Carbon dioxide. 2.32 per cent.
Sulphureted hydrogen. 2.84 "
Total sulphur per 100 cu. ft. = 6.67
Ammonia. nil
Bisulphide of carbon. nil
Gas produced Naphtha used
Gals. Pts.
1st. Make. 3,600 cu. ft. 10 7
2d. " 2,800 " 7 6
3d. " 2,300 " 5 3
------ --- --
8,700 24 0
The last portion of the table shows the economy which arises as the
whole apparatus gets properly heated. Thus the first make used 3
gallons naphtha per 1,000 cubic feet, the second 2 gallons 6 pints per
1,000 cubic feet, and the third 2 gallons 4 pints per 1,000 cubic
feet, and it is, therefore, not unreasonable to suppose that in a
continuous make these figures could be kept up, if not actually
reduced still lower.
In introducing the oil it is not injected, but is simply allowed to
flow in by gravity, at a point about half way up the column of fuel,
the taps for its admission being placed at intervals around the
circumference of the generator, and oil at first begins to flow down
the inside wall of the generator, but being vaporized by the heat, the
vapor is borne up by the rush of steam and water gas, and is cracked
to a permanent gas in the upper layer of fuel. This I think is the
secret of not being able to use heavier grades of oil, these being
sufficiently non-volatile to trickle down the side into the fire box
at the bottom, and so to escape volatilization. I have tried to
steam-inject the oil, but have not found that it yields any better
results.
One of the first things that strikes any one on seeing a make of gas
by this system is the enormous rapidity of generation. Mr. Leicester
Greville, who is chemist to the Commercial Gas Company, in reporting
on the process, says, "The make of gas was at the rate of about 86,000
cubic feet in 24 hours. A remarkable result, taking into consideration
the size of the apparatus." It is quite possible, with the small
apparatus, to make 100,000 cubic feet in 24 hours; indeed the run for
which the figures are given are over this estimate; and it must be
borne in mind that this rapidity of make gives the gas manager
complete control over any such sudden strains as result from fog or
other unexpected demands on the gas-producing power of his works;
while a still more important point is that it does away with the
necessity of keeping an enormous bulk of gas ready to meet any such
emergency, and so renders unnecessary the enormous gasholders, which
add so much to the expense of a works, and take up so much room.
Perhaps the greatest objection to water gas in the public mind is the
dread of its poisonous properties, due to the carbon monoxide which it
contains; but if we come to consider the evidence before us on the
increase of accidents due to this cause, we are struck by the poor
case which the opponents of water gas are able to make out. No one can
for a moment doubt the fact that carbon monoxide is one of the
deadliest of poisons. It acts by diffusing through the air cells of
the lungs, and forming, with the coloring matter of the blood
corpuscles, a definite compound, which prevents them carrying on their
normal function of taking up oxygen and distributing it throughout the
body, to carry on that marvelous process of slow combustion which not
only gives warmth to the body, but also removes the waste tissue used
up by every action, be it voluntary or involuntary, and by hindering
this, it at once stops life.
All researches on this subject point to the fact that something under
one per cent. only of carbon monoxide in air renders it fatal to
animal life, and this at first seems an insuperable objection to the
use of water gas, and has, indeed, influenced the authorities in
several towns, notably Paris, to forbid its introduction for domestic
consumption. Let us, however, carefully examine the subject, and see,
by the aid of actual figures, what the risk amounts to compared with
the risks of ordinary coal gas.
Many experiments have been made with the view of determining the
percentage of carbon monoxide in air which is fatal to human or,
rather, animal life, and the most reliable as well as the latest
results are those obtained by Dr. Stevenson, of Guy's Hospital, in
consequence of the two deaths which took place at the Leeds forge from
inhaling uncarbureted water gas containing 40 per cent. of carbon
monoxide. He found that one per cent. visibly affected a mouse in one
and a half minutes, and in one hour and three quarters killed it,
while one-tenth of a per cent. was highly injurious. Let us, for the
sake of argument, take this last figure 0.1 per cent. as being a fatal
quantity, so as to be well within the mark.
In ordinary carbureted water gas as supplied by the superheater
processes, such as the Lowe, Springer, etc., the usual percentage of
carbon monoxide is 26 per cent., but in the Van Steenbergh gas--for
certain chemical reasons to be discussed later on--it is generally
about 18 per cent., and rarely rises to 20 per cent. An ordinary
bedroom will be say 12 ft. X 15 ft. X 10 ft., and will therefore
contain 1,800 cubic feet of air, and such a room would be lighted by a
single bats-wing burner consuming not more than four cubic feet of gas
per hour. Suppose now the inmate of that room retires to bed in such a
condition of mental aberration that he prefers to blow out the gas
rather than take the ordinary course of turning it off--a process, by
the way, of putting out gas which is decidedly easier in theory than
in practice, especially in his presumed mental condition--you would
have in one hour the 1,800 cubic feet of gas in the room mixed with
four fifths of a cubic foot of carbon monoxide--the carbureted water
gas being supposed to contain 20 per cent.--or 0.04 per cent. In such
a room, however, if the doors and windows were absolutely air tight,
and there was no fireplace, diffusion through the walls would change
the entire air once an hour, so that the percentage would not rise
above 0.04; while in any ordinary room imperfect workmanship and an
open chimney would change it four times in the hour, reducing the
percentage to 0.01, a quantity which the most inveterate enemy of
water gas could not claim would do more than produce a bad headache,
an ailment quite as likely to have been caused by the same factor that
brought about the blowing out of the gas.
Moreover, we are now talking about the use of carbureted water gas as
an enricher of coal gas, and not as an illuminant to be consumed _per
se._ and we may calculate that it would be probably used to enrich a
16-candle coal gas up to 17.5 candle power. To do this 25 per cent. of
22 candle power carbureted water gas would have to be mixed with it,
and taking the percentage of carbon monoxide in London gas at 5 per
cent.--a very fair average figure--and 18 per cent. as the amount
present in the Van Steenbergh gas, we have 8.25 per cent. of carbon
monoxide in the gas as sent out--a percentage hardly exceeding that
which is found in the rich cannel gas supplied to such towns as
Glasgow, where I am not aware of an unusual number of deaths occurring
from carbon monoxide poisoning.
The carbureted water gas has a smell every bit as strong as coal gas,
and a leak would be detected with equal facility by the nose; and I
think you will agree with me that the cry raised against the use of
carbureted water gas, for this reason, is one of the same character
that hampered the introduction of coal gas itself at the commencement
of this century.
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.
Taking 21/2 gallons of American naphtha, it would give roughly 180 cubic
feet of gas of the above composition, while the remaining gas would be
the ordinary water gas. Taking the analysis of this as given, and
calculating from it what would be the composition of a mixture of it
with the naphtha gas, we obtain:
Calculated. Actual.
Hydrogen...................... 47.09 42.09
Methane....................... 5.48 11.27
Olefines...................... 2.53 7.59
Ethane........................ 2.17 6.32
Carbon monoxide............... 30.07 18.65
Carbon dioxide................ 3.78 2.32
Oxygen........................ 0.56 0.17
Nitrogen...................... 7.17 8.25
Sulphureted hydrogen.......... 1.15 2.84
------ ------
100.00 100.00
Showing how great the effect is of the diluents in the water gas in
preventing the overcracking of the hydrocarbons, as shown by the
increase in the percentage of them present in the finished gas; while
the enormous reduction in the amount of carbon monoxide present is due
to the interaction between it and the paraffin hydrocarbons in the
presence of red-hot carbon, a point which makes the Van Steenbergh
apparatus enormously superior to any of the superheater forms of
plant.
After all said and done, however, the reactions taking place, although
they have an intense fascination for the chemist, are not the factors
which the gas manager deems the most important, the cost of any given
process being the test by which it must stand or fall; and it will be
well now to consider, as far as it is possible, the expense of
enriching coal gas by the various methods I have brought before you.
In order to be well above the prescribed limit of illuminating power
at all parts of an extended service, the gas at the works must be sent
out at an illuminating power of 17.5 candles and we may, I think,
fairly take it that 16 candle coal gas, as made by the big London
companies, costs, as nearly as can be, 1s. per 1,000 cubic feet in the
holder, and the question we have now to solve is the cost of enriching
it from 16 to 17.5 candle power. When this is done by cannel, the cost
is 2.6 pence per candle power, so that the extra 11/2 would cost 4d. per
1,000.
Carbureting by the vapors of gasoline by the Maxim-Clarke process
costs 13/4d. per 1,000, so that the extra candle power would mean an
expenditure of 2.62 d. Unfortunately I have no figures upon which to
calculate the cost of producing such a gas by the Dinsmore process,
but with the three important water gas enrichers we can deal.
Using Russian fuel oil, which can be obtained in bulk in London at 3d.
per gallon, the proprietors of the Springer plant guarantee 51/2 candle
power per 1,000 cubic feet of gas per gallon used, so that, to produce
a 22 candle gas, 4 gallons would be used. The cost per 1,000 cubic
feet may be roughly tabulated, as the coke used amounts to about 40
lb.
s. d.
Oil.................................... 1 0
Coke................................... 0 3
Labor and purification................. 0 2
Charge on plant........................ 0 1
----
1 6
Twenty five per cent. of 12-candle gas when mixed with 75 per cent. of
the 16-candle gas gives the required 17.5 candle gas, which would
therefore cost 1s. 11/2d., or the enrichment would have cost 11/2d.
By the Lowe process, an increase of 5.3-candle power is guaranteed for
the consumption of a gallon of the same oil, so that the cost would be
a shade higher, all other factors remaining the same, while with the
Van Steenbergh process both grade of oil and consumption of fuel vary
from either of these processes. In order to obtain a thousand cubic
feet of 22-candle gas, two and a half gallons of the lighter grade oil
would be consumed, and I am informed that there is now no difficulty
in obtaining oil of the right grade in London in bulk at 4d. per
gallon, which would make the cost:
s. d.
Two and a half gallons of oil........... 0 10
Thirty pounds of coke................... 0 21/4
Labor and purification.................. 0 2
Charge on plant......................... 0 03/4
------
1 3
And the enriched coal gas would, therefore, cost 1s. 3/4d. per thousand,
the extra 11/2-candle power having been gained at an expense of 3/4d. or
1/2d. per candle.
Tabulating these results we have--Cost of enriching a 16-candle gas up
to 17.5 candle power per 1,000 cubic feet by cannel coal, 4d.; by
Maxim-Clarke process, 2-6/10d.; by Lowe or Springer water gas, 11/2d.;
by Van Steenbergh water gas, 3/4d.
In reviewing this important subject, and bringing a wide range of
experimental work to bear upon it, I have, as far as is possible,
divested my mind of bias toward any particular process, and I can
honestly claim that the fact of the Van Steenbergh process showing
such great superiority is due to the force of carefully obtained
experimental figures, corroborated by an experienced and widely known
gas chemist, and by the chief gas examiner of the city.
In adopting any new method, the mind of the gas manager must to a
great extent be influenced by the circumstances of the times, and the
enormous importance of the labor question is a main factor at the
present moment; with masters and men living in a strained condition
which may at any moment break into open warfare, the adoption of such
water gas processes would relieve the manager of a burden which is
growing almost too heavy to be borne.
Combining, as such processes do, the maximum rate of production with
the minimum amount of labor, they practically solve the labor
question. Requiring only one-tenth the number of retort house hands
that are at present employed, the carbureted water gas can be used for
enrichment until troubles arise, and then the gas can be used pure and
simple, with a hardly perceptible increase in expense, while the
rapidity of make will also give the gas manager an important ally in
the hour of fog, or in case of any other unexpected strain on his
resources.
One of the first questions asked by the practical gas maker will be:
"What guarantee can you give that as soon as we have erected plant,
and got used to the new process of manufacture, a sudden rise in the
price of oil will not take place, and leave us in worse plight than we
were before?" and the only answer to this is that, as far as it is
possible to judge anything, this event is not likely to take place in
our time. A year ago the prospects of the oil trade looked black, as
the output of American oil was in the hands of a powerful ring, who
seemed likely also to obtain control of the Russian supplies; but,
fortunately, this was averted, and, at the present moment, the Russian
pipe lines are flooding the market with an abundant supply, which
those best able to judge tell us is practically inexhaustible, so that
prices may be expected to have a downward rather than an upward
tendency. But even should a huge monopoly be created, I think I have
found a source of light at home which will hold its own against any
foreign illuminant in the market.
For a long time I have felt that in this country we had sources of
light and power which only needed development, and the discovery of
the right way to use them, in order to give an entirely new complexion
to the question of carbureting; and now by the aid of the engineering
skill and technical knowledge of Mr. Staveley, of Baghill, near
Pontefract, I think it is found.
At three or four of the Scotch iron works the Furnace Gases Co. are
paying a yearly rental for the right of collecting the smoke and gases
from the blast furnaces. These are passed through several miles of
wrought iron tubing, diminishing in size from 6 feet down to about 18
inches; and as the gases cool, so there is deposited a considerable
yield of oil.
At Messrs. Dixon's, at Glasgow, which is the smallest of these
installations, they pump and collect about 60,000,000 cubic feet of
furnace gas per day; and recover, on an average, 25,000 gallons of
furnace oils per week, using the residual gases, consisting chiefly of
carbon monoxide, as fuel for distilling and other purposes, while a
considerable yield of sulphate of ammonia is also obtained. In the
same way a small percentage of the coke ovens are fitted with
condensing gear, and produce a considerable yield of oil, for which,
however, there is a very limited market, the chief use being for
lucigen and other lamps of the same description, and for pickling
timber for railway sleepers, etc.; the result being that, four years
ago, it could be obtained in any quantity at 1/2d. per gallon, while
since that it has been as high as 21/2d. a gallon, but is now about 2d.,
and shows a falling tendency. Make a market for this product, and the
supply will be practically unlimited, as every blast furnace and coke
oven in the kingdom will put up plant for the recovery of the oil, and
as with the limited plant now at work it would be perfectly easy to
obtain 4,000,000 or 5,000,000 gallons per annum, an extension of the
recovery process would mean a supply sufficiently large to meet all
demands.
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: