Foams and Emulsions in Steelmaking

The bloating behavior of metal droplets and the dephosphorization behavior of bloated droplets at 1853 K (1580°C) were investigated using X-ray fluoroscopy coupled with constant volume pressure change measurements and chemical analysis of quenched samples. The effect of sulfur content on dephosphorization kinetics was studied during the decarburization period. The slag foamed during the reaction forming a foamy layer over a dense layer. After a short incubation period, the droplets became bloated due to internal decarburization. The bloated droplets floated from the dense slag into the foamy slag. The behavioral changes are directly related to the effect of sulfur on the incubation time for swelling. The dephosphorization reaction was very fast; droplets with low sulfur contents experienced phosphorus reversion shortly after entering the foamy slag, while those with higher sulfur content took a longer time to swell and went through reversion before they entered the foam. The dephosphorization rate and maximum phosphorus partition were higher at lower CO evolution rates because the dynamic interfacial oxygen potential increased with the decreasing oxygen consumption rate. The rate controlling step for dephosphorization was initially a combination of mass transport in both the metal and the slag. As the iron oxide in the slag was depleted, the rate control shifted to mass transport in slag.

Section: Introductionmentioning

confidence: 99%

The Influence of Sulfur on Dephosphorization Kinetics Between Bloated Metal Droplets and Slag Containing FeO

Dogan

Coley

2017

“…Reported residence times ranging from 0.4 to 120 seconds are given, with an average of around 40 seconds. [24][25][26][27][28][29][30] The amount of metal in the emulsion has been reported in a complete range of up to 50 pct of the tap weight dependant on blow time. [31,32] With regard to the kinetics of a specific metal droplet in the emulsion, several authors have investigated variable aspects (point 3 & 4 above).…”

Section: Introductionmentioning

confidence: 99%

Investigation into the Cause of Spontaneous Emulsification of a Free Steel Droplet; Validation of the Chemical Exchange Pathway

Spooner

Assis

Warnett

et al. 2016

Small Fe-based droplets have been heated to a molten phase suspended within a slag medium to replicate a partial environment within the basic oxygen furnace (BOF). The confocal scanning laser microscope (CSLM) has been used as a heating platform to interrogate the effect of impurities and their transfer across the metal/slag interface, on the emulsification of the droplet into the slag medium. The samples were then examined through X-ray computer tomography (XCT) giving the mapping of emulsion dispersion in 3D space, calculating the changing of interfacial area between the two materials, and changes of material volume due to material transfer between metal and slag. Null experiments to rule out thermal gradients being the cause of emulsification have been conducted as well as replication of the previously reported study by Assis et al. [1] which has given insights into the mechanism of emulsification. Finally chemical analysis was conducted to discover the transfer of oxygen to be the cause of emulsification, leading to a new study of a system with undergoing oxygen equilibration.

“…For a given h/de, equating Eq. [9] and Eq. [10], enthalpy H at impingement point of the jet can be calculated.…”

Section: Modelling Of Jet Axial Velocity and Density At Impingement Pmentioning

confidence: 99%

“…There are several high temperature experimental results available in the literature, in which the amount of metal in the emulsion is measured in a real BOF process. [8,9,11,20] In the recent study by IMPHOS [20] in a 6 tonne pilot scale converter, it was observed that the estimated droplet mass in emulsion calculated by using blowing number correlation only accounts for ~0.25% of hot metal weight as compared to experimentally observed value of ~21% during the entire blowing period. In addition, the authors reported that the ejected hot metal predicted from the Subagyo's correlation is not sufficient to explain the observed phosphorus removal rate in slag-metal emulsion.…”

Section: Introductionmentioning

confidence: 99%

“…[1][2][3][4][5][6][7] The existence of large quantities of these small sized drops generated from splashing along with their bloating behaviour in slag-metal-gas emulsion creates a large interfacial area, that in part explains the fast refining kinetics of reactions in a BOF. [8][9][10][11] In the recent past, several researchers attempted to simulate the physical phenomena of refining process inside the BOF by use of computational models. Those models include capturing the complex dynamic events associated with the process such as cavity formation, droplet generation [12][13] , bloating of droplets in slag-metal emulsion [14] for simulating the overall reaction kinetics.…”

Section: Introductionmentioning

confidence: 99%

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Modeling of Droplet Generation in a Top Blowing Steelmaking Process

Rout

Brooks

Subagyo

et al. 2016

Quantification of metal droplets ejected due to impinging gas jet on the surface of liquid metal is an important parameter for the understanding and for the modelling of the refining kinetics of reactions in slag-metal emulsion zone. In the present work a numerical study has been carried out to critically examine the applicability of droplet generation rate correlation previously proposed by Subagyo et al. on the basis of dimensionless blowing number (NB). The blowing number was re-evaluated at the impingement point of jet with taking into account for the temperature effect of change in density and velocity of the gas jet. The result obtained from the work shows that the modified blowing number NB,T at the furnace temperature of 1873K (1600 °C) is found to be approximately double in magnitude compared to NB calculated by Subagyo and co-workers. When NB,T has been employed to the Subagyo's empirical correlation for droplet generation, a wide mismatch is observed between the experimental data obtained from cold model and hot model experiments. The reason for this large deviation has been investigated in the current study and a theoretical approach to estimate the droplet generation rate has been proposed. The suitability of the proposed model has been tested by numerically calculating the amount of metals in slag. The study shows that the weight of metals in emulsion falls in the range of 0 to 21 wt pct of hot metal weight when droplet generation rate has been calculated at ambient furnace temperature of 1873K (1600 °C).