Week 4 assignments
Bryan Tiong
Question:
Coal is a dirty and polluting fuel but it is comparatively cheap. How
would one use coal more cleanly?
Introduction
Coal is a combustible black or brownish-black sedimentary rock. Coal is composed
mostly of carbon and hydrocarbons along with variable quantities of other elements,
chiefly hydrogen, sulfur, oxygen, and nitrogen. It is the most abundant fossil fuel
produced in the United States.
Formation of coal
Coal is a nonrenewable energy source because it takes millions of years to create.
The energy in coal comes from the energy stored by plants that lived hundreds of
millions of years ago, when the Earth was partly covered with swampy forests.
For millions of years, a layer of dead plants at the bottom of the swamps was
covered by layers of water and dirt, trapping the energy of the dead plants. The heat
and pressure from the top layers helped the plant remains turn into what we today
call coal.
History of coal
Due to its abundance, coal has been mined in various parts of the world throughout
history and continues to be an important economic activity today. Compared to wood
fuels, coal yields a higher amount of energy per mass and could be obtained in
areas where wood is not readily available.
The Industrial Revolution, which began in Britain in the 18th century, and later
spread to continental Europe, North America, and Japan, was based on the
availability of coal to power steam engines. Coal was cheaper and much more
efficient than wood fuel in most steam engines.
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Week 4 assignments
Bryan Tiong
Methods of coal mining
Surface mining and deep underground mining are the two basic methods of mining.
Surface mining began in the mid-sixteenth century and is practiced throughout the
world, although the majority of surface mining occurs in North America . However,
surface mining can leave behind large areas of infertile waste rock, as 70% of
material excavated is waste. The other method is underground mining, a method that
currently accounts for about 60 percent of world coal production. This method of
mining contributes less pollution to the environment than surface mining.
Pollution from coal mining
Coal mining can result in a number of adverse effects on the environment. Surface
mining of coal completely eliminates existing vegetation, destroys the genetic soil
profile, displaces or destroys wildlife and habitat, degrades air quality, alters current
land uses, and to some extent permanently changes the general topography of the
area mined. These are the substances resulted from coal mining that polluted the
environment:
 Carbon dioxide gas (CO2) contributes to global warming
 Sulfur dioxide (SO2) leads to acid rain
 Nitrogen oxide (NOx) causes smog, and also acid rain.
 Hydrocarbons that do not burn completely are released into the air. Thus,
causing smog
 Carbon monoxide (CO) is a poisonous gas and contributes to global warming
 Mercury emissions from coal plants are suspected of contaminating lakes and
rivers
Mine tailing dumps produce acid mine drainage which can seep into waterways and
aquifers, with consequences on ecological and human health.
How can coal be used cleanly?
Coal is no sooty remnant of the Industrial Revolution -- it generates half of
the electricity in the United States and will likely continue to do so as long as it's
cheap and plentiful. Clean coal technology seeks to reduce harsh environmental
effects by using multiple technologies to clean coal and contain its emissions.
Some of the techniques that would be used to accomplish this include chemically
washing minerals and impurities from the coal, gasification ,treating the flue gases
with steam to remove sulfur dioxide, carbon capture and storage technologies to
capture the carbon dioxide from the flue gas and dewatering lower rank coals (brown
coals) to improve the calorific value, and thus the efficiency of the conversion
into electricity.
Coal gasifiers convert coal into syngas via partial oxidation reactions with oxygen or
with steam and oxygen under elevated pressures.14,62”(Li et. Al 252). Syngas is
made of carbon monoxide and hydrogen. It is then cleaned and burned in place of
coal to make electricity.
But this project have been critised by many. Environmentalists such as Dan Becker,
director of the Sierra Club's Global Warming and Energy Program, believes that the
term clean coal is misleading: "There is no such thing as clean coal and there never
will be. It's an oxymoron".
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Week 4 assignments
References:
http://www.eia.gov/energyexplained/index.cfm?page=coal_home
http://en.wikipedia.org/wiki/Coal
http://www.desmogblog.com/coal-power-industry-united-states-facts
http://en.wikipedia.org/wiki/Clean_coal
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Bryan Tiong