METHOD OF PROCESSING MOLTEN MATERIAL

Abstract

In a method of processing molten material, in the form of non-metallic melt such as slag, into amorphous material, in which the molten material is vitrified by cooling, wherein the molten material for being vitrified is brought into contact with a metal bath and then discharged as amorphous material from the metal bath, the molten material is introduced into the metal bath via an open end of a dip tube immersing into the metal bath and is in the metal bath conveyed away from the area of the open end of the dip tube, preferably by means of a mechanical disintegrator, preferably a rotor.

Claims

1. A method of processing molten material (5), in the form of non-metallic melt (5) such as slag, into amorphous material (11), in which the molten material (5) is vitrified by cooling, wherein the molten material (5) for being vitrified is brought into contact with a metal bath (3) and then discharged as amorphous material (11) from the metal bath (3), characterized in that the molten material (5) is introduced into the metal bath (3) via an open end (4″) of a dip tube (4′) immersing into the metal bath (3) and in the metal bath (3) is conveyed away from the area of the open end (4″) of the dip tube (4′), preferably by means of a mechanical disintegrator (8), preferably rotor (8).

2. The method according to claim 1, characterized in that the molten material (5) is conveyed from the area of the open end (4″) of the dip tube (4′) at least partially by means of a gas flow introduced into the metal bath (3) via a lance (39), wherein guide vanes (40) for directing a flow are preferably arranged in the metal bath (3) in the region of the mouth of the lance (39).

3. The method according to claim 2, characterized in that the lance (39) is guided inside the dip tube (4′) and dips into the metal bath (3) from above, or the lance (39′) is directed from the metal bath (3) towards the open end (4″) of the dip tube (4′).

4. The method according to claim 1, 2 or 3, characterized in that the molten material (5) is charged onto a reactive metal bath (51), preferably a reactive tin bath (51), that is arranged upstream of the metal bath (3), wherein the reactive metal bath (51) is prepared to adjust the basicity (CaO/SiO.sub.2) of the molten material to a target basicity of 0.85 to 1.6, preferably 1.3 to 1.6, by adding reactive components selected from the group consisting of lime carriers and SiO.sub.2 carriers.

5. The method according to claim 4, characterized in that the reactive metal bath is prepared by adding Al.sub.2O.sub.3 carriers to set an Al.sub.2O.sub.3 content in the molten material of 4 wt.-% to 18 wt.-%.

6. The method according to any one of claims 1 to 5, characterized in that the molten material (5) is sucked or pressed into the metal bath (3) by the action of a mechanical disintegrator (8).

7. The method according to any one of claims 1 to 6, characterized in that the metal bath (3) is formed from tin, preferably alloyed to 3% by weight with silver and 1% by weight with copper.

8. The method according to any one of claims 1 to 7, characterized in that the metal bath (3) is kept at a temperature below the recrystallization temperature of the molten material, in particular at a temperature of between 300° C. and 600° C.

9. The method according to any one of claims 1 to 8, characterized in that the heat introduced into the metal bath (3) by the molten material (5) is dissipated by means of a coolant (19) flowing through a heat exchanger (18).

10. The method according to claim 9, characterized in that the coolant (19) is selected from the group consisting of liquid oxygen, air, inert gas, thermal oil, water and ionic liquids, in particular aqueous solutions of sodium, magnesium and calcium chloride and potassium carbonate.

11. The method according to claim 9 or 10, characterized in that the heat of the coolant (19) is recovered as mechanical and/or electrical energy, in particular in a gas turbine (24) or a pressurized water heat exchanger with combined heat and power.

12. The method according to claim 9, 10 or 11, characterized in that the heat of the coolant (19) is used to promote chemical reactions.

13. The method according to any one of claims 9 to 12, characterized in that the heat of the coolant (19) is used for the depolymerization of plastics, in particular of polyethylene, polypropylene and polyethylene terephthalate.

14. The method according to any one of claims 1 to 13, characterized in that the amorphous material (11) is discharged with the aid of a conveying means selected from the group consisting of a conveyor belt and a conveyor wheel (12).

15. The method according to any one of claims 1 to 14, characterized in that the metal bath (3) is flushed with an inert gas, in particular nitrogen.

16. The method according to any one of claims 1 to 15, characterized in that the amorphous material (11), after having been discharged, is sprayed with at least one liquid selected from the group consisting of water, an aqueous sulfuric acid solution, an aqueous lignin sulfonate solution and sulfonated aromatics, in particular aniline, pyridine, naphthalene, anthracene, phenol and/or cresol derivatives, in particular up to a temperature of the vitrified material of between 120° C. and 250° C.

17. The method according to claim 16, characterized in that the vapors formed during spraying are condensed and recovered.

18. The method according to any one of claims 1 to 17, characterized in that the amorphous material (11) is filtered and/or centrifuged to remove metal entrained from the metal bath.

19. A device for carrying out the method according to any one of claims 1 to 18, comprising a granulating tundish (2) with a preferably annular or rectangular cross-section for receiving a metal bath (3), a dip tube (4′) having an open end (4″) in the granulating area (27) of the granulating tundish (2) provided for the metal bath (3), and a discharge region (14) for the amorphous material (11), characterized in that a mechanical disintegrator (8), preferably rotor (8), is arranged in the area of the open end (4″) of the dip tube (4′).

20. The device according to claim 19, characterized in that a lance (39) immersed in the metal bath (3) for ejecting a gas flow is guided inside the dip tube (4′) and that preferably guide vanes (40) for directing a gas flow are arranged in the metal bath (3) in the area of the mouth of the lance (39).

21. The device according to claim 19, characterized in that a lance (39′) is directed from the metal bath (3) towards the open end (4″) of the dip tube (4′) immersed in the metal bath (3) for ejecting a gas stream and that preferably guide vanes (40′) for directing a gas flow are arranged in the metal bath (3) in the area of the mouth of the lance (39′).

22. The device according to claim 19, 20 or 21, characterized in that the dip tube (4′) is connected to a discharge opening of a storage tundish (4) which receives the molten material (5) and that a weir tube (6) for forming an optionally interrupted annular space (6′) is immersed in the molten material (5).

23. The device according to claim 22, characterized in that a reactive metal bath (51), preferably reactive tin bath (51), is kept in the storage tundish (4), wherein the reactive metal bath (51) comprises reactive components selected from the group consisting of lime carriers and SiO.sub.2 carriers for adjusting the basicity (CaO/SiO.sub.2) of the molten material (5) to a target basicity of 0.85 to 1.6, preferably 1.3 to 1.6.

24. The device according to claim 23, characterized in that the reactive metal bath (51) contains Al.sub.2O.sub.3 carriers for setting an Al.sub.2O.sub.3 content in the molten material of 4 wt.-% to 18 wt.-%.

25. The device according to any one of claims 19 to 24, characterized in that the mechanical disintegrator (8) is formed by a plurality of actuators (29) which can be driven to rotate and by stators (30) emerging from the wall (2′) of the granulating tundish (2).

26 The device according to claim 25, characterized in that the stators (30) and/or the actuators (29) are designed to emit inert gas, preferably nitrogen, into the metal bath (3).

27. The device according to any one of claims 19 to 26, characterized in that the gas space (23) of the granulating tundish (2) is connected to a line for inert gas.

28. The device according to any one of claims 19 to 27, characterized in that a heat exchanger (18) is arranged as a cooling body in or on the wall (2′) of the granulating tundish (2).

29. The device according to any one of claims 19 to 28, characterized in that a heat exchanger (18) is arranged as a cooling body in the granulating tundish (2) in the volume for the metal bath (3).

30. The device according to any one of claims 19 to 29, characterized in that a discharge device in the form of a conveyor wheel (12) is arranged in the discharge region (14).

31. The device according to any one of claims 19 to 29, characterized in that a discharge device (41) in the form of a plurality of conveyor belts (43), for example made of steel belt, guided over pulleys (42) and arranged downstream of one another, is arranged in the discharge region (14), wherein the conveyor belts (43) are conducted out of the metal bath (3) in an ascending way, preferably at an angle of 30° to 50°, particularly preferably 40°, relative to the surface of the metal bath (3), wherein in each case a discharge (44) for the amorphous material (11) and/or for metal carried along from the metal bath (3) is formed at an upper pulley (42) and wherein in each case a discharge (44) of a conveyor belt (43) is arranged above a downstream conveyor belt (43) for forming a cascade of conveyor belts (43).

32. The device according to claim 31, characterized in that a further pulley (45) is each held, preferably resiliently held, against the conveyor belt (43) in the area of the upper pulley (42).

33. The device according to claim 31 or 32, characterized in that the discharge (44) of the last of the successive conveyor belts (43) is arranged above an insertion opening (47) of a cooling device (48) for the amorphous material (11), wherein the cooling device (48) can preferably be flowed through by a coolant (49), preferably in countercurrent.

Description

[0045] The invention is explained in more detail below with reference to an exemplary embodiment shown in the drawing. In the drawings

[0046] FIG. 1 is a schematic representation of a device according to the invention with a dip tube and a mechanical disintegrator for conveying and disintegrating the melt and a heat exchanger in the volume for the metal bath in the granulating tundish.

[0047] FIG. 2 shows a variant according to the invention of a device according to the invention with a mechanical disintegrator in the form of a rotor,

[0048] FIG. 3 shows a preferred design of a rotor,

[0049] FIG. 4 shows a partial plan view of the mechanical disintegrator according to FIG. 3,

[0050] FIG. 5 shows an illustration of a discharge device according to the invention in the form of a hollow roller,

[0051] FIG. 6 shows a variant according to the invention of a device according to the invention with a disintegrator in the form of a lance guided inside the dip tube and immersed in the metal bath,

[0052] FIG. 7 shows a variant according to the invention of a device according to the invention with a disintegrator in the form of a lance directed from the metal bath to the open end of the dip tube immersed in the metal bath,

[0053] FIG. 8 shows a discharge device and

[0054] FIG. 9 shows a preferred variant of a design of a storage tundish.

[0055] A device or granulating device 1 according to the invention for use in carrying out the method according to the invention comprises, according to FIG. 1, a granulating tundish 2 in which a metal bath 3 made of liquid tin is held. From a storage tundish 4, in which the molten material 5 to be vitrified or the melt 5 is located, the molten material 5 is dosed by means of a weir tube 6, which together with the storage tundish 4 forms an annular space 6′, via the open end 4″ of the dip tube 4′ into the underlying granulating tundish 2 with the metal bath 3. The melt 5 hits the surface 7 of the metal bath 3 as an essentially hollow cylindrical jacket and in the metal bath 3 it is subjected to large shear forces by the action of the mechanical disintegrator 8, in this case the rotor 8, which is driven by the shaft 9 to rotate in the direction of the arrow 10. This leads to a disintegration of the melt 5 in the metal bath, which is cooled in finely divided form in the metal bath 3 and instantaneously solidifies in the glass-like, amorphous state and is thus granulated. The granulate 11 or the amorphous material 11 is discharged with the aid of the conveyor wheel 12, which is driven to rotate in the direction of the arrow 13, in the discharge region 14 of the granulating tundish 2 and ejected into a container (not shown). In the area of the mechanical disintegrator 8 or rotor 8, the granulating tundish 2 has a mixing chamber 15 which is kept as constant as possible at a temperature of 300° C., for example, by a heat exchanger 16. The melt 5 flows into the mixing chamber 15 and is mixed into the metal bath 3 there. The base of the mixing chamber has an opening 17 through which molten tin is sucked in from the metal bath 3 by the action of the rotor 8, which leads to an increase in the turbulence in the area of the rotor 8 in order to optimize the disintegration of the melt 5.

[0056] Reference numeral 18 denotes a heat exchanger in the volume for the metal bath 3 in the granulating tundish 2, in which a coolant 19 flows and via which the majority of the heat introduced by the melt 5 is transported away from the metal bath 3 or from the granulating device 1 and is recycled. The gas space 23 of the granulating tundish 2 is covered by a cover 22.

[0057] In FIG. 2, the same features are provided with the same reference signs. In particular, a granulating tundish 2 with a metal bath 3 made of tin is again shown. Via the annular space 6′, the height h.sub.1 of which can be adjusted by raising and lowering the weir tube 6 in the direction of the double arrow 6″, the melt 5 can be introduced into the metal bath 3 via the open end 4″ of the dip tube 4′ and can be disintegrated by means of the rotor 8. The melt 5 is cooled in finely divided form in the metal bath 3 and immediately solidifies in the glass-like, amorphous state and is thus granulated. The granulate 11 is discharged in the discharge region 14 and ejected into a container (not shown). Here, too, the metal bath 3 is kept at a temperature of approximately 300° C., which temperature is maintained by means of the heat exchanger 18. The granulating tundish 2 is covered by the storage tundish 4 and the gas space 23 above the metal bath 3 can preferably be flushed with an inert gas, in particular with nitrogen, to protect and thus extend the service life of the metal bath 3.

[0058] In the example shown in FIG. 2, the heat exchanger 18 conveys air as coolant 19, the heat of the coolant being recovered as electrical energy via a combined heat and power system in the form of a gas turbine 24, which is coupled to a generator 25. A fuel can preferably be added to the hot exhaust air or the coolant in a combustion chamber 26, in order to, e.g., usefully dispose of inferior fuels in the form of dusts, gases or liquids such as tar, which for example occur in small amounts in the production of the molten material from sewage sludge. In FIG. 2, the height of the metal bath 3 is to be understood as a granulating zone 27, followed by a filtering zone 28 in the gas space 23, in the area of the amorphous material 11 or granulate 11, in which any tin can drip off.

[0059] In FIGS. 3 and 4, the mechanical disintegrator 8 is formed by a plurality of actuators 29 that can be driven to rotate by means of a shaft 9 and stators 30 emerging from the wall 2′ of the granulating tundish 2. The actuators 29 and/or the stators 30 can be designed to emit inert gas into the metal bath 3. As can be seen from FIG. 3, there is only a relatively small distance h.sub.2 between the actuators 29 and the stators 30, as a result of which the melt 5 introduced into the metal bath 3 via the open end 4″ of the dip tube 4′ is exposed to high shear forces for disintegration when the stators 30 are swept over by the actuators 29, as is shown schematically in FIG. 4.

[0060] In FIG. 5, instead of a conveyor wheel, a hollow roller 31 which can be driven to rotate in the direction of arrow 31′ is arranged in the discharge region 14, which has a perforated surface 32 to allow any tin adhering to the granulate 11 to run off after it has been picked up by the hollow roller 31 in the direction of the arrow 33 and while the granulate 11 is conveyed to a discharge end 34 of the hollow roller 31 in order to be blown off the surface 32 by a fan 35 there. In addition to this, a scraper 36 can also be provided in order to scrape granules 11 from the surface 32 of the hollow roller 31. Reference numeral 37 denotes a register from which a gas stream in the sense of arrows 38, in particular of air or an inert gas kept isothermally with the tin bath temperature, optionally mixed with reducing gas (H.sub.2, CO, NH.sub.3), in particular nitrogen, is directed onto the perforated surface 32 of the hollow roller 31 for separating adhering tin from the granulate 11.

[0061] In FIG. 6, the same features are denoted by the same reference numerals as in FIG. 2 and it can be seen that a lance 39 guided inside the dip tube 4′ and immersed in the metal bath 3 is provided. A gas stream of inert gases such as nitrogen or CO.sub.2 and/or of reactive gases such as H.sub.2 or CO or NH.sub.3 can be ejected from the lance 39 into the area of the open end 4″ and into the top layer of the metal bath 3 in order to convey the molten material 5 into the metal bath 3 by means of the resulting suction and at the same time to subject it to high shear forces for comminution. The amorphous material 11 or granulate 11 formed is conveyed out of the area of the open end 4″ of the dip tube 4′ by the resulting flow. Reference numeral 40 designates guide vanes for directing a flow. The lance 39 can be rotatably mounted and used as a shaft for an optional disintegrator 8.

[0062] Furthermore, a lance 39′ directed from the metal bath 3 to the open end 4″ of the dip tube immersed in the metal bath 3 is shown in FIG. 7. In the area of the mouth of the lance 39, guide vanes 40″ are arranged for directing a flow. A gas stream of inert gases such as nitrogen or CO.sub.2 and/or of reactive gases such as H.sub.2, CO or NH.sub.3 can be ejected from the lance 39 through the guide vanes 40′ into the area of the open end 4″ and into the top layer of the metal bath 3, in order to convey the molten material 5 into the metal bath 3 by the resulting suction and at the same time to subject it to high shear forces for comminution. The amorphous material 11 or granulate 11 formed is conveyed out of the area of the open end 4″ of the dip tube 4′ by the resulting flow.

[0063] In FIG. 8 a discharge device 41 is shown in the form of a plurality of conveyor belts 43 made of steel belt, guided over pulleys 42 and arranged downstream of one another, wherein the conveyor belts 43 are conducted out of the metal bath 3 in an ascending way, preferably at an angle of about 30° to 50° relative to the surface of the metal bath 3, wherein in each case a discharge 44 for the amorphous material 11 and for metal carried along from the metal bath 3 is formed at an upper pulley 42 and wherein in each case a discharge 44 of a conveyor belt 43 is arranged above a downstream conveyor belt 43 for forming a cascade of conveyor belts 43. In each case in the area of the upper pulley 42, a further roller 45 is held against the conveyor belt 43 by means of a spring 46. These further rollers 45, which can also be referred to as squeezing rollers, exert an adjustable pressure on the amorphous material 11 and thus squeeze adhering molten metal from the mass of the amorphous material 11. The discharge 44 of the last of the conveyor belts 43 arranged downstream of one another is arranged above an insertion opening 47 of a cooling device 48 for the amorphous material, the cooling device 48 preferably being flowed through by a coolant 49, preferably in countercurrent. The coolant 49 can in turn be used to cool the granulating tundish 2 and for this purpose it can be fed to the wall of the granulating tundish 2, as shown in FIG. 2. The cooling device 48 has a screw conveyor 48′ for conveying the granulate 11.

[0064] In the illustration according to FIG. 9 it can be seen that the provision of an annular weir 50 or weir stone 50 creates a volume 50′ for holding a reactive metal bath 51, wherein the annular space 6′ in this case is formed between the weir 50 and the weir tube 6. The arrows 52 symbolize that the storage tundish 4 can be heated if this should be necessary.