Drying unit and drying method for drying pasta or snack products

Abstract

A drying unit and a drying method for drying pasta or snack products. The drying unit includes: a dryer belonging to a type having a circulating air flow; a heat exchanger associated with the dryer such that the airflow is heated prior to drying the product; a heat pump; a first circuit of a first heat transfer medium receiving heat from the heat pump and transferring it to the airflow in the heat exchanger; a heat recovery system comprising:-a second circuit of a second heat transfer medium associated with the heat pump for use as a heat source; -at least a first heat recovery unit and a second heat recovery unit arranged on the second circuit upstream of the heat pump to heat the second heat transfer medium; -at least a first heat source line and a second heat source line, each heat source line being configured to transfer waste fluid used in the process inside the drying unit to one of the heat recovery units for heating the second heat transfer medium, at least one of the first heat source line and the second heat source line being an extraction line for exhaust gas from the dryer.

Description

TECHNICAL FIELD

[0001] The present invention relates to a drying unit and a drying method for drying a pasta or snack product.

[0002] The present invention can be applied in the field of manufacturing pasta or snack products, in particular in the drying phase. BACKGROUND

[0003] In the pasta or snack making process, drying involves the step of contacting the product with a hot air flow.

[0004] In other sectors such as tobacco, fruit and wood, drying machine solutions comprising an energy recovery system are already known on the market. They are usually static drying machines with only one climate zone associated with air heated directly by a heat pump.

[0005] The main drawback of these solutions is that they are implemented to manage the heat recovery on a single climate zone, thus failing when multiple heat sources are available. In particular, drying machines for pasta or snack products usually work in the case of multiple climate zones. Each climate zone has its own temperature and humidity set point. The above-mentioned solutions cannot be used in this context.

[0006] There is a need to obtain a drying machine with a heat recovery system capable of managing different heat sources, in particular the different climate zones of the drying machine. SUMMARY

[0007] In this context, the technical task on which the present invention is based is to propose a drying unit and a drying method for drying a pasta or snack product which overcome the above-mentioned drawbacks of the prior art.

[0008] In particular, the aim of the present invention is to propose a drying unit and a drying method for drying a pasta or snack product which is able to manage the heat recovery of different heat sources coming from different temperature levels, while maximizing the coefficient of performance (COP).

[0009] Another aim of the present invention is to propose a drying unit and a drying method for drying a pasta or snack product which is able to manage the heat recovery with high flexibility, to independently manage the heat recovery coming from different climate zones (with different values of operating parameters such as temperature, humidity, etc.).

[0010] The stated technical task and the specified aims are substantially achieved by a drying unit for drying a pasta or snack product, comprising:

[0011] a drying machine of the type with circulating air flow;

[0012] a heat exchanger associated with the drying machine such that the air flow is heated before drying the product;

[0013] a heat pump;

[0014] a first circuit of a first heat transfer medium, said first circuit extending between the heat pump and the heat exchanger such that the first heat transfer medium receives heat from the heat pump and transfers it to the air flow in the heat exchanger;

[0015] a heat recovery system comprising:

[0016] a second circuit of a second heat transfer medium, said second circuit being associated with the heat pump such that the second heat transfer medium transfers heat to the heat pump;

[0017] a first heat recovery unit and a second heat recovery unit arranged on the second circuit to heat the second heat transfer medium and located upstream of the heat pump;

[0018] a first heat source line and a second heat source line, each heat source line being configured to convey a waste fluid used in a process inside the drying unit to one of the heat recovery units for heating the second heat transfer medium,

[0019] at least one of the first heat source line and the second heat source line is an extraction line of waste air from the drying machine.

[0020] Preferably, the drying machine comprises at least a first climate zone and a second climate zone configured to perform a drying process of the product with different parameters.

[0021] According to a first embodiment, the first heat source line and the second heat source line are extraction lines of waste air from the first climate zone and the second climate zone.

[0022] According to a first embodiment of the heat recovery units, the first heat source line is configured to carry waste air having a lower dew point than the waste air carried by the second heat source line, the first heat recovery unit is arranged in series with the second heat recovery unit and upstream of the second heat recovery unit, the first heat recovery unit is associated with the first heat source line such that the heat recovery is performed in ascending order of the dew point of the waste air.

[0023] According to a second embodiment of the heat recovery units, the second circuit comprises a bifurcation thereby defining at least a first branch and a second branch in parallel, the first heat recovery unit is arranged on the first branch and the second heat recovery unit is arranged on the second branch, the first branch is shaped to flow back into the second branch downstream of the second heat recovery unit and upstream of the heat pump.

[0024] Preferably, the first heat recovery unit comprises:

[0025] - an additional heat pump associated with the first branch to transfer heat to the second heat transfer medium;

[0026] - a third circuit of the third heat transfer medium associated to the heat pump as a heat source;

[0027] - a heat exchanger arranged on the third circuit upstream of the heat pump, the heat exchanger being associated with one of the heat source lines to transfer heat to the third heat transfer medium.

[0028] According to a second embodiment, the first heat source line is an extraction line of waste water from a cooling line of utilities of the drying unit, while the second heat source line is an extraction line of waste air from the drying machine.

[0029] According to an embodiment, the heat source line in the form of an extraction line of waste air comprises a discharge path for discharging the waste air in the environment.

[0030] According to an embodiment, the drying machine comprises at least one climate zone in which the product is dried, and a system for regulating the value of the relative humidity in said at least one climate zone, the system comprising at least one relative humidity sensor for monitoring the relative humidity of the air in the climate zone and a control unit configured to at least perform the following operations:

[0031] - receive the relative humidity data from the relative humidity sensor;

[0032] - compare the data with a predefined range;

[0033] - regulate the air flow rate towards the heat recovery unit and the air flow rate discharged in the environment to keep the relative humidity level within the climate zone within the predefined range.

[0034] The stated technical task and the specified aim are substantially achieved by a drying method for drying a pasta or snack product, comprising the following steps:

[0035] drying the product by means of a circulating air flow, the drying step resulting in the production of waste air after the absorption of moisture from the product;

[0036] heating the circulating air flow in a heat exchanger, the heating step being performed before the step of drying the product;

[0037] circulating a first heat transfer medium in a first circuit, the step of heating the circulating air flow occurring by heat transfer from the first heat transfer medium to the circulating air flow. The first circuit extends between a heat pump and the heat exchanger, so that the first heat transfer medium receives heat from the heat pump and transfers it to the air flow in the heat exchanger;

[0038] circulating a second heat transfer medium in a second circuit, said second circuit being associated with a heat pump, such that the second heat transfer medium transfers heat to the first heat transfer medium via the heat pump;

[0039] heating the second heat transfer medium circulating in the second circuit, the step of heating the second heat transfer medium being performed before the heat transfer of the second heat transfer medium to the heat pump;

[0040] The step of heating the second heat transfer medium comprises at least a first heating step and a second heating step, both the first heating step and the second heating step comprising a heat recovery step of a waste fluid used in the process inside the drying process, at least one of the first step and the second step of heating the second heat transfer medium being performed by heat recovery from a waste gas from a drying step.

[0041] According to a first aspect of the application, the step of drying comprises two different drying steps performed in a first climate zone and in a second climate zone, the first heating step being performed by heat recovery from a waste gas extracted from the first climate zone and the second heating step being performed by heat recovery from a waste gas extracted from the second climate zone.

[0042] According to an embodiment, the first heating step and the second heating step occur sequentially, the first heating step occurring by heat recovery of a waste gas having a lower dew point and the second heating step occurring by heat recovery of a waste gas having a higher dew point.

[0043] According to an alternative embodiment, the second circuit comprises a bifurcation, thereby defining at least a first branch and a second branch in parallel. The first heating step and the second heating step are performed in parallel by means of a first heat recovery unit arranged on the first branch and a second heat recovery unit arranged on the second branch, respectively, the first branch being shaped to flow back into the second branch downstream of the second heat recovery unit and upstream of the heat pump.

[0044] According to a second aspect of the application, the first heating step occurs by heat recovery of a waste water extracted from a cooling line of utilities associated with the drying process.

[0045] According to an aspect of the application, the step of drying is performed in a corresponding climate zone, the drying process comprising a step of regulating the relative humidity value in the climate zone; the step of regulating comprises the steps of:

[0046] monitoring the relative humidity of the air in the climate zone;

[0047] comparing the acquired data with a predefined range of relative humidity of the air;

[0048] - Adjust the airflow rate intended for heat recovery and the airflow rate emitted into the environment to maintain the relative humidity level within the climate zone within a predefined range. Attached Figure Description

[0049] Further features and advantages of the invention will become more apparent from the non-limiting description of preferred, but not exclusive, embodiments of the drying unit and drying method for drying pasta products or snack products, as depicted in the accompanying drawings, in which:

[0050] - Figure 1 and Figure 2 The first embodiment of the drying unit for drying pasta products or snack products is illustrated in the first embodiment and the second embodiment of the heat recovery unit according to the present invention.

[0051] - Figure 3 A second embodiment of a drying unit for drying pasta products or snack products according to an embodiment of the present invention is illustrated in schematic diagram.

[0052] - Figure 4 It shows Figures 1 to 3 A schematic diagram of a part of the drying unit (dryer). Detailed Implementation

[0053] Referring to the accompanying drawings, number 1 relates to a drying unit for drying pasta products or snack products.

[0054] Drying unit 1 includes a dryer 10. The dryer 10 is of the type with a circulating airflow for drying the product. Air comes into contact with the product and absorbs moisture, thus becoming humid air. In the following text, the humid air that has dried the product is referred to as exhaust gas.

[0055] Preferably, the dryer 10 includes at least one climate zone 11. As is well known, the climate zone 11 is a closed area where the product is processed according to the set values ​​of the operating parameters.

[0056] Specifically, as mentioned above, the dryer 10 is used to dry pasta products or snack products. Therefore, it typically includes multiple climate zones 11 (the number of which varies depending on the application). Each climate zone 11 is managed independently of the other climate zones and is specifically configured to operate under predefined temperature and humidity conditions.

[0057] Preferably, the dryer 10 includes a conveying device 12 for conveying products through the dryer, particularly at least through climate zone 11. In this case, the dryer is of a dynamic type. The conveying device 12 can be implemented according to a variety of alternatives available to those skilled in the art. For example, the conveying device 12 can be a conveyor belt on which the products are placed.

[0058] The dryer 10 is associated with a heat exchanger 20 in which the air stream is heated before the drying product. Preferably, the dryer 10 comprises the heat exchanger 20. In particular, the dryer 10 can comprise one or more heat exchangers 20 cooperating with each other. The term "heat exchanger 20" refers to a system implementing the heating of the air stream before the drying product.

[0059] The drying unit 1 further comprises a heat pump 30 and a first circuit 40 of a first heat transfer medium. The first circuit 40 extends between the heat pump 30 and the heat exchanger 20 so that the first heat transfer medium transfers heat from the heat pump to the air in the heat exchanger 20.

[0060] According to a preferred embodiment, the first heat transfer medium is water.

[0061] As known, a heat pump has a source side and a sink side. The heat pump extracts heat from the source side to transfer heat to the sink side by means of a fluid of its internal thermal circuit.

[0062] The first circuit 40 is therefore on the sink side of the heat pump 30.

[0063] The drying unit 1 comprises a heat recovery system 50 associated with the heat pump 30. In particular, the heat recovery system 50 is arranged on the source side of the heat pump 30 so that the recovered heat is used as a source heat for the heat pump 30, as will be further described below.

[0064] The heat recovery system 50 comprises a second circuit 51 of a second heat transfer medium. The second circuit 51 is associated with the heat pump 30 so that the second heat transfer medium transfers heat to the heat pump 30 (to the fluid of its internal thermal circuit). In other words, the second heat transfer medium of the second circuit 51 is the heat source of the heat pump. The heat pump 30 is used to transfer heat from the heat recovery system 50 to the first circuit 40 and subsequently to the heat exchanger 20 of the dryer 10.

[0065] The heat recovery system 50 comprises at least a first heat recovery unit 52 and a second heat recovery unit 53 associated with the second circuit 51 to heat the second heat transfer medium. According to the flow direction of the second heat transfer medium, the two heat recovery units 52, 53 are arranged upstream of the heat pump 30. In fact, the second heat transfer medium takes heat from these units 52, 53 and transfers heat to the heat pump 30.

[0066] The drying unit 1 comprises a first heat source line 60 and a second heat source line 70. Each heat source line 60, 70 conveys a waste fluid, which is a fluid that has been used in the processes inside the drying unit. The waste fluid is a heat source for recovery.

[0067] In particular, both heat sources are inside the drying unit 1. This means that heat from the processes inside the drying unit is recovered.

[0068] Each heat source line 60, 70 is configured to convey a waste fluid used in a process inside the drying unit 1 to one of the heat recovery units 52, 53 for heating a second heat transfer medium.

[0069] Preferably, the first heat source line 60 passes through the first heat recovery unit 52, where the first heat source transfers heat to the second heat transfer medium of the second circuit 51.

[0070] Preferably, the second heat source line 70 passes through the second heat recovery unit 53, where the second heat source transfers heat to the second heat transfer medium of the second circuit 51.

[0071] At least one of the first heat source line 60 and the second heat source line 70 is an extraction line of a waste gas from the drying machine 10. The corresponding heat source is the waste gas.

[0072] In particular, the extraction line is configured to extract the waste gas from the corresponding climate zone 11.

[0073] The proposed invention allows to recover energy from heat sources at different temperature levels.

[0074] In particular, the first heat source line 60 and the second heat source line 70 and the first heat recovery unit 52 and the second heat recovery unit 53 are arranged to each other such that the heat recovery of the internal heat sources is performed according to an ascending order of the temperature of the second heat transfer medium depending on the entity of the available heat sources.

[0075] In other words, the proposed invention allows to perform heat recovery with ascending temperature levels. The minimum configuration of two heat recovery units can be extended following the same principle.

[0076] This is further deepened in the multiple embodiments described below.

[0077] Preferably, the drying machine 10 comprises at least a first climate zone 11 and a second climate zone 11.

[0078] According to Figure 1 and Figure 2 The first embodiment shown in Fig. 1, the first heat source line 60 is an extraction line of a waste gas from the first climate zone 11 and the second heat source line 70 is an extraction line of a waste gas from the second climate zone 11. In other words, the first heat recovery unit 52 and the second heat recovery unit 53 both recover heat from waste gases from two different areas and / or processes of the drying machine 10.

[0079] The first climate zone 11 and the second climate zone 11 are configured to operate under different conditions. This means that the exhaust gas extracted from the first climate zone 11 has different parameters than the exhaust gas extracted from the second climate zone 11. As is well known, the exhaust gas from the drying process is moist air (air containing water vapor). The key parameter for moist air / exhaust gas is the dew point, which is the temperature at which the air must be cooled to condense the water vapor in it into dew.

[0080] Preferably, the exhaust gases extracted from the two climate zones 11 have different dew points. The heat source lines 60, 70 and the heat recovery units 52, 53 are arranged such that exhaust gases with lower dew points are guided to the first heat recovery unit 52, while exhaust gases with higher dew points are guided to the second heat recovery unit 53.

[0081] For example, the first climate zone 11 is intended for pre-drying products (therefore it is a pre-drying zone), while the second climate zone 11 is used for drying products (therefore it is a drying zone). In this case, the exhaust gas from the pre-drying process has a lower dew point compared to the exhaust gas from the drying process. Therefore, the exhaust gas from the pre-drying zone 11 transfers heat to the second heat transfer medium in the first heat recovery unit 52. The exhaust gas from the drying zone 11 transfers heat to the second heat transfer medium in the second heat recovery unit 53.

[0082] according to Figure 1 In the first embodiment of the heat recovery unit shown, the first heat recovery unit 52 and the second heat recovery unit 53 are arranged in series along the second loop 51. This solution allows for the recovery of most of the latent heat of vaporization used in different drying processes.

[0083] The first heat recovery unit 52 (which receives exhaust gas with a lower dew point) is located upstream of the second heat recovery unit 53 (which receives exhaust gas with a higher dew point) along the second loop 51. Therefore, generally, the heat recovery units 52 and 53 are arranged sequentially according to the ascending order of the dew point of the exhaust gas (from which these heat recovery units recover heat) based on the flow direction of the second heat transfer medium in the second loop.

[0084] In other words, the second heat transfer medium of the second loop 51 receives heat from the exhaust gas with a lower dew point in the first heat recovery unit 52, and then receives heat from the exhaust gas with a higher dew point in the second heat recovery unit 53. This minimum configuration can be expanded for multiple heat recovery units 52, 53 arranged in the second loop 51 in order of increasing dew point.

[0085] In this embodiment, the second heat transfer medium sequentially receives heat recovered from the two heat sources.

[0086] This embodiment is particularly advantageous when a heat pump that can operate at the high temperature difference between the source and sink without affecting its COP can be used.

[0087] Preferably, the first heat recovery unit 52 and the second heat recovery unit 53 are in the form of heat exchangers.

[0088] In a preferred embodiment, the second heat transfer medium is water. The first heat recovery unit 52 and the second heat recovery unit 53 are air / water heat exchangers.

[0089] according to Figure 2 In a second embodiment of the heat recovery unit shown, the second loop 51 includes a branch, thereby defining at least a first branch 511 and a second branch 512 connected in parallel. A first heat recovery unit 52 is disposed on the first branch 511, and a second heat recovery unit 53 is disposed on the second branch 512. The first branch 511 is configured to flow back into the second branch 512 downstream of the second heat recovery unit 53 and upstream of the heat pump 30.

[0090] In this configuration, the first heat recovery unit 52 includes: an additional heat pump 521 associated with a first branch 511 to transfer heat to a second heat transfer medium; a third loop 522 of a third heat transfer medium associated with the heat pump 30 as a heat source; and a heat exchanger 523 disposed upstream of the heat pump 30 on the third loop 522. The heat exchanger 523 is associated with one of the heat source lines 60 and 70 to transfer heat to the third heat transfer medium.

[0091] According to the illustrated embodiment, the first heat source line is configured to carry exhaust gas with a lower dew point than the exhaust gas carried by the second heat source line 70. Therefore, a heat exchanger 523 is associated with the first heat source line 60 to recover heat from the exhaust gas with the lower dew point.

[0092] Then, the third heat transfer medium transfers heat to the second heat transfer medium in the first branch 511 via an additional heat pump 521.

[0093] In this embodiment, the second heat transfer medium receives heat recovered from the two heat sources in parallel.

[0094] This embodiment is particularly advantageous when the heat pump can operate with a limited temperature difference between the source and sink to avoid excessive inclusion of COP. In these cases, solutions with two or more different heat pumps, as described later, are necessary for recovering energy from the extraction of humid air with different dew points.

[0095] In a preferred embodiment, the second heat transfer medium is water, and the third heat transfer medium is also water. The heat exchanger 523 of the first recovery unit 52 is an air / water heat exchanger, and the second recovery unit 53 is also an air / water heat exchanger.

[0096] according toFigure 3 In the second embodiment shown, the first heat source line 60 is a wastewater extraction line from the cooling line of the utility facility of the drying unit 1. Therefore, the wastewater is the first heat source. Here, wastewater refers to water that has already been used in the cooling process inside the drying unit 1.

[0097] The extraction pipeline can be a different pipeline from the cooling pipeline, a branch of the cooling pipeline, or a part of the cooling pipeline.

[0098] There are usually several utilities that are cooled during the operating conditions of drying unit 1, and these vary depending on the specific application. For example, utilities may include a compressor, vacuum pump, die head, final cooler, dryer stabilization zone, etc.

[0099] The second heat source pipeline 70 is an extraction pipeline for the exhaust gas from the dryer 10.

[0100] Preferably, the first heat recovery unit 52 and the second heat recovery unit 53 are arranged in series along the second circuit 51.

[0101] The first heat recovery unit 52 (which is the unit that receives wastewater) is located upstream of the second heat recovery unit 53 (which is the unit that receives exhaust gas) along the second circuit 51. In other words, the second heat transfer medium of the second circuit 51 receives heat from the wastewater in the first heat recovery unit 52 and then receives heat from the exhaust gas in the second heat recovery unit 53.

[0102] In this embodiment, the second heat transfer medium sequentially receives heat recovered from the two heat sources.

[0103] This embodiment is particularly advantageous when the temperature setpoint of the first heat transfer medium leaving the heat pump 30 is lower than in other embodiments, thereby enabling the second heat transfer medium leaving the heat pump 30 to reach a low temperature at the source side.

[0104] In a preferred embodiment, the second heat transfer medium is water. The first heat recovery unit 52 is a water / water heat exchanger, while the second heat recovery unit 53 is an air / water heat exchanger.

[0105] Specifically, the air / water heat exchangers mentioned in the text are condensing heat exchangers, therefore they have a secondary outlet for condensate.

[0106] According to one embodiment, the heat source lines 60, 70 (hereinafter simply referred to as "exhaust gas extraction lines 60, 70") in the form of exhaust gas extraction lines include re-injection lines 61, 71 for air entering the dryer 10 (particularly in the corresponding climate zone 11). The re-injection lines 61, 71 extend through the heat exchanger 20.

[0107] Specifically, the re-injection lines 61 and 71 extend downstream of the heat recovery units 52 and 53 to deliver the airflow back to the dryer 10.

[0108] According to one embodiment, the exhaust gas extraction lines 60, 70 include emission paths 62, 72 for discharging the exhaust gas into the environment.

[0109] Preferably, the dryer 10 includes a system for adjusting the relative humidity value in climate zone 11.

[0110] The system includes: at least one relative humidity sensor 81 for monitoring the relative humidity of the air in climate zone 11; and a control unit 82 configured to receive relative humidity data from the relative humidity sensor 81, compare the data with a predefined range, and adjust the airflow velocity toward the heat recovery units 52, 53 and the airflow velocity discharged into the environment to maintain the relative humidity level in climate zone 11 within the predefined range.

[0111] Specifically, the control unit 82 is configured to increase the air velocity discharged into the environment when the inlet temperature of the second heat transfer medium in the heat pump 30 is too high (thereby reducing the air velocity of the air supplied to the heat recovery unit).

[0112] In practice, the COP of the system depends on the heat power at the sink side and the input and output temperatures of the first heat transfer medium, and on the input and output temperatures of the second heat transfer medium at the source side. The necessary heat power for the recovery system can be obtained from the COP, and thus the flow rate of the fluid (second heat transfer medium 51) at the source side.

[0113] If the energy recovery power exceeds the heat pump's requirements (higher return water temperature), the discharge will be activated.

[0114] This solution offers greater flexibility and allows the drying process to be independent of the operation of heat pump 30.

[0115] As described above, the presence of two heat recovery units and related components represents a minimum configuration. Multiple heat recovery units are also conceivable, following the same heat recovery principle in order of increasing temperature levels. In the case of heat recovery from exhaust gases from different climate zones of the dryer, the multiple heat recovery units should follow the same heat recovery principle in order of increasing dew points. Furthermore, combinations of different embodiments are also possible (e.g., heat recovery via two extraction lines for the dryer's exhaust gases and one extraction line for wastewater from the cooling lines of the common facilities of drying unit 1).

[0116] The drying process for drying pasta products or snack products is also an object of the present invention. The drying process is advantageously achieved by the drying unit described above.

[0117] The drying process includes the step of drying the product by means of a circulating airflow. This step is preferably carried out in a dryer 10 of the type with a circulating airflow, and particularly in the climate zone 11 of the dryer 10. As is known, the climate zone 11 is a closed area in which the product is processed according to the set values ​​of the operating parameters.

[0118] The product drying process involves drawing moisture from the product into the air, thus creating humid air. In the following text, the humid air from which the product has been dried is referred to as exhaust gas.

[0119] The drying process includes a step of heating the circulating airflow prior to the drying step. This step takes place in heat exchanger 20.

[0120] The drying process includes the step of circulating a first heat transfer medium in a first loop 40. The step of heating the circulating gas flow occurs through heat transfer from the first heat transfer medium to the circulating gas flow.

[0121] Specifically, the first loop 40 extends in the loop between the heat pump 30 and the heat exchanger 20, such that the first heat transfer medium receives heat from the heat pump and transfers it to the airflow in the heat exchanger 20.

[0122] According to a preferred embodiment, the first heat transfer medium is water.

[0123] As is well known, a heat pump has a source side and a sink side. The heat pump extracts heat from the source side and transfers the heat to the sink side by means of the fluid in its internal heat loop.

[0124] Therefore, the first loop 40 is on the junction side of the heat pump 30.

[0125] The drying process includes the step of circulating a second heat transfer medium in a second loop 51. The second loop 51 is associated with a heat pump 30, such that the second heat transfer medium transfers heat to the first heat transfer medium via the heat pump 30.

[0126] In other words, the second heat transfer medium in the second loop 51 is the heat source of the heat pump. The heat pump 30 is used to transfer heat from the heat recovery system 50 to the first loop 40, and then to the heat exchanger 20 of the dryer 10.

[0127] The drying process includes the step of heating the second heat transfer medium. This step occurs before the second heat transfer medium transfers heat to the heat pump 30.

[0128] The step of heating the second heat transfer medium includes at least a first heating step and a second heating step. The distinction between the "first" step and the "second" step does not necessarily imply a temporal relationship between the two steps.

[0129] Both the first and second heating steps of the second heat transfer medium include a heat recovery step of the waste fluid used in the drying process.

[0130] This means that the heat source for both heating and recovery steps is inside the drying process.

[0131] At least one of the first and second steps of heating the second heat transfer medium is carried out by heat recovery from the waste gas extracted from the dryer 10.

[0132] The proposed invention allows for the recovery of energy from heat sources at different temperature levels. In particular, heat recovery occurs according to the increasing temperature level. This principle can also be applied in the case of multiple heat recovery operations.

[0133] This is further elaborated in the several detailed embodiments described below.

[0134] Preferably, the dryer 10 includes at least a first climate zone 11 and a second climate zone 11.

[0135] According to the first embodiment, the first heating step is performed by heat recovery of the waste gas extracted from the first climate zone 11, and the second heating step is performed by heat recovery of the waste gas extracted from the second climate zone 11.

[0136] The first climate zone 11 and the second climate zone 11 are configured to operate under different conditions. This means that the exhaust gas extracted from the first climate zone 11 has different parameters than the exhaust gas extracted from the second climate zone 11. As is well known, the exhaust gas from the drying process is moist air (air containing water vapor). The key parameter for moist air / exhaust gas is the dew point, which is the temperature at which the air must be cooled to condense the water vapor in it into dew.

[0137] Therefore, the exhaust gases extracted from the two different climate zones 11 have different dew points.

[0138] For example, the first climate zone 11 is intended for pre-drying products (therefore it is a pre-drying zone), while the second climate zone 11 is used for drying products (therefore it is a drying zone). In this case, the exhaust gas from the pre-drying process has a lower dew point compared to the exhaust gas from the drying process. Therefore, the second heat transfer medium is heated by first recovering heat from the exhaust gas from the pre-drying zone 11 and then from the exhaust gas from the drying zone 11.

[0139] According to a first embodiment of the heating steps for the second heat transfer medium, the first heating step and the second heating step occur sequentially. This means that the second heat transfer medium undergoes heating twice in sequence.

[0140] This solution allows for the recovery of most of the latent heat of vaporization used in different drying processes.

[0141] Preferably, the first heating step occurs by heat recovery of exhaust gas with a low dew point, while the second heating step occurs by heat recovery of exhaust gas with a high dew point.

[0142] Therefore, in general, the step of heating the second heat transfer medium occurs in cases of multiple sequential heat recovery processes involving exhaust gases with ascending dew points. This means that the same principle applies in cases of two or more heat recovery processes.

[0143] In this embodiment, the second heat transfer medium sequentially receives heat recovered from two or more heat sources.

[0144] This embodiment is particularly advantageous when a heat pump that can operate under the high temperature difference between the source and sink without affecting its COP can be used.

[0145] Preferably, heat recovery is carried out in a heat exchanger.

[0146] In a preferred embodiment, the second heat transfer medium is water. Heat recovery is carried out in an air / water heat exchanger.

[0147] According to a second embodiment of the step of heating the second heat transfer medium, the second circuit 51 includes a branch, thereby defining at least a first branch 511 and a second branch 512 connected in parallel. The first heating step and the second heating step occur in parallel by means of a first heat recovery unit 52 arranged on the first branch 511 and a second heat recovery unit 53 arranged on the second branch 512, respectively. The first branch 511 is configured to flow back into the second branch 512 downstream of the second heat recovery unit 53 and upstream of the heat pump 30.

[0148] In this configuration, the first heat recovery unit 52 includes: an additional heat pump 521 associated with the first branch 511 to transfer heat to the second heat transfer medium; a third loop 522 of the third heat transfer medium associated with the heat pump 30 as a heat source; and a heat exchanger 523 disposed on the third loop 522 upstream of the heat pump 30.

[0149] Therefore, the first heating step of the second heat transfer medium is carried out via an additional heat pump, which in turn receives source heat from the third heat transfer medium, which in turn receives heat from the heat recovery of the exhaust gas in the heat exchanger 523. Preferably, the exhaust gas has a low dew point.

[0150] In this embodiment, the second heat transfer medium receives heat recovered from the two heat sources in parallel.

[0151] This embodiment is particularly advantageous when the heat pump can operate under a limited temperature difference from the source and sink without excessively incorporating COP. In these cases, a solution with two or more different heat pumps, as described later, is necessary for recovering energy from the extraction of humid air with different dew points.

[0152] In a preferred embodiment, the second heat transfer medium is water, and the third heat transfer medium is also water. The heat exchanger 523 of the first recovery unit 52 is an air / water heat exchanger, and the second recovery unit 53 is also an air / water heat exchanger.

[0153] According to the second embodiment, the first heating step occurs through heat recovery of wastewater extracted from the cooling lines of utilities. These utilities are located within the drying process.

[0154] The wastewater referred to here is water that has already exchanged heat with public utilities and is awaiting cooling.

[0155] As described above, the second heating step occurs through heat recovery from the exhaust gas.

[0156] This embodiment is particularly advantageous when the temperature setpoint of the first heat transfer medium leaving the heat pump 30 is lower than in other embodiments, thereby enabling the second heat transfer medium leaving the heat pump 30 to reach a low temperature at the source side.

[0157] In a preferred embodiment, the second heat transfer medium is water. The first heat recovery unit 52 is a water / water heat exchanger, while the second heat recovery unit 53 is an air / water heat exchanger.

[0158] Specifically, the air / water heat exchangers mentioned throughout the text are condensing heat exchangers, and therefore they have a secondary outlet for condensate.

[0159] According to one embodiment, the drying process includes the step of re-injecting air into the dryer 10.

[0160] According to one embodiment, the drying process includes the step of adjusting the relative humidity value in climate zone 11 of the dryer 10. The adjustment step includes the following steps:

[0161] - Monitor the relative humidity of the air in climate zone 11;

[0162] - Compare the acquired data with a predefined range of relative humidity of the air;

[0163] - Adjust the airflow rate intended for heat recovery and the airflow rate emitted into the environment to maintain the relative humidity level within climate zone 11 within a predefined range.

[0164] Specifically, the step of adjusting the airflow rate is carried out by increasing the airflow rate discharged into the environment when the inlet temperature of the second heat transfer medium in the heat pump 30 is too high (thereby reducing the airflow rate of the air sent to the heat recovery unit).

[0165] In practice, the system's COP depends on the heat power and temperature difference on the sink side and on the input and output temperatures of the second heat transfer medium on the source side. The necessary heat power for the recovery system can be obtained from the COP, and thus the flow rate of the fluid (second heat transfer medium 51) on the source side. If the energy recovery power exceeds the heat pump's requirements (higher return water temperature), the discharge will be activated.

[0166] This solution offers greater flexibility and allows the drying process to be independent of the operation of heat pump 30.

[0167] The features and advantages of the drying unit and drying process for drying pasta products or snack products according to the present invention are obvious, and the benefits are also obvious.

[0168] In particular, by employing the described recovery system, energy absorption can be reduced by 60%-70% compared to dryers that do not achieve energy recovery. A significant reduction in CO2 emissions is also achieved.

[0169] The proposed solution allows energy to be recovered from different heat sources within the drying process via a heat pump, which are at different temperature levels, typical for dryers used for pasta and snack products.

[0170] In embodiments that perform two different exhaust gas extractions, the proposed solution allows for the organization of heat recovery based on the dew point of the exhaust gas, wherein the two different embodiments of the heat recovery unit depend on the type of heat pump available.

[0171] If possible, based on the temperature parameters required for the drying process, the proposed solution can be used to perform heat recovery on the cooling water used in the cooling lines of utilities.

[0172] Furthermore, the modulation and balancing system for the airflow rate extracted from the heat recovery unit and the environment allows for adjustment of the humidity and temperature of the air in the dryer thanks to sensors.

Claims

1. A drying unit for drying pasta products or snack products, comprising: Dryer, the dryer being of the type with circulating airflow; A heat exchanger associated with the dryer, such that the airflow is heated before the product is dried; Heat pump; A first loop of a first heat transfer medium, the first loop extending between the heat pump and the heat exchanger, such that the first heat transfer medium receives heat from the heat pump and transfers the heat to the airflow in the heat exchanger; A heat recovery system, comprising: - A second loop of the second heat transfer medium, the second loop being associated with the heat pump, such that the second heat transfer medium transfers heat to the heat pump; - At least a first heat recovery unit and a second heat recovery unit, the first heat recovery unit and the second heat recovery unit being arranged on the second circuit to heat the second heat transfer medium and being located upstream of the heat pump; - At least a first heat source line and a second heat source line, each heat source line being configured to transfer waste fluid used in the process within the drying unit to a heat recovery unit within the heat recovery unit for heating the second heat transfer medium. At least one of the first heat source pipeline and the second heat source pipeline is an extraction pipeline for exhaust gas from the dryer.

2. The drying unit according to claim 1, wherein, The dryer includes at least a first climate zone and a second climate zone, which are configured to perform drying treatment on the product with different parameters. The first heat source line and the second heat source line are extraction lines for exhaust gases from the first climate zone and the second climate zone, respectively.

3. The drying unit according to claim 2, wherein, The first heat source pipeline is configured to carry exhaust gas with a lower dew point than the exhaust gas carried by the second heat source pipeline. The first heat recovery unit is arranged in series with the second heat recovery unit and is located upstream of the second heat recovery unit. The first heat recovery unit is associated with the first heat source pipeline such that heat recovery is performed in ascending order of the dew point of the exhaust gas.

4. The drying unit according to claim 2, wherein, The second circuit includes a branch, thereby defining at least a first branch and a second branch in parallel, the first heat recovery unit being arranged on the first branch and the second heat recovery unit being arranged on the second branch, the first branch being configured to flow back into the second branch downstream of the second heat recovery unit and upstream of the heat pump.

5. The drying unit according to claim 4, wherein, The first heat recovery unit includes: - An additional heat pump, which is associated with the first branch, to transfer heat to the second heat transfer medium; - A third loop of a third heat transfer medium, the third loop being associated with the heat pump as a heat source; - A heat exchanger arranged in the third loop upstream of the heat pump, the heat exchanger being associated with one of the heat source lines to transfer heat to the third heat transfer medium.

6. The drying unit according to claim 1, wherein, The first heat source pipeline is a wastewater extraction pipeline from the cooling pipeline of the utility of the drying unit, while the second heat source pipeline is a waste gas extraction pipeline from the dryer.

7. The drying unit according to claim 1, wherein, The heat source pipeline, in the form of an exhaust gas extraction pipeline, includes an emission path for discharging the exhaust gas into the environment.

8. The drying unit according to claim 7, wherein, The dryer includes: at least one climate zone in which the product is dried; and a system for adjusting the relative humidity value in the at least one climate zone, the system including at least one relative humidity sensor for monitoring the relative humidity of the air in the climate zone and a control unit configured to perform at least the following operations: - Receive relative humidity data from the relative humidity sensor; - Compare this data with a predefined range; - Adjust the airflow velocity toward the heat recovery unit and the airflow velocity discharged into the environment to maintain the relative humidity level within the climate zone within the predefined range.

9. A drying method for drying pasta products or snack products, comprising the following steps: The product is dried by means of a circulating airflow, and the drying process causes the air to collect moisture from the product, thereby becoming exhaust gas; The circulating airflow is heated prior to the drying step, and the heating step is carried out in a heat exchanger; A first heat transfer medium circulates in a first loop, and the step of heating the circulating airflow occurs through heat transfer from the first heat transfer medium to the circulating airflow. The first loop extends between the heat pump and the heat exchanger, such that the first heat transfer medium receives heat from the heat pump and transfers it to the airflow in the heat exchanger. A second heat transfer medium circulates in a second loop, which is associated with the heat pump, such that the second heat transfer medium transfers heat to the first heat transfer medium via the heat pump. Before the heat transfer from the second heat transfer medium to the heat pump, the second heat transfer medium circulating in the second circuit is heated; The step of heating the second heat transfer medium includes at least a first heating step and a second heating step. Both the first heating step and the second heating step include a heat recovery step of the waste fluid used in the process within the drying process. At least one of the first step and the second step of heating the second heat transfer medium is carried out by heat recovery of the waste gas from the drying step.

10. The drying method according to claim 9, wherein, The drying process includes two distinct drying steps performed in a first climate zone and a second climate zone. The first heating step is performed by heat recovery from waste gas extracted from the first climate zone, and the second heating step is performed by heat recovery from waste gas extracted from the second climate zone.

11. The drying method according to claim 10, wherein, The first heating step and the second heating step occur sequentially. The first heating step occurs by heat recovery of exhaust gas with a low dew point, while the second heating step occurs by heat recovery of exhaust gas with a high dew point.

12. The drying method according to claim 10, wherein, The second circuit includes a branch, thereby defining at least a first branch and a second branch in parallel; the first heating step and the second heating step are performed in parallel by means of a first heat recovery unit arranged on the first branch and a second heat recovery unit arranged on the second branch, respectively, the first branch being configured to flow back into the second branch downstream of the second heat recovery unit and upstream of the heat pump.

13. The drying method according to claim 9, wherein, The first heating step occurs by heat recovery of wastewater extracted from cooling lines of utilities associated with the drying process.

14. The drying method according to claim 9, wherein, The drying process is carried out in the corresponding climate zone, and includes adjusting the relative humidity value of the climate zone. The adjustment process includes the following steps: - Monitor the relative humidity of the air in the climate zone; - Compare the acquired data with a predefined range of relative humidity for the air; - Adjust the airflow rate intended for the heat recovery and the airflow rate emitted into the environment to maintain the relative humidity level within the climate zone within a predefined range.

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