Experimental Study on Mixing in Gas-Stirred Ladles with and without the Slag Phase through a Water Physical Model

Abstract

A 1/6 th gas-stirred water physical model of a 140 ton steel ladle is used to evaluate mixing in air-water and air-water-oil systems to model argon-steel and argon-steel-slag systems respectively. Thickness of the slag layer is kept constant at 0.004 m. The effect of the gas flow rate (7, 17, and 37 l/min), plug position (0, 1/3, ½, and 2/3 of the ladle radius, R), and number of plugs (1, 2, and 3) on mixing time is also analyzed in this work. Gas is injected at the bottom of the ladle under several plug configurations varying both position and number of plugs. Chemical uniformity of 95% is selected as mixing criterion. Mixing times are experimentally determined when a tracer is suddenly injected into the ladle and the model is instrumented with a pH meter to track the time evolution of the tracer concentration (NaOH 1 M solution) in a given location inside the ladle. Process conditions for best mixing in both water-gas and water-gas-slag systems are: a single plug located at 2/3 of the ladle radius with a gas flow rate of 17 l/min.

Effect of Slag on Mixing Time in Gas-Stirred Ladles Assisted with a Physical Model

“…Physical properties of all the other substances in the model and in the ladle furnace are also presented in Table I. Further details on the experimental conditions and experimental setup can be found in [10]. Table I.…”

“…Some of these factors (which do not include the slag layer yet) may be estimated by experimental measurements or by using equations (6), (7) and (8) which are related to the dissipation of energy due to the conversion of input energy to turbulence energy dissipation ( TED ), due to the bubbles ( Bub ) and due the walls ( Wall ) respectively. It is also assumed that when the opening of the slag occurs, during bubbling, the exposed surface present some factors of energy dissipated computed by equations (9) and (10). Calculations of all these factors are shown in Table II, which are used to estimate the effect of the slag layer on the mixing time in the ladle furnace.…”

Physical Simulation of Molten Steel Homogenization and Slag Entrapment in Argon Blown Ladle

“…Therefore, considering the mixing time and slag entrainment, the optimized injection mode for the prototype ladle is the double porous plug with a flow rate of 36-42 m 3 /h. Using multiple linear regression, the relationship between dimensionless mixing time, dimensionless flow rate and dimensionless oil layer thickness was fitted by Equation (13). The coefficient of determination (R square) of fitting Equation (13) is equal to 0.942, which indicates that the equation has a high fitting degree and may be used to calculate the mixing time of the ladle with double porous plugs.…”

“…% = 21.30098 − 660.60213 ⋅ ℎ * + 45.37523 ⋅ * (14) where, S% is the percentage of the slag eye area to the molten bath surface area. Equations (13) and (14) use dimensionless experimental data, and the determinant coefficient shows that equations have a high fitting degree, so for the general ladles, Equations (13) and (14) can be used to calculate the mixing time and bare steel area by flow rate and slag layer thickness. However, in the process of dimensionless data processing, the characteristic flow rate is a fixed value, geometric similarity ratio has an effect on dimensionless flow rate, so the equations can not be directly used in the ladle.…”

“…Some researchers found that eccentric bottom blowing is in favor of bath mixing in the ladle [7,10]. Some investigators also found that the position of porous plugs, gas flow rate and the size of ladle have an abundant influence on bath mixing in the ladle [4,5,[11][12][13][14][15][16][17]. It was discovered that the top slag layer could consume some part of kinetic energy of flow and enlarge the mixing time of the ladle [18][19][20][21][22].…”