Hot metal flow in a blast furnace hearth – model tests

Very recent operation measurements and test bore holes made in solidified blast furnace hearths indicate the presence of a downward‐arching, convex‐shaped coke zone in blast furnace hearths. By means of model tests using a two‐dimensional electric simulator that stands out against previously used models because of its easy handling, simulations were made of the effects of this convex‐shaped coke zone base on hot metal flows in blast furnace hearths. It was possible to detect a hot metal flow that has a different path to those known so far in the hearth bath and runs radially along the periphery of the hearth bottom to the tap hole. This flow path occurs when the coke zone rests partially on the hearth bottom centre. It causes increased stress on the refractory lining at the junction between the hearth bottom and hearth wall and in the long run can lead to extensive disintegration of the lining in these areas. When a coke zone with a convex base floats in the hearth bath, compared with a flat base, it produces no appreciable changes in the hot metal flows. As further tests showed, it is only possible to a limited extent to directly influence the hot metal flows by applying such operational measures as longer tap holes and a lower bath level.