IMPROVEMENTS IN THE PURIFICATION OF IRON. COPPER, AND ZINC
Year: 1872

page_text: LETTERS PATENT to Karl Wenzel Zenger, of Prague, Bohemia, in the
Empire of Austria, at present residing at the Charing Cross Hotel,.
in the County of Middlesex, for the Invention of "IMPROVEMENTS
IN THE PURIFICATION OF IRON. COPPER, AND ZINC."
PROVISIONAL SPECIFICATION left by the said Karl Wenzel Zenger
at the Office of the Commissioners of Patents, with his Petition,
on the 10th April 1872.
I, KARL WENZEL ZENGER, of Prague, Bohemia, in the Empire of
Austria, at present residing at the Charing Cross Hotel, in the County of
Middlesex, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN THE PURIFICATION OF IRON, COPPER, AND ZINC," to be as
follows:-
:-
This Invention has for its. object the removal of the phosphorus and
sulphur from pig iron by means of the hydrates of alkalies and alkaline
earths separately or together with the hydrates of the oxides of manga-
nese and iron.

page_text: It is well known that at a full red heat iron in scraps or filings or in
a melted state will decompose water, evolving hydrogen; now in the
same way when the iron is nearly at a white heat it will decompose the
water of the above-named hydrates, and the hydrogen thus liberated
combining with the oxygen of the oxides will thereby free the potassium,
sodium, or other base, which if volatile at a white heat will escape with
the superfluous hydrogen; but if the iron contain phosphorus and
sulphur the reduced alkaline metals will unite with them and form
sulphides and phosphides of the alkaline metals.
I conduct the process in the following manner :-The melted pig iron
is run either direct from the blast furnace or from a cupola into an iron
vessel lined with coal dust or graphite mixed with fire-clay, a ton or
more of iron being operated on at once. The surface of the melted
metal is covered with a layer of small pieces of charcoal, small chopped
wood, or good coal containing little ash or sulphur. The blast is then
directed on to the surface of the molten iron, and is so regulated that no
free oxygen may come into contact with the surface of the metal, which
should be covered with a layer of gas, consisting of oxide of carbon and
nitrogen. The required quantity of the hydrate, together with sawdust,
coal dust, or tar, is put on the surface of the metal, the quantity of the
hydrate being so regulated that the iron shall not be deteriorated by
alloying with the alkaline metal. The most economical mixture consists
of three parts hydrate of lime with one part of sawdust or tar, forming a
crumbling mass. This mixture should be continually stirred on the
metal with a rabble to renew the surfaces. The hydrate gradually dis-
appears, being absorbed, and on the surface a reddish slag is formed
containing a large proportion of sulphur and part of the phosphorus,
the remainder of the sulphur and phosphorus escaping as sulphuretted
and phosphoretted hydrogen. After 20 or 30 minutes continued stirring
the metal is allowed to stand for some minutes, and the slag, which
rapidly separates, is removed by a ladle or rabble. In 50 minutes a ton
of pig iron may be purified by this process, the resulting metal contain-
ing scarcely a trace of sulphur, and even if the iron originally contained
2 per cent. of phosphorus the resulting metal will contain not more
than to 2 per cent.
The loss in the above described process is from 2 to 5 per cent., but if
the hd motor of the
11

page_text: the hydrate of lime with the wood or tar, it will be found that there is a
gain of some per cent. of metal.
If the iron is to be treated by the Bessemer process, the above process
should not be carried so far if the hydrates of the oxides of manganese
and iron are used, as otherwise a large proportion of the silicon would be
removed and the temperature of the converter in consequence lowered,
but if they are not used or only used in a small proportion the silicon is
not attacked.
The hydrate of lime should not be used in sufficient quantity to alloy,
the iron with calcium after having removed the sulphur and phosphorus,
the calcium rendering the iron white, brittle, and highly crystalline..
By the above-described processes even the worst pig iron may be
made suitable for the Bessemer process, a greater proportion of phos-
phorus being removed than by any known mechanical puddling
process.
This method may also be used to remove the phosphorus or arsenic
in distilling zinc, and to purify copper from phosphorus, antimony, and
angonia
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Karl Wenzel Zenger in the Great Seal Patent
Office on the 9th October 1872.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, KARL
WENZEL ZENGER, of Prague, Bohemia, in the Empire of Austria, at
present residing at the Charing Cross Hotel, in the County of Middlesex,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Tenth day of April, in the year
of our Lord One thousand eight hundred and seventy-two, in the thirty-
fifth year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said Karl Wenzel Zenger, Her special license
that I, the said Karl Wenzel Zenger, my executors, administrators, and
assigns, or such others as I, the said Karl Wenzel Zenger, my executors,
administrators, and assigns, should at any time agree with, and no others,

page_text: from time to time and at all times thereafter during the term therein
expressed, should and lawfully might make, use, exercise, and vend,
within the United Kingdom of Great Britain and Ireland, the Channel
Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN THE PURI-
FICATION OF IRON, COPPER, AND ZINC," upon the condition (amongst others)
that I, the said Karl Wenzel Zenger, my exccutors, or administrators,
by an instrument in writing under my, or their, or one of their hands
and seals, should particularly describe and ascertain the nature of the
said Invention, and in what manner the same was to be performed, and
cause the same to be filed in the Great Seal Patent Office within six
calendar months next and immediately after the date of the said Letters

page_text: coal dust, or tar, or other substance containing carbon, or preferably
carbon and hydrogen, is put on the surface of the metal, the quantity
of the hydrate being so regulated that the iron shall not be deteriorated
by alloying with the alkaline metal. I find that a suitable and
economical mixture may be made by mixing three parts hydrate of
lime with one part of sawdust or tar, forming a crumbling mass. This
mixture should be continually stirred on the metal with a rabble to
renew the surfaces. The hydrate gradually disappears, being absorbed,
and on the surface a reddish slag is formed containing a large propor-
tion of sulphur and part of the phosphorus, the remainder of the sulphur
and phosphorus escaping as sulphuretted and phosphoretted hydrogen.
The vessel which I employ is cylindrical, and made of wrought iron lined
with a refractory lining about three inches thick, and is of a size
sufficient to work a charge of one ton weight. The interior of the vessel
should measure within the lining about 17 inches in depth by 28 inches
in diameter. The vessel is provided with a domed cover of cast iron
similarly lined, and the metal cover is provided with ribs to support the
lining. The use of this cover is to prevent loss of heat; it does not
close tightly on to the cylindrical vessel, but a sufficiently free escape
is permitted between the vessel and the cover all round, and there is a
larger opening to serve as a working hole on one side. There is a hole.
in the centre of the cover through which a vertical nozzle or tuyere
descends so as to introduce the required blast. It is covered externally
with a refractory coating and can be raised or lowered at pleasure. The
orifice of the nozzle or tuyere is two and a half inches in diameter, and
the pressure of the blast should not exceed one-eighth or one-tenth of
an atmosphere. The height of the tuyere from the surface of the metal
should be about ten inches more or less, and the quantity of air should
be sufficient to keep the metal thoroughly liquid. The colour of the
slag should be watched, and when the process is properly worked should
be of a reddish colour. If it becomes dark it is a sign that the blast has
not been properly regulated, and it is injuriously coming into contact
with the metal. When the metal is at a proper heat and quite fluid
the mixture of hydrate of lime and sawdust or tar is gradually added.
The quantity of this mixture to be used depends on the quantity of
phosphorus and sulphur known or ascertained by analysis to be con-
tained in the iron. For each per cent. of phosphorus it will be found
that as a rule about one per cent. of the mixture is required, and for.
each per cent. of sulphur one-half per cent.; thus for instance for a ton.

page_text: of pig iron (or 2240 lbs.) containing two and a half per cent. of phos-
phorus and one and four-fifths per cent. of sulphur the calculation may
be thus made:-
so that in this case a little more than seventy-six pounds of the mixture
is required. The mixture is added in three portions at intervals of ten
minutes, each quantity is well stirred about over the surface of the
metal with an iron rabble so as to bring it as much into contact there-
with as possible. After stirring for six or seven minutes the metal
is allowed to rest for two or three minutes in order that the slag may
separate, and the slag is skimmed off and removed by the working hole
before the next portion of the mixture is added.
The entire time occupied by my improved process applied to the
quantity of metal above referred to will be found to be about fifty
minutes, and the metal may then be run into a Bessemer converter or
into a puddling furnace to be made into wrought iron or steel, or it may
be cast into moulds. The purified metal will contain scarcely a trace of
sulphur, and even if the iron originally contained two and a half per
cent. of phosphorus, the resulting metal will contain not more than
1/10th to 12th per cent. The loss of metal in the above-described process
will be found to be from 2 to 5 per cent.; but if the hydrates of the
oxides of manganese and iron be used in addition to the hydrate of lime
with the wood or tar it will be found that there is a gain of some per
cent. of metal.
When the iron is to be treated by the Bessemer process, if the hydrates
of the oxides of manganese and iron are used, it should be only to a
small extent, as otherwise a large proportion of the silicon would be
removed, and the temperature of the converter in consequence lowered;
but if they are not used, or only used in a small proportion, the silicon is
not attacked.
The hydrate of lime should not be used in sufficient quantity to alloy
the iron with calcium after having removed the sulphur and phosphorus,
the calcium rendering the iron white, brittle, and highly crystalline. If

page_text: the metal is to be submitted to the Bessemer process this precaution is'
not so important, as in the operation of that process the calcium would
be separated.
By the employment of my process even the worst pig iron may
be made suitable for the Bessemer process, a greater proportion of
phosphorus being removed than by any known mechanical puddling
process.
The method by which the metal is kept hot and protected during the
process may be varied; thus, for example, a gas flame so regulated as to
contain no free oxygen may be employed in place of air being blown
upon carbonaceous matter on the surface of the metal; but it should be
remembered that the separation of phosphorus and sulphur can only
be properly performed whilst free oxygen is excluded, and this exclusion
is necessary until the metal is no longer in contact with the slag, in
which the alkaline or earthy phosphide and sulphide are contained. In
conformity with these principles the process may be conducted in the
Bessemer converter. In this case the metal is blown in the usual way
until, when the metal is at its hottest, the converter is tipped and the
blast shut off. The slag is skimmed off the metal, and the proper pro-
portion of the purifying mixture is added. There being at this time no
draught of air through the converter, and a copious evolution of hydro-
carbonaceous gas taking place immediately the purifying materials are
put in, the metal and slag are sufficiently protected from contact with
free oxygen.
In consequence of the intense heat of the iron in the
converter, a few moments, say a minute or less, suffices for the com-
pletion of the purification. The slag containing the phosphorus and
sulphur is skimmed off, and then the blast is again put on and the
converter turned up. The blast is continued until the flame shews the
usual indications of the operation being complete. The converter is then
again turned down, melted cast iron of suitable quality is added in the
proper proportion, as is usual, and the steel is poured into ingot
moulds

page_text: "
The mixture is moulded into balls, each of about a pound weight.
The balls soon become quite hard, and in this state they are used.
The operation may also be conducted in a gas reverberatory furnace
where the supply of gas and air is sufficiently under command and a
high heat can be obtained. A furnace such as is suitable for the manu-
facture of puddled steel being employed, the iron is puddled until it is
coming to nature," and then the heat is raised so that the metal may
be as fluid as possible. The supply of air is then checked so as to give
a deoxidising nature to the flame, and the slag is skimmed off the metal.
This being done, the purifying mixture prepared as already described for
the Bessemer process is added and stirred in. As the slag rises it is care-
fully skimmed off, and this being done the full supply of air may be
readmitted. The metal may then be finished in the usual manner, and
either by the addition of cast iron of suitable quality, in which case the
whole charge is run out of the furnace in a melted state as cast steel;
or the metal may be balled and removed from the furnace as puddle
balls and hammered and rolled in the usual way.
My process may also be used to purify copper from phosphorus,
antimony, and arsenic.
The operation is conducted as already described, and in the calculation
of the quantity of the hydrate of lime mixture to be employed allow-
ance is to be made for antimony and arsenic on the same scale as for
phosphorus.
In the application of my Invention to zinc the process is modified,
the hydrate of an alkali or alkaline earth mixed with sawdust, coal dust, 2
or other carbonaceous or preferably hydrocarbonaceous substance is
added to the charge of the retort from which the zinc is distilled, and
which consists of crushed and roasted zinc ore mixed with ground coal.
The said addition to the ordinary charge of the retorts should be pro-
portioned to the quantity of sulphur and phosphorus which the ore 3
contains according to the rules herein-before stated, and the distillation
of the zinc is then conducted in the ordinary manner.
In this manner
a purer metal is obtained, and the yield is largely increased.
Having thus described the nature of my said Invention, and the
manner of performing the same, I would have it understood that what I 3
claim is, the process of purifying iron or copper by means of the hydrate
of an alkali, or of an alkaline earth, and sawdust, coal tar, or other

page_text: carbonaceous matter brought in contact with and caused to permeate
the metal whilst it is melted and protected from contact with free
oxygen and consequent oxidation, in manner substantially as herein-
before described.
I also claim the purification of zinc by means of the hydrate of an
alkali or of an alkaline earth, in manner substantially as herein
described.
In witness whereof, I, the said Karl Wenzel Zenger, have here-
unto set my hand and seal, this Sixth day of October, in the
year of our Lord One thousand eight hundred and seventy-two.
K. W. ZENGER. (L.S.)