An Improved Manufacture of Iron and Steel, and Method of Extracting Gold and Silver from Ores.
Year: 1896

page_text: Date of Application, 18.h Jan., 1896
Complete Specification Left, 4th Sept., 1896-Accepted, 9th Jan., 1897
An Improved Manufacture of Iron and Steel, and Method of
Extracting Gold and Silver from Ores.
A communication from CARL JOHANN LUDWIG OTTO, of Dresden, Saxony, in
the Empire of Germany.
I ALFRED JULIUS BOULT of 323 High Holborn, in the County of Middlesex,
Chartered Patent Agent, do hereby declare the nature of this invention to be as
follows:-
Direct production of wrought iron from the ores has not led hitherto to a scientific
success, as after a long process and considerable consumption of fuel the result was
spongy iron, saturated with slag, the further treatment of which was not only
complicated and expensive, but also considerably diminished the quality of the
product on account of oxydising influences, which it was impossible to avoid.
To obviate these drawbacks it is proposed to melt the received iron in a reduction
chamber in a neutral atmosphere under high pressure, but to let the reduction
proper take place quickly at such a low temperature, that iron of incomparable
purity remains and at the same time the formation of slags is prevented. My
correspondent completely rejects the present view, that in mixture of iron ore
and coal a direct reduction takes place at a moderate heat, that is to say that the
carbon combines directly with the oxygen of the ore. As accepted already in
similar processes, the process here is to be considered in the sense, that the
reduction is produced by the previously formed carbonic acid. This shows that in
the old process it was a mistake to have let the carbonic acid, which was strongly
heated in open furnaces, expand freely and so act on the ore in an insufficiently
dense state.
With regard to this, a furnace could be used in this process in which
the consumption of the fuel and the reduction of the ore take place under pressure.
Such a furnace with compressed air fulfils at the same time the conditions of
melting the spongy iron, for in such furnaces, as known from Bessemer's experiments,
the highest melting temperature can be reached in a quick and secure mai ner
even with a pressure of one atmosphere. Decomposition of iron oxide by the
same quantity of heat as became free at the formation of the oxide from metallic
iron and the oxygen of the atmosphere, could not be accomplished without
expenditure of work, as the oxygen returning into its gaseous state has to overcome
the atmospheric pressure. In limiting by using high pressure this work, which
necessitates an extra expenditure of beat, the heat, equivalent to the work saved
s itself saved and used to furnish some of the heat, which must be absorbed in the
lecomposition of the remaining portion of the ore, which has not yet been
lecomposed. The loss of heat, which arises in course of the process in producing
he pressure, is easily recovered afterwards from the outgoing gases during the
quick decrease of temperature in these gases as they subsequently expand. Under
pressure a part of that waste heat can therefore be used for the reduction, which
s of great economical importance. The heat expenditure for the reduction, which
atter is helped and made more rapid by the pressure, increases at the same rate,
t which the heat production for accelerating the process is increased in the high
ressure furnace; therefore there is no necessity to overstep the moderate
CD

page_text: with the other canals communicating with it. is the path for the blast coming from
underneath, the other blast branch with its connections conducts the blast from the
top to the flame; there is a great heating of the compressed air on its way through
the zig-zag channels.
The flame produced at the hearth develops in the furnace shaft under the
crucible which is surrounded by gaseous products of combustion in spiral flues.
These flues are formed by the crucible resting close against the edges of stepped
brickwork, which edges have the shape of a spiral on a cone. Therefore the
crucible opening is closed to the fire-gases which escape laterally through suitable
exits. On the crucible there is placed a loose cover which does not close
hermetically and which allows the carbonic oxide developed in the crucible to
escape. From the hollow space above the crucible lid this oxide is led through a
canal to the hearth. The canal leading from the spiral channels is forked in the
lower part of the furnace and two branches thereof lead to chambers which,
according to former explanations herein, are used for utilising the heat of the
out-going gases and decreasing the loss of that heat. For this purpose in these
chambers can be placed cementing boxes. From the chambers finally, go canals
which merge in a canal which leads to a reservoir or to a compressed air motor.
To start the furnace the outer jacket thereof is lifted by means of books by a
crane and the inner furnace structure made accessible by lifting the cover thereof
and the cover of the crucible, and by taking out certain parts of the structure.
Then follows charging of the crucible and firing through the grate. The charge
of the crucible ought to consist of a thorough mixture of ores and coal with the
fluxes necessary for the formation of fusible slag, or if desired should also
comprise a bottom lining of iron or steel pieces for producing a molten bath.
When all the apertures are closed, the jacket is let down and screwed tightly in
place. Valves are then opened in order to enable compressed air to be forced
through the blast branches, the outlet canal being temporarily closed. The blast
from underneath enters through into the generator chambers below the hearth
while the top blast is supplied through its special canals and tuyeres to the
combustion hearth to be mixed with combustible gases escaping from the generator
chambers. For the combustion hearth a peep-hole with a mica lens is provided
through which lens the progress of the firing can be observed. According to that
the conical piece aforesaid can be adjusted when it is not possible to follow the
changes of pressure. As the temperature at the beginning ought to be a moderate
one and as the quantity of generator gases is increased by addition of the carbonic
oxide resulting from the process of reduction, the blast from the top has to be
kept up strong in the beginning, and then gradually to be decreased till finally an
intense combustion takes place without superfluous air, which combustion secures
melting of the extracted iron. When the process is finished, which is recognisable
by the fact of the waste heat increasing in temperature, the furnace is opened,
after the blast supply has been closed and the still remaining pressure relieved, in
order to lift out the crucible for producing the intended castings after the slug has
been taken off.
If the furnace is supported by trunnions like Bessemer convertors, then the
casting can be accomplished by inelining the furnace. For the process on a large
scale the crucible can be widened or given any suitable shape or can be replaced
by retorts. In many cases it is advisable to make the furnace horizontal.
Dated this 18th day of January 1896.
BOULT & WADE,
Agents for the Applicant.

page_text: Figure 5 is a longitudinal section and Figure 6 is a cross section through the
oscillating furnace, the latter section being made at the level of the trunnions.
The furnace is in all parts similar to the fixed one, only it is suspended so as to
be capable of oscillating in hollow trunnions u u and oo supported in bearings U U
and O O. The lower blast pipe E¹ is connected to uu by stuffing boxes u
and oo (as in Bessemer convertors), uu being in communication with the
passage u, and the upper blast pipe E' is connectel to o o, which is in communi-
cation with the passage o. The pipe (as in fixed furnaces) must in this.
construction lead to the atmosphere or be connected with the further combustion
gas conduits by means of jointed pieces.
For using the process on a large scale the crucible can be widened or given any
suitable shape cr can be replaced by retorts. In many cases it is advisable to
make the furnace horizontal.
Having now particularly described and ascertained the nature of the said inven-
tion as communicated to me by my foreign correspondent, and in what manner the
same is to be performed, I declare that what I claim is ;-
1. A process for the direct production of iron and steel in a reduction vessel
heated from the outside and closed to the fire gases a characteristic feature of
which process is that inside and outside of this vessel a high pressure-atmosphere
is kept up and that the gas developed in the reduction vessel is led to the hearth.
substantially as set forth.
2. In the treatment of iron-ores containing gold and silver separating the
precious metals by such an increase of temperature at the finish of the process that
liquation of precious metals takes place substantially as set forth.
3. A furnace for the direct production of iron and steel characterised by a
space (R) and a canal (R') leading the gases developed in the reduction vessel (T).
from the space (R) to the combustion hearth (d) and by side spaces or
chambers (BB) through which compressed outgoing gases are led for utilising
their heat and decreasing the loss thereof.
4. A furnace of the kind described supported in hollow trunnions.
5. The combination and arrangement of parts of a furnace for the production
of iron and steel substantially as described and illustrated in the drawings.
Dated this 4th day of September 1896
BOULT & WADE,
Agents for the Applicant..