Physical Modeling of Bottom-Blown Continuous Steelmaking, Part I: The Decarburization Reaction Model and Water Modeling Results

摘要

Several of the previous continuous steel-making processes were reviewed. Since many of the processes were rather complex, difficult to control and not commercially feasible, a simple continuous stirred tank reactor was considered in one of the flow sheets proposed by the AISI Direct Steelmaking Initiative. A decarburization model for the continuous refiner was developed to predict the steady-state carbon content being tapped as a function of metal throughput, input carbon content and decarburization constant. The model assumes perfect mixing, a first order reaction rate and an overall reaction that is mass transfer controlled. Mixing time experiments showed that mixing times decrease rapidly as gas flow rate increases. Water modeling results from this study and those reported by other investigators were combined to yield a correlation that relates mixing time to specific energy input (pin = 89eppsilon~(-.036)). The mixing times of both the water model and industrial vessels experience a similar dependence on the specific stirring energy, but the mixing times in the smaller water model vessels are almost an order of magnitude lower than the industrial vessels. Residence time distribution experiments indicated that the vessel is perfectly mixed. This was further supported by the fact that the mixing time was two orders of magnitude smaller than the average retention time and less than the minimum residence time.