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Increasing the oxygen supply intensity of a converter is the main method of shortening the smelting time. However, the increase in oxygen supply intensity increases the splashing rate of the smelti...

Top blown O2 + CO2 mixed injection technology with a swirling oxygen lance nozzle, which supports a larger jet radial velocity than the conventional oxygen lance nozzle, improves the impact area of the jet and thus the process efficiency of converter smelting. In this study, the jet characteristics of a 90% O2 + 10% CO2 mixture injected through a full-scale four-hole swirl nozzle was simulated and the effects of preheating temperature and gas flow rate on the jet characteristics were analyzed. Increasing the preheating temperature and gas flow rate increases the axial velocity of the jet, the core section, and the mixing degree of multiple jets. At the same injection distance, increasing the preheating temperature of the mixture increases the impact strength and area of the jet. These results can be used to adjust the gas flow rate and preheating temperature of the mixed gases in large-scale smelting operations.

The dephosphorization of converters is greatly influenced by the amount of lime added and method used. At present, the oxygen jet mixing of a certain proportion of CO2 to participate in converter smelting has been successfully applied; however, there is little research on the jet characteristics and the relationship between gas and solid particles in the process of oxygen jet mixing injection with a swirl oxygen lance.In this study, the effects of ambient temperature and powder gas ratio on the jet characteristics and particle distribution of four hole swirl oxygen lance nozzle were simulated.The results show that with an increase in the ambient temperature, the velocities of the carrier gas jet and CaO particles increase, and the distribution of CaO particles is more concentrated.

To increase the refining efficiency of the Ruhrstahl–Heraeus (RH) reactor used in steelmaking, extra gas was blown into the molten bath through the bottom of the ladle. Both water experimental and numerical simulation models were established to analyze the flow field behavior to select the optimal bottom-blowing position and to study the effects of the bottom-blowing flow rate on the flow field of the molten bath, slag eye formation, and snorkel refractory materials. The results show that the recirculation flow rate increases and the mixing time decreases with an increase in the bottom-blowing flow rate. When blowing at the optimal position, the velocity of the molten steel in the ladle increases with increasing gas flow rate, and the low-velocity zone between the down-snorkel and ladle wall disappears, but the slag eye is easily formed. The simulation and experimental results were applied to an industrial 150 t RH reactor, where the optimal bottom-blowing flow rate and position improved the refining effect without forming a slag eye or having adverse effects on the snorkel refractory. To reduce the mass fraction of hydrogen to 2.0 ppm, the required processing time was shortened by 16.40 pct, and the dehydrogenation rate was increased by 19.51 pct.

The jet performance of an oxygen lance nozzle influences the smelting rhythm, smelting index, and energy consumption of a converter. Due to the complexity of the process of converter smelting, the changing temperature and gas composition in the converter significantly impact the jet characteristics of the oxygen lance nozzle in the smelting process; however, research on the change law of jet characteristics in different smelting periods is limited. In this study, we used Ansys Fluent 17.0, which is commercially available fluid simulation software, to simulate the variation of jet characteristics of a mixed injection comprising 6% CO2 and 94% O2; the mixed injection was tested using a dual-parameter oxygen lance nozzle in the early, middle, and late stages of smelting. The results show that the increase of CO concentration and ambient temperature in the converter lead to a decrease in the attenuation rate of jet velocity, improved independence of multiple jets, and an increase in the impact area of jets on the molten pool. Thus, when designing and employing oxygen lance nozzles, the influence of ambient temperature and furnace gas composition on jet characteristics must be considered.

Iron and steel industry is a large carbon dioxide (CO2) emitter, and it is important for iron and steel enterprises to utilize CO2 as a resource in the steelmaking process. The study involves reviewing recent innovations and advances in CO2 injection in the basic oxygen furnace (BOF)–Rheinsahl Heraeus (RH) steelmaking process. In BOF steelmaking tests, CO2 injection reduces the amount of dust generation with 11.15%, increases CO concentration of the converter gas with 2.66%, increases dephosphorization rate with 6.99% and reduces the endpoint nitrogen content about 6 ppm, and protects bottom-blowing elements. In the RH refining process, CO2 injection benefits the process of dehydrogenation and removal of inclusions. Besides, some drawbacks and corresponding solutions of this technology are presented. Based on the results of a large number of theoretical and experimental studies, combining the mature technology of CO2 capture at present, a new cyclic utilization of CO2 in the BOF–RH steelmaking process is proposed to adapt for actual production in the iron and steel industry.

Supersonic jet characteristics of oxygen lance nozzles have a significant influence on smelting; however, presently, little research has been carried out to investigate the influence of wear on the jet characteristics at the nozzle exit. A numerical model and aerodynamic testing platform were developed to analyze supersonic jet characteristics under different inlet pressures and wear levels at the nozzle exit. The numerical model was first validated by comparing the numerical results with the measured data of the aerodynamic testing experiment. Then, the effects of the inlet pressure and nozzle exit wear on the jet velocity and degree of aggregation were studied. An increase in the nozzle inlet pressure is conducive to an increase in jet velocity but also causes earlier jet convergence. An increase in the nozzle exit wear results in the faster attenuation of jet velocity, not only reducing the jet velocity but also leading to an earlier convergence point for each jet. The results of this study can provide theoretical support for the design of an oxygen lance nozzle and process optimization of smelting in industrial application.

CO2 injection into RH as lifting gas was recently proposed instead of Ar. In this study, FactSage software was used for calculating the mass changes of elements in thermodynamic equilibrium with CO2 injection under vacuum condition. Compared with Ar, CO2 as RH lifting gas can be used for a small amount of decarburization without a significant increase in oxygen content of molten steel. And the carbon content of alloys can be theoretically increased by more than 12% if all CO2 participates in the reaction between CO2 and [C]. Furthermore, the industrial application research of CO2 injection into RH as lifting gas was carried out in a commercial 150t RH. The results agreed with the above theoretical trends. And the problem of aluminum loss can be solved by reducing the additive amount of aluminum alloy in the ladle furnace (LF) and replenishing the aluminum during the RH refining later stage.