Behavior of fluxed lime iron oxide pellets in hot metal bath during melting and refining

Lump lime as a fiux material in a basic oxygen furnace （BOF） often creates problems in operation due to its high melting point, poor dissolution property, hygroscopic nature, and fines generation tendency. To alleviate these problems, fluxed lime iron oxide pellets （FLIP） containing 30% CaO were developed in this study using waste iron oxide fines and lime. The suitable handling strengths of the pellet （crushing strength： 300 N; drop strength： 130 times） of FLIP were developed by treating with CO2 or industrial waste gas at room temperature, while no separate binders were used. When the pellet was added into hot metal bath （carbon-containing molten iron）, it was decomposed, melted, and transformed to produce low melting oxidizing slag, because it is a combination of main CaO and Fe2O3. This slag is suitable for facilitating P and C removal in refining. Furthermore, the pellet enhances waste utilization and use of CO2 in waste gas. In this article, emphasis is given on studying the behavior of these pellets in hot metal bath during melting and refining along with thermodynamics and kinetics analysis. The observed behaviors of the pellet in hot metal bath confirm that it is suitable and beneficial for use in BOF and replaces lump lime.

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 ef-fect 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 de-creases, 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.

Performance Assessment of Partially Pre-fused Synthetic Flux in Basic Oxygen Steel Making

Lump lime as the most common flux and iron ore as a coolant are used in basic oxygen steel making. However, high melting point, poor dissolution property, fines generation tendency and hygroscopic nature of lump lime often create problems in operation. As the combination of both iron oxide （Fe2O3） and CaO shows eutectic at 1 230 ℃, a combined mass of iron oxide and lime melts at lower temperature and dissolves faster in a molten bath. A partially pre-fused synthetic flux （PSF） was prepared through an innovative way in combination of iron oxide fines viz. Linz Donawitz converter sludge and blast furnace flue dust and lime fines by micro-pelletization of the mix followed by coke breeze free sintering. The developed PSF shows good cold handling strength, low melting point （1 180 ℃）, good thermal shock resistance, etc. As a low melting synthetic flux, its performance was assessed through dissolution/melting study in hot metal bath and refining of hot metal in a simulated bottom blown converter using （i） PSF, （ii） only lump lime and （iii） lump lime with iron ore when keeping other conditions identical. Very fast dissolution （27 80 s for 1-3 g lumps）, enhanced removal of C and P （11-12 min）, controlled slag foaming, and reduced oxygen consumption was obtained for using PSF.