This unit is designed for seventh and eighth grade students. The purpose of this unit is a provide a historical aspect to the developments which lead to the discovery of coal and coal mining through the origins a d kinds of coal; types a d methods of coal mining, hazards of mining, measures of safety a d chemical by-products of coal.
The unit could be utilized in three separate ways. First, an instructor could use the unit as a reference and teach only one or two parts or portions of it. The information provided in the first section which is of an historical nature and where teachers are involved in team or cluster situations, could be shared with either or all the history, science, math and english teachers.
The unit is divided into three sections. The first section focuses on coal and coal mining with five different quizzes. The second section focuses on word problems and math dealing with the measurement and computation of different polygons. The final section deals with problems based upon energy and its resources.
Before the students attempt a solve the problems on energy they should solve related problems. The activities in this section are non-threatening and help a alleviate any anxieties students may have concerning the problems on coal, coal mining, energy and miscellaneous problems.
The problems are as follows
:
A. Introductory
-
B. Problems on Coal
-
C. Volume and Density Calculations
-
D. Patio and Proportion Problems
E. Energy Problems
It is not known when or by whom coal was first used. It is referred to by Greek historians as early as 300 B.C., and it was used in Great Britain as early as 852 A.D. It is supposed that the Britains were the first people a make practical use of it and coal mining was in successful operation in the island more than three hundred years before Columbus discovered America. The first discovery of coal in the United States, of which we have any record, was made by Father Hennipin near Ottawa, Illinois, in 1878. The first mine worked in the United States was Opened in Richmond, Virginia, in 1750.
Coal is a combustible rocklike substance formed from accumulations of plant matter that have undergone physical and chemical changes through geological processes. Coal varies in color from brown a black, has a dull a bright luster and may be soft or hard. Most coal occurs in large deposits called coal beds and they are made up of bands or seams separated by layers of clay, rocks and other mineral substance. The seams of the coal vary in thickness from a fraction of an inch to several hundred feet. Coal lies at various depth in the earth and some is found just below the surface of the ground. Although coal is found on every continent, it is unevenly distributed. The world’s reserve supply is more than five trillion tons. Forty percent of these reserves are located in North America. (See Appendix A)
Coal is of organic origin, formed from the remains of living things such as trees, herbs, shrubs, vines and other plant materials that flourished millions of years. From this variety of vegetation and its complex carbon compounds came a great assortment of coals, from brown coal and lignite or peat to the hardest kind of anthracite.
Coal consists chiefly of carbon, derived directly from organic carbon compounds. It is fossilized plant material, preserved by burial and altered by earth forces. The character of a coal depends Upon the nature of the original plant debris. The different types of coal are lignite, subituminous, bituminous and anthracite.
Some coal was formed millions of years ago. The most high ranked coal was formed more than two hundred fifty million years ago, during the carboniferous period. At that time a warm moist climate prevailed and swamps covered a large part of the world. The air was damp and steamy. Most of the plants were huge strange-looking ferns, reeds, mosses and trees that had no flowers. As these plants died, others grew on top of them. The accumulation of this partly decayed plant matter formed a brown fibrous material called peat, the first stage in the formation of coal.
Variations in the conditions under which coal is formed result in different varieties of coal. Coal has no fixed chemical composition but varies according to the composition of the original materials and the state of development reached in the coal-forming process.
The plant materials from which coal is formed consist primarily of carbon, hydrogen, and oxygen. Under heat and pressure, the hydrogen and oxygen are driven off in the form of water and gases, such as carbon dioxide and methane. The material that remains is composed mostly of carbon. The more heat and pressure applied, the greater the percentage of carbon that remains and the harder the coal.
Coal also contains varying amounts of water, combustible gases and other volatile materials, and mineral impurities. Common mineral impurities include sulfur, silica, iron sulfide, calcium and magnesium carbonates, phosphates and clay. These remain in the ash when coal is burned.
The amount of heat produced when coal is burned depends on the composition of the coal. The heating value of coal is measured in British thermal units (B.t.u.). One British thermal unit is the amount of heat required to raise the temperature of one pound of water one degree Fahrenheit, usually from 38° F. a 40°. (See Appendix B&C)
Coal is graded in “ranks” according to the percentage of carbon it contains. Generally, the higher the rank, the higher the percentage of carbon and the lower the percentage of volatile materials and moisture in the coal. The principal ranks of coal are anthracite, bituminous lignite.
Anthracite. Anthracite, the highest rank of coal, contains the highest percentage of carbon and the lowest percentage of mineral impurities and volatile materials. Anthracite is a hard, shiny, black coal that burns with a short, blue, smokeless flame. It is valuable as a home fuel because it leaves very little ash and has a high heating value, from 12,700 to 13,700 B.t.u. per pound.
Bituminous Coal
. Bituminous coal, the next rank, is subdivided into semibituminous, bituminous, and subbituminous coal. Semibituminous coal is a hard, black, lustrous coal with a high carbon content. Because it has a high heating value and burns with very little smoke, it is widely used for heating homes and other buildings.
Bituminous coal has a lower percentage of carbon and contains more moisture than semibituminous coal. It is soft to hard, is dull to shiny black, and burns with a long, smoky flame. Some bituminous coal, called coking coal, is used to make coke. An other kind, called gas coal, is used to produce combustible gases.
Subbituminous coal is usually dull brown or black in color, is soft, and flakes into thin pieces. It burns with a long, smoky flame and is used to produce steam.
The heating values of the three bituminous types range from 9,500 to 14,000 B.t.u. per pound. Bituminous coals are the most plentiful and widely used of all coals. There are bituminous coal deposits on every continent. (See Appendix D)
Lignite
. The lowest rank of coal is lignite, also called brown coal, because of its color. Lignite has the lowest percentage of carbon and the highest percentage of moisture, volatile materials, and mineral impurities. It has a soft, woody texture and crumbles easily when dry. Lignite burns with a long, smoky flame and has a relatively low heating value, ranging from 6,700 to 8,300 British thermal units per pound. Lignite is sometimes dried and pressed ink briquets for use in fireplaces. Nearly all the lignite mined is used to produce steam and electrical power.
Coal is also classified by the material from which it is formed. Different types of coal are produced from different plant materials. Three common types of coal are banded coal, cannel coal, and splint coal. Each rank may theoretically include coal of each type but seldom does.
Banded coal has visible layers of various materials and often contains a highly lustrous substance called vitrain. The bands are formed by the different layers of plant material from which the coal was formed. Most bituminous coal is banded.
Cannel coal is unbanded and uniform in texture. It has a silky or greasy luster and usually is formed from spores and pollen grains. Cannel coal ignites easily and burns with a bright flame.
Splint coal is dull, with fine ridges. It is hard and has a metallic ring when struck. Splint coal is used as fuel for steam power plants.
Deposits of coal vary in thickness from less than 1 inch to more than 100 feet. Most coal is mined from beds which are from 2 1/2 to 8 feet thick. These deposits are sometimes called seams (veins), but geologists prefer to use the word bed, because coal was formed in wide bedding areas. Coal deposits are sandwiched between layers of rock and dirt. The deposits may be level, sloping, or tipped on end, depending on whether they have been affected by the cracking and folding of the earth’s crust. Coal beds may lie deep in the ground or near the surface. In hilly or mountainous country, the coal often is exposed on the hillside. But it is likely to be covered with dirt or weathered from exposure and hard to recognize. Excavations for buildings or highways frequently uncover coal beds. Sometimes coal is found in drilling for water, oil, or gas. But the principal method of locating coal is to use core drillings. This is done by drilling out a core (column) from the earth’s crust to indicate, layer by layer, what is under ground.
Coal beds are made up of bands, or seams, of coal separated by layers of clay, rock, shale, or other mineral substances. The seams vary in thickness from a fraction of an inch to several hundred feet. Most of the coal beds mined in the United States have seams 3 to 7 feet thick, but the great anthracite bed is 50 to 60 feet thick, and some beds of brown coal are over 300 feet thick.
Coal lies at various depths in the earth. Some coal is found just below the surface of the ground. Geologists estimate that some coal reserves lie as deep as 6,000 feet beneath the earth’s surface. In the United States many large coal beds are close to the surface, but in Great Britain most of the coal lies at great depths. Coal seams may be flat or sharply folded because of the buckling and shifting of the earth.
Coal, although found on every continent, is unevenly distributed. According to an estimate of the U.S. Bureau of Mines, the world’s reserve supply of coal is more than 5 trillion tons.
There are two general methods of mining coal: underground or deep mining, and surface or strip mining. Underground mining is of three types, depending on the nature of the terrain, the thickness of the coal seam or vein and on whether the coal is embedded in a hilly or a mountainous country or in flat areas. These are shaft mining, drift mining, and slope mining. The methods of mining are, room-and-pillar-and-breast techniques and hard-and-pillar system.
There are two general methods used to mine coal. These are (1) strip (surface) mining, and (2) underground (deep) mining. Miners usually use strip mining when the coal beds lie close to the surface of the earth. Otherwise, they use underground mining methods.
Strip Mining
In this method, giant power shovels or other earth-moving equipment remove the overburden, the layer of earth and rock that covers the coal seam. When the coal is exposed, it is broken up usually by explosives, and loaded by smaller power shovels into huge trucks. The trucks carry the coal to preparation plants. Strip mining is fast and efficient. However, it can ruin the appearance or an area and leave banks of land exposed to erosion. For these reasons, many states have restricted strip mining or required that the land be made productive again after it has been mined. The coal industry has developed many ways of reclaiming strip-mined areas, including planting crops on the land or turning it into a recreation area.
Underground Mining
Includes several types of mines. The most important of these are (1) shaft mines, (2) drift mines, and (3) slope mines. Each type of mine is best suited to removing the coal from a particular type of coal bed. (See Appendix E & G)
Shaft Mines
Reach coal beds that lie far below the earth’s surface. A hole is dug straight down to the coal. The miners then dig horizontal entries through the seams of coal. Elevators carry the miners, equipment and coal between the coal seam and the surface. Separate shafts are dug to provide ventilation for the working rooms far underground. The average depth of shaft mines in the United States is 260 feet.
Drift Mines
They are also used to reach coal beds in hillsides. The entrance is located where the coal is exposed on the hillside, and the tunnel is dug through the coal bed.
Slope Mines
They are also used to reach coal beds in hilly areas. Miners open a sloping tunnel through the ground to the coal bed level. The miners and their machines are moved in and out of the mine on cars that are pulled by electric locomotives along steel tracks. Coal is taken out in similar cars, or by conveyor belts.
Coal is mined according to a definite plan. The plan must allow as much coal to be removed as possible, in the safest and most efficient way possible.
The wall of the bed from which the coal is taken is called the mine face. In cutting into this mine face, there are two general mining systems: (1) the room-and-pillar system, and (2) the longwall system.
Room-and-Pillar Mines
are composed of a series of rooms cut into the coal bed from numerous entries. The miners leave pillars (columns) of coal standing to help support the roof until they mine cut a particular area. Then, as the miners move back to the main entry they systematically remove the pillars and permit the roof to fall. This system is used in most of the underground coal mines of the United States.
Longwall Mines
are common in Europe and are now found in the United States. In this system, coal is mined by a machine which is pulled back and forth across a face 240 feet or more in length. The loosened coal falls onto a conveyor belt which carries it away. Moveable steel props support are advanced. The roof behind is allowed to fall. Miners equipment, and coal move to and from the face through haulageways that open along each side of the face. One advantage of the longwall system is that almost all of the coal can be removed because no pillars are left standing.
After the coal has been mined it is hauled to the surface. Two or three types of haulage equipment are used to deliver the coal to the surface or to the hoisting facilities. Shuttle cars, which are electrically powered rubber-tired trucks, receive the coal from the loading machine and relay it to the next haulage unit. This unit is commonly a belt conveyor, called a panel conveyor, that feeds the coal to a mainline conveyor or to the mine railway. In many mines, however, the shuttle cars deliver to cars on the mine railway. These cars are then pulled by electric locomotives 7 to 10 miles to the surface or to the hoisting facilities.
Coal is transported by rail in large open cars called gondolas or hoppers. Mines rear waterways is often shipped by barge, a less expensive method than railway transportation. Coal may be moved to ports by rail and then shipped to its final destination. Trucking coal is less expensive and convenient for short distances. It is also moved by pipeline.
Coal is the source for many chemical products, most of them by-products of the carbonization or coking process. There are believed to be more than 200,000 chemical by-products. Aside from physical warmth and comfort coals principal by-product is coke, which makes possible the manufacture of steel and thousands of other products. The refrigerants, carbon dioxide for dry ice and ammonia, the synthetic in electric refrigerators are coal derivatives. All edible dyes and hundreds of medicine and antiseptics are produced from coal.
