Cascade heat exchange system and process based on absorption refrigeration

Abstract

The invention discloses a cascade heat exchange system and process based on absorption refrigeration in the technical field of heat exchange. The cascade heat exchange system comprises a high-pressure generator, a condenser, an evaporator, a low-pressure absorber, a medium-pressure heat exchanger, a medium-pressure generator and a medium-pressure absorber. The high-pressure generator and the medium-pressure generator sequentially absorb heat of a high-temperature medium, the low-pressure absorber and the medium-pressure absorber sequentially absorb cold energy of an ultralow-temperature medium, and the condenser is used for reheating the ultralow-temperature medium used by the medium heat exchanger through the heat absorbed by the high-pressure generator and producing cold energy. According to the cascade heat exchange system, the cascade heat exchange system is used as an intermediate medium for the high-temperature medium and the ultralow-temperature medium to pass through cascade heat exchange, and the problems that the high-temperature medium and the ultralow-temperature medium directly pass through a dividing wall for heat exchange, the temperature difference between the cold medium and the hot medium is large, and the temperature difference between the cold medium and the hot medium is large are solved. And the requirements on the material and the structure of the dividing wall type heat exchanger are harsh.

Description

Technical Field

[0001] The present invention relates to the field of heat exchange technology, and in particular to a cascade heat exchange system and process based on absorption refrigeration. Background Art

[0002] In actual industrial production, it is often necessary to exchange heat between a certain ultra-low temperature medium and a certain high temperature medium to achieve heating of the ultra-low temperature medium and cooling of the high temperature medium. The traditional approach is to directly exchange heat between the two through a partition heat exchanger, but due to the large temperature difference between the cold and hot media, the partition heat exchanger needs to withstand great thermal stress in terms of materials and structure, so the requirements for the high and low temperature resistance of the material and the strength of the structure are extremely stringent, which significantly increases the manufacturing cost and maintenance difficulty of the heat exchanger. Summary of the invention

[0003] The purpose of the present invention is to provide a stepped heat exchange system and process based on absorption refrigeration to solve the problem raised in the above background technology that due to the large temperature difference between the cold and hot media, the partition wall heat exchanger needs to withstand great thermal stress in terms of material and structure.

[0004] To achieve the above object, the present invention provides the following technical solution: a step heat exchange system based on absorption refrigeration, comprising: a high-pressure generator, a condenser, an evaporator, a low-pressure absorber, a medium heat exchanger, a medium-pressure generator and a medium-pressure absorber; The high-pressure generator and the medium-pressure generator absorb the heat of the high-temperature medium in turn, so that the high-temperature medium is cooled twice. The low-pressure absorber and the medium-pressure absorber absorb the cold of the ultra-low-temperature medium in turn, so that the ultra-low-temperature medium is heated twice. The medium heat exchanger is used to exchange heat between the used high-temperature medium and the ultra-low-temperature medium to cool the high-temperature medium and heat the ultra-low-temperature medium. The condenser is used to use the heat absorbed by the high-pressure generator to reheat the ultra-low-temperature medium after use in the medium heat exchanger and produce cold. The evaporator is used to use the cold produced by the condenser to recool the high-temperature medium after use in the medium heat exchanger.

[0005] Preferably, the cascade heat exchange system further includes an expansion valve, a first pressure reducing valve, a first solution pump, a second pressure reducing valve and a second solution pump; Among them, the expansion valve is used to reduce the pressure of liquid refrigerant entering the evaporator from the condenser, the first pressure reducing valve and the second pressure reducing valve are used to reduce the pressure of lean liquid entering the low-pressure absorber from the medium-pressure generator and the lean liquid entering the medium-pressure absorber from the high-pressure generator, respectively, and the first solution pump and the second solution pump are used to increase the pressure of rich liquid entering the medium-pressure generator from the low-pressure absorber and the rich liquid entering the high-pressure generator from the medium-pressure absorber, respectively.

[0006] Preferably, an upper heat exchanger is used to replace the medium-pressure generator and the medium-pressure absorber, and a lower heat exchanger is used to replace the high-pressure generator, condenser, evaporator and low-pressure absorber. The upper heat exchanger, the middle heat exchanger and the lower heat exchanger are all fixed tube sheet heat exchangers whose main structure is composed of a head, a tube box barrel section, a tube sheet, heat exchange tubes and a shell.

[0007] Preferably, the middle heat exchanger is arranged above the lower heat exchanger, and the upper heat exchanger is arranged above the middle heat exchanger.

[0008] Preferably, a first partition is provided in the lower heat exchanger, the first partition is in a cross shape, and the first partition is used to divide the inner cavity of the lower heat exchanger into an evaporation cavity, a condensation cavity, a high-pressure generating cavity and a low-pressure absorption cavity.

[0009] Preferably, a second partition is provided in the upper heat exchanger, and the second partition is used to divide the inner cavity of the upper heat exchanger into a medium-pressure generating cavity and a medium-pressure absorbing cavity; Among them, the high-pressure generating chamber and the medium-pressure generating chamber are used to absorb the heat of the high-temperature medium in turn, the low-pressure absorption chamber and the medium-pressure absorption chamber are used to absorb the cold of the ultra-low-temperature medium in turn, the medium heat exchanger is used to exchange heat between the used high-temperature medium and the ultra-low-temperature medium, the condensing chamber uses the heat absorbed by the high-pressure generating chamber to heat the ultra-low-temperature medium after use in the medium heat exchanger and produce cold, and the evaporating chamber is used to use the cold produced by the condensing chamber to cool the high-temperature medium after use in the medium heat exchanger.

[0010] Preferably, the first partition includes a second partition plate arranged in the tube box cylinder section of the lower heat exchanger and a first partition plate arranged in the lower heat exchanger shell, an opening is provided on the first partition plate between the evaporation chamber and the low-pressure absorption chamber, and an opening is provided on the first partition plate between the condensation chamber and the high-pressure generating chamber, and liquid baffles are provided in both openings.

[0011] Preferably, the shells of the medium-pressure generating chamber and the medium-pressure absorbing chamber are both provided with liquid distribution components, and the shells of the evaporating chamber, the high-pressure generating chamber and the low-pressure absorbing chamber are all provided with liquid distribution components.

[0012] Preferably, a step heat exchange process based on absorption refrigeration, using the above-mentioned step heat exchange system based on absorption refrigeration, comprises the following steps: The high-temperature medium enters the high-pressure generating chamber and the medium-pressure generating chamber in turn, absorbs heat, and becomes a medium-temperature medium; The ultra-low temperature medium enters the low-pressure absorption chamber and the medium-pressure absorption chamber in turn to absorb heat and become a sub-low temperature medium; The intermediate heat exchanger exchanges heat between the intermediate temperature medium and the sub-low temperature medium, so that the intermediate temperature medium becomes the sub-intermediate temperature medium and the sub-low temperature medium becomes the normal temperature medium. Normal temperature medium enters the condensation chamber and is heated to medium-high temperature medium by the heat absorbed by the high pressure generating chamber, and the condensation chamber produces cold capacity; The medium at sub-medium temperature enters the evaporation chamber and is cooled into medium-normal temperature by the cold produced by the condensation chamber. A step heat exchange process based on absorption refrigeration, also using the above-mentioned step heat exchange system based on absorption refrigeration, comprises the following steps: The high-temperature medium enters the high-pressure generator and the medium-pressure generator in turn, absorbs heat, and becomes a medium-temperature medium; The ultra-low temperature medium enters the low-pressure absorber and the medium-pressure absorber in turn to absorb heat and become a sub-low temperature medium; The intermediate heat exchanger exchanges heat between the intermediate temperature medium and the sub-low temperature medium, so that the intermediate temperature medium becomes the sub-intermediate temperature medium and the sub-low temperature medium becomes the normal temperature medium. Normal temperature medium enters the condenser and is heated to medium-high temperature medium by the heat absorbed by the high-pressure generator, and the condenser produces cold capacity; The sub-medium temperature medium enters the evaporator and is cooled into medium-normal temperature medium by the cold energy produced by the condenser.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. Use the cascade heat exchange system as the intermediate medium for high temperature medium and ultra-low temperature medium to exchange heat in cascade, thereby meeting the process requirements of high temperature medium and ultra-low temperature medium to exchange heat in cascade in actual production, solving the problem that the temperature difference between hot and cold media is large when high temperature medium and ultra-low temperature medium directly exchange heat through the partition wall, and the material and structure of the partition wall heat exchanger are required to be strict, thus avoiding the excessive cost of the partition wall heat exchanger; 2. The cascade heat exchange process can also meet the process requirements of actual production, where ultra-low temperature media need to be heated step by step to generate intermediate products, and in scientific research, where a certain ultra-low temperature medium needs to be heated step by step to study its certain physical properties at each temperature. This cascade heat exchange process can not only broaden the application scenarios of absorption refrigeration, but also realize the efficient use of energy, achieve the goal of energy conservation and emission reduction, and thus achieve higher economic value; 3. Use the upper heat exchanger to replace the medium-pressure generator and medium-pressure absorber, and use the lower heat exchanger to replace the high-pressure generator, condenser, evaporator and low-pressure absorber to integrate some equipment of the cascade heat exchange process together, which can reduce the cost of equipment and pipelines and greatly reduce the footprint of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the cascade heat exchange system of the present invention; Figure 2 This is a schematic diagram of a connection module between an upper heat exchanger and a lower heat exchanger of the present invention; Figure 3This is a schematic diagram of the connection structure between the upper heat exchanger and the lower heat exchanger of the present invention; Figure 4 For the present invention Figure 3 Schematic diagram of the middle AA direction.

[0015] In the figure: 1. high-pressure generator; 2. condenser; 3. evaporator; 4. low-pressure absorber; 5. medium heat exchanger; 6. medium-pressure generator; 7. medium-pressure absorber; 8. expansion valve; 9. first pressure reducing valve; 10. first solution pump; 11. second pressure reducing valve; 12. second solution pump; 13. lower heat exchanger; 131. evaporation chamber; 132. condensation chamber; 133. high-pressure generating chamber; 134. low-pressure absorption chamber; 135. first partition; 1351. first partition; 1352. second partition; 136. liquid baffle; 14. upper heat exchanger; 141. medium-pressure generating chamber; 142. medium-pressure absorption chamber; 143. second partition; 15. liquid distribution assembly. DETAILED DESCRIPTION

[0016] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] Example 1

[0018] See also Figure 1 , a cascade heat exchange system based on absorption refrigeration, comprising: a high pressure generator 1, a condenser 2, an evaporator 3, a low pressure absorber 4, a medium heat exchanger 5, a medium pressure generator 6, a medium pressure absorber 7, an expansion valve 8, a first pressure reducing valve 9, a first solution pump 10, a second pressure reducing valve 11 and a second solution pump 12; Among them, see Figure 1 , the heat source outlet of the high-pressure generator 1 is connected to the heat source inlet of the medium-pressure generator 6, the high-pressure gaseous refrigerant outlet of the high-pressure generator 1 is connected to the high-pressure gaseous refrigerant inlet of the condenser 2, the high-pressure lean liquid outlet of the high-pressure generator 1 is connected to the medium-pressure lean liquid inlet of the medium-pressure absorber 7 through the second pressure reducing valve 11, and the high-pressure rich liquid inlet of the high-pressure generator 1 is connected to the medium-pressure rich liquid outlet of the medium-pressure absorber 7 through the second solution pump 12; See also Figure 1 The high-pressure liquid refrigerant outlet of the condenser 2 is connected to the low-pressure liquid refrigerant inlet of the evaporator 3 through the expansion valve 8, and the normal temperature medium inlet of the condenser 2 is connected to an outlet of the intermediate heat exchanger 5; See also Figure 1, the low-pressure gaseous refrigerant outlet of the evaporator 3 is connected to the low-pressure gaseous refrigerant inlet of the low-pressure absorber 4, and the sub-intermediate temperature medium inlet of the evaporator 3 is connected to another outlet of the intermediate heat exchanger 5; See also Figure 1 The low-pressure lean liquid inlet of the low-pressure absorber 4 is connected to the medium-pressure lean liquid outlet of the medium-pressure generator 6 through the first pressure reducing valve 9, the low-pressure rich liquid outlet of the low-pressure absorber 4 is connected to the medium-pressure rich liquid inlet of the medium-pressure generator 6 through the first solution pump 10, and the low-temperature medium outlet of the low-pressure absorber 4 is connected to the low-temperature medium inlet of the medium-pressure absorber 7; See also Figure 1 , the medium-pressure gaseous refrigerant outlet of the medium-pressure generator 6 is connected to the medium-pressure gaseous refrigerant inlet of the medium-pressure absorber 7, and the heat source outlet of the medium-pressure generator 6 is connected to an inlet of the medium heat exchanger 5; See also Figure 1 The sub-low temperature medium outlet of the medium-pressure absorber 7 is connected to another inlet of the medium heat exchanger 5.

[0019] A step heat exchange process based on absorption refrigeration comprises the following steps: The high-temperature medium is used as a heat source to heat the high-pressure rich liquid delivered by the second solution pump 12 in the high-pressure generator 1, so that most of the low-boiling-point refrigerant in the high-pressure rich liquid is desorbed to become a high-pressure gaseous refrigerant and enter the condenser 2, and is condensed into a high-pressure liquid refrigerant by the normal-temperature medium. The normal-temperature medium absorbs the heat of the high-pressure gaseous refrigerant and is heated to a medium-high temperature medium; the high-pressure liquid refrigerant flowing out of the condenser 2 is decompressed into a low-pressure liquid refrigerant through the expansion valve 8, and the low-pressure liquid refrigerant enters the evaporator 3, absorbs the heat of the sub-medium-temperature medium entering the evaporator 3 and vaporizes into a low-pressure gaseous refrigerant; The high-pressure lean liquid remaining after the generation process in the high-pressure generator 1 is reduced in pressure to medium-pressure lean liquid through the second pressure reducing valve 11 and enters the medium-pressure absorber 7; the high-temperature medium is transformed into a sub-high-temperature medium after being heat-absorbed by the high-pressure generator 1, and the sub-high-temperature medium enters the medium-pressure generator 6, heats the medium-pressure rich liquid delivered by the first solution pump 10, and desorbs most of the low-boiling-point refrigerant in the medium-pressure rich liquid, and becomes a medium-pressure gaseous refrigerant and enters the medium-pressure absorber 7, and is mixed and absorbed with the medium-pressure lean liquid entering the medium-pressure absorber 7 to become a medium-pressure rich liquid, and the medium-pressure rich liquid is pressurized by the second solution pump 12 and sent to the high-pressure generator 1 to continue the circulation work; The medium-pressure lean liquid remaining after the generation process in the medium-pressure generator 6 is decompressed into low-pressure lean liquid through the first pressure reducing valve 9, enters the low-pressure absorber 4, and is mixed and absorbed with the low-pressure gaseous refrigerant coming out of the evaporator 3 to become low-pressure rich liquid. The low-pressure rich liquid is pressurized by the first solution pump 10 and then sent to the medium-pressure generator 6 to continue the circulation work; As a heat source in the generation process, the high-temperature medium enters the high-pressure generator 1 and the medium-pressure generator 6 in turn, and becomes a sub-high-temperature medium and a medium-temperature medium in turn after absorbing heat, and then enters the medium heat exchanger 5; as a cold source in the absorption process, the ultra-low-temperature medium enters the low-pressure absorber 4 and the medium-pressure absorber 7 in turn, and becomes a low-temperature medium and a sub-low-temperature medium in turn after being heated, and then enters the medium heat exchanger 5, and is heated by the medium-temperature medium entering and becomes a normal-temperature medium, and the medium-temperature medium becomes a sub-medium-temperature medium after absorbing heat; the sub-medium-temperature medium finally enters the evaporator 3, and becomes a medium-normal-temperature medium after continuing to absorb heat, and the normal-temperature medium flowing out of the medium heat exchanger 5 finally enters the condenser 2, and becomes a medium-high-temperature medium after being heated.

[0020] It should be noted that the high-temperature medium and the ultra-low-temperature medium are subjected to step-by-step heat exchange. The high-temperature medium is cooled down step by step and becomes a sub-high-temperature medium, a medium-temperature medium, a sub-medium-temperature medium, and a medium-normal-temperature medium in sequence; the ultra-low-temperature medium is heated step by step and becomes a low-temperature medium, a sub-low-temperature medium, a normal-temperature medium, and a medium-high-temperature medium in sequence.

[0021] Example 2

[0022] As a further optimized solution of Example 1, please refer to Figure 2 , Figure 3 and Figure 4 , the medium-pressure generator 6 and the medium-pressure absorber 7 are integrated into the upper heat exchanger 14, and the high-pressure generator 1, the condenser 2, the evaporator 3 and the low-pressure absorber 4 are integrated into the lower heat exchanger 13; wherein, the upper heat exchanger 14, the medium heat exchanger 5 and the lower heat exchanger 13 are all fixed tube-sheet heat exchangers whose main structures are composed of a head, a tube box barrel section, a tube sheet, heat exchange tubes and a shell; the left and right heads and the tube box barrel section are respectively welded and fixed on the left and right tube sheets, the shell is welded and fixed between the left and right tube sheets, and the heat exchange tubes are welded and fixed on the left and right tube sheets.

[0023] See also Figure 3 and Figure 4 A second partition 143 is provided in the inner cavity of the upper heat exchanger 14, and the second partition 143 is used to divide the inner cavity of the upper heat exchanger 14 into a medium-pressure generating cavity 141 and a medium-pressure absorbing cavity 142, and the medium-pressure generating cavity 141 is located above the medium-pressure absorbing cavity 142; a first partition 135 is provided in the inner cavity of the lower heat exchanger 13, and the cross section of the first partition 135 is cross-shaped, and the first partition 135 is used to divide the inner cavity of the lower heat exchanger 13 into an evaporation cavity 131, a condensation cavity 132, a high-pressure generating cavity 133 and a low-pressure absorbing cavity 134; See also Figure 3 and Figure 4 The two tube box sections of the high-pressure generating chamber 133 are respectively provided with a heat source inlet and a heat source outlet, and the shell of the high-pressure generating chamber 133 is provided with a high-pressure gaseous refrigerant outlet, a high-pressure lean liquid outlet and a high-pressure rich liquid inlet; See also Figure 3 and Figure 4 The two tube box sections of the condensing chamber 132 are respectively provided with a normal temperature medium inlet and a medium and high temperature medium outlet, and the shell of the condensing chamber 132 is provided with a high pressure gaseous refrigerant inlet and a high pressure liquid refrigerant outlet; See also Figure 3 and Figure 4 The two tube box sections of the evaporation chamber 131 are respectively provided with a sub-medium temperature medium inlet and a medium normal temperature medium outlet, and the shell of the evaporation chamber 131 is provided with a low-pressure liquid refrigerant inlet and a low-pressure gaseous refrigerant outlet; See also Figure 3 and Figure 4 The two tube box sections of the low-pressure absorption chamber 134 are respectively provided with an ultra-low temperature medium inlet and a low temperature medium outlet, and the shell of the low-pressure absorption chamber 134 is provided with a low-pressure gaseous refrigerant inlet, a low-pressure lean liquid inlet, and a low-pressure rich liquid outlet; See also Figure 3 and Figure 4 The two tube box sections of the medium-pressure generating chamber 141 are respectively provided with a heat source inlet and a heat source outlet, and the shell of the medium-pressure generating chamber 141 is provided with a medium-pressure gaseous refrigerant outlet, a medium-pressure lean liquid outlet, and a medium-pressure rich liquid inlet; See also Figure 3 and Figure 4 The two tube box sections of the medium-pressure absorption chamber 142 are respectively provided with a low-temperature medium inlet and a sub-low-temperature medium outlet, and the shell of the medium-pressure absorption chamber 142 is provided with a medium-pressure lean liquid inlet, a medium-pressure rich liquid outlet, and a medium-pressure gaseous refrigerant inlet; See also Figure 3 and Figure 4 The two tube box sections of the middle heat exchanger 5 are respectively provided with a medium temperature medium inlet and a sub-medium temperature medium outlet, and the shell of the middle heat exchanger 5 is provided with a sub-low temperature medium inlet and a normal temperature medium outlet; See also Figure 3 and Figure 4The heat source outlet of the high-pressure generating chamber 133 is connected to the heat source inlet of the medium-pressure generating chamber 141, the high-pressure gaseous refrigerant outlet of the high-pressure generating chamber 133 is connected to the high-pressure gaseous refrigerant inlet of the condensing chamber 132, the high-pressure lean liquid outlet of the high-pressure generating chamber 133 is connected to the medium-pressure lean liquid inlet of the medium-pressure absorption chamber 142 through the second pressure reducing valve 11, and the high-pressure rich liquid inlet of the high-pressure generating chamber 133 is connected to the medium-pressure rich liquid outlet of the medium-pressure absorption chamber 142 through the second solution pump 12; the high-pressure liquid refrigerant outlet of the condensing chamber 132 is connected to the low-pressure liquid refrigerant inlet of the evaporation chamber 131 through the expansion valve 8, and the normal-temperature medium inlet of the condensing chamber 132 is connected to the normal-temperature medium outlet of the medium heat exchanger 5; the low-pressure gaseous refrigerant outlet of the evaporation chamber 131 is connected to the low-pressure gaseous refrigerant outlet of the low-pressure absorption chamber 134. The refrigerant inlet is connected, and the sub-medium temperature medium inlet of the evaporation chamber 131 is connected with the sub-medium temperature medium outlet of the medium heat exchanger 5; the low-pressure lean liquid inlet of the low-pressure absorption chamber 134 is connected with the medium-pressure lean liquid outlet of the medium-pressure generating chamber 141 through the first reducing valve 9, the low-pressure rich liquid outlet of the low-pressure absorption chamber 134 is connected with the medium-pressure rich liquid inlet of the medium-pressure generating chamber 141 through the first solution pump 10, the low-temperature medium outlet of the low-pressure absorption chamber 134 is connected with the low-temperature medium inlet of the medium-pressure absorption chamber 142; the medium-pressure gaseous refrigerant outlet of the medium-pressure generating chamber 141 is connected with the medium-pressure gaseous refrigerant inlet of the medium-pressure absorption chamber 142, and the heat source outlet of the medium-pressure generating chamber 141 is connected with the medium-temperature medium inlet of the medium heat exchanger 5; the sub-low-temperature medium outlet of the medium-pressure absorber 7 is connected with the sub-low-temperature medium inlet of the medium heat exchanger 5.

[0024] It should be noted that the middle heat exchanger 5 is installed on the top of the lower heat exchanger 13 through a support plate, and the upper heat exchanger 14 is installed on the top of the middle heat exchanger 5 through a support plate.

[0025] In this embodiment, as a further optimized solution, please refer to Figure 3 and Figure 4The first partition plate 135 includes a first partition plate 1351 and a second partition plate 1352. The second partition plate 1352 is arranged in the inner cavity of the tube box barrel section of the lower heat exchanger 13. The first partition plate 1351 is arranged in the inner cavity of the shell of the lower heat exchanger 13. The cross-sections of the first partition plate 1351 and the second partition plate 1352 are both cross-shaped, which are used to divide the inner cavity of the tube box barrel section and the shell into four parts (corresponding to the evaporation chamber 131, the condensation chamber 132, the high-pressure generating chamber 133 and the low-pressure absorption chamber 134). The evaporation chamber 131 and the An opening is provided on the first partition plate 1351 between the low-pressure absorption chambers 134, and the opening is both the low-pressure gaseous refrigerant outlet of the evaporation chamber 131 and the low-pressure gaseous refrigerant inlet of the low-pressure absorption chamber 134. An opening is provided on the first partition plate 1351 between the condensation chamber 132 and the high-pressure generating chamber 133, and the opening is both the high-pressure gaseous refrigerant outlet of the high-pressure generating chamber 133 and the high-pressure gaseous refrigerant inlet of the condensation chamber 132. Liquid baffles 136 are provided in the two openings. By setting the openings, the layout of the pipelines is reduced.

[0026] In this embodiment, as a further optimized solution, please refer to Figure 3 and Figure 4 A liquid distribution assembly 15 is installed in the shell of the medium-pressure generating chamber 141, and the liquid distribution assembly 15 is connected to the medium-pressure rich liquid inlet. A liquid distribution assembly 15 is provided in the shell of the medium-pressure absorption chamber 142, and the liquid distribution assembly 15 is connected to the medium-pressure lean liquid inlet. A liquid distribution assembly 15 is installed in the shell inner cavity of the evaporation chamber 131, and the liquid distribution assembly 15 is connected to the low-pressure liquid refrigerant inlet. A liquid distribution assembly 15 is installed in the shell of the high-pressure generating chamber 133, and the liquid distribution assembly 15 is connected to the high-pressure rich liquid inlet; a liquid distribution assembly 15 is provided in the shell of the low-pressure absorption chamber 134, and the liquid distribution assembly 15 is connected to the low-pressure lean liquid inlet; the liquid distribution assembly 15 includes a pipeline and a nozzle arranged on the pipeline, and the nozzle is used to atomize the transported liquid and spray it onto the heat exchange tube, thereby increasing the heat exchange area and improving the heat exchange efficiency.

[0027] After the upper heat exchanger 14 and the lower heat exchanger 13 are used to replace some components in the cascade heat exchange system, the cascade heat exchange process includes the following steps: The high-temperature medium, as a heat source, enters the heat exchange tube of the high-pressure generating chamber 133, heats the high-pressure rich liquid delivered by the second solution pump 12 and sprayed on the outer surface of the heat exchange tube, desorbs most of the low-boiling-point refrigerant in the high-pressure rich liquid, and becomes a high-pressure gaseous refrigerant. The high-pressure gaseous refrigerant enters the shell of the condensing chamber 132 through the liquid baffle 136, and is condensed into a high-pressure liquid refrigerant by the normal-temperature medium in the heat exchange tube. The normal-temperature medium in the tube of the condensing chamber 132 absorbs the heat of the high-pressure gaseous refrigerant and is heated to a medium-high temperature medium. The high-pressure liquid refrigerant flowing out of the condensing chamber 132 is decompressed into a low-pressure liquid refrigerant through the expansion valve 8. The low-pressure liquid refrigerant enters the shell of the evaporating chamber 131 and is evenly sprinkled on the outer surface of the heat exchange tube after being sprayed, and absorbs the heat of the sub-medium-temperature medium in the heat exchange tube of the evaporating chamber 131 and is vaporized into a low-pressure gaseous refrigerant. The low-pressure gaseous refrigerant enters the shell of the low-pressure absorption chamber 134 through the liquid baffle 136. The high-pressure lean liquid remaining after the generation process in the shell of the high-pressure generating chamber 133 is reduced in pressure to medium-pressure lean liquid through the second pressure reducing valve 11, enters the medium-pressure absorption chamber 142 and is evenly sprinkled on the outer surface of the heat exchange tube through spraying; the high-temperature medium is transformed into a sub-high-temperature medium after being absorbed by the high-pressure generating chamber 133, and the sub-high-temperature medium enters the heat exchange tube of the medium-pressure generating chamber 141, heating the medium-pressure rich liquid on the outer surface of the heat exchange tube that is transported and sprayed by the first solution pump 10, so that most of the low-boiling-point refrigerant in the medium-pressure rich liquid is desorbed and becomes medium-pressure gaseous refrigerant that enters the shell of the medium-pressure absorption chamber 142, and is mixed with the medium-pressure lean liquid on the outer surface of the heat exchange tube and absorbed to become medium-pressure rich liquid, which is pressurized by the second solution pump 12 and sent to the high-pressure generating chamber 133 to continue circulating; The medium-pressure lean liquid remaining after the generation process in the medium-pressure generating chamber 141 is decompressed into low-pressure lean liquid through the first pressure reducing valve 9, enters the shell of the low-pressure absorption chamber 134 and is evenly sprinkled on the outer surface of the heat exchange tube by spraying, and is mixed and absorbed with the low-pressure gaseous refrigerant coming out of the shell of the evaporation chamber 131 to become low-pressure rich liquid. The low-pressure rich liquid is pressurized by the first solution pump 10 and sent to the medium-pressure generating chamber 141 to continue the circulation work; As a heat source in the generation process, the high-temperature medium enters the tube side of the high-pressure generation chamber 133 and the tube side of the medium-pressure generation chamber 141 in turn, and is transformed into a sub-high-temperature medium and a medium-temperature medium in turn after absorbing heat, and then enters the tube side of the medium heat exchanger 5; as a cold source in the absorption process, the ultra-low-temperature medium enters the tube side of the low-pressure absorption chamber 134 and the tube side of the medium-pressure absorption chamber 142 in turn, and is transformed into a low-temperature medium and a sub-low-temperature medium in turn after being heated, and then enters the shell side of the medium heat exchanger 5, and is heated by the medium-temperature medium in the heat exchange tube to become a normal-temperature medium, and the medium-temperature medium in the tube is transformed into a sub-medium-temperature medium after absorbing heat, and the sub-medium-temperature medium finally enters the tube side of the evaporation chamber 131, continues to be transformed into a medium-normal-temperature medium after being absorbed heat, and the normal-temperature medium flowing out of the shell side of the medium heat exchanger 5 finally enters the tube side of the condensation chamber 132, and is transformed into a medium-high-temperature medium after being heated.

[0028] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A cascade heat exchange system based on absorption refrigeration, characterized in that: include: A high-pressure generator (1), a condenser (2), an evaporator (3), a low-pressure absorber (4), a medium heat exchanger (5), a medium-pressure generator (6) and a medium-pressure absorber (7); The high-pressure generator (1) and the medium-pressure generator (6) absorb heat from the high-temperature medium in turn, so that the high-temperature medium is cooled twice; the low-pressure absorber (4) and the medium-pressure absorber (7) absorb cold from the ultra-low-temperature medium in turn, so that the ultra-low-temperature medium is heated twice; the medium heat exchanger (5) is used to exchange heat between the used high-temperature medium and the ultra-low-temperature medium, so as to cool the high-temperature medium and heat the ultra-low-temperature medium; the condenser (2) is used to use the heat absorbed by the high-pressure generator (1) to reheat the ultra-low-temperature medium used by the medium heat exchanger (5) and generate cold; and the evaporator (3) is used to use the cold generated by the condenser (2) to recool the high-temperature medium used by the medium heat exchanger (5).

2. The step heat exchange system based on absorption refrigeration according to claim 1, characterized in that: The cascade heat exchange system further comprises an expansion valve (8), a first pressure reducing valve (9), a first solution pump (10), a second pressure reducing valve (11) and a second solution pump (12); The expansion valve (8) is used to reduce the pressure of liquid refrigerant entering the evaporator (3) from the condenser (2); the first pressure reducing valve (9) and the second pressure reducing valve (11) are used to reduce the pressure of lean liquid entering the low-pressure absorber (4) from the medium-pressure generator (6) and the high-pressure generator (1) from the medium-pressure absorber (7); and the first solution pump (10) and the second solution pump (12) are used to increase the pressure of rich liquid entering the medium-pressure generator (6) from the low-pressure absorber (4) and the medium-pressure absorber (7) from the high-pressure generator (1).

3. The step heat exchange system based on absorption refrigeration according to claim 1, characterized in that: An upper heat exchanger (14) is used to replace the medium-pressure generator (6) and the medium-pressure absorber (7), and a lower heat exchanger (13) is used to replace the high-pressure generator (1), the condenser (2), the evaporator (3) and the low-pressure absorber (4). The upper heat exchanger (14), the middle heat exchanger (5) and the lower heat exchanger (13) are all fixed tube-sheet heat exchangers whose main structures are composed of a head, a tube box barrel section, a tube sheet, heat exchange tubes and a shell.

4. The step heat exchange system based on absorption refrigeration according to claim 3 is characterized in that: The middle heat exchanger (5) is arranged above the lower heat exchanger (13), and the upper heat exchanger (14) is arranged above the middle heat exchanger (5).

5. The step heat exchange system based on absorption refrigeration according to claim 3 is characterized in that: A first partition (135) is provided in the lower heat exchanger (13), the first partition (135) being in a cross shape, and the first partition (135) is used to divide the inner cavity of the lower heat exchanger (13) into an evaporation cavity (131), a condensation cavity (132), a high-pressure generating cavity (133), and a low-pressure absorbing cavity (134).

6. A cascade heat exchange system based on absorption refrigeration according to claim 5, characterized in that: A second partition plate (143) is provided in the upper heat exchanger (14), and the second partition plate (143) is used to divide the inner cavity of the upper heat exchanger (14) into a medium-pressure generating cavity (141) and a medium-pressure absorbing cavity (142); The high-pressure generating chamber (133) and the medium-pressure generating chamber (141) are used to absorb heat from a high-temperature medium in sequence, the low-pressure absorbing chamber (134) and the medium-pressure absorbing chamber (142) are used to absorb cold from an ultra-low-temperature medium in sequence, the medium heat exchanger (5) is used to exchange heat between the used high-temperature medium and the ultra-low-temperature medium, the condensing chamber (132) uses the heat absorbed by the high-pressure generating chamber (133) to heat the ultra-low-temperature medium in the medium heat exchanger (5) and produce cold, and the evaporating chamber (131) uses the cold produced by the condensing chamber (132) to cool the high-temperature medium in the medium heat exchanger (5) after use.

7. The step heat exchange system based on absorption refrigeration according to claim 5, characterized in that: The first partition plate (135) comprises a second partition plate (1352) arranged in the tube box section of the lower heat exchanger (13) and a first partition plate (1351) arranged in the shell of the lower heat exchanger (13); an opening is provided on the first partition plate (1351) between the evaporation chamber (131) and the low-pressure absorption chamber (134); an opening is provided on the first partition plate (1351) between the condensation chamber (132) and the high-pressure generating chamber (133); and liquid baffles (136) are provided in both openings.

8. The step heat exchange system based on absorption refrigeration according to claim 6, characterized in that: The shells of the medium-pressure generating chamber (141) and the medium-pressure absorbing chamber (142) are both provided with liquid distribution components (15), and the shells of the evaporating chamber (131), the high-pressure generating chamber (133), and the low-pressure absorbing chamber (134) are both provided with liquid distribution components (15).

9. A cascade heat exchange process based on absorption refrigeration, using a cascade heat exchange system based on absorption refrigeration as claimed in claim 2, characterized in that: The following steps are involved: The high-temperature medium enters the high-pressure generator (1) and the medium-pressure generator (6) in sequence, absorbs heat, and becomes a medium-temperature medium; The ultra-low temperature medium enters the low-pressure absorber (4) and the medium-pressure absorber (7) in sequence to absorb heat and becomes a sub-low temperature medium; The intermediate heat exchanger (5) performs heat exchange between the intermediate temperature medium and the sub-low temperature medium, so that the intermediate temperature medium becomes the sub-intermediate temperature medium and the sub-low temperature medium becomes the normal temperature medium; The normal temperature medium enters the condenser (2) and is heated by the heat absorbed by the high pressure generator (1) to become a medium-high temperature medium, and the condenser (2) generates cooling capacity; The sub-medium temperature medium enters the evaporator (3) and is cooled by the cold energy produced by the condenser (2) to become a medium-normal temperature medium.

10. A cascade heat exchange process based on absorption refrigeration, using a cascade heat exchange system based on absorption refrigeration as claimed in any one of claims 3 to 8, characterized in that: The following steps are involved: The high-temperature medium enters the high-pressure generating chamber (133) and the medium-pressure generating chamber (141) in sequence, absorbs heat, and becomes a medium-temperature medium; The ultra-low temperature medium enters the low-pressure absorption chamber (134) and the medium-pressure absorption chamber (142) in sequence to absorb heat and becomes a sub-low temperature medium; The intermediate heat exchanger (5) performs heat exchange between the intermediate temperature medium and the sub-low temperature medium, so that the intermediate temperature medium becomes the sub-intermediate temperature medium and the sub-low temperature medium becomes the normal temperature medium; Normal temperature medium enters the condensation chamber (132) and is heated by the heat absorbed by the high pressure generating chamber (133) to become medium-high temperature medium, and the condensation chamber (132) generates cold energy; The sub-medium temperature medium enters the evaporation chamber (131) and is cooled into a medium normal temperature medium by the cold energy produced by the condensation chamber (132).

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