Preparation method of sucrose seed crystal

Abstract

The invention relates to a preparation method of sucrose seed crystals, a rotational flow-jet device is adopted, the rotational flow-jet device comprises a venturi tube body, and a sucrose solution inlet and an ethanol inlet are tangentially formed in the venturi tube body; the method comprises the following specific operation steps: preparing a sucrose solution, enabling the sucrose solution to enter a rotational flow-jet flow device through a sucrose solution inlet, enabling ethanol to enter the rotational flow-jet flow device through an ethanol inlet, performing rotational flow mixing on the sucrose solution and the ethanol at an inlet section in the rotational flow-jet flow device, and then performing jet flow to a sucrose seed crystal storage box, and staying in the sucrose seed crystal storage box for 60-300 seconds to obtain the sucrose seed crystal. According to the method, the sucrose seed crystal is prepared in a reinforced manner by adopting a rotational flow-jet flow cavitation synergistic method, two streams of fluid are simultaneously introduced into the rotational flow-jet flow device, the two streams of fluid are firstly subjected to rotational flow mixing and then are subjected to jet flow mixing, and the prepared sucrose seed crystal is few in pseudo crystal, uniform in particle, complete and regular in surface and good in seed crystal quality.

Description

Technical Field

[0001] The invention belongs to the field of sugar industry, and specifically relates to a method for preparing sucrose crystal seeds, and particularly relates to a method for preparing sucrose crystal seeds based on swirl-jet. Background Art

[0002] In the cooking and crystallization process of sugarcane or beet sugar production, industrial crystallization is carried out by adding seed crystals. The quality of the seed crystals, i.e., particle size distribution, morphology, etc., and the number of seed crystals directly affect the production efficiency, product quality and sugar recovery rate.

[0003] At present, in the initial stage of production in the sugar industry, the commonly used crystal seeds are mostly made by grinding sugar products. Although this crystal seed method is simple, it has the following inevitable disadvantages. The number of such crystal seeds is not easy to control, the particle size distribution range is large, the crystal seeds contain a large number of fine crystals, and the crystal shape is irregular and uneven, the edges and corners are unclear or even absent, and the surface is rough, which makes the color-forming substances easily wrapped in the finished white sugar, and the particle size of the crystal product is uneven. In addition, when using such crystal seeds for industrial crystallization of sucrose, it is often necessary to boil water to form crystals due to the uneven crystals, which makes the crystallization and boiling process take a long time, consumes a lot of energy, and the product is difficult to recover during separation, resulting in certain losses, and it is difficult to achieve continuous automatic sugar boiling.

[0004] The study on strengthening sucrose dissolution and crystallization by hydrodynamic cavitation discloses the use of the impinging stream-jet cavitation synergy method to strengthen the preparation of sucrose seed crystals by dissolution and crystallization. In this method, a high-pressure pump introduces two liquids into the impinging stream-jet device for rapid collision, and the antisolvent and sucrose solution are fully mixed. When the fluid enters the throat of the venturi tube, the diameter of the tube becomes smaller, which increases the flow rate of the fluid, and the pressure is reduced to below the saturated vapor pressure of the liquid, generating cavitation bubbles. When the pressure is restored, the cavitation bubbles collapse, and an extreme environment of high temperature, high pressure, and high flow rate is generated, thereby reducing the viscosity and surface tension of the sucrose solution, weakening the intermolecular force, and prompting the antisolvent to seize the water molecules around the sucrose molecules, precipitate the sucrose molecules, and crystallize them into nuclei. This method uses the forward collision of two fluids (sucrose solution and antisolvent) to strengthen the interphase transfer process, accelerate the mixing speed of the solution, and make it fully mixed instantly; due to the use of forward collision, the energy offsets each other during the collision, resulting in a large loss. If sucrose microcrystals are generated in the process, they are easily destroyed due to the instantaneous and violent collision. Summary of the invention

[0005] The technical problem to be solved by the present invention is: to provide a method for preparing sucrose crystal seeds, which adopts a swirl-jet cavitation synergistic method to strengthen the preparation of sucrose crystal seeds, and introduces two fluids into a swirl-jet device at the same time. The two fluids are first swirl mixed and then jet mixed. The prepared sucrose crystal seeds have uniform particles, complete and regular surfaces, good seed quality, and the number of seed crystals is easy to control.

[0006] The technical solution to solve the above technical problems is: a method for preparing sucrose seed crystals, using a swirl-jet device, the swirl-jet device comprising a venturi tube body, the venturi tube body is sequentially arranged as an inlet section, a contraction section, a throat, an expansion section and an outlet section, the end of the inlet section is sealed, the inlet section is provided with a sucrose solution inlet and an ethanol inlet, the sucrose solution inlet and the ethanol inlet are arranged tangent to the outer shell of the venturi tube body; The specific operation steps are as follows: under the temperature condition of 70-90°C, a sucrose solution with a supersaturation of 1.5-1.9 at the corresponding temperature is prepared, the sucrose solution enters the swirl-jet device through the sucrose solution inlet, and ethanol enters the swirl-jet device through the ethanol inlet, the sucrose solution and ethanol are swirl-mixed in the inlet section of the swirl-jet device, and then pass through the contraction section, throat and expansion section, and outlet section to swirl-jet to the sucrose seed storage tank, and the sucrose seed crystals are obtained after staying in the sucrose seed storage tank for 60-300 seconds.

[0007] Furthermore, the process conditions in the specific operation steps are: (1) Sucrose solution temperature: 70-90°C; (2) Sucrose supersaturation: 1.5-1.9; (3) Ethanol temperature: -25℃~room temperature; (4) The mass ratio of sucrose solution and ethanol is (0.5-2):1; (5) Sucrose solution inlet and ethanol inlet pressure: 0.2-1.0MPa.

[0008] Furthermore, the contraction section angle α of the venturi tube body satisfies 15°≤α≤180°, and the expansion section angle β satisfies 15°≤β≤180°.

[0009] Furthermore, the ratio of the throat length L of the venturi body to the throat diameter d is in the range of 1.6 to 3.2.

[0010] Furthermore, the openings of the sucrose solution inlet and the ethanol inlet are in opposite directions.

[0011] Due to the adoption of the above technical solution, the present invention has the following beneficial effects: (1) The prepared sucrose seed crystal particles are uniform and have a complete and regular surface.

[0012] (2) It can make the sucrose crystal growth process in the scouring process smooth, with fewer pseudocrystals, reduce the number of sand washing times, and greatly reduce the chance of impurities and pigments being included in the crystals. As a result, the sugar particles of the second type and the finished sugar are uniform, high in purity, and low in color value, shortening the sugar scouring time and improving product quality.

[0013] (3) Compared with impinging flow mixing, swirl mixing has less energy loss and the shape of the microcrystals can be maintained, which is beneficial to the preparation of microcrystals. The swirl used in the present invention is that two fluids (sucrose solution and antisolvent) rotate in the same direction along the inner wall of a circular device, and one fluid pushes the movement of the other fluid from behind, promoting each other, thereby strengthening the interphase transfer process and accelerating the solution mixing speed under mild conditions. Since one fluid pushes the movement of another fluid from behind, the energy is not offset, and there is no energy loss due to the mixing of the two fluids. If sucrose microcrystals are produced in the process, since there is no instantaneous violent collision, the shape of the microcrystals can be maintained and not damaged, which is beneficial to the preparation of microcrystals.

[0014] (4) By calculating and controlling the amount of sucrose added, the number of seed crystals can be accurately controlled and kept stable.

[0015] The technical features of a method for preparing sucrose seed crystals of the present invention are further described below in conjunction with the accompanying drawings and examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the overall preparation device including the swirl-jet device of the present invention.

[0017] Figure 2 It is a top view of the swirl-jet device of the present invention.

[0018] Figure 3 for Figure 2 AA section view.

[0019] Figure 4 This is a microscope observation image of the sucrose seed crystals prepared in Example 1 of the present invention.

[0020] Figure 5 This is a microscope observation image of the sucrose seed crystals prepared in Example 2 of the present invention.

[0021] Figure 6 This is a microscopic observation of sucrose seed crystals prepared by impinging stream-jet as described in the background art. Implementation

[0022] The overall preparation device used in each embodiment of the present invention is as follows Figure 1 As shown, it includes a sucrose solution tank 1, an ethanol tank 2, a swirl-jet device 4 and a seed collection tank 3, wherein the swirl-jet device (such as Figure 2-Figure 34, wherein the venturi tube body is sequentially provided with an inlet section 43, a contraction section 44, a throat 45, an expansion section 46 and an outlet section 47, the end of the inlet section is sealed, and the end of the outlet section 47 is not sealed, and the liquid mixed by the swirl and the jet flows out from the outlet section; the inlet section is provided with a sucrose solution inlet 41 and an ethanol inlet 42, the sucrose solution inlet and the ethanol inlet are tangent to the outer shell of the venturi tube body, and the openings of the sucrose solution inlet and the ethanol inlet are opposite to each other, as shown in FIG. Figure 2 As shown, the opening of the sucrose solution inlet 41 faces left and the opening of the ethanol inlet 42 faces right. The sucrose solution tank 1 is connected to the sucrose solution inlet 41 through a pipeline, and the ethanol tank 2 is connected to the ethanol inlet 42 through a pipeline. The seed collection tank 3 is located below the venturi body, and the liquid flowing out of the venturi body enters the seed collection tank 3.

[0023] Table 1: List of several parameters of the venturi tube body of the present invention Example 1

[0024] A method for preparing sucrose seed crystals, the specific steps are as follows: (1) Dissolve white sugar with a sucrose content of ≥99.8% in water to prepare a sugar solution with a supersaturation of 1.9 at 70°C, and place the solution in a sucrose solution tank. Place ethanol in an ethanol tank at room temperature.

[0025] (2) The sugar solution and anhydrous ethanol with a mass of 0.5 times that of the sugar solution are pumped into the swirl-jet device through the sucrose solution inlet and the ethanol inlet, respectively. The pressure of the sugar solution inlet and the ethanol inlet is 0.2 MPa. The sugar solution generates a swirl when entering the inlet section of the swirl-jet device, and the ethanol also generates a swirl when entering the inlet section of the swirl-jet device. After the swirl is mixed, the sugar solution and the ethanol are mixed by jet flow through the contraction section, throat and expansion section, and outlet section. The swirl-jet device uses the Venturi tube body with serial number 1 in Table 1.

[0026] (3) After being mixed by the swirl-jet device, the liquid flows into the seed crystal collection tank, and after stirring for 150 seconds, the sucrose seeds are collected and dispersed in anhydrous alcohol with a volume 5 times that of the sucrose seeds, and then stored.

[0027] The sucrose seed crystals prepared in this example were observed under a microscope (see Figure 4 ), with clear edges and corners and a smooth surface. The particle size is in the range of 20-35μm as determined by a particle size analyzer, and the sucrose content is ≥99.8%.

[0028] Under the condition of the same quality, the sucrose seeds prepared in this embodiment and the sucrose seeds obtained by grinding were respectively put into the sugar boiling tank to complete the sugar boiling process. Compared with the sucrose seeds obtained by grinding, the sucrose seeds prepared in this embodiment have an average sugar boiling time reduced by 20%, an average increase in boiling recovery by 0.5%, and an average color value of the boiled granulated sugar reduced by 30 IU. Example 2

[0029] A method for preparing sucrose seed crystals, the specific steps are as follows: (1) Dissolve white sugar with a sucrose content of ≥99.8% in water to prepare a sugar solution with a supersaturation of 1.8 at 80°C, and place the solution in a sucrose solution tank. Place ethanol in an ethanol tank.

[0030] (2) Sugar solution and anhydrous ethanol with a mass of 1 times that of sugar solution are pumped into the swirl-jet device through the sucrose solution inlet and the ethanol inlet, respectively. The pressure of the sugar solution inlet and the ethanol inlet is 0.5 MPa. The sugar solution generates a swirl when entering the inlet section of the swirl-jet device, and the ethanol also generates a swirl when entering the inlet section of the swirl-jet device. The sugar solution and the ethanol are mixed by jet flow through the contraction section, the throat and the expansion section, and the outlet section. The swirl-jet device uses the Venturi tube body with serial number 2 in Table 1.

[0031] (3) After being mixed by the swirl-jet device, the liquid flows into the seed crystal collection tank, and after stirring for 150 seconds, the sucrose seed crystals are collected and dispersed in anhydrous alcohol with a volume 8 times that of the sucrose seed crystals for dispersion and storage.

[0032] The sucrose seed crystals prepared in this example were observed under a microscope (see Figure 5 ), with clear edges and corners and smooth surface, the particle size is in the range of 30-50μm as determined by a particle size analyzer, and the sucrose content is ≥99.8%.

[0033] Under the condition of the same quality, the sucrose seeds prepared in this embodiment and the sucrose seeds obtained by grinding were respectively put into the sugar boiling tank to complete the sugar boiling process. Compared with the sucrose seeds obtained by grinding, the sucrose seeds prepared in this embodiment have an average sugar boiling time reduced by 25%, an average increase in boiling recovery by 0.8%, and an average color value of the boiled granulated sugar reduced by 20 IU. Example 3

[0034] A method for preparing sucrose seed crystals, the specific steps are as follows: (1) Dissolve white sugar with a sucrose content of ≥99.8% in water to prepare a sugar solution with a supersaturation of 1.6 at 90°C, and place the solution in a sucrose solution tank. Place ethanol in an ethanol tank.

[0035] (2) The sugar solution and anhydrous ethanol with a mass of 1.5 times that of the sugar solution are pumped into the swirl-jet device through the sucrose solution inlet and the ethanol inlet, respectively. The pressure of the sugar solution inlet and the ethanol inlet is 0.8 MPa. The sugar solution generates a swirl when entering the inlet section of the swirl-jet device, and the ethanol also generates a swirl when entering the inlet section of the swirl-jet device. The sugar solution and the ethanol are mixed by jet flow through the contraction section, the throat and the expansion section, and the outlet section. The swirl-jet device uses the Venturi tube body with serial number 5 in Table 1.

[0036] (3) After being mixed by the swirl-jet device, the liquid flows into the seed crystal collection tank, and after stirring for 150 seconds, the sucrose seed crystals are collected and dispersed in anhydrous alcohol with a volume three times that of the sucrose crystals for dispersion and storage.

[0037] The sucrose seed crystals prepared in this example were observed under a microscope and had clear edges and corners and a smooth surface. The particle size was determined by a particle size analyzer to be in the range of 30-40 μm. The sucrose content was determined to be ≥99.8%.

[0038] Under the condition of the same quality, the sucrose seed crystals prepared in this embodiment and the sucrose seed crystals obtained by grinding were respectively put into the sugar boiling tank to complete the sugar boiling process. Compared with the sucrose seed crystals obtained by grinding, the sucrose seed crystals prepared in this embodiment reduced the average sugar boiling time by 30%, increased the average boiling recovery by 1%, and reduced the average color value of the boiled granulated sugar by 35 IU.

[0039] Figure 6 The following is a microscope observation picture of sucrose seed crystals prepared by impinging stream-jet according to the background technology. It can be seen from the picture that the sucrose microcrystals produced in the impinging stream preparation process are severely damaged due to the instantaneous violent collision. The sucrose seed crystals prepared in Examples 1 and 2 of the present invention, such as Figure 4 , Figure 5 As shown in the figure, sucrose microcrystals are produced in the cyclone preparation process. Since there is no instantaneous violent collision, the shape of the microcrystals is maintained and not damaged. The shape of the seed crystal is well maintained. On the one hand, the prepared white sugar product particles are uniform and uniform, which is conducive to improving the quality of white sugar products; on the other hand, it can be formed in one time without repeatedly boiling sugar for crystallization, with low production energy consumption and short time difference. In addition, it is roughly calculated through experiments that the energy loss of the impinging flow method is about 80%, while the energy loss of the cyclone method is about 10%. It can be seen that the energy loss of the impinging flow method is significantly higher than that of the cyclone method.

[0040] In summary, the essential difference between impinging flow and swirling flow is that impinging flow strengthens mixing through relative impact, while swirling flow strengthens mixing in circular co-directional motion. The difference between the two effects is that the former has a large energy loss and produces a strong shear force that damages the grains, while the latter has a small energy loss and does not damage the grains.

[0041] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing sucrose seed crystals, characterized in that: A swirl-jet device (4) is used, wherein the swirl-jet device comprises a venturi tube body, wherein the venturi tube body is sequentially arranged as an inlet section (43), a contraction section (44), a throat (45), an expansion section (46) and an outlet section (47), wherein the end of the inlet section is sealed, and a sucrose solution inlet (41) and an ethanol inlet (42) are arranged on the inlet section, wherein the sucrose solution inlet and the ethanol inlet are arranged tangentially to the outer shell of the venturi tube body; The specific operation steps are as follows: under the temperature condition of 70-90°C, a sucrose solution with a supersaturation of 1.5-1.9 at the corresponding temperature is prepared, the sucrose solution enters the swirl-jet device through the sucrose solution inlet, and ethanol enters the swirl-jet device through the ethanol inlet, the sucrose solution and ethanol are swirl-mixed in the inlet section of the swirl-jet device, and then pass through the contraction section, throat and expansion section, and outlet section to swirl-jet to the sucrose seed storage tank, and the sucrose seed crystals are obtained after staying in the sucrose seed storage tank for 60-300 seconds.

2. The method for preparing sucrose seed crystals according to claim 1, characterized in that: The process conditions in the specific operation steps are: (1) Sucrose solution temperature: 70-90°C; (2) Sucrose supersaturation: 1.5-1.9; (3) Ethanol temperature: -25℃~room temperature; (4) The mass ratio of sucrose solution and ethanol is (0.5-2):1; (5) Sucrose solution inlet and ethanol inlet pressure: 0.2-1.0MPa.

3. A method for preparing sucrose seed crystals according to claim 1 or 2, characterized in that: The contraction section angle α of the venturi tube body satisfies 15º≤α≤180º, and the expansion section angle β satisfies 15º≤β≤180º.

4. The method for preparing sucrose seed crystals according to claim 3, characterized in that: The ratio of the throat length L of the venturi tube body to the throat diameter d is in the range of 1.6 to 3.

2.

5. The method for preparing a sucrose seed crystal according to claim 1 or 2, characterized in that: The openings of the sucrose solution inlet and the ethanol inlet are oriented in opposite directions.

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