EP0975812A1

EP0975812A1 - Method for granulating and grinding liquid slag and device for realising the same

Info

Publication number: EP0975812A1
Application number: EP99904606A
Authority: EP
Inventors: Alfred Edlinger
Original assignee: Holderbank Financiere Glarus AG
Current assignee: Holcim Ltd
Priority date: 1998-02-18
Filing date: 1999-02-17
Publication date: 2000-02-02
Also published as: SK140499A3; AU2502399A; CZ9903530A3; BR9904830A; US6319434B1; WO1999042623A1

Abstract

The present invention relates to a method for granulating and grinding liquid slag, in particular slag from a blast-furnace, using water. This method comprises supplying a stream of pressurised water into the slag so that said slag can be ejected in the shape of an envelope (7) about said stream. The device for realising this method comprises a slag container for liquid slag with an outlet opening (2) for said liquid slag. A lance (4) opens in the axis of the slag outlet opening so that the liquid slag can be ejected together with the pressurised water or steam introduced through said lance.

Description

Process for granulating and comminuting liquid slags and device for carrying out this process

The invention relates to a method for granulating and comminuting liquid slags, in particular blast furnace slags, with water, in which a pressure water jet is directed into the slag, and a device for carrying out this method comprising a slag container for liquid slag, which has an outlet opening for the has liquid slag.

A method for granulating and comminuting molten material is described, for example, in AT-B 400 140. In this known procedure, melt was introduced into a mixing chamber under pressure, with pressurized water vapor or water-steam mixtures being injected into the mixing chamber. An education for the implementation of this procedure comprised a multi-component nozzle, whereby due to the rapid expansion a pressure was built up which led to the ejection of the solidified particles via a diffuser. The kinetic energy of the particles was used for comminution, for which purpose, for example, baffle plates were arranged after the diffuser or the exit jet of the diffuser was directed against the exit jet of another diffuser.

In addition to water granulation, processes have also already been proposed in which the slags have been spread to a small slag height or thickness and have been solidified with air or compressed air.

With these known methods, granules with grain sizes of approximately 2 to 6 mm have been obtained, provided that the technical complexity of the plant and in particular the size of the plant should not increase disproportionately. Different mill types and in particular jet mills have already been proposed for the further comminution of the material. A prerequisite for the use of jet mills is, however, that the granulate is in a pneumatically conveyable form.

ERSATZBL _Ä TT (RULE 26) In Austrian application A 1826/97 it was already proposed to convey the liquid slag through a slag atomizer in which pressurized water was applied to the liquid slag. The liquid slag came freely from a pressure-resistant space into the area of the slag atomizer and was granulated by essentially radially directed pressurized water. The granules produced in this way were conveyed directly into a countercurrent mill together with steam and, if appropriate, additional steam or additional propellant gases. Even after such a training, the actual comminution work was carried out in the mill, the liquid slag having to be introduced into a pressure-tightly closable container before it can be brought into the granulating device in the free jet.

The invention now aims to further develop a device of the type mentioned at the outset in such a way that the handling of the slag is considerably simplified and that conventional devices in the area of the slag task can be used. At the same time, the method according to the invention aims to ensure high comminution performance in a small space already during granulation, and to create a granulate which can be ground or comminuted with less additional energy than would be the case with conventional granules.

To achieve this object, the method according to the invention essentially consists in that gases, in particular 02, air and / or oxygen-inert gas mixtures are dissolved in the slag before being discharged with the pressurized water jet and that iron parts of the slag are oxidized quantitatively, that the slag with the pressure of the pressurized water is pressed out through a slag opening and is expelled as a jacket of the pressurized water jet. The handling is designed in that the slag is present in a slag channel or slag pan without prior introduction into a pressure-resistant vessel the slag compared to known proposals substantially simpler, whereby in that a pressurized water jet is pressed into the slag coaxially with the slag outlet from the slag container, the water jet over a distance corresponding to the pressure of, for example, about 0.5 to 1.5 m deep immersed in the slag stream. In this way, a kind of "water soul" is formed over the water jet penetration path, the evaporation of this "water soul" occurring with a short delay, which is sufficient, and which is encased with solidifying or at least partially solidified slag To apply the beam. Relatively low mechanical requirements are placed on such a discharge, and the slag outlet can be made much simpler in comparison to complicated multi-component nozzles. Immediately after the outlet of the slag jet applied with a "water-soul", boiling and the sudden, explosive evaporation of the water begin, the kinetics of the water jet penetrating overcoming relatively high back pressures. With the explosive expansion of the jet at temperatures of around 800 to 1200 ° C, a high degree of comminution is ensured while the granulate solidifies at the same time.

Blast furnace slag to be granulated generally has a low residual pig iron content which, if the process is carried out correctly, is less than 0.5% by weight. If the blast furnace operation is improperly managed, the pig iron content can increase up to 5% by weight. The oxidation of iron fractions by oxygen or air reduces the risk of ■ explosions due to the formation of hydrogen gas, whereby the solubility of gases in the slag and, in particular, the saturation of the slag with gases also significantly improve the size reduction effect. The solubility of gases decreases sharply with falling slag temperature, so that in the area of sudden cooling by the pressurized water jet there is also an explosive segregation of the dissolved gases due to the falling slag temperature and thus the rapid decrease in the saturation concentration of gases in the liquid slag is observed. The gases released in this way from the solidifying slag expand violently due to the relatively high temperatures, as a result of which an improved disintegration of the slag particles is observed. For example, at ambient pressure and 1000 ° C, such a release of dissolved air results in approximately 11.2 m3 of air or nitrogen / t slag, the internal slag gas pressure possibly being a few 100 bar to over 1000 bar. Overall, a slag particle size of consistently less than 0.1 mm is achieved in this way, and to make matters worse, such a slag can be further comminuted with less effort and less energy consumption due to its porosity due to the suddenly released and originally dissolved gases .

The process according to the invention is advantageously carried out in such a way that the pressurized water is introduced at a pressure of 35 to 160 bar. In this way it is ensured that the "water-soul" is formed over a length which is sufficient for the jacketed jet to leave the outlet part of the slag container or a slag tundish safely and for the outlet part to be protected from excessive mechanical stress.

A further improvement in the size reduction effect and the granulation can be achieved in that the solidified shell of the slag surrounding the pressurized water jet is cut or split with further pressurized water.

In principle can. a pneumatically conveyable mixture can be achieved directly by the procedure according to the invention, so that following the expansion of the slag particles by collecting these slag particles together with the expanding gases in a expansion vessel, a mixture is provided which can be introduced directly into gas countercurrent mills and a further comminution could be fed. The steam that forms is used as the propellant gas together with the gases that are created by degassing and were originally dissolved in the slag. Particularly when using additional pressurized water jets to cut or split the jet, the sealing problem between a connected expansion vessel and a slag tundish is particularly simple, since a seal can be designed in the manner of a pneumatic seal and remaining leaks as throttle cross sections taking into account the enable high pressure to seal efficiently.

The device according to the invention for granulating liquid slags, in particular blast furnace slags, with water, with a slag container for liquid slag, which has an outlet opening for the liquid slag, is essentially characterized in that the slag container is designed as a slag tundish and at the deepest point of the slag tundish nozzles for air, oxygen and / or oxygen / inert gas mixtures are provided that a lance opens into the axis of the slag outlet opening so that the liquid slag is expelled with pressurized water or steam introduced via the lance. The lance provided for introducing pressurized water can be designed as a nozzle lance, it only being necessary to feed the pressurized water in such a way that the "water soul" mentioned at the outset is formed in the area of the slag outlet. This can be achieved in a particularly simple manner in that the slag tundish has a tubular, possibly interchangeable outlet part with the slag outlet opening. Are provided by the formation of the slag vessel as a slag tundish, wherein at the lowest point nozzles for air, oxygen and / or oxygen / inert gas mixtures, a most extensive saturation of the liquid slag with gases and a quantitative oxidation of residual ^¬ is achieved iron proportions. To further comminute and increase the cooling rate, ring nozzles can be provided in a particularly advantageous manner on the tubular outlet part for the injection of water and / or steam in a direction that is inclined radially or towards the axis of the tubular part in the direction of the outlet end.

A further improvement in the cooling parameters and the comminution effect can be achieved in that an expansion vessel is connected to the outlet part, wherein further nozzles for introducing water or steam in the radial and / or tangential direction preferably open into the expansion vessel. Such nozzles opening into an expansion vessel can serve in the event of a junction in the radial direction directly for further comminution and cutting up the slag jet, a kind of cyclone effect being able to be exerted on junction of the additional nozzles in the tangential direction, as a result of which the available reaction space for the Cooling can be better used. The result of this is that the device can be made smaller overall and yet the desired cooling is ensured to the extent required.

In a particularly simple manner, the discharge opening of the expansion vessel is connected to a mill for further comminution, the downstream mill coaxially with the outlet opening of the expansion vessel having a rotor designed as a centrifugal wheel, a baffle plate or a counterflow nozzle for steam and / or regrind.

It has been shown in comparative experiments that a slag which is suddenly degassed in the manner according to the invention requires a significantly lower specific grinding work than slag which has not been gas-treated. At a target fineness of about 6500 Blaine example, a "gas-free" slag requires a specific grinding work of about 120 KWh / _h 1sc paints • ^{D; Le for} the inventive manner, first with gas saturated and Terminal degassed slag requires for the same grinding fineness below 50 kWh / ts _chla c _k e Surprisingly, it was further found that in the case of mixing cement in the use of about 60 wt .-% slag and 40 wt .-% clinker and gypsum in the framework of the process according to the invention, granulated and comminuted slag leads to increased initial strength compared to conventionally granulated slag.

In view of the high pressures that arise during expansion, a large part of the pressure can subsequently be reduced in counter-current mills. Jet mills are thus a preferred variant of the use of the granules produced according to the invention, it being possible to take additional measures for energy recovery in the context of such jet mills. In particular, it is possible to work in the grinding chamber under subatmospheric pressure if the water vapor introduced is condensed externally, as a result of which the rapid pressure reduction can be achieved. In addition to the use of baffle plates, as mentioned above, the design of the baffle surface as a centrifugal wheel is particularly advantageous, the rotor in the form of a centrifugal wheel itself being able to be used to generate energy. The oversize size that may still remain can be separated off, for example, using a classifier or a cyclone, it being possible for coarse particles to be returned to the process and in particular to the mill.

Particularly small dimensions result from the vertical arrangement of the expansion vessel and the downstream mill. Naturally, the pneumatically conveyable mixtures can also be introduced horizontally into corresponding conventional countercurrent jet mills using slag injectors.

The invention is explained in more detail below on the basis of exemplary embodiments schematically shown in the drawing for the device according to the invention. 1 shows a cross section through part of the granulating device, FIG. 2 shows a cross section through a slag tundish with as 2 a modified arrangement of the device according to FIG. 2 with a modified expansion vessel, FIG. 4 a horizontal arrangement of the slag granulating device with a counter jet mill connected to the expansion vessel, partly in section, FIG. 5 an embodiment with coaxial to the expansion vessel 6 a modified embodiment in which additional grinding flows are introduced into the jet mill, FIG. 7 a further modified embodiment of the device according to FIG. 5 with baffles designed as a centrifugal wheel, and FIG. 8 a plan view on the centrifugal wheel according to FIG. 7.

In Fig. 1 is designed as a slag tundish container for the slag partially shown in section and designated 1. In the bottom of the slag tundish 1, an outlet part 2 made of a correspondingly mechanically and thermally resistant material is inserted. A water jet 5 with a pressure of about 60 to 100 bar is pressed into the slag bath in the slag melt 3 via a high-pressure water lance 4, a "water or steam soul" 6 being formed in the region of the outlet part 2 and the slag as a jacket 7 this "water soul" is carried out. The slag jet encasing the pressurized water jet arrives in an expansion vessel indicated schematically by 8, the internal pressure of the "water soul" expanding and tearing the jacket.

Additional pressurized water nozzles 9 are provided in the area of the inlet into the expansion vessel 8, the supply being effected via a ring line 10. The pressurized water or the water cone is directed onto the jacket 7 of the slag jet and causes it to be broken up and further crushed.

The high-pressure water jet also forms a sealing element, which relieves the sealing surfaces in the area of the connection of the outlet 2 to the expansion vessel 8. 2, the complete slag tundish 1 can be seen, a nozzle block 11 being arranged at the deepest point of the tundish, at which a metal bath can accumulate below the slag melt, via which compressed air can be blown in to oxidize residual iron. In addition to such compressed air or air-oxygen mixtures, inert gas can be injected in order to achieve the greatest possible saturation of the slag with gases. The slag itself can be kept molten using a schematic with 12 indicated electrical heating. The "water soul" 6 leads to an explosive expansion of the jacket during evaporation and thus to rapid cooling and comminution. The shredding effect is accelerated by the segregation of the dissolved gases, which occurs explosively with decreasing temperature and thus decreasing gas solubility.

A secondary pressure water lance or nozzle 13 also opens into the expansion vessel 8 and sets the disintegrating particles in a rotating cyclone movement, so that intensive cooling over a short drop height is achieved.

The steam-slag-granulate mixture with a particle size of about 0.1 mm is drawn off via the outlet opening 14 of the expansion vessel 8 and can be fed directly to a jet mill or another further comminution system.

3, the expansion vessel 8 is not designed as a cyclone. Rather, pressurized water is fed in via a ring line 15 and guided to the wall of the expansion vessel 8 in the manner of a curtain 16. In the area of the collision with the disintegrating particles, a vapor cushion is built up so that the walls of the expansion vessel 8 are effectively cooled and, at the same time, additional steam is generated to form a pneumatically conveyable mixture. The steam-granulate mixture is piped 17 a crushing plant, such as a jet mill, abandoned.

The length over which the injected high-pressure water jet 5 is present as a “water soul” in the form covered by the slag is denoted by a in FIG. 3. Following this section a, the "water-soul" is rapidly evaporated, at the same time being intensively assisted by the originally dissolved gas, which is released rapidly as the temperature decreases, with the aid of a comminuting effect.

4, an annular melt slag channel 18 is provided, to which the high pressure water lances 4 are connected laterally. The high-pressure water core is in turn formed via the high-pressure water lances 4, the expansion vessels 8 being connected diametrically opposite one another to a fluidized bed or fluidized bed mill. The jets directed against each other, containing the particles and the steam formed, are guided in the manner of a counter jet mill to a grinding point 20 located inside the mill 19. The ground material is drawn off via a classifier, the classifying wheel of which is designated by 21, via the axis of the wheel 21 which is designated by 22, whereupon steam is condensed. Due to the condensation of steam outside the mill 19, the pressure level can be lowered quickly, so that the shredding performance is further improved by this pressure reduction.

In the area of the entry into the expansion vessels, in turn, ring lines 10 with water nozzles oriented transversely to the slag jet are arranged, the high-pressure water from the ring lines 10 dividing and crushing the slag jacket.

In the embodiment according to FIG. 5, a counter jet mill 23 is provided in the vertical direction coaxially with the expansion vessel 8, the counter jet mill 23 being inserted into the counter jet mill 23 from above a steam jet particle mixture flowing in below is supplied with a counter jet via a lance 24 from externally generated steam. The outlet opening of the expansion vessel 8 is designed as a 2-phase nozzle, whereas the lance 24 is designed only as a 1-phase nozzle. The grinding point is again with

Designated 20. The regrind is in turn over the classifier wheel

21 carried out, with subsequent steam condensation outside the mill 23 a pressure inside the mill 23 of far below an atmosphere, for example 0.3 to 0.75 bar, can be achieved. The gases flowing in at high speed due to the much higher pressure cause intensive grinding.

In the embodiment according to FIG. 6, the expansion vessel 8 again opens into a counter jet mill 23, a negative pressure of about 0.3 to 0.75 bar being set here again by the condensation of the steam outside the mill. In the counter-jet mill 23, diametrically opposed jet nozzles 25 and 26 open, wherein coarse material from a coarse material separation in the separator 27 is fed into the jet nozzle 26 and returned to the mill. Following the coarse material separator 27, a conventional classifier is again provided, the steam condensation carried out outside the mill 23 not being shown for the sake of clarity. The gas in the mill 23 consists of about 75% water vapor and about 25% of the air drawn in. The desired negative pressure in the mill 23 can be additionally reduced by a suction fan (not shown).

In the embodiment according to FIG. 7, the gas-particle mixture passes from the expansion vessel 8 into an impact mill 28. The impact mill can contain a stationary impact plate or, as in the case of the embodiment according to FIG. 7, a centrifugal wheel with an impact plate 29. The particle stream sets the centrifugal wheel 29 in motion, the particles being thrown against an annular armor 30 of the mill 28 and being further comminuted. The centrifugal wheel is in plan view in Fig. 8 shown and has wings 31 which cause a direction of rotation 32 of the centrifugal wheel. A generator for generating energy can thus be connected to the rotor, for example, and relatively high speeds of 5,000 to 20,000 rpm can be easily achieved with the centrifugal wheel. As an alternative to using the centrifugal wheel as a radial turbine, the centrifugal wheel can be connected to a drive for extreme fineness of grinding, which increases the impact impulse on the ring-shaped shell of the mill shell. The ground material is in turn drawn off from the mill 28, for example via a classifier, it being possible for a pressure to be reduced to about 0.3 bar by the subsequent steam condensation inside the mill 28.

Claims

Claims:

1. A process for granulating and comminuting liquid slags, in particular blast furnace slags with water, in which a pressurized water jet (5) is directed into the slag, characterized in that gases, in particular 02, in the slag prior to discharge with the pressurized water jet / Air and / or oxygen-inert gas mixtures are dissolved, iron portions of the slag being oxidized quantitatively, the slag being pressed out through a slag opening with the pressure of the pressurized water and being expelled as a jacket (7) of the pressurized water jet.

2. The method according to claim 1, characterized in that the pressurized water is introduced under a pressure of 35-160 bar.

3. The method according to claim 1 or 2, characterized in that the solidified jacket (7) of the slag surrounding the pressurized water jet (5) is cut or split with further pressurized water.

4. Device for granulating liquid slag, in particular blast furnace slag with water with a slag container for liquid slag, which has an outlet opening for the liquid slag, according to one of claims 1, 2 or 3, characterized in that the slag container as a slag tundish ( 1) it is designed that nozzles (11) for air, oxygen and / or oxygen / inert gas mixtures are provided at the lowest point of the slag tundish (1) and that a lance (4) opens into the axis of the slag outlet opening so that the liquid Slag (3) is expelled with pressurized water or steam introduced via the lance.

5. Device according to claim 4, characterized in that the slag tundish (1) is a tubular, possibly interchangeable the outlet part (2) with the slag outlet opening.

6. Device according to claim 4 or 5, characterized in that on the tubular outlet part (2) ring nozzles (9) for the injection of water and / or steam in the radial or to the axis of the tubular part (2) in the direction towards the outlet end inclined direction are provided.

7. Device according to one of claims 4, 5 or 6, characterized in that an expansion vessel (8) is connected to the outlet part (2).

8. Device according to one of claims 4 to 7, characterized in that further nozzles in the expansion vessel (8)

(13) for the introduction of water or steam in the radial and / or tangential direction.

9. Device according to one of claims 4 to 8, characterized in that the discharge opening of the expansion vessel

(8) is connected to a mill (19).

10. Device according to one of claims 4 to 9, characterized in that the downstream mill (19) coaxially to the outlet opening of the expansion vessel (8) as a centrifugal wheel (29) formed rotor, a baffle plate or a counterflow nozzle for steam and / or regrind .