Question

which product of coal is used as a reducing agent in extraction of metal?

Answer 1

Coke is a tough and porous black solid substance Coke is prepared by heating coal in the absence of air. Coke is an almost pure form of carbon. Coke is mainly used as a reducing agent in the extraction of metals (like iron, zinc etc.) Coke is used in the manufacture of steel.

Answer 2

Why is Coke used as a reducing agent in the extraction of metals? The short answer is: we use coke, because we want the carbon in the coal, but we don’t want the volatiles.  Now, here’s the long answer for the case of making steel.  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 16 to 18 hours, depending on the capacity of the oven, 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 Fe2O3 – sometimes a little Fe3O4 and some limestone as flux (flux to form slag, containing the impurities), and hot air is blown in to burn the coke and also to use it to reduce the Fe2O3 to Fe plus CO and CO2. 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.  That’s the answer to your question, but I might as well add the next step, for completeness.  This molten iron is taken to a steelmaking furnace, where it is dumped into a 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, to reduce the carbon content to 0.10% to 0.40% by removing carbon as CO (90%) and CO2 (10%). The result is now called steel. Manganese Mn and other elements such as Mo, Cr, Si, Ni, etc., are added, according to the grade of steel being produced.