Heat recycling device of multi-stage waste heat boiler and back-cutting method

Abstract

The invention relates to the technical field of synthesis ammonia conversion waste heat recovery, in particular to a heat recycling device of a multi-stage waste heat boiler and a back-off method, a conversion furnace of the heat recycling device is communicated with a 1.3 MPa waste heat boiler, the 1.3 MPa waste heat boiler is communicated with a first water separator, the first water separator is respectively communicated with a first 0.5 MPa waste heat boiler and a second 0.5 MPa waste heat boiler, and the second 0.5 MPa waste heat boiler is communicated with a second water separator. Both the first 0.5 MPa waste boiler and the second 0.5 MPa waste boiler are communicated with the first water separator, both the first 0.5 MPa waste boiler and the second 0.5 MPa waste boiler are communicated with the second water separator, the 1.3 MPa waste boiler is communicated with a 1.3 MPa steam pipe network, the 1.3 MPa steam pipe network is respectively communicated with a high-temperature heater, a low-methane separation tower reboiler and a 1.3 MPa minus 0.5 MPa steam pipeline, and the 1.3 MPa minus 0.5 MPa steam pipeline is communicated with a 0.5 MPa steam pipe network. According to the heat recycling device provided by the invention, part of low-quality steam can be converted into high-quality steam, waste heat of converted gas is fully utilized, and meanwhile, on-line reverse switching use of a 1.3 MPa waste boiler is realized through control of a temporary temperature and pressure rising pipeline and a drain valve.

Description

Technical Field

[0001] The invention relates to the technical field of waste heat recovery from synthetic ammonia conversion, and in particular to a heat recovery and utilization device for a multi-stage waste boiler and a reverse cutting method. Background Art

[0002] The conversion system of the synthetic ammonia unit uses more isothermal conversion furnace processes and is equipped with a start-up electric heater. The start-up electric heater is not suitable for small flow. The waste boiler of the heat recovery system can generally produce 0.5MPa steam as a by-product. Due to the low quality of 0.5MPa steam and the small number of subsequent use devices, many synthetic ammonia plants have excess 0.5MPa steam, and the economic benefits of using steam to generate electricity or drive water pumps are not high. The high-temperature heater of the boiler directly uses the steam produced by the boiler itself to heat the deoxygenated water, and the low-temperature methanol washing system also consumes part of the 2.5MPa steam. These steam consumptions affect the power coal consumption and comprehensive energy consumption of the synthetic ammonia unit. Summary of the invention

[0003] The purpose of the present invention is to provide a heat recovery and utilization device and a back-cutting method for a multi-stage waste boiler, so that part of the low-quality steam can be converted into high-quality steam, and the waste heat can be efficiently utilized.

[0004] To achieve the above-mentioned purpose, the present invention provides a heat recovery and utilization device for a multi-stage waste boiler, comprising a heat recovery and utilization device, wherein the conversion furnace of the heat recovery and utilization device is connected to the 1.3MPa waste boiler, the 1.3MPa waste boiler is connected to the first water separator, the first water separator is respectively connected to the first 0.5MPa waste boiler and the second 0.5MPa waste boiler, the first 0.5MPa waste boiler and the second 0.5MPa waste boiler are both connected to the second water separator, the 1.3MPa waste boiler is connected to the 1.3MPa steam pipeline network, the 1.3MPa steam pipeline network is respectively connected to the high-temperature heater, the low-methane separation tower reboiler and the 1.3MPa minus 0.5MPa steam pipeline, and the 1.3MPa minus 0.5MPa steam pipeline is connected to the 0.5MPa steam pipeline network.

[0005] Preferably, the first water separator is communicated with the first process condensate pump, and the second water separator is communicated with the second process condensate pump.

[0006] Preferably, the process deaerator is connected to the 1.3 MPa waste boiler via a first feed water pump, and the process deaerator is connected to the first 0.5 MPa waste boiler and the second 0.5 MPa waste boiler via a second feed water pump.

[0007] Preferably, the first 0.5 MPa waste boiler and the second 0.5 MPa waste boiler are both connected to the 0.5 MPa steam pipeline network.

[0008] Preferably, a pressure reducing valve is provided on the 1.3MPa minus 0.5MPa steam pipeline.

[0009] Preferably, the 2.5 MPa steam network is connected to the high temperature heater and the reboiler of the low-methane separation tower respectively.

[0010] Preferably, the reboiler of the low-methane separation tower is in circular communication with the separation tower.

[0011] Preferably, the outlet of the conversion furnace is connected to the original process pipeline and the temporary temperature and pressure increase pipeline respectively. The original process pipeline connects the outlet of the conversion furnace and the first 0.5MPa waste boiler, and the temporary temperature and pressure increase pipeline connects the outlet of the conversion furnace and the 1.3MPa waste boiler through a shower valve.

[0012] The above-mentioned back-cutting method of the heat recovery and utilization device of a multi-stage waste boiler comprises the following steps: S1. Close the second valve and the third valve, open the first valve and the fourth valve, and the conversion gas in the conversion furnace enters the original process pipeline; S2. Nitrogen is introduced into the 1.3MPa waste boiler and the pipeline connected thereto for replacement. After nitrogen replacement is completed, the shower valve and the vent valve are opened; S3. Slowly introduce the conversion gas into the 1.3MPa waste boiler and the pipeline connected to it through the temporary temperature and pressure increase pipeline. When the temperature and pressure rise to the normal value of the system, slowly open the second valve and the third valve, and gradually close the first valve and the fourth valve.

[0013] Preferably, the first valve and the fourth valve are located on the original process pipeline, the second valve is located between the two shower valves, and the third valve is located between the first water separator and the first 0.5 MPa waste boiler.

[0014] Therefore, the present invention adopts a multi-stage waste boiler heat recovery device and a back-cutting method of the above structure, and its beneficial effects are: 1. According to the outlet temperature of the conversion furnace, by adding a 1.3MPa waste boiler and a corresponding water separator and process condensate pump, and connecting the 1.3MPa waste boiler in series with the first 0.5MPa waste boiler and the second 0.5MPa waste boiler, part of the low-quality steam can be converted into high-quality steam; 2. By replacing the 2.5MPa steam used for the high-temperature heater and the reboiler of the low-methane separation tower with the by-product steam of the 1.3MPa waste boiler, the boiler load can be further reduced, and the waste heat can be efficiently utilized, because part of the 2.5MPa steam used for the high-temperature heater is directly produced by the boiler; 3. Through the temporary temperature and pressure increase pipeline, the temperature and pressure of the new pipeline are raised to normal operating conditions by using the conversion gas. Since this process is controlled by the shower valve, the temperature and pressure are fully controllable, and since it is conversion gas itself, the gas composition does not change at all, thus realizing the online reverse cutting and commissioning of the 1.3MPa waste boiler; 4. The heat recovery device provided by the present invention has reasonable design, simple structure, safety and reliability, and is easy to use, and has great promotion and use value.

[0015] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of a heat recovery and utilization device of a multi-stage waste boiler of the present invention.

[0017] Reference numerals: 1. Separation tower; 2. Low-methane separation tower reboiler; 3. Shift furnace; 4. 1.3MPa steam network; 5. 2.5MPa steam network; 6. High-temperature heater; 7. 1.3MPa minus 0.5MPa steam pipeline; 8. Pressure reducing valve; 9. First water separator; 10. First process condensate pump; 11. 0.5MPa steam network; 12. Second process condensate pump; 13. Second water separator; 14. Process deaerator; 15. First feed water pump; 16. Second feed water pump; 17. Temporary temperature and pressure increase pipeline; 18. Drain valve; 19. Vent valve; 20. Original process pipeline; 21. 1.3MPa waste boiler; 22. First 0.5MPa waste boiler; 23. Second 0.5MPa waste boiler; 24. First valve; 25. Second valve; 26. Third valve; 27. Fourth valve. DETAILED DESCRIPTION

[0018] The present invention is further described below in conjunction with the accompanying drawings and embodiments. Unless otherwise defined, the technical terms or scientific terms used in the present invention should be the common meanings understood by people with ordinary skills in the field to which the present invention belongs. The above-mentioned features or features mentioned in the specific examples mentioned in the present invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0019] Example 1 like Figure 1 As shown, the present invention provides a heat recovery device for a multi-stage waste boiler, including a heat recovery device, wherein the conversion furnace 3 of the heat recovery device is connected to the 1.3MPa waste boiler 21, and the 1.3MPa waste boiler 21 is connected to the first water separator 9. The first water separator 9 is respectively connected to the first 0.5MPa waste boiler 22 and the second 0.5MPa waste boiler 23, and the first 0.5MPa waste boiler 22 and the second 0.5MPa waste boiler 23 are both connected to the second water separator 13. The 1.3MPa waste boiler 21 is connected to the 1.3MPa steam network 4, and the 1.3MPa steam network 4 is respectively connected to the high temperature heater 6, the low-methane separation tower reboiler 2 and the 1.3MPa minus 0.5MPa steam pipeline 7, and the 1.3MPa minus 0.5MPa steam pipeline 7 is connected to the 0.5MPa steam network 11.

[0020] The process gas at 237°C in the shift furnace 3 first enters the 1.3MPa waste boiler 21, cools down to 195°C and enters the first water separator 9. The gas phase in the first water separator 9 enters the first 0.5MPa waste boiler 22 and the second 0.5MPa waste boiler 23 respectively, and the outlet gas of the first 0.5MPa waste boiler 22 and the second 0.5MPa waste boiler 23 enters the second water separator 13. The first water separator 9 is connected to the first process condensate pump 10, and the second water separator 13 is connected to the second process condensate pump 12. The condensate separated by the first water separator 9 and the second water separator 13 is respectively sent to gasification after passing through the first process condensate pump 10 and the second process condensate pump 12. The outlet gas of the first water separator 9 goes to the flare through the vent pipeline, and the vent pipeline is provided with a vent valve 19 to control the direction of the outlet gas of the first water separator 9.

[0021] The process deaerator 14 is connected to the 1.3 MPa waste boiler 21 through the first feed water pump 15 , and the process deaerator 14 is connected to the first 0.5 MPa waste boiler 22 and the second 0.5 MPa waste boiler 23 through the second feed water pump 16 .

[0022] The steam produced by the 1.3MPa waste boiler 21 enters the 1.3MPa steam pipeline 4, the first 0.5MPa waste boiler 22 and the second 0.5MPa waste boiler 23 are both connected to the 0.5MPa steam pipeline 11, and the steam produced by the first 0.5MPa waste boiler 22 and the second 0.5MPa waste boiler 23 enters the 0.5MPa steam pipeline 11. Part of the steam in the 1.3MPa steam pipeline 4 is sent to the high-temperature heater 6, and part is sent to the low-methane separation tower reboiler 2, and the remaining steam is sent to the 0.5MPa steam pipeline 11 through the 1.3MPa minus 0.5MPa steam pipeline 7.

[0023] A pressure reducing valve 8 is provided on the 1.3MPa minus 0.5MPa steam pipeline 7. The arrangement of the pressure reducing valve 8 and the 1.3MPa minus 0.5MPa steam pipeline 7 enables the 1.3MPa steam produced by the 1.3MPa waste boiler 21 to be connected with the original 0.5MPa steam pipeline network 11. When the 1.3MPa steam is in excess, it can be decompressed and sent to the 0.5MPa steam pipeline network 11, which, on the one hand, achieves the balance of the 1.3MPa steam pipeline network 4, and on the other hand, can also increase the superheat of the 0.5MPa steam.

[0024] The 2.5MPa steam network 5 is connected to the high temperature heater 6 and the low-methane separation tower reboiler 2 respectively. The high temperature heater 6 heats the boiler feed water through steam, and the condensate of the high temperature heater 6 enters the boiler deaerator.

[0025] The reboiler 2 of the low-methane separation tower is in circulation communication with the separation tower 1 .

[0026] The outlet of the conversion furnace 3 is connected to the original process pipeline 20 and the temporary temperature and pressure increase pipeline 17 respectively. The original process pipeline 20 connects the outlet of the conversion furnace 3 with the first 0.5MPa waste boiler 22, and the temporary temperature and pressure increase pipeline 17 connects the outlet of the conversion furnace 3 with the 1.3MPa waste boiler 21 through the drain valve 18.

[0027] The first valve 24 and the fourth valve 27 are located on the original process pipeline 20 , the second valve 25 is located between the two shower valves 18 , and the third valve 26 is located between the first water separator 9 and the first 0.5 MPa waste boiler 22 .

[0028] Example 2 A back-cutting method of a heat recovery device for a multi-stage waste boiler in Example 1 comprises the following steps: S1. Close the second valve 25 and the third valve 26, open the first valve 24 and the fourth valve 27, and the conversion gas in the conversion furnace 3 enters the original process pipeline 20.

[0029] S2. Nitrogen is introduced into the 1.3 MPa waste boiler 21 and the pipeline connected thereto for replacement. After the nitrogen replacement is completed, the drain valve 18 and the vent valve 19 are opened.

[0030] S3. Slowly introduce the conversion gas into the 1.3MPa waste boiler 21 and the pipeline connected to it through the temporary temperature and pressure increase pipeline 17. When the temperature and pressure rise to the normal value of the system, slowly open the second valve 25 and the third valve 26, and gradually close the first valve 24 and the fourth valve 27.

[0031] Therefore, the present invention adopts a multi-stage waste boiler heat recovery device and reverse cutting method of the above-mentioned structure, which can convert part of the low-quality steam into high-quality steam and make full use of the waste heat of the conversion gas. At the same time, through the control of the temporary temperature and pressure boosting pipeline and the shower valve, the online reverse cutting and commissioning of the 1.3MPa waste boiler is realized.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A heat recovery device for a multi-stage waste boiler, characterized in that: It includes a heat recovery device, the conversion furnace of the heat recovery device is connected to the 1.3MPa waste boiler, the 1.3MPa waste boiler is connected to the first water separator, the first water separator is connected to the first 0.5MPa waste boiler and the second 0.5MPa waste boiler respectively, the first 0.5MPa waste boiler and the second 0.5MPa waste boiler are both connected to the second water separator, the 1.3MPa waste boiler is connected to the 1.3MPa steam pipeline network, the 1.3MPa steam pipeline network is respectively connected to the high-temperature heater, the low-methane separation tower reboiler and the 1.3MPa minus 0.5MPa steam pipeline, and the 1.3MPa minus 0.5MPa steam pipeline is connected to the 0.5MPa steam pipeline network.

2. The heat recovery device for a multi-stage waste boiler according to claim 1 is characterized in that: The first water separator is communicated with the first process condensate pump, and the second water separator is communicated with the second process condensate pump.

3. The heat recovery device for a multi-stage waste boiler according to claim 1 is characterized in that: The process deaerator is connected to the 1.3MPa waste boiler through the first feed water pump, and the process deaerator is connected to the first 0.5MPa waste boiler and the second 0.5MPa waste boiler through the second feed water pump.

4. The heat recovery device for a multi-stage waste boiler according to claim 1 is characterized in that: The first 0.5MPa waste boiler and the second 0.5MPa waste boiler are both connected to the 0.5MPa steam pipeline network.

5. The heat recovery device for a multi-stage waste boiler according to claim 1 is characterized in that: A pressure reducing valve is installed on the 1.3MPa minus 0.5MPa steam pipeline.

6. The heat recovery device for a multi-stage waste boiler according to claim 1 is characterized in that: The 2.5MPa steam network is connected to the high temperature heater and the reboiler of the low-methane separation tower respectively.

7. The heat recovery device for a multi-stage waste boiler according to claim 1 is characterized in that: The reboiler of the low-methane separation tower is connected to the separation tower circulation.

8. The heat recovery device for a multi-stage waste boiler according to claim 1 is characterized in that: The outlet of the conversion furnace is connected to the original process pipeline and the temporary temperature and pressure increase pipeline respectively. The original process pipeline connects the outlet of the conversion furnace and the first 0.5MPa waste boiler, and the temporary temperature and pressure increase pipeline connects the outlet of the conversion furnace and the 1.3MPa waste boiler through a shower valve.

9. The method for cutting back a heat recovery device for a multi-stage waste boiler according to any one of claims 1 to 8, characterized in that: The following steps are included: S1. Close the second valve and the third valve, open the first valve and the fourth valve, and the conversion gas in the conversion furnace enters the original process pipeline; S2. Nitrogen is introduced into the 1.3MPa waste boiler and the pipeline connected thereto for replacement. After nitrogen replacement is completed, the shower valve and the vent valve are opened; S3. Slowly introduce the conversion gas into the 1.3MPa waste boiler and the pipeline connected to it through the temporary temperature and pressure increase pipeline. When the temperature and pressure rise to the normal value of the system, slowly open the second valve and the third valve, and gradually close the first valve and the fourth valve.

10. The method for cutting back a heat recovery device for a multi-stage waste boiler according to claim 9, characterized in that: The first valve and the fourth valve are located on the original process pipeline, the second valve is located between the two shower valves, and the third valve is located between the first water separator and the first 0.5MPa waste boiler.

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