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.
Detonation of fuel coolant explosions
IN certain circumstances the mixing of a hot liquid and a cooler, vaporisable one leads to an explosive rate of vapour production. Such explosions have occured in foundries when molten metals and water mix1, and when liquid natural gas is spilt on to water2; they may also occur in liquid-cooled nuclear reactors under accident conditions. It seems likely3,4 that in these events an initial disturbance causes motions which fragment some of the material and so allow rapid heat transfer; this produces explosive expansion and further fragmentation, and so the reaction propagates through the medium. We give here a simple one-dimensional model of a system in which the two liquids are initially coarsely mixed, and show that there is the possibility of an extremely violent thermal explosion, the structure of which is analogous to that of a detonating chemical explosion.
The solubility of hydrogen in solid binary aluminum-lithium alloys
The solubility of hydrogen in solid binary aluminum alloys with 1,2, and 3 wt pet lithium has been determined for the temperature range of 473 to 873 K and the pressure range of 26,700 to 113,300 Pa (0.26 to 1.12 atm), using an absorption/quench/desorption technique. The results fit the Van't Hoff isobar and Sieverts' isotherm and are given by log (S/S°)- log (p/p°) =-A/T/K +B whereS, S° are, respectively, the solubility and a standard value of solubility equal to 1 cm3 of diatomic hydrogen measured at 273 K and 101,325 Pa/100 g of metal;p, p° are, respectively, the pressure and a standard value of pressure equal to 101,325 Pa (1 atm). The values of the constantsA andB are Al-1 pet Li 473T/K 680:A = 358;B = 0.576 680T/K 873:A = 604;B = 0.620 Al-2 pet Li 473T/K 740:A = 273;B = 0.597 740T/K 873:A = 676;B = 0.767 Al-3 pet Li 523T/K770:A = 615;B = 1.272 770T/K 873:A = 830;B = 1.166 The solubility of hydrogen is one or two orders of magnitude greater in the alloys than in the pure metal and increases with lithium content. The results are consistent with the dissociative dissolution of a diatomic gas. The isobars are discontinuous at critical temperatures which lie within the a-phase field,i.e., 680, 740, and 770 K for Al-1 pet Li, Al-2 pet Li, and Al-3 pet Li, respectively, indicating a change in the character of the solution at lower temperatures due to an increase in the solute binding energy, which is attributed provisionally to an unidentified change in thea matrix.