EP2882874B1 - Hot-blast lance - Google Patents

Description

The invention relates to a hot blast lance for use in metallurgical processes, such as bpsw. steel production, with which hot air is blown above a molten bath of a steel converter, which consists of an outer shell, and at least one inner shell, and disposed between the outer and an inner shell at least one coolant-flowing gap or cooling channel, according to the preamble of claim 1.

In the production of steel in reaction vessels, such as in converters, both pig iron and scrap are used as feedstock. In addition, however, also produced in the so-called direct reduction process sponge iron in the form of DRI (Direct Reduced Iron) or HBI (Hot Briquetted Iron) can be used. An example of this is from the EP 1 920 075 B1 known. From the WO 03/006693 A1 a gas injection lance is known, which is cooled in an inner jacket and an outer jacket. The gas injection lance is thus well protected as such, but it is withdrawn when using hot wind relatively much heat energy from the hot blast, which is then bad for the overall energy balance, if you want to go with high scrap rates.
Another procedure is from the DE 43 43 957 A1 in which in the operating phase of the converter fuels, oxygen-containing gases and iron raw materials, and scrap are introduced, and the reaction gases above the melt in the gas space of the converter with oxidizing gases are post-combusted. The resulting heat is transferred to the melt transfer. In addition, oxygen and / or fuels are supplied via bottom nozzles.

So far, the combination of the bottom-side insufflation with oxygen and the inflating hot blast on the melt is known as such.

Hot air is understood as meaning an oxygen-containing gas heated to 1,200 ° C. (500-1,400 ° C.). The gas is typically composed of the main components oxygen, nitrogen and argon. The oxygen content is in the range of normal air (21%) and can be up to 35% or even 50% enriched with oxygen. In principle, a synthesis gas could be understood as a hot blast, which is obtained, for example, from the exhaust gases of a combustion reaction of a fuel such as blast furnace gas, coke gas, converter gas or natural gas or other gaseous or liquid hydrocarbon with air. The O 2 content of the synthesis gas can be adjusted by the air ratio of the combustion and, if appropriate, simultaneous enrichment of the combustion air with oxygen and / or the mixing of the combustion exhaust gases with pure oxygen.

In contrast to normal hot blast, the hot blast produced in this process has levels of CO2 and water as combustion products.

The invention is therefore the object of further developing a hot blast lance that hot blast can be particularly effective, so with minimal temperature losses in a reaction vessel, eg a steel converter can be introduced, and the lance better adapted to this environment of use.

The object is achieved in a hot blast lance of the generic type by the characterizing feature of claim 1.

Further advantageous embodiments are specified in the dependent claims 2 to 12.

A corresponding use of such a lance is specified in claim 13.

The core of the invention is that the inner jacket or the innermost jacket at least partially consists of a thermally insulating additional jacket, or a thermally insulating jacket, or is coated with a thermally insulating layer. This makes the hot blast lance considerably more robust and can be used in processes in which the reaction processes, for example, in the steelmaking process in the converter, are significantly influenced and optimized by the application of hot blast. As a result of the resulting afterburning and the transfer of the heat released in this way to the molten bath, the usable scrap rate becomes significantly higher.

The Heißluftnachverbrennung requires a special device for forwarding the hot blast from the hot blast source and for introducing the hot blast in the reaction vessel, via a corresponding, designed here according to the invention hot blast lance.

As a reaction vessel, a converter can be used, as it is known from steel production. Basically, an afterburning can be done with Hot wind also operate in any other usual in metallurgy reaction vessel, it is irrelevant whether the walls of the vessel are completely, partially or not cooled with cooling water.

In the interior of a metallurgical reaction vessel typically prevail temperatures of about 1,000 ° C, wherein in the gas phase, temperatures of up to 2,000 ° C can be achieved. For a permanent operation of a blowing lance in the region of a reaction vessel, for example. For metallurgical reactions, above the liquid bath surface, it is essential to cool the injection lance, in this case so the hot blast lance intensively with water. Water cooling protects the hot blast lance from the high gas temperatures prevailing in the upper chamber of the reaction vessel. The high gas temperatures go to a considerable extent on the in the reaction vessel (eg, in a steel converter) running and possibly. The injection lance maintained idR exothermic reactions. As such, water-cooled lances are known per se.

In a lance in pipe-web-tube construction, the water-cooled shell of juxtaposed, cooling water pipes is constructed, which are interconnected with narrow, solid webs. In general, two adjacent tubes are connected at one end to a manifold, the other two ends are each connected to a flow and a return header. As a special case of this embodiment, a pipe-to-pipe construction is introduced in which the pipes are welded directly to each other without web.

In an embodiment of the lance in tube-in-tube construction, three tubes of ever smaller diameter are arranged concentrically to each other. This creates between the outer and the middle tube, as well as between the middle and the inner tube each have a concentric space. If one connects the outer and the inner pipe at one end of the lance and shortens the middle pipe, the result is a geometry in which the two interspaces can be used as supply and return for the lance cooling water. In order to ensure a concentric positioning of the three tubes running into each other even with a large lance length, spacers are introduced between the tubes. Often these spacers are designed as welded in the longitudinal direction on the respective thinner pipe narrow webs.

An essential design feature of efficient water cooling is the highest possible heat transfer from the hot ambient atmosphere in the reaction vessel into the cooling water. Only then is a consistently sufficiently low temperature level ensured on the material surface of the water-cooled component. To ensure these properties, water cooling systems are designed so that they flow through the cooling water at a flow rate of 2m / s (1 to 3 m / s).

In the present technical task of continuing and introducing hot blast into a reaction vessel, the described water-cooled device is used with regard to protection of heat entry.

A special feature lies in the fact that hot wind is not a cold but a typical one 1200 ° C hot medium is. Furthermore, the hot-blast process is not always a continuous process, but is a batch process, especially in the converter process. Accordingly, the plant components provided for this purpose are always exposed to hot blast phases, whereby the plant parts cool down during the process breaks regularly. The result is an uneven load profile, which leads to a significant thermal cycling (TWB) of the applied equipment parts. This results in a special requirement profile on the side facing the media of the hot blast lance. This is taken into account with the present invention.

The material surface of the innermost of the three tubes through which hot wind flows is exposed to high thermal, oxidative and abrasive loads. To protect the side facing the hot wind, this can be protected by a suitable coating against the aforementioned loads. In view of the considerable thermal load, it will generally be possible to work only with thin (<10 μm) layers, since thicker layers tend to embrittle and chip due to the different thermal expansion compared to the base material. Suitable layer systems are ceramic layers, overlay layers or application layers, which can be applied by conventional application methods, chemical vapor deposition or thermal vapor deposition, thermal spraying, build-up welding or application of SolGel systems, the layers possibly still being formed by a thermal step (by curing, diffusion, crosslinking, etc.) can be improved in their functionality.

It has been shown that can be achieved by the water-cooled construction of the lance sufficiently long service life when operating in high-temperature reaction vessels. Surprisingly, however, it has also been shown that the water cooling also causes a considerable heat release from the hot blast stream into the water-cooled wall of the hot blast lance. This effect is in particular reinforced by the fact that with regard to still structurally manageable external dimensions, the lance must be designed so that the hot wind inevitably flows through the lance at speeds of 100 to 300 m / s, preferably 150 m / s. With increasing speed but also increases the heat loss from the hot blast stream in the hot blast stream facing wall of the innermost lance tube.

This is counteracted by the design according to the invention.

The further advantageous embodiments therefore support the above statements in accordance with the invention.

In a further advantageous embodiment is stated that the inner shell or the innermost shell is provided at least on the inside with a protective layer or coating.

At least on the inside of the inner shell, the lance advantageously still has a good resistance to abrasion and corrosion. This is important insofar as the flow rate of hot air because of the lower density of the hot air compared to air under normal conditions is significantly larger. The mechanical load of the inner shell of the lance due to the flow of hot air is thereby greater than is the case with an oxygen lance, in which the oxygen is conveyed substantially in a cold state and usually under high pressure through the lance.

Due to the thermally insulating effect of the material can be advantageous implement that the outer jacket is cooled against the high ambient temperatures in converter operation. Nevertheless, it can be achieved that the hot air flowing through the inner jacket, if necessary, is cooled to a slight extent.

This has proven to be important in order to bring the hot air with the highest possible temperature in the converter can.

In this embodiment, it also proves to be advantageous that the cooling channel through which water flows is separated by two walls from the inner tube of the lance, through which the hot air flows. Due to the flowing hot air, the inner tube is mechanically, thermally and chemically stressed comparatively strong. This can lead to cracks in the jacket of the inner tube. By the embodiment described with the intermediate jacket is then advantageously achieved that in case of damage to the inner tube by the flowing hot air not immediately coolant can reach the interior of the lance and is conveyed from there with the flowing hot air into the converter. In the described embodiment, only hot air then passes into the region between the inner jacket and the intermediate jacket. Because the Hot air there can not continue to flow with the comparatively high flow velocity, the intermediate coat is then no longer mechanically stressed.

Furthermore, it is configured that the inner shell or the innermost shell consists of several layers, and that at least the innermost of these layers, namely layer consists of an abrasion and / or corrosion resistant material.

Furthermore, it is configured that the inner shell or the innermost shell consists of a ceramic material or is coated with the same.
Ceramic materials advantageously meet the requirements outlined above.

Therefore, it is advantageously provided that the abrasion and / or corrosion-resistant material or the ceramic material is provided on the adhering to the inner or innermost shell side with a temperature-resistant bonding agent or liner.

In this case, the bonding agent or liner is so elastic that it compensates for the difference in the coefficient of expansion of the inner or innermost shell to abrasions- and / or corrosion-resistant material or to the ceramic material.

A particular specific embodiment is that the abrasion- and / or corrosion-resistant material or the ceramic material consists of a layer system in which the surface to which the hot wind flows consists of a dense ceramic material and the surface facing away from the hot wind consists of a ceramic foam material. The ceramic foam material has a higher elasticity than the solid ceramic material.

It proves to be advantageous that the coating is relatively thin. This makes it possible to keep the weight of the lance within limits. This proves to be advantageous insofar as the lance must be moved in the vertical direction relative to the converter during operation. A small layer thickness also proves advantageous because of the thermal cycling of the hot air lance in converter operation. This alternating stress is due to the fact that before the tapping of the converter, the lance is moved out. This stops the delivery of hot air through the lance. The lance then cools until hot air is conveyed through the lance at the next converter operation. The lance is heated again accordingly.

A suitable material for a coating may consist, for example, of Al ₂ O ₃ , SiC, SiSiC or a super-Alloy. This material can be applied for example by sputtering, electrochemical or electrolytic coating, flame spraying, paint comparable to a color or by applying a suspension in which the liquid evaporates and the solid particles cover the outer surface or inner surface of the inner shell of the lance.

It has been found that this ceramic material has good thermal insulation properties (ie low thermal conductivity). The material is also sufficiently mechanically stable (especially against abrasion) and has a sufficient Shock resistance to the occurring temperature fluctuations.

It should be noted that the operation is intermittent. This means that hot air is not continuously conveyed through the inner jacket. When the converter is emptied and prepared after emptying, for the next melting process, for example, by removing slag from the converter, refurbishing the refractory lining of the steel converter. During this time, the hot blast source in the form of a pebble heater is re-fired to store heat for the production of hot air for the next melting process. During this time, no hot air is conveyed through the lance, so that the inner jacket of the lance cools. At the beginning of the next melting process hot air is again conveyed through the inner shell of the lance, so that the inner shell is then exposed to correspondingly high temperatures.

For integrated coolant guidance is stated that between the inner shell and the outer shell, at least one intermediate jacket or gap is arranged, and is flowed through with coolant.

But it may also be advantageous if the space between the outer jacket and the inner jacket is evacuated.

In a further advantageous embodiment, it is stated that a Temperierungskanal is disposed between the outer shell and the innermost shell, which in Blasbetrieb the hot blast is also flowed through with hot blast.

It may be possible for the inner jacket to be kept at a high temperature on its outside as well, due to the hot air flowing in the tempering channel. The hot air, which flows through the inner jacket, is introduced largely without cooling at a high temperature in the converter.

The hot air, which flows through the Temperierungskanal is cooled in this embodiment to some extent.

This hot air, which has flowed through the tempering channel, can be introduced via diffusely distributed outlet nozzles on the outlet side of the lance into the space of the converter above the steel bath. In this case, it must be avoided by the design of the nozzles that this hot air, which has flowed through the tempering channel, is mixed with the hot air which has been conveyed through the inner shell. As a result, mixing these two hot air components would nevertheless mean a reduction of the hot air temperature for the process.

As an alternative to introducing the hot air which has flowed through the tempering channel into the gas space of the converter, it is also possible to design the tempering channel in such a way that the hot air in the tempering channel is circulated from the upper end (inlet end of the hot air into the lance) to the lower end (lance head, Outlet end of the hot air from the lance into the converter) flows and is returned from there in the Temperierungskanal, in the direction the upper end of the lance. From there, the hot air can then be led out of the lance and released to the environment. For this purpose, this hot air flowing out of the tempering channel is advantageously led out of the hall of the factory. In the converter then only the hot air is introduced, which was conveyed through the inner shell of the lance.

Especially in this embodiment of the lance, it is advantageously also possible to realize before the actual melting process in the converter a Aufwärmbetrieb the lines through which the hot air is to be promoted during the melting process. If the pebble heater is already heated, hot air is then conveyed from the pebble heater to the lance through the supply line of the hot air before the actual melting process. It is advantageous that the area can be shut off by a slide, in which the hot air is introduced through the inner shell of the lance in the converter during the melting process. In this Aufwärmbetrieb the hot air is then conveyed through the Temperierungskanal and then discharged. As a result, the lines are advantageously preheated, through which the hot air is supplied to the converter in the melting process. This advantageously prevents the temperature of the hot air from being cooled, especially at the beginning of the melting process, because the hot air initially releases heat to the lines in this phase.

It is part of the invention when the innermost shell is floatingly mounted in the hot blast lance. This proves to be necessary because a heat exchange between the inner shell and the outer jacket or the intermediate jacket is avoided by mechanical fastening and contacting. Likewise, this achieves that the mechanical stresses within the lance are reduced. Due to the intermittent operation, in which hot air is conveyed through the lance in periods of converter operation and in phases of preparation of the next converter operation no hot air is conveyed through the lance, especially the inner jacket of the lance is subject to strong temperature fluctuations. Due to the cooling, only comparatively small temperature fluctuations occur on the outer jacket. In view of the mechanical stresses, it is therefore necessary when the inner shell is floatingly mounted in the lance. The length changes due to the temperature changes then only lead to a lower mechanical load on the lance, because by the floating bearing, the change in length of the inner shell can be made largely independent of the change in length of the outer shell.

In order to allow the high thermal length expansions at the said high temperatures harmless, is further configured that at least the inner or innermost shell along its longitudinal direction consists of several sections or sleeves, which are designed partially overlapping at the points of contact of the individual sections or sleeves.

It proves to be advantageous if in the flow direction of the hot air, the rear end of a section is widened to receive the end of the upstream in the flow direction of the hot air section is used.

By this type of connection of the sections, the changes in length in the temperature fluctuations of the inner shell can be better absorbed.

An embodiment is particularly advantageous when the floating inner shell of the hot blast lance is provided with an insulating layer, such as rock wool, in relation to the water-cooled jacket area.

The reason for this is that the heat transfer due to temperature radiation from the innermost shell into the water-cooled shell is impeded especially effectively in the temperature range above 800 ° C. Carry on a little further. Basically enough even a temperature radiation obstruction in the form of a thin layer as a kind of radiation shield so that the removal of energy from the hot wind into the cooling water is stronger prevented.

Furthermore, in an advantageous embodiment, it is provided that the innermost surface or coating surface, which is in direct contact with the hot blast, is structurally or microstructured with reduced flow resistance and / or reduced adhesion.

It is a use of a hot blast lance according to one of claims 1 to 12, for blowing hot blast above a steel bath and / or a scrap heap, and / or a heap in a steel converter provided. The thermal insulation described above proves to be particularly advantageous in a process in which hot air is introduced into the converter during the melting process. In the widespread introduction of Pure oxygen in the melting of steel for refining does not depend on the temperature of the oxygen due to the process. In contrast, the application of one of the aforementioned embodiments of a lance but especially in the introduction of hot air proves to be advantageous in the converter.

Optionally, it may be useful in a lance according to the embodiments described above, to provide the inner surface of the inner shell with a surface profile in order to improve the flow profile. This surface profile can be designed, for example, in the manner of a sharkskin. This surface profile can be produced by a corresponding processing of the surface or by a corresponding coating.

The invention is illustrated in an embodiment example and briefly described below

FIG. 1 shows a hot wind source as a so-called Pebble Heater 30. The Pebble Heater is a special type of regenerator. Here, cold wind is passed through a previously heated with burner gas firing stocking of bulk material, and withdrawn as a heated hot blast.

The hot blast outlet of the Pebble Heater 30 or regenerator opens into a hot blast line, not shown here, which is connected to the hot air lance or is connected to the hot blast line in the inflating operating position.

Since the converter operation is a batch operation, the hot blast only for the time of the batch operated To be available. Between the batches, the burner is then operated in the Pebble Heater, and this heats up the stocking of bulk material in this time again until hot wind is generated again by cold wind supply in the Pebble Heater for the next converter batch.

FIG. 2 shows the hot blast lance 10 in the operating position in which it is retracted in a converter 20. In converter operation, the components listed above in the text are additionally added via the bottom nozzles and also oxygen is blown in on the bottom side. This presentation is the above already made statements again.

The process runs in the manner already described above.

FIG. 3 now shows the in FIG. 2 illustrated hot blast lance 10 in its layer structure according to the invention.

The innermost tube is usually the so-called actual blowpipe dar. FIG. 3 shows only one side of a short section a longitudinal section through the hot blast lance. The dashed line represents the central axis of the hot blast lance. The wall of the hot blast lance 10 is shown here for simplicity only on one side of the central axis. Nevertheless, the layer or sheath sequence becomes clear from outside to inside.

The outer shell 1 forms here together with the inner shell 2 a composite with a gap 3. The intermediate space 3 is designed as a cooling jacket, which is flowed through by a coolant. This inner shell 2 can be coated with a thin layer 41, which serves as a transition layer to a another inner jacket 42 is used. This jacket 42 may already be a ceramic tube, or a ceramic coated tube. The innermost tube or the innermost jacket 45 may be provided as a floating tube, and at least on the innermost surface in turn be provided with a corrosion and / or abrasion resistant layer 46.

The given between the innermost floating jacket or tube 45 space 5 can be filled with rock wool, or other thermally well insulating materials.

A structure like this follows several measures at the same time, namely on the one hand a good thermal insulation from the inside out, so that the hot air does not cool in the hot blast lance, and on the other hand causes the coating system that a good corrosion and abrasion resistance.

In particular, the floating support of the innermost tube or shell 46 allows for different thermally induced linear expansion of different materials used.

This can also be taken into account again in the case of coatings, in that, as described above, adhesion-promoting layers or liners can at least partially absorb thermal stresses in a compensatory manner.

reference numeral

1

outer coat

2

inner coat

3

gap

4

Another inner coat

5

gap

41, 43, 44, 46

coatings

42

coat

45

innermost coat, floating

Claims (13)

1. Hot-blast lance for use in metallurgical processes, such as for example steel production, with which hot air can be blown in above a molten bath of a steel converter, which consists of an outer shell (1) and at least one inner shell (2) and an innermost shell, and arranged between the outer shell and an inner shell is at least one intermediate space (3) or cooling channel through which coolant flows, characterized in that the innermost shell is defined by an innermost lance tube through which hot air can flow, and the inner shell (2) or the innermost shell (4) consists at least partially of a thermally insulating further shell (4), or a thermally insulating shell, or is provided with such a shell, or is coated with a thermally insulating layer, and the innermost shell (45) is mounted in the hot-blast lance in a floating manner.
2. Hot-blast lance according to Claim 1, characterized in that the inner shell (2) or the innermost shell (4) is provided at least on the inner side with a protective layer (41) or (46).
3. Hot-blast lance according to Claim 1 or 2, characterized in that the inner shell (2) or the innermost shell (4) consists of a number of layers (41, 42, 43, 44, 45, 46), and in that at least the innermost of these layers, to be specific layer (46) or layer (43), consists of an abrasion- and/or corrosion-resistant material.
4. Hot-blast lance according to one of Claims 1 to 3, characterized in that the inner shell (2) or the innermost shell (4) consists of a ceramic material or is coated with the same.
5. Hot-blast lance according to Claim 3 or 4, characterized in that the abrasion- and/or corrosion-resistant material or the ceramic material is provided on the side adhering to the inner or innermost shell with a temperature-resistant adhesion promoter or liner.
6. Hot-blast lance according to Claim 5, characterized in that the adhesion promoter or liner is elastic in such a way that it compensates for the difference in the coefficient of expansion of the inner or innermost shell and the abrasion- and/or corrosion-resistant material or the ceramic material.
7. Hot-blast lance according to one of Claims 1 to 6, characterized in that the abrasion- and/or corrosion-resistant material or the ceramic material consists of a system of layers in which the surface facing the hot air consists of a dense ceramic material and the surface facing away from the hot air consists of a ceramic foam material.
8. Hot-blast lance according to one of Claims 1 to 7, characterized in that at least one intermediate shell or intermediate space (3) is arranged between the inner shell (2) and the outer shell (1) and is flowed through by a coolant.
9. Hot-blast lance according to Claims 1 to 7, characterized in that, to ensure protection from heat transfer by thermal radiation, the space (3) between the outer shell (1) and the inner shell (2) is filled with a thermal radiation inhibitor or is provided with a thin thermal radiation inhibiting layer.
10. Hot-blast lance according to Claims 1 to 7, characterized in that arranged between the outer shell (1) and the innermost shell (46) is a temperature control channel, which during hot-air blasting operation can likewise be flowed through by hot air.
11. Hot-blast lance according to one of Claims 1 to 10, characterized in that at least the inner shell (42) or the innermost shell (45) consists along its longitudinal direction of a number of pieces or sleeves, which are designed as partially overlapping at the points of contact of the individual pieces or sleeves.
12. Hot-blast lance according to one of Claims 1 to 11, characterized in that the innermost surface (46) or coating surface that is directly in flow connection with the hot air is structured or microstructured in a flow-resistance and/or adhesion reduced manner.
13. Use of a hot-blast lance according to one of Claims 1 to 12, for blowing in hot air above a steel bath and/or a pile of scrap and/or a pile in a steel converter.

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