Flow induced stress distribution on wall of blast furnace hearth

Abstract

The flow induced shear stress on the wall of a blast furnace hearth has been computed by solving the Navier–Stokes and Darcy flow equations in the hearth numerically. The Navier–Stokes equations are utilised to compute the flow field in the coke free zone while the Darcy flow equations are utilised for the flow of liquid metal in the coke packed porous zone, known as the deadman. The shape of the deadman was taken to be hemispherical and it was simulated to be porous in nature. The taphole was placed through a block of refractory material 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 length and size of the taphole when the hearth was filled with liquid metal. It has been found that the peak stress value at the bottom plane, midplane (halfway between the bottom and the taphole exit plane), and at the plane of the taphole reduces significantly compared with the case of having no taphole block at all. However, the effect of the size of the taphole on the wall shear stress was not found to be very significant. It was also found that the peak stress decreases with an increase in the taphole length and the location of the peak stress shifts slightly in the increasing direction of θ. Such an arrangement of placement of the block does not produce any more peak stress anywhere in the azimuthal direction at a particular plane; rather, it helps to smooth out the peaks in the stresses arising due to fluid flow. The reasons for mechanical erosion inside the hearth are complicated. However, flow induced shear stresses play a very important role in initiating and aggravating the amount of erosion along with other factors. This has provided the main motivation to compute the flow induced shear stress on the inside wall of the hearth and study the effect of various parameters on it in the present work.