Study On Flow Field Of Post Combustion At The Initial Stage On BOF By PIV

Particle Image Velocimetry (PIV), as a newly developed technique in the latest decade, is a non-intrusive measurement means for acquiring velocities and related properties in fluids through analyzing the correlation of flow field images, avoiding the drawback of the intrusive single-point measurement apparatus. Hence it has been considered as a promising technique for the non-intrusive flow field measurements.Post-combustion technology, as an efficient method to improve thermal supply and enhance thermal efficiency during the process of converter steelmaking, is of a number of advantages such as promoting thermal balance significantly, increasing scrap steel ratio, low investment and high benefit, etc. The flow behavior of the sub-oxygen jet and its interaction with the gas flow field in the converter are very important to design and optimize the sub-oxygen supply, and maximizing the benefits of post-combustion in steelmaking.A water modeling apparatus was established to measure the post-combustion flow field in the Basic Oxygen Furnace (BOF) at the initial stage of steelmaking by using PIV technique at the guide of the similarity principle. The effects of the angel between the axis of the sub-oxygen orifice and that of the oxygen lance, the sub-oxygen orifice number and the distance of the sub-oxygen orifice from the top surface of molten iron on the structures of flow field were studied.The results show that the major post-combustion region in BOF comprises the inner reflux, the sub-oxygen jet and the outer reflux. The angle between the axis of sub-oxygen orifice and that of oxygen lance greatly influences the gas flow. With the increase of the angle, the volume of the inner reflux increases, thus which enhances the mixing and combustion of oxygen jet with rising CO. However, too large angle deteriorates the erosion of the furnace lining and reduces the efficiency of thermal transport. In addition, it was found that the increase of the sub-oxygen orifice number leads to increase the volume of the inner reflux, widen the oxygen jet boundary layer and decrease the outer reflux. As for the impact of the distance of the sub-oxygen orifice from the top surface of molten iron, it was observed that as the distance increases, the oxygen jet expands perpendicularly to the flow direction, the volume of the inner flux increases, and the volume of the outer flux decreases. Furthermore, when the height of the sub-oxygen orifice rose from 300 to 400 mm, the diffusion of the sub-oxygen jet is obviously better than the operating situation when the height was changed from 400 to 500mm. The contribution of this study is to provide important guidance on improving the design of the post-combustion oxygen lance and optimizing the BOF steelmaking techniques.