RH真空室内气泡行为的研究

Ruhrstahl-Hereaeus (RH)上升管内的气液两相流是整个装置的重要动力源,并对钢液的流动、混匀及精炼过程有重要影响.上升管及真空室内的气液两相流决定了钢包内钢液的流动状态,为了研究真空室及上升管内气液两相流,通过1:6的300 t RH的物理模型模拟了RH上升管及真空室内气泡行为过程,并测量了RH循环流量的变化用于计算上升管内含气率以及气泡运动速度最终得到气泡在真空室内的停留时间,同时记录了气泡在真空室内的存在形式.气泡在真空室的存在形式的主要影响因素为提升气体流量,研究发现了气泡从规则独立的大气泡经历聚合长大,碰撞破碎成小气泡,最后变成小气泡和不规则大气泡共存的现象.液面高度达到80 mm之后,气泡在真空室内的停留时间达到一个平衡值,不再随真空室液面高度的增加而发生改变.当提升气体量达3000 L·min-1,气泡停留时间减小趋势弱,对应3000 L·min-1情况下,真空室内气泡开始聚合长大.研究认为对于300 t RH的真空室液面高度应为80 mm,提升气体量应在3500 L·min-1左右,优化后,脱碳时间由原工艺的21.4 min缩短至现工艺的17.5 min. 

Complex bubble formation in the vacuum chamber and the up leg of the Rheinsahl-Heraeus

The gas-liquid two-phase flow in the up leg of the Ruhrstahl-Hereaeus (RH) unit is one of the main momentum sources of the whole device, and it affects the flow state of the molten steel in the ladle. A physical model of 300 t RH in 1:6 ratio was set up to simulate the bubble behavior process and to measure the change of the RH circulation flow in the up leg and in the vacuum chamber. The gas-liquid fraction and the movement velocity of bubbles were measured to assess the residence time of the bubbles in the vacuum chamber. In addition, the formation of the bubbles at different values of the RH circulation flow and liquid-level height in the vacuum chamber were recorded by a high-speed camera. One of the main factors influencing the bubble formation is the increase of the lifting gas flow in the vacuum chamber. With the increase of blowing gas, the large independent bubbles undergo multiple collisions, break into small bubbles, and finally small and large irregular-sized bubbles coexist. When the liquid height is>80 mm, the residence time of the bubbles in the vacuum chamber achieves a stable value and cannot be further affected by the increase of the liquid-level height in the vacuum chamber. At a lifting gas flow of 3000 L·min-1, a weak decreasing trend of the residence time of bubbles is observed, and the bubbles start polymerizing in the vacuum chamber. In conclusion, for the 300 t RH physical model, the liquid height in the vacuum chamber is recommended to be 80 mm, whereas the lifting gas flow should be set at 3500 L·min-1. After these optimization steps, the decarburization time decreases from 21.4 to 17.5 min.