X-ray Radioscopic Visualization of Bubbly Flows Injected Through a Top Submerged Lance into a Liquid Metal
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We present an experimental study on the formation and behavior of a liquid metal bubbly flow arising from a downward gas injection through a top submerged lance (TSL). A visualization of the bubble dynamics was achieved by the X-ray radiography combined with high-speed imaging. The experiments were carried out in a parallelepiped container (144 9 144 9 12 mm3) using GaInSn, a ternary alloy that is liquid at room temperature. The gas flow rate Qgas was adjusted in a range between 0.033 and 0.1 L/s. Three different injection positions were considered with respect to the submergence depth L. X-ray images allow for a characterization of the flow regimes and provide the properties of the individual bubbles such as size, shape, and trajectory. Formation and entrainment of smaller gas bubbles are observed at the free surface. These small bubbles can be trapped in the fluid for a long time by recirculation vortices. Bubble size distributions are determined for different Qgas. The bubble detachment frequency is measured as a function of Qgas and L. The results are compared with previously published data for water. The X-ray radiography offers an effective method for determining the local void fraction and allows for an estimation of the bubble volume. https://doi.org/10.1007/s11663-019-01720-y The Minerals, Metals & Materials Society and ASM International 2019
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INTRODUCTION
SINCE the emergence of first ideas and concepts about 50 years ago, the TSL (top submerged lance) process has become an essential component of the non-ferrous metallurgical industry.[1] Originally, the method was developed by CSIRO and became known as SIROSMELT. Today, also the names AUSMELT and ISASMELT stand for industrial processes based on the top submerged lancing technology. The technique, which is characterized by blowing reactive gas through the submerged lance into a liquid slag bath, is applied for waste treatment, E-Waste recycling, or the production of several metals such as tin, copper, nickel, lead, platinum group elements, or zinc. The gas injection nozzle is designed as a straight lance which is aligned vertically and is immersed in the liquid bath from above. The attractiveness of the TSL process results from the simple configuration, the robustness and the variability MEGUMI AKASHI, OLGA KEPLINGER, NATALIA SHEVCHENKO, STEN ANDERS, MARKUS A. REUTER, and SVEN ECKERT are with the Helmholtz Zentrum DresdenRossendorf (HZDR), Bautzner Landstraße 400, 01328 Dresden, Germany. Contact e-mail: [email protected] Manuscript submitted April 15, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS B
of the operating conditions. The process can be readily controlled by variations of the gas composition, the gas flow rate, or the submergence depth of the lance in the bath. The productivity of the reactor is determined by the efficiency of the chemical reaction between the gas (or solid particles transported in it) and the liquid. Achieving a high reaction rate requires an excellent exchange between the phases and therefore a large interface. This, in turn, var
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