Method for granulating a metallurgical slag

Abstract

A method for the granulation of a metallurgical slag includes blowing, from a blower or air nozzle, heated air onto liquid slag to atomize the liquid slag and subsequently form granulated slag as the atomized slag cools. The granulated slag is blown into and collected by a working chamber. In order to ensure a high quality of the granulated slag and operate in an energy-efficient manner, the atomization is provided by blowing a heated air jet free from the addition of water onto the liquid slag. The granulated slag particles are collected in the floor region of the working chamber. Air that is released from the working chamber is either supplied to a heat exchanger, which further heats the air jet blown onto the liquid slag, or the released air is directly recirculated to the blower or air nozzle in order to atomize the supply of liquid slag.

Claims

1. A method for the granulation of a metallurgical slag, the method comprising: blowing, from a blower, heated air onto a supply of liquid slag such that the liquid slag is transformed to atomized slag, wherein atomization is provided by blowing the heated air free of water onto the liquid slag; directing the atomized slag into a single working chamber in which the atomized slag forms into granulated slag particles which are collected in a floor region of the single working chamber; releasing, from the single working chamber, the heated air either to a heat exchanger, which further heats the released air and directs the further heated released air to an air inlet of the blower for blowing onto the liquid slag, or directly recirculating the released air from the single working chamber to the air inlet of the blower in order to atomize the liquid slag; and wherein the supply of the liquid slag and the blowing of heated air from the blower onto the liquid slag occurs in a first section of the single working chamber and the granulated slag particles accumulate in a second section of the single working chamber, at a distance from the first section, wherein the released air from the single working chamber is removed from the single working chamber in a region of the first section, and wherein the first section and the second section of the single working chamber are separated from each other by a baffle plate located in a ceiling region of the single working chamber, wherein a portion of energy contained in the released air is used to supply a consumer.

2. The method according to claim 1, wherein the liquid slag is kept free from water from the supply of slag and through formation and accumulation of granulated slag particles on the floor region of the single working chamber.

3. The method according to claim 1, wherein the heated air used to blow onto the liquid slag is preheated to at least 60 C.

4. The method according to claim 1, wherein the heated air, after having been used for the atomization of the liquid slag, has a temperature of at least 250 C.

5. The method according to claim 1, wherein the consumer is a steam generator that is connected to a steam turbine/generator system for generating electrical energy.

6. The method according to claim 1, wherein the further heated released air from the heat exchanger is blown onto the granulated slag particles from a secondary air inlet.

7. The method according to claim 6, wherein heat recovered in the heat exchanger is used to supply the consumer.

8. The method according to claim 1, wherein the consumer is a heating system which is used for heating facilities or buildings.

9. The method according to claim 1, wherein the metallurgical slag is a nonferrous slag.

10. The method according to claim 1, wherein a venting site provided in the region of the first section for the released air is vertically above a site for supplying the liquid slag and blowing the heated air onto the supply of liquid slag.

11. The method according to claim 1, wherein the released air from the single working chamber is guided vertically upward, then deflected by 180, then guided vertically downward, and then supplied again to the single working chamber through the blower.

12. The method according to claim 1, wherein a receiving or removal element for defective products is located in the first section of the single working chamber and at least one receiving or removal element for granulated slag particles is located in the second section of the single working chamber.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of the invention are represented in the drawing, in which:

(2) FIG. 1 shows schematically a system for the granulation of liquid slag, in which a heat recovery takes place in order to preheat the air required for the atomization of the liquid slag,

(3) FIG. 2 shows schematically a system in which a further utilization of the recovered energy is also provided,

(4) FIG. 3 shows schematically a side view of the working chamber of the system, indicating the flight of the granulated slag particles after air has been blown onto them,

(5) FIG. 4 shows schematically a side view of the working chamber in an alternative embodiment, where the course of the flow of air through the working chamber and out from it is indicated, and

(6) FIG. 5 shows schematically a side view (left) and a front view (right) of the working chamber and the later route of the air including a heat exchanger.

(7) The aforementioned prior art offers various solutions for the technology of slag granulation and also for the recovery of energy contained in the slag. By contrast, the present invention is based on a combination of dry granulation and energy recovery.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(8) To this end, FIG. 1 shows an exemplary embodiment of the invention. Liquid slag 1 is supplied to the air flow 2 created by a blower 10. The slag 1 atomized by means of the air 2 (being present with a temperature of around 1300 C.) reaches a working chamber 4, where slag particles 3 granulated in the dry air flow are formed, and fall into the floor region of the working chamber 4 and can be transported away from underneath with a conveyor belt 11.

(9) The air 5 escaping from the working chamber 4 (having a temperature of around 500 C.) is guided to a heat exchanger 6, where the escaping air 5 preheats intake air and guides it to the blower 10 (along the path shown schematically by broken lines) in order to atomize liquid slag 1.

(10) Alternatively, it is also equally possible for the air 5 escaping from the working chamber 4 to be conveyed directly (without a heat exchanger) to the blower 10 and used for the atomization of the liquid slag 1. In the latter case, the air is guided in a closed circuit (recirculating) and used in its heated state for the atomizing of the liquid slag 1.

(11) A combination of the two mentioned procedures is also possible: accordingly, the air 5 escaping from the working chamber 4 is recirculated, i.e., again guided to the blower 10 and used to atomize liquid slag 1. Prior, however, the escaping air 5 passed through the heat exchanger 6, so that a concept can be realized as shown in FIG. 2.

(12) At the left of the figure, still schematically, it is illustrated how air 2 is used for atomizing the liquid slag 1. The air 5 escaping from the working chamber 4 passes through the heat exchanger 6, while the granulated slag particles 3 are collected in a floor region of the system.

(13) At the right side of the figure it is indicated that the heat obtained from the escaping air 5 in the heat exchanger 6 is reused. Two alternative or additive possibilities are outlined for this at the right side of the figure.

(14) In the upper area on the right side of the figure there is shown a consumer 7 in the form of a steam generator 7, in which water is evaporated by using the recovered energy. The steam is supplied to a steam turbine/generator system 8, in which electrical energy can be produced in familiar manner.

(15) In the lower area at right side of the figure there is shown a consumer 7 in the form of a heating system 7 The energy from the escaping air 5 is used for heating purposes in this case.

(16) The escaping air 5 that was guided through the heat exchanger 6 can be guided back to the starting point in order to be used as air 2 for atomizing the liquid slag 1. If recirculating air is used, this air should have a temperature not less than 120 C. upon reaching the blower 10.

(17) FIG. 2 shows yet another advantageous development of the invention. The granulated slag particles 3 accumulating in the floor region of the working chamber 4 at first still have a temperature of around 500 C. This effect can be utilized for further heat recovery.

(18) For this purpose, a further air stream 9 is guided through the bottom region, which heats up as it is passed through the slag particles 3 and supplied to a heat exchanger 6 (this may be the same heat exchanger as mentioned above, as shown, but it can also be a separate one). The heat from the heated air stream 9 can be utilized in the described manner and be made available to one or more consumers 7. It is desirable to remove as much heat as possible from the slag particles by the further air stream 9, so that the slag particles only have a temperature of around 80 C.

(19) Of course, the removal of heat from the slag particles need not occur directly in the floor region of the working chamber 4. It is also possible to select a downstream location for this purpose, such as the region of the conveyor belt 11.

(20) It would also be possible to utilize the heated further air stream 9 by supplying it to the blower 10 and performing the atomization of the liquid slag 1 by means of the air which has thus been preheated.

(21) FIG. 3 shows the working chamber 4 once more in further detail, indicating by flight parabolas 18 how the granulated slag particles 3, by blowing air onto them, are moving from the (left) end region of the working chamber 4 and then accumulate in the floor region of the working chamber 4. Defective products 19 mostly fall down directly in the air injection region and accumulate in a location from which they can be disposed (especially in the form of a drop hatch beneath the slag channel). Thus, a receiving or removal element 16 for these defective products 19 is arranged here. The properly granulated slag particles 3, however, accumulate in other locations of the floor and are removed here by receiving or removal elements 17 from the working chamber 4. The removal site 15 for the air 5 escaping from the working chamber 4 again is in the region of the air inlet site, i.e., in the left region of the working chamber 4; the air is thus guided in a special manner (cf., FIG. 4). FIG. 3 provides one configuration of the floor of the working chamber 4, where the floor has a straight shape. The granulated slag particles 3 can be transported away either by a wheel loader, by manual unloading, or by an extraction device on the floor.

(22) FIG. 4 shows an alternative configuration. As regards the design of the floor of the working chamber 4, it is evident from the figure that the floor has slight sloping surfaces by which the working chamber 4 is divided into segments or sections in which different product sizes can be roughly separated and transported to separate outlets.

(23) In either case, the floor of the working chamber can be configured either as a simple sheet or as a perforated sheet in order to pass air through the resulting granulate material, so that it becomes possible on the one hand to further cool the granulate material and on the other hand to also remove further energy from the granulate material, which can then be utilized elsewhere (see above). The perforated sheet is designated as the air baffle 23 in FIG. 4.

(24) FIG. 4 furthermore shows how the air blown in from the blower 10 reaches the working chamber 4, is guided therein, and then exits again through the removal site 15. Accordingly, the working chamber 4 is divided into a first section 12 and a second section 13. The two sections in the exemplary embodiment are separated from each other by a baffle plate 14, which is arranged in the ceiling region of the working chamber 4. The first section 12 is in the region where the air and the liquid slag 1 are introduced into the working chamber 4; the length of the first section 12 is preferably between 15% and 35% of the overall length of the working chamber 4, length meaning here the width of the working chamber 4 as viewed according to FIG. 4.

(25) As a result, the air enters into the working chamber in the left end region of the working chamber 4 (see FIG. 4) and takes the path shown by the arrows. The air must then flow around the baffle plate 14 and reaches the removal site 15, where it escapes from the working chamber 4. This ensures that only a minimal fraction of granulate material or dust is present in the air 5 when it leaves the working chamber.

(26) FIG. 5 shows how the hot air is advantageously guided as soon as it has left the working chamber 4. As can be seen from considering both the side view (left side of FIG. 5) and the front view (right side of FIG. 5), the air, after leaving the working chamber 4 at the removal site 15, is at first guided vertically upward along a first section 20 of the air conduit. At the end of the section 20 there is arranged a deflection point 21, by which the air is deflected by 180 and guided into a second section of the air conduit 22, which guides the air vertically downward. At the lower end, the air is returned to the blower 10, which blows it once more into the working chamber 4. An especially convenient site for the arrangement of the heat exchanger 6 is located in the region of the second section 22 of the air conduit.

LIST OF REFERENCE NUMERALS

(27) 1 Liquid slag 2 Air 3 Granulated slag particles 4 Working chamber 5 Air escaping from the working chamber 6 Heat exchanger 7 Consumer 7 Steam generator 7 Heating system 8 Steam turbine/generator system 9 Further air stream 10 Blower 11 Conveyor belt 12 First section of the working chamber 13 Second section of the working chamber 14 Baffle plate 15 Removal site for escaping air 16 Receiving or removal element for defective products 17 Receiving or removal element for granulated slag particles 18 Flight parabola 19 Defective product 20 First section of the air conduit 21 Deflection 22 Second section of the air conduit 23 Air baffle