A crystal seed suitable for a crystallization fluidized bed and its preparation method and application

Abstract

The present invention provides a novel crystal seed suitable for a crystallization fluidized bed, a preparation method thereof, and an application thereof. The performance and function of the crystal seed are optimized and improved, the crystallization rate is accelerated, the crystallization speed is shortened, and the crystal nuclei can be effectively fixed on the surface of the crystal seed during the hardness removal process, thereby avoiding the formation of microcrystalline nuclei in the water body, reducing scaling, and accelerating the start-up speed of crystallization. In addition, the preparation method of the novel crystal seed is simple and the performance is stable. According to tests, when the novel crystal seed prepared by the present invention is put into a crystallization fluidized bed reactor for a hardness removal process, the hardness removal rate can reach 85%-95%.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and further relates to a crystal seed suitable for a crystallization fluidized bed, a preparation method thereof, and an application thereof. Background Art

[0002] Fluidized bed crystallization granulation technology is currently being used to replace coagulation, sedimentation, and dehydration processes, removing precipitable ions from wastewater through crystallization. It is suitable for wastewaters with high hardness, heavy metal content, and fluoride content, and is widely used in industrial circulating water. In particular, high-salinity wastewater from the coal chemical industry (such as cooling water and RO concentrate) is characterized by high hardness and salinity, approximately 1800-2200 mg / L, for advanced treatment and zero-discharge. Chemical pretreatment is typically used for softening. Fluidized bed crystallization granulation utilizes fluidization principles to enhance the crystallization process. By pre-adding a crystallization carrier (seed crystals) and then adding chemicals to the water, calcium ions in the water react to form calcium carbonate crystals, which adhere to the surface of the pre-added carrier (seed crystals), reducing the water's hardness. When the crystals reach a certain particle size, they are discharged. Compared with traditional chemical precipitation, the advantages of this method include: relatively high calcium ion hardness removal rate and stable effluent water quality; a single reagent that can be accurately added to achieve reagent reduction without generating chemical sludge and other by-products; it can meet high-load and high-flow conditions and occupies a small area; no cleaning waste liquid is generated during the process, and there is no wastewater backflow, thus avoiding additional system processing load; the generated calcium carbonate particles can be recycled as a desulfurization agent and other products.

[0003] Currently, the crystallization fluidized bed processes on the market are mostly centered on the optimization of the reactor, the optimization of the water and drug distribution structure, and the control system, while ignoring the role of the seed in the reaction system. The seeds used in the industrial application of the crystallization fluidized bed are mostly industrial crude product crystals obtained by grinding and screening, such as quartz sand, calcite, dolomite, apatite, etc. Although such industrial crude crystals are relatively easy to obtain, they usually contain certain impurities, resulting in a high impurity content in the product, and the impurities may induce secondary nucleation, resulting in needle-shaped, flaky and other crystal forms. In addition, in addition to the grinding and screening steps, the seed preparation method lacks the processing of washing and dissolving processes, resulting in a large range of seed particle size distribution, a large number of fine crystals in the seed product, and an uneven crystal shape, resulting in uneven particle size of the crystal product, and the product is prone to agglomeration and growth, making it difficult to recover the product during separation, resulting in economic losses. The general principles for selecting seed are: strong ability to induce precipitation reaction, good adhesion to the precipitate, good sedimentation performance, good fluidization, stable properties, high strength, and non-magnetic.

[0004] In addition to seed selection, from the perspective of crystallization principles, during the crystallization process, solutes, driven by supersaturation, begin to form microcrystalline nuclei. These nuclei migrate toward the pre-formed nuclei and accumulate in an orderly manner on their surfaces, causing the nuclei to grow and form crystals. The particle size and distribution of the resulting crystal product are primarily determined by the nucleation rate and crystal growth rate, as well as the average residence time of the crystals in the reactor. In highly supersaturated solutions, the nucleation rate is high, primarily used to generate new nuclei. The resulting crystals are uneven, small, and even amorphous. In low-supersaturated solutions, the ratio of the crystal growth rate to the nucleation rate is greater, resulting in larger crystals with more complete shapes. Additional seed crystals act similarly to pre-formed nuclei, increasing the crystal growth rate, but they cannot inhibit the nucleation rate in the water column.

[0005] Therefore, fluidized bed crystallization typically maintains a relatively low supersaturation level, keeping the rate of nucleation much lower than the rate of crystal growth. This results in crystals of uniform shape and size. However, this also results in a slower crystallization rate, potentially leading to scaling within the reactor and a host of other issues. This issue currently hinders the widespread industrial application of fluidized bed crystallization.

[0006] Chinese patent CN 110550747 B provides a method and device for removing hardness from high-hardness water. This method primarily maintains the ion concentration product in the reaction system at a low level by controlling the dosing method. Under low ion concentration product conditions, homogeneous crystallization in the reaction system is effectively suppressed, and calcium and magnesium ions and precipitant ions form heterogeneous surface crystallization on the seed crystal surface in the form of crystal-forming ions, significantly reducing the yield of microcrystals. A small amount of microcrystals will re-enter the crystallization zone with the circulating water flow and serve as seed crystals. Although this method effectively reduces the formation of microcrystal nuclei, it is only applicable to wastewater with a total hardness of less than 300 mg / L and cannot solve the problem of high-hardness wastewater.

[0007] The above patents mainly optimize the structural design and system of the crystallization fluidized bed, but ignore the optimization of the seed crystals. Chinese patent CN 115159765 B provides a magnetic crystal-inducing material, its preparation method, and a water treatment process for removing hardness and turbidity using the same. The method prepares a ferrite-type composite metal oxide loaded with scaling salt micron particles as a crystal-inducing material, and disperses them into a precipitation reaction system under alkaline conditions to induce crystallization and remove hardness. The process adds a magnetic crystal-inducing material to the precipitation reaction system to promote precipitation crystallization and rapid sedimentation, thereby shortening the process time, and then realizing magnetic separation and recovery of the crystal-inducing material. Although this magnetic seed crystal can accelerate the rate of precipitation crystallization and material recovery, the magnetic material is easily attracted and combined with each other by magnetic action under the interference of the magnetic field, resulting in the production of larger particles or agglomerates, which is not conducive to the fluidized reaction effect, and the resulting scaling problem will also increase the maintenance cost of the reactor.

[0008] Therefore, it is urgent to design a seed crystal to comprehensively solve the problems existing in the existing technology. Summary of the Invention

[0009] In response to the problems of slow crystallization rate and easy formation of microcrystalline nuclei in the crystallization fluidized bed hardness removal process in the prior art, the purpose of the present invention is to provide a crystal seed suitable for a crystallization fluidized bed and its preparation method and application, optimize and improve the performance and function of the crystal seed, accelerate the crystallization rate, shorten the crystallization speed, and effectively fix the crystal nucleus on the surface of the crystal seed during the hardness removal process, avoid the formation of microcrystalline nuclei in the water body, reduce scaling, and accelerate the start-up speed of crystallization. Moreover, the preparation method of the crystal seed is simple and the performance is stable. After testing, the crystal seed prepared by the present invention is put into a crystallization fluidized bed reactor for hardness removal process, and its hardness removal rate can reach 85%-95%.

[0010] In order to achieve the above object, the present invention provides the following technical solutions:

[0011] A seed crystal suitable for a crystallization fluidized bed, characterized in that the seed crystal is composed of a solid mixture, a strong base and an adhesive, the solid mixture including components in the following mass ratio: calcium-containing component: silicon-containing component: aluminum-containing component = 1: (0.45-0.65): (0.15-0.35); the mass ratio of the solid mixture to a mixed solution of the strong base and the adhesive is 1: (0.32-0.56).

[0012] In some embodiments, the calcium-containing component is one or more of calcium oxide, calcium hydroxide, calcium carbonate or calcium silicate; the silicon-containing component is one or more of silicon dioxide, sodium silicate or calcium silicate; and the aluminum-containing component is one or more of aluminum oxide, aluminum sulfate or sodium aluminate.

[0013] In some embodiments, the strong base is one or more of sodium hydroxide or potassium hydroxide; the binder is one or more of sodium silicate liquid or aluminum phosphate liquid.

[0014] The present invention also provides a method for preparing the above-mentioned seed crystal, comprising the following steps:

[0015] S1, measuring each component according to the composition ratio of the seed crystal, drying and sieving the calcium-containing component, the silicon-containing component, and the aluminum-containing component, and then mixing them to obtain a solid mixture;

[0016] S2, dissolving the strong base in water to form a strong base solution, adding the adhesive and mixing uniformly to form a mixed solution, mixing the solid mixture with the mixed solution, and stirring uniformly to obtain a slurry;

[0017] S3, placing the slurry into a fixed mold for aging until it is completely hardened to obtain a solid sample;

[0018] S4, demoulding the solid sample and placing it in an oven for heat preservation and activation;

[0019] S5. Crushing, screening, washing and drying the activated solid sample to obtain the seed crystal.

[0020] In some embodiments, in step S2, the concentration of the strong base solution is 25%-40% vol.

[0021] In some embodiments, in step S2, the stirring time is 10-20 minutes; in step S3, the aging time is 12-24 hours, and the aging temperature is room temperature; in step S4, the activation temperature is 100-150° C., and the activation time is 1-3 days.

[0022] In some embodiments, in step S5, the particle size of the crushed solid sample is 0.01-5 mm; the particle size of the sieved solid sample is 0.18-0.55 mm; and the drying temperature is 80-105°C.

[0023] In some embodiments, in step S3, the fixed mold is a hollow plastic mold.

[0024] The present invention also provides the application of the crystals, and the seed crystals are applied in a crystallization fluidized bed reactor for treating high-hardness wastewater.

[0025] Compared with the prior art, the present invention can bring the following beneficial effects:

[0026] 1. The seed crystals provided by the present invention are high-calcium seed crystal materials based on aluminosilicate. Compared with commercially available seed crystal materials, they have a porous structure and high surface energy. They contain a large number of hydroxyl functional groups on the surface and in the pores of the seed crystal material, and have strong adsorption capacity. When used in a crystallization fluidized bed reactor, these seed crystals can effectively reduce the hardness of wastewater. According to tests, the hardness removal rate of these crystals reaches 85%-95%.

[0027] 2. The hydroxyl functional groups contained in the seed crystals provided by the present invention can quickly bind to calcium, magnesium and other ions in the wastewater, and firmly adsorb and fix them on the surface of the seed crystals in the form of chemical bonds, making them difficult to fall off, effectively reducing the formation of microcrystalline nuclei under conditions of excessive hardness and avoiding the occurrence of scaling;

[0028] 3. The seed crystals provided by the present invention are used in a crystallization fluidized bed reactor. They can release a certain amount of hydroxide ions in the water, thereby increasing the pH value of the water and reducing the amount of alkali added by 35%-40%, thereby reducing the cost of reagents.

[0029] 4. The seed crystals provided by the present invention have high wear resistance and crushing strength, the hydroxyl components are densely attached and firmly bonded, not easily lost, and have a long service life, thereby reducing the cost of the crystallization fluidized bed hardness removal process;

[0030] 5. The seed crystals provided by the present invention have a high crystallization rate. Compared with existing seed crystal materials such as quartz sand, the crystallization rate is increased by 40%, which greatly shortens the crystallization time, shortens the reaction time for removing wastewater hardness, and reduces the operating cost of the equipment;

[0031] 6. The seed crystal preparation method provided by the present invention is simple, has a short cycle, low cost, stable properties, and good hardness removal effect, and has industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The preferred embodiments will be described below in a clear and understandable manner with reference to the accompanying drawings to further illustrate the above-mentioned characteristics, technical features, advantages and implementation methods of the present invention.

[0033] Figure 1 The present invention provides a flow chart of the method for preparing seed crystals.

[0034] Figure 2 The different crystal seeds provided by the present invention are applied to a crystallization fluidized bed reactor to measure the change in average crystal particle size over reaction time. DETAILED DESCRIPTION

[0035] The following examples are only used to illustrate the technical solution of the present invention more clearly, and are not intended to limit the scope of protection of the present invention.

[0036] Example 1

[0037] The present invention provides a seed crystal suitable for a fluidized bed crystallization. The seed crystal is composed of a solid mixture, a strong base, and an adhesive. Specifically:

[0038] The above-mentioned solid mixture comprises the following components in mass ratio:

[0039] Calcium-containing component: silicon-containing component: aluminum-containing component = 1: (0.45-0.65): (0.15-0.35).

[0040] The mass ratio of the solid mixture to the mixed solution of the strong base and the adhesive is 1:(0.32-0.56).

[0041] Furthermore, the calcium-containing component is one or more of calcium oxide, calcium hydroxide, calcium carbonate or calcium silicate.

[0042] The silicon-containing component is one or more of silicon dioxide, sodium silicate or calcium silicate;

[0043] The aluminum-containing component is one or more of aluminum oxide, aluminum sulfate or sodium metaaluminate;

[0044] The above-mentioned strong base is one or more of sodium hydroxide or potassium hydroxide;

[0045] The above-mentioned binder is one or more of sodium silicate liquid or aluminum phosphate liquid.

[0046] Example 2

[0047] On the basis of Example 1, the present invention also provides a method for preparing the above-mentioned seed crystals suitable for a crystallization fluidized bed, such as Figure 1 As shown, the following steps are included:

[0048] S1. Measure each component according to the composition ratio of the seed crystal in Example 1, dry and sieve the calcium-containing component, the silicon-containing component, and the aluminum-containing component, and then mix them to obtain a solid mixture;

[0049] S2. dissolving a strong base in water to form a strong base solution, adding a binder and mixing uniformly to form a mixed solution, mixing the solid mixture with the mixed solution, and stirring uniformly to obtain a slurry;

[0050] S3, placing the slurry into a fixed mold for aging until it is completely hardened to obtain a solid sample;

[0051] S4, demoulding the solid sample and placing it in an oven for heat preservation and activation;

[0052] S5. Crushing, sieving, washing and drying the activated solid sample to obtain seed crystals.

[0053] In some embodiments, in step S2, the concentration of the strong base solution is 25%-40% vol, and the stirring time is 10-20 min.

[0054] In some embodiments, in step S3, the aging time is 12-24 hours, and the aging temperature is room temperature.

[0055] Furthermore, the above-mentioned fixed mold is a hollow plastic mold, and the shape of the hollow mold is a cube, a cylinder, etc. The shape of the fixed mold is not limited here.

[0056] In some embodiments, in step S4, the activation temperature is 100-150° C., and the activation time is 1-3 days.

[0057] In some embodiments, in step S5, crushing refers to crushing the solid sample into amorphous solid particles by a crusher, and the particle size of the crushed solid sample is 0.01-5 mm.

[0058] The above-mentioned screening refers to screening the crushed solid sample through a screening machine to screen out target particles (particle size is 30-80 mesh). The particle size of the solid sample after screening is 0.18-0.55mm;

[0059] The above-mentioned washing refers to washing away the powder on the surface of the sieved solid sample with clean water, so that there is no impurity on the surface of the solid sample and the growth of the crystal is not affected.

[0060] The above-mentioned drying refers to placing the washed solid sample in an oven to remove moisture, and the drying temperature is 80-105°C.

[0061] The calcium-rich seed crystals based on aluminosilicate prepared by the above-mentioned preparation method have a porous interface and high surface energy compared with commercially available seed crystal materials. The large number of hydroxyl functional groups contained in the surface and pores give it a strong adsorption capacity.

[0062] Example 3

[0063] Based on Example 1 and Example 2, the present invention also provides the application of the above-mentioned seed crystals. Specifically:

[0064] A certain amount of the above-mentioned crystal seeds are added to the crystallization fluidized bed for treating high-hardness wastewater. The surface and voids of the crystal seeds contain a large number of hydroxyl functional groups, which can quickly combine with metal ions such as calcium and magnesium in the wastewater, and firmly adsorb and fix them on the surface of the crystal seeds in the form of chemical bonds. The crystals continue to grow to form crystals, and the hardness of the wastewater is reduced accordingly.

[0065] According to tests, the seed crystals provided by the present invention can be used in a crystallization fluidized bed to effectively remove the hardness of high-hardness wastewater, and the hardness removal rate can reach 85%-95%.

[0066] In order to better understand and apply the above scheme and effectively demonstrate the corresponding benefits, the seeds suitable for the crystallization fluidized bed provided by the present invention, as well as their preparation method and application are further described below in conjunction with specific embodiments.

[0067] Example 4

[0068] S1. Weigh 1000 g of calcium oxide powder, 450 g of silicon dioxide powder, and 150 g of aluminum oxide powder, respectively, and evenly mix the three raw materials to obtain a solid mixture;

[0069] S2. Prepare a strong alkaline solution with a concentration of 30% vol by hydrogenation, uniformly mix the solid mixture, the strong alkaline solution and the sodium silicate liquid in a mass ratio of 1:0.28:0.28, and continue stirring for 10 minutes to obtain a slurry;

[0070] S3. Pour the slurry into a 10x10x10cm 3 Place the sample in a cubic hollow mold and allow it to stand at room temperature for 24 hours until it is completely hardened to obtain a solid sample.

[0071] S4. De-molding the solid sample, taking it out, placing it in an oven, and activating it at 150°C for 3 days;

[0072] S5. The activated solid sample is crushed into coarse particles of different sizes. Solid particles with a particle size of 0.18-0.55 mm are screened out by a sieving machine. The solid particles are rinsed with clean water and then placed in an oven. After drying at 105° C. for 24 hours, SAC-1 seed crystals are obtained.

[0073] The SAC-1 seed crystal was used in a crystallization fluidized bed reactor for treating high-hardness wastewater from coal gasification in a certain enterprise:

[0074] The inlet water hardness was set to about 1800 mg / L, the amount of SAC-1 seed crystals added was 15% of the volume of the crystallization fluidized bed reactor, and the reaction time was 25 days. The hardness removal effect and the final crystal particle size are shown in Table 1, and the change of the average crystal particle size with the reaction time is shown in Table 2. Figure 1 .

[0075] Example 5

[0076] Reference Example 4, except that:

[0077] In step S1, 1000 g of calcium oxide powder, 550 g of silicon dioxide powder, and 150 g of aluminum oxide powder are weighed respectively, and the three raw materials are uniformly mixed to obtain a solid mixture;

[0078] In step S2, the solid mixture, the strong base solution and the sodium silicate liquid are uniformly mixed in a mass ratio of 1:0.26:0.26;

[0079] The remaining preparation steps were the same as those in Example 4 to obtain SAC-2 seed crystals.

[0080] The application process of SAC-2 seed crystals is the same as that of Example 4. The hardness removal effect and the final crystal particle size are shown in Table 1. The change of the average crystal particle size with the reaction time is shown in Table 1. Figure 1 .

[0081] Example 6

[0082] Reference Example 4, except that:

[0083] In step S1, 1000 g of calcium oxide powder, 650 g of silicon dioxide powder, and 150 g of aluminum oxide powder are weighed respectively, and the three raw materials are uniformly mixed to obtain a solid mixture;

[0084] In step S2, the solid mixture, the strong base solution and the sodium silicate liquid are uniformly mixed in a mass ratio of 1:0.25:0.25;

[0085] The remaining preparation steps were the same as those in Example 4 to obtain SAC-3 seed crystals.

[0086] The application process of SAC-3 seed crystals is the same as that of Example 4. The hardness removal effect and the final crystal particle size are shown in Table 1. The change of the average crystal particle size with the reaction time is shown in Table 1. Figure 1 .

[0087] Example 7

[0088] Reference Example 4, except that:

[0089] In step S1, 1000 g of calcium oxide powder, 450 g of silicon dioxide powder, and 250 g of aluminum oxide powder are weighed respectively, and the three raw materials are uniformly mixed to obtain a solid mixture;

[0090] In step S2, the solid mixture, the strong base solution and the sodium silicate liquid are uniformly mixed in a mass ratio of 1:0.26:0.26;

[0091] The remaining preparation steps were the same as those in Example 4 to obtain SAC-4 seed crystals.

[0092] The application process of SAC-4 seed crystals is the same as that of Example 4. The hardness removal effect and the final crystal particle size are shown in Table 1. The change of the average crystal particle size with the reaction time is shown in Table 1. Figure 1 .

[0093] Example 8

[0094] Reference Example 4, except that:

[0095] In step S1, 1000 g of calcium oxide powder, 550 g of silicon dioxide powder, and 250 g of aluminum oxide powder are weighed respectively, and the three raw materials are uniformly mixed to obtain a solid mixture;

[0096] In step S2, the solid mixture, the strong base solution and the sodium silicate liquid are uniformly mixed in a mass ratio of 1:0.25:0.25;

[0097] The remaining preparation steps were the same as those in Example 4 to obtain SAC-5 seed crystals.

[0098] The application process of SAC-5 seed crystals is the same as that of Example 4. The hardness removal effect and the final crystal particle size are shown in Table 1. The change of the average crystal particle size with the reaction time is shown in Table 1. Figure 1 .

[0099] Example 9

[0100] Reference Example 4, except that:

[0101] In step S1, 1000 g of calcium oxide powder, 650 g of silicon dioxide powder, and 250 g of aluminum oxide powder are weighed respectively, and the three raw materials are uniformly mixed to obtain a solid mixture;

[0102] In step S2, the solid mixture, the strong base solution and the sodium silicate liquid are uniformly mixed in a mass ratio of 1:0.24:0.24;

[0103] The remaining preparation steps were the same as those in Example 4 to obtain SAC-6 seed crystals.

[0104] The application process of SAC-6 seed crystals is the same as that of Example 4. The hardness removal effect and the final crystal particle size are shown in Table 1. The change of the average crystal particle size with the reaction time is shown in Table 1. Figure 1 .

[0105] Example 10

[0106] Reference Example 4, except that:

[0107] In step S1, 1000 g of calcium oxide powder, 450 g of silicon dioxide powder, and 350 g of aluminum oxide powder are weighed respectively, and the three raw materials are uniformly mixed to obtain a solid mixture;

[0108] In step S2, the solid mixture, the strong base solution and the sodium silicate liquid are uniformly mixed in a mass ratio of 1:0.25:0.25;

[0109] The remaining preparation steps were the same as those in Example 4 to obtain SAC-7 seed crystals.

[0110] The application process of SAC-7 seed crystals is the same as that of Example 4. The hardness removal effect and the final crystal particle size are shown in Table 1. The change of the average crystal particle size with the reaction time is shown in Table 1. Figure 1 .

[0111] Example 11

[0112] Reference Example 4, except that:

[0113] In step S1, 1000 g of calcium oxide powder, 550 g of silicon dioxide powder, and 350 g of aluminum oxide powder were weighed respectively, and the three raw materials were evenly mixed to obtain a solid mixture;

[0114] In step S2, the solid mixture, the strong base solution and the sodium silicate liquid are uniformly mixed in a mass ratio of 1:0.24:0.24;

[0115] The remaining preparation steps were the same as those in Example 4 to obtain SAC-8 seed crystals.

[0116] The application process of SAC-8 seed crystals is the same as that of Example 4. The hardness removal effect and the final crystal particle size are shown in Table 1. The change of the average crystal particle size with the reaction time is shown in Table 1. Figure 1 .

[0117] Example 12

[0118] Reference Example 4, except that:

[0119] In step S1, 1000 g of calcium oxide powder, 650 g of silicon dioxide powder, and 350 g of aluminum oxide powder were weighed respectively, and the three raw materials were uniformly mixed to obtain a solid mixture;

[0120] In step S2, the solid mixture, the strong base solution and the sodium silicate liquid are uniformly mixed in a mass ratio of 1:0.23:0.23;

[0121] The remaining preparation steps were the same as those in Example 4 to obtain SAC-9 seed crystals.

[0122] The application process of SAC-9 seed crystals is the same as that of Example 4. The hardness removal effect and the final crystal particle size are shown in Table 1. The change of the average crystal particle size with the reaction time is shown in Table 1. Figure 1 .

[0123] Example 13

[0124] Reference Example 4, except that:

[0125] In step S1, 1000 g of calcium oxide powder, 650 g of silicon dioxide powder, and 250 g of aluminum oxide powder are weighed respectively, and the three raw materials are uniformly mixed to obtain a solid mixture;

[0126] In step S2, the solid mixture, the strong base solution and the sodium silicate liquid are uniformly mixed in a mass ratio of 1:0.24:0.18;

[0127] The remaining preparation steps were the same as those in Example 4 to obtain SAC-10 seed crystals.

[0128] The application process of SAC-10 seed crystals is the same as that of Example 4. The hardness removal effect and the final crystal particle size are shown in Table 1. The change of the average crystal particle size with the reaction time is shown in Table 1. Figure 1 .

[0129] Example 14

[0130] Reference Example 4, except that:

[0131] In step S1, 1000 g of calcium oxide powder, 650 g of silicon dioxide powder, and 250 g of aluminum oxide powder are weighed respectively, and the three raw materials are uniformly mixed to obtain a solid mixture;

[0132] In step S2, the solid mixture, the strong base solution and the sodium silicate liquid are uniformly mixed in a mass ratio of 1:0.24:0.13;

[0133] The remaining preparation steps were the same as those in Example 4 to obtain SAC-11 seed crystals.

[0134] The application process of SAC-11 seed crystals is the same as that of Example 4. The hardness removal effect and the final crystal particle size are shown in Table 1. The change of the average crystal particle size with the reaction time is shown in Table 1. Figure 1 .

[0135] Example 15

[0136] Reference Example 4, except that:

[0137] In step S1, 1000 g of calcium oxide powder, 650 g of silicon dioxide powder, and 250 g of aluminum oxide powder are weighed respectively, and the three raw materials are uniformly mixed to obtain a solid mixture;

[0138] In step S2, the solid mixture, the strong base solution and the sodium silicate liquid are uniformly mixed in a mass ratio of 1:0.24:0.08;

[0139] The remaining preparation steps were the same as those in Example 4 to obtain SAC-12 seed crystals.

[0140] The application process of SAC-12 seed crystals is the same as that of Example 4. The hardness removal effect and the final crystal particle size are shown in Table 1. The change of the average crystal particle size with the reaction time is shown in Table 1. Figure 1 .

[0141] Example 16

[0142] Reference Example 4, except that:

[0143] In step S1, 1000 g of calcium oxide powder, 650 g of silicon dioxide powder, and 150 g of aluminum oxide powder are weighed respectively, and the three raw materials are uniformly mixed to obtain a solid mixture;

[0144] In step S2, the solid mixture, the strong base solution and the aluminum phosphate liquid are uniformly mixed in a mass ratio of 1:0.25:0.14;

[0145] The remaining preparation steps were the same as those in Example 4 to obtain SAC-13 seed crystals.

[0146] The application process of SAC-13 seed crystals is the same as that of Example 4. The hardness removal effect and the final crystal particle size are shown in Table 1. The change of the average crystal particle size with the reaction time is shown in Table 1. Figure 1 .

[0147] Example 17

[0148] Reference Example 4, except that:

[0149] In step S1, 1000 g of calcium oxide powder, 650 g of silicon dioxide powder, and 150 g of aluminum oxide powder are weighed respectively, and the three raw materials are uniformly mixed to obtain a solid mixture;

[0150] In step S2, the solid mixture, the strong base solution and the aluminum phosphate liquid are uniformly mixed in a mass ratio of 1:0.25:0.08;

[0151] The remaining preparation steps were the same as those in Example 4 to obtain SAC-14 seed crystals.

[0152] The application process of SAC-14 seed crystals is the same as that of Example 4. The hardness removal effect and the final crystal particle size are shown in Table 1. The change of the average crystal particle size with the reaction time is shown in Table 1. Figure 1 .

[0153] Example 18

[0154] Reference Example 4, except that:

[0155] In step S1, 1000 g of calcium oxide powder, 650 g of silicon dioxide powder, and 150 g of aluminum oxide powder are weighed respectively, and the three raw materials are uniformly mixed to obtain a solid mixture;

[0156] In step S2, the solid mixture, the strong alkaline solution, the sodium silicate liquid and the aluminum phosphate liquid are uniformly mixed in a mass ratio of 1:0.25:0.03:0.08;

[0157] The remaining preparation steps were the same as those in Example 4 to obtain SAC-15 seed crystals.

[0158] The application process of SAC-15 seed crystals is the same as that of Example 4. The hardness removal effect and the final crystal particle size are shown in Table 1. The change of the average crystal particle size with the reaction time is shown in Table 1. Figure 1 .

[0159] Example 19

[0160] Reference Example 4, except that:

[0161] In step S1, 1000 g of calcium oxide powder, 650 g of silicon dioxide powder, and 150 g of aluminum oxide powder are weighed respectively, and the three raw materials are uniformly mixed to obtain a solid mixture;

[0162] In step S2, the solid mixture, the strong alkaline solution, the sodium silicate liquid and the aluminum phosphate liquid are uniformly mixed in a mass ratio of 1:0.25:0.08:0.08;

[0163] The remaining preparation steps were the same as those in Example 4 to obtain SAC-16 seed crystals.

[0164] The application process of SAC-16 seed crystals is the same as that of Example 4. The hardness removal effect and the final crystal particle size are shown in Table 1. The change of the average crystal particle size with the reaction time is shown in Table 1. Figure 1 .

[0165] Example 20

[0166] Reference Example 4, except that:

[0167] In step S1, 1000 g of calcium oxide powder, 650 g of silicon dioxide powder, and 150 g of aluminum oxide powder are weighed respectively, and the three raw materials are uniformly mixed to obtain a solid mixture;

[0168] In step S2, the solid mixture, the strong alkaline solution, the sodium silicate liquid and the aluminum phosphate liquid are uniformly mixed in a mass ratio of 1:0.25:0.14:0.08;

[0169] The remaining preparation steps were the same as those in Example 4 to obtain SAC-17 seed crystals.

[0170] The application process of SAC-17 seed crystals is the same as that of Example 4. The hardness removal effect and the final crystal particle size are shown in Table 1. The change of the average crystal particle size with the reaction time is shown in Table 1. Figure 1 .

[0171] Comparative Example 1

[0172] Reference Example 4, except that:

[0173] In Comparative Example 1, quartz sand is directly used as the seed material, and the average particle size of the quartz sand is 0.2-0.5 mm.

[0174] The application process of quartz sand is the same as that of Example 4. The hardness removal effect and the final crystal particle size are shown in Table 1. The change of the average crystal particle size with the reaction time is shown in Table 1. Figure 1 .

[0175] Comparative Example 2

[0176] Reference Example 4, except that:

[0177] In Comparative Example 2, calcite is directly used as the seed material, and the average particle size of the calcite is 0.2-0.5 mm.

[0178] The application process of calcite is the same as that of Example 4. The hardness removal effect and the final crystal particle size are shown in Table 1. The change of the average crystal particle size with the reaction time is shown in Table 1. Figure 1 .

[0179] Comparative Example 3

[0180] Reference Example 4, except that:

[0181] In Comparative Example 3, white corundum sand is directly used as the seed material, and the average particle size of the white corundum sand is 0.2-0.5 mm.

[0182] The application process of white corundum sand is the same as that of Example 4. The hardness removal effect and the final crystal particle size are shown in Table 1. The change of the average crystal particle size with the reaction time is shown in Table 1. Figure 1 .

[0183] Table 1 Effect of different seed crystals on influent hardness removal and final crystal size in a crystallization fluidized bed reactor.

[0184]

[0185] As can be seen from Table 1, the hardness removal rate of the seed crystals provided by Examples 4-20 is 85.28%-94.67%, and the final average crystal particle size is above 4.155 mm. Figure 2 It can be seen that when the crystals are just put into the reactor (0.5-1 day), the average particle size of the crystals of Examples 4-20 and Comparative Examples 1-3 is not much different. On the second day, the average particle size of the crystal seeds provided by Example 4-20 is significantly higher than the existing crystal seeds of Comparative Examples 1-3. As the number of reaction days increases, the average particle size of the crystal seeds is significantly higher than that of Comparative Examples 1-3. It can be seen that the crystal seeds provided by the present invention have a higher crystallization rate, can shorten the crystallization time, reduce the operating time of the reactor, reduce the operating cost, and have a high removal rate of wastewater hardness, saving the cost of reagents.

[0186] The above are only preferred embodiments of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A seed crystal suitable for a fluidized bed crystallization, characterized in that: The seed crystals are composed of a solid mixture, a strong base and a binder. The solid mixture includes the following components in mass ratio: Calcium-containing component: silicon-containing component: aluminum-containing component = 1: (0.45-0.65): (0.15-0.35); The mass ratio of the solid mixture to the mixed solution of the strong base and the adhesive is 1:(0.32-0.56); The calcium-containing component is one or more of calcium oxide, calcium hydroxide, calcium carbonate or calcium silicate; The silicon-containing component is one or more of silicon dioxide, sodium silicate or calcium silicate; The aluminum-containing component is one or more of aluminum oxide, aluminum sulfate or sodium metaaluminate; The seed crystals are prepared using the following process: S1, measuring each component according to the composition ratio of the seed crystal, drying and sieving the calcium-containing component, the silicon-containing component, and the aluminum-containing component, and then mixing them to obtain a solid mixture; S2, dissolving the strong base in water to form a strong base solution, adding the adhesive and mixing uniformly to form a mixed solution, mixing the solid mixture with the mixed solution, and stirring uniformly to obtain a slurry; S3, placing the slurry into a fixed mold for aging until it is completely hardened to obtain a solid sample; S4, demoulding the solid sample and placing it in an oven for heat preservation and activation; S5. Crushing, screening, washing and drying the activated solid sample to obtain the seed crystal.

2. The seed crystal according to claim 1, characterized in that The strong base is one or more of sodium hydroxide or potassium hydroxide; The adhesive is one or more of sodium silicate liquid and aluminum phosphate liquid.

3. A method for preparing seed crystals suitable for a fluidized bed crystallization, characterized in that: The steps include: S1. Measure each component according to the component ratio of the seed crystal, dry and sieve the calcium-containing component, the silicon-containing component, and the aluminum-containing component, and then mix them to obtain a solid mixture, wherein the mass ratio of the calcium-containing component, the silicon-containing component, and the aluminum-containing component is 1:(0.45-0.65):(0.15-0.35); the calcium-containing component is one or more of calcium oxide, calcium hydroxide, calcium carbonate, or calcium silicate; the silicon-containing component is one or more of silicon dioxide, sodium silicate, or calcium silicate; and the aluminum-containing component is one or more of aluminum oxide, aluminum sulfate, or sodium metaaluminate; S2. dissolving a strong base in water to form a strong base solution, adding a binder and mixing uniformly to form a mixed solution, mixing the solid mixture with the mixed solution, and stirring uniformly to obtain a slurry, wherein the mass ratio of the solid mixture to the mixed solution is 1:(0.32-0.56); S3, placing the slurry into a fixed mold for aging until it is completely hardened to obtain a solid sample; S4, demoulding the solid sample and placing it in an oven for heat preservation and activation; S5. Crushing, screening, washing and drying the activated solid sample to obtain the seed crystal.

4. The preparation method according to claim 3, characterized in that In step S2, the concentration of the strong alkaline solution is 25%-40% vol.

5. The preparation method according to claim 3, characterized in that In step S2, the stirring time is 10-20 minutes; In step S3, the aging time is 12-24 hours, and the aging temperature is room temperature; In the step S4, the activation temperature is 100-150° C., and the activation time is 1-3 days.

6. The preparation method according to claim 3, characterized in that In the step S5, the particle size of the crushed solid sample is 0.01-5 mm; The particle size of the solid sample after screening is 0.18-0.55 mm; The drying temperature is 80-105°C.

7. The preparation method according to claim 3, characterized in that In step S3, the fixed mold is a hollow plastic mold.

8. An application of seed crystals suitable for a crystallization fluidized bed, characterized in that: The seed crystals according to any one of claims 1 to 2 or the seed crystals prepared by the preparation method according to any one of claims 3 to 7 are used in a crystallization fluidized bed reactor for treating high-hardness wastewater.

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