High-purity quartz product prepared from waste high-purity quartz glass and preparation method

Abstract

The invention provides a high-purity quartz product prepared from waste high-purity quartz glass and a preparation method. The preparation method comprises the following steps: pretreating the waste high-purity quartz glass to obtain quartz glass sand; carrying out flotation, washing, filtering and drying on the quartz glass sand to obtain an intermediate product; the intermediate product is subjected to aftertreatment, a high-purity quartz product is obtained, and the high-purity quartz product comprises high-purity cristobalite sand and / or high-purity quartz glass sand. The content of SiO2 in the prepared high-purity cristobalite sand is 99%-99.999%, and the content of SiO2 in the high-purity quartz glass sand is 99%-99.999%. According to the method, the cristobalite-containing waste high-purity quartz glass is prepared into the high-purity cristobalite sand and the high-purity quartz glass sand by a flotation method, so that the pollution to the sample caused by modes such as mechanical separation can be effectively avoided, the obtained sample is uniform in particle size and high in purity, and the high-added-value utilization of the cristobalite-containing quartz glass is favorably realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of recycling waste high-purity quartz glass materials and preparing new high-purity cristobalite materials and high-purity quartz glass materials. Specifically, it relates to a high-purity quartz product prepared from waste high-purity quartz glass and a preparation method. Background Art

[0002] Quartz glass products such as quartz tubes, quartz ingots and quartz crucibles are made by melting high-purity natural quartz at high temperatures. They have excellent properties such as small thermal expansion coefficient, good chemical stability and high temperature resistance, and are widely used in photovoltaics, semiconductors and various instruments.

[0003] Due to the excellent high-temperature resistance of quartz glass, high-purity quartz glass products are widely used under high-temperature conditions. When used under high-temperature conditions, quartz glass products will undergo crystallization under certain conditions. The crystal phase precipitated by quartz glass at high temperature is β-cristobalite phase. During the cooling process, the β-cristobalite phase is converted into the low-temperature α-cristobalite phase. Therefore, quartz glass and cristobalite coexist in quartz glass products after use and retirement. Since the melting temperatures of the two are different, that is, the melting temperature of quartz glass is lower than that of cristobalite, this is not conducive to the subsequent high-value recycling of quartz glass products. At present, there is no effective technical method for effectively separating quartz glass and cristobalite in quartz glass products. Summary of the Invention

[0004] The present invention aims to address at least one of the aforementioned deficiencies in the prior art. For example, one object of the present invention is to provide a method for preparing a high-purity quartz product from discarded high-purity quartz glass. A second object of the present invention is to provide a high-purity quartz product.

[0005] In order to achieve the above object, the present invention provides a method for preparing a high-purity quartz product from discarded high-purity quartz glass, the preparation method comprising the following steps:

[0006] Pre-treating waste high-purity quartz glass to obtain quartz glass sand;

[0007] flotation, washing, filtering and drying the quartz glass sand to obtain an intermediate product, wherein the intermediate product includes cristobalite sand and / or quartz glass sand;

[0008] The intermediate product is post-processed to obtain a high-purity quartz product, which includes high-purity cristobalite sand and / or high-purity quartz glass sand.

[0009] Optionally, the waste high-purity quartz glass is quartz glass containing cristobalite; the cristobalite content in the waste high-purity quartz glass is 2% to 98%. If the cristobalite content is less than 2%, it needs to be crystallized at a high temperature of 1400° C. to 1700° C. for a crystallization time of 1 to 50 hours.

[0010] The shape of the waste high-purity quartz glass includes one or more of a tubular shape, a flat plate shape, a crucible shape and a special-shaped quartz glass product.

[0011] Optionally, the pretreatment includes washing, calcining and water quenching, crushing, grinding, screening and dust removal; the calcining and water quenching is to heat the waste high-purity quartz glass to above the phase transition temperature of cristobalite to achieve preliminary dissociation of the quartz glass and cristobalite; the crushing is to crush the quartz glass using a jaw crusher, a hammer crusher or an impact crusher; the grinding is to grind the crushed quartz glass using a jaw crusher, a ball mill or a sample making machine; the screening is to use a vibrating screen or a fixed screen for inspection and screening, and the dust removal uses a dust removal system that is matched with the screening line.

[0012] Optionally, the calcination and water quenching time is 10 to 600 minutes, the calcination and water quenching temperature is 270 to 1200° C.; and the inspection screening mesh size is 20 to 200 meshes.

[0013] Alternatively, the flotation is a process of separating quartz glass sand from quartz glass sand by a single flotation, wherein the single flotation can obtain a foam product and a bottom product, the foam product is quartz glass sand, and the bottom product is cristobalite sand.

[0014] Optionally, the flotation process parameters include: the concentration of the quartz glass sand slurry is 5% to 30%; the pH adjuster is sodium hydroxide, potassium hydroxide, or a mixture of sodium hydroxide and potassium hydroxide; the pH of the slurry after the pH adjuster is added is adjusted to 7 to 9; the collector includes sodium oleate or sodium dodecyl sulfate, wherein the concentration of sodium oleate is 1×10 -4 ~1×10 -3 mol / L, the concentration of sodium dodecyl sulfate is 5×10 -4 ~5×10 -3 mol / L.

[0015] Optionally, the washing and filtering include using industrial pure water on a belt filter washer; the drying is performed using air drying or an electric heating drying device, and the drying temperature is 100-270°C; the moisture content of the cristobalite sand and quartz glass sand is ≤1.5%.

[0016] Optionally, the post-treatment includes acid leaching, washing, filtering and drying;

[0017] The solid-liquid ratio of the quartz sand to the acid leaching solution in the acid leaching is 1:3 to 1:6; the solid-liquid ratio of the quartz glass sand to the acid leaching solution in the acid leaching is 1:3 to 1:6; the acid leaching solution includes 0.5 to 3 mol / L nitric acid solution and 0 to 2 mol / L hydrofluoric acid solution.

[0018] Optionally, the acid leaching includes atmospheric pressure acid leaching and hot pressure acid leaching. The acid leaching temperature of the atmospheric pressure acid leaching is 50-90° C. and the acid leaching time is 90-480 min; the acid leaching temperature of the hot pressure acid leaching is 100-220° C. and the acid leaching time is 30-360 min.

[0019] Another aspect of the present invention provides a high-purity quartz product, which is prepared by the above method.

[0020] Optionally, the high-purity quartz product includes high-purity quartz glass sand and high-purity cristobalite sand; wherein, the SiO2 content in the high-purity quartz glass sand is 99% to 99.999%, and the particle size is 20 to 200 meshes; the SiO2 content in the high-purity cristobalite sand is 99% to 99.999%, and the particle size is 20 to 200 meshes.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] (1) The present invention proposes for the first time a method for separating cristobalite sand from quartz glass sand by flotation from waste high-purity quartz glass containing cristobalite, and the method is simple and has high preparation efficiency.

[0023] (2) The flotation conditions in the present invention are neutral or weakly alkaline, and the amount of collector used is small, which has little harm to the environment.

[0024] (3) The present invention prepares high-purity cristobalite sand and high-purity quartz glass sand from quartz glass containing cristobalite by flotation, which can effectively avoid the contamination of samples caused by separation by mechanical means, etc., and obtains samples with uniform particle size and high purity, which is conducive to the high added value utilization of quartz glass containing cristobalite. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above and other objects and / or features of the present invention will become more apparent from the following description in conjunction with the accompanying drawings, in which:

[0026] Figure 1 A schematic flow chart of the preparation method of the present invention is shown.

[0027] Figure 2 The figure shows a photograph of broken pieces of a quartz glass container after long-term use at high temperature.

[0028] Figure 3 The XRD patterns and sample photos of the quartz glass samples used in Examples 1 and 2 of the present invention are shown.

[0029] Figure 4 The XRD pattern of the bottom product obtained by flotation in Example 1 of the present invention, namely, the cristobalite sand sample and its sample photo are shown.

[0030] Figure 5 The XRD pattern of the quartz glass sand sample, a foam product obtained by flotation in Example 1 of the present invention, and its sample photo are shown.

[0031] Figure 6 The XRD spectrum of the bottom product obtained by flotation in Example 2 of the present invention, namely, the cristobalite sand sample, is shown.

[0032] Figure 7 The XRD spectrum of the froth product obtained by flotation in Example 2 of the present invention, namely the quartz glass sand sample, is shown. DETAILED DESCRIPTION

[0033] Hereinafter, the high-purity quartz product prepared from waste high-purity quartz glass and the preparation method thereof will be described in detail with reference to exemplary embodiments.

[0034] Exemplary embodiment 1

[0035] This exemplary embodiment provides a method for preparing a high-purity quartz product from waste high-purity quartz glass, such as Figure 1 The preparation method may include the following steps:

[0036] S1. Pre-treating waste high-purity quartz glass to obtain quartz glass sand.

[0037] In this embodiment, the waste high-purity quartz glass is quartz glass containing cristobalite. The waste high-purity quartz glass may include a solid product retired after use at high temperature and a product obtained by high-temperature crystallization of the retired solid product. The high-temperature crystallization is a process in which the solid phase of a quartz glass body is transformed into cristobalite under high temperature conditions.

[0038] The quartz glass has a cristobalite content of 2% to 98%, such as 2.1%, 10%, 25%, 70%, and 97.5%. If the cristobalite content is less than 2%, the quartz glass must first be crystallized at a high temperature of 1400° C. to 1700° C., such as 1410° C., 1460° C., 1520° C., 1600° C., and 1690° C.; and the crystallization time is 1 to 50 hours, such as 1.1 hours, 10 hours, 25 hours, 25.5 hours, and 49 hours.

[0039] Among them, the mass percentage of cristobalite in the quartz glass containing cristobalite is 2% to 98% in order to ensure that the floatability difference is enhanced during the flotation process and to ensure the high efficiency of the flotation separation of cristobalite and quartz samples. When the cristobalite content is lower than 2%, a high-temperature crystallization method can be used to increase the cristobalite content in the sample. When the cristobalite content is higher than 98%, high-temperature crystallization can be considered to completely crystallize it into cristobalite, which is more conducive to its direct utilization and more economical and simple.

[0040] In this embodiment, the shape of the waste high-purity quartz glass may include one or more of a tubular shape, a flat plate shape, a crucible shape, and a special-shaped quartz glass product.

[0041] In this embodiment, the pretreatment may include washing, calcining and water quenching, crushing, grinding, screening and dust removal; the calcining and water quenching is to heat the quartz glass to above the cristobalite phase transition temperature to achieve preliminary dissociation of the quartz glass and cristobalite; the crushing is to crush the quartz glass using a jaw crusher, a hammer crusher or an impact crusher; the grinding is to grind the crushed quartz glass using a jaw crusher, a ball mill or a sample making machine; the screening is to use a vibrating screen or a fixed screen for inspection and screening, and the dust removal is to use a dust removal system supporting the screening line.

[0042] Among them, screening is to obtain samples of any particle size within 20 to 200 meshes, so as to prepare for the next flotation; dust removal is to prevent excessive dust concentration in the air and cause safety accidents.

[0043] In this embodiment, the calcination and water quenching time is 10 to 600 min, for example, 15 min, 50 min, 120 min, 310 min and 590 min; the calcination and water quenching temperature is 270 to 1200 ° C, for example, 280 ° C, 500 ° C, 670 ° C, 1000 ° C and 1150 ° C; the inspection screening mesh size is 20 to 200 mesh, for example, 50 mesh, 100 mesh, 120 mesh, 150 mesh and 200 mesh.

[0044] The main purpose of calcining and water quenching is to separate quartz from cristobalite by taking advantage of the difference in thermal expansion coefficients between quartz glass and cristobalite. The phase transition temperature of cristobalite is around 270°C, and a volume change of about 5% will occur during the phase transition. The thermal expansion coefficient of quartz glass is extremely small (4.9×10 -7 K -1 ~5.5×10 -7 K -1 When quartz glass containing cristobalite is heated to above the cristobalite phase transition temperature and then water quenched, significant stress is generated at the quartz glass-cristobalite interface, causing numerous cracks to form at the interface, thereby achieving a preliminary separation of the quartz glass from the cristobalite. Simultaneously, the generation of these crack defects promotes further dissociation of the cristobalite and quartz glass during the crushing and grinding process. Furthermore, some quartz glass contains bubbles, which expand at high temperatures. Because these bubbles increase the selectivity of the quartz glass sample to fracture along the bubbles, quartz glass with a lower bubble content can be obtained through high-temperature calcination.

[0045] S2. Float, wash, filter, and dry the quartz glass sand to obtain an intermediate product, which includes cristobalite sand and / or quartz glass sand.

[0046] In this embodiment, the flotation is a process of separating quartz glass sand from quartz glass sand through a single flotation, wherein the single flotation can obtain a foam product and a bottom product, the foam product is quartz glass sand, and the bottom product is cristobalite sand.

[0047] In this embodiment, the flotation process parameters may include: the concentration of the quartz glass sand slurry is 5% to 30%, such as 6%, 11%, 15%, 20% and 28%; the pH adjuster is sodium hydroxide, potassium hydroxide or a mixture of sodium hydroxide and potassium hydroxide; the pH of the slurry after the pH adjuster is added is adjusted to 7 to 9, such as 7, 7.2, 8 and 8.5; the collector is an anionic collector, and the collector includes but is not limited to sodium oleate and sodium dodecyl sulfate, wherein the concentration of sodium oleate is 1×10 -4 ~1×10 -3 mol / L, for example 1.1×10 -4 mol / L, 2×10 -4 mol / L、5×10 -4 mol / L and 0.9×10 -3 mol / L, etc.; the concentration of sodium dodecylsulfonate is 5×10 -4 ~5×10 -3 mol / L, for example 5.1×10 -4 mol / L、8×10 -4 mol / L, 2×10 -3 mol / L and 4.9×10 -3 mol / L, etc.

[0048] Among them, since the pulp concentration has a great influence on the flotation recovery rate, concentrate quality, reagent consumption, flotation time, production capacity, etc.; when the pulp is very thin, the recovery rate is low. Properly increasing the pulp concentration can not only save reagents and water, but also improve the recovery rate. However, if the pulp is too thick, the flotation index will decrease due to the deterioration of the working conditions of the flotation machine. Generally, when flotation is carried out with a thinner pulp, the concentrate quality is higher, while when flotation is carried out with a thicker pulp, the concentrate quality will decrease. Therefore, the pulp concentration is selected to be 5% to 30%;

[0049] When the adjusting agent is sodium hydroxide or potassium hydroxide, a very small amount of the adjusting agent can be used to achieve the pH. The pH is adjusted to 7-9 because the zeta potential of quartz is close to the zero charge point in this range, while the zeta potential of quartz glass is negative. The difference between the zeta potentials of the two is large, and the quartz glass can be efficiently floated out by the collector.

[0050] Sodium oleate or sodium dodecyl sulfate is mainly used as the collector because such collectors have high collection efficiency, small dosage and little harm to the environment; washing is to completely remove the residual collector and regulator on the surface of the sample, and after drying, cristobalite sand and quartz glass sand are obtained.

[0051] In this embodiment, the washing and filtering include using industrial pure water on a belt suction filter washer; the drying can be performed using air drying or an electric heating drying device, such as an air flow dryer, a fluidized bed dryer, and a rotary drum dryer, and the drying temperature is 100 to 270°C, for example, 110°C, 150°C, 180°C, 200°C, and 260°C; the moisture content of the cristobalite sand and the quartz glass sand is ≤1.5%, for example, 0.5, 0.8, 1.0, and 1.4, etc.

[0052] S3. Post-processing the intermediate product to obtain a high-purity quartz product, wherein the high-purity quartz product includes high-purity cristobalite sand and / or high-purity quartz glass sand.

[0053] In this embodiment, the post-treatment may include acid leaching, washing, filtering and drying.

[0054] In this embodiment, the solid-liquid ratio of the quartz sand to the acid leaching solution in the acid leaching is 1:3 to 1:6, for example, 1:3.1, 1:4.2, 1:5 and 1:5.8; the solid-liquid ratio of the quartz glass sand to the acid leaching solution in the acid leaching is 1:3 to 1:6, for example, 1:3.2, 1:4, 1:5.1 and 1:5.9.

[0055] In this embodiment, the acid leaching solution may include a nitric acid solution and / or a hydrofluoric acid solution; wherein the nitric acid solution is 0.5 to 3 mol / L, for example, 0.6 mol / L, 1.1 mol / L, 2.2 mol / L, 2.93 mol / L, etc.; the hydrofluoric acid solution is 0 to 2 mol / L, for example, 0 mol / L, 0.5 mol / L, 1.2 mol / L, 1.9 mol / L, etc.

[0056] In this embodiment, the acid leaching may include atmospheric pressure acid leaching and hot pressure acid leaching;

[0057] The acid leaching temperature of the atmospheric pressure acid leaching is 50-90° C., such as 54° C., 70° C., 75° C., and 89° C., and the acid leaching time is 90-480 min, such as 95 min, 120 min, 220 min, 360 min, and 470 min.

[0058] The acid leaching temperature of the hot press acid leaching is 100-220° C., such as 105° C., 130° C., 180° C. and 215° C., and the acid leaching time is 30-360 min, such as 35 min, 100 min, 180 min, 250 min and 350 min.

[0059] In this example, acid leaching is performed to dissolve surface impurities, thereby improving the purity of the cristobalite sand and quartz glass sand samples. Washing and filtering are performed using industrial purified water in a belt filter washer until the filtrate has a pH of 7. This completely removes residual collectors and conditioning agents from the sample surface after flotation, as well as residual acid and soluble impurities from the acid leaching. Drying is performed by air drying or using an electrically heated drying device such as an airflow dryer, fluidized bed dryer, or rotary drum dryer at a temperature of 100-270°C to a moisture content of ≤1.5%. High-purity quartz sand and high-purity cristobalite sand are obtained after drying.

[0060] Exemplary embodiment 2

[0061] This exemplary embodiment provides a high-purity quartz product, which can be prepared by the method described in exemplary embodiment 1. The high-purity quartz product includes high-purity quartz glass sand and high-purity cristobalite sand.

[0062] In this embodiment, the SiO2 content in the high-purity quartz glass sand is 99% to 99.999%, for example, 99.2%, 99.8%, 99.95% and 99.998%; the particle size is 20 to 200 mesh, for example, 40 mesh, 80 mesh, 120 mesh and 200 mesh.

[0063] In this embodiment, the SiO2 content in the high-purity cristobalite sand is 99% to 99.999%, such as 99.5%, 99.9%, 99.99% and 99.998%; the particle size is 20 to 200 mesh, such as 50 mesh, 100 mesh, 150 mesh and 200 mesh.

[0064] In order to better understand the above exemplary embodiments of the present invention, they are further described below with reference to specific examples.

[0065] Example 1

[0066] like Figure 2 The figure shows a discarded high-purity quartz glass crucible that has been used for a long time at high temperature. The white crystal layer on its surface is cristobalite, and the transparent part is quartz glass, and the two are in a transitional relationship.

[0067] The discarded high-purity quartz glass crucible was crushed and ground to less than 200 mesh, and then subjected to powder XRD diffraction analysis. The analysis results are shown in the attached Figure 3 As shown by Figure 3 It can be seen that the physical composition of the sample is a mixture of quartz glass and cristobalite. A standard curve of the integral of the diffraction peak area of ​​cristobalite (101) crystal plane and the cristobalite content was established by the external standard method, and the cristobalite content was calculated to be 34%.

[0068] This example uses discarded high-purity quartz glass crucibles to prepare high-purity quartz products, and the preparation method includes the following steps:

[0069] 1) Pretreatment: The discarded high-purity quartz glass crucible was washed with ultrapure water, calcined at 300° C. for 20 min, and then water quenched. The sample after water quenching and drying was crushed and ground, and sieved to obtain quartz glass sand containing 40-70 mesh quartz sand.

[0070] 2) Slurry preparation: Quartz glass sand containing cristobalite sand was weighed and placed in a flotation tank, and industrial ultrapure water was added to prepare slurry with a slurry concentration of 10%.

[0071] 3) Adjusting pH: Adding pH adjuster sodium hydroxide to the slurry until the pH of the slurry is 8.

[0072] 4) Add collector: add sodium oleate to the slurry. The concentration of sodium oleate in the slurry is 2.5×10 - 4 mol / L.

[0073] 5) Scraping bubble flotation: Open the flotation machine air valve and scrape the bubbles.

[0074] 6) Collection, washing, and drying: The precipitated product, i.e., cristobalite sand (YR-1), and the foamed product, i.e., quartz glass sand (YR-2), were washed with ultrapure water until the pH of the filtrate reached 7, and then dried to obtain cristobalite sand and quartz glass sand.

[0075] 7) Phase analysis of the obtained cristobalite sand and quartz glass sand: grind the foam product cristobalite sand and the bottom product quartz glass sand to less than 100 mesh respectively, and perform powder XRD diffraction analysis. The analysis results are as follows: Figure 4 and Figure 5 As shown. Figure 4 It can be seen that the bottom product cristobalite sand has a sharp cristobalite peak and no obvious bun peak, so its phase is cristobalite phase. The standard curve of the integral of the diffraction peak area of ​​cristobalite (101) crystal plane and the content of cristobalite is established by the external standard method, and the content of cristobalite is calculated to be 95%. Figure 5 It can be seen that the foam product quartz glass sand sample has an obvious bun peak, so its main component is the glass phase. The standard curve of the integral of the diffraction peak area of ​​cristobalite (101) crystal plane and the cristobalite content was established by the external standard method. The calculated cristobalite content is less than 2%, indicating that the separation of cristobalite and quartz glass is effective.

[0076] 8) Acid leaching: the above-mentioned cristobalite sand was mixed with an acid leaching solution of 0.5 mol / L hydrofluoric acid and 1.5 mol / L nitric acid at a solid-liquid ratio of 1:5, and the mixture was hot-pressed and acid-leached at 180° C. for 90 min, washed with industrial ultrapure water until the pH of the filtrate was 7, and dried at 150° C. to obtain high-purity cristobalite sand; the above-mentioned quartz glass sand was mixed with a mixed acid leaching solution of 0.5 mol / L hydrofluoric acid and 1.2 mol / L nitric acid at a solid-liquid ratio of 1:5, and the mixture was acid-leached at 90° C. under normal pressure for 240 min, washed with industrial ultrapure water until the pH of the filtrate was 7, and dried at 150° C. to obtain high-purity quartz glass sand.

[0077] 9) Purity testing of high-purity quartz glass sand and high-purity cristobalite sand: The high-purity quartz glass sand and high-purity cristobalite sand were digested with hydrofluoric acid (MOS grade) and fixed to volume. The impurity ion content in the solution was determined by ICP-OES and ICP-MS. The impurity content in the sample and the SiO2 content of the high-purity quartz glass sand and high-purity cristobalite sand were calculated.

[0078] According to Table 1, the SiO2 content in the obtained high-purity cristobalite sand and high-purity quartz glass sand both reached 99.998%.

[0079] Table 1 Impurity element content (ppm) of high-purity cristobalite sand and high-purity quartz glass sand obtained in Example 1

[0080]

[0081] Note: - indicates below the detection limit.

[0082] Example 2

[0083] The raw materials in this example are the same as those in Example 1. Figure 2 As shown, the preparation method comprises the following steps:

[0084] 1) Pretreatment: The discarded high-purity quartz glass crucible is washed with ultrapure water, calcined at 310° C. for 20 min, and then water quenched. The dried discarded high-purity quartz glass crucible is crushed and ground, and sieved to obtain quartz glass sand containing 70-150 mesh quartz sand.

[0085] 2) Slurry preparation: Weigh a certain amount of quartz glass sand containing cristobalite sand into a flotation tank, add pure water to prepare a slurry with a slurry concentration of 15%.

[0086] 3) Adjusting pH: Adding pH adjuster potassium hydroxide to the slurry until the pH of the slurry is 9.

[0087] 4) Add collector: add sodium oleate to the slurry. The concentration of sodium oleate in the slurry is 2.0×10 -4 mol / L.

[0088] 5) Scraping bubble flotation: Open the flotation machine air valve and scrape the bubbles.

[0089] 6) Collection, washing, and drying: The precipitated product, i.e., cristobalite sand (YR-3), and the foamed product, i.e., quartz glass sand (YR-4), were collected separately, washed with industrial ultrapure water until the pH of the filtrate reached 7, and then dried to obtain cristobalite sand and quartz glass sand.

[0090] 7) Phase analysis of the separated cristobalite sand and quartz glass sand: The separated samples YR-3 and YR-4 were ground to less than 200 mesh respectively and subjected to powder XRD diffraction analysis. The precipitated product cristobalite sand sample was as follows: Figure 6 As shown, the foam product quartz glass sand sample is as follows Figure 7 As shown. Figure 6 It can be seen that sample YR-3 has a sharp cristobalite peak and no obvious bun peak, so its physical phase is cristobalite phase. The standard curve of the integral of the diffraction peak area of ​​cristobalite (101) crystal plane and the content of cristobalite is established by external standard method, and the content of cristobalite is calculated to be 93%. Figure 7 It can be seen that sample YR-4 has an obvious steamed bun peak, so its main component is glass phase; this example has a significant effect in separating cristobalite from quartz glass. The standard curve of the integral of the diffraction peak area of ​​cristobalite (101) crystal plane and the cristobalite content was established by the external standard method, and the cristobalite content was calculated to be less than 1%.

[0091] 8) Acid leaching: the above-mentioned cristobalite sand was mixed with an acid leaching solution of 1.0 mol / L hydrofluoric acid and 2.0 mol / L nitric acid at a solid-liquid ratio of 1:3, and the mixture was hot-pressed and acid-leached at 190° C. for 120 min, washed with industrial ultrapure water until the pH of the filtrate was 7, and dried at 110° C. to obtain high-purity cristobalite sand; the above-mentioned quartz glass sand was mixed with an acid leaching solution of 2.5 mol / L nitric acid at a solid-liquid ratio of 1:3, and the mixture was acid-leached at 90° C. under normal pressure for 150 min, washed with industrial ultrapure water until the pH of the filtrate was 7, and dried at 110° C. to obtain high-purity quartz glass sand.

[0092] 9) Purity testing of high-purity quartz glass sand and high-purity cristobalite sand: The obtained high-purity quartz glass sand and high-purity cristobalite sand were digested with hydrofluoric acid (MOS grade) and fixed to volume. The impurity ion content in the digestion solution was determined by ICP-OES and ICP-MS. The impurity content in the sample and the SiO2 content of the high-purity quartz glass sand and high-purity cristobalite sand were calculated.

[0093] According to Table 2, the SiO2 content in the obtained high-purity cristobalite sand and high-purity quartz glass sand both reached 99.998%.

[0094] Table 2 Impurity element content (ppm) of high-purity cristobalite sand and high-purity quartz glass sand obtained in Example 2

[0095]

[0096] Note: - indicates below the detection limit.

[0097] Although the present invention has been described above with reference to the exemplary embodiments and the accompanying drawings, it will be apparent to those skilled in the art that various modifications and changes may be made to the exemplary embodiments of the present invention without departing from the spirit and scope defined in the claims.

Claims

1. A method for preparing high-purity quartz products from discarded high-purity quartz glass, characterized in that: The method comprises the following steps: Pre-treating waste high-purity quartz glass to obtain quartz glass sand; flotation, washing, filtering and drying the quartz glass sand to obtain an intermediate product, wherein the intermediate product includes cristobalite sand and / or quartz glass sand; The intermediate product is post-processed to obtain a high-purity quartz product, which includes high-purity cristobalite sand and / or high-purity quartz glass sand.

2. The method for preparing a high-purity quartz product from waste high-purity quartz glass according to claim 1, wherein: The waste high-purity quartz glass is quartz glass containing cristobalite; the cristobalite content in the waste high-purity quartz glass is 2% to 98%. If the cristobalite content is less than 2%, it needs to be crystallized at a high temperature of 1400° C. to 1700° C. for 1 to 50 hours. The waste high-purity quartz glass is discarded after high-temperature use and has a shape including one or more of a tubular, flat, crucible, and special-shaped quartz glass product.

3. The method for preparing a high-purity quartz product from waste high-purity quartz glass according to claim 1, wherein: The pretreatment includes washing, calcining and water quenching, crushing, grinding, screening and dust removal; the calcining and water quenching is to heat the quartz glass to above the phase transition temperature of cristobalite to achieve preliminary dissociation of the quartz glass and cristobalite; the crushing is to crush the quartz glass using a jaw crusher, a hammer crusher or an impact crusher; the grinding is to grind the crushed quartz glass using a jaw crusher, a ball mill or a sample making machine; the screening is to use a vibrating screen or a fixed screen for inspection and screening, and the dust removal uses a dust removal system supporting the screening line.

4. The method for preparing a high-purity quartz product from waste high-purity quartz glass according to claim 3, wherein: The time of calcination and water quenching is 10 to 600 minutes, the temperature of calcination and water quenching is 270 to 1200° C.; the mesh number of inspection screening is 20 to 200 meshes.

5. The method for preparing a high-purity quartz product from waste high-purity quartz glass according to claim 1, wherein: The flotation is a process of separating quartz glass sand from quartz glass sand through a single flotation, wherein the single flotation can obtain a foam product and a bottom product, the foam product is quartz glass sand, and the bottom product is cristobalite sand.

6. The method for preparing a high-purity quartz product from waste high-purity quartz glass according to claim 1, wherein: The flotation process parameters include: the concentration of the quartz glass sand slurry is 5% to 30%; the pH adjuster is sodium hydroxide, potassium hydroxide or a mixture of sodium hydroxide and potassium hydroxide; the pH of the slurry after the pH adjuster is added is adjusted to 7 to 9; the collector includes sodium oleate or sodium dodecyl sulfate, wherein the concentration of sodium oleate is 1×10 -4 ~1×10 -3 mol / L, the concentration of sodium dodecyl sulfate is 5×10 -4 ~5×10 -3 mol / L.

7. The method for preparing a high-purity quartz product from waste high-purity quartz glass according to claim 1, wherein: The washing and filtering are performed on a belt filter washer using industrial pure water; the drying is performed using air drying or an electric heating drying device, and the drying temperature is 100-270° C.; the moisture content of the cristobalite sand and the quartz glass sand is ≤1.5%.

8. The method for preparing a high-purity quartz product from waste high-purity quartz glass according to claim 1, wherein: The post-treatment includes acid leaching, washing, filtering and drying; The solid-liquid ratio of the quartz sand to the acid leaching solution in the acid leaching is 1:3 to 1:6; the solid-liquid ratio of the quartz glass sand to the acid leaching solution in the acid leaching is 1:3 to 1:6; the acid leaching solution includes 0.5 to 3 mol / L nitric acid solution and 0 to 2 mol / L hydrofluoric acid solution; The acid leaching includes normal pressure acid leaching and hot pressure acid leaching. The acid leaching temperature of the normal pressure acid leaching is 50-90° C. and the acid leaching time is 90-480 minutes; the acid leaching temperature of the hot pressure acid leaching is 100-220° C. and the acid leaching time is 30-360 minutes.

9. A high-purity quartz product, characterized in that: The high-purity quartz product is prepared by the method for preparing a high-purity quartz product from waste high-purity quartz glass according to any one of claims 1 to 8.

10. The high-purity quartz product according to claim 9, characterized in that: The high-purity quartz products include high-purity quartz glass sand and high-purity cristobalite sand; The SiO2 content in the high-purity quartz glass sand is 99% to 99.999%, and the particle size is 20 to 200 meshes; the SiO2 content in the high-purity cristobalite sand is 99% to 99.999%, and the particle size is 20 to 200 meshes.

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