EP0738334B1 - Magnesium melting furnace and process for melting magnesium - Google Patents

Magnesium melting furnace and process for melting magnesium Download PDF

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Publication number
EP0738334B1
EP0738334B1 EP95937021A EP95937021A EP0738334B1 EP 0738334 B1 EP0738334 B1 EP 0738334B1 EP 95937021 A EP95937021 A EP 95937021A EP 95937021 A EP95937021 A EP 95937021A EP 0738334 B1 EP0738334 B1 EP 0738334B1
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EP
European Patent Office
Prior art keywords
chamber
melt
magnesium
melting furnace
passage
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP95937021A
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German (de)
French (fr)
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EP0738334A1 (en
Inventor
Dominik Schroeder
Erich Rauch
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ing Rauch Fertigungstechnik GmbH
Schmitz and Apelt LOI Industrieofenanlagen GmbH
Original Assignee
Ing Rauch Fertigungstechnik GmbH
Schmitz and Apelt LOI Industrieofenanlagen GmbH
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Application filed by Ing Rauch Fertigungstechnik GmbH, Schmitz and Apelt LOI Industrieofenanlagen GmbH filed Critical Ing Rauch Fertigungstechnik GmbH
Publication of EP0738334A1 publication Critical patent/EP0738334A1/en
Application granted granted Critical
Publication of EP0738334B1 publication Critical patent/EP0738334B1/en
Anticipated expiration legal-status Critical
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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D27/00—Stirring devices for molten material
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B26/00—Obtaining alkali, alkaline earth metals or magnesium
    • C22B26/20—Obtaining alkaline earth metals or magnesium
    • C22B26/22—Obtaining magnesium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
    • C22B9/05—Refining by treating with gases, e.g. gas flushing also refining by means of a material generating gas in situ
    • C22B9/055—Refining by treating with gases, e.g. gas flushing also refining by means of a material generating gas in situ while the metal is circulating, e.g. combined with filtration
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D3/00—Charging; Discharging; Manipulation of charge
    • F27D3/14—Charging or discharging liquid or molten material
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D3/00—Charging; Discharging; Manipulation of charge
    • F27D2003/0034—Means for moving, conveying, transporting the charge in the furnace or in the charging facilities
    • F27D2003/0054—Means to move molten metal, e.g. electromagnetic pump
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D3/00—Charging; Discharging; Manipulation of charge
    • F27D2003/0034—Means for moving, conveying, transporting the charge in the furnace or in the charging facilities
    • F27D2003/0063—Means for moving, conveying, transporting the charge in the furnace or in the charging facilities comprising endless belts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D3/00—Charging; Discharging; Manipulation of charge
    • F27D3/08—Screw feeders; Screw dischargers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D99/00—Subject matter not provided for in other groups of this subclass
    • F27D99/0001—Heating elements or systems
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S266/00—Metallurgical apparatus
    • Y10S266/90—Metal melting furnaces, e.g. cupola type
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S266/00—Metallurgical apparatus
    • Y10S266/901—Scrap metal preheating or melting

Definitions

  • the invention relates to a magnesium melting furnace and a method for melting and cleaning magnesium.
  • Magnesium is increasingly used as a material, especially for the production of castings used. Magnesium, like aluminum, is made from an electrolysis process won and cast into bars, press bolts or ingots. These will be in front of yours Further processing melted down in special melting furnaces. This will return scrap added. The growing share of return scrap leads to a higher one Contamination (contamination) of the starting material fed to the melting furnace.
  • EP-A-0055815 describes a method and an oven for processing or cleaning known from magnesium melt.
  • the furnace has several chambers for processing or cleaning the melt.
  • the melt is in a separate Melting furnace produced.
  • the material is usually added by means of electrolysis melted by salt.
  • the mixture of magnesium melt and salt becomes the first treatment chamber of the known furnace supplied. Since the molten salt z. T. is heavier than the molten magnesium, it settles on the ground with the Impurities.
  • the bottom of the first processing chamber assigns a slope a sludge collection chamber, which is located in front of the treatment chambers.
  • the chambers are formed by means of partitions, which are above the furnace floor ends, so that first passages are formed in the floor area. In the partitions there are additional passages to ensure that the magnesium gradually flows through the chambers.
  • a melting furnace is made of material to be melted over one above the melt located refill opening supplied. Via a siphon-like connecting line the melt is removed from the furnace below the surface of the melt and fed to a casting furnace. The melt in the casting furnace serves as a supply for the Further processing into castings. The melted is used for further processing Magnesium via a second siphon-like connecting line from the casting furnace removed and fed to a mold.
  • the disadvantage of this known system is the high cost of commissioning due to the use of two ovens and the siphon-like connecting lines.
  • the entire system including the siphon-like connecting lines must be the melting point of the magnesium are heated, so that both in the casting furnace there is also a liquid melt in the melting furnace. Then must a special pressure line, the pressure in the casting furnace can be increased so that the siphon-like connecting lines are completely filled with liquid magnesium. After the pressure has been reduced again, the melt levels are equal in the two furnaces, so that when liquid magnesium is removed from the Pouring furnace for further processing via the siphon-like magnesium connecting line is fed out of the melting furnace.
  • the object of the invention is to reduce the energy loss when melting the magnesium and in the provision of an environmentally friendly, cleaned melt with reduction to reduce the structural effort.
  • this object is achieved with a magnesium melting furnace
  • the use of at least one second chamber makes it possible to melt and combining the cleaning of the melt in a melting furnace. Due to the Melt cleaning is the use of a more contaminated starting material, For example, the use of a higher proportion of old scrap is possible. Due to the special guidance of the melt flow through a suitable arrangement of the A large part of the contaminants can pass through the outlet or outlet Melt surface rise or sink to the bottom of the chambers from where from which contamination can be easily removed. Eddies in the first chamber (the melting chamber) by immersing the one to be melted Material and caused by the convection currents generated by the burners prevent impurities from settling or rising. This The disadvantage is the overflow of the melt into the at least one second Compensated chamber (the rest chamber). There are no swirls in this chamber instead of; the contaminants can rise or settle. The order of the passage and that of the outlet are chosen so that as few as possible Contamination parts pass through with the flow.
  • the walls of the first and the second chamber are steel walls. Steel walls allow good heat transfer. It is advantageous to all Chambers, partitions and partitions also to be designed as steel walls. The Use of steel walls allows an arrangement of burners for direct heating of the chambers via the walls of the first and the second chamber. It is also possible to use an electrical one that acts in the same way Resistance heating.
  • the spaces of the first and second chambers and possibly also the third chamber above the melt are insulated from one another by the first partition or further partition walls and can be filled separately with protective gas, different protective gas compositions and concentrations being present in the spaces the first and the second (and possibly the third) chamber can be generated.
  • the shielding gas composition to be set as a function of the reaction parameters on the surface of the respective chambers.
  • the protective gas usually contains an SF 6 component. The separation of the rooms above the chambers enables different SF 6 proportions above the melts in the chambers.
  • a protective gas with a higher SF 6 content is present in the space above the melt in the first chamber than in the space above the melt in the second chamber.
  • the SF 6 proportion is chosen to be relatively high (0.5%) only where such a high concentration is required.
  • the SF 6 content above the second chamber and possibly other chambers is only 0.2 to 0.3%. This reduces the corrosion effects of the sulfuric acid formed from SF 6 in these chambers, which leads to a longer service life of the melting furnace.
  • the at least one first passage and the at least one outlet are one in the gap extending substantially over the entire width of the first partition.
  • the first and the second chamber can have a substantially rectangular base area and the first partition and the downstream one, the outlet having wall of the second chamber are arranged flat and parallel to each other. This simplifies the flow conditions in the second chamber and lowers the Effort in the manufacture of the melting furnace.
  • the length of the second chamber in the flow direction can be chosen sufficiently large.
  • the distances between the first Partition, the middle wall and the wall having the outlet and the height the middle wall is dimensioned such that a melt flows through it in the second chamber meandering channel of essentially constant flow cross-section is formed.
  • the flow is more Partitions and middle walls deflecting the melt are conceivable. The flow conditions so influenced that the settling or rising of contaminants is improved.
  • the bottoms of the first and the second chamber inclined surfaces which are arranged so that a gutter is formed, at the lowest point of falling impurities the melt, in particular melt sludge containing heavy metals collect.
  • This concentration of impurities at certain points on the chamber floors enables easy removal.
  • a first and a second suction device is arranged in the first or in the second chamber, that they have the sunk contaminants at the deepest point of the chamber floors can suction. This allows the maximum height of the melt sludge in the chambers are kept low, which allows a deeper arrangement of the passages and thus leads to better utilization of the chamber volume.
  • the gutter can be formed both by sloping floor plates as well as by arching the floors.
  • the suction device can both one pipe inserted into the melt from above and one from below to the Have a chamber-mounted drain.
  • the minimum area is calculated from a maximum flow velocity Melt melted in the passage for a given material flow Magnesium through the magnesium melting furnace.
  • Limiting the flow rate in the passage serves to avoid this of turbulence in the flowing melt at the passage. This prevents that Entrainment of contaminants, for example from the melt sludge Floor of the chamber.
  • a maximum flow rate is preferred selected below 0.05 m / sec.
  • the magnesium is preferably replaced by one below the melting surface the charging chamber is inserted into the first chamber.
  • the material to be melted does not fall onto the surface of the melt pool and thus only tears very little on the surface inside the charging shaft any dross in the bath. It will also be a more targeted intake of the material to be melted with less swirling of the melt pool enables.
  • the material to be melted becomes the first one before being fed Chamber thermally pretreated, contaminants swelling and / or evaporating.
  • the material to be melted for example magnesium scrap contaminated with oil, z. B. brought up to the melting furnace via an encapsulated conveyor.
  • a section of the conveyor has a heating section in which the continuous Material is heated, whereby the contaminants (e.g. oil residues) evaporate and / or evaporate.
  • the resulting gas is encapsulated in the conveyor (Carbonization gas) and can be used for other purposes.
  • the heated material is fed into the charging shaft via locks and dips under the melt surface.
  • the thermal pre-treatment lowers the proportion of impurities in the material supplied to the weld pool and thus leads to less itching and the avoidance of otherwise necessary deduction of the reaction gases, which are above the would form in the first chamber. This will make the use of a higher proportion of return and old scrap.
  • the material to be melted is at a temperature of about 300 ° C heated up to 450 ° C.
  • the carbonization gases collected during the thermal pretreatment can either a burner for heating the material to be melted in the desoldering device (indirect heating; radiant tubes) or a burner for melting the Materials are fed.
  • the carbonization gases collected can be can be supplied with a heat exchanger coupled burner, the heat exchanger can serve to preheat the combustion air.
  • the weight of the melting furnace is preferably determined and the one to be melted Material fed depending on the furnace weight so that the furnace weight and thus the fill level of the melt remains approximately constant.
  • the mass of the supplied material to be melted corresponds to the mass loss the furnace by removing molten magnesium and / or removing it of impurities (suction of the sludge from the ground). So the fill level the chamber kept approximately constant, so that the material to be melted always immersed under the melt surface and the flow conditions in the Chambers remain constant.
  • the melt is fed by means of a metering pump to which a transfer tube filled with protective gas is attached is connected across the melt surface of the third chamber discharged laterally under a lid insulation. Flushing the transfer tube with Shielding gas prevents oxidation of the extracted magnesium.
  • a magnesium melting furnace 1 shows a magnesium melting furnace 1 according to the invention with three chambers that melt, clean and dispense of magnesium.
  • a first chamber, the Melting chamber 2, the material to be melted is fed.
  • the molten magnesium flows into one second chamber, the stand-off chamber 4, in the during the stay of the molten magnesium or sink.
  • the cleaned molten magnesium reaches a metering chamber 6, in which it is provided for removal.
  • the chambers 2, 4 and 6 of the magnesium melting furnace 1 are from Surrounded steel walls 10. The steel walls ensure one relatively good heat transfer. Between the melting chamber 2 and the stand-off chamber 4, a first partition 11 is arranged and between the stand-off chamber 4 and the metering chamber 6 one second partition 12. The first and second partition 11 and 12 are also made of steel. The three chambers are surrounded by a heat-insulating jacket 13. The floors 14, 15 and 16 of the three chambers lie on the casing 13 on while between the side walls 10 of the chambers and the lateral parts of the casing 13 a combustion chamber 9 is formed is. An arrangement is also conceivable in which the Oven chambers are placed on a steel frame, so that too heating of the steel wall from below is possible.
  • the Heating the melting chamber 2 are on the front and on two burners 17 and 18 on each of the two lateral outer walls arranged in the casing 13 so that their flames and Heat radiation on the outer wall 10 of the melting chamber 2 are directed.
  • the burners 17 heat the end face of the Melting chamber 2 and the burner 18 the side walls.
  • On Each side wall of the holding chamber 4 is another burner 21 arranged, which is located in the holding chamber 4 Melt additionally heated.
  • a burner 21a be provided for heating the metering chamber 6. That burner 21a then takes over the additional heating of the withdrawing melt in the chamber 6 when the burners 17, 18th and 21 are not active because no material is supplied and is melted.
  • the The number, size and distribution of the burners can be varied.
  • the burner 17, 18, 21 and 21a in the Combustion chamber 9 introduced hot exhaust gases flow along the outer walls 10 to the exhaust outlet 19, which in the Sheath 13 is arranged behind the metering chamber 6.
  • Exhaust gases can also be extracted below the chambers. In order to could have additional heating surface and thus melting capacity be won.
  • the material to be melted is transferred to the melting chamber 2 a charging shaft 20 supplied.
  • the charging shaft 20 dips under the melt surface with its lower end the melting chamber 2.
  • the material immersed in the melt of the melting chamber 2 is melted, leaving impurities in the melt be included.
  • Part of the contaminants, in particular heavy metal-containing melt sludge sinks to the bottom 14 the melting chamber 2.
  • the impurities collect on the surface of the weld pool in the form of scabies.
  • the first passage 3 is formed in the first partition 11 as a horizontal gap. The lower edge of the gap 3 is sufficient Height above that settling on the bottom 14 of the melting chamber 2 Layer of impurities to carry or transfer of impurities from the melt sludge into the holding chamber 4 to avoid.
  • the passage is about 150 mm above the floor 14.
  • the Gap 3 is sufficiently large to have a low flow rate of the melt passing through at a given to achieve maximum throughput of the magnesium melting furnace 1. For a furnace with a throughput of around 1t / h the size of the gap 3 about 50mm x 500mm.
  • a sink 22 can optionally be arranged in the holding chamber 4, which is gassed with a protective gas (N 2 with 0.2 to 0.5% SF 6 ).
  • a protective gas N 2 with 0.2 to 0.5% SF 6 .
  • the escaping protective gas rises to the surface in the stand-off chamber and entrains contaminants.
  • an overflow weir 23 arranged in the middle of the storage chamber 4 between the first partition 11 and the second partition 12 .
  • the height of the overcurrent weir is about 50% to 80%, preferably 70% of the melt level.
  • This overflow weir 23 is used, among other things. avoided the melt entering through the first passage 3 directly to the second passage 5 flows straight ahead and so too small Time in the rest room. This will make cleaning the melt in the holding chamber 4 improved.
  • a part sinks as it flows through the holding chamber 4 the impurities, in particular melt sludges containing heavy metals, on the floor 15 of the chamber 4.
  • Another Part of the contamination rises to the surface of the melt and forms a layer (scabies) there.
  • Passage 5 enters the melt cleaned in the holding chamber 4 into the dosing chamber 6.
  • the second passage 5 is as well the first passage 3 is arranged at a low height above the floor 15, to let a melt as pure as possible pass through.
  • the lower edge is to avoid sunken contamination of the second passage 5 above the maximum height of the layer of impurities depositing on the bottom 15 of the holding chamber 4 arranged.
  • the second passage 5 is the same as the first Passage 3 formed as a horizontal gap.
  • the second Passage is at a height of about 100 mm above the Floor 15.
  • a ceramic filter 25 can be attached Immediately behind the second passage 5 can in the metering chamber 6 .
  • the ceramic filter 25 is used for further cleaning in the dosing chamber 6 entering melt.
  • a metering pump 27 is arranged in the metering chamber 6. This lifts the molten magnesium to be removed from the surface of the melt and transfers the melt into a transfer tube 28.
  • the transfer tube 28 is under the lid insulation 29 led laterally outwards.
  • To drain the melted To effect magnesium is the transfer tube 28 slightly inclined downwards.
  • the one emerging from the casing 13 Part of the transfer tube 28 is provided with a heater 30, for example, an electric heater.
  • the removed Magnesium melt is a die casting machine or fed to a transport container.
  • the transfer tube is the preferred Embodiment filled with a protective gas.
  • the Shielding gas is passed through the transfer tube 28 where pulsed fumigation is provided to save inert gas is.
  • the spaces above the melt surface in the three chambers 2, 4 and 6 are filled with protective gas to avoid oxidation.
  • the partition walls 11 and 12 are guided up to the cover insulation 29 in order to achieve a separation of the spaces filled with inert gas.
  • the shielding gas is supplied via a system 31 of pipes and valves. The valves are controlled so that the compositions of the protective gas atmospheres located above the three chambers can be adjusted separately.
  • a staggered protective gassing is possible in such a way that a protective gas atmosphere with a higher SF 6 content in the space above the melt in the melting chamber 2 and a lower SF 6 content in the rooms above the melt in the stand-off and metering chamber (4 and 6). Share can be set.
  • the SF 6 content above the melt of the melting chamber 2 is approximately 0.5% and above the melt of the stand-off chamber 4 and the metering chamber 6 is approximately 0.2 to 0.3%.
  • This staggered protective gassing enables SF 6 to be saved; In addition, the corrosion caused by the SF 6 in the stand-off and in the dosing chamber is reduced.
  • the stand-off chamber 4 has an additional shaft 32, through the material for re-alloying the molten magnesium can be introduced. That through this shaft 32 in the Abstandhunt 4 introduced material is relatively pure, so that it creates no further contaminants in the holding chamber.
  • the additional shaft 32 dips just like the charging shaft 20 below the melt pool surface to insert parts to be melted entrainment of contaminants from the melt pool surface and to avoid turbulence. Furthermore, the additional shaft 32 is via the system 31 from Pipes and valves can be filled with protective gas.
  • Fig. 2 shows a device for suctioning off the floor 41 of a chamber 40 settling impurities 45
  • Fig. 2 shows a section perpendicular to the plane of the view according to 1 through the melting chamber 2 or the stand-off chamber 4, hereinafter generally referred to as chamber 40.
  • the bottom 41 of the chamber 40 has inclined surfaces 42 and 43 on, which are arranged so that in the middle of the chamber 40 forms a groove 44 as the deepest point. In this gutter 44 melt sludge 45.
  • a tube 46 projects from above into the chamber 40 and into the Melt into it, with the tube 46 in the immediate vicinity of the Channel 44 in melt sludge 45 ends.
  • a line 47 is attached to a suction pump 48 leads. With the help of the suction pump 48, the melt sludge 45 aspirated from the bottom 41 of the chamber 40 and into a container 49 promoted.
  • Fig. 3 shows a device for feeding the to be melted Materials in the magnesium melting furnace 1.
  • the starting material 50 which is both relatively pure magnesium raw material in the form of ingots and return scrap as also contaminated with oil and other contaminants Contains old scrap, a filling opening 52 one Desoldering device 51 supplied.
  • a transport device 53 with a slowly moving conveyor belt that transports it fed material through a diagonally upward, encapsulated shaft 54 on all sides up to the upper opening 55 of the Chargierschacht 20 provided with locks 56 upward leading shaft 54 that on the Transport device 53 overlying material with the help of a heated from above onto the material radiating heater 57.
  • heating to about 450 ° C smoldering and / or steaming part of the contaminants (oily contaminants).
  • the decaying or evaporating dirt form a Smoldering gas rising in the shaft 54 and at the upper end 58 of the shaft 54 enters a drain channel 59.
  • the heated Magnesium material to be melted falls at the end of 58 Shaft 54 from the transport device 53 in the with locks 56 provided charging shaft 20 and further into the weld pool.
  • the drain channel 59 has a fan 60 for sucking in Smolder gases on. 3 in the exemplary embodiment the carbonized gases sucked in are burned by a burner 61.
  • the hot exhaust gases reach a via a heat exchanger 62 Chimney 63.
  • the heat energy obtained in the heat exchanger can used to heat the combustion air for the burners 17 become.
  • the quantity to be fed to the magnesium melting furnace 1 to be melted Material is driven by the conveyor 53 controlled. Controlling the supply of the material to be melted takes place depending on the weight of the melting furnace 1.
  • the magnesium melting furnace is on one edge of the bottom of the casing 13 rotatably mounted. On the opposite edge a bearing provided with a load cell is provided. The force measured with the help of this measuring cell is converted into a weight of the magnesium melting furnace 1. From the determined time-dependent weight difference becomes the required Determines the amount of material to be fed to the furnace. By keeping it constant of the weight of the magnesium melting furnace concerned that the melt level in the furnace chambers approximately remains constant. This ensures an uninterrupted Immerse the lower limit of the charging shaft 20 below the melt surface. In addition, the Flow conditions in the furnace kept approximately constant.

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  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geology (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Vertical, Hearth, Or Arc Furnaces (AREA)
  • Waste-Gas Treatment And Other Accessory Devices For Furnaces (AREA)
  • Processing Of Solid Wastes (AREA)
  • Furnace Details (AREA)
  • Feeding, Discharge, Calcimining, Fusing, And Gas-Generation Devices (AREA)

Abstract

PCT No. PCT/EP95/04232 Sec. 371 Date Jul. 2, 1996 Sec. 102(e) Date Jul. 2, 1996 PCT Filed Sep. 27, 1995 PCT Pub. No. WO96/14439 PCT Pub. Date May 17, 1995The magnesium melting furnace (1) has a plurality of chambers. The material to be melted is fed into a melting chamber (2) through a charging chute (20), one end of which terminates under the surface of the melting bath. The melt is slowly transferred into a holding chamber (4) through a passage (3) situated in the lower third of a dividing wall (11) above a layer of impurities settling at the bottom (14) of the melting chamber (2). The melt slowly flows through the holding chamber (4), with impurities rising to the surface or settling on the bottom (15). The purified melt flows through a second passage (5) situated in the lower third of a second dividing wall (12) into a metering chamber (6). The melt can be removed from the metering chamber (6) through a transfer pipe (28) using a metering pump (27). The magnesium melting furnace (1) makes it possible to simultaneously melt, purify and remove the magnesium in metered quantities.

Description

Die Erfindung betrifft einen Magnesium-Schmelzofen und ein Verfahren zum Schmelzen und Reinigen von Magnesium.The invention relates to a magnesium melting furnace and a method for melting and cleaning magnesium.

Magnesium wird zunehmend als Werkstoff, insbesondere zur Herstellung von Gußteilen eingesetzt. Magnesium wird, ähnlich wie Aluminium, aus einem Elektrolyseverfahren gewonnen und zu Barren, Preßbolzen oder Masseln vergossen. Diese werden vor ihrer Weiterverarbeitung in speziellen Schmelzöfen eingeschmolzen. Dabei werden Rücklaufschrotte zugesetzt. Der wachsende Anteil an Rücklaufschrotten führt zu einer höheren Verunreinigung (Kontamination) des dem Schmelzofen zugeführten Ausgangsmaterials.Magnesium is increasingly used as a material, especially for the production of castings used. Magnesium, like aluminum, is made from an electrolysis process won and cast into bars, press bolts or ingots. These will be in front of yours Further processing melted down in special melting furnaces. This will return scrap added. The growing share of return scrap leads to a higher one Contamination (contamination) of the starting material fed to the melting furnace.

Aus der EP-A-0055815 ist ein Verfahren und ein Ofen zum Aufbereiten bzw. Reinigen von Magnesiumschmelze bekannt. Der Ofen weist mehrere Kammern zum Aufbereiten bzw. Reinigen der Schmelze auf. Die Schmelze wird in einem gesonderten Schmelzofen erzeugt. Üblicherweise wird das Material mittels Elektrolyse unter Zugabe von Salz geschmolzen. Das Gemisch aus Magnesiumschmelze und Salz wird der ersten Aufbereitungskammer des bekannten Ofens zugeführt. Da das Schmelzsalz z. T. schwerer als das geschmolzene Magnesium ist, setzt es sich am Boden mit den Verunreinigungen ab. Der Boden der ersten Aufbereitungskammer weist ein Gefälle zu einer Schlamm-Sammelkammer auf, die sich vor den Aufbereitungskammem befindet. Die Kammern werden mittels Trennwänden gebildet, die oberhalb des Ofenbodens enden, so daß im Bodenbereich erste Durchlässe gebildet werden. In den Trennwänden befinden sich weitere Durchlässe, um zu gewährleisten, daß das Magnesium nach und nach durch die Kammern strömt.EP-A-0055815 describes a method and an oven for processing or cleaning known from magnesium melt. The furnace has several chambers for processing or cleaning the melt. The melt is in a separate Melting furnace produced. The material is usually added by means of electrolysis melted by salt. The mixture of magnesium melt and salt becomes the first treatment chamber of the known furnace supplied. Since the molten salt z. T. is heavier than the molten magnesium, it settles on the ground with the Impurities. The bottom of the first processing chamber assigns a slope a sludge collection chamber, which is located in front of the treatment chambers. The chambers are formed by means of partitions, which are above the furnace floor ends, so that first passages are formed in the floor area. In the partitions there are additional passages to ensure that the magnesium gradually flows through the chambers.

Weiterhin ist eine Anordnung zum Schmelzen von Preßbolzen und Masseln und zur Weiterverarbeitung des geschmolzenen Magnesiums aus der DE 41 16 998 A1 bekannt. Einem Schmelzofen wird zu schmelzendes Material über eine über der Schmelze befindliche Nachfüllöffnung zugeführt. Über eine syphonartige Verbindungsleitung wird die Schmelze unterhalb der Schmelzenoberfläche dem Schmelzofen entnommen und einem Gießofen zugeführt. Die Schmelze in dem Gießofen dient als Vorrat für die Weiterverarbeitung zu Gußteilen. Zur Weiterverarbeitung wird das geschmolzene Magnesium über eine zweite syphonartige Verbindungsleitung aus dem Gießofen entnommen und einer Kokille zugeführt.Furthermore, there is an arrangement for melting press bolts and ingots and for Further processing of the molten magnesium is known from DE 41 16 998 A1. A melting furnace is made of material to be melted over one above the melt located refill opening supplied. Via a siphon-like connecting line the melt is removed from the furnace below the surface of the melt and fed to a casting furnace. The melt in the casting furnace serves as a supply for the Further processing into castings. The melted is used for further processing Magnesium via a second siphon-like connecting line from the casting furnace removed and fed to a mold.

Nachteilig bei dieser bekannten Anlage ist der hohe Aufwand bei der Inbetriebnahme aufgrund der Verwendung zweier Öfen und der syphonartigen Verbindungsleitungen. Die gesamte Anlage einschließlich der syphonartigen Verbindungsleitungen muß über den Schmelzpunkt des Magnesiums aufgeheizt werden, damit sowohl im Gießofen als auch im Schmelzofen eine flüssige Schmelze vorhanden ist. Anschließend muß mit einer speziellen Druckleitung der Druck im Gießofen soweit erhöht werden, daß die syphonartigen Verbindungsleitungen vollständig mit flüssigem Magnesium gefüllt werden. Nachdem der Druck wieder reduziert worden ist, gleichen sich die Schmelzenspiegel in den beiden Öfen aus, so daß bei einer Entnahme flüssigen Magnesiums aus dem Gießofen zur weiteren Verarbeitung über die syphonartige Verbindungsleitung Magnesium aus dem Schmelzofen nachgeführt wird.The disadvantage of this known system is the high cost of commissioning due to the use of two ovens and the siphon-like connecting lines. The entire system including the siphon-like connecting lines must be the melting point of the magnesium are heated, so that both in the casting furnace there is also a liquid melt in the melting furnace. Then must a special pressure line, the pressure in the casting furnace can be increased so that the siphon-like connecting lines are completely filled with liquid magnesium. After the pressure has been reduced again, the melt levels are equal in the two furnaces, so that when liquid magnesium is removed from the Pouring furnace for further processing via the siphon-like magnesium connecting line is fed out of the melting furnace.

Die Verwendung zweier separater Öfen ist energetisch ungünstig und führt zu einem relativ hohen baulichen Aufwand.The use of two separate stoves is energetically unfavorable and leads to one relatively high construction costs.

Ferner erlaubt eine solche Anordnung nicht die Verwendung kontaminierter Rücklaufschrotte, da die Schmelze im Schmelzofen, wie sie von der syphonartigen Verbindungsleitung abgeführt wird, bereits relativ rein sein muß, weil keine weitere Reinigung im Gießofen erfolgt.Furthermore, such an arrangement does not allow the use of contaminated return scrap, since the melt in the melting furnace, as it comes from the siphon-like connecting line dissipated, must already be relatively pure, because no further cleaning in Casting furnace takes place.

Aufgabe der Erfindung ist es, den Energieverlust beim Schmelzen des Magnesiums und bei der Bereitstellung einer umweltschonenden gereinigten Schmelze unter Verminderung des baulichen Aufwands zu reduzieren.The object of the invention is to reduce the energy loss when melting the magnesium and in the provision of an environmentally friendly, cleaned melt with reduction to reduce the structural effort.

Erfindungsgemäß wird diese Aufgabe durch einen Magnesiumschmelzofen mit den Merkmalen des Anspruchs 1, die Verwendung dieses Ofens nach Anspruch 9 und ein Verfahren mit den Merkmalen des Anspruchs 10 gelöst.According to the invention, this object is achieved with a magnesium melting furnace Features of claim 1, the use of this furnace according to claim 9 and a method having the features of claim 10 solved.

Bevorzugte Ausführungsformen werden in den Unteransprüchen beansprucht.Preferred embodiments are claimed in the subclaims.

Die Verwendung wenigstens einer zweiten Kammer ermöglicht es, das Schmelzen und das Reinigen der Schmelze in einem Schmelzofen zu kombinieren. Aufgrund der Schmelzenreinigung ist die Verwendung eines stärker verunreinigten Ausgangsmaterials, beispielsweise die Verwendung eines höheren Anteils von Altschrotten, möglich. Durch die spezielle Führung der Schmeizenströmung durch geeignete Anordnung des Durchlasses bzw. des Auslasses kann ein großer Teil der Verunreinigungen an die Schmelzenoberfläche aufsteigen bzw. auf den Boden der Kammern absinken, von wo aus die Verunreinigungen leicht entfernt werden können. Verwirbelungen, die in der ersten Kammer (der Schmelzkammer) durch das Eintauchen des zu schmelzenden Materials und durch die von den Brennern erzeugten Konvektionsströmungen hervorgerufen werden, behindern das Absetzen bzw. Aufsteigen von Verunreinigungen. Dieser Nachteil wird durch das Überströmen der Schmelze in die mindestens eine zweite Kammer (die Abstehkammer) kompensiert. In dieser Kammer finden keine Verwirbelungen statt; die Verunreinigungen können aufsteigen bzw. sich absetzen. Die Anordnung des Durchlasses und die des Auslasses sind so gewählt, daß möglichst wenige Verunreinigungsanteile mit der Strömung hindurchtreten.The use of at least one second chamber makes it possible to melt and combining the cleaning of the melt in a melting furnace. Due to the Melt cleaning is the use of a more contaminated starting material, For example, the use of a higher proportion of old scrap is possible. Due to the special guidance of the melt flow through a suitable arrangement of the A large part of the contaminants can pass through the outlet or outlet Melt surface rise or sink to the bottom of the chambers from where from which contamination can be easily removed. Eddies in the first chamber (the melting chamber) by immersing the one to be melted Material and caused by the convection currents generated by the burners prevent impurities from settling or rising. This The disadvantage is the overflow of the melt into the at least one second Compensated chamber (the rest chamber). There are no swirls in this chamber instead of; the contaminants can rise or settle. The order of the passage and that of the outlet are chosen so that as few as possible Contamination parts pass through with the flow.

Durch die Strömungsführung in dem erfindungsgemäßen Mehrkammerofen ist eine ausreichende Reinigung der Schmelze auch ohne Zugabe von Reinigungssalzen zum Schmelzbad möglich. Durch den Wegfall der Salzzugabe wird die Umweltbelastung verringert und hohe Kosten für die Entsorgung von Rückständen werden vermieden.Due to the flow in the multi-chamber furnace according to the invention, one is sufficient cleaning of the melt even without the addition of cleaning salts for Melting pool possible. By eliminating the addition of salt, the environmental impact reduced and high costs for the disposal of residues are avoided.

Die Wandungen der ersten und der zweiten Kammer sind Stahlwandungen. Stahlwandungen erlauben einen guten Wärmeübergang. Vorteilhaft ist es, sämtliche Kammern, Trenn- und Zwischenwände ebenfalls als Stahlwandungen auszubilden. Die Verwendung von Wandungen aus Stahl erlaubt eine Anordnung von Brennern zum direkten Beheizen der Kammern über die Wandungen der ersten und der zweiten Kammer. Möglich ist auch der Einsatz einer in gleicher Weise wirkenden elektrischen Widerstandsbeheizung.The walls of the first and the second chamber are steel walls. Steel walls allow good heat transfer. It is advantageous to all Chambers, partitions and partitions also to be designed as steel walls. The Use of steel walls allows an arrangement of burners for direct heating of the chambers via the walls of the first and the second chamber. It is also possible to use an electrical one that acts in the same way Resistance heating.

Bei einer vorteilhaften Weiterbildung der Erfindung sind die Räume der ersten und zweiten Kammern und ggf. auch der dritten Kammer über der Schmelze durch die erste Trennwand bzw. weitere Trennwände voneinander isoliert und separat mit Schutzgas füllbar, wobei unterschiedliche Schutzgaszusammensetzungen und -konzentrationen in den Räumen über der ersten und der zweiten (und ggf. der dritten) Kammer erzeugt werden können. Dies erlaubt die Einstellung der Schutzgaszusammensetzung in Abhängigkeit von den Reaktionsparametern an der Oberfläche der jeweiligen Kammern. Zur Vermeidung von Oxydationsreaktionen enthält das Schutzgas üblicherweise einen SF6-Anteil. Die Trennung der Räume über den Kammern ermöglicht unterschiedliche SF6-Anteile über den Schmelzen in den Kammern. Bei einem bevorzugten Ausführungsbeispiel ist im Raum über der Schmelze der ersten Kammer ein Schutzgas mit einem höheren SF6-Anteil als in dem Raum über der Schmelze in der zweiten Kammer vorhanden. Der SF6-Anteil wird nur dort relativ hoch gewählt (0,5 %), wo eine solch hohe Konzentration erforderlich ist. Über der zweiten Kammer und ggf. weiteren Kammern beträgt der SF6-Anteil nur 0,2 bis 0,3 %. Dies verringert die Korrosionswirkungen der sich aus SF6 bildenden Schwefelsäure in diesen Kammern, was zu einer höheren Lebensdauer des Schmelzofens führt.In an advantageous development of the invention, the spaces of the first and second chambers and possibly also the third chamber above the melt are insulated from one another by the first partition or further partition walls and can be filled separately with protective gas, different protective gas compositions and concentrations being present in the spaces the first and the second (and possibly the third) chamber can be generated. This allows the shielding gas composition to be set as a function of the reaction parameters on the surface of the respective chambers. To avoid oxidation reactions, the protective gas usually contains an SF 6 component. The separation of the rooms above the chambers enables different SF 6 proportions above the melts in the chambers. In a preferred embodiment, a protective gas with a higher SF 6 content is present in the space above the melt in the first chamber than in the space above the melt in the second chamber. The SF 6 proportion is chosen to be relatively high (0.5%) only where such a high concentration is required. The SF 6 content above the second chamber and possibly other chambers is only 0.2 to 0.3%. This reduces the corrosion effects of the sulfuric acid formed from SF 6 in these chambers, which leads to a longer service life of the melting furnace.

Um die Forderungen nach einer tiefen Anordnung des Durchlasses (im unteren Drittel der Trennwand), nach einer ausreichenden Höhe des Durchlasses über dem sich absetzenden Schmelzenschlamm und nach einer möglichst großen Querschnittsfläche in Einklang zu bringen, ist es bei einem bevorzugten Ausführungsbeispiel vorgesehen, daß der wenigstens eine erste Durchlaß und der wenigstens eine Auslaß ein sich im wesentlichen über die gesamte Breite der ersten Trennwand erstreckender Spalt ist.To meet the demands for a deep arrangement of the culvert (in the lower third the partition), after a sufficient height of the passage above the settling Melt sludge and after the largest possible cross sectional area in In a preferred exemplary embodiment, it is provided that that the at least one first passage and the at least one outlet are one in the gap extending substantially over the entire width of the first partition.

Zur Verbesserung der Strömungsverhältnisse in der zweiten Kammer weist eine vorteilhafte Weiterbildung der Erfindung am oberen Rand des den Auslaß bildenden Spalts ein horizontal in die zweite Kammer hineinragendes Wehr auf.To improve the flow conditions in the second chamber has an advantageous Development of the invention at the top of the gap forming the outlet a weir protruding horizontally into the second chamber.

Die erste und die zweite Kammer können eine im wesentlichen rechteckige Grundfläche aufweisen und die erste Trennwand und die stromabwärts angeordnete, den Auslaß aufweisende Wand der zweiten Kammer eben und parallel zueinander angeordnet sind. Dies vereinfacht die Strömungsverhältnisse in der zweiten Kammer und senkt den Aufwand bei der Fertigung des Schmelzofens.The first and the second chamber can have a substantially rectangular base area and the first partition and the downstream one, the outlet having wall of the second chamber are arranged flat and parallel to each other. This simplifies the flow conditions in the second chamber and lowers the Effort in the manufacture of the melting furnace.

Damit die Zeit, in der die Schmelze die zweite Kammer durchströmt, für ein Absetzen bzw. Aufsteigen eines großen Teils der Verunreinigungen ausreicht, muß die Länge der zweiten Kammer in Strömungsrichtung ausreichend groß gewählt werden.So that the time in which the melt flows through the second chamber for a settling or rise of a large part of the impurities is sufficient, the length of the second chamber in the flow direction can be chosen sufficiently large.

Bei einer vorteilhaften Weiterbildung der Erfindung ist in der zweiten Kammer zwischen der ersten Trennwand und der den Auslaß aufweisenden Wand im wesentlichen mittig und parallel zu diesen beiden Wänden eine mit dem Boden und den Seitenwänden abschließende Mittelwand angeordnet, deren Höhe größer als die halbe maximale Füllstandshöhe und kleiner als die minimale Füllstandshöhe der Schmelze in der zweiten Kammer ist. Diese Mittelwand lenkt die Strömung in der zweiten Kammer um, so daß auch bei einem relativ kurzen Abstand zwischen der ersten Trennwand und der den Auslaß aufweisenden Wand, d.h. bei einer relativ kurzen zweiten Kammer, ein Strömungskurzschluß zwischen dem ersten Durchlaß und dem Auslaß vermieden wird.In an advantageous development of the invention, in the second chamber between the first partition and the wall having the outlet substantially in the center and parallel to these two walls one with the bottom and the side walls Middle wall arranged, the height of which is greater than half the maximum fill level and less than the minimum fill level of the melt in the second Chamber is. This middle wall redirects the flow in the second chamber so that even with a relatively short distance between the first partition and the Wall with outlet, i.e. with a relatively short second chamber, a flow short circuit between the first passage and the outlet is avoided.

Bei einem bevorzugten Ausführungsbeispiel werden die Abstände zwischen der ersten Trennwand, der Mittelwand und der den Auslaß aufweisenden Wand sowie die Höhe der Mittelwand so bemessen, daß in der zweiten Kammer ein von der Schmelze durchströmter mäanderförmiger Kanal von im wesentlichen konstantem Strömungsquerschnitt gebildet wird. Bei anderen Ausführungsformen sind weitere die Strömung der Schmelze umlenkende Trenn- und Mittelwände denkbar. Dabei werden die Strömungsverhältnisse so beeinflußt, daß das Absetzen bzw. Aufsteigen von Verunreinigungen verbessert wird.In a preferred embodiment, the distances between the first Partition, the middle wall and the wall having the outlet and the height the middle wall is dimensioned such that a melt flows through it in the second chamber meandering channel of essentially constant flow cross-section is formed. In other embodiments, the flow is more Partitions and middle walls deflecting the melt are conceivable. The flow conditions so influenced that the settling or rising of contaminants is improved.

Ferner ist es möglich, in der zweiten Kammer unmittelbar unter dem Durchlaß, durch den die Schmelze aus der ersten Kammer eintritt, einen Spülstein anzuordnen. Der Spülstein wird begast, und die eingangs der zweiten Kammer aufsteigenden Gase verbessern die Reinigungswirkung und die Strömungsverhältnisse in der zweiten Kammer.It is also possible to pass through in the second chamber immediately below the passage the melt enters from the first chamber to arrange a sink. The Flushing stone is gassed, and the gases rising at the entrance to the second chamber improve the cleaning effect and the flow conditions in the second chamber.

Bei einem bevorzugten Ausführungsbeispiel weisen die Böden der ersten und der zweiten Kammer geneigte Flächen auf, die so angeordnet sind, daß eine Rinne gebildet wird, an deren tiefster Stelle sich absinkende Verunreinigungen der Schmelze, insbesondere schwermetallhaltige Schmelzenschlämme sammeln. Diese Konzentration der Verunreinigungen an bestimmten Stellen der Kammerböden ermöglicht eine einfache Entfernung. Vorteilhafterweise sind eine erste und eine zweite Absaugvorrichtung in der ersten bzw. in der zweiten Kammer so angeordnet, daß sie die abgesunkenen Verunreinigungen an der tiefsten Stelle der Kammerböden absaugen können. Dadurch kann die Maximalhöhe der Schmelzenschlämme in den Kammern gering gehalten werden, was eine tiefere Anordnung der Durchlässe erlaubt und so zu einer besseren Ausnutzung des Kammervolumens führt. Die Rinne kann sowohl durch schräg gegeneinander gestellte ebene Bodenplatten gebildet werden als auch durch eine Durchwölbung der Böden. Die Absaugvorrichtung kann sowohl ein von oben in die Schmelze eingeführtes Rohr als auch einen von unten an den Kammerboden montierten Ablaß aufweisen.In a preferred embodiment, the bottoms of the first and the second chamber inclined surfaces which are arranged so that a gutter is formed, at the lowest point of falling impurities the melt, in particular melt sludge containing heavy metals collect. This concentration of impurities at certain points on the chamber floors enables easy removal. Advantageously, a first and a second suction device is arranged in the first or in the second chamber, that they have the sunk contaminants at the deepest point of the chamber floors can suction. This allows the maximum height of the melt sludge in the chambers are kept low, which allows a deeper arrangement of the passages and thus leads to better utilization of the chamber volume. The gutter can be formed both by sloping floor plates as well as by arching the floors. The suction device can both one pipe inserted into the melt from above and one from below to the Have a chamber-mounted drain.

Die Verwendung des Magnesiumsschmelzofens zum Reinigen von Magnesium ist dadurch gekennzeichnet, daß die Gesamtfläche des wenigstens einen ersten Durchlasses größer als eine erste Mindestfläche (Amin,1) und daß die Gesamtfläche des wenigstens einen Auslasses größer als eine zweite Mindestfläche (Amin, 2) ist, wobei die Mindestflächen (Amin,1,2) sich aus einer ersten maximalen Strömungsgeschwindigkeit (Vmax.,1) der Schmelze in dem Durchlaß und einer zweiten maximalen Geschwindigkeit vmax., 2) der Schmelze im Auslaß bei gegebenem Materialdurchsatz geschmolzenen Magnesiums durch den Ofen nach der Gleichung Amin.,1,2 = Materialdurchsatz des Schmelzofens / ρ · vmax., 1,2 ergeben, wobei

  • ρ die Dichte des geschmolzenen Magnesiums
  • vmax,1 < 0,1 m/sec und
  • vmax,2 < 0,05 m/sec ist.
The use of the magnesium melting furnace for cleaning magnesium is characterized in that the total area of the at least one first passage is larger than a first minimum area (A min, 1 ) and that the total area of the at least one outlet is larger than a second minimum area (A min, 2 ) is, the minimum areas (A min, 1,2 ) being melted from a first maximum flow velocity (V max., 1 ) of the melt in the passage and a second maximum velocity v max., 2 ) of the melt in the outlet for a given material throughput Magnesium through the furnace according to the equation A min., 1.2 = material throughput of the melting furnace / ρ · v max., 1.2 , where
  • ρ the density of the molten magnesium
  • v max, 1 <0.1 m / sec and
  • v max, 2 <0.05 m / sec.

Die Mindestfläche berechnet sich aus einer maximalen Strömungsgeschwindigkeit der Schmelze in dem Durchlaß bzw. Auslaß bei einem gegebenen Materialdurchsatz geschmolzenen Magnesiums durch den Magnesiumschmelzofen.The minimum area is calculated from a maximum flow velocity Melt melted in the passage for a given material flow Magnesium through the magnesium melting furnace.

Die Begrenzung der Strömungsgeschwindigkeit in dem Durchlaß dient einer Vermeidung von Verwirbelungen der strömenden Schmelze am Durchlaß. Dies verhindert das Mitreißen von Verunreinigungen, beispielsweise aus den Schmelzenschlämmen am Boden der Kammer.Limiting the flow rate in the passage serves to avoid this of turbulence in the flowing melt at the passage. This prevents that Entrainment of contaminants, for example from the melt sludge Floor of the chamber.

Vorteilhaft ist eine Begrenzung der Strömungsgeschwindigkeit im Durchlaß auf unter 0,1 m/sec. Vorzugsweise wird eine deutlich geringere Strömungsgeschwindigkeit gewählt, indem der Durchlaß ausreichend breit gewählt wird.It is advantageous to limit the flow velocity in the passage to below 0.1 m / sec. A significantly lower flow rate is preferably selected, by choosing the passage sufficiently wide.

Durch das Wählen der geringen Strömungsgeschwindigkeit der Schmelze in dem Auslaß wird ein Mitreißen von Verunreinigungen aus der zweiten Kammer und ein Überführen der Verunreinigungen in die dritte Kammer vermieden. Vorzugsweise wird eine Maximalströmungsgeschwindigkeit unter 0,05 m/sec gewählt.By choosing the slow flow rate of the melt in the outlet entrainment of contaminants from the second chamber and transfer the contamination in the third chamber avoided. A maximum flow rate is preferred selected below 0.05 m / sec.

Vorzugsweise wird das Magnesium durch einen unterhalb der Schmelzoberfläche der ersten Kammer eintauchenden Chargierschacht zugeführt. Das zugeführte zu schmelzende Material fällt nicht auf die Schmelzbadoberfläche und reißt somit nur sehr geringe, an der Oberfläche innerhalb des Chargierschachts befindliche Krätzenanteile in das Bad mit. Außerdem wird eine gezieltere Zufuhr des zu schmelzenden Materials bei einer geringeren Verwirbelung des Schmelzbads ermöglicht.The magnesium is preferably replaced by one below the melting surface the charging chamber is inserted into the first chamber. The material to be melted does not fall onto the surface of the melt pool and thus only tears very little on the surface inside the charging shaft any dross in the bath. It will also be a more targeted intake of the material to be melted with less swirling of the melt pool enables.

Vorteilhafterweise wird das zu schmelzende Material vor dem Zuführen zu der ersten Kammer thermisch vorbehandelt, wobei Kontaminate abschwelen und/oder verdampfen. Advantageously, the material to be melted becomes the first one before being fed Chamber thermally pretreated, contaminants swelling and / or evaporating.

Das zu schmelzende Material, beispielsweise mit Öl kontaminierter Magnesiumschrott, wird z. B. über eine gekapselte Fördereinrichtung an den Schmelzofen herangeführt. Ein Abschnitt der Fördereinrichtung weist eine Heizstrecke auf, in der das durchlaufende Material erhitzt wird, wobei die Kontaminate (z.B. Ölreste) abschwelen und/oder verdampfen. Über die Kapselung der Fördereinrichtung wird das entstehende Gas (Schwelgas) aufgefangen und kann weiteren Verwendungen zugeführt werden. Das erhitzte Material wird über Schleusen dem Chargierschacht zugeführt und taucht unter die Schmelzbadoberfläche ein. Die thermische Vorbehandlung senkt die Anteile der Verunreinigungen in dem dem Schmelzbad zugeführten Material und führt somit zu einem geringeren Krätzeaufkommen sowie zur Vermeidung eines anderenfalls erforderlichen Abziehens der Reaktionsschwelgase, die sich über der Schmelze in der ersten Kammer bilden würden. Dadurch wird die Verwendung eines höheren Anteils von Rücklauf und Altschrotten ermöglicht.The material to be melted, for example magnesium scrap contaminated with oil, z. B. brought up to the melting furnace via an encapsulated conveyor. A section of the conveyor has a heating section in which the continuous Material is heated, whereby the contaminants (e.g. oil residues) evaporate and / or evaporate. The resulting gas is encapsulated in the conveyor (Carbonization gas) and can be used for other purposes. The heated material is fed into the charging shaft via locks and dips under the melt surface. The thermal pre-treatment lowers the proportion of impurities in the material supplied to the weld pool and thus leads to less itching and the avoidance of otherwise necessary deduction of the reaction gases, which are above the Would form in the first chamber. This will make the use of a higher proportion of return and old scrap.

Vorzugsweise wird das zu schmelzende Material auf eine Temperatur von etwa 300 °C bis 450 °C aufgeheizt.Preferably, the material to be melted is at a temperature of about 300 ° C heated up to 450 ° C.

Die bei der thermischen Vorbehandlung aufgefangenen Schwelgase können entweder einem Brenner zum Aufheizen des zu schmelzenden Materials in der Abschwelvorrichtung (indirekte Beheizung; Strahlrohre) oder einem Brenner zum Schmelzen des Materials zugeführt werden. Alternativ können die aufgefangenen Schwelgase einem mit einem Wärmetauscher gekoppelten Brenner zugeführt werden, wobei der Wärmetauscher zur Luftvorwärmung der Verbrennungsluft dienen kann.The carbonization gases collected during the thermal pretreatment can either a burner for heating the material to be melted in the desoldering device (indirect heating; radiant tubes) or a burner for melting the Materials are fed. Alternatively, the carbonization gases collected can be can be supplied with a heat exchanger coupled burner, the heat exchanger can serve to preheat the combustion air.

Vorzugsweise wird das Gewicht des Schmelzofens bestimmt und das zu schmelzende Material in Abhängigkeit vom Ofengewicht so zugeführt, daß das Ofengewicht und somit der Füllstand der Schmelze näherungsweise konstant bleiben.The weight of the melting furnace is preferably determined and the one to be melted Material fed depending on the furnace weight so that the furnace weight and thus the fill level of the melt remains approximately constant.

Die Masse des zugeführten zu schmelzenden Materials entspricht dem Massenverlust des Schmelzofens durch Entnahme geschmolzenen Magnesiums und/oder Entnahme von Verunreinigungen (Absaugen des Schlamms vom Boden). So wird der Füllstand der Kammer näherungsweise konstant gehalten, so daß das zu schmelzende Material stets unter die Schmelzenoberfläche eintaucht und die Strömungsverhältnisse in den Kammern konstant bleiben.The mass of the supplied material to be melted corresponds to the mass loss the furnace by removing molten magnesium and / or removing it of impurities (suction of the sludge from the ground). So the fill level the chamber kept approximately constant, so that the material to be melted always immersed under the melt surface and the flow conditions in the Chambers remain constant.

Die Schmelze wird mittels einer Dosierpumpe, an die ein mit Schutzgas gefülltes Überführungsrohr angeschlossen ist, über die Schmelzenoberfläche der dritten Kammer unter einer Deckelisolierung seitlich abgeführt. Das Spülen des Überführungsrohrs mit Schutzgas verhindert eine Oxydation des entnommenen Magnesiums.The melt is fed by means of a metering pump to which a transfer tube filled with protective gas is attached is connected across the melt surface of the third chamber discharged laterally under a lid insulation. Flushing the transfer tube with Shielding gas prevents oxidation of the extracted magnesium.

Im folgenden wird die Erfindung anhand von in der Zeichnung dargestellten Ausführungsbeispielen näher beschrieben. In der Zeichnung zeigt:

Fig. 1
ein bevorzugtes Ausführungsbeispiel des erfindungsgemäßen Magnesiumschmelzofens;
Fig. 2
eine Vorrichtung zum Absaugen von Schmelzenschlämmen aus einer am Boden einer Kammer befindlichen Rinne; und
Fig. 3
ein Ausführungsbeispiel einer Einrichtung zum Zuführen des zu schmelzenden Materials mit Abschwelvorrichtung und Chargierschacht.
The invention is described in more detail below with reference to exemplary embodiments shown in the drawing. The drawing shows:
Fig. 1
a preferred embodiment of the magnesium melting furnace according to the invention;
Fig. 2
a device for suctioning melt sludge from a channel located at the bottom of a chamber; and
Fig. 3
an embodiment of a device for supplying the material to be melted with a desoldering device and charging shaft.

Fig. 1 zeigt einen erfindungsgemäßen Magnesiumschmelzofen 1 mit drei Kammern, der ein Schmelzen, Reinigen und dosiertes Abgeben des Magnesiums ermöglicht. Einer ersten Kammer, der Schmelzkammer 2, wird das zu schmelzende Material zugeführt. Durch einen Durchlaß 3 strömt das geschmolzene Magnesium in eine zweite Kammer, der Abstehkammer 4, in der während der Verweildauer des geschmolzenen Magnesiums Verunreinigungen aufsteigen bzw. absinken können. Durch einen zweiten Durchlaß 5 gelangt das gereinigte geschmolzene Magnesium in eine Dosierkammer 6, in welcher es für eine Entnahme bereitgestellt wird.1 shows a magnesium melting furnace 1 according to the invention with three chambers that melt, clean and dispense of magnesium. A first chamber, the Melting chamber 2, the material to be melted is fed. Through a passage 3, the molten magnesium flows into one second chamber, the stand-off chamber 4, in the during the stay of the molten magnesium or sink. Through a second passage 5 the cleaned molten magnesium reaches a metering chamber 6, in which it is provided for removal.

Die Kammern 2, 4 und 6 des Magnesiumschmelzofens 1 sind von Stahlwandungen 10 umgeben. Die Stahlwandungen gewährleisten einen relativ guten Wärmeübergang. Zwischen der Schmelzkammer 2 und der Abstehkammer 4 ist eine erste Trennwand 11 angeordnet und zwischen der Abstehkammer 4 und der Dosierkammer 6 eine zweite Trennwand 12. Die erste und die zweite Trennwand 11 und 12 sind ebenfalls aus Stahl gefertigt. Die drei Kammern sind von einer wärmeisolierenden Ummantelung 13 umgeben. Die Böden 14, 15 und 16 der drei Kammern liegen auf der Ummantelung 13 auf, während zwischen den Seitenwänden 10 der Kammern und den seitlichen Teilen der Ummantelung 13 ein Verbrennungsraum 9 gebildet ist. Denkbar ist auch eine Anordnung, bei der die Ofenkammern auf ein Stahlgerüst aufgesetzt sind, so daß auch von unten eine Beheizung der Stahlwandung möglich ist. Zum Beheizen der Schmelzkammer 2 sind an deren Stirnseite und an beiden seitlichen Außenwandungen jeweils zwei Brenner 17 und 18 in der Ummantelung 13 so angeordnet, daß ihre Flammen und Wärmestrahlungen auf die Außenwandung 10 der Schmelzkammer 2 gerichtet sind. Die Brenner 17 beheizen die Stirnseite der Schmelzkammer 2 und die Brenner 18 die Seitenwandungen. An jeder Seitenwandung der Abstehkammer 4 ist ein weiterer Brenner 21 angeordnet, der die in der Abstehkammer 4 befindliche Schmelze zusätzlich aufheizt. Zusätzlich kann ein Brenner 21a zum Beheizen der Dosierkammer 6 vorgesehen sein. Dieser Brenner 21a übernimmt insbesondere dann das zusätzliche Beheizen der zu entnehmenden Schmelze in der Kammer 6, wenn die Brenner 17, 18 und 21 nicht tätig sind, weil kein Material zugeführt und geschmolzen wird. In anderen Ausführungsbeispielen kann die Anzahl, Größe und Verteilung der Brenner variiert werden.The chambers 2, 4 and 6 of the magnesium melting furnace 1 are from Surrounded steel walls 10. The steel walls ensure one relatively good heat transfer. Between the melting chamber 2 and the stand-off chamber 4, a first partition 11 is arranged and between the stand-off chamber 4 and the metering chamber 6 one second partition 12. The first and second partition 11 and 12 are also made of steel. The three chambers are surrounded by a heat-insulating jacket 13. The floors 14, 15 and 16 of the three chambers lie on the casing 13 on while between the side walls 10 of the chambers and the lateral parts of the casing 13 a combustion chamber 9 is formed is. An arrangement is also conceivable in which the Oven chambers are placed on a steel frame, so that too heating of the steel wall from below is possible. To the Heating the melting chamber 2 are on the front and on two burners 17 and 18 on each of the two lateral outer walls arranged in the casing 13 so that their flames and Heat radiation on the outer wall 10 of the melting chamber 2 are directed. The burners 17 heat the end face of the Melting chamber 2 and the burner 18 the side walls. On Each side wall of the holding chamber 4 is another burner 21 arranged, which is located in the holding chamber 4 Melt additionally heated. In addition, a burner 21a be provided for heating the metering chamber 6. That burner 21a then takes over the additional heating of the withdrawing melt in the chamber 6 when the burners 17, 18th and 21 are not active because no material is supplied and is melted. In other embodiments, the The number, size and distribution of the burners can be varied.

Die durch die Brenner 17, 18, 21 und 21a in den Verbrennungsraum 9 eingebrachten heißen Abgase strömen entlang der Außenwandungen 10 bis zum Abgasauslaß 19, der in der Ummantelung 13 hinter der Dosierkammer 6 angeordnet ist. Bei Anordnung der Ofenkammern auf einem Stahlgerüst könnten die Abgase auch unterhalb der Kammern abgesaugt werden. Damit könnte zusätzliche Heizfläche und somit Schmelzleistung gewonnen werden.The burner 17, 18, 21 and 21a in the Combustion chamber 9 introduced hot exhaust gases flow along the outer walls 10 to the exhaust outlet 19, which in the Sheath 13 is arranged behind the metering chamber 6. At The arrangement of the furnace chambers on a steel frame could Exhaust gases can also be extracted below the chambers. In order to could have additional heating surface and thus melting capacity be won.

Das zu schmelzende Material wird der Schmelzkammer 2 über einen Chargierschacht 20 zugeführt. Der Chargierschacht 20 taucht mit seinem unteren Ende unter die Schmelzenoberfläche in der Schmelzkammer 2 ein.The material to be melted is transferred to the melting chamber 2 a charging shaft 20 supplied. The charging shaft 20 dips under the melt surface with its lower end the melting chamber 2.

Das in die Schmelze der Schmelzkammer 2 eintauchende Material wird geschmolzen, wobei Verunreinigungen in die Schmelze aufgenommen werden. Ein Teil der Verunreinigungen, insbesondere schwermetallhaltige Schmelzenschlämme, sinkt auf den Boden 14 der Schmelzkammer 2 ab. Ein anderer Teil der Verunreinigungen, insbesondere Magnesiumoxid, steigt zur Schmelzenoberfläche auf. An der Oberfläche des Schmelzbads sammeln sich die Verunreinigungen in Form von Krätze an. Durch den ersten Durchlaß 3 strömt die Schmelze zur Abstehkammer 4. Der erste Durchlaß 3 ist in der ersten Trennwand 11 als waagerechter Spalt ausgebildet. Die Unterkante des Spalts 3 befindet sich in ausreichender Höhe über der sich am Boden 14 der Schmelzkammer 2 absetzenden Schicht von Verunreinigungen, um ein Mitreißen bzw. einen Übertritt von Verunreinigungen aus dem Schmelzenschlamm in die Abstehkammer 4 zu vermeiden. Beim bevorzugten Ausführungsbeispiel befindet sich der Durchlaß etwa 150 mm über dem Boden 14. Der Spalt 3 ist ausreichend groß, um eine geringe Strömungsgeschwindigkeit der hindurchtretenden Schmelze bei einem gegebenen maximalen Durchsatz des Magnesiumschmelzofens 1 zu erreichen. Bei einem Ofen mit einem Durchsatz von etwa 1t/h beträgt die Größe des Spalts 3 etwa 50mm x 500mm.The material immersed in the melt of the melting chamber 2 is melted, leaving impurities in the melt be included. Part of the contaminants, in particular heavy metal-containing melt sludge, sinks to the bottom 14 the melting chamber 2. Another part of the contaminants, especially magnesium oxide, rises to the surface of the melt. The impurities collect on the surface of the weld pool in the form of scabies. Through the first passage 3 the melt flows to the stand-off chamber 4. The first passage 3 is formed in the first partition 11 as a horizontal gap. The lower edge of the gap 3 is sufficient Height above that settling on the bottom 14 of the melting chamber 2 Layer of impurities to carry or transfer of impurities from the melt sludge into the holding chamber 4 to avoid. In the preferred embodiment the passage is about 150 mm above the floor 14. The Gap 3 is sufficiently large to have a low flow rate of the melt passing through at a given to achieve maximum throughput of the magnesium melting furnace 1. For a furnace with a throughput of around 1t / h the size of the gap 3 about 50mm x 500mm.

Hinter dem Durchlaß 3 kann in der Abstehkammer 4 wahlweise ein Spülstein 22 angeordnet sein, welcher mit einem Schutzgas (N2 mit 0,2 bis 0,5 % SF6) begast wird. Das austretende Schutzgas steigt in der Abstehkammer an die Oberfläche und reißt dabei Verunreinigungen mit.Behind the passage 3, a sink 22 can optionally be arranged in the holding chamber 4, which is gassed with a protective gas (N 2 with 0.2 to 0.5% SF 6 ). The escaping protective gas rises to the surface in the stand-off chamber and entrains contaminants.

In der Mitte der Abstehkammer 4 zwischen der ersten Trennwand 11 und der zweiten Trennwand 12 ist ein Überströmwehr 23 angeordnet. Die Höhe des Überstromwehrs beträgt etwa 50 % bis 80 %, vorzugsweise 70 % der Schmelzenstandhöhe. Durch die Einbringung dieses Überströmwehrs 23 wird u.a. vermieden, daß die durch den ersten Durchlaß 3 eintretende Schmelze direkt zum zweiten Durchlaß 5 geradeaus weiterströmt und so eine zu geringe Zeit in der Abstehkammer verweilt. Dadurch wird die Reinigung der Schmelze in der Abstehkammer 4 verbessert.In the middle of the storage chamber 4 between the first partition 11 and the second partition 12 is an overflow weir 23 arranged. The height of the overcurrent weir is about 50% to 80%, preferably 70% of the melt level. Through the introduction This overflow weir 23 is used, among other things. avoided the melt entering through the first passage 3 directly to the second passage 5 flows straight ahead and so too small Time in the rest room. This will make cleaning the melt in the holding chamber 4 improved.

Während des Durchströmens der Abstehkammer 4 sinkt ein Teil der Verunreinigungen, insbesondere schwermetallhaltige Schmelzenschlämme, auf den Boden 15 der Kammer 4 ab. Ein weiterer Teil der Verunreinigungen steigt an die Oberfläche der Schmelze auf und bildet dort eine Schicht (Krätze).A part sinks as it flows through the holding chamber 4 the impurities, in particular melt sludges containing heavy metals, on the floor 15 of the chamber 4. Another Part of the contamination rises to the surface of the melt and forms a layer (scabies) there.

Durch den in der zweiten Trennwand 12 befindlichen zweiten Durchlaß 5 tritt die in der Abstehkammer 4 gereinigte Schmelze in die Dosierkammer 6 ein. Der zweite Durchlaß 5 ist ebenso wie der erste Durchlaß 3 in geringer Höhe über dem Boden 15 angeordnet, um eine möglichst reine Schmelze hindurchtreten zu lassen. Um ein Mitreißen der auf den Boden 15 der Abstehkammer 4 abgesunkenen Verunreinigungen zu vermeiden, ist die Unterkante des zweiten Durchlasses 5 oberhalb der maximalen Höhe der sich am Boden 15 der Abstehkammer 4 absetzenden Schicht von Verunreinigungen angeordnet. Beim bevorzugten Ausführungsbeispiel gemäß Fig. 1 ist der zweite Durchlaß 5 ebenso wie der erste Durchlaß 3 als horizontaler Spalt ausgebildet. Der zweite Durchlaß befindet sich in einer Höhe von etwa 100 mm über dem Boden 15.Through the second located in the second partition 12 Passage 5 enters the melt cleaned in the holding chamber 4 into the dosing chamber 6. The second passage 5 is as well the first passage 3 is arranged at a low height above the floor 15, to let a melt as pure as possible pass through. In order to entrain the floor 15 of the holding chamber 4 The lower edge is to avoid sunken contamination of the second passage 5 above the maximum height of the layer of impurities depositing on the bottom 15 of the holding chamber 4 arranged. In the preferred embodiment 1, the second passage 5 is the same as the first Passage 3 formed as a horizontal gap. The second Passage is at a height of about 100 mm above the Floor 15.

Ferner befindet sich an der Oberkante des zweiten Durchlasses 5 ein waagerecht in die zweite Kammer 4 hineinragendes Wehr 24, das die Strömungsverhältnisse bei Überströmen der Schmelze in die dritte Kammer 6 verbessert.It is also located on the upper edge of the second passage 5 a weir protruding horizontally into the second chamber 4 24, the flow conditions when overflowing the melt improved in the third chamber 6.

Unmittelbar hinter dem zweiten Durchlaß 5 kann in der Dosierkammer 6 ein Keramikfilter 25 angebracht werden. Das Keramikfilter 25 dient der weiteren Reinigung der in die Dosierkammer 6 eintretenden Schmelze.Immediately behind the second passage 5 can in the metering chamber 6 a ceramic filter 25 can be attached. The ceramic filter 25 is used for further cleaning in the dosing chamber 6 entering melt.

Vor Entnahme des geschmolzenen und gereinigten Magnesiums ist in der Dosierkammer 6 eine Dosierpumpe 27 angeordnet. Diese hebt das zu entnehmende geschmolzene Magnesium über die Schmelzenoberfläche und überführt die Schmelze in ein Überführungsrohr 28. Das Überführungsrohr 28 ist unter der Deckelisolierung 29 seitlich nach außen geführt. Um ein Ausfließen des geschmolzenen Magnesiums zu bewirken, ist das Überführungsrohr 28 leicht nach unten geneigt. Der aus der Ummantelung 13 austretende Teil des Überführungsrohrs 28 ist mit einer Heizung 30, beispielsweise einer elektrischen Beheizung, versehen. Die entnommene Magnesiumschmelze wird einer Druckgußmaschine oder einem Transportbehälter zugeführt.Before removing the molten and cleaned magnesium a metering pump 27 is arranged in the metering chamber 6. This lifts the molten magnesium to be removed from the surface of the melt and transfers the melt into a transfer tube 28. The transfer tube 28 is under the lid insulation 29 led laterally outwards. To drain the melted To effect magnesium is the transfer tube 28 slightly inclined downwards. The one emerging from the casing 13 Part of the transfer tube 28 is provided with a heater 30, for example, an electric heater. The removed Magnesium melt is a die casting machine or fed to a transport container.

Um eine Oxydation der entnommenen Schmelze in dem Überführungsrohr 28 zu vermeiden, ist das Überführungsrohr beim bevorzugten Ausführungsbeispiel mit einem Schutzgas gefüllt. Das Schutzgas wird durch das Überführungsrohr 28 hindurchgeleitet, wobei zur Einsparung von Schutzgas eine Impulsbegasung vorgesehen ist.For an oxidation of the withdrawn melt in the transfer tube 28 to avoid, the transfer tube is the preferred Embodiment filled with a protective gas. The Shielding gas is passed through the transfer tube 28 where pulsed fumigation is provided to save inert gas is.

Die Räume über der Schmelzenoberfläche in den drei Kammern 2, 4 und 6 sind zur Vermeidung einer Oxydation mit Schutzgas gefüllt. Bei dem bevorzugten Ausführungsbeispiel sind die Trennwände 11 und 12 bis zur Deckelisolierung 29 geführt, um ein Trennen der schutzgasbefüllten Räume zu erreichen. Die Schutzgaszufuhr erfolgt über ein System 31 von Rohren und Ventilen. Dabei werden die Ventile so gesteuert, daß die Zusammensetzungen der über den drei Kammern befindlichen Schutzgasatmosphären separat eingestellt werden können. Damit ist eine gestaffelte Schutzbegasung derart möglich, daß im Raum über der Schmelze in der Schmelzkammer 2 eine Schutzgasatmosphäre mit einem höheren SF6-Anteil und in den Räumen über der Schmelze in der Absteh- und der Dosierkammer (4 und 6) ein geringerer SF6-Anteil eingestellt werden kann. Bei dem bevorzugten Ausführungsbeispiel beträgt der SF6-Anteil über der Schmelze der Schmelzkammer 2 etwa 0,5% und über der Schmelze der Abstehkammer 4 und der Dosierkammer 6 etwa 0,2 bis 0,3%. Durch diese gestaffelte Schutzbegasung ist eine Einsparung von SF6 möglich; außerdem wird die von dem SF6 bewirkte Korrosion in der Abstehund in der Dosierkammer verringert. The spaces above the melt surface in the three chambers 2, 4 and 6 are filled with protective gas to avoid oxidation. In the preferred exemplary embodiment, the partition walls 11 and 12 are guided up to the cover insulation 29 in order to achieve a separation of the spaces filled with inert gas. The shielding gas is supplied via a system 31 of pipes and valves. The valves are controlled so that the compositions of the protective gas atmospheres located above the three chambers can be adjusted separately. A staggered protective gassing is possible in such a way that a protective gas atmosphere with a higher SF 6 content in the space above the melt in the melting chamber 2 and a lower SF 6 content in the rooms above the melt in the stand-off and metering chamber (4 and 6). Share can be set. In the preferred embodiment, the SF 6 content above the melt of the melting chamber 2 is approximately 0.5% and above the melt of the stand-off chamber 4 and the metering chamber 6 is approximately 0.2 to 0.3%. This staggered protective gassing enables SF 6 to be saved; In addition, the corrosion caused by the SF 6 in the stand-off and in the dosing chamber is reduced.

Über das System 31 von Rohren und Ventilen ist außerdem eine Schutzbegasung des Chargierschachts 20 und des Überführungsrohrs 28 möglich. Im normalen Betrieb, d.h. bei geschlossenen Deckeln, werden die Räume oberhalb der Schmelze in den Kammern über die Ventile 33 begast. Werden die Deckel über den jeweiligen Kammern zum Zwecke der Reinigung der Schmelzbadoberfläche geöffnet, so wird der plötzlich erhöhte Schutzgasbedarf durch automatisches Öffnen von Bypaß-Ventilen 34 gedeckt. Die Bypaß-Ventile 34 liefern in geöffnetem Zustand bei gleichem Gasdruck etwa einen 5-10fach größeren Volumenstrom als die Ventile 33. Die Verwendung der Bypaß-Ventilanordnung hat gegenüber der Regelung eines einzigen Ventils den Vorteil, daß ein schnelles Reagieren auf einen sprunghaft angestiegenen Bedarf möglich ist.There is also a system 31 of pipes and valves Protective gassing of the charging shaft 20 and the transfer pipe 28 possible. In normal operation, i.e. when closed Cover the spaces above the melt in the chambers fumigated via the valves 33. Are the lids over the respective chambers for the purpose of cleaning the If the melt surface is opened, it is suddenly raised Shielding gas required by automatically opening bypass valves 34 covered. The bypass valves 34 deliver in the open state at the same gas pressure, a 5-10 times larger volume flow than the valves 33. The use of the bypass valve arrangement has the advantage over the control of a single valve that a quick response to a jumped up Need is possible.

Die Abstehkammer 4 weist einen zusätzlichen Schacht 32 auf, durch den Material zum Nachlegieren des geschmolzenen Magnesiums eingebracht werden kann. Das durch diesen Schacht 32 in der Abstehkammer 4 eingebrachte Material ist relativ rein, so daß es keine weiteren Verunreinigungen in der Abstehkammer erzeugt. Der zusätzliche Schacht 32 taucht ebenso wie der Chargierschacht 20 unter die Schmelzbadoberfläche ein, um beim Einführen zu schmelzender Teile ein Mitreißen von Verunreinigungen von der Schmelzbadoberfläche und Verwirbelungen zu vermeiden. Ferner ist der zusätzliche Schacht 32 über das System 31 von Rohren und Ventilen mit Schutzgas füllbar.The stand-off chamber 4 has an additional shaft 32, through the material for re-alloying the molten magnesium can be introduced. That through this shaft 32 in the Abstandkammer 4 introduced material is relatively pure, so that it creates no further contaminants in the holding chamber. The additional shaft 32 dips just like the charging shaft 20 below the melt pool surface to insert parts to be melted entrainment of contaminants from the melt pool surface and to avoid turbulence. Furthermore, the additional shaft 32 is via the system 31 from Pipes and valves can be filled with protective gas.

Fig. 2 zeigt eine Vorrichtung zum Absaugen der sich am Boden 41 einer Kammer 40 absetzenden Verunreinigungen 45. Dabei zeigt Fig. 2 einen Schnitt senkrecht zur Ebene der Ansicht gemäß Fig. 1 durch die Schmelzkammer 2 oder die Abstehkammer 4, im folgenden allgemein als Kammer 40 bezeichnet.Fig. 2 shows a device for suctioning off the floor 41 of a chamber 40 settling impurities 45 Fig. 2 shows a section perpendicular to the plane of the view according to 1 through the melting chamber 2 or the stand-off chamber 4, hereinafter generally referred to as chamber 40.

Der Boden 41 der Kammer 40 weist geneigte Flächen 42 und 43 auf, die so angeordnet sind, daß sich in der Mitte der Kammer 40 eine Rinne 44 als tiefste Stelle ausbildet. In dieser Rinne 44 sammeln sich Schmelzenschlämme 45. The bottom 41 of the chamber 40 has inclined surfaces 42 and 43 on, which are arranged so that in the middle of the chamber 40 forms a groove 44 as the deepest point. In this gutter 44 melt sludge 45.

Ein Rohr 46 ragt von oben in die Kammer 40 und in die Schmelze hinein, wobei das Rohr 46 in unmittelbarer Nähe der Rinne 44 im Schmelzenschlamm 45 endet. Am oberen Ende des Rohres 46 ist eine Leitung 47 befestigt, die zu einer Saugpumpe 48 führt. Mit Hilfe der Saugpumpe 48 wird der Schmelzenschlamm 45 vom Boden 41 der Kammer 40 abgesaugt und in einen Behälter 49 gefördert.A tube 46 projects from above into the chamber 40 and into the Melt into it, with the tube 46 in the immediate vicinity of the Channel 44 in melt sludge 45 ends. At the top of the tube 46, a line 47 is attached to a suction pump 48 leads. With the help of the suction pump 48, the melt sludge 45 aspirated from the bottom 41 of the chamber 40 and into a container 49 promoted.

Fig. 3 zeigt eine Einrichtung zum Zuführen des zu schmelzenden Materials in den Magnesiumschmelzofen 1.Fig. 3 shows a device for feeding the to be melted Materials in the magnesium melting furnace 1.

Das Ausgangsmaterial 50, das sowohl relativ reines Magnesium-Rohmaterial in Form von Masseln sowie Rücklaufschrotte als auch mit Öl und anderen Verschmutzungen kontaminierte Altschrotte enthält, wird über eine Einfüllöffnung 52 einer Abschwelvorrichtung 51 zugeführt. Eine Transporteinrichtung 53 mit einem langsam bewegten Förderband transportiert das zugeführte Material durch einen schräg nach oben laufenden, allseitig gekapselten Schacht 54 bis zur oberen Öffnung 55 des mit Schleusen 56 versehenen Chargierschachts 20. Innerhalb des nach oben führenden Schachtes 54 wird das auf der Transporteinrichtung 53 aufliegende Material mit Hilfe einer von oben auf das Material einstrahlenden Heizung 57 erhitzt. Während des Erhitzens auf etwa 450° C schwelt und/oder dampft ein Teil der Kontaminate (ölige Verschmutzungen) ab. Die abschwelenden bzw. abdampfenden Verschmutzungen bilden ein Schwelgas, das in dem Schacht 54 aufsteigt und am oberen Ende 58 des Schachtes 54 in einen Abzugskanal 59 eintritt. Das erhitzte, zu schmelzende Magnesiummaterial fällt am Ende 58 des Schachtes 54 von der Transporteinrichtung 53 in den mit Schleusen 56 versehenen Chargierschacht 20 und weiter in das Schmelzbad.The starting material 50, which is both relatively pure magnesium raw material in the form of ingots and return scrap as also contaminated with oil and other contaminants Contains old scrap, a filling opening 52 one Desoldering device 51 supplied. A transport device 53 with a slowly moving conveyor belt that transports it fed material through a diagonally upward, encapsulated shaft 54 on all sides up to the upper opening 55 of the Chargierschacht 20 provided with locks 56 upward leading shaft 54 that on the Transport device 53 overlying material with the help of a heated from above onto the material radiating heater 57. During heating to about 450 ° C smoldering and / or steaming part of the contaminants (oily contaminants). The decaying or evaporating dirt form a Smoldering gas rising in the shaft 54 and at the upper end 58 of the shaft 54 enters a drain channel 59. The heated Magnesium material to be melted falls at the end of 58 Shaft 54 from the transport device 53 in the with locks 56 provided charging shaft 20 and further into the weld pool.

Der Abzugskanal 59 weist ein Gebläse 60 zum Ansaugen der Schwelgase auf. In dem Ausführungsbeispiel gemäß Fig. 3 werden die angesaugten Schwelgase von einem Brenner 61 nachverbrannt. Die heißen Abgase gelangen über einen Wärmetauscher 62 zu einem Kamin 63. Die in dem Wärmetauscher gewonnene Wärmeenergie kann zum Erwärmen der Verbrennungsluft für die Brenner 17 verwendet werden.The drain channel 59 has a fan 60 for sucking in Smolder gases on. 3 in the exemplary embodiment the carbonized gases sucked in are burned by a burner 61. The hot exhaust gases reach a via a heat exchanger 62 Chimney 63. The heat energy obtained in the heat exchanger can used to heat the combustion air for the burners 17 become.

Die dem Magnesiumschmelzofen 1 zugeführte Menge zu schmelzenden Materials wird über den Antrieb der Transporteinrichtung 53 gesteuert. Die Steuerung der Zufuhr des zu schmelzenden Materials erfolgt in Abhängigkeit vom Gewicht des Schmelzofens 1. Der Magnesiumschmelzofen ist an einer Kante des Bodens der Ummantelung 13 drehbar gelagert. An der gegenüberliegenden Kante ist eine mit einer Kraftmeßzelle versehene Lagerung vorgesehen. Die mit Hilfe dieser Meßzelle gemessene Kraft wird in ein Gewicht des Magnesiumsschmelzofens 1 umgerechnet. Aus der ermittelten zeitabhängigen Gewichtsdifferenz wird die erforderliche Menge des dem Ofen zuzuführendem Materials bestimmt. Durch Konstanthalten des Gewichts des Magnesiumsschmelzofens wird dafür gesorgt, daß der Schmelzenspiegel in den Ofenkammern näherungsweise konstant bleibt. Dies gewährleistet ein ununterbrochenes Eintauchen der unteren Begrenzung des Chargierschachts 20 unter die Schmelzenoberfläche. Außerdem werden auf diese Weise die Strömungsverhältnisse in dem Ofen näherungsweise konstant gehalten.The quantity to be fed to the magnesium melting furnace 1 to be melted Material is driven by the conveyor 53 controlled. Controlling the supply of the material to be melted takes place depending on the weight of the melting furnace 1. The magnesium melting furnace is on one edge of the bottom of the casing 13 rotatably mounted. On the opposite edge a bearing provided with a load cell is provided. The force measured with the help of this measuring cell is converted into a weight of the magnesium melting furnace 1. From the determined time-dependent weight difference becomes the required Determines the amount of material to be fed to the furnace. By keeping it constant of the weight of the magnesium melting furnace worried that the melt level in the furnace chambers approximately remains constant. This ensures an uninterrupted Immerse the lower limit of the charging shaft 20 below the melt surface. In addition, the Flow conditions in the furnace kept approximately constant.

Claims (18)

  1. A magnesium melting furnace with a first chamber (2) to accommodate the melt and a device (20) to feed the material to be melted into the first chamber,
    characterised in that
    at least one second chamber (4) is provided to accommodate the melt, a common first dividing wall (11) being provided between the first and the second chamber, that at least one first passage (3) through which the melt flows is arranged in the first dividing wall (11) in the bottom third of the melt height, the lower limit of said passage (3) being at a height above the bottom (14) of the first chamber (2) which is greater than the maximum height of a layer of impurities settling on the bottom of the first chamber, that at least one outlet (5) through which the melt flows is arranged in the bottom third of a wall (12) of the second chamber (4) arranged downstream, and that the first and the second chamber (2, 4) are made of steel walls which are heated from outside with burners (14, 18, 21) or electrical resistance heaters.
  2. A magnesium melting furnace according to claim 1, characterised in that the spaces in the first (2) and the second (4) chambers above the melt are isolated from each other by means of the first dividing wall (11) and can be separately filled with protective gas, it being possible to produce different protective gas compositions and concentrations in the spaces above the first and the second chambers (2, 4).
  3. A magnesium melting furnace according to either claim 1 or claim 2, characterised in that the at least one first passage (3) and the at least one outlet (5) are shaped as a gap stretching essentially over the entire width over the first dividing wall (11) and the wall (12), respectively.
  4. A magnesium melting furnace according to claim 3, characterised in that a weir (24) protruding horizontally into the second chamber (4) is arranged on the upper edge of the gap (5) forming the outlet.
  5. A magnesium melting furnace according to any one of claims 1 through 4, characterised in that a middle wall (23) ending with the bottom (15) and the side walls is arranged in the second chamber (4) between the first dividing wall (11) and the wall (12) exhibiting the outlet essentially in the middle between and parallel to said walls, the height of said middle wall being greater than half the maximum filling level and smaller than the minimum filling level of the melt in the second chamber (4).
  6. A magnesium melting furnace according to claim 5, characterised in that the distances between the first dividing wall (11), the middle wall (23) and the wall (12) exhibiting the outlet (5) as well as the height of the middle wall are selected so that in the second chamber (4) a meander-shaped duct of essentially constant flow cross-section is formed through which the melt flows.
  7. A magnesium melting furnace according to any one of claims 1 through 6, characterised in that the bottoms (14, 15, 41) of the first and the second chamber exhibit inclined surfaces (42, 43) which are arranged in such a manner that a channel (44) is formed in the longitudinal direction of the furnace, at the lowest point of which sinking impurities in the melt, in particular heavy metal-containing melt sludges, collect.
  8. A magnesium melting furnace according to claim 7, characterised in that a first and a second suction device (46-48) are arranged in the first chamber respectively in the second chamber (2, 4) so that the impurities which have sunk to the bottom can be extracted by suction at the lowest points (44) of the chamber floors (41, 14, 15).
  9. Use of the magnesium melting furnace according to any one of claims 1 through 8 for melting and purifying magnesium, characterised in that the total area of the at least one first passage (3) is greater than a first minimum area (Amin,1) and that the total area of the at least one outlet (5) is greater than a second minimum area (Amin,2), the minimum areas (Amin,1,2) being calculated from a first maximum flow velocity (Vmax,1) of the melt in the passage (3) and a second maximum flow velocity (Vmax,2) of the melt in the outlet (5) with a given material throughput of molten magnesium through the magnesium melting furnace (1) in accordance with the equation A min,1 = material throughput of the melting furnace ρ·νmax,1.2 where
    ρ is the density of the molten magnesium
    Vmax,1 < 0.1 m/sec and
    Vmax,2 < 0.05 m/sec.
  10. A method for melting and purifying magnesium, characterised in that the material to be melted is fed into a magnesium melting furnace with several chambers whose walls are of steel and which are heated from the outside with burners or electrical resistance heaters, and is melted in a first chamber, that the melt forming in the first chamber is fed into a second chamber through a passage at a flow velocity of less than 0.1 m/sec, that the melt remains in the second chamber whilst flowing slowly, impurities thereby settling or rising to the surface of the melt, that the purified melt is transferred into a third chamber through an outlet at a flow velocity of less than 0.05 m/sec and that the purified melt is removed from the third chamber for further processing.
  11. A method according to claim 10, characterised in that protective gas is passed over the melt surface, the protective gas present in the space above the melt in the first chamber (2) having a higher SF6 content than that in the space above the melt in the second chamber (4).
  12. A method according to claim 10 or 11, characterised in that the melt of the second chamber (4) is fed through the passage (3) in the first dividing wall (11) and that of the third chamber (6) through the outlet in the wall (12) in the bottom third of the melt height, the lower limit of the passage and the outlet being at a height above the bottom of the chambers which is greater than the maximum height of a layer of impurities, in particular heavy metal-containing melt sludges, settling on the bottom of the chambers,
  13. A method according to any one of claims 10 through 12, characterised in that the magnesium material of the first chamber (2) is fed in below the melt surface.
  14. A method according to any one of claims 10 through 13, characterised in that the material to be melted is thermally pre-treated before being fed into the first chamber, contaminants being carbonised at low temperature and/or vaporised.
  15. A method according to claim 14, characterised in that the low-temperature carbonisation gases are collected and post-combusted.
  16. A method according to claim 14, characterised in that the material to be melted is heated to a temperature of approx. 300 °C to 450 °C.
  17. A method according to any one of claims 10 through 16, characterised in that the weight of the melting furnace is determined and that the material to be melted is fed in as a function of the furnace weight so that the furnace weight and thus the filling level of the melt remain more or less constant.
  18. A method according to any one of claims 10 through 17, characterised in that the melt is removed from the side over the melt surface of the third chamber (6) under a cover insulation (29) by means of a metering pump (27) which is connected to a transfer pipe (28)
EP95937021A 1994-11-03 1995-10-27 Magnesium melting furnace and process for melting magnesium Expired - Lifetime EP0738334B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE4439214A DE4439214A1 (en) 1994-11-03 1994-11-03 Magnesium melting furnace and method for melting magnesium
DE4439214 1994-11-03
PCT/EP1995/004232 WO1996014439A2 (en) 1994-11-03 1995-10-27 Magnesium melting furnace and process for melting magnesium

Publications (2)

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EP0738334A1 EP0738334A1 (en) 1996-10-23
EP0738334B1 true EP0738334B1 (en) 2001-10-10

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EP95937021A Expired - Lifetime EP0738334B1 (en) 1994-11-03 1995-10-27 Magnesium melting furnace and process for melting magnesium

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US (1) US5908488A (en)
EP (1) EP0738334B1 (en)
AT (1) ATE206770T1 (en)
AU (1) AU3925895A (en)
CA (1) CA2180351A1 (en)
DE (2) DE4439214A1 (en)
WO (1) WO1996014439A2 (en)

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Also Published As

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ATE206770T1 (en) 2001-10-15
AU3925895A (en) 1996-05-31
US5908488A (en) 1999-06-01
WO1996014439A2 (en) 1996-05-17
DE4439214A1 (en) 1996-05-09
EP0738334A1 (en) 1996-10-23
DE59509688D1 (en) 2001-11-15
CA2180351A1 (en) 1996-05-17
WO1996014439A3 (en) 1996-08-15

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