Waste heat recovery system applied to propane dehydrogenation unit

Abstract

This invention relates to the field of chemical production technology, specifically to a waste heat recovery system for a propane dehydrogenation unit. The system includes a flash tank heat exchanger, which is installed between the feed pipe of the wastewater stripping tower and the steam condensate pipe of the boiler water blowdown flash tank. The flash tank heat exchanger utilizes the heat of the steam condensate flowing from the boiler water blowdown flash tank to heat the feed to the wastewater stripping tower. The tube side of the flash tank heat exchanger is used for the flow of the wastewater stripping tower feed, while the shell side is used for the flow of steam condensate. Thus, by recovering the waste heat within the propane dehydrogenation unit—specifically, the heat of the steam condensate from the boiler water blowdown flash tank—to heat the wastewater stripping tower feed, the steam consumption of the wastewater stripping tower is reduced, improving the overall energy efficiency and economy of the propane dehydrogenation unit.

Description

Technical Field

[0001] This invention relates to the field of chemical production technology, and specifically to a waste heat recovery system applied to a propane dehydrogenation unit. Background Technology

[0002] In existing technologies, the wastewater stripping tower in propane dehydrogenation units typically uses low-pressure steam to heat the feed to separate hydrocarbon components. However, this consumes a large amount of steam and requires additional cooling of the bottom of the tower with circulating water, further increasing energy consumption and costs. Therefore, there is an urgent need for an efficient and low-cost waste heat recovery method to reduce the steam consumption of the wastewater stripping tower and improve the system's energy efficiency. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a waste heat recovery system for propane dehydrogenation units, so as to overcome the problems of high energy consumption and serious waste in the current use of wastewater stripping towers in propane dehydrogenation units.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] This application provides a waste heat recovery system for a propane dehydrogenation unit, including: a flash tank heat exchanger;

[0006] The flash tank heat exchanger is located between the feed pipe of the wastewater stripping tower of the propane dehydrogenation unit and the steam condensate pipe of the boiler water blowdown flash tank.

[0007] The flash tank heat exchanger is used to heat the feed of the wastewater stripping tower by utilizing the heat of the steam condensate flowing out of the boiler water blowdown flash tank.

[0008] The tube side of the flash tank heat exchanger is used for the feed of the wastewater stripping tower, and the shell side of the flash tank heat exchanger is used for the steam condensate.

[0009] Furthermore, in some embodiments of this application, the flash tank heat exchanger is provided with a feed inlet, a discharge outlet, a heat source inlet, and a heat source outlet;

[0010] The feed inlet is connected to the first pipe position of the feed pipeline of the wastewater stripping tower, and the discharge outlet is connected to the second pipe position of the feed pipeline of the wastewater stripping tower. The first pipe position is located after the feed flow meter and before the feed control valve on the feed pipeline of the wastewater stripping tower, and close to the feed flow meter. The second pipe position is located after the feed flow meter and before the feed control valve on the feed pipeline of the wastewater stripping tower, and close to the feed control valve.

[0011] The feed control valve is installed on the feed pipe at the feed inlet of the wastewater stripping tower, and the feed flow meter is installed on the feed pipe on the side of the feed control valve away from the feed inlet of the wastewater stripping tower. The side of the feed pipe closest to the feed inlet of the wastewater stripping tower is after the feed flow meter, and the side of the feed control valve away from the feed inlet of the wastewater stripping tower is before the feed control valve. A valve is installed between the first and second pipe positions on the feed pipe of the wastewater stripping tower.

[0012] The heat source inlet is connected to the first steam condensate outlet of the boiler water blowdown flash tank via a pipeline, and the heat source outlet is connected to the second steam condensate outlet of the boiler water blowdown flash tank via a pipeline.

[0013] Furthermore, in some embodiments of this application, a wastewater stripping tower heat exchanger module is also included;

[0014] The wastewater stripping tower heat exchanger module includes a first heat exchanger and a second heat exchanger.

[0015] Both the first heat exchanger and the second heat exchanger module are provided with a feed inlet, a discharge outlet, a heat source inlet, and a heat source outlet;

[0016] Wherein, the outlet of the first heat exchanger is connected to the inlet of the second heat exchanger, and the heat source inlet of the first heat exchanger is connected to the heat source outlet of the second heat exchanger.

[0017] The heat source inlet of the second heat exchanger is connected to the outlet of the wastewater stripping tower via a pipeline, and the heat source outlet of the first heat exchanger is connected to the discharge collection device of the wastewater stripping tower via a pipeline.

[0018] The inlet of the first heat exchanger is connected to the third pipe of the feed pipeline of the wastewater stripping tower, and the outlet of the second heat exchanger is connected to the fourth pipe of the feed pipeline of the wastewater stripping tower. The third pipe is located before and close to the feed flow meter on the feed pipeline of the wastewater stripping tower. The fourth pipe is located before the feed flow meter on the feed pipeline of the wastewater stripping tower and away from the feed control valve.

[0019] Furthermore, in some embodiments of this application, the second steam condensate outlet of the boiler water blowdown flash tank is connected to a condensate recovery device through a first pipe, and a manual valve is provided on the first pipe.

[0020] Furthermore, in some embodiments of this application, a second pipe is also provided, with both ends of the second pipe connected to the first pipe on both sides of the manual valve of the first pipe, and an automatic valve is provided on the second pipe.

[0021] Furthermore, in some embodiments of this application, the heat source outlet of the flash tank heat exchanger is connected to the first pipe via a third pipe before the manual valve of the first pipe; wherein, the first pipe before the manual valve is the end of the first pipe near the second steam condensate outlet of the boiler water blowdown flash tank.

[0022] Furthermore, in some embodiments of this application, a fourth conduit is also included;

[0023] The two ends of the fourth pipeline are respectively connected to the feed control valve on both sides of the feed pipeline of the wastewater stripping tower, and an automatic valve is installed on the fourth pipeline.

[0024] Furthermore, in some embodiments of this application, the feed control valve is a manual valve.

[0025] Furthermore, in some embodiments of this application, the tube-side pressure of the flash tank heat exchanger is ≥2.99 MPaG, and the shell-side pressure is ≤0.6 MPaG.

[0026] Furthermore, in some embodiments of this application, temperature sensors are provided on the pipe connected to the feed end of the first heat exchanger, the pipe connected to the heat source outlet of the first heat exchanger, and the pipe connected to the discharge port of the second heat exchanger.

[0027] This invention relates to the field of chemical production technology, specifically to a waste heat recovery system for a propane dehydrogenation unit. The system includes a flash tank heat exchanger. The flash tank heat exchanger is located between the feed pipe of the wastewater stripping tower in the propane dehydrogenation unit and the steam condensate pipe of the boiler water blowdown flash tank. The flash tank heat exchanger utilizes the heat of the steam condensate flowing from the boiler water blowdown flash tank to heat the feed to the wastewater stripping tower. The tube side of the flash tank heat exchanger is used for the flow of the wastewater stripping tower feed, and the shell side is used for the flow of the steam condensate. Thus, by recovering the waste heat within the propane dehydrogenation unit—specifically the heat of the steam condensate from the boiler water blowdown flash tank—to heat the wastewater stripping tower feed, the steam consumption of the wastewater stripping tower is reduced, improving the overall energy efficiency and economy of the propane dehydrogenation unit. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1This is a schematic diagram of a waste heat recovery system for a propane dehydrogenation unit provided in an embodiment of the present invention.

[0030] Figure 2 This is a schematic diagram of the waste heat recovery system applied to a propane dehydrogenation unit provided in an embodiment of the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0032] Figure 1 This is a schematic diagram of a waste heat recovery system applied to a propane dehydrogenation unit according to an embodiment of the present invention. Please refer to [link / reference]. Figure 1 The waste heat recovery system for a propane dehydrogenation unit provided in this embodiment includes a flash tank heat exchanger.

[0033] Specifically, firstly, in existing propane dehydrogenation units, the feed pipe of the wastewater stripping tower is the same pipe connected to the inlet of the wastewater stripping tower, used to transport the feed (such as hydrocarbon-containing wastewater) to the inlet of the wastewater stripping tower. Similarly, the steam condensate pipe of the boiler water blowdown flash tank is the same pipe connected to the steam condensate outlet of the boiler water blowdown flash tank, used to transport the steam condensate. In the existing technology, there is no actual operational connection between the wastewater stripping tower and the boiler water blowdown flash tank.

[0034] In this application, the flash tank heat exchanger is installed between the feed pipe of the wastewater stripping tower in the propane dehydrogenation unit and the steam condensate pipe of the boiler water blowdown flash tank. Thus, the heat from the steam condensate flowing out of the boiler water blowdown flash tank is used to heat the feed to the wastewater stripping tower through the flash tank heat exchanger, thereby achieving heat recovery.

[0035] Furthermore, in this application, the tube side of the flash tank heat exchanger is used for the flow of feed to the wastewater stripping tower, while the shell side is used for the flow of steam condensate, in order to reduce coking and facilitate cleaning. In some embodiments, the tube-side pressure of the flash tank heat exchanger is ≥2.99 MPaG, and the shell-side pressure is ≤0.6 MPaG.

[0036] The waste heat recovery system for a propane dehydrogenation unit provided in this application involves placing a flash tank heat exchanger between the feed pipe of the wastewater stripping tower and the steam condensate pipe of the boiler water blowdown flash tank. The flash tank heat exchanger utilizes the heat from the steam condensate flowing from the boiler water blowdown flash tank to heat the feed to the wastewater stripping tower. Specifically, the tube side of the flash tank heat exchanger is used for the wastewater stripping tower feed, while the shell side is used for the steam condensate. Thus, by recovering the waste heat within the propane dehydrogenation unit—specifically, the heat from the steam condensate in the boiler water blowdown flash tank—to heat the wastewater stripping tower feed, steam consumption in the wastewater stripping tower is reduced. Simultaneously, the amount of circulating water used for cooling the effluent from the boiler water blowdown flash tank is reduced, improving the overall energy efficiency and economy of the propane dehydrogenation unit.

[0037] Figure 2 This is a schematic diagram of the waste heat recovery system applied to a propane dehydrogenation unit provided in an embodiment of the present invention, as shown below. Figure 2 As shown, in some embodiments of this application, the flash tank heat exchanger ( Figure 2 The flash tank heat exchanger (shown as EA-O) is equipped with a feed inlet, a discharge outlet, a heat source inlet, and a heat source outlet. It can be understood that the feed inlet is the port where the flash tank heat exchanger receives the material that needs to be heated, and the discharge outlet is the port where the flash tank heat exchanger outputs the material that has been heated inside. In this application, the aforementioned material refers to the feed of the wastewater stripping tower, such as hydrocarbon-containing wastewater.

[0038] Similarly, the heat source inlet is the port where the flash tank heat exchanger receives the heat source, and the heat source outlet is the port where the flash tank heat exchanger discharges the heat source. In this application, the aforementioned heat source refers to the steam condensate from the boiler water blowdown flash tank.

[0039] Based on this, the location of the feed inlet of the aforementioned flash tank heat exchanger and the first pipe of the feed pipeline of the wastewater stripping tower ( Figure 2 The outlet is connected to the second pipe position of the feed pipe of the wastewater stripping tower (position A in the diagram). Figure 2 (Position B in the diagram) is connected; wherein, the first pipeline position is located at the feed flow meter on the feed pipeline of the wastewater stripping tower ( Figure 2 (Shown in FT) after, feed control valve ( Figure 2 The first pipeline is located before and near the feed flow meter of the wastewater stripping tower feed pipeline; the second pipeline is located after the feed flow meter of the wastewater stripping tower feed pipeline, before and near the feed control valve. The heat source inlet is connected to the boiler water blowdown flash tank via a pipeline. Figure 2 The first steam condensate outlet (shown as FA-A in the text) Figure 2 The outlet is connected to the lower left side of the boiler water blowdown flash tank, and the heat source outlet is connected to the second steam condensate outlet of the boiler water blowdown flash tank (i.e., the outlet on the left side of the flash tank). Figure 2Connect the outlet on the right side below the boiler water blowdown flash tank.

[0040] The feed control valve is installed on the feed pipe at the feed inlet of the wastewater stripping tower, and the feed flow meter is installed on the feed pipe on the side of the feed pipe away from the feed inlet of the wastewater stripping tower from the feed control valve. "After the feed flow meter" refers to the side of the feed pipe where the feed flow meter is closest to the feed inlet of the wastewater stripping tower, and "before the feed control valve" refers to the side of the feed pipe where the feed control valve is away from the feed inlet of the wastewater stripping tower; similarly, "before the feed flow meter" refers to the side of the feed pipe where the feed flow meter is away from the feed inlet of the wastewater stripping tower, and "after the feed control valve" refers to the side of the feed pipe where the feed control valve is closest to the feed inlet of the wastewater stripping tower.

[0041] In addition, a valve is installed between the first and second pipe positions on the feed pipeline of the wastewater stripping tower. When the valve is closed, the feed of the wastewater stripping tower can enter the flash tank heat exchanger through the first pipe position, be heated by the flash tank heat exchanger, and then enter the feed pipeline of the wastewater stripping tower through the second pipe position, and finally enter the wastewater stripping tower.

[0042] It should be noted that, since the waste heat recovery system for propane dehydrogenation unit provided in this application is carried out in the original propane dehydrogenation unit, the feed pipe of the wastewater stripping tower mentioned refers to the original feed pipe of the wastewater stripping tower.

[0043] Furthermore, in some embodiments of this application, the waste heat recovery system further includes a wastewater stripping tower heat exchanger module; the wastewater stripping tower heat exchanger module includes a first heat exchanger ( Figure 2 (shown as EA-A) and the second heat exchanger ( Figure 2 (As shown in EA-B). Both the first and second heat exchanger modules are equipped with a feed inlet, a discharge outlet, a heat source inlet, and a heat source outlet. The functions of each port can be understood by referring to the functions of the corresponding ports of the flash tank heat exchanger mentioned above, and will not be repeated here.

[0044] Specifically, the outlet of the first heat exchanger is connected to the inlet of the second heat exchanger, and the heat source inlet of the first heat exchanger is connected to the heat source outlet of the second heat exchanger; the heat source inlet of the second heat exchanger is connected to the outlet of the wastewater stripping tower via a pipeline, and the heat source outlet of the first heat exchanger is connected to the effluent collection device of the wastewater stripping tower via a pipeline; and the location of the third pipeline connecting the inlet of the first heat exchanger to the feed pipeline of the wastewater stripping tower (…). Figure 2 The outlet of the second heat exchanger is connected to the fourth pipe of the feed pipe of the wastewater stripping tower (position C). Figure 2The third pipe is located before and close to the feed flow meter on the feed pipe of the wastewater stripping tower; the fourth pipe is located before the feed flow meter on the feed pipe of the wastewater stripping tower and away from the feed control valve.

[0045] In this way, by using the heat from the high-temperature discharge of the wastewater stripping tower through the first and second heat exchangers to heat the feed to the subsequent wastewater stripping tower, the consumption of heating the feed to the subsequent wastewater stripping tower can be reduced on the one hand, and the consumption of cooling the discharge of the wastewater stripping tower can be reduced on the other hand.

[0046] Furthermore, in some embodiments of this application, to achieve the above-mentioned functions, a level control valve can be installed in the boiler water blowdown flash tank. Figure 2 A three-way branch is installed at the short section before (shown as LV), and the liquid level control valve can be set as a manual valve to control the flow direction of steam condensate.

[0047] Specifically, such as Figure 2 As shown, firstly, the second steam condensate outlet of the boiler water blowdown flash tank is directly connected to the condensate recovery device through the first pipeline. Figure 2 (Seen as FA-B in the diagram), and a manual valve is installed on the first pipe, which is the first passage. Further, a second pipe (i.e., the second passage) is also provided, with both ends of the second pipe connected to the first pipe on either side of the manual valve, and an automatic valve is installed on the second pipe. The heat source outlet of the flash tank heat exchanger is connected to the first pipe via a third pipe before the manual valve of the first pipe, forming a third passage; wherein, before the manual valve of the first pipe is the end of the first pipe near the second steam condensate outlet of the boiler water blowdown flash tank.

[0048] Additionally, a fourth pipeline can be installed, with both ends of the fourth pipeline connected to the feed control valve on both sides of the feed pipeline of the wastewater stripping tower. An automatic valve is installed on the fourth pipeline, while the feed control valve is a manual valve.

[0049] Furthermore, such as Figure 2 As shown, in some embodiments of this application, temperature sensors can also be installed on the pipe connected to the feed end of the first heat exchanger, the pipe connected to the heat source outlet of the first heat exchanger, and the pipe connected to the discharge outlet of the second heat exchanger. Figure 2 (Indicated by TT).

[0050] In practical applications, the feed to the wastewater stripping tower is provided by... Figure 2 The lowest end of the pump ( Figure 2Driven by the pump (shown as GA), the feed enters the feed pipe of the wastewater stripping tower. The temperature of the feed is detected by a temperature sensor at the pump output. When heating of the feed is required (which is generally necessary in practical applications), valves on the feed pipe of the wastewater stripping tower and on the pipe connected to the feed inlet of the first heat exchanger are controlled. This allows the feed to be heated by the first and second heat exchangers and then return to the feed pipe of the wastewater stripping tower (the return location varies; here it specifically refers to reaching the third pipe position on the feed pipe). (The feed is placed near the location of the wastewater stripper). The temperature is then detected by a temperature sensor. If further heating is required, the valve between the first and second feed pipe positions is closed (and the first steam condensate outlet of the boiler water blowdown flash tank is opened). This allows the wastewater stripper feed, heated by the heat exchanger module, to be heated again by the flash tank heat exchanger, and finally return to the wastewater stripper feed pipe via the first pipe position. The feed is then controlled by a feed control valve to enter the wastewater stripper through a pipe equipped with a feed control valve or a parallel pipe equipped with an automatic valve. Additionally, the wastewater stripper discharge, after being processed by the first and second heat exchangers, is discharged after temperature detection by a temperature sensor.

[0051] It should be noted that the above workflow is only for describing the working principle of the system. In actual applications, the opening or closing time of each valve can be controlled in advance according to actual needs. After the temperature is detected by the temperature sensor, the opening and closing of each valve can be flexibly adjusted according to the actual working conditions to adapt to different working conditions (such as heating without the wastewater stripping tower heat exchanger module, but only through the steam tank heat exchanger).

[0052] In addition, in practical applications, because the temperature of the steam condensate flowing out of the boiler water blowdown flash tank may be relatively fixed (for example, in some systems, the temperature can generally be stable at around 150℃), the above-mentioned temperature sensor can also be used only for detection and recording, without participating in the relevant control logic. Furthermore, based on the detection results of the temperature sensor, the opening degree of each valve can be flexibly controlled to heat the feed to the target temperature, such as 65℃.

[0053] The waste heat recovery system for a propane dehydrogenation unit provided in this application ensures flexibility in system operation switching by adding a branch pipeline after the feed flow meter and before the feed control valve, and configuring a manual valve. A three-way branch is installed at a short section before the level control valve of the boiler water blowdown flash tank, and the steam condensate flow direction is controlled by a manual valve, enabling dynamic adjustment of the waste heat recovery amount and ensuring stable system operation. Furthermore, the waste heat recovery effect is further improved by incorporating a wastewater stripping tower heat exchanger module. Simultaneously, because it utilizes existing pipelines and equipment for improvement (for example, existing idle equipment in the propane dehydrogenation unit can be used as a flash tank heat exchanger), the modification cost can be significantly reduced.

[0054] It should be noted that in the description of this invention, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means at least two.

[0055] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of the invention pertain.

[0056] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0057] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0058] Furthermore, the functional units in the various embodiments of the present invention can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0059] The storage media mentioned above can be read-only memory, disk, or optical disk, etc.

[0060] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0061] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A waste heat recovery system for a propane dehydrogenation unit, characterized in that, include: Flash tank heat exchanger; The flash tank heat exchanger is located between the feed pipe of the wastewater stripping tower of the propane dehydrogenation unit and the steam condensate pipe of the boiler water blowdown flash tank. The flash tank heat exchanger is used to heat the feed of the wastewater stripping tower by utilizing the heat of the steam condensate flowing out of the boiler water blowdown flash tank. The tube side of the flash tank heat exchanger is used to flow the feed to the wastewater stripping tower, and the shell side of the flash tank heat exchanger is used to flow the steam condensate. The flash tank heat exchanger is equipped with a feed inlet, a discharge outlet, a heat source inlet, and a heat source outlet; The feed inlet is connected to the second pipe of the feed pipeline of the wastewater stripping tower, and the discharge outlet is connected to the first pipe of the feed pipeline of the wastewater stripping tower. The first pipe is located after the feed flow meter and before the feed control valve on the feed pipeline of the wastewater stripping tower, and close to the feed flow meter. The second pipe is located after the feed flow meter and before the feed control valve on the feed pipeline of the wastewater stripping tower, and close to the feed control valve. The feed control valve is installed on the feed pipe at the feed inlet of the wastewater stripping tower, and the feed flow meter is installed on the feed pipe on the side of the feed control valve away from the feed inlet of the wastewater stripping tower. The side of the feed pipe closest to the feed inlet of the wastewater stripping tower is after the feed flow meter, and the side of the feed control valve away from the feed inlet of the wastewater stripping tower is before the feed control valve. A valve is installed between the first and second pipe positions on the feed pipe of the wastewater stripping tower. The heat source inlet is connected to the first steam condensate outlet of the boiler water blowdown flash tank via a pipeline, and the heat source outlet is connected to the second steam condensate outlet of the boiler water blowdown flash tank via a pipeline. It also includes a wastewater stripping tower heat exchanger module; The wastewater stripping tower heat exchanger module includes a first heat exchanger and a second heat exchanger. Both the first heat exchanger and the second heat exchanger module are provided with a feed inlet, a discharge outlet, a heat source inlet, and a heat source outlet; Wherein, the outlet of the first heat exchanger is connected to the inlet of the second heat exchanger, and the heat source inlet of the first heat exchanger is connected to the heat source outlet of the second heat exchanger. The heat source inlet of the second heat exchanger is connected to the outlet of the wastewater stripping tower via a pipeline, and the heat source outlet of the first heat exchanger is connected to the discharge collection device of the wastewater stripping tower via a pipeline. The inlet of the second heat exchanger is connected to the third pipe of the feed pipeline of the wastewater stripping tower, and the outlet of the first heat exchanger is connected to the fourth pipe of the feed pipeline of the wastewater stripping tower. The third pipe is located before and close to the feed flow meter on the feed pipeline of the wastewater stripping tower. The fourth pipe is located before the feed flow meter on the feed pipeline of the wastewater stripping tower and away from the feed control valve. The heat source outlet of the flash tank heat exchanger is connected to the first pipe via a third pipe before the manual valve of the first pipe; wherein, the first pipe is connected to the first pipe at the end of the manual valve near the second steam condensate outlet of the boiler water blowdown flash tank.

2. The waste heat recovery system applied to a propane dehydrogenation unit according to claim 1, characterized in that, The second steam condensate outlet of the boiler water blowdown flash tank is connected to the condensate recovery device via a pipeline, and a manual valve is installed on the pipeline.

3. The waste heat recovery system applied to a propane dehydrogenation unit according to claim 2, characterized in that, A second pipe is also provided, with both ends of the second pipe connected to the first pipe on both sides of the manual valve of the first pipe, and an automatic valve is provided on the second pipe.

4. The waste heat recovery system applied to a propane dehydrogenation unit according to claim 1, characterized in that, It also includes a fifth pipeline; The fifth pipeline has two ends connected to the feed control valve on both sides of the feed pipeline of the wastewater stripping tower, and an automatic valve is installed on the fifth pipeline.

5. The waste heat recovery system applied to a propane dehydrogenation unit according to claim 1, characterized in that, The feed control valve is a manual valve.

6. The waste heat recovery system applied to a propane dehydrogenation unit according to claim 1, characterized in that, The tube-side pressure of the flash tank heat exchanger is ≥2.99 MPaG, and the shell-side pressure is ≤0.6 MPaG.

7. The waste heat recovery system applied to a propane dehydrogenation unit according to claim 1, characterized in that, Temperature sensors are installed on the pipe connected to the feed end of the first heat exchanger, the pipe connected to the heat source outlet of the first heat exchanger, and the pipe connected to the discharge port of the second heat exchanger.

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