Improvements in the Reduction of Iron Ores.
Year: 1890

page_text: Date of Application, 10th June, 1890-Accepted, 23rd Aug., 1890
COMPLETE SPECIFICATION.
Improvements in the Reduction of Iron Ores.
We, HORACE WORTH LASH of the Hotel Anderson and JAMES JOHNSON of
223, 36th Street, Metallurgists, both in Pittsburgh, in the County of Allegheny, Stato
of Pennsylvania, United States of America, do hereby declare the nature of our
invention for IMPROVEMENTS IN THE REDUCTION OF ORES, and in what manner the
same is to be performed, to be particularly described and ascertained in and by the
following statement :-
In nearly all the direct methods heretofore tried the great waste by oxidation of
metallic iron, amounting in some cases to 35% of iron contained in the ore, has
precluded the practical adoption of the direct methods. Although this percentage of
loss has been reduced by employing. a refractory carbonaceous material, as graphite,
or by retarding the combustion of the more combustible forms of carbonaceous
material to such an extent as to fully justify the working these methods commercially,
the percentage of loss is still higher than desired
The object of this invention is to provide for the direct reduction of ore in such
manner as will ensure the production of a better and purer iron or steel with a very
much smaller percentage of loss than has been heretofore practically attainable; the
loss being as low as and even lower than 4% of the contained iron.
In the direct methods heretofore practised the ore and carbonaceous material have
been reduced or ground to about the size of coarse sand, and then more or less
thoroughly mixed or stirred together either with or without other materials. The
mixture thus formed is then spread upon the hearth of a reverberatory furnace, or
else pressed into shapes which are then arranged on the hearth of the furnace, and
subjected to a reducing heat. In such a charge the ingredients are so coarse com-
paratively speaking that they are separated from each other or lie loosely together as
to afford an opportunity for the access of the heat and air to the carbonaceous
material and the consequent combustion thereof, before the ore can be sufficiently
heated for the evolution of oxygen, that is to say, the heat can percolate rapidly
through the charge, causing, a considerable combustion-of-the-carbon-before-the ore
is sufficiently heated to give up its oxygen. In short there is no such intimate mixing
together of the ore and carbonaceous material, that they will have a close contactual
relation to each other in a finely divided state.
In the practice of our invention the carbonaceous material, (as coke, coal or
charcoal) and the ore are ground up independently of each other until the particles
thus produced will pass through a quarter inch mesh screen, more or less, thus
ensuring a uniform or approximately uniform size of the particles of both ingredients.
The ore and a sufficient amount of the carbonaceous material, i.e. twenty to
thirty per cent. more or less by weight of the ore (as for example, twenty or thirty
pounds of carbon for one hundred pounds of ore) are then mingled together in a heap
and passed together through a half inch mesh screen to ensure a good commingling
together of the ore and carbonaceous material. This mixture is then transferred to
a grinding pan or other suitable apparatus and thoroughly ground together, and
during such grinding operation it is preferred to moisten the materials either by a
jet of water allowed to run into the pan or by pouring in oil or other suitable fluid,
20 as to form a pasty mass. It is in this step or manipulation that our method
differs so radically from the practice heretofore in vogue, in which the particles of.ore
and coke simply rested against each other, whereas in our practice, the grinding is
continued until both the carbonaceous material and ore are not only finely pulverized,
but ground into each other atom to atom until their relation to each other
resembles or partakes, as near as is possible in a mechanical treatment, of the

page_text: nature of a chemical union or homogeneous mass. This amalgam, as it may be
properly termed, is then spread upon the hot hearth of a reverberatory or other
suitable furnace, levelled off, and covered with a "blanket" of pulverized carbon
about a quarter of an inch thick. It will be readily understood from the nature
of the material and the character of the preparatory treatment, that the charge is
very dense and compact, and that the heat will penetrate slowly and equally through
the mass from the surface downward. The reducing heat acting on the pasty mass
cements it together into a homogeneous mass, thus holding the carbon in bondage,
until permeating through the charge particle by particle and atom by atom, it permits
the oxygen of the ore and the carbonic oxide produced by the combustion of the
Parbonaceous material to combine. By reason of the intimate relation of the ore
nd carbonaceous material the latter cannot be sufficiently heated to form carbonic
oxidė, without at the same time, heating the ore sufficiently to liberate its oxygen.
As reduction occurs, the charge swells off the furnace bottom becoming quite porous
and spongy (the swelling or raising up beginning at the surface where reduction is
first effected), thus affording opportunity for the liquid cinder and slag to percolate
through the spongy mass to the furnace hottom, where it may be tapped off,
leaving the reduced iron practically free from impurities. This swelling and opening
up of the charge as reduction progresses, thereby permitting of the escape of the
cinder and slag, is an important result due to the manner in which the material is
treated and charged into the furnace. Heretofore the mingled ore and carbonaceous
material were charged in loose porous mass onto the hearth of the furnace, and
when subjected to heat sunk down into a dense mass from which the cinder and
slag could not escape and were therefore incorporated in the sponge when the latter
was balled up. But in our practice the ore and carbonaceous material are charged
onto the hearth at a maximum density, and when heated expand and swell up as herein-
before stated. As the metal is reduced it is balled up and removed from the furnace,
the balls being either charged into an open hearth furnace for the production of steel,
passed through the squeezers preparatory to subsequent treatment, or utilized in any
other suitable manner.
In the practice of our invention we have been able to produce iron of a high
degree or purity with a loss in the transition from ore to squeezer or hammer
blooms, of four per cent. and less of the metallic iron contained in the ore. As
for example, in reducing a ton (2240 lbs.) of 65% ore, we have obtained, and
that not as
an exceptional thing, fourteen hundred pounds of squeezer blooms
containing 98% of pure iron.
If desired the ore and carbonaceous material may be ground together and charged
into the furnace in a dry condition, but in order to prevent any waste of the
charge from the cutting action of the reducing flame on the powdery material, a
protecting blanket of moistened pulverized carbonaceous material spread over the
charge.
In lieu of water, any suitable oil, as linseed, refined or crude petroleum, etc., may
be employed for moistening the powdered ore and carbonaceous material, to render
the same pasty as hereinbefore described.
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 1
claim is:
1. The method herein described of reducing iron direct from ore, which consists
in grinding ore and carbonaceous material into a pulverized homogeneous mass,
spreading the material thus formed on the hearth of a furnace and subjecting the
same to a reducing heat, substantially as set forth.
2. The method herein described of reducing iron direct from ore, which consists in
grinding moistened ore and carbonaceous material together into a pulverized
homogeneous paste, spreading the paste thus formed on the hearth of a furnace and
subjecting the same to a reducing heat, substantially as set forth.

page_text: 3. The method herein described of reducing iron direct from ore, which consists
in grinding together ore and carbonaceous material moistened with oil into
a pulverized homogeneous pasie, spreading the paste thus formed on the hearth of a
furnace and subjecting the same to a reducing heat, substantially as set forth.
Signed at Pittsburgh, Pa., U.S.A., this Twenty-first day of May 1890.
Witnesses:
DARWIN S. WOLCOTT.
R. H. WHITTLESEY.
HORACE WORTH LASH.
JAMES JOHNSON.