Underground Mining Methods

Drift Mining

This type of mining is one of the earliest coal mining techniques. Drift mining is done when the coal seam is at the same elevation as the outside is so miners can simply enter the mine without having to go down shafts. It can be used when the coal seam intersects the surface while the mine layout follows a horizontal direction with the coal. 

 

Advantages:

-         Cheapest way to mine.

-         Doesn’t demand much machinery.

-         Less effort is needed to reach the coal.

Disadvantages:

-         Coal located below the drift cannot be accessed using this method only.

-         Tunnels could collapse and trap miners inside.

 

Simple Drift Mine Diagram

Shaft Mining

            When coal is not accessible through drift mining, shaft mining is used. Shaft mining is used when coal is located well below the surface and must be accessed by going deep underground, sometimes 1000 feet or more. Working elevators are placed into shafts and extend down to the same level as the coal seam. One shaft is used for the transportation of miners and their equipment and the other is used for the transferring of coal to the surface where it can be processed.

Shaft Mining Diagram

 

 

Advantages:

-         Coal found deeper in the Earth can be accessed.

-         Two elevator system moves coal and miners separately, saving time.

Disadvantages:

-         Can become expensive if coal is located deep in the earth.

-         Potentially dangerous because exit requires an elevator.

 

 

Room and Pillar Mining

            Room and pillar mining is used after shafts have been dug underground to transport miners to coal waiting to be mined. Once the miners and their equipment reach the coal, pillars of soft, bituminous coal hold up the roof of where the miners are working and the coal around them is extracted. This is not a safe and effective way to mine; roof falls are common due to the pillars “squeezing” and putting pressure on other pillars and the roof can collapse. Half of the coal in the mine must be left alone because it holds up the roof, making this mining method ineffective and unsafe.

Room and Pillar Mine

 

Advantages:

-         Manmade pillars don’t need to be transported down to the mines.

-         Mining areas can have a flat surface, making it easier to use machinery.

Disadvantages:

-         Dangerous due to soft, coal pillars holding up immense amounts of pressure above the mine.

-        Very inefficient; half of the coal must remain unused to provide support for the roof.

 

Continuous Mining

            Continuous mining is a mining method commonly used alongside drift and room and pillar mining with technological innovation added in. Heavy machinery is used to greatly increase mining efficiency. These machines are equipped with tungsten carbide teeth to capture many tons of coal in a small amount of time. Along with the mining machines, conveyor belts transfer the coal to its appropriate location after extraction. The technological advances make continuous mining much more economical than the traditional pick and shovel and donkey-pulled cart system.

 

Continous Mining Machine

 

Advantages:

-         More coal can be mined quicker with the use of the machines.

-         The job only requires one miner to operate the machinery, saving the company money and if an accident were to occur, only one miner could be harmed instead of many.

Disadvantages:

-         Room and pillar mining is still used in conjunction with continuous mining, which still leaves potential danger for roof collapses.

-         Machinery may be difficult to transport and upkeep in the mine, sometimes deep in the earth.

 

Longwall Mining

          Longwall mining is the most productive mining technique. This procedure uses a gargantuan machine that supports the roof above while steadily collecting all of the coal in its path. When finished, the machine retreats and the coal roof above falls. After the roof falls, the machine proceeds to pick up the remaining coal from the roof and is transported out. This is the most efficient way to mine due to all of the coal being mined, including the coal above, and none being left behind for support like in room and pillar mining.

 

 

Longwall Mining Machine with hydraulic roof

 

Advantages:

-         The most productive way to mine; no coal is left behind and can be done in less time.

-         Danger from roof falls are gone because of the machine’s hydraulic support system.

Disadvantages:

-         Large machines are not always reliable and may break down on occasion.

-         Costs to purchase and operate these machines may be out of range for some companies.

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November and December Graphs

December Data

November Data


 

Aerosols, Urban Heat Island Effect and Greenhouse Gases Conclusion

Aerosols, the urban heat island effect and greenhouse gases all affect climate change in different ways. They all have their respective roles, but most data and scientists agree that the collective result is yet to be discovered. Despite this, we do have solid evidence and data of each of these effects which can be used to draw a conclusion that the effects caused by all of these factors balance each other out.

                The urban heat island effect is one of the pieces of evidence we do know about. The effect takes place when solar radiation, or sunlight, hits solid or dark surfaces and is absorbed. The heat from the sunlight is then reflected back at a longer wave length and heats up the area around it. The reemitted light turns into long wavelength infrared radiation.  Urban areas are warmer than rural areas because of the low albedo, or reflectivity, of the surfaces in cities like asphalt, concrete and other dark colored surfaces. Greenhouse gases trap the heat from the radiation and the heat stays on Earth and continues to heat it up as it has no way of escape.

The Formation of Coal

The formation of coal is a long process. The coal around the Appalachian region has formed from the remains of swamp plants that used to cover the area 300-400 million years ago. The plants became buried in the swamp, but didn’t rot due to the lack of oxygen. Instead of rotting, the dead plants formed into peat over very long periods of time.

 Peat doesn’t have a very high heat value and isn’t as valuable. Peat is not coal, but a precursor to it. Lignite is the next type of coal in the process. The carbon concentration is only at 30% and has a low heat value, yet it is still used to generate electrical power.  Over time with heat and pressure, the peat is converted into lignite and then into bituminous coal, the most common form. This type of coal has a highly variable carbon value and is coked for use in the steel industry. Bituminous coal can be used in factories to create electrical energy as well. Anthracite coal is different in regards to rock type: it’s metamorphic instead of sedimentary. It has the highest carbon content (85-95%) and the highest heat value. Finally, metallurgical coke is bituminous coal heated up to a temperature around 2,000 degrees Celsius in the absence of oxygen. With the extreme heat affecting it, water, tar, gas and other volatiles are taken away to leave a higher carbon fuel.

                That is how coal forms and the different types and stages of coal.