Modeling the heat flow to an operating sirosmelt lance

Abstract

A mathematical model of the heat flow to a Sirosmelt lance is presented, which predicts lance wall and air temperatures and the thickness of the slag layer on the lance. By measuring the distribution of wall temperature and slag thickness on an operating Sirosmelt lance, the model was used to determine both the heat-transfer coefficient between the vessel contents and the lance and the thermal conductivity of the slag layer. The slag layer thermal conductivity was found to be within the range of 0.5 to 1.1 W m⁻¹ K⁻¹, while the outside heat-transfer coefficient varied from 80 to 150 W m⁻² K⁻¹, both of which are smaller than quoted in the literature for metal/slag systems. The discrepancy was attributed primarily to the large quantities of combustion gases that envelop the lance and reduce convection and conduction from the melt to the lance. Other factors causing low thermal conductivity and a low heat-transfer coefficient include the thermal resistance at the slag/lance interface and the mushy region on the outside of the slag layer.