Estimation of thermal stress in lump coke

Permeability in the blast furnace is maintained by lump coke and is governed by the mean size and size distribution of the coke. Coke lump size is determined mainly by the growth of macro-cracks from the wall side to the centre of the coke oven charge, their formation behaviour depending on the property of the coal charged and the operating conditions. In the formation process, micro-cracks are simultaneously formed in all directions and their formation also plays a part in determining the strength and therefore the lump size of coke for the blast furnace. This study estimates the deformation behaviour of coke and the thermal stress distribution by assuming the size of lump coke formed in the coke oven (distance between macro-cracks) and the conditions required for fissure propagation, considering radiative heat transfer within the fissures. The tensile stress parallel to the oven wall is estimated to reach ∼ 10-20 MPa near the wall side. The growth of fissures arising from the wall side is successfully estimated. No fissure parallel to the oven wall is recognized, since only compressive stress is predicted.