Improvements in Apparatus for and Process of Treating Zinc Ores.
Year: 1891

page_text: Date of Application, 20th Jan., 1891
Complete Specification Left, 20th Oct., 1891-Accepted, 21st Nov., 1891
PROVISIONAL SPECIFICATION.
Improvements in Apparatus for and Process of Treating Zinc Ores.
I, WILLIAM WEST of 527 Santa Fe Avenue, Denver, in the County of
Arapahoe and State of Colorado, United States of America, Chemist and
Metallurgist, do hereby declare the nature of this invention to be as follows
There are in many parts of the United States of America, especially in. the
West and South, large bodies of mineral composed of zinc and lead sulphides
carrying gold and silver with more or less iron and copper, which ores are almost
valueless owing to the presence of zinc. The smelting for silver is difficult in
the case of this combination and the lead hinders the use for smelting for zinc.
Many schemes have been devised to save the metals zinc, lead, gold, and silver.
My invention consists in a new apparatus for, and process of, working, these
ores, whereby the zinc is separated and recovered from the other metals as a
sulphite, in a single economical operation and the remaining metals left in good
condition for further treatment.
The furnace comprises a roasting chamber provided with a floor of tiling, a
fireplace placed midway of the ends of the furnace and at one side of the
longitudinal centre of the floor, and flues arranged beneath the floor and com-
municating with each other at their ends. The fire passes each way under the
bed by the front flues and returns by the back flues to the outlet to the chimney
stack. The furnace bed which is made of flanged tiles, has working doors through
which the ore is charged and raked. The sulphurous acid gas from the ore passes
to a dust chamber and from there goes to flués, formed by partitions and which
are covered with iron plates to form a drying floor for the ore after it leaves
the leaching tanks bereafter referred to and also a cooling chamber for the gas.
From these flues the gas passes to a pipe or pipes leading to the blower (which
pipe may be placed in a tank of water to further cool the gas before it enters the
blower) and this blower exhausts the gas from the furnace and forces it to the
ore tanks. From the blower the gas enters a pipe leading to a trunk with which
a steam, pipe is connected, through which steam.is forced into and mixes with
the gas in the trunk. From the trunk, short pipes convey the steam and. gas
under a false bottom in the leaching tanks where the ore is dampened and placed
to be treated. The temperature of the gas should be below 180° Fahrenheit.
When the ore is sufficiently acted upon, I immediately subject the ore to treatment
with water at a temperature less than 180° Fahr., which water is run upon the
ore and the soluble sulphite of zinc is leached out into a tank in the floor. The
liquor after settling is pumped to a tank where a stream of ammonia gas from
a still is introduced and precipitates the zinc as hydrated oxide. The liquor in
which the zinc is suspended is then run off into a tank where the hydrated.zinc
oxide deposits. The ammonia solution is syphoned off and sent back to the still
to be liberated by the use of lime and used on the next charge of zinc solution.
A-filter press is used to free the hydrated zinc oxide of the ammoniacal liquor.
The zinc is then dried and smelted in the ordinary way to metallic form.
•
In operating, my process with this apparatus a charge of ground ore is first
placed upon the tile hearth and the ore roasted till the zinc is in the form of
oxide. When the raw ore is placed upon the tile hearth it is generally of about
the following composition: silica 12%, lead 14%, zinc 26% to 30%, iron 12%
to 15%, copper 2%, and, as the metals are all in the state of sulphides; there is

page_text: from 27% to 30% of sulphur. The effect of the roasting upon these ingredients
is to convert the iron and zinc into oxides, with a very slight loss of zinc, the
proportion of zinc remaining being reduced to about 23% which involves only
about the usual loss of 3% to 7%. The lead and copper remain as partly
converted oxides and partly unacted-upon sulphides.
The above describes as
nearly as possible the condition of the charge when it leaves the furnace. This
charge is then removed and placed upon the false bottom of the tanks and
dampened. A new charge of ore is then placed on the hearth and while it is
being roasted the sulphurous acid gas is drawn off by the blower, reduced in
temperature below 180° Fahrenheit, and forced, at a pressure of about one pound
to the inch, in connection with steam, through the dampened ore in the tanks
until the oxide of zinc is converted into soluble sulphite of zinc. The object of
the steam is to keep the ore damp enough for chemical action to take place
between the gas and the oxide of zinc and also to keep the ore in a porous
condition so that the gas can penetrate it. Care should be taken to prevent air
from reaching the ore so as to avoid oxidizing the sulphite of zinc into sulphate.
The sulphite of zinc is then removed by successive leachings of warm water,
below 180° Fahrenheit. The remaining ore containing the other metals, is taken
out and put upon the drying floor where the heat of the hot gases in transit
serves to dry it for subsequent treatment in separation of the remaining metals.
The heat abstracted by this drying of the wet ore, also profitably serves to cool
the gases as they pass to the blower and thus prepare them for admission to the
leaching tanks. The charge from the hearth is then transferred to the tanks,
and a new charge placed upon the hearth and the triple operation of roasting the
ore, drying the residual ores of the previous charge, and eliminating the zinc from
the roasted ore in the tanks, is simultaneously carried on with a great economy
of working and very satisfactory results.
In defining my invention with greater clearness, I would state that I am aware
that it is not new to roast ores of the class I treat, and to take off the fumes of
sulphurous acid and make an aqueous solution of the same and then to treat this
roasted ore to successive leachings with this bulky solution of the gas in water,
to form a soluble sulphite of zinc. This process involves the use of a very large
amount of water with the incident cost of handling, the cost of evaporating so
large a bulk of solution and also the precipitation of a large amount of insoluble
matter back upon the ore being leached, as well as the objectionable conversion
of a large amount of the sulphurous acid into sulphuric acid by the water during
the time required for the successive leachings with the sulphurous acid solution.
All these objections are overcome by my process. I am also aware that sulphurous
acid gas from a charge of roasted ore in connection with binoxide of nitrogen and
steam, has been admitted in gaseous form to a roasted charge of ores for the
purpose of converting the oxides into sulphates, the commingled gases serving in
such case to convert the sulphurous acid into sulphuric acid before converting the
oxides into sulphates. This process is not designed for, nor applied to, the
separation of zinc ores as mine is and could not separate the zinc from the iron
and copper, for the reason that both the oxides of zinc and the iron and copper
would be converted into soluble sulphates by the sulphuric acid and all would be
leached out together, unseparated. By my process, the composition of sulphurous
acid is preserved without being allowed to reach, any higher oxidation and while
this sulphurous acid attacks the zinc oxide and makes a soluble sulphite of zinc
the iron and copper are unacted upon and hence a separation of zinc is at once
effected. I am also further aware that the sulphurous gas has been brought into
aqueous solution and put upon the roasted ore in tanks which are placed upon
the flues, through which the hot gases pass. In this case the presence of water
and heat together cause the salts that are formed to be sulphates, and this process
could not be applied to the separation of zinc, even if it were present, for the
reasons before given. I am also further aware that the ore has been reduced to

page_text: a matt or regulus and then introduced into a retort and the oxide acted upon by.
acids without reference to the separation of zinc, and I make no claim to such
process.
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1901
W..WEST.
By A. M. & Wm. Clark,
53, Chancery Lane, London, Patent Agents.
COMPLETE
SPECIFICATION.
Improvements in Apparatus for and Process of Treating Zinc Ores..
1, WILLIAM WEST of 527, Santa Fe Avenue, Denver, in the County of
Arapahoe and State of Colorado, United States of America, Chemist and
Metallurgist, 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 :-
There are in many parts of the United States of America, especially in the
West and South, large bodies of mineral composed of zinc and lead sulphides
carrying gold and silver with more or less iron and copper, which ores are almost
valueless owing to the presence of zinc. The smelting for silver is difficult in the
case of this combination and the lead hinders the use for smelting for zinc. Many
schemes have been devised to save the metals zinc, lead, gold, and silver.
My invention consists in a new apparatus for, and process of, working these ores
whereby the zinc is separated and recovered from the other metals as a sulphite, in
a single economical operation, and the remaining metals left in good condition for
further treatment.
The invention will be described with reference to the accompanying drawings,
forming part of this Specification, wherein
Figure 1 is a horizontal section, on line 1-1 Figure 2, of a furnace and
connections with the pressure blower which exhausts the gas from the furnace and
forces it to the ore tanks; and
Figure 2 is a vertical longitudinal section of the same, through line 2-2 Figure 1.,
Figure 3 is a horizontal section, through line y-y, Figure 4, of two tanks and
their connections for treating the roasted ore with the gas; and
Figure 4 is a vertical section of the same, through line x--x, Figure 3.
Figure 5 is a vertical sectional view of the precipitating apparatus.
A is the fireplace in the centre of the furnace, B are the flues which carry the
heat of the fire under the tile bed D upon which the ore is placed. The fire passes
each way under the bed, by the front flues B and returns by the back flues B' to
the outlet-flue C which leads to the chimney-stack. The furnace bed D, which is
made of flanged tiles, has working doors, marked D2, through which the ore is
charged and raked. The sulphurous acid gas from the ore, passing through the
flue E, enters the dust-chamber F and from there goes to the flues G formed by
partitions g and which are covered with iron plates P, thereby forming a drying
Hoor for the ore, after it leaves the leaching tanks, and also a cooling chamber for
the gas. From these flues the gas passes to a pipe or pipes H leading to the
blower, which pipe may be placed in a tank of water, to further cool the gas before
it enters the blower. I is this blower which exhausts the as from the furnace and
forces it to the ore tanks. From the blower the gas enters the pipe J leading to
the trunk K (Figure 3). A steam pipe L is connected to this part, through which
From the trunk K
steam is forced into, and mixes with, the gas in the trunk K.
are short pipes M which convey the steam and gas under the false bottom N in
the tanks where the ore is dampened and placed to be treated. The temperature
of the gas should be below 180° F. When the ore is sufficiently acted upon, I.

page_text: immediately subject the ore to treatment with water at a temperature less 180° F.,
which-water is run upon the ore and the soluble sulphite of zinc is leached out
into a tank in the floor but not shewn in the drawing. The liquor after settling in
the settling tank is pumped to tank P' (Figure 5) where a stream of ammonia gas
from still T through pipe U precipitates the zine as hydrated oxide. The liquor
in which the zinc is suspended is then run off into tank Q where the hydrated zinc
oxide deposits. The ammonia solution is syphoned off and sent back to still T to
be liberated by the use of lime and used on the next charge of zinc solution. R is
a filter press to free the hydrated zinc oxide of the ammoniacal liquor. The zinc
is then dried and smelted in the ordinary way to metallic form.
In operating my process with this apparatus, a charge of ground ore is first placed
upon the tile hearth D and the ore roasted till the zinc is in the form of oxide.
When the raw ore is placed upon the tile hearth D it is generally of about the
following composition: silica 12%, lead 14%, zinc 26% to 30%, iron 12%
to 15%, copper 2%, and as the metals are all in the state of sulphides there is
from 27% to 30% of sulphur. The effect of the roasting upon these ingredients
is to convert the iron and zinc into oxides, with a very slight loss of zinc, the
proportion of zinc remaining being reduced to about 23% which involves only
about the usual loss of 3% to 7% The lead and copper remain as partly
converted oxides and partly unacted-upon sulphides.
The above describes as
nearly as possible the condition of the charge when it leaves the furnace. This
charge is then removed and placed upon the false bottom N of tanks and
dampened. A new charge of ore is then placed on the hearth D and while it is
being roasted, the sulphorous acid gas is drawn off by the blower, reduced in
temperature below 180° F., and forced, at a pressure of about one pound to the
inch, in connection with steam, through the dampened ore in tanks until the
oxide of zinc is converted into soluble sulphite of zinc. The object of the steam
is to keep the ore damp enough for chemical action to take place between the gas
and the oxide of zinc and also to keep the ore in a porous condition, so that the gas
can penetrate it. Care should be taken to prevent air from reaching the ore, so as.
to avoid oxidizing the sulphite of zinc into sulphate. The sulphite of zinc is then
removed by successive leachings of warm water, below 180° F. The remaining
ore, containing the other metals, is taken out and put upon the drying floor P
where the heat of the hot gases in transit serves to dry it for subsequent treatment
in separation of the remaining metals. The heat abstracted by this drying of the
wet ore also profitably serves to cool the gases as they pass to the blower and thus
prepare t!.em for admission to the leaching tanks. The charge from the hearth D
is then transferred to the tanks O and a new charge placed upon the hearth and
the triple operation of roasting the ore, drying the residual ores of the previous
charge, and eliminating the zinc from the roasted ore in tanks O is simultaneously
carried on with a great economy of working and very satisfactory results.
In defining my invention with greater clearness, I would state that I am aware
that it is not new to roast ores of the class I treat and to take off the fumes of
sulphurous acid and make an aqueous solution of the same and then to treat this
roasted ore to successive leachings with this bulky solution of the gas in water to
form a soluble sulphite of zinc. This process involves the use of a very large
amount of water, with the incident cost of handling, the cost of evaporating so
large a bulk of solution, and also the precipitation of a large amount of insoluble
matter back upon the ore being leached, as well as the objectionable conversion of
a large amount of the sulphorous acid into sulphuric acid by the water, during the
time required for the successive leachings with the sulphurous acid solution. All
these objections are overcome by my process. I am also aware that sulphurous.
acid gas from a charge of roasted ore, in connection with binoxide of nitrogen and
steam, has been admitted in gaseous form to a roasted charge of ores for the purpose
of converting the oxides into sulphates, the commingled gases serving, in such case,
to convert the sulphurous acid into sulphuric acid before converting the oxides into

page_text: sulphates. This process is not designed for, nor applied to, the separation of zinc
ores, as mine is, and could not separate the zinc from the iron and copper for the
reason that both the oxides of zinc and the iron and copper would be converted
into soluble sulphates by the sulphuric acid and all would be leached out together,
unseparated. By my process, the composition of sulphurous acid is preserved
without being allowed to reach any higher oxidation and while this sulphurous
acid attacks the zinc oxide and makes a soluble sulphite of zinc, the iron and copper
are unacted upon and hence a separation of zinc is at once effected. I am also
further aware that the sulphurous gas has been brought into aqueous solution and
put upon the roasted ore in tanks which are placed upon the flues through which
the hot gases pass.
In this case the presence of water and heat together cause the
salts that are formed to be sulphates and this process could not be applied to the
separation of zinc, even if it were present, for the reasons before given. I am also
further aware that the ore has been reduced to a matt or regulus and then introduced
into a retort and the oxide acted upon by acids, without reference to the separation
of zinc, and I make no claim to such process.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, I declare that what I
claim is―
1. The process herein described of eliminating zinc from complex ores, as
described, which consists in roasting the ore to drive off sulphurous acid gas and
oxidize the zinc, then cooling this gas and simultaneously passing the sulphurous
acid in gaseous form in conjunction with steam and without oxidation into sulphuric
acid through a previously roasted charge, to form soluble sulphite of zinc without
forming soluble salts of the other metals and then immediately leaching out and
separating the zinc sulphite with water at a temperature below 180° F., as
described.
2. The process herein described of eliminating zinc from complex ores, which
consists in roasting the ore, passing the sulphurous acid gas arising therefrom in
conjunction with steam through a previously roasted charge, to form soluble sulphite
of zinc without forming soluble salts of the other metals and simultaneously drying
the leached ore residuum by the transit of the hot sulphurous acid gas and thereby
cooling said gas, substantially as shewn and described.
3. The furnace, comprising a roasting chamber provided with a floor of tiling,
flues B B longitudinally arranged beneath the floor and communicating with each
other at their ends, and a fire place A located half-way the ends of the furnace
beneath the floor and at one side of the longitudinal centre of the same and
communicating with the flue B whereby the hot gases of combustion are caused to
pass longitudinally outward from the fireplace through flues B and inwardly through
flues B to the stack, substantially as shewn and described.
4. The furnace, comprising a roasting chamber provided with a floor of tiling,
flues B B longitudinally arranged beneath the floor and communicating with each
other at their ends, and a fire place A located midway the ends of the furnace
beneath the floor and at one side of the longitudinal centre of the same and
communicating with the flues B, in combination with the chamber F arranged at
the end of the furnace and communicating with the space above the tile floor, and
the drying floor arranged at the end of the chamber F and composed of partitions g,
with flues G communicating with chamber F, and covering plates or tiles P,
substantially as shewn and described.
g
5. The combination, with a roasting furnace, of a drying floor arranged at the
end of the furnace and at or near the ground level, the said drying floor consisting
of tiles or plates P and sustaining partitions 9 forming flues communicating with
the furnace, the leaching tanks O with false bottom N, a blower I with pipes H J
interposed between the flues of the drying floor and the false bottom of the leaching
tanks, to draw the gases from the flues of the drying floor and force them beneath

page_text: the false bottom, and a steam pipe connected with the gas-pipe leading beneath the
false bottom, substantially as shewn and described.
Dated this 20th day of October 1891.
By A. M. & Wm. Clark,
W. WEST.
53, Chancery Lane, London, Chartered Patent Agents.