Overlapped compression heat full recovery steam generation system and method

Abstract

The present application relates to the field of energy saving and environmental protection, and provides a mixed compression heat full-recovery steam generation system and method, comprising: a multi-stream heat exchanger, including a high-temperature heat exchange section and a low-temperature heat exchange section; a high-temperature working medium-steam generator, the high-temperature heat exchange section forms a first circulation pipeline through a first compressor and the high-temperature working medium-steam generator; a high-temperature working medium-low-temperature working medium heat exchanger, the high-temperature working medium-steam generator further forms a second circulation pipeline through the high-temperature working medium-low-temperature working medium heat exchanger and the first compressor in sequence, and the high-temperature working medium-low-temperature working medium heat exchanger forms a third circulation pipeline through the low-temperature heat exchange section and a second compressor; a gas-liquid separator, connected to a steam generation cycle liquid input port and a steam output port, and forming a fourth circulation pipeline with the high-temperature working medium-steam generator through a circulating pump. The present application uses mixed compression heat full-recovery technology to generate steam, obtain high-grade heat source, has wide application range, significant energy saving benefit, and is of great significance to reduce the energy consumption and carbon emission of the compression process.

Description

Technical Field

[0001] This invention relates to the field of energy conservation and environmental protection technology, and more specifically, to a cascade compression heat recovery steam generation system and method. Background Technology

[0002] In industrial production, compressors are crucial power equipment, including air compressors, CO2 compressors, and process compressors. To ensure efficient compressor operation, interstage coolers are required to control the compressor's intake air temperature. The common interstage cooling method for compressor equipment uses circulating water as a cold source to cool the high-temperature compressed gas. With the increasing emphasis on energy conservation and emission reduction, the demand for energy-saving compressors is growing, and the utilization of compressor compression heat is receiving increasing attention.

[0003] There are already some applications of waste heat recovery from interstage cooling in existing compressors. The common practice is to recover the waste heat (above 80°C) from the high-temperature section after compression, producing hot water for domestic heating, industrial heating, etc. The waste heat below 80°C is then cooled by circulating water in an interstage cooler, effectively recovering part of the compression heat. While this method is relatively simple, its energy-saving benefits are limited, and the grade of recovered heat is relatively low, thus restricting its application.

[0004] Some current technologies propose full recovery of compression heat, but they can only produce hot water at 70℃-80℃, resulting in relatively low heating quality and limited heating applications. Furthermore, using water as a medium involves multiple intermediate steps: the compressed gas exchanges heat with the water first, then the water exchanges heat with the working fluid, and finally the working fluid exchanges heat with the hot water. Because indirect heat exchange using heat exchangers introduces a temperature difference, requiring at least 5℃-10℃ to increase the heat exchange temperature difference, thus reducing heat exchange efficiency and increasing heat recovery costs.

[0005] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of the present invention, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] In view of this, the present invention provides a cascade compression heat recovery steam generation system and method, which utilizes cascade technology to fully recover compression heat and generate steam, thereby obtaining a high-grade heat source. It has a wider range of applications and more significant energy-saving benefits, and is of great significance for reducing energy consumption and carbon emissions in compression processes.

[0007] According to one aspect of the present invention, a cascaded compression heat recovery steam generation system is provided, comprising: a multi-stream heat exchanger including a high-temperature heat exchange section and a low-temperature heat exchange section, wherein the high-temperature heat exchange section and the low-temperature heat exchange section respectively include a first pipeline and a second pipeline for heat exchange, the first pipeline of the high-temperature heat exchange section being connected to the first pipeline of the low-temperature heat exchange section and supplying process gas; a high-temperature working fluid-steam generator including a first pipeline and a second pipeline for heat exchange, wherein the second pipeline of the high-temperature heat exchange section sequentially passes through a first compressor and the first pipeline of the high-temperature working fluid-steam generator to form a first circulation pipeline, the first circulation pipeline supplying high-temperature working fluid; and a high-temperature working fluid-low-temperature working fluid heat exchanger, comprising... The system includes a first pipeline and a second pipeline for heat exchange. The first pipeline of the high-temperature working fluid-steam generator is further connected to the first pipeline of the high-temperature working fluid-low-temperature working fluid heat exchanger and the first compressor to form a second circulation pipeline, which supplies high-temperature working fluid. The second pipeline of the high-temperature working fluid-low-temperature working fluid heat exchanger is connected to the second pipeline of the low-temperature heat exchange section and the second compressor to form a third circulation pipeline, which supplies low-temperature working fluid. A gas-liquid separator is connected to the second pipeline of the high-temperature working fluid-steam generator via a circulation pump to form a fourth circulation pipeline, which supplies steam-generating circulating liquid. The gas-liquid separator is also connected to a steam-generating circulating liquid inlet and a steam outlet.

[0008] In some embodiments, the cascade compression heat recovery steam generation system further includes: a third compressor connected to the front end of the first pipeline in the high-temperature heat exchange section, the third compressor also being connected to a process gas inlet; wherein the process gas temperature increases after being compressed by the third compressor, decreases after exiting the high-temperature heat exchange section, and continues to decrease after exiting the low-temperature heat exchange section. For example, the temperature of the process gas before entering the third compressor is 35℃~40℃, the temperature of the process gas after being compressed by the third compressor is 100℃~150℃, the temperature of the process gas exiting the high-temperature heat exchange section is 60℃~90℃, and the temperature of the process gas exiting the low-temperature heat exchange section is 35℃~40℃.

[0009] In some embodiments, the cascaded compression heat recovery steam generation system further includes a gas buffer tank connected to the rear end of the first pipeline of the low-temperature heat exchange section, and the gas buffer tank is also connected to the process gas outlet.

[0010] In some embodiments, the cascaded compression heat recovery steam generation system further includes: a first throttling expansion valve connected in a pipe from the first pipeline of the high-temperature working fluid-steam generator to the second pipeline of the high-temperature heat exchange section.

[0011] In some embodiments, the cascaded compression heat recovery steam generation system further includes: a second throttling expansion valve connected in a pipe from the first pipeline of the high-temperature working fluid-steam generator to the first pipeline of the high-temperature working fluid-low-temperature working fluid heat exchanger.

[0012] In some embodiments, the cascaded compression heat recovery steam generation system further includes: a third throttling expansion valve connected in a pipe leading from the second pipe of the high-temperature working fluid-low-temperature working fluid heat exchanger to the second pipe of the low-temperature heat exchange section.

[0013] In some embodiments, the cascaded compression heat recovery steam generation system further includes a level control valve connected between the steam generation circulating liquid inlet and the gas-liquid separator.

[0014] In some embodiments, the cascaded compression heat recovery steam generation system further includes a steam compressor connected between the gas-liquid separator and the steam outlet.

[0015] In some embodiments, the cascaded compression heat recovery steam generation system further includes a temperature control valve connected between the steam generation circulating liquid inlet and the steam compressor.

[0016] In some embodiments, the high-temperature working fluid flowing in the first and second circulation pipelines is trans-1-chloro-3,3,3-trifluoropropylene, and the low-temperature working fluid flowing in the third circulation pipeline is trans-1,3,3,3-tetrafluoropropylene. The temperature of the high-temperature working fluid flowing in the second pipeline of the high-temperature heat exchange section is 50°C to 80°C; the temperature of the low-temperature working fluid flowing in the second pipeline of the low-temperature heat exchange section is 30°C to 35°C.

[0017] According to another aspect of the present invention, a method for generating steam through cascade compression heat recovery is provided, comprising:

[0018] The process gas is output after passing through a high-temperature heat exchange section and a low-temperature heat exchange section.

[0019] The steam-generating circulating liquid is located at the bottom of the gas-liquid separator and is output after passing through the fourth circulation pipeline and the gas-liquid separator.

[0020] The high-temperature working fluid flows in the first and second circulation pipelines, and some sections of the first and second circulation pipelines overlap; the low-temperature working fluid flows in the third circulation pipeline.

[0021] The high-temperature working fluid exchanges heat with the process gas in the high-temperature heat exchange section through the first circulation pipeline; the low-temperature working fluid exchanges heat with the process gas in the low-temperature heat exchange section through the third circulation pipeline.

[0022] The low-temperature working fluid exchanges heat in the high-temperature working fluid-low-temperature working fluid heat exchanger through the third circulation pipeline and the high-temperature working fluid through the second circulation pipeline.

[0023] The high-temperature working fluid exchanges heat in the high-temperature working fluid-steam generator through the first and second circulation pipelines, and the steam-generating circulating liquid exchanges heat through the fourth circulation pipeline.

[0024] The beneficial effects of this invention compared to the prior art include at least the following:

[0025] The cascade steam generation process proposed in this invention, based on the principles of waste heat cascade utilization and reverse Carnot cycle, uses a multi-stream heat exchanger instead of an interstage cooler to divide the compression heat into heat in a high-temperature heat exchange section and a heat in a low-temperature heat exchange section, which are then matched with high-temperature and low-temperature working fluids respectively. The process gas in the high-temperature heat exchange section exchanges heat with the high-temperature working fluid in the first circulation pipeline, while the process gas in the low-temperature heat exchange section exchanges heat with the low-temperature working fluid in the third circulation pipeline. The low-temperature working fluid then overlaps with the high-temperature working fluid in the second circulation pipeline, allowing part of the high-temperature working fluid to directly exchange heat and evaporate, and the other part to overlap and couple with the low-temperature working fluid for evaporation, thus forming a cascade process.

[0026] Compared to the direct heat exchange process, the cascade steam generation process makes fuller use of the heat of compression and can achieve full recovery of the heat of compression. This allows the circulating liquid in the gas-liquid separator to fully absorb the heat of the high-temperature working fluid and produce enough steam. Compared to the cascade process, it achieves tiered recovery of the heat of compression, reduces the input of compression work, and results in lower energy consumption for steam generation.

[0027] This invention can also reduce the circulating cooling water consumption of the interstage cooler by fully recovering the heat of compression.

[0028] Therefore, this invention utilizes the heat of compression in a cascade manner, employs cascade technology to fully recover the heat of compression and generate steam, thus obtaining a high-grade heat source. It has a wider range of applications and more significant energy-saving benefits, and is of great significance for reducing energy consumption and carbon emissions in the compression process.

[0029] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Attached Figure Description

[0030] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0031] Figure 1 and Figure 2This diagram illustrates the structure of a cascaded compression heat recovery steam generation system according to an embodiment of the present invention. Figure 1 The components of the cascade compression heat recovery steam generation system are labeled. Figure 2 This indicates the flow medium in a cascaded compression heat recovery steam generation system. Detailed Implementation

[0032] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to those described herein. Rather, these embodiments are provided to make the invention more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art.

[0033] The accompanying drawings are merely illustrative of the invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore, repeated descriptions of them will be omitted.

[0034] The use of terms such as "first," "second," and similar terms in the specific description does not indicate any order, quantity, or importance, but is merely used to distinguish different components. Furthermore, in the description of this invention, when it is said that a device is "connected" to another device, this includes not only direct connections but also indirect connections via other elements.

[0035] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features in different embodiments can be combined with each other.

[0036] Figure 1 The diagram illustrates the structure of a cascaded compression heat recovery steam generation system according to an embodiment of the present invention, with each component of the cascaded compression heat recovery steam generation system labeled. (Refer to...) Figure 1 As shown, the cascade compression heat recovery steam generation system provided in this embodiment of the invention includes:

[0037] The multi-flow heat exchanger 10 includes a high-temperature heat exchange section 11 and a low-temperature heat exchange section 12. The high-temperature heat exchange section 11 includes a first pipe 111 and a second pipe 112 for heat exchange. The low-temperature heat exchange section 12 includes a first pipe 121 and a second pipe 122 for heat exchange. The first pipe 111 of the high-temperature heat exchange section 11 is connected to the first pipe 121 of the low-temperature heat exchange section 12 and supplies process gas for flow.

[0038] The high-temperature working fluid-steam generator 30 includes a first pipeline 301 and a second pipeline 302 for heat exchange. The second pipeline 112 of the high-temperature heat exchange section 11 passes through the first compressor 20 and the first pipeline 301 of the high-temperature working fluid-steam generator 30 to form a first circulation pipeline P1, which supplies high-temperature working fluid.

[0039] The high-temperature working fluid-low-temperature working fluid heat exchanger 40 includes a first pipe 401 and a second pipe 402 for heat exchange. The first pipe 301 of the high-temperature working fluid-steam generator 30 also forms a second circulation pipe P2 through the first pipe 401 of the high-temperature working fluid-low-temperature working fluid heat exchanger 40 and the first compressor 20. The second circulation pipe P2 is used for the flow of high-temperature working fluid. The second pipe 402 of the high-temperature working fluid-low-temperature working fluid heat exchanger 40 forms a third circulation pipe P3 through the second pipe 122 of the low-temperature heat exchange section 12 and the second compressor 50. The third circulation pipe P3 is used for the flow of low-temperature working fluid.

[0040] The gas-liquid separator 60, through the circulation pump 61, forms a fourth circulation pipeline P4 with the second pipeline 302 of the high-temperature working medium-steam generator 30. The fourth circulation pipeline P4 supplies the steam-generating circulating liquid. The gas-liquid separator 60 is also connected to the steam-generating circulating liquid inlet IN2 and the steam outlet OUT2.

[0041] It should be noted that in this invention, high temperature and low temperature are relative concepts, not used to define specific temperature ranges. The multi-stream heat exchanger 10 includes a high-temperature heat exchange section 11 and a low-temperature heat exchange section 12. The process gas flows sequentially through the high-temperature heat exchange section 11 and the low-temperature heat exchange section 12, with its temperature in the high-temperature heat exchange section 11 being higher than its temperature in the low-temperature heat exchange section 12. The high-temperature working fluid is used for heat exchange with the process gas in the high-temperature heat exchange section 11, and the low-temperature working fluid is used for heat exchange with the process gas in the low-temperature heat exchange section 12.

[0042] The cascade steam generation process proposed in this invention, based on the principles of waste heat cascade utilization and reverse Carnot cycle, uses a multi-stream heat exchanger 10 to replace the interstage cooler, dividing the heat of compression into heat in a high-temperature heat exchange section 11 and a low-temperature heat exchange section 12, which are then matched with high-temperature and low-temperature working fluids respectively. The process gas in the high-temperature heat exchange section 11 exchanges heat with the high-temperature working fluid in the first circulation pipeline P1, and the process gas in the low-temperature heat exchange section 12 exchanges heat with the low-temperature working fluid in the third circulation pipeline P3. The low-temperature working fluid then overlaps with the high-temperature working fluid in the second circulation pipeline P2, so that part of the high-temperature working fluid directly exchanges heat and evaporates, and the other part overlaps and couples with the low-temperature working fluid to evaporate, thus forming a cascade process.

[0043] Compared to the direct heat exchange process, the cascade steam generation process makes fuller use of the heat of compression and can achieve full recovery of the heat of compression. This allows the circulating liquid in the gas-liquid separator to fully absorb the heat of the high-temperature working fluid and produce enough steam. Compared to the cascade process, it achieves tiered recovery of the heat of compression, reduces the input of compression work, and results in lower energy consumption for steam generation.

[0044] This invention can also reduce the circulating cooling water consumption of the interstage cooler by fully recovering the heat of compression.

[0045] Therefore, this invention utilizes the heat of compression in a cascade manner, employs cascade technology to fully recover the heat of compression and generate steam, thus obtaining a high-grade heat source. It has a wider range of applications and more significant energy-saving benefits, and is of great significance for reducing energy consumption and carbon emissions in the compression process.

[0046] Continue to refer to Figure 1 As shown, in some embodiments, the cascade compression heat recovery steam generation system further includes: a third compressor 70, connected to the front end of the first pipeline 111 of the high-temperature heat exchange section 11, and the third compressor 70 is also connected to the process gas inlet IN1; wherein, the temperature of the process gas before entering the third compressor 70 is 35℃~40℃, the temperature of the process gas after being compressed by the third compressor 70 is 100℃~150℃, the temperature of the process gas exiting the high-temperature heat exchange section 11 is 60℃~90℃, and the temperature of the process gas exiting the low-temperature heat exchange section 12 is 35℃~40℃.

[0047] The process gas from upstream is pressurized by the third compressor 70 to bring its pressure and temperature to appropriate values.

[0048] In some embodiments, the cascaded compression heat recovery steam generation system further includes a gas buffer tank 80, which is connected to the rear end of the first pipeline 121 of the cryogenic heat exchange section 12, and the gas buffer tank 80 is also connected to the process gas outlet OUT1.

[0049] The process gas is buffered by the gas buffer tank 80, and the treated gas can flow downstream.

[0050] In some embodiments, the cascaded compression heat recovery steam generation system further includes: a first throttling expansion valve K1, connected in the pipeline from the first pipeline 301 of the high-temperature working fluid-steam generator 30 to the second pipeline 112 of the high-temperature heat exchange section 11.

[0051] The pressure and temperature of the working fluid in the second pipeline 112 entering the high-temperature heat exchange section 11 are regulated by the first throttling expansion valve K1.

[0052] In some embodiments, the cascaded compression heat recovery steam generation system further includes: a second throttling expansion valve K2, connected in the pipeline from the first pipeline 301 of the high-temperature working fluid-steam generator 30 to the first pipeline 401 of the high-temperature working fluid-low-temperature working fluid heat exchanger 40.

[0053] The pressure and temperature of the working fluid in the first pipeline 401 of the high-temperature working fluid-low-temperature working fluid heat exchanger 40 are regulated by the second throttling expansion valve K2.

[0054] In some embodiments, the cascaded compression heat recovery steam generation system further includes a third throttling expansion valve K3, which is connected in the pipeline from the second pipeline 402 of the high-temperature working fluid-low-temperature working fluid heat exchanger 40 to the second pipeline 122 of the low-temperature heat exchange section 12.

[0055] The pressure and temperature of the working fluid in the second pipeline 122 entering the low-temperature heat exchange section 12 are regulated by the third throttling expansion valve K3.

[0056] In some embodiments, the cascaded compression heat recovery steam generation system further includes a level control valve K4, connected between the steam generation circulating liquid inlet IN2 and the gas-liquid separator 60.

[0057] The flow rate of the steam-generating circulating liquid (e.g., deoxygenated water) entering through the steam-generating circulating liquid inlet IN2 is controlled by the liquid level control valve K4, thereby controlling the liquid level in the gas-liquid separator 60.

[0058] In some embodiments, the cascade compression heat recovery steam generation system further includes a steam compressor 90 connected between the gas-liquid separator 60 and the steam outlet OUT2.

[0059] The steam compressor 90 can continuously and stably produce different grades of steam according to user needs, thus expanding the application range of the steam production system.

[0060] In some embodiments, the cascaded compression heat recovery steam generation system further includes a temperature control valve K5, connected between the steam generation circulating liquid inlet IN2 and the steam compressor 90.

[0061] The temperature control valve K5 can control the gas supply temperature of the steam compressor 90.

[0062] Furthermore, in the above embodiments, the high-temperature working fluid flowing in the first circulation pipe P1 and the second circulation pipe P2 is R1233zd (Chinese name: trans-1-chloro-3,3,3-trifluoropropylene, CAS number: 102687-65-0), which has a GWP < 1, making it very energy-efficient and environmentally friendly. The temperature of the high-temperature working fluid flowing in the second pipe 112 of the high-temperature heat exchange section 11 is 50℃~80℃. The low-temperature working fluid flowing in the third circulation pipe P3 is R1234ze(E) (Chinese name: trans-1,3,3,3-tetrafluoropropylene, CAS number: 29118-24-9), which has a GWP < 1, making it very energy-efficient and environmentally friendly. The temperature of the low-temperature working fluid flowing in the second pipe 122 of the low-temperature heat exchange section 12 is 30℃~35℃.

[0063] Figure 2 The diagram illustrates the structure of a cascaded compression heat recovery steam generation system according to an embodiment of the present invention, wherein the flow medium in the cascaded compression heat recovery steam generation system is indicated. (Refer to...) Figure 2As shown, the cascade compression heat recovery steam generation method proposed in this invention includes: process gas is output after passing through a high-temperature heat exchange section 11 and a low-temperature heat exchange section 12; the steam generation circulating liquid is located at the bottom of the gas-liquid separator 60, and is output after passing through the fourth circulation pipeline P4 and the gas-liquid separator 60; the high-temperature working fluid flows in the first circulation pipeline P1 and the second circulation pipeline P2, and part of the pipelines in the first circulation pipeline P1 and the second circulation pipeline P2 overlap; the low-temperature working fluid flows in the third circulation pipeline P3.

[0064] The high-temperature working fluid exchanges heat with the process gas in the high-temperature heat exchange section 11 through the first circulation pipeline P1; the low-temperature working fluid exchanges heat with the process gas in the low-temperature heat exchange section 12 through the third circulation pipeline P3; the low-temperature working fluid exchanges heat with the process gas in the high-temperature working fluid-low-temperature working fluid heat exchanger 40 through the third circulation pipeline P3 and the high-temperature working fluid exchanges heat with the process gas in the second circulation pipeline P2; the high-temperature working fluid exchanges heat with the process gas in the high-temperature working fluid-steam generator 30 through the first circulation pipeline P1 and the second circulation pipeline P2 and the steam generation circulating liquid exchanges heat with the process gas in the high-temperature working fluid-steam generator 30 through the fourth circulation pipeline P4.

[0065] Specifically, the process flow of the cascade compression heat recovery steam generation system includes:

[0066] Before pressurization, process gas S-1 comes from upstream and first enters the third compressor 70. After pressurization, process gas S-2 (approximately 100℃-150℃) enters the high-temperature heat exchange section 11 of the multi-stream heat exchanger 10, where it exchanges heat with the high-temperature working fluid S-13 (approximately 50℃-80℃) entering the high-temperature heat exchange section 11. The high-temperature working fluid S-13 evaporates from the gas-liquid two-phase flow into a gas phase working fluid S-14, which merges with another high-temperature gas phase working fluid S-10 to form S-15. Then, it enters the first compressor 20, where it is pressurized to the set pressure. The high-temperature, high-pressure gas phase working fluid S-16 is then output and enters the high-temperature working fluid-steam generator 30, where it exchanges heat efficiently with the steam-generating circulating liquid S-18. The high-temperature, high-pressure gaseous working fluid S-16 condenses and releases heat to become a high-pressure, high-temperature liquid working fluid S-17. It then splits into two streams. One stream, S-12, expands through the first throttling expansion valve K1 to become a two-phase high-temperature working fluid S-13, which then undergoes heat exchange and evaporation with the high-temperature heat exchange section 11 of the multi-stream heat exchanger 10. The other stream, S-11, expands through the second throttling expansion valve K2 to become a two-phase gaseous working fluid S-9, which then absorbs heat and evaporates into a high-temperature gaseous working fluid S-10 through the high-temperature working fluid-low-temperature working fluid heat exchanger 40, forming a small circulation of the high-temperature working fluid. The high-temperature working fluid undergoes direct heat exchange in one stream and is coupled with the low-temperature working fluid in the other, forming a hybrid structure of partial direct heat exchange and partial coupling.

[0067] The process gas temperature exiting the high-temperature heat exchange section 11 of the multi-stream heat exchanger 10 drops to 60℃-90℃, and then enters the low-temperature heat exchange section 12 of the multi-stream heat exchanger 10 to exchange heat with the low-temperature working medium S-5 (approximately 30℃-35℃). The low-temperature working medium S-5 evaporates from the gas-liquid two-phase system to the gas phase working medium S-6, which enters the second compressor 50. After being pressurized to the set pressure by the second compressor 50, the high-temperature and high-pressure gas phase working medium S-7 is output and enters the high-temperature working medium-low-temperature working medium heat exchanger 40 to exchange heat efficiently with the gas-liquid two-phase working medium S-9 after throttling and expansion. The high-temperature and high-pressure gas phase working medium S-7 condenses and releases heat to become the high-pressure and high-temperature liquid phase working medium S-8, and then becomes the low-pressure and low-temperature gas-liquid two-phase working medium after throttling and expansion by the third throttling expansion valve K3, i.e., the low-temperature working medium S-5, forming a small cycle of the low-temperature working medium. The process gas S-3 flowing out from the multi-stream heat exchanger 10 is processed by the gas buffer tank 80 and becomes gas S-4, which then flows downstream.

[0068] Deoxygenated water S-24 enters the system in two streams. One stream, S-25, has its flow rate adjusted to S-20 via level control valve K4, and then enters gas-liquid separator 60. At the bottom of gas-liquid separator 60 is liquid-phase steam-generating circulating liquid S-21. After being pressurized by circulating pump 61, the steam-generating circulating liquid S-18 enters high-temperature working fluid-steam generator 30. After absorbing heat, part of the steam-generating circulating liquid evaporates into S-19, and then returns to gas-liquid separator 60. Steam S-22 is separated at the top of gas-liquid separator 60. Steam S-22 enters steam compressor 90 for compression, increasing the steam pressure to the set pressure before discharging the target steam S-23. The steam compressor 90 is equipped with a desuperheating water inlet to control the superheat of the steam. The desuperheating water comes from another route of the deoxygenated water S-24. After passing through the temperature control valve K5, the steam S-26 enters the desuperheating water inlet of the steam compressor 90 to control the steam temperature to the set temperature. Finally, the steam temperature and pressure meet the set requirements and are stably output to the outside by the target steam S-23.

[0069] As described above, the cascade steam generation process of the present invention, based on the principles of waste heat cascade utilization and reverse Carnot cycle, uses a multi-stream heat exchanger 10 to replace the original interstage cooler, dividing the compression heat into heat in the high-temperature heat exchange section 11 and the low-temperature heat exchange section 12, and then matching the high-temperature working fluid and the low-temperature working fluid respectively. The process gas in the high-temperature heat exchange section 11 exchanges heat with the high-temperature working fluid in the first circulation pipeline P1, and the process gas in the low-temperature heat exchange section 12 exchanges heat with the low-temperature working fluid in the third circulation pipeline P3. The low-temperature working fluid then overlaps with the high-temperature working fluid in the second circulation pipeline P2, so that part of the high-temperature working fluid directly exchanges heat and evaporates, and the other part overlaps and couples with the low-temperature working fluid to evaporate, thereby forming a cascade process.

[0070] Compared to the direct heat exchange process, the cascade steam generation process makes fuller use of the heat of compression and can achieve full recovery of the heat of compression. This allows the circulating liquid in the gas-liquid separator to fully absorb the heat of the high-temperature working fluid and produce enough steam. Compared to the cascade process, it achieves tiered recovery of the heat of compression, reduces the input of compression work, and results in lower energy consumption for steam generation.

[0071] This invention can also reduce the circulating cooling water consumption of the interstage cooler by fully recovering the heat of compression.

[0072] Furthermore, this invention uses a novel environmentally friendly working fluid to replace the traditional working fluid, with a global warming potential (GWP) not exceeding 150. Specifically, the low-temperature working fluid uses R1234ze(E) (GWP < 1) instead of R134a (GWP approximately 1430), and the high-temperature working fluid uses R1233zd (GWP < 1) instead of R245fa (GWP approximately 1030). The selected working fluids are more environmentally friendly and energy-efficient.

[0073] The present invention also includes a steam compressor 90, which can continuously and stably produce steam of different grades according to user needs, thereby increasing the application range of the steam production system.

[0074] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be considered as limitations upon the present invention.

[0075] This case study uses a company with an annual production capacity of 200,000 tons of CO2 liquefaction compressor as an example, as shown in Table 1 below.

[0076] Table 1. Parameters of CO2 liquefaction compressors produced annually by a certain enterprise.

[0077]

[0078]

[0079] After implementation, this case study demonstrates the ability to recover all interstage compression heat from the compressor, eliminate the need for interstage cooler circulating water, and produce 0.2–0.4 MPa of steam. The COP for steam production and heating reaches 2.7–3.0, with an electricity consumption of 213–240 kW / t per ton of steam. Based on an electricity price of 0.6 yuan / kW, the equivalent steam production cost is 127.8–144 yuan / t, and the steam production energy consumption is 49–55.2 kgEO / t.

[0080] Compared with boiler steam production, the steam production cost is reduced by 42.4-48.9%, and the steam production energy consumption is reduced by 16.4-25.8%; compared with electric heating steam production, the steam production cost is reduced by 62.7-66.6%, and the steam production energy consumption is reduced by 62.7-66.6%.

[0081] Thus, this invention achieves full recovery of compression heat to produce steam, resulting in high-grade steam, significantly reduced steam production costs and energy consumption compared to traditional processes, and significant energy-saving benefits.

[0082] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A cascaded compression heat recovery steam generation system, characterized in that, include: A multi-flow heat exchanger includes a high-temperature heat exchange section and a low-temperature heat exchange section. The high-temperature heat exchange section and the low-temperature heat exchange section each include a first pipeline and a second pipeline for heat exchange. The first pipeline of the high-temperature heat exchange section is connected to the first pipeline of the low-temperature heat exchange section and supplies process gas for flow. A high-temperature working fluid-steam generator includes a first pipeline and a second pipeline for heat exchange. The second pipeline of the high-temperature heat exchange section passes through a first compressor and the first pipeline of the high-temperature working fluid-steam generator to form a first circulation pipeline. The first circulation pipeline is used for the flow of high-temperature working fluid. A high-temperature working fluid-low-temperature working fluid heat exchanger includes a first pipeline and a second pipeline for heat exchange. The first pipeline of the high-temperature working fluid-steam generator further forms a second circulation pipeline by sequentially passing through the first pipeline of the high-temperature working fluid-low-temperature working fluid heat exchanger and the first compressor. The second circulation pipeline supplies high-temperature working fluid. The second pipeline of the high-temperature working fluid-low-temperature working fluid heat exchanger forms a third circulation pipeline by sequentially passing through the second pipeline of the low-temperature heat exchange section and the second compressor. The third circulation pipeline supplies low-temperature working fluid. The gas-liquid separator, via a circulating pump, forms a fourth circulating pipeline with the second pipeline of the high-temperature working fluid-steam generator. The fourth circulating pipeline supplies the steam-generating circulating liquid. The gas-liquid separator is also connected to the steam-generating circulating liquid inlet and the steam outlet.

2. The cascade compression heat recovery steam generation system as described in claim 1, characterized in that, Also includes: The third compressor is connected to the front end of the first pipeline in the high-temperature heat exchange section, and the third compressor is also connected to the process gas inlet. The process gas temperature increases after being compressed by the third compressor, decreases after exiting the high-temperature heat exchange section, and continues to decrease after exiting the low-temperature heat exchange section.

3. The cascade compression heat recovery steam generation system as described in claim 1, characterized in that, Also includes: A gas buffer tank is connected to the rear end of the first pipeline in the low-temperature heat exchange section, and the gas buffer tank is also connected to the process gas outlet.

4. The cascade compression heat recovery steam generation system as described in claim 1, characterized in that, Also includes: The first throttling expansion valve is connected in the pipeline from the first pipeline of the high-temperature working fluid-steam generator to the second pipeline of the high-temperature heat exchange section.

5. The cascade compression heat recovery steam generation system as described in claim 1, characterized in that, Also includes: The second throttling expansion valve is connected in the pipeline from the first pipeline of the high-temperature working fluid-steam generator to the first pipeline of the high-temperature working fluid-low-temperature working fluid heat exchanger.

6. The cascade compression heat recovery steam generation system as described in claim 1, characterized in that, Also includes: The third throttling expansion valve is connected in the pipe from the second pipeline of the high-temperature working fluid-low-temperature working fluid heat exchanger to the second pipeline of the low-temperature heat exchange section.

7. The cascade compression heat recovery steam generation system as described in claim 1, characterized in that, Also includes: A liquid level control valve is connected between the steam-generating circulating liquid inlet and the gas-liquid separator.

8. The cascade compression heat recovery steam generation system as described in claim 1, characterized in that, Also includes: A steam compressor is connected between the gas-liquid separator and the steam outlet.

9. The cascade compression heat recovery steam generation system as described in claim 8, characterized in that, Also includes: A temperature control valve is connected between the steam-generating circulating liquid inlet and the steam compressor.

10. The cascade compression heat recovery steam generation system according to any one of claims 1-9, characterized in that: The high-temperature working fluid flowing in the first and second circulation pipelines is trans-1-chloro-3,3,3-trifluoropropylene; The cryogenic working fluid flowing in the third circulation pipeline is trans-1,3,3,3-tetrafluoropropylene.

11. A method for generating steam with full heat recovery from cascade compression as described in claim 1, characterized in that, include: The process gas is output after passing through a high-temperature heat exchange section and a low-temperature heat exchange section. The circulating liquid for steam generation is located at the bottom of the gas-liquid separator and is output after passing through the fourth circulation pipeline and the gas-liquid separator. The high-temperature working fluid flows in the first and second circulation pipelines, and some sections of the first and second circulation pipelines overlap; the low-temperature working fluid flows in the third circulation pipeline. The high-temperature working fluid exchanges heat with the process gas in the high-temperature heat exchange section through the first circulation pipeline; the low-temperature working fluid exchanges heat with the process gas in the low-temperature heat exchange section through the third circulation pipeline. The low-temperature working fluid exchanges heat in the high-temperature working fluid-low-temperature working fluid heat exchanger through the third circulation pipeline and the high-temperature working fluid through the second circulation pipeline. The high-temperature working fluid exchanges heat in the high-temperature working fluid-steam generator through the first and second circulation pipelines, and the steam-generating circulating liquid exchanges heat through the fourth circulation pipeline.

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