A cascaded heat exchange system and process based on absorption refrigeration

Abstract

The present invention discloses a cascade heat exchange system and process based on absorption refrigeration in the field of heat exchange technology, 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 sequentially absorb the heat of a high-temperature medium, the low-pressure absorber and the medium-pressure absorber sequentially absorb the cold of an ultra-low-temperature medium, the condenser is used to reheat the ultra-low-temperature medium after being used by the medium heat exchanger with the heat absorbed by the high-pressure generator and produce cold, and the evaporator is used to cool the high-temperature medium after being used by the medium heat exchanger again with the cold produced by the condenser. The present invention uses the cascade heat exchange system as an intermediate medium for the high-temperature medium and the ultra-low-temperature medium to carry out cascade heat exchange, and solves the problem that when the high-temperature medium and the ultra-low-temperature medium directly carry out heat exchange through a partition wall, the temperature difference between the hot and cold media is large, and the requirements for the materials and structure of the partition wall heat exchanger are harsh.

Description

Technical Field

[0001] The present invention relates to the technical field of heat exchange, and specifically to a cascaded heat exchange system and process based on absorption refrigeration. Background Technique

[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 method is to directly exchange heat between the two through a shell-and-tube heat exchanger. However, due to the large temperature difference between the hot and cold media, the shell-and-tube heat exchanger needs to withstand extremely large thermal stresses in terms of materials and structure. Therefore, extremely high requirements are imposed on the high-temperature and low-temperature resistance of the materials and the strength of the structure, 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 cascaded heat exchange system and process based on absorption refrigeration to solve the problem in the above background technique that due to the large temperature difference between the hot and cold media, the shell-and-tube heat exchanger needs to withstand extremely large thermal stresses in terms of materials and structure.

[0004] To achieve the above purpose, the present invention provides the following technical solution: A cascaded heat exchange system based on absorption refrigeration, including: 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;

[0005] The high-pressure generator and the medium-pressure generator sequentially absorb the heat of the high-temperature medium to cool the high-temperature medium twice. The low-pressure absorber and the medium-pressure absorber sequentially absorb the cold of the ultra-low temperature medium to heat the ultra-low temperature medium 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 being used by the medium heat exchanger and produce cold. The evaporator is used to use the cold produced by the condenser to cool the high-temperature medium after being used by the medium heat exchanger again.

[0006] Preferably, the cascaded 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;

[0007] Among them, the expansion valve is used to reduce the pressure of the liquid refrigerant entering the evaporator from the condenser. The first pressure reducing valve and the second pressure reducing valve are respectively used to reduce the pressure of the lean liquid entering the low-pressure absorber from the medium-pressure generator and entering the medium-pressure absorber from the high-pressure generator. The first solution pump and the second solution pump are respectively used to boost the pressure of the rich liquid entering the medium-pressure generator from the low-pressure absorber and entering the high-pressure generator from the medium-pressure absorber.

[0008] 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, the condenser, the evaporator and the 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 structures are composed of a head, a tube sheet cylinder section, a tube sheet, heat exchange tubes and a shell.

[0009] Preferably, the middle heat exchanger is arranged above the lower heat exchanger, and the upper heat exchanger is arranged above the middle heat exchanger.

[0010] Preferably, a first partition plate is arranged in the lower heat exchanger. The first partition plate is in a cross shape and is used to divide the inner cavity of the lower heat exchanger into an evaporation chamber, a condensation chamber, a high-pressure generation chamber and a low-pressure absorption chamber.

[0011] Preferably, a second partition plate is arranged in the upper heat exchanger. The second partition plate is used to divide the inner cavity of the upper heat exchanger into a medium-pressure generation chamber and a medium-pressure absorption chamber;

[0012] Among them, the high-pressure generation chamber and the medium-pressure generation chamber are used to sequentially absorb the heat of the high-temperature medium, and the low-pressure absorption chamber and the medium-pressure absorption chamber are used to sequentially absorb the cold of the ultra-low temperature medium. The middle heat exchanger is used to exchange heat between the used high-temperature medium and the ultra-low temperature medium. The condensation chamber uses the heat absorbed by the high-pressure generation chamber to heat the ultra-low temperature medium after the middle heat exchanger is used and produce cold. The evaporation chamber uses the cold produced by the condensation chamber to cool the high-temperature medium after the middle heat exchanger is used.

[0013] Preferably, the first partition plate includes a second partition plate arranged in the tube sheet cylinder section of the lower heat exchanger and a first partition plate arranged in the shell of the lower heat exchanger. Openings are arranged on the first partition plate between the evaporation chamber and the low-pressure absorption chamber, and openings are arranged on the first partition plate between the condensation chamber and the high-pressure generation chamber. Liquid baffle plates are arranged in both of the two openings.

[0014] Preferably, liquid distribution assemblies are arranged in the shells of both the medium-pressure generation chamber and the medium-pressure absorption chamber, and liquid distribution assemblies are arranged in the shells of the evaporation chamber, the high-pressure generation chamber and the low-pressure absorption chamber.

[0015] Preferably, a cascade heat exchange process based on absorption refrigeration uses the above-mentioned cascade heat exchange system based on absorption refrigeration, and includes the following steps:

[0016] The high-temperature medium sequentially enters the high-pressure generation chamber and the medium-pressure generation chamber to be absorbed of heat and becomes a medium-temperature medium;

[0017] The ultra-low temperature medium sequentially enters the low-pressure absorption chamber and the medium-pressure absorption chamber to absorb heat and becomes a sub-low temperature medium;

[0018] The medium-temperature heat exchanger exchanges heat between the medium-temperature medium and the sub-low-temperature medium, converting the medium-temperature medium into a sub-medium-temperature medium and the sub-low-temperature medium into a normal-temperature medium;

[0019] The normal-temperature medium enters the condensation chamber and is heated into a medium-high-temperature medium by the heat absorbed by the high-pressure generation chamber, and the condensation chamber produces cooling capacity;

[0020] The sub-medium-temperature medium enters the evaporation chamber and is cooled into a medium-normal-temperature medium by the cooling capacity produced by the condensation chamber;

[0021] A cascade heat exchange process based on absorption refrigeration also uses the above-mentioned cascade heat exchange system based on absorption refrigeration, including the following steps:

[0022] The high-temperature medium sequentially enters the high-pressure generator and the medium-pressure generator to be heat-absorbed and becomes a medium-temperature medium;

[0023] The ultra-low-temperature medium sequentially enters the low-pressure absorber and the medium-pressure absorber to absorb heat and becomes a sub-low-temperature medium;

[0024] The medium-temperature heat exchanger exchanges heat between the medium-temperature medium and the sub-low-temperature medium, converting the medium-temperature medium into a sub-medium-temperature medium and the sub-low-temperature medium into a normal-temperature medium;

[0025] The normal-temperature medium enters the condenser and is heated into a medium-high-temperature medium by the heat absorbed by the high-pressure generator, and the condenser produces cooling capacity;

[0026] The sub-medium-temperature medium enters the evaporator and is cooled into a medium-normal-temperature medium by the cooling capacity produced by the condenser.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] 1. Using the cascade heat exchange system as an intermediate medium for the high-temperature medium and the ultra-low-temperature medium to perform cascade heat exchange, thereby meeting the process requirements in actual production that require the high-temperature medium and the ultra-low-temperature medium to perform cascade heat exchange, solving the problem that the direct through-wall heat exchange between the high-temperature medium and the ultra-low-temperature medium results in a large temperature difference between the hot and cold media, which imposes strict requirements on the materials and structure of the through-wall heat exchanger, and avoiding the excessively high cost of the through-wall heat exchanger;

[0029] 2. The cascade heat exchange process can also meet the process requirements in actual production that require the ultra-low-temperature medium to be gradually heated to generate intermediate products, as well as in scientific research, where a certain ultra-low-temperature medium needs to be gradually heated to study its physical properties at each temperature level. This cascade heat exchange process can not only broaden the application scenarios of absorption refrigeration, but also achieve efficient utilization of energy, achieve the goal of energy conservation and emission reduction, and thus realize higher economic value;

[0030] 3. Use the upper heat exchanger to replace the medium-pressure generator and the medium-pressure absorber, and use the lower heat exchanger to replace the high-pressure generator, condenser, evaporator, and low-pressure absorber, so as to integrate some equipment of the cascade heat exchange process together, which can reduce the cost of equipment and pipelines and greatly reduce the floor area of the unit. Brief Description of the Drawings

[0031] Figure 1 Schematic diagram of the cascade heat exchange system of the present invention;

[0032] Figure 2 Schematic diagram of the connection module of the upper heat exchanger and the lower heat exchanger of the present invention;

[0033] Figure 3 Schematic diagram of the connection structure of the upper heat exchanger and the lower heat exchanger of the present invention;

[0034] Figure 4 For the present invention Figure 3 Schematic diagram in the A-A direction of the present invention.

[0035] 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 generation chamber; 134. Low-pressure absorption chamber; 135. First partition; 1351. First dividing plate; 1352. Second dividing plate; 136. Liquid baffle; 14. Upper heat exchanger; 141. Medium-pressure generation chamber; 142. Medium-pressure absorption chamber; 143. Second partition; 15. Liquid distribution assembly. Detailed Embodiment

[0036] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0037] Embodiment 1

[0038] Please refer to Figure 1 , a cascade heat exchange system based on absorption refrigeration, including: 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;

[0039] Among them, please refer to 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;

[0040] Please refer to 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 one outlet of the medium heat exchanger 5;

[0041] Please refer to 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-medium temperature medium inlet of the evaporator 3 is connected to the other outlet of the medium heat exchanger 5;

[0042] Please refer to 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;

[0043] Please refer to 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 one inlet of the medium heat exchanger 5;

[0044] Please refer to Figure 1 , the sub-low temperature medium outlet of the medium-pressure absorber 7 is connected to the other inlet of the medium heat exchanger 5.

[0045] A cascade heat exchange process based on absorption refrigeration includes the following steps:

[0046] Using the high-temperature medium as the heat source, heating the high-pressure rich liquid transported by the second solution pump 12 in the high-pressure generator 1 to desorb most of the low-boiling refrigerants in the high-pressure rich liquid, becoming high-pressure gaseous refrigerant and entering the condenser 2, where it is condensed into high-pressure liquid refrigerant by the normal temperature medium, and the normal temperature medium absorbs the heat of the high-pressure gaseous refrigerant and is heated into medium-high temperature medium; the high-pressure liquid refrigerant flowing out of the condenser 2 is decompressed into low-pressure liquid refrigerant through the expansion valve 8, and the low-pressure liquid refrigerant enters the evaporator 3, absorbing the heat of the sub-medium temperature medium entering the evaporator 3 and vaporizing into low-pressure gaseous refrigerant;

[0047] The high-pressure lean liquid remaining after the generation process in the high-pressure generator 1 is depressurized by the second pressure reducing valve 11 into medium-pressure lean liquid and enters the medium-pressure absorber 7; the high-temperature medium is heated in the high-pressure generator 1 and becomes a sub-high-temperature medium, and the sub-high-temperature medium enters the medium-pressure generator 6, heating the medium-pressure rich liquid transported by the first solution pump 10, so that most of the low-boiling refrigerants in the medium-pressure rich liquid are desorbed and become medium-pressure gaseous refrigerants and enter the medium-pressure absorber 7, where they are mixed with the medium-pressure lean liquid entering the medium-pressure absorber 7 and absorbed to become medium-pressure rich liquid. The medium-pressure rich liquid is boosted by the second solution pump 12 and sent into the high-pressure generator 1 to continue the cycle;

[0048] The medium-pressure lean liquid remaining after the generation process in the medium-pressure generator 6 is depressurized by the first pressure reducing valve 9 into low-pressure lean liquid and enters the low-pressure absorber 4, where it is mixed with the low-pressure gaseous refrigerant coming out of the evaporator 3 and absorbed to become low-pressure rich liquid. The low-pressure rich liquid is boosted by the first solution pump 10 and sent into the medium-pressure generator 6 to continue the cycle;

[0049] The high-temperature medium serves as the heat source in the generation process and enters the high-pressure generator 1 and the medium-pressure generator 6 in sequence. After being heated, it becomes a sub-high-temperature medium and a medium-temperature medium in sequence, and then enters the medium heat exchanger 5; the ultra-low-temperature medium serves as the cold source in the absorption process and enters the low-pressure absorber 4 and the medium-pressure absorber 7 in sequence. After being heated, it becomes a low-temperature medium and a sub-low-temperature medium in sequence, and then enters the medium heat exchanger 5, where it is heated by the incoming medium-temperature medium to become a normal-temperature medium, while the medium-temperature medium becomes a sub-medium-temperature medium after being heated; the sub-medium-temperature medium finally enters the evaporator 3 and continues to be heated to become a medium-normal-temperature medium, and the normal-temperature medium flowing out of the medium heat exchanger 5 finally enters the condenser 2 and is heated to become a medium-high-temperature medium.

[0050] It should be noted that the high-temperature medium and the ultra-low-temperature medium exchange heat in a cascaded manner. The high-temperature medium cools down in a cascaded manner 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 in a cascaded manner and becomes a low-temperature medium, a sub-low-temperature medium, a normal-temperature medium, and a medium-high-temperature medium in sequence.

[0051] Embodiment 2

[0052] As a further optimized solution of Embodiment 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; among them, 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 heads, tube sheet barrels, tube sheets, heat exchange tubes and shells; the left and right heads and tube sheet barrels 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.

[0053] Please refer to 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 generation cavity 141 and a medium-pressure absorption cavity 142, and the medium-pressure generation cavity 141 is located above the medium-pressure absorption 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 generation cavity 133 and a low-pressure absorption cavity 134;

[0054] Please refer to Figure 3 and Figure 4 , a heat source inlet and a heat source outlet are respectively provided on the two tube sheet barrels of the high-pressure generation cavity 133, and a high-pressure gaseous refrigerant outlet, a high-pressure lean liquid outlet and a high-pressure rich liquid inlet are provided on the shell of the high-pressure generation cavity 133;

[0055] Please refer to Figure 3 and Figure 4 , a normal-temperature medium inlet and a medium-high temperature medium outlet are respectively provided on the two tube sheet barrels of the condensation cavity 132, and a high-pressure gaseous refrigerant inlet and a high-pressure liquid refrigerant outlet are provided on the shell of the condensation cavity 132;

[0056] Please refer to Figure 3 and Figure 4 , a sub-medium temperature medium inlet and a medium-normal temperature medium outlet are respectively provided on the two tube sheet barrels of the evaporation cavity 131, and a low-pressure liquid refrigerant inlet and a low-pressure gaseous refrigerant outlet are provided on the shell of the evaporation cavity 131;

[0057] Please refer to Figure 3 and Figure 4 , a cryogenic medium inlet and a low-temperature medium outlet are respectively provided on the two tube sheet barrels of the low-pressure absorption cavity 134, and a low-pressure gaseous refrigerant inlet, a low-pressure lean liquid inlet and a low-pressure rich liquid outlet are provided on the shell of the low-pressure absorption cavity 134;

[0058] Please refer to Figure 3 and Figure 4, on the two tube sheet cylinders of the medium-pressure generating chamber 141, there are respectively a heat source inlet and a heat source outlet, and on the shell of the medium-pressure generating chamber 141, there are a medium-pressure gaseous refrigerant outlet, a medium-pressure lean liquid outlet, and a medium-pressure rich liquid inlet;

[0059] Please refer to Figure 3 and Figure 4 , on the two tube sheet cylinders of the medium-pressure absorption chamber 142, there are respectively a low-temperature medium inlet and a sub-low-temperature medium outlet, and on the shell of the medium-pressure absorption chamber 142, there are a medium-pressure lean liquid inlet, a medium-pressure rich liquid outlet, and a medium-pressure gaseous refrigerant inlet;

[0060] Please refer to Figure 3 and Figure 4 , on the two tube sheet cylinders of the medium heat exchanger 5, there are respectively a medium-temperature medium inlet and a sub-medium-temperature medium outlet, and on the shell of the medium heat exchanger 5, there are a sub-low-temperature medium inlet and a normal-temperature medium outlet;

[0061] Please refer to Figure 3 and Figure 4 , the heat source outlet of the high-pressure generating chamber 133 is communicated with 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 communicated with the high-pressure gaseous refrigerant inlet of the condensation chamber 132, the high-pressure lean liquid outlet of the high-pressure generating chamber 133 is communicated with 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 communicated with 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 condensation chamber 132 is communicated with the low-pressure liquid refrigerant inlet of the evaporation chamber 131 through the expansion valve 8, and the normal-temperature medium inlet of the condensation chamber 132 is communicated with the normal-temperature medium outlet of the medium heat exchanger 5; the low-pressure gaseous refrigerant outlet of the evaporation chamber 131 is communicated with the low-pressure gaseous refrigerant inlet of the low-pressure absorption chamber 134, and the sub-medium-temperature medium inlet of the evaporation chamber 131 is communicated 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 communicated with the medium-pressure lean liquid outlet of the medium-pressure generating chamber 141 through the first pressure reducing valve 9, the low-pressure rich liquid outlet of the low-pressure absorption chamber 134 is communicated with the medium-pressure rich liquid inlet of the medium-pressure generating chamber 141 through the first solution pump 10, and the low-temperature medium outlet of the low-pressure absorption chamber 134 is communicated 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 communicated 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 communicated 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 communicated with the sub-low-temperature medium inlet of the medium heat exchanger 5.

[0062] It should be noted that the medium 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 medium heat exchanger 5 through a support plate.

[0063] In this embodiment, as a further optimized solution, please refer to Figure 3 and Figure 4 , the first partition plate 135 includes a first dividing plate 1351 and a second dividing plate 1352. The second dividing plate 1352 is arranged in the inner cavity of the tube sheet section of the lower heat exchanger 13, and the first dividing plate 1351 is arranged in the inner cavity of the shell of the lower heat exchanger 13. The cross-sections of the first dividing plate 1351 and the second dividing plate 1352 are both cross-shaped, and are used to divide the inner cavities of the tube sheet section and the shell into four parts (corresponding to the evaporation chamber 131, the condensation chamber 132, the high-pressure generation chamber 133, and the low-pressure absorption chamber 134). An opening is provided on the first dividing plate 1351 between the evaporation chamber 131 and the low-pressure absorption chamber 134. This 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 dividing plate 1351 between the condensation chamber 132 and the high-pressure generation chamber 133. This opening is both the high-pressure gaseous refrigerant outlet of the high-pressure generation chamber 133 and the high-pressure gaseous refrigerant inlet of the condensation chamber 132. Liquid baffle plates 136 are provided in both openings; through the setting of the openings, the laying of pipelines is reduced.

[0064] 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 generation chamber 141. This liquid distribution assembly 15 is communicated with the medium-pressure rich liquid inlet. A liquid distribution assembly 15 is provided in the shell of the medium-pressure absorption chamber 142. This liquid distribution assembly 15 is communicated with the medium-pressure lean liquid inlet. A liquid distribution assembly 15 is installed in the inner cavity of the shell of the evaporation chamber 131. This liquid distribution assembly 15 is communicated with the low-pressure liquid refrigerant inlet. A liquid distribution assembly 15 is installed in the shell of the high-pressure generation chamber 133. This liquid distribution assembly 15 is communicated with the high-pressure rich liquid inlet; a liquid distribution assembly 15 is provided in the shell of the low-pressure absorption chamber 134. This liquid distribution assembly 15 is communicated with the low-pressure lean liquid inlet; the liquid distribution assembly 15 includes a pipeline and spray heads provided on the pipeline. The spray heads are used to atomize and spray the transported liquid onto the heat exchange tubes, increasing the heat exchange area and improving the heat exchange efficiency.

[0065] After using the upper heat exchanger 14 and the lower heat exchanger 13 to replace some components in the cascade heat exchange system, the cascade heat exchange process includes the following steps:

[0066] The high-temperature medium, as a heat source, enters the heat exchange tubes in the high-pressure generating chamber 133, heating the high-pressure rich solution that is transported by the second solution pump 12 and sprayed onto the outer surface of the heat exchange tubes, causing most of the low-boiling refrigerants in the high-pressure rich solution to desorb and become high-pressure gaseous refrigerants. The high-pressure gaseous refrigerants enter the shell of the condensation chamber 132 through the liquid baffle 136 and are condensed into high-pressure liquid refrigerants by the normal-temperature medium in the heat exchange tubes. The normal-temperature medium in the tube side of the condensation chamber 132 absorbs the heat of the high-pressure gaseous refrigerants and is heated into a medium-high temperature medium; the high-pressure liquid refrigerants flowing out of the condensation chamber 132 are decompressed into low-pressure liquid refrigerants through the expansion valve 8. The low-pressure liquid refrigerants enter the shell of the evaporation chamber 131 and are evenly sprayed onto the outer surface of the heat exchange tubes through spraying, absorbing the heat of the sub-medium-temperature medium in the heat exchange tubes in the evaporation chamber 131 and vaporizing into low-pressure gaseous refrigerants. The low-pressure gaseous refrigerants enter the shell of the low-pressure absorption chamber 134 through the liquid baffle 136;

[0067] The high-pressure lean solution remaining after the generation process in the shell of the high-pressure generating chamber 133 is decompressed into medium-pressure lean solution through the second pressure reducing valve 11, enters the medium-pressure absorption chamber 142, and is evenly sprayed onto the outer surface of the heat exchange tubes through spraying; the high-temperature medium becomes a sub-high temperature medium after absorbing heat in the high-pressure generating chamber 133. The sub-high temperature medium enters the heat exchange tubes in the medium-pressure generating chamber 141, heating the medium-pressure rich solution that is transported by the first solution pump 10 and sprayed onto the outer surface of the heat exchange tubes, causing most of the low-boiling refrigerants in the medium-pressure rich solution to desorb and become medium-pressure gaseous refrigerants, which enter the shell of the medium-pressure absorption chamber 142 and are mixed with the medium-pressure lean solution on the outer surface of the heat exchange tubes to absorb and become medium-pressure rich solution. The medium-pressure rich solution is boosted by the second solution pump 12 and sent into the high-pressure generating chamber 133 to continue the cycle;

[0068] The medium-pressure lean solution remaining after the generation process in the medium-pressure generating chamber 141 is decompressed into low-pressure lean solution through the first pressure reducing valve 9, enters the shell of the low-pressure absorption chamber 134, and is evenly sprayed onto the outer surface of the heat exchange tubes through spraying, being mixed with the low-pressure gaseous refrigerants coming out of the shell of the evaporation chamber 131 to absorb and become low-pressure rich solution. The low-pressure rich solution is boosted by the first solution pump 10 and sent into the medium-pressure generating chamber 141 to continue the cycle;

[0069] 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.

[0070] 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; 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); 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.

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: 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.

6. The step heat exchange system based on absorption refrigeration according to claim 3, 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).

7. 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.

8. 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 6, 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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