Question

Explain about coal and petroleum from basics

Answer 1

Coal is a flammable black hard rock used as a solid fossil fuel. It is mainly made up of 65-95% carbon and also contains hydrogen, sulphur, oxygen and nitrogen. It is a sedimentary rock formed from peat, by the pressure of rocks laid down later on top. The harder forms of coal, such as anthracite, are metamorphic rocks because they were changed by higher temperature and pressure.

Peat, and therefore coal, is formed from the remains of plants which lived millions of years ago in tropical wetlands, such as those of the late Carboniferous period (the Pennsylvanian). A similar substance made from wood by heating it in an airless space is called charcoal.

Coal can be burned for energy or heat. About two-thirds of the coal mined today is burned in power stations to make electricity. Coal is becoming less popular in new power plants as less expensive and less polluting technologies such as natural gas and hydroelectricity take over.

Coal can be roasted (heated in high temperature in a place where there is no oxygen) to produce coke. Coke is even better fuel than coal, and can be used in smelting to reduce metals from their ores.

Coal Mining:

There are two ways to remove coal from the ground: surface mining and underground mining.

Surface mining is used when a coal seam is relatively close to the surface, usually within 200 feet. The first step in surface mining is to remove and store the soil and rock covering the coal (called the "overburden"). Workers use a variety of heavy equipment--draglines, power shovels, bulldozers, and front-end loaders-to expose the coal seam for mining.

After surface mining, workers replace the overburden, grade it, cover it with topsoil, and fertilize and seed the area. These steps help restore the biological balance of the area and prevent erosion. The land can then be used for croplands, wildlife habitats, recreation, or as sites for commercial development.

Although only about 32 percent of the nation's coal can be extracted by surface mining, some 63 percent of all U.S. coal is mined using this method today. Why? Because surface mining is typically much cheaper than underground mining.

Underground mining is used when the coal seam is buried several hundred feet below the surface. In underground mining, workers and machinery go down a vertical "shaft" or a slanted tunnel called a "slope" to remove the coal. Mine shafts may sink as much as 1,000 feet deep.

One underground mining method is called room-and-pillar mining. With this method, much of the coal must be left behind to support the mine's roofs and walls. Sometimes as much as half the coal is left behind in large column formations to keep the mine from collapsing.

A more efficient and safer underground mining method, called longwall mining, uses a specially shielded machine which allows a mined-out area to collapse in a controlled manner. This method is called "longwall" mining because huge blocks of coal up to several hundred feet wide can be removed.

Processing and Transporting Coal:

After coal comes out of the ground, it typically goes on a conveyor belt to a preparation plant that is located at the mining site. A "prep" plant cleans and processes coal to remove dirt, rock, ash, sulfur, and other impurities. Removing the impurities increases the heating value of coal.

After the coal is mined and processed, it is ready to go to market. Transportation is a very important consideration in coal's competitiveness with other fuels because sometimes transporting the coal can cost more than mining it.

Underground pipelines can easily move petroleum and natural gas to market. But that's not so for coal. Huge trains transport most coal (almost 60 percent) for at least part of its journey to market. It is cheaper to transport coal on river barges, but this option isn't always available. Coal can also be moved by trucks and conveyors if the coal mine Is close by. Ideally, coal-fired electric power plants are built near coal mines to minimize transportation costs.

Petroleum:
Petroleum is a naturally occurring, yellow-to-black liquid found in geological formations beneath the Earth's surface. It is commonly refined into various types of fuels. Components of petroleum are separated using a technique called fractional distillation i.e. separation of a liquid mixture into fractions differing in boiling point by means of distillation, typically using a fractionating column.

It consists of hydrocarbons of various molecular weights and other organic compounds. The name petroleum covers both naturally occurring unprocessed crude oil and petroleum products that are made up of refined crude oil. A fossil fuel, petroleum is formed when large quantities of dead organisms, usually zooplankton and algae, are buried underneath sedimentary rock and subjected to both intense heat and pressure.
Petroleum has mostly been recovered by oil drilling (natural petroleum springs are rare). Drilling is carried out after studies of structural geology (at the reservoir scale), sedimentary basin analysis, and reservoir characterisation (mainly in terms of the porosity and permeability of geologic reservoir structures) have been completed. It is refined and separated, most easily by distillation, into a large number of consumer products, from gasoline (petrol) and kerosene to asphalt and chemical reagents used to make plastics and pharmaceuticals. Petroleum is used in manufacturing a wide variety of materials, and it is estimated that the world consumes about 95 million barrels each day.

Concern over the depletion of the earth's finite reserves of oil, and the effect this would have on a society dependent on it, is a concept known as peak oil. The use of fossil fuels, such as petroleum, has a negative impact on Earth's biosphere, damaging ecosystems through events such as oil spills and releasing a range of pollutants into the air including ground-level ozone and sulfur dioxide from sulfur impurities in fossil fuels. The burning of fossil fuels plays a major role in the current episode of global warming.