Treatment of pelletized iron ores

A system for providing thermal and chemical energies for the production of pelletized iron ore concentrates while allowing a reduction of a portion of the material in process. The material in process is introduced as ore fines, pelletized and fired in an indurator to produce feedstock for reduction by further processing. A portion of the material in process is diverted to a reduction plant. The reduction plant provides thermal and chemical energies for the indurator. In a preferred embodiment, a low temperature plasma generator is employed, either as the reduction plant or to provide thermal and chemical energies for reduction. When a distinct reduction plant is employed, top gases from such plant may be supplied to the indurator to provide thermal and chemical energies therefor and to the plasma generator for recarburization thereof. The material in process may be diverted as ore fines or as fired or unfired pelletized ore concentrates.

BACKGROUND OF THE INVENTION 
The production of pelletized iron ore concentrates for reduction by further 
processing is known to the prior art. For example, taconite concentrates, 
available as finely comminuted and highly refractory powders, are commonly 
pelletized to meet the currently prevailing feedstock requirements of 
existing blast furnaces. The pelletizing process requires the formation 
and induration of pellets from ore powders or fines. This process, and 
particularly the induration process, consumes considerable quantities of 
energy. 
Escalating costs for oil and/or natural gas have increased the interest in 
coal fired systems. A major problem in coal systems is the ash associated 
with coal firing and the fact that coal, with appropriate ash fusion 
characteristics, is relatively limited and expensive. Thus, studies have 
been undertaken to assess the suitability of separate coal gasification 
processes utilizing known techniques. It has been shown that the 
relatively low energy gas produced by these known processes is acceptable 
for powering known taconite pellet induration plants. However, known coal 
gasification techniques require large capital expenditures for plant 
construction. 
Known taconite pelletizing systems produce a pelletized iron ore 
concentrate from a material which is introduced to the system as ore 
powders or fines. As noted above, the material in process is pelletized 
and fired in an indurator to produce a feedstock for reduction by further 
processing. Typically, this further processing is by a blast furnace at a 
location remote from the equipment forming the pelletizing system and the 
supply of ore fines itself. Indeed, pelletizing systems are typically 
located adjacent the supply of raw material to minimize transportation. 
However, the requirements for reduced metal at the location of the 
pelletizing operation requires shipment of the ore pellets for further 
processing and a return shipment of the reduced metal. 
SUMMARY OF THE INVENTION 
The present invention allows the continued large-scale production of 
pelletized ore concentrates in accordance with known techniques while 
allowing a diversion of a portion of the material in process for on-site 
reduction. On-site reduction, in accordance with the present invention, 
provides an economical source of thermal and chemical energies for 
induration plants of existing design. Thus, both energy and transportation 
considerations are addressed by the present invention. 
Any existing induration plant (e.g., grate, crate-kiln, shaft, etc.) may be 
integrated with any type of reduction plant in accordance with the present 
invention. In preferred embodiments, a low temperature plasma reactor is 
employed to convert a solid fuel into a gaseous fuel and provide at least 
a significant portion of the thermal and chemical energies necessary for 
pellet induration. As required, an on-site reduction plant may be powered 
by the plasma reactor. Top gases from the reduction plant may also be 
employed to provide thermal and chemical energies for the pellet 
indurator. Alternatively, the plasma reactor may, itself, be employed for 
reduction with its effluent being directed to the indurator for the 
purposes discussed. 
Many known low temperature plasma reactors may be advantageously employed 
in the practice of the present invention. However, varying efficiencies 
and abilities to entrain solid fuels in their effluents render some 
reactors preferable to others. A plasma reactor capable of high solids 
entrainment and high gasification rates is the sustained-shock-wave, 
low-temperature plasma reactor disclosed in U.S. application Ser. No. 
138,693, filed Apr. 9, 1980, now U.S. Pat. No. 4,361,441, entitled 
"Treatment of Matter in Low Temperature Plasmas", which is commonly owned 
with the present invention and which is hereby incorporated by reference.

DETAILED DESCRIPTION OF THE DRAWINGS 
Throughout the drawings, functionally similar or identical components are 
designated with the same reference numeral. For example, each of the 
drawings include a taconite pelletizing system formed of components 
designated by reference numerals 10-15. Reference numeral 10 represents a 
supply of ore fines which is delivered to a pelletizing plant 12 as 
represented by line 11. Pelleitzing plant 12 produces green or unfired 
pellets, in known manner, which are fed to an induration plant 14 as 
represented by line 13. Induration plant 14 produces fired pellets whose 
output, at line 15, may be shipped for further processing as by reduction 
in a blast furnace. 
Components 10-15 may be of any known design and may be associated, in 
accordance with the present invention, with any type of reduction plant. 
In this manner, a large-scale production of indurated pellets may be 
continued, while a portion of the ore concentrates in process is diverted 
for on-site reduction. The material reduced on-site eliminates the need 
for shipment of pellets for further processing and reshipment of reduced 
metal for local requirements. For the on-site reduction, thermal and 
chemical energies are produced which may be selectively provided to the 
indurator 14 to at least partially address its high energy requirements 
and attendant high cost. In a preferred embodiment, thermal and chemical 
energies for on-site reduction are provided by a plasma reactor 16 which 
is preferably of a type capable of high solids entrainment and high 
gasification rates as is the reactor disclosed in the specification 
incorporated hereinabove. The reactor of the incorporated specification is 
capable of high ionization and rapid starting and stopping with good 
control characteristics. Essentially, any material that burns may be 
employed as a feedstock for the reactor of the incorporated specification, 
including peat, garbage, coal, wood chips, etc., all of which need to be 
pulverized prior to being fed to the reactor. It has been found that solid 
feedstocks of comminuted, carbonacious materials having individual 
particle sizes up to 1/8 inch or more may be successfully employed within 
the reactor of the incorporated specification. The reactor feedstock is 
represented in the drawings at reference number 17 while the feeding of 
that feedstock to the reactor 16 is represented by the line 18. The 
reactor 16 converts the solid fuel feedstock into a gaseous fuel, the 
reactor of the incorporated specification having a high efficiency and the 
ability to entrain solid fuels in its effluent, the effluent being 
conducted via duct 19. 
The embodiments of FIGS. 1 and 2 employ a reduction plant 20 which may be 
of known design. Reduction plant 20 may be a direct reduction plant--a 
reduction plant other than a blast furnace. A valve 21 connected to the 
duct 19 selectively directs effluent from the reactor 16 to the reduction 
plant 20, via duct 22, and to the indurator 14, via duct 23. 
As described to this point, the plasma reactor 16 converts solid fuel from 
the supply 17 to a gaseous fuel which is conducted, selectively via valve 
21, to the reduction plant 20 and/or indurator 14 as plasma reactor 
effluents. Normally, the bulk of the reactor effluent will be conducted to 
the indurator 14 to continue a large-scale pelletizing operation. However, 
as local requirements for reduced metal dictate, reduction plant 20 may be 
powered, in known manner, by effluent from the plasma reactor 16 under the 
control of the valve 21. Local requirements for reduced metals may include 
the requirements for specialized steels which are easily satisfied by the 
present invention. Top gases from the reduction plant 20 may be withdrawn 
via a pump 24 to be selectively directed by a valve 25 to the indurator 14 
for the provision of additional thermal and chemical energies therefor 
and/or to the plasma reactor 16 for recarburization therein, in known 
manner. 
In the embodiment of FIG. 1, the feedstock to the reduction plant 20 is in 
the form of fired, pelletized ore concentrates drawn from the output 15 of 
the indurator 14 via valve 28. The embodiment of FIG. 2 is identical to 
that of FIG. 1, with the exception that the feedstock input to the 
reduction plant 20 is in the form of unfired, pellitized ore concentrates 
(green pellets) drawn from the output 13 of pelletizing 12 via valve 28. 
Reduced and metallized product from the reduction plants 20 are 
illustrated at 26 in FIGS. 1 and 2 while the solid or liquid output of 
plasma reactor 16 is illustrated at 27 in FIGS. 1 and 2. 
Obviously, many modifications and variations of the present invention are 
possible in light of the above tachings. For example, FIG. 3 illustrates 
an alternative embodiment wherein the plasma reactor 16 functions as the 
reduction plant having, as an input, ore fines as fed to the pelletizing 
plant 12. In each of the illustrated embodiments, material in process in 
the pelletizing operation is diverted for reduction, either to the 
reduction plant 20 or plasma reactor 16, by a valve 28. Valve 28 allows a 
selection of the amount of material in process for reduction and/or 
pelletizing for further processing, in known manner. As disclosed in the 
incorporated specification, the output 29 of plasma reactor 16, as applied 
in the embodiment of FIG. 3, is a reduced and metallized product. Other 
modifications and variations will be apparent to those skilled in the art. 
It is therefore to be understood that, within the scope of the appended 
claims, the invention may be practiced otherwise than is specifically 
described.