The message about coal can be used in preparation for the lesson. The story about coal for children can be supplemented with interesting facts.
Report about hard coal
Coal is a solid, exhaustible, non-renewable mineral that a person uses to obtain heat by burning it. According to the classification, it belongs to sedimentary rocks. Coal as a source of energy, people began to use in antiquity along with firewood.
How is coal formed?
Coal appeared on Earth about 300-350 million years ago, when tree-like ferns flourished on primeval swamps and the first gymnosperms began to appear.
It is believed that coal was formed as a result of the deposition of wood. There were ancient forests, the trees of which accumulated in swamps, where, without access to oxygen, the activity of bacteria decomposing plant residues is reduced to zero, peat is formed, and then, in the process of burying these residues, coal is formed under high pressure and temperature.
So for the formation of coal requires the occurrence of peat at a depth of three kilometers. At this depth, a twenty-meter layer of peat will turn into coal with a seam thickness of two meters.
Types of coal
All types of coal lie in layers and their locations are called coal basins. Today, different types of coal are mined.
- Anthracites are the hardest grades with great depth and maximum combustion temperature.
- Coal - many varieties mined in mines and open pit. It is widely used in many areas of human activity.
- Brown coal - formed from the remains of peat, the youngest type of coal. It has the lowest combustion temperature.
How is coal mined?
Previously, hard coal was simply collected in places where the seam came to the surface. This could have happened as a result of the displacement of the layers of the earth's crust.
Often, after landslides in mountainous areas, such outcrops of the deposit were exposed, and people got the opportunity to get to pieces of “combustible stone”.
Later, when the first technique appeared, coal began to be developed in an open way. Some coal mines plunged to a depth of more than 300 meters.
Today, thanks to modern technology, people descend to a depth of more than 1000 m, where high-quality coal is mined.
Different types of coal can be used to generate heat. When burned, it releases much more than can be obtained from wood or other solid fuels. The hottest grades of coal are used in metallurgy, where high temperatures are needed.
In addition, coal is a valuable raw material for the chemical industry. A lot of necessary and useful substances are extracted from it.
We hope that the above information about coal has helped you. And you can leave your report about coal through the comment form.
Stuart E. Nevins, MS.
Accumulated, compacted and processed plants form a sedimentary rock, which is called coal. Coal is not only a source of great economic value, but also a breed that has a special appeal to the student of earth history. Despite the fact that coal forms less than one percent of all sedimentary rocks on earth, it is of great importance to geologists who trust the Bible. It is coal that gives the Christian geologist one of the strongest geological arguments in favor of the reality of the global Noah's Flood.
Two theories have been proposed to explain the formation of coal. The popular theory, held by most uniformitarian geologists, is that the plants that make up coal accumulated in huge freshwater swamps or peat bogs over many thousands of years. This first theory, which assumes the growth of plant material at the site of its discovery, is called autochthonous theory .
The second theory suggests that the coal seams accumulated from plants that were quickly transported from other places and deposited under flooding conditions. This second theory, according to which there was a movement of plant debris, is called allochthonous theory .
fossils in coal
The types of fossil plants that are found in coal are obviously do not support the autochthonous theory. Fossil trees of club mosses (for example, Lepidodendron and Sigillaria) and giant ferns (especially Psaronius) characteristic of Pennsylvania coal deposits may have had some ecological tolerance to swampy conditions, while other fossil plants of the Pennsylvania Basin (for example, conifer Cordaites, wintering giant horsetail Calamites, various extinct fern-like gymnosperms) in accordance with their basic structure must have preferred well-dried soils rather than swamps. Many researchers believe that the anatomical structure of fossil plants indicates that they grew in tropical or subtropical climates (an argument that can be used against the autochthonous theory), since modern swamps are the most extensive and have the deepest accumulation of peat in cooler climates. higher latitudes. Due to the increased evaporative power of the sun, modern tropical and subtropical areas are the poorest in peat.
Often found in the corner marine fossils, such as fossil fish, molluscs, and brachiopods (brachiopods). Coal seams are found to be balls of coal, which are rounded masses of crumpled and incredibly well-preserved plants, as well as fossil animals (including marine animals) that are directly related to these coal seams. The small marine annelids, Spirorbis, are generally found attached to coal plants in Europe and North America that date back to the Carboniferous. Since the anatomical structure of fossil plants shows little evidence that they were adapted to sea swamps, the occurrence of marine animals along with non-marine plants suggests that mixing occurred during movement, thus supporting the allochthonous theory model.
Among the most amazing types of fossils that are found in coal layers are vertical tree trunks, which are perpendicular to the bedding often intersect tens of feet of rock. These upright trees are often found in seams that are associated with coal deposits, and in rare cases they are found in the coal itself. In any case, sediment must accumulate quickly in order to cover the trees before they deteriorate and fall.
How long does it take for layers of sedimentary rocks to form? Take a look at this ten meter petrified tree, one of hundreds discovered in the coal mines of Cookeville, Tennessee, USA. This tree starts in one coal bed, goes up through numerous layers, and finally ends in another coal seam. Think about this: what would happen to the top of the tree in the thousands of years it takes (according to evolution) to form sedimentary layers and coal seams? Obviously, the formation of sedimentary layers and seams of coal had to be catastrophic (rapid) in order to bury the tree in an upright position before it rots and falls. Such "standing trees" are found in numerous places on the earth and at different levels. Despite the evidence, long periods of time (required for evolution) are squeezed between the layers, for which there is no evidence.
One might get the impression that these trees are in their original growth position, but some evidence indicates that this is not the case at all, and even vice versa. Some trees cross the layers diagonally, and some are found upside down. Sometimes vertical trees appear to have taken root in a growth position in layers that are completely penetrated by a second vertical tree. The hollow trunks of fossil trees are usually filled with sedimentary rock that is different from the nearby surrounding rocks. Applicable to the examples described, the logic indicates the movement of these trunks.
fossil roots
The most important fossil, which is directly related to disputes over the origin of coal, is stigmaria- Fossil root or rhizome. Stigmaria it is most commonly found in seams that lie beneath coal seams and is generally associated with vertical trees. It was believed that stigmaria, which was studied 140 years ago by Charles Lyell and D.W. Dawson in the Carboniferous coal sequence in Nova Scotia, is clear evidence that the plant grew in this location.
Many modern geologists continue to insist that stigmaria is a root that formed in this place, and which goes into the soil below the coal marsh. The coal sequence of Nova Scotia was recently re-examined by H.A. Rupke, who found four arguments in favor of allochthonous origin of stigmaria obtained on the basis of the study of sedimentary deposits. The discovered fossil is usually clastic and rarely attached to the trunk, indicating a preferred orientation of its horizontal axis, which was created as a result of the action of the current. In addition, the stem is filled with sediment that is unlike the rock surrounding the stem, and is often found at many levels in strata that are completely pierced by vertical trees. Rupke's research cast serious doubts on the popular autochthonous explanation of other strata in which stigmaria.
Cyclothemes
Coal usually occurs in a sequence of sedimentary rocks called cyclotheme .idealized Pennsylvania cyclotheme may have strata deposited in the following ascending order: sandstone, shale, limestone, underlying clay, coal, shale, limestone, shale. V typical cyclotheme, as a rule, one of the constituent layers is missing. At each site cyclothemes each deposition cycle is usually repeated dozens of times, with each deposition resting on the previous deposition. In Illinois is fifty sequentially arranged cycles, and more than a hundred such cycles occur in West Virginia.
Although the coal seam that forms part of a typical cyclothemes, usually quite thin (typically one inch to several feet thick) the lateral arrangement of coal has incredible dimensions. In one of the recent stratigraphic studies4, a relationship was drawn between coal deposits: Broken Arrow (Oklahoma), Crowberg (Missouri), Whitebrest (Iowa), Colchester number 2 (Illinois), Coal IIIa (Indiana), Schultztown ( Western Kentucky), Princess Number 6 (Eastern Kentucky), and Lower Kittanning (Ohio and Pennsylvania). They all form one, huge coal seam that extends for hundreds of thousands of square kilometers in the central and eastern United States. No modern swamp has an area that even slightly approaches the size of the Pennsylvania coal deposits.
If the autochthonous model of coal formation is correct, then very unusual circumstances must have prevailed. The entire area, often comprising tens of thousands of square kilometers, would have to simultaneously rise above sea level in order for the swamp to accumulate, and then it would have to sink in order to be flooded by the ocean. If the fossil forests rose too high above sea level, the swamp and its antiseptic water needed to accumulate peat would simply evaporate. If the marsh was invaded by the sea during the accumulation of peat, the marine conditions would destroy the plants and other sediments and the peat would not be deposited. Then, according to the popular model, the formation of a thick coal seam would indicate the maintenance of an incredible balance over many thousands of years between the rate of peat accumulation and sea level rise. This situation seems the most improbable, especially if we remember that the cyclotheme is repeated in a vertical section hundreds of times or even more. Or perhaps these cycles can best be explained as accumulation that occurred during the successive rise and retreat of the flood waters?
Shale
When it comes to the cyclotheme, the underlying clay is of most interest. The underlying clay is a soft layer of clay that is not arranged in layers and often lies beneath the coal seam. Many geologists believe that this is a fossil soil on which a swamp existed. The presence of underlying clay, especially when found in it stigmaria, often interpreted as enough proof autochthonous origin of coal-forming plants.
However, a recent study has questioned the interpretation of the underlying clay as fossil soil. No soil characteristics that were similar to those of modern soil have been found in the underlying clay. Some of the minerals found in the underlying soil are not the types of minerals that should be found in the soil. On the contrary, the underlying clays, as a rule, have rhythmic layering (larger granular material is located at the very bottom) and signs of the formation of clay flakes. These are simple characteristics of sedimentary rocks that would form in any layer that accumulated in water.
Many coal layers do not rest on the underlying clays, and there are no signs of soil existence. In some cases, coal seams rest on granite, slate, limestone, conglomerate, or other rocks that do not resemble soil. Underlayment clay without an overlying coal seam is common, and underlayment clay often overlies the coal seam. The absence of recognizable soils below the coal seams indicates that no type of lush vegetation could grow here and supports the idea that coal-forming plants were moved here.
Structure of coal
The study of the microscopic structure and structure of peat and coal helps to understand the origin of coal. A.D. Cohen initiated a comparative structural study of modern autochthonous peat formed from mangrove trees and a rare modern allochthonous coastal peat from south Florida. Most autochthonous peat contained plant fragments that had a disordered orientation with a predominant matrix of finer material, while allochthonous peat had an orientation formed by water flows with elongated axes of plant fragments, which were located, as a rule, parallel to the coastal surface with a characteristic absence of finer material. matrix. Poorly sorted plant debris in autochthonous peat had a large structure due to the intertwined mass of roots, while autochthonous peat had a characteristic microlayering due to the absence of ingrown roots.
In conducting this study, Cohen noted: "In the course of the study of allochthonous peat, one feature was revealed, which was that vertical sections of this material, made using a microtome, looked more like thin sections of coal than any autochthonous sample studied". Cohen drew attention to the fact that the characteristics of this autochthonous peat (orientation of elongated fragments, sorted granular structure with an overall lack of finer matrix, micro-layering with no entangled root structure) are also characteristics of coals of the Carboniferous period!
Lumps in the coal
One of the most impressive external features of coal is the presence of large blocks in it. For more than a hundred years, these large blocks have been found in coal seams around the world. P.H. Price conducted a study in which he studied large blocks of the Sewell coal deposit, which is located in West Virginia. The average weight of 40 boulders collected was 12 pounds, and the largest boulder weighed 161 pounds. Many cobblestones were volcanic or metamorphic rock, unlike all other rock outcrops in West Virginia. Price surmised that the large boulders could have weaved themselves into the roots of the trees and been transported here from afar. Thus, the presence of large blocks in the coal supports the allochthonous model.
coalification
Disputes regarding the nature of the process of turning peat into coal have been going on for many years. One existing theory suggests that it is time is the main factor in the coalification process. However, this theory fell out of favor because it was found that there was no systematic increase in the metamorphic stage of coal over time. There are several apparent inconsistencies: lignites, which are the lowest stage of metamorphism, occur in some of the oldest coal-bearing strata, while anthracites, which represent the highest grade of coal metamorphism, occur in younger strata.
The second theory regarding the process of turning peat into coal suggests that the main factor in the process of coal metamorphism is pressure. However, this theory is refuted by numerous geological examples in which the stage of coal metamorphism does not increase in highly deformed and folded seams. Moreover, laboratory experiments show that an increase in pressure can actually slow down chemical conversion of peat into coal.
The third theory (by far the most popular) suggests that the most important factor in the process of coal metamorphism is temperature. Geological examples (volcanic intrusions in coal seams and underground fires in mines) show that elevated temperatures can cause coalification. Laboratory experiments have also been quite successful in confirming this theory. In one experiment, using a rapid heating process, an anthracite-like substance was formed in just a few minutes, with most of the heat generated as a result of the transformation of the cellulose material. Thus, the metamorphism of coal does not require millions of years of exposure to heat and pressure - it can be formed as a result of rapid heating.
Conclusion
We see that a lot of corroborating evidence decisively proves the truth of the allochthonous theory and confirms the accumulation of multiple coal layers during Noah's Flood. Upright fossil trees inside coal layers confirm the rapid accumulation plant residues. Marine animals and terrestrial (rather than growing and living in a swamp) plants found in coal imply their movement. The microstructure of many coal seams has a specific particle orientation, sorted grain structure, and microlayering, which indicates movement (rather than in situ growth) of plant material. The large blocks present in the coal testify to the processes of movement. The absence of soil under many coal seams confirms the fact that coal-forming plants floated with the flow. Charcoal has been shown to form systematic and typical portions cyclothemes, which obviously, like other rocks, were deposited by water. Experiments to study the change in plant material show that coal-like anthracite does not need millions of years to form - it can be formed quickly under the influence of heat.
Links
*Professor of Geology and Archaeology, Christian Heritage College, El Cajon, California.
Wood has long been used to heat houses, but in order to constantly keep burning, it is necessary to put logs on again and again. With the development of the coal mining industry, more and more people began to use coal: it gives more heat, burns longer. With the correct laying of the furnace, a portion of coal, poured into the boiler in the evening, will maintain a stable temperature all night.
The history of the formation of coal and its types
The whole process of coal formation can be divided into two main stages: the formation of peat and the process of coalification itself - the transformation of peat into coal.
Peat was formed on vast expanses covered with water from plant residues of varying degrees of decomposition. Some of the plants rotted completely to a gel-like state, some retained their cellular structure. Their remains accumulated at the bottom of reservoirs, which gradually turned into swamps. A prerequisite for the formation of peat is the absence of oxygen. There was little oxygen under the water column; during the decomposition of the remains, hydrogen sulfide, methane and carbon dioxide were released, which contributed to the hardening of the remains. Peat was formed.
But not all peatlands were converted to coal. The coalification process requires: high pressure, high temperature and a long period of time. Depending on the presence of these conditions, the formation of coal took place or not. First, the peat was brought in by sedimentary rocks, which increased the pressure and raised the temperature inside the peat layer. Under such conditions, brown coal was formed - the first stage of coalification. Seam displacement has occurred in some areas, causing brown coal seams to subside (some of the discovered deposits are at depths of more than 6,000 meters). In places, these processes were accompanied by the rise of magma and volcanic eruptions. High pressure, lack of oxygen and high temperatures contributed to the fact that there was less and less moisture and natural gases in brown coal, and more and more carbon. With the displacement of water and gases, brown coal turned into bituminous, then, in the presence of high temperature, into anthracite. The main difference between brown coal and hard coal is that brown coal contains more moisture and natural gases and less carbon, which affects the amount of heat released during combustion.
Today, the age of coal deposits is determined by plant remains. The most ancient date back to the Carboniferous period (345-280 million years ago). During this period, most of the coal basins of North America (east and center of the USA), the center and west of Europe, southern Africa, China, and India were formed. In Eurasia, most of the coal deposits were formed in the Permian period, some of the small coal basins in Europe date back to the Triassic period. The activity of coal formation increases towards the end of the Jurassic and in the Cretaceous. Around this time, deposits were formed in the east of Europe, in the Rocky Mountains of America, in Indochina and the center of Asia. Later, mainly brown coals and peat deposits were formed.
Types of coal
Coal is classified according to its moisture content, natural gases and carbon content. With an increase in the amount of carbon, its calorific value increases. The less moisture and volatile substances (gases), the better it tolerates storage and transportation.
Lignite- coal of the first stage of coalification. It differs from brown coal in a smaller amount of water (45%) in the composition and in a large release of heat. The structure is fibrous, the color is from brown to black (higher quality). It is most often used in the energy sector (at thermal power plants) for heating private houses it is rarely used, as it is poorly stored and has a low calorific value in conventional furnaces.
Subbitominous coal- black color, less pronounced fibrous structure, higher calorific value compared to lignite, lower moisture content (30%). It crumbles during transportation, and weathers in the open air. When burned, it releases 5-6 kW / kg. It is used both in power engineering and in housing and communal services for heating.
bituminous coal has the highest calorific value, does not lose its qualities during transportation and storage. It emits 7-9 kW / kg of heat during combustion. Some of its species are used for coking.
Anthracite- jet black charcoal. It has the highest hydrocarbon content. It is difficult to ignite it, but it burns for a long time and without soot, it releases a large amount of heat (more than 9 kW / kg). It is anthracite that is most often used for heating.
What kind of coal is used for heating
In Russia and the CIS countries, there is a system adopted back in 1988. Coal is classified according to GOST 25543-88, which is divided into 7 categories. Only a few are used for heating:
Long-flame coal (D). It got its name due to the long combustion process with the release of a large amount of heat (5600-5800 kcal / kg). For its ignition and combustion, special blowing is not required, therefore long-flame coals are often used in domestic solid fuel boilers. Depending on the size, it happens:
- WPC - large slab - the size of the pieces is 50-200 mm;
- DPKO - slab fist-nut - sizes of pieces 25-100 mm;
- PO - walnut - 26-50 mm;
- DM - small - sizes 13-25 mm;
- DS - seed - 6-13 mm;
- DR - private - no standard sizes.
Long-flame coal is optimal for heating: the flame is long (similar to firewood), a lot of heat is released, it ignites and burns easily - natural draft is enough for normal combustion. Its relatively low cost, combined with excellent characteristics, determined the popularity of this brand of coal. It is purchased not only for heating private houses, but also for boiler rooms of educational and medical institutions. Moreover, fuel of any fraction is used: from large "K" to small "M".
Long-flame gas (DG). Differs from grade D in greater calorific value. All fractions are used for heating private houses: from “large” to “ordinary”. More demanding than long-flame to storage conditions, tk. more intensively weathered.
Anthracite (A). It emits a lot of body, has a low ash content (ash residue 10%), burns for a long time and evenly, the smoke during combustion is white (all other brands “give” black smoke). Despite the high performance, it is impossible to unequivocally recommend it for heating private houses: anthracite has a high cost and is difficult to kindle.
In some cases, they buy lean coals "T", fat "G" or slightly caking "SS". The rest of the classes have predominantly industrial uses. They are used in energy and metallurgy, some grades for coking and enrichment. When choosing coal, you need to pay attention not only to its characteristics, but also to the cost of delivery. If your area does not sell long flame or anthracite, then most likely you will have to make do with what is on the market. You also need to pay attention to the recommendations of the manufacturers of your boiler: the documents usually indicate the brands for which the equipment was designed. They must be used.
To increase comfort and in order to save money, many people prefer to have several fractions: it is more convenient to melt with the “nut” or “large” fraction, and pour the “seed” for a long burning. For the coldest periods, a certain amount of anthracite is stored, which, although it is difficult to kindle, burns long and hot in a heated boiler.
Coking and enriched coals undergo special treatment to increase their calorific value. These species are used in metallurgy and energy. Such fuel is not suitable for domestic boilers: due to the excessively high combustion temperature, the furnace can break.
If you listen to people with experience, they say that the best effect is given by the following sequence of pouring fuel into the boiler: melt with a long flame, then fill in anthracite of the “nut” fraction - it burns for a long time, you give a lot of heat, and at night add “seeds” to the stove, which will burn until morning.
The order of kindling brick ovens is recommended differently: they kindle the oven with firewood, when it flares up well, fall asleep with a “seed” or (open the blower and damper for better oxygen supply). If there is a lot of dust in the seed, it can be moistened with water - this way it flares up more easily. When the heat in the oven is sufficient, the "fist" can be used.
What is charcoal and what is it used for
Charcoal has been used by people for many thousands of years: it was found during excavations in the settlements of cavemen. It is unlikely that they made it themselves, rather they collected it on fires or preserved the remains of fires, but, apparently, they knew about its properties and knew how to use it.
Today, in our country, this type of fuel is mainly used for cooking: it is used in barbecues and barbecues, put in fires. Sometimes they are used for fireplaces: it burns for a long time, emits a lot of heat (7800 KC / kg), and there is almost no smoke and soot. The remaining ash is an excellent fertilizer and is used to fertilize forest land or agricultural fields. Charcoal ash is also used for the production of fertilizers.
In industry, charcoal is used for iron smelting. It takes only 0.5 tons of this fuel to produce a ton of alloy. At the same time, cast iron receives increased resistance to corrosion and strength. As a flux, coal is used in the smelting of brass, bronze, copper, manganese, zinc and nickel. It is used to make a solid lubricant for mechanical engineering, is used for grinding in instrument making and printing, etc. Filters for various purposes are made from charcoal.
Today, charcoal is beginning to be seen as an alternative to traditional fuels: unlike coal, oil and gas, it is a renewable material. Moreover, modern technologies make it possible to obtain charcoal even from industrial waste: from sawdust, dust, shrubs, etc. Briquettes are formed from such crushed raw materials, which give 1.5 times more heat than ordinary charcoal. In this case, heat is released for a longer period of time and the heat is uniform.
How is charcoal made
Until the 20th century, charcoal was obtained by burning wood or specially shaped piles. Wood was laid in them, covered with earth, set on fire through special holes made. This technology is publicly available and is still used in some countries. But it has low efficiency: up to 12 kg of wood is consumed per 1 kg of coal, and it is also impossible to control the quality of the resulting charcoal. The next stage in the development of charcoal burning was the use of pipes in earth furnaces. This improvement increased the efficiency of the process: 8 kg of timber was consumed per kilogram.
In modern charcoal burners, 3-4 kg of raw materials are consumed per kilogram of product. At the same time, great attention is paid to the environmental friendliness of the process: during the production of charcoal, a lot of smoke, soot and harmful gases are released into the atmosphere. Modern installations capture the emitted gases, send them to special chambers, where it is used to heat the furnace to the coking temperature.
The transformation of wood into charcoal takes place in an oxygen-free atmosphere at high temperature (pyrolysis reaction). The whole process is divided into three stages:
- at 150 ° C, moisture is removed from the wood;
- at 150-350 about With the release of gases and the formation of organic products;
- at 350-550 ° C, resins and non-condensable gases are separated.
According to GOST, charcoal is divided into several grades depending on the type of wood used:
- A - hardwood species;
- B - hard and soft hardwood, coniferous species (o).
Grades B and C - most often these are charcoal briquettes, for the manufacture of which waste from wood processing enterprises is used. This is an excellent type of biofuel that has long been used in Europe for heating and even in power plants: when they are burned, sulfur compounds are not formed (there is no sulfur in charcoal), and hydrocarbons are contained in minimal quantities. Using the technology of ancestors, you can burn coal for your own needs yourself. .
Almost 200 years ago, the brilliant Russian scientist M. V. Lomonosov quite correctly explained the formation of fossil coal from plant residues, just as peat is now formed. Lomonosov also indicated the conditions necessary for the transformation of peat into coal: the decomposition of vegetation "without free air", the high temperature inside the Earth and the "burden of the roof", that is, the pressure of rocks.
It takes a very long time for peat to turn into coal. Peat accumulates in the swamp, and from above the swamp is overgrown with more and more new layers of plants. At depth, peat is constantly changing. The complex chemical compounds that make up plants break down into simpler ones. One part dissolves and is carried away with water, the other passes into a gaseous state: carbon dioxide and light gas - methane (the same gas burns in our stoves). An important role in the formation of coal is played by fungi and bacteria that inhabit all peat bogs. They help the destruction of plant tissue. In the process of these changes in peat, the most stable substance, carbon, accumulates in it. As it changes, peat becomes more and more rich in carbon.
The accumulation of carbon in peat occurs without access to oxygen, otherwise carbon, combining with oxygen, would turn completely into carbon dioxide and evaporate. The resulting layers of peat are first isolated from the oxygen of the air by the water covering them, then by newly emerging layers of peat.
This is how the process of turning peat into fossil coal gradually proceeds. There are several main types of fossil coal: lignite, brown coal, bituminous coal, anthracite, boghead, etc.
The most similar to peat is lignite - loose brown coal, of not very old origin. It clearly shows the remains of plants, mainly wood (hence the name "lignite", which means "wooden"). Lignite is woody peat. In modern temperate peat bogs, peat is formed mainly from peat moss, sedge, reeds, but in the subtropical zone of the globe, for example, in Florida forest bogs in the USA, woody peat is also formed, very similar to fossil lignite.
With a stronger decomposition and change in plant residues, brown coal is created. Its color is dark brown or black; it is stronger than lignite, wood remains are less common in it and it is more difficult to see them. When burning brown coal gives off more heat than lignite, since it is richer in carbon. Brown coal does not always turn into hard coal over time. It is known that the brown coal of the Moscow Basin is of the same age as the hard coal on the western slope of the Urals (Kizel basin). The process of turning brown coal into hard coal occurs only when layers of brown coal sink into deeper horizons of the earth's crust or mountain building processes occur. For the transformation of brown coal into - stone or anthracite, a very high temperature and great pressure in the bowels of the Earth are needed. In coal, only under a microscope are the remains of plants visible; it is heavy, lustrous, and often very strong. Some grades of coal themselves or together with other grades coke, that is, they turn into coke.
The largest amount of carbon contains black shiny coal - anthracite. You can find the remains of plants in it only under a microscope. When burned, anthracite gives off more heat than all other grades of coal.
Boghead - dense black coal with a conchoidal fracture surface; dry distillation gives a large amount of coal tar - a valuable raw material for the chemical industry. Boghead is formed from algae and sapropel.
The longer the coal lies in the earth's layers and the more it is subjected to pressure and the action of deep heat, the more carbon it contains. Anthracite contains about 95% carbon, brown coal - about 70%, and peat - from 50 to 65%.
In the swamp, where peat initially accumulates, clay, sand and various dissolved substances usually get along with water. They form mineral impurities in peat, which then remain in coal. These impurities often form interlayers that separate the coal seam into several layers. The admixture contaminates the coal and makes it difficult to develop.
When coal is burned, all mineral impurities remain in the form of ash. The better the coal, the less ash it should contain. In good grades of coal, it is only a few percent, but sometimes the amount of ash reaches 30-40%. If the ash is more than 60%, then coal does not burn at all and is not suitable for fuel.
Coal seams are different not only in their composition, but also in structure. Sometimes the entire seam is composed of pure coal throughout its entire thickness. This means that it was formed in a peat bog, where water polluted with clay and sand almost did not get. Such coal can be burned immediately. More often, coal seams alternate with clayey or sandy interlayers. Such seams of coal are called complex. In them, for example, a seam of 1 m thick often has 10-15 layers of clay, several centimeters thick each, and pure coal accounts for only 60-70 cm; while the coal can be of very good quality.
To obtain fuel with a low content of foreign impurities from coal, coal is enriched. From the mine, the rock is immediately sent to the processing plant. There, the rock mined in the mine is crushed into small pieces in special machines, and then all clay lumps are separated from the coal. Clay is always heavier than coal, so the mixture of coal and clay is washed with a stream of water. The strength of the jet is chosen so that it takes out coal, and heavier clay would remain below. Then water with coal is passed through a frequent grate. The water drains and the coal, now clean and free of clay particles, collects on the surface of the grate. Such coal is called enriched. There will be very little ash left in it. It happens that the ash in coal is not a harmful impurity, but a mineral. Thus, for example, thin, clayey turbidity, brought into the swamp by streams and rivers, often forms interlayers of valuable refractory clay. It is specially developed or collected from the ash remaining after the combustion of coal, and then used to make porcelain dishes and other products. Sometimes found in the ashes of coal.
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This article presents information about one interesting sedimentary rock, which is a source of great economic importance. This breed, amazing in its history, is called "coal". His education is quite interesting. It should be noted that, despite the fact that this rock makes up less than one percent of all sedimentary rocks that exist on earth, it is of great importance in many areas of human life.
general information
How was coal formed? Its formation includes many processes occurring in nature.
Coal appeared on Earth about 350 million years ago. To put it simply, it happened in the following way. Tree trunks, falling into the water with other vegetation, gradually formed huge layers of organic undecomposed mass. The limited access of oxygen did not allow this mess to decompose and rot, which gradually, under its own weight, sank deeper and deeper. For a long time and due to the displacement of the layers of the earth's crust, these layers went to a considerable depth, where, under the influence of elevated temperatures and high pressure, this mass was converted into coal.
Below we will take a closer look at how coal appeared, the formation of which is very interesting and curious.
Types of coal
Different types of hard coal are mined in modern coal deposits of the world:
1. Anthracites. These are the hardest varieties, mined from great depths and having the highest combustion temperature.
2. Coal. Many of its varieties are mined in an open way and in mines. This type is the most common in the fields of human activity.
3. Brown coal. This is the youngest species formed from peat residues and has the lowest combustion temperature.
All of the listed forms of coal occur in layers, and the places of their accumulation are called coal basins.
Theories of the origin of coal
What is hard coal? Simply put, this sedimentary rock is the accumulated, compacted and processed plants over time.
There are two theories, the more popular of which is the one held by many geologists. It is as follows: the plants that make up coal accumulated in large peat or freshwater swamps for many thousands of years. This theory assumes the growth of vegetation in the place of discovery of rocks and is called "autochthonous".
Another theory is based on the fact that the coal seams accumulated from plants transferred from other places, which were deposited in a new site under flooding conditions. In other words, the charcoal originated from the transferred plant debris. The second theory is called allochthonous.
In both cases, the source of coal formation is plants.
Why is this stone on fire?
The main chemical element in coal, which has useful properties, is carbon.
Depending on the formation conditions, processes and age of the seams, each coal deposit contains its own specific percentage of carbon. This indicator determines the quality of natural fuel, since the level of heat transfer is directly related to the amount of carbon oxidized during combustion. The higher the calorific value of a given rock, the more suitable it is as a source of heat and energy.
What is coal for people all over the world? First of all, it is the best fuel suitable for various spheres of life.
About fossils in coal
Fossil plant species found in coal do not support the autochthonous theory of origin. Why? For example, clubmosses and giant ferns, characteristic of the coal deposits of Pennsylvania, could grow in marshy conditions, while other fossil plants of the same basin (coniferous tree or giant horsetail, etc.) preferred more dried soils rather than swampy places. It turns out that they were transferred somehow to these places.
How did coal originate? Education in nature is amazing. Marine fossils are often found in the coal: mollusks, fish and brachiopods (or brachiopods). Coal seams also contain coal balls (rounded crumpled masses of perfectly preserved fossil plants and animals, including marine ones). For example, the small sea worm is commonly found attached to plants in the coals of North America and Europe. They belong to the Carboniferous period.
The occurrence of marine animals interspersed with non-marine plants in coal-sedimentary rocks suggests that they mixed in the process of moving. Amazing and lengthy processes took place in nature before coal was finally formed. Its formation in this way confirms the allochthonous theory.
Amazing finds
The most interesting finds in the layers of coal are tree trunks, lying vertically. They often cross huge strata of rocks perpendicular to the coal bed. Trees in such an upright position are often found in seams associated with coal deposits, and a little less often in the coal itself. Many are of the opinion about the movement of tree trunks.
The amazing thing is that sediment had to accumulate so quickly to cover these trees before they deteriorated (rotted) and fell.
Here is such a rather interesting story of the formation of a rock called coal. The formation of such layers in the bowels of the earth is a reason for further research in search of answers to numerous questions.
Where are the lumps in the coal?
An impressive external feature of coal is the content of huge blocks in it. These large blocks have been found in the coal seams of many deposits for more than a hundred years. The average weight of 40 blocks collected from the West Virginia coalfield was about 12 pounds, and the largest was 161 pounds. Moreover, many of them were metamorphic or volcanic rock.
Researcher Price suggested that they could have traveled to the coalfield in Virginia from afar, weaving into the roots of trees. And this conclusion also supports the allochthonous model of coal formation.
Conclusion
Many studies prove the truth of the allochthonous theory of the formation of coal: the presence of the remains of terrestrial and marine animals and plants implies their movement.
Also, studies have shown that the metamorphism of this rock does not require a long time (millions of years) of exposure to pressure and heat - it can also be formed as a result of rapid heating. And the trees vertically located in the coal sediments confirm the fairly rapid accumulation of vegetation residues.
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