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Page 38
Many gas managers have, from time to time, tried if they could not use
some of their creosote for gas producing, but on heating it in
retorts, etc., they have found the result has generally been a copious
deposit of carbon, and a gas which has possessed little or no
illuminating value. Now, the furnace and coke oven oils are in
composition somewhat akin to the creosote oil, so that at first sight
it does not seem a hopeful field for search after a good carbureter,
but the furnace oils have several points in which they differ from the
coal tar products. In the first place, they contain a certain
percentage of paraffin oil, and in the next, do not contain much
naphthalene, in which the coal tar oil is especially rich, and which
would be a distinct drawback to their use.
The furnace oil as condensed contains about 30 to 50 per cent. of
water, and in any case this has to be removed by distilling; and Mr.
Staveley has patented a process by which the distillation is continued
after the water has gone off, and by condensing in a fractionating
column of special construction, he is able to remove all the paraffin
oil, a considerable quantity of cresol, a small quantity of phenol,
and about 10 per cent. of pyridine bases, leaving the remainder of the
oil in a better condition, and more valuable for pickling timber,
which is its chief use.
If the mixed oil so obtained, which we may call "phenoloid oil," is
cracked by itself, no very striking result is obtained, the 40
percent. of paraffin present cracking in the usual way, and yielding a
certain amount of illuminants, but if this oil be cracked in the
presence of carbon, and be made to pass over and through a body of
carbon heated to a dull red heat, then it is converted largely into
benzene, the most valuable of the illuminants, and also being the one
to which coal gas owes the largest proportion of its illuminating
power, it is manifestly the right one to use in order to enrich it.
On cracking the phenoloid oil, the paraffins yield ethane, propane,
and marsh gas, etc., in the usual way, while the phenol interacts with
the carbon to form benzene--
Phenol. Benzene.
C6H5HO + C = C6H6 + CO.
And in the same way the cresol first breaks down to toluene in the
presence of the carbon, and this in turn is broken down by the heat to
benzene.
A great advantage of this oil is that the flashing point is 110, and
so is well above the limit, thus doing away with the dangers and
troubles inseparable from the storage of light naphtha in bulk.
In using this oil as an enricher, it must be cracked in the presence
of carbon, and it is of the greatest importance that the temperature
should not be too high, as the benzene is easily broken down to
simpler hydrocarbons of far lower illuminating value. This fact is
very clearly brought out by a series of experiments I have made, in
which the phenoloid oil was cracked by passing it through an iron tube
packed with coke and heated to various temperatures, the hydrocarbons
being much more easily broken up under these conditions than if mixed
with diluents, such as water gas:
RESULTS OBTAINED ON CRACKING PHENOLOID OIL.
I. II. III.
Temperature. 600� C. 800� C. 1,000� C.
Volume of gas per gallon. 41.6 c.f. 76.8 c.f. 121.6 c.f.
COMPOSITION OF THE GAS.
Hydrogen. 34.0 36.0 37.0
Methane. 20.0 26.0 49.0
Olefines. 11.0 5.0 Nil.
Ethane. 16.0 9.0 Nil.
Carbon monoxide. 13.0 15.0 12.0
Carbon dioxide. 2.0 4.0 2.0
Oxygen. 2.0 1.0 Nil.
Nitrogen. 2.0 4.0 Nil.
This analysis shows that if the temperature is allowed to reach a
cherry red, complete decomposition of the illuminating hydrocarbons is
taking place, and a gas of practically no illuminating value results.
The power of regulating the temperature and the body of carbon as a
cracking medium in the Van Steenbergh water gas plant especially fits
it for using this oil, and removes the objections which could have
been urged against the lighter naphthas.
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