Microalgae membrane concentration system and method

Abstract

The invention discloses a microalgae membrane concentration system and method. The system comprises a microalgae culture solution storage tank, a pretreatment unit, a membrane concentration unit and a concentrated solution collection tank which are connected in sequence, the microalgae culture solution storage tank is provided with a stirring device, a liquid level sensor and a temperature sensor; the pretreatment unit comprises a filter assembly, and the filter assembly adopts multi-stage filtration and comprises a coarse filter screen and a fine filter screen; the membrane concentration unit is internally provided with a filter membrane, the filter membrane adopts a hollow fiber membrane component, the membrane is made of polyvinylidene fluoride or polyether sulfone, a cross-flow filtration mode is adopted, the membrane concentration unit is provided with a pressure regulating device, a circulating pump and a backwashing system, and the backwashing system adopts gas and liquid for alternate washing. The pressure adjusting device is used for adjusting the pressure difference between the two sides of the fiber membrane component; and the concentrated solution collecting tank is provided with a cooling device and a concentration monitoring device. According to the system and the method, the cleaning and concentration efficiency is higher, and the quality of microalgae obtained through concentration is higher.

Description

Technical Field

[0001] The present invention relates to the technical field of microalgae cultivation and processing, and in particular to a membrane concentration system and method for concentrating microalgae. Background Art

[0002] Microalgae are a type of tiny photosynthetic organisms that are widely found in aquatic environments. They have the advantages of fast growth, high photosynthetic efficiency, and rich in a variety of bioactive substances (such as proteins, oils, polysaccharides, pigments, etc.). They have great application potential in many fields such as food, feed, energy, medicine and cosmetics. In the industrial production process of microalgae, the concentration of microalgae culture solution is usually low. In order to reduce the subsequent processing cost and improve product quality and stability, the microalgae needs to be concentrated.

[0003] Traditional methods for concentrating microalgae mainly include centrifugation and flocculation sedimentation. Although the centrifugation method has a high concentration efficiency, it requires large equipment investment, high energy consumption, and expensive operating costs. It is also easy to damage microalgae cells, affecting the biological activity of microalgae and product quality. The flocculation sedimentation method requires the addition of flocculants, which may introduce impurities and have an adverse effect on the purity and safety of microalgae products. At the same time, the separation and cleaning process of microalgae after flocculation is also relatively cumbersome.

[0004] Therefore, it is of great practical significance to develop a high-efficiency, low-cost, low-energy-consumption concentration system and method that can ensure the quality of microalgae. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a microalgae membrane concentration system, which has higher cleaning and concentration efficiency. The technical problem to be solved by the present invention also includes providing a microalgae membrane concentration method implemented by using the above microalgae membrane concentration system.

[0006] To this end, the present invention provides a microalgae membrane concentration system, comprising a microalgae culture solution storage tank, a pretreatment unit, a membrane concentration unit and a concentrated solution collection tank connected in sequence;

[0007] The microalgae culture liquid storage tank is provided with a stirring device, a liquid level sensor and a temperature sensor;

[0008] The pretreatment unit includes a filter assembly, and the filter assembly adopts multi-stage filtration, including a coarse filter and a fine filter;

[0009] The membrane concentration unit is provided with a filter membrane, which adopts a hollow fiber membrane assembly, and the membrane material is polyvinylidene fluoride or polyether sulfone, and a cross-flow filtration method is adopted. The membrane concentration unit is equipped with a pressure regulating device, a circulation pump and a backwashing system. The backwashing system adopts gas and liquid alternately for flushing, and the pressure regulating device adjusts the pressure difference on both sides of the fiber membrane assembly;

[0010] The concentrated liquid collecting tank is provided with a cooling device and a concentration monitoring device.

[0011] Preferably, a plurality of membrane concentrating units are configured, each membrane concentrating unit includes a group of concentrating tanks and a pressure regulating device, the pressure regulating device is a self-priming booster pump, the self-priming booster pump and the concentrating tank are connected by a left connecting pipe, a right connecting pipe and a negative pressure pipe, the left connecting pipe and the right connecting pipe are respectively arranged at the two ends of the concentrating tank, the negative pressure pipe is connected to one end of the concentrating tank, and control valves are arranged on the left connecting pipe, the right connecting pipe and the negative pressure pipe.

[0012] Preferably, the microalgae culture solution storage tank comprises an inner tank and an outer tank, the inner tank is rotatably installed in the outer tank, an annular cavity is left between the inner tank and the outer tank, a rotating shaft is fixedly provided at the center of the inner tank, a stirring blade is installed on the rotating shaft, the inner tank is equipped with a rotary drive mechanism, the side wall of the inner tank is densely covered with water permeable holes, a filter membrane passing through the inner tank is provided at the water permeable holes, a hollow channel is provided at the center of the rotating shaft, a water flow hole communicating the inside and the outside is provided at the lower part of the rotating shaft, a water outlet hole is provided at the lower part of the hollow channel, a valve is provided at the water outlet hole to control the on-off, the water outlet hole is connected to the pretreatment unit through a pipeline, and the rotary drive mechanism drives the inner tank to rotate around the rotating shaft, and simultaneously completes stirring and preliminary concentration and filtration.

[0013] Preferably, the pore size range of the coarse filter is 100-500 microns, the pore size range of the fine filter is 10-100 microns; the pore size range of the hollow fiber membrane is 0.1-1 microns, the pressure difference range is controlled at 0.1-0.5 MPa, the backwash pressure is 0.2-0.6 MPa, the backwash time is 1-5 minutes, and the backwash cycle is 30-120 minutes.

[0014] Preferably, the pore size range of the coarse filter is 100-500 microns, the pore size range of the fine filter is 10-100 microns; the pore size range of the hollow fiber membrane is 0.1-1 microns, the pressure difference range is controlled at 0.1-0.5 MPa, the backwash pressure is 0.2-0.6 MPa, the backwash time is 1-5 minutes, and the backwash cycle is 30-120 minutes.

[0015] The present invention also provides a microalgae membrane concentration method implemented by the above-mentioned microalgae membrane concentration system, comprising the following steps:

[0016] Preparation of microalgae culture solution: transport the microalgae culture solution to the microalgae culture solution storage tank, start the stirring device, and monitor the liquid level and temperature;

[0017] Pretreatment: The microalgae culture solution is transported to the pretreatment unit and sequentially filtered through multiple stages;

[0018] Membrane concentration: The pretreated microalgae culture solution is transported to the membrane concentration unit, where it is cross-flow filtered under pressure drive, the pressure difference on both sides of the filter membrane is controlled, the concentrated solution is circulated by a circulating pump, and backwashing is performed regularly;

[0019] Concentrate collection and storage: The microalgae concentrate after membrane concentration flows into the concentrate collection tank, where it is cooled and the concentration is monitored. When the set concentration multiple is reached, the concentration process is stopped.

[0020] Preferably, in the step of preparing the microalgae culture solution, the stirring speed of the stirring device is 50-100 rpm.

[0021] Preferably, in the pretreatment step, the pore size of the coarse filter is in the range of 100-500 microns, and the pore size of the fine filter is in the range of 10-100 microns.

[0022] Preferably, in the membrane concentration step, the pore size range of the hollow fiber membrane is 0.1-1 micron, the pressure difference range is controlled at 0.1-0.5 MPa, the circulation pump ensures a circulation flow rate of the concentrate of 1-10 times the cross flow rate, the backwash pressure is 0.2-0.6 MPa, the backwash time is 1-5 minutes, and the backwash cycle is 30-120 minutes.

[0023] Preferably, in the concentrate collection and storage step, the concentrate is cooled to 4-10°C.

[0024] The technical effects of the present invention are as follows:

[0025] 1) The present invention provides a backwashing system, which uses gas and liquid to automatically backwash alternately. For example, compressed air (pressure is 0.3 MPa) and deionized water (pressure is 0.3 MPa) are used to alternately backwash the membrane every 30 minutes, and the backwashing time is 3 minutes. This can reduce impurities in the microalgae, improve the quality of the microalgae, prevent equipment clogging, and improve the operating efficiency of the equipment.

[0026] 2) The filter membrane of the present invention adopts a hollow fiber membrane component, the membrane material is polyvinylidene fluoride or polyethersulfone, and the cross-flow filtration method is adopted, which can improve the efficiency of filtration and improve the quality. In addition, the membrane concentration unit is equipped with a pressure regulating device and a circulation pump. The pressure regulating device adjusts the pressure difference on both sides of the fiber membrane component to adjust the pressure to adapt to the concentrated culture of different types of microalgae, improve the filtration capacity, and realize the synchronous operation of multiple miniaturized units. The circulation pump ensures that the equipment circulates and repeatedly concentrates, which is conducive to quickly increasing the concentration. Therefore, the overall equipment has the advantages of high concentration efficiency, low energy consumption, small membrane pollution, and can better maintain the biological activity and quality of microalgae.

[0027] 3) The microalgae culture liquid storage tank of the present invention includes an inner tank and an outer tank, the inner tank is rotatably installed in the outer tank, an annular cavity is left between the inner tank and the outer tank, a rotating shaft is fixedly arranged at the center of the inner tank, a stirring blade is installed on the rotating shaft, the inner tank is equipped with a rotating drive mechanism, the side wall of the inner tank is densely covered with water-permeable holes, and a filter membrane for passing through the inner tank is arranged at the water-permeable holes, a hollow channel is arranged in the center of the rotating shaft, the lower part of the rotating shaft has a water flow hole for communicating the inside and the outside, and the lower part of the hollow channel has a water outlet hole. When the driving mechanism drives the inner tank to rotate around the rotating shaft, the liquid in the inner tank is driven to rotate as a whole, and the stirring blades on the rotating shaft passively stir the liquid. When the inner tank rotates, it can initially pass part of the water through the inner tank filter membrane to reach the annular cavity, thereby completing stirring and preliminary concentration filtration at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the process of the microalgae membrane concentration system provided by the present invention.

[0029] Figure 2 for Figure 1 Schematic diagram of the membrane concentration unit structure.

[0030] Figure 3 for Figure 1 Schematic diagram of the structural cross-section of the microalgae culture solution storage tank. DETAILED DESCRIPTION

[0031] The specific implementation of a microalgae membrane concentration system and method provided by the present invention is described in detail below with reference to the accompanying drawings.

[0032] Reference Figure 1 As shown, a microalgae membrane concentration system provided by the present invention comprises a microalgae culture solution storage tank 1, a pretreatment unit 2, a membrane concentration unit 3 and a concentrated solution collection tank 4 connected in sequence;

[0033] The microalgae culture liquid storage tank 1 is provided with a stirring device, a liquid level sensor and a temperature sensor;

[0034] The pretreatment unit 2 includes a filtering component, which adopts multi-stage filtering, including a coarse filter 21 and a fine filter 22; the pore size range of the coarse filter 21 is 100-500 microns, and the pore size range of the fine filter 22 is 10-100 microns;

[0035] A filter membrane is provided in the membrane concentration unit 3. The filter membrane adopts a hollow fiber membrane assembly 31. The membrane material is polyvinylidene fluoride or polyethersulfone. A cross-flow filtration method is adopted. The membrane concentration unit 3 is equipped with a pressure regulating device, a circulation pump 33 and a backwashing system 54. The circulation pump 33 is a circulation backwashing pump. The backwashing system 54 adopts gas and liquid alternately for flushing. The pressure regulating device adjusts the pressure difference on both sides of the fiber membrane assembly during the concentration operation. The pressure regulating device is a self-priming booster pump 35. When the liquid is difficult to pass through the filter membrane, the self-priming booster pump 35 is adjusted to a suction state. During operation, the control valve is closed to close the space on both sides of the filter membrane. When the self-priming booster pump 35 is sucked, a pressure difference is generated on both sides of the filter membrane. The pressure difference range is controlled within 0.1-0.5MPa. The pore size range of the hollow fiber membrane 31 is 0.1-1 micron, the backwashing pressure is 0.2-0.6MPa, the backwashing time is 1-5 minutes, and the backwashing cycle is 30-120 minutes.

[0036] The concentrated liquid collecting tank 4 is provided with a cooling device 41 and a concentration monitoring device 42 .

[0037] Reference Figure 1 As shown, the present invention also provides a microalgae membrane concentration method implemented by the above-mentioned microalgae membrane concentration system, comprising the following steps:

[0038] Preparation of microalgae culture solution: transport the microalgae culture solution to the microalgae culture solution storage tank 1, start the stirring device, and monitor the liquid level and temperature; in the microalgae culture solution preparation step, the stirring speed of the stirring device is 50-100 rpm.

[0039] Pretreatment: The microalgae culture solution is transported to the pretreatment unit 2 and sequentially filtered through multiple stages; in the pretreatment step, the pore size of the coarse filter 21 is in the range of 100-500 microns, and the pore size of the fine filter 22 is in the range of 10-100 microns.

[0040] Membrane concentration: The pretreated microalgae culture solution is transported to the membrane concentration unit 3, and cross-flow filtration is performed under pressure drive, the pressure difference on both sides of the filter membrane is controlled, the concentrated solution is circulated by the circulation pump 33, and backwashing is performed regularly;

[0041] Concentrate collection and storage: The microalgae concentrate after membrane concentration flows into the concentrate collection tank 4, cools and monitors the concentration, and stops the concentration process when the set concentration multiple is reached. In the membrane concentration step, the pore size range of the hollow fiber membrane 31 is 0.1-1 micron, the pressure difference range is controlled at 0.1-0.5MPa, the circulation pump 33 ensures a 1-10 times flow rate of the concentrated solution circulation, the backwash pressure is 0.2-0.6MPa, the backwash time is 1-5 minutes, and the backwash cycle is 30-120 minutes. In the concentrate collection and storage step, the concentrate is cooled to 4-10°C.

[0042] Reference Figure 2 As shown, Example 2 of the present invention is basically the same as Example 1, and the only difference is that: in order to improve the concentration effect and concentration efficiency, the membrane concentration unit 3 is configured in plurality, each membrane concentration unit 3 includes a group of concentration tanks 34 and a pressure regulating device, the pressure regulating device is a self-priming booster pump 35, the self-priming booster pump 35 and the concentration tank 34 are connected by a left connecting pipe 36, a right connecting pipe 37 and a negative pressure pipe 38, the left connecting pipe 36 and the right connecting pipe 37 are respectively arranged at both ends of the concentration tank 34, the negative pressure pipe 38 is connected to one end of the concentration tank 34, the left connecting pipe 36, the right connecting pipe 37 and the negative pressure pipe 38 are provided with a control valve, wherein the attached Figure 1 F1, F3, F6 and F46 are pressure regulating valves.

[0043] Reference Figure 3 As shown, in order to improve the concentration efficiency, increase the concentration, and save operation time, the microalgae culture solution storage tank includes an inner tank 11 and an outer tank 12, the inner tank 11 is rotatably installed in the outer tank 12, an annular cavity 13 is left between the inner tank 11 and the outer tank 12, the annular cavity 13 is connected to the external drainage mechanism, a rotating shaft 14 is fixedly arranged at the center of the inner tank 11, a stirring blade 15 is installed on the rotating shaft 14, the inner tank 11 is equipped with a rotating drive mechanism 16, the side wall of the inner tank 11 is densely covered with water holes, and an inner tank filter membrane 17 is arranged at the water holes, the rotating shaft 14 has a hollow channel 18 in the center, the rotating shaft 14 has a water flow hole 19 communicating with the inside and outside at the bottom, the hollow channel 18 has a water outlet 181 at the bottom, a valve is arranged at the water outlet 181 to control the on and off, the water outlet 181 is connected to the pretreatment unit 2 through a pipeline, and the rotating drive mechanism 16 drives the inner tank 11 to rotate around the rotating shaft 14, and completes stirring and preliminary concentration and filtration at the same time.

[0044] The following two examples are used to describe in detail the microalgae membrane concentration method of the present invention:

[0045] Embodiment 1:

[0046] Taking the chlorella culture solution as an example, the chlorella culture solution is first transported to the microalgae culture solution storage tank 1, and the stirring device in the microalgae culture solution storage tank 1 stirs at a speed of 50-100 rpm to make the culture solution uniform. At this time, the liquid level sensor shows that the culture solution level is 3000 liters, and the temperature sensor shows that the temperature is 25°C. Then, the culture solution enters the pretreatment unit 2, and is filtered through a coarse filter 21 with a pore size of 300 microns and a fine filter 22 with a pore size of 50 microns. Next, the culture solution enters the membrane concentration unit 3, and a polyvinylidene fluoride hollow fiber membrane assembly 31 with a pore size of 0.5 microns is used. The pressure difference on both sides of the membrane is controlled at 0.3MPa through the pressure regulating device 3, and the circulating pump 33 circulates the concentrated solution in the membrane assembly at a flow rate of 20 cubic meters / hour. Compressed air (pressure of 0.3MPa) and deionized water (pressure of 0.3MPa) are used alternately every 30 minutes to backwash the membrane, and the backwashing time is 3 minutes. The chlorella concentrate after membrane concentration flows into the concentrate collection tank 4, the cooling device 41 cools the concentrate to 6°C, and the concentration monitoring device 42 monitors the concentration in real time. When the chlorella concentration reaches the set concentration multiple (such as 10 times), the membrane concentration process is stopped to obtain high-quality chlorella concentrate.

[0047] Example 2

[0048] For the spirulina culture solution, the operation process is similar to that of Example 1, but the filter membrane with a pore size of 250um metal mesh is used for filtration in the pretreatment unit 2, the pore size of the hollow fiber membrane 31 in the membrane concentration unit 3 is 0.3 micrometers, the pressure difference on both sides of the filter membrane is controlled at 0.2MPa, the flow rate of the circulation pump is 8 cubic meters / hour, the backwashing cycle is 45 minutes, and the backwashing pressure and time are the same as those of Example 1. Finally, a spirulina concentrate meeting the requirements is obtained.

[0049] It can be seen from the above embodiments that the microalgae membrane concentration system and method of the present invention can effectively concentrate the microalgae culture solution, has the advantages of high concentration efficiency, low energy consumption, small membrane pollution, and can better maintain the biological activity and quality of microalgae, and has broad application prospects in the industrial production of microalgae.

Claims

1. A microalgae membrane concentration system, characterized in that: It includes a microalgae culture liquid storage tank, a pretreatment unit, a membrane concentration unit and a concentrated liquid collection tank which are connected in sequence; The microalgae culture liquid storage tank is provided with a stirring device, a liquid level sensor and a temperature sensor; The pre-treatment unit includes a filter assembly, and the filter assembly adopts multi-stage filtration, including a coarse filter and a fine filter; The membrane concentration unit is provided with a filter membrane, which adopts a hollow fiber membrane assembly, and the membrane material is polyvinylidene fluoride or polyether sulfone, and a cross-flow filtration method is adopted. The membrane concentration unit is equipped with a pressure regulating device, a circulation pump and a backwashing system. The backwashing system adopts gas and liquid alternately for flushing, and the pressure regulating device adjusts the pressure difference on both sides of the fiber membrane assembly; The concentrated liquid collecting tank is provided with a cooling device and a concentration monitoring device.

2. The microalgae membrane concentration system according to claim 1 is characterized in that: There are a plurality of membrane concentrating units, each of which includes a group of concentrating tanks and a pressure regulating device. The pressure regulating device is a self-priming booster pump. The self-priming booster pump and the concentrating tank are connected by a left connecting pipe, a right connecting pipe and a negative pressure pipe. The left connecting pipe and the right connecting pipe are respectively arranged at the two ends of the concentrating tank, and the negative pressure pipe is connected to one end of the concentrating tank. Control valves are arranged on the left connecting pipe, the right connecting pipe and the negative pressure pipe.

3. The microalgae membrane concentration system according to claim 1 or 2, characterized in that: The microalgae culture liquid storage tank comprises an inner tank and an outer tank, wherein the inner tank is rotatably installed in the outer tank, an annular cavity is left between the inner tank and the outer tank, a rotating shaft is fixedly arranged at the center of the inner tank, a stirring blade is installed on the rotating shaft, the inner tank is equipped with a rotating drive mechanism, the side wall of the inner tank is densely covered with water permeable holes, a filter membrane passing through the inner tank is arranged at the water permeable holes, a hollow channel is arranged at the center of the rotating shaft, a water flow hole for communicating the inside and the outside is arranged at the lower part of the rotating shaft, a water outlet hole is arranged at the lower part of the hollow channel, a valve is arranged at the water outlet hole to control the on-off, the water outlet hole is connected to the pretreatment unit through a pipeline, and the rotating drive mechanism drives the inner tank to rotate around the rotating shaft, and simultaneously completes stirring and preliminary concentration and filtration.

4. The microalgae membrane concentration system according to claim 1 or 2, characterized in that: The pore size range of the coarse filter is 100-500 microns, and the pore size range of the fine filter is 10-100 microns; the pore size range of the hollow fiber membrane is 0.1-1 microns, the pressure difference range is controlled at 0.1-0.5MPa, the backwash pressure is 0.2-0.6MPa, the backwash time is 1-5 minutes, and the backwash cycle is 30-120 minutes.

5. The microalgae membrane concentration system according to claim 3, characterized in that: The pore size range of the coarse filter is 100-500 microns, and the pore size range of the fine filter is 10-100 microns; the pore size range of the hollow fiber membrane is 0.1-1 microns, the pressure difference range is controlled at 0.1-0.5MPa, the backwash pressure is 0.2-0.6MPa, the backwash time is 1-5 minutes, and the backwash cycle is 30-120 minutes.

6. A microalgae membrane concentration method implemented by the microalgae membrane concentration system according to claim 1 or 2, characterized in that: The following steps are involved: Preparation of microalgae culture solution: transport the microalgae culture solution to the microalgae culture solution storage tank, start the stirring device, and monitor the liquid level and temperature; Pretreatment: The microalgae culture solution is transported to the pretreatment unit and sequentially filtered through multiple stages; Membrane concentration: The pretreated microalgae culture solution is transported to the membrane concentration unit, where it is cross-flow filtered under pressure drive, the pressure difference on both sides of the filter membrane is controlled, the concentrated solution is circulated by a circulating pump, and backwashing is performed regularly; Concentrate collection and storage: The microalgae concentrate after membrane concentration flows into the concentrate collection tank, where it is cooled and the concentration is monitored. When the set concentration multiple is reached, the concentration process is stopped.

7. The microalgae membrane concentration method according to claim 6, characterized in that: In the step of preparing the microalgae culture solution, the stirring speed of the stirring device is 50-100 revolutions per minute.

8. The microalgae membrane concentration method according to claim 6, characterized in that: In the pretreatment step, the pore size of the coarse filter is in the range of 100-500 microns, and the pore size of the fine filter is in the range of 10-100 microns.

9. The microalgae membrane concentration method according to claim 6, characterized in that: In the membrane concentration step, the pore size range of the hollow fiber membrane is 0.1-1 micron, the pressure difference range is controlled at 0.1-0.5 MPa, the circulation pump ensures a circulation flow rate of 1-10 times the reverse flow rate of the concentrated solution, the backwash pressure is 0.2-0.6 MPa, the backwash time is 1-5 minutes, and the backwash cycle is 30-120 minutes.

10. The microalgae membrane concentration method according to claim 6, characterized in that: In the concentrate collection and storage step, the concentrate is cooled to 4-10°C.

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