IMPROVEMENTS IN THE MANUFACTURE OF ZINC WHITE AND METALLIC ZINC, AND IN APPARATUS TO BE EMPLOYED IN MANUFACTURES.
Year: 1880

page_text: LETTERS PATENT to Sydney Pitt, of Sutton, in the County of Surrey, for
an Invention of "IMPROVEMENTS IN THE MANUFACTURE OF ZINC WHITE
AND METALLIC ZINC, AND IN APPARATUS TO BE EMPLOYED IN
MANUFACTURES.' A communication from abroad by Henri Guillaume
Harmet, of Denain, Department of Nord, in the Republic of France.
"
SUCH
PROVISIONAL SPECIFICATION left by the said Sydney Pitt at the Office
of the Commissioners of Patents on the 17th March 1880.
SYDNEY PITT, of Sutton, in the County of Surrey. "IMPROVEMENTS IN THE
MANUFACTURE OF ZINC WHITE AND METALLIC ZINC, AND IN APPARATUS TO BE
EMPLOYED IN SUCH MANUFACTURES." [A communication from abroad by
Henri Guillaume Harmet, of Denain, Department of Nord, in the Republic of
France.]
This Invention has for its object improvements in the manufacture of zinc
white and metallic zinc, and in apparatus to be employed in such manufactures.
For the continuous and economical production of zinc white a furnace is employed
consisting of the following parts:
It has a cylindrical upright barrel in which the ore is reduced under the influence
of carbonic oxide and carbon. Below the barrel there is a funnel like part in
which a highly elevated temperature is maintained and in which the zinc is
volatised. The volatilizing zone of the furnace communicates at the bottom with
a receptacle or crucible which receives the slag resulting from the fusion of the
gangue and flux.
Where the barrel of the furnace terminates and the volatilizing zone commences
two orifices are formed on opposite sides of the furnace, and by these the volatile
matters pass out into burners or conduits within which the zinc vapour is burned
or oxidised into zinc white. At the upper part of the barrel two or more twyeres
are provided, and by these a blast, by preference of heated air, is thrown in. Thus
a portion of the combustible in the upper part of the barrel is burnt and the.
contents are raised to a sufficiently high temperature to effect the reduction.
very uniform temperature can thus be maintained throughout the mass.
A

page_text: The furnace is almost completely closed at the top and the products of com-
bustion mainly descend, only a very small part is permitted to escape at the top.
A highly reducing atmosphere is maintained in the lower part of the barrel by the
excess of combustible which is there present.
The roasted ore, together with the flux and the combustible, by preference wood
charcoal, are charged in suitable proportions into the furnace by a central hopper
furnished with double covers to prevent any large escape of gas in charging.
A small sounding hole is provided at the side of the hopper, affording at any
moment information respecting the descent of the materials in the furnace; this
hole also permits the escape of a small quantity of gas, which facilitates the
heating of the combustible and the ignition of the gas in front of the twyeres.
The proportion of combustible and of blast thrown in by the upper twyeres is
such that a complete reduction is obtained by the time the charge reaches the
bottom of the furnace barrel, leaving besides such an excess of combustible as
suffices to raise the temperature to the degree requisite for volatilization.
The descending current of gaseous liquid and solid matters passing from the
bottom of the barrel into the volatising zone of the furnace meet the highly heated
gaseous products generated by the active combustion in the volatilising zone, and
thus their temperature is greatly raised; all the volatile matters, the metallic zinc
included, pass off by the side orifices, whilst the solid matters continue their
descent towards the lower twyeres in the crucible portion of the furnace, and here
the combustible is completely consumed and the gangue is melted.
The refractory lining of the furnace may be of any suitable material, but
a basic lining is preferred, and the slags should be kept as little acid as possible.
The matters issuing from the side apertures consist principally of oxide of carbon,
carbonic acid, zinc vapour, and dust of various sorts, and with these matters a
small quantity of oxide of zinc is already mingled if the twyeres of the crucible are
at all near to the orifices by which the gases pass out.
Each of the orifices opens into a large burner trunk in which several twyeres are
arranged directed different ways, and these introduce air, by preference cold and
moist air, at a pressure sufficient to carry the products forward into the ordinary
depositing chambers.
The pressure in the furnace, in the burners, and in the depositing chambers is
kept sufficiently high to compel all the gaseous products to pass through the sacks
of woven fabric in which the chambers terminate without its being necessary to
employ a fan.
When it is desired to obtain metallic zinc a somewhat different arrangement is
employed; the vaporising zone or portion of the furnace is increased in depth, so
that the outlet orifices may be further removed from the crucible twyeres,
and so that a reducing region at a high temperature may exist between the
two.
The volatile products issuing from the side orifices enter two upright cylinders
charged with charcoal, which becomes highly heated and effects the reduction of
the whole of the carbonic acid into carbonic oxide, and the reduction of any traces
of oxide of zinc which may enter. These chambers are long and narrow so that
the volatile products cannot pass through them without being submitted to the
reducing action of the carbon.
The reducing chambers are charged from time to time, as may be required, through
hoppers at the top similar to the hoppers upon the barrel of the furnace, but the
sounding holes are stopped so as to prevent all escape of gas. Small apertures are
provided at the bottom, which can be opened from time to time for the insertion
of a rod to remove clinkers and ashes when necessary. The pressure of gas in the
interior of the side chambers is kept sufficiently high to prevent the entrance of
atmospheric air. The temperature is also elevated sufficiently to ensure that
the vapours on leaving shall pass forward into the condensor.
The condensor, with which depositing chambers may advantageously be combined,

page_text: separates the zinc from the carburated gases, and these are at once utilised in the
melting furnaces or in the hot blast stoves or otherwise.
Special features of the zine white furnace are the twyeres for forcing in air at the
upper part of the barrel of the furnace, whilst others force in air at the lower part
or crucible; the descending course of the greater part of the volatile matters
produced in the barrel; the sharp separation of the zones of reduction and of zinc
volatilization, each of these zones having its own independent source of heat; the
gas and vapour outlets situate between these two zones.
The employment of the basic lining and the but slightly siliceous slag; the
arrangement of the burners and dispensing with the need for a fan in the depositing
chambers..
Besides these, in respect to the furnace for producing metallic zinc, there is
the passage of the volatile products through long upright reducing chambers
charged with carbon.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Sydney Pitt in the Great Seal Patent Office on the 16th September
1880.
SYDNEY PITT, of Sutton, in the County of Surrey. "IMPROVEMENTS IN THE
MANUFACTURE OF ZINC WHITE AND METALLIC ZINC, AND IN APPARATUS TO
BE EMPLOYED IN SUCH MANUFACTURES." A communication from abroad by
Henri Guillaume Harmet, of Denain, Department of Nord, in the Republic of
France.
This Invention has for its object improvements in the manufacture of zinc
white and metallic zinc, and in apparatus to be employed in such manufactures.
For the continuous and economical production of zinc white a furnace is
employed such as is represented in section by Figure 1 of the annexed Drawings,
and consisting of the following parts:-
It has a cylindrical upright barrel C in which the ore is reduced under the
influence of carbonic oxide and carbon. Below the barrel there is a funnel like
part A in which a highly elevated temperature is maintained, and in which the zinc is
volatilised. The volatilising zone of the furnace communicates at the bottom with
a receptacle or crucible B which receives the slag resulting from the fusion of the
gangue and flux.
Where the barrel of the furnace terminates and the volatilising zone commences
two orifices o, o, are formed on opposite sides of the furnace, and by these the
volatile matters pass out into burners D, D, or conduits within which the zinc
vapour is burned or oxidised into zinc white. At the upper part of the barrel two
or more tuyeres T', T2, are provided, and by these a blast, by preference of heated
air, is thrown in. Thus a portion of the combustible in the upper part of the
barrel is burnt and the contents are raised to a sufficiently high temperature to
effect the reduction. A very uniform temperature can thus be maintained
throughout the mass.
The furnace is almost completely closed at the top and the products of com-
bustion mainly descend, only a very small part is permitted to escape at the top.
A highly reducing atmosphere is maintained in the lower part of the barrel by the
excess of combustible which is there present.
The roasted ore, together with the flux and the combustible, by preference wood
charcoal, are charged in suitable proportions into the furnace by a central hopper
furnished with double covers to prevent any large escape of gas in charging.
A small sounding hole is provided at the side of the hopper affording at any
moment information respecting the descent of the materials in the furnace; this
hole also permits the escape of a small quantity of gas, which facilitates the heating
of the combustible and the ignition of the gas in front of the tuyeres T', T².
The proportion of combustible and of blast thrown in by the upper tuyeres T¹, T²,
is such that a complete reduction is obtained by the time the charge reaches the
bottom of the furnace barrel, leaving besides such an excess of combustible as
suffices to raise the temperature to the degree requisite for volatilisation.
The descending current of gaseous liquid and solid matters passing from the
bottom of the barrel into the volatilising zone of the furnace meet the highly
heated gaseous products generated by the active combustion in the volatilising
zone A, and thus their temperature is greatly raised; all the volatile matters, the
metallic zinc included, pass off by the side orifices o, whilst the solid matters
continue their descent towards the lower tuycres T in the crucible portion B of the
furnace, and here the combustible is completely consumed and the gangue is
melted. When the object is simply the manufacture of zinc white the height of

page_text: the part A of the furnace may be decreased without much inconvenience so as to
bring the orifices o nearer to the oxidizing zone of the lower tuyeres T.
The refractory lining of the furnace may be of any suitable material, but a basic
lining is preferred, and the slags should be kept as little acid as possible.
The matters issuing from the side apertures o consists principally of oxide of
carbon, carbonic acid, zinc vapour, and dust of various sorts, and with these matters
a small quantity of oxide of zinc is already mingled if the tuyeres of the crucible T
are at all near to the orifices by which the gases pass out.
Each of the orifices o opens into a large burner trunk D, in which several
tuyeres t, t, are arranged directed different ways, and these introduce air, by
preference cold and moist air, at a pressure sufficient to carry the products forward
into the ordinary depositing chambers.
The pressure in the furnace, in the burners, and in the depositing chambers is
kept sufficiently high to compel all the gaseous products to pass through the sacks
of woven fabric in which the chambers terminate without its being necessary to
employ a fan.
When it is desired to obtain metallic zinc a somewhat different arrangement is
employed, such as is represented in section by Figure 2 of the annexed Drawings;
the vaporising zone or portion of the furnace A is increased in depth, so that the
outlet orifices o may be further removed from the crucible tuyeres T, and so that a
reducing region at a high temperature may exist between the two.
In this way
the descent of any of the metal to the lower tuyeres is prevented, and the
production of zinc white is avoided. An energetic combustion should be
maintained.
The volatile products issuing from the side orifices o enter two upright cylinders
K, K, charged with charcoal, which becomes highly heated, and effects the reduction
of the whole of the carbonic acid into carbonic oxide, and the reduction of any
traces of oxide of zinc which may enter. These chambers are long and narrow,
so that the volatile products cannot pass through them without being submitted
to the reducing action of the carbon.
Small
The reducing chambers are charged from time to time, as may be required,
through hoppers at the top similar to the hoppers upon the barrel of the furnace,
but the sounding holes are stopped so as to prevent all escape of gas.
apertures r, which can be stopped with clay, are provided at the bottom, which
can be opened from time to time for the insertion of a rod to stir the fire and cause
the descent of clinkers and ashes when necessary. The pressure of gas in the
interior of the side chambers is kept sufficiently high to prevent the entrance of
atmospheric air. The temperature is also elevated sufficiently to ensure that the
vapours on leaving shall pass forward by the inclined conduits V, V, into the
condenser.
The condenser, with which depositing chambers may advantageously be com-
bined, separates the zinc from the carburated gases, and these are at once utilized
in the melting furnaces or in the hot blast stoves or otherwise. All the materials
charged into the body of the furnace, and more especially into the reducing
chambers K, should be perfectly dry and free from all oxidising gas.
Special features of the zinc white furnace are the tuyeres for forcing in air at
the upper part of the barrel of the furnace, whilst others force in air at the lower
part or crucible; the descending course of the greater part of the volatile matters
produced in the barrel; the sharp separation of the zones of reduction and of zinc
volatilization, each of these zones having its own independent source of heat, the
reduction taking place in the barrel and the fusion of the slags in the part A ; the
gas and vapour outlets situate between these two zones.
The employment of the basic lining and the but slightly siliceous slag; the
arrangement of the burners, and dispensing with the need for a fan in the
depositing chambers.-
Besides these, and especially the important features consisting in the presence of
air tuveres in the upper part of the body, as well as in the crucible there is in

page_text: respect to the furnace for producing metallic zinc the passage of the volatile products
through long upright reducing chambers charged with carbon effecting the trans-
formation of carbonic acid into carbonic oxide, and the reduction of traces of zinc
white which might be formed in the part A. There is also the descending course
of the greater part of the volatile matters in the body of the furnace; also, the
sharp separation of the zones of reduction and of zinc volatization, which may be
considered, strictly speaking, as separate apparatus; also the employment of the
basic lining and the but slightly siliceous slag.
What I claim is the construction and employment in the manufacture of zinc
white and metallic zinc of furnaces, substantially as herein described.
In witness whereof, I, the said Sydney Pitt, have hereunto set my hand
and seal, this Fourteenth day of September, in the year of our Lord One
thousand eight hundred and eighty.