Question

Explain the purpose of each of these materials in the blast-furnace conversion of iron ore to iron. (a) Air (b) Limestone (c) Coke

Short answer

Air provides oxygen, limestone removes impurities, and coke acts as both a fuel and a reducing agent.

Step-by-step solution

Role of Air

Air supplies oxygen necessary for the oxidation of carbon in coke to carbon dioxide. This reaction provides the heat required for the iron extraction process. The air enriches the furnace environment with oxygen, facilitating the combustion reactions.

Role of Limestone

Limestone acts as a flux in the blast furnace. It decomposes to form lime (CaO) and CO2 at high temperatures. The lime reacts with impurities like silica (SiO2) present in the ore to form slag, which is less dense than iron and can be easily separated.

Role of Coke

Coke serves as both a fuel and reducing agent. It burns in the presence of oxygen to produce heat and carbon monoxide, which reduces iron oxide in the ore to iron. Coke also supports the ore and limestone in the furnace, allowing proper chemical and physical interactions.

Key concepts

Iron Ore Conversion

The process of converting iron ore into iron through a blast furnace is an essential part of steel production. The transformation starts with iron ore, typically composed of iron oxides such as hematite (Fe₂O₃) and magnetite (Fe₃O₄). The goal is to remove the oxygen from these iron compounds to produce metallic iron. Achieving this involves several chemical reactions that occur when the iron ore is heated in the blast furnace. Each of these reactions is facilitated by other materials that play specific roles and make the overall process efficient and effective. The core components in this transformation include air, limestone, and coke, each contributing in its unique way to ensure that iron is extracted efficiently.

Role of Air

Air plays a critical role in the operation of a blast furnace. It supplies the required oxygen needed for oxidizing coke, which is burned to produce the necessary heat for processing. - Air is introduced into the furnace environment, providing oxygen which reacts with the carbon present in coke. - This reaction forms carbon dioxide ( ext{CO}_2), releasing a significant amount of heat. - The generated heat not only melts the iron ore but also supports other necessary reactions inside the furnace by maintaining a consistently high temperature. Thus, air ensures that the blast furnace operates under the optimal conditions needed for efficient iron production.

Role of Limestone

Limestone plays a key part as a flux in the blast furnace process. It undergoes a series of reactions critical for removing impurities from the iron ore. - At the high temperatures inside the furnace, limestone (CaCO₃) decomposes into lime (CaO) and carbon dioxide ( ext{CO}_2). - The produced lime reacts with impurities present in the ore, such as silica (SiO₂), to form a liquid slag. - This slag, being less dense than iron, floats to the top and is periodically removed from the furnace to ensure pure iron is extracted. This process of impurity removal makes limestone indispensable in the steelmaking process.

Role of Coke

Coke serves multiple purposes in the operation of a blast furnace, acting both as a fuel and a reducing agent. - As a fuel, coke burns in the presence of the oxygen supplied by air, producing heat essential for melting the iron ore. - As a reducing agent, it generates carbon monoxide ( ext{CO}) through the reaction of coke carbon with ext{CO}_2. This carbon monoxide then reacts with the iron oxides from the iron ore, reducing them to metallic iron. Moreover, coke provides physical support within the furnace, helping to maintain an even distribution of materials, allowing for optimal chemical reactions. This makes it an integral part of the iron extraction process.