Arrangement for heat recovery from process exhaust air

Abstract

Arrangement (1) for heat recovery from process exhaust air, comprising at least one heat exchanger (12) through which the process exhaust air flows, with a plurality of hollow profiles (121) through which a medium to be heated flows, which are spaced apart from each other by intermediate spaces (122), characterized in that a cleaning device (11) is assigned to the intermediate spaces (122), which comprises at least one nozzle bar (112) that can be pressurized with a cleaning fluid, which has a plurality of spray nozzles (113) for spraying the cleaning fluid into the intermediate spaces (122) and is movable in such a way that all intermediate spaces (122) between the hollow profiles (121) can be sprayed with the cleaning fluid.

Description

[0001] The invention relates to an arrangement for heat recovery from process exhaust air, comprising at least one heat exchanger through which the process exhaust air flows, with a plurality of hollow profiles through which a medium to be heated flows, and which are spaced apart from one another by intermediate spaces.

[0002] Energy-intensive industrial production processes often generate exhaust air that is contaminated with particles of varying fraction sizes (fibers, dust, oil droplets, aerosols) and volatile substances. The temperature and humidity of this exhaust air often represent a significant potential energy loss. For sustainability and cost-efficiency, it is desirable to harness this energy potential through heat recovery. Examples of applications include textile finishing processes on treadles, such as heat treatment, wet finishing, and coating, which often involve contaminated exhaust air at temperatures ranging from 120°C to 220°C.

[0003] Heat recovery from contaminated process exhaust air is achieved via heat exchangers – either air-to-air, particularly using cross-flow heat exchangers, or air-to-liquid medium such as water, especially using finned tube heat exchangers. The medium to be heated is passed through a multitude of hollow profiles, such as tubes or fins, with gaps between the profiles through which the process exhaust air flows. The walls of the hollow profiles thus facilitate separation of the substances and simultaneously enable heat transfer. For efficient operation, the heat exchangers require a large contact surface with the process exhaust air, i.e., sufficiently narrow gaps between the profiles / fins through which the process exhaust air flows. The problem is that the contamination of the process exhaust air, particularly particles and condensate, precipitates in the heat exchangers. The high exhaust air temperatures typically lead to...This process dries and allows the soiling to encrustle / crackle. The heat exchangers develop a coating on the surface of the hollow profiles, becoming clogged and thus blocking the exhaust airflow and heat transfer. The heat exchangers then typically have to be removed and cleaned or replaced. This is time-consuming and causes downtime, which seems to require improvement.

[0004] The object of the present invention is to propose an arrangement for heat recovery from process exhaust air that overcomes the disadvantages of the prior art.

[0005] To solve the problem posed, the invention proposes the design of an arrangement according to the features of claim 1.

[0006] Advantageous embodiments and further developments of the invention are the subject of the dependent claims.

[0007] The inventive proposal provides an arrangement for heat recovery from process exhaust air, which is designed such that a cleaning device is assigned to the spaces between the hollow profiles of the heat exchanger, which comprises at least one nozzle bar that can be pressurized with a cleaning fluid, which has a plurality of spray nozzles for spraying the cleaning fluid into the spaces and is movable in such a way that all spaces between the hollow profiles can be sprayed with the cleaning fluid.

[0008] According to the invention, it is thus possible to periodically or as needed clean the spaces between the hollow profiles, and consequently the surfaces of the hollow profiles defining these spaces, with the sprayed cleaning fluid in order to remove particles and contaminants that have precipitated from the process exhaust air and settled on the hollow profiles. In this way, labor-intensive replacement and cleaning measures on the hollow profiles of the heat exchangers are minimized, and downtime is avoided.

[0009] According to one proposal of the invention, the at least one nozzle bar is designed to rotate or pivot about its longitudinal axis, i.e., to move back and forth by a predetermined angle, in order to reach all the spaces of the associated heat exchanger and to spray the cleaning fluid onto it.

[0010] Alternatively, the nozzle bar can be moved linearly across the gaps, preferably perpendicular to the flow direction of the process exhaust air, to reach all gaps of the heat exchanger equally. This movement can be achieved, for example, by a chain or spindle drive, or by means of a hydraulically or pneumatically driven piston actuator.

[0011] According to another suggestion of the invention, the nozzle bars of the cleaning device are arranged in front of or behind the heat exchanger when viewed in the direction of flow of the process exhaust air through the heat exchanger.

[0012] Another aspect of the invention provides that each heat exchanger is arranged in a heat exchanger housing and the associated cleaning device in a cleaning housing, both of which are modular or stackable like building blocks and through which the process exhaust air flows. The arrangement according to the invention can thus be configured by stacking the desired number of heat exchanger housings and associated cleaning housings to suit the specific system configuration. Such a modular arrangement according to the invention can also include a process exhaust air inlet module and a process exhaust air outlet module, between which the heat exchangers and cleaning devices are arranged in corresponding modules. The process exhaust air inlet module and the process exhaust air outlet module serve to supply and expel the process exhaust air, respectively.Discharge of the process exhaust air into the modularly assembled heat exchangers and cleaning devices, whereby the flow direction of the process exhaust air may be redirected.

[0013] According to a further aspect of the invention, the cleaning fluid is heated to an elevated temperature to improve its cleaning effect. Typically, the cleaning fluid is water, to which, according to another aspect of the invention, a dirt-dissolving cleaning agent is automatically added via a dosing device, either manually or preferably automatically. The dosing of the cleaning agent can be achieved, for example, by a dosing pump or a proportional dosing system. Heating the fluid to, for example, 80 °C further enhances the cleaning effect, and the pressure at which the cleaning fluid is sprayed from the nozzle bar can also be adjusted to the specific situation.

[0014] The invention provides that the cleaning device comprises a tank for the cleaning fluid, a heating device, and a conveying device for conveying the cleaning fluid, heated in the heating device, to the at least one nozzle bar. These aforementioned devices can be adjusted by a person skilled in the art to apply the temperature and pressure settings described above.

[0015] The heating system can, for example, include electric heating elements or a steam inlet to heat the cleaning fluid to the desired temperature. The pumping system can, for example, consist of an electrically driven pump with valve-controlled pressure lines leading to at least one nozzle bar.

[0016] According to a further aspect of the invention, the cleaning fluid sprayed into the spaces of the at least one heat exchanger is collected, purified, and reused. For this purpose, a collection and filter device for the sprayed cleaning fluid is provided, from which the cleaning fluid can be returned to the tank. The cleaning fluid therefore circulates in the arrangement according to the invention.

[0017] Since, according to the invention, the cleaning fluid dissolves and removes contaminants from the heat exchangers, the contaminants are transported into the tank along with the cleaning fluid. Filters upstream of the conveying device prevent the recirculation of larger solids within the cleaning system. Furthermore, the used cleaning fluid must be replaced as needed and subjected to appropriate wastewater treatment.

[0018] According to a further aspect of the invention, the cleaning device can be activated by a control unit that operates based on sensor data for the relative air pressure within the arrangement. The cleaning of the arrangement according to the invention is therefore preferably carried out automatically via a parameterization control, via a network interface, or also by manual triggering, whereby the temperature and duration of the cleaning, i.e., the spraying of the cleaning fluid, as well as the control of the valves and dosing systems can be adjusted as required. By monitoring the relative air pressure at various points in the arrangement according to the invention, the degree of soiling of the heat exchangers can be monitored and the cleaning requirement can be reported to the control unit.

[0019] Since the arrangement according to the invention can be assembled in a modular fashion, the existing heat exchangers can comprise any combination of single or multiple heat exchangers arranged in series, and can be either air-to-air or air-to-water heat exchangers in any combination and sequence. According to the invention, a cleaning device can be assigned to each of these heat exchangers.

[0020] According to a further proposal of the invention, the arrangement according to the invention can also be extended by an electrostatic particle separator downstream in the flow direction of the process exhaust air, by means of which particles carried in the process exhaust air can be electrostatically separated in a manner known per se.

[0021] The heat recovery provided in the arrangement according to the invention first cools the hot process exhaust air, which has a beneficial effect on the efficiency of the downstream electrostatic particle separation. The electrostatic particle separator can also be equipped with a cleaning system similar to that described in the arrangement according to the invention, in order to clean the electrostatic particle separator periodically or as needed from contaminants.

[0022] Further embodiments and details of the invention are explained below with reference to the drawings illustrating the exemplary embodiments. These show: Fig. 1 in schematic representation a first embodiment of the invention; Fig. 2 in schematic representation a second embodiment of the invention; Fig. 3 in schematic representation a third embodiment of the invention; Fig. 4 a nozzle bar according to the invention in further details.

[0023] From the Fig. Figure 1 shows a schematic side view of a first embodiment of the arrangement 1 according to the invention for heat recovery from process exhaust air. The process exhaust air can be generated, for example, in textile finishing, such as during heat treatment. The arrangement 1 used for heat recovery from the warm process exhaust air comprises several vertically stacked and interconnected modular units, with a process exhaust air inlet module 10 with a housing 100 as the uppermost unit. A cleaning device 11 with a modular housing 111 is connected to the underside of this unit, followed vertically below by a heat exchanger 12 with a modular housing 120, and finally, a process exhaust air outlet module 13 with a modular housing 130 as the lower termination.

[0024] All the aforementioned functional units or modules 10, 11, 12, 13 are stacked on top of each other and connected to one another, whereby a process exhaust air stream supplied from the top in the manner to be described below is enabled to flow vertically downwards from the process exhaust air inlet module 10 through the cleaning device 11, the heat exchanger 12 and the process exhaust air outlet module 13, i.e. the corresponding housing sides of the successive modules 10, 11, 12 and 13 are open to each other and communicate with each other.

[0025] The warm process exhaust air is fed to the arrangement 1 via a pipe system (not shown) according to arrow P1 and enters the process exhaust air inlet module 10 via a connection nozzle with inlet opening 101, for example, arranged laterally, and is deflected vertically downwards by 90° within the process exhaust air inlet module 10.

[0026] The process exhaust air then enters the heat exchanger 12 via the cleaning device 11, which is open to both the process exhaust air inlet module 10 and the subsequent heat exchanger 12. The heat exchanger 12 has a plurality of hollow profiles 121, for example heat exchanger plates or fins arranged parallel to each other, for the purpose of heat transfer. Spaces 122 remain between these profiles, through which the process exhaust air flows on its way through the arrangement 1.

[0027] In the illustrated embodiment according to Fig. 1 The heat exchanger 12 is designed as an air / air heat exchanger and the additional airflow serving as the heat exchange medium enters the heat exchanger 12 via lateral supply and exhaust air openings according to arrow W1 and exits the heat exchanger 12 as a heated airflow according to arrow W2.

[0028] The process exhaust air, cooled in this way in the heat exchanger 12, then flows on its further path through the arrangement 1 into the process exhaust air outlet module 13, is deflected there again by 90° and leaves the arrangement 1 according to arrow P2 via the outlet opening 134.

[0029] The air heated in the heat exchanger 12, for example fresh air supplied according to arrow W1 and discharged according to arrow W2, can then be fed into the production process to achieve energy savings there.

[0030] To ensure a high efficiency, the heat exchanger 12 has a large number of hollow profiles 121 with correspondingly large contact surfaces to the process exhaust air, i.e. the individual hollow profiles 121 are separated from each other only by small gaps 122.

[0031] Since the process exhaust air not only has an elevated and usable temperature, but also carries particles and condensates, these precipitate on the hollow profiles 121 of the heat exchanger 12 and dry there, forming crusts or cracks on the surface due to the high temperatures of the process exhaust air. The resulting deposit impedes both the passage of the process exhaust air and the heat transfer within the heat exchanger 12.

[0032] To address this problem, the cleaning device 11 is arranged upstream of the heat exchanger 12 in the direction of flow of the process exhaust air, as further details are also provided in the Fig. 4 is evident.

[0033] The cleaning device 11 comprises a housing 111 that is modularly compatible with the other components of the arrangement 1 and has at least one nozzle bar 112 extending horizontally within the cleaning device 11 along a longitudinal axis, which is led out of the housing 111 on one side and ends in a connection nozzle 110 to which a pipeline (not shown) for a cleaning fluid can be connected.

[0034] Furthermore, the nozzle bar 112 is in its Fig. The orientation shown in 4 is designed to rotate or pivot back and forth around its longitudinal axis M according to arrow A, which can be achieved via a corresponding swivel drive.

[0035] The nozzle bar 112 has a plurality of spray nozzles 113 communicating with an internal cavity within the nozzle bar 112, through which the cleaning fluid supplied at the connection port 110 and introduced into the nozzle bar 112 can be sprayed evenly. The spray nozzles 113 are arranged along the nozzle bar 112 such that each is aligned with a space 122 between adjacent hollow profiles 121 of the heat exchanger 12 connected to the cleaning device 11. If required, several such nozzle bars 112 can also be arranged parallel to each other, e.g., one behind the other in the plane of the drawing, to ensure that all spaces 122 between the hollow profiles can be sprayed evenly and sufficiently with the cleaning fluid.

[0036] For example, as soon as an air pressure measurement inside the arrangement 1 detects a pressure drop in the supplied process exhaust air, indicating contamination of the surfaces of the hollow profiles 121 of the heat exchanger 12, a pump (not shown) is activated to deliver a cleaning fluid, which is stored in a tank and heated to a suitable temperature by a heating device. This fluid could, for example, be water with a dosed cleaning agent. The pump delivers the cleaning fluid to the nozzle bar 112, which then sprays the cleaning fluid into the spaces 122 of the heat exchanger 12 to clean the surfaces of the hollow profiles 121 of the adhering contaminants.

[0037] Similarly, the cleaning process can be scheduled for specific time intervals or at specific times, or it can be initiated manually.

[0038] The cleaning fluid, sprayed vertically downwards through the heat exchanger 12, ultimately enters the process exhaust air outlet module 13, which is equipped with a collection device 131 and a collection tray 132 for the cleaning fluid. From there, the cleaning fluid is conveyed back into the tank (not shown) via the drain 133, thus circulating through the arrangement 1. Contaminants carried out of the cleaning fluid can be removed from the tank by means of appropriate filter devices.

[0039] Instead of the one in the Fig. The arrangement shown in Figure 1 with only one heat exchanger 12 and associated cleaning device 11 positioned upstream in the flow direction can be the arrangement according to the invention as shown in Figure 1. Fig. 2. For example, two successive heat exchangers 12 may also have, which are modularly stacked on top of each other, between the upper process exhaust air inlet module 10 and the lower process exhaust air outlet module 13, with an associated cleaning device 11 arranged upstream of each heat exchanger 12. The further design of the cleaning device 11 and its function are not explained again below to avoid repetition; this corresponds to the descriptions in the exemplary embodiment according to [reference to relevant section]. Fig. 1.

[0040] For the heat exchangers 12 according to Fig. 2. In contrast to the air / air heat exchanger 12, according to Fig. 1 also include air / water heat exchangers, whose heat exchange medium is supplied in liquid form as stream W10 and discharged as W20 and is guided through the hollow profiles 121 or fins separated from each other by means of spaces 122, without coming into contact with the process exhaust air.

[0041] Finally, according to the exemplary embodiment of the Fig. 3. A combination of a first heat exchanger 12 viewed in the direction of flow as an air / air heat exchanger and a downstream air / water heat exchanger 12 may also be provided; these heat exchangers with different media can be combined as desired and arranged in any order.

[0042] The cleaning devices 11, which in the exemplary embodiments are always located upstream of the respective heat exchanger 12, can also be arranged downstream of the respective heat exchanger 12 when viewed in the direction of flow, so that they then spray the cleaning fluid vertically from bottom to top instead of vertically from top to bottom. Reference symbol list: 1. Arrangement 10 Process exhaust air inlet module 11 Cleaning device 12 heat exchangers 13 Process exhaust air outlet module 100 cases 101 Entrance 110 connection spigots 111 Housings 112 nozzle bars 113 spray nozzles 120 cases 121 Hollow profile 122 space 130 cases 131 Containment device 132 Drip tray 133 Drain 134 Exit opening A Direction of rotation M Longitudinal axis P1 Process exhaust air inlet P2 Process exhaust air outlet W1 Heat exchanger medium inlet W2 Heat exchanger medium outlet W10 Heat exchanger medium inlet W20 Heat exchanger medium outlet

Claims

[1] Arrangement (1) for heat recovery from process exhaust air, comprising at least one heat exchanger (12) through which the process exhaust air flows, with a plurality of hollow profiles (121) through which a medium to be heated flows, which are spaced apart from each other by spaces (122), characterized by , that a cleaning device (11) is associated with the spaces (122) which comprises at least one nozzle bar (112) that can be pressurized with a cleaning fluid, which has a plurality of spray nozzles (113) for spraying the cleaning fluid into the spaces (122) and is movable in such a way that all spaces (122) between the hollow profiles (121) can be sprayed with the cleaning fluid. [2] Arrangement (1) according to claim 1, characterized by , that the at least one nozzle bar (112) is designed to rotate or pivot about its longitudinal axis (M) or to be linearly movable. [3] Arrangement (1) according to claim 1 or 2, characterized by , that, viewed in the direction of flow of the process exhaust air, the cleaning device (11) is arranged in front of or behind the heat exchanger (12). [4] Arrangement (1) according to any one of claims 1 to 3, characterized by , that each heat exchanger (12) is arranged in a heat exchanger housing (120) and the associated cleaning device (11) is arranged in a cleaning housing (111), which can each be placed on top of each other in a modular fashion and can be jointly supplied with process exhaust air. [5] Arrangement (1) according to claim 4, characterized by , that it has a process exhaust air inlet module (10) and a process exhaust air outlet module (13), between which the heat exchangers (12) and cleaning devices (11) are arranged in corresponding modules. [6] Arrangement (1) according to any one of claims 1 to 5, characterized by, that the cleaning device (11) comprises a tank for the cleaning fluid, a heating device and a delivery pump for conveying the cleaning fluid tempered in the heating device to the at least one nozzle bar. [7] Arrangement (1) according to claim 6, characterized by that a collection and filtering device is provided for the sprayed cleaning fluid, from which the cleaning fluid can be returned to the tank. [8] Arrangement (1) according to any one of claims 1 to 7, characterized by , that the cleaning device (11) can be activated by a control device and that the activation can be effected depending on sensor data for the relative air pressure within the arrangement (1) or manually. [9] Arrangement (1) according to any one of claims 1 to 8, characterized by , that at least one air / air heat exchanger and / or at least one air / water heat exchanger is provided as a heat exchanger (12). [10] Arrangement (1) according to any one of claims 1 to 9, characterized by , that an electrostatic particle separator is provided downstream of the arrangement (1) in the direction of flow of the process exhaust air for the electrostatic separation of particles carried in the process exhaust air.

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