Ultrasonic combined stirring and filtering device and control method thereof

Abstract

The invention relates to an ultrasonic combined stirring and filtering device which comprises a shell, a stirrer arranged in the shell, an ultrasonic transducer used for assisting crystallization and an ultrasonic generator connected with the ultrasonic transducer, the ultrasonic generator is a frequency conversion type ultrasonic generator, and a filtering mechanism and a thickness sensor used for detecting the thickness of a filter cake are arranged in the shell. The filter cake thickness sensor is in signal connection with the ultrasonic generator through the controller so as to adjust the ultrasonic frequency. The control method of the ultrasonic combined stirring and filtering device comprises the following steps that in the stirring process of the stirrer, the thickness of a filter cake is detected through the filter cake thickness sensor, and the controller adjusts the ultrasonic frequency of the ultrasonic generator according to the thickness of the filter cake. And the initial formation of a filter cake is accelerated by utilizing the cavitation effect generated by ultrasonic waves in the feed liquid. The thickness of the filter cake is monitored through the variable-frequency ultrasonic generator, so that the filtering effect is improved, and the continuous cavitation effect is prevented from damaging the mature filter cake structure.

Description

Technical Field

[0001] The invention belongs to the technical field of filtering equipment, and relates to a stirring filtering device and a control method thereof, and in particular to an ultrasonic combined stirring filtering device and a control method thereof. Background Art

[0002] Stirring and filtering operations are widely used in many fields of industrial production. For example, in the pharmaceutical industry, most of the products produced are crystals, so stirring operations are needed to strengthen the mixing effect of raw materials and accelerate the crystallization reaction. These crystal products must be effectively separated from their mother liquor through filtering operations. In addition, stirring and filtering operations are also used in the fields of material purification and protein crystallization. Generally, the stirring and filtering device can be divided into two parts, the upper part is the stirring and mixing area, and the lower filtering structure intercepts suspended particles and allows the filtrate to pass. When stirring and mixing is for the purpose of crystallization, the cavitation effect of ultrasound can effectively assist the crystallization process.

[0003] For example, Chinese utility model patent with publication number CN210410679U discloses a reaction device for ultrasonic assisted crystallization, which includes a kettle, a kettle cover, an agitator, a hollow baffle plate arranged on the inner wall of the kettle, and an ultrasonic generator built into the hollow baffle plate.

[0004] However, in an ultrasonic-assisted stirred filtration device, a large number of bubbles will be generated when cavitation occurs. These bubbles gather near the radiation surface of the transducer to form a sound barrier, which in turn hinders the increase of sound power and reduces the effect of ultrasonic-assisted crystallization. The filter cake filtration process occupies an important position in liquid filtration. During the filter cake filtration process, the structure of the filter cake and the small porosity of the filter cake will increase the resistance of the filtrate when it flows through, affecting the filtration effect and reducing the filtration efficiency. Filter cake filtration is also called surface filtration. During filtration, the filter medium first intercepts the suspended particles to form a filter cake, and then the filter cake layer gradually thickens and continues to intercept solid particles. At the same time, the filter medium will have the problem of contaminant clogging after long-term use. Since most of the contaminants are attached to the narrow gaps in the filter medium, it is difficult to clean using conventional methods. Summary of the invention

[0005] The purpose of the present invention is to provide an ultrasonic combined stirring filtration device in view of the above problems.

[0006] Another object of the present invention is to provide a control method for an ultrasonic combined stirring filtration device in order to solve the above problems.

[0007] The present invention creatively proposes an ultrasonic combined stirring and filtering device, comprising a shell, a stirrer arranged in the shell, an ultrasonic transducer for assisting crystallization and an ultrasonic generator connected to the ultrasonic transducer, wherein the ultrasonic generator is a variable frequency ultrasonic generator, and a filtering mechanism and a thickness sensor for detecting the thickness of the filter cake are arranged in the shell, and the filter cake thickness sensor is connected to the ultrasonic generator signal through a controller to adjust the ultrasonic frequency.

[0008] By monitoring the thickness of the filter cake and feeding it back to the controller, the ultrasonic frequency is adjusted according to the different thickness of the filter cake, thus solving the problems of low filtration efficiency when the filter cake exceeds the set thickness and the difficulty in cleaning the filter medium due to contaminants.

[0009] In the above-mentioned ultrasonic combined stirring and filtering device, the front end of the ultrasonic transducer is connected to the shell, and an auxiliary stirring paddle is arranged inside the shell at the front end of the ultrasonic transducer.

[0010] When the cavitation effect generated by ultrasound is needed, the large number of bubbles gathered near the front end of the ultrasonic transducer will be dispersed in time to prevent a large number of bubbles from gathering to form a sound barrier, thereby improving the cavitation effect.

[0011] During stirring, the auxiliary stirring paddle can also enhance turbulence, further enhance the mixing effect of the feed liquid, and accelerate the reaction rate.

[0012] In the above-mentioned ultrasonic combined stirring filtration device, the ultrasonic transducer has a through hole in the center, and the outer end of the auxiliary stirring paddle is connected to the auxiliary stirring motor. The auxiliary stirring motor is sleeved in the through hole of the ultrasonic transducer so that the axis of the auxiliary stirring motor coincides with the axis of the ultrasonic generator.

[0013] The auxiliary stirring paddle is coaxially arranged with the ultrasonic transducer, so that the auxiliary stirring paddle can evenly disturb and disperse the ultrasonic wave.

[0014] In the above-mentioned ultrasonic combined stirring and filtering device, the two ultrasonic transducers are axially arranged on both sides of the shell in a horizontal direction, and the two auxiliary stirring paddles are axially arranged in a horizontal direction and parallel to the upper surface of the filtering mechanism.

[0015] In the above-mentioned ultrasonic combined stirring filtration device, the auxiliary stirring paddle is located below the paddle of the stirrer.

[0016] In the above-mentioned ultrasonic combined stirring and filtration device, the diameter of the auxiliary stirring paddle is greater than or equal to the diameter of the ultrasonic transducer.

[0017] In the above-mentioned ultrasonic combined stirring filtration device, the filtration mechanism includes a filtration medium.

[0018] The present invention creatively provides a control method for an ultrasonic combined stirring and filtering device, comprising the following steps:

[0019] During the stirring process of the stirrer, the filter cake thickness is detected by the filter cake thickness sensor, and the controller adjusts the ultrasonic frequency of the ultrasonic generator according to the filter cake thickness.

[0020] In the above-mentioned control method of an ultrasonic combined stirring filtration device, in the initial stage, the ultrasonic generator operates at an initial frequency f0 higher than the intensity limit value that can form the cavitation effect;

[0021] When the filter cake thickness sensor detects that the filter cake thickness reaches X, the controller controls the ultrasonic generator to work at a low frequency f1;

[0022] In the filter cake cleaning stage, the controller controls the ultrasonic generator to work at high frequency f2;

[0023] Among them, the range of X is 5.5≥X>7.5, the range of the initial frequency f0 of the ultrasonic generator is 100KHz≥f0>1MHz, the range of the low frequency f1 is 20KHz≥f1>100KHz, and the range of the high frequency f2 is 1MHz≥f2≥3MHz.

[0024] In the initial stage of stirring operation, the ultrasonic frequency is adjusted to be greater than the minimum intensity value that can form the cavitation effect, that is, the ultrasonic frequency is increased to the ultrasonic frequency that can just form the cavitation effect. Under the cavitation effect, a large number of tiny bubbles in the liquid undergo a series of growth, contraction, regrowth, and contraction under the action of ultrasonic alternating sound pressure. When sufficient ultrasonic energy is absorbed, the bubbles will collapse. The high temperature and high pressure generated at the moment of bubble collapse weaken the intermolecular interaction force, increase the probability of molecular collision, and then promote the formation of crystal nuclei and improve the generation efficiency of crystallized products.

[0025] When the thickness of the filter cake reaches a certain value, the ultrasonic frequency is adjusted to a low frequency. The particles forming the filter cake in the sound field are acted upon by various forces mainly causing coagulation. The particles approach each other until they collide to form a larger particle group, which increases the pores of the formed filter cake and reduces the filtration resistance, thereby strengthening the filtration operation process.

[0026] During the filter cake cleaning stage, when cleaning the filter medium, the ultrasonic frequency is adjusted to a high frequency to produce a cavitation effect to clean the pollutants attached to the filter medium and improve the filtering effect.

[0027] In the above-mentioned control method of the ultrasonic combined stirring filtration device, when the ultrasonic generator is working, the auxiliary stirring paddle is started at the same time.

[0028] Compared with the prior art, the advantages of the present invention are:

[0029] 1. The cavitation effect produced by ultrasound in the liquid feed is used to improve the efficiency of the formation of crystallized products in the initial stage of stirring, so that the filter medium can more efficiently intercept suspended particles and accelerate the initial formation of the filter cake. The thickness of the filter cake is monitored by a variable frequency ultrasonic generator, and the ultrasonic frequency is changed to improve the filtration effect, while avoiding the damage of the mature filter cake structure to the continuous cavitation effect.

[0030] 2. By setting an auxiliary stirring paddle at the front end of the ultrasonic transducer, when the cavitation effect generated by ultrasound is needed, a large number of bubbles gathered near the front end of the ultrasonic transducer will be dispersed in time to prevent a large number of bubbles from gathering to form a sound barrier and improve the cavitation effect. At the same time, during the stirring period, the auxiliary stirring paddle can enhance the turbulence, further enhance the mixing effect of the feed liquid, and accelerate the reaction rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a structural schematic diagram of an ultrasonic combined stirring filtration device.

[0032] Figure 2 for Figure 1 A partial enlarged schematic diagram of .

[0033] Figure 3 Schematic diagram of the cake filtration stage.

[0034] Figure 4 Schematic diagram of the ultrasonic cleaning stage.

[0035] Figure 5 It is the control structure block diagram.

[0036] In the figure, the shell 1, the stirrer 2, the ultrasonic transducer 3, the ultrasonic generator 4, the filtering mechanism 5, the thickness sensor 6, the controller 7, the auxiliary stirring paddle 8, the auxiliary stirring motor 9, the filter cake 10, the filter medium 11, and the pollutant 12. DETAILED DESCRIPTION

[0037] Further described by the following specific examples;

[0038] The present invention will be further described below in conjunction with specific examples, and it should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope limited by the appended claims of the application.

[0039] like Figure 1 and Figure 2 As shown, an ultrasonic combined stirring filtration device includes a shell 1, a stirrer 2 arranged in the shell 1, an ultrasonic transducer 3 for assisting crystallization, and an ultrasonic generator 4 connected to the ultrasonic transducer 3.

[0040] The stirring shaft of the stirrer 2 is arranged in the vertical direction, and a filtering mechanism 5 is arranged at the bottom of the stirrer 2, and the filtering mechanism 5 includes a filtering medium 11 arranged horizontally in the housing 1. An ultrasonic transducer 3 is arranged on both sides of the housing 1 located on the filtering mechanism 5. The two ultrasonic transducers 3 are opposite to each other in the axial direction, and a through hole is arranged in the middle of the ultrasonic transducer 3. The front end of the ultrasonic transducer 3 is connected to the housing 1, and an auxiliary stirring paddle 8 is arranged on the inner side of the housing 1 at the front end of the ultrasonic transducer 3. The auxiliary stirring motor 9 is sleeved in the through hole of the ultrasonic transducer 3, so that the axis of the auxiliary stirring motor 9 coincides with the axis of the ultrasonic generator 4. The two auxiliary stirring paddles 8 are opposite to each other in the horizontal direction and parallel to the upper surface of the filtering mechanism 5, and the auxiliary stirring paddle 8 is located below the paddle of the stirrer 2. The two ultrasonic transducers 3 are connected to the ultrasonic generator 4 respectively. The ultrasonic generator 4 is a variable frequency ultrasonic generator, and a filtering mechanism 5 and a thickness sensor 6 for detecting the thickness of the filter cake are arranged in the housing 1.

[0041] like Figure 5 As shown, the filter cake thickness sensor 6 is connected to the ultrasonic generator 4 through the controller 7 to adjust the ultrasonic frequency.

[0042] Furthermore, the diameter of the auxiliary stirring paddle 8 is greater than or equal to the diameter of the ultrasonic transducer 3, so as to fully disturb a large number of bubbles near the front end of the ultrasonic transducer and prevent the bubbles from gathering to form a barrier.

[0043] A control method for an ultrasonic combined stirring filtration device comprises the following steps:

[0044] like Figure 1 As shown, the stirrer 2, the ultrasonic generator 4, the auxiliary stirring paddle motor 9 and the filter cake thickness sensor 6 are started. During stirring, the auxiliary stirring paddle 8 can enhance the turbulence, further enhance the mixing effect of the feed liquid, and accelerate the reaction rate.

[0045] In the initial stage, the ultrasonic generator 4 operates at an initial frequency f0 higher than the strength limit of the cavitation effect to generate the cavitation effect. The cavitation effect generated by the ultrasonic wave in the liquid feed is used to improve the efficiency of forming the crystallized product in the initial stirring stage, so that the filter medium 11 can more efficiently intercept the suspended particles and accelerate the initial formation of the filter cake. After the tiny bubbles in the liquid feed absorb enough ultrasonic energy, the high temperature and high pressure generated by the collapse weaken the intermolecular interaction force, increase the probability of molecular collision, and then promote the generation of crystal nuclei and improve the generation efficiency of the crystallized product.

[0046] Combination Figure 1 , Figure 2 and Figure 5 During the stirring process of the stirrer 2, the filter cake thickness is detected by the filter cake thickness sensor 6, and the controller 7 adjusts the ultrasonic frequency of the ultrasonic generator 4 according to the filter cake thickness.

[0047] When the filter cake thickness sensor 6 detects that the filter cake thickness reaches X, the controller 7 controls the ultrasonic generator 4 to operate at a low frequency f1. Figure 3 As shown, the various forces acting on the particles forming the filter cake 10 in the sound field mainly cause coagulation, and the particles approach each other until they collide to form a larger particle group, which increases the pores of the formed filter cake 10 and reduces the filtration resistance, thereby strengthening the filtration operation process.

[0048] After the filtration is completed, the filter cake 10 is cleaned. During the filter cake cleaning stage, the controller 7 controls the ultrasonic generator 4 to operate at a high frequency f2. Figure 4 As shown, the high temperature and high pressure impact generated when the cavitation bubbles burst is used to peel off the pollutants 12 from the surface of the filter medium 11, thereby achieving a cleaning effect.

[0049] The range of X is 5.5≥X>7.5, the range of initial frequency f0 of ultrasonic generator 4 is 100KHz≥f0>1MHz, the range of low frequency f1 is 20KHz≥f1>100KHz, and the range of high frequency f2 is 1MHz≥f2≥3MHz. It is set according to the feed liquid and the filter medium.

[0050] The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

[0051] Although the terms such as housing 1, stirrer 2, ultrasonic transducer 3, ultrasonic generator 4, filtering mechanism 5, thickness sensor 6, controller 7, auxiliary stirring paddle 8, auxiliary stirring motor 9, filter cake 10, filter medium 11, pollutant 12, etc. are used more frequently in this document, these terms are used only to more conveniently describe and explain the essence of the present invention, and interpreting them as any additional limitation is contrary to the spirit of the present invention.

Claims

1. An ultrasonic combined stirring and filtering device, comprising a housing (1) and a stirrer (2) arranged in the housing (1), characterized in that: The invention also comprises an ultrasonic transducer (3) for assisting crystallization and an ultrasonic generator (4) connected to the ultrasonic transducer (3); the ultrasonic generator (4) is a variable frequency ultrasonic generator; a filtering mechanism (5) and a thickness sensor (6) for detecting the thickness of a filter cake are arranged in the housing (1); the filter cake thickness sensor (6) is connected to the ultrasonic generator (4) through a controller (7) to adjust the ultrasonic frequency.

2. The ultrasonic combined stirring filtration device according to claim 1, characterized in that: The front end of the ultrasonic transducer (3) is connected to the housing (1), and an auxiliary stirring paddle (8) is arranged inside the housing (1) at the front end of the ultrasonic transducer (3).

3. The ultrasonic combined stirring filtration device according to claim 2, characterized in that: The ultrasonic transducer (3) has a through hole at its center, and the outer end of the auxiliary stirring paddle (8) is connected to an auxiliary stirring motor (9). The auxiliary stirring motor (9) is sleeved in the through hole of the ultrasonic transducer (3), so that the axis of the auxiliary stirring motor (9) coincides with the axis of the ultrasonic generator (4).

4. The ultrasonic combined stirring filtration device according to claim 2, characterized in that: The two ultrasonic transducers (3) are axially arranged on opposite sides of the housing (1) in a horizontal direction, and the two auxiliary stirring paddles (8) are axially arranged in a horizontal direction and parallel to the upper surface of the filtering mechanism (5).

5. The ultrasonic combined stirring filtration device according to claim 4, characterized in that: The auxiliary stirring paddle (8) is located below the paddles of the stirrer (2).

6. The ultrasonic combined stirring filtration device according to claim 1, characterized in that: The diameter of the auxiliary stirring paddle (8) is greater than or equal to the diameter of the ultrasonic transducer (3).

7. The ultrasonic combined stirring filtration device according to claim 1, characterized in that: The filtering mechanism (5) comprises a filtering medium (11).

8. A control method for the ultrasonic combined stirring filtration device according to any one of claims 1 to 7, characterized in that: The following steps are involved: During the stirring process of the stirrer (2), the filter cake thickness is detected by the filter cake thickness sensor (6), and the controller (7) adjusts the ultrasonic frequency of the ultrasonic generator (4) according to the filter cake thickness.

9. The control method of the ultrasonic combined stirring filtration device according to claim 8, characterized in that: In the initial stage, the ultrasonic generator (4) operates at an initial frequency f0 higher than the intensity limit value capable of forming the cavitation effect; When the filter cake thickness sensor (6) detects that the filter cake thickness reaches X, the controller (7) controls the ultrasonic generator (4) to operate at a low frequency f1; During the filter cake cleaning stage, the controller (7) controls the ultrasonic generator (4) to operate at a high frequency f2; Wherein, the range of X is 5.5≥X>7.5, the range of the initial frequency f0 of the ultrasonic generator (4) is 100KHz≥f0>1MHz, the range of the low frequency f1 is 20KHz≥f1>100KHz, and the range of the high frequency f2 is 1MHz≥f2≥3MHz.

10. The control method of the ultrasonic combined stirring filtration device according to claim 8, characterized in that: When the ultrasonic generator (4) is working, the auxiliary stirring paddle (8) is started simultaneously.

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