HK1062459A

HK1062459A - A gas injection lance

Info

Publication number: HK1062459A
Application number: HK04104675.0A
Authority: HK
Inventors: Joseph Dunne Martin; John Hardie Gregory
Original assignee: Technological Resources Pty Ltd
Priority date: 2001-07-10
Filing date: 2002-07-08
Publication date: 2004-11-05

Description

Gas injection gun

Technical Field

The present invention provides a lance for injecting a preheated gas into a vessel.

The invention is particularly, but not exclusively, applicable to lances for injecting a preheated gas stream into a vessel at elevated temperatures.

Metallurgical vessels may for example be direct smelting vessels in which molten metal can be produced by a direct smelting process.

The invention also provides a direct smelting device which comprises a gun for injecting the preheated gas into the direct smelting container.

Background

Generally, the processes described in the prior art for direct melting of iron-bearing materials into molten iron and based on a molten bath (molten bath-based) require post-combustion (post-combustion) of reaction products, such as CO and H2, released from the molten bath in order to generate sufficient heat to maintain the temperature of the molten bath.

The prior art generally suggests that post-combustion be achieved by injecting oxygen-containing gas through lances that extend into the headspace of the direct smelting vessel.

For economic reasons, it is desirable that the direct smelting period be relatively long, typically at least one year, and it is therefore important that the gas injection lances be able to withstand the high temperature environment, typically around 2000 ℃, in the head space of the direct smelting vessel for a long period of time.

One option for providing the oxygen containing gas is to use air or oxygen enriched air that is preheated to above 800 ℃.

For preheated air or oxygen enriched air, a furnace or pebble heater is currently the only viable option. One result of using a furnace or pebble heater is: the air or oxygen enriched air entrains hard particulate material as it passes through the furnace and the pebble heater and this material causes considerable wear on the internal surfaces of the lance.

The use of air or oxygen-enriched air also means that a greater quantity of gas is required to achieve a given post-combustion level than would otherwise be required if oxygen was used as the oxygen-containing gas. Therefore, the structure of the direct smelting vessel working with air or oxygen-enriched air is necessarily much larger than that of the direct smelting vessel working with oxygen.

Thus, the lance used to inject the air or oxygen-enriched air into the direct smelting vessel must be of a relatively large construction which can extend a substantial distance into the direct smelting vessel and at least a substantial part of the length of the lance is unsupported. From the context it is clear that a 6 metre diameter HI smelting vessel proposed by the applicant comprises a lance having an outer diameter of 1.2 metres, weighing about 60 tonnes and projecting into the vessel for about 10 metres.

In addition, such lances must be capable of delivering a large volumetric flow of preheated air or oxygen-enriched air and be able to resist wear on the interior of the lance over extended periods of smelting due to the presence of aggressive particles in the air or oxygen-enriched air.

Carbon steel is an ideal material for constructing a lance for injecting preheated air or oxygen-enriched air for economic and structural reasons.

However, carbon steel is not an ideal material in terms of resistance to internal wear of the gun, especially considering the risk of rapid oxidation of the steel under hot injection conditions.

It will be apparent from the foregoing that the use of preheated air or oxygen-enriched air presents significant problems for the construction of lances for injecting air or oxygen-enriched air into a direct smelting vessel over a prolonged smelting period.

Disclosure of Invention

The object of the present invention is to provide a water cooled lance which can be constructed using carbon steel as the main structural component of the lance and which is capable of injecting preheated air or oxygen-enriched air into the direct smelting vessel over a long period of operation.

According to the present invention there is provided a lance for injecting a preheated oxygen-containing gas into a vessel having a pool of molten material, the lance comprising:

(a) an elongated gas flow duct extending from a rear end of the duct to a duct front end for discharging gas in the duct, the duct comprising: (i) inner and outer concentric carbon steel tubes which provide the primary structural support for the duct, (ii) cooling water supply and return passage means extending through the duct wall from the rear end of the duct to the front end of the duct for supplying and returning cooling water to the front end of the duct, (iii) an outer surface comprising mechanical means adapted to retain the frozen slag on the duct;

(b) a gas inlet for introducing hot gas into the rear end of the duct;

(c) a terminal device connected to the coaxial pipe at the front end of the pipe;

(d) a protective lining formed of a refractory material or other material capable of protecting the conduit from exposure to gas flows through the conduit at 800 ℃ @and1400 ℃, said lining being of a non-metallic material having thermal insulating properties compared to said steel conduit;

(e) means disposed in the duct for imparting a swirl to the air flow passing through the forward end of the duct.

Preferably, the conduit comprises three or more coaxial steel tubes extending to the forward end of the conduit.

The gas inlet preferably comprises a refractory body defining a first tubular gas passage aligned with and extending directly to the rear end of the duct and a second tubular gas passage transverse to the first passage for receiving hot gas and directing it into the first passage so that the hot gas and any particles contained therein impinge on the refractory wall of the first passage and the gas flow changes direction as it flows from the second passage to the first passage.

Preferably, the mechanical means on the outer surface of the pipe comprise projections shaped to engage the condensed slag and retain the slag on the pipe.

Preferably, the projections are abutment platforms each having a slot or dovetail profile so that the abutment platforms are in an outwardly flared configuration and are capable of acting as a slag-setting keying formation.

Preferably, the end device is a hollow ring structure and is made of a copper-containing material.

Preferably, the front end of the pipe is formed in a hollow ring-shaped end structure and the pipe includes pipe end cooling water supply and return passages for supplying cooling water to the end device forward along the pipe and returning the cooling water backward along the pipe.

Preferably, the lance includes an elongate body centrally disposed within the forward end of the duct so that gas flowing through the forward end of the duct flows along the elongate central body throughout the central body.

Preferably, the front end of the elongate body and the end fitting act together and form an annular nozzle for the gas to flow out of the conduit by means of the vortex imparted by the vortex fitting.

Preferably, the swirling means comprises a plurality of guide vanes connected to the elongate body to impart swirl to the air flow passing through the forward end of the duct.

In one embodiment of the invention, the elongate body is an elongate central tubular member extending within the airflow duct, extending from a rear end of the airflow duct to a front end thereof, and the vanes are arranged around the central tubular member adjacent the front end of the duct to impart swirl to the airflow flowing towards the front end of the duct.

Preferably, the central tubular member includes a water-cooled channel for forward flow of cooling water to the forward end thereof.

More preferably, the central tubular member includes cooling water passages for passing cooling water forwardly through the central member from its rear end to its front end, and internally cooling the front end and then returning through the central member to its rear end.

Preferably, the central tubular member defines a central water flow passage for water to flow forwardly through the member directly to the front end of the central member, and an annular water flow passage is provided around the central passage for returning water from the front end of the central member back to the rear end of the member.

The central annular member may comprise a central tube providing a central water flow passage and further tubes arranged around the central tube so as to define the annular water flow passage between the tubes.

Preferably, the central tubular member includes an insulating outer layer to inhibit heat transfer from the gas in the gas flow conduit into the cooling water passage in the central member.

The insulation layer comprises a number of tubular sections of insulating material arranged end to end so that the insulation layer forms a substantially continuous tube extending from the rear end to the front end of the central member around an annular air gap arranged directly in the insulation layer.

The void may be formed between the annular insulating layer and another tube defining an annular return water flow passage.

Preferably, the tubular sections of the insulation pack are supported to accommodate longitudinal expansion of each tubular section independently of the other tubular sections.

The forward end of the central tubular member may include a hemispherical nose portion with a single helical cooling water passage disposed within the nose portion to receive water from the central water flow passage in the central tubular member at the distal end of the nose portion and direct the water in a single stream around and rearwardly along the nose to cool the nose with a single continuous stream of cooling water.

The central tubular member extends centrally through the first gas flow passage of the gas inlet arrangement and rearwardly beyond the gas inlet. Thus, the rear end of the central tubular member may be disposed rearwardly of the gas inlet and provided with a water connection for the flow of cooling water to and from the central member.

In another embodiment of the invention, which is not the only further embodiment of the invention, guide vanes are provided between the elongate central body and the duct to impart swirl to the airflow passing through the forward end of the duct.

In the case of this embodiment, the gun preferably includes:

(a) internal cooling water passage means within the end fitting communicating with the cooling water supply and return passage means of the duct for receiving and returning a flow of cooling water to internally cool the end of the duct; and

(b) cooling water flow passages within the vanes and the elongate central body which communicate with cooling water supply and return passage means in the forward end of the duct for water to flow inwardly through the vanes from the supply passage means into the cooling passages of the elongate central body and outwardly through the vanes from these passages to the return passage means of the duct.

Preferably the cooling water supply and return passage means of the conduit comprises first supply and return passages communicating with the internal cooling water passage in the tip means and second supply and return passages communicating with the water flow passage in the blade and elongate central body.

The end of the conduit is formed as a hollow annular structure with a hollow structure defining an annular passage constituting the internal cooling water passage means of the end means.

The coaxial carbon steel tubes of the conduit may define a series of annular spaces for providing cooling water supply and return passage means.

The elongated central body may be generally cylindrical in configuration with hemispherical ends.

The shape of the blade preferably adopts a multi-head spiral structure. The vanes may be connected to the pipe at a plurality of locations spaced circumferentially around the pipe. In particular, four vanes may be provided, arranged in a four-start helical configuration and connected to the pipe at four positions spaced at 90 ° around the pipe at the leading ends of the vanes.

The cooling water supply and return channel means of the duct may then comprise a suitable number of separate water flow channels, each capable of supplying cooling water to one of the blades. These separate water flow passages are formed by means of partitions in said appropriate annular passages between the pipes extending helically along the pipe.

The front ends of the coaxial carbon steel tubes may be connected at their front ends to a tip device. The rear ends of the tubes may be mounted to allow relative longitudinal movement therebetween to accommodate varying degrees of thermal expansion and contraction of the tubes.

It is possible to connect the blades to the duct and to the central body only at their front ends, so as to be able to move freely along the duct from these connections under the effect of thermal expansion.

The present invention also provides an apparatus for producing ferrous metal from a ferrous process feed material by a direct smelting process, the apparatus including a vessel containing a bath containing molten metal and molten slag and a gas continuous space above the bath, the vessel including:

(a) a hearth formed of refractory material and having a bottom and sides;

(b) a sidewall extending upwardly from a hearth side, the sidewall comprising a water cooled wall panel;

(c) means for supplying iron-containing process feed material and carbonaceous material into the vessel;

(d) means for generating a gas flow in the molten bath, conveying molten material upwardly above a nominal quiescent surface of the molten bath and forming a raised pool;

(e) at least one gas injection lance as described in any one of the preceding paragraphs extending downwardly into the vessel so as to inject an oxygen-containing gas at a temperature of from 800 ℃ to 1400 ℃ into the vessel at an angle of from 20 ° to 90 ° relative to the horizontal axis at a velocity of from 200 m/s to 600m/s, said lance being arranged:

(i) the gun extends into the container for a distance which is at least the outer diameter of the front end of the gun; and

(ii) the distance of the front end of the gun above the static surface of the molten pool is at least 3 times of the outer diameter of the front end of the gun;

(f) apparatus for discharging molten metal and slag from a vessel.

Preferably, the ferrous working feed material and carbonaceous material supply means and the gas flow generating means comprise a plurality of lances/tuyeres for injecting the ferrous working feed material and carbonaceous material into the molten bath using a carrier gas and generating the gas flow.

Drawings

The invention is explained in more detail with reference to the following figures:

FIG. 1 is a vertical cross-sectional view through a direct smelting vessel including a pair of solids injection lances and a hot air blast lance constructed in accordance with the present invention;

FIG. 2 is a longitudinal cross-sectional view through one embodiment of a hot air injection gun;

FIG. 3 is an enlarged longitudinal cross-sectional view through the front of the central structure of the gun;

FIG. 4 further illustrates the front end of the central structure;

FIGS. 5 and 6 illustrate the configuration of the front nose end of the central structure;

FIG. 7 is a longitudinal cross-sectional view through the central structure;

FIG. 8 is a detail view of area 8 of FIG. 7;

FIG. 9 is a cross-section taken on line 9-9 of FIG. 8;

FIG. 10 is a cross-section taken on line 10-10 of FIG. 8;

FIG. 11 is a longitudinal cross-sectional view through another embodiment of the hot air injection gun;

FIG. 12 is an enlarged longitudinal cross-sectional view through the forward end portion of the gun of FIG. 11;

FIG. 13 is a cross-section taken on line 13-13 of FIG. 12;

FIG. 14 is a cross-section taken on line 14-14 of FIG. 12;

FIG. 15 is a cross-section taken on line 15-15 of FIG. 14;

FIG. 16 is a cross-section taken on line 16-16 of FIG. 15;

FIG. 17 illustrates the water flow passages formed in the front of the central body with the gun front end shown in FIGS. 11-16;

FIG. 18 is a modified form showing the arrangement of the water inlet and return passages of the four swirl vanes and the central body portion of the gun front shown in FIGS. 11-17;

fig. 19 is an enlarged sectional view through the rear of the gun shown in fig. 11-18.

Detailed Description

The following description is in the context of smelting iron ore to produce molten iron and it will be appreciated that the invention is not limited to this use and may be applied to any suitable iron-containing ore and/or concentrate including partially reduced iron-containing ore and waste return material.

The direct smelting apparatus shown in figure 1 comprises a metallurgical vessel generally indicated at 11. The vessel 11 has a hearth comprising a bottom 12 formed of refractory bricks and sides 13; a side wall 14 forming a generally cylindrical barrel extending upwardly from the side 13 of the hearth and including an upper barrel portion 151 formed of water-cooled panels and a lower barrel portion 153 formed of water-cooled panels, the lower barrel portion being lined with refractory bricks; a furnace roof 17; an outlet 18 for exhaust gases; a forehearth 19 for continuously discharging molten metal; and a tap hole 21 for discharging molten slag.

In use, the vessel contains a molten bath of iron and slag which, in a quiescent state, includes a layer of molten metal 22 and a layer of molten slag 23 on the metal layer 22. The term "metal layer" is understood herein to mean the molten pool region of predominantly metal. The term "slag layer" is understood here to mean the region of the bath which is predominantly slag. The arrow marked by reference numeral 24 indicates the position of the nominal quiescent surface of the metal layer 22 and the arrow marked by reference numeral 25 indicates the position of the nominal quiescent surface of the slag layer 23 (i.e. the molten bath). The term "stationary layer" is understood to mean the surface when no gas and solids are injected into the vessel.

The vessel is fitted with downwardly extending hot air injection lances 26 for feeding hot gas streams at temperatures in the range 800-. The gun 26 has an outer diameter D at its lower end. The gun 26 should be set to:

(i) the central axis of the gun 26 is at an angle of 20-90 ° with respect to the horizontal axis, so that the injection angle of the hot air is in this range;

(ii) the gun 26 extends into the container at least the outer diameter D of its lower end;

(iii) the lower end of the lance 26 is at least 3 times its lower outer diameter D above the quiescent surface 25 of the molten bath.

The vessel is also fitted with solids injection lances 27 (two shown) which extend downwardly and inwardly through the side wall 14 and into the bath to inject iron ore, solid carbonaceous material and slag entrained in an oxygen-deficient carrier gas into the bath. The position of the spray gun 27 is selected so that the outlet end 82 of the spray gun 27 is above the stationary surface of the metal layer 22. This position of the gun can reduce the risk of damage through contact with the molten metal and also enables cooling of the gun by forced internal water cooling without creating a significant risk of water coming into contact with the molten metal in the vessel.

From the context, it is clear that an industrial vessel manufactured by the applicant's related company has a hearth with a diameter of 6m and a hot air injection lance 26 which weighs about 60 tons, has an outer diameter of 1.2m and protrudes into the vessel by about 10 m.

The structure of one embodiment of the hot air injection lance 26 is illustrated in fig. 2-10.

As shown in the drawings, the gun 26 includes an elongated duct 31 capable of receiving hot gases through an air inlet member 32 and injecting the hot gases into the upper region of the vessel. The gun comprises an elongate central tubular member 33, which member 33 extends within the airflow duct 31 from the rear end of the airflow duct 31 to the front end of the airflow duct 31. Adjacent the forward end of the duct, the central member 33 carries a series of four swirl imparting vanes 34 for imparting swirl to the air stream exiting the duct. The front end of the central member 33 has a hemispherical nose 35 which projects forwardly beyond the end 36 of the duct 31, so that the front end of the central body and the duct end 36 co-act to form an annular nozzle for effecting diffusion of gas from the duct by means of the vortex imparted by the vanes 34. The vanes 34 are arranged in a four-start helical configuration and are a sliding fit within the forward end of the tube.

The wall of the main part of the duct 31 extending downstream from the gas inlet 32 is internally water-cooled. This section of the duct is made up of a series of three coaxial steel tubes 37, 38, 39 which extend to the forward end of the duct where they connect to the end 36 of the duct. The end 36 of the pipe is of hollow annular configuration and is internally water cooled by cooling water supplied and returned through passages in the wall of the pipe 31. In particular, cooling water is supplied via an inlet 41 and an annular inlet manifold 42 into an internal annular water flow passage 43 defined between the tubes 38, 39 of the tube, the cooling water being supplied to the hollow interior of the tube end 36 through circumferentially spaced openings in the tube end 36. The return water enters an outer annular return water flow channel 44 defined between the tubes 37, 38 from a distal end through circumferentially spaced openings and returns back to a water flow outlet 45 at the rear end of the water cooled portion of the conduit 31.

The outer surface of the outermost metal tube 37 in the conduit 31 is machined using a conventional pattern of rectangular projection engaging lands in the form of projections 136, each having a notched or dovetail profile, so that the projections have an outwardly flared configuration and a keying formation capable of solidifying as slag on the outer surface of the lance 26. Solidification of the slag on the gun helps to minimize the temperature of the metal parts of the gun.

The water cooled section of tube 31 is internally lined with an inner refractory lining 46 which fits within the innermost tube 39 of the tube and extends to the water cooled end 36 of the tube. The inner periphery of the pipe end 36 is generally flush with the inner periphery of the refractory lining which defines the effective flow path for gas through the pipe. The forward end of the refractory lining has a slightly reduced diameter portion 47 which is able to receive the swirl vanes 34 with a suitable sliding fit. From said portion 47, the refractory lining has a slightly enlarged diameter to enable the central member to be inserted down through the duct when the gun is assembled until the swirl vanes 34 reach the front end of the duct, where they are guided into suitable engagement with the refractory portion 47 by means of the provision of a conical refractory zone 48 which guides the vanes into the refractory portion 47.

The front end of the central member 33 with the swirl vanes 34 is internally water cooled by cooling water which is fed forward from the rear end of the gun to the front end of the gun through the central member and then back along the central member to the rear end of the gun. This enables a very strong flow of cooling water directly towards the front end of the central member and the hemispherical nose 35 which is affected by a very strong heat flow, in particular during operation of the gun.

The central member 33 comprises inner and outer coaxial steel tubes 50, 51 formed from tube sections which are joined end to end and welded together. The inner tube 50 defines a central water flow passage 52, between which is defined an annular water return passage 54, through which central water flow passage 53 water flows forwardly from an inlet 53 at the rear end of the gun through the central member to the nose 35 at the front end of the central member, through which return passage 54 cooling water returns from the nose 35 rearwardly through the central member to a water outlet 55 at the rear end of the gun.

The nose end 35 of the central member 33 includes an inner copper body 61 that fits within an outer hemispherical nose housing 62 also made of copper. The inner copper piece 61 is formed with a central water flow channel 63 to receive water from the central channel 52 of the member 33 and direct it to the tip of the nose. Nose end 35 is formed with raised ribs 64 that fit snugly within nose housing 62 to define a single continuous cooling water passage 65 between inner portion 61 and outer nose housing 62. As can be seen in particular in fig. 5 and 6, the shape of the ribs 64 is such that a single continuous channel 65 extends as an annular channel portion 66, which annular channel portions 66 are interconnected by a channel portion 67 that slopes from one annular portion to the other. Thus, the channel 65 extends in a helical pattern from the distal end of the nose, although the helix is not of a standard helical shape, but rotates around and back along the nose to enter at the rear end of the nose into the annular return channel formed between the tubes 51, 52 of the central member 33.

The forced flow of cooling water in a single continuous stream through the spiral channel 65, said spiral channel 65 surrounding and extending back along the nose end 35 of the central member, ensures effective heat removal and avoids the formation of "hot spots" on the nose that could be generated if the cooling water were allowed to be divided into a plurality of independent streams at the nose. In the illustrated construction, the cooling water is confined to a single stream from its entry nib end 35 to its exit nib end.

The inner member 33 is provided with an outer insulation 69 to prevent heat transfer from the incoming hot gas flow in the duct 31 to the cooling water flowing within the central member 33. The solid refractory protective layer can only provide a short duration of action if subjected to the very high temperatures and strong gas flows required in large smelting plants. In the illustrated construction, the protective layer 69 is formed by a tubular sleeve made of a ceramic material known under the trade name UMCO. These sleeves are joined end to form a continuous ceramic protective layer surrounding the air gap 70 between the protective layer and the outermost tube 51 of the central member. In particular, the protective layer may be formed from a tube of UMCO50, wherein UMCO50 includes, by weight, 0.05% to 0.12% carbon, 0.5% to 1% silicon, a maximum of 0.5% and a minimum of 0.02% phosphorus, a maximum of 0.02% sulfur, 27% to 29% chromium, 48% to 52% cobalt, and the balance substantially iron. This material provides excellent thermal insulation but undergoes significant thermal expansion at high temperatures. To address this problem, individual sections of insulation are formed and installed as shown in fig. 7-10 to enable longitudinal expansion of the sections independently of each other while maintaining substantially continuous shielding at all times. As shown in these figures, the respective sleeves are mounted on positioning slats 71 and plate supports 72 fitted on the outer tubes 51 of the central member 33, the rear end of each guard tube being stepped at 73 so as to be able to fit over the plate supports with an end gap 74 so as to enable independent longitudinal thermal expansion of each slat. An anti-rotation plate bar 75 can also be fitted to each sleeve to fit around the upstanding toothed plate bar 76 on the tube 52 to prevent rotation of the protective sleeve.

The hot gas is conveyed to the duct 31 through the gas inlet portion 32. The hot gas may be oxygen enriched air at about 1200 c supplied from a furnace. The air must be transported through the refractory lined pipe and if the air is fed directly into the main water cooled section of the pipe 31 at high speed, it will carry away the refractory grit, creating a serious erosion problem. The gas inlet 32 should be designed to enable the duct to receive a large volume of hot air exhaust with refractory particles while minimizing damage to the water cooled portion of the duct. The inlet 32 comprises a T-shaped body 81 moulded as a unit from a wear resistant refractory material and disposed within a thin walled outer metal casing 82. The main body 81 defines a first tubular channel 83 aligned with the central channel of the duct 31 and a second tubular channel 84, the second tubular channel 84 being perpendicular to the channel 83 to receive the hot gas flow delivered from the furnace (not shown). The channel 83 is aligned with the gas flow channel of the duct 31 and is connected to said gas flow channel of the duct 31 by a central channel 85 in the refractory connection 86 of the inlet 32.

The hot air delivered to inlet 32 passes through tubular passage 84 of body 81 and impacts the wear resistant refractory wall of the thicker refractory body 82 which is erosion resistant. The air flow then changes direction, flows downwardly at right angles through the passage 83 of the T-shaped body 81 and the central passage 85 of the transition piece 86, and into the main portion of the duct. The walls of the channel 83 may be tapered in the forward flow direction to accelerate the airflow into the duct. For example, it may be tapered at an included angle of about 7 °. The transition refractory body 86 is tapered in thickness to enable fitting of the much thinner refractory lining 46 in the thick walls of the refractory body 81 at one end and the main part of the duct 31. Therefore, water cooling is enabled by the annular cooling water jacket 87, through which cooling water is circulated through the inlet 88 and the outlet 89. The rear end of the central member 33 extends through the tubular passage 83 of the gas inlet 32. So that it is disposed within refractory lined spigot 91 which closes the rear end of passage 83, the rear end of central member 33 extending rearwardly from gas inlet 32 to water inlet 53 and outlet 55.

The illustrated apparatus is capable of injecting large quantities of hot gases into the smelting vessel 11 at high temperatures. The center member 33 can deliver a large amount of coolant rapidly and directly to the nose portion of the center member, and the forced flow of coolant water in unseparated coolant fluid around the nose structure can achieve very effective heat removal from the front end of the center member. The separate water flow to the end of the duct also enables very efficient heat removal from the other high heat flux portions of the lance. The delivery of a hot gas stream into an inlet where it impinges upon the thick walls of a refractory chamber or channel before flowing down into the duct enables large volumes of air doped with refractory sand to be treated without significant erosion of the refractory lining and insulation within the main portion of the lance.

The structure of another embodiment of the hot air injection lance 26 is shown in fig. 11-19 and is not the only additional embodiment.

As shown in these figures, the lance 26 comprises an elongated tube 31 through which a hot gas stream can flow, wherein the hot gas stream may be enriched in oxygen. The tube 31 comprises a series of four coaxial steel tubes 32, 33, 34, 35 which extend to the front end portion 36 of the conduit connecting them to an end piece 37. An elongate main body portion 38 is centrally disposed within the duct nose portion 36 and the main body portion 38 carries a series of four swirl imparting vanes 39. The central body portion 38 is of an elongated cylindrical shape with bullnose or spherical front and rear ends 41, 42. The blades 39 are arranged in a four-start helical configuration and are connected at their forward ends to the front of the duct by radially outwardly extending blade ends 45.

The duct 31 is internally lined over most of its length with an internal refractory lining 43 which fits inside the innermost metal tube 35 of the duct and extends to the front end portions 42 of the blades, the blades 39 being neatly mounted in the refractory lining behind these front end portions 42.

The end piece 37 of the pipe has a hollow annular head or end structure 44, which end structure 44 projects forwardly from the remainder of the pipe so as to be substantially flush with the inner surface of the refractory lining 43, said refractory lining 43 defining an effective flow passage for gas through the pipe. The forward end of the central body portion 38 projects forwardly beyond the end formation 44 so that the forward end of the body portion and the end formation can co-operate to form an annular nozzle from which the hot gas stream is discharged in an annular diverging stream by means of the strong rotational or swirling motion produced by the vanes 39.

According to the invention, the tube end structure 44, the central body portion 38 and the blades 39 are internally water-cooled by a flow of cooling water supplied by cooling water flow channel means, indicated by reference numeral 51, which extend through the tube wall. The cooling water passage means 51 comprises a water supply passage 52 defined by an annular space between the conduits 33, 34 for supplying cooling water to a hollow interior 53 of the conduit end structure 44 via circumferentially spaced openings 54 in the end piece 37. The water is returned from the end piece through circumferentially spaced openings 55 into the annular return water flow passage defined between the pipes 32 and 33 of the conduit and which also forms part of the water flow passage means 51. Thus, the hollow interior 53 of the end piece 37 can be continuously supplied with cooling water to function as an internal cooling channel. Cooling water for the lance end is delivered into the feed channel 52 through a water inlet 57 at the lance rear end and return water exits the lance through an outlet 58 also at the lance rear end.

The annular space 59 between the tubes 34 and 35 is divided by a helically wound dividing strip into eight separate helical channels 60 extending from the rear end of the tube to the front end portion 36 of the tube. Four of these channels are individually supplied with water through four circumferentially spaced water inlets 62 to provide separate water sources for cooling of the blades 39 and the main body portion 38. The water inlet 62 communicates with a common water supply line 80 via an annular supply manifold 90. The other four channels 60 function as return channels and are connected to a common annular return manifold channel 63 and a single water outlet 64.

The blades 39 are hollow and internally partitioned to form inlet and outlet passages through which water can flow to and from the central body portion 38, which is also formed with water flow passages to effect internal water cooling, and out of the central body portion 38. The forward end portions 45 of the vanes 39 are connected to the forward ends of the innermost conduit tubes 35 around four water inlet slots 65 through which water flows from four independently supplied water inlet passages into radially inwardly directed water inlet passages 66 at the forward ends of the vanes. Subsequently, the cooling water flows into the front end of the central body portion.

The central body portion 38 includes front and rear inner body portions 68, 69 and hemispherical front and rear end pieces 41, 42, the front and rear inner body portions 68, 69 being mounted within a housing 70 formed by a main cylindrical portion 71, the hemispherical front and rear end pieces 41, 42 having hard surfaces to resist wear from refractory grit or other particulate material carried by the hot gas stream. The clearance space 74 between the inner portions 68, 69 and the outer shell of the central body portion is subdivided into two sets of peripheral water flow channels 75, 76 by means of partition ribs 77, 78 formed on the outer peripheral surfaces of the inner body portions 68, 69. The front set of peripheral water flow passages 75 are arranged to fan out from the front end of the central body and to wrap back around the body in the manner shown in figure 17. A flow directing insert 81 is provided at the center of the inner body portion 68 to extend through the water flow passage 67 and divide the passage into four circumferentially spaced water flow passages which are capable of independently receiving the water flow entering through the water inlet passage 66 at the forward end of the vane, thereby maintaining four independent water inlet flows to the forward end of the central body portion. These separate water flows communicate with four front peripheral water flow channels 75, through which channels 75 water flows back around the front end of the central body portion.

The partition 82 separates the water inlet passages 66, 67 at the front ends of the vanes and central body portion from the water flow passages in the rear portions of the vanes and central body portion. The water flowing back through the forward peripheral channels 75 passes through the slits 83 in the partition provided between the water inlet channels 66 to flow back into the central channel 84 in the rear body portion 69. The central channel is also divided into four independent flow channels by means of a central flow guide 85 to continue four independent flows of water to the rear end of the central body. At the forward end of the central body, rear peripheral flow channels 76 are also provided in groups of four similar to the bypass tubes 75 to receive four separate streams at the rear end of the body and return these streams around the periphery of the body to four circumferentially spaced outlet slots 96 in the housing through which the water flows into the water return channels 87 in the vanes.

The hollow blades are internally divided by longitudinal partitions 89 so that the cooling water passages extend rearwardly from the inner front end of the blade to the rear end of the blade and then outwardly and forwardly along the outer longitudinal end of the blade to radially extending outlet passages 91 in the front end 42 of the blade which communicate via outlet slots 93 with four circumferentially spaced return passages extending rearwardly through the duct wall to a common outlet 64 at the rear end of the duct. The partition 82 partitions the water inlet and outlet passages 66, 91 inside the blades, and the water inlet and outlet slits 65, 93 of each blade are formed in the front end of the internal pipe tube 35 at an angle from the longitudinal direction so as to be able to fit the helix angle of the blade shown in fig. 3.

The front ends of the four coaxial conduit tubes 32, 33, 34, 35 are welded to the three flanges 94, 95, 96 of the end piece 37 to securely join them into one solid component at the front end of the gun. The rear ends of the conduit tubes are longitudinally movable relative to each other to allow differential thermal expansion during operation of the gun. As can be seen most clearly in fig. 19, the rear end of the ducting tube 32 is provided with a projecting flange 101 onto which is welded a continuous member 102 with different water inlets and outlets 57, 58, 80, 64. The member 102 comprises an inner annular flange 103 fitted with an O-ring seal 104 which serves as a sliding fit for the trailing end of the ducting tube 33 so as to allow longitudinal expansion and contraction of the ducting tube 33 independently of the external ducting tube 32. The component 105 welded to the rear end of the conduit tube 34 comprises annular flanges 106, 107 fitted with O-ring seals 108, 109, said seals 108, 109 providing a sliding fit for the rear end of the conduit tube 34 within the outer component 102 secured to the rear end of the conduit tube 32, so that the conduit tube 34 can also expand and contract independently of the conduit tube 32. The rear end of the innermost ducting tube 35 is provided with a projecting flange 111 fitted with an O-ring seal 112, said seal 112 engaging with an annular ring 103 fitted to the outer member 102 to also provide a sliding fit for said innermost ducting tube allowing independent longitudinal expansion and contraction to occur.

Thermal expansion of the guide vanes 39 and the inner body part 38 should also be ensured. The vanes 39 are connected to the pipe and inner body part only at the front end and there is in particular water flow in and out the inner and outer parts of the vane front end. The main part of the blade is simply fitted between the refractory lining 43 of the duct and the shell of the central body portion 38 and is free to expand longitudinally. The water flow divider 85 in the rear of the inner body portion has a circular front end plate which is able to slide within a machined surface of a tubular sleeve 122 on the partition 82 to allow the front and rear of the central body portion to move away under thermal expansion whilst maintaining a seal between the separate water flow passages. A thermal expansion joint 133 is also provided to accommodate thermal expansion between the forward end and the forward end of the central body portion.

To further allow for thermal expansion, the vanes 39 may take a shape such that when the vanes are viewed in cross-section, the vanes do not extend radially outwardly between the casing of the central body portion and the refractory lining of the duct, but rather are slightly angled away from a purely radial direction when the tube and central body of the lance are in a cooled condition. Subsequent expansion of the duct tube during gun operation will allow the vanes to be drawn towards a fully radial position while maintaining proper contact with the duct liner and the central body portion while avoiding radial stresses on the vanes due to thermal expansion.

In the illustrated operation of the hot air injection lance, separate streams of cooling water are delivered to the four swirl vanes 39 so as not to cause a loss of cooling efficiency due to differential flow effects. Separate cooling water is also provided to the front and rear ends of the central body portion 38 to eliminate "hot spots" caused by water starvation due to possible preferential flow effects. This is particularly important for cooling the forward end 41 of the central body portion which is exposed to very high temperature conditions within the smelting vessel.

The duct tubes are capable of independent longitudinal expansion and contraction under the effects of thermal expansion and contraction, and the vanes and central body portion are also capable of expansion and contraction without compromising the structural integrity of the gun or maintaining various independent cooling water flows.

The illustrated lance is capable of operating under extreme temperature conditions within a direct smelting vessel in which molten iron is produced by a high smelting process. Typically, the cooling water flow rate through the four swirl vanes and the central body portion is about 90m³Hr, and a flow rate of about 400m through the outer housing and the gun tip³and/Hr. Thus, at a maximum operating pressure of about 1500kPag, the total flow rate is about 490m³/Hr。

Although the illustrated lance has been designed for injecting a hot gas stream into a direct smelting vessel, it will be appreciated that a similar lance may be used to inject gas into any vessel, often at high temperature conditions, for example for injecting oxygen, air or fuel gas into a smelting vessel.

It is, therefore, to be understood that the invention is not to be limited to the details described and that various modifications and changes may be made to the invention described.

Claims

1. A lance for injecting a preheated oxygen-containing gas into a vessel having a pool of molten material, the lance comprising:

(b) a gas inlet for introducing hot gas into the rear end of the duct;

2. The lance defined in claim 1 wherein the duct includes three or more coaxial steel tubes extending to the forward end of the duct.

3. The lance defined in claim 1 or claim 2 wherein the gas inlet includes a refractory body defining a first tubular gas passage aligned with and extending directly to the rear end of the duct and a second tubular gas passage transverse to the first passage to receive hot gas and direct it into the first passage so that the hot gas and any particles contained therein will impinge on the refractory wall of the first passage and the gas flow will change direction as it flows from the first passage to the second passage.

4. The lance defined in any one of the preceding claims wherein the mechanical means on the outer surface of the duct includes projections that are shaped to engage and retain the frozen slag on the duct.

5. The lance defined in claim 4 wherein the projections are abutment platforms (lands) each having a slot or dovetail profile so that the abutment platforms are in an outwardly flared configuration and can act as a keying formation for slag solidification.

6. A lance as claimed in any one of the preceding claims, in which the tip means is of hollow annular configuration and is made of a copper-containing material.

7. The lance defined in claim 6 wherein the forward end of the duct is formed as a hollow annular tip structure and the duct includes tip means cooling water supply and return passages for supplying cooling water to the duct tip forwardly along the duct and for returning cooling water rearwardly along the duct.

8. The lance defined in any one of the preceding claims further includes an elongate body that is centrally disposed within the forward end of the duct so that gas flowing through the forward end of the duct flows along the elongate central body throughout the central body.

9. The lance defined in claim 8 wherein the forward end of the elongate body and the tip means act together and form an annular nozzle so that gas flows from the duct with a vortex imparted by the vortex means.

10. A lance as claimed in claim 8 or claim 9 wherein the swirl means comprises a plurality of guide vanes connected to the elongate body to impart swirl to the gas flow through the forward end of the duct.

11. The lance defined in claim 10 wherein the elongate body is an elongate central tubular member extending within the gas flow duct from a rear end thereof to a forward end thereof and the vanes are disposed about the central tubular member adjacent the forward end of the duct to impart swirl to the gas flow directed towards the forward end of the duct.

12. The lance defined in claim 11 wherein the central tubular member includes a water cooled passage for forward flow of cooling water to the forward end thereof.

13. The lance defined in claim 12 wherein the central tubular member includes cooling water passages for cooling water to flow through the central member forwardly from its rear end to its forward end and internally cool the forward end and then return through the central member to its rear end.

14. The lance defined in claim 13 wherein the central tubular member defines a central water flow passage for water to flow forwardly through the member directly to the forward end of the central member and an annular water flow passage disposed about the central passage for returning water rearwardly from the forward end of the central member to the rearward end of the member.

15. The lance defined in claim 14 wherein the central annular member includes a central tube providing a central water flow passage and further tubes disposed about the central tube so as to define the annular water flow passage between the tubes.

16. The lance defined in any one of claims 13 to 15 wherein the central tubular member includes an insulating outer layer to inhibit heat transfer from the gas in the gas flow duct to the cooling water passage in the central member.

17. The lance defined in claim 16 wherein the insulation includes a plurality of tubular sections of insulating material arranged end to end such that the insulation forms a substantially continuous tube extending from the rear end to the forward end of the central tubular member around an annular air gap provided directly in the insulation.

18. The lance defined in claim 17 wherein the air gap is formed between the annular insulating layer and another tube defining an outer wall of the annular return water flow passage.

19. The lance defined in claim 14 wherein the forward end of the central tubular member includes a hemispherical nose portion within which is disposed a single helical cooling water passage to receive water from the central water flow passage in the central tubular member at the tip of the nose portion and direct the water in a single stream around and rearwardly along the nose portion to cool the nose with a single coherent flow of cooling water.

20. The lance defined in any one of claims 11 to 19 wherein the central tubular member extends centrally through the first gas flow passage of the gas inlet and rearwardly beyond the gas inlet.

21. The lance defined in claim 20 wherein the rear end of the central tubular member is located rearwardly of the gas inlet and the lance includes a water connection for the flow of cooling water to and from the central member.

22. The lance defined in claim 10 wherein guide vanes are provided between the elongate central body and the duct to impart swirl to the gas flow through the forward end of the duct.

23. The gun of claim 22, comprising:

(a) internal cooling water passage means within the tip, the passage means communicating with the cooling water supply and return passage means of the duct to receive and return a flow of cooling water to internally cool the tip of the duct; and

24. The lance defined in claim 23 wherein the cooling water supply and return passage means of the duct includes a first supply and return passage in communication with an internal cooling water passage in the tip means and a second supply and return passage in communication with the water flow passage in the long central body and the vanes.

25. The lance defined in claim 23 wherein the end of the duct is formed as a hollow annular structure defining an annular passage constituting internal cooling water passage means of the end means.

26. The lance defined in any one of the preceding claims wherein the coaxial carbon steel tubes of the duct define a series of annular spaces for providing cooling water supply and return passage means.

27. The lance defined in any one of claims 22 to 25 wherein the blades are shaped in the form of a multi-start helix.

28. The lance defined in claim 26 wherein the vanes are connected to the duct at a plurality of locations spaced circumferentially around the duct.

29. The lance defined in claim 27 wherein four vanes are provided, the vanes being arranged in a four-start helical configuration and being connected to the duct at four locations spaced at 90 ° intervals around the duct at the forward ends of the vanes.

30. The lance defined in claim 28 wherein the cooling water supply and return passage means of the duct includes a suitable number of separate water flow passages, each capable of supplying cooling water to one of the vanes.

31. The lance defined in claim 29 wherein the separate water flow passages are formed by dividers within an appropriate number of annular passages between duct tubes extending helically along the duct.

32. The lance defined in any one of the preceding claims wherein the forward ends of the coaxial carbon steel tubes are connected at their forward ends to a tip means.

33. The lance defined in claim 31 wherein the rear ends of the coaxial carbon steel tubes are mounted to permit relative longitudinal movement therebetween so as to accommodate varying degrees of thermal expansion and contraction of the tubes.

34. An apparatus for producing ferrous metal from a ferrous process feed material by a direct smelting process, the apparatus including a vessel containing a bath of molten metal and molten slag and a gas continuous space above the bath, the vessel including:

(a) a hearth formed of refractory material and having a bottom and sides;

(e) at least one gas injection lance defined in any one of the preceding claims extending downwardly into the vessel for injecting an oxygen-containing gas at a temperature of from 800 ℃ to 1400 ℃ into the vessel at an angle of from 20 ° to 90 ° to the horizontal axis at a velocity of from 200 m/s to 600m/s, said lance being arranged to:

(f) apparatus for discharging molten metal and slag from a vessel.

35. The apparatus defined in claim 34 wherein the ferrous working feed material and carbonaceous material supply means and the gas flow generating means includes a plurality of lances/tuyeres for injecting the ferrous working feed material and carbonaceous material into the molten bath using a carrier gas and generating the gas flow.