System and method for co-producing biological protein feed by separating, coupling and distilling zymophyte

Abstract

The invention relates to a system and a method for co-producing biological protein feed by separating, coupling and distilling zymophyte, the system comprises a fermentation tank, a water permeable membrane group, a first centrifugal machine and a flash evaporation drying unit which are connected in sequence, and a water permeable side outlet of the water permeable membrane group is also connected with an alcohol permeable membrane group; and the retentate of the alcohol-permeable membrane group and the light phase outlet of the first centrifugal machine are respectively connected with a clear liquid tank through pipelines. The water-permeable membrane group and the alcohol-permeable membrane group are used, thalli in fermentation liquor can be effectively separated, biological protein feed production is carried out, and heat exchanger and tower blockage caused by protein temperature rise denaturation in the distillation process of thalli protein in the fermentation liquor is avoided to a certain extent; the concentration of ethanol in the fermentation liquor can be increased from 4V / V% to 30V / V% or more, and then the fermentation liquor is sent to a distillation system for ethanol extraction.

Description

Technical Field

[0001] The present invention belongs to the technical field of fermentation broth treatment, and relates to a system and method for separating and coupling fermentation bacteria and co-producing biological protein feed by distillation. Background Art

[0002] Syngas fermentation is a technology that uses anaerobic gas-eating bacteria as strains, and uses CO and CO in syngas 2 and H 2 as carbon sources and energy sources for reproduction and metabolism to produce renewable energy such as ethanol. Syngas is widely sourced from coal chemical industry, petrochemical industry, industrial waste gas (such as steel mill waste gas), municipal solid waste, and biomass. At present, the production of ethanol by syngas fermentation has achieved large-scale production. The main product is ethanol, and the by-product is high-value-added biological protein feed.

[0003] Anaerobic gas-eating bacteria carry out metabolic activities in the fermentation tank to produce ethanol. When distilling and extracting ethanol from the fermentation broth, since the fermentation broth contains bacteria (mainly proteins), the heat exchanger and tray will be blocked due to protein denaturation caused by heating, affecting the mass transfer and heat transfer of the equipment, and causing interruptions in the entire production process. When the equipment is blocked, it is necessary to regularly carry out on-line cleaning of the heat exchanger and tray with lye to continue the production. Therefore, according to Chinese patents CN111647496A "A continuous fermentation bacteria circulation separation coupling system", CN1450166A "A method for producing anhydrous ethanol by biomass fermentation and membrane pervaporation", and CN217628354U "A fermentation system", the existing syngas-to-ethanol processes currently separate the bacteria (proteins) in the fermentation broth using a centrifuge or microfiltration / ultrafiltration device before the fermentation broth enters the distillation system. One is to prevent membrane fouling; the other is to avoid blockage of the heat exchanger and tray caused by protein denaturation in the fermentation broth. The separated bacteria are then returned to the fermentation tank to control the bacteria concentration and continue to utilize the nutrients in the fermentation substrate. By detecting the bacteria concentration in the fermentation tank, the excess separated liquid is sent to the distillation system for ethanol extraction. However, this separation method will cause damage and death to the bacteria, and there is a risk of contaminating the fermentation tank when the separated matter comes into contact with air; and since the ethanol concentration in syngas fermentation is 3.5 - 4.5 V / V%, compared with the ethanol fermentation concentration of 13 - 16 V / V% in grain-to-ethanol fermentation, it increases the steam consumption during the distillation system's ethanol extraction.

[0004] Therefore, researching a solution that can avoid blockage of the heat exchanger and tray when extracting ethanol from the fermentation broth, make the process of producing biological protein feed smooth, and at the same time increase the ethanol concentration in the fermentation broth and reduce the steam unit consumption during distillation ethanol extraction is of great significance for promoting the development of the syngas-to-ethanol process. Summary of the Invention

[0005] The object of the present invention is to provide a system and method for coupling fermentation thallus separation and distillation to produce biological protein feed. By using a water permeable membrane group and an alcohol permeable membrane group, not only can the thallus in the fermentation broth be effectively separated for the production of biological protein feed, to a certain extent, avoiding the blockage of heat exchangers and towers caused by protein thermal denaturation of thallus protein in the distillation process; but also can increase the ethanol concentration in the fermentation broth from 4V / V% to 30V / V% or more, and then send it to the distillation system for ethanol extraction.

[0006] The object of the present invention can be achieved by the following technical solutions:

[0007] One of the technical solutions of the present invention provides a system for coupling fermentation thallus separation and distillation to produce biological protein feed, including a fermentation tank, a water permeable membrane group, a first centrifuge and a flash drying unit connected in sequence. The water permeable side outlet of the water permeable membrane group is also connected to an alcohol permeable membrane group. The retentate of the alcohol permeable membrane group and the light phase outlet of the first centrifuge are respectively connected to a clear liquid tank through pipelines.

[0008] Further, a diaphragm filter press is also provided between the first centrifuge and the flash drying unit.

[0009] Even further, the light phase outlet on the diaphragm filter press is also connected to the clear liquid tank through a pipeline.

[0010] Even further, the diaphragm filter press and the flash drying unit are connected through a filter cake conveyor line.

[0011] Further, a feed pump is also provided between the fermentation tank and the water permeable membrane group.

[0012] Further, the first centrifuge is a horizontal scroll centrifuge.

[0013] Further, the water permeable membrane in the water permeable membrane group is a NaA, NaX type, NaY type or T type molecular sieve membrane; and the alcohol permeable membrane used in the alcohol permeable membrane group can adopt an alcohol permeable membrane with high permeation flux and high separation coefficient such as Silicalite-1.

[0014] Further, the alcohol permeable side outlet of the alcohol permeable membrane group is also connected to an external distillation system through a pipeline.

[0015] Further, the clear liquid tank is also connected to an external distillation system through a clear liquid second pipeline.

[0016] Further, a biological protein feed conveyor line for externally outputting biological protein feed is also provided on the flash drying unit.

[0017] The second technical solution of the present invention provides a method for separating fermented bacteria and coupling with distillation to produce biological protein feed, which is based on the system described in any one of the above. The method includes the following steps:

[0018] (1) The fermentation broth in the fermenter is transported to the permeable membrane group for primary filtration separation, and a light-phase liquid is generated on the permeate side, which enters the alcohol-permeable membrane group for secondary filtration separation, and a heavy-phase liquid is generated on the retentate side and enters the first centrifuge for centrifugal separation;

[0019] (2) The light-phase liquid generated on the alcohol-permeate side in the alcohol-permeable membrane group is sent to an external distillation system, and the heavy-phase liquid generated on the retentate side is sent to the clear liquid tank;

[0020] (3) The light-phase liquid generated at the first centrifuge is sent to the clear liquid tank, and the heavy-phase liquid enters the flash drying unit to produce biological protein feed;

[0021] (4) The liquid collected in the clear liquid tank is sent to an external distillation system. After ethanol is extracted, the bottom liquid generated is heated, sterilized, cooled, and then returned to the fermenter.

[0022] In the present invention, the permeable membrane is responsible for separating the bacteria and most of the ethanol / water mixture in the fermentation broth, and the alcohol-permeable membrane is responsible for separating ethanol and water in the ethanol / water mixture. The permeable membrane is composed of a molecular sieve membrane with a low silicon-aluminum ratio (the lower the silicon-aluminum ratio, the better the water permeability). It is known that the diameter of a water molecule is 0.28 nm, and the diameter of an ethanol molecule is 0.44 nm. Most of the diameters of the bacterial suspension solid particles in the fermentation broth of this project are about 1 μm. The pore diameter of the molecular sieve of the permeable membrane used in the present invention can be set at about 0.5 nm. Therefore, the ethanol / water mixture can pass through the permeable membrane well, and the larger-diameter bacterial suspensions are blocked and enter the retentate side.

[0023] Most of the current syngas-to-ethanol processes separate the bacteria (protein) in the fermentation broth using a centrifuge or microfiltration / ultrafiltration device before the fermentation broth enters the distillation system. The disc centrifuge operates under a centrifugal gravity of 1600G, and the bacterial structure is easily damaged, even leading to the death of the bacteria. For example, in Chinese patents CN111647496A, CN1450166A, CN217628354U, etc., solid-liquid separation of bacteria and ethanol / water mixture is carried out through a disc centrifuge or microfiltration device, and the solid phase containing bacteria is recycled to the fermenter at a certain ratio. In the present invention, the bacteria separated by the permeable membrane are not recycled. Even if the bacteria are damaged or dead, it will not affect the ongoing fermentation activity and greatly reduce the risk of contamination in the fermenter.

[0024] The present invention uses known high-performance NaA, NaX, NaY and T-type molecular sieve membranes as water-permeable membranes, which can improve the water permeation efficiency of the membrane and increase the solid-phase concentration of the bacteria in the retentate side. In combination with a horizontal screw centrifuge and a diaphragm filter press, the solid content of the heavy phase is further concentrated, and the resulting filter cake is sent to a flash drying system to produce bio-protein feed, which will reduce the equipment investment of the drying system and the unit steam consumption of the product. Using an alcohol-permeable membrane module with high permeation flux and high separation coefficient such as Silicalite-1, the concentration of the ethanol solution is increased from 4 V / V% to 30 V / V% and above, which will greatly reduce the steam energy consumption for distillation.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] 1) For the fermentation broth containing bacteria, a water-permeable membrane module is used to filter and separate the bacteria, and an alcohol-permeable membrane module is used to concentrate the ethanol in the fermentation broth. The ethanol clear liquid separated by the alcohol-permeable membrane and the light phase separated by the centrifuge can be sent to the rough distillation tower of the distillation system for ethanol separation and extraction, and the bottom liquid of the tower is sterilized at high temperature and then returned to the fermentation tank for reuse; for the solid phase generated by the filtration and separation of the water-permeable membrane, after being concentrated by the horizontal screw centrifuge, it is directly sent to the flash drying system to produce bio-protein feed.

[0027] 2) The bacteria in the fermentation broth are separated and concentrated by the water-permeable membrane module and the horizontal screw centrifuge, and are retained in the solid phase for producing bio-protein feed, so that the clear liquid sent to the distillation system is basically free of bacterial protein, which reduces the probability of blockage of the heat exchanger and the trays, and there is no need to stop the machine for online flushing of the heat exchanger and the trays with lye, making the entire production process smoother.

[0028] 3) The ethanol concentration in the fermentation broth is concentrated by the alcohol-permeable membrane module from 4 V / V% to 30 V / V% and above, which will greatly reduce the steam energy consumption for distillation.

[0029] 4) The light phase generated by the water-permeable membrane module and the centrifuge, after separating and extracting ethanol by the distillation system, is heated and sterilized and then returned to the fermentation tank for reuse, reducing the risk of contamination of the fermentation tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic process flow diagram of Example 1;

[0031] Figure 2 It is a schematic process flow diagram of Example 2;

[0032] Explanation of the marks in the figure:

[0033] 1 - Fermentation tank, 2 - Fermentation broth input pipeline, 3 - Feed pump, 4 - Fermentation broth transfer pipeline, 5 - Permeable membrane module, 6 - Light phase one pipeline, 7 - Heavy phase one pipeline, 8 - Horizontal spiral centrifuge, 9 - Light phase two pipeline, 10 - Heavy phase two pipeline, 11 - Alcohol permeable membrane module, 12 - Clear liquid one pipeline, 13 - Retentate pipeline, 14 - Clear liquid tank, 15 - Clear liquid two pipeline, 16 - Flash drying unit, 17 - Biological protein feed transfer line, 18 - Heavy phase three pipeline, 19 - Filter cake transfer line, 20 - Light phase three pipeline, 21 - Diaphragm filter press. Detailed implementation manners

[0034] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. These embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0035] In the following embodiments or implementation manners, unless otherwise specified, functional components or structures indicate that they are all conventional components or structures adopted in the art to achieve corresponding functions.

[0036] In order to effectively separate the bacteria in the fermentation broth, produce biological protein feed, and to a certain extent avoid blockages of heat exchangers and towers caused by protein denaturation due to temperature rise of the bacterial protein in the distillation process, the present invention provides a system for coupling fermentation bacteria separation and distillation to produce biological protein feed. Its structure can be seen in Figure 1 or Figure 2 as shown, including a fermentation tank 1, a permeable membrane module 5, a first centrifuge, and a flash drying unit 16 connected in sequence. The permeate side outlet of the permeable membrane module 5 is also connected to an alcohol permeable membrane module 11. The retentate of the alcohol permeable membrane module 11 and the light phase outlet of the first centrifuge are respectively connected to a clear liquid tank 14 through pipelines. In addition, it should be noted that the flash drying unit 16 can adopt commonly used flash drying equipment in the art.

[0037] In some specific implementation manners, a diaphragm filter press 21 is further provided between the first centrifuge and the flash drying unit 16.

[0038] Furthermore, the light phase outlet on the diaphragm filter press 21 is also connected to the clear liquid tank 14 through a pipeline.

[0039] Furthermore, the diaphragm filter press 21 and the flash drying unit 16 are connected through a filter cake transfer line.

[0040] In some specific implementation manners, a feed pump 3 is further provided between the fermentation tank 1 and the permeable membrane module 5.

[0041] In some specific implementation manners, the first centrifuge is a horizontal spiral centrifuge 8.

[0042] In some specific embodiments, the outlet of the alcohol-permeable side of the alcohol-permeable membrane group 11 is also connected to an external distillation system through a pipeline.

[0043] In some specific embodiments, the clear liquid tank 14 is also connected to an external distillation system through a second clear liquid pipeline.

[0044] In some specific embodiments, a biological protein feed conveying line 17 for outputting biological protein feed externally is further provided on the flash drying unit 16.

[0045] Each of the above embodiments can be implemented alone, or can be combined in any pairwise manner or in more combinations.

[0046] The above embodiments will be described in more detail below in conjunction with specific examples.

[0047] Example 1:

[0048] As Figure 1 shown, the inventive method in this embodiment includes: a fermentation tank 1, a fermentation broth input pipeline 2, a feed pump 3, a fermentation broth conveying pipeline 4, a water-permeable membrane group 5, a light phase first pipeline 6, a heavy phase first pipeline 7, a horizontal screw centrifuge 8, a light phase second pipeline 9, a heavy phase second pipeline 10, an alcohol-permeable membrane group 11, a first clear liquid pipeline 12, a retentate pipeline 13, a clear liquid tank 14, a second clear liquid pipeline 15, a flash drying system 16, and a biological protein feed conveying line 17.

[0049] In this embodiment, when separating the bacterial cells in the fermentation broth, concentrating the ethanol content, extracting ethanol, and producing biological protein feed, the fermentation broth in the fermentation tank 1 is conveyed to the feed pump 3 through the fermentation broth input pipeline 2 by its own pressure, and the feed pump 3 sends the fermentation broth to the water-permeable membrane group 5 through the fermentation broth conveying pipeline 4 for filtration and separation. The water-permeable membrane group 5 generates a light phase liquid from the water-permeable side and enters the alcohol-permeable membrane group 11 through the light phase first pipeline 6; the heavy phase liquid generated on the retentate side of the water-permeable membrane group 5 enters the horizontal screw centrifuge 8 through the heavy phase first pipeline 7 for centrifugal separation. The clear liquid separated from the alcohol-permeable side of the alcohol-permeable membrane group 11 enters the distillation system through the first clear liquid pipeline 12, and the generated retentate enters the clear liquid tank 14 through the retentate pipeline 13. The light phase liquid generated by the horizontal screw centrifuge 8 through centrifugal separation enters the clear liquid tank 14 through the light phase second pipeline 9, and together with the retentate generated by the alcohol-permeable membrane group 11, is conveyed to the distillation system through the second clear liquid pipeline 15. After the distillation system extracts ethanol, the generated bottom liquid is heated, sterilized, cooled, and then returned to the fermentation tank 1 for supplementing the liquid level and nutrients (the pipeline is not shown). The heavy phase liquid generated by the horizontal screw centrifuge 8 enters the flash drying system 16 through the heavy phase second pipeline 10 to produce biological protein feed, and the product is stored and sold externally through the biological protein feed conveying line 17.

[0050] Example 2:

[0051] As Figure 2 shown, the inventive method in this embodiment includes: a fermentation tank 1, a fermentation broth input pipeline 2, a feeding pump 3, a fermentation broth conveying pipeline 4, a permeable membrane group 5, a light phase I pipeline 6, a heavy phase I pipeline 7, a horizontal spiral centrifuge 8, a light phase II pipeline 9, a heavy phase III pipeline 18, a filter cake conveying line 19, a light phase III pipeline 20, a diaphragm filter press 21, an alcohol-permeable membrane group 11, a clear liquid I pipeline 12, a retentate pipeline 13, a clear liquid tank 14, a clear liquid II pipeline 15,, a flash drying system 16 and a biological protein feed conveying line 17.

[0052] In this embodiment, when separating the bacteria in the fermentation broth, concentrating the ethanol content, performing ethanol extraction and producing biological protein feed, the fermentation broth in the fermentation tank 1 is conveyed to the feeding pump 3 through the fermentation broth input pipeline 2 by its own pressure, and the feeding pump 3 sends the fermentation broth to the permeable membrane group 5 through the fermentation broth conveying pipeline 4 for filtration separation. The permeable membrane group 5 generates light phase liquid from the permeate side and enters the alcohol-permeable membrane group 11 through the light phase I pipeline 6; the heavy phase liquid generated on the retentate side of the permeable membrane group 5 enters the horizontal spiral centrifuge 8 through the heavy phase I pipeline 7 for centrifugal separation. The clear liquid generated by the alcohol-permeable membrane group 11 through membrane separation enters the distillation system through the clear liquid I pipeline 12, and the retentate generated enters the clear liquid tank 14 through the retentate pipeline 13. The light phase liquid generated by the horizontal spiral centrifuge 8 through centrifugal separation enters the clear liquid tank 14 through the light phase II pipeline 9; the heavy phase liquid generated by the horizontal spiral centrifuge 8 enters the diaphragm filter press 21 through the heavy phase III pipeline 18. The light phase generated by the diaphragm filter press 21 enters the clear liquid tank 14 through the light phase III pipeline 20, and together with the retentate generated by the alcohol-permeable membrane group 11 and the light phase generated by the horizontal spiral centrifuge 8, is conveyed to the distillation system through the clear liquid II pipeline 15. After the distillation system extracts ethanol, the bottom liquid generated is heated, sterilized, cooled and then returned to the fermentation tank for supplementing liquid and nutrients (not shown); the filter cake generated by the diaphragm filter press is conveyed to the flash drying system 16 through the filter cake conveying line 19 to produce biological protein feed, which is stored and sold externally through the biological protein feed conveying line 17.

[0053] The above description of the embodiments is for the convenience of those of ordinary skill in the art to understand and use the invention. Those skilled in the art can obviously make various modifications to these embodiments easily and apply the general principles described herein to other embodiments without creative labor. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A system for coupling fermentation thallus separation and distillation to produce biological protein feed, characterized in that, it includes a fermentation tank, a permeable membrane group, a first centrifuge and a flash drying unit connected in sequence. The permeate side outlet of the permeable membrane group is also connected to an alcohol permeable membrane group. The retentate of the alcohol permeable membrane group and the light phase outlet of the first centrifuge are respectively connected to a clear liquid tank through pipelines.

2. The system for coupling fermentation thallus separation and distillation to produce biological protein feed according to claim 1, characterized in that, a diaphragm filter press is also provided between the first centrifuge and the flash drying unit.

3. The system for coupling fermentation thallus separation and distillation to produce biological protein feed according to claim 2, characterized in that, the light phase outlet on the diaphragm filter press is also connected to the clear liquid tank through a pipeline.

4. The system for coupling fermentation thallus separation and distillation to produce biological protein feed according to claim 2, characterized in that, the diaphragm filter press and the flash drying unit are connected by a filter cake conveying line.

5. The system for coupling fermentation thallus separation and distillation to produce biological protein feed according to claim 1, characterized in that, a feed pump is also provided between the fermentation tank and the permeable membrane group.

6. The system for coupling fermentation thallus separation and distillation to produce biological protein feed according to claim 1, characterized in that, the first centrifuge is a horizontal screw centrifuge.

7. The system for coupling fermentation thallus separation and distillation to produce biological protein feed according to claim 1, characterized in that, the alcohol permeate side outlet of the alcohol permeable membrane group is also connected to an external distillation system through a pipeline.

8. The system for coupling fermentation thallus separation and distillation to produce biological protein feed according to claim 1, characterized in that, the clear liquid tank is also connected to an external distillation system through a clear liquid second pipeline.

9. The system for coupling fermentation thallus separation and distillation to produce biological protein feed according to claim 1, characterized in that, a biological protein feed conveying line for externally outputting biological protein feed is also provided on the flash drying unit.

10. A method for coupling fermentation thallus separation and distillation to produce biological protein feed, which is based on the system according to any one of claims 1-9, characterized in that, the method includes the following steps: (1) The fermentation broth in the fermentation tank is transported to the permeable membrane group for primary filtration separation. Light phase liquid is generated on the permeate side and enters the alcohol permeable membrane group for secondary filtration separation. Heavy phase liquid is generated on the retentate side and enters the first centrifuge for centrifugal separation; (2) The light phase liquid generated on the alcohol permeate side in the alcohol permeable membrane group is sent to an external distillation system, and the heavy phase liquid generated on the retentate side is sent to the clear liquid tank; (3) The light phase liquid generated at the first centrifuge is sent to the clear liquid tank, and the heavy phase liquid enters the flash drying unit to produce biological protein feed; (4) The liquid collected in the clear liquid tank is sent to an external distillation system. After ethanol is extracted, the resulting bottom liquid is heated, sterilized, cooled, and then returned to the fermentation tank.

Images