Improvements in Superheaters.
Year: 1895

page_text: Date of Application, 10th June, 1895-Accepted, 13th July, 1835
COMPLETE SPECIFICATION.
Improvements in Superheaters.
1 JAMES YATE JOHNSON of 47, Lincoln's Inn Fields in the County of
London, Gentleman do hereby declare the nature of this invention (which has
been communicated to me from abroad by the Firm of Carl Pieper of 40 Hindersin-
strasse 3 Berlin in the Empire of Germany, Engineers) and in what manner the
same is to be performed to be particularly described and ascertained in and by the
following statement:-
The inconvenience hitherto experienced in superheating steam or gas by the
direct action of the fire arises from the fact that the gaseous products of combustion
evolved above the grate are too hot to be capable of being conducted along the
heating surfaces of the superheater without injury to the material thereof. In
consequence of this the said gaseous products have hitherto been cooled by cold
air mixed with the said products behind the fire-bridge, but this method of cooling
makes it very difficult to take full advantage of the heat generated, the whole
furnace arrangement being caused to operate under unfavourable conditions as the
quantity of air which escapes into the chimney at the high temperature required
for sustaining the chimney draught is far greater than is necessary for total
combustion.
The object of this invention is to avoid such loss of heat the products of
combustion being cooled in the rear of the fire bridge by cold air; not however
by mixing such air with the said products but by surface transmission, so that the
air remains fit for subsequent utilization of the heat absorbed by it.
In the arrangement shewn in vertical section in the accompanying drawing the
grate whereon the fuel is burnt is shewn at a. The volatile products of combustion
on their way to the chimney envelope the tubes or flues situated behind the fire
bridge. Air is passed through the said tubes 6 and the said air takes up from the
products of combustion an amount of heat which may be determined at will by
correspondingly proportioning the extent of the heating surface. The products
of combustion, on being thus slightly cooled, thence pass on to one portion c of
the superheater, and thence escape into the chimney. The air heated within the
tubes 6 is conducted to another portion d of the superheater, being at the same
time cooled down again as far as practicable. The heat which may not be utilized
here, may be made serviceable by conducting the hot air, after it has left the
portion d of the superheater either through the air conduit e to beneath the grate
or into the chamber beneath the tubes or flues b to pass again therethrough. The
steam to be superheated may pass through the superheater coils c and d either
simultaneously or successively that is to say first through the coil d and theu
through the coil c and it may pass through the coils either in reverse direction to
that of the heating gases or in the same direction as that of the heating gases
which gases preferably enter the superheating chambers at the bottom and escape
at the top as shewn.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed I declare that what I
claim is:-
1. In superheaters, air passages passing through the flue leading from the fire
place to a superheater chamber and opening into another superheater chamber
so that the products of combustion lowered in temperature by contact with the

page_text: said air passages enters one superheater chamber and the air heated by the contact
with the said air passages passes into another superheater chamber substantially as
herein before described.
2. A superheater arranged substantially as herein before described so that the
products of combustion from the fire lose part of their heat before they reach the
superheater proper; such heat being absorbed by air by means of surface trans-
mission; the air thus heated being conducted to a second superheater proper, and
then after having been partially cooled down in contact with the last mentioned
superheater either passing to beneath the fire place or being returned to re-absorb
heat from the products of combustion.
3. The arrangement and combination of parts constituting a superheater
substantially as hereinbefore described and illustrated in the accompanying
drawings.
Dated this 10th day of June 1895.
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.