Desalting water system utilizing low-grade waste heat of synthetic ammonia system
By designing a demineralized water system in the ammonia synthesis system, the low-grade waste heat from gasification black water and shift gas is used to conduct cascade heat exchange with the demineralized water, solving the problem of the difficulty in utilizing low-grade waste heat and achieving efficient utilization of thermal energy and saving of cooling water.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- HENAN XINLIANXIN FERTILIZER
- Filing Date
- 2025-07-17
- Publication Date
- 2026-07-24
AI Technical Summary
Low-grade waste heat in ammonia synthesis systems is difficult to utilize directly, leading to energy waste and excessive consumption of circulating cooling water. Existing demineralized water heating processes rely on external heat sources, resulting in low efficiency.
Design a demineralized water system that couples with the gasified black water and shift gas in the ammonia synthesis system, utilizes the first, second and third heat exchangers for cascade heat exchange, and combines a lithium bromide heat pump unit and a refrigeration unit to achieve effective exchange between demineralized water and low-grade waste heat, thereby reducing the consumption of circulating cooling water.
It achieves effective utilization of low-grade thermal energy, reduces the amount of circulating cooling water used, improves energy utilization efficiency, and reduces the power required to cool ammonia synthesis gas.
Smart Images
Figure CN224551879U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of thermal energy reuse technology of ammonia synthesis system, specifically a demineralized water system that utilizes the low-grade waste heat of ammonia synthesis system. Background Technology
[0002] In ammonia synthesis systems, a large amount of low-grade waste heat is generated during the specific ammonia and methanol production processes. This waste heat is usually difficult to utilize directly due to its relatively low temperature. Based on this, existing technologies typically use circulating cooling water to cool it down before discharging it into the environment, which not only wastes energy but also consumes a large amount of circulating cooling water. Existing demineralized water heating processes usually rely on external heat sources or high-grade heat energy, failing to effectively utilize the low-grade waste heat inside the system, resulting in low energy utilization efficiency. Utility Model Content
[0003] To overcome the above deficiencies, this utility model provides a demineralized water system that utilizes the low-grade waste heat of the ammonia synthesis system, thereby solving the technical problems existing in the prior art.
[0004] The technical solution adopted by this utility model to solve its technical problem is:
[0005] A demineralized water system utilizing low-grade waste heat from a synthetic ammonia system includes a gasified black water feedwater pipeline and a shift gas pipeline in the synthetic ammonia system. The demineralized water pipeline of the demineralized water and condensate refining unit is connected to a first stream separator. The first outlet of the first stream separator is connected to the inlet of a deaerator via a first heat exchange channel of a first heat exchanger. The second outlet of the first stream separator is connected to the inlet of the deaerator via a first heat exchange channel of a second heat exchanger. The first outlet of the deaerator is connected to a first boiler feedwater pump. The second outlet of the deaerator is connected to the first heat exchange channel of a third heat exchanger via a first demineralized water closed-loop circulation section. The gasified black water pipeline is connected to the gasified black water return water pipeline via a second heat exchange channel of the first heat exchanger. The shift gas pipeline is connected to the inlet of a circulating water cooler via a second heat exchange channel of the third heat exchanger and a second heat exchange channel of the second heat exchanger. The outlet of the circulating water cooler is connected to an ammonia washing tower.
[0006] The beneficial effects of this invention are as follows: This invention utilizes the coupling of demineralized water with the ammonia synthesis system, allowing the waste heat from the ammonia synthesis system to heat the demineralized water, thereby reducing the consumption of circulating cooling water and achieving effective utilization of low-grade heat energy. Based on the characteristics of gasified black water and shift gas, this invention designs different heat exchange processes. Specifically, since gasified black water is in the liquid phase and has a relatively low temperature, a first heat exchanger is used for heat exchange. Since shift gas is in the gas phase and has a relatively high temperature, a third heat exchanger and a second heat exchanger are connected in series to achieve the characteristic of cascade heat exchange. The above methods can effectively utilize the low-grade heat energy of the ammonia synthesis system while simultaneously reducing the consumption of circulating cooling water.
[0007] Preferably, the first demineralized water closed-loop circulation section includes a lithium bromide heat pump unit. The first inlet of the lithium bromide heat pump unit is connected to the second outlet of the deaerator via a second boiler feed water pump, and the first outlet of the lithium bromide heat pump unit is connected to the steam pipeline network. The second outlet of the lithium bromide heat pump unit is connected to the inlet of the first heat exchange channel of the third heat exchanger via a first demineralized water closed-loop circulation pump, and the outlet of the second heat exchange channel of the third heat exchanger is connected to the second inlet of the lithium bromide heat pump unit.
[0008] Preferably, a first tee is provided between the gas exchange pipeline and the second heat exchange channel of the third heat exchanger, and a second tee is provided between the second heat exchange channel of the third heat exchanger and the second heat exchange channel of the second heat exchanger. A shortcut pipeline with a valve is provided between the third end of the first tee and the third end of the second tee.
[0009] Preferably, the first outlet of the lithium bromide heat pump unit is connected to the steam pipeline network through the first outlet of the second stream separator, and the second outlet of the second stream separator is connected to the ammonia synthesis gas cooling unit.
[0010] Preferably, the ammonia synthesis gas cooling unit includes a second demineralized water closed-loop circulation section with a lithium bromide refrigeration unit and an ammonia synthesis gas inlet pipe; the ammonia synthesis gas inlet pipe is connected to the ammonia cooler through the first heat exchange channel of the fourth heat exchanger; the second outlet of the second stream separator is connected to the first inlet of the lithium bromide refrigeration unit, the second outlet of the lithium bromide refrigeration unit is connected to the second heat exchange channel of the fourth heat exchanger through the second demineralized water closed-loop circulation pump, and the outlet of the second heat exchange channel of the fourth heat exchanger is connected to the second inlet of the lithium bromide refrigeration unit.
[0011] Preferably, the first outlet of the lithium bromide refrigeration unit is connected to a demineralized water pipeline.
[0012] According to the above scheme, a demineralized water system utilizing the low-grade waste heat of a synthetic ammonia system is manufactured. This invention couples the gasified black water and shift gas in the synthetic ammonia system with the demineralized water system, allowing the demineralized water to exchange heat with the gasified black water and shift gas before entering the deaerator. A portion of the demineralized water in the deaerator is coupled with the first demineralized water closed-loop circulation section to achieve the characteristic of reducing the temperature of the shift gas while producing by-product steam. Furthermore, this invention allows a portion of the aforementioned by-product steam to enter the ammonia synthesis gas cooling unit to cool the ammonia synthesis gas. It features a reasonable process design, effectively reducing the consumption of circulating cooling water while fully utilizing thermal energy. Attached Figure Description
[0013] To more clearly illustrate the technical solutions in the embodiments of this utility model 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 some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0014] Figure 1 This is a schematic diagram of the structure of this utility model.
[0015] In the diagram: 1. Gasification black water pipeline; 2. Shift gas pipeline; 3. Demineralized water pipeline; 4. First stream separator; 5. First heat exchanger; 6. Deaerator; 7. Second heat exchanger; 8. First boiler feed pump; 9. Third heat exchanger; 10. Gasification black water return pipeline; 11. Circulating water cooler; 12. Ammonia washing tower; 13. Lithium bromide heat pump unit; 14. Second boiler feed pump; 15. Steam network; 16. Second demineralized water closed-loop circulation pump; 17. First demineralized water closed-loop circulation pump; 18. First tee; 19. Second tee; 20. Valve; 21. Second stream separator; 22. Lithium bromide refrigeration unit; 23. Ammonia synthesis gas inlet pipeline; 24. Fourth heat exchanger; 25. Ammonia cooler. Detailed Implementation
[0016] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present utility model.
[0017] The following is in conjunction with the appendix Figure 1To further describe this application in detail, this utility model is a demineralized water system utilizing the low-grade waste heat of a synthetic ammonia system. The system includes a gasified black water feedwater pipeline 1 and a shift gas pipeline 2 in the synthetic ammonia system. A demineralized water pipeline 3 from the demineralized water and condensate refining unit is connected to a first stream separator 4. The first outlet of the first stream separator 4 is connected to the inlet of a deaerator 6 via the first heat exchange channel of a first heat exchanger 5. The second outlet of the first stream separator 4 is connected to the inlet of a deaerator 6 via the first heat exchange channel of a second heat exchanger 7. The first outlet of the deaerator 6 is connected to a first boiler feedwater pump 8. The second outlet of the deaerator 6 is connected to the first heat exchange channel of a third heat exchanger 9 via a first demineralized water closed-loop circulation section. The gasified black water pipeline 1 is connected to a gasified black water return water pipeline 10 via the second heat exchange channel of the first heat exchanger 5. The shift gas pipeline 2 is connected to the inlet of a circulating water cooler 11 via the second heat exchange channels of the third heat exchanger 9 and the second heat exchange channels of the second heat exchanger 7. The outlet of the circulating water cooler 11 is connected to an ammonia washing tower 12. The temperature of the gasified black water is generally around 139℃, the pressure is around 0.3 MPaG, and the flow rate is 250 t / h. In traditional technology, after primary and secondary flash evaporation, it enters a vacuum flash condenser and is cooled to around 75℃ by circulating water before being sent to the clarification tank. The circulating water consumption for cooling in this process is approximately 2000 t / h. The temperature of the shift gas is approximately 150℃. Conventional technology involves cooling it to around 40℃ via a heat exchanger before it enters the ammonia washing tower 12 for ammonia removal. This process requires approximately 3500 t / h of cooling circulating water. From the above, it can be seen that... Traditional technologies require a large amount of cooling circulating water, while this invention uses demineralized water as a cold source for heat exchange. The heat exchange process involves one stream of demineralized water exchanging heat with gasified black water through the first heat exchanger 5, and another stream of demineralized water exchanging heat with shifted gas through the second heat exchanger 7, thereby improving the thermal energy utilization rate. Furthermore, in order to fully utilize the thermal energy, this invention sets a third heat exchanger 9 in front of the second heat exchanger 7, and uses the demineralized water passing through the deaerator 6 to couple with the first demineralized water in a closed loop, thereby achieving the characteristic of producing by-product steam while reducing the temperature of the shifted gas.
[0018] Furthermore, the first demineralized water closed-loop circulation section includes a lithium bromide heat pump unit 13. The first inlet of the lithium bromide heat pump unit 13 is connected to the second outlet of the deaerator 6 via a second boiler feed water pump 14, and the first outlet of the lithium bromide heat pump unit 13 is connected to the steam pipeline network 15. The second outlet of the lithium bromide heat pump unit 13 is connected to the inlet of the first heat exchange channel of the third heat exchanger 9 via a first demineralized water closed-loop circulation pump 17, and the outlet of the second heat exchange channel of the third heat exchanger 9 is connected to the second inlet of the lithium bromide heat pump unit 13. This invention, employing a first demineralized water closed-loop circulation section, avoids contamination of the deoxygenated demineralized water and utilizes the heat of the shift gas to generate steam from the deoxygenated demineralized water, thereby achieving the characteristic of cooling the shift gas.
[0019] Furthermore, a first tee 18 is provided between the shift gas pipeline 2 and the second heat exchange channel of the third heat exchanger 9, and a second tee 19 is provided between the second heat exchange channel of the third heat exchanger 9 and the second heat exchange channel of the second heat exchanger 7. A bypass pipeline with a valve 20 is provided between the third end of the first tee 18 and the third end of the second tee 19. By setting the bypass pipeline with the valve 20, the process can be adjusted according to the actual operating conditions such as the flow rate and temperature of the shift gas to ensure the stable operation of the system. It should be noted that in actual use, this utility model prioritizes heating the demineralized water that does not enter the deaerator. When the temperature of the demineralized water that does not enter the deaerator is guaranteed, the shift gas can be further cooled through the third heat exchanger 9, while achieving the characteristic of producing by-product steam.
[0020] Furthermore, the first outlet of the lithium bromide heat pump unit 13 is connected to the steam pipeline network 15 through the first outlet of the second stream separator 21, and the second outlet of the second stream separator 21 is connected to the ammonia synthesis gas cooling unit. Traditionally, ammonia synthesis gas needs to be cooled to 29°C before passing through a primary ammonia cooler and a secondary ammonia cooler to separate liquid ammonia, requiring an ammonia compressor with a power of approximately 10,000 kW. This invention, through the above technical solution, can cool the ammonia synthesis gas to 14°C, thereby reducing the power consumption of the ammonia compressor.
[0021] Furthermore, the ammonia synthesis gas cooling unit includes a second demineralized water closed-loop circulation section with a lithium bromide refrigeration unit 22 and an ammonia synthesis gas inlet pipe 23. The ammonia synthesis gas inlet pipe 23 is connected to the ammonia cooler 25 through the first heat exchange channel of the fourth heat exchanger 24. The second outlet of the second stream separator 21 is connected to the first inlet of the lithium bromide refrigeration unit 22, and the second outlet of the lithium bromide refrigeration unit 22 is connected to the second heat exchange channel of the fourth heat exchanger 24 through the second demineralized water closed-loop circulation pump 16. The outlet of the second heat exchange channel of the fourth heat exchanger 24 is connected to the second inlet of the lithium bromide refrigeration unit 22. This invention uses the steam produced as a byproduct in the lithium bromide heat pump unit 13 as a heat source to drive the lithium bromide refrigeration unit 22, using the demineralized water in the second demineralized water closed-loop circulation section as a medium to cool the ammonia synthesis gas, thereby reducing the power of the subsequent ammonia compressor.
[0022] Furthermore, the first outlet of the lithium bromide refrigeration unit 22 is connected to the demineralized water pipeline 3. The steam from the lithium bromide refrigeration unit 22 is condensed into condensate, which can then be recycled within the demineralized water pipeline 3.
[0023] The specific working process of this utility model is as follows: The temperature of the demineralized water in the demineralized water pipeline 3 of the demineralized water and condensate refining unit is about 40℃, the pressure is 1.0 MPaG, and the flow rate is 500-600 t / h; the demineralized water is divided into two streams by the first stream separator 4 (each stream has a flow rate of about 250-300 t / h). The first stream of demineralized water exchanges heat with the gasified black water through the first heat exchanger 5. The temperature of the gasified black water before heat exchange is about 139℃, and the temperature after heat exchange is about 75℃. The gasified black water at about 75℃ can enter the subsequent clarification tank through the gasified black water return pipeline 10; through the first heat exchanger 5 The demineralized water after heat exchange (temperature of 110℃) enters deaerator 6; the primary stream of demineralized water exchanges heat with the shift gas through the second heat exchanger 7, and the demineralized water after heat exchange enters deaerator 6; most of the demineralized water after thermal deoxygenation in deaerator 6 enters the first boiler feed pump 8 to supply demineralized water to the boiler; a small portion of the demineralized water enters the lithium bromide heat pump unit 13 through the second boiler feed pump 14, where the small portion of demineralized water is heated to produce 0.5MPaG saturated steam; simultaneously, the closed-loop demineralized water in the first demineralized water closed-loop circulation section enters the third heat exchanger... Heater 9 cools the shift gas at approximately 150°C to approximately 100°C. The shift gas at approximately 100°C then exchanges heat with demineralized water through the second heat exchanger 7. After heat exchange, the shift gas temperature is approximately 45°C. This 45°C shift gas is then cooled to 40°C by the circulating water cooler 11 before entering the ammonia scrubbing tower 12 to remove ammonia and other impurities. When cooling of the ammonia synthesis gas is required, 0.5 MPaG saturated steam passes through the second stream separator 21. Part of the steam enters the steam network 15, while the other part serves as a heat source in the lithium bromide refrigeration unit 22. The condensate from the steam can then enter the demineralized water. The demineralized water, after being cooled in the lithium bromide refrigeration unit 22, is recycled in pipe 3 and enters the fourth heat exchanger 24 to cool the ammonia synthesis gas, which is at a temperature of about 29°C in the ammonia synthesis gas inlet pipe 23. After cooling, the temperature of the ammonia synthesis gas is 14°C and it is sent to the ammonia cooler 25 for further cooling. The power of the ammonia compressor in the above process is about 8800KW, which reduces power consumption. This invention changes the use of a large amount of cooling circulating water to using demineralized water for heat exchange and combines it with a closed-loop demineralized water circulation section, which reduces the amount of cooling circulating water used while ensuring that the boiler demineralized water is not contaminated.
[0024] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this utility model. Various changes and modifications can be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed utility model.
Claims
1. A demineralized water system utilizing low-grade waste heat from a synthetic ammonia system, the system comprising a gasification black water feedwater pipeline (1) and a shift gas pipeline (2) in the synthetic ammonia system, characterized in that: The demineralized water pipeline (3) of the demineralized water and condensate refining unit is connected to the first stream separator (4). The first outlet of the first stream separator (4) is connected to the inlet of the deaerator (6) through the first heat exchange channel of the first heat exchanger (5). The second outlet of the first stream separator (4) is connected to the inlet of the deaerator (6) through the first heat exchange channel of the second heat exchanger (7). The first outlet of the deaerator (6) is connected to the first boiler feed pump (8). The second outlet of the deaerator (6) is connected to the first heat exchange channel of the third heat exchanger (9) through the first demineralized water closed circulation section. The gasified black water pipeline (1) is connected to the gasified black water return pipeline (10) through the second heat exchange channel of the first heat exchanger (5); The shift gas pipeline (2) is connected to the inlet of the circulating water cooler (11) through the second heat exchange channel of the third heat exchanger (9) and the second heat exchange channel of the second heat exchanger (7), and the outlet of the circulating water cooler (11) is connected to the ammonia washing tower (12).
2. The demineralized water system utilizing low-grade waste heat from a synthetic ammonia system according to claim 1, characterized in that: The first demineralized water closed circulation section includes a lithium bromide heat pump unit (13). The first inlet of the lithium bromide heat pump unit (13) is connected to the second outlet of the deaerator (6) through the second boiler feed water pump (14). The first outlet of the lithium bromide heat pump unit (13) is connected to the steam pipeline network (15). The second outlet of the lithium bromide heat pump unit (13) is connected to the inlet of the first heat exchange channel of the third heat exchanger (9) via the first demineralized water closed circulation pump (17), and the outlet of the second heat exchange channel of the third heat exchanger (9) is connected to the second inlet of the lithium bromide heat pump unit (13).
3. A demineralized water system utilizing low-grade waste heat from a synthetic ammonia system according to claim 2, characterized in that: A first tee (18) is provided between the gas exchange pipe (2) and the second heat exchange channel of the third heat exchanger (9), and a second tee (19) is provided between the second heat exchange channel of the third heat exchanger (9) and the second heat exchange channel of the second heat exchanger (7). A shortcut pipe with a valve (20) is provided between the third end of the first tee (18) and the third end of the second tee (19).
4. A demineralized water system utilizing low-grade waste heat from a synthetic ammonia system according to claim 2, characterized in that: The first outlet of the lithium bromide heat pump unit (13) is connected to the steam network (15) through the first outlet of the second stream separator (21), and the second outlet of the second stream separator (21) is connected to the ammonia synthesis gas cooling unit.
5. A demineralized water system utilizing low-grade waste heat from a synthetic ammonia system according to claim 4, characterized in that: The ammonia synthesis gas cooling unit includes a second demineralized water closed circulation section with a lithium bromide refrigeration unit (22) and an ammonia synthesis gas inlet pipe (23); The ammonia synthesis gas inlet pipe (23) is connected to the ammonia cooler (25) through the first heat exchange channel of the fourth heat exchanger (24); The second outlet of the second stream separator (21) is connected to the first inlet of the lithium bromide refrigeration unit (22). The second outlet of the lithium bromide refrigeration unit (22) is connected to the second heat exchange channel of the fourth heat exchanger (24) via the second demineralized water closed circulation pump (16). The outlet of the second heat exchange channel of the fourth heat exchanger (24) is connected to the second inlet of the lithium bromide refrigeration unit (22).
6. A demineralized water system utilizing low-grade waste heat from a synthetic ammonia system according to claim 4, characterized in that: The first outlet of the lithium bromide refrigeration unit (22) is connected to the demineralized water pipeline (3).