GOOD
COAL
GOOD
GOOD
GOOD
COAL
COAL IS GOOOOOD!!!!!
COAL
GOOD
GOOD
COAL
COAL
GOOD
GOOD
COAL
COAL
COAL
COAL IS GOOOOOD!!!!!
Coal was discovered in eastern north America in the 18th
century. We needed to fuel steam engines, and coal was a
readily available fuel. Fuel was burned to create steam to turn
a turbine. Today 50% of U.S. electricity comes from coal. We
have 300 years’ worth of coal!
COAL IS GOOOOOD!!!!!
Underground Mining
Room and Pillar Mining – rooms are cut into the coal bed leaving a
series of pillars or columns of coal to help support the mine roof
and control the flow of air. The miners advance while cutting out
pillars. Once they reach the edge of the mine, they work
backwards in what’s called “retreat mining.”
Long Wall Mining – hydraulic roof supports are used while a
cutting head goes back and forth along the coal face. When the
cutting head reaches one end of the coal face, it dumps the coal
onto a conveyor belt.
Surface Coal Mining
Surface mining occurs at exposed coal seams. It involves drilling
above ground and blasting to remove overburden. After the
overburden is removed, the mined coal is harvested.
Coal is pretty cheap. In 2004, the average price for a short ton of
coal in the U.S. was $19.93 (although this does represent an
increase from the 2003 price of $17.85).
It is estimated that there 265 billion short tons of coal available in the
United States to be mined.
Mmmmmm,
Coal. D’oh!
Energy in coal:
Lignite – 13 million Btu per ton
Subbituminous – 18 million Btu per ton
Bituminous – 24 million Btu per ton
Anthricite – 23 million Btu per ton
But… Coal is DIRTY!!!!!!
There are several negative externalities attributed to the combustion of
coal, including:
- sulfer and acid rain,
- carbon Dioxide, and
- general destruction to the environment due to the actual coal mining.
A 500 megawatt coal power plant will produce 10,000 tons of
Sulfur dioxide, 10,200 tons of nitrogen dioxide and 3.7 million
Tons of carbon dioxide per year.
OVERBURDEN
When mining, “overburden” is left over. Mining one ton of coal leaves
25 tons of overburden. Pyrite is contained in overburden; when pyrite
is exposed to water and air, it forms dangerous substances like
sulfuric acid and iron hydroxide. When this mixes with water, it forms
acid lime drainage which is highly destructive to the environment. So
sad .
COAL IS GOOOOOD!!!!!
Coal gasification reduces greenhouse gas emissions
(really low sulfur oxide and nitrogen oxide emission).
Coal gasification is much more efficient than normal
coal burning
Efficiencies table
Current normal: 30%
Current gasification: 50%
Future gasification: 70-80%
The UK is developing underground coal gasification (UCG)!
This is a very clean method, as only gas is removed from the
ground, leaving all the overburden and ash underground.
One must also remember that gasified coal is not
only very clean, but is a far more versatile fuel
than regular coal. Think about it: would you rather
fuel your car with lumps of coal or gasified coal?
COAL IS GOOOOOD!!!!!
Here are two of several ways: Direct, and Indirect
Direct liquefaction – involves the introduction of hydrogen gas
and catalysts into finely crushed coal to produce synthetic
crude oil. Need temperatures of 430-450*C and pressures of
50 to 25 MPA. Hydrogen is needed to remove the oxygen
sulfur and nitrogen. The product of direct liquefaction must still
be refined to gasoline or diesel.
Indirect liquefaction – first converted to gas through gasification.
Then methanol synthesis is used to convert the coal gas into
methanol, then the methanol can either be directly converted to
gasoline, or it can be used as fuel in and of itself.
COAL IS GOOOOOD!!!!!
Deep ocean
Mines
Plants (aquatic and land)
COAL IS GOOOOOD!!!!!
Captured by electrostatic precipitators.
Used to replace 10%-30% of Portland cement.
Can also be used as “flowable fill” to build highways.
Unfortunately, current rates of recycling fly ash is only 35%.
Fly ash
Cole coke is created from bituminous coal (very dirty!!). The
bituminous coal is put in to an airless “coke oven” where it is
heated to over 1,000*C. This removes much of its volatile
content such as water, tar, and sulfur. Can be used for
things that require “clean coal.”
Coal coke
Advanced Combustion