Optimisation of taphole angle to minimise flow induced wall shear stress on the hearth

Abstract

The flow induced shear stress on the wall of the blast furnace hearth has been computed by solving the Navier–Stokes equations along with a momentum source to represent numerically the pressure drop caused by the porous bed in the hearth. The Navier–Stokes equations are utilised to compute the flow field in the coke free zone as well as for the flow of liquid metal in the coke packed porous zone, normally known as the deadman. The effect of turbulence has been incorporated in to the momentum equation by solving the two equation k–ϵ turbulence model separately. The shape of the deadman is taken to be almost matching with the contour of the hearth but away from the wall by 0.4 m and from the bottom also. So a floating as well as a coke packed hearth could be simulated for the flow conditions. The deadman is simulated to be porous in nature. The taphole was placed through a block of refractory material or mud mass through which the metal was allowed to flow out of the hearth. From the resulting flow field the shear stresses on the side wall of the hearth were computed as a function of the angle of the taphole when the hearth is having a floating deadman or is fully coke packed. It was observed that there exists an optimum taphole angle for which the wall shear stress can be minimum. The optimum angle was found to be nearly 15 for both the floating deadman as well as for the coke packed hearth.