Recycling of Sludge and Dust to the BOF Converter by Cold Bonded Pelletizing

Abstract

With the aim to increase the recycling of fine sludge and dust disposed normally in landfill, cold bonded pelletizing of the sludge and dust using cement as binder was investigated in laboratory scale as well as in the pilot scale pelletizing plant. The influence of BF flue dust, BOF fine sludge and oily mill scale sludge on the cold strength, capacity and reduction degree of cold bond pellets was studied experimentally on the basis of a statistical procedure. With a coarser representative particle size, oily mill scale sludge has the greatest effect on the cold strength. BF flue dust has a negative effect for increasing both the cold strength and capacity for levels of over 25% of the mixture. The BOF fine sludge has the positive effect on cold strength, while its interaction with BF flue dust has the negative effect on reduction degree.
The results of pelletizing tests in pilot scale show that the maximum cold strength (TTH 94%) and capacity (13-15 t/h) of products is obtained at the conditions given by the optimal mixture design and cure time. The industrial tests on charging cold bonded pellets as burden material in the BOF converter were described. The charging weight of cold bonded pellets varied from 0.5 to 2.5 tons. The results of industrial tests indicated that the converter process was not subject to any adverse disturbances due to the addition of 2.5 tons of cold bonded pellets.