BR112019000380B1 - PROCESS AND INSTALLATION FOR THE TREATMENT OF HEAT SENSITIVE LIQUID FOOD PRODUCTS, AND CENTRIFUGAL PUMP FOR TRANSPORTING THESE PRODUCTS - Google Patents

Abstract

The invention relates to a process for treating heat-sensitive liquid food products, to an installation for carrying out the process and to a centrifugal pump for such installation. This is achieved with the process technique, with the following treatment steps (a) and (d): the liquid food product (p), (c) undergoes a third cooling (k3) in a housing lid (8) of a pump housing (12) of the centrifugal pump (54), connected to the outlet pipe (52) or suction nozzle (76); (d) serves, with a part of its volumetric flow conveyed, in an impeller wheel (100) of the centrifugal pump (54), configured open to the housing cover (8) of the centrifugal pump (54), a planned washing of the housing of the pump (12) and the impeller wheel (100), through a rear slot (s1) of the impeller wheel which is provided between a housing wall (10) of the centrifugal pump (54) and the impeller wheel (100), and through an anterior slot (s2) of the impeller wheel which is provided between the housing cover (8) and the impeller wheel (100), the volumetric flows of the planned washings exceed by up to a multiple the forced compensation flows within the impeller housing. pump (12), which result from a hydraulically optimized design of the centrifugal pump (54) with a respective minimum rear gap and a minimum front gap (s1*, s2*), which guarantee the mechanical functionality of the centrifugal pump (54) .

Description

TECHNICAL FIELD

[001] The invention relates to a process and installation for treating heat-sensitive liquid baby food concentrates, nutritional drinks or milk for making cheese, in which water vapor directly heats the liquid food product to form of a germ-free additive in an infusion vessel, into which, by distension to a lower pressure, water is withdrawn from the food product in an amount corresponding to that of the previously fed water vapor, and in which the food product The liquid undergoes transport via a first conveyor device configured as a centrifugal pump, between heating and distension. The invention further relates to a centrifugal pump for such an installation and to a driving wheel for such a centrifugal pump.

[002] Heat-sensitive liquid food products of the type mentioned initially contain relatively a lot of protein, a lot of dry mass and little water, and they can have a low, medium or high viscosity. The concept of sensitivity to heat must be understood, next, in such a way that these food products, preferably at temperatures above 100°C, tend to ignite, that is, under these conditions they tend to form encrustation on the walls of the container infusion pump and the centrifugal pump that transports them. This incrustation is also called "produkt-Fouling". Product-fouling reduces the useful life or operating time of the infusion container and especially the centrifugal pump between two cleaning cycles.

STATE OF THE TECHNIQUE

[003] Especially critical regions of the installation for carrying out the process are the bottom region of the infusion container, which tapers downwards to an exit opening, and a conveyor device, which is arranged in a connection line between the outlet opening of the infusion container and a vacuum chamber that serves to distend the heated liquid food product. In the case of the conveyor device, it may be a displacement pump, for example a toothed wheel pump, or also a centrifugal pump. The conveyor device is arranged at a distance from the infusion container or immediately at its exit opening. An accumulation of heated liquid food product in the bottom region of the brewing vessel and in the connection line connected to the conveyor device leads to an undesirable and indefinite residence time. An accumulation of liquid food products in the brewing container must be avoided. Therefore, there is a lack of proposals to overcome this deficiency.

[004] In heating installations with an infusion container, it is known to transport the heated liquid food product directly from the infusion container with a rotary displacement pump, for example a gear wheel pump, its housing having a cooling medium and the housing connects directly to the outlet opening of the infusion container (EP 0784706 B1). A gearwheel pump has, under constructive constructions, a self-cleaning capability, because the gearwheels closely engage each other and scrape along the associated housing walls and consequently prevent increasing scale formation (Produkt-Fouling).

[005] Document WO 2011/101077 A1, which claims the priority of DE 10 2010 008 448 A1, discloses a UHT installation for treating heat-sensitive liquid food foods, in which, among other things, downstream of a container infusion system, in a connection line to a vacuum chamber, a conveyor device is arranged, which is configured as a displacement pump. The infusion container has, in a lower region, a bottom part that leads to an exit opening, a means of cooling this bottom part. The displacement pump may then be arranged at an unquantified distance from the outlet opening from the infusion container. In the case of the displacement pump, a rotary pump is preferably used, which can be configured, for example, as previously mentioned, as a gear wheel pump or also as a vane cell, helical wheel, impeller or rotary piston pump. . Displacement pumps that operate in an oscillating mode are also basically usable when the volumetric current oscillations conditioned by the oscillatory operation are compensated by appropriate means or are of no importance in the treatment process.

[006] In document WO 2016/012026 A1 it is known from EP 0794706B1 an installation for thermal treatment of heat-sensitive liquid foods altered in such a way that now, in an unchanged configuration of the individual aggregates of the installation, the refrigeration envelope surrounding the bottom of the infusion container, which serves for bottom cooling, extends towards the pump and, according to an advantageous configuration, even into the pump housing. In the case of the pump, it is a displacement pump, preferably a gear or piston pump. However, a centrifugal pump is also claimed, without specifically indicating how this centrifugal pump is constructively configured. Therefore, it can be assumed that a conventional, hydraulically optimized centrifugal pump is envisaged here, known to a person skilled in the art in its basic construction.

[007] In document WO 2010/086082 A1, which claims the priority of DE 10 2009 006 248 A1, an infusion system for a liquid food product to be heated is described, in which an infusion chamber has a bottom part bottom with a cooling medium. The infusion chamber continues into an outlet tube that connects to an outlet opening at the bottom, also featuring a cooling medium. It is not known whether the outlet pipe leads to a conveyor device also configured as usual, directly or indirectly via a connecting line.

[008] A centrifugal pump for non-problematic liquid food products, such as water, is well known in its basic construction. It is configured and designed in such a way that it presents as high a degree of hydraulic effect as possible, that is, with a given drive energy, it achieves as large a product as possible from volumetric current and transport height. In a pump housing consisting, as a rule, of at least two housing parts, an impeller wheel with blades is arranged on a shaft. Within the pump housing a distributing apparatus in the form of a spiral housing or an annular space without blades connects to an outlet cross-section of the annular circumferential impeller wheel. In the housing frame on the suction side, a housing cover, there is an inlet axial to the axis of the push wheel, configured, as a rule, as so-called suction nozzles and an outlet that opens tangentially on the circumferential side, which , as a rule, is configured as so-called pressure nozzles. With the housing part facing the suction side towards the rear housing wall, the pressure side of the drive wheel forms a so-called back space on the wheel side, which has, as a rule, a small axial extension with views to a good degree of hydraulic effect of the centrifugal pump. This axial or narrow slot extension is narrowly dimensioned in such a way that, with measured manufacturing tolerances, the mechanical functional capacity of the centrifugal pump is assured. In a similar way, the front side of the driving wheel, and here are front side free blade edges, front, so-called open, is adapted to the course of the housing cover with slot as narrow as possible. To reduce an axial force, which results from the pressure forces acting on the push wheel on both sides, several pressure compensation perforations of relatively small diameters are arranged, as a rule, in the region adjacent to the push wheel and distributed along its side. circumference on the drive wheel side.

[009] In heat-sensitive liquid food products of the type mentioned initially, it is mainly observed that, in the case of their transport through a centrifugal pump, there is a minimal tendency for scale to form on the walls of the centrifugal pump. For example, in the case of direct heating of heat-sensitive liquid food products in an infusion vessel and then transport of the heated liquid food product from the infusion vessel by means of a centrifugal pump of common construction, i.e. of optimized construction hydraulically, connected downstream, it was found that this centrifugal pump is closed in a short time, in this sense it is about seconds to a few minutes, through "produkt-fouling" (formation of product encrustations) and thus thrown away of operation. Especially critical regions here are the suction region of the pusher wheel, because undissolved gases here and especially uncondensed water vapor can increase "product-fouling", and the narrow rear side space of the wheel.

[0010] For the concrete configuration of a centrifugal pump in a plant for treating heat-sensitive liquid food products, in which the product undergoes direct heating by means of culinary water vapor, so far no satisfactory solution has been known with aimed at a sufficiently long service life of the centrifugal pump.

[0011] It is the objective of the present invention to provide a process of the type mentioned initially, an installation for carrying out the process as well as a centrifugal pump for this installation and a driving wheel for this centrifugal pump, which, when treating sensitive liquid food products to heat of the type mentioned initially, prevent the tendency for product fouling to form in the infusion container and then even inside the centrifugal pump, with the centrifugal pump in particular having a significantly extended useful life compared to centrifugal pumps. hydraulically optimized according to the state of the art. Another objective is to modify a centrifugal pump, preferably a commercial type, in such a way that it prevents the growth of scale formation in its critical regions and thus achieves the desired service life extension.

SUMMARY OF THE INVENTION

[0012] This objective is achieved through a process with the characteristics of claim 1. Advantageous configurations of the process according to the invention are the subject of the associated dependent claims. An installation for carrying out the process is the object of coordinated claim 10. Advantageous configurations of the installation according to the invention are described in the associated dependent claims. A centrifugal pump for an installation according to claim 10 is the subject of claim 17. Advantageous configurations of the centrifugal pump according to the invention are the subject of the associated dependent claims. An impeller wheel for the centrifugal pump of the claimed type is the subject of claim 38.

[0013] In the process art, the invention starts from a process for treating heat-sensitive liquid food products, such as whey protein concentrates, baby food, liquid baby food concentrates, nutritional drinks or milk for cheese production, in which water vapor directly heats the liquid food product to form a germ-free state in an infusion vessel, in which water is removed from the liquid food product through pressure attenuation to a lower pressure in an amount that corresponds to the amount of previously fed water vapor, in which the liquid food product, between heating and pressure attenuation, undergoes transport by means of a first conveyor device configured as a centrifugal pump.

[0014] The objective of the invention is achieved when, in the generic type process, after direct heating, the following treatment steps (a) to (d) are envisaged, in which the liquid food product: undergoes a first known cooling in si at least at the bottom of the container of the infusion container to an outlet opening therein; undergoes a second cooling in a tubular section that connects directly to the outlet opening, which is configured either through an outlet tube that flows from the infusion container or through a suction nozzle of the centrifugal pump; undergoes a third cooling in a housing cover of a pump housing of the centrifugal pump, which connects directly to the outlet pipe or suction nozzle; serves, with a part of its volumetric stream carried in a centrifugal pump impeller wheel, which is configured open to the centrifugal pump housing cover, at least one planned washing of the pump housing and the impeller wheel through a slot rear in the impeller wheel, which is provided between a rear housing wall of the centrifugal pump and the impeller wheel, and through an anterior slot of the impeller wheel, which is provided between the housing cover and the impeller wheel, with the volumetric currents from planned washings exceed by up to a multiple the forced compensation flows within the pump housing, which result from the hydraulically optimized design of the centrifugal pump with a respective minimum rear gap and a respective front gap of the impeller wheel, which guarantee the mechanical functionality of the centrifugal pump.

[0015] In step (d) it is an essentially inventive solution idea. Steps (a) to (c) ensure that another basic inventive idea, namely: the continuous cooling of the heated liquid food product, present in the bottom region of the infusion container and transported to the pressure nozzle of the centrifugal pump, leads to a concrete solution.

[0016] To intensify cooling, a process configuration provides that the liquid food product undergoes a fourth cooling on the rear wall of the pump housing housing.

[0017] A first and second wash of the pump housing and the impeller wheel, according to a preferred process configuration, are generated through respective recirculation through the impeller wheel, driven through respective pressure differences in the pump housing. In this case, the first wash occurs through the rear slot of the push wheel between the push wheel and the rear housing wall, with the first wash interfering with the flow through the push wheel. The second wash occurs through the front slot of the push wheel between the housing cover and the push wheel, with the second wash also interfering with the flow through the push wheel. Furthermore, a third wash occurs through compensation flows between a respective pressure and suction side of an open pusher roller blade and through the anterior slot of the pusher wheel, and the measures that generate the second wash have the consequence of fourth wash forcibly.

[0018] Continuous cooling of the heated liquid food product is achieved, as envisaged in a first proposal in this regard, when the cooling units are operated separately from each other. A second proposal, which reduces the cost of cooling techniques in this sense, provides, in relation to cooling, that at least two cooling systems are connected to each other in series. In both cases, to optimize the cold transfer line, as this is foreseen by a third proposal, the cooling operations are carried out countercurrently in relation to the heated liquid food product.

[0019] An installation according to the invention for carrying out the process according to the invention presents the combination of the following characteristics partially known per se: • an infusion container, in which water vapor directly heats the liquid food product to form of a germ-free state; • a vacuum chamber in fluid connection with the brewing vessel via a connecting line, in which water in an amount corresponding to that of the previously fed water vapor is withdrawn from the heated liquid food product through reduction of surface tension at a lower pressure; • a first conveyor device, configured as a centrifugal pump, arranged in the connection line, for transporting the heated liquid food product from the infusion container to the vacuum chamber; • an outlet opening arranged in a container bottom of the infusion container for withdrawing the heated liquid food product; • a tubular section that connects to the outlet opening for conveying the heated liquid food product, which is formed either through an outlet tube that flows from the infusion container or through a suction nozzle of the centrifugal pump; • a cooling agent space on the container bottom side for cooling the heated liquid food product applying to the container bottom; • a cooling agent space on the outlet side or a cooling agent space on the suction nozzle side for cooling the heated liquid food product traveling through the tubular section; • a pump housing of the centrifugal pump, which is formed from a housing cover and a housing wall and has a cooling agent space on the side of the housing cover for cooling the transported heated liquid food product; • the centrifugal pump, which has an impeller wheel open to the housing cover and is configured in such a way that, with a part of the volumetric flow of heated liquid food product conveyed in the impeller wheel, at least one planned washing of the pump housing and impeller wheel through a rear slot of the impeller wheel, which is provided between the rear wall of the housing and the impeller wheel, and through a front slot of the impeller wheel, which is provided between the housing cover and the impeller wheel, and since the volumetric flows of the planned washes exceed by up to a multiple the forced compensation flows within the pump housing, which result from a hydraulically optimized design of the centrifugal pump with a respective minimum rear gap and a minimum back pressure of the impeller wheel, which guarantee the mechanical functionality of the centrifugal pump.

[0020] The previously mentioned complex of characteristics represents, in addition to the characteristics for cooling, an essential aspect of the installation according to the invention.

[0021] To intensify cooling, another configuration provides for the pump housing to have a cooling agent space on the rear wall side of the housing.

[0022] To carry out a first wash, it is proposed that this occurs through the rear slot of the pusher wheel between the pusher wheel and the rear wall of the housing via at least one wash perforation arranged on the rear side of the pusher wheel. Regarding a second wash, another proposal envisages that it occurs through the front slot of the push wheel between the housing cover and the push wheel. Furthermore, a third wash occurs through compensating flows between a respective pressure and suction side of an open impeller wheel blade and through the anterior slot of the impeller wheel, and the measures that generate the second wash result in the third wash. forcibly.

[0023] Continuous cooling of the heated liquid food product is achieved, as this is predicted by a first proposal in this regard, when the cooling agent space on the container bottom side, the cooling agent space on the tube side outlet or suction nozzle side, the cooling agent space on the cover side of the housing or the cooling agent space on the rear wall side of the housing are ordered with cooling agent separately from each other. A second proposal, which reduces the cost of cooling techniques, provides for cooling that at least two cooling agent spaces are connected to each other in series.

[0024] A centrifugal pump according to the invention, which is suitable for an installation for treating heat-sensitive liquid food products, is part of a known centrifugal pump per se with an inlet, an outlet, a pump housing, the which is formed by at least one housing cover and a rear housing wall, a pump chamber configured in the pump housing and in fluid communication with an inlet and an outlet, and a vaned impeller wheel rotatably received in the pump chamber. . Between the two adjacent blades a respective blade channel is configured, which is configured open towards the housing cover and closed towards the rear wall of the housing through a rear side of the push wheel. A rear drive wheel slot is provided between the housing wall and the drive wheel and a front drive wheel gap is provided between the housing cover and the drive wheel.

[0025] The basic inventive idea consists of washing the impulsive wheel itself and its adjacent critical regions up to the immediate edge of the anterior side of the impeller wheel, on the pump housing side, and the rear side of the impeller wheel, with the liquid food product to be transported and thereby prevent the formation of scale, and another basic inventive idea consists of simultaneously cooling, during washing according to the invention, at least edges on the side of the pump housing in the region of the housing cover.

[0026] The liquid food product thus serves, with a part of its transported volumetric flow, for planned washings of the pump housing and the impeller wheel itself. Therefore, the volumetric flows of the planned washes exceed by up to a multiple the forced compensation flows in the pump housing, which result from a hydraulically optimized design known in the art of centrifugal pumps. This compensation region should not be understood by the person skilled in the art as an indication of an open region upwards, but rather is designed, in the case of specific application, in such a way that the required useful life of the centrifugal pump is achieved with guarantee of the required efficiency. of the installation and, consequently, of the centrifugal pump, under economic criteria. The relationship of the planned volumetric flows, resulting from the measurements according to the invention, with the volumetric flows of the forced compensation flows, conditioned through the hydraulically optimized design and known in the art, in the concrete implementation and depending on the application case, is between 1.5 to 10, preferably between 2 and 5. Cooling prevents the tendency of the liquid food product to ignite on the walls of the centrifugal pump. This happens with planned dispensation of an optimum degree of hydraulic effect. In the centrifugal pump according to the invention, a volumetric flow is transported in the impeller wheel which is increased by the sum of all recirculating volumetric washing flows in relation to the volumetric flow sucked through the suction nozzle. The volumetric washing flows carry volumes from the core of the blade channels to the cooled walls of the housing and then back into the impeller wheel, and the cooling attack does not cause uncondensed water vapor to condense and, consequently, the tendency to scale formation is avoided.

[0027] The contexts represented above indicate that a centrifugal pump washed according to the invention with the liquid food product transported by it has an impeller wheel whose hydraulic transport performance, in relation to the impeller wheel, has to be higher than the hydraulic conveying performance that actually adjusts to the pressure nozzle in the end result. If, to realize a flushed centrifugal pump of the type in question, a hydraulically optimized centrifugal pump is chosen, then its nominal transport performance has to be chosen correspondingly higher in the transport performance efficiency mentioned above. With equal nominal transport performance, an external diameter of the impeller wheel of the washed centrifugal pump must therefore be larger than such a diameter for a hydraulically optimized centrifugal pump.

[0028] The concrete solution for realizing the aforementioned basic inventive ideas is that the rear and/or lower slot of the impeller wheel, which must be necessarily indicated between the impeller wheel and the pump housing, in relation to a respective minimum front slot and a minimum rear slot of the impeller wheel, which guarantees the mechanical functionality of the centrifugal pump, is/are enlarged up to a multiple by reducing the width of the impeller wheel in the region of the front slot and the rear slot of the impeller wheel . By enlarging these impeller wheel slots, it is possible to generate the desired and necessary washing flows. The respective width of the front slit and the rear slit of the drive wheel can be dimensioned depending on specific properties of the liquid food product.

[0029] To intensify cooling, another configuration provides that the rear wall of the housing is also provided with a cooling agent space that can be passed through by a cooling agent.

[0030] Failure-free cooling of the pump housing is guaranteed when, as is also proposed, in addition to the cooling agent space on the cover side of the housing and the cooling agent space on the back wall side of the housing, the centrifugal pump inlet is configured in the form of a suction nozzle protruding from the housing cover. Such a configuration is not mandatory in relation to the centrifugal pump according to the invention. It is suitable, in the same way as a centrifugal pump, in which the configuration of a suction nozzle is not required, for a direct connection between the suction nozzle of the centrifugal pump and an infusion container provided in a bottom part, with this cooling agent space extends downwards to an outlet opening that opens from the bottom part, which then represents the final end of the infusion container. The suction nozzle can perform, in this configuration, the function of a tubular section, which connects to the final outlet opening of the infusion container. An arrangement with the centrifugal pump according to the invention is also possible, in which the outlet opening is arranged as the final end of the infusion container directly on the housing cover of the centrifugal pump, thus eliminating the need for the configuration of a nozzle. suction.

[0031] In all configurations, namely: in a centrifugal pump according to the invention with or without suction nozzles in combination with an infusion container, in which the outlet opening or a tubular section connected thereto represents the end Finally, an accumulation of heated liquid food product in the bottom part of the infusion container and in the regions that eventually connect to it until it enters the centrifugal pump is undesirable, since such accumulation leads to an undesirable and indefinite residence time, which must be prevented. The centrifugal pump according to the invention, in connection with an infusion container, has the task of removing liquid food product occurring in the latter immediately and completely, without causing clogging, even in the case of intermittent accumulation.

[0032] To intensify washing, it is further proposed that each helical channel between two adjacent blades of the impeller wheel in the region of its bordering impeller wheel rear side is in fluid connection with the rear slot of the impeller wheel through at least one perforation of wash that crosses the back side of the impeller wheel. This allows the radial attack depth of the associated wash flow to be fixed. In the case of wash perforation, these are, in general, continuous openings of any shape, that is, a simple circular shape is not mandatory to be produced.

[0033] A preferred configuration provides that the front slot of the push wheel undergoes a maximum enlargement in an external diameter of the push wheel, and that this enlargement continuously decreases to a minimum front slot of the push wheel up to the region of the entry into the blade channel. In this sense it is proposed that a reduction in the width of the push wheel in the outer diameter of the push wheel is 40 to 55%, preferably 50 to 55% of the width of a hydraulically optimized push wheel. In the region of the anterior slot of the impeller wheel, a second washing flow is formed, which extends from the region of the centrifugal pump outlet to the region of the inlet of the impeller wheel. By enlarging the front slit of the impeller wheel, the circulation of the free front edge of the open impeller wheel blades present there, even with a narrow impeller wheel slit, driven by the pressure difference between the pressure side and the suction side of the blades, is clearly intensified, whereby a third wash flow is generated according to plan.

[0034] Regarding the sizing of the rear slot of the push wheel, it was found that it is favorable, to achieve the objective, that access to the minimum radially oriented rear slot of the push wheel, which starts from the outer diameter of the push force and extends to a hub of the drive wheel, is enlarged by reducing the outer diameter of the drive wheel by up to 5 mm. Furthermore, an advantageous enlargement, according to the invention, of the rear slot of the push wheel consists in the fact that the rear side of the push wheel in the region between the washing perforation and the hub of the push wheel remains an expansion in the form of an annular surface, the axial depth is up to 2 mm, preferably 0.5 to 1 mm.

[0035] The positioning, configuration according to the shape and dimensioning of the washing perforation are characteristics with which the associated washing flow is fixed in relation to its radial attack depth, its conformation and quantitative intensity. In the case of arranging a single wash perforation in the blade channel, it is convenient, with regard to flow and manufacturing technique, that all these wash perforations are arranged in a single circle of holes with corresponding separation.

[0036] In relation to the positioning of the washing perforation within the blade channel, it has been shown to be advantageous that the geometric location for the respective point of penetration of the washing perforation is determined with the rear side of the impeller wheel, which also determines a diameter circle of holes, as follows: • approximately through the center of the blade channel, relative to the spacing of the blades at the point of penetration, and • approximately through the center of an extension of a flow wire from the blade channel between its entry and exit.

[0037] The wash perforation is configured either circular with a perforation diameter or has a shape other than the circular shape with a hydraulic diameter decisive for this shape. The hydraulic diameter is known to be sized as a quotient of the fourfold passage cross-section of the wash hole and the circumference of the wash hole. It proved to be favorable to achieve the objective that the drilling diameter or hydraulic diameter is 30 to 50% and in this region preferably 40 to 50% of the spacing of the blades at the point of penetration.

[0038] The invention provides, according to another configuration, more than one washing perforation in each blade channel, each of the several washing perforations of a blade channel being arranged in an associated circle of holes and the circles of holes are radially distanced from each other. In this case, it is convenient that the cross-sections of the washing perforations in the various hole circles are smaller, with the diameter of the hole circle decreasing, because the pressure difference acting on the washing perforation becomes greater with the decrease in radial distance. of the washing hole of the centrifugal pump rotation shaft.

[0039] To ensure cooling that satisfies the specific properties of the heated liquid food product, the invention provides for the following connections of the cooling agent spaces. According to a first proposal in this regard, the cooling agent space on the possibly existing suction nozzle side, the cooling agent space on the cover side of the housing and the cooling agent space on the rear wall side of the housing are ordered with cooling agent separately from each other. A second proposal envisages a variant of configuration in which said at least two of the aforementioned cooling agent spaces are connected together in series. According to a third proposal, it is envisaged that the cooling agent space on the suction nozzle side is an integral portion of the cooling agent space on the cover side of the housing.

[0040] To provide the conditions for washing the rear slot and/or the front slot of the impeller wheel, the invention provides, from a hydraulic centrifugal pump of a commercially common centrifugal pump, that the rear slot and the front slot of the drive wheel are enlarged. This is carried out: • either by rotating the impeller wheel on both sides • or by means of a spacer element acting axially in the direction of a pump shaft, which is arranged between the housing cover and the rear wall of the housing, whereby the impeller wheel is not axially out of phase with respect to the rear wall of the housing or is axially out of phase correspondingly with the pump shaft in the pump chamber.

[0041] The choice of the hydraulically optimized centrifugal pump for this purpose is made with a view to the previously discussed difference in nominal transport performance between flushed centrifugal pump and hydraulically optimized centrifugal pump.

[0042] The invention also comprises an impeller wheel for a centrifugal pump, wherein the impeller wheel is rotatably received in the pump chamber of the centrifugal pump and the centrifugal pump is configured as set out above.

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] A detailed representation of the invention results from the following description and the attached drawing figures, as well as the claims. While the invention is carried out in the various configurations of a generic type process, in the various embodiments of an installation for carrying out the process and in the various embodiments of a centrifugal pump for such installation, the following is described, with the aid of the drawing, an example of an embodiment of a centrifugal pump according to the invention, which receives, in its pump housing, an impeller wheel according to the invention and which is in fluid communication with an outlet opening of an infusion container . They are shown:

[0044] Figure 1 - in schematic representation, an installation for treating heat-sensitive liquid food products according to the state of the art;

[0045] Figure 2 - in schematic representation, an infusion container for direct heating of a liquid food product in a direct connection with a rotary displacement pump, the arrangement being known from the prior art;

[0046] Figure 3 - a view of the centrifugal pump in a perpendicular direction, both its axis of rotation and the longitudinal axis of its pressure nozzle, with the axis of rotation being oriented in the direction of the force of gravity and the centrifugal pump is disposed directly into an outlet opening of an infusion container;

[0047] Figure 4 - a front view of the impeller wheel of the centrifugal pump according to figure 3 with an approximate indication of a first and a third washing perforation S1, S3, and

[0048] Figure 5 - in side view, a meridian section through the push wheel according to figure 4 corresponding to a cut line marked A-A with an approximate indication of the first and a second wash perforation S1, S2.

[0049] An installation 1000 known from the prior art according to figure 1 (for example, WO 2011/101077 A1) contains an infusion container 50, which presents, as a known infusion container of the first type 50* (e.g. example, WO 2010/086082 A1), in its headspace a product inlet 60, through which a liquid food product P, which is to be heat treated, is fed to this infusion container of the first type 50* centrally and in circular shape. A first water vapor D1 is fed, radially from the outside, to the fed liquid food product P, through an external water vapor inlet 61 for direct heating, and through an internal water vapor inlet 64 it is fed , radially inside, a second water vapor D2. The first type infusion container 50* undergoes a cooling agent feed through a cooling agent inlet 66 on the brewing side to a cooling agent space 50.4 on the bottom side of the container, for cooling K of a bottom From the first type infusion chamber 50*, the withdrawal of the cooling agent occurs through a cooling agent outlet 68 on the infusion side.

[0050] A first-type infusion container outlet opening 50* is connected to a first conveyor device 54 via an outlet tube 52, which is surrounded by a cooling agent space 52.1 on the side of the outlet tube. which device 54 is configured as a displacement pump, preferably as a rotary displacement pump, and is arranged in a connection line 70 leading from the first conveyor device 54 to an inlet of a vacuum chamber 56. The first conveyor device 54 conveys the heated liquid food product P from the first type infusion vessel 50* to the vacuum chamber 56. The vacuum chamber 56 is configured to withdraw from the cooled heated liquid food product P by reducing pressure the amount of water W as the called exhaust steam, which is fed to the infusion vessel of the first type 50* in the form of water vapor D, in the present case consisting of the first water vapor D1 and the second water vapor D2, and diverted through of a vapor outlet section 72 preferably arranged in the upper region. A liquid food product P* treated in this way leaves the vacuum chamber 56 through a withdrawal line arranged preferably at a bottom that tapers in the lower region in the trajectory through a second conveying device 58, which is preferably configured as a centrifugal pump. .

[0051] Figure 2 shows an infusion container 50, which, at an outlet opening, as an infusion container of the second known type 500, is directly connected to a rotary displacement pump, which removes the liquid food product P heated downwards (see WO 2016/012026 A1). The liquid food product P is fed centrally to the head region of the second type infusion container 540 through the product inlet 60 and the first water vapor D1 is introduced through the water vapor inlet 62 radially from the outside, which surrounds the central product jet. A bottom portion of the second type infusion vessel 500 is provided with a cooling element K, which extends downwardly to the rotary displacement pump 540 and into the pump housing. The cooling agent is fed into a rotary displacement pump 540 through a cooling agent inlet 67 on the pump side, its withdrawal occurs through the cooling agent outlet 68 on the infusion side.

[0052] The arrangement represented in figure 3 of a centrifugal pump 54 according to the invention, in which the geometric axis of rotation of a pump shaft 98 is oriented in the direction of the force of gravity, is suitable for connecting this centrifugal pump 54 with an inlet 76 configured as a suction nozzle directly to an outlet opening 50.3 in a container bottom 50.2 of an infusion container 50, which may be configured as a first or second type infusion container 50*, 500 and then is used for these configurations. The infusion container 50 transitions to a preferably cylindrical container wrap 50.1 above the container bottom 50.2 which preferably tapers downwards. The container bottom 50.2 and a portion of the attached portion of the container shell 50.1 are provided with a cooling agent space 50.4 on the side of the container, which has a first cooling agent inlet 78 for feeding and a first cooling agent outlet. 80 for removing a cooling agent for cooling the bottom of container K1.

[0053] The centrifugal pump 54 is especially suitable for transporting heat-sensitive liquid food products, such as whey protein concentrates, baby food, baby food concentrates, nutritional drinks or milk for making cheese, the which enter through an inlet 76 and exit through an outlet 94 configured as a pressure nozzle for the connection line 70 leading to the vacuum chamber 56. The centrifugal pump 54 also has, in a manner known per se, a pump housing 12 , which is formed by at least one housing cover 8 and a rear housing wall 10. In the pump housing 12 a pump chamber 98 is configured which is in fluid communication with the inlet 76 and the outlet 94, which receives rotatably a push wheel 100 (see figures 4 and 5). A tubular section 52, 76 is connected to the outlet opening 50.3, which may be formed either through the outlet tube 52 that flows from the infusion container 50 or through a suction nozzle 76 of the centrifugal pump 54. If the tubular section 52, 76 is configured as an outlet tube 52, then it may be surrounded by the cooling agent space 52.1 on the outlet side; if it is configured as suction nozzle 76.1, then it may be surrounded by a cooling agent space 76.1 on the suction nozzle side. In both cases the cooling agent space 52.1, 76.1 cooling agent is fed through a second cooling agent inlet 82 for cooling the outlet tube or suction nozzle K2 and withdrawn through a second cooling agent outlet. cooling 84.

[0054] The housing cover 8 is provided with a cooling agent space 8.1 on the housing cover side, which surrounds the housing cover 8, preferably completely or partially, or limits, for example, in the form of a a cooling bag. Cooling agent is fed to the cooling agent space 8.1 on the side of the housing cover through a third cooling agent inlet 86 for cooling the housing cover K3 and is withdrawn through a third cooling agent outlet 88. rear housing wall 10 may be provided with a cooling agent space 10.1 on the side of the rear housing wall 10, which surrounds the rear housing wall 10, preferably completely or partially, or limits, for example, in the form of cooling bag. Cooling agent is fed to the cooling agent space 10.1 on the side of the housing rear wall through a fourth cooling agent inlet 90 for cooling the housing rear wall K4 and is withdrawn through a fourth cooling agent outlet 92 Finally, figure 3 shows, approximately and schematically, a first washing flow S1, a second washing flow S2 and a third washing flow S3 according to the invention, which are explained in more detail in figures 4 and 5.

[0055] Figures 4 and 5 show the push wheel 100 open to the housing cover 8 and closed to the rear housing wall 10 with a plane and blades 2 curved backwards in relation to a direction of rotation n (see figure 4 ), which are preferably perpendicular to the side of the driving wheel 4, with a respective blade channel 2.1 being formed between two adjacent blades 2. The arrangement of backward curved blades is not a mandatory feature of the impeller wheel 100 for the centrifugal pump 54 according to the invention. An arrangement of blades oriented in a forward-curved or purely radial manner in flat or spatial curvature can be realized without restriction with a view to creating a centrifugal pump 54 flushed according to the invention. A push wheel side RS 100 formed substantially through the push wheel rear side 4 is spaced from the rear housing wall 10 in a rear push wheel slot s1 (figure 5). A front side VS of the push wheel 100 formed substantially across the front edges of the blades 2 is also spaced from the housing cover 8 in a front push wheel slot s2.

[0056] The trailing edge and/or the leading edge of pusher wheel s1, s2 are/are enlarged up to a multiple by reducing the width of the pusher wheel 100 in the region of the anterior slot and the rear slot of pusher wheel s1, s2 up to (factor 1.5 to 10, preferably 2 to 5) in relation to a respective minimum front gap and minimum rear gap of impeller wheel s1*, s2*, which guarantees the mechanical functionality of the centrifugal pump 54.

[0057] A preferred embodiment provides that the front drive wheel slot s2 undergoes a maximum enlargement in a drive wheel outer diameter DL of the drive wheel 100, which enlargement continuously decreases up to the region of the inlet for the blade channel 2.1 up to a minimum anterior drive wheel crack s2*. A reduction in this direction of the width of the push wheel 100 in the push wheel outer diameter DL is preferably 40 to 55%, preferably here 50 to 55% of the width of a hydraulically optimized push wheel.

[0058] Another preferred configuration provides that access to the minimum rear slot of radially oriented push wheel s1 *, which starts from the push wheel outer diameter DL of the push wheel 100 and extends to a hub of the push wheel 100, is enlarged by reducing the external diameter of the impeller wheel DL by up to 5 mm, whereby the impeller wheel 100 recedes a little radially on the outside in relation to the pump housing 12. An enlargement of the rear impeller wheel slot s1 consists, in accordance with the invention and preferably, in which the rear side of the push wheel 4 is enlarged in the form of a circular surface, in the region between the washing perforation 6 and the hub of the push wheel 100 (see figure 5), whose axial depth is up to 2mm, preferably 0.5 to 1 mm. A sizing of the front slit and/or the rear slit of driving wheel s1, s2 in the manner described above depends on the specific properties of the heated liquid food product P and is preferably determined in the field experiment.

[0059] Each blade channel 2.1 between two adjacent blades 2 of the push wheel 100 is in fluid communication (figure 5) with the rear push wheel slot s1 through at least one wash perforation 6 that penetrates the rear side of the push wheel 4 in the region of its bordering push wheel 4 posterior side.

[0060] According to a preferred configuration, in a single wash perforation 6 in each blade channel 2.1, all these perforations are arranged in a single hole circle 2.2 with a hole circle diameter d. In this case the geometric location for the respective point of penetration of the washing perforation 6 is determined with the rear side of the push wheel, which also determines a hole circle diameter d, approximately through the center of the vane channel 2.1, in relation to the spacing of the blades 2 at the point of penetration, and approximately through the center of a flow wire extension of the blade channel 2.1 between its inlet and outlet.

[0061] The washing perforation 6 is preferably made circular with a perforation diameter Db or it has a shape different from the circular shape with a decisive hydraulic diameter for this shape Dh (figure 4). In this case, it is preferably proposed that the drilling diameter Db or the hydraulic diameter Dh is 30 to 50% and in this region preferably 40 to 50% of the spacing of the blades 2 at the point of penetration.

[0062] The invention further provides that more than one washing perforation 6 is provided in each blade channel 2.1, that each of the several washing perforations 6 of the blade channel 2.1 is arranged in an associated circle of holes 2.2, and that the hole circles 2.2 are radially distanced from each other. The washing perforations 6 in the different hole circles 2.2 can be configured with the same diameter Db or hydraulic diameter Dh or with different diameters Db or hydraulic diameters Dh from hole circle to hole circle. Because of the decreasing pressure difference from the inside to the outside, in the radial direction, between the rear space on the wheel side and the blade channel 2.1, an advantageous configuration provides that the cross-sections of passage of the washing perforations 6 in the various circles of 2.2 holes are smaller with increasing hole circle diameter d. The perforation diameter Db or the hydraulic diameter Dh of the washing perforations 6 are therefore tangentially smaller the closer they approach the hub region of the driving wheel 10, when a certain volumetric washing flow must be achieved.

[0063] At least the housing cover 8 is provided with the cooling agent space 8.1 on the housing cover side that can be passed through by a cooling agent. If necessary, the rear housing wall 10 can be cooled through a cooling agent space 10.1 on the rear housing wall side. According to an advantageous configuration, in addition to the cooling agent space 8.1 on the housing cover side and the cooling agent space 10.1 on the rear housing wall side, the inlet 76, when it is configured as a suction nozzle, is provided with cooling agent space 76.1 on the suction nozzle side. It is proposed that the cooling agent space 76.1 on the suction nozzle side, the cooling agent space 8.1 on the housing cover side and the cooling agent space 10.1 on the housing back wall side are filled with cooling agent. cooling separately from each other. Another configuration provides that at least two cooling agent spaces 76.1, 8.1, 10.1 are connected together in series. According to another proposal, the cooling agent space 76.1 on the suction nozzle side is an integral portion of the cooling agent space 8.1 on the housing cover side.

[0064] The following measures, with which a centrifugal pump according to the state of the art can be modified according to the invention, guarantee, in combination with each other or also separately, the washing according to the invention of the impeller wheel 100 : • widening of the rear slot s1 of the push wheel and/or the front slot s2 of the push wheel (see figure 5), o through rotation of both sides of the push wheel 100 o or through a spacer element acting axially in the direction of the pump shaft 96, which is arranged between the housing cover 8 and the rear housing wall 10, with the impeller wheel 100 not being out of phase with the housing wall 10 or being axially out of phase with the pump shaft 96 in pump chamber 98, correspondingly; • arrangement of previously mentioned washing perforations 6 in the manner described above.

[0065] Figures 4 and 5 clarify the effects of the previous measures according to the invention. By widening the rear slot s1 of the drive wheel or by enlarging access to this gap, the rear space on the associated wheel side is tightened, more or less free from strangulation, with the static pressure prevailing on the output side of the drive wheel 2 , which has the outer diameter of the push wheel DL, throughout its entire radial extension region. In the respective wash hole 6, in the blade channel 2.1, there is a lower static pressure than in the rear space on the wheel side. This results in, in the blade channel 2.1, due to the causal passage flow from the wash perforation 6 from the rear space on the wheel side to the blade channel 2.1, the first wash flow S1 being oriented radially from the inside to the outside, as this is represented in figure 5 and figure 4, shown in the latter, as an example, in a blade channel 2.1. As the heated liquid food product P, which is located in the rear space on the wheel side, can be cooled in the rear housing wall 10, whereby the cooling of the rear housing wall K4 is eventually provided, liquid food product P is permanently cooled now through the first washing flow S1 preferably reaches the core region of the flow in the blade channel 2.1.

[0066] Through the described enlargement of the anterior slot s2 of the pusher wheel, as shown in figure 4 in the upper left quadrant of the pusher wheel 100, the third washing perforation S3 can be configured through the respective free edge of the blades 2 on the front side and through its radial extension region. The driving forces for this third wash flow S3 result from the pressure difference across each blade 2, which is given through the static pressure on the upper blade side, a pressure side Ds, and through the static pressure on the lower side paddle, one suction side SS. The third washing flow S3 provides additional movement relative to the housing cover 8 and mainly in the radial direction thereof and thus provides forced cooling of the liquid food food P, because the cooling housing cover K3 is installed in this housing cover 8 (see figure 5). The third washing flow S3 also causes here an exchange of the liquid food product to and from the core region of the flow in the associated blade channel 2.1. Through the widened front slot s2 of the push wheel, due to the difference in the static pressure at the outlet of the push wheel 100 and the static pressure at the suction side inlet of the push wheel 100, the second radially oriented washing flow S2 can be formed ( see figure 5), on which the third washing flow S3 is superimposed. This second wash flow S2 also provides an exchange of the liquid food product P to and from the core region of the flow in the associated vane channel 2.1.

[0067] Example of embodiment of a centrifugal pump 54 according to the invention:

[0068] The centrifugal pump 54 is driven by a drive motor with a nominal power of 15 kW with a nominal rotation number n = 2900 1/min. The outer diameter of the DL thrust wheel is reduced from 205 mm to 195. The width of the thrust wheel in the outer diameter of the DL thrust wheel is reduced from originally 19 mm to 9 mm, with the reduction decreasing to an inlet region for the channel of blades 2.1 continuously up to the minimum front gap of impeller wheel s2*. The rear slot s1 of the push wheel is enlarged in relation to the minimum rear slot s1* of the push wheel, in the enlargement region 2.3 in the form of an annular surface, by 0.7 mm. Each wash hole 6 in the associated blade channel 2.1 of the total six blade channels 2.1 is made circularly and has a hole diameter Db = 10 mm.

[0069] The measures according to the invention described above are also transferable to a closed impeller wheel, whereby a third washing flow S3 is then not necessarily possible in the manner described above through the leading edge of the front side of the respective blades 2. As a replacement for these wash paths, a push wheel cover disc 100 could be provided with a plurality of wash perforations, which connect the respective associated vane channel with a front drive wheel space, formed between the cover disc and the wash path. housing cap 8. A suitable washing flow would then be established for the first washing flow S1 described above. LIST OF REFERENCE NUMBERS OF ABBREVIATIONS USED Figures 1 and 2 (state of the art) 1000 installation 50 infusion container, general 50* infusion container of the first type 500 infusion container of the second type 50.4 cooling agent space on the bottom side of container 52 outlet tube 52.1 refrigerant space on outlet tube side 54 first conveyor device 540 rotary displacement pump 56 vacuum chamber 58 second conveyor device 60 product inlet 62 external water vapor inlet 64 internal inlet of water vapor 66 cooling agent inlet on the infusion side 67 cooling agent inlet on the pump side 68 cooling agent outlet on the infusion side 70 connection line 72 vapor outlet 74 withdrawal line (for product treated food) D water vapor D1 first water vapor D2 second water vapor K cooling P fluid food product P* treated food product W water Figure 3 50 infusion container 50* first type infusion container 500 infusion container infusion of the second type 50.1 container envelope 50.2 container bottom 50.3 outlet opening 50.4 cooling agent space on the side of the container bottom 8 housing lid 8.1 cooling agent space on the side of the housing lid 10 rear housing wall 10.1 coolant space on the side of the rear housing wall 12 pump housing 54 centrifugal pump 76 inlet (suction nozzle) 76.1 coolant space on the side of the suction nozzle 78 first coolant inlet 80 first agent outlet cooling agent inlet 82 second cooling agent inlet 84 second cooling agent outlet 86 third cooling agent inlet 88 third cooling agent outlet 90 fourth cooling agent inlet 92 fourth cooling agent outlet 94 outlet (pressure nozzle ) 96 pump shaft 98 pump chamber 100 impeller wheel K1 cooling the bottom of the container K2 cooling the outlet tube or suction nozzle K3 cooling the housing cover K4 cooling the rear housing wall S1 first wash S2 second wash S3 third washing Figures 4 and 5 2 blade 2.1 blade channel 2.2 circle of holes 2.3 enlargement in the form of annular surface 4 back side of the push wheel 6 wash perforation DL external diameter of the push wheel Db perforation diameter Dh hydraulic diameter DS pressure side ( paddle) RS rear side (push wheel) SS suction side (blade) VS front side (push wheel) d diameter of circle of holes s1 rear slot of push wheel s1* minimum rear slot of push wheel s2 front slot of push wheel s2 * minimum front gap of the drive wheel n direction of rotation

Claims (37)

1. Process for treating heat-sensitive liquid food products (P), in which water vapor (D) directly heats the liquid food product (P) to form a germ-free state in an infusion container (50; 50*, 500), in which water (W) is removed from the liquid food product (P), through voltage reduction at a lower pressure, in an amount that corresponds to that of the water vapor (D) previously fed, in which the liquid food product (P) is transported by means of a first conveyor device (54) configured as a centrifugal pump, between heating and voltage reduction, and in which, after direct heating, the following steps are provided of treatment (a) and (b), in which the liquid food product (P): (a) undergoes a first cooling (K1) at least at the bottom of the container (50.2) of the infusion container (50; 50*; 500 ) until inside an exit opening (50.3); (b) undergoes a second cooling (K2) in a tubular section (52, 76) that connects directly to the outlet opening (50.3), which is formed through an outlet tube (52) that opens from the container infusion (50; 50*; 500) or through a suction nozzle (76) of the centrifugal pump; the process being characterized by the fact that it further comprises the following treatment steps, in which the liquid food product (P): (c) undergoes a third cooling (K3) in a housing cover (8) of a pump housing (12 ) of the centrifugal pump (54), which connects directly to the outlet tube (52) or the suction nozzle (76); (d) serves, with a part of its volumetric flow conveyed in an impeller wheel (100) of the centrifugal pump (54), which is configured open to the housing cover (8) of the centrifugal pump (54), of at least a planned washing of the pump housing (12) and the impeller wheel (100) through a rear slot (s1) of the impeller wheel, which is provided between a rear housing wall (10) of the centrifugal pump (54) and the impeller wheel (100), and through an anterior slot (s2) of the impeller wheel, which is provided between the housing cover (8) and the impeller wheel (100), with the volumetric flows of the planned washes exceeding by up to a multiple of the forced compensation flows within the pump housing (12), which result from a hydraulically optimized design of the centrifugal pump (54) with a respective minimum rear gap and a respective minimum front gap of the impeller wheel (s1*, s2 *), which guarantee the mechanical functionality of the centrifugal pump (54). 2. Process according to claim 1, characterized by the fact that the liquid food product (P) undergoes a fourth cooling (K4) in the housing wall (10) of the pump housing (12). 3. Process according to any one of claims 1 or 2, characterized by the fact that the first and second wash (S1, D2) are generated through a respective recirculation through the impeller wheel (100), driven through respective differences pressure in the pump housing (12). 4. Process according to claim 3, characterized by the fact that the first washing (S1) occurs through the rear slot (s1) of the pusher wheel between the pusher wheel (100) and the rear housing wall (10), being that the first wash (S1) interferes with the flow through the impeller wheel (100). 5. Process according to any one of claims 3 or 4, characterized by the fact that the second washing (S2) occurs through the front slot (s2) of the push wheel between the housing cover (8) and the push wheel (100 ), and the second wash (S2) interferes with the flow through the impeller wheel (100). 6. Process according to any one of the preceding claims, characterized by the fact that a third wash (S3) occurs between a respective pressure and suction side of a blade (2) of the open push wheel (100) and through the previous slit (s2) of the impeller wheel. 7. Process according to any one of claims 2 to 6, characterized in that the cooling units (K1, K2, K3, K4) are operated separately from each other. 8. Process according to any one of claims 2 to 6, characterized by the fact that the cooling units (K1, K2, K3, K4) are connected in series. 9. Process according to any one of claims 2 to 6, characterized by the fact that the coolants (K1, K2, K3, K4) are operated in counterflow to the heated liquid food product (P). 10. Installation (1000) for treating heat-sensitive liquid food products (P), • with an infusion container (50; 50*; 500), in which water vapor (D) directly heats the liquid food product ( P) for the formation of a germ-free state; • with a vacuum chamber (56) which is in fluid communication with the infusion container (50; 50*; 500) via a connecting line (70), in which water (W) is withdrawn from the liquid food product ( P) heated through voltage reduction to a lower pressure in an amount corresponding to that of the associated water vapor (D); • with a first conveyor device (54) configured as a centrifugal pump, arranged in the connection line (70), for transporting the heated liquid food product (P) from the infusion container (50; 50*; 500) to the vacuum chamber (56); • with an outlet opening (50.3) arranged in a container bottom (50.2) of the infusion container (50; 50*; 500) for removing the heated liquid food product (P); • with a tubular section (52, 76) that connects to the outlet opening (50.3) for conveying the heated liquid food product (P), which is formed through an outlet tube (52) that flows from the container infusion (50; 50*; 500) or through a suction nozzle (76) of the centrifugal pump (54); • with a cooling agent space (50.4) on the bottom side of the housing for cooling the heated liquid food product (P) that applies to the bottom of the container (50.2); • with a cooling agent space (52.1) on the side of the outlet tube or a cooling agent space (76.1) for cooling the heated liquid food product (P) traveling through the tubular section (52, 76); the installation being characterized by further comprising • a pump housing (12) of the centrifugal pump (54), which is formed by at least one housing cover (8) and a rear housing wall (10) and has a storage space cooling agent (8.1) on the housing cover side for cooling the transported heated liquid food product (P); and • the centrifugal pump (54), which has an impeller wheel (100) open to the housing cover (8) and is configured in such a way that, with a portion of the volumetric flow of the liquid food product (P) heated, carried on the impeller wheel (100), at least one planned washing of the pump housing (12) and the impeller wheel (100) takes place through a rear slot (s1) of the impeller wheel, which is provided between the rear housing wall (10) and the impeller wheel (100), and through a front slot (s2) of the impeller wheel, which is provided between the housing cover (8) and the impeller wheel (100), and the volumetric flows of planned washes exceed the forced compensation flows within the pump housing (12) by up to a multiple, which result from a hydraulically optimal design of the centrifugal pump (54) with a respective minimum rear gap and a respective minimum front gap (s1 *, s2*), which guarantee the mechanical functionality of the centrifugal pump (54). 11. Installation according to claim 10, characterized in that the pump housing (12) has a cooling agent space (10.1) on the side of the rear housing wall. 12. Installation according to any one of claims 10 or 11, characterized by the fact that a first wash (S1) occurs through the rear drive wheel slot (S1) between the push wheel (100) and the rear housing wall ( 10) in the path through at least one washing perforation (6) arranged on the rear side of the drive wheel (4), 13. Installation according to any one of claims 10 to 12, characterized by the fact that a second wash (S2) occurs through the previous push wheel slot (S2) between the housing cover (8) and the push wheel (100 ). 14. Installation according to any one of claims 11 to 13, characterized by the fact that a third wash (S3) occurs through compensation flows between a respective pressure and suction side of a blade (2) of the impeller wheel ( 100) open and through the front slot (s2) of the push wheel. 15. Installation according to any one of claims 11 to 14, characterized in that the cooling agent space (50.4) on the container bottom side, the cooling agent space (52.1, 76.1) on the tube side outlet or suction nozzle side, the cooling agent space (8.1) on the housing cover side and the cooling agent space (10.1) on the housing back wall side are ordered with cooling agent separately from each other. other. 16. Installation according to one of claims 11 to 14, characterized in that at least two cooling agent spaces (50.4, 52.1, 76.1, 8.1, 10.1) are connected together in series. 17. Centrifugal pump (54) for transporting heat-sensitive liquid food products (P), with an inlet (76), an outlet (94), a pump housing (12), which is formed by at least one cover housing (8) and a rear housing wall (1), a pump chamber (98) configured in the pump housing (12) and which is in fluid communication with the inlet (76) and outlet (94), a impeller wheel (100) rotatably received in the pump chamber (98) with blades (2), a respective blade channel (2.1) configured between two adjacent blades (2), which is configured open to the housing cover ( 8) and closed to the rear housing wall (10 via a pressure side (4) of the push wheel, a rear slot (s1) provided between the rear housing wall (10) and the push wheel (100) and a front slot (s2) provided between the housing cover (8) and the push wheel (100), characterized by the fact that: • the rear slot and/or the front slot (s1, s2) of the push wheel are/are enlarged / enlarged by up to a multiple in relation to a respective minimum rear gap and a respective minimum front gap (s1*, s2* of impeller wheel, which guarantees the mechanical functionality of the centrifugal pump (54), by reducing the width of the wheel impeller (100) in the region of the front slot and the rear slot (s1, s2) of the impeller wheel, and • that at least the housing cover (8) is provided with a cooling agent space (8.1) that can be passed through by a cooling agent. 18. Centrifugal pump according to claim 17, characterized in that the rear housing wall (10) is provided with a cooling agent space (10.1) that can be passed through by a cooling agent. 19. Centrifugal pump according to claim 17 or 18, characterized in that in addition to the cooling agent space (8.1) on the housing cover side and the cooling agent space (101.1) on the rear wall side housing, the inlet (76) is configured in the form of a suction nozzle protruding from the housing cover (8), which is provided with a cooling agent space (76.1) on the suction nozzle side. 20. Centrifugal pump according to any one of claims 17 to 19, characterized in that each vane channel (2.1) is in fluid communication with the rear slot (s1) of the impeller wheel through at least one flushing perforation ( 6) that penetrates the rear side (4) of the driving wheel, in the region of its rear side (4) bordering the driving wheel. 21. Centrifugal pump according to any one of claims 17 to 20, characterized in that the front slot (s2) of the impeller wheel undergoes a maximum enlargement by an outer diameter of the impeller wheel (DL) of the impeller wheel (100), which continuously decreases to the minimum anterior gap (s2*) of the driving wheel until the region of the entrance to the blade channels (2.1). 22. Centrifugal pump according to claim 21, characterized in that a reduction in the width of the impeller wheel (100) in the impeller wheel outer diameter (DL) is 40 to 55% of the width of a hydraulically optimized impeller wheel. 23. Centrifugal pump according to claim 22, characterized in that the reduction is 50 to 55% of the width of a hydraulically optimized impeller wheel (100). 24. Centrifugal pump according to one of claims 21 to 23, characterized by the fact that: • that access to the minimum rear slot, radially oriented (s1*), which starts from the outer diameter of the impeller wheel (DL) of the push wheel (100) and extends to a push wheel hub (100), is enlarged by up to 5 mm by reducing the push wheel outer diameter (DL), and • that an enlargement of the rear slot (s1) of drive wheel (100) impeller consists in that the rear side of the impeller wheel (4) undergoes an enlargement (2.3) in the form of an annular surface in the region between the washing perforation (6) and the hub of the impeller wheel (100), whose axial depth is up to 2mm. 25. Centrifugal pump according to claim 24, characterized by the fact that the axial depth of the flare (2.3) is 0.5 to 1 mm. 26. Centrifugal pump according to any one of claims 20 to 25, characterized by the fact that, in a single washing perforation (6) in each vane channel (2.1), all washing perforations (6) are arranged in a single circle of holes (2.2) 27. Centrifugal pump according to any one of claims 20 to 26, characterized in that the geometric location for the respective point of penetration of the washing perforation (6) with the rear side of the impeller wheel (4), which also fixes a circle diameter of holes (d), is determined • approximately through the center of the blade channel (2.1), in relation to the spacing of the blades (2) at the drilling point, and • approximately through the center of a length of wire of maximum flow of the vane channel (2.1) between its inlet and outlet. 28. Centrifugal pump according to any one of claims 20 to 27, characterized in that the washing perforation (6) is configured circularly with a perforation diameter (Db). 29. Centrifugal pump according to any one of claims 20 to 28, characterized in that the washing perforation (6) has a shape other than the circular shape with a hydraulic diameter (Dh) decisive for this shape. 30. Centrifugal pump according to any one of claims 28 or 29, characterized by the fact that the perforation diameter (Db) or the hydraulic diameter (Dh) is 30% to 50% of the spacing of the blades (2) at the point of penetration. 31. Centrifugal pump according to claim 30, characterized by the fact that the perforation diameter (Db) or the hydraulic diameter (Dh) is 40 to 50% of the spacing of the blades (2) at the point of penetration. 32. Centrifugal pump according to any one of claims 20 to 31, characterized by the fact that: • that more than one washing perforation (6) is provided in each blade channel (2.1), • that each of the several washing perforations (6) washing (6) of a blade channel (2.1) is arranged in an associated circle of holes (2.2), and • that the circles of holes (2.2) are radially distanced from each other. 33. Centrifugal pump according to claim 32, characterized in that the cross-sections of passage of the washing perforations (6) are smaller in the various hole circles (2.2) with a decreasing hole circle diameter. 34. Centrifugal pump according to any one of claims 19 to 33, characterized in that the cooling agent space (76.1) on the suction nozzle side, the cooling agent side (8.1) on the cover side housing and the cooling agent space (10.1) on the side of the housing rear wall are ordered with cooling agent separately from each other. 35. Centrifugal pump according to any one of claims 19 to 33, characterized in that at least two cooling agent spaces (76.1, 8.1, 10.1) are connected together in series. 36. Centrifugal pump according to any one of claims 19 to 35, characterized in that the cooling agent space (76.1) on the suction nozzle side is an integral section of the cooling agent space (8.1) on the suction nozzle side. of the housing cover. 37. Centrifugal pump according to any one of claims 17 to 36, characterized by the fact that, starting from a hydraulically optimized centrifugal pump, the rear slot and/or the front slot (s1, s2) of the impeller wheel are enlarged: • through rotation of both sides of the impeller wheel (100) • or through a distancing element acting axially in the direction of a pump shaft (96), which is arranged between the housing cover (8) and the rear wall housing (10), with the impeller wheel (100) not being out of phase with the rear housing wall (10) or being axially out of phase correspondingly on or with the pump shaft (96) in the pump chamber (98 ).