Method for preparing high-purity quartz by flash oxidation of silicon wafer cutting waste

Abstract

The invention relates to a method for preparing high-purity quartz by flash oxidation of silicon wafer cutting waste, and belongs to the technical field of recovery and utilization of silicon wafer cutting waste. Aiming at the characteristics that the granularity of the silicon wafer cutting waste is submicron and the silicon wafer cutting waste is easy to oxidize, the method comprises the following steps: drying and crushing the silicon wafer cutting waste, and removing impurities in the silicon wafer cutting waste through acid leaching to obtain high-purity silicon powder; the method comprises the following steps: introducing high-purity silicon powder from the top of a fluidized bed reactor, introducing thermal oxidizing air flow from the bottom to enable the silicon powder to form a fluidized state, and controlling the temperature of hot air at a discharge port of a fluidized bed to enable the high-purity silicon powder and the oxidizing air flow to be subjected to flash oxidation to generate a high-purity quartz product. The method has the advantages of being high in raw material adaptability, high in production efficiency, short in operation process, high in added value of products, suitable for large-scale industrial production and the like, and the industrial problem of shortage of high-purity quartz resources is solved.

Description

Technical Field

[0001] The invention relates to a method for preparing high-purity quartz by flash oxidation of silicon slice cutting waste, belonging to the technical field of recycling and utilization of silicon slice cutting waste. Background Art

[0002] Silicon wafer cutting waste has the characteristics of high silicon content, fine particle size, high surface activity and easy surface oxidation. During the purification process, the surface oxide layer shields impurities, limits the purity and recovery rate of recycled silicon, and brings great challenges to the value-added utilization of silicon wafer cutting waste. Silicon wafer cutting technology is developing in the direction of thinning and thinning, which not only reduces the loss of high-purity silicon, reduces production costs, but also improves production efficiency. However, this development direction makes the particle size of silicon wafer cutting waste finer, the surface activity stronger, and the oxidation phenomenon more severe, which further increases the difficulty of purifying silicon.

[0003] Due to its excellent physical and chemical properties, high-purity quartz occupies an important position in many high-tech industries such as semiconductors, photovoltaics, aviation, aerospace, and electronics. The demand for high-purity quartz is increasing, especially in the fields of photovoltaics and semiconductors. At present, high-purity quartz is mainly prepared by purifying quartz minerals such as vein quartz, but to achieve a purity of 4N8 or above, the cost is extremely high and it is difficult to achieve industrialization. The existing preparation methods of high-purity quartz mainly include physical and chemical methods. Physical purification mainly includes color sorting, scrubbing, gravity separation, magnetic separation, and flotation. Chemical deep purification mainly includes acid (alkali, salt) treatment and heat treatment. However, these methods have some common technical difficulties: limited raw material selection, difficulty in impurity removal, high equipment requirements, environmental and safety issues, and cost control. Especially when achieving high purity requirements, chemical purification is complicated and costly, and physical purification cannot remove gas-liquid inclusions and isomorphous impurities inside the lattice, which restricts the preparation of high-purity quartz products.

[0004] Therefore, purifying the easily oxidizable silicon wafer cutting waste and then oxidizing it to prepare high-purity quartz can not only increase the economic added value of silicon wafer cutting waste, but also promote the industrial production of high-purity quartz materials. Summary of the invention

[0005] In view of the problems of silicon waste in existing silicon wafer cutting waste and limited raw material selection and difficulty in removing impurities in the preparation process of high-purity quartz, the present invention proposes a method for preparing high-purity quartz by flash oxidation of silicon wafer cutting waste. In view of the characteristics of silicon wafer cutting waste being submicron-level and easy to oxidize, the silicon wafer cutting waste is dried and crushed, and impurities in the silicon wafer cutting waste are removed by acid leaching to obtain high-purity silicon powder; the high-purity silicon powder is introduced from the top of the fluidized bed reactor, and the hot oxidizing airflow is introduced from the bottom to form a fluidized state of the silicon powder, and the hot air temperature of the fluidized bed outlet is controlled to flash oxidize the high-purity silicon powder with the oxidizing airflow to generate a high-purity quartz product. The present invention has the advantages of strong raw material adaptability, high production efficiency, short operation process, high product added value, and suitability for large-scale industrial production, which helps to alleviate the industrial problem of shortage of high-purity quartz resources.

[0006] A method for preparing high-purity quartz by flash oxidation of silicon wafer cutting waste, the specific steps are as follows:

[0007] (1) drying and dehydrating the silicon wafer cutting waste block material, and crushing it to obtain silicon wafer cutting waste particles;

[0008] (2) subjecting silicon wafer cutting waste particles to acid leaching to deeply remove impurities to obtain high-purity silicon powder with a purity greater than 4N8;

[0009] (3) High-purity silicon powder is introduced into the fluidized bed reactor from the top, and a high-temperature oxidizing gas flow is introduced into the fluidized bed reactor from the bottom, so that the high-purity silicon powder is suspended under the action of the oxidizing gas flow, and the hot air temperature at the fluidized bed outlet is controlled to allow the high-purity silicon powder to fully contact and oxidize with the oxidizing gas flow, and high-purity quartz is obtained by gas-solid separation.

[0010] The particle size of the silicon wafer cutting waste particles in step (1) is less than 1 μm.

[0011] Preferably, the acid solution used in the wet acid leaching in step (2) is one or more of sulfuric acid, hydrochloric acid, hydrofluoric acid, nitric acid, citric acid, and tartaric acid.

[0012] More preferably, the acid solution contains H + The concentration is 0.5-6 mol / L, the liquid-solid ratio of the acid solution to the silicon wafer cutting waste particles is 5-20:1, the leaching temperature is 40-300° C., and the stirring rate is 100-1000 rpm.

[0013] Preferably, in step (3), the feeding rate of high-purity silicon powder is 50-300 kg / min, the thickness of high-purity silicon powder is 1-200 mm, the temperature of the oxidizing gas flow is 200-800° C., and the speed of the oxidizing gas flow is 10-400 m / min. 3 / h, and the hot air temperature at the fluidized bed outlet is 100-500℃.

[0014] Preferably, the oxidizing gas flow in step (3) is oxygen, air or water vapor.

[0015] The gas-solid separation methods include but are not limited to cyclone separation, gravity separation, bag separation, and electrostatic separation.

[0016] The beneficial effects of the present invention are:

[0017] (1) The present invention performs acid leaching to deeply purify silicon wafer cutting waste particles, introduces high-purity silicon powder into a fluidized bed reactor from the top, introduces a high-temperature oxidizing airflow from the bottom, fluidizes the silicon powder, controls the hot air temperature at the fluidized bed outlet, flash-oxidizes the high-purity silicon powder and the oxidizing airflow to generate a high-purity quartz product, and realizes high-value utilization of silicon wafer cutting waste;

[0018] (2) The raw materials of the present invention are easy to use and have low requirements on the raw material morphology, particle size, impurity content and other parameters of silicon wafer cutting waste;

[0019] (3) The high-purity quartz product of the present invention has high economic added value, avoids silicon loss caused by removal of silicon oxide layer, utilizes the characteristic that impurities mainly exist on the surface, deeply removes impurities from silicon powder through acid dissolution, and is used to prepare high-purity quartz products with a purity as high as 4N8;

[0020] (4) The present invention utilizes flash oxidation to rapidly prepare high-purity quartz products, which has the advantages of high production efficiency, short operation process, high product added value, and suitability for large-scale industrial production, and realizes the recycling and reuse of silicon wafer cutting waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below in conjunction with specific implementation modes, but the protection scope of the present invention is not limited to the described contents.

[0023] Example 1: The silicon wafer cutting waste in this example is a filter cake obtained by plate and frame filtration of silicon wafer cutting slurry, with an initial water content of 58.17% and an initial block particle size of 5 to 10 cm;

[0024] A method for preparing high-purity quartz by flash oxidation of silicon wafer cutting waste (see Figure 1 ), the specific steps are as follows:

[0025] (1) drying and dehydrating the silicon wafer cutting waste block material, and crushing it to obtain silicon wafer cutting waste particles with a particle size of less than 1 μm;

[0026] (2) adding the silicon wafer cutting waste particles into hydrochloric acid with a concentration of 4 mol / L, and performing acid leaching for 3 hours at a temperature of 90° C. and a stirring rate of 500 r / min to deeply remove impurities, thereby obtaining silicon powder with a purity greater than 4N8, wherein the total impurity content in the silicon powder is 17.16 ppmw; the liquid-to-solid ratio of the hydrochloric acid to the silicon wafer cutting waste particles is 5:1 in mL:g;

[0027] (3) High-purity silicon powder was introduced into the fluidized bed reactor from the top at a feeding rate of 200 kg / h, and then introduced into the fluidized bed reactor from the bottom at a rate of (50 m / s). 3 / h) introduces oxygen at a temperature (500°C) to keep the high-purity silicon powder in a suspended state under the action of the oxygen gas flow, and controls the hot air temperature (220°C) at the outlet of the fluidized bed to allow the high-purity silicon powder to fully contact and oxidize with oxygen, and obtain high-purity quartz by gas-solid separation;

[0028] After testing, the total impurity content of the high-purity quartz in this embodiment is 17.16 ppmw.

[0029] Example 2: The silicon wafer cutting waste in this example is a filter cake obtained by plate and frame filtration of silicon wafer cutting slurry, with an initial water content of 55.51% and an initial block particle size of 5 to 10 cm;

[0030] A method for preparing high-purity quartz by flash oxidation of silicon wafer cutting waste (see Figure 1 ), the specific steps are as follows:

[0031] (1) drying and dehydrating the silicon wafer cutting waste block material, and crushing it to obtain silicon wafer cutting waste particles with a particle size of less than 1 μm;

[0032] (2) adding the silicon wafer cutting waste particles to citric acid with a concentration of 6 mol / L, and performing acid leaching for 3.5 hours at a temperature of 80° C. and a stirring rate of 600 r / min to deeply remove impurities, thereby obtaining silicon powder with a purity greater than 4N8, wherein the total impurity content in the silicon powder is 19.14 ppmw; the liquid-to-solid ratio of the citric acid to the silicon wafer cutting waste particles is 10:1 in mL:g;

[0033] (3) High-purity silicon powder was fed into the fluidized bed reactor from the top at a feeding rate of 150 kg / h, and then fed into the fluidized bed reactor from the bottom at a rate of (80 m / s). 3 / h) introduces water vapor at a temperature of 550°C to keep the high-purity silicon powder in a suspended state under the action of water vapor, and controls the hot air temperature (260°C) at the outlet of the fluidized bed to allow the high-purity silicon powder to fully contact and oxidize with the high-temperature water vapor, and obtain high-purity quartz through gas-solid separation;

[0034] After testing, the total impurity content of the high-purity quartz in this embodiment is 19.14 ppmw.

[0035] Example 3: The silicon wafer cutting waste in this example is a filter cake obtained by plate and frame filtration of silicon wafer cutting slurry, with an initial water content of 59.67% and an initial block particle size of 5 to 10 cm;

[0036] A method for preparing high-purity quartz by flash oxidation of silicon wafer cutting waste (see Figure 1 ), the specific steps are as follows:

[0037] (1) drying and dehydrating the silicon wafer cutting waste block material, and crushing it to obtain silicon wafer cutting waste particles with a particle size of less than 1 μm;

[0038] (2) adding the silicon wafer cutting waste particles into sulfuric acid with a concentration of 6 mol / L, and performing acid leaching for 3 hours at a temperature of 80° C. and a stirring rate of 700 r / min to deeply remove impurities, thereby obtaining silicon powder with a purity greater than 4N8, wherein the total impurity content in the silicon powder is 15.78 ppmw; the liquid-to-solid ratio of the sulfuric acid to the silicon wafer cutting waste particles is 12:1 in mL:g;

[0039] (3) High-purity silicon powder was fed into the fluidized bed reactor from the top at a feeding rate of 140 kg / h, and then fed into the fluidized bed reactor from the bottom at a rate of (85 m / h). 3 / h) introduces air at a temperature of 600°C to keep the high-purity silicon powder in suspension under the action of the oxygen flow, and controls the hot air temperature (300°C) at the outlet of the fluidized bed to make the high-purity silicon powder fully contact and oxidize with the high-temperature air, and obtain high-purity quartz by gas-solid separation;

[0040] After testing, the total impurity content of the high-purity quartz in this embodiment is 15.78 ppmw.

[0041] Example 4: The silicon wafer cutting waste in this example is a filter cake obtained by plate and frame filtration of silicon wafer cutting slurry, with an initial water content of 59.45% and an initial block particle size of 5 to 10 cm;

[0042] A method for preparing high-purity quartz by flash oxidation of silicon wafer cutting waste (see Figure 1 ), the specific steps are as follows:

[0043] (1) drying and dehydrating the silicon wafer cutting waste block material, and crushing it to obtain silicon wafer cutting waste particles with a particle size of less than 1 μm;

[0044] (2) adding the silicon wafer cutting waste particles into hydrochloric acid with a concentration of 6 mol / L, and performing acid leaching for 4 hours at a temperature of 90° C. and a stirring rate of 750 r / min to deeply remove impurities, thereby obtaining silicon powder with a purity greater than 4N8, wherein the total impurity content in the silicon powder is 10.41 ppmw; the liquid-to-solid ratio of the hydrochloric acid to the silicon wafer cutting waste particles is 14:1 in mL:g;

[0045] (3) High-purity silicon powder was fed into the fluidized bed reactor from the top at a feeding rate of 220 kg / h, and then fed into the fluidized bed reactor from the bottom at a rate of (80 m 3 / h) introduces oxygen at a temperature (450°C) to keep the high-purity silicon powder in a suspended state under the action of the oxygen gas flow, and controls the hot air temperature (180°C) at the outlet of the fluidized bed to allow the high-purity silicon powder to fully contact and oxidize with oxygen, and obtain high-purity quartz through gas-solid separation;

[0046] After testing, the total impurity content of the high-purity quartz in this embodiment is 7.41 ppmw.

[0047] Example 5: The silicon wafer cutting waste in this example is a filter cake obtained by plate and frame filtration of silicon wafer cutting slurry, with an initial water content of 57.64% and an initial block particle size of 5 to 10 cm;

[0048] A method for preparing high-purity quartz by flash oxidation of silicon wafer cutting waste (see Figure 1 ), the specific steps are as follows:

[0049] (1) drying and dehydrating the silicon wafer cutting waste block material, and crushing it to obtain silicon wafer cutting waste particles with a particle size of less than 1 μm;

[0050] (2) adding the silicon wafer cutting waste particles into a mixed acid (the concentration of hydrofluoric acid in the mixed acid is 2 mol / L, and the concentration of sulfuric acid in the mixed acid is 2 mol / L), and performing acid leaching for 4 hours at a temperature of 80° C. and a stirring rate of 800 r / min to deeply remove impurities, thereby obtaining silicon powder with a purity greater than 4N8, wherein the total impurity content in the silicon powder is 18.41 ppmw; the liquid-to-solid ratio of the mixed acid to the silicon wafer cutting waste particles is 16:1 in mL:g;

[0051] (3) High-purity silicon powder was fed into the fluidized bed reactor from the top at a feeding rate of 300 kg / h, and then fed into the fluidized bed reactor from the bottom at a rate of (90 m / s). 3 / h) introduces oxygen at a temperature of 550°C to keep the high-purity silicon powder in a suspended state under the action of the oxygen gas flow, and controls the hot air temperature (280°C) at the outlet of the fluidized bed to allow the high-purity silicon powder to fully contact and oxidize with oxygen, and obtain high-purity quartz through gas-solid separation;

[0052] After testing, the total impurity content of the high-purity quartz in this embodiment is 18.17 ppmw;

[0053] The impurity content results of the high purity quartz products in Examples 1 to 5 are shown in Table 1;

[0054] Table 1 Impurity content results of high purity quartz products in Examples 1 to 5 (ppmw)

[0055]

[0056] As can be seen from Table 1, in Examples 1 to 5 of the present invention, high-purity silicon powder is introduced into a fluidized bed reactor from the top, and a high-temperature oxidizing gas flow is introduced from the bottom to fluidize the silicon powder, and the hot air temperature at the fluidized bed outlet is controlled to flash-oxidize the high-purity silicon powder with the oxidizing gas flow to generate a high-purity quartz product, the contents of the impurity elements Fe, Al and Ni of which are relatively low.

[0057] The specific implementation modes of the present invention are described in detail above, but the present invention is not limited to the above implementation modes, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A method for preparing high-purity quartz by flash oxidation of silicon wafer cutting waste, characterized in that: The specific steps are as follows: (1) drying and dehydrating the silicon wafer cutting waste block material, and crushing it to obtain silicon wafer cutting waste particles; (2) subjecting silicon wafer cutting waste particles to acid leaching to deeply remove impurities to obtain high-purity silicon powder with a purity greater than 4N8; (3) High-purity silicon powder is introduced into the fluidized bed reactor from the top, and a high-temperature oxidizing gas flow is introduced into the fluidized bed reactor from the bottom, so that the high-purity silicon powder is suspended under the action of the oxidizing gas flow, and the hot air temperature at the fluidized bed outlet is controlled to allow the high-purity silicon powder to fully contact and oxidize with the oxidizing gas flow, and high-purity quartz is obtained by gas-solid separation.

2. The method for preparing high-purity quartz by flash oxidation of silicon wafer cutting waste according to claim 1, characterized in that: The particle size of the silicon wafer cutting waste particles in step (1) is less than 1 μm.

3. The method for preparing high-purity quartz by flash oxidation of silicon wafer cutting waste according to claim 1, characterized in that: The acid solution used in the wet acid leaching in step (2) is one or more of sulfuric acid, hydrochloric acid, hydrofluoric acid, nitric acid, citric acid, and tartaric acid.

4. The method for preparing high-purity quartz by flash oxidation of silicon wafer cutting waste according to claim 2, characterized in that: The acid solution contains H + The concentration is 0.5-6 mol / L, the liquid-solid ratio of the acid solution to the silicon wafer cutting waste particles is 5-20:1 in mL:g, the leaching temperature is 40-300°C, and the stirring rate is 100-1000 rpm.

5. The method for preparing high-purity quartz by flash oxidation of silicon wafer cutting waste according to claim 1, characterized in that: In step (3), the feeding rate of high-purity silicon powder is 0.1-500 kg / h, the thickness of the material layer to be oxidized at the bottom of the fluidized bed is 1-200 mm, the temperature of the oxidizing gas flow is 200-800° C., and the speed of the oxidizing gas flow is 1-100 m / s. 3 / h, and the hot air temperature at the fluidized bed outlet is 100-500℃.

6. The method for preparing high-purity quartz by flash oxidation of silicon wafer cutting waste according to claim 1, characterized in that: In step (3), the oxidizing gas flow is oxygen, air or water vapor.

Images