Effect of nut coke on blast furnace shaft permeability

Abstract

The majority of blast furnaces nowadays use nut coke of different grain sizes primarily to reduce costs. Operation of many blast furnaces has proved the possibility of coke saving and increase of furnace productivity when using nut coke in mixture with burden but reasons and the mechanism of this phenomenon, and consequently the limit for nut coke consumption, are not very clear yet.

A method for quantitative analysis of the change in shaft permeability and furnace productivity when using nut coke - burden mixture has been developed. Calculations were conducted for a wide range of nut coke rate and grain size.

To validate the analytical model results, experimental simulations of streaming conditions in the blast furnace shaft have been carried out using two cold rigs at RWTH Aachen, Germany, and at DNTU, Donetsk, Ukraine. The effect of layer thickness (both ratio of coke/burden layer thickness and their absolute value), gas velocity or flow rate and nut coke rate on the pressure drop in different packaged beds was examined. The combined effect of various factors such as the effect of nut coke rate for a changing flow rate and layer thickness was investigated as well.