Modification method of ammonium sulfate solid in semiconductor industry

Abstract

The invention relates to a modification method of an ammonium sulfate solid in the semiconductor industry, which comprises the following steps: (1) winnowing the ammonium sulfate solid in the semiconductor industry to obtain ammonium sulfate particles and volatile impurities; and (2) mixing the ammonium sulfate particles with a carboxylic acid crystal modifier, and then carrying out vacuum drying to obtain the crystal-transformed ammonium sulfate. According to the modification method provided by the invention, through winnowing, the ammonium sulfate solid is in a fluidized state, and volatile impurities are taken out along with gas, so that subsequent adsorption through activated carbon is facilitated; purified ammonium sulfate particles are mixed with a carboxylic acid crystal modifier to induce the crystal growth direction of ammonium sulfate to change, so that an original orthorhombic system is converted into a cubic system with higher stability, and the surface energy and hygroscopicity are reduced; the sodium content of the finally obtained crystal transformation ammonium sulfate is less than or equal to 0.05 wt%, the heavy metal content is less than or equal to 2ppm, the volatile impurity content is less than or equal to 0.005%, the crystal form is a cubic crystal system, the critical relative humidity at 25 DEG C is more than or equal to 85%, and no obvious deliquescence and caking exist after the crystal transformation ammonium sulfate is placed for 30 days.

Description

Technical Field

[0001] This invention belongs to the field of solid waste recycling technology, and relates to a method for modifying ammonium sulfate solid, and more particularly to a method for modifying ammonium sulfate solid in the semiconductor industry. Background Technology

[0002] In the chip manufacturing industry, processes such as wafer cleaning and etching generate ammonia-containing waste gas. This gas is typically purified using a sulfuric acid absorption tower to produce an ammonia-containing sulfuric acid solution. To achieve resource recovery, sodium hydroxide can be added to adjust the pH to neutral, followed by evaporation and crystallization to obtain solid ammonium sulfate.

[0003] However, this process has significant technical defects: First, the crystallized product contains a variety of impurities, including sodium ions introduced by pH adjustment, heavy metals and volatile organic impurities brought in by process waste gas, resulting in insufficient product purity. It cannot be sold directly as fertilizer or industrial raw material, and can only be disposed of as solid waste or treated at low price, resulting in resource waste. Second, most existing ammonium sulfate crystals are orthorhombic crystals, which are highly hygroscopic and easily deliquesce and clump during storage, further limiting their resource application.

[0004] Currently, there is a lack of purification and modification technologies for low-purity ammonium sulfate: conventional purification methods such as recrystallization are energy-intensive and struggle to simultaneously remove volatile organic impurities; existing anti-caking agents are mostly inorganic additives, which easily introduce new impurities and have limited modification effects. Therefore, developing a process that can efficiently remove multiple types of impurities and improve crystal morphology to achieve the resource utilization of ammonium sulfate is of great significance for solid waste reduction and resource recycling in the chip industry. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for modifying solid ammonium sulfate for the semiconductor industry. This method utilizes air classification to fluidize the solid ammonium sulfate, allowing volatile impurities to be carried away by the gas, facilitating subsequent adsorption by activated carbon. The purified ammonium sulfate particles are then mixed with a carboxylic acid crystallization agent, inducing a change in the crystal growth direction of the ammonium sulfate, transforming the original orthorhombic crystal system into a more stable cubic crystal system, reducing surface energy and hygroscopicity. The resulting transformed ammonium sulfate has a sodium content ≤0.05wt%, a heavy metal content ≤2ppm, a volatile impurity content ≤0.005%, a cubic crystal morphology, a critical relative humidity of ≥85% at 25°C, and shows no significant deliquescence or clumping after 30 days of storage.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] This invention provides a method for modifying solid ammonium sulfate used in the semiconductor industry, the modification method comprising:

[0008] (1) In the semiconductor industry, solid ammonium sulfate is air-classified to obtain ammonium sulfate particles and volatile impurities;

[0009] (2) Ammonium sulfate particles are mixed with carboxylic acid crystallizing agent and then vacuum dried to obtain crystallized ammonium sulfate.

[0010] The modification method provided by this invention uses air classification to fluidize the ammonium sulfate solid, allowing volatile impurities to be carried out with the gas, facilitating subsequent adsorption by activated carbon. The purified ammonium sulfate particles are mixed with a carboxylic acid crystallization agent, inducing a change in the crystal growth direction of the ammonium sulfate, transforming the original orthorhombic crystal system into a more stable cubic crystal system, reducing surface energy and hygroscopicity. The final obtained crystallized ammonium sulfate has a sodium content ≤0.05wt%, a heavy metal content ≤2ppm, a volatile impurity content ≤0.005%, a cubic crystal morphology, a critical relative humidity of ≥85% at 25℃, and no obvious deliquescence or clumping after 30 days of storage.

[0011] In some embodiments, the content of volatile impurities in the semiconductor industry ammonium sulfate solid is 0.01 wt% to 0.2 wt%.

[0012] In some embodiments, the average particle size of the semiconductor industry ammonium sulfate solid is 0.5 mm to 2 mm.

[0013] In some embodiments, the temperature of the air separation is 60°C to 80°C.

[0014] In some embodiments, the gas being air-separated is nitrogen and / or air.

[0015] In some embodiments, the gas flow rate of the air separation is 0.8 m / s to 1.5 m / s.

[0016] In some embodiments, the volatile impurities are absorbed using activated carbon.

[0017] In some embodiments, the carboxylic acid crystallization agent includes any one or a combination of at least two of citric acid, maleic acid, or adipic acid.

[0018] In some embodiments, the amount of the carboxylic acid crystallization agent is 0.3 wt% to 0.8 wt% of the ammonium sulfate particles.

[0019] In some embodiments, the mixing in step (2) includes preparing a slurry using deionized water and stirring it.

[0020] In some embodiments, the solid-liquid ratio of the slurry is 1:0.5 to 1:1, and the unit of the solid-liquid ratio is g / mL.

[0021] In some embodiments, the stirring speed is 300 rpm to 50 rpm.

[0022] In some embodiments, the mixing temperature is 50°C to 60°C and the mixing time is 40 min to 60 min.

[0023] In some embodiments, the vacuum degree of the vacuum drying is -0.08MPa to -0.09MPa.

[0024] In some embodiments, the vacuum drying temperature is 70°C to 80°C.

[0025] In some embodiments, the vacuum drying time is 2 to 3 hours.

[0026] In some embodiments, the modification method includes:

[0027] (1) Semiconductor industry ammonium sulfate solid with an average particle size of 0.5 mm to 2 mm and a volatile impurity content of 0.01 wt% to 0.2 wt% is obtained by air classification to obtain ammonium sulfate particles and volatile impurities;

[0028] The gas used in the air separation is nitrogen and / or air, with a temperature of 60℃~80℃ and a gas flow rate of 0.8m / s~1.5m / s;

[0029] (2) Ammonium sulfate particles and carboxylic acid crystallization agent are stirred and mixed in deionized water to form a slurry, and then vacuum dried at a vacuum degree of -0.08MPa to -0.09MPa, a temperature of 70℃ to 80℃ and a time of 2h to 3h to obtain crystallized ammonium sulfate;

[0030] The carboxylic acid crystallization agent includes any one or a combination of at least two of citric acid, maleic acid, or adipic acid.

[0031] The amount of the carboxylic acid crystallization agent used is 0.3wt% to 0.8wt% of the ammonium sulfate particles;

[0032] The solid-liquid ratio of the slurry is 1:0.5 to 1:1, and the unit of the solid-liquid ratio is g / mL;

[0033] The stirring speed is 300 rpm to 500 rpm, the temperature is 50°C to 60°C, and the time is 40 min to 60 min.

[0034] (3) The volatile impurities are absorbed using activated carbon;

[0035] Steps (2) and (3) are not in any particular order.

[0036] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The modification method provided by this invention uses air classification to fluidize the ammonium sulfate solid, allowing volatile impurities to be carried out with the gas, facilitating subsequent adsorption by activated carbon. The purified ammonium sulfate particles are mixed with a carboxylic acid crystallization agent, inducing a change in the crystal growth direction of the ammonium sulfate, transforming the original orthorhombic crystal system into a more stable cubic crystal system, reducing surface energy and hygroscopicity. The final obtained crystallized ammonium sulfate has a sodium content ≤0.05wt%, a heavy metal content ≤2ppm, a volatile impurity content ≤0.005%, a cubic crystal morphology, a critical relative humidity of ≥85% at 25℃, and no obvious deliquescence or clumping after 30 days of storage. Attached Figure Description

[0039] Figure 1 A process flow diagram is provided for the modification method of this invention. Detailed Implementation

[0040] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0041] The "range" disclosed in this invention can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for specific parameters, it is understood that ranges of 60–110 and 80–120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and maximum range values ​​of 3, 4, and 5 are also listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this invention, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0042] In this invention, "a combination of at least two" refers to a quantity greater than or equal to two, unless otherwise specified. For example, "any combination of one or at least two" means one or more or more items. It can be understood that when referring to "a combination of at least two," it refers to any suitable combination of multiple items, that is, a combination of "at least two" items carried out in a manner that does not conflict with and enables the implementation of this invention.

[0043] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0044] The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0045] Those skilled in the art will understand that the order in which the steps are written in the methods of the various embodiments does not imply a strict execution order. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), meaning that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0046] In this invention, open-ended technical features or solutions described using terms such as "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or exclude additional members. This can be considered as providing both technical features or solutions where "A is composed of a1, a2, and a3" or "A is selected from a1, a2, and a3," and technical features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0047] In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0048] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0049] In this invention, "optional" means that something is optional, that is, it refers to any one of the two parallel solutions of "having" or "not having". If there are multiple "optional" options in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, then each "optional" option is independent.

[0050] In this invention, "room temperature" generally refers to 4℃ to 35℃, and may refer to 20℃ ± 5℃. In some embodiments of this invention, room temperature refers to 20℃ to 30℃.

[0051] This invention provides a method for modifying solid ammonium sulfate used in the semiconductor industry, the modification method comprising:

[0052] (1) In the semiconductor industry, solid ammonium sulfate is air-classified to obtain ammonium sulfate particles and volatile impurities;

[0053] (2) Ammonium sulfate particles are mixed with carboxylic acid crystallizing agent and then vacuum dried to obtain crystallized ammonium sulfate.

[0054] The modification method provided by this invention uses air classification to fluidize the ammonium sulfate solid, allowing volatile impurities to be carried out with the gas, facilitating subsequent adsorption by activated carbon. The purified ammonium sulfate particles are mixed with a carboxylic acid crystallization agent, inducing a change in the crystal growth direction of the ammonium sulfate, transforming the original orthorhombic crystal system into a more stable cubic crystal system, reducing surface energy and hygroscopicity. The final obtained crystallized ammonium sulfate has a sodium content ≤0.05wt%, a heavy metal content ≤2ppm, a volatile impurity content ≤0.005%, a cubic crystal morphology, a critical relative humidity of ≥85% at 25℃, and no obvious deliquescence or clumping after 30 days of storage.

[0055] In some embodiments, the content of volatile impurities in the semiconductor industry ammonium sulfate solid is 0.01wt% to 0.2wt%, for example, it can be 0.01wt%, 0.05wt%, 0.1wt%, 0.15wt% or 0.2wt%, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0056] The volatile impurities in this invention refer to organic volatile impurities, which can be substances such as isopropanol, ethanol, methylamine, ethyl acetate, acetone, etc. This invention does not make specific limitations. The content of volatile impurities in solid ammonium sulfate in the semiconductor industry can be reduced to below 0.005 wt% after air classification.

[0057] In some embodiments, the average particle size of the semiconductor industry ammonium sulfate solid is 0.5 mm to 2 mm, for example, it can be 0.5 mm, 0.8 mm, 1 mm, 1.2 mm, 1.5 mm, 1.8 mm or 2 mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0058] Optionally, methods for achieving an average particle size of 0.5 mm to 2 mm for ammonium sulfate solids in the semiconductor industry include, but are not limited to, crushing with a jaw crusher to remove mechanical impurities and other particulate foreign matter, thereby ensuring uniform particle size of ammonium sulfate solids in the semiconductor industry.

[0059] In some embodiments, the temperature of the air separation is 60°C to 80°C, for example, it can be 60°C, 65°C, 70°C, 75°C or 80°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0060] If the air classification temperature is too low, it cannot provide sufficient desorption energy for volatile impurities, and cannot reduce the content of volatile impurities in ammonium sulfate solids in the semiconductor industry to below 0.005 wt%. Moreover, it is easy for ammonium sulfate solids to absorb environmental moisture, which will damage the air classification effect. If the air classification temperature is too high, although the melting point of ammonium sulfate is 235℃, it will cause ammonium sulfate to decompose slightly to produce ammonia and ammonium bisulfate, and increase the hygroscopicity of the crystal surface, which is not conducive to achieving the technical effect of no obvious deliquescence and agglomeration.

[0061] In some embodiments, the gas being air-separated is nitrogen and / or air.

[0062] In some embodiments, the gas flow rate of the air separator is 0.8 m / s to 1.5 m / s, for example, it can be 0.8 m / s, 1 m / s, 1.2 m / s, 1.4 m / s or 1.5 m / s, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0063] In some embodiments, the volatile impurities are absorbed using activated carbon.

[0064] Saturated activated carbon can be desorbed using hot air at a temperature of 120℃~150℃, and then volatile impurities can be condensed and recovered.

[0065] In some embodiments, the carboxylic acid crystallization agent includes any one or a combination of at least two of citric acid, maleic acid, or adipic acid. Typical but non-limiting combinations include combinations of citric acid and maleic acid, combinations of citric acid and adipic acid, combinations of maleic acid and adipic acid, or combinations of citric acid, maleic acid, and adipic acid, preferably citric acid.

[0066] In some embodiments, the amount of the carboxylic acid crystallization agent is 0.3wt% to 0.8wt% of the ammonium sulfate particles, for example, it can be 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt% or 0.8wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0067] If the amount of carboxylic acid crystal conversion agent is insufficient, it will not be able to fully cover the surface of ammonium sulfate crystals, making it difficult to induce the transformation from orthorhombic to cubic crystal systems, resulting in incomplete crystal form modification, easy deliquescence and clumping of the product, and a decrease in the critical relative humidity at 25°C; if the amount of carboxylic acid crystal conversion agent is excessive, it will lead to a decrease in the purity of the final crystallized ammonium sulfate.

[0068] In some embodiments, the mixing in step (2) includes preparing a slurry using deionized water and stirring it.

[0069] In some embodiments, the solid-liquid ratio of the slurry is 1:0.5 to 1:1, for example, it can be 1:0.5, 1:0.6, 1:0.8, 1:0.9 or 1:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable. The unit of solid-liquid ratio is g / mL.

[0070] In some embodiments, the stirring speed is 300 rpm to 500 rpm, for example, 300 rpm, 350 rpm, 400 rpm, 450 rpm or 500 rpm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0071] In some embodiments, the mixing temperature is 50°C to 60°C and the mixing time is 40 min to 60 min.

[0072] The mixing temperature is 50℃~60℃, for example, it can be 50℃, 52℃, 55℃, 58℃ or 60℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0073] The mixing time is 40 min to 60 min, for example, 40 min, 45 min, 50 min, 55 min or 60 min, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0074] Before vacuum drying, the slurry provided by this invention is first centrifuged to obtain a wet material.

[0075] In some embodiments, the vacuum degree of the vacuum drying is -0.08MPa to -0.09MPa, for example, it can be -0.08MPa, -0.085MPa or -0.09MPa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0076] In some embodiments, the vacuum drying temperature is 70°C to 80°C, for example, 70°C, 72°C, 75°C, 78°C or 80°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0077] If the vacuum drying temperature is too low, the residual moisture will increase, accelerating deliquescence during storage; if the vacuum drying temperature is too high, it will cause the decomposition of the crystal conversion agent, destroying the already formed cubic crystal structure and reducing the critical relative humidity at 25°C.

[0078] In some embodiments, the vacuum drying time is 2h to 3h, for example, it can be 2h, 2.5h or 3h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0079] In some embodiments, the modification method includes:

[0080] (1) Semiconductor industry ammonium sulfate solid with an average particle size of 0.5 mm to 2 mm and a volatile impurity content of 0.01 wt% to 0.2 wt% is obtained by air classification to obtain ammonium sulfate particles and volatile impurities;

[0081] The gas used in the air separation is nitrogen and / or air, with a temperature of 60℃~80℃ and a gas flow rate of 0.8m / s~1.5m / s;

[0082] (2) Ammonium sulfate particles and carboxylic acid crystallization agent are stirred and mixed in deionized water to form a slurry. The wet material is obtained by centrifugation and then vacuum drying at a vacuum degree of -0.08MPa to -0.09MPa, a temperature of 70℃ to 80℃ and a time of 2h to 3h to obtain crystallized ammonium sulfate.

[0083] The carboxylic acid crystallization agent includes any one or a combination of at least two of citric acid, maleic acid, or adipic acid.

[0084] The amount of the carboxylic acid crystallization agent used is 0.3wt% to 0.8wt% of the ammonium sulfate particles;

[0085] The solid-liquid ratio of the slurry is 1:0.5 to 1:1, and the unit of the solid-liquid ratio is g / mL;

[0086] The stirring speed is 300 rpm to 500 rpm, the temperature is 50°C to 60°C, and the time is 40 min to 60 min.

[0087] (3) The volatile impurities are absorbed using activated carbon;

[0088] Steps (2) and (3) are not in any particular order.

[0089] To clearly illustrate the technical solution of the present invention, the content of volatile impurities in the solid ammonium sulfate for the semiconductor industry in the embodiments of the present invention is 0.2 wt%.

[0090] Example 1

[0091] This invention provides a method for modifying solid ammonium sulfate for the semiconductor industry, and the process flow diagram of the modification method is shown below. Figure 1 As shown, it includes:

[0092] (1) Solid ammonium sulfate for the semiconductor industry with an average particle size of 1 mm is air-classified to obtain ammonium sulfate particles and volatile impurities;

[0093] The gas used in the air separation is nitrogen, at a temperature of 70°C, and with a flow rate of 1.2 m / s.

[0094] (2) Ammonium sulfate granules and carboxylic acid crystallization agent are stirred and mixed in deionized water to form a slurry. The wet material is obtained by centrifugation and then vacuum dried at a vacuum degree of -0.085MPa, a temperature of 75℃ and a time of 2.5h to obtain crystallized ammonium sulfate. The sodium content of the obtained crystallized ammonium sulfate is ≤0.05wt%, the heavy metal content is ≤2ppm and the volatile impurity content is ≤0.005%.

[0095] The carboxylic acid crystallization agent is citric acid; the amount of the carboxylic acid crystallization agent is 0.5 wt% of the ammonium sulfate particles;

[0096] The solid-liquid ratio of the slurry is 1:0.8, and the unit of the solid-liquid ratio is g / mL;

[0097] The stirring speed was 400 rpm, the temperature was 55°C, and the time was 50 min.

[0098] (3) The volatile impurities are absorbed using activated carbon.

[0099] Example 2

[0100] This invention provides a method for modifying solid ammonium sulfate used in the semiconductor industry, the modification method comprising:

[0101] (1) Solid ammonium sulfate for the semiconductor industry with an average particle size of 0.5 mm is air-classified to obtain ammonium sulfate particles and volatile impurities;

[0102] The gas used in the air separation is nitrogen, at a temperature of 60°C, and with a flow rate of 1.5 m / s.

[0103] (2) Ammonium sulfate granules and carboxylic acid crystallization agent are stirred and mixed in deionized water to form a slurry. The wet material is obtained by centrifugation and then vacuum dried at a vacuum degree of -0.08MPa, a temperature of 70℃ and a time of 3h to obtain crystallized ammonium sulfate. The sodium content of the obtained crystallized ammonium sulfate is ≤0.05wt%, the heavy metal content is ≤2ppm and the volatile impurity content is ≤0.005%.

[0104] The carboxylic acid crystallization agent is citric acid; the amount of the carboxylic acid crystallization agent is 0.3 wt% of the ammonium sulfate particles;

[0105] The solid-liquid ratio of the slurry is 1:0.5, and the unit of the solid-liquid ratio is g / mL;

[0106] The stirring speed is 300 rpm, the temperature is 50°C, and the time is 60 min.

[0107] (3) The volatile impurities are absorbed using activated carbon.

[0108] Example 3

[0109] This invention provides a method for modifying solid ammonium sulfate used in the semiconductor industry, the modification method comprising:

[0110] (1) Solid ammonium sulfate for the semiconductor industry with an average particle size of 2 mm is air-classified to obtain ammonium sulfate particles and volatile impurities;

[0111] The gas used in the air separation is nitrogen, with a temperature of 80°C and a gas flow rate of 0.8 m / s;

[0112] (2) Ammonium sulfate granules and carboxylic acid crystallization agent are stirred and mixed in deionized water to form a slurry. The wet material is obtained by centrifugation and then vacuum dried at a vacuum degree of -0.09MPa, a temperature of 80℃ and a time of 2h to obtain crystallized ammonium sulfate. The sodium content of the obtained crystallized ammonium sulfate is ≤0.05wt%, the heavy metal content is ≤2ppm and the volatile impurity content is ≤0.005%.

[0113] The carboxylic acid crystallization agent is citric acid; the amount of the carboxylic acid crystallization agent is 0.8 wt% of the ammonium sulfate particles;

[0114] The solid-liquid ratio of the slurry is 1:1, and the unit of the solid-liquid ratio is g / mL;

[0115] The mixing speed is 500 rpm, the temperature is 60°C, and the mixing time is 40 min;

[0116] (3) The volatile impurities are absorbed using activated carbon.

[0117] Example 4

[0118] This invention provides a method for modifying solid ammonium sulfate in the semiconductor industry. Except for the air classification temperature of 50°C, the method is the same as in Example 1.

[0119] Example 5

[0120] This invention provides a method for modifying solid ammonium sulfate in the semiconductor industry. Except for the air classification temperature of 90°C, the method is the same as in Example 1.

[0121] Example 6

[0122] This invention provides a method for modifying solid ammonium sulfate for the semiconductor industry. Except that the amount of carboxylic acid crystallization agent used is 0.1 wt% of the ammonium sulfate particles, the rest is the same as in Example 1.

[0123] Example 7

[0124] This invention provides a method for modifying solid ammonium sulfate for the semiconductor industry. Except that the amount of carboxylic acid crystallization agent used is 1 wt% of the ammonium sulfate particles, the method is the same as in Example 1.

[0125] Example 8

[0126] This invention provides a method for modifying solid ammonium sulfate for the semiconductor industry. Except for the vacuum drying temperature of 50°C, the method is the same as in Example 1.

[0127] Example 9

[0128] This invention provides a method for modifying solid ammonium sulfate for the semiconductor industry. Except for the vacuum drying temperature of 90°C, the method is the same as in Example 1.

[0129] Performance Characterization

[0130] The critical relative humidity of the transcrystalline ammonium sulfate obtained in the above examples and whether it deliquesces and clumps after 30 days of storage were measured. The results are shown in Table 1.

[0131] The test method for critical relative humidity is as follows: take transcrystalline ammonium sulfate and place it in a constant temperature environment of 25℃±1℃, and equilibrate with the closed humidity system formed by the saturated salt solution for 24 hours. Weigh the sample weight gain rate. When the weight gain rate exceeds 5% or the sample shows obvious deliquescence, the relative humidity of the corresponding salt solution is the critical relative humidity. The lowest value is taken as the final result.

[0132] Test method for presence of deliquescence and clumping after 30 days: Take transcrystalline ammonium sulfate and spread it in an open polyethylene container with a thickness of 5 mm. Place it in a constant temperature and humidity chamber at 25℃±1℃ and relative humidity of 85±2% and let it stand for 30 days. After the period, observe whether clumping occurs. If lumps appear, sieve them with a 10-mesh standard sieve and record the mass percentage of the residue on the sieve. If the percentage is <5wt%, it is recorded as no deliquescence or clumping. If the percentage is 5wt% to 20wt%, it is recorded as slight clumping. If the percentage is >20%, it is recorded as severe clumping.

[0133] Table 1

[0134] Critical relative humidity (%) Does it deliquesce and clump after 30 days? Example 1 88 No deliquescence or agglomeration was observed (2.1 wt%). Example 2 85 No deliquescence or agglomeration was observed (3.5 wt%). Example 3 87 No deliquescence or agglomeration was observed (2.8 wt%). Example 4 80 Slight clumping (12.3 wt%) Example 5 78 Slight clumping (18.5 wt%) Example 6 82 Severe clumping (25.6 wt%) Example 7 81 Severe clumping (28.3 wt%) Example 8 83 Slight clumping (15.7 wt%) Example 9 80 Slight clumping (19.2 wt%)

[0135] In summary, the modification method provided by this invention uses air classification to fluidize the ammonium sulfate solid, allowing volatile impurities to be carried out with the gas, facilitating subsequent adsorption by activated carbon. The purified ammonium sulfate particles are mixed with a carboxylic acid crystallization agent, inducing a change in the crystal growth direction of the ammonium sulfate, transforming the original orthorhombic crystal system into a more stable cubic crystal system, reducing surface energy and hygroscopicity. The final obtained crystallized ammonium sulfate has a sodium content ≤0.05wt%, a heavy metal content ≤2ppm, a volatile impurity content ≤0.005%, a cubic crystal morphology, a critical relative humidity of ≥85% at 25℃, and no obvious deliquescence or clumping after 30 days of storage.

[0136] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for modifying solid ammonium sulfate in the semiconductor industry, characterized in that, The modification method includes: (1) In the semiconductor industry, solid ammonium sulfate is air-classified to obtain ammonium sulfate particles and volatile impurities; (2) Ammonium sulfate particles are mixed with carboxylic acid crystallizing agent and then vacuum dried to obtain crystallized ammonium sulfate.

2. The modification method according to claim 1, characterized in that, The content of volatile impurities in the solid ammonium sulfate used in the semiconductor industry is 0.01wt% to 0.2wt%. And / or, the average particle size of the ammonium sulfate solids used in the semiconductor industry is 0.5 mm to 2 mm.

3. The modification method according to claim 1 or 2, characterized in that, The temperature of the air separator is 60℃~80℃; And / or, the gas in the air separation is nitrogen and / or air; And / or, the gas flow rate of the air separation is 0.8 m / s to 1.5 m / s.

4. The modification method according to any one of claims 1 to 3, characterized in that, The volatile impurities are absorbed using activated carbon.

5. The modification method according to any one of claims 1 to 4, characterized in that, The carboxylic acid crystallization agent includes any one or a combination of at least two of citric acid, maleic acid, or adipic acid.

6. The modification method according to claim 5, characterized in that, The amount of the carboxylic acid crystallization agent used is 0.3wt% to 0.8wt% of the ammonium sulfate particles.

7. The modification method according to claim 5 or 6, characterized in that, The mixing in step (2) includes preparing a slurry using deionized water and stirring it.

8. The modification method according to claim 7, characterized in that, The solid-liquid ratio of the slurry is 1:0.5 to 1:1, and the unit of the solid-liquid ratio is g / mL; And / or, the stirring speed of the mixing is 300 rpm to 500 rpm; And / or, the mixing temperature is 50℃~60℃ and the time is 40min~60min.

9. The modification method according to any one of claims 1 to 8, characterized in that, The vacuum degree of the vacuum drying is -0.08MPa to -0.09MPa; And / or, the vacuum drying temperature is 70℃~80℃; And / or, the vacuum drying time is 2h to 3h.

10. The modification method according to claim 1, characterized in that, The modification method includes: (1) Semiconductor industry ammonium sulfate solid with an average particle size of 0.5 mm to 2 mm and a volatile impurity content of 0.01 wt% to 0.2 wt% is obtained by air classification to obtain ammonium sulfate particles and volatile impurities; The gas used in the air separation is nitrogen and / or air, with a temperature of 60℃~80℃ and a gas flow rate of 0.8m / s~1.5m / s; (2) Ammonium sulfate particles and carboxylic acid crystallization agent are stirred and mixed in deionized water to form a slurry, and then vacuum dried at a vacuum degree of -0.08MPa to -0.09MPa, a temperature of 70℃ to 80℃ and a time of 2h to 3h to obtain crystallized ammonium sulfate; The carboxylic acid crystallization agent includes any one or a combination of at least two of citric acid, maleic acid, or adipic acid. The amount of the carboxylic acid crystallization agent used is 0.3wt% to 0.8wt% of the ammonium sulfate particles; The solid-liquid ratio of the slurry is 1:0.5 to 1:1, and the unit of the solid-liquid ratio is g / mL; The stirring speed is 300 rpm to 500 rpm, the temperature is 50°C to 60°C, and the time is 40 min to 60 min. (3) The volatile impurities are absorbed using activated carbon; Steps (2) and (3) are not in any particular order.

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