IMPROVEMENTS IN FURNACES FOR STEAM BOILERS AND OTHER HEATING PURPOSES
Year: 1855

page_text: LETTERS PATENT to John Henry Johnson, of 47, Lincoln's Inn Fields, in
the County of Middlesex, and of Glasgow, North Britain, Gentleman,
for the Invention of "IMPROVEMENTS IN FURNACES FOR STEAM BOILERS AND
OTHER HEATING PURPOSES."-A communication.
Scaled the 3rd June 1856, and dated the 22nd December 1855.
PROVISIONAL SPECIFICATION left by the said John Henry Johnson
at the Office of the Commissioners of Patents, with his Pétition, on the
22nd December 1855.
I, JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County, of
Middlesex, and of Glasgow, North Britain, Gentleman, do hereby declare the
nature of the said Invention for "IMPROVEMENTS IN FURNACES FOR STEAM
BOILERS AND OTHER HEATING PURPOSES," a communication to me from abroad, to
be as follows:-
This Invention relates to an improved form of furnace for steam boilers,
stills, ovens, and other similar purposes, whereby a saving of fuel and preven-
tion of smoke is effected. The improvements consist in making or dividing
the furnace into a number of divisions, or separate grates or fire-places, divided
from each other by low walls of fire brick, or other suitable material, so that
the unconsumed smoke and gases may pass from one grate over the other, and
be thereby perfectly consumed. This subdivided furnace is placed at a con-
siderable distance below the boiler or other vessel or apparatus to be heated,
the distance varying from 4 to 20 feet, more or less. A part of the chimney
or flue is placed before the boiler, and is built of fire bricks and serves as
a combustion chamber, wherein the combustion of the smoke and gases is
entirely effected before they reach the boiler. The grate bars should be very
thin, and arranged to give the largest possible surface contact for the burning

page_text: fuel to be acted upon by the air, whilst at the same time the incoming air or
draught keeps the bars comparatively cool, and thus prevents their burning.
The several fire-places stand apart and are separated from the surrounding
walls by air passages which prevent altogether the distribution or loss of heat
by radiation through the surrounding brickwork, which remains cold. The
air in these air passages, however, becomes gradually heated, and is then
drawn up through small openings into the combustion chamber in front of the
boiler. By this arrangement of furnace the tall chimney or stalk may be
dispensed with, as the chimney need not be more than or four feet above the
surrounding buildings. In cases where there is not sufficient room to admit of
several fire-places, as in steam boat furnaces, for example, then a self-acting
ventilator or similar apparatus will be necessary.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said John Henry Johnson in the Great Seal Patent Office on
the 21st June 1856.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of Middlesex,
and of Glasgow, North Britain, Gentleman, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-second day of December, in the year of our
Lord One thousand eight hundred and fifty-five, in the nineteenth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said John Henry Johnson, Her special license that I, the said John
Henry Johnson, my executors, administrators, and assigns, or such others as
I; the said John Henry Johnson, my executors, administrators, or assigns,
should at any time agree with, and no others, from time to time and at all
times thereafter during the term therein expressed, should and lawfully might
make, use, exercise, and vend, within the United Kingdom of Great Britain
and Ireland, the Channel Islands, and Isle of, the said Invention for "IMPROVE-
MENTS IN FURNACES FOR STEAM BOILERS AND OTHER HEATING PURPOSES," a com-
munication from abroad, upon the condition (amongst others) that I, the
said John Henry Johnson, by an instrument in writing under my hand and
seal, should particularly describe and ascertain the nature of the said Inven-
tion, and in what manner the same was to be performed, and cause the same
to be filed in the Great Seal Patent Office within six calendar months next
and immediately after the date of the said Letters Patent.

page_text: NOW KNOW YE, that I, the said John Henry Johnson, do hereby
declare the nature of the said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement, reference being had to the accompanying Drawings, and to the
letters and figures marked thereon, that is to say:-
The said Invention relates to an improved construction and arrangement of
furnace for steam boilers, stills, ovens, and other similar purposes, whereby a
saving of fuel and prevention of smoke is effected. The improvements consist
in making several divisions in the furnace so as to form separate grates or fire-
places, separated from each other by low walls of fire brick or other suitable
material, with the view of making the unconsumed smoke and gases to pass
from one division or grate over the incandescent fuel in some one or more of
the other divisions or grates, and of being thereby perfectly consumed. This
subdivided furnace is placed at a considerable distance below the boiler or other
vessel or apparatus to be heated, the distance varying from four to twelve'
feet. A part of the opening or flue is placed before the boiler, and is built
of fire bricks, and serves as a combustion chamber wherein the combustion
of the smoke and gases is entirely effected before they reach the boiler, whilst
it also increases the draught. The grate bars should be very thin, say, from
five-sixteenths to half an inch in width, with from one-eighth to one-fourth of
an inch space between them, in order to give the largest possible surface con-
tact for the burning fuel to the action of the air which enters, and also to usė
with profit coal dust or ashes, whilst at the same time the incoming air or
draught keeps the bars comparatively cool, and thus prevents their burning.
The several fire-places (I prefer using from 3 to 8) stand apart, and are sepa-
rated from the surrounding walls by air passages, which prevent altogether the
distribution or loss of heat by radiation through the surrounding brickwork,
which thus remains cold. The air in these air passages, however, becomes
gradually heated, and is then drawn up through small openings into the com-
bustion chamber in front of the boiler.
By this arrangement of furnace the tall chimney or stalk may be dispensed
with, as the chimney need not stand higher than three or four feet above the
surrounding buildings. In cases where there is not sufficient room to admit
of several fire-places, as for example, in steam boat furnaces, then a self-acting
ventilator or similar apparatus will be necessary.
And in order that the said Invention may be fully understood, I shall now pro-
ceed more particularly to describe the same, and for that purpose I shall refer
to the several Figures on the Sheet of Drawings hereunto annexed, the same
letters of reference indicating corresponding parts throughout all the Figures.

page_text: Figure 1 of the Drawings represents a longitudinal vertical section of the
improved furnace, shewing its application to an ordinary cylindrical internal
flue boiler; Figure 2 is a corresponding transverse vertical section of the same,
taken along the line 1, 2, in Figure 1; Figure 3 is a transverse vertical section
of the furnace, taken along the line, 3, 4, in Figure 1; Figure 4 is a borizontal
section, taken through the combustion chamber along the line 5, 6; Figure 5
is a simiiar section, taken along the line 7, 8, above the furnace bars; and
Figure 6 is a front elevation of the boiler and furnace. A, A, are the fire
grates, which may range in number from 3 to 8.. They are composed of bars
of from five-sixteenths to half an inch in width, and about eighteen inches in
length, four sets or series being shewn in each grate; B, B, are low, walls or
partitions of fire brick, to separate one fire-place from another; C is the
crown or arch of the combined furnace; D is the combustion chamber, formed
either underneath the front end of the boiler E, as shewn in the Drawings,
or entirely in front of the same, and opening in the latter case directly into
the central flue F of the boiler; G, G, are air spaces surrounding. the
whole of the combustion chamber and furnaces, partly for the purpose of. pre-
venting any loss or waste of heat by radiation from the brickwork, and partly
in order that the air which flows towards the furnaces may not enter them in
too cold a state; H, H, are binding bricks or stops, which impede the flow of
air, and prevent it from being discharged before it has had time to become
heated; I, I, are conical air passages, through which the heated air from the
air spaces G, G, passes into the combustion chamber D; J, J, are the furnace
doors, which are perforated to admit air, and are constructed so as to direct
such air upwards. The grates A, A, A, three of which are shewn in the
Drawing, should be from four to twelve feet or more below the apparatus
or boiler E to be heated, as by this means the boiler will receive the whole.
of the heat derived from the fuel.
When the fire-bars are as at present placed from twelve to eighteen inches,
or at most twenty-four inches, below the boiler, the unconsumed combustible
products come into direct contact with the boiler holding water, at a tempera-
ture of not; more than 212° Fahrenheit, and therefore in a cold state in com-
parison with the flames, which therefore lose heat before they are fully formed,
or in other words, the combustible products are cooled and deprived of their
power before the gaseous products which are inflammable, but require a high
temperature to bring them into flame, are ignited and enabled perfectly to
consume the smoke.
.It is to obviate this defect therefore that I place the fire-grate much deeper
than usual, in order to afford the gases sufficient space to mix and become

page_text: ignited in the "combustion chamber" D. It is easy to perceive that by this
method the greatest possible amount of heat arrives at the boiler. This com-
bustion chamber is of a peculiar construction, and has for its object, firstly, to
impart to all the products of combustion the temperature necessary to effect
their entire consumption; secondly, to materially assist the draught. The
products of the burning fuel, as they are evolved from all the hearths or fire-
places, cross each other on their passage, as shewn by the arrows (Figure 2),
and become thoroughly mixed in the combustion chamber, which is formed
expressly for this purpose of fireproof bricks, and with the view of imparting
the full and necessary temperature to effect the combustion of the unburnt
products given off from any one of the hearths to which fresh fuel has just been
applied, such products being consumed by passing through the flames from
the other fire-places.
The combustion chamber D being composed of fireproof bricks, it retains
always a white heat, and exercises by its high temperature a great influence
in effecting combustion. This chamber draws in the heat, and when raking or
stirring takes place in any of the fire-places, and any part of the products from
the fuel arrives in a low state of temperature in this chamber, it will become
highly heated, and will be effectually consumed.
I have herein-before stated that the combustion chamber conveys the heat
to the boiler, and that thereby the greatest possible degree of heat arrives at
the latter without loss; this is easily explained, inasmuch as the fire-places
stand apart, and are separated from the surrounding walls by the air passages
G, of from three to four inches in width. These air passages prevent altogether
any distribution or loss of heat through the surrounding brickwork, which
remains cold; the air in these air passages, however, becomes gradually heated,
and is then drawn up naturally through the small conical openings I, I, into
the combustion chamber, where it supplies oxygen to assist combustion, and
thereby carries back the heat otherwise given off. By this means no portion
of the heat is lost, but a perfect combustion is produced, more effect obtained
from the fuel, and more advantage taken of the heat, which would otherwise
impart itself to surrounding objects. I have also herein-before stated that the
combustion chamber promotes the draught. This arises from its constant high
temperature, for when the air becomes heated it flows upwards, and causes by
rarefaction a constant current of atmospheric air. The effect called "draught"
must here be very powerful, as the air in the combustion chamber, which is at
a white heat, must be at least two thousand. degrees Fahrenheit, or ten times
more than the chimney. This "chamber" is still to be considered as part of
the chimney, or acting as such. If the chimney can be male five feet high,

page_text: then the effect, that is, the draught, will be equally strong as with a chimney
under the old system fifty feet high; consequently the chimney at the back of
the boiler can be so low as merely to exceed the height of the surrounding
buildings by three or four feet. The perfect combustion of the fuel is effected
in the chamber, which is in full activity before the flues or chimney are even
warm. The lower the chimney is, the less quickly will the heat be carried off,
and the better can heat be imparted to the boiler up to a certain point. A
low chimney is therefore valuable in economising fuel, is cheaper to construct,
and, in connection with the combustion chamber, admits of the temperature
being more regularly retained. Upon this point is based my Invention, that
no part of the chimney is placed before the boiler for the purpose of forcing
the draught, and the heat which has been used to produce the draught is used
for heating the boiler, whilst by the common chimneys the heat passes away
after a single application.
Amongst the advantages derived from the use of these furnaces are, first,
the lessening of the difficulty of regulating the firing, and the lightening the
work; for the charging of six furnaces of five feet square each easier than the
charging of one furnace thirty feet square, and it is much easier to keep
the grate constantly supplied with fuel; second, the supplying of small quan-
tities of fuel at one time, for two shovelfuls may ordinarily be given for a
supply, less time is lost; whilst there is less liability of any part cooling down,
the fuel supplied being as one to three, or as one to six, one to eight, and
(according to the number of fire places) the power to consume the smoke will
be in inverse proportions, instead of as only one to one. The charges of fuel
must of course be made several times oftener than when there is only one fire-
place. The air which enters always finds fresh fuel, and an equal quantity of
fuel will always be in an equal state of combustion. The cooling down by
the opening of the furnace doors for the purpose of charging will be very
slight, and will be counteracted by the red-hot walls of so many fire-places.
"This cooling down will also never act directly upon the boiler itself, as it
cannot reach further than the combustion chamber. The small fire-places
are narrow and long, and the combustion chamber is placed over the furthest
end of the furnaces, which are low and vaulted in front, in order that a
continued drying may go on together with a distillation; here then is effected
an imperfect combustion, the gases being brought into perfect combustion in
the combustion chamber; when the fire burns clear, the burning fuel is to be
pushed to the back of the furnace, and the fresh fuel is to be always placed at
the front. The narrow grate bars, which if desirable can be made of bar iron,
will be kept so cool by the atmosphere that they will remain in perfectly good

page_text: order, and will not become bent if not made of too great a length. A large
extent of heating surface will still be obtained, and also slow combustion; the
economy of fuel by this furnace will be fifteen per cent., and there will be no
smoke. This furnace has perfect solidity and simplicity of construction, and can
be applied in all cases and places; the fire-places can even be placed in the
cellar whilst the boiler is above, thus lessening the danger of fire.
Having now described and particularly ascertained the nature of the said
Invention, and the manner in which the same is or may be used or carried
into effect, I would observe, in conclusion, that I do not confine or restrict
myself to the precise details or arrangements which I have had occasion to
describe or refer to, as many variations may be made therefrom without
deviating from the principles or main features of the said Invention; but what
I consider to be novel and original, and therefore claim as the Invention
secured to me by the herein-before in part recited Letters Patent, is,-
First, the general construction and arrangement of furnaces or fire-places
for steam boilers, stills, ovens, or for other similar heating purposes, as herein-
before described.
Second, the subdividing of furnaces for steam boilers, stills, ovens, and
other similar purposes, into separate grates or fire-places, as herein-before
described.
Third, the placing of the grates of furnaces for steam boilers, stills, ovens,
or other similar purposes, at a distance varying from four to twelve feet
below the boiler or object to be heated.
Fourth, the placing of a portion of the chimney at the front end or before
the boiler or other object to be heated, and making such portion of the
chimney of fire-clay bricks or lumps, so as to form a combustion chamber.
Fifth, the peculiar arrangement of air passages round the, combustion
chamber and furnaces, for the twofold purpose of preventing loss of heat by
radiation, & for supplying heated air to the combustion chamber, as herein-
before described.
In witness whereof, I, the said John Henry Johnson, have hereunto set
my hand and seal, the Twenty-first day of June, One thousand
eight hundred and fifty-six.
J. HENRY JOHNSON. (L.S.)