CN111043785A - Rectification type self-cascade refrigeration system with precooling function - Google Patents
Rectification type self-cascade refrigeration system with precooling function Download PDFInfo
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B7/00—Compression machines, plants or systems, with cascade operation, i.e. with two or more circuits, the heat from the condenser of one circuit being absorbed by the evaporator of the next circuit
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B33/00—Boilers; Analysers; Rectifiers
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B40/00—Subcoolers, desuperheaters or superheaters
- F25B40/06—Superheaters
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B41/00—Fluid-circulation arrangements
- F25B41/30—Expansion means; Dispositions thereof
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B43/00—Arrangements for separating or purifying gases or liquids; Arrangements for vaporising the residuum of liquid refrigerant, e.g. by heat
- F25B43/02—Arrangements for separating or purifying gases or liquids; Arrangements for vaporising the residuum of liquid refrigerant, e.g. by heat for separating lubricants from the refrigerant
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Abstract
The invention relates to the technical field of refrigeration, and discloses a rectification type self-cascade refrigeration system with precooling, which comprises a rectification type self-cascade refrigeration loop and a precooling loop; the precooling loop is coupled with the tower top subcooler, the tower top heat exchanger and the kettle bottom subcooler in the rectification type self-cascade refrigeration loop into a whole, thereby providing cold energy for the rectification process, ensuring the stable tower top temperature of the rectification device and the target temperature, ensuring the separation effect and the oil removal effect in the rectification process, enhancing the capability of the system for coping with severe working conditions, simultaneously providing the supercooling degree for two working media at the tower top and the kettle bottom, reducing the suction temperature of the compressor, improving the operating condition of the compressor, ensuring the reliable and stable operation of the system, improving the refrigeration performance coefficient of the system and reducing the operation cost.
Description
Technical Field
The invention relates to the technical field of refrigeration, in particular to a rectification type self-cascade refrigeration system with precooling.
Background
With the continuous development of society, the practical application puts higher and higher requirements on refrigeration technology. In order to meet the requirement of lower refrigeration temperature, various refrigeration systems with various structures and various forms are continuously proposed and used in the fields of deep low temperature refrigeration, gas liquefaction and the like.
In the field of deep low temperature refrigeration, the mixed working medium is widely applied to self-cascade refrigeration. Patent CN102494467A discloses a refrigerating storage box with two-stage fractional condensation and separation regenerative throttling refrigeration of mixed working medium, wherein two gas-liquid separators are used in the adopted refrigerating system to realize the separation of high and low boiling point components of the mixed working medium. However, as the refrigeration temperature decreases, such a refrigeration system requires more gas-liquid separators to separate high and low boiling point components, which complicates the system structure and leads to deterioration in system environmental suitability and operational stability.
The patent CN 1152218C discloses a deep refrigeration device, which is mainly characterized in that the high-efficiency separation of the high and low boiling point components of the mixed working medium is realized by the rectification process of the rectification device, i.e. the rectification device is used to replace a multi-stage gas-liquid separator, thereby simplifying the system and improving the operation stability of the system.
Patent CN 101776358A discloses a variable-concentration mixed working medium auto-cascade refrigerator, and the rectifying device in the refrigeration system adopted by the refrigerator is the improvement and simplification of the above patent, namely, the cold quantity required by the rectifying process in the rectifying device is provided by the heat exchanger at the top of the tower.
Both of the above patents have problems in that when the ambient temperature rises, the condensing conditions deteriorate, resulting in an increase in the temperature of the working fluid entering the rectifying unit, and in turn, an increase in the temperature of the top of the tower. If the temperature at the top of the tower is too high, the rectification effect is poor, components with high and low boiling points of the mixed working medium cannot be effectively separated, and lubricating oil carried by the mixed working medium cannot be effectively separated, and if the lubricating oil enters a low-temperature part of a refrigeration system, the lubricating oil is easy to solidify, so that blockage is caused. Meanwhile, when the ambient temperature is higher, the temperature of the mixed working medium entering the rectifying device rises, the backflow working medium cannot provide enough cold for the tower top heat exchanger of the rectifying device, the superheat degree of the working medium of an air suction port of the compressor is increased, the exhaust temperature of the compressor is increased, and the operation condition of the compressor is deteriorated.
In order to increase the refrigerating capacity of the system, the common method in the prior art is to use deep well water for supercooling or adopt a partial cascade refrigeration system, and aims to increase the supercooling degree of a working medium, obtain lower outlet temperature of a subcooler and improve the refrigeration performance coefficient of the system.
Patent CN 110057124A proposes a partially overlapping type commercial CO2The invention relates to a transcritical two-stage compression refrigeration system, which supercools CO by adding a single-stage compression cycle2The transcritical double-stage compression refrigeration system increases the refrigeration capacity and improves the system performance, thereby improving the utilization efficiency of energy.
The partial cascade refrigeration system of patent CN 110057124 a and the conventional subcooling or other partial cascade refrigeration systems all consider that the objects are working mediums at the outlet of the condenser, and the purpose is to increase the degree of subcooling to improve the system cooling capacity and the refrigeration coefficient. However, for the rectification type self-cascade refrigeration system, if the method is adopted, the dryness of the mixed working medium entering the rectification device is reduced, so that the main flow rate is reduced, the refrigerating capacity is further insufficient, and the system performance is reduced.
Therefore, under the condition of ensuring the operation stability of the system, the problem that the rectification type self-cascade refrigeration system is greatly influenced by the external environment is solved, and the refrigeration performance of the system is not adversely influenced, so that the problem to be solved is urgently needed.
Disclosure of Invention
The invention aims to solve the problems that a rectification type self-cascade refrigeration system in the prior art is greatly influenced by external environment and is unstable in operation, and meanwhile, the adverse influence on the refrigeration performance of the rectification type self-cascade refrigeration system is avoided.
In order to achieve the purpose, the invention adopts the technical scheme that:
a rectification type self-cascade refrigeration system with precooling comprises a rectification type self-cascade refrigeration loop and a precooling loop, wherein the rectification type self-cascade refrigeration loop comprises a rectification device, a tower top subcooler and a kettle bottom subcooler; the rectifying device comprises a tower kettle, a tower body and a tower top heat exchanger communicated with the top of the tower body;
the pre-cooling loop comprises a first compressor, a first condenser and a first throttling element;
the outlet of the first compressor is connected with the inlet of the first condenser; the outlet of the first condenser is connected with the inlet of the first throttling element; the precooling loop is coupled with the rectification type self-cascade refrigeration loop into a whole through the tower top subcooler, the tower top heat exchanger and the kettle bottom subcooler.
First working medium pipelines are arranged in the tower top subcooler, the tower top heat exchanger and the kettle bottom subcooler; the first working medium is used in the precooling loop.
The outlet of the first throttling element is connected with the inlet of a first working medium pipeline of the subcooler at the top of the tower; the outlet of the first working medium pipeline of the subcooler at the tower top is connected with the inlet of the first working medium pipeline of the heat exchanger at the tower top; the outlet of the first working medium pipeline of the tower top heat exchanger is connected with the inlet of the first working medium pipeline of the kettle bottom subcooler; and the outlet of the first working medium pipeline of the subcooler at the bottom of the kettle is connected with the air suction port of the first compressor.
The rectification type self-cascade refrigeration loop further comprises: the system comprises a first compressor, a first condenser, a first throttling element, a high-temperature heat regenerator, a low-temperature heat regenerator, a third throttling element and an evaporator;
the outlet of the second compressor is connected with the inlet of the second condenser; the outlet of the second condenser is connected with the inlet of the rectifying device;
second working medium positive flow pipelines are arranged in the tower top subcooler, the kettle bottom subcooler, the high-temperature heat regenerator and the low-temperature heat regenerator; second working medium backflow pipelines are arranged in the tower top heat exchanger, the high-temperature heat regenerator and the low-temperature heat regenerator; the second working medium is used by a rectification type auto-cascade refrigeration loop.
The outlet of the top of the rectifying device is connected with the inlet of a second working medium positive flow pipeline of the subcooler at the top of the tower; the outlet of the second working medium positive flow pipeline of the subcooler at the tower top is connected with the inlet of the second working medium positive flow pipeline of the high-temperature heat regenerator; the outlet of the second working medium positive flow pipeline of the high-temperature heat regenerator is connected with the inlet of the second working medium positive flow pipeline of the low-temperature heat regenerator; the outlet of the second working medium positive flow pipeline of the low-temperature heat regenerator is connected with the inlet of the third throttling element; the outlet of the third throttling element is connected with the inlet of the evaporator;
the outlet of the evaporator is connected with the inlet of a second working medium reflux pipeline of the low-temperature heat regenerator; the outlet of the second working medium backflow pipeline of the low-temperature heat regenerator is connected with the inlet of the second working medium backflow pipeline of the high-temperature heat regenerator; the outlet of the second working medium backflow pipeline of the high-temperature heat regenerator is connected with the inlet of the second working medium backflow pipeline of the tower top heat exchanger; the outlet of the second working medium backflow pipeline of the tower top heat exchanger is connected with the air suction port of the second compressor;
the outlet at the bottom of the rectifying device is connected with the inlet of a second working medium positive flow pipeline of the subcooler at the bottom of the rectifying device; the outlet of the second working medium positive flow pipeline of the kettle bottom subcooler is connected with the inlet of the second throttling element; and the outlet of the second throttling element and the outlet of the second working medium backflow pipeline of the low-temperature heat regenerator are converged to the inlet of the second working medium backflow pipeline of the high-temperature heat regenerator.
The working principle of the device is as follows:
in the precooling loop, a first working medium sequentially passes through a first compressor, a first condenser and a first throttling element to realize cooling, then passes through a tower top subcooler to provide cooling capacity for the tower top subcooler, the temperature of a second working medium at the inlet of a high-temperature heat regenerator forward flow pipeline is reduced, the temperature of the second working medium at the outlet of a high-temperature heat regenerator reverse flow pipeline is further reduced, the suction temperature of the second compressor is finally reduced, and the operation condition of the compressor is improved; then, the main cold energy is provided for the tower top heat exchanger through the tower top heat exchanger, the stable tower top temperature of the rectifying device is ensured, and the tower top temperature of the rectifying device can be in a target value by adjusting the flow of the refrigerant in the precooling loop; then, the cold energy is provided for the kettle bottom subcooler through the kettle bottom subcooler, the dryness of the second working medium at the outlet of the second throttling element is reduced, namely, the loss of the second working medium mixed with the working medium at the outlet of the reflux pipeline of the low-temperature heat regenerator is reduced, and the dryness of the mixed working medium is reduced; and finally, returning the first working medium to the first compressor for continuous circulation.
In the rectification type self-cascade refrigeration loop, a second working medium is cooled through a second compressor and a second condenser, and the separation of high and low boiling point components is realized in a rectification device;
working medium mainly comprising low boiling point components passes through a tower top subcooler, a high temperature heat regenerator, a low temperature heat regenerator and a third throttling element in sequence through a tower top outlet of the rectifying device to be cooled and cooled, and the effect of supplying cold for the cold environment is realized in the evaporator; the working medium mainly comprising the low-boiling-point component continuously flows back to the low-temperature heat regenerator;
after passing through a still bottom subcooler and a second throttling element in sequence from a still bottom outlet of the rectification device, the working medium mainly containing the high-boiling-point component converges with the working medium mainly containing the low-boiling-point component which flows back in the low-temperature heat regenerator, and then flows back to the high-temperature heat regenerator to perform heat regeneration, and then provides secondary cooling capacity for the tower top heat exchanger, and finally returns to the second compressor to continue to circulate.
The first working medium is pure working medium or binary and above non-azeotropic mixed working medium.
The second working medium is a binary and above non-azeotropic mixed working medium.
Each throttling element is a manual throttling valve, an automatic throttling valve or a capillary tube.
The refrigeration temperature range of the precooling loop is-40 to-10 ℃, and the refrigeration temperature in the interval can meet the requirements of the rectification type auto-cascade refrigeration system with precooling on the tower top temperature and the supercooling temperature at different evaporation temperatures.
The refrigerating system is also provided with accessories such as a gas-liquid separator, an air storage tank, an oil separator, a liquid sight glass, a temperature sensor, a pressure sensor and the like.
The heat exchanger used is a double-pipe heat exchanger, a plate heat exchanger or a shell-and-tube heat exchanger.
The tower top subcooler and the kettle bottom subcooler can be combined into a three-channel heat exchanger.
Compared with the prior art, the invention has the following beneficial effects:
(1) the cold quantity required by the rectifying device is provided by the precooling loop and the rectifying type self-cascade refrigerating loop together, and is mainly provided by the precooling loop, so that the tower top temperature of the rectifying device can be ensured to be stable and at the target temperature, the separation effect and the oil removal effect in the rectifying process are ensured, and the capability of the system for coping with severe working conditions is enhanced.
(2) The difference with the conventional supercooling or partially overlapping refrigerating system is that the rectification type self-overlapping refrigerating system with precooling of the invention provides main cold energy for the tower top heat exchanger by using precooling circulation, thereby not only stabilizing the temperature of the tower top and improving the rectification effect, but also not reducing the dryness of the mixed working medium entering the rectification device, influencing the quantity of the working medium participating in the rectification process, ensuring the main flow rate, simultaneously providing supercooling degrees for the two working media of the tower top and the kettle bottom, reducing the suction temperature of the compressor and improving the operation condition of the compressor.
(3) The refrigerating system of the invention improves the tolerance to severe external environment, ensures the reliable and stable operation of the system, can exert the advantages of the rectification process, improves the operation condition of the compressor, can also improve the refrigeration performance coefficient of the system and reduces the operation cost.
Drawings
Fig. 1 is a schematic cycle diagram of a rectification-type self-cascade refrigeration system with precooling in example 1.
Fig. 2 is a schematic diagram of a rectification type self-cascade refrigeration system cycle in general in the prior art.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Those skilled in the art should understand that they can make modifications and equivalents without departing from the spirit and scope of the present invention, and all such modifications and equivalents are intended to be included within the scope of the present invention.
Example 1
As shown in fig. 1, a rectification-type auto-cascade refrigeration system with precooling comprises a first compressor 12, a first condenser 13, a first throttling element 14, a second compressor 1, a second condenser 2, a rectification device 3, a tower top subcooler 5, a kettle bottom subcooler 6, a second throttling element 7, a high temperature regenerator 8, a low temperature regenerator 9, a third throttling element 10 and an evaporator 11; the rectifying device 3 comprises a tower kettle, a tower body and a tower top heat exchanger 4 communicated with the top of the tower body. All the components form two loops, namely a precooling loop and a rectification type self-cascade refrigeration loop, and the two loops are coupled into a whole by a tower top heat exchanger 4, a tower top subcooler 5 and a kettle bottom subcooler 6.
First working medium pipelines are arranged in the tower top heat exchanger 4, the tower top subcooler 5 and the kettle bottom subcooler 6; second working medium positive flow pipelines are arranged in the tower top subcooler 5, the kettle bottom subcooler 6, the high-temperature heat regenerator 8 and the low-temperature heat regenerator 9; and second working medium backflow pipelines are arranged in the tower top heat exchanger 4, the high-temperature heat regenerator 8 and the low-temperature heat regenerator 9.
The connection mode of components included in the precooling loop is as follows: the outlet 12b of the first compressor 12 is connected with the inlet 13a of the first condenser 13; the outlet 13b of the first condenser 13 is connected to the inlet 14a of the first throttling element 14; the outlet 14b of the first throttling element 14 is connected with the inlet 5c of the first working medium pipeline of the tower top subcooler 5; a first working medium pipeline outlet 5d of the tower top subcooler 5 is connected with a first working medium pipeline inlet 4c of the tower top heat exchanger 4; a first working medium pipeline outlet 4d of the tower top heat exchanger 4 is connected with a first working medium pipeline inlet 6c of the kettle bottom subcooler 6; and a first working medium pipeline outlet 6d of the kettle bottom subcooler 6 is connected with an air suction port 12a of the first compressor 12 to form a circulation loop.
The rectification type self-cascade refrigeration loop comprises the following components in a connection mode:
the outlet 1b of the second compressor 1 is connected with the inlet 2a of the second condenser 2; an outlet 2b of the second condenser 2 is connected with an inlet 3a of the rectifying device 3; an outlet 3b at the top of the rectifying device 3 is connected with an inlet 5a of a second working medium positive flow pipeline of the subcooler 5 at the top of the tower; the outlet 5b of the second working medium positive flow pipeline of the tower top subcooler 5 is connected with the inlet 8a of the second working medium positive flow pipeline of the high-temperature heat regenerator 8; the outlet 8b of the second working medium positive flow pipeline of the high-temperature heat regenerator 8 is connected with the inlet 9a of the second working medium positive flow pipeline of the low-temperature heat regenerator 9; an outlet 9b of a second working medium positive flow pipeline of the low-temperature heat regenerator 9 is connected with an inlet 10a of a third throttling element 10; the outlet 10b of the third throttling element 10 is connected to the inlet 11a of the evaporator 11; an outlet 11b of the evaporator 11 is connected with an inlet 9c of a second working medium reflux pipeline of the low-temperature heat regenerator 9; a second working medium backflow pipeline outlet 9d of the low-temperature heat regenerator 9 is connected with a second working medium backflow pipeline inlet 8c of the high-temperature heat regenerator 8; the outlet 8d of the second working medium backflow pipeline of the high-temperature heat regenerator 8 is connected with the inlet 4a of the second working medium backflow pipeline of the tower top heat exchanger 4; an outlet 4b of a second working medium backflow pipeline of the tower top heat exchanger 4 is connected with an air suction port 1a of the second compressor 1;
a kettle bottom liquid phase outlet 3c of the rectifying device 3 is connected with a second working medium positive flow pipeline inlet 6a of the kettle bottom subcooler 6; an outlet 6b of a second working medium positive flow pipeline of the kettle bottom subcooler 6 is connected with an inlet 7a of a second throttling element 7; the outlet 7b of the second throttling element 7 and the outlet 9d of the second working medium reflux pipeline of the low-temperature heat regenerator 9 are converged to the inlet 8c of the second working medium reflux pipeline of the high-temperature heat regenerator 8.
For the sake of understanding, the refrigeration system is divided into a rectification type self-cascade refrigeration loop and a precooling loop, and the following is a detailed work flow:
in a rectification type auto-cascade refrigeration loop, a second working medium is a binary or above non-azeotropic mixed working medium, and is cooled by a second compressor 1 and a second condenser 2 in sequence, so that the separation of high and low boiling point components is realized in a rectification device 3; the working medium which mainly comprises low boiling point components in the second working medium is led out from an outlet 3b at the top of the rectifying device 3, sequentially passes through the subcooler 5 at the top of the tower, the high-temperature heat regenerator 8, the low-temperature heat regenerator 9 and the third throttling element 10 for cooling, then enters the evaporator 11 for providing cooling capacity, sequentially flows back through the low-temperature heat regenerator 9, the high-temperature heat regenerator 8 and the heat exchanger 4 at the top of the tower, respectively provides cooling capacity at corresponding temperature level for the environment needing cooling in the evaporator and provides secondary cooling capacity for the rectifying process in the heat exchanger at the top of the tower, and finally returns to an air suction port of the second compressor 1.
The liquid working medium which is mainly composed of high boiling point components flows out from the kettle bottom 3c of the rectifying device 3, sequentially passes through the kettle bottom subcooler 6 and the second throttling element 7, and is mixed with the reflux working medium which is mainly composed of low boiling point components at the reflux outlet of the second working medium of the low-temperature heat regenerator 9, so that the dryness of the reflux working medium is reduced, and cold is provided for the high-temperature heat regenerator.
In the precooling loop, a first working medium is a pure working medium or a binary and above non-azeotropic mixed working medium, and is cooled sequentially through a first compressor 12, a first condenser 13 and a first throttling element 14, and then passes through an overhead subcooler 5 to provide cold energy for the overhead subcooler 5, so that the temperature of a second working medium at the inlet of a positive flow pipeline of a high-temperature heat regenerator 8 is reduced, the temperature of the second working medium at the outlet of a reverse flow pipeline of the high-temperature heat regenerator 8 is further reduced, the suction temperature of a second compressor 1 is finally reduced, and the operation condition of the compressor is improved; then, the main cold energy is provided for the tower top heat exchanger 4 through the tower top heat exchanger 4, the stable tower top temperature of the rectifying device is ensured, and the tower top temperature of the rectifying device can be in a target value by adjusting the flow of the refrigerant in the precooling loop; then, the cold energy is provided for the kettle bottom subcooler 6 through the kettle bottom subcooler 6, the dryness of the second working medium at the outlet of the second throttling element 7 is reduced, namely, the loss of the second working medium mixed with the working medium at the outlet of the reflux pipeline of the low-temperature heat regenerator 9 is reduced, and the dryness of the mixed working medium is reduced; finally, the first working medium returns to the first compressor 12 to continue circulation.
Each throttling element used in the device is a manual throttling valve, an automatic throttling valve or a capillary tube, and plays a role in throttling and cooling; the used heat exchanger is a sleeve type heat exchanger, a plate type heat exchanger or a shell and tube type heat exchanger; the connection among all parts adopts the pipeline connection, and waterproof heat preservation material is wrapped outside the low-temperature pipeline.
To further illustrate the features and advantages of the present invention, the refrigeration system of the present invention is now compared to the operating parameters of the prior art rectification-type self-cascade refrigeration system for optimal concentration at the same pressure level.
As shown in fig. 2, the rectification type self-cascade refrigeration system of the prior art comprises a compressor 1, a condenser 2, a rectification device 3, a second throttling element 7, a high temperature regenerator 8, a low temperature regenerator 9, a third throttling element 10 and an evaporator 11; the rectifying device 3 comprises a tower kettle, a tower body and a tower top heat exchanger 4 communicated with the top of the tower body.
The connection mode is as follows:
the outlet 1b of the compressor 1 is connected with the inlet 2a of the condenser 2; an outlet 2b of the condenser 2 is connected with an inlet 3a of the rectifying device 3; an outlet 3b at the top of the rectifying device 3 is connected with an inlet 8a of a positive flow pipeline of a high-temperature heat regenerator 8; the outlet 8b of the positive flow pipeline of the high-temperature heat regenerator 8 is connected with the inlet 9a of the positive flow pipeline of the low-temperature heat regenerator 9; the outlet 9b of the positive flow pipeline of the low-temperature regenerator 9 is connected with the inlet 10a of the third throttling element 10; the outlet 10b of the third throttling element 10 is connected to the inlet 11a of the evaporator 11; the outlet 11b of the evaporator 11 is connected with the inlet 9c of the reflux pipeline of the low-temperature heat regenerator 9; the outlet 9d of the backflow pipeline of the low-temperature heat regenerator 9 is connected with the inlet 8c of the backflow pipeline of the high-temperature heat regenerator 8; a reflux pipeline outlet 8d of the high-temperature heat regenerator 8 is connected with a reflux pipeline inlet 4a of the tower top heat exchanger 4; a reflux pipeline outlet 4b of the tower top heat exchanger 4 is connected with an air suction port 1a of the compressor 1;
a kettle bottom liquid phase outlet 3c of the rectifying device 3 is connected with an inlet 7a of the second throttling element 7; outlet 7b of second throttling element 7 merges with low temperature regenerator 9 return conduit outlet 9d to high temperature regenerator 8 return conduit inlet 8 c.
In embodiment 1, the rectification type self-cascade refrigeration loop of the refrigeration system adopts five-membered mixed working media which are respectively nitrogen, methane, ethylene, propane and n-butane; the precooling loop adopts pure working medium which is propane. The general rectification-type self-cascade refrigeration system shown in fig. 2 adopts five-membered mixed working media, namely nitrogen, methane, ethylene, propane and n-butane. The comparative results are shown in Table 1.
As can be seen from table 1, at the same refrigeration temperature, when the ambient temperature is higher, the refrigeration system of the present invention can effectively maintain the temperature at the top of the tower at the target value, and will not rise with the rise of the ambient temperature, thereby ensuring the separation effect and oil removal effect of high and low boiling point components in the rectification process, and at the same time, effectively reducing the suction and discharge temperatures of the compressor, and improving the operation condition of the compressor. In addition, the refrigeration coefficient of performance of the refrigeration system of the invention is improved by more than 10% compared with the existing general rectification type auto-cascade refrigeration system.
In conclusion, the rectification type self-cascade refrigeration system with precooling has unique advantages in the aspects of coping with severe external environment, ensuring the reliable and stable operation of the system and the like, not only can exert the advantages of the rectification process, but also can improve the operation working condition of a compressor, can improve the refrigeration performance coefficient of the system and reduce the operation cost.
Table 1 comparison of the performance of the refrigeration system of the present invention with a typical rectification-type auto-cascade refrigeration system
Claims (8)
1. A rectification type self-cascade refrigeration system with precooling comprises a rectification type self-cascade refrigeration loop; the rectification type self-cascade refrigeration loop comprises a rectification device (3), a tower top subcooler (5) and a kettle bottom subcooler (6); the rectifying device (3) comprises a tower kettle, a tower body and a tower top heat exchanger (4) communicated with the top of the tower body;
the refrigeration system is characterized by further comprising a precooling loop; the pre-cooling circuit comprises a first compressor (12), a first condenser (13) and a first throttling element (14);
the outlet of the first compressor (12) is connected with the inlet of a first condenser (13); the outlet of the first condenser (13) is connected with the inlet of a first throttling element (14);
the tower top heat exchanger (4), the tower top subcooler (5) and the kettle bottom subcooler (6) are internally provided with first working medium pipelines;
the outlet of the first throttling element (14) is connected with the inlet of a first working medium pipeline of the tower top subcooler (5); the outlet of the first working medium pipeline of the tower top subcooler (5) is connected with the inlet of the first working medium pipeline of the tower top heat exchanger (4); the outlet of the first working medium pipeline of the tower top heat exchanger (4) is connected with the inlet of the first working medium pipeline of the kettle bottom subcooler (6); and the outlet of the first working medium pipeline of the kettle bottom subcooler (6) is connected with the air suction port of the first compressor (12).
2. The rectified self-cascade refrigeration system with pre-cooling of claim 1, wherein the rectified self-cascade refrigeration loop further comprises: the system comprises a second compressor (1), a second condenser (2), a second throttling element (7), a high-temperature regenerator (8), a low-temperature regenerator (9), a third throttling element (10) and an evaporator (11);
second working medium positive flow pipelines are arranged in the tower top subcooler (5), the kettle bottom subcooler (6), the high-temperature heat regenerator (8) and the low-temperature heat regenerator (9); second working medium backflow pipelines are arranged in the tower top heat exchanger (4), the high-temperature heat regenerator (8) and the low-temperature heat regenerator (9);
the outlet of the second compressor (1) is connected with the inlet of the second condenser (2); the outlet of the second condenser (2) is connected with the inlet of the rectifying device (3);
the outlet of the tower top of the rectifying device (3) is connected with the inlet of a second working medium positive flow pipeline of the tower top subcooler (5); the outlet of the second working medium positive flow pipeline of the tower top subcooler (5) is connected with the inlet of the second working medium positive flow pipeline of the high-temperature heat regenerator (8); the outlet of the second working medium positive flow pipeline of the high-temperature heat regenerator (8) is connected with the inlet of the second working medium positive flow pipeline of the low-temperature heat regenerator (9); the outlet of the second working medium positive flow pipeline of the low-temperature heat regenerator (9) is connected with the inlet of a third throttling element (10); the outlet of the third throttling element (10) is connected with the inlet of the evaporator (11);
the outlet of the evaporator (11) is connected with the inlet of a second working medium reflux pipeline of the low-temperature heat regenerator (9); the outlet of a second working medium backflow pipeline of the low-temperature heat regenerator (9) is connected with the inlet of a second working medium backflow pipeline of the high-temperature heat regenerator (8); the outlet of the second working medium backflow pipeline of the high-temperature heat regenerator (8) is connected with the inlet of the second working medium backflow pipeline of the tower top heat exchanger (4); the outlet of the second working medium backflow pipeline of the tower top heat exchanger (4) is connected with the air suction port of the second compressor (1);
the kettle bottom outlet of the rectifying device (3) is connected with the inlet of a second working medium positive flow pipeline of the kettle bottom subcooler (6); the outlet of the second working medium positive flow pipeline of the kettle bottom subcooler (6) is connected with the inlet of a second throttling element (7); and the outlet of the second throttling element (7) and the outlet of a second working medium backflow pipeline of the low-temperature heat regenerator (9) are converged to the inlet of the second working medium backflow pipeline of the high-temperature heat regenerator (8).
3. The rectifying type self-cascade refrigeration system with precooling according to claim 1, wherein the first working medium is a pure working medium or a binary and above non-azeotropic mixed working medium.
4. The rectifying type self-cascade refrigeration system with precooling according to claim 1, wherein the second working medium is a binary and higher non-azeotropic mixed working medium.
5. A rectification-type self-cascade refrigeration system with pre-cooling as claimed in claim 1 wherein each throttling element is a manual throttling valve, an automatic throttling valve or a capillary tube.
6. A rectification-type auto-cascade refrigeration system with pre-cooling as claimed in claim 1, wherein the refrigeration temperature of the pre-cooling loop is in the range of-40 ℃ to-10 ℃.
7. A rectification-type self-cascade refrigeration system with precooling according to claim 1, wherein the heat exchanger used is a double-pipe heat exchanger, a plate heat exchanger or a shell-and-tube heat exchanger.
8. The rectifying self-cascade refrigeration system with precooling according to claim 1, wherein the overhead subcooler (5) and the kettle-bottom subcooler (6) are combined into a three-channel heat exchanger.
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