Co2 emission rate per MWh of energy generated from coal fired plants

COCO22 Emission Rate per MWh of Energy Emission Rate per MWh of Energy

Generated from Coal-Fired Plants Generated from Coal-Fired Plants

© Copyright 2008 David Palmer

CoalCoal

Coal is one type of Coal is one type of

fossil fuelfossil fuel

It is the largest single It is the largest single

source of:source of:

fuel for the fuel for the

generation of generation of

electricityelectricity

carbon dioxide carbon dioxide

emissionsemissions


Complete Combustion of CoalComplete Combustion of Coal

OHy

xCOOy

xHC yx 222 )2

()4

( +⇒++

WaterCO heat oxygen fuel 2++⇒+


The Energy Density of CoalThe Energy Density of Coal

Energy density ‘Q’ is also referred to fuel Energy density ‘Q’ is also referred to fuel content or heating ability (MJ / kg) content or heating ability (MJ / kg)

1000

93)8

(1442337 SO

HCQ

+−+=

where; C is the mass percent of carbon, H is the mass percent of hydrogen, O is the mass percent of oxygen, and S is the mass percent of sulfur in the coal

The energy density of coal is roughly 24 kgMJ


Various Types of CoalVarious Types of Coal

ASTM classASTM class ASTM groupASTM group MJ/kgMJ/kg

LigniteLignite Lignite ALignite A <14.6<14.6

Lignite BLignite B 14.6-19.314.6-19.3

Sub-bituminousSub-bituminous Sub-bituminous CSub-bituminous C 19.3-22.119.3-22.1

Sub-bituminous BSub-bituminous B 22.1-24.422.1-24.4

Sub-bituminous ASub-bituminous A 24.4-26.724.4-26.7

High volatile CHigh volatile C 24.4-30.224.4-30.2

BituminousBituminous High Volatile BHigh Volatile B 30.2-32.530.2-32.5

High Volatile AHigh Volatile A >32.5>32.5

Medium volatileMedium volatile >32.5>32.5

Low volatileLow volatile >32.5>32.5

AnthraciteAnthracite Semi-anthrciteSemi-anthrcite >32.5>32.5

AnthraciteAnthracite >32.5>32.5

Meta-anthraciteMeta-anthracite >32.5>32.5


As mentioned earlier the energy density of As mentioned earlier the energy density of coal is 24 , this converts to coal is 24 , this converts to from,from,

Energy Density of CoalEnergy Density of Coal

kg

hkW ⋅kgMJ

kg

hkW

MW

kWh

sJ

Ws

kg

MJ ⋅=×××× 67.61000min6060

min24


Thermodynamic Efficiency Thermodynamic Efficiency of Coal-Fired Plantsof Coal-Fired Plants

Typical thermodynamic efficiency of coal Typical thermodynamic efficiency of coal

plants is about 30%.plants is about 30%.

Coal has 6.67 kW·h of energy per Coal has 6.67 kW·h of energy per

kilogram and approximately 30% can kilogram and approximately 30% can

successfully be turned into electricity – the successfully be turned into electricity – the

remaining energy is heat waste. remaining energy is heat waste.

Coal power plants obtain approximately Coal power plants obtain approximately

2.0 kW·h per kg of burned coal.2.0 kW·h per kg of burned coal.


Energy Consumption ExampleEnergy Consumption Example

As an example, running one 100 watt light bulb for As an example, running one 100 watt light bulb for one year requires 876 kW·h. one year requires 876 kW·h.

(100 W × 24 h/day × 365 {days in a year} (100 W × 24 h/day × 365 {days in a year}

= 876000 W·h = 876000 W·h

= 876 kW·h = 876 kW·h

Converting this power usage into physical coal Converting this power usage into physical coal consumption: consumption:

coal of lbs 966coal of kg 438kghkW 2.0

hkW 876 ==⋅

⋅


COCO22 Production Production

Coal is at least 50% carbon (by mass), then 1 kg Coal is at least 50% carbon (by mass), then 1 kg of coal contains at least 0.5 kg of carbon.of coal contains at least 0.5 kg of carbon.Carbon has an atomic weight of 12 kg / kmol, Carbon has an atomic weight of 12 kg / kmol, where 1 mol is equal to NA (Avogardo’s where 1 mol is equal to NA (Avogardo’s Number)Number)Therefore, 0.5 kg of carbon is,Therefore, 0.5 kg of carbon is,

Carbon reacts with oxygen during combustion, Carbon reacts with oxygen during combustion, producing carbon dioxide, COproducing carbon dioxide, CO22, which has an , which has an atomic weight of (12 + 16 × 2 = 44 kg / kmol) atomic weight of (12 + 16 × 2 = 44 kg / kmol)

kmol24

1

12

5.0 =⋅ kmolkg

kg


Kilograms of COKilograms of CO22 Produced Produced

per Kilogram of Coalper Kilogram of Coal

As mentioned earlier,As mentioned earlier,

The same number of ‘x’carbon atoms are found in coal (CxHy) The same number of ‘x’carbon atoms are found in coal (CxHy) before combustion as seen in carbon dioxide CObefore combustion as seen in carbon dioxide CO22 after after

combustion then,combustion then,

1 / 24 kmol of CO1 / 24 kmol of CO22 is produced from the 1 / 24 kmol present in is produced from the 1 / 24 kmol present in

every kilogram of coal, which weighs approximately,every kilogram of coal, which weighs approximately,

OHy

xCOOy

xHC yx 222 )2

()4

( +⇒++

kg 1.83 kmol

kg 44kmol

24

1 ≈⋅


Carbon Cost of Energy Carbon Cost of Energy with the use of Coal Powerwith the use of Coal Power

Variables: Variables:

Thermodynamic efficiency of coal fired plant = 30% Thermodynamic efficiency of coal fired plant = 30%

Energy density = 6.67 kW·h of energy per kilogram of coalEnergy density = 6.67 kW·h of energy per kilogram of coal

Energy produced = 2.0 kW·h/kg (coal)Energy produced = 2.0 kW·h/kg (coal)

As calculated earlier,As calculated earlier,

1 kg of coal produces roughly 1.83 kg C01 kg of coal produces roughly 1.83 kg C022, then using electricity from coal , then using electricity from coal

produces COproduces CO22 at a rate of, at a rate of,

or,or,hkW

kg915.0

kghkW 2.0

kg 1.83

⋅=

⋅

MJ

kg254.0

MJ

kJ1000

kJ

kWs

60s

min

60min

h

hkW

kg915.0 =××××

⋅


Comparison with Comparison with U.S Energy ReportU.S Energy Report

This estimate compares with the U.S Energy Information This estimate compares with the U.S Energy Information

Agency’s Report on COAgency’s Report on CO22 emissions for energy emissions for energy

generation, which quotes a production rate of generation, which quotes a production rate of

By comparison COBy comparison CO22 generation from oil was generation from oil was

and natural gas was and natural gas was

hkW

kg950.0

⋅

hkW

kg0.890

⋅

hkW

kg600.0

⋅


SummarySummary

Using electricity from coal produces COUsing electricity from coal produces CO22

at a rate of, , which is also equal to,at a rate of, , which is also equal to,hkW

kg915.0

⋅

hMW

kg915

MW

kW1000

hkW

kg915.0

⋅=×

⋅


Ontario’s Five Coal-Fired PlantsOntario’s Five Coal-Fired Plants

Lambton Nanticoke

Atikokan

Thunder BayLennox


Ontario’s Lambton Coal-Fired PlantOntario’s Lambton Coal-Fired Plant

The following table shows the COThe following table shows the CO22 emission rates, in kilograms per emission rates, in kilograms per

megawatt-hour (kg / MWh) of each of the Lambton Generating megawatt-hour (kg / MWh) of each of the Lambton Generating Station’s coal-fired boilers, (results from 2005).Station’s coal-fired boilers, (results from 2005).

EmissionRates

kg / MWh

LambtonUnit 1

LambtonUnit 2

LambtonUnit 3

LambtonUnit 4

CarbonDioxide

CO2

927.80 927.35 926.87 926.57


Resistance and Heating Resistance and Heating in the Power Linesin the Power Lines

One should also take into account transmission and One should also take into account transmission and distribution losses caused by resistance and heating in distribution losses caused by resistance and heating in the power lines. Which is in the order of 5–10%, the power lines. Which is in the order of 5–10%, depending on the distance from the power station and depending on the distance from the power station and other factors.other factors.

If this was taken into account our earlier calculation of If this was taken into account our earlier calculation of

would equal,would equal,hkW

kg915.0

⋅

hkW

kg960.005.1

hkW

kg915.0

⋅=×

⋅


Other Types of COOther Types of CO22 Production Production

Steel-making Steel-making 1.97 ton CO1.97 ton CO22 / ton of steel produced / ton of steel produced

Cement makingCement making 0.87 to 0.97 ton CO0.87 to 0.97 ton CO22 / ton of cement produced / ton of cement produced

AutomobliesAutomoblies 165 g CO165 g CO22 / km driven or, / km driven or,

2.5 kg CO2.5 kg CO22 / Litre of gasoline consumed / Litre of gasoline consumed


Science

Co2 emission rate per MWh of energy generated from coal fired plants