Ammonia preheating mutual backup device based on multi-heat source switching

Abstract

The utility model relates to a heat exchange technology field of urea production is a kind of ammonia preheating mutual backup device based on multiple heat source switching, it includes one section evaporative heater, first preheater, second preheater, one section evaporative heater middle part includes upper heater and lower heater, and first hot water pipeline is communicated between lower heater and first preheater, first preheater is communicated with first hot water condensing pipeline, first preheater is communicated with first liquid ammonia pipeline, second liquid ammonia pipeline is communicated between first preheater and second preheater, third liquid ammonia pipeline is communicated with second preheater, first steam pipeline is communicated with second preheater, and first steam condensing pipeline is communicated with second preheater.The utility model is reasonable and compact in structure, convenient to use, it realizes the ammonia preheating mutual backup system of multiple heat source switching, guarantees the stable, efficient operation of urea production system, also reduce the steam cost input of ammonia preheating equipment.

Description

Technical Field

[0001] This utility model relates to the field of heat exchange technology in urea production, and is an ammonia preheating backup device based on multiple heat source switching. Background Technology

[0002] In chemical urea production systems, heat exchangers are the core equipment for heat exchange. Their metal components (such as carbon steel, stainless steel, copper alloys, etc.) are often corroded due to contact with the medium (liquid ammonia, hot water, etc.), which leads to shortened equipment life, leakage, and even safety accidents.

[0003] Pure anhydrous liquid ammonia is chemically stable and has very weak corrosiveness to most metals (such as carbon steel and stainless steel) (it can be considered an "inert medium"). However, in actual production, liquid ammonia often contains impurities such as water, oxygen, and carbon dioxide, or residual stress in the equipment can exacerbate the corrosion of heat exchangers. Hot water (usually referring to water between 40℃ and 150℃, such as heating water and process cooling water) is a commonly used medium for heat exchangers. Its corrosion of heat exchangers is essentially electrochemical corrosion, and the corrosion process is significantly accelerated by increasing the temperature. However, due to various factors in the chemical production process, heat exchangers are at risk of scouring and leakage. Once a heat exchanger leaks, the traditional approach requires shutting down the entire production system before repairing the heat exchanger. This not only interrupts urea production and affects production efficiency but also results in a large amount of condensate being discharged, leading to resource waste.

[0004] In summary, the problems of urea production system shutdowns caused by heat exchanger scouring and leakage, and the resource waste caused by the discharge of condensate before heat exchanger maintenance, have become urgent technical challenges that enterprises need to solve. Summary of the Invention

[0005] This invention provides an ammonia preheating backup device based on multiple heat source switching, which overcomes the shortcomings of the prior art. It can effectively solve the problems of urea production system shutdown and interruption caused by heat exchanger failure in existing liquid ammonia heat exchange systems and the waste of resources caused by condensate discharge before heat exchanger maintenance.

[0006] The technical solution of this utility model is achieved through the following measures: an ammonia preheating backup device based on multi-heat source switching, comprising a first evaporator heater, a first preheater, and a second preheater. The bottom inlet of the first evaporator heater is fixedly connected to a first urine pipeline, and the upper outlet of the first evaporator heater is fixedly connected to a second urine pipeline. The middle section of the first evaporator heater includes an upper heater and a lower heater. The lower inlet of the lower heater is fixedly connected to a process condensate pipeline. The medium inlet and outlet of both the first and second preheaters include a bottom tube-side inlet, a top tube-side outlet, a top shell-side inlet, and a bottom... A first hot water pipeline is fixedly connected between the shell-side outlet of the lower heater and the top shell-side inlet of the first preheater. A first hot water condenser pipeline is fixedly connected to the bottom shell-side outlet of the first preheater. A first liquid ammonia pipeline is fixedly connected to the bottom tube-side inlet of the first preheater. A second liquid ammonia pipeline is fixedly connected between the top tube-side outlet of the first preheater and the bottom tube-side inlet of the second preheater. A third liquid ammonia pipeline is fixedly connected to the top tube-side outlet of the second preheater. A first steam pipeline is fixedly connected to the top shell-side inlet of the second preheater. A first steam condenser pipeline is fixedly connected to the bottom shell-side outlet of the second preheater.

[0007] The following are further optimizations and / or improvements to the above-mentioned utility model technical solution: The first steam pipeline is fixedly installed with a first regulating valve, a first regulating valve, and a first regulating valve in sequence along the direction of medium flow; the first hot water condensate pipeline and the first hot water pipeline are fixedly connected by an interconnecting pipeline, and the interconnecting pipeline is fixedly connected with a second regulating valve, a second regulating valve, and a second regulating valve in sequence along the direction of medium flow.

[0008] A second hot water condensate pipeline is fixedly connected between the interconnection pipeline between the second regulating valve and the second regulating valve and the first steam pipeline between the first regulating valve and the first regulating valve.

[0009] The aforementioned device also includes a third preheater, the medium inlet and outlet of which include a bottom tube side inlet, a top tube side outlet, a top shell side inlet, and a bottom shell side outlet. A third liquid ammonia pipeline is fixedly connected between the top tube side outlet of the second preheater and the bottom tube side inlet of the third preheater. A fourth liquid ammonia pipeline is fixedly connected to the top tube side outlet of the third preheater. A second steam pipeline is fixedly connected to the top shell side inlet of the third preheater. A second steam condensation pipeline is fixedly connected to the bottom shell side outlet of the third preheater.

[0010] The upper inlet of the aforementioned upper section heater is fixedly connected to a third steam pipeline, and the lower outlet of the upper section heater is fixedly connected to a third steam condensation pipeline.

[0011] A first shut-off valve is fixedly installed on the aforementioned second hot water condensate pipeline.

[0012] A second shut-off valve is fixedly installed on the first hot water pipeline between the aforementioned interconnection pipeline and the top shell inlet of the first preheater.

[0013] A third shut-off valve is fixedly installed on the first hot water condensate pipeline between the aforementioned interconnection pipeline and the outlet of the first hot water condensate pipeline.

[0014] A first bypass pipeline is fixedly connected between the left inlet of the first regulating valve and the right outlet of the first regulating valve, and a first bypass valve is fixedly installed on the first bypass pipeline; a first drain pipeline is fixedly connected between the right outlet of the first regulating valve and the second hot water condensate pipeline, and a first drain valve is fixedly installed on the first drain pipeline.

[0015] A second bypass pipeline is fixedly connected between the interconnecting pipeline on the right inlet of the second regulating valve and the left outlet of the second regulating valve, and a second bypass valve is fixedly installed on the second bypass pipeline; a second drain pipeline is fixedly connected between the interconnecting pipeline on the right outlet of the second regulating valve and the second hot water condensate pipeline, and a second drain valve is fixedly installed on the second drain pipeline.

[0016] This utility model has a reasonable and compact structure and is easy to use. It realizes a multi-heat source switching ammonia preheating mutual backup system, ensuring the stable and efficient operation of the urea production system, and also reducing the steam cost of ammonia preheating equipment. Attached Figure Description

[0017] Appendix Figure 1 This is a schematic diagram of the process flow of this utility model.

[0018] The codes in the attached diagram are as follows: 1 is a first-stage evaporator heater, 2 is the first preheater, 3 is the second preheater, 4 is the first urine line, 5 is the second urine line, 6 is the upper heater, 7 is the lower heater, 8 is the process condensate line, 9 is the bottom tube-side inlet, 10 is the top tube-side outlet, 11 is the top shell-side inlet, 12 is the bottom shell-side outlet, 13 is the first hot water line, 14 is the first hot water condensate line, 15 is the first liquid ammonia line, 16 is the second liquid ammonia line, 17 is the third liquid ammonia line, 18 is the first steam line, 19 is the first steam condensate line, 20 is the first regulating valve, 21 is the first regulating valve, and 22 is the first regulating valve. The valves are as follows: 23 is the interconnection pipeline, 24 is the second pre-regulation valve, 25 is the second regulating valve, 26 is the second post-regulation valve, 27 is the second hot water condensate pipeline, 28 is the third preheater, 29 is the fourth liquid ammonia pipeline, 30 is the second steam pipeline, 31 is the second steam condensate pipeline, 32 is the third steam pipeline, 33 is the third steam condensate pipeline, 34 is the first shut-off valve, 35 is the second shut-off valve, 36 is the third shut-off valve, 37 is the first bypass pipeline, 38 is the first bypass valve, 39 is the first drain pipeline, 40 is the first drain valve, 41 is the second bypass pipeline, 42 is the second bypass valve, 43 is the second drain pipeline, and 44 is the second drain valve. Detailed Implementation

[0019] This utility model is not limited to the following embodiments, and the specific implementation method can be determined according to the technical solution of this utility model and the actual situation.

[0020] Unless otherwise specified, all equipment and devices used in this invention are existing, publicly known, and commonly used equipment and devices in the field.

[0021] In this utility model, for ease of description, the description of the relative positional relationships of the components is based on the appendix to the specification. Figure 1 The layout is described using a diagrammatic method, such as the positional relationships of front, back, top, bottom, left, and right, which are based on the instructions attached. Figure 1 The orientation of the layout is determined by the direction of the map.

[0022] The present invention will be further described below with reference to the embodiments and accompanying drawings: Example 1: As shown in the attached document Figure 1As shown, the ammonia preheating backup device based on multi-heat source switching includes a first-stage evaporator heater 1, a first preheater 2, and a second preheater 3. The bottom inlet of the first-stage evaporator heater 1 is fixedly connected to a first urine pipeline 4, and the upper outlet of the first-stage evaporator heater 1 is fixedly connected to a second urine pipeline 5. The middle section of the first-stage evaporator heater 1 includes an upper section heater 6 and a lower section heater 7. The lower inlet of the lower section heater 7 is fixedly connected to a process condensate pipeline 8. The medium inlet and outlet of the first preheater 2 and the second preheater 3 both include a bottom tube-side inlet 9, a top tube-side outlet 10, a top shell-side inlet 11, and a bottom shell-side outlet 12. The upper outlet of the lower section heater 7 is connected to the first... A first hot water pipeline 13 is fixedly connected between the top shell-side inlet 11 of the first preheater 2 and the bottom shell-side outlet 12 of the first preheater 2. A first hot water condenser pipeline 14 is fixedly connected to the bottom tube-side inlet 9 of the first preheater 2. A first liquid ammonia pipeline 15 is fixedly connected to the top tube-side outlet 10 of the first preheater 2 and the bottom tube-side inlet 9 of the second preheater 3. A second liquid ammonia pipeline 16 is fixedly connected to the top tube-side outlet 10 of the second preheater 3. A third liquid ammonia pipeline 17 is fixedly connected to the top tube-side outlet 10 of the second preheater 3. A first steam pipeline 18 is fixedly connected to the top shell-side inlet 11 of the second preheater 3. A first steam condenser pipeline 19 is fixedly connected to the bottom shell-side outlet 12 of the second preheater 3.

[0023] In the urea production system, the ammonia preheater plays a crucial role. This invention utilizes the high-temperature hot water discharged from the lower heater 7 of the first-stage evaporator heater 1 to input into the first preheater 2 for preliminary preheating of liquid ammonia. The preheated liquid ammonia is then input into the second preheater 3, where the steam in the second preheater 3 further preheats the liquid ammonia. This fully utilizes the heat from the high-temperature hot water discharged from the first-stage evaporator heater 1, reducing the steam input cost for ammonia preheating.

[0024] As needed, the heat source for the second preheater 3 can be 0.5MPa steam, 1.3MPa steam, or low-pressure steam from the outer pipe.

[0025] The above-mentioned ammonia preheating and backup device based on multi-heat source switching can be further optimized and / or improved according to actual needs: Example 2: Its difference from Example 1 is as follows: (See attached) Figure 1 As shown, a first regulating valve 20, a first regulating valve 21, and a first regulating valve 22 are fixedly installed on the first steam pipeline 18 along the direction of medium flow; an interconnecting pipeline 23 is fixedly connected between the first hot water condensate pipeline 14 and the first hot water pipeline 13, and a second regulating valve 24, a second regulating valve 25, and a second regulating valve 26 are fixedly connected on the interconnecting pipeline 23 along the direction of medium flow.

[0026] As needed, the first regulating valve 21 is used to regulate the steam flow rate in the first steam pipeline 18. When the first regulating valve 21 malfunctions, the first regulating valve 20 and the first regulating valve 22 are closed, and the first regulating valve 21 is repaired.

[0027] Example 3: Its difference from Examples 1 to 2 is as follows: (See attached) Figure 1 As shown, a second hot water condensate pipeline 27 is fixedly connected between the interconnection pipeline 23 between the second regulating valve 24 and the second regulating valve 25 and the first steam pipeline 18 between the first regulating valve 20 and the first regulating valve 21.

[0028] If a leak occurs in the inner tube of the first preheater 2 as needed, the residual hot water condensate in the first preheater 2 will be discharged into the second preheater 3 in sequence through the first hot water condensate pipeline 14, the interconnection pipeline 23, the second hot water condensate pipeline 27 and the first steam pipeline 18, so as to provide heat source replenishment for the second preheater 3.

[0029] The high-temperature hot water from the lower heater 7 can sequentially enter the second preheater 3 through the first hot water pipeline 13, the interconnection pipeline 23, the second hot water pipeline 27 and the first steam pipeline 18, serving as the main heat source for the second preheater 3.

[0030] Example 4: Its difference from Examples 1 to 3 is as follows: (See attached) Figure 1 As shown, the device also includes a third preheater 28. The medium inlet and outlet of the third preheater 28 include a bottom tube inlet 9, a top tube outlet 10, a top shell inlet 11, and a bottom shell outlet 12. A third liquid ammonia pipeline 17 is fixedly connected between the top tube outlet 10 of the second preheater 3 and the bottom tube inlet 9 of the third preheater 28. A fourth liquid ammonia pipeline 9 is fixedly connected to the top tube outlet 10 of the third preheater 28. A second steam pipeline 30 is fixedly connected to the top shell inlet 11 of the third preheater 28. A second steam condensation pipeline 31 is fixedly connected to the bottom shell outlet 12 of the third preheater 28.

[0031] As required, the first preheater 2, the second preheater 3 and the third preheater 28 are all tubular heat exchangers. The tubular heat exchanger includes a tube side and a shell side. The tube side contains liquid ammonia medium and the shell side contains heat source medium.

[0032] The second preheater 3 can serve as a backup preheater for the first preheater 2. Simultaneous startup of the first preheater 2 and the third preheater 28 can meet the preheating process parameters of liquid ammonia.

[0033] Example 5: It differs from Examples 1 to 4 in that, as shown in the appendix... Figure 1 As shown, the upper inlet of the upper section heater 6 is fixedly connected to the third steam pipeline 32, and the lower outlet of the upper section heater 6 is fixedly connected to the third steam condensation pipeline 33.

[0034] As needed, the urine discharged from the lower heater 7 enters the upper heater 6, where steam heats the urine.

[0035] Example 6: Its difference from Examples 1 to 5 is as follows: (See attached) Figure 1 As shown, a first shut-off valve 34 is fixedly installed on the second hot water condensate pipeline 27.

[0036] Example 7: Its difference from Examples 1 to 6 is as follows: (See attached) Figure 1 As shown, a second shut-off valve 35 is fixedly installed on the first hot water pipeline 13 between the interconnecting pipeline 23 and the top shell inlet 11 of the first preheater 2.

[0037] Example 8: It differs from Examples 1 to 7 in that, as shown in the appendix... Figure 1 As shown, a third shut-off valve 36 is fixedly installed on the first hot water condensate pipeline 14 between the interconnection pipeline 23 and the outlet of the first hot water condensate pipeline 14.

[0038] As needed, the first shut-off valve 34, the second shut-off valve 35, and the third shut-off valve 36 are used to cut off the flow of media in the corresponding process pipelines.

[0039] Example 9: It differs from Examples 1 to 8 in that: as shown in the appendix Figure 1 As shown, a first bypass pipeline 37 is fixedly connected between the left inlet of the first regulating valve 20 and the right outlet of the first regulating valve 22, and a first bypass valve 38 is fixedly installed on the first bypass pipeline 37; a first drain pipeline 39 is fixedly connected between the right outlet of the first regulating valve 20 and the second hot water condensate pipeline 27, and a first drain valve 40 is fixedly installed on the first drain pipeline 39.

[0040] If maintenance is required on the first regulating valve 21, the first regulating front valve 20 and the first regulating rear valve 22 are closed, and the first drain line 39 is used to discharge the residual medium in the first steam line 18 between the first regulating front valve 20 and the first regulating rear valve 22.

[0041] Example 10: It differs from Examples 1 to 9 in that, as shown in the appendix... Figure 1 As shown, a second bypass pipeline 41 is fixedly connected between the right inlet of the second regulating valve 24 and the left outlet of the second regulating valve 26, and a second bypass valve 42 is fixedly installed on the second bypass pipeline 41; a second drain pipeline 43 is fixedly connected between the right outlet of the second regulating valve 26 and the second hot water condensate pipeline 27, and a second drain valve 44 is fixedly installed on the second drain pipeline 43.

[0042] If necessary, when the second regulating valve 25 needs maintenance, the second regulating front valve 24 and the second regulating rear valve 26 are closed, and the second drain line 43 is used to drain the residual medium in the interconnecting line 23 between the second regulating front valve 24 and the second regulating rear valve 26.

[0043] Depending on the needs, the pipelines and equipment of this ammonia preheating backup device based on multiple heat source switching can also be equipped with conventional valves, thermometers and pressure gauges known in the art, as required by production.

[0044] The above technical features constitute various embodiments of this utility model, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

[0045] The usage process of this utility model is as follows: First, upstream process condensate enters the lower heater 7 through process condensate pipeline 8, and upstream process urine enters the lower heater 7 through the first urine pipeline 4. Heat exchange occurs between the urine and condensate in the lower heater 7, resulting in condensed urine and high-temperature hot water. The condensed urine then enters the upper heater 6. Next, liquid ammonia enters the first preheater 2 through the first liquid ammonia pipeline 15, and high-temperature hot water enters the first preheater 2 through the first hot water pipeline 13. Heat exchange occurs between the high-temperature hot water and liquid ammonia in the first preheater 2, resulting in... The hot water condensate and preheated liquid ammonia are then introduced. The preheated liquid ammonia first enters the second preheater 3 through the second liquid ammonia pipeline 16, and steam enters the second preheater 3 through the first steam pipeline 18. The steam in the second preheater 3 further preheats the preheated liquid ammonia to obtain steam condensate and high-temperature liquid ammonia. Finally, the high-temperature liquid ammonia enters the third preheater 28 through the third liquid ammonia pipeline 17. The steam heat source of the third preheater 28 is not used. The third preheater 28 is only a single medium channel for high-temperature liquid ammonia. The high-temperature liquid ammonia enters the downstream process system through the fourth liquid ammonia pipeline 9.

[0046] The use of this utility model also includes: (1) When a leak occurs in the internal pipe of the first preheater 2, the first preheater 2 is only a single medium channel for liquid ammonia. After closing the third shut-off valve 36, the second regulating valve 26 and the first regulating valve 20, the residual hot water condensate in the first preheater 2 is discharged into the second preheater 3 through the first hot water condensate pipeline 14, the interconnecting pipeline 23, the second hot water condensate pipeline 27 and the first steam pipeline 18. Then, the second regulating valve 25 and the second shut-off valve 35 are closed. The high-temperature hot water of the lower section heater 7 passes through the first hot water pipeline 13, the interconnecting pipeline 23 and the second hot water pipeline 18. The condenser line 27 and the first steam line 18 enter the second preheater 3. The liquid ammonia enters the first preheater 2 and then the second preheater 3. The high-temperature hot water in the second preheater 3 exchanges heat with the liquid ammonia to obtain hot water condensate and preheated liquid ammonia. The preheated liquid ammonia enters the third preheater 28 through the third liquid ammonia line 17. Steam enters the third preheater 28 through the second steam line 30. The steam in the third preheater 28 preheats the preheated liquid ammonia again to obtain steam condensate and high-temperature liquid ammonia. The high-temperature liquid ammonia enters the downstream process system through the fourth liquid ammonia line 9.

[0047] (2) When a leak occurs in the internal tubes of the second preheater 3, the second preheater 3 is only a single medium channel for liquid ammonia. The first regulating valve 20, the second regulating valve 24 and the first shut-off valve 34 are closed. The high-temperature hot water of the lower heater 7 enters the first preheater 2 through the first hot water pipeline 13. The liquid ammonia enters the first preheater 2 through the first liquid ammonia pipeline 15. The high-temperature hot water and liquid ammonia in the first preheater 2 exchange heat to obtain hot water condensate and preheated liquid ammonia. The preheated liquid ammonia enters the second preheater 3 through the second liquid ammonia pipeline 16, and then enters the third preheater 28 through the third liquid ammonia pipeline 17. Steam enters the third preheater 28 through the second steam pipeline 30. The steam in the third preheater 28 preheats the preheated liquid ammonia again to obtain steam condensate and high-temperature liquid ammonia. The high-temperature liquid ammonia enters the downstream process system through the fourth liquid ammonia pipeline 9.

Claims

1. An ammonia preheating and backup device based on multi-heat source switching, characterized in that... The system includes an evaporator heater, a first preheater, and a second preheater. The bottom inlet of the first evaporator heater is fixedly connected to a first urine pipeline, and the upper outlet of the first evaporator heater is fixedly connected to a second urine pipeline. The middle section of the first evaporator heater includes an upper heater and a lower heater. The lower inlet of the lower heater is fixedly connected to a process condensate pipeline. The medium inlet and outlet of both the first and second preheaters include a bottom tube-side inlet, a top tube-side outlet, a top shell-side inlet, and a bottom shell-side outlet. The upper outlet of the lower heater is fixedly connected to the top shell-side inlet of the first preheater, and a first hot water pipeline is fixedly connected to the bottom shell-side outlet of the first preheater. The bottom shell-side outlet of the first preheater is fixedly connected to a first hot water condensate pipeline. The bottom tube-side inlet of the first preheater is fixedly connected to a first liquid ammonia pipeline. The top tube-side outlet of the first preheater and the bottom tube-side inlet of the second preheater are fixedly connected to a second liquid ammonia pipeline. The top tube-side outlet of the second preheater is fixedly connected to a third liquid ammonia pipeline. The top shell-side inlet of the second preheater is fixedly connected to a first steam pipeline, and the bottom shell-side outlet of the second preheater is fixedly connected to a first steam condensate pipeline.

2. The ammonia preheating and backup device based on multi-heat source switching according to claim 1, characterized in that... A first regulating valve, a first regulating valve, and a first regulating valve are fixedly installed sequentially along the direction of medium flow on the first steam pipeline; or / and, an interconnecting pipeline is fixedly connected between the first hot water condensate pipeline and the first hot water pipeline, and a second regulating valve, a second regulating valve, and a second regulating valve are fixedly connected sequentially along the direction of medium flow on the interconnecting pipeline.

3. The ammonia preheating backup device based on multi-heat source switching according to claim 2, characterized in that... A second hot water condensate pipeline is fixedly connected between the interconnection pipeline between the second regulating valve and the second regulating valve and the first steam pipeline between the first regulating valve and the first regulating valve.

4. The ammonia preheating and backup device based on multi-heat source switching according to claim 1, 2, or 3, characterized in that... It also includes a third preheater, whose medium inlet and outlet include a bottom tube side inlet, a top tube side outlet, a top shell side inlet, and a bottom shell side outlet. A third liquid ammonia pipeline is fixedly connected between the top tube side outlet of the second preheater and the bottom tube side inlet of the third preheater. A fourth liquid ammonia pipeline is fixedly connected to the top tube side outlet of the third preheater. A second steam pipeline is fixedly connected to the top shell side inlet of the third preheater. A second steam condensation pipeline is fixedly connected to the bottom shell side outlet of the third preheater.

5. The ammonia preheating backup device based on multi-heat source switching according to claim 4, characterized in that... The upper inlet of the upper section heater is fixedly connected to a third steam pipeline, and the lower outlet of the upper section heater is fixedly connected to a third steam condensation pipeline.

6. The ammonia preheating backup device based on multi-heat source switching according to claim 3 or 5, characterized in that... A first shut-off valve is fixedly installed on the second hot water condensate pipeline.

7. The ammonia preheating backup device based on multi-heat source switching according to claim 2, 3, or 5, characterized in that... A second shut-off valve is fixedly installed on the first hot water pipeline between the interconnection pipeline and the top shell inlet of the first preheater.

8. The ammonia preheating backup device based on multi-heat source switching according to claim 7, characterized in that... A third shut-off valve is fixedly installed on the first hot water condensate pipeline between the interconnection pipeline and the outlet of the first hot water condensate pipeline.

9. The ammonia preheating backup device based on multi-heat source switching according to claim 3, 5, or 8, characterized in that... A first bypass pipeline is fixedly connected between the left inlet of the first regulating valve and the right outlet of the first regulating valve, and a first bypass valve is fixedly installed on the first bypass pipeline; or / and, a first drain pipeline is fixedly connected between the right outlet of the first regulating valve and the second hot water condensate pipeline, and a first drain valve is fixedly installed on the first drain pipeline.

10. The ammonia preheating backup device based on multi-heat source switching according to claim 9, characterized in that... A second bypass pipeline is fixedly connected between the interconnecting pipeline on the right inlet of the second regulating valve and the left outlet of the second regulating valve, and a second bypass valve is fixedly installed on the second bypass pipeline; or / and, a second drain pipeline is fixedly connected between the interconnecting pipeline on the right outlet of the second regulating valve and the second hot water condensate pipeline, and a second drain valve is fixedly installed on the second drain pipeline.

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