A system for co-producing ethanol and hexanoic acid through syngas fermentation

Abstract

This application provides a system for the co-production of ethanol and hexanoic acid through syngas fermentation, belonging to the field of syngas fermentation. The system includes: a primary reactor through which feed gas is introduced; a microbial cell separation device, the inlet of which is connected to the outlet of the primary bioreactor; a distillation device, the inlet of which is connected to the clear liquid outlet of the microbial cell separation device; and a secondary reactor, the inlet of which is connected to the residual distillate outlet of the distillation device. This system enables primary fermentation to produce metabolites such as ethanol and acetic acid. After ethanol is extracted by distillation, acetic acid is used as a substrate in the secondary fermentation system to produce hexanoic acid. Therefore, this system avoids the acetic acid produced during primary fermentation from entering the downstream wastewater system, reducing the wastewater treatment load, and simultaneously converting low-value products into high-value products, thus improving economic efficiency.

Description

Technical Field

[0001] This application relates to the field of syngas fermentation technology, and more particularly to a system for co-producing ethanol and hexanoic acid through syngas fermentation. Background Technology

[0002] Existing syngas fermentation technologies for ethanol production mainly utilize Clostridium ethanolans. This continuous gaseous bio-fermentation by Clostridium ethanolans is accomplished through a specific bacterial metabolic pathway—the Wood-Ljungdahl pathway (reduced acetyl-CoA pathway). The microbial cells produce ethanol through anaerobic fermentation of CO and H2 / CO2 via the Wood-Ljungdahl metabolic pathway.

[0003] In current syngas fermentation technology, the fermentation feed gas is pressurized and purified before being sent to the fermenter. Under the action of acetic acid-producing bacteria such as Clostridium ethanoliferum, metabolites such as acetic acid, ethanol, and 2,3-butanediol are synthesized. The fermentation system uses a membrane circulation system to retain the microbial population, achieving independent and stable control of microbial biomass and metabolite concentration. When the ethanol concentration in the fermentation broth reaches a certain level, the fermentation broth containing and without microorganisms enters the downstream distillation and protein drying systems to extract ethanol and protein. After ethanol and protein extraction, the fermentation broth still contains a large amount of nutrients required for the fermentation of the microorganisms and the metabolite acetic acid. A portion of this is recycled back to the fermentation system for secondary conversion, while the remainder enters the downstream wastewater treatment system. When the carbon source entering the fermentation system is insufficient, the acetic acid content will rise, and high concentrations of acetic acid can be toxic to the microorganisms. The acetic acid produced in the fermentation system, recycled back to the fermentation system with the water after ethanol extraction, will further accumulate and affect the activity of the microorganisms. Furthermore, the acetic acid in the fermentation wastewater entering the wastewater treatment system also wastes carbon sources. Utility Model Content

[0004] This application provides a system for co-producing ethanol and hexanoic acid through syngas fermentation to solve the following technical problem: how to prevent acetic acid produced in the primary fermentation process from entering the downstream wastewater system, thereby reducing the wastewater treatment load.

[0005] This application provides an embodiment of a system for co-producing ethanol and hexanoic acid through syngas fermentation, the system comprising:

[0006] A primary reactor, wherein raw material gas is introduced into the primary reactor to carry out primary fermentation of the raw material gas to obtain a bacterial solution containing ethanol and acetic acid;

[0007] A microbial cell separation device, wherein the inlet of the microbial cell separation device is connected to the outlet of the primary reactor, for separating the microbial strains in the bacterial liquid to obtain fermentation broth;

[0008] A distillation apparatus, wherein the inlet of the distillation apparatus is connected to the outlet of the supernatant from the cell separation apparatus, is used to distill the fermentation supernatant to obtain ethanol and residual water containing acetic acid; and

[0009] A secondary reactor is provided, the inlet of which is connected to the outlet of the residual distillate of the distillation apparatus, for secondary fermentation of the acetic acid-containing residual distillate to obtain mash containing hexanoic acid.

[0010] Optionally, the system further includes:

[0011] A concentration device is provided, the inlet of which is connected to the outlet of the secondary reactor, for concentrating the mash to obtain hexanoic acid product.

[0012] Optionally, the concentration device includes:

[0013] The filter section has its inlet connected to the outlet of the secondary reactor.

[0014] The vacuum concentration section has its inlet connected to the clear liquid outlet of the filtration section.

[0015] Optionally, the concentration device further includes:

[0016] The distillation section has its inlet connected to the outlet of the vacuum concentration section.

[0017] Optionally, the system further includes:

[0018] A nutrient solution supply device is connected to both the primary reactor and the secondary reactor.

[0019] Optionally, the bacterial cell separation device is a membrane filtration device.

[0020] Optionally, the bacterial cell separation device is a centrifuge.

[0021] Optionally, the distillation apparatus is a distillation column.

[0022] Optionally, the temperature of the distillation column bottom is in the range of 110℃ to 120℃, and the pressure at the top of the column is 60 kPa.

[0023] Optionally, both the primary reactor and the secondary reactor are equipped with stirring components.

[0024] The technical solutions provided in this application have the following advantages compared with the prior art:

[0025] This application provides a system for the co-production of ethanol and hexanoic acid through syngas fermentation. The system integrates multiple unit operations, including a primary reactor, a cell separation device, a distillation device, and a secondary reactor, forming a complete process flow for the co-production of ethanol and hexanoic acid through syngas fermentation. This system enables primary fermentation to produce metabolites such as ethanol and acetic acid. After distillation to extract the ethanol product, acetic acid is used as the substrate for secondary fermentation to produce hexanoic acid. Therefore, this system avoids the acetic acid produced during primary fermentation entering the downstream wastewater system, reducing the wastewater treatment load, and simultaneously converting low-value products into high-value products, thereby improving economic efficiency. Attached Figure Description

[0026] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0027] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 A schematic diagram of a system for co-producing ethanol and hexanoic acid by syngas fermentation, provided in an embodiment of this application;

[0029] Figure label:

[0030] 1- Primary reactor, 2- Microbial cell separation device, 3- Distillation device, 4- Secondary reactor, 5- Concentration device, 51- Filtration section, 52- Reduced pressure concentration section, 53- Rectification section, 6- Nutrient solution supply device, 10- Air inlet pipeline, 20- Microbial liquid pipeline, 30- Fermentation broth pipeline, 40- Residual distillate pipeline, 50- Ethanol pipeline, 60- Mash pipeline, 70- Hexanoic acid pipeline, 80- Nutrient solution pipeline. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0032] It should be noted that all directional indications in this utility model embodiment, such as up, down, left, right, front, back, etc., are only used to explain the relative positional relationship and movement of the components in a specific posture, as shown in the attached figure. If the specific posture changes, the directional indication will also change accordingly.

[0033] In this utility model, unless otherwise explicitly specified and limited, the terms "connection" and "fixation" should be interpreted broadly. For example, "fixation" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection, an electrical connection, or a magnetic connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0034] Figure 1 This is a schematic diagram of a system for co-producing ethanol and hexanoic acid through syngas fermentation, as provided in an embodiment of this application.

[0035] like Figure 1 As shown, this application provides a system for the co-production of ethanol and hexanoic acid through syngas fermentation, the system comprising:

[0036] A primary reactor 1 is introduced into the primary reactor 1 to carry out primary fermentation of the raw material gas to obtain a bacterial solution containing ethanol and acetic acid;

[0037] The bacterial cell separation device 2 has its inlet connected to the outlet of the primary bioreactor, and is used to separate the bacterial strains in the bacterial solution to obtain fermentation broth.

[0038] Distillation apparatus 3, wherein the inlet of distillation apparatus 3 is connected to the outlet of the supernatant of cell separation apparatus 2, is used to distill the fermentation supernatant to obtain ethanol product and residual water containing acetic acid; and

[0039] Secondary reactor 4, the inlet of which is connected to the outlet of the residual distillate of the distillation device 3, is used to carry out secondary fermentation of the acetic acid-containing residual distillate to obtain mash containing hexanoic acid.

[0040] The primary reactor 1 converts the purified raw gas (mainly CO or mainly CO, H2, and CO2) into ethanol and acetic acid through a fermentation reaction, while simultaneously enabling the growth and reproduction of the microbial strain. The raw gas enters the primary reactor 1 through the inlet pipeline 10, and the reactor maintains suitable temperature, pressure, and pH to promote the growth and metabolism of the microbial strain.

[0041] The bacterial separation system uses membrane filtration or centrifugation to separate the bacterial strains from the bacterial broth, obtaining a sterile fermentation broth to facilitate subsequent distillation and secondary fermentation. The bacterial broth enters the bacterial separation system from the outlet of the primary reactor 1, where membrane filtration or centrifugation separates the bacterial strains from the fermentation broth.

[0042] Distillation unit 3 extracts ethanol from the sterile fermentation broth, simultaneously obtaining distillate containing acetic acid. After the fermentation broth enters distillation unit 3, the ethanol is evaporated and collected by heating and depressurization to obtain the ethanol product. The distillate in the bottoms contains acetic acid and other components, which are used for subsequent secondary fermentation.

[0043] Secondary reactor 4 utilizes hexanoic acid-producing bacteria to convert acetic acid-containing residual distillate into hexanoic acid. After entering secondary reactor 4, the acetic acid-containing residual distillate is maintained at suitable temperature, pH, and nutrient conditions to promote the growth and metabolism of the hexanoic acid-producing bacteria. The resulting hexanoic acid-containing mash then enters the subsequent concentration system.

[0044] In some embodiments, the system further includes:

[0045] The concentration device 5 is connected to the outlet of the secondary reactor 4 to concentrate the mash and obtain hexanoic acid product.

[0046] In some embodiments, the concentration device 5 includes:

[0047] The filter section 51 has an inlet that is connected to the outlet of the secondary reactor 4.

[0048] The vacuum concentration section 52 is connected to the clear liquid outlet of the filtration section 51.

[0049] The distillation section 53 has its inlet connected to the outlet of the vacuum concentration section 52.

[0050] The hexanoic acid concentration system extracts high-purity hexanoic acid product from hexanoic acid-containing mash through filtration, vacuum concentration, and distillation. The hexanoic acid-containing mash is first filtered to remove impurities, then enters the vacuum concentration unit 52 for concentration. The concentrated hexanoic acid solution enters the distillation unit 53 for further purification, ultimately yielding the high-purity hexanoic acid product.

[0051] In some embodiments, the system further includes:

[0052] Nutrient solution supply device 6 is connected to the primary reactor 1 and the secondary reactor 4 respectively.

[0053] The nutrient solution supply system provides the necessary nutrients to the primary and secondary reactors 4 to support the growth and metabolism of the microorganisms. The nutrient solution, containing iron, potassium, magnesium, trace metals, vitamins, and other nutrients, is delivered to the primary reactor 1 and secondary reactor 4 via pipelines to meet the needs of microbial growth and metabolism.

[0054] In some embodiments, the bacterial cell separation device 2 is a membrane filtration device or a centrifuge.

[0055] In some embodiments, the distillation apparatus is a distillation column.

[0056] In some embodiments, the distillation column has a bottom temperature in the range of 110°C to 120°C and a top pressure of 60 kPa.

[0057] In some embodiments, both the primary reactor and the secondary reactor are equipped with stirring components.

[0058] This application's embodiments enable primary fermentation to produce metabolites such as ethanol and acetic acid. After distillation to extract the ethanol product, the acetic acid is used as a substrate in a secondary fermentation system to produce hexanoic acid. This system avoids the acetic acid produced during primary fermentation from entering the downstream wastewater system, reducing the wastewater treatment load, and simultaneously converting low-value products into high-value products, thereby improving economic efficiency.

[0059] In summary, the system for co-producing ethanol and hexanoic acid through syngas fermentation proposed in this application has the following significant advantages:

[0060] (1) High-efficiency utilization of resources: The system maximizes the utilization of raw gas through a series of primary and secondary fermentation processes. Ethanol and acetic acid produced by primary fermentation are extracted as valuable products, and acetic acid is further used as a substrate for secondary fermentation to be converted into high-value hexanoic acid, thereby improving the overall resource utilization efficiency.

[0061] (2) Environmentally friendly: This system avoids the direct entry of acetic acid produced during primary fermentation into the downstream wastewater system, significantly reducing the load on wastewater treatment. This not only benefits environmental protection but also reduces wastewater treatment costs.

[0062] (3) Improved economic benefits: By converting low-value acetic acid into high-value hexanoic acid, the system enhances product value. Furthermore, ethanol and hexanoic acid, as two important chemicals, have broad application prospects in the market, thus increasing the system's economic benefits.

[0063] (4) Technological integration and innovation: The system integrates multiple unit operations such as fermentation, distillation, and concentration, forming a complete process chain. The synergistic effect and optimized design between the units improve the efficiency and stability of the overall system.

[0064] (5) Flexibility and scalability: The system design has a certain degree of flexibility and scalability, and the production scale and product structure can be adjusted according to market demand and raw material supply. In addition, the introduction of the nutrient solution supply device provides the system with the necessary nutritional support, ensuring the stable growth and metabolism of the strain.

[0065] The embodiments of this application are further illustrated below with reference to specific examples. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to industry standards; if there is no corresponding industry standard, they are performed according to general international standards, conventional conditions, or conditions recommended by the manufacturer.

[0066] Example 1

[0067] like Figure 1 As shown, the purified raw gas, generally composed mainly of CO / H2 / CO2, enters the primary reactor 1 through the inlet pipeline 10. Fermentation occurs in the primary reactor, yielding a bacterial solution containing ethanol and acetic acid; the ethanol concentration reaches 40 g / L, and the acetic acid concentration is 5 g / L to 10 g / L. The bacterial solution containing ethanol and acetic acid is transported to the bacterial cell separation device 2 through the bacterial solution pipeline 20. A ceramic membrane device is used as the bacterial cell separation device 2 to increase the bacterial concentration. After the bacterial cell separation device retains the inoculum, the filtered fermentation broth enters the distillation column 3 through the fermentation broth pipeline 30. The column bottom temperature is maintained within the range of 110℃ to 120℃, and the pressure at the top of the column is 60 kPa. Ethanol product with a purity of 95% is collected at the top of the column through the ethanol pipeline 50. The acetic acid concentration in the residual water from the acetic acid extraction tower is in the range of 5 g / L to 10 g / L. This residual water enters the secondary reactor 4 through the residual water pipeline 40. The secondary reactor 4 uses hexanoic acid-producing bacteria for fermentation, and the resulting hexanoic acid-containing mash enters the subsequent concentration unit 5 through the mash pipeline 60, ultimately yielding hexanoic acid product with a purity of 95%. The hexanoic acid product is collected through the hexanoic acid pipeline 50. The nutrient solution required for fermentation, generally including iron, potassium, magnesium, trace metals, and vitamins, is delivered to the primary reactor 1 and the secondary reactor 4 through the nutrient solution supply system 6 and the nutrient solution pipeline 80.

[0068] Furthermore, one or more technical solutions in the embodiments of this application have at least the following technical effects or advantages:

[0069] In this embodiment, the acetic acid inhibition effect of the existing solution can be solved, and at the same time, a brand-new high-value product - hexanoic acid - can be obtained, and the wastewater treatment load can be reduced.

[0070] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.

[0071] Obviously, those skilled in the art can make various modifications and variations to this utility model without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this utility model and their equivalents, this utility model also intends to include these modifications and variations.

Claims

1. A system for co-producing ethanol and hexanoic acid through syngas fermentation, characterized in that, The system includes: A primary reactor (1) is introduced into the primary reactor (1) to carry out primary fermentation of the raw material gas to obtain a bacterial liquid containing ethanol and acetic acid; The bacterial cell separation device (2) is connected to the discharge port of the primary reactor (1) to separate the bacterial strains in the bacterial liquid and obtain fermentation liquid; A distillation apparatus (3), the inlet of which is connected to the outlet of the cell separation apparatus (2), is used to distill the fermentation liquid to obtain ethanol and residual water containing acetic acid; and A secondary reactor (4) is connected to the outlet of the distillation apparatus (3) for secondary fermentation of the acetic acid-containing residual distillate to obtain mash containing hexanoic acid.

2. The system according to claim 1, characterized in that, The system also includes: The concentration device (5) is connected to the outlet of the secondary reactor (4) to concentrate the mash and obtain hexanoic acid product.

3. The system according to claim 2, characterized in that, The concentration device (5) includes: The filter section (51) has an inlet that is connected to the outlet of the secondary reactor (4). The vacuum concentration section (52) is connected to the clear liquid outlet of the filtration section (51).

4. The system according to claim 3, characterized in that, The concentration device (5) further includes: The distillation section (53) has its inlet connected to the outlet of the vacuum concentration section (52).

5. The system according to claim 1, characterized in that, The system also includes: Nutrient solution supply device (6) is connected to the primary reactor (1) and the secondary reactor (4) respectively.

6. The system according to claim 1, characterized in that, The bacterial separation device (2) is a membrane filtration device.

7. The system according to claim 1, characterized in that, The bacterial cell separation device (2) is a centrifuge.

8. The system according to claim 1, characterized in that, The distillation apparatus (3) is a distillation column.

9. The system according to claim 8, characterized in that, The distillation column has a bottom temperature in the range of 110℃ to 120℃ and a top pressure of 60 kPa.

10. The system according to claim 1, characterized in that, Both the primary reactor (1) and the secondary reactor (4) are equipped with stirring components.

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