WO2009084068A1 - Procédé de séparation et de récupération des fluides en suspension contenus dans des boues évacuées suite à l'usinage de silicone - Google Patents

Procédé de séparation et de récupération des fluides en suspension contenus dans des boues évacuées suite à l'usinage de silicone Download PDF

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Publication number
WO2009084068A1
WO2009084068A1 PCT/IT2008/000789 IT2008000789W WO2009084068A1 WO 2009084068 A1 WO2009084068 A1 WO 2009084068A1 IT 2008000789 W IT2008000789 W IT 2008000789W WO 2009084068 A1 WO2009084068 A1 WO 2009084068A1
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Prior art keywords
solvent
mixture
process according
recovery
solvents
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PCT/IT2008/000789
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English (en)
Inventor
Guido Fragiacomo
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Garbo S.R.L.
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Priority to JP2010540229A priority Critical patent/JP2011509187A/ja
Publication of WO2009084068A1 publication Critical patent/WO2009084068A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B55/00—Safety devices for grinding or polishing machines; Accessories fitted to grinding or polishing machines for keeping tools or parts of the machine in good working condition
    • B24B55/12—Devices for exhausting mist of oil or coolant; Devices for collecting or recovering materials resulting from grinding or polishing, e.g. of precious metals, precious stones, diamonds or the like
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D21/00—Separation of suspended solid particles from liquids by sedimentation
    • B01D21/0012—Settling tanks making use of filters, e.g. by floating layers of particulate material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D21/00—Separation of suspended solid particles from liquids by sedimentation
    • B01D21/26—Separation of sediment aided by centrifugal force or centripetal force
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D21/00—Separation of suspended solid particles from liquids by sedimentation
    • B01D21/26—Separation of sediment aided by centrifugal force or centripetal force
    • B01D21/267—Separation of sediment aided by centrifugal force or centripetal force by using a cyclone
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B57/00—Devices for feeding, applying, grading or recovering grinding, polishing or lapping agents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B28—WORKING CEMENT, CLAY, OR STONE
    • B28D—WORKING STONE OR STONE-LIKE MATERIALS
    • B28D5/00—Fine working of gems, jewels, crystals, e.g. of semiconductor material; apparatus or devices therefor
    • B28D5/0058—Accessories specially adapted for use with machines for fine working of gems, jewels, crystals, e.g. of semiconductor material
    • B28D5/007—Use, recovery or regeneration of abrasive mediums
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2221/00—Applications of separation devices
    • B01D2221/14—Separation devices for workshops, car or semiconductor industry, e.g. for separating chips and other machining residues
    • 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/10—Greenhouse gas [GHG] capture, material saving, heat recovery or other energy efficient measures, e.g. motor control, characterised by manufacturing processes, e.g. for rolling metal or metal working

Definitions

  • the present invention concerns a process for separating and recovering the suspending fluids contained in exhausted slurries from the machining of silicon. More specifically, the invention concerns a process, with the necessary equipment for implementing it, for the complete separation of the sus- pending fluid from the solid components contained in an exhausted suspension, either abrasive or not, coming from the cutting operation or other mechanical working of materials of monocrystalline or polycrystalline silicon, or of quartz or other ceramic materials, or contained in the sludge as obtained, for instance, from a previous centrifugation of such exhausted suspension.
  • the conventional abrasive slurries used for cutting silicon, quartz or other ceramic materials with a wire saw consist of a suspending, lubricant or cooling fluid, such as a mineral oil or water-soluble organic liquids of high molecular weight - in particular, polyethylene glycol, PEG - in which abrasive particles of suitable hardness, generally of silicon carbide (SiC), are suspended.
  • a suspending, lubricant or cooling fluid such as a mineral oil or water-soluble organic liquids of high molecular weight - in particular, polyethylene glycol, PEG - in which abrasive particles of suitable hardness, generally of silicon carbide (SiC), are suspended.
  • Other abrasive suspensions, prepared using abrasives different from silicon carbide, such as alumina (AI 2 O 3 ) are used in other silicon machining operations different from cutting, such as lapping or the final thickness reduction of the slices, known as "back lapping".
  • Such operations are carried out after cutting by means of lapping machines, essentially consisting of two perfectly flat and round horizontal cast-iron plates, that are able to overlap and rotate in opposite directions to one another.
  • the silicon slices coming from the cutting operation are placed between these plates and the slurry of abrasive particles is fed therein.
  • the slurry normally consists of a mixture of suspending fluid, proper abrasive - typically made of alumina - and a commercial suspending additive.
  • part of the abrasive grains lose their characteristics useful for the functioning of the process and, at the same time, the abrasive slurry becomes enriched with fine silicon particulate, coming from the silicon ingot or form the silicon slices, and also with fine iron particulate, coming from the cutter wire or from the lapping machine plates.
  • the abrasive slurry loses its mechanical characteristics; the efficiency of the slicing operation and the product quality decrease, to the extent that the slurry becomes ineffective and must be discarded and replaced with fresh abrasive slurry.
  • the exhausted slurry is sent to recovery of the reusable components, namely the abrasive grains having size above a given threshold and the suspending fluid used in the slurry itself.
  • the latter (be it based on mineral oil or on organic liquids such as PEG), if efficiently purified from the suspended fine particles of metal residues and of silicon, as well as from the non-reusable abrasive grains, would be perfectly reusable in the process because it keeps its own characteristics unaltered in the course of the process.
  • the conventional approach to this recovery it to first separate the suspending liquid from the solids contained therein by filtration or by centrifu- gation, and then recover the abrasive grains that maintained a minimum size necessary to the cutting operation.
  • the high viscosity of the ex- hausted suspensions and the presence of fine particles of silicon, abrasive and iron makes the filtration very difficult, and sometimes impossible, to carry out in a cheap way, specially in the case of oil-based slurries.
  • the alternative operation consisting of centrifugation only allows to ob- tain some thickened products (commonly referred to as "sludge"), that still contain, however, a significant amount of suspending liquid.
  • the suspending fluids used for machining silicon for electronic and photovoltaic applications are oil-based, or PEG- based (where PEG has different molecular weights).
  • the oils used as suspending agents may be mineral oils with linear chains Ci 0 - C 2 A or synthetic oils with aromatic chains Ci ⁇ - C 26 , to which small amounts of additives are added, these additives being specific for each application and having a proprietary formulation, which is unknown at the moment of treating the slurry for the recovery and the separation of the suspending agent from the fines.
  • These additives, in combination with the abrasive fines and the fines of silicon and other metals may render the direct filtration not applicable or, at least, very difficult.
  • the powders representing the solid part of the exhausted slurries mentioned above typically consist of the following components:
  • SiC silicon carbide
  • SiC or other abrasives, such as for instance diamond or alumina (AI 2 O 3 ), with grain size above 5 ⁇ m, reusable as abrasive in the machining operations on the slices or the ingots of monocrystalline or polycrystalline silicon
  • SiC silicon carbide
  • SiC or other abrasives, referred to as fines, having grain size below 5 ⁇ m, which are not reusable as abrasives in the machining operations cited above ;
  • Si silicon wastes
  • Fe iron wastes
  • the proposed techniques variously combine the following basic operations: a) preliminarily reducing the viscosity of the exhausted slurry, in particular by dilution with a solvent or by heating, in order to be able to treat it in the further operations; b) separating the recoverable abrasive grains by wet size-sorting, such as by centrifugation or by passing the slurry through a hydrocyclone (a static separator of solid particles entrained by a liquid, which exploits the action of centrifugal force); c) separating the recoverable abrasive grains by treating the exhausted slurry with a solvent miscible with the basic suspending fluid of the slurry; d) filtering the liquid phases resulting from abrasive grain separation; e) distilling the liquid mixtures of solvent and cooling fluid making up the filtrate; f) drying the following basic operations: a) preliminarily reducing the viscosity of the exhausted slurry, in particular by dilution with a solvent or
  • the feed to be treated is fed from the top at high speed and tangentially into the apparatus, so that the centrifugal force pushes the heavier particles towards the outer walls the container. Moving in a spiral manner, the heavier particles are then collected in the container's conical bottom (underflow), while the clarified liquid comes out at the top from a central duct (overflow).
  • the hydrocyclone overflow that contains the oily suspending fluid, water and all those solid particles that have not been sorted out by passing through the hydrocyclone, is then fractioned into three phases by centrifugation. This operation yields an oily phase that is reused in the cutting process, the water that is reused in the preliminary exhausted slurry dilution phase, and a residue suspension containing the solids to be discarded, that is sent to the waste treatment plant.
  • the diluting fluid is selected from among the lipophilic solvents (such as n-hexane or n-heptane), while in the case of water soluble-based slurries amphiphilic solvents are used (such as acetone). Since in this case the liquid added is miscible with the suspending fluid, the suspension obtained after separating the reusable abrasive grains must be treated by distillation, after the necessary filtering of the suspended fine solids, in order to recover the suspending fluid and the solvent. In this way, however, as the distillation separates the lower-boiling component, i.e. the solvent. The fines left in the suspension after the separation of the recoverable abrasive remain in the recovered suspending fluid and when the latter is reused they gradually build up.
  • the lipophilic solvents such as n-hexane or n-heptane
  • amphiphilic solvents such as acetone
  • the European patent EP 0791385 (Shin-Etsu Handotai Co. et al.) describes a method for the separation and reuse of exhausted abrasive slur- ries similar to the two methods described above, but mainly intended for use in the case of water soluble-based slurries.
  • the first operation consists of diluting with water the suspension to be treated, in order to reduce its viscosity.
  • the mixture is treated by wet size-sorting to separate the reusable abrasive grains; here, too, the preferred apparatus is a hydrocyclone.
  • the part of the process that differs most from the aforesaid two systems concerns the recovery and separation treatment of the liquid suspension obtained from the overflow of the hydrocyclone.
  • a coagulating agent is added to this liquid suspension in order to favor the separation of suspended solids, and then the whole lot undergoes distillation, from which water is recovered, as the lightest fraction, which is reused for the initial dilution of the exhausted s
  • the mixture of water-soluble slurry, suspended solids and coagulant undergoes solid-liquid separation treatment, preferably by centrifugation, to obtain, on the one hand, a solid residue to be discarded and, on the other, the water-soluble slurry.
  • This can be reused in the cutting process after further treatments, among which the addition of a dispersion agent to adjust the viscosity of the slurry.
  • a dispersion agent to adjust the viscosity of the slurry.
  • the structure of the condensate may be different from the one of new oil, while if the liquid is polyethylene glycol (PEG), the process would not work since PEG, having a high molecular weight, cannot be evaporated without damaging its structure because of the high temperature necessary for evaporation.
  • PEG polyethylene glycol
  • the European patent EP 0968801 (MEMC Electronic Materials and Garbo Servizi) describes a method aimed at regenerating an exhausted abrasive slurry of the water soluble-based type, wherein the exhausted abrasive is firstly heated to reduce its viscosity and then subjected to an initial separation by filtering. This yields a clarified liquid largely composed of cutting fluid with traces of fine powders, and an agglomerate of wet powders containing, along with a small quantity of cutting liquid, almost all the solids suspended in the exhausted slurry.
  • the wet powders are then diluted with water and separated using a hydrocyclone, which produces a fraction of grains of larger size (underflow) and an "overflow" fraction composed of the fine particles suspended in water, mixed with a smaller amount of suspending fluid.
  • the "overflow" fraction from the top of the hydrocyclone is filtered, recovering the aqueous flow that serves to dilute the wet powders before the hydrocyclone separation process.
  • the European patent EP 0968801 (MEMC Electronic Materials and Garbo Servizi) describes a method aimed at regenerating an exhausted abrasive slurry of the water soluble-based type, wherein the exhausted abrasive is firstly heated to reduce its viscosity and then subjected to an initial separation by filtering.
  • the fraction containing the abrasive grains is oven dried, while the overflow fraction from the top of the hydrocyclone is filtered, recovering the aqueous flow that serves to dilute the wet powders before the hydrocyclone separation process and obtaining a solid residue essentially composed of silicon powder and metals.
  • the suspending liquid which is recovered from the first filtering of the hot exhausted slurry, is freed from further traces of powders by means of a further filtering operation, after which it is sent to the cutting process.
  • a non-negligible drawback in the process under examination besides the need to heat the exhausted slurry beforehand in order to reduce its viscosity, is the need to add considerable amounts of water to the wet powders obtained from the first filtering in order to carry out the separation process in the hydrocyclone. Further, it must also be noted that a smaller amount of cutting fluid is lost because it is left in the solid after the first filtering, thus reducing the yield of recovery of the suspending fluid.
  • the filtrate obtained from the aforesaid operation is then treated with an acid leaching agent in order to effect the dissolution of the metal powders and eliminate them, thus obtaining from the subsequent washing of the solid fraction a mixture of only grains of reusable and non-reusable abrasive material.
  • the yield of recovery of the suspending agent is negatively affected by the loss of a part of suspending agent in the first filtration.
  • the process described involves a first solid-liquid separation by centrifugation, from which the thickened fraction is sent to a section for recovery of the abrasive grains comprising a battery of hydrocyclones connected in series and a subsequent apparatus for filtering and chemically treating the grains, while the liquid fraction, containing most of the fines and the suspending fluid, is treated in a section for the recovery of the latter.
  • Such recovery is carried out, according to one of the solutions proposed, through subsequent operations of filtration, addition of alkaline solutions to the clarified solution, microfiltration, neutralization of the clarified liquid obtained, distillation of the minor amount of water that is added to the process, filtration and recovery of anhydrous PEG for reuse.
  • an object of the present invention is to provide a process for the treatment of exhausted slurries from the machining of silicon, or from other similar working procedures on quartz or ceramic materials, which allows to recover in a cheap and flexible way the suspending liquid contained in the slurry in order to reuse it in the preparation of a fresh slurry.
  • Such a process may represent a simple and convenient alternative to the complex processes for separating the suspending fluid already described.
  • the process should be advantageously applicable to the exhausted slurries, either abrasive or not, and also to the centrifugates or thickened products (i.e., sludge) obtained from the said slurries, namely to those products derived from a pre-treatment phase, in which there are still present, typically, significant amounts of suspending fluid, for instance up to as much as 40%.
  • the particles with greater diameter thus, essentially consist of silicon carbide, with prismatic shape and diameter above 5 ⁇ m; further, the presence of particles agglomerates is sometimes noted.
  • the silicon particles have a much more spherical shape and give rise to agglomerates having size comprised between 2 and 5 ⁇ m.
  • u t is the terminal velocity
  • D is the diameter of the solid particle precipitating during settling
  • p s and p are respectively the density of the solid and that of the liquid (in this case the density of the mixture oil/PEG/solvent
  • g is the gravity acceleration
  • ⁇ is the viscosity of the oil/PEG/solvent mixture.
  • K is, finally, a factor the takes into account the sphericity of the particle of diame- ter D; typically, such factor is 1 for the silica particles and 0.81 for the silicon carbide particles.
  • an object of the present invention is to carry out a complete separation of the suspending fluid from all of the solids present in suspension by means of a procedure simple and economi- cally convenient wherein the suspending fluid of the exhausted slurry, consisting of oil or PEG, is immediately separated from all of the solid components contained in the suspension, in the cases where filtration is not possible, by extraction with a suitable solvent.
  • the solid components may then be separated by chemical species and size-sorted by means of a further dedicated process, if necessary.
  • the separation of the suspending fluid is carried out, according to the invention, by means of one or more consecutive steps of extraction of the suspending liquid with a suitable solvent, carried out in counter-current, each followed by settling of the suspension for a suitable period of time and recovery by overflow of the surnatant, consisting of a mix- ture of suspending fluid and solvent.
  • the suspending fluid withdrawn with the first recovery by overflow which is has the highest content of suspending fluid, is fed to the recovery of the suspending fluid by distillation, while the slurry left in the last settler, consisting of the solid powders dispersed in the solvent, with a very little residual amount of suspending fluid, is diluted with a further amount of solvent and undergoes a final filtration after the extraction, for the separation of all the solids present.
  • the cake resulting from the filtration is washed, thus recovering the solvent and the last traces of suspending fluid and then the filtration cake is dried.
  • the products obtained by treating an exhausted slurry or a thick- ened sludge thereof with the proposed process are the following: a) the basic suspending fluid of the slurry, which is sent to the reuse, with a recovery yield > 99%; b) a dry powder containing all the solid components of the slurry; the possible chemical separation or the size-sorting of this powder into its com- ponents may be carried out with techniques which do not fall within the scope of the present invention.
  • the present invention specifically provides a process for separating and recovering the suspending liquid contained in an exhausted slurry, either abrasive or not, coming from the cutting operation or from other machining of silicon materials, or quartz or other ceramic materials, or contained in a thickened fraction of the said exhausted slurry, comprising the following operations: a) extraction of the suspending liquid from the said exhausted slurry/ thickened fraction by dilution with a solvent or a mixture of solvents miscible with the suspending liquid; b) treatment of the diluted suspension resulting from the previous opera- tion by means of a liquid-solid separation; c) recovery of the surnatant obtained from the previous operation, consisting of a mixture of the suspending liquid with the solvent or mixture of solvents; the said sequence of operations a)-c) of the first stage being optionally re- peated in one or two further stages, in counter-current, d) separation of the solvent or mixture of solvents from the surnatant obtained from the operation c) of the first stage by distillation
  • the operation b) of liquid-solid separation may be carried out by means of a separation by density difference, in particular a centrifugation process, which affords a thickened product containing the whole amount of solid particles on one hand, and on the other hand the liquid phase, consisting of the suspending liquid diluted in the solvent (or in the mixture of solvents).
  • a separation by density difference in particular a centrifugation process, which affords a thickened product containing the whole amount of solid particles on one hand, and on the other hand the liquid phase, consisting of the suspending liquid diluted in the solvent (or in the mixture of solvents).
  • Such separation by density difference is preferably realized through an operation of sedimentation or settling, carried out for a period of time nec- essary and sufficient to afford the sedimentation of all the particles.
  • This operation is followed by the said operation c) of recovery of the surnatant obtained from the previous operation, which consists of an operation of recovery by overflow of the mixture of suspending liquid and solvent.
  • the operations (a), (b), (c) may be repeated in the proposed process up to a maximum of two times, thus bringing, according to the preferred solution that employs sedimentation, to a total of three the operations of extraction-settling and recovery by overflow.
  • the number of times the operation of extraction-sedimentation-recovery by overflow is repeated is chosen in dependence of the characteristics of the suspending fluid to be separated from the powders contained therein and also in dependence of the solvent used for the extraction of the suspending fluid, as a last issue, however, the parameter that indicates how may times such operations are to be repeated is the filter- ability of the suspension that is obtained after the last recovery by overflow, which consists of solvent, powders and of the suspending agent is minimal amount.
  • the sedimentation time is set so as to give to all the silicon carbide particles, and the fine particles of silicon and "attrition materials" (substantially iron) fines, independently of their size, the necessary time for a complete sedimentation.
  • the times experimentally established for a complete sedimentation to occur are from 1 to 24 hours, using a solvent to suspension dilution ratio from 1 :3 to 1 :20.
  • the liquid-solid separation by density difference may be replaced by a liquid-solid separation by filtration.
  • the filtration may be performed in one only step, for instance in a filter-press, where it also possible to wash the filtration cake to fully recover the suspending fluid and finally dry the cake.
  • the dilution ratio of solvent or mixture of solvents to exhausted slurry/thickened fraction is normally comprised between 2:1 and 10:1 v/v, and is preferably equal to 1 :7.
  • the sedimentation operation b), which follows the mixing with the solvent, has a duration comprised between 1 and 7 hours, and preferably has a duration of about 4 hours.
  • the solvent for the extraction of the suspending fluid is preferably methylene chloride (also known as dichloro- methane, DCM), which is suitable both for the treatment of PEG-based suspending fluids and for the treatment of oil-based suspending fluids.
  • the solvent may also be selected from perchloroethyl- ene and n-hexane, while when the suspending fluid is polyethylene glycol two additional preferred choices for the solvent are ethyl acetate and 2-buthanol.
  • a mixture of solvents may be advantageously used, in particular a mixture of methylene chloride and toluene, the features of which are reported in the following, ore a mixture of cyclo- hexane and methylene chloride.
  • the last recovery by overflow leaves in the reactor a solvent-solids slurry very rich in solids and having a low content of residual suspending fluid; this slurry is mixed with some fresh solvent and is then fed to the final separation, by filtration, of all the solids present.
  • the cited dilution e) of the residual phase coming from the operation c) of recovery of the last stage with fresh solvent is carried out with a dilution ratio of the sol- vent (or the solvents mixture) to the exhausted slurry/thickened fraction comprised between 2:1 and 10:1 v/v, the preferred ratio being about 7:1 v/v.
  • the cake washing is performed, the solvent and the last traces of suspending fluid are recovered and finally the filtration cake is dried.
  • the said operation f) of washing the filtration cake is carried out with an amount of solvent (or mixture of solvents) equal to about 0.5 times the volume of exhausted slurry fed to the process.
  • the object of the proposed process is the complete separation of all the suspended solids, in order to obtain on one hand the purified suspending liquid and, on the other hand, all of the solids present in the starting exhausted slurry/thickened sludge in the form of a dry powder free from any residues of suspending liquid.
  • the proposed process may equally be applied, besides the exhausted slurries, to the respective thickened fractions (sludges) obtained, for instance, by centrifugation, coming from the machining operations of the semiconductors industry as well as from analogous operations of the photovoltaic energy industry, which as is known, contain considerable amounts of suspending fluid.
  • sludges thickened fractions obtained, for instance, by centrifugation, coming from the machining operations of the semiconductors industry as well as from analogous operations of the photovoltaic energy industry, which as is known, contain considerable amounts of suspending fluid.
  • the process also may be applied in those cases where machining operations on silicon are performed without involving the use of an abrasive added to the cutting wire, but still in the presence of an oil- or PEG- based cooling fluid that is to be recovered.
  • the solids of the slurry from which the suspending liquid s to be recovered will consist of silicon fines and metal fines (coming from the cutting tool).
  • the criteria of choice are given by the following objects: a) in order to use the same solvent for the suspending fluids extraction both from oil-based and from PEG-based slurries the solvent must have affinity with both apolar liquids, such as oil, and polar liquids, such as
  • the choice of using a mixture of two or more suitably dosed solvents allows to better adjust the characteristics of the solvents to be used for the extraction of the suspending fluid on the basis of the characteristics of the suspending fluid itself, thus improving the suspending fluid extraction, with respect to the use of one only pure solvent.
  • An alternative to the use of the pure methylene chloride is, for instance, a mixture of toluene and DCM, or a mixture of cyclohexane and DCM.
  • the two solvents are miscible, and therefore their use in a mixture will require a distillation column with 5-6 trays in enrichment and 3-4 trays in exhaustion instead of the simple evaporation.
  • Figure 1 shows an overall block diagram of a process for separating and recovering the suspending liquid contained in an exhausted slurry, ac- cording to a preferred embodiment of the invention.
  • n stages n ranging from 1 to 3 of extraction-sedimentation-recovery by overflow in counter-current.
  • the example is referred to a total of 3 stages. ist STAGE
  • the exhausted slurry is mixed in the reactor R01 with the mixture coming from the recovery by overflow of the reactor R02, with a dilution ratio, in volume, ranging from 1:2 to 1:10 - volumes of exhausted slurry : volumes of solvent - depending on the type of suspending liquid that characterises the exhausted slurry and on the type of solvent employed.
  • the suspension so diluted 1 :7 is left to settle, for a period of time such that all solid particles in suspension are able to reach the terminal equilibrium velocity and to reach the zone below the level at which the recovery by overflow of the mixture of solvent and suspending liquid will be effected.
  • the se- dimentation time varies as a function of the suspending liquid (whether oil or PEG) and of the solvent used (e.g. DCM, or hexane o mixtures of co-solvents) and may be comprised between 1 hour and 7 hours; typically, it is about 4 hours.
  • reactor R01 This operation consists of withdrawing the sumatant of the diluted suspension settled in the reactor R01; the surnatant is fed to a collection tank (suspending liquid + solvent) D1 and then to a separation system for separat- ing the solvent from the suspending liquid by distillation, that operates with a yield not lower than 99%.
  • the amount of suspending agent present in the liquid form the 1st recovery by overflow is about 6-7%.
  • the volume of the clear phase withdrawn is equal to 7 times the volume of the exhausted slurry fed to the reactor R01.
  • the rest of the slurry left from the recovery by overflow I (the volume of which is equal to the volume of the exhausted slurry loaded in the reactor for the extraction I), is sent to the reactor R02 and then mixed with the solvent- suspending liquid mixture coming from the recovery by overflow III (reactor R03), again with a dilution ratio equal, in volume, to about 1 :7.
  • reactor R02 The suspension so diluted 1 :7 is left to settle, for a period of time comprised between 1 hour and 7 hours; typically, it is about 4 hours.
  • This operation consists of withdrawing the surnatant of the diluted suspension settled in the reactor R02; the surnatant is fed to a collection tank D2 and then to the sedimentation in the reactor R01.
  • the amount of suspending agent present in the liquid form the 1st recovery by overflow is about 2-3%.
  • the volume of the clear phase withdrawn is equal to 7 times the volume of the exhausted slurry fed to the reactor R01. 3rd STAGE
  • the rest of the slurry left from the recovery by overflow Il (the volume of which is equal to the volume of the exhausted slurry loaded in the reactor for the extraction I), is sent to the reactor R03 and then mixed with the solvent- suspending liquid mixture coming from the filtration operation, again with a fixed dilution ratio equal, in volume, to about 1 :7.
  • Sedimentation III, reactor R03 The so resuspended solids are left to settle, for a period of time such that the solid particles in suspension are able to reach the terminal equilibrium velocity and to reach the zone below the level at which the recovery by overflow III will be effected.
  • the sedimentation time comprised between 1 hour and 7 hours and is, typically, about 4 hours.
  • This operation consists of withdrawing the surnatant of the diluted suspension settled in the reactor R03; the surnatant is fed to a collection tank D3 and then to the sedimentation in the reactor R02.
  • the amount of suspending agent present in the liquid form the 1st recovery by overflow is about 0.5%.
  • the volume of the clear phase withdrawn is equal to 7 times the volume of the exhausted slurry fed to the reactor R01.
  • the filtration cake is then washed with a small amount of pure solvent (about 0.5 V); this operation brings the residual content of suspending agent, with respect to the solid to about a few tens of ppm.
  • the solvent used for washing the cake is added to the liquid coming from the extraction itself and then sent to the extraction in the reactor R03.
  • the final yield of recovery of the suspending liquid present in the exhausted suspension appears to be above 99%.
  • Solid Fraction The filtration cake consists of all of the solid components present in the starting exhausted slurry/thickened sludge and wet as a result of the residual presence of the washing solvent. For this reason, therefore, the filtration cake is sent to a drying operation, from which the dry powder making up the solid constituents are obtained, while the solvent vapours are sent to condensation and recovery.
  • Liquid fraction The liquid fraction consists essentially of the solvent, with a residual content of suspending agent lower than 0.5%; from the filtration this fraction is sent to the tank D5, and from this it is sent for settling to the reactor R03.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Grinding-Machine Dressing And Accessory Apparatuses (AREA)
  • Treatment Of Sludge (AREA)

Abstract

La présente invention concerne un procédé de séparation complète du fluide en suspension des composants solides contenus dans une suspension épaisse, de nature abrasive ou non, évacuée suite à l'opération de coupe ou à un autre travail mécanique de matériaux de silicium monocristallin ou polycristallin, de quartz ou d'autres matériaux céramiques, ou contenus dans la boue obtenue suite à la centrifugation préalable de cette suspension évacuée. Le procédé implique la séparation immédiate de tous les composants solides contenus dans la suspension épaisse par le biais d'une ou plusieurs étapes d'extraction, à contre-courant, du fluide en suspension avec un solvant adapté ou un mélange de solvants adapté, suivie par la sédimentation de la suspension diluée avec le solvant et par la récupération par débordement du surnageant composé du mélange de fluide en suspension et de solvant. La phase résiduelle laissée par la dernière récupération par débordement subit une séparation finale par filtration de tous les solides présents, tandis que l'on récupère le fluide en suspension par distillation à partir du mélange de fluide en suspension et de solvant obtenu suite à la première récupération.
PCT/IT2008/000789 2007-12-27 2008-12-23 Procédé de séparation et de récupération des fluides en suspension contenus dans des boues évacuées suite à l'usinage de silicone WO2009084068A1 (fr)

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JP2010540229A JP2011509187A (ja) 2007-12-27 2008-12-23 シリコンの機械加工により排出されたスラリー中に含まれる懸濁流体を分離及び回収する方法

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ITRM2007A000677 2007-12-27
IT000677A ITRM20070677A1 (it) 2007-12-27 2007-12-27 Procedimento per la separazione e il recupero dei sospendenti contenuti nelle sospensioni esauste provenienti dalle lavorazioni meccaniche del silicio.

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WO2009084068A1 true WO2009084068A1 (fr) 2009-07-09

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JP (1) JP2011509187A (fr)
IT (1) ITRM20070677A1 (fr)
TW (1) TW200950927A (fr)
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WO2011003782A1 (fr) * 2009-07-09 2011-01-13 Akw Apparate + Verfahren Gmbh Procédé pour préparer une suspension
DE102010025606A1 (de) 2010-06-30 2012-01-05 Schott Solar Ag Verfahren zur Wiederaufbereitung von verbrauchten Sägeflüssigkeiten aus der Herstellung von Siliziumwafern
JP2012115758A (ja) * 2010-11-30 2012-06-21 Sanwa Biotech Kk シリコン切削廃液の処理方法
CN105764620A (zh) * 2013-10-24 2016-07-13 麦拓卡夫特有限公司 清洁污染碳化硅粒子的方法与系统
WO2016120663A1 (fr) * 2015-01-27 2016-08-04 Metallkraft As Procédé non chimique et système pour récupérer des particules de carbure de silicium et le glycol contenus dans des boues
CN112919415A (zh) * 2021-04-21 2021-06-08 沧州华宇特种气体科技有限公司 一种合成乙硼烷用溶剂的回收方法及回收装置

Families Citing this family (2)

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JP2012245582A (ja) * 2011-05-27 2012-12-13 Nippon Electric Glass Co Ltd 酸化セリウム系研磨材の製造方法
TW201312638A (zh) * 2012-03-03 2013-03-16 Hong Tung Resource Co Ltd 矽晶圓切割廢料之處理方法

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WO2006137098A1 (fr) * 2005-06-24 2006-12-28 Sic Processing Ag Procede et appareil de traitement de boues abrasives d'echappement en vue de la recuperation de leurs composants reutilisables

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EP0791385A1 (fr) * 1996-02-21 1997-08-27 Shin-Etsu Handotai Company Limited Procédé de récupération de suspension liquide résiduaire soluble dans l'eau
WO2001043933A1 (fr) * 1999-12-14 2001-06-21 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Procede pour fractionner une suspension produite lors de l'usinage par enlevement de copeaux
WO2006137098A1 (fr) * 2005-06-24 2006-12-28 Sic Processing Ag Procede et appareil de traitement de boues abrasives d'echappement en vue de la recuperation de leurs composants reutilisables

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011003782A1 (fr) * 2009-07-09 2011-01-13 Akw Apparate + Verfahren Gmbh Procédé pour préparer une suspension
DE102009034949A1 (de) * 2009-07-09 2011-01-13 Akw Apparate + Verfahren Gmbh Verfahren zur Aufbereitung einer Suspension
DE102010025606A1 (de) 2010-06-30 2012-01-05 Schott Solar Ag Verfahren zur Wiederaufbereitung von verbrauchten Sägeflüssigkeiten aus der Herstellung von Siliziumwafern
JP2012115758A (ja) * 2010-11-30 2012-06-21 Sanwa Biotech Kk シリコン切削廃液の処理方法
CN105764620A (zh) * 2013-10-24 2016-07-13 麦拓卡夫特有限公司 清洁污染碳化硅粒子的方法与系统
WO2016120663A1 (fr) * 2015-01-27 2016-08-04 Metallkraft As Procédé non chimique et système pour récupérer des particules de carbure de silicium et le glycol contenus dans des boues
CN112919415A (zh) * 2021-04-21 2021-06-08 沧州华宇特种气体科技有限公司 一种合成乙硼烷用溶剂的回收方法及回收装置

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ITRM20070677A1 (it) 2009-06-28
JP2011509187A (ja) 2011-03-24
TW200950927A (en) 2009-12-16

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