CA3004119A1 - Method and device for controlling foaming in a degassing device for liquids and heat-exchanger system for such a device - Google Patents

Abstract

The invention relates to a method and to a device for controlling foaming in a degassing device (10; 10.1, 10.2) for liquids (P), in particular liquid foods such as milk, semi-skimmed milk, skimmed milk, or fruit juices, and to a heat-exchanger system (20) for such a device. The aim of the invention is for the method, the device for performing the method, and the heat-exchanger system to effectively control and limit foaming and to prevent the growth of the foam beyond a tolerable amount while ensuring the sanitary and hygienic process-control requirements in the field of the treatment and processing of liquid foods. This aim is achieved in respect of process engineering, inter alia in that the growing foam (S), beginning at a first heating distance (h1) from the free surface (N) releasing the foam (S) and beginning at a second heating distance (h2) from the liquid film (F) releasing the foam (S), first experiences heating from the liquid temperature (T3) to a heating temperature (T1) in the heat-exchanger system (20), which consists of a heating heat exchanger (20.1) and a cooling heat exchanger (20.2), and that the further growing heated foam (S), beginning at a first cooling distance (k1) from the first heating distance (h1) and beginning at a second cooling distance (k2) from the second heating distance (h2), then experiences cooling to a cooling temperature (T2) in the heat-exchanger system (20).

Description

Method and device for controlling foaming in a degassing device for liquids and heat-exchanger system for such a device Technical Field The invention relates to a method and to an apparatus for controlling the foam formation in a degassing apparatus for liquids, and to a register system for an apparatus of this type. The liquids to be degassed (called liquids for short in the following text) are preferably liquid foodstuffs such as milk, semi-skimmed milk or fruit juices.
Prior Art In the case of the liquids under scrutiny, admixed gases, in particular admixed air with its proportion of atmospheric oxygen, are harmful in many ways. For this reason, degassing apparatuses are arranged in process plants which treat and process the abovementioned gas-charged liquid foodstuffs. Said process plants can be, for example, pasteurizing plants, UHT
plants or evaporators.
In the following text, two issues will be presented briefly which explain in greater detail the necessity of degassing milk, in particular, with regard to said process plants.
1. It is well known that the charging capacity, for example, of the milk with air or atmospheric oxygen is also dependent, inter alia, on its fat content, skimmed milk or standardized milk with a fat content between 1.5 and 3.5% being used, for example, in UHT plants, in which the milk is heat-treated in order to prolong its shelf life. It has proven advantageous for the service life of the UHT plants with indirect heating if the air content lies below 8 mg of air/dm3 (8 ppm) of milk.
Above a limit value in this regard, there is the increased risk of scorching, in particular in the heat exchangers of the heater zone and of the heat holder, as a result of which the service life of said heat exchangers is shortened significantly.

2. In heat exchangers of dairy technology process plants, independently of the configuration as plate heat exchangers or tube heat exchangers, the raw milk or thermophilic microorganisms or bacteria which come from its fractions (skimmed milk, cream), have not been subjected to high temperature heating and therefore have not been inactivated, or the metabolic products of said bacteria can be deposited and can form what is known as a biofilm. Said biofilm is primarily produced in a heat exchanger, in which the milk is treated thermally in the temperature range of approximately from 50 C to 70 C. Although pathogenic bacteria can no longer grow at temperatures above 50 C, other germs can, namely the abovementioned thermophilic microorganisms or bacteria (for short: thermophilic germs). Thermophilic germs utilize a temperature range of approximately from 40 C to 80 C, the temperature range for the optimum growth of the thermophilic germs lying in the range of approximately from 63 C to 68 C.
In addition to said optimum temperature, there have to be sufficient nutrients and oxygen for the growth. Since the abovementioned biofilm significantly shortens the service life of the suitable heat exchangers, it is a case of preventing or at least inhibiting the growth of the thermophilic germs.
This is accomplished primarily by the fact that the content of the air or the atmospheric oxygen is reduced, preferably in degassing apparatuses at issue here. Here, the liquid to be degassed is treated in a temperature range of from 40 C to 80 C, preferably between 50 C and 70 C.
In the two abovementioned applications, degassing apparatuses are used to reduce the air content, in particular. A degassing apparatus in this regard is known from EP 1 866 046 81. Herein, the semi-skimmed milk to be degassed is fed centrally from below to a degassing container, and is introduced via an outwardly dropping distributor screen in the form of a liquid film above a free surface of the milk supply which is situated in the degassing container. The liquid film is configured on a surface of the distributor screen and enters into the free surface at a greater or smaller radial spacing from the shell surface of the degassing container. Here, the distributor screen can be configured so as to be very flat and therefore so as to drop only slightly in the axial direction. Embodiments are also known, however, in which the distributor screen is configured as a cone or in a conical manner, the apex angle of which can be reduced as far as 45 degrees. If the flatly dropping or the tapered or conical distributor screen ends at a relatively great spacing from the shell surface of the degassing container, the free surface which is as a rule level-controlled or a free level of the liquid supply in the degassing container is configured in the region of said spacing. Here, as is the case as a rule, the outer edge of the distributor screen can dip into the free surface or else can end above the free surface at a small spacing. The discharge of the degassed milk takes place via the lowermost, central region of the degassing container.
As a rule, the degassing in the known degassing apparatuses is accelerated by virtue of the fact that the liquid is subjected to a vacuum which is generated by way of a vacuum source, for example a liquid ring pump, which is connected to the head space of the degassing container.
During the degassing in the known degassing apparatuses, the output liquid film which is configured on the surface of the distributor screen and, if significantly present, the free surface of the liquid supply in each case generate foam which grows on the surface of the liquid film and on the free surface of the liquid supply in the direction of a head space of the degassing container. Here, the foam formation can be so intensive, and this is the case, for example, during the

3 degassing of skimmed milk, that the entire head space of the degassing container is filled with foam and, as a result, the foam brings the degassing operation to a standstill or at least impedes it considerably, with the result that the process management is made much more difficult overall. If the foam passes here into a possibly present vacuum source, the degassing process has to be stopped anyway.
It is known to combat foam in a chemical, mechanical and thermal way. Combating by way of the addition of chemical media is disqualified as a rule in the case of liquid foodstuff products, in order to avoid contamination. In the case of high foam formation rates, mechanical foam breakers deliver unsatisfactory results on account of excessively low performance and a relatively great and partially also complicated construction effort which has to be made with regard to the production and/or the adaptation to a very wide variety of application requirements.
The breaking of undesired foam bubbles proceeds from the finding that the foam bubble collapses when its volume is no longer stable. The volume of a foam bubble is defined by the equilibrium between firstly the pressure of the trapped gas and secondly the sum of two pressures, namely the pressure, at which the treatment process of the liquid takes place, and the pressure which is produced by way of the surface tension of the foam bubble.
It therefore has to be the aim of foam breaking in a thermal way, namely either by way of heating or by way of cooling, to significantly disrupt the abovementioned equilibrium state.
Heating of the foam bubbles brings about an increase and cooling leads to a decrease of the respective internal pressure of the foam bubbles. In this regard, document DE 21 63 666 Al discloses it being expedient to disrupt the equilibrium state between the surface tension and the internal pressure of all or part of the foam bubbles to be broken by

4 way of a change in the internal pressure of the foam bubbles.
It is proposed in this regard to increase the internal pressure by way of heating of all or part of the foam bubbles, to be precise, for example, by way of heating of the foam bubbles in an electric way by way of the installation of an electrically conducting resistance wire in the foam zone.
A further proposal provides heating the foam bubbles by way of hot heating gases being blown into the foam zone. In the case of the first proposal, the operational reliability and the temperature control are problematic and, in the case of the second proposal, there is no longer the necessary product and quality assurance on account of possible contaminations.
Another proposal which complies with the sanitary and hygienic requirements which apply to the liquid foodstuff products to be treated within the context of the invention, at least in the case of a suitable configuration of its solvents, provides that the foam bubbles are heated by way of a heat exchanger which is loaded with warmer gaseous or liquid media and is attached in the foam zone.
The disclosure of document DE 37 27 132 Al falls short of the last-mentioned proposal, since it is proposed herein, in the case of a method for destabilizing and breaking foams, to greatly reduce the mechanical strength of the foam in a manner known per se by way of the introduction of thermal energy, but the introduction in this regard within the context of the problem addressed here consists in a problematic feed of steam or heated gas. Moreover, the problematic feed of said materials is combined with means for mechanical foam breaking or with means for ultrasound generation which require an additional structural and costly effort.
DE 43 04 808 Al describes a method and an apparatus for filling milk into containers. Bottles are used as containers, the object being achieved of eliminating the foam which is produced during the filling of milk into the containers even during the filling process and at the same time of ensuring a

5 precise filling quantity in the container. Said object is achieved, inter alia, by the bottle being overfilled with milk in the vacuum region and the excess milk then being extracted, with all the foam which has formed, by way of vacuum as far as the predefined filling level and being collected in a separate container. From said prior art, an appropriate person skilled in the art gathers the indications that it is not possible or is at least problematic to break the foam (in particular, milk foam) by way of heating by devices which protrude into the foam. Instead, it is proposed to extract the foam which has formed by suction and to collect it in a separate container.
DE 1 017 140 Al discloses an apparatus for foam breaking in liquid evaporators, in which the evaporation of the liquid also takes place, in particular, under vacuum. Here, the vacuum serves to lower the evaporation temperature and not, for instance, to extract the foam. In order to stiffen the vacuum-tight evaporator shell, it is known to provide a reinforcing ring. The subject matter of the application utilizes the known finding that foam bubbles collapse on cooled walls, and solves the objective problem of configuring the steam separator shell with an easy-to-clean reinforcement and at the same time of utilizing said reinforcement for foam breaking. The solution of said problem consists in providing a welded ring, for instance, in the center of the stepped evaporator shell, which welded ring serves to reinforce the shell and to channel a coolant. From said prior art, an appropriate person skilled in the art gathers the indication that it is known to disrupt the equilibrium of the foam bubbles by way of cooling and, as a result, to bring about breaking of the foam and, furthermore, to step the diameter of the container shell from the outside to the inside in the region of the foam formation, the stepped portion being formed by way of a pipe ring. Here, the cooling zone which is formed by way of the pipe ring acts only tangentially from the outside on the foam which grows over the entire evaporator cross section.

6 DE 10 2004 062 804 B3 describes an apparatus for controlling the temperature of objects and/or media. Said temperature control (heating or cooling) takes place by way of at least one so-called thermal element block. Said thermal element block is a flat structure which consists of a plurality of Peltier elements which are connected in an alternating manner in series electrically and in parallel thermally, and are covered toward the outside by way of an electrically insulating and thermally conducting layer. Here, the medium to be heated or to be cooled is received in at least one funnel-shaped depression which has an inflow opening at its lowest point and a circumferential outflow channel at the upper edge, which outflow channel is loaded via an overflow edge. The depression is flowed through by the medium from the inflow opening toward the outflow channel. The outflow channel is enclosed on the outside by a seal, via which the interior space of the depression is closed in a sealed manner with the thermal element block. A direct heat exchange (heating or cooling) takes place between the medium which flows through the depression and the flat thermal element block which acts, as it were, as a cover of the depression. Said prior art does not disclose an application which indicates breaking of foam which is formed from a liquid, or render an application in this regard obvious. Furthermore, the flat thermal element block which heats or cools the respective medium can neither be flowed around on the outside nor flowed through on the inside.
It is an object of the present invention to specify a method and an apparatus for controlling the foam formation in a degassing apparatus for liquids, which method and apparatus effectively control and limit the foam formation and, in the process, prevent the growth of the foam beyond a tolerable extent with ensuring of the sanitary and hygienic requirements of the process control in the field of the treatment and processing of liquid foodstuffs.

7 Summary of the Invention Said object is achieved by way of a method having the features of independent claim 1. Advantageous refinements of the method are the subject matter of the subclaims. A degassing apparatus for liquids having an apparatus for controlling the foam formation in the degassing apparatus, suitable for carrying out the method according to the invention, is the subject matter of independent claim 9. Advantageous refinements of the apparatus are the subject matter of the associated subclaims.
A register system for the apparatus for controlling the foam formation in the degassing apparatus is the subject matter of claim 14. Advantageous refinements of the register system are claimed in the associated subclaims.
The method according to the invention is carried out by way of a degassing apparatus for liquids, which degassing apparatus is fed the liquid, in which degassing apparatus the liquid is treated for the purpose of gas separation and/or dwells for a mean dwell time, and from which degassing apparatus the liquid is discharged as a degassed liquid below a free surface which is formed by the liquid in the degassing apparatus. The liquid is configured as a liquid film above the free surface and on a surface of a distributor screen, and enters from there into the free surface. The liquid film is preferably of screen-shaped configuration.
In its general operating principle, the method according to the invention treats a foam which is generated on the surface of the liquid and out of the latter, and which, starting from said surface, grows over it into the free space. Said surface can be a free surface of the liquid supply in the degassing container, a level of said liquid supply, which level is as a rule height-controlled, and/or the surface of a liquid film which is configured on the surface of the possibly present distributor screen. The surface in question of the liquid film

8 is that surface which faces away from that surface of the distributor screen which forms the liquid film.
In the case of the degassing apparatus, from which the present invention proceeds, the foam is released in each case above and from the free surface and/or above the liquid film and from the liquid film, and in both cases grows into a free space above the liquid which generates the foam, in particular into a head space of the degassing container. Here, the foam is at the temperature of the liquid, possibly at a slightly lower temperature. In the following text, the terms "grow" and "growth direction" are intended to be understood as the movement direction of the foam which takes place, it also being possible for said movement direction to run in a manner which differs from the direction of gravity.
In all the above-described cases, therefore, said growth of the foam is a dynamic process of foam propagation. The inventive basic concept starts at the boundary surface of the foam propagation. Beginning at a first heating spacing from the free surface which releases the foam and beginning at a second heating spacing from the liquid film which releases the foam, the respective foam which grows at the liquid temperature first of all experiences heating from the liquid temperature to a heating temperature in a register system which consists of a heating register and a cooling register.
Said heating spacing has to first of all be crossed by the associated growing foam, before the heating starts. The respective heating spacing can be predetermined fixedly in a manner which is dependent on the liquid, or else can be capable of being set in the degassing container. Here, the region, in which the heating takes place, is limited and predefined as measured in the growth direction. The foam bubbles will necessarily expand as a result of the local heating, primarily limited in said region, as a result of the thermodynamic laws, the above-discussed equilibrium state is disrupted, and the foam bubbles become unstable. The boundary surface of the foam

9 propagation will spread out in a manner which is forced by way of the heating.
Subsequently, beginning at a first cooling spacing from the first heating spacing and beginning at a second cooling spacing from the second heating spacing, the respective further-growing heated foam experiences cooling to a cooling temperature which can undershoot the liquid temperature. The first and the second cooling spacing can also be related to the respective associated foam-generating surface, the first cooling spacing then being greater than the first heating spacing, and the second cooling spacing then being greater than the second heating spacing. Here, the region, in which the cooling takes place, is likewise limited and predefined as measured in the growth direction. As a result of the sudden cooling of the liquid lamellae which enclose the foam bubbles, the equilibrium state of the foam bubbles is once again disrupted, to be precise in an opposite manner to the heating.
The foam bubbles become more unstable and burst as a result of the changing viscosity of the liquid lamellae, as a result of which the foam in said region collapses and is reduced to an associated liquid volume which flows away in the direction of gravity. In this way, the foam propagation, as viewed in the growth direction, is ended at the end of the cooling or cooling zone or at a tolerable spacing from said end.
The means for carrying out the heat exchange for heating and cooling the foam, namely the register system which consists of a heating register and a cooling register, are configured in a manner which is permeable to flow in a growth direction of the foam.
The heating temperature and/or the cooling temperature are/is set in a manner which is dependent on the properties of the liquid and/or the physical boundary conditions. The properties of the liquid are understood to mean the volumetric flow, the viscosity, the pressure, the temperature and/or the composition of the liquid in the region of the feed into the degassing apparatus. The properties of the degassed liquid are understood to mean the oxygen concentration in the region of the discharge from the degassing apparatus, and the physical boundary conditions are understood to mean the pressure and/or the result of the foam breaking in the degassing apparatus.
The result of the foam breaking is shown in the fact whether foam is still present above the cooling of the foam and possibly grows further. A signal which is generated from said foam can then be used to set the heating temperature and/or cooling temperature.
The heating spacings and cooling spacings (in each case viewed separately) are not necessarily different. Within the context of method simplification and optimization, they are advantageously designed to be identical to one another (in each case viewed separately).
The method according to the invention is fundamentally applied in such a way that the foam regions which are temperature-controlled differently, owing to their heating and their cooling, either engage into one another or overlap to a limited extent or are side by side, without engaging into one another or overlapping in this regard. It has proven advantageous, as one proposal provides, if an extent region of the heating and heated foam and an extent region of the cooling and cooled foam are directly side by side, as viewed in an associated growth direction of the foam, without overlapping mutually completely or at least partially. In this refinement of the method, the foam can first of all be heated and expanded in an unimpeded manner over its entire generation front, from which it grows, in order then subsequently to experience unimpeded cooling and breaking under the same geometrical conditions.
The hygienic and sanitary requirements which are to be made of the treatment and processing of liquid foodstuffs are complied with sufficiently within the context of the method according to the invention by virtue of the fact that the heating and the cooling of the foam take place by way of an indirect heat exchange, for example on walls of heat exchangers which are as far as possible permeable for foam in the growth direction of said foam. A heating medium, preferably hot water, and a coolant, preferably cold water, are provided as heat exchange medium for the indirect heat exchange. Hot steam or hot gas can also be used, however. The heating medium preferably has a heating medium temperature of up to 90 C in a manner which is expedient and dependent on the liquid temperature of the liquid. The coolant preferably has a coolant temperature of as low as from 12 to 14 C for milk and as low as 6 C for fruit juices in a manner which is expedient and likewise dependent on the respective liquid temperature, as a result of which cooling of the foam can also be realized to a temperature level below the liquid temperature.
Furthermore, the invention proposes that the heating and/or the cooling of the foam takes/takes place by way of a direct heat exchange on the basis of the Peltier effect. In this case, in the case of a suitable configuration of the Peltier elements, the heating register and cooling register can be of very easy-to-clean configuration with regard to CIP cleaning.
It has proven particularly expedient if a cooling capacity in the region of the cooling of the foam is designed to be greater than a heating capacity in the region of the heating of the foam. Beyond the dimensional relationship between a necessary heating area and cooling area, as a result of the geometric design conditions, the relationship between the heating capacity and the cooling capacity can be changed via the effective driving temperature difference in the respective heat exchangers of the heating zone and cooling zone. Here, the heating medium temperature and coolant temperature are available as influencing variables which can be changed within limits.
As a further proposal provides, the heating temperature and/or the cooling temperature are/is set by means of a setting function which is generated and stored before or during the start up of the degassing apparatus. Firstly the optimum condition relationships between the properties of the liquid to be degassed and the degassed liquid and/or the physical boundary conditions and secondly the heating temperature and the cooling temperature are stored in said setting function, with the result that a fully automated method for controlling the foam formation in the degassing apparatus for liquids can be carried out.
The degassing apparatus for liquids having an apparatus for controlling the foam formation in the degassing apparatus, suitable for carrying out the method according to the invention, consists in a manner known per se of a degassing container which has an inlet for the liquid and has an outlet for a degassed liquid, which outlet opens out of the degassing container in the lowermost, central region. In the degassing container, the liquid configures a free surface, the level of which is preferably controlled by a level control device. A
distributor screen is arranged above the free surface, which distributor screen is preferably of screen-shaped configuration and on the surface of which distributor screen the liquid is configured as a liquid film. A feed pipe is provided which is connected on one side on the end side to the inlet and on the other side on the end side to a circumferential annular gap which opens out at the upper end of the distributor screen. The liquid for the liquid film is output via the circumferential annular gap.
According to the invention, the apparatus for controlling the foam formation in the degassing apparatus is distinguished by the fact that a register system which consists of a heating register and a cooling register is provided, which register system encloses, by way of the heating register, the free surface and that surface of the distributor screen which forms the liquid film, in a manner which is annular in the region of the foam formation and which is spaced apart at a first heating spacing from the free surface and at a second heating spacing from that surface of the distributor screen which forms the liquid film. The cooling register is arranged offset, as viewed in a respective growth direction of the foam, with respect to the heating register by a first cooling spacing in the region of the free surface and by a second cooling spacing in the region of the distributor screen.
The heating register and the cooling register for the indirect heat exchange are to be understood to mean in each case a heat exchanger which has a multiplicity of hollow structures which are delimited in each case by planar or curved walls. The hollow structures are flowed through on the inner side by the heat exchange medium, the heating medium or coolant. The hollow structures in combination with one another are permeable to flow on the outer side in the growth direction of the foam. The planar walls form chambers which can be flowed through and can have different geometries, such as rectangular, square or triangular geometries. The curved walls delimit, for example, oval, elliptical or circular throughflow cross sections. The hollow structures are flowed through on the inner side by a heat exchange medium, a heating medium in the heating register and a coolant in the cooling register.
In accordance with one proposal, the heating register and/or the cooling register for the direct heat exchange are/is configured in each case as a Peltier element.
The register system is assigned a control device which changes a heating capacity of the heating register and/or a cooling capacity of the cooling register in a manner which is dependent on the properties of the liquid and/or the physical boundary conditions. The control device is connected to a measuring device which determines at least one of the properties of the liquid and the degassed liquid and/or the physical boundary conditions. With regard to the physical boundary conditions, the measuring device can be set up in such a way that it is a measuring device for the detection of foam (for example, a foam sensor), said foam growing above the cooling register and generating a foam signal there, which foam signal is transmitted to the control device.
It has proven advantageous and particularly expedient if the control of the foam formation in the degassing apparatus is oriented directly toward the result of the degassing operation. To this end, one refinement provides that the measuring device is a measuring device for oxygen, which measuring device determines an oxygen concentration of the degassed liquid in or at the outlet or in a pipeline which opens out of the outlet, and transmits it to the control device.
The degassing operation is intensified if a vacuum source in the form of a liquid ring pump or in the form of a single stage or multiple stage ejector is connected to a head space of the degassing container.
Furthermore, for the indirect heat exchange using in each case one heat exchange medium, the invention proposes embodiments of the register system for the apparatus for controlling the foam formation in the degassing apparatus for liquids, the register system consisting of a heating register and a cooling register, and the degassing apparatus, suitable for carrying out the method according to the invention, having been described in the above text.
A uniform treatment and breaking of the foam and a simplified structural embodiment are achieved if the heating register and cooling register in each case enclose the distributor screen in an axially symmetrical manner and if, moreover, both the first and the second heating spacing among themselves and the first and the second cooling spacing among themselves are in each case identical to one another.
It has proven particularly expedient with regard to effective foam breaking if an overall cooling area of the cooling register is designed to be greater than an overall heating area of the heating register. The entire cooling area and the entire heating area are to be understood in each case to mean the sum of all heat exchanger areas of the cooling register and the heating register which act on the foam in a heating or cooling manner.
One embodiment which is structurally simple and ensures the hygienic and sanitary requirements during the treatment and processing of liquid foodstuff products is provided in accordance with one proposal if the heating register consists of first pipes, and the cooling register consists of second pipes. Here, the first pipes and the second pipes, in each case among themselves, are arranged in a row next to one another and spaced apart from one another. In relation to the respective foam-generating surface in the degassing container, the first pipes are positioned at the first heating spacing from the free surface and at the second heating spacing from that surface of the distributor screen which forms the liquid film. The cooling register which is likewise realized with pipes in this way is arranged offset with respect to the heating register, as viewed in the respective growth direction of the foam, to be precise by virtue of the fact that the second pipes are positioned at the first cooling spacing, starting from the first heating spacing, and at the second cooling spacing, starting from the second heating spacing.
Transversely with respect to the respective growth direction, the first and second pipes are likewise arranged offset with respect to one another, to be precise in a simple way such that second pipes are positioned in and distributed to the respective gaps between the first pipes.
In order to prevent the cooling register which is realized by way of pipes not engaging into the heating register or overlapping with the latter entirely or in part regions, it is proposed that the first and the second cooling spacing are in each case consistently greater than a greatest first diameter of the first pipes at the associated cooling spacing.
There is a simplification of the respective construction if the first pipes and the second pipes in each case have identical diameters among themselves, and the desired relationship between the cooling area and the heating area can be designed more easily and more flexibly under the above diameter conditions if the first pipe has a greater diameter than the second pipe.
It is proposed, furthermore, to configure the first pipes and/or the second pipes in each case as a monopipe. As a result of said embodiment, problems in terms of the flow are avoided during the distribution of the heating medium and the coolant.
Furthermore, it is proposed for the first pipe and the second pipe, in each case configured as a monopipe, to be in each case of spiral configuration in a region which is assigned to the free surface, and to be in each case of helically wound configuration in a region which is assigned to that surface of the distributor screen which forms the liquid film.
Furthermore, this embodiment provides the possibility to arrange the monopipes which are wound in this way, in relation to the growth direction of the foam and transversely with respect thereto, very simply in such a way that, as viewed in the growth direction, they are firstly in each case permeable to flow and secondly realize the required series connection of the heating register and the cooling register. This is expediently achieved by virtue of the fact that the monopipes of the cooling zone are firstly arranged in the growth direction axially offset with respect to the monopipes of the heating zone, and secondly are positioned in the radial direction over the respective gaps between the monopipes of the heating zone. One advantageous embodiment in this regard provides that in each case two second pipes are positioned in a symmetrical and uniformly distributed manner over the respective gap between two adjacent first pipes.
With regard to a simple and easily variable adjustment and fastening of the register system in any desired configuration or in the configuration with first and second pipes, two solutions are proposed. The two solutions both propose that the heating register and cooling register are supported on the degassing container via a plurality of carriers which are arranged in a uniformly distributed manner over the circumference of the degassing container and extend in a star-shaped manner toward the center of the degassing container.
The first solution is distinguished by the fact that the course of each carrier in relation to the heating register results from a lower contour of the heating register, against which lower contour each carrier bears tightly from below. In the case of the second solution, the course of each carrier in relation to the heating register results from the positioning of the first pipe, against which each carrier bears tightly tangentially from below. In the case of the two solutions, four carriers are preferably provided.
In the case of the refinement of the register system with first and second pipes, the positioning and fastening of the pipes which are required according to the invention both in the growth direction of the foam and also transversely with respect thereto are achieved in a very simple way by virtue of the fact that an imaginary contact line is utilized as reference line for positioning and fastening, which imaginary contact line results from the contact points between the first pipes and the carrier which bears in each case tangentially against them. Securing means for the first and the second pipes are provided on the carrier in the course of the contact line, which securing means are connected fixedly to the carrier. The securing means are preferably of plate-shaped configuration and are oriented upright firstly in the direction of a longitudinal axis of the degassing container and secondly in the direction of the contact line, as a result of which the growth of the foam is impeded as little as possible. Here, two adjacent securing means in each case fix a first pipe and .at least one second pipe non-displaceably in the direction of the contact line.
Brief Description of the Drawings A more detailed summary of the invention results from the following description and the appended figures of the drawing, and from the claims. Whereas the invention is realized in a very wide variety of embodiments, the drawing describes one preferred exemplary embodiment of a degassing apparatus for liquids, configured with a lower, lateral inlet and combined with an apparatus according to the invention for controlling the foam formation in the degassing apparatus, suitable for carrying out the method according to the invention. Moreover, one preferred exemplary embodiment of a register system which consists of a heating register and a cooling register is shown for the apparatus according to the invention, and will be described in the following text with respect to the construction and function. In the drawing:
figure 1 shows a degassing apparatus of a second type in accordance with the prior art, configured with a lower, central inlet, from which the present invention proceeds apart from a modification of the positioning of the inlet, shown in figure 2, figure 2 shows a perspective and transparent illustration of one preferred embodiment of a degassing apparatus of a first type, configured with a lower, lateral inlet, from which the present invention proceeds, together with the apparatus according to the invention, and a register system, consisting of a heating register and a cooling register, figure 3 shows a perspective illustration of the degassing apparatus in accordance with figure 2, the apparatus according to the invention being exposed by way of the omission of a shell and an upper floor of the degassing container, and a diagrammatic illustration of a control device with associated means for loading a heating register and a cooling register with a heating medium and a coolant, figure 4 shows the front view of the degassing apparatus in accordance with figures 2 and 3 in a viewing direction which is labeled by "Z" in figure 3, figure 5 shows the plan view of the degassing apparatus in accordance with figures 2 to 4, figure 6 shows a meridian section of the degassing apparatus in accordance with figures 2 to 5 in accordance with a sectional course which is labeled by A-A in figure 5, figure 7 shows an enlarged illustration of a first detail (labeled by "B" in figure 6) in the region of the apparatus according to the invention, figure 8 shows a once again enlarged illustration of a second detail (labeled by "C" in figure 7) from the first detail in accordance with figure 7, and figure 9 shows a front view and a plan view of a securing means (shown in figures 7 and 8) for pipes of the heating register and cooling register according to the invention in an enlarged illustration.
Detailed Description The invention proceeds from a degassing apparatus 10 for liquids P in accordance with the prior art, to be precise either in an embodiment of a second type, called a degassing apparatus 10.2 in the following text, as shown in figure 1 for the description of the general construction of the degassing apparatus in question, or in an embodiment of a first type, called a degassing apparatus 10.1 in the following text, as disclosed in figures 2 to 6 in conjunction with an apparatus according to the invention, the essential part of which consists of a register system 20. The degassing apparatus 10,

10.2 consists of a degassing container 2 in the form of a substantially cylindrical container shell 2c with a lower floor 2b and an upper floor 2a. The lower floor 2b has a central outlet stub 2d with an outlet A for a degassed liquid P', the outlet stub 2d being penetrated concentrically by a feed pipe 4 which engages from below into the degassing container 2 with an inlet E for the liquid P. A distributor screen 3 is connected fixedly to the feed pipe 4 at the upper end of said feed pipe 4 which is guided into the degassing container 2, in such a way that the feed pipe 4 opens out centrally in the distributor screen 3 on the inner side via an outlet opening 4a which is preferably sufficiently rounded with respect to the distributor screen 3. The feed pipe 4 establishes a connection to a circumferential annular gap 6 which is formed between the upper end of the distributor screen 3 and a baffle plate 5 which is arranged concentrically with respect to and spaced apart above said distributor screen 3.
Here, the baffle plate 5 reaches over the upper end of the distributor screen 3 to a certain extent, and is guided axially and fastened on its side which faces the upper floor 2a, and can be adjusted within limits in terms of its spacing from the upper end of the distributor screen 3. The liquid P which is fed in via the inlet E leaves the feed pipe 4 via the outlet opening 4a, is deflected there by the baffle plate 5, and is applied to the distributor screen 3 in a star-shaped manner via the circumferential annular gap 6 and, as viewed radially, from the inside to the outside, and is configured as a liquid film F on the surface of said distributor screen 3. Admixed gases can be separated easily from the surface (facing away from the distributor screen 3) of the liquid film F which runs down over the distributor screen 3, as a consequence of the buoyancy. A free surface N or a level N of the liquid P', P
which has already been degassed to a very great extent or is still to be degassed and forms a liquid supply in the degassing container 2 is set by way of a level control device (not shown). The liquid film F which has been partially degassed or degassed to a very great extent enters at the lower end of the distributor screen 3 into the free surface N. The liquid fractions which are layered via the distributor screen 3 in the form of the liquid film F onto the free surface N and enter into the latter dwell in the degassing container 2 for a mean dwell time and can degas further there with the aid of the gas bubble buoyancy over the free surface N.
The distributor screen 3 and the first baffle plate 5 which corresponds with it are expediently of circular and in each case screen-shaped configuration, that is to say so as to fall radially to the outside. In one preferred embodiment, the distributor screen 3 (as shown) has a tapered or conical configuration, it being possible for the angle at the cone tip to be reduced to approximately from 80 to 90 . As a rule, the lower end of the distributor screen 3 reaches as far as the free surface N or dips slightly into the latter.
If foam S is formed during the degassing of the liquid P, said foam S is generated in part from the liquid supply below the free level N and in part from the liquid film F. Said foam S
is released in each case above and out of the free surface N
and/or above the liquid film F and out of the liquid film F, and grows in the direction of an interior space which is formed by the container shell 2c and in the direction of a head space which is formed by the upper floor 2a. A respective growth direction of the foam is denoted by r(S).
Just like the lower and central arrangement of the inlet E, the further components which are shown in figure 1 and are not denoted, such as a head hole, various connectors and stubs as well as level indicator windows, are not of significance for the invention in question here.
The invention is configured specifically in the degassing apparatus 10.1 for liquids P, an embodiment of the second type (figures 2 to 6). It differs substantially only by way of the location of the arrangement of the inlet E of the degassing apparatus 10.2, the embodiment of the second type. The inlet pipe 4 is introduced from the side into the lower floor 2b, and the outlet stub 2d with its outlet A therefore remains free and undiminished. Said difference is insignificant for the present invention. In the transparent illustration of figure 2 and in figures 3 to 8, in contrast to the degassing apparatus 10.2, a register system 20 according to the invention can be seen, consisting of a heating register 20.1 and a cooling register 20.2, which register system 20 will be described in more detail in the following text.
The register system 20 in a generalized embodiment which is not shown in detail encloses the free surface N and that surface of the distributor screen 3 which forms the liquid film in the region of the foam formation in an annular manner by way of its heating register 20.1, and is spaced apart here from the free surface N at a first heating spacing hl and from that surface of the distributor screen 3 which forms the liquid film at a second heating spacing h2 (figures 7, 8 and 6). The heating register 20.1 is designed for the indirect and the direct heat exchange with a heating capacity HL, and the cooling register 20.2 is designed in the corresponding method of operation with a cooling capacity KL.
Within the context of the indirect heat exchange, the heating register 20.1 is flowed through by a heating medium WH which is at a heating medium temperature TH, and the cooling register 20.2 is flowed through by a coolant WK which is at a coolant temperature TK (figures 3 and 5). As viewed in the respective growth direction of the foam r(S), the cooling register 20.2 is arranged offset with respect to the heating register 20.1 by a first cooling spacing kl in the region of the free surface N and by a second cooling spacing k2 in the region of the distributor screen 3 (figures 7, 8 and 6). The heating and cooling register 20 preferably in each case enclose the distributor screen 3 in an axially symmetrical manner. The first and the second heating spacing hl, h2 and/or the first and the second cooling spacing kl, k2 are in each case preferably of identical configuration among themselves. An overall cooling area OK of the cooling register 20.2 is preferably designed to be greater than an overall heating area OH of the heating register 20.1.
The heating and cooling register 20 is assigned a control device 13 which changes the heating capacity HL (in the present exemplary embodiment, the volumetric flow of the heating medium WO and/or the cooling capacity KL (in accordance with the volumetric flow of the coolant WK) in a manner which is dependent on the properties of the liquids P, P' and/or the physical boundary conditions (figure 3). The control device 13 is connected to a measuring device 14, 14.1 which determines at least one of the properties of the liquids P, P' and/or the physical boundary conditions. Via a first valve 15 which is connected by way of signaling components to the control device 13, the throughflow of the heating medium WH through the heating register 20.1 is controlled, and the throughflow of the coolant WK through the cooling register 20.2 is controlled via a second valve 16.
According to one advantageous and preferred embodiment, the heating register 20.1 consists of first pipes 8, and the cooling register 20.2 consists of second pipes 9 (figures 2 to 8). In each case among themselves, the first pipes 8 and the second pipes 9 are arranged in rows next to one another and spaced apart from one another (figures 6 to 8). The first pipes 8 are positioned at the first heating spacing h1 from the free surface N and at the second heating spacing h2 from that surface of the distributor screen 3 which forms the liquid film. The necessary offset of the first and the second pipes with respect to one another and as viewed in the growth direction r(S) of the foam S is ensured by virtue of the fact that the second pipes 9 are positioned at the first cooling spacing kl, starting from the first heating spacing hl, and at the second cooling spacing k2, starting from the second heating spacing h2. A complete coverage of the foam-generating surfaces is ensured by virtue of the fact that second pipes 9 are arranged over and distributed to the respective gaps between the first pipes 8.
If, as is preferably provided, the first and the second cooling spacing kl, k2 are in each case consistently greater than a greatest first diameter DE of the first pipes 8 at the associated cooling spacing kl, k2, complete or at least partial engagement into one another or overlapping in this regard of the heating and cooling registers 20.1, 20.2 is prevented.
The first pipes 8 and the second pipes 9 are preferably configured with identical diameters in each case among themselves, and the first pipe 8 preferably has a greater diameter (the first diameter DH) here than the second pipe 9 with a second diameter DK.

The construction of the register system 20 in the pipe embodiment is simplified substantially if the first pipes 8 and/or the second pipes 9 are configured in each case as a monopipe. Further simplification of the construction results from the fact that the first pipe 8 and the second pipe 9, in each case configured as a monopipe, are in each case of spiral configuration in a region which is assigned to the free surface N, and are in each case of helically wound configuration in a region which is assigned to that surface of the distributor screen 3 which forms the liquid film. A simple and gap-free coverage of the foam-generating surfaces is preferably achieved by virtue of the fact that in each case two second pipes 9 are positioned in a symmetrical and uniformly distributed manner over the respective gap between two adjacent first pipes 8 (figures 8 and 9).
With regard to an appropriate and expedient design of the register system 20 in the tubular embodiment and, here, preferably in the respective embodiment as a monopipe heat exchanger, in particular with regard to the ratio between the heating area and the cooling area OH, OK, the specific objective embodiment in this regard provides, for example, to design the cooling area OK over the second pipe 9 in such a way that it has the second diameter DK = 8 mm and an overall length, a second length LK. In the context of the abovementioned cooling area OK, the heating area OH is designed over the first pipe 8 in such a way that it has the first diameter DH = 10 mm and an overall length, a first length LH =
LK/2. With regard to the ratio required above between the cooling capacity KL and the heating capacity HL, a ratio of the cooling area OK and heating area OH of OK/OH - dkLK/dFILH = 8 LK/10 LH = 8 LK/(10 LK/2) = 2 x 8/10 = 1.6 thus results in the exemplary embodiment, whereby the condition that the cooling area OK is to be designed to be greater than the heating area OH is sufficiently met.

The register system 20 has a form, as can be seen from figures 2 to 7, in particular, and is owing to the course of the free surface N and the course of the distributor screen 3. It is essential in the case of the embodiment of the register system 20 that the foam formation in the growth direction of the foam r(S) is not impeded or is impeded merely insignificantly by the first and second pipes 8, 9. For this purpose, the first and second pipes 8, 9 are firstly spaced apart from one another sufficiently and are secondly, however, so numerous that a universal and sufficient thermal treatment of the foam S is ensured.
A heating temperature and/or a cooling temperature T1, T2 of the foam S (figures 7 and 8) are/is set in a manner which is dependent on the properties of the liquid P and the physical boundary conditions via the control device 13 (figure 3) with the aid of the heating medium WH at the heating medium temperature TH and the coolant WK at the coolant temperature TK, with the result that it is possible to control the foam formation by way of this.
The foam S grows approximately at a liquid temperature T3 out of the free surface N and/or out of the liquid film F and is situated first of all in the region of the first and the second heating spacing hi, h2 (figures 7, 8). A foam SH which is being heated and is heated on the heating area OH (said heated foam being at the heating temperature Tl) is situated in the region of the first and the second cooling spacing kl, k2, and a cooling and cooled foam SK (said cooled foam being at the cooling temperature T2) which disintegrates during the cooling to form liquid is situated in the region above the first and the second cooling spacing kl, k2.
The register system 20 is preferably supported on the degassing container 2 via a plurality of carriers 7 which are preferably arranged in a uniformly distributed manner over the circumference of the degassing container 2 and preferably extend in a star-shaped manner toward the center of the degassing container 2 (figures 2 to 8). Four carriers 7 are preferably provided (figure 3), it being possible for said number to also vary by from one to two in both directions. In a generalized embodiment (not shown) of the register system 20, the course of each carrier 7 in relation to the heating register 20.1 preferably results from a lower contour of the heating register 20.1, against which lower contour each carrier 7 bears tightly from below.
In the above-described specific embodiment of the register system 20 in the form of a monopipe at least for the heating register 20.1, the course of each carrier 7 (as shown in figures 2 to 8) in relation to the heating register 20.1 results from the positioning of the first pipes 8, against which each carrier 7 bears tightly from below in a tangential manner. The contact points between the first pipes 8 and the respective carrier 7 which bears tangentially against them result in an imaginary contact line PL on each carrier 7. In the course of the contact line PL, securing means 12 for the first and the second pipes 8, 9 are provided on the carrier 7, which securing means 12 are connected fixedly to the carrier 7. The securing means 12 are preferably of plate-shaped configuration and are oriented upright firstly in the direction of a longitudinal axis of the degassing container 2 and secondly in the direction of the contact line PL. Two adjacent securing means 12 in each case fix a first pipe 8 non-displaceably in the direction of the contact line PL, and each securing means 12 likewise fixes at least one second pipe 9 non-displaceably in the direction of the contact line PL.
In the embodiment which is shown by way of example, the register system 20 consists of the first and the second pipe 8, 9 which are configured in each case as a monopipe and are preferably spirally or helically wound. The first pipe lies on the carriers 7 and is positionally fixed between two securing means 12. It acts as a heating pipe and, as measured from the free surface N, is at the first heating spacing hl, and is at the second heating spacing h2 from the distributor screen 3 (figures 7, 8), which therefore defines the inlet of the foam S into a warming or heating zone in the respective growth direction of the foam r(S). In relation to the intermediate spacing between two adjacent first pipes 8, two immediately adjacent second pipes 9 are arranged in the region above the first cooling spacing kl, as measured from the first heating spacing hl, and in the region of the second cooling spacing k2, as measured from the second heating spacing h2.
The second pipes 9 are supported in recesses of the securing means 12 in such a way that there is the spacing both among one another and in relation to the first pipes 8, also with a view to ensuring the first and the second cooling spacing kl, k2.
Merely the carriers 7 and the securing means 12 which are of as narrow configuration as possible in terms of strength lie in the growth direction of the foam r(S), without appreciably treating said foam thermally. In relation to the growth direction of the foam r(S), in a correspondingly projected direction, they contribute rather to a mechanical impairment of the foam S and therefore to the desired foam breaking.
It has proven advantageous if the heating and/or the cooling temperature Ti, T2 of the foam S are/is set indirectly via the heating medium temperature and the coolant temperature TH, TK
in a manner which is dependent on an oxygen concentration 0(02) of the degassed liquid P', which oxygen concentration 0(02) is measured in or at the outlet A or in a pipeline which opens out of the outlet A. To this end, it is provided that the measuring device 14 is a measuring device for oxygen 14.1 which determines the oxygen concentration c(02) and transmits it to the control device 13 (figure 3). Furthermore, a measuring device 14 can be arranged in the head space of the degassing apparatus 10, 10.1, 10.2 above the cooling register 20.2, which measuring device 14 is a measuring device for the detection of foam (for example, a foam sensor), said foam growing above the cooling register 20.2 and generating a foam signal LS there, which foam signal LS is transmitted to the control device 13 (figure 3).
Tests with the degassing apparatus 10, 10.1, 10.2 according to the invention have shown that the oxygen concentration in skimmed milk or semi-skimmed milk of c(02) = 9 ppm can be reduced to 0.9 ppm. The effective control of the foam formation which leads as a result to breaking of the foam S which is formed and grows ensures that the degassing apparatus 10, 10.1, 10.2 operates over the entire operating time under optimum degassing conditions, which is ultimately reflected in the above-specified measuring result.
Moreover, the method according to the invention and the apparatus for carrying it out show a further positive result.
This consists in that the highly effective foam breaking at the location of the foam generation leads to a recovery of pure liquid. The aromas which are contained in the foam S and are possibly highly volatile and therefore readily leave the head space of the degassing container 2 under the forcing action of a possibly present vacuum source remain in the recovered liquid and are returned on a short path via the free surface N into the liquid supply and via the surface of the liquid film F into the latter.

List of Designations of the Abbreviations which are Used Figure 1 (Prior Art) 10 Degassing apparatus (general) 10.1 Degassing apparatus of a first type (with a lower, lateral inlet) 10.2 Degassing apparatus of a second type (with a lower, central inlet) 2 Degassing container 2a Upper floor 2b Lower floor 2c Container shell 2d Outlet stub 3 Distributor screen 4 Feed pipe 4a Outlet opening 5 Baffle plate 6 Circumferential annular gap A Outlet E Inlet F Liquid film N Free surface (free level) P Liquid to be degassed (liquid food product) P' Degassed liquid S Foam /(S) Growth direction of the foam Figures 2 to 9 7 Carrier 8 First pipe (heating pipe) 9 Second pipe (cooling pipe) 12 Securing means 13 Control device 14 Measuring device 14.1 Measuring device for oxygen First valve 10 16 Second valve Register system 20.1 Heating register 20.2 Cooling register DH First diameter (first pipe; heating pipe) DK Second diameter (second pipe; cooling pipe) HL Heating capacity KL Cooling capacity LH First length (first pipe; heating pipe) LK Second length (second pipe; cooling pipe) LS Foam signal OH Heating area (first pipe; heating pipe) OK Cooling area (second pipe; cooling pipe) PL Contact line SH Heating and heated foam SK Cooling and cooled foam Ti Heating temperature (of the foam S) T2 Cooling temperature (of the foam S) T3 Liquid temperature (of the liquid P, P') TH Heating medium temperature TK Coolant temperature WH Heating medium WK Coolant c(02) Oxygen concentration hl First heating spacing (first pipe; heating pipe) h2 Second spacing (first pipe; heating pipe) kl First cooling spacing (second pipe; cooling pipe) k2 Second cooling spacing (second pipe; cooling pipe)

Claims (28)

Claims

1. A method for controlling the foam formation in a degassing apparatus (10; 10.1, 10.2) for liquids (P), .cndot. the liquid (P) being fed to the degassing apparatus (10;
10.1, 10.2), dwelling there for the purpose of gas separation, and being discharged as a degassed liquid (P') below a free surface (N) which is formed from the liquid (P) in the degassing apparatus (10; 10.1, 10.2), .cndot. the liquid (P) being configured as a liquid film (F) above the free surface (N) and on a surface of a distributor screen (3), and entering from there into the free surface (N), .cndot. the liquid film (F) being of screen-shaped configuration, .cndot. a foam (S) which is formed from the liquid (P) at a liquid temperature (T3) being released and growing in each case above the free surface (N) and out of the latter and/or above the liquid film (F) and out of the latter, .cndot. the respective growing foam (S), beginning at a first heating spacing (h1) from the free surface (N) which releases the foam (S) and beginning at a second heating spacing (h2) from the liquid film (F) which releases the foam (S), first of all experiencing heating from the liquid temperature (T3) to a heating temperature (T1) in a register system (20) consisting of a heating register (20.1) and a cooling register (20.2), .cndot. the respective further-growing heated foam (S) subsequently, beginning at a first cooling spacing (k1) from the first heating spacing (h1) and beginning at a second cooling spacing (k2) from the second heating spacing (h2), experiencing cooling to a cooling temperature (T2) in the register system (20), .cndot. means for carrying out the heat exchange for heating and cooling the foam (S) being permeable to flow in a growing direction of the foam (r(S)), .cndot. the heating and/or the cooling temperature (T1, T2) being set in a manner which is dependent on the properties of the liquid (P; P') and/or the physical boundary conditions, and .cndot. the volumetric flow, the viscosity, the pressure, the temperature and/or the composition of the liquid (P) in the region of the feed into the degassing apparatus (10;
10.1, 10.2) being understood as being among the properties of the liquid (P), and the oxygen concentration (c(O2)) in the region of the discharge from the degassing apparatus (10; 10.1, 10.2) being understood as being among the properties of the degassed liquid (P'), and the pressure and/or the result of the foam breaking in the degassing apparatus (10; 10.1, 10.2) being understood as being among the physical boundary conditions.

2. The method as claimed in claim 1, characterized in that the heating of the foam (S) starts in each case after the first heating spacing (h1) and the second heating spacing (h2) which are identical to one another, and/or in that the cooling of the foam (S) starts in each case after the first cooling spacing (k1) and the second cooling spacing (k2) which are identical to one another.

3. The method as claimed in claim 1 or 2, characterized in that an extent region of the heated foam (S) and an extent region of the cooled foam (S) are directly side by side, as viewed in an associated growth direction of the foam (r(S)), without overlapping one another completely or at least partially.

4. The method as claimed in one of the preceding claims, characterized in that the heating and the cooling of the foam (S) take place by way of indirect heat exchange.

5. The method as claimed in one of claims 1 to 3, characterized in that the heating and/or the cooling of the foam (S) take/takes place by way of direct heat exchange on the basis of the Peltier effect.

6. The method as claimed in claim 4, characterized in that a heating medium (W H) and a coolant (W K) are provided as heat exchange medium for the indirect heat exchange.

7. The method as claimed in one of claims 1 to 6, characterized in that a cooling capacity (KL) in the region of the cooling of the foam (S) is designed to be greater than a heating capacity (HL) in the region of the heating of the foam (S).

8. The method as claimed in one of claims 1 to 7, characterized in that the heating and/or the cooling temperature (T1, T2) are/is set by means of a setting function which is generated and stored before or during the start up of the degassing apparatus (10; 10.1, 10.2).

9. A degassing apparatus for liquids (P) having an apparatus for controlling the foam formation in the degassing apparatus (10; 10.1, 10.2), suitable for carrying out the method as claimed in claim 1, having a degassing container (2) which has an inlet (E) for the liquid (P), having an outlet (A) for a degassed liquid (P'), which outlet (A) opens from the degassing container (2) at the lower end, having a free surface (N) which is formed by the liquid (P) in the degassing container (2), having a distributor screen (3) which is arranged above the free surface (N), is of screen-shaped configuration, and on the surface of which the liquid (P) is configured as a liquid film (F), having a feed pipe (4) which is connected on one side on the end side to the inlet (E) and on the other side on the end side to a circumferential annular gap (6) which opens at the upper end of the distributor screen (3), having the circumferential annular gap (6), via which the liquid (P) for the liquid film (F) is output, characterized .cndot. in that a register system (20) which consists of a heating register (20.1) and a cooling register (20.2) is provided, which register system (20) encloses, by way of the heating register (20.1), the free surface (N) and that surface of the distributor screen (3) which forms the liquid film, in a manner which is annular in the region of the foam formation and which is spaced apart at a first heating spacing (h1) from the free surface (N) and at a second heating spacing (h2) from that surface of the distributor screen (3) which forms the liquid film, .cndot. in that the cooling register (20.2) is arranged offset, as viewed in a respective growth direction of the foam (r(S)), with respect to the heating register (20.1) by a first cooling spacing (kl) in the region of the free surface (N) and by a second cooling spacing (k2) in the region of the distributor screen (3), .cndot. in that the register system (20) is assigned a control device (13) which changes a heating capacity (HL) of the heating register (20.1) and/or a cooling capacity (KL) of the cooling register (20.2) in a manner which is dependent on the properties of the liquid (P, P') and/or the physical boundary conditions, and .cndot. in that the control device (13) is connected to a measuring device (14, 14.1) which determines at least one of the properties of the liquid (P, P') and/or the physical boundary conditions.

10. The degassing apparatus as claimed in claim 9, characterized in that the measuring device (14) is a measuring device for oxygen (14.1), which measuring device determines an oxygen concentration (c(O2)) of the degassed liquid (P') in or at the outlet (A) or in a pipeline which opens out of the outlet (A), and transmits it to the control device (13).

11. The degassing apparatus as claimed in claim 9 or 10, characterized in that a vacuum source in the form of a liquid ring pump or in the form of a single stage or multiple stage ejector is connected to a head space of the degassing container (2).

12. The degassing apparatus as claimed in one of claims 9 to 11, characterized in that the heating register (20.1) is flowed through by a heating medium (W H(, and the cooling register (20.2) is flowed through by a coolant (W K).

13. The degassing apparatus as claimed in one of claims 9 to 11, characterized in that the heating register (20.1) and/or the cooling register (20.2) are/is configured in each case as a Peltier element.

14. A register system for the apparatus for controlling the foam formation in the degassing apparatus (10; 10.1, 10.2), which register system consists of a heating register (20.1) and a cooling register (20.2), as claimed in one of claims 9 to 12.

15. A register system for the apparatus for controlling the foam formation in the degassing apparatus (10; 10.1, 10.2), which register system consists of a heating register (20.1) and a cooling register (20.2), as claimed in one of claims 9 to 11 and 13.

16. The register system as claimed in claim 14 or 15, characterized in that the heating register (20.1) and the cooling register (20.2) in each case enclose the distributor screen (3) in an axially symmetrical manner.

17. The register system as claimed in one of claims 14 to 16, characterized in that the first heating spacing (h1) and the second heating spacing (h2) are identical to one another, and/or in that the first cooling spacing (kl) and the second cooling spacing (k2) are identical to one another.

18. The register system as claimed in one of claims 14 to 17, characterized in that an overall cooling area (O K) of the cooling register (20.2) is designed to be greater than an overall heating area (OH) of the heating register (20.1).

19. The register system as claimed in claim 14, characterized .cndot. in that the heating register (20.1) consists of first pipes (8), and the cooling register (20.2) consists of second pipes (9), .cndot. in that the first pipes (8) and the second pipes (9), in each case per se, are arranged in a row next to one another and spaced apart from one another, .cndot. in that the first pipes (8) are positioned at the first heating spacing (hl) from the free surface (N) and at the second heating spacing (h2) from that surface of the distributor screen (3) which forms the liquid film, .cndot. in that the second pipes (9) are positioned at the first cooling spacing (kl), starting from the first heating spacing (h1), and at the second cooling spacing (k2), starting from the second heating spacing (h2), .cndot. and in that second pipes (9) are arranged over and distributed to the respective gaps between the first pipes (8).

20. The register system as claimed in claim 19, characterized in that the first and the second cooling spacing (k1, k2) are in each case consistently greater than a greatest first diameter (DB) of the first pipes (8) at the associated cooling spacing (k1, k2).

21. The register system as claimed in claim 19 or 20, characterized in that the first pipes (8) and the second pipes (9) in each case have identical diameters among themselves, and in that the first pipe (8) has a greater diameter than the second pipe (9).

22. The register system as claimed in one of claims 19 to 21, characterized in that the first pipes (8) and/or the second pipes (9) are configured in each case as a monopipe.

23. The register system as claimed in claim 22, characterized in that the first pipe (8) and the second pipe (9), in each case configured as a monopipe, are in each case of spiral configuration in a region which is assigned to the free surface (N), and are in each case of helically wound configuration in a region which is assigned to that surface of the distributor screen (3) which forms the liquid film.

24. The register system as claimed in one of claims 19 to 23, characterized in that in each case two second pipes (9) are positioned in a symmetrical and uniformly distributed manner over the respective gap between two adjacent first pipes (8).

25. The register system as claimed in one of claims 14 to 24, characterized in that the register system (20) is supported on the degassing container (2) via a plurality of carriers (7) which are arranged in a uniformly distributed manner over the circumference of the degassing container (2) and extend in a star-shaped manner toward the center of the degassing container (2), and in that the course of each carrier (7) in relation to the heating register (20.1) results from a lower contour of the heating register (20.1), against which lower contour each carrier (7) bears tightly from below.

26. The register system as claimed in one of claims 19 to 24, characterized in that the register system (20) is supported on the degassing container (2) via a plurality of carriers (7) which are arranged in a uniformly distributed manner over the circumference of the degassing container (2) and extend in a star-shaped manner toward the center of the degassing container (2), and in that the course of each carrier (7) in relation to the heating register (20.1) results from the positioning of the first pipes (8), against which each carrier (7) bears tightly tangentially from below.

27. The register system as claimed in claim 25 or 26, characterized in that four carriers (7) are provided.

28. The register system as claimed in claim 26 or 27, characterized .cndot. in that there is an imaginary contact line (PL) on each carrier (7) comprising the contact points between the first pipes (8) and the carrier (7) which bears in each case tangentially against them, .cndot. in that securing means (12) for the first and the second pipes (8, 9) are provided on the carrier (7) in the course of the contact line (PL), .cndot. in that the securing means (12) are connected fixedly to the carrier (7), .cndot. in that the securing means (12) are of plate-shaped configuration and are oriented upright firstly in the direction of a longitudinal axis of the degassing container (2) and secondly in the direction of the contact line (PL), .cndot. in that two adjacent securing means (12) in each case fix a first pipe (8) non-displaceably in the direction of the contact line (PL), and .cndot. in that each securing means (12) fixes at least one second pipe (9) non-displaceably in the direction of the contact line (PL).