Fuhai Liu

Effect of Ambient and Oxygen Temperature on Flow Field Characteristics of Coherent Jet

The coherent jets are now used widely in electric arc furnace steelmaking process to increase the stirring ability, reaction rates, and energy efficiency. However, there has been limited research on the basic physics of the coherent jets. In the present study, the characteristics of flow field of supersonic coherent jet in hot and cold condition were studied. The total temperature and axial velocity were measured by combustion experiment. Flow field characteristics of supersonic coherent jet were simulated by Fluent software. The detailed chemical kinetic mechanism is presently used for the modeling of reactions. It consists of 53 species, plus Ar and N2, for a total of 325 reversible reactions. The present study showed that the shrouding flame decreases the entrainment of the ambient gas to the central supersonic jet, which results in a low expansion rate for the coherent supersonic jet. The higher ambient temperature can prolong the potential core of coherent jet and conventional jet. However, the potential core of coherent jet reduces with oxygen temperature increasing, which is opposite to conventional jet.

Circulation and accumulation of harmful elements in blast furnace and their impact on the fuel consumption

The circulation and accumulation of harmful elements in blast furnace were investigated. The results show that the maximum concentration of K and Na in the belly is about 50 times of that in the charge. The zinc increased by 80 times and the Pb is insignificant. The impact of the circulation and accumulation of K, Na, Pb and Zn on the fuel consumption was quantitatively analyzed using Rist diagram. The results show that the gas utilization decreased and the coke rate increased linearly with the increase of load and accumulation times of each harmful element. Given the accumulation times of each element, the loading of Na, K, Zn and Pb into BF leads to the increase of coke rate by 13.99 kg/tHM, 6.25 kg/tHM, 3.63 kg/tHM and 0.02 kg/tHM, respectively. The increased coke rate and the decreased gas utilization under various loads and accumulation times of each element was estimated.

Effect of nozzle twisted oxygen lance on flow field and dephosphorisation rate in converter steelmaking process

The stirring ability and flow field characteristic of conventional and nozzle twisted oxygen lance (Twisted angles are 4°, 8° and 12°, respectively) on the molten bath were analysed. The mixing time, impacting depth and impacting radius are measured. Flow field characteristics of multi-phase flow are calculated by numerical simulation. Compared with conventional oxygen lance at industrial application research, it shows that the 8° oxygen lance could stir molten better in steelmaking process for the 120t dephosphorisation converter. These findings agree well with the experimental results of the water experiments and the numerical simulations. Finally, an optimal twisted angle is determined.

Simulation of three-phase flow and lance height effect on the cavity shape

A three-dimensional computational fluid dynamics (CFD) model was developed to simulate a 150-t top-blown converter. The effect of different lance heights on the cavity shape was investigated using the volume of fluid (VOF) method. Numerical simulation results can reflect the actual molten bath surface waves impinged by the supersonic oxygen jets. With increasing lance height, the cavity depth decreases, and the cavity area, varying like a parabola, increases and then decreases. The cavity area maximizes at the lance height of 1.3 m. Under the three different lance heights simulated in this study, all of the largest impact velocities at the molten bath surface are between 50 m/s and 100 m/s.

Effect of Shrouding Gas Temperature on Characteristics of a Supersonic Jet Flow Field with a Shrouding Laval Nozzle Structure

Coherent jet technology was been widely used in the electric arc furnace steelmaking process to protect the kinetic energy of supersonic oxygen jets and achieve a better mixing effect. For this technology, the total temperature distribution of the shrouding jet has a great impact on the velocity of the main oxygen jet. In this article, a supersonic shrouding nozzle using a preheating shrouding jet is proposed to increase the shrouding jet velocity. Both numerical simulation and experimental studies were carried out to analyze its effect on the axial velocity, total temperature and turbulence kinetic energy profiles of the main oxygen jet. Based on these results, it was found that a significant amount of kinetic energy was removed from the main oxygen jet when it passed though the shock wave using a high-temperature shrouding jet, which made the average axial velocity of the coherent jet lower than for a conventional jet in the potential core region. However, the supersonic shrouding nozzle and preheating technology employed for this nozzle design significantly improved the shrouding gas velocity, forming a low-density gas zone at the exit of the main oxygen jet and prolonging the velocity potential core length.

Effect of shrouding Mach number and ambient temperature on the flow field of coherent jet with shrouding Laval nozzle structure

ABSTRACT The coherent jet technology was widely used to improve the stirring effect of molten bath in steelmaking field, and the key to this technology was to form a low-density zone around the main oxygen jet by a high-temperature shrouding flame. With this revelation, a shrouding nozzle was processed to a Laval nozzle structure fitted with a loop arrangement for increasing the velocity of shrouding jet. For further increasing the area of the low-density zone, the preheating method was also adopted in this new coherent lance structure. In this paper, the effect of Mach number of the shrouding nozzle on the flow field of the coherent jet was investigated at room and high ambient temperature using numerical simulation and experimental studies. The result represented the simulation model used in this research showed good agreement with the experimental data at the texted conditions. Although the shock wave formed by the shrouding jet removed more kinetic energy form the main oxygen jet, the impaction ability of the coherent jet was much bigger than that of conventional supersonic jet, and this phenomenon would be further strengthen if ambient temperature and Mach number of the shrouding nozzle increases.

The preparation process of nitrogenous ferrovanadium with bottom-blowing nitriding in electrical arc furnace

The flow field characteristics and stirring abilities of five kinds of bottom-blowing arrangements on the molten bath were researched in a 3t electrical arc furnace (EAF) with regular shape. The mixing time was measured by water experiment under different flow rates. Flow field characteristics of three-phase flow were simulated by numerical simulation. The average mixing time decreased with the flow rate and the radius of circle coincide increasing for the EAF with regular shape. Moreover, weakening counteracting force of counter-swirls could efficiently reduce mixing time than weakening impeding forces of sidewall with concentric circle arrangements at the tested conditions. Compared with 6R bottom-blowing arrangement at industrial application research, the 7R bottom-blowing arrangement, which was determined by the water model experiments and the simulations, could stir molten better in nitriding process, which agreed well with the experimental results of the water experiment and the numerical simulation.

Numerical Simulation for the Mixing Process of Converter with Preheating Oxygen

By making use of the heat of converter fume, a way to preheating the top-blowing oxygen has been proposed and researched. The three-dimensional model has been developed to analyze the mixing process of molten bath in converter with preheating oxygen. The volume of Fluid (VOF) method was employed to model three-phases including oxygen, molten steel, and liquid slag to simulate the behaviors of molten bath. The results show that as temperature of oxygen is raised from 300 K to 1200 K, the impacting depth, impacting diameter and velocity of molten bath first Increase obviously, and then decrease. The research results revealed a way of the heat of fume utilization, and the optimized preheating temperature of oxygen was obtained.