Coal

In-depth explanation of Coal

Coal is a combustible sedimentary rock formed from plant material that was buried and transformed over millions of years. Its carbon content and energy density increase with rank, from lignite through bituminous coal to anthracite, which has the highest carbon content. Combustion releases CO2, sulfur dioxide, nitrogen oxides, particulates and ash, making coal the most carbon-intensive major energy source. Coal is used for electricity and, as coke made by heating it in the absence of air, for reducing iron ore in blast furnaces. Gasification converts coal into syngas for chemicals and fuels.

Going deeper: Coal

Key ideas: Ranks by carbon content and energy: peat, lignite (about 25 to 35 percent C), sub-bituminous, bituminous (about 45 to 86), anthracite (over 86 percent, highest heating value). Coke from heating coal without air is used in blast furnaces; coal tar gives aromatics; gasification gives syngas. Burning releases CO2, SO2, NOx, mercury and fly ash.

Common mistakes and connections: Mistake: viewing coal as pure carbon; it has H, O, N, S and minerals. Coal formed from ancient plants through coalification under heat and pressure. Scrubbers (limestone, flue gas desulfurization, CaCO3 plus SO2 plus O2 gives CaSO4) cut SO2. Links to acid rain and metallurgy.

Visualization of Coal

Approximate carbon content by coal rank. Carbon content and energy density rise from lignite to anthracite. The interactive lesson shows this as a live animation or chart.

Worked example and use case

Coke reduces iron oxide in a blast furnace to molten iron, releasing CO2 in the process.

Where Coal fits in Biochemistry, Environment & Industry

Coal is topic 98 of 127 in Biochemistry, Environment & Industry.

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