Specialized metallurgical processes – compositions for use therei – Processes – Producing or treating free metal
Patent
1998-06-05
2000-11-14
King, Roy V.
Specialized metallurgical processes, compositions for use therei
Processes
Producing or treating free metal
75500, 75961, C21B 1310
Patent
active
061464414
DESCRIPTION:
BRIEF SUMMARY
This application is a national stage of PCT/AU96/00496 filed Aug. 7, 1996.
The present invention relates to a process for partially reducing iron oxides in a rotary hearth furnace.
A known rotary hearth-based process for partially reducing iron oxides is the FASTMET process of Midrex Steel Corporation. A particular form of the FASTMET process is described in U.S. Pat. No. 4,701,214 in the name of Kaneko et al (assigned to Midrex International BV Rotterdam).
The FASTMET process as described in the technical literature, including the U.S. patent, comprises the steps of: binder to form pellets that typically are of the order of 20 mm diameter (a preferred range of 10-25 mm is disclosed in the U.S. patent); of one to three layers deep on a hearth of the rotary hearth furnace, typically with an intermediate layer of iron ore separating the pellets from the furnace hearth to protect the hearth; hearth to a temperature of 1100-1370.degree. C. to reduce the iron oxides to metallic iron.
The technical literature reports that the FASTMET process has achieved metallisation of the order of 90%.
The reduced pellets produced in the FASTMET process may be used to produce pig iron or steel in a range of equipment such as electric arc furnaces and HIsmelt smelt reduction vessels.
An advantage of the FASTMET process is that it operates with iron ore fines and coal fines. The use of iron ore fines and coal fines is a desirable objective because iron ore fines are inexpensive and cannot be used in a number of other processes and coal is relatively inexpensive compared with coke.
An object of the present invention is to provide a process for at least partially reducing iron oxides in a rotary hearth furnace which is an improvement of the FASTMET process.
According to the present invention there is provided a process for at least partially reducing iron oxides, which process comprises: reactants comprising (a) a mixture of iron ore fines and particulate carbonaceous material and/or (b) micro-agglomerates of iron ore fines and particulate carbonaceous material; and furnace to at least partially reduce the iron oxides.
The present invention is based on the realisation that it is not necessary to pelletise iron oxide fines and coal to operate a rotary hearth furnace efficiently and effectively. It is evident from the technical literature that the FASTMET process depends on the use of pellets. The elimination of the pelletising step simplifies considerably the process and could significantly increase productivity and reduce capital and operating costs.
The term "micro-agglomerates" is understood herein to mean agglomerates that are less than 1400 microns (and preferably more than 500 microns) in diameter.
It is preferred that micro-agglomerates form a substantial proportion of the bed of reactants.
It is preferred that the metallisation of the product produced in step (ii) be at least 50%.
The mixture of iron ore fines and carbonaceous material may be formed prior to feeding the mixture to the rotary hearth furnace.
Alternatively, the iron ore fines and carbonaceous material may be supplied separately to the rotary hearth furnace and the mixture formed in situ on the hearth.
The carbonaceous material may be any suitable material, such as coal.
It is preferred that the carbonaceous material be coal.
It is preferred that the coal be pulverised.
The micro-agglomerates may be formed by any suitable means.
The bed of reactants on the rotary hearth furnace may be of any suitable depth. Typically, the depth of the bed is of the order of 20-25 mm.
According to the present invention there is also provided an apparatus for at least partially reducing iron oxides, which apparatus comprises: particulate carbonaceous material, and of micro-agglomerates produced by the micro-agglomerate forming means.
The at least partially reduced product produced by the process and the apparatus of the present invention may be used in a range of applications. A preferred, although by no means exclusive, application is in the production of metallic iron.
In ord
REFERENCES:
patent: 1452627 (1923-04-01), Thornhill
patent: 3890138 (1975-06-01), Hockin
patent: 4701214 (1987-10-01), Kaneko et al.
patent: 4971622 (1990-11-01), Slatter
patent: 5169307 (1992-12-01), Frye
patent: 5637133 (1997-06-01), Munnix et al.
patent: 5730775 (1998-03-01), Meissner et al.
King Roy V.
McGuthry-Banks Tima
Technological Resources Pty Ltd
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