Steam Explosions of Single Drops of Molten Silicon-Rich Alloys
Commercial quantities of ferrosilicon alloys and silicon metal in the form of granules are available. They are produced in water granulation, a process involving the risk of large-scale steam explosions. To learn about these steam explosions, we have investigated single drops of molten alloys when released into water. When single drops of molten ferrosilicon alloy with 75 wt.% Si (FeSi75) or silicon metal at its liquidus or melting temperature were released into cold, room temperature or hot water, spontaneous explosions never occurred. We could, however, initiate steam explosions by exposing the drops to upwarddirected pressure transients generated in the water with an encapsulated impactor. For water at room temperature, we determined (a) the strength of the pressure transients needed to initiate the steam explosion of a single drop, and (b) the range of fall depths over which the drop can be triggered to explode with this transient. When varying the water temperature we learned that the triggered explosions became less vigorous as the temperature increased. The explosions became more vigorous also when the Al and/or Ca content in the molten drop decreased. Photographic images of the bubbles generated during the steam explosions indicate that the maximum energies released correspond to about 1 % to 2% (dependent on drop size) of the total enthalpy of the molten ferrosilicon at its liquidus temperature. During the explosions, tiny bubbles of a permanent gas, presumably hydrogen, were generated. Video images show that ferrosilicon drops with diameters between 3 mm and 11 mm fall through water at about 0.5 m/s. Shutter wheel photographs confirm these fall rates and also indicate the onset of solidification of the drops and show that steam explosions can occur in partially solidified drops.
An experimental study on the intense heat transfer and phase change during melt and water interactions
ABSTRACT Accidental contact between hot melt and cold water poses fatal hazard in several industries. Vapor explosion during melt-water contact in nuclear power plant accident can result in catastrophic containment failure. The fast transient phenomena as vapor explosion is not comprehensively understood despite several advances in research. It is not clear why certain parameters of melt and water exhibit differences in fragmentation behavior. To examine the influential parameters, we perform a series of experiments. The interactions between melt and water is visualized by high-speed video and X-ray radiograph.
Present status of detonations in two-phase systems
Abstract A review of two-phase detonations is presented. Similarities and differences with homogeneous detonations are outlined and advances in their understanding are indicated. Because of recent and present interest, particular attention is devoted to spray detonations. However, the survey does include film and solid-gas detonations as well as detonations in monopropellant sprays. Areas in need of further research are outlined.