Device and method for emission control on a gas-carrying container, in particular on a digester of a biogas plant

Abstract

The present invention relates to a device and a method for emission control in a gas-carrying container, in particular a digester of a biogas plant, comprising a gas-carrying container (2) which has a gas phase (6) in its interior (5), an overpressure and / or underpressure safety device (7) with a liquid barrier chamber (12) which is fluidically connected to the interior (5), a detection device which is designed and configured to detect and / or record a gas escape from the gas-carrying container (2) and the internal pressure in the gas phase (6) of the interior (5), a liquid refilling device (22) which is designed and configured to refill barrier fluid directly or indirectly into the liquid barrier chamber (12), and a control unit (26) which is designed and configured toto automatically activate or not activate the liquid refilling device (22) depending on a detected and / or recorded gas leakage from the gas-carrying container (2) and a detected and / or recorded internal pressure in the gas phase (6) of the container interior (5).

Description

The present invention relates to a device and a method for emission control on a gas-carrying container, in particular on a fermentation tank of a biogas plant. In gas-carrying containers, such as those typically used in biogas plants for storing and fermenting organic substrates, pressure fluctuations occur regularly as a result of biological and physical processes. These fluctuations can occur in the direction of both overpressure and underpressure relative to atmospheric pressure. Overpressure arises particularly from gas production during active fermentation or from thermal expansion of the existing gas volume. However, excessive pressure increases can occur not only as a result of natural gas production processes or thermal volume changes, but also as a consequence of operational malfunctions, such as the abrupt shutdown of a gas-consuming unit, the unintentional closure of a gas line, or the blockage of a gas outlet. In such cases, there is a risk of uncontrolled pressure buildup in the tank. To prevent structural damage to membrane roofs, foil systems, concrete ceilings, or other pressure-sensitive components, the maximum permissible operating overpressure is typically limited to approximately 6 mbar for foil roofs and approximately 10 mbar for concrete ceilings.If this value is reached or exceeded, a controlled gas release must occur, for example via an overpressure protection device based on a liquid column that allows the gas to escape to the outside. A negative pressure can arise, for example, from gas cooling, sudden gas withdrawal, or purging processes. Even a slight negative pressure of 1.5 to 2 mbar can lead to undesirable deformations of the container structure, the ingestion of foreign substances, or the collapse of flexible gas storage tanks. To ensure operational safety even in these cases, a negative pressure safety device is required, which allows controlled venting of the container when a defined negative pressure level is reached. To protect against impermissible pressure conditions, so-called overpressure and / or underpressure safety devices (OPDs) are used in practice. These devices allow both gas to escape in case of overpressure and air to enter in case of underpressure in a physically simple manner. The operating mechanism of such devices is usually based on hydrostatic principles, for example, through liquid barriers with defined immersion depths or siphon systems where the opening pressure is determined by the respective height of the liquid column. A common type of such device is based on the principle of a liquid barrier, in which a riser pipe, fluidically connected to the gas space of the container, is immersed in a liquid to seal the gas space from the environment. This liquid – also referred to as a liquid column – is typically located in a section of the respective overpressure and / or underpressure protection device, situated outside the gas space of the container. This system remains gas-tight until the gas pressure in the gas chamber of the gas-carrying container is lower than the hydrostatic pressure of the liquid column in the riser pipe. Only when the internal pressure exceeds a critical value is the gas forced upwards through the riser pipe and penetrates the liquid column as a gas bubble. In this way, excess gas can be discharged without the need for moving mechanical components or control valves. A significant problem with conventional liquid barriers, however, is that the liquid is partially displaced or splashed out by the overpressure event (gas bubbling). Evaporation can also cause the liquid level to drop during operation. Therefore, after the overpressure event ends, the liquid column in the riser pipe is often no longer high enough to ensure a reliable seal against the environment. This results in an unwanted gas leak, which—especially with biogas, which has a high methane content—can represent not only a significant environmental hazard and safety risk, but also an economic loss. Such gas leaks often go unnoticed in purely passive systems and therefore pose a safety risk. Accordingly, the object of the present invention is to provide a device and a method for emission control on a gas-carrying container, in particular on a fermentation tank, of a biogas plant, with which unnecessary emissions from liquid barriers can be reliably and reliably prevented. This task is solved using the features of the independent claims. Advantageous embodiments are the subject of the dependent claims relating thereto. According to the invention, an emission control device is provided for a gas-carrying container, in particular a digester of a biogas plant, comprising the following: - a gas-carrying container which has a gas phase in its interior, - an overpressure and / or underpressure protection device with a liquid barrier chamber which is fluidically connected to the interior of the container, - a detection device which is designed and configured to detect and / or record a gas leak from the gas-carrying container as well as the internal pressure in the gas phase of the interior of the container, - a liquid refilling device which is designed and configured to refill barrier fluid directly or indirectly into the liquid barrier chamber, - a control unit which is designed and configured toThe liquid refilling device is to be automatically activated or deactivated depending on a detected and / or recorded gas leak from the gas-carrying container and a detected and / or recorded internal pressure in the gas phase of the container interior. The solution according to the invention enables active and automatic monitoring and control of the tightness of a liquid barrier on a gas-carrying container. While conventional systems generally require either manual checks or less sophisticated automatic control, the device according to the invention independently detects and identifies gas leaks and assesses their cause. If necessary, it automatically initiates a refill of the barrier fluid, thus ensuring that the liquid barrier functions reliably. The core of the solution according to the invention lies in the inclusion of both gas leakage and internal pressure. Monitoring only one of these two physical quantities would be less reliable and could lead either to uncontrolled gas leakage or to an impediment to the desired gas pressure reduction. The combined evaluation of both physical quantities achieves a particularly reliable, operationally safe, and low-emission control automation. The detection device, designed to determine gas leaks and internal pressure within a container, can be hardware-based, such as a gas detector and gas pressure sensor, or it can be configured so that the measured values ​​are calculated from other parameters or indicators using software-based algorithms. This flexibility in the design of the detection device allows for a high degree of adaptability to different system configurations and operating conditions. It is understood that the invention, as already stated at the outset, is not limited to certain types of container construction, but can be used in designs with foil roofs as well as with concrete ceilings or comparable pressure-sensitive closures. The phrase "to refill the liquid containment chamber directly or indirectly" means that the liquid serving as the containment fluid can be introduced into the containment chamber in various ways. "Directly" refers to the liquid being fed directly from the liquid refilling device (e.g., a liquid supply line or a container) into the containment chamber. In this case, the liquid is filled directly into the chamber where it fulfills its containment function, without any further detours. "Indirectly" means that the liquid is not introduced directly into the containment chamber, but rather reaches it indirectly or via an intermediate step.This offers additional flexibility in the design of the device, so that the sealing fluid can also be refilled from an external fluid reservoir or through various filling mechanisms without affecting the functionality of the system. Particularly preferred is a specific solution in which the control unit is designed and configured to, in the event of a detected and / or recorded gas leak, (i) in the case of no overpressure in the gas phase of the container interior, activate the liquid refilling device and automatically trigger a liquid refill, and (ii) in the case of an existing overpressure in the gas phase of the container interior, not activate the liquid refilling device and thus not trigger a liquid refill. In this preferred implementation, if a gas leak is detected and / or recorded, and there is simultaneously no overpressure in the gas phase of the container interior, the control unit interprets this as an indication of an insufficient liquid column and activates the liquid refilling device to automatically replenish the sealing liquid. However, if overpressure is detected during a gas leak, no refilling occurs, and the liquid barrier remains open to allow controlled pressure release without unnecessarily impeding the gas flow. This differentiated response ensures that the system is precisely adapted to the respective operating situation, reduces the risk of unintended gas leaks, and minimizes the emission of climate-relevant gases, particularly methane.Furthermore, the device sustainably increases the operational reliability of the biogas plant and reduces maintenance costs, as unnecessary interventions are avoided. According to a particularly preferred, simple, and reliable embodiment, the detection device comprises at least one gas detector located in an exhaust air section of the overpressure and / or underpressure safety device, wherein the at least one gas detector is designed and configured to detect a gas leak. This embodiment ensures that gas leaks, for example of methane-containing biogas, are detected quickly and reliably, leading to an immediate system response to minimize unnecessary emissions. According to a further particularly preferred, simple and reliable embodiment, the detection device comprises at least one gas pressure sensor designed and configured to detect the internal pressure in the gas phase of the container interior and / or arranged in the gas phase of the container interior. The gas pressure sensor continuously monitors the system pressure, thereby enabling precise control of the system's functionality, particularly with regard to overpressure and underpressure ranges. In conjunction with the two previously described specific embodiments, it is also advantageous if the control unit is coupled to the at least one gas detector, the at least one gas pressure sensor, and the liquid refilling device. The control unit is designed and configured to automatically control the liquid refilling device based on the measured values ​​acquired by the at least one gas detector and the at least one gas pressure sensor. This configuration enables highly automated emission control, guaranteeing an efficient and accurate response to gas leaks without operator intervention.Preferably, in the event of a gas leak detected by means of the at least one gas detector, (i) in the case of no overpressure in the gas phase of the container interior, the liquid refilling device is activated and a liquid refill is triggered automatically, and (ii) in the case of an existing overpressure in the gas phase of the container interior, the liquid refilling device is not activated and thus no liquid refill is triggered. This sophisticated control system ensures precise adaptation to each situation: In the event of a low liquid level, the system automatically refills, while in the case of overpressure, gas release can occur in a controlled manner without obstructing gas discharge. This leads to a significant reduction in emissions, improved operational efficiency, and a substantial decrease in maintenance requirements. The system's high flexibility and autonomy ensure reliable emission control even under changing operating conditions, minimizing the risk of gas leaks and their environmental impact. In preferred embodiments, the at least one gas detector and the at least one gas pressure sensor are designed and / or positioned in such a way that measurement errors caused by liquid influences, temperature influences or mechanical loads are minimized. According to a particularly preferred embodiment, the overpressure and / or underpressure protection device comprises a liquid basin arranged in the gas phase of the container interior for receiving a sealing liquid. Furthermore, the overpressure and / or underpressure protection device comprises an upwardly open exhaust pipe projecting into the liquid basin from above, with respect to the vertical axis. The lower end of the pipe, with respect to the vertical axis, is located at a distance from the bottom of the liquid basin, and in the sealed state, the lower end of the pipe lies below the liquid level of any sealing liquid contained in the liquid basin. The liquid basin and the exhaust pipe are designed and configured to form a liquid column in a liquid sealing chamber within the exhaust pipe, creating a gas-tight barrier against the environment.The at least one gas detector is located in an exhaust air section of the exhaust pipe. This gas detector is designed and configured to detect any gas leakage via the exhaust pipe. The design of the overpressure and / or underpressure protection device, featuring a liquid tray located in the gas phase of the container's interior and an exhaust pipe immersed therein, creates a particularly simple, structurally robust, and highly reliable liquid barrier. The formation of a liquid column within the exhaust pipe enables defined and reproducible pressure protection, while the surrounding environment remains gas-tightly separated from the gas phase of the container by the liquid column.At the same time, the direct detection of a gas leak in the exhaust air area of ​​the exhaust pipe allows for extremely precise detection of even small leaks directly at the intended venting point, enabling the system to react to possible malfunctions particularly early. According to a particularly preferred embodiment, an overflow pipe is provided that penetrates the bottom of the liquid basin and whose upper end, relative to the vertical axis, projects into the liquid containment space of the exhaust pipe. The overflow pipe is designed and configured to allow the containment liquid to drain through the overflow pipe when the pressure in the gas phase exceeds the hydrostatic pressure of the liquid column, and gas escapes through the exhaust pipe. By additionally providing an overflow pipe whose upper end projects into the liquid containment space of the exhaust pipe, a defined maximum permissible overpressure in the gas phase of the vessel interior is set in a particularly simple and reliable manner.The height of the overflow pipe relative to the liquid level determines the hydrostatic pressure of the liquid column and thus the overpressure at which gas venting is initiated. As soon as the pressure in the gas phase of the container exceeds the hydrostatic pressure of the liquid column, the liquid level in the vent pipe rises, and the sealing fluid flows out through the overflow pipe. In this way, the liquid level in the vent pipe remains within a defined range, ensuring the reliable maintenance of a gas-tight seal. Simultaneously, this ensures that any gas escape is controlled and occurs exclusively through the vent pipe, thus enabling precise detection of gas events. In connection with such a structure, a further particularly preferred embodiment provides that a lower end of the overflow pipe, relative to the vertical axis, is fluidically connected to the gas phase of the container interior via a siphon section. This siphon section of the overflow pipe is designed and configured to prevent gas from escaping the gas phase of the container interior via the overflow pipe when filled with a sealing liquid. By forming a siphon section at the lower end of the overflow pipe that is fluidically connected to the gas phase of the container interior, it is ensured that uncontrolled gas escape from the container interior, even via the overflow pipe, is reliably prevented.When sufficiently filled with sealing fluid, the siphon section forms a gas-tight barrier against the environment, preventing emissions from the overflow pipe during normal operation. This reliably complements the function of the liquid barrier in both flow directions – for both overpressure and underpressure situations – and significantly improves the operational reliability of the entire overpressure and / or underpressure protection system. Furthermore, it minimizes unwanted leakage without requiring additional mechanical closures or check valves, considerably increasing the system's ease of maintenance and reliability. According to a particularly preferred embodiment, the liquid containment chamber and the overflow pipe are designed and configured to form a liquid column of a defined height, preferably between 3 cm and 11 cm, within the liquid containment chamber. By designing the liquid containment chamber and the overflow pipe in such a way that a liquid column of a defined height, preferably in the range of 3 cm to 11 cm, is formed within the liquid containment chamber, a targeted and reproducible adjustment of the maximum permissible overpressure inside the container is achieved. Since the hydrostatic pressure of the liquid column is proportional to its height, the pressure at which a controlled outflow of the containment liquid via the overflow pipe and thus a gas escape from the container can be precisely determined via the defined liquid height.In typical biogas plants, overpressure protection is often set in the range of approximately 3 mbar to 11 mbar to ensure adequate sealing and prevent damage or uncontrolled gas releases under overpressure. In practice, starting from an operating pressure of, for example, 4 mbar, the overpressure protection system can be designed for a release pressure of around 6 mbar for tanks with foil roofs, while for concrete roofs, release pressures up to approximately 10 mbar are common to accommodate the higher structural loads and longer pipe runs. The selected liquid column height meets these technical requirements and allows the overpressure protection system to be adapted to different operational conditions without the need for complex mechanical or electronic control mechanisms.This allows the emission behavior of the overpressure and / or underpressure safety device to be precisely adapted to the requirements of the respective system, while at the same time achieving high operational safety and reliable functioning even under fluctuating operating conditions. According to a further particularly preferred embodiment, the overflow pipe projects essentially straight along a vertical axis from the bottom of the liquid basin into the liquid containment chamber. This essentially straight design of the overflow pipe along a vertical axis enables particularly simple, reliable, and trouble-free discharge of the containment fluid in the event of overpressure. The vertical orientation ensures that, in the event of a rise in the liquid level due to increased internal pressure, the containment fluid can drain through the overflow pipe without significant flow losses or backflow. At the same time, the risk of deposits, bubble formation, or uneven flow is minimized, which considerably improves the operational reliability of the overpressure protection system.The simple geometry also allows for a very compact and low-maintenance design, which is particularly advantageous for use in harsh environments such as biogas plants. The overflow pipe, for example, has an inner diameter of approximately 5 mm to 15 mm, particularly 7 mm to 12 mm. This diameter is large enough to ensure reliable and rapid drainage of excess sealing fluid, even in the event of sudden overpressure, while simultaneously preventing excessive fluid loss or the ingress of larger foreign materials that could clog the siphon section. This achieves an optimal balance between drainage capacity and operational reliability. Preferably, the liquid basin and / or the overflow pipe is made of a corrosion-resistant material, in particular stainless steel, PVC, PP (polypropylene), or PE-HD (high-density polyethylene). These materials ensure high chemical resistance to the barrier fluid typically used in biogas plants (e.g., water or water-glycol mixtures) as well as to aggressive environmental conditions such as humidity, ammonia, or hydrogen sulfide. Furthermore, they enable a long service life with low maintenance costs, which is of particular importance in the field of industrial biogas plants. According to a further particularly preferred embodiment, the liquid tray is designed to surround the exhaust pipe circumferentially with an overhanging rim and to have a peripheral wall that is raised in the vertical direction relative to the base of the liquid tray. By designing the liquid tray such that it surrounds the exhaust pipe circumferentially with an overhanging rim and has a peripheral wall that is raised relative to the base of the liquid tray, a vacuum protection function can be implemented in a particularly simple and structurally robust manner. The peripheral wall ensures that even in the event of evaporation, splashing, or slight liquid loss, a sufficient liquid level is maintained so that ambient air can be reliably drawn into the container via the liquid column, even if a vacuum develops in the gas-carrying vessel.The height of the perimeter wall determines the minimum amount of liquid required to maintain the barrier effect and simultaneously defines the maximum permissible negative pressure before the liquid column collapses. This allows the permissible negative pressure range to be designed and adjusted, for example, from an operating pressure of approximately 4 mbar, to typical operating values ​​of approximately 1 mbar to 3 mbar, particularly around 2 mbar, as are commonly required in biogas plants. At the same time, the perimeter wall prevents uncontrolled overflow of the liquid from the tank under dynamic influences such as vibrations or shock loads, ensuring that the liquid barrier can reliably perform its function even under changing operating conditions. According to a preferred, specific embodiment, the circumferential wall has a height of at least 1 cm, preferably 1 cm to 5 cm, relative to the bottom of the liquid basin in the vertical axis direction. This targeted dimensioning of the circumferential wall ensures the reliable functionality of the liquid barrier, particularly under negative pressure. The selected height range makes it possible to maintain a sufficiently high liquid column even at typical negative pressures in biogas plants of approximately 1 mbar to 3 mbar, and especially approximately 2 mbar. This allows ambient air to enter the container via the liquid column without the barrier liquid sinking uncontrollably or the seal collapsing. At the same time, oversizing is avoided, which would result in unnecessarily large liquid volumes or excessive structural requirements.The chosen height thus achieves a particularly advantageous balance between functionality, space optimization and operational reliability. In preferred embodiments, the exhaust pipe has an equivalent hydraulic diameter, based on a corresponding circular cross-section, of approximately 100 mm to 300 mm. The liquid basin has a larger free cross-section than the exhaust pipe, with the equivalent hydraulic diameter of the liquid basin preferably being approximately 10 mm to 50 mm larger than that of the exhaust pipe. By increasing the hydraulic diameter of the liquid basin compared to the exhaust pipe, a sufficient volume of barrier fluid is provided to ensure reliable emission control even in the event of fluid losses, evaporation, or dynamic loads. In a particularly preferred embodiment, the liquid volume of the liquid tray is dimensioned relative to the volume of the liquid column in the exhaust pipe such that any volume shift due to pressure changes can be completely compensated within the system. Preferably, the liquid volume of the liquid tray, particularly under normal operating conditions, corresponds essentially to the liquid volume of a liquid column built up in the exhaust pipe. "Normal operating conditions" here refers to a situation without overpressure or underpressure, in which a desired, stable operating state exists at a typical operating pressure, for example, in the range of 3 to 5 mbar, and particularly around 4 mbar. This allows any increase in the liquid level in the exhaust pipe to be compensated for without refilling the liquid from the tray volume.The liquid volume of the liquid tray used for the calculation corresponds to the total liquid volume contained in the liquid tray, minus the portion of the liquid volume enclosed by the immersed exhaust pipe, which is added to the volume of the liquid column. Accordingly, the volume of the liquid column built up in the exhaust pipe is calculated by multiplying the internal cross-sectional area of ​​the pipe by the corresponding column height. According to a further particularly preferred embodiment, the liquid refilling device has at least one liquid supply line designed and configured to introduce barrier fluid into the exhaust duct. This provides a particularly simple and compact way to introduce the required barrier fluid precisely and with minimal loss to the location of the liquid barrier. This allows the liquid barrier to be restored quickly and reliably when needed, without the need for extensive piping systems or separate refilling areas. Furthermore, the liquid refilling process is carried out directly within the protected area of ​​the exhaust system, independent of the ambient air or external influences, thereby further improving operational reliability and emission control. According to a particularly preferred embodiment, the liquid supply line, relative to the vertical axis, terminates in the exhaust pipe in the area above the overflow pipe projecting into the exhaust pipe. The liquid supply line is designed and configured to fill both the liquid containment chamber and the siphon section of the overflow pipe with the containment liquid. By strategically positioning the liquid supply line above the overflow pipe projecting into the exhaust pipe, a particularly effective and loss-free filling of both the liquid containment chamber and the siphon section of the overflow pipe is ensured.This ensures that after refilling the liquid, not only is the gas-tight sealing liquid column in the exhaust pipe restored, but the siphon section is also reliably filled with sealing liquid, thus preventing uncontrolled gas escape via the overflow pipe. This dual function of the liquid supply significantly increases operational reliability and reduces maintenance, as separate monitoring or targeted refilling of the siphon becomes unnecessary. According to a further particularly preferred embodiment, the liquid refilling device, preferably the liquid supply line, comprises a controllable valve element, preferably a solenoid valve, which is coupled to the control unit and can be actuated by the control unit depending on an output signal from the at least one gas detector and / or the at least one gas pressure sensor, preferably such that the control unit opens the controllable valve element when no overpressure is detected in the gas phase of the container interior upon detection of gas leakage. By integrating a controllable valve element, preferably a solenoid valve, the liquid refilling device is coupled to the control unit in such a way that the liquid refilling can be controlled fully automatically and according to demand.In particular, the control unit can selectively open the valve when a gas leak is detected, even without an indication of overpressure inside the container – precisely when an uncontrolled gas leak is imminent due to liquid loss. This achieves maximum automation, emission control, and safety, as operator intervention is unnecessary and malfunctions resulting from delayed or omitted manual interventions are reliably prevented. Valve elements, especially solenoid valves, are technically sophisticated, extremely robust, and industrially proven components that enable highly reliable and precise control. They are characterized by a short response time, a long service life, and high resistance to environmental influences such as moisture, dirt, and temperature fluctuations. Furthermore, solenoid valves can be easily integrated into existing control systems.Especially in safety-relevant applications such as emission control at biogas plants, the use of a solenoid valve therefore offers particularly high operational reliability and process stability. According to a further particularly preferred embodiment, the liquid supply line is routed from outside the exhaust pipe, through a wall of the exhaust pipe, preferably in a sealed manner, into the interior of the exhaust pipe, and is coupled to a liquid reservoir, preferably located outside the gas-carrying container. Routing the liquid supply line from outside through the wall of the exhaust pipe into its interior results in a particularly compact, space-optimized, and safe integration of the liquid replenishment system. The preferably sealed penetration reliably prevents leaks at the interface and protects the surrounding area from uncontrolled gas escape. Furthermore, the coupling to an externally arranged liquid reservoir extends the system's autonomy, as large quantities of liquid are available or can be stored. According to a further particularly preferred embodiment, the exhaust pipe is designed in multiple sections and has a dividing plane in the area above the point where the liquid supply line enters the exhaust pipe. This multi-section design allows for particularly easy assembly, inspection, and maintenance of the device. In particular, the upper pipe segment can be easily removed if necessary without damaging or disconnecting the liquid supply line. This significantly simplifies and speeds up maintenance work, such as cleaning the liquid barrier or replacing components. According to a further particularly preferred embodiment, the exhaust pipe is formed by an elongated and / or cylindrical tube, and / or the at least one gas detector is arranged in a region of the exhaust pipe located above the barrier fluid with respect to the vertical axis, preferably in an outlet opening region of the exhaust pipe. The design of the exhaust pipe as an elongated and / or cylindrical tube ensures efficient flow of the escaping gas, minimizes flow losses, and facilitates the detection of gas leaks in the upper region. By arranging the gas detector in a region above the barrier fluid, particularly in the region of the outlet opening of the exhaust pipe, particularly reliable and early detection of even minor gas leaks is achieved. This improves the sensitivity and responsiveness of the entire emission control system.The exhaust pipe can be made of various materials to meet the specific requirements for resistance, durability, and cost-effectiveness in a biogas plant. For example, polypropylene (PP) and polyethylene (PE) can be used because these materials exhibit excellent corrosion resistance to the chemicals contained in biogas, especially hydrogen sulfide. They are also chemically stable, durable, and offer a cost-effective solution for use in biogas plants. In applications with particularly high demands on mechanical strength and corrosion resistance, stainless steel can be used, as this material offers exceptional resistance to mechanical and chemical stresses and ensures a long service life.Overall, the choice of material for the exhaust pipe depends on the specific requirements of the respective biogas plant and the associated operating conditions. The device according to the invention can be used particularly advantageously in a biogas plant, where, due to the specific properties of biogas, especially its high methane content, reliable emission control is of paramount importance. Accordingly, the present invention explicitly claims a biogas plant with at least one digester as a gas-carrying vessel, wherein the at least one digester has a device as described above. The integration of the device achieves a significant reduction in uncontrolled methane emissions, particularly in biogas plants, thereby enabling compliance with stricter environmental regulations and substantially increasing operational reliability. However, the device is not limited to use in biogas plants.It can also be used in other gas-carrying containers or systems, such as sewage gas, landfill gas, or industrial fermentation plants—anywhere pressure fluctuations occur and a liquid barrier is used as overpressure or underpressure protection. The invention thus offers broad technical applicability and opens up diverse application possibilities beyond the field of biogas plants. The invention further claims a method for emission control in a gas-carrying container, in particular in a digester of a biogas plant, wherein the gas-carrying container has a gas phase in its interior, and wherein the gas-carrying container is equipped with an overpressure and / or underpressure protection device which has a liquid barrier chamber fluidically connected to the interior of the container. The method essentially comprises the following steps: - Detecting and / or recording a gas leak from the overpressure and / or underpressure protection device, preferably and optionally by means of at least one gas detector arranged in an exhaust air area of ​​the overpressure and / or underpressure protection device, - Determining and / or recording the internal pressure in the gas phase of the container interior, preferably and optionally by means of at least one gas pressure sensor.- Evaluating the determined and / or recorded measured values ​​in a control unit, preferably and optionally in a control unit coupled with the at least one gas detector and the at least one gas pressure sensor, and - Automatically controlling a liquid refilling device by means of the control unit depending on a determined and / or recorded gas escape from the gas-carrying container as well as a determined and / or recorded internal pressure in the gas phase of the container interior for the direct or indirect refilling of barrier liquid into the liquid barrier chamber. According to a particularly preferred method, it is optionally provided that the control unit performs one of the following actions depending on the evaluated measured values: (i) automatic activation of the liquid refilling device to refill the sealing liquid into the liquid sealing chamber in the event of a detected gas leak and simultaneous absence of overpressure in the gas phase of the container interior, or (ii) omission of activation of the liquid refilling device in the event of a detected gas leak and simultaneous presence of overpressure in the gas phase of the container interior. The advantages arising in connection with the method are identical to those of the device according to the invention, which has already been discussed in detail above. Therefore, to avoid repetition, reference is made to the explanations given previously regarding the device. The invention is explained below only schematically and by way of example with reference to the figures. Fig. 1 is a schematic and perspective top view of a section of an opening edge area of ​​a fermentation tank of a biogas plant (not shown in further detail here). Fig. 2 is a schematic cross-section along line AA of Fig. 1. Fig. 3a is a schematic diagram of a normal operating situation with a desired operating pressure. Fig. 3b is a schematic diagram of an overpressure situation. Fig. 3c is a schematic diagram of an underpressure situation. Fig. 1 shows an example of a perspective top view of a section of the opening edge of a digester 2 of a biogas plant (not shown in detail here). The digester 2 is a gas-carrying container, for example, a main fermenter or post-fermenter of a biogas plant. In the example shown here, a toolbox 3 with a walkable platform 4 on its upper side is arranged at the opening edge of the fermentation tank 2. The toolbox 3 serves to store and arrange equipment and assemblies required for the operational use of the fermentation tank 2 or the biogas plant, such as agitators, control units and / or elements, etc. However, this will only be discussed in more detail in this description of the figures insofar as it is relevant to an emission control device 1, which is also an exemplary component of the toolbox 3 and is the subject of the present invention. The toolbox 3 rests tightly on or against the edge of the opening by means of its walkable platform 4. A tent roof, for example, serves as a gas-tight cover, adjoining both the toolbox 3 and the remaining edge of the opening; however, this is not shown here for clarity. The fermentation tank 2 contains, for example, a substrate to be fermented, which produces a methane-rich gas (biogas) that collects in the upper part of the tank interior 5 and forms a gas phase 6. In the example shown here, the gas phase 6 also extends into the toolbox, which is open downwards towards the interior of the tank 5, as can be seen particularly in Fig. 2, which shows a section along line AA of Fig. 1. As can be seen in particular from Fig. 2, the emission control device 1 comprises an overpressure and / or underpressure safety device 7, which in the specific example shown here has a liquid tray 8 arranged in the gas phase 6 of the interior of the container 5 for receiving a sealing liquid which is not shown in detail here. This overpressure and / or underpressure protection device has an upwardly open exhaust pipe 9 projecting from above into the liquid tray 8 with respect to the vertical axis x, the lower end 10 of which, with respect to the vertical axis x, lies below the liquid level (not shown here) of a sealing liquid contained in the liquid tray 8 when sealed. This creates a liquid column 11 (shown with a dashed line) in a liquid sealing chamber 12 of the exhaust pipe 9, which forms a gas-tight barrier against the environment with respect to the fluid connection between the exhaust pipe 9 and the surroundings. As can be clearly seen in Fig. 2, a gas detector 13 is arranged in an upper, near-terminal exhaust air region of the exhaust pipe 9, with respect to the vertical axis direction, wherein the gas detector 13 is designed and configured to detect a gas escape via the exhaust pipe. In particular, the gas detector 13 is designed and configured to detect an escape of methane-rich biogas. Fig. 2 can also be seen to show that the emission control device 1 further comprises a gas pressure sensor 14, which is designed and configured to detect the internal pressure in the gas phase 6 of the container interior 5. Fig. 2 further shows that the overpressure and / or underpressure safety device 7 has an overflow pipe 15 which penetrates the bottom 16 of the liquid basin 8, and whose upper pipe end 17, with respect to the vertical axis x, projects into the liquid sealing chamber 12 of the exhaust pipe 9, wherein the overflow pipe 15 is able, in the event of an increase in the pressure in the gas phase 6 of the interior of the container 5 above the hydrostatic pressure of the liquid column 11, to allow the sealing liquid to drain over the overflow pipe 15, whereby gas also escapes via the exhaust pipe 9, as is schematically illustrated in Fig. 2 by the arrows 18. A lower pipe end 19 of the overflow pipe 15, with respect to the vertical axis direction x, is fluidically connected to the gas phase 6 of the container interior 5 via a siphon section 20, wherein the siphon section 20, which is designed in an exemplary U-shape here, reliably prevents gas from escaping from the gas phase 6 of the container interior 5 via the overflow pipe 15 and further via the exhaust pipe 9 when filled with sealing liquid. To set an overpressure protection typical for biogas plants in the range of about 3 mbar to 11 mbar, it is provided that the liquid containment chamber 12 and the overflow pipe 15 are dimensioned such that a liquid column 11 with a defined height, preferably with a height of 3 cm to 11 cm, is formed in the liquid containment chamber 12. In the example shown here, the overflow pipe 15 also projects essentially in a straight line along a vertical axis and thus in the vertical axis direction x from the bottom 16 of the liquid basin 8 into the liquid containment chamber 12. The overflow pipe 15 has an inner diameter that ensures reliable and rapid drainage of the excess sealing fluid, for example a diameter in the range of approximately 5 mm to 15 mm. As can be seen in Fig. 2, the liquid tray 8 surrounds the exhaust pipe 9 with a circumferential overhang and has a peripheral wall 21 that is raised above the base 16 of the liquid tray 8. Specifically, the peripheral wall 21 can, for example, have a height such that it extends above the base 16 of the liquid tray 8, particularly in the area near the perimeter wall, by a defined height, for example, 1 cm to 3 cm. In this way, the permissible negative pressure range can also be adjusted by design and, for example, adapted to typical operating values ​​of approximately 1 mbar to 3 mbar, as are usually required in biogas plants. The emission control device 1 also includes a liquid refilling device 22, which has a liquid supply line 23 through which sealing fluid can be metered into the exhaust pipe 9. For this purpose, the liquid supply line 23 can open into the exhaust pipe 9 in the area above the overflow pipe 15, which projects into the exhaust pipe 9, relative to the vertical axis x. As indicated by the spray cone 24, the liquid supply line 23 is thus able to fill not only the liquid sealing chamber 12, but also the siphon section 20 with sealing fluid via the overflow pipe 15. The liquid supply line 23 is equipped with a controllable valve element 25, for example a solenoid valve, which is coupled to a control unit 26 via signal transmission. This control unit 26 is further coupled to the gas detector 13 and the gas pressure sensor 14 via signal transmission, so that the liquid refilling device 22, as will be explained in more detail below, can be actuated depending on an output signal from the gas detector 13 and the gas pressure sensor 14. Specifically, the liquid supply line 23 is routed from outside the exhaust pipe 9, through a wall of the exhaust pipe 9, preferably tightly, into the interior of the exhaust pipe 9. For the supply of liquid, for example water or a water-glycol mixture, the liquid supply line 23 is coupled to a liquid reservoir (not shown). In the example shown here, the exhaust pipe 9 itself is formed by an elongated, cylindrical tube, with the gas detector, as previously described, being arranged in an outlet opening area of ​​the exhaust pipe 9. The exhaust pipe 9 is designed in multiple sections and has a dividing plane 27 in the area above the point where the liquid supply line 23 enters the exhaust pipe 9, so that the upper part of the exhaust pipe 9 can be easily removed and the lower part of the exhaust pipe 9, including the liquid tray 8, overflow pipe 15, and liquid supply line 23, is readily accessible for assembly and maintenance purposes. As symbolized by the upward-pointing arrows 18 in Fig. 2, in the event of overpressure, biogas flows from the gas phase 6 of the interior of the container 5 through the barrier liquid contained in the liquid tray 8 into the liquid barrier chamber 12 of the exhaust pipe 9, thereby breaking through the liquid column 11, so that it subsequently escapes into the environment via the exhaust pipe 9. This gas escape is detected and registered by the gas detector 13 and signaled to the control unit 26. Since, in the event of overpressure, the gas pressure sensor 14 simultaneously detects overpressure in the gas phase of the interior of the container 5, the liquid refill device 22 is not activated by the control unit 26 and thus no liquid refill is triggered. If sealing fluid were added in the event of overpressure, the liquid column would rise again, which could hinder or even block the gas flow, leading to an undesirable hazard scenario, namely the undesirable pressure build-up inside the container. However, if no overpressure is detected by the gas pressure sensor 14 in the fermentation vessel 2 or in the gas phase 6 of the vessel interior 5, this means that the liquid barrier is defective or incomplete, for example, the liquid level is too low. In this case, barrier fluid must be added immediately to restore the seal and prevent uncontrolled gas leakage into the environment. The control unit 26 then automatically activates the valve element 25 and supplies a specific quantity of liquid via the liquid supply line 23 for a specific period of time. This can be controlled, for example, by quantity or time. Fig. 3a shows a schematic diagram of a cross-section of an exemplary embodiment of the overpressure and / or underpressure protection device 7 with the exhaust pipe 9, which here, by way of example, is immersed approximately coaxially in the liquid basin 8. The operating pressure in the fermentation vessel 2 is, for example, 4 mbar. Due to this pressure, a liquid column 11 of a certain height builds up in the exhaust pipe 9, which is open to the ambient atmosphere. The height of the liquid column 11 is measured from the lower, free end 10 of the exhaust pipe 9. The liquid volume of the liquid basin 8, based on normal operation, preferably corresponds substantially to the liquid volume of the liquid column 11 built up in the exhaust pipe 9. The reference to normal operation means the situation shown in Fig. 3a without overpressure or underpressure.The liquid volume of the liquid tray 8 used as the basis for the calculation here corresponds to the total liquid volume contained in the liquid tray 8, less the portion of the liquid volume enclosed by the immersed exhaust pipe 9, which is to be added to the volume of the liquid column 11. Accordingly, the volume of the liquid column 11 built up in the exhaust pipe 9 is obtained by multiplying the internal cross-sectional area of ​​the pipe by the corresponding column height, measured from the lower end 10 of the pipe. Figure 3b shows a schematic diagram, essentially corresponding to Figure 3a, of an overpressure situation within the fermentation vessel 2, where the pressure in the fermentation vessel 2 is increased compared to the normal operating pressure, for example, by 6 mbar. Due to the increased pressure, the liquid column 11 in the exhaust pipe 9 rises to a greater height than the normal height shown in Figure 3a (arrow 28). At the same time, the liquid level in the liquid tray 8 drops as a result of the volume shift, so that a lower fill level results in the liquid tray 8. As shown in Fig. 3b, the overpressure and / or underpressure safety device 7 is preferably configured or designed such that the liquid level in the liquid tray 8 is approximately flush with the lower free end 10 of the exhaust pipe when the height of the liquid column 11 reaches the height of the free upper pipe end 17 of the overflow pipe 15.If a certain maximum permissible internal pressure is exceeded, the gas contained in the fermentation vessel 2 escapes to the outside through the exhaust pipe 9. If the pressure in the gas phase rises above the hydrostatic pressure of the liquid column 11, the barrier liquid overflows through the overflow pipe 15. In this way, the liquid column 11 in the exhaust pipe 9 can be maintained within a defined range. This means that the height of the overflow pipe 15 relative to the liquid column 11 determines the maximum permissible overpressure. As soon as the internal pressure in the fermentation vessel 2 exceeds this value, controlled gas release occurs through the liquid column 11, and, if necessary, the barrier liquid overflows through the overflow pipe 15. Finally, Fig. 3c shows a schematic diagram of a negative pressure situation inside the fermentation vessel 2, where the pressure in the fermentation vessel 2 is below the ambient pressure, for example at -2 mbar. As a result of this negative pressure, the liquid column 11 in the exhaust pipe 9 sinks, resulting in a reduced height of the liquid column 11 compared to the height of the liquid column 11 in the normal operating condition shown in Fig. 3a, measured from the lower end of the pipe 10. At the same time, the liquid level in the liquid tray 8 rises, which is reflected in an increased fill level on the tray side (arrow 29). As shown in Fig. 3c, the overpressure and / or underpressure safety device 7 is preferably configured or designed such that, when the liquid level in the liquid tray 8 reaches the upper edge of the liquid tray 21, the height of the liquid column 11 is approximately flush with the lower free end 10 of the exhaust pipe. If the pressure in the fermentation vessel 2 falls below a certain threshold, ambient air can be drawn into the fermentation vessel 2 through the liquid column 11 via the exhaust pipe 9, thereby equalizing the pressure. Here, too, the liquid tray 8 provides the necessary liquid volume to compensate for the level difference within the system without emptying or overflowing. Reference symbol list 1 Device 2 Fermentation vessel 3 Toolbox 4 Platform 5 Vessel interior 6 Gas phase 7 Overpressure and / or underpressure safety device 8 Liquid tray 9 Exhaust pipe 10 Lower pipe end 11 Liquid column 12 Liquid barrier chamber 13 Gas detector 14 Gas pressure sensor 15 Overflow pipe 16 Bottom 17 Upper pipe end 18 Arrow 19 Lower pipe end 20 Siphon section 21 Perimeter wall 22 Liquid refill device 23 Liquid feed line 24 Spray cone 25 Valve element 26 Control unit 27 Separation plane 28 Arrow 29 Arrow

Claims

Device for emission control on a gas-carrying container, in particular on a digester of a biogas plant, comprising: - a gas-carrying container (2) which has a gas phase (6) in its interior (5), - an overpressure and / or underpressure safety device (7) with a liquid barrier chamber (12) which is fluidically connected to the interior (5) of the container, - a detection device which is designed and configured to detect and / or record a gas leak from the gas-carrying container (2) as well as the internal pressure in the gas phase (6) of the interior (5) of the container, - a liquid refilling device (22) which is designed and configured to refill barrier fluid directly or indirectly into the liquid barrier chamber (12), - a control unit (26) which is designed and configured toto automatically activate or not activate the liquid refilling device (22) depending on a detected and / or recorded gas leakage from the gas-carrying container (2) and a detected and / or recorded internal pressure in the gas phase (6) of the container interior (5). Device according to claim 1, characterized in that the control unit (26) is designed and configured to, in the event of a detected and / or recorded gas leakage, (i) in the case of no overpressure in the gas phase (6) of the container interior (5), to control the liquid refilling device (22) and to automatically trigger a liquid refill, and (ii) in the case of an existing overpressure in the gas phase (6) of the container interior (5), not to control the liquid refilling device (22) and thus not to trigger a liquid refill. Device according to claim 1 or 2, characterized in that the detection device has at least one gas detector (13) which is arranged in an exhaust air area of ​​the overpressure and / or underpressure safety device (7), wherein the at least one gas detector (15) is designed and configured to detect a gas leak. Device according to one of the preceding claims, characterized in that the detection device has at least one gas pressure sensor (14) which is designed and configured to detect the internal pressure in the gas phase (6) of the container interior (5) and / or is arranged in the gas phase (6) of the container interior (5). Device according to claims 3 and 4, characterized in that the control unit (26) is coupled to the at least one gas detector (13), to the at least one gas pressure sensor (14) and to the liquid refilling device (22), that the control unit (26) is designed and configured to automatically control the liquid refilling device (22) depending on the measured values ​​detected by means of the at least one gas detector (13) and the at least one gas pressure sensor (14), preferably in the event of a gas leak (i) detected by means of the at least one gas detector (13) in the case of a lack of overpressure in the gas phase (6) of the container interior (5), to control the liquid refilling device (22) and to automatically trigger a liquid refill,and (ii) in the event of an existing overpressure in the gas phase (6) of the container interior (5) not to activate the liquid refilling device (22) and thus not to trigger any liquid refilling. Device according to one of the preceding claims, characterized in that the overpressure and / or underpressure safety device (7) has a liquid tray arranged in the gas phase of the container interior (5) for receiving a barrier liquid, that the overpressure and / or underpressure safety device (7) has an upwardly open exhaust pipe (9) projecting from above into the liquid tray (8) with respect to the vertical axis direction, the lower pipe end (10) of which, with respect to the vertical axis direction, is located at a distance from the bottom (16) of the liquid tray, wherein the lower pipe end (10) lies below the liquid level of a barrier liquid received in the liquid tray (8) in the sealed state, and wherein the liquid tray (8) and the exhaust pipe (9) are designed and configured to form a liquid column (11) in a liquid barrier space (12) in the exhaust pipe (9).forming a gas-tight barrier against the environment, wherein the at least one gas detector (13) is arranged in an exhaust air area of ​​the exhaust pipe (9), and wherein the at least one gas detector (13) is designed and configured to detect a gas escape via the exhaust pipe (9). Device according to claim 6, characterized in that an overflow pipe (15) is provided which penetrates the bottom (16) of the liquid basin and whose upper pipe end (17), with respect to the vertical axis direction, projects into the liquid containment space (12) of the exhaust pipe (9), wherein the overflow pipe (15) is designed and configured to allow the containment liquid to drain via the overflow pipe (15) and gas to escape via the exhaust pipe (9) when the pressure in the gas phase (6) rises above the hydrostatic pressure of the liquid column (11). Device according to claim 7, characterized in that a lower pipe end (19) of the overflow pipe, with respect to the vertical axis direction, is fluidically connected to the gas phase (6) of the container interior (5) via a siphon section (20), wherein the siphon section (20) of the overflow pipe (15) is designed and configured to prevent gas from escaping from the gas phase (6) of the container interior (5) via the overflow pipe (15) in a state filled with sealing liquid. Device according to claim 7 or 8, characterized in that the liquid containment chamber (12) and the overflow pipe (15) are designed and configured to form a liquid column (11) with a defined height, preferably with a height of 3 cm to 11 cm, in the liquid containment chamber (12). Device according to claim 9, characterized in that the overflow pipe (15) projects substantially in a straight line along a vertical axis and with respect to the vertical axis direction from the bottom (16) of the liquid trough (8) into the liquid containment chamber (12). Device according to one of claims 6 to 10, characterized in that the liquid tray (8) surrounds the exhaust pipe (9) circumferentially with an edge overhang and has a peripheral circumferential wall (21) which is raised in the vertical axis direction with respect to the bottom (16) of the liquid tray (8). Device according to claim 11, characterized in that the circumferential wall (21) has a height of at least 1 cm, preferably of 1 cm to 5 cm, in the vertical axis direction with respect to the bottom (16) of the liquid tray (8). Device according to one of claims 6 to 12, characterized in that the liquid volume of the liquid tray (8), preferably with reference to normal operation without overpressure or underpressure situation, corresponds essentially to the liquid volume of a liquid column built up in the exhaust pipe (9). Device according to one of the preceding claims, characterized in that the liquid refilling device (22) has at least one liquid supply line (23) which is designed and configured to introduce sealing liquid into the exhaust pipe (9). Device according to one of claims 7 to 13 and according to claim 14, characterized in that the liquid supply line (23), with respect to the vertical axis direction, opens into the exhaust pipe (9) in the area above the overflow pipe (15) projecting into the exhaust pipe (9), wherein the liquid supply line (23) is designed and configured to fill both the liquid sealing chamber (12) and the siphon section (20) of the overflow pipe (15) with sealing liquid. Device according to one of the preceding claims, characterized in that the liquid refilling device (22), preferably the liquid supply line (23), has a controllable valve element (25), preferably a solenoid valve, which is coupled to the control unit (26) and can be actuated by the control unit (26) depending on an output signal of the at least one gas detector (13) and / or the at least one gas pressure sensor (14), preferably in such a way that the control unit (26) opens the controllable valve element (25) when no overpressure is detected in the gas phase (6) of the container interior (5) upon detection of gas leakage. Device according to one of claims 14 to 16, characterized in that the liquid supply line (23) is led from outside the exhaust pipe (9) through a wall of the exhaust pipe (9), preferably tightly, into the interior of the exhaust pipe (9), wherein the liquid supply line (23) is coupled to a liquid reservoir, preferably arranged outside the gas-carrying container (2). Device according to one of claims 14 to 17, characterized in that the exhaust pipe (9) is formed in multiple parts and has a separating plane (27) in the area above the supply of the liquid supply line (23) into the exhaust pipe. Device according to one of the preceding claims, characterized in that the exhaust pipe (9) is formed by an elongated and / or cylindrical tube, and / or that the at least one gas detector (13) is arranged in a region of the exhaust pipe (9) located above the barrier fluid with respect to the vertical axis direction, preferably in an outlet opening region of the exhaust pipe (9). Biogas plant with at least one digester as a gas-carrying container (2), wherein the at least one digester has a device (1) according to one of the preceding claims. Method for emission control in a gas-carrying container, in particular with a device according to any one of claims 1 to 19, wherein the gas-carrying container (2) has a gas phase (6) in its interior (5), and wherein the gas-carrying container (2) is equipped with an overpressure and / or underpressure safety device (7) which has a liquid barrier chamber (12) fluidically connected to the interior of the container (2), wherein the method comprises the following steps: - Detecting and / or recording a gas leak from the overpressure and / or underpressure safety device (7), preferably by means of at least one gas detector (13) arranged in an exhaust air area of ​​the overpressure and / or underpressure safety device (7), - Determining and / or recording the internal pressure in the gas phase (6) of the interior (5) of the container, preferably by means of at least one gas pressure sensor (14),- Evaluating the determined and / or recorded measured values ​​in a control unit (26), preferably a control unit (26) that is coupled to the at least one gas detector (13) and the at least one gas pressure sensor (14), and - Automatically controlling a liquid refilling device (22) by means of the control unit (26) depending on a determined and / or recorded gas escape from the gas-carrying container (2) as well as a determined and / or recorded internal pressure in the gas phase (6) of the container interior (5) for the direct or indirect refilling of sealing liquid into the liquid sealing chamber (12). Method according to claim 21, characterized in that the control unit (26) performs one of the following measures depending on the evaluated measured values: (i) automatic activation of the liquid refilling device (22) to refill the sealing liquid (12) into the liquid sealing chamber in the event of a detected gas leak and simultaneous absence of overpressure in the gas phase (6) of the container interior (5), or (ii) refraining from activating the liquid refilling device (22) in the event of a detected gas leak and simultaneous presence of overpressure in the gas phase (6) of the container interior (5).

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