Multi-stage absorption type refrigeration system for separation of synthetic ammonia
By designing a multi-stage absorption refrigeration system, the problems of temperature difference loss and high pressure caused by lithium bromide chillers were solved, resulting in reduced energy consumption and improved safety of the ammonia synthesis system.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- ANHUI METAENERGY TECHNOLOGIES CO LTD
- Filing Date
- 2025-01-27
- Publication Date
- 2026-04-21
AI Technical Summary
In existing ammonia synthesis systems, the use of lithium bromide chillers leads to increased temperature difference losses and high pressure, resulting in design pressure and safety hazards for the units, as well as increased energy consumption and production costs.
The absorption refrigeration system employs a multi-stage absorption process, including a generator, a condenser, a first ammonia cooler, a second ammonia cooler, and a dual absorption assembly. By connecting low-pressure and medium-pressure absorbers in series, circulating water is used for cooling, reducing the evaporation temperature and the power consumption of the circulating pump, increasing the solution circulation rate, and reducing the number of devices and control complexity.
It effectively reduces evaporation temperature and circulating pump power consumption, reduces energy consumption and equipment costs, improves system thermal efficiency and load regulation, and reduces safety hazards.
Smart Images
Figure CN224151191U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of synthetic ammonia separation technology, specifically to a multi-stage absorption refrigeration system for synthetic ammonia separation. Background Technology
[0002] The synthesis reaction is a volume-reduced, catalyst-containing, reversible, and exothermic reaction. In the ammonia synthesis process, a large amount of heat is released during ammonia synthesis, resulting in a high temperature of the ammonia synthesis process gas. However, due to the incomplete synthesis reaction, the liquid ammonia in the process gas needs to be separated at low temperatures after ammonia synthesis. Therefore, the ammonia synthesis process is one that generates both heat and requires cooling.
[0003] In the ammonia synthesis process, the high-temperature synthesis gas recovers its heat through a waste heat recovery system, then cools to ambient temperature with circulating water, recovers its cold energy through a cold exchanger, and finally liquefies and separates the gaseous ammonia in the process gas by generating low-temperature cold energy to obtain the product ammonia. Since existing ammonia synthesis systems utilize electric compression or steam compression refrigeration systems to generate cold energy, a large amount of electrical energy or high-grade steam is consumed during the refrigeration process, ultimately leading to increased production costs. Simultaneously, the process generates a significant amount of waste heat, the utilization of which presents a challenge. Therefore, the existing ammonia synthesis system suffers from a significant drawback in terms of heat and cold balance.
[0004] Some have proposed applying lithium bromide absorption chillers to the ammonia synthesis process, using the process heat from production to generate the cooling required for liquefaction. This would undoubtedly improve the ammonia synthesis process and reduce system energy consumption. However, in practice, if lithium bromide chillers are used, the temperature difference caused by the sensible heat of the chilled water would raise the outlet temperature of the process gas from the primary ammonia chiller. This would cause the operating process to deviate from the design process package and increase the cooling load of the secondary ammonia chiller. If the process gas is directly condensed and liquefied in the lithium bromide chiller, the high pressure of the synthesis process gas would greatly increase the design pressure of the unit and create safety hazards, thereby increasing the unit's production costs. It would also have a significant impact on the main process due to system instability and leakage. Utility Model Content
[0005] The purpose of this invention is to provide a multi-stage absorption refrigeration system for ammonia synthesis separation, in order to solve the problem of increased design pressure and safety hazards of the unit mentioned in the background art, which leads to increased production costs of the unit.
[0006] To achieve the above objectives, this utility model provides the following technical solution: a multi-stage absorption refrigeration system for ammonia synthesis separation, comprising: a generator, a condenser, a first ammonia cooler, a second ammonia cooler, and a dual absorption assembly;
[0007] The first ammonia cooler uses the cold source generated by the condenser to cool the synthetic ammonia, and the second ammonia cooler uses the remaining cold source in the first ammonia cooler to cool the synthetic ammonia again. The dual absorption component is used to absorb the cold source after the first ammonia cooler and the second ammonia cooler have been heated.
[0008] Preferably, the dual absorption assembly includes a low-pressure absorber, a medium-pressure absorber, and two pumps;
[0009] The low-pressure absorber's lean liquid inlet is connected to the generator's lean liquid outlet; the low-pressure absorber's gas inlet is connected to the second ammonia cooler's gas outlet; the low-pressure absorber's solution outlet is connected to the medium-pressure absorber's solution inlet via a pump; the medium-pressure absorber's gas inlet is connected to the first ammonia cooler's gas outlet; and the medium-pressure absorber's solution outlet is connected to the generator's rich liquid inlet via a pump.
[0010] Preferably, the absorption refrigeration system further includes a buffer tank, a first heat exchanger, and a second heat exchanger;
[0011] The inlet of the buffer tank is connected to the cold source outlet of the condenser, and the outlet of the buffer tank is connected to the cold source inlet of the first ammonia cooler. The first heat exchanger is used to exchange heat between the cold source discharged from the buffer tank and the cold source discharged from the first ammonia cooler and the second ammonia cooler. The second heat exchanger is used to exchange heat between the lean solution discharged from the generator and the solution discharged from the medium-pressure absorber.
[0012] Preferably, the cold source inlet of the first ammonia cooler is connected to an expansion valve, and the cold source inlet of the second ammonia cooler is also connected to an expansion valve.
[0013] Preferably, the low-pressure absorber is provided with a liquid distribution assembly for communicating with the lean liquid inlet of the low-pressure absorber, and the medium-pressure absorber is provided with a liquid distribution assembly for communicating with the solution inlet of the medium-pressure absorber.
[0014] Preferably, both the low-pressure absorber and the medium-pressure absorber utilize external circulating water for cooling.
[0015] Preferably, the external circulating water enters the low-pressure absorber and the medium-pressure absorber in sequence.
[0016] Preferably, the external circulating water enters the low-pressure absorber and the medium-pressure absorber respectively.
[0017] Compared with the prior art, the beneficial effects of this utility model are:
[0018] 1. The first ammonia cooler and the second ammonia cooler have different evaporation temperatures. Since the second ammonia cooler requires a lower refrigeration temperature, the low-pressure absorber and the medium-pressure absorber are connected in series. Because the ammonia content of the lean solution from the generator is very low, it can be directly absorbed into the low-pressure absorber at a lower absorption pressure, effectively reducing the evaporation temperature of the second ammonia cooler. Moreover, by having circulating water enter the low-pressure absorber first, the absorption temperature of the low-pressure absorber can be reduced, ultimately resulting in the maximum reduction in the evaporation temperature of the low-pressure evaporator.
[0019] 2. By connecting the low-pressure absorber and the medium-pressure absorber in series, the head of the circulating pump is reduced from 1~1.5MPa to 0.1~0.5MPa, which can effectively reduce the power consumption of the circulating pump and reduce the operating cost of the unit. Moreover, the series absorption method can increase the concentration difference between the lean solution and the rich solution through multiple absorptions, increase the solution circulation ratio, and reduce the solution circulation volume, which can also reduce the energy consumption of the unit and increase the thermal efficiency of the unit.
[0020] 3. Combining two refrigeration systems with different cooling temperatures into a single refrigeration unit can effectively reduce the number of equipment, reduce the complexity of the control system, and significantly reduce equipment costs. Since the ammonia synthesis process only needs to control the final condensation temperature of the ammonia, the process gas temperature at the ammonia refrigeration outlet can be organically adjusted to the optimal state of the system as the ammonia synthesis process load fluctuates and the refrigeration system changes. The adaptability of the refrigeration unit to load fluctuations during the production process is enhanced. Attached Figure Description
[0021] Figure 1 This is a schematic diagram of the absorption refrigeration system of this utility model;
[0022] Figure 2 This is a schematic diagram of one embodiment of the absorption refrigeration system of this utility model.
[0023] In the diagram: 1. Generator; 2. Condenser; 3. Buffer tank; 4. First heat exchanger; 5. First ammonia cooler; 6. Second ammonia cooler; 7. Second heat exchanger; 8. Low-pressure absorber; 9. Medium-pressure absorber; 10. Pump. Detailed Implementation
[0024] 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 protection scope of the present utility model.
[0025] Example 1
[0026] Please see Figure 1 An absorption refrigeration system for ammonia synthesis separation with multi-stage absorption includes: a generator 1, a condenser 2, a first ammonia cooler 5, a second ammonia cooler 6, a dual absorption assembly, a buffer tank 3, a first heat exchanger 4, and a second heat exchanger 7.
[0027] Please refer to Figure 1 The dual absorption assembly includes a low-pressure absorber 8, a medium-pressure absorber 9, and two pumps 10.
[0028] Please see Figure 1 The ammonia outlet of generator 1 (located on the shell of generator 1) is connected to the ammonia inlet of condenser 2 (located on the shell of condenser 2). The inlet of buffer tank 3 is connected to the cold source outlet of condenser 2 (located on the shell of condenser 2). The outlet of buffer tank 3 is connected to the shell inlet of the first heat exchanger 4. The shell outlet of the first heat exchanger 4 is connected to the cold source inlet of the first ammonia cooler 5 (located on the shell of the first ammonia cooler 5) via an expansion valve. The cold source outlet of the first ammonia cooler 5 (located on the shell of the first ammonia cooler 5) is connected to the cold source inlet of the second ammonia cooler 6 (located on the shell of the second ammonia cooler 6) via an expansion valve. The first heat exchanger 4 is connected to the shell of the first ammonia cooler 5 and the second ammonia cooler 6 respectively. The first heat exchanger 4 has two sets of heat exchange pipes installed inside. The inlets of the two sets of heat exchange pipes are connected to the gas outlets of the first ammonia cooler 5 and the second ammonia cooler 6 respectively (the gas outlets are located on the shells of the first ammonia cooler 5 and the second ammonia cooler 6). The outlet of the heat exchange pipe in the first heat exchanger 4 connected to the first ammonia cooler 5 is connected to the gas inlet of the medium pressure absorber 9 (located on the shell of the medium pressure absorber 9). The outlet of the heat exchange pipe in the first heat exchanger 4 connected to the second ammonia cooler 6 is connected to the gas inlet of the low pressure absorber 8 (located on the shell of the low pressure absorber 8).
[0029] Please see Figure 1 The lean liquid outlet of generator 1 is connected to the shell inlet of the second heat exchanger 7. The shell outlet of the second heat exchanger 7 is connected to the lean liquid inlet of the low-pressure absorber 8 (located on the shell of the low-pressure absorber 8). The solution outlet of the low-pressure absorber 8 (located on the shell of the low-pressure absorber 8) is connected to the solution inlet of the medium-pressure absorber 9 (located on the shell of the medium-pressure absorber 9) through pump 10. The solution outlet of the medium-pressure absorber 9 (located on the shell of the medium-pressure absorber 9) is connected to the pipe inlet of the second heat exchanger 7 through pump 10. The pipe outlet of the second heat exchanger 7 is connected to the rich liquid inlet of generator 1.
[0030] It should be noted that the generator 1 has heat exchange pipes installed inside for the flow of heat source (steam); the condenser 2 has heat exchange pipes installed inside for the flow of circulating water; the first ammonia cooler 5 and the second ammonia cooler 6 both have heat exchange pipes installed inside, and the outlet of the heat exchange pipe of the first ammonia cooler 5 is connected to the inlet of the heat exchange pipe of the second ammonia cooler 6 for supplying synthetic ammonia (i.e., synthesis process gas).
[0031] Please see Figure 1 Both the low-pressure absorber 8 and the medium-pressure absorber 9 are equipped with heat exchange pipes for circulating water to absorb the heat generated by the operation of the low-pressure absorber 8 and the medium-pressure absorber 9.
[0032] In this embodiment, as a further optimization, please refer to... Figure 2 External circulating water enters the low-pressure absorber 8 and the medium-pressure absorber 9 in sequence. The circulating water outlet of the low-pressure absorber 8 is connected to the circulating water inlet of the medium-pressure absorber 9, so that the external circulating water first enters the low-pressure absorber 8 and then enters the interior of the medium-pressure absorber 9.
[0033] In this embodiment, as a further optimization, please refer to... Figure 1 External circulating water enters the low-pressure absorber 8 and the medium-pressure absorber 9 respectively, allowing the external circulating water to enter the interior of the low-pressure absorber 8 and the medium-pressure absorber 9 respectively.
[0034] In this embodiment, as a further optimization, please refer to... Figure 1 The inner cavity of the low-pressure absorber 8 is provided with a liquid distribution assembly for communicating with the lean liquid inlet of the low-pressure absorber 8, and the inner cavity of the medium-pressure absorber 9 is provided with a liquid distribution assembly for communicating with the solution inlet of the medium-pressure absorber 9. The liquid distribution assembly includes a pipe and a nozzle installed on the pipe. The nozzle is used to atomize and disperse the solution entering the low-pressure absorber 8 and the medium-pressure absorber 9, so that it can fully contact and exchange heat with the circulating water; and so that the solution can more fully absorb the vaporized cold source discharged from the first ammonia cooler 5 and the second ammonia cooler 6.
[0035] Working principle:
[0036] A heat source (steam) enters generator 1 to heat the absorbent, releasing gaseous ammonia. After the gaseous ammonia in the absorbent is discharged, it becomes a lean solution. The lean solution is cooled by heat exchange in the second heat exchanger 7 and then enters the low-pressure absorber 8 to absorb low-pressure gaseous ammonia from the second ammonia cooler 6. The solution after absorbing gaseous ammonia is pressurized by pump 10 to the medium-pressure absorber 9 and absorbs medium-pressure gaseous ammonia from the first ammonia cooler 5. After forming a rich solution, it is pressurized by pump 10, heated by heat exchange in the second heat exchanger 7, and then enters generator 1 for recycling.
[0037] The gaseous ammonia released from generator 1 enters condenser 2, where it is condensed into liquid ammonia by circulating water and enters buffer tank 3. The liquid ammonia from buffer tank 3 is then heated by the first heat exchanger 4 and then depressurized by the expansion valve before entering the first ammonia cooler 5. In the first ammonia cooler 5, it evaporates and cools the synthetic ammonia, and some of the liquid ammonia is converted into gaseous ammonia. After being heated by the first heat exchanger 4, it enters the medium-pressure absorber 9 and is absorbed. The remaining liquid ammonia in the first ammonia cooler 5 is depressurized by the expansion valve and enters the second ammonia cooler 6 for evaporation and cooling, further cooling the synthetic ammonia that has been cooled by the first ammonia cooler 5. The liquid ammonia absorbs heat and is converted into gaseous ammonia. After being heated by the first heat exchanger 4, it enters the low-pressure absorber 8 and is absorbed.
[0038] It should be noted that the synthesized ammonia first enters the first ammonia cooler 5 and is cooled to 5~15℃, and then enters the second ammonia cooler 6 and is cooled to -10℃.
[0039] It should also be noted that, since the inlet temperature and final temperature of the process gas (synthetic ammonia) differ significantly, but only the final cooled temperature needs to be precisely controlled, using a single cooling temperature results in significant waste of cooling energy in the high-temperature cooling range. However, setting multiple cooling temperatures increases the complexity of the system process and equipment costs. Therefore, using two-stage cooling is more economical. Since the absorption refrigeration system controls the amount of ammonia gas extracted by the heating of the heat source during operation, thereby controlling the load, theoretically, the cooling load of the refrigeration system can fluctuate within the range of 0-100%. The absorption refrigeration system is significantly better at responding to load fluctuations in the ammonia synthesis process than the compression refrigeration system.
[0040] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. An absorption refrigeration system for multi-stage absorption of ammonia separation, characterized by: include: Generator (1), condenser (2), first ammonia cooler (5), second ammonia cooler (6) and dual absorption assembly; The first ammonia cooler (5) uses the cold source generated by the condenser (2) to cool the synthetic ammonia, and the second ammonia cooler (6) uses the remaining cold source in the first ammonia cooler (5) to cool the synthetic ammonia again. The dual absorption component is used to absorb the cold source after the first ammonia cooler (5) and the second ammonia cooler (6) have been heated.
2. An absorption refrigeration system for use in multi-stage absorption for ammonia separation according to claim 1, characterized in that: The dual absorption assembly includes a low-pressure absorber (8), a medium-pressure absorber (9), and two pumps (10). The lean liquid inlet of the low-pressure absorber (8) is connected to the lean liquid outlet of the generator (1), the gas inlet of the low-pressure absorber (8) is connected to the gas outlet of the second ammonia cooler (6), the solution outlet of the low-pressure absorber (8) is connected to the solution inlet of the medium-pressure absorber (9) through a pump (10), the gas inlet of the medium-pressure absorber (9) is connected to the gas outlet of the first ammonia cooler (5), and the solution outlet of the medium-pressure absorber (9) is connected to the rich liquid inlet of the generator (1) through a pump (10).
3. An absorption refrigeration system for use in multi-stage absorption for ammonia separation according to claim 2, characterized in that: The absorption refrigeration system also includes a buffer tank (3), a first heat exchanger (4) and a second heat exchanger (7). The inlet of the buffer tank (3) is connected to the cold source outlet of the condenser (2), and the outlet of the buffer tank (3) is connected to the cold source inlet of the first ammonia cooler (5). The first heat exchanger (4) is used to exchange heat between the cold source discharged from the buffer tank (3) and the cold source discharged from the first ammonia cooler (5) and the second ammonia cooler (6). The second heat exchanger (7) is used to exchange heat between the lean solution discharged from the generator (1) and the solution discharged from the medium-pressure absorber (9).
4. The multi-stage absorption refrigeration system for ammonia synthesis separation according to claim 2, characterized in that: An expansion valve is connected to the cold source inlet of the first ammonia cooler (5), and an expansion valve is connected to the cold source inlet of the second ammonia cooler (6).
5. An absorption refrigeration system for use in multi-stage absorption for ammonia separation as claimed in claim 2, wherein: The low-pressure absorber (8) is provided with a liquid distribution assembly for communicating with the lean liquid inlet of the low-pressure absorber (8), and the medium-pressure absorber (9) is provided with a liquid distribution assembly for communicating with the solution inlet of the medium-pressure absorber (9).
6. An absorption refrigeration system for use in multi-stage absorption for ammonia separation as claimed in claim 2, wherein: Both the low-pressure absorber (8) and the medium-pressure absorber (9) utilize external circulating water for cooling.
7. An absorption refrigeration system for use in a multi-stage absorption for ammonia separation according to claim 6, characterized in that: The external circulating water sequentially enters the low-pressure absorber (8) and the medium-pressure absorber (9).
8. An absorption refrigeration system for use in multi-stage absorption for ammonia separation according to claim 6, characterized in that: The external circulating water enters the low-pressure absorber (8) and the medium-pressure absorber (9) respectively.