Synthesis gas fermentation liquid cooling system and method

Abstract

The invention relates to a syngas fermentation broth cooling system and method.The system comprises a circulating discharging unit (2) and a circulating feeding unit (3) which are connected with a biological reaction unit (1), the circulating feeding unit (3) comprises a circulating pipe A (31) and a circulating pipe B (32), the inlet end of the circulating pipe A (31) is connected with the circulating discharging unit (2), and the outlet end of the circulating pipe A (31) is connected with the biological reaction unit (1); the inlet end of the circulating pipe B (32) is connected with the circulating discharge unit (2), and the outlet end is connected with the biological reaction unit (1) through the heat exchange unit (4). Compared with the prior art, the method has the advantages that the fermentation activity of the synthesis gas biological reaction unit can be continuously and stably operated, the cleaning frequency of the heat exchanger can be reduced, or even if the heat exchanger is cleaned, the fermentation activity cannot be impacted, and the method has great significance in promoting the development of a synthesis gas fermentation technology.

Description

Technical Field

[0001] This invention relates to the field of syngas fermentation technology, and in particular to a syngas fermentation liquid cooling system and method. Background Technology

[0002] Syngas fermentation involves anaerobic aerobic bacteria using syngas (CO, CO2, and H2) as both a carbon and energy source for reproduction and growth. Depending on the bacterial strain, the bacteria metabolize to produce biofuels such as ethanol and butanol. Anaerobic aerobic bacteria exist in nature and can be artificially selected and domesticated. Syngas is widely derived from coal chemical industry, petrochemical industry, industrial waste gas (such as steel mill waste gas), municipal waste, and biomass. Currently, various types of bioreactors are used for syngas fermentation, including continuous stirred tank reactors, trickle bed reactors, hollow fiber membrane bioreactors, bubble column bioreactors, and airlift bioreactors. Regardless of the reactor type, maintaining the reactor temperature is essential to create the conditions necessary for the fermentation activity of the bacteria.

[0003] Currently, the reactor temperature is mostly maintained through external circulation heat exchange using plate heat exchangers. During normal operation of syngas fermentation, chilled water (or circulating water) is used to cool the fermentation broth to stabilize the reactor temperature. However, because the fermentation broth contains microbial cells (mainly proteins), and the gaps between the heat exchange plates in the plate heat exchanger are small, proteins adhere to the contact surfaces of the equipment after a period of operation, eventually leading to blockage and decreased mass transfer efficiency. Therefore, during the circulation cooling of the fermentation broth, the plate heat exchanger needs to be stopped periodically for CIP cleaning, making it difficult to maintain continuous and stable fermentation activity in the reactor. Summary of the Invention

[0004] The purpose of this invention is to provide a syngas fermentation liquid cooling system and method, which is beneficial to the continuous and stable operation of fermentation activities.

[0005] The objective of this invention can be achieved through the following technical solution: a syngas fermentation liquid cooling system, comprising a circulating discharge unit and a circulating feed unit connected to a bioreactor unit. The circulating feed unit includes a circulating pipe A and a circulating pipe B. The inlet end of the circulating pipe A is connected to the circulating discharge unit, and the outlet end is connected to the bioreactor unit. The inlet end of the circulating pipe B is connected to the circulating discharge unit, and the outlet end is connected to the bioreactor unit via a heat exchange unit.

[0006] Preferably, the heat exchange unit includes one or more sets of shell-and-tube heat exchangers.

[0007] More preferably, the heat exchange unit includes multiple sets of parallel shell-and-tube heat exchangers, each of which is connected to a corresponding on / off valve and flow regulating valve.

[0008] More preferably, the heat exchange unit includes five sets of parallel shell-and-tube heat exchangers. The function of the shell-and-tube heat exchangers (sets) is to cool the circulating fermentation broth (10% of the total circulation volume) with chilled water at 7°C. A total of 5 sets of shell-and-tube heat exchangers are configured, and the operating state during normal production of the bioreactor unit is 4 on and 1 on standby.

[0009] More preferably, each shell-and-tube heat exchanger is equipped with a switch valve at the inlet end and a flow meter and flow regulating valve at the outlet end.

[0010] Preferably, the circulating discharge unit includes a circulating liquid discharge port, a circulating liquid discharge pipe, and a circulating pump;

[0011] The circulating liquid discharge pipe is connected to the bioreactor unit through the circulating liquid discharge port, and is connected to circulating pipe A and circulating pipe B through a circulating pump.

[0012] The circulating pump is connected to the circulating liquid outlet pipe and the circulating liquid inlet. The circulating pump outputs the fermentation broth. Most of the fermentation broth (90% of the total circulation volume) flows into the main circulating pump pipe through circulating pipe A, and then enters the bioreactor unit through the circulating liquid inlet. A small portion (10% of the total circulation volume) of the fermentation broth is transported to the shell and tube heat exchanger (group) for cooling. The cooled fermentation broth also flows into the main circulating pump pipe and enters the bioreactor unit through the circulating liquid inlet.

[0013] Preferably, the circulating feed unit further includes a main circulating pump pipe and a circulating liquid inlet. The outlet ends of circulating pipe A and circulating pipe B are connected to the bioreactor unit via the main circulating pump pipe and the circulating liquid inlet, that is, the uncooled circulating fermentation broth and the cooled circulating fermentation broth enter the bioreactor unit through the main circulating pump pipe.

[0014] Preferably, the bioreactor unit is connected to a syngas inlet unit.

[0015] More preferably, the syngas intake unit includes a syngas intake pipe and a syngas inlet, the syngas intake pipe is connected to the bioreactor unit through the syngas inlet, and syngas is introduced into the bioreactor unit through the inlet.

[0016] Preferably, the bioreactor unit includes a fermenter and a gas-liquid mixing assembly disposed within the fermenter. The fermenter is the site where the microorganisms carry out fermentation activities, and it contains the gas-liquid mixing assembly. The microorganisms and syngas in the fermentation broth undergo a bioconversion reaction in the gas-liquid mixing assembly. The microorganisms convert the introduced syngas into the target product—ethanol—in a single step. After the bioconversion reaction, the fermentation broth heats up and flows out from the bottom of the fermenter. After being cooled by an external circulation heat exchanger, it returns to the fermenter.

[0017] More preferably, the syngas inlet unit and the circulating feed unit are connected to the gas-liquid mixing assembly. The circulating fermentation broth and syngas are mixed in the gas-liquid mixing assembly, generating microbubbles, enabling the microorganisms to complete the conversion of the syngas. The bioreactor unit has requirements for the gas / liquid ratio and requires a fixed flow rate of circulating liquid.

[0018] More preferably, the gas-liquid ratio of the bioreactor unit is (1-5):1, i.e., 1-5 Nm 3 Synthesis gas, corresponding to 1m 3 Fermentation broth.

[0019] Preferably, the bioreactor unit and / or heat exchange unit is connected to a CIP cleaning unit.

[0020] More preferably, the circulating fermentation broth route is the tube side of a shell-and-tube heat exchanger, while the shell side of the heat exchanger is equipped with chilled water inlet and return lines. Each heat exchanger group is equipped with a CIP cleaning unit, allowing each heat exchanger to be cleaned independently. The normal operating state of the shell-and-tube heat exchanger (group) is 4 active and 1 standby. When cleaning is required for the 4 operating heat exchanger groups (referred to as the "original state"), the operation of one heat exchanger group is stopped, and the inlet shut-off valve (on / off valve) and outlet regulating valve of that group are closed, isolating it from the others for independent CIP cleaning. At this time, the standby heat exchanger group is put into use, and the current operating state is 4 active and 1 standby (the standby group awaiting cleaning). The heat exchanger (group) switching is complete. Then, the heat exchanger group that just stopped operating is subjected to CIP flushing, with a total flushing time of approximately 10-20 minutes. After flushing, the other three heat exchangers that required CIP flushing in their "original state" are then flushed in turn, until all three heat exchangers have been CIP flushed. Finally, the operating status of the heat exchangers (groups) is 4 operating and 1 standby. Alternatively, after the fermenter is drained, the CIP flushing system built into the fermenter can be used to perform CIP flushing on the shell-and-tube heat exchangers (groups). The flushing solution after cleaning the tank is stored in the fermenter, and then a circulating pump is used to transport the flushing solution to achieve CIP flushing of the heat exchangers (groups).

[0021] A method for cooling syngas fermentation broth, using the above-mentioned system, includes the following steps:

[0022] The fermentation broth in the bioreactor unit is transported to circulation pipe A and circulation pipe B through the circulation discharge unit. The fermentation broth in circulation pipe A is directly returned to the bioreactor unit, while the fermentation broth in circulation pipe B is cooled by the heat exchange unit and then returned to the bioreactor unit. The flow rate of circulation pipe A is greater than that of circulation pipe B.

[0023] Preferably, the flow rate of the circulation pipe A accounts for 85-95% of the total discharge flow rate of the circulation discharge unit, and the flow rate of the circulation pipe B accounts for 5-15% of the total discharge flow rate of the circulation discharge unit.

[0024] More preferably, the flow rate of the circulation pipe A accounts for 90% of the total discharge flow rate of the circulation discharge unit, and the flow rate of the circulation pipe B accounts for 10% of the total discharge flow rate of the circulation discharge unit.

[0025] Preferably, the fermentation broth in the circulation pipe B is cooled to 10-30°C by the heat exchange unit and then returned to the bioreactor unit.

[0026] Preferably, the heat exchange unit uses chilled water at 7–12°C.

[0027] More preferably, the heat exchange unit uses chilled water at 7°C.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The present invention, through the coordinated arrangement of circulation pipe A, circulation pipe B and heat exchange unit, enables a small portion of the syngas fermentation liquid to achieve external circulation heat exchange and maintain the temperature of the fermenter at the set temperature. This arrangement can reduce the investment and cleaning costs of the heat exchange unit.

[0030] 2. The heat exchange unit of this invention, through the setting of multiple sets of parallel tube-and-shell heat exchangers and corresponding valves, can reduce the probability of protein blockage and realize the alternating cleaning of heat exchangers, so as to ensure the normal operation of the bioreactor unit and facilitate the continuous and stable operation of fermentation activities.

[0031] 3. The syngas fermentation broth cooling process of this invention uses 7°C chilled water to cool a small portion (10% of the total circulation volume) of the fermentation broth, eliminating the need to cool all the circulating fermentation broth. This reduces the total heat exchange area of ​​the heat exchangers and lowers equipment investment. Since the shell-and-tube heat exchangers (groups) can also be CIP cleaned together with the reactor, each group of heat exchangers does not require a separate CIP cleaning system, further reducing investment in the CIP process.

[0032] 4. This invention uses a shell-and-tube heat exchanger instead of a plate heat exchanger. Due to the different equipment structures, the shell-and-tube heat exchanger can significantly reduce the probability of protein blockage. Furthermore, compared to plate heat exchangers, the shell-and-tube heat exchanger is more convenient for CIP cleaning. With four shell-and-tube heat exchangers in operation and one as a backup, each can be replaced and cleaned individually without shutting down all heat exchange equipment. This reduces the frequency of scale buildup affecting the normal operation of the fermenter reactor and the cost of CIP cleaning. Moreover, CIP cleaning of the heat exchangers can be performed during fermenter cleaning, ensuring that the cleaning process does not affect the normal operation of the fermenter reactor.

[0033] 5. Depending on the season, the number of shell-and-tube heat exchangers used can be flexibly adjusted. Especially when the reactor is operating in winter, the circulating fermentation broth may not need cooling. In this case, the entire flow of circulating fermentation broth can be directly returned to the reactor, putting the five shell-and-tube heat exchangers into standby mode.

[0034] 6. This invention provides a process flow that enables the fermentation activities of a bioreactor to operate continuously and stably, and reduces the number of times the heat exchanger needs to be cleaned, or even if the heat exchanger needs to be cleaned, it will not impact the fermentation activities. This is of great significance for promoting the development of syngas fermentation technology. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the structure of a syngas fermentation liquid cooling system according to the present invention;

[0036] Figure 2 This is a schematic diagram of the structure of the bioreactor unit of the present invention;

[0037] Figure 3 This is a schematic diagram of the structure of the circulating discharge unit of the present invention;

[0038] Figure 4 This is a schematic diagram of the structure of the circulating feeding unit of the present invention;

[0039] Figure 5 This is a schematic diagram of the synthesis gas intake unit of the present invention;

[0040] Figure 6 This is a schematic diagram of another syngas fermentation liquid cooling system according to the present invention;

[0041] In the diagram: 1-Bioreactor unit, 11-Fermenter, 12-Gas-liquid mixing assembly, 2-Circulating discharge unit, 21-Circulating liquid outlet, 22-Circulating liquid outlet pipe, 23-Circulating pump, 3-Circulating feed unit, 31-Circulating pipe A, 32-Circulating pipe B, 33-Main circulating pump pipe, 34-Circulating liquid inlet, 4-Heat exchange unit, 5-Synthetic gas inlet unit, 51-Synthetic gas inlet pipe, 52-Synthetic gas inlet, CHWS-Chilled water inlet, CHWR-Chilled water return, TE-Thermometer, FE-Flow meter. Detailed Implementation

[0042] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0043] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0044] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0045] Example 1

[0046] A syngas fermentation liquid cooling system includes a circulating discharge unit 2, a circulating feed unit 3, and a heat exchange unit 4.

[0047] Both the circulating discharge unit 2 and the circulating feed unit 3 are connected to the bioreactor unit 1. The circulating feed unit 3 includes a circulating pipe A31 and a circulating pipe B32. The inlet end of the circulating pipe A31 is connected to the circulating discharge unit 2, and the outlet end is connected to the bioreactor unit 1. The inlet end of the circulating pipe B32 is connected to the circulating discharge unit 2, and the outlet end is connected to the bioreactor unit 1 via a heat exchange unit 4. The syngas fermentation liquid in the circulating pipe A31 is directly returned to the bioreactor unit 1, and the syngas fermentation liquid in the circulating pipe B32 is cooled by the heat exchange unit 4 and then returned to the bioreactor unit 1.

[0048] Example 2

[0049] A syngas fermentation liquid cooling system, such as Figures 1-5 As shown, the circulating discharge unit 2 includes a circulating liquid discharge port 21, a circulating liquid discharge pipe 22, and a circulating pump 23, which are connected to the circulating pipe A31 and the circulating pipe B32. The circulating feed unit 3 also includes a main circulating pump pipe 33 and a circulating liquid inlet 34. The heat exchange unit 4 includes five parallel shell-and-tube heat exchangers, each of which is connected to a corresponding on / off valve and a flow regulating valve, and uses chilled water at 7°C. The syngas intake unit 5 includes a syngas intake pipe 51 and a syngas inlet 52.

[0050] Specifically, the syngas fermentation broth in bioreactor 1 is transported to circulation pipe A31 and circulation pipe B32 through circulation outlet 21, circulation pipe 22 and circulation pump 23. The syngas fermentation broth in circulation pipe A31 is returned to bioreactor 1 through main circulation pump pipe 33 and circulation inlet 34. The syngas fermentation broth in circulation pipe B32 is cooled by heat exchange in the shell and tube heat exchanger of heat exchange unit 4 and then returned to bioreactor 1 through main circulation pump pipe 33 and circulation inlet 34.

[0051] Furthermore, in this embodiment, each shell-and-tube heat exchanger is connected to a CIP cleaning unit at both its inlet and outlet. Everything else is the same as in Embodiment 1.

[0052] Example 3

[0053] A syngas fermentation liquid cooling system, such as Figure 6 As shown, unlike Example 2, each shell-and-tube heat exchanger is not connected to the CIP cleaning unit, but the bioreactor 1 is connected to the CIP cleaning unit.

[0054] Example 4

[0055] A syngas fermentation broth cooling system, comprising:

[0056] The bioreactor 1 includes a fermenter 11 and a gas-liquid mixing assembly 12 disposed within the fermenter 11.

[0057] Syngas intake unit 5 includes syngas intake pipe 51 and syngas inlet 52;

[0058] The fermentation broth circulation cooling unit includes a circulation pump 23, a circulation broth outlet 21, a circulation broth outlet pipe 22, a circulation pipe A 31, a circulation pipe B 32, a shell and tube heat exchanger (group), a main circulation pump pipe 33, and a circulation broth inlet 34.

[0059] In this embodiment, during the operation of the cooling system, the shell-and-tube heat exchangers (groups) operate with 4 active and 1 standby under normal load in bioreactor unit 1. The chilled water automatically controls the discharge temperature on the material side of each heat exchanger; the outlet flow regulating valve on the material side of the heat exchanger maintains the circulating fermentation broth of each group at a fixed flow rate. When the shell-and-tube heat exchangers (groups) require CIP cleaning, the idle heat exchangers are gradually replaced to ensure that the CIP cleaning of the shell-and-tube heat exchangers does not affect the normal operation of the bioreactor unit.

[0060] Furthermore, the number of shell-and-tube heat exchangers can be flexibly adjusted according to the season. When the bioreactor is operating in winter, the circulating fermentation broth may not require cooling. In this case, all the circulating fermentation broth can be directly returned to the bioreactor, putting the five shell-and-tube heat exchangers into standby mode.

[0061] Example 5

[0062] A syngas fermentation broth cooling system, comprising:

[0063] The bioreactor 1 includes a fermenter 11 and a gas-liquid mixing assembly 12 disposed within the fermenter 11.

[0064] Syngas intake unit 5 includes syngas intake pipe 51 and syngas inlet 52;

[0065] The fermentation broth circulation cooling unit includes a circulation pump 23, a circulation broth outlet 21, a circulation broth outlet pipe 22, a circulation pipe A 31, a circulation pipe B 32, a shell and tube heat exchanger (group), a main circulation pump pipe 33, and a circulation broth inlet 34.

[0066] The heat exchange process in Example 5 is basically the same as in Example 4, except that an independent CIP cleaning system is not configured for each group of shell-and-tube heat exchangers. Because the fermentation strain has a limited lifespan, it is necessary to re-cultivate the strain when its activity decreases, and the fermenter must be transferred to another tank. After the fermenter transfer is completed, the shell-and-tube heat exchangers (groups) can be CIP cleaned together with the bioreactor unit.

[0067] The fermenter is equipped with a CIP cleaning system, which can inject a certain volume of cleaning solution into the fermenter and start the circulation pump to circulate and clean the shell and tube heat exchangers (groups), thus further reducing the investment in the CIP process.

[0068] In syngas fermentation, plate heat exchangers are used to cool the fermentation broth. However, due to bacterial proteins causing blockages, the heat exchangers require CIP cleaning 1-2 times per week, which disrupts the reactor's normal operation. This invention designs a new process for cooling the syngas fermentation broth, using a shell-and-tube heat exchanger instead of a plate heat exchanger. The fermentation broth is cooled with 7°C chilled water, and the distribution flow rate of the circulating fermentation broth has been adjusted to meet the flow requirements of the bioreactor unit. The use of a shell-and-tube heat exchanger significantly reduces the likelihood of blockage, requiring cleaning only once every 1-2 months during normal fermentation operation, or even eliminating the need for cleaning during normal operation. This process maintains the fermenter temperature and ensures that normal fermentation activities within the fermenter are not disrupted, even when heat exchanger cleaning is required.

[0069] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A syngas fermentation broth cooling system, characterized in that, It includes a circulating discharge unit (2) and a circulating feed unit (3) connected to the bioreactor unit (1). The circulating feed unit (3) includes a circulating pipe A (31) and a circulating pipe B (32). The inlet end of the circulating pipe A (31) is connected to the circulating discharge unit (2), and the outlet end is connected to the bioreactor unit (1). The inlet end of the circulating pipe B (32) is connected to the circulating discharge unit (2), and the outlet end is connected to the bioreactor unit (1) via a heat exchange unit (4).

2. The syngas fermentation broth cooling system according to claim 1, characterized in that, The heat exchange unit (4) includes one or more sets of shell and tube heat exchangers.

3. The syngas fermentation broth cooling system according to claim 2, characterized in that, The heat exchange unit (4) includes multiple parallel shell-and-tube heat exchangers, each of which is connected to a corresponding on / off valve and flow regulating valve.

4. The syngas fermentation broth cooling system according to claim 3, characterized in that, Each shell-and-tube heat exchanger is equipped with an on / off valve at the inlet and a flow meter and flow regulating valve at the outlet.

5. The syngas fermentation broth cooling system according to claim 1, characterized in that, The circulating discharge unit (2) includes a circulating liquid discharge port (21), a circulating liquid discharge pipe (22), and a circulating pump (23); The circulating liquid outlet pipe (22) is connected to the bioreactor unit (1) through the circulating liquid outlet (21), and is connected to the circulating pipe A (31) and the circulating pipe B (32) through the circulating pump (23).

6. The syngas fermentation broth cooling system according to claim 1, characterized in that, The circulating feed unit (3) also includes a main circulating pump pipe (33) and a circulating liquid inlet (34). The outlet ends of the circulating pipe A (31) and the circulating pipe B (32) are connected to the bioreactor unit (1) via the main circulating pump pipe (33) and the circulating liquid inlet (34).

7. The syngas fermentation broth cooling system according to claim 1, characterized in that, The bioreactor (1) is connected to a syngas inlet unit (5); The syngas intake unit (5) includes a syngas intake pipe (51) and a syngas inlet (52), and the syngas intake pipe (51) is connected to the bioreactor unit (1) through the syngas inlet (52).

8. The syngas fermentation broth cooling system according to claim 1, characterized in that, The bioreactor unit (1) and / or heat exchange unit (4) are connected to a CIP cleaning unit.

9. A method for cooling syngas fermentation broth, characterized in that, Using the system according to any one of claims 1 to 8, the process includes the following steps: The fermentation broth in the bioreactor unit (1) is transported to the circulation pipe A (31) and circulation pipe B (32) through the circulation discharge unit (2). The fermentation broth in the circulation pipe A (31) is directly returned to the bioreactor unit (1), and the fermentation broth in the circulation pipe B (32) is cooled by the heat exchange unit (4) and then returned to the bioreactor unit (1). The flow rate of the circulation pipe A (31) is greater than that of the circulation pipe B (32).

10. The method for cooling syngas fermentation broth according to claim 9, characterized in that, The flow rate of the circulation pipe A (31) accounts for 85-95% of the total discharge flow rate of the circulation discharge unit (2), and the flow rate of the circulation pipe B (32) accounts for 5-15% of the total discharge flow rate of the circulation discharge unit (2). The fermentation liquid in the circulation pipe B (32) is cooled by the heat exchange unit (4) and then returned to the bioreactor unit (1).

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