A deaerator exhaust steam recovery and drain utilization system

Abstract

This invention provides a deaerator exhaust steam recovery and condensate utilization system, including a front shaft seal assembly, a rear shaft seal assembly, a steam turbine, a condensing assembly, a shaft seal heater assembly, an exhaust steam condensation device, a deaerator, and a pressure equalization box. The front and rear shaft seal assemblies are respectively installed at the steam inlet and outlet ends of the steam turbine. The steam outlet of the front shaft seal assembly is connected to the first inlet of the pressure equalization box, the inlet of the exhaust steam condensation device is connected to the steam outlet of the deaerator, the outlet of the exhaust steam condensation device is connected to the second inlet of the pressure equalization box via a first switching valve, the outlet of the exhaust steam condensation device is also connected to the first steam inlet of the shaft seal heater assembly, and the outlet of the pressure equalization box is connected to the inlet of the rear shaft seal assembly. This invention uses exhaust steam condensate from the deaerator instead of deoxygenated water to reduce the temperature of the high-temperature medium-pressure steam leaking from the front shaft seal assembly, thereby reducing the temperature of the rear shaft seal assembly and achieving a sealing effect. This is beneficial for improving the efficiency of the steam turbine unit, avoiding the use of demineralized water, and reducing costs.

Description

Technical Field

[0001] This invention relates to the field of deaerator heat energy recovery technology, and in particular to a deaerator exhaust steam recovery and condensate utilization system. Background Technology

[0002] Waste incineration is a common method of municipal solid waste treatment in China. In waste-to-energy incineration, the high-temperature flue gas obtained from incinerating waste is usually used to heat feedwater to generate steam.

[0003] In the waste incineration industry, deaerators typically operate at a pressure of 0.27 MPa. During operation, the exhaust steam generated by the deaerator is usually released into the air, affecting the overall appearance of the plant and the recycling of the entire thermal system. Furthermore, during normal operation of the turbine, the steam pressure gradually decreases as it converts thermal energy into mechanical energy. Therefore, the steam pressure in the front shaft seal is higher than the maximum steam pressure, causing the steam to tend to flow towards the air; conversely, the steam pressure in the rear shaft seal is lower than the maximum steam pressure, causing the air to tend to flow towards the rear shaft seal. In traditional waste-to-energy plant turbine designs, the leaking steam (0.15 MPa–0.3 MPa, ~300℃) from the intermediate-temperature, low-pressure shaft seal of the front shaft seal is typically fed into the rear shaft seal. This low-pressure steam seals the shaft seal, preventing air from leaking into the low-pressure cylinder and affecting its efficiency. However, in this process, the intermediate-temperature, low-pressure steam heats the rear bearing, increasing the temperature of the lubricating oil and reducing the overall turbine efficiency. To reduce the temperature of the rear shaft seal and improve turbine efficiency, medium-pressure, low-temperature demineralized water is usually injected for cooling. This process actually results in the loss of demineralized water in waste-to-energy projects. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a deaerator exhaust steam recovery and condensate utilization system that can improve turbine efficiency and reduce the use of demineralized water.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A deaerator exhaust steam recovery and condensate utilization system includes a front shaft seal assembly, a rear shaft seal assembly, a steam turbine, a condenser assembly, a shaft seal heater assembly, an exhaust steam condensation device, a deaerator, and a pressure equalization box.

[0007] The front shaft seal assembly and the rear shaft seal assembly are respectively installed on the steam inlet end and the steam outlet end of the steam turbine. The outlet end is connected to the inlet of the condensing assembly, the outlet of the condensing assembly is connected to the water-side inlet of the shaft seal heater assembly, and the water-side outlet of the shaft seal heater assembly is connected to the water-side inlet of the deaerator.

[0008] The steam outlet of the front shaft seal assembly is connected to the first inlet of the equalizing box and the second steam inlet of the shaft seal heater assembly, respectively. The inlet of the exhaust steam condenser is connected to the steam outlet of the deaerator. The outlet of the exhaust steam condenser is connected to the second inlet of the equalizing box through a first switching valve. The outlet of the exhaust steam condenser is also connected to the first steam inlet of the shaft seal heater assembly. The outlet of the equalizing box is connected to the inlet of the rear shaft seal assembly.

[0009] When the steam turbine is operating normally, the first switching valve is open;

[0010] When the steam turbine is running at low load, the first switching valve is closed.

[0011] In one specific implementation, the deaerator exhaust steam recovery and condensate utilization system further includes a first check valve, a second check valve, and a third check valve;

[0012] The two ends of the first check valve are respectively connected to the steam outlet of the front shaft seal assembly and the first inlet of the equalizing box;

[0013] One end of the second check valve is connected to the outlet of the exhaust steam condenser, and the other end of the second check valve is connected to the first steam inlet of the first switching valve and the shaft seal heater assembly and the inlet of the first switching valve, respectively.

[0014] The two ends of the third check valve are respectively connected to the exhaust steam outlet of the rear shaft seal assembly and the first steam inlet of the shaft seal heater assembly.

[0015] In another specific embodiment, the deaerator exhaust steam recovery and condensate utilization system further includes a second switching valve, a third switching valve, and a fourth switching valve;

[0016] The two ends of the second switching valve are respectively connected to the steam outlet of the front shaft seal assembly and the inlet of the first check valve;

[0017] The two ends of the third switching valve are respectively connected to the first steam inlet of the shaft seal heater assembly and the outlet of the second check valve;

[0018] The two ends of the fourth switching valve are respectively connected to the outlet of the first check valve and the second steam inlet of the shaft seal heater assembly.

[0019] In another specific implementation, the opening degrees of the first switching valve, the second switching valve, the third switching valve, and the fourth switching valve are all adjustable.

[0020] In another specific implementation, the first switching valve, the second switching valve, the third switching valve, and the fourth switching valve are all electrically operated shut-off valves.

[0021] In another specific embodiment, the shaft seal heater assembly includes a first shaft seal heater and a second shaft seal heater;

[0022] The water-side inlet of the first shaft seal heater is connected to the outlet of the condenser assembly, the water-side outlet of the first shaft seal heater is connected to the water-side inlet of the second shaft seal heater, and the water-side outlet of the second shaft seal heater is connected to the water-side inlet of the deaerator.

[0023] The steam inlet of the first shaft seal heater is the first steam inlet of the shaft seal heater assembly, and the steam inlet of the second shaft seal heater is the second steam inlet of the shaft seal heater assembly.

[0024] In another specific embodiment, the shaft seal heater assembly further includes a low-pressure heater;

[0025] The two ends of the low-pressure heater are respectively connected to the water-side outlet of the second shaft seal heater and the water-side inlet of the deaerator.

[0026] In another specific embodiment, the condensing assembly includes a condenser and a condensate pump;

[0027] The inlet of the condenser is connected to the outlet of the steam outlet pipe, the outlet of the condenser is connected to the inlet of the condensate pump, and the outlet of the condensate pump is connected to the water-side inlet of the shaft seal heater assembly.

[0028] In another specific embodiment, the deaerator exhaust steam recovery and condensate utilization system also includes a boiler;

[0029] The boiler inlet is connected to the water-side outlet of the deaerator.

[0030] In another specific embodiment, the deaerator exhaust steam recovery and condensate utilization system further includes a feedwater pump;

[0031] The two ends of the water pump are connected to the inlet of the boiler and the water-side outlet of the deaerator, respectively.

[0032] The various embodiments of the present invention can be combined arbitrarily as needed, and the resulting embodiments are also within the scope of the present invention and are part of the specific implementation of the present invention.

[0033] According to the above technical solution, the deaerator exhaust steam recovery and condensate utilization system provided by the present invention, when the steam turbine is running normally, the first switch valve is opened. At this time, the steam outlet of the front shaft seal assembly is simultaneously connected to the second steam inlet of the equalization box and the shaft seal heater assembly, and the exhaust steam condensation device is simultaneously connected to the first steam inlet of the equalization box and the shaft seal heater assembly. The exhaust steam discharged from the deaerator is condensed into exhaust steam condensate after being condensed by the exhaust steam condensation device. The high-temperature and medium-pressure steam leaking from the front shaft seal assembly and the exhaust steam condensate output by the exhaust steam condensation device enter the equalization box. Due to the expansion effect and the heating by the high-temperature and medium-pressure steam of the front shaft seal assembly, the exhaust steam condensate becomes low-pressure and low-temperature steam. The low-temperature and low-pressure steam enters the rear shaft seal assembly.

[0034] When the turbine is running at low load, the first switch valve is closed, and the steam outlet of the front shaft seal assembly is simultaneously connected to the second steam inlet of the equalization box and the shaft seal heater assembly. The steam from the front shaft seal assembly is simultaneously sent into the equalization box and the shaft seal heater assembly. The exhaust steam drain of the deaerator and the steam from the front shaft seal assembly enter the shaft seal heater assembly to heat the condensate. The steam in the equalization box enters the rear shaft seal assembly.

[0035] This invention controls the opening and closing of the first switching valve according to different operating conditions of the steam turbine, enabling the use of exhaust steam condensate in different scenarios. By using the exhaust steam condensate from the deaerator instead of deoxygenated water to reduce the temperature of the high-temperature medium-pressure steam leaking from the front shaft seal assembly, this invention achieves effective utilization of the exhaust steam condensate from the deaerator, reduces the temperature of the rear shaft seal assembly, and achieves a sealing effect, which is beneficial to improving the efficiency of the steam turbine unit. On the other hand, it avoids the use of demineralized water, thus reducing costs. Attached Figure Description

[0036] 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 embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the deaerator exhaust steam recovery and condensate utilization system provided by the present invention.

[0038] in, Figure 1 middle:

[0039] The system includes: a deaerator exhaust steam recovery and condensate utilization system 100; a deaerator exhaust steam condensation device 113; a front shaft seal assembly 101; a first front shaft seal 101a; a second front shaft seal 101b; a third front shaft seal 101c; a rear shaft seal assembly 102; a first rear shaft seal 102a; a second rear shaft seal 102b; a steam turbine 103; a condensing assembly 104; a shaft seal heater assembly 105; a deaerator 106; a pressure equalization tank 107; a first switching valve 108; a first check valve 109; a second check valve 110; a third check valve 117; a second switching valve 111; a third switching valve 112; a fourth switching valve 118; a first shaft seal heater 105a; a second shaft seal heater 105b; a low-pressure heater 105c; a condenser 104a; a condensate pump 104b; a boiler 114; a feedwater pump 115; and a generator 116. Detailed Implementation

[0040] The following will refer to the appendices in the embodiments of the present invention. Figure 1 The technical solutions in the embodiments of the present invention are clearly and completely described herein. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0041] In the description of this invention, it should be understood that the terms "upper," "lower," "top surface," "bottom surface," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the indicated position or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0042] like Figure 1 As shown, the present invention discloses a deaerator exhaust steam recovery and condensate utilization system 100 to improve the efficiency of the steam turbine 103 and reduce the use of demineralized water.

[0043] The deaerator exhaust steam recovery and condensate utilization system 100 includes a front shaft seal assembly 101, a rear shaft seal assembly 102, a steam turbine 103, a condenser assembly 104, a shaft seal heater assembly 105, a deaerator 106, an equalizing tank 107, and a deaerator exhaust steam condensation device 113.

[0044] The front shaft seal assembly 101 and the rear shaft seal assembly 102 are respectively installed on the steam inlet pipe and the steam outlet pipe of the steam turbine 103. The steam turbine 103 is connected to the generator 116. The inlet of the steam inlet pipe is used to input the main steam. Specifically, the main steam is medium-temperature and medium-pressure steam, medium-temperature and sub-high-pressure steam, or medium-temperature and ultra-high-pressure steam.

[0045] The front axle seal assembly 101 is used to prevent leakage of high-pressure steam from the inlet pipe. For example... Figure 1 As shown, the front axle seal assembly 101 includes a first front axle seal 101a, a second front axle seal 101b, and a third front axle seal 101c, which are arranged sequentially along the steam inlet direction in the steam inlet pipe. It should be noted that the front axle seal assembly 101 including the first front axle seal 101a, the second front axle seal 101b, and the third front axle seal 101c is only one specific embodiment of the present invention. In practical applications, it may also include one, two, four, or more front axle seals.

[0046] The rear axle seal assembly 102 is used to prevent air leakage into the exhaust pipe, specifically, such as... Figure 1 As shown, the rear shaft seal assembly 102 includes a first rear shaft seal 102a and a second rear shaft seal 102b, which are arranged sequentially along the steam discharge direction in the steam outlet pipe. It should be noted that the rear shaft seal assembly 102 including the first rear shaft seal 102a and the second rear shaft seal 102b is only one specific embodiment of the present invention. In practical applications, it may also include one, two, four, or more rear shaft seals.

[0047] The outlet of the steam pipe is connected to the inlet of the condenser assembly 104, the outlet of the condenser assembly 104 is connected to the water-side inlet of the shaft seal heater assembly 105, and the water-side outlet of the shaft seal heater assembly 105 is connected to the water-side inlet of the deaerator 106.

[0048] The steam outlet of the front shaft seal assembly 101 is connected to the first inlet of the equalizing tank 107 and the second steam inlet of the shaft seal heater assembly 105. The inlet of the exhaust steam condenser 113 is connected to the steam outlet of the deaerator 106. The outlet of the exhaust steam condenser 113 is connected to the second inlet of the equalizing tank 107 through the first switching valve 108. The outlet of the exhaust steam condenser 113 is also connected to the first steam inlet of the shaft seal heater assembly 105. The outlet of the equalizing tank 107 is connected to the inlet of the rear shaft seal assembly 102.

[0049] When the turbine 103 is running normally, the first switch valve 108 is opened. The exhaust steam discharged from the deaerator 106 is condensed into exhaust steam condensate after passing through the exhaust steam condensation device 113. The high-temperature and medium-pressure steam leaking from the front shaft seal assembly 101 and the exhaust steam condensate from the deaerator 106 enter the equalization tank 107. Due to the expansion effect and the heating effect of the high-temperature and medium-pressure steam from the front shaft seal assembly 101, the exhaust steam condensate from the deaerator 106 becomes low-pressure and low-temperature steam. The low-temperature and low-pressure steam enters the rear shaft seal assembly 102.

[0050] When the steam turbine 103 is running at low load, the first switching valve 108 is closed, and the steam outlet of the front shaft seal assembly 101 is simultaneously connected to the second steam inlet of the equalization tank 107 and the shaft seal heater assembly 105. The exhaust steam condensate output from the exhaust steam condenser 113 is only connected to the first steam inlet of the shaft seal heater assembly 105. The steam from the front shaft seal assembly 101 is simultaneously fed into the equalization tank 107 and the shaft seal heater assembly 105. The exhaust steam condensate from the deaerator 106 and the steam from the front shaft seal assembly 101 enter the shaft seal heater assembly 105 to heat the condensate. The steam in the equalization tank 107 enters the rear shaft seal assembly 102.

[0051] According to different operating conditions of the steam turbine 103, this invention sets the opening and closing of the first switching valve 108 to realize different uses of the exhaust steam condensate. By using the exhaust steam condensate of the deaerator 106 instead of deaerated water to reduce the temperature of the high-temperature medium-pressure steam leaking from the front shaft seal assembly 101, this invention achieves effective utilization of the exhaust steam condensate of the deaerator 106, prevents air from entering the low-pressure cylinder of the steam turbine 103, reduces the temperature of the low-pressure cylinder bearing lubricating oil, effectively utilizes the heat and pressure of the condensate of the deaerator 106, reduces the loss of demineralized water, and improves the efficiency of the steam turbine 103. On the other hand, it avoids the use of demineralized water, thus reducing costs.

[0052] In some embodiments, the deaerator exhaust steam recovery and condensate utilization system 100 further includes a first check valve 109, a second check valve 110, and a third check valve 117.

[0053] The two ends of the first check valve 109 are connected to the steam outlet of the front shaft seal assembly 101 and the first inlet of the equalizing box 107, respectively.

[0054] One end of the second check valve 110 is connected to the outlet of the exhaust steam condenser 113, and the other end of the second check valve 110 is connected to the first steam inlet of the first switching valve 108 and the shaft seal heater assembly 105, respectively.

[0055] The two ends of the third check valve 117 are respectively connected to the exhaust steam outlet of the rear shaft seal assembly 102 and the first steam inlet of the shaft seal heater assembly 105.

[0056] The first check valve 109, the second check valve 110, and the third check valve 117 are used to prevent water or steam from flowing back.

[0057] Furthermore, the deaerator exhaust steam recovery and condensate utilization system 100 also includes a second switching valve 111, a third switching valve 112, and a fourth switching valve 118.

[0058] The two ends of the second switching valve 111 are respectively connected to the steam outlet of the front shaft seal assembly 101 and the inlet of the first check valve 109; the two ends of the third switching valve 112 are respectively connected to the first steam inlet of the shaft seal heater assembly 105 and the outlet of the second check valve 110; the two ends of the fourth switching valve 118 are respectively connected to the outlet of the first check valve 109 and the second steam inlet of the shaft seal heater assembly 105.

[0059] The second switching valve 111, the third switching valve 112 and the fourth switching valve 118 are designed to facilitate the adjustment of the amount of steam entering the shaft seal heater assembly 105, the amount of exhaust steam condensate entering the equalizing tank 107 and the amount of steam delivered from the front shaft seal assembly 101 to the equalizing tank 107.

[0060] In order to facilitate further adjustment of the amount of steam entering the shaft seal heater assembly 105, the amount of exhaust steam condensate entering the equalizing tank 107, and the amount of steam delivered from the front shaft seal assembly 101 to the equalizing tank 107, so as to achieve the purpose of controlling the steam temperature, the present invention discloses that the opening degree of the first switching valve 108, the second switching valve 111, the third switching valve 112 and the fourth switching valve 118 are all adjustable.

[0061] Furthermore, the present invention discloses that the first switching valve 108, the second switching valve 111, the third switching valve 112 and the fourth switching valve 118 are all electrically operated shut-off valves, which facilitates automatic adjustment of the opening degree of the first switching valve 108, the second switching valve 111, the third switching valve 112 and the fourth switching valve 118.

[0062] In some embodiments, the deaerator exhaust steam recovery and condensate utilization system 100 further includes a deaerator exhaust steam condensation device 113, the inlet of which is connected to the steam outlet of the deaerator 106, and the outlet of which is connected to the inlet of the third switching valve 112.

[0063] The deaerator exhaust steam condensation device 113 is used for condensing the exhaust steam output from the deaerator 106.

[0064] In some embodiments, the shaft seal heater assembly 105 includes a first shaft seal heater 105a and a second shaft seal heater 105b, which are used to recover heat and heat condensate.

[0065] The water-side inlet of the first shaft seal heater 105a is connected to the outlet of the condenser assembly 104, the water-side outlet of the first shaft seal heater 105a is connected to the water-side inlet of the second shaft seal heater 105b, and the water-side outlet of the second shaft seal heater 105b is connected to the water-side inlet of the deaerator 106.

[0066] The steam inlet of the first shaft seal heater 105a is the first steam inlet of the shaft seal heater assembly 105, and the steam inlet of the second shaft seal heater 105b is the second steam inlet of the shaft seal heater assembly 105.

[0067] It should be noted that the shaft seal heater assembly 105 is not limited to including only the first shaft seal heater 105a and the second shaft seal heater 105b. In practical applications, it may also include three or more shaft seal heaters.

[0068] Furthermore, the present invention discloses that the shaft seal heater assembly 105 further includes a low-pressure heater 105c, the two ends of which are respectively connected to the water-side outlet of the second shaft seal heater 105b and the water-side inlet of the deaerator 106.

[0069] The low-pressure heater 105c is used to further heat the condensate.

[0070] In some embodiments, the condensing assembly 104 includes a condenser 104a and a condensate pump 104b. The inlet of the condenser 104a is connected to the outlet of the steam outlet pipe, the outlet of the condenser 104a is connected to the inlet of the condensate pump 104b, and the outlet of the condensate pump 104b is connected to the water-side inlet of the shaft seal heater assembly 105.

[0071] Condenser 104a condenses the exhaust steam (steam without the ability to do work) discharged from turbine 103 and uses circulating water at room temperature as the cooling medium.

[0072] Condensate pump 104b delivers condensate to shaft seal heater assembly 105.

[0073] In some embodiments, the deaerator exhaust steam recovery and condensate utilization system 100 further includes a boiler 114, the inlet of which is connected to the water-side outlet of the deaerator 106. The deaerator 106 delivers deoxygenated condensate to the boiler 114 for supply.

[0074] Furthermore, the present invention discloses that the deaerator exhaust steam recovery and condensate utilization system 100 also includes a feed water pump 115, the two ends of which are respectively connected to the inlet of the boiler 114 and the water-side outlet of the deaerator 106.

[0075] The feedwater pump 115 is used to send condensate into the boiler 114.

[0076] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0077] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and inventive features disclosed herein.

[0078] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," 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, 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.

Claims

1. A deaerator exhaust steam recovery and drain utilization system, characterized by, The front shaft seal assembly, the rear shaft seal assembly, the steam turbine, the condensing assembly, the shaft seal heater assembly, the exhaust steam condensing device, the deaerator and the equalizing tank are connected in series. The front shaft seal assembly and the rear shaft seal assembly are respectively arranged at the steam inlet end and the steam outlet end of the steam turbine, the outlet of the steam outlet end is communicated with the inlet of the condensing assembly, the outlet of the condensing assembly is communicated with the water side inlet of the shaft seal heater assembly, and the water side outlet of the shaft seal heater assembly is communicated with the water side inlet of the deaerator. The steam outlet of the front shaft seal assembly is communicated with the first inlet of the equalizing tank and the second steam inlet of the shaft seal heater assembly, the inlet of the exhaust steam condensing device is communicated with the steam outlet of the deaerator, the outlet of the exhaust steam condensing device is communicated with the second inlet of the equalizing tank through the first switch valve, the outlet of the exhaust steam condensing device is also communicated with the first steam inlet of the shaft seal heater assembly, and the outlet of the equalizing tank is communicated with the inlet of the rear shaft seal assembly. When the steam turbine is normally operated, the first switch valve is opened. When the steam turbine is operated at low load, the first switch valve is closed. The first non-return valve, the second non-return valve and the third non-return valve are further arranged. The two ends of the first non-return valve are respectively communicated with the steam outlet of the front shaft seal assembly and the first inlet of the equalizing tank. One end of the second non-return valve is communicated with the outlet of the exhaust steam condensing device, and the other end of the second non-return valve is respectively communicated with the first switch valve and the first steam inlet of the shaft seal heater assembly. The two ends of the third non-return valve are respectively communicated with the exhaust steam outlet of the rear shaft seal assembly and the first steam inlet of the shaft seal heater assembly.

2. The deaerator exhaust steam recovery and drain utilization system of claim 1, wherein The second switch valve, the third switch valve and the fourth switch valve are further arranged. The two ends of the second switch valve are respectively communicated with the steam outlet of the front shaft seal assembly and the inlet of the first non-return valve. The two ends of the third switch valve are respectively communicated with the first steam inlet of the shaft seal heater assembly and the outlet of the second non-return valve. The two ends of the fourth switch valve are respectively communicated with the outlet of the first non-return valve and the second steam inlet of the shaft seal heater assembly.

3. The deaerator steam recovery and drain utilization system of claim 2, wherein, The opening degrees of the first switch valve, the second switch valve, the third switch valve and the fourth switch valve are adjustable.

4. The deaerator steam recovery and drain utilization system of claim 3, wherein, The first switch valve, the second switch valve, the third switch valve and the fourth switch valve are electrically controlled stop valves.

5. The deaerator steam recovery and drain utilization system of claim 1, wherein, The shaft seal heater assembly comprises a first shaft seal heater and a second shaft seal heater. The water side inlet of the first shaft seal heater is communicated with the outlet of the condensing assembly, the water side outlet of the first shaft seal heater is communicated with the water side inlet of the second shaft seal heater, and the water side outlet of the second shaft seal heater is communicated with the water side inlet of the deaerator. The steam inlet of the first shaft seal heater is the first steam inlet of the shaft seal heater assembly, and the steam inlet of the second shaft seal heater is the second steam inlet of the shaft seal heater assembly.

6. The deaerator steam recovery drain utilization system of claim 5, wherein, The shaft seal heater assembly further comprises a low-pressure heater. The two ends of the low-pressure heater are respectively communicated with the water side outlet of the second shaft seal heater and the water side inlet of the deaerator.

7. The deaerator steam recovery and drain utilization system of claim 1, wherein, The condensing assembly comprises a condenser and a condensate pump. An outlet of the condenser is in communication with an inlet of the condensate pump, and an outlet of the condensate pump is in communication with a water side inlet of the shaft seal heater assembly.

8. The deaerator steam recovery and drain utilization system of any of claims 1-7, wherein, Further comprising a boiler; An outlet of the condenser is in communication with an inlet of the condensate pump, and an outlet of the condensate pump is in communication with a water side inlet of the shaft seal heater assembly.

9. The deaerator steam recovery drain utilization system of claim 8, wherein, Further comprising a feed water pump; An outlet of the condenser is in communication with an inlet of the condensate pump, and an outlet of the condensate pump is in communication with a water side inlet of the shaft seal heater assembly.

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