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-04 AB Issue 3
The Cost of Steam - Imperial
The cost of steam is usually expressed in terms of the cost to raise 1000lbs. 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 overleaf. Example : Boiler operating pressure - 150 psi g, feedwater temperatures 180 °F. Fuel used is heavy oil at £1.80 / gallon and boiler efficiency is 80%.
Steam pressure
Feedwater temperature
150 psi g
180 °F
Mathematical operation
Units
Heat input required (see table 1)
Btu/lb
1049
x
lb
1000
=
Total heat input
Btu
1049000
Btu/lb coal or oil Btu/Therm gas
÷
Calorific value of fuel (see table 2)
18300
lb coal or oil Therm gas
=
Net fuel needed
57.3
85% x 1.18 80% x 1.25 75% x 1.34 70% x 1.43
x
Boiler efficiency
1.25
7.5 5
lb coal or oil Therm 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
÷
2240
lb/ton
÷
9.7
x
£/therm
=
ton
=
gallon
7.38
x
£ / ton
x
£/gallon
£1.80
£ / 1000 lb steam
÷ 100 =
£ / 1000 lb steam
£ / 1000 lb steam
=
=
£29.65
11.5.3
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-04 AB Issue 3
Page 1 of 3
The Cost of Steam - Imperial
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