ES832 Lect4 Fuel

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ENERGY CONVERSIONES 832a

Eric Savorywww.eng.uwo.ca/people/esavory/es832.htm

Lecture 4 Fuels

Department of Mechanical and Material EngineeringUniversity of Western Ontario

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Aim: To examine the different fuel sources

These include:

Fossil fuels

- Coal- Fuel oil- Natural gas- Bitumen

Synthetic fuel

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Fossil fuels Four main types: Coal, fuel oil, natural gas and bitumen

Fossil Fuels are hydrocarbons, formed from the remainsof dead plants and animals. Fossil fuel is a general termfor buried combustible geological deposits of organicmaterials, formed from decayed plants and animals thathave been converted to crude oil, coal, natural gas or

heavy oils by exposure to heat and pressure in theearth's crust over hundreds of millions of years.

The chemical compound is Cx(H20)y, which is producedby plants through photosynthesis where solar energy is

converted to chemical energy. Most of the fossil fuels were produced in the

Carboniferous Period of the Paleozoic Era: 299 - 359million years ago.

The fuel formulation is: CnH2n+2.

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Fossil fuels

Coal - it is composed primarily of carbon

along with assorted other elements, includingsulphur.

Fuel oil - it is made of long hydrocarbon

chains, particularly alkanes, cycloalkanes andaromatics.

Natural gas - consisting primarily of methane(CH4) but including significant quantities of

ethane (C2H6), propane (C3H8), butane (C4H10),carbon dioxide, nitrogen, helium andhydrogen sulphide. It is found in oil fields,

natural gas fields and in coal beds.

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Bitumen it is a mixture of organic liquids that

are highly viscous, black, sticky, entirely solublein carbon disulphide (CS2), and composedprimarily of highly condensed polycyclic aromatichydrocarbons (PAHs).

Bitumen is primarily used for paving roads.Its other uses are for general waterproofingproducts, including the its use in the

production of roofing felt.

Oil shale - is a general term applied to a groupof rocks rich enough in organic material (called

kerogen) to yield petroleum upon distillation.

Fossil fuels

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Coal Coal is formed from plant remains that have been

compacted, hardened, chemically altered, and

metamorphosed by heat and pressure overgeological time.

Coal was formed in swamp ecosystems which

persisted in lowland sedimentary basins. Theseswamp environments were formed during slowsubsidence of passive continental margins, andmost seem to have formed adjacent to estuarine and

marine sediments. When plants die in these peat swamp environments,

their biomass is deposited in anaerobic aquaticenvironments where low oxygen levels prevent their

complete decay by bacteria and oxidation.

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Burial by sedimentary loading on top of the peatswamp converts organic matter to coal by:

- Compaction, due to loading of the sediments on the

coal which flattens the organic matter- Removal of water held within the peat in between theplant fragments- Ongoing compaction removal of water from the inter-

cellular structure of fossilized plants- Heat and compaction removal of water- Methanogenesis; similar to treating wood in a pressurecooker, methane is produced, which removes hydrogenand some carbon, and some further oxygen (as water)

- Dehydrogenation, which removes hydroxyl groups(OH) from the cellulose and other plant molecules,resulting in the production of hydrogen-reduced coals

Generally, to form a coal seam 1m thick, some 10 - 30m of

peat is required. Peat has a moisture content of up to 90%.

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Coal formation

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Coal mining The most economical method of coal extraction from coal

seams depends on the depth and quality of the seams,

and also the geology and environmental factors of thearea being mined. Surface and mountain top mining

If the coal seams are near the surface, the coal is extracted by

strip mining. Strip mining exposes the coal by the advancement ofan open pit or strip.

Mountain top removal is a form of surface mining that takes placeat the topmost portion of a mountain. Utilized for the past 30years, mountain top mining involves removing the highest part ofthe mountain for the maximum recovery of coal.

Underground mining

Most coal seams are too deep underground for open cast miningand thus this type of mining is called underground mining. In deepmining, the room and pillar method progresses along the

Mammoth coal veinseam, while pillars and timber are left standingto support the coal mine roof.

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Petroleum (oil, gas)Petroleum forms from the remains of plants and animalsthat lived in the ocean 10-160 million years ago.

When organisms died and sank to the bottom, they werecovered in mud, sand, and other mineral deposits. Thisrapid burial prevented immediate decay, which would

normally occur if the organisms remained exposed on thesea floor.

The lack of oxygen in the sedimentary layers causedorganisms to slowly decay into carbon-rich compounds.

These compounds mixed with surrounding sediments andformed source rock, which is a type of fine-grained shale.

As more layers were deposited on top of one another,pressure and heat acting on the source rock compressed

the organic material into crude oil.

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Discovering the location of oil within the earth is difficultbecause of the presence of cap rock, which can be miles

thick in some locations. Oil geologists study surfacerocks and the terrain to determine if any oil is presentunderground, but the best evidence comes from varioussatellite imaging techniques.

Oil flows may disrupt the earth's gravitational ormagnetic field and so gravity meters and magnetometerscan detect some oil sources.

The most reliable method for finding oil is through the

use of shock waves in a process called seismology.

In a seismological survey a shock wave is aimed at the surface of thewater or land and the length of time it takes for the waves to reflectback to the sensor is recorded. The speed of the shock wavedepends on the type of rock it travels through, and by comparing the

travel times to known densities of rock, seismologists can determinewhat rocks are underground and predict if they might contain oil.

Petroleum finding oil

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The most common method of obtainingpetroleum is extracting it from oil wells found in

oil fields. Primary recovery methods are used to extract

oil that is brought to the surface byunderground pressure and can generally

recover about 20% of the oil present. After the oil pressure has depleted to the point

that the oil is no longer brought to the surface,secondary recovery methods draw another 5 to

10% of the oil in the well to the surface. Finally, when secondary oil recovery methods

are no longer viable, tertiary recovery methodsreduce the viscosity of the oil in order to bringmore to the surface.

Petroleum production

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Crude oilrefinement

fractional

distillation

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Oil shale fine grained sedimentary rockcontaining kerogen

The kerogen in oil shale can be converted to oil by the

chemical process of pyrolysis, during which the oilshale is heated to 445 - 500C in the absence of air(=pyrolysis) and the kerogen is converted to oil andseparated out, a process called "retorting".

Oil shale has been burnt directly as a low-grade fuel. It was estimated that in earths crust there are 6.5x1015

Tons of oil shale, about 1,000 times more than coal.

The US Energy Information Administration estimates the

world supply of oil shale at 2.6 trillion barrels ofrecoverable oil, 1.0-1.2 trillion barrels of which are in theUS. However, attempts to develop these reserves havebeen going on for over 100 years with limited success.

The caloric value of oil shale is 100 times smaller than

coal.

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Crude oil production from oil shale

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Energy overview

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Crude oil and natural gas field counts, cumulativeproduction, proven reserves, and ultimate recovery

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US Coal Demonstrated Reserve Base (as at 1 January 2005)

Energy Information Administration / Annual Energy Review 2005

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US Uranium Reserves and Resources

Energy Information Administration / Annual Energy Review 2005

W ld P i E P d ti b R i d C t

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World Primary Energy Production by Region and Country

Energy Information Administration/Annual Energy Review 2005

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World Crude Oil and Natural Gas Reserves (as at 1 Jan 2005)

DOE-EIA /AnnualEnergy Review 2005

W ld C d Oil P d ti

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World Crude Oil Production

DOE-EIA / Annual Energy Review 2005

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Retail Motor Gasoline Prices in Selected Countries 2005

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Retail Motor Gasoline Prices in Selected Countries, 2005

DOE-EIA/Annual Energy Review 2005

W ld P l C i

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World Petroleum Consumption


W ld D N l G C i

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World Dry Natural Gas Consumption


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Synthetic Fuels

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Introduction

Synthetic fuel or synfuel is any liquid fuel

obtained from coal, natural gas, or biomass. Itcan sometimes refer to fuels derived from othersolids such as oil shale, tar sand, wasteplastics, or from the fermentation of biomatter.

It can also refer to gaseous fuels produced in asimilar way.

The process of producing synfuels is oftenreferred to as Coal-To-Liquids (CTL), Gas-To-Liquids (GTL) or Biomass-To-Liquids (BTL),depending on the initial feedstock.

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Motivation Synthetic fuels require a relatively high price of crude

oil in order to be competitive with petroleum-based

fuels without subsidies. However, they offer thepotential to supplement or replace petroleum-basedfuels if oil prices continue to rise. Several factors makesynthetic fuels attractive relative to competing

technologies such as biofuels, ethanol / methanol orhydrogen:

The raw material (coal) is available in quantitiessufficient to meet current demand for centuries

It can produce gasoline, diesel or kerosene directlywithout the need for additional steps such asreforming or cracking

There is no need to convert vehicle engines to use adifferent fuel

There is no need to build a new distribution network

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Substitute Natural Gas (SNG)

Infrastructure of gas supply near coal mining. The obtained gas is often Methane; CH4 which

has a caloric value of ~ 1,000 Btu/scf.

Gasification is a process that converts

carbonaceous materials, such as coal,petroleum, or biomass, into carbon monoxideand hydrogen.

Produces High Btu Gas (1,000) & Low Btu Gas(500).

The gas tends to be cheaper than coal.

The gas production technology is simple.

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Gasification processes using coal

1. COAL + H2 CH4 + C + (heat)

2. COAL + 2H2 CH4 + (heat)

3. COAL + H2O CO + H2 + (-heat)

4. 4C + O2 CO2 + heat

5. 2C + O2 2CO2 + heat

H20

O2 (AIR)

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Upgrading

CH4, CO, H2 Raw Gas (500 Btu/scf) CO2, H2S, NH3 Residual

1. CO + H2O CO2 + H22. CO2 + H2, H2S Acid gases removal

3. CO + 3H2 CH4 + H2O Catalytic methanation

Pipe line gas 1000 Btu/scf

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Technological parameters

Type of coal being used

Preparation

Feeding technique to the reactor

Reactor type

Fixed bed

Fluidized bed

Entrained flow Heat supply - external / internal

Temperature and pressure

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Fischer-Tropsch process

Oil gasification is a catalyzed chemicalreaction in which carbon monoxide andhydrogen are converted into liquidhydrocarbons of various forms. Typicalcatalysts used are based on iron and cobalt.The principal purpose of this process is toproduce a synthetic petroleum substitute for

use as synthetic lubrication oil or as syntheticfuel.

I di t th d

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In-direct method

Following the gasification process, by usingH

2and CO, these reactions can occur:

(2m+1)H2+ mCO CmH2m+2 + mH2O

(n+1)H2+ 2mCO CmH2m+2 + nCO2

CmH2m+2is fuel C8H18

Direct method

Coal dissolving and by adding H2 (at temp. of~5000C):

nC + (n+1)H2 C

nH2

n+2

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Contamination

CO unburned fuel

Hydrocarbons unburned fuel

NOx, N2OS, NO2 reaction at high temp.

SO2 after oxidation, once in contact withwater turns to H2SO4

More information on these processes canbe found at SASOL Technology

www.sasol.com
http://www.sasol.com/http://www.sasol.com/

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ES832 Lect4 Fuel