PHYS 1211 - Energy and Environmental Physics

1. PHYS 1211 - Energy and Environmental Physics Lecture 10 Fossil Fuels Michael Burton

2. This Lecture • Nature of Fossil Fuels • Origin, Properties and Production of: • Coal • Oil • Natural Gas

3. Fossil Fuels • Fossil fuels (coal, oil and natural gas) are the most important source of energy at present. • They currently account for more than 80% of world energy usage.

4. Source: BP Statistical Review of World Energy — 2012

5. Origin of Fossil Fuels • Fossil fuels are the remains of living organisms that lived millions of years ago. • The energy we extract from them is energy they extracted from sunlight when they were alive. • Photosynthesis

6. Formation of Coal Coal is formed from the decay of plant material from ancient forests.

7. Formation of coal The formation of coal (or any fossil fuel) requires very special conditions. Normally dead organic material is rapidly degraded through oxidation and biodegradation (by microbes). To prevent degradation the material must be buried in an environment that excludes oxygen and bacteria. This most likely occurs with burial in a waterlogged environment. Peat bogs - such as those found in Ireland - are believed to be the first stage in the formation of what will eventually become coal.

8. Peat Bogs Peat can be cut from these bogs, dried, and used as a fuel, but its energy value is low. Mummified bodies have been found preserved in peat bogs over thousands of years - showing the slow rate of degradation of organic material.

9. Coal Formation • Coal is formed when the peat-like material is buried beneath other sediments. • Pressure and heat removes water from the plant material producing a denser substance. • It takes about a 7 metre thickness of plant material to produce about 1 metre thickness of coal.

10. Ranks of Coal • Brown Coal (or Lignite) • Sub-Bituminous • Black Coal (Bituminous coal) • Anthracite • The highest quality coal

11. Ranks of Coal • Higher ranks of coal have more carbon and a higher energy content.

12. Sydney Basin Coal The Sydney basin is the location of much of the coal in New South Wales. The coal is mined at locations in the Hunter Valley and near Lithgow. It dates from the Permian period (275 to 245 million years ago). It was deposited in cold temperature swamps containing trees and shrubs of the glossopterid flora. Fossil glossopteris leaves (Newcastle, NSW)

13. Composition of coal Coal is a mixture of complex aromatic (i.e. ring structure) hydrocarbons. Typically this gives a H:C ratio off a little over one. By weight good quality coal is mostly carbon, but includes significant amounts of Sulfur, Nitrogen and other elements Typical molecular structure found in coal.

14. Coal Seams Coal is found in layers called coal seams usually interspersed with other rocks.

15. Underground Coal Mine

16. Open Cut Mining Also called strip mining in the USA. Open cut coal mine, Hunter Valley, NSW

17. Source: BP Statistical review of World Energy - 2012

18. Source: BP Statistical review of World Energy - 2012

19. Australia • World’s 3rd biggest coal producer • World’s 4th biggest coal reserves • Enough for nearly 200 years at current production rates. • World’s biggest coal exporter

20. Uses of Coal • Coal was the fuel that powered the industrial revolution (~1760–1840). • It was used to power the steam engines used in early factories. A Watt Steam Engine (~1770)

21. Coal for Transport Steam locomotives fuelled with coal revolutionized transportation providing fast rail travel. They were widely used up to the 1960s, being replaced with diesel and electric locomotives. Evening Star (1960) George Stephenson’s Rocket (1830)

22. Coal for Transport Steam engines fuelled with coal also powered ships, once again being largely replaced with diesel power in the second half of the 20th century. RMS Titanic (1912) — Engines: 2 Triple expansion reciprocating engines + turbine 59,000 hp RMS Queen Elizabeth (1940) — Engines Steam turbines 180,000 hp

23. Domestic Fuel • Coal was once widely used as a domestic fuel for cooking and heating but is now largely replaced by gas and electricity. Coal cooking stove (from Popular Mechanics 1933)

24. Modern Coal Usage • You might think with the phasing out of coal for transport, industrial and domestic use its role as a fuel was in decline. • Not true — Coal usage as an energy source is continuing to grow. • The age of steam is not over.

25. Electricity Generation • This is the major use of coal today. • Coal fired power stations burn coal and use it to generate steam. • The steam drives steam turbines that are used to drive the generators. Turbine Blades from a modern power station

26. Coal Fired Power Station Cooling Tower Boiler Exhaust Flue Turbines Generator Transformer Coal hopper

27. Electricity from Coal • Coal is the main source of electricity in many countries with abundant coal supplies. • Australia (77%) • China (78%) • USA (49%)

28. Origin of Oil • Oil is believed to form from the remains of marine organisms such as zooplankton and algae, which are deposited on the bottom of an ocean or lake. • As opposed to coal which forms from land plants. • As with coal the material must be preserved in anoxic conditions where it is protected from immediate decay.

29. Origin of Oil The organic material in the sediments is in the form of a waxy material known as kerogen. To form oil the kerogen containing material (the oil source rock) has to be heated to chemically modify it. This requires that Earth movements result in the sediment being buried at a certain depth known as the “oil window”.

30. Oil Window • The depth of the oil window is from about 3 to 6 km. • The corresponding temperatures are 70 to 150 oC. • At these temperatures kerogen is slowly converted into liquid hydrocarbons. • Too high a temperature (below the oil window) will produce natural gas rather than oil.

31. Biomarkers • The biological origin of oil is demonstrated by the presence of organic biomarkers “or molecular fossils”. • These are molecules that represent the carbon skeleton of certain molecules (such as lipids) in the original material.

32. Oil Traps Oil collects in locations called oil traps or petroleum traps. The oil is contained in a permeable rock, but is held in place by a layer of an impermeable rock above it.

33. Oil Drilling Oil is located by drilling an oil well using an oil drilling derrick. Mud is circulated into the hole to bring the rock fragments to the surface. Steel Casings are placed in the hole and cemented in place to prevent the hole collapsing. Oil Drilling Bit.

34. Oil Extraction Once oil is located the drilling derrick is replaced by a wellhead that allows the oil to be brought to the surface. In some cases the pressure in the reservoir will be sufficient to extract the oil. In other cases a pump may be needed. The oil extracted is “crude” oil. It contains a mixture of a range of different hydrocarbons ranging from light to heavy molecules. Further processing is carried out at an oil refinery.

35. Composition of Oil Oil is composed of a mixture of hydrocarbon molecules of different sizes (different numbers of carbons). The simplest hydrocarbon molecules are the alkanes. The first 8 are shown at right. Actual molecules can include branched chains as well as the straight ones here. Gases Volatile Liquids Higher carbon numbers (up to 70) correspond to heavier oils.

36. Oil Refining Fractional distillation (or fractionation) is used to split crude oil into components of different densities. Different fractions condense at different temperatures. CN is the number of carbon atoms in the molecules. e.g. Hexane has 6 carbons (C6)

37. Oil Refining Oil Refining may also involve “cracking”. This breaks down the larger hydrocarbon molecules into the more valuable smaller molecules needed to make petrol. A catalytic cracker breaks down hydrocarbons by heating with a catalyst.

38. Unconventional Oil Oil is also extracted from so-called “unconventional” sources – in particular the oil sands in Alberta, Canada.

39. Source: BP Statistical review of World Energy - 2012

40. World Total 234.3 Billion Tonnes (54.2 years supply at current production rate) OPEC Countries 72.4% (91.5 years) Non-OPEC 27.6% (26.3 years) Source: BP Statistical review of World Energy - 2012

41. Australian Oil • Australia is a relatively minor producer of oil with 0.5% of World production. • Most of this comes from offshore oil fields off Western Australia.

42. Natural Gas • Most Natural Gas originates from essentially the same processes as oil. • The source rock has been more deeply buried and heated to higher temperatures. • Natural gas is mostly methane (CH4) with small amounts of ethane, propane and butane.

43. Source: BP Statistical review of World Energy - 2012

44. Unconventional Gas • Shale Gas • Natural Gas trapped within shale formations. • Coal Seam Gas • Gas trapped within coal seams

45. Coal Seam Gas • A source of gas is coal seam (or coal bed) gas. • Very much in the news recently in Australia. • This is gas associated with coal deposits. • It is extracted by drilling wells and fracturing of “fracking” the coal to allow gas to be released.

47. Shale Gas • Also released by “fracking” • In the USA • 1% of gas production in 2000 • 20% of gas production in 2010

48. Unconventional Gas

49. Gas Pipelines Natural gas is most easily transported by pipeline. Gas from Russia, the biggest producer, is piped all over Europe. It can also be liquefied and transported as liquefied natural gas (LNG) at a temperature of –163oC, requiring well insulated storage tanks.

50. World Total 187.6 Billion Tonnes Oil Equivalent 63.6 years supply at current production rate) Source: BP Statistical review of World Energy - 2012