Direct smelting process and apparatus

Abstract

A process and apparatus for direct smelting metalliferous material is disclosed. The invention concentrates injection of solid feed materials comprising metalliferous material and carbonaceous material into a direct smelting vessel during the course of the process into a relatively small region within a metal layer in a molten bath in the vessel in order to generate a substantial upward movement of molten material and gas from the metal layer into a region in the vessel that is above the molten bath. In particular, the invention injects the solid food materials with sufficient momentum and/or velocity via an opposed pair of lances that are oriented within the vessel and arranged to form overlapping plumes of injected material in the molten bath.

Claims

1. A direct smelting apparatus for direct smelting metalliferous material and producing molten metal that comprises: (a) a direct smelting vessel having a hearth, including a floor and a side wall, defining a volume for containing a molten bath of metal and slag, the direct smelting vessel further having (i) at least one pair of opposed lances extending downwardly and inwardly into the direct smelting vessel through the side wall to inject solid material into the direct smelting vessel during a direct smelting process, the at least one pair of opposed lances each having an inlet end outside the direct smelting vessel for receiving the solid materials and an outlet end inside the vessel and having longitudinal axes, (ii) a tap-hole defined on the side wall of the direct smelting vessel to discharge the slag during the direct smelting process, wherein at least one pair of opposed lances are oriented such that the outlet end of each of the at least one pair of opposed lances extends below a plane of the tap-hole, and the longitudinal axes of the at least one pair of opposed lances intersect above the vessel floor, and (iii) at least one additional lance extending downwardly and inwardly into the direct smelting vessel through the side wall to inject a solid carbonaceous material into the direct smelting vessel during start-up of the direct smelting process, each of the at least one additional lance having an inlet end outside the direct smelting vessel for receiving the solid carbonaceous material and an outlet end inside the direct smelting vessel, and (b) a material supply apparatus in communication with a source of solid metalliferous material and in communication with a source of the solid carbonaceous material and in communication with the at least one pair of opposed lances, wherein the material supply apparatus delivers the solid metalliferous material and the solid carbonaceous material to the inlet ends of the at least one pair of opposed lances and delivers the solid carbonaceous material to each of the at least one additional lance.

2. The apparatus defined in claim 1 wherein the material supply apparatus for the at least one pair of opposed lances and the at least one additional lance, comprises: (i) a first solids supply line that connects a metalliferous material dispensing/metering unit to the inlet end of at least one opposed pair of lances and the first solids supply line is adapted to communicate heated solid metalliferous feed material from the dispensing/metering unit to the inlet end; and (ii) an assembly that connects a carbonaceous material dispensing/metering unit directly into the at least one additional lance or to the first solids supply line downstream of the metalliferous material dispensing/metering unit so that there can be co-injection of heated metalliferous material and the solid carbonaceous material from the at least one additional lance into the direct smelting vessel.

3. The apparatus defined in claim 1 wherein the direct smelting vessel has a minimum diameter of 5 m in a hearth region of the direct smelting vessel.

4. The apparatus defined in claim 1 wherein each lance in the pair of opposed lances is at an angle of less than 50 to the vertical.

5. The apparatus defined in claim 1 wherein the at least one additional lance is at an angle of at least 50 to the vertical.

6. The apparatus defined in claim 1 wherein the solid metalliferous material dispensing/metering unit comprises a plurality of bins that receive heated solid metalliferous material at atmospheric conditions and transfer the heated solid metalliferous material to a pressurised carrier gas environment.

7. The apparatus defined in claim 1 wherein the solid carbonaceous material dispensing/metering unit comprises a plurality of bins that receive the solid carbonaceous material at atmospheric conditions and transfer the solid carbonaceous material to a pressurised carrier gas environment.

8. A direct smelting plant that comprises: (a) the direct smelting apparatus defined in claim 1; and (b) a pre-treatment unit in communication with and upstream of the solid metalliferous material dispensing/metering unit, for heating a solid metalliferous material and delivering the heated solid metalliferous material to the metalliferous material dispensing/metering unit.

9. The plant as defined in claim 8 wherein the pre-treatment unit comprises a pre-heater.

10. The apparatus as defined in claim 1 wherein the at least one pair of opposed lances are oriented with respect to the side wall and the tap-hole such that, during the direct smelting process, the longitudinal axes of each of the at least one pair of opposed lances intersect at about a top three-quarter of the metal layer of the molten metal as measured from the floor.

11. The apparatus as defined in claim 1, comprises a forehearth in communication with the hearth, and is configured to discharge molten metal during the direct smelting process.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is described further by way of example only with reference to the accompanying drawings, of which:

(2) FIG. 1 is a vertical cross-section through one embodiment of a direct smelting vessel in accordance with the present invention;

(3) FIG. 2 is a cross-section along the line 2-2 in FIG. 1 that illustrates the overlapping plumes of injected material in accordance with one embodiment of a direct smelting process in accordance with the present invention, and

(4) FIG. 3 is a schematic view that illustrates one embodiment of a direct smelting plant in accordance with the present invention.

DETAILED DESCRIPTION

(5) FIG. 1 shows a direct smelting vessel 11 that forms a part of a plant that is suitable particularly to be used to carry out the HIsmelt process as described in International application PCT/AU96/00197. The subject process can be considered to be a form of the HIsmelt process as described in that International application.

(6) The following description is in the context of smelting metalliferous material in the form of iron ore fines to produce molten iron in accordance with the HIsmelt process. However, it will be appreciated that the present invention is not confined to iron ore and is applicable to smelting any metalliferous material in any form of the material. Ore is one example of a form of metalliferous material. The invention also extends to other forms, including by way of example partly reduced ores and metal-containing waste streams.

(7) The vessel 11 has a hearth for containing a molten bath of iron and slag that includes a base 12 and sides 13 formed from refractory bricks, a side wall 14, which forms a generally cylindrical barrel extending upwardly from the sides 13 of the hearth, and a roof 17. The side wall 14 and the roof 17 comprise water-cooled panels (not shown) for transferring heat from the side wall 14 and the roof 17. The water cooling of the panels is the main mechanism for controlling the temperature of the side wall 14 and the roof 17 and ensuring that the temperature does not increase to a level that has an impact on the integrity of the side wall 14 and the roof 15. The vessel 11 is further provided with a forehearth 19, through which molten iron is continuously discharged during smelting, and a tap-hole 21, through which molten slag is periodically discharged during smelting. The roof 17 is provided with an outlet 18 through which process off gases are discharged.

(8) In use of the vessel 11 to smelt iron ore fines to produce molten iron in accordance with the process of the present invention, the vessel 11 contains a molten bath of iron and slag, which includes a layer 22 that is predominantly molten iron and a layer 23 that is predominantly molten slag on the iron layer 22. The position of a nominal quiescent surface of the iron layer 22 is indicated by arrow 24. The position of a nominal quiescent surface of the slag layer 23 is indicated by arrow 25. The term quiescent surface is understood to mean the surface when there is no injection of gas and solids into the vessel 11. Under normal operating conditions, the process operates in a range of pressures between 0.5 barg and 1.2 barg, and preferably between 0.6 to 1.0 barg.

(9) The vessel 11 is provided with solids injection lances 27 that extend downwardly and inwardly through openings (not shown) in the side wall 14 of the vessel and into the slag layer 23.

(10) The lances 27 are oriented within the vessel so that outlet ends 28 of the lances 27 are above the surface of the iron layer 22 during operation of the process. This position of the lances 27 reduces the risk of damage through contact with molten metal and also makes it possible to cool the lances by forced internal water cooling without significant risk of water coming into contact with the molten metal in the vessel 11.

(11) In use, under normal operating conditions, solid feed materials in the form of iron ore fines, solid carbonaceous material (such as, for example, coal or coke breeze) and fluxes are co-injected through outlet ends 28 of the lances 27 into the molten bath with sufficient momentum and/or velocity to penetrate into the iron layer 22. The iron ore fines, solid carbonaceous material, and fluxes are entrained in an oxygen-deficient carrier gas, such as nitrogen. The coal is devolatilised and thereby produces gas. Carbon partially dissolves into the 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 iron layer 22 and generated via devolatilisation and smelting produce significant buoyancy uplift of molten material (including metal and slag) and solid carbon and gas from the molten bath. The buoyancy uplift generates an upward movement of splashes, droplets and streams of molten material and gas into an upper region 83, i.e. an upper gas space, of the vessel. The upper movement is shown in FIG. 1 as a region identified by the numeral 69. The buoyancy uplift also causes substantial agitation in the molten bath and, in effect, expands the molten bath. The extent of agitation is such that there is strong mixing of the molten material within the molten bath to the extent that there is reasonably uniform temperaturetypically, 1450-1550 C. with a temperature variation of the order of 30 throughout the molten bath.

(12) With reference to FIG. 2, the lances 27 comprise one pair of diametrically opposed lances 27a that extend downwardly and inwardly through the side wall 14 of the vessel 11, typically at an angle of 45 to the vertical. The lances 27a are oriented within the vessel 11 so that longitudinal axes 81 of the lances 27a intersect in the iron layer 22 within a top three quarters, preferably within a top half, of the iron layer 22, as measured from a floor 83 of the base 12 of the vessel 11, in a central region of the iron layer 22. In use, under normal operating conditions, plumes 71 of iron ore fines and solid carbonaceous material are injected via the lances 27a with sufficient momentum and/or sufficient velocity so that the ends of the plumes overlap in the central region of the iron layer 22 (i.e. the plumes may be said to intersect in the central region or alternatively the plumes may be said to coalesce in the central region).

(13) The applicant believes that two overlapping plumes of iron ore fines and carbonaceous material generate more intense turbulence within a localised region of the bath than is the case where equivalent plumes are injected into the bath but do not overlap.

(14) Each plume 71 from a lance 27a comprises a stream of (a) injected metalliferous material and solid carbonaceous material and (b) products produced as a result of such injection into the direct smelting vessel via the lance 27a. The products include, by way of example, volatiles released from the carbonaceous material and reaction products such as CO and CO.sub.2 and H.sub.2O. As indicated above, the injected materials and the products resulting from the injection cause a significant upward movement of molten material and solid carbon and gas from the central region of the metal layer 22 into the upper region 83 of the vessel 11. The upward movement of molten material and solid carbon and gas from the iron layer 22, by virtue of the concentration of injection and penetration into the iron layer 22, is sufficient to the wet water-cooled panels that form the side wall 14 and the roof 15 of the vessel 11 to minimise heat loss to an extent that heat loss through the panels is less than 3000 kW/m.sup.2 of panel, more preferably less than 2000 kW/m.sup.2 of panel and to cause substantial agitation. In addition, this upward movement of molten material and solid carbon and gas from the iron layer 22 causes substantial agitation in the molten bath and facilitates heat transfer for the upper region of the vessel 11 into the molten bath.

(15) Typically, for a vessel 11 that has a hearth diameter of at least 5 m and produces at least 60 tonne/hour molten iron, the overlapping plumes 71 are at least 400 mm below the quiescent interface 24 between the iron layer 22 and the slag layer 23. Typically, with this size vessel and production rate, the overlapping plumes 71 are within 200 mm of a vertical centreline of the vessel.

(16) With further reference to FIG. 2, the lances 27 also comprise a pair of diametrically opposed lances 27b extending downwardly and inwardly through the side wall 14 of the vessel 11, typically at an angle of 50 to the vertical. These lances 27b are provided to inject solid carbonaceous material into the vessel during start up of the process on during process perturbations that make such injection of carbonaceous material appropriate. During normal operating conditions of the process, injection of iron ore fines and solid carbonaceous material is via the lances 27a only.

(17) The vessel 11 also has a gas injection lance 26 for delivering a hot air blast into the upper region of the vessel 11. The lance 26 extends downwardly through the roof 17 of the vessel 11 into the upper region of the vessel 11. In use, the lance 26 receives an oxygen-enriched hot air flow through a hot gas delivery duct (not shown), which extends from a hot gas supply station (also not shown).

(18) FIG. 3 shows schematically one embodiment of a direct smelting plant in accordance with the present invention.

(19) The plant includes the direct smelting vessel 11.

(20) The plant also includes a pre-treatment unit 34 in the form of a pre-heater for heating iron ore fines.

(21) The plant also includes an ore dispensing/metering unit 32 for dispensing heated iron ore fines from the pre-heater 34.

(22) The ore dispensing/metering unit 32 is constructed to dispense heated iron ore fines with a carrier gas, which is typically nitrogen. The ore dispensing/metering unit 32 can be in the form of a plurality of bins that allow the heated iron ore fines to be transferred from standard atmospheric conditions to an environment of pressurized carrier gas. However, for the purposes of the present invention, the ore dispensing/metering unit 32 can be considered as a single unit.

(23) In use, iron ore fines are fed to the pre-heater 34 from a stockpile (not shown) and the pre-heater heats the fines. The pre-heater 34 is arranged to heat the fines such that the iron ore fines are at a temperature of the order of 600 C. to 700 C. at the point of injection into the vessel 11. Off gases can be supplied from the outlet 18 to the pre-heater 34, such that heat can be transferred from the off gases to the iron ore fines. The pre-heater 34 is arranged to supply the heated iron ore fines to the ore dispensing/metering unit 32.

(24) The plant also includes a material supply apparatus 30 for supplying heated iron ore fines and solid carbonaceous material (such as in the form of coal) to the lances 27a.

(25) The material supply apparatus 30 includes a first supply line 36 for receiving heated iron ore fines from the ore dispensing/metering unit 32 and transporting the heated iron ore fines to one of the lances 27a. Accordingly, in use, iron ore fines are discharged from the ore dispensing/metering unit 32 into the supply line 36 and are transported to the lance 27a and injected into the vessel 11 via the lance 27a.

(26) The material supply apparatus 30 also includes an assembly for supplying carbonaceous material to the first supply line 36 downstream of the ore dispensing/metering unit 32 and as close as possible to the lance 27a to facilitate co-injection of carbonaceous material and heated iron ore fines into the vessel 11. The assembly is in the form of a carbonaceous material dispensing assembly 38 which receives carbonaceous material from a stockpile (not shown) and a second supply line 40.

(27) The carbonaceous material dispensing assembly 38 can be in the form of a plurality of bins that allow carbonaceous material to be transferred from standard atmospheric conditions to an environment of pressurized carrier gas. However, for the purposes of the present invention, the carbonaceous material dispensing assembly 38 can be considered to be a single unit.

(28) The first supply line 36 is positioned approximately level with the base 12 of the vessel 11.

(29) The supply line 36 includes an upwardly extending section 42, which conveys the heat iron ore fines from a position that is approximately level with the base 12 to at least the height of the inlet of the lance 27a.

(30) The supply line 36 also includes a downwardly extending section 46 which connects the line to an inlet end of the lance 27a. The section 46 is formed to be co-axial with the lance 27a when in an operating position as shown in FIG. 3.

(31) The supply line 36 also includes an upwardly extending section 48 that is co-axial with the section 46 and forms an inlet section for coal into the line 36.

(32) The second supply line 40 is connected to section 48 of the supply line 36 and therefore is connected to the line as close to the inlet to the lance 27a.

(33) In use, carbonaceous material at ambient temperature is discharged from the carbonaceous material dispensing assembly 38 into the second supply line 40 and then into the sections 48 and 46 of the first supply line 36 and mixes with the heated iron fines being transported in the line 36. The combined heated iron ore fines and carbonaceous material are subsequently transported via the section 46 of the supply line 36 to the inlet end of the lance 27 and are co-injected via the lance 27a into the vessel 11.

(34) Thus, it can be seen that, in use, iron ore fines are heated in the pre-heater 34 to an elevated temperature. The iron ore fines are subsequently transported along the supply line 36 to the lance 27a. The carbonaceous material is injected into the supply line 36 with the heated iron ore fines as close as possible to the inlet of the lance 27awith minimal risk of tar formation and undesirable reactions between the heated iron ore fines. The heated iron ore fines and carbonaceous material are transported to the inlet end of the lance 27a and then into the vessel 11.

(35) The carbonaceous material may be injected into the supply line 36 with the heated iron ore fines at any location on the line 36 upstream of the location shown in FIG. 3 subject to the location being sufficiently close to the lance 27a so that there is minimal risk of tar formation and undesirable reactions between the heated iron ore fines. Typically, such a location can be described as being within 50% of the length of the supply line 36 from the inlet end of the lance 27a, with the length of the line being measured between the location and the inlet end of the lance 27a. Typically, such a location can also be described as being less than 0.5 seconds conveying time to the inlet end of the lance 27a.

(36) Many modifications may be made to the embodiments described above without departing from the spirit and scope of the present invention.

(37) By way of example, whilst the embodiment of the direct smelting vessel described above with reference to the Figures includes one pair of lances 27a, the present invention is not so limited and extends to arrangements that comprise two or more such pairs of lances 27a.

(38) By way of further example, whilst the embodiment described above operates under pressure in the range of pressures between 0.5 barg and 1.2 barg, the present invention is not limited to this pressure range and moreover is not limited to operation under pressure and may operate at atmospheric pressure.

(39) By way of further example, whilst the side wall 14 and the roof 17 of the embodiment described above comprise water-cooled panels, the present invention is not limited to the use of these panels. For example, the vessel walls and roof may be completely constructed from refractory material.

(40) In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word comprise or variations such as comprises or comprising is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.