Numerical study of geometrical effects on blast furnace (BF) flow and performance

Abstract

Blast furnace (BF) geometry is of significant importance to BF process because it can affect in-furnace multiphase flows, BF stability and efficiency. In the past several decades, the BFs have been frequently enlarged during their relining or rebuilding. However, thus far, the effects of BF geometrical parameters are largely known empirically and the underlying reasons for the enlargement of BF are still not obvious. This thesis presents a numerical study of BF geometrical parameters by means of the BF process model. This model is based on the one recently developed by Dong et al. [1]. The previous model has been improved in terms of the following two aspects: (i), the raw material, operational and geometrical conditions are allowed to vary in a flexible range rather than fixed; and (ii), the variation of the stock line with BF inner state as encountered in practice is considered by controlling burden charge rate according to the global coke balance inside the considered BF. Firstly, the applicability of the improved model has been examined by comparing the predicted BF performances with those practically observed for BFs operated with different coke ratios and blast rates. The model was then used to study the effects of BF geometrical parameters on BF performances and inner states. The calculated results reveal that the enlargement of BF inner volume by mean of expanding any of the BF dimensions improves BF efficiency in terms of the achievable coke ratio. The expansion of BF lateral dimensions lowers the in-furnace pressure drop while the elongation of BF height tends to increase the packed bed resistance to gas flow against the BF operational stability and larger productivity. Certain ratios of the horizontal dimensions are desirable to maintain a well-controlled gas throughflow and smooth descent of burden materials. Therefore, the adjustments of the BF inner liners corresponding to the enlargement of BF inner volume have been proven to be reasonable and necessary.