Compiled By Mr. Eric A. McKenzie. PhD. BA. DSM
Coal Convertions FACT 2013
FACT SHEET 01
Basis of Analysis
Definitions
As Received (ar) : includes Total Moisture (TM)
Air Dried (ad) : includes
Inherent Moisture (IM) only
Dry Basis (db) : excludes all
Moisture
Dry Ash Free (daf) : excludes all Moisture
& Ash
The Proximate
Analysis of any coal i.e. the % content of Moisture, Ash (A). Volatile Matter (VM), Fixed Carbon (FC) – also Sulphur
(S) and Calorific Value (CV) –
can be expressed on any of the above bases.
Convertions
To obtain:-
|
Air Dry
|
Dry Basis
|
As Received
|
multiply
|
|||
ar
by:
|
100 - IM%
|
100
|
—
|
100 - TM%
|
100 - TM%
|
||
ad
by:
|
—
|
100
|
100 - TM%
|
100 - TM%
|
100 - IM%
|
||
db
by:
|
100 - IM%
|
—
|
100 - TM%
|
100
|
100
|
||
[For daf, multiply db
by 100/(100-A)]
|
|||
Example:
|
||||
ar
|
ad
|
db
|
daf
|
|
TM
|
11.0
|
-
|
-
|
-
|
IM
|
2.0
|
2.0
|
-
|
-
|
Ash
|
12.0
|
13.2
|
13.5
|
-
|
VM
|
30.0
|
33.0
|
33.7
|
39.0
|
FC
|
47.0
|
51.8
|
52.8
|
61.0
|
Sulphur
|
1.0
|
1.1
|
1.12
|
-
|
FACT SHEET 02
Mass
Units:
Metric ton (t) = tonne = 1000
kilograms (= 2204.6 lb)
Imperial or long ton (lt) =
1016.05 kilograms (= 2240 lb)
Short (US) ton (st) = 907.19
kilograms (= 2000 lb)
Conversions:
From long ton to metric ton
multiply by 1.016
From short ton to metric ton
multiply by 0.9072
Mt million tonnes
Mtce million tonnes of coal equivalent
(= 0.697 Mtoe)
Mtoe million tonnes of oil equivalent
Calorific Values (CV)
Units:
kcal/kg – kilocalories per kilogram
MJ/kg* – Megajoules per kilogram
Btu/lb – British thermal units per pound
* 1 MJ/kg = 1 Gigajoule/tonne
(GJ/t)
Gross & Net Calorific Values
Gross CV or ‘higher heating value’ (HHV)
is the CV under laboratory conditions.
Net CV or ‘lower heating value’ (LHV)
is the useful calorific value in boiler plant.
The difference is essentially the
latent heat of the water vapour produced.
Conversions – Units
From kcal/kg to MJ/kg
multiply kcal/kg by 0.004187
From kcal/kg to Btu/lb
multiply kcal/kg by 1.8
From MJ/kg to kcal/kg
multiply MJ/kg by 238.8
From MJ/kg to Btu/lb multiply
MJ/kg by 429.9
From Btu/lb to kcal/kg
multiply Btu/lb by 0.5556
From Btu/lb to MJ/kg multiply
Btu/lb by 0.002326
Conversions – Gross/Net (per ISO, for As Received
figures)
kcal/kg: Net CV = Gross CV - 50.6H - 5.85M - 0.191O
MJ/kg: Net CV = Gross CV - 0.212H - 0.0245M - 0.0008O
Btu/lb: Net CV = Gross CV - 91.2H - 10.5M - 0.34O
– where M is % Moisture, H is %
Hydrogen, O is % Oxygen (from
ultimate
analysis*, also As Received).
*Ultimate analysis determines the
amount of carbon, hydrogen, oxygen, nitrogen & sulphur.
For typical bituminous coal with
10% M and 25% Volatile Matter, the
differences between gross and net
calorific values are approximately as follows:
260 kcal/kg 1.09
MJ/kg 470
Btu/lb
FACT SHEET 03
Power Generation
1 MWh = 3600 MJ
1 MW = 1 MJ/s
1 MW (thermal power) [MWth] = approx 1000 kg steam/hour
1 MW (electrical power) [MWe] = approx MW (thermal power)
3
A 600 MWe coal-fired power
station operating at 38% efficiency and 75%
overall availability will consume
approximately:
– Bituminous coal (CV 6000
kcal/kg NAR*): 1.5 Mt/year
– Brown coal (CV 2250 kcal/kg NAR*): 4.0 Mt/year
Sources: GWC Coal Handbook &
IEA Clean Coal Centre
From GAR to NAR
The
difference between net and gross as received (NAR v/s GAR) specific energy values is the latent heat of the
water vapor which lowers the effective calorific value in the boiler.
To convert from GAR to NAR for bituminous coals subtract approximately:
1.09 mj/kg 260 kcal/kg 470 btu/lb
Applicable for bituminous coal. Not to be considered exact!
FC = Fixed Carbon % by weight on Moisture and Ash Free basis
VM = Volatile Matter % by Weight on Moisture and Ash Free Basis
To convert from GAR to NAR for bituminous coals subtract approximately:
1.09 mj/kg 260 kcal/kg 470 btu/lb
Applicable for bituminous coal. Not to be considered exact!
FC = Fixed Carbon % by weight on Moisture and Ash Free basis
VM = Volatile Matter % by Weight on Moisture and Ash Free Basis
Hydrogen % ( Moisture and Ash free basis ) = VM * [ 7.35 / (VM
+ 10) - 0.013 ]Nitrogen % ( Moisture and Ash free basis ) = 2.1 – 0.012 * VM)
Carbon % ( Moisture and Ash free basis) = { [FC + 0.9 * (VM-14)] – Sulphur %}
Sulphur % has to be assumed based on some previous analysis.
Convert all the above to Air Dried Basis or As Received Basis, as per the Ash % and Moisture % in the proximate sample. Then Subtract from 100 to get Oxygen %.
From ADB to GAR
GCV (ARB) = GCV (ADB)
X (100-TM)/(100-IM)
e.g.
ADB 6300 x (100-18)/(100-12) = 5870 GAR
NAR (kcal/kg) = GAR (kcal/kg) – 50.7H – 5.83TM
NAR is NCV ARB.
GAR is GCV ARB.
H = Hydrogen is usually in DB or DAF and needs to be converted to ARB
H is assumed as 5.4 DAF (regional variance used in lieu of Ultimate Analysis)
GCV (ADB) ke GCV (ARB) = 5,514 kcal/kg
H (DAF) ke H (ARB) = 4.18%
NCV (ARB) = 5,191 kcal/kg
Gross ADB (GAD) = 5,766 kcal/kg
Gross ARB (GAR) = 5,514 kcal/kg
Net ARB (NAR) = 5,191 kcal/kg
e.g.
ADB 6300 x (100-18)/(100-12) = 5870 GAR
NAR (kcal/kg) = GAR (kcal/kg) – 50.7H – 5.83TM
NAR is NCV ARB.
GAR is GCV ARB.
H = Hydrogen is usually in DB or DAF and needs to be converted to ARB
H is assumed as 5.4 DAF (regional variance used in lieu of Ultimate Analysis)
GCV (ADB) ke GCV (ARB) = 5,514 kcal/kg
H (DAF) ke H (ARB) = 4.18%
NCV (ARB) = 5,191 kcal/kg
Gross ADB (GAD) = 5,766 kcal/kg
Gross ARB (GAR) = 5,514 kcal/kg
Net ARB (NAR) = 5,191 kcal/kg
