WO2009081725A1 - Silicon reclamation method - Google Patents
Silicon reclamation method Download PDFInfo
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- WO2009081725A1 WO2009081725A1 PCT/JP2008/072329 JP2008072329W WO2009081725A1 WO 2009081725 A1 WO2009081725 A1 WO 2009081725A1 JP 2008072329 W JP2008072329 W JP 2008072329W WO 2009081725 A1 WO2009081725 A1 WO 2009081725A1
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/02—Silicon
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/02—Silicon
- C01B33/037—Purification
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- the present invention relates to a method for regenerating silicon from waste slurry used in a silicon wafer manufacturing process or the like.
- the recycled silicon obtained by the method of the present invention has high purity and can be suitably used as a solar cell material.
- silicon wafer In the manufacturing process of a thin plate made of silicon single crystal or polycrystal (hereinafter referred to as “silicon wafer”) widely used for IC chips and solar cells, about 60% of the raw material silicon is waste liquid by cutting, chamfering or polishing. The cost to the product and the environmental impact associated with disposal (this waste liquid is generally disposed of in landfill after concentrating and collecting some materials) is a major problem. It has become.
- solid content is recovered from waste slurry discharged from a process of cutting or polishing a silicon single crystal or polycrystalline ingot using a slurry in which abrasive grains are dispersed in a coolant, and the recovered solid content
- organic solvent cleaning to remove coolant, water cleaning to wash away organic solvent, metals (iron, copper, etc.) contained in waste slurry are dissolved in acid aqueous solution (hydrofluoric acid aqueous solution, etc.) Acid cleaning for removing the water and water cleaning for washing away the acid aqueous solution are performed.
- Patent Document 1 describes that the solid content inevitably remains in the solid content obtained by the disclosed recovery method, and further purification is necessary to obtain silicon for solar cells from this solid content. It is stated that. JP 2001-278612 A
- the present inventors have found that the solid content for silicon recovery contains a large amount of phosphorus that adversely affects the characteristics of the solar cell. Thus, it has been found that it is difficult to obtain regenerated silicon that can be preferably used as solar cell silicon simply by removing metal (iron, copper, aluminum, etc.) from the solid content for silicon recovery.
- the present invention has been made in view of such circumstances, and provides a silicon regeneration method capable of efficiently removing phosphorus contained in the solid content for silicon recovery.
- phosphorus contained in the solid content for silicon recovery is derived from, for example, metal scraps such as wire scraps generated from the wire used for cutting the silicon wafer (which cannot be completely removed even by cleaning and remain unavoidably) This is considered (specifically, described later).
- a silicon slurry using a slurry containing abrasive grains and a coolant or a silicon lump or a silicon wafer is cut or polished to solid-liquid separate a waste slurry in which silicon scrap is mixed into the slurry or a concentrated component thereof.
- a process is provided.
- phosphorus contained in the solid content for silicon recovery can be removed relatively easily. This will be described below.
- phosphorus (or phosphorus compound) is directly removed from the metal scrap at a temperature lower than the melting point of silicon without melting the metal scrap containing phosphorus in silicon. This makes it possible to remove phosphorus contained in the solid content for silicon recovery relatively easily.
- the present inventors have found that the metal impurities remaining in the solids for silicon recovery contain a lot of phosphorus that adversely affects the characteristics of the solar cell. Has been found to greatly deteriorate. Furthermore, after the silicon recovery solid content is washed with a cleaning solution comprising an acid solution, the silicon recovery solid content is baked at a temperature of 200 ° C. or higher and 1000 ° C. or lower, so that phosphorus in the silicon recovery solid content is efficiently removed. The inventors have found that it can be removed, and have completed the present invention.
- the silicon recycling method of the present invention is a waste slurry in which silicon waste is mixed into a slurry by cutting or polishing a silicon lump or a silicon wafer using a slurry containing abrasive grains and a coolant, or a concentrated portion thereof.
- the waste slurry is a slurry in which silicon scraps are mixed by cutting or polishing a silicon lump or a silicon wafer using a slurry containing abrasive grains and coolant.
- the concentrated portion of the waste slurry is a concentrate of the waste slurry.
- the silicon lump is a lump of silicon, for example, a silicon ingot.
- the shape of the silicon lump is not particularly limited, but in an example, it is a columnar shape or a quadrangular prism shape.
- An example of the cutting device is a multi-wire saw device (hereinafter referred to as “MWS”) that is widely used as a silicon ingot cutting device.
- MWS is a cutting device that wraps and winds a wire between a plurality of rollers, runs slurry while supplying slurry containing abrasive grains and coolant, and presses an object to be cut against the wire for cutting. .
- An example of a polishing apparatus is a wheel-type polishing apparatus, which is an apparatus that performs polishing by rotating a wheel having abrasive grains fixed with an adhesive and moving a silicon ingot.
- a silicon ingot is cut or polished using these devices, silicon scraps, crushed abrasive grains and non-crushed abrasive grains in the slurry, and metal scraps that are worn pieces of wires and polishing wheels, etc. It will be mixed.
- the results of analyzing the composition of typical silicon ingots, wires and metal wheels are shown in Table 1. Although silicon contains almost no metal impurities and phosphorus, it shows that the wire and polishing wheel contain a lot of phosphorus in addition to metal impurities.
- the slurry is composed of abrasive grains and a coolant that disperses the abrasive grains.
- the type of abrasive grains is not limited and is made of, for example, SiC, diamond, CBN, alumina, or the like.
- the type of the coolant is not limited.
- an oil-based coolant oil based on mineral oil
- an aqueous coolant a water-based glycol-based solvent (for example, ethylene glycol, propylene glycol or polyethylene glycol), surfactant) Or an organic acid added thereto).
- the coolant is mainly composed of an organic solvent (water-soluble organic solvent) such as ethylene glycol, propylene glycol or polyethylene glycol, and an additive such as an organic acid or bentonite is added thereto at 10 wt% or less (preferably 3 wt% or less). It may be.
- an organic solvent water-soluble organic solvent
- an additive such as an organic acid or bentonite is added thereto at 10 wt% or less (preferably 3 wt% or less). It may be.
- the phrase “having the organic solvent as a main component” here means that, for example, the coolant may contain 20 wt% or less (preferably 15 wt% or less) of water.
- Solid-liquid separation step First, the waste slurry or its concentrated component is subjected to solid-liquid separation in the separation unit 1 to obtain a solid content for silicon recovery.
- the configuration of the separation unit 1 is not particularly limited as long as it is a configuration capable of solid-liquid separation of the waste slurry or its concentrated component to obtain a solid content for silicon recovery.
- the separation unit 1 is, for example, a centrifuge.
- the solid-liquid separation device such as a filtration device or a distillation device is used alone or in combination of two or more thereof in series. Specific examples of the combination are (1) a centrifuge and a distillation device, (2) a centrifuge and a filtration device, or (3) a filtration device and a distillation device.
- each separation unit may send either the separated liquid or solid content to the next solid-liquid separation device, and a part of liquid and a mixture of solids or a part of solid and a mixture of liquids. You may send to the following solid-liquid separator.
- the silicon recovery solid content is cleaned with a cleaning liquid made of an acid solution.
- the cleaning unit 2 includes a cleaning bowl 2a and a stirrer 2b provided in the cleaning bowl 2a.
- This acid cleaning step is (1) removing residual organic substances derived from coolant such as glycol solvents and additives contained in the solid content for silicon recovery by dissolving them in an acid solution, and (2) wear pieces of wires. It is performed for the purpose of dissolving and removing metal scraps in an acid solution.
- the particle size of the solids for silicon recovery is preferably in the range of 0.01 ⁇ m or more and less than 10 mm. More preferably, it is in the range of 0.1 ⁇ m or more and less than 5 ⁇ m.
- particle size means a value measured by a method according to JIS R1629.
- the “powder having a particle size of less than X ⁇ m” means a powder having a particle size of 98% of particles in the powder of less than X ⁇ m.
- the “powder of powder Y ⁇ m or more and less than Z ⁇ m” means a powder remaining after removing “powder of particle size less than Y ⁇ m” from “powder of particle size less than Z ⁇ m”.
- the acid solution is a solution obtained by dissolving an acidic substance in a solvent containing water.
- the pH of the acid solution may be less than 7, but is preferably 0-4.
- the pH of the acid solution is, for example, 0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, or 4.
- the pH of the acid solution may be within a range between any two of the numerical values exemplified herein.
- the solvent of the acid solution preferably consists essentially of water, but may contain components other than water.
- the ratio of water in the solvent of the acid solution is preferably 50 wt% or more, for example, 50, 60, 70, 80, 90, 95, 99, 99.9, 100 wt%.
- the ratio of water may be within a range between any two of the numerical values exemplified here.
- Components other than water in the solvent preferably have compatibility with the coolant and have a boiling point lower than that of the coolant, for example, 1 to 6 carbon atoms (preferably 1, 2, 3, 4, 5, and 6 in the range between any two of 6) or a ketone having 3 to 6 carbon atoms (preferably in the range between any two of 3, 4, 5 and 6). In this case, it becomes easy to remove the residual coolant by dissolving it in the acid solution.
- Examples of acidic substances include inorganic or organic acidic substances.
- examples of inorganic acidic substances include hydrogen chloride, sulfuric acid, nitric acid, hydrogen fluoride, and hydrogen bromide.
- examples of the organic acidic substance include citric acid, acetic acid, formic acid, oxalic acid, and lactic acid.
- the acid solution only needs to contain at least one kind of acidic substance, and may contain both an inorganic acidic substance and an organic acidic substance.
- an acid solution containing only an inorganic acidic substance is called an inorganic acid solution
- an acid solution containing only an organic acidic substance is called an organic acid solution.
- the acid solution is preferably composed of an inorganic acid solution. This is because the phosphorus compound produced by the reaction with the inorganic acid generally has a lower boiling point than the phosphorus compound produced by the reaction with the organic acid.
- the acid solution is preferably non-oxidizing with respect to silicon.
- “non-oxidizing” means that the oxidizing power of silicon is weaker than that of sulfuric acid.
- the acid solution is non-oxidizing with respect to silicon, it is possible to suppress a decrease in silicon recovery rate due to silicon oxidation.
- Examples of the acid solution that is non-oxidizing with respect to silicon include hydrochloric acid, hydrofluoric acid, citric acid, and an aqueous ammonium fluoride solution.
- the acid solution may contain hydrogen peroxide.
- the ratio of hydrogen peroxide is, for example, 0.1 to 5 wt%, and specifically, for example, 0.1, 0.5, 1, 2, 3, 4, 5 wt%.
- the ratio of hydrogen peroxide may be in a range between any two of the numerical values exemplified here.
- Neutralization treatment step Next, the washing solution after washing the solids for silicon recovery is transferred to the neutralization treatment vessel 3 to neutralize the acid solution.
- This neutralization treatment step is performed for the purpose of preventing the device from corroding in the next solid-liquid separation step, but may be omitted depending on the configuration of the device.
- a solvent such as water may be added to the cleaning solution to dilute the acid solution, thereby reducing the concentration of protons in the acid solution to prevent corrosion of the apparatus.
- the neutralization method is not particularly limited.
- basic substances such as sodium hydroxide, calcium hydroxide, and ammonia (dissolve in a solvent such as water to release hydroxide ions or become proton acceptors).
- base solution a method of adding a substance) solution
- the pH value of the cleaning solution after neutralization or dilution is not particularly limited, but is 2 to 4, for example. In this case, it is possible to suppress the precipitation of phosphorus as a hardly soluble solid material that is difficult to remove.
- Separation / Washing Step Next, in the separation / water washing section 4, the washing liquid after acid washing and the solid content for silicon recovery are separated into solid and liquid, and washed with pure water to obtain the solid content for silicon collection after washing. Note that this step may be omitted and the cleaning liquid may be volatilized in, for example, a drying step or a baking step.
- the separation / water washing unit 4 is configured by combining two or more pure water supply devices in series with a solid-liquid separation device such as a centrifuge, a filtration device, or a distillation device, for example.
- the cleaning unit 5 includes a cleaning bowl 5a and a stirrer 5b provided in the cleaning bowl 5a.
- the impurity removal effect can be further enhanced by the cleaning in the cleaning unit 5.
- a cleaning liquid made of pure water, an inorganic acid solution or an organic solvent can be used.
- the inorganic acid solution is preferably non-oxidizing with respect to silicon.
- the organic solvent preferably has a boiling point lower than the firing temperature in the firing step. In this case, since the organic solvent is removed at a temperature lower than the firing temperature, generation of SiC is prevented.
- the organic solvent preferably has compatibility with the coolant and has a lower boiling point than the coolant.
- the organic solvent has 1 to 6 carbon atoms (preferably any one of 1, 2, 3, 4, 5, and 6). Or a ketone having 3 to 6 carbon atoms (preferably, a range between any two of 3, 4, 5 and 6). In this case, it becomes easy to remove the residual coolant by dissolving it in an organic solvent.
- the separation / water washing unit 6 is configured by combining two or more solid-liquid separation devices such as a centrifuge, a filtration device, or a distillation device, and two or more pure water supply devices in series.
- Drying step 7 in the dryer 7, the solid content for silicon recovery after washing obtained in the steps so far is dried. Drying can be performed, for example, by heating the solid content for silicon recovery or reducing the ambient atmosphere.
- the solid content for silicon recovery may be naturally dried, or the solid content for silicon recovery may be dried at the same time as another step such as a baking step described later. Therefore, this step can be omitted as an independent step.
- baking process Next, in the baking apparatus 8, baking of the solid content for silicon
- a drum type airflow dryer etc. can be used, for example.
- the solid content for silicon recovery is baked by blowing a gas stream of heated gas to the solid content for silicon recovery while rotating and rotating the solid content for silicon recovery by rotating the drum.
- This firing step is performed by (1) removing residual organic substances derived from coolant such as glycol solvent and additives in solids before washing, and (2) recovering silicon. The purpose is to remove phosphorus remaining in the solid content.
- the firing temperature is set to 200 ° C. or more and 1000 ° C. or less.
- the firing temperature is 200 ° C. or more, phosphorus is easily removed by volatilization of phosphorus (single phosphorus or a phosphorus-containing compound).
- the firing temperature is 1000 ° C. or lower, the oxidation of silicon is suppressed and the formation of an alloy between phosphorus and silicon is suppressed. As a result, the silicon recovery rate is improved and phosphorus is efficiently removed.
- the firing temperature is 200 ° C. or more and 1000 ° C. or less, for example, 300 ° C. or more and 800 ° C. or less. Specifically, for example, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000 ° C.
- the firing temperature may be within a range between any two of the numerical values exemplified here.
- the firing time is, for example, 0.5 to 10 hours. Specifically, for example, 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 8 9, 10 hours.
- the firing time may be within a range between any two of the numerical values exemplified here. In one example, it is preferable to perform treatment for 1 hour or more per 200 kg of the solid content for recovery.
- Calcination is preferably performed in an inert gas atmosphere in order to further suppress oxidation of silicon during calcination.
- the inert gas is, for example, a rare gas (eg, argon) or nitrogen gas.
- the firing is preferably performed in a reduced pressure atmosphere.
- the atmospheric pressure during decompression is, for example, 0.1 to 0.9 atm, and specifically, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0 0.7, 0.8 and 0.9 atm.
- the atmospheric pressure at the time of depressurization may be within a range between any two of the numerical values exemplified here.
- the solid content for silicon recovery from which phosphorus has been removed can be obtained.
- the obtained solid content for silicon recovery can be recovered as recycled silicon.
- Heating / refining step Further, the solid content for recovering silicon from which phosphorus has been removed is melted in the heating / purifying device 9 at a temperature equal to or higher than the melting point of silicon (generally 1410 ° C to 1420 ° C) and then solidified Alternatively, a silicon lump may be used.
- the heating / purification device 9 is preferably a hermetically sealed system and suppresses the oxidation of silicon, and has an inert gas introduction part. The obtained silicon mass can be recovered as recycled silicon.
- the silicon lump can be purified to remove the remaining metal components.
- the purification method for example, various known purification techniques (for example, removal of segregated impurities by unidirectional solidification) at the time of conventional polycrystalline silicon casting can be used. As a result, a silicon lump from which impurities such as metal components have been removed can be obtained and recovered as recycled silicon.
- the heating / refining device 9 includes, for example, a vacuum heating and melting furnace and two or more unidirectional solidification furnaces combined in series.
- the pulverization step refers to all known methods for pulverizing the solid content for silicon recovery to a specific size, and devices such as a ball mill, a jet mill, and a vibration vacuum dryer can be used.
- the molding process can be performed as a pretreatment for melting to increase bulk specific gravity and increase transport efficiency, or to increase thermal conductivity and facilitate melting, and pressurizes silicon-containing powder to form a plate, An apparatus having any configuration can be used as long as the apparatus granulates in a block shape, a pellet shape, or the like.
- the powder separation process includes, for example, classification of particles based on physical parameters such as particle size and density using an inertia classifier or a centrifugal classifier, and a method of removing magnetic impurities such as iron using a magnet. .
- Example 1 Silicon was regenerated in the above-described process using the waste slurry obtained by cutting the solar cell wafer using a wire saw.
- Example 1 To the solid content, 500 L of pure water was added and again stirred and washed for 1 hour, followed by filtration to recover the solid content. The solid content thus obtained was dried by heating to 60 ° C. in 1 atm air and holding for 2 hours. Next, the sample was thrown into the drum of a drum-type baking machine that performs baking while rotating the inclined drum slowly.
- the drum is provided with a heating tube, and the temperature of the firing object can be controlled by feeding heated nitrogen gas into the drum.
- the firing target was controlled to be in the range of 400 to 500 ° C., and firing was performed for 1.5 hours to obtain a dry powder.
- the dry powder is heated to 1800 ° C. at a rate of 300 ° C./hour in an argon 1 atm atmosphere using an externally heated blast furnace and melted by holding for 2 hours to obtain 60 kg of silicon lump. It was.
- Table 2 shows the results of analyzing the concentration of typical impurities for the solid content obtained from the waste slurry, the solid content after washing twice, the dried powder after firing, and the silicon lump after melting in Example 1. It can be seen that impurities were reduced by washing, but the concentration of phosphorus (P) was greatly reduced by firing. Since the concentration of phosphorus is greatly reduced by firing, the silicon mass after melting can be made into a solar cell material by removing the remaining metal by an appropriate method without removing phosphorus particularly under vacuum melting. .
- purification is performed by unidirectional solidification in an atmosphere of 1 atm of argon, sliced into a polycrystalline silicon substrate, and a solar cell is created.
- the conversion efficiency from sunlight to electrical energy is 13 to 14.2%.
- a characteristic close to that of a normal commercial product was obtained.
- Comparative Example 1 In Comparative Example 1, the solid content obtained by filtering the waste slurry was subjected to the same method as in Example 1 up to twice washing, solid-liquid separation, and drying. In this case, melting was performed in the same manner as in Example 1 using an externally heated blast furnace as it was without firing with a firing machine.
- Table 3 shows the results of analysis of the silicon mass after melting in Comparative Example 1. Compared with Example 1, the residue of phosphorus is particularly large. This is presumed to be because phosphorus was taken into silicon and was not efficiently removed because the holding time was below the melting point of silicon.
- Comparative Example 1 As in Example 1, purification by unidirectional solidification was performed in an atmosphere of 1 atm of argon, and a solar cell was created by slicing to a polycrystalline silicon substrate. 1% or less. This is considered to be improved by going through a dephosphorization step, but in this case, the production cost is remarkably increased.
Abstract
Description
まず、前記廃スラリー又はその濃縮分について、分離部1にて固液分離してシリコン回収用固形分を取得する。分離部1の構成は、廃スラリー又はその濃縮分を固液分離してシリコン回収用固形分を取得することが可能な構成であれば特に限定されず、分離部1は、例えば、遠心分離機、濾過装置又は蒸留装置などの固液分離装置を単独で又はこれらを2つ以上直列に組み合わせて構成される。組合せの具体例としては、(1)遠心分離機と蒸留装置、(2)遠心分離機と濾過装置又は(3)濾過装置と蒸留装置などである。(1)~(3)において、遠心分離機、濾過装置又は蒸留装置は、それぞれ2つ以上含まれていてもよい。各分離部は、分離後の液分と固形分の何れを次の固液分離装置に送ってもよく、液分の一部と固形分の混合物又は固形分の一部と液分の混合物を次の固液分離装置に送ってもよい。 1. Solid-liquid separation step First, the waste slurry or its concentrated component is subjected to solid-liquid separation in the separation unit 1 to obtain a solid content for silicon recovery. The configuration of the separation unit 1 is not particularly limited as long as it is a configuration capable of solid-liquid separation of the waste slurry or its concentrated component to obtain a solid content for silicon recovery. The separation unit 1 is, for example, a centrifuge. The solid-liquid separation device such as a filtration device or a distillation device is used alone or in combination of two or more thereof in series. Specific examples of the combination are (1) a centrifuge and a distillation device, (2) a centrifuge and a filtration device, or (3) a filtration device and a distillation device. In (1) to (3), two or more centrifuges, filtration devices or distillation devices may be included. Each separation unit may send either the separated liquid or solid content to the next solid-liquid separation device, and a part of liquid and a mixture of solids or a part of solid and a mixture of liquids. You may send to the following solid-liquid separator.
次に、洗浄部2において、酸溶液からなる洗浄液でシリコン回収用固形分の洗浄を行う。洗浄部2は、一例では、洗浄漕2aと、洗浄漕2a内に設けられた攪拌機2bとで構成される。 2. Acid Cleaning Step Next, in the
次に、シリコン回収用固形分の洗浄した後の洗浄液を中和処理漕3に移し、酸溶液の中和処理を行う。この中和処理工程は次の固液分離工程において装置を腐食しないようにする目的で行うが、装置の構成によっては省略してもよい。また、中和処理の代わりに、洗浄液に水等の溶媒を添加して酸溶液を希釈することによって酸溶液中のプロトンの濃度を下げて装置の腐食を防いでもよい。
中和の方法は、特に限定されず、例えば、水酸化ナトリウム、水酸化カルシウム、アンモニア等の塩基性物質(水等の溶媒に溶解して水酸化物イオンを放出するかプロトンの受容体となる物質)の溶液(以下、「塩基溶液」と呼ぶ。)を洗浄液に添加する方法や、塩基性物質を洗浄液に直接添加する方法等が挙げられる。 3. Neutralization treatment step Next, the washing solution after washing the solids for silicon recovery is transferred to the neutralization treatment vessel 3 to neutralize the acid solution. This neutralization treatment step is performed for the purpose of preventing the device from corroding in the next solid-liquid separation step, but may be omitted depending on the configuration of the device. Further, instead of neutralization, a solvent such as water may be added to the cleaning solution to dilute the acid solution, thereby reducing the concentration of protons in the acid solution to prevent corrosion of the apparatus.
The neutralization method is not particularly limited. For example, basic substances such as sodium hydroxide, calcium hydroxide, and ammonia (dissolve in a solvent such as water to release hydroxide ions or become proton acceptors). For example, a method of adding a substance) solution (hereinafter referred to as “base solution”) to the cleaning liquid, and a method of adding a basic substance directly to the cleaning liquid.
次に、分離・水洗部4において、酸洗浄後の洗浄液と前記シリコン回収用固形分を固液分離し、純水により洗浄を行い洗浄後のシリコン回収用固形分を取得する。なお、この工程を省略して例えば乾燥工程又は焼成工程で洗浄液を揮発させてもよい。
分離・水洗部4は、例えば、遠心分離機、濾過装置又は蒸留装置などの固液分離装置と、純水供給装置を2つ以上直列に組み合わせて構成される。 4). Separation / Washing Step Next, in the separation / water washing section 4, the washing liquid after acid washing and the solid content for silicon recovery are separated into solid and liquid, and washed with pure water to obtain the solid content for silicon collection after washing. Note that this step may be omitted and the cleaning liquid may be volatilized in, for example, a drying step or a baking step.
The separation / water washing unit 4 is configured by combining two or more pure water supply devices in series with a solid-liquid separation device such as a centrifuge, a filtration device, or a distillation device, for example.
次に、洗浄部5において、洗浄液でシリコン回収用固形分の洗浄を行う。洗浄部5は、一例では、洗浄漕5aと、洗浄漕5a内に設けられた攪拌機5bとで構成される。洗浄部5での洗浄により不純物除去効果をさらに高めることができる。 5). Cleaning Step Next, in the
次に、分離・水洗部6において、上記洗浄後の洗浄液と前記シリコン回収用固形分を固液分離し、純水により洗浄を行い洗浄後のシリコン回収用固形分を取得する。
分離・水洗部6は、例えば、遠心分離機、濾過装置又は蒸留装置などの固液分離装置と、純水供給装置を2つ以上直列に組み合わせて構成される。 6). Separation and
Next, in the separation / water washing section 6, the washed cleaning liquid and the silicon recovery solid are separated into solid and liquid, and washed with pure water to obtain the cleaned silicon recovery solid.
The separation / water washing unit 6 is configured by combining two or more solid-liquid separation devices such as a centrifuge, a filtration device, or a distillation device, and two or more pure water supply devices in series.
次に、乾燥機7において、ここまでの工程で得られた洗浄後のシリコン回収用固形分を乾燥させる。乾燥は、例えば、シリコン回収用固形分を加熱するか周囲雰囲気を減圧することによって行うことができる。シリコン回収用固形分は自然乾燥させてもよく、後述する焼成工程などの別の工程と同時にシリコン回収用固形分の乾燥を行ってもよい。従って、本工程は、独立した工程としては省略可能である。 7). Drying step Next, in the
次に、焼成装置8において、200℃以上1000℃以下の温度でシリコン回収用固形分の焼成を行う。 8). Baking process Next, in the
この焼成工程は、(1)洗浄前の固形分のグリコール系溶媒や添加物などのクーラント由来の残留有機物のうち、洗浄工程において除去しきれなかった残留分を除去すること、(2)シリコン回収用固形分に残留するリンを除去することを目的として行われる。 As the
This firing step is performed by (1) removing residual organic substances derived from coolant such as glycol solvent and additives in solids before washing, and (2) recovering silicon. The purpose is to remove phosphorus remaining in the solid content.
さらに、リンを除去したシリコン回収用固形分について、加熱・精製装置9において、シリコンの融点(一般に1410℃~1420℃とされる)以上の加熱において融解し、次いで固化させることにより、シリコン塊としてもよい。加熱・精製装置9は、シリコンの酸化を抑えるため、密閉された系であり、不活性ガスの導入部を有することが好ましい。得られたシリコン塊を再生シリコンとして回収することができる。 9. Heating / refining step Further, the solid content for recovering silicon from which phosphorus has been removed is melted in the heating /
ワイヤソーを用いて太陽電池用ウェハを切断した廃スラリーを用いて、上述した工程においてシリコンを再生した。 1. Example 1
Silicon was regenerated in the above-described process using the waste slurry obtained by cutting the solar cell wafer using a wire saw.
比較例1においては、廃スラリーを濾過して得た固形分に対して、2回の洗浄及び固液分離、乾燥までは実施例1と同様の方法で行った。その上で、この場合は、焼成機による焼成を行うことなく、そのまま外熱式の溶鉱炉を用いて実施例1と同様の方法で融解を行った。 2. Comparative Example 1
In Comparative Example 1, the solid content obtained by filtering the waste slurry was subjected to the same method as in Example 1 up to twice washing, solid-liquid separation, and drying. In this case, melting was performed in the same manner as in Example 1 using an externally heated blast furnace as it was without firing with a firing machine.
Claims (10)
- 砥粒とクーラントを含むスラリーを用いたシリコン塊又はシリコンウェハの切断又は研磨によって前記スラリーにシリコン屑が混入された廃スラリー又はその濃縮分を固液分離してシリコン屑を含有するシリコン回収用固形分を取得し、
前記シリコン回収用固形分を酸溶液からなる洗浄液で洗浄し、
前記洗浄後に200℃以上1000℃以下の温度で前記シリコン回収用固形分を焼成する工程を備えることを特徴とするシリコン再生方法。 Solid silicon for recovery of silicon containing silicon waste by solid-liquid separation of waste slurry mixed with silicon scrap by cutting or polishing of silicon lump or silicon wafer using slurry containing abrasive grains and coolant Get the minute
The solid content for silicon recovery is washed with a cleaning solution comprising an acid solution,
A silicon regeneration method comprising a step of firing the solid content for silicon recovery at a temperature of 200 ° C. or higher and 1000 ° C. or lower after the cleaning. - 前記酸溶液は、無機酸溶液からなる請求項1に記載の方法。 The method of claim 1, wherein the acid solution comprises an inorganic acid solution.
- 酸洗浄後の洗浄液と前記シリコン回収用固形分を固液分離することによって得られる固形分を純水又は非酸化性の無機酸溶液又は有機溶媒により再度洗浄処理する工程をさらに備える請求項1に記載の方法。 The solid content obtained by carrying out solid-liquid separation of the washing | cleaning liquid after acid washing | cleaning and the said solid content for silicon | silicone collection | recovery is further equipped with the process of wash-processing again with a pure water, a non-oxidizing inorganic acid solution, or an organic solvent. The method described.
- 酸洗浄後の洗浄液を中和又は希釈する工程をさらに備える請求項1に記載の方法。 The method according to claim 1, further comprising a step of neutralizing or diluting the cleaning liquid after the acid cleaning.
- 前記中和又は希釈は、中和又は希釈後の洗浄液のpHが2~4になるように行われる請求項4に記載の方法。 The method according to claim 4, wherein the neutralization or dilution is performed such that the pH of the washing solution after neutralization or dilution is 2 to 4.
- 前記焼成の温度は、300℃以上800℃以下である請求項1に記載の方法。 The method according to claim 1, wherein the firing temperature is 300 ° C. or higher and 800 ° C. or lower.
- 前記焼成は、不活性ガス雰囲気下で行われる請求項1に記載の方法。 The method according to claim 1, wherein the firing is performed in an inert gas atmosphere.
- 前記焼成は、減圧下で行われる請求項1に記載の方法。 The method according to claim 1, wherein the firing is performed under reduced pressure.
- 前記焼成後に、前記シリコン回収用固形分を融解する工程をさらに備える請求項1に記載の方法。 The method according to claim 1, further comprising a step of melting the solid content for silicon recovery after the baking.
- 前記融解後に前記シリコン回収用固形分を精製する工程をさらに備える請求項9に記載の方法。 The method according to claim 9, further comprising the step of purifying the silicon recovery solids after the melting.
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WO2019239067A1 (en) * | 2018-06-14 | 2019-12-19 | Rosi | Treatment process for recycling silicon ingot cutting waste |
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DE102011115081B4 (en) * | 2011-09-19 | 2017-08-31 | Baufeld-Mineralölraffinerie GmbH | Process for the recovery of solar silicon from sawed waste |
JP6172030B2 (en) * | 2014-04-03 | 2017-08-02 | 信越半導体株式会社 | Workpiece cutting method and machining fluid |
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