A cold and heat energy cascade utilization refrigeration system

Abstract

The application provides a cold and hot energy cascade utilization refrigeration system, comprising a lithium bromide refrigerating unit, an electric refrigerating unit, a high-temperature stage cooling water system and a high-temperature stage hot water system; a chilled water return water outlet of a first evaporator of the lithium bromide refrigerating unit is connected with a cooling water return water outlet of a condenser of the electric refrigerating unit through an electric refrigerating unit cooling water return water pipeline, an inter-stage cooling water circulating pump is arranged on the electric refrigerating unit cooling water return water pipeline; a chilled water supply water outlet of the first evaporator of the lithium bromide refrigerating unit is connected with a cooling water inlet of the condenser of the electric refrigerating unit through a lithium bromide refrigerating unit chilled water supply water pipeline; the application can significantly reduce operation cost while reducing system operation energy consumption, has the benefits of environmental protection and low carbon, and is used for meeting more extensive application scenarios.

Description

Technical Field

[0001] This invention relates to the field of refrigeration unit technology, and more particularly to a refrigeration system that utilizes cold and heat energy in a cascade manner. Background Technology

[0002] With the development of modern industry, refrigeration technology plays a vital role in numerous fields. Lithium bromide refrigeration units, as heat-driven refrigeration equipment based on the absorption refrigeration principle, use water as the refrigerant and lithium bromide solution as the absorbent. They utilize waste heat from high-temperature flue gas, low-pressure steam, and industrial waste hot water to drive the refrigeration cycle, achieving a cooling effect on low-temperature heat sources. They demonstrate significant advantages in waste heat recovery and environmental protection, and are widely used in many industries such as steel, petrochemicals, coal chemicals, pharmaceuticals, and municipal engineering, making important contributions to the efficient recovery and utilization of energy.

[0003] Currently, the refrigeration field mainly utilizes two technologies: lithium bromide refrigeration units and electric refrigeration units. Lithium bromide refrigeration units utilize waste heat for efficient energy recovery and utilization; while electric refrigeration units use an electrically driven compressor as their core, achieving refrigeration through a compression refrigeration cycle. They leverage the phase change of the refrigerant to transfer heat from a low-temperature environment to a high-temperature environment, achieving cooling or maintaining a low temperature. Furthermore, they can be categorized into various compressor types, such as centrifugal and screw compressors. Because electric refrigeration units rely entirely on electric power to drive the compressor, they have become the most widely used refrigeration technology, especially when producing cooling capacity above 0°C, achieving a coefficient of performance (COP) as high as 6.0, far exceeding the maximum COP of 1.7 for lithium bromide refrigeration units, demonstrating high refrigeration efficiency and broad application prospects.

[0004] However, existing refrigeration technologies still have many shortcomings. Lithium bromide chillers, limited by the 0°C freezing point of water (the refrigerant in the working fluid), are only suitable for temperatures above 0°C and are ineffective in applications below 0°C, failing to provide a suitable operating condition. While electric chillers are widely used, their coefficient of performance (COP) decreases significantly with decreasing operating temperature. At -15°C, the COP drops to 3.0, meaning a substantial increase in energy consumption. Furthermore, at -100°C, the system loses its energy-saving advantages. Although academic research and practical applications have attempted to improve the COP of electric chillers through adjustable volume ratios, optimized heat exchanger design, variable frequency technology, and the development of magnetic levitation compressors, the improvement has been limited, only about 15%. With increasingly stringent environmental regulations and technological upgrades, electric chillers urgently need to evolve towards lower carbon emissions and greater energy efficiency. There is an urgent need to propose a new solution to improve the coefficient of performance (COP) of various refrigeration units and meet the cooling capacity supply requirements in a wide temperature range from 0°C to -100°C, so as to optimize the energy efficiency and economy of existing refrigeration systems. Summary of the Invention

[0005] To address the technical problem that existing electric refrigeration units no longer offer energy-saving and consumption-reducing advantages as the operating temperature decreases, this invention provides a cascaded utilization refrigeration system for both heating and cooling energy. This invention constructs a synergistic operation mechanism that combines waste heat drive with complementary electrical energy, achieving efficient energy conversion by producing cooling capacity over a wide temperature range from 0°C to -100°C with energy consumption as low as 0.5 times lower.

[0006] The technical means employed in this invention are as follows:

[0007] A cascaded energy utilization refrigeration system includes: a lithium bromide refrigeration unit, an electric refrigeration unit, a high-temperature cooling water system, and a high-temperature hot water system. The core design objective of this invention is to construct a synergistic operation mechanism that combines waste heat drive and electric energy complementarity. Through cascaded energy utilization, it simultaneously solves the problems of lithium bromide refrigeration units being unable to produce cooling below 0°C and electric refrigeration units experiencing a sharp drop in coefficient of performance (COP) and high energy consumption under low-temperature conditions. This allows for the production of cooling over a wide temperature range from 0°C to -100°C with energy consumption as low as 0.5 times lower.

[0008] The high-temperature hot water system constitutes the driving heat source for the entire system, including a waste heat source. This waste heat source is connected to the generator inlet of the lithium bromide chiller unit via a waste hot water supply pipeline. A high-temperature hot water circulation pump is installed on the waste hot water supply pipeline. The generator outlet of the lithium bromide chiller unit is connected to the waste heat source via a waste hot water return pipeline. This system design fully utilizes waste heat generated in industrial processes (such as high-temperature flue gas, low-pressure steam, and industrial waste hot water) as the driving energy for the lithium bromide absorption refrigeration cycle, achieving the recovery and utilization of waste heat resources and reducing the system's external energy consumption at the source.

[0009] The high-temperature cooling water system provides a cold source for the absorber and condenser of the lithium bromide refrigeration unit. It includes a cold source connected to the absorber inlet of the lithium bromide refrigeration unit via a cooling water supply pipeline. A high-temperature cooling water circulation pump is installed on the cooling water supply pipeline. The absorber outlet of the lithium bromide refrigeration unit is connected to the inlet of the first condenser of the lithium bromide refrigeration unit. The first condenser outlet of the lithium bromide refrigeration unit is connected to the cold source via a cooling water return pipeline. This system can utilize natural or low-cost cold sources such as seawater or cooling towers to complete the cooling and condensation process of the lithium bromide solution in the absorber and condenser, ensuring the efficient operation of the lithium bromide refrigeration cycle.

[0010] The most critical innovation of this invention lies in the coupling connection method between the lithium bromide chiller and the electric chiller. Specifically, the chilled water return port of the first evaporator of the lithium bromide chiller is connected to the cooling water return port of the condenser of the electric chiller through the cooling water return pipe of the electric chiller, and an interstage cooling water circulation pump is installed on the cooling water return pipe of the electric chiller. The chilled water supply port of the first evaporator of the lithium bromide chiller is connected to the cooling water inlet of the condenser of the electric chiller through the chilled water supply pipe of the lithium bromide chiller. This coupling design establishes the core path for energy cascade utilization: chilled water at 5-12°C produced by the lithium bromide chiller using waste heat is used as the cooling water for the condenser of the electric chiller. Compared to the traditional use of ambient cooling water at 25-32°C by electric chillers, this significantly reduces the condensing temperature of the electric chiller, thereby greatly reducing the shaft power of its compressor and directly improving the coefficient of performance (COP) of the electric chiller. This is the key to achieving energy saving and consumption reduction in the entire system.

[0011] The chilled water return port of the evaporator of the electric chiller unit is connected to the chilled water return port of the terminal cooling process unit via the chilled water return pipeline of the electric chiller unit. A low-temperature chilled water circulation pump is installed on the chilled water return pipeline of the electric chiller unit, and the chilled water supply port of the evaporator of the electric chiller unit is connected to the chilled water inlet of the terminal cooling process unit via the chilled water supply pipeline of the electric chiller unit. This low-temperature chilled water system ultimately delivers the deep cooling capacity produced by the electric chiller unit to the terminal process unit, completing the entire energy transfer process from high-temperature waste heat to cascaded cooling energy, and finally to the deep cooling capacity that meets the process requirements.

[0012] Furthermore, the lithium bromide refrigeration unit includes a generator, a first condenser, a first evaporator, and an absorber connected in sequence;

[0013] When producing cooling capacity in the temperature range of -35℃ to 0℃, the electric refrigeration unit includes a compressor, a second condenser, a first throttle valve, and a second evaporator. To cover a wide cooling temperature range, the electric refrigeration unit has optimized its internal structure for different temperature ranges. The purpose of this design is to ensure that the electric refrigeration unit always operates at the highest COP in its respective temperature range by configuring the optimal refrigeration cycle process (such as single-stage compression, two-stage compression, cascade system with economizer or subcooler) for a specific temperature range.

[0014] When producing cooling capacity in the temperature range of -50℃ to -35℃, the electric refrigeration unit includes a first low-pressure stage compressor, a first high-pressure stage compressor, a third condenser, a first economizer, a second throttle valve, a third throttle valve, and a third evaporator;

[0015] When producing cooling capacity in the temperature range of -60℃ to -40℃, the electric refrigeration unit includes a second low-pressure stage compressor, a second high-pressure stage compressor, a fourth condenser, a first subcooler, a second economizer, a fourth throttle valve, a fifth throttle valve, a sixth throttle valve, and a fourth evaporator;

[0016] When producing cooling capacity in the temperature range of -100℃ to -60℃, the electric refrigeration unit includes a low-temperature stage compressor, a high-temperature stage compressor, a fifth condenser, a third economizer, a condenser-evaporator, a second subcooler, a regenerator, a seventh throttle valve, an eighth throttle valve, a ninth throttle valve, a tenth throttle valve, and a fifth evaporator.

[0017] Furthermore, when producing cooling capacity in the temperature range of -35℃ to 0℃, the outlet of the second evaporator of the electric refrigeration unit is connected to the inlet of the compressor, the outlet of the compressor is connected to the inlet of the second condenser, the outlet of the second condenser is connected to the inlet of the first throttle valve, the outlet of the first throttle valve is connected to the inlet of the second evaporator, and the outlet of the second evaporator is connected to the inlet of the compressor.

[0018] When producing cooling capacity in the temperature range of -50℃ to -35℃, the outlet of the third evaporator is connected to the inlet of the first low-pressure stage compressor, the outlet of the first low-pressure stage compressor is connected to the inlet of the first high-pressure stage compressor, the outlet of the first high-pressure stage compressor is connected to the inlet of the third condenser, the outlet of the third condenser is connected to the inlet of the first economizer, the first outlet of the first economizer is connected to the inlet of the second throttling valve, the throttled refrigerant enters the evaporator side of the first economizer to absorb heat and evaporate, and the evaporated medium-temperature and medium-pressure refrigerant gas is connected to the inlet of the first high-pressure stage compressor; the second outlet of the first economizer is connected to the inlet of the third throttling valve, the throttled refrigerant enters the inlet of the third evaporator, and the evaporated low-temperature and low-pressure refrigerant gas is connected to the inlet of the first low-pressure stage compressor;

[0019] When producing cooling capacity in the temperature range of -60℃ to -40℃, the outlet of the fourth evaporator is connected to the inlet of the second low-pressure stage compressor, the outlet of the second low-pressure stage compressor is connected to the inlet of the second high-pressure stage compressor, the outlet of the second high-pressure stage compressor is connected to the inlet of the fourth condenser, and the first outlet of the fourth condenser is connected to the subcooling side inlet of the first subcooler; the second outlet of the fourth condenser is connected to the inlet of the fourth throttling valve, and the throttled refrigerant enters the evaporation side of the first subcooler to absorb heat and evaporate, and the evaporated medium-temperature, medium-pressure refrigerant gas is connected to the inlet of the second high-pressure stage compressor; the first outlet of the subcooling side of the first subcooler is connected to the subcooling side inlet of the second economizer, the second outlet of the subcooling side of the first subcooler is connected to the inlet of the fifth throttling valve, and the throttled refrigerant enters the evaporation side of the second economizer to absorb heat and evaporate, and the evaporated low-temperature, low-pressure refrigerant gas is connected to the inlet of the second low-pressure stage compressor; the subcooling side outlet of the second economizer is connected to the inlet of the sixth throttling valve, and the throttled refrigerant enters the inlet of the fourth evaporator;

[0020] When producing cooling capacity in the temperature range of -100℃ to -60℃, the low-temperature stage cycle connection relationship of the electric refrigeration unit is as follows:

[0021] The gas-side outlet of the regenerator is connected to the inlet of the cryogenic stage compressor. The outlet of the cryogenic stage compressor is connected to the cryogenic side inlet of the condenser-evaporator. The cryogenic side outlet of the condenser-evaporator is connected to the liquid-side inlet of the regenerator. The first liquid-side outlet of the regenerator is connected to the subcooling side inlet of the second subcooler. The second liquid-side outlet of the regenerator is connected to the inlet of the ninth throttling valve. The throttled refrigerant enters the evaporator side of the second subcooler to absorb heat and evaporate. The evaporated cryogenic, low-pressure refrigerant gas is connected to the inlet of the cryogenic stage compressor. The subcooling side outlet of the second subcooler is connected to the inlet of the tenth throttling valve. The throttled refrigerant enters the inlet of the fifth evaporator. The outlet of the fifth evaporator is connected to the gas-side inlet of the regenerator.

[0022] When producing cooling capacity in the temperature range of -100℃ to -60℃, the high-temperature stage cycle connection relationship of the electric refrigeration unit is as follows:

[0023] The high-temperature gas outlet of the condenser-evaporator is connected to the inlet of the high-temperature stage compressor. The outlet of the high-temperature stage compressor is connected to the inlet of the fifth condenser. The first outlet of the fifth condenser is connected to the subcooling side inlet of the third economizer. The second outlet of the fifth condenser is connected to the inlet of the seventh throttling valve. The throttled refrigerant enters the evaporation side of the third economizer to absorb heat and evaporate. The evaporated medium-temperature and medium-pressure refrigerant gas is connected to the inlet of the high-temperature stage compressor. The subcooling side outlet of the third economizer is connected to the inlet of the eighth throttling valve. The throttled refrigerant enters the high-temperature side inlet of the condenser-evaporator.

[0024] Furthermore, the bypass of the high-temperature hot water circulation pump is equipped with a spare hot water supply pipeline, and a high-temperature hot water backup pump is installed on the spare hot water supply pipeline.

[0025] The bypass of the high-temperature cooling water circulation pump is equipped with a backup cooling water supply pipeline, and the backup cooling water supply pipeline is equipped with a backup high-temperature cooling water pump.

[0026] The bypass of the interstage cooling water circulation pump is equipped with a backup pipeline for the return cooling water of the electric chiller unit, and the backup cooling water return pipeline for the electric chiller unit is equipped with an interstage cooling water backup pump.

[0027] The bypass of the low-temperature chilled water circulating pump is equipped with a backup chilled water return pipeline for the electric chiller unit, and a backup low-temperature chilled water pump is installed on the backup chilled water return pipeline for the electric chiller unit.

[0028] Furthermore, a heat source-side electric three-way valve is installed on the waste hot water return pipeline, and the three-way pipeline of the heat source-side electric three-way valve is connected to the inlet / outlet of the waste hot water return pipeline and the waste hot water supply bypass pipeline, respectively.

[0029] A cold source side electric three-way valve is installed on the cooling water supply pipeline. The three-way pipeline of the cold source side electric three-way valve is connected to the inlet / outlet of the cooling water supply pipeline and the waste hot water return bypass pipeline, respectively.

[0030] The control strategy of the electric three-way valve on the heat source side is as follows: Set the outlet temperature of the electric three-way regulating valve on the heat source side as the target temperature, adjust the accuracy range of the target temperature, and send the residual hot water return temperature parameter at the inlet of the electric three-way regulating valve on the heat source side as a control signal to the actuator of the electric three-way regulating valve on the heat source side. When the residual hot water return temperature at the inlet of the electric three-way regulating valve on the heat source side is lower than the target temperature at the outlet, the flow rate of the high-temperature residual hot water in the residual hot water supply bypass pipeline is controlled by adjusting the opening of the bypass valve of the electric three-way regulating valve on the heat source side, so that the temperature of the two water sources mixed at the inlet of the electric three-way regulating valve on the heat source side reaches the target temperature, and the supply side valve is opened. If the target temperature is not reached, the electric three-way regulating valve on the heat source side is closed, and the internal circulation continues.

[0031] The control strategy of the cold source side electric three-way valve is as follows: Set the outlet temperature of the cold source side electric three-way regulating valve as the target temperature, adjust the accuracy range of the target temperature, and send the cooling water supply temperature parameter at the inlet of the cold source side electric three-way regulating valve as a control signal to the actuator of the cold source side electric three-way regulating valve. When the cooling water supply temperature at the inlet of the cold source side electric three-way regulating valve is lower than the target temperature at the outlet, the flow rate of high-temperature waste hot water in the waste hot water return bypass pipeline is controlled by adjusting the opening of the bypass valve of the cold source side electric three-way regulating valve, so that the temperature of the two water sources mixed at the inlet of the cold source side electric three-way regulating valve reaches the target temperature, and the supply side valve is opened. If the target temperature is not reached, the cold source side electric three-way regulating valve is closed, and internal circulation continues.

[0032] Furthermore, it also includes a chilled water constant pressure water supply device and a soft water constant pressure water supply device;

[0033] The chilled water constant pressure water supply device is connected to the chilled water return water pipeline of the electric refrigeration unit, where the inlet of the low-temperature chilled water circulation pump is located, through the chilled water supply pipeline.

[0034] The soft water constant pressure water supply device is connected to the cooling water return water pipeline of the electric chiller unit, where the inlet of the interstage cooling water circulation pump is located, through a soft water supply pipeline.

[0035] Furthermore, it also includes a cooling water flushing device and a waste heat cleaning device;

[0036] The cooling water flushing device is connected to the cooling water supply pipe through the flushing device inlet pipe;

[0037] The waste heat cleaning device is connected to the waste hot water supply pipe through the cleaning device inlet pipe.

[0038] Furthermore, the cooling water for the high-temperature cooling water system between the cold source and the lithium bromide chiller unit is supplied by seawater or a cooling tower. When seawater is used as the cooling water, an electric three-way regulating valve on the cold source side is installed on the water supply pipeline to prevent extreme low temperatures from affecting equipment performance. By adjusting the valve opening, waste heat return water from the high-temperature hot water system is introduced to ensure stable system operation. When a cooling tower is used to supply cooling water, the system between the cooling tower and the absorber of the lithium bromide chiller unit is a closed system, and a chemical dosing and water replenishment device is added.

[0039] Furthermore, when producing cooling capacity in the temperature range of 0 to -15°C, the electric refrigeration unit is a centrifugal refrigeration compressor unit;

[0040] When producing cooling capacity in the temperature range of -15 to -100℃, the electric refrigeration unit is a screw-type refrigeration compressor unit.

[0041] Furthermore, the supply water temperature range of the waste heat source is 70~120℃, and the return water temperature range of the waste heat source is 50~100℃.

[0042] The cooling water supply temperature range of the cold source is 25~32℃, and the return water temperature range is 33~40℃.

[0043] The interstage cooling water supply temperature range is 5~12℃, and the interstage cooling water return temperature range is 10~17℃.

[0044] The supply temperature range of the low-temperature chilled water is 0~-100℃, and the return temperature range of the low-temperature chilled water is 5~-95℃.

[0045] Compared with the prior art, the present invention has the following advantages:

[0046] This invention develops a novel coupled design refrigeration system that avoids the drawback of lithium bromide refrigeration units being limited to applications with temperatures above 0°C due to the freezing point of the refrigerant "water" in its working fluid being 0°C. It also solves the problem of high energy consumption in electric refrigeration units, where the coefficient of performance (COP) decreases as the production temperature decreases, eventually reaching -100°C, at which point the system loses its energy-saving advantage.

[0047] This invention uses industrial waste heat as the driving heat source for the lithium bromide refrigeration unit generator and natural cold sources such as seawater as the cold source for the absorber and condenser of the lithium bromide refrigeration unit. Through an absorption refrigeration cycle, heat exchange occurs in the evaporator, producing low-temperature chilled water. A collaborative operation mechanism of the two refrigeration units is employed, with the low-temperature chilled water used in a cascaded coupling design as the cooling water for the condenser in the electric refrigeration unit, effectively reducing the condensing temperature of the electric refrigeration system. Compared to the existing technology's independent operation mode of the electric refrigeration unit, the coefficient of performance (COP) of the electric refrigeration unit is improved. Compared to other coupling methods in the prior art, a wider temperature range of cooling capacity can be supplied under optimal COP. This achieves efficient energy conversion throughout the entire refrigeration process, significantly reducing operating costs while lowering system energy consumption, and also offering environmental and low-carbon benefits. It can meet a wider range of application scenarios, has a short investment payback period, and significant energy-saving and consumption-reducing effects.

[0048] This invention, by adjusting the internal structure and equipment configuration of the electric refrigeration unit, can produce cooling capacity in multiple temperature ranges at optimal COP, including -100℃ to -60℃, -60℃ to -40℃, -50℃ to -35℃, -35℃ to -0℃, and -15℃ to 0℃. By providing lower-temperature cooling water to the electric refrigeration unit through the lithium bromide refrigeration unit, the condensing temperature of the electric refrigeration unit can be reduced, thereby reducing the motor shaft power and improving the unit's COP. The coupling system of the lithium bromide refrigeration unit and the electric refrigeration unit utilizes high-temperature thermal energy to convert into medium-temperature cold energy, and uses the medium-temperature cold energy to produce tiered low-temperature cold energy, realizing tiered energy utilization and providing tiered temperature range cooling capacity supply within a wide temperature range of -100℃ to 0℃. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0050] Figure 1 This is a schematic diagram of the system of the present invention operating within the temperature range of -35℃ to 0℃.

[0051] Figure 2 This is a schematic diagram of the system of the present invention operating in the range of -50℃ to -35℃.

[0052] Figure 3 This is a schematic diagram of the system of the present invention operating in the range of -60℃ to -40℃.

[0053] Figure 4 This is a schematic diagram of the system of the present invention operating in the range of -100℃ to -60℃.

[0054] Figure 5 This is a schematic diagram of the lithium bromide refrigeration unit of the present invention.

[0055] Figure 6 This is a schematic diagram of the high-temperature hot water system of the present invention.

[0056] Figure 7 This is a schematic diagram of the high-temperature cooling water system of the present invention.

[0057] Figure 8 This is a schematic diagram of the interstage cooling water system of the present invention.

[0058] Figure 9 This is a schematic diagram of the low-temperature chilled water system of the present invention.

[0059] Figure 10This is a schematic diagram of the electric refrigeration unit of the present invention operating in the range of -35℃ to 0℃.

[0060] Figure 11 This is a schematic diagram of the electric refrigeration unit of the present invention operating in the range of -50℃ to -35℃.

[0061] Figure 12 This is a schematic diagram of the electric refrigeration unit of the present invention operating in the range of -60℃ to -40℃.

[0062] Figure 13 This is a schematic diagram of the electric refrigeration unit of the present invention operating in the range of -100℃ to -60℃.

[0063] In the diagram: 1. Lithium bromide refrigeration unit; 2. Generator; 3. First condenser; 4. Evaporator; 5. Absorber; 6. Electric refrigeration unit; 7. Compressor; 8. Second condenser; 9. Throttling valve; 10. Evaporator; 11. Waste heat source; 12. High-temperature hot water circulation pump; 13. High-temperature hot water standby pump; 14. Electric three-way valve on the heat source side; 15. Waste hot water supply pipeline; 16. Waste hot water supply standby pipeline; 17. Waste hot water supply bypass pipeline; 18. Waste hot water return pipeline; 19. Waste hot water return bypass pipeline; 20. Cold source; 21. High-temperature cooling water circulation pump; 22. High-temperature cooling water standby pump; 23. Electric three-way valve on the cold source side; 24. Cooling water supply pipeline; 25. Standby cooling water supply pipeline; 26. Cooling water return pipeline; 27. Interstage cooling water circulation pump; 28. Standby interstage cooling water pump; 29. ​​Chilled water supply pipeline for lithium bromide unit; 30. Cooling water return pipeline for electric chiller unit; 31. Standby cooling water return pipeline for electric chiller unit; 32. Low-temperature stage chilled water circulation pump; 33. Standby low-temperature stage chilled water pump; 34. Chilled water supply pipeline for electric chiller unit; 35. Chilled water return pipeline for electric chiller unit; 36. Standby chilled water return pipeline for electric chiller unit; 37. Terminal cooling process unit; 38. 39. Chilled water constant pressure water supply device; 40. Chilled water supply pipeline; 41. Soft water constant pressure water supply device; 42. Soft water supply pipeline; 43. Cooling water flushing device; 44. Flushing device inlet pipeline; 45. Flushing device return pipeline; 46. Waste heat cleaning device; 47. Cleaning device inlet pipeline; 48. Cleaning device return pipeline; 49. High temperature stage hot water system; 50. High temperature stage cooling water system; 51. Interstage cooling water system; 52. Low temperature stage chilled water system; 53. First low pressure stage compressor; 54. First high pressure stage compressor; 55. Third condenser; 56. First economizer; 57. Second throttle valve; 58. Third throttle valve; 59. Third evaporator; 60. Second low-pressure stage compressor; 61. Second high-pressure stage compressor; 62. Fourth condenser; 63. First subcooler; 64. Second economizer; 65. Fourth throttle valve; 66. Fifth throttle valve; 67. Sixth throttle valve; 68. Fourth evaporator; 69. Low-temperature stage compressor; 70. High-temperature stage compressor; 71. Fifth condenser; 72. Third economizer; 73. Condenser-evaporator; 74. Second subcooler; 75. Regenerator; 76. Seventh throttle valve; 77. Eighth throttle valve; 78. Ninth throttle valve; 79. Tenth throttle valve; 70. Fifth evaporator. Detailed Implementation

[0064] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0065] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0066] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0067] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0068] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0069] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0070] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0071] The technical problem to be solved by this invention is to expand the application scenarios of lithium bromide refrigeration units that are limited to a temperature range above 0°C, and to solve the problem that the coefficient of performance (COP) of electric refrigeration units no longer has the advantage of energy saving and consumption reduction as the production temperature decreases, while providing cooling capacity supply in a wide temperature range of 0 to -100°C.

[0072] The present invention provides a cascaded utilization refrigeration system for cold and heat energy, comprising: a lithium bromide refrigeration unit 1, an electric refrigeration unit 6, a high-temperature stage hot water system 48, a high-temperature stage cooling water system 49, an interstage cooling water system 50, and a low-temperature stage chilled water system 51.

[0073] like Figure 5 As shown, the lithium bromide refrigeration unit 1 includes basic components such as a generator 2, a first condenser 3, a first evaporator 4, and an absorber 5.

[0074] like Figure 6As shown, the high-temperature hot water system 48 includes a lithium bromide chiller unit 1, a waste heat source 11, a high-temperature hot water circulation pump 12, a high-temperature hot water standby pump 13, an electric three-way valve 14 on the heat source side, a waste hot water supply pipeline 15, a waste hot water supply standby pipeline 16, a waste hot water supply bypass pipeline 17, and a waste hot water return pipeline 18. The waste heat source 11 is connected to the inlet of the generator 2 of the lithium bromide chiller unit 1 via the waste hot water supply pipeline 15 and the high-temperature hot water circulation pump 12. After heat exchange between the waste heat source 11 and the lithium bromide solution in the generator 2, the waste heat source 11 returns to the waste heat source 11 via the waste hot water return pipeline 18 for recycling. The high-temperature hot water standby pump 13 and the waste hot water supply standby pipeline 16 are installed on the bypass of the high-temperature hot water circulation pump 12 to provide backup for the high-temperature hot water system. The electric three-way valve 14 on the heat source side is installed on the waste hot water return pipe 18. The three-way pipe is connected to the inlet / outlet of the waste hot water return pipe 18 and the waste hot water supply bypass pipe 17 respectively. By adjusting the opening of the electric three-way valve 14 on the heat source side, the system can be kept running stably.

[0075] like Figure 7 As shown, the high-temperature cooling water system 49 includes a waste hot water return bypass pipe 19, a cold source 20, a high-temperature cooling water circulation pump 21, a high-temperature cooling water standby pump 22, a cold source-side electric three-way valve 23, a cooling water supply pipe 24, a cooling water supply standby pipe 25, and a cooling water return pipe 26. The cold source 20 is connected to the inlet of the absorber 5 of the lithium bromide refrigeration unit 1 via the cooling water supply pipe 24 and the high-temperature cooling water circulation pump 21. After heat exchange with the lithium bromide solution in the absorber 5, the cold source 20 enters the first condenser 3. After heat exchange with the lithium bromide solution in the first condenser 3, the cold source 20 returns to the cold source 20 via the cooling water return pipe 26 for recycling. The high-temperature cooling water standby pump 22 and the cooling water supply standby pipe 25 are installed on the bypass of the high-temperature cooling water circulation pump 21 to provide backup for the high-temperature cooling water system. The cold source side electric three-way valve 23 is installed on the cooling water supply pipeline 24. The three-way pipeline is connected to the inlet / outlet of the cooling water supply pipeline 24 and the waste hot water return bypass pipeline 19 respectively. By adjusting the opening of the cold source side electric three-way valve 23, the system can be kept running stably.

[0076] like Figure 8As shown, the interstage cooling water system 50 includes a lithium bromide chiller unit 1, an electric chiller unit 6, an interstage cooling water circulation pump 27, an interstage cooling water standby pump 28, a chilled water supply pipeline 29 for the lithium bromide chiller unit, a cooling water return pipeline 30 for the electric chiller unit, a standby cooling water return pipeline 31 for the electric chiller unit, a soft water constant pressure water supply device 40, and a soft water supply pipeline 41. The interstage cooling water circulation pump 27 is connected to the cooling water return port of the second condenser 8 of the electric chiller unit 6 through the cooling water return pipeline 30 of the electric chiller unit, and pumps the cooling water that has been heated by heat exchange with the refrigerant in the second condenser 8 to the chilled water return port of the first evaporator 4 of the lithium bromide chiller unit 1, where it is cooled by heat exchange in the first evaporator 4. The chilled water supply port of the first evaporator 4 is connected to the cooling water inlet of the second condenser 8 of the electric chiller unit 6 via the chilled water supply pipeline 29 of the lithium bromide chiller unit. This allows the cooled chilled water from the lithium bromide chiller unit to exchange heat with the refrigerant in the second condenser 8 of the electric chiller unit 6, forming an interstage cooling water circulation. The interstage cooling water standby pump 28 and the electric chiller unit cooling water return standby pipeline 31 are installed in the bypass of the interstage cooling water circulation pump 27 to provide backup for the interstage cooling water circulation system.

[0077] like Figure 9 As shown, the low-temperature chilled water system 51 includes an electric chiller unit 6, a low-temperature chilled water circulation pump 32, a low-temperature chilled water standby pump 33, a chilled water supply pipeline 34 for the electric chiller unit, a chilled water return pipeline 35 for the electric chiller unit, a chilled water return standby pipeline 36 for the electric chiller unit, a terminal cooling process unit 37, a chilled water constant pressure water supply device 38, and a chilled water supply pipeline 39. The low-temperature chilled water circulation pump 32 is connected to the chilled water return port of the second evaporator 10 of the electric chiller unit 6 through the chilled water return pipeline 35 of the electric chiller unit, and pumps the chilled water that has been heated by heat exchange with the material in the terminal cooling process unit 37 to the chilled water return port of the second evaporator 10 of the electric chiller unit 6, where it is cooled by heat exchange within the second evaporator 10. The chilled water supply port of the second evaporator 10 is connected to the chilled water inlet of the terminal cooling process unit 37 via the chilled water supply pipeline 34 of the electric chiller unit, so that the cooled chilled water of the electric chiller unit exchanges heat with the materials in the terminal cooling process unit 37 to form a chilled water circulation. The low-temperature chilled water standby pump 33 and the electric chiller unit chilled water return standby pipeline 36 are installed in the bypass of the low-temperature chilled water circulation pump 32 to provide backup for the low-temperature chilled water circulation system.

[0078] like Figure 1 and Figure 10As shown, the electric refrigeration unit 6 operates within the range of -35℃ to 0℃ and includes basic components such as a compressor 7, a second condenser 8, a first throttling valve 9, and a second evaporator 10. The working process of the electric refrigeration unit 6 operating within the range of -35℃ to 0℃ is as follows: the compressor 7 draws in the low-temperature, low-pressure refrigerant gas from the outlet of the second evaporator 10, compresses it to a high-temperature, high-pressure gas state, and then enters the second condenser 8 for cooling and condensation. The condensed high-temperature, high-pressure refrigerant liquid enters the first throttling valve 9 for throttling and pressure reduction. The throttled low-temperature, low-pressure refrigerant liquid then enters the second evaporator 10 to absorb heat and evaporate into low-temperature, low-pressure refrigerant gas, which is then drawn in by the compressor 7, completing the refrigeration cycle.

[0079] like Figure 2 and Figure 11 As shown, the electric refrigeration unit 6, operating within the temperature range of -50℃ to -35℃, comprises basic components including a first low-pressure stage compressor 52, a first high-pressure stage compressor 53, a third condenser 54, a first economizer 55, a second throttle valve 56, a third throttle valve 57, and a third evaporator 58. The operating process of the electric refrigeration unit 6 within this temperature range is as follows: the first low-pressure stage compressor 52 draws in low-temperature, low-pressure refrigerant gas from the outlet of the third evaporator 58, compresses it to a medium-temperature, medium-pressure state, and then it enters the first high-pressure stage compressor 53 for further compression, compressing it to a high-temperature, high-pressure state before entering the first high-pressure stage compressor 53. The refrigerant liquid enters the third condenser 54 for cooling and condensation. The condensed high-temperature and high-pressure refrigerant liquid enters the first economizer 55 for cooling and subcooling. Part of the subcooled medium-temperature and high-pressure refrigerant liquid passes through the second throttling valve 56 for pressure reduction and then enters the first economizer 55 to absorb heat and evaporate the subcooled high-temperature and high-pressure refrigerant liquid. The evaporated medium-temperature and medium-pressure refrigerant gas is drawn into the first high-pressure stage compressor 53. The other part passes through the third throttling valve 57 for pressure reduction and then enters the third evaporator 58 to absorb heat and evaporate into low-temperature and low-pressure refrigerant gas, which is then drawn into the first low-pressure stage compressor 52, completing the refrigeration cycle.

[0080] like Figure 3 and Figure 12As shown, the electric refrigeration unit 6, operating within the temperature range of -60℃ to -40℃, includes a second low-pressure stage compressor 59, a second high-pressure stage compressor 60, a fourth condenser 61, a first subcooler 62, a second economizer 63, a fourth throttle valve 64, a fifth throttle valve 65, a sixth throttle valve 66, and a fourth evaporator 67. The operating process of the electric refrigeration unit 6 within this range is as follows: the second low-pressure stage compressor 59 draws in the low-temperature, low-pressure refrigerant gas from the outlet of the fourth evaporator 67, compresses it to a medium-temperature, medium-pressure state, and then enters the second high-pressure stage compressor 60 for further compression. After being compressed to a high-temperature, high-pressure state, the gas enters the fourth condenser 61 for cooling and condensation. Part of the condensed high-temperature, high-pressure refrigerant liquid enters the first subcooler 62 for cooling and subcooling, while the other part passes through the fourth throttle valve 64. After being depressurized, the refrigerant liquid enters the first subcooler 62 to absorb heat and evaporate, becoming subcooled high-temperature, high-pressure refrigerant liquid. The evaporated medium-temperature, medium-pressure refrigerant gas is then drawn into the second high-pressure stage compressor 60. Part of the subcooled medium-temperature, high-pressure refrigerant liquid from the first subcooler 62 enters the second economizer 63 for further subcooling, while the other part passes through the fifth throttling valve 65 and is depressurized before entering the second economizer 63 to absorb heat and evaporate, becoming subcooled medium-temperature, high-pressure refrigerant liquid. The evaporated low-temperature, low-pressure refrigerant gas is then drawn into the second low-pressure stage compressor 59. After being subcooled by the second economizer 63, the low-temperature, high-pressure refrigerant liquid passes through the sixth throttling valve 66 and is depressurized. The throttled low-temperature, low-pressure refrigerant liquid then enters the fourth evaporator 67 to absorb heat and evaporate into low-temperature, low-pressure refrigerant gas, which is then drawn into the second low-pressure stage compressor 59, completing the refrigeration cycle.

[0081] like Figure 4 and Figure 13As shown, the electric refrigeration unit 6, operating within the temperature range of -100℃ to -60℃, includes a low-temperature stage compressor 68, a high-temperature stage compressor 69, a fifth condenser 70, a third economizer 71, a condenser-evaporator 72, a second subcooler 73, a regenerator 74, a seventh throttle valve 75, an eighth throttle valve 76, a ninth throttle valve 77, a tenth throttle valve 78, and a fifth evaporator 79. The operating process of the electric refrigeration unit 6 within the temperature range of -100℃ to -60℃ is as follows: the low-temperature stage compressor 68 draws in the low-temperature, low-pressure air from the outlet of the regenerator 74. The refrigerant gas, compressed to a high-temperature, high-pressure gaseous state, enters the low-temperature side of the condenser-evaporator 72 for cooling and condensation. The condensed high-temperature, high-pressure refrigerant liquid then enters the regenerator 74 for subcooling. Part of the subcooled medium-temperature, high-pressure refrigerant liquid is further cooled by the second subcooler 73, while the other part is throttled and depressurized by the ninth throttle valve 77 before entering the second subcooler 73 to absorb heat and evaporate, thus subcooling the medium-temperature, high-pressure refrigerant liquid. The evaporated low-temperature, low-pressure refrigerant gas is then drawn into the low-temperature compressor 68 and further cooled by the second subcooler 73. The refrigerant liquid is throttled and depressurized through the tenth throttle valve 78. The throttled, low-temperature, low-pressure refrigerant liquid then enters the fifth evaporator 79, where it absorbs heat and evaporates into a low-temperature, low-pressure refrigerant gas. After being superheated by the regenerator 74, it is drawn into the low-temperature stage compressor 68, completing the low-temperature stage refrigeration cycle. The high-temperature stage compressor 69 draws in the low-temperature, low-pressure refrigerant gas evaporated on the high-temperature side of the condenser evaporator 72, compresses it to a high-temperature, high-pressure gaseous state, and then enters the fifth condenser 70 for cooling and condensation. A portion of the condensed, high-temperature, high-pressure refrigerant liquid then enters the third economizer 71. After being cooled to a low temperature, another portion of the refrigerant liquid is throttled and depressurized by the seventh throttle valve 75 and then enters the third economizer 71 to absorb heat and evaporate the subcooled high-temperature and high-pressure refrigerant liquid. The evaporated medium-temperature and medium-pressure refrigerant gas is then drawn into the high-temperature stage compressor 69. After being cooled and depressurized by the third economizer 71, the medium-temperature and high-pressure refrigerant liquid is throttled and depressurized by the eighth throttle valve 76. The throttled low-temperature and low-pressure refrigerant liquid enters the high-temperature side of the condenser-evaporator 72 to absorb heat and evaporate into low-temperature and low-pressure refrigerant gas, which is then drawn into the high-temperature stage compressor 69, completing the high-temperature stage refrigeration cycle.

[0082] The chilled water constant pressure water supply device 38 is connected to the chilled water return water pipeline 35 of the electric chiller unit where the inlet of the low temperature chilled water circulation pump 32 is located through the chilled water supply pipeline 39, to ensure the stable operation of the low temperature chilled water circulation system.

[0083] The soft water constant pressure water supply device 40 is connected to the cooling water return water pipeline 30 of the electric chiller unit where the inlet of the interstage cooling water circulation pump 27 is located through the soft water supply pipeline 41, to ensure the stable operation of the interstage cooling water circulation system.

[0084] The cooling water flushing device 42 is connected to the cooling water supply pipe 24 through the flushing device inlet pipe 43 and to the cooling water return pipe 26 through the flushing device return pipe 44, ensuring the stable operation of the high-temperature cooling water circulation system.

[0085] Waste heat cleaning device 45 is connected to waste hot water supply pipe 15 through cleaning device inlet pipe 46 and to waste hot water return pipe 18 through cleaning device return pipe 47, ensuring stable operation of high temperature hot water system 48.

[0086] The specific working principle of this invention is as follows: Utilizing the absorption refrigeration principle, water is used as the refrigerant, and lithium bromide solution as the absorbent. A refrigeration cycle is driven by thermal energy. The lithium bromide solution is heated in the generator, causing the refrigerant water to evaporate. This evaporated water is then sent to the condenser to condense into a liquid. The pressure is reduced to the evaporation pressure by a throttling valve, and the refrigerant water vapor is evaporated and cooled in the evaporator. The evaporated refrigerant water vapor is absorbed by the remaining solution after the generation process in the generator, restoring the solution to its original concentration. The solution is then pumped back to the generator for reuse. The lithium bromide refrigeration unit using the absorption refrigeration principle serves as an interstage cooling device, and the chilled water produced through heat exchange with its evaporator is used as the cooling water for the electric refrigeration unit. Electric refrigeration units use refrigerants such as Freon, ammonia, and propylene. They utilize electricity to drive a compressor that draws in low-temperature, low-pressure refrigerant gas, compresses it into high-temperature, high-pressure gas, and sends it to a condenser to condense into a liquid. The liquid is then depressurized by a throttling valve to the evaporation pressure, where it evaporates and cools the air. The evaporated refrigerant gas is then drawn back into the compressor, completing a compression refrigeration cycle. By adjusting the internal structure and equipment configuration of the electric refrigeration unit, it can provide cooling capacity in multiple temperature ranges at optimal COP, including -100℃ to -60℃, -60℃ to -40℃, -50℃ to -35℃, -35℃ to -0℃, and -15℃ to 0℃. By using a lithium bromide refrigeration unit to provide even lower-temperature cooling water to the electric refrigeration unit, the condensing temperature of the electric refrigeration unit can be reduced, thereby reducing motor shaft power and improving the unit's COP. The coupling system of the lithium bromide refrigeration unit and the electric refrigeration unit utilizes high-temperature thermal energy to convert into medium-temperature cold energy, and uses the medium-temperature cold energy to produce cascaded low-temperature cold energy, realizing cascaded energy utilization and providing cascaded temperature range cooling supply in a wide temperature range of -100℃ to 0℃.

[0087] Preferably, the high-temperature hot water system 48 between the waste heat source 11 and the lithium bromide chiller unit 1 can employ either indirect heat exchange, i.e., primary heat exchange with waste heat sources such as high-temperature flue gas, low-pressure steam, and industrial waste hot water via an isolation heat exchanger, followed by secondary heat exchange with the generator of the lithium bromide chiller unit; or direct heat exchange, i.e., direct heat exchange between the waste heat sources such as high-temperature flue gas, low-pressure steam, and industrial waste hot water and the generator of the lithium bromide chiller unit. When the high-temperature hot water system 48 employs indirect heat exchange, an electric three-way regulating valve 14 on the heat source side can be installed on the waste hot water return pipe 18 to maintain stable system operation. The control strategy is as follows: the outlet temperature of the electric three-way regulating valve 14 on the heat source side is set as the target temperature, the accuracy range of the target temperature is adjusted, and the temperature parameter of the waste hot water return water at the inlet of the electric three-way regulating valve 14 on the heat source side is sent as a control signal to the actuator of the electric three-way regulating valve 14 on the heat source side. When the temperature of the waste hot water return water at the inlet of the electric three-way regulating valve 14 on the heat source side is lower than the target temperature at the outlet, the flow rate of the high-temperature waste hot water in the waste hot water supply bypass pipeline 17 is controlled by adjusting the opening of the bypass valve of the electric three-way regulating valve 14 on the heat source side. This ensures that the temperature of the two water sources mixed at the inlet of the electric three-way regulating valve 14 on the heat source side reaches the target temperature, and the supply side valve is opened. If the target temperature is not reached, the valve is closed, and internal circulation continues, thereby maintaining the stability of the system operation.

[0088] As a preferred option, the high-temperature cooling water system 49 between the cold source 20 and the lithium bromide refrigeration unit 1 can use either seawater as cooling water or a cooling tower to provide cooling water for stable operation. When the high-temperature cooling water system 49 uses seawater as cooling water, an electric three-way regulating valve 23 on the cold source side can be installed on the cooling water supply pipeline 24 for overcooling protection to prevent extreme low temperatures from affecting equipment performance and to maintain stable system operation. The control strategy is as follows: the outlet temperature of the electric three-way regulating valve 23 on the cold source side is set as the target temperature, the accuracy range of the target temperature is adjusted, and the cooling water supply temperature parameter at the inlet of the electric three-way regulating valve 23 on the cold source side is sent as a control signal to the actuator of the electric three-way regulating valve 23 on the cold source side. When the cooling water supply temperature at the inlet of the electric three-way regulating valve 23 on the cold source side is lower than the target temperature at the outlet, the flow rate of the high-temperature waste hot water in the waste hot water return bypass pipeline 19 is controlled by adjusting the opening of the bypass valve of the electric three-way regulating valve 23 on the cold source side. This ensures that the temperature of the two water sources mixed at the inlet of the electric three-way regulating valve 23 on the cold source side reaches the target temperature, and the supply side valve is opened. If the target temperature is not reached, the valve is closed, and internal circulation continues. This provides overcooling protection to prevent extreme low temperatures from affecting equipment performance and to maintain stable system operation.

[0089] As a preferred option, the high-temperature cooling water system 49 between the cold source and the lithium bromide chiller can use either seawater as cooling water or a cooling tower to provide cooling water for stable operation. When a cooling tower is used to provide cooling water, the system between the cooling tower and the absorber of the lithium bromide chiller is a closed system, and a chemical dosing and water replenishment device needs to be added to ensure stable operation of the system.

[0090] Preferably, the low-temperature cooling water system 51 between the electric chiller unit 6 and the terminal cooling process unit 37 can adopt either indirect heat exchange, that is, using a refrigerant to transport the cooling capacity produced by the electric chiller unit 6 to the terminal process unit 37 through the low-temperature chilled water circulation pump 32, or direct heat exchange, that is, placing the evaporator of the electric chiller unit 6 on the side of the terminal process unit 37, and directly transporting the high-temperature and high-pressure refrigerant liquid in the electric chiller unit 6 to the evaporator on the side of the terminal process unit 37 to absorb heat and evaporate for cooling, so as to reach the operating temperature required by the terminal process.

[0091] As a preferred option, the chilled water constant pressure water supply device 38 can select a suitable constant pressure water supply method, such as a constant pressure water supply device, expansion tank, expansion vessel, or expansion bladder, according to the requirements of chilled water circulation volume, circulation water pressure, system installation, and operation.

[0092] As a preferred option, the soft water constant pressure water supply device 40 can select a suitable constant pressure water supply method such as a constant pressure water supply device, expansion tank, expansion vessel, or expansion bladder according to the requirements of soft water circulation volume, circulation water pressure, system installation, and operation.

[0093] As a preferred option, electric refrigeration units can be selected from centrifugal refrigeration compressor units or screw refrigeration compressor units, depending on the type of compressor. The two types of compressors have different advantages at different pressure ratios. Centrifugal refrigeration compressor units are suitable for producing cooling capacity in the temperature range of 0 to -15℃, while screw refrigeration compressor units are suitable for producing cooling capacity in the temperature range of -15 to -100℃, depending on the internal equipment configuration of the unit.

[0094] Preferably, the supply water temperature range of the high-temperature waste heat source is 70~120℃, and the return water temperature range is 50~100℃.

[0095] Preferably, the cooling water supply temperature range of the high-temperature cold source is 25~32℃, and the return water temperature range is 33~40℃.

[0096] Preferably, the interstage cooling water supply temperature range is 5~12℃, and the return water temperature range is 10~17℃.

[0097] Preferably, the supply water temperature range for low-temperature chilled water is 0 to -100℃, and the return water temperature range is 5 to -95℃.

[0098] This invention is particularly applicable to industries with high waste heat emissions such as refining, steel, and chemicals, as well as scenarios requiring precise cooling in multiple temperature zones from 0°C to -100°C, such as biopharmaceuticals and food freezing, providing a groundbreaking technical solution for industrial energy conservation and special refrigeration.

[0099] Example

[0100] A cascaded utilization refrigeration system for cold and heat energy is applied to produce -15℃ low-temperature chilled water for use in the ABS / PS end-of-line cooling process of a petrochemical industry. The waste heat source is industrial waste hot water at 95℃, and the cold source is seawater cooling water at 25℃. The chilled water produced by the lithium bromide chiller unit is at 6℃, and this 6℃ chilled water is used as cooling water for a screw-type electric chiller unit. This screw-type electric chiller unit uses propylene as refrigerant. To produce a cooling capacity of -15℃ and 4726kW, it consumes 777kW of shaft power, with a coefficient of performance (COP) of 6.08. In comparison, under the same operating conditions and refrigerant, operating the screw-type electric chiller unit alone to produce the same cooling capacity requires 1540kW of shaft power, with a COP of 3.07. The COP is doubled, demonstrating significant energy savings. The specific implementation process is as follows:

[0101] Waste heat source 11 at 95℃ is connected to the inlet of generator 2 of lithium bromide chiller unit 1 via waste hot water supply pipeline 15 and high-temperature hot water circulation pump 12. After heat exchange between waste heat source 11 and lithium bromide solution in generator 2, the temperature drops to 75℃ and returns to waste heat source 11 via waste hot water return pipeline 18 for recycling. High-temperature hot water standby pump 13 and waste hot water supply standby pipeline 16 are installed in the bypass of high-temperature hot water circulation pump 12 to provide backup for high-temperature hot water system 48. Electric three-way valve 14 on the heat source side is installed on waste hot water return pipeline 18. The three-way pipeline is connected to the inlet / outlet of waste hot water return pipeline 18 and waste hot water supply bypass pipeline 17, respectively. By adjusting the opening of electric three-way valve 14 on the heat source side, the stable operation of the system is ensured.

[0102] A 25°C seawater cold source 20 is connected to the inlet of the absorber 5 of the lithium bromide refrigeration unit 1 via a cooling water supply pipeline 24 and a high-temperature cooling water circulation pump 21. After heat exchange between the cold source 20 and the lithium bromide solution in the absorber 5, it enters the first condenser 3. After heat exchange between the cold source 20 and the lithium bromide solution in the first condenser 3, the temperature rises to 33°C. The cold source then returns to the cold source 20 via the cooling water return pipeline 26 for recycling. A high-temperature cooling water standby pump 22 and a cooling water supply standby pipeline 25 are installed on the bypass of the high-temperature cooling water circulation pump 21 to provide backup for the high-temperature cooling water system 49. An electric three-way valve 23 on the cold source side is installed on the cooling water supply pipeline 24. The three-way valve is connected to the inlet / outlet of the cooling water supply pipeline 24 and the waste hot water return bypass pipeline 19. By adjusting the opening of the electric three-way valve 23 on the cold source side, the stable operation of the system is ensured.

[0103] Interstage cooling water circulation pump 27 is connected to the cooling water return port of the second condenser 8 of the electric chiller unit 6 via the electric chiller unit cooling water return pipe 30. It pumps cooling water, heated to 11°C after heat exchange with the refrigerant in the second condenser 8, to the chilled water return port of the first evaporator 4 of the lithium bromide chiller unit 1, where it is cooled to 6°C through heat exchange. The chilled water supply port of the first evaporator 4 is connected to the cooling water inlet of the second condenser 8 of the electric chiller unit 6 via the lithium bromide chiller unit chilled water supply pipe 29. This allows the cooled 6°C chilled water from the lithium bromide chiller unit to exchange heat with the refrigerant in the second condenser 8 of the electric chiller unit 6, raising its temperature to 11°C and forming an interstage cooling water circulation. An interstage cooling water standby pump 28 and an electric chiller unit cooling water return standby pipe 31 are installed in the bypass of the interstage cooling water circulation pump 27 to provide backup for the interstage cooling water system 50.

[0104] The low-temperature chilled water circulation pump 32 is connected to the chilled water return port of the second evaporator 10 of the electric chiller unit 6 via the chilled water return pipe 35 of the electric chiller unit. It pumps chilled water, heated to -10°C by heat exchange with the material in the end-use cooling process unit 37, to the chilled water return port of the second evaporator 10 of the electric chiller unit 6, where it is cooled to -15°C through heat exchange. The chilled water supply port of the second evaporator 10 is connected to the chilled water inlet of the end-use cooling process unit 37 via the chilled water supply pipe 34 of the electric chiller unit, allowing the cooled -15°C chilled water from the electric chiller unit to exchange heat with the material in the end-use cooling process unit 37, raising its temperature to -10°C and forming a chilled water circulation system. The low-temperature chilled water standby pump 33 and the electric chiller unit chilled water return standby pipe 36 are installed in the bypass of the low-temperature chilled water circulation pump 32, providing backup for the low-temperature chilled water system 51.

[0105] The chilled water constant pressure water supply device 38 is connected to the chilled water return water pipeline 35 of the electric chiller unit where the inlet of the low temperature chilled water circulation pump 32 is located through the chilled water supply pipeline 39, to ensure the stable operation of the low temperature chilled water circulation system 51.

[0106] The soft water constant pressure water supply device 40 is connected to the cooling water return water pipeline 30 of the electric chiller unit where the inlet of the interstage cooling water circulation pump 27 is located through the soft water supply pipeline 41, to ensure the stable operation of the interstage cooling water system 50.

[0107] The cooling water flushing device 42 is connected to the cooling water supply pipe 24 through the flushing device inlet pipe 43 and to the cooling water return pipe 26 through the flushing device return pipe 44, ensuring the stable operation of the high-temperature cooling water system 49.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cold and heat energy cascade utilization refrigeration system, characterized in that, The system comprises: a lithium bromide refrigeration unit, an electric refrigeration unit, a high-temperature cooling water system, and a high-temperature hot water system; the high-temperature hot water system comprises a waste heat source, the waste heat source is connected with the generator inlet of the lithium bromide refrigeration unit through a waste heat water supply pipeline, a high-temperature hot water circulating pump is arranged on the waste heat water supply pipeline, and the generator outlet of the lithium bromide refrigeration unit is connected with the waste heat source through a waste heat water return pipeline; the high-temperature cooling water system comprises a cold source, the cold source is connected with the absorber inlet of the lithium bromide refrigeration unit through a cooling water supply pipeline, a high-temperature cooling water circulating pump is arranged on the cooling water supply pipeline, the absorber outlet of the lithium bromide refrigeration unit is connected with the first condenser inlet of the lithium bromide refrigeration unit, the first condenser outlet of the lithium bromide refrigeration unit is connected with the cold source through a cooling water return pipeline; the chilled water return port of the first evaporator of the lithium bromide refrigeration unit is connected with the chilled water return port of the condenser of the electric refrigeration unit through an electric refrigeration unit chilled water return pipeline, an inter-stage cooling water circulating pump is arranged on the electric refrigeration unit chilled water return pipeline, and the chilled water supply port of the first evaporator of the lithium bromide refrigeration unit is connected with the chilled water inlet port of the condenser of the electric refrigeration unit through a lithium bromide refrigeration unit chilled water supply pipeline; the lithium bromide refrigeration unit comprises a generator, a first condenser, a first evaporator and an absorber connected in sequence; when the cold energy in the temperature range of -35℃ to 0℃ is generated, the electric refrigeration unit comprises a compressor, a second condenser, a first throttling valve and a second evaporator; when the cold energy in the temperature range of -50℃ to -35℃ is generated, the electric refrigeration unit comprises a first low-pressure stage compressor, a first high-pressure stage compressor, a third condenser, a first economizer, a second throttling valve, a third throttling valve and a third evaporator; when the cold energy in the temperature range of -60℃ to -40℃ is generated, the electric refrigeration unit comprises a second low-pressure stage compressor, a second high-pressure stage compressor, a fourth condenser, a first supercooler, a second economizer, a fourth throttling valve, a fifth throttling valve, a sixth throttling valve and a fourth evaporator; when the cold energy in the temperature range of -100℃ to -60℃ is generated, the electric refrigeration unit comprises a low-temperature stage compressor, a high-temperature stage compressor, a fifth condenser, a third economizer, a condensation evaporator, a second supercooler, a regenerator, a seventh throttling valve, an eighth throttling valve, a ninth throttling valve, a tenth throttling valve and a fifth evaporator; the chilled water return port of the evaporator of the electric refrigeration unit is connected with the chilled water return port of the end-use cold process device through an electric refrigeration unit chilled water return pipeline, a low-temperature stage chilled water circulating pump is arranged on the electric refrigeration unit chilled water return pipeline, and the chilled water supply port of the evaporator of the electric refrigeration unit is connected with the chilled water inlet port of the end-use cold process device through an electric refrigeration unit chilled water supply pipeline.

2. The cold and heat energy cascade utilization refrigeration system according to claim 1, wherein: When the cold quantity in the temperature range of -35℃ to 0℃ is produced, the outlet of the second evaporator is connected with the inlet of the compressor, the outlet of the compressor is connected with the inlet of the second condenser, the outlet of the second condenser is connected with the inlet of the first throttling valve, the outlet of the first throttling valve is connected with the inlet of the second evaporator, and the outlet of the second evaporator is connected with the inlet of the compressor; When the cold quantity in the temperature range of -50℃ to -35℃ is produced, the outlet of the third evaporator is connected with the inlet of the first low-pressure stage compressor, the outlet of the first low-pressure stage compressor is connected with the inlet of the first high-pressure stage compressor, the outlet of the first high-pressure stage compressor is connected with the inlet of the third condenser, the outlet of the third condenser is connected with the inlet of the first economizer, the first outlet of the first economizer is connected with the inlet of the second throttling valve, the throttled refrigerant enters the evaporation side of the first economizer to be evaporated and absorb heat, and the evaporated medium-temperature medium-pressure refrigerant gas is connected with the inlet of the first high-pressure stage compressor; the second outlet of the first economizer is connected with the inlet of the third throttling valve, the throttled refrigerant enters the inlet of the third evaporator, and the evaporated low-temperature low-pressure refrigerant gas is connected with the inlet of the first low-pressure stage compressor; When the cold quantity in the temperature range of -60℃ to -40℃ is produced, the outlet of the fourth evaporator is connected with the inlet of the second low-pressure stage compressor, the outlet of the second low-pressure stage compressor is connected with the inlet of the second high-pressure stage compressor, the outlet of the second high-pressure stage compressor is connected with the inlet of the fourth condenser, the first outlet of the fourth condenser is connected with the inlet of the supercooling side of the first supercooler, the second outlet of the fourth condenser is connected with the inlet of the fourth throttling valve, the throttled refrigerant enters the evaporation side of the first supercooler to be evaporated and absorb heat, and the evaporated medium-temperature medium-pressure refrigerant gas is connected with the inlet of the second high-pressure stage compressor; the first outlet of the supercooling side of the first supercooler is connected with the inlet of the supercooling side of the second economizer, the second outlet of the supercooling side of the first supercooler is connected with the inlet of the fifth throttling valve, the throttled refrigerant enters the evaporation side of the second economizer to be evaporated and absorb heat, and the evaporated low-temperature low-pressure refrigerant gas is connected with the inlet of the second low-pressure stage compressor; the outlet of the supercooling side of the second economizer is connected with the inlet of the sixth throttling valve, the throttled refrigerant enters the inlet of the fourth evaporator; When the cold quantity in the temperature range of -100℃ to -60℃ is produced, the low-temperature stage circulation connection relationship of the electric refrigerating unit is as follows: The gas side outlet of the regenerator is connected with the inlet of the low-temperature stage compressor, the outlet of the low-temperature stage compressor is connected with the low-temperature side inlet of the condensation evaporator, the low-temperature side outlet of the condensation evaporator is connected with the liquid side inlet of the regenerator, the first outlet of the liquid side of the regenerator is connected with the inlet of the supercooling side of the second supercooler, the second outlet of the liquid side of the regenerator is connected with the inlet of the ninth throttling valve, the throttled refrigerant enters the evaporation side of the second supercooler to be evaporated and absorb heat, and the evaporated low-temperature low-pressure refrigerant gas is connected with the inlet of the low-temperature stage compressor; the outlet of the supercooling side of the second supercooler is connected with the inlet of the tenth throttling valve, and the throttled refrigerant enters the inlet of the fifth evaporator; The outlet of the fifth evaporator is connected with the gas side inlet of the regenerator. When the cold energy in the temperature range of -100℃ to -60℃ is produced, the high-temperature stage circulation connection relationship of the electric refrigerating unit is as follows: The high-temperature side gas outlet of the condensing evaporator is connected with the inlet of the high-temperature stage compressor, the outlet of the high-temperature stage compressor is connected with the inlet of the fifth condenser, the first outlet of the fifth condenser is connected with the supercooling side inlet of the third economizer, the second outlet of the fifth condenser is connected with the inlet of the seventh throttling valve, the throttled refrigerant enters the evaporation side of the third economizer to be absorbed and evaporated, and the evaporated medium-temperature medium-pressure refrigerant gas is connected with the inlet of the high-temperature stage compressor; the supercooling side outlet of the third economizer is connected with the inlet of the eighth throttling valve, and the throttled refrigerant enters the high-temperature side inlet of the condensing evaporator.

3. The cold and heat energy cascade utilization refrigeration system according to claim 1, characterized in that: a waste heat water supply standby pipeline is installed on the bypass of the high-temperature stage hot water circulating pump, and a high-temperature stage hot water standby pump is installed on the waste heat water supply standby pipeline; a cooling water supply standby pipeline is installed on the bypass of the high-temperature stage cooling water circulating pump, and a high-temperature stage cooling water standby pump is installed on the cooling water supply standby pipeline; an electric refrigerating unit cooling water return standby pipeline is installed on the bypass of the inter-stage cooling water circulating pump, and an inter-stage cooling water standby pump is installed on the electric refrigerating unit cooling water return standby pipeline; an electric refrigerating unit chilled water return standby pipeline is installed on the bypass of the low-temperature stage chilled water circulating pump, and a low-temperature stage chilled water standby pump is installed on the electric refrigerating unit chilled water return standby pipeline.

4. The cold and heat energy cascade utilization refrigeration system according to claim 1, characterized in that: a heat source side electric three-way valve is installed on the waste heat water return pipeline, and the three-way pipeline of the heat source side electric three-way valve is connected with the inlet / outlet of the waste heat water return pipeline and the waste heat water supply bypass pipeline, respectively; a cold source side electric three-way valve is installed on the cooling water supply pipeline, and the three-way pipeline of the cold source side electric three-way valve is connected with the inlet / outlet of the cooling water supply pipeline and the waste heat water return bypass pipeline, respectively; the control strategy of the heat source side electric three-way valve is as follows: the outlet temperature of the heat source side electric three-way regulating valve is set as a target temperature, the target temperature precision range is adjusted, the waste heat water return temperature parameter at the inlet of the heat source side electric three-way regulating valve is taken as a control signal and is sent to the actuator of the heat source side electric three-way regulating valve, when the waste heat water return temperature at the inlet of the heat source side electric three-way regulating valve is lower than the target temperature at the outlet, the water inflow in the waste heat water supply bypass pipeline is controlled by adjusting the bypass valve opening degree of the heat source side electric three-way regulating valve, so that the temperature of the mixed water from the two water sources at the inlet of the heat source side electric three-way regulating valve reaches the target temperature, and the supply side valve is opened, if the target temperature is not reached, the heat source side electric three-way regulating valve is closed, and the internal circulation is continued. The control strategy of the cold source side electric three-way valve is as follows: the outlet temperature of the cold source side electric three-way regulating valve is set as a target temperature, the target temperature precision range is adjusted, the cooling water supply temperature parameter of the cold source side electric three-way regulating valve inlet is taken as a control signal and is sent to the actuator of the cold source side electric three-way regulating valve, when the cooling water supply temperature of the cold source side electric three-way regulating valve inlet is lower than the target temperature of the outlet, the inlet water flow of the high-temperature waste heat water return pipeline in the waste heat water return pipeline is controlled by adjusting the bypass valve opening degree of the cold source side electric three-way regulating valve, so that the temperature of the mixed water of the two water sources of the cold source side electric three-way regulating valve inlet reaches the target temperature, the water supply side valve is opened, and if the target temperature is not reached, the cold source side electric three-way regulating valve is closed, and the internal circulation is continued.

5. The cold heat energy cascade utilization refrigeration system according to claim 1, characterized in that: The system further comprises a chilled water constant pressure water supply device and a soft water constant pressure water supply device. The chilled water constant pressure water supply device is connected with the chilled water return pipeline of the electric refrigerating unit through a chilled water supply pipeline. The soft water constant pressure water supply device is connected with the cooling water return pipeline of the electric refrigerating unit through a soft water supply pipeline.

6. The cold heat energy cascade utilization refrigeration system according to claim 1, characterized in that: The system further comprises a cooling water flushing device and a waste heat cleaning device. The cooling water flushing device is connected with the cooling water supply pipeline through a flushing device water inlet pipeline. The waste heat cleaning device is connected with the waste heat water supply pipeline through a cleaning device water inlet pipeline.

7. The cold and heat energy cascade utilization refrigeration system according to claim 1, wherein: The cooling water of the high-temperature stage cooling water system between the cold source and the lithium bromide refrigerating unit is sea water or cooling tower cooling water; when sea water is used as the cooling water, in order to prevent the performance of the equipment from being affected by extremely low temperature, a cold source side electric three-way regulating valve is installed on the water supply pipeline, the valve opening degree is adjusted, the waste heat return water of the high-temperature stage heat water system is introduced, and the system is ensured to operate stably; when the cooling tower is used to provide the cooling water, the cooling tower and the lithium bromide refrigerating unit absorber are a closed system, and a dosing water supply device is additionally provided.

8. The cold and heat energy cascade utilization refrigeration system according to claim 1, wherein: When the cold energy in the temperature range of 0~-15℃ is generated, the electric refrigerating unit is a centrifugal refrigeration compressor unit; When the cold energy in the temperature range of -15~-100℃ is generated, the electric refrigerating unit is a screw refrigeration compressor unit.

9. The cold and heat energy cascade utilization refrigeration system according to claim 1, wherein: The water supply temperature range of the waste heat source is 70~120℃, and the waste heat source return water temperature range is 50~100℃; The cooling water supply temperature range of the cold source is 25~32℃, and the return water temperature range is 33~40℃; The inter-stage cooling water supply temperature range is 5~12℃, and the inter-stage cooling water return temperature range is 10~17℃; The low-temperature stage chilled water supply temperature range is 0~-100℃, and the low-temperature stage chilled water return temperature range is 5~-95℃.

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