Drying system and method for drying a coating for tins
Patent Information
- Application Number
- EP2023776700
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-09-13
- Filing Date
- 2023-09-13
- Publication Date
- 2025-07-23
AI Technical Summary
Existing drying systems for can coatings face issues with condensation and particle contamination, leading to clogging and hazardous manual cleaning, especially with the use of BPA-free paints which increase these problems.
A drying system with a preheating section and polymerization chamber, where cans are heated to a lower temperature in the first preheating chamber and a higher temperature in the second preheating chamber, creating a temperature gradient that reduces sublimation and condensation, and a heating system with a transfer temperature below 800°C to minimize particle contamination.
The system effectively reduces condensation and particle contamination, improving efficiency and safety by slowing down the heating process and using lower temperatures to prevent clogging and hazardous conditions.
Smart Images
Figure 1.1
Abstract
Description
DRYING SYSTEM AND METHOD FOR DRYING A CAN COATING OF CANS FIELD OF TECHNOLOGY
[0001] The invention relates to a drying system and method for drying a can coating of cans. STATE OF THE ART
[0002] Drying systems for drying can coatings are generally known. Such drying systems can be designed to dry a can coating on an inner or outer surface of a can. Drying systems for drying a can coating inside cans are also referred to as interior dryers or internal baking ovens (IBOs). Drying systems for drying can coatings on an outer surface of a can are also referred to as pin ovens.
[0003] In a process step prior to the drying system, a coating is applied to the interior wall forming the cavity. This coating is then dried and / or polymerized in the drying system. For this purpose, the cans are moved through the drying system and exposed to hot air. Similarly, a coating is applied to the outer wall of the cans and then dried and / or polymerized in a pin oven.
[0004] Drying systems can have several drying chambers arranged one after the other in which water contained in the paint is evaporated, the cans are heated to a polymerization temperature and / or are kept at the polymerization temperature for a predefined period of time for polymerization.
[0005] Condensation is produced during the drying of can coatings. Particles also settle during the drying process. The condensate and particles clog the drying systems mentioned above to such an extent that they require extensive cleaning at regular intervals. In normal operation, such drying systems are cleaned manually and / or with dry ice, but this cleaning is so time-consuming that several million cans are not produced per cleaning cycle. Furthermore, such cleaning can be hazardous to the health of the person performing the cleaning.
[0006] In the past, bisphenol-containing paints were regularly coated, with bisphenol (BPA) being used as a binder. However, bisphenol can have carcinogenic effects, so the use of BPA-containing paints has been banned in many countries. A disadvantage of using BPA-free paints is that they lead to significantly higher condensate deposits and increased particle contamination. The already existing problem of condensate and particle deposits is therefore exacerbated by the use of BPA-free paints.
[0007] It is an object of the invention to provide a drying system and method that reduce or eliminate one or more of the aforementioned disadvantages. In particular, it is an object of the invention to provide a solution that reduces condensate deposits and / or particle contamination during the drying of can coatings. SUMMARY OF THE INVENTION
[0008] This object is achieved with a drying system and method according to the features of the independent patent claims. Further advantageous embodiments of these aspects are specified in the respective dependent patent claims. The features described and shown in the patent claims, the description, and the drawings can be combined with one another in any technologically expedient manner, whereby further embodiments of the invention are shown.
[0009] According to a first aspect, the object mentioned at the outset is achieved by a drying system for drying a can coating of cans, comprising a drying chamber with a drying section which has a preheating section and a polymerization chamber, a conveying device with which the cans can be moved through the drying chamber, a heating system for applying a temperature-controlled process fluid to the cans within the drying chamber, wherein the heating system is signal-coupled to a control device, the preheating section has a first preheating chamber and a second preheating chamber downstream of the first preheating chamber, and the control device is designed to control the heating system in such a way that the cans in the first preheating chamber are heated to a first temperature, preferably below 80°C, in particular below 70°C, for example 65°C, and the cans in the second preheating chamber are heated to a second temperature,preferably below 120°C, in particular below 110°C, for example 100°C, wherein the second temperature is higher than the first temperature, so that a temperature gradient of the cans along the drying section such that is low so that sublimation of the can coating is reduced in order to avoid condensate formation, and / or wherein the heating system is arranged and designed to act on the process fluid with a transfer temperature of less than 800°C, in particular less than 700°C, preferably less than 600°C, so that particle-containing combustion products are reduced in order to reduce particle contamination.
[0010] The invention is based on the finding that condensate formation within the drying system is primarily caused by sublimation of the can coating or the paint forming the can coating. In the prior art, the often water-based can coatings are typically heated so rapidly that the water evaporates rapidly, taking components of the can coating or paint with it during the evaporation process. The effect underlying this finding is also referred to as steam distillation.
[0011] The invention is further based on the finding that by slowing down the heating of the cans in a first section of the drying section, sublimation of the can coating can be reduced or avoided, thus reducing condensate formation. To achieve this, the drying system comprises a first preheating chamber and a second preheating chamber, with the cans being heated to a lower temperature in the first preheating chamber than in the second preheating chamber.
[0012] Furthermore, the invention is based on the finding that the process fluid can advantageously be heated only at a low transfer temperature of less than 800°C, thereby reducing particle-containing combustion products and thus minimizing particle contamination of the drying system. It should be noted that the process fluid in such drying systems generally does not consist, or does not consist exclusively, of fresh air, but is usually operated using recirculated air to improve energy efficiency. This recirculated air typically contains already evaporated can coating components, which, upon reheating, for example, using a gas burner at 1200°C, generate particles that subsequently contaminate the drying system.The invention is further based on the finding that this particle deposition can be reduced with a transfer temperature of less than 800°C, for example with a porous burner which will be explained in more detail below.
[0013] The drying system is designed to dry a can coating on cans. The cans can be, for example, cans for containing food, in particular food and / or beverages. The can coating can be a lacquer for Coating of the inner and / or outer wall of a can. The drying system itself can be an interior dryer and / or a pin oven.
[0014] The drying system comprises the drying chamber with the drying section, which has a preheating section and a polymerization chamber. The drying chamber preferably comprises an inlet side and an outlet side. The drying chamber further preferably has a chamber inlet on the inlet side for the cans to enter and a chamber outlet on the outlet side for the cans to exit. The cans are moved between the chamber inlet and the chamber outlet, for example, using the conveyor belt of the conveying device. The conveyor belt can, for example, be fluid-permeable. The polymerization chamber preferably has a heating section and a temperature-maintaining section, wherein the cans are heated to a polymerization temperature, for example from 100°C to 200°C, in the heating section and maintained at the polymerization temperature in the temperature-maintaining section.The heating section and / or the temperature-maintaining section can be designed as separate sub-chambers that are, for example, fluidically separated from each other or separable. Fluidic separation can be achieved, for example, with an airlock.
[0015] In an IBO, the cans are typically exposed to a hot process fluid from above, which then passes through the conveyor belt and is then fed into either recirculating air and / or exhaust air. Furthermore, the drying chamber can have different flow media to ensure the most even application of the process fluid to the cans.
[0016] Furthermore, the drying chamber preferably has one, two, or more fluid inlets, which are particularly arranged and configured to supply recirculating air and / or fresh air to the drying chamber. Furthermore, it is preferred that the drying chamber be substantially fluid-tight, for example, by means of a chamber wall.
[0017] The drying system includes the conveyor device, which moves the cans through the drying chamber. The conveyor device can, for example, comprise the conveyor belt described above or be designed as a pin chain.
[0018] The drying system comprises the heating system for applying the tempered process fluid to the cans within the drying chamber. For this purpose, the heating system can have a fluid supply, fluid discharges and / or a recirculating air supply. It is particularly preferred that the heating system is arranged and designed to heat the cans in the preheating section, in particular in the first preheating chamber and the second preheating chamber, and in the polymerization chamber independently of one another with the temperature-controlled process fluid, so that the process fluid supplied to the aforementioned chambers can be adjusted and / or controlled in terms of fluid volume and / or fluid temperature depending on the chamber. Preferably, the temperature-controlled process fluid is provided to the polymerization chamber such that the cans in the polymerization chamber have a temperature between 150°C and 250°C, for example, 200°C.
[0019] The process fluid is preferably air. The process fluid may include or consist of fresh air and / or recirculated air.
[0020] In an alternative, the heating system is signal-coupled to the control device. The preheating section comprises the first preheating chamber and the second preheating chamber located downstream of the first preheating chamber. "Downstream" refers specifically to the direction of movement of the cans. The cans thus enter the drying system, first pass through the first preheating chamber, then enter the second preheating chamber, and are then guided through the polymerization chamber.
[0021] The control device is configured to control the heating system such that the cans in the first preheating chamber are heated to a first temperature and the cans in the second preheating chamber are heated to a second temperature. This causes the cans in the first preheating chamber to be slowly heated to a lower temperature, in particular below 80°C. As a result, the expected sublimation is reduced. In the second preheating chamber, the can is then heated to a temperature such that the water components of the can coating are evaporated.
[0022] The first preheating chamber and the second preheating chamber are designed, in particular, as separate chambers. In particular, these can have drying sections of different lengths, allowing the temperature gradient of the cans to be specifically adjusted.
[0023] It is preferred that the first drying chamber, the second drying chamber and / or the conveying device are arranged and designed in such a way and / or the control device is set up in such a way that the cans are moved through the first drying chamber with a first passage time between 20-90 seconds, in particular between 30-60 seconds, and through the second drying chamber with a second passage time between 20-90 seconds, in particular between 30-60 seconds.
[0024] In a second alternative, the heating system is arranged and designed to act on the process fluid with a transfer temperature of less than 800°C, so that particle-containing combustion products are reduced in order to minimize particle contamination. The transfer temperature is understood to mean, in particular, the temperature at which the process fluid is heated. This can be, for example, a unit of the heating system that heats the process fluid, such as an electric heating wire or a porous burner. This contrasts with the approach pursued in the prior art, in which the process fluid is usually heated with a gas burner whose gas flame is, for example, 1200°C. Thus, the heating system described above enables the process fluid to be heated to a lower temperature, namely below 800°C, so that the formation of particles is reduced or avoided.
[0025] In a preferred embodiment of the drying system, it is provided that it comprises both alternatives, namely that the heating system is signal-coupled to the control device, the preheating section has the first preheating chamber and the second preheating chamber downstream of the first preheating chamber, and the control device is configured to control the heating system such that the cans in the first preheating chamber are heated to the first temperature and the cans in the second preheating chamber are heated to the second temperature, wherein the second temperature is higher than the first temperature, so that the temperature gradient of the cans along the drying section is so small that sublimation of the can coating is reduced in order to avoid condensate formation, and that the heating system is arranged and designed to act on the process fluid with a transfer temperature of less than 800°C,so that particulate combustion products are reduced to reduce particulate contamination.
[0026] A preferred embodiment of the drying system is characterized in that the first preheating chamber, the second preheating chamber and the polymerization chamber each have an exhaust air fan, so that a first exhaust air volume of an exhaust air of the first preheating chamber, a second exhaust air volume of an exhaust air of the second preheating chamber and a third exhaust air volume of an exhaust air of the polymerization chamber can be adjusted independently of one another.
[0027] The first preheating chamber may, for example, have a first exhaust fan, the second preheating chamber a second exhaust fan, and the polymerization chamber a third exhaust fan. These exhaust fans may, in particular, be coupled to the exhaust ducts described in more detail below. By means of separate Exhaust fans allow fresh air volumes to be adjusted independently in each chamber.
[0028] In a further preferred embodiment of the drying system, it is provided that the first preheating chamber has a first drying section, the second preheating chamber has a second drying section and the polymerization chamber has a polymerization section, and the first drying section is longer than the second drying section, and / or the first drying section and the second drying section together are longer than the polymerization section.
[0029] A long first drying section keeps the temperature gradient low during heating of the cans, as the first temperature is lower than the second temperature. This low temperature gradient ensures that sublimation is minimized or avoided. In particular, it is preferred that the preheating section, consisting of the first drying section and the second drying section, be long enough to prevent sublimation. This can be achieved, among other things, by making the preheating section longer than the polymerization section.
[0030] A preferred development of the drying system is characterized in that the first preheating chamber, the second preheating chamber and the polymerization chamber each have an exhaust air duct for discharging exhaust air, so that the exhaust air of the first preheating chamber, the second preheating chamber and the polymerization chamber are essentially not mixed with one another, so that condensation in the exhaust air ducts is reduced.
[0031] The invention was also based on the realization that the typically contaminated exhaust air ducts in drying systems are caused by the fact that exhaust air streams from different chambers have different temperatures. As soon as these exhaust air streams, which have different temperatures, mix with each other, condensate typically forms. This condensate settles in the exhaust air ducts and clogs them, making the cleaning mentioned above necessary. The separate design of the exhaust air ducts prevents this condensate formation.
[0032] It is particularly preferred that these exhaust air ducts open into a condensate chamber, and that the condensate chamber is arranged and configured to separate condensate from the exhaust air. The condensate is thus deliberately formed only in the condensate chamber and not in the exhaust air ducts themselves. The condensate chamber can, for example, have a cooling element so that condensate is deliberately formed there.
[0033] In a preferred development of the drying system, it is further provided that the condensate chamber has a removable condensate separator. The condensate separator can, for example, be cassette-shaped. A removable condensate separator has the advantage of being easy to clean. The condensate separator can, for example, have the cooling element or be the cooling element itself.
[0034] In a further preferred embodiment of the drying system, it is provided that it comprises a fluid interface which is arranged and designed to fluidically and / or thermally couple the first preheating chamber and / or the second preheating chamber to a can-manufacturing device, so that the process fluid introduced into the first preheating chamber and / or second preheating chamber can be at least partially provided by the can-manufacturing device and / or can be thermally influenced by the can-manufacturing device.
[0035] The can-making device can be any device within a can factory. This includes the direct can-making device, for example, a forming device, but also an indirect device, such as an exhaust air purifier. An exhaust air purifier, in particular, has a high exhaust air temperature, with which the process fluid can advantageously be heated. This can further increase the energy efficiency of the drying system. For this purpose, the exhaust air from the can-making device can be used directly as the process fluid. Alternatively, this exhaust air can be thermally coupled to the process fluid by means of a heat exchanger, so that the thermal energy of the exhaust air from the can-making device can be decoupled into the process fluid.
[0036] In a further preferred embodiment of the drying system, it is provided that the heating system has a firing unit and / or an electric heating unit which is or are arranged and designed such that the transfer temperature is less than 800°C, preferably less than 700°C, in particular less than 600°C.
[0037] The combustion unit can be a gas burner, for example. The gas used can be LNG, natural gas, and / or hydrogen. The electric heating unit can, for example, have a heating wire.
[0038] In a further preferred embodiment, the combustion unit is or comprises a porous burner. A porous burner has, in particular, a porous structure in which the combustion reaction takes place. Consequently, a Porous burners usually do not have an open flame, so the transfer temperature is reduced.
[0039] In a further preferred embodiment of the drying system, fresh air can be supplied to the process fluid, so that the temperature of the process fluid can be adjusted by adjusting the volume of fresh air. For this purpose, the drying system preferably has an air supply duct. In particular, it is preferred that the first preheating chamber, the second preheating chamber, and / or the polymerization chamber each have an air supply duct.
[0040] A preferred development of the drying system is characterized in that an airlock is arranged between the first preheating chamber, the second preheating chamber and / or the polymerization chamber, so that during normal operation, fluid exchange between the first preheating chamber, the second preheating chamber and / or the polymerization chamber is at least reduced.
[0041] Such an airlock between the individual chambers has the advantage that the target temperatures can be adjusted in a particularly advantageous manner, in particular that the predefined temperatures are actually set.
[0042] In a further preferred embodiment of the drying system, it is further provided that the first preheating chamber, the second preheating chamber and / or the polymerization chamber have a cleaning unit which is arranged and designed to separate a condensate and / or particles.
[0043] The invention was based on the discovery that condensate and / or particles can also form within the individual chambers, so that during operation, condensate and / or particles can also settle in the chambers and not only in the exhaust air ducts. Condensate formation and / or particle formation can thus be further reduced by a single cleaning unit or by a cleaning unit arranged in the respective chambers. It is preferred that the first preheating chamber has a first cleaning unit, the second preheating chamber has a second cleaning unit, and / or the polymerization chamber has a third cleaning unit.
[0044] In a preferred embodiment, the cleaning unit, in particular the first cleaning unit, the second cleaning unit and / or the third cleaning unit, is designed to act mechanically, electrostatically and / or pressure-based. With such a cleaning unit, particles and / or condensate can advantageously be separated in the individual chambers so that they can be selectively removed in the cleaning unit. and do not contaminate areas of the drying system that are difficult or impossible to clean.
[0045] According to a further aspect, the object mentioned at the outset is achieved by a method for drying a can coating on cans, in particular with a drying system according to one of the embodiments described above, comprising the steps of: conveying the cans along a drying section with a first preheating chamber and a second preheating chamber downstream of the first preheating chamber, heating the cans to a first temperature, preferably below 80°C, in the first preheating chamber by applying a temperature-controlled process fluid, heating the cans to a second temperature, preferably below 120°C, in the second preheating chamber by applying a temperature-controlled process fluid, wherein the second temperature is higher than the first temperature, such that a temperature gradient of the cans along the drying section is so small that sublimation of the can coating is reduced in order to avoid condensate formation.
[0046] It may be preferred that the method comprises the step of: tempering the process fluid with a transfer temperature of less than 800°C, in particular less than 700°C, preferably less than 600°C, so that particle-containing combustion products are reduced in order to reduce particle contamination.
[0047] According to a further aspect, the object mentioned at the outset is achieved by a method for drying a can coating of cans, in particular with a drying system according to one of the embodiments described above, comprising the steps of: conveying the cans along a drying section which has a preheating section and a polymerization chamber, applying a temperature-controlled process fluid to the cans, and tempering the process fluid to a transfer temperature of less than 800°C, preferably less than 700°C, in particular less than 600°C, so that particle-containing combustion products are reduced in order to reduce particle contamination.
[0048] The method and its possible further developments have features or process steps that make them particularly suitable for use in a drying system and its further development.
[0049] For further advantages, variants and details of the aspects and their possible further developments, please refer to the previous description of the corresponding features and further developments of the other aspects. BRIEF DESCRIPTION OF THE DRAWINGS
[0050] Preferred embodiments are explained using the accompanying figures. They show:
[0051] Figure 1: a schematic, two-dimensional view of an exemplary embodiment of a drying system;
[0052] Figure 2: a schematic, two-dimensional sectional view of the drying system shown in Figure 1;
[0053] Figure 3: a schematic view of an exemplary process for drying a can coating of cans; and
[0054] Figure 4: a schematic view of another method for drying a can coating of cans. DESCRIPTION OF THE EMBODIMENTS
[0055] In the figures, identical or essentially functionally identical or similar elements are designated by the same reference numerals.
[0056] The drying system 100 shown in Figures 1 and 2 is designed for drying cans 102. The drying system 100 comprises a drying chamber 104 through which a drying section 106 extends. The drying section 106 extends from an inlet at the left end of the drying system 100 to an outlet at the right end of the drying system 100. The drying chamber 104 has a preheating section 108, which includes a first preheating chamber 110 and a second preheating chamber 112, and a polymerization chamber 114. The polymerization chamber 114 is shown in a simplified manner, as it typically comprises two separate chambers, with the cans 102 being heated to a polymerization temperature in a heating chamber and the polymerization temperature being maintained in a temperature-maintaining chamber.
[0057] During normal operation, the cans 102 are moved by the conveyor device 124 first into the first preheating chamber 110, then into the second preheating chamber 112, and then into the polymerization chamber 114. A heating system comprising a first heating unit 116, a second heating unit 118, and a third heating unit 120 applies a temperature-controlled process fluid to the cans 102 within the drying chamber 104.
[0058] In particular, the cans 102 are subjected to the process fluid in such a way that they are first heated slowly in the first preheating chamber 110, for example to 65°C, and then heated to a temperature of 100°C in the second preheating chamber 112 in order to subsequently heated in the polymerization chamber 114 to a polymerization temperature of, for example, 200°C and maintained at this temperature.
[0059] For this purpose, the drying system comprises a control device 122 that is signal-coupled to the heating system. The control device 122 is configured to control the heating system such that the cans 102 in the first preheating chamber 110 are heated to a first temperature, for example 65°C, and the cans 102 in the second preheating chamber 112 are heated to a second temperature, for example 100°C. This occurs such that the second temperature is higher than the first temperature. As a result, a temperature gradient of the cans 102 along the drying section 106 is so small that sublimation of the can coating of the cans 102 is reduced in order to avoid condensation. This is due in particular to the fact that excessively rapid heating of the can coating, which usually contains water, leads to the formation of bubbles, so that the evaporating water entrains color components.
[0060] The drying system 100 is configured such that a fluid is conducted in each of the chambers 110, 112, 114, this fluid circulates as part of a recirculating air flow, and can also be disposed of. For this purpose, for example, the first preheating chamber 110 has a fluid interface 148. Fresh air can be supplied through the fluid interface 148. Alternatively, the first preheating chamber 110 can be fluidically and / or thermally coupled to a can-making device via the fluid interface 148, so that the process fluid introduced into the first preheating chamber 110 can be at least partially provided by the can-making device and / or thermally influenced by the can-making device.
[0061] Furthermore, the first preheating chamber 110 comprises a recirculation fan arranged between the chamber space and the mixing chamber 150 for circulating recirculating air. This recirculating air is fed back to the mixing chamber 150 from the preheating chamber 110 through the fluid return 156, among other things. Upstream of the mixing chamber 150, the recirculating air is thermally influenced, in particular tempered, by a first combustion unit 152 and / or a first electric heating unit 154. The recirculating air, which acts, among other things, as a process fluid, is tempered by the combustion unit 152 and / or the electric heating unit to a transfer temperature of less than 800°C, so that particle-containing combustion products are reduced in order to prevent particle contamination. The second preheating chamber 112 and the polymerization chamber 114 similarly have a second combustion unit 164, a second electric heating unit 166, a third combustion unit 168, and a third electric heating unit 170.
[0062] Furthermore, a first exhaust air duct 138 is provided for discharging a first exhaust air 132 from the first preheating chamber 110. The first exhaust air duct 138 is coupled to a first exhaust air fan 126 to evacuate the first exhaust air 132 from the first preheating chamber 110. Similarly, a second exhaust air 134 can be evacuated from the second preheating chamber 112 by means of a second exhaust air fan 128 and a second exhaust air duct 140. Furthermore, a third exhaust air 136 can be evacuated from the polymerization chamber 114 by means of a third exhaust air fan 130 and a third exhaust air duct 142.
[0063] The exhaust air ducts 138, 140, 142 are each formed separately from one another and end in a condensate chamber 144. The condensate chamber 144 further comprises a condensate separator 146, in which condensate from the first exhaust air 132, the second exhaust air 134, and the third exhaust air 136 is to be selectively separated. The condensate separator 146 can, in particular, be designed to be removable from the condensate chamber 144. The condensate separator 146 can, for example, be designed in the shape of a cassette and can therefore be removed like a cassette.
[0064] Figure 3 shows a method for drying a can coating on cans 102. The method comprises step 200: conveying the cans 102 along a drying line 106 having a first preheating chamber 110 and a second preheating chamber 112 downstream of the first preheating chamber 110.
[0065] The method further comprises step 202: heating the cans 102 to a first temperature, preferably below 80°C, in the first preheating chamber 110 by applying a temperature-controlled process fluid. The method further comprises step 204: heating the cans 102 to a second temperature, preferably below 120°C, in the second preheating chamber 112 by applying a temperature-controlled process fluid.
[0066] Steps 202 and 204 are performed such that the second temperature is higher than the first temperature, so that a temperature gradient of the cans 102 along the drying section 106 is so small that sublimation of the can coating is reduced in order to avoid condensation formation.
[0067] Figure 4 shows another method for drying a can coating on cans 102. The method comprises step 300: conveying the cans 102 along the drying section 106, which has a preheating section 108 and a polymerization chamber 114. In step 302, the cans 102 are exposed to a temperature-controlled process fluid. In step 304, the process fluid is heated to a transfer temperature of less than 800°C, so that particle-containing combustion products are reduced to reduce particle contamination.
[0068] The drying system 100 described above and the corresponding methods have the advantage that condensate formation and particle formation within the drying system 100 are significantly reduced. This is achieved, on the one hand, by reducing sublimation during heating of the cans or the can coating by maintaining a low temperature gradient in the preheating section 106. This is made possible, among other things, by providing a first preheating chamber 110, in which the cans 102 are heated to a first temperature, and a second preheating chamber 112, in which the cans 102 are heated to a second temperature. This reduced or avoided sublimation is achieved in particular by skillfully selecting the temperature, in particular the first temperature below 80°C, for example to 65°C, and the second temperature at approximately 100°C.
[0069] Furthermore, the reduced condensate and dust formation is achieved through a special form of temperature control of the process fluid, namely by keeping a transfer temperature below 800°C, especially below 600°C. It has been found that this reduces dust formation in the process fluid, which is operated, among other things, as recirculating air.
[0070] A further advantage of the drying system described is that the condensate and process formation can be specifically influenced so that, for example, the condensate settles in the condensate chamber in a defined manner, which simplifies cleaning of the drying system. REFERENCE SYMBOL 100 drying system 102 cans 104 Drying chamber 106 Drying section 108 Preheating section 110 first preheating chamber 112 second preheating chamber 114 Polymerization chamber 116 first heating unit 118 second heating unit 120 third heating unit 122 Control device 124 Conveyor device 126 first exhaust fan 128 second exhaust fan 130 third exhaust fan 132 first exhaust air 134 second exhaust air 136 third exhaust air 138 first exhaust air duct 140 second exhaust air duct 142 third exhaust air duct 144 Condensate chamber 146 condensate separators 148 Fluid interface 150 mixing chamber 152 first firing unit 154 first electric heating unit 156 Fluid return 158 first cleaning unit 160 second cleaning unit 162 third cleaning unit 164 second firing unit 166 second electric heating unit 168 third firing unit 170 third electric heating unit
Claims
CLAIMS Drying system (100) for drying a can coating of cans (102), comprising a drying chamber (104) with a drying section (106) which has a preheating section (108) and a polymerization chamber (114), a conveyor device (124) with which the cans (102) can be moved through the drying chamber (104), a heating system for applying a temperature-controlled process fluid to the cans (102) within the drying chamber (104), wherein the heating system is signal-coupled to a control device (122), the preheating section (108) has a first preheating chamber (110) and a second preheating chamber (112) downstream of the first preheating chamber (110), and the control device (122) is configured to control the heating system in such a way that the cans (102) in the first preheating chamber (110) are heated to a first temperature, preferably below 80°C, and the cans (102) in the second preheating chamber (112) to a second temperature,preferably below 120°C, wherein the second temperature is higher than the first temperature, so that a temperature gradient of the cans (102) along the drying section (106) is so small that sublimation of the can coating is reduced in order to avoid condensate formation, and / or wherein the heating system is arranged and designed to act on the process fluid with a transfer temperature of less than 800°C, so that particle-containing combustion products are reduced in order to reduce particle contamination. Drying system (100) according to claim 1, wherein the first preheating chamber (110), the second preheating chamber (112), and the polymerization chamber (114) each have an exhaust air fan (126, 128, 130), so that a first exhaust air volume of an exhaust air of the first preheating chamber (110),a second exhaust air volume of an exhaust air from the second preheating chamber (112) and a third exhaust air volume of an exhaust air from the polymerization chamber (114) are independently adjustable. Drying system (100) according to one of the preceding claims, wherein, the first preheating chamber (110) has a first drying section, the second preheating chamber (112) has a second drying section, and the polymerization chamber (114) has a polymerization section, and the first drying section is longer than the second drying section, and / or the first drying section and the second drying section together are longer than the polymerization section. The heating system (100) according to any one of the preceding claims, wherein the first preheating chamber (110), the second preheating chamber (112), and the polymerization chamber (114) each have an exhaust air duct (138, 140, 142) for discharging exhaust air, such that the exhaust air from the first preheating chamber (110), the second preheating chamber (112), and the polymerization chamber (114) are substantially not mixed with one another, thus reducing condensation in the exhaust air ducts (138, 140, 142).Ventilation system (100) according to one of the preceding claims, wherein the exhaust air ducts (138, 140, 142) open into a condensate chamber (144), and the condensate chamber (144) is arranged and configured to separate condensate from the exhaust air. Ventilation system (100) according to one of the preceding claims, wherein the condensate chamber (144) has a removable condensate separator (146). A heating system (100) according to any one of the preceding claims, comprising a fluid interface (148) arranged and designed to fluidically and / or thermally couple the first preheating chamber (110) and / or the second preheating chamber (112) to a can-manufacturing device, such that the process fluid introduced into the first preheating chamber (110) and / or second preheating chamber (112) can be at least partially provided by the can-manufacturing device and / or thermally influenced by the can-manufacturing device. A heating system (100) according to any one of the preceding claims, wherein. the heating system comprises a firing unit (152, 164, 168) and / or an electric heating unit (154, 166, 170) which is / are arranged and designed such that the transfer temperature is less than 800°C.
9. Drying system (100) according to one of the preceding claims, wherein the combustion unit (152, 164, 168) is or comprises a pore burner 10. Drying system (100) according to one of the preceding claims, wherein fresh air can be supplied to the process fluid so that a temperature of the process fluid can be adjusted by a fresh air volume of the fresh air.
11. Drying system (100) according to one of the preceding claims, wherein an airlock is arranged between the first preheating chamber (110), the second preheating chamber (112) and / or the polymerization chamber (114) in each case, so that during normal operation, fluid exchange between the first preheating chamber (110), the second preheating chamber (112) and / or the polymerization chamber (114) is at least reduced.
12. Drying system (100) according to one of the preceding claims, wherein the first preheating chamber (110), the second preheating chamber (112) and / or the polymerization chamber (114) comprises a cleaning unit (158, 160, 162) arranged and designed to separate a condensate and / or particles.
13. Drying system (100) according to one of the preceding claims, wherein the cleaning unit (158, 160, 162) is designed to act mechanically, electrostatically and / or pressure-based.
14. A method for drying a can coating of cans, comprising the steps of: Conveying the cans along a drying section (106) with a first preheating chamber (110) and a second preheating chamber (112) downstream of the first preheating chamber (110); - heating the cans to a first temperature, preferably below 80°C, in the first preheating chamber (110) by applying a temperature-controlled process fluid; - Heating the cans to a second temperature, preferably below 120°C, in the second preheating chamber (112) by applying a temperature-controlled process fluid, wherein the second temperature is higher than the first temperature, so that a temperature gradient of the cans along the drying section (106) is so small that sublimation of the can coating is reduced in order to avoid condensate formation. Method for drying a can coating of cans, comprising the steps of: conveying the cans along a drying section (106) which has a preheating section (108) and a polymerization chamber (114); - Applying a temperature-controlled process fluid to the cans; Tempering the process fluid with a transfer temperature of less than 800°C so that particle-containing combustion products are reduced in order to reduce particle contamination.