Device and method for cleaning a plate heat exchanger

Abstract

Device (1) for cleaning a plate heat exchanger (2), wherein the device (1) has the following features: a. A compressed air source (3) for providing compressed air for dry cleaning of the plate heat exchanger (2); b. A control box (4) which is connected to the compressed air source (3) via a first compressed air line (5) and to a slot nozzle (9) via a second compressed air line (8), wherein an electrically controllable valve (6) is arranged in the control box (4) between the compressed air lines (5, 8) connected to the control box (4), wherein the valve (6) is designed to open when actuated, so that compressed air flows to the slot nozzle (9); c. The slot nozzle (9) has at least one nozzle gap (16) which is surrounded circumferentially by a slot-shaped mouthpiece (11) which projects in the direction of flow (P) of the compressed air opposite the at least one nozzle gap (16).

Description

[0001] The invention relates to a device for cleaning a plate heat exchanger according to the features of claim 1 and a method for cleaning a plate heat exchanger according to the features of claim 10.

[0002] Plate heat exchangers, particularly as recuperative air preheaters or recuperative gas preheaters, can achieve very high heat recovery rates as gas-to-gas heat exchangers. The heat transfer surfaces consist of profiled plates with high specific power. These can be welded together to form self-supporting blocks. The two gases flow through the plates, preferably in counterflow, and are separated from each other without leakage. Due to the accumulation of contaminants in the media involved in heat transfer, plate heat exchangers must be cleaned periodically. Wet cleaning is the state of the art. This wet cleaning process uses conventional cleaning lances and water under high pressure. The contaminated water must be collected, neutralized, and disposed of at considerable expense.If plate heat exchangers are made of ferritic materials, it is also necessary to protect the surfaces from rust after cleaning. Any protective agent applied must be collected, neutralized, and disposed of at considerable expense, insofar as it does not adhere to the heat exchanger surfaces. The cleaning process for large systems takes approximately two to three weeks. This is followed by a drying process, which also lasts at least three days. During this time, the heat exchanger cannot be used. Wet cleaning of the heat exchanger is extremely time-consuming and expensive, and drying is also extremely energy-intensive.

[0003] EP 1 933 107 A1 discloses a multi-channel nozzle head and a device for cleaning finned heat exchangers in air handling systems, in particular air conditioning systems for buildings and vehicles. The nozzles of a multi-channel nozzle head are positioned between the fins to prevent damage to the fins and to enable cleaning at significantly higher pressures. Comb fingers are provided for aligning the multi-channel nozzle head with respect to the fins; these fingers can be inserted into the space defined by the fins. The nozzles are arranged within these comb fingers. The precise alignment of the nozzles by the comb fingers improves the cleaning effect.

[0004] Based on this, the invention aims to provide a device and a method for cleaning a plate heat exchanger that does not have the aforementioned disadvantages, i.e., can be carried out in a shorter processing time, produces less waste and can be carried out in a more energy-efficient manner.

[0005] This problem is solved in a device according to the features of claim 1. The method according to the invention is the subject of claim 10.

[0006] According to the invention, dry cleaning is carried out. No liquids are used. The surfaces of the heat exchanger are only exposed to compressed air. For this purpose, the air is preferably dried so that no additional moisture comes into contact with the surfaces of the plate heat exchanger.

[0007] For this purpose, the invention provides for a compressed air source, in particular a compressor. The compressor generates the necessary compressed air with respect to the pressure level and volume required for the dry cleaning of a plate heat exchanger. In this context, it should be mentioned that the device according to the invention is particularly suited to stationary large-scale industrial plants where several tons of dust are generated and need to be removed during the cleaning process.

[0008] The compressed air source is connected to a control box via a compressed air line. A second compressed air line leads from the control box to a slot nozzle. An electrically controlled valve is located in the control box and is connected between the compressed air lines. The valve is designed to open when actuated, allowing compressed air to flow from the compressed air source to the slot nozzle. The slot nozzle itself has at least one nozzle slot, which is circumferentially surrounded by a slot-shaped nozzle tip that projects beyond the nozzle slot in the direction of compressed air flow. The slot nozzle, with its nozzle tip, can be inserted into a slot in the plate heat exchanger to be cleaned. A slot nozzle is used in which the width of the nozzle tip is matched to the width of the slot. The slot width is typically between 5 and 15 mm, particularly 5 to 8 mm.After inserting the slot nozzle, cleaning can begin. For this purpose, the valve is opened for an adjustable period, generating a pressure pulse of defined length. Both the pressure, the duration, and the frequency can be set via the control box. The pressure is preferably in the range of 5 to 7 bar. By manually opening the control valve multiple times, several compressed air pulses can be delivered at a specific time. The invention can also provide for the delivery of several compressed air pulses sequentially.

[0009] Cleaning is usually carried out in very confined and enclosed spaces. This makes handling rigid cleaning equipment, such as cleaning lances, extremely difficult. Safety regulations stipulate that cleaning must be supervised by a second person, severely restricting the operating personnel's freedom of movement. Furthermore, cleaning is performed while wearing respiratory protection and protective clothing, which negatively impacts visibility and freedom of movement. The invention improves operating conditions by allowing the control box to be placed outside of these confined and enclosed spaces and by eliminating the need for a rigid cleaning lance. The compressed air line to the slot nozzle is flexible, preferably designed as a hose. This makes handling a slot nozzle significantly easier than handling a lance with additional valves for opening and closing the media supply.

[0010] Another advantage is that no valves requiring control are located within the confined workspace, but rather within the control box. The shut-off valve is preferably controlled wirelessly, and depending on the application, also by means of a safety radio remote control suitable for operation in potentially explosive atmospheres.

[0011] Relocating the valve assembly to the control box, i.e., away from a cleaning lance or cleaning head, allows for the integration of advanced control features into the control box. The compressed air source in the control box preferably provides a high volume flow at a significantly higher pressure than required for cleaning. This, according to the invention, makes it possible to adjust the pressure parameters specific to the cleaning process via a control curve. In particular, the pressure can be adjusted variably while maintaining a constant volume flow.

[0012] Another essential element of the invention is the slot nozzle, which is inserted into a gap in the plate heat exchanger to be cleaned, along with its nozzle tip. The aim is to minimize the escape of compressed air so that the compressed air pulse can exert the necessary momentum on the walls of the gap. To this end, not only should the width of the nozzle tip be matched to the width of the gap, but, more importantly, the nozzle base, which is positioned laterally to the nozzle tip, should cover the gap to be cleaned outside the nozzle tip. Preferably, the slot nozzle is matched to the length and width of the gap to be cleaned, so that the entire gap is covered by the slot nozzle and its nozzle base during cleaning. The momentum exerted by the compressed air pulse should elastically deform the walls of the plate heat exchanger that define the gap. This deformation can also loosen stubborn deposits on the walls.Simultaneously, the compressed air serves to transport the deposits to the outlet end of the gap. Depending on the load-bearing capacity of the plate heat exchanger walls, the pressure of the compressed air pulse can be regulated via a pressure control valve in the control box.

[0013] The device according to the invention is operated via a remote control that can be wirelessly connected to the control box. The remote control is preferably a handheld device. In practice, the second person, who is monitoring the cleaning process, can also take over the remote control when the first person at the slot nozzle signals this. This allows the first person to hold the slot nozzle with both hands. The slot nozzle must be pressed firmly onto the opening of the slot to prevent the compressed air from escaping laterally. The device is preferably operated by a single person and monitored by the second person. For this purpose, a holder for the remote control can be arranged on the slot nozzle. The remote control is preferably detachably connected to the slot nozzle.

[0014] Preferably, a set of different slot nozzles with mouthpieces of varying widths is provided. The slot nozzles are detachably connected to the pressure hose. This allows the device to be used with different heat exchangers, which often have different gap widths.

[0015] The nozzle itself is designed to be slot-shaped and its outer dimensions are matched to the width of the slot in the plate heat exchanger. The nozzle orients the slot nozzle within the heat exchanger slot. At least one nozzle slot is arranged within the nozzle. Preferably, there are several nozzle slots arranged one behind the other in the longitudinal direction and surrounded by a common nozzle. The nozzle slots are preferably elongated. A single long nozzle slot is also conceivable; however, the nozzle slot could widen in width during the impulsive pressure surges. Deformation of the slot nozzle cannot be tolerated, as otherwise it cannot be guaranteed that the nozzle will fit into other slots of the same dimensions. Therefore, the nozzle body is configured to be sufficiently dimensionally stable.The ribs running between two nozzle gaps create the necessary stability in the area of ​​the nozzle base.

[0016] The nozzle base serves as a support for the nozzle tip. Ideally, the nozzle tip's width and length are adapted to the size of the gap. For this purpose, the nozzle tip has parallel side walls that determine its width. Only if the nozzle tip's width is smaller than the gap's width can the corresponding slot nozzle be used with the plate heat exchanger being cleaned. The nozzle base, which contains the nozzle slots, is wider than the nozzle tip to bridge the remaining gap between the nozzle tip's outer surfaces and the gap. It can also be longer than the nozzle tip. The nozzle base acts as a cover for the gap, preventing compressed air from escaping between the nozzle base and the plate heat exchanger's tube sheet. Optionally, a sealing device can be incorporated into the nozzle base to further reduce compressed air leakage.The nozzle base is preferably at least twice as wide as the mouthpiece.

[0017] To exert a sufficiently large impulse on the walls of the gap, compressed air with a high volume flow rate must be supplied. The pressure line has a sufficiently large cross-section, which is significantly larger than the width of the gap in the plate heat exchanger to be cleaned. The nozzle body is relatively narrow in the area of ​​the nozzle tip and relatively wide in the area of ​​the connection for the second pressure line. The nozzle body surrounds the nozzle chamber between the connection and the nozzle gap.

[0018] To prevent the nozzle body from deforming under the compressed air pulse, struts are advantageously arranged within the nozzle chamber, connecting opposing walls of the chamber. These are, in particular, the walls that run parallel to the longitudinal sides of the nozzle slots. The walls can be inclined relative to each other, so that the nozzle chamber tapers from the connection for the second pressure line towards the at least one nozzle slot. In particular, the nozzle chamber has a trapezoidal cross-section with a narrower nozzle base and a wider nozzle back. The connection can be located on the nozzle back or in one of the opposing walls. The struts connecting the walls are preferably welded to the walls at substantially equal intervals.

[0019] For handling the slot nozzle, the nozzle body has at least one handle designed to press the nozzle body with its nozzle against the plate heat exchanger to be cleaned. Preferably, there are two handles for two-handed operation. As mentioned above, the compressed air pulse generates considerable recoil at the slot nozzle. This recoil must be prevented from the nozzle slipping out of the slot of the plate heat exchanger being cleaned. For this purpose, pressure is exerted on the slot nozzle in the direction of the nozzle via the handle(s). If the plate heat exchanger has a top-mounted end, it is also possible to stand on the slot nozzles or the handles. It may even be advantageous for two people to stand on the handles to exert sufficient pressure on the slot nozzle.The less compressed air escapes, the greater the cleaning impulse and therefore the cleaning effect.

[0020] After the slot nozzle has been correctly positioned and loaded via the handles, the valve is opened by remote control for an adjustable or preset period of time in order to release one or more compressed air pulses of defined length and frequency.

[0021] The inventive method and device used in this dry cleaning process for plate heat exchangers offer significant advantages over wet cleaning: First, by completely covering the gap, it is ensured that the gap can be cleaned across its entire cross-section. The debris can then be easily removed from the bottom or the outlet of the cleaned gap using an industrial vacuum cleaner. The inventive method and device allow for the easy cleaning of the entire range of plate heat exchangers. The method can be used for both steel and stainless steel heat exchangers. The cleaning effect is very high due to the adjustable air pressure and frequency of the compressed air pulses. At the same time, the risk of damage is minimal.Unlike wet cleaning, which is significantly more labor-intensive and takes considerably longer, dry cleaning using compressed air requires no subsequent drying phase. Drying is very energy-intensive. Since drying is eliminated, the cleaning process is significantly more energy-efficient overall.

[0022] With the device according to the invention, cleaning can be completed in approximately 8 days, compared to wet cleaning, which typically takes 2 to 3 weeks, without the need for a subsequent drying process. This example refers to a setup where approximately 30 tons of dust must be removed from the plate heat exchangers, which then have to be transported away using a vacuum truck. The invention makes it possible to precisely determine the cleaning effort required, allowing the plate heat exchangers to be put back into operation sooner. Production downtime can be reduced.

[0023] As a result, cleaning can be carried out cost-effectively even in shorter periods. The purpose of cleaning is to reduce pressure losses in the heat exchangers. A heat exchanger with high pressure loss does not operate efficiently and requires more energy. With this invention, it is possible to remove deposits from the heat exchangers cost-effectively and at shorter intervals, thereby enabling longer, more energy-efficient operation.

[0024] The invention is explained in more detail below with reference to exemplary embodiments shown in the drawings. The drawings show: Fig. 1 a perspective view of a slot nozzle according to a first embodiment; Fig. 2 a front view of the slot nozzle of the Fig. 1 ; Fig. 3 a front view of the slot nozzle of the Fig. 1 ; Fig. 4 a sectional view along line IV-IV from Fig. 2; Fig. 5 a sectional view along line VV of the Fig. 3; Fig. 6 a sectional view along line VI-VI of the Fig. 4; Fig. 7 a second embodiment of a slot nozzle in perspective view; Fig. 8 the slot nozzle of the Fig. 7 in a front view and Fig. 9 A schematic representation of a device for cleaning a plate heat exchanger.

[0025] The Fig. Figure 9 shows a device 1 for cleaning a plate heat exchanger 2. The device 1 includes a compressed air source 3 for supplying compressed air for the dry cleaning of the plate heat exchanger 2. A control box 4 is connected to the compressed air source 3 via a first compressed air line 5. The control box 4 contains an electrically controlled valve 6. The valve 6 can be operated wirelessly via a remote control 7. When the valve 6 is operated, compressed air flows from the first compressed air line 5 into a second compressed air line 8, to which a slot nozzle 9 is connected. Details of the slot nozzle 9 are described in the following sections. Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7 to Fig. 8 explained. The presentation of the Fig. In this sense, 9 is purely schematic.

[0026] The slot nozzle 9 has a connection 10 for the second compressed air line 8. The second compressed air line 8 is particularly flexible, i.e., designed as a hose, just like the first compressed air line 5, since the device according to the invention is used in a mobile manner and because the slot nozzle 9 must be constantly repositioned during operation. The slot nozzle 9 has a rib-like projecting nozzle tip 11 on a nozzle base 12 that is wider than the nozzle tip 11. The width B1 of the nozzle tip 11 is 11 mm in this example. The width B2 of the nozzle base 12 is 30 mm ( Fig. 5) The nozzle base 12 is also longer than the mouthpiece 11 ( Fig. 4) The nozzle 11 is inserted into a gap 13 of the plate heat exchanger 2 to be cleaned. The wider nozzle base 12 closes off the upper end of the gap 13. By actuating the remote control 7, the valve 6 is opened and a burst of compressed air flows through the nozzle 11 into the gap 13 of the plate heat exchanger 2 to dislodge unwanted deposits 14 by means of the pressure pulse. This causes the walls 15 of the plate heat exchanger 2, which define the gap 13, to be elastically deformed. The arrow P indicates the direction in which the deposits 14 are carried out of the gap 13 by the compressed air. In the inventive method, the deposits 14 can then be removed by a vacuum suction device. After cleaning a first gap 13, the nozzle 11 is placed on the next gap 13 to continue the cleaning process in this manner.

[0027] The Fig. Figure 1 shows the slot nozzle 9 in a perspective view. The slot nozzle is significantly longer than it is wide and has a connection 10 with a large cross-section, in particular > 50 mm, so that a large volume of air can be introduced into the nozzle body 10 of the slot nozzle 9 via the connection. Based on the Fig. 1 and Fig. Figure 2 shows that the nozzle body 10 tapers in a trapezoidal shape towards the mouthpiece 11. At the lower end (in the plane of the image) are outlet openings for the compressed air. Fig. Figure 4 shows in longitudinal section that several nozzle slots 16 are arranged one behind the other in the longitudinal direction adjacent to the nozzle slot 16. The nozzle slots 16 are completely surrounded by the nozzle slot 11 in a mantle-like manner. Fig. Figure 6 shows a bottom view of the five nozzle slots of this embodiment. The nozzle slots are located in the nozzle base 12, to which opposing walls 17 and 18 are also welded.

[0028] The Fig. Figure 5 shows a cross-sectional view along line VV of the Fig. 3. The walls 17, 18 are at an acute angle to each other and define the nozzle chamber 19 of the nozzle body 24. These opposing walls 17, 18 are connected to each other by several struts 20. In this embodiment, the struts 20 are arranged at a uniform distance of approximately 30 to 60 mm from each other. They serve to stiffen the nozzle body 24 in order to transmit high pressure impulses with a thin wall. The cleaning effect should not be reduced by the nozzle body 24 yielding under the pressure impulse. At the same time, the nozzle body 24 should be lightweight so that the entire slot nozzle 9 is easy to handle.

[0029] To position the slot nozzle 9 at the desired gap 13 of the plate heat exchanger 2, two handles 21, 22 are arranged on the nozzle body 9. They are located on a nozzle back 23, which is opposite the nozzle base 12 and extends over the areas between the walls 17, 18 at the edges that are not covered by the nozzle base 12. The nozzle back 23 is angled several times along its course. As a result, the handles 21, 22 are at an angle to each other. They are positioned in the plane of the image. Fig. 4 upwards over the nozzle back 23. In this embodiment, the connection 10 is located on the wall 17. The compressed air is supplied, so to speak, from the broad side.

[0030] The exemplary embodiment of the Fig. 7 and Fig. 8 differs from that of the Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5 to Fig.6 differs only in the positioning of the connection 10, which is alternatively attached to the nozzle back 23. All other components are identical, so the same reference numerals are used.

[0031] The invention further comprises a set of such slot nozzles 9 adapted to gaps 13 of different widths or lengths. The individual slot nozzles 9 therefore differ in the dimensions of their mouthpieces 11. Reference symbol: 1 Device for cleaning a plate heat exchanger 2 plate heat exchangers 3 Compressed air source 4 control boxes 5 First compressed air line 6 valve 7 Remote control for control box 8 Second compressed air line 9 slot nozzle 10 connections for 8 11 Mouthpiece 12 nozzle bases 13 Gap of plate heat exchanger 14. Attachment 15 wall of 13 16 nozzle gap 17 Wall 18 Wall 19 Nozzle room 20 strut 21 Handle 22 Handle 23 nozzle backs 24 nozzle bodies B1 width of 11 B2 width of 12 P Flow direction of the compressed air

Claims

[1] Device (1) for cleaning a plate heat exchanger (2), wherein the device (1) has the following features: a. A compressed air source (3) for providing compressed air for dry cleaning of the plate heat exchanger (2); b. A control box (4) which is connected to the compressed air source (3) via a first compressed air line (5) and to a slot nozzle (9) via a second compressed air line (8), wherein an electrically controllable valve (6) is arranged in the control box (4) between the compressed air lines (5, 8) connected to the control box (4), wherein the valve (6) is designed to open when actuated, so that compressed air flows to the slot nozzle (9); c. The slot nozzle (9) has at least one nozzle gap (16) which is surrounded circumferentially by a slot-shaped mouthpiece (11) which projects in the direction of flow (P) of the compressed air opposite the at least one nozzle gap (16). [2] Device (1) according to claim 1, characterized by , that several nozzle slots (16) are arranged one behind the other in the longitudinal direction of the nozzle slots (16) and are surrounded by a common mouthpiece (11). [3] Device (1) according to claim 1 or 2, characterized by , that the mouthpiece (11) has parallel side walls which determine a width (B1) of the mouthpiece (11). [4] Device (1) according to claim 3, characterized by , that the slot nozzle (9) has a nozzle body (24) with a nozzle base (12) on which the mouthpiece (11) is arranged, wherein the nozzle base (12) has a width (B2) which is greater than the width (B1) of the mouthpiece (11). [5] Device (1) according to any one of claims 1 to 4, characterized by, that the nozzle body (24) surrounds a nozzle chamber (19) between a connection (10) for the second pressure line (8) and the at least one nozzle gap (16), wherein struts (20) are arranged in the nozzle chamber (19) which connect opposite walls (17,18) to each other. [6] Device (1) according to any one of claims 1 to 5, characterized by , that the nozzle chamber (19) tapers from a connection (10) for the second pressure line (8) towards the at least one nozzle gap (16). [7] Device according to any one of claims 1 to 6, characterized by , that the slot nozzle (9) has at least one handle (21,22) on its nozzle body (24) which is designed to press the nozzle body (24) with the mouthpiece (11) against a plate heat exchanger (2) to be cleaned. [8] Device according to any one of claims 1 to 7, characterized by, that a set of different slot nozzles (9) with mouthpieces (11) of different widths (B1) is provided, wherein the slot nozzles (9) are detachably connectable to the second pressure hose (8). [9] Device (1) according to any one of claims 1 to 8, characterized by , that a control of the control box (4) is designed and configured to open the valve (6) for at least an adjustable period of time in order to release one or more compressed air pulses of defined length. [10] Method for dry cleaning a plate heat exchanger (2) using a device (1) having the features of any one of claims 1 to 9, characterized by , that the slot nozzle (9) with the mouthpiece (11) is inserted into a gap (13) of the plate heat exchanger (2) to be cleaned, wherein the width (B1) of the mouthpiece (11) is matched to the width of the gap (13). [11] Method according to claim 10, characterized by, that the nozzle base (12) covers the gap (13) to be cleaned outside the mouthpiece (11). [12] Method according to claim 10 or 11, characterized by that dry cleaning is carried out by means of compressed air pulses, wherein the compressed air pulse is intended to elastically deform the walls (15) of the plate heat exchanger (2) limiting the gap (13) in order to loosen adhesions (14). [13] Method according to any one of claims 10 to 12, characterized by , that the pressure of the compressed air pulse is regulated via a pressure regulating valve in the control box (4). [14] Method according to any one of claims 10 to 13, characterized by , that the pressure pulse is triggered by means of a remote control (7) connected to the control box. [15] Method according to any one of claims 10 to 14, characterized by that it is used in stationary gas-to-gas heat exchangers.

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