The present invention relates to an iron-making process and an iron-making plant.

The present invention relates particularly, although by no means exclusively, to an iron-making process that includes a direct reduction step of reducing the iron-containing feed material and forming a reduced iron material by passing a reducing gas upwardly through a bed of the feed material .

The term "reducing" is understood herein to mean removal of some or all of the oxygen in the iron- containing material while the material is in a solid state.

The term "reduced iron material" is understood herein to include products that have at least 80% by weight iron .

By way of example, the term "iron" when discussing the end product extends to products generally described as direct reduced iron ("DRI") .

The present invention relates more particularly, although by no means exclusively, to an iron-making process that includes the above-described bed-based direct reduction step that is characterized in that it is capable of processing iron ore that would generally be considered to be unsuitable (at least on its own) for forming a bed with acceptable gas flow characteristics .

One such ore is lump ore from the Corumba deposit in Brazil. Typically, Corumba ore comprises tabular lump that can tend to form packed beds that does

not readily permit uniform upward flow of reducing gas across the width of the bed. The gas flow tends to be channeled, with the result that there is poor contact between the reducing gas and a substantial part of the iron ore in the bed, leading to poor reduction of the material .

One known solution to the problem described in the preceding paragraph is to blend tabular lump iron ore with other ores or lump ferrous material, for example pellets. However, this is not necessarily an acceptable solution in all situations from the viewpoint of capital cost and/or technical considerations, particularly in remote locations such as the location of the Corumba deposit.

The iron making process of the present invention includes a direct reduction step that uses a bed forming material that facilitates forming a bed of an iron- containing material, such as tabular lump ore, in a shaft furnace or other suitable furnace so that there is optimum upward flow of the reducing gas through the bed. The process also includes separating the reduced iron material produced in the furnace and the bed forming material . As a consequence, the bed forming material may be re-used in the direct reduction step.

According to the present invention there is provided a process for producing iron from an iron- containing material that includes the steps of :

(a) reducing the iron-containing feed material and forming a reduced iron material therefrom by passing a reducing gas upwardly through a bed of the feed material and a bed forming material and reducing the feed material, with the amount and the physical characteristics of the bed forming material being selected so that the bed allows

optimum upward flow of the reducing gas through the bed; and

(b) separating the reduced iron material and the bed forming material discharged from the bed.

The separated reduced iron material may be further processed at the same plant or transported to another plant for processing, as required.

For example, the process may include a further step of smelting the reduced iron material and forming molten iron . The smelting step may be carried out at the same plant as the direct reduction plant or at a separate plant.

As is indicated above, the purpose of the bed forming material is to facilitate forming a bed of the iron-containing material in a shaft furnace or other suitable furnace so that there is optimum upward flow of the reducing gas through the bed.

Generally "optimum" upward flow through the bed is upward flow that results in uniform contact between the reducing gas and at least a substantial amount of the iron-containing material in the bed so that there is substantially uniform reduction of iron-containing material throughout the bed.

The use of the bed forming material is particularly important in situations where the shape of the iron-containing material tends to form closely packed beds that have poor gas flow characteristics , with the result that there is poor reduction of material in a significant proportion of the bed. As discussed above, tabular lump iron ore may be one such iron-containing material in this category.

- A -

The amount and the physical characteristics of the bed forming material required in any given situation will depend at least in part on the physical characteristics , such as size and/or shape , of the iron- containing material .

For example, in a situation in which the iron- containing material is in the form of tabular lump ore, preferably the bed forming material has a different size and/or a different shape to the iron-containing material , such as being in the form of spherical balls , which ensures that the bed does not closely pack and prevent uniform optimum upward flow of the reducing gas through the bed.

The separation step (b) is a further factor in the selection of the physical characteristics of the bed forming material .

For example, in a situation in which the separation step includes separation that is based on size and/or shape, such as in a trommel screen assembly, these characteristics will need to be taken into account when selecting the size and/or shape of the bed forming material .

Preferably the bed forming material is material that is at least substantially non-reactive with the iron- containing material in that the material does not cause contamination of the reduced iron material that has an impact in downstream processing of the reduced iron material produced in step (b) , such as in a smelting step.

Preferably the bed forming material is a nonreducible material in the conditions in reduction step (a).

Preferably the bed forming material is at least substantially resistant to heat and abrasion and thereby maintains structural integrity in the operating conditions of reduction step (a) and separation step (b) .

By way of example, the bed forming material may be a steel or a ceramic .

Preferably the bed forming material is spherical in shape .

The iron-containing feed material may include materials such as iron ore, partly reduced iron ore and iron-containing waste streams (for example, from steelmaking plants) .

Preferably the iron-containing feed material is substantially iron ore.

Preferably the iron ore is in the form of lump iron ore .

More preferably the lump iron ore includes tabular lumps .

Preferably the process includes re-using separated bed forming material in reduction step (a) .

Preferably the process includes continuously or periodically supplying the iron-containing feed material and the bed forming material to an upper end of a shaft furnace or another suitable furnace and continuously or periodically discharging reduced iron material and bed forming material from a lower end of the furnace, thereby operating the reduction step (a) as a downwardly moving bed of material in the furnace .

Preferably the process includes mixing the iron- containing material and the bed forming material prior to supplying the mixed material to the upper end of the shaft furnace or another suitable furnace .

Preferably the process includes crushing the reduced iron material from separation step (b) to a required particle size before supplying the material to a direct smelting vessel for smelting in the smelting step.

Preferably reduction step (a) produces reduced iron material having a metallisation of at least 80% .

Preferably reduction step (a) produces reduced iron material having a metallisation of no more than 90% .

Preferably reduction step (a) is a Midrex process, as described herein.

Preferably smelting step is a molten bath-based direct smelting process .

Preferably the molten bath-based direct smelting process includes supplying solid feed materials in the form of the reduced iron material from separation step (b) and solid carbonaceous material to a bath of molten iron and molten slag in a direct smelting vessel and supplying oxygen-containing gas into a space above the molten bath and smelting the reduced iron material and producing molten iron in the molten bath.

The oxygen-containing gas may be oxygen, air, or oxygen-enriched air.

Preferably the direct smelting process includes supplying solid feed materials to the molten bath by

injecting solid feed materials and a carrier gas via one or more than one solids injection lance extending into the vessel .

The carrier gas may be any suitable gas .

Preferably the direct smelting process is a HIsmelt process, as described herein.

Preferably the HIsmelt process includes injecting solid feed materials in the form of the reduced iron material from separation step (b) and solid carbonaceous material and flux into a molten bath in a direct smelting vessel through a number of lances/tuyeres that are inclined to the vertical so as to extend downwardly and inwardly through a side wall of the vessel and into a lower region of the vessel so as to deliver at least part of the solid feed materials into a metal layer in the bottom of the vessel .

Preferably the HIsmelt process includes injecting an oxygen-containing gas into an upper region of the vessel through a downwardly extending lance to promote the post-combustion of reaction gases in the upper region of the vessel process.

Preferably the HIsmelt process includes discharging off-gas resulting from the post-combustion of reaction gases in the vessel through an off-gas duct in the upper part of the vessel.

The term "smelting" is herein understood to mean thermal processing wherein chemical reactions that reduce iron oxides take place to produce molten iron.

According to the present invention there is also provided a plant for producing iron from an iron-

containing material that includes :

(a) a plant for reducing the iron-containing feed material and forming a reduced iron material by passing a reducing gas upwardly through a bed of the feed material and a bed forming material (as described herein) ; and

(b) an apparatus for separating the reduced iron material and the bed forming material discharged from the reduction apparatus .

Preferably the iron making plant includes a plant for smelting the reduced iron material and forming molten iron.

Preferably the reduction plant (a) is a Midrex Direct Reduction plant.

Preferably separation apparatus (b) is a trommel screen assembly.

Preferably the smelting plant is a HIsmelt plant.

Preferably the plant further includes an apparatus for crushing reduced iron material from separation apparatus (b) as required for feed material to the smelting plant.

The present invention is described further by way of example with reference to the accompany drawings, of which :

Figure 1 is a flowsheet of a Midrex Direct Reduction process;

Figure 2 is a transverse cross-section of a trommel screen for separating solid material produced in the Midrex Direct Reduction process shown in the flowsheet of Figure 1 ; and

Figure 3 is a diagram that illustrates one embodiment of a HTsmelt vessel for carrying out the HIsmelt process.

One, although not the only, embodiment of an iron-making process that produces molten iron from iron- containing feed material in the form of lump iron ore in accordance with the present invention includes the steps of:

(a) reducing lump iron ore in a solid state and producing reduced ore having a metallisation of at least 80% using a Midrex Direct Reduction process operating in a shaft furnace containing a bed of the lump ore and a bed forming material ;

(b) separating the reduced ore and the bed forming material discharged from the bed;

(c) crushing the reduced ore to a preferred particle size distribution of minus 6 mm for subsequent smelting of the ore; and

(d) smelting the reduced and crushed ore to molten iron using a HIsmelt molten bath-based direct smelting process operating in a direct smelting vessel .

More particularly, with reference to the process flow sheet of Figure 1 , the Midrex Direct Reduction process is based upon a shaft furnace 31 containing a downwardly moving bed of solid material and an upwardly moving counter-current flow of a reducing gas . The

reducing gas, which includes from 10-20% CO and 80-90% H ₂ , is produced from natural gas using a Midrex CO ₂ reforming process and a proprietary catalyst.

As is described above, the present invention is characterised by using a bed forming material that facilitates forming a bed of the lump ore and the bed forming material in the furnace 31 (or other suitable furnace) that enables optimum contact between the upwardly flowing reducing gas and the lump ore in the bed.

The subject embodiment is described in the context of processing lump ore from the Corumba deposit. For this ore and the described process operating conditions, the bed forming material is selected to be spherical steel balls of 12.5 mm.

The selected proportions of the lump ore and the bed forming material, typically 70:30 on a volume basis, are mixed together and thereafter supplied to a feed hopper 37 on top of the furnace 31 and thereafter are supplied as required as feed material to the furnace 31 via a proportioning hopper 38 that evenly distributes the solids into the furnace 31.

The furnace 31 operates at a low pressure of less than 1 bar gauge. The feed material in the furnace 31 is first heated and thereafter reduced by upward flowing counter-current reducing gas that is injected through tuyeres 39 located in a bustle distributor at the bottom of a cylindrical section of the furnace 31. The lump ore is reduced to a metallization of at least 80% by the time it reaches the bustle area.

Below the bustle area, the feed material goes through a transition zone and then reaches a lower conical section 41 of the furnace 31. Lower carbon reduced iron

(<1.5%C) is cooled using a circulating stream of cooled exhaust gas that is introduced in the conical section for cold DRI discharge . Higher carbon DRI (up to 4.0%C) can be produced by introduction of natural gas into this cooling gas. It readily reacts (and cracks) with the highly reactive metallic DRI .

The Midrex gas generation system includes a CO2 reformer 33 that uses a Midrex catalyst. The feed to the reformer is a mixture of process gas recycled from the furnace 31 and makeup natural gas . The top gas leaves the furnace 31 at a temperature of 400 to 450 ⁰ C and is cooled and dust is removed in a top gas scrubber 35. About two- thirds of the gas is recycled back to the process (process gas) and the rest is used as a fuel. The process gas is compressed, mixed with natural gas and is preheated in a reformer recuperator before entering the tubes of the reformer 33.

The reformed gas, comprising CO and H ₂ , exits the reformer 33 at about 850 ⁰ C and passes through collection headers to a reformed gas line . The ratio of H ₂ to CO is controlled at about 1.5 to 1.8.

With reference to Figure 2 , reduced ore and bed forming material discharged from the Midrex shaft furnace 31 are supplied to a trommel screen assembly shown in Figure 2 and are separated into separate streams of reduced ore and bed forming material .

The trommel screen assembly is a generally cylindrical assembly and is inclined to the horizontal and is arranged to rotate about a central longitudinal axis "X" of the assembly in the direction of the arrow shown in Figure 2.

The higher end of the assembly is a supply end for feed material and the lower end of the assembly is a discharge end for separated streams of material .

The assembly includes an outer cylindrical shell 61 that retains material in the assembly. The assembly also includes a series of concentric screens 63, 65, 71, each of which has a pre-selected mesh size marked on Figure 2. The assembly also includes a series of baffles 69 extending inwardly from the innermost screen 71 to facilitate distribution of material as it moves down the screen .

In use of the assembly, reduced ore or bed forming material from the Midrex plant is supplied as a feed material via the supply end of the assembly to the central cylindrical passage defined by the innermost screen 69. Rotation of the assembly about the longitudinal axis moves the material progressively down the passage. The +13 mm material remains in the central passage and is discharged via the discharge end of the assembly. This material is predominately reduced ore. The -13 mm material passes outwardly through the screen 71 into an annular passage defined by the screens 65, 71. The screen 65 allows -12mm material to pass outwardly through the screen and retains +12mm material in the passage . This material is predominately the bed forming material . The material is discharged via the discharge end of the assembly. The -12mm material passes outwardly through the screen 65 into an outer annular passage way defined by the screens 63 , 65. The outer screen 63 retains +6mm material in the passage. The +6mm material is predominately reduced ore. The material is discharged from the assembly via the discharge end of the assembly. The -6mm material passes outwardly through the screen 63 into an outermost passage defined by the shell 61 and the screen 63. The -6mm material in the passage way is

predominately reduced ore . The material is discharged from the assembly via the discharge end of the assembly.

The bed forming material discharged from the trommel assembly is re-cycled to the Midrex Direct Reduction process .

The +6 mm and +13mm reduced ore in the separate streams discharged from the trommel assembly is crushed to form -6 mm particle size distribution for the HIsineIt process . The crushed material and the -6 mm reduced ore discharged from the trommel assembly are mixed together and are supplied as reduced ore fines to the HIsmelt plant.

With reference to Figure 3, the reduced ore, solid carbonaceous material in the form of coal, flux (lime and dolomite) , and hot air are supplied to a vessel 3 of a HIsmelt direct smelting plant and the reduced ore is smelted to molten iron using the HIsmelt process.

By way of example, the HIsmelt process is as described in International application PCT/AU96/00197 , the HIsmelt plant is as described in Australian provisional application 2005902022, and the vessel 3 is described in detail in International applications PCT/AU2004/000472 and PCT/AU2004/000473, all in the name of the applicant. The disclosure in the patent specifications lodged with these patent applications is incorporated herein by cross- reference .

With reference to Figure 3, the vessel 3 has a hearth in a lower section of the vessel that includes a base 81 and side walls 83 formed from refractory bricks/ side walls 85 which form a generally cylindrical barrel extending upwardly from the sides of the hearth and include an upper barrel section and a lower barrel

section, a roof 87 that includes a central off-gas chamber 89, an off-gas duct 9 extending from the off-gas chamber 89, a forehearth 67 for discharging molten iron continuously from the vessel 3, and a tap hole (not shown in the Figure) for discharging molten slag periodically from the vessel 3.

The vessel 3 is fitted with a downwardly extending water-cooled hot air blast ("HAB") lance 7 extending into a top space of the vessel 3 and eight water-cooled solids injection lances 5 extending downwardly and inwardly through the side wall 85 to deliver solid materials into the hearth.

In use, the vessel 3 contains a molten iron bath.

Reduced ore, coal and flux are directly injected into the bath via the solids injection lances 5.

Specifically, one set of lances 5 is used for injecting reduced ore and flux and another set of lances 5 is used for injecting coal and flux.

Reduced ore may be pretreated by being preheated to a temperature in the range of 600-700 ⁰ C and prereduced in a fluidised bed preheater (not shown) before being injected into the bath.

Coal and fluxes are stored in a series of lock hoppers (not shown) before being injected at ambient temperatures into the bath. The coal is supplied to the lock hoppers via a coal drying and milling plant (not shown) .

The injected coal de-volatilises in the bath, thereby liberating H ₂ and CO. These gases act as reductants and sources of energy. The carbon in the coal is rapidly dissolved in the bath. The dissolved carbon

and the solid carbon also act as reductants, producing CO as a product of reduction .

The injected reduced ore is smelted to molten iron in the bath and is discharged continuously via the forehearth 67.

Molten slag produced in the process is discharged periodically via the slag tap hole (not shown) .

The typical reduction reactions involved in smelting injected iron-containing feed material to molten iron that occur in the bath are endothermic . The energy required to sustain the process and, more particularly these endothermic reactions, is provided by reacting CO and H ₂ released from the bath with oxygen-enriched air injected at high temperatures, typically 1200 ⁰ C, into the vessel 3 via the HAB lance 7.

Energy released from the above-described post combustion reactions in the vessel top space is transferred to the molten iron bath via a "transition zone" in the form of highly turbulent regions above the bath that contain droplets of slag and iron. The droplets are heated in the transition zone by the heat generated from post combustion reactions and return to the slag/iron bath thereby transferring energy to the bath.

The hot, oxygen-enriched air injected into the vessel 3 via the HAB lance 7 is generated in hot blast stoves (not shown) by passing a stream of oxygen-enriched air (nominally containing 30 to 35% by volume O ₂ ) through the stoves and heating the air and thereafter transferring the hot oxygen-enriched air to the HAB lance 7 via a hot blast main (not shown) .

Many modifications may be made to the embodiments of the present invention shown in the Figures without departing from the spirit and scope of the invention.

By way of example, whilst the above-described embodiment includes direct smelting the separated reduced iron material, and more particularly smelting the material in the same plant, the present invention is not confined to smelting the material and, more particularly is not confined to smelting the material in the same plant.