New or Improved Regenerating Double Shaft Furnaces with Change of Current.
Year: 1889

page_text: COMPLETE SPECIFICATION.
New or Improved Regenerating Double Shaft Furnaces with
Change of Current.
I JOSEF VON EHRENWERTH of Leoben in the Empire of Austria, Professor do
hereby declare the nature of this invention and in what manner the same is to
be performed to be particularly described and ascertained in and by the following
statement:
This invention relates to furnaces for heating ingots, for tempering or annealing
wire, rivets, sheet metal, castings etc., for smelting metals, etc. for burning bricks and
other purposes and it consists in a double shaft furnace with regenerative gas heating
and change of current.
As a shaft furnace; it is to be understood in the present case furnaces without
difference of dimensions with upward or downward circulating current of heat.
Two shafts of a double furnace I and II Figs. 1, 2, 3, 4. are connected with one
another at their upper ends by a suitable passage c which can be constructed in the
brickwork, Figs. 1 and 2, or by the arrangement of suitably shaped covers as in
Figs. 3 and 4. These shafts are also connected at the lower ends with the heating
chambers or regenerators R for heating either firstly air and vapour and secondly, air
only, or thirdly vapour only.
In the second case the air-vapour, in the third case the vapour is added direct, that
is without passing special warming apparatus..
In order to avoid or prevent as far as possible the damaging influence of unmixed
currents of gas and air on the charge of the furnaces, as for instance, the oxydizing
effect upon iron blocks, iron-pots, castings etc. there should be provided in the com-
munications between the furnace shafts and the regenerators, that is to say the gas or
air chambers aforesaid, a mixing space for the gas and air currents before their
entering the furnace proper, within which the combustion takes place or is at least
arranged, that is to say the combustion space.
ย
The mixing spaces may be arranged at the circumference of the bottom, Figs. 1,
2, 3, 4, as well as below the centre thereof as in Fig. 6.
The shape of cross section and dimensions of the furnace shafts, naturally depend
upon the purpose for which the furnace is intended.
Similarly it has to be decided whether air and gas or only one of these and if so
which one is to be heated so that the construction can be made accordingly and
according also to the quality or nature of the fuel and temperature of the gases but
such will in no wise affect the general principle of the arrangement of the connection
and inlet channels of the furnaces.
In working with a lew furnace temperature or with badly inflammable vapours it is
preferable to connect some or all of the combustion spaces v Figs. 1 and 3 of both
furnace shafts by any suitable passages which can be shut off by dampers.
The nature and arrangement of the apparatus for the change of current depends
upon the temperature of the vapours and the arrangement of the regenerators and of
the channels.
Figs. 1 and 2 represent as an example, a furnace with heating of gas and air (the
most general kind) a furnace for heating ingots or faggots for example for rolling
mills etc.
The cover is composed of lids placed in a row and lined with a fire proof material.
If necessary, a cinder channel is arranged at the bottom for carrying off the
cinders etc.
For using the furnace for heating bars etc. it is arched over at the ceiling, provided
with platforms for carrying the bars and with side charging doors along one of its
longer sides, similarly when used for the purpose of plate heating in which case
however, the platforms are omitted and the charging doors are preferably arranged at
one of the shorter sides T Fig. 2.

page_text: The same construction is good for the manufacture of blister steel and cast steel
the combustion space being preferably arranged centrally under the furnace bottom.
Figs. 3 and 4 represent a double furnace as an example, in which only the com-
bustion air is heated, the gas however is introduced direct from the generator. It
is constructed for heated gases and intended for annealing wire, rivets, etc.
The same construction can also be used for annealing castings.
The connecting channel c of both shafts I and II is here composed of specially
shaped lids with contral gas opening, the reversing is done by one single apparatus
(two way cock).
As special covers are intended those which, while shutting the furnaces from
without are arranged at the same time in connection with one another in such a
manner that the flame current goes out or enters respectively into each furnace. This
can be arrived at in different ways.
One can use for instance, ordinary lids, perhaps with sand-packing, which have a
central opening, to which can be attached a bent pipe, the other end of which rests
upon the central opening of the lid of the neighbouring furnace.
Figs. 3 and 4 represent a construction which has proved of good practical use.
A flue (Figs. 3 and 4) constructed of the same material as the lid (cast-iron)
opens at the one end centrally into the furnace and at the other end into the
connecting flue constructed in the separating wall of two furnaces. Sand packings at
the upper and lower edge make a perfect closing of the furnace from without. The
neighbouring furnace is also connected by a like lid to the connecting flue in the
partition wall.
Where two furnaces are in connection the reversing valves are intended for
changing the inlet of gas and air and the outlet of burning gases respectively, that
is to say, to direct periodically the inlet towards the first or second furnace, the
outlet towards the second or first furnace respectively.
In the drawing a double-storey cock is used one which contains in the upper
storey only one channel, but two channels in the lower storey which diverge at right
angles. The upper channel, which serves for the passage of gas is lined to with-
stand the heat of the gases. Of the lower channels one serves periodically for the
outlet of the burning gases from one of the regenerators into the flue (to the flue
in front) the other one serves for the inlet of the burning gases into the other one
of the regenerators (from the other side).
In reversing the cock is slightly lifted, turned for 90° and lowered again.
If one wishes to warm the gases as well the upper part should comprise two
channels also.
Instead of the cocks one can also use two traps situated one above the other.
In both cases Figs. 1 and 4, the connecting channels of the two shaft furnaces are
above, the gas and air channels and therefore also the combustion spaces v below.
Likewise the contrary arrangement can be constructed and Fig. 7 represents a
complete furnace of this kind.
With sufficient cool gases one can also use, for reversing in all cases, traps situated
one above the other.
In all the figures of the drawings I II are the furnace shafts, g g the gas channels,
the air channels. R the air chambers Rg the gas chambers not shown in the
second example, c c are the connecting channels of both shafts, vv the combustion
spaces, ww the current changers, ff the ignition channels.
The manner of working this improved furnace system is as follows:
After one of the shafts (for instance 1) or if necessary also the second one II has
been heated so far by ignition of solid fuel inserted therein until the gases ignite and
continue to burn without bindrance, the two furnaces are supplied with the material
to be heated, such as ingots, bars, castings etc.; the furnaces are shut and now the
proper gas heating is started by the previously heated furnace and continued with
the same current direction until tho contents of this furnace 1 are completely
heated.
The outlet current from this furnace I travels through the other furnace II and

page_text: its regenerators into the chimney and thus heats further this furnace with the charge
and its regenerators.
If the contents are further to be worked upon as is the case for instance with
ingots etc., they are removed, the furnace I refilled and lastly the direction of current
changed.
Now the previously indirectly heated furnace II is directly heated the refilled one
now being indirectly heated. This period lasts until II is completely heated when
it is cleared and refilled and the current changed again and so on.
Thus the regular working is commenced which consequently consists therein, that
one furnace is completely heated by the flame protruding from the combustion
space while the other one however is indirectly heated by the combustion gases
coming from said space and that this method of working is periodically changed
or alternated in each furnace.
If the inserted material is not further worked upon when hot but if the same has to
cool after heating which for instance is the case with the annealing of wire, rivets,
castings etc., it is better to reverse the current before drawing the charge and
according to circumstances to cool down the charge partly within the furnace itself.
The drawing of the charge should take place in such cases at the latest when the
heated wire etc. is superficially cooled down to the temperature of the products of
combustion entering that furnace.
The first cooling takes place with this method of working in the atmosphere of the
products of combustion which is especially useful for avoiding or lessening the
oxydising of the articles treated.
In using the system of furnace for smelting purposes for producing blister steel or
cast steel the respective crucibles and cementing troughs are inserted, that is to say
built therein.
In order to protect the operators during the changing of the charge from gases
escaping from the furnace the said gases should be at such time caused to pass from
the connecting channel of both furnaces direct to the chimney by a channel provided
with a slide.
The position of the furnaces depends upon local circumstances. If practical it is
advisable to put them entirely or partly beneath the ground. If necessary several
pairs of furnaces can be added to the same regenerator system.
If it is desired to make use also of the heat of the finished heated charge for the
heating of a part of both or either air or gas introducing however the other part
direct, either the whole gas or the whole combustion air channel is removed to the
connecting channel g¹ of both shafts Figs. 1 and 3 in which case the direct current
does not require change of direction or this channel can be led to the ends of the
shafts g¹¹ (Fig. 7) in which case a change of direction is practical for the direct
current.
g and g (Figs. 1, 3 and 7) are channels which on the one hand end in the
connecting channel device of both shafts (Fig. 7) on the other band are in connection
with the generator or with the outer atmosphere in order to convey either the heating
gases or the combustion air direct that is without any special heating. Therefore in
the first case the air, in the latter case the heating gas is conducted through the
regenerator and the finished heated charge, and by this treatment making use also of
the heat of the latter. The distribution of the current from the channels g¹ and g" on
arrival into the connecting channel and into the furnace depends of course on the
shape and the dimensions of the shafts and of the purpose for which the furnace
serves.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is
1. In regenerative furnaces with upward or downward inlet flame foed the com-
bination of two furnace shafts, connected together at their ends remote from the inlets
by a passage or passages and having each, at or near said inlets, combustion

page_text: chambers v whereby the combustion of the gases may be at least commenced before
inlet into the furnace shafts, each of said furnace shafts communicating through their
respective combustion chambers with a regenerator or regenerators, together with
suitable devices for changing the direction of current, whereby said furnaces are
respectively directly and indirectly heated alternately substantially as set forth.
2. In regenerative furnaces with upward or downward inlet, flame feed the com-
bination of two furnace shafts connected together at their ends remote from the inlets,
by a passage or passages, each of said shafts communicating at their inlets direct with
a regenerator or regenerators; together with suitable devices for changing the
direction of current, whereby said furnaces are respectively directly and indirectly
heated alternately substantially as set forth.
3. In a regenerative furnace having two furnace shafts with connecting passage
and current changing device substantially as set forth, the construction of a divided
air or vapour feed device therefor, whereby part of said feed may be heated by the
heated charge in one shaft and the remainder of said feed conducted direct to the
connecting passage of said shafts or to the said shafts near to said passage.
4. The combination of two or more pairs of furnace shafts, each pair with
connecting passage and current changers substantially as set forth with one and
the same regenerator or set of regenerators as set forth."
Dated this 12th day of Anril 1880
HERBERT & Co.,
18, Buckingham Street, Strand, London, W.C., Agents to Applicant.