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EP2707330A1 - Procédé et dispositif pour séparer des cristaux d'une solution - Google Patents

Procédé et dispositif pour séparer des cristaux d'une solution

Info

Publication number
EP2707330A1
EP2707330A1 EP12720850.2A EP12720850A EP2707330A1 EP 2707330 A1 EP2707330 A1 EP 2707330A1 EP 12720850 A EP12720850 A EP 12720850A EP 2707330 A1 EP2707330 A1 EP 2707330A1
Authority
EP
European Patent Office
Prior art keywords
centrifuge
solution
crystallization
crystals
liquid phase
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.)
Withdrawn
Application number
EP12720850.2A
Other languages
German (de)
English (en)
Inventor
Martin Offermann
Sascha Dyschy
Magnus Rastelbauer
Georg VAN LINN
Recep ÖCALAN
Andreas STEINHOFF
Alexander Bekurdts
Reimund SCHULZ
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.)
Sachtleben Pigment GmbH
Original Assignee
Sachtleben Pigment GmbH
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Sachtleben Pigment GmbH filed Critical Sachtleben Pigment GmbH
Publication of EP2707330A1 publication Critical patent/EP2707330A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G23/00—Compounds of titanium
    • C01G23/04—Oxides; Hydroxides
    • C01G23/047—Titanium dioxide
    • C01G23/053—Producing by wet processes, e.g. hydrolysing titanium salts
    • C01G23/0532—Producing by wet processes, e.g. hydrolysing titanium salts by hydrolysing sulfate-containing salts
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G49/00—Compounds of iron
    • C01G49/14—Sulfates

Definitions

  • the invention is directed to a process for solid-liquid separation of crystals obtained by crystallization from a solution from a liquid phase containing them, wherein a liquid phase containing the resulting crystals is supplied to a solid-liquid separation apparatus comprising a pusher centrifuge.
  • the invention is directed to a device comprising a crystallization stage, which has at least one first crystallizer with at least one downstream, comprising a pusher centrifuge solid-liquid separation device.
  • the invention is also directed to the use of such a device in at least two stages continuously operated crystallization of a titanium-containing Auf gleichans or digestion solution mixture.
  • crystals which precipitate out of a solution or suspension during crystallization often entail undesirably high amounts of the solution or suspension from which they pass through even after screening or passing through a solid-liquid separation Crystallization were excreted.
  • the adhering solution or suspension represents the actually desirable product to be produced, it is desirable to liberate the crystals as completely as possible from the adhering liquid.
  • this is often difficult and problematic because of the crystal form, since it makes it difficult to sufficiently separate the crystals from the adhering liquid. For example, in crystallization conditions where the crystals grow irregularly, there is a difference between the crystals forming are trapped in the liquid to be removed or separated.
  • This problem particularly occurs in the production of titanium dioxide when the production process comprises a crystallization process.
  • Titanium dioxide is known as a pigment with very good properties which make it suitable for use in e.g. Make paints, coating compounds and plastic materials suitable.
  • a titanium-containing raw material in particular titanium-containing ore such as ilmenite (FeTiO3) or titanium slag or another titanium-containing material
  • ilmenite FeTiO3
  • titanium slag titanium-containing material
  • concentrated sulfuric acid fresh acid, oleum and / or recycled sulfuric acid
  • This "digestion" reaction is very vigorous and strongly exothermic
  • the digestion can be carried out both continuously and batchwise
  • the resulting solid digestion cake is then matured for several hours at temperatures between 100 ° C and 200 ° C and then with Water or dilute sulfuric acid.
  • the solution may contain various salts in dissolved form.
  • the digestion solution When using ilmenites or other titanium ores, the digestion solution essentially contains titanium oxide sulfate (titanyl sulfate, TiOS0 4 ) and iron (III) sulfate (Fe 2 (SO 4 ) 3) in dissolved form.
  • titanium oxide sulfate titanium oxide sulfate
  • iron (III) sulfate Fe 2 (SO 4 ) 3
  • the digestion solution contains titanyl sulfate, titanium (III) sulfate (Ti 2 (S0 4 ) 3 ) and Iron (II) sulfate (FeS0 4 ).
  • the titanium slags can be digested with concentrated sulfuric acid at 100-180 ° C, the digestion must be done in acid, otherwise T1O 2 would precipitate. Furthermore, the digestion solutions of titanium ores and / or titanium slags contain various other metal sulfates from the materials used for the digestion (ore, acid, etc.), such as aluminum sulfate, magnesium sulfate, chromium (III) sulfate, etc. in dissolved form and solid, not open-minded gait.
  • Divalent iron can be separated by crystallization, for example cooling crystallization, in the form of green salt (FeS0 4 -7H 2 O) from titanium dioxide-containing sulfuric acid solutions.
  • the green salt can be used for wastewater treatment, ie for the precipitation of the phosphates contained in the wastewater in the form of sparingly soluble iron phosphate, for fertilizer production or for the Production of iron oxide pigments can be used. Alternatively, it may also be dehydrated and thermally decomposed to ferric oxide and sulfur dioxide. If the dissolution solution is obtained from a titanium slag, no further reduction measures are usually required. However, with regard to a solution of titanium ores, eg from ilmenites, it is necessary to reduce the Fe (III) to Fe (II). This reduction is generally carried out by adding metallic iron when dissolving the digestion cake in the digestion vessel or after dissolving the digestion cake by reducing the digestion solution in reduction towers with metallic iron. Alternatively, other reducing agents such as sulfide ores, sulfide iron compounds or Ti (III) -containing solutions may be added to digest the titanium ore.
  • reducing agents such as sulfide ores, sulfide iron compounds or Ti (III
  • the resulting iron and titanium sulfate solution is freed by crystallization of iron (II) sulfate heptahydrate.
  • the resulting titanyl sulfate solution is then hydrolyzed at elevated temperature to titania hydrate. This can then be calcined in an oven to separate the water of hydration and to obtain anhydrous titanium dioxide pigment.
  • titanium chloride tailings solutions containing about 5-6% by weight and etch-nitrate solutions from ilmenite contain about 16-20% by weight of iron (II) sulfate after reduction of Fe 3+ .
  • a vacuum crystallization method used This can be done as a batch or continuous process. Common processes are batch crystallization by evaporation crystallization or surface cooling crystallization in stirred / unstirred Crystallizers with or without a subsequent concentration stage or the continuous crystallization by evaporation or surface cooling crystallization in weighing crystallizers, forced-through horizontal crystallizers or stirred / unstirred stirred reactor cascades.
  • a two-stage vacuum crystallization process is known from DE 10 2007 032 418 AI.
  • titanium dioxide pigments are produced on the basis of the sulfate process, with firstly titania-containing ores (ilmenite) and other prepared ores, so-called titanium slags, separately digested with concentrated sulfuric acid and thus the metal oxides contained in the respective titanium-containing raw material (ore) to a large extent be brought into solution as sulfates.
  • a nearly solid-free solution having This is precisely specified levels of T1O2, Fe 2+, Ti 3+ is then generated and slag H2SO4 solution and by sedimentation or filtration methods.
  • the T1O2 present in the solution is subsequently precipitated specifically by hydrolysis with water.
  • This process involves a reduction and crystallization step, which can significantly increase the use of ilmenites for the production of T1O2.
  • the Fe (III) present in the ilmenite solution is reduced and, on the other hand, the iron content of the digestion solution or digestion solution mixture is subsequently reduced by crystallization of the green salt (FeS ⁇ -V7 H 2 O; ferrous sulfate (II) heptahydrate).
  • the highest possible production of green salt ie a high precipitation of crystallized green salt from the original digestion solution or decomposition
  • the first crystallization stage filtrate ie the remaining digestion solution or digestion solution mixture
  • green salt as far as possible and best possible to separate. This is achieved when, on the one hand, the least possible filter / centrifugate is passed on to the second crystallization stage and, on the other hand, a solution having the highest possible proportion of green salt solids is obtained.
  • this can not be achieved to the desired extent by simple and customary green salt removal devices or green salt concentrations, for example lamellar clarifiers.
  • any crystals formed having a platelet-like structure of the green salt crystals can pass through the gaps of the slotted screen of a pusher centrifuge and produce an increased filter breakdown, which then reduces the solid-liquid separation efficiency of the pusher centrifuge and this solids content in the optionally subsequent second crystallization stage can pass, which then has to be removed there by means of the second crystallizer downstream Grünsalzabtrennvorraumides from the resulting solution prior to further processing.
  • a further problem is that a sufficient "dehydration" of the solution containing green salt is made more difficult by the fact that the usually platelet-shaped crystal structure of the green salt in such cases water solution (black solution) holds by capillary forces between them and thus a "drainage" leads, for example by thickening in clarifiers and / or screening only insufficient results.
  • the invention is therefore based on the object to provide a solution with which in a manufacturing process comprising a crystallization process, after a first crystallization stage, an improved separation of the solution or liquid phase still adhering to the crystals obtained can be achieved, in particular in a liquid phase Provide crystal solids content in a sufficient amount for an economical operation of a pusher centrifuge.
  • this object is achieved in that the crystallized crystals containing liquid phase before entering the pusher centrifuge initially a Siebschnecken- centrifuge, a decanter centrifuge or a Siebdekanter fed and separated therein from a part of the liquid phase.
  • this object is achieved in that between the first crystallizer and a pusher centrifuge at least one of the pusher centrifuge upstream Siebschneckenzentrifuge or at least one of the pusher centrifuge upstream decanter centrifuge or at least one of the pusher centrifuge upstream Siebdekanter is arranged.
  • the process according to the invention makes it possible to operate a crystallization stage with subsequent solid-liquid separation continuously and economically, although one or both types of centrifuge may possibly only be operated suboptimally according to customary ideas, ie the achievable with regard to the achievable degree of concentration or separation Possibilities of the respective devices are not fully exhausted.
  • the invention is therefore further characterized in that the crystals holding liquid phase in the screen screw centrifuge, the decanter centrifuge or the Siebdekanter to a concentration of crystalline solids content of more than 30 wt .-%, preferably more than 45 wt .-%, is thickened.
  • the invention provides in a further development that the liquid phase containing the crystals in the screen screw centrifuge, the decanter centrifuge or the Siebdekanter to a concentration of crystalline solids content of 30-50 wt. % is thickened. 50% by weight solids content in the liquid phase represents approximately the limit above which no more liquid is present but already a solid which would then have to be transported or conveyed as a solid, ie could no longer be pumped.
  • the invention is therefore also distinguished by the fact that the crystals, preferably in already thickened liquid phase, are washed in the pusher centrifuge with a washing medium. It is of particular advantage to use the method according to the invention in the production of titanium dioxide if the production method comprises a crystallization step for the digestion solution or digestion solution mixture (black solution).
  • the invention is therefore further distinguished by the fact that the method is part of a process for the production of titanium dioxide, which comprises the digestion of a titanium-containing raw material with sulfuric acid to a digestion solution (black solution) or digestion solution mixture and at least one downstream treatment stage ne at least two-stage crystallization of green salt (FeS0 * 7 H 2 O) from the digestion solution or digestion solution mixture, wherein a solution containing the crystallized in a first crystallization step (FeSOfl H 2 O) containing solution of a pusher centrifuge (first) Grünsalzabtrennvorraum is supplied and the crystallized green salt-containing liquid phase before entering the pusher centrifuge first a Siebschneckenzentrifuge or a decanter centrifuge or a Siebdekanter fed and therein by separation of a portion of the liquid phase to a concentration of Grünsalzfeststoffanteil of ⁇ 30 wt .-%, preferably ⁇ 45 wt.%, Thick
  • the residence time of the green salt in a Siebschneckenzentrifuge or a decanter centrifuge or Siebdekanter may be only about a maximum of five seconds, so that built in these devices usually at most a comparatively thin cake of about 1 cm thickness can be.
  • These conditions prevent adequate washing of the green cake or mash, ie the black liquor / digestion solution / digestion solution mixture concentrated with the increased and sufficiently high green salt solids content.
  • a concentration of green salt solids content in or part of the solution obtained in the crystallization of> 30% by weight, preferably ⁇ 45% by weight can be produced with a screen screw centrifuge or a decanter centrifuge or a screen decanter.
  • a downstream pusher centrifuge can then be operated in an economical manner. If, for example, a pusher centrifuge is characterized in that a residence time of the green salt or green salt cake of approx. 25 seconds is achieved, a solid cake, ie green salt cake, of about 6 cm in thickness can be built up here. As a result of the higher residence time in the pusher centrifuge, time and larger solid cake starch can also be done the necessary washing of the green salt.
  • the solution containing a crystallizer of the first crystallization stage and containing the crystallized green salt is first fed to an upstream lamellar clarifier before it is fed and fed into a Siebschneckenzentrifuge or a decanter centrifuge or Siebdekanter.
  • a concentration, ie thickening of a part of the solution and a green salt solids content of about 26% by weight and to supply a clarified filtrate fraction for further processing or processing.
  • the centrifuges downstream of the lamellar clarifier no longer have to be designed for the complete liquid solution fraction.
  • the method according to the invention is therefore distinguished Furthermore, characterized in that the solution or liquid phase containing the crystals or the crystallized green salt is first supplied to one of the screen screw centrifuge or the decanter centrifuge or the plate decanter upstream lamella clarifier.
  • the device according to the invention is further distinguished by the fact that at least one screen screw centrifuge or decanter centrifuge or Siebdekanter a lamellar clarifier is connected upstream.
  • This intermediate or collecting tank or hopper parallel untreated solution from the first crystallization stage or outlet from the lamellar clarifier or thickener which may also be prepared before entering the intermediate or collecting container with admixed untreated solution from the first crystallization stage, fed and with the Green salt pulp containing green salt solids content, from the Siebschneckenzentrifuge or the decanter centrifuge or the associated Siebdekanter leaking to be mixed to a desired Grünsalzfeststoffanteil having solution. This mixed solution is then fed to the downstream pusher centrifuge.
  • the process according to the invention is therefore further distinguished by the fact that the crystals or the crystallized out Green salt containing and preferably thickened solution or liquid phase is fed to an intermediate or collecting container before feeding to the pusher centrifuge and there with a partial stream of crystals containing the crystallized in the first crystallization stage green salt (FeS0 4 -7 H 2 0) containing solution or liquid phase on the desired concentration of solids or Grünsalzfeststoffanteil is mixed.
  • the invention provides that the thickened liquid phase flowing out of the lamellar clarifier, preferably before it enters the screen screw centrifuge, is a partial stream of a green salt (FeSO 4 .7H 2 O ) crystallized out in the first crystallization stage ) is mixed.
  • a green salt FeSO 4 .7H 2 O
  • the device according to the invention is characterized in an embodiment in that an intermediate or collecting container is connected between the screw conveyor centrifuge and the pusher centrifuge.
  • the thickening or concentration of the liquid phase or solution containing the crystals or the crystallized green salt can be carried out continuously or discontinuously, which the invention also provides.
  • the crystallization of green salt (FeS0 4 -7 H 2 0) from the digestion solution or digestion solution mixture is carried out continuously in at least two successive crystallization stages, wherein the temperature in the first crystallization stage is adjusted so that there preferably more than 40% of the total crystallization occurring in the green salt (FeS0 4 -7 H 2 0) crystallized out as a coarse crystalline salt and the temperature in a subsequent second crystallization stage is adjusted so that in this crystallization step over the green salt obtained in the first crystallization step finely crystalline green salt (FeS0 4 -7 H 2 0) is obtained.
  • the temperature of the first crystallization stage is adjusted to a value between 25 ° C and 35 ° C and the temperature of the second crystallization stage is set to a value between 10 ° C and 20 ° C.
  • inventive method in that it allows to use different titanium-containing raw materials as starting materials and to mix their digestion solutions.
  • the invention is therefore further characterized in that the downstream treatment stage, a digestion solution (black solution) or digestion solution mixture is supplied, which is obtained by selective mixing of Fe (III) -containing ilmenite digestion solution with titanium (III) - containing slag digestion solution.
  • the first crystal separation device comprises one or more pusher centrifuges.
  • the crystallization stage can be formed as a continuously operable, at least two-stage crystallization stage and the first crystallizer and at least one second crystallizer serially connected in series with at least one downstream second solid-liquid separation device, in particular a downstream second crystal (green salt) separation device -
  • the device is characterized by the fact that the second solid-liquid separation device or the second crystal separation device comprises one or more peeler centrifuges.
  • Fig. 1 in a schematic representation of the arrangement of
  • FIG. 2 performed in a plant according to FIG. 1
  • two-stage crystallization stage is part of a production plant for the production of titanium dioxide, in particular titanium dioxide pigment by the sulfate process.
  • digestion solution or digestion solution mixture of the downstream treatment stage or process stage shown in FIGS. 1 and 2 is fed from an upstream process stage for carrying out a crystallization.
  • This treatment stage or stage comprises a feed tank 17 designed as a stirred tank, which is connected via a line 18 to a first crystallizer 19.
  • This first crystallizer 19 forms the first crystallization stage of the overall two-stage crystallization process.
  • the first crystallizer 19 is connected via a line 20 to a first solid-liquid separation device or first crystal separation device, here a first green salt separation device, designated as 21 first green salt separation device, the crystals obtained in the crystallization, here Green salt, are supplied with a solution containing these crystals.
  • This first crystal (green salt) separation device 21 comprises a lamellar keller 21a, a screw conveyor centrifuge 21b, and a reciprocating centrifuge 21c, and an intermediate or collection container 36 connected in conduit communication between the screw conveyor centrifuge 21b and the pusher centrifuge 21c.
  • the first crystallizer 19 is operated at a temperature between 25 ° C. and 35 ° C. as a vacuum crystallizer, so that from the digestion solution (mixture) the green salt crystallizes essentially and in the predominant amount as a coarsely crystalline salt.
  • This crystallized green salt is then separated from the solution containing it in the first solid-liquid separation device or first crystal separation device 21.
  • This first crystal separation device comprises a plurality of centrifuges 21b, 21c connected in series with an upstream static thickener 21a in the form of a lamella clarifier.
  • the first crystal separation device 21 via lines 22a, 22b, 22c with a further (second) storage tank 23, the filtrate or Zentrifugat matterser, formed as a stirred tank, to which through the lines 22a, 22b, 22c respectively the clear flow or the centrifugate of the respectively associated solid-liquid separator 21a, 21b or 21c is supplied ,
  • the second storage tank 23 is connected via a further line 24 to the input side of a second crystallizer 25 in line connection, so that clarified by the line 24, "dehydrated” and cleared of green salt (digestion) solution or (digestion) solution mixture from the second storage tank 23 the
  • the second crystallizer 25 is connected via a further line 26 to a second solid-liquid separator or second crystal separator, here a second Grünsalzabtrennvoretti 27 in line connection, which in the Crystallization in the second crystallizer 25 obtained as a green salt crystals are supplied with a solution containing them.
  • the second crystallizer 25 is connected via a
  • This second green salt removal device 27 comprises a thickener in the form of a lamella clarifier 27a and two peeler centrifuges 27b, in which a suspension reservoir tank 27c is connected between the lamellar clarifier 27a and the peeler centrifuges 27b. From the second crystal separation device 27, further lines 28a, 28b leading to the respective clear flow or the respective centrifugation lead to a transfer tank 29 designed as a stirred vessel, from which then a discharge line 30 leads, which connects the crystallization stage for transferring of the crystals, here the green salt, liberated (digestion) solution or (digestion) solution mixture with a hydrolysis step.
  • digestion solution or digestion solution mixture is introduced into the stirred feed tank 17 after a sedimentation and filtration step, from which it is pumped into the first crystallizer 19.
  • the crystallized green salt in the first crystal separation device 21 is separated from the solution containing the obtained crystals (arrow 31), and the (digestion) solution is passed as filtrate or clear flow via line 22a into the second storage tank 23. From this, it is then pumped into the second crystallizer 25, in which further green salt is crystallized out.
  • the crystals which form in the second crystallizer 25 in the form of finely crystalline green salt are separated from the solution containing them (arrows 32a / 32b) in the second crystal separation device 27 and the (digestion) solution or (digestion) solution mixture which only has a low level of finely crystalline green salt, is pumped through line 28a into transfer tank 29. From this tank 29, the titanium-containing (digestion) solution then passes into a downstream hydrolysis stage, advantageously recycling the cold, effluent (digestion) solution or (digestion) solution mixture by heat exchange with the warm digestion solution or digestion solution mixture flowing into the crystallization process he follows.
  • the solution which is in the form of a salt slurry from the second crystallization stage and contains the crystallized (green salt) crystals, is fed through the conduit 26 to a second thickener 27a of the second crystal (green salt) separation apparatus 27.
  • the resulting from liquid phase, thickened and the crystallized crystals containing crystal slurry (34) is separated from the liquid phase via the peeler centrifuges 27b (32a / 32b) and fed to a further use.
  • the clear water of the sludge clarifier / thickener 27a and the liquid phase centrifugate are supplied to the transfer tank 29 via the conduits 28a and 28b, and then the solution is passed through the discharge line 30 for subsequent hydrolysis.
  • a Grünsalzbrei produced as a liquid phase, which a Kristallfeststoffanteiel (here: Grünsalzfeststoffanteil) of about 26 wt. -% and which is derived via a line 33 from the static thickener or lamella clarifier 21a and the Siebschneckenzentrifuge 21b is fed.
  • the Siebschneckenzentrifuge rotates at about 1000 revolutions / min and thereby separates from the liquid phase in the crystals enclosed or adhering to (digestion) solution or (digestion) solution mixture, so-called black solution, as a centrifugate from the salt slurry.
  • This centrifugate is supplied to the storage tank 23 via the line 22b.
  • the discharge screw of the Siebschneckenzentrifuge 21b rotates at about 15 revolutions / min faster than the drum rotating at 1000 revolutions / min and carries the thickened salt slurry as a liquid phase via a line 35.
  • the salt slurry or liquid phase then has a green salt solids content (generally a crystal solids content) of about 45% by weight and is then fed to the pusher centrifuge 21c.
  • a green salt solids content generally a crystal solids content
  • an intermediate or collecting container 36 or hopper container is interposed in the embodiment.
  • the crystal solids content here the green salt solids content of the Siebschneckenzentrifuge 21b leaving liquid phase (here salt slurry) in a range of about 30 wt .-% to approximately 100 wt .-%
  • it is within it is possible to pump a partial flow of the underflow leaving the lamellar clarifier or thickener 21a via the line 33 as a liquid phase via a branch line or parallel line 37 parallel to the screen worm centrifuge 21b into the intermediate or collecting container 36 or funnel container and here with the much higher concentrated to mix the Siebschneckenzentrifuge 21b on the line 35 leaving salt slurry and thus in the intermediate or collecting container 36 a salt slurry with the desired total concentration of Grünsalzfeststoffanteil (generally crystalline solids content) of for example about 45 wt .-% set.
  • Grünsalzfeststoffanteil generally crystalline solids content
  • the possibility is provided to supply the line 33 and thus the partial stream of the liquid phase leaving the lamellar clarifier 21a via a first branch line 38 to a solution containing saline salt, as it exits from the first crystallizer 15, and to mix it.
  • a second branch line 38a solution containing saline as it exits from the first crystallizer 15
  • the parallel line 37 are supplied and / or can via a third branch line 38b saline solution, as it exits the first crystallizer 15, in the intermediate or collecting container 36 or funnel container are introduced.
  • the salt slurry produced there is then supplied by means of a line 39 as liquid phase of the scoop centrifuge 21c.
  • the screen screw centrifuge 21a is one which consists of a drive part arranged in a bearing housing, a screen holding drum, a sieve insert, a transport screw and a product housing enclosing the rotating parts.
  • the solid / liquid mixture here salt slurry as a liquid phase
  • the transport screw turns in the same direction of rotation as the screen holding drum, but at a slightly different speed and ensures even product acceleration and product distribution on the screen section.
  • a Siebschneckenzentrifuge 21b may be used instead of a Siebschneckenzentrifuge 21b but also a decanter centrifuge or a Siebdekanter use.
  • a decanter centrifuge or a Siebdekanter use may be used instead of several of these filtration centrifuges.
  • several of these filtration centrifuges can be connected in parallel and / or in series.
  • Part of a first solid-liquid separator or first crystal separator or first green salt separator 21 and / or a second solid-liquid separator or second crystal separator or second green salt separator 27 be.
  • the liquid or suspension to be separated is applied approximately in the middle of a drum of the decanter centrifuge, so that the solid is conveyed through the differential speed to the drum rotating screw towards the smaller diameter of the drum, while the clarified liquid at the opposite end the drum overflows.
  • a Siebdekanter is a combination of Vollmantel- decanter centrifuge and Siebschneckenzentrifuge.
  • the feed suspension or solution is initially pre-thickened, that is to say largely dehydrated on the conical part of the full-width drum.
  • the liquid is clarified in the cylindrical part and thrown off at the end.
  • the pre-thickened solid is transported by the transport screw into the cylindrical sieve part where it is freed from the adhering residual liquid.
  • the first solid-liquid separation device 21 has only one screen screw centrifuge 21b and a pusher centrifuge 21c connected in series therewith in fluid line fashion and a plate clarifier 21a connected in series with both centrifuges in fluid-line connection. It is, of course, also possible to form any combination of one or more screen screw centrifuges 21b with one or more pusher centrifuges 21c. This with and without upstream thickener or lamellar clarifier 21a.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geology (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

L'invention concerne un procédé pour la séparation solide-liquide de cristaux, obtenus par cristallisation (19) à partir d'une solution, d'une phase liquide les contenant, lesdits cristaux étant, au cours duquel une phase liquide contenant les cristaux obtenus est amenée dans un dispositif de séparation solide-liquide (21) comprenant une centrifugeuse à poussoir (21c). L'invention a pour but de fournir une solution permettant d'obtenir une meilleure séparation de la phase liquide ou de la solution adhérant encore aux cristaux obtenus, lors d'un procédé de production comprenant un processus de cristallisation après une première étape de cristallisation, et il est notamment possible de fournir de manière sûre dans une phase liquide une proportion de matières solides cristallines en quantité suffisante pour assurer le fonctionnement économique de la centrifugeuse à poussoir. On atteint ce but en transférant la phase liquide contenant les cristaux ayant cristallisé dans une centrifugeuse (21b) à tamis et à vis sans fin, dans un décanteur centrifuge ou dans un décanteur à tamis où une partie de la phase liquide est séparée, avant son entrée dans la centrifugeuse à poussoir (21c).
EP12720850.2A 2011-05-11 2012-05-04 Procédé et dispositif pour séparer des cristaux d'une solution Withdrawn EP2707330A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE201110050288 DE102011050288A1 (de) 2011-05-11 2011-05-11 Verfahren und Vorrichtung zur Abtrennung von Kristallen aus einer Lösung
PCT/EP2012/058225 WO2012152682A1 (fr) 2011-05-11 2012-05-04 Procédé et dispositif pour séparer des cristaux d'une solution

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EP2707330A1 true EP2707330A1 (fr) 2014-03-19

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EP (1) EP2707330A1 (fr)
DE (1) DE102011050288A1 (fr)
WO (1) WO2012152682A1 (fr)

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CN112794401A (zh) * 2021-01-28 2021-05-14 昆山三一环保科技有限公司 废水结晶出盐系统及其控制方法
CN113144660B (zh) * 2021-02-05 2023-03-03 成都思达能环保设备有限公司 一种结晶方法及系统
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