Positive and negative pressure protection device and anaerobic fermentation system

Abstract

The utility model provides a positive and negative pressure protection device and an anaerobic fermentation system, the anaerobic fermentation system comprises an anaerobic fermentation tank and the positive and negative pressure protection device, and the positive and negative pressure protection device is connected to the positive and negative pressure protection interface of the anaerobic fermentation tank. The positive and negative pressure protection device comprises a box body capable of storing liquid, the box body is provided with an air inlet, an air outlet and an overflow port, the air inlet is used for being connected with the positive and negative pressure protection interface of the anaerobic fermentation tank, and the air inlet and the air outlet are both higher than the overflow port; an inner extending pipe extends on the inner side wall of the box body corresponding to the position of the air inlet; in a normal state, the liquid level in the box body is higher than the bottom end of the inner extending pipe and lower than the overflow opening. By means of the arrangement, when the pressure of the anaerobic fermentation tank is too large, biogas can enter the box body through the gas inlet, liquid is pushed to rise and overflow from the overflow opening, the pressure is released, and biogas leakage is avoided; and when the pressure in the anaerobic fermentation tank is too small, external gas pushes the liquid to enter the inner extension pipe, so that the air pressure in the anaerobic fermentation tank quickly returns to normal.

Description

Technical Field

[0001] This application belongs to the field of positive and negative pressure protection technology, and more specifically, relates to a positive and negative pressure protection device and an anaerobic fermentation system. Background Technology

[0002] Anaerobic fermentation is a biochemical reaction process carried out by microorganisms under anaerobic conditions. These microorganisms decompose organic matter to produce energy and metabolic products. It can be applied to agricultural waste, kitchen waste centrifuges, wastewater, and other fields to generate biogas energy. The fermentation process mainly takes place in an anaerobic digester. The internal pressure of the digester fluctuates due to changes in feed and discharge, external temperature, and the gas supply system. When the internal pressure exceeds or falls below the normal pressure range, the digester will be damaged. Utility Model Content

[0003] The purpose of this application is to provide a positive and negative pressure protection device and an anaerobic fermentation system to solve the technical problem that the anaerobic fermenter will be damaged when the internal pressure exceeds or falls below the normal pressure in the prior art.

[0004] To achieve the above objectives, the technical solution adopted in this application is as follows: a positive and negative pressure protection device is provided for positive and negative pressure protection of an anaerobic fermenter. The device comprises a box capable of storing liquid, the box having an air inlet, an air outlet, and an overflow outlet. The air inlet is connected to the positive and negative pressure protection interface of the anaerobic fermenter, and both the air inlet and the air outlet are higher than the overflow outlet. An inner extension pipe extends from the inner sidewall of the box corresponding to the position of the air inlet. Under normal conditions, the liquid level inside the box is higher than the bottom end of the inner extension pipe and lower than the overflow outlet.

[0005] In some embodiments, the air inlet is located on the top side wall of the housing, and the inner extension tube extends vertically downward from the top inner wall of the housing.

[0006] And / or, the air outlet is located on the top side wall of the housing.

[0007] In some embodiments, the bottom end face of the inner tube has a first distance from the bottom inner wall of the box, the first distance being in the range of 100mm-200mm.

[0008] In some embodiments, the air inlet and the air outlet are both located on the top sidewall of the housing; the first center line of the air inlet and the second center line of the air outlet are both located on the first center surface of the housing along the first direction;

[0009] The air inlet and the air outlet are symmetrically arranged relative to the second center face of the housing along the second direction; wherein the first direction is perpendicular to the second direction.

[0010] In some embodiments, the housing is further provided with a level gauge for detecting the liquid level inside the housing; the level gauge is a glass level gauge that communicates with the housing, the overflow port and the level gauge are both located on the peripheral side wall of the housing, the bottom end of the level gauge is higher than the bottom end of the inner extension tube and lower than the overflow port, and the top end of the level gauge is higher than the overflow port.

[0011] In some embodiments, the level gauge and the overflow port are disposed on two side walls of the housing that are opposite to each other along the second direction, and the two side walls of the housing that are opposite to each other along the first direction are respectively provided with fixing ears.

[0012] In some embodiments, the housing further has a liquid injection port for injecting liquid into the housing, the liquid injection port being normally closed;

[0013] The housing has a drain outlet for discharging liquid, which is normally closed.

[0014] In some embodiments, the housing has an outwardly protruding pipe at the positions corresponding to the air inlet, air outlet and overflow port, and the outer peripheral wall of the outwardly protruding pipe is provided with a flange.

[0015] In some embodiments, the housing includes a top plate, a bottom plate, and side plates. The top plate and the bottom plate are disposed opposite to each other. The side plates are welded to the bottom periphery of the top plate and to the top periphery of the bottom plate. The side plates include multiple sub-plates welded end to end. The inner extension tube is welded to the top plate. The top plate, the bottom plate, the side plates, and the inner extension tube are all made of stainless steel.

[0016] On the other hand, this application also provides an anaerobic fermentation system, including an anaerobic fermenter and the above-mentioned positive and negative pressure protection device, wherein the positive and negative pressure protection device is connected to the positive and negative pressure protection interface of the anaerobic fermenter.

[0017] The beneficial effects of the positive and negative pressure protection device and anaerobic fermentation system provided in this application are as follows: By setting up a box capable of storing liquid, and providing an air inlet, an air outlet, and an overflow outlet on the box, the air inlet is connected to the positive and negative pressure protection interface of the anaerobic fermenter. An inner extension pipe extends from the box corresponding to the air inlet. Under normal conditions, the liquid level in the box is higher than the bottom of the inner extension pipe and lower than the overflow outlet. This arrangement ensures that when the pressure inside the anaerobic fermenter is too high, the biogas in the anaerobic fermenter enters the inner extension pipe through the air inlet and enters the liquid in the box from the bottom of the inner extension pipe, thereby pushing the liquid upward. When the liquid rises to the overflow port, it overflows outwards, thus releasing the pressure inside the anaerobic digester and preventing the digester from bursting due to excessive pressure and causing biogas leakage. When the pressure inside the anaerobic digester is too low, external gas enters the upper part of the tank through the gas outlet. The external gas pushes the liquid so that it enters the inner extension pipe through the bottom end, thereby quickly restoring the gas pressure inside the anaerobic digester to normal. This achieves positive and negative pressure protection for the anaerobic digester, preventing damage caused by excessively low or high internal pressure. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A side view of the positive and negative pressure protection device provided in the embodiments of this application along the first direction;

[0020] Figure 2 A side view of the positive and negative pressure protection device provided in the embodiments of this application along the second direction;

[0021] Figure 3 This is a top view of the positive and negative pressure protection device provided in the embodiments of this application.

[0022] The following are the labeling elements in the figure:

[0023] 100. Housing; 110. Top plate; 111. Air inlet; 112. Air outlet; 113. Liquid inlet; 120. Bottom plate; 130. Side plate; 131. Divider plate; 132. Overflow outlet; 133. Drain outlet; 140. Inner extension pipe; 150. Fixing lug; 160. Outer extension pipe; 170. Flange; 200. Level gauge; D1. First distance; D2. Second distance; O1. First centerline; O2. Second centerline; M1. First center plane; M2. Second center plane; X. First direction; Y. Second direction. Detailed Implementation

[0024] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0025] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0026] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0027] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0028] Please see Figures 1 to 3 The positive and negative pressure protection device provided in the embodiments of this application will now be described. This positive and negative pressure protection device is used to connect to the positive and negative pressure protection interface of the anaerobic digester to protect the anaerobic digester from positive and negative pressure, preventing damage to the anaerobic digester due to excessively low or high internal pressure.

[0029] The positive and negative pressure protection device includes a tank 100 capable of storing liquid. The tank 100 has an air inlet 111, an air outlet 112, and an overflow outlet 132. The air inlet 111 is used to connect to the positive and negative pressure protection interface of the anaerobic digester. Both the air inlet 111 and the air outlet 112 are higher than the overflow outlet 132. An inner extension pipe 140 extends from the inner side wall of the tank 100 at the position corresponding to the air inlet 111. Under normal conditions, the liquid level in the tank 100 is higher than the bottom end of the inner extension pipe 140 and lower than the overflow outlet 132.

[0030] It should be noted that the above-mentioned normal state means that the positive and negative pressure protection device has been connected to the positive and negative pressure protection interface of the anaerobic digester and is in a positive and negative pressure protection state.

[0031] When using the positive and negative pressure protection device, first connect the air inlet 111 of the box 100 to the positive and negative pressure protection interface of the anaerobic fermenter, then inject liquid into the box 100 and make the liquid level reach the preset height, specifically, the liquid level should be higher than the bottom of the inner extension pipe 140 and lower than the overflow port 132.

[0032] When the pressure inside the anaerobic digester becomes too high, the biogas enters the inner pipe 140 through the inlet 111 and then flows into the liquid in the tank 100 from the bottom of the inner pipe 140. Since the bottom of the inner pipe 140 is below the liquid level, the biogas pushes the liquid upward. When the liquid rises to the overflow port 132, it overflows outward from the overflow port 132. This releases the pressure inside the anaerobic digester and prevents the digester from bursting due to excessive pressure and causing biogas leakage. Of course, when too much biogas is released, some biogas will also be discharged from the outlet 112. For example, a flare can be connected to the outlet 112 to properly manage the biogas.

[0033] When the pressure inside the anaerobic digester is too low, external gas enters the upper part of the chamber 100 through the gas outlet 112. The external gas pushes the liquid so that the liquid enters the inner extension pipe 140 through the bottom end of the inner extension pipe 140, thereby quickly restoring the gas pressure inside the anaerobic digester to normal.

[0034] The positive and negative pressure protection device in this embodiment of the application is configured with a liquid storage tank 100, and an air inlet 111, an air outlet 112, and an overflow outlet 132 on the tank 100. The air inlet 111 is connected to the positive and negative pressure protection interface of the anaerobic digester. An inner extension pipe 140 extends from the tank 100 corresponding to the position of the air inlet 111. Under normal conditions, the liquid level in the tank 100 is higher than the bottom end of the inner extension pipe 140 and lower than the overflow outlet 132. This configuration ensures that when the pressure inside the anaerobic digester is too high, the biogas in the anaerobic digester enters the inner extension pipe 140 through the air inlet 111 and enters the liquid storage tank 100 from the bottom end of the inner extension pipe 140. The liquid inside the tank is pushed upwards, and when it reaches the overflow port 132, it overflows outwards. This releases the pressure inside the anaerobic digester, preventing it from bursting due to excessive pressure and causing biogas leakage. When the pressure inside the anaerobic digester is too low, external gas enters the upper part of the housing 100 through the gas outlet 112. The external gas pushes the liquid so that it enters the inner extension pipe 140 through the bottom end, thereby quickly restoring the gas pressure inside the anaerobic digester to normal. This provides positive and negative pressure protection for the anaerobic digester, preventing damage caused by excessively low or high internal pressure.

[0035] In some embodiments, the air inlet 111 can be located on the top side wall of the housing 100 or on the peripheral side wall of the housing 100, and the specific design can be made according to the actual situation.

[0036] As an example, please see Figure 1 and Figure 2 An air inlet 111 is located on the top side wall of the housing 100, and an inner extension pipe 140 extends vertically downward from the top inner wall of the housing 100. By placing the air inlet 111 on the top side wall of the housing 100, the inner extension pipe 140 can extend vertically downward from the top inner wall of the housing 100, allowing biogas to quickly enter the inner extension pipe 140 from the air inlet 111, and also allowing liquid inside the housing 100 to quickly enter the inner extension pipe 140. This also results in a simple structure and ease of manufacture for the inner extension pipe 140.

[0037] In some embodiments, please refer to Figure 1The bottom end face of the inner extension pipe 140 is at a first distance D1 from the bottom inner wall of the box 100. The range of the first distance D1 can be 100mm-200mm, that is, the first distance D1 can be 100mm, 110mm, 120mm, 130mm, 140mm, 150mm, 160mm, 170mm, 180mm, 190mm or 200mm, etc. By separating the bottom end face of the inner extension pipe 140 from the bottom inner wall of the box 100 by the first distance D1, on the one hand, the inner extension pipe 140 can extend as far as possible to the bottom of the box 100, so that the biogas in the inner extension pipe 140 can push the liquid upward from the bottom of the box 100 and flow out from the overflow port 132 to achieve pressure relief. At the same time, under negative pressure, the water at the bottom of the box 100 can quickly enter the inner extension pipe 140 to balance the pressure in the anaerobic digester. This also prevents the bottom end face of the inner extension pipe 140 from being too close to the bottom inner wall of the box 100, and prevents the biogas in the inner extension pipe 140 from entering the bottom of the box 100 quickly due to the first distance D1 being too small, and also prevents the liquid at the bottom of the box 100 from entering the inner extension pipe 140 quickly.

[0038] In some embodiments, please refer to Figure 1 The vent 112 is located on the top side wall of the housing 100. This arrangement allows the vent 112 to be higher than the overflow port 132, and keeps the anaerobic digester under negative pressure, enabling external gas to quickly enter the housing 100 from top to bottom through the vent 112 to push the liquid into the inner extension pipe 140. It is understood that in other embodiments of this application, if space permits, the vent 112 may also be located on the peripheral side wall of the housing 100 and higher than the overflow port 132; this is not a limiting factor.

[0039] In some embodiments, please refer to Figure 1 and Figure 3 Both the air inlet 111 and the air outlet 112 are located on the top sidewall of the housing 100. The first center line O1 of the air inlet 111 and the second center line O2 of the air outlet 112 are both located on the first center plane M1 of the housing 100 along the first direction X. The air inlet 111 and the air outlet 112 are symmetrically arranged relative to the second center plane M2 of the housing 100 along the second direction Y. The first direction X is perpendicular to the second direction Y. This arrangement not only makes the surface of the housing 100 neat and aesthetically pleasing, but also makes the air inlet 111 and the air outlet 112 structurally identical, facilitating their joint fabrication. Furthermore, it allows for a smaller cross-sectional area and less space occupation of the entire housing 100 while meeting the dimensional requirements of the air inlet 111 and the air outlet 112. It is understood that in other embodiments of this application, the air inlet 111 and the air outlet 112 only need to be spaced apart from each other on the top sidewall of the housing 100 to avoid structural interference.

[0040] In some embodiments, please refer to Figures 1 to 3 The tank 100 is also equipped with a level gauge 200 for detecting the liquid level inside the tank 100. Specifically, before normal use, the positive and negative pressure protection device needs to be filled with liquid to a preset level so that the liquid level is below the overflow port 132 and above the bottom of the inner extension pipe 140. This ensures that the positive and negative pressure protection device can function as a positive and negative pressure protection device. The level gauge 200 can detect the liquid level inside the tank 100 in real time, ensuring that the initially added liquid meets the liquid level requirements and that the liquid level meets the usage needs during use.

[0041] In some embodiments, please refer to Figures 1 to 3 The level gauge 200 is a glass level gauge 200 that is connected to the housing 100; the overflow port 132 and the level gauge 200 are both located on the peripheral side wall of the housing 100. The bottom end of the level gauge 200 is higher than the bottom end of the inner extension tube 140 and lower than the overflow port 132, and the top end of the level gauge 200 is higher than the overflow port 132.

[0042] Among them, the glass level gauge 200 is a level measuring gauge that utilizes the principle of communicating vessels. It forms a communicating vessel with the tank 100 through a glass tube. When the liquid in the tank 100 enters the glass tube, due to the principle of communicating vessels, the liquid level in the glass tube is the same as the liquid level in the tank 100, so the liquid level in the tank 100 can be read directly.

[0043] In addition, both the overflow port 132 and the level gauge 200 are located on the peripheral side wall of the tank 100. The bottom of the level gauge 200 is higher than the bottom of the inner extension pipe 140 and lower than the overflow port 132, and the top of the level gauge 200 is higher than the overflow port 132. That is, the level gauge 200 can detect the liquid level below the overflow port 132 and can detect the liquid level above the overflow port 132. Furthermore, the liquid level that the level gauge 200 can detect is higher than the bottom of the inner extension pipe 140, thereby ensuring that the liquid level injected into the tank 100 is higher than the bottom of the inner extension pipe 140, and the length of the level gauge 200 does not need to be very long.

[0044] In some embodiments, please refer to Figure 1 The second distance D2 between the bottom end of the level gauge 200 and the bottom outer wall of the housing 100 can be 200mm-300mm. For example, the second distance D2 can be 200mm, 210mm, 220mm, 230mm, 240mm, 250mm, 260mm, 270mm, 280mm, 290mm or 300mm. This setting allows the level gauge 200 to detect liquid levels above the bottom end of the inner tube 140, and also prevents the bottom end of the level gauge 200 from being too low, which means that the length of the level gauge 200 does not need to be too long.

[0045] In some embodiments, please refer to Figure 3 The level gauge 200 and the overflow port 132 are located on two opposite side walls of the housing 100 along the second direction Y. The two opposite side walls of the housing 100 along the first direction X are each provided with a fixing lug 150. During installation, the bottom outer wall of the housing 100 is supported on a mounting platform, and then the fixing lugs 150 are locked to their corresponding positions on the mounting platform using bolts or screws to install the housing 100. This structural distribution allows the level gauge 200 and the overflow port 132 to avoid the fixing lugs 150, facilitating the handling and installation of the housing 100 via the fixing lugs 150 on both sides.

[0046] Optionally, the two fixing ears 150 are arranged opposite each other along the first direction X, and the housing 100 has two fixing ears 150 on each opposite side along the first direction X. The center surfaces of the two fixing ears 150 arranged opposite each other along the first direction X pass through the first center line O1 of the air inlet 111, and the center surfaces of the other two fixing ears 150 arranged opposite each other along the first direction X pass through the second center line O2 of the air outlet 112. This arrangement allows the housing 100 to be stably installed using the two fixing ears 150.

[0047] In some embodiments, please refer to Figures 1 to 3 The housing 100 also has a liquid inlet 113 for injecting liquid into the housing 100, and the liquid inlet 113 is normally closed. Before use, liquid of a preset level can be injected into the housing 100 through the liquid inlet 113, and then the liquid inlet 113 can be closed. In addition, after the positive and negative pressure protection device has been used for a period of time, the liquid inlet 113 can be opened to replenish liquid into the housing 100 to ensure that the liquid level in the housing 100 is within the preset range.

[0048] Optionally, the injection port 113 is located on the top side wall of the housing 100, which facilitates the injection of liquid into the housing 100. Of course, in other embodiments, the injection port 113 may also be located on the peripheral side wall of the housing 100, and this is not a unique limitation.

[0049] In some embodiments, please refer to Figure 1 and Figure 2 The housing 100 has a drain port 133 for draining liquid, which is normally closed. After the positive and negative pressure protection device has been used for a period of time, the liquid in the housing 100 will contain certain impurities, and it is necessary to periodically drain and clean all the liquid in the housing 100, and then refill the housing 100 with clean water through the liquid inlet 113.

[0050] Optionally, the drain outlet 133 is located on the peripheral side wall of the housing 100, near the bottom. By placing the drain outlet 133 on the peripheral side wall of the housing 100, the surface of the bottom side wall of the housing 100 can be smooth, facilitating the support of the bottom side wall of the housing 100 on the mounting platform. It is understood that in other embodiments of this application, the drain outlet 133 may also be located on the bottom side wall of the housing 100, where circumstances permit; this is not a limiting factor.

[0051] In some embodiments, please refer to Figure 1 and Figure 3 The housing 100 has protruding extension pipes 160 at the positions corresponding to the air inlet 111, air outlet 112, and overflow outlet 132. Flanges 170 protrude from the outer peripheral wall of the extension pipes 160. The extension pipes 160 and flanges 170 facilitate the connection of the housing 100 to external structures, such as the anaerobic digester, the flare, and the overflow collection tank.

[0052] The length of the extended tube 160 can be set according to actual assembly requirements, such as 100mm, 150mm, or 200mm. The extended tube 160 extends vertically outward from the top or peripheral side wall of the housing 100, and the flange 170 extends radially outward from the outer peripheral wall of the end of the extended tube 160 away from the housing 100. The flange 170 has multiple spaced mounting holes distributed circumferentially to facilitate locking connection with external structures.

[0053] In some embodiments, please refer to Figures 1 to 3 The enclosure 100 includes a top plate 110, a bottom plate 120, and a side plate 130. The top plate 110 and the bottom plate 120 are arranged opposite to each other. The side plate 130 is welded to the bottom periphery of the top plate 110 and to the top periphery of the bottom plate 120. The side plate 130 includes multiple sub-plates 131 welded end to end. The inner extension tube 140 is welded to the top plate 110. The top plate 110, the bottom plate 120, the side plate 130, and the inner extension tube 140 are all made of stainless steel.

[0054] Furthermore, in embodiments with an extension tube 160 and a flange 170, the extension tube 160 and flange 170 are also made of stainless steel and connected by welding. Overall, the entire housing 100 is welded from stainless steel.

[0055] In this embodiment, the enclosure 100 is made of stainless steel, which improves the corrosion resistance and durability of the enclosure 100, while also reducing costs.

[0056] Optionally, the box body 100 is square box-shaped, and the top plate 110 and bottom plate 120 are both rectangular plate structures.

[0057] On the other hand, this application also provides an anaerobic fermentation system, including an anaerobic fermenter and the aforementioned positive and negative pressure protection device, wherein the positive and negative pressure protection device is connected to the positive and negative pressure protection interface of the anaerobic fermenter. In this embodiment, the anaerobic fermentation system, through the aforementioned positive and negative pressure protection device, can provide positive and negative pressure protection for the anaerobic fermenter, thereby preventing damage to the anaerobic fermenter due to excessive or insufficient internal pressure.

[0058] In addition, a water seal structure can be installed at the top of the anaerobic fermenter. The sidewalls of the water seal structure have positive and negative pressure protection interfaces, and the positive and negative pressure protection devices are connected to the positive and negative pressure protection interfaces.

[0059] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A positive and negative pressure protection device for providing positive and negative pressure protection to an anaerobic fermenter, characterized in that, The positive and negative pressure protection device includes a tank capable of storing liquid. The tank has an air inlet, an air outlet, and an overflow outlet. The air inlet is used to connect to the positive and negative pressure protection interface of the anaerobic fermenter. Both the air inlet and the air outlet are higher than the overflow outlet. An inner extension pipe extends from the inner side wall of the tank corresponding to the position of the air inlet. Under normal conditions, the liquid level in the tank is higher than the bottom end of the inner extension pipe and lower than the overflow outlet.

2. The positive and negative pressure protection device as described in claim 1, characterized in that, The air inlet is located on the top side wall of the housing, and the inner extension pipe extends vertically downward from the top inner wall of the housing. And / or, the air outlet is located on the top side wall of the housing.

3. The positive and negative pressure protection device as described in claim 1, characterized in that, The bottom end face of the inner tube has a first distance from the bottom inner wall of the box body, and the first distance ranges from 100mm to 200mm.

4. The positive and negative pressure protection device as described in claim 1, characterized in that, Both the air inlet and the air outlet are located on the top side wall of the housing; the first center line of the air inlet and the second center line of the air outlet are both located on the first center surface of the housing along the first direction; The air inlet and the air outlet are symmetrically arranged relative to the second center face of the housing along the second direction; wherein the first direction is perpendicular to the second direction.

5. The positive and negative pressure protection device as described in any one of claims 1 to 4, characterized in that, The housing is also equipped with a level gauge for detecting the liquid level inside the housing; the level gauge is a glass level gauge that communicates with the housing, the overflow port and the level gauge are both located on the peripheral side wall of the housing, the bottom end of the level gauge is higher than the bottom end of the inner extension tube and lower than the overflow port, and the top end of the level gauge is higher than the overflow port.

6. The positive and negative pressure protection device as described in claim 5, characterized in that, The level gauge and the overflow port are located on two side walls of the housing that are opposite each other along the second direction, and the two side walls of the housing that are opposite each other along the first direction are respectively provided with fixing ears.

7. The positive and negative pressure protection device as described in any one of claims 1 to 4, characterized in that, The housing also has a liquid injection port for injecting liquid into the housing, and the liquid injection port is normally closed. The housing has a drain outlet for discharging liquid, which is normally closed.

8. The positive and negative pressure protection device as described in any one of claims 1 to 4, characterized in that, The housing has protruding pipes at the positions corresponding to the air inlet, air outlet and overflow outlet, and the outer peripheral wall of the protruding pipes is provided with flanges.

9. The positive and negative pressure protection device as described in any one of claims 1 to 4, characterized in that, The enclosure includes a top plate, a bottom plate, and side plates. The top plate and the bottom plate are arranged opposite to each other. The side plates are welded to the bottom periphery of the top plate and to the top periphery of the bottom plate. The side plates include multiple sub-plates welded end to end. The inner tube is welded to the top plate. The top plate, the bottom plate, the side plates, and the inner tube are all made of stainless steel.

10. An anaerobic fermentation system, characterized in that, It includes an anaerobic fermenter and a positive and negative pressure protection device as described in any one of claims 1 to 9, wherein the positive and negative pressure protection device is connected to the positive and negative pressure protection interface of the anaerobic fermenter.

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