Abstract
Increasing permeability of packed burdens and decreasing reducing agent rate in a blast furnace process take an important role to improve productivity. Especially, the softening property during reduction and reducibility of sinter are important. Effects of blending dolomite as raw materials at low SiO2 sinter (SiO2<5 mass%) on these properties were examined by using variously prepared sinter samples. The softening property was estimated by vertical pressure drop of sinter packed bed (70mmφ×100mm) during reduction with elevating temperature up to 1600°C under vertical loading force (0.098×106 Pa). The reducibility was estimated on the basis of the reduction degree obtained by CO/N2(30/70 vol%) gas at constant temperature conditions (900°C, 1100°C).
Results were summarized as follows:
(1) Sinter using dolomite instead of serpentine and increasing MgO concentration in sinter with dolomite shows superior sinter reducibility.
(2) Increasing MgO concentration in sinter with dolomite also shows both superior sinter reducibility and sinter softening property.
(3) Superiority of sinter reducibility described in (1) and (2) is based on decreasing silicate slag in sinter. Decreasing silicate slag is considered to be caused by increasing both Si and Mg concentration in calcium ferrite with chemical reaction between calcium ferrite and MgO in dolomite.
(4) Superiority of sinter softening property described in (2) is based on decreasing temperature range of high pressure drop. Decreasing the temperature range is considered to be caused by decreasing liquid phase ratio at high temperature (>1100°C) with MgO addition.
