Ruhrstahl-Heraeus Process Research Articles

Numerical Simulation of the Density Effect on the Macroscopic Transport Process of Tracer in the Ruhrstahl–Heraeus (RH) Vacuum Degasser

Silicon steel (electrical steel) has been used in electric motors that are important components in sustainable new energy Electrical Vehicles (EVs). The Ruhrstahl–Heraeus process is commonly used in the refining process of silicon steel. The refining effect inside the RH degasser is closely related to the flow and mixing of molten steel. In this study, a 260 t RH was used as the prototype, and the transport process of the passive scalar tracer (virtual tracer) and salt tracer (considering density effect) was studied using numerical simulation and water model research methods. The results indicate that the tracer transports from the up snorkel of the down snorkel to the bottom of the ladle, and then upwards from the bottom of the ladle to the top of the ladle. Density and gravity, respectively, play a promoting and hindering role in these two stages. In different areas of the ladle, density and gravity play a different degree of promotion and obstruction. Moreover, in different regions of the ladle, the different circulation strength leads to the different promotion degrees and obstruction degrees of the density. This results in the difference between the concentration growth rate of the salt tracer and the passive scalar in different regions of the ladle top. From the perspective of mixing time, density and gravity have no effect on the mixing time at the bottom of the ladle, and the difference between the passive scalar and NaCl solution tracer is within the range of 1–5%. For a larger dosage of tracer case, the difference range is reduced. However, at the top of the ladle, the average mixing time for the NaCl solution case is significantly longer than that of the passive scalar case, within the range of 3–14.7%. For a larger dosage of tracer case, the difference range is increased to 17.4–41.1%. It indicates that density and gravity delay the mixing of substances at the top area of the ladle, and this should be paid more attention when adding denser alloys in RH degasser.

Kinetic Analysis for Steel Desulfurization during Ruhrstahl–Heraeus Process

A kinetic model for the Ruhrstahl–Heraeus (RH) desulfurization process is established based on the FactSage Macro Processing. The desulfurizer addition, the desulfurization reaction, the steel mixing, the flow circulation, and the desulfurizer floating during the RH refining process are considered in the model. Simulated results agree well measured results, indicating that the current model can be used to predict the desulfurization reactions during the RH refining process. The CaO activity increases with a higher CaO/Al2O3 ratio and a lower SiO2 content, which exhibits a similar tendency with the desulfurization ratio. It is indicated that it is necessary to increase the CaO activity in the desulfurizer to improve the desulfurization ratio. The S content in the molten steel decreases with time and a higher ratio of the powder blowing. The cost increases with time due to the refractory erosion and the steam consumption. The cost of the desulfurizer added by the powder blowing is lower than that of the gravity sinking.

Comparative Study of the Cleanliness of Interstitial‐Free Steel with Low and High Phosphorus Contents

Herein, a study comparatively investigating the total oxygen (TO) and nitrogen (N) contents, evolution of inclusions, variations in slag composition, and nozzle clogging during the production of an interstitial‐free (IF) steel and a P‐containing high‐strength (HS) IF steel is presented. The results show that during the production of both steels, the TO content gradually decreases after the deoxidation, with the TO content in the molten steel in the tundish below 30 ppm. There is no significant variance in the N content. The two steels have similar quantities of small inclusions of similar types and sizes. However, the P‐containing HS IF steel has a much higher content of large inclusions, which mainly come from the entrapped mold powder and peeled‐off nozzle clogging. Compared to the common IF steel, the P‐containing HS IF steel has a higher MnO content in the slag during the Ruhrstahl–Heraeus process, compromising cleanliness control; the P‐containing HS IF steel has more significant mold liquid‐level fluctuations and more nozzle clogging, which mainly consists of Al2O3 and TiO2. The cause of these issues during the production of the P‐containing HS IF steel is concluded to be related to the high P content.

Gray-Box Model to Control Molten Steel Temperature in Tundish

Controlling molten steel temperature in a tundish is crucial for stable and efficient production of steel products. In this research, a gray-box model is developed by combining a first-principle model and a statistical model. The first-principle model predicts the molten steel temperature in the tundish, and the statistical model predicts the prediction error of the first-principle model. The derived model was then used to derive the molten steel temperature in the Ruhrstahl-Heraeus process at the end of its operation from the target molten steel temperature in the tundish and other process variables. The result of applying the proposed model to real operation data has demonstrated its practicability.

863. Steel degassing. Part 3: The Ruhrstahl-Heraeus process: J D Sharp, Iron Steel, 38, June 1965, 334–336

This paper investigates the usefulness of the Hazard and Operability technique, (HAZOP) as a tool for predicting relevant accident scenarios by applying this technique, together with a specific design analysis technique, in a Dutch steelworks. Adaptation of the hazop guide words to the steelworks process functions enables the identification of possible production deviations in the newly built ladle arc furnace and in the transport to and from the furnace. The deviations, which are all related to disturbances in the production process, are clustered on a common consequence base and by assigning high and low incidence grades to the clusters, 13 accident scenarios can be formulated. Reviewing 16 months of experience with the ladle arc furnace shows that 58% of actual deviations can be brought under the defined production-related accident scenarios. Another 28% can be explained by introducing three additional maintenance-related accident scenarios.