EP3536811B1

EP3536811B1 - Leather desiccation plant

Info

Publication number: EP3536811B1
Application number: EP19160573.2A
Authority: EP
Inventors: Marco AGOSTINI
Original assignee: Individual
Current assignee: Individual
Priority date: 2018-03-05
Filing date: 2019-03-04
Publication date: 2020-11-25
Anticipated expiration: 2039-03-04
Also published as: IT201800003290A1; EP3536811A1

Description

TECHNICAL FIELD OF THE INVENTION

The present invention regards the technical field of the tanning industry.
In particular, the present invention regards a plant for drying hides or skins.

STATE OF THE ART

Carrying out several treatments, both physical and chemical, on hides or skins so as to obtain a product that does not deteriorate is known in the tanning industry.
Such process provides for various steps that use water, according to several operations of the so-called "wet" type, at the end of which the hides or skins are wet and must be dried so as to undergo the subsequent treatment steps up to obtaining a finished product or product to be subjected to further finishing processes.
Various processes for drying wet hides or skins are known. The choice of one drying process with respect to another may depend on the characteristics and on the type of hide or skin, on its designated use, on as well as economic factors.
For example, it is known to hang the hides or skins to be dried on special frames which are moved along a tunnel or a chamber in which hot air circulates at controlled temperature and humidity. The use of a catalytic gas, infrared rays or microwaves can be provided for as an alternative to hot air to cause the evaporation of the water present in the hides or skins.
In plants that provide for the use of a hot airflow, the drying temperatures are generally close to 75° C or above such value. The heating of the air at such temperature entails considerable energy costs as well as the fact that the hides or skins deteriorate partially during the drying and they are at a high temperature at the end of the process and thus need to be cooled down prior to being handled.
The cooling down of the hides or skins, which is carried out using special cooling devices, requires high energy consumption, thus further increasing the operating costs required to implement such drying method, besides increasing the overall times required for the drying process.
Another process provides for heating the hides or skins in a low-pressure environment, so as to allow the evaporation of the water at a lower temperature with respect to the evaporation temperature at atmospheric pressure.
Such method only partly allows overcoming the drawbacks regarding the operating costs relating to drying the hides or skins by means of hot air.
As a matter of fact, the use of a heating circuit whose temperature must be controlled and maintained constant so as to guarantee an optimal and uniform drying of the treated hides or skins is provided for so as to be able to heat the hides or skins.
A cooling system whose operating costs may considerably weigh on the overall operating costs of the plant is provided for condensing the humidity extracted from the hides or skins.
The international patent application n° WO2014/1846521 describes a system for drying hides or skins by means of a vacuum system.
Thus, in the tanning industry there arises the need for providing a plant for drying hides or skins that, with respect to the methods of the conventional type, guarantees an optimal treatment of the hides or skins through a solution capable of considerably increasing the performance of the plant leaving the management costs thereof intact.

OBJECTS OF THE INVENTION

An object of the present invention is to improve the prior art regarding a plant for drying hides or skins.
In the context of such technical task, an object of the present invention is to provide a plant for drying hides or skins capable of guaranteeing an effective drying method, in which the operating temperature is lower than the one used in drying plants of the conventional type.
A further object of the present invention is to provide a plant for drying hides or skins with characteristics of high effectiveness and with low operating costs with respect to the quality of the products at the end of the treatment carried out by means of such plant.
Another object of the present invention is to provide a plant for drying hides or skins capable of keeping the temperature at which the hides or skins are dried constant irrespective of the atmospheric conditions outside the drying plant, through a solution characterised by high operating regularity.
According to an aspect of the present invention, provided is a plant for drying hides or skins according to claim 1.
The dependent claims refer to preferred and advantageous embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the present invention will be more apparent from the detailed description of a preferred but non-exclusive embodiment of a plant for drying hides or skins, illustrated by way of non-limiting example in the attached drawings wherein:

figure 1 is a block diagram of a plant for drying hides or skins according to the present invention;
figure 2 is a block diagram of a further version of the plant for drying hides or skins according to the present invention;
figure 3 is a block diagram of yet another version of the plant for drying hides or skins according to the present invention;
figures 4 and 5 are top perspective views of some components of a plant for drying hides or skins according to the present invention.

EMBODIMENTS OF THE INVENTION

With reference to the attached figures, a plant for drying hides or skins is indicated in its entirety with reference number 1.
The drying plant 1 according to the present invention is of the vacuum type.
Generally, the drying plant 1 comprises at least one desiccation and drying chamber in which at least one hide or skin L is to be positioned.
The at least one drying chamber is operatively connected to means for heating and adjusting the temperature and to vacuum means, so as to carry out the drying of the at least one hide or skin L under low-pressure conditions.
In particular, the drying plant 1 comprises at least one dryer, indicated in its entirety with 2, operatively connected to a vacuum system 3 (see figures 4 and 5).
The vacuum system 3 is configured to determine a low pressure in the dryer 2 and, more precisely, in the single drying chambers present in the dryer 2.
The vacuum system 3 comprises vacuum generation means, not illustrated in detail in the attached figures, for example a vacuum pump or the like.
The dryer 2 comprises a frame 4 and work planes 5, on which to lay the hides or skins L to be dried. The work planes 5 can be used moveable along the frame 4.
According to a preferred embodiment, the frame 4 has a portal structure.
The work planes 5 are stacked and/or can be stacked in succession with respect to each other.
Each of the work planes 5 extends horizontally (for example with respect to the ground). In particular, each of the work planes 5 is substantially rectangular-shaped and it is provided with an upper surface 5a, also substantially rectangular, on which the hides or skins L to be dried are laid (see figures 4 and 5).
Each of the work planes 5 can be slidably moved in the vertical direction along the frame 4. Thus, the work planes 5 displacement direction is perpendicular to the horizontal plane on which the work planes 5 extend.
The work planes 5 are displaced through displacement means of the known type, such as for example pistons, for example of the hydraulic type.
The work planes 5 lie on horizontal planes substantially parallel with respect to each other.
Two consecutive work planes 5, in mutual abutment, delimit a drying chamber between them, as indicated above, not illustrated in the attached figures. The drying chamber, inside which at least one hide or skin L to be dried can be comprised, is an airtight chamber and/or an airtight-sealed chamber.
Figure 5 illustrates, by way of non-limiting example, a work plane 5 on which two hides or skins L are laid.
Basically, after positioning the at least one hide or skin L on a first work plane 5, such first work plane 5 is displaced upwards along the vertical direction and/or along the frame 4. In this manner, the first work plane 5 presses against the lower surface 5b of a second work plane 5, successive to the first one along the frame 4. Thus, the second work plane 5 is in upper abutment against the first work plane 5. The first and the second work plane 5, abutting one against the other, delimit between them the airtight drying chamber enclosed in which is the at least one hide or skin L to be dried. Specifically, such chamber is enclosed between the upper surface 5a of a first work plane 5 and the lower surface 5b of a second work plane 5, arranged above the first one. Naturally, the work planes 5 may also be displaced in the opposite direction, by lowering a first upper work plane 5 on a second work plane 5, arranged beneath the first one. In such case, the drying chamber is delimited between the upper surface 5a of the second work plane 5 and the lower surface 5b of the first work plane 5.
Each drying chamber can be operatively connected to the vacuum system 3 and/or to the vacuum generation means thereof, so as to be able to vary the pressure inside the chamber, in particular reducing it up to a pre-established value, lower than the atmospheric pressure value. Thus, vacuum is created inside the drying chamber.
In detail, the vacuum system 3 and/or the vacuum generation means are operatively connected to each work plane 5.
Furthermore, the work planes 5 can be heated to allow the drying of the at least one hide or skin L.
Regarding this, according to a preferred embodiment, each of the work planes 5 comprise, therein, a coil, not illustrated in the attached figures.
The coil can be configured as a hollow pipe in which a hot fluid, preferably water, is circulated. The coil extends substantially over the entire work plane 5, so as to spread the heat uniformly through it and/or transmit the heat to the upper surface 5a.
In a version of the invention, the heated surface of each work plane 5 is at least the upper surface 5a, on which the at least one hide or skin L is laid.
Through the two ends thereof, each coil is connected to a first hydraulic circuit 6, to allow the circulation of the heating fluid therein.
Further embodiments of the work plane 5 comprising special ducts for the circulation of a hot fluid therein, so as to determine the heating of the work plane 5 and/or the upper surface 5a thereof, are also possible.
As mentioned, the drying plant 1 comprises a first hydraulic circuit 6, or hot fluid circuit, along which the hot fluid used for heating the single work planes 5 is made to flow.
The drying plant 1 comprises a first delivery manifold 7 and a first return manifold 8 for operatively connecting the first hydraulic circuit 6 to the dryer 2.
By means of the first delivery manifold 7 and the first return manifold 8, the heating fluid is respectively introduced into the dryer 2 - delivery - and then discharged or drawn by the same - return.
More in detail, the heating fluid is introduced into each work plane 5 and thus drawn or made to flow out from the same.
Should each work plane 5 comprises at least one respective coil, the heating fluid is introduced into the coil and made to flow out from the same respectively by means of the first delivery manifold 7 and the first return manifold 8.
More in detail, the first delivery manifold 7 is in fluid communication with the single work planes 5 by means of the respective flexible delivery ducts 9, to introduce the hot fluid into the coils or the special ducts comprised in the single work planes 5.
Similarly, the first return duct 8 is in fluid communication by means of the flexible ducts 9' with the coils or the ducts comprised in the single work planes 5, to allow the outflow of the hot fluid therefrom.
The use of flexible ducts 9, 9' allows to operatively connect respectively the first delivery manifold 7 and the first return manifold 8 to the single work planes 5 though guaranteeing the mobility of the latter along the frame 4.
Supplying the heating fluid into each work plane 5, for example in the coils or in the special ducts, allows heating the at least one work plane 5 (or the upper surface 5a thereof) on which at least one hide or skin L is made to lie, heating it, up to determining the evaporation of the water contained therein. In particular, the combined effect of the heat and the pressure drop, in each drying chamber, determines the drying of the hides or skins L.
With the aim of reducing the pressure in the drying chamber, it should be observed that the vacuum system 3 is in communication with the internal of the drying chamber (which is airtight-sealed it should be borne in mind), which is delimited between two work planes 5 in mutual abutment.
Actuating the vacuum system 3 allows to reduce the value of pressure in the drying chamber up to a value lower than that of the atmospheric pressure.
Reducing the pressure inside the drying chamber to below the atmospheric value, allows reducing the boiling temperature of the water, and thus, the temperature at which the evaporation of the water from the wet hides or skins L occurs.
By way of example, it is clear that adjusting the vacuum system 3 so as to ideally obtain a reduction of pressure up to a pressure value of about 5 mBars, considering losses of sealing that may occur in the drying plant 1, for example with reference to leakages that occur at the drying chamber, allows reaching - during the work step - a pressure value of about 20 mBars at which the water boiling point drops from 100° C (boiling temperature at standard atmospheric pressure equal to about 1000 mBars) to about 40° C.
Being able to dry the hides or skins at a much lower temperature with respect to 100° C allows to maintain the properties of the hides or skins intact, thus obtaining a higher quality product with respect to the conventional drying methods.
Furthermore, at the end of the drying process according to the present invention the hides or skins L can be handled right away (in that the temperature thereof is approximately comprised between 20° C and 30° C), without having to wait for them to cool down as it instead occurs in the drying systems of the conventional type. In this manner, the drying plant 1 according to the present invention also allows to drastically reduce the hides or skins L processing times.
The drying plant 1 comprises at least one condensing unit 10 operatively associated to a respective work plane 5.
According to a version of the invention, each work plane 5 is associated to at least one condenser unit 10.
According to version of the invention, not illustrated, the at least one condenser unit can be external and connected to each work plane by means of special ducts.
The at least one condensing unit 10 is configured to reduce the moisture content that develops inside the single drying chambers during the drying process. As a matter of fact, during the drying, the hide or skin L releases the water present in it in form of vapour. Such vapour expands in the drying chamber (airtight chamber delimited by two work adjacent work planes 5). In order to empty the drying chamber, it is necessary to provide for that such at least one condenser unit 10, which re-transforms the vapour in form of water or condensate.
According to a version of the present invention, not indicated in detail in the attached figures, the at least one condenser unit 10 may be operatively connected to a condensate collection container, by means of a special duct, to recover the condensate formed during the work step and possibly be able to use it for further purposes according to the specific needs.
In a version of the invention, each work plane 5 comprises at least two condensing units 10 which extend longitudinally along the work plane 5, on respective opposite sides.
According to an embodiment, each condensing unit 10 comprises a heat exchanger of the tube bundle type, in turn comprising two hydraulic circuits in mutual heat exchange. A first hydraulic circuit is traversed by the vapour which is generated inside a respective airtight chamber during the drying step and a second hydraulic circuit is traversed by a coolant fluid with the aim of condensing the vapour.
As better described hereinafter, the vapour that is generated inside each airtight chamber is returned into the first hydraulic circuit of each or of the at least one condensing unit 10 due to the vacuum generated by the vacuum system 3.
With reference to the coolant fluid, it should be observed that the drying plant 1 comprises a second hydraulic circuit 11 operatively connected to the dryer 2 for the circulation of a coolant fluid inside the latter.
More precisely, the coolant fluid is supplied in the at least one condensing unit 10 of the dryer 2 with the aim of condensing the vapour released by the hides or skins L during the drying step. Such condensation occurs in single condensing units 10.
It should be observed that the single condensing units 10 are operatively connected to the vacuum system 3, to return the vapour present in the single drying chambers into the condensing units 10 and, thus, for conveying the condensed phase outside the same. The second hydraulic circuit 11 is operatively connected to the dryer 2 by means of a second delivery manifold 12 and a second return manifold 13, according to methods similar to the ones described regarding the connection between the first delivery manifold 7 and the first return manifold 8 with the respective work planes 5.
In particular, the second hydraulic circuit 11 is operatively connected to the at least one condensing unit 10 present in the dryer 2.
The second delivery manifold 12 is operatively connected - in fluid communication - to the at least one condensing unit 10 for introducing a coolant fluid in the dryer 2.
The second return manifold 13 is instead connected to the dryer 2 to receive the coolant fluid flowing out from the latter, and in particular flowing out from the at least one condensing unit 10.
It should be observed that the coolant fluid flowing out from the at least one condensing unit 10 has a higher temperature with respect to that of the coolant fluid flowing thereinto, having absorbed part of the heat contained in the vapour which is returned into the at least one condensing unit 10. As a matter of fact, the at least one condensing unit 10 condensates the vapour extracted from the hides or skins L, making it return to the water or condensate form. In this manner, the amount of fluid to be suctioned reduces considerably, thus facilitating the elimination of the water produced by the drying of the hides or skins L.
The second delivery manifold 12 and the second return manifold 13 are connected to the at least one condensing unit 10 by means of respective flexible ducts 14 and 14' similarly to what is described regarding the first flexible ducts 9, 9'.
In particular, the second delivery manifold 12 is operatively connected to the work planes 5 by means of flexible ducts 14 and the second return manifold 13 is operatively connected to the work planes 5 by means of flexible ducts 14'.
The dryer 2 and/or the frame 4 comprises a sealing element 15. The sealing element 15 is substantially shaped similarly to the work planes 5 and it lies on a plane substantially parallel to the one on which the work planes 5 lie.
Furthermore, the sealing element 15 is arranged at the top part of the dryer 2 and/or of the frame 4.
The sealing element 15 is suitable to define an airtight sealing for the highest work plane 5 from among those stacked along the frame 4.
Basically, the sealing element 15, when approached in abutment with the highest work plane 5 from among those present in the stack of work planes 5 along the frame 4, delimits the first airtight chamber of the dryer 2 starting from the top.
In a version of the invention, the sealing element 15 can be slidably displaced in the vertical direction along the frame 4 similarly to what is described relating to the single work planes 5.
In an alternative version of the invention, the sealing element 15 is fixed, and the work planes 5 are the ones moved upwards, up to abutting against the same.
The first hydraulic circuit 6, or heating fluid circuit, may be operatively connected to a heat source outside the drying plant 1 by means of at least one heat exchanger indicated in its entirety with 16. The at least one heat exchanger 16 allows to adjust, possibly increasing it, the temperature of the heating fluid to be introduced into the work planes 5 of the dryer 2. The operation of a heat exchanger is considered known and thus it will not be described further hereinafter.
The second hydraulic circuit 11, or coolant fluid circuit, comprises a heat exchanger unit, indicated in its entirety with 17, through which one can adjust the temperature of the coolant fluid to be introduced into the at least one condensing unit 10.
In particular, the heat exchanger unit 17 is configured to lower the value of the temperature of the coolant fluid flowing out from the condensing unit/s 10 up to taking it to a pre-established value before introducing the coolant fluid into the condensing unit/s 10 once again.
In particular, the heat exchanger unit 17 comprises at least one absorber 18.
According to an example of the present invention, the absorber 18 can be a refrigeration machine conformed as a refrigerator or absorption chiller or, simply, an absorption chiller.
The description of the operation of an absorber will be limited to the characteristics useful to understand the drying plant 1 according to the present invention, considering that the operating principles of a such thermal machine are part of the common technical knowledge.
According to an aspect of the present invention, it should be observed that the at least one absorber 18 can be operatively connected to the first hydraulic circuit 6 and/or to the second hydraulic circuit 11, for the purposes to be described hereinafter.
An absorber 18 is a particular type of thermal machine which differs from a compression chiller as concerns the electrical consumption required for the operation thereof.
As known, compression chillers comprise one or more high power electric motors, for the actuation of a compression unit for compressing a coolant gas that can be used to reduce the temperature of a fluid to be cooled. Contrary to an absorber which basically has substantially zero electrical consumption, such compression chillers require high electrical energy consumption for their operation.
By way of example, the at least one absorber 18 used in the present invention comprises at least one generator 19, one condenser 20, one evaporator 21 and one absorber device 22 operatively connected to each other according to the known methods.
In particular, in at least one version of the absorber 18, a hot fluid - capable of heating and/or bringing a diluted solute solution (usually lithium bromide or ammonia) to boiling temperature - is made to flow in the generator 19. The generated vapour is conveyed towards the condenser 20. In the meanwhile, due to the evaporation, the diluted solution of the generator 19 becomes a concentrated solute solution.
An endothermic type of process occurs in the generator 19.
In the condenser 20, the vapour coming from the generator 19 condensates, hence cooling and forming a coolant liquid which flows into the evaporator 21 through a special opening.
An exothermic type of process occurs in the condenser 20.
The pressure existing in the evaporator 21 is lower than the one present in the generator 19 and in the condenser 20 (due to the absorber device 22). Thus, upon flowing into the evaporator 21 the coolant liquid boils and absorbs heat hence evaporating: in this manner, such coolant vapour removes heat and thus cools the temperature of the fluid to be cooled which thus flows out from the absorber 18 and is conveyed into the devices of the present invention as described hereinafter.
An endothermic type of process occurs in the evaporator 21.
As regards the coolant vapour which is formed in the evaporator 21, it flows into the absorber device 22 and - here - it contributes towards diluting the solute solution which had been concentrated in the generator 19 and which had been transferred into the absorber device 22 after the first step of the cycle. As a matter of fact, the concentrated solution absorbs the coolant vapour and simultaneously reduces the pressure present in the absorber device 22.
An exothermic type of process occurs in the absorber device 22.
The solute solution, diluted once again, is directly or indirectly transferred into the generator 19 once again.
According to a version of the present invention, the heat exchanger unit 17 may further comprise at least one evaporative tower 23 and/or a further cooling system, similar to the evaporative tower. The evaporative tower 23 will be indicated hereinafter but any other similar cooling systems will also be referred to.
The at least one evaporative tower 23 is operatively connected to the second hydraulic circuit 11.
As known, an evaporative tower 23 is configured to cool a fluid, which in this case can be the coolant fluid to be introduced into the condensing unit/s 10.
The first hydraulic circuit 6 can have several sub-circuits along which the heating fluid can be diverted as a function of the specific use needs.
Though such forced circulation means are deemed to be comprised in the drying plant 1 according to the present invention, the means suitable to determine a forced circulation of the heating fluid and the coolant fluid along the drying plant 1 will not be indicated or illustrated in the description that follows and in the attached figures.
The first hydraulic circuit 6 comprises a first sub-circuit 6' configured to mutually connect the first return manifold 8 and the first delivery manifold 7 in fluid communication.
The first sub-circuit 6' comprises at least one first section 24, connected downstream of the first return manifold 8, at least one second section 25 connected upstream of the first delivery manifold 7 and at least one intermediate section 26 for connection between the first section 24 and the second section 25 (for example see figures 1 to 3).
Basically, in at least one version, the first sub-circuit 6' defines a short-circuit for the circulation of the heating fluid regarding the dryer 2.
Such configuration can be used should it be no longer necessary to heat the heating fluid flowing out from the work planes 5 of the dryer 2, thus being able to re-introduce it directly thereinto.
In a further version of the invention for example illustrated in figure 2, the first hydraulic circuit 6 also comprises a second sub-circuit 6" configured to heat the heating fluid before introducing it into the single work planes 5 present in the dryer 2.
The second sub-circuit 6" is in selective fluid communication with the first sub-circuit 6' (as indicated in figure 2) or it is not in selective fluid communication with the first sub-circuit 6' (as indicated in figure 3).
More in detail, the second sub-circuit 6" comprises at least one heat exchanger 16.
The at least one heat exchanger 16 comprises a first heat exchange circuit not illustrated in the attached figures, in fluid communication with a heat source, and a second heat exchange circuit in fluid communication with the at least one absorber 18.
More in detail, the second sub-circuit 6" comprises a delivery section 27, for sending a hot fluid towards the at least one absorber 18 and a return section 28 for the return of the hot fluid, previously sent to the absorber 18, towards the at least one exchanger 16.
In the version illustrated in figure 2, the second sub-circuit 6" is in selective fluid communication with the first sub-circuit 6' by means of an intermediate bleeding section 29 which connects the return section 28 and/or the delivery section 27 with the first sub-circuit 6'. For example, the intermediate bleeding section 29 may be connected to the second section 25.
It should be observed that the intermediate bleeding section 29 could be connected to the first sub-circuit 6' along the intermediate section 26, though falling within the same inventive concept.
A valve 30 for shutting off the flow, to be used to adjust the amount of heating fluid which is bled by the second sub-circuit 6" towards the first sub-circuit 6', can be provided along the intermediate bleeding section 29.
The second sub-circuit 6" may comprise a second intermediate bleeding section 31, suitable to place the first sub-circuit 6' and the second sub-circuit 6" in selective fluid communication.
According to such version, the intermediate bleeding section 29 and the second intermediate bleeding section 31 respectively act as a delivery branch and as a return branch of the heating fluid between the second sub-circuit 6" and the first sub-circuit 6'.
Inside the at least one heat exchanger 16, the heating fluid absorbs part of the heat coming from a heat carrier fluid at a higher temperature, for example a liquid, a vapour or a mixture thereof, increasing the temperature thereof.
Basically, should the need to heat the heating fluid flowing out from the dryer 2 arise, the fluid flowing out from the first section 24 is at least partly diverted towards the second sub-circuit 6" and a corresponding amount of heating fluid coming from the second sub-circuit 6" is drawn.
By way of example, the intermediate bleeding section 29 can be configured to allow the drawing of at least one part of the heating fluid that circulates in the second sub-circuit 6", drawing it from the return section 28 and/or from the delivery section 27 of the sub-circuit 6".
The circulation of the heating fluid along the first hydraulic circuit 6, and the relative sub-circuits 6', 6", can be adjusted by means of special valves suitable for the purpose, not illustrated in the attached figures.
According to a further version of the present invention, the first hydraulic circuit 6 may comprise a further heat exchanger 16' arranged along the first sub-circuit 6' (for example see figures 1 and 3).
According to such version, the bleeding of the heating fluid from the second sub-circuit 6" to the first sub-circuit 6' can be eliminated. Such version differs from the embodiment illustrated in figure 2, regarding the presence of the further heat exchanger 16'.
As mentioned, the drying plant 1 comprises at least one absorber 18 which can be used to reduce the temperature of the coolant fluid.
In order to allow the operation of such thermal machine there arises the need to provide a heat source to be introduced into the generator 19 of the at least one absorber 18, so as to determine the boiling of the diluted solution present therein, according to the known methods indicated above and which will not be described further.
According to a version of the present invention, the heat source can be the heating fluid flowing out from the heat exchanger 16 (for example see figures 2 and 3) or a heat source or fluid available in proximity of the drying plant 1, such as for example saturated vapour, possibly pressurised (see figure 1).
As regards the possibility of adjusting the temperature of the coolant liquid, reducing it, as mentioned, the drying plant 1 comprises a second hydraulic circuit 11 comprising the at least one absorber 18.
According to a further version of the present invention, the second hydraulic circuit 11 comprises at least one evaporative tower 23 additionally to the at least one absorber 18. Basically, the first hydraulic circuit 6 and the second hydraulic circuit 11 mutually share or can share the at least one absorber 18.
Similarly to what has been described regarding the first hydraulic circuit 6, it should be observed that the second hydraulic circuit 11 may comprise sub-circuits, for diverting the path of the coolant fluid with respect to the dryer 2, as a function of specific use needs.
The second hydraulic circuit 11 comprises valves suitable to adjust the flow of the coolant fluid along the second hydraulic circuit 11 not illustrated in detail in the attached figures.
The second hydraulic circuit 11 comprises a first cold sub-circuit 11', for connection between the second delivery manifold 12, the second return manifold 13 and the at least one absorber 18.
The second hydraulic circuit 11 may comprise a second cold sub-circuit 11" for connection between the second delivery manifold 12, the second return manifold 13 and the at least one evaporative tower 23 if present.
The second hydraulic circuit 11 may comprise bypass sections for selectively diverting the path of the coolant fluid between the first cold sub-circuit 11' and the second cold sub-circuit 11", as better described hereinafter.
With reference to the first cold sub-circuit 11', it comprises a delivery duct 33 for sending the coolant fluid to the dryer 2.
The delivery duct 33 basically connects the at least one absorber 18 to the second delivery manifold 12 of the dryer 2.
The first cold sub-circuit 11' also comprises a return duct 34 which connects the second return duct 13 of the dryer 2 with the absorber 18.
Basically, the dryer 2 is connected to the at least one absorber 18 through the first cold sub-circuit 11'.
More precisely, the condensing units 10 present in the dryer 2 are connected with the at least one absorber 18.
As mentioned, according to a version of the present invention, the second hydraulic circuit 11 may comprise at least one evaporative tower 23 operatively connected to the dryer 2 through one second cold sub-circuit 11".
The second cold sub-circuit 11" comprises, in the moving away flow order of the dryer 2, at least one section of the return duct 34, a linking duct 35 suitable to connect such section of the return duct 34 with the inlet of a cooling circuit present in the at least one evaporative tower 23 and a second linking duct 36 suitable to connect the outlet of the cooling circuit of the evaporative tower 23 with a section of the delivery duct 33 downstream of the at least one absorber 18.
Basically, the second cold sub-circuit 11" shares - with the first cold sub-circuit 11' - at least one section of the delivery duct 33 and one section of the return duct 34.
Should the second hydraulic circuit 11 comprise at least one evaporative tower 23, a third cold sub-circuit 11"' can be provided for mutually operatively connecting the at least one absorber 18 and the at least one evaporative tower 23.
The third cold sub-circuit 11"', if present, comprises a third linking duct 37 which mutually operatively connects the absorber 18 with the at least one evaporative tower 23, equivalently to a delivery for the at least one absorber 18, and a fourth linking duct 38 which mutually operatively connects the at least one evaporative tower 23 and the at least one absorber 18, equivalently to a return for the at least one absorber 18.
More precisely, the third linking duct 37 mutually operatively connects the absorber 18 with a section of the linking duct 35 upstream of the at least one evaporative tower 23, while the fourth linking duct 38 connects a section of the second linking duct 36, downstream of the at least one evaporative tower 23 with the at least one absorber 18.
The use of at least one absorber 18 in the drying plant 1 according to the present invention allows to obtain an efficient control of the coolant fluid, intended as the reduction of the temperature of the latter, considering a solution with extremely low operating costs, with particular reference to the costs of electrical energy that actually drop drastically due to the use of the at least one absorber 18.
As mentioned, with respect to the refrigeration machines of the conventional type that comprise a compressor, the absorber 18 uses the chemical transformation of a solute to determine endothermic and exothermic reactions (described above) to be used to reduce the temperature of a fluid that is made to flow through the evaporator 21 of the absorber 18.
The presence of at least one absorber 18 in the second hydraulic circuit 11, in collaboration with at least one evaporative tower 23, if present, allows to maintain the coolant fluid at a low temperature value, for example of about 7° C, in a constant manner irrespective of the external conditions that occur in the various seasons (with particular reference to the extreme summer and winter conditions). Maintaining the temperature of the coolant fluid constant facilitates greater thermal stability of the process for drying hides or skins, to the advantage of the quality of the product that can be obtained.
Furthermore, using at least one absorber 18 and at least one evaporative tower 23 it allows to considerably adjust the temperature of the coolant fluid irrespective of the external atmospheric conditions, with particular reference to the ambient temperature value.
The use of an absorber 18 in the drying plant 1 allows to cool the coolant fluid up to a temperature of about 7° C. In this manner, it is possible to limit the temperature of the hot fluid given that in order to guarantee full condensation of the vapour released by the hides or skins L during the drying step, it is sufficient to guarantee an approximately 20° C heat excursion between the vapour temperature and the coolant fluid temperature. Basically, in the drying plant 1 it is possible to fully dry the hides or skins L at a temperature of about 30-40° C, thus avoiding subjecting the same to heat stress and deteriorating them.
As mentioned, the operating costs of the drying plant 1 according to the present invention are lesser than those of the solutions of the conventional type which provide for the use of compressor refrigeration machines, and relative electric motors, for cooling the coolant fluid to be used during the drying process.
Thus, the drying plant 1 allows to achieve two results, i.e. obtain a quality product, whose initial features remain intact, at a low production cost. Furthermore, such result can be obtained throughout the year, without being subjected to heat excursions due to the differences of the ambient temperature that can occur in various seasons. In countries where the environmental conditions remain substantially constant throughout the year, the drying plant 1 allows to optimise the production costs given that it has basically zero electrical consumption with respect to that of plants comprising the use of compressor refrigeration machines.
The drying plant 1 described above can be subjected to numerous modifications and variants falling within the scope of protection of the claims that follow.

Claims

Plant for drying hides or skins comprising a drier (2), wherein said drier (2) comprises a frame (4) and at least a working plane (5), wherein along said frame (4) said at least one working plane (5) is movable engaged, wherein said at least one working plane (5) comprises at least one upper surface (5a) on which to lay at least one hide or skin (L) to be dried, said at least one working plane (5) and/or said at least one upper surface (5a) being heated to determine the desiccation of said at least one hide or skin (L), wherein said drying plant (1) comprises at least a first hydraulic circuit (6), operatively connected to said at least one working plane (5), along which a heating fluid is circulated, for heating said at least one working plane (5) and/or said at least one upper surface (5a), and at least one second hydraulic circuit (11), along which a cooling fluid is circulated, operatively connected to said at least one working plane (5), wherein said second hydraulic circuit (11) comprises at least one heat exchanger unit (17), characterized in that said heat exchanger unit (17) comprises at least one absorber (18), wherein said absorber (18) is an absorption chiller suitable for cooling the temperature of said cooling fluid and comprising at least one generator (19), one condenser (20), one evaporator (21) and one absorber device (22) operatively connected to each other.
Plant for drying hides or skins according to claim 1, wherein said absorber (18) has a hot fluid introduced into said generator (19) so as to determine the boiling of a diluted solution containing a solute present into said generator (19), so using the chemical transformation of said solute to determine endothermic and exothermic reactions through which reducing the temperature of said cooling fluid that flows through said evaporator (21) of said absorber (18).
Plant for drying hides or skins according to claim 1, wherein said second hydraulic circuit (11) is operatively connected to said first hydraulic circuit (6) through said heat exchanger unit (17).
Plant for drying hides or skins according to claim 1 or 2 or 3, wherein said heat exchanger unit (17) comprises at least one evaporative tower (23), or similar cooling systems, operatively connected to said absorber (18), for cooling said cooling fluid to be fed to said drier (2).
Plant for drying hides or skins according to claim 1, wherein said at least one working plane (5) comprises a first working plane and a second working plane (5), stacked together in succession, and wherein said first and said second working planes (5), placed in mutual contact, determine at least one hermetic drying chamber.
Plant for drying hides or skins according to the preceding claim, wherein said drying chamber is determined between said upper surface (5a) of said first working plane (5) and a lower surface (5b) of a second working plane (5) or between said upper surface (5a) of said second working plane (5) and a lower surface (5b) of a first working plane (5).
Plant for drying hides or skins according to any one of the preceding claims, wherein said drying plant (1) comprises a vacuum system (3), suitable to determine a low pressure inside said at least one drying chamber.
Plant for drying hides or skins according to any one of the preceding claims when dependent on claim 5 and 7, wherein said drier (2) comprises at least one condensation unit (10) which develops longitudinally along said at least one working plane (5), or two condensation units (10) placed on opposite sides with respect to said at least one working plane (5), wherein said at least one condensation unit (10) is in fluid connection with the inside of a respective drying chamber, being operatively connected to said vacuum system (3) and being configured to condense a steam flow rate which develops in said at least one drying chamber during the drying of said at least one hide or skin (L).
Plant for drying hides or skins according to claim 1, wherein said first hydraulic circuit (6) comprises at least one heat exchanger (16 and/or 16') for heating said hot fluid to be fed into said at least one working plane (5) of said drier (2).
Plant for drying hides or skins according to the preceding claim, wherein said heat exchanger (16) is operatively connected to said heat exchanger unit (17) and/or to said dryer (2).
Plant for drying hides or skins according to any one of the preceding claims, wherein said at least one working plane (5) comprises at least one hollow coil or a duct which can be travelled by said heating fluid, said at least one hollow coil or duct being in fluid communication, through its two ends, with said first hydraulic circuit (6).
Plant for drying hides or skins according to any one of the preceding claims when dependent on claim 8, wherein said at least one absorber (18) is connected to said at least one condensation unit (10) by means of a first cold sub-circuit (11') of said second hydraulic circuit (11).
Plant for drying hides or skins according to any one of the preceding claims when dependent on claim 4, wherein said at least one evaporative tower (23) comprises a cooling circuit for said cooling fluid, wherein said at least one evaporative tower (23) is connected in fluid communication with said at least one condensation unit (10) through a second cold sub-circuit (11") of said second hydraulic circuit (11), wherein said second sub-circuit shares, at least partially, some portions of said first cold sub-circuit (11').
Plant for drying hides or skins according to any one of the preceding claims when dependent on claim 4, wherein said at least one absorber (18) and said at least one evaporative tower (23), or similar cooling systems, are operatively connected to each other through a third cold sub-circuit (11"') of said second hydraulic circuit (11).
Plant for drying hides or skins according to claim 1, wherein said at least one of said heating fluid and said cooling fluid is water.