ANS:B - 1.1-1.4

The basicity of slag in a blast furnace is a measure of the ratio of basic oxides (primarily CaO and MgO) to acidic oxides (primarily SiO2). This ratio influences various properties of the slag, including its fluidity, melting temperature, and ability to dissolve impurities. In the range of 1.1-1.4, the basicity indicates that the slag contains a higher concentration of basic oxides compared to acidic oxides, albeit to a lesser extent compared to higher basicity ranges. Here's an explanation of what this range signifies:

• Higher Basicity: A basicity range of 1.1-1.4 indicates that there is a moderate concentration of basic oxides relative to acidic oxides in the slag. This means that there is a sufficient amount of basic oxides, such as calcium oxide (CaO) and magnesium oxide (MgO), to react with acidic impurities in the ore and fluxes, thereby forming a slag that can effectively absorb and remove these impurities.
• Slag Properties: Slags with a basicity in this range typically exhibit properties suitable for efficient iron smelting. They have adequate fluidity to flow smoothly in the blast furnace, facilitating the removal of impurities and maintaining a stable operating condition. Additionally, the melting temperature of the slag is within a desirable range for efficient operation of the blast furnace.
• Process Efficiency: Maintaining a basicity in the range of 1.1-1.4 helps ensure that the slag effectively captures impurities, such as silica (SiO2), alumina (Al2O3), and phosphorus (P2O5), thereby producing high-quality molten iron with minimal impurity content.