Carbon dioxide gas recovery system and recovery method in brayton cycle
By designing a carbon dioxide gas recovery system within the Bretton cycle system, and utilizing phase change physics to separate and pressurize pure carbon dioxide, the leakage problem caused by dry gas sealing was solved, achieving zero carbon emissions and energy-saving and environmentally friendly effects for the system.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SUZHOU OULA TURBINE MASCH CO LTD
- Filing Date
- 2023-09-15
- Publication Date
- 2026-05-15
AI Technical Summary
In supercritical carbon dioxide Brayton cycle systems, the problem of trace carbon dioxide leakage caused by dry gas seals and the long-term carbon emissions have not been effectively solved.
Design a carbon dioxide gas recovery system in a Brayton cycle. By combining components such as a cooler, compressor, gas collector, heat exchanger, expander, and separator, pure carbon dioxide is separated and pressurized using phase change physics methods and recovered into the Brayton cycle system, achieving a balance between leakage and replenishment phases.
It achieves a balance between carbon dioxide leakage and replenishment in the Brayton cycle system, ensuring long-term safe operation of the system, and realizes energy-saving and environmental protection functions by recovering the cooling energy generated by the system.
Smart Images
Figure CN117167108B_ABST
Abstract
Description
Technical Field
[0001] This application relates to gas recovery technology, specifically to a carbon dioxide gas recovery system and method in a Brayton cycle. Background Technology
[0002] In a Brayton cycle system using supercritical carbon dioxide, the dynamic seals of the compressor and expander employ dry gas seals. Since the Brayton cycle is a closed system, and dry gas seals involve minute leaks of sealing gas and isolation gas, these minute leaks can lead to a reduction in carbon dioxide levels during long-term system operation, requiring replenishment. Furthermore, even though these leaks are small, they still contribute to carbon emissions over time. Summary of the Invention
[0003] To overcome the above-mentioned defects, this application provides a carbon dioxide gas recovery system in a Brayton cycle. This recovery system collects the mixed gas in the Brayton cycle system, separates and processes the pure carbon dioxide gas, and then reintroduces it into the Brayton cycle system, thereby achieving a balance between leakage and replenishment.
[0004] The technical solution adopted by this application to solve its technical problem is:
[0005] A carbon dioxide gas recovery system in a Brayton cycle includes a cooler, a first compressor, a gas collector, a second compressor, a heat exchanger, an expander, and a separator connected in sequence by pipelines. The upper end of the separator is connected to the cooler by a pipeline, and a mixed gas inlet pipe and a condensate drain pipe are connected to the cooler. The lower end of the separator is connected to the heat exchanger by a pipeline.
[0006] Optionally, the system also includes a sublimator and a third compressor, with the heat exchanger connected to the sublimator and the sublimator connected to the third compressor, which is connected to the Brayton cycle system via a clean gas recovery pipe.
[0007] Optionally, the mixed gas enters the cooler through the mixed gas inlet pipe, the mixed gas including carbon dioxide and a barrier gas, the barrier gas including compressed air, compressed nitrogen or atmospheric pressure air.
[0008] Optionally, the mixed gas is collected through a collection pipe and then enters the cooler through the mixed gas inlet pipe. The pressure inside the cooler is P1, and the pressure inside the collection pipe is P, then P1 < P.
[0009] Optionally, when the isolation gas is compressed air or compressed nitrogen, P1 is less than the pressure of compressed air or compressed nitrogen; when the isolation gas is atmospheric pressure air, P1 is negative pressure.
[0010] Optionally, the outlet pressure of the first compressor is P2, where P2 > P1.
[0011] Optionally, the temperature of the gas mixture after expansion by the expander is T7, which is lower than the phase transition temperature when carbon dioxide turns into dry ice or liquid carbon dioxide.
[0012] Optionally, the temperature T1 inside the cooler is lower than the dew point temperature.
[0013] The present invention also provides a method for recovering carbon dioxide gas using a Brayton cycle carbon dioxide gas recovery system, comprising the following steps:
[0014] Collection: The mixture of carbon dioxide and isolation gas leaking from the dry gas seal in the Brayton cycle system is collected through the collection pipeline and then enters the cooler through the mixed gas inlet pipe;
[0015] Separation: The cooler performs freeze dehydration treatment on the isolation gas, cooling the water vapor in the mixed gas into condensate, which is then discharged through the condensate drain pipe. The temperature T1 inside the cooler is lower than the dew point temperature, and the pressure P1 inside the cooler is lower than the pressure P in the collection pipe.
[0016] Compression: After the dehydrated low-temperature mixed gas enters the first compressor, it is compressed into the gas collecting tank by the first compressor. The outlet pressure of the first compressor is P2, P2 > P1.
[0017] Pressurization: After the mixed gas in the gas collecting cabinet enters the second compressor, it is pressurized by the second compressor and then enters the heat exchanger for cooling;
[0018] Expansion: The cooled mixed gas enters the expander and expands. The temperature T7 of the expanded mixed gas is lower than the phase change temperature of carbon dioxide, causing carbon dioxide to condense into non-gaseous copper dioxide. The non-gaseous carbon dioxide includes at least one of dry ice and liquid carbon dioxide.
[0019] Separation: The expanded low-temperature mixed gas enters the separator, which completely separates the refrigerated isolation gas from the non-gaseous carbon dioxide. The pure non-gaseous carbon dioxide enters the heat exchanger, and the refrigerated isolation gas enters the cooler, serving as a cold source for the refrigeration and dehydration of the mixed gas.
[0020] Recovery: Non-gaseous carbon dioxide passing through the heat exchanger enters the sublimator, which sublimates the non-gaseous carbon dioxide into pure carbon dioxide gas. The carbon dioxide gas is then pressurized by the third compressor to the inlet pressure of the Brayton cycle compressor and enters the Brayton cycle system, achieving zero carbon emissions from the Brayton cycle system.
[0021] The beneficial effects of this application are:
[0022] 1) In this recovery system, the sealing gas and isolation gas leaking from the dry gas seal in the supercritical carbon dioxide Brayton cycle are collected as a mixed gas using relative negative pressure. Pure carbon dioxide is separated using a phase change physical method, and the separated carbon dioxide is pressurized and sent back to the supercritical carbon dioxide Brayton cycle system. This achieves a balance between carbon dioxide leakage and replenishment in the Brayton cycle system, enabling the supercritical carbon dioxide Brayton cycle system to operate safely for a long time.
[0023] 2) This application utilizes the cold isolation gas generated by the recovery system as a cold source for the complete dehumidification of the mixed gas in the cooler. While thoroughly drying the mixed gas, it makes full use of the system's own energy to achieve energy-saving and environmentally friendly functions.
[0024] 3) In this application, after the carbon dioxide phase change non-gaseous carbon dioxide is purified, the high-temperature mixed gas that needs to be cooled after compression by the second compressor is used as the heat source for the sublimation of non-gaseous carbon dioxide. This not only saves the heat required for sublimation, but also cools down the high-pressure mixed gas, so that the temperature of the expanded mixed gas is further reduced, which can reduce the pressure ratio of the second compressor and achieve the purpose of energy saving. Attached Figure Description
[0025] Figure 1 This is a simplified diagram of the recycling system in this application;
[0026] In the diagram: 10-cooler, 11-mixed gas inlet pipe, 12-condensate drain pipe, 13-vent pipe, 20-first compressor, 30-gas collector, 40-second compressor, 50-heat exchanger, 60-expander, 70-separator, 80-sublimator, 90-third compressor, 91-pure gas recovery pipe. Detailed Implementation
[0027] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the embodiments described in this application are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.
[0028] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such uses of the terms can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.
[0029] For ease of description, spatial relative terms such as "above," "on top of," "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 beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" 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.
[0030] Example: Figure 1 As shown in the figure, the arrows indicate the direction of medium flow inside the pipe. A carbon dioxide gas recovery system in a Brayton cycle includes a cooler 10, a first compressor 20, a gas collector 30, a second compressor 40, a heat exchanger 50, an expander 60, and a separator 70 connected in sequence by pipelines. The upper end of the separator 70 is connected to the cooler 10 by a pipeline. The cooler 10 is connected to a mixed gas inlet pipe 11 and a condensate drain pipe 12. The lower end of the separator 70 is connected to the heat exchanger 50 by a pipeline.
[0031] The expander 60 is a standard expander or expansion valve, and the cooler 10 is also connected to an vent pipe 13. Carbon dioxide leaked from the Brayton cycle system is recovered and treated by this recovery system before being reused in the Brayton cycle system.
[0032] After the mixed gas is cooled by the cooler 10, condensate is separated out. The condensate is discharged from the cooler 10 through the condensate drain pipe 12. The dehydrated mixed gas is compressed by the first compressor 20 and enters the gas collection cabinet 30. The second compressor 40 pressurizes the mixed gas in the gas collection cabinet 30 and then cools it through the heat exchanger 50 before entering the expander 60. The expanded low-temperature mixed gas enters the separator 70, where carbon dioxide condenses into non-gaseous carbon dioxide, which includes at least one of dry ice and liquid carbon dioxide. In the separator 70, the non-gaseous carbon dioxide and the refrigeration gas are separated. The separated pure non-gaseous carbon dioxide enters the heat exchanger 50 as a cold source. The non-gaseous carbon dioxide after heat exchange is then returned to the Breno cycle system after post-processing. The separated refrigerated air is sent to the cooler 10 as a cold source for the freezing and dehydration of the mixed gas.
[0033] This recovery system uses relative negative pressure to collect the leaked sealing gas and isolation gas from the supercritical carbon dioxide Brayton cycle as a mixture. Pure carbon dioxide is separated using a phase change physical method, and the separated carbon dioxide is pressurized and sent back to the supercritical carbon dioxide Brayton cycle system. This achieves a balance between leakage and replenishment in the Brayton cycle system, enabling the supercritical carbon dioxide Brayton cycle system to operate safely and economically for a long time.
[0034] The recovery system also includes a sublimator 80 and a third compressor 90. A heat exchanger 50 is connected to the sublimator 80, and the sublimator 80 is connected to the third compressor 90. The third compressor 90 is connected to the Brayton cycle system via a pure gas recovery pipe 91. The dry ice and / or liquid carbon dioxide, after being heated in the heat exchanger 50, re-enter the sublimator 80 and sublimate into carbon dioxide gas. The pure carbon dioxide gas is then pressurized by the third compressor 90 to the compressor inlet pressure of the Brayton cycle system and sent into the Brayton cycle system, achieving zero carbon emissions from the Brayton cycle system.
[0035] The mixed gas enters the cooler 10 through the mixed gas inlet pipe 11. The mixed gas includes carbon dioxide and isolation gas, and the isolation gas includes compressed air, compressed nitrogen or atmospheric pressure air.
[0036] The mixed gas is collected through the collection pipe and then enters the cooler 10 through the mixed gas inlet pipe 11. The pressure inside the cooler 10 is P1, and the pressure inside the collection pipe is P, so P1 < P.
[0037] When the isolation gas is compressed air or compressed nitrogen, P1 is less than the pressure of compressed air or compressed nitrogen; when the isolation gas is atmospheric pressure air, P1 is negative. This ensures that leaked gas from the dry gas seal can only enter the recovery system through the collection pipe and will not be lost into the atmosphere. The outlet pressure of the first compressor 20 is P2, where P2 > P1.
[0038] The temperature of the gas mixture after expansion by the expander 60 is T7, which is lower than the phase transition temperature at which carbon dioxide turns into dry ice or liquid carbon dioxide. That is, the carbon dioxide expanded by the expander 60 turns into dry ice and / or liquid carbon dioxide. The temperature T1 inside the cooler 10 is lower than the dew point temperature.
[0039] A method for recovering carbon dioxide gas using a Brayton cycle carbon dioxide gas recovery system includes the following steps:
[0040] Collection: The mixture of carbon dioxide and isolation gas leaking from the dry gas seal in the Brayton cycle system is collected through a collection pipe and then enters the cooler 10 through the mixed gas inlet pipe 11; the isolation gas includes compressed air, compressed nitrogen or atmospheric pressure air;
[0041] Separation: The cooler 10 performs freeze dehydration treatment on the isolation gas, cooling the water vapor in the mixed gas into condensate, which is then discharged through the condensate drain pipe 12. The temperature T1 inside the cooler 10 is lower than the dew point temperature, and the pressure P1 inside the cooler 10 is lower than the pressure P in the collection pipe. The cold source for the cooler 10 can be the subsequently recovered freeze isolation gas.
[0042] Compression: After the dehydrated low-temperature mixed gas enters the first compressor 20, it is compressed into the gas collection tank 30 by the first compressor 20. The outlet pressure of the first compressor 20 is P2, P2 > P1; the low-temperature mixed gas can reduce the energy consumption of the compressor.
[0043] Pressurization: After the mixed gas in the gas collecting cabinet 30 enters the second compressor 40, it is pressurized by the second compressor 40 and then enters the heat exchanger 50 for cooling; the pressurization pressure reaches P4 and the cooling temperature reaches T5. Dry ice or liquid carbon dioxide can be used in the heat exchanger 50 to cool the high-temperature mixed gas, thereby improving the energy utilization rate.
[0044] Expansion: The cooled mixed gas enters the expander 60 for expansion. The temperature T7 of the expanded mixed gas is lower than the phase change temperature of carbon dioxide, causing carbon dioxide to condense into non-gaseous copper dioxide. The non-gaseous carbon dioxide includes at least one of dry ice and liquid carbon dioxide. The pressure P4 and temperature T5 mentioned above should meet the pressure and temperature requirements of the expanded temperature T7.
[0045] Separation: The expanded low-temperature mixed gas enters the separator 70, which completely separates the refrigerated isolation gas from the non-gaseous carbon dioxide. The pure non-gaseous carbon dioxide enters the heat exchanger 50, and the refrigerated isolation gas enters the cooler 10 as a cold source for the refrigeration and dehydration of the mixed gas.
[0046] Recovery: Non-gaseous carbon dioxide from the heat exchanger 50 enters the sublimator 80, where it sublimates into pure carbon dioxide gas. This carbon dioxide gas is then pressurized by the third compressor 90 to the inlet pressure of the Brayton cycle compressor and enters the Brayton cycle system, achieving zero carbon emissions. In the heat exchanger 50, the non-gaseous carbon dioxide exchanges heat with the high-temperature mixed gas. Because the sources of the isolation gases differ, the flow rates of the collected mixed gas components will vary. Therefore, the flow rates and pressure ratios of the first compressor 20, the second compressor 40, and the third compressor 90 must be calculated and set based on the component flow rates.
[0047] Since pure dry ice or liquid carbon dioxide absorbs a large amount of heat when it changes from a phase to a gas, using dry ice or liquid carbon dioxide for high-temperature cooling of the compressed gas mixture makes full use of the heat in the mixture and reduces energy waste.
[0048] It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. Therefore, the scope of protection of this patent application shall be determined by the appended claims.
Claims
1. A carbon dioxide gas recovery system in a Brayton cycle, characterized in that: The system includes a cooler (10), a first compressor (20), a gas collector (30), a second compressor (40), a heat exchanger (50), an expander (60), and a separator (70) connected in sequence by pipelines. The upper end of the separator (70) is connected to the cooler (10) by pipelines. The cooler (10) is connected to a mixed gas inlet pipe (11) and a condensate drain pipe (12). The lower end of the separator (70) is connected to the heat exchanger (50) by pipelines. The mixed gas enters the cooler (10) through the mixed gas inlet pipe (11). The mixed gas includes carbon dioxide and isolation gas, which includes compressed air, compressed nitrogen or atmospheric pressure air.
2. The carbon dioxide gas recovery system in the Brayton cycle according to claim 1, characterized in that: It also includes a sublimator (80) and a third compressor (90), the heat exchanger (50) being connected to the sublimator (80), the sublimator (80) being connected to the third compressor (90), and the third compressor (90) being connected to the Brayton cycle system via a pure gas recovery pipe (91).
3. The carbon dioxide gas recovery system in the Brayton cycle according to claim 1, characterized in that: The mixed gas is collected through the collection pipe and then enters the cooler (10) through the mixed gas inlet pipe (11). The pressure in the cooler (10) is P1 and the pressure in the collection pipe is P. Then P1 < P.
4. The carbon dioxide gas recovery system in the Brayton cycle according to claim 3, characterized in that: When the isolation gas is compressed air or compressed nitrogen, P1 is less than the pressure of compressed air or compressed nitrogen; when the isolation gas is atmospheric pressure air, P1 is negative pressure.
5. The carbon dioxide gas recovery system in the Brayton cycle according to claim 3, characterized in that: The outlet pressure of the first compressor (20) is P2, where P2 > P1.
6. The carbon dioxide gas recovery system in the Brayton cycle according to claim 1, characterized in that: The temperature of the mixed gas after expansion by the expander (60) is T7, which is lower than the phase change temperature when carbon dioxide turns into dry ice or liquid carbon dioxide.
7. The carbon dioxide gas recovery system in the Brayton cycle according to claim 1, characterized in that: The temperature T1 inside the cooler (10) is lower than the dew point temperature.
8. A method for recovering carbon dioxide gas using a Brayton cycle carbon dioxide gas recovery system according to any one of claims 1-7, characterized in that: Includes the following steps: Collection: The mixture of carbon dioxide and isolation gas leaking from the dry gas seal in the Brayton cycle system is collected through the collection pipe and then enters the cooler (10) through the mixed gas inlet pipe (11); Separation: The cooler (10) performs freeze dehydration treatment on the isolation gas, cools the water vapor in the mixed gas into condensate, and discharges it through the condensate drain pipe (12). The temperature T1 inside the cooler (10) is lower than the dew point temperature, and the pressure P1 inside the cooler (10) is less than the pressure P in the collection pipe. Compression: After the dehydrated low-temperature mixed gas enters the first compressor (20), it is compressed into the gas collection tank (30) by the first compressor (20). The outlet pressure of the first compressor (20) is P2, P2 > P1; Pressurization: After the mixed gas in the gas collecting cabinet (30) enters the second compressor (40), it is pressurized by the second compressor (40) and then enters the heat exchanger (50) for cooling; Expansion: The cooled mixed gas enters the expander (60) for expansion. The temperature T7 of the expanded mixed gas is less than the phase change temperature of carbon dioxide, causing carbon dioxide to condense into non-gaseous carbon dioxide. The non-gaseous carbon dioxide includes at least one of dry ice and liquid carbon dioxide. Separation: The expanded low-temperature mixed gas enters the separator (70), which completely separates the refrigerated isolation gas from the non-gaseous carbon dioxide. The pure non-gaseous carbon dioxide enters the heat exchanger (50), and the refrigerated isolation gas enters the cooler (10) as a cold source for the refrigeration and dehydration of the mixed gas. Recovery: Non-gaseous carbon dioxide from the heat exchanger (50) enters the sublimator (80), which sublimates the non-gaseous carbon dioxide into pure carbon dioxide gas. The carbon dioxide gas is pressurized to the compressor inlet pressure of the Brayton cycle through the third compressor (90) and enters the Brayton cycle system, achieving zero carbon emissions of the Brayton cycle system.