Behavior of phosphorus in DRI/HBI during electric furnace steelmaking

In modern electric arc furnace (EAF) steelmaking, ore based scrap substitute materials are often used to control the chemistry of the steel produced and/or improve the efficiency of the process.; Metallographic investigation of commercial direct reduced iron/hot briquetted iron, DRI/HBI materials indicates that before melting, phosphorus in DRI/HBI is contained as a calcium phosphate phase in the unreduced oxide “gangue” portion of the material.; It was assumed that the kinetics of phosphorus transfer between slag and metal are limited by liquid phase mass transfer of phosphorus in the slag, metal, or both phases. An overall mass transfer coefficient, ko, was defined, which includes the effects of mass transfer in both the slag and the metal. Fundamental laboratory kinetic experiments indicate that either the slag-metal interfacial area, A, and/or the overall liquid phase mass transfer coefficient, ko, change during dephosphorization experiments. Because the contributions of the reaction area and the mass transfer coefficient to the overall rate are difficult to separate, experimental results were analyzed in terms of the mass transfer parameter, A*ko. The liquid phase mass transfer parameter for dephosphorization was found to range between 10−7 to 1 × 10−3 cm3/s for different experimental conditions.; Plant trials were conducted to directly evaluate the conditions of mass transfer in the electric furnace. Controlled mass transfer experiments were conducted on a 150 ton DC electric arc furnace. The mass transfer parameter, A*ko, for this furnace was determined to be between 1.7*104 and 3.5*105 cm3/s. An additional series of plant trials were conducted on a 150 ton AC electric furnace to examine the effects of different scrap substitute materials upon the slag chemistry, the behavior of phosphorus in the steel, and upon furnace yield. The data from these trials were also used to develop empirical models for the slag chemistry and furnace temperature as functions of time during a single heat.; A numerical process model was used to evaluate the influence of various EAF operating parameters upon phosphorus mass transfer between the slag and metal. (Abstract shortened by UMI.)...