FR3087253A1 - SYSTEM FOR CLEANING AT LEAST ONE HEAT EXCHANGER AND ASSOCIATED METHOD - Google Patents

Abstract

System for cleaning a plurality of heat exchangers (10), the cleaning system comprising: - a tank capable of containing an external cleaning fluid, the tank defining a plurality of locations (56) for receiving one of exchangers, each location (56) comprising at least one fixing member (60) and circulation ports (62) arranged to communicate with an internal space of the exchanger (10); - a hydraulic circuit connecting the circulation ports (62) of the locations (56) to each other; - a pump connected to the hydraulic circuit, capable of circulating an internal cleaning fluid through the exchangers (10); and - at least one transducer (48) disposed in the tank, suitable for emitting ultrasound, disposed opposite at least one of the locations (56).

Description

System for cleaning at least one heat exchanger and associated method

The present invention relates to a system for cleaning a plurality of heat exchangers. The invention also relates to a cleaning method using such a system.

The system is especially intended for the large-scale cleaning of used plate heat exchangers of mixed boilers.

Mixed boilers commonly use plate heat exchangers to optimize heat exchange between two fluids without putting them in direct contact with each other.

It is known that plate heat exchangers end up scaling (sanitary use) and becoming muddy (heating use) and that their replacement by a new exchanger represents a significant cost for the maintenance of boilers and sanitary heating devices.

It is therefore advantageous to clean and restore used plate heat exchangers to operating condition, rather than systematically replacing them with new exchangers. This has the effect of increasing their lifespan according to the number of recycling operations thus carried out. This principle on the one hand reduces the maintenance costs of said boilers and on the other hand reduces the environmental impact of their use.

It is possible to clean the plate heat exchangers by soaking in a bath of cleaning fluid. Such a soaking makes it possible to clean a large number of used exchangers simultaneously, and cleans both the inside and the outside of the exchangers, which is a prerequisite for their reuse.

However, this method requires very long soaking times, on the order of 10 to 15 hours, which can lead to corrosion of the metal of the exchangers. In addition, the internal cleaning of the exchangers may be insufficient, especially when there is magnetite sludge.

Alternative solutions such as the circulation of a cleaning fluid in the internal space of the exchangers are conceivable, and make it possible to reduce the exposure time of the exchangers and therefore the risks of corrosion, while improving internal cleaning.

However, these methods require additional external cleaning afterwards. In addition, the circulation devices used are difficult to adapt to different models of exchangers having different geometries and different inlet and outlet ports from one model to another.

Thus, an object of the invention is to provide a system for cleaning heat exchangers making it possible to clean the interior and exterior of the exchangers in a reduced time, and having good adaptability to different models of exchangers.

To this end, the invention relates to a cleaning system of the aforementioned type, comprising:

a tank capable of containing an external cleaning fluid for the exchangers, the tank defining a plurality of locations for receiving one of the exchangers, each location comprising at least one member for fixing the exchanger on the location and ports circulation arranged to communicate fluidly with an internal space of the exchanger received on the site;

- a hydraulic circuit fluidly connecting the circulation ports of the locations to each other;

a pump fluidly connected to the hydraulic circuit, capable of circulating an internal cleaning fluid through the hydraulic circuit and the exchangers received by the locations; and

- at least one transducer arranged in the tank, capable of emitting ultrasound, the at least one transducer being arranged opposite at least one of the locations.

According to particular embodiments, the cleaning system according to the invention has one or more of the following characteristics, taken alone or in any technically feasible combination:

- the internal cleaning fluid comprises an acid, in particular phosphoric acid;

- the cleaning system includes an acid reservoir supplying the pump, as well as a probe for controlling the acidity of the contents of the reservoir;

- The locations are arranged in lines parallel to each other, the fixing members being shared between the locations of two neighboring lines;

- the circulation ports and the fixing members are mounted on support bars movable in translation in a transverse direction orthogonal to the location lines, so that the width of the locations of each line is adjustable;

- the fixing members are flanges mounted on rods fixed to the tank;

- The hydraulic circuit comprises at least two valves arranged to modify a direction of circulation of the internal cleaning fluid through the hydraulic circuit and the exchangers;

- The hydraulic circuit comprises at least one inlet valve suitable for selecting a fluid circulating in the hydraulic circuit, from the internal cleaning fluid, a rinsing fluid and a drying fluid; and

- The tray has a length between 1.5 m and 2 m and a width between 1 m and 1.5 m, the tray defining at least fifty locations.

The subject of the invention is also a method of cleaning a plurality of heat exchangers, the method implementing a cleaning system as described above, the method comprising the following steps:

- installation of at least one exchanger to be cleaned on one of the locations, and communication of the internal space of each exchanger with the circulation ports;

- fixing of each exchanger on the site by means of each corresponding fixing member;

- filling the tank with the external cleaning fluid;

- circulation of the internal cleaning fluid in the internal space of each exchanger;

- simultaneously with the circulation of the internal cleaning fluid, emission of ultrasound by the transducers in the direction of the exchangers; and

- emptying the tank and removing the exchangers.

The invention will be better understood on reading the description which follows, given solely by way of example and made with reference to the accompanying drawings, among which:

- Figure 1 is a schematic view of a plate heat exchanger;

- Figure 2 is a perspective view of a cleaning system according to the invention;

- Figure 3 is a top view of the cleaning system of Figure 2;

- Figure 4 is a side view of the exchanger of Figure 1 attached to a location of the cleaning system of Figures 2 and 3;

FIG. 5 is a schematic representation of the hydraulic circuit of the cleaning system of FIGS. 2 to 4.

A plate heat exchanger 10 is shown diagrammatically in FIG. 1. The exchanger 10 comprises a plurality of plates 12 stacked one on the other, each plate 12 having a substantially rectangular shape and defining four orifices 14 in the vicinity of each of the corners .

The exchanger 10 is intended to circulate two fluids in an internal space and to allow heat exchange between the fluids without direct contact. The two fluids can be the same or different from each other.

The orifices 14 are intended to circulate the two fluids along separate paths A and B, shown in FIG. 1, with each fluid entering through the orifice 14 from one of the corners of the exchanger 10 and emerging through the orifice 14 from the opposite corner.

Each plate 12 further comprises a peripheral seal 16 extending along the edge of the plate 12 and defining a closed contour, as well as two closure seals 18 surrounding two of the orifices 14 located in the vicinity of two opposite corners of the plate

12.

The plates 12 are stacked on top of each other and kept in compression, so that the peripheral seal 16 and the closure seals 18 are compressed between the two adjacent plates 12.

The peripheral seal 16 defines a circulation space 20 for fluid extending between two orifices 14 located in opposite corners. The closure seals 18 isolate the other two orifices 14 from the circulation space 20.

The orifices 14 surrounded by the closure seals 18 alternate from one plate 12 to the next plate 12 in the exchanger 10. Each circulation space 20 is thus intended to circulate one of the fluids while the circulation spaces 20 neighbors circulate the other fluid.

Thus, the two fluids circulating in the exchanger 10 are in heat exchange through the plates 12 through a very large exchange surface, without being in direct contact with each other.

FIG. 2 represents a cleaning system 30 of a plurality of exchangers 10 as previously described.

The cleaning system 30 comprises a frame 32 carrying a tank 34, as well as a hydraulic circuit 36.

The frame 32 is a structure, in particular a metallic structure, carrying the tank 34 and receiving and protecting the hydraulic circuit 36. The frame 32 has a height of between 90 cm and 120 cm, typically 100 cm, allowing practical access to the tank 34 by a user for fitting and removing exchangers 10.

The container 34 is a substantially parallelepiped receptacle, open on an upper face, and comprising a removable cover 38 making it possible to close it in a substantially sealed manner.

The tray 34 has a length of, for example, between 150 cm and 200 cm and a width of, for example, between 100 cm and 150 cm, which allows easy access for the operator to the entire tray 34 in order to facilitate placing. in place and removal of the exchangers 10.

The tray 36 has a height for example between 20 cm and 40 cm, in particular 30 cm.

The tank 34 also includes a filling valve 40 and a drain valve 42, respectively suitable for filling the tank 34 with an external cleaning fluid and for emptying it.

Advantageously, the tank 34 comprises a probe for monitoring the level of external cleaning fluid in the tank 34.

The external cleaning fluid is for example water, in particular soapy water.

The cleaning system 30 comprises a plurality of support bars 46 and a plurality of ramps 48 of ultrasonic transducers, contained in the tank 34, extending in particular in the vicinity of the bottom of the tank 34.

As shown in Figure 3, the support bars 46 and the ramps 48 of transducers have elongated shapes and are arranged substantially parallel to each other and alternated in a direction perpendicular to a common direction of elongation X-X ’.

For example, the cleaning system 30 comprises seven support bars 46 and six ramps 48 of transducers extending between the support bars 46.

The support bars 46 are arranged to carry the ends of the exchangers 10 placed in the tank 34.

Advantageously, the support bars 46 can be moved in a transverse direction YY 'perpendicular to their direction of extent X-X', in order to be able to vary the spacing between two successive support bars 46, so as to adapt the spacing at different lengths of the exchangers 10.

For example, each support bar 46 has two ends slidably mounted on a rail extending in the transverse direction Y-Y ’.

The ramps 48 each comprise at least one ultrasonic transducer, capable of emitting acoustic vibrations having a frequency in the ultrasonic range, which propagate through the external cleaning fluid in the direction of the exchangers 10.

Advantageously, the ramps 48 are movable, in the same way as the support bars 46.

In particular, each ramp 48 comprises thirteen transducers, each transducer being positioned so as to be opposite the center of a heat exchanger 10 disposed in the tank.

As shown in FIG. 3, the tank 34 defines a plurality of locations 56 for receiving one of the exchangers 10, each location 56 comprising at least one member 60 for fixing the exchanger 10 to the location and ports for circulation 62 arranged to communicate fluidly with an internal space of the exchanger 10 received at location 56. Each location 56 further extends opposite an ultrasonic transducer.

The locations 56 are arranged in lines parallel to each other, extending between the support bars 46.

The tray 34 advantageously defines at least fifty locations 56. For example, the tray 34 defines seventy-eight locations 56 distributed in six lines 64 of thirteen locations 56.

A width / of the locations 56 of each line 64 is adjustable by moving one or the other of the two support bars 46 bordering the line 64 in the transverse direction Y-Y ’.

In the embodiment shown in FIG. 4, each location 56 comprises two fixing members 60 located on either side of the location 56, at two opposite ends of the exchanger 10.

The fixing members 60 are flanges, comprising a rod 70 fixed to the support bar 46, a cross member 72 and at least one adjusting screw 74. The fixing members 60 are shared between the locations 56 of the two lines 64 adjacent to the support bar 46.

The rod 70 extends substantially vertically, projecting from the support bar 46, between two neighboring locations 56. The rod 70 has at a top end a stud 76 having an end collar 78.

The crosspiece 72 is fixed to the upper end of the rod 70, in particular by a buttonhole receiving the stud 76, the collar 78 coming to bear on the crosspiece 72.

As a variant, the crosspiece 72 is fixed to the rod 70 by a screw.

The crosspiece 72 extends substantially perpendicularly to the rod 70, in the transverse direction Y-Y ’. It has two ends 80 extending above the two neighboring locations 56. The crosspiece 72 also has two threaded orifices 82 in the vicinity of its two ends 80, in which the screws 74 are engaged.

Each screw 74 has an external thread 84 engaged in the threaded orifice 82 of the crosspiece 72, and one end 86 adjustable in height by rotation of the screw 74, suitable for coming to bear on one end of the exchanger 10 to fix it on location 56, bearing against the traffic ports 62.

The screws 74 are for example made in one piece, made of polypropylene.

According to one embodiment, the fastening members 60 fixed to the support bars 46 located closest to the lateral edges of the container 64, which run along only one line 64 of locations 56, are half-flanges and not flanges. By this is meant that the crosspiece 72 extends only above a single location 56, has only one threaded hole 80 and therefore receives only one screw 74.

The circulation ports 62 are orifices opening out from the hydraulic circuit 36, carried by the support bars 46, and positioned so as to come opposite the orifices 14 of the exchangers 10 placed on the locations 56.

Each circulation port 62 comprises an O-ring 88 disposed along the periphery of the circulation port 62, intended to seal between the circulation port 62 and the orifice 14 of the exchanger 10 when the exchanger 10 is fixed in abutment against the support bar 46.

The hydraulic circuit 36, shown schematically in FIG. 5, comprises a pipe 90 fluidly connecting the circulation ports 62 of the locations 56 to one another, so as to connect the exchangers 10 placed on the locations 56 one after the other .

The hydraulic circuit 36 further comprises a reservoir 92 of an internal cleaning fluid and a pump 94 suitable for circulating the internal cleaning fluid in the piping 90 and in the internal spaces of the exchangers 10.

The cleaning fluid comprises for example an acid, and is in particular a mixture of phosphoric acid and a surfactant. The internal cleaning fluid then has a pH of between 0.5 and 2, and more particularly an initial pH of between 0.5 and 0.6 before use.

The reservoir 92 is capable of containing the internal cleaning fluid, and in particular comprises a filter 96 adapted to remove the impurities from the internal cleaning fluid during the circulation thereof.

The filter 96 is notably mounted on the inlet of the conduit leading to the pump 94, in a removable manner to be cleaned or replaced during the maintenance of the cleaning system 20.

The reservoir 92 advantageously comprises a probe 98 for controlling the acidity of the content of the reservoir 92, suitable for measuring the pH of the internal cleaning fluid contained in the reservoir 92.

Advantageously, the reservoir 92 comprises at least one tube pierced with recirculation of the internal cleaning fluid in order to prevent the internal cleaning fluid from foaming in the reservoir 92 when it returns to be reinjected. The pierced tubing extends in particular along an upper face of the reservoir, in order to discharge the internal cleaning fluid of a certain height when it returns to the reservoir 92.

Advantageously, the reservoir 92 further comprises at least one decompression vent, in order to balance the pressure in the reservoir 92 and to prevent the vortex effect during filling and emptying of the reservoir 92.

The pump 94 is in particular an electric pump, preferably a membrane pump, optionally centrifugal. The pump 94 has a power of between 5 kW and 10 kW, in particular 7.5 kW for the simultaneous cleaning of seventy-eight exchangers 10.

The hydraulic circuit 38 is fluidly connected to a supply 100 of a rinsing fluid and to a supply 102 of a drying fluid, through two respective supply valves 104.

The rinsing fluid is for example water, in particular running water at a standard dispensing pressure, and the drying fluid is for example compressed air.

The hydraulic circuit 38 comprises a three-way inlet valve 106, arranged to select the fluid entering the pipe 90 and the exchangers 10 and a three-way outlet valve 108, arranged to select a destination for the fluid leaving the pipe 90 and exchangers 10.

The inlet valve 106 is in particular arranged to take a configuration from a cleaning configuration, in which it places the pump 94 and the reservoir 92 of internal flushing fluid in communication with the piping 90 and a flushing / drying configuration, in which it communicates the piping 90 with the supplies 100, 102 of rinsing fluid and drying fluid.

The outlet valve 108 is in particular arranged to take a configuration from a recirculation configuration, in which it returns the fluid at the outlet to the reservoir 92, and an evacuation configuration, in which it returns the fluid to an outlet 110 opening out through example to a wastewater treatment plant.

The fluid flowing in the pipe 90 is thus selected from the internal cleaning fluid, the rinsing fluid and the drying fluid by switching the inlet 106 and outlet 108 and supply valves 104.

The hydraulic circuit 38 further comprises valves 112 for reversing the direction of circulation of the fluid, arranged to reverse the direction of travel of the fluid through the piping 90 and the exchangers 10.

Advantageously, the hydraulic circuit 38 includes a relief valve 114, capable of opening in the event of overpressure to evacuate part of the fluid in a safety tank.

Advantageously, the hydraulic circuit 38 also includes a flow sensor 116 arranged to measure a flow rate of the internal cleaning fluid through the exchangers 10.

According to an advantageous embodiment, the cleaning system 30 comprises an automated control module (not shown), comprising at least one processor and a memory.

The control module is adapted to receive the information from the monitoring probe 44 of the level of the tank 34 and control the filling 40 and emptying valves 42 of the tank 34 as a function of the level.

The control module is also suitable for controlling the ultrasonic transducers of the ramps 48.

The control module is also suitable for controlling the level and pH of the internal cleaning fluid in the reservoir 92, and for emptying and renewing the internal cleaning fluid when the pH of the latter exceeds a predetermined threshold value, for example when the pH exceeds 2.

The control module is also adapted to control the inlet 106, outlet 108 and reversal 112 direction of flow valves, to implement cleaning, rinsing and drying cycles of the exchangers 10.

A method of cleaning a plurality of exchangers 10, implementing the cleaning system 30 described above, will now be described.

The method comprises a preliminary step of setting up the exchangers 10 to be cleaned on the locations 56, and putting the internal space of each exchanger 10 into communication with the circulation ports 62.

Each exchanger 10 is placed opposite an ultrasonic transducer.

The method then comprises a step of fixing each exchanger 10 to the location 56 by means of the fixing members 60 associated with the location, by adjusting the height of the screws 74 until the end 86 of each screw 74 is in abutment against the exchanger 10.

The method then comprises a step of closing the cover 38 and filling the tank 34 with the external cleaning fluid, then starting the ultrasonic transducers.

The method then comprises an external cleaning of the exchangers 10, under the effect of ultrasound and of the external cleaning fluid.

The method simultaneously comprises a step of passing the inlet valve 106 in the cleaning configuration and the outlet valve 108 in the recirculation configuration, starting the pump 94, and circulating the internal cleaning fluid in the internal space of the exchangers 10.

During the internal cleaning fluid circulation step, the direction of circulation of said internal cleaning fluid is regularly reversed by actuation of the reversing valves 112.

The method then comprises an internal cleaning of the exchangers 10 under the effect of the internal cleaning fluid and ultrasound.

The method then includes a step of recovering the internal cleaning fluid. The ultrasonic transducers are stopped. The inlet valve 106 has switched to the rinse / drying configuration and the supply valve 102 for drying fluid is open. The outlet valve 108 remains in the recirculation configuration. The drying fluid expels the internal cleaning fluid contained in the internal space of the exchangers 10 towards the reservoir 92.

The method then comprises a rinsing step, during which the inlet valve 106 remains in the rinsing / drying configuration, the supply valve 102 in drying fluid is closed and the supply valve 100 in rinsing fluid is open. The outlet valve 108 has changed to the exhaust configuration. The rinsing fluid flows through the exchangers 10 and rinses their internal space, then is sent to the outlet 110 for further treatment.

Advantageously, the direction of circulation of the rinsing fluid is regularly reversed during the rinsing step, by actuation of the reversing valves 112.

The method then comprises a drying step, in which the supply valve 100 for rinsing fluid is closed and the supply valve 102 for drying fluid open. The drying fluid flows through the internal space of the exchangers 10 and dries it, then is sent to the outlet 110 and into the atmosphere.

The method finally comprises a step of emptying the external cleaning fluid contained in the tank 34, opening the cover 38 and removing the cleaned exchangers 10.

If the state of one or more exchangers 10 is unsatisfactory after a cleaning cycle, the exchanger (s) 10 are replaced in the cleaning system 30 for a new cycle.

The cleaning system 30 and the cleaning method described above allow the cleaning of a large number of exchangers 10 simultaneously, both internally and externally, and in a reduced duration, of the order of 2.5 hours, through the combination of soaking cleaning, fluid circulation cleaning, and ultrasonic cleaning.

In particular, the use of ultrasound makes it possible to more effectively clean the magnetite sludge which is otherwise difficult to remove.

The reduction in duration of the cleaning cycle allows greater efficiency, and reduces the delay in the event of a heat exchanger 10 being returned for a new cleaning cycle.

In addition, the reduction in the duration of exposure of the exchanger 10 to the internal cleaning fluid reduces the likelihood of corrosion attacks and increases the lifetime.

The cleaning system 30 is also adaptable to many types of exchangers 10, since the width / of the locations 56 is adjustable and the contact between the circulation ports 62 and the orifices 14 is made by pressing on an O-ring 88, regardless of the geometry of the orifice 14.

Claims (10)

1. -Cleaning system (30) of a plurality of heat exchangers (10), the cleaning system (30) comprising: - A tank (34) capable of containing an external cleaning fluid for the exchangers (10), the tank (34) defining a plurality of locations (56) for receiving one of the exchangers (10), each location (56) comprising at least one fixing member (60) of the exchanger (10) on the location (56) and circulation ports (62) arranged to communicate fluidly with an internal space of the exchanger (10) received on the 'location (56); - a hydraulic circuit (36) fluidly connecting the circulation ports (62) of the locations (56) to each other; - a pump (94) fluidly connected to the hydraulic circuit (36), capable of circulating an internal cleaning fluid through the hydraulic circuit (36) and the exchangers (10) received by the locations (56); and - at least one transducer (48) disposed in the tank (34), capable of emitting ultrasound, the at least one transducer (48) being arranged opposite at least one of the locations (56). 2. - cleaning system (30) according to claim 1, wherein the internal cleaning fluid comprises an acid, in particular phosphoric acid. 3. - cleaning system (30) according to claim 2, comprising a reservoir (92) of acid supplying the pump (94), as well as a probe (98) for controlling the acidity of the contents of the reservoir (92 ). 4. - cleaning system (30) according to any one of claims 1 to 3, wherein the locations (56) are arranged in lines (64) parallel to each other, the fixing members (60) being shared between the locations (56) of two neighboring lines (64). 5. - cleaning system (30) according to claim 4, wherein the circulation ports (62) and the fixing members (60) are mounted on support bars (46) movable in translation in a transverse direction (Y -Y ') orthogonal to the lines (64) of locations (56), so that the width (/) of the locations (56) of each line (64) is adjustable. 6. - Cleaning system (30) according to any one of claims 1 to 5, in which the fixing members (60) are flanges mounted on rods (70) fixed to the tank (34). 7. - cleaning system (30) according to any one of claims 1 to 6, wherein the hydraulic circuit (36) comprises at least two valves (112) arranged to modify a direction of circulation of the internal cleaning fluid through the hydraulic circuit (36) and the exchangers (10). 8. - cleaning system (30) according to any one of claims 1 to 7, in which the hydraulic circuit (36) comprises at least one inlet valve (106) capable of selecting a fluid circulating in the hydraulic circuit ( 36), among the internal cleaning fluid, a rinsing fluid and a drying fluid. 9. - cleaning system (30) according to any one of claims 1 to 8, in which the tank (34) has a length of between 1.5 m and 2 m and a width of between 1 m and 1.5 m, the tank (34) defining at least fifty locations (56). 10. - Method for cleaning a plurality of heat exchangers (10), the method implementing a cleaning system (30) according to any one of claims 1 to 9, the method comprising the following steps: - Installation of at least one exchanger (10) to be cleaned on one of the locations (56), and communication of the internal space of each exchanger (10) with the circulation ports (62); - fixing of each exchanger (10) on the location (56) by means of each corresponding fixing member (60); - filling the tank (34) with the external cleaning fluid; - circulation of the internal cleaning fluid in the internal space of each exchanger (10); - simultaneously with the circulation of the internal cleaning fluid, emission of ultrasound by the transducers (48) in the direction of the exchangers (10); and - emptying of the tank (34) and removal of the exchangers (10).