Improvements in Refining Copper.
Year: 1890

page_text: Date of Application, 27th Oct., 1890
Complete Specification Left, 26th Aug., 1891-Accepted, 26th Sept., 1891
PROVISIONAL SPECIFICATION.
Improvements in Refining Copper.
I, JOHANNES CATILARINUS BULL of 18 Bexley Road, Erith in the' County of
Kent, Engineer, do bereby declare the nature of this invention to be as follows:-
It has before been proposed to effect the purification of copper by blowing air
through it as in the treatment of cast iron by the well known Bessemer process.
But when treating copper in this way the refining of the copper cannot be carried
beyond a certain point owing to the metal being cooled by the air passing through
it so soon as the percentage of substances with which the air will combine is
insufficient to produce sufficient heat to keep the metal molten.
To remedy this it has been suggested to carry in with the air matters capable of
combining with it or to heat the air to a high heat before introducing it into the
metal. Both these methods have however their disadvantages.
According to my invention I effect the oxidation and elimination of the impurities
contained in copper matte or regulus or impure copper by acting upon it when in
a molten state with nitrate of soda or other nitrate or chlorate capable of yielding
oxygen and oxidising gases when exposed to heat whilst at the same time the metal
has kept in contact with it an acid flux which is capable of taking up the oxidized.
metallic impurities climinated from the copper.
I may mix the nitrate &c. with inert bodies as for instance sand or clay of
suitable composition in order to reduce the energy of the oxidizing materials when
desirable.
The impure molten matte or metal to be acted upon may either be poured into
a crucible or converter at the bottom of which a quantity of nitrate &c. is
retained or the nitrate &c. may be blown into the metal through tuyeres together"
with a blast of air.
When the nitrate &c. is to be retained at the bottom of a crucible or converter,
the converter may be formed with the bottom readily removable and formed with a
hollow for containing the nitrate &c. and with a cover of perforated refractory
material to fit to and close the bottom of the converter and retain the nitrate &c.
below it.
When the nitrate &c. must be fed in a more regulated manner and blast is not
available this can be effected by keeping it in a fused state in a closed vessel
outside the converter and pressing it in below the copper by suitable means, for
instance an air pump which presses air into the closed vessel the action of which is
controllable.
When the nitrate &c. is to be blown in together with an air blast it may-in a
powdered or fused state-be fed to the blast in regulated quantities by suitable
measuring or controlling apparatus.
By thus acting upon the copper with a highly energetic oxidizing agent the
cooling of the metal during the purifying process is obviated and a very pure copper
is obtained..
Dated this 25th day of October 1890.

page_text: COMPLETE SPECIFICATION.
Improvements in Refining Copper.
I, JOHANNES CATHARINUS BULL, of 18 Bexley Road, Erith in the County of
Kent, Engineer, 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 :-
My invention relates to improvements in refining copper by oxidation which is
attained by the introduction of nitrates or other similar substances into the copper
below the surface thereof while the metal is in a melting or molten state in measured
and controllable quantities and at a controllable speed. The nitrates or other
similar substances are introduced in such manner from below or into or about the
middle of the melting or molten unrefined copper while in the furnace or convertor
so that the whole of the copper in the said furnace or convertor is exposed to the
action of the oxygen or oxydizing gases or substances into which the injected
bodies are decomposed by the heat of the melting or molten charge or by the.
chemical reactions which take place.
"1
"Chili bars or "pig copper" generally contain about 95% metallic copper and
about 5% impurities, such as sulphur, iron, arsenic, tin, antimony, bismuth, zinc
lead. Now by my process I am enabled to refine copper commercially to such an
extent that it only contains % of impurities or less.
In order that my invention and the method of carrying out the same may be
more fully understood I will describe the same with reference to the accompanying
drawings of which :-
Figure 1 is a sectional elevation of a convertor somewhat after the style of a
Bessemer convertor and suitable for refining small quantities of copper say three or
four hundredweight at a time.
Figure 2 is a similar view of a convertor adapted for working on a somewhat.
larger scale.
Figure 3 is sectional elevation of apparatus which I prefer to use in working
my invention commercially.
Figure 4 is a sectional plan view on line X Y Figure 3, and
Figure 5 is a side elevation partly in section on line Z Z Figure 3.
I prefer to use as shown on the drawings a furnace or convertor A of the
"Bessemer convertor" type provided with trunnions d to allow of inversion.
Referring more particularly to Figure 1 the bottom part a¹ can be bolted or other-
wise fixed on to the convertor A. I prefer to make the lining A' of the convertor
and the bottom part of "ganister" or other suitable fire proof material such as a
mixture of sand and clay. In the bottom part a' of the convertor A is firmly"
embedded an open vessel b with a conical or other suitably shaped upper part or
top c, both made of fireclay or other refractory material. The top c has a number
of holes c¹, say from 10 to 15, of a diameter of from to of an inch. The conical
top c of the vessel has the same taper as a metal fin a formed on the bottom of the
convertor and the lining A' thereof after the point where the said fin a ceases, so
that the top c is kept in place by the fin and the lining when the bottom part a¹ is
fixed in its place. In using this form of convertor or furnace I proceed as
follows:-
:-
Into the vessel b I introduce oxydizing agents such as nitrate or chlorate of
soda or potash, the cover c is then put on and the bottom part a' is fixed in its
place at the bottom by means of bolts as shown or in any other convenient manner.
The weight of the charge of nitrate of soda corresponds to about 5% of that of
the copper intended to be refined and in these proportions good results have been
obtained. It should however be noted that the amount of oxygen produced by
different oxydizing agents varies and the proportions have to be varied to suit
different cases and that wherever the expression "nitrate" is used herein it should

page_text: be understood that any suitable oxydizing agent is intended.
The impure copper
is melted with a suitable silicious slag for the scorification of ferrous and other
oxides while in the convertor, and is then poured into the said convertor A where-
upon a portion of it will sink through holes c¹ into the vessel b, and by the intense
heat decompose part of the "nitrate" and cause a strong current of oxydizing gases
or matter to pass up and through the molten copper which gases for a time exert
sufficient pressure to prevent further quantities of the copper from entering the
vessel b. After a while however the pressure decreases so that more copper can
enter through the lowest holes e¹, more gases are disengaged and the process is
continued until all the nitrate or other oxydizing agent in the vessel bis
decomposed. The number and size of the holes are so arranged that the speed
of the decomposition is regulated. During the process the iron is oxydized and
scorified by the slag which should be rich in silica, the sulphur is oxydized and
removed as sulphurous acid, the arsenic and antimony are oxydized and volatilized
at the high temperature developed and the other impurities are either gasified or
scorified by the slag or the lining. When the reaction becomes languid the slag may
be removed through the opening closed by a door and the copper, after "poling,"
tapped through an opening y, or it may be "poled" outside the convertor or if as
shown the convertor be invertible the copper may be poured out through its
mouth. The bottom part a' is then detached and any copper that may remain in
the vessel is emptied out, a new charge of oxydizing agent inserted and the process
repeated as before described.
When it is required to treat larger quantities the arrangement shown in Figure 2
may be conveniently employed. The vessel in this case is replaced by a conical
block C made of the same material and secured in place by the fins a as before
described. This block C has a horizontal channel C2 with six or more vertical
tapering passages or holes C' as shown. The channel C2 is in communication with
a tube which is embedded in the lining of the convertor and is provided on the
outside of the convertor with a stop valve or cock for opening and shutting off
communication with the tube which is lagged or covered with non-conducting
material. The tube is carried up above the level of the copper in the convertor.
and communicates with a vessel B which is also preferably lagged or coated with
non-conducting composition. The vessel B is provided with a heat producer n.
The oxydizing agents are introduced into the vessel B and melted by heat in a.
convenient manner, and as the impure molten copper is poured into the convertor,
an air pump o is put in motion the valve opened and by the air pressure on the
surface of the liquid, or semi liquid nitrate, jets of the latter are forced into the
copper through the holes C¹ at such a rate that about 5% of the nitrate compared.
with the weight of the copper is forced in during a period of from ten to fifteen
minutes, providing the copper does not contain more than 5 to 8% of impurities.
The period is of course extended if the percentage be higher. If the supply of
oxydizing agent contained in the vessel B be not sufficient for the amount of copper
contained in the convertor I may in order not to interrupt the process provide
duplicate parts for the supply of the oxydizing agents or as shown the vessel B
may be connected to another similar vessel situated at a higher level and connected
thereto by a pipe p having a cock or valve p'. The valve being closed during
the refilling of the vessel to prevent the copper rising in the tube and opened
when sufficient oxidizing agent is obtained ready for the continuation of the
supply thereof; otherwise this form of apparatus works in the same manner as
that described with reference to Eigure with this exception that the supply of
the nitrate or other oxydizing agent is under better control. If the convertor or
furnace be of the invertible type the supply pipe is led through the trunnion.
The poling may either take place outside the convertor or whilst the latter is
laid over so far that the metal cannot enter the channels C¹. About eight or ten
hundredweight is a suitable charge for a furnace of this description.
The reason for making the inside bottom of the convertor of the approximately
coned form shown is that a better distribution of the oxydizing agent is effected

page_text: while at the same time where required facilities are given for the purest grade of
copper to sink below the level of the holes C₁ and the said copper may when
desired be easily drawn off by an opening normally closed by a plug.
"
. When working on a large scale and particularly when treating
"matte
"regulus" or coarse copper with large percentages of impurities, I prefer to use
a convertor constructed on the lines of an ordinary Bessemer convertor being
however modified to a certain extent to adapt it to the work in question as shewn
with reference to Figures 3, 4 and 5. In this case I have shown a method of
supplying the oxidizing agent in a dry and powdered form by-means of a blast.
A vessel is filled with the powdered nitrate and closed with a lid either
screwed or sufficiently heavy to prevent its being raised by the pressure of the
blast. In the bottom part of the said vessel I mount a wheel 2 provided with a
number of pockets or series of revolving hoppers which wheel is revolved at a
controllable speed by any suitable means and thus regulates the amount of powdered
nitrate to be discharged from the vessel into the pipes by means of the blast
coming from any suitable source by the pipe t. The wheel 2 is fitted to work
tightly against the walls of the vessel r so that no appreciable amount of blast
can pass into the vessel r. I may however also provide a bye pass pipe in order
to equalize the pressure above and below the nitrate in the vessel. By regulating
the speed of the wheel which is actuated preferably by worm and worm wheel
gear the amount of powdered nitrate can be accurately controlled.
open
If the copper to be refined contains less than 80% of metallic copper say 50
to 60, the process should proceed as follows:-A suitable charge of say 2500 to
3000 lbs. is melted with some slag rich in silica and poured into the convertor in
the usual way and the blast is put on, the atmospheric air alone being sufficient to
oxidize the impurities at a sufficient rate to keep the metal fluid for some time,
but partly to accelerate the reactions and partly to keep the tuyeres a clear and
it is advisable to start the nitrate feeding apparatus at once at a slow rate,
the nitrate decomposing at the openings and acting on the impurities of the copper
sufficient heat is evolved to make it sure that the openings do not become choked.
To further assist this clearing action I make as shown one or more of the cells or
hoppers of the wheel with a larger capacity than the others thuis generating a
larger quantity of gases and consequently a great evolution of heat at suitable
intervals. During the first 15 to 20 minutes about 1 per cent. of nitrate should be
introduced, after which the convertor is turned over so far that the slag can be
removed, the blast stopped or reduced, fresh slag introduced and the blast continued
as before for another 15 or 20 minutes with an injection of 2 to 4 per cent. of nitrate,
increasing the speed of injection as the amount of impurities and consequently the
heat evolved through their combustion. diminishes. When the absence of flame
and smoke or vapour denote the end of the process, the metal is poured after poling
unless, the latter process is carried on outside the convertor. With metal having
about 80 per cent. or more of metallic copper or when the convertor is fixed the
process is carried on without interruption to the end. When the matte is very
poor it may be necessary to pour out the whole of the contents of the convertor
after the first "blow." in order to give the matte and slag sufficient time to separate,
the slag can then be removed and the blast continued.
23
The oxydizing agent that I prefer to use is Chili saltpetre (nitrate of soda) as
being the cheapest and not under the conditions too violently explosive when
subjected to heat but other materials capable of evolving large quantities of
oxygen or oxydizing gases or matters or mixtures thereof may be employed.
The matters referred to may also be decomposed by heat or otherwise outside
of the apparatus and the resulting bodies or gases evolved forced in in any suitable
manner.
I have only described and shown apparatus for carrying on the process inter-
mittently but it is evident that the latter might be made continuous by passing
the refined copper out at the bottom while feeding in the molten unpurified metal.
Or the process, herein before described may be carried out directly in a reverberatory

page_text: or blast furnace during the smelting of the ores or the refining of mattes or coarse
copper or generally impure copper. It should also be noted that the purest
copper, having a greater specific gravity than that which is impure, sinks to the
bottom.
I am aware that it has been heretofore proposed to use nitrates for the purpose
of purifying copper, but the practice was to throw such into a convertor or furnace
from the top which caused great waste of metal owing to the explosions which took
place and had to be abandoned as absolutely worthless.
I am also aware that it has been proposed to purify copper while in a molten
state in a Bessemer convertor by the introduction of air.
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. The method of refining copper consisting in the introduction of an oxydizing
agent below the surface while the copper is in a molten state substantially as
described.
2. The method of refining copper consisting of the introduction of nitrate of
soda, or other materials capable of evolving oxygen or oxydizing gases into the
molten copper from below or under the surface of the metal substantially as
described.
3. The method of refining copper consisting in the introduction into the molten
copper of an oxidizing agent together with a current of air substantially as
described.
4. Apparatus for the refining of copper consisting of a convertor provided with
a receptacle having a perforated top for the oxydizing agent and arranged for
easy removal for recharging substantially as described and shewn in respect to
Figure 1.
5. Apparatus for refining copper consisting of a convertor provided with a series
of passages communicating with a receptacle for containing the oxydizing agent
the said receptacle being provided with means for forcing the oxydizing agent into
the molten metal in the convertor substantially as described and shewn in respect
to Figure 2.
6. Apparatus for refining copper consisting of a convertor provided with a
bottom raised in the middle having a series of passages communicating with a
receptacle for containing the oxidizing agent, said receptacle being provided
with a wheel having cells or hoppers for supplying the oxidizing agents in
measured quantities and a blast pipe for carrying such oxidizing agent to the
interior of the convertor substantially as described and shewn in respect to Figures 3,
4 and 5.
7. Convertors provided with raised bottoms and suitably arranged for the
introduction of oxidizing material such as nitrate of soda into the midst of the
molten metal by perforations in the said raised bottom substantially as described
and shewn.
Dated this 25th day of September 1891
JOHANNES CATHARINUS BULL.