EP3784830B1 - Drier and method for operating a drier - Google Patents

Description

The invention relates to a dryer with a holder for items to be dried, an air duct for guiding circulating air and/or fresh air to the holder, a heating device and at least one sensor for determining relative humidity and/or temperature, the air duct comprising at least one adjustment element, see above that the proportion of circulating air led to the recording can be changed via the setting element. The invention also relates to a method for controlling or regulating a dryer according to the invention.

Dryers of the type mentioned are known from practice and exist in different embodiments. This is only an example on the document WO 2016/184462 A1 referred.

In general, after the washing process with mechanical dewatering, the residual water is removed from the textiles under the influence of heat. Depending on the type of laundry, pre-drying takes place in the drum dryer (tumbler) as preparation for ironing flat laundry or for finishing shaped parts. Certain parts (e.g. terry goods) are subjected to "full drying". Pre- and full drying differ in the water content (residual moisture) of the laundry items at the end of the drying process. Depending on the type of laundry and subsequent treatment, the final residual moisture content of the textile (water content based on the dry laundry mass) is between 35% and 50% (pre-drying) or 5% and 0% (full drying). A significant problem in the removal of residual water under the influence of heat with the known dryers is the extremely unfavorable efficiency.

The desired residual textile moisture determines the required drying time, the drying energy requirement and the textile damage caused by drying, the service life of the laundry items and thus the economic situation of the mostly small and medium-sized laundry companies.

The energy requirements for heating the exhaust air dryers currently used in laundries are up to 1.5 kWh/kg of dried textile. The reason for this high thermal energy requirement, compared to the theoretically required for evaporating the water, is that the porous material to be dried is heated by hot air, which is directed to the textiles by means of a blower and at the same time takes over the removal of the evaporated water. Directly gas-heated dryers have prevailed over steam-heated dryers due to the lower installation costs, the easier control of the thermal energy supply and the lower energy consumption. Electrical heating is only used in small commercial machines or for household appliances

The damage caused by drying is, in particular, damage to textiles such as changes in the dimensions of the textile, a reduction in the degree of whiteness and color, and chemical damage to the fiber substrate. This type of damage to textiles occurs in particular as a result of "overdrying" of the items of laundry (removal of the water contained in textiles at normal humidity levels, around 10% in the case of cotton) at elevated temperatures and drying times. Prolonged drying time - even at low temperatures - promotes fiber abrasion due to intensive "drying mechanics".

A dryer and a method for operating a dryer according to the prior art are from EP 0 503 586 A1 known.

The present invention is therefore based on the object of designing and developing a dryer and a method for operating a dryer in such a way that gentle drying with the lowest possible energy requirement is made possible with structurally simple means.

According to the invention, the above object is achieved by the features of claim 1.

In a manner according to the invention, it was first recognized that the drying process can be significantly optimized in terms of energy efficiency and gentle treatment of textiles if the proportion of circulating air and/or the heating output can be regulated or controlled during operation. In concrete terms, the proportion of circulating air and/or the heating output can be changed by a control or regulation device, taking into account the different drying phases, which means that drying can be carried out overall with an extremely high degree of saturation of the process air and the lowest possible air temperature. As a result of the structural design according to the invention, in addition to a high utilization of the amount of heat, the drying process is extremely gentle on the textiles, since overheating of the material to be dried is avoided. It is pointed out that the proportion of recirculated air can be routed inside--for example in a hood--and/or outside--for example in pipes.

In the context of this invention, the term "fresh air" refers to ambient air that is supplied to the dryer, for example the receiver or the burner.

The term "process air" refers to the air contained in the receptacle during the drying process. "Exhaust air" means the air removed from the receptacle. If the exhaust air is returned to the intake and thus forms part of the process air, it is referred to as "circulating air".

The "goods to be dried" can be textiles or goods made of other materials, for example rubber mats or mats made of polyamide pile.

In the case of a single dryer, the “receptacle” can be designed in particular as a drum. In an embodiment with several, for example behind or modules arranged next to one another, the recording of the entire device can be formed, for example, by the respective drums of the modules, ie also be modular.

The setting element can advantageously be a ventilation flap and/or a circulating air fan. The ventilation flap can be arranged in an air duct in such a way that in the open position of the ventilation flap, exhaust air is fed back to the intake and thus serves as circulating air. In a particularly advantageous manner, the ventilation flap and, if necessary, the air duct are designed in such a way that a proportion of circulating air of 100% can be realized in a completely open ventilation flap position and a proportion of circulating air of 0% can be realized in a closed ventilation flap position. Alternatively or additionally, a circulating air fan can be arranged in the air duct in order to convey exhaust air to the receptacle as circulating air.

In order to enable a particularly precise setting of the proportion of circulating air, it is conceivable that the ventilation flap position and/or the circulating air fan output can be adjusted at least essentially continuously. This design measure enables a particularly energy-efficient control or regulation of the drying process. In concrete terms, it is possible for the ventilation flap to be operable by means of a servomotor or a cylinder-piston device (e.g. pneumatic cylinder).

In a further advantageous manner, it is conceivable that the sensor is used to determine the relative humidity of the exhaust air discharged from the inlet. This sensor can have a filter element to protect the sensor from fluff. A fabric filter or sintered steel element, in particular with a pore size of 5 μm, can be used as the filter element. At this point it is pointed out that the term "relative exhaust air humidity" is to be understood in the broadest sense, since the measurement of the relative air humidity can also take place inside the recording and thus affect the process air. Alternatively or additionally, a sensor for determining the surface temperature of the material to be dried can be arranged. For example, this can be an infrared sensor or any other temperature sensor. also is it is possible that a combined temperature and humidity sensor is provided. It is also conceivable that a sensor for determining the inlet air temperature and/or the outlet air temperature is arranged. The inlet air is the air that is introduced into the receptacle, while the outlet air is the air that is exhausted from the receptacle. Any combination of the above sensors can thus be arranged. In a modular configuration, the number and mode of operation of the sensors in the individual modules can differ from one another, so that the sensors are provided in accordance with the defined task of the modules. The inlet air temperature and/or the outlet air temperature can be taken into account when controlling or regulating the proportion of circulating air and/or the heat output.

According to an advantageous embodiment, the adjustment element, in particular the ventilation flap position and/or the circulating air fan, can be controlled with the relative exhaust air humidity and/or with the surface temperature of the material to be dried as a measured variable and the circulating air proportion as a manipulated variable. Such a design ensures that the proportion of circulating air can be adapted to the relevant, variable parameters during operation, which results in a significant improvement in efficiency and avoids damage to the material to be dried.

Alternatively or additionally, it is also conceivable for the heating device to be controlled using the relative exhaust air humidity and/or the surface temperature of the material to be dried as the measured variable and the heating power as the manipulated variable. In this way, the heat output of the burner can be adjusted to the essential parameters that change during the drying process.

In a further advantageous manner, the receptacle can have several modules arranged one after the other and/or next to one another, which are suitably designed for heating, drying or cooling the material to be dried; in particular, each module can have its own heating device. In this case, the receptacle can have two or more modules arranged one after the other and/or next to one another. This offers the possibility of carrying out individual process steps in a particularly efficient manner, with the proportion of circulating air and/or the heat output of the heating device of each module can be controllable during the drying process. For example, a structure with a module for heating, one or more modules for drying, a module for checking the moisture content of the material to be dried and a module for cooling the material to be dried is particularly efficient. Furthermore, the dryer can have at least one transport device assigned to a module for transporting the material to be dried onward from this module to another module. Such a transport device enables safe transport or safe transfer of the material to be dried in the drying process effected by the modules.

In an advantageous exemplary embodiment, the air duct can be designed in such a way that the circulating air supplied to a module is exhaust air from this module and/or exhaust air from at least one other module. In particular, it can be the exhaust air from a module arranged in front of it, viewed in the direction of transport of the material to be dried, preferably the module arranged directly in front of it or a plurality of modules arranged in front of it. By at least partially using exhaust air as circulating air, the heat contained in the exhaust air can be used in one or more other modules. As an alternative or in addition to such use of the exhaust air as supply air or circulating air, the exhaust air can also be used as combustion air for the heating device if the heating device is operated by means of a combustion process. In addition to such a mode of operation of the heating device, the air can also be heated by means of steam or electrical energy—without a combustion process. In this case, exhaust air from a module is not required for the heating device.

As an alternative or in addition to using the exhaust air from a module or multiple modules as described above, heat from the exhaust air from a module or multiple modules can be at least partially transferred to supply air and/or circulating air, in particular one that is arranged in front of it, preferably the one that is arranged directly in front of it. Module or several, in particular modules arranged in front of it, can be transferred. Such a transfer process can be carried out by means of one or more heat exchangers, preferably air/air heat exchangers, take place. This type of use of waste heat from an exhaust air differs from a direct transmission of the heat due to the means of transmission used - the heat exchanger - as is the case, for example, in a case where exhaust air from one module at least partially forms supply air from another or several other modules. A heat exchanger can be integrated into a module, for example, or can be assigned directly to a module, for example to enable air recirculation of the module. Alternatively or additionally, a heat exchanger or several heat exchangers can be provided, which are arranged in an air duct or integrated into an air duct in order, if necessary, to preheat, for example, supply air for a module using exhaust air from a module.

To ensure a particularly good drying result and to ensure efficient use of the energy required, a module for checking the moisture content of the material to be dried can be arranged in front of a module for cooling the material to be dried. Such a control module can form the end of an arrangement of modules for heating and for drying, in order to control the moisture content before the material to be dried is cooled and, if necessary, to carry out additional post-drying in the control module.

With regard to a particularly efficient use of the energy required, air supply to a module for controlling the moisture content of the material to be dried can be at least partially air that is heated by means of a heat exchanger, preferably an air/air heat exchanger, which uses thermal energy from the exhaust air of a module to heat up the Material to be dried and/or from the exhaust air of another module or the module for controlling the moisture content of the material to be dried itself. In this case, energy can be used efficiently by supplying preheated supply air. In a particularly advantageous manner, the supply air to this control module is formed exclusively by air that has been preheated in the manner described.

One or more modules for cooling the items to be dried, usually arranged at the end of the arrangement of different modules supply air or fresh air can be supplied from the installation room in which this module or the modules are located, or from outside the building.

In a further advantageous manner, it is conceivable that the air duct, which can be formed, for example, at least partially in the form of corresponding tubes, has additional blowers or fans. This makes it possible to support the air flow, so that a reliable functioning of the dryer is ensured, particularly when the air is ducted over larger distances.

In a particularly advantageous embodiment, a transport device can be arranged between two modules in each case. The transport device can preferably have a conveyor belt or a chute or a chute. In the case of a chute or chute, a suitable height offset between the modules makes sense so that the drying goods can be moved from one module to the next module by gravity. If necessary, a compressed air support can be provided, which ensures a safe further transport of the material to be dried. As an alternative to the aforementioned embodiments, the transport device can be designed as an internal mechanism of a module or can be integrated into a module. Such a transport device or mechanism can move the goods to be transported between modules by means of suitable gripping and/or guiding elements. When selecting a suitable transport device, the required quantity of drying material to be transported can be taken into account.

With regard to a reliable supply of the drying material to the receptacle, a drying material feed device can be arranged in front of the receptacle, which preferably has a weighing device for the drying material. This ensures that the dryer and specifically the recording is loaded with a suitable amount of drying material. This prevents the dryer from being overloaded.

To further optimize the drying process, it is possible for the control or regulation device to record the material to be dried (type of material to be dried), the heating temperature, the residual drying moisture, the initial drying moisture, the load quantity, the filling ratio, the process air condition variables, the blower output (of a circulating air blower and /or a heater fan), the drum movement and/or the burner temperature is taken into account. For example, the user can specify that the items to be dried are rubber mats or mats made of polyamide pile with a specific load. Corresponding parameters can be entered, for example, via an input device and taken into account by the open-loop or closed-loop control device. In other words, the user can select a specific program for an item to be dried in order to carry out the drying process. It is also conceivable that the setting element or the setting elements can be regulated as a function of the pressure prevailing in the air duct. One or more air pressure sensors can be arranged for this purpose.

With regard to the method, the underlying object is achieved by the features of independent claim 12 . According to this, a method for operating a dryer, in particular according to one of Claims 1 to 11, with a holder for drying material, an air duct for guiding circulating air and/or fresh air to the holder, a heating device and at least one sensor for determining relative humidity and /or temperature, the air ducting comprising at least one adjusting element, so that the proportion of circulating air led to the receptacle is changed via the adjusting element, characterized in that a proportion of circulating air directed to the receptacle and/or the heat output of the heating device during the drying process via a control or control device is controlled or regulated.

In accordance with the invention, it has been recognized that a significant improvement in efficiency can be achieved by adapting the proportion of circulating air and/or the heat output during the drying process.

It is pointed out that the device claims 1 to 9 also have features with a procedural form. These can expressly also represent part of the method according to the invention as claimed in claim 10 . The same applies to the above general description of the dryer according to the invention.

According to the invention, a high proportion of circulating air and a small proportion of fresh air are directed to the receptacle during a heating phase, with the proportion of circulating air being reduced during a drying phase as a function of the measured relative exhaust air humidity, with a small proportion of circulating air and a high proportion of fresh air being directed to the receptacle during a cooling phase. wherein the duration of the drying phase and/or the reduction in the proportion of circulating air during the drying phase is adjusted taking into account at least one external parameter.

With regard to gentle and efficient drying, it can be provided that the duration of the drying phase and/or the reduction in the proportion of circulating air is adjusted during the drying phase, taking into account at least one external parameter. The type of material to be dried, the heating temperature, the residual moisture of the material to be dried, the initial moisture of the material to be dried, the load, the filling ratio, process air condition variables, the fan output (of a circulating air fan and/or a heating fan), the drum movement and/or the burner temperature can serve as external parameters. There are now various possibilities for embodying and developing the teaching of the present invention in an advantageous manner. This is on the one hand on the claims subordinate to claims 1 and 10 and on the other hand to refer to the following explanation of preferred exemplary embodiments of the invention with reference to the drawing. In connection with the explanation of the preferred embodiments of the invention with reference to the drawings are also

Fig. 1

zeigt den typischen Verlauf der Gewebetemperatur in Abhängigkeit der Trockenzeit bei einem Trocknungsprozess,

Fig. 2

zeigt in einer schematischen, geschnittenen Darstellung ein erstes Ausführungsbeispiel eines erfindungsgemäßen Trockners zur Durchführung des erfindungsgemäßen Verfahrens,

Fig. 3

zeigt in einer schematischen, perspektivischen Darstellung ein zweites Ausführungsbeispiel eines erfindungsgemäßen Trockners zur Durchführung des erfindungsgemäßen Verfahrens,

Fig. 4

zeigt in einer schematischen, seitlichen Darstellung das Ausführungsbeispiel gemäß Fig. 3,

Fig. 5

zeigt in einer schematischen, seitlichen und teilweise geschnittenen Darstellung das Ausführungsbeispiel gemäß Fig. 3,

Fig. 6

zeigt in einer schematischen, Draufsicht das Ausführungsbeispiel gemäß Fig. 3.

generally preferred configurations and developments of the teaching are explained. Show in the drawing

1

shows the typical course of the fabric temperature depending on the drying time in a drying process,

2

shows a first exemplary embodiment of a dryer according to the invention for carrying out the method according to the invention in a schematic, sectional view,

3

shows a schematic, perspective representation of a second exemplary embodiment of a dryer according to the invention for carrying out the method according to the invention,

4

shows the exemplary embodiment according to FIG 3 ,

figure 5

shows the exemplary embodiment according to FIG 3 ,

6

shows the embodiment according to FIG 3 .

1 shows the typical temperature profile over time in the material to be dried for the duration of the drying process, with the fabric temperature being plotted as a function of the drying time. The three phases 1, 2, 3 of the drying process can be seen. In the first phase 1, the temperature rises rapidly to the value of the evaporation temperature (cooling limit temperature) in order to keep this constant during the second phase 2 as long as the moisture is evaporated from the surface of the textile. In the third phase 3, the remaining moisture is evaporated from the capillaries of the textiles, which leads to a sharp rise in temperature up to the level of hot air. This Phase indicates that the drying process is complete, the heat supply has stopped and the cool-down can be initiated.

2 shows a first embodiment of a dryer according to the invention. The dryer is designed as a single dryer and has a receptacle 4 for the material to be dried, which is not shown. The recording 4 can be designed as a drum. The receptacle 4 can be supplied with fresh air 5 from outside the device, which is guided transversely through the receptacle 4 and there, as process air 6, removes moisture from the material to be dried. The exhaust air 7 discharged from the receptacle passes through a fluff filter 8 . A circulating air fan 9 and a moisture sensor 10 are arranged after the fluff filter 8 , viewed in the flow direction of the exhaust air 7 . This arrangement prevents the moisture sensor 10 from becoming full of fluff. However, it is also possible to arrange the moisture sensor 10 in front of the fluff filter 8 as viewed in the direction of flow.

Furthermore, in 2 a ventilation flap 11 is shown. If the ventilation flap 11 is closed, the exhaust air 7 is led out of the dryer. When the ventilation flap 11 is fully or partially opened, the exhaust air 7 can be supplied entirely or partially to the receptacle 4 as circulating air 12 .

At the in 2 shown device, which is suitable for carrying out the method according to the invention, the position of the ventilation flap 11 and / or the power of the circulating air fan 9 can be adjusted depending on the humidity of the exhaust air 7 measured with the humidity sensor 10 during operation. Furthermore, it is conceivable that a temperature sensor 13 is arranged in the receptacle 4, which is used to determine the surface temperature of the drying material. A sensor for determining the inlet air temperature and/or a sensor for determining the outlet air temperature can also be provided.

In the Figures 3 to 6 Another exemplary embodiment of a device according to the invention, which is suitable for carrying out a method according to the invention, is shown in different schematic representations. At In this exemplary embodiment, the receptacle 4 is formed by a plurality of modules 14, 14', 14" arranged one after the other, for example for heating, drying or cooling the material to be dried. The individual modules 14, 14', 14" can be configured in accordance with the 2 illustrated embodiment may be formed, so that reference is made to the relevant statements. In such an embodiment, the receptacle 4 of the entire device can be formed by the individual receptacles or drums of the modules 14, 14', 14''.

From the Figures 3 to 6 also shows that fresh air can be routed to the individual modules via a fresh air duct 15 . Furthermore, each module has a circulating air duct 16, via which circulating air can be supplied to the receptacle 4, i.e. to each module 14, 14', 14", by regulating or controlling the setting elements (not shown). The exhaust air of the respective module 14 , 14', 14" can be discharged via an exhaust air duct 21.

Furthermore, a heat exchanger 17 is arranged, via which the heat from the exhaust air can be transferred to the incoming air.

To further improve the energy efficiency, the first module 14 has a heating air supply 18 via which the heating device 19 can be supplied with fresh air which can be preheated via the heat exchanger 17 . It is conceivable that all modules 14, 14', 14'' have a corresponding heating air supply 18.

In front of the first module 14 there is a drying material feed, via which the module 14 is loaded with the drying material. Between the modules 14 and module 14′ and between module 14′ and module 14″ there is a transport device 20 for further transport of the material to be dried.

Due to the modular design of the device, the material to be dried can be heated, for example, in the first module 14 , ie the heating-up phase takes place in this module 14 . The actual drying of the material to be dried can take place in the second module 14', ie the drying phase takes place in this module 14'. In the last module 14″, for example, the material to be dried can be cooled, ie the cooling phase takes place The proportion of circulating air supplied to individual modules 14, 14' and 14" can take place during the drying process as a function of the measured humidity and/or surface temperature of the material to be dried. Alternatively or additionally, the heat output of the heating devices of modules 14, 14' and 14" can be adjusted as a function of these measured values become.

With regard to further advantageous configurations of the device according to the invention and the method according to the invention, to avoid repetition, reference is made to the general part of the description and to the appended claims.

Finally, it should be expressly pointed out that the above-described exemplary embodiments of the device according to the invention and the method according to the invention only serve to explain the claimed teaching, but do not restrict it to the exemplary embodiments.

Reference List

1

first phase

2

second phase

3

third phase

4

Recording

5

fresh air

6

process air

7

exhaust air

8th

fluff filter

9

circulating fan

10

humidity sensor

11

ventilation flap

12

circulating air

13

temperature sensor

14, 14', 14"

module

15

fresh air intake

16

circulating air supply

17

heat exchanger

18

heating air supply

19

heating device

20

transport device

21

exhaust duct

Claims (14)

1. Dryer having a receiving member (4) for material to be dried, an air guide for guiding circulating air (12) and/or fresh air (5) to the receiving member (4), a heating device (19) and at least one sensor (13, 17) for determining relative air humidity and/or temperature, wherein the air guide comprises at least one adjustment element (9, 11) so that the circulating air proportion which is guided to the receiving member (4) can be changed by means of the adjustment element (9, 11), wherein a control and/or regulation device is arranged so that the circulating air proportion which is guided to the receiving member and/or the heating power of the heating device (19) can be controlled or regulated during the drying process,
   characterised in that during a heating phase a high circulating air proportion and a low fresh air proportion are directed to the receiving member (4), wherein the circulating air proportion during a drying phase is reduced in accordance with the measured relative exhaust air humidity, wherein during a cooling phase a low circulating air proportion and a high fresh air proportion is directed to the receiving member (4), wherein the duration of the drying phase and/or the reduction of the circulating air proportion is adapted during the drying phase taking into account at least one external parameter.
2. Dryer according to claim 1, characterised in that the adjustment element is in the form of a ventilation flap (11) and/or a circulating air fan (9), wherein the ventilation flap position and/or the circulating air fan power can be varied at least substantially in a stepless manner.
3. Dryer according to claim 1 or 2, characterised in that the sensor (10) serves to determine the relative exhaust air humidity of the exhaust air (7) discharged from the input (4).
4. Dryer according to any one of claims 1 to 3, characterised in that the sensor (13) serves to determine the surface temperature of the material to be dried and/or to determine an input air temperature and/or output air temperature.
5. Dryer according to claim 3 or 4, characterised in that the control of the adjustment element (9, 11) is carried out with the relative exhaust air humidity as a measurement variable and the circulating air proportion as a manipulated variable.
6. Dryer according to any one of claims 3 to 5, characterised in that the control of the adjustment element (9, 13) is carried out with the surface temperature of the material to be dried as a measurement variable and the circulating air proportion as a manipulated variable.
7. Dryer according to any one of claims 3 to 6, characterised in that the control of the heating device (19) is carried out with the relative exhaust air humidity and/or the surface temperature of the material to be dried as a measurement variable and the heating power as a manipulated variable.
8. Dryer according to any one of claims 1 to 7, characterised in that the receiving member (4) has a plurality of modules (14, 14', 14") which are arranged one after the other and/or beside each other for heating, drying or cooling the material to be dried and in that a transport device (20) for the onward transport of the material to be dried from this module (14, 14', 14") to another module (14, 14', 14") is associated with at least one module (14, 14', 14"), wherein the air guide may be configured in such a manner that the circulating air supplied to one module (14, 14', 14") is exhaust air (7) of this module (14, 14', 14") and/or exhaust air (7) of at least one other module (14, 14', 14").
9. Dryer according to any one of claims 1 to 8, characterised in that the control or regulation device takes into account as additional parameters the material to be dried and/or the heating temperature and/or the residual humidity of the material to be dried and/or the initial humidity of the material to be dried and/or the load quantity and/or the filling ratio and/or process air state variables and/or the fan power and/or the drum movement and/or the burner temperature.
10. Method for operating a dryer, in particular according to any one of claims 1 to 9, having a receiving member (4) for material to be dried, an air guide for guiding circulating air (12) and/or fresh air (5) to the receiving member (4), a heating device (19) and at least one sensor (10, 13) for determining relative air humidity and/or temperature, wherein the air guide comprises at least one adjustment element (9, 11) so that the circulating air proportion which is guided to the receiving member (4) is changed by means of the adjustment element (9, 11), wherein a circulating air proportion which is guided to the receiving member (4) and/or the heating power of the heating device (19) is controlled or regulated during the drying process by means of a control and/or regulation device,
    characterised in that during a heating phase a high circulating air proportion and a low fresh air proportion is directed to the receiving member (4), wherein the circulating air proportion during a drying phase is reduced in accordance with the measured relative exhaust air humidity, wherein during a cooling phase a low circulating air proportion and a high fresh air proportion is directed to the receiving member (4), wherein the duration of the drying phase and/or the reduction of the circulating air proportion during the drying phase is adapted taking into account at least one external parameter.
11. Method according to claim 10, characterised in that during a heating phase a high circulating air proportion between 90% and 100% of circulating air and a low fresh air proportion between 0% and 10% of fresh air is directed to the receiving member (4).
12. Method according to claim 10 or 11, characterised in that during a drying phase the heating power of the heating device (19) is reduced.
13. Method according to any one of claims 10 to 12, characterised in that during a cooling phase a low circulating air proportion of from 0% to 10% and a high fresh air proportion of from 90% to 100% is directed to the receiving member (4).
14. Method according to claim 10, characterised in that the material to be dried and/or the heating temperature and/or the residual humidity of the material to be dried and/or the initial humidity of the material to be dried and/or the load quantity and/or the filling ratio and/or process air state variables and/or the fan power and/or the drum movement and/or the burner temperature is used as an external parameter.

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