Cleaning device for a heat exchanger, in particular for a plate heat exchanger

Abstract

A cleaning device (14) for a heat exchanger (10), in particular a plate heat exchanger, the cleaning device employing a charge (15) of cleaning media to be circulated through the heat exchanger and comprising an inlet pipe (14U) upstream of the heat exchanger (10) and an outlet pipe (14D) downstream of the heat exchanger (10), the cleaning device (14) comprising a downstream filter apparatus (17) configured to collect the cleaning media exiting through the outlet pipe (14D) and a recirculation pipe (33) configured to reintroduce the cleaning media collected by the downstream filter apparatus (17) into the inlet pipe (14U), characterized in that the recirculation pipe (33) comprises a hybrid positive displacement and centrifugal pump (35) for driving the cleaning media and a check valve (34) disposed downstream of said pump (35).Figure for the abbreviation: Figure 1.

Description

Title of the invention: Cleaning device for a heat exchanger, in particular for a plate heat exchanger technical field

[0001] The present invention relates to a cleaning device for a heat exchanger, in particular for a plate heat exchanger. Technological background

[0002] It is well known that a heat exchanger needs to be cleaned regularly to maintain satisfactory performance over time. In the case of a heat exchanger that is part of an industrial installation such as a power plant or chemical plant, this regular cleaning must be able to be carried out without dismantling the heat exchanger, because otherwise the industrial installation would have to be shut down for an extended period.

[0003] For this purpose, it is known to pass small cleaning bodies through the heat exchanger. These cleaning bodies are injected into the supply line of the heat exchanger's cooling fluid, after which they pass through the heat exchanger and clean the internal surfaces of the heat exchanger which are fouled, and then exit the heat exchanger.

[0004] In practice, this known method is very well suited to tubular heat exchangers, because the cleaning bodies, in the form of rubber balls with a diameter only slightly larger than the dimensions of the tubular heat exchanger tubes, effectively clean these tubes.

[0005] However, there is now a growing trend towards using plate heat exchangers rather than tubular heat exchangers, particularly because plate heat exchangers are more compact and easier to configure to achieve the desired performance. But cleaning a plate heat exchanger using cleaning media according to the known method is more difficult. In particular, the cleaning media are in the form of beads or granules with a diameter of approximately 1 to 2 millimeters, but the gap between the plates is only a few millimeters, which means that the cleaning media do not move very easily between the plates.

[0006] Furthermore, for cost reasons, it is necessary to avoid losing cleaning bodies with each cleaning of the heat exchanger.

[0007] In patent FR 2 668 083 Bl, the inventor has already proposed a cleaning device that overcomes these two difficulties. This cleaning device essentially comprises a self-cleaning filtration apparatus on the supply line of the A cooling fluid is used to remove particles and debris from the water that could clog the heat exchanger, and a multi-cartridge filtration unit is installed at the heat exchanger outlet to collect the cleaning particles. Through the operation of at least four valves, the collected cleaning particles are sent to a third filtration unit where they are consolidated. After this consolidation, the third filtration unit is supplied with cold water by actuation of the valves, and the cleaning particles are injected in a single burst upstream of the heat exchanger. This operation is usually repeated several times per hour to maintain the cleanliness of the heat exchanger.

[0008] Such a cleaning device works very well in practice but has the following disadvantages.

[0009] The cleaning media (synthetic beads or granules) are fragile and require special valves that do not crush the media when closing. These valves are quite expensive. Furthermore, the filtration devices are complex and costly. The piping includes venturis, which are also complex and expensive. Finally, the valves are subjected to numerous and frequent cycles and therefore require rather costly periodic maintenance. Summary of the invention

[0010] The invention therefore aims to provide a cleaning device for a heat exchanger, in particular for a plate heat exchanger, which is simple and inexpensive.

[0011] According to the invention, a cleaning device for a heat exchanger, in particular a plate heat exchanger, is proposed, the cleaning device implementing a charge of cleaning bodies to be circulated in the heat exchanger and comprising an inlet pipe upstream of the heat exchanger and an outlet pipe downstream of the heat exchanger, the cleaning device comprising a downstream filter apparatus configured to collect the cleaning bodies exiting through the outlet pipe and a recirculation pipe configured to reintroduce the cleaning bodies collected by the downstream filter apparatus into the inlet pipe, characterized in that the recirculation pipe includes a hybrid volumetric and centrifugal type pump to drive the cleaning bodies and a non-return valve disposed downstream of said pump.

[0012] With the downstream filter apparatus, the pump, and the check valve, the cleaning media can be injected in bursts from time to time to clean the heat exchanger, then collected to be injected in bursts again, and so on. Since the pump is of a hybrid positive displacement and centrifugal type, it can drive cleaning media such as plastic beads or granules without damaging them. On the other hand, since the movement of the cleaning elements is ensured by the pump, the recirculation line can be free of valves other than the check valve, which would be costly and could damage the cleaning elements. In this case, apart from the pump, whose intervention is brief and momentary, the recirculation line contains no moving mechanical parts. It is therefore clear that the cleaning system ensures regular cleaning of the heat exchanger, without loss of the cleaning elements and with very low wear on the cleaning elements, at a moderate cost both during installation and operation of the cleaning system.

[0013] In some embodiments, the cleaning bodies are plastic beads or granules. The diameter of these beads or granules can be between 0.8 mm and 2.5 mm, in particular between 1.0 mm and 2.0 mm.

[0014] In certain embodiments, said pump comprises a pump body and an impeller mounted for movability and rotation within the pump body, the impeller comprising a worm gear which has: - a frustoconical portion housed within a frustoconical portion of the pump body, thus forming a volumetric section of said pump; and - a cylindrical portion housed in an annular part of the pump body, thus forming a centrifugal section of said pump.

[0015] In some embodiments, the recirculation pipe is configured to reintroduce the cleaning bodies collected by the downstream co-current filtering equipment into the inlet pipe.

[0016] In some embodiments, the downstream filtering apparatus comprises a first hollow body and a first cylindrical filter wall disposed in said first hollow body.

[0017] In some embodiments, the first hollow body comprises a side wall surrounding the first cylindrical filter wall and an internal partition disposed at a lower end of the first cylindrical filter wall, the outlet pipe opening into the side wall so that a fluid charged with cleaning bodies begins to rotate around the first cylindrical filter wall, so that the cleaning bodies are centrifuged towards the side wall and collect by gravity on the internal partition.

[0018] In some embodiments, the first cylindrical filter wall has parallel slots which form meshes of the first cylindrical filter wall.

[0019] In certain embodiments, the cleaning device further comprises an upstream filtering apparatus disposed upstream of the inlet pipe, the apparatus upstream filter comprising a second hollow body and a second cylindrical filter wall disposed in said second hollow body.

[0020] In certain embodiments, the second hollow body comprises a lower end wall, the second cylindrical filter wall extending to said lower end wall, and the cleaning device further comprises: - a bypass pipe opening through the lower end wall into a volume delimited by the second cylindrical filter wall; and - a valve closing said bypass pipe.

[0021] In some embodiments, the cleaning device further includes a control unit configured to start said pump.

[0022] In some embodiments, the control unit is configured to determine an efficiency of the heat exchanger and is configured to start said pump at least according to the efficiency thus determined.

[0023] In certain embodiments, said control unit is further configured to actuate said valve.

[0024] In certain embodiments, said control unit is configured to determine a pressure drop in the upstream filtration equipment and to actuate said valve at least according to the pressure drop thus determined. Brief description of the figures

[0025] The following description, with reference to the accompanying drawings, given by way of non-limiting examples, will clearly explain what the invention consists of and how it can be implemented. In the accompanying figures:

[0026] [Fig-1] Fig. 1 is a schematic representation of a cleaning device according to one embodiment of the invention;

[0027] [Fig.2] The [Fig.2] is a three-dimensional view of the downstream filtering apparatus used to collect the cleaning bodies exiting the heat exchanger;

[0028] [Fig.3] The [Fig.3] is a detailed view of the filter wall of the downstream filtering apparatus;

[0029] [Fig.4] Fig.4 is a cross-sectional view of the pump used to recirculate the cleaning bodies according to an example embodiment. Description of method(s) of implementation

[0030] In the figures, and unless otherwise specified, identical elements shall bear the same reference symbols.

[0031] Figure 1 schematically represents a heat exchanger 10 and a cleaning device 14 associated with this heat exchanger 10. The heat exchanger 10 is, in particular, a plate heat exchanger. However, the cleaning device 14 is applicable to any other type of heat exchanger. Since the internal structure of the heat exchanger 10 is known as such, it has been omitted from the drawing in [Fig.1].

[0032] The cleaning device 14 is arranged between a fluid inlet 11 and a fluid outlet 12. In the following description, it is assumed that this fluid is liquid water used as a coolant. However, the fluid may be another coolant in liquid or gaseous form. The lines used to supply and discharge the other fluid that exchanges heat with this coolant have been omitted from the drawing in [Fig. 1]. Drain valves and vents known per se have also been omitted from the drawing.

[0033] The water arriving via the inlet 11 passes through an upstream filtration apparatus 16, then enters the heat exchanger 10 through an inlet pipe 14U, then exits the heat exchanger 10 through an outlet pipe 14D, then passes through a downstream filtration apparatus 17 and finally is discharged via the outlet 12.

[0034] The cleaning device 14 uses a charge 15 of cleaning media to circulate in the heat exchanger 10. These cleaning media are, for example, plastic beads or granules. The diameter of these beads or granules can be between 0.8 mm and 2.5 mm, in particular between 1.0 mm and 2.0 mm.

[0035] According to the invention, the downstream filter apparatus 17 is configured to collect the cleaning particles exiting through the outlet pipe 14D. The cleaning particles collected by the downstream filter apparatus 17 are reintroduced into the inlet pipe 14U via a recirculation pipe 33. The recirculation pipe 33 includes a hybrid positive displacement and centrifugal pump 35 for driving the cleaning particles and a non-return valve 34 disposed downstream of said pump 33.

[0036] The term "hybrid positive displacement pump" refers to any pump which, within the same pump body, comprises a section operating as a positive displacement pump and a section operating as a centrifugal pump. Such pumps are known as such and are used to move the most delicate food products and live fish.

[0037] Figure 4 is a cross-sectional view of such a pump 35 according to an exemplary embodiment. This pump 35 comprises a pump body 340 and a worm gear 350 mounted for rotation within the pump body 340 and functioning as the impeller of the pump 35. The worm gear 350 has a frustoconical portion 351 and a cylindrical portion 352. By "fruconical portion," it is meant that when the worm gear 350 rotates about its axis of rotation R, the volume swept by the portion 351 is frustoconical. Similarly, by "cylindrical portion," it is meant that when the worm gear 350 rotates about the axis of rotation R, the volume swept by the portion 352 is cylindrical. The frustoconical portion 351 is housed within a frustoconical portion. 341 of the pump body 340. Due to the corresponding shape between the frustoconical portion 341 and the frustoconical portion 351, these together form a volumetric section VS of the pump 35, i.e., a section functioning as a positive displacement pump. The cylindrical portion 352 is housed within an annular portion 342 of the pump body 340. The cylindrical portion 352 and the annular portion 342 together form a centrifugal section CS of the pump 35, i.e., a section functioning as a centrifugal pump. During operation, the water admitted through the inlet pipe 320 first encounters the volumetric section VS and then the centrifugal section CS before being discharged through the outlet pipe 360.

[0038] Figure 2 represents the downstream filtering apparatus 17 according to a preferred embodiment. The downstream filtering apparatus 17 comprises a hollow body 30 and a cylindrical filter wall 31 disposed within the hollow body 30. In the example shown, the hollow body 30 is cylindrical and coaxial with the cylindrical filter wall 31, and therefore has a side wall 30A with a cylindrical cross-section.

[0039] The hollow body 30 is closed by a lid 37. Opposite the lid 37, the filter wall 31 joins an internal partition 38 within the hollow body 30. The outlet pipe 14D opens into the side wall 30A via a conduit 32 offset from the filter wall 31. In this way, when water containing cleaning agents passes through the heat exchanger 10 and exits through the outlet pipe 14D (arrow F6 in [Fig. 1]), this water enters via the conduit 32 and is set into rotation around the filter wall 31. Since the cleaning agents have a higher density than water, they are thus centrifuged towards the side wall 30A. They then collect by gravity on the internal partition 38, which separates the water containing cleaning agents from the water without cleaning agents.The water which has passed through the filter wall 31, and has therefore been freed of cleaning bodies, then passes through the internal partition 38 to finally exit at 36 of the downstream filter apparatus 17 and join the outlet 12. Thus, the downstream filter apparatus 17 collects the cleaning bodies exiting through the outlet pipe 14D and collects them on the internal partition 38.

[0040] As can be seen more clearly in [Fig. 3], the filter wall 31 is advantageously a strainer formed of wires 47 with a triangular cross-section. These wires 47 are spaced apart to form slots 48 which constitute the mesh of the filter wall 31. Spacers 49 encircle the wires 47 to hold them in place. Naturally, the width of the slots 48 is suitably chosen to stop the cleaning particles. Alternatively, the filter wall 31 can be made in other ways as long as it allows the cleaning particles to be filtered as described above.

[0041] Returning to [Fig. 1], when the volumetric and centrifugal pump 35 is started, it abruptly sucks up the cleaning bodies waiting on the Internal partition 38. They are propelled in a burst by the recirculation line 33 along F4, pass through the non-return valve 34 before joining the cold water flow F3 at F41, which enters the heat exchanger 10 via the inlet pipe 14U. They thus enter the heat exchanger 10 to clean it. Preferably, and as shown in [Fig. 1], the recirculation line 33 reintroduces the cleaning media in a co-current flow into the inlet pipe 14U, for example by means of an injection nozzle 33B. This tends to prevent the cleaning media from flowing back towards the non-return valve 34, and thus ensures that the cleaning media are injected in a very brief burst.

[0042] When the pump 35 stops, the non-return valve 34 closes and prevents cold water from bypassing the heat exchanger 10. Indeed, due to pressure losses, and in particular due to the pressure losses in the heat exchanger 10, the pressure in the downstream filter unit 17 is lower than that in the upstream filter unit 16 described below.

[0043] The start-up of the pump 35 can be controlled in various ways. In a very simple embodiment, the start-up of the pump 35 is controlled purely manually. However, it is more advantageous for the start-up of the pump 35 to be controlled by a control unit 70, shown schematically in [Fig. 1]. In a simple embodiment, the control unit 70 can start the pump 35 at regular time intervals, these regular time intervals optionally being adjustable according to the state of the water entering 11. In a preferred embodiment, in addition to or as an alternative to starting the pump 35 at regular intervals, the control unit 70 is configured to determine an efficiency of the heat exchanger 10 and to start the pump 35 according to the efficiency thus determined.The methods for determining the efficiency of a heat exchanger 10, and the sensors to be implemented for this purpose, being well known as such, are not described in detail here.

[0044] In any event, with the downstream filter apparatus 17, the pump 35, and the check valve 34, the cleaning media can be injected in bursts from time to time to clean the heat exchanger 10, then collected to be injected in bursts again, and so on. As mentioned above, since the pump 35 is of the hybrid positive displacement and centrifugal type, it can move even the most fragile food products and live fish without damaging them; all the more so, it can move cleaning media such as plastic balls or granules without damaging them. Furthermore, since the movement of the cleaning media is ensured by the pump 35, the recirculation line 33 can be free of valves other than the check valve 34, which would be costly and could damage the cleaning elements. In this case, with the exception of pump 35, whose intervention is brief and momentary, the recirculation line 33 contains no moving mechanical parts. It is therefore clear that the cleaning device 14 ensures regular cleaning of the heat exchanger 10, without loss of the cleaning elements and with very low wear on the cleaning elements, at a moderate cost both during installation of the cleaning device 14 and during its operation.

[0045] An access hatch NA can be provided near the internal partition 38 to collect the cleaning media when it is necessary to replace them. This access hatch NA, or another access hatch NB in ​​the recirculation pipe 33, can be used to supply new cleaning media.

[0046] Purely by way of example, the rotational speed of the screw 350 may be less than or equal to 1500 revolutions per minute, to ensure a flow rate of the pump 35 of approximately 250 liters per second. The circulation speed of the cleaning media in the recirculation line 33 may be less than 3 meters per second, in particular less than 2 meters per second, to avoid excessive abrasion by the cleaning media.

[0047] So far, only a downstream filtering apparatus 17 has been described for filtering the water loaded with cleaning bodies exiting the heat exchanger 10. But in practice, the water entering the heat exchanger 10 is taken from the environment, for example from a river, and must therefore be filtered before entering the heat exchanger 10. For this purpose, the cleaning device 14 includes an upstream filtering apparatus 16 arranged upstream of the inlet pipe 14U, more precisely upstream of the point (such as the injection nozzle 33B) where the recirculation pipe 33 reintroduces the cleaning bodies into the inlet pipe 14U.

[0048] In the example shown in [Fig. 1], the upstream filter unit 16 has a construction generally similar to that of the downstream filter unit 17, that is to say, it has a hollow body 20, for example cylindrical, and a cylindrical filter wall 21 disposed within the hollow body 20. The filter wall 21 can be made in the same way as the filter wall 31, in particular in the form of a strainer as described above in relation to [Fig. 3]. Alternatively, the filter wall 21 can be made in other ways as long as it allows the filtering of the raw water arriving through the inlet 11 and entering the upstream filter unit 16 at Fl via a pipe 22 thereof. Of course, the mesh size of the filter wall 21 is sufficiently small to stop any debris that may be carried by the raw water. For example, it is between 1.0 mm and 3.0 mm, specifically between 1.0 mm and 1.5 mm.Note that the mesh of the filter wall 31 can be larger than the mesh of the wall. filter wall 21, because the filter wall 21 having stopped the incoming debris, the filter wall 31 only has to stop the cleaning bodies.

[0049] When the filtered water exits through the pipe 27 via the heat exchanger 10, according to F3, the filter wall 21 gradually becomes fouled due to impurities deposited on its inner surface. Advantageously, and to avoid periodic replacement of the filter wall 21, which would necessitate shutting down the heat exchanger 10, the cleaning device 14 is provided to include a bypass pipe 26 that opens through a lower end wall 28 of the hollow body 20. This bypass pipe 26 opens into a volume delimited by the filter wall 21. A valve 23 closes the bypass pipe 26. The filter wall 21 can thus be cleaned by opening the valve 23 for a short period. The impurities are thus swept away and are evacuated according to F2, towards exit 12 via bypass pipe 26.In a very simple embodiment, the valve 23 is operated purely manually. However, it is more advantageous for the valve 23 to be operated by a control unit, which may or may not be the same control unit 70 that starts the pump 35. In a simpler embodiment, the control unit 70 operates the valve 23 at regular time intervals, these regular time intervals possibly being adjustable according to the condition of the water entering 11. In a preferred embodiment, as a complement to or alternative to operating the valve 23 at regular intervals, the control unit 70 is configured to determine a pressure drop in the upstream filtering equipment 16 and to operate the valve 23 based on this determined pressure drop.The methods for determining pressure loss, and the sensors to be implemented for this purpose, being well known as such, are not described in detail here.

Claims

Demands

1. Cleaning device (14) for a heat exchanger (10), in particular a plate heat exchanger, the cleaning device employing a charge (15) of cleaning media to be circulated in the heat exchanger and comprising an inlet pipe (14U) upstream of the heat exchanger (10) and an outlet pipe (14D) downstream of the heat exchanger (10), the cleaning device (14) comprising a downstream filter apparatus (17) configured to collect the cleaning media exiting through the outlet pipe (14D) and a recirculation pipe (33) configured to reintroduce the cleaning media collected by the downstream filter apparatus (17) into the inlet pipe (14U),characterized in that the recirculation pipe (33) comprises a hybrid volumetric and centrifugal pump (35) for driving the cleaning bodies and a non-return valve (34) disposed downstream of said pump (35).

2. Cleaning device (14) according to claim 1, wherein said pump (35) comprises a pump body (340) and an impeller mounted movably for rotation in the pump body (340), the impeller comprising a worm screw (350) which has: - a frustoconical portion (351) housed in a frustoconical portion (341) of the pump body (340), thus forming a volumetric section (VS) of said pump (35); and - a cylindrical portion (352) housed in an annular portion (342) of the pump body, thus forming a centrifugal section (CS) of said pump (35).

3. Cleaning device (14) according to any one of claims 1 to 2, wherein the recirculation pipe (33) is configured to reintroduce the cleaning bodies collected by the downstream co-current filtering apparatus (17) into the inlet pipe (14U).

4. Cleaning device (14) according to any one of claims 1 to 3, wherein the downstream filtering apparatus (17) comprises a first hollow body (30) and a first cylindrical filter wall (31) disposed in said first hollow body (30).

5. Cleaning device (14) according to claim 4, wherein the first hollow body (30) comprises a side wall (30A) surrounding the first cylindrical filter wall (31) and an internal partition (38) disposed at a lower end of the first cylindrical filter wall (31), the outlet pipe (14D) opening into the side wall (30A) so that a fluid charged with cleaning bodies begins to rotate around the first cylindrical filter wall (31), so that the cleaning bodies are centrifuged towards the side wall (30A) and collect by gravity on the internal partition (38).

6. Cleaning device (14) according to any one of claims 4 to 5, wherein the first cylindrical filter wall (31) has parallel slots (48) which constitute meshes of the first cylindrical filter wall (31).

7. Cleaning device (14) according to any one of claims 1 to 6, wherein the cleaning device further comprises an upstream filter apparatus (16) disposed upstream of the inlet pipe, the upstream filter apparatus (16) comprising a second hollow body (20) and a second cylindrical filter wall (21) disposed in said second hollow body (20).

8. Cleaning device (14) according to claim 7, wherein the second hollow body (20) has a lower end wall (28), the second cylindrical filter wall (21) extending to said lower end wall (28), and wherein the cleaning device further comprises: - a bypass pipe (26) opening through the lower end wall (28) into a volume delimited by the second cylindrical filter wall (21); and - a valve (23) closing said bypass pipe (26).

9. Cleaning device (14) according to any one of claims 1 to 8, wherein the cleaning device (14) further comprises a control unit (70) configured to start said pump (35).

10. Cleaning device (14) according to claim 9, wherein the control unit (70) is configured to determine an efficiency of the heat exchanger (10) and is configured to start said pump (35) at least according to the efficiency so determined.

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