Adsorption dryer

Abstract

The invention relates to a method for drying a compressed gas, in particular compressed air, using an adsorption dryer which has at least one pressure vessel with an adsorption material for adsorbing moisture from the compressed gas, wherein, in drying operation for drying the compressed gas, the compressed gas flows through the pressure vessel along the adsorption material from a drying inlet, through a drying section, to a drying outlet and exits as dried compressed gas; in regeneration operation for regenerating the adsorption material, a regeneration gas flows through the pressure vessel along the adsorption medium from the drying outlet, through the drying section, to the drying inlet and in the process draws moisture from the adsorption material; and in regeneration operation, partial heating takes place in a heating region in the pressure chamber, wherein the heating region is arranged only in a subregion of the pressure vessel, adjacent to the drying inlet.

Description

[0001] Adsorption dryer

[0002] The present invention relates to a method for drying a compressed gas and an adsorption dryer.

[0003] Adsorption dryers are well-known and are used, among other things, for compressed air drying or for drying other gases. Any design for compressed air drying can also be applied to drying other gases.

[0004] Adsorption processes are often used for compressed air drying. These processes involve bringing the compressed air stream into contact with a solid adsorption material. The adsorption material absorbs some of the water vapor contained in the compressed air stream, thus drying the compressed air. This increases the amount of water bound (adsorbed) in the adsorption material. If the adsorption material has absorbed so much water that further compressed air can no longer be adequately dried, the water contained in the adsorption material must first be at least partially removed before the adsorption material can be used to dry the compressed air. The removal of water from the desiccant is called regeneration of the adsorption material.For the technical realization of continuous drying, several containers are typically provided so that when the adsorption material of one container is regenerated, another already regenerated container is always available for drying.

[0005] A well-known regeneration method involves expanding a portion of the already dried compressed air to a low pressure and passing it through the vessel whose adsorption material is to be regenerated. The flow direction is usually opposite to the flow direction during compressed air drying. Dryers that use this method are called heatless adsorption dryers.

[0006] The partial pressure of water vapor in an air stream can assume a maximum of the vapor pressure of water. This limits the partial density of the water vapor in the air. The compressed air to be dried is usually 100% saturated with water vapor, i.e. the vapor pressure of the water and thus the maximum possible partial density are reached. At approximately the same temperature during drying and regeneration, the volume of the regeneration air must therefore be at least as large as the volume of the previously dried compressed air. The proportion of compressed air that needs to be expanded must therefore, at approximately the same temperature, be at least as large as the ratio of the pressures during regeneration and drying. This is because the density of ideal gases is proportional to the pressure at approximately constant temperature.

[0007] The disadvantage of this process is that the significant portion of compressed air released for regeneration is no longer available for further use and therefore has to be compressed in addition to the actual required amount of compressed air. This makes this process very energy-intensive.

[0008] Another well-known regeneration method involves performing the regeneration at elevated temperatures. The higher the temperature, the higher the water vapor pressure. Heated ambient air is used for regeneration. The temperature during regeneration is chosen so high that the water vapor pressure is sufficiently above the partial pressure of the water vapor contained in the ambient air. This makes regeneration possible despite the water vapor already naturally present in the ambient air. Dryers that use this method are called heat-regenerating adsorption dryers.

[0009] With this method, sufficient heat must be introduced via the heated ambient air to heat the dry material to a high temperature, e.g., 150 °C, and the water is desorbed from the dry material. "Desorbed" means that the water changes from the bound (adsorbed) state to the gaseous state. The heating energy required for this method is less than the energy required to produce the compressed air, which is expanded for regeneration, in the previously described method.

[0010] The disadvantage is that at the end of regeneration, the dry material is at a high temperature. As a result, the compressed air flows through warm dry material immediately after switching a container. This heats the compressed air to undesirably high temperatures and also results in less effective drying, since the warmer the dry material is, the less moisture it can remove from the compressed air.

[0011] To mitigate these disadvantages, the dry material is cooled before being reused for compressed air drying. Ambient air and / or expanded compressed air can be used to cool the dry material. Cooling with ambient air is limited by the fact that the dry material absorbs water vapor from the ambient air during the cooling process, thus reducing the amount of compressed air that can dry it. Cooling with expanded compressed air can also only be used to a very limited extent if an energy advantage is to be achieved compared to the method that regenerates with expanded compressed air.

[0012] The disadvantage of the high temperature and residual moisture immediately after switching a container to compressed air drying can therefore only be slightly reduced, but not avoided.

[0013] US Pat. No. 5,087,178 A describes a drying process in which regeneration is carried out using expanded compressed air, similar to a cold-regenerating adsorption dryer. Before the compressed air is expanded, it is heated by oil from an oil-injected screw compressor. The added heat improves desorption. However, the heat input is limited by the heat capacity of the regeneration air. Therefore, a significant portion of the compressed air is still required for regeneration. Another disadvantage here is that the desiccant is heated after regeneration, and this residual heat, as already described, leads to a significant increase in temperature and residual moisture after switching to drying.

[0014] A similar drying process is also described in US Pat. No. 4,898,599 A. However, to improve regeneration, the respective vessel is heated directly during regeneration using warm oil from a screw compressor with oil injection. As an alternative to using expanded compressed air for regeneration, it is proposed to extract the water vapor. However, given the low vapor pressure of water, this would require the vessel to be evacuated to a very low pressure.

[0015] An advantage over US 5,087,178 A is that the heat input can occur independently of the regeneration air. However, the disadvantage of the large residual heat is also present in US 4,898,599 A.

[0016] In EP 1 010 452 B1, at least a portion of the dry material is heated independently of the compressed air by a resistance or microwave heater. Here, the heating of the dry material is achieved by two or more independently activatable heating devices, so that the heating of the dry material in the upper container section can be stopped while the heating in the lower container section is still active. This can achieve a certain reduction in the amount of compressed air required for cooling. However, a large amount of cooling air is still required to cool the entire container contents. An adsorption buffer is described in US 3,204,388 A. Vacuum regeneration is described in KR 101214541 B1.

[0017] The present invention is therefore based on the object of addressing at least one of the aforementioned problems. In particular, a method is to be developed that has the lowest possible energy consumption and exhibits lower temperatures and humidities in the compressed air after switching a regenerated container to compressed air drying. At the very least, an alternative solution to previously known solutions is to be proposed.

[0018] According to the invention, a method according to claim 1 is proposed. The method thus relates to the drying of a compressed gas, in particular compressed air, using an adsorption dryer. Such an adsorption dryer comprises at least one pressure vessel containing an adsorption material for adsorbing moisture from the compressed gas. Such an adsorption material can be a suitable granulate arranged in the pressure vessel and through which the compressed air flows during operation.

[0019] The process works in such a way that, in a drying operation for drying the compressed gas, the compressed gas flows from a drying inlet through a drying section to a drying outlet through the pressure vessel along the adsorption material, exiting as dried compressed gas. The compressed gas thus flows through the pressure vessel along the adsorption material, which may be present as granules, and releases moisture to this adsorption material. The dried compressed gas therefore has less moisture than before it flowed along the adsorption material immediately after entering the drying inlet.

[0020] For structural reasons and / or for functional purposes, the pressure vessel may not be completely filled with adsorption material. In this case, it has a transition zone up to the adsorption material in the area of ​​the drying inlet and / or the drying outlet, in which no adsorption material is arranged. Each transition zone can take up approximately 2%-10% of the length from the drying inlet to the drying outlet. The drying section is a section in the adsorption material, i.e. a section from the drying inlet to the drying outlet, minus the at least one transition zone. In a regeneration operation for regenerating the adsorption material, a regeneration gas flows from the drying outlet through the drying section to the drying inlet through the pressure vessel along the adsorption material, thereby removing moisture from the adsorption material.Thus, in regeneration mode, the flow direction is reversed compared to the drying mode, so that the regeneration gas flows opposite to the compressed gas to be dried and removes the moisture from the adsorption material that the adsorption material has absorbed from the compressed gas to be dried.

[0021] Furthermore, it is proposed that partial heating be provided in a heating zone within the pressure vessel during regeneration. The pressure vessel is thus heated during regeneration, but not across the entire zone. The heating zone is located only in a portion of the pressure vessel, adjacent to the drying inlet. The regeneration gas thus flows first through an unheated zone within the pressure vessel and then through the heating zone.

[0022] Heating the regeneration gas increases its water vapor absorption capacity, allowing it to absorb more water. The adsorption material, which is also heated, can also release its moisture more effectively.

[0023] However, it was recognized that the compressed air to be dried releases the most moisture in the area where it flows in, i.e., near the drying inlet. The adsorption material therefore essentially has the highest moisture content near the drying inlet, which decreases towards the drying outlet. The proposed process exploits precisely this finding. During regeneration operation, the regeneration gas first flows into the area of ​​the pressure vessel where the adsorption material has absorbed comparatively little moisture. Furthermore, the regeneration gas itself is initially very dry, meaning it has not yet absorbed any or very little moisture. This comparatively dry regeneration gas can therefore quite effectively absorb the small amount of moisture contained in the adsorption material in the area of ​​this drying outlet.

[0024] In this sense, the amount of moisture absorbed by the regeneration gas increases from the drying outlet to the drying inlet. Towards the drying inlet, from which the regeneration gas will flow out, it has thus absorbed a lot of moisture, but still needs to absorb a lot of moisture from the adsorption material, because the adsorption material has a lot of moisture near the drying inlet.

[0025] Therefore, the pressure vessel is heated in this area, near the drying inlet. This also heats up the regeneration gas, especially the air, and allows it to absorb more moisture, as its water vapor absorption capacity increases with the heating.

[0026] However, it is proposed that this heating be carried out only in a portion of the pressure vessel. It is only heated where the increased water vapor absorption capacity is needed. It has been recognized that this is, as described above, in the area of ​​the drying inlet.

[0027] It was also recognized that it is particularly advantageous for the drying air to flow in one direction while the regeneration gas flows in the opposite direction. The flow direction of the compressed gas to be dried leads to a corresponding gradient of the absorbed moisture in the pressure vessel, to which the flow of the regeneration gas in the opposite direction is well adapted, especially with the targeted heating of the regeneration gas before its exit.

[0028] An improvement in the process compared to the state of the art is thus achieved by specifically introducing heat only where it is needed to improve efficiency. The majority of the water vapor during drying is already adsorbed in the lower part of the pressure vessel if the pressure inlet is at the bottom of the vessel. By specifically introducing heat in this lower part of the vessel, through which the regeneration air flows directly before it exits the vessel, the water vapor absorption capacity of the regeneration air is only increased from the point where a higher capacity is necessary, since only there can a large amount of water be released into the air. This avoids unnecessarily heating up large amounts of dry material.

[0029] According to one aspect, it is proposed that the heating region be arranged in a section from 0% to 80%, preferably 0% to 60%, and in particular 0% to 50% of the drying section. The heating region is thus provided in the region towards the drying inlet. For this purpose or alternatively, it is proposed that the heating region extend over at least 20% of the drying section, preferably over at least 30% of the drying section, in particular over at least 40% of the drying section. In particular, it is provided that no heating takes place outside the heating region, or at most reduced heating with less than 30% energy input per volume, compared to the heating region.

[0030] It has been recognized that it is particularly advantageous to heat approximately one half of the drying section, namely the section toward the drying inlet. The heating region is therefore arranged close to the drying inlet. It is in a section from 0% to 80% and thus in any case not in the section from 80% to 100%. This section can remain free and does not need to be heated, for the reasons explained above. However, it has been recognized that it may be sufficient to provide heating in the range from 0% to 60%. 0% to 50% is particularly advantageous, as this allows approximately half of the drying section to be heated. The pressure vessel can, for example, be positioned vertically, so that the drying inlet is at the bottom and the drying outlet at the top. In such a substantially cylindrical vessel, the adsorption material or a frame that accommodates the adsorption material can be set up in the pressure vessel, e.g.on feet, so that the distance between the adsorption material and thus the beginning of the drying section can be about 5% from the drying inlet.

[0031] It is proposed here or alternatively that the heating region extends over at least 30% of the drying section, in particular over at least 40% of the drying section, wherein it is preferably arranged in the said section from 0% to 80%, 0% to 60% or 5% to 50%. In this way, a significant area of ​​the drying section, namely at least 30%, can be heated. A greater regeneration effect can be achieved by a larger area of ​​at least 40%, which can, however, lead to a higher energy input. The heating region should not extend over the entire drying section and should therefore preferably extend over a maximum of 70%, in particular a maximum of 60% of the drying section.

[0032] No heating should take place outside the heating zone. Therefore, no heating will take place outside the heating zone during the entire regeneration operation. Reduced heating with less than 30% energy input per volume compared to the heating zone is generally possible. However, the energy input per volume can also be less than 10% compared to the heating zone. Heating outside the heating zone is generally not intended. However, should heating be provided there for other reasons, which could possibly be intended for drying operation, this cannot be ruled out and would only lead to undesirable energy input, which should be avoided if possible.

[0033] According to one aspect, it is proposed that a compressed gas portion is used as part of the dried compressed gas as regeneration gas, the compressed gas portion is admitted into the pressure vessel at the drying outlet, and the compressed gas portion undergoes a pressure reduction during or before admission into the pressure vessel.

[0034] This allows a portion of the dried compressed gas to be used for regeneration, i.e., for drying the adsorption material. One practical implementation involves using two pressure vessels that alternately operate in drying or regeneration mode. If one pressure vessel operates in drying mode, it continuously outputs dried compressed air, which can be used in the other vessel, which operates in regeneration mode, for regeneration, i.e., for drying the adsorption material. To ensure that this dried compressed gas, and particularly the dried compressed air, can absorb more moisture from the adsorption material, even in the unheated area, it is subjected to a pressure reduction. The compressed gas is thus dried itself at higher pressure and can, in a sense, reabsorb its own moisture from the adsorption material due to the reduced pressure.

[0035] After this compressed gas portion has been used for regeneration, it can be released as moist gas or moist compressed air, possibly no longer under pressure or under overpressure, or it can release some of its moisture in a water separator. Such a water separator can operate, for example, via condensation.

[0036] According to one aspect, it is proposed that heating in the pressure vessel be carried out by means of a heat exchanger, with heat transfer sections of the heat exchanger being surrounded by the adsorption material in order to transfer heat to the adsorption material. However, during regeneration operation, the heat exchanger also transfers heat directly to the regeneration gas, i.e., in particular, the regeneration air.

[0037] Here, it was recognized that by using a heat exchanger, heat generated elsewhere in the system can be used to heat the pressure vessel. The heat exchanger has heat transfer sections arranged within the pressure vessel. These heat transfer sections are designed to be surrounded by adsorption material within the pressure vessel. In particular, the adsorption material is provided as granules and thus as bulk material. The heat transfer sections are designed and arranged within the pressure vessel such that such granular bulk material can surround these heat transfer sections. In particular, it can be poured or poured between sections of the heat transfer sections.

[0038] For this purpose, the heat transfer sections can be designed, for example, in the shape of a cylindrical disk or with circular sections or with several flat sections arranged parallel to one another, which are designed in such a way that the granulate can be poured around them and, in the case of sections arranged parallel to one another, there is sufficient distance between them so that the granulate can be poured in between.

[0039] Here, it was particularly recognized that the regeneration gas can be heated both directly and indirectly: namely, directly by the regeneration gas flowing past these heat transfer sections. It can be heated indirectly by heating the adsorption material surrounding the heat transfer sections, and the regeneration gas is then heated by the adsorption material it flows past or through.

[0040] According to one aspect, it is proposed that the compressed gas be generated by a pressure generating device, in particular a compressor, and that waste heat from the pressure generating device be used to heat the heating area during regeneration. In particular, it is proposed that heated oil from a screw compressor with oil injection be used to heat the heating area during regeneration.

[0041] It was particularly recognized here that a large amount of heat is generated to generate the pressure of the compressed gas, which can then be used effectively for heating during regeneration. By using a small heating zone that only heats a portion of the drying section, the suitability of such a heating zone to heat using waste heat from a pressure generation device or compressor and thus to generate sufficient heating energy is increased. A compressed air system that incorporates the adsorption dryer and the pressure generation device can thus be designed efficiently. The use of a screw compressor with oil injection means that it heats oil by its nature, and this oil can be used for heating via the heat exchanger; in particular, it can be used as a liquid heat transfer medium in such a heat exchanger.The term heat transfer medium can also be referred to synonymously as heat medium.

[0042] According to one aspect, it is proposed that the heating of the heating region is carried out using waste heat of the pressure generating device and active heating from an energy source, in particular such that a temperature of a heating medium heated from the waste heat is further increased to a predetermined temperature by the active heating.

[0043] The heating area can thus utilize waste heat from the pressure generation device, in particular the screw compressor, even if this waste heat alone is insufficient for heating. Active heating can be supplemented by further heating the heating medium, which was heated by the waste heat from the pressure generation device, through active heating. For example, the oil of an oil-injecting screw compressor can have a temperature of 60 to 100°C. If the temperature is, for example, 60°C, but a temperature of 100°C is appropriate in the heat exchanger, particularly in the heat transfer section of the heat exchanger, the oil can be heated by 40°C to 100°C at the example 60°C and then used accordingly in the heat exchanger.

[0044] A particular advantage of any system that utilizes the heated oil from an oil-injected screw compressor is that it simultaneously cools the screw compressor. This, of course, only applies if the active additional heating of the heated oil does not generate more energy than is released in the heating system.

[0045] According to one aspect, it is proposed that at least two pressure vessels are used. In a combined operation, at least one of the pressure vessels operates in the drying mode, while another operates in the regeneration mode. The pressure vessel operating in the drying mode outputs dried compressed gas, a portion of which is branched off as the compressed gas portion and fed to the pressure vessel operating in the regeneration mode, where it is used as regeneration gas. In particular, exactly two pressure vessels are used, which can essentially operate alternately, so that one operates in the drying mode and the other in the regeneration mode. The pressure vessel operating in the drying mode then not only supplies the requested compressed gas, in particular the requested compressed air, but also additionally supplies the regeneration gas, i.e., regeneration air in the case of compressed air.The advantages described above for using the compressed gas portion for regeneration can be easily implemented in this way.

[0046] Combined operation describes the situation in which drying and regeneration operate in parallel. However, there can also be situations in which only drying is active.

[0047] It should be noted, however, that drying and regeneration operations do not necessarily have to be carried out simultaneously. For example, regeneration and thus regeneration operations may already be completed, while drying operations continue for a while. In this case, drying operations produce only dried compressed gas, which is then used without any of it being diverted for regeneration.

[0048] Drying operation continues as long as the adsorption material in the pressure vessel operating in drying mode can still absorb sufficient moisture. As soon as the adsorption material can no longer absorb sufficient moisture, or even somewhat sooner, the pressure vessel operating in drying mode can be switched over to regeneration mode. The pressure vessel operating in regeneration mode then operates in drying mode.

[0049] The principle was described using two pressure vessels that can operate alternately. However, more pressure vessels can also be provided. In particular, it is conceivable that several pressure vessels operate in drying mode and several in regeneration mode. Whether two or more pressure vessels are used can also depend on the standard size of the pressure vessels, together with the question of how much volume of compressed gas is to be dried per unit of time. If more than two pressure vessels are used, it is also conceivable that at least one operates in drying mode, at least one operates in regeneration mode, and at least one is in standby mode.According to one aspect, it is proposed that when switching from drying mode to regeneration mode, the flow of the compressed gas from the drying inlet to the drying outlet is first interrupted, heating of the heating zone is then started, and after heating has started, a predetermined heating period is waited until the regeneration gas is admitted into the container. This makes it possible to heat the adsorption material in the heating zone first, and only then admit the regeneration gas, so that the regeneration gas flows through a heated heating zone from the outset and can therefore exhibit the increased water vapor absorption capacity in the heating zone from the outset.

[0050] This prevents regeneration gas from being wasted or not fully utilized initially. It was also recognized that, especially in combination with heating using waste heat, early heating of the heating zone before regeneration gas flows through it results in no or only minimal energy loss. It was also recognized that the adsorption material can have a high heat capacity, and therefore early heating essentially only results in the heating energy being stored rather than being released unused.

[0051] It was also recognized that sufficient time is available for regeneration during operation of the adsorption device. This is especially true in the advantageous alternating mode, where at least two containers alternate between drying and regeneration modes.

[0052] The predeterminable heating time can be calculated based on the heat capacity of the adsorption material in the heating zone and the amount of heat introduced per unit time, i.e., the heat energy. An adsorption device is designed so that the introduced heat and the heat capacity of the adsorption material in the heating zone are coordinated. The heating time will then range from 3 minutes to 25 minutes.

[0053] According to one aspect, it is proposed that when switching from regeneration mode to drying mode, heating is first stopped, and after heating has stopped, a predeterminable cooling period is waited for until the compressed gas is admitted into the pressure vessel. In particular, it is provided that after heating has stopped, regeneration gas continues to flow through the pressure vessel for part or all of the cooling period. By stopping heating before compressed gas is admitted for drying during drying mode, cooling of the pressure vessel, in particular of the adsorption material in the heating zone, but also of other elements in the heating zone, can be achieved. This prevents the compressed gas to be dried from being heated in the heating zone, which would increase its water vapor absorption capacity and thus reduce the release of moisture. There would therefore be a risk that the compressed gas to be dried would not be sufficiently dried.

[0054] Cooling can be particularly enhanced by allowing regeneration gas to continue flowing through the pressure vessel and thus also through the heating zone after heating has ended. This regeneration gas can thus cool the heating zone. Ideally, this occurs over the entire cooling period, but for technical reasons, this can also be somewhat shorter.

[0055] Particularly in alternating operation, in which at least two pressure vessels alternate between drying and regeneration operations, the drying operation can be continued in at least one pressure vessel while the drying operation is being prepared in the other pressure vessel. This preparation is achieved by the aforementioned cessation of heating while the regeneration gas continues to flow through it. This regeneration gas, which then continues to flow through the pressure vessel during the cooling period, can thus continue to be provided by the pressure vessel still operating in drying mode.

[0056] It is also possible for the pressure vessel operating in drying mode to switch to a standby mode. In this standby mode, the flow of compressed gas to be dried through the pressure vessel is interrupted, especially if no compressed gas is required at that moment. No other gas then flows through the pressure vessel either. This standby mode must be distinguished from the cooling phase after heating has ended, before the actual drying operation begins with the intake of compressed gas to be dried. During the cooling phase, regeneration gas is specifically designed to flow through the pressure vessel.

[0057] The cooling time can be calculated as a function of the flowing mass of regeneration gas relative to the mass of the heated adsorption material that is now to be cooled. The adsorption material can also be referred to as a desiccant. It has been found that the ratio of the mass of regeneration gas to the mass of the heated adsorption material for cooling is in the range of 0.025 kg / kg to 0.22 kg / kg. The cooling time can therefore be the time required for the corresponding mass of regeneration gas to flow through the pressure gas vessel.

[0058] The cooling time therefore also depends on the flow rate, i.e., the mass of regeneration gas flowing through the pressure vessel per unit of time. This flow rate and the mass of the heated and then recooled adsorption material are usually coordinated. This results in a predeterminable cooling time in the range of approximately 1 to 30 minutes.

[0059] According to one aspect, it is proposed that compressed air is dried as the compressed gas, and a portion of the dried compressed air is used for the regeneration gas, so that regeneration air is used as the regeneration gas, wherein the regeneration air flows out into an environment of the adsorption dryer after flowing through the drying section.

[0060] The proposed process can therefore be used particularly for drying compressed air. This also has the advantage that ambient air can be used, which is converted into compressed air through compression and then dried. A portion of the dried compressed air can then be reused for regeneration and can be safely released back into the atmosphere. This makes it possible to forgo further drying of the moisture-enriched regeneration air.

[0061] According to one aspect, it is proposed that, during regeneration operation, the pressure in the pressure vessel is reduced below the pressure outside the pressure vessel, in particular below atmospheric pressure. This also reduces the pressure of the regeneration gas admitted into this pressure vessel. This allows this regeneration gas to absorb more moisture, thus increasing the drying process of the adsorption material—i.e., the regeneration of the adsorption material—compared to a case with higher pressure.

[0062] A special compressor may be present to achieve this low pressure, which can also be referred to as negative pressure. One possible implementation is for the regeneration gas to be admitted as regeneration air and expelled from the pressure vessel by a compressor that reduces the pressure in the pressure vessel, particularly into the environment if the regeneration gas is air. According to one aspect, it is proposed that dried compressed air, after flowing out of the drying outlet, flows through an additional pressure vessel containing an adsorption material, and that the additional pressure vessel is not involved in the regeneration operation.

[0063] It has been recognized that switching between drying and regeneration modes can cause the degree of dryness of the dried compressed air, which is reflected in the pressure dew point of the dried compressed air, to fluctuate. This pressure dew point can be elevated, particularly after switching from regeneration to drying mode. The compressed air is then more humid than desired and can therefore release moisture more easily.

[0064] It is proposed that this additional pressure vessel be provided for this purpose, in which moisture can be released to the adsorption material at this elevated pressure dew point. However, this adsorption material does not need to be dried again through a separate process. Rather, the dried compressed air can reabsorb moisture from the adsorption material of this additional pressure vessel itself once its pressure dew point has dropped again. The additional pressure vessel is thus not subject to switching between drying mode and regeneration mode.

[0065] A measure of the proportion of water vapor in the compressed air is the pressure dew point, i.e. the temperature at which the partial pressure of the water vapor in the compressed air at operating pressure is exactly equal to the vapor pressure of the water.

[0066] Despite the improvements achieved, the proposed adsorption drying process according to the proposed adsorption dryer also results in certain increases in the pressure dew point after switching a vessel from regeneration to drying.

[0067] The maximum pressure dew point can therefore also be above an average pressure dew point in the proposed solution. It was also recognized that the maximum pressure dew point can be an important criterion, and a solution was found here to lower the maximum pressure dew point. In particular, this should be achieved without significantly increasing energy consumption, as would have been necessary to lower the average pressure dew point. It should be achieved at least without increasing the heating output, without increasing the amount of regeneration air, and without reducing the drying times. As a solution, it is proposed that dried compressed air flows through the additional pressure vessel containing the adsorption material after flowing out of the drying outlet. It is therefore proposed that the dried compressed air flows through an adsorption buffer. This adsorption buffer is the vessel filled with drying material, namely the additional pressure vessel.

[0068] If the residual moisture in the compressed air temporarily increases, this desiccant initially absorbs a large portion of the additional water, so that the pressure dew point at the outlet of the adsorption buffer is significantly lower than that at the inlet. When the compressed air subsequently returns to a lower pressure dew point, the desiccant releases the additional water. This results in a slight increase in the pressure dew point as it flows through the adsorption buffer over a longer period.

[0069] Over the entire operating time of the adsorption buffer, the amount of water vapor in the compressed air is not reduced, but the maximum pressure dew point is significantly lowered. This reduction is achieved very energy-efficiently, as only the energy required to overcome the low flow resistance of the adsorption buffer is required for operation.

[0070] According to the invention, an adsorption dryer is also proposed. Thus, an adsorption dryer is proposed for drying a compressed gas, in particular compressed air, and the adsorption dryer comprises at least one pressure vessel with an adsorption material for adsorbing moisture from the compressed gas. The adsorption dryer is prepared to carry out a method in which, in a drying operation for drying the compressed gas, the compressed gas flows from a drying inlet through a drying section to a drying outlet through the pressure vessel along the adsorption material and exits as dried compressed gas. In a regeneration operation for regenerating the adsorption material, a regeneration gas flows from the drying outlet through the drying section to the drying inlet through the pressure vessel along the adsorption material, thereby removing moisture from the adsorption material.and in the regeneration mode, partial heating takes place in a heating area in the pressure vessel, the heating area being arranged only in a partial area of ​​the pressure vessel, adjacent to the drying inlet.

[0071] In particular, it is proposed that the adsorption dryer be designed to carry out a method according to one of the aspects or embodiments described above. The adsorption dryer is preferably interconnected accordingly, so that the compressed gas and the regeneration gas can flow through the pressure vessels accordingly and can also be guided through corresponding interconnections. For control purposes, a corresponding control device can be provided, which in particular starts, controls, and terminates the drying operation and the regeneration operation, respectively. A corresponding heating device is provided for heating purposes. Furthermore, the adsorption dryer is intended to be connected to a pressure generating device, in particular a compressor, and a line system for receiving and / or passing on the compressed gas.

[0072] The operation and advantages of such an adsorption dryer are explained in the explanations given for the process for drying a compressed gas.

[0073] According to one aspect, it is proposed for the adsorption dryer that the heating region is arranged in a section from 0% to 80%, preferably 0% to 60%, in particular 0% to 50% of the drying section, measured from the drying inlet to the drying outlet, and extends over at least 20% of the drying section, preferably over at least 30% of the drying section and in particular over at least 40% of the drying section, preferably a maximum of 70%, in particular a maximum of 60% of the drying section, and / or that a heat exchanger is provided for heating in the pressure vessel, which has heat transfer sections arranged in the heating region and surrounded by the adsorption material. Thus, a heating region is proposed that is specifically provided where the regeneration of the adsorption material is thereby improved.

[0074] According to one aspect, it is proposed for the adsorption dryer that at least two pressure vessels are provided, and the adsorption dryer is prepared for a combined operation in which at least one of the pressure vessels operates in the drying mode while another operates in the regeneration mode, wherein the pressure vessels are interconnected in such a way that they interact in such a way that the pressure vessel operating in the drying mode outputs dried compressed gas, a part of which is branched off as compressed gas portion and fed to the pressure vessel operating in the regeneration mode and used as regeneration gas, and / or that an additional pressure vessel with an adsorption material is provided, wherein the additional pressure vessel is interconnected with the other pressure vessels in such a way that it is not integrated into the regeneration mode.

[0075] Thus, an adsorption dryer is specifically designed in which several pressure vessels can alternate between drying and regeneration modes. The pressure vessel operating in drying mode can supply regeneration gas to the other pressure vessel operating in regeneration mode. The pressure vessels are interconnected so that the corresponding compressed gas can flow from one pressure vessel to the other, and this can also be controlled specifically by appropriate valves.

[0076] The additional vessel can, in particular, be arranged such that a portion of the dried compressed gas is diverted from one pressure vessel for use as regeneration gas in the other pressure vessel at a location that lies upstream of the additional pressure vessel with respect to a flow direction of the dried compressed gas. The additional pressure vessel with its adsorption material can, in particular, be designed to be completely passive, so that neither a pressure change nor heating or cooling is actively carried out in the additional pressure vessel. Further aspects have been described in connection with the drying method, to which reference is hereby made.

[0077] According to the invention, a compressed gas system for providing dried compressed gas is also proposed. Thus, a compressed gas system is proposed comprising a pressure generating device, in particular a compressor for compressing gas to form the compressed gas, an adsorption dryer with a plurality of pressure vessels filled with an adsorption material, each pressure vessel having a drying section for drying the compressed gas, and a heating zone extending over only part of the drying section. A heat exchanger is provided, which is connected to the compressor for heating the heating zone and uses waste heat from the compressor to heat the heating zone.

[0078] This compressed gas system preferably comprises an adsorption dryer according to one of the aspects described above. The compressed gas system thus benefits from the advantages already described above for the adsorption dryer or the drying process.

[0079] What is particularly advantageous is that by using the waste heat from the compressor for heating in the heating area of ​​the adsorption dryer, a synergy effect is achieved in which the waste heat from the compressor can be advantageously used in the adsorption dryer.

[0080] The invention will now be explained in more detail below by way of example using embodiments with reference to the accompanying figures.

[0081] Figures 1a to 1e show a compressed gas system with an adsorption dryer for different process steps. Figures 2a to 2e show a compressed gas system with an adsorption dryer for different process steps according to a further embodiment.

[0082] Figures 3a to 4b show different heat transfer sections of a heat exchanger.

[0083] Figure 1a shows a schematic representation of a compressed gas system 100. The compressed gas system 100 comprises a compressor 1 and an adsorption dryer 102. The compressor 1, which can also be referred to as a compressor, interacts with an oil cooler 2, an oil separator tank 3, and a compressed air cooler 4, which will be described in further detail below. The compressor 1 supplies compressed air to the adsorption device 102, which is provided between the two valves 5 and 6.

[0084] The adsorption dryer 102 has two pressure vessels 7 and 8, which can also be referred to as containers for simplification. Specifically, these two pressure vessels 7 and 8 operate alternately, so that one operates in drying mode and the other in regeneration mode. For this purpose, by appropriately positioning the valves 5 and 6, the compressed gas for drying can be supplied to one of the two vessels 7 and 8 in drying mode.

[0085] Each of the two containers 7 and 8 has an upper part 7a and 8a, respectively, and a lower part 7b and 8b, respectively. Both containers are filled with an adsorption material, indicated as a granular material.

[0086] Both containers 7 and 8 each have a drying inlet 103 and 104, respectively, as well as a drying outlet 105 and 106, respectively. In the embodiment shown, the drying inlets 103 and 104 are located at the bottom, and the drying outlets 105 and 106 are located at the top. During drying operation, the compressed air to be dried flows from bottom to top, and the regeneration air flows from top to bottom.

[0087] The lower part 7b or 8b of the containers 7 or 8 can be heated by means of a heater 16 or 17, respectively, which thus each form a heating device. When compressed air flows in from the drying inlet 103 or 104, it first flows through the heating area, although this is switched off during drying operation, and then through the upper part 7a or 8a. During regeneration operation, the regeneration air flows from top to bottom, thus entering at the drying outlet 105 or 106, first flowing through the upper part 7a or 8a and then the lower part 7b or 8b, which accommodates or can form the heating area. During regeneration operation, the heater 16 or 17 is in operation.

[0088] During drying operation, the dried compressed air flows out either from the drying outlet 105 or the drying outlet 106, depending on which of the two containers 7 and 8 is operating in drying mode, and flows essentially to the valve 12, which can also be referred to as the outlet valve, and from there to the dryer outlet 13, namely the outlet of the adsorption device 102 as a whole. However, an additional container with adsorption material can be connected to compensate for fluctuations in the humidity level of the dried compressed air, which is provided according to one embodiment but is not shown here for the sake of simplicity.

[0089] At the same time, a portion of the dried compressed air is passed upstream of valve 12 through throttles 10 and 11, one or both of which reduce the pressure of the dried compressed air, in particular to approximately ambient pressure. Which of the two throttles 10 or 11 reduces the pressure, or which performs a pressure reduction to what extent, depends on which of the two vessels 7 and 8 is in drying mode and which is in regeneration mode. In any case, a portion of the dried compressed air is transferred from the vessel operating in drying mode to the vessel operating in regeneration mode via these two throttles 10 and 11, controlled by the valve 9 arranged between them.

[0090] The vessel operating in regeneration mode thus receives regeneration air at the drying outlet 105 or 106, which flows through the respective vessel 7 or 8, passing through the lower part 7b or 8b, which can be considered the heating area, and finally exits at the drying inlet 103 or 104. From there, the regeneration air can be vented to the environment via the valve 18 or 19 and a downstream silencer 20 or 21.

[0091] A possible embodiment is thus shown in simplified form in Fig. 1a. The air is compressed in the compressor 1. Oil, which has been cooled in the oil cooler 2, is injected into the compressor. The warm compressed air-oil mixture is separated in the oil separator tank 3. The compressed air flows from the oil separator tank through the compressed air cooler 4 and is cooled there. Likewise, the temperature or a temperature level of the oil can be increased by bypassing all or part of the oil past the compressor's oil heat exchanger 2, thereby feeding it to the compressor block at a higher temperature.

[0092] In the illustration according to Fig. 1b, for example, container 7 is used for drying, and container 8 is regenerated. Valves 5, 9, and 19 are open, and valves 6 and 18 are closed. The 3-way valve 12 connects the container ? with the dryer outlet 13.

[0093] The compressed air flows via valve 5 through tank 7 and is dried there. A large portion of the water removed from the compressed air is absorbed by the desiccant in the lower part 7b of the tank, which contains the heater 16. While tank 7 is being used for drying, the heater 16 is inactive, so the drying material is not heated. The larger portion of the dried compressed air flows via valve 12 to the dryer outlet 13. A smaller portion of the dried compressed air flows from tank 7 via valve 9 and to tank 8. Throttle valves 10, 11 reduce the pressure to approximately ambient pressure in order to generate the largest possible volume of regeneration air. The expanded air absorbs water from the drying material in tank 8 and leaves the tank via valve 19 and silencer 21.

[0094] The heater 17 heats the drying material in the lower part 8b of the container 8. In this part of the container, i.e. the lower part 8b, a large part of the water was bound during the previous drying process. Heating the drying material increases the desorption of the water, and heating the air allows a larger amount of water vapor per air mass to be transported out of the container. This requires a much smaller amount of regeneration air than with a cold-regenerating adsorption dryer. This makes the process according to Fig. 1 a, b and c significantly more efficient than such previous processes. In Fig. 1 c, in reverse operation, container 8 is used for drying and container 7 is regenerated.

[0095] To further reduce the amount of regeneration air, valve 9 can remain closed at the start of regeneration until the drying material in region 8b is sufficiently heated by heater 17, allowing efficient regeneration from the start of the regeneration air supply. Such an operation is shown in Fig. 1d. Compared to a conventional heat-regenerating adsorption dryer, much less heat is stored in the adsorption material after regeneration, since only a portion of the material has been heated. Furthermore, the use of expanded compressed air allows for lower temperatures during regeneration.

[0096] To further reduce the stored heat, the heater 17 can be deactivated during the final part of the regeneration, allowing the final part of the regeneration to be carried out without heat input. The regeneration air mass used per mass of heated desiccant is suitably in a range of approximately 0.025 kg / kg to 0.22 kg / kg. Such operation is shown in Fig. 1 e.

[0097] A particularly efficient embodiment that utilizes the waste heat from the compression process is shown in Fig. 2a. The structure corresponds to that in Fig. 1a with a specific embodiment for the heaters 16 and 17.

[0098] Heaters 16 and 17 can be supplied with warm oil from the compressor by opening valves 14 or 15. If neither heater is active, valves 14 and 15 are closed and valve 22 is opened instead.

[0099] Fig. 2b shows the operation in which container 7 is used for drying and container 8 is regenerated. Accordingly, valve 15 is open and valve 14 and valve 22 are closed.

[0100] Fig. 2c shows the operation in which the container 8 is used for drying and the container

[0101] 7 is regenerated. Here, valve 14 is open and valve 15 and valve 22 are closed.

[0102] Fig. 2d shows the operation in which the container 7 is used for drying and the container

[0103] 8 is preheated at the beginning of regeneration. Accordingly, valve 15 is open and valve 9 is still closed.

[0104] Fig. 2e shows the operation in which tank 7 is used for drying and tank 8 is not heated during the final part of the regeneration. Accordingly, valve 15 is closed and valve 9 is still open.

[0105] The embodiment of Figures 2a to 2e shows an advantageous, compact combination of compressor 1 and dryer. However, it is not necessary for a dryer to be directly coupled to a compressor. In particular, several compressors can supply compressed air to one dryer, one compressor can supply compressed air to several dryers, or several compressors can supply compressed air to several dryers. To transfer the heat output from the compressor to the dryer, another heat transfer medium can be used instead of compressor oil. To optimize the process, the heat transfer medium can also be heated above the temperature level at which the waste heat is available, e.g., with an electric heater.

[0106] Further aspects or additional explanations of the invention are given below.

[0107] The following description assumes that the flow through the containers is from bottom to top during drying and from top to bottom during regeneration. However, other installation positions are also possible.

[0108] The core aspects of the invention are:

[0109] The method of a cold-regenerating adsorption dryer is used.

[0110] Heat is only supplied to the lower part of the tank via a heating device during regeneration mode.

[0111] Advantageously, existing waste heat, such as the heat contained in the oil of a screw compressor, can be used for the heating device. In water-cooled systems, warm water can also be used. Other heat sources that are conveniently available near the dryer can also be used. The process can also be carried out with electric heating.

[0112] A reasonable proportion of the heated lower part of the container to the total container is approximately 20% to 70%.

[0113] Direct heating also offers the possibility of supplying more heat per air volume than if the air were first heated and then allowed to heat the desiccant and desorb the water. This reduces the amount of regeneration air required. The amount of regeneration air can be further reduced by first heating the desiccant material without any airflow before the regeneration air is passed through the container to be regenerated. Because dry air is used for regeneration, temperatures are not as high as those required in dryers that regenerate with heated ambient air. This allows existing waste heat to be utilized at a low temperature level.

[0114] In one embodiment, the warm oil from an oil-injected screw compressor is used for heating during regeneration. This oil typically has temperatures between 60 and 100 °C.

[0115] Since the dry material is heated directly, the regeneration air is only needed to transport the desorbed water vapor. By lowering the pressure during regeneration, the amount of regeneration air can be further reduced. The lower the regeneration pressure, the less compressed air needs to be expanded to generate the required volume flow.

[0116] Figures 3a, 3b, 4a, and 4b show pressure vessels with different or differently arranged heating zones. For the sake of better comparability, the same reference numerals are sometimes used in the figures for elements or zones that are not necessarily identical. In particular, all four figures show a pressure vessel 300 with an adsorbent bed 302, i.e., a bed of, in particular, granular adsorption material, and a heating zone 304 with a symbolically represented heat exchanger 306. The adsorbent bed 302, i.e., the zone in which it is arranged, is hatched with dotted lines. The heating zone 304 is framed by a dash-dotted line and also hatched with dash-dotted lines. The heating zone 304 is thus arranged in the zone of the adsorbent bed 302, which is illustrated by the superimposed hatching. A vessel height h is also shown in all four figures for orientation of the proportional dimensions.In all four figures, a drying inlet 322 and a drying outlet 324 are also shown.

[0117] Regarding heat exchanger 306, it should be noted that it is shown symbolically in the figures. It extends across the entire cross-section of the adsorbent bed 302. Particularly, but not exclusively, the pressure vessel and, accordingly, the adsorbent bed can have a cylindrical cross-section over which the heat exchanger 306 extends completely. Figures 3a, 3b, 4a, and 4b are intended to illustrate, in particular, the different dimensions of the heat exchanger 306 in the flow direction, i.e., in the direction of height h. The heating region 304 of the heat exchanger 306 corresponds approximately in size to the installation space of the heat exchanger 306. Adsorbent, which can also be synonymously referred to as adsorption material, is also located here. The heat exchanger 306 is therefore surrounded by adsorbent.

[0118] There are basically embodiments of adsorption dryers that do not have a sieve bottom, perforated plate, or similar at the lower end of the pressure vessel 300. In such embodiments, the adsorbent bed, which can also be referred to simply as bed, rests on the bottom of the vessel.

[0119] Figures 3a and 3b show such pressure vessels. In Figure 3a, the heating zone 304, due to the design-related heat exchanger, begins at approximately 2% of the vessel height h and extends to approximately 30% of the vessel height h. The vessel height h is the length from the drying inlet to the drying outlet.

[0120] In Figure 3b, the heating zone 304, due to the design-related heat exchanger, begins at approximately 2% of the vessel height h and extends to approximately 60% of the vessel height h. Here, a drying section 326 in Figures 3a and 3b extends over the entire height h. The drying section is only illustrated here by an arrow showing the length of the drying section. In fact, the drying section runs within the pressure vessel 300, namely within the adsorbent bed 302. The same applies to a drying section 426 in Figures 4a and 4b, which will be explained further below. Essentially, the area of ​​the adsorbent bed 302 defines the drying section 326 or 426.

[0121] Furthermore, there are designs of adsorption dryers that have a sieve bottom, perforated plate, or similar in the lower area of ​​the pressure vessel, which is referred to here as a stepped bottom section 308. This stepped bottom section is some distance from the bottom of the pressure vessel and has perforations that are so small that the adsorbent granules cannot pass through, but the process air can. The adsorbent bed therefore rests on the stepped bottom section 308, which can be a sieve bottom, for example. As a result, the process air can distribute itself in the space below the stepped bottom section 308 after flowing in from below before flowing upwards through the bed. It is advantageous that if condensate or liquid water enters the bottom of the vessel with the compressed air and the condensate has not been completely separated after the heat exchanger, it can collect below the sieve bottom on the vessel floor.The adsorbent is then not located in the "liquid water." Such embodiments with a stepped bottom section 308 are shown in Figures 4a and 4b. As a result, the drying section 426 in Figures 4a and 4b does not extend over the entire height h.

[0122] Figure 4a shows a pressure vessel 300 with a stepped bottom section 308, which can be designed as a sieve bottom or perforated plate, and the stepped bottom section 308 is located at approximately 3% of the vessel height h. Due to the design-related heat exchanger, the heating region 304 begins only at approximately 5% of the vessel height h and extends to approximately 30% of the vessel height h.

[0123] The bed can be pressed down from above using, for example, a perforated plate 310 with a compression spring 312, so that a change in the direction of the compressed gas flow, i.e., a flow reversal, prevents the granules from moving or being stirred up. This protects the granules from mechanical wear. The granules extend up to approximately 92% of the container height h.

[0124] Figure 4b shows a pressure vessel 300 with a stepped bottom section 308, which can be designed as a sieve bottom or perforated plate, and the stepped bottom section 308 is located at approximately 3% of the vessel height h. Due to the design-related heat exchanger, the heating region 304 begins only at approximately 5% of the vessel height h and extends to approximately 60% of the vessel height h.

[0125] Here, too, the bed can be pressed down from above, for example, using a perforated plate 310 with a compression spring 312, so that a change in the direction of the compressed gas flow, i.e., a flow reversal, prevents the granules from moving or being stirred up. This protects the granules from mechanical wear. The granules extend to approximately 92% of the container height h.

Claims

Claims 1. A method for drying a compressed gas, in particular compressed air, using an adsorption dryer having at least one pressure vessel with an adsorption material for adsorbing moisture from the compressed gas, wherein in a drying operation for drying the compressed gas, the compressed gas flows from a drying inlet through a drying section to a drying outlet through the pressure vessel along the adsorption material and exits as dried compressed gas, in a regeneration operation for regenerating the adsorption material, a regeneration gas flows from the drying outlet through the drying section to the drying inlet through the pressure vessel along the adsorption material and thereby removes moisture from the adsorption material, and in the regeneration operation, partial heating takes place in a heating region in the pressure vessel, wherein the heating region only in a partial region of the pressure vessel,is located adjacent to the drying inlet.

2. Method according to claim 1, characterized in that the heating area is arranged in a section of 0% to 80%, preferably 0% to 60%, in particular 0% to 50% of the drying section, measured from the drying inlet to the drying outlet, and / or the heating area extends over at least 20% of the drying section, preferably over at least 30% of the drying section, in particular over at least 40% of the drying section, preferably at most over 70%, in particular at most over 60% of the drying section, and in particular no heating takes place outside the heating area, or reduced heating with less than 30% energy input per volume, compared to the heating area.

3. A method according to claim 1 or 2, characterized in that a compressed gas portion as part of the dried compressed gas is used as regeneration gas, the compressed gas portion is admitted into the pressure vessel at the drying outlet, and the compressed gas portion undergoes a pressure reduction during or before admission into the pressure vessel.

4. Method according to one of the preceding claims, characterized in that the heating in the pressure vessel takes place by means of a heat exchanger, wherein heat transfer sections of the heat exchanger are surrounded by the adsorption material in order to transfer heat to the adsorption material.

5. Method according to one of the preceding claims, characterized in that the compressed gas is generated by a pressure generating device, in particular a compressor, and Waste heat from the pressure generating device is used to heat the heating area during regeneration, wherein in particular heated oil from a screw compressor with oil injection is used to heat the heating area during regeneration.

6. Method according to one of the preceding claims, characterized in that the heating of the heating area is carried out using Waste heat from or of the pressure generating device and active heating from an energy source, in particular such that a temperature of a heating medium heated from the waste heat is further increased to a predetermined temperature by the active heating.

7. Method according to one of the preceding claims, characterized in that at least two pressure vessels are used, in a combination operation at least one of the pressure vessels operates in the drying mode while another operates in the regeneration mode, and the pressure vessel operating in the drying mode outputs dried compressed gas, a part of which is branched off as compressed gas portion and fed to the pressure vessel operating in the regeneration mode and used as regeneration gas.

8. Method according to one of the preceding claims, characterized in that when switching from drying operation to regeneration operation, first the flow of the compressed gas from the drying inlet to the drying outlet is interrupted, then the heating of the heating area is started, and after starting the heating, a predeterminable heating period is waited until the regeneration gas is admitted into the pressure vessel.

9. Method according to one of the preceding claims, characterized in that when switching from regeneration operation to drying operation, heating is first stopped and, after heating has stopped, a predeterminable cooling period is waited for until the compressed gas is admitted into the pressure vessel, wherein, in particular, after heating has stopped, regeneration gas continues to flow through the pressure vessel during part or all of the cooling period.

10. Method according to one of the preceding claims, characterized in that compressed air is dried as the compressed gas, and in particular a part of the dried compressed air is used for the regeneration gas, so that regeneration air is used as the regeneration gas, wherein the regeneration air flows out into an environment of the adsorption dryer after flowing through the drying section. 11 . Method according to one of the preceding claims, characterized in that in the regeneration operation a pressure in the pressure vessel is reduced below a pressure outside the pressure vessel, in particular below atmospheric pressure.

12. Method according to one of the preceding claims, characterized in that dried compressed air, after flowing out of the drying outlet, flows through an additional pressure vessel with an adsorption material, and the additional pressure vessel is not integrated into the regeneration operation.

13. An adsorption dryer for drying a compressed gas, in particular compressed air, and the adsorption dryer comprises at least one pressure vessel with an adsorption material for adsorbing moisture from the compressed gas, and is prepared to carry out a process in which, in a drying operation for drying the compressed gas, the compressed gas flows from a drying inlet through a drying section to a drying outlet through the pressure vessel along the adsorption material and exits as dried compressed gas; in a regeneration operation for regenerating the adsorption material, a regeneration gas flows from the drying outlet through the drying section to the drying inlet through the pressure vessel along the adsorption material and thereby removes moisture from the adsorption material; and in the regeneration operation, partial heating takes place in a heating region in the pressure vessel, and the heating region is only in a partial region of the pressure vessel,is arranged adjacent to the drying inlet and / or that the adsorption dryer is designed to carry out a method according to one of the preceding claims., 14. Adsorption dryer according to claim 13, characterized in that the heating area is arranged in a section from 0% to 80%, preferably 0% to 60%, in particular 0% to 50% of the drying section, measured from the drying inlet to the drying outlet, and extends over at least 20% of the drying section, preferably over at least 30% of the drying section, in particular over at least 40% of the drying section, and / or that a heat exchanger is provided in the pressure vessel for heating, which has heat transfer sections arranged in the heating area which are surrounded by the adsorption material.

15. Adsorption dryer according to claim 13 or 14, characterized in that at least two pressure vessels are provided, and the adsorption dryer is prepared for a combined operation in which at least one of the pressure vessels operates in the drying mode while another operates in the regeneration mode, wherein the pressure vessels are interconnected in such a way that they interact in such a way that the pressure vessel operating in the drying mode outputs dried compressed gas, a part of which is branched off as compressed gas portion and fed to the pressure vessel operating in the regeneration mode and used as regeneration gas, and / or that an additional pressure vessel with an adsorption material is provided, wherein the additional pressure vessel is interconnected with the other pressure vessels in such a way that it is not involved in the regeneration mode.

16. Compressed gas system for providing dried compressed gas with a pressure generating device, in particular a compressor for compressing gas to the compressed gas, an adsorption dryer with several pressure vessels filled with an adsorption material, wherein the pressure vessels each have a drying section for drying the compressed gas, and a heating area which extends only over a part of the drying section, wherein a heat exchanger is provided which is connected to the compressor for heating the heating area in order to heat the heating area with waste heat from the compressor, wherein in particular an adsorption dryer according to one of claims 13 to 15 is used.

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