Improvements in the Reduction of Iron Ores.
Year: 1890

page_text: Date of Application, 25th Nov., 1890-Accepted, 14th Mar., 1891
COMPLETE SPECIFICATION.
Improvements in the Reduction of Iron Ores.
I, JAMES JOHNSON, Metallurgist, residing at Pittsburgh, in the County of
Allegheny, State of Pennsylvania, and United States of America, do hereby
declare the nature of this invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement:-
The invention described herein relates to certain improvements in the direct
reduction of ores to metallic iron, and has for its object in addition to the reduction
of the ore, the elimination to a great extent of the sulphur and phosphorous
therefrom.
It has been necessary heretofore, when treating ores high in sulphur and
phosphorous, by the direct process, to subject such ores to a preliminary
roasting in order to remove the sulphur, and then treat the roasted ores in the usual
manner.
In the practice of my invention the ore is reduced in a crusher or other suitable
apparatus, to lumps of about nut-size. The crushed ore is then charged directly
into the hot hearth of a reverberatory or other suitable furnace preferably having
a cinder bottom, and there subjected to a strong reducing flame, until the water of
hydration is driven off and the ore is in condition to readily part with its oxygen
and is hungry, so to speak, for the carbon. When the ore is in this condition from
twenty to forty per cent. (20% to 40%) of finely pulverized carbon, (determined by
weight of the ore), i.e., twenty to forty pounds, more or less, of carbon for every
hundred pounds of ore, is shovelled loosely onto the red-hot ore. The whole mass
is then well rabbled to permit of the carbon passing down through and around the
lumps of ore and effect a thorough commingling of the two. The pulverized
carbon is slightly dampened prior to being charged into the furnace to prevent
dusting. After the ore and carbonaceous materal have been thoroughly rabbled,
the entire charge is protected by a light covering of pulverized carbon which is
also slightly dampened. The heat is now gradually raised, its reducing charac-
teristics being maintained, until the iron becomes pasty. It is then balled in the
usual manner and removed from the furnace.
While any pulverized carbonaceous material can be employed in this process,
it is particularly adapted to the employment of easily combustible carbons such as
coke, charcoal, petroleum-coke, etc., which cannot be advantageously employed in
the old processes where the ore and carbon are mixed and charged simultaneously
into the furnace, for the reason that the carbon will be consumed before the ore can
be sufficiently heated to yield up its oxygen and take up the carbon. But in my
process, the carbon is not brought into play until the ore is rendered quite porous
by the heat to which it is subjected and the consequent driving off of the water of
hydration. This calcination of the ore lessens its tendency to fuse, in which
condition it is less permeable by the reducing gas. Thus it will be seen that the
steps necessary to bring the ore to a condition requisite to the successful action of
the reducing agent are effected before the reducing agent is placed in the furnace,
thereby avoiding any loss or deterioration of the reducing agent incident to the
practice of charging the ore and reducing agent simultaneously into the furnace.
This preliminary heating not only prepares the ore for the action of the reducing
agent, as hereinbefore stated, but also effects an elimination of the sulphur.
As is well known, oxide of iron will effect a reduction or elimination of the
silica and phosphorous of ore, but as the oxide has a greater affinity for the silica
than the phosphorous, the latter can be eliminated only when there is an excess of
oxide beyond that required for the silica. An enrichment of the slag in oxide of

page_text: 1
iron, can be effected in this process in several ways, e.g. by increasing the heat in
the preliminary operation; or by the addition of iron or steel scale to the charge, the
latter being the preferable manner of obtaining an increase of oxide. While
the iron or steel scale may be added to the charge at any time, it is preferred to
add it immediately before charging in the carbonaceous material.
The pulverized carbonaceous material may be dampened with water or oil or
preferably with water and oil, as the latter when subjected to the heat in the
furnace will form a hydrocarbon gas, which by its combustion will prevent an
injurious chilling of the ore.
If high carbon iron is desired, it is only necessary that manganese be present
during the reduction. This manganese can be obtained by adding to the charge in
the reverberatory furnace, the slag from open hearth furnaces, a waste product rich
in lime and manganese.
The process is the same whether hematite or magnetic or separated ores are used,
and the results are equally good in all cases.
No claim is made herein broadly, to the roasting of ores for the elimination of
sulphur, but such roasting has been heretofore practiced as an operation distinct
from and independent of any subsequent treatment of the ores, the roasting and
reducing operations being effected in different furnaces. In my process, however,
the ores are roasted not only to eliminate the sulphur and drive off the water of
hydration, but also to prepare them for the action of the reducing agent.
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. As an improvement in the art of reducing iron direct from ore, the method
herein described, which consists in charging the ore onto the hearth of a suitable
furnace, subjecting it to a reducing heat for the elimination of the sulphur and
water of hydration, adding carbonaceous material to the charge and rabbling or
stirring it into the ore, and then subjecting the entire charge to a reducing heat,
substantially as set forth.
2. As an improvement in the art of reducing iron direct from ore, the method
herein described, which consists in charging the ore onto the hearth of a suitable
furnace, subjecting it to a reducing heat for the elimination of sulphur and water
of hydration, increasing the oxide of iron in the slag by the addition of any
suitable material as iron or steel scale, adding carbonaceous material to the
charge, and rabbling or stirring it into the ore, and then subjecting the entire
charge to a reducing heat, substantially as set forth.
3. As an improvement in the art of reducing iron direct from ore, the method
herein described, which consists in charging the ore onto the hearth of a suitable
furnace, subjecting it to a reducing heat, adding dampened pulverized carbonaceous
material to the charge and rabbling or stirring it into the ore, and then subjecting
the entire charge to a reducing heat, substantially as set forth.
4. As an improvement in the art of reducing iron direct from ore, the
method herein described, which consists in charging the ore onto the hearth
of a suitable furnace, subjecting it to a reducing heat, adding pulverized
carbonaceous material to the charge and rabbling it into the ore, covering
the entire charge with dampened pulverized carbonaceous material and then
subjecting it to an increasing reducing heat, substantially as set forth.'
TY
D
TT &
I
Witnesses.:
DARWIN S. WOLCOTT.
R. H. WHITTLESEY.
JAMES JOHNSON.