Chapter 7. Fossil Fuels. Verve Publishers - Energy and Environment by Toossi (All Rights Reserved)

Transcription

1 Chapter 7 Fossil Fuels

2 Outline Fossil Fuel Carbon Cycle Combustion of Fossil fuels Fossil Resources Petroleum History From Oil-well to Gas Pump (Finding Oil, Recovery, Refining, Reserves) Coal Types of coals Extraction Reserves and Resources Oil shale and Tar-sands Environment concerns Natural gas Conversion of solid fuels to liquids and gases Summary

3 Facts: Fossil Fuels Most widely used form of energy in the world. The United States is the largest consumer of fossil fuels, which account for about 86% of its energy needs. Two-thirds of the electricity generated and almost all of the fuel used in transportation, comes from fossil fuels. Among the fossil fuels, oil and natural gas are the most popular because of ease of transport, handling, use, and somewhat lower emissions. As these supplies are exhausted, they must be substituted by other forms of fossils, such as coal, oil shale, and tar sands.

4 What is Fossil Fuel? Fossil remains of animals, plants, or other life forms that have been protected from decomposition and oxidation for a very long time. Fuel anything that can be burned as a source of energy. Fossil fuels are the remains of animals and plants that have formed into materials that can be burned. Fossil fuels can be in the form of solid (coal), liquid (petroleum), or gas. The main components of all fossil fuels are hydrogen and carbon, with H/C ratio increasing from solid to liquid to gaseous fuels: coal (~0.75), oil shale (1.6), tar sand (1.5), crude oil (~1.7), and methane (4.0). Since the source of these materials is living matter, they have the same composition as living organisms. They consist of fats, oils, paraffin (waxes), carbohydrates (sugars, starch, and cellulose), and proteins. Sulfur, phosphorous, and metals although they can be burned are not considered fossils because they do not originate from organic matter. The most likely sources are ancient trees, animals, fish, and tiny organisms that flourished in the oceans. Marshlands, subtropical and tropical swamps, lakes, lagoons, and river deltas are ideal sites.

5 Carbon Cycle Carbon Cycle: 1.Carbon is present in form of carbon dioxide (in the atmosphere, dissolved in ocean water, or trapped in sedimentary rocks and in plants). 2.Through the process of photosynthesis, carbon dioxide and water vapor in the presence of sunlight of appropriate frequency combine to produce carbohydrate. 3.Depending on conditions that dead animals and plants are exposed, carbon may return to the atmosphere as carbon dioxide or turn into fossil fuel; if the environment dries up, dead plants and animals will become exposed to air and react with it to produce carbon dioxide, thus completing the carbon cycle.

6 FAQ Carbon Cycle Question: How can we make hydrocarbons renewable? Answer: By accelerating the rate of conversion of carbon dioxide to carbohydrate to match the rate of its release into the atmosphere. Scientists are, therefore, hooked into finding plants that can grow as fast as they are being used. One possibility is algae -- burn the algae at the power plant, capture that carbon dioxide and pump it back into the greenhouse, and grow more algae.

7 Combustion of Fossil Fuels In general, Fossil Fuel + Oxidizer Products + Heat For example, Methane: Gasoline: Coal: The stoichiometric combustion of gasoline in air would be:

8 Incomplete Combustion Unfortunately, these reactions do not reach completion and other gases such as nitric oxides (NO and NO 2 ) and carbon monoxide (CO) are always present. The degree to which the reaction completes depends upon combustion temperature and pressure, residence time, and mixture ratios.

9 FAQ -- Combustion Question: As a result of fossil fuel consumption, roughly six billion tons of carbon is produced each year. It is estimated from geological evidence that each year about 30 million tons of carbon go into the formation of new fossil sediments. What is the significance of this data in estimating the lifetime of remaining fossil fuels? Answer: The rate of consumption of fossil fuels is 200 times faster than the rate at which they are replenished by nature. This means fossil fuels are gradually being depleted and must be considered as a non-renewable source of energy.

10 FAQ -- Combustion Question: Calculate the stoichiometric air-to-fuel ratio necessary for burning natural gas in air. Natural gas consists mainly of methane. Answer: The stoichiometric reaction of methane is 16 kg methane+ 275 kg air 44 kg carbon dioxide + 36 kg water vapor kg nitrogen; or 1 kg methane kg air 2.75 kg carbon dioxide kg water vapor kg nitrogen

11 Calorific Value / Heating Value / Heat of Combustion Heating value refers to the amount of thermal energy that is released by burning a unit amount of fuel. Per unit mass, different fossil fuels have relatively similar calorific values. Except for a slight variation in energy trapped between different bonds which form their molecules, these hydrocarbons are expected to release similar amounts of heat. Depending on the shares of carbon, volatile matter, moisture, ash, and sulfur, coal energy content can vary by a factor of three. Heating Values for Common Fuels* Fuel Calorific Value (kj/kg) Coal 10,000-30,000 Kerosene 43,000 Gasoline 44,000 Methane 55,600 Propane 50,500 Coal Gas 34,000 Methanol 19,800 Garbage** 19,800 Wood 20,000 Hydrogen 143,000 * Approximate; can vary somewhat depending on fuel purity. ** From typical U.S. households

12 Compare Fossil Fuels 1 liter of petroleum = 1 kg of coal = 1 m 3 of natural gas 1 gal of petroleum = 10 pounds of coal = 150 ft 3 of natural gas

13 Fossil Resources Fossil fuel proven reserves in the world.

14 Fossil Data (2008)

15 Petroleum (BLACK GOLD) Rock oil and refers to gaseous, liquid, or solid hydrocarbons found beneath the earth s surface under very high pressures and temperatures underground Underground oil reservoir

16 Crude Oil Composed of a multitude of hydrocarbons consisting of paraffins, aromatics, and more complex molecules containing carbon, hydrogen, oxygen in addition of traces of metals. Convenient source of energy for generating electricity and powering our cars. Main ingredient in much of the plastics, waxes, medicines, cosmetics, solvents, lubricants, feedstock, and a host of other petrochemical products.

17 Oil Exploration in United States The first commercial oil well in the United States Edwin L. Drake in 1859 produced about 1000 gallons a day Within one year, 2000 new oil wells were dug (Born of OIL Industry!) In 1864, John David Rockefeller, first oil refinery in Cleveland, Ohio. November 1, 1879, Thomas Edison was awarded a patent for his most famous invention the electric lamp. The switch to electricity (which was generated primarily by burning coal) could adversely impact oil demand and price of the crude. Henry Ford automobiles (the horseless carriage), which was running on gasoline, a by-product of distillation of crude. Between , nearly half a million automobiles were sold, and with it petroleum found its prominent place in the American economy, and in doing so solidified Rockefeller s power to control the price of oil. New oil discovery in Texas in Colonel Edwin Drake first commercial oil well in Pennsylvania.

18 OPEC Organization of Petroleum Exporting Countries Established in Aim: to stabilize the sharply declining oil prices after WWII, and coordinate policies. OPEC members collectively control 80% of the world s proven oil reserves and produce 41% of the world s oil, but consume only 8% of the oil. Current member states are: Algeria, Indonesia, Iran, Iraq, Kuwait, Libya, Nigeria, Qatar, Saudi Arabia, Venezuela, and the United Arab Emirates

19 World Petroleum Reserves, Production, and Consumption (2007 data) Petroleum Saudi Arabia Iran Iraq Kuwait Venezuela UAE Russia Libya All Others Top Suppliers and Consumers of Petroleum (as of Jan 1, 2009)* Who has it? 19.9% 10.1% 8.6% 7.7% 7.4% 7.3% 4.5% 3.3% 18% U.S. China Japan India Russia Germany Canada Brazil All Others Who uses it? 22.7% 9.1% 5.6% 3.5% 3.4% 3.0% 2.8% 2.9% 47% *Excluding Canadian tar sands Source: U.S. EIA International Energy Statistics, 2009 U.S. petroleum consumption and production. The difference is met through the import of foreign oil

20 From Oil Well to Gas Pump

21 Finding Oil Advancement in technologies Gravimetric Method uses variations in the local earth s density as an indication of the presence of local deposits of coal, petroleum, or other ores. Petroleum is often found in porous rocks, so lower bulk density of a region relative to its neighboring strata can be an indication of existing porous structure and thus one indication of presence of petroleum reserves. Seismic Method It exploits changes in the velocity of sound as it travels from one medium to another. Techniques have been developed that monitor differences in the electrical resistance and other properties of the surrounding rocks and porous media; liquids rich in petroleum have a much higher electrical resistance than brine and its surrounding rock. Recent innovations in underground imaging and directional drilling has allowed searching for oil in depths of up to 6 kilometers and exploring areas previously inaccessible to geologists. Data collected on density, conductivity, and other physical properties can then be used to construct 4-D geological maps to track the motion of the fluid and improve chances of oil discovery and recovery.

22 Recovery Enhanced Oil Recovery Primary Recovery (conventional method of production) Initially, oil is under sufficiently high pressure, which causes it to gush out naturally and no pumps are needed (flush production). 30% of the oil can be extracted. Secondary recovery involves injecting water, natural gas, or carbon dioxide into dead wells to raise the pressure or push the remaining oil into neighboring wells where they can be extracted. (additional 10-15% of the available oil can be recovered, unfortunately it raises the cost of oil production by 50 to 100 percent.) Tertiary recovery technique relies on reducing the oil viscosity. A small underground detonation results in a shock wave that propagates across the oil deposit. The shock wave heats the oil and breaks it into smaller molecules, making it flow more easily. (10-15% of the oil can be recovered) Secondary - water flooding The combined primary, secondary, and tertiary methods can recover about 50-60% of the oil deposit. Once these techniques are exhausted, the well is no longer usable and must be capped. Tertiary - steam injection

23 Refining Crude oil extracted from the ground, impure contains sand, water, and a number of salts. Therefore, requires refining. Sand settles to the bottom of storage tanks and is easiest to remove. Other contaminants are removed by electric or chemical means. Distillation column depending on the boiling points, crude oil separate into heating oil, kerosene, gasoline, and various gaseous fuels such as butane, propane, and methane. Product Gaseous fuels Ether Gasoline Kerosene Fuel oil Greases Paraffins (waxes) Asphalt and tar Product of Petroleum Distillation Molecular Structure C1-C4 C5-C7 C5-C12 C12-C16 C15-C18 C18 and up C20 and up --- Boiling Point ( o C) -164 to to to to 275 Up to 375 Semisolid Solid Residue in column Use Gas stoves, RVs Solvent Motor fuel Diesel and jet fuel Furnace Lubricant Candles Roofing and paving

24 Reserves Proven reserves: quantity of oil that can be economically exploited using the technologies available before the wells are abandoned. FACTORS: The reserve amount is expected to change, depending on who makes the estimates and the time that estimates are made. Sate of technology advances in enhanced oil recovery, offshore and horizontal drilling, and better diagnostic techniques Availability of reliable data

25 Reserve Estimates of Proven Fossil Reserves, R/P (2009)* Coal (billion metric tons,r/p) Oil (billion barrels,r/p # ) Natural Gas (trillion cubic meters,r/p) United States Middle East The World 257 (224 yrs) negligible 909 (122 yrs) # Reserves /production (years) * All numbers are rounded to closest integer ** Including Canadian tar sands Source: BP Statistical Review of world Energy, 2009, 30 (12 yrs) 754 (79 yrs) 1,258** (42 yrs) 7 (12 yrs) 76 (>100 yrs) 185 (60 yrs)

26 Coal (Black Rock) Merits: relatively cheap and plentiful can be transported by truck, ship, and rail easy to store and burn can be liquefied to produce synthetic oil Demerits: probably the dirtiest of all fossil resources produces more carbon per unit energy content (highest percentage of sulfur and produces more NOx). the relative impact on global warming and overall air quality is considered to be the greatest, producing twice carbon dioxide as oil for the same amount of energy.

27 Coal - Formation Dead plants Decomposed by aerobic bacteria yielding CO 2, CH 4, etc. Decomposed anaerobically (without air) if covered by mud for a long time. Occurs in stratified deposits, feet thick in average depth of about 300 feet

28 Coal (History) In past, the coal extracted from shallow seams was high in sulfur and burned with an irritating smell but at higher temperatures than wood which made coal more desirable for the smelting of irons and other metals. By early twentieth century, coal accounted for 90% of all energy supplies in the world. Today, 6.6 billion metric tons of coal is produced each year. It accounts for a quarter of the world s primary energy consumption, and generating 40% of all electricity. In the United States, coal production grew exponentially from 1860 to 1910 before it lost its dominance as an energy source to petroleum, a liquid most suitable to be used in internal combustion engines. The consumption remained largely steady until 1972, whereupon the rate started to rise again. Today, coal provides 40% of U. S. total energy need and fuels over one half of all electricity generated. The U.S. consumption of coal reached one billion metric tons in 2008.

29 Types of Coal The first stage of coal formation involves the compression of vegetable and organic matter under the heavy weights of water and ground where it gradually turns into a dark-brown, compact material known as peat. Over time, peat is compressed and heated to form lignite. Lignite is a soft, brownish-black coal, containing about 30% carbon. It is also of the lowest quality and the most abundant type of coal in the world. At greater depths, lignite is transformed into sub- bituminous, bituminous, and ultimately anthracite coal. Quality of coal typically categorized by its rank and grade. Rank represents its morphological development from peat to lignite (brown coal), sub-bituminous, bituminous (soft coal), and anthracite (hard coal). The higher the coal is ranked, the greater is its carbon content, resulting in more energy being liberated when it is burned. Grade determines its purity. Coal is of a better grade if its sulfur content is less and burns with lower emissions; coal is classified into low, medium, and high grades. Rank Anthracite Bituminous Sub-bituminous Lignite *Higher Heating Values. Coal Ranks and their Properties Age (million years) Carbon Content Heating Value * (kj/kg) 85-95% 45-85% 35-45% 25-35% 34,000 and up 25,000-35,000 20,000-25,000 10,000-20,000

30 Coal Types Anthracite Oldest (350 million years) Highest quality(95% carbon) Most clean Pennsylvania (14,000 Btu/lb) Bituminous 300 million years Medium quality (50-80% carbon) Pennsylvania, Illinois, Michigan, Utah (12,500 Btu/lb) Lignite million years Low quality (<50% carbon) North Dakota (10,000 Btu/lb), Texas (7,000 Btu/lb) * Peat (mix of coals of different ranks such as brown coal, lignite, bituminous)

31 Extraction Depending on how deep the coal is buried, and its local geology, coal can be extracted by (1) Surface (opencast) mining Area mining applies to shallow mines where surface is relatively flat. Contour mining refer to surface mines on steep hills or mountainous regions. Auger mining uses horizontal drilling to recover additional coal from a seam located behind the last contour cut. (2) Underground (deep) mining Room-and-pillar mining the coal is mined by cutting a network of "rooms" into the seam. Up to half of coal is extracted in this manner, leaving the other half (pillars) to support the weight of the roof. As drills retreat, the standing pillars are removed allowing the roof to collapse. Long-wall mining essentially all the coal contained in a large rectangular block or panel of coal is excavated. Each rectangular panel is up to two kilometers in length, m in width and 2-3 meters in height. As coal cutting machine runs back and forth along the face, they cut coals of about one-meter thick during each pass. The coal is loaded on a chain conveyor running along the length of the face for transport out of the mine.

32 Reserves and Resources Only five countries, the U.S., Russia, China, Australia, and India, own about three quarters of all world coal reserves estimated at 909 billion metric tons. Despite what one might expect, there are no coal mines in the Middle East. Anthracite (hard coal) is most commonly found in Pennsylvania and accounts for only 1% of U.S. coal reserves. About 70% of coal is bituminous (soft coal); the rest is essentially lignite.

33 Coal - Resources US: Appalachian Basin (West Virginia, Pennsylvania) Illinois Basin (Illinois, Indiana) Rocky Mountains (Montana, Wyoming, Colorado, New Mexico, N. Dakota) World: Former Soviet Union (56%) United States (20%) Asia (9%)

34 Oil Shale and Tar Sands Oil shale is actually a misnomer. is not shale, but a rock, and it doesn t contain oil, but rather a solid waxy organic compound called kerogen, which is tightly packed in clay, mud, and silt. Tar sands are grains of sand containing a thick, viscous, soluble organic liquid called bitumen.

35 Shale Oil Carbon bearing mudstone or marlstone containing organic kerogen (HC wax-like substance) Found in bottom of Green River (Colorado, Utah, and Wyoming) US reserves are even larger than petroleum reserves Verve Publishers - Energy and Environment by Toossi (All Rights Reserved)

36 Shale Oil - Problems Must be extracted, retorted (heated to 1000 F to drive out the HC) and refined. High sulfur content Low yield (10-25 gallons/ton) Requires a lot of water for processing Disposal of spent shale a problem Cost is prohibitive except for the best quality shale oil

37 Tar Sands Deposits of sand impregnated with a thick, viscous oil called bitumen. Must be mined and transported for processing. Processing involves extraction of bitumen by steam and hot water followed by refining. Main deposits in Alberta, Canada Production prices started to be comparable to that of crude oil.

38 Oil shale and Tar sands Environmental Concerns In addition to their low yield ( liters per ton of rock), they are not clean. The production of petroleum products derived from these resources entail substantially more carbon dioxide and other greenhouse gases. Water quality also is affected adversely, since the extraction processes require substantial water. The leaching of salt, minerals, and other toxins produced from spent shale will put additional burden on nearby rivers and water reservoirs. The extent to which land is disturbed and possibly becomes unstable and useless for agricultural and pastoral use. The flora and fauna also may undergo permanent changes. The extraction involves producing lots of residues (called tailing), which occupy many times the volume of crude they produce.

39 NATURAL GAS Associated and Non- Associated Gas Composition Natural Gas LPG and LNG CNG Verve Publishers - Energy and Environment by Toossi (All Rights Reserved)

40 Advantages of natural gas Reliable Cheaper Environmentally friendly fewer emissions almost no ash particles 45% less CO 2 than coal 30% less CO 2 than oil

41 Natural Gas Reserves

42 Conversion of Solid Fuels to Liquids and Gases Integrated Gasification Combined Cycle (IGCC) technology uses coal gas to operate gas turbines at very high efficiency. The combined gas and steam turbines provide both heat and power with efficiencies much higher than traditional power plants. Coal gas (town gas or illumination gas) is produced by heating the coal in the absence of oxygen (destructive distillation). Coal powder is heated to form volatile products (carbon monoxide, carbon dioxide, methane, nitrogen, and unburned hydrocarbon), which then are collected at various points along a distillation column.

43 Conversion Coal(S) Coal (L): can be used as a transportation fuel. Process: Fischer-Tropsch developed by the Germans during WWII to produce much needed petroleum to run their military machines. Demerits: quite costly and the yield was rather low, around three barrels of petroleum per ton of coal. The same process can be used today using coal or even biomass as the primary source, on a much larger scale. Steam Reforming: Natural gas is converted to liquid. The process requires breaking methane s chemical bonds using steam, heat, metal catalysts, and a limited amount of oxygen, to produce a mixture of carbon monoxide and hydrogen gas called syngas (known as producer gas, manufactured gas, or wood gas), which then is compressed to high pressures and blown over more catalysts to be transformed into gasoline, diesel, and other liquid fuels. FACT: Ninety-five percent of all hydrogen used in the United States is produced by this method.

44 Steps: production of gaseous fuel from coal A. Gasification: Coal is heated to drive off its volatile components. Steam and heat are added to the nonvolatile coal to break it down to smaller molecules. The product is mainly gas -- largely carbon monoxide and hydrogen. Ash is removed from the mixture and discarded. B. Purification: Impurities such as hydrogen sulfides, tar, and ash are removed. C. Catalytic Reaction: The gas is passed through a bed of catalysts where carbon monoxide-hydrogen gases react to produce methane and carbon dioxide. Carbon monoxide is removed and stored. Note that this reaction is obtained as a combination of (ii)+(iii)-(i).

45 Chapter 7 Additional Information Slides Verve Publishers - Energy and Environment by Toossi (All Rights Reserved)

46 Formation

47 Calorific Value Natural Gas 1000 BTU/cu.ft 58 MJ/kg Petroleum BTU/lb or 5.8 million BTU/bbl 44 MJ/kg Coal BTU/lb MJ/kg * 1 kg = 2.2 lb. ; 1 m3 = 35.3 ft3; 1 bbl = 42 U.S. gallons = lit

48 Fossil Fuels Reserves (percentage of world reserves) Coal Oil Gas United States 27% 2% 4% Russia 13% 6% 25% China 17% 1% 1%

49 US Oil Balance in 2007 Import (5 billion barrels) 44% from OPEC (16% from Persian Gulf) 18% from Canada 11% from Mexico 3% from Russia Export

50 Fossil vs. Non-fossil use in US (1999) Energy Source Quads Percent of Total Coal Petroleum Natural Gas Nuclear Hydroelectric Biomass Geothermal Solar Wind Total

51 World Oil (2000) Who has it? Who uses it? Saudi Arabia 26% U.S. 26% Iraq 10% Japan 7% Kuwait 10% China 6% UAE 9% Germany 4% Iran 9% Russia 3% Venezuela 6% Brazil 3% Russia 5% South Korea 3% Mexico 5% India 3% U.S. 3% France 3% Verve Publishers - Energy and Environment by Toossi (All Rights Reserved) All Others 17% All Others 43%

52 World Oil (2007) Who has it? Who uses it? Saudi Arabia 22% U.S. 25% Iran* 11% China 8% Iraq 9% Japan 6% Kuwait 8% Russia 3% UAE 8% Germany 4% Venezuela 7% India 3% Russia 6% Brazil 3% Libya 3% South Korea 3% Nigeria 3% Saudi Arabia 2% Verve Publishers - Energy and All Others 17% Environment by All Toossi Others (All Rights 44% Reserved)

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