DE102008022237A1 - Slurry preparation involves adding water into non-conducting slurry in container at room temperature for acquiring electrical conductivity, where cationic flocculating agent is also mixed together - Google Patents

Abstract

Slurry preparation involves adding water into non-conducting slurry in a container (H1) at room temperature for acquiring electrical conductivity. A cationic flocculating agent (HS1) is also mixed together and kept homogeneous continuously by agitator. Silicon carbide is chopped with grit (P1) as pellet like filter cakes, and with additives including cast-chip, gypsum or lime. The slurry (A1) is obtained as grinding suspension from mechanical processing of silicon, glass or quartz by wire cutting technology and comprises a suspension of silicon carbide, grit and polyethylene glycol.

Description

The The invention relates to a process for the preparation of a after mechanical machining of silicon, glass, ceramic or quartz grinding slurry obtained by means of wire cutting technology, consisting of a suspension of silicon carbide (SiC), abrasion and polyethylene glycol (PEG).

At the abrasive separation of hard to very hard materials by means of Precision wire saws become grinding suspensions, preferably used by using SiC as Schneidkörnung. With increasing service life, the grinding suspension in his Cutting performance and quality are so affected, that it becomes unusable and so as Altslurry in large Quantities accrues and must be disposed of. The charge remaining, Landfilled landfills represents a large, costly problem dar. The most then evaporated residues and require a landfill.

The introduction of abrasion and the crystalline wear of SiC during wire sawing increases the density of the slurry and, at a certain height, the sawing properties change drastically at the expense of the quality of the products to be produced. In order to maintain a certain consistency in the sawing process, according to the state of the art, after each sawing process a technologically determined part of the slurry loaded with foreign substances is removed and fresh slurry is added to the cutting fluid. So revealed US 5,799,643 such a method a mixing device for mixing fresh slurry to used slurry, supply and measuring devices for cutting means and cutting fluid. A disadvantage of such an admixture is that a defined mixing ratio in the slurrymix obtained is difficult or impossible to adjust.

In the published patent application DE 10032819 A1 A slurry management system is described which includes a recycle unit for waste slurry and for cutting fluid, a mixing unit with central cutting fluid reservoir, for providing fresh slurry, and a slurry presentation unit for the slurry mixing and a loop supply system for the wire saw. With such a solution, a permanent production and use of slurry especially for the application in the sawing of semiconductor wafers is shown under high equipment use of separation, mixing and weighing technology. The cutting fluid is evaporated under vacuum, separated from the solids and recovered via condenser. The resulting silicon abrasion, metal abrasion and worn SiC are disposed of. When using PEG as the cutting fluid, this method is unsuitable for thermal treatment and related decay phenomena.

It is also known to centrifuge Altslurry and to disperse the recovered abrasive particles in fresh cutting fluid ( JP 1-316170 ). Disadvantageously, the abrasion thus remains in the dispersion and this must be disposed of as soon as possible.

The publication DE 19743721 A1 describes a process for reprocessing a grinding slurry. Here is separated from Altslurry by vacuum evaporation above the boiling temperature of the cutting fluid, SiC with abrasion and thermally recovered the cutting fluid condensed. SiC and abrasion are separated by classifying and the SiC is subsequently redispersed in cutting fluid. Here, too, the consumed SiC accumulate in the system constantly and at the same time PEG is not applicable as a cutting fluid due to prescribed thermal treatment.

Out Publications are known to be among those in industrial Applying technologies for the treatment of Altslurry ultimately to a partial or complete disposal comes.

It the task with a procedure is economically favorable large quantities, used slurry, which is used as grinding and cutting means in glass processing for wafer production in Photovoltaic production accrues to work up, that a complete reuse of all Components can be made in the economic cycle.

slurry based on polyethylene glycol (PEG) and silicon carbide (SiC) should be gently separated and processed, at the same time one Residue-free and full-value reuse of the polymer in the glass industry as well as the production of a SiC aggregate in the right shape for metallurgy, especially through residue and emission-free technological processes, to reach.

These The object is achieved by the features specified in the patent claim 1 and procedural steps solved.

advantageous Refinements and developments of the invention will become apparent the dependent claims.

implemented the object is achieved by a method for reprocessing used, during mechanical processing consisting of silicon, glass, quartz or ceramic used slurry from a cutting fluid PEG in the a cutting grain SiC and abrasion are dispersed, which characterized is that in a first step the approximate non-conductive slurry by adding water and cationic Flocculant gently by conventional filtration in a Solid and a liquid component is separated and in one weitern process step, the solid component SiC and abrasion comminuted and mixed with additives and pressed, briquetted or in forms is brought.

Of the Abrasion comes mainly from the cutting material, such as silicon, Glass, quartz or ceramic, and also from the cutting wire and abrasive grain.

The Liquid Component Recycling PEG is used in further process steps by distillation and subsequent azeotropic distillation / absorption brought to the necessary purity of 99.98 mass% PEG.

in the The first step in the process involves the application of slurry and water an electrical conductivity of between 320 and 360 μS / cm brought and in the ratio 1: 1.7 to 2.5 mixed intensively.

Preferably separately is the approach of water and cationic flocculant in the ratio 1: 0,02 also intensive about 10-15 mixed, agglomerated and subsequently with the batch of slurry and water in a container and there together kept homogeneous by means of a stirrer. About a in the tank reaching dip tube is the slurry approach preferably at room temperature in a known belt filter press with introduced the stages pre-thickening and main thickening and it succeeds surprisingly accurate, gentle and clean in solid component and liquid component.

The accumulating recycled PEG is surprisingly clear Gained liquid.

In Further process steps are the solid component SiC and abrasion and the liquid component PEG independently in technical processes for a respective industrial Prepared for use.

Of the filter cake obtained from the filter press from SiC and abrasion is intensively crushed evenly. Preferred should while a basically existing agglomerate structure can be obtained.

The so crushed solid component is used as additive with cast shavings mixed intensively, then pressed and as stable shaped pieces Foundries provided as aggregate.

Of the crushed solid component may instead of cast shavings but also a binder, such as gypsum, mixed in and brought into forms, Foundries are provided as an aggregate.

The Preparation of the liquid component Recycling PEG will be in made two distillation process steps. In the first stage is carried out under atmospheric pressure or under vacuum evaporation using conventional technology at up to 140 ° C over a period until the azeotropic Point of the binary system PEG water reached 97.6 mass% becomes. In the second stage is called azeotropic distillation / absorption an adjuvant, such as acetic acid ester, or a mole sieve, such as ceolite sodium A, used. This procedure is surprising recovered a PEG in which the chemical chain compounds remain undamaged and a purity of 99.98% by mass PEG is achieved. This product is as in the industry, in particular the glass industry, fully usable.

With the inventive combined process stages for gentle separation of used slurry (slurry), in the solid component silicon carbide (SiC) and abrasion and the liquid component polyethylene glycol (PEG) and the combined process stages for the preparation of SIC and abrasion for use as aggregate for the metallurgy and the processing of recycled PEG into a fully fledged reusable PEG in the glass industry.

The guaranteed overall method according to the invention in all his steps, a completely residue-free and emission-free technological process.

The invention is described below with reference to the schematic drawing 1 explained in more detail.

The representation 1 shows the schematic sequence of a treatment of slurry in the individual process steps.

embodiment

A Slurry suspension from the mechanical processing of Glass for Waverherstellung, consisting of polyethylene glycol (PEG) and silicon carbide (SiC) and abrasion should be gently separated, all components prepared and sent for reuse become.

While mechanical processing of the glass / silicon blocks is the dispersed in the slurry cutting grain (SiC crystals) guided by the VA-wire through the silicon blocks and ensures its exact cutting effect there.

The slurry composition is: PEG 49.1 mass%, SiC and abrasion dry substance 49.89% by mass, water 0.7% by mass.

For the preparation of the gentle separation process of slurry at room temperature becomes spent, almost non-conductive Slurry (A1) in a container (H1) with the addition of water in the ratio 1: 2.2 intensively mixed for about 15 minutes and so on brought to a conductivity of about 330 μS / cm. In another container, water becomes common cationic flocculants in the ratio 1: 0.02 as Flocculant mixture (HS1) intensively mixed for about 15 minutes. following the two approaches are merged and in a container continuously through a common Agitator kept homogeneous.

This Slurry batch is used as emulsion (Z1) via a dip tube a known belt filter press (H2) with the stages of pre-thickening and main thickening supplied and gently solid separated.

Of the obtained pellet-like filter cake from SiC and attrition (P1) is uniform to about 1 mm grain size crushed and thus obtained the agglomerate structure.

This crushed filter cake is awarded as cast iron shavings in a ratio of 1: 9 mixed thoroughly and in a briquetting plant pressed out of the mixture into stable shaped pieces.

Corresponding The requirements of metallurgy, the fittings as an additive with SiC also in desired formulations be adjusted and made.

SiC and abrasion may also be with binder, for example Gypsum, mixed and poured into fittings.

The obtained from the liquid separation of the belt filter press Recycled PEG filtrate (Z2) is treated and purified by it is distilled in 2 stages.

In the first stage is the recycled PEG by evaporation / rectification (H3) treated at about 120 ° C under atmospheric pressure for so long, until the azeotropic point of the binary system is PEG-water is reached at 97.6% by mass. The accumulating water (HS2) becomes returned to the process cycle (receiver) (H1).

Subsequently is the present in this form PEG distillate (Z3) in a further stage of absorption (H4) supplied, wherein a Mol sieve is used with the commercial granules "Ceolit sodium A", to a purity of PEG (P2) of 99.98% by mass for a achieve full reuse of the PEG in the glass industry.

The Absorption granulate is after its use by drying treatment / Molsiebregenerierung (H5) also again without restriction and lossless for the absorption process (H4) can be used (HS3).

In combination of its process steps, the overall process on a small scale tested as a pollutant and emission-free with full success.

spent Slurry is processed in such a way that all ingredients and components very cost-effective in the economic Circulation can be returned.

in the Circulation also becomes water within the overall process and auxiliaries.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• US 5799643 [0003]
• - DE 10032819 A1 [0004]
• - JP 1-316170 [0005]
• DE 19743721 A1 [0006]

Claims (7)

Process for the preparation of slurry, which is obtained as a grinding suspension from the mechanical processing of silicon, glass or quartz by wire cutting technology and consists of a suspension of silicon carbide (SiC), abrasion and polyethylene glycol (PEG), characterized in that the approximately non-conductive slurry in a container with the addition of water in its electrical conductivity brought to a value between 320 and 360 μS / cm, so mixed in the ratio 1: 1.7 to 2.5 and at room temperature water with the addition of a cationic flocculant in the ratio of water to flocculant. 1 0.02 agglomerated, mixed together and kept continuously homogeneous by means of agitator, then fed to a customary gentle solid-liquid separation process and separated in SiC and attrition and PEG, each placed in containers and subsequently SiC with abrasion and PEG are each worked up separately by - SIC with abrasion as a pellet-like fil crushed and with additives, such as cast shavings, gypsum, lime, intensively mixed and pressed, briquetted or brought into forms metallurgical industry is provided, - recovered PEG as a clear liquid as a filtrate and a new use in the glass industry by distillation and subsequent azeotropic distillation / Absorption is brought to the necessary purity of 99.98% by mass PEG. Method according to claim 1, characterized in that that the approach of slurry and water and separately the approach of water and cationic flocculant each 10-15 min mixed intensively and subsequently brought together and continue be kept homogeneous by means of agitator. Method according to Claims 1 and 2, characterized that the slurry approach that is spent slurry, water and flocculants over a container Dip tube in a conventional belt filter press with the stages Pre-thickening and main thickening incorporated and gently separated solid-liquid becomes. Method according to claim 1, characterized in that that the filter cake obtained from the filter press of SiC and Abrasion comminuted, while maintaining the agglomerate structure but lasting becomes. Method according to claim 1, characterized that the shredded filter cake as additive for Cast shavings used and pressed as a briquette foundries provided. Method according to claim 1, characterized that the shredded filter cake by means of binders, such as gypsum is processed to manageable fittings. Method according to claim 1, characterized that the distillation of the PEG obtained from the filter press in two stages of the process is carried out, wherein in the first stage an evaporation at up to 140 ° C under atmospheric pressure or at vacuum until the azeotropic point of the binary system PEG water (97.6% by mass) is achieved and in the second stage as an azeotropic distillation / absorption an excipient, such as acetic acid ester, or a mole sieve such as Ceolite Sodium A is used.