EP0904415B1 - Device for producing sponge iron - Google Patents

Description

The invention relates to a device according to Preamble of claim 1.

When reducing lumpy iron oxides in one Reduction shaft with dusty and carbon monoxide rich Reduction gas from a melter gasifier in an iron ore reduction smelter only part of the gap volume of the fill in the reduction shaft to pick up the dust that comes with the Reduction gas entered in the reduction shaft will be used. In addition to the dust that comes with the Reduction gas is entered in plants, at those of the reduction shaft via downpipes with the Smelting gasifier is connected, an additional Amount of dust with the gasifier gas through the downpipes and Discharge devices in the lower area of the reduction shaft registered. The dust content of this Gasification gas is several times higher than that of the specifically inserted in the reduction shaft Reduction gas, previously in hot gas cyclones was dusted. In addition to this dust is over the Downpipes additionally the dust due to the wind classification of the discharged sponge iron and if necessary of the calcined aggregates by the inflowing Carburetor gas is returned to the reduction shaft. The total dust leads to a stronger one Dusting of the lower area of the reduction shaft, to form channels, to get caught the bulk as well as an uncontrolled discharge of the sponge iron through the discharge devices. It is particularly disadvantageous that the over Downpipes from the melter into the reduction shaft dust coming from tar and only for Partially degassed coal particles and other components, which lead to agglomerate formation.

If the iron oxide fill is heavily dusted in the bustle or inlet area of the reducing gas the pressure difference between that increases Smelting gasifier and the lower part of the reduction shaft and accordingly of the downpipes and the discharge screws are pouring strongly dusty gasifier gas, through which this one direct access to the little dusty bed in has the middle of the reduction shaft. By the increased The wind sifting acts in the pressure difference Downpipes are getting stronger, the dust content of the flowing back Gases are getting higher and the fill in the lower area of the reduction shaft with the cycle dust are so enriched that because the high frictional forces in the dust-enriched Very small pressure differences are sufficient, to get the bed stuck, leading to the well-known phenomena of channel formation and the undisturbed flow of the gas with very high Dust content from the melter gasifier into the reduction shaft has the consequence. Part of the dust becomes continue from the lower part of the reduction shaft transported upwards into the reduction zone and also leads to dusting of the fill and to a channel formation. Such strong dustiness of the Bustle area can occur if there is too much undersize is entered with the coal when in the coal mixture a larger amount of coal is used, which disintegrates strongly at high temperatures, if extreme High temperatures occur in the carburetor lead to a greater coal breakdown, with a stronger one Ore decay in the reduction shaft and at one Failure or partial failure of the dust return. If the reduction shaft needs such cases quite a long time before he Has cleaned dust because part of the dust gets through formed channels are always promoted upwards becomes.

Part of the remaining gap volume is filled with fine particles, which are introduced with the raw material and partly in the reduction shaft by reducing the iron carriers or calcining the additives. The absorption capacity of the reduction shaft for this is severely limited, since a larger part of the gap volume for the flow of the reduction gas through the bed must be preserved, so that the minimum amount of specific reduction gas required for the reduction of the iron oxides and the calcination of the additives with moderate and limited pressure loss can be passed through the reduction shaft. If a certain pressure loss, which is dependent on the grain size, the grain composition and the gap volume of the bed, is exceeded, the known "hanging" of the bed and the formation and passage of part of the reducing gas through the channels occur without being involved in the reduction process. The result of this is a low degree of metallization, a low carburization of the sponge iron, a low degree of calcination of the additives, a low performance of the plant and a poor quality of the pig iron. For normal operation, therefore, a minimum specific amount of the reducing gas is required, which is passed through the reduction shaft without channel formation and without the bed becoming stuck. This specifically required amount of reducing gas depends on the degree of oxidation of the reducing gas, the iron content of the iron oxides, the decomposition properties of the iron oxides used at low temperatures, the amount and the decomposition properties of the additives and other factors and is approximately 1050 m _n ³ reducing gas per ton of iron oxides. Because of the high temperatures of the gasifier gas and because of a low pressure drop in the bed serving as a gas barrier for the non-dedusted gasifier gas via the downpipes, which is given by a large cross-section of the reduction shaft in the lower area, bricked-up hot gas cyclones with moderate efficiency are used as dedusting units for the reducing gas used, so that this still contains considerable amounts of dust and thus there is a relatively small margin for the specific amount of reducing gas upwards. By introducing the reducing gas in the bustle area only at the circumference of the reduction shaft, the part of the gap volume of the bed still freely available for the separation of the dust in the radial center of the reduction shaft is hardly used, so that the enforceable specific amount of reducing gas is even smaller and the outer ring of the bed in the area the gas inlets are dusted more than necessary. In this outer ring, the channel formation and the filling get caught. The larger the diameter of the reduction shaft, the smaller is the specific amount of reducing gas which can be passed through the reduction shaft without getting stuck and without channel formation.

A device is already known from JP-A-52294127 for the production of sponge iron from iron oxides in a reduction shaft using a reduction gas known. This will work across several in the same Height arranged on the circumference of a reduction shaft Gas inlets introduced into the reduction shaft. In addition, this is below the level side gas inlets another gas inlet for the Reduction gas in the radial center of the reduction shaft intended. This gas inlet is through the inner open end of a radially from the outside to the middle of the reduction shaft pipe formed, which is closed in its longitudinal direction and the reducing gas through its outer open end is fed. This measure is intended to more uniform reduction of iron oxides over the Shaft cross-section can be reached. The problem the introduction of a dust-laden reducing gas is not discussed here.

Furthermore, US-A-4 118 017 discloses an apparatus for the production of sponge iron from iron oxides in a reduction shaft using a hot reducing gas, which is about in the middle Height of the reduction shaft over several others Scope arranged gas inlets is supplied. At the the lower end tapers, this end consisting of several interlocked frustoconical sections. On the outside Each of these sections contains gas inlets for used as cooling gas for the sponge iron cold reducing gas. Again, is not on the problem of using a dust-laden Reduced gas received.

It is therefore the object of the present invention to improve a generic device to the extent that carburization and intensified reduction of the sponge iron are obtained in the radial little dusty bed for the middle area Separation of dust is used that a larger one Pressure loss in the bed in the lower area of the Reduction shaft occurs, so that hot gas cyclones with a greater pressure loss and thus a higher one Degree of separation for dedusting as a reducing gas used gasifier gas can be used that the amount of the down pipes in the reduction shaft flowing dusty gasifier gases is severely limited, and that by an even Dusting of the entire bed no additional Pressure difference across the connecting lines or Downpipes between the melter and the lower part of the reduction shaft occurs.

This object is achieved by the characterizing Part of claim 1 specified features solved. Advantageous further developments of the invention Device result from the subclaims.

Fig. 1

einen senkrechten Schnitt durch einen Reduktionsschacht,

Fig. 2

einen horizontalen Schnitt durch den Reduktionsschacht nach Fig. 1 zwischen dem Bustlebereich und dem Bereich der Kanäle für die zusätzliche Einleitung von Reduktionsgas, und

Fig. 3

einen senkrechten Schnitt durch einen Kanal für die Zuführung von Reduktionsgas.

The invention is explained below with reference to an embodiment shown in the figures. Show it:

Fig. 1

a vertical section through a reduction shaft,

Fig. 2

a horizontal section through the reduction shaft of FIG. 1 between the bustle area and the area of the channels for the additional introduction of reducing gas, and

Fig. 3

a vertical section through a channel for the supply of reducing gas.

The one from above, i.e. above the reduction zone via manifolds 4, of which only two in FIG. 1 are reproduced, fed cylindrical reduction shaft 1 has a flaring down Cross section and has a in its upper area A. Taper of about 2 °, in its middle, about 5 m high area B a taper of about 0.5 ° and in its lower area C, about 2 m high, has a conicity from 2.5 ° to. Furthermore, he has in his lower Area of several funnel-shaped product outlets 5, only two of which are shown in FIG. 1 and six in FIG. 2 are. The preferably funnel-shaped Extensions or connecting lines 5a of the product outlets 5 lead directly into the horizontal or slightly arched bottom of the reduction shaft 1. The product outlets 5 are by internals made of refractory material, namely partitions 9 and a conical block 10 in the radial center of the reduction shaft 1 with water or nitrogen-cooled Brackets 6 formed. A water-cooled Carrier 12 with a protective tube 13 surrounding it and insulation in the lower area between them eccentrically arranged tubes as well as a placed on the carrier 12 and down open channel 11 in the form of a half-pipe shell with elongated side walls is shown in Fig. 3. The carrier 12 with the channels 11 are above the product outlets 5 arranged and are with its radially inner end on the brackets 6 of the Blocks 10 supported from refractory material. In the Channels 11 and lines 8 are reducing gas from the outside initiated, as indicated by arrows 15. In the area of the introduction of the reducing gas the side walls of channels 11 are drawn deeper and the lining is carried out more to horizontal Areas on which the deposited dust lies can stay to avoid. A larger gradient can can be achieved when the gas connections 15 laterally and be arranged obliquely with respect to the carrier 12. Located at the lower end of the connecting lines 5a each advantageous in the figures Discharge device, not shown, for the sponge iron.

A normal operation of such a system with the Initiation of a hot, dusty and carbon monoxide rich Reduction gas only on the circumference of the reduction shaft 1 via a bustle channel 2 and reducing gas inlets 3 is when using piece ore only good with smaller ones and when using pellets Quality possible with larger reduction shafts. For large systems that run on normal raw materials it is almost inevitable that part of the reducing gas in the radial center of the Reduction shaft 1 is initiated to a stable Operation in a wider performance range and with more scope for the specific amount of reducing gas, the dust content of the reducing gas and the To achieve raw material selection. A diameter of the Reduction shaft of about 5 to 6 m can serve as a limit viewed between these two embodiments become.

With larger reduction shafts and when used of a hot, dusty and high carbon monoxide Reducing gas are thus in the lower range of the Reduction shaft several funnel-shaped product outlets 5 formed by internals made of refractory material, that of the partitions 9 and the conical Block 10 in the middle area and the with the holders cooled with water or nitrogen 6 are provided through the bottom of the reduction shaft 1 protrude into the internals. These brackets also serve as supports for the water-cooled carrier 12 on which the channels 11 for the introduction of the reducing gas into the lower, predominantly radially central area of the reduction shaft 1 can be hung. Through the bricked up, preferably funnel-shaped connecting lines 5a on the bottom of the reduction shaft 1 welded or with flange connections are attached and the funnel-shaped product outlets Extend 5 is a steep one, for slipping of the material required angle and at the same time a greater height of the bed than gas barrier for reducing the pressure difference between the melter and the reduction shaft 1. The introduction of part of the reducing gas over the inlets 15 in the radially central region of the Reduction shaft 1 should be about 2 m below the Level of the side reducing gas inlets 3 through at least one channel 11 each made of heat-resistant Steel and / or a water-cooled line 8, the preferably directly above each product outlet 5 or are arranged above each intermediate wall 9, respectively. The channels 11 for the introduction and distribution of the reducing gas are in the form of half-pipe shells made of heat-resistant steel with extended side walls executed and from above on the water-cooled tubular support 12 placed so that the extended sides of the half-pipe shells after form open channels 11 at the bottom. This version has the advantage that the wide horizontal or light downward sloping open channels 11 not with material or clog dust that very large Areas of the bed for the introduction of the reducing gas stand by and that through a quick downward sinking and strongly loosened fill good conditions for deposition in this area the dust from the introduced reducing gas and for the removal of the in the upper areas separated dust can be created. The dusty one Reducing gas is applied across the entire cross section of the reduction shaft 1 access in allows less dusty areas of the fill.

The lower volume part of the reduction shaft 1, which is almost a third of the volume of the Reduction shaft 1, which as Gas barrier serves and does not participate in the reduction process, is by introducing colder reducing gas for a stronger carburization and residual reduction of the sponge iron. This allows the reduction zone and thus the entire reduction shaft be built smaller and lighter, which makes Medium-sized reduction shafts with a total weight of about 1500 tons and more as well as one large span of the beams a considerable advantage results.

A higher carbon content and a higher metallization of the iron sponge reduce the energy requirement of the melter gasifier and contribute to a more uniform Operation and better quality of cast iron at. The reducing gas is therefore on the Inlets 15 with a lower temperature than that of the remaining reducing gas supplied to better Conditions for carburizing the sponge iron in the to create the lower region of the reduction shaft 1. A 50 ° to 100 ° C lower is considered optimal Temperature for this partial flow of the reducing gas to watch. Another cooling down to about 650 ° C, which is ideal for carburizing the sponge iron would, however, would cool down in the Center of the shaft and thus to a lower metallization lead in this area.

By introducing a colder reducing gas despite the strongly exothermic Boudouard reaction the bed in this for agglomerate formation critical area cooled and in connection with relieving the load from the weight of the bulk located material column through the water-cooled Carrier 12 the formation of agglomerates avoided. As is well known play in the formation of agglomerates from calcined aggregates and from not fully degassed and tar-containing coal particles, their degassing products also contain water vapor, both of which as binders and main components of the agglomerates with trapped iron sponge particles and the rest Dust components act, the temperature of the Filling and pressing a crucial Role. Above once agglomerates are formed the bulk material sinks in the overlying areas of the Reduction shaft 1 at a lower speed. There may also be areas in the reduction zone excessive dust and local overheating due to the strongly exothermic Boudouard reaction come. As an advantageous training Arrangement of the discharge screws at the lower end of the To view connecting lines 5a. In this version the reduction shaft 1 needs for an exchange or a major repair of the discharge screws no longer being cleared out, thereby long production downtimes and high start-up costs be avoided.

Because the channels 11 are open at the bottom, are the best conditions for the separation and the Removed dust is removed. The Half-pipe shells of channels 11 with the extended ones side walls can be made in one piece or with very few welds at uncritical points are manufactured and serve as wear protection and Thermal insulation for the water-cooled beams 12. Um to keep the heat losses of the beams 12 low, they are made with the additional protective tube 13 heat-resistant steel. The lower, temperature more stressed area between the two tubes lying eccentrically to each other stuffed with insulating wool 14, and the protective tube 13 is preferably in the upper region transverse to it Slotted axially at a certain distance to a Deformation due to different heat loads avoid. The carrier 12 and / or the lines 8 are in the wall of the reduction shaft 1 and on the embedded in the partitions 9 and the block 10 Brackets 6 supported so that none long and strong carrier 12 and / or lines 8 for the construction of large reduction shafts required are. It is advantageous to use the conical block 10 embedded brackets 6 for supporting the Pipe support 12 and the channels 11 to use.

When choosing the conicity of the reduction zone of the Reduction shaft 1 are the amount of dust entered, the swelling of the iron oxides, the decay properties and grain composition of the iron oxides and additives and the content of carbon monoxide in the Reducing gas to be considered. In the area of the side inlets 3 for the reducing gas up to a height of about 2 m above which the largest Dust and the greatest risk of sticking of the fill will be high conicity of about 2.5 ° so that the bed opens and can pick up the dust. Another strong one Reducing the cross section upwards would be for that Intake of the dust is beneficial, but it would too a greater increase in the specific pressure drop in the upper areas of the reduction shaft 1 due to an increase in gas temperature or gas velocity to lead. In this area the Carburizing the sponge iron and heating the entire area due to the strongly exothermic Boudouard reaction taking place, the decrease in the amount of gas by carburizing the sponge iron with a Increase in the amount of gas due to intensive calcination the aggregates are more than balanced. At an increase in the gas temperature of 80 ° C specific pressure loss with constant cross-section increase up to 15%. For this reason a smaller one in this approximately 3 to 5 m high area Taper angle of about 0.5 ° selected. For one small angle and a larger specific pressure drop due to more dust than in the Upper areas also speak of greater weight the material column above. This allows a higher pressure drop and more dust be approved in this area. In the area about a taper of about 2 ° is considered viewed optimally.

The loading of the reduction shaft 1 with iron oxides, which may be mixed with additives are done via the in the upper area in a circle with the center in the longitudinal axis of the Reduction shaft 1 arranged manifolds 4. Their number is at least twice that Number of product outlets 5. For larger reduction shafts the manifolds should be in two Circles and larger numbers can be built in to the To minimize segregation of the corrugation and a reinforced Gas flow in the edge area and in the middle the reduction shaft, due to a strong M-profile, to avoid. The distribution pipes 4 are symmetrical arranged to the axes of the product outlets 5. This ensures that the bed below the manifolds 4, which are richer in fine grain and which is at a lower speed than the coarser bed sinks through two distribution pipes 4, which is directly above the two catchment areas the discharge screws, between the respective channel 11 and its two neighboring ones Partitions 9 are located at an increased speed sinks.

The in the middle area of the reduction shaft 1 through the inlets 15 introduced amount of the reducing gas is medium in the case of reduction shafts Size advantageous at about 30% of the total Reducing gas, so that a large outer ring with about 70% of the reducing gas over the Bustlekanal 2 and the inlets 3 is supplied. By the reduction of the supplied via the Bustlekanal 2 The amount of gas is also reduced by about 30% Loading of the fill in this area with the Dust around 30%, causing the formation of channels and stuck the bed in a normal Operation is no longer expected. A smaller one Part of the introduced via the downwardly open channels 11 Reducing gas is also in the outer ring, the main amount, however, in the radially central area into the less dusty bed of the reduction shaft 1 flow into it. With large reduction shafts becomes the introduced amount of the reducing gas in the radially central area of the reduction shaft increase accordingly.

The carriers 12 also carry one large part of the weight of the material column above, so they put the bulk in the production outlets 5 relieve and loosen it up and in this funnel-shaped areas narrowed downwards does not come to bridging.

The channels 11 can be star-like or parallel to each other be installed. The leads to these are laid on a slope so that this through dust deposits and kicking back the bed in the event of pressure fluctuations in the system do not clog.

The elongated side walls of the open to the bottom Channels 11 are stiffened at certain intervals and spacers 16 so that a Narrowing of the canal by pressing together parallel walls avoided by the fill becomes.

Claims (19)

1. Device for producing sponge iron from lumps of iron oxides in a reduction shaft (1), using a hot, dust containing and carbon monoxide rich reduction gas, and the reduction gas is produced in a gas generator by partial oxidation of solid carbon containing materials and introduced, via a plurality of lateral reduction gas inlets (3) arranged at the same level on the circumference of the reduction shaft (1), into the reduction shaft (1) at the lower end of the reduction zone, and the iron oxide lumps are entered in the upper area of the reduction shaft (1) and at its lower end discharged as sponge iron, characterised in that below the level of the lateral reduction gas inlets (3) are provided additional reduction gas inlets (15) in the form of at least one channel (11) which is over its length downwardly open and extends from the outside into the radially central area of the reduction shaft (1).
2. Device according to Claim 1, characterised in that the gas generator is a melt-down gasifier and that the lower end of the reduction shaft (1) is connected via at least one downpipe to the head of the melt-down gasifier for the purpose of delivering sponge iron from the reduction shaft (1) into the melt-down gasifier.
3. Device according to Claim 1 or 2, characterised in that in the lower area of the reduction shaft (1) are formed funnelshaped product outlets (5) by way of installations (9, 10) of refractory material.
4. Device according to Claim 3, characterised in that the installations are composed of radially extending intermediate walls (9) and a conically downward extending block (10) in the central area of the reduction shaft (1) as seen in the radial direction.
5. Device according to Claim 3 or 4, characterised in that the supports (6) for the inner ends of the at least one channel (11) are embedded in the installations (9, 10).
6. Device according to one of Claims 3 to 5, characterised in that a respective channel (11) is arranged above each product outlet (5).
7. Device according to one of Claims 1 to 6, characterised in that each channel (11) is made of a heat-resistant steel and arranged below a water-cooled support (12) which extends in the same direction and is suspended therefrom.
8. Device according to Claim 7, characterised in that the channels (11) are designed as downwardly open semi-tubular cups which are placed on the supports (12) and provided with downwardly extended parallel walls.
9. Device according to Claim 7 or 8, characterised in that the supports (12) are respectively surrounded by a protective pipe (13), and the space between them is filled with insulating wool (14).
10. Device according to Claims 8 or 9, characterised in that the height of the parallel walls reduces towards the centre of the reduction shaft (1).
11. Device according to one of Claims 1 to 10, characterised in that the channels (11) or arranged starlike or parallel to each other.
12. Device according to one of Claims 1 to 11, characterised in that the feeds to the channels (11) have a drop towards the latter.
13. Device according to one of Claims 3 to 12, characterised in that at the lower end of each production outlet (5) is provided a delivery screw.
14. Device according to one of Claims 1 to 13, characterised in that the reduction shaft (1) expands from the top towards the bottom with stacked conicity so that it equals in the lower area from the lateral reduction inlets (3) up to approximately 2 m above thereof approximately 2.5°, from approximately 2 m up to approximately 5 m thereabove approximately 0.5°, and thereabove approximately 2.0°.
15. Device according to one of Claims 3 to 14, characterised in that in the upper area of the reduction shall (1) are provided distributor pipes (4) for feeding iron oxides and additives, if appropriate, the number of which equals double the number of product outlets (5) and which are in the circumferential direction arranged circularly and symmetrically thereto.
16. Process for producing sponge iron of lumps of iron oxides using a device according to Claim 1, characterised in that the reduction gas, which is delivered via the channels (11), has a lower temperature than the reduction gas delivered at the lower end of the reduction zone.
17. Process according to Claim 16, characterised in that the temperature of the reduction gas which is delivered via channels (11) is approximately 50°C lower than the temperature of the reduction gas delivered at the lower end of the reduction zone.
18. Process for producing sponge iron from lumps of iron oxide using a device as in Claim 1, characterised in that the proportion of reduction gas delivered via the channels (11) is approximately 30% of the total volume of the reduction gas.
19. Process for producing sponge iron of lumps of iron oxides using a device as in Claim 1, characterised in that reduction gas introduced at the lower end of the reduction zone is extensively freed from dust.

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