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FOSSIL FUELS III. Coal. Formed from ancient plants. Coal beds were prehistoric swamps. Can be considered to be “stored” solar energy. Photosynthesis: CO 2 + H 2 0 + solar energy carbohydrates + O 2 We run the process backward and burn carbs to get energy, water and carbon dioxide.
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FOSSIL FUELS III Coal
Formed from ancient plants. Coal beds were prehistoric swamps. Can be considered to be “stored” solar energy. Photosynthesis: CO2 + H20 + solar energy carbohydrates + O2 We run the process backward and burn carbs to get energy, water and carbon dioxide.
Normally, when a plant dies it decomposes. If there is not enough oxygen, it can’t completely decompose, thus we get a slow accumulation of energy. In a swamp, the bacteria that decompose the plants also use up the oxygen. Coal found today formed between 1 and 440 million years ago.
As geological processes apply pressure to peat over time, it is transformed successively into * Lignite, also referred to as brown coal, is the lowest rank of coal and used almost exclusively as fuel for steam-electric power generation. Jet is a compact form of lignite that is sometimes polished and has been used as an ornamental stone since the Iron Age. (60 – 75 % carbon) * Sub-bituminous coal, whose properties range from those of lignite to those of bituminous coal and are used primarily as fuel for steam-electric power generation. (75 – 85 % carbon) * Bituminous coal, a dense coal, usually black, sometimes dark brown, often with well-defined bands of bright and dull material, used primarily as fuel in steam-electric power generation, with substantial quantities also used for heat and power applications in manufacturing and to make coke. (85 – 90 % carbon) * Anthracite, the highest rank; a harder, glossy, black boto used primarily for residential and commercial space heating. (> 91% carbon)
The largest amount of US coal is Bituminous. • Approximately 1% is Anthracite. (Found in Pennsylvania.) • Many coal veins have a high sulfur content. • Significant contributor to acid rain. • S + O2 SO2 • SO2 combines with water in atmosphere to form sulfuric acid. • Limits the use of those coals
Coal Mining • Coal veins can be 1 in to 400 ft thick. • Must be at least 2 ft thick to make mining profitable. • Two basic ways to get to it • Tunnels (deep reserves) (40%) • Strip mining (near surface) (60%)
Strip Mining Eighteenth-century mining for pit-coal had left comparatively minor scars on the landscape. But strip-mining in the mid-twentieth century literally laid waste to thousands of acres of formerly productive land. The overburden - the soil and gravel built up over millions of years .was scraped off the coal veins, shoved aside, and left in long, steep, parallel ridges. The coal was removed, and the whole mess, pits and piles together, was eventually abandoned. Because the process was purely extractive, without regard for the structure of the overburden, there is little or no hope of restoring it simply by leveling it off and planting grass and trees. Only in due time, thousands of years-worth of time, will natural processes prove able to restore the land to anything like its original condition.
Estimated that we have enough reserves for 200-300 years at current production rates. • Use may be expanded • Replace aging oil/natural gas/nuclear electric plants • More demand for electrical energy • Alternative uses such as coal gasification.
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