WO2001016382A1 - Device for granulating and comminuting liquid slag or foamed slag - Google Patents

Abstract

The invention relates to a device for granulating and comminuting liquid slag or foamed slag. The slag is impinged upon by steam and/or water. The inventive device comprises a slag tundish (1) and a slag outlet (2) arranged in the bottom of the tundish (1). The outlet (2) for the slag is configured as an annular overflow weir (3), whereby a water and/or steam feed pipe (7) is arranged in a coaxial or concentric position with respect to said annular weir (3), and the discharge openings thereof (12) protrude into the slag discharge pipe or out of said slag outlet (2). Slag melt is used as a foamed slag in the inventive method.

Description

 Device for granulating and crushing liquid slags or foam slags

The invention relates to a device for granulating and comminuting liquid slags or foam slags, in which steam and / or water are applied to the slags, with a slag tundish and a slag outlet opening arranged in the bottom of the slag tundish. The slag tundish can be under pressure.

Methods have already become known for granulating and comminuting liquid slags, in which pressurized water or steam jets have been directed against a slag jet. In WO 95/15402, for example, the melt was introduced under pressure into a mixing chamber and pressurized water vapor or water vapor mixtures were injected into the mixing chamber. Due to the rapid expansion, a pressure is built up in this process, which leads to the ejection of the solidified particles via a diffuser, whereby the kinetic energy of the particles can be used for comminution. In the method according to SU 1 761 704 AI, a steam jet is directed against a free-flowing slag jet, a defined jet speed being maintained for the steam jet, so that the quality of the granules can be improved. Other processes of this type are described, for example, in SU 903 328 A, in DE 32 40 142 AI, in DE 39 19 155 AI, in WO 86/5818 and in DE 43 27 124 C2.

For the granulation and comminution of liquid slags, it has also already been proposed to eject them into the granulation rooms with steam or propellant gas, with subsequent comminution in jet mills using propellant gas jets. Such a method is known for example from WO 99/42623. Slags usually occur at temperatures between 1400 ° C and 1600 ° C, and due to the relatively high temperature difference between the propellant gas jet and the liquid slag, such processes exist Risk of the formation of more or less large agglomerates as well as the danger of thread formation, which consequently increases the size reduction and significantly reduces the cooling rate. Priority has been given to cooling the slags as quickly as possible in the case of all proposals, although this can naturally be impaired by agglomerate formation and thread formation.

It has also already been proposed to eject the liquid slag with combustion exhaust gases into a pelletizing room in order to reduce the risk of the slag outlet opening being moved out of the slag tundish by solidifying slag. In processes of this type, the slag particles which have entered the granulation chamber enter a downstream cooling zone at a much higher temperature, the higher temperatures resulting in lower slag viscosity and a reduction in the surface tension of the slag droplets, so that a finer distribution of the slag droplets is achieved when they enter the cooling zone can. The fine dispersion of slag droplets leads to correspondingly small droplets with a relatively high specific surface area, so that cooling can be achieved in small cooling chambers. Such designs, however, require the installation of burners in the area of the tundish slag outlet, which leads to a high level of construction and equipment.

Overall, in the known proposals, fluid under pressure was used to eject liquid slag from a slag tundish into a downstream pelletizing chamber, so that, in particular when steam was used as the propellant, a corresponding steam generation for producing the high-pressure steam had to be connected upstream of the injection opening.

The invention now aims to simplify the construction of a device of the type mentioned and to separate upstream steam generators when using steam as

Renounce propellant. To solve this problem there is Device according to the invention essentially in that the slag outlet opening is designed as an annular overflow weir and that a water and / or steam supply pipe is arranged coaxially or concentrically with the annular weir, the outlet openings of which protrude inside a slag outlet pipe or out of the slag outlet opening. The fact that the slag outlet opening is designed as a π-shaped overflow weir makes it possible to directly achieve a jacket-like, liquid melt stream which flows out in the manner of a hollow hollow cylinder, the wall thickness being very simple owing to the slag throughput and owing to the annular overflow weir the viscosity can be adjusted. Due to the fact that a water and / or steam supply pipe, preferably with a spray head, is arranged coaxially or concentrically within this hollow melt cylinder, the spray openings of which are projecting inside or out of the slag outlet opening and are preferably at least partially radially oriented, rapid heating of the supplied pressurized water and corresponding evaporation is achieved in the area of the slag outlet, the slag temperature being lowered at the same time. Starting from the usual slag temperatures of around 1500 ° C, cooling the molten slag to 1350 ° C is not critical, since melts in this temperature range are still fluid enough. However, cooling from 1500 ° C to 1350 ° C permits corresponding evaporation or heating (overheating) of the medium supplied via the feed pipe arranged coaxially or concentrically with the annular weir, so that steam can be obtained via the spray head arranged inside or below the opening can be sprayed out and rapid atomization and thus efficient comminution can be achieved without difficulty. If pressurized water, for example at 10 bar at about 80 ° C., is supplied in such a configuration, it is possible to heat this pressurized water up to 1350 ° C., which naturally leads to evaporation. In this way, up to 50 kg of pressurized water can easily be evaporated per ton of slag melt, with a steam volume of about 20 to 40 m ³ Steam / t slag results. The speed of sound in water vapor is about 960 / sec at 1350 ° C. The flow rate usually results, for example, when using pressurized water under a pressure of 10 bar after the corresponding evaporation, subcritical conditions, so that it can be found with conventional nozzles. The droplet cooling process following the atomization process can subsequently take place by radiation cooling or else by direct injection of water, hot water or wet steam.

The device according to the invention is advantageously designed such that the feed pipe is coiled in the area of the annular weir or is designed as a fin tube, in the borderline case the tubes with or without fins can be wound so closely that a hollow cylinder is formed. Such a coiled tube allows particularly good heat transfer and rapid evaporation of the pressurized water supplied. In a particularly simple manner, the device can be designed such that a tubular wall with radial through openings for steam and / or high pressure water is arranged after the slag outlet opening, the inside diameter of which is larger than the inside width of the slag outlet opening. Pressurized water, hot water, wet steam or even superheated steam can be supplied from the outside via such radial passage openings, the wall of such a pipe being able to be cooled and itself acting as a radiation cooler. The training is preferably carried out in such a way that the tubular wall following the slag outlet opening is surrounded by an evaporator and that the evaporator chamber is connected to the steam feed pipe via a steam line with the interposition of a steam drum.

A further improvement in the size reduction performance can be achieved in that the radial openings in the tubular wall and the radial spray openings of the spray head are at least partially arranged in different radial planes. The melt hollow cylinder is in this way and alternatively acted upon from the inside and from the outside with pressurized water or steam, it being possible to induce vibrations which result in further shear forces and thereby further increase the disintegration. Depending on the temperature of the injected steam, there can be quasi isothermal atomization of the hollow melt cylinder, with droplet diameters of less than 50 μm being easily achieved. Together with the pressurized water or steam supplied via the coaxial or concentric tube, a total of about 400 kg of pressurized water or the resulting amount of steam per ton of melt can be supplied via the outer walls in the subsequent cooling chamber, so that the temperature of the emerging Microgranulate vapor mixture can be brought to below 460 ° C. At such temperatures, glass-like solidification is complete.

Advantageously, the design according to the invention is further developed such that the coiled or fin tube section of the feed pipe carrying the spray head is designed as a radiation steam generator and that the outer diameter of the coiled section is smaller than the inside diameter of the slag outlet opening reduced by twice the wall thickness of the over the ring-shaped weir overflowing jacket-shaped slag jet. This ensures that the hollow melt cylinder does not collide with the spray head or the wall at any point, so that wear is minimized. Overall, the training is advantageously made such that the spray openings of the spray head are designed for pressurized water at a pressure between 5 and 25 bar, the spray openings of the spray head advantageously being used for a supply pressure of less than about 10 bar as convergent nozzles and supercritical pressure conditions as Laval nozzles are formed, steam with temperatures between 700 ° C and 1350 ° C, in particular about 800 ° C, is expelled. With a correspondingly higher pressure, critical conditions are reached, so that Laval nozzles are required. The slag is preferably fed in tangentially to the annular overflow weir, so that a high slag throughput with a uniform jacket thickness of the emerging hollow cylindrical slag jet is also ensured.

The process according to the invention for granulating and comminuting slags with the device described above is advantageously carried out in such a way that the slag melt is used as foam slag. In principle, compact slags can of course be crushed and atomized just as easily. However, if certain compositions of the granulate are to be achieved, it is generally necessary to adjust the slag accordingly. Liquid blast furnace slag is primarily suitable as feed slag, although liquid steel slag can of course advantageously be mixed in to increase the basicity. If the Al ₂ θ ₃ ~ content is also to be increased for the desired end product, fly ash from hard coal-fired power plants or bauxite can also be added. In order to ensure intensive mixing of such mixed slags, air can be blown into such melts, and it has surprisingly been found that this mixed slag tends to form a lot of foam. In order to maintain the required temperature, coarse-grained coal can also be added to such slag foams, which further supports the formation of foam, and the iron oxide of the foam slag, as results, for example, from the addition of steel slag, can be reduced practically completely to metallic iron droplets. A foam slag overflow can be micro-granulated particularly easily by injecting water. Chromium, manganese and vanadium oxides in the slag can also be at least partially reduced, and the desired slag composition can be set in a particularly simple manner in such foam slags without complex additional equipment.

The process according to the invention is advantageously carried out in such a way that 30 to 150 kg of water are added to the water and / or Steam supply pipe and a total of 400 to 500 kg of water, per t slag, are used, preferably pressurized water at a pressure of 5 to 25 bar being fed to the spray head.

The invention is explained in more detail below on the basis of an exemplary embodiment shown schematically in the drawing. 1 shows a first embodiment of a slag tundish with the spray head according to the invention, FIG. 2 shows a modified embodiment in a sectional view analogous to FIG. 1, FIG. 3 shows another embodiment with an improved steam circuit, FIG. 4 shows a modified embodiment in 3, FIG. 5 a top view of the plate tundish, FIG. 6 a further embodiment and FIG. 7 a schematic partial view of a fin tube.

In Fig. 1, 1 denotes a plate tundish, the outlet opening of which is designated 2. The tundish has an annular weir 3, which forms an overflow 4, via which the slag flows out as a hollow cylinder with a jacket 5. A coiled pressurized water supply pipe 7 is arranged concentrically to the weir 3, the axis of which is designated 6, and merges into a spray head 9 below the slag outlet 8 of the slag tundish. A tubular wall 10 with openings 11 for steam or pressurized water nozzles is also arranged concentrically, the openings of which are directed onto the slag jacket 5 in radial planes. In the area between the overflow 4 and the slag outlet 8, the medium supplied via the helix 7 is heated intensively, which in the case of pressurized water largely evaporates and can be expelled via the nozzles 12 of the spray head 9. If these nozzles are directed essentially radially, they can be arranged in radial planes which are different from the radial planes in which the nozzles 11 are arranged, so that the jacket 5 of the molten slag is excited to schematically indicated vibrations with 13, so that more Shear forces act on the solidifying slag stream. The extremely fine microgranulated solidified particles 14 can subsequently be drawn off after a further cooling section in which pressurized water can be sprayed in via the nozzles 11.

In the representation according to FIG. 2, a tubular extension 15 made of refractory material is connected to the outlet opening 8 of the plate tundish 1, so that the height of the coil 7, via which fluid is supplied under pressure, can be increased accordingly in order to ensure appropriate steam generation, and the tube wall 10 is protected in the upper area. The helix 7 acts here as a radiation steam generator, the steam formed in turn being expelled from the spray head 9 via the nozzles 12 and further downwardly directed nozzles 16. The nozzles 11 provided in the subsequent tubular part 10 can, as indicated schematically, be designed as Laval nozzles in order to ensure a corresponding cooling speed and rapid granulation even under supercritical pressure conditions.

In the area of the slag outlet or the radiation steam generator, the slag is cooled down, for example from 1500 ° C to 1350 ° C, whereupon the hot slag melt escaping at approximately 1350 ° C is cooled and atomized to about 800 ° C with pressurized water and steam. For this purpose, for example, about 130 kg of pressurized water can be used at 20 bar / t molten slag. In this case, since the enthalpy of the evaporated water in relation to the enthalpy of the water vapor in the granulating room leads to steam supersonic velocity, the steam nozzle head must be expanded via Laval nozzles.

If for the cooling of the slag from 1350 ° to 800 ° C pressurized water at only 5 bar with a final steam temperature of up to 800 ° C is used, about 130 kg water / t melt are also required, although Laval nozzles can be dispensed with. Since steam can be produced both at high temperature and at comparatively low temperature in the device according to the invention, the high temperature steam circuit can be operated separately from the low temperature steam circuit in order to achieve exerergic improvements in this way. The limit temperature for the separate energetic utilization of the steam is chosen, for example, at about 650 ° C.

3 shows a further embodiment with an exergetically improved steam circuit, the same reference numerals being used for the same parts. 1 in turn designates a plate tundish which can be under a pressure of approximately 5 bar and to which the tubular part designed as a cam 17 is connected. The elbow 17 is encased by an evaporator coil 18 which is supplied with pressurized water 19 via a line. The pressurized water is conducted in the evaporator coil in counterflow to the solidifying slag jet flowing in the manifold 17 and is expelled in a first section as pressurized water, in a second section as wet steam and in a third section as superheated steam via nozzles 11 into the manifold 17. In this way, an ideal countercurrent heat exchanger for the heat exchange between slag and water or steam is formed, heat exchange by convection and radiation simultaneously taking place and, moreover, effective disintegration of the slag being achieved. The redirection of the vertical 2-phase flow (microgranulate and steam) m to the horizontal is greatly favored by the water and / or steam spraying arranged in Krummer 17. As a result, the microgranulator can be designed with a lower overall height, which makes handling easier. The superheated steam is drawn off from the evaporator coil via a line 20 and then fed to the feed pipe 21 for the spray head 9. In this embodiment, the feed pipe 21 is not designed to be coiled, since intensive heating of the supplied medium is no longer necessary. A portion of the superheated steam can optionally be drawn from line 20 for further energetic use. Overall, the circulation of the steam results in a particularly favorable configuration in terms of energy. 4 shows a modified embodiment corresponding to FIG. 3, in which the plate tundish 1 is made of graphite. The ring-shaped overflow weir 3 is designed as a separate component and can consist of ceramic material. The choice of a material other than graphite is particularly important here, since graphite should not come into direct contact with water vapor at the high temperatures, since this could lead to the formation of C02 and hydrogen. The graphite tundish 1 can be electrically heated here by a coil, indicated schematically by 22, the central outlet tube of the tundish being able to be correspondingly extended downwards. Following the slag outlet, an annular chamber 23 is provided which acts as an evaporator chamber. In the embodiment according to FIG. 4, pressurized water is again supplied via the connection 19, this last subarea, which acts as a radiation cooler, not necessarily leading to the evaporation of the pressurized water. The pressurized water reaches a further chamber 24 provided in the area of the elbow, in which evaporation already occurs at least in part. From the box 24 corresponding to the manifold area, steam or pressurized water is injected into the particle stream via the nozzles 11, the corresponding valves possibly being controllable, as indicated by 25, and can be closed accordingly. The steam or the pressurized water subsequently passes via a line 26 into the already mentioned annular chamber 23, in which rapid evaporation takes place due to the high temperature difference. Again, controlled valves can be provided, the valve closing members of which are indicated by 27, via which steam can subsequently be expelled against the outflowing liquid slag. The steam formed in this evaporator chamber 23 now, as already indicated in FIG. 3, returns via line 20 to the steam supply pipe 21. This steam supply pipe 21 can in turn be provided with a spray head 9. With appropriate dimensioning of the pipe adjoining the slag outlet, but also a direct spraying out of pressurized water or steam can be provided without using a separate spray head 9. With 28 a separate steam connection is indicated schematically.

5 that the slag is introduced into the slag tundish 1 tangentially to the ring-shaped weir designated by 3. This creates a circulating flow in the plate tundish, which ensures that a constant wall thickness of the jacket of the outflowing slag is guaranteed even with high slag throughput.

In the representation according to FIG. 6, in which the reference numerals from previous figures have been largely retained, the steam line 21 already opens out of the slag tundish 1 in the interior of the outlet pipe 2. In a first subsequent section, intensive cooling takes place by injecting water and / or Steam via the nozzles 11, whereupon the comminuted and essentially already solidified material reaches an underlying fluidized bed chamber 29. Cooling coils 30, which can also be referred to as immersion cooling surfaces, are arranged within this fluidized bed chamber 29. These cooling surfaces or cooling coils are supplied with pressurized water via a connection 31, the pressurized water emerging from the cooling coils being able to be fed to the nozzles 11 via line 32. The material can be brought from the fluidized bed space 29 via a line 33 into a downstream sifter or a sieve 34, the fine material being discharged via a lock 35. The gas phase, which contains a large amount of steam, is fed to a condenser via line 36.

3 and 4, which comprises line 20, a steam drum 37 can be switched on, which can also be used as a distributor for the steam required in the process. For this purpose, for example, via line 38 Steam Steam is fed into the fluidized bed chamber 29 to maintain a fluidized bed, export steam is drawn off via a line 39 and additional steam which may be required is introduced via a line 40.

Finally, in FIG. 7, a wall section of a fin tube can be seen schematically as a replacement for the helical design of the feed tube 21. The turns corresponding to the coils are hereby formed by helically extending tubes 41 which are welded to one another via webs, so that overall a coherent wall with an essentially cylindrical shape can be formed, through which helical water or steam can flow. With the preferred use of foam slags, different slag qualities can be mixed with one another. This is effortlessly accomplished in the production of a foam slag, as will be described below. Blast furnace slag, steel slag and fly ash with the following compositions were mixed together.

Als Zielzusammensetzung der entstehenden Schlacken wurden folgende Parameter gewählt:

The following parameters were selected as the target composition of the slags produced:

C / S - basicity = _ 1 - 1.5

Al ₂ 0 ₃ content = 6 - 16

FeO content <2%

Ti0 ₂ - content <2%

MgO content <15%

Glass content> 95 Q, * 6

These parameters guarantee a high-quality synthetic blast furnace slag with cement technology, while at the same time the crushing when spraying the foam slag results in Blaine numbers of over 4500.

In order to achieve the parameters mentioned at the outset and to set a C / S basicity of 1.5, the amount of steel slag to be added (x) is calculated as follows:

x = (C / S). SiO (HOS) - CaO (HOS)

CaO (SS) - (C / S). Si0 ₂ (SS)

thus it follows

x = 1.5. 37-32 ₌ 1,044

42 - 1.5. 13

So 1 part blast furnace slag was mixed with 1 part steel slag in order to achieve a C / S target basicity of approx. 1.5. The corresponding mixed slag gave the following picture:

The slag foam reduction produced 138 kg of pig iron per ton of mixed slag.

This mixed slag itself already represents a valuable cement technology component. In order to increase the early strength, the Al ₂ θ ₃ content of the final slag was raised from 11.6 to 16%.

The fly ash described was used for this. The necessary addition of the fly ash can again be obtained very simply from chemical balance considerations:

y (fly ash) = AI ₂ Q3 (mixed slag) - Z (Al ₂ θ ₃ _L_

Z (A1 ₂ 0 ₃ ) - A1 ₂ 0 ₃ (fly ash)

It follows :

y (fly ash) = 11, 6 - 16 _ o, 1913

16-39 1 part of mixed slag was blended with 0.1913 parts of fly ash. The corresponding slag showed the following analysis:

This foam slag mixture was granulated to d <50 μm and showed early strength values that are at least equivalent to OPC cements.

The addition of solids such as lime, fly ash, coal, etc. to the foam slag is extremely easy due to the large difference in density.

The slagging reactions take place very quickly in the foam slag, as does the metal oxide reduction, so that the process can be operated continuously. The oxidizing agent air can be enriched with oxygen to lower the specific gas load.

Floor nozzles can be dispensed with. The afterburning reaction (CO + 1/2 0 ₂ -> C0 ₂ ) also takes place in the foam slag with high heat transfer rates (> 70%), and only slight metal re-slagging is observed. The Metal sump (metal bath) can, for example, be drawn off continuously via a siphon.

Due to the high Al2θ3 content of the slag and the relatively low C / S basicity, high-alumina material (stones, FF materials) was preferred as the refractory material.

The foam slag results in a low refractory consumption, since foam slag is well insulated. The energy input can also take place via electrodes, similar to the foam slag practice in the E steelworks. However, the energy input is preferably carried out by means of afterburning.

Claims

Claims: 1. Device for granulating and comminuting liquid slags or foam slags, in which the slags are subjected to steam and / or water, with a slag tundish (1) and a slag outlet opening (2) arranged in the bottom of the slag tundish, characterized in that the slag outlet opening (2) is designed as an annular overflow weir (3) and that a water and / or steam supply pipe (7) is arranged coaxially or concentrically with the annular weir (3), the outlet openings (12) of which are inside a slag outlet pipe or out the slag outlet opening (2) project outstandingly. 2. Apparatus according to claim 1, characterized in that the water and / or steam supply pipe (7) is connected to a spray head (9), the spray openings (12) inside the slag outlet opening (2) or from the slag outlet opening (2) projecting and are at least partially radially oriented. 3. Apparatus according to claim 1 or 2, characterized in that the feed pipe (7) in the region of the annular weir (3) is designed helically. 4. Apparatus according to claim 1, 2 or 3, characterized in that a tubular wall (10) with radial through openings (11) for steam and / or high pressure water is connected to the slag outlet opening (2), the clear width of which is greater than that is the clear width of the slag outlet opening (2). 5. Device according to one of claims 1 to 4, characterized in that the radial openings (11) in the tubular wall (10) and the radial spray openings (12) of the spray head (9) are at least partially arranged in different radial planes , 6. Device according to one of claims 1 to 5, characterized in that the coiled section of the spray head (9) carrying the feed pipe (7) is designed as a steam generator and that the outer diameter of the coiled section is smaller than the inside width of the slag-out - Step opening (2) reduced by twice the wall thickness of the jacket-shaped slag jet (5) overflowing over the ring-shaped weir (3). 7. Device according to one of / claims 1 to 6, characterized in that the spray openings (12) of the spray head (9) are designed for pressurized water with a pressure between 5 and 25 bar. 8. Device according to one of claims 1 to 7, characterized in that the spray openings (12) of the spray head (9) for a supply pressure of less than about 10 bar as convergent nozzles and at supercritical pressure conditions as Laval nozzles and for steam with temperatures between 700 ° C and 1350 ° C, in particular about 800 ° C, are formed. 9. Device according to one of claims 1 to 8, characterized in that the slag supply tangential to the overflow weir (3) is connected to the slag tundish (1). 10. The device according to claim 4, characterized in that the tubular wall (10) following the slag outlet opening (2) is surrounded by an evaporator chamber (23) and that the evaporator chamber (23) via a steam line (20) with the interposition of a steam drum (37) is connected to the steam supply pipe (7). 11. The device according to one of claims 1 to 10, characterized in that below the slag outlet (2) Fluidized bed chamber (29) with immersion cooling surfaces or cooling coils (30) is arranged. 12. The device according to one of claims 2 to 11, characterized in that the coiled area of the water or steam supply pipe (7) is designed as a fin tube. 13. A method for granulating and crushing slag with a device according to any one of / claims 1 to 12, characterized in that the slag melt is used as a foam slag. 14. The method according to claim 13, characterized in that 30 to 150 kg of water via the water and / or steam supply pipe and a total of 400 to 500 kg of water, per t slag are used. 15. The method according to claim 13 or 14, characterized in that pressurized water is supplied to the spray head at a pressure of 5 to 25 bar.