Device for cleaning exhaust air from a livestock barn

Abstract

The present invention relates to a device (2) for cleaning exhaust air from a livestock barn (4) with an exhaust air duct (6) in which at least one dry filter stage (14) having a filter material (16) is arranged for separating solid particles from the exhaust air stream (10) flowing through the exhaust air duct (6), wherein the device (2) can be operated in an exhaust air mode (A) and in a cleaning mode (B). In order to achieve good separation efficiency with a comparatively low pressure loss in the exhaust air duct (6), it is proposed that the filter material (16) be designed as a woven, braided or knitted fabric of metallic wires held in a frame (20), the frame (20) be connected to at least one vibration generator (24) via a connecting element (22), the vibration generator (24) be operable in cleaning mode (B) and transmit the vibrations it generates to the frame (20) via the connecting element (22).

Description

[0001] The present invention relates to a device for cleaning exhaust air from a livestock barn according to the preamble of claim 1.

[0002] Agriculture is the main source of ammonia, an air pollutant, in Germany. The majority of ammonia emissions originate from livestock farming, escaping from manure and slurry produced during the housing of farm animals. Ammonia is formed in livestock barns during the breakdown of protein and urea by anaerobic bacteria. The ammonia released into the barn air spreads, reacts with other air pollutants, and forms particulate matter. Further dust particles enter the barn air as feed dust, dust from bedding material, and skin debris. Ammonia itself and the resulting particulate matter pose a risk to the health of the animals housed there. Therefore, continuous forced ventilation of livestock barns is essential for the health of the animals.

[0003] Ammonia and particulate matter with adsorbed ammonia are released into the environment during forced ventilation, where they can harm human health, plants, and ecosystems. To reduce ammonia and dust emissions from livestock barns, various exhaust air purification devices are known from the prior art. The purification task is not easy to solve because the exhaust air from livestock barns contains different fractions of contaminants, namely gaseous contaminants and solid contaminants such as dust. The purification systems should remove the contaminants efficiently, while being as cost-effective as possible to manufacture, consuming little energy, generating as little new problematic waste as possible, and being operable continuously with a long service life without maintenance and minimal personnel requirements.These different requirements lead to conflicting objectives that must be resolved when designing the cleaning systems.

[0004] In the prior art, exhaust air scrubbers are known in particular that bind the ammonia and dust contained in the exhaust air in water, whereby the contaminants then contained in the water must be removed again in a further purification stage. An example of this can be found in German patent application DE 20 2014 005 398 U1. An exhaust air stream is passed through a motor-driven, air-permeable filter drum, which is partially immersed in a water bath. Inside the filter drum are packing materials whose surfaces are continuously wetted with water as the filter drum rotates. The dust and ammonia contained in the exhaust air are bound to the moist surfaces of the packing materials and washed off when they are immersed in the water bath again during the rotation of the filter drum.The exhaust air then exits the filter drum with a significantly reduced dust and ammonia content, however, the water bath is enriched with the dirt load washed out of the exhaust air.

[0005] Another exhaust air scrubber is known from German patent application DE 201 13 965 U1. The device disclosed therein proposes vertically arranged filter walls, each equipped with a humidification device for continuously moistening the filter wall. Here, too, the constantly circulating cleaning fluid is continuously enriched with the dirt load absorbed from the exhaust air, so that it must be replaced and disposed of more frequently depending on the amount of dirt.

[0006] From German patent application DE 44 03 634 A1, a dry filter is known that enables the filtration of dust from an exhaust air stream using a pleated filter material. The contaminated exhaust air passes through the filter material in a first direction from the outside to the inside. The dust particles contained in the exhaust air are retained on the outward-facing surface of the filter material. The filter material is cleaned by rotating air nozzles located inside the filter, which periodically blow cleaning air from the inside to the outside through the dry filter stage.

[0007] German patent DE 197 22 840 A1 also discloses a dry filter in which the filter material is cleaned by pulses of compressed air against the filtration flow. The dry filter is closed for the duration of the pulses by means of pivotally suspended flap devices.

[0008] The object of the present invention is to improve the cleaning of the dry filter.

[0009] The problem is solved for a generic device by the characterizing features of claim 1.

[0010] The filter material is designed as a woven, braided or knitted fabric made of metallic wires held in a frame.

[0011] Metallic wires have the advantage of not becoming statically charged, or only to a very small extent, through friction with the particles contained in the exhaust air flowing through the filter material. Static electricity is generated by friction between two dissimilar materials. This friction causes electrons to be transferred from one material to the other, creating an electrical imbalance or static charge. Synthetic materials such as polyester or acrylic, due to their chemical structure, tend to transfer electrons more readily and are therefore more prone to static charging, while electrical potentials in metallic materials are distributed more evenly and do not build up any electrical potential. When materials are statically charged, dirt and dust adhere more strongly to the surfaces of the charged materials.Since it is desirable in cleaning mode to detach particles adhering to the filter material from the support material as easily and quickly as possible, this is easier with metallic wires than with filter materials that build up an electrical potential.

[0012] Metallic wires offer advantages over other fibrous organic materials such as paper or cotton because the specific surface area of ​​metallic wires in the outer boundary layers of the material is smaller than that of organic materials. Due to this smoother and smaller surface area, particles that have been deposited from the exhaust air stream and adhere to the metallic wire can be more easily detached during cleaning. The hardness of the metallic wire material also makes mechanical adhesion of the adhering particles to the wires virtually impossible.

[0013] By forming the metallic wires as a woven, braided, or knitted fabric, they can effectively cover the cross-sectional area of ​​the exhaust duct without obstructing it. Depending on the type and fineness of the woven, braided, or knitted fabric and the thickness of the metallic wires used, fine perforations are created between the wires. These perforations allow the exhaust air to pass through while reliably retaining solid particles above a certain size. The metallic wires used can be made of stainless steel. Fine fabrics made of this material are corrosion-resistant, allow for a large, stable filter area with high airflow, and are easy to clean. The pressure drop with a lightly soiled filter can be less than 5%. A lower pressure drop is advantageous for the dimensioning of the components, which can be designed with lower power output for the same throughput capacity.The energy efficiency and operating costs of the exhaust air system are lower with less powerful components.

[0014] The frame holds the metallic wires in their installed position within the exhaust duct. Because the metallic wires of the fabric, braid, or knitted material are held within a frame, they can be easily installed in the device and, if necessary, easily removed again. At the edges, the frame secures the fabric, braid, or knitted material within the exhaust duct in such a way that no large gaps remain through which the exhaust air could flow unfiltered.

[0015] The fabric, braid, or knitted material can easily be set into desired vibrations via the frame. For this purpose, the frame is connected to at least one vibration generator via a connecting element. Electrically, pneumatically, or hydraulically driven vibrators and / or tappers can be used as vibration generators. Various connecting elements can be used, the selection of which depends on the specific mounting situation within the device. In a simple version, the connecting element consists, for example, of a welded, adhesive, clamped, or screwed connection through which the vibration generator is attached to the frame, such as when the vibration generator is mounted directly to the frame. However, the vibration generator can also be mounted at a distance from the frame within the device.In this case, the vibration transmission can be achieved by means of a connecting arm, a link arm, a connecting tab or the like.

[0016] The vibration generator can be operated in cleaning mode. Cleaning the filter material may be necessary if so much fine dust and other contaminants adhere to it that the flow resistance generated by the filter material increases, the device's throughput decreases, and the energy consumed by the device increases in order to expel a constant target throughput volume of exhaust air from the connected livestock barn. The cleaning mode can also be activated for other reasons.

[0017] To clean the filter material of adhering dust and dirt particles, the device is operated in cleaning mode. In cleaning mode, the vibrator is switched on to create vibrations that cause the filter material to vibrate strongly enough to dislodge the adhering dust and contaminants. These vibrations are generated to overcome, or at least loosen, the adhesion of particles filtered from the exhaust air stream to the metallic wires. The vibrations produced by the vibrator are transmitted via the connecting element to the frame and thus indirectly to the fabric, braid, or knit of the metallic wires.To set the metallic wires into vibration, a single vibration generator can be operated, but it is also possible to provide several vibration generators that are operated in parallel temporarily or permanently, especially to generate different frequencies, operating intervals, pulse strengths and the like.

[0018] The frequencies and amplitudes of the vibrations are selected to effectively remove the particles adhering to the metallic wires. They can also be varied within a cleaning cycle, for example, by increasing and decreasing in intensity to address different particle sizes.

[0019] According to one embodiment of the invention, the metallic wires of the filter material are made of stainless steel. Fine fabrics made of this material are corrosion-resistant, they allow for a large, stable filter surface with high air permeability, and they are easy to clean.

[0020] According to one embodiment of the invention, the device includes an exhaust fan in the exhaust duct, which draws or blows the cleaning air through the drying filter stage in the second direction during cleaning mode. The exhaust fan can, for example, be the same exhaust fan that, in a first embodiment, is designed to operate bidirectionally, for instance, by means of adjustable air guide vanes. In this case, the exhaust fan and the cleaning fan are the same fan, whose fan blades can be rotated in different directions about their longitudinal axis in order to operate as either an exhaust fan or a cleaning fan. However, according to another embodiment, one or more cleaning fans can also be provided that serve only to generate an airflow directed in the second direction.The separate cleaning blowers can be motorized and swung from a rest position (exhaust mode) to an operating position (cleaning mode) within the exhaust duct. This prevents unnecessarily increasing air resistance and pressure loss in the duct when it is operating in exhaust mode. A cleaning blower positioned within the exhaust duct blows the dust and dirt accumulated on the filter material back into the livestock barn.Because the particles accumulated on the surface of the filter material are at least partially clumped together into larger, heavier clumps by the continuous air pressure of the exhaust air stream, they do not float back into the air of the livestock barn after being blown back into the air. Instead, they fall to the floor shortly after leaving the exhaust duct, where they initially remain and can later be disposed of without any additional effort when the bedding is changed. In this way, the air in the livestock barn remains clean, and the orderly disposal of the filtered dust and other contaminants accumulated on the filter material is ensured without any additional effort.

[0021] According to one embodiment of the invention, a collecting device is connected to the exhaust air duct, into which the cleaning air flowing in the second direction through the exhaust air duct is diverted by means of a switchable deflecting device.

[0022] If it is not desired to blow the dust and dirt accumulated in the filter material back into the livestock barn, it is optionally possible to divert the cleaning air into a collection device via the switchable deflection device, in which the dust and dirt particles transported with the cleaning air can be collected and disposed of separately.

[0023] According to one embodiment of the invention, the dry filter stage is arranged upstream of a wet cleaning stage in the direction of exhaust air flow through the exhaust duct. By cleaning the exhaust air of dust and other solids that can be removed from the exhaust air by a filter material before the exhaust air is cleaned in the wet cleaning stage, the amount of dirt particles that accumulate and concentrate in the washing liquid is reduced. However, by combining a dry filter stage with a downstream wet cleaning stage, it is also possible to bind in the washing liquid those fine dust particles that have penetrated the remaining openings in the filter material and are still suspended freely in the exhaust air stream even after it has passed through the dry filter stage.By combining the dry filter stage with a downstream wet cleaning stage, it is possible to filter out at least 70%, and if necessary, more than 70% of the dust transported in an exhaust air stream. The washing liquid used in the wet cleaning stage can remain in the wet cleaning stage longer without needing to be replaced, thanks to the upstream dry filter stage, and the storage, post-cleaning, and disposal of the used washing liquid are simplified.

[0024] The dry cleaning stage can be easily retrofitted modularly into a device for cleaning exhaust air from livestock barns that currently only has a wet cleaning stage. Similarly, it is possible to initially install only the dry filter stage in a device for cleaning exhaust air from livestock barns. If the cleaning performance of this dry filter stage needs to be increased at a later date by retrofitting a wet cleaning stage, because this appears necessary and / or legal requirements and / or official regulations for the operation of the livestock barn mandate such an increase in cleaning performance, this can also be done retroactively without major difficulties.Investing in an exhaust air system that either already has a dry filter stage or where the cleaning performance of an existing wet cleaning stage is to be subsequently increased is therefore a future-proof investment, because it is possible at any time without major effort by purchasing and installing a corresponding additional cleaning module in the exhaust air system.

[0025] According to one embodiment of the invention, the device has an electronic control unit, wherein the control unit is connected to at least one sensor whose sensor signal indicates the degree of clogging of the dry filter stage. The sensor signal is evaluated by the control unit, and the control unit has programming that switches the device from exhaust air mode to cleaning mode when the sensor value exceeds or falls below a threshold. The at least one sensor can, for example, measure the pressure drop in the exhaust air stream caused by the dry filter stage. In a simple first embodiment, only a single pressure sensor can be arranged downstream of the dry filter stage, measuring the air pressure in the exhaust air duct.The control system has a pre-programmed setpoint that the air pressure in the exhaust duct must reach at a minimum when the device is operating in exhaust mode and the filter material of the dry filter stage is not clogged. If the value measured by the pressure sensor falls below the pre-programmed setpoint by more than a pre-programmed threshold value, the control system can interpret this as an indication that the filter material is becoming increasingly clogged and the dry filter stage needs cleaning. In a more sophisticated version, two pressure sensors can be used. One pressure sensor is located upstream of the dry filter stage (viewed from the exhaust air flow direction), and the other is located downstream of the dry filter stage in the exhaust duct. The sensor readings from both pressure sensors can be continuously compared during exhaust mode.If the difference between the sensor readings of the two pressure sensors exceeds a certain threshold, the control unit can interpret this as a switching command to change from exhaust air mode to cleaning mode. Instead of or in addition to measuring pressure values, one or more sensors can also be arranged in the device to measure the flow velocity of the exhaust air stream. Here again, for example, only a single sensor might be positioned downstream of the dry filter stage, its reading compared to a pre-programmed setpoint. Alternatively, at least two sensors could be arranged upstream and downstream of the dry filter stage, their readings being compared. If the difference between the flow velocities becomes too great, the control unit switches from exhaust air mode to cleaning mode.Of course, it is also possible to switch from exhaust mode to cleaning mode at timed intervals, independent of the values ​​of one or more sensors. The return from cleaning mode to exhaust mode can also be timed, and / or a test run can be performed after the return from cleaning mode to exhaust mode. During this test run, the sensor(s) measure whether the cleaning is satisfactory for continued operation of the device in exhaust mode.

[0026] According to one embodiment of the invention, the control unit switches on the cleaning fan when switching from exhaust mode to cleaning mode. The cleaning air generated by the cleaning fan is an important component for cleaning the filter material in the dry filter stage. The vibration produced by the vibrator and the cleaning air complement each other to loosen and remove dust and dirt particles adhering to the filter material. The cleaning fan can be a single, additional fan that is switched on when the control unit has switched the device to cleaning mode.The single fan can also be a bidirectional fan that generates the exhaust airflow in exhaust mode. In such a fan, the fan blades rotate when the controller switches between exhaust and cleaning modes to create the required airflow direction for each mode. Alternatively, multiple fans can be used to create a dedicated cleaning blower that generates the cleaning airflow. The controller can adjust the cleaning blower's speed to vary depending on the cleaning mode. This variation in speed can be matched to a corresponding variation in the vibration generated by the vibration generator.By using different frequencies of the vibration generator and different flow rates of the cleaning air, it is possible to detach and remove particles of different sizes from the filter material.

[0027] According to one embodiment of the invention, the control system deactivates the exhaust fan when switching from exhaust mode to cleaning mode. To generate the strongest possible cleaning airflow, an exhaust fan operating even in cleaning mode would be counterproductive. In addition to or as an alternative to deactivating the exhaust fan, it is also possible to arrange ventilation flaps in the exhaust airflow. These flaps block the inflow of exhaust air into the exhaust duct or the outflow of exhaust air from the exhaust duct, or they separate the exhaust fan from the exhaust airflow.

[0028] According to one embodiment of the invention, the control unit has a program that switches the device, operating in cleaning mode, to exhaust air mode for testing purposes. During the test run, the control unit automatically switches the device back to cleaning mode if the sensor signal is above or below a threshold value specified in the program. This test run allows the time the device operates in cleaning mode to be reduced to the absolute minimum.

[0029] According to one embodiment of the invention, the frame is sealed to the exhaust duct by means of a seal made of an elastic material, thus isolating vibrations. With a rigid connection between the frame and the exhaust duct, the vibrations generated by the vibration source during cleaning mode and transmitted to the frame could also be transmitted from the frame to the exhaust duct. This would place mechanical stress on the frame's connection points on the exhaust duct, and the vibrations transmitted to the exhaust duct could also manifest as disturbing noise. To prevent such vibration transmission from the frame to the exhaust duct, the frame is sealed to the exhaust duct by means of a seal made of an elastic material, thus isolating vibrations.The vibrations transmitted from the frame to the seal are neutralized by the elastic material of the seal, so that the seal does not transmit the vibrations to the exhaust duct, or at least only transmits them in a significantly dampened form.

[0030] The invention will be described below using an example of a Fig. The schematically illustrated embodiment will be explained in more detail below. Fig. Figure 1 shows an embodiment of a device 2 for cleaning exhaust air from an animal barn 4. The device 2 has an exhaust air duct 6 in which an exhaust air fan 8 is arranged. The exhaust air fan 8 generates an airflow 10 that flows from the animal barn 4 through the exhaust air duct 6 to the outside. The exhaust airflow 10 flows in a first direction 12. In doing so, it passes through the dry filter stage 14, in which a filter material 16 is arranged, positioned transversely to the flow direction of the airflow 10 in the exhaust air duct 6. Solid particles from the exhaust airflow 10 flowing through the exhaust air duct 6 can accumulate in the filter material 16 and thus be filtered out of the exhaust airflow 10. The filter material 16 is in the Fig. 1 indicated by dots held within frame 20. The dots symbolize metallic wires formed as a woven, braided, or knitted fabric and held within frame 20. The metallic wires of the filter material 16 may be made of stainless steel.

[0031] The device 2 can be operated in an exhaust air mode A and in a cleaning mode B, wherein in exhaust air mode A the exhaust air stream 10 generated by the exhaust air blower 8 flows from the livestock barn 4 in the first direction 12 through the dry filter stage 14 to the outside. In exhaust air mode A, exhaust air laden with dust and dirt particles flows through the filter material 16. In cleaning mode B, cleaning air, which is blown or drawn from the outside by a cleaning blower 26 in the second direction 18 towards the livestock barn 4 through the filter material 16 of the dry filter stage 14, also flows through the filter material 16, whereby the cleaning air detaches dust and dirt particles accumulated on the side of the filter material 16 facing the livestock barn 4 from the filter material 16 and carries them along in the second direction 18.

[0032] In the illustrated embodiment, the cleaning blower 26 is also present in the exhaust air duct 6, wherein in the Fig. In the embodiment shown in Figure 1, the exhaust fan 8 and the cleaning fan 26 are operated alternately depending on whether the device 2 is in exhaust mode A or in cleaning mode B. As shown in Figure 1, the exhaust fan 8 and the cleaning fan 26 are operated alternately depending on whether the device 2 is in exhaust mode A or in cleaning mode B. Fig. As can be seen in the sketch shown, the cleaning blower 26 is arranged as a fixed fan in the exhaust air duct 6. Alternatively, the cleaning blower 26 can also be designed to be motorized or manually foldable in and out of the exhaust air duct 6. Several cleaning blowers 26 can also be provided to generate the cleaning airflow with which the filter material 16 is cleaned.

[0033] The frame 20 is connected to at least one vibration generator 24 via a connecting element 22. The vibration generator 24 can be actively operated in cleaning mode B; the vibrations it generates are transmitted to the frame 20 via the connecting element 22. The frame 20 can be sealed to the exhaust air duct 6 by means of a seal 38 made of an elastic material, thus isolating it from vibrations.

[0034] In the exemplary embodiment, a collecting device 28 is connected to the exhaust air duct 6, into which the cleaning air flowing in the second direction 18 through the exhaust air duct 6 can be diverted by means of a switchable deflector 30. The deflector 30 is in Fig.1. The adjustable flap is indicated by dotted lines and is adjustable along the double arrow. The deflector 30 can also be used to stop the exhaust airflow 10 in order to clean the filter material 16 as effectively as possible with cleaning air, removing the dust and dirt particles that have accumulated there. The dust and dirt particles blown out of the filter material 16 can be collected in the collection device 28 and disposed of from there as needed.

[0035] In the illustrated embodiment, the dry filter stage 14 is arranged upstream of a wet cleaning stage 32 in the direction of exhaust air flow through the exhaust air duct 6. The exhaust air stream 10 is thus first cleaned of coarser dust and dirt particles in the dry filter stage 14 before it enters the operating area of ​​the wet cleaning stage 32. There, further dirt particles can be filtered out of the exhaust air stream 10, bound in the circulating water, and removed.

[0036] The device 2 has an electronic control unit 34, the control unit 34 being connected to at least one sensor 36 whose sensor signal indicates the degree of clogging of the dry filter stage 14. The sensor signal is evaluated by the control unit 34, and the control unit 34 has programming that switches the device 2 from exhaust mode A to cleaning mode B when the sensor value of the sensor 36 exceeds or falls below a threshold value. The control unit 34 switches on the cleaning fan 26 when switching from exhaust mode A to cleaning mode B. The control unit 34 also deactivates the exhaust fan 8 when switching from exhaust mode A to cleaning mode B.The control unit 34 can have a programming with which the device 2, operating in cleaning mode B, is switched to exhaust mode A for testing purposes, and the control unit 34 automatically switches the device 2 back to cleaning mode B during the test run if the sensor signal of sensor 36 is above or below a threshold value specified in the programming. Reference symbol list 2 Device 4 Livestock barn 6 Exhaust air duct 8 exhaust fans 10 Exhaust air flow 12 first direction 14 Dry filter stage 16 filter material 18 second direction 20 frames 22 Fasteners 24 vibration generators 26 cleaning blowers 28 Collecting device 30 Deflection device 32 Wet cleaning level 34 Control 36 Sensor 38 Seal A Exhaust mode B Cleaning mode QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 20 2014 005 398 U1

[0004] DE 201 13 965 U1

[0005] DE 44 03 634 A1

[0006] DE 197 22 840 A1

[0007]

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