Sustainable drying system with reduced energy consumption

Abstract

Drying system for drying a drying medium, in particular for drying fibrous materials, the drying system (1) comprising at least the following components: - an air-to-air heat exchanger (20) with an air-to-air exhaust volume (21) and an air-to-air fresh air volume (22), comprising the air-to-air heat exchanger (20): - a feed-in LLW exhaust air flow arrangement (100) for supplying exhaust air (K) with an initial temperature (T_I) into the LLW exhaust air volume (21) and - a discharging LLW exhaust air flow arrangement (200) with an exhaust air follow-up temperature (T_AF) for discharging exhaust air (K) from the LLW exhaust air volume (21), - a feed-in LLW fresh air flow arrangement (2000) for supplying fresh air (F) with a fresh air flow temperature (T_G) into the LLW fresh air volume (22) and - a discharge LLW fresh air flow arrangement (3000) for discharging fresh air (F) with an LLW outlet temperature (T_AT) from the LLW fresh air volume (22), wherein the LLW exhaust air volume (21) and the LLW fresh air volume (22) are designed such that heat can be transferred from the LLW exhaust air volume (21) to the LLW fresh air volume (22) to warm the fresh air (F); - a media heat exchanger (40) configured to be supplied with a circulating heat medium (U) in order to adjust the fresh air (F) with the LLW outlet temperature (T_AT) from the supplying LLW fresh air flow arrangement (3000) to a process temperature (T_P), wherein the fresh air (F) set to the process temperature (T_P) is supplied to the drying system (30) via a flow arrangement (4000) encompassed by the drying system (1); - a drying system (30) designed for drying the drying medium, wherein the drying system (30) is designed such that the fresh air (F) which is heated at least by the air-to-air heat exchanger (20) and the media heat exchanger (40) and which flows out at least indirectly from the LLW fresh air flow arrangement (3000) and flow-through arrangement (4000) interacts with the drying medium as drying air and absorbs evaporated moisture from the drying medium and discharges it as moisture-laden exhaust air (K) to an exhaust air duct arrangement (5000);wherein the drying system (1) is configured to direct the exhaust air (K) from the drying system (30) via the exhaust air duct arrangement (5000) and via the LLW exhaust air flow arrangement (100) at least indirectly to the air-to-air heat exchanger (20), so that at least an indirect transfer of heat from the exhaust air (K) in the exhaust air duct arrangement (5000) to the fresh air (F) in the air-to-air heat exchanger (20) takes place; ; - a flow heat exchanger (60) with a heat transfer volume (61) and a heating volume (62), comprising the flow heat exchanger (60): - a heat inlet arrangement (300) for introducing a first flow heat medium (S1) with a flow temperature (T_S) into the heat transfer volume (61) and - a discharge heat outlet arrangement (350) with a flow sequence temperature (T_SF) for the discharge of the first flow heat medium (S1) from the heat transfer volume (61), - a feed-in circuit inlet arrangement (450) for the inflow of a second flow heat medium (S2) with a circuit inlet temperature (T_KE) into the heating volume (62) and - a discharge circuit outlet arrangement (400) for the discharge of the second flow heat medium (S2) with a circuit outlet temperature (T_KA) from the heating volume (62), wherein the heat transfer volume (61) and the heating volume (62) are designed such that heat can be transferred from the heat transfer volume (61) to the heating volume (62) in order to heat the second flowing heat medium (S2), wherein the first flow heat medium (S1) of the heat inlet arrangement (300) has flow components from the LLW exhaust air flow arrangement (200) and / or other flow components (SB), - a heat transfer device (70) with a cooling transfer volume (71) and a heating transfer volume (72), comprising the heat transfer device (70): - a heat transfer inlet arrangement (600) for introducing the second flow heat medium (S2) with a heat transfer inlet temperature (T_WTE) into the cooling transfer volume (71) and - a discharge heat transfer outlet arrangement (650) with a heat transfer outlet temperature (T_WTA) for the discharge of the second flow heat medium (S2) from the cooling transfer volume (71), - a circulating inlet arrangement (700) for introducing a circulating heat medium (U) with a circulating inlet temperature (T_UE) into the heat transfer volume (72) and - a discharge circulating outlet arrangement (750) for discharging the circulating heat medium (U) with a circulating outlet temperature (T_UA) from the heat transfer volume (72), and for at least indirect and / or at least partial inflow into the media heat exchanger (40), wherein the cooling transfer volume (71) and the heating transfer volume (72) are designed such that heat can be transferred from the cooling transfer volume (71) to the heating transfer volume (72) in order to heat the circulating heat medium (U); where the recirculation outlet temperature (T_UA) is greater than the fresh air flow temperature (T_G) and greater than the LLW outlet temperature (T_AT).

Description

[0001] A drying system for drying a drying medium is proposed.

[0002] A retrofit system is also proposed. Technical background

[0003] It is currently known that waste heat from a fiber drying process, such as paper or cardboard drying, is generally used to preheat fresh air or drying air. Drying air refers to the air used in the drying process of fibers like paper or cardboard to absorb and remove the moisture it contains.

[0004] For this purpose, ambient air at outside temperature is drawn from the surroundings and regularly preheated in an air-to-air heat exchanger. Such a heat exchanger is thus a waste heat recovery system in which fresh air is preheated by warm exhaust air from the drying process to provide drying air. Fresh air is defined as air drawn from the surroundings, for example, from the exterior of a production hall or from the production hall itself. Exhaust air is defined as air that has absorbed moisture during the drying process; therefore, it is moisture-enriched drying air.

[0005] In an air-to-air heat exchanger, warm, moisture-laden exhaust air flows, for example, through thin-walled smooth tubes. This cools and condenses the exhaust air within the heat exchanger. Cold fresh air then flows around the thin-walled tubes and is preheated by the exhaust air before exiting the heat exchanger and entering the drying process. Air-to-air heat exchangers are available in cross-flow or cross-counterflow configurations, often with reversing caps. Plate heat exchangers, made of thin-walled materials such as aluminum, stainless steel, glass, or other materials, are also used. It is essential that the exhaust and fresh air flows remain separate.

[0006] It is well known and widely established that air-to-air heat exchangers are designed for regional winter temperatures. For example, in Germany, drying systems are dimensioned for operation at an outside temperature of -15°C. If, in summer, the outside temperature reaches, say, 35°C, this represents a temperature difference of 50°C compared to the system's design basis. This means that in summer, air-to-air heat recovery through the oversized air-to-air heat exchanger becomes uneconomical, as the drying system is designed for winter operation. The rationale behind the winter operating design, or winter mode, is to preheat the fresh air to the highest possible temperature in the air-to-air heat exchanger, even in cold months, to ensure smooth operation of the drying system.Due to the low temperatures in winter, an oversized air-to-air heat exchanger and thus an oversized drying system are also common in summer months. Description of the provided solution

[0007] Given this situation, the task is to provide an energy-optimized drying system for year-round operation.

[0008] This problem is solved by the features of the independent main claims. Advantageous embodiments are specified in the dependent claims. Where technically feasible, the teachings of the dependent claims can be combined arbitrarily with those of the main and dependent claims.

[0009] In particular, the problem is solved by a drying system for drying a drying medium, especially for drying fibrous materials, the drying system comprising at least the following components: - an air-to-air heat exchanger, LLW, with an LLW exhaust air volume and an LLW fresh air volume, comprising the air-to-air heat exchanger: - a feed-in LLW exhaust air flow arrangement for the inflow of exhaust air with an initial temperature into the LLW exhaust air volume and - a discharge LLW exhaust air flow arrangement with an exhaust air follow-up temperature for the discharge of exhaust air from the LLW exhaust air volume, - a supplying LLW fresh air flow arrangement for the inflow of fresh air with a, in particular controlled, fresh air flow temperature into the LLW fresh air volume and - an exhaust air fresh air flow arrangement for the discharge of fresh air with an air fresh air outlet temperature from the air fresh air volume, wherein the air fresh air exhaust volume and the air fresh air volume are designed in such a way that heat can be transferred from the air fresh air exhaust volume to the air fresh air volume in order to warm the fresh air; - a media heat exchanger designed to be supplied with a circulating heat medium to adjust the fresh air with the LLW outlet temperature from the supplying LLW fresh air flow arrangement to a process temperature, wherein the fresh air adjusted to the process temperature is supplied to the drying system via a flow arrangement encompassed by the drying system; - a drying system designed for drying the drying medium, wherein the drying system is designed such that the fresh air, which is heated at least by the air-to-air heat exchanger and the media heat exchanger and which flows out at least indirectly from the LLW fresh air flow arrangement and flow-through arrangement, interacts with the drying medium as drying air and absorbs evaporated moisture from the drying medium and discharges it as moisture-laden exhaust air to an exhaust air duct arrangement; wherein the drying system is designed to direct the exhaust air from the drying system at least indirectly to the air-to-air heat exchanger via the exhaust air duct arrangement and the LLW exhaust air flow arrangement, so that at least an indirect transfer of heat from the exhaust air in the exhaust air duct arrangement to the fresh air in the air-to-air heat exchanger takes place; whereupon the air-to-air heat exchanger in particular reduces the energy of the exhaust air from the supplying LLW exhaust air flow arrangement; - a flow heat exchanger with a heat transfer volume and a heating volume, comprising a flow heat exchanger: - a heat inlet arrangement for introducing a first flowing heat medium with a flow temperature into the heat transfer volume and - a heat discharge arrangement with a flow sequence temperature for the outflow of the first flow heat medium from the heat transfer volume, - a feed-in circuit inlet arrangement for the inflow of a second flow heat medium with a circuit inlet temperature into the heating volume and - a discharge circuit outlet arrangement for the discharge of the second flow heat medium with a circuit outlet temperature from the heating volume, wherein the heat transfer volume and the heating volume are designed such that heat can be transferred from the heat transfer volume to the heating volume in order to heat the second flowing heat medium, wherein the first flow heat medium of the heat inlet arrangement contains flow components from the LLW exhaust air flow arrangement and / or other flow components, - a heat transfer device with a cooling transfer volume and a heating transfer volume, comprising the heat transfer device: - a heat transfer inlet arrangement for the inflow of the second flow heat medium with a heat transfer inlet temperature into the cooling transfer volume and - a discharge heat transfer outlet arrangement with a heat transfer outlet temperature for the discharge of the second flow heat medium from the cooling transfer volume, - a circulating inlet arrangement for introducing a circulating heat medium with a circulating inlet temperature into the heating transfer volume and - a discharge circulating outlet arrangement for the discharge of the circulating heat medium with a circulating outlet temperature from the heat transfer volume, and for at least indirect and / or at least partial flow into the media heat exchanger, wherein the cooling transfer volume and the heating transfer volume are designed such that heat can be transferred from the cooling transfer volume to the heating transfer volume in order to heat the circulating heat medium; where the recirculation outlet temperature is higher than the fresh air flow temperature and higher than the LLW outlet temperature.

[0010] The following sections explain the advantageous aspects of the proposed solution, followed by a description of preferred modified embodiments. Explanations, particularly regarding advantages and definitions of features, are essentially descriptive and preferred examples, but not limiting ones. If an explanation is limiting, this will be explicitly stated.

[0011] In other words, the heat transfer device is specifically designed to provide a technological solution that allows for the simulation of year-round summer conditions within the drying system. The heat transfer device, in conjunction with the recirculating air outlet, allows for the adjustment of the supply air to a constantly regulated recirculating air temperature, for example, 90 degrees Celsius. This enables the warming of the fresh air to the process temperature year-round, but especially during the winter. For instance, the heat transfer device can either be switched off in the summer to maintain constant operation year-round, or it can regulate the fresh air outlet temperature to a higher level to further increase system efficiency.This eliminates or at least reduces the need for environmentally harmful temperature increases in the media heat exchanger through conventional supplemental heating, for example, by methane gas combustion and / or similar means, thus increasing the overall efficiency of the drying system using sustainable methods. If such supplemental heating is required and / or at least used in an exemplary embodiment of the drying system to achieve the process temperature, it should be smaller than in previously known drying system solutions. Such supplemental heating can serve as the media heat exchanger itself.

[0012] The annual energy demand is subject to fluctuations in the ambient temperature, also referred to here as the external peripheral temperature. These fluctuations also occur throughout the day. For example, the lowest outside temperature is regularly observed between approximately 4 and 6 a.m. The aspects described above even out the temperature fluctuations of the fresh air, particularly the ambient air. This leads to a more consistent demand for any supplementary heating of the media heat exchanger or the media heat exchanger itself. Conventional drying systems with unregulated fresh air flow temperature and / or unregulated LLW outlet temperature do not have such qualitative equalization with regard to the process temperature. Rather, in classic drying systems, the intensive combustion operation of the supplementary heating of the media heat exchanger reduces the overall efficiency of the drying system.

[0013] Compared to conventional media heat exchangers, heat is now fed into the media heat exchanger of the proposed drying system via the recirculating outlet arrangement. The fresh air flowing into the media heat exchanger at the LLW outlet temperature through the LLW fresh air flow arrangement is thereby heated, particularly within a heat exchanger medium of the media heat exchanger, to such an extent that the fresh air is preferably heated directly to the required process temperature or, compared to the prior art, with reduced energy input in the media heat exchanger, for example, by using one or more additional heat exchangers. This advantage is even greater when the fresh air with a non-uniform LLW outlet temperature flows into the media heat exchanger through the LLW fresh air flow arrangement.The uneven LLW outlet temperature can be related to the season and / or the time of day.

[0014] In other words, advantages arise, among other things, from the fact that the proposed drying system allows the process temperature of the fresh air, starting from its LLW outlet temperature, to be achieved essentially through heat input from the circulating heat transfer medium at the circulating outlet temperature, particularly with further heat input in the media heat exchanger. The fact that the process temperature is achieved essentially through heat input from the circulating heat transfer medium at the circulating outlet temperature means, in particular, that its contribution to the process temperature is at least 60 percent, preferably at least 70 percent, particularly preferably at least 80 percent, and most preferably at least 90 percent. Ideally, the process temperature of the fresh air, starting from its LLW outlet temperature, is achieved entirely through heat input from the circulating heat transfer medium at the circulating outlet temperature.

[0015] Preferably, the process temperature is between at least 80 degrees Celsius and at most 140 degrees Celsius.

[0016] A key finding is the departure from the established approach of heating the fresh air in relatively constant stages, where the air-to-air heat exchanger typically performed the main heating work, while the media heat exchanger served a temperature-regulating function. This approach regularly resulted in reduced efficiency due to high heat losses. Instead, the plan now is to deliver the greatest heat input during the final heating stage in such a way as to minimize heat losses. It should be noted that this technical effect occurs independently of both the specific fresh air flow temperature and the specific air-to-water heat exchanger outlet temperature.

[0017] It is generally known that paper and cardboard machines have an air-to-air heat exchanger. The origins of this technology date back more than 50 years. At that time, there were numerous designs, including various heat exchanger configurations such as tube or plate heat exchangers. Humid exhaust air was a particular problem. When humid exhaust air comes into contact with cold supply air, the moisture condenses. The resulting corrosion was a significant issue at the time. Additionally, the dimensional stability of the connection between any tubes and the walls was compromised. Furthermore, short circuits or contact between exhaust air and supply air had to be avoided, as the drier supply air would be contaminated by the more humid exhaust air. Solving these problems, the company Langbein & Engelbracht developed a glass tube heat exchanger.The major advantage of this solution was the use of glass, a material that is dimensionally stable and resistant to acids, alkalis, water, oil, etc. Additionally, the corrosiveness of water was no longer a significant problem. Over the years, various air-to-air heat exchangers have become established.

[0018] The integration of a flow heat exchanger and a heat transfer device into a drying system was previously considered impractical due to their production costs and space requirements. Such an increase in the overall system's infrastructure complexity was initially deemed unlikely. However, the current development has demonstrated that the increased efficiency of integrating the flow heat exchanger and heat transfer device enables significantly more efficient operation of the drying system, thus offsetting the costs of acquiring and operating the system. In other words, the results show that the overall efficiency of the drying system is increased on average throughout the year, regardless of whether it operates in summer or winter.

[0019] Preferably, the heat transfer device, particularly when configured as a compression heat pump, can also include a speed-controlled compressor designed to continuously adjust its output to the current heat demand of the drying system. This stepless speed control allows the compressor to operate in a partial load range, where the coefficient of performance (COP) is improved compared to full load operation, especially when the temperature difference between the heat transfer inlet temperature and the circulating outlet temperature is small, for example, during summer operating phases. This enables a demand-driven and energy-efficient supply of the circulating outlet temperature throughout the entire annual cycle, thereby avoiding oversupply of heat and the associated efficiency losses, particularly during transitional periods.

[0020] All flow or conduit arrangements are not limited to pipes; they can represent any volume of material flow. Pipelines, channels, and / or similar devices are also possible.

[0021] Where water is mentioned below, this medium can also be a medium used as an exchanger or a supplementary substance with a similar function and effect. For example, the water for an air-to-water heat exchanger could be a water-glycol mixture. Other media with freezing-point-lowering properties are also possible, such as salt, oil, or other substances. This is partly implied by the phrase "essentially water."

[0022] Further aspects of the drying system will be discussed below.

[0023] The drying system is in particular a fiber drying system, especially preferably a paper and / or cardboard drying system.

[0024] The drying system features an air-to-air heat exchanger (LLW) with an exhaust air volume and a fresh air volume. The air-to-air heat exchanger can be, for example, a tube or plate heat exchanger, but this is not a limiting factor.

[0025] As mentioned earlier, tube heat exchangers and plate heat exchangers are specific types of heat exchangers used to transfer thermal energy from one medium to another. However, they differ in their design and operation.

[0026] An exemplary and non-limiting tube heat exchanger consists of a pipe system in which a warm medium, for example air, flows in the inner pipe and a cool medium, for example air, flows in the outer pipe. The pipes, or the hot-cold configuration, can be reversed. It is also generally accepted that a different medium, for example water, can be used instead of air.

[0027] The media flow in opposite directions, in particular, causing the hot medium in the inner pipe to heat the cooler medium in the outer pipe.

[0028] Tube heat exchangers are frequently installed in heating systems and heat the medium in the heat storage tank. Tube heat exchangers are relatively easy to clean and descale. If the exhaust air is routed through an inner tube, this can be cleaned using a cleaning projectile that is pressurized with compressed air and / or a liquid, especially water. The supply air around the outer tube is regularly filtered, so cleaning processes are not necessary at this point.

[0029] An exemplary and non-limiting plate heat exchanger consists of corrugated profiled plates arranged in such a way that the medium to be heated and then the heat-emitting medium flow in the successive spaces between them.

[0030] Plate heat exchangers are very flexible in terms of flow design, can be built very compactly and have a high heat flux density.

[0031] Plate heat exchangers must be cleaned if they become dirty or scaled. Bolted plate heat exchangers can be disassembled into their individual parts for cleaning, while brazed plate heat exchangers must be replaced.

[0032] Both types of heat exchangers serve to transfer heat energy from one medium to another.

[0033] Tube heat exchangers, for example and not limited to glass tube heat exchangers, use a pipe system for heat exchange, while plate heat exchangers use corrugated profiled plates.

[0034] Plate heat exchangers can be built more compactly and have a higher heat flux density than tube heat exchangers. However, large plate heat exchangers have the disadvantage of increasingly laminar heat transfer with increasing length, whereas in tube heat exchangers the tubes repeatedly break the flowing medium, enabling or even promoting turbulent flow.

[0035] Cleaning a tube heat exchanger is simpler than cleaning a plate heat exchanger, especially if it is a brazed plate heat exchanger. Therefore, the choice of heat exchanger depends on the specific requirements.

[0036] If a heat exchanger is specified in this context, other heat exchanger systems besides tube heat exchangers and plate heat exchangers can also be used.

[0037] The air-to-air heat exchanger features an inlet air-to-air (ATO) exhaust air flow arrangement for the inflow of exhaust air with an initial temperature into the ATO exhaust air volume. Specifically, "initial temperature" refers to the temperature of the exhaust air immediately before it enters the ATO exhaust air volume.

[0038] The exhaust air is an example, not a limiting factor, of air that has already been part of a drying process and therefore has a higher humidity than fresh air, especially ambient air. The initial temperature can be, for example, 85 degrees Celsius, also not a limiting factor.

[0039] The air-to-air heat exchanger also features a discharge LLW exhaust air flow arrangement with an exhaust air follow-up temperature for the outflow of exhaust air from the LLW exhaust air volume.

[0040] The air-to-air heat exchanger also features an inlet fresh air flow arrangement for supplying fresh air at a controlled fresh air flow temperature into the fresh air volume. If a preheating heat exchanger is used and installed upstream of the air-to-air heat exchanger, the fresh air can have a regulated fresh air flow temperature.

[0041] Fresh air is defined as, by way of example and not as a limiting factor, air that has not yet been a deliberate, internal component of a drying process. Ambient air is preferably considered fresh air. Preferably, the fresh air has a lower humidity level than the exhaust air. This fresh air may be preheated, for example, in a preheating heat exchanger, and / or dehumidified, for example, in a dehumidifying heat exchanger. As already mentioned, fresh air can be understood as air taken from the environment, for example, from the exterior of a production hall and / or from the production hall itself.

[0042] The air-to-air heat exchanger further features a discharge LLW fresh air flow arrangement for the discharge of fresh air with an LLW outlet temperature from the LLW fresh air volume.

[0043] The LLW exhaust air volume and the LLW fresh air volume are designed in such a way that heat can be transferred from the LLW exhaust air volume to the LLW fresh air volume to warm the fresh air. The warmed fresh air is then used, or can be used, in a later process step to dry the drying medium.

[0044] The LLW outlet temperature can be, for example, 65 degrees Celsius, and this is not a limiting factor.

[0045] The drying system further includes a drying unit designed to utilize heated fresh air for drying the drying medium. The drying unit is configured such that the fresh air, heated at least by the air-to-air heat exchanger and the media heat exchanger, and at least indirectly discharged from the LLW fresh air flow arrangement, interacts with the drying medium as drying air. During this interaction, moisture is absorbed from the drying medium and discharged as moisture-laden exhaust air to an exhaust air duct arrangement. Preferably, the temperature in the exhaust air duct arrangement corresponds at least to the initial temperature.

[0046] Preferably, the exhaust air from the exhaust air duct assembly is directly transferred to the LLW exhaust air flow assembly, so that essentially a similar temperature, namely the initial temperature, prevails in both assembly. However, it is also possible that one or more heat exchangers are interposed between the exhaust air duct assembly and the subsequent LLW exhaust air flow assembly, so that, for example, the temperature at the exhaust air duct assembly is higher than the initial temperature.

[0047] Therefore, the drying system is designed to direct the exhaust air from the drying system via the exhaust air duct arrangement and subsequently via the LLW exhaust air flow arrangement at least indirectly to the air-to-air heat exchanger, so that at least an indirect transfer of heat from the exhaust air in the exhaust air duct arrangement to the fresh air in the air-to-air heat exchanger takes place.

[0048] As a result, the air-to-air heat exchanger reduces the energy of the exhaust air from the supplying LLW exhaust air flow arrangement. This means that heat energy from the exhaust air is transferred from the LLW exhaust air volume to the fresh air in the LLW fresh air volume.

[0049] The drying system also includes a flow heat exchanger with a heat transfer volume and a heating volume. The flow heat exchanger can be, for example, a tube or plate heat exchanger, such as an air-to-water heat exchanger, but this is not the limiting factor. For further information on this type of heat exchanger, please refer to the above descriptions.

[0050] The flow heat exchanger further features a discharge circuit outlet arrangement with a circuit outlet temperature for the discharge of a second flow heat transfer medium from the heating volume. The circuit outlet temperature can be, for example, 12 degrees Celsius, and this is not a limiting factor.

[0051] The flow heat exchanger further comprises a feed-in recirculation inlet arrangement with a recirculation inlet temperature for the flow of the second flow heat medium, also with a recirculation inlet temperature, into the heating volume. The recirculation inlet temperature can, for example, be 6 degrees Celsius, and this is not a limiting factor.

[0052] Preferably, the circuit of the second flow heat medium can also be designed as a closed intermediate circuit, in which, after passing through the cooling transfer volume of the heat transfer device, the second flow heat medium is fed at least indirectly to the inlet circuit of the flow heat exchanger via the discharge heat transfer outlet arrangement, thus creating a substantially closed circuit between the flow heat exchanger and the heat transfer device. Such a closed intermediate circuit enables precise control of the volume flow and temperature of the second flow heat medium, independent of external influences, and simplifies the hydraulic design of the overall system.In particular, in a closed intermediate circuit, the second flow heat medium can be used as a water-glycol mixture or as another medium with freezing point lowering properties without any risk of loss to the environment.

[0053] The flow heat exchanger further comprises a discharge heat outlet arrangement with a flow follow temperature for the discharge of a first flow heat medium from the heat transfer volume. The flow follow temperature can, for example, and is not limiting, be greater than the circuit inlet temperature. The medium discharged from the heat outlet arrangement can, for example, and is not limiting, be partially or completely returned to the drying system as fresh air, in particular to a dehumidification heat exchanger and / or a preheating heat exchanger. In particular, the flow follow temperature can be below the external peripheral temperature, regardless of the season and / or the time of day.

[0054] The flow temperature can, for example, range from 5 to 50 degrees Celsius and is not a limiting factor. The temperature should preferably not fall below 4 degrees Celsius, as freezing cannot be ruled out otherwise.

[0055] The flow heat exchanger further comprises a heat inlet arrangement for the introduction of the first flow heat medium at a flow temperature into the heat transfer volume. The flow temperature can be, for example, 30 degrees Celsius, and this is not a limiting factor.

[0056] The heat transfer volume and the heating volume are designed in such a way that heat can be transferred from the heat transfer volume to the heating volume in order to heat the second flowing heat medium.

[0057] The first flowing heat medium of the heat inlet arrangement contains flow components from the LLW exhaust air flow arrangement and / or other flow components. Such additional flow components can include, but are not limited to, other media flows. In particular, media whose energy level has previously hindered or prevented further energy recovery are also possible, for example, water with high anergy, i.e., with hardly any usable energy. A medium is considered to have high anergy when its temperature is below the external peripheral temperature. It is essential that the existing media with high anergy can now be used year-round or, in fact, made usable for the first time.

[0058] Preferably, the first flow heat medium of the heat inlet arrangement can also contain waste heat flows from processes external to the drying system, in addition to flow components from the LLW exhaust air flow arrangement. These waste heat flows can include, but are not limited to, waste heat from compressed air generation, cooling water circuits, exhaust gas heat exchangers of combined heat and power plants, data centers, and / or industrial process cooling systems. The synergistic effect is that such external low-temperature waste heat flows, which were previously released to the environment via recoolers or cooling towers, are used as an additional heat source for the flow heat exchanger. This increases the heat supply for the heat transfer device and reduces its electrical energy requirement for the temperature lift. This not only improves the overall efficiency of the drying system but also the energy balance of the higher-level plant or site.

[0059] The drying system also includes a heat transfer device with a cooling transfer volume and a heating transfer volume. The heat transfer device can be, for example, a temperature lift system, which may be electrically operated, but this is not the limiting factor.

[0060] The heat transfer device further comprises a discharge heat transfer outlet arrangement with a heat transfer outlet temperature for the discharge of the second flowing heat medium from the cooling transfer volume. The heat transfer outlet temperature can be, for example, 6 degrees Celsius, and this temperature is not a limiting factor.

[0061] The heat transfer device further comprises a heat transfer inlet arrangement for the introduction of the second flowing heat medium into the cooling transfer volume at a heat transfer inlet temperature. The heat transfer inlet temperature can, for example, be 12 degrees Celsius, and this is not a limiting factor.

[0062] The heat transfer device further comprises a discharge circulating outlet arrangement for the discharge of the circulating heat medium at a specific discharge temperature from the heat transfer volume, and for its at least indirect, preferably direct, and / or at least partial, preferably complete, flow into the media heat exchanger. The circulating discharge temperature can, for example, and is not limited to, 90 degrees Celsius. The circulating heat medium discharged from the circulating outlet arrangement can, for example, and is not limited to, be partially or completely introduced into the media heat exchanger, in particular into a heat exchange medium of the media heat exchanger.

[0063] The heat transfer device further comprises a circulating inlet arrangement for introducing a circulating heat transfer medium with a circulating inlet temperature into the heat transfer volume. The circulating inlet temperature can be, for example, 70 degrees Celsius, and this is not a limiting factor.

[0064] The cooling transfer volume and the heating transfer volume are designed in such a way that heat can be transferred from the cooling transfer volume to the heating transfer volume in order to heat the circulating heat medium, in particular with the addition of energy, preferably electrical energy.

[0065] According to an optional embodiment, the heat transfer device can be designed as a temperature lift system configured to extract heat from the cooling transfer volume and, with the addition of energy, in particular electrical energy, to supply it to the heating transfer volume at an elevated temperature level. Such a temperature lift system can be, for example, but is not limited to, a compression heat pump, an absorption heat pump, an adsorption heat pump, a thermoelectric module, and / or any other device suitable for transferring heat from a lower to a higher temperature level.The addition of energy is particularly advantageous when the heat transfer inlet temperature of the second flowing heat medium is below the desired circulating outlet temperature of the circulating heat medium, such that purely passive heat transfer from the cooling transfer volume to the heating transfer volume is thermodynamically insufficient to achieve the desired circulating outlet temperature. In such a configuration, the electrical energy supplied to the heat transfer device can be used, at least partially, as additional heat in the heating transfer volume, so that the coefficient of performance (COP) of the temperature transfer system influences the overall efficiency of the drying system. Preferably, the added energy is supplied from renewable sources, in particular from photovoltaics, wind power, and / or grid electricity with a high renewable share, in order to maintain the sustainable nature of the drying system.It is preferred that the addition of energy is provided at least when the heat transfer inlet temperature of the second flowing heat medium is below the desired circulating outlet temperature of the circulating heat medium. In embodiments where the temperature level of the second flowing heat medium allows passive heat transfer to the circulating heat medium, the heat transfer device can also be operated without additional energy input. In both cases, the scope of protection of the claims is not limited.

[0066] The recirculating air outlet temperature is higher than the fresh air flow temperature and higher than the LLW outlet temperature. It may be preferable for the fresh air flow temperature and the LLW outlet temperature to be preheated, at least partially, under the influence of a preheating heat exchanger. However, a significant portion of the thermal lift occurs via the recirculating heat medium heated in the heat transfer device and thus indirectly via the second circulating heat medium heated in the flow heat exchanger. This allows the inherently high anergy of the first circulating heat medium to be utilized in a system-relevant manner.

[0067] Where ordinal numbers, for example "first," "second," etc., are used, for instance to designate a component or element, such as a flowing heat transfer medium, these ordinal numbers are solely for differentiation in the designation and do not indicate any dependencies or sequences. This means, in particular, that a device does not need to have a "first component" to have a "second component." A device can also have a "first component" and a "third component" without necessarily having a "second component." Multiple units with the same ordinal number are also possible, for example, multiple "first components."

[0068] According to a modification, it is alternatively or additionally provided that the drying system has: - a preheating heat exchanger with a preheating volume and a preheating flow volume, comprising: - an air supply duct arrangement for feeding fresh air at an outside temperature into the preheating volume, - a warm fresh air discharge arrangement for the discharge of fresh air at a fresh air flow temperature from the preheating volume, and for at least indirect inflow into the LLW fresh air volume, wherein the preheating volume and the preheating flow volume are designed such that heat can be transferred from the preheating flow volume to the preheating volume in order to heat the fresh air, wherein in particular the discharging warm fresh air outlet arrangement corresponds to the incoming LLW fresh air flow arrangement, so that the preheating heat exchanger can be connected at least indirectly to the air-to-air heat exchanger in order to provide the fresh air with the fresh air flow temperature for the LLW fresh air volume.

[0069] In other words, the drying system can, for example, also include a preheating heat exchanger with a preheating volume and a preheating flow rate. The preheating heat exchanger is designed to heat the fresh air, particularly the ambient air, from an outside temperature to the then-controlled fresh air flow temperature. Thus, the preheating heat exchanger serves primarily as a means of regulating the fresh air flow temperature. This is particularly advantageous when a dehumidification heat exchanger is installed upstream of the air-to-air heat exchanger, since dehumidified air typically also loses energy during the dehumidification process.Since this dehumidified fresh air is preferably used for drying in the drying system in a later step, it should have the highest possible temperature so that the preheating heat exchanger compensates for the temperature-reducing effect that occurs during dehumidification. Dry fresh air is a significant advantage for the drying process because air is ultimately a medium that must be circulated accordingly. This can significantly impact system efficiency, especially in regions and / or during seasons with high humidity. While the use of a preheating heat exchanger is preferred, it is not essential, particularly without the use of a dehumidification heat exchanger.

[0070] A preferred dehumidification heat exchanger removes moisture from the air, thereby reducing the temperature of the air flowing through it. At first glance, this seems to contradict the classic drying logic, which aims to use the hottest possible air for drying. However, this apparent contradiction is balanced by the heat input from the heat transfer device, so that the air previously cooled in the dehumidification heat exchanger remains usable for the intended drying process despite the dehumidification, and with an optimized efficiency compared to conventional drying systems.

[0071] The outside temperature, also referred to here as external peripheral temperature or ambient temperature, can be, for example, minus 20 degrees Celsius in winter and 35 degrees Celsius in summer, and this is not a limiting factor. This cannot usually be influenced, as ambient air is regularly supplied, which sometimes has different temperatures depending on the season. Therefore, the outside temperature is defined, for example, as a temperature outside the drying system, in particular a not significantly heated hall temperature and / or the hall's exterior temperature, and this is not a limiting factor.

[0072] Preheating is not limited to a single preheating heat exchanger; two or more different heat exchange systems can also be used.

[0073] The preferred drying system further comprises an air supply duct arrangement for feeding in fresh air at the outside temperature. The fresh air is preferably fed into the preheating heat exchanger, and particularly preferably into the preheating volume of the preheating heat exchanger.

[0074] The feeding LLW fresh air flow arrangement connects the preheating heat exchanger at least indirectly with the air-to-air heat exchanger in order to provide the fresh air with the fresh air flow temperature for the air-to-air heat exchanger, in particular for the LLW fresh air volume of the air-to-air heat exchanger.

[0075] The regulated fresh air flow temperature can, for example, be 35 degrees Celsius and is not a limiting factor.

[0076] Since in conventional drying systems the hottest air within the drying system—namely, the exhaust air from the completed drying process—meets the coldest air—namely, the fresh air, especially ambient air—from the incoming air-to-air heat exchanger, the high temperature of the exhaust air is already fully utilized in the air-to-air heat exchanger. This results in a physically limited achievable air-to-air outlet temperature compared to a proposed solution. The resulting air-to-air outlet temperature is therefore essentially an average of the initial temperature and the unregulated fresh air flow temperature. Consequently, the air-to-air outlet temperature is highly dependent on the season and the outside temperature of the required fresh air.

[0077] This means, for example (and this is not a limiting factor), that in a conventional drying system in winter, with an outside fresh air temperature of minus 20 degrees Celsius and an initial exhaust air temperature of 85 degrees Celsius, the available LLW (low-temperature water) outlet temperature of the heated fresh air for drying the fiber material is only approximately 45 degrees Celsius. If a fresh air drying temperature of approximately 85 degrees Celsius is required in the drying system, the temperature difference of 40 degrees Celsius must be compensated for in a later process step, but before the drying system, by one or more additional heat exchangers. This represents a very energy-intensive process step and generally requires further heat input from higher-calorific energy sources, such as gas burners.The initial exhaust air temperature drops from 85 degrees Celsius to 55 degrees Celsius through this process, so that the subsequent exhaust air temperature usable in further process steps is essentially limited to a maximum of 55 degrees Celsius. This exemplary mode is referred to as winter mode.

[0078] Assuming that in the same conventional drying system, the fresh air outside temperature in summer is 35 degrees Celsius and the initial exhaust air temperature is 85 degrees Celsius, the available LLW outlet temperature of the heated fresh air for the exemplary drying of the fiber material is approximately 65 degrees Celsius. If a fresh air drying temperature of approximately 85 degrees Celsius is required in the drying system, the temperature difference of 20 degrees Celsius must be compensated for in a later process step, but before the drying system, by one or more additional heat exchangers. This represents a less energy-intensive process step compared to the winter mode and generally requires additional heat input from higher-calorific energy sources, such as gas burners.The initial exhaust air temperature drops from 85 degrees Celsius to 70 degrees Celsius through this process, so that the subsequent exhaust air temperature usable in further process steps is essentially limited to a maximum of 70 degrees Celsius. This exemplary mode is referred to as summer mode.

[0079] The aforementioned conventional drying system has the disadvantage that the usable LLW outlet temperature and the usable exhaust air temperature depend significantly on the outside temperature. To ensure that the drying system can operate flawlessly year-round, it must therefore be designed for winter operation, resulting in considerable production and operating costs for the higher-calorific energy sources. Only the present solution enables the simulation or imitation of a continuous summer mode, utilizing a controlled fresh air flow temperature, thus eliminating the need to consider winter temperatures for system design.

[0080] It is worth noting that the energy input in the preheating heat exchanger is used to raise the fresh air temperature from the outside temperature to the controlled, low-temperature fresh air flow temperature. This has the advantage of utilizing a temperature level that is unused in conventional drying systems, thus increasing the overall efficiency of the drying system with regard to the usable exhaust air temperature.

[0081] Since the regulated fresh air flow temperature is higher in winter than in conventional drying systems, the exhaust air temperature in the proposed solution remains similar to the summer mode year-round, thus enabling year-round use of the exhaust air at this temperature for the first time. Due to the constantly simulated summer mode and the associated higher temperature level compared to the winter mode, the overall efficiency of the drying system is increased compared to conventional drying systems. This is because the medium conveyed in the discharge LLW exhaust air flow arrangement, with its consistently higher exhaust air temperature compared to the winter mode, allows for the operation of higher-temperature downstream systems that would otherwise not be possible at the same temperature level in winter.

[0082] In other words, conventional drying systems without a preheating heat exchanger required a heat exchanger downstream of the discharge LLW fresh air flow arrangement in winter mode to achieve the desired LLW outlet temperature of the conveyed medium. A heat exchanger was also connected downstream of the discharge LLW exhaust air flow arrangement if the exhaust air temperature available in winter mode was insufficient for subsequent processes. The proposed solution, therefore, eliminates the need for an entire heating stage by integrating the preheating heat exchanger.

[0083] When the terms "caloric," particularly "low-caloric" or "high-caloric," are used, "low-caloric" refers to any heat in the medium that is less than the heat of the medium in the exhaust air flow arrangement. Similarly, "higher-caloric" refers to any heat in the medium that is greater than the heat of the medium in the exhaust air flow arrangement. Temperatures can also be used as a comparative value, in which case the exhaust air temperature in the exhaust air flow arrangement is considered the transition from low-caloric to high-caloric.

[0084] In particular, this enables the direct or indirect utilization of low-temperature waste heat as a preliminary step to air-to-air heat recovery. The waste heat can be sourced from the actual drying process or from other processes. Furthermore, an optimized, year-round design for air-to-air heat recovery based on typical summer temperatures is proposed.

[0085] One particularly advantageous aspect is the use of the preheating solution as an "anti-icing substitute" in cold climates. In this case, a portion of the preheated supply air is mixed back into the intake air. This prevents the previously problematic freezing during air-to-air heat recovery. It is also possible to preheat to ambient temperatures using a suitable heat transfer fluid.

[0086] This type of application can be retrofitted to any existing heat recovery system. The proposed solution has proven to meet the current goal of reducing primary energy consumption. Ultimately, high utilization of exhaust air energy throughout the year is beneficial, both for reducing primary energy use and for lowering CO2 emissions.

[0087] According to a modification, it is alternatively or additionally provided that the drying system includes a dehumidification heat exchanger device with a process medium heating volume and a dehumidification volume.

[0088] The dehumidification heat exchanger device features: - a feed-in process medium inflow arrangement for the inflow of a process medium with a process medium inflow temperature into the process medium heating volume and - a discharging process medium outlet arrangement with a process medium outlet temperature for the discharge of the process medium from the process medium heating volume, - a fresh air inlet arrangement for the flow of fresh air with an initial fresh air temperature into the dehumidification volume and - a dry fresh air discharge arrangement for the discharge of fresh air at a dry fresh air temperature from the dehumidification volume, and for at least indirect inflow into the air-to-air heat exchanger, in particular via a / the preheating heat exchanger.

[0089] For this purpose, the process medium heating volume and the dehumidification volume are designed such that heat can be transferred from the dehumidification volume to the process medium heating volume in order to heat the process medium and reduce the moisture content of the fresh air. Simultaneously, heat is extracted from the fresh air along with the moisture. Fresh air cooling is a thermodynamic consequence of this moisture reduction.

[0090] The process medium inlet temperature can be, for example, -20 to 40 degrees Celsius, and is not a limiting factor, with a particularly preferred range of 6 to 12 degrees Celsius. The process medium outlet temperature can be within the aforementioned ranges of the process medium inlet temperature, but should be higher than the process medium inlet temperature.

[0091] The purpose of the dehumidification heat exchanger is to dehumidify the fresh air. This means that the conditioned fresh air can absorb more moisture from the drying medium during the subsequent drying process in the drying system, as it releases moisture beforehand as a result of passing through the dehumidification heat exchanger. In other words, compared to conventional drying processes, the fresh air can absorb more moisture until it reaches a saturation level comparable to that found in drying systems using conventional processes. A related disadvantage is that the dry fresh air temperature is lower than the initial fresh air temperature. However, this can be compensated for by the heat input from the circulating heat transfer medium, which has a significantly higher circulating outlet temperature.A further advantage of this design using dehumidified air is that, due to the already removed vapor molecules, less air volume needs to be transported for the same drying or moisture absorption process, and thus for the same moisture absorption volume. Consequently, the drying system components from the dehumidification heat exchanger to the drying unit can generally be smaller, since less air volume needs to be moved while maintaining or even increasing drying performance. If the drying system components from the dehumidification heat exchanger to the drying unit remain unchanged, the drying performance can be increased compared to previously known drying systems.

[0092] Preferably, the condensate produced during the dehumidification of fresh air in the dehumidification heat exchanger can be collected and fed back into the drying process as process water, particularly for diluting fiber suspensions, cleaning drying system components, and / or spraying rollers and screens. Since the condensate is obtained from the dehumidification of ambient air, it typically has a low salt content and low hardness, making it particularly suitable as demineralized or partially demineralized water for use in moisture-sensitive process steps. The synergistic effect is that using the dehumidification condensate reduces the overall process's fresh water demand, especially in water-scarce regions, while simultaneously lowering water treatment operating costs.

[0093] The process medium flowing out of the process medium heating volume via the discharging process medium outlet arrangement can flow, at least partially or completely, into the cooling transfer volume via the incoming heat transfer inlet arrangement as a second flowing heat medium with a heat transfer inlet temperature. In particular, the process medium can be, at least partially or completely, the second flowing heat medium. Specifically, the second flowing heat medium can contain components from the process medium from the discharging process medium outlet arrangement in the process medium heating volume and / or components from the second flowing heat medium in the heating volume. Each of these features applies alternatively or in addition to other features.

[0094] As described above, the proposed drying system can make media with high anergy usable year-round. In particular, it allows a second flowing heat medium exiting the heat transfer outlet to flow into the heat transfer inlet and / or the process medium inlet for further thermodynamic utilization. Previously, media with low temperatures, such as the heat transfer outlet temperature of, for example, 6 degrees Celsius, were considered to be high anergy media that could not be used further. Each of these characteristics applies alternatively or in addition to other characteristics.

[0095] Optionally, a preheating heat exchanger can be used to warm the fresh air between the dehumidification heat exchanger and the air-to-air heat exchanger, thus at least partially compensating for the cooling effect of the dehumidification heat exchanger. In other words, the fresh air initially has a fresh air temperature and a first humidity level. After passing through the dehumidification chamber, it has a dry fresh air temperature, which is lower than the initial fresh air temperature, and a second humidity level, which is lower than the first.

[0096] The dry fresh air temperature can correspond to the external peripheral temperature and is raised again after passing through the preheating volume, for example, to the initial fresh air temperature, thus establishing a fresh air flow temperature. The fresh air flow temperature exiting the preheating volume can be lower than, equal to, or higher than the initial fresh air temperature. In particular, a combination of a preheating heat exchanger and a dehumidification heat exchanger can simulate a fresh air configuration with an initial fresh air temperature and low humidity. This fresh air, for example, has a temperature similar to summer and a humidity similar to winter, thus combining the advantages of both seasons year-round and enabling optimized drying in the drying system.Overall, this reduces energy consumption compared to conventional drying systems.

[0097] Preferably, the drying system can also include at least one humidity sensor configured to detect the absolute and / or relative humidity of the fresh air at at least one point along the fresh air path, in particular downstream of the dehumidification heat exchanger and / or upstream of the air-to-air heat exchanger. The detected humidity can be used as a control variable to adjust the cooling capacity of the dehumidification heat exchanger as needed, for example, via the volume flow rate and / or the temperature of the process medium.The synergistic effect consists of the fact that the dehumidification intensity is dynamically adjusted to the actual moisture content of the ambient air, so that in already dry ambient air, especially in winter months, the dehumidification performance is reduced and thus the energy requirement of the dehumidification heat exchanger device and the downstream preheating stage is minimized, without impairing the drying performance in the drying system.

[0098] It is understood that in embodiments where the preheating heat exchanger is arranged downstream of a dehumidification heat exchanger, the supply air duct arrangement does not supply outside air as fresh air in an unaltered thermodynamic state to the preheating volume. In such cases, "fresh air" is understood to mean air taken from the outside air and previously conditioned, in particular dehumidified, within the supply air duct arrangement, which is then supplied to the preheating heat exchanger.

[0099] The initial fresh air temperature can, for example, correspond to the external peripheral temperature without being limiting. The initial fresh air temperature can also be influenced by the subsequent flow temperature of the first flowing heat medium.

[0100] According to a modification, it is alternatively or additionally provided that the supplying process medium inlet arrangement is designed to supply the second flow heat medium completely or at least partially from the cooling transfer volume of the heat transfer device, so that the process medium at least partially contains or corresponds to the second flow heat medium. In particular, this enables the use of the second flow heat medium with high low energy. Otherwise, the aforementioned advantages apply. Alternatively or additionally, it is then provided that the dry fresh air outlet arrangement corresponds to the supply air duct arrangement.

[0101] According to a modification, the flow heat exchanger and the heat transfer device are optionally or additionally arranged in a single assembly unit. This enables a compact design and, in practice, easier assembly. Previously, the combined use of a flow heat exchanger and a heat transfer device was considered impractical, and consequently, a single assembly unit was also considered impractical. The combined assembly unit, consisting of the flow heat exchanger and heat transfer device, offers far more than just space-saving integration. For example, all media lines, such as those for water, air, or refrigerant flows, can optionally be routed very short distances within the module, typically reducing pressure losses and parasitic heat dissipation, and potentially increasing hydraulic efficiency.At the same time, a portion of the separate insulation, steel construction and pipe bridge costs is often eliminated, resulting in lower material and assembly costs.

[0102] The module could also be supplied as a pre-assembled "plug-and-play" skid, already piped, wired, and factory-tested; ideally, on-site installation would then be limited to just a few flange or plug connections, resulting in minimal downtime. Depending on the design, the control technology can also be integrated into a single control box, allowing temperature, pressure, and flow sensors to be centrally monitored and controlled with a short response time. Maintenance openings, drains, and test points can be grouped together; identical wear parts such as seals or valves simplify spare parts inventory.

[0103] Should a larger production capacity be required in the future, the concept can be expanded modularly by connecting additional units, particularly skid units, in parallel; this would usually eliminate the need for major modifications. Furthermore, a shared housing can act as a sound dampener, thus reducing noise levels in the installation room. All these aspects, each optionally available, contribute to lowering investment and operating costs over the system's life cycle and facilitate the implementation of the energy-optimized drying concept.

[0104] Preferably, the combined assembly unit consisting of the flow heat exchanger and heat transfer device can also be equipped with sensors and a data processing unit designed to continuously record operating parameters, in particular temperatures, pressures, flow rates, and electrical power consumption, and transmit them to a higher-level control system and / or a cloud-based platform. Based on this operating data, a digital twin of the assembly unit can be created, enabling predictive maintenance planning, optimization of operating points, and long-term monitoring of the coefficient of performance (COP).The synergistic effect is that degradation phenomena, especially soiling of heat exchanger surfaces and refrigerant losses, are detected early, so that maintenance interventions can be planned and unplanned downtimes are avoided, which is of considerable economic advantage, especially for continuously operated paper and board machines.

[0105] According to a modification, the drying system is optionally or additionally provided for with one or more heat exchanger devices between the air-to-air heat exchanger and the flow heat exchanger, designed to modify the energy of a fluid flow between the air-to-air heat exchanger and the flow heat exchanger. The flow heat exchanger is optionally an air-to-water heat exchanger. This allows for the advantageous adjustment of the fluid flow's energy as needed. This is particularly beneficial for reducing the energy and / or increasing the energy of the fluid flow at other points of entry.

[0106] According to a modification, it is alternatively or additionally provided that one or more heat exchanger devices are designed to increase the energy of the media flow between the air-to-air heat exchanger and the flow heat exchanger, in particular at least indirectly under the influence of a high-calorie heat flow.

[0107] Such a high-calorie heat flow can, for example, be waste heat from drying and / or from entirely external processes, such as power plant waste heat. This not only increases the efficiency of the existing drying system, but also the efficiency of the application upstream of this drying system.

[0108] According to one modification, it is alternatively or additionally provided that one or more heat exchanger devices are designed to reduce the energy of the media flow between the air-to-air heat exchanger and the flow heat exchanger, particularly for subsequent conveyance to one or more system components that are at least indirectly and / or at least partially downstream of the air-to-air heat exchanger. The energy of the first flow heat medium coming from the air-to-air heat exchanger to the flow heat exchanger is reduced, preferably such that the first flow heat medium changes from a high-calorific medium to a medium with high anergy. The flow heat exchanger is used particularly in processes with media that exhibit increased anergy.If higher-energy media from the air-to-air heat exchanger were fed directly into the flow heat exchanger, this would leave heat from the air-to-air heat exchanger unused, heat which would otherwise be utilized. Therefore, the goal is to optimize the use of heat from the air-to-air heat exchanger, so one consequence of using the heat exchanger device(s) is that the first flow heat medium has a high low energy before it reaches the flow heat exchanger.

[0109] In one exemplary embodiment, the heat exchanger device or devices can be configured such that the flow rate of the medium between the air-to-air heat exchanger and the flow heat exchanger can be selectively increased or decreased as needed. In other words, the heat exchanger device mode can be changed to adapt to the operating and / or environmental conditions.

[0110] According to a modification, the drying system is alternatively or additionally provided for with a media heat exchanger comprising at least one heat exchange medium to increase the energy of the fresh air introduced into the media heat exchanger from the LLW fresh air flow arrangement, at least indirectly and / or at least partially, by means of the circulating heat medium of the discharging circulating outlet arrangement. By coupling the heat exchange medium to the circulating heat medium, the main heat input is specifically shifted to the media heat exchanger as the final heating stage. In particular, this reduces conduction and radiation losses, smooths out temperature fluctuations of the supplied fresh air, and allows for a process-oriented, precisely controllable approach to the process temperature. "Increase energy" refers specifically to an increase in the temperature and / or specific enthalpy of the fresh air at a constant or varying volume or mass flow rate."At least indirectly" encompasses both direct thermal coupling, e.g., tube, plate, or finned heat exchangers in the airflow, and indirect coupling via further heat exchangers or an intermediate medium, e.g., thermal oil or hot water, without restricting the required functional relationship. The "heat exchange medium" is understood as a functional transfer element that enables efficient heat transfer from the circulating heat medium to the fresh air; its design, construction, surface, and flow pattern are freely selectable and adaptable to different volume flows and temperature levels. Overall, this modification leads to higher overall efficiency, reduced need for additional heating, improved seasonal independence, and robust, dynamic control of the drying process.

[0111] According to a modification, it is provided, either alternatively or additionally, that after the energy of the fresh air introduced into the media heat exchanger has been increased, the circulating heat transfer medium can be conveyed, at least indirectly and / or at least partially, into the heat transfer volume by means of a recirculation arrangement. This is a largely controllable and closed process that contributes to a reproducible increase in efficiency regardless of the season. If the circulating heat transfer medium flows directly from the recirculation arrangement into the circulating inlet arrangement, then the recirculation arrangement corresponds to the circulating inlet arrangement.

[0112] Preferably, the drying system can also include a differential temperature control system designed to regulate the difference between the circulating outlet temperature and the circulating inlet temperature to a predefined setpoint, in particular by adjusting the volume flow rate of the circulating heat transfer medium and / or the power of the heat transfer device. Such differential temperature control makes it possible to keep the heat transfer in the media heat exchanger constant, independent of fluctuations in the fresh air temperature and volume flow rate. The synergistic effect is that the process temperature of the fresh air entering the drying system can be set with a small control deviation, thus ensuring a more uniform quality of the dried drying medium and simultaneously allowing the heat transfer device to operate at an energy-optimized operating point.

[0113] According to a modification, the media heat exchanger is alternatively or additionally provided for by a flash evaporation heat exchanger, designed for the essentially direct intake and heating of fresh air from the LLW fresh air flow arrangement. In the paper industry, flash evaporation primarily refers to steam that is spontaneously generated when hot condensate under pressure is suddenly expanded into a lower-pressure area. In the context of the paper industry, flash evaporation occurs, for example, during the transfer of condensate from a high-pressure system, such as the dryer section or calender rolls, into a low-pressure vessel, and / or through the pressure release of hot condensate that was previously used in steam drying cylinders. This flash evaporation contains energy that can be used in a targeted manner for other process steps.The efficient use of flash evaporation can lead to significant energy savings and improve the overall energy efficiency of paper production. Ideally, the flash evaporation steam in this context has a temperature below 100°C. Accordingly, a flash evaporation heat exchanger can be a device designed to directly capture the steam generated during flash evaporation and transfer its thermal energy to the supplied fresh air. In particular, such a heat exchanger can be designed so that the steam generated during pressure reduction is passed directly through the heat exchanger to transfer its latent heat energy as completely and with as little loss as possible. Optionally, this heat exchanger may include specially designed exchange surfaces or piping systems that enable efficient heat transfer from flash evaporation steam to fresh air.The flash evaporation heat exchanger can preferably be designed to react dynamically to fluctuations in steam generation and always ensure optimized heat recovery. Furthermore, the heat exchanger can be modular or designed with variable dimensions to allow flexible adaptation to different process conditions and flow rates. The phrase "essentially" refers to the direct intake and heating of the fresh air, as it is possible that other media components are added to the fresh air. Preferably, nothing is added to the fresh air, so that it flows directly from the LLW fresh air flow arrangement into the flash evaporation heat exchanger and is heated there.

[0114] Alternatively or additionally, the media heat exchanger includes a heat exchange medium designed to interact with the circulating heat medium of the supplying recirculating outlet arrangement to warm the fresh air. The heat exchange medium can be designed, in particular, to come into thermal contact with the circulating heat medium, which has been previously heated by the heat transfer device, and to transfer its thermal energy, at least indirectly, preferably directly, to the supplied fresh air. Optionally, the heat exchange medium can be a self-contained device that alone constitutes the media heat exchanger, thus eliminating the need for additional heat exchanger units. Furthermore, it is preferably provided that the heat exchange medium comprises a design with optimized heat transfer surfaces to enable efficient heat extraction from the circulating heat medium and thereby improve heat transfer to the fresh air.Furthermore, the heat exchanger medium can be dimensioned or designed in such a way that it can take into account varying volume flows or temperature levels of the circulating heat medium and thus be flexibly adapted to different operating conditions.

[0115] If a dehumidification heat exchanger device is used which dehumidifies the fresh air but also reduces its energy content, this heat exchanger medium is particularly preferred because the fresh air is raised back to a higher energy level by the heat of the circulating heat medium, which has already utilized low-energy energy.

[0116] Alternatively or additionally, the media heat exchanger includes a liquid heat exchanger designed to preheat the fresh air. This is specifically a condensate stage in which hot condensate from a steam and condensate system is used to heat the fresh air. This liquid heat exchanger is preferably designed to efficiently transfer the heat energy contained in the hot condensate to the fresh air before the condensate is returned to the cycle or fed into other process steps. Optionally, the liquid heat exchanger may have specially dimensioned and designed heat transfer surfaces to maximize the thermal efficiency of the condensate stage.Furthermore, the condensate stage can be flexibly designed to optimally respond to different condensate temperatures or flow rates, thus enabling year-round and efficient use of the condensate's energy potential. If a flash evaporation heat exchanger and / or a heat exchanger medium is / are installed upstream of the liquid heat exchanger, less energy needs to be extracted from the condensate to bring the fresh air to the desired target temperature, allowing the energy remaining in the condensate to be used for other purposes.

[0117] Alternatively or additionally, the media heat exchanger features a media heat exchanger designed to heat and convey fresh air into the drying system via a flow-through arrangement. The media heat exchanger is heated, particularly with steam, to reliably achieve the desired process temperature. The heating medium used is the one with the highest calorific value in the entire media heat exchanger. If other components such as flash evaporation heat exchangers, heat exchangers, and / or liquid heat exchangers are used, the media heat exchanger represents the medium with the highest energy potential, ensuring rapid, efficient, and reliable achievement of the target temperature even under fluctuating operating conditions.Optionally, the media heat exchanger can be designed to react flexibly to different volume flows or temperature levels, thus enabling stable operation of the drying system throughout the year.

[0118] According to a modification, it is alternatively or additionally provided that the media heat exchanger is designed to be supplied with live steam, oil, hot water, brine, hydrogen, district heating, electricity, in particular induction, gas combustion, biomass combustion, autothermal combustion, solar thermal process heat, geothermal process heat, waste heat from neighboring plants, process heat from high-temperature heat pumps, steam generated by electrode or resistance boilers, waste heat from fuel cells, microwave or radio frequency energy, infrared or near-infrared radiation, heat from thermal energy storage systems, in particular molten salts or thermochemical storage systems, process steam from small modular nuclear reactors and / or a mixture thereof, in order to adjust the fresh air to the process temperature.

[0119] The media heat exchanger is in particular one of the aforementioned media heat exchangers, wherein the flash evaporation heat exchanger, the heat exchange medium, the liquid heat exchanger and / or the media heat exchange medium is / are designed to be supplied with live steam, oil, hot water, salt solution, hydrogen, district heating, electricity, in particular induction, gas combustion, biomass combustion, autothermal combustion, solar thermal process heat, geothermal process heat, waste heat from neighboring plants, process heat from high-temperature heat pumps, steam generated by electrode or resistance boilers, waste heat from fuel cells, microwave or radio frequency energy, infrared or near-infrared radiation, heat from thermal energy storage devices, in particular molten salts or thermochemical storage devices, process steam from small modular nuclear reactors and / or a mixture thereof, in order to adjust the fresh air to the process temperature.

[0120] It has been shown that the energy sources mentioned above enable reliable operation of the media heat exchanger. This applies in particular to the flash evaporation heat exchanger, the heat exchanger fluid, the liquid heat exchanger, and / or the media heat exchanger. The advantages of this design include great flexibility in the selection of the energy source, allowing the drying system to be optimally adapted to locally available and economically viable energy carriers. The ability to combine different media allows for extremely efficient and demand-oriented control of the energy supply. Furthermore, high operational reliability is ensured, as switching between or combining different energy carriers is possible at any time.This enables, in particular, a continuous, year-round energy supply and thus stable operation of the drying system regardless of temporary availability or price developments of the individual energy sources.

[0121] Furthermore, additional advantages arise, such as the possibility of using sustainable and renewable energy sources, thereby improving the environmental friendliness and sustainability of the entire drying process. Economic benefits also result, as the system can flexibly respond to favorable or surplus energy sources, contributing to lower overall operating costs. The wide variety of usable energy sources also provides redundancy, minimizing the risk of production downtime and increasing the reliability and robustness of the system. Finally, this comprehensive flexibility allows for easy integration of the system into existing plants and infrastructure, reducing investment costs and increasing acceptance.

[0122] According to a modification, it is provided that the media heat exchanger has one or more waste heat exchangers between the air-to-air heat exchanger and the drying system. The waste heat exchanger(s) of the media heat exchanger utilize, at least indirectly, heat from a self-contained steam condensate system designed to dry the drying medium in the drying system. This system heats the fresh air of the LLW fresh air flow arrangement to the predefined process temperature and then transfers it to the drying system via the flow arrangement. A steam condensate system is a technical system that utilizes steam that would otherwise escape unused into the environment. It is therefore a self-contained system for providing the heat from the steam to the drying process in an energy-efficient manner.It has been shown that this enables reliable operation of the media heat exchanger and provides a system-efficient design.

[0123] The heating of the fresh air can preferably be done using waste heat from the overall process, but also, for example, in isolation or additionally through the steam condensate system.

[0124] According to a modification, it is alternatively or additionally provided that the flow heat exchanger and / or the heat transfer device is / are designed such that the circuit inlet temperature and / or the circuit outlet temperature is / are less than or equal to a peripheral temperature external to the drying system.

[0125] In particular, the inlet temperature and / or outlet temperature of the cycle and / or the external peripheral temperature of the drying system are controlled by temperature control agents to ensure that this condition is met. This modification offers the particular advantage of further increasing the efficiency of the drying process. Since the inlet temperature and / or outlet temperature of the cycle are lower than or at least equal to the external peripheral temperature of the drying system, i.e., the external ambient temperature, thermal energy, which was previously considered unused low-temperature energy, can be usefully integrated into the process. Consequently, through suitable thermal processes and heat exchanger steps, this previously unusable low-temperature energy can be specifically utilized to efficiently increase the temperature of the fresh air in the media heat exchanger.This results in a lower primary energy requirement, as a significant portion of the fresh air heating is now powered by a previously unusable heat source. Overall, this leads to a substantial reduction in total energy consumption and thus an increase in the sustainability and cost-effectiveness of the drying system.

[0126] According to a modification, it is alternatively or additionally provided that the first flow heat medium from the heat transfer volume can be fed at least partially and / or at least indirectly into the supply fresh air inlet assembly with a fresh air initial temperature and / or into the preheating flow volume via the discharging heat outlet arrangement with a flow sequence temperature and / or via a media flow arrangement encompassed by the drying system with a recuperation temperature of the preheating heat exchanger. According to this modification, the following advantages result in particular: The flow sequence temperature essentially corresponds to the fresh air initial temperature and / or the recuperation temperature. The recuperation temperature can, for example, and is not limiting, be between 5 and 60 degrees Celsius. The phrase "essentially" here implies the consideration of heat flow losses and / or the admixture of other media.When the first flow heat medium is fed into the fresh air inlet assembly and the media flow assembly, this means, in particular, that the first flow heat medium, as part of the fresh air, is initially cooled down in the dehumidification heat exchanger device, in order to be subsequently reheated by means of the uncooled first flow heat medium in the preheating flow volume. This advantageously results in the creation of a nearly closed, cycle-like system.

[0127] The advantage of such a closed-loop system lies particularly in the fact that the available thermal energy can be used efficiently and partially or completely recuperated within the system. The initial heat transfer medium, which was fed into the preheating flow volume via the media flow arrangement for thermal treatment, is either completely returned to the system, thus creating a closed loop, or partially discharged from the system, resulting in a closed-loop system.

[0128] This configuration ensures optimal use of available thermal energy, reduces primary energy consumption, and further increases the overall efficiency of the drying system. At the same time, operational reliability is enhanced, as continuous control and adaptation to changing operating conditions become easily achievable. Overall, this results in a significant improvement in the sustainability, cost-effectiveness, and flexibility of the entire drying process.

[0129] Furthermore, a retrofit system is proposed, designed to expand an existing drying system with an air-to-air heat exchanger, a media heat exchanger, and a drying unit into the aforementioned drying system. The retrofit system includes at least the following components, and / or the drying system components are modified with respect to at least one of the aforementioned preheating heat exchangers, at least one of the aforementioned air-to-air heat exchangers, at least one of the aforementioned drying unit, at least one of the aforementioned media heat exchangers, at least one of the aforementioned heat exchanger device, at least one of the aforementioned flow heat exchanger, at least one of the aforementioned heat transfer device, and / or at least one of the aforementioned dehumidification heat exchanger device.

[0130] The proposed retrofit system enables operators of existing plants to realize the described energy and process advantages without a complete rebuild. All modules, from the preheating heat exchanger and the flow and media heat exchanger to the heat transfer unit and dehumidification heat exchanger, are designed as retrofittable assemblies that can be integrated in various stages. This allows the existing drying system to be modernized step by step, with each stage delivering a measurable efficiency gain. The mechanical interfaces and the control concept are designed so that installation can largely be carried out during operation, and existing pipework can be largely retained. This reduces investment costs, minimizes downtime, and simultaneously raises the energy performance to the level of a new plant.This makes a significant contribution to sustainability, operational reliability and long-term economic viability.

[0131] By selectively transferring heat from the preheating flow volume to the preheating volume, a further energy synergy effect is achieved. The fresh air, intentionally "cooled" and nearly dry in the dehumidification volume, receives an initial low-temperature upgrade here before entering the air-to-air heat exchanger. Since this heat originates from an internal airflow that already flows through the preheating flow volume at a higher temperature, no additional primary energy source is required. Instead, latently present low-temperature energy is recirculated and fed into the fresh air path. The result is an air quality that simultaneously exhibits the low humidity of a "winter climate" and the temperate level of a "summer climate"—optimal for rapid and uniform moisture absorption in the subsequent drying process.

[0132] Another advantage of this internal heat circuit is that temperature peaks within the preheating heat exchanger are smoothed out. The otherwise highly variable outside temperatures have less of a direct impact on the process because the fresh air has already reached a moderate temperature level before entering the preheating heat exchanger. This not only reduces the control effort for the valve and burner, but also reduces thermal stresses in tube bundles and plate packs; a significant factor for the service life of the components.

[0133] Finally, this additional preheating stage also improves the overall system during partial load or start-up operation. Especially during transitional seasons, such as spring and autumn, outdoor and indoor temperatures are often just above the dew point; a situation in which conventional systems operate inefficiently and condensation problems occur. The internal reheating described here ensures that a stable "thermal buffer" is available even with slight fluctuations in outdoor temperature. This keeps exhaust air condensation in the air-to-air heat exchanger under control, further reduces the risk of corrosion, and allows the system to reach its optimal operating point more quickly.

[0134] According to a preferred embodiment, the drying system can include a higher-level control unit configured to control the heat transfer device, the flow heat exchanger, the preheating heat exchanger, and / or the dehumidification heat exchanger in a coordinated manner. The control unit can, in particular, be configured to acquire one or more measured variables, such as the external peripheral temperature, the fresh air flow temperature, the LLW outlet temperature, the recirculating outlet temperature, the relative humidity of the fresh air, and / or the volume flow rate of the fresh air, and to control the actuators of the aforementioned components based on these measurements. Preferably, the control unit can include a predictive control system that proactively adjusts the operating parameters based on weather forecast data and / or historical operating data in order to optimize the overall efficiency of the drying system.In particular, the control unit can be designed so that, in the event of a predicted temperature drop, the heat transfer device is pre-activated before the external peripheral temperature actually decreases. This smooths out process temperature fluctuations and reduces control peaks in the media heat exchanger. The synergistic effect of such predictive control, in conjunction with the preheating heat exchanger and the heat transfer device, is that the overall system's energy demand is more evened out throughout the day, thus reducing the peak load on the heat transfer device and consequently its required size.

[0135] According to a further optional embodiment, the drying system can include a thermal buffer storage tank integrated into the circuit of the circulating heat medium and / or the second flowing heat medium. Such a buffer storage tank can be designed, for example, but is not limited to, a hot water storage tank, a stratified storage tank, a latent heat storage tank, and / or a storage tank containing a phase-change material. The buffer storage tank makes it possible to temporarily store excess heat when heat demand is low, particularly during summer operating phases or low production loads, and to provide it at a later time when heat demand is high, particularly during winter operating phases or peak loads. This allows the heat transfer device to operate at a more consistent operating point, which leads to an improved coefficient of performance (COP), especially when configured as a compression heat pump.The synergistic effect of the buffer storage in conjunction with the heat transfer device and the media heat exchanger is that the thermal inertia of the overall system is increased, so that short-term fluctuations in the external peripheral temperature and / or the production load are absorbed without affecting the process temperature.

[0136] According to a further optional embodiment, the drying system can have one or more bypass arrangements designed to completely or partially bypass individual components of the drying system, in particular the dehumidification heat exchanger, the preheating heat exchanger, the flow heat exchanger, and / or the heat transfer device. This allows the drying system to be adapted to different operating conditions, for example, but not limited to, partial load operation, start-up operation, maintenance operation, and / or seasonal variations in the external peripheral temperature. Preferably, the bypass arrangements are equipped with control valves and / or flaps that can be controlled via the aforementioned control unit.In particular, under summer operating conditions, the dehumidification heat exchanger can be partially or completely bypassed, provided the relative humidity of the fresh air is already below a predefined threshold. This saves pump energy and reduces pressure losses in the fresh air path without impairing drying performance. The synergistic effect of the bypass arrangements is that the drying system can operate at an optimized operating point in every operating condition, minimizing overall pressure losses and thus the energy required for fans and pumps.

[0137] According to a further optional embodiment, the condensate produced during the dehumidification of fresh air in the dehumidification heat exchanger can be used for energy recovery. In particular, the condensate, which results from the cooling of the fresh air below the dew point, can have a temperature higher than the inlet temperature of the second flow heat medium. In a preferred embodiment, the condensate is at least partially fed to a condensate heat exchanger designed to transfer the residual heat contained in the condensate to the second flow heat medium and / or to the fresh air before the condensate is discharged. The synergistic effect of this condensate heat recovery is that a heat source previously considered a loss is returned to the cycle, further increasing the overall efficiency of the drying system and reducing the energy consumption of the heat transfer device.

[0138] According to a further optional embodiment, the heat transfer device can be designed as a cascaded temperature lift system comprising at least two temperature lift stages connected in series. In this configuration, a first temperature lift stage transfers heat from the second circulating heat medium to an intermediate medium at a specific temperature, and a second temperature lift stage transfers heat from the intermediate medium to the circulating heat medium. Distributing the total temperature lift across multiple stages allows each individual stage to operate with a smaller temperature difference, thus improving the coefficient of performance (COP) of each stage compared to a single-stage solution.The synergistic effect of a cascaded heat transfer device is that the total energy requirement for the temperature lift from the circuit outlet temperature to the circulation outlet temperature decreases, so that, especially with large temperature differences, for example under winter operating conditions with low circuit outlet temperature and high circulation outlet temperature, the electrical energy requirement of the heat transfer device is significantly reduced.

[0139] According to a further optional embodiment, the exhaust air exiting the discharge LLW exhaust air flow arrangement can be used, at least partially, as a heat source for the preheating heat exchanger, particularly in addition to or as an alternative to the first flow heat medium supplied via the media flow arrangement. In a preferred embodiment, a portion of the exhaust air, after passing through the air-to-air heat exchanger, is fed to the preheating flow volume via an exhaust air branch, so that the residual heat remaining in the exhaust air after heat transfer in the air-to-air heat exchanger contributes to preheating the fresh air. The synergistic effect of this additional exhaust air utilization in the preheating heat exchanger is that the exhaust air temperature can be further reduced without heat being released unused to the environment, while simultaneously stabilizing the fresh air flow temperature.This allows in particular a further reduction in the dimensioning of the heat transfer device, since a larger proportion of the required preheating is covered by the process-internal waste heat.

[0140] Where temperature values ​​are mentioned as limit values, this also includes the temperatures themselves. For example, if temperatures from 6 to 12 degrees Celsius are mentioned, the temperature value of 6.00 degrees Celsius is also included, as is the temperature value of 12.00 degrees Celsius. Brief description of the drawing

[0141] The following section explains a solution in more detail with reference to the attached drawing and using preferred embodiments.

[0142] The drawing shows Fig. 1. A diagram of a drying system according to an embodiment of a proposed solution; and Fig. 2 a scheme of a drying system according to a fully developed embodiment of a proposed solution. Detailed description of an exemplary implementation

[0143] The described embodiment of a drying system is merely an example that can be modified and / or supplemented in various ways within the scope of the claims. Each described feature can be used independently or in combination with other features in any other embodiment.

[0144] Fig. Figure 1 shows a drying system 1 for drying a drying medium. The drying of the drying medium is, in particular, the drying of fibrous materials, for example, but not limited to, paper or cardboard.

[0145] The in Fig. The drying system 1 shown in a preferred embodiment comprises the components described below.

[0146] The in Fig. The arrows shown in Figure 1, in particular the arrangements with reference numerals 100, 200, 300, 350, 400, 450, 600, 650, 700, 750, 2000, 3000, 4000 and 5000, are schematic representations of fluid-carrying flow systems, especially pipes or ducts, with the flow direction indicated. This further includes Fig. 2 corresponding arrangements with the reference numbers 500, 660, 670, 710, 800, 850, 1000 and 1500.

[0147] Preferably, consistent media exhibit consistent hatching patterns in the arrows. The term "consistent" here preferably refers to temperature and / or media pressure. Optionally or additionally, this can also refer to the media composition.

[0148] It should be clarified that the Fig. 1 and Fig. Section 2 is a schematic representation which is not limited to direct current or cross-counterflow designs for heat transfer. In principle, both or more heat transfer methods are covered by the scope of protection.

[0149] The drying system 1 includes an air-to-air heat exchanger, abbreviated LLW, 20 with an LLW exhaust air volume 21 and an LLW fresh air volume 22. Here, the air-to-air heat exchanger LLW 20 is, for example, a tube or plate heat exchanger.

[0150] The air-to-air heat exchanger 20 has a feed-in LLW exhaust air flow arrangement 100 for the inflow of exhaust air K with an initial temperature T_I into the LLW exhaust air volume 21.

[0151] The exhaust air K is an example and not a limiting factor; it is air that has already been part of a drying process and therefore has a higher humidity than fresh air F, especially ambient air. The initial temperature T_I can be, for example, 85 degrees Celsius, and this is not a limiting factor.

[0152] The air-to-air heat exchanger 20 further features a discharge LLW exhaust air flow arrangement 200 with an exhaust air follow-up temperature T_AF for the discharge of exhaust air K from the LLW exhaust air volume 21.

[0153] The air-to-air heat exchanger 20 further comprises a feed-in LLW fresh air flow arrangement 2000 for supplying fresh air F with a fresh air flow temperature T_G into the LLW fresh air volume 22. The fresh air flow temperature T_G is preferably controlled, independent of other features mentioned herein, particularly preferably via a preheating heat exchanger 10. This applies regardless of this embodiment and can also be extracted separately or combined with other features.

[0154] Fresh air is defined as, by way of example and not as a limiting factor, air that has not yet been an internal component of a drying process. Preferably, ambient air, treated or untreated, is considered fresh air F. Particularly preferably, the fresh air has a lower humidity level than the exhaust air K.

[0155] The air-to-air heat exchanger 20 further features a discharge LLW fresh air flow arrangement 3000 for the discharge of fresh air F with an LLW outlet temperature T_AT from the LLW fresh air volume 22.

[0156] The LLW exhaust air volume 21 and the LLW fresh air volume 22 are designed in such a way that heat can be transferred from the LLW exhaust air volume 21 to the LLW fresh air volume 22 in order to heat the fresh air F.

[0157] The outlet temperature T_AT can be, for example, 67 degrees Celsius and is not a limiting factor.

[0158] The drying system 1 has at least one media heat exchanger 40, which is configured to be supplied with a circulating heat transfer medium U in order to adjust the fresh air F with the LLW outlet temperature T_AT from the supplying LLW fresh air flow arrangement 3000 to a process temperature T_P, which is predefined, in particular and independently of other features mentioned herein. The fresh air F, adjusted to the process temperature T_P, is supplied to a drying system 30 from the media heat exchanger 40 via a flow arrangement 4000 encompassed by the drying system 1.

[0159] The media heat exchanger 40 is designed to be supplied with live steam, oil, hot water, salt solution, hydrogen, district heating, electricity, in particular induction, gas combustion, biomass combustion, autothermal combustion, solar thermal process heat, geothermal process heat, waste heat from neighboring plants, process heat from high-temperature heat pumps, steam generated by electrode or resistance boilers, waste heat from fuel cells, microwave or radio frequency energy, infrared or near-infrared radiation, heat from thermal energy storage systems, in particular molten salts or thermochemical storage systems, process steam from small modular nuclear reactors and / or a mixture thereof, in order to adjust the fresh air to the predefined process temperature T_P.

[0160] For example, after Fig. 2 The media heat exchanger 40 comprises: a flash evaporation heat exchanger 41, designed for the essentially direct intake and heating of the fresh air F from the LLW fresh air flow arrangement 3000, a heat exchange medium 42, designed for interaction with the circulating heat medium U of the discharging circulating discharge arrangement 750 for heating the fresh air F, a liquid heat exchanger 43, designed for heating the fresh air F and / or a media heat exchange medium 44, designed for heating and conveying the fresh air F by means of the flow arrangement 4000 into the drying system 30.

[0161] The expansion evaporation heat exchanger 41, the heat exchange medium 42, the liquid heat exchanger 43 and / or the media heat exchange medium 44 are designed to be supplied with live steam, oil, hot water, salt solution, hydrogen, district heating, electricity, in particular induction, gas combustion, biomass combustion, autothermal combustion, solar thermal process heat, geothermal process heat, waste heat from neighboring plants, process heat from high-temperature heat pumps, steam generated by electrode or resistance boilers, waste heat from fuel cells, microwave or radio frequency energy, infrared or near-infrared radiation, heat from thermal energy storage devices, in particular molten salts or thermochemical storage devices, process steam from small modular nuclear reactors and / or a mixture thereof, in order to adjust the fresh air F to the process temperature T_P.

[0162] The exemplary in Fig. The media heat exchanger 40 shown in Figure 2 has at least one heat exchange medium 42 to increase the energy of the fresh air F introduced into the media heat exchanger 40 from the LLW fresh air flow arrangement 3000, at least indirectly and / or at least partially, by means of the circulating heat medium U of the discharging circulating outlet arrangement 750. Preferably, after the energy increase of the fresh air F introduced into the media heat exchanger 40, the circulating heat medium U can be conveyed at least indirectly and / or at least partially into the heat transfer volume 72 by means of a recirculation arrangement 710, wherein the recirculation arrangement 710 corresponds in particular to the circulating inlet arrangement 700.

[0163] Furthermore, it is provided that the media heat exchanger 40 has one or more waste heat exchangers between the air-to-air heat exchanger 20 and the drying system 30. The waste heat exchanger, or several waste heat exchangers, of the media heat exchanger 40 utilize heat, at least indirectly, from a self-contained steam condensate system designed for drying the drying medium in the drying system 30, in order to heat the fresh air of the LLW fresh air flow arrangement 3000 to the predefined process temperature T_P and to convey it to the drying system 30 via the flow arrangement 4000.

[0164] The drying system 1 further comprises a drying unit 30, which is designed for drying the drying medium. The drying unit 30 is configured such that the fresh air F, which is heated at least by the air-to-air heat exchanger 20 and at least indirectly discharged from the LLW fresh air flow arrangement 3000, interacts with the drying medium as drying air. Evaporated moisture is absorbed from the drying medium and discharged as moisture-laden exhaust air K to an exhaust air duct arrangement 5000. Preferably, the temperature in the exhaust air duct arrangement 5000 corresponds at least to the initial temperature T_I. Preferably, the exhaust air K from the exhaust air duct arrangement 5000 is directly transferred to the LLW exhaust air flow arrangement 100, so that essentially a similar temperature, namely the initial temperature T_I, prevails in both arrangements 100 and 5000.However, it is also possible that one or more heat exchangers are interposed between the exhaust air duct arrangement 5000 and the subsequent LLW exhaust air flow arrangement 100, so that the temperature at the exhaust air duct arrangement 5000 is greater than the initial temperature T_I.

[0165] Thus, the drying system 1 is designed to direct the exhaust air K from the drying system 30 via the exhaust air duct arrangement 5000 and subsequently via the LLW exhaust air flow arrangement 100 at least indirectly to the air-to-air heat exchanger 20, so that at least an indirect transfer of heat from the exhaust air K in the exhaust air duct arrangement 5000 to the fresh air in the air-to-air heat exchanger 20 takes place.

[0166] As a result, the air-to-air heat exchanger 20 reduces the energy of the exhaust air K from the supplying LLW exhaust air flow arrangement 100. This means that heat energy from the exhaust air K is transferred from the LLW exhaust air volume 21 to the fresh air in the LLW fresh air volume 22.

[0167] According to the preferred embodiment, the drying system 1 demonstrates Fig. 2 a preheating heat exchanger 10 with a preheating volume 11 and a preheating flow volume 12, wherein the preheating heat exchanger 10 is designed to heat the fresh air F, in particular the ambient air, from an outside temperature T_A to the controlled fresh air flow temperature T_G.

[0168] The outside temperature T_A can be, for example, minus 20 degrees Celsius and is not a limiting factor.

[0169] The drying system 1 also includes a supply air duct arrangement 1000 for supplying fresh air at the outside temperature T_A.

[0170] The feeding LLW fresh air flow arrangement 2000 connects the preheating heat exchanger 10 at least indirectly with the air-to-air heat exchanger 20 in order to provide the fresh air with the fresh air flow temperature T_G for the air-to-air heat exchanger 20, in particular for the LLW fresh air volume 22 of the air-to-air heat exchanger 20.

[0171] The regulated fresh air flow temperature T_G can, for example, be 35 degrees Celsius and is not limiting.

[0172] The exhaust air temperature T_AF can, for example, be 70 degrees Celsius and is not limiting.

[0173] In particular, the drying system 1 comprises a warm fresh air discharge arrangement 1500 for discharging fresh air F with a fresh air flow temperature T_G from the preheating volume 11 and for at least indirectly flowing into the LLW fresh air volume 22. The preheating volume 11 and the preheating flow volume 12 are designed such that heat can be transferred from the preheating flow volume 12 to the preheating volume 11 to warm the fresh air F. Specifically, the warm fresh air discharge arrangement 1500 corresponds to the supplying LLW fresh air flow arrangement 2000, so that the preheating heat exchanger 10 can be connected at least indirectly to the air-to-air heat exchanger 20 to provide the fresh air F with the fresh air flow temperature T_G for the LLW fresh air volume 22.

[0174] The drying system 1 comprises a flow heat exchanger 60 with a heat transfer volume 61 and a heating volume 62. The flow heat exchanger 60 includes a feed heat inlet arrangement 300 for the inflow of a first flow heat medium S1 with a flow temperature T_S into the heat transfer volume 61 and a discharge heat outlet arrangement 350 with a flow sequence temperature T_SF for the discharge of the first flow heat medium S1 from the heat transfer volume 61. The flow heat exchanger 60 further comprises a feed recirculation inlet arrangement 450 for the inflow of a second flow heat medium S2 with a recirculation inlet temperature T_KE into the heating volume 62 and a discharge recirculation outlet arrangement 400 for the discharge of the second flow heat medium S2 with a recirculation outlet temperature T_KA from the heating volume 62.The heat transfer volume 61 and the heating volume 62 are designed such that heat can be transferred from the heat transfer volume 61 to the heating volume 62 in order to heat the second flow heat medium S2.

[0175] The first flow heat medium S1 of the heat inlet arrangement 300 has flow components from the LLW exhaust air flow arrangement 200 and / or other flow components SB.

[0176] The drying system 1 comprises a heat transfer device 70 with a cooling transfer volume 71 and a heating transfer volume 72. The heat transfer device 70 includes a feed-in heat transfer inlet arrangement 600 for the flow of the second flowing heat medium S2 with a heat transfer inlet temperature T_WTE into the cooling transfer volume 71 and a discharge heat transfer outlet arrangement 650 with a heat transfer outlet temperature T_WTA for the discharge of the second flowing heat medium S2 from the cooling transfer volume 71.The heat transfer device 70 further comprises a feed-in circulating inlet arrangement 700 for feeding a circulating heat medium U with a circulating inlet temperature T_UE into the heating transfer volume 72 and a discharge circulating outlet arrangement 750 for feeding the circulating heat medium U with a circulating outlet temperature T_UA out of the heating transfer volume 72, and for at least indirect and / or at least partial flow into the media heat exchanger 40. The cooling transfer volume 71 and the heating transfer volume 72 are configured such that heat can be transferred from the cooling transfer volume 71 to the heating transfer volume 72 to heat the circulating heat medium U. The circulating outlet temperature T_UA is higher than the fresh air flow temperature T_G and higher than the LLW outlet temperature T_AT.

[0177] The drying system 1 comprises, according to Fig.2 a dehumidification heat exchanger device 80 with a process medium heating volume 81 and a dehumidification volume 82. The dehumidification heat exchanger device 80 has a feed-in process medium inlet arrangement 660 for feeding a process medium P with a process medium inlet temperature T_PME into the process medium heating volume 81 and a discharge process medium outlet arrangement 670 with a process medium outlet temperature T_PMA for discharge of the process medium P from the process medium heating volume 81.The dehumidification heat exchanger device 80 further comprises a fresh air inlet arrangement 800 for the inflow of fresh air F with an initial fresh air temperature T_FI into the dehumidification volume 82 and a dry fresh air outlet arrangement 850 for the outflow of fresh air F with a dry fresh air temperature T_T from the dehumidification volume 82, and for at least indirect inflow into the air-to-air heat exchanger 20, in particular via a preheating heat exchanger 10, wherein the process medium heating volume 81 and the dehumidification volume 82 are designed such that heat can be transferred from the dehumidification volume 82 to the process medium heating volume 81 in order to heat the process medium P and reduce moisture from the fresh air F.

[0178] Furthermore, the feeding process medium inlet arrangement 660 is designed to feed the second flow heat medium S2 completely or at least partially from the cooling transfer volume 71 of the heat transfer device 70, so that the process medium P has at least partially the second flow heat medium S2 or corresponds to it and / or the dry fresh air outlet arrangement 850 corresponds to the supply air duct arrangement 1000.

[0179] Furthermore, the flow heat exchanger 60 and the heat transfer device 70 are arranged in a common assembly unit.

[0180] The drying system 1 comprises one or more heat exchanger devices 50 between the air-to-air heat exchanger 20 and the flow heat exchanger 60, designed to energetically modify a media flow between the air-to-air heat exchanger 20 and the flow heat exchanger 60. The one or more heat exchanger devices 50 are designed to energetically increase the media flow between the air-to-air heat exchanger 20 and the flow heat exchanger 60, in particular at least indirectly under the influence of a high-calorie heat flow. The one or more heat exchanger devices 50 is / are designed to reduce the energy of the media flow between the air-to-air heat exchanger 20 and the flow heat exchanger 60, in particular for subsequent conveyance to one or more system components downstream of the air-to-air heat exchanger, LLW, 20, at least indirectly and / or at least partially.

[0181] The flow heat exchanger 60 and / or the heat transfer device 70 is / are designed such that the circuit inlet temperature T_KE and / or the circuit outlet temperature T_KA is / are less than or equal to a drying system external peripheral temperature T_EX.

[0182] Furthermore, the drying system 1 is designed such that the first flow heat medium S1 from the heat transfer volume 61 can be fed at least partially and / or at least indirectly into the supplying fresh air inlet arrangement 800 with a fresh air initial temperature T_FI and / or into the preheating flow volume 12 by means of the supplying heat outlet arrangement 350 with a flow sequence temperature T_SF via the supplying fresh air inlet arrangement 350 with a fresh air initial temperature T_FI and / or by means of a media flow arrangement 500 encompassed by the drying system 1 with a recuperation temperature T_R of the preheating heat exchanger 10 via a media flow arrangement 500 with a recuperation temperature T_R of the preheating heat exchanger 10. Reference symbol list 1 drying system 10 preheating heat exchangers 11 Preheating volume 12 Preheating flow volume 20 air-to-air heat exchangers, LLW 21 LLW exhaust air volume 22 LLW fresh air volume 30 drying plant 40 media heat exchangers 41 Expansion evaporative heat exchangers 42 Heat exchanger fluid 43 liquid heat exchangers 44 Media heat exchanger 50 Heat exchanger device 60 flow heat exchangers 61 Heat transfer volume 62 heating volume 70 Heat transfer device 71 Cooling transfer volume 72 Heat transfer volume 80 Dehumidification heat exchanger device 81 Process medium heating volume 82 dehumidification volume 100 Feed-in LLW exhaust air flow arrangement 200 Discharge LLW exhaust air flow arrangement 300 Feed-in heat inlet arrangement 350 Discharge heat outlet arrangement 400 Discharge circuit outlet arrangement 450 Feed-in circuit inlet arrangement 500 Media flow arrangement 600 Feed-in heat transfer inlet arrangement 650 Discharge heat transfer outlet arrangement 660 Feed-in process medium inflow arrangement 670 Discharge process medium discharge arrangement 700 Feed-in circulating inlet arrangement 710 Return order 750 Discharge Circulating Discharge Arrangement 800 Fresh air inlet arrangement 850 Discharge dry fresh air outlet arrangement 1000 Supply air duct arrangement 1500 Warm fresh air outlet arrangement 2000 Feed-in LLW fresh air flow arrangement 3000 Discharge LLW fresh air flow arrangement 4000 flow arrangement 5000 Exhaust air duct arrangement Fresh air K Exhaust air U Circulating heat medium P Process medium S1 First flow heat medium S2 Second flow heat medium SB Other flow components T_A Outside temperature T_I Initial temperature T_AF exhaust air follow-up temperature T_G Fresh air flow temperature T_AT LLW outlet temperature T_P Process temperature T_S Flow temperature of the first flowing heat medium T_SF Flow sequence temperature of the first flow heat medium T_KE is the inlet temperature of the second flowing heat medium. T_KA is the circuit outlet temperature of the second flowing heat medium. T_WTE Heat transfer inlet temperature of the second flowing heat medium T_WTA Heat transfer outlet temperature of the second flowing heat medium T_UE Circulation inlet temperature of the circulating heat medium T_UA Circulation outlet temperature of the circulating heat medium T_PME Process medium inflow temperature T_PMA process medium outlet temperature T_FI Fresh air initial temperature T_T Dry fresh air temperature T_EX External peripheral temperature T_R Recuperation temperature

Claims

Drying system for drying a drying medium, in particular for drying fibrous materials, the drying system (1) comprising at least the following components: - an air-to-air heat exchanger (20) with an air-to-air exhaust volume (21) and an air-to-air fresh air volume (22), the air-to-air heat exchanger (20) comprising: - an inlet air-to-air exhaust air flow arrangement (100) for supplying exhaust air (K) with an initial temperature (T_I) into the air-to-air exhaust volume (21) and - an outlet air-to-air exhaust air flow arrangement (200) with a subsequent exhaust air temperature (T_AF) for exhaust air (K) flowing out of the air-to-air exhaust volume (21), - an inlet air-to-air fresh air flow arrangement (2000) for supplying fresh air (F) with a fresh air flow temperature (T_G) into the LLW fresh air volume (22) and a discharging LLW fresh air flow arrangement (3000) for discharging fresh air (F) with an LLW outlet temperature (T_AT) from the LLW fresh air volume (22),wherein the LLW exhaust air volume (21) and the LLW fresh air volume (22) are configured such that heat can be transferred from the LLW exhaust air volume (21) to the LLW fresh air volume (22) to heat the fresh air (F); - a media heat exchanger (40) configured to be supplied with a circulating heat transfer medium (U) to adjust the fresh air (F) with the LLW outlet temperature (T_AT) from the supplying LLW fresh air flow arrangement (3000) to a process temperature (T_P), wherein the fresh air (F) set to the process temperature (T_P) is supplied to the drying system (30) via a flow arrangement (4000) encompassed by the drying system (1); - a drying system (30) configured for drying the drying medium, wherein the drying system (30) is trained in this waythat the fresh air (F) which is heated at least by the air-to-air heat exchanger (20) and the media heat exchanger (40) and which flows out at least indirectly from the LLW fresh air flow arrangement (3000) and flow-through arrangement (4000) interacts with the drying medium as drying air and absorbs evaporated moisture from the drying medium and discharges it as moisture-laden exhaust air (K) to an exhaust air duct arrangement (5000); wherein the drying system (1) is configured to direct the exhaust air (K) from the drying system (30) at least indirectly to the air-to-air heat exchanger (20) via the exhaust air duct arrangement (5000) and the LLW exhaust air flow arrangement (100), so that at least an indirect transfer of heat from the exhaust air (K) in the exhaust air duct arrangement (5000) to the fresh air (F) in the air-to-air heat exchanger (20) takes place;- a flow heat exchanger (60) with a heat transfer volume (61) and a heating volume (62),the flow heat exchanger (60) comprising: - an inlet heat inlet arrangement (300) for the inflow of a first flow heat medium (S1) with a flow temperature (T_S) into the heat transfer volume (61) and - an outlet heat outlet arrangement (350) with a flow sequence temperature (T_SF) for the outflow of the first flow heat medium (S1) from the heat transfer volume (61), - an inlet recirculation inlet arrangement (450) for the inflow of a second flow heat medium (S2) with a recirculation inlet temperature (T_KE) into the heating volume (62) and - an outlet recirculation outlet arrangement (400) for the outflow of the second flow heat medium (S2) with a recirculation outlet temperature (T_KA) from the heating volume (62), wherein the heat transfer volume (61) and the heating volume (62) are designed such that heat from the heat transfer volume (61) is transferable to the heating volume (62),to heat the second flow heat medium (S2), wherein the first flow heat medium (S1) of the heat inlet arrangement (300) comprises flow components from the LLW exhaust air flow arrangement (200) and / or other flow components (SB), - a heat transfer device (70) with a cooling transfer volume (71) and a heating transfer volume (72), the heat transfer device (70) comprising: - a supply heat transfer inlet arrangement (600) for the second flow heat medium (S2) with a heat transfer inlet temperature (T_WTE) into the cooling transfer volume (71) and - a supply heat transfer outlet arrangement (650) with a heat transfer outlet temperature (T_WTA) for the second flow heat medium (S2) to flow out of the cooling transfer volume (71),- a supply circulating inlet arrangement (700) for supplying a circulating heat transfer medium (U) with a circulating inlet temperature (T_UE) into the heat transfer volume (72) and - a supply circulating outlet arrangement (750) for supplying the circulating heat transfer medium (U) with a circulating outlet temperature (T_UA) from the heat transfer volume (72), and for at least indirect and / or at least partial supply to the media heat exchanger (40), wherein the cooling transfer volume (71) and the heat transfer volume (72) are configured such that heat can be transferred from the cooling transfer volume (71) to the heat transfer volume (72) to heat the circulating heat transfer medium (U); wherein the circulating outlet temperature (T_UA) is higher than the fresh air flow temperature (T_G) and higher than the LLW outlet temperature (T_AT). Drying system according to claim 1, the drying system (1) comprising: - a preheating heat exchanger (10) with a preheating volume (11) and a preheating flow volume (12), the preheating heat exchanger (10) comprising: a supply air duct arrangement (1000) for supplying fresh air (F) with an outside temperature (T_A) into the preheating volume (11), a warm fresh air discharge arrangement (1500) for discharging fresh air (F) with a fresh air flow temperature (T_G) from the preheating volume (11), and for at least indirect flow into the LLW fresh air volume (22), wherein the preheating volume (11) and the preheating flow volume (12) are designed such that heat can be transferred from the preheating flow volume (12) to the preheating volume (11) in order to heat the fresh air (F), wherein in particular the discharging warm fresh air discharge arrangement (1500) corresponds to the incoming LLW fresh air flow arrangement (2000),so that the preheating heat exchanger (10) can be connected at least indirectly to the air-to-air heat exchanger (20) in order to provide the fresh air (F) with the fresh air flow temperature (T_G) for the LLW fresh air volume (22). Drying system according to claim 1 or 2, the drying system (1) comprising: - a dehumidification heat exchanger device (80) with a process medium heating volume (81) and a dehumidification volume (82), the dehumidification heat exchanger device (80) comprising: - a feed-in process medium inlet arrangement (660) for feeding a process medium (P) with a process medium inlet temperature (T_PME) into the process medium heating volume (81) and - a discharge process medium outlet arrangement (670) with a process medium outlet temperature (T_PMA) for the process medium (P) to flow out of the process medium (P) from the process medium heating volume (81), - a feed-in fresh air inlet arrangement (800) for feeding fresh air (F) with a fresh air initial temperature (T_FI) into the dehumidification volume (82) and - a discharge dry fresh air outlet arrangement (850) for the fresh air (F) to flow out with a Dry fresh air temperature (T_T) from the dehumidification volume (82),and for at least indirect inflow into the air-to-air heat exchanger (20), in particular via a preheating heat exchanger (10), wherein the process medium heating volume (81) and the dehumidification volume (82) are designed such that heat can be transferred from the dehumidification volume (82) to the process medium heating volume (81) in order to heat the process medium (P) and reduce moisture from the fresh air (F). Drying system according to claim 3, wherein the feeding process medium inlet arrangement (660) is configured to feed the second flow heat medium (S2) completely or at least partially from the cooling transfer volume (71) of the heat transfer device (70), such that the process medium (P) at least partially comprises or corresponds to the second flow heat medium (S2) and / or the dry fresh air outlet arrangement (850) corresponds to the supply air duct arrangement (1000). Drying system according to at least one of claims 1 to 4, wherein the flow heat exchanger (60) and the heat transfer device (70) are arranged in a common assembly unit. Drying system according to at least one of claims 1 to 5, the drying system (1) comprising: - one or more heat exchanger devices (50) between the air-to-air heat exchanger (20) and the flow heat exchanger (60), designed for the energetic change of a media flow between the air-to-air heat exchanger (20) and the flow heat exchanger (60). Drying system according to claim 6, wherein one or more heat exchanger devices (50) is / are designed to increase the energy of the media flow between the air-to-air heat exchanger (20) and the flow heat exchanger (60), in particular at least indirectly under the influence of a high-calorie heat flow. Drying system according to claim 6 or 7, wherein one or more heat exchanger devices (50) are configured to reduce the energy of the media flow between the air-to-air heat exchanger (20) and the flow heat exchanger (60), in particular for subsequent conveyance to one or more system components at least indirectly and / or at least partially downstream of the air-to-air heat exchanger (AHP) (20). Drying system according to at least one of claims 1 to 8, wherein the media heat exchanger (40) has at least one heat exchanger medium (42) in order to increase the energy of the fresh air (F) introduced into the media heat exchanger (40) at least indirectly and / or at least partially by means of the circulating heat medium (U) of the discharging circulating outlet arrangement (750) from the LLW fresh air flow arrangement (3000) at least indirectly and / or at least partially by means of the circulating heat medium (U) of the discharging circulating outlet arrangement (750). Drying system according to claim 9, wherein the circulating heat medium (U) after the energetic increase of the fresh air (F) introduced into the media heat exchanger (40) by means of a recirculation arrangement (710) can be conveyed at least indirectly and / or at least partially into the heating transfer volume (72), wherein in particular the recirculation arrangement (710) corresponds to the circulating inflow arrangement (700). Drying system according to at least one of claims 1 to 10, wherein the media heat exchanger (40) comprises at least one of the following units: - a flash evaporation heat exchanger (41) designed for the substantially direct intake and heating of the fresh air (F) from the LLW fresh air flow arrangement (3000), - a heat exchange medium (42) designed for interaction with the circulating heat medium (U) of the discharging circulating discharge arrangement (750) for heating the fresh air (F), - a liquid heat exchanger (43) designed for heating the fresh air (F), and / or - a media heat exchange medium (44) designed for heating and conveying the fresh air (F) by means of the flow arrangement (4000) into the drying system (30). Drying system according to at least one of claims 1 to 11, wherein the media heat exchanger (40) is configured to use live steam, oil, hot water, salt solution, hydrogen, district heating, electricity, in particular induction, gas combustion, biomass combustion, autothermal combustion, solar thermal process heat, geothermal process heat, waste heat from neighboring plants, process heat from high-temperature heat pumps, steam generated by electrode or resistance boilers, waste heat from fuel cells, microwave or radio frequency energy, infrared orNear-infrared radiation, heat from thermal energy storage devices, in particular molten salts or thermochemical storage devices, process steam from small modular nuclear reactors and / or a mixture thereof, to be applied to adjust the fresh air (F) to the process temperature (T_P), wherein the media heat exchanger (40) is in particular one according to claim 11, wherein the flash evaporation heat exchanger (41), the heat exchange medium (42), the liquid heat exchanger (43) and / or the media heat exchange medium (44) is / are configured to be supplied with fresh steam, oil, hot water, salt solution, hydrogen, district heating, electricity, in particular induction, gas combustion, biomass combustion, autothermal combustion, solar thermal process heat, geothermal process heat, waste heat from neighboring plants, process heat from high-temperature heat pumps, steam generated by electrode or resistance boilers, waste heat from fuel cells, microwave orRadio frequency energy, infrared or near-infrared radiation, heat from thermal energy storage devices, in particular molten salts or thermochemical storage devices, process steam from small modular nuclear reactors and / or a mixture thereof, are used to adjust the fresh air (F) to the process temperature (T_P). Drying system according to at least one of claims 1 to 12, wherein the flow heat exchanger (60) and / or the heat transfer device (70) is / are designed such that the circuit inlet temperature (T_KE) and / or the circuit outlet temperature (T_KA) is / are less than or equal to a drying system external peripheral temperature (T_EX). Drying system according to at least one of claims 2 to 13, wherein the first flow heat medium (S1) from the heat transfer volume (61) can be fed at least partially and / or at least indirectly into the supplying fresh air inlet arrangement (800) with a fresh air initial temperature (T_FI) and / or into the preheating flow volume (12) by means of the supplying heat outlet arrangement (350) with a flow sequence temperature (T_SF) and / or by means of a media flow arrangement (500) encompassed by the drying system (1) with a recuperation temperature (T_R) of the preheating heat exchanger (10). Retrofit system, configured for extending an existing drying system with an air-to-air heat exchanger (20), a media heat exchanger (40), and a drying unit (30) to a drying system (1) according to at least one of claims 1 to 14, the retrofit system comprising at least the following and / or modified drying system components: - at least one preheating heat exchanger (10) according to one of claims 2, 3, or 14, - at least one air-to-air heat exchanger (20) according to one of claims 1 to 3 or 6 to 8, - at least one drying unit (30) according to one of claims 1 or 11, - at least one media heat exchanger (40) according to one of claims 1 or 9 to 12, - at least one heat exchanger device (50) according to one of claims 6 to 8, - at least one flow heat exchanger (60) according to one of claims 1, 5 up to 8 or 13 ,- at least one heat transfer device (70) according to one of claims 1 , 4 , 5 , or 13,and / or at least one dehumidification heat exchanger device (80) according to claim 3.

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