The Influence of Lance Orientation and Gas Evolution on Particle-Liquid Contact During Submerged Powder Injection

Thermal similarity criteria for submerged powder injection into liquid metals were developed. It was calculated that direct particle-liquid contact is by far the most important mechanism for particle heating. Therefore, the bath cooling rate during powder injection is an indicator of particle-liquid contact. Using the similarity criteria it was shown that the decomposition of calcium carbonate or vaporization of magnesium or calcium in iron or steel can be simulated by the injection of aluminum hydroxide into lead. Experiments were conducted in which silica (30, 130 and 450μm) and aluminum hydroxide (90μm) were injected into liquid lead. For most of the experiments the gas and particles were injected adjacent to a window so the flow patterns could be photographed. The bath cooling rate for straight, vertical injection was only 30% of that expected for complete contact. It could be improved to 50–70% with straight, inclined lances or hockey-stick lances. The bath cooling rate for aluminum hydroxide corresponded to complete particle-liquid contact. Therefore angled injection and the use of gas-evolving compounds are important mechanisms for improving particle-liquid contact.