Year: 1896

page_text: Date of Application, 31st Dec., 1896
Complete Specification Left, 30th Sept., 1897-Accepted, 31st Dec., 1897
The distillation of zinc, which is the only method practically carried out, for
recovering zinc by dry process from its ores, comprises two parts:-
1. The separation of the zinc from the non-volatile constituents of the raw material
(earthy matters, gangue, etc.) by vapourization of the metal; and
2. The condensation of the zinc from the vapours to liquid metal.
The Invention has for its first object to improve this second part of the metallurgical
treatment of zinc, that is to say the condensation, to such an extent as to enable the
zinc contained even in gaseous mixtures in which the metal occurs highly diluted by
other gases, to be recovered in the molten state.
The Invention has further for object to apply the new condensation process to the
ordinary dry methods of producing zinc and to the shaft furnace process.
Experiments for the purpose of discovering a suitable condensation process for
coudensing the gases resulting from the melting down or smelting of zinciferous ores
in the blast furnace bave heretofore always been unsuccessful, and it has cousequently
been thought that the condensation of the zinc contained in blast furnace gases to
liquid metal was practically iinpossible. The grounds for this opinion consisted partly
in the supposed unavoidable admixture of carbonic acid in such gases, and partly in
the dilution of the zinc by said gases. But it has been forgotten that on the Lower
Harz the condensation of shaft furnace gases containing an extremely small
percentage of zinc has been carried out for very many years with practical success.
The following general rules may be laid down regarding the condensation of
ziņc :—
1. Gases of the highest possible degree of concentration should be employed
because the condensation is thereby considerably facilitated;
2. The access of air, steam, or water vapour and carbonic acid to the gases
should be prevented;
3. The temperature of tho gases should not fall below about 450° C. before the
completion of the condensation ;
4. The deposition of the liquid globules of zinc into drops should be facilitated
and accelerated by suitable means.
As regards the first point, this is generally sought to be effected as far as possible
n the ordinary process of distillation in vessels, by using coke that is poor in gas, or
Pin 17

page_text: authracite, as reducing agenta. The position is however less favourable regarding
the shaft furnace processes that have been proposed or tried. In this case there are
produced, in addition to the carbonic oxide that is formed also in the muffle in the
reduction of the zine oxide, also the products of combustion of the whole of the fuel
that is employed to vaporize the zinc and to melt the charge. Furthermore the
carbonic acid of the products of combustion must be converted into carbonic oxide
before it enters the condenser; this causes a further increase of the gases. An
extremely important means of reducing the products of combustion mingled with
the zine vapours consists in the partial employment of heated air instead of fuel.
The heating of the blast should, for this reason alone, be intensified as far as
possible, especially because the gases deprived of their zine offer a suitable fuel for
this purpose without cost. Another means, also valuable, for enriching the shaft
furnace guses, which forms a part of our Invention, consists in heating the shaft of
the furnace as far as the mouth whilst however taking care that there should be no
appreciable volatilization of zinc to be feared, by introducing air or blast and by
not passing the gases (issuing from the charge) through the condenser, whereby the
whole of the zinc is concentrated in the remainder of the gases tapped from the
lower part of the furnace.
The second precept, the exclusion of oxidizing gases, is carried out in distillation
in vessels to the extent that the gasea passing out of the distilling vessel into the
condenser or nozzle are usually almost free Trom oxidizing constituenta. Iu the
shaft furnace process air, water and carbonic acid may enter the furnace with
the charge and may pass over into the gases that issue from the mouth. But as,
according to our process, as was already stated in respect of precept 1, these gases
remain separated from the zinciferous vapours issuing from the lower part of the
furnace, the constituents of such gases cannot have any injurious action upon
the zinc. The case is however different with the carbonic acid that is formed in the
crucible of the furnace in front of the air tuyeres. This carbonic acid must be
rendered innocuous according to the equation C 0,+C 2 C0, by causing these gases
to pass on their way to the outlet apertures in the crucible of the furnace through a
sufficiently doop and highly incandescent layer of coke. To keep such a layer in
permanent operation it is preferable to pass abundant quantities of highly heated
blast into the crucible.
The third precept, via-to keep the temperature of the gases aufficiently elevated
as far as possible until after the completion of the separation of the zinc, is neglected
in the process of distilling in vessels. As the gases leave the condenser at a very
low temperature before all the zinc has been precipitated from them, the remainder
of the zine is naturally converted into "poussière" (dust) which by reason of its
fineness and lightness can only be imperfectly deposited. In the shaft furnace
process the zinc-bank presents an excellent and pertinent example in this caso. The
high temperature, which exceeds in all its parts dark red heat by a considerable
amount and does not fall at any part below 600° C, is one of the two causes of its
success. Of all other experiments and proposals, so far as we know them, it may be
said that without exception the much too low temperature of the gases in the
condenser was necessarily the reason of the want of success. In the majority of
cases the necessity for a high temperature during condensation was in fact not
clearly understood, as will be readily perceived from the very frequently prescribed
cooling of the entire condenser. But where, by way of exception, a high tempemture
was the object in view, this object was however not satisfactorily achieved because the
zinciferous vapours lost too much heat by contact with the cold charge, whilst the
condensing chambers were generally made so large that the gases on entering
unavoidably underwent a rapid fall in temperature. As the shaft furnnce gases
already undergo an unavoidable fall of temperature by reasou of the conversion of
the carbonic acid into carbonic oxide which takes place with absorption of heat, every
further loss of heat must be carefully obviated. This invention effects this object by
means of the arrangement which has already been described and which also serves
for other purposes, acconling to which the zinciferous gases do not pass through the

page_text: entire furnace but, without having any share in heating up the charge, are conveyed
through openings formed in the upper portion of the arucible by the shortest path to
the condenser, the arrangement being such that they come in contact only with
highly heated masses. If the gases in the condenser are to give up the whole of their
contained xino, the cooling of Raid gases must take place but very slowly, this being
promoted by surrounding the condenser with bad conductors of heat, etc. However,
As a rule, the temperature will fall too soon below the point of solidification of the
zinc and then nothing more can be done except to cause the remainder of the metal
to be deposited in the form of dust. This dust will be deposited in the rear parts of
the chainber, situated nearest to the outlet openings for the gases. In order to
recover this zine dust also in the form of liquid metal, this Invention comprises the
following process which also brings with it further advantages. When a certain
amount of dast has been deposited, that is to say after a certain time, a reversing
valve or any other suitable device is operated to reverse the direction of the gases in
their passage through the chamber. The gases now pass at their highest temperature
and with the highest percentage of contained zino into that part of the chamber
which has up to now been the hindinost part and the said gases impinge here upon
the dust that was therein deposited and act to re-volatilize the same and by
agglomeration with fresh globales of sine to convert said dust into dropa. Again,
after a certain period has elapsed, there will be deposited at the other end of the
chamber a sufficient amount of zinc dust which is recovered in the same manner, that
is to say by again reversing the gases, namely, by causing them to pass again in their
original direction. By this reversal of the direction of How of the current of gas
being repeated at certain intervals of time, too great a deposit of dust which would
otherwise choke up the chamber is prevented, and the gases are also enriched by
means of the dust which is deposited at their point of entry luto their condenser; this
resulting in considerable advantages as already stated. This most important part of
the Invention which alone probably renders it possible to recover in a liquid form
the whole of the zine contained in a gaseous mixture, can be applied to riol, as also
to poor gases of all kinds.
A special means of promoting the deposition of the zino globules or vesicles and
to facilitate their union to drops has been practically carried out in the case of the
zinc bank. The success of the zinc bank is solely based on this means in combination
with the high temperature. It consisted in filling up the niches with wood charcoal.
If the niches had been left unoccupied, the the sine vesicles suspended in
comparatively small number in the gases would have had no time to form drops in
their short path to the condensing space. In passing the niches they would have
been carried along by the gases and conveyed by these into the mouth of the furnace.
The filling with charcoal acted not only as a means for reducing the carbonic acid
but what is the sole consideration in this case acted also as a filter in the pores of
which the zinc vesicles were deposited. Close to one globule another globule was
soon deposited and so on until drops were formed which descended to at once make
room for fresh globules. It will be therefore readily understood that in this manuer
zino could be recovered even from the very poorest gases, and it is to be wondered
at that so little attention has been paid to this means so that it hardly appears to
have been revived for practical use. By means of a porous filter not only is the
deposition of the zino considerably accelerated, but also all the solid parts are filtered
out of the gaseous mixture and thus a complete extraction of the zino contained
therein is rendered possible. The acceleration further allows of considerably
hortening the path to be tmversed by the gases in the condenser whilst it also
reventa premature cooling of the gases which would be unavoidable with a longer
ath. It would be giving up these advantages and jeopardising a successful result if
he chamber were to be made of greater dimensions than are absolutely necessary
rom this point of view. As a material for filling, it is preferable to employ wood
harcoal, because charcoal is not only an extremely porous filter, but it is also most
uitable for reducing to carbonic oxide any carbonio noid that may still be contained
n the gases. A cheaper and also still useful means is porous coke. Bodies that do

page_text: not contain any carbon can only be employed when the gases are quite free from
admixtures that have an oxidizing action upon zinc. But even in such cases coke or
charcoal is preferable because the filling material which is impregnated with zinc can
he smelted to zinc again in the shaft furnace or in the muffle furnace when it is
necessary to clean out the condensers. The most suitable form for the condenser is
a symmetrical shape of circular cross-section, such for example as that of an inverted
syphon the upwardly directed legs of which are either vertical or are inclined to each
other. At the ends of the legs are provided the inlet and outlet openings for the
gases whilst in the connecting piece of the legs situated at the lower part there is
formed a well provided with a tap hole for the accumulation of the zinc.
The Invention thus consists mainly of oue or more condensers arranged side by
side or in series one behind the other in the form of tubes or pipes, conduits, or
chambers for the condensation of zinc from zinciferous gases in which the gases are
subjected during their passage to a dry filtration by means of a filling of wood
charcoal, coke, pumice-stone, or in any other suitable manner and further in which
for the purpose of redissolving the products of condensation that have become solid
in the colder parts of the condenser that were last traversed by the gases, the current
of gas is caused at certain intervals by means of a suitable reversing device to flow
alternately in a direction opposed to its previous movement.
APPLICATION OF THE NEW PROCESS TO DISTILLATION IN VESSELS AND TO THE
SHAFT FURNACE PROCESS.
1. Application of the process to distillation in vessels. In the usual method of
distilling in vessels (such as muffles, pipes, and the like) the gases are generated so
slowly, and the amount of heat they contain is consequently so small, that after even
a very short travel the temperature of dust-formation is reached, for which reason the
condensers can only be made very short. Now if the new condenser were to be
employed directly without alteration in place of the old condenser the probable result
would be merely a formation of dust.
In order to obtain a current of gas of rather high temperature and of greater
intensity, the Inventor proceeds as follows:-The muffles or pipes are made of ench
a length as to extend up to the opposite end from the front to the rear of the furnace.
The distilling vessles are charged only from the said rear end of the furnace and also
discharged therefrom. At the front end of the furnace the vessels are connected by
means of a forked passage as short as possible, with the two end pieces or legs of the
syphon-shaped condenser which is arranged vertically in frout of the furnace. At the
fork of the passage there is arranged a reversing flap which enables the gases of
the muffle to enter alternately into one or the other leg of the siphon, that is to say
the path of the gases to the condenser can therefore be reversed as required. The
gases of a number of distilling vessels arranged over one another or side by side can
be united and passed together through the condenser.
Instead of using vertical condensers of syphon shape they may have an inclined or
entirely horizontal position. In such a case the sump or well is also situated in the
iniddle, whence the soles or base pieces of the two limbs or legs of the syphon extend
right and left with a gentle rise in order that the liquid zinc may flow backward to
the well. A horisontal condensing chamber of this kind is preferable when the
reversal of the flow of the gases is desired to be effected only after complete distillation
of the charge of one or more vessels, because by this means the alternate operation of
distilling vessels situated at a distance from one another is facilitated. The gases
then pass out of one or more muffles by means of a simple pipe into the leg of the
condenser. When the charge has been distilled, the muffle is shut off and charged
anew, whilst at the same time one or more muffles situated on the other side of the
condenser are placed in communication with the other leg for the purpose of sending
their gases through the chamber in the opposite direction.
It need scarcely be mentioned that ab every reversal, the openings through which
the gases deprived of their sino escape must also be alternately opened and closed.

page_text: If, as is to be preferred, all the muffles of one furnace are provided with a
common condenser, the said condenser is made approximately of the length of the
whole furnace. In this case the condenser may be provided with several wells, instend
of with only one; this is generally to be preferred for condensers of great extent.
If, for example, twelve muffles are arranged side by side, the gases of the six
muffles situated on the right hand side of the furnace are passed towards the left
hand through the condenser, and the gases of the muffles situated on the left hand
side of the furnace are passed towards the right through the condenser. In this case
the several muffles on the right hand side may pass their gases through the condenser
alternately with those on the left. band side, or a number of the vessels situated over
one another or side by side on one side of the furnace may unite their gases together.
Muffles or pipes situated over one another are for this purpose connected by means of
a short piece of pipe (that can be closed when desired) with a common vertical pipe
extending down in front of the ends of the muffles and which opens at its lower end
iuto the condenser.
If it is thought desirable that the gases should always describe a path of the same
length through the condenser the arrangement is made such that portions of the
latter are adapted to be cut off by means of vertical dainpers or by any other
suitable means. For this purpose the requisite number of escape apertures (adapted
to be closed) for the gases deprived of their zine are arranged at suitable points. By
means of these devices larger or sinaller portions of the condenser can be thrown out
of operation and its operative length can be regulated as desired.
By allowing the distilling vessels to extend up to the opposite side of the furnace
they are made in comparison to heretofore more than double the capacity. The
aforesaid union of the gases of adjacent muffles affords a furthers means of
intensifying the current of the gases. If the temperature in the condenser should
however not be high enough, which will be the case for instance in portions of the
condenser that have been temporarily thrown out of operation, it is advisable to heat
the condenser or certain parts of the same from the ontside. For this purpose the
condenser or its legs are surrounded at a certain distance with a casing or jacket and
in the intermediate space thereby formed a solid or gaseous fuel is burned. As fuel
for such purpose it is particularly advantageous to burn the gases which have been
deprived of their zine and which escapes free from the condenser, and which when
they pass out of the inner leg are led through the shortest way into the intermediate
space between the leg and the jacket and can be burnt therein. As these gases leave
the condenser at those parts thereof which are the coolest for the time being it is
most simple and most advantageons to heat this portion first in the manner above
indicated, and to cause the gases to pass outside the condenser in the opposite
direction to their path inside the condenser. Then on reversing the flow of the xine
vapours, the direction of the heating gases will also be reversed each time.
When the process is carried out as above assumed, the object in view should be
perfectly attained, but the fact has not been borne in mind, namely, that the zine
will probably become condensed in the connecting passages between the distilling
vessels and the condenser and will obstruct said passages. Also the above described
heating of the condenser is only effective when there is a sufficient amount of heating
gases always at one's disposal which is however not always the case.
same.
In order to obviate these difficulties and also to enable the intensity of the gae
flow in the condenser to be always adjusted according to requirement, it is proposed
during the distillation period to send from the rear side of the distilling vessely a
current of hot gases free as far as possible from water and carbonic acid through the
The most suitable means for this purpose are producer gases which are
obtained by incomplete combustion of coke or anthracite and consist of a mixture of
carbonic oxide and nitrogen. By means of these gases the temperature is enabled
to be considerably increased, not alone within the distilling vessels, but also in the
condenser, and there are also afforded hereby abundant quantities of finally escaping
gases for the purpose of heating the latter. Furthermore the following advantages
are obtained in connection therewith :-

page_text: 1. As the distilling vessels are also heated internally, they can be made much more
capacious, that is to say higher and wider;
2. The votalization of the zinc is accelerated in a high degree by the current of
hot gas because the gases saturated with zinc vapour are at ouce discharged to make
room for gases free from zinc. The charge can therefore be made considerably greater
and yet it can be distilled in a shorter time than heretofore. The consequence of this
is a great saving of fuel, cost of distilling vessels, and cost of labour. Further the
yield is greater in comparison with present methods in consequence of the new method
of condensing, so that the new process constitutes an important advance. Certainly
this process does not yet constitute the ideal of a theoretically and practically perfect
process of metallurgical production of zinc. This ideal will however be probably
effected only by means of a rationally arranged shaft furnace process. Yet this new
process well deserves to be considered the most perfect ouo of those methods that
are based on distillation in vessels. It has also at least this advantage as compared
with the shaft furnace process; namely that its introduction in existing works will
cause incomparably less expense because the existing furnaces, chimneys, producers,
regenerators, muffle-works, drying-rooms, etc. can be used without alteration. Also
it forms an important step towards the shaft furnace process, because for the first
time gases are employed for condensation which are similar in composition to those
of the shaft furnace and which may be made by way of experiment of exactly the
same composition as the shaft furnace gases that are to be expected.
There inay certainly be raised against the proposed introduction of producer gases
into the muffle the objection that the percentage of zinc in the gases should not be
unuecessarily reduced, so long as it is not shewn that the advantages of the new
condenser cannot be obtained without those means. This is however only correct in
the case in which the gases escaping from the condenser still contain appreciable
amounts of zinc, which can only be the case where the dimensions of the condenser
are not properly proportioned to the amount of gas passing through the same; that
is to say when the current of gas is too great. So long as the condenser fulfils its
purpose as a perfect filter for the gases, it is quite immaterial as regards the yield
whether the gases enter with a high or with a low percentage of zinc."
If however the final gases shew a percentage of zinc, then of course any dilution
of the gases to be condensed will result in a progressive increase of the loss. The
limit for the introduction of producer gases into the distilling vessels is thus given
where the advantages resulting therefrom are compensated by any loss of zinc.
2. Application to the shaft furnace process. If it were desired to subject the
shaft furnace gases to the condensing process just as they escape from the throat of
the furnace, no liquid zine would be obtained, not only because they are too rich in
constituents that have an oxidizing action upon sine, but also because they have a
too low temperature. As no metallurgical process operates entirely without loss, the
further possibility must be borne in mind that the gases subjected to the new
condensing process may have on leaving the condenser still a percentage, although a
very small one, of zinc. But the loss thereby caused would amount in the case of
poor gases to a more considerable percentage of their contained zinc than in the
case of rich gases, so that it is very desirable, although not absolutely necessary, that
the gases should be supplied to the condenser with a higher percentage of sine than
the gases can have coming from the throat of the furnace. The way proposed
by the Inventors for the purpose of obtaining, instead of the furnace gases that are
useless for condensing zinc, such gases which are hot enough and are free from
water and carbonic acid and which are also considerably richer in zine, has already
been described before. That way consists in working the upper portion of the furnace
-say from the boshes to the mouth or throat of the furnace-with a supply of air or
blast separately, and as far as possible separate from the lower portion which
comprises the inelting space (the crucible) and the hearth-and in regulating the
temperature of this upper part of the furnace in such manner that the houting of the
charge and the reduction of metals (such as lead, copper, and iron, which are reduced
at a lower temperature than zinc) are there effected, whilst the reduction and the

page_text: volatilization of the zinc and the melting of the.charge is effected in the lower part
of the furnace. In this manner the upper part of the furnace produces gases free
from zine which are led away separately from the zino-containing gases that rise up
from the lower part of the furnace. Only the latter gases which contain the whole
of the zine need be subjected to the condensing operation. They contain (in addition
to the carbonic oxide which results froin the reduction of the zino oxide and which is
unavoidably even in distillation in vessels) only the products of combustion (which
have been converted into a mixture of carbonic oxide and nitrogen and are therefore.
free from carbonic acid) of the fuel which is necessary to volatilize the zinc and
to melt the charge which has been heated up to nearly the melting point. These
products of combustion may however be considerably diminished by introducing
highly heated blast into the crucible of the furnace.
Still more favourable are the conditions in smelting unroasted zinc sulphide (which
is to be decomposed according to the formula ZnS + Fe FeS + Zn), because
this decomposition takes place without the development of carbonic oxide which
always accompanies the reduction of zinc oxide. It may be assumed that in this
case the shaft furnace gases will not have a much smaller percentage of zinc than
the gases which are produced in the muffle.
The sulphide of iron produced is tapped from the hearth together with the metals
(lead, etc.) that may have been reduced, and the slag is also ran off at intervals, or
better still continuously. The expense of the iron to be added in a metallic or in
an oxidized state-in which case the reduction of the oxide to metal takes place
in the upper part of the furnace-can be considerably lessened by again adding the
iron oxide that is obtained by the roasting of the iron aulphide produced.
The advantages which the smelting of zinc ores in the shaft furnace possesses
over the distillation in vessels are mainly as follows:-Saving of the expensive vessels,
considerably smaller consumption of fuel, less coat of labour, and larger yield. In
treating zinc blende there are further the advantages:-the substitution, for the
expensive roasting of the ore, by the cheaper roasting of the iron sulphide (said
roasting not requiring noy separate fuel) and better utilization of the contained
sulphur in consequence of richer roasting gases. In connection with this are:-
Saving in costly coudensing plant for the fumes, and avoidance of damage to the
surroundings, because it is not necessary to roast the iron sulphide completely; or
the roasting of the same can be wholly avoided by purchasing it from sulphuric acid
works or depositing it upon the waste heaps. In this case the necessary iron
for precipitation would have to be provided for by an addition of rich iron ores or
the like.
The working of the shaft furnace is as follows The furnace may have a high
and steep or quite vertical crucible with one or more tuyeres. At the upper part of
the crucible, or at the commencement of the boshes, there are forined in the wall
of the furnace one or preferably several apertures for the escape of the gases. The
heating of the upper part of the furnace may be effected in two different ways.
The first way consists in introducing at a point not too far down below the mouth of
the furnace, a blast of low pressure or air from wide nozzles. The furnace gases pass
downwards and leave the furnace through apertures formed in the boabes. In order
to prevent the gases from changing their direction and thus escaping out at the
mouth of the furnace during the charging of the latter, the mouth of the furnace is
provided with a double closure such for example as a Parry hopper with a bell.
These allow the furnace to be charged whilst its mouth is closed. Also the blast can
be stopped during the charge. Or there may be arranged in the gas conduit which is
counected with the outlet apertures a fan for the purpose of facilitating the
downward travel of the gases from the mouth to the bosh. Between the apertures
on both sides for the escape of the gases that flow from top to botton and froin the
bottom to the top there is left a sufficient vertical space which serves to form a
neutral zone that has for object to prevent the mingling of the gases that are free
from zine with the gases that contain zinc. The escape apertures for the zinc-
containing gases are connected along the shortest possible path with the two legs of

page_text: the condenser, and each of these connections is alternately shut off and re-opened
at certain intervals of time by means of a reversing valve or in any other suitable
manner. The gases freed from zine are, as in the case of distillation in muffles,
especially suitable for heating the condenser. But they may also be used for heating
the blast, or heating steam boilers, or for other purposes. This also holds good
in the case of the gases that are free from zinc and which escape from the shaft of
the furnace.
The second method of heating the upper part of the furnace separately
differs from the above described method, mainly in two respects. First, the
upper part of the furnace is not worked simultaneously with the lower part, but is
worked alternately with the same; and secondly, the gases which serves to heat the
upper part of the furnace do. not flow contrary to their natural direction,
from top to bottom but they follow their natural direction that is to say thoy
rise up to the mouth of the furnace from the tuyeres which
provided in the boshes. Two exactly similar shaft furnaces are required, arranged
at a distance apart from each other such as to allow of the condenser which is
common to both being situated between them. This condenser is preferably inade
with two wings which are inclined upwardly from its centre towards the two furnaces
and each of which is connected at the upper part by means of a conduit (which is us
short as possible and is capable of being closed) with the gas outlet openings of its
adjacent furnace that are provided in the crucible or immediately above the latter.
In the centre of the condenser, that is to say at its lowest point, there is situated the
sump or well for the collection of the zino. Each of the two wings of the condenser
is also provided near to the conduits leading to the furnace with outlet openings
(adapted to be closed) for the gases that have been freed from zinc. The condenser
inay, if required, be constructed so as to be capable of being heated in the manner
above stated. The construction and arrangement of the furnaces as regards their
lower portious, is exactly the same as in the case of those described relatively to the
first method. The upper part of the furnace is provided at the boshes, or imme-
diately above the same and at a suitable distance from the gas outlet openings, with
inlet openings for blast and air.
The working is as follows:-The first furnace is first, for the purpose of blowing in,
charged to a certain height with fnel and then alternately with fuel and with slag-
forming materials. As soon as the latter appear in front of the upper tuyeres these are
closed. The connections of the two furnaces with the condenser have already been
previously closed. Then blast is introduced through the lower tuyeres into the
crucible and the furnace gases are allowed to pass out at the mouth. Then gradually
increasing quantities of ore are added to the charges until the normal composition of
charge has been reached. The second furnace is then blown in, in exactly the same
manner but one or two hours later than the first one. As soon as the first vapours of
zine appear in the furnace-mouth, gases of furnace No 1, the working is altered.
The heating up in coupleted, and the furnace enters into the smelting and zine-
producing stage. The charging is now stopped: the connection with the condenser
is made: and the mouth of the furnace that was quite filled up before is carefully
closed. The concentration of the heat promoted by the hot blast, and by the narrow
high crucible, facilitates the melting of the mass and the volatilization of the zine.
The gases rich in zinc leave the furnace and pass down through the nearest wing of the
condenser, then pass over the sump into the other wing that leads up to furnace
No 2. At the end of this wing the said gases leave the condenser through the out-
let passage which has been previously opened. If these gases still contain zinc-dust,
the gases are caused to pass further through a purifying shaft or tower filled with
coke or the like, which is intended to retain the last particles of zinc. In order to
facilitate this flow of the gases, and to reuder their escape from the closed mouth of
the furnace quite impossible, it is advisable to provide au exhausting fan in the gas
passage behind the purifying tower. The gases thus freed from zino may finally be
utilized as fuel for the purposes above set forth. After a certain time the charge in
furnace No 2, whose gases have up till now been escaping from the mouth of the
furnace, has become so hot as to cause zino vapours to be found at the mouth. In

page_text: consequence of this, reversal must again take place. Furnace No 2. now enters on
the melting stage, whilst in furnace No 1. there begins again a heating-up stage. The
reversal is commenced by shutting off the blast tuyeres in the crucible of furnace
No 1. and by closing the gas passage so as to shut off communication with the
condenser. Then the escape pipe for the gases passing out of the furnace mouth is
opened, and the blast or air is introduced into the bosh. At the same time the
charge which had sunk during the melting period, during which the charging was
stopped in order not to disturb the draught of the gases in the oondenser and to
avoid all cooling of the same, is now replenished whereby the charge is kept at its
normal height. In order to provent the materials from melting aud the zinc from
being volatilized in consequence of too high a temperature during this period, which
zinc would be lost in the furnace-mouth gases, the nozzles that open into the boshes
are made of large cross-sectional area, and the blast is introduced through the same
at a low pressure or only air is passed through. Also these nozzles are arranged at
one level where the furnace widene out considerably, in order that the hot products
of combustion shall become rapidly spread over large masses and shall be able to
impart their heat uniformly to the same. After the reversing of this furnace into
the heating-up stage has thus been effected furnace No 2. is then brought into the
melting and distilling stage. This is effected in the manner already described for
furnace No 1. by establishing communicatiou between the gas passages leading from
the crucible, and the corresponding wing of the condenser; by opening the outlet
aperture for the gases freed from zine in the opposite wing; and by closing the mouth
of the furnace or the furnace-mouth gas tube of the furnace which is previously.
completely filled up. After having thus terminated the reversal in this manner of
the two furnaces the gases rich in zinc pass through the condenser in a direction
opposite to their previous direction. By means of the aforesaid exhausting fan,
these gases may also be led through the purifying tower which is arranged at a point
such that it can be reached by an equally short path by the gases that issue
alternately from the left and from the right wing of the condenser. Again, after the
expiration of a certain period, furnace No 1. is again brought into the sino-producing
stage and furance No 2. into ita second heating-up stage and in this manner the two
furnaces alternate continually in their two stages so that one furnace is always being
heated up whilst the other furnace is occupied in inelting the heated-up charge and
in produsing zine.
A modification of the above described process may be set forth here and which I
also desire to patent. This modification has for object to utilize the gases coming
from the condenser in heating up the charge. For this purpose the outlet-apertures
of the condenser are connected along the shortest path with the glass nozzles that
open into the boshes of the two shaft furnaces. As soon as, in the course of the
reversal, the outlet aperture in that wing of the condenser which is situated nearest
to the shaft furnace that is entering upon the beating-up stage, is opened, and the
tuyeres connected therewith are set in operation, the gases drawn from out of the
condenser by the flow of the blast, are forced into the furnace, and are at once burnt
up therein. The blast in this connection has the same action upon the gases as the
steain jet in the well known steam jet blower has upon the air drawn in by it. As
the gases leave the condenser at a temperature of about 400° C. the heat which they
still contain serves to aid in heating up the charge. Any zino dust that these gases
may still contain is deposited on their way to the furnace mouth in the loose masses.
The said dust is therefore utilized in the simplest manner, because the shaft furnace
acts as a substitute for the purifying tower. Thus these gases changing with every
furnace reversal are continually aiding the heating up, and if the quantity of blast is
regulated in such a manner as to be just sufficient for complete combustion of the
gases it may be assumed that the amount of heat necessary to hent up the charge can
be supplied alone by the combustion of the gases. At least this should be possible so
long as the heating up has not advanced to such an extent as to cause any fear of a
considerable re-formation of carbonic oxide from the carbonic acid which is produced
by the combustion of the gases.

page_text: It may finally be stated that the preceding special description of the various methods
which it is desired to patent does not describe the only way of carrying out the Inven-
tion, but has merely for object to give a clear idea and example of the same.
Naturally the details can be considerably modified in many cases from the arrange-
ments described in this Specification. It need here only be stated that the condenser
may be connected up in any desired manner, thus it may be divided into chambers by
means of a series of partitions. Or it may be composed of a number of upwardly and
downwardly directed or zig-zag passages or pipes and so forth, so long as it retains its
characteristic arrangement of alternating reversal. Also the form of the shaft furnace
to be employed, may be of any desired type, and although the levels or height at
which the blast or air is supplied to the furnace and the gases are drawn from the same,
have been specially designated by the words "boshes" "crucible" etc. it has only been
intended by this to indicate the relative positions of their apertures, tuyeres, eto.
without intending to bind oneself to the statement that the said openings must
necessarily be situated in that specific part of the furnace referred to. Thus there are
shaft furnaces which become gradually wider from the hearth towards the mouth, but
have no visible limit or boundary between crucible and boshes, nor any such limit
between the bosbes and the shaft. Consequently these designations are only intended
to indicate approximately the level or height in the shaft furnace at which the said
openings are to be arranged. But wherever in this Specification the expression
"shaft furnace "has been employed, there is exclusively meant thereby a blast
furnace or blast shaft furnace, that is to say a furnace in which the zino ores are
situated in immediate contact not only with the reducing agent but also with the fuel
intended to produce the heat, whereas in the distillation in vessels the combustion of the
fuel, which serves to produce the heat, takes place outside of the vessel in which the
volatilization of the zinc is effected. It may also be added that instead of the blast
from tuyeres, other neaus may be employed for conveying the gases from the
condenser into the sliaft furnace. Thus for example there may be employed for this
purpose a current of steam or a device (centrifugal fan or the like) arranged between
the condenser and the furnace and acting to suck or to force or to both suck and
force; or an exhausting fan may be arranged in the furnace-mouth gas-passage behind
the furnace. This fan has the advantage that is not to be under estimated, vis:-
that not only is there no need of a strong blast but also that even in this case air can
be used instead of the blast during the heating up stage the said air being in this
case also drawn in by the fau. By this means the apparatus or plant is considerably
simplified as regards its construction.
DI
Demba 1000
A. M. & WM. CLARK.
Chartered Patent Agents. 53. Chancery Lane London.
COMPLETE SPECIFICATION.
"Process of Recovering Zinc from Zinciferous Gases in the
Distillation and Smelting of Zino."
I, ALEXANDER MELVILLE. CLARK of the Firm of A. M. and Win Clark of 53. Chancery
Lane in the County of Middlesex, Fellow of the Chartered Institute of Patent Agents;
do hereby declare the nature of this Invention (a communication to me by Professor
Robert Heinrich Theodor Biewend of Clansthal; and Actien Gesellschaff Für Zink
Industrie Vormals Wilhelm Grillo of Neumühl-Hamborn; both in the Empire of

page_text: Germany) and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement :-
The distillation of zine, which is the only method practically carried out, for
recovering zinc by dry process from its ores, comprises two parta:-
1. The separation of the zinc from the non-volatile constituents of the raw material
(earthy matters, gangue, etc.) by vapourization of the metal; and
2. The condensation of the zinc from the vapours to liquid metal.
The Invention has for its first object to improve this second part of the metal-
lurgical treatment of zinc that is to say the condensation, to auch an extent as to
enable the zinc, contained even in gaseous mixtures in which the metal occurs highly
diluted by other gases, to be recovered in the molten state.
The invention has further for object to apply the new condensation process to the
ordinary dry methods of producing zice and to the shaft furnace process.
Experiments for the purpose of discovering a suitable condensation process for
condensing the gases resulting from the melting down or smelting of zinciferous ores
in the blast furnace have heretofore always been unsuccessful, and it has consequently
been thought that the condensation of the zinc contained in blast furnace gases to
liquid metal was practically impossible. The grounds for this opinion consisted
partly in the supposed unavoidable admixture of carbonic acid in such gases and
partly in the dilution of the xino by said gases. But it had been forgotten that on
the Lower Harz the coudensation of shaft farnace gases containing an extremely
small percentage of zinc has been carried out for very many years with practical
Buccess.
The following general rules may be laid down regarding the condensation of
zinc :-
1. Gases of the highest possible degree of concentration should be employed
because the condensation is thereby considerably facilitated;
2. The access of air, steam, or water vapour and carbonic acid to the gases should
be prevented;
3. The temperature of the gases should not fall below about 450° C. before the
completion of the condensation;
4. The deposition of the liquid globules of zine into drops should be facilitated and
accelerated by suitable means.
As regards the first point, this is generally sought to be effected as far as possible
in the ordinary process of distillation in vossels, by using coke that is poor in gas,
or anthracite, as reducing agents. The position is however less favourable regarding
the shaft. furnace processes that have been proposed or tried. In this case there are
also produced, in addition to the carbonic oxide formed in the muffle in the reduction
of the zine oxide, the products of combustion of the whole of the fuel employed to
vapourize the zinc and to melt the charge. Furthermore the carbonic acid of the
products of combustion must be converted into carbonic oxide before it enters the
coudenser; this causes a further increase of the gases. An extremely important
means of reducing the products of combustion mingled with the zinc vapours consists
in the partial employment of heated air instead of fuel. The heating of the blast
should, for this reason alone, be intensified as far as possible, especially because the
gases deprived of their zinc offer a suitable fuel for this purpose without cost.
Another means, also valuable, for enriching the shaft furnace gason, which forms a
part of our Invention, consists in heating the shaft of the furnace as far as the mouth
whilst however taking care that there should be no appreciable volatilization of zine,
by introducing air or blast and by not passing the gases (issuing from the charge)
through the condenser, whereby the whole of the zinc is concentrated in the
remainder of the gasea tapped from the lowor part of the furnace.
The second precept, the exclusion of oxidizing gases, is carried out in distillation
in vessels to the extent that the gases passing out of the distilling vessel into the
condenser or nozzle are usually almost free from oxidizing constituenta. In the shaft
furnace process air, water, and carbonic acid may enter the furnace with the charge
and may pass over into the gases that issue from the mouth, But as these gases,

page_text: according to our process, as already stated in respect to Precept 1 remain separated
from the ziuciferous vapours issuing from the lower part of the furnace, the
constitutents of such gases cannot have any injurious action upon the zinc. The
case is however different with the carbonic acid formed in the crucible of the furnace
in front of the air tuyeres. This carbonic acid must be rendered innocuous according
to the equation CO, + C = 2 CO by causing these gases to pass on their way to
the outlet apertures in the crucible of the furnace through a sufficiently deep and
highly incandescent layor of coke. To keep such a layer in permanent operation it.
is preferable to pass abundant quantities of highly beated blast into the crucible.
In the
The third precept, viz:-the maintenance of the temperature of the gases
sufficiently elevated as far as possible until after the completion of the separation of
the zinc, is neglected in the process of distilling in vessels. As the gases leave the
condenser at a very low temperature before all the zinc has been precipitated from
them, the remainder of the zine is naturally converted into "poussière" (dust) which
by reason of its fineness and lightness can only be imperfectly deposited.
majority of cases the necessity for a high temperature during condensation was not
clearly understood, as will be evident from the very frequently prescribed cooling of
the entire condenser. But where, by way of exception, a high temperature was
aimed at, it was not satisfactorily achieved because the zinciferous vapours lost too
much heat by contact with the cold charge, whilst the condensing chambers were
generally made so large that the gases on entering unavoidably underwent a rapid
fall in temperature. As the shaft furnace gases already undergo an unavoidable fall
of temperature by reason of the conversion of the carbonic acid into carbonic oxide
which takes place with absorption of heat, every further loss of heat must be carefully
obviated.
This invention attains this object, amongst others, by means of the arrangement
already described, according to which the zinciferous gases do not pass through the
entire furnace but, without having any share in heating up the charge, are conveyed
through openings formed in the upper portion of the crucible by the shortest path
to the condensor, the arrangement being such that they come in contact only with
highly heated masses. If the gases in the condenser are to give up the whole of
their contained zinc, the cooling of said gases must be retarded by surrounding the
condenser with bad conductors of heat, etc. However, as a rule, the temperature
will fall too soon below the point of solidification of the zinc and then nothing more
can be done except to cause the remainder of the metal to be deposited in the form of
dust. This dust will be deposited in the rear parts of the chamber, situated nearest
to the outlet openings for the gases.
In order to recover this zinc dust. also in the form of liquid metal, this Invention
comprises the following process which also brings with it further advantages. When
a certain amount of dust has been deposited, that is to say after a certain time, a
reversing valve or any other suitable device is operated to reverse the direction of the
gases in their passage through the chamber. The gases now pass at their highest,
temperature and with the highest percentage of contained zinc into that part of the
chamber which has up to now been the hindmost part and the said gases impinge
here upon the dust that was therein deposited and act to re-volatilize the same and
by agglomeration with fresh globules of zinc to convert said dust into drops. Again,
after a certain period has elapsed, there will be deposited at the other end of the
chamber a sufficient amount of zinc dust, which is recovered in the same manner, that is
to say by again reversing the gases, namely, by causing them to pass again in their
original direction. By this reversal of the direction of flow of the current of gas
being repeated at certain intervals of time, too great a deposit of dust which would
otherwise choke up the chamber is prevented, and the gases are also enriched by
means of the dust which is deposited at their point of entry into the condenser ;
this resulting in considerable advantages as already stated. This most important part
of the Invention, which alone probably renders it possible to recover in a liquid form
the whole of the zine contained in a gaseous mixture, can be applied to rich as also
to poor gases of all kinds.

page_text: By means of porous filtering material in the condensers not only is the deposition
of the zine considerably accelerated hut also all the solid parts are filtered out of the
gaseous mixture and thus a complete extraction of the zinc contained therein is
rendered possible. The acceleration further allows of considerably shortening the
path to be tmversed by the gases in the condenser whilst it also prevents prematuro,
cooling of the gases which would be unavoidable with a longer path. It would be
giving up these advantages and jeopardizing a successful result if the chamber were
to be made of greater dimensions than are absolutely necessary from this point of
view. As a material for filling it is preferable to employ wood charcoal because
charcoal is not only an extremely porous filter but it is also most suitable for reducing
to carbonic oxide any carbonic acid that may still be contained in the gases. A
cheaper aud also still useful means is porous coke. Bodies that do not contain any
carbon can only be employed when the gases are quite free from admixtures that have
an oxidizing action upon zine. But even in such cases coke or charcoal is preferable
because the filling material which is impregnated with zine can be smelted to zine
again in the shaft furnace or in the muffle furnace when it is necessary to clean out
the condensers. The most suitable form for the condenser is a symmetrical shape of
circular cross-section, such for example as that of an inverted syphon the upwardly
directed legs of which are either vertical or are inclined to each other. At the ends
of the legs are provided the inlet and outlet openings for the gases whilst in the
connecting piece of the legs situated at the lower part there is formed a well provided
with a tap hole for the accumulation of the zinc.
The invention thus consists mainly of one or more condensers arranged side by side
or in series one behind the other in the form of tubes or pipes, conduits, or chambers
for the condensation of ziue from zinciferous gases in which the gases are subjected
during their passage to a dry filtration by means of a filling of wood charcoal, coke,
punice-stone, or in any other suitable manner and further in which for the purpose
of re-dissolving the products of condensation that have become solid in the colder
parts of the condenser that were last traversed by the gases, the current of gas is
caused at certain intervals by means of a suitable reversing device to flow alternately
in a direction opposed to its previous movement.
APPLICATION OF THE NEW PROCESS TO DISTILLATION IN VESSELS AND TO THE
SHAFT FURNACE PROCESS.
1. Application of the process to distillation in vessels. In the usual method of
distilling in vessels (such as muttles, pipes, and the like) the gases are generated so
slowly, and the amount of heat they contain is consequently so small, that after even
a very short travel the temperature of dust-formation is reached, for which reason the
condeusers can only be made very short. Now if the new condenser were to be
employed directly without alteration in place of the old condenser the probable result
would be inerely a formation of dust.
In order to obtain a current of gas of rather high temperature and of greater
intensity, the Inventors proceed as follows:-The muffles or pipes are made of such a
length as to extend up to the opposite end from the front to the rear of the furnace.
The distilling vessels are charged ouly from the said rear end of the furnace and also
discharged therefrom. At the front end of the furnace the vessels are connected by
means of a forked passage as short as possible, with the two end pieces or legs of the
syphon-shaped condenser which is arranged vertically in front of the furnace. At the
fork of the passage there is arranged a reversing flap which enables the gases of
the inuffle to enter alternately into one or the other leg of the siphon, that is to say
the path of the gases to the condenser can therefore be reversed as required. The
gases of a number of distilling vessels arranged over one another or side by side can
be united and passed together through the condenser.
Instead of using vertical condensers of syphon shape they may have an inclined or
entirely hotizontal position. In such a case the sump or well is also situated in the
middle, whence the soles or base pieces of the two limbs or legs of the syphon extend

page_text: right and left with a gentle rise in order that the liquid zine may flow hackward to
A horizontal condensing chaber of this kind is preferable when the
reversal of the flow of the gases is desired to be effected only after complete
distillation of the charge of one or more vessels, because by this means the alternate
operation of distilling vessels sitnated at a distance from oue auotber is facilitated.
The gases then pass out of one or more muffles by means of a simple pipe into the
leg of the condenser. When the charge has been distilled, the muffle is shut off and
charged anew whilst at the same time one or more muffles situated on the other Aide
of the condenser are placed in communication with the other leg for the purpose of
sending their gases through the chamber in the opposite direction.
It need scarcely be mentioned thnt at every reversal, the openings through
which the gases deprived of their zino escape must also be alternately opened and
closed.
If, as is to be preferred, all the muffles of one furnace are provided with a common
condenser, the said condenser is made approximately of the length of the whole
furnace. In this case the condenser may be provided with several wells, instead of
with only one; this is generally to be preferred for condensers of great exteut..
If, for example, twelve muffles are arranged side by side, the gases of the six muffles
situated on the right hand side of the furnace are passed towards the left hand
through the condenser and the gases of the muffles situated on the left hand side of
the furnace are passed towards the right through the condenser. In this case the
several muffles on the right hand side may pass their gases through the condenser
alternately with those on the left hand side, or a number of the vessels situated over
one another or side by side on one side of the furnace may unite their gases together.
Muffles or pipes situated over one another are for this purpose connected by means of
a short piece of pipe (that can be closed when desired) with a common vertical pipe
extending down in front of the ends of the muffles and which opens at its lower end
into the condenser.
If it is thought desirable that the gases should always describe a path of the
same length through the condenser the arrangement is made such that portious
of the latter are adapted to be cut off by means of vertical dampers or by any others
anitable means. For this purpose the requisite number of escape apertures
(adapted to be closed) for the gases deprived of their zinc are arranged at suitable
points. By means of these devices larger or smaller portions of the condenser can
be thrown out of operation and its operative length can be regulated as desired.
By allowing the distilling vessels to extend up to the opposite side of the furnace
they are made in comparison to heretofore more than double the capacity. The
aforesaid union of the gases of adjacent muffles affords a further means of intensifying
the current of the gases. If the temperature in the condenser should however not be
high enough, which will be the case for instance in portions of the condenser that
have been temporarily thrown out of operation, it is advisable to heat the condenser
or certain parts of the same from the outside. For this purpose the condenser or
its legs are surrounded at a certain distance with a casing or jacket and in the
intermediate space thereby formed a solid or gaseous fuel is burned.
fuel for such purpose it is particularly advantageous to burn the gases which have
been deprived of their zinc sud which escape free from the condenser, and which
when they pass out of the inner leg are led through the shortest way into the
intermediate space between the leg and the jacket and can be burnt therein. As
these gases leave the condenser at those parts thereof which are the coolest for
the time being it is most simple and most advantageous to heat this portion first
in the manner above indicated, and to cause the gases to pass outside the
condenser in the opposite direction to their path inside the condenser. Then on
reversing the flow of the zino vapours the direction of the heating gases will also
be reversed each time.
When the process is carried out as above assumed, the object in view should be
perfectly attained but the fact has not been borne in nine, namely, that the zinc will
probably become condensed in the connecting passages between the distilling vessels

page_text: and the condenser and will obstruct said passages. Also the above described heating
of the condenser is only effective where there is a sufficient amount of heating gases
always at one's disposal which is however not always the case.
In order to obviate these difficulties and also to enable the intensity of the gas flow
in the condenser to be always adjusted according to requirements, it is proposed
during the distillation period to send from the rear side of the distilling vessels a
current of hot gases free as far as possible from water and carbonic acid through the
saine. The most suitable means for this purpose are producer gases which are
obtained by incomplete combustion of coke or anthracite and consist of a mixture of
carbonic oxide and nitrogen. By means of these gases the temperature is enabled to
be considerably increased, not alone within the distilling vessels, but also in the
condenser, and there are also afforded horeby abundant quantities of finally escaping
gases for the purpose of heating the latter. Furthermore the following advantages
are obtained in connection therewith:-
1. As the distilling vessels are also heated internally they can be made much more
capacious, that is to say higher and wider;
Yet
2. The volutilization of the zinc is accelerated in a high degree by the current of
hot gas because the gases saturated with zine vapour are at once discharged to make
room for gases free from zinc. The charge can therefore be made considerably greater
aud yet it can be distilled in a shorter time than heretofore. The consequence of this
is a great saving of fuel, cost of distilling vessels, and cost of labour. Further the
yield is greater in comparison with present methods in consequence of the new
method of condensing so that the new process constitutes an important advance.
Certainly this process does not yet constitute the ideal of a theoreticallyandpractically
perfect process of metallurgical production of zinc. This ideal will however be
probably effected only by means of a rationally arranged shaft furnace process.
this new process well deserves to be considered the most perfect one of those methods
that are based on distillation in vessels. It has also at least this advantage as
compared with the shaft furnace process; namely that its introduction in existing
works will cause incomparably less expense becase the existing furnaces, chimneys,
producers, regenerators, muffle-works, drying-rooms, elc. can be used without
alteration. Also it forms an important step towards the shaft furnace process, because
for the first time gases are employed for condensation which are similar in composition
to those of the shaft furnace and which may be made by way of experiment of
exactly the same composition as the shaft furnace gases that are to be expected.
There may certainly be raised against the proposed introduction of producer gases
into the muffle the objection that the percentage of zinc in the gases should not be
unnecessarily reduced, so long as it is not shewn that the advantages of the new
condenser cannot be obtained without those means. This is however only correct in
the case in which the gases escaping from the condenser still contain appreciable
amounts of zinc which can only be the case where the dimensions of the condenser
are not properly proportioned to the amount of gas passing through the same; that
is to say when the current of gas is too great. So long as the condenser fulfils its
purpose as a perfect filter for the gases it is quite immaterial as regards the yield
whether the gases enter with a high or with a low percentage of xine."
If however the final gases shew a percentage of zinc, then of course any dilution of
the gases to be condensed will result in a progressive increase of the loss. The limit
for the introduction of producer gases into the distilling vessels is thus given where
the advantages resulting therefrom are compensated by any loss of zinc,
2. Application to the shaft furnace process. If it were desired to subject the shaft
furnace gases to the condensing process just as they escape from the throat of the
furnace, no liquid ziuc would be obtained, not only because they are too rich in con-
stituents that have an oxidizing action apon zine, but also because they have a too
low temperature. As no metallurgical process operates entirely without loss, the
further possibility must be borne in mind that the gases subjected to the now
condensing process may have on leaving the condenser still a percentage, although a
a very small one, of zinc. But the loss thereby caused would amount in the case of

page_text: poor gases to a more considerable percentage of their contained aine than in the case
of rich gases, so that it is very desirable, although not absolutely neccessary, that the
gases should be supplied to the condenser with a higher percentage of zinc than the
gaaes can have coming from the throat of the furnace. The way proposed by
the Inventors for the purpose of obtaining, instead of the furnace gases that are
useless for condensing zinc, such gases which are hot enough and are free from water
and carbonic acid and which are also considerably richer in sinc, has already been
described before. That way consists in working the upper portion of the furnace-
say from the boshes to the mouth or throat of the furnace with a supply of air or
blast separately and as far as possible separate from the lower portion which
comprises the melting space (the crucible) and the hearth-and in regulating the
temperature of this upper part of the furnace in such manner that the heating of the
charge and the reduction of metals (such as lead, copper, and iron, which are reduced
at a lower temporature than zine) are there effected, whilst the reduction and the
volatilization of the zinc and the melting of the oharge is effected in the lower part
of the furnace. In this manner the upper part of the furnace produces gases free
from zine which are led away separately from the zine-containing gases that
rise up from the lower part of the furnace. Only the latter gases which contain
the whole of the zinc need be subjected to the condensing operation. They contain
(in addition to the carbonic oxide which results from the reluction of the zinc oxide
and which is unavoidable oven in distillation in vessels) only the products of combus-
tion (which have been converted into a mixture of carbonic oxide and nitrogen and
are therefore free from carbonic acid) of the fuel which is necessary to volatilize the
zino and to melt the charge which has been heated up to nearly the melting point.
These products of combustion may however be considerably diminished by intro-
ducing highly heated blast into the crucible of the furnace.
Still more favourable are the conditions in smelting unroasted zinc sulhpide (which
is to be decomposed according to the formula ZnS + FeFe S+ Zn) because this
decomposition takes place without the development of carbonic oxide which always
accompanios the reduction of zinc oxide. It inay be assumed that in this case the
shaft furnace gases will not have a much smaller percentage of sine than the gases
which are produced in the muffle.
The sulphide of iron produced is tapped from the hearth together with the metals
(lead, etc.) that may have been reduced, and the slag is also ran off at intervals or
better still continuously. The expense of the iron to be added in a metallic or in an
oxidized state-in which case the reduction of the oxide to metal takes place in the
upper part of the furnace-oan be considerably lessened by again adding the iron
oxide that is obtained by the roasting of the iron sulphide produced.
The advantages which the sunelting of zine ores in the shaft furnace possess over the
distillation in vessels are mainly as follows:-Saving of the expensive vessels, con-
siderably smaller consumption of fuel, leas coat of labour, aud larger yield. In treating
zine blende there are the further advantages:-the substitution, for the expensive
roasting of the ore, by the cheaper roasting of the iron sulphide (said
roasting not requiring any separate fuel) and better utilization of the contained
sulphur in consequence of richer roasting gases. In connection with this are:-
Saving in costly condensing plant for the fumes, and avoidance of damage to the
surroundings, because it is not necessary to roast the iron sulphide completely; or
the roasting of the same can be wholly avoided by purchasing it from sulphurio neid
works or depositing it upon the waste heaps. In this case the necessary iron for
precipitation would have to be provided for by an addition of rich iron orea or
the like.
The working of the shaft furnace is as follows The furnace may have a high and
steep or quite vertical crucible with one or more tuyeres. At the upper part of the
crucible, or at the commencement of the boshes, there are formed in the wall of
..the furnace one or preferably several apertures for the escape of the gases. The
heating of the upper part of the furnace may be effected in two different ways. The
first way consists in introducing at a point not too far down below the mouth of

page_text: the furnace, a blast of low pressure or air from wide nozzles. The furnace gases pass
downwards and leave the furnace through apertures formed in the boshes. In order to
prevent the gases from changing their direction and thus escaping out at the mouth
of the furnace during the charging of the latter, the mouth of the furnace is
provided with a double closure snch for example as n Parry hopper with a bell.
These allow the furnace to be charged whilst its mouth is closed. Also the blast
can be stopped during the charge. Or there any be arranged in the gas conduit
which is connected with the outlet apertures a fan for the purpose of facilitating the
downward travel of the gases from the mouth to the bosh. Between the apertures
on both sides for the escape of the gases that flos from top to bottom and from the
bottom to the top there is left a sufficient vertical space which serves to form a
neutral zone that has for object to prevent the iningling of the gases that are free
from zinc with the gases that contain zinc. The escape apertures for the zinc-
containing gases are connected along the shortest possible path with the two legs
of the condenser, and each of these connections is alternately shutoff and re-opened
at certain intervals of time by means of a reversing valve or in any other suitable
manner. The gases freed from zinc are, as in the case of distillation in muffles,
especially suitable for heating the condenser. But they may also be used for heating
the blast, or heating steam boilers, or for other purposes. This also holds good in
the case of the gases that are free from zinc and which escape from the shaft of the
furnace.
The second method of heating the upper part of the furnace separately differs
from the above described method, mainly in two respects. Firat, the upper part of
the furnace is not worked simultaneously with the lower part bat is worked
alternately with the same; and secondly, the gases which serve to heat the upper
part of the furnace do not flow contrary to their natural direction from top to bottom
but they follow their natural direction, that is to say they rise up to the mouth of
the furnace from the tuyeres which are now provided in the boshes. Two exactly
similar shaft furnaces are required, arranged at a distance apart from each other such
as to allow of the condenser which is common to both being situated between them.
This condenser is preferably made with two wings which are inclined upwardly from
its centre towards the two furnaces and each of which is connected at the upper part
by means of a conduit (which is as short as possible and is capable of being closed)
with the gas outlet openings of its adjacent furnace that are provided in the crucible
or immediately above the latter. In the centre of the condenser, that is to say at its
lowest point, there is situated the sump or well for the collection of the zinc. Ench
of the two wings of the condenser is also provided near to the conduits leading to the
furnace with outlet openings (adapted to be closed) for the gases that have been freed
from zinc. The condenser may, if required, he constructed so as to be capable of
being heated in the manner above stated. The construction and arrangement of the
furnaces as regards their lower portions, is exactly the same as in the case of those
described relatively to the first method. The upper part of the furnace is provided
at the boshes, or immediately above the same and at a suitable distance froin the gas
outlet openings, with inlet openings for blast and air.
The working is as follows:-The first furnace is first, for the purpose of blowing in,
charged to a certain height with fuel and then alternately with fuel and with slag-
forming materials. As soon as the latter appear in front of the upper tuyeres these
are closed. The connections of the two furnaces with the condenser have already
been previously closed. Then blast is introduced through the lower tuyeres into the
crucible and the furnace gases are allowed to pass out at the mouth. Then gradually
ncreasing quantities of ore are added to the charges until the normal composition of
charge has been reached. The second furnace is then blown in, in exactly the same
nanner but one or two hours later than the first one. As soon as the first vapors of
ine appear in the furnace-mouth gases of furnace No 1, the working is altered. The
heating-up is completed, and the furnace enters into the smelting and zinc-producing
tage. The charging is now stopped; the connection with the condenser is made;
nd the mouth of the furnace that was quite filled up before is carefully closed. The

page_text: CIUIC
concentration of the heat promoted by the hot blast, and by the narrow
facilitates the melting of the mass and the volatilization of the zinc. The gases rich
in zinc leave the furnace and pass down through the nearest wing of the condenser,
then pass over the sump into the other wing that leads up to furnace No 2. At the
end of this wing the said gases leave the condenser through the outlet passage which
has been previously opened. If these gases still contain zinc-dust, the gases are
caused to pass further through a purifying shaft or tower filled with coke or the like,
which is intended to retain the last particles of zinc. In order to facilitate this flow of
the gases, and to render their escape from the closed mouth of the furnace quite
impossible, it is advisable to provide an exhausting fan in the gas passage behind the
purifying tower. The gases thus freed froin zine may finally be utilized as fuel for
the purposes above set forth. After a certain time the charge in furnace No 2, whose
gases have up till now been escaping from the mouth of the furnace, has become ao
hot as to cause zinc vapours to be found at the mouth. In consequence of this,
reversal must again take place. Furnace No 2 now enters on the melting stage,
whilst in furnace No 1 thore begins again a heating-up stage. The reversal is
commenced by shutting off the blast tuyeres in the crucible of furnace No 1, aud by
closing the gas passage so as to shut off communication with the condenser. Then
the escape pipe for the gases passing out of the furnace mouth is opened and the
blast or air is introduced into the bosh. At the same time the charge which had
Bunk during the melting period, during which the charging was stopped in order
not to disturb the draught of the gases in the condenser and to avoid all cooling of
the same, is now replenished whereby the charge is kept at its normal height. In
order to prevent the materials from melting and the zine from being volatilized in
consequence of too high a temperature during this period which zinc would be lost
in the furnace-mouth gases the nozzles that open into the boshes are made of large
cross-sectional area, and the blast is introduced through the same at a low pressure
or only air is passed through. Also these nozzles are arranged at one level where
the furnace widens out considerably, in order that the bot products of combustion
alall become rapidly spread over large masses and shall be able to impart their heat
uniformly to the same. After the reversing of this furnace into the heating-up
stage has thus been effected, furnace No 2 is then brought into the melting aud
distilling stage. This is effected in the manner already described for furnace No I
by establishing communication between the gas passages leading from the crucible
and the corresponding wing of the condenser; by opening the outlet aperture for the
gases freed froin zine in the opposite wing; and by closing the mouth of the furnace
or the furnace-mouth gas tube of the furnace which is previously completely filled
up, After having thus terminated the reversal in this maner of the two furnaces
the gases rich in zine pass through the condenser in a direction opposite to their
previous direction. By means of the aforesaid exhausting fan, these gases may also be
led through the purifying tower which is arrauged at a point such that it can be
reached by an equally short path by the gases that issue alternately from the left
and from the right wing of the condenser. Again, after the expiration of a certain
period furnace No 1 is again brought into the zinc-producing stage and furnace
No 2 into its second-beating-up stage and in this manner the two furnaces alternate
continually in their two stages so that one furnace is always being heated up whilst
the other furnace is occupied in melting the heated-up charge aud in producing
zinc.
A modification of the above described process may be set forth here and which I
also desire to patent. This modification has for object to utilize the gases coming
from the condenser in heating-up the charge. For this purpose the outlet-apertures
of the condenser are connected along the shortest path with the blast nozzles that
open into the boshes of the two shaft furnaces. As soon as, in the course of the
reversal, the outlet aperture in that wing of the condenser which is situated nearest
to the shaft furnace that is entering upon the heating-up stage is opened, and the
tuyeres connected therewith are set in operation, the gases drawn from out of the
condenser by the flow of the blast are forced into the furnace and are at once burnt

page_text: up therein. The blast in this connection has the same action upon the gases as the
steam jet in the well known steam jet blower has upon the air drawn in by it. As
the gases leave the condenser at a temperature of about 400° C. the heat which they
still contain serves to aid in heating up the charge. Any zinc dust that these gases
may still contain is deposited on their way to the furnace mouth in the loose masses.
The said dust is therefore utilized in the simplest manner, because the shaft furnace
acts as a substitute for the purifying tower. Thus these gases changing with every
furnace reversal are continually aiding the heating-up, and if the quantity of blast is
regulated in such a manner as to be just sufficient for complete combustion of the
gases it may be assumed that the amount of heat necessary to heat up the charge
can be supplied alone by the combustion of the gases. At least this should be
possible so long as the heating-up has not advanced to such an extent as to cause
any fear of a considerable re-formation of carbonic oxide from the carbonic acid
which is produced by the combustion of the gases.
It may finally be stated that the preceding special description of the various
methods which it is desired to patent does not describe the only way of carrying out
the Invention bat has merely for object to give a clear idea and example of the same.
Naturally the details can be considerably modified in many cases from the arrange-
ments described in this Specification. It need here only be stated that the condenser
may be connected up in any desired manner, thus it may be divided into chambers
by means of a series of partitions. Or it may be composed of a number of upwardly
and downwardly directed or zig-zag passages or pipes and so forth, so long as it
retains its characteristic arrangement of alternating reversal. Also the form of the
shaft furnace to be employed, may be of any desired type, and although the levels
or heights at which the blast or air is supplied to the furnace and the gases are
drawn from the same, have been specially designated by the words "boshes",
"crucible", etc. it has only been intended by this to indicate the relative positions
of their apertures, tuyeres, elc. without intending to bind oneself to the statement
that the said openings inust necessarily be situated in that specific part of the furnace
referred to. Thus there are shaft furnaces which become gradnally wider from the
hearth towards the mouth but have no visible limit or boundary between crucible and
boshes, nor any such limit between the boshes and the shaft. Consequently these
designations are only intended to indicate approximately the level or height in the
shaft furnace at which the said openings are to be arranged. But wherever in this
Specification expression "shaft furnace" has been employed, there is exclusively
meant. thera blast furnace or blast shaft furnace, that is to say a furnace in which
the zinc are situated in immediate contact not only with the reducing agent but
also w the fuel intended to produce the heat, whereas in the distillation in vessels
the bustion of the fuel, which serves to produce the heat, takes place outside of
thressel in which the volatilization of the zinc is effected. It may also be added
fat instead of the blast from tnyeres, other means may be employed for conveying
the gases from the condenser into the shaft furnace. Thus for example there may
be employed for this purpose a current of steam or a device (centrifugal fan or the
like) arranged between the condenser and the furnace and acting to suck or to force
or to both suck and force; or an exhausting fan may be arranged in the furnace-
mouth gas-passage behind the furnace. This fan has the advantage that is not to be
under estimated, vis:-that not only is there no need of a strong blast but also that
even in this case air can be used instead of the blast during the heating-up stage, the
said air being in this case also drawn in by the fan. By this means the apparatus or
plant is considerably simplified as regards its construction.
The accompanying drawings illustrate several examples of the practical application
of this Invention. Figures 1 and 2 represent a condenser in vertical and cross section
respectively.
The two trunks or chambers A A¹ which communicate at their lower ends as shewn,
are charged with condensing material through apertures a and a¹. The gases entering
by the pipe B are directed by the flap valve alternately to the one or other trunk or

page_text: chamber whilst the exhaust gases escape through the flue B. The zino can be
discharged at m.
Figures 8 and 9 represent two separate furnaces with a condenser between them,
the arrangement being such that one furnace may be heated up whilst the other is in
operation.
Each furnace is provided with two sets of blast tuyeres and wheu zine is being
produced in the furnace A the working is as follows-The blast through C¹ being
shut off the blast supplied from the main D enters at the tuyeres d at the lower part
of the furnace whereby fusion is there effeoted, the metal being tapped off at z and
the slag at y. The top of the furnace being closed by valves a and f, the gases
produced pass through the outlets g into an annular chainber h filled with wood
charcoal in which condensation of the zinc commences and whence the gases and the
liquid zinc pass into the condenser K which is also filled with wood charcoal through
the charging doors l, the zino being drawn off at m. The gases pass through the
flue o to the blast tuyeres and enter furnace A' along with the blast from the main
Cand are burned, the products of combustion escaping through pipe f. After a
certain time the direction of working is reversed so that the current of gas flows from
the furnace A¹ to the furnace A.
Figure 7 illustrates a furnace which works continuously and in which air blast
inlets C and C' are provided at top and bottom, whilst the gases freed from zine
escape at Z and the zinoiferous gases pass off at M and pass thence into a passage B
as shewn in Figure 2. The passage must be slightly inclined so as to convey any
previously condensed zinc into the condenser.
The arrangement when retorts are used is shewn in Figure 3. The thirty-six
muffles R are divided into two groups of eighteen each and the gases from each set
of three superposed muffles R pass down through n pipe r to the condenser K.
Supposing the left-hand group of retorts to be in operation, the gases are deflected
beneath a plate m¹ and the zino is drawn off from the sump through the aperture m,
the gases freed from zine passing out at h. When the right-hand group of muffles
is in operation the course of the gases is reversed.
Figure 6 illustrates a condenser in which the gases deprived of zinc are burned so
as to heat the condenser. The gases enter at p into the condenser K; they traverse
the latter and pass at 7 to a blast nozzle whereby the air blast entering at s blows
the gases into the space between the condenser K and its cusing Q and there burns
them, the products of combustion escaping at P.
Figure 4 illustrates in plan the use of generator gases. The muffles R are divided
into two groups as before and the generator gases (which must be free from aqueous
vapour and carbonio acid) entering the left-hand group for instance at n. The air
blast enters at n¹, and the gases flow along the paths indicated by the arrows, the
xine being drawn off at m
A portion of the condenser is enclosed in a heated chamber Z and Figure 5 shews
a section through this heating chamber, on a slighly smaller scale, 8 being the
fire-place.
Having now particularly described and. ascertained the nature of the said Iuven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. The process of recovering metallic zino from zinciferons gases in condensing
chambers (condensers) which are filled with porous or rough bodies or are provided
with other devices that serve to dry-filter the gases, the arrangement being such that
the gases are caused by suitable reversals to pass alternately in opposite directions
through the chambers
2. A mode of carrying out the process specified in Claim 1, according to which
the zinciferous gases of two or more distilling vessels (muffles, pipes, etc.) or shaft
furnaces arranged singly, or in groups connected to a common condenser, are caused
to pass alternately in opposite directions through the condenser.
3. A mode of carrying out the process specified in Claim 1, by the use of condensing

page_text: chambers in which the length of the path along-which the gases are to travel is
rendered adjustable according to requirements by the shutting off of single portions
of the chambers."
4. A mode of carrying out the process specified in Claim 1, applied to distillation
in vessels, according to which during the distillation hot gases which consist as a rule
of a mixture of carbonic oxide and nitrogen are led through the distilling vessels
(muffles, pipes, etc.) and then together with the zinc vapours through the condenser.
5. A mode of carrying out the process specified in Claim 1, appiled to distillation
in the blast furnace according to which the products of combustion produced by the
introduction of blast into the crucible of the furnace are after they have taken up
the zinc from the melting masses and after their carbonic acid produced in front
of the tuyeres has been converted into carbonic oxide) passed into the condenser
through one or more apertures provided in the wall of the furnace, without first
passing through the upper portion of the furnace, whilst said upper portion of the
furnace is supplied with blast or air by means of nozzles arranged just below the
mouth of the furnace so that the products of combustion thereby produced heat-up
the charge and pass down through the latter until they leave the furnace at a suitable
distance from the outlet apertures (designed for the zine vapours) through one or
more openings provided in the wall of the furnace above the said zinc vapour
outlets and are, if necessary, aided by the action of a condenser arranged outside
the furnace.
6. A modification of the process specified in Claim 5, according to which two blast
furnaces connected with a common condenser according to Claim 2 into which they
pass their gases alternately in opposite directions are worked in such a manner that
in each furnace the melting takes place in the lower portion of the furnace not
simultaneously as according to Clain 5 with the heating-up in the upper portion of
the furnace, but alternately with said heating-up, the arrangement being such that
the melting and zinc distilling period (changing at each reversal of the furnace) of
one furnace always coincides with the heating up period of the other furnace (which
beating-up period also changes its furnace) and the arrangement being also Buch
that blast or air is supplied to the furnace occupied with the heating-up stage, not as
according to Claim 5 below the furnace mouth, but in the vicinity of the outlet
apertures for the zino vapours, whilst the products of combustion thus produced rise
up from thence and passing up through the charge, leave the furnace at the mouth
of the latter.
7. A mode of carrying out the process according to Claim 6, according to which the
gases freed from zinc and coming from the condenser are always supplied to that
furnace (changing with every reversal) in which the heating-up stage is taking place
at the time and are burnt in the said furnace by means of the air which is introduced
therein.
8. For carrying out the process according to Claims 1, 2, 3, 4, 5, and 6, condensers
endered capable of being heated from outside wholly or partially, viz-by said con-
lensers or single portions thereof being enclosed or surrounded by a jacket for the
purpose of burning fuel in the intermediate space thereby formed between the con-
lenser and the jacket.