AU8153901A - A direct smelting vessel - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant(s): TECHNOLOGICAL RESOURCES PTY LTD A.C.N. 002 183 557 Invention Title: A DIRECT SMELTING VESSEL The following statement is a full description of this invention, including the best method of performing it known to me/us: 2 A DIRECT SMELTING VESSEL The present invention relates to a direct smelting vessel for producing iron and/or ferroalloys from ferruginous material, including iron ores, other ores containing iron such as chromite ores, partially reduced ores, and iron-containing waste streams such as steel reverts.

The present invention relates particularly to a direct smelting vessel that can be used for molten metal bath-based direct smelting processes for producing molten iron and/or ferroalloys.

There are significant issues involved in constructing vessels that can contain direct smelting processes.

For example, for economic and safety reasons it is important that the vessels contain direct smelting processes with minimal heat loss and be capable of withstanding the erosive/corrosive conditions that are a characteristic of such processes over long term operating campaigns.

~Process containment must also be combined with means to inject and to mix reactants to form and maintain different zones in the vessels and to separate products of the processes.

Process chemistry of direct smelting processes generally requires a region of low oxygen potential to smelt metalliferous feed material and a region of high oxygen potential to combust hydrogen and carbon monoxide to obtain combustion energy. As a consequence, typically, there are wide variations in temperature and chemical composition throughout the vessels that contain direct H:\Bkiot\Keep\speci\TRFL\E125.doc 19/10/01 3 smelting processes which place different demands on the design of vessels.

Some planned and tested direct smelting vessels include an outer steel jacket and an internal lining of a refractory material, typically in the form of bricks and/or castables. It is known to use bricks of different composition and physical properties in different sections of the vessels to maximise resistance to thermal and chemical attack and erosion.

For example, refractory bricks in the base of the vessels are usually exposed to molten material that is predominantly metal whereas the refractory bricks in the mid-section of the side walls of the vessels are usually exposed to molten material that is predominantly slag and to gaseous reactants such as CO, H 2

CO

2 and H 2 0. The bricks exposed to molten metal and the bricks exposed to molten slag require different chemical properties to resist chemical attack by metal and slag.

Furthermore, in general terms, post-combustion of .oeoei reaction gases generates high temperatures of the order of 2000 0 C or higher and, as a consequence, the bricks exposed 25 to the top space in which post-combustion occurs require ooeoe Sphysical and chemical properties to withstand high temperatures.

An object of the present invention is to provide an improved direct smelting vessel.

The present invention provides a direct smelting vessel for producing iron and/or ferroalloys by a molten bath-based direct smelting process, the vessel including: a hearth that has a base and sides that have an inner refractory brick lining; side walls extending upwardly from the sides of the hearth, the side walls including water- H :\Bkrot\Keep\speci\TRPL\P125.,doc 19/10/01 4 cooled panels and an inner refractory brick lining at least in a lower section of the side walls; a roof; a means for tapping molten metal and slag from the vessel; a means for supplying solid feed materials including solid ferruginous material and carbonaceous material into the vessel; and a means for supplying an oxygen-containing gas into the vessel to post-combust gaseous reaction products generated in the direct smelting process; and the vessel being characterised by a plurality of water-cooled members positioned below and adjacent the water-cooled panels and extending inwardly into the vessel beyond the water-cooled panels.

The purpose of the water cooled members is to prevent undercutting of the water-cooled panels by molten material and to at least partially shield the refractory brick lining of the sides of the hearth that is below the members from molten material runback in the vessel.

20 Preferably the members extend across and thereby S: cover at least 80% of the refractory brick lining of the S: sides of the hearth that is below the members.

Preferably the members are at least partially covered by the refractory brick lining in the lower section "of the side walls.

More preferably the members are substantially covered by the refractory brick lining in the lower section of the side walls.

ee .Preferably each member includes a water inlet, a water outlet, and a passageway for water flow within the member.

Each member may include: H:\Bk rot\Keep\peci\TRPL\Pl25.doc 19/10/01 5 an external shell with openings that define the water inlet and the water outlet; and an internal flow former that divides a volume enclosed by the shell into the passageway.

In an alternative, although not the only other possible alternative, embodiment each member may include a cast or forged piece with the passageway drilled in the piece.

Preferably, the vessel is generally cylindrical.

With such an arrangement, preferably each member includes parallel top and bottom faces that are generally trapezium shaped, parallel inner and outer faces extending between and interconnecting the top and bottom faces, and side faces extending between and interconnecting the top 20 and bottom faces and converging from the outer face towards the inner face.

oo o• •Preferably the members are arranged in a circular array.

S" Preferably the members form a continuous circular array.

Preferably the top, bottom and inner faces of 30 each member include machined grooves that promote build-up of accretions on the faces.

Preferably the thickness of each member, i.e. the spacing between the top and bottom faces, is of the order of the thickness of a single refractory brick or multiple refractory bricks. As a consequence, the water-cooled members can be provided as a replacement of at least part H \Bkrot\Keep\spec i \TRPL\P125 doc 19/10/01 6 of a course or courses of refractory bricks.

Preferably the refractory brick lining in the lower section of the side walls progressively steps outwardly with increasing height from an intersection of the lining and the refractory brick lining of the sides of the hearth.

Preferably the members are positioned at the intersection of the refractory brick lining of the side walls and the refractory brick lining of the sides of the hearth.

Preferably the members extend generally horizontally into the vessel.

According to the present invention there is also provided a water-cooled member for a direct smelting vessel that includes: an external shell with opening that define a water inlet and a water outlet; and an internal flow former that divides a volume enclosed by the shell into a passageway for water flow from the inlet to the outlet.

The present invention is described further by way 30 of example with reference to the accompanying drawings of which: Figure 1 is a vertical section though a vessel that is suitable for carrying out a direct smelting process; Figure 2 is a section along the line 2-2 of H: \Bkrot\Keep\speci\TRPL\ P25 .doc 19/10/01 7 Figure 1; Figure 3 is a top plan view of a water-cooled member that forms part of the vessel shown in Figures 1 and 2; Figures 4 and 5 are elevations of the front and back faces of an internal flow former that is part of the water-cooled member; Figure 6 is a top plan view of the flow former; and Figure 7 is a cross-section of an upper part of the water-cooled member which illustrates the position of the top and outer faces of the water-cooled member in relation to other components of the vessel, The following description is in the context of 20 smelting iron ore to produce molten iron and it is understood that the present invention is not limited to this application and is applicable to a smelting any •suitable feed materials.

The direct smelting vessel shown in the figures is denoted generally by the numeral 11 and includes: a hearth that has a base 12 and sides 13 formed from refractory bricks; side walls 14 that extend upwardly from the sides 13 of the hearth; a roof 17; an outlet 18 for off-gases; H:\Bkrot\Keep\speci\TRPL\P125.doc 19/10/01 8 a forehearth 19 for discharging molten iron continuously from the vessel; and a tap-hole 21 for discharging molten slag from the vessel.

The side walls 14 include a generally cylindrical steel outer-jacket 16 and a series of water-cooled panels 51 mounted to the jacket. A lower section of the side walls 14 includes an inner lining of refractory bricks 53.

The hearth and an upper section of the side walls 14 define cylindrical regions within the vessel. The lower section of the side walls 14 defines a generally frustoconical cylindrical region within the vessel which provides a transition between the narrower diameter hearth and the wider diameter upper section of the side walls 14. In a commercial scale plant, ie a plant producing at least 500,000 tonnes/year of molten iron, the diameter of the 20 hearth is at least 4 meters, more preferably at least 6 meters.

The vessel also includes a downwardly extending hot air injection lance 26 for delivering a hot air blast into a central, upper region 91 of the vessel and post- •combusting reaction gases released from the molten bath.

It is noted that, depending on a range of interrelated factors, including the size and geometry of the 30 vessel, there may be more than one lance 26.

S" The vessel also includes a number of solids "injection lances 27 (four of which are shown in the figures) extending downwardly and inwardly through the side walls 14 and into the molten bath at an angle of 20-70° to the horizontal for injecting feed materials being iron ore, solid carbonaceous material, and fluxes entrained in an H:\Bkiot\Keep\speci\TRFIL\F'125 .doc 19/10/01 9 oxygen-deficient carrier gas into the molten bath.

The lances 27 are positioned so that outlet ends 39 of the lances 27 are equi-spaced apart around the central axis of the vessel.

The vessel also includes an assembly of a plurality of horizontally disposed water-cooled members generally identified by the numeral 75 in the figures that are provided to prevent undercutting of the water-cooled panels in the lower section of the side walls 14 by molten material and to shield the refractory bricks in the sides 13 of the hearth that are below the members 75 from molten material runback in the vessel. In effect, the members form a horizontally disposed shelf at the boundary between the side walls 14 and the hearth. In pilot plant work that the applicant has carried out on the HIsmelt process, the applicant has identified the location of the assembly of members 75 as being particularly important in terms of long 20 term operating life of the vessel.

The water-cooled members 75 are positioned side by side in abutting relationship around the circumference of the vessel. The members 75 are constructed so that the assembly of the members 75 replaces a single course of refractory bricks and the members 75 cover a substantial section, at least 80%, of an upper surface of the refractory bricks in the sides 13 of the hearth that are below the members 75. Specifically, for the vessel shown 30 in the figures, typically each member 75 has a thickness of 150 mm and other dimensions as marked on Figures 3 to 6.

With reference to Figures 3 to 7, each watercooled member 75 includes: a cast copper external shell generally identified by the numeral 77; and H: \Bkrot\Keep\speci\TRFL\ P125 .doc 19/10/01 10 a steel flow former generally identified by the numeral 79 located within a volume enclosed by the shell 77.

The shell 77 is generally trapezium-shaped in top plan. The shell 77 includes 50mm thick parallel top and bottom faces 81, parallel inner and outer faces 83, 85, and side faces 87. The side faces 87 converge towards the inner face 83 from the outer face 85. The shell 77 further includes an inlet and an outlet, generally identified by the arrows A and B in Figure 3, in the outer face 85 to allow supply of cooling water to and removal of cooling water from the volume enclosed by the shell 77.

The flow former 79 is positioned within the shell 77 and divides the volume enclosed by the shell into a series of passageways for water flow between the inlet and the outlet.

*o The flow former 79 includes a central plate that extends between the outer face 85 and the inner face 83 of the shell 77 and divides the volume enclosed by the shell into an upper section and a lower section. The flow former 79 further includes a series of walls 57 that extend upwardly and downwardly from the central plate 80 and contact the top and bottom faces 81 of the shell 77 and form passageways in the upper section and the lower section.

Figure 4 illustrates the front face of the flow former 79. In the assembled member 75 the front face of the flow former 79 contacts the inner face 83 of the shell 77.

Figure 5 illustrates the back face of the flow former 79. In the assembled member 75 the back face of the H:\Bktot\Keep\speci\TRFL,\P125 .doc 19/10/01 11 flow former 79 contacts the outer face 85 of the shell 77.

The passageways in the upper section and the lower section extend between the outer face 85 and the inner face 83 of the shell 77.

In view of the converging side faces 57, the walls 87 are formed so that the passageways taper inwardly from the outer face 85 to the inner face 83 of the shell.

With reference to Figure 6, two of the walls 57.

On the upper side of the plate 80 terminate a short distance back from the end of the central plate 80 at the front face of the flow former 79. These walls are the 2 nd and 4 th walls 57 as viewed from the left side of Figure 6.

In addition, whilst not shown, the 1 st 3 rd, and 5 th walls 57 on the lower side, i.e the opposite side to that shown in Figure 6, of the central plate 80 terminate a short distance back from the end of the central plate 80 at the 20 back face of the flow former 79. While the other three *walls 57 on the other side of the central plate 80 do likewise. As a consequence, water can flow between passageways that are separated by these upper and lower 0 walls 57. In addition, with further reference to Figure 6, all of the walls 57 at the front face of the flow former 79 extend forwardly of the end of the central plate 80. As a consequence, water can flow downwardly from a passageway in the upper section to a corresponding passage in the lower section, and vice versa. The flow of water as described above is illustrated by the arrows in Figure 6.

e.

The inlet is located in the outer face 85 of the shell 77 so that water can flow via the inlet into the top left hand passageway, as viewed in Figure 6. The outlet is located in the outer face 85 of the shell 77 so that water can flow via the outlet from the top right hand passageway as viewed in Figure 6.

H:\Bkrot\Keep\speci\TRPL\P125 .doc 19/10/01 12 With such an arrangement, in use, water flows via the inlet initially along the top left-hand passageway, as viewed in the figures, to the inner face 83 and downwardly around the forward end of the central plate 80 into the corresponding bottom passageway, ie the bottom left hand passageway as viewed in the figures. The water then flows back along that passageway towards the outer face 85 and then into the immediately adjacent bottom passageway via the interconnection between the passageways. Thereafter, the water flows forwardly along that adjacent bottom passageway towards the inner face 83 and upwardly around the forward end of the central plate 80 into the corresponding top passageway. The water then flows back along that passageway towards the outer face 85, and so on until the water reaches the outlet.

With reference to Figure 7, each water-cooled member 75 is positioned in the vessel with a maximum 20 allowance of 25mm to accommodate thermal expansion of refractories. An initial gap of 30mm is set to ensure that Sothere is no contact between the top faces 81 of the members *75 and the water cooling tubes 63 of the lowest watercooled panels 51. Depending on the extent of thermal S 25 expansion of refractories, it is possible that the gap between the top faces 81 of the members 75 and the water cooling tubes 63 of the lowest water-cooled panels 51 will be above a maximum allowable spacing. In order to prevent S•this from occurring each member 75 includes a fin 61 that is an extension of an outer face 85 of the shell 77 above the top face 81 of the shell.

The above-described vessel is particularly suited, although by no means exclusively suited, to carry out the HIsmelt process as described by way of example in Australian provisional application PQ8907 and the disclosure in the patent specification of the provisional H:\Bkrot\Keep\spec i \TRPL\P25 .doc 19 10/01 13 application is incorporated herein by cross-reference.

In use, the vessel to carry out the HIsmelt process contains a molten bath that has a layer 15 of molten iron and a layer 16 of molten slag under quiescent conditions. The dashed line marked by the numeral 41 indicates the quiescent level of molten metal and the dashed line marked by the numeral 43 indicated the quiescent level of molten slag. The term "quiescent surface" is understood to mean the surface in situations where there is no injection of materials into the vessel.

In the HIsmelt process, iron ore, solid carbonaceous material (typically coal), and fluxes (typically lime and magnesia) entrained in a carrier gas (typically N 2 are injected into the molten bath via the lances 27 at a velocity of at least 40 m/s, preferably 100 m/s. The momentum of the solid material/carrier gas carries the solid material and gas towards the base 12 of 20 the hearth into regions that are spaced around the central axis of the vessel. These regions are referred to in the following description as regions of high concentration of solids/gas injection. The coal is devolatilised and thereby produces gas. Carbon partially dissolves into the 25 metal and partially remains as solid carbon. The iron ore is smelted to metal and the smelting reaction generates carbon monoxide gas. The gases transported into the molten bath and generated via devolatilisation and smelting •produce significant buoyancy uplift of molten material (including metal and slag) and solid carbon from the molten bath.

The buoyancy uplift of molten material and solid carbon causes substantial agitation in the molten bath, particularly immediately above and outwardly spaced from the regions of high concentration of solids/gas injection, with the result that an expanded molten bath zone 28 that H:\Bkl'ot\Keep\spei\TR'L\F'125 .doc 19/10/01 14 has a surface indicated by the arrow 30 forms. More particularly, the surface of the expanded molten bath zone 28 forms an annular raised region 70 between the central region 91 and the vessel side walls 14. The extent of agitation is such that there is substantial movement of molten material within the expanded molten bath zone 28 and strong mixing of the molten material within this zone to the extent that there is reasonably uniform temperature typically, 1450 1550 0 C with a temperature variation of the order of 300 throughout the zone.

Notwithstanding the strong mixing of molten material in the expanded molten bath zone 28, molten iron progressively settles towards the lower part of the hearth and forms a metal-rich zone and is continuously removed via the forehearth 19.

The interface between the expanded molten bath zone 28 and the metal-rich zone is determined largely by 20 the regions of high concentration of solids/gas injection.

The substantial upward movement of molten material from these regions is compensated for by the continual supply of **further feed materials via the lances 27 and the downward movement of already-molten material.

In addition, the upward gas flow from the regions of high concentration of solids/gas injection projects some molten material (predominantly slag) as splashes, droplets •and streams beyond the raised region of the expanded molten bath zone 28 and forms a curtain (not shown). The molten material in the curtain contacts the upper barrel section 51 of the side walls 14 that is above the expanded molten bath zone 28 and the roof 17.

In addition to the above, in use, hot air at a temperature of 800-1400 0 C and a velocity of 200-600 m/s is injected into the central region 91 of the vessel via lance H:\Bki~ot\Keep\speci\TRF'L\F125 .r1oc 19/10/01 15 26 and deflects upwardly projected molten material in that region and causes an essentially metal/slag free space 29 to form around the end of the lance 26. This downward blast of hot air contributes to shaping projected molten material into the above-described curtain.

The hot air blast via the lance 26 post-combusts reaction gases CO and H 2 in the free space 29 around the end of the lance 26 and in the surrounding molten material and generates high temperatures of the order of 2000 0 C or higher. The heat is transferred to the molten material in the region of gas injection and the heat is then partially transferred via the molten material to the metal-rich zone.

It is to be understood that this invention is in no way limited to the details of the illustrated construction and that many modifications and variations will fall within the spirit and scope of the invention.

H:\Bkrot\Keep\speci\TRPL\P125 .doc 19/10/01

Claims (21)

1. A direct smelting vessel for producing iron and/or ferroalloys by a molten bath-based direct smelting process, the vessel including: a hearth that has a base and sides that have an inner refractory brick lining; side walls extending upwardly from the sides of the hearth, the side walls including water-cooled panels and an inner refractory brick lining at least in a lower section of the side walls; a roof; a means for tapping molten metal and slag from the vessel; a means for supplying solid feed materials including solid ferruginous material and carbonaceous material into the vessel; and a means for supplying an oxygen-containing gas into the vessel to post- combust gaseous reaction products generated in the direct smelting process; and the vessel being characterised by a plurality of water-cooled members positioned below and adjacent the water-cooled panels and extending inwardly S"into the vessel beyond the water-cooled panels.

2. The vessel defined in claim 1 wherein the members extend across and thereby cover at least 80% of the "refractory brick lining of the sides of the hearth that is below the members.

3. The vessel defined in claim 1 or claim 2 wherein the members are at least partially covered by the refractory brick lining in the lower section of the side 000 a •walls. The vessel defined in claim 3 wherein the members a.

S"are substantially covered by the refractory brick lining in the lower section of the side walls.

5. The vessel defined in any one of the preceding claims wherein each member includes a water inlet, a water outlet, and a passageway for water flow within the member. H:\Bkrot\Keep\speci\TRF'L\P12 .doc 19/10/01 17

6. The member defined in claim 5 wherein each member includes: an external shell with openings that define the water inlet and the water outlet; and an internal flow former that divides a volume enclosed by the shell into the passageway.

7. The vessel defined in any one of the preceding claims wherein each member includes parallel top and bottom faces that are generally trapezium shaped, parallel inner and outer faces extending between and interconnecting the top and bottom faces, and side faces extending between and interconnecting the top and bottom faces and converging from the outer face towards the inner face. 20

8. The vessel defined in claim 7 wherein the members are arranged in a circular array.

9. The vessel defined in claim 8 wherein the members form a continuous circular array.

The vessel defined in any one of claims 7 to 9 wherein the top, bottom and inner faces of each member include machined grooves that promote build-up of .ooooi r accretions on the faces.

11. The vessel defined in any one of the preceding S"claims wherein the thickness of each member is of the order of the thickness of a single refractory brick or multiple refractory bricks.

12. The vessel defined in any one of the preceding claims wherein the refractory brick lining in the lower 19/10/01 18 section of the side walls progressively steps outwardly with increasing height from an intersection of the lining and the refractory brick lining of the sides of the hearth.

13. The vessel defined in claims 12 wherein the members are positioned at the intersection of the refractory brick lining of the side walls and the refractory brick lining of the sides of the hearth.

14. The vessel defined in any one of the preceding claims wherein the members extend generally horizontally into the vessel.

A member for water cooling a part of a direct smelting vessel that includes: an external shell with opening that define a water inlet and a water outlet; and an internal flow former that divides a volume enclosed by the shell into a •passageway for water flow from the inlet to the outlet. 25

16. The member defined in claim 15 wherein the shell includes top and bottom faces, inner and outer faces, extending between and interconnecting the top and bottom faces, and side faces extending between and interconnecting oooo° S"the top and bottom faces.

S°17. The vessel defined in claim 15 or claim 16 S"wherein the flow former includes a central plate that divides the volume enclosed by the shell into an upper section and lower section.

18. The vessel defined in claim 17 wherein the flow former includes a series of walls that extend upwardly and H: \Bkrot\Kee\speci\TRPL\FP125 .doc 19/10/01 19 downwardly from the central plate and divide the upper section and the lower section into a series of sections of the passageway.

19. The vessel defined in claim 18 wherein the inlet and outlet are in the outer face of the shell, the passageway sections in the upper and lower sections of the volume enclosed by the shell extend between the outer and inner faces of the shell, and the in faces of the flow former that are adjacent the outer and the inner ends of the shell are formed so that there are interconnections between the passageway sections.

The direct smelting vessel substantially as hereinbefore described with reference to the accompanying drawings.

21. A member for water cooling a part of a direct smelting vessel substantially as hereinbefore described 20 with reference to Figures 3 to 7. *e o• a H:\Bkrot\Keep\speci\TRPL\P125.doc 19/10/01