Determination of the fuel moisture
Fuel moisture, Mar, in arrival state:
M ar =
(m1 − m2)
× 100
(m1 )
m1
m2
[1]
Wet material weight (g)
Dried material weight
More detailed calculation of the moisture content: CEN/TS 14774-2.
Effective heating value of moist fuel
Effective heating value of moist fuel (arrival state) is determined after equation:
q p ,net ,ar = q p ,net ,d × (
qp,net,ar
qp,net,d
Mar
0.02443
100 − M ar
) − 0.02443 × M ar
100
[2]
Net heating value of the fuel (MJ/kg), in arrival state
Net heating value of dry material (MJ/kg) (determined after prCEN/TS 14918 or by
using average dry material heating values)
Total moisture of the comparable fuel amount in arrival stage, weighted with the
mass of the moist fuel
Amount of heat required in vaporization of water (+25˚C)
An example:
Calculation of the net heating value for forest chips made of spruce top ends and branches with 50
% moisture. Chips include also needles. Net heating value of the dry material is 19 MJ/kg (=5.3
kWh/kg).
q p ,net , ar = 19 × (
100 − 50
) − 0,02443 × 50
100
qp,net,ar = 8.2785 MJ/kg = 8.2785 / 3.6 MWh/t = 2.3 MWh/t
Calculation of the energy density
When fuel trade is made in volumetric units, energy density is calculated by using fuel net heating
value and bulk density.
E ar =
1
× q p ,net , ar × BDar
3600
Ear
qp,net,ar
BDar
1/3600
[3]
Energy density of the fuel (MWh/loose m3)
Net heating value of the moist fuel (MJ/kg)
Bulk density (kg/loose m3)
Transfer coefficient (MJ to MWh)
Result is usually reported with two decimals (MWh/loose m3)
An example:
E ar =
1
× 8.2785 × 350
3600
(MWh/loose m3)
Ear = 0.80 MWh/loose m3
Transfer coefficients:
toe
MWh
GJ
Gcal
toe
1
0.0886
0.02388
0.1
MWh
11.63
1
0.2778
1.163
GJ
40.868
3.600
1
4.1868
Gcal
10.0
0.86
0.2388
1
An example:
1 toe = 11.63 MWh
1 kWh = 3.6 MJ
References:
Alakangas, E. 2000. Suomessa käytettyjen polttoaineiden ominaisuuksia, Valtion teknillinen
tutkimuskeskus, VTT Tiedotteita 2045. Espoo.
Kokkonen, A & I. Lappalainen (eds.) 2005. Hakelämmöstä yritystoimintaa. Pohjois-Karjalan
ammattikorkeakoulu, Motiva Oy ja Työtehoseura. Kuopio 2005.