Improvements in and relating to the Furnaces and Flues of Hot Water Boilers and the like.
Year: 1897

page_text: Date of Application, 4th Nov., 1897-Accepted, 23rd July, 1898
[Communicated from abroad by STANBURY ARTHUR BUDDEN, Engineer, of New
York Life Building, Montreal, Canada.]
Improvements in and relating to the Furnaces and Flues of Hot
Water Boilers and the like.
I, JOHN WILLIAM MACKENZIE, of the Firm of Wheatley and Mackenzie, Engi-
neers and Patent Agents, 40, Chancery Lane, London, W.C., do hereby declare
the nature of this invention and in what manner the same is to be performed to
be particularly described and ascertained in and by the following statement:-
The object of my invention is to increase the efficiency of heating apparatus by
the more complete combustion of the fuel consumed, and applying the heat
generated to the greatest advantage.
In order to obtain this result, I employ a down draft grate, whereby the products
of combustion pass from beneath the grate to the flues and then to chimney. One
portion of the grate surface over an enclosed mixing chamber has an up draft, by
means of which air and gas are fed into the burning fuel. The heat of the fire
gradually converts the coal into coke and the gases which rise above the coal are
carried off and fed into the mixing chamber, where they are mixed with air
before passing into the fire. The area above the fire is closed in, except for the
flues which carry off the gas. An additional supply of air is admitted to the down
draft fire and fed into the burning coke just above the grate. bars from the sides
of the fire box. The object in view being to separate the constituents of the coal,
volatile and solid, and burn them at their highest efficiency. The mixing of air
with the gas before feeding to the fire reduces the quantity of air required for com-
plete combustion, and results in obtaining much higher temperatures than from
the usual methods. The combustion is more perfect, and the products are very
clean and most efficient. In order to illustrate the invention, 1 will describe the
application of it to a steam boiler of the ordinary return tubular type. It is
equally applicable however, to every form of heating apparatus, or fuel consumers.
Reference is made to the annexed drawings, in which like signs represent like
parts.
Fig. 1 is a sectional elevation on the line - Fig. 2.
Fig. 2 is a horizontal section, one half at the level q-q, the other half at the
level R-R of Fig. 1.
Fig. 3 is a sectional elevation on the line y-y Fig. 1.
Fig. 4 is a sectional elevation on the line - Fig. 1.
The ash pit is divided by the division walls 4" 4" into 3 compartments, the
middle one of which is closed up at the back end by the bridge wall 2", while the
side compartments 77 which are combustion chambers open into the flame bed 11.
The space 1 over the grate is closed in by the wall 2, at the back, and the side
walls 1b, 1 the front 1d and the roof or boiler 10.
Flues 33 lead from the upper part of the chamber 1ª to the middle compartment
or mixing chamber, 4 air inlets thereto are shewn at 9.
Above the grate in the walls 1° 1° are the air inlets 8.
The grate consists of the dry bars 5 over the mixing chamber and the water
grate, 6 over the combustion chambers 7 7, with the header, 6ª, which is divided,
the inlet pipe 6³ feeding the lower bars, and the outlets Cº leading back to boiler

page_text: from the upper bars. Bends 6d connect each pair of water bars, at the front of
the grate.
Other forms of water grates may be adapted to the system, but I have found
this to work well in practice.
The operation of the apparatus is as follows:-
The ordinary draft circuit is from above the grate, down through the grate
bars, 6 through the combustion chamber, 7, and thence through the flame bed or
flues to chimney. To this extent the device is similar to other down draft furnaces.
The coal which is above the fire in actual combustion is gradually coked, and
the gases which are given off in the chamber 1ª are carried off by the flues 33
into the mixing chamber 4, and with the addition of air from the inlets 9, they are
fed up through the grate bars 5 into the burning coke, and are consumed in the
down draft fire. By means of the air inlets 8, and the surplus air entering through
the mixing chamber 4, the coke is supplied with the necessary amount of air, and
the draft being local near the grate does not exhaust the chamber 1" directly to
chimney.
The draft circuit from the chamber 1 through the flues 33 to mixing chamber 4
is perfectly independent of, and distinct from the ordinary chimney draft. That
this is the case, is clear, for the flues 3 may be closed and the gas in chamber 1"
led off and used separately or collected, and air alone fed into the mixing
chamber 4.
All the air and gas fed to the fire must pass through the burning coke on the
grate, and the combustion is most complete and a very high temperature attained.
The flame which passes from the combustion chamber 7, to the flame bed 11,
is a transparent and clear flame, and carries with it a minimum of solid matter,
and the result is perfect smokelessness, and the absence of the deposit of carbon
in the flues.
By means of dampers, 8ª, 9ª & 13 to the air inlets, and the chimney draft, the
rate of combustion is readily controlled, and the excess of air required is reduced
to a minimum.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is:
1. A method of burning fuel in which the volatile gases above the fuel on a
down draft furnace are drawn off, mixed with air and fed into the burning fuel.
2. In a heating apparatus, a down draft grate, air inlets above the same, a closed
chamber over the fire box with one or more flues leading therefrom to a mixing
chamber to which there are also air inlets and openings from mixing chamber to
the area of combustion.
3. In a heating apparatus, a grate consisting of two portions, one of which is a
down draft water tube grate over a combustion chamber leading to chimney, the
other is a dry bar up draft grate over a mixing chamber. A closed chamber over
the grate area with flues connecting such chamber with the mixing chamber.
Air inlets to down draft grate and also to mixing chamber as described.
4. In a heating apparatus, a draft circuit independent of and distinct from a
fire outlet from furnace to chimney.
5. The method of drawing the volatile gases from above the fuel in a heating
apparatus, and feeding them with the addition of air to the burning fuel by a
draught circuit, independent of the draught to chimney.
Dated this 4th day of November 1897.
WHEATLEY & MACKENZIE,
40, Chancery Lane, London, W.C., Agents.