Calcium Carbide

Calcium carbide is also called calcium acetylide, which is a chemical compound having the chemical formula of CaC2. Mainly, it is used industrially for the production of calcium cyanamide and acetylene.

This is a pure material of colorless, and, however, the pieces of technical-grade calcium carbide compound are either brown or grey and consist of about 80–85% of CaC2 (the remaining is CaO - calcium oxide), Ca3P2 (calcium phosphide), Ca3N2 (calcium nitride), CaS (calcium sulfide), SiC (silicon carbide), and more). In trace moisture presence, the calcium carbide’s technical-grade emits an unpleasant odor, which is reminiscent of garlic.

Note: The calcium carbide applications include acetylene gas manufacturing and for the generation of acetylene in carbide lamps; chemicals manufacturing for fertilizer; and also in steelmaking.

CaC2 Structure

Let's look at the calcium carbide structure.

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Production of Calcium Carbide

Calcium carbide is industrially produced in an electric arc furnace with a mixture of coke and lime, approximately at 2,200 °C (3,990 °F). This is an endothermic reaction that requires a high temperature to drive off the carbon monoxide at 110 kilocalories (460 kJ) per mole. Since its invention in 1892, this method has not changed.

CaO + 3C → CaC2 + CO

The high temperature that is required for this reaction is practically not achievable by traditional combustion. So, this reaction is performed in an electric arc furnace using graphite electrodes.By weight, the produced carbide product will contain around 80% of the calcium carbide. Also, carbide is further crushed to produce small lumps that can range up to a maximum of 50 mm, and the impurities are concentrated in the finer fractions.

The CaC2 content, that product is assayed by measuring the produced acetylene amount on hydrolysis. As an example, the German and British standards for the coarser fractions content are 295 L/kg and 300 L/kg, respectively (at a pressure of 101 kPa and 20 °C (68 °F) temperature). The impurities of carbide include phosphide, which produces phosphine when hydrolyzed.

In chemistry, this reaction was not an important part of the industrial revolution and was made possible in the United States as a result of excessive amounts of inexpensive hydroelectric power that was produced at Niagara Falls before the 20th century turn off.

Production of Calcium Cyanamide

Calcium carbide compound reacts with nitrogen at higher temperatures to produce calcium cyanamide. It is represented by using the below equation.

CaC2 + N2 → CaCN2 + C

Commonly the term called nitrolime, which is a calcium cyanamide, can be used as fertilizer. It is also hydrolyzed to cyanamide, H2NCN.

Steel Making

Let us look at the steel making uses of calcium cyanamide as listed below:

• Calcium carbide can be used in the iron desulfurization (which are cast iron, pig iron, and steel).

• We can use it as a powerful deoxidizer at the facilities of ladle treatment.

• It can be used as a fuel in steelmaking to extend the scrap ratio to liquid iron, depending on the economics.

Carbide Lamps

Calcium carbide can be used in the carbide lamps. Dripping of water on the carbide produces acetylene gas, which in turn burns and produces light. While these lamps gave steadier and brighter light to that of candles, they were so dangerous in coal mines, a flammable methane gas that made them a serious hazard.

These flammable gases presence in coal mines led to miner safety lamps like the Davy lamp, where a wire gauze reduces the methane ignition risk. Still, carbide lamps were used extensively in copper, tin, and slate mines where methane is not considered a serious hazard. Most lamps of the miners have now been replaced by electric lamps.

But, still, the carbide lamps are used for mining in a few less wealthy countries. The silver mines near Potosí, Bolivia is an example. They are also used currently by a few cavers exploring caves and other underground areas, although they are increasingly replaced in this use by the LED lights.

Uses of Calcium Carbide (CaC2)

• Calcium Carbide is used in producing polyvinyl chloride as acetylene, which is the derivative of calcium carbide and is used as a raw material for PVC production.

• Calcium Carbide is also used in the production of acetylene and calcium hydroxide.

• It can be used in the removal of sulphur from iron. The removal of sulphur from any material is referred to as desulphurization.

• We can use it to produce calcium cyanamide.

• This compound can also be used as a ripening agent such as ethylene.

• It can be used in lamps like carbide lamps. Earlier, it was used as automobile headlights.

• It is also used as a deoxidizer, which means it helps in oxygen removal during steel manufacturing.

• It is also used in bamboo cannons and big-bang cannons.