An absorption refrigeration system for a low temperature methanol washing device
By absorbing and pressurizing gaseous ammonia through spraying with liquid absorbent in the refrigeration system, and combining this with low-quality steam heating and desorption, the problems of high energy consumption and low thermal energy utilization in traditional ammonia refrigeration systems have been solved, achieving reduced energy consumption and improved thermal energy utilization.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- JIANGSU HENGFENG NENGHUAN TECH CORP LTD
- Filing Date
- 2025-07-21
- Publication Date
- 2026-05-26
AI Technical Summary
Traditional low-temperature methanol washing units have high energy consumption in their ammonia refrigeration systems and low steam thermal energy utilization rates. In addition, the icing system has high energy consumption, especially the high steam pressure of the turbine, which leads to energy waste and low thermal energy utilization.
An absorption refrigeration system is adopted, which uses a liquid ammonia evaporation unit, an absorption pressurization unit, and a heating and decomposition unit to spray and absorb gaseous ammonia with a liquid absorbent and pressurize it, combined with heating and decomposition of low-quality steam, to replace the compression process of a traditional ammonia compressor.
This reduced the energy consumption of the ice machine system, improved the utilization rate of steam heat energy, reduced the consumption of high-pressure steam, and achieved the effect of saving coal and reducing carbon emissions.
Smart Images
Figure CN224284980U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of chemical equipment technology, and more specifically, to an absorption refrigeration system for a low-temperature methanol washing unit. Background Technology
[0002] Coal chemical industry commonly produces coal gas (H2+CO+CO2) through fluidized bed coal gasification (whether it is coal-water slurry or pulverized coal gasification). The coal gas then needs to be purified, desulfurized and decarbonized to obtain qualified syngas. Among these processes, the purification process currently mostly adopts the low-temperature methanol washing process.
[0003] The principle of low-temperature methanol washing is to use methanol at -50 to -60°C as an absorbent to remove hydrogen sulfide and CO2 from coal gas. At low temperatures, the absorption rates of hydrogen sulfide and carbon dioxide are very high, while the absorption rates of hydrogen and carbon monoxide are relatively low, thus separating them. Finally, the methanol saturated with hydrogen sulfide and carbon dioxide is heated to about 100°C to release hydrogen sulfide and carbon dioxide, becoming lean methanol. This lean methanol is then cooled to -50 to -60°C by an ammonia cooler and then recycled for absorption.
[0004] The large amount of cooling required in the low-temperature methanol washing process is achieved through ammonia refrigeration. Liquid ammonia undergoes a phase change in the liquid ammonia evaporator as its temperature decreases, absorbing heat and simultaneously cooling the methanol flowing into the evaporator. The liquid ammonia is heated by the methanol and vaporizes into gaseous ammonia. The gaseous ammonia is then compressed to approximately 1.0–2.0 MPa by a compressor, and then cooled by circulating cooling water, undergoing another phase change back to liquid ammonia. The liquid ammonia then returns to the evaporator to cool the methanol. Throughout the entire process, ammonia acts as a refrigerant, continuously evaporating and condensing, undergoing continuous phase changes to achieve refrigeration.
[0005] The compression process of gaseous ammonia requires power input to the ammonia compressor. Generally, the power can be driven by an electric motor, or it can be driven by a steam turbine using traditional processes. A common form of gaseous ammonia compression driven by a steam turbine is carried out through an ice machine system that includes a steam turbine and an ammonia compressor.
[0006] The steam turbines in the ice machine system are basically back-pressure or fully condensing types. Superheated steam of 2.0 to 9.8 MPa is fed into the steam turbine for driving. The exhaust steam of the back-pressure steam turbine is fed into the steam pipeline network for reuse. The fully condensing steam turbine is equipped with a condenser at the tail end, which is responsible for condensing the steam exhaust gas into condensate water, thereby realizing steam driving.
[0007] The aforementioned traditional processes have certain drawbacks. First, the compressors require high power and energy consumption, typically driven by steam or electricity. Industrial steam turbines require approximately 40 t / h of superheated steam, and even the smallest electric-driven turbines start at 500 kW. Second, the steam used in steam turbines is high-pressure superheated steam, generally 2.0–9.8 MPa. After the superheated steam performs work on the turbine, it becomes exhaust steam, resulting in a low thermal energy utilization rate of only 20%. Third, because the exhaust steam from back-pressure steam turbines is depressurized and cooled, it becomes low-quality steam, leading to low utilization efficiency, or it may condense entirely into liquid. The steam phase change heat energy relies entirely on circulating water for cooling, resulting in high cooling energy consumption. Utility Model Content
[0008] The purpose of this application is to provide an absorption refrigeration system for a low-temperature methanol washing device, which can compress gaseous ammonia by absorbing, pressurizing, and then desorbing the gaseous ammonia through an absorbent, thereby effectively reducing the energy consumption of the ice machine system and improving the utilization rate of steam thermal energy. In the form of combining the steam turbine of the ice machine system with the absorption refrigeration system, the energy consumption of the ice machine can be reduced or it can completely replace the gaseous ammonia compression and condensation of the traditional ice machine system.
[0009] To achieve the above objectives, this utility model provides an absorption refrigeration system for a low-temperature methanol washing device, comprising a liquid ammonia evaporation unit, an absorption pressurization unit, a heating and desorption unit, and a gaseous ammonia condensation unit arranged sequentially.
[0010] The liquid ammonia evaporation unit is used to supply methanol to the low-temperature methanol washing device and cool the methanol through the phase change of liquid ammonia evaporation.
[0011] The absorption and pressurization unit is used to spray and absorb the gaseous ammonia after the phase change of evaporation in the liquid ammonia evaporation unit, and to pressurize the rich liquid after absorbing the gaseous ammonia.
[0012] The heating and desorption unit is used to heat the pressurized rich liquid and desorb ammonia gas to obtain pressurized gaseous ammonia.
[0013] The gaseous ammonia condensation unit is used to receive and condense the gaseous ammonia pressurized by the heating and desorption unit, and to circulate the condensed liquid ammonia back to the liquid ammonia evaporation unit.
[0014] The absorption and pressurization unit includes a gaseous ammonia absorber for spray absorption of gaseous ammonia, and the gaseous ammonia absorber is connected to a rich liquid pressurization pump through a rich liquid output pipeline.
[0015] The heating and desorption unit includes a lean and rich liquid heat exchanger and a liquid ammonia desorber. The rich liquid pressurization pump is connected to the lean and rich liquid heat exchanger through a rich liquid pressurization pipeline, and the lean and rich liquid heat exchanger is connected to the liquid ammonia desorber through a rich liquid desorption pipeline.
[0016] A lean liquid delivery pipeline connects the liquid ammonia desorber to the lean and rich liquid heat exchanger, and a lean liquid output pipeline connects the lean and rich liquid heat exchanger to the gaseous ammonia absorber.
[0017] The liquid ammonia analyzer is connected to a heating steam pipeline for heating the pressurized rich liquid. The heating steam pipeline includes a low-quality steam pipeline outside the plant area or a steam exhaust pipeline of the turbine in the refrigeration system.
[0018] In an optional embodiment, the gaseous ammonia absorber is provided with a circulating water cooling pipe, which is used to cool the rich liquid in the gaseous ammonia absorber.
[0019] In an optional embodiment, the lean liquid output pipeline is provided with a lean liquid pressure reducing valve for reducing the pressure of the output lean liquid.
[0020] In an optional embodiment, the gaseous ammonia absorber is provided with a lean liquid spray pipe inside, which is connected to the lean liquid output pipe.
[0021] In an optional embodiment, the liquid ammonia analyzer is connected to the steam exhaust pipe, and the absorption refrigeration system is also connected to the ice machine system by a liquid ammonia inlet main pipe and a gaseous ammonia outlet pipe.
[0022] In an optional embodiment, the liquid ammonia evaporation unit includes a first liquid ammonia evaporator and a second liquid ammonia evaporator, and the main liquid ammonia supply pipe is branched to a first liquid ammonia supply pipe and a second liquid ammonia supply pipe, and the first liquid ammonia supply pipe and the second liquid ammonia supply pipe are respectively connected to the first liquid ammonia evaporator and the second liquid ammonia evaporator.
[0023] The first liquid ammonia evaporator and the second liquid ammonia evaporator are respectively connected to a methanol input pipe and a methanol output pipe.
[0024] In an optional embodiment, the first liquid ammonia evaporator and the second liquid ammonia evaporator are respectively connected to a first gaseous ammonia output pipe and a second gaseous ammonia output pipe, the first gaseous ammonia output pipe and the second gaseous ammonia output pipe are connected to a gaseous ammonia output main pipe, and the gaseous ammonia output main pipe is connected to the gaseous ammonia absorber.
[0025] In an optional embodiment, the ice machine system includes an inlet separator and a liquid ammonia storage tank;
[0026] The root of the ammonia gaseous export pipeline is connected to the main ammonia gaseous export pipeline, and the other end is connected to the inlet separator.
[0027] The root of the liquid ammonia replenishment main pipe is connected to the liquid ammonia storage tank.
[0028] In an optional embodiment, the steam turbine is coaxially connected to the high-pressure cylinder and the low-pressure cylinder of the ammonia compressor, and the first-stage inlet separator is connected to the low-pressure cylinder through a low-pressure ammonia gas delivery pipeline;
[0029] The steam turbine is connected to a back pressure exhaust pipe. One end of the steam exhaust pipe is connected to the liquid ammonia analyzer, and the other end is connected to the back pressure exhaust pipe.
[0030] In an optional embodiment, the liquid ammonia desorber is connected to a vapor condensate output pipe for discharging the converted vapor condensate to the outside.
[0031] The absorption refrigeration system for a low-temperature methanol washing device of this invention can obtain a rich absorbent liquid by spraying ammonia gas, which is used as a refrigerant, with a liquid absorbent. The rich absorbent liquid after absorbing ammonia gas is pressurized to 1.0-2.0 MPa by a pump, and the pressurized rich absorbent liquid is heated to release the ammonia gas in the rich absorbent liquid, thereby obtaining pressurized ammonia gas at 1.0-2.0 MPa. This achieves the pressurization of ammonia gas, which is conducive to the condensation of the pressurized ammonia gas.
[0032] By using liquid absorbents for ammonia compression and condensation, the energy consumption of traditional ammonia compression ice machine systems can be reduced. Under conditions of low ammonia circulation, it can even completely replace the ammonia compression operation of the ice machine system, minimizing the energy consumption required for refrigeration.
[0033] By combining the use of low-quality steam from the plant area or exhaust steam from the turbine of the refrigeration system to heat the rich absorbent liquid, the pressurized rich absorbent liquid can be desorbed into ammonia gas, thereby improving the utilization rate of steam thermal energy.
[0034] When the absorption refrigeration system is combined with the ice machine system, the exhaust steam from the back-pressure turbine can be effectively utilized to reduce the amount of circulating ammonia, thereby reducing the energy consumption of the ice machine system in compressing ammonia and reducing the amount of high-pressure steam used to achieve the purpose of saving coal and reducing carbon. At the same time, the absorption refrigeration system and the ice machine system can be matched for refrigeration operation to meet the operating requirements of different application scenarios.
[0035] Other features and advantages of this application will be described in detail in the following detailed description section. Attached Figure Description
[0036] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0037] Figure 1 This is a schematic diagram of the absorption refrigeration system used in the low-temperature methanol washing device in this application;
[0038] Figure 2 This is a schematic diagram of the ice machine system.
[0039] icon:
[0040] 1-Liquid ammonia evaporation unit; 1a-First liquid ammonia evaporator; 1b-Second liquid ammonia evaporator; 11-First gaseous ammonia output pipe; 12-Second gaseous ammonia output pipe; 13-Main gaseous ammonia output pipe;
[0041] 2-Absorption and pressurization unit; 21-Gasmic ammonia absorber; 22-Rich solution output pipe; 23-Rich solution pressurization pump; 24-Rich solution booster pipe; 25-Circulating water cooling pipe; 26-Lean solution spray pipe;
[0042] 3-Heating and desorption unit; 31-Lean and rich liquid heat exchanger; 32-Liquid ammonia desorption unit; 33-Rich liquid desorption pipeline; 34-Lean liquid conveying pipeline; 35-Lean liquid output pipeline; 36-Lean liquid pressure reducing valve; 37-Steam condensate output pipeline;
[0043] 4-Ammonia condensation unit; 41-Ammonia condenser; 42-Liquid ammonia output pipeline; 43-Liquid ammonia pressure reducing valve;
[0044] 5- Heating steam pipes;
[0045] 10 - Liquid ammonia inlet main pipe; 10a - First liquid ammonia inlet pipe; 10b - Second liquid ammonia inlet pipe;
[0046] 20-Ammonia gas export pipeline;
[0047] 30-Methanol input pipeline;
[0048] 40-Methanol output pipeline;
[0049] 50-Ice machine system; 51-First stage inlet separator; 52-Liquid ammonia storage tank; 53-Steam turbine; 54-Back pressure exhaust pipe. Detailed Implementation
[0050] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.
[0051] In the description of this application, it should be noted that the terms "inner" and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use. They are used only for the convenience of describing this application and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.
[0052] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "setup" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.
[0053] The absorption refrigeration system for the low-temperature methanol washing device in this application is specifically an absorption refrigeration system. It uses an absorbent to spray and absorb gaseous ammonia, which is converted from liquid ammonia after the methanol is cooled, and then pressurizes the absorbent rich liquid to 1.0-2.0 MPa using a pump. Combined with the heating operation of the absorbent rich liquid with low-quality steam, the pressurized absorbent rich liquid can decompose and release gaseous ammonia, and obtain gaseous ammonia at 1.0-2.0 MPa, thereby realizing the compression of gaseous ammonia after the liquid ammonia evaporates and cools the methanol.
[0054] After being pressurized, gaseous ammonia can be cooled into liquid ammonia by circulating water. The liquid ammonia is then depressurized and transported to the liquid ammonia evaporation unit to cool down the methanol. At the same time, the liquid ammonia undergoes a phase change and is converted into gaseous ammonia, which is then sprayed and absorbed by the absorbent. This cycle repeats continuously.
[0055] Based on the above-described process of pressurizing gaseous ammonia and cooling methanol in the low-temperature methanol washing unit, see [reference needed]. Figure 1 The absorption refrigeration system for a low-temperature methanol washing device in this invention includes a liquid ammonia evaporation unit 1, an absorption pressurization unit 2, a heating and desorption unit 3, and a gaseous ammonia condensation unit 4 arranged in sequence.
[0056] The liquid ammonia evaporation unit 1 is used to supply methanol to the low-temperature methanol washing device and cool the methanol through the phase change of liquid ammonia evaporation. During the cooling process of methanol, the liquid ammonia absorbs heat from the methanol and undergoes a phase change to transform into gaseous ammonia.
[0057] The absorption and pressurization unit 2 is mainly used to pressurize the gaseous ammonia after phase change in the liquid ammonia evaporation unit 1. Specifically, it includes spraying and absorbing the gaseous ammonia after phase change in the liquid ammonia evaporation unit 1, and pressurizing the rich absorbent liquid after absorbing the gaseous ammonia with a pump.
[0058] Compared to the traditional method of pressurizing the ammonia compressor by driving a steam turbine 53, the method of pressurizing the absorbent rich liquid using a pump can effectively utilize the lower compressibility ratio of the liquid, allowing the ammonia dissolved in the absorbent rich liquid to be pressurized efficiently, greatly reducing the power consumption of the steam turbine 53. The liquid pressure boosting efficiency is much greater than the gas pressure boosting efficiency, thereby reducing the steam consumption of the refrigeration system.
[0059] The heating and desorption unit 3 is used to heat the pressurized absorbent rich liquid under the heating action of low-quality steam, and to release gaseous ammonia gas by desorption while heating the absorbent rich liquid. Based on the pressurization of the absorbent rich liquid, pressurized gaseous ammonia gas is obtained. At the same time, after the gaseous ammonia gas is desorbed and released, the absorbent rich liquid is converted into an ammonia-free absorbent lean liquid.
[0060] The ammonia condensation unit 4 specifically includes an ammonia condenser 41, which is used to receive and condense the ammonia gas after it is pressurized by the refrigeration unit, converting the ammonia gas into liquid ammonia, and then circulating the condensed liquid ammonia back to the liquid ammonia evaporation unit 1 to cool the methanol.
[0061] The absorption refrigeration system in this application is mainly characterized by the absorption pressurization unit 2 and the heating and desorption unit 3. The absorption pressurization unit 2 and the heating and desorption unit 3, combined with the absorbent that can absorb gaseous ammonia and desorb it after heating, compress and pressurize the gaseous ammonia.
[0062] From a specific composition perspective, the absorption pressurization unit 2 includes a gaseous ammonia absorber 21 for spray absorption of gaseous ammonia. Specifically, the gaseous ammonia absorber 21 absorbs gaseous ammonia by spray absorption of a lean absorbent solution, so that the lean absorbent solution is transformed into a rich absorbent solution after being saturated with gaseous ammonia adsorption.
[0063] The lean absorbent solution in this application is an absorbent solution without ammonia components after the gaseous ammonia is desorbed in the heating and desorption unit 3, while the rich absorbent solution is an absorbent solution saturated with gaseous ammonia after being sprayed and absorbed in the absorption and pressurization unit 2.
[0064] The ammonia absorber 21 is connected to a rich liquid pressurization pump 23 through a rich liquid output pipe 22. The pressurization of the absorbent rich liquid is specifically carried out by the rich liquid pressurization pump 23.
[0065] The heating and desorption unit 3 includes a lean and rich liquid heat exchanger 31 and a liquid ammonia desorber 32. The rich liquid pressurization pump 23 is connected to the lean and rich liquid heat exchanger 31 through the rich liquid pressurization pipeline 24, and the lean and rich liquid heat exchanger 31 is connected to the liquid ammonia desorber 32 through the rich liquid desorption pipeline 33.
[0066] The lean-rich liquid heat exchanger 31 is located between the liquid ammonia desorber 32 and the gaseous ammonia absorber 21. The rich absorbent liquid, after being pressurized by the rich liquid pressurization pump 23, is introduced into the tube side of the lean-rich liquid heat exchanger 31 through the rich liquid pressurization pipe 24. After exchanging heat with the lean absorbent liquid discharged from the liquid ammonia desorber 32 and gaining a temperature rise, it is input into the liquid ammonia desorber 32 through the rich liquid desorption pipe 33 for further heating and desorption of gaseous ammonia.
[0067] A lean liquid delivery pipe 34 is connected between the liquid ammonia analyzer 32 and the lean and rich liquid heat exchanger 31, and a lean liquid output pipe 35 is connected between the lean and rich liquid heat exchanger 31 and the gaseous ammonia absorber 21.
[0068] The lean absorbent solution in the liquid ammonia desorber 32 is fed into the shell side of the lean-rich solution heat exchanger 31 through the lean solution delivery pipe 34. After exchanging heat with the pressurized rich absorbent solution and being cooled, it is fed into the gaseous ammonia absorber 21 through the lean solution output pipe 35 for gaseous ammonia spray absorption.
[0069] In addition to reducing power consumption by efficiently boosting pressure through the rich liquid pressurization pump 23, this application also reduces energy consumption by utilizing the low-quality steam of the liquid ammonia desorber 32.
[0070] The liquid ammonia analyzer 32 is connected to a heating steam pipe 5, which is used to heat the rich absorbent liquid after pressurization and temperature rise. By setting the heating steam pipe 5 to be a low-quality steam pipe in the external plant area or a steam exhaust pipe of the steam turbine 53 in the ice machine system 50, the low-quality steam or the exhaust steam of the steam turbine 53 in the ice machine system 50 can be fully utilized, thereby improving the steam thermal energy utilization rate and minimizing the energy consumption of the ice machine system 50. In the case of using low-quality steam in the external plant area, it can even completely replace the gaseous ammonia compression and condensation performed by the traditional ice machine system 50.
[0071] To ensure the absorption effect of the lean absorbent solution on gaseous ammonia during spraying, the gaseous ammonia absorber 21 needs to be maintained at a relatively low temperature. At the same time, the solution in the gaseous ammonia absorber 21 needs to be controlled at a relatively low temperature. The gaseous ammonia absorber 21 is equipped with a circulating water cooling pipe 25, which cools the rich absorbent solution after spraying, so that it can be kept at a relatively low temperature of 20°C.
[0072] A lean liquid pressure reducing valve 36 is installed on the lean liquid output pipe 35 to reduce the pressure of the absorbent lean liquid output from the lean-rich liquid heat exchanger 31. By reducing the pressure of the absorbent lean liquid input from the lean-rich liquid heat exchanger 31 to the gaseous ammonia absorber 21, and by installing a lean liquid spray pipe 26 inside the gaseous ammonia absorber 21, and connecting the lean liquid spray pipe 26 to the lean liquid output pipe 35, the reduced pressure absorbent lean liquid can be passed into the lean liquid spray pipe 26 and sprayed to absorb the incoming gaseous ammonia.
[0073] From the perspective of the process flow of the absorption pressurization unit 2 and the heating desorption unit 3, gaseous ammonia is output from the liquid ammonia evaporation unit 1 at 0.06 MPa / -38℃ and enters the gaseous ammonia absorber 21. The lean absorbent solution sprays the input gaseous ammonia in the gaseous ammonia absorber 21, and the spray absorption obtains a rich absorbent solution at 0.2 MPa / 20℃. The rich absorbent solution is transported to the rich absorbent pressurization pump 23 through the rich absorbent solution output pipe 22. After being pressurized by the rich absorbent pressurization pump 23, the absorbent solution is absorbed. The absorbent-rich solution, under conditions of 1.5 MPa / 20℃, is transported through the rich solution pressurization pipe 24 into the tube side of the lean-rich solution heat exchanger 31. In the lean-rich solution heat exchanger 31, it exchanges heat with the absorbent-lean solution released from the liquid ammonia desorber 32, resulting in a temperature-raised absorbent-rich solution. This solution, under conditions of 1.5 MPa / 50℃, is then introduced into the liquid ammonia desorber 32 through the rich solution desorption pipe 33. The liquid ammonia desorber 32 is specifically in the form of a heat exchanger, resulting in a temperature-raised absorbent solution. The rich liquid is introduced into the tube side of the liquid ammonia desorber 32, and under the heating effect of the low-quality steam in the shell side of the liquid ammonia desorber 32, gaseous ammonia is desorbed and released, resulting in gaseous ammonia at 1.5 MPa / 80℃. The pressurized gaseous ammonia is introduced into the tube side of the gaseous ammonia condenser 41, and condensed under the cooling effect of the circulating cooling water in the shell side of the gaseous ammonia condenser 41, converting it into liquid ammonia at 1.5 MPa / 35℃. The liquid ammonia is input into the liquid ammonia evaporation unit 1 through the liquid ammonia output pipe 42. The liquid ammonia evaporation unit 1 includes a liquid ammonia evaporator. A liquid ammonia pressure reducing valve 43 is installed on the liquid ammonia output pipe 42. After the liquid ammonia at 1.5 MPa / 35℃ is reduced by the liquid ammonia pressure reducing valve 43, it is converted into liquid ammonia at 0.2 MPa / -18℃. After the pressure is reduced, it is introduced into the shell side of the liquid ammonia evaporator to cool the methanol in the low-temperature methanol washing device that is input into the tube side of the liquid ammonia evaporator. Under the cooling effect of the liquid ammonia evaporator, the methanol in the low-temperature methanol washing device is converted from methanol at 10℃ to methanol at -7℃.
[0074] After passing through the liquid ammonia evaporator, the liquid ammonia is converted into gaseous ammonia at 0.06 MPa / -38℃ and then re-entered into the gaseous ammonia absorber 21 for circulation.
[0075] After the rich absorbent solution releases gaseous ammonia in the liquid ammonia desorber 32, it is converted into a lean absorbent solution at 1.5 MPa / 90℃. This lean absorbent solution is then introduced into the shell side of the rich-lean-lean heat exchanger 31 via the lean absorbent delivery pipe 34. After heat exchange with the rich absorbent solution in the tube side of the heat exchanger 31, it is converted into a lean absorbent solution at 1.5 MPa / 25℃. After pressure reduction by the lean absorbent pressure reducing valve 36 on the lean absorbent output pipe 35, it is converted into a lean absorbent solution at 0.2 MPa / 20℃. This lean absorbent solution is then sent to the lean absorbent spray pipe 26 to spray and absorb the gaseous ammonia output from the liquid ammonia evaporator. After absorbing the gaseous ammonia, it is converted into a rich absorbent solution at 0.2 MPa / 20℃.
[0076] The core improvement of the absorption refrigeration system in this invention lies in the pressurization of the absorbent rich liquid by the rich liquid booster pump, and the use of low-quality steam to heat and desorb ammonia from the absorbent rich liquid.
[0077] By using a pump to pressurize the absorbent-rich liquid, compared to the conventional method of pressurizing gaseous ammonia using an ammonia compressor, the lower compressibility of the liquid is fully utilized. This allows for efficient pressurization of the liquid containing gaseous ammonia, reducing the power consumption associated with pressurizing high-compression-ratio gaseous ammonia. The liquid pressure boosting efficiency is far greater than that of the gas pressure boosting efficiency, thereby reducing the steam consumption of the refrigeration system.
[0078] By using low-quality steam for heating and analysis, the low-quality steam in the plant area can be fully utilized, or the exhaust steam from the turbine 53 can be effectively utilized when the absorption refrigeration system and the ice machine system 50 are operating in combination. This maximizes the thermal energy utilization rate of low-quality steam, reduces the energy consumption of the ice machine system 50, and achieves the ultimate technical goal of energy conservation and emission reduction.
[0079] To ensure a stable output of cooling capacity from the absorption refrigeration system, the absorption refrigeration system in this invention is preferably operated in conjunction with the ice machine system 50. The ice machine system 50 provides ample support for the absorption refrigeration system, while the absorption refrigeration system shares the operating load of the ice machine system 50, reducing the energy consumption of ammonia compression in the ice machine system 50. Furthermore, the combined operation of the ice machine system 50 and the absorption refrigeration system creates a mutually supportive and backup-oriented operating state.
[0080] Specifically, the liquid ammonia analyzer 32 is connected to the steam exhaust pipe of the steam turbine 53 of the ice machine system 50, and external heat is supplemented by the exhaust steam of the steam turbine 53 through the steam exhaust pipe.
[0081] Meanwhile, the absorption refrigeration system and the ice machine system 50 are also connected by a liquid ammonia inlet main pipe 10 and a gaseous ammonia outlet pipe 20. The liquid ammonia inlet main pipe 10 is mainly responsible for ensuring the cooling capacity of the ice machine system 50. It provides the necessary liquid ammonia to the liquid ammonia evaporator through the ice machine system 50 to meet the situation where the cooling capacity provided by the absorption refrigeration system alone cannot meet the overall operation.
[0082] The ammonia gas export pipeline 20 is more about sharing the operating load of the ice machine system 50. By using the absorption refrigeration system to pressurize a portion of the ammonia gas through absorption pressurization, and then feeding the other portion of the ammonia gas into the ice machine system 50, the absorption refrigeration system can share the pressurization load of the ammonia gas, reduce the ammonia gas compression load of the ice machine system 50, and thus reduce the consumption of superheated steam.
[0083] The liquid ammonia evaporation unit 1 includes a first liquid ammonia evaporator 1a and a second liquid ammonia evaporator 1b, with one operating and the other on standby, simultaneously serving the ice machine system 50. In this invention, the gaseous ammonia condenser 41 is connected to the first liquid ammonia evaporator 1a via a liquid ammonia output pipe 42. When the gaseous ammonia circulation volume is small, the cooling demand can be met solely through the first liquid ammonia evaporator 1a. Under this condition, it can completely replace the gaseous ammonia compression and condensation performed by the traditional ice machine system 50.
[0084] Under conditions where the gaseous ammonia circulation volume is large, the first liquid ammonia evaporator 1a and the second liquid ammonia evaporator 1b need to cool the methanol simultaneously.
[0085] The first liquid ammonia evaporator 1a and the second liquid ammonia evaporator 1b are respectively connected to a methanol inlet pipe 30 and a methanol outlet pipe 40. The methanol inlet pipe 30 and the methanol outlet pipe 40 are used to introduce methanol from the low-temperature methanol washing device into the tube side of the liquid ammonia evaporator, and to achieve cooling through the evaporation phase change of the liquid ammonia introduced into the shell side of the liquid ammonia evaporator.
[0086] The main liquid ammonia supply pipe 10 is branched to a first liquid ammonia supply pipe 10a and a second liquid ammonia supply pipe 10b. The first liquid ammonia supply pipe 10a and the second liquid ammonia supply pipe 10b are respectively connected to the first liquid ammonia evaporator 1a and the second liquid ammonia evaporator 1b, which can supply liquid ammonia from the ice machine system 50 to the two liquid ammonia evaporators to ensure the normal supply of cooling capacity.
[0087] The first liquid ammonia evaporator 1a and the second liquid ammonia evaporator 1b are respectively connected to the first gaseous ammonia output pipe 11 and the second gaseous ammonia output pipe 12. The first gaseous ammonia output pipe 11 and the second gaseous ammonia output pipe 12 are connected to the gaseous ammonia output main pipe 13. The gaseous ammonia output main pipe 13 is connected to the gaseous ammonia absorber 21, thereby circulating gaseous ammonia.
[0088] From the perspective of ensuring that the total amount of ammonia gas is compressed in the ice machine system 50, the ammonia gas export pipe 20 is connected to the ammonia gas output main pipe 13, which can introduce the ammonia gas exceeding the load of the absorption refrigeration system into the ice machine system 50 and obtain normal compression.
[0089] Combination Figure 2 The refrigeration system 50 includes an inlet separator 51 and a liquid ammonia storage tank 52. The root of the gaseous ammonia export pipe 20 is connected to the gaseous ammonia output main pipe 13, and the other end is connected to the inlet separator 51. This allows the gaseous ammonia exported from the absorption refrigeration system to be introduced into the inlet separator 51, and the gaseous ammonia introduced into the inlet separator 51 to be compressed by the ammonia compressor.
[0090] The root of the liquid ammonia inlet main pipe 10 is connected to the liquid ammonia storage tank 52, which can be used to replenish liquid ammonia from the ice machine system 50 to the absorption refrigeration system.
[0091] The steam turbine 53 in the ice machine system 50 is coaxially connected to the high-pressure cylinder and low-pressure cylinder of the ammonia compressor, enabling the ammonia compressor to operate under the action of superheated steam introduced into the steam turbine 53.
[0092] A first-stage inlet separator 51 is connected to a low-pressure cylinder via a low-pressure ammonia delivery pipeline. The ammonia gas exported from the absorption refrigeration system first enters the low-pressure cylinder, and then enters the high-pressure cylinder where it is compressed and pressurized.
[0093] The steam turbine 53 includes a back-pressure steam turbine 53, which is connected to a back-pressure exhaust pipe 54. One end of the steam exhaust pipe is connected to the liquid ammonia desorber 32, and the other end is connected to the back-pressure exhaust pipe 54. This allows the liquid ammonia desorber 32 to fully utilize the heat from the exhaust steam discharged from the steam turbine 53 to heat the pressurized absorbent liquid and desorb and release the gaseous ammonia.
[0094] The liquid ammonia analyzer 32 is connected to a steam condensate output pipe 37, which is used to discharge the steam condensate converted from low-quality steam to the outside and to recycle it.
[0095] In addition to the back-pressure turbine 53 mentioned above, the turbine 53 can also be a fully condensing turbine 53. The ammonia compressor is driven by a back-pressure or fully condensing turbine 53, using medium-pressure superheated steam of 2.0-9.8MPa. By passing the exhaust steam of the turbine 53 into the liquid ammonia desorber 32, the technical effect of effectively improving the steam thermal energy utilization rate can also be achieved.
[0096] While providing cooling capacity to the low-temperature methanol washing device, the absorption refrigeration system in this invention can also recover gaseous ammonia that has escaped from the liquid ammonia evaporation in the ammonia tank area.
[0097] The absorption refrigeration system of this invention uses a liquid absorbent to efficiently absorb gaseous ammonia. The pressure is increased by a pump, and the recovered low-grade heat energy is fully utilized to heat the rich liquid absorbent. After heating, the ammonia inside the rich liquid absorbent is released, and the gaseous ammonia pressure reaches 1.0-2.0 MPa. It directly enters the water cooler to condense into liquid ammonia, which is then reused as a liquid refrigerant.
[0098] Liquid absorbents have the characteristic of absorbing and desorbing gaseous ammonia. They can be in the form of lithium bromide aqueous solution. By changing the external operating conditions, the solubility of ammonia can be changed. For example, heating the pressurized absorbent rich solution can reduce the solubility of ammonia in the liquid absorbent, thus allowing the gaseous ammonia to be desorbed. At the same time, spraying the depressurized and cooled absorbent lean solution (which does not contain ammonia) can fully absorb the gaseous ammonia, achieving the technical effect of gaseous ammonia absorption and desorption cycle.
[0099] By utilizing the low-grade heat energy of the exhaust steam from back-pressure or fully condensing steam turbines, no additional heat energy is required. The operation is simple, no personnel are needed on-site after commissioning, the operating conditions are mild, it is green and environmentally friendly, and the cost is low.
[0100] Traditionally, when 2.5-4.0 MPa steam enters the steam turbine 53, only the steam pressure difference is utilized. The final phase change heat of the steam is not utilized, but instead, the pressure and temperature are reduced, wasting the latent heat energy of the steam. By using low-grade heat energy for heating, the efficiency can be improved by 40-50%.
[0101] By drawing a certain amount of steam from the exhaust pipe of the back-pressure steam turbine 53, the steam thermal energy utilization rate can be increased from 40% to 80%.
[0102] In the absorption refrigeration system, in the absorption pressurization unit 2, the pressure of the absorbent rich liquid can be raised to 1.0-2.0 MPa by a 75KW rich liquid pressurization pump 23. After heating, pressurized ammonia gas is released directly without the need for a high-power compressor to pressurize, thus minimizing energy consumption.
[0103] To illustrate that this utility model can achieve good energy-saving and consumption-reducing effects, the following different embodiments will be used for explanation.
[0104] Example 1
[0105] The specific operation process of the low-temperature methanol washing unit in the purification workshop of a coal chemical enterprise in Anhui Province, which uses liquid ammonia as a refrigerant, is as follows:
[0106] The process of using liquid ammonia as a refrigerant to lower the temperature of lean methanol is as follows:
[0107] (1) The methanol-rich liquid absorbed by the low-temperature methanol washing device is heated to about 100°C in the stripping tower.
[0108] (2) The hydrogen sulfide and CO2 in the absorbed methanol-rich liquid are desorbed at high temperature, and the methanol becomes lean methanol and regains its absorption properties.
[0109] (3) After the analysis is completed, the lean methanol is 100°C and exits the analysis tower into the water cooler to be cooled to 40°C.
[0110] (4) Because lean methanol only has high absorption properties when its temperature is reduced to -50 to -60℃, lean methanol is cooled by heat exchange with multiple heat exchangers before entering the absorption tower, and finally cooled to -50 to -60℃ by liquid ammonia evaporator before entering the absorption tower.
[0111] (5) By using the absorption refrigeration system in this utility model, the 40℃ lean methanol can be pre-cooled in advance to reduce the temperature of the lean methanol to 0℃~-5℃. Since the methanol is pre-cooled in advance, the load of the ammonia cooler in the later stage is reduced, thereby reducing the power load of the ice machine.
[0112] Based on the process data of the absorption refrigeration system pre-cooling lean methanol in this embodiment, energy consumption is saved by 4300 KW / h per hour, which is equivalent to an annual saving of 7.705 million kWh of electricity, 1000 t / a of standard coal, and a reduction of carbon emissions by 4400 t / a. This optimizes the low-temperature methanol washing refrigeration process and reduces energy consumption.
[0113] Example 2
[0114] Taking a coal chemical enterprise in Ordos, Inner Mongolia as an example, the low-temperature methanol washing uses liquid ammonia as the refrigerant, and the gaseous ammonia compression cooling is driven by a fully condensing steam turbine. The specific energy-saving methods include the following steps:
[0115] The refrigeration process involves absorbing and pressurizing gaseous ammonia using an absorbent solution and recovering the exhaust steam from the turbine after it has performed work.
[0116] (1) The methanol-rich liquid that has absorbed hydrogen sulfide and CO2 is heated to about 100°C in the regeneration tower.
[0117] (2) The hydrogen sulfide and CO2 in the methanol-rich liquid are released at high temperature, so that methanol can regain its absorption properties.
[0118] (3) Because methanol has a high absorption rate under high pressure and low temperature, the methanol exiting the stripping tower is first cooled to 40°C by a water cooler, then heats up through multiple methanol-rich heat exchangers, and finally cooled to -50 to -60°C by a liquid ammonia evaporator before entering the absorption tower.
[0119] (4) By using the absorption refrigeration system in this utility model, the 40℃ lean methanol can be pre-cooled in advance to reduce the temperature of the lean methanol to 0 to -5℃. Since the methanol is pre-cooled in advance, the load of the ammonia cooler in the later stage is reduced, thereby reducing the load of the ice machine.
[0120] (5) The low-pressure flash steam in the original gasification workshop was directly vented due to its low thermal quality. By introducing this part of the low-pressure flash steam to the liquid ammonia desorber, heat energy is provided to the liquid ammonia desorber, which not only recovers the steam but also reduces the carbon dioxide emissions.
[0121] Based on the process data of the absorption refrigeration system pre-cooling lean methanol in this embodiment, the ice machine load is reduced by 2100KW / h, saving 11,708,040KWh of electricity per year, saving 1450 tons of standard coal per year, and reducing carbon emissions by 6700 tons per year.
[0122] Example 3
[0123] Taking a coal chemical enterprise in Shandong Province as an example, the low-temperature methanol washing uses liquid ammonia as the refrigerant, and the gaseous ammonia compression cooling is driven by a fully condensing steam turbine. The specific energy-saving methods include the following steps:
[0124] The refrigeration process is achieved by absorbing and pressurizing gaseous ammonia with an absorbent solution and recovering the exhaust steam after the back-pressure steam turbine has performed its work, as follows:
[0125] (1) The methanol-rich liquid that has absorbed hydrogen sulfide and CO2 is heated to about 100°C in the regeneration tower.
[0126] (2) The hydrogen sulfide and CO2 in the methanol-rich liquid are released at high temperature, so that methanol can regain its absorption properties.
[0127] (3) Because methanol has a high absorption rate under high pressure and low temperature, the methanol exiting the stripping tower is first cooled to 40°C by a water cooler, then heats up through multiple methanol-rich heat exchangers, and finally cooled to -50 to -60°C by a liquid ammonia evaporator before entering the absorption tower.
[0128] (4) By using the absorption refrigeration system in this utility model, the 40℃ lean methanol can be pre-cooled in advance to reduce the temperature of the lean methanol to 0 to -5℃. Since the methanol is pre-cooled in advance, the load of the ammonia cooler in the later stage is reduced, thereby reducing the load of the ice machine.
[0129] (5) Extract 8-10 t / h of low-grade heat energy steam from the exhaust steam of the back-pressure steam turbine to provide heat energy for the generator.
[0130] Based on the process data of the absorption refrigeration system pre-cooling lean methanol in this embodiment, the ice machine load is reduced by 2100KW / h, annual electricity savings are 7780000KWh, standard coal savings are 950t / a, annual carbon emission reduction is 4950t / a, and the ice machine steam load is reduced.
[0131] It should be noted that, where there is no conflict, the features in the embodiments of this application can be combined with each other.
[0132] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. An absorption refrigeration system for a low temperature methanol wash unit, characterized in that, It includes a liquid ammonia evaporation unit, an absorption and pressurization unit, a heating and desorption unit, and a gaseous ammonia condensation unit arranged in sequence. The liquid ammonia evaporation unit is used to supply methanol to the low-temperature methanol washing device and cool the methanol through the phase change of liquid ammonia evaporation. The absorption and pressurization unit is used to spray and absorb the gaseous ammonia after the phase change of evaporation in the liquid ammonia evaporation unit, and to pressurize the rich liquid after absorbing the gaseous ammonia. The heating and desorption unit is used to heat the pressurized rich liquid and desorb ammonia gas to obtain pressurized gaseous ammonia. The gaseous ammonia condensation unit is used to receive and condense the gaseous ammonia pressurized by the heating and desorption unit, and to circulate the condensed liquid ammonia back to the liquid ammonia evaporation unit. The absorption and pressurization unit includes a gaseous ammonia absorber for spray absorption of gaseous ammonia, and the gaseous ammonia absorber is connected to a rich liquid pressurization pump through a rich liquid output pipeline. The heating and desorption unit includes a lean and rich liquid heat exchanger and a liquid ammonia desorber. The rich liquid pressurization pump is connected to the lean and rich liquid heat exchanger through a rich liquid pressurization pipeline, and the lean and rich liquid heat exchanger is connected to the liquid ammonia desorber through a rich liquid desorption pipeline. A lean liquid delivery pipeline connects the liquid ammonia desorber to the lean and rich liquid heat exchanger, and a lean liquid output pipeline connects the lean and rich liquid heat exchanger to the gaseous ammonia absorber. The liquid ammonia analyzer is connected to a heating steam pipeline for heating the pressurized rich liquid. The heating steam pipeline includes a low-quality steam pipeline outside the plant area or a steam exhaust pipeline of the turbine in the refrigeration system.
2. The rectisol system for a rectisol unit according to claim 1, wherein, The gaseous ammonia absorber is equipped with a circulating water cooling pipe, which is used to cool the rich liquid in the gaseous ammonia absorber.
3. The rectisol system for a rectisol unit according to claim 1, wherein, The lean liquid output pipeline is equipped with a lean liquid pressure reducing valve for reducing the pressure of the output lean liquid.
4. The rectisol system for low temperature methanol wash unit as claimed in claim 1 wherein, The gaseous ammonia absorber is equipped with a lean liquid spray pipe inside, which is connected to the lean liquid output pipe.
5. The rectisol system for low temperature methanol wash unit as claimed in claim 1 wherein, The liquid ammonia analyzer is connected to the steam exhaust pipe, and the absorption refrigeration system is also connected to the ice machine system by a liquid ammonia inlet main pipe and a gaseous ammonia outlet pipe.
6. The absorption refrigeration system for a low-temperature methanol washing device according to claim 5, characterized in that, The liquid ammonia evaporation unit includes a first liquid ammonia evaporator and a second liquid ammonia evaporator. The main liquid ammonia supply pipe is branched to a first liquid ammonia supply pipe and a second liquid ammonia supply pipe. The first liquid ammonia supply pipe and the second liquid ammonia supply pipe are respectively connected to the first liquid ammonia evaporator and the second liquid ammonia evaporator. The first liquid ammonia evaporator and the second liquid ammonia evaporator are respectively connected to a methanol input pipe and a methanol output pipe.
7. The absorption refrigeration system for a low-temperature methanol washing device according to claim 6, characterized in that, The first liquid ammonia evaporator and the second liquid ammonia evaporator are respectively connected to a first gaseous ammonia output pipe and a second gaseous ammonia output pipe. The first gaseous ammonia output pipe and the second gaseous ammonia output pipe are connected to a gaseous ammonia output main pipe, which is connected to the gaseous ammonia absorber.
8. The absorption refrigeration system for a low-temperature methanol washing device according to claim 7, characterized in that, The ice machine system includes an inlet separator and a liquid ammonia storage tank; The root of the ammonia gaseous export pipeline is connected to the main ammonia gaseous export pipeline, and the other end is connected to the inlet separator. The root of the liquid ammonia replenishment main pipe is connected to the liquid ammonia storage tank.
9. The absorption refrigeration system for a low-temperature methanol washing device according to claim 8, characterized in that, The steam turbine is coaxially connected to the high-pressure cylinder and low-pressure cylinder of the ammonia compressor, and the first-stage inlet separator is connected to the low-pressure cylinder through a low-pressure ammonia gas delivery pipeline; The steam turbine is connected to a back pressure exhaust pipe. One end of the steam exhaust pipe is connected to the liquid ammonia analyzer, and the other end is connected to the back pressure exhaust pipe.
10. The absorption refrigeration system for a low-temperature methanol washing device according to claim 5, characterized in that, The liquid ammonia desorber is connected to a steam condensate output pipe, which is used to discharge the converted steam condensate to the outside.