Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
  • F27B14/00—Crucible or pot furnaces
  • F27B14/06—Crucible or pot furnaces heated electrically, e.g. induction crucible furnaces with or without any other source of heat
  • F27B14/061—Induction furnaces
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
  • F23G5/00—Incineration of waste; Incinerator constructions; Details, accessories or control therefor
  • F23G5/02—Incineration of waste; Incinerator constructions; Details, accessories or control therefor with pretreatment
  • F23G5/027—Incineration of waste; Incinerator constructions; Details, accessories or control therefor with pretreatment pyrolising or gasifying stage
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
  • F23G7/00—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals
  • F23G7/003—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals for used articles

Definitions

• the invention relates to a process for the treatment of carbonaceous bulk material containing impurities and to a reactor for carrying out the process.
• Carbonaceous shaped articles find application in high temperature furnace liners or cathodes.
• cathodes made of amorphous carbon, graphite-added amorphous carbon or graphite in electrolysis cells are also called “pots" are used for aluminum electrolysis at the end of the life of the cathodes, these fluorine and cyanide, and aluminum and / or aluminum compounds Due to stricter legal requirements, such spent carbon linings, also known as spent potlining (SPL), must not be stored in landfills without treatment, used as fuel or reused as raw material.
• SPL spent potlining
• a method for treating SPL is described, for example, in US Pat. No. 5,164,174.
• a conventional rotary kiln is used, which is heated directly with a gas flame.
• a gas flame In an oxidizing atmosphere, at least a majority of the carbon is converted to carbon monoxide and dioxide.
• the carbon is consumed, and in addition there are large quantities of gases that make large dimensions of the rotary kiln and the subsequent gas purification stages necessary.
• the object of the present invention is to provide a method by means of which spent potlining and carbonaceous stones can be processed with the aid of a small-volume reactor.
• carbon-containing bulk material containing impurities is heated directly inductively for its preparation in a reactor.
• Direct inductive heating is possible because the bulk material has such an electrical conductivity that frequencies of an induction heater couple into the bulk material and heat it directly, without the need for coupling into an additional medium.
• the inventive method has the advantage that do not incur by combustion reactions large amounts of combustion gases that make a correspondingly large volume reactor required.
• a reactor wall does not need to be heated, resulting in only a small heat loss across the reactor wall and thus a very high energy efficiency of the process.
• treatment is understood to mean a treatment of carbonaceous stones, with which toxic impurities are removed from the stones and / or converted into non-toxic compounds, wherein this treatment is carried out to such an extent that these stones do not endanger the environment or people can be stored in landfills, used as raw material and / or used as fuel.
• the carbon of the bulk material can be present, for example, as amorphous carbon, natural graphite, synthetic graphite or in any other arbitrary form. All that needs to be done is inductive coupling.
• the bulk material contains at least one bulk material selected from the group consisting of broken cathodes from an aluminum melt recovery process, broken anodes, crushed carbon liners from a steelmelt, a steel blast furnace or other metal smelting furnace, a glass melting furnace, a ceramic melting furnace, and other carbonaceous bricks to be processed.
• the impurities may contain at least one impurity selected from the group consisting of cyanides and soluble fluorides.
• these impurities accumulate in the cell lining during molten aluminum electrolysis and are toxic contaminants that prevent storage or reuse of the bulk material.
• the impurities may also contain, for example, sulfur and / or alkalis, such as Na and Ka, and non-ferrous metals, such as Zn.
• bulk material which has over 50 wt .-%, a particle size of about 30 mm, in particular to over 50 wt .-%, a particle size between 50 and 150 mm.
• inductive fields couple very well into the bulk material.
• Such high particle sizes have the advantage that not consuming and therefore energy and cost intensive grinding steps are required, but relatively coarse cracked bulk material can be used.
• the bulk material can be obtained by breaking up reprocessed moldings and / or bricks with an example conventional crusher.
• This may advantageously be a jaw crusher, cone crusher, gyratory crusher or similar crusher. These are suitable for achieving desired coarse grain sizes and are readily available as conventionally used crushers.
• carbonaceous stones to be crushed into bulk material are broken out of an SPL, a cathode block, a furnace lining or a similar installation situation prior to breaking.
• a substantially regular arrangement of stones at a place of their use in which they fulfill their task, such as high-temperature resistance and containing a melt understood.
• the bricks need not be removed one by one, but can be "mined", for example, by conventional machines which are conventionally used for demolishing the building, enabling the bulk material to be obtained with little effort and therefore at low cost and in a short time frame.
• the impurities may contain aluminum.
• the aluminum may be present in metallic form, as an oxide, as a carbide and / or in another chemical compound. Particularly in aluminum-melt electrolysis, a carbon lining or a cathode is contaminated with aluminum as a metal or as a chemical compound.
• the impurities may contain iron.
• the iron can be present in metallic form, as oxide, as carbide and / or in another chemical compound.
• a carbon lining becomes contaminated with iron as a metal or as a chemical compound.
• induction fields are generated with frequencies between 1 and 50 kHz, in particular between 1 and 10 kHz, in particular between 2 and 5 kHz. At these low frequencies, the induction fields couple well into coarse grains. Maximum temperatures up to 2500 ° C can be generated in the reactor. This is possible by the direct coupling of the induction fields in the bulk material.
• maximum temperatures between 1250 and 1800 ° C., in particular between 1300 and 1750 ° C., in particular between 1450 and 1700 ° C., are preferably set. These temperatures are high enough that cyanides decompose under the action of water vapor, which starts at around 700 ° C and cyanides are cracked and AIF3 is sublimated, which starts at around 1300 ° C. In contrast, these temperatures are low enough that no or at least hardly forms silicon carbide, because from a thermodynamic point of view, the formation of SiC begins only from 1700 ° C.
• At least a portion of the contaminants may be dissolved in an existing and / or forming slag in the process.
• This slag can be formed from the already existing impurities with Al compounds and / or Fe compounds as main constituents.
• At least one slag image and / or a flux are added to the reactor.
• Slag formers facilitate the formation of a slag, fluxes lower their viscosity, so that the slag can flow more easily and thereby absorb impurities. Impurities present on a surface of the bulk material can thus be washed off the bulk material by means of the slag.
• a calcium-containing compound such as CaO, CaCO 3 or dolomite, and / or a silicon-containing compound such as SiO 2 or a silicate, and / or an iron-containing compound such as an iron oxide or Iron ore, added.
• Si compounds can act as flux.
• a slag can form even in the absence of aluminum.
• the said added compounds can advantageously also as Slag to be added.
• Iron-containing compounds are suitable, for example, to bind sulfur present as an impurity as iron sulfide.
• the slag can advantageously flow into a lower zone of the reactor, where it collects and is removed from there. This allows the process to be carried out continuously.
• the slag can be mixed with bulk material.
• the slag may at least partially solidify in the lower zone. This occurs, for example, in that the lower zone is not inductively heated. Nevertheless, in addition to the solidified slag in the lower zone, there may also be a liquid fraction of slag.
• the slag is removed. This can be done by means of a slider and / or a crusher. After removal, bulk material and slag advantageously slip into the lower zone.
• water and / or water vapor is introduced at least in one zone of the reactor. This can be done by atomizing or misting.
• water and / or water vapor are also only referred to as water, which may of course be present in gaseous and / or vapor form at the corresponding temperatures.
• chemical compounds can be hydrolytically and / or pyrohydrolytically decomposed.
• cyanides can be decomposed pyrohydrolytically.
• bulk material and / or additives can be introduced into the reactor in a moist state.
• the water thus introduced can also fulfill the functions described above.
• moist bulk material induction fields can be coupled as described for dry bulk material.
• the slag and the carbonaceous bulk material can be separated from one another by quenching with water. This can advantageously be done in the lower zone and / or a lower region of a central zone of the reactor, where the slag melt, especially in a low-viscosity state, strongly wets the bulk material.
• By contact with water slag and bulk material are cooled quickly, which leads to mechanical stresses that can cause a slipping of the slag from the bulk material. This has the advantage that in a mixture taken from the reactor slag and bulk material, although juxtaposed, but already separated from each other.
• Slag and processed bulk material can be separated from one another by conventional methods, for example by flotation methods.
• the slag and the then cleaned bulk material can be reused after removal.
• the slag can be used as an additive for example in construction materials, such as cement. For this purpose, it is advantageously ground.
• the carbonaceous bulk material can be used for example as a fuel.
• the carbonaceous bulk material can be used as a material in, for example, wear liners, such as gutters. This is possible because the bulk material after the process still has a very high strength and has retained its graininess.
• the carbon of the bulk material can be used for all other applications in which conventional carbon is used that has not already been industrially used and subsequently processed.
• at least part of the impurities is advantageously converted into a gas phase. This facilitates removal of the contaminants.
• Sublimating compounds such as AIF 3 , - Melting and evaporation of compounds such as reduced alkali and non-ferrous metals and their compounds, in particular zinc and zinc compounds.
• Impurities transferred into a gaseous phase are advantageously washed out with a liquid, in particular water.
• a washing out of gaseous compounds is advantageously carried out spatially separated from the reactor space, for example in a gas scrubber, such as a sprinkler tower, which is connected to the reactor space.
• the object of the present invention is further achieved with the features of the reactor according to claim 22.
• Advantageous developments are specified in the dependent claims 23 to 33.
• the reactor has induction coils which are suitable for directly heating the bulk material inductively.
• the induction coils are suitable for setting a predetermined temperature gradient in the radial and / or axial direction of the reactor.
• a temperature gradient can be used selectively to control the inventive method.
• the induction coils are suitable for heating the bulk material without temperature gradients or with a low temperature gradient.
• a radial temperature gradient is possible which is less than 100 K / m, in particular less than 50 K / m, in particular less than 30 K / m.
• the reactor has a high-temperature-resistant inner wall into which the induction fields generated by the induction coils at the frequencies used for heating the bulk material do not or at least hardly couple. This reduces the temperature load on the inner wall and significantly increases their life expectancy compared to conventional heaters.
• the inner wall may have a lining containing at least one of carbon, oxidic refractory, non-oxidic refractories and chamotte.
• the lining has clay-bonded graphite. Despite the high carbon content, clay-bound graphite has such a low electrical conductivity that it can not be heated inductively.
• the reactor has a reactor space which has an upper zone, a middle zone and a lower zone in the axial direction, the reactor in particular being designed so that bulk material to be processed in the upper zone can be introduced, the middle zone is provided with the at least partially extending around the reactor induction coil and accumulate in the lower zone slag and / or purified bulk material and can be removed from it.
• a continuous process can be carried out with the reactor.
• the reactor has a diameter of more than 50 cm in the region of the induction coils in order to achieve the highest possible throughput.
• the diameter is greater than 1 m, in particular 1 m up to 1, 5 m.
• the reactor may be designed to widen conically downwards in the lower zone and / or in a lower region of the middle zone. This facilitates a slipping of bulk material and slag down.
• the reactor has an entry lock, such as a cell sluice, over which the reactor can be supplied with bulk material, the entry lock is suitable, an uncontrolled escape of gases to prevent the reactor.
• the entry lock is suitable, an uncontrolled escape of gases to prevent the reactor.
• bulk material and additives and any other necessary substances may be added to the reactor space without uncontrolled escape of gases.
• a gas scrubber connected to the reactor space such as a sprinkler tower, may be provided, which is suitable for washing out impurities transferred into a gaseous phase with a liquid, such as water.
• gaseous toxic compounds can be liquid bound from the gas phase and condense due to a low temperature in the gas scrubber. Large volumes of gas can be reduced to smaller amounts of liquid.
• the gas scrubber further, in particular chemical, processes can take place.
• zinc can be oxidized with steam to zinc oxide and then filtered off.
• At least one injection device can be provided in the reactor which is suitable for introducing water and / or water vapor into the reactor space in at least one of the upper, middle and lower zones.
• water can be brought directly to the impurities, so that the above-described reactions run faster.
• At least one induction coil is cooled. Since the induction fields do not couple into the reactor wall, they are not heated directly and therefore do not need to be actively cooled. However, the reactor wall is advantageously cooled by convection.
• a reactor 1 shows a schematic representation of a reactor according to the invention.
• a reactor 1 according to the invention has a reactor space 2 with a diameter of 1.5 m, around which induction coils 3 are arranged, which are suitable at frequencies between 1 and 50 kHz and which contain carbonaceous bulk material 4 present in the reactor space 2 Heat temperatures up to 1800 ° C.
• the reactor space 2 is surrounded by a high-temperature-resistant lining 5 of a reactor wall 6.
• the lining 5 is made of firebricks.
• all other high temperature resistant materials are suitable which do not couple to a field generated by the induction coils 3, such as clay-bonded carbon.
• the reactor 1 has an upper zone 7, a middle zone 8 and a lower zone 9.
• a filling opening 10 is provided, via which bulk material 4, slag formers, flow formers and the like can be introduced into the reactor space 2.
• a rotary feeder is set as an entry lock 1 1 on the filling opening 10.
• the induction coils 3 are provided in the central zone 8.
• a slide 23 is provided, which acts as a breaker for breaking slag and bulk material 4 for their removal.
• the upper zone 7 is provided with a connecting piece 13, which connects the reactor space 2 with a sprinkler tower 14, which acts as a gas scrubber 14.
• a sprinkler tower 14 which acts as a gas scrubber 14.
• at least one water nozzle 15 is provided for injecting water into the sprinkler tower 14. Trapped water 17 can be discharged via a valve 16.
• bulk material 4 For operation of the reactor 1, bulk material 4, together with, for example, slag from the blast furnace as slag former and flux, is filled into the reactor space 2 via the rotary valve 11. Slag formers, as well as fluxes can also be added as individual components.
• the bulk material 4 is in this example cathode outbreak from a Aluminiumschmelzelektrolysezelle.
• the Bulk material 4 is except with chamotte, which was at the outbreak of the cathode from the aluminum smelting electrolysis cell in the bulk material 4, contaminated with metallic aluminum and aluminum compounds, with sodium cyanide and soluble fluorine compounds.
• the induction coils 3 heat the contaminated bulk material 4 directly inductively by coupling the induction fields directly into the cathode outbreak.
• the slag and the flux are heated.
• a liquid slag is formed, into which the aluminum impurities also melt. Due to the flux, the viscosity of the slag is lowered so that the slag flows into the lower zone of the reactor 1.
• the slag also transports the chamotte.
• the slag cools down.
• the slag is additionally cooled by the water cooling 12 and solidifies.
• steam 21 is injected into the upper zone 7 via a nozzle.
• the water vapor 21 causes in the reactor chamber 2 a pyrohydrolysis of the existing cyanides already from about 700 ° C. In particular, carbon monoxide, nitrogen and hydrogen are formed. Furthermore, the water vapor 21 in the lower zone leads to a quenching of the slag, whereby it is blasted off of the bulk material 4. About the slider 23, the brittle slag is broken and the lower zone 9 taken. Slag and purified bulk material can then be separated by conventional separation methods due to their density difference.
• the cleaned carbonaceous bulk material can be used, for example, as an additive for building materials, such as cement.
• the carbon of the bulk material may be used as fuel or for use in, for example, wear liners such as gutters.
• Washed fluorine compounds in the water 17 of the sprinkling tower 14, which is taken over the valve 16, can also be reused, for example, by returning to an aluminum electrolysis to adjust the ratio of NaF to AIF 3 in the melt.
• the method according to the invention was simulated in a miniature structure (not shown).
• the reactor used was a clay-bonded graphite crucible with a diameter of 150 mm and a height of 200 mm.
• An induction coil operated at 4 kHz heats an amorphous carbon cathode fracture material having an anthracite content of about 60% by weight as a bulk material.
• the bulk material was heated to 1600 ° C in 45 min.
• the resulting exhaust gases were sucked off and condensed in a filter unit with rock wool fibers.
• the fluorine and cyanide contents before and after heating the bulk material were analyzed by wet chemistry and by X-ray fluorescence analysis. Likewise, the bulk material was analyzed before and after heating.
• the slag-forming components can be derived from both the impurities and the added slag-forming agent. Depending on the provenance of the carbonaceous stones and thus of the impurities, if slag-forming constituents are present as impurities, they must no longer be added as slag formers. A treatment can also be carried out without slag formation.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Environmental & Geological Engineering (AREA)
• Processing Of Solid Wastes (AREA)
• Manufacture And Refinement Of Metals (AREA)
• Furnace Details (AREA)
• Carbon And Carbon Compounds (AREA)

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• 2009
  • 2009-09-23 DE DE102009042449A patent/DE102009042449A1/de not_active Ceased
• 2010
  • 2010-09-23 EP EP10755191A patent/EP2480349A1/de not_active Withdrawn
  • 2010-09-23 BR BR112012006143A patent/BR112012006143A8/pt not_active Application Discontinuation
  • 2010-09-23 AU AU2010299920A patent/AU2010299920B2/en not_active Ceased
  • 2010-09-23 WO PCT/EP2010/064051 patent/WO2011036208A1/de active Application Filing
  • 2010-09-23 CN CN2010800425393A patent/CN102574173A/zh active Pending
  • 2010-09-23 US US13/497,610 patent/US20120251434A1/en not_active Abandoned
  • 2010-09-23 CA CA2775154A patent/CA2775154C/en not_active Expired - Fee Related
  • 2010-09-23 RU RU2012116068/03A patent/RU2586350C2/ru not_active IP Right Cessation
  • 2010-09-23 IN IN2402DEN2012 patent/IN2012DN02402A/en unknown
• 2012
  • 2012-03-15 ZA ZA2012/01946A patent/ZA201201946B/en unknown

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