differences between coal used iron and electric iron
Answers
Answer:
A mix of high-volatile, medium volatile and low-volatile coal (volatile meaning the relative content of xylene, toluene, butadiene and other aromatic hydrocarbons) is coked (meaning heated without air) for 17 or 18 hours to drive off the volatiles. The result is called “coke” and it consists of carbon and about 9% to 12% ash.
The coke is dumped into a blast furnace, together with iron ore, mostly Fe2O3, and some limestone as flux (flux to form slag, containing the impurities), and hot air is blown in to burn the coke to produce CO and CO2, and the CO reduces the Fe2O3 to Fe. The reduction of iron oxides is not achieved by carbon directly, as reactions between solids are typically very slow, but by the carbon monoxide (Fe2O3 + 3CO = 2Fe + 3CO2). Any carbon dioxide resulting from the combustion of the coke undergoes a reverse Boudouard reaction (CO2 + C ↔ 2CO) upon contact with the carbon in coke.
The result is liquid iron, tapped from the blast furnace at approximately 1400C. This iron contains 4.2 wt% carbon, because that’s the saturation level for carbon in iron. This iron is called “pig iron”.
This molten iron is taken to a basic oxygen furnace, where it is dumped into the furnace containing 15% to 25% ferrous scrap (meaning 15% to 25% of the total metallic charge is ferrous scrap). Oxygen is then blown into the liquid iron at high velocity (around Mach 3), to reduce the carbon content by removing carbon as CO (90%) and CO2 (10%).
If we take the carbon down to 2.7% - 3.4% and add ferrosilicon and ferromanganese to get the desired levels of Si and Mn, we will have cast iron.
If, on the other hand, we blow the carbon down below 2%, we will have steel. Manganese Mn and other elements such as Mo, Cr, Si, Ni, etc., are added, according to the grade of steel being produced.
Explanation: