IMPROVEMENTS IN POTTERY AND OTHER KILNS."
Year: 1868

page_text: LETTERS PATENT to Henry Young Darracott Scott, of Ealing, in the
County of Middlesex, Lieutenant-Colonel in the Royal Engineers,
for the Invention of "IMPROVEMENTS IN POTTERY AND OTHER KILNS."
for the Invention of IMPROVEMENTS IN POTTERY AND OTHER KILNS.'
Sealed the 12th February 1869, and dated the 15th August 1868..
PROVISIONAL SPECIFICATION left by the said Henry Young Darracott
Scott at the Office of the Commissioners of Patents, with his Petition,
on the loth August 1868.
I, HENRY YOUNG DARRACOTT SCOTT, of Ealing, in the County of
Middlesex, Lieutenant-Colonel in the Royal Engineers, do hereby declare
the nature of the said Invention for "IMPROVEMENTS IN POTTERY AND OTHER
KILNS," to be as follows:-
The objects of these improvements is to save fuel, economize in the
construction of kilns, and to better prepare the goods or materials to be
fired.
In carrying out my Invention for a muffle kiln the arches or domes
of the kiln may be made of a circular, elliptical, or other suitable curve,
and should spring from the ground or from an equally secure foundation;

page_text: by this means the necessity of iron ties and buttresses, which are usually
required to counteract the thrust on the vertical walls now used to
support the domes or arches, may be dispensed with. The internal
casing will spring in like manner from an immoveable abutment, but
the curves of the two casings are not concentric or parallel, but
gradually converge at the crown, while sufficient space is left between
them at their springings for the introduction of the fires which are to
supply the heat. The grates are constructed so as to admit of either
a thick or a thin layer of fuel being spread over them, and they may be
either self-feeding or not. A thin layer of fuel is used during the drying
or smoking process which prepares the goods for firing, but as soon
as it is wished to raise the heat the thickness of the layer of fuel
on the fire-bars is increased to that point at which the production of
gaseous fuel is found to be most perfect. These gascous products are
subsequently completely consumed by the admission of streamlets of
atmospheric air (which may be graduated or regulated in quantity) at
various points of the flues (more and more distant from the fire-grates)
as the burning proceeds; at first the air is admitted immediately over
the fires; at the conclusion of the burning it is admitted to a point which
may be 30 feet more or less distant from the bottom of the chimney
shaft which produces the draft.
For a pipe kiln the exterior arch or dome springs as in the muffle
kiln from a secure foundation, so that the masonry of the arch may rise
and fall, or expand and contract freely as a whole under the influence
of the variations of temperature, which as is well known, cause it to
expand and contract, the abutments alone being unyielding. The
casing wall may be either a vertical wall, such as is at present used
(but having raking buttresses between the two casings to prevent its
being forced out) or it may be made of an arched or domed form, as in
the muffle kiln, and provided with perforations sufficiently large to give
free course to the products of combustion into the firing chamber. The
fires are placed, as in the muffle kiln, as far as possible detached from
the arches or shells of brickwork between which they are situated, and
these fire-places may if desired be arranged for the generation and
combustion of gaseous fuel. The flues or openings for the supply of
atmospheric air are however differently managed in this kiln. A tier of
openings is made immediately above the fire, and are to be used in the
"smoking" process and in the earlier stages of the firing, but to produce

page_text: the requisite degree of heat at a later period air flues are introduced
underneath or between the fires, so as to admit air into the inner casing,
and are there carried up to the level at which the flames are intended
to enter the firing chamber, so that the atmospheric air admitted through
them may perfectly consume (in and amongst the pipes) the gaseous
fuel arising from the fire-places. The other arrangements of the pipe
kiln with reference to floor and chimney are as at present used. I
prefer to make both my muffle and pipe kilns with waggon-shaped
centres and semi-dome or curved ends.
In the case of lime kilns I take as the basis of my operations the
principle of the flare kilns of the Medway, but the firing chamber is
made of greater height, and for some distance up division walls are
raised between the fires. These division walls with the side walls carry
brick arches with perforations through them sufficiently large to give
free passage to the products of combustion from the grates below.
Sometimes the division walls and perforated arches are carried up another
or second story, but the uppermost compartment is left without them,
as they are not needed there. In loading the kiln arches of chalk are
built as at present over the fires to carry the charge, and smaller arches
are again constructed over the openings in the arches, which in turn
carry their charges. On each side of the fires (in the cheeks of the
fire-places) are flues which convey atmospheric air to the fuel, and
which are used chiefly in the earlier stages of the process, and at each
arch level (above) air flues are again introduced, by which the gaseous
fuel arising from the fire-grates is to be burned as soon as the lower
chamber has been brought to a full glow adequate to the expulsion of
the carbonic acid gas from the chalk or limestone, and so on. In this
manner the over-burning of the "arch lime," as it is called, may be
avoided, and the flare may be readily carried without loss of combustible
gas towards the upper layers of the chalk, which on the present system
are so difficult to burn. In fact, comparatively speaking, an equable
temperature is kept throughout the kiln without the lime being in
actual contact with the solid fuel, which as is well known greatly injures
its estimation in the market.
The whole of the above arrangements admit of being combined with
the system of saving fuel by the transmission of the waste heat from
one kiln to another. and in each case the production of gaseous fuel

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Henry Young Darracott Scott in the Great Seal
Patent Office on the 15th February 1869.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, HENRY
YOUNG DARRACOTT SCOTT, of Ealing, in the County of Middlesex,
Lieutenant-Colonel in the Royal Engineers, send greeting..
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Fifteenth day of August, in the year of
our Lord One thousand eight hundred and sixty-eight, in the thirty-
second year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said Henry Young Darracott Scott, Her special
licence that I, the said Henry Young Darracott Scott, my executors,
administrators, and assigns, or such others as I, the said Henry Young
Darracott Scott, my executors, administrators, and 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, excrcise, and vend, within the United Kingdom of
Great Britain and Ireland, the Channel Islands, and Isle of Man, an
Invention for "IMPROVEMENTS IN POTTERY AND OTHER KILNS," upon the con-
dition (amongst others) that I, the said Henry Young Darracott Scott,
my executors or administrators, by an instrument in writing under my,
or their, or one of their hands and seals, should particularly describe and
ascertain the nature of the said Invention, and in what manner the same
was to be performed, and cause the same to be filed in the Great Scal
Patent Office within six calendar months next and immediately after the
date of the said Letters Patent..
NOW KNOW YE, that I, the said Henry Young Darracott Scott, do
hereby declare the nature of my 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 Drawings
hereunto annexed, and to the letters and figures marked thereon (that is
to say):-
---
The objects sought to be attained by my "Improvements in Pottery

page_text: and other Kilns"
are stability and durability of structure in the oven
or kiln, equality of burning in the goods to be operated upon, and
economy in the use of the fuel.
The Invention applics to the burning of lime as well as to that of
bricks, tiles, pottery, and other ware.
The principles upon which the Invention is based are equally adapted
to the improvement of kilns similar in general features to those now in
use and to other forms such as are hereafter described. These principles
consist essentially,―
First. In giving the containing walls of the oven or kiln arched
forms resting on immoveable abutments or foundations instead of ou
vertical walls held together by iron bands as is now practised.
Second. In the introduction of air passages at different points in the
length of the flues, so as to command the means of completing the
combustion of the unburned combustible gases derived from the fires
wherever heat is required for the complete firing of the goods.
Third. In the employment of fire-places adapted to the production of
combustible gases, and the use of small or refuse coal and slack for the
production of the gaseous fuel.
In the accompanying Drawings Fig. 1, Sheet I., is a sectional plan
view, and Fig. 2 a vertical section of a muflle kiln taken in the.
line A, B, of Fig. 1, and resembling in general plan those now in use,
Both the inner and outer
but modified according to my Invention.
casings a and b are arched from their foundations, and the profiles of
the casings are struck from different centres, so as to allow a larger
space c between the casings nearer the springing of the arches than at
their crowns.
A space of ten inches at the springing and six inches
at the crown gives good results with a kiln such as is shewn at Figures 1
and 2; but I do not confine myself to these dimensions, nor to the
varying space between the casings, for the casings may be struck with
the same centre, and space may be obtained for the fires by making
pockets or recesses in the inner casing projecting into the interior of
the kiln. I prefer however the arrangement shown in the Drawing,
and I consider it a matter of importance that the ignited fuel shall
lie between the casings and not immediately under or rather in an
arch in the outer wall, which would be liable to be destroyed by the

page_text: action of the fire. I prefer to give to the fires a depth of from two to
three feet or three feet six inches (according to the nature of the fuel)
in the direction traversed by the air entering the ash-pit in order that
large quantities of carbonic oxide gas and other combustible gases may
pass off from the fuel unconsumed, and be conducted into the space
between the arches a and b. These gases can always by my arrange-
ments be fully burned at such points of the flues as may be necessary,
whether near to or at a distance from the fires by the admission of
fresh atmospheric air at different points. I sometimes also increase the
quantity of these inflammable gases by causing currents of vapour of
water to traverse a deep mass of ignited fuel in the fire-places, according
to well-known principles, such as are followed when the production of
gaseous fuel is especially aimed at. By employing the fuel in this
manner I gain complete control over it; I am enabled to vary the
amount of heat without loss of fuel by reducing or enlarging simul-
taneously both the indraft through the ash-pit and through the inlet
holes; I can also vary the point or points at which the final and
complete combustion of that portion of the fuel which is compelled to
take the gaseous inflammable form shall be effected. The inlets for the
admission of fresh air into the flues are made at different points of their
length, as at 1, 2, 3, 4, and 5, in Figures 1 and 2, one set of inlets or
indraft holes under the floor will be found of very great advantage as
compared with the present system, but I prefer several sets, as shown at
3, 4, 5, so as the better to equalize the temperature throughout the kiln.
In order to define the amount of air which should be admitted at
different points to complete the combustion of the fuel in the most
economical manner I will assume that a ton of coal requires from three
to four hundred thousand cubic feet of air to consume it (the quantity
varying according to the nature of the coal). It is found in practice
that about one-third of this quantity of air should be supplied through
the ash-pit, so as to promote the combustion of the solid fuel and convert
it into combustible gases, and the remainder of the air may be supplied
through the inlets 1, 2, 3, 4, and 5, so as to consume the gases at
different points. The inlet holes 1, 2, 3, 4, and 5 are furnished with
regulating slides to enlarge or contract the openings according to the a
heat required at the different parts of the kiln. The results obtained
by the admission of air at the different points may be observed through
peep holes covered with glass or tale; I can thus observe the nature of

page_text: the flame that is passing, as unconsumed hydrocarbons make themselves
very visible in the heated current.
On commencing the hot firing after the goods have been carefully
and well dried and heated by slow fires I admit air freely through the
ashi-pits and enough air at the points 1, 1, Fig. 2, immediately over the
fires, so as to raise the first portions c, c, of the flues to a sufficient
temperature, unless indeed the layer of fuel employed in the fire-places is
sufficiently thin to allow of a considerable quantity of the fuel to be fully
consumed by the air passing through it from the ash-pit; I then reduce
the openings 1, 1, to that point which is requisite merely to maintain the
necessary amount of heat in this part of the fluos; and I open the
inlet 2, Fig. 2, to the required extent for the full combustion of the
gases at this point; this will soon raise the next length of flue space to
the required temperature. The opening at 2 may then be reduced, and
the others 3, 4, and 5 opened in succession, and so on until the whole
length of the flue space has been raised to one uniform temperature. At
this point the flucs may be kept without difficulty until the goods are
sufficiently fired.
The fire-places may be constructed either with or without bars
according to the nature of the fuel to be employed, but in all cases with
the form of fire-place which I prefer, and which is shewn in Fig. 2, slack
may be used with advantage. Fire-bars may be used with a coal
yielding a powdery ash, but they must be dispensed with, as shewn in
the Drawings, when the ash runs to slags and might adhere to and choke
up the,bars.
From what has been stated it will be apparent that whilst I use by
preference deep layers of coal in the fire-places as giving more command
over the combustion (and enabling the flues at a distance from the fire
to be as well heated as those near them) my system of inlets for the
admission of fresh air into the flues will be advantageous in all cases in
which the access of air through the ash-pit does not effect the complete
combustion of the fuel, and this rarely or never happens during the hot
firing in the fire-places commonly used.
Fig. 3 represents a vertical section of an ordinary pipe kiln arranged
according to my Invention. The containing wall springs as an arch

page_text: from the ground for abutments, and the air to consume the inflammable
gases derived from the fuel is supplied in the form of streamlets passing
up the inner casing and shewn at 1, 1, in the Figure.
In order to adapt the present form of flare lime kilns for my process
I divide the two fires ordinarily used by a partition wall carried to a
height of six feet more or less above the floor of the kiln. This wall
at the top is formed to a skew back to take arches which have their
other extremities resting on skew backs formed in the sides of the kilns.
The arches themselves are perforated with openings in each side of
the crown two feet wide, and two feet six inches long, and four feet
from centre to centre more or less. The openings are rounded at the
top and bottom in order not to weaken the arch too much. This arch
is perforated with flues communicating with the external atmosphere
so as to admit fresh air to consume at the upper part of the kiln the
inflammable gases emitted by the fires below; the flues terminate in
the arch openings described. The lower fire-place is arched over with
chalk (when the kiln is loaded) in the usual manner, and arches are
also roughly built in chalk over the openings in the brick arch above
so as to support the upper part of the charge free of the inlet holes
in the arch openings. The side walls of the kiln can be raised with
advantage to a height of eight or ten feet above the brick arch, and
the fire-bars may be sunk one foot six inches or two feet below the
level of the floor of the kiln to obtain sufficient depth of fuel, the ash-
pit being sunk for the purpose.
In this case inlet holes for fresh air
are likewise brought in somewhat above the level of the top of the
layer of fuel in order to command a greater temperature below. But
with this form of fire-place enough fuel for burning the bottom portions
of the charge will generally be consumed by the air passing through the
fire-bars.
So far in the description of my Invention I have dealt with its
application to such forms of oven or kiln as are commonly met with.
I now proceed to describe its application in the forms which I consider

page_text: end. The products of the partial combustion of the fuel in the fire-
places d pass along the flues both around the arched inner casing
and under the floor, as indicated by the arrows in Fig. 4, and return
again to the chimney through the inner central flue e. Inlet holes 1,
1, 1, 1, and 2, 3, 4, 5, 6, for the admission of fresh air occur at intervals
through the outer arched casing and into the flues under the floor of
the oven.
The sets of inlet holes may be from ten to fifteen feet or
more apart. The management of the inlet holes will be readily under-
stood from the description above given in treating of the muffle oven
of circular form.
Figures 6, 7, 8, and 9, Sheet II., represent a kiln or oven suitable for
burning all kinds of ware on which the direct action of flame would
exert no injurious influence. It is well adapted for burning bricks,
tiles, and lime. Fig. 6 is a longitudinal vertical section taken in the
line A, B, of Fig. 7, which is a sectional plan view, Fig. 8 is an end
elevation, and Fig. 9 a transverse vertical section of the kiln taken
in the line C, D, of Fig. 7. In this oven the fresh air for the con-
sumption of the inflammable gases is admitted through vertical pipes
having perforations through their side to allow the air to escape into
the body of the oven, as shewn at 2, 3, 4. Flues are also carried
through the arch rings above the vertical pipes 2, 3, 4, and have per-
forations made therein for the purpose of allowing the air to escape
as from the vertical pipes 2, 3, 4. These arch rings also serve to deflect
the flames down among the goods to be burned. The arched flues f, ff,
underneath the floor of the oven also serve a double purpose; they will
keep out of the oven the damp which would otherwise rise from the earth
through the floor, and thus enable the heated products of combustion
to be taken into a neighboring kiln through the flues d, d, so as to
dry and heat the goods therein. When also the goods which have been
burned off are not such as to be injured by the indraft of cold air the
supply of air for the inlets at 1*, 2, 3, and 4, can be brought through
an oven which has been burned off. For this purpose the flues leading
to the chimney C, Fig. 7, are closed, and the communication between
the two ovens is established through the arched flues f, f, which are
provided with dampers to enable the current of air, &c., to be turned
in the required direction. The inlets from the flues to the upright
pipes 2, 3, 4, and the perforated arches above them convey and distribute

page_text: the fresh but heated air through the kiln, and may be regulated by
dampers not shewn in the Drawing. As soon as the goods have
been dried and gradually heated in preparation for the strong firing,
sufficient air for the combustion of the gases evolved from the fuel in
the fire-places is first introduced through the openings 1, 1, in the dome
over the fires, and through the flucs 1* beneath them. When the
requisite temperature has been reached so much air only is admitted
at 1, 1, at 1*, 1*, as is necessary to maintain this temperature in the
goods, and the remainder of the combustible gases if any are consumed
by the admission of air at 2, 3, and 4. When it is considered that
the goods in the first part of the kiln are sufficiently burned the whole
of the openings 1, 1, and 1*, 1*, are closed, and those at 2 are opened
so as to bring another length of the oven to the required temperature,
and so on at 3 and 4, until the whole contents of the kilns are burned.
By this means the excess of heat of the portion of the oven which
has just had the hot firing will be taken on by the inflammable gases
to the next portion and then assist in increasing the temperature.
Ovens of the pattern I have described admit of a circular arrangement
around a central chimney with which each oven in succession may
be brought into communication. It will be evident that instead of
every kiln being provided with separate fire-places, one capacious gas
generating furnace may be employed, and any convenient number of
kilns may be arranged around it and supplied with gaseous fuel there-
from, such gaseous fuel being consumed by the admission of air thereto
in either of the ways above set forth. In all these cases I sometimes
employ steam in connection with the fire-places to increase the quantity
of combustible gas through its decomposition as it passes through the
ignited fuel. The steam may be produced by keeping the ash-pit moist
or in any other convenient way.
Having described my Invention, and the manner in which I carry
the same into effect, I wish it to be understood that I claim,-
First. For constructing the containing walls of the kilns wholly of
an arched form springing from the ground as herein set forth.
Secondly. For the general arrangement and construction of the kilns
or ovens herein shewn and described, combined with the admission of
air in the manner herein set forth to complete the combustion of the

page_text: unburned inflammable gases at points distant from the fire-place so
as to be able to subject all the goods contained in the kilns or ovens
to the same temperature.
Thirdly. For the employment for the purposes of my Invention of
fire-places for the production of large quantities of inflammable gases
as herein set forth.
In witness whereof, I, the said Henry Young Darracott Scott,
have hereunto set my hand and seal, the Thirteenth day of
February, in the year of our Lord One thousand eight hundred
and sixty-nine.
HENRY Y. D. SCOTT. (L.S.)