General information Useful calculation data
7
Local regulations may restrict the use of this product to below the conditions quoted. In the interests of development and improvement of the product, we reserve the right to change the specification without notice. © Copyright 2013
AI-GAB-03 AB Issue 4
The Cost of Steam - Metric
The cost of steam is usually expressed in terms of the cost to raise 1000 kg. The calculation itself is relatively straight forward and this AIS simplifies the task by the use of a forced path calculation sheet. A blank format is available on page 3. Example: Boiler operating pressure - 10 bar g, feedwater temperatures 80 °C. Fuel used is heavy oil at £0.40/litre and boiler efficiency is 80%.
Steam pressure
Feedwater temperature
10 bar g
80 °C
Mathematical operation
Units
Heat input required (see table 1)
kJ/kg
2445
x
kg
1000
=
Total heat input
kJ
2445000
kJ/kg coal or oil kJ/kWh gas kJ/kg coal or oil kWh gas
÷
Calorific value of fuel (see table 2)
42500
=
Net fuel needed
57.53
85% x 1.18 80% x 1.25 75% x 1.34 70% x 1.43
x
Boiler efficiency
1.25
7.5 1
kJ/kg coal or oil kWh gas
=
Actual fuel needed
71.9
COAL
OIL
GAS
S.G Heavy 9.7 Medium 9.5 Light 9.35
Mathematical operation
Mathematical operation
Mathematical operation
÷
1000 kg/tonne
÷
0.97
x
pkWh
=
tonne
=
litre
74.1
x
£/tonne
x
£/litre
£0.40
£/1000 kg steam
÷ 100 =
£/1000 kg steam
£/1000 kg steam
=
=
£29.65
11.5.1
These tables are on the next page Table 1 Heat input in Kilojoules (kJ) required to raise one kilogram (kg) of steam. Table 2 Calorific value of various fuels (approximate values)
AI-GAB-03 AB Issue 4
Page 1 of 3
The Cost of Steam - Metric
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