WO2001047623A1 - Device and method for granulating and comminuting slag melts - Google Patents

Abstract

The invention relates to a method for granulating and comminuting slag melts for the production of hydraulically active binding agents or binding agent additives. According to said method, the slags are expelled into a cooling chamber or expansion chamber with the aid of a propulsion jet in a direction which is counter to gravity. The device for carrying out the above method comprises a slag tundish and a propellant feed line connected to said tundish. Said feed line leads into an annular weir inside the tundish. The inventive device for carrying out the above-mentioned method also comprises a cooling chamber or an expansion chamber. The feed line leads into the bottom of the slag tundish. The tundish is pivotably mounted, perpendicular to the axis of the propulsion jet. The cooling chamber or expansion chamber is arranged above the melt level in the tundish.

Description

 Method and device for granulating and crushing slag melts

The invention relates to a method for granulating and comminuting slag melts for the production of hydraulically active binders or binder additives, in which the slags are ejected with a propellant jet into a cooling or expansion chamber and an apparatus for carrying out this method.

For the granulation and comminution of liquid slag melts, a number of processes have been proposed in which the liquid slag particles have been expelled with a fuel into a cooling or expansion chamber and have been subjected to water or water vapor, so that the melts rapidly cool and solidify has been. Such processes can be found, for example, in AT-B 405 511, EP 683 824 or EP 963 447. For cooling, it has already been proposed, inter alia, to inject hydrocarbons into the cooling or expansion chamber, as a result of which the temperature gradient of the cooling could be increased significantly and at the same time the sensible heat of the slag melt could be stored as chemical energy. In addition to water and steam, hot combustion exhaust gases have also been proposed as the propellant jet for the discharge of liquid slag melts, the known devices having a relatively large cooling or. Expansion chamber required. The slag melt passed through a tundish outlet on the underside of the slag tundish into the cooling or expansion chamber underneath, whereby if additional propellant gases are injected and the particles are accelerated accordingly, in order to achieve a quick and fine dispersion of the slag particles, this takes a correspondingly long time Cooling section was required.

The method according to the invention is now aimed at significantly reducing the dimensions of the required cooling and expansion chamber and with particularly small - 2 -

directions to find enough and thus to achieve rapid cooling and glassy solidification of slag melts on a much shorter route. To achieve this object, the method according to the invention essentially consists in that the ejection is carried out against the direction of gravity. Because the droplet droplets are ejected in the opposite direction to the direction of gravity, the discharged droplet droplets come into intensive collision in the state of solidification with particles which in turn sink due to the force of gravity, so that in addition to the comminution effect, such as that caused by the atomization and expulsion of the slags a propulsive jet and the subsequent spraying or blowing up of cooling gases is achieved, there is an additional comminution effect, which results from the counter-flowing fine particles due to a direct collision with them. Overall, in addition to intensive atomization, a high degree of mechanical collisions is also guaranteed at the same time, which leads to rapid disintegration and to a much finer particle breakdown, which in turn allows the cooling rate and the temperature gradient of the cooling to be increased at the same time, resulting in a much smaller overall size Cooling or expansion chambers that can be found.

The process according to the invention is advantageously carried out in such a way that the powder-steam mixture drawn off from the cooling and expansion chamber is subjected to a solid separation and that the gas stream containing fine dust and steam is passed from the solid separation via a condenser, which fresh water to supplement the water or Steam losses are added, whereupon, after a clarifier, the clarified water is used to cool the walls of the cooling or expansion chamber. Another essential factor for the economical implementation of the process is the water requirement and the accumulation of large amounts of wastewater to be cleaned. By carrying out the process according to the invention, in which that which is drawn off from the cooling and expansion chamber Powder-vapor mixture is first subjected to a solid separation, for example dust separation in the form of a filter or a cyclone, a gas stream containing only fine dust and steam can be removed from the solid separation, which can subsequently be passed through a condenser. Since steam or water losses cannot naturally be ruled out in such processes, fresh water must be added, fresh water also usually having to be subjected to water treatment and, in particular, softening in the process according to the invention, in order to ensure that steam nozzles or steam lines are not in the course of the process of the company. However, since the fresh water is now added to the steam, which still contains fine dust, to supplement the water or steam losses, a large part of the temporary hardness can be reduced directly in the condenser and in the subsequent clarifier. If the water hardness is high, it is also possible to add an appropriate amount of already deposited slag powder. The reaction of calcium hydrogen carbonate with calcium hydroxide from the basic slags, which is also contained in the discharged fine dust, leads directly to the precipitation of calcium carbonate, since calcium carbonate, in contrast to calcium hydrogen carbonate, has only a low residual solubility. The fresh water added is thus effectively decalcified and, in the process according to the invention, is recirculated into the process together with the condensed and purified steam after the clarifier and used, for example, to cool the walls of the cooling or expansion chamber. If necessary, the procedure can be such that the clarified water after precipitation and separation of CaCO3 in the clarifier is passed through a further water treatment, such as an ion exchanger or softener, which can also be used, for example, to convert sulfate hardness and other troublesome salts into solution-stable alkali salts.

The water used to cool the walls of the cooling and expansion chamber can subsequently in the cooling or expansion Chamber for quenching the liquid slag melts are used in the cooling and expansion chamber, for which it is advantageously carried out in such a way that the water used for cooling the walls of the cooling or expansion chamber is passed over a steam superheater and used as a propellant.

Overall, the amount of water originally used is largely able to be circulated in this way and, if necessary, fresh water required to supplement it can be economically softened as part of the process, so that it can be used directly for the granulation and comminution process.

In principle, it can be assumed that the steam extracted from the dust separator generally contains a maximum of 60 mg fine dust / no steam. Since the oxidic slag melts, which are atomized to produce hydraulically active binders or binder additives, have a high calcium oxide content, such an amount of very fine dust can raise the pH value of the condensate to 11 with the formation of CaOH2. These preconditions allow calcium carbonate to be precipitated quickly and safely from calcium hydrogen carbonate, so that practically hardness-free feed water remains after the addition of fresh water. In the event that H2S or SO2 development is observed in the system, the high calcium oxide content of the fine dust can also be used to desulfurize. The reaction H2S + CaO -> CaS + H2O or SO2 + CaO -> CaS03 taking place can be observed in the dust collector, but also on the way from the cooling and expansion chamber to the dust collector. If an ion exchanger, for example an acidic ion exchanger loaded with sodium ions, is also used for the residual softening, complete softening of the feed water is achieved, the remaining sodium ions being subsequently quantitatively incorporated into the solidifying slag melt, so that an enrichment of the alkali salts in the slag melt. Such additional enrichment of the glassy solidified slag particles brings a number of advantages in terms of cement technology and leads to an activation, which is particularly evident in particularly high early strengths of hydraulically active binders or binder additives produced in this way.

When the slag is expelled into the cooling or expansion chamber by means of the propellant jet, there is also an uncontrolled intake of ambient air, which causes disruptive recirculation flows in the area of the propellant jet. According to the invention, the procedure is therefore preferably such that a barrier medium, such as e.g. Steam, air, hydrocarbon or coal dust-vapor mixtures, is introduced to reduce recirculation flows. In this way, uncontrolled turbulence in the area of the propulsion jet can be avoided and the atomization effect can be improved. The barrier medium to be introduced can also be throttled so that the drive jet oscillates. This leads to an optimization of the droplet tearing behavior and thus to a better atomization.

The device according to the invention for carrying out the method has a slag tundish and a feed line for propellant gas connected to the slag tundish. Furthermore, a cooling and expansion chamber is provided, which is arranged below the slag tundish in the known devices. The device according to the invention is essentially characterized in that the feed line opens at the bottom of the slag tundish and that the tundish is pivotally mounted transversely to the axis of the driving jet and that the cooling or expansion chamber is arranged above the melt level in the tundish. The swiveling arrangement of the slag tundish makes it possible to pivot the operation without the risk of liquid slag escaping in the direction of the jet nozzles, with an annular weir surrounding the feed line for the jet jet - -

Leakage can be prevented at this point. At the same time, the pivotability of the slag tundish enables the height of the slag level to be dusted by the propellant jet to be adjusted by means of a corresponding pivot position, so that the desired atomization effect and the impact on the quench can be set within wide limits. According to a preferred embodiment, the inlet opening provided for the propellant gas in the bottom of the slag tundish is designed as a Laval nozzle, a guide body immersed in the slag being arranged in the region of the nozzle opening, which is preferably arranged to be adjustable in height. The guide body assigned to the nozzle mouth, together with the Laval nozzle, produces a directed, strongly accelerated jet of propellant gas, which promotes atomization of the melt. Very short free jet lengths were observed here, so that the efficiency of the atomization could be increased. The guide body can also be used to close the inlet openings provided in the bottom of the slag tundish, with the height adjustment of the guide body and the pivotability of the tundish making it possible to set the atomization parameters precisely. As is known per se, cooling gas, for example wet water vapor or also hydrocarbons, is injected into the quench or the cooling or expansion chamber, the design preferably being such that at least one ring-shaped is located between the melt level and the cooling or expansion chamber Atomizer nozzle is arranged, the jet axes of which intersect the axis of the driving jet.

In a particularly simple manner, the procedure according to the invention and the operation of the device according to the invention are such that the temperature of the propellant gas is set higher than the temperature of the atomizer nozzle gas, the pressure in the feed line to the atomizer nozzle preferably being greater than in the feed line to Propellant gas nozzle is set and that the axes of the atomizing nozzles are directed upwards in the direction of the axis of the propellant jet. In this way, an intensive quench and rapid cooling in the glassy state ensured at the same time high particle size reduction. The pressure range used in the process according to the invention is generally between 2 and 16 bar, with temperatures between 600 ° and 1200 ° C. preferably being used. A total of about 150 to 1000 kg of hot gas are used per t of slag, the temperature of the slag melt being between 1430 ° and 1560 ° C. Due to the use of a propellant gas jet, the slag is expelled into the cooling or expansion chamber as a jacket of the propellant gas jet, so that only the thin wall of this jet has to be solidified by the action of the cooling gases, thereby ensuring rapid glassy solidification and the hydraulic properties of the product are not impaired.

In order to prevent overflowing when the slag tundish is pivoted, the design is advantageously made such that a wall which is immersed in the melt level from above as a slag surge breaker is installed in the slag tundish when the tun dish is pivoted.

The invention is explained in more detail below with reference to an exemplary embodiment of the device according to the invention which is shown schematically in the drawing. 1 shows an overall view of the device according to the invention, FIG. 2 shows a detailed illustration of the tundish with the driving jet, and FIG. 3 shows a modified embodiment with guide bodies.

In Fig.l a slag tundish 1 can be seen, which is pivotally mounted about an axis 2 on a bearing block 3. The slag tundish 1 can thus be pivoted about the pivot axis 2. The slag tundish has an annular weir 4 in its interior, which concentrically surrounds a feed line 5 for propellant gas. By pivoting the slag tundish 1 about the axis 2 in the direction of arrow 6, the liquid slag 7 comes out of the area of the annular weir to the left, so that with such a pivoting even when the slag is switched off Propellant gas prevents slag from escaping downwards.

The slag is introduced into the tundish from a slag reservoir 29.

Above the slag tundish 1 there is a cooling or expansion chamber 8, the walls of which are cooled by radiant heat exchangers 9. An annular nozzle 10 is connected to this cooling and expansion chamber, through which quench gases can be injected in order to permit rapid cooling of the particles expelled upward with the propellant gas from the feed line 5 into the cooling and expansion chamber. The particles are thus thrown upwards and collide with particles, which sink down again due to gravity in the cooling or expansion chamber.

Fresh water is supplied via a line 11 for cooling the walls or the radiant heat exchanger 9. After this fresh water has been heated, this fresh water passes via line 12 into a steam drum 13, from which steam is drawn off and passed over a superheater 14. The superheated steam can subsequently be used as a propellant gas stream via the feed line 5. From the steam drum 13, hot water is drawn off via line 15, which via the ring nozzles 10 in the cooling or. Expansion space is pushed in, the pressure here being generally chosen so that it is above the pressure of the propellant jet. Instead of hot water, hot steam can also be injected here, since the particles are rapidly comminuted, so that a sufficiently high temperature gradient is available for rapid glass-like cooling of the particles. The circulation of water or steam can also be carried out as shown in dashed lines in Fig.l. The feed water is fed to the steam drum 13 via the line 11, hot water is removed from the steam drum 13 and fed to the radiant heat exchanger 9. From the cooling and expansion chamber 8, a Pulver-Dampfge iseh is withdrawn via a line 16, which is fed to a dust separator 17. The powder removed from the dust separator 17 represents a high-quality hydraulically active binder product which can be used directly as a cement substitute or as a binder additive.

Fine dust and steam are drawn off from the dust separator via line 18 and fed to a condenser 19. At this point, water or steam loss can be supplemented by supplying fresh water via line 20, the mixture of condensed steam and added fresh water reaching a clarifier 22 via line 21. At the latest in the clarifier, due to the fine dust content with high lime content contained in the steam, a rapid reaction with precipitation of calcium carbonate takes place, so that largely softened water can be drawn off via line 23 and can be fed to a further water treatment, such as an ion exchanger 24. Via a feed water pump 25, the softened and purified water in turn passes into line 11, which leads to the radiant heat exchangers 9.

The process water used can thus be almost entirely recycled, which means that the total waste water pollution can be significantly reduced. At the same time, the fine dust content in the steam can be used for rapid softening of fresh water, the sodium ions remaining essentially after the ion exchanger 24 being incorporated into the slag particles in the cooling or expansion space 8.

Sludge is discharged from the clarifier via a line 26. This essentially calcium carbonate-containing sludge can subsequently be injected into the quench or the cooling and expansion space, for example, via multi-component nozzles, and can be incorporated directly into the slag droplets to improve the cement technology properties, as a result of which no additional sludge is obtained here either. - 10 -

FIG. 2 now shows a detailed view of the tundish with the propellant jet, a chamber 27 being visible through which a barrier medium is introduced into the cooling or expansion chamber in order to prevent recirculation flows through uncontrolled suction of ambient air. The blocking medium can also be introduced via a throttle valve 28, as a result of which the drive jet is oscillated.

3 shows a detailed view of the tundish in a modified embodiment. A slag tundish 1 can be seen, which is pivotably mounted on a bearing block 3 about an axis 2. The supply line for propellant gas is denoted by 5 and opens into a plurality of inlet openings 30 provided in the bottom of the tundish. The inlet openings 30 are designed as Laval nozzles, with guide bodies 31 being immersed in the slag in the region of the nozzle opening of the inlet openings 30. In order to set the atomization parameters, the guide bodies 31 are arranged such that they can be adjusted in height in the direction of the double arrow 32, the guide bodies 31 also being able to serve as plugs for closing the inlet openings. In order to achieve appropriate flow conditions, line 5, for example, propellant steam at a pressure of 3 to 25 bar and a temperature of 650 to 1350 ° C. can be supplied.

Overall, the method according to the invention results in an extremely low-wastewater method, the entire feed water treatment being able to be inexpensively processed within the method due to components contained in the fine dust.

Claims

Claims: 1. A method for granulating and crushing slag melts for the production of hydraulically active binders or binder additives, in which the slags are ejected with a propellant jet into a cooling or expansion chamber, characterized in that the ejection is carried out against the direction of gravity. 2. The method according to claim 1, characterized in that in the cooling and expansion chamber water and / or water vapor is introduced in the direction of the slag propellant fluid jet that the withdrawn from the cooling and expansion chamber powder-steam mixture is subjected to a solid separation and that Gas stream containing fine dust and steam from the solid separation is passed through a condenser, to which fresh water is added to supplement the water or steam losses, whereupon, after a clarifier, the clarified water is used to cool the walls of the cooling or expansion chamber. 3. The method according to claim 1 or 2, characterized in that the clarified water after precipitation and separation of CaCθ3 in the clarifier via a further water treatment, such as. an ion exchanger, e.g. a mixed-bed demineralizer or softener. 4. The method according to claim 1, 2 or 3, characterized in that the water used for cooling the walls of the cooling or expansion chamber is passed through a steam superheater and is used as a propellant. 5. The method according to any one of claims 1 to 4, characterized in that a barrier medium, such as steam, air, hydrocarbon or coal dust-steam mixtures, is introduced concentrically to the propellant jet to reduce recirculation flows. 6. Device for performing the method according to one of claims 1 to 5 with a slag tundish, a supply line for propellant gas connected to the slag tundish and a cooling or expansion chamber, characterized in that the supply line (5) at the bottom of the slag tundish (1) opens and that the tundish (1) is pivotally mounted transversely to the axis of the driving jet and that the cooling or expansion chamber (8) is arranged above the melt level in the tundish (1). 7. The device according to claim 6, characterized in that the supply line (5) for propellant gas opens into an annular weir in the tundish. 8. The device according to claim 6, characterized in that the inlet opening provided for the propellant gas in the bottom of the slag tundish is designed as a Laval nozzle and in the region of the nozzle opening of the inlet opening, a guide body immersed in the slag is arranged. 9. The device according to claim 6, 7 or 8, characterized in that between the melt level and the cooling or expansion chamber (8) at least one annular atomizer nozzle (10) is arranged, the jet axes of which intersect the axis of the propellant jet. 10. Device according to one of claims 6 to 9, characterized in that the temperature of the propellant gas is set higher than the temperature of the atomizing nozzle gas. 11. Device according to one of claims 6 to 10, characterized in that the pressure in the feed line (15) to the atomizer nozzle (10) is set greater than in the feed line (5) to the propellant gas nozzle and that the axes of the atomizer nozzles (10 ) are directed upwards in the direction of the axis of the driving jet. 12. The device according to one of claims 6 to 11, characterized in that in the slag tundish (1) a plunging into the melt level from above wall is installed as a slag surge breaker when pivoting the tundish (1). 13. Device according to one of claims 8 to 12, characterized in that the guide body is arranged adjustable in height.