Integrated gasification and stirring unit for gas-liquid reactors

Abstract

The invention relates to a gas introduction unit for introducing a process gas into a liquid located in a reactor without producing bubbles. The gas introduction unit comprises at least: - a first gas receiving chamber and a second gas receiving chamber at a certain distance from the first for receiving a process gas, both gas receiving chambers being connected to each other by at least two flat, gas-conducting diffusion membranes made of hollow fibers spaced apart and at least partially fixed to each other; - a receiving area for gas feeding in at least one of the gas receiving chambers; and - a receiving area for a shaft in at least one of the gas receiving chambers.Where the gas introduction unit can receive process gas through the gas feed receiving area to introduce gas into the reactor liquid, the gas introduction unit can rotate through the receiving area for the shaft, and a convection flow can be formed within the reactor by the rotational movement of the gas introduction unit in the liquid. The invention further relates to a method for introducing gas into a process liquid, to a gas-liquid reactor having a gas introduction unit according to the invention, and to the use of a gas introduction unit according to the invention to supply process gases to biological cultures.

Description

[0001] The present invention relates to a gassing unit for the bubble-free introduction of a process gas into a liquid located in a reactor, wherein the gassing unit comprises at least: a first and, spaced apart from it, a second gas intake chamber for receiving a process gas, wherein both gas intake chambers are connected to each other via at least two planar, gas-carrying diffusion membranes made of spaced-apart and at least partially fixed hollow fibers; a receptacle for a gas supply on at least one of the gas intake chambers; a receptacle for a shaft on at least one of the gas intake chambers; wherein the gassing unit for gassing the liquid in the reactor can be supplied with process gas via the gas supply inlet, set into a rotational movement via the shaft receptacle, and a convection flow within the reactor can be generated by the rotational movement of the gassing unit in the liquid. Furthermore, the present invention relates to a method for gassing a process liquid, comprising a gas-liquid reactor, a gassing unit according to the invention, and the use of a gassing unit according to the invention for supplying biological cultures with process gases.

[0002] The reliable production of essential raw materials using more sustainable methods is increasingly the focus of public interest. This approach encompasses not only the production method itself, but also the properties of the substances after their intended service life. This is particularly evident in the growing development of alternative and biological production methods for many classes of chemicals synthesized from petroleum in recent decades. These methods aim to provide not only more resource- and energy-efficient manufacturing processes, but also improved chemical and biological properties, such as faster biodegradability.

[0003] This approach is currently being pursued for surfactant biomolecules, as these substances can have a lasting impact on the environment, and their added value, for example in cosmetic or pharmaceutical products, allows for compensation of the currently higher production costs. A more environmentally friendly production alternative is based on fermentation processes in biological systems using renewable raw materials as nutrient media and with oxygen input. However, a disadvantage is that the biosynthesis of proteins and surfactants typically results in significant foaming in the fermenters, which is detrimental to efficiency and the entire process. The preferred method for aerating these systems to date has been bubble aeration followed by the disruption of the bubbles using a stirrer, or the use of antifoaming agents. This should ensure a fermentation process with as few bubbles as possible and without loss of biomass.However, bubble aeration, including foam crushing, is disadvantageous because additional control parameters complicate process management, and the mechanical foam destruction increases energy consumption and overall process costs. Antifoaming agents do not represent a sustainable alternative, as the additional purification required in downstream processes significantly impacts process costs. Therefore, current fermentation methods and the equipment used for them require improvement to ensure a simple and reproducible fermentation process without foam formation.

[0004] Several approaches to bubble-free aeration of fermentation liquids can also be found in patent literature.

[0005] For example, DE 10 2006 008 687 A1 describes a method for gassing liquids, particularly in biotechnology and especially cell cultures, with gas exchange via one or more immersed membrane surfaces such as hoses, cylinders or modules, characterized in that this membrane surface performs any rotationally oscillating movement in the liquid.

[0006] Furthermore, DE 44 046 00 C1 discloses a method for bubble-free gassing of microorganisms immobilized in a reactor on a support material, wherein the support material with the microorganisms is exposed to an aqueous solution which has been enriched with oxygen in front of the support material via membranes which are exposed on one side to an oxygen-containing gas.

[0007] In another patent document, DE 41 42 502 A1, a method for the bubble-free introduction of hydrogen into aqueous liquids is disclosed, wherein the hydrogen is introduced into the aqueous liquid via a membrane. The method is characterized by the use of a membrane comprising a) a support structure formed from a porous polymer, and b) at least one layer of non-porous polymer, wherein the aqueous liquid is in contact with the membrane on the side of the non-porous polymer layer.

[0008] Furthermore, DE 10 2005 053 334 A1 discloses a device for gassing liquid media by means of hose gassing, special hose modules contained therein, and the use of the device for gassing liquid media. Further possibilities for gassing process liquids are also disclosed in DE 10 2006 008 687 A1 and DE 10 2005 053 333 A1.

[0009] Such solutions known from the state of the art can offer further potential for improvement, particularly with regard to the efficiency in supplying process liquids with process gases and especially with regard to reliably preventing foam formation, even for systems with difficult product properties.

[0010] It is therefore the object of the present invention to overcome, at least in part, the disadvantages known from the prior art. In particular, it is the object of the present invention to provide a gassing unit and a gas-liquid reactor with this unit, which is characterized by a particularly efficient and uniform gas supply to process liquids, with a significant reduction in foam formation during injection.

[0011] The problem is solved by the features of the respective independent claims, which relate to the gassing unit, the gas-liquid reactor, the method, and the use according to the invention. Preferred embodiments of the invention are described in the dependent claims, the description, or the figures, wherein further features described or shown in the dependent claims, the description, or the figures, individually or in any combination, may constitute an object of the invention, unless the context clearly indicates otherwise.

[0012] According to the invention, the problem is solved by a gassing unit for the bubble-free introduction of a process gas into a liquid located in a reactor, wherein the gassing unit comprises at least: a first and, spaced apart from it, a second gas intake chamber for receiving a process gas, wherein both gas intake chambers are connected to each other via at least two planar, gas-carrying diffusion membranes made of spaced-apart and at least partially fixed hollow fibers; a receptacle for a gas supply on at least one of the gas intake chambers; a receptacle for a shaft on at least one of the gas intake chambers; wherein the gassing unit for gassing the liquid in the reactor can be supplied with process gas via the gas supply inlet, can be set into a rotational movement via the inlet for the shaft and a convection flow can be formed within the reactor via the rotational movement of the gassing unit in the liquid.

[0013] Surprisingly, the above-described design has proven to be an extremely efficient and robust aerator-gas combination, suitable for a wide range of aeration applications in various (bio)reactors. The introduction of process gases into a process liquid is highly homogeneous and gentle. The combination of simultaneous aeration and stirring surfaces allows for the uniform introduction of particularly large quantities of process gas into the liquid via the exchange surface. This is primarily due to the use of hollow fiber membrane exchange surfaces, which are continuously and actively cleaned of diffusing process gas by the constant movement within the liquid.Thus, the inventive design, with its hollow fiber membranes, allows for larger exchange surfaces than previously known and utilizes them even more efficiently than in prior art solutions. This is because the simultaneous shearing of the gases at the membrane surface completely prevents diffusion blockage by adhering gas bubbles. Furthermore, the design, with its central feed of the process gas and its uniform distribution across a gas receiving chamber, is so robust that high velocities and thus strong convection currents can be generated via the firmly anchored hollow fibers. The combination of gassing and stirring also ensures that the hollow fibers are not only indirectly exposed to, but actively flushed with, the process fluid.No stagnant dead spaces are created within the module itself, which contributes to the efficiency of the gas feed and the uniformity of the liquid aeration. Furthermore, the shearing action keeps the bubble size small. This allows even challenging fermentation tasks with live cultures to be mastered, for example, in the production of foam-promoting substances, since the uniformity of the gas feed, the sheer volume of gas, and the control of the bubble size through simultaneous shearing largely prevent bubble and / or foam formation in the liquid medium. The aeration unit can also be constructed from any number of serially connected units, which simplifies the cleaning and sterilization of individual modules and facilitates scaling up to larger reactor volumes.

[0014] The aeration unit according to the invention is suitable for the bubble-free introduction of a process gas into a liquid contained in a reactor. Process liquids in reactors can be simultaneously stirred and treated with a process gas by the aeration unit according to the invention. This means that a process gas is introduced into the process liquid continuously or discontinuously at time intervals via the aeration unit. By introducing the process gas, the concentration of the process gas in the liquid in the reactor is increased, at least temporarily, at the injection point. Possible process gases include, for example, oxygen, nitrogen, carbon dioxide, carbon monoxide, hydrogen, or similar gases or mixtures thereof. Typically, the process gases act as reactants for carrying out further chemical reactions in the process liquid.The design according to the invention enables the bubble-free injection of process gases into process liquids. "Bubble-free" within the meaning of the invention refers in particular to the fact that the bubble size of the process gas is within a range where the bubbles on the surface of the membranes are not visible to the naked eye or are only visible with great difficulty. The bubble size can, for example, be on the order of a few micrometers. The design according to the invention particularly prevents the formation or deposition of foam on the surface of the process liquid during the process. The liquids in the reactor can be, for example, aqueous solutions, dispersions, or emulsions. However, the injection is not limited to aqueous systems. Non-aqueous, liquid systems can also be gassed without bubbles.

[0015] The gassing unit comprises at least one primary and, spaced apart from it, a secondary gas intake chamber for receiving a process gas. A process gas can be fed into one of the two gas intake chambers via a gas supply line and distribute itself evenly within it. The gas intake chamber forms a reservoir for the process gas and, unlike direct injection into the membranes, can also compensate for potential pressure fluctuations. From this gas intake chamber, the process gas is then guided through the hollow fiber membranes into the secondary gas intake chamber. The distance between the two intake chambers can be selected as a function of the reactor dimensions, the length and mechanical stability of the hollow fibers, the desired gas input, and the desired flow mechanics. The gas intake chambers themselves can be made of, for example, metal or plastic and exhibit rotationally symmetrical symmetry.The two gas collection chambers also feature receptacles for the hollow fiber membranes, allowing for independent fixation of each individual membrane. These receptacles can, for example, consist of grooves in the surface of the gas collection chamber, in which the membranes can be mechanically clamped or glued, thus creating a gas-tight seal.

[0016] The two gas collection chambers are connected by at least two planar, gas-conducting diffusion membranes made of spaced-apart hollow fibers that are at least partially fixed to one another. The introduction of process gases into the liquid therefore does not occur via the gas collection chambers themselves, but rather via hollow fiber membranes that are gas-conducting and connected to the two gas collection chambers. The hollow fibers are not isolated, i.e., used individually. Several hollow fibers are arranged side by side or one behind the other, so that the arrangement of the hollow fibers forms a planar membrane. To further stabilize the membrane, the individual hollow fibers can also be fastened to one another by additional mechanical means. For example, the individual hollow fibers can be stabilized in a woven structure with non-gas-conducting threads or fibers running perpendicular or nearly perpendicular to the hollow fibers.For example, preferably one, more preferably two, and more preferably three fixations in the form of an inert polymer thread can be inserted per cm² of hollow fiber membrane, the thread being passed alternately over and under the hollow fibers and fixing the hollow fibers to each other. Suitable diffusion or microfiltration membranes are those in which the gas first diffuses into the membrane and, after passing through the hollow fiber shell, into the process fluid. The membranes can be dense or porous, with the porosity of the membrane being within a range such that, with sufficient flow, concentration polarization on the outside of the membrane—and the associated outgassing of the introduced gas in the form of bubbles—is prevented. Possible pore sizes of non-dense membranes can range from 20 nm to 20 µm. Dense diffusion membranes can have a multilayer structure.Additional layers can prevent the penetration of the process fluid or, if necessary, the back-diffusion of unwanted gases into the membrane. Furthermore, the layered composite structure allows for an extremely thin film of dense material, representing the active layer (e.g., PMP, TMCTS, or PDMS / silicone), to be supported on a mechanically rigid layer, such as porous PMP. This thin, dense layer is crucial for the permeability of the gases used. A thinner layer ensures a high mass transfer rate. The ratio of mass transfer through the membrane to its thickness is inversely proportional for dense membranes. However, a thin active layer is usually mechanically unstable and requires a support. A highly porous support offers negligible resistance to gas transfer into the process fluid.Suitable hollow fibers can, for example, consist of PMP (polymethylpentene) and have an inner diameter of 0.2 mm and an outer diameter of 0.38 mm. Alternatively, PDMS (polydimethylsiloxane) / silicone membranes with an inner diameter of approximately 0.3 mm and an outer diameter of approximately 0.5 mm can be used. Preferably, to form a planar membrane arrangement, more than 50, more preferably more than 100, and more preferably more than 500 hollow fibers are arranged side by side or one behind the other. A planar arrangement is achieved when preferably more than 40%, more preferably more than 50%, and more preferably more than 60% of the area between two spaced-apart, but not directly adjacent, hollow fibers is covered with further hollow fibers.Such a planar arrangement can be achieved, for example, by fixing hollow fibers with the aforementioned dimensions in the gas-collecting chamber at a distance of greater than or equal to 0.05 mm and less than or equal to 2.5 mm, and preferably also at a distance of greater than or equal to 0.1 mm and less than or equal to 1 mm. The gas flows through the gas-collecting chamber into the hollow fibers, which are joined together to form membranes, and exits into the liquid phase on the outside of the fiber, depending on the driving force.

[0017] The gassing unit has at least two diffusion membranes. This means that, starting from the gas intake chamber, not only does a membrane made of several hollow fibers with a continuous gas path extend into the process liquid to the second gas intake chamber, but at least two spaced-apart membranes made of several hollow fibers are arranged at the first gas intake chamber, which can supply the process liquid with gas via a separate gas path. Preferably, more than 10, more preferably more than 50, and even more preferably more than 100 individual membrane surfaces made of arranged hollow fibers can be present, extending from the first gas intake chamber into the process liquid.

[0018] The connection of the individual hollow fibers to the gas collection chamber can be achieved by mechanically clamping the hollow fibers in specially designed devices on the gas collection chamber, or by bonding the membranes to the gas collection chamber itself. Preferably, the individual hollow fiber membranes can be bonded to the gas collection chamber.

[0019] One of the gas intake chambers has a connection for a gas supply. The gas intake chamber can be supplied with process gas from the outside via a supply line running through the reactor. For this purpose, an external gas source can be routed into the reactor interior to the gas intake chamber via a hose or capillary system. There, the hose or capillary can be connected to a designated connection on the gas intake chamber. This connection can be made gas-tight, for example, using a fitting. Preferably, metric flangeless flat-bottom connectors with a flangeless ferrule are used as fittings. The fittings can be made of metal or plastic, such as PEEK. The connection can be arranged centrally or asymmetrically on the gas intake chamber, advantageously being located on the side opposite the hollow fiber membranes on the gas intake chamber.Depending on the operating mode of the gassing unit, either one or both gas intake chambers can be equipped with gas supply connections. In particular, the gassing unit can be operated in two modes. Firstly, gassing can occur in a "cross-flow" mode, or alternatively in a "dead-end" mode. In the "dead-end" mode, gas is only fed into one gas intake chamber of the gassing unit. In this mode, no connection is required for the discharge of the unintroduced process gas, for example, at the other gas intake chamber.

[0020] One of the gas intake chambers has a shaft mount. To supply the necessary mechanical energy for moving the gassing unit, one of the gas intake chambers has a shaft mount. The shaft can be guided through the reactor and connected to a drive or gearbox that sets the shaft into rotation. The rotating shaft also sets the gassing unit in rotation, allowing it to move the process fluid across the flat hollow fiber membranes. The movement of the shaft, and thus of the gassing unit, can be in one direction only, or preferably in two directions. This allows for constant or alternating rotation of the gassing unit at different speeds.

[0021] The gassing unit can be supplied with process gas via the gas supply inlet to aerate the liquid in the reactor. The shaft mount allows the gassing unit to rotate, and this rotation creates a convection current within the liquid in the reactor. Both mechanical energy and process gas can be transferred to the gassing unit via the gas supply and shaft mounts. Process gas is released into the process liquid through the hollow fiber membranes, and the rotation of the gassing unit—specifically, the flat hollow fiber membranes—generates a directed flow within the liquid in the reactor.

[0022] In a preferred embodiment of the gassing unit, the projections of the diffusion membranes onto the receiving chambers can have a circular arc geometry. To create a uniform flow profile within the reactor fluid and to ensure uniform flow over the individual hollow fibers within the gassing unit, it has proven particularly suitable to arrange the individual hollow fibers not in a straight line, but rather spaced apart from one another both longitudinally and transversely on the gas receiving chamber. Thus, within the context of the planar design of the membranes, a curved, rather than a straight, surface of arranged hollow fibers is formed. Besides improving and homogenizing the flow profile, this design can also contribute, in particular, to improving the gas input into the liquid by uniformly shearing the gas bubbles from the hollow fiber membrane surface.In particular, the formation of larger gas bubbles on the membrane surface can be delayed or completely prevented. One possible embodiment of the circular arc geometry is shown in the figures. Preferably, the circular arc can have a curvature greater than or equal to 1 m and less than or equal to 100 m, and more preferably greater than or equal to 5 m and less than or equal to 70 m.

[0023] In a further preferred embodiment of the gassing unit, the gas supply inlet and the shaft connection can be arranged on a single gas intake chamber. To homogenize the flow profile in the reactor, it has proven particularly advantageous to arrange the gas intake and the drive shaft connection centrally on a single gas intake chamber. Furthermore, and preferably, both the gas intake and the shaft connection can be combined, for example, in the form of a hollow shaft, so that both connections are located within a single port on the gassing unit. This can help reduce the number of mechanical components on the gassing unit. Moreover, this combined port can preferably be located centrally on the gassing unit.Preferably, the gassing unit can be supplied with process gas and the necessary kinetic energy simultaneously via a single combined inlet on one of the gas intake chambers. This can keep the flow profile of the gassing unit particularly homogeneous and reduce the complexity of the equipment connections. The latter can also contribute to improved cleaning and sterilization of the gassing unit.

[0024] In a further preferred aspect of the gassing unit, the two gas intake chambers can each be cylindrical and connected to each other by one or more mechanical supports. A rotationally symmetrical, cylindrical geometry has proven particularly advantageous for generating the most efficient convection flow possible within most reactor geometries. This design of the gas intake chambers allows for the reproducible induction of very uniform and strong flows both within the gassing unit and in the reactor itself, contributing to a particularly good supply of process gases to the process fluid. In addition to fixing the relative position of the two gas intake chambers to each other via the hollow fiber membranes, it has also proven advantageous to fix the two gas intake chambers in their relative position to each other by means of one or more mechanical supports.This measure can reduce the smooth running and unwanted vibrations of the gassing unit at high speeds. Preferably, the support can be guided through the center of the two cylindrically shaped gas intake chambers. Such an embodiment can improve the flow profile within the gassing unit, and in particular between the individual hollow fiber membranes.

[0025] According to a preferred characteristic of the gassing unit, at least one retaining disk can be arranged between the two gas intake chambers on the mechanical support, which is designed to mechanically hold the diffusion membranes. For the formation of a mirror-symmetrical convection flow within a large number of different reactor geometries, it has proven particularly advantageous to arrange a retaining disk between the two gas intake chambers on the support, which mechanically contacts the hollow fiber membranes. The hollow fiber membranes can either be "loosely" fixed by the retaining disk or also be stretched or twisted out of their symmetrical position by the retaining disk.In the first case, the hollow fiber membranes can withstand greater mechanical forces, for example, through higher rotational speeds of the gassing unit, without the risk of damaging the membranes. More fragile hollow fibers can also be used. In addition to the mechanical function of holding the membranes, the achievable flow geometry can also be influenced by the retaining disc. The individual hollow fiber membranes can be selectively deflected or rotated from the geometry defined by their connection to the gas intake chambers. This deflection alters the planar geometry of the membranes and can create specific convection patterns in the liquid. In this way, the membranes can be adapted to specific gassing tasks and reactor geometries.

[0026] In a preferred embodiment of the gassing unit, the mechanical support can be configured to transport process gas from the gas receiving chambers. To achieve the most compact design possible for the gassing unit while improving the unit's supply during cross-flow operation, it has proven particularly suitable for the mechanical supports to be designed as hollow shafts, which can also direct process gas to and from the gas receiving chambers.

[0027] In a further preferred embodiment of the gassing unit, the ratio of the total hollow fiber cross-sectional area to the cross-sectional area of ​​the gas receiving chamber can be greater than or equal to 5% and less than or equal to 45%. The proposed design allows for the provision of compact gassing units which, compared to the solutions described in the prior art, exhibit a significantly larger process gas exchange area. These large exchange areas show only a low tendency to form bubbles and also result in more favorable flow characteristics of the gassing unit. The total hollow fiber cross-sectional area is calculated by multiplying the cross-sectional area of ​​a single hollow fiber by the number of fibers arranged in the gas receiving chamber. The cross-sectional area of ​​the gas receiving chamber is determined by the area of ​​the gas receiving chamber supplied with process gas.In the event that the gas receiving chamber has a central or outer surface to which hollow fiber membranes cannot be attached due to a lack of process gas supply, this surface does not contribute to the aforementioned ratio, even though the gas receiving chamber encompasses this surface. In a preferred embodiment, the surface area ratio can be greater than or equal to 7.5% and less than or equal to 20%, and more preferably greater than or equal to 10% and less than or equal to 15%. Within these ratios of gas exchange surface to gas receiving chamber, large quantities of process gas can be introduced under homogeneous flow conditions.

[0028] In a further preferred embodiment of the gassing unit, the packing density of the diffusion membranes, expressed as the surface area of ​​the hollow fibers divided by the volume of the gassing unit, can be greater than or equal to 0.1 cm² and less than or equal to 7.5 cm². The total surface area of ​​the hollow fibers can be calculated from the number of hollow fibers and the surface area freely accessible to process fluids. The total volume of the gassing unit, in the case of cylindrical or non-cylindrical geometries, is determined by the volume of the gassing unit accessible to process fluids between the gas intake chambers. The design according to the invention allows for very large active gassing areas to be accommodated in a small space, which, in addition to a high process gas flow rate in combination with simultaneous stirring, can also contribute to the efficient supply of very large reactor volumes.Preferably, the ratio can also be greater than or equal to 0.25 cm -1< and less than or equal to 6 cm -1<, and further preferably greater than or equal to 0.5 cm -1< and less than or equal to 3 cm -1<.

[0029] Furthermore, according to the invention, a method for gassing a process liquid within a reactor is described, wherein the gas is introduced via a gassing unit according to the invention. The process step of gassing a process liquid via a gassing unit according to the invention can have several advantages. In this process step, large quantities of process gas can be provided homogeneously within the liquid volume, whereby the combination of stirring and gassing allows for introduction with no or only very small bubble sizes. Due to direct contact with the fluid boundary and the immediate shearing of the bubbles from the membrane surfaces, diffusion inhibition caused by concentration polarization at the surface of the hollow fibers is avoided, and, in contrast to stationary arrangements, a larger liquid volume in the reactor is supplied by the uniform movement of all fibers.In particular, dead zones in the reactor and within the gassing unit can be avoided by the controlled formation of convection within this process step.

[0030] In a preferred embodiment of the method, the rotational speed of the membrane surface at the outermost edge of the aeration unit can be greater than or equal to 0.1 m / s and less than or equal to 5 m / s. Using the inventive design, even inherently mechanically unstable diffusion membranes can be operated in the liquid at high shear rates. Without being bound by theory, this is achieved by the fact that the spaced hollow membrane surfaces are either flowed through or over, thus absorbing only a portion of the liquid's momentum. This advantageously results in the removal of the diffused process gas and a reduction in mechanical stress. The speed of the aeration unit can be adjusted via the dimensions of the gas-receiving chambers and the rotational speed of the aeration unit itself.The maximum rotational speed for the hollow fibers is determined by reference to the hollow fiber located furthest from the center of the gassing unit. Hollow fibers located further inward within the gassing unit consequently exhibit a lower rotational speed. Preferably, the rotational speed of the membrane area at the outermost edge of the gassing unit can be greater than or equal to 0.25 m / s and less than or equal to 4 m / s, and more preferably greater than or equal to 0.5 m / s and less than or equal to 3 m / s.

[0031] Furthermore, according to the invention, a gas-liquid reactor comprises at least an outer reactor shell, a drive unit, a gas supply, and a gassing unit according to the invention. The reactor according to the invention is a gas-liquid reactor for bubble-free gassing of a process liquid with a process gas. A gas-liquid reactor according to the invention is bounded by an outer shell, which can be made, for example, of steel or glass, and which forms an interior space that can be filled with a process liquid to varying fill levels. In particular, its use in single-use reactors made of plastics such as PP, PC, PET, LDPE, EVA, PVDC, and composite systems made of these plastics is also advantageous. In addition to the liquid itself, the process liquid can also contain other components such as reactants, suspended cells or organisms, salts, pH regulators, or other substances.The process fluid can be in the form of an aqueous solution, dispersion, or emulsion, for example. The aeration unit can be connected to a gas supply line via a gas inlet. The process gas can be stored in a separate reservoir, such as a gas cylinder, and released in a controlled manner via regulating valves. A control unit allows adjustment of the gas flow and composition to the aeration unit. For example, a gas valve can be used to set a transmembrane pressure between the inside of the aeration unit's membranes and the process fluid, such as fermenter broth, on the outside of the membrane. The gas input into the broth typically scales proportionally with the transmembrane pressure. If the membrane is continuously supplied with gas on the inside, the operating mode is "cross-flow."Temporary flushing of the membrane lumen is also possible; for this, a gas valve is opened intermittently in a dead-end operation. This is particularly useful when gases from the process, such as CO₂ in classic aerobic fermentations, enter the membrane along the concentration gradient and concentrate there. This concentration can reduce the overall gas input rate because the partial pressure of the gas being introduced decreases, thus reducing the driving force. Furthermore, condensation water that has entered the membrane through the pores can also be quickly / pulsed out in this way. A particularly noteworthy advantage of dead-end aeration is that stoichiometrically, only those gas molecules are introduced and thus used that are actually metabolized in the process. This is relevant with regard to the economic efficiency of a (bio)process.In addition to these minimum components, the reactor can of course also have further internal components. For example, it is possible that additional components such as sensors, supply and discharge lines, heating and / or cooling devices are located inside the reactor. The heating or cooling devices can also be located outside the reactor.

[0032] In a preferred embodiment of the gas-liquid reactor, the reactor may not have any further stirring unit besides the aeration unit. To achieve a particularly efficient flow profile with homogeneous mixing, including of the process liquid located inside the aeration unit, it has proven advantageous for the reactor to lack any other actively moving devices for generating a directed flow in the process liquid. In these cases, the hollow fibers can be targeted by the process liquid flow, and a large proportion of the process gases diffusing out of them can be sheared off. Additional active stirring units could disrupt the symmetry of the achievable convection and lead to varying gas input rates per unit volume of process liquid.

[0033] In a further preferred embodiment of the gas-liquid reactor, at least one flow breaker can be arranged between the reactor shell and a gas receiving chamber. Besides ensuring a highly symmetrical convection flow, it can be advantageous to redirect the convection induced by the gassing and stirring unit according to the invention by means of flow breakers in specific areas of the reactor. This can contribute to better adaptability to specific reactor geometries. The flow breakers can be arranged both between the gassing unit and the reactor walls, as well as between the gassing unit and the reactor bottom and lid. Particularly preferably, at least one flow breaker can be arranged between the gassing unit and the reactor lid. This flow breaker can also be disc-shaped.This flow breaker can be particularly helpful in preventing uncontrolled gas intake from the reactor's headspace, especially with large exchange surfaces and high circulation speeds of the aeration unit. In particular, it effectively prevents the formation of a cone of process fluid towards the aeration unit. Preferably, a disc-shaped flow breaker can be installed at a height greater than or equal to ¼ and less than or equal to ¾ of the distance from the top edge of the aeration unit to the fluid level.

[0034] A further aspect of the invention is the use of a gas-liquid reactor according to the invention for supplying process gases to biological cultures suspended in a process solution or adhering to the reactor interior or the aeration unit. Biological cultures, for example in the form of bacteria or fungi, can in principle be propagated in bioreactors in two different ways. Firstly, the organisms can be present in solution, for example in the form of a suspension, or they can be adhering to surfaces. Cultivation as a biofilm can, in principle, take place on the walls of the reactor or on the aeration unit according to the invention. The latter is preferred according to the invention because a more uniform supply of nutrients can be ensured under the dynamic aeration and stirring conditions. In this respect, higher yields and faster conversions can be achieved.The reactor design according to the invention has proven particularly suitable for the propagation of microorganisms in an aqueous fermentation medium. The reactor design allows for the targeted and reproducible introduction of adjustable gas quantities into the reaction medium, with the mixing of the entire reactor volume being only minimally impeded by the aeration unit. This eliminates dead zones with reduced mixing, and the required process gas, such as oxygen, can be distributed evenly and rapidly throughout the entire volume of the process liquid. Microorganisms are living organisms that can be propagated within the reactor. Further advantages of the process according to the invention are explicitly detailed in the advantages of the aeration unit.

[0035] A further aspect of the invention is the use of the gas-liquid reactor for supplying bacteria in a nutrient medium with oxygen. The reactor according to the invention can be used, in particular, to supply bacteria within a nutrient medium with oxygen. Bacteria, in particular, exhibit varying process gas requirements as a function of their growth phase in nutrient media. The homogeneous dispersion and uniform distribution of the introduced oxygen is especially difficult in these cases, as the aeration system must have sufficient reserves to introduce both small and large quantities of oxygen into the nutrient medium in a controlled manner. In these cases, for example, the transmembrane pressure must be highly flexible so that small quantities can be introduced reproducibly and large quantities can be introduced without bubble formation. An example of a bacterium that can be used is... Pseudomonas putida ( P. putida), a Gram-negative rod-shaped bacterium that occurs in water, soil, and on plants. In Germany, the laboratory strain is P. putida KT2440 is classified as an S1 organism and has GRAS status. It is used in industrial biotechnology. P. putida KT2440 is an extremely interesting organism because, in addition to a versatile metabolism, it also possesses a pronounced tolerance to organic solvents. Furthermore, it P. putida a popular organism for the heterologous expression of genes and possesses a high growth rate on glucose.

[0036] Within a further preferred aspect of the application, the biological cultures can be configured to produce foaming substances. Foaming substances, and among them especially biosurfactants, are particularly difficult to ferment in conventional reactors because these surfactants naturally contribute to particularly strong foam formation. Rhamnolipids, which are surface-active molecules produced by biocatalysts, can serve as an example of a biosurfactant. These biosurfactants have the ecological advantage that, unlike petroleum-based surfactants, they can be rapidly metabolized biologically and are therefore more environmentally friendly. They can be produced particularly advantageously in the reactor according to the invention with the gassing unit according to the invention. Other biosurfactants also exist that are produced by various microorganisms.These include sophorolipids, which are produced by yeast. Sophorolipids belong to the glycolipids. Furthermore, there are biosurfactants that belong to the class of lipopeptides, such as surfactin, which is produced by [unclear]. Bacillus subtilis Surfactin is produced. It is primarily used in the medical field. These can be produced with very low foam or foam-free results using the gassing unit according to the invention.

[0037] In a preferred embodiment, the membrane area of ​​the diffusion membranes, expressed as cm² membrane area divided by cm³ reactor volume, can be greater than or equal to 0.05 cm⁻¹ and less than or equal to 1.0 cm⁻¹ relative to the reactor filling volume, can be greater than or equal to 0.05 cm⁻¹ and less than or equal to 1.0 cm⁻¹. The aforementioned ratio of membrane area to reactor volume has proven particularly advantageous for cell cultivation in bioreactors and for the synthesis of biomolecules. This ratio allows for the adequate supply of process gas to the different growth phases with significantly varying amounts of biomass, while also ensuring sufficient control of the process gas input at the beginning of cell proliferation. This design allows for the precise controllability of the process gas supply, and, in later growth phases, for the adjustment of the process gas input at sufficiently low transmembrane pressures.

[0038] Further advantages and advantageous embodiments of the invention are illustrated by the figures and explained in the following examples. It should be noted that the figures are for descriptive purposes only and are not intended to limit the invention in any way.

[0039] It shows the figure as 1. A top view of a gas intake chamber according to the invention; 2. A further top view of a gas intake chamber according to the invention; 3. A side view of a gassing unit according to the invention; 4. A front view of a gassing unit according to the invention; 5. A schematic section through a gassing unit according to the invention; 6. A section through a gassing unit according to the invention; 7. A schematic section through a reactor according to the invention with a gassing unit according to the invention; 8. A schematic front view of a reactor according to the invention with a gassing unit according to the invention, including a possible convective flow profile; 9. A schematic front view of a gassing unit according to the invention consisting of two gassing units connected in series; 10. A schematic side view of a gassing unit according to the invention consisting of two gassing units connected in series;11 A schematic front view of a gassing unit according to the invention, consisting of two gassing units connected in series with media supply; 12 A schematic front view of a reactor according to the invention with two gassing units connected in series with media supply; 13 A schematic front view of a reactor according to the invention with two gassing units connected in series, including a possible convective flow profile; 14 A schematic exploded view of a gassing unit according to the invention.

[0040] The Figure 1Figure 1 schematically shows a top view of a gas intake chamber 1. The gas intake chamber 1 is cylindrical and divided into an inner area, which includes a receptacle for a process gas 4 and / or a receptacle for a shaft 4. The gas intake chamber 1 is supplied with both process gas and mechanical drive energy via this receptacle 4. The process gas is directed from the receptacle 4 into the actual gas intake chamber 1 via the trapezoidal connecting pieces 5. The gas intake chamber 1 has a closed surface 2, which is provided with corresponding recesses 3 for receiving the diffusion membranes (not shown in this figure).The diffusion membranes, in the form of hollow fibers, can be clamped or glued into the recesses 3. The diffusion membranes extend into the interior of the gas collection chamber 1, thus creating a continuous gas-carrying path from the collection point 4, via the connecting pieces 5, into the actual interior of the gas collection chamber 1 and into the hollow fiber membranes. The recesses 3 can also be referred to as the diffusion membrane fixing surface 3. The geometry of the diffusion membrane fixing surface 3 determines the planar design of the diffusion membranes. In this configuration, the diffusion membrane fixing surface 3 has an arc-shaped form, with the consequence that the hollow fibers attached in these recesses together form a curved membrane surface. The upper and lower gas collection chambers 1 can be designed as mirror images of each other.However, it is also possible that one of the two gas collection chambers 1 does not have a capacity for additional process media. During operation, the gas collection chambers 1 can be protected from direct access by process media by covers on the underside or top.

[0041] The Figure 2 essentially shows the same design as the Figure 1 with the surface of the gas intake chamber 2, the diffusion membrane fixing agent 3, the intake for a process gas and / or a shaft 4, as well as the connection 5 of the gas intake interior with the gas intake 4. In contrast to the Figure 1It is indicated here that individual cylindrical hollow fibers are inserted into the diffusion membrane fixation surface 3. This clarifies that the surface is not a continuous, planar membrane, but rather is formed from many individual hollow fibers that are offset from one another in both the X and Y directions, so that they follow the arc-shaped configuration of the diffusion membrane fixation surface 3. Thus, the diffusion membranes have an arc-shaped geometry. In addition to being fixed in the two gas-receiving chambers 1, the individual hollow fibers can also be mechanically fixed to one another (not shown in this figure). This additional fixing can be achieved, for example, by fibers that are woven or braided into the membrane perpendicular to the axis of symmetry of the hollow fibers.A grid of hollow fibers and the fibers of the additional fixation is thus formed, which can be adapted to the necessary mechanical load-bearing capacity of the diffusion membranes as a function of the number of additional fixation points and as a function of the mechanical properties of the additional fibers.

[0042] The Figure 3Figure 1 shows an embodiment of a gassing unit 10 according to the invention. The entire gassing unit 10 is shown in this figure. The gassing unit 10 is supplied with the process media, process gas and energy, via a supply line 9. The supply line opens into the receptacle 4 for the gas supply / shaft of the first gas receiving chamber 1 (not shown). The gas receiving chamber 1 is provided with an upper cover at this point. The individual diffusion membranes 6 extend from the gas receiving chamber 1, extending in total from the first gas receiving chamber 1 (shown here at the top) to the lower gas receiving chamber 1. In this figure, the planar design of the diffusion membranes 6, which is achieved by a targeted arrangement of hollow fibers, can be seen in particular. The diffusion membranes 6 extend from the first to the second gas receiving chamber 1 and are held in the middle by a retaining disc 7.The gas flow between the individual diffusion membranes 6 is therefore not interrupted between the gas receiving chambers 1. The diffusion membranes 6 can either be held in place, deflected from their original position, or mechanically tensioned by the retaining disk 7. The retaining disk 7 thus allows the orientation of the individual diffusion membranes 6 to be changed, which naturally influences the achievable convection of the gassing unit 10. This figure also shows a flow breaker 8, which is arranged above the gassing unit 10 in the direction of the reactor headspace. This flow breaker 8 is optional and can prevent vortex formation in the reactor fluid, particularly at very high circulation speeds of the gassing unit 10. This can contribute to a further reduction in bubble formation.

[0043] The Figure 4Figure 1 shows a front view of an embodiment of a gassing unit 10 according to the invention. The gassing unit 10 is supplied with the process media (process gas) and mechanical energy via a supply line 9. The supply line terminates in the receptacle for the gas supply / shaft of the first gas receiving chamber 1 (not shown). Individual diffusion membranes 6 extend from the gas receiving chamber 1, extending in total from the upper to the lower gas receiving chamber 1. The diffusion membranes 6 extend from the first to the second gas receiving chamber 1 and are held in the middle by a retaining disc 7. A flow baffle 8, arranged above the gassing unit 10 towards the reactor headspace, is also shown in this figure.

[0044] The Figure 5Figure 1 shows an example of the media flow within a gassing unit 10 according to the invention. The gassing unit 10 is driven by a hollow shaft 9, which is connected to the gas receiving chamber 1 via the receptacle 4 for the gas supply / shaft. The shaft transports both the mechanical energy and the process gas to the gas receiving chamber 1. The gas is directed into the inner gas receiving chamber 11 via the receptacle 4 for the gas supply and the connection between the gas receiving chamber and the gas receiving chamber. The individual hollow fiber membranes 6 are arranged on the gas receiving chamber 1 such that they extend into the inner gas receiving chamber 11. The hollow fiber membranes are thus supplied with process gas via the inner gas receiving chamber 11, which is then directed through the hollow fibers of the diffusion membranes 6 into the other gas receiving chamber 1. The process gas can pass from the hollow fibers of the diffusion membranes 6 into the process liquid, thus supplying the liquid with process gas.Both gas intake chambers 1 are additionally connected to each other via a mechanical support 12. This support can be used for other technical functions besides purely mechanical support. In this embodiment, the second (lower) gas intake chamber 1 also includes a receptacle 4 for the process gas. The process gas that does not diffuse out of the membranes 6 is guided from the gas supply unit 10 via the support 12 in the form of a hollow shaft. The gas supply unit 10 is thus operated in a "cross-flow" mode. In general, both the discharge and the supply of the process gas can be effected via a central hollow shaft 12, which can also function as a mechanical support. This latter configuration, in particular, can reduce the number of necessary connection points.

[0045] The Figure 6 shows, also how the Figure 5The media flow within a gassing unit 10 according to the invention. The gassing unit 10 is supplied with process gas and / or mechanical energy via the intake 4. The intake 4 is connected to the gas intake chamber 1, with the process gas being directed into the inner gas intake chamber 11. The individual hollow fiber membranes 6 are arranged on and extend into the gas intake chamber 1. The hollow fiber membranes 6 are thus supplied with process gas via the inner gas intake chamber 11, which is directed through the hollow fibers of the diffusion membranes 6 into the other gas intake chamber 1. The process gas can pass from the hollow fibers of the diffusion membranes 6 into the process liquid, thus supplying the liquid with process gas. Both gas intake chambers 1 are additionally connected to each other via a mechanical support 12, which can optionally also guide process gas.In this embodiment, the second (lower) gas intake chamber 1 also includes a receptacle 4 for the process gas. The process gas that does not diffuse out of the membranes 6 is routed from the gas supply unit 10 via a gas line in the mechanical support 12. In this configuration, the gas supply unit 10 can be operated in a "cross-flow" mode. Generally, both the discharge and the supply 4 of the process gas can be effected via a central mechanical support 12 in the form of a hollow shaft. This latter configuration, in particular, can reduce the number of required connection points.

[0046] The Figure 7Figure 1 shows a bioreactor 20 according to the invention with the gassing unit 10 according to the invention located therein. The reactor 20 is filled with a process fluid, the process fluid being present in the reactor 20 up to the process fluid level 21. The gassing unit 10 is held in the reactor 20 and moved by the process gas / mechanical energy supply in the form of a hollow shaft 9. The further construction of the gassing unit 10 can be found in the description to the Figure 5 can be extracted. It is also possible that further flow breakers or conduits 8 are arranged on the reactor walls 22 or in the liquid volume of the reactor 20 (not shown in this figure), whereby the convection of the process fluid can be influenced by this further flow breaker 8.

[0047] The Figure 8Figure 1 shows one possible configuration of a reactor 20 according to the invention with a gassing unit 10 according to the invention. This figure illustrates one way in which convection currents can be generated within the reactor 20. The convection currents result from a simulation of the flow behavior as a function of the geometry of the reactor 20 and the gassing unit 10. This figure shows that the gassing unit 10 leads to the formation of a highly symmetrical convection current, whereby the interior of the gassing unit 10 is also actively surrounded by the process fluid. The latter, in particular, can contribute to a particularly efficient introduction of process gas through the diffusion membranes 6 into the process fluid.The convection of the process fluid around the individual hollow fibers 6 forms small gas bubbles, which are sheared off the surface of the hollow fibers 6 and thus supply the process fluid with process gas. This also ensures that the bubble size on the surface of the hollow fibers is kept small.

[0048] The Figure 9Figure 1 shows a series-connected gassing unit 30 consisting of two individual gassing units 10, which are coupled via a modular coupling 31. The modular coupling 31 transmits both the process gas and the mechanical movement from the upper gassing unit 10 to the lower gassing unit 10. By connecting several gassing units 10, different reactor geometries and sizes can be supplied with process gas very efficiently. This results in a setup with as few connections as possible and a reliably predictable convection flow. Therefore, upscaling to larger reactors 20 can be easily carried out, especially using series-connected gassing units 30.

[0049] The Figure 10 shows the design of Figure 9 from a different perspective.

[0050] The Figure 11Figure 1 illustrates the media flow within an arrangement of two series-connected gassing units 10. The gassing unit 10 is driven by a hollow shaft 9, which is connected to the gas intake chamber 1 via the gas supply / shaft receptacle 4. The gas is guided through the individual hollow fiber membranes 6 into the other gas intake chamber 1 via the gas supply receptacle 4 and the connection between the gas intake chamber and the gas intake chamber 5. From this second gas intake chamber 1, the remaining process gas can transfer to the second gassing unit 10 via a modular coupling 31. The modular coupling 31 between the two gassing units 10 enables both the transfer of the process gas and the transmission of the mechanical drive energy between the individual gassing units 10.

[0051] The Figure 12Figure 1 shows an embodiment of a reactor 20 according to the invention with two series-connected gassing units 30, each consisting of two individual gassing units 10. By connecting several gassing units 10 in series, reactors 20 with a large aspect ratio can also be reliably supplied with process gas.

[0052] The Figure 13 Figure 1 shows a possible flow profile of a reactor 20, which is equipped with two series-connected gassing units 30. This results in uniform convection of the process fluid both across the entire reactor area and within the series-connected gassing unit 30.

[0053] The Figure 14Figure 1 shows an exploded view of a gassing unit 10 according to the invention. The gassing unit 10 can, for example, be driven by a hollow shaft (not shown in this figure) and supplied with process gas, which is connected to the gas receiving chamber 1 at the receptacle 4. The shaft provides both the mechanical energy of the unit and transports the process gas to the gas receiving chamber 1. The individual hollow fiber membranes 6 are arranged on the gas receiving chamber 1 such that they extend into the inner gas receiving chamber 11. The hollow fiber membranes are thus supplied with process gas via the inner gas receiving chamber 11, which is guided through the hollow fibers of the diffusion membranes 6 into the other (lower) gas receiving chamber 1. The process gas can pass from the hollow fibers of the diffusion membranes 6 into the process liquid and thus supply the liquid with process gas.Both gas intake chambers 1 are additionally connected to each other via a mechanical support 12. This support 12 can be used for other technical functions besides purely mechanical support. In this embodiment, the second (lower) gas intake chamber 1 also includes a receptacle 4 for process gas. The process gas that does not diffuse out of the membranes 6 is returned to the gas supply unit 10 via the hollow shaft of the mechanical support 12. In this configuration, the gas supply unit 10 is thus operated in a "cross-flow" mode. Generally, the discharge as well as the supply of the process gas can be effected via a central hollow shaft in the mechanical support 12, which is connected to the outer periphery via receptacles 4 at one or both gas intake chambers 1. The latter configuration, in particular, can reduce the number of necessary connection points and contribute to a compact design.Furthermore, this design shows that the individual gas intake chambers 1 can be protected above and below by cover plates. Reference sign

[0054] 1 Gas intake chamber 2 Surface of gas intake chamber 3 Diffusion membrane fixing surface 4 Gas supply / shaft inlet 5 Connection between gas intake chamber interior and gas intake 6 Diffusion membranes 7 Retaining disc 8 Flow breaker 9 Process gas / mechanical energy supply 10 Gas purging unit 11 Inner gas intake chamber 12 Support 20 Gas-liquid reactor 21 Process liquid level 22 Reactor shell 30 Series-connected gas purging units 31 Module coupling

Claims

1. A gassing unit (10) for bubble-free introduction of a process gas into a liquid located in a reactor (20), characterized in that the gassing unit (10) at least comprises: - a first gas receiving chamber and, spaced therefrom, a second gas receiving chamber (1) for receiving a process gas, the two gas receiving chambers (1) being connected to one another via at least two two-dimensional, gas-conducting diffusion membranes (6) comprising hollow fibers (6) spaced apart from one another and at least partially fixed to one another; - a receptacle for a gas supply (4) on at least one of the gas receiving chambers (1); - a receptacle (4) for a shaft (9) on at least one of the gas receiving chambers (1); wherein the gassing unit (10) for gassing the liquid in the reactor (20) can be supplied with process gas via the gas supply receptacle (4), can be set into a rotational movement via the receptacle (4) for the shaft (9) and can form a convection flow within the reactor (20) via the rotational movement of the gassing unit (10) in the liquid.

2. Gassing unit according to claim 1, wherein the projections of the diffusion membranes (6) onto the gas receiving chambers (1) have a circular arc geometry.

3. Gassing unit according to any one of the preceding claims, wherein the receptacle for the gas supply (4) and the receptacle (4) for the shaft (9) are arranged at only one gas receiving chamber (1).

4. Gassing unit according to any one of the preceding claims, wherein the two gas receiving chambers (1) are each of cylindrical shape and are interconnected via one or more mechanical supports (12).

5. Gassing unit according to claim 4, wherein at least one retaining disk (7) is arranged between the two gas receiving chambers (1) on the mechanical support (12), which is set up to mechanically retain the diffusion membranes (6).

6. Gassing unit according to any one of claims 4 or 5, wherein the mechanical support (12) is adapted to transport process gas from the gas receiving chambers (1).

7. Gassing unit according to any one of the preceding claims, wherein the area ratio of total hollow fiber cross-sectional area to the cross-sectional area of the gas receiving chamber is greater than or equal to 5% and less than or equal to 45%.

8. Gassing unit according to any one of the preceding claims, wherein the packing density of the diffusion membranes (6) relative to the volume of the gassing unit (10), expressed as the surface area of the hollow fibers divided by the volume of the gassing unit (10), is greater than or equal to 0.1 cm-1 and less than or equal to 7.5 cm-19. Method for gassing a process liquid within a reactor (20), characterized in that the gas input is effected by a gassing unit (10) according to any one of claims 1 - 8.

10. The method of claim 9, wherein the rotational speed of the membrane surface (6) at the outermost edge of the gassing unit (10) is greater than or equal to 0.1 m / s and less than or equal to 5 m / s.

11. Gas-liquid reactor (20) at least comprising an outer reactor shell (22), a drive unit, a gas supply (9) and a gassing unit (10) according to any one of claims 1-8.

12. Gas-liquid reactor according to claim 11, wherein the reactor (20) does not comprise a stirring unit other than the gassing unit (10).

13. Gas-liquid reactor according to claim 12, wherein at least one flow breaker (8) is arranged between the reactor shell (22) and a gas receiving chamber (1).

14. Use of a gas-liquid reactor (20) according to any one of claims 11 - 13 for supplying process gases to biological cultures suspended in a process solution or adhering to the reactor interior or to the gassing unit.

15. Use according to claim 14, wherein the biological cultures are adapted to produce foam-forming substances.

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