Plant and method for concentrating a liquid food product

Abstract

Plant for concentrating a liquid food product, in particular tomato juice, comprising: i) heating means (2) for heating the liquid product; ii) a first concentrator (3) for the liquid product; said first concentrator (3) being placed downstream of the heating means; iii) a second concentrator (5) for the liquid product placed downstream of the heating means (2). The first and second concentrator (3, 5) being fluid-dynamically connected in parallel.

Description

[0001] DESCRIPTION

[0002] PLANT AND METHOD FOR CONCENTRATING A LIQUID FOOD PRODUCT

[0003] Technical field

[0004] The present invention relates to a plant and a method for concentrating a liquid food product, typically tomato juice or juice obtained from fruit, milk or whey, water solutions of proteins or other.

[0005] Prior art

[0006] Solutions are known in which the extracted juice or puree are heated to obtain deactivation of endogenous enzymes such as Polyphenol oxidase (PPO), Peroxidase (PO) or Pectin methylesterase (PMO). For example, with a solution known technically as Hot Break.

[0007] The juice or puree are then directed to a first concentrator from which a semi-concentrated product and water vapour obtained from the water present in the incoming juice or puree are extracted.

[0008] Subsequently the product is introduced into a second concentrator in series to the first and then typically into a third concentrator arranged in series to the second. These concentrators can be at different temperatures with the vapours exiting one concentrator that heat the product in the next concentrator (in this case it is referred to as a multipleeffect evaporator) or they can all be at the same temperature as in the case mechanical vapour recompression (known as MVR) is used.

[0009] Aim of the invention

[0010] The task of the present invention is to provide a plant and a method for concentrating a liquid food product that are capable of optimizing heat exchange.

[0011] Another aim is to minimize maintenance operations and product losses by allowing non-stop operation for several months.

[0012] Further characteristics and advantages of the present invention will appear clearer from the indicative, and therefore non-limiting, description of an embodiment of a plant and a method for concentrating a liquid food product.

[0013] Brief description of the drawings

[0014] Such a description will be set out below with reference to the accompanying drawings, which are provided solely for illustrative and therefore non-limiting purposes, in which:

[0015] - figure 1 shows a schematic view of a plant according to the present invention;

[0016] - figures 2 and 3 show two alternative solutions of a portion of the plant of figure 1 ;

[0017] - figures 4 and 5 show two alternative solutions of a portion of the plant of figure 1 .

[0018] Detailed description of preferred embodiments of the invention

[0019] A plant for concentrating a liquid food product (this liquid product can be more or less viscous) has been indicated in the attached figures with reference number 1. In particular, such a food product could be tomato juice.

[0020] The plant 1 comprises heating means 2 for heating the liquid product. In the technical sector, when these means achieve rapid heating of the product, they are often called "hot breaks". They presuppose a hot deactivation of the endogenous enzymes present within the liquid product (juice) obtained from crushing solid plant products. The heating means, for the production of juices and purees of plant origin, is followed by refiners that separate foreign bodies, skins and seeds by sieving.

[0021] Suitably upstream of the heating means 2 there may be crushing means 9 and / or refining means 90 for feeding the liquid product to the heating means 2.

[0022] The plant 1 also comprises a first concentrator 3 for the liquid product. This allows a greater degree of concentration to be achieved, minimising damage to the organoleptic characteristics typical of the natural product.

[0023] The first concentrator 3 is placed downstream of the heating means 2 and the refiners, if present. Upstream and downstream are intended with reference to the flow direction of the liquid product.

[0024] The first concentrator 3 comprises first means 31 causing a pressure reduction on the liquid product to induce the formation of vapour by flash evaporation (sometimes also known in the art as "self-evaporation"). Said first means 31 causing a pressure reduction may comprise means that reduces the pressure in a (typically initial) part of the first concentrator 3, for example first constriction means 310 that causes an acceleration of the product and a pressure loss that generate a consequent pressure reduction. In fact, the reduction of pressure on a hot liquid product (thanks to the action of the heating means 2) causes an instantaneous and intense flash evaporation.

[0025] The pressure reduction induced by the constriction means 310, together with the fact that the product is at a temperature higher than saturation temperature (by virtue of the heated product coming from the heating means 2) causes the formation of a two-phase motion that greatly increases the heat exchange coefficient. The same product in a two-phase motion inside the tubes can generate increases in exchange coefficients of up to 400%.

[0026] The first concentrator 3 also comprises first heat transfer means 32 for transferring heat to the liquid product to produce vapour by evaporation of a part of water present in the liquid product. Therefore, the first means 32 allows heat to be transferred to the liquid product present in the first concentrator 3 to increase the concentration.

[0027] The first heat transfer means 32 comprises a heat exchanger. In this heat exchanger a heating fluid (typically vapour) heats the liquid product causing / helping to cause the formation of vapour and the concentration of the liquid product itself.

[0028] In a particular embodiment solution, the first heat transfer means 32 comprises a battery 320 of tubes in which the liquid product passes and which are externally lapped by a heating fluid (typically vapour). Suitably the tubes of the battery 320 are downflow tubes. Advantageously in the first means 32 the tubes of the battery 320 are only downflow tubes.

[0029] The first heat transfer means 32 comprises an upstream plate 321 and a downstream plate 322 (upstream and downstream of the battery 320) to which corresponding ends of the tubes of the battery 320 are connected. The upstream plate 321 and the downstream plate 322 are perforated at the ends of the tubes of the battery 320 (to allow the passage of the liquid product and the vapour that is freed from the liquid product). Conveniently, but not necessarily, at the inlet and / or inside the tubes of the battery 320 (typically in the vicinity of the upstream plate 321 ) there may be a local constriction 311 for the tubes (e.g. a bushing or a nozzle) which reduces the tube passage section. The first concentrator 3 comprises an outer shell that surrounds the battery 320. The upstream plate 321 and the downstream plate 322 are constrained to the outer shell. The heating fluid is introduced internally to the outer shell and subsequently extracted respectively from an inlet mouth and an outlet mouth which is interposed between the plate 321 and the plate 322. The battery 320 of tubes is completely lapped by such a heating fluid.

[0030] The first concentrator 3 preferably comprises a first chamber (or distributor) 323. Advantageously, the first chamber 323 is located immediately upstream of said battery 320 of tubes and partially delimited by said plate 321 .

[0031] The entry of the product into the battery 320 typically takes place through said first chamber 323 (or distributor) formed for example by a cone; the first chamber 323 distributes the product on the plate 321 from which the battery 320 of tubes departs. As previously indicated at the beginning of the tubes, tightening bushings 311 are often installed to cause greater back pressure inside the first chamber 323 (distributor) and facilitate flash evaporation downstream.

[0032] The passage from the first chamber 323 to the battery 320 of tubes may define the first constriction means 310.

[0033] The first concentrator 3 suitably comprises a second chamber 324. Suitably the second chamber 324 is immediately downstream of said battery 320 of tubes and partially delimited by said plate 322 downstream. The second chamber 324 may also be referred to as a separation chamber 324.

[0034] The first concentrator 3 comprises first evacuation means 33 for evacuating the vapour extracted from the liquid product (which is different from the vapour used as heating fluid in the first means 32). The first evacuation means 33 is in communication with said second chamber 324. For example, it may comprise a mouth for evacuating the vapour from the first concentrator 3.

[0035] The plant 1 also comprises first recirculation means 4 for recirculating the liquid product. The first recirculation means 4 allows to move the liquid product from downstream to upstream of the first heat transfer means 32.

[0036] The first recirculation means 4 may for example comprise a first recirculation line 40 for recirculating the liquid product from downstream to upstream of the first heat transfer means 32. The first recirculation means 4 may also comprise a first recirculation pump 41 , advantageously placed along said line 40. The first recirculation pump 41 pumps the liquid product along the recirculation line 40. In other words, the product coming from the second chamber 324 (at the saturation temperature) is withdrawn by the first pump 41 , pushed through the recirculation line 40 and arrives at the first heat transfer means 32 (for example of the tube bundle type) where the heat exchange takes place between the external vapour (shell side) and the product inside the tubes of the battery 320.

[0037] The entry of the hot product coming from the heating means 2 inside the recirculation line 40 brings thermal energy into the product flow being recirculated. At the delivery of the first pump 41 , the pressure of the product constantly drops from the value present on the pump delivery (maximum value), up to the pressure value inside the second chamber 324 (corresponding to the saturation pressure relative to the temperature of the product in the chamber). The supply of thermal energy coming from the product coming from the heating means 2, causes the recirculated product to begin to evaporate by flash evaporation, as it approaches the pressure of the separation chamber. Typically, this flash evaporation begins in the first chamber 323 before the battery 320 or more desirably, in the first part of the tubes of the battery 320. At the typical working temperatures of the evaporators for food products, between 60 and 80°C, the specific volume of the liquid can for example vary between 7.7 m3 / kg and 3.4 m3 / kg. So every kilogram of water that evaporates at 60°C, could generate 7.7 m3of volume.

[0038] In an advantageous solution the liquid product coming from the heating means 2 is introduced along the first recirculation line 40 downstream of the first recirculation pump 41 and upstream of the first heat transfer means 32. This allows to reduce the risk of cavitation of the first recirculation pump 41 .

[0039] In this regard, the liquid product coming from the heating means 2 is introduced into the first chamber 323 (distributor). The ratio between the mass flow rate of the liquid product coming from the heating means 2 and the mass flow rate recirculating in the first line 40 is typically comprised between 1 / 2 and 1 / 100. Notwithstanding this, the liquid product coming from the heating means 2 supplies thermal energy to the recirculated liquid product with consequent increase in temperature.

[0040] In this regard, the first concentrator 3 comprises an introduction conduit 30 for introducing the liquid coming from the heating means 2 into the first chamber 323 (distributor). The introduction conduit 30 may for example comprise an outlet mouth placed at the end of the conduit 30 and possibly also a plurality of lateral openings immersed in the first chamber 323. More generally, the introduction conduit 30 for introducing the liquid from the heating means 2 can merge into the first recirculation line 40.

[0041] Suitably, the plant 1 comprises first extraction means 34 for extracting the concentrated liquid product from the first recirculation means 4. The first extraction means 34 for extracting the liquid product may for example comprise a first extraction pump 342 for extracting the liquid product and a first extraction conduit 341 . Such extraction conduit 341 may extend from the first recirculation line 40. The extraction conduit 341 has one end at the first recirculation line 40 and another end at a liquid product storage tank 8.

[0042] The plant 1 also comprises a second concentrator 5 for the liquid product located downstream of the heating means 2. The first and second concentrator 3, 5 are not in series from the point of view of product transfer but in parallel. Advantageously they operate independently of each other.

[0043] Suitably, what is indicated for the first concentrator 3 can be repeated for the second concentrator 5. The second concentrator 5 comprises in particular second means 51 causing a pressure reduction on the liquid product to induce the formation of vapour by flash evaporation (sometimes also known in the art as "self-evaporation"). Said second means 51 causing a pressure reduction may comprise means that reduces the pressure in a part of the first concentrator 3 (for example second constriction means 510 advantageously placed at the inlet of the tubes of the concentrator 3) that causes an acceleration of the product and a consequent pressure reduction. In fact, the pressure reduction causes an instantaneous and intense flash evaporation, made possible by the heat supplied by the incoming fluid. This causes an increase in volume which in turn induces an acceleration of the liquid product. So there is a propulsive thrust along the second concentrator 5.

[0044] The second concentrator 5 also comprises second heat transfer means 52 for transferring heat to the liquid product to produce vapour by evaporation of a part of water present in the liquid product. In particular, what is described above for the first heat transfer means 32 may be repeated for the second heat transfer means 52.

[0045] The second concentrator 5 may also comprise second evacuation means 53 for evacuating the vapour extracted from the liquid product.

[0046] Suitably, the plant 1 comprises second recirculation means 6 for recirculating the liquid product from upstream to downstream of the second heat transfer means 52.

[0047] Suitably the plant 1 comprises second extraction means 54 for extracting the concentrated liquid product from the second recirculation means 6. The second extraction means 54 for extracting the liquid product may for example comprise a second extraction pump 542 for extracting the liquid product and a second extraction conduit 541. The second extraction conduit 541 opens into the liquid product storage tank 8.

[0048] The first and second extraction means 34, 54 allow the product to be conveyed to a common area downstream of the first and second concentrator 3, 5.

[0049] Conveniently, a third concentrator 9 may be present whereby one or more of the characteristics described with reference to the first concentrator 3 may be repeated.

[0050] More generally, a plurality of concentrators may be present whereby for each of them one or more of the characteristics described with reference to the first concentrator 3 may be repeated.

[0051] The concentrators 3, 5, 9 could be structurally identical to each other; preferably they are the same.

[0052] The plant 1 also comprises fluid-dynamic connection means 7 for the fluiddynamic connection of the heating means 2 with the first and with the second concentrator 3, 5. The fluid-dynamic connection means 7 connects the heating means 2 with both the first and the second concentrator 3, 5. The means 2 directs a part of the liquid product exiting the heating means 2 towards the first concentrator 3 without passing through the second concentrator 5 and a part of the liquid product exiting the heating means 2 towards the second concentrator 5 without passing through the first concentrator 3. In this regard, the connection means 7 branches off feeding the concentrators in parallel.

[0053] Advantageously the first and second concentrator 3, 5 are fluid- dynamically in parallel. Suitably also the third concentrator 9 is parallel to the first and second concentrator 3, 5. The liquid product processed by the first concentrator 3 is re-joined to the liquid product processed by the second concentrator 5 downstream of the first and second concentrator 3, 5. This re-joining takes place in the storage tank 8.

[0054] An object of the present invention is also a method for concentrating a liquid food product. Suitably, said method is implemented by a plant for concentrating a food product having one or more of the characteristics described above.

[0055] The method comprises the step of heating the liquid product; this occurs in the heating means 2. This step typically takes place in an enzymatic deactivation plant, for example in the technical sector also called hot break when such deactivation takes place quickly and with product recirculation. The method also comprises the step of directing the heated liquid product (in the heating means 2) in part towards a first concentrator 3 and in part towards a second concentrator 5. Suitably, the method may provide for directing the heated liquid product (in the heating means 2) also towards a third concentrator 9 and / or further concentrators. These concentrators operate fluid-dynamically in parallel with each other. In this way, the hot incoming product generates flash evaporation, with consequent acceleration of the product and generation of a two-phase motion with significant increases in the exchange coefficients in all three concentrators. The concentrators lie downstream of the heating means 2.

[0056] The method also comprises the step of processing the liquid product in the first concentrator 3. This step comprises the sub-step of generating a flash evaporation in the first concentrator 3; this is obtained with a pressure reduction on the liquid product and thanks to the supply of heat from the incoming hot fluid. For example, to obtain this pressure reduction, the liquid product is made to pass through first constriction means 310 (for example by passing through bushings or restrictors). This results in an expansion and acceleration of the liquid product. This acceleration takes place along first heat transfer means 32 for transferring heat to the liquid product. The first means 32 transfers heat to the liquid product to produce vapour by evaporation of a part of water present in the liquid product. This evaporation is additional to flash evaporation that occurs earlier (typically starting when the liquid product enters into the first concentrator 3). In these first heat transfer means 32 the liquid product flows downwards into a battery 320 of tubes that connect a first chamber 323 (distributor) and a second chamber 324 (separator). The first chamber 323 is an upper chamber and placed upstream, the second chamber 324 is a lower chamber and placed downstream. The liquid product in the battery 320 of tubes advantageously internally laps the wall of the tube (motion known as falling film) (leaving a central space of the tube in which the vapour is placed free). Alternatively, the product fills the entire tube (motion known as forced circulation) and the vapour begins to be generated in the form of gaseous bubbles of increasing size the further one descends along the tubes.

[0057] The method provides for recirculating a part of the concentrated liquid product processed by the first concentrator 3 from downstream to upstream of the first heat transfer means 32. A part of the concentrated liquid product is not recirculated; in particular it is extracted during recirculation and combined with the concentrated product coming from another concentrator. The recirculated liquid product is instead mixed with the liquid product coming from the heating means 2 placed upstream of the first concentrator 3. The liquid product coming from the heating means 2 is at a higher temperature than the recirculated liquid product. This heating allows flash evaporation described above. The method also comprises at least partly evacuating the vapour produced with the concentration of the liquid product in the first concentrator 3.

[0058] The method also provides for processing the liquid product in the second concentrator 5. This comprises the sub-step of generating a flash evaporation in the second concentrator 5; this is achieved with a pressure reduction on the liquid product. For example, it is achieved by making the liquid product pass through second constriction means 510. This causes an expansion and an acceleration of the liquid product which is conveyed in second heat transfer means 52 to the liquid product. In the second means 52 a heating fluid heats the liquid product and in this way further vapour is separated (by evaporation of a part of water present in the liquid product). This evaporation follows the flash evaporation that occurred previously.

[0059] The method also provides for evacuating the vapour produced during the step of concentrating the liquid product in the second concentrator 5.

[0060] The method further provides for recirculating a part of the concentrated liquid product processed by the second concentrator 5 from downstream to upstream of the second heat transfer means 52. The method also comprises the step of extracting (typically during recirculation) a part of the liquid product processed by the second concentrator 5 by joining it downstream of the second concentrator 5 with a part of the product processed by the first concentrator 3.

[0061] Suitably the method comprising the step of performing a washing cycle of the first concentrator 3 with condensates obtained by condensing vapour extracted from the liquid product. The liquid product is extracted by the concentrator 3 and the condensates push out the residual product replacing it entirely. At that point, the condensates are recirculated inside the evaporator and in particular the exchanger to wash it. The following advantages are obtained thereby:

[0062] - no generation of pollution of the liquid product present in the second concentrator with respect to the use of chemical washing products; and

[0063] - the concentration process is allowed to continue with only one of the evaporators which enters the washing step while the others remain in production without therefore completely stopping the line.

[0064] The invention achieves important advantages.

[0065] First of all, it allows optimizing the heat exchange, taking advantage of flash evaporation (or self-evaporation) in all the concentrators available and not only in the first one, increasing the speed of the liquid product inside the exchanger and triggering the two-phase motion characterized by high exchange coefficients (up to 400% higher than the single-phase motion). In this regard, the heat transferred to the liquid product by the heating means 2 is exploited, which makes flash evaporation possible.

[0066] In addition, flash evaporation causes a strong expansion and a very high speed of the fluid immediately downstream (in the heat transfer means that is typically a battery of conduits). This high speed makes it possible to minimize scale deposits, to limit cleaning and maintenance interventions and increase the heat exchange coefficient. This allows prolonged operation of the machine for several months, possibly throughout the campaign.

[0067] A further advantage is the use of recirculation pumps (for example 41 ) with low head and high flow rate. These pumps are easier to find than high head, low flow pumps.

[0068] The invention thus conceived is susceptible of numerous modifications and variants, all falling within the scope of the inventive concept that characterises it. Moreover, all the details may be replaced by other technically equivalent elements. All the materials used, as well the dimensions, may in practice be any whatsoever according to needs.

Claims

CLAIMS1 . A plant for concentrating a liquid food product, in particular tomato juice, comprising: i) heating means (2) for heating the liquid product; ii) a first concentrator (3) for the liquid product; said first concentrator (3) being placed downstream of the heating means; the first concentrator (3) comprising:- first means (31 ) causing a pressure reduction on the liquid product to induce the formation of vapour by flash evaporation;- first heat transfer means (32) for transferring heat to the liquid product to produce vapour by evaporation of a part of water present in the liquid product;- first evacuation means (33) for evacuating the vapour extracted from the liquid product; iii) first recirculation means (4) for recirculating the liquid product from downstream to upstream of the first heat transfer means (32); iv) a second concentrator (5) for the liquid product placed downstream of the heating means (2); the second concentrator (5) comprising:- second means (51 ) causing a pressure reduction on the liquid product to induce the formation of vapour by flash evaporation;- second heat transfer means (52) for transferring heat to the liquid product to produce vapour by evaporation of a part of water present in the liquid product;- second evacuation means (53) for evacuating the vapour extracted from the liquid product; v) second recirculation means (6) for recirculating the liquid product from upstream to downstream of the second heat transfer means (52); characterized in that it comprises fluid-dynamic connection means (7) for the fluid-dynamic connection of the heating means (2) with the first and with the second concentrator (3, 5); said fluid-dynamic connection means (7) branching off to connect the heating means (2) with both the first andwith the second concentrator (3, 5) and to direct a part of the liquid product exiting the heating means (2) towards the first concentrator (3) without passing through the second concentrator (5) and a part of the liquid product exiting the heating means (2) towards the second concentrator (5) without passing through the first concentrator (3).

2. The plant according to claim 1 , the first and the second concentrator (3, 5) are fluid-dynamically in parallel and the liquid product processed by the first and second concentrator (3, 5) is re-joined downstream of the first and second concentrator (3, 5).

3. The plant according to claim 1 or 2, wherein the first heat transfer means (32) comprises a battery (320) of downflow tubes externally lapped by a heating fluid.

4. The plant according to claim 3, wherein the first heat transfer means (32) comprises an upstream plate (321 ) and a downstream plate (322) to which corresponding ends of the tubes of the battery (320) are connected; the first concentrator (3) comprising: a first chamber (323) located immediately upstream of said battery (320) of tubes and partially delimited by said plate (321 ) upstream;- a second chamber (324) immediately downstream of said battery (320) of tubes and partially delimited by said plate (322) downstream.

5. The plant according to any one of the preceding claims, wherein the first recirculation means (4) comprises:- a first recirculation line (40) for recirculating the liquid product from downstream to upstream of the first heat transfer means (32);- a first recirculation pump (41 ); the liquid product coming from the heating means (2) is introduced along the first recirculation line (40) downstream of the first recirculation pump (41 ) and upstream of the first heat transfer means (32).

6. The plant according to claim 5 when directly or indirectly dependent on claim 4, wherein the liquid product coming from the heating means (2) is introduced into said first chamber (323).

7. The plant according to claim 6, wherein the first concentrator (3) comprises an introduction conduit (30) for introducing the liquid coming from the heating means (2) into the first chamber (323); said introduction conduit (30) comprising an end outlet mouth and a plurality of lateral openings immersed in the first chamber (323).

8. The plant according to any one of the preceding claims, comprising first extraction means (34) for extracting the concentrated liquid product from the first recirculation means (4).

9. A method for concentrating a liquid food product comprising the steps of: i) heating the liquid product; ii) directing the heated liquid product partly towards a first concentrator (3) and partly towards a second concentrator (5); iii) processing the liquid product in the first concentrator (3), said step comprising the following sub-steps:-generating a flash evaporation in the first concentrator (3) by reducing the pressure in an area of the first concentrator (3), this causing an expansion and an acceleration of the liquid product;- letting the liquid product pass through first heat transfer means (32) for transferring heat to the liquid product; this causing the production of vapour by evaporation of a part of water present in the liquid product;-recirculating at least a part of the concentrated liquid product processed by the first concentrator (3) from downstream to upstream of the first heat transfer means (32); iv) processing the liquid product in the second concentrator (5), said step comprising the following sub-steps:-generating a flash evaporation in the second concentrator (5) by reducing the pressure in an area of the second concentrator (5), this causing an expansion and an acceleration of the liquid product;- letting the liquid product pass through second heat transfer means (52) for transferring heat to the liquid product; this causing the production ofvapour by evaporation of a part of water present in the liquid product; -recirculating a part of the concentrated liquid product processed by the second concentrator (5) from downstream to upstream of the second heat transfer means (52); v) extracting and combining a part of the concentrated liquid processed by the first concentrator (3) with a part of the concentrated liquid processed by the second concentrator (5).

10. The method according to claim 9, comprising the step of performing a washing cycle for the first concentrator (3) with washing liquid obtained by condensing vapour extracted from the liquid product; said washing liquid replacing the liquid product inside the concentrator.

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