Petroleum is practically the only liquid fuel sufficiently abundant and
cheap to be used for the generation of steam. It possesses many
advantages over coal and is extensively used in many localities.
There are three kinds of petroleum in use, namely those yielding on
distillation: 1st, paraffin; 2nd, asphalt; 3rd, olefine. To the first
group belong the oils of the Appalachian Range and the Middle West of
the United States. These are a dark brown in color with a greenish
tinge. Upon their distillation such a variety of valuable light oils are
obtained that their use as fuel is prohibitive because of price.
To the second group belong the oils found in Texas and California. These
vary in color from a reddish brown to a jet black and are used very
largely as fuel.
The third group comprises the oils from Russia, which, like the second,
are used largely for fuel purposes.
The light and easily ignited constituents of petroleum, such as naphtha,
gasolene and kerosene, are oftentimes driven off by a partial
distillation, these products being of greater value for other purposes
than for use as fuel. This partial distillation does not decrease the
value of petroleum as a fuel; in fact, the residuum known in trade as
"fuel oil" has a slightly higher calorific value than petroleum and
because of its higher flash point, it may be more safely handled.
Statements made with reference to petroleum apply as well to fuel oil.
In general crude oil consists of carbon and hydrogen, though it also
contains varying quantities of moisture, sulphur, nitrogen, arsenic,
phosphorus and silt. The moisture contained may vary from less than 1 to
over 30 per cent, depending upon the care taken to separate the water
from the oil in pumping from the well. As in any fuel, this moisture
affects the available heat of the oil, and in contracting for the
purchase of fuel of this nature it is well to limit the per cent of
moisture it may contain. A large portion of any contained moisture can
be separated by settling and for this reason sufficient storage capacity
should be supplied to provide time for such action.
A method of obtaining approximately the percentage of moisture in crude
oil which may be used successfully, particularly with lighter oils, is
as follows. A burette graduated into 200 divisions is filled to the 100
mark with gasolene, and the remaining 100 divisions with the oil, which
should be slightly warmed before mixing. The two are then shaken
together and any shrinkage below the 200 mark filled up with oil. The
mixture should then be allowed to stand in a warm place for 24 hours,
during which the water and silt will settle to the bottom. Their
percentage by volume can then be correctly read on the burette
divisions, and the percentage by weight calculated from the specific
gravities. This method is exceedingly approximate and where accurate
results are required it should not be used. For such work, the
distillation method should be used as follows:
Gradually heat 100 cubic centimeters of the oil in a distillation flask
to a temperature of 150 degrees centigrade; collect the distillate in a
graduated tube and measure the resulting water. Such a method insures
complete removal of water and reduces the error arising from the slight
solubility of the water in gasolene. Two samples checked by the two
methods for the amount of moisture present gave,
_Distillation_ _Dilution_
_Per Cent_ _Per Cent_
8.71 6.25
8.82 6.26