Calcium carbide powder injection into hot metal. Part 1 - heat transfer to particles

Calcium carbide powder was injected into an induction furnace containing 70 kg of carbon saturated iron to understand the transport phenomena associated with desulphurization. In Part 1 of this two part paper, the thermal aspects of injection are addressed. The melt temperatures were measured before, during, and after the injection of gas alone and gas and calcium carbide particles. A heat transfer analysis of the results was carried out. Without injection, most of the heat was lost to the water cooled coil. During gas injection, the first order rate constant for bath cooling increased linearly with gas flowrate. During powder injection, heat transfer to the particles caused much greater additional heat losses from the melt, but only 30-50% of that expected if the particles were heated to the melt temperature. It was concluded that this corresponded to the percentage of the particles contacting the melt; the remaining particles were transported to the bath surface by the carrier gas bubbles. At solid-gas loadings below 60 kg/Nm^-3, only 30% of the particles contacted the melt, whereas above this loading the contact increased to 50%. This transition was attributed to a change of flow regime from bubbling to jetting. In Part 2 (this issue) the kinetics of simultaneous desulphurization and deoxidation is addressed.