AN IMPROVED METHOD OF HEATING ZINC-FURNACES
Year: 1882

page_text: LETTERS PATENT to William Robert Lake, of the Firm of Haseltine, Lake,
& Co., Patent Agents, Southampton Buildings, London, for an Invention
of "AN IMPROVED METHOD OF HEATING ZINC-FURNACES." A communica-
tion from abroad by La Société Oeschger Mesdach & Cie., of Paris, France,
Manufacturers
COMPLETE SPECIFICATION filed by the said William Robert Lake at the
Office of the Commissioners of Patents on the 15th March 1882.
WILLIAM ROBERT LAKE of the Firm of Haseltine, Lake, & Co Patent Agents,
Southampton Buildings, London. "AN IMPROVED METHOD OF HEATING ZINC-
FURNACES." A communication from abroad by La Société Oeschger Mesdach et Cie
of Paris, France, Manufacturers.
This Invention relates to an improved method of heating, by means of gas, furnaces
employed for the reduction of zinc ores; it consists chiefly in a distribution of the
combustion of the gas effected by means hereinafter described.
The combustible elements of gas, produced in a gas generator separated from the
reducing furnace, are burnt successively at several places in combustion chambers of
peculiar construction for the purpose of obtaining the greatest possible uniformity of
temperature in all parts of the furnace, and the degree of temperature most suitable
for the reduction of the zinc, without there being, at any part in the principal
furnace too intense a combustion, even at that part where the gas enters the
furnace. The gas-generator may be of any kind; and all the heating is effected
under the natural draught of a chimney. This application of the gas is in itself
very simple and does not require a special regenerator of heat.
In carrying the said Invention into practice a gradual and regular combustion
of the gas is effected in several combustion-chambers arranged in such a manner as
to obtain within each of them the precise degree of temperature required for the
reduction of the zinc. For this purpose I not only regulate the quantity of air
introduced into each combustion-chamber, but I also regulate the temperature of
the air which is introduced to assist in the combustion of the gas, and this regulation

page_text: forms an important feature of the said Invention. At the part where the gas enters
the furnace, and where, in the methods hitherto employed a combustion, is produced
which is too intense for the end to be attained in zinc-furnaces I moderate, to a
suitable degree, the intensity of the combustion by admitting cold air at this
point.
The employment of cold air introduced into the gas in thin flat jets or sheets
and in moderate quantities, prevents the production of too high a temperature,
within certain limits, and effects the combustion of the gas in long flames, at a
moderate temperature which envelop the crucibles or muffles. Along the passage
of the gaseous current thus inflamed, and in the other combustion-chambers, where
it is designed to successively consume the other portions of the combustible elements
contained in the gas and for the purpose of continuing as much as possible the
production of long flames, I introduce gradually and in suitable quantities, air,
more and more highly heated as the quality of the gas and its richness in combustible
elements diminish.
The arrangement of the inlets for air into the combustion-chambers is effected in
such a manner as to avoid any jets of flame being directed against the crucibles or
muffles. The power of production of the gas-generator is regulated in such a manner
that, in the last part of the furnace, as well as in the first compartiment, the degree of
temperature developed may be suitable for the reduction of the zinc. This method
of distributing the air, which is cold, at first, and may be more and more highly
heated as the gas loses its combustible elements, also forms an important feature
of the said Invention.
Generally in the other methods of heating, and especially in the methods of
heating by gas, hitherto employed for zinc-furnaces, the action of the fire is greatest
in the first part of the furnace; and subsequent inlets for air (when such are
used) along the passage of the gaseous current, are only for the purpose of rendering
the combustion as complete as possible, with a view to economy of fuel and to
consume those portions of the combustible elements which may have escaped the
action of the first or principal fire. In the method of heating zinc-furnaces by gas
as herein described the combustion of the gas is effected in several fire-boxes or
centres of combustion, each of which is in the manner described of nearly equal
importance.
In the accompanying Drawing are shewn two arrangements of furnaces to which
the said Invention may be applied as hereinafter described to obtain a regular and
uniform distribution of the heat in the furnace; these two arrangements are
included in my Invention as particular applications of my method of heating.
Figure 1 represents a longitudinal section shewing the first of these arrangements.
Figure 2 is a sectional plan, and,
Figure 3 is a transverse section of the same.
Figure 4 is a longitudinal section shewing the second arrangement.
Figure 5 is a transverse section through the first compartment, and
Figure 6 is a transverse section through the second compartment.
The first arrangement shewn in Figures 1, 2, and 3, consists of two ordinary
"Liegeois" furnaces placed back to back, the second furnace being heated by flames
descending from the first. This general arrangement (one of those which Siemens
has adopted for some time, for the application of his special method of heating by
gas) has appeared to me to be suitable for the application, under the most simple
form; of my principles of combustion. I have shewn two combustion-chambers
but, the method may be carried out in the same way and the same results be
obtained by other forms of furuaces in which three or four combustion-chambers
are used.
As a second example of the application of my method I have shewn in Figures
4, 5 and 6 an arrangement of apparatus for a furnace with one face composed of
four compartments having each a special combustion-chamber, the first and the
third being heated by ascending flames; and the second and fourth by descending
flames.

page_text: Another very suitable arrangement, also included in my Invention, as an applica-
tion of my method, consists in a long furnace with one face divided into several
compartments by vertical partitions, and in which the flames follow a directly
horizontal course, passing through orifices made in the said partitions, these spaces
or compartments being transformed into successive combustion-chambers by the
distribution of air according to the method hereinbefore described.
In Figures 1, 2 and 3 A is a gas-generator which may be of any suitable kind
separated from the furnace, B is a conducting channel for the gas, C is an enlarge-
ment of this channel, for the purpose of spreading the gas into a sheet in the first
combustion-chamber D. E E are cast iron boxes with slides serving to regulate the
first admission of cold air, the said air being distributed in thin flat jets or sheets
by numerous openings F F F. The long flames thus produced rise and envelop
all the crucibles in the first part of the furnace, and pass by the longitudinal
opening I at the top of the partition wall, to descend into the second department.
These flames still possess the quantity of combustible elements necessary in order
that their complete combustion may permit of producing in the second compartment
the same conditions of temperature as in the first.
K is the second combustion-chamber. The distribution of air is there effected
by the openings L L L, and the air admitted is highly heated by its passage
through the channels or flues M M M. The arrangement of these channels or flues
is represented in its simplest form. The heating of the air designed to assist the
combustion of the gas is effected in the same manner as in other cases where hot
air is employed in furnaces that is by making it circulate around the pipes or flues
for the smoke or unconsumed gases, or within the hot walls or sides of the furnace
which may be cooled without inconvenience, but the arrangement of the channels
for the circulation of air may be varied and I do not attach any special importance
thereto. The products of combustion at the outlet of the furnace pass out by the
openings N N into the flue P, which conducts them to a chimney.
In Figures 4, 5 and 6 of the accompanying Drawing
B' is a conducting channel for the gas, C is the inlet for the gas into the
furnace, D is the first combustion-chamber, E¹ the inlet for the cold air, the air
being distributed by the openings F¹ F' F'. I is the passage for the flames
from the first compartment into the second. K¹ is the second combustion-chamber.
LL L' are the means for distributing the air in this second combustion-
chamber. I and I are passages for the flames from the second compartment into
the third and from the third into the fourth. K" K¹ are the third and fourth
combustion chambers. L L L and L L L are inlets for air into the third
and fourth combustion chambers. MM and M11 are channels or flues for the
circulation of air previously heated in any suitable manner and, as usual, by the
employment of the lost or waste heat. The air passed through the channel or
flue M into the second combustion chamber is moderately heated. The air passed
through the channel M is more highly heated and that which is introduced into
the fourth combustion-chamber by the channel M₁ is as highly heated as possible:
N¹ N are outlet orifices for the products of combustion, and P is the chimney-flue.
The furnace represented in Figures 4 and 5 comprises five rows of six crucibles
each. The front of the furnace is shown by the dotted lines. The cells or cases of
the front corresponding to the sixth row are closed by a front plate of fire-bricks
allowing access to the passage orifices and to the inlets for air. As already stated,
the gas-generator may be of any form; it works under a rather strong draught
and there should be maintained in it a suitable thickness of fuel which may be
rather thin. The form of the crucibles, the number of the same in each row, and
the number of such rows may be varied. It is evident that the distance of the gas-
generator from the furnace is arbitrary as well as the position of the chimney-
flue. The employment of cold air in the first part of the furnace allows of the
inspection of the colours of the flames in the adinission channel by the orifices
E E', and of ascertaining thereby the state of the gas-generator at any moment.
Having thus fully described the said Invention as communicated to me by my

page_text: foreign corespondents and the manner of performing the same I wish it understood
that I claim :
The method herein before described of heating zinc-furnaces by gas, for the
purpose of obtaining great regularity of heat in all parts of the furnace, the heat
being developed successively and the temperature maintained within the limits
suitable for the reduction of zinc, whereby the consumption of crucibles or muffles
is reduced and an improvement in the yield of zinc from the ore is obtained.
In witness whereof I the said William Robert Lake have hereunto set my
hand and seal this Fifteenth day of March in the year of our Lord
One thousand eight hundred and eighty two.