Can drying moisture control system

Abstract

A heating system for use with a can dryer or oven includes a gas burner, an electric heating element, a heating chamber configured to heat cans with air heated by the gas burner and / or the electric heating element, a circulation system configured to move air from the gas burner and the electric heating element to the heating chamber, and a control system configured to selectively control the gas burner and the electric heating element to switch between a first mode in which the gas burner and the electric heating element are activated and both heat air supplied to the heating chamber, and a second mode in which the gas burner is not activated and the electric heating element is activated.

Description

Technical Field

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[0001] <Cross - Reference to Related Applications> This application claims priority to U.S. Patent Application No. 63 / 233,355, filed on August 16, 2021, with the title "Can Drying and Moisture Control System".

[0002] The disclosed concepts generally relate to can manufacturing, and more specifically, to heating systems and methods for can dryers or can ovens.

Background Art

[0003] Metal beverage and food containers (e.g., cans) are mechanically made using a forming tool and die system. To prevent damage to the product, oil is used to lubricate the surface during the forming process. After the forming process, the oil and other contaminants are washed away from the surface through a plurality of washing steps. Before spraying lacquer, decorating with ink, and filling with food or beverage products, the metal surface needs to be completely clean and dry.

[0004] As an example, the drying of cans following a typical multi - stage washer is used. A schematic diagram of a typical drying system is shown in FIG. 1. This process is very energy - consuming, and the dryer 15 works most effectively in the container manufacturing process.

[0005] When the cans leave the washing process, they are sent to a continuous conveyor 5 that transports the cans through the drying process. The cans entering the dryer 15 have a film of residual water that needs to be removed.

[0006] The drying process is designed to evaporate and eliminate the water film using hot air before the cans exit the dryer.

[0007] High-temperature air is blown onto the can through a plenum chamber 1 equipped with a nozzle, a recirculating centrifugal fan 2, and a duct. Natural gas 12 and combustion air 13 are supplied to a direct-fired gas burner 13 to burn the natural gas 12 in the combustion chamber 4. The released energy heats the air flowing around the combustion chamber 4 to the desired operating temperature.

[0008] The energy of the high-temperature air is used to raise the temperature of the incoming container, causing water to evaporate from the metal surface. The air is cooled as it transfers its thermal energy to the heating and vaporization process. The cooled air is drawn in through the conveyor 5, sent through a duct, and passes through the combustion chamber 4, where it is reheated to the desired temperature. The reheated air is then supplied to the suction side of the recirculation centrifugal fan 2, completing the recirculation cycle.

[0009] The recirculating high-temperature air absorbs moisture that has vaporized or evaporated from the surface of the metal container. The water vapor absorbed into the air mixes with the products of gas combustion.

[0010] A portion of the high-temperature recirculated air is drawn out via a damper 6 and an exhaust centrifugal fan 7. The exhaust centrifugal fan 7 blows the air into the exhaust chimney and discharges it into the outside atmosphere 8.

[0011] Cold, fresh air 14 from inside or outside the building is drawn into the recirculating airflow via the damper 9 to equalize the pressure inside the dryer 15. It is important to generate equilibrium pressure to prevent the generation of uncontrolled air that enters the drying cavity through the can's inlet port 10 and outlet port 11 and causes instability. More importantly, equalizing the pressure suppresses the escape of hot air and contains combustion gases that escape from the drying cavity into the work area where the technicians work.

[0012] Conventional drying processes consume a lot of energy and are very wasteful. Can drying systems have room for improvement. [Overview of the project]

[0013] According to one embodiment of the disclosed concept, a heating system for use with a can dryer or can oven comprises a gas burner, an electric heating element, a heating chamber configured to heat cans using air heated by the gas burner and / or the electric heating element, a circulation system configured to move air from the gas burner and the electric heating element to the heating chamber, and a control system configured to selectively control the gas burner and the electric heating element to switch between a first mode in which both the gas burner and the electric heating element are activated and both heat the air supplied to the heating chamber, and a second mode in which the gas burner is not activated and only the electric heating element is activated.

[0014] According to another aspect of the disclosed concept, a method for heating cans in a can dryer or can oven includes providing a gas burner, an electric heating element, a heating chamber configured to heat the cans using air heated by the gas burner and / or the electric heating element, and a circulation system configured to move air from the gas burner and the electric heating element to the heating chamber, and selectively controlling the gas burner and the electric heating element to switch between a first mode in which the gas burner and the electric heating element are activated and both heat the air supplied to the heating chamber, and a second mode in which the gas burner is not activated and only the electric heating element is activated. [Brief explanation of the drawing]

[0015] The present invention can be fully understood from the following description relating to preferred embodiments, in conjunction with the accompanying drawings.

[0016] [Figure 1] Figure 1 is a schematic diagram of a typical drying system. [Figure 2] Figure 2 is a schematic diagram of a drying system according to an exemplary embodiment of the disclosed concept. [Modes for carrying out the invention]

[0017] It is understood that the specific elements shown in the drawings and described below are merely illustrative embodiments of the disclosed concept and are provided as non-limiting examples for illustrative purposes only. Accordingly, specific dimensions, orientations, assemblies, the number of components used, the configuration of the embodiments, and other physical characteristics of the embodiments disclosed herein should not be considered limitations on the scope of the disclosed concept.

[0018] The directional terms used herein, such as clockwise, counterclockwise, left, right, up, down, upward, downward, and their derivatives, relate to the orientation of the illustrated elements and do not limit the claims unless expressly provided in the claims.

[0019] In this specification, the singular forms of "aru" and "sono" include the plural form unless otherwise specified in the context.

[0020] The primary costs in the rapid drying of any product are the sustainable source and cost of the energy used.

[0021] Electricity is rapidly gaining attention as a sustainable energy source and is increasingly being generated using primary sources such as wave, wind, solar, hydro, and nuclear power. To ensure resource optimization, exemplary embodiments of the disclosed concept provide a hybrid heating system that uses natural gas and electricity as energy sources to heat air to a temperature that dries metal beverage cans.

[0022] In some exemplary embodiments, an online moisture temperature measurement system is used. The generated electrical signals are used to control the moisture level in the drying process, and the required amount of energy is determined and adjusted. When the amount of energy is well controlled, the primary energy source can be optimized, which can reduce the carbon dioxide emissions of this energy-intensive operation.

[0023] Conventional dryers using direct-fired gas burners require a certain level of fresh air to be introduced into the combustion chamber to ensure the stoichiometric conditions necessary for optimal combustion. During the combustion process, other gases harmful to humans are produced. To ensure people remain safe, these harmful gases are vented into the atmosphere outside the building structure via a chimney, as shown in the drying system in Figure 1. The harmful gases produced by the combustion of natural gas are also detrimental to the environment, and it is strongly believed that the accumulation of these gases in the upper atmosphere contributes to global warming.

[0024] Figure 2 is a schematic diagram of a drying system based on an exemplary embodiment of the disclosed concept. The drying system uses a gas burner 21 and an electric heating element 22, which work together to provide a hybrid heating system. The gas burner 21 is supplied with combustion air 31 and natural gas 32. The electric heating element 22 is supplied with power 33. By using both units of the gas burner 21 and the electric heating element 22, the temperature of the drying system can be raised to the desired operating point in a short, desired time. Once the drying system reaches the desired operating temperature, the gas burner 21 is turned off and heating is maintained using only the electric heating element 22. If necessary, the gas burner 21 can be used in short bursts to smooth out external changes that the electric heating element 22 cannot handle. The control system 38 can control the gas burner 21 and the electric heating element 22 to switch between a first mode in which both the gas burner 21 and the electric heating element 22 are activated and both heat the air supplied to the plenum chamber 24 (also called the heating chamber), and a second mode in which the gas burner 21 is not activated and only the electric heating element 22 is activated.

[0025] The drying system is designed to use hot air to evaporate the water film until it disappears before the cans exit the dryer 50. The cans enter the dryer 50 at the inlet port 40 and are conveyed through the dryer 50 via the conveyor 25 to the outlet port 41. The hot air is blown onto the cans via a centrifugal recirculation fan 23. The centrifugal recirculation fan 23 blows the hot air into a plenum chamber 24 to which nozzles are attached via a series of ducts. Elements that facilitate the movement of air from the gas burner 21 and the electric heating element 22 to the plenum chamber 24 can be called a circulation system (e.g., centrifugal recirculation fan 24, ducts, etc.). The hot air raises the temperature of the cans and also provides the energy to evaporate the water into steam, and the steam is absorbed into the air stream. The air loses energy and is cooled by the heating and vaporization process. The cooled air is drawn in through the conveyor 25 and sent through ducts, passes through the electric heating element 22 and the gas burner 21, and is reheated by one or both of the electric heating element 22 and the gas burner 21 according to each current operating state. The air is then drawn into the suction side of the centrifugal fan 23, and the dry air cycle is completed.

[0026] The recirculating hot air passing through the surface of the container absorbs the water evaporated from the surface of the container being dried. The water vapor is absorbed by the hot air. A portion of the hot, moist air is drawn out of the recirculation air system via a control damper 27 by a centrifugal exhaust fan 26.

[0027] That air removed from the recirculating dry air stream passes through a condensation heat exchanger 28 and reaches a switching damper 36 via a set of ductwork. The position of the switching damper 36 is determined by a computer signal that identifies whether the gas burner 21 is in use. When the gas burner 21 is in use, the switching damper 36 sends the gas out to the atmosphere 35 through an exhaust chimney outside the building. If the control system 38 identifies that the gas burner 21 is not in use, the switching damper 36 sends the hot, moist stream through a set of ducts to a preheating plenum chamber 30 (also called a secondary heating chamber).

[0028] A humidity sensor 29 may be attached to the interconnect duct between the exhaust fan 26 and the condensation heat exchanger 28 to measure the temperature and humidity of the air removed from the recirculation air system. The signal from the humidity sensor 29 is analyzed by the control system 38, and the generated signal is used to control the amount of hot air removed from the recirculating dry air stream and the amount of cold fresh air (also called makeup air) 34 added to maintain the pressure balance in the drying cavity. The makeup air flow is controlled by a control system 38 having dampers 27, 37.

[0029] By combining a heating source in a hybrid dryer that uses both gas and electricity, the size of the gas burner 21 can be reduced without deteriorating the warm-up time of the dryer. The warm-up operation of the dryer system provides heat using both heating sources. When the dryer reaches its operating temperature, the gas burner 21 is turned off and the dryer is operated with the more efficient electric heating element 22 left on. Note that using a smaller gas burner 21 means that it operates at optimal efficiency during high-fire operation. Large gas burners are usually specified to handle unexpected situations and are adjusted to operate at 50% - 60% of their design capacity during operation after the warm-up period, which is not efficient.

[0030] The disclosed concept has the advantage that when the gas burner 21 is turned off, no combustion products are produced. Since the use of the electric heating element 22 is considered clean heat, there is no need to protect the operator from harmful gases. The condensing air-to-air heat exchanger 28 uses the high-temperature / humidified air removed from the drying cycle to preheat the low-temperature / dry feed air before it enters the drying cycle. Water evaporated from the can is absorbed into the drying cycle air as steam. As the removed air cools within the heat exchanger 28, the steam condenses into water 39. Since this liquid water is considered pure, it can be reused in the washing process, reducing overall water consumption and making the process more efficient when using valuable raw materials.

[0031] The operation of the dryer can be further improved by installing a humidity control system that measures the amount of water absorbed by the heated air, i.e., the relative humidity. This drying concept allows the humidity of the air in the drying system to be raised to the highest possible level before the drying of the container stops. By reducing the amount of air removed and, consequently, the amount of fresh air added, this optimizes the system and ensures that a high proportion of hot / humid air is discharged, rather than hot dry air.

[0032] Humidity control reduces the amount of cold, fresh air added to the drying cycle by reducing the amount of air removed from the cycle. This reduces the amount of colder supply air needed, and therefore less heating is required compared to when colder supply air is introduced into the cycle. The air removed from the drying cycle is usually discharged into the atmosphere outside the building when direct-fired gas heating is used. To maintain a balance of the various pressures within the dryer, the amount of hot air removed and the amount of cold, fresh air added are regulated to prevent the can from being blown out and to prevent harmful emissions from leaking from the can's feed and exhaust ports. Heat is added to the drying cycle to raise the temperature of the fresh, cold air to the required operating temperature, and the air is then used to raise the temperature of the can and evaporate water from the can's surface.

[0033] Since a small amount of residual water in the airflow does not affect the operation of the dryer, the disclosed concept incorporates further optimization of electric thermal energy by using the warm, moist air exiting the condensing heat exchanger 28 to preheat the incoming moist can through the preheating plenum chamber 30. If electric heating alone is used, the leaking air is considered low-grade heat and would not contain harmful combustion products.

[0034] A further feature is that moisture in the humid air removed from the recirculated high-temperature air system by the heat exchanger 28 condenses into water 39, and this water 39 does not contain harmful chemicals used to replenish the water supply to the washing process.

[0035] In some exemplary embodiments of the disclosed concept, hybrid heating, i.e., electric gas burner heating, may be used in any suitable type of can dryer or oven system, such as a wash dryer, pin oven, built-in bake oven, or external bake oven. For example, a wash dryer is used to remove only water, while pin ovens, built-in bake ovens, and external bake ovens can remove solvents, water, volatile organic compounds, or mixtures thereof, leaving the solid elements of the coating or ink on the can. Once the solids are deposited on the can, they harden or fuse together at high temperatures, sealing the solid elements on the can surface and resulting in a homogeneous coating. It will be understood that the hybrid heating system of the disclosed concept can be employed in any of these types of dryers or ovens. It will also be understood that in some applications, certain elements, such as heat recovery elements, may be omitted or modified without departing from the scope of the disclosed concept.

[0036] While specific embodiments of the invention have been described in detail, it will be understood by those skilled in the art that various modifications and substitutions can be made to those details in light of the overall teachings of this disclosure. Accordingly, the specific configurations disclosed are intended to be illustrative only and not to limit the scope of the invention as given in the entire scope of the appended claims and any and all equivalents thereof.

Claims

1. A heating system for use with a can dryer or can oven, Gas burner (21), Electric heating element (22) and A heating chamber (24) configured to heat the can using air heated by the gas burner (21) and / or the electric heating element (22), A circulation system configured to move air from the gas burner (21) and the electric heating element (22) to the heating chamber (24), A control system (38) is configured to selectively control the gas burner (21) and the electric heating element (22) to switch between a first mode in which the gas burner (21) and the electric heating element (22) are activated and both heat the air supplied to the heating chamber (24), and a second mode in which the gas burner (21) is not activated and the electric heating element (22) is activated. A secondary heating chamber (30) configured to preheat a can that enters the heating chamber (24), It is equipped with, The control system (38) is configured to selectively discharge a portion of the air from the heating chamber (24) or direct a portion of the air from the heating chamber (24) to the secondary heating chamber (30) based on whether or not the gas burner (21) is operating, in a heating system.

2. The system further includes a humidity sensor (29) that monitors the humidity of the air within the circulation system. The heating system according to claim 1, wherein the control system (38) is configured to control the circulation system to introduce fresh air into the circulation system when the monitored humidity reaches a predetermined level.

3. The heating system according to claim 2, further comprising a heat exchanger (28) configured to heat the fresh air using the air from the heating chamber.

4. A first damper (27) is positioned between the heating chamber (24) and the heat exchanger (28), A second damper (37) is positioned between the heat exchanger (28) and the gas burner (21) or the electric heating element (22), It also has the following features: The heating system according to claim 3, wherein the control system (38) is configured to control the amount of air recirculated in the circulation system and the amount of fresh air added to the circulation system via the first and second dampers (27, 37).

5. The heating system according to claim 3, wherein the humidity sensor (29) is located between the heating chamber (24) and the heat exchanger (28).

6. The heating system according to claim 3, wherein the heat exchanger (28) is configured to remove moisture from the air received from the heating chamber (24) and to condense the removed moisture into water.

7. The system further includes a switching damper (36) positioned between the heating chamber (24) and the secondary heating chamber (30), The heating system according to claim 1, wherein the control system (38) is configured to selectively control the switching damper (36) to discharge a portion of the air from the heating chamber (24) or to direct a portion of the air from the heating chamber (24) to the secondary heating chamber (30), based on whether or not the gas burner (21) is operating.

8. The heating system according to claim 1, wherein the control system (38) is configured to control the gas burner (21) and the electric heating element (22) in the first mode when the air in the circulation system is below a predetermined temperature, and to control the gas burner (21) and the electric heating element (22) in the second mode when the air in the circulation system is above a predetermined temperature.

9. The heating system according to claim 1, wherein the gas burner (21) is powered by natural gas (32).

10. The heating system according to claim 1, wherein the electric heating element (22) is powered by electricity (33).

11. The heating system according to claim 1, further comprising a conveyor (25) configured to move cans through the heating chamber.

12. In a method of heating cans in a can dryer or can oven, The system includes a gas burner (21), an electric heating element (22), a heating chamber (24) configured to heat the can using air heated by the gas burner (21) and / or the electric heating element (22), and a circulation system configured to move air from the gas burner (21) and the electric heating element (22) to the heating chamber (24). The gas burner (21) and the electric heating element (22) are selectively controlled to switch between a first mode in which both the gas burner (21) and the electric heating element (22) operate to heat the air supplied to the heating chamber (24), and a second mode in which the gas burner (21) does not operate and only the electric heating element (22) operates. A secondary heating chamber (30) is provided, which is configured to preheat the can that enters the heating chamber (24). Based on whether the gas burner (21) is operating, selectively discharge a portion of the air from the heating chamber (24) or guide a portion of the air from the heating chamber (24) to the secondary heating chamber (30), A method that includes this.

13. A humidity sensor (29) configured to monitor the humidity of the air in the circulation system is provided, When the monitored humidity reaches a predetermined level, the circulation system is controlled to introduce fresh air into the circulation system. The method according to claim 12, including the method described in claim 12.

14. A heat exchanger (28) is provided that is configured to heat the fresh air using the air from the heating chamber (24), Controlling the amount of fresh air added to the circulation system, The method according to claim 13, including the method described in claim 13.

15. The heat exchanger (28) is used to remove moisture from the air received from the heating chamber (24), The removed water is condensed into water in the heat exchanger (28), The method according to claim 14, including the method described in claim 14.

16. The method according to claim 12, wherein selectively controlling the gas burner (21) and the electric heating element (22) to switch between a first mode in which the gas burner (21) and the electric heating element (22) are operated and both heat the air supplied to the heating chamber (24) and a second mode in which the gas burner (21) is not operated and the electric heating element (22) is operated includes controlling the gas burner (21) and the electric heating element (22) in the first mode when the air in the circulation system is below a predetermined temperature, and controlling the gas burner (21) and the electric heating element (22) in the second mode when the air in the circulation system exceeds the predetermined temperature.

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