Modeling on Heat Transfer in a Steel Ladle During Holding Period

A 1/4-scale hot-water model of industrial 107-tonne steel ladles was established in the laboratory. With this physical model, thermal stratification phenomena due to natural convection in steel ladles during the holding period before casting were investigated. By controlling the cooling intensity of the water model to correspond to the heat loss rate of steel ladles, which is governed by dimensionless numbers Fr and βΔT, temperature distributions in the water model can simulate those in the steel ladles. Consequently, the temperature profile in the hot-water bath in the model can be used to deduce the thermal stratification phenomena in liquid steel bath in the ladles. In addition, mathematical simulations on fluid flow and heat transfer both in the water model and in the prototype steel ladle were performed using a computational fluid dynamics (CFD) numerical method. The CFD model was validated against temperatures measured in the water model. Comparisons between mathematically simulated temperature profiles in the prototype steel ladle and those physically simulated by scaling-up the measured temperature profiles in the water model showed a good agreement. Therefore, it can be concluded that, as long as accurate heat loss information is known, it is feasible to use a 1/4-scale water model to non-isothermally simulate fluid flow and heat transfer in steel ladles during the holding period before casting.

By means of CFD numerical modeling, a systematic analysis of the similarity between steel ladles and hot-water model regarding natural convection phenomena was studied. The key similarity criteria we found to be dependent on the dimensionless numbers Fr and βΔT. These similarity criteria suggested that hot-water models with scale in the range between 1/5 and 1/3 and using hot water with temperature of 45 °C or higher are appropriate for simulating natural convection in steel ladles.With this physical model, thermal stratification phenomena due to natural convection in steel ladles were investigated. By controlling the cooling intensity of water model to correspond to the heat loss rate of steel ladles, which is governed by Fr and βΔT, the temperature profiles measured in the water bath of the model were to deduce the extent of thermal stratification in liquid steel bath in the ladles. Comparisons between mathematically simulated temperature profiles in the prototype steel ladles and those physically simulated by scaling-up the measured temperatures profiles in the water model showed good agreement. This proved that it is feasible to use a 1/5 scale water model with 45 °C hot water to simulate natural convection in steel ladles. Therefore, besides mathematical CFD models, the physical hot-water model provided an additional means of studying fluid flow and heat transfer in steel ladles.

The present paper describes a numerical investigation of thermal stratification in a ladle with molten steel with and without gas injection. Transient flow and thermal stratification in the ladle without gas injection is first simulated. The ladle refractory layers including the working lining, safety lining, insulation layer and steel shell were simultaneously taken into account. The results were then used for the simulation of transient flow and heat transfer in the ladle with gas injection from the central bottom. The flow patterns, the histories of both steel and inside ladle wall temperature, the thermal stratification history and the heat loss rate from the steel to the ladle refractory layers are given. Predictions are compared with experimental data in an identical industrial ladle for the flow and heat transfer behaviour for the cases with and without gas injection and good agreement is achieved.Le présent document décrit une investigation numérique de la stratification thermique dans une poche de coulée d'acier fondu, avec et sans injection de gaz. On a d'abord simulé l'écoulement transitoire et la stratification thermique dans la poche de coulée, sans injection de gaz. On a pris en compte simultanément les couches réfractaires de la poche de coulée, incluant le revêtement de travail, le revêtement sécuritaire, la couche d'isolation et l'enveloppe d'acier. On a ensuite utilisé les résultats pour la simulation de l'écoulement transitoire et du transfert de chaleur dans la poche de coulée avec injection de gaz par le bas, au milieu. On donne les patrons d'écoulement, l'histoire de la température, tant de l'acier que de la paroi interne de la poche de coulée ainsi que l'histoire de stratification thermique et le taux de perte de chaleur de l'acier vers les couches réfractaires. On compare, avec les données expérimentales d'une poche de coulée industrielle identique, les prédictions du comportement d'écoulement et de transfert de chaleur pour les cas avec et sans injection de gaz, et l'on obtient un bon accord.

This work presents a summary of the main tools and contributions, since the 2000s, to solve temperature control problems and to predict thermal temperatures in steel ladles. We discuss different modeling strategies implemented to several applications related to heat transfer in steel ladles and their most relevant contributions, as well we show some of the main process parameters. Finally, future perspectives are described, mainly the advantages of the implementations based on machine learning.

Numerical experiments were performed on fluid flow and heat transfer in 107‐tonne steel ladles by 3‐step implementations of numerical models. In the first step, a 1‐dimensional numerical model was used to predict heat conduction fluxes through the ladle wall, bottom and top slag layer. In the second step, by means of computational fluid dynamics (CFD) modelling and employing the predicted heat loss fluxes as thermal boundary conditions, a 2‐dimensional CFD model was applied to simulate natural convection in steel ladles during the holding period before teeming. In the third step, a 3‐dimensional CFD model was implemented to further simulate fluid dynamics in the same ladles with drainage flows during teeming. Using these mathematical numerical models, the bulk cooling rate of the steel melt, the extent of thermal stratification during holding and the steel stream temperature during teeming were investigated for 2 types of 107‐tonne steel ladles lined, respectively, with alumina and spinel in walls. In these investigations, the following 4 parameters were considered: (i) ladle lining inside surface (hot‐face) temperature before tapping, (ii) top slag layer thickness, (iii) holding time and (iv) teeming rate. An important result of these investigations is that the concerned parameters all significantly influence the steel stream temperature during teeming, and the differences in teeming stream temperatures among different ladles, caused by these parameters, can be up to 20°C, which may be essential to temperature control in tundishes during continuous casting.

Numerical analysis for the heat transfer behavior of steel ladle as the thermoelectric waste-heat source

Desulphurization Kinetic Prediction into a Steel Ladle by Coupling Thermodynamic Correlations, Fluidynamics and Heat Transfer

This paper formulates and substantiates the list of topical problems of thermal physics in relation to hazardous production facilities that constantly arise and require prompt solutions at a metallurgical enterprise. Many problems can be successfully solved using optoelectronic equipment, such as a thermal imager. Thermal imager allows to scan the entire object completely without contact. Topical tasks that can be solved with the help of a thermal imager: monitoring and evaluation of the probability of trouble-free operation of the steel ladle lining during its heating, wear resistance of the converter during oxygen purging of the metal melt, spills of the metal melt from the converter, damage of the exit edges of the nozzles of gas-air burners, determination of the surface temperature of the walls of various furnaces, etc. In the converter, electric steel-making and other workshops, with the help of a measuring thermal imager or pyrometer, it is possible to monitor heat leaks from the production premises, to obtain the distribution of the local heat transfer coefficient on various parts of the thermal surface. It is also possible to predict the temperature condition in emergency situations, confirm the requirements for the thermal mode of the operated object, identify and control ingots and billets with regard to their grain size and uniformity in the ingot cross-section, etc. Paper presents the examples of thermograms obtained both for the steel ladle and for other objects. Formulated list and experimentally confirmed solutions of thermal problems clearly show that with the help of a thermal imager it is possible to quickly, efficiently, and reliably solve the complex problems of heat exchange and heat transfer in the subdivisions of a metallurgical enterprise.

In the current study, the fluid flow and thermal stratification during the holding period are numerically simulated. The standard k–e two-equation turbulence model is adopted to describe the turbulence. The trajectories of inclusions are calculated by the discrete phase model (DPM) considering the stochastic effect of turbulence. Two different initial conditions for the flow field are compared: the quiescent state of flow and the fluid flow induced by gas stirring. Significant differences are observed between these cases. In practice, the holding period starts from the shut-off of the gas blowing. Thus, it is proposed that the flow field at the terminal of gas stirring should be considered for the simulation of the fluid flow, heat transfer, and inclusion motion during the holding period.

Numerical Simulation of Transient Flow and Heat Transfer in a Steel Ladle During Holding Period

A numerical model has been developed to analyze the transient three-dimensional and three-phase flow in a bottom stirring ladle with a centered porous plug, which takes into account the steel, gas, and slag phases; it enables us to predict the fluid flow and heat transfer in the very important steel/slag region. The numerical results of the present model show that the obtained relationship between nondimensional areas of slag eye and the Froude number is in good agreement with the reported data.

A theoretical investigation of heat transfer in a ladle of molten steel during pouring

The effect of nozzle erosion on heat transfer in a ladle of molten steel during pouring

Numerical and experimental analysis of heat transfer behavior in a steel ladle during holding process

A two dimensional Computational Fluid Dynamics (CFD) model was developed to simulate the fluid flow and heat transfer of the molten steel in a ladle during the holding time, with gas purging from the bottom. Transient analysis of the temperature and the velocity distribution of the liquid steel during ladle standing and subsequent gas stirring was conducted, by employing a pressure-based fully-implicit finite volume approach. Stratification, which can adversely affect the quality of steel products, was seen to develop due to natural convection. Therefore, particular attention was paid to study the effect of bottom gas stirring in minimizing the thermal stratification. This was accomplished by introducing a novel approach of coupling the effects of natural convection and axisymmetric bottom gas injection. Various parametric studies was undertaken to examine the effects of standing time, gas flow rate and geometry of the ladle on the resultant thermal field. It was observed, that bottom purging situation induces a strong recirculatory flow in the molten steel bath, with an increase in the order of turbulence giving rise to thermal homogenization. The results indicate that the thermal- stratification can be effectively eliminated by a relatively gentle agitation. Homogenization takes place at a faster rate with an increase in the amount of bottom gas flow. The effect of ladle size was found to be inconsequential, in comparison to other parameters.