A multi-stage waste heat boiler heat recovery device and cutting method

Abstract

The present application relates to the technical fields of synthetic ammonia waste heat recovery, in particular to a multi-stage waste heat boiler heat recovery device and a switching method, wherein the heat recovery device is connected with a 1.3MPa waste heat boiler, the 1.3MPa waste heat boiler is connected with a first water separator, the first water separator is connected with a first 0.5MPa waste heat boiler and a second 0.5MPa waste heat boiler, the first 0.5MPa waste heat boiler and the second 0.5MPa waste heat boiler are connected with a second water separator, the 1.3MPa waste heat boiler is connected with a 1.3MPa steam pipe network, the 1.3MPa steam pipe network is connected with a high-temperature heater, a low-methane separation tower reboiler and a 1.3MPa-0.5MPa steam pipeline, and the 1.3MPa-0.5MPa steam pipeline is connected with a 0.5MPa steam pipe network. The heat recovery device can convert part of low-quality steam into high-quality steam, fully utilize the waste heat of the shift gas, and realize the online switching of the 1.3MPa waste heat boiler through the control of the temporary temperature and pressure increasing pipeline and the guide valve.

Description

Technical Field

[0001] This invention relates to the field of waste heat recovery technology in ammonia synthesis conversion, and in particular to a multi-stage waste boiler heat recovery and utilization device and a cutting method. Background Technology

[0002] The conversion system of ammonia synthesis plants often uses isothermal conversion furnaces and is equipped with start-up electric heaters. These start-up electric heaters are not suitable for low-flow-rate applications. The waste boiler of the heat recovery system typically produces 0.5MPa steam as a byproduct. Because the quality of 0.5MPa steam is low, it is rarely used by subsequent equipment, and many ammonia synthesis plants have a surplus of 0.5MPa steam. Using this steam for power generation or to drive water pumps is not economically efficient. The boiler's high-temperature heater directly uses steam produced by the boiler itself to heat the deoxygenated water, and the low-temperature methanol washing system also consumes some 2.5MPa steam. These steam consumptions all affect the power coal consumption and overall energy consumption of the ammonia synthesis plant. Summary of the Invention

[0003] The purpose of this invention is to provide a multi-stage waste boiler heat recovery and utilization device and a reverse cutting method, in which some low-quality steam can be converted into high-quality steam, and waste heat can be utilized efficiently.

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

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

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

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

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

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

[0010] Preferably, the reboiler of the low-methane separation tower is in a circulating connection with the separation tower.

[0011] Preferably, the converter outlet is connected to the original process pipeline and the temporary heating and pressurization pipeline respectively. The original process pipeline connects the converter outlet to the first 0.5MPa waste boiler, and the temporary heating and pressurization pipeline connects the converter outlet to the 1.3MPa waste boiler through a drain valve.

[0012] The above-mentioned method for reversing the heat recovery and utilization of multi-stage waste boilers includes the following steps:

[0013] S1. Close the second and third valves, and open the first and fourth valves to allow the shift gas in the shift furnace to enter the original process pipeline.

[0014] S2. Nitrogen gas is introduced into the 1.3MPa waste boiler and the pipeline connected to it for replacement. After the nitrogen replacement is completed, the drain valve and the vent valve are opened.

[0015] S3. Slowly introduce the changeover gas into the 1.3MPa waste boiler and its connected pipeline through the temporary heating and pressurization pipeline. When the temperature and pressure rise to the normal value of the system, slowly open the second and third valves, and gradually close the first and fourth valves.

[0016] Preferably, the first and fourth valves are located on the original process pipeline, the second valve is located between the two drain valves, and the third valve is located between the first water separator and the first 0.5MPa waste boiler.

[0017] Therefore, the present invention provides a multi-stage waste boiler heat recovery and utilization device and a cutting method with the above-described structure, the advantages of which are as follows:

[0018] 1. Based on the outlet temperature of the converter, by adding a 1.3MPa waste boiler and 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, some low-quality steam can be converted into high-quality steam.

[0019] 2. By replacing the 2.5MPa steam used in the high-temperature heater and the reboiler of the low-methane separation tower with the by-product steam from the 1.3MPa waste boiler, since part of the 2.5MPa steam used in the high-temperature heater is directly produced by the boiler, the boiler load can be further reduced, and the waste heat can be utilized efficiently.

[0020] 3. By using temporary heating and pressurization pipelines and switching gas, the temperature and pressure of the new pipeline are raised to normal operating conditions. Since this process is controlled by a drain valve, the temperature and pressure are completely controllable. Furthermore, since the gas itself is switching gas, the gas composition remains unchanged, thus enabling the online reverse switching and commissioning of the 1.3MPa waste boiler.

[0021] 4. The heat recovery and utilization device provided by the present invention is reasonably designed, simple in structure, safe and reliable, and easy to use, and has great value for promotion and application.

[0022] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of a multi-stage waste boiler heat recovery and utilization device according to the present invention.

[0024] Figure label:

[0025] 1. Separation tower; 2. Low-methane separation tower reboiler; 3. Shift converter; 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 feedwater pump; 16. Second feedwater pump; 17. Temporary heating and pressurization 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 Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments. Unless otherwise defined, the technical or scientific terms used in this invention should be understood in their ordinary sense by those skilled in the art. The features mentioned above or in the specific examples mentioned in this invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the invention and are not intended to limit the scope of the invention.

[0027] Example 1

[0028] like Figure 1As shown, this invention provides a multi-stage waste boiler heat recovery and utilization device, including a heat recovery and utilization device. The converter 3 of the heat recovery and utilization device is connected to a 1.3MPa waste boiler 21, and the 1.3MPa waste boiler 21 is connected to a first water separator 9. The first water separator 9 is connected to a first 0.5MPa waste boiler 22 and a second 0.5MPa waste boiler 23, respectively. Both the first 0.5MPa waste boiler 22 and the second 0.5MPa waste boiler 23 are connected to a second water separator 13. The 1.3MPa waste boiler 21 is connected to a 1.3MPa steam network 4, and the 1.3MPa steam network 4 is connected to a high-temperature heater 6, a low-methane separation tower reboiler 2, and a 1.3MPa minus 0.5MPa steam line 7, which is connected to a 0.5MPa steam network 11.

[0029] The process gas at 237°C in converter 3 first enters the 1.3MPa waste heat boiler 21, cools to 195°C, and then enters the first water separator 9. The gas phase in the first water separator 9 enters the first 0.5MPa waste heat boiler 22 and the second 0.5MPa waste heat boiler 23, respectively. The effluent from the first 0.5MPa waste heat boiler 22 and the second 0.5MPa waste heat 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 sent to gasification after passing through the first process condensate pump 10 and the second process condensate pump 12, respectively. The effluent from the first water separator 9 goes to the flare through a vent pipeline, which is equipped with a vent valve 19 to control the destination of the effluent from the first water separator 9.

[0030] The process deaerator 14 is connected to the 1.3MPa waste boiler 21 via the first feed water pump 15, and the process deaerator 14 is connected to the first 0.5MPa waste boiler 22 and the second 0.5MPa waste boiler 23 via the second feed water pump 16.

[0031] Steam generated from the 1.3MPa waste boiler 21 enters the 1.3MPa steam network 4. The first 0.5MPa waste boiler 22 and the second 0.5MPa waste boiler 23 are both connected to the 0.5MPa steam network 11, and steam generated from both enters the 0.5MPa steam network 11. A portion of the steam in the 1.3MPa steam network 4 is sent to the high-temperature heater 6, and another portion is sent to the low-methane separation tower reboiler 2. The remaining steam is sent to the 0.5MPa steam network 11 via the 1.3MPa minus 0.5MPa steam pipeline 7.

[0032] A pressure reducing valve 8 is installed on the 1.3MPa minus 0.5MPa steam pipeline 7. The installation of the pressure reducing valve 8 and the 1.3MPa minus 0.5MPa steam pipeline 7 connects the 1.3MPa steam produced by the 1.3MPa waste boiler 21 with the existing 0.5MPa steam network 11. When there is excess 1.3MPa steam, it can be reduced in pressure and sent to the 0.5MPa steam network 11. This achieves balance in the 1.3MPa steam network 4 and also increases the superheat of the 0.5MPa steam.

[0033] The 2.5MPa steam pipeline 5 is connected to the high-temperature heater 6 and the low-ammonia separation tower reboiler 2 respectively. The high-temperature heater 6 heats the boiler feedwater through steam, and the condensate of the high-temperature heater 6 enters the boiler deaerator.

[0034] The reboiler 2 of the low-methane separation tower is circulated and connected to the separation tower 1.

[0035] The outlet of converter 3 is connected to the original process pipeline 20 and the temporary heating and pressurization pipeline 17 respectively. The original process pipeline 20 connects the outlet of converter 3 to the first 0.5MPa waste boiler 22. The temporary heating and pressurization pipeline 17 connects the outlet of converter 3 to the 1.3MPa waste boiler 21 through the drain valve 18.

[0036] 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 drain valves 18, and the third valve 26 is located between the first water separator 9 and the first 0.5MPa waste boiler 22.

[0037] Example 2

[0038] The method for reversing the heat recovery and utilization device of a multi-stage waste boiler in Example 1 includes the following steps:

[0039] S1. Close the second valve 25 and the third valve 26, and open the first valve 24 and the fourth valve 27. The shift gas in the shift furnace 3 enters the original process pipeline 20.

[0040] S2. Nitrogen gas is introduced into the 1.3MPa waste boiler 21 and the pipeline connected to it for replacement. After the nitrogen replacement is completed, the drain valve 18 and the vent valve 19 are opened.

[0041] S3. The change gas is slowly introduced into the 1.3MPa waste boiler 21 and the pipeline connected to it through the temporary heating and pressurization pipeline 17. When the temperature and pressure rise to the normal value of the system, the second valve 25 and the third valve 26 are slowly opened, and the first valve 24 and the fourth valve 27 are gradually closed.

[0042] Therefore, the present invention employs a multi-stage waste boiler heat recovery and utilization device and a reverse cutting method with the above-mentioned structure, which can convert some low-quality steam into high-quality steam and make full use of the waste heat of the shift gas. At the same time, through the control of temporary heating and pressurization pipelines and drain valves, the online reverse cutting and commissioning of the 1.3MPa waste boiler is realized.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A multi-stage waste boiler heat recovery and utilization device, characterized in that: The device includes a heat recovery unit, whose converter is connected to a 1.3MPa waste boiler, which is connected to a first water separator. The first water separator is connected to a first 0.5MPa waste boiler and a second 0.5MPa waste boiler. Both the first 0.5MPa waste boiler and the second 0.5MPa waste boiler are connected to the second water separator. The 1.3MPa waste boiler is connected to a 1.3MPa steam network. The 1.3MPa steam network is connected to a high-temperature heater, a low-methane separation tower reboiler, and a 1.3MPa minus 0.5MPa steam pipeline. The 1.3MPa minus 0.5MPa steam pipeline is connected to a 0.5MPa steam network. The first water separator is connected to the first process condensate pump, and the second water separator is connected to the second process condensate pump. The process deaerator is connected to the 1.3MPa waste boiler via 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 via the second feed water pump. Both the first 0.5MPa waste boiler and the second 0.5MPa waste boiler are connected to the 0.5MPa steam pipeline network.

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

3. The multi-stage waste boiler heat recovery and utilization device according to claim 1, characterized in that: The 2.5MPa steam pipeline is connected to the high-temperature heater and the reboiler of the low-methane separation tower.

4. The multi-stage waste boiler heat recovery and utilization device according to claim 1, characterized in that: The reboiler of the low-methane separation tower is connected to the separation tower in a loop.

5. The multi-stage waste boiler heat recovery and utilization device according to claim 1, characterized in that: The converter outlet is connected to the original process pipeline and the temporary heating and pressurization pipeline. The original process pipeline connects the converter outlet to the first 0.5MPa waste boiler, and the temporary heating and pressurization pipeline connects the converter outlet to the 1.3MPa waste boiler through a drain valve.

6. The method for reverse cutting of a multi-stage waste boiler heat recovery and utilization device according to any one of claims 1-5, characterized in that: Includes the following steps, S1. Close the second and third valves, and open the first and fourth valves to allow the shift gas in the shift furnace to enter the original process pipeline. S2. Nitrogen gas is introduced into the 1.3MPa waste boiler and the pipeline connected to it for replacement. After the nitrogen replacement is completed, the drain valve and the vent valve are opened. S3. Slowly introduce the changeover gas into the 1.3MPa waste boiler and its connected pipeline through the temporary heating and pressurization pipeline. When the temperature and pressure rise to the normal value of the system, slowly open the second and third valves, and gradually close the first and fourth valves.

7. The method for reverse cutting in a multi-stage waste boiler heat recovery and utilization device according to claim 6, characterized in that: The first and fourth valves are located on the original process pipeline, the second valve is located between the two drain valves, and the third valve is located between the first water separator and the first 0.5MPa waste boiler.

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