Use of physical modelling to study how to increase the production capacity by implementing a novel oblong AOD converter

Abstract

There is no known example of an AOD converter with oblong cross sections in the literature. Changing the geometry of the converter vessel, from the traditional circular cross sections, to increase converter volume could potentially influence the performance of the converter and in particular the decarburisation rate. To study the feasibility of implementing an oblong converter, physical modelling was used to study the fluid flow of the proposed converter configuration, geometry and number of tuyeres, and the potential influence on the decarburisation rate. Two water models were employed using water containing NaOH and gas injected through six or eight tuyeres as fluids. In the model, CO 2 gas was injected and the reaction of CO 2 and NaOH was indirectly measured by detecting the pH value of the water. The mixing time is considered to be a good indicator of the decarburisation as kinetics will be diffusion controlled in the latter period of the process. The following three configurations were studied: (i) a circular converter with six tuyeres, (ii) an oblong converter with six tuyeres, and (iii) an oblong converter with eight tuyeres. The mixing time can be used to evaluate the different converter configurations. The average CO 2 concentrations based on several experiments, differed by less than 5% between the circular and oblong models after 165 s of injection of air and CO 2 . The results also showed that no difference in mixing time could be found when using 6 and 8 tuyeres, respectively in the oblong model, where the CO 2 concentrations differed by less than 2% after 165 s of injection time of air and CO 2 . Based on the findings, it has been observed that the influence of converter geometry on mixing time is small, it was concluded that decarburisation rate is likely to be the same irrespectively of converter geometry.

Physical Modeling Study on the Mixing in the New IronArc Process

“…Even though the mixing time have been investigated earlier by using water modeling, it is not common that the effect of the tuyere number on the mixing has been investigated. Samuelsson et al investigated the influence of the nozzle number on the mixing time for an oblong converter, by using a small scale AOD model. Their results showed that the amount of tuyeres has an insignificant effect on the mixing time, when comparing the use of 6 and 8 tuyeres.…”

“…Thus, they works as a counterpart to each other so that the circular movement of the surface is greatly reduced. It becomes more of an extreme case when comparing 3 and 1 gas inlets, with inlets placed on opposite sides to each other, compared to 6 and 8 inlets positioned at the same side, as investigated by Samuelsson et al With the same flow rate for the three inlet case, the flow rate per inlet was one third compared to when only one inlet was used. Hence, the velocity per inlet was reduced to 14.7 m s −1 compared to 44 m s −1 for the one‐inlet case.…”

“…The flow rate was scaled based on Equation . This is frequently used for scaling of flow rates when the modified Froude number is used as the similarity criteria where Q m (m 3 s −1 ) is the flowrate for the downscaled model, Q R (m 3 s −1 ) is the flowrate in the real process, and is the scale factor with the value of 1/3 in this case.…”

“…The tracer used for the determination of mixing time was a food color and a photometer probe connected to a photometer was used to determine the concentration of the tracer in the water. Also, Samuelsson et al investigated the mixing time of a 1:4.6 scaled of a 120 t AOD vessel with the aim to increase the production capacity. Also, a comparison between 6 and 8 gas inlets were made.…”

A Physical Modeling Study on Slag Behavior in the AOD Converter Process

“…Therefore, physical modeling has become an important way to understand some phenomena in the AOD process. Previous physical modeling work focusing on AOD processes includes studies of the mixing time in AOD converters, the effect of fluid flow on erosion and wear of the refractory, the penetration depth of gas injection, the oscillation phenomenon, and so on. Parameters which influence these phenomena have been vastly investigated, with the aim to improve the control of the production process and to increase the understanding of the process.…”