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Coal Conversion Statistics

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.

Conversions

To obtain:-Air DryDry BasisAs Received
- multiply
ar by:(100 - IM%) / (100 - TM%)100 / (100 - TM%)-
ad by:-100 / (100 - IM%)(100 - TM%) / (100 - IM%)
db by:(100 - IM%) / 100-(100 - TM%) / 100

[For daf, multiplydb by 100/(100-A)]

Example:

araddbdaf
TM11.0---
IM2.02.0--
Ash12.013.213.5-
VM30.033.033.739.0
FC47.051.852.861.0
Sulphur1.01.11.12-

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 tonmultiply by 1.016
From short ton to metric tonmultiply 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 by 0.004187
From kcal/kg to Btu/lb multiply by 1.800
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/kgmultiply 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 and 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/kg1.09 MJ/kg470 Btu/lb

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 MWth / 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/annum
- Brown coal (CV 2250 kcal/kg NAR*): 4.0 Mt/annum

* Net As Received

Sources: GWC Coal Handbook & IEA Clean Coal Centre

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