Effect of Gas Blown Modes on Mixing Phenomena in a Bottom Stirring Ladle with Dual Plugs

Abstract

Gas stirring plays a significant role in steelmaking process. The stirring effect is often assessed by the mixing time. In the past, the effects of many factors such as the number and position and relative angle of porous plugs in a ladle, as well as gas flowrate on the mixing time have been studied and some beneficial results used in industrial practice. However, for a ladle with dual plugs, the researches on gas flowrate basically focused on the blowing mode with the same gas flowrates for every plug (Mode-S), while the mode with different flowrates (Mode-D) has not yet been reported. In the present work, a water model for a 120 t ladle is carried out to mainly compare the effect of the two gas blowing modes on mixing. Two porous plugs are located at 0.55-0.70R (R is the radius of ladle bottom), with different relative angles (45-180°) and total flowrates (6.92-18.45 NL/min). The results show that Mode-D can significantly change the mixing time. Compared with Mode-S, the mixing time is respectively decreased by 50 seconds at 6.92 NL/min and 30 seconds at 18.45 NL/min when the plug positions are located at 0.64R. The results of mathematical simulation explain the phenomena. In the Mode-D, the strong gas plume forms a larger circulation flow to stir the ladle and the weak plume forms a smaller one. Under this case, the interference and collision from two plumes are weakened and the dissipation of stirring energy is decreased, thus the mixing time is shortened.

Physical Modeling Evaluation on Refining Effects of Ladle with Different Purging Plug Designs

“…This may be a consequence of the effective increase in the blown area for the same gas flow. As has been previously reported, stirring energy is a crucial factor during molten mixing in the ladle, and mainly depends on the gas flow rate . Figure also shows that the difference in the mixing time for different slit diameters is insignificant when the gas flow rate is larger than 3.01 NL min −1 ; this trend agrees well with the previous research .…”

“…In a typical secondary refining technique, argon gas is blown into the molten steel from the bottom of the ladle furnace through purging plugs. Bubbles are successively formed at the exit of the purging plugs, rise upward entraining the surrounding molten steel into their wakes, turn horizontally at the bath surface, push the slag layer to the periphery of the ladle, and escape from the bath surface into the atmosphere . Meanwhile, the inclusions are attached to the rising bubbles and come up to the slag layer with the bubbles .…”

Optimization of the Mixing Time Using Asymmetrical Arrays in Both Gas Flow and Injection Positions in a Dual-plug Ladle

“…distribution 14) or in the location of the plugs. 15) On the other hand, there have been reports that correlate the mixing time with the gas flow and the slag layer. [16][17][18][19][20][21][22] However, there are numerous variables that affect the mixing time such as gas flow rate, number and location of porous plugs, slag layer type and thickness, ladle capacity, etc.…”

“…In this work, the best cases employing dual porous plug to reduce the mixing times of some studies [5][6][7]11,15,26,27) have been used to build the experimental design. The total argon flow was 1.0 Nm 3 ·min − 1 , divided between the two injections.…”

Numerical Modeling of Open-Eye Formation and Mixing Time in Argon Stirred Industrial Ladle

“…Haiyan et al [21] and Madan et al [22] studied the effect of gas flow rate on the mixing phenomenon in a bottom-stirring ladle with dual plugs. Wu et al [23] and Thunman et al [24] studied the effect of gas flow rate and slag layer thickness on the open-eye formation and slag entrainment in water model ladles.…”