WO2016131090A1

WO2016131090A1 - Solids injection lance and conveying system maintenance without slag drain

Info

Publication number: WO2016131090A1
Application number: PCT/AU2016/050078
Authority: WO
Inventors: Rodney James Dry; Jacques Pilote
Original assignee: Technological Resources Pty. Limited
Priority date: 2015-02-17
Filing date: 2016-02-10
Publication date: 2016-08-25
Also published as: CN107429305A

Abstract

A method of maintaining solids injection laces and solids supply lines is disclosed. In particular, the method involves of accessing a solids injection lance and a linked solids supply line for maintenance, where the solids injection lance extends into a metallurgical vessel. The vessel includes (i) the solids injection lance, (ii) a molten bath of metal and slag, such that an outlet end of the lance is submerged in the slag under quiescent conditions, (iii) a gas space above the molten bath pressurized to above atmospheric pressure and (iv) the supply line for conveying solid feed material in a carrier gas to an inlet end of the solids injection lance. The method includes (a) closing an outlet end of the solids injection lance so as to prevent molten slag entering the outlet end when the gas pressure in the supply line and the solids injection lance upstream of the outlet end is reduced to a pressure below the pressure in the vessel and (b) accessing the solids injection lance and/or the supply line for maintenance by removing a section of the supply line.

Description

SOLIDS INJECTION LANCE AND CONVEYING SYSTEM MAINTENANCE

WITHOUT SLAG DRAIN

TECHNICAL FIELD

The present invention relates to metallurgical vessels that have lances or tuyeres which inject pneumatically conveyed solids materials into the vessel. In particular, it relates to metallurgical vessels that have solids injection lances with wear-resistant liners. More particularly, the invention relates to a method for maintaining solids injection lances and the conveying system for solids materials.

The present invention has particular, although not exclusive, application to solids injection lances of a direct smelting vessel, such as a molten bath-based direct smelting vessel for producing molten metal, such as iron, in a direct smelting process.

BACKGROUND

A known molten bath-based smelting process is generally referred to as the "HIsmelt" process and is described in a considerable number of patents and patent applications in the name of the applicant.

The HIsmelt process is applicable to smelting metalliferous material generally but is associated particularly with producing molten iron from iron ore or another iron- containing material.

In the context of producing molten iron, the HIsmelt process includes the steps of:

(a) forming a bath of molten iron and slag in a main chamber of a direct smelting vessel;

(b) injecting into the molten bath: (i) iron ore, typically in the form of fines; and (ii) a solid carbonaceous material, typically coal, which acts as a reductant of the iron ore feed material and a source of energy; and

(c) smelting iron ore to iron in the bath. The term "smelting" is herein understood to mean thermal processing wherein chemical reactions that reduce metal oxides take place to produce molten metal.

In the HIsmelt process solid feed materials in the form of metalliferous material (which may be pre-heated) and carbonaceous material and optionally flux material are injected with a carrier gas into the molten bath through a number of water-cooled solids injection lances which are inclined to the vertical so as to extend downwardly and inwardly through the side wall of the main chamber of the smelting vessel and into a lower region of the vessel so as to deliver at least part of the solid feed materials into the metal layer in the bottom of the main chamber. The solid feed materials and the carrier gas penetrate the molten bath and cause molten metal and/or slag to be projected into a space above the surface of the bath and form a transition zone. A blast of oxygen-containing gas, typically oxygen-enriched air or pure oxygen, is injected into an upper region of the main chamber of the vessel through a downwardly extending lance to cause post-combustion of reaction gases released from the molten bath in the upper region of the vessel. In the transition zone there is a favourable mass of ascending and thereafter descending droplets or splashes or streams of molten metal and/or slag which provide an effective medium to transfer to the bath the thermal energy generated by post-combusting reaction gases above the bath.

Typically, in the case of producing molten iron, when oxygen-enriched air is used, the oxygen-enriched air is generated in hot blast stoves and fed at a temperature of the order of 1200°C into the upper region of the main chamber of the vessel. If technical -grade cold oxygen is used, the technical -grade cold oxygen is typically fed into the upper region of the main chamber at or close to ambient temperature.

Off-gases resulting from the post-combustion of reaction gases in the smelting vessel are taken away from the upper region of the smelting vessel through an off-gas duct.

The smelting vessel includes a main chamber for smelting metalliferous material and a forehearth connected to the main chamber via a forehearth connection that allows continuous metal product outflow from the vessel. The main chamber includes refractory-lined sections in a lower hearth and water-cooled panels in side walls and a roof of the main chamber. Water is circulated continuously through the panels in a continuous circuit. The forehearth operates as a molten metal-filled siphon seal, naturally "spilling" excess molten metal from the smelting vessel as it is produced. This allows the molten metal level in the main chamber of the smelting vessel to be known and controlled to within a small tolerance - this is essential for plant safety.

The applicant has found that the smelting process is aided by operating the vessel at a pressure above atmospheric pressure. As the smelting process relies on having a bath of molten material, the elevated pressure affects the level of the molten bath in the vessel and also affects the level of molten metal in the forehearth. Care must be taken when adjusting the pressure in the vessel, including when taking the vessel off- pressure for maintenance operations.

The metalliferous material and the carbonaceous material may be injected into the smelting vessel either through separate lances designated specifically for coal or iron ore injection or together through the same lances. As shown in Figure 1, the injection lances extend into the vessel so that their outlet ends extend below the surface of the molten bath. Examples of separate iron ore and coal injection lances are disclosed in US patent 7722800 (Williams). The iron ore is in the form of fines and is particularly abrasive. Therefore, the injection lances disclosed in Williams for injecting iron ore include a liner in the form of a central core tube of wear resistant material, such as hard ceramic material, for protecting a surrounding annular water-cooled jacket from the erosive effects of the iron ore injection.

Under normal operating conditions, the pneumatic injection of iron ore through the central core tube causes it to wear so that it needs to be replaced every 2 to 6 months or more frequently to coincide with other regular maintenance operations. In contrast, a typical smelting campaign is around 12 months.

The current process for replacing the central core tube involves draining slag from the smelting vessel to expose the outlet end of the injection lances and further involves depressurising the vessel. Supply pipes connecting a supply of iron ore to the injection lances is removed and the central core tube is removed and replaced while the injection lance remains in position in the vessel. However, the aggressive nature of slag in a direct smelting vessel causes damage to the refractory lining around the slag drain each time the slag is drained. The cumulative effect of frequent slag drains is refractory corrosion (as shown in Figure 2) to the extent that refractory repairs are required. The refractory maintenance results in further vessel down-time, i.e. loss of production. The same considerations apply to accessing the supply line immediately upstream of the solids injection lance for maintenance.

Generally speaking, there is a need to provide maintenance access to a solids injection lance and the supply line upstream of the lance in a manner that has a reduced impact on production.

It would be advantageous for the access be sufficient to enable the liner in the solids injection lance to be replaced with the same reduced impact.

The above description is not to be taken as an admission of the common general knowledge in Australia or elsewhere.

SUMMARY OF THE DISCLOSURE

In one aspect, the invention provides a method of accessing a solids injection lance and a linked solids supply line for maintenance, wherein the solids injection lance extends into a metallurgical vessel that includes (i) a molten bath of metal and slag, such that an outlet end of the lance is submerged in the slag under quiescent conditions,

(ii) a gas space above the molten bath pressurized to above atmospheric pressure and

(iii) a supply line conveying solid feed material in a carrier gas to an inlet end of the solids injection lance, the method including:

(a) closing an outlet end of the solids injection lance so as to prevent molten slag entering the outlet end when the gas pressure in the supply line and the solids injection lance upstream of the outlet end is reduced to a pressure below the pressure in the vessel; and

(b) accessing the solids injection lance and/or the supply line for

maintenance by removing a section of the supply line.

In preventing the flow of slag from within the vessel into the outlet end of the lance, this method avoids the need to drain slag from the vessel in order to carry out maintenance on the solids injection lance and the supply line at atmospheric pressure. It also, therefore, avoids any damage that would occur to the slag tap hole if the slag were drained. The result is that maintenance of the refractory surrounding the slag tap hole is less frequent and contributes to a longer smelting campaign. Additionally, although the smelting process is stopped during the maintenance, it can be restarted and ramped-up to full production rate in a significantly shorter time than when the molten bath is fully, or even partially, drained prior to maintenance work commencing.

The invention may further include causing a blockage in the outlet ends of the solids injection lance, whereby to prevent the flow of slag from the molten bath into the solids injection lance upstream of the blockage.

The term "outlet end" is a reference to a section of the solids injection lance that is at or beyond an end of a liner (as described above) within the solids injection lance. The term is taken to include frozen slag formations that extend from the actual end of the solids injection lances, such as a pipe extension (also known as an "elephant trunk"). In other words, it is anticipated that "closing the outlet end" includes forming a blockage or seal in the elephant trunk such that slag from the molten bath is prevented from entering the elephant trunk or the solids injection lance upstream of the blockage or seal.

The blockage may be caused by locating an object in the outlet end of the solids injection lance. For example, pumice stone may be located at the outlet end. As another example, sand may be located at the outlet end so as to cause slag to freeze at the outlet end and, therefore, form the blockage.

Alternatively, the blockage may be formed by controlling injection of feed materials and carrier gas through the solids injection lance so as to cause the blockage. For example, the flow of solids and carrier gas may be controlled to cause slag to freeze at the outlet end.

The method may include removing a liner from within the solids injection lance and replacing it with a new liner, under atmospheric pressure conditions, before opening the outlet end. The new liner may be closed at its outlet. The new liner may be closed by a pre-formed blockage that is cleared after the liner is installed.

The method may further include opening the outlet end by increasing the pressure upstream of the outlet end to a pressure greater than the gas pressure in the vessel and drilling through the blockage. The elevated pressure in the solids injection lance and the supply line will cause gas to flow through the supply line and lance and into the vessel. In this manner, the flow path through the lance and the outlet end is cleared and, at the same time, molten slag is prevented from entering the outlet end. The lance is then ready to recommence injection of solid materials.

This method allows the liner of the solids injection lance to be removed and replaced without having to drain slag or tap molten metal from the metallurgical vessel. More specifically, if the solids injection lance were not pressurised upstream of the outlet end to a pressure greater than the gas pressure in the vessel when the outlet is opened, molten material from the molten bath would enter the lance through its outlet end and freeze within the lance, thereby preventing subsequent supply of solid materials through the lance and also preventing subsequent removal and replacement of the liner. The current approach drains the slag and incurs refractory damage around the slag drain. The method described above avoids this problem altogether by maintaining pressurised conditions in the solids injection lance. This means that the slag does not need to be drained and, consequently, means that there is no damage to the refractory around the slag drain as a result of maintaining the solids injection lance.

The vessel may include a plurality of solids injection lances and whereby the method includes continuing the supply of solid materials to the metallurgical vessel through one or more of those lances at least for part the period that the liner is being replaced.

The gas pressure in the vessel may above atmospheric pressure for at least part of the period that the liner is being replaced.

The gas pressure in the vessel during steps (a) and (b) may be at a normal operating pressure for operating a direct smelting process to produce molten metal under normal production conditions.

The method may involve retaining a full inventory of molten metal and slag within the vessel during steps (a) and (b).

The term "full inventory" is a reference to the amount of molten metal and slag required to operate a direct smelting process to produce molten metal under normal production conditions. In this circumstance, the outlet end of the solids injection lances is submerged in the slag layer of the molten bath under quiescent conditions.

The step of removing a section of the supply line may include removing an elbow section and a downwardly extending section that is co-axial with a solids flow path through the solids injection lance. The method may further include isolating the elbow section and the downwardly extending section via a valve upstream of the elbow section.

The method may include reconnecting the elbow section and the downwardly extending section to link an upstream portion of the solids supply line to the solids injection lances, re-pressurising the elbow section, the downwardly extending section and the solids injection lance and opening the outlet end, whereby to re-establish a flow of gas through the supply line, out of the outlet end and into the molten bath.

The direct smelting process may be a HIsmelt process.

The solids supply line may supply metalliferous material to the inlet end of the lance.

The metalliferous material may be iron ore.

The method may include opening the outlet end by advancing a tool through the downwardly extending section and through the solids injection lance to the outlet end and operating the tool to open the outlet end when the downwardly extending section and the solids injection lance are at an elevated pressure relative to the gas pressure in the direct smelting vessel.

The method may further include retracting the tool from the solids injection lance and the downwardly extending section before recommencing supply of solid materials to the direct smelting vessel via the solids injection lance.

The tool may be a drill and opening the outlet end may include drilling through the blockage.

The metallurgical vessel may be a direct smelting vessel into which, under normal operating conditions, solid metalliferous material and carbonaceous material are injected by one or more solids injection lances for smelting in the molten bath to produce molten metal.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the invention is described, by way of example only, below with reference to the accompanying drawings, of which: Figure 1 is a vertical cross-section through a direct smelting vessel that forms part of an embodiment of a direct smelting plant in accordance with the present invention;

Figure 2 is a schematic view that illustrates a metalliferous material and carbonaceous material injection system that supplies entrained solids material to a solids injection lance of a direct smelting vessel;

Figure 3 is a partial cross-section through a side wall of a direct smelting vessel, solids injection lance, lance removal equipment and part of a supply line delivering metalliferous material to an inlet end of the solids injection lance;

Figure 4 is a partial cross-section of the lance and direct smelting vessel in Figure 3;

Figure 5 is the partial cross-section of Figure 3, but showing part of a hot ore conveying line being removed via the lance removal equipment;

Figure 6 is the partial cross-section of Figure 5, but showing removal of an acceleration spool via the lance removal equipment;

Figures 7 and 8 are the partial cross-section of Figure 6, but showing the solids injection lance liner being removed via the lance removal equipment;

Figure 9 is a partial cross-section view of a direct smelting vessel, solids injection lance, hot ore conveying line and an embodiment of an apparatus for removing blockages in the hot ore conveying line and the solids injection lance; and

Figure 10 is a cross-sectional view of a ball valve and drill housing shown in Figure 4 along a longitudinal axis of the drill housing;

Figures 11 A and 1 IB are side plan views of a drill head and an extension bar; and

Figure 12 is side plan view of the apparatus for removing blockages shown in Figure 9, with the drill housing partially cut-away showing a drill head inside the drill housing. DESCRIPTION OF EMBODIMENT

Figure 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 following description is in the context of smelting iron ore fines to produce molten iron in accordance with the HIsmelt process.

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.

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.

In use of the vessel 11 to smelt iron ore fines to produce molten iron in accordance with the HIsmelt process, the vessel 1 1 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.

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. Two solids injection lances 27 are shown in Figure 1. However, it can be appreciated that the vessel 11 may have any suitable number of such lances 27. In use, heated iron ore fines and ambient temperature coal (and fluxes, typically lime) are entrained in a suitable carrier gas (such as an oxygen-deficient carrier gas, typically nitrogen) and are separately supplied to the lances 27 and co- injected through outlet ends 28 of the lances 27 into the molten bath and preferably into metal layer 22. The following description is in the context that the carrier gas for the iron ore fines and coal is nitrogen.

The outlet ends 28 of the solids injection lances 27 are above the surface of the metal layer 22 during operation of the process and are submerged in the slag layer 23. 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.

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).

Figure 2 shows schematically one embodiment of a direct smelting plant in accordance with the invention insofar as the plant is concerned with supplying heated iron ore fines and ambient temperature coal to one solids injection lance 27.

The plant includes the direct smelting vessel 11 shown in Figure 1.

The plant also includes a pre-treatment unit 34 in the form of a pre-heater for heating iron ore fines, typically to a temperature of at least 600°C. The pre-heater may be any suitable type of pre-heater.

The plant also includes an ore delivery system for supplying iron ore fines to the lances 27.

The ore delivery system includes (a) an ore storage/dispensing unit 32 for storing and dispensing heated iron ore fines and (b) an ore supply line 36 for supplying heated ore from the ore storage/dispensing unit 32 to the lances 27.

The ore storage/dispensing unit 32 is constructed to store and dispense heated iron ore fines entrained in nitrogen carrier gas. The ore storage/dispensing unit 32 can be in the form of a plurality of bins that allow 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 storage/dispensing unit 32 can be considered as a single unit.

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 fines are at a temperature of at least 500°C and typically 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 storage/dispensing unit 32.

The ore supply line 36 for transporting heated iron ore fines from the storage/dispensing unit 32 to the lance 27 includes (a) a first section 48 that carries the fines to a location proximate the vessel 11, (b) an upwardly extending section 42 which conveys the fines from a position that is approximately level with the base 12 of the vessel 11 to at least the height of the lance 27, and (c) a downwardly extending section 46 which connects the line to an ore inlet in the lance 27. The section 46 is formed to be co-axial with the lance 27 when in an operating position as shown in Figure 2.

The plant also includes a separate coal delivery system for supplying coal to the lance 27.

The coal delivery system is in the same form as the ore delivery system described above with the exception that the coal is not pre-heated before supply to lance 27. Additionally, the coal delivery system typically supplies coal and flux material, such as lime.

The coal is delivered from a stockpile to a coal storage/dispensing unit 38 which stores the coal under ambient temperature. Flux 50 is supplied separately to the coal storage/dispensing unit 38. A supply line 40 connects the coal storage/dispensing unit 38 to the ore supply line 36. In the case of the ore being pre-heated, the supply line 40 delivers the coal and flux into the section 46. For simplicity, however, the supply line is shown in Figure 2 as delivering coal and flux into the first section 48 of the ore supply line 36.

In use, coal and flux at ambient temperature are discharged from the coal storage/dispensing unit 38 entrained in nitrogen carrier gas and transferred via the coal supply line 40 into the first section 48 of the ore supply line 36 so that the ore and the coal are carried together into the lance 27.

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

The solids injection lance 27 is shown in more detail in Figure 3. Specifically, the solids injection lance 27 extends through the side wall 14 of the vessel 11 and into the slag layer 23. The solids injection lance 27 includes a liner 30 (shown in dashed lines) surrounded by a cooling jacket 31 throughout its length. The cooling jacket 31 is water cooled and thus forms a layer of frozen slag 32 which acts to insulate the solids injection lance from the high temperature of the molten bath. The frozen slag additionally forms a slag pipe 29 (also known as an "elephant trunk") at the outlet end 28 of the solids injection lance 27 as a result of the comparatively low temperature of the injected metalliferous material with respect to the temperature of the liquid slag 23.

An inlet end 33 of the solids injection lance 27 accommodates an inlet and an outlet for cooling water (not shown) and mounting flanges 132 for coupling to the downwardly extending section 46. Elbow 44 redirects the feed of metalliferous material from the upwardly extending section 42 downwardly and inwardly into the downwardly extending section 46. However, expansion joints 63 connect the elbow 44 to both of the upwardly extending section 42 and the downwardly extending section 46 in order to accommodate thermal expansion of each.

The elbow 44 includes an extension 49 that is coaxial with the downwardly extending section 46.

Lance removal equipment 120 is located above the inlet end 33, the downwardly extending section 46 and the elbow 44. The lance removal equipment 120 includes a support frame 122 and a support rail 124 suspended from the support frame 122. In the event that the lance 27 needs to be removed or in the event that the downwardly extending section 46 and the elbow 44 need to be removed, they are connected to the rail 124 for support while being drawn upwardly and outwardly in the direction of the rail 124 away from the side wall 14. In this manner, the removal of components is assisted by an overhead crane (not shown) rather than equipment on a platform through which the upwardly extending section 42 extends. This reduces the extent to which the platform becomes crowded by equipment and plant components whilst the removal operation occurs.

During normal production, slag is periodically tapped through slag tap hole 21. However, the replacement of the liner 30 in the past has involved completely draining the slag from the vessel 1 1 via a slag drain 20 located at the level of the interface between the slag layer 23 and the metal layer 22. After draining slag, the outlet end 28 of the solids injection lance 27 is spaced from the molten metal 22 remaining in the vessel 11. The process further involves depressurising the vessel to allow the liner removal operation to occur at ambient pressure outside the vessel and inside the vessel. In which case, the elbow 44 and the downwardly extending section 46 are removed and the liner 30 is removed from the solids injection lance 27 and replaced before reinstalling the downwardly extending section 46 and the elbow 44.

This process causes problems, as described above, in terms of vessel down-time and lost productivity, together with the problem of carefully managing the level of molten metal that remains in the vessel 11. Additionally, the high-FeO content in the slag causes corrosion of the refractory in the region of the slag drain channel, as shown in Figure 4. This is more problematic than the lost down-time and controlling the level of molten metal because it can only be rectified by completely draining the vessel 11 of slag and molten metal and replacing the refractory. The applicant has, therefore, arrived at the method of carrying out maintenance work on the solids injection lance 27, the elbow 44 and the downwardly extending section 46 (including replacing a liner 30 in a solids injection lance 27) whilst a full inventory of slag and molten metal required for normal production is retained in the vessel 11.

In broad terms, the method includes (a) closing the outlet end of the lance 27 and (b) accessing the solids inject lance 27 and the supply line for maintenance by removing the elbow 44 and the downwardly extending section 46. Although the maintenance work could be carried out at an elevated pressure typical of the elevated pressure required to inject feed materials into the vessel 11, the maintenance work can be carried out at atmospheric pressure. This greatly simplifies maintenance work because equipment (such as a lance liner) does not need to be shifted through pressure seals. It is understood, however, that closing and opening the outlet end 28 will need to be done under elevated pressure conditions to ensure that molten slag does not enter the outlet end 28 of the lance 27, but the other maintenance work can be carried out at atmospheric pressure.

The sections 42 and 46 of the ore supply line 36 have the same internal diameter for conveying entrained solid materials to the solids injection lance 27. An upper end of the elbow 44 extends upwardly and outwardly beyond the line of the section 42 to a lance purge system 54 that is operable to remove solids and gas from within the sections 42 and 46. The lance purge system 54 includes a take-of line 56 extending initially perpendicularly from the upper end of section 46 and further includes a venting valve 58 that controls the flow of gas and solids through the take-of line 56. The uppermost end of the extension 49 terminates at a flange 59 (Figure 9, 10 and 12) to which the lance drilling assembly 60 can be mounted.

The lance drilling assembly 60 includes a ball valve 62 with flanges 64 disposed at each end. One flange 64 is connected to the flange 59 of the first section 46 and the other flange 64 is connected to an end flange 78 of a drill housing 76. As shown in Figure 12, a drill bar 90 is contained within the drill housing 76. A body 94 of the drill bar 90 is contained in a sleeve section 79 of the drill housing 76. A gland bar 84 has a series of handles and an external thread that co-operates with an internal thread of the sleeve section 79. Rotation of the gland bar 84 relative to sleeve section 79 advances the gland bar 84 within the sleeve 79 and compacts a graphite gland 80 which causes it to form a gas-type seal around the internal wall of the sleeve section 79 and around the external wall of the body 94 of the drill bar 90. A locking bar 82 is provided with an internal thread that co-operates with the external thread of the gland bar 84. When a gas-tight seal is formed by the gland bar 84 compressing the graphite gland 80, the locking bar 82 is advanced along the thread on the gland bar 84 until it is tightened fast against the sleeve section 79. This stops the gland bar 82 from becoming loose during drilling. When the lance drilling assembly 60 is not in operation, the ball valve 62 is closed to isolate the lance drilling assembly 60 from the ore supply line 36.

Extending from the drill housing 76 is a support frame assembly 66 which comprises a zig-zag shaped mounting arm 68, a drill support rail 70 extending parallel to the drill housing 76 and a brace 72 extending between the mounting arm 68 and the drill support rail 70. A car 74 is mounted to the drill support rail 70 to travel freely along the rail 70. A drill 77 is mounted to the car 74 and has a drill head 75 having an axis of rotation that is coaxial with the section 46 and the solids injection lance 27.

The outlet end 28 is closed by locating a shaped pumice stone on the end of an arm and placing the end of the arm and the pumice stone in the drill housing 76, in place of the drill bar 90. A gas-tight seal is formed with by the gland bar 84 and the locking bar 82. The supply of feed material through the supply line 48, 42 and 46 is discontinued, but the supply of carrier gas is continued so that the flow of gas through the lance 27 and through the outlet end 28 prevents slag from entering the outlet end 28 of the lance 27.

The ball valve 62 is then opened and the arm is advanced through the downwardly extending section 46 and through the lance 27 to the outlet end 28. The pumice stone is shaped to have an outer diameter slightly less than the inner diameter of the downwardly extending section 46 and the lance 27 so that the pumice stone is able to pass through them. The inner diameter of the slag pipe 29 is less than the outer diameter of the pumice stone so that become lodged in the slag pipe 29 at or adjacent the end of the lance 27. The molten slag will flow into the slag pipe 29 on account of the reduced gas pressure cause by the pumice stone obstructing the flow path through the slag pipe 29. The slag freezes in the slag pipe 29 and, therefore, closes the outlet end

28 of the lance 27. Water-cooling of the lance 27 continues to ensure that the slag pipe

29 remains in place.

Once closed (as indicated by an increased back pressure in the supply line 48, 42 and 46), isolation valve 52 is actuated to isolate the elbow 44, downwardly extending section 46 and the lance 27 from the supply line 48. The pressure in those sections can then be reduced to atmospheric pressure via the take-off line 56 and the venting valve 58. When atmospheric pressure is reached, the gas-tight seal about the arm at the drill housing 76 is removed and the arm is removed from the downwardly extending section 46 and the lance 27. The drill assembly 60 is removed and the elbow 44 and the downwardly extending section 46 are removed via the lance removal equipment 60. Access to the solids injection lance is then available for removing the worn liner 30 and for replacing it with a new liner, all under atmospheric conditions.

The new liner is closed at its outlet end by way of a pre-formed blockage, typically in the form of a pumice stone. The pre-formed blockage will reinforce the initial blockage in the outlet end 28 of the lance. In the event, the initial blockage leaks or is disrupted by the installation of the new liner, the pre-formed blockage will prevent the ingress of slag until the lance 27 is re-pressurised. The pre-formed blockage may be formed of materials other than pumice stone, provided that a blockage formed of such materials can be removed from the liner, for example by drilling as described below, to open the outlet end 28.

The lance 27 is returned to an operative state by reconnecting the downwardly extending section 46 to the lance 27 and reconnecting the elbow 44 to the downwardly extending section 46 and the upwardly extending section 42. Once gas-tight seals are formed between these components and before isolation valve 52 is opened, the drill assembly 60 is reconnected to the ball valve 62 and the drill bar 90 is advanced through the downwardly extending section 46 and the lance 27 to the pumice stone. A gas-tight seal is then formed about an extension bar residing in the drill housing 76 and to which is connected the drill bar 90. The isolation valve 52 is opened so that carrier gas pressurises the elbow 44, the downwardly extending section 46 and the lance 27 to a pressure that is greater than the gas pressure in the vessel 11.

The drill bar 90 includes a hollow cylindrical head 92 extending forwardly of a body 94 and has teeth extending from the head 92 for cutting into the pumice stone and frozen slag in the lance 27 and the slag pipe 29.

The body 94 includes a connection recess 96 in the end of the drill bar 90 opposite to the head 92. The connection recess 96 has a profile corresponding to the profile of a connection lug 104 on an extension bar 102 (Figure 1 IB). Both the drill bar 90 and the extension bar 102 include a connection hole 98 adjacent the respective connection recess 96 and connection lug 104. A link pin (not shown) is used to link adjacent extension bars 102 and to link an extension bar 102 to the body 94.

Specifically, the link passes through the connection hole 98 on each adjacent extension bar 102 or body 94.

The retaining holes 100 accommodate the retaining pin 88 so that extension bars 102 and the drill bar 90 can be locked relative to the housing 76 while further extension bars 102 are added or removed as the drill bar 90 is advance or retracted. Specifically, in the course of retracting the drill bar 90, the gas pressure in the section 46 will tend to force the drill bar 90 and extensions 102 out of the section 46. Accordingly, each extension bar 102 is locked by the retaining pin 88 with the gland bar 84 while the drill 77 is connected to the extension bar 102. When that connection is made, the retaining pin 88 is removed and the drill 77 and car 74 controls the extraction of the extension bar 102. The next consecutive extension bar 102 coming through the housing 76 will then be locked by the retaining pin 88 to the gland bar 84 while the drill 77 is further retracted and the exposed extension bar 102 is decoupled from the locked extension bar 102. The process is repeated until all extension bars are removed and the drill bar 90 is retained in the housing 76.

The drill bar 90 is advanced to be pumice stone by connecting an extension bar 102 to the rear end of the drill bar 90 by fitting the connection lug 104 into the connection recess 96 on the drill bar 90. The retaining pin 88 is removed from the drill bar 90 and placed in the connection hole 98 in the extension bar 102. The extension bar 102 is then advanced into the drill housing 76 up to the point where the retaining pin 88 abuts the gland bar 84. The process of connecting further extension bars 102 and an advancing them into the drill housing 76 has the effect of advancing previous extension bars 102 and the drill bar 90 along the section 46 until the drill bar 90 reaches the pumice stone. At this point the gland bar 84 is rotated so that it advances within the sleeve section 79 to compact the graphite gland 80 and to form a gas-tight seal in the drill housing 76 about the extension bar 102. The locking bar 82 is then advanced to lock the gland bar 84 in position. The drill 77 is then advanced along the drill support rail 70 so that the drill head 75 engages a connection recess 76 on an extension bar 102 extending outwardly from the drill housing 76.

The pressure in the sections 42 and 46 and the solids injection lance 27 is equivalent to the gas pressure inside the direct smelting vessel plus at least an additional lOkPa such that when the drill head 92 breaks through the blockage, the gas pressure upstream of the blockage is greater than the gas pressure within the direct smelting vessel plus the hydrostatic pressure of the slag 23 at the outlet end 28 of the lance 27 so that the purge gas flows through the section 46 and the solids injection lance 27 and into the direct smelting vessel. Slag is, therefore, prevented from flowing back into the solids injection lance 27 once the blockage is removed and during the time to retract while the drill bar 90 and extension bars 102 from the solids injection lance 27 and the section 46. The drill 77 is retracted along the drill support rail 70 so that extension bars can be retracted from the section 46 and sequentially removed until the drill bar 90 is contained within the drill housing 76. The retaining pin 88 is placed in the retaining hole 100 in the drill bar 90 to retain the drill bar 90 in the drill housing 76. The ball valve 62 is then closed to isolate the lance drilling assembly 60 from the section 46. At this stage, the gas pressure in the housing 76 is still at the elevated carrier-gas pressure. Accordingly, the sleeve section 79 includes a bleed valve 81 for venting pressurised gas from the housing 76 in a controlled manner.

Pumice stone is suitable for closing the outlet end 28 because it is stable at the high temperatures. The drilling process will break down the pumice stone and its relatively light weight will result in it being held in the slag until removed from the vessel 11 by a slag tap.

It will be appreciated, however, that the closure may be formed by other materials that are suitable. One option is a sand plug formed by a mixture of sand and an adhesive or resin, such as that used in forming sand moulds for casting molten metal.

Additionally, the rate of solids and carrier gas injection may be controlled to cause molten slag to enter the slag pipe 29 and freeze, thereby closing the outlet end 28. This includes reducing the flow of carrier gas to allow slag to freeze at the outlet end 28.

Another option includes supplying water in the conveying gas into the lance 27 to enhance freezing of slag at the outlet end 28. The water will turn into steam and enhance the freezing of the slag. Optionally, a solid plugging device can be inserted to secure the initial slag blockage.

Whilst a number of specific apparatus and method embodiments have been described, it should be appreciated that the apparatus and method may be embodied in many other forms.

For example, the method of closing the outlet end 28 of the lance 27 may be used when maintenance is required on the supply line downstream of the isolation valve 52, i.e. on the elbow 44 and the downwardly extending section 46. While maintenance may be carried out on the lance 27 at the same time (such as to replace a worn liner), this is not a pre-requisite for carrying our maintenance on the elbow 44 and the downwardly extending section 46. In the claims which follow, and in the preceding description, except where the context requires otherwise due to express language or necessary implication, the word "comprise" and variations such as "comprises" or "comprising" are 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 apparatus and method as disclosed herein.

Claims

1. A method of accessing a solids injection lance and a linked solids supply line for maintenance, wherein the solids injection lance extends into a metallurgical vessel that includes (i) a molten bath of metal and slag, such that an outlet end of the lance is submerged in the slag under quiescent conditions, (ii) a gas space above the molten bath pressurized to above atmospheric pressure and (iii) a supply line conveying solid feed material in a carrier gas to an inlet end of the solids injection lance, the method including:

(b) accessing the solids injection lance and/or the supply line for

maintenance by removing a section of the supply line.

2. The method defined in claim 1, wherein the method further includes opening the outlet end and recommencing supply of solid feed material in a carrier gas to the inlet end of the solids injection lance after maintenance work is completed.

3. The method defined in claim 2, wherein opening the outlet end includes increasing the pressure upstream of the outlet end to a pressure greater than the gas pressure in the vessel.

4. The method defined in any one of claims 1 to 3, wherein closing the outlet end includes causing a blockage in the outlet ends of the solids injection lance, whereby to prevent the flow of slag from the molten bath into the solids injection lance upstream of the blockage.

5. The method defined in claim 4, wherein opening the outlet end includes advancing a tool through the downwardly extending section and through the solids injection lance to the outlet end and operating the tool to open the outlet end when the downwardly extending section and the solids injection lance are at an elevated pressure relative to the gas pressure in the direct smelting vessel.

6. The method defined in claim 5, wherein the method further includes retracting the tool from the solids injection lance and the downwardly extending section before recommencing supply of solid materials to the direct smelting vessel via the solids injection lance.

7. The method defined in claim 5 or claim 6, wherein the tool is a drill and opening the outlet end includes drilling through the blockage.

8. The method defined in claim 4, wherein the blockage is caused by locating an object at the outlet end of the solids injection lance.

9. The method defined in claim 8, wherein the object is a shaped pumice stone.

10. The method defined in claim 4, wherein the blockage is formed by controlling injection of feed materials and carrier gas through the solids injection lance so as to cause the blockage.

11. The method defined in claim 4, wherein the method includes controlling water- cooling of the solids injection lance to assist with formation of a frozen slag blockage.

12. The method defined in any one of the preceding claims, wherein the method includes removing a liner from within the solids injection lance and replacing it with a new liner, under atmospheric pressure conditions.

13. The method defined in claim 12, wherein the new liner is closed at its outlet by a pre-formed blockage that is removed after the new liner is installed.

14. The method defined in any one of the preceding claims, wherein the vessel may include a plurality of solids injection lances and whereby the method includes continuing the supply of solid materials to the metallurgical vessel through one or more of those lances at least part for the period that the liner is being replaced.

15. The method defined in any one of the preceding claims, wherein the gas pressure in the vessel is above atmospheric pressure for at least part of the period that the maintenance work is being carried out.

16. The method defined in any one of the preceding claims, wherein the method involves retaining a full inventory of molten metal and slag within the vessel during steps (a) and (b).

17. The method defined in any one of the preceding claims, wherein the step of removing a section of the supply line includes removing an elbow section and a downwardly extending section that is co-axial with a solids flow path through the solids injection lance.

18. The method defined in any one of the preceding claims, wherein the method further includes isolating the elbow section and the downwardly extending section via a valve upstream of the elbow section.

19. The method defined in claim 18, wherein the method includes reconnecting the elbow section and the downwardly extending section to link an upstream portion of the solids supply line to the solids injection lances, re-pressurising the elbow section, the downwardly extending section and the solids injection lance and opening the outlet end, whereby to re-establish a flow of gas through the supply line, out of the outlet end and into the molten bath.

20. The method defined in any one of the preceding claims, wherein the gas pressure in the vessel during steps (a) and (b) is at a normal operating pressure for operating a direct smelting process to produce molten metal under normal production conditions.

21. The method defined in claim 20, wherein the direct smelting process is a HIsmelt process.

22. The method defined in any one of the preceding claims, wherein the solids supply line supplies metalliferous material to the inlet end of the lance.

23. The method defined in claim 22, wherein the metalliferous material may be iron ore.