Solids injection lance

Abstract

A solids injection lance includes (a) a tube that defines a passageway for solid feed material to be injected through the tube and has an inlet for solid material at a rear end and an outlet for discharging solid material at a forward end of the tube and (b) a puncture detection system for detecting a puncture in the solids injection tube.

Claims

1. A solids injection lance includes a tube that defines a passageway for solid feed material to be injected through the tube and has an inlet for the solid feed material at a rear end and an outlet for discharging the solid feed material at a forward end of the tube and a system for detecting a puncture in the tube, the system includes an annular chamber radially outwardly of the tube, wherein the annular chamber contains an inert gas and the system is adapted to detect a change in pressure of the inert gas for detecting the puncture in the tube.

2. The solids injection lance defined in claim 1 wherein the system for detecting the puncture is adapted to detect a change of pressure in the tube or a flow of gas into or from the tube as a result of the puncture in the tube.

3. The solids injection lance defined in claim 1 includes a water cooling system, and the system for detecting the puncture is located between the tube and the water cooling system.

4. The solids injection lance defined in claim 1 includes a gas injection system for injecting an oxygen-containing gas through the solids injection lance from a rearward end to a forward end of the solids injection lance, and the system for detecting the puncture is located between the tube and the gas injection system.

5. The solids injection lance defined in claim 1 wherein the tube is a central core tube of the solids injection lance.

6. The solids injection lance defined in claim 5 wherein the the system for detecting the puncture is adapted to detect a change of pressure in the annular chamber or a flow of gas into or from the annular chamber as a result of a puncture in the tube.

7. The solids injection lance defined in claim 5 wherein the system for detecting the puncture includes the annular chamber radially outwardly of the tube, a sensor for detecting a change of pressure in the annular chamber or the tube or a flow of gas into or from the annular chamber or the tube which indicates that there is a puncture in the tube, and an alarm that is responsive to the sensor to indicate the puncture in the tube.

8. The solids injection lance defined in claim 6 wherein the change of pressure or gas flow is a decrease in pressure in the annular chamber or an inward flow of gas into the annular chamber when the tube is punctured.

9. The solids injection lance defined in claim 8 wherein the inert gas in the annular chamber is under a pressure that is higher than average gas pressure in the tube so that in use, inert gas flows into the passageway in the tube from the chamber when the tube is punctured.

10. The solids injection lance defined in claim 9 wherein the annular chamber includes an inlet through which the inert gas is supplied to the annular chamber to maintain the gas pressure in the annular chamber.

11. The solids injection lance defined in claim 6 wherein the change of pressure or gas flow is an increase in pressure in the annular chamber or an increase in outward flow of gas from the annular chamber due to gas flowing into the annular chamber from the passageway in the tube when the tube is punctured.

12. The solids injection lance defined in claim 11 wherein the annular chamber contains the inert gas under a pressure that is lower than average gas pressure in the tube.

13. The solids injection lance defined in claim 11 wherein the annular chamber is under vacuum.

14. The solids injection lance defined in claim 1 wherein the annular chamber is defined with a radial depth of 1-5 mm.

15. The solids injection lance defined in claim 1 wherein the annular chamber extends substantially along length of an annular cooling jacket.

16. The solids injection lance defined in claim 1 wherein the inert gas is nitrogen.

17. A molten bath-based direct smelting process for producing a molten metal from a solid metalliferous feed material that includes: injecting the solid feed material into a molten bath in a direct smelting vessel via at least one solids injection lance defined in claim 1 and monitoring the solids injection lance by a system to detect a puncture in the solids injection lance.

18. The molten bath-based direct smelting process defined in claim 17 includes checking for a change of pressure in the tube of the solids injection lance or a flow of a gas into or from the tube as a result of the puncture in the tube.

19. The molten bath-based direct smelting process defined in claim 17 includes supplying an inert gas to the annular chamber of the solids injection lance to maintain internal gas pressure in the annular chamber and checking for a change of inert gas flow into to maintain the internal gas pressure.

20. An apparatus for a molten bath-based smelting process for producing molten metal from a metalliferous feed material which includes: a direct smelting vessel having at least one solids injection lance defined in claim 1; and at least one gas injection lance for injecting an oxygen-containing gas, the direct smelting vessel containing a bath of molten material in the form of molten metal and molten slag and generating a bath/slag fountain via gas evolution in the molten bath and generating an offgas and smelting preheated metalliferous feed material and forming molten metal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The 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 a direct smelting vessel;

(3) FIG. 2 is a longitudinal partial cross-section view of one embodiment of a solids injection lance in accordance with the present invention for injecting ore into the vessel shown in FIG. 1; and

(4) FIG. 3 is a diagrammatic cross-sectional view of a section of the lance shown in FIG. 2 which illustrates puncture injection system of the lance.

DESCRIPTION OF EMBODIMENT

(5) FIG. 1 shows a direct smelting vessel 11 that is suitable particularly for carrying out the HIsmelt process as described by way of example in International patent application PCT/AU96/00197 (WO 1996/031627) in the name of the applicant. The vessel 11 forms part of a direct smelting plant (not shown) that includes apparatus for storing and supplying feed materials to the vessel 11 and for handling/processing molten metal, slag and off-gas discharged from the vessel 11.

(6) The following description is in the context of smelting iron ore fines to produce molten iron in accordance with the HIsmelt process.

(7) It will be appreciated that the present invention is applicable to smelting any metalliferous material, including ores, partly reduced ores, and metal-containing waste streams via any suitable molten bath-based direct smelting process and is not confined to the HIsmelt process. It will also be appreciated that the ores can be in the form of iron ore fines.

(8) The vessel 11 has a hearth that includes a base 12 and sides 13 formed from refractory bricks, side walls 14, which form a generally cylindrical barrel extending upwardly from the sides 13 of the hearth, and a roof 17. Water-cooled panels (not shown) are provided for transferring heat from the side walls 14 and the roof 17. The vessel 11 is further provided with a forehearth 19, through which molten metal 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.

(9) In use of the vessel 11 to smelt iron ore fines to produce molten iron in accordance with the HIsmelt process, the vessel 11 contains a molten bath of iron and slag, which includes a layer 22 of molten metal and a layer 23 of molten slag on the metal layer 22. The position of the nominal quiescent surface of the metal layer 22 is indicated by arrow 24. The position of the 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.

(10) The vessel 11 is provided with solids injection lances 27 that extend downwardly and inwardly through openings (not shown) in the side walls 14 of the vessel and into the slag layer 23. In use, feed materials in the form of iron ore fines and/or solid carbonaceous material (such as, for example, coal or coke breeze) and fluxes are entrained in a suitable carrier gas (such as an oxygen-deficient carrier gas, typically nitrogen) and injected through outlet ends 28 of the lances 27 into the metal layer 22.

(11) The outlet ends 28 of the lances 27 are above the surface of the metal 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, as described further below, without significant risk of water coming into contact with the molten metal in the vessel 11.

(12) The vessel 11 also has a gas injection lance 26 for delivering a hot air blast into an 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).

(13) FIGS. 2 and 3 illustrate the general construction of one embodiment of a solids injection lance 27 in accordance with the present invention.

(14) The lance 27 comprises a core tube in the form of a core tube assembly 31 in the form of a tube that defines a passageway 71 for solid material in the form of iron ore fines and/or carbonaceous material entrained in a suitable carrier gas to pass from an inlet end 60 to a forward end 62 of the lance 27 in the direction of the arrows in the Figures.

(15) With reference to FIG. 2, the core tube assembly 31 comprises an outer tube section 56 of a structural material, such as a stainless steel, and an inner tube section 72 of a wear resistant material, such as a ferrochromium white cast iron. The inner and outer tube sections 56 and 72 are bonded together metallurgically. Typically, the metallurgical bond is across the entire surface area of the interface between the tube sections. The inner and outer tube sections 56 and 72 may be any suitable thicknesses. The outer tube section 56 provides the structural requirements of the core tube assembly 31. The inner tube section 72 provides the wear resistance requirements of the core tube assembly 31. Each tube section 56, 72 is separately formed to optimise the structural and the wear resistance requirements.

(16) The lance 27 also comprises an annular cooling jacket 32 surrounding the core tube assembly 31 and extending over a substantial part of the length of the core tube assembly 31. The annular cooling jacket 32 includes a cooling water system for the lance 27.

(17) The annular cooling jacket 32 is in the form of a long hollow annular structure 41 having outer and inner tubes 42 and 43 respectively interconnected by a front end connector piece 44. An elongate tubular structure 45 is disposed within the hollow annular structure 41 so as to divide the interior of the structure 41 into an inner elongate annular water flow passage 46 and an outer elongate annular water flow passage 47. The rear end (not shown) of the annular cooling jacket 32 of the lance 27 is provided with a water inlet (also not shown) through which a flow of cooling water can be directed into the inner annular water flow passage 46 and a water outlet (also not shown) from which water is extracted from the outer annular passage 47 at the rear end of the lance 27. This arrangement of water flow passages 46, 47 and water inlets and outlets defines the cooling water system. Accordingly, in use of the lance 27, cooling water flows forwardly down the lance through the inner annular water flow passage 46, radially outward through the connector piece 44, and then backwardly through the outer annular passage 47 along the lance 27. Thus, cooling water provides effective cooling of the lance 27 when exposed to the heat generated within the smelting vessel 11, when in use.

(18) The lance 27 also comprises a puncture detection system for detecting a puncture in a wall of the core tube assembly 31 located between the core tube assembly 31 and the cooling water system housed in the annular cooling jacket 32.

(19) With particular reference to FIG. 3, the puncture detection system includes an annular chamber 58 between the core tube assembly 31 and the annular cooling jacket 32 (and therefore the cooling water system). The annular chamber 58 may be any suitable radial thickness. Typically, the radial thickness of the annular chamber 58 is 1-5 mm. The annular chamber 58 contains nitrogen or any other suitable inert gas or any other suitable gas under pressure. The nitrogen is supplied to the annular chamber 58 via an inlet 74 to maintain the chamber at a predetermined gas pressure. The gas pressure is selected to be sufficient to cause a flow of nitrogen from the annular chamber 58 into the core tube assembly 31 via a puncture in the core tube assembly 31 against the internal pressure in the core tube assembly 31. The preferred gas pressure in any given situation will depend on a range of factors including the mechanical design in this section of the lance 27 and the operating pressures for solid feed material injection via the core tube assembly 31. Typically, the gas pressure will be at least 2 bar gauge, more typically in a range of 2-15 bar gauge, and more typically again in a range of 5-12 bar gauge.

(20) The puncture detection system also includes a sensor (not shown) for detecting a flow of nitrogen into the annular chamber 58 via the inlet 74 which indicates that there is a drop in the pressure in the annular chamber 58 and thereby a puncture in the core tube assembly 31. By way of example, the sensor may be arranged to detect an increase in the flow of the inert gas into the annular chamber 58 via the inlet 74 that is required to maintain the predetermined gas pressure in the chamber 58.

(21) The puncture detection system also includes an alarm (not shown) that is responsive to the gas flow sensor to indicate a puncture in the core tube assembly 31. The alarm may be any suitable alarm, visual and/or audible, in a control room for the vessel 11

(22) In use, if solid particulate material, such as hot iron ore fines, wears through the core tube assembly 31 and forms a puncture (shown by the numeral 76 in FIG. 3) in the assembly 31, the nitrogen gas under pressure in the annular chamber 58 flows through the puncture into the passageway defined by the core tube assembly 31 and stops altogether or minimises further wear of the core tube assembly 31 in that part of the core tube assembly 31 by the feed material in the core tube and is advantageous on this basis alone. Furthermore, the flow of nitrogen from the annular chamber 58 into the core tube assembly 31 results in an increase in the flow of nitrogen into the annular chamber 58 via the inlet 74, and the flow increase is detected by the sensor. The sensor activates an alarm that the core tube assembly 31 has been punctured. The alarm initiates a procedure to replace the lance 27. This procedure may be any suitable procedure including (a) changing HIsmelt process operating conditions to a hold state to allow safe replacement of the lance 27, including stopping supply of feed materials to the lance 27, (b) disconnecting the lance 27 from feed material supply lines, (c) removing the lance 27 from the vessel 11, (d) inserting a replacement lance 27, (e) connecting the replacement lance 27 to feed material supply lines, and (f) changing HIsmelt process operating conditions from the hold state to the steady-state. The flow of nitrogen under pressure in the annular chamber 58 through the puncture provides a reasonable time window to initiate the replacement procedure and replace the lance 27.

(23) The puncture detection system of the lance 27 provides the following advantages: Safetyboth in terms of detecting a puncture and allowing time (typically several hours) for lance replacement. An opportunity for longer operating runs before core tube replacementthis will maximise lance life. This opportunity arises because the puncture detection system provides a clear indication of the maximum operating life of the lance 27. An opportunity to modify the injection parameters, the core tube material or the manufacturing techniques of the core tube which may affect its life without having to rebuild a history to judge the life expectancy.

(24) Many modifications may be made to the embodiment of the solids injection lance of the present invention described in relation to the Figures without departing from the spirit and scope of the invention.

(25) By way of example, whilst the puncture detection system is described in relation to the Figures in the context of a water-cooled solids injection lance and the purpose of the puncture detection system is to detect a puncture in the solids injection tube of the lance (which is described as but is not necessarily limited to a central core tube) before it extends to the water cooling system, it can readily be appreciated that the invention is not limited to this type of lance and purpose of the puncture detection system. By way of example, the invention also extends to lances that do not include water cooling systems and separately inject solid feed materials and an oxygen-containing gas and it is important to detect a puncture in the solids injection component of the lance before the puncture can extend to the oxygen gas injection component of the lance.

(26) By way of example, the present invention is not limited to the particular construction of the lance components of the core tube assembly 31 and the annular cooling jacket 32 and the materials from which these lance components are constructed described in relation to the Figures. The present invention is applicable to any water-cooled solids injection lance made from any suitable materials.

(27) By way of example, the present invention is not limited to the core tube assembly 31 comprising an outer tube section 56 of a structural material and an inner tube section 72 of a wear resistant material bonded together metallurgically described in relation to the Figures.

(28) By way of example, whilst the puncture detection system of the lance 27 shown in the drawings includes the annular chamber 58 that contains nitrogen under pressure, with the annular chamber 58 including an inlet 74 through which nitrogen is supplied to the annular chamber 58 to maintain a gas pressure in the chamber, a sensor for detecting a flow of inert gas into the annular chamber which indicates that there is a puncture in the core tube, and an alarm that is responsive to the gas flow sensor to indicate a puncture in the core tube assembly 31, the present invention is not so limited and extends to any system for detecting a puncture in the core tube assembly 31.

(29) For example, the present invention extends to any system for detecting a change in pressure in the core tube assembly 31 or the annular chamber 58 that indicates a puncture in the core tube assembly 31. The pressure change may be an increase in pressure in the annular chamber 58 or a decrease in the pressure in the annular chamber 58.

(30) By way of example, whilst the embodiment of the solids injection lance is described in the context of the HIsmelt direct smelting process, it can readily be appreciated that the present invention is not so limited and extends to any molten bath-based smelting process.

(31) By way of example, whilst the embodiment of the solids injection lance is described in the context of smelting iron ore, it can readily be appreciated that the present invention is not limited to this material and extends to any suitable metalliferous material.

(32) 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.