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DEFINITION : LPG
may be defined as those hydrocarbons which are gaseous at normal atmospheric pressure, but
may be condensed to the liquid state at normal temperature, by the application of moderate
pressures. Although they are normally used as gases, they are stored and transported as
liquids under pressure for convenience and ease of handling. Liquid LPG evaporates to
produce about 250 times volume of gas. Thus, a large quantity of energy can be packed,
stored, transported and used in small containers.
COMPOSITION
LPG is a predominant mixture of propane and
Butane with a small percentage of unsaturates (Propylene and Butylene) and some lighter
C2
as well as heavier C5 fractions.
Included in the LPG range are propane
(C3H8), Propylene(C3H6), normal and iso-butane
(C4H10)and Butylene(C4H8). Commercial LP gases
invariably contains traces of lighter hydrocarbons like ethane (C2H6) and ethylene
(C2H4)
and heavier hydrocarbons like pentane (C5H12). MANUFACTURE OF LPG:
There are two
main sources from which LP gases are produced, namely:
(A) Wet Natural
Gas or Associated Gas &
(B) Refinery
Operations.
LP gases prepared
from wet natural gas consist entirely of "saturated" hydrocarbons i.e. propane
and butane .
LP Gases produced
from straight distillation process will have "saturated" hydrocarbons i.e.
propane and butane (both normal and iso)
LP Gases produced
by both cracking and reforming processes will have, in addition to saturated hydrocarbons,
some quantities of unsaturated hydrocarbons also ( i.e. propylene and butylene)
LP Gases produced will have impurities like moisture
& sulphur compounds like hydrogen sulphide and mercaptans. Moisture may lead to
clogging of regulators, valves, etc. and sulphur compounds cause corrosion. Moisture and
sulphur compounds are, therefore, removed by suitable treatment at the refinery.
However, to alert the user of LPG in case of a leak takes
place, "ethyle mercaptan" which has a distinctive odour is added in minute
quantities at the refinery.
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