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Page 35
We must now turn to the chemical actions which are taking place in the
generator of the water gas plant, and these are more complex in the
case of the Van Steenbergh plant than in those of the Lowe type, and,
for that reason, yield a gas of more satisfactory composition.
Taking gas as made by the Lowe or Springer process, and contrasting it
with the Van Steenbergh gas, we are at once struck by several marked
differences.
In the first place the hydrogen is far higher and the marsh gas or
methane lower in the Van Steenbergh than in the Lowe process, this
being due to the sharper cracking that takes place in the short column
of cherry red coke, as compared with the lower temperature employed
for a longer space of time in the Lowe superheater. Next we notice a
difference of 10 per cent. in the carbon monoxide, which is greatly
reduced in the Steenbergh generator by the carbon monoxide and marsh
gas reacting on each other as they pass over the red hot surface of
coke with formation of acetylene, which adds to the illuminants, this
action also reducing the quantity of marsh gas present.
Lowe Van Steenbergh
gas. gas.
Hydrogen..................... 27.14 46.75
Marsh gas.................... 25.35 11.27
Carbon monoxide.............. 26.84 18.65
Illuminants.................. 14.63 7.59
Ethane....................... ---- 6.82
Carbon dioxide............... 3.02 0.50
Oxygen....................... 0.15 0.17
Nitrogen..................... 2.87 8.25
------ ------
100.00 100.00
In the illuminants, if we add the higher members of the methane series
present to the olefines, we see they are about equal in each gas,
while the low percentage of nitrogen in the Lowe gas is due to more
careful working, and could easily be attained with the Van Steenbergh
plant by allowing the first portion of water gas to wash out the
producer gas before the hopper on top is closed.
The cracking of the naphtha by the red hot coke is undoubtedly a great
advantage, for, as I have pointed out, the cracking of rushing
petroleum is an exothermic reaction, so that the coke at the top of
the generator gets hotter and hotter, and it is no unusual thing to
see the coke at the beginning of the make cherry red at the bottom
and dull red at the top, while at the end of the make it is almost
black at the bottom and cherry red at the top, in this way attaining
the same advantage in working that the Springer and Loomis do by their
down blast, that is, having the fuel at its hottest where the gas
finally leaves it, so as to reduce the quantity of carbon dioxide, and
so lessen the expense of purification.
It will be well now to turn for a few moments to the gas obtained by
cracking the light petroleum oils by themselves. The Russian and
American petroleum differ so widely in composition that it was
necessary to see in what way the gases obtained from them differed;
and to do this, equal quantities of American naphtha and a Russian
naphtha were cracked, by passing through an iron tube filled with
coke, and in each case heated to a cherry red heat, the gases being
measured, and then analyzed, with the following results:
American. Russian.
No. of cubic feet per gallon... 72 104
---- ----
Hydrogen....................... 26.0 45.3
Methane........................ 41.6 22.3
Ethane......................... 12.5 13.9
Olefines....................... 14.1 11.6
Carbon monoxide................ 3.3 3.5
Carbon dioxide................. 1.7 2.3
Oxygen......................... 0.8 1.1
Nitrogen....................... Nil. Nil.
----- -----
100.0 100.0
Showing that, if the Russian oil is a little lower in illuminants, it
quite makes up by extra volume, but it seemed to me to deposit a much
larger proportion of carbon.
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