CN217051988U

CN217051988U - Circulation of air filter equipment suitable for birds animal manure fermentation cylinder

Info

Publication number: CN217051988U
Application number: CN202220727162.5U
Authority: CN
Inventors: 李文海
Original assignee: Tongliao Tonghe Animal Husbandry Co ltd
Current assignee: Tongliao Tonghe Animal Husbandry Co ltd
Priority date: 2022-03-31
Filing date: 2022-03-31
Publication date: 2022-07-26
Anticipated expiration: 2032-03-31

Abstract

The utility model belongs to the technical field of filtration environmental protection equipment, specifically a circulation of air filter equipment suitable for birds animal manure fermentation cylinder. The existing air filtering device of the fermentation tank is complex in structure, inconvenient to clean after use, complex in steps, and most air filtering devices do not have a sterilization function, so that the sterilization efficiency is limited, and the mixed bacteria compete for nutrients of the fermentation bacteria in the fermentation process, and are not beneficial to the fermentation process. The circulation filtering device is arranged on a fermentation tank, the fermentation tank comprises a tank body and a support, the tank body is in a horizontal cylindrical shape, openings are formed in two ends of the tank body, the tank body is movably assembled on the support, and a driving device capable of driving the tank body to rotate along an axis is arranged between the support and the tank body. The special fermentation tank can realize the circulation and filtration of air in the tank body while rotating by itself by adopting the air circulation and filtration device matched with the overlong fermentation tank, thereby solving the problems of air pollution and the like in the excrement fermentation process.

Description

Circulation of air filter equipment suitable for birds animal manure fermentation cylinder

Technical Field

The utility model belongs to the technical field of filtration environmental protection equipment, specifically a circulation of air filter equipment suitable for birds animal manure fermentation cylinder.

Background

The fertilizer treated by fermentation not only can improve the nutrient absorption level of the feed and degrade possible toxins in the fertilizer raw materials, but also can greatly reduce the use of pharmaceutical additives such as antibiotics and the like, and improve the health level of animals, thereby improving the food safety of the fertilizer. Air control is an important part of the control of the fermentation process. Documents of the prior art: CN110342962A a cow dung fermentation machine provides a cow dung fermentation machine of environmental protection and energy saving, continuous production, is equipped with double-deck cylinder, has filled heat-conducting medium in the double-deck, is equipped with the heat preservation at the cylinder skin, and a plurality of flight of inner wall evenly distributed of cylinder, the below of cylinder is equipped with the frame, and the top of frame is equipped with the multiunit bearing roller, and the cylinder is placed on the bearing roller, and the centre of cylinder is equipped with transmission system. The method solves the problems that the prior cow dung fermentation tank pollutes the environment, has poor heat preservation performance, low fermentation efficiency, can not carry out continuous production and the like, and has the effects of controllable fermentation temperature, energy conservation, environmental protection, sufficient oxygen supply, high efficiency and continuity.

Current fertilizer fermentation cylinder air filter has certain limitation when using, if the filter equipment structure is complicated, inconvenient washing after the use, need dismantle the back widget and wash, the step is loaded down with trivial details, and most air filter do not possess the function of disinfecting, and the efficiency of disinfecting is limited, and miscellaneous fungus can compete for the nutrient of zymophyte in fermentation process, is unfavorable for going on of fermentation process.

In the process of biological fermentation, the use of air is essential for the growth of microorganisms, the use amount of the air is large, generally 0.5-1.2 VVM, but a large amount of air which is not used by the microorganisms needs to be discharged into the atmosphere along with tail gas discharged from a fermentation tank, so that part of fermentation metabolites generated by the growth of the microorganisms are taken out of the fermentation tank along with the tail gas and are discharged into the ambient air, and the metabolites generated by the growth of the microorganisms usually have certain smell and taste and can have certain influence on the ambient environment, so that the fermentation tail gas needs to be treated and then discharged.

Disclosure of Invention

The purpose of the utility model is to develop a circulating and filtering function for the inside and/or outside air (waste gas and tail gas) of the fermentation device based on the prior art documents recorded in the background technology or based on the fermentation device which is obtained by taking the fermentation device as a basic structure and improving the structure.

The above purpose is realized by the following technical scheme:

the utility model provides an air circulation filter equipment suitable for birds animal manure fermentation cylinder, this circulation filter equipment sets up on the fermentation cylinder, and the fermentation cylinder is horizontal cylindric, both ends including a jar body, support, jar body, and the jar body has the opening, and jar body assembles on the support movably, is equipped with between the support and jar body to drive jar body along the rotatory drive arrangement in axle center, its characterized in that:

the tank body is provided with an air inlet device and an air outlet device, the air inlet device is used for supplying air into the tank body, and the air outlet device is used for pumping out air in the tank body;

the circulating filter device comprises a circulating device and/or a filter, the filter is communicated with the air inlet device and/or the air exhaust device through a pipeline, the filter is used for carrying out any one or more operations including but not limited to filtering, sterilization, disinfection, purification, drying, temperature rise and temperature reduction on air sent into the filter through the air exhaust device, the circulating device (namely a fan) is provided with a plurality of pipes which are connected between the filter and the air inlet device and/or the air exhaust device, and the circulating device is used for driving air in the pipes to flow.

The length of the tank body along the central axis direction is 10-30 meters, the openings at the two ends of the tank body are respectively a feed port and a discharge port, the tank body is inclined by 1-10 degrees, and the feed port is higher than the discharge port.

The tank body comprises a tank front section, a tank middle section and a tank rear section, wherein the tank front section is the side with the feed inlet, and the tank rear section is the side with the discharge outlet;

the air inlet device is arranged at the front tank section and/or the middle tank section, and the air exhaust device is arranged at the rear tank section and/or the middle tank section and/or the front tank section.

[ detailed parts ] 1

The exhaust fan comprises a base, a movable valve and a control rail;

the base is a cylindrical tubular structure which penetrates through the tank body, is fixed on the tank body and is vertical to the outer wall of the tank body;

the movable valve is arranged in the base and can slide along the axis direction of the base, and comprises a valve rod and a valve cap;

the valve rod is cylindrical and barrel-shaped, the side wall of the valve rod is provided with an air vent, the valve rod extends towards the axial direction of the tank body, the front end of the valve rod is fixed with a valve cap, and the tail end of the valve rod is in sliding fit with the base;

the valve cap is fixed at one end of the valve rod facing the axis of the tank body, and two side edges of the valve cap protrude out of the side wall of the valve rod;

a rubber pad is arranged on the inner wall of the tank body and around the valve rod, when the valve rod extends out of the tank body, the valve cap is separated from the rubber pad, and the vent hole is opened; on the contrary, when the valve rod retracts towards the base, the valve cap is contacted with the rubber gasket and is pressed and compacted, and the vent hole is closed;

the tail end of the valve rod is provided with a control rod which extends out of the base, and the base is provided with a closed chute which allows the control rod to move up and down;

the outermost end of the control rod is provided with a pulley assembly;

the control rail is arranged at the outer side of the tank body and at a position corresponding to the control rod, the control rail is fixed on the bracket, and the control rail is separated from the tank body; the control rail is provided with a ring groove which is matched with the control rod pulley component and limits the sliding track of the control rod pulley component, and the ring groove is circular;

the annular groove on the control rail comprises a first groove section and a second groove section, the radius of the first groove section is smaller than that of the second groove section, and the first groove section is in smooth transition connection with the second groove section.

[ detailed parts ] 2

The air exhaust device comprises an air guide box, the air guide box is annular, the air guide box is arranged outside the tank body and fixed on the bracket, and the air guide box is separated from the tank body;

one side of the air guide box is fixedly connected with the pipeline, and the other side of the air guide box is movably connected with the base;

one side of the air guide box connected with the base is provided with a movable ring, and the movable ring is movably and hermetically assembled and connected with the air guide box main body.

[ concrete parts ] 3

The circulator adopts any one or more fans including but not limited to an axial flow fan, a centrifugal fan and a cross flow fan to realize air circulation.

The flow-through filtration device includes an in-tank conduit.

The utility model has the advantages that: the special fermentation tank can realize the circulation and filtration of air in the tank body while rotating by itself by adopting the air circulation and filtration device matched with the overlong fermentation tank, thereby solving the problems of air pollution and the like in the excrement fermentation process.

Drawings

The attached drawings are as follows:

FIG. 1 is a schematic diagram of a prior art fermenter (or modified fermenter) and a partial flow-through filtration apparatus according to an embodiment of the present invention;

FIG. 2 is a schematic view of an assembly structure of a fermentation tank and a flow-through filtration device according to an embodiment of the present invention;

FIG. 3 is a schematic view of an exhaust fan according to an embodiment of the present invention;

FIG. 4 is a schematic view of the structure of the exhaust fan, the fermentation tank and the pipeline according to the first embodiment of the present invention.

Wherein:

100 fermentation cylinder 10 jar 11 jar of jar anterior segment 12 jar middle sections 13 jar back end 14 feed inlets 15 discharge gate 20 supports

200 circulation filter equipment 30 air inlet device 40 air exhauster 41 base 42 air guide box 43 movable ring

50 movable valve 51 valve rod 52 valve cap 53 air vent 54 rubber gasket 55 control rod 56 pulley assembly

60 control rail 61, ring groove 62, first groove section 63, second groove section

70 circulator 80 filter 90 piping.

Detailed Description

[ example 1 ] infrastructure

As shown in fig. 1 and 2, an air circulation filter equipment suitable for birds animal manure fermentation cylinder, this circulation filter equipment sets up on the fermentation cylinder, and the fermentation cylinder is including a jar body, support, and jar body is horizontal cylindric, both ends have the opening, and jar body assembles on the support with moving ground, is equipped with between the support and jar body to drive jar body along the rotatory drive arrangement in axle center, its characterized in that:

The length of the tank body along the central axis direction is 10-30 meters, the openings at the two ends of the tank body are respectively a feed port and a discharge port, the tank body is inclined by 1-10 degrees, and the feed port is higher than the discharge port. As mentioned in the prior art, the tank of the present application has substantially the same structure, that is, the tank rotates around the central axis, so that the material therein is continuously stirred and tumbled to facilitate the fermentation, and the material is slowly transferred from the inlet end to the outlet end. Further, in this prior art document, a spiral blade or the like rotating together with the tank is further provided in the tank, thereby limiting the technical solution of axially and directly arranging the ventilation duct into the tank.

[ EXAMPLE 2 ] air exhauster

As shown in fig. 2-4, on the basis of the above embodiments, the exhaust fan of this embodiment includes a base, a movable valve, and a control rail;

the movable valve is arranged in the base and can slide along the axial direction of the base, and the movable valve comprises a valve rod and a valve cap;

the outermost end of the control rod is provided with a pulley assembly;

[ embodiment 3 ] air guide box

As shown in fig. 2 to 4, on the basis of the above embodiments, the air exhauster of this embodiment includes an air guide box, which is annular, the air guide box is disposed outside the tank body and fixed on the bracket, and the air guide box is separated from the tank body;

In the above embodiment 2, the exhaust fan and the air guiding box in embodiment 3, two components of the circulation filtering device are described in detail, and in order to further understand the operation method of the above device, the above device is further described as follows:

the base and the movable valve on the exhaust fan are both fixedly assembled on the tank body, so that when the tank body rotates, the base and the movable valve also rotate along with the tank body. The valve rod on the movable valve is provided with a control rod, the control rod is provided with a control rail, the control rail is fixed on the support, namely, the control rail cannot rotate along with the tank body, and the control rail is provided with a first groove section and a second groove section with different radiuses. As shown in fig. 4, when the exhaust fan moves to the upper part of the tank, namely the control rod on the movable valve is positioned in the first groove section, and the radius of the first groove section is small, so that the control rod slides towards the tank, and the vent hole on the valve rod is opened, and the air on the upper part of the tank can be smoothly exhausted from the vent hole. On the contrary, when the exhaust fan runs to the middle lower part of the tank body, namely the control rod is positioned at the second groove section, the radius of the second groove section is larger than that of the first groove section, the control rod can slide towards the direction away from the tank body, the valve rod retracts into the base, the vent hole is closed, and the valve cap on the valve rod is in close contact with the rubber mat on the wall of the tank body and the periphery of the valve rod, so that the aim of sealing the exhaust fan is fulfilled. Furthermore, a spraying device can be arranged in the tank body, so that when the exhaust fan runs from the second tank section to the first tank section, water is sprayed to the exhaust fan to clean dirt on the exhaust fan.

[ example 4 ] flow-through device

As shown in fig. 2, on the basis of the above embodiments, the ventilator of the present embodiment uses any one or more fans including, but not limited to, an axial flow fan, a centrifugal fan, and a cross flow fan to achieve air circulation.

[ example 5 ]

For the implementation of air filtration sterilization, see the following description, which can be used as a reference for the application of the present application to achieve the corresponding functions.

Air sterilization method

1. Heating sterilization method

Heat sterilization is an effective and reliable sterilization method, and bacterial spores are heat-resistant but can be destroyed and killed within 24 seconds at 218 ℃ at high temperature. However, the use of steam or electricity to heat a large amount of air for sterilization purposes requires a large amount of energy and an additional large amount of heat exchange equipment, which is uneconomical.

2. Radiation sterilization method

In theory, sound waves, high-energy cathode rays, X rays, gamma rays, beta rays and ultraviolet rays can be used for air sterilization, and the sterilization mechanism is thought to act by destroying the activity of proteins in microbial organisms, but the equipment investment is high, so the method is rarely adopted in the fermentation industry. At present, ultraviolet rays are mainly used in environments with little air convection, such as a sterile room, a hospital operating room and the like, but the sterilization efficiency is low, the sterilization time is long, and the high sterility degree of the sterile room is generally ensured by combining formaldehyde steam sterilization, phenol spraying and the like.

3. Chemical sterilization method

A small amount of bactericide (such as phenol, ethylene oxide, heavy metal salt, benzalkonium bromide, etc.) is dissolved in water, and air is passed through or sprayed in the bactericide solution to destroy microorganisms in the air. However, the bactericide brought in by the sterilized air has the same killing or inhibiting effect on the microorganisms growing in the fermentation tank, thereby influencing the fermentation effect. Therefore, after the production of sterile air by chemical sterilization, it is necessary to remove moisture and mist with the bactericide, and thus it is rarely used in the fermentation industry.

4. Electrostatic sterilization method

Is characterized in that: the energy consumption is low, and only 0.4-0.8kW is consumed for processing 1000m3 air; the air head loss is about 400-2000 Pa; the collection efficiency of dust particles with the particle size of 1 micron can reach more than 99 percent;

the disadvantages are that: the equipment is bulky and the efficiency is not very significant for particles smaller than 1 μm. Activity, but high equipment investment, and thus, the method is rarely adopted in the fermentation industry.

5. Filtration sterilization method

The medium filtration sterilization is widely adopted for preparing sterile air by fermentation. Sterile air is obtained by using a filter medium which is periodically sterilized to intercept microorganisms contained in the air flowing therethrough. At present, ultraviolet rays are mainly used in environments with small air convection, such as a sterile room, a hospital operating room and the like, but the sterilization efficiency is low, the sterilization time is long, and the high sterility of the sterile room is generally ensured by combining formaldehyde steam sterilization, phenol spraying and the like.

Commonly used filter media: cotton, activated carbon, glass fibers, organic synthetic fibers, asbestos filter plates and other sintered materials (sintered metals, sintered ceramics, sintered plastics, etc.). Cotton was used as the filter medium in the early days and was gradually replaced by glass fibers later. Polyvinyl alcohol (PVA) filters are now gradually replacing conventional filters.

Second, mechanism of filtration sterilization

1. Inertial impaction retention

The medium filtering layer in the filter is interlaced with countless fibers to form layer-by-layer meshes which are arranged in a staggered way. As the fiber diameter decreases, the packing density increases, the formed grid is compact and has more layers, and the fiber-to-fiber gaps are smaller. When air with particles of microorganisms and the like passes through the filter layer, only the air can pass through the gaps among the fibers. The air is forced to change the flowing direction and moving speed continuously to pass through the filter layer because of being blocked by the staggered fibers. When the particles move along with the airflow in a direction perpendicular to the fiber direction at a certain speed, the air is blocked, namely the movement direction is changed, the particles move around the fiber, the movement direction cannot be changed in time due to the movement inertia of the particles, the particles move along with the main airflow, and then the particles directly impact the surface of the fiber and are retained on the surface of the fiber due to friction adhesion.

2. Interception and retention

When the air velocity is reduced below the critical velocity, the particles can not be retained on the fiber due to inertial collision, so that the degerming efficiency is obviously reduced, but the degerming efficiency of the particles by the fiber is increased again as the air velocity is reduced continuously.

When the microorganism particles flow with low-speed airflow and slowly approach the fiber, the main airflow streamline of the particles is blocked by the fiber, the flow direction is changed, the microorganism particles go around the fiber, and a boundary stagnant zone is formed at the periphery of the fiber. The velocity of the gas flow in the stagnant zone is slower and particles entering this stagnant zone slowly approach and contact the fibers and are retained by adhesion.

3. Brown diffusion Effect

Particles with a small diameter can produce an irregular linear motion in a gas stream with a small flow rate, called brownian diffusion. The brownian diffusion has a short moving distance and is ineffective in a large gas velocity and a large fiber gap, but in a small gas velocity and a small fiber gap, the brownian diffusion greatly increases a contact detention machine of particles and fibers, thereby increasing the capturing efficiency of the fibers.

4. Gravity settling effect

Gravity settling is a stable separation action, and when the gravity borne by a particle is greater than the drag force of an air flow on the particle, the particle is easy to settle, and under the condition of single gravity settling, large particles have a remarkable effect compared with small particles, and the particle can only play a role when the speed of the air flow is very slow. Generally, it is combined with interception, i.e. in the boundary retention zone of the fiber, the settling action of the particles can improve the trapping efficiency of the interception retention.

5. Electrostatic adsorption

When dry air rubs against a non-conductive substance in a relative motion, induced charges are generated, and the treated fibers and resins, especially some synthetic fibers, are more significant. The airborne microbial particles are mostly charged differently and these charged particles are attracted to and settle by the oppositely charged objects. Furthermore, surface adsorption also falls into this category, for example, most of the filtration performance of activated carbon should be the role of surface adsorption.

Third, air filtration sterilization process flow

1. Two-stage cooling and heating sterilization process

The process is a relatively perfect air sterilization process, can adapt to various climatic conditions, can fully separate oil and water, and enables air to enter a filter under the condition of low relative humidity so as to improve the filtering efficiency;

the method is characterized in that: twice cooling, twice separation and proper heating. The method is particularly suitable for wet areas, and other areas can increase or decrease equipment in the process appropriately according to local conditions.

2. Cold and hot air direct mixing type air sterilization process

The compressed air is divided into two parts after coming out of the storage tank, one part enters a cooler to be cooled to a lower temperature, and is mixed with the other part of untreated high-temperature compressed air after water and oil mist are separated by a separator;

the method is characterized in that: the separation equipment and the air heating equipment after the second cooling can be saved, the flow is simpler, the compressed air is used for heating the air after the water separation, the consumption of the cooling water is less, and the like. It is suitable for medium moisture areas, but not for areas with high air moisture content.

3. Efficient pre-filtering air sterilization process

The suction effect of the compressor is utilized to ensure that the air enters the air compressor after being filtered by medium and high efficiency, so that the load of the main filter and the abrasion of the air compressor are reduced;

the method is characterized in that: the high-efficiency pre-filtering equipment is adopted, so that the air is filtered for multiple times, and the obtained air has high aseptic degree which reaches 99.99 percent;

the high-efficiency prefilter uses foam plastics (electrostatic sterilization) and superfine fibre paper as filter medium in series.

4. Process for heating cold air by using hot air

The compressed hot air and the cooled cold air are exchanged to raise the temperature of the cold air and lower the relative humidity. The flow has good effect when a turbine air compressor or an oil-free lubrication air compressor is used, while the common air compressor causes oil mist to pollute the filter, and a wire mesh separator is arranged to remove the oil mist and then the oil mist enters the filter.

Fourth, air sterilization process equipment

1. Air suction tower

The high-altitude wind collection has the dust content of less than 1mg/m3, so that: the height is more than or equal to 10, and a foam plastic medium coarse filter is arranged in the air suction chamber.

2. Front filter

Install the coarse filter before the air compressor machine, its effect: larger dust particles are trapped, preventing damage to the compressor, while also reducing the overall filter load. The filter generally requires high filtering efficiency and small resistance, otherwise, the suction load of the air compressor can be increased and the air displacement of the air compressor can be reduced;

the appearance is like the container, and is provided with two filter medium layers inside, wherein the front layer is a coarse filter layer, and the back layer is a sub-efficient filter layer. The following are commonly used: cloth bag filtration, filler type filtration, water mist dust removal, oil bath washing and the like. The oil bath washing dust removal has the defects that the air quality is influenced due to excessive entrained oil foam, and the oil bath washing dust removal is not adopted at present.

3. Air compressor

A reciprocating air compressor: air is drawn in and forced out by the reciprocating motion of the piston within the cylinder. The disadvantages of unstable pulsating pressure and greasy dirt;

a turbine type air compressor: the turbine speed generates cavity suction air driven by an electric or steam turbine. The air output is large and uniform, and oil contamination is avoided. An air reservoir need not be provided. But the technical requirements for installation and maintenance are high;

a screw air compressor: a cavity is formed instantly in the cylinder by utilizing a screw rod rotating at a high speed, and air in the cavity is compressed and then output by the movement of the screw rod. The installation occupies a small area, the compressed gas does not contain oil mist, and the airflow is stable. But the maintenance technical requirements are high.

4. Air storage tank

The air storage tank has the following functions:

(1) the pulsation is eliminated to maintain the stability of the tank pressure;

(2) allowing a portion of the particulate matter to settle in the tank;

(3) and (5) preserving heat and sterilizing.

5. Air cooler

Vertical shell and tube heat exchanger: the cooling water is led out of the pipe or the pipe, and a multi-pass (2-4 passes) heat exchanger can be adopted. The flow rate of cooling water is 0.5-3m/s, and the flow rate of air is 2-15 m/s;

spray heat exchanger: the air flow rate is 5-10 m/s;

submerged heat exchanger: the air flow rate is 5-10 m/s.

6. Gas-liquid separator

A cyclone separator: has high effect on separating particles with the particle size of more than 10 mu m. A screen separator: capturing fine particles having a particle size of 10 μm or less. The screen mesh is 20-80 meshes.

7. Air heater

And heating the air from which the water mist is removed, reducing the relative humidity to lower the humidity to 70%, and keeping the filter medium dry. The temperature of the air was controlled to 10 ℃ which did not exceed the fermentation temperature. The heat exchanger is usually a shell-and-tube heat exchanger, with air flowing through the tube side and steam flowing through the shell side.

8. Total filter

Structure of primary filter

(1) A microporous filter membrane filter: YUD-Z-type microporous membrane total filter

(2) A deep cotton filter: the upper and lower cotton layers have a thickness of 1/4-1/3% of the total filter layer, the middle activated carbon layer has a thickness of 1/3-1/2, and before the cotton layer is laid, a layer of 30-40 mesh wire mesh and fabric (such as linen) is laid on the lower hole plate, so that air can uniformly enter the cotton filter layer. The fillers are installed in the following order: the hole plate → the wire netting → the linen → the cotton → the linen → the activated carbon → the linen → the cotton → the linen → the wire netting → the hole plate.

Structure of (II) filter

(1) Microporous filter membrane filter

(2) Fiber paper separating filter

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting, and although the present invention is described in detail with reference to examples, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, which should be covered by the claims of the present invention.

Claims

1. The utility model provides an air circulation filter equipment suitable for birds animal manure fermentation cylinder, this circulation filter equipment sets up on the fermentation cylinder, and the fermentation cylinder is horizontal cylindric, both ends including a jar body, support, jar body, and the jar body has the opening, and jar body assembles on the support movably, is equipped with between the support and jar body to drive jar body along the rotatory drive arrangement in axle center, its characterized in that:

the circulation filter equipment includes circulation ware and/or filter, and the filter is linked together through pipeline and air inlet ware and/or exhaust fan, and the filter is used for carrying out including but not limited to filtration, disinfection, sterilization, purification, drying, intensification, cooling any one or several kinds of operation in the air that sends into the filter through the exhaust fan, and the circulation ware is equipped with a plurality ofly, all inserts on the pipeline between filter and air inlet ware and/or the exhaust fan, and the circulation ware is used for driving the air flow in the pipeline.

2. The air circulation filter device suitable for the fermentation tank for livestock manure as claimed in claim 1, characterized in that:

3. An air circulation filter unit adapted for use in a fermentation tank for animal manure according to claim 1, wherein:

4. An air circulation filter unit adapted for use in a fermentation tank for animal manure according to any one of claims 1 to 3, wherein:

the exhaust fan comprises a base, a movable valve and a control rail;

the tail end of the valve rod is provided with a control rod, the control rod extends out of the base, and the base is provided with a closed sliding groove allowing the control rod to move up and down;

the outermost end of the control rod is provided with a pulley assembly;

5. An air circulation filter unit adapted for use in a fermentation tank for animal manure according to claim 4, wherein:

6. An air circulation filter unit adapted for use in a fermentation tank for animal manure according to claim 1, wherein: