Waste heat recovery system for ethylene device

Abstract

The utility model relates to the technical field of ethylene devices, and discloses a waste heat recovery system for an ethylene device, which comprises a first heat exchanger, a second heat exchanger, a process water sewage unit, a desalted water unit and a circulating water unit, the process water sewage unit comprises a sewage input pipe, a first sewage conveying pipe, a second sewage conveying pipe and a sewage discharge pipe; the desalted water unit comprises a desalted water input pipe, a desalted water conveying pipe, a deaerator, a desalted water discharge pipe and a steam input pipe; the circulating water unit comprises a circulating water input pipe and a circulating water output pipe; according to the waste heat recovery system for the ethylene device, through the first heat exchanger, the second heat exchanger, the sewage input pipe, the first sewage conveying pipe, the second sewage conveying pipe, the sewage discharge pipe, the desalted water input pipe and the desalted water conveying pipe, heat of process water sewage can be used for heating desalted water; the use amount of circulating water and the use amount of steam are reduced, and the energy consumption of an ethylene device is reduced.

Description

TECHNICAL FIELD

[0001] The utility model relates to ethylene device technical field especially relates to a waste heat recovery system for ethylene device. BACKGROUND

[0002] In the ethylene device, the produced sewage is mainly the process water sewage of dilution steam generation tower, and the sewage discharge amount is about 12% of the steam generation amount of the dilution steam generation tower. The temperature before cooling is 165-172 DEG C, in order to reduce the discharge temperature of the process water sewage to below 60 DEG C, the existing ethylene device directly uses the circulating water to cool the process water sewage and then discharges the process water sewage. This method cannot recycle the heat of the process water sewage, and increases the energy consumption of the ethylene device. SUMMARY

[0003] The utility model provides a waste heat recovery system for ethylene device, which can reduce the energy consumption of the ethylene device.

[0004] In order to realize the above-mentioned purpose, the utility model provides a waste heat recovery system for ethylene device, including first heat exchanger, second heat exchanger, process water sewage unit, desalted water unit and circulating water unit, the process water sewage unit includes sewage input pipe, first sewage delivery pipe, second sewage delivery pipe and sewage discharge pipe, the outlet end of sewage input pipe is linked with first heat exchanger, the import end of first sewage delivery pipe is linked with sewage input pipe, the outlet end of first sewage delivery pipe is linked with second heat exchanger, the import end of second sewage delivery pipe is linked with first heat exchanger, the outlet end of second sewage delivery pipe is linked with first sewage delivery pipe, the desalted water unit includes desalted water input pipe, desalted water delivery pipe, deaerator, desalted water discharge pipe and steam input pipe, the outlet end of desalted water input pipe is linked with first heat exchanger, the import end of desalted water delivery pipe is linked with first heat exchanger, the outlet end of desalted water delivery pipe is linked with deaerator, the import end of desalted water discharge pipe is linked with deaerator, the outlet end of steam input pipe is linked with deaerator, the circulating water unit includes circulating water input pipe and circulating water output pipe, the outlet end of circulating water input pipe is linked with second heat exchanger, and the import end of circulating water output pipe is linked with second heat exchanger.

[0005] In some embodiments, the waste heat recovery system for ethylene plant further comprises a third heat exchanger and a quench water unit; the process water sewage unit further comprises a third sewage conveying pipe and a fourth sewage conveying pipe, the inlet end of the third sewage conveying pipe is connected with the second sewage conveying pipe, the outlet end of the third sewage conveying pipe is connected with the third heat exchanger, the inlet end of the fourth sewage conveying pipe is connected with the third heat exchanger, the outlet end of the fourth sewage conveying pipe is connected with the second sewage conveying pipe, and the outlet end of the fourth sewage conveying pipe is located between the inlet end of the third sewage conveying pipe and the outlet end of the second sewage conveying pipe; the quench water unit comprises a quench water input pipe and a quench water output pipe, the outlet end of the quench water input pipe is connected with the third heat exchanger, and the inlet end of the quench water output pipe is connected with the third heat exchanger.

[0006] In some embodiments, the waste heat recovery system for ethylene plant further comprises an air preheating unit, the air preheating unit comprises an air preheater, an air input pipe and an air output pipe, the outlet end of the air input pipe is connected with the air preheater, and the inlet end of the air output pipe is connected with the air preheater; the process water sewage unit further comprises a fifth sewage conveying pipe and a sixth sewage conveying pipe, the inlet end of the fifth sewage conveying pipe is connected with the first sewage conveying pipe, and the inlet end of the fifth sewage conveying pipe is located between the outlet end of the second sewage conveying pipe and the outlet end of the first sewage conveying pipe, the outlet end of the fifth sewage conveying pipe is connected with the air preheater, the inlet end of the sixth sewage conveying pipe is connected with the air preheater, the outlet end of the sixth sewage conveying pipe is connected with the first sewage conveying pipe, and the outlet end of the sixth sewage conveying pipe is located between the inlet end of the fifth sewage conveying pipe and the outlet end of the first sewage conveying pipe.

[0007] In some embodiments, the process water sewage unit further comprises a sewage bypass pipe, the inlet end of the sewage bypass pipe is connected with the sewage input pipe, the inlet end of the sewage bypass pipe is located between the inlet end of the first sewage conveying pipe and the outlet end of the sewage input pipe, the outlet end of the sewage bypass pipe is connected with the second sewage conveying pipe, and a first bypass valve is installed on the sewage bypass pipe; a first feeding valve is installed on the sewage input pipe, and the first feeding valve is located between the inlet end of the sewage bypass pipe and the first heat exchanger.

[0008] In some embodiments, a second feeding valve is installed on the third sewage conveying pipe, and a first control valve is installed on the fourth sewage conveying pipe.

[0009] In some embodiments, a second bypass valve is installed on the second sewage conveying pipe, and the second bypass valve is located between the inlet end of the third sewage conveying pipe and the outlet end of the fourth sewage conveying pipe.

[0010] In some embodiments, the desalted water unit further comprises a desalted water bypass pipe, an inlet end of the desalted water bypass pipe is in communication with the desalted water input pipe, an outlet end of the desalted water bypass pipe is in communication with the desalted water conveying pipe, and a third bypass valve is installed on the desalted water bypass pipe; a second control valve is installed on the desalted water input pipe, and the second control valve is located between the inlet end of the desalted water bypass pipe and the first heat exchanger; and a third control valve is installed on the desalted water conveying pipe, and the third control valve is located between the outlet end of the desalted water bypass pipe and the first heat exchanger.

[0011] In some embodiments, a fourth control valve is installed on the first sewage conveying pipe, and the fourth control valve is located between the inlet end of the first sewage conveying pipe and the outlet end of the second sewage conveying pipe.

[0012] In some embodiments, a third feed valve is installed on the fifth sewage conveying pipe.

[0013] In some embodiments, a fourth bypass valve is installed on the first sewage conveying pipe, and the fourth bypass valve is located between the inlet end of the fifth sewage conveying pipe and the outlet end of the sixth sewage conveying pipe.

[0014] Compared with the prior art, the waste heat recovery system for the ethylene device has the beneficial effects that: the process water sewage generated by the dilution steam generation tower can be sent into the first heat exchanger through the sewage input pipe and the desalted water in the pipe network can be sent into the first heat exchanger through the desalted water input pipe, the process water sewage and the desalted water are heat-exchanged in the first heat exchanger, so that the temperature of the desalted water is increased and the temperature of the process water sewage is reduced, and the heat of the process water sewage is recycled; the process water sewage after the heat exchange in the first heat exchanger is sent to the first sewage conveying pipe through the second sewage conveying pipe and is sent into the second heat exchanger through the first sewage conveying pipe, the circulating water is sent into the second heat exchanger through the circulating water input pipe, the circulating water and the process water sewage are heat-exchanged in the second heat exchanger, and the temperature of the process water sewage is reduced to below the first preset temperature, since the temperature of the process water sewage is reduced in the first heat exchanger, the use amount of the circulating water required to reduce the temperature of the process water sewage to below the first preset temperature in the second heat exchanger is reduced; the process water sewage after the heat exchange in the second heat exchanger is discharged to outside the ethylene device through the sewage discharge pipe; the desalted water after the heat exchange in the first heat exchanger is sent to the deaerator through the desalted water conveying pipe, the steam is sent into the deaerator through the steam input pipe, and the temperature of the desalted water is heated to the second preset temperature, since the temperature of the desalted water is increased in the first heat exchanger, the use amount of the steam required to increase the temperature of the desalted water to the second preset temperature in the deaerator is reduced, and the energy consumption is reduced; the desalted water after the deaeration and temperature increase in the deaerator is sent to the boiler feed water pipe network through the desalted water discharge pipe; therefore, the waste heat recovery system for the ethylene device provided by the utility model can heat the desalted water by the heat of the process water sewage through the first heat exchanger, the sewage input pipe, the first sewage conveying pipe, the second sewage conveying pipe, the desalted water input pipe and the desalted water conveying pipe, the heat of the process water sewage is recycled, and thus the use amount of the circulating water and the use amount of the steam can be reduced, and the energy consumption of the ethylene device is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a structure schematic view of a waste heat recovery system for an ethylene device provided by an embodiment of the utility model;

[0016] Figure 2 is a connection schematic view of a process water sewage unit and a desalted water unit provided by an embodiment of the utility model;

[0017] Figure 3 is a connection schematic view of a process water sewage unit and a quenching water unit provided by an embodiment of the utility model;

[0018] Figure 4 is a connection schematic view of a process water sewage unit and an air preheating unit provided by an embodiment of the utility model.

[0019] In the drawing, 1, first heat exchanger;

[0020] 2. a second heat exchanger;

[0021] 3. a process water sewage unit; 31, a sewage input pipe; 32, a first sewage delivery pipe; 33, a second sewage delivery pipe; 34, a sewage discharge pipe; 35, a third sewage delivery pipe; 36, a fourth sewage delivery pipe; 37, a fifth sewage delivery pipe; 38, a sixth sewage delivery pipe; 39, a sewage bypass pipe; 311, a first feed valve; 321, a fourth bypass valve; 322, a fourth control valve; 331, a second bypass valve; 351, a second feed valve; 361, a first control valve; 371, a third feed valve; 391, a first bypass valve;

[0022] 4. a desalination water unit; 41, a desalination water input pipe; 42, a desalination water delivery pipe; 43, a deaerator; 44, a desalination water discharge pipe; 45, a steam input pipe; 46, a desalination water bypass pipe; 411, a second control valve; 421, a third control valve; 461, a third bypass valve;

[0023] 5. a circulating water unit; 51, a circulating water input pipe; 52, a circulating water output pipe;

[0024] 6. a third heat exchanger;

[0025] 7. a quench water unit; 71, a quench water input pipe; 72, a quench water output pipe;

[0026] 8. an air preheating unit; 81, an air preheater; 82, an air input pipe; 83, an air output pipe. DETAILED DESCRIPTION

[0027] The specific embodiments of the present application will be further described in conjunction with the drawings and examples. The following examples are used to illustrate the present application, but not to limit the scope of the present application.

[0028] In the description of the present application, it is to be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0029] The terms "first", "second", "third", "fourth", "fifth", "sixth", "seventh" and "eighth" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or a specific number of the technical features indicated.

[0030] In the present application, unless specifically defined otherwise and limited, the terms "mounting", "connecting", "connecting", "fixing" and the like should be broadly understood, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0031] In the present application, unless specifically defined otherwise and limited, the first feature is "on" or "under" the second feature, which can include direct contact between the first and second features, or indirect contact between the first and second features through another feature therebetween. Moreover, the first feature "on", "above" and "above" the second feature includes the first feature directly above and obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "below" and "below" the second feature includes the first feature directly below and obliquely below the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

[0032] As shown in Figures 1-4 The utility model discloses an ethylene device waste heat recovery system, including first heat exchanger 1, second heat exchanger 2, process water sewage unit 3, desalted water unit 4 and circulating water unit 5.

[0033] The process water sewage unit includes a sewage input pipe 31, a first sewage delivery pipe 32, a second sewage delivery pipe 33 and a sewage discharge pipe 34. The outlet end of the sewage input pipe 31 is connected to the first heat exchanger 1. The inlet end of the first sewage delivery pipe 32 is connected to the sewage input pipe 31. The outlet end of the first sewage delivery pipe 32 is connected to the second heat exchanger 2. The inlet end of the second sewage delivery pipe 33 is connected to the first heat exchanger 1. The outlet end of the second sewage delivery pipe 33 is connected to the first sewage delivery pipe 32.

[0034] The desalinated water unit 4 comprises a desalinated water input pipe 41, a desalinated water delivery pipe 42, an oxygen remover 43, a desalinated water discharge pipe 44 and a steam input pipe 45, the outlet end of the desalinated water input pipe 41 is connected with the first heat exchanger 1, the inlet end of the desalinated water delivery pipe 42 is connected with the first heat exchanger 1, the outlet end of the desalinated water delivery pipe 42 is connected with the oxygen remover 43, the inlet end of the desalinated water discharge pipe 44 is connected with the oxygen remover 43, and the outlet end of the steam input pipe 45 is connected with the oxygen remover 43.

[0035] The circulating water unit 5 comprises a circulating water input pipe 51 and a circulating water output pipe 52, the outlet end of the circulating water input pipe 51 is connected with the second heat exchanger 2, and the inlet end of the circulating water output pipe 52 is connected with the second heat exchanger 2.

[0036] Based on the technical scheme, the process water sewage generated by the dilution steam generation tower can be sent into the first heat exchanger 1 through the sewage input pipe 31, and the desalted water in the pipe network can be sent into the first heat exchanger 1 through the desalted water input pipe 41, the process water sewage and the desalted water are heat-exchanged in the first heat exchanger 1, so that the temperature of the desalted water is increased and the temperature of the process water sewage is decreased, and the heat of the process water sewage is recycled; the process water sewage after heat exchange in the first heat exchanger 1 is sent to the first sewage conveying pipe 32 through the second sewage conveying pipe 33 and is sent into the second heat exchanger 2 through the first sewage conveying pipe 32, the circulating water is sent into the second heat exchanger 2 through the circulating water input pipe 51, the circulating water and the process water sewage are heat-exchanged in the second heat exchanger 2, and the temperature of the process water sewage is decreased to below the first preset temperature, and since the temperature of the process water sewage is decreased in the first heat exchanger 1, the use amount of the circulating water required for decreasing the temperature of the process water sewage to below the first preset temperature in the second heat exchanger 2 can be reduced; the process water sewage after heat exchange in the second heat exchanger 2 is discharged to outside the ethylene device through the sewage discharge pipe 34; the desalted water after heat exchange in the first heat exchanger 1 is sent to the deaerator 43 through the desalted water conveying pipe 42, the steam is sent into the deaerator 43 through the steam input pipe 45, and the temperature of the desalted water is increased to the second preset temperature, and since the temperature of the desalted water is increased in the first heat exchanger 1, the use amount of the steam required for increasing the temperature of the desalted water to the second preset temperature in the deaerator 43 can be reduced, and the energy consumption is reduced; the desalted water after deaeration and temperature increase in the deaerator 43 is sent to the boiler feed water pipe network through the desalted water discharge pipe 44; therefore, the waste heat recovery system for the ethylene device provided by the utility model can utilize the heat of the process water sewage to heat the desalted water, recycle the heat of the process water sewage, and thus the use amount of the circulating water and the use amount of the steam can be reduced, and the energy consumption of the ethylene device is reduced.

[0037] It should be noted that, in the accompanying drawings, Figures 1-4 The arrow represents the flow direction of the fluid in the pipeline, and the end where the arrow is located is the outlet end of the pipeline. The other end of the pipeline opposite to the outlet end is the inlet end of the pipeline.

[0038] In the embodiment, the first preset temperature is 60℃.

[0039] The second preset temperature is 115℃.

[0040] The desalted water in the deaerator 43 needs to be heated from 75 DEG C to 115 DEG C, and the temperature of the desalted water can be raised from 75 DEG C to above 95 DEG C by the process water sewage in the first heat exchanger 1, therefore, the waste heat of the process water sewage can be used to heat the desalted water before the desalted water enters the deaerator 43, the steam usage in the deaerator 43 is reduced, and the energy consumption of the ethylene device is reduced.

[0041] In the embodiment, the first heat exchanger 1 is a shell-and-tube heat exchanger, the tube side of the shell-and-tube heat exchanger is the desalted water from the desalted water unit, and the shell side of the shell-and-tube heat exchanger is the process water sewage from the process water sewage unit.

[0042] Referring to Figures 1-3 The waste heat recovery system for the ethylene device provided in the embodiment of the utility model further includes a third heat exchanger 6 and a quenching water unit 7.

[0043] The process water sewage unit 3 further includes a third sewage conveying pipe 35 and a fourth sewage conveying pipe 36, the inlet end of the third sewage conveying pipe 35 is communicated with the second sewage conveying pipe 33, the outlet end of the third sewage conveying pipe 35 is communicated with the third heat exchanger 6, the inlet end of the fourth sewage conveying pipe 36 is communicated with the third heat exchanger 6, the outlet end of the fourth sewage conveying pipe 36 is communicated with the second sewage conveying pipe 33, and the outlet end of the fourth sewage conveying pipe 36 is located between the inlet end of the third sewage conveying pipe 35 and the outlet end of the second sewage conveying pipe 33.

[0044] The quenching water unit 7 includes a quenching water input pipe 71 and a quenching water output pipe 72, the outlet end of the quenching water input pipe 71 is communicated with the third heat exchanger 6, and the inlet end of the quenching water output pipe 72 is communicated with the third heat exchanger 6.

[0045] The quenching water in the pipe network is sent into the third heat exchanger 6 through the quenching water input pipe 71, and the quenching water that is heated in the third heat exchanger 6 is sent into the pipe network through the quenching water output pipe 72.

[0046] The process water sewage unit 3 further includes a sewage bypass pipe 39, the inlet end of the sewage bypass pipe 39 is communicated with the sewage input pipe 31, the inlet end of the sewage bypass pipe 39 is located between the inlet end of the first sewage conveying pipe 32 and the outlet end of the sewage input pipe 31, the outlet end of the sewage bypass pipe 39 is communicated with the second sewage conveying pipe 33, and the first bypass valve 391 is installed on the sewage bypass pipe 39.

[0047] The first feed valve 311 is installed on the sewage input pipe 31 and is located between the inlet end of the sewage bypass pipe 39 and the first heat exchanger 1. The worker can determine whether to deliver the process water sewage to the first heat exchanger 1 to heat the desalted water by opening or closing the first feed valve 311, and can also determine whether to deliver the process water sewage in the sewage input pipe 31 to the second sewage delivery pipe 33 by opening or closing the first bypass valve 391. At the same time, since the circulating water unit 5 is retained, the circulating water unit 5 can adjust the use amount of circulating water according to the heat exchange condition of the process water sewage in the first heat exchanger 1 to ensure that the temperature of the process water sewage discharged by the sewage discharge pipe 34 is below the first preset temperature, so that closing the first feed valve 311 will not adversely affect the cooling of the process water sewage. The worker can change the flow loop of the process water sewage by opening or closing the first bypass valve 391, which is flexible in use. When the first heat exchanger 1 needs to be maintained, the worker can isolate the first heat exchanger 1 from the process water sewage flow loop by closing the first feed valve 311 and opening the first bypass valve 391, which is convenient for maintenance.

[0048] The second feed valve 351 is installed on the third sewage delivery pipe 35. The worker can determine whether to deliver the process water sewage to the third heat exchanger 6 to heat the quenching water by opening or closing the second feed valve 351, which is flexible in use.

[0049] The first control valve 361 is installed on the fourth sewage delivery pipe 36.

[0050] The second bypass valve 331 is installed on the second sewage delivery pipe 33 and is located between the inlet end of the third sewage delivery pipe 35 and the outlet end of the fourth sewage delivery pipe 36. The worker can change the flow loop of the process water sewage by opening or closing the second bypass valve 331, which is flexible in use. When the third heat exchanger 6 needs to be maintained, the worker can isolate the third heat exchanger 6 from the process water sewage flow loop by closing the second feed valve 351 and the first control valve 361 and opening the second bypass valve 331, which is convenient for maintenance.

[0051] The desalted water unit 4 further comprises a desalted water bypass pipe 46, an inlet end of the desalted water bypass pipe 46 being communicated with the desalted water input pipe 41, an outlet end of the desalted water bypass pipe 46 being communicated with the desalted water delivery pipe 42, and a third bypass valve 461 being installed on the desalted water bypass pipe 46. A second control valve 411 is installed on the desalted water input pipe 41 and located between the inlet end of the desalted water bypass pipe 46 and the first heat exchanger 1; and a third control valve 421 is installed on the desalted water delivery pipe 42 and located between the outlet end of the desalted water bypass pipe 46 and the first heat exchanger 1. In this way, when the second control valve 411 and the third control valve 421 are closed, the first heat exchanger 1 can be isolated from the process water sewage flow loop, facilitating the maintenance of the first heat exchanger 1, and meanwhile the third bypass valve 461 can be opened to ensure that the desalted water can flow into the deaerator 43, so that the closing of the second control valve 411 and the third control valve 421 will not adversely affect the temperature rise of the desalted water in the deaerator 43.

[0052] Referring to Figure 1 and Figure 4 The waste heat recovery system for the ethylene device further comprises an air preheating unit 8, which comprises an air preheater 81, an air input pipe 82 and an air output pipe 83. An outlet end of the air input pipe 82 is communicated with the air preheater 81, and an inlet end of the air output pipe 83 is communicated with the air preheater 81.

[0053] The process water sewage unit 3 further comprises a fifth sewage delivery pipe 37 and a sixth sewage delivery pipe 38. An inlet end of the fifth sewage delivery pipe 37 is communicated with the first sewage delivery pipe 32, and the inlet end of the fifth sewage delivery pipe 37 is located between an outlet end of the second sewage delivery pipe 33 and an outlet end of the first sewage delivery pipe 32. An outlet end of the fifth sewage delivery pipe 37 is communicated with the air preheater 81. An inlet end of the sixth sewage delivery pipe 38 is communicated with the air preheater 81, and an outlet end of the sixth sewage delivery pipe 38 is communicated with the first sewage delivery pipe 32 and located between the inlet end of the fifth sewage delivery pipe 37 and the outlet end of the first sewage delivery pipe. By using the air preheating unit 8, the fifth sewage delivery pipe 37 and the sixth sewage delivery pipe 38, the process water sewage can be heat-exchanged with air in the air preheater 81 to increase the temperature of the air and reduce the temperature of the process water sewage, so as to further recover and utilize the heat of the process water sewage and help to further reduce the energy consumption of the ethylene device.

[0054] The air in the environment is sent into the air preheater 81 through the air input pipe 82, and the air whose temperature is raised in the air preheater 81 is delivered to the furnace chamber of the cracking furnace through the air output pipe 83.

[0055] The process water sewage can be sent to the first heat exchanger 1, the third heat exchanger 6 and the air preheater 81 in sequence through the sewage input pipe 31, the first sewage conveying pipe 32, the second sewage conveying pipe 33, the third sewage conveying pipe 35, the fourth sewage conveying pipe 36, the fifth sewage conveying pipe 37 and the sixth sewage conveying pipe 38, the heat of the process water sewage can be recovered step by step, the temperature of the desalted water before the deaerator 43 can be increased from 75℃ to not more than 100℃, the temperature of the quenching water can be increased from 80℃ to 82℃, and the air entering the furnace of the cracking furnace can be preheated from room temperature to 50-80℃, the temperature of the process water sewage before heat exchange with the circulating water can be reduced to below 60℃, the steam usage of the deaerator 43 and the air preheater 81 can be reduced, the heat of the process water sewage is recovered, the heat required outside the ethylene plant is reduced, the usage of the circulating water of the ethylene plant is reduced, and the energy consumption of the ethylene plant is reduced.

[0056] The third feeding valve 371 is installed on the fifth sewage conveying pipe 37. The worker can determine whether to send the process water sewage to the air preheater 81 to heat the air by opening or closing the third feeding valve 371.

[0057] The fourth bypass valve 321 is installed on the first sewage conveying pipe 32, and is located between the inlet end of the fifth sewage conveying pipe 37 and the outlet end of the sixth sewage conveying pipe 38. The worker can change the flow loop of the process water sewage by opening or closing the fourth bypass valve 321, the usage is flexible, and when the air preheater 81 needs to be maintained, the worker can isolate the air preheater 81 from the flow loop of the process water sewage by closing the third feeding valve 371 and opening the fourth bypass valve 321, so as to facilitate the maintenance of the air preheater 81.

[0058] The fourth control valve 322 is installed on the first sewage conveying pipe 32, and is located between the inlet end of the first sewage conveying pipe 32 and the outlet end of the second sewage conveying pipe 33. The worker can determine whether to send the process water sewage to the air preheater unit 8 through the first sewage conveying pipe 32 by opening or closing the fourth control valve 322.

[0059] The waste heat recovery system for the ethylene device provided by the embodiment of the utility model can make the staff decide to cut one or more of the first heat exchanger 1, the third heat exchanger 6 and the air preheater 81 into the process water sewage flow loop or cut one or more of the first heat exchanger 1, the third heat exchanger 6 and the air preheater 81 from the process water flow loop according to the needs, that is, the staff can decide whether to use one or more of the process water sewage to heat the desalted water, the quenching water and the air, and the use is flexible.

[0060] The heat source and the heat sink of the desalted water unit 4, the circulating water unit 5, the quenching water unit 7 and the air preheating unit 8 are all original of the ethylene device, and the applicability to each ethylene device is strong, the investment is small and the modification is easy.

[0061] The above is only the preferred embodiment of the utility model, and it should be pointed out that, for the ordinary skilled in the art, without departing from the technical principles of the utility model, a number of improvements and substitutions can be made, and these improvements and substitutions should also be considered as the protection range of the utility model.

Claims

1. A waste heat recovery system for an ethylene plant, characterized in that, include: First heat exchanger; Second heat exchanger; The process water and wastewater unit includes a wastewater inlet pipe, a first wastewater conveying pipe, a second wastewater conveying pipe, and a wastewater discharge pipe. The outlet end of the wastewater inlet pipe is connected to the first heat exchanger, the inlet end of the first wastewater conveying pipe is connected to the wastewater inlet pipe, the outlet end of the first wastewater conveying pipe is connected to the second heat exchanger, the inlet end of the second wastewater conveying pipe is connected to the first heat exchanger, and the outlet end of the second wastewater conveying pipe is connected to the first wastewater conveying pipe. The demineralized water unit includes a demineralized water inlet pipe, a demineralized water delivery pipe, a deaerator, a demineralized water outlet pipe, and a steam inlet pipe. The outlet end of the demineralized water inlet pipe is connected to the first heat exchanger, the inlet end of the demineralized water delivery pipe is connected to the first heat exchanger, the outlet end of the demineralized water delivery pipe is connected to the deaerator, the inlet end of the demineralized water outlet pipe is connected to the deaerator, and the outlet end of the steam inlet pipe is connected to the deaerator. A circulating water unit, comprising a circulating water inlet pipe and a circulating water outlet pipe, wherein the outlet end of the circulating water inlet pipe is connected to the second heat exchanger, and the inlet end of the circulating water outlet pipe is connected to the second heat exchanger.

2. The waste heat recovery system for an ethylene plant according to claim 1, characterized in that, It also includes a third heat exchanger and a quench water unit; The process water and wastewater unit also includes a third wastewater conveying pipe and a fourth wastewater conveying pipe. The inlet end of the third wastewater conveying pipe is connected to the second wastewater conveying pipe, and the outlet end of the third wastewater conveying pipe is connected to the third heat exchanger. The inlet end of the fourth wastewater conveying pipe is connected to the third heat exchanger, and the outlet end of the fourth wastewater conveying pipe is connected to the second wastewater conveying pipe. The outlet end of the fourth wastewater conveying pipe is located between the inlet end of the third wastewater conveying pipe and the outlet end of the second wastewater conveying pipe. The quench water unit includes a quench water inlet pipe and a quench water outlet pipe. The outlet end of the quench water inlet pipe is connected to the third heat exchanger, and the inlet end of the quench water outlet pipe is connected to the third heat exchanger.

3. The waste heat recovery system for an ethylene plant according to claim 1 or claim 2, characterized in that, It also includes an air preheating unit, which includes an air preheater, an air inlet pipe and an air outlet pipe. The outlet end of the air inlet pipe is connected to the air preheater, and the inlet end of the air outlet pipe is connected to the air preheater. The process water and wastewater unit further includes a fifth wastewater conveying pipe and a sixth wastewater conveying pipe. The inlet end of the fifth wastewater conveying pipe is connected to the first wastewater conveying pipe, and the inlet end of the fifth wastewater conveying pipe is located between the outlet end of the second wastewater conveying pipe and the outlet end of the first wastewater conveying pipe. The outlet end of the fifth wastewater conveying pipe is connected to the air preheater. The inlet end of the sixth wastewater conveying pipe is connected to the air preheater, and the outlet end of the sixth wastewater conveying pipe is connected to the first wastewater conveying pipe, and the outlet end of the sixth wastewater conveying pipe is located between the inlet end of the fifth wastewater conveying pipe and the outlet end of the first wastewater conveying pipe.

4. The waste heat recovery system for an ethylene plant according to claim 3, characterized in that, The process water and wastewater unit also includes a wastewater bypass pipe. The inlet end of the wastewater bypass pipe is connected to the wastewater input pipe. The inlet end of the wastewater bypass pipe is located between the inlet end of the first wastewater conveying pipe and the outlet end of the wastewater input pipe. The outlet end of the wastewater bypass pipe is connected to the second wastewater conveying pipe. A first bypass valve is installed on the wastewater bypass pipe. A first feed valve is installed on the sewage input pipe, and the first feed valve is located between the inlet end of the sewage bypass pipe and the first heat exchanger.

5. The waste heat recovery system for an ethylene plant according to claim 3, characterized in that, A second feed valve is installed on the third sewage conveying pipe, and a first control valve is installed on the fourth sewage conveying pipe.

6. The waste heat recovery system for an ethylene plant according to claim 5, characterized in that, A second bypass valve is installed on the second sewage conveying pipe, and the second bypass valve is located between the inlet end of the third sewage conveying pipe and the outlet end of the fourth sewage conveying pipe.

7. The waste heat recovery system for an ethylene plant according to claim 6, characterized in that, The demineralized water unit also includes a demineralized water bypass pipe, the inlet end of which is connected to the demineralized water input pipe, the outlet end of which is connected to the demineralized water delivery pipe, and a third bypass valve is installed on the demineralized water bypass pipe. A second control valve is installed on the demineralized water input pipe, and the second control valve is located between the inlet end of the demineralized water bypass pipe and the first heat exchanger. A third control valve is installed on the demineralized water delivery pipe, and the third control valve is located between the outlet end of the demineralized water bypass pipe and the first heat exchanger.

8. The waste heat recovery system for an ethylene plant according to claim 3, characterized in that, A fourth control valve is installed on the first sewage conveying pipe, and the fourth control valve is located between the inlet end of the first sewage conveying pipe and the outlet end of the second sewage conveying pipe.

9. The waste heat recovery system for an ethylene plant according to claim 3, characterized in that, A third feed valve is installed on the fifth sewage conveying pipe.

10. The waste heat recovery system for an ethylene plant according to claim 9, characterized in that, A fourth bypass valve is installed on the first sewage conveying pipe, and the fourth bypass valve is located between the inlet end of the fifth sewage conveying pipe and the outlet end of the sixth sewage conveying pipe.

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