The heat of the furnace decomposes the limestone to give calcium oxide. This is an endothermic reaction, absorbing heat from the furnace. ... Calcium oxide reacts with silicon dioxide to give calcium silicate. The calcium silicate melts and runs down through the furnace to form a layer on top of the molten iron.
Why is calcium oxide used to make steel?
Calcium Oxide is used in metallurgy industry with different purposes. In Steel is incorporated during iron and steel process as clinker agent, for then be able to eliminate impurities existing in metal parts. Calcium Oxide (lime) must contain of a high purity to improve its reactivity and performance .
Why is calcium oxide added to blast furnace?
Calcium oxide also plays an important part in the Basic Oxygen Steelmaking furnace. Here it helps to remove impurities such as phosphorus and sulphur from the steel . Phosphorus is a non-metal and produces an acidic oxide, P2O5. In the BOS furnace P2O5 combines with the basic calcium oxide to make calcium phosphate.
How does calcium carbonate purify iron?
Calcium carbonate is also used in the purification of iron from iron ore in a blast furnace . The carbonate is calcined in situ to give calcium oxide, which forms a slag with various impurities present, and separates from the purified iron.
How is calcium silicate removed from blast furnace?
6.1 Slag Materials
The calcium silicate material combines with other impurities in the melt, and this material is removed as slag and then dried and ground . Phosphorus slag is produced in a similar manner during the production elemental phosphorus in an electric furnace where phosphate rock is used as the raw material.
Why is iron converted into steel?
Blowing oxygen forces impurities (oxides, silicates, phosphates, etc.) to react with flux to form slag or escape through the top of the furnace as fumes. Flux (limestone) acts as the chemical cleaning agent, absorbing the iron impurities and leaving behind molten steel.
Which reaction is used to keep the furnace hot?
The hot air blast to the furnace burns the coke and maintains the very high temperatures that are needed to reduce the ore to iron. The reaction between air and the fuel generates carbon monoxide .
What happens to calcium oxide when heated?
When calcium oxide is heated near its melting point, it gives off a brilliant white light .
What is the function of calcium oxide?
Calcium oxide is widely used in industry, e.g., in making porcelain and glass ; in purifying sugar; in preparing bleaching powder, calcium carbide, and calcium cyanamide; in water softeners; and in mortars and cements. In agriculture it is used for treating acidic soils (liming).
Is calcium oxide a slag?
Calcium oxide is basic (as it is a metal oxide) and silica is acidic (as it is a non-metal oxide). Molten slag is tapped off at the bottom of the blast furnace above the molten iron as molten slag is less dense than molten iron.
Why is calcium carbonate used in iron extraction?
Limestone removes impurities present in the iron ore. This is achieved because, at high temperatures, calcium carbonate will undergo thermal decomposition to calcium oxide . The calcium oxide then reacts with the acidic impurities (mainly silica) present in the iron ore to form molten slag (calcium silicate).
What is the function of calcium carbonate in the process of iron extraction?
| Raw material Contains Function | Limestone Calcium carbonate Helps to remove acidic impurities from the iron by reacting with them to form molten slag | Air Oxygen Allows the coke to burn, and so produces heat |
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Does iron react with calcium carbonate?
The reaction is accompanied by carbonatite melt formation . ... In iron-containing systems at 6 GPa, calcium carbonate melts in the range 1473–1573 K, which is consistent with aragonite disappearance from complex carbonate systems. The composition of calcium carbonate liquid is not influenced by metallic Fe.
Which substance is added to a blast furnace to remove impurities?
Iron ore often has silicon dioxide (sand) impurity which must be removed during the process. To do this limestone is added to the charge. The limestone (chemically, calcium carbonate) decomposes in the heat of the furnace to calcium oxide.
Which is the waste gas in the blast furnace?
(top gas), the waste gas from blast furnaces; mainly the products of the incomplete combustion of carbon. Its chemical composition during the smelting of cast iron on coal coke is 12–20 percent carbon dioxide, 20–30 percent carbon monoxide, up to 0.5 percent methane , 1–4 percent hydrogen, and 55–58 percent nitrogen.
Is slag a contaminant?
Because of its characteristics, ferrous slag is commonly used for construction and environmental applications, whereas both non-ferrous and ferrous slag may be reprocessed for secondary metal recovery. Both types of slag have been a source of some environmental contamination .
