IMPROVEMENTS IN APPARATUS OR ARRANGEMENTS FOR PREVENTING OR REDUCING THE PRODUCTION OF SMOKE IN FURNACES
Year: 1870

page_text: LETTERS PATENT to David Walker, of Leith, in the County of Mid
Lothian, North Britain, Engineer, for the Invention of "IMPROVEMENTS
IN APPARATUS OR ARRANGEMENTS FOR PREVENTING OR REDUCING THE
PRODUCTION OF SMOKE IN FURNACES."
Sealed the 1st November 1870, and dated the 6th May 1870.
PROVISIONAL SPECIFICATION left by the said David Walker at the
Office of the Commissioners of Patents, with his Petition, on the
6th May 1870.
I, DAVID WALKER, of Leith, in the County of Mid Lothian, North
Britain, Engineer, do hereby declare the nature of the said Invention for
“IMPROVEMENTS IN APPARATUS OR ARRANGEMENTS FOR PREVENTING OR REDUCING
THE PRODUCTION OF SMOKE IN FURNACES," to be as follows, that is to say:—
This Invention has for its object to prevent or reduce the production
of smoke in furnaces, and it consists in causing air to traverse piping
placed in the flue or flues leading from the furnace, and then to issue
amongst and mingle with the fire gases at the back of the furnace.. The
air is made to traverse, the piping in the flues by means of a fan or other
blowing apparatus, and when the furnace or the furnace and steam
boiler or other apparatus heated by it are situated in a shed, building, or

page_text: other enclosure so that the air over and about them is heated by radiation,
the blowing apparatus is arranged to take up such heated air and force
it through the piping. A double or broad bridge is constructed at the
back of the furnace, and the piping leads the heated air into a space
formed in the lower part of this bridge. One or more narrow slits or
openings in the top of the bridge allow the air to issue from the space
below and it mingles with the fire gases as they pass over the bridge
and insures the thorough combustion of any incompletely burnt portions,
the space over the bridge being contracted so as to compel a thorough
intermingling of the air and gases. With the described arrangements a
sufficient quantity of air can be blown in to suit any condition of the
furnace, but whilst in many attempts hitherto to prevent smoke by the
introduction of air amongst the fire gases the object has been defeated by
the deficiency of heat in the air so introduced, such deficiency is
prevented according to the present Invention by the very efficient mode
of heating the air by placing the air piping in the flues, which piping
may be made to traverse the flues to any extent that may be found
requisite or advantageous in practice. It may however be stated by way
of example that in an internally fired steam boiler of moderate dimen-
sions, it has been found quite sufficient to introduce an air pipe into the
first fluo at the back end of the boiler, and to lead it directly along the
bottom of the internal flue forward to the bridge at the inner end of the
furnace.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said David Walker in the Great Seal Patent Office
on the 4th November 1870.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, DAVI 30
WALKER, of Leith, in the County of Mid Lothian, North Britain, Engineer,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Sixth day of May, in the year of our
Lord One thousand eight hundred and seventy, in the thirty-fourth 3

page_text: year of Her reign, did, for Herself, Her beirs and successors, give and
grant unto me, the said David Walker, Her special licence that I, the
said David Walker, my executors, administrators, and assigns, or such
others as I, the said David Walker, 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, exercise, and vend, within the United
Kingdom of Great Britain and Ireland, the Channel Islands, and Isle of
Man, an Invention for "IMPROVEMENTS IN APPARATUS OR ARRANGEMENTS FOR
PREVENTING OR REDUCING THE PRODUCTION OF SMOKE IN FURNACES," upon the
condition (amongst others) that I, the said David Walker, 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 Seal. Patent
Office within six calendar months next and immediately after the date of
the said Letters Patent.
NOW KNOW YE, that I, the said David Walker, 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 in writing, reference being had to the accompanying
Drawings, that is to say :-
My said Invention has for its object to prevent or reduce the
production of smoke in furnaces, and it consists in causing air to
traverse piping in the flue leading immediately from the furnace and
then to issue amongst and mingle with the fire gases at the back or
inner end of the furnace. Numerous plans have been tried for reducing
or preventing smoke in which air has been introduced amongst the
fire gases at the inner end of the furnace, and in many of these plans
the desirability of heating the air so introduced has been recognised, but
such heating has been effected by what is termed "waste" heat, that is
to say, either by the comparatively cool fire gases after they have
traversed the flues through or in contact with the boiler or object which
the furnace has to heat, or by heat unavoidably radiated through the
outer walls of the flues. I, however, consider that air so heated by
mere "waste" heat as referred to, cannot be thereby sufficiently heated
for effecting the desired object of preventing smoke in the best and most
certain manner, and so as to economise coal, as any efficient smoke

page_text: preventing arrangement ought to do. Therefore by my present Invention
I ensure a thorough heating of the air to be introduced for perfecting
the combustion of the fuel gases by placing the air pipes or ducts in the
hottest part of the flues, and whilst it might seem at first sight that to do
so must cause the abstraction of heat (by the air) from the fire gases
before those gases have done all their possible duty upon the boiler or
other object, it must on the other hand be observed that such abstraction
of heat does not in reality occasion loss as it is wholly returned with the
air into the same flues.
And in order that my said Invention and the manner of performing
the same may be properly understood I have hereunto appended a Sheet
of explanatory Drawings to be herein-after referred to, and showing by
way of example the application of my improved arrangements in con-
nection with the furnaces of a steam boiler of a common type.
Figures 1 and 2 are respectively a longitudinal vertical section and a
transverse vertical section. The boiler 1 is a horizontal cylindrical one
with two large flues 2, and internal furnaces 3, the front and door of one
of the furnaces being supposed to be removed in Figure 2. Piping 4 of
cast iron or fire-clay is placed in the flue 2 so as to be exposed to the fire
gases when at their hottest, and air is made to traverse this piping and to
issue amongst and mingle with the fire gases just as they leave the
furnace 3. The air is made to traverse the piping 4 in the flues by
means of a fan 5 or other blowing apparatus, and when the furnace or
the furnace and steam boiler or other apparatus or object heated by it
are situated in a shed, building, or other enclosure, as shown in the
Drawings, so that the air over and about them is heated by radiation,
the blowing apparatus 5 is arranged to take up such heated air and force
it through the piping 4. The fan 5 is shown as driven by a belt 6 from
a pulley on a revolving shaft 7 supposed to be part of the machinery
driven by the engine supplied by the boiler 1, but it may in many cases
be more convenient to drive the fan or blowing apparatus by means
of a small donkey engine.
One fan or piece of blowing apparatus may be used to supply air to
two or more furnaces, each branch pipe 4 being fitted with a valve or
damper 8 to regulate the supply by it. A double or broad bridge 9, 10,
is constructed at the back or inner end of each furnace 3, and the
piping 4 leads the highly heated air into a space 11 formed in the lower
part of this bridge. One or more narrow slits or openings 12 in the top

page_text: of the bridge allow the air to issue from the space 11 below, and it mingles
with the fire gases as they pass over the bridge and insures the thorough
combustion of any incompletely burnt portions, the space over the
bridge, and more particularly above the inner part 10, being contracted
so as to compel a thorough intermingling of the heated air and gases.
With these arrangements' a sufficient quantity of thoroughly heated air
can be blown in to suit any condition of the fire so as to reduce the
production of smoke to a minimum, and so as to realise the economy in
fuel to be expected from the perfected combustion of the constituents
of the fuel. It has in practice been found sufficient to introduce into
the flues the comparatively short extent of air piping shown in the case
of steam boilers, such as the one shown, but the air piping may be
made to traverse the flues to any desired extent, provided that it is
finally led through the hottest flues prior to delivering the air at the
bridge 9, 10.
Having thus particularly described my said Invention and the manner
in which the same is to be performed, I have to state that I do not
restrict myself to the precise details herein described or delineated, and
that I do not claim every mode of using heated air for preventing smoke;
but that what I believe to be novel and original, and claim as the
Invention secured to me by the herein-before in part recited Letters
Patent is, the preventing or reducing of the production of smoke in
furnaces by means of improved apparatus or arrangements substantially
such as are herein-before described, and more particularly the placing of
the air piping in the hottest parts of the flues.
In witness whereof, I, the said David Walker, have hereunto
set my hand and seal, this Third day of November, in the year
of our Lord One thousand eight hundred and seventy.
80 Witness,
WILLIAM WILSON,
Swanfield Flour Mills,
Leith.
DAVID WALKER. (L.S.)