Download Energy from Fossil Fuels

Energy from Fossil Fuels
Energy from Chemistry
• Question
– What is “chemical” energy?
• A form of potential energy
• Potential energy is stored in the (valence) electrons of atoms and
molecules
• Lecture Questions
– What are exothermic and endothermic chemical reactions?
• Exothermic reaction: produces energy, usually as heat or light
• Endothermic reaction: consumes energy as it proceeds
– Why do some reactions produce energy (and some consume it)?
• Chemical reactions
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Consists of breaking and forming bonds
The formation of bonds always yields energy
The breaking of bonds always requires energy
The balance between these two processes determines the net energy
yield/requirement of a chemical reaction
The Fossil Fuels
• What are the main fossil fuels?
– Coal, oil (petroleum), natural gas
Gas
26%
Coal
30%
Coal
25%
Gas
26%
OECD
Global
Oil
44%
• How are they mostly used?
– Coal: electricity
– Oil: transportation, heating
– Natural gas: heating, electricity, cooking
Oil
49%
Use of Coal
Use of Natural Gas
Use of Oil
King Coal
• Lecture Questions
– What is coal?
• A solid mixture consisting largely (about 85%) of carbon
– Representative formula is C135H96O9NS
– Plenty of other impurities
» Toxic metals like Pb, Hg, As
» Radioactive isotopes of various types
– Three broad grades of coal
» Anthracite (hard coal). Highest carbon content and heat value.
» Bituminous coal (soft coal)
» Lignite (brown coal). Lowest carbon content and heat value.
– How is coal formed?
• Originated as plant matter in hot, muggy regions
– Most current coal formed 200-350 million years ago
– Plant matter decays under conditions of low oxygen, high heat and
pressure
» First converted to peat
Natural Gas
• What is natural gas?
– Gaseous mixture of hydrocarbons
• Mostly methane, CH4 (60-80%)
• Others: C2 HCs (5-9%), C3 HCs (3-18%), C4 HCs(2-14%)
• How is it formed?
– Decomposition of plant and animal remains that had been buried
• Again: lack of oxygen, high heat and pressure
• Methane is produced by anaerobic respiration
– Plenty produced in sediments and landfills
– Often accompanies coal and oil deposits
Oil
• What is oil (petroleum)?
– A very complicated liquid mixture of hydrocarbons
– Liquid HCs start at C4-C5
– Almost always contains dissolved natural gas as well
• How is it formed?
– Again, decomposition of biological matter
• Most probably originated from ocean-dwelling microorganisms
Oil Recovery
Primary Recovery of Oil
Secondary Recovery of Oil
Oil Recovery
Oil Distillation
Oil Distillate Refinement
• Gasoline Formation
– Conversion of other oil fractions to gasoline
– Cracking
• Breaking apart larger molecules into smaller ones
• Thermal cracking
• Catalytic cracking
• Gasoline enhancement
– Purpose
• Make it burn better of cleaner
• Example: antiknock agents
– Tetraethyl lead (TEL)
– MTBE
– Oxygenated Gasoline
• Reduce CO emissions
• MTBE, ethanol, methanol
– Reformulated Gasoline (RFG)
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•
•
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Oxygenated gasolines with fewer volatile hydrocarbons
Reduce CO emissions
Reduced smog
May have reduced impact on groundwater (lower BTEX)
Environmental Impacts of Fossil Fuels
• What are the environmental impacts of using fossil fuels
as energy sources?
– Extraction
• Coal mining
• Oil and gas drilling
– Storage and Transport
• Leaks, spills
– Combustion
• Contributes to global warming, acid rain, smog, PM, eutrophication,
toxic metals, exposure to radioactivity
– All contribute to global warming, nitrate PM, eutrophication, and
acidification due to HNO3
– Coal is the main culprit for SO2, metal and radionuclide emissions. It is
also the worst of the three for PM.
The Future of Fossil Fuels
• Nonrenewable resources
– They will eventually be exhausted and need to be replaced
– Global warming may accelerate the replacement (or not)
• Reserves and Resources
Peak Oil
• When will we run out of oil (and natural gas)?
– Most important question is maybe: when will production begin to
decline? (ie, “when will peak oil production occur?”)
– In March 1998, two retired petroleum geologists (Campbell and Laherre)
claimed that oil would peak in the first decade of the 21st century
Peak Oil: Other Estimates
Peak Oil
•
Unconventional Sources of Oil
– Potentially a very large resource
• Oil shales, tar sands, heavy oil
• Extends peak production by 2-3 decades
– Problems
• More energy intensive (thus more expensive); more environmentally damaging