A defoaming device for an anaerobic digestion tank

Abstract

The utility model provides an anaerobic digestion tank's defoaming device, defoaming device is located outside digestion tank, defoaming device includes defoaming tank, PLC control cabinet and the vacuum generator, air compressor respectively with defoaming tank intercommunication, the inside of defoaming tank is equipped with stirring shaft, is equipped with propeller blade on stirring shaft, is equipped with the discharge port in the upper position of defoaming tank, and the high point of propeller blade is flush with discharge port, and the bottom of defoaming tank is equipped with return port and discharge port, and return port intercommunication to digestion tank, the upper part of digestion tank is equipped with a foam extraction port, and the foam extraction port is communicated to the defoaming tank through the foam extraction pipe, and the opening and closing of PLC control cabinet control foam extraction port, discharge port, return port, discharge port and the work of vacuum generator, air compressor, stirring shaft. The utility model discloses can carry out automatic defoaming to digestion tank, and low in cost, more environmental protection.

Description

Technical Field

[0001] This utility model relates to the field of biological fermentation devices, and more specifically to a defoaming device for an anaerobic digester. Background Technology

[0002] Anaerobic digesters are industrial devices used for microbial fermentation. In China, anaerobic digestion is often used as an important technology for food waste and kitchen waste. Anaerobic digestion treatment requires the use of anaerobic digesters.

[0003] Anaerobic digestion easily generates a large amount of foam. If not eliminated in time, this can lead to a rise in the digester's liquid level, foam entering and clogging biogas pipelines, pressure fluctuations within the digester, safety valve activation, and digester overflow, among other safety accidents. Current anaerobic digesters eliminate foam by adding defoamers, but there is a lack of corresponding defoaming devices. Adding defoamers is inconvenient for adjusting the dosage, and excessive chemical reagents can negatively impact fermentation and are also environmentally unfriendly. Furthermore, the anaerobic fermentation sludge from kitchen waste contains proteins, oils, and surfactants, making its foam difficult to break and highly stable. Due to the high viscosity and high impurity content of the sludge (light impurities such as plastic bags are suspended in the foam layer), suitable defoaming equipment is needed to adapt to these material conditions, leading to this case study. Utility Model Content

[0004] The purpose of this invention is to provide a defoaming device for anaerobic digesters that is automated, low-cost, and more environmentally friendly.

[0005] To achieve the above objectives, the solution of this utility model is: A defoaming device for an anaerobic digester is located outside the digester. The defoaming device includes a defoaming tank, a PLC control cabinet, and a vacuum generator and an air compressor connected to the defoaming tank. The defoaming tank has an internal stirring shaft with propeller blades. A foam discharge port is located at the upper middle position of the defoaming tank, with the highest point of the propeller blades flush with the foam discharge port. A return port and a discharge port are located at the bottom of the defoaming tank, with the return port connected to the digester. A foam extraction port is located at the upper middle part of the digester, connected to the defoaming tank via a foam extraction pipe. The PLC control cabinet controls the opening and closing of the foam extraction port, foam discharge port, return port, and discharge port, as well as the operation of the vacuum generator, air compressor, and stirring shaft.

[0006] Furthermore, the stirring shaft is equipped with two sets of propeller blades that intersect to form a double helix.

[0007] Furthermore, a first valve is installed on the foam extraction pipe, and a second valve and a third valve are installed on the outside of the foam discharge port and the outside of the material discharge port, respectively. The return port is connected to the digestion tank through the return pipe, and a fourth valve is installed on the return pipe. A fifth valve and a sixth valve are installed on the connecting pipe between the vacuum generator, the air compressor and the defoaming tank, respectively. The PLC control cabinet controls the opening and closing of each valve.

[0008] Furthermore, the stirring shaft is connected to a motor located outside the defoaming tank, and the motor is connected to the PLC control cabinet.

[0009] Furthermore, the defoaming tank has an inlet connected to a foam extraction pipe, with the inlet located above the foam discharge port. Inside the defoaming tank, a liquid level sensor is located between the inlet and the foam discharge port.

[0010] Furthermore, the bottom of the defoaming tank is formed into a conical bottom, with the discharge port located at the center of the bottom of the conical bottom and the return port located above the discharge port.

[0011] Furthermore, the propeller blades rotate forward or backward under the drive of the stirring shaft. They rotate forward during defoaming and switch to reverse after the foam discharge port is opened.

[0012] Furthermore, before the foam extraction port of the digester is opened, the defoaming tank is evacuated to a negative pressure of -0.3 bar by the vacuum generator; after the defoaming tank completes the material extraction, the vacuum generator continues to work and evacuates to a negative pressure of -0.5 bar; after the negative pressure is stopped, the air compressor delivers a positive pressure of 2.0-3.0 bar into the defoaming tank.

[0013] With the above structure, the defoaming device of the anaerobic digester of this utility model can automatically defoam the digester periodically or intermittently without the need for defoaming agent. It has low operating costs, high efficiency, and is more environmentally friendly. It does not affect the normal fermentation of the digester. It can also reduce the amount of sludge and debris returned to the digester by using the propeller blades. The defoamed material can be reused through recycling without loss of organic matter. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of this utility model.

[0015] Label Explanation: A. Digestion tank; 1. Defoaming tank; 10. Feed inlet; 11. Foam outlet; 12 Return port; 13 Discharge port; 14 Foam extraction port; 15 Foam extraction pipe; 16 return pipes; 2 PLC control cabinet; 3 vacuum generator; 4 air compressor; 51. Agitator shaft; 52. Propeller blades; 53. Motor; 61. First valve; 62 Second valve; 64 Fourth valve; 65 Fifth valve; 66 Sixth valve. Detailed Implementation

[0016] To further explain the technical solution of this utility model, the following detailed description is provided through specific embodiments.

[0017] like Figure 1 As shown, this utility model discloses a defoaming device for an anaerobic digester. The defoaming device is located outside the digester A to periodically defoam the material in digester A, which is an anaerobic digester. The defoaming device includes a defoaming tank 1, a PLC control cabinet 2, and a vacuum generator 3 and an air compressor 4, which are respectively connected to the defoaming tank 1. The defoaming tank 1 is equipped with a stirring shaft 51, and the stirring shaft 51 is equipped with propeller blades 52. In this embodiment, the stirring shaft 51 is equipped with two sets of propeller blades 52 that cross to form a double helix. The propeller blades have a large area and high throughput. The rotating propeller blades 52 can generate shear force to destroy the foam film. The helical shape of the propeller blades can also prevent large particles of impurities such as plastic bags and garden branches in the sludge from getting entangled in the propeller blades.

[0018] A foam discharge port 11 is located at the upper middle position of the defoaming tank 1. The highest point of the propeller blade 52 is flush with the foam discharge port 11. When the foam discharge port 11 is open, the propeller blade 52 can push and scrape the foam floating on the inner surface of the defoaming tank 1 towards the foam discharge port 11. The propeller blade 52 can rotate forward or backward under the drive of the stirring shaft 51. It rotates forward during defoaming and switches to reverse after the foam discharge port 11 is opened, so as to gradually discharge the undefoamed top layer foam through the foam discharge port 11. During the foam extraction process, the defoaming tank 1 sucks in some large-diameter lightweight impurities (such as plastic bags and bottles). These lightweight impurities float at the top of the liquid level along with the foam. After defoaming, the suspended impurities can be discharged from the discharge port 11 using the reverse-rotating propeller blades 52 (the design of the propeller blades 52 allows them to scrape the material twice to the discharge port 11 with each rotation, preventing excessive floating impurities from clogging the discharge port 11). The material (sludge) after impurity removal will not accumulate again when it is returned to the digester. The propeller blades 52 also have a conveying function while performing mechanical defoaming. During the reverse rotation, the propeller blades 52 only remove the upper floating matter and do not affect the middle and lower layers of sludge material. This facilitates the collection of floating impurities, reduces the amount of fermented sludge mixed in, facilitates downstream processing, reduces the loss of fermented sludge, and allows the sludge material to be returned to the digester for continued fermentation and biogas production.

[0019] The bottom of the defoaming tank 1 is also provided with a return port 12 and a discharge port 13. The return port 12 is connected to the digester A. The middle and upper part of the digester A is provided with a foam extraction port 14. The foam extraction port 14 can be connected to the defoaming tank 1 through a foam extraction pipe 15. The sludge that produces foam in the upper part of the digester A can be sucked out and enter the defoaming tank 1 through the foam extraction pipe 15.

[0020] In this embodiment, the bottom of the defoaming tank 1 is formed into a conical bottom, the discharge port 13 is located at the center of the bottom of the conical bottom, and the return port 12 is located above the discharge port 13.

[0021] The PLC control cabinet 2 can control the opening and closing of the foam extraction port 14, the foam discharge port 11, the return port 12, and the discharge port 13, as well as the operation of the vacuum generator 3, the air compressor 4, and the stirring shaft 51. Specifically, the foam extraction pipe 15 is equipped with a first valve 61, and the outer sides of the foam discharge port 11 and the discharge port 13 are respectively equipped with a second valve 62 and a third valve (not shown in the figure). The return port 12 is connected to the digestion tank A through the return pipe 16, which is equipped with a fourth valve 64. The connecting pipes between the vacuum generator 3, the air compressor 4, and the defoaming tank 1 are respectively equipped with a fifth valve and a sixth valve. The PLC control cabinet 2 can control the opening and closing of each valve. The stirring shaft 51 is connected to a motor 53 located outside the defoaming tank 1. The motor 53 is also connected to the PLC control cabinet 2 and rotates according to the commands issued by the PLC control cabinet 2.

[0022] The defoaming tank 1 has an inlet 10 connected to a foam extraction pipe 15. The inlet 10 is located above the foam discharge port 11. Inside the tank of the defoaming tank 1, there is also a liquid level sensor (not shown in the figure) located between the height difference between the inlet 10 and the foam discharge port 11. The liquid level sensor can send signals to the PLC control cabinet 2. For example, the liquid level sensor can control the opening and closing of the first valve 61 or the second valve 61 based on the detected liquid level signal.

[0023] The working process of this utility model is as follows: 1. The defoaming tank 1 is evacuated to a negative pressure of -0.3 bar by the vacuum generator 3; 2. Start the propeller blade 52 inside the defoaming tank 1, set it to forward rotation, and run it continuously; 3. Open the foam extraction port 14 of the digestion tank A, and the foam in the digestion tank A is extracted into the defoaming tank 1. During this process, the propeller blade 52 continues to rotate in the forward direction to break the foam by mechanical stirring. 4. After the foam pumping tank 1 is full (signal can be transmitted through the liquid level sensor), the vacuum generator 3 continues to work, and the negative pressure is drawn to -0.5 bar. The negative pressure can cause the gas inside the foam to expand and exceed the limit of the foam film to rupture, thus eliminating some large foams that are easy to break. 5. After defoaming under negative pressure (-0.5 bar to eliminate large foam) for a certain period of time, stop the negative pressure and start the air compressor 4 to deliver positive pressure to the defoaming tank 1 to 2.0-3.0 bar. Use the high pressure to directly squeeze the foam to break it, eliminating some local foam accumulation and foam in high viscosity materials. 6. During steps 3-5 above, propeller blade 52 continues to rotate forward, continuously mechanically shearing and defoaming; 7. After the foam has basically disappeared, the sludge is returned to the digester A through the return port 16, or discharged to the back end for treatment through the discharge port 13. 8. If some foam that is difficult to eliminate still remains after the above process, open the foam discharge port 11, set the propeller blade 52 to reverse, and gradually discharge the top foam and floating debris through the foam discharge port 11 to the back end for processing. 9. The above completes one defoaming process. Repeat the above steps to achieve intermittent defoaming production.

[0024] The above embodiments and figures are not intended to limit the product form and style of this utility model. Any appropriate changes or modifications made by those skilled in the art should be considered as not departing from the patent scope of this utility model.

Claims

1. A defoaming device for an anaerobic digester, wherein the defoaming device is located outside the digester, characterized in that: The defoaming device includes a defoaming tank, a PLC control cabinet, and a vacuum generator and an air compressor connected to the defoaming tank. The defoaming tank has an internal stirring shaft with propeller blades. A vent is located in the upper middle part of the defoaming tank, with the highest point of the propeller blades flush with the vent. The bottom of the defoaming tank has a return port and a discharge port, with the return port connected to the digestion tank. The digestion tank has a froth extraction port in the upper middle part, connected to the defoaming tank via a froth extraction pipe. The PLC control cabinet controls the opening and closing of the froth extraction port, vent, return port, and discharge port, as well as the operation of the vacuum generator, air compressor, and stirring shaft.

2. The defoaming device for an anaerobic digester as described in claim 1, characterized in that: The stirring shaft is equipped with two sets of propeller blades that cross to form a double helix.

3. The defoaming device for an anaerobic digester as described in claim 1, characterized in that: The foam extraction pipe is equipped with a first valve, and the outside of the foam discharge port and the outside of the material discharge port are respectively equipped with a second valve and a third valve. The return port is connected to the digestion tank through the return pipe, and the return pipe is equipped with a fourth valve. The connecting pipe between the vacuum generator, the air compressor and the defoaming tank is equipped with a fifth valve and a sixth valve, respectively. The PLC control cabinet controls the opening and closing of each valve.

4. The defoaming device for an anaerobic digester as described in claim 1, characterized in that: The stirring shaft is connected to a motor located outside the defoaming tank, and the motor is connected to the PLC control cabinet.

5. The defoaming device for an anaerobic digester as described in claim 1, characterized in that: The defoaming tank has an inlet connected to a foam removal pipe, with the inlet located above the foam discharge port. Inside the defoaming tank, a liquid level sensor is located between the inlet and the foam discharge port.

6. The defoaming device for an anaerobic digester as described in claim 1, characterized in that: The bottom of the defoaming tank is conical, with the discharge port located at the center of the bottom of the conical bottom and the return port located above the discharge port.

7. The defoaming device for an anaerobic digester as described in claim 1 or 5, characterized in that: The propeller blades rotate forward or backward under the drive of the stirring shaft. They rotate forward during defoaming and switch to reverse after the foam discharge port is opened.

8. The defoaming device for an anaerobic digester as described in claim 1, characterized in that: Before the defoaming port of the digester is opened, the defoaming tank is evacuated to a negative pressure of -0.3 bar by the vacuum generator; after the defoaming tank completes the material extraction, the vacuum generator continues to work and evacuates to a negative pressure of -0.5 bar; after the negative pressure extraction stops, the air compressor delivers a positive pressure of 2.0-3.0 bar into the defoaming tank.

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