Preparation process and use method of sodium percarbonate suspension seed crystals

Abstract

This application provides a preparation process and application method for sodium percarbonate suspension seed crystals, comprising (S1) preparation of a diluent: mixing a mother liquor, soda ash, and a dispersant to prepare a diluent; (S2) a sodium percarbonate seed crystal synthesis stage: reacting an alkaline solution with hydrogen peroxide to produce a granular seed crystal mixture with a particle size of 150µm to 210µm and a solid content of 25% to 30%; (S3) preparation of sodium percarbonate suspension seed crystals: diluting the sodium percarbonate seed crystal mixture prepared in (S2) with the diluent prepared in (S1), adding a dispersing aid, and producing a suspension seed crystal liquid with a solid content of 10% to 15%, and maintaining a constant temperature of 10°C to 20°C; (S4) directly injecting the sodium percarbonate suspension seed crystal liquid prepared in (S3) into a reactor through a pipeline to induce crystallization and prepare a sodium percarbonate product. The preparation method of this application is simple, and the suspension seed crystals can be transported by pipeline and automatically added online, which facilitates the timeliness and continuity of the reaction. Furthermore, the product produced from a uniformly dispersed suspension seed crystal liquid has better quality.

Description

Technical Field

[0001] The invention relates to a preparation process and a use method of sodium percarbonate suspension seed crystals, belonging to the technical field of inorganic chemical industry. Background Art

[0002] Sodium percarbonate, commonly known as solid hydrogen peroxide, is a novel oxygen-based bleaching agent formed from a combination of sodium carbonate and hydrogen peroxide. Its structural formula is 2Na2CO3·3H2O2, and it possesses the dual properties of sodium carbonate and hydrogen peroxide. When exposed to moisture, it releases oxygen atoms, exhibiting strong oxidizing properties, making it suitable for use as a bleaching agent and disinfectant. Because it is environmentally friendly and non-toxic, it is suitable for use as a detergent additive, food and tableware disinfectant, fruit preservation agent, medical oxygen supply agent, sewage treatment agent, and polymer polymerization initiator. It is one of the inorganic fine chemicals with promising development prospects in recent years.

[0003] Sodium percarbonate is an unstable complex formed by hydrogen bonding between sodium carbonate and hydrogen peroxide. The applicant's previously applied-for invention patent, publication number CN1463913A, titled "A Method for Preparing Sodium Percarbonate," proposes a two-step wet process. Recycled mother liquor or water is emulsified with anhydrous sodium carbonate to form a hydrated sodium carbonate suspension. A 25% to 70% aqueous hydrogen peroxide solution is then added dropwise to initiate a crystallization reaction. Sodium percarbonate seed crystals with an average particle size of 100 μm are added at the initial stage of the reaction. Crystallization aids include one or a mixture of sodium silicate, organophosphoric acid, ethylenediaminetetraacetic acid and its sodium salt, and polyacrylamide. The reaction temperature is controlled between 16 and 30°C, and the reaction time is 30 to 50 minutes. This method produces high-quality sodium percarbonate. The wet process, which incorporates seed crystals to induce crystallization, offers advantages such as maturity and ease of operation. However, with the rapid development of industrial automation upgrade goals, this operation method has gradually revealed the following limitations: (1) During the seed reaction preparation process, seed extraction takes a long time, requiring 2 to 3 hours, with low work efficiency and high energy consumption; (2) The degree of automation is low, and dedicated shovelers and feeders are required to add seed crystals regularly; (3) Manual confirmation of seed addition may result in omissions or delays, which is not conducive to the timeliness and continuity of the reaction. Summary of the Invention

[0004] To solve the above problems, the present invention proposes a method for preparing sodium percarbonate suspended crystal seeds with automatic online addition, the purpose of which is to simplify the preparation method and feeding method of the crystal seeds, reduce energy consumption, improve the degree of production automation, optimize the integrity and continuity of the reaction process, and improve product quality to a certain extent.

[0005] The present application proposes a preparation process and a method for using sodium percarbonate suspension seed crystals, comprising the following steps: (S1) preparation of a diluent: mixing a mother liquor, soda ash and a dispersant to prepare a diluent, wherein the mass ratio of the mother liquor: the soda ash: the dispersant is 62-100: 3.3-10: 1, and the mother liquor comprises 8.0%-10.0% soda ash; 0.5%-1.5% hydrogen peroxide; 17%-22% salt, and the balance is water; (S2) synthesis of sodium percarbonate seed crystals: mixing the mother liquor with soda ash, sodium chloride and water to prepare an alkaline solution with a soda ash content of 31%-32%; mixing the hydrogen peroxide mother liquor with a crystallization aid to prepare a hydrogen peroxide solution; and then mixing the alkaline solution and the hydrogen peroxide solution to react to prepare a sodium percarbonate seed crystal mixture, wherein the sodium percarbonate seed crystal particle size is 150 µm-210 µm. µm, the solid content of the sodium percarbonate seed mixture is 25% to 30%; (S3) preparation of sodium percarbonate suspended seed crystals: diluting the sodium percarbonate seed mixture prepared in (S2) with the diluent prepared in (S1), and adding a dispersing aid, the amount of the dispersant added is 1% to 3% of the amount of soda ash, to prepare a sodium percarbonate suspended seed liquid with a solid content of 10% to 15%, and maintaining the sodium percarbonate suspended seed liquid at a constant temperature of 10°C to 20°C; (S4) directly injecting the sodium percarbonate suspended seed liquid prepared in (S3) into a reactor through a pipeline to induce crystallization to prepare a sodium percarbonate product, wherein the sodium percarbonate product has round particles, uniform particle size, and an active oxygen content of the product ≥13.5%; the bulk density is 800 g / L to 1000 g / L; the thermal stability is greater than 80%; and the wet stability is greater than 60%.

[0006] Furthermore, the mass ratio of the mother liquor of the alkali solution in (S2): soda ash: sodium chloride is 12-13:4.3-4.6:1.

[0007] Furthermore, the crystallization aid in the hydrogen peroxide solution in (S2) is sodium ethylenediaminetetraacetate or a mixture of sodium ethylenediaminetetraacetate and polyacrylic acid; and the component ratio of the hydrogen peroxide solution, hydrogen peroxide mother liquor: crystallization aid is 20-30:1.

[0008] Furthermore, the dispersing aid added in (S3) is selected from sodium tripolyphosphate, sodium hexametaphosphate, and sodium metasilicate pentahydrate.

[0009] Furthermore, for every 1000 kg of sodium percarbonate product produced, the input amount of sodium percarbonate suspension seed crystals is 40 to 100 kg.

[0010] Furthermore, the input amount of sodium percarbonate suspension seed crystals is 45 kg to 65 kg.

[0011] The above technical solution has the following advantages or beneficial effects: the seed preparation process does not require a filtration step, which reduces energy consumption and improves production capacity; since the suspended seed crystals can be transported by pipeline and added automatically online, it is beneficial to the timeliness and continuity of the reaction; and the product quality of the evenly dispersed suspended seed crystal liquid is better than that of the solid seed crystals added manually. DETAILED DESCRIPTION

[0012] Implementation Case 1

[0013] A preparation process and use method of sodium percarbonate suspension seed crystals, comprising the following steps:

[0014] (S1) 400 kg of mother liquor, 20 kg of soda ash, and 6 kg of sodium tripolyphosphate are introduced into a double cone mixer and mixed uniformly to prepare a dilution solution for use. The mother liquor consists of 9% soda ash; 1.0% hydrogen peroxide; 20% sodium chloride; and 70% water.

[0015] (S2) 860 kg of mother liquor (the mother liquor components are the same as those in (S1)), 300 kg of soda ash, 67 kg of sodium chloride and water are mixed to prepare an alkaline solution with a soda ash content of 31.5%; 320 kg of hydrogen peroxide with a concentration of 50% and 16 kg of sodium ethylenediaminetetraacetic acid are uniformly mixed to form a hydrogen peroxide solution, and then the alkaline solution and the hydrogen peroxide solution are put into a reactor and reacted at a constant temperature of 30°C for 35 min to prepare a sodium percarbonate seed mixture. The sodium percarbonate seed crystal particle size is 150 µm to 200 µm, and the solid content of the sodium percarbonate seed mixture is 28%.

[0016] (S3) The sodium percarbonate seed crystal mixture prepared in step (S2) is diluted with the diluent prepared in step (S1), and sodium silicate is added as a dispersing aid to prepare a uniformly dispersed sodium percarbonate seed crystal suspension having a solid content of 12% (mass). The system is maintained at a constant temperature of 15°C.

[0017] (S4) The sodium percarbonate seed suspension prepared in step (S3) is piped. The amount of sodium percarbonate seed suspension is calculated based on the required amount of seed solids. The suspension is then added directly to the reactor via a metering pump under program control. This serves as an initiator for sodium percarbonate production, guiding the reaction and eliminating manual addition steps. For every 1000 kg of finished sodium percarbonate product produced, 40 kg of suspended seed crystals are added. The resulting sodium percarbonate product has an active oxygen content of 13.9%, a bulk density of 897 g / L, a thermal stability of 83%, and a wet stability of 70%.

[0018] Example 2

[0019] A preparation process and use method of sodium percarbonate suspension seed crystals, comprising the following steps:

[0020] (S1) 400 kg of mother liquor, 32 kg of soda ash and 6.4 kg of sodium hexametaphosphate are added to a double cone mixer and mixed uniformly for later use. The mother liquor comprises 8% soda ash, 1.5% hydrogen peroxide, 22% sodium chloride and 68.5% water.

[0021] (S2) 865 kg of mother liquor (the mother liquor components are the same as those of the mother liquor in step (S1)), 303 kg of soda ash, 68 kg of sodium chloride and water are mixed to prepare an alkaline solution with a soda ash content of 31.5%; 458.6 kg of hydrogen peroxide (with a concentration of 35%), 16.1 kg of sodium ethylenediaminetetraacetic acid and polyacrylic acid are evenly mixed, and then the alkaline solution and hydrogen peroxide solution are put into a reactor, and the reaction is carried out at a constant temperature of 30° C. for 35 minutes to obtain a sodium percarbonate seed crystal mixture, wherein the sodium percarbonate seed crystal particle size is 120 μm to 170 μm, and the sodium percarbonate seed crystal mixture has a solid content of 29.8%.

[0022] (S3) Using the diluent prepared in the above step (S1) to dilute the sodium percarbonate seed crystal mixture prepared in (S2), adding sodium silicate as a dispersing aid to prepare a uniformly dispersed suspension with a solid content of 10.5% (mass), the system is maintained at a constant temperature of 18°C.

[0023] (S4) The sodium percarbonate seed suspension prepared in step (S3) is piped. The amount of sodium percarbonate seed suspension is calculated based on the required amount of seed solids. The suspension is then added directly to the reactor via a metering pump under program control. This serves as an initiator for sodium percarbonate production, guiding the sodium percarbonate reaction and eliminating manual addition steps. For every 1000 kg of finished sodium percarbonate product produced, 55 kg of suspended seed crystals are added. The resulting sodium percarbonate product has an active oxygen content of 13.6%, a bulk density of 952 g / L, a thermal stability of 86%, and a wet stability of 75%.

[0024] Example 3

[0025] A preparation process and use method of sodium percarbonate suspension seed crystals, comprising the following steps:

[0026] (S1) 400 kg of mother liquor, 40 kg of soda ash and 4 kg of sodium metasilicate pentahydrate are added to a double cone mixer and mixed evenly for later use. The mother liquor comprises 10% soda ash, 0.5% hydrogen peroxide, 17% sodium chloride and 72.5% water.

[0027] (S2) 850 kg of mother liquor (the mother liquor components are the same as those of the mother liquor in step (S1)), 295 kg of soda ash, 66 kg of sodium chloride and water are mixed to prepare an alkaline solution with a soda ash content of 31.4%; 452.9 kg of hydrogen peroxide (with a concentration of 35%) and 15.8 kg of sodium ethylenediaminetetraacetic acid are evenly mixed, and then the alkaline solution and hydrogen peroxide solution are put into a reactor, and the reaction is carried out at a constant temperature of 25°C for 38 minutes to obtain a sodium percarbonate seed crystal mixture, wherein the sodium percarbonate seed crystal particle size is 155 µm to 210 µm, and the solid content of the sodium percarbonate seed crystal mixture is 25.3%.

[0028] (S3) Using the diluent prepared in the above step (S1) to dilute the sodium percarbonate seed crystal mixture prepared in (S2), adding sodium silicate as a dispersing aid, a uniformly dispersed suspension having a solid content of 14.8% (mass) is prepared, and the system is maintained at a constant temperature of 12°C.

[0029] (S4) The sodium percarbonate seed suspension prepared in step (S3) is piped. The amount of sodium percarbonate seed suspension is calculated based on the required amount of seed solids. The suspension is then added directly to the reactor via a metering pump under program control, acting as an initiator for sodium percarbonate production and guiding the reaction, thereby eliminating manual addition steps. For every 1000 kg of finished sodium percarbonate product produced, 60 kg of suspended seed crystals are added. The resulting sodium percarbonate product has an active oxygen content of 14.1%, a bulk density of 989 g / L, a thermal stability of 82%, and a wet stability of 73%.

[0030] Although the embodiments of the present application have been shown and described above, it is understood that the above embodiments are illustrative and should not be construed as limiting the present application. Various changes and modifications may be made to the present application without departing from the spirit and scope of the present application, and such changes and modifications fall within the scope of the present application for which protection is sought.

Claims

1. A method for using sodium percarbonate suspension seed crystals, characterized in that The steps include: (S1) Preparation of dilution liquid: Mixing mother liquor, soda ash and dispersant to prepare dilution liquid, wherein the mass ratio of mother liquor: soda ash: dispersant is 62-100:3.3-10:1, wherein the mother liquor comprises 8.0%-10.0% soda ash; 0.5%-1.5% hydrogen peroxide; 17%-22% salt, and the balance is water; (S2) Synthesis of sodium percarbonate seed crystals: mixing the mother liquor with soda ash, sodium chloride, and water to prepare an alkaline solution having a soda ash content of 31% to 32%; mixing the hydrogen peroxide mother liquor with a crystallization aid to prepare a hydrogen peroxide solution; and then mixing the alkaline solution and the hydrogen peroxide solution to react to prepare a sodium percarbonate seed crystal mixture, wherein the sodium percarbonate seed crystals have a particle size of 150 μm to 210 μm and a solid content of 25% to 30%; (S3) Preparation of sodium percarbonate seed suspension: diluting the sodium percarbonate seed mixture prepared in (S2) with the diluent prepared in (S1), and adding a dispersing aid in an amount of 1% to 3% of the amount of soda ash to prepare a sodium percarbonate seed suspension liquid with a solid content of 10% to 15%, and maintaining the sodium percarbonate seed suspension liquid at a constant temperature of 10°C to 20°C; (S4) injecting the sodium percarbonate suspension seed liquid prepared in (S3) directly into a reactor through a pipeline to induce crystallization to prepare a sodium percarbonate product, wherein the sodium percarbonate product has round particles, uniform particle size, and an active oxygen content of ≥13.5%; a bulk density of 800 g / L to 1000 g / L; a thermal stability greater than 80%; and a wet stability greater than 60%.

2. the using method of a kind of sodium percarbonate suspension type crystal seed according to claim 1, is characterized in that: The mass ratio of the mother liquor of the alkali solution (S2): soda ash: sodium chloride is 12-13:4.3-4.6:

1.

3. the using method of a kind of sodium percarbonate suspension type crystal seed according to claim 1, is characterized in that: The crystallization aid in the hydrogen peroxide solution in (S2) is sodium ethylenediaminetetraacetate or a mixture of sodium ethylenediaminetetraacetate and polyacrylic acid; the component ratio of the hydrogen peroxide solution is hydrogen peroxide mother liquor: crystallization aid is 20-30:

1.

4. the using method of a kind of sodium percarbonate suspension type crystal seed according to claim 1, is characterized in that: The dispersing aid added in (S3) is selected from sodium tripolyphosphate, sodium hexametaphosphate, and sodium metasilicate pentahydrate.

5. the using method of a kind of sodium percarbonate suspension type crystal seed according to claim 1, is characterized in that: For every 1000 kg of sodium percarbonate finished product produced, the input amount of sodium percarbonate suspension seed crystals is 40 to 100 kg.

6. The method for using a sodium percarbonate suspension crystal seed according to claim 5, wherein: The input amount of sodium percarbonate suspension seed crystals is 45 kg to 65 kg.