Method for preparing ultra-pure synthetic quartz sand

Abstract

The present application relates to the technical field of quartz sand preparation, and particularly relates to a preparation method of super-pure synthetic quartz sand. The flat-shaped silica xerogel is obtained by pretreating the silica wet gel determined to be qualified based on a viscosity growth rate; whether the pretreatment is up to standard is determined based on a purification potential index; a calcination index is determined based on the impurity content rate after the pretreatment is up to standard; high-temperature calcination is started on the flat-shaped silica xerogel based on a calcination access index; calcination parameters are determined based on a benchmark calcination intensity; whether the impurity removal rate is up to standard is determined based on a reaction intensity index; and whether the quality of the quartz sand product of a single batch is qualified is determined based on the purity value of the quartz sand product, so as to adjust the flat thickness value or the preset calcination temperature in the preparation process of the next batch. The present application improves the purity of the quartz sand.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of quartz sand preparation, and in particular to a preparation method of super-pure synthetic quartz sand. BACKGROUND

[0002] With the rapid development of the semiconductor, optical communication and photovoltaic industries, the demand for high-purity synthetic quartz sand is increasing, and the purity directly affects the performance and reliability of downstream products. When dealing with ultra-high purity requirements, the traditional quartz sand preparation process faces technical bottlenecks such as unstable control of metal impurities, dependence on experience adjustment of process parameters, and poor batch consistency. Existing synthetic quartz sand preparation methods mainly focus on the optimization of a single process, lack systematic control of the correlation between precursor quality and final purity, and result in large fluctuations in product quality.

[0003] The existing preparation process generally has the problem of disconnection of quality control between processes, and lacks effective quality transmission and feedback mechanisms between production links. In particular, in key processes such as gelation, aging and drying, there is a lack of monitoring and quantitative evaluation means for key parameters that affect the final purity (such as gel network structure, pore characteristics, organic matter residues, etc.), resulting in process parameter adjustment lagging behind quality fluctuations. At the same time, the control of metal impurities in the traditional method mainly depends on the subsequent purification process, and a systematic purity control strategy is not established from the precursor formation stage, making it difficult for the final metal content of the product to stably reach the ultra-pure standard below 100 ppb, resulting in waste of energy and raw materials, and restricting the supply of materials for high-end application fields.

[0004] Chinese Patent Publication No. CN115490240A discloses a preparation method and system for high-purity quartz sand. The preparation method for high-purity quartz sand includes: step S1, mixing a silicon-containing compound and water to perform a hydrolysis reaction to obtain a paste product; step S2, purifying the paste product to obtain a quartz sand precursor; and step S3, sintering the quartz sand precursor to obtain high-purity quartz sand. The silicon-containing compound includes at least one of tetrachlorosilane or tetraethyl orthosilicate. The preparation method for high-purity quartz sand provided by the application synthesizes a paste product using a silicon-containing compound and water as raw materials, purifies the paste product, and then sintering to obtain high-purity quartz sand. The raw materials are inexpensive and easy to obtain, the process is simple, the purity of the obtained high-purity quartz sand is 99.998%, and the production demand of domestic photovoltaic monocrystalline silicon wafers and semiconductor silicon wafers can be effectively met.

[0005] Therefore, the preparation method and system for high-purity quartz sand have the following problems:

[0006] 1. The process is extensive and lacks fine precursor quality evaluation and access control;

[0007] 2. The quality control link is lagging and single, lack of adaptive and cross-batch optimization capability. SUMMARY

[0008] Therefore, the application provides a method for preparing ultra-pure synthetic quartz sand to overcome the problem of poor consistency and lagging purity control of quartz sand in the prior art.

[0009] To achieve the above-mentioned purpose, the application provides a method for preparing ultra-pure synthetic quartz sand, comprising:

[0010] The flat silica xerogel is obtained by pretreating the silica wet gel determined to be prepared according to the viscosity growth rate;

[0011] Based on the average pore size and loss on ignition of the flat silica xerogel, the purification potential index of the flat silica xerogel is determined, and whether the pretreatment is qualified is determined based on the comparison result of the purification potential index and the preset purification potential index;

[0012] Based on the impurity content determined after the flat silica xerogel pretreatment is qualified, the calcination index of the flat silica xerogel is determined;

[0013] Based on the purification potential index and the calcination index, the calcination access index is determined to start high-temperature calcination of the flat silica xerogel;

[0014] Based on the calcination access index, the reference calcination intensity is determined to determine the calcination parameters of the flat silica xerogel;

[0015] Based on the infrared thermal image characteristics in the calcination process, the reaction intensity index of the flat silica xerogel is determined to determine whether the impurity removal rate of the flat silica xerogel is qualified;

[0016] Based on the quartz sand finished product obtained after the calcination is completed, the purity value of the quartz sand finished product is measured to determine whether the quality of the quartz sand finished product of a single batch is qualified, so as to adjust the flat thickness value or the preset calcination temperature of the next batch preparation process.

[0017] Further, the process of determining the silica wet gel to be prepared based on the viscosity growth rate comprises:

[0018] The viscosity growth rate is compared with the preset maximum viscosity growth rate and the preset minimum viscosity growth rate, respectively;

[0019] Based on the viscosity growth rate being greater than or equal to the preset minimum viscosity growth rate and the viscosity growth rate being less than or equal to the preset maximum viscosity growth rate, it is determined that the silica wet gel is qualified;

[0020] determine that the quality of the silica wet gel is unqualified based on the viscosity growth rate being less than a preset minimum viscosity growth rate;

[0021] determine that the quality of the silica wet gel is unqualified based on the viscosity growth rate being greater than a preset maximum viscosity growth rate.

[0022] Further, the process of determining whether the pretreatment is qualified based on the purification potential index comprises:

[0023] comparing the purification potential index with a preset purification potential index;

[0024] determining that the pretreatment is qualified based on the purification potential index being greater than or equal to the preset purification potential index;

[0025] determining that the pretreatment is unqualified based on the purification potential index being less than the preset purification potential index.

[0026] Further, the process of determining the calcination index after the pretreatment is qualified comprises:

[0027] comparing the impurity content rate with a preset impurity content rate;

[0028] determining that the calcination index is a first calcination index based on the impurity content rate being greater than or equal to the preset impurity content rate;

[0029] determining that the calcination index is a second calcination index based on the impurity content rate being less than the preset impurity content rate.

[0030] Further, the process of determining the calcination access index to start high-temperature calcination of the flat-shaped silica xerogel comprises:

[0031] comparing the calcination access index with a preset calcination access index interval;

[0032] determining to start calcination of the flat-shaped silica xerogel based on the calcination access index being in the preset calcination access index interval.

[0033] Further, the process of determining the reference calcination intensity to determine the calcination parameters of the flat-shaped silica xerogel comprises:

[0034] comparing the reference calcination intensity with a preset calcination intensity;

[0035] determining that the calcination parameters of the flat-shaped silica xerogel are first calcination parameters based on the reference calcination intensity being greater than or equal to the preset calcination intensity;

[0036] determining that the calcination parameters of the flat-shaped silica xerogel are second calcination parameters if the reference calcination intensity is less than the preset calcination intensity.

[0037] Further, the process of determining whether the flat silica xerogel impurity removal rate meets the standard comprises:

[0038] comparing the reaction intensity index with a preset reaction intensity index;

[0039] based on the reaction intensity index being greater than or equal to the preset reaction intensity index, determining that the flat silica xerogel impurity removal rate meets the standard;

[0040] based on the reaction intensity index being less than the preset reaction intensity index, determining that the flat silica xerogel impurity removal rate does not meet the standard.

[0041] Further, the process of determining whether the quality of the quartz sand product of the single batch is qualified comprises:

[0042] comparing the purity value of the quartz sand product with a preset purity value;

[0043] based on the purity value being greater than or equal to the preset purity value, determining that the quality of the quartz sand product of the single batch is qualified;

[0044] based on the purity value being less than the preset purity value, determining that the quality of the quartz sand product of the single batch is unqualified.

[0045] Further, based on the quality of the quartz sand product of the single batch being unqualified, the process of determining to adjust the flat thickness value in the preparation process of the next batch comprises:

[0046] obtaining a purity deviation value of the purity value and the preset purity value;

[0047] comparing the purity deviation value with a preset purity deviation threshold value;

[0048] based on the purity deviation value being less than or equal to the preset purity deviation threshold value, determining to increase the flat thickness value in the preparation process of the next batch by a first adjustment coefficient.

[0049] Further, based on the purity deviation value being greater than the preset purity deviation threshold value, determining to increase the preset roasting temperature in the preparation process of the next batch by a second adjustment coefficient.

[0050] Compared with the prior art, the beneficial effects of the present application are that, in particular, the present application realizes the control of the ultra-pure quartz sand preparation process through multi-parameter synergy, evaluates the gel quality compliance based on the viscosity growth rate, determines the purification potential index combining the average pore size and the ignition loss, and determines whether the pretreatment is up to standard, determines the calcination index of the flat-shaped silica xerogel according to the impurity content, determines the start of high-temperature calcination according to the purification potential index and the calcination index, optimizes the calcination process parameters combining the benchmark calcination intensity, realizes batch quality closed-loop feedback through the purity deviation value, improves the ultra-pure quartz sand preparation precision, and the flat-shaped silica xerogel quality evaluation and the calcination intensity matching provide data support for the dynamic regulation of process parameters, avoid energy waste, optimize production resource allocation, construct a multi-dimensional index system to quantify process standards, and improve the quality control efficiency of the ultra-pure quartz sand preparation process, thereby improving the consistency and reliability of the synthetic quartz sand product purity control.

[0051] Further, the present application realizes the monitoring and regulation of the hydrolysis and polycondensation reaction kinetics based on the comparison results of the viscosity growth rate and the preset viscosity growth rate, and the viscosity growth rate less than the minimum value of the preset viscosity growth rate indicates that the reaction activity is insufficient or the mixing is uneven, and the mixing needs to be enhanced to promote mass transfer and reaction integrity, and the viscosity growth rate greater than the maximum value of the preset viscosity growth rate indicates that the reaction is intense and may cause local overheating and network structure stress concentration, and the mixing needs to be weakened to smooth the reaction process. This adjustment mechanism ensures the uniformity and mechanical stability of the silica gel network structure, provides high-quality flat-shaped silica xerogel for subsequent aging, drying and calcination processes, and guarantees the ultra-high purity of the final synthetic quartz sand from the source, thereby improving the robustness and product consistency of the entire preparation process.

[0052] Further, the present application determines the purification potential index of the flat-shaped silica xerogel by the average pore size and the ignition loss, which establishes a clear compliance standard for pretreatment, indicating that the flat-shaped silica xerogel has good impurity diffusion channels and pollutant loading levels, and the purification potential index performs a preliminary evaluation for subsequent calcination processing, significantly improving the predictability and controllability of the ultra-pure quartz sand preparation process, optimizing energy consumption while ensuring quartz sand purity, and reducing production costs, thereby improving the effectiveness and consistency of synthetic quartz sand product purity control.

[0053] Further, the application obtains a calcination access index of the flat silica xerogel through the purification potential index and the calcination index, establishes a quantitative standard for the start of the high-temperature calcination process, when the calcination access index is in the qualified interval, it indicates that the flat silica xerogel has ideal heat treatment characteristics and can directly enter the calcination link, when the calcination access index deviates from the qualified interval, the corresponding optimization treatment of the flat silica xerogel is started according to the deviation direction, the controllability and intelligent level of the preparation process of the ultra-pure quartz sand are significantly improved through structure improvement or pollutant removal, while ensuring the purity of the quartz sand, energy waste and production interruption are effectively avoided, thereby improving the consistency of the quality of the synthetic quartz sand product and the economy of the production process.

[0054] Further, the application determines the reference calcination intensity based on the calcination access index, establishes a quantitative correlation between the precursor quality characteristics and the heat treatment intensity, a high reference calcination intensity indicates that the flat silica xerogel network has good uniformity and large impurity removal potential, and a strengthened calcination scheme can fully develop the upper limit of material purification, a low reference calcination intensity indicates that the flat silica xerogel has structural defects or pollution risks, and a mild calcination scheme is adopted to avoid lattice defects caused by excessive treatment. This kind of hierarchical calcination parameter control realizes the precise matching of the calcination process and the flat silica xerogel, breaks through the limitations of traditional fixed calcination curves, ensures the purity of the quartz sand product, and improves the adaptability of the preparation process of the ultra-pure quartz sand.

[0055] Further, the application determines the purity value of the quartz sand product, determines the qualification of the quality of the quartz sand product prepared in this batch according to the comparison result of the purity value of the quartz sand product, improves the consistency and stability of the quality of the quartz sand, reduces the energy consumption and material loss in the production process, avoids the waste of resources caused by the flow of unqualified quartz sand into the subsequent link, adapts to the influence of the fluctuation of the raw material characteristics on the production process, shortens the response time of the identification and adjustment of the abnormal quality of the quartz sand, and improves the adaptability of the production. BRIEF DESCRIPTION OF DRAWINGS

[0056] Figure 1 The step flow chart of the ultra-pure synthetic quartz sand preparation method of the embodiment of the application;

[0057] Figure 2 The logic judgment chart for determining whether the pretreatment of the flat silica xerogel meets the standard in the embodiment of the application;

[0058] Figure 3 The logic judgment chart for determining the calcination index of the flat silica xerogel in the embodiment of the application;

[0059] Figure 4 The logic judgment chart for determining the calcination parameters of the flat silica xerogel in the embodiment of the application. DETAILED DESCRIPTION

[0060] In order to make the objectives and advantages of the present application clearer, the following further describes the present application with reference to examples; it should be understood that the specific examples described herein are merely used to explain the present application and do not limit the present application.

[0061] The preferred embodiments of the present application are described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the present application and are not intended to limit the protection scope of the present application.

[0062] In addition, it should be further noted that, in the description of the present application, unless explicitly defined and limited, the terms "mounting", "connection" and "linking" should be understood in a broad sense, for example, can be fixed connection, can also be detachable connection, or integrally connected; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be the communication inside two elements. Those skilled in the art can understand the specific meaning of the above terms in the present application according to the specific circumstances.

[0063] Please refer to Figure 1 As shown in the figure, it is a step flow chart of the preparation method of the ultra-pure synthetic quartz sand of the present application.

[0064] The preparation method of the ultra-pure synthetic quartz sand of the present application embodiment comprises:

[0065] S1, based on the viscosity growth rate, the pre-processing of the silica wet gel for preparing qualified silica dry gel is determined to obtain the flat silica dry gel;

[0066] S2, based on the average pore size and the loss on ignition of the flat silica dry gel, the purification potential index of the flat silica dry gel is determined, and whether the pre-processing is qualified is determined based on the comparison result of the purification potential index and the preset purification potential index;

[0067] S3, based on the impurity content after the pre-processing of the flat silica dry gel is qualified, the calcination index of the flat silica dry gel is determined;

[0068] S4, based on the purification potential index and the calcination index, the calcination access index is determined to start high-temperature calcination of the flat silica dry gel;

[0069] S5, based on the calcination access index, the reference calcination intensity is determined to determine the calcination parameters of the flat silica dry gel;

[0070] S6, based on the infrared thermal image characteristics in the calcination process, the reaction intensity index of the flat silica dry gel is determined to determine whether the impurity removal rate of the flat silica dry gel is qualified;

[0071] S7, based on the quartz sand product after roasting, measuring the purity value of the quartz sand product to determine whether the quality of the quartz sand product of a single batch is qualified, to adjust the flat thickness value or the preset roasting temperature of the next batch preparation process.

[0072] In the embodiment of the application, the preparation process of the silica wet gel is as follows: 40 mL of electronic grade tetraethyl orthosilicate (TEOS) and 80 mL of anhydrous ethanol are mixed in a quartz beaker to prepare A liquid; at the same time, 20 mL of ultrapure water, 80 mL of anhydrous ethanol and 0.5 mL of high-purity hydrochloric acid are mixed in another beaker to prepare B liquid; then, A liquid is transferred to a 500 mL three-necked quartz flask, which is placed in a 60℃ constant temperature water bath and a magnetic stirrer is started to mix uniformly at a speed of 300 rpm; then, B liquid is slowly added to the reaction system at a rate of 2 mL / min through a constant pressure dropping funnel, and constant temperature and stirring are continued after the addition is completed, and the viscosity change of the system is continuously monitored by a rotary viscometer, and when the silica wet gel reaches the gel point, the gel time at this time is recorded.

[0073] In the embodiment of the application, the viscosity growth rate is a process kinetics index for monitoring sol to gel, which reflects the hydrolysis and condensation reaction of electronic grade tetraethyl orthosilicate under acidic conditions to form a silica network, and the viscosity growth rate directly reflects the formation speed of the three-dimensional network structure, when the viscosity growth rate is too slow, it indicates that the reaction is insufficient, the network structure is loose and the strength is insufficient, and when the viscosity growth rate is too fast, it may cause excessive local crosslinking, causing network stress concentration and uneven pore size distribution, which may cause hidden troubles for subsequent impurity residues.

[0074] In the embodiment of the application, the determination of the gel point adopts the pouring method: when the container containing the silica wet gel is inclined at an angle of 45°, the liquid surface of the silica wet gel remains stable and no longer flows, that is, it is determined that the gel point is reached. The measurement accuracy of the rotary viscometer is ±1%, and the measurement frequency is to record data once every 5 minutes.

[0075] In the embodiment of the application, the non-contact mixing method includes but is not limited to bubbling method, magnetic stirring method and ultrasonic method, and the non-contact mixing ensures that the reaction system is not contaminated by metal, and the constant temperature control ensures the consistency of the reaction kinetics.

[0076] Specifically, the present application realizes the control of the preparation process of ultra-pure quartz sand through multi-parameter cooperation, evaluates the gel quality standard based on the viscosity growth rate, determines the purification potential index combining the average pore size and the ignition loss, and determines whether the pretreatment is up to standard, determines the calcination index of flat silica xerogel according to the impurity content, determines the start of high-temperature calcination according to the purification potential index and the calcination index, optimizes the calcination process parameters combining the reference calcination intensity, realizes batch quality closed-loop feedback through the purity deviation value, improves the preparation precision of ultra-pure quartz sand, and the quality evaluation of flat silica xerogel and the matching of calcination intensity provide data support for dynamic regulation of process parameters, avoid energy waste, optimize production resource allocation, build quantitative process standards with multi-dimensional index system, improve the quality control efficiency of the preparation process of ultra-pure quartz sand, and improve the consistency and reliability of the purity control of synthetic quartz sand products.

[0077] Specifically, the viscosity growth rate is obtained based on the viscosity, and the process of preparing qualified silica wet gel is determined according to the comparison result of the viscosity growth rate and the preset viscosity growth rate.

[0078] If the viscosity growth rate is greater than or equal to the preset viscosity growth rate minimum value, and the viscosity growth rate is less than or equal to the preset viscosity growth rate maximum value, it is determined that the quality of the silica wet gel is qualified.

[0079] If the viscosity growth rate is less than the preset viscosity growth rate minimum value, it is determined that the quality of the silica wet gel is unqualified.

[0080] If the viscosity growth rate is greater than the preset viscosity growth rate maximum value, it is determined that the quality of the silica wet gel is unqualified.

[0081] In the embodiment of the present application, the preset viscosity growth rate has a value range of [6.0, 10.0] (mPa·s) / min, the preset viscosity growth rate minimum value is preferably set to 6.0 (mPa·s) / min, and the preset viscosity growth rate maximum value is preferably set to 10.0 (mPa·s) / min, but the above value is not limited thereto, and the person skilled in the art can also adjust the value according to actual needs.

[0082] In the embodiment of the present application, the viscosity growth rate is obtained by the ratio of the gel point viscosity to the gel time, the gel point viscosity is the instantaneous viscosity when the reaction system reaches the gel point, which is obtained by measuring with a rotary viscometer, and the gel time is counted from the start of adding B liquid to the end of reaching the gel point.

[0083] Specifically, under the condition that the quality of the silica wet gel is determined to be unqualified, a reference value of the non-contact mixing intensity of the next batch of silica wet gel is determined according to a comparison result of the viscosity growth rate and a preset maximum or minimum value of the viscosity growth rate;

[0084] If the viscosity growth rate is less than the preset minimum value of the viscosity growth rate, it is determined that the reference value of the non-contact mixing intensity of the next batch is increased to a corresponding value by a first adjustment coefficient 1.1.

[0085] If the viscosity growth rate is greater than the preset maximum value of the viscosity growth rate, it is determined that the reference value of the non-contact mixing intensity of the next batch is reduced to a corresponding value by a second adjustment coefficient 0.9.

[0086] In the embodiment of the present application, the non-contact mixing intensity is the gas flow for the bubble method, the reference value is 2.0 L / min; the rotation speed for the magnetic stirring method, the reference value is 400 rpm; and the power for the ultrasonic method, the reference value is 500 W.

[0087] In the embodiment of the present application, the pretreatment process of the silica wet gel is as follows: the wet gel reaching the gel point is sealed with a fresh-keeping film (a gas permeable hole is reserved) together with a container, placed in a constant temperature and humidity box, and aged at 40 DEG C and 80% relative humidity for 48 h. After aging, the silica wet gel block is rolled into a continuous gel flat sheet with a thickness of 1.5 mm by a polytetrafluoroethylene double-roller device, and then transferred to a program-controlled temperature drying oven. The silica wet gel is dried by a stepwise temperature rising mode: first dried at 60 DEG C for 12 h, then dried at 80 DEG C for 8 h, and finally dried at 100 DEG C for 4 h, to obtain a flat silica dry gel.

[0088] In the embodiment of the present application, the temperature rising rate of the program-controlled temperature drying oven is 2 DEG C / min, and the temperature uniformity is ±1 DEG C. During the drying process, the mass change of the silica wet gel is recorded every 2 h until the mass difference is less than 0.1% for two times in succession, and the drying is determined to be completed. The crushing treatment is performed by a polytetrafluoroethylene cutter to avoid metal pollution.

[0089] In the embodiment of the present application, the aging process makes the silica wet gel network further condense and enhances the mechanical stability thereof. Rolling into a flat shape greatly increases the specific surface area and optimizes the mass transfer and heat transfer efficiency during heat treatment.

[0090] Specifically, the present application realizes the monitoring and regulation of the hydrolysis and polycondensation reaction kinetics by comparing the viscosity growth rate with the preset viscosity growth rate. If the viscosity growth rate is less than the minimum value of the preset viscosity growth rate, it indicates that the reaction activity is insufficient or the mixing is uneven, and the mixing needs to be enhanced to promote mass transfer and reaction integrity. If the viscosity growth rate is greater than the maximum value of the preset viscosity growth rate, it indicates that the reaction is intense and may cause local overheating and network structure stress concentration, and the mixing needs to be weakened to moderate the reaction progress. This adjustment mechanism ensures the uniformity and mechanical stability of the silica gel network structure, providing high-quality flat silica xerogel for subsequent aging, drying and calcination processes, and ensuring the ultra-high purity of the final synthetic quartz sand from the source, thereby improving the robustness and consistency of the entire preparation process.

[0091] Referring to Figure 2 As shown in the logic judgment diagram for determining whether the pretreatment of the flat silica xerogel meets the standard in the embodiment of the present application.

[0092] Specifically, based on the average pore size and the loss on ignition of the flat silica xerogel, a purification potential index of the flat silica xerogel is determined, and based on the comparison between the purification potential index and the preset purification potential index, it is determined whether the pretreatment meets the standard.

[0093] If the purification potential index is greater than or equal to the preset purification potential index, it is determined that the pretreatment of the silica wet gel meets the standard.

[0094] If the purification potential index is less than the preset purification potential index, it is determined that the pretreatment of the silica xerogel does not meet the standard.

[0095] In the embodiment of the present application, the measurement process of the average pore size is as follows: about 0.3 g of the flat silica xerogel sample after aging and drying is degassed at 150℃ in a vacuum environment for 6 h, and adsorption-desorption isotherm test is performed at 77 K using a nitrogen adsorption instrument. The test process conforms to the GB / T 19587-2017 standard.

[0096] In the embodiment of the present application, the measurement process of the loss on ignition is as follows: about 2.0 g of the flat silica xerogel sample of the same batch is placed in a quartz crucible with a constant weight, and the initial mass M1 is accurately measured and recorded using an analytical balance (accuracy ±0.0001 g). The sample is placed in a muffle furnace, heated to 800℃ at a rate of 5℃ / min and held for 2 h. After taking out, it is cooled to room temperature in a desiccator, and then weighed again to obtain the mass M2 after ignition. The loss on ignition value is calculated by the loss on ignition (%) = [(M1-M2) / M1]x100%, and the arithmetic mean of three parallel measurements is taken as the loss on ignition.

[0097] In the embodiment of the present application, the preset purification potential index is in the range of [0.7, 1.3], preferably 1.0, the preset average pore size is in the range of [24, 26] nm, preferably 25 nm, and the preset loss on ignition is in the range of [2%, 4%], preferably 3%. However, the above values are not limited thereto, and those skilled in the art can adjust the values according to actual needs.

[0098] In the embodiment of the present application, the purification potential index is obtained by multiplying the ratio of the average pore size to the preset average pore size and the ratio of the loss on ignition to the preset loss on ignition.

[0099] In the embodiment of the present application, the suitable pore size (24-26 nm) provides a smooth channel for the diffusion of impurity elements (such as Fe and Al) and the escape of gaseous products (such as chlorides) in the subsequent calcination process. The loss on ignition is mainly derived from residual ethanol, water and incompletely condensed silicon hydroxyl groups. The loss on ignition (2%-4%) indicates that the organic solvent has been sufficiently volatilized, and an appropriate amount of silicon hydroxyl groups is retained, which can participate in the reaction to generate Si-Cl in the chlorine atmosphere calcination, thereby helping to remove metal impurities bonded to the silicon-oxygen network.

[0100] Specifically, the present application determines the purification potential index of the flat-shaped silica xerogel by the average pore size and the loss on ignition. The purification potential index establishes a clear standard for pre-treatment, indicating that the flat-shaped silica xerogel has good impurity diffusion channels and pollutant loading levels. The purification potential index performs a preliminary evaluation for the subsequent calcination process, significantly improves the predictability and controllability of the preparation process of ultra-pure quartz sand, optimizes energy consumption while ensuring the purity of quartz sand, reduces production costs, and thus improves the effectiveness and consistency of the purity control of synthetic quartz sand products.

[0101] Please refer to Figure 3 As shown in the figure, it is a logic judgment diagram for determining the calcination index of the flat-shaped silica xerogel according to the embodiment of the present application.

[0102] Specifically, the impurity content is determined based on the pre-treatment of the flat-shaped silica xerogel to determine the calcination index of the flat-shaped silica xerogel.

[0103] If the impurity content is greater than or equal to the preset impurity content, the calcination index is determined as the first calcination index.

[0104] If the impurity content is less than the preset impurity content, the calcination index is determined as the second calcination index.

[0105] In the embodiment of the present application, the impurity content is obtained by non-destructive measurement of the flat silica xerogel by X-ray fluorescence spectrometry. The specific measurement process is as follows: three samples are randomly selected from the same batch of flat silica xerogel, and a wavelength dispersive X-ray fluorescence spectrometer is used to test under the conditions of a Rh target X-ray tube, a voltage of 50 kV, a current of 50 mA, a measurement time of 300 seconds, and a standard curve established by historical data to calculate the total metal impurity content. The arithmetic mean of the three samples is taken as the impurity content of the flat silica xerogel in this batch. The preset impurity content is in the range of [10 ppm, 15 ppm], preferably 12 ppm. Based on the statistical analysis of historical production data, when the impurity content of the xerogel is controlled within this range, there is more than 95% probability that the total metal impurity content of the final quartz sand product can be stably controlled below 100 ppb after subsequent calcination process.

[0106] In the embodiment of the present application, the first calcination index is the ratio of the impurity content to the preset impurity content, and the second calcination index is the product of the ratio of the impurity content to the preset impurity content and the compensation coefficient. The value of the compensation coefficient is in the range of [0.1, 0.3], preferably 0.2.

[0107] In the embodiment of the present application, the impurity content directly determines the difficulty of calcination. Impurities in silica gel may exist in the form of surface adsorption, network wrapping or lattice substitution. High impurity content (≥12 ppm) usually means more stubborn impurities in the form of wrapping or lattice, which requires higher energy (temperature / time) to diffuse to the surface and react to remove.

[0108] Specifically, the calcination admission index is determined based on the purification potential index and the calcination index to start high-temperature calcination of the flat silica xerogel.

[0109] If the calcination admission index is in the preset calcination admission index interval, it is determined to start calcination of the flat silica xerogel.

[0110] In the embodiment of the present application, the preset calcination admission index interval is [0.5, 2.0], but the above value is not limited thereto, and the skilled person in the art can also adjust the value according to actual needs.

[0111] In the embodiment of the present application, the calcination admission index is the product of the ratio of the purification potential index to the preset purification potential index and the ratio of the preset calcination index to the calcination index.

[0112] Specifically, if the calcination access index is not in the preset calcination access index interval, it is determined to start high-temperature calcination after processing the current flat silica xerogel;

[0113] If the calcination access index is less than the minimum value of the preset calcination access index interval, it is determined to re-age and dry the current flat silica xerogel;

[0114] If the calcination access index is greater than the maximum value of the preset calcination access index interval, it is determined to crush, extract and dry the current flat silica xerogel.

[0115] In the embodiment of the present application, the process of re-aging and drying the current flat silica xerogel is to return the current flat silica xerogel to the aging process, re-age for 72 h at 40℃, and use a three-step drying procedure, first dry at 60℃ for 12 h, then dry at 80℃ for 8 h, and finally dry at 100℃ for 4 h.

[0116] In the embodiment of the present application, the process of crushing, extracting and drying the current flat silica xerogel is to crush the current flat silica xerogel to a particle size of 0.5-1.0 mm, use a mixed solvent prepared by mixing anhydrous ethanol and deionized water at a volume ratio of 1:1, extract and process for 4 h at 60℃, and the solvent dosage is 5 times the mass of the xerogel, and after extraction, dry at 80℃ for 24 h.

[0117] Specifically, the present application obtains the calcination access index of flat silica xerogel by the purification potential index and the calcination index, establishes a quantitative standard for the start of the high-temperature calcination process, when the calcination access index is in the qualified interval, it indicates that the flat silica xerogel has ideal heat treatment characteristics and can directly enter the calcination link, when the calcination access index deviates from the qualified interval, the corresponding optimization processing of the flat silica xerogel is started according to the deviation direction, through structure improvement or pollutant removal, the controllability and intelligent level of the preparation process of ultra-pure quartz sand are significantly improved, while ensuring the purity of quartz sand, energy waste and production interruption are effectively avoided, thereby improving the consistency of synthetic quartz sand product quality and the economy of the production process.

[0118] Please refer to Figure 4 shown, which is the logic judgment diagram for determining the calcination parameters of flat silica xerogel in the embodiment of the present application.

[0119] Specifically, based on the calcination access index, the reference calcination intensity of flat silica xerogel is obtained, and according to the comparison result of the reference calcination intensity and the preset calcination intensity, the calcination parameters of flat silica xerogel are determined;

[0120] If the reference calcination intensity is greater than or equal to the preset calcination intensity, then the calcination parameters of the flat silica dry gel are determined as the first calcination parameters.

[0121] If the reference calcination intensity is less than the preset calcination intensity, then the calcination parameters of the flat silica dry gel are determined as the second calcination parameters.

[0122] In this embodiment of the invention, the preset calcination intensity ranges from [0.4, 2.5], preferably set to 1.0, but the above value is not limited to this, and those skilled in the art can adjust the value according to actual needs.

[0123] In this embodiment of the invention, the reference calcination intensity is the product of the calcination admission index and the weighting coefficient. The value of the weighting coefficient is determined based on the calcination index. If the calcination index is the first calcination index, the weighting coefficient is 1.2. If the calcination index is the second calcination index, the weighting coefficient is 0.8. The first calcination parameter is to heat to [1200, 1250]℃ at 5℃ / min and hold for [170, 190]min. The second calcination parameter is to heat to [1100, 1200]℃ at 3℃ / min and hold for [110, 130]min.

[0124] In this embodiment of the invention, the first calcination parameters are used under high calcination intensity conditions. By increasing the final temperature and extending the holding time, structural densification and sufficient volatilization of impurities are ensured. Historical experiments have verified that these parameters effectively remove encapsulated metallic impurities, achieving deep densification of the silica network. Sufficient activation energy is provided for encapsulated metallic impurities deep in the lattice or with high diffusion resistance, allowing them to diffuse and vaporize fully. This has been verified to be particularly effective in removing impurities such as Fe and Al encapsulated in the SiO2 network in an ionic state. The second calcination parameters are suitable for low calcination intensity conditions. While ensuring effective removal of surface and free impurities, they significantly reduce the risk of lattice defects caused by over-sintering.

[0125] In this embodiment of the invention, the infrared irradiation calcination process of the flat silica dry gel is executed according to the following procedure based on the determined calcination parameter instructions:

[0126] Under the condition of using the first calcination parameters, the following enhanced calcination procedure is performed:

[0127] (1) Preheating stage: Start the medium-wave infrared tube (wavelength 2.0-3.5 μm), heat up to 600℃ at 8℃ / min, and keep warm for 30 min;

[0128] (2) High temperature stage: switch to short-wave infrared tube (wavelength 1.0-1.8 μm), continue to heat up to 1250℃ at 5℃ / min, and keep warm for 180 min;

[0129] (3) Atmosphere control: throughout the process, 1% chlorine-containing nitrogen mixed gas was passed, and the flow rate was 1.0 L / min.

[0130] Under the condition of determining to adopt the second roasting parameter, the following mild roasting procedure was performed:

[0131] (1) Preheating stage: start the medium wave infrared tube (wavelength 2.0-3.5 μm), and heat to 600℃ at a rate of 5℃ / min, and keep for 30 min;

[0132] (2) High temperature stage: switch to the short wave infrared tube (wavelength 1.0-1.8 μm), and continue to heat to 1150℃ at a rate of 3℃ / min, and keep for 120 min;

[0133] (3) Atmosphere control: throughout the process, 0.5% chlorine-containing nitrogen mixed gas was passed, and the flow rate was 0.8 L / min.

[0134] In the embodiment of the present application, the temperature monitoring is monitored in real time by using a non-contact infrared thermometer, and the control accuracy is ±3℃.

[0135] Specifically, the present application determines the reference roasting intensity based on the roasting access index, establishes the quantitative correlation between the precursor quality characteristics and the heat treatment intensity, and the high reference roasting intensity indicates that the flat-shaped silica xerogel network has good uniformity and large impurity removal potential, and the use of the enhanced roasting scheme can fully develop the upper limit of material purification, and the low reference roasting intensity indicates that the flat-shaped silica xerogel structure has defects or pollution risk, and the use of the mild roasting scheme avoids the lattice defects caused by excessive processing. This kind of graded roasting parameter control realizes the accurate matching of the roasting process and the flat-shaped silica xerogel, breaks through the limitations of the traditional fixed roasting curve, ensures the purity of the quartz sand product, and improves the adaptability of the preparation process of the ultra-pure quartz sand.

[0136] Specifically, the reaction intensity index of the flat-shaped silica xerogel is determined based on the infrared thermal image characteristics in the roasting process, so as to determine whether the impurity removal rate of the flat-shaped silica xerogel meets the standard;

[0137] If the reaction intensity index is greater than or equal to the preset reaction intensity index, it is determined that the impurity removal rate of the flat-shaped silica xerogel meets the standard;

[0138] If the reaction intensity index is less than the preset reaction intensity index, it is determined that the impurity removal rate of the flat-shaped silica xerogel does not meet the standard.

[0139] In the embodiment of the present application, the acquisition and processing process of the infrared thermal image features includes: collecting the temperature field distribution of the surface of the flat silica xerogel through the high-temperature-resistant infrared thermal imager installed on the observation window of the calcination furnace, processing the collected thermal image data, and extracting at least one feature parameter related to the intensity of the impurity gasification reaction, wherein the reaction intensity index is a quantitative value calculated based on the at least one feature parameter.

[0140] In the embodiment of the present application, the reaction intensity index is the product of the hot spot area ratio, the hot spot temperature coefficient and the distribution uniformity index, and the value range of the preset reaction intensity index is [0.15, 0.35], preferably 0.25, but the above value is not limited thereto, and the skilled person in the art can also adjust the value according to the actual needs.

[0141] In the embodiment of the present application, under the chlorine atmosphere, the reaction of impurities with chlorine is an exothermic or endothermic process, which forms a temperature anomaly zone ("hot spot") on the surface of the sample. The reaction intensity index integrates the area, temperature and distribution uniformity of the hot spot, and is a quantitative index of the in-situ chemical reaction intensity and breadth. If the index meets the standard, it indicates that the chlorination reaction is active and uniform, and the impurities are being effectively removed.

[0142] Specifically, based on the quartz sand finished product obtained after calcination, the purity value of the quartz sand finished product is measured to determine whether the quality of the quartz sand finished product of a single batch is qualified, so as to adjust the flat thickness value or the preset calcination temperature of the preparation process of the next batch;

[0143] If the purity value is greater than or equal to the preset purity value, it is determined that the quality of the quartz sand finished product of a single batch is qualified;

[0144] If the purity value is less than the preset purity value, it is determined that the quality of the quartz sand finished product of a single batch is unqualified.

[0145] Specifically, based on the unqualified quality of the quartz sand finished product of a single batch, the flat thickness or the preset calcination temperature of the preparation process of the next batch is adjusted;

[0146] If the purity deviation value is less than or equal to the preset purity deviation threshold, it is determined that the flat thickness value of the preparation process of the next batch is increased to the corresponding value by a first adjustment coefficient 1.05;

[0147] If the purity deviation value is greater than the preset purity deviation threshold, it is determined that the preset calcination temperature of the preparation process of the next batch is increased to the corresponding value by a second adjustment coefficient 1.1.

[0148] In the embodiment of the present application, the preset purity value is in the range of [0, 0.2], preferably 0, and the preset purity value is based on the total metal impurity content of not more than 100 ppb, and the value range [0, 0.2] corresponds to the control target of the actual impurity content of 100-80 ppb, but the above value is not limited thereto, and the person skilled in the art can adjust it according to the actual requirement.

[0149] In the embodiment of the present application, the process of obtaining the purity value of the quartz sand product is: purity value = 100% - (measured total metal impurity content (ppb) / 10 7 ).

[0150] In the embodiment of the present application, the process of obtaining the purity deviation value is the difference between the purity value of the quartz sand product and the preset purity value.

[0151] In the embodiment of the present application, the preset purity deviation threshold value is in the range of [0.05, 0.15], but the above value is not limited thereto, and the person skilled in the art can adjust it according to the actual requirement.

[0152] In the embodiment of the present application, moderately increasing the thickness can slightly prolong the impurity diffusion path, giving more sufficient reaction time under the same roasting conditions, which helps to remove the deeply embedded impurities, and a larger purity deviation usually means that the existing thermodynamic conditions are not sufficient to remove stubborn impurities, and increasing the temperature can directly provide higher activation energy, and strengthen the diffusion and reaction kinetics.

[0153] Specifically, the present application determines the purity value of the quartz sand product, and determines the quality of the quartz sand product of the batch according to the comparison result of the purity value of the quartz sand product, which improves the consistency and stability of the quartz sand quality, reduces the energy consumption and material loss in the production process, avoids the waste of resources caused by the flow of unqualified quartz sand into the subsequent link, adapts to the influence of raw material characteristics fluctuation on the production process, shortens the response time of quartz sand quality abnormal identification and adjustment, and improves the adaptability of production.

[0154] So far, the technical scheme of the present application has been described in combination with the preferred embodiments shown in the drawings, but the person skilled in the art can easily understand that the protection scope of the present application is obviously not limited to these specific embodiments. The person skilled in the art can make equivalent changes or replacements to the related technical features without departing from the principles of the present application, and the technical scheme after the changes or replacements will fall within the protection scope of the present application.

Claims

1. A method for preparing ultrapure synthetic quartz sand, characterized in that, include: The pretreatment of qualified silica wet gel based on viscosity growth rate was used to obtain flat silica dry gel; Based on the average pore size and loss on ignition of the flat silica dry gel, the purification potential index of the flat silica dry gel is determined, and the pretreatment is determined to meet the standard based on the comparison result between the purification potential index and the preset purification potential index. The impurity content was determined after the pretreatment of the flat silica dry gel met the standards, so as to determine the calcination index of the flat silica dry gel. The calcination admission index is determined based on the purification potential index and the calcination index to initiate calcination of the flat silica dry gel. The benchmark calcination intensity is determined based on the calcination access index in order to determine the calcination parameters of the flat silica dry gel. The reaction intensity index of the flat silica dry gel was determined based on the infrared thermographic characteristics during the calcination process, in order to determine whether the impurity removal rate of the flat silica dry gel met the standard. After the quartz sand product is obtained after calcination, the purity value of the quartz sand product is measured to determine whether the quality of a single batch of the quartz sand product is qualified, so as to adjust the flatness thickness value or preset calcination temperature of the next batch preparation process.

2. The method for preparing ultrapure synthetic quartz sand according to claim 1, characterized in that, The process of determining the preparation of qualified silica wet gel based on viscosity growth rate includes: The viscosity growth rate is compared with the preset maximum viscosity growth rate and the preset minimum viscosity growth rate, respectively; Based on the viscosity growth rate being greater than or equal to the preset minimum viscosity growth rate and the viscosity growth rate being less than or equal to the preset maximum viscosity growth rate, the silica wet gel is determined to be of qualified quality. Based on the fact that the viscosity growth rate is less than the preset minimum viscosity growth rate, the silica wet gel is determined to be of substandard quality. Based on the viscosity growth rate being greater than the preset maximum viscosity growth rate, the silica wet gel is determined to be of substandard quality.

3. The method for preparing ultrapure synthetic quartz sand according to claim 1, characterized in that, The process of determining whether the pretreatment meets the standard based on the purification potential index includes: The purification potential index is compared with the preset purification potential index; Based on the purification potential index being greater than or equal to the preset purification potential index, the pretreatment is determined to be up to standard; Based on the fact that the purification potential index is less than the preset purification potential index, it is determined that the pretreatment is substandard.

4. The method for preparing ultrapure synthetic quartz sand according to claim 1, characterized in that, The process of determining the calcination index based on the pretreatment standards includes: The impurity content is compared with the preset impurity content; Based on the impurity content being greater than or equal to a preset impurity content, the roasting index is determined to be the first roasting index. Based on the fact that the impurity content is less than the preset impurity content, the roasting index is determined to be the second roasting index.

5. The method for preparing ultrapure synthetic quartz sand according to claim 1, characterized in that, The process of determining the calcination admission index to initiate calcination of the flat silica dry gel includes: The roasting access index is compared with the preset roasting access index range; Based on the fact that the calcination access index is within the preset calcination access index range, it is determined that calcination will be initiated on the flat silica dry gel.

6. The method for preparing ultrapure synthetic quartz sand according to claim 1, characterized in that, The process of determining the baseline calcination intensity to determine the calcination parameters of the flat silica dry gel includes: Compare the benchmark roasting intensity with the preset roasting intensity; Based on the benchmark calcination intensity being greater than or equal to the preset calcination intensity, the calcination parameters of the flat silica dry gel are determined as the first calcination parameters. If the reference calcination intensity is less than the preset calcination intensity, the calcination parameters of the flat silica dry gel are determined as the second calcination parameters.

7. The method for preparing ultrapure synthetic quartz sand according to claim 1, characterized in that, The process for determining whether the impurity removal rate of the flat silica dry gel meets the standard includes: The reaction intensity index is compared with the preset reaction intensity index; Based on the reaction intensity index being greater than or equal to the preset reaction intensity index, it is determined that the impurity removal rate of the flat silica dry gel meets the standard. Based on the fact that the reaction intensity index is less than the preset reaction intensity index, it is determined that the impurity removal rate of the flat silica dry gel does not meet the standard.

8. The method for preparing ultrapure synthetic quartz sand according to claim 1, characterized in that, The process of determining whether the quality of a single batch of finished quartz sand is up to standard includes: The purity value of the finished quartz sand product is compared with the preset purity value; Based on the purity value being greater than or equal to a preset purity value, the quality of a single batch of the finished quartz sand is determined to be qualified. Based on the purity value being less than the preset purity value, it is determined that the quality of a single batch of the finished quartz sand is unqualified.

9. The method for preparing ultrapure synthetic quartz sand according to claim 8, characterized in that, The process of determining the flatness thickness value for the next batch of quartz sand preparation process based on the substandard quality of the single batch includes: Obtain the purity deviation value between the purity value and the preset purity value; The purity deviation value is compared with a preset purity deviation threshold. Based on the purity deviation value being less than or equal to a preset purity deviation threshold, the flatness thickness value for the next batch preparation process is determined to be increased by a first adjustment coefficient.

10. The method for preparing ultrapure synthetic quartz sand according to claim 9, characterized in that, Based on the fact that the purity deviation value is greater than the preset purity deviation threshold, the preset calcination temperature for the next batch preparation process is determined to be increased by a second adjustment coefficient.

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