EP0013871A1 - Process and apparatus for cooling burnt material such as sinters or pellets - Google Patents

Abstract

To cool fired material (8), such as sinter or pellets, it is broken after leaving a continuously operating furnace system (1) and cooled in a separate cooler (11) with blown air. To return the cooling heat to the combustion process, the cooling air is pressed in countercurrent through the material (8) passing through the cooler (11) and then the entire air quantity is fed to the heat treatment zone (5) in the furnace system (1). A device for carrying out this cooling process has a standing shaft cooler (11) which contains an annularly movable, annular push table (18). The push table (18) interacts with a pyramid or conical material slide (21) which is arranged coaxially to the shaft cooler (11) at a distance above the push table (18) and with its tip below the mouth area (22) one via a crusher ( 9) or the like. Filling shaft (10) connected to the material outlet of the furnace system (1). The inlet opening (14 ') for the cooling air is provided in the area of the push table (18) and the shaft cooler (11) connects with a tapered upper part (11a) to a pipe (15,) leading to the heat treatment zone (5) of the furnace system (1). 17).

Description

The invention relates to a method for cooling fired material, such as sinter or pellets, which is broken after leaving a continuously operating furnace system and cooled in a separate cooler with blown air, and to an apparatus for performing this method.

The increasing demand for crude steel and pig iron has to be met predominantly by procuring processed, ie fine-grained iron ores. For the agglomeration of these fine-grained ores and concentrates, on the one hand the sintering process and on the other hand the pelletizing has prevailed, and both the sintering, in particular the sintering of fine ores, and the firing of pellets is carried out almost exclusively in continuously operating furnace systems, i.e. traveling grate systems, because this is the only way to achieve the required high throughput. The material leaves the furnace system after passing through an ignition zone and a heat treatment zone as a hot sinter cake or as a fired pellet layer and must subsequently be cooled in its own, also continuously working coolers, for which purpose it is broken and subjected to cooling air. To cool this hot, lumpy Up to now, materials such as coolers, pressure ring coolers, cell coolers or stripping coolers have been used, which differ in their design, but work according to the same process, namely the hot material is distributed over a large area in a thin layer and cooled in cross flow. As a result, very large amounts of cooling air are necessary, which means that the temperature of the air after cooling is only about 200 ° C, which means that it is uneconomical to return this cooling heat for heat treatment of the material in the furnace system and the exhaust air is usually used without further use Atmosphere is released. Another disadvantage of this cross-flow cooling is that the material has to be screened before entering the cooler. This heat screening of the fine particles is necessary in order not to hinder the passage of the cooling air through the lumpy material.

Attempts have also already been made to recycle at least part of the cooling heat during the combustion process by dividing the cooling air flow after cooling and only the warmer part, which reaches a temperature of approximately 340 ^° C., being fed to the combustion process. However, the heat content of the remaining cooling air is lost here.

To burn pellets, it is also already known to combine a traveling grate system with a shaft furnace, the pellets being burned and cooled in the shaft furnace and the cooling air penetrating directly from the cooling zone into the burning zone of the harmful furnace. This entails a considerable amount of construction work for the shaft furnace, which also only has a low throughput, so that a belt system must be assigned at least two, but preferably three to six, shaft furnaces.

From the clinker industry itself is already a pure countercurrent cooling is known, for which a shaft cooler directly adjoining a rotary kiln is used. However, this "shaft cooler is equipped with a roller grate and is therefore unusable for sintering or pelletizing plants. A design of such a cooler for higher capacities, as is required, for example, in sintering plants, would lead to unacceptable wear on the roller grate Cooling air circulated and not used for a burning process.

The invention is therefore based on the object of specifying a cooling method of the type described at the outset, which allows the heat from the cooling to be virtually completely returned to the combustion process in an economical manner without any particular effort. In addition, a simple, practical device for performing this method is to be created.

To achieve this object, the cooling air is pressed in countercurrent through the material passing through the cooler and then the entire amount of air is fed to the heat treatment zone in the furnace system. Counter-current cooling allows the required amount of cooling air to be kept small in comparison to cross-flow cooling, and the cooling air is warmed up as it passes through the material to be cooled, practically up to the entry temperature of this material into the cooler, ie approximately to 500 to 600 ° C. Because of this high temperature, economic and complete utilization of the cooling air is possible and the entire cooling heat can be returned to the combustion process. This results in a saving of additional fuels for the heat treatment zone of the furnace system, which not only improves the efficiency of the entire system, but also simplifies environmental protection measures, since pollutants mainly come from the fuel. In addition, since the entire cooling air flow is fed to the furnace system, no dedusting of cooling air to be discharged from the cooler into the open is required. In addition, if the flow rate of the countercurrent cooling air is correctly designed, a wind separation and thus the separation of the hot fines in the material to be cooled can be carried out before cooling in the simplest way, so that there is a separate hot screening after breaking the material and before the radiator is unnecessary.

In a particularly favorable further development of the method according to the invention, the fired material layer emerging from the furnace system is separated in height into a lower, hotter and an upper, cooler part, and only the hotter parts are passed on to the cooler. As measurements have shown, the fired material layer coming out of the furnace has a temperature of approx. 1100 ° C in its lower third, while its upper part, about two thirds of the layer height, has cooled almost to room temperature. The temperature transition does not occur continuously, but in narrow thickness ranges. The material layer can therefore be split into a hot and a cold part, whereby only the hot material part of approx. 900 ° C needs to be fed to the cooler and the cold part of approx. 30 ° C can be conveyed directly to cold screening. As material with a higher temperature reaches the cooler, the cooling air is also heated to a higher temperature and is more economical to use. In addition, the amount of material to be cooled remains less.

Since there is also a wind sifting during cooling, can for separating the hot and entrained goods, which are entrained by the cooling air, that is the hot fine fraction of the material to be cooled, according to the invention the air stream coming from the cooler is passed through a solids separator before the heat treatment zone.

In order to be able to carry out the method according to the invention in a simple manner that meets all requirements, a device with a standing shaft cooler is used, which according to a further development of the invention is characterized in that the shaft cooler receives a known, transversely movable, ring-shaped sliding table, which cooperates with a pyramid or conical material slide, which is arranged coaxially to the shaft cooler at a distance above the drawer and with its tip below the mouth area of a filling shaft connected via a crusher or the like to the material outlet of the furnace system, and that Inlet opening for the cooling air is provided in the area of the sliding table and the cooler connects with a tapering upper part to a pipeline leading to the heat treatment zone of the furnace system. The material that is constantly introduced into the cooler via the filling shaft is divided into a ring by the interaction of the material slide and the sliding table and is continuously discharged. The cooling air flowing from the bottom up finds a large contact surface and can penetrate the material well. This results in a very even cooling of the material, because on the one hand the discharge speed for the material on the outer circumference of the push table is greater than on the inner circumference and on the other hand because of the cone of bulk the mass flow density of the cooling air on the outside is greater than in the center of the shaft cooler, so that the greater Throughput speed of the material with the greater cooling speed conforms due to the greater mass flow density of the air. The drawer, which is driven eccentrically and oscillating, does not require any special design effort and is extremely wear-resistant. It allows the material to be discharged over a very large area, so that a high throughput can be achieved even with a low overall height of the cooler.

It is also advantageous if the shaft cooler according to the invention has guide plates or the like which run around the sides in the area of the material chute and which, together with the material chute, form a material guide directed towards the drawer. This not only ensures trouble-free throughput of the material through the cooler, but also forces the cooling air blown between the hot and the already cooled material to flow entirely through the migrating material and provide the full cooling effect.

Acceleration of the cooling can also be achieved in that, according to the invention, air passage openings are provided in the material chute, through which cooling air can also penetrate into the material sliding on the chute.

Since the material introduced into the cooler is air-sifted on the surface by the escaping cooling air and thus hot return material is contained in the cooling air flow, a solid separator can advantageously be installed in the pipeline between the cooler and the heat treatment zone, with which this hot return material is separated from the cooling air .

In a particularly advantageous embodiment of the invention, the cooler is preceded by a separating device for dividing the fired material into a hotter and a cooler part, the separating device being a conveyor leading to the cooler fill shaft shaft for the hotter and a leading shaft for cold screening or the like for the cooler parts. Since the material layer coming from the kiln has very different temperatures in height, such a separating device makes it possible to split off the cooler material, which no longer has to be fed to the cooler and can immediately be cold-screened. The remaining hotter part of the material is supplied to the filler shaft of the cooler and cooled in the cooler, whereby on the one hand hotter air gets from the cooler into the heat treatment zone and on the other hand only a smaller amount of material has to pass through the cooler.

In order to achieve a simple separation of the material layer into a hotter and a cooler part, the separating device according to the invention consists of a wedge-shaped hammer tool, for example a pneumatic hammer, which strikes from the bottom up and a guide grate which brings the fired material from the furnace system into the effective range of the tool od. The like. The hot material coming from the furnace system is gripped by the guide grate, deflected accordingly in its path and fed to the tool from above, whereby it is split up. The wedge-shaped tool not only separates the material pieces, but also forms sliding surfaces for the separated material parts.

It is advantageous if the guide grate has end sections that are adjustable relative to the tool center plane. This adjustment of the grate relative to the direction of action of the tool makes it possible to vary the ratio of the split material parts and the temperature or amount of the portion to be supplied to the cooler or the cold sieve to influence.

• Eig. 1 die gesamte Sinteranlage,
• Fig. 2 und 3 zwei Ausführungsbeispiele eines erfindungsgemäßen Kühlers und
• Fig. 4 eine erfindungsgemäße Trenneinrichtung.

In the drawing, the subject of the invention is shown purely schematically, namely show

• Own 1 the entire sintering plant,
• 2 and 3 two embodiments of a cooler according to the invention and
• Fig. 4 shows a separation device according to the invention.

In a continuously operating furnace system 1 for sintering fine ores or the like, the material to be sintered is applied via a feed device 2 to a traveling grate 3, which leads it through an ignition zone 4 and a heat treatment zone 5. An induced draft fan 6 directs the cooler exhaust gases resulting from the sintering process to the outside, while the hotter exhaust gases are conveyed back into the ignition zone 4 via a fan 7. The finished sintered sinter cake 8 falls off from the traveling grate 3 in larger pieces after leaving the furnace system and comes into a sting crusher 9, where it is broken up into small pieces. The broken sinter cake then passes through a filling shaft 10 into a shaft cooler 11, which it leaves cooled by an emptying shaft 12 and a discharge chute 13 (arrows 8 '). To cool the sintered material, cooling air is blown into the cooler 11 via a fan 14, where it penetrates the feed in counterflow. The heated cooling air is drawn off via a pipeline 15, fed to a solids separator 16, which frees it from the hot return material, and then fed entirely through line 17 to the heat treatment zone 5, so that practically all of the cooling heat can be reused in the sintering process.

The shaft cooler 11, which can have a round or angular cross section, has an upwardly tapering upper part 11a, which is connected to the pipe line 15 connects, and a funnel-shaped lower part 11b, which merges into the drainage shaft 12. The shaft cooler 11 receives an annular push table 18, which is mounted so as to be movable transversely on a cross support 19 and can be set into eccentric or oscillating movement by means of a drive 20. At a distance above the sliding table 18, a conical or pyramid-shaped material slide 21, which interacts with the sliding table 18, is fixedly mounted on the cross support 19. The tip of the material slide 21 lies below the mouth region 22 of the filling shaft 10, so that the broken sintered material 8a to be cooled is applied to the slide table 18 evenly distributed through the material slide 21 and evenly on the outside of the slide table and through the gap between the slide table movement Drawer and material slide is carried out on the inside of the drawer. Baffles 23 rotating on the side of the shaft cooler serve to regulate the material flow and to direct the cooling air through the material flow. The cooling air is then blown into the shaft cooler 11 by the blower 14 in the area of the push table 18, that is to say between the already cooled material and the still hot material, through inlet openings 14 ′ and penetrates the material to be cooled in counterflow, as indicated by the arrows 24. The filling shaft 10 is now long enough so that the sintered material 8a introduced is self-sealing and only minimal amounts of cooling air can escape through the cooling shaft. The same applies to the emptying shaft 12 if it is long enough, but a known double flap system can also be used for sealing with a low overall height.

In order to achieve accelerated cooling, additional air passage openings 25 can be provided in the material chute 21, which is indicated in the exemplary embodiment according to FIG. 3.

As illustrated in FIG. 4, the cooler 11 can now be preceded by a separating device 26 which divides the sinter cake 8 into two parts in terms of height. As measurements have shown, the sinter cake is namely much hotter on its side resting on the traveling grate 3 than on its free surface, so that only the hotter portion needs to be fed to the cooler 11 through this separating device 26 and the cooler portion is immediately subjected to cold screening, for example can be. The separating device 26 now consists of a wedge-shaped pneumatic hammer 27 which strikes from below and which interacts with a guide grate 28. The sinter cake pieces 8b falling off the traveling grate are gripped by the guide grate 28 on both sides and brought into the effective area of the hammer 27, which divides them into a cooler portion 8b 'and a hotter portion 8b ", which portions are discharged via separate conveyor shafts 29a; 29b to be able to vary the ratio between the two parts, the guide grate 28 has adjustable end sections 30, as a result of which the action level of the hammer 27 can be adjusted relative to the height of the sinter cake pieces 8b and the part 8b "supplied to the cooler can be selected in terms of quantity and temperature.

Claims (10)

1. A method for cooling fired material, such as sinter or pellets, which is broken after leaving a continuously operating furnace system and cooled in a separate cooler with blown air, characterized in that the cooling air is pressed in countercurrent through the material passing through the cooler and then the entire amount of air is fed to the heat treatment zone in the furnace system. 2. The method according to claim 1, characterized in that the fired material layer emerging from the furnace system is separated in height into a lower, hotter and an upper, cooler part and only the hotter parts are passed on to the cooler. 3. The method according to claim 1 or 2, characterized in that the air stream coming from the cooler is passed through a solid separator before the heat treatment zone. 4. Device for performing the method according to one of claims 1 to 3, with a standing shaft cooler, characterized in that the shaft cooler (11) receives a known, transversely movable, annular sliding table (18) with a pyramid or Conical material slide (21) cooperates, which is arranged coaxially to the shaft cooler at a distance above the drawer and with its tip below the mouth area (22) of a via a crusher (9) or the like. In connection with the material outlet of the furnace system (1) Filling shaft (10), and that the inlet opening (14 ') for the cooling air is provided in the area of the drawer and the cooler with a tapered upper part (11a) to a to the heat treatment zone (5) of the furnace Plant (1) leading pipeline (15, 17) connects. 5. The device according to claim 4, characterized in that the shaft cooler (11) in the region of the material chute (21) has laterally circumferential guide plates (23) or the like, which together with the material chute form a material guide directed onto the slide table (18) . 6. Apparatus according to claim 4 or 5, characterized in that in the material slide (21) air passage openings (25) are provided. 7. Device according to one of claims 4 to 6, characterized in that in the pipeline (15, 17) between the cooler (11) and the heat treatment zone (5) a solid separator (16) is installed. 8. Device for performing the method according to claim 2, characterized in that the cooler (11) is preceded by a separating device (26) for dividing the fired material (8b) into a hotter (8b ") and a cooler part (8b ') , wherein the separating device has a feed shaft (29b) leading to the cooler filling shaft for the hotter parts and a feed shaft (29a) leading to cold screening or the like for the cooler parts. 9. The device according to claim 8, characterized in that the separating device (26) from a bottom-up wedge-shaped hammer tool, for example pneumatic jack (27), and one of the fired material (8b) from the furnace system (1) in the effective range of Tool-carrying guide grate (28) or the like. 10. The device according to claim 9, characterized in that the guide grate (28) relative to the tool center plane has adjustable end portions (30).

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