Runzao Liu

Development and application of electric arc furnace combined blowing technology

A number of electric arc furnace (EAF) plants in China use high proportions of hot metal in the charge because of availability of excess liquid iron at the steelworks and/or because of the high price of scrap relative to hot metal. Liquid steel costs are still higher than the basic oxygen furnace as the EAF is not as efficient when refining liquid iron. EAF combined blowing technology has been modelled and installed in industrial plants with the aim of increasing stirring and hence improving refining. The industrial application of the combined blowing technology in a number of steel plants indicates that the combined blowing technology of EAF can effectively improve the pool stirring strength and reaction dynamics condition of the molten pool, and optimise production.

Modelling on the penetration depth of the coherent supersonic jet in EAF steelmaking

ABSTRACT The coherent supersonic oxygen supplying technology is now widely adopted in EAF steelmaking process. However, there has been limited research on the impact characteristics of the coherent supersonic jet. In this work, integrating theoretical modelling and numerical simulations, a hybrid computing model was developed to predict the penetration depth of the coherent and conventional supersonic jet. The results show that the lance height has much significant influence on the jet penetration depth, and the penetration depth of the coherent supersonic jet is much larger than that of the conventional supersonic jet at the same lance height. The k value reflects the velocity attenuation of the main supersonic jet, which is a key parameter of the hybrid computing model. Finally, the hybrid computing model and its modified models can well predict the penetration depth of the coherent and conventional supersonic jet with the error being no more than 3.92u2005pct.

Research on the Flow Properties and Erosion Characteristics in Combined Blown Converter at Steelmaking Temperature

The coupling stirring effect driven by top blown supersonic jets and bottom blown jets plays a crucial role in converter bath movement. Based on numerical simulation, jet-bath interactions inside a 110-ton commercial converter at room temperature and at steelmaking temperature were compared. Penetration depth and flow velocity in molten bath are larger at steelmaking temperature because the velocity attenuation of supersonic jet is suppressed. The mathematical model was then used to investigate the effect of radial angle between oxygen lance nozzles and bottom blowing tuyeres on molten bath flow properties, which revealed the fluid flow mechanism in combined blown converter. Based on the molten bath flow field, mathematical model describing the erosion behavior of converter lining was established and erosion characteristics in combined blown converter was researched. The results showed that radial angle between oxygen lance nozzles and bottom blowing tuyeres has an important influence on converter bath velocity field distribution and lining erosion.

Research on Selective Oxidation of Carbon and Aluminum with Introduction of CO2 in RH Refining of Low-Carbon Steel Process

The injection of CO2 during the Rheinstahl–Heraeus (RH) refining process as a lifting gas is a new attempt for the steel industry, and can promote refining effect and realize the utilization of CO2 as a resource. In the present study, the thermodynamic equilibrium of the RH refining process through CO2 injection instead of Ar was calculated using FactSage software. A selective oxidation sequence of [C] and [Al] with CO2 was studied and analyzed under the RH refining temperature and vacuum degree. In addition, the oxidation zones of carbon and aluminum were both defined. Industrial trials were preliminarily conducted to verify the above theory. The results show that CO2 has the potential to be used to refine low-carbon steel in RH, but its refining effect is affected by the [Al] content in steel. By reducing the additive amount of aluminum alloy in the ladle furnace and replenishing the aluminum during the late stage of the RH refining process, CO2 injection can achieve a lower temperature drop of molten steel and a better refining effect than Ar during the RH degassing process.

Fluid–Solid Coupling Simulation on the Temperature Distribution of Tuyere Used for Oxygen Bottom Blowing Converter

For an oxygen bottom blowing converter, a high-temperature fire spot zone forms above the tuyere owing to oxygen reaction. The bottom blowing tuyere and surrounding brick are simultaneously heated by high-temperature fire spot and flowing molten steel. High-speed fluids flowing in the inner tube and the annular gap of the tuyere can remove part of the heat transferred from the fire spot zone and molten steel, playing a vital role in cooling the tuyere. To determine the temperature distributions of the tuyere and surrounding brick under the condition of oxygen bottom blowing, a fluid–solid coupling heat transfer numerical model that considers both the radiation of the fire spot and convection of the molten steel was established in this study. The simulation results agree well with previous experimental results; thus, the numerical model was validated. Utilizing the validated model, the influences of the tuyere inner tube material and fire spot zone temperature on the tuyere temperature distribution were studied in detail. Along with an increase in the material thermal conductivity, the maximum temperature of the inner tube at the hot face decreased, verifying the superiority of copper as the inner tube. More importantly, it was found that reducing the fire spot zone temperature by mixing CO2 in the bottom blowing oxygen fundamentally alleviated the burning loss of the tuyere and the surrounding brick.

Numerical Simulation and Industrial Experimental Research on the Coherent Jet with “CH 4 + N 2 ” Mixed Fuel Gas

Coherent jet technology is widely used in the electric arc furnace (EAF) steelmaking process to deliver more energy and momentum into the molten steel bath. Meanwhile, the characteristics of a coherent jet using pure CH4 as the fuel gas have been well investigated in previous studies. To reduce the consumption of CH4, coherent jet technology using “CH4xa0+xa0N2” mixed fuel gas instead of pure CH4 was proposed and studied in detail by numerical simulation in the present work. The Eddy Dissipation Concept model, which has detailed chemical kinetic mechanisms, was adopted to model the fuel gas combustion reactions. Experimental measurements were carried out to validate the accuracy of the computational model. The present study shows that the jet characteristics of the main oxygen improve along with the increase of the CH4 ratio in fuel gas and with the increase of the flow rate of fuel gas. When the CH4 ratio in the fuel gas is 25 pct, the fuel gas flow rate only has a limited influence on the jet characteristics, unlike the rest of the fuel gas compositions, because a high N2 proportion deteriorates the combustion performance and leads to severe incomplete combustion. Moreover, a false potential core phenomenon was observed and explained in the present study. Based on the average values, the jet length of a coherent jet with 75 pct CH4 can achieve 89.8 pct of that with 100 pct CH4. Finally, an industrial experiment was carried out on a commercial 100t EAF using coherent jet with 75 pct CH4, showing that the average CH4 consumption was reduced from 3.84 to 3.05 Nm3xa0t−1 under the premise of no obvious changes in the other production indexes.

Simulation and application of pulsating bottom-blowing in EAF steelmaking

ABSTRACT Pulsating bottom-blowing was proposed to strengthen the electric arc furnace (EAF) molten bath stirring. The fluid flow characteristics and stirring effects of different pulsating bottom-blowing modes on EAF molten bath were studied through water model experiments and numerical simulations. The mixing time was measured by water model experiments and the flow field characteristics of EAF molten bath were simulated by numerical simulations. Compared with conventional bottom-blowing, pulsating bottom-blowing can accelerate the fluid flow velocity and improve the stirring of molten bath. With pulsating bottom-blowing, the molten bath fluid flow field is more disorder, the fluid flow velocity increases and the dead zone volume decreases. Compared with EAF steelmaking with conventional bottom-blowing conditions, pulsating bottom-blowing technology can improve the metallurgical effects and the molten steel quality in EAF steelmaking with lower FeO content of final slag, lower phosphorus content and carbon-oxygen equilibrium of final molten steel, and lower temperature deviation.