The coal (Walloon word francized), is a carbonaceous Roche. It is also a Roche Combustible solid Fossile coming from the decomposition of organizations of the Carbonifère.

Used since the 11th century, the extraction of this fuel in the mine S.A. made possible the Industrial revolution at the 19th century. During decades, the coal constituted the independent source of énergie  ; also its name was declined to indicate natural energies potentially usable for the industriels  needs;:

Characterization of the coal

The coal is a specific quality of coal , generic term which recovers three categories of solid fuels of the same origin (Kérogène), but whose layers are at various stages of transformation : the Peat, the Lignite and finally the coal , whose anthracite is a variety of higher quality.

For the industrial and domestic needs, a coal is characterized par :

  • its volatile content (MV) expressed as a percentage compared to the total mass. Those are made up mainly of Méthane and Hydrogène   ; under the effect of a rise in temperature, the volatile matters are released from fuel, ignite easily, and accelerate the Combustion.
  • its calorific value (expressed in kJ/kg), quantity of heat provided by the combustion of one kg coal.
  • its water content expressed as a percentage.
  • its content of Ash S expressed as a percentage. Ashes are the solid residues of the combustion of coal, and can contain pollutants, metal in particular, an even little radioactive metals.
  • its content of Sulfur expressed as a percentage   ; the presence of Sulfur dioxide in the flue gases contributes to the Pollution of the environment.

Uses of the coal

The coal is especially used actuellement :

  • in the thermo plants used for the electrical production or the heating urbain  ;
  • in the Iron and steel industry, primarily for the manufacture of the coke used in the blast furnaces   ; between 600 and 700  kg of coal are necessary to produce a ton of Acier.
  • it should be noted that the individual Chauffage with coal is in retreat compared to other energy sources.

Electrical production

The use of coal in the thermo plants is very importante  ; these power stations provide 40  % of the worldwide production of electricity, half with the the United States and in Germany. Regarded as exceeded a long time, the interest of coal returns when the energy needs reach the maximum capacities of production of Pétrole or Natural gas, increasing their cost. The use of coal, in particular in the powerplants, made and continuous make enormous progress as regards reduction of the pollution emissions such as the Soufre, nitrogen oxides and the fine particles. On the other hand nothing or almost changed as regards emission of Gaz to greenhouse effect. A current coal center emits appreciably less CO per kilowatt-hour produces than old (because of the best output) but twice as much as one power station with gas. The return of coal will be thus (and is already) a disaster as regards climate warming. the sequestration of CO {{ind|2}} seems an interesting solution, but it will not be available to large scales before many years.

; The United States

Thus, the United States had built only one handle of new powerplants to coal during the years 1990, the electric companies preferring to build power stations with gas. Now that the price of gas increases and becomes extremely unstable, because of the decline of the American production, a hundred new coal stations are in project, for a total from some 60 gigawatts, over the period 2005-2013. It is however little in comparison with China. Research is directed towards a more ecological use of coal and towards the production of fuels of synthesis manufactured starting from coal. In 2003, the American Département of energy moreover launched the FutureGen research program, in order to fulfill the environmental requirements.

; China

In 2003, the Popular republic of China produces 79% of its electricity starting from coal. Beijing envisages to add approximately 70 new coal stations per annum; in 2006, five coal stations were built per week. This country should become the largest carbon dioxide transmitter from here at 2009. Indeed, the majority of the thermal powerplants are decayed and very polluting, because they function thanks to the technique of pulverization of coal. In 2007, China has 13% of coal world reserves is 118 billion tons. The most important coal companies are Shenhua Group and Yankuang.

Production of Gas by recovery

In some cases, one recovers natural gas naturally degassing veins of abandoned underground workings. This gas is naturally upwards thorough by the increase of tablecloth. In the north of France the installations of Méthamine and Gazonor recover it (except in the ends East and West of the field) and reinject it in the network of Gaz de France. It is also a means of making so that quantities large of Méthane (gas with important Greenhouse effect) do not join the atmosphere without being burned and transformed into CO {{ind|2}}.

Synthesis of hydrocarbons and others made up

Coal can be used with manufacture of chemicals and fuel as synthesis, and this use could intensify.

Since 1931, one can transform coal while carburizing thanks to its liquefication according to various processes (in particular the Procédé Fischer-Tropsch). However, this production remained marginal since the fuels derived from oil were much less expensive. In 2005, only the company Sasol , in South Africa produced hydrocarbons in industrial quantity according to this process.

In the same way, one can gasify coal and to produce with gas obtained of the petrochemical products like Méthanol, Ammoniac, Hydrogène, Propylène, but one prefers to use natural gas or oil.

Vis-a-vis supplies oil as out of gases which become more difficult, many countries start again to take these dies of production to serious, and in particular the the United States and China.

Exploitation of the coal

Until worms the year 2000, the worldwide production of coal was overall relatively stable, in increase in the reduction, but developing countries in the rich Western countries because of its character polluting and less practical than the gas or liquid fuels, or because of the exhaustion of the resources. The field of the Nord-Pas-de-Calais exploited, of 1850 to 1990, the Western part of a coal seam stretching France with the Belgium and the Germany. Nevertheless, these last years, the production strongly increased, mainly under the impulse of the China, which accounted for 45% of the production in 2005, against 19% in 1990.


Production:

  • 3564 million tons in 1990 (coal only);
  • 3650 million tons in 2000;
  • 4973 million tons in 2005, plus 900 lignite MT.

Here the first eight coal producer countries in 2005, according to the International agency of Energy, the production including coal " noir" and lignite:

Contrary to oil, coal is mainly consumed in the country which produces it, some 15% of the worldwide production, only, are exported. The first are Australia (231 MT), Indonesia, Russia and South Africa. Chinese exports decreased these last years, the production, in spite of a rise of 50% in three years, not managing to maintain the rate/rhythm of the gigantic request of the Chinese powerplants.

Health

In addition to the accident risks (collapses and blows of Grisou) remain important in the coal mines, the chronic exposure to dust of coal and the Radon in the mines or to their accesses is a factor of Silicose and risk of Lung cancer, retained by the tables of occupational diseases. The minors formerly used a Canari out of cage, which when he would die gave the signal of an urgent increase because of the lack of oxygen or of a CO superabundance and/or CO.

Downstream, smoke resulting from the combustion of the coal is also acid and polluting, in particular containing vapor traces of mercury and some heavy metals and/or radioactive in certain coals. Ashes of thermo plants to coal are also sometimes charged in Heavy metals, with traces, sometimes significant of Radioactivité, of HAP or others Polluant S. These ashes often accumulated on several meters height on dumps to some extent are carried by the wind or the rain. sometimes one uses them like melts of road layer, construction or filling materials to the risk to pollute the tablecloth.

Radon can continue to degas in the mines or the ground fractured by mining Affaissements, a long time after the end of the exploitation.

Coal has, as of the 19th century associated with heavy and very polluting industrial activities, of which the Carbochimie and the Métallurgie, often in edge of river, channel or on the littoral for reasons of transport. Environmental after-effects persist a long time after the stop of these activities, with serious impacts on health. For example in the field of the north of France, the intermediate duration of life was ten years lower than the national average, and it remained five years lower in the years 1980-1990.

See too

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