Ultralow-temperature waste heat recycling, upgrading and utilizing system

Abstract

The invention relates to the technical field of energy-saving equipment, and discloses an ultralow-temperature waste heat recovery upgrading utilization system which comprises a cold storage module, a heat regeneration module, a power generation module and a cold recovery module. A heat exchange working medium is stored in a buffer tank, and after the liquid heat exchange working medium flows through a heat return module and is heated and evaporated to be in a gas state, a power generation module is driven to complete expansion work, so that low-temperature waste heat recovery and efficient energy utilization are achieved; the ultra-low-temperature waste heat is condensed into a liquid state in the cold recovery module and flows back into the buffer tank, and through liquid-gas-liquid circulation, ultra-low-temperature waste heat recovery upgrading utilization and recycling are achieved, so that energy loss is reduced, and the energy utilization rate of the whole system is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of energy-saving equipment, and in particular to an ultra-low temperature waste heat recovery and upgrading utilization system. Background Art

[0003] Low-temperature waste heat is generated in large industrial production such as petroleum, chemical industry, metallurgy, and light industry. Low-temperature heat recovery systems are usually set up. Most of them are directly used for low-temperature heat sinks such as heating, heating and desalted water. There is still plenty of heat, and lithium bromide units, low-temperature waste heat power generation and other technologies are used to recover energy. This recovery method is subject to certain limitations: heat sources with a temperature above 160°C are high-grade waste heat, which can produce low-grade steam as a by-product, and are simple to recover and have a wide range of uses; secondly, waste heat with a temperature between 80-160°C is medium- and low-grade waste heat, which can produce low-temperature hot water or be directly heated, or used as a heat source for lithium bromide units and low-temperature waste heat power generation, to produce chilled water or power generation for upgraded use, which is simple to recover and has a wide range of uses; thirdly, waste heat with a temperature below 80°C is ultra-low-temperature waste heat, also known as "garbage heat source". Due to factors such as the temperature of the heat source and system limitations, ultra-low-temperature waste heat is rarely recovered. Summary of the invention

[0004] In view of this, the present invention provides an ultra-low temperature waste heat recovery and upgrading utilization system to solve the problem of difficulty in ultra-low temperature waste heat recovery in the prior art.

[0005] In order to solve the above technical problems, the technical solution of the present invention is as follows:

[0006] The present invention provides an ultra-low temperature waste heat recovery and upgrading utilization system, comprising: a cold storage module, a heat recovery module, a power generation module and a cold recovery module; the cold storage module comprises a cache tank, and the cache tank is filled with liquid heat exchange medium; the outlet of the cache tank is connected to the inlet end of the heat recovery module, and the liquid heat exchange medium enters the heat recovery module, and evaporates to become a gaseous heat exchange medium under the heat exchange action of the heat recovery module; the inlet end of the power generation module is connected to the outlet end of the heat recovery module, and the gaseous heat exchange medium expands and does work in the power generation module to achieve power generation; the inlet end of the cold recovery module is connected to the outlet end of the power generation module, and the outlet end of the cold recovery module is connected to the cache tank, and the gaseous heat exchange medium condenses in the cold recovery module to form the liquid heat exchange medium that flows back to the cache tank.

[0007] It has the following advantages: the heat exchange medium is stored in the cache tank, the liquid heat exchange medium flows through the heat recovery module, and after being heated and evaporated into a gaseous state, it drives the power generation module to complete expansion work, thereby realizing the recovery of low-temperature waste heat and efficient utilization of energy. After the power generation module completes the expansion work, the gaseous heat exchange medium flows through the cold recovery module, condenses into liquid in the cold recovery module and flows back to the cache tank. Through the liquid-gas-liquid cycle, the ultra-low temperature waste heat recovery and upgrading utilization are realized, and circular use is realized, thereby reducing energy loss and improving the energy utilization rate of the overall system.

[0008] According to some embodiments of the present invention, the heat recovery module includes several groups of low-temperature heat source evaporator tube bundles, the power generation module includes several expansion generator sets, the number of the low-temperature heat source evaporator tube bundles and the expansion generator sets are the same, and multiple groups of the low-temperature heat source evaporator tube bundles and multiple expansion generator sets are alternately connected in sequence.

[0009] According to some embodiments of the present invention, the cold storage module includes a driving pump, which is arranged between the cache tank and the heat recovery module, and the driving pump is suitable for driving the liquid heat exchange medium in the cache tank to flow toward the heat recovery module.

[0010] According to some embodiments of the present invention, the cold recovery module includes a first cooler and a cold source supplement device, the inlet end of the first cooler is connected to the outlet end of the power generation module, the outlet end of the first cooler is connected to the cache tank, and the cold source supplement device is connected to the first cooler to be suitable for providing a cold source to the first cooler.

[0011] According to some embodiments of the present invention, the cold recovery module also includes a second cooler, which is provided with a cold side inlet, a cold side outlet, a hot side inlet and a hot side outlet, the outlet of the cache tank is connected to the cold side inlet, the inlet end of the heat recovery module is connected to the cold side outlet, the outlet end of the power generation module is connected to the hot side inlet of the second cooler, and the hot side outlet of the second cooler is connected to the inlet end of the first cooler.

[0012] According to some embodiments of the present invention, a heat exchanger is provided between the cold side outlet and the inlet end of the heat recovery module.

[0013] According to some embodiments of the present invention, the cold storage module further includes a working fluid replenishing device, the cache tank is provided with a replenishing port, and the working fluid replenishing device is connected to the replenishing port so as to be suitable for replenishing heat exchange working fluid to the cache tank.

[0014] According to some embodiments of the present invention, the cold storage module also includes a liquid level regulating device, which is arranged between the cache tank and the working fluid replenishing device, and the liquid level regulating device is suitable for detecting the liquid level height in the cache tank and controlling the connection between the working fluid replenishing device and the cache tank.

[0015] According to some embodiments of the present invention, the outlet pressure range of the driving pump is 4-25 MPa.

[0016] According to some embodiments of the present invention, the inlet temperature of the heat exchange medium at the power generation module is greater than 32° C., and the outlet exhaust pressure of the power generation module is 0.1-4.0 MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 It is a schematic diagram of the operation of the ultra-low temperature waste heat recovery and upgrading utilization system provided in some embodiments of the present invention;

[0019] Figure 2 This is a schematic diagram of the operation of an ultra-low temperature waste heat recovery and upgrading utilization system provided in another embodiment of the present invention.

[0020] Description of reference numerals:

[0021] 1. Cold storage module; 11. Cache tank; 12. Driving pump; 13. Working fluid replenishing device; 14. Liquid level regulating device; 2. Heat recovery module; 21. Low-temperature heat source evaporation tube bundle; 3. Power generation module; 31. Expansion generator set; 4. Cold recovery module; 41. First cooler; 42. Cold source replenishing device; 43. Second cooler. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0023] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0024] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0025] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0026] Reference Figure 1 and Figure 2 As shown, the present invention provides an ultra-low temperature waste heat recovery and upgrading utilization system, comprising: a cold storage module 1, a heat recovery module 2, a power generation module 3 and a cold recovery module 4; the cold storage module 1 includes a cache tank 11, and the cache tank 11 is filled with liquid heat exchange medium; the outlet of the cache tank 11 is connected to the inlet end of the heat recovery module 2, and the liquid heat exchange medium enters the heat recovery module 2, and evaporates to become a gaseous heat exchange medium under the heat exchange action of the heat recovery module 2; the inlet end of the power generation module 3 is connected to the outlet end of the heat recovery module 2, and the gaseous heat exchange medium expands and does work in the power generation module 3 to achieve power generation; the inlet end of the cold recovery module 4 is connected to the outlet end of the power generation module 3, and the outlet end of the cold recovery module 4 is connected to the cache tank 11, and the gaseous heat exchange medium condenses in the cold recovery module 4 to form a liquid heat exchange medium that flows back to the cache tank 11.

[0027] Specifically, the heat exchange medium is stored in the buffer tank 11, and the liquid heat exchange medium flows through the heat recovery module 2. After being heated and evaporated into a gaseous state, the power generation module 3 is driven to complete expansion work, thereby realizing the recovery of low-temperature waste heat and efficient utilization of energy. After the expansion work is completed in the power generation module 3, the gaseous heat exchange medium flows through the cold recovery module 4, condenses into liquid in the cold recovery module 4 and flows back to the buffer tank 11. Through the liquid-gas-liquid cycle, the ultra-low temperature waste heat recovery and upgrading utilization are realized, and circular use is realized, thereby reducing energy loss and improving the energy utilization rate of the overall system.

[0028] It is understandable that the present invention adopts a modular design, including a cold storage module 1, a heat recovery module 2, a power generation module 3 and a cold recovery module 4. Each module has a clear division of labor, a compact structure, and is easy to maintain and optimize. By heating, evaporating and refluxing the liquid heat exchange medium of the low-temperature heat source, the system can adapt to different types of low-temperature waste heat sources and has a wide range of applicability. The system adopts a circulating medium design, which effectively reduces energy waste and heat emissions to the environment, is conducive to energy conservation and emission reduction, and meets the requirements of green development.

[0029] It should be noted that the heat exchange medium is carbon dioxide, and the operating pressure of the buffer tank 11 is determined by factors such as the back pressure of the final expansion generator set 31, the cold source cold load, and the ultra-low temperature heat source load, and is determined by optimizing the total thermal efficiency of the system.

[0030] Ultra-low temperature waste heat sources refer to but are not limited to low temperature waste heat from the fields of petroleum, chemical industry, metallurgy, light industry, etc. Through system coupling, the air cooler or circulating water cooler of the existing device is replaced, and carbon dioxide is used as the medium to recover the ultra-low temperature waste heat or the surplus cooling capacity of the device for recycling and upgrading, providing high-quality electricity.

[0031] In some embodiments of the present invention, the heat recovery module 2 includes several groups of low-temperature heat source evaporator tube bundles 21, and the power generation module 3 includes several expansion generator sets 31. The number of low-temperature heat source evaporator tube bundles 21 and the number of expansion generator sets 31 are the same, and multiple groups of low-temperature heat source evaporator tube bundles 21 and multiple expansion generator sets 31 are alternately connected in sequence.

[0032] Specifically, the heat recovery module 2 includes several groups of low-temperature heat source evaporator tube bundles 21, and the power generation module 3 includes several expansion generator sets 31. The inlet of the first low-temperature heat source evaporator tube bundle 21 is connected to the storage tank, the outlet of the first low-temperature heat source evaporator tube bundle 21 is connected to the inlet of the first expansion generator set 31, and the outlet of the first expansion generator set 31 is connected to the inlet of the second low-temperature heat source evaporator tube bundle 21. That is, multiple groups of low-temperature heat source evaporator tube bundles 21 and multiple expansion generator sets 31 are alternately connected in sequence, so as to realize the heat recovery-expansion-heat recovery cycle of the heat exchange working fluid in sequence, until the outlet of the final expansion generator set 31 is connected to the inlet end of the cold recovery module 4, realizing multi-stage adiabatic expansion power generation and improving energy efficiency.

[0033] It can be understood that the number of low-temperature heat source evaporator tube bundles 21 and expansion generator sets 31 is consistent, and the expansion stages of the low-temperature heat source evaporator tube bundles 21 and the expansion generator sets 31 are related to factors such as the ultra-low temperature waste heat source energy, temperature level, and back pressure of the expansion generator sets 31, and can be determined by optimizing the total thermal efficiency of the system to maximize the efficiency.

[0034] In some embodiments of the present invention, the cold storage module 1 includes a driving pump 12, which is arranged between the cache tank 11 and the heat recovery module 2, and the driving pump 12 is suitable for driving the liquid heat exchange medium in the cache tank 11 to flow toward the heat recovery module 2.

[0035] Specifically, a driving pump 12 is arranged between the buffer tank 11 and the heat recovery module 2, so as to drive the liquid heat exchange medium in the buffer tank 11 to flow toward the heat recovery module 2, thereby realizing the pressure increase of the liquid heat exchange medium. It can be understood that the head of the driving pump 12 is determined by the evaporation pressure of the low-temperature heat source evaporator tube bundle 21 and the system resistance drop. The resistance drop refers to the phenomenon of reduced resistance encountered by the fluid during the flow process, which is usually used to describe the flow state of the fluid in a pipe, channel or other flow path. The outlet pressure range of the driving pump 12 is 4-25MPa.

[0036] In some embodiments of the present invention, the cold recovery module 4 includes a first cooler 41 and a cold source supplement device 42, the inlet end of the first cooler 41 is connected to the outlet end of the power generation module 3, the outlet end of the first cooler 41 is connected to the cache tank 11, and the cold source supplement device 42 is connected to the first cooler 41 to be suitable for providing a cold source to the first cooler 41.

[0037] Reference Figure 2 As shown, in some embodiments of the present invention, the cold recovery module 4 also includes a second cooler 43, the second cooler 43 is provided with a cold side inlet, a cold side outlet, a hot side inlet and a hot side outlet, the outlet of the cache tank 11 is connected to the cold side inlet, the inlet end of the heat recovery module 2 is connected to the cold side outlet, the outlet end of the power generation module 3 is connected to the hot side inlet of the second cooler 43, and the hot side outlet of the second cooler 43 is connected to the inlet end of the first cooler 41.

[0038] Specifically, the cold recovery module 4 includes a first cooler 41, a second cooler 43 and a cold source supplement device 42, wherein the second cooler 43 is provided with a cold side inlet, a cold side outlet, a hot side inlet and a hot side outlet, the outlet of the cache tank 11 is connected to the cold side inlet of the second cooler 43, the inlet end of the heat recovery module 2 is connected to the cold side outlet, the heat exchange medium absorbs heat and evaporates initially when passing through the second cooler 43, the outlet end of the power generation module 3 is connected to the hot side inlet of the second cooler 43, the hot side outlet of the second cooler 43 is connected to the inlet end of the first cooler 41, the heat exchange medium flowing out of the power generation module 3 releases heat in the second cooler 43, and through the circulation setting, the expanded heat exchange medium provides heat for the liquid heat exchange medium at the front end, and the heat exchange medium at the rear end reduces the temperature at the same time, thereby reducing the supplementary energy consumption.

[0039] It can be understood that the cold source supplement device 42 can be one or more types, which are determined by the surplus cooling load of the factory.

[0040] In some embodiments of the present invention, a heat exchanger is provided between the cold side outlet and the inlet end of the heat recovery module 2 .

[0041] Specifically, the setting of the heat exchanger can further recover the coldness of the circulating heat exchange medium, reduce the heat load of the supplementary cold source, reduce the project investment, and improve the overall thermal efficiency of the system.

[0042] In some embodiments of the present invention, the cold storage module 1 further includes a working fluid replenishing device 13 , the cache tank 11 is provided with a replenishing port, and the working fluid replenishing device 13 is connected to the replenishing port so as to be suitable for replenishing heat exchange working fluid to the cache tank 11 .

[0043] In some embodiments of the present invention, the cold storage module 1 also includes a liquid level regulating device 14, which is arranged between the cache tank 11 and the working fluid replenishing device 13. The liquid level regulating device 14 is suitable for detecting the liquid level height in the cache tank 11 and controlling the connection between the working fluid replenishing device 13 and the cache tank 11.

[0044] Specifically, the liquid level height of the heat exchange medium in the buffer tank 11 is detected by the liquid level regulating device 14. When the liquid level height is lower than a preset value, the liquid level regulating device 14 controls the communication between the medium replenishing device 13 and the buffer tank 11 to replenish the heat exchange medium in the buffer tank 11. When the replenished heat exchange medium reaches the preset liquid level height, the medium replenishing device 13 is blocked from the buffer tank 11. The liquid level regulating device 14 and the medium replenishing device 13 improve the reliability of the system and ensure the normal operation of the system.

[0045] In some embodiments of the present invention, the outlet pressure of the driving pump 12 is in the range of 4-25 MPa.

[0046] In some embodiments of the present invention, the inlet temperature of the heat exchange medium at the power generation module 3 is greater than 32° C., and the outlet exhaust pressure of the power generation module 3 is 0.1-4.0 MPa.

[0047] In some embodiments of the present invention, ultra-low temperature waste heat energy is recovered through a carbon dioxide evaporation system device, and ethylene cooling is coupled to fully utilize the efficiency advantage of the carbon dioxide cycle, and expansion work is used to provide high-quality electricity. Specifically, the 4.0MPaG, 5.3°C liquid CO2 in the cache tank 11 enters the drive pump 12 and is raised to 7.4MPaG, then heated to 70°C by the heat recovery module 2, and enters the expansion generator set 31 to generate electricity, with a back pressure of 4.0MPaG. The CO2 exhaust gas enters the cold recovery module 4 and is cooled to 5.3°C, and finally enters the cache tank 11 to complete the cycle. In this embodiment, the design parameters of the system modules include:

[0048] The outlet pressure of the driving pump 12: 7.4 MPaG;

[0049] CO2 outlet temperature of heat recovery module 2: 70°C;

[0050] Inlet parameters of expansion generator set 31: pressure: 7.3MPaG, temperature: 70°C;

[0051] Expansion generator set 31 outlet parameters: pressure: 4.0MPaG, temperature: 20.3℃;

[0052] Outlet parameters of the first cooler 41: pressure: 4.0 MPaG, temperature: 5.3°C;

[0053] Cold source outlet parameters of the first cooler 41: pressure: 3.5 MPaG, temperature: 10°C;

[0054] The cold source inlet parameters of the first cooler 41 are: pressure: 3.5 MPaG, temperature: -32°C.

[0055] The effect of this implementation case:

[0056] It absorbs 5089kw of ultra-low temperature heat source load, saves 6.8t / h of ethylene heating steam, the system power generation capacity is about 510kw, the system net power generation is about 463KW, the system net power generation efficiency is 9.1%, and the system total thermal efficiency is about 98%.

[0057] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A system for recovering and upgrading ultra-low temperature waste heat, characterized in that: include: The cold storage module (1) comprises a buffer tank (11), wherein the buffer tank (11) contains a liquid heat exchange medium; A heat recovery module (2), wherein the outlet of the buffer tank (11) is connected to the inlet of the heat recovery module (2), and the liquid heat exchange medium enters the heat recovery module (2) and evaporates to become a gaseous heat exchange medium under the heat exchange action of the heat recovery module (2); A power generation module (3), wherein the inlet end of the power generation module (3) is connected to the outlet end of the heat recovery module (2), and the gaseous heat exchange medium expands in the power generation module (3) to perform work, thereby realizing power generation; A cold recovery module (4), wherein the inlet end of the cold recovery module (4) is connected to the outlet end of the power generation module (3), and the outlet end of the cold recovery module (4) is connected to the cache tank (11); the gaseous heat exchange medium is condensed in the cold recovery module (4) to form the liquid heat exchange medium which flows back into the cache tank (11).

2. The ultra-low temperature waste heat recovery and upgrading system according to claim 1 is characterized in that: The heat recovery module (2) comprises a plurality of groups of low-temperature heat source evaporation tube bundles (21), and the power generation module (3) comprises a plurality of expansion generator sets (31). The number of the low-temperature heat source evaporation tube bundles (21) and the number of the expansion generator sets (31) are the same, and a plurality of groups of the low-temperature heat source evaporation tube bundles (21) and a plurality of the expansion generator sets (31) are alternately connected in sequence.

3. The ultra-low temperature waste heat recovery and upgrading system according to claim 1 is characterized in that: The cold storage module (1) comprises a driving pump (12), wherein the driving pump (12) is arranged between the cache tank (11) and the heat recovery module (2), and the driving pump (12) is suitable for driving the liquid heat exchange medium in the cache tank (11) to flow toward the heat recovery module (2).

4. The ultra-low temperature waste heat recovery and upgrading system according to any one of claims 1 to 3, characterized in that: The cold recovery module (4) includes a first cooler (41) and a cold source supplement device (42), the inlet end of the first cooler (41) is connected to the outlet end of the power generation module (3), the outlet end of the first cooler (41) is connected to the cache tank (11), and the cold source supplement device (42) is connected to the first cooler (41) to provide a cold source to the first cooler (41).

5. The ultra-low temperature waste heat recovery and upgrading system according to claim 4 is characterized in that: The cold recovery module (4) also includes a second cooler (43), the second cooler (43) is provided with a cold side inlet, a cold side outlet, a hot side inlet and a hot side outlet, the outlet of the cache tank (11) is connected to the cold side inlet, the inlet end of the heat recovery module (2) is connected to the cold side outlet, the outlet end of the power generation module (3) is connected to the hot side inlet of the second cooler (43), and the hot side outlet of the second cooler (43) is connected to the inlet end of the first cooler (41).

6. The ultra-low temperature waste heat recovery and upgrading system according to claim 5 is characterized in that: A heat exchanger is provided between the cold side outlet and the inlet end of the heat recovery module (2).

7. The ultra-low temperature waste heat recovery and upgrading system according to any one of claims 1 to 3, characterized in that: The cold storage module (1) further comprises a working medium replenishing device (13), the cache tank (11) is provided with a replenishing port, and the working medium replenishing device (13) is connected to the replenishing port so as to be suitable for replenishing heat exchange working medium to the cache tank (11).

8. The ultra-low temperature waste heat recovery and upgrading system according to claim 7 is characterized in that: The cold storage module (1) further comprises a liquid level regulating device (14), wherein the liquid level regulating device (14) is arranged between the cache tank (11) and the working fluid replenishing device (13), and the liquid level regulating device (14) is suitable for detecting the liquid level height in the cache tank (11) and controlling the connection between the working fluid replenishing device (13) and the cache tank (11).

9. The ultra-low temperature waste heat recovery and upgrading system according to claim 3 is characterized in that: The outlet pressure of the driving pump (12) is in the range of 4-25 MPa.

10. The ultra-low temperature waste heat recovery and upgrading system according to claim 1 is characterized in that: The inlet temperature of the heat exchange medium in the power generation module (3) is greater than 32° C., and the outlet exhaust pressure of the power generation module (3) is 0.1-4.0 MPa.

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