Scientific American Supplement, No. 401, September 8, 1883

V >> Various >> Scientific American Supplement, No. 401, September 8, 1883

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The fuel employed is the coke or char resulting from cannel coal when it
has yielded up its hydrocarbons and other gases during the process of
carbonization in the gas retorts. Being entirely made from Scotch cannel
the coke is very poor in quality, as it contains a large percentage of
mineral matter or ash relatively to its fixed carbon. The retorts are
worked with three-hour charges, but the producer is only charged once in
every six hours For each set of eight retorts the charge of raw cannel
is about 18 cwt., and it is found in practice that the coke drawn from
five of the retorts is quite sufficient to fill up the producer to the
top. Formerly a set of seven retorts fired in the ordinary way from a
furnace underneath, required from 60 to 75 per cent. of the coke made,
but now, with eight retorts in each oven, the quantity has been reduced
to about 30 per cent., or less than one-half of what it formerly was.
Before the retorts are drawn the lid is removed from the top of the
producer, and any fuel still remaining unconsumed is touched up a bit by
way of leveling it on the surface, and as soon as it has been filled up
to the constricted portion a shovelful of soft luting is spread over the
top of the coke, and the lid is laid upon it and driven home, thereby
making a perfectly air-tight joint. The contents of the other three
retorts, as also the contents of the whole of the retorts at each
alternate drawing, are taken to the coke heap in the yard. We have
already spoken of a charge of cannel as being about 18 cwt. for each set
of eight retorts, but in connection with that matter we should mention
that it was formerly about 13 cwt. per oven containing seven retorts,
and that there is every prospect of it being increased without
increasing the length of time occupied in carbonizing the cannel of each
charge.

It may be worth while now to notice briefly what takes place among the
mass of coke in the gas producer. The atmospheric air admitted at the
several openings previously spoken of ascends through the lower layers
of the incandescent coke, the carbon of which burns to carbonic acid
gas at the expense of the oxygen of the air. Among the middle and upper
layers of the incandescent coke the carbonic acid gas takes up a further
quantity of the fixed carbon, and becomes transformed into carbonic
oxide gas (CO_{2}+C=2CO), which is an inflammable body, and possesses
considerable calorific power. Unless the carbonic acid gas is very
completely "baffled" in its ascent through the coke in the producer, a
quantity of it passes into the furnace along with the carbonic oxide,
the efficiency of which is diminished in proportion as the former
increases in quantity. Of course, also, the nitrogen associated with
the oxygen in the air admitted to the gas generator passes on with the
carbonic oxide gas, this nitrogen acting as a dilutant and being of
course absolutely useless as a generator of heat. The steam which
we previously spoke of serves two good purposes. In contact with
incandescent coke it suffers decomposition, its oxygen uniting with some
of the fixed carbon to form carbonic oxide, while the hydrogen which
is set free passes onward, and mixes with the other gases to be
subsequently consumed with them. The admission of the steam thus causes
the absorption of heat in the gas generator where the decomposition
takes place, this heat being again evolved on the subsequent combustion
of the hydrogen. Then, again, as the steam is delivered in among the
coke in a jet, or a series of jets, it has the effect of almost entirely
preventing any clinkering or slagging of the earthy and silicious
materials, which form such a large portion of the substance of the coke
obtained from Scotch cannels, sometimes as much as from 15 to 20 per
cent. It is scarcely necessary for the stokers to go down below to the
bottom of the producers to remove the ash above once in every six hours.
Referring to the composition of the gaseous fuel obtained from cannel
coke in one of these gas producers, we give the following typical
analysis on the authority of Dr. William Wallace, F.R.S.E., gas
examiner, and one of the public analysts for the city of Glasgow:

Per cent.
Hydrogen 8.7
Carbonic oxide 28.1
Carbonic acid 3.5
Oxygen 0.4
Nitrogen 59.3
-----
100.0

By again referring to Fig. 2, it will be observed that an opening is
provided for the passage of the gaseous matter as it is formed into the
mass of brickwork, the upper half of which is occupied by the retorts of
the setting and the lower by the regenerators.

Before following the gas we may first direct attention to the
arrangements for dealing with it, and with the air that has to be
admitted for the combustion of so much of it as is of a combustible
nature. It will be seen by reference to Fig. 1 that the oven proper is
occupied by eight [Inline Illustration] shaped retorts. These are 9 ft.
long (set back to back) by 18 in. by 13 in., and they are placed on
arches which are 8 ft. 6 in. wide. Underneath the level of the retort
oven there are two regenerators or regenerator chambers, which differ
very materially in form from the regenerators formerly applied by Dr.
Siemens to gas retort ovens, and which are still employed for high
temperature furnaces like those used for steel and glass melting. In
the case of these latter the regenerators are on the alternating
system--that is to say, a mass of brickwork is heated by the waste heat
of the effluent gases, and when that is made sufficiently hot, the
current of waste gases is turned into a second mass of brickwork, while
air is admitted to pass through the brickwork already heated. The system
thus briefly described entails a certain amount of attention on the part
of the workmen in the altering of the valves or dampers to reverse the
currents. The regenerator now adopted consists of an arrangement of six
zigzag flues, three on each side of the setting. These flues run the
whole length of the setting. As indicated by the arrows pointing
downward in Fig. 3, the waste gases on their way to the chimney stack
pass to and fro through the side flues, thus giving up a large portion
of their contained heat by the process of conduction or contact to the
central flue through which the incoming air passes. The air necessary
for combustion is first admitted into a large chamber in the center, and
then it is divided into two currents, which pass right and left into the
central passages of the two regenerators. As the air flue is at a very
bright heat for a considerable distance before the air leaves it, the
temperature of the air must be equally great, or nearly so. In its most
improved form one of these heat regenerative furnaces provides an amount
of heating surface extending to 234 square ft., which is exposed to the
air on its way to the combustion chamber.

Passing from the producer through the flue provided for it, the gas
enters the retort setting underneath the side retorts, where it meets
the air coming from the regenerator. It enters the setting, not by a
number of small openings, but by one large opening on each side, and
meets the air entering also by a large opening, the effect of which is
to avoid the localization of intense heat, as all the retorts of the
setting become enveloped in an intensely heating flame, due to the
combustion of the carbonic oxide and hydrogen gases.

There are various advantages attending this system of firing gas
retorts. First of all, there is already a saving of fuel to the extent
of one-half, and not unlikely there will soon be a further very decided
increase in the saving of fuel to record, inasmuch as it has been
experimentally determined within the past two or three weeks that, by
increasing its diameter to 3 ft. 4 in., one producer can be made to
provide a sufficient amount of gaseous fuel to fire two sets of eight
retorts. By the arrangement just hinted at the relative amount of fuel
used will be still further reduced. Then, again, an additional retort
can well be placed in each oven, as it occupies the position of the fire
in ordinary settings. In the third place, by the greater heat which is
obtained, the charges can be more rapidly distilled; or heavier charges
can be carbonized in a given space of time. When all the gains are put
together, the amount of coal carbonized is increased by about 40 per
cent. over any specified time. Of course, in the new or regenerator
settings there is much greater regularity of heat; and as the gaseous
fuel is perfectly free from all solid matter, and burns without any
trace of smoke, there is a total absence of deposit on the outside of
the retorts. From these two circumstances combined it is but natural to
expect that there should be greater durability of the retorts--which
is really the case. Another advantage is that, as the fuel used in
the furnaces is wholly gaseous, choking of the flues cannot by any
possibility arise. It is the confident opinion of Mr. Foulis that the
system in question can be applied with advantage to all sizes of gas
works, and that it is certainly well adapted for all works where the
summer consumption of gas is sufficiently large to give employment to
eight retorts.

As this is the first instance of the new form of gas producer and
regenerator having been adopted in any gas works, a very great amount
of scientific and practical interest attaches to it. Many persons have
visited the Dalmarnock Gas Works during their reconstruction, in order
to see the system in operation, and doubtless many more will go and do
likewise when they learn of the numerous advantages which it possesses,
and which are likely to increase rather than diminish.--_Engineering_.

* * * * *

A NEW GAS-HEATED BAKER'S OVEN.

During the past few weeks, a highly interesting experiment--and one,
moreover, destined to materially influence the development of the uses
of gas in a fresh field--has been in progress, under the guidance of Mr.
Booer, at a baker's shop in the Blackfriars Road, London. The experiment
in question is nothing less than the application of gas for heating
bakers' ovens, in a manner not hitherto attempted, and such as to bring
the system within the means of the poorest tradesman in all but the
smallest towns. It will be remembered that the success of the gas-heated
muffles for burning tiles and glass led to the attempted construction of
a model baker's oven, heated by the same fuel, which was shown in action
at the Smoke Abatement Exhibition at South Kensington in the winter
of 1881-82. This model attained considerable success; but its design
demanded either a new structure in every case, or considerable
alteration of any existing oven. In the proposed system, moreover,
the oven was heated wholly from without--a condition supposed to be
necessary to meet the objections of the bakers. It is evident, however,
that there must be considerable waste of gas in heating a mass of tiles
and brickwork, such as go to the construction of a common baker's oven,
from the outside; and the objection to handicapping such a costly fuel
as gas in this manner becomes more apparent when it is remembered that
in the usual way the oven is always heated by an internal coal fire.
When it is further considered that the coal commonly used by bakers is
of the most ordinary quality, full of dirt that would condemn it in the
estimation of a gas manager, the sentimental objection to allowing a
purified gas flame to burn in a place which this rubbish is permitted to
fill with foul smoke becomes supremely ridiculous. Consequently, when
Mr. Booer, whose work in connection with the gas muffle is well known
in England and America, seriously addressed himself to construct, upon
altogether new lines, a cheap and practical baker's oven, he wisely put
the gas inside.

There are many other conditions which Mr. Booer, after consultation with
practical bakers and others, set himself to fulfill, the observance
of which lends to the present Blackfriars experiment much of its
interesting character. Thus it was observed that, while it is not
difficult to build an oven in a given spot, and bake bread in it, this
cannot truly be called a _baker's_ oven. By this term must be understood
in particular an oven in an ordinary bakehouse, set in the usual style
and worked by a man with his living to get by it. Before the problem of
extending gas to bakers' ovens could be considered solved, it had to be
attacked from this aspect. Mr. Booer, to do him full credit, seems to
have early appreciated this fact in all its bearings. He not only saw
that it was necessary to save gas, as much as possible, by putting it
inside the oven; but he was told that, in order to meet with any general
success, the cost of converting an oven to the gas system must be
rigidly kept down to about ten or twelve guineas. The latter seems
a particularly hard condition, when it is remembered that the only
improved baker's oven in practical use at the present day is the steam
oven invented by Mr. Perkins, which costs two or three hundred pounds to
erect. Mr. Booer also had in mind the necessity that everything possible
for a coal oven must likewise be performed by a gas oven; and in this
respect he set himself to surpass the costly Perkins oven, which will
not bake the common "batch" or household bread, generally the principal
article of sale, more especially in populous and poor neighborhoods. The
peculiar efficacy of the common coal fire in this respect proceeds from
the essential principle of action of a brick oven, which is found simply
in the fact that the work is done entirely by heat previously imparted
to the tile bottom, roof, and sides of the oven, and thence radiated to
the bread. No other kind of heat will bake batch-bread--i.e., loaves
packed in contact with one another--which requires to be thoroughly
soaked by a radiant heat in a close atmosphere of its own steam. Now,
as a coal fire is eminently qualified to impart, by radiation and
otherwise, this necessary store of heat to the brickwork, it is plainly
a difficulty to effect the same purpose with a fuel which, of
itself, can scarcely radiate heat at all. The system of the gas
cooking-oven--the utilization of the heat of the combustion products as
formed--is clearly inapplicable here; for a different kind of heat is
needed, under conditions that would not sustain continuous combustion.
Therefore, there is nothing for it but to heat the bottom and sides
of the brick oven by the direct contact of powerful gas-flames; thus
supplanting the coal fire, but leaving the actual work of baking to be
done afterward by stored-up heat in the regular way.

Having settled the general principles of a system of this kind, there
still remain a number of scarcely less important details, in the dealing
with which lies the difference between practical success and failure.
Thus it is not merely sufficient to heat an oven for bread baking; it is
also necessary to heat it within the times and according to the habits
of work to which the baker has been accustomed. Work in town bakeries
begins at about midnight, or shortly after, and the condition of the
oven must conform to the requirements of the dough, which vary from day
to day and from season to season. In order to master all these niceties,
as far as a knowledge of them is necessary to his purpose, Mr. Booer
has spent many nights in the bakehouse in the Blackfriars Road; and has
thereby obtained a command over the technicalities of the work which has
served him in good stead, not merely for adjusting his gas heat, but in
answering the innumerable objections always raised when a revolution in
an immemorial trade is threatened. It is with considerable satisfaction
that we are enabled to declare, after duly weighing all the conditions
as to first cost and otherwise imposed by himself and others, that Mr.
Booer has succeeded, upon these terms, in vindicating the claims of gas
to be a cheap, efficient, and cleanly fuel for heating ovens under the
control and according to the methods of working of the baker himself.

The oven with which this success has been achieved is one of two in the
bakehouse of Mr. Loeber, of 161 Blackfriars Road. It measures 7 feet by
6 feet internally; being what is technically termed a 6 bushel oven. The
alterations made by Mr. Booer consist in the first place in the removal
of the flooring tiles, and the laying down of a new bottom, under which
run a number of flues radiating from the side furnace. The throat of the
furnace, where it enters the angle of the oven, is bricked up, and eight
pieces of 3/4-inch gun-barrel tubing project above this dwarf wall,
and radiate fan-shaped under the dome of the roof. These are the
gas-burners, which are supplied from a 11/2-inch pipe led into the old
furnace. The same pipe supplies the similar burners which are inserted
in the flues under the oven bottom. This is really all the plant
required. It should be remarked that these bottom flues are carried to
different points of the side walls, and the products of combustion are
allowed to rise upward into the oven through gaps left for the purpose.
A supplementary supply of heated air is provided to help the combustion
of the gas in these flues, which would otherwise be languid. When the
gas is turned on from the main cock in the furnace either to the top or
the bottom set of burners, a long match is used to light them from
the same point. This is effected without risk of firing back, by the
adoption of a specially constructed atmospheric nipple and shield, the
pattern of which is registered. The flame from the top burners unites in
a sheet of fire, which spreads out all over the crown of the oven, at
the same time that the burners below are doing their work, and the
products of combustion flow together through the oven to the chimney,
which is the same that was used for coal. At first, as might be
expected, there was considerable difficulty in finding the most suitable
position of the chimney damper, aggravated in this case by the fact that
the other oven worked with a coal fire into the same shaft. Finally,
however, the two flues were disconnected with the happiest results.
During the past fortnight the oven has been in regular use, and the
bread has been sold over the counter in the ordinary course of trade.
Two and three batches of bread have been baked in one day in this oven;
the economy of its use, of course, increasing with the number of loaves
turned out. As a rule the gas is lighted for about an hour before the
oven is wanted, and about 250 cubic feet are used. Then the cocks are
shut and the oven is allowed to stand closed up for ten minutes, in
which time it ventilates itself, and the heat spreads over it. Then the
batch is set, and the baking occupies from an hour to an hour and a
half, according to the different classes of loaves. Two batches are
baked with a consumption of about 620 cubic feet of gas; costing, at 2s.
10d. per 1000 cubic feet, just 11d. each batch for fuel. This cannot be
considered costly. But the system possesses many other advantages. In
the first place, it is much more cleanly than coal; for the oven never
requires wiping out, which is usually done with a bundle of old rope
called a "scuffle" and the operation is attended with a most unpleasant
odor. Then there is no smoke--a great advantage from the point of
view of the Smoke Abatement Institution. More to the purpose of the
journeyman baker, however, is the fact that there is no stoking to be
done, and he can therefore take his repose at night without having to
attend to the furnace. Besides this the master has the satisfaction of
knowing that the oven will always be hot enough if he simply attends to
the time of lighting the gas--a consideration of no small moment. It is
no mean testimony to the reality of Mr. Booer's success that Mr. Loeber,
having seen his difficulties and troubles from the beginning, and marked
how they have been overcome, is content to acknowledge that even this
first example is capable of turning out bread in a condition to be sold
over the counter. There is a good opening in this direction, for there
are 6,000 bakeries in London alone, to every one of which Mr. Booer's
system might be applied with advantage to the tradesman and his
customers. And what may be done with gas at about 3s. per 1,000 cubic
feet may certainly be done to still greater advantage in many towns
where the price is lower. Mr. Booer has entered upon his work in a
proper spirit. He has begun at the beginning, with the necessities of
the baker; and has gone plodding on quietly, until he has achieved a
noteworthy success. It may be hoped he will receive the reward which his
perseverance merits.--_Jour. of Gas Lighting_.

* * * * *

CAPTAIN MATTHEW WEBB.

Who was drowned on July 24 in attempting to swim through the whirlpool
and rapids at the foot of the Falls of Niagara, was born at Irongate,
near Dawley, in Shropshire, January 18, 1848. He was 5 feet 8 inches in
height, measured 43 inches round the chest, and weighed about 141/2 stone.
He learnt to swim when about seven years old, and was trained as a
sailor on board the Conway training-ship in the Mersey, where he saved
the life of a fellow seaman. In 1870 he dived under his ship in the Suez
Canal and cleared a foul hawser; and, on April 23, 1873, when serving on
board the Cunard steamer Russia, he jumped overboard to save the life of
a hand who had fallen from aloft, but failed, and it was an hour before
he was picked up almost exhausted. For this he received a gold and
other medals. He became captain of a merchant ship, but soon after he
relinquished the sea and devoted himself to the sport of swimming.

At long distance swimming in salt water he was _facile princeps_, but he
did not show to such advantage in fresh water. In June, 1874, he swam
from Dover to the North-East Varne Buoy, a distance of 11 statute miles.
On July 3, 1875, he swam from Blackwall Pier to Gravesend Town Pier,
nearly 18 statute miles, in 4 hours 52 minutes. On the 19th of the same
month he swam from Dover to Ramsgate, 191/4 statute miles, in 8 hours 45
minutes. On August 12, 1875, he tried to cross from England to France,
and although he failed, owing to the heavy sea, he compassed the
distance from Dover to the South Sand Head, 151/2 statute miles, in 6
hours 48 minutes. On the 24th of the same month he made another attempt,
which rendered his name famous all over the English-speaking world.
Starting from Dover, he reached the French coast at Calais, after being
immersed in the water for 21 hours 44 minutes. He had swum over 39
miles, or, according to another calculation, 451/2 miles, without having
touched a boat or artificial support of any kind. Subsequently he swam
at the Lambeth Baths, and the Westminster Aquarium, and last year, at
Boston, U.S., he remained in a tank nearly 1281/2 hours. Latterly he had
suffered from congestion of the lungs, and his health had become much
impaired.

[Illustration: CAPT. MATTHEW WEBB.]

The story of his final and fatal effort needs here but a brief
description. At two minutes past four, on July 24, Webb dived from the
boat opposite the Maid of the Mist landing, and, amid the shouts and
applause of the crowd, struck the water. He swam leisurely down the
river, but made good progress. He passed along the rapids at a great
pace, and six minutes after making the first plunge passed under the
Suspension Bridge. Immediately below the bridge the river becomes
exceedingly violent, and as the water was clear every movement of Webb
could be seen. At one moment he was lifted high on the crest of a wave,
and the next he sank into the awful hollow created. As the river became
narrower, and still more impetuous, Webb would sometimes be struck by a
wave, and for a few moments would sink out of sight. He, however, rose
to the surface without apparent effort. But his speed momentarily
increased, and he was hurried along at a frightful pace. At length he
was swept into the neck of the whirlpool. Rising on the crest of the
highest wave, he lifted his hands once, and then was precipitated into
the yawning gulf. For one moment his head appeared above the angry
waters, but he was motionless, and evidently at the mercy of the waves.
He was again drawn under the water, and was seen no more alive. Some
days later his body was found four miles below the fatal Rapids. It bore
tokens of the fearful violence of the struggle which he had undergone.
His bathing drawers were torn to fragments, and there was a deep wound
in his head. An inquest was held, and the jury returned a verdict of
"Found drowned."

Captain Webb was married about three years ago, and leaves a widow and
two children. It is understood that he risked his life in this last
fatal attempt to obtain money for the support of his family.--_London
Graphic_.

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