Page 636 - The City and Guilds Textbook: Plumbing Book 1 for the Level 3 Apprenticeship (9189), Level 2 Technical Certificate (8202) and Level 2 Diploma (6035)

The City & Guilds Textbook: Plumbing Book 1

 Table 10.2 The composition of LPG fuels

LPG attributes Propane Butane
Chemical formula C 3 H 8 C 4 H 10
Energy content: MJ/m 3 95.8 111.4
Energy content: MJ/kg 49.58 47.39
Boiling temp.: °C −42 −4
Pressure @ 21°C: kPa 858.7 215.1
Flame temp.: °C 1967 1970
Gas volume: m 3 /kg 0.540 0.405
Relative density: H 2 O 0.51 0.58
Relative density: air 1.53 2.00
L per kg 1.96 1.724
kg per L 0.51 0.58
Specific gravity @ 25°C 1.55 2.07
Density @ 15°C: kg/m 3 1.899 2.544
Combustion temp.: °C 482–540 410–470

 Table 10.3 The uses of LPG fuels
Compound Uses
Used for portable supplies, such as camping equipment, boats and
Butane C 4 H 10
barbecues. Not much use for plumbing or heating installation as it boils
(turns from a liquid to a gas) at −4°C.
Has a very low boiling point at −42°C. Can be used in domestic
Propane C 3 H 8
situations as an alternative to natural gas where the mains gas supply
is not available. Many appliances are available for use with propane,
including boilers, cookers, fires and water heaters.
Iso-butane Used as a refrigerant in domestic refrigerators and fridge-freezers.

Both of these compounds are heavier than air in their gaseous form, with
propane having a specific gravity of 1.5 and butane having a specific gravity of
2.0. In liquid form, both are thinner than water, butane having a relative density
of 0.58 and propane 0.51.
When LPG gas is subjected to high pressure it turns into a liquid,
but it also takes up less space than the gas; 1 litre of LPG in its
liquid state makes 274 litres of LPG gas. This means that one
274 litres cylinder of LPG liquid is equivalent to 274 cylinders of LPG gas.
LPG gas
Environmentally, LPG is relatively clean when compared to other
fuels such as coal or oil, creating far less air pollution in the form
of soot and carbon particulates, sulphur and carbon dioxide, and
1 litre
LPG liquid therefore adds less to global warming than might be realised.
p Figure 10.1 Liquid to gas ratio Cost, however, is an issue, since LPG is much more expensive
than conventional natural gas.

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