The United States has the largest coal reserves in the world, while China, USA, India, Russia, and Japan are the largest users of this fossil fuel. These five countries account for about 76% of global coal use.
It is believed that during that period, much of the Earth was covered by swamps and lagoons, where many giant plant species grew. Due to natural processes like flood, plants and other organic matter got buried at the bottom of such water bodies.
Over a period of time, more and more soil and sediments deposited over them. As a result, the dead plant and organic matter got compressed, and then slowly formed the peat bogs.
The peat bogs were deeply buried under the Earth's surface due to the accumulation of sediments over them. The compressed peat then gradually metamorphosed into coal under the effects of extreme heat and pressure. The conversion of dead organic or plant matter into coal is known as carbonification.
Types of Coal
It is softer than bituminous coal, but relatively harder than lignite. Its moisture content is lower than lignite.
The bituminous coal contains very little moisture, and is harder than both sub-bituminous and lignite coal.
It is the hardest coal with highest carbon content, and lowest moisture and ash content. The quality of anthracite is much higher than bituminous, sub-bituminous, and lignite.
What is Coal Used for?
Coal and its by-products have found numerous uses over the years. The following are some of the most noteworthy uses of this fossil fuel.
In coal-fired power plants, this fossil fuel is first pulverized, and then burned. It is burned in a furnace with a boiler, so that the heat produced in the furnace can boil water and produce steam.
The steam is then used to spin turbines, in order to generate electricity. A turbine is a rotary mechanical device capable of converting kinetic energy of a moving fluid into mechanical energy, by rotating the bladed rotor.
The bituminous coal is used to make coke, which is primarily used in the steel industry. Coke is basically a coal residue that is used as a fuel and as a reducing agent. It used in smelting iron ore in a blast furnace, in order to produce pig iron. Pig iron is further treated to produce steel.
To produce coke, the bituminous coal is heated under controlled conditions, and in the absence of air at temperatures as high as 1,000°C. The bituminous coal that has low-sulfur and low-ash content is usually used for producing coke.
The anthracite coal is used for both residential and commercial space heating, as it is considered to be a good heating fuel. Along with space heating, it is used for electricity generation as well.
The bituminous coal is a constituent of 'molding sand', which is also known as 'foundry sand'. Foundry sand is primarily used in making molds for metal casting. To make molding sand, the sand (silica or olivine) is mixed with a mixture of clay and water, finely ground bituminous coal (at a ratio of less than 5%), and several other substances.
When the molten metal is poured into the mold, the coal burns at a slow pace and releases reducing gases, and thus prevents the metal from penetrating the pores of the sand.
Coal tar is a thick and black-colored residue that is obtained during coal distillation. It has numerous applications in the industrial sector, right from insulating buildings and making buildings waterproof, to the production of a wide range of products, which include:
- Fabric and paints
The soaps and shampoos containing coal tar are used for conditions, like dandruff, skin sores, and psoriasis.
Not many people are aware of the fact that coal can be turned into ammonia and urea, which are used as fertilizers. Coal is first broken down into its constituent elements by a process called coal gasification.
In this process, coal is subjected to high pressure and temperature conditions in the presence of steam. As a result, a mixture of gases, called syngas is obtained. Syngas is mainly composed of carbon monoxide, hydrogen, carbon dioxide, and water vapor. The hydrogen obtained in this process can be used to make ammonia by combining it with nitrogen.
Gasoline and Diesel
The syngas obtained during the coal gasification process can also be converted into gasoline and diesel. The process of converting coal into hydrocarbons is known as Fischer-Tropsch process. In this process, a mixture of carbon monoxide and hydrogen is converted into liquid hydrocarbons with the help of a number of chemical reactions.
Coal is also employed for making concrete. Concrete is a building material that is made with cement, and coal is used as a source energy in the production of cement and bricks. Coal combustion products, such as 'fly ash' are also used in manufacturing cement.
Other Important Industrial Uses
Apart from these uses, coal is used in producing many other important industrial products, which include:
- Synthetic rubber and fiber (rayon and nylon)
- Carbon fiber
- Activated carbon (used in water filtration and air purification)
It is true that fossil fuels, like coal are indispensable for economic growth and development. But our increasing reliance on them has escalated the problem of environmental pollution. The combustion of fossil fuels accounts for more than 90% of greenhouse gas emissions in the United States.
The coal-fired power stations are responsible for emitting not only carbon dioxide, but several other noxious gases, volatile organic compounds, and heavy metals, like mercury, arsenic, and uranium.
However, it is possible to limit the emission of such pollutants with the judicious use of fossil fuels, effective pollution control measures, and stringent environmental regulation laws. Also important is to reduce our dependence on fossil fuels as much as possible, and encourage research on alternative energy sources.