IMPROVE- MENTS IN THE MANUFACTURE OF ZINC, AND IN THE APPARATUS EMPLOYED THEREIN
Year: 1850

page_text: BROOMAN'S SPECIFICATION
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, RICHARD
ARCHIBALD BROOMAN, of the firm of J. C. Robertson and Co., of 166, Fleet
Street, in the City of London, Patent Agents, send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Royal Letters Patent under the Great Seal of the United Kingdom of Great
Britain and Ireland, bearing date at Westminster, the Twentieth day of April,
One thousand eight hundred and fifty, in the thirteenth year of Her reign, did,
for Herself, Her heirs and successors, give and grant unto me, the said
Richard Archibald Brooman, my exors, admors, and assigns, Her especial
licence, full power, sole privilege and authority, that I, the said Richard
Archibald Brooman, my exors, adñors, and assigns, or such others as I, the
said Richard Archibald Brooman, my exors, admors, or assigns, should at any
time agree with, and no others, from time to time and at all times during the
term of years therein expressed, should and lawfully might make, use, exercise,
and vend, within England, Wales, and the Town of Berwick-upon-Tweed, and
in the Islands of Guernsey, Jersey, Alderney, Sark, and Man, and also in all Her
said Majesty's Colonies and Plantations abroad, an Invention for "IMPROVE-
MENTS IN THE MANUFACTURE OF ZINC, AND IN THE APPARATUS EMPLOYED THEREIN,"
communicated to me by a certain foreigner residing abroad; in which said
Letters Patent is contained a proviso, that I, the said Richard Archibald
Brooman, shall cause a particular description of the nature of the said
Invention, and in what manner the same is to be performed, by an instrument

page_text: in writing under my hand and seal, to be inrolled in Her said Majesty's High
Court of Chancery within six calendar months next and immediately after the
date of the said in part recited Letters Patent, as in and by the same, reference
being thereunto had, will more fully and at large appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
Richard Archibald Brooman, do hereby declare that the nature of the said
Invention, and in what manner the same is to be performed, are fully described
and ascertained in and by the present Specification thereof, reference being had
to the Drawings hereunto annexed (that is to say) :-
The said Invention has for its object to do away with the troublesome and
expensive preparatory processes of assorting, pounding, and crushing, now
ordinarily followed, in order to the extraction of zinc from its ores, and to
effect such extraction by direct reduction from the ores; and the manner of
performing or accomplishing the said object is as follows:-
The Inventor employs for the purpose a smelting furnace of the improved
.description represented in the Drawings hereunto annexed, Figure 1 being
a vertical section of the same on the line A, D, of Figure 2, which is a
ĥorizontal section on the (dotted) line A, B, C, D, of Figure 1. C¹ is the
hearth of the furnace; T', T¹, T', are the tuyeres, which are three in number;
N is the shoot; U, the chamber of the furnace. (So far the parts of the
structure are very similar to those of a small blast furnace). At I, K, the
upper part of the chamber U is suddenly contracted, so as to form a
neck V, or narrow passage, constituting the upper part of the furnace. The
charge as it falls through this neck leaves necessarily a vacant annular
space at x, x, between it and the sides of the furnace, where the volatilizable
matters may collect. F, F, are four rectangular passages formed of cast
or sheet iron, which lead off at right angles and in an inclined direction
from the annular space x, x, and each passage is encased for a certain
distance within a chamber G, through which cold water is kept continually
circulating, flowing in from the tube P, Q, R, and escaping through the
pipe S, S. At the lower end of each of the rectangular passages there
is a tubular passage A¹, by which the uncondensed gases of the furnace
aré carried off to different points to be employed for heating purposes,
as herein-after. explained, and each passage (F) is provided at its lower end
with a sliding door A, by which it may be closed or opened as required. W
is a nd or cover, by which the furnace is closed at top, and which fits into a
groove made for it, so that there may be no escape of the gases at that part.
All the interior parts of the furnace are formed of fire-brick, with an outer wall

page_text: or casing V¹, which may be made of ordinary brick, and between the outer and
inner walls there is left a space Z, Z, which is filled with some substance which
is a bad conductor of heat. H, H, are strengthening plates of cast iron,
which are inserted into the lower brickwork V¹ immediately over the tuyere
openings E', E'; L', are cast-iron frames, which carry the passages F, F,
and cold-water chamber G. The mode of operating with the apparatus is as
follows: After the furnace has been built it is left to dry for some time, then
a fire is kindled on the hearth, and kept up for about three weeks by supplies
of fuel (by preference coke) introduced through the throat. The furnace
being in this manner filled with incandescent fuel, a small charge of quick-
lime is thrown in; as soon as this charge has descended as far down as the
tuyeres, a mixture of ore, flux, and fuel is fed into the furnace, the top of the
furnace closed and a moderate blast of atmospheric air applied by means of a
blowing machine. The fuel, the flux, and the ore are in such proportions to
one another that the whole of the zinc contained in the ore shall be reduced
and then volatilized, while all the foreign matters shall form with the flux
a residual slag of more or less fluidity when in the heated state. The fuel
employed may be either charcoal, or coke, or common coal, or anthracite, or
turf, taking care always that it is of a sufficiently hard nature to resist the
incumbent pressure of the charge in the furnace.
The quantity of fuel employed should be greater at the commencement than
during the subsequent stages, and should in all cases be sufficient not only
for the complete reduction of the zinc, but also to leave so considerable an
excess, that when it arrives directly before the twyers the combustion of the
fuel shall not give rise to any gaseous oxydating product, such, for example,
as carbonic acid. The flux (the selection of which as well as that of the fuol
depends on the quality of the ore) must be used in such a state as not to
produce any oxydating matter during the formation of the slag. For this
reason, when the nature of the ore requires the employment of lime as a flux
the lime should be used in a caustic state, and not as a carbonate, and for the
same reason it is advisable to use a blast of dry air, that is to say, air deprived
of aqueous vapour. The products of the furnace are, in the first place, the.
gases arising from the combustion of the fuel; secondly, the vapours of zinc;
thirdly, the non-volatilizable matters, consisting of scoria or slag, and of reduced
metallic substances of greater density than the zinc. The throat of the furnace
being closed, the gases arising from the combustion of the fuel pass off through
the passages A', and are made use of either for the purpose of heating the
boiler of the steam-engine which drives the blowing machine, or to burn lime.

page_text: when used for a flux, or to melt the zinc which is carried over in a state of
vapour, or to dry and roast the ores. The vapours of zinc are condensed in
the passages F, F, and may be easily withdrawn therefrom by means of a
rake, (the rectangular form of the passages F, F, affording great facilities for
this purpose,) after which they are reduced and formed into ingots or bars, the
-non-volatilized or residual matters which collect on the sole or hearth of the
furnace are run off from time to time according as they accumulate. The ores
containing zinc may be divided into two classes: firstly, those in the state
of oxide, either free or combined with carbonic or silicic acid; secondly,
those containing sulphuret of zinc (blende). When the ores are of the
first class (oxides) they are first dried, and if they contain a carbonate they
are subjected to a roasting process. The flux employed for the treatment
of ores of this class is quicklime, the quantity of which varies according
to the quantity of carthy matters contained in the ore, but should be sufficient
for the formation of a bisilicate, or, as it is commonly called, a good slag
("laitier"). When the ores contain any other metals, such as iron or lead, these
metals are reduced to the metallic state, when they collect on the earth of the
furnace where they arrange themselves in different strata, according to their
respective densities, and may be drawn off separately. When the ores are of
the second class (blende) they are treated in one of two ways, either by roast-
ing, which brings them into the state of oxide, which oxide is then mixed with
a little damp clay and formed into blocks, which (after being dried) are treated
in the manner before described; or (which is considered the preferable way)
these sulphurous ores are mixed with a quantity of iron ore, so that when the
metals are fused the iron shall combine with the sulphur and set the zinc at
liberty. The flux employed in this case is quicklime, and if the ore contain
a portion of baryta or gypsum then fluorine is added; the quantity of quick-
.iime employed depends on the quantity of earthy matters contained both in
the zinc and iron ores. The iron ore best suited for this purpose is that con-
taining zinc, but in too small a quantity to be treated, separately as a zinc ore.
When, however, the iron ore contains water or carbonic acid, it is necessary
that these should be expelled by roasting, in order that no substance susceptible
of oxydizing the zinc way may be introduced into the furnace. If the iron ore
I contain too great a quantity of oxidating matter, then it is preferable to expel
the sulphur. from the zinc ore by means of cast iron or malleable iron. This
plan presents the advantage of driving off the whole of the substances capable
of re-oxydizing the zinc which has been reduced. When a sulphuret of zinc in
which there are several other metals, such as iron, copper, lead, silver, &c., is

page_text: treated in the furnace, there collects on the hearth, besides the slag, a stratum
of argentiferous lead, on which is superimposed a stratum of cast iron, arising
from the excess of iron ore used in the process. Again, above the stratum of
iron there collects a mass composed principally of sulphuret of iron, sulphuret
of copper, and portions of the sulphurets of other metals. If white, grey, or
yellowish oxide of zinc should be formed accidently in the passages F, F, it can
be made use of directly as a colouring matter, and sold as such, or else it can
be mixed with damp clay made up into blocks, dried and again passed through
the furnace, in which case a sufficient quantity of quicklime should be added
to convert all the clay into a fusible slag. When ores containing zinc in a
state of oxide have to be treated, they should be previously assayed, in order to
effect an analysis, and to ascertain the quantity of earthy matters contained
therein capable of being converted into scoria, which will determine the proper
proportion of quicklime to be added. The lime and magnesia contained in the
ore are also to be taken into account.
When ores containing zinc in the state of sulphurets have to be treated,
the quantities of sulphur, earthy matters, and metallic substances contained
therein should also be ascertained by preliminary assay, so that the quan-
tity of iron ore used in the charge shall be sufficient to produce the cast iron
requisite for combining with all the sulphur that may be in the zinc. In
order that the combination of the sulphur and iron may be the more com-
pletely effected it is advisable to employ a slight excess of iron ore;
but if there should be reason to apprehend that the iron ores might pro-
duce too great a quantity of oxydating matter, and thereby create too great
a quantity of oxide of zinc, then cast or malleable iron may be directly used
for the purpose of combining with the sulphur, in which case the proportion
of cast or malleable iron is to be determined by the quantity of sulphur
contained in the ore, always employing a slight excess of the iron. The
proportion of quicklime or fluorine used for making a fusible slag will depend
on the quantity of earthy matters contained in the ore to be treated, as well
as in the iron ore, when used for combining with the sulphur. The quantity
of fuel employed in this case depends not only on what has been already stated,
but also on the richness and fusibility of the iron ores, and in all cases should
be so regulated that the working of the furnace shall in all respects resemble
that of a blast furnace for casting purposes. As sulphuretted ores contain
generally other metallic substances besides zinc, a great quantity of reduced
metals, and of crude metals, composed principally of sulphuret of iron, will
collect on the hearth of the furnace, and combine with the sulphuret of copper,

page_text: and a portion of the sulphurets of the other metals. In this case, therefore, it is
better to run off the metal more frequently than in the preceding cases. The
lead thereby obtained can be recast into pigs ready for sale, or submitted to
the process of cupellation if it should contain silver, and any other masses of
crude metal may be treated by any of the well-known processes in order to
extract the copper therefrom. As in the preceding cases, the whole of the
zinc will be volatilized and collected, and condensed in the passages F, F.
From the preceding description it will be seen that the distinguishing
features of the improved apparatus and process which form the subject of this
Invention are these:-
Firstly, the direct reduction of the ores of zinc by means of a smelting
furnace and blasting apparatus, without any previous assorting, pounding, or
crushing..
Second, the employment of a smelting furnace for this purpose of the реси-
liar description represented in the Drawings before described, that is to say, of
a furnace having a narrow neck or passage, by the descent through which of
the charge an annular space is formed around it in the top or crown of the
chamber of the furnace, where the vapours of zinc collect, but are prevented
by the heat from condensing, having also passages of a rectilineal form,
through which the vapours of zinc pass off to be condensed, a form which
allows of the rake traversing and completely clearing the passages from end to
end, and further condensing chambers, through which a current of cold water
is kept continually flowing, in order to aid the process of condensation.
Third, the avoidance of introducing into the furnace any substance capable
of re-oxydizing the zinc produced, which is effected by the selection of quick-
lime as a flux, by the drying and roasting of the hydrated and carbonated ores
of zinc and iron, by the drying (in certain cases) by means of hot blast, and
by the employment of cast or malleable iron, for the purpose of combining
with and (extracting) the sulphur contained in sulphuretted zinc ores.
Fourth, the direct treatment of blende which has not been roasted, and
the reduction thereof by means of the iron employed, that is, either the cast
or malleable iron, or the iron produced by the ore, which becomes converted
into cast iron or sulphuret of iron in the furnace itself.
Fifth, the peculiar method of treating sulphuretted or arseniuretted ores of
lead and copper containing zinc, whereby the zinc is separated from the other
metals and obtained in a metallic state.
And sixth, the method of turning the zinc contained in ores of iron to good
account without injuring the latter metal.

page_text: And having now described the nature of the said Invention, and the
manner in which the same is performed, I declare that the improvements
claimed under this Patent are as follows:-.
First, the direct reduction of zinc from its ores by means of the apparatus
and processes (all or any of them) before described.
And, second, the peculiar construction of smelting furnace, before described.
In witness whereof, I, the said Richard Archibald Brooman, have here-
unto set my hand and seal, this Nineteenth day of October, in the
year of our Lord One thousand eight hundred and fifty.