IMPROVEMENTS IN THE MODES AND MEANS OF TREATING AND SMELTING THE ORES OR OXIDES AND SALTS OF IRON
Year: 1871

page_text: PROVISIONAL SPECIFICATION left by Thomas Thomson at the Office
of the Commissioners of Patents, with his Petition, on the 28th
July 1871.
I, THOMAS THOMSON, of the Town of Denny, in the County of
Stirling, North Britain, Engineer, do hereby declare the nature of the
said Invention for "IMPROVEMENTS IN THE MODES AND MEANS OF TREATING
AND SMELTING THE ORES OR OXIDES AND SALTS OF IRON " :-
This said Invention has reference substantially to new or improved
modes and means of treating and smelting the ores which contain much
iron greatly in the form of the oxide and the salts of iron, and which in
one form is left in or after the treatment of most of the copper ores
(which come to this country from Spain and other places to have the
copper extracted from them) and also the hematite and other natural
rich oxides of iron ores found in considerable beds in this and other
countries all in a more economical and less wasteful manner than these
metallic residues and iron ores have been treated heretofore; and which
is well known have not yet been able to be so simply and easily treated

page_text: by the ordinary means or smelted in the ordinary furnaces used for
the more plentiful and common black and gray band ironstone ores,
and for the treatment of which latter this Invention may not be so
useful or economical.
And the nature of this said Invention consists in treating and reducing
or sinelting the said iron ores or oxides and salts of iron into a metallic
state within a reverberatory furnace on the top of a bath of molten
cast iron, the ore in a granular or pulverized state being charged or
spread over the surface of the molten iron in a layer of one, two, three,
or more inches in thickness mixed with a due proportion of solid
carbon (as coal or wood, or the coke or charcoal of these) and of
limestone, both also in a granular or pulverized state, and by preference,
mixed with the powdered ore, either before charging or otherwise, while
in the act of doing so, by laying them in thin layers over each other,
all in the suitable proportions requisite and well known, so as to yield
the carbon necessary to raise and maintain the ore at the high white heat
required to smelt the iron and unite with it and the quantity of lime
sufficient to form a flux over it and prevent the iron from burning and
flying off and in close contact with the bath of molten iron (previously
melted in the hearth of the furnace in the ordinary manner). The
actual melting of the ore being assisted at the time the charge has
attained the proper heat by a slight agitation of the bath of molten
metal, (with the mixed charge over it) by the insertion and motion of
"
a picce of " green or other wood, the gases streaming from the burning
wood agitating the whole sufficiently, or when desired this agitation
may be effected by the use of small jets of air or other gases through
the hearth, or from the end or surfaces of a hollow stirring or portable
hand bar, such as used in some iron and steel preparing or refining
and puddling furnaces.
"
The iron ore which is most suitable and preferred to be used and
treated by this Invention is an ordinary residue from the ores used at
copper works, where the copper is extracted by what is known as the
"wet process
and which residue or ore contains about ninety (90) per
cent. of oxide of iron, and is already in a granular or pulverized state,
thus being in a condition to be mixed with the granular or pulverized
coal or other carbonaceous substance and lime before referred to
(although in this light and pulverized state this residue or ore is most
difficult to be used and treated by the ordinary process of iron smelting).

page_text: One mode and means of carrying out this Invention in the treatment
and smelting of the said oxide of iron or ore residues from copper works
is as follows
First. The following mixture and proportions of the materials are
preferred and employed, for one ton of the said pulverized oxide of
iron or residue about seven hundredweight of ground coal is taken
and about one hundredweight of ground lime, all three being well
mixed, and either ground separately or together, and then mixed while
being ground or afterwards in any ordinary grinding or mixing mill
used for pigments and other powdered matters.
Second. A reverberatory furnace (substantially of an ordinary con-
struction, such as used for puddling and other purposes) with a deep
or dish formed hearth is prepared with a melting bath of ordinary or
gray cast iron.
Third. A layer of about two inches thick of the said mixture (referred
to under the first part of the operation) is put or spread over the whole
surface of the hot bath of molten iron within the furnace and the
doors closed again, in about half an hour, in a good going furnace, the
iron ore of the mixture will be reduced to a metallic state and sink down
amongst the fluid cast iron, and this system of charging the mixture
is continued until the hearth or furnace is full (allowing an interval
between each charge of half an hour or so, and until the iron ore in
the mixture is reduced into a metallic state, before a fresh charge of
mixture is added), and when the furnace is thus full the slag is skimmed
off the top of the metal, and a piece of wood is put in and moved
within and amongst the metal, which causes a violent agitation of the
metal, and destroys the silicon that is in it at this stage, when the
resultant metal thus made is found to be of a very homogeneous good
quality, and all ready for being drawn off at a door or tapping hole
for the purpose (and run into moulds in the form of ingots or "pigs"
ready for general use) down to the level of the original bath of cast iron
at first starting; when this is done the door or tapping hole is closed
and the operation of charging the mixture of pulverized ore, coal, and
lime in layers at intervals is then proceeded with, all as herein-before
described, and the reduced metal thus run off from time to time as the
hearth of the furnace becomes full.
The said new or improved mode and means of treating, reducing, and
smelting the said oxide of iron residue of copper ores (referred to in the

page_text: descriptive operation under part first to third inclusive) is also capable
of being applied to the same or like treatment of hematites and other
oxide of iron ores, and of the residue of iron pyrites (after the sulphur
has been extracted from them) and other sulphates or salts of iron, by
slight modifications of the proportions of the coal or other carbon
substance used in the mixture and mentioned in clause first of the
process) to suit the particular iron ore or residues to be treated and
mixed therewith, and the amount of carbon it is desired to have in the
pig iron made by this improved process, and the amount of lime must
also be modified or added to suit the amount of silica in the iron ore,
and other carbonaceous substances may be used besides that of coal,
as the ground coke residues from gas works, or ground peat or bog, or
other cheap or plentiful carbon substances.