic injection of fine-grained de-sulphurisation reagents into the molten metal. For maximum efficiency the particles must be dispersed in the ladle as widely as possible to increase the total interfacial area which is primarily controlled by the lance design. Seven different lance configurations were modelled and simulated to determine the most efficient design using physical and mathematical modelling approach. A 0.25 scale plexi-glass model of the 100 T hot metal ladle was fabricated for the study. Residence time and mixing time studies were carried out using the electrical conductivity measurement technique through stimulus response of injected saturated salt solution. Mathematical modelling approach using momentum balance was used to simulate fluid flow profile of lance-ladle assembly under operating conditions using computational fluid dynamics package ANSYS-CFX. Based on the studies a new curved port lance has been designed which resulted in uniform and swirling flow profile inside the ladle without rotating the lance. Injection through the new lance increased the residence time of the particles and reduced the dead zones. The new design was fabricated and experimented at de-sulphurisation stations and has resulted in reduced flux consumption and treatment time.

A Review of Modeling Hot Metal Desulfurization

“…The flow fields calculated for reagent injection with a submerged lance in ladles are qualitatively similar to the results of the CFD simulations by Pirker et al for slag regeneration using an injection of oxygen with an eccentrically positioned submerged lance. Similar to El‐Kaddah and Szekely, Pirker et al reported that the bath movement was more vigorous using deeper position of the lance.…”

“…Recently, Tripathi et al used physical modeling and a multiphase CFD model to study the effect of seven different lance port designs on mixing time in the case of desulfurization with CaC 2 in a ladle. As for simulations for a real ladle, hot metal, gas, and particles were considered as continuous phase, dispersed gas phase, and dispersed solid phase, respectively.…”

“…Contours of velocity at the central plane of a physical model with different submerged lance designs: a) straight lance, b) T‐lance, c) two ports included at 45° angle in mutually opposite directions (T‐45), d) two ports included at 15° angle in mutually opposite directions (T‐15), e) four ports in mutually perpendicular directions (TT), f) two curved ports in mutually opposite directions (C‐45), and g) two spiral ports in mutually opposite directions (H‐45). Reproduced with permission . Copyright 2017, Taylor & Francis.…”

“…The residence time of reagent particles affects their microkinetic efficiency to a great extent. In the study by Tripathi et al, the longest particle residence times were achieved with a lance with two spiral ports in mutually opposite directions (H‐45), followed by a using a lance with two curved ports in mutually opposite directions (C‐45). The residence times associated with straight and T‐lances used in typical operating practice were 25 and 23 s, respectively.…”

“…Relatively early on there were attempts to predict the overall desulfurization kinetics on the process scale with the help of mathematical modeling. In addition to thermodynamic‐kinetic aspects, research has been directed at studying different physical aspects of hot metal desulfurization, including fluid flows, bath mixing, reagent injection, and reagent dispersion …”