Top Submerged Lance Technology (TSL) have been successively applied to recovery of a range of metals like tin, lead, copper, zinc, silver, nickel, aluminium, gold etc. around the world. Floyd has described the details of Top Submerged Lance technology and its development since the 1970s. An investigation of fluid flow into a TSL system to reveal the detail process kinetics in a cold flow water model has been carried out by the present authors by using 3-D Computational Fluid Dynamic modelling technique. As a continuation of that research, a Computational Fluid Dynamic (CFD) model of the high temperature combustion phenomena in a TSL furnace was developed by incorporating the detail chemical reactions involving combustion. In the first stage, a single-phase 3-D combustion model for CH4 combustion was developed and temperature profile and mass fractions of fuel and air were investigated inside the combustion chamber at the lance tip. Then the model was extended to Multiphase flow simulation of zinc fuming process of a pilot plant with heat, mass, momentum and turbulence interfacial interaction between the phases. The chemical reactions between the slag components and gaseous species were also taken into account.