Device and method for preparing high-pressure CO through nitrogen throttling expansion CO pump pressurization dehydrogenation and demethanization

Abstract

The invention discloses a device and a method for preparing high-pressure CO through pressurization dehydrogenation and demethanization of a nitrogen throttling expansion CO pump, and belongs to the technical field of chemical cryogenic separation. The specific structure is as follows: purified gas from the upstream is cooled by a first heat exchanger, a stripping tower reboiler and a second heat exchanger in sequence and then enters a hydrogen-rich gas flash tank; a liquid phase at the bottom of the hydrogen-rich gas flash tank enters a stripping tower for continuous separation; a liquid phase at the bottom of the stripping tower enters a demethanizing tower for demethanizing treatment; a gas phase at the top of the demethanization tower is completely condensed by a demethanization tower condenser and then enters a demethanization tower separation tank, a liquid phase at the bottom of the separation tank is pressurized by a CO liquid pump and then is reheated by a second heat exchanger and a first heat exchanger in sequence, and a high-pressure CO product is obtained and discharged out of the cold box. The nitrogen circulation compressor provides nitrogen circulation refrigeration for the cold box, one part of circulation nitrogen provides cold energy for the demethanizer condenser after being pre-cooled and throttled and then flows back to the nitrogen circulation compressor, and the other part of circulation nitrogen is expanded and refrigerated through the nitrogen expansion machine and provides additional cold energy supplement for the cold box.

Description

Technical Field

[0001] This invention belongs to the field of cryogenic separation technology in the chemical industry, specifically relating to an apparatus and method for preparing high-pressure CO by pressurizing dehydrogenation and demethanization using a nitrogen-throttling expansion CO pump. Background Technology

[0002] In chemical production, high-pressure CO is a direct raw material for the synthesis reactions of various fine chemicals such as methanol, acetic acid, and polycarbonate. Its purity and pressure stability directly affect the operating efficiency and product yield of downstream reactors. The HyCO separation process, commonly used in industry, enables large-scale separation and purification of CO. This process mainly includes multiple units such as hydrogen-rich flash tank separation of hydrogen-rich gas, stripping tower distillation dehydrogenation, and demethanizing tower distillation demethanization. To provide sufficient cooling for the cold box separation process and meet the output requirements of high-pressure CO, a multi-stage CO circulation compression system is typically installed outside the cold box. However, this compression system has a complex structure, high equipment investment and maintenance costs, making backup configuration difficult and hindering the implementation of a "one-for-one" operation mode. A malfunction or the need for maintenance will cause the entire CO pressurization system to shut down. Furthermore, the low integration of this system and long delivery and installation cycles limit the integrated design and rapid engineering implementation of the unit. Simultaneously, CO, as a toxic gas, poses a potential leakage risk during long-term operation, posing significant safety hazards and requiring high levels of equipment sealing and safety.

[0003] Therefore, while ensuring the purity of CO products separated by the HyCO separation system, it is urgent to develop a simpler CO compression and cold box refrigeration system and method to reduce system complexity, reduce investment costs, and shorten the construction period. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and to provide an apparatus and method for preparing high-pressure CO by pressurizing dehydrogenation and demethanization using a nitrogen-throttling expansion CO pump.

[0005] The specific technical solution adopted in this invention is as follows:

[0006] In a first aspect, the present invention provides an apparatus for preparing high-pressure CO by pressurizing dehydrogenation and demethanization using a nitrogen throttling expansion CO pump, comprising a nitrogen circulating compressor and a first heat exchanger, a second heat exchanger, a stripping tower reboiler, a hydrogen-rich flash tank, a stripping tower, a demethanization tower, a demethanization tower reboiler, a demethanization tower condenser, a demethanization tower separator, a CO liquid pump, and a nitrogen expander, all disposed in a cold box.

[0007] The purified gas from upstream passes through the first heat exchanger, the stripping tower reboiler, and the second heat exchanger for cooling before entering the hydrogen-rich flash tank. The liquid phase at the bottom of the hydrogen-rich flash tank enters the stripping tower for further separation. The liquid phase at the bottom of the stripping tower enters the demethanizer for demethanization treatment. The gas phase at the top of the demethanizer is completely condensed by the demethanizer condenser and then enters the demethanizer separator. The liquid phase at the bottom of the demethanizer separator is pressurized by the CO liquid pump and then passes through the second heat exchanger and the first heat exchanger for reheating, resulting in high-pressure CO product exiting the cold box.

[0008] The nitrogen cycle compressor provides nitrogen cycle refrigeration for the cold box. A portion of the circulating nitrogen is cooled by the first heat exchanger and then enters the demethanizer reboiler to provide heat to the demethanizer. It is then divided into two paths: one path is throttled and passes through the second and first heat exchangers to participate in the heat exchange balance of the cold box, while the other path is throttled and enters the demethanizer condenser to provide cooling capacity. Another portion of the circulating nitrogen is expanded and cooled by the nitrogen expander to provide additional cooling capacity to the cold box.

[0009] As a preferred option, the specific structure is as follows:

[0010] The first hot-side inlet of the first heat exchanger receives purified gas from upstream, and the first cold-side outlet of the first heat exchanger is connected to the hot-side inlet of the stripping tower reboiler through a pipeline; the cold-side outlet of the stripping tower reboiler is connected to the two-phase inlet of the hydrogen-rich flash tank through a pipeline in sequence through the first hot-side inlet of the second heat exchanger and the first cold-side outlet of the second heat exchanger.

[0011] The hydrogen-rich gas outlet of the hydrogen-rich flash tank passes through the first cold-side inlet of the second heat exchanger, the first hot-side outlet of the second heat exchanger, the first cold-side inlet of the first heat exchanger, and the first hot-side outlet of the first heat exchanger in sequence via a pipeline before exiting the cold box and connecting to an external hydrogen-rich gas recovery device; the liquid phase outlet at the bottom of the hydrogen-rich flash tank is connected to the feed inlet of the stripping tower via a pipeline.

[0012] The flash steam outlet at the top of the stripping tower passes through the second cold-side inlet of the second heat exchanger, the second hot-side outlet of the second heat exchanger, the second cold-side inlet of the first heat exchanger, and the second hot-side outlet of the first heat exchanger in sequence via a pipeline before exiting the cold box and connecting to an external flash steam recovery device; the liquid phase outlet at the bottom of the stripping tower is connected to the feed inlet in the middle of the demethanizer tower via a pipeline.

[0013] The methane-rich gas outlet at the bottom of the demethanizer passes through a pipeline sequentially through the fourth cold-side inlet of the second heat exchanger, the fourth hot-side outlet of the second heat exchanger, the fourth cold-side inlet of the first heat exchanger, and the fourth hot-side outlet of the first heat exchanger before exiting the cold box and connecting to an external methane-rich gas recovery device. The gas phase outlet at the top of the demethanizer passes through the demethanizer condenser and connects to the top inlet of the demethanizer separator. The liquid phase outlet at the bottom of the demethanizer separator is divided into two branches: one branch connects to the feed inlet at the top of the demethanizer, and the other branch connects to the inlet of the CO liquid pump.

[0014] The outlet of the CO liquid pump is divided into two branches. One branch is connected to the inlet in the middle of the demethanizer separator, and the other branch passes through the third cold side inlet of the second heat exchanger, the third hot side outlet of the second heat exchanger, the third cold side inlet of the first heat exchanger, and the third hot side outlet of the first heat exchanger before exiting the cold box and connecting to the external high-pressure CO product recovery device.

[0015] Furthermore, a throttling valve is installed on the pipeline between the liquid phase outlet at the bottom of the hydrogen-rich flash tank and the feed inlet of the stripping tower.

[0016] Furthermore, a throttling valve is installed on the pipeline between the bottom liquid phase outlet of the stripping tower and the middle feed inlet of the demethanizer tower.

[0017] Furthermore, a pressure regulating valve is installed on the pipeline between the CO liquid pump outlet and the middle inlet of the demethanizer separator.

[0018] Furthermore, a flow regulating valve is installed on the pipeline between the third hot-side outlet of the first heat exchanger and the external high-pressure CO product recovery device.

[0019] Furthermore, the nitrogen cycle refrigeration is specifically as follows:

[0020] The final stage outlet of the nitrogen cycle compressor is divided into two branches. The first branch passes sequentially through the second hot-side inlet of the first heat exchanger and the second cold-side outlet of the first heat exchanger before connecting to the hot-side inlet of the demethanizer reboiler. The cold-side outlet of the demethanizer reboiler is also divided into two branches. One branch passes sequentially through the fifth cold-side inlet of the second heat exchanger, the fifth hot-side outlet of the second heat exchanger, the fifth cold-side inlet of the first heat exchanger, and the fifth hot-side outlet of the first heat exchanger before connecting to the first stage inlet of the nitrogen cycle compressor. The other branch passes sequentially through the demethanizer condenser, the sixth cold-side inlet of the second heat exchanger, the sixth hot-side outlet of the second heat exchanger, the sixth cold-side inlet of the first heat exchanger, and the sixth hot-side outlet of the first heat exchanger before connecting to the second stage inlet of the nitrogen cycle compressor.

[0021] The second branch of the final stage outlet of the nitrogen cycle compressor passes sequentially through the boosting end of the nitrogen expander, the third hot-side inlet of the first heat exchanger, the third cold-side outlet of the first heat exchanger, and the expansion end of the nitrogen expander before connecting to the sixth cold-side inlet of the first heat exchanger.

[0022] Furthermore, a throttling valve is provided on the pipe connecting the cold-side outlet of the demethanizer reboiler to the fifth cold-side inlet of the second heat exchanger.

[0023] Furthermore, a throttling valve is installed on the pipe connecting the cold side outlet of the demethanizer reboiler to the demethanizer condenser.

[0024] Secondly, the present invention provides a method for preparing high-pressure CO using the apparatus for pressurized dehydrogenation and demethanization of a nitrogen-throttling expansion CO pump described in the first aspect, as follows:

[0025] The purified gas from upstream enters the first heat exchanger through a pipeline to cool down and then enters the stripping tower reboiler to provide heat for the stripping tower. After cooling down, the purified gas enters the hydrogen-rich flash tank for separation after being further cooled by the second heat exchanger.

[0026] The hydrogen-rich gas at the top of the hydrogen-rich flash tank is reheated by passing through the second heat exchanger and the first heat exchanger in sequence, and then exits the cold box as ambient temperature hydrogen-rich gas; the liquid phase at the bottom of the hydrogen-rich flash tank is throttled and then enters the stripping tower for dehydrogenation treatment.

[0027] The low-temperature flash steam at the top of the stripping tower is reheated by passing through the second heat exchanger and the first heat exchanger in sequence, and then exits the cold box as ambient temperature flash steam; the liquid phase at the bottom of the stripping tower is throttled and then enters the demethanizer for demethanization treatment.

[0028] The methane-rich gas at the bottom of the demethanizer passes through the second heat exchanger and the first heat exchanger in sequence to be reheated, and then exits the cold box as ambient temperature methane-rich gas; the gas phase at the top of the demethanizer enters the demethanizer condenser and is completely condensed before entering the demethanizer separator.

[0029] Part of the liquid phase at the bottom of the demethanizer separator is returned to the top of the demethanizer, and the other part is pressurized to the product pressure by the CO liquid pump and then reheated by the second heat exchanger and the first heat exchanger to obtain high-pressure CO product exiting the cold box.

[0030] The circulating nitrogen from the nitrogen cycle compressor is divided into two branches. One part of the circulating nitrogen is cooled by the first heat exchanger and then enters the reboiler of the demethanizer to provide heat for the demethanizer. The nitrogen flowing out of the cold side outlet of the demethanizer reboiler is throttled and then reheated by passing through the second and first heat exchangers before flowing back to the first-stage inlet of the nitrogen cycle compressor to provide cooling for the cold box. The other part is throttled and enters the demethanizer condenser to provide cooling for the vapor phase condensation at the top of the demethanizer. After being reheated by passing through the second and first heat exchangers, it flows back to the second-stage inlet of the nitrogen cycle compressor to provide cooling for the cold box.

[0031] Another portion of the circulating nitrogen from the nitrogen cycle compressor is pressurized at the booster end of the nitrogen expander and then enters the first heat exchanger for cooling. After that, it enters the expansion end of the nitrogen expander for expansion and cooling. It then merges with the circulating nitrogen from the second heat exchanger and enters the first heat exchanger to provide additional cooling capacity for the cold box.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] (1) This invention adopts an integrated scheme combining a nitrogen circulating compressor, a nitrogen expander, and a CO liquid pump, replacing the original complex multi-stage CO compression system. The device provided by this invention utilizes circulating nitrogen to condense the gaseous CO product at the top of the demethanizer into a liquid phase in the demethanizer condenser, and provides multi-temperature cooling capacity for the cold box, achieving system cooling capacity balance; simultaneously, the condensed liquid CO product is directly pressurized to the required high pressure by the CO liquid pump, and high-pressure CO product is obtained after reheating. This improvement significantly simplifies the system structure and improves the compactness and coordination of the process flow.

[0034] (2) The device provided by the present invention has advantages such as high compression efficiency, wide selection of models, and short delivery cycle, which facilitates rapid deployment and system optimization. At the same time, nitrogen, as an inert gas, has a higher level of process safety, and the system operates more stably and reliably.

[0035] (3) The cost of CO liquid pump equipment is significantly lower than that of multi-stage compressors, with a compact structure and convenient maintenance. Based on its low investment cost, a flexible "one-in-use, one-out-of-service" operation scheme can be configured, enabling non-stop switching and maintenance of the unit, effectively ensuring production continuity and operational flexibility. Attached Figure Description

[0036] Figure 1 A schematic diagram of the process for preparing high-pressure CO using a nitrogen-throttling expansion CO pump for pressurized dehydrogenation and demethanization, provided by the present invention;

[0037] Figure 2 A schematic diagram of the preferred apparatus for producing high-pressure CO using a nitrogen-throttling expansion CO pump for pressurized dehydrogenation and demethanization, as provided in this embodiment;

[0038] Figure 3 This is a schematic diagram of nitrogen cycle refrigeration in the embodiment;

[0039] Figure 4 A partial schematic diagram of the demethanizing device in the embodiment;

[0040] In the diagram: 1. First heat exchanger; 2. Second heat exchanger; 3. Stripper reboiler; 4. Hydrogen-rich flash tank; 5. Stripper; 6. Demethanizer; 7. Demethanizer reboiler; 8. Demethanizer condenser; 9. Demethanizer separator; 10. CO liquid pump; 11. Nitrogen cycle compressor; 12. Nitrogen expander. Detailed Implementation

[0041] The present invention will be further described and illustrated below with reference to the accompanying drawings and specific embodiments. The technical features of each embodiment of the present invention can be combined accordingly, provided that there is no mutual conflict.

[0042] In the description of this invention, it should be understood that the terms "first" and "second" are used only for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" and "second" may explicitly or implicitly include at least one of those features.

[0043] In the description of this invention, it should be understood that the terms “low temperature”, “normal temperature”, “low pressure”, and “high pressure” refer to the temperature or pressure relative to the same medium in the same passage, and should not be construed as indicating or implying relative importance or implicitly specifying the temperature and pressure values ​​of the indicated technical features.

[0044] like Figure 1 As shown in the preferred embodiment of the present invention, this embodiment provides an apparatus for producing high-pressure CO by pressurized dehydrogenation and demethanization using a nitrogen-throttling expansion CO pump. The apparatus includes a nitrogen cycle compressor 11, and is housed within a cold box, comprising a first heat exchanger 1, a second heat exchanger 2, a stripping tower reboiler 3, a hydrogen-rich flash tank 4, a stripping tower 5, a demethanizing tower 6, a demethanizing tower reboiler 7, a demethanizing tower condenser 8, a demethanizing tower separator 9, a CO liquid pump 10, and a nitrogen expander 12. The nitrogen expander 12 includes a pressurization end and an expansion end. The expansion end is the core part of the nitrogen expander 12, primarily reducing the pressure to lower the nitrogen gas temperature and generate cooling. The pressurization end increases the nitrogen pressure, resulting in a higher pressure entering the expansion end, a larger expansion ratio per unit working fluid, and thus a greater temperature drop and cooling capacity, significantly improving the energy efficiency of the entire expander and even the air separation unit.

[0045] In the apparatus provided by this invention, purified gas from upstream passes sequentially through a first heat exchanger 1, a stripping tower reboiler 3, and a second heat exchanger 2 for cooling before entering a hydrogen-rich flash tank 4. The liquid phase at the bottom of the hydrogen-rich flash tank 4 enters a stripping tower 5 for further separation. The liquid phase at the bottom of the stripping tower 5 enters a demethanizer 6 for demethanization treatment. The gas phase at the top of the demethanizer 6 is completely condensed by the demethanizer condenser 8 and then enters a demethanizer separator 9. The liquid phase at the bottom of the demethanizer separator 9 is pressurized by a CO liquid pump 10 and then sequentially passes through a second heat exchanger 2 and a first heat exchanger 1 for reheating, resulting in high-pressure CO product exiting the cold box, which is connected to an external high-pressure CO product recovery device. The main function of the CO liquid pump 10 is to further pressurize the liquid CO from the bottom of the demethanizer separator 9 to the pressure required for the product, replacing the conventional CO multi-stage circulating compressor for pressurizing the CO product. This system can improve system compression efficiency, reduce equipment cost investment, reduce the complexity of the compression system, and shorten the project construction cycle.

[0046] The connection methods of the various components in the apparatus for producing high-pressure CO using a nitrogen-throttling expansion CO pump for pressurized dehydrogenation and demethanization provided in this embodiment are described in detail below:

[0047] In the apparatus provided in this embodiment, the first hot-side inlet of the first heat exchanger 1 receives purified gas from upstream, and the first cold-side outlet of the first heat exchanger 1 is connected to the hot-side inlet of the stripping tower reboiler 3 via a pipeline. The cold-side outlet of the stripping tower reboiler 3 is connected to the two-phase inlet of the hydrogen-rich flash tank 4 via a pipeline, passing sequentially through the first hot-side inlet and the first cold-side outlet of the second heat exchanger 2.

[0048] In the device provided in this embodiment, the hydrogen-rich gas outlet of the hydrogen-rich flash tank 4 is provided with a pipeline that sequentially passes through the first cold side inlet of the second heat exchanger 2, the first hot side outlet of the second heat exchanger 2, the first cold side inlet of the first heat exchanger 1, and the first hot side outlet of the first heat exchanger 1 before exiting the cold box and connecting to the external hydrogen-rich gas recovery device.

[0049] In the apparatus provided in this embodiment, the liquid phase outlet at the bottom of the hydrogen-rich flash tank 4 is connected to the feed inlet of the stripping tower 5 via a pipe equipped with a throttling valve. The flash vapor outlet at the top of the stripping tower 5 is connected via a pipe that sequentially passes through the second cold-side inlet of the second heat exchanger 2, the second hot-side outlet of the second heat exchanger 2, the second cold-side inlet of the first heat exchanger 1, and the second hot-side outlet of the first heat exchanger 1 before exiting the cold box and connecting to an external flash vapor recovery device.

[0050] In the apparatus provided in this embodiment, the liquid phase outlet at the bottom of the stripping tower 5 is connected to the feed inlet in the middle of the demethanizer 6 via a pipe equipped with a throttling valve. The methane-rich gas outlet at the bottom of the demethanizer 6 passes through the fourth cold-side inlet of the second heat exchanger 2, the fourth hot-side outlet of the second heat exchanger 2, the fourth cold-side inlet of the first heat exchanger 1, and the fourth hot-side outlet of the first heat exchanger 1 in sequence via a pipe before exiting the cold box and connecting to an external methane-rich gas recovery device.

[0051] In the device provided in this embodiment, such as Figure 4 As shown, the gas phase outlet pipe at the top of the demethanizer 6 connects to the top inlet of the demethanizer separator 9 after passing through the demethanizer condenser 8. The liquid phase outlet at the bottom of the demethanizer separator 9 is divided into two branches: one branch connects to the feed inlet at the top of the demethanizer 6, and the other branch connects to the inlet of the CO liquid pump 10. The outlet of the CO liquid pump 10 is divided into two branches: one branch connects to the inlet in the middle of the demethanizer separator 9, and the other branch passes sequentially through the third cold-side inlet of the second heat exchanger 2, the third hot-side outlet of the second heat exchanger 2, the third cold-side inlet of the first heat exchanger 1, and the third hot-side outlet of the first heat exchanger 1 before exiting the cold box and connecting to the external high-pressure CO product recovery device. It should be noted that, as a preferred embodiment of the present invention, a pressure regulating valve is provided on the pipe between the outlet of the CO liquid pump 10 and the inlet in the middle of the demethanizer separator 9 in this embodiment to indicate and control the pressure of the CO gas. A flow regulating valve is installed on the pipeline between the third hot-side outlet of the first heat exchanger 1 and the external high-pressure CO product recovery device to indicate and control the flow rate of the high-pressure CO product, specifically as follows: Figure 2 As shown.

[0052] In the apparatus provided in this embodiment, the nitrogen cycle compressor 11 provides nitrogen cycle refrigeration for the cold box, such as... Figure 3 As shown, the specific connection structure is as follows:

[0053] The final stage outlet of the nitrogen cycle compressor 11 is divided into two branches. The first branch passes sequentially through the second hot-side inlet and the second cold-side outlet of the first heat exchanger 1, and then connects to the hot-side inlet of the demethanizer reboiler 7. The cold-side outlet of the demethanizer reboiler 7 is also divided into two branches. One branch passes sequentially through the fifth cold-side inlet, the fifth hot-side outlet of the second heat exchanger 2, the fifth cold-side inlet and the fifth hot-side outlet of the first heat exchanger 1, and then connects to the first-stage inlet of the nitrogen cycle compressor 11. A throttling valve is installed on the pipe connecting the cold-side outlet of the demethanizer reboiler 7 and the fifth cold-side inlet of the second heat exchanger 2. Another branch of the cold side outlet of the demethanizer reboiler 7 passes sequentially through the demethanizer condenser 8, the sixth cold side inlet of the second heat exchanger 2, the sixth hot side outlet of the second heat exchanger 2, the sixth cold side inlet of the first heat exchanger 1, and the sixth hot side outlet of the first heat exchanger 1 before connecting to the secondary air inlet of the nitrogen cycle compressor 11. A throttling valve is provided on the pipe connecting the cold side outlet of the demethanizer reboiler 7 and the demethanizer condenser 8.

[0054] The second branch of the final stage outlet of the nitrogen cycle compressor 11 passes sequentially through the boosting end of the nitrogen expander 12, the third hot side inlet of the first heat exchanger 1, the third cold side outlet of the first heat exchanger 1, and the expansion end of the nitrogen expander 12 before connecting to the sixth cold side inlet of the first heat exchanger 1.

[0055] This embodiment also provides a method for preparing high-pressure CO using the above-mentioned device through nitrogen throttling expansion refrigeration, as follows:

[0056] (1) Pre-cooling and preliminary separation of purified gas

[0057] Purified gas (including CO and H2) from upstream enters the first heat exchanger 1 through a pipeline for cooling. The cooled purified gas then enters the stripping tower reboiler 3, serving as a heat source to provide heat to the bottom of the stripping tower 5, while being further cooled itself. Subsequently, the purified gas enters the second heat exchanger 2 for further cooling before entering the hydrogen-rich flash tank 4 for gas-liquid separation.

[0058] (2) Hydrogen separation and stripping dehydrogenation

[0059] In the hydrogen-rich flash tank 4, the hydrogen-rich gas at the top is reheated by passing through the second heat exchanger 2 and the first heat exchanger 1, resulting in ambient temperature hydrogen-rich gas exiting the cold box as the hydrogen-rich product. The liquid phase at the bottom of the hydrogen-rich flash tank 4 enters the stripping tower 5 after throttling. Inside the stripping tower 5, the rising gas desorbs most of the dissolved hydrogen from the liquid phase, performing dehydrogenation treatment.

[0060] The low-temperature flash vapor at the top of stripper 5 is reheated by passing through the second heat exchanger 2 and the first heat exchanger 1 in sequence, and then exits the cold box as ambient temperature flash vapor, which is output as the flash vapor product. The liquid phase at the bottom of stripper 5 enters the subsequent demethanization process.

[0061] (3) Demethanization distillation and high-pressure CO product preparation

[0062] The liquid phase at the bottom of stripping tower 5 is throttled and then enters demethanizing tower 6 for demethanization treatment. The methane-rich gas at the bottom of demethanizing tower 6 is then reheated by passing through the second heat exchanger 2 and the first heat exchanger 1 in sequence, and then exits the cold box as ambient temperature methane-rich gas, which is output as the methane-rich gas product.

[0063] The gas phase at the top of the demethanizer 6 enters the demethanizer condenser 8, where it is completely condensed into liquid by throttled low-temperature nitrogen gas and enters the demethanizer separator 9. Part of the liquid phase at the bottom of the separator 9 flows back to the top of the demethanizer 6, while the other part enters the crucial CO liquid pump 10, where it is directly pressurized to the product pressure. The pressurized high-pressure CO then passes sequentially through the second heat exchanger 2 and the first heat exchanger 1, and after reheating, the high-pressure CO product exits the cold box, yielding the final high-pressure CO product.

[0064] (4) Nitrogen circulation refrigeration

[0065] The circulating nitrogen from the nitrogen cycle compressor 11 is divided into two branches. One part of the circulating nitrogen is cooled by the first heat exchanger 1 and then enters the demethanizer reboiler 7, serving as a heat source to provide heat for the demethanizer 6. The nitrogen flowing out of the cold side outlet of the demethanizer reboiler 7 is partially throttled and then reheated by passing through the second heat exchanger 2 and the first heat exchanger 1 before flowing back to the first-stage inlet of the nitrogen cycle compressor 11 to provide cooling for the cold box. The other part is throttled and enters the demethanizer condenser 8 to provide cooling for the vapor-phase condensation at the top of the demethanizer 6. It then reheats by passing through the second heat exchanger 2 and the first heat exchanger 1 before flowing back to the second-stage inlet of the nitrogen cycle compressor 11 to provide cooling for the cold box.

[0066] Another portion of the circulating nitrogen from the nitrogen cycle compressor 11 is compressed to a higher pressure at the booster end of the nitrogen expander 12, then enters the first heat exchanger 1 for cooling, and then enters the expansion end of the nitrogen expander 12 for expansion and refrigeration, providing additional cooling capacity to the cold box. The expanded nitrogen merges with the circulating nitrogen from the second heat exchanger 2 and then enters the first heat exchanger 1.

[0067] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all technical solutions obtained through equivalent substitution or transformation fall within the protection scope of the present invention.

Claims

1. An apparatus for producing high-pressure CO by pressurized dehydrogenation and demethanization using a nitrogen-throttling expansion CO pump, characterized in that, It includes a nitrogen cycle compressor (11) and a first heat exchanger (1), a second heat exchanger (2), a stripper reboiler (3), a hydrogen-rich flash tank (4), a stripper (5), a demethanizer (6), a demethanizer reboiler (7), a demethanizer condenser (8), a demethanizer separator (9), a CO liquid pump (10), and a nitrogen expander (12). The purified gas from upstream passes through the first heat exchanger (1), the stripper reboiler (3), and the second heat exchanger (2) in sequence to cool down before entering the hydrogen-rich flash tank (4); the liquid phase at the bottom of the hydrogen-rich flash tank (4) enters the stripper (5) for further separation; the liquid phase at the bottom of the stripper (5) enters the demethanizer (6) for demethanization treatment; the gas phase at the top of the demethanizer (6) is completely condensed by the demethanizer condenser (8) and then enters the demethanizer separator (9); the liquid phase at the bottom of the demethanizer separator (9) is pressurized by the CO liquid pump (10) and then passes through the second heat exchanger (2) and the first heat exchanger (1) in sequence for reheating to obtain high-pressure CO product exiting the cold box; The nitrogen cycle compressor (11) provides nitrogen cycle refrigeration for the cold box. A portion of the circulating nitrogen is cooled by the first heat exchanger (1) and enters the demethanizer reboiler (7) to provide heat to the demethanizer (6). It is then divided into two paths. One path is throttled and passes through the second heat exchanger (2) and the first heat exchanger (1) to participate in the heat exchange balance of the cold box. The other path is throttled and enters the demethanizer condenser (8) to provide cooling. Another portion of the circulating nitrogen is expanded and cooled by the nitrogen expander (12) to provide additional cooling for the cold box.

2. The apparatus for producing high-pressure CO by pressurized dehydrogenation and demethane using a nitrogen-throttling expansion CO pump according to claim 1, characterized in that, The specific structure is as follows: The first hot side inlet of the first heat exchanger (1) receives purified gas from upstream, and the first cold side outlet of the first heat exchanger (1) is connected to the hot side inlet of the stripping tower reboiler (3) through a pipeline; the cold side outlet of the stripping tower reboiler (3) is connected to the two-phase inlet of the hydrogen-rich flash tank (4) through a pipeline, passing sequentially through the first hot side inlet of the second heat exchanger (2) and the first cold side outlet of the second heat exchanger (2); The hydrogen-rich flash tank (4) has its hydrogen-rich outlet passing through the first cold-side inlet of the second heat exchanger (2), the first hot-side outlet of the second heat exchanger (2), the first cold-side inlet of the first heat exchanger (1), and the first hot-side outlet of the first heat exchanger (1) before exiting the cold box and connecting to an external hydrogen-rich recovery device. The liquid phase outlet at the bottom of the hydrogen-rich flash tank (4) is connected to the feed inlet of the stripping tower (5) through a pipeline. The flash steam outlet at the top of the stripping tower (5) passes through the second cold side inlet of the second heat exchanger (2), the second hot side outlet of the second heat exchanger (2), the second cold side inlet of the first heat exchanger (1), and the second hot side outlet of the first heat exchanger (1) in sequence via a pipeline before exiting the cold box and connecting to the flash steam recovery device in the outside; the liquid phase outlet at the bottom of the stripping tower (5) is connected to the feed port in the middle of the demethanizer tower (6) via a pipeline; The methane-rich gas outlet at the bottom of the demethanizer (6) passes through the fourth cold-side inlet of the second heat exchanger (2), the fourth hot-side outlet of the second heat exchanger (2), the fourth cold-side inlet of the first heat exchanger (1), and the fourth hot-side outlet of the first heat exchanger (1) before exiting the cold box and connecting to the external methane-rich gas recovery device. The gas phase outlet at the top of the demethanizer (6) passes through the demethanizer condenser (8) and connects to the top inlet of the demethanizer separator (9). The liquid phase outlet at the bottom of the demethanizer separator (9) is divided into two branches, one branch connecting to the feed inlet at the top of the demethanizer (6), and the other branch connecting to the inlet of the CO liquid pump (10). The outlet of the CO liquid pump (10) is divided into two branches. One branch is connected to the inlet in the middle of the demethanizer separator (9). The other branch passes through the third cold side inlet of the second heat exchanger (2), the third hot side outlet of the second heat exchanger (2), the third cold side inlet of the first heat exchanger (1), and the third hot side outlet of the first heat exchanger (1) before exiting the cold box and connecting with the external high-pressure CO product recovery device.

3. The apparatus for producing high-pressure CO by pressurized dehydrogenation and demethanization using a nitrogen-throttling expansion CO pump according to claim 2, characterized in that, A throttling valve is installed on the pipeline between the bottom liquid phase outlet of the hydrogen-rich flash tank (4) and the feed inlet of the stripping tower (5).

4. The apparatus for preparing high-pressure CO by pressurized dehydrogenation and demethanization using a nitrogen-throttling expansion CO pump according to claim 2, characterized in that, A throttling valve is installed on the pipeline between the bottom liquid outlet of the stripping tower (5) and the middle feed inlet of the demethanizer tower (6).

5. The apparatus for producing high-pressure CO by pressurized dehydrogenation and demethanization using a nitrogen-throttling expansion CO pump according to claim 2, characterized in that, A pressure regulating valve is provided on the pipeline between the outlet of the CO liquid pump (10) and the middle inlet of the demethanizer separator (9).

6. The apparatus for producing high-pressure CO by pressurized dehydrogenation and demethanization using a nitrogen-throttling expansion CO pump according to claim 2, characterized in that, A flow regulating valve is installed on the pipeline between the third hot side outlet of the first heat exchanger (1) and the external high-pressure CO product recovery device.

7. The apparatus for producing high-pressure CO by pressurized dehydrogenation and demethanization using a nitrogen-throttling expansion CO pump according to claim 2, characterized in that, The nitrogen cycle refrigeration is described in the following details: The final stage outlet of the nitrogen cycle compressor (11) is divided into two branches. The first branch passes through the second hot side inlet of the first heat exchanger (1) and the second cold side outlet of the first heat exchanger (1) in sequence, and then connects to the hot side inlet of the demethanizer reboiler (7). The cold side outlet of the demethanizer reboiler (7) is also divided into two branches. One branch passes through the fifth cold side inlet of the second heat exchanger (2), the fifth hot side outlet of the second heat exchanger (2), the fifth cold side inlet of the first heat exchanger (1), and the fifth hot side outlet of the first heat exchanger (1) in sequence, and then connects to the first stage inlet of the nitrogen cycle compressor (11). The other branch passes through the demethanizer condenser (8), the sixth cold side inlet of the second heat exchanger (2), the sixth hot side outlet of the second heat exchanger (2), the sixth cold side inlet of the first heat exchanger (1), and the sixth hot side outlet of the first heat exchanger (1) in sequence, and then connects to the second stage inlet of the nitrogen cycle compressor (11). The second branch of the final stage outlet of the nitrogen cycle compressor (11) passes sequentially through the boosting end of the nitrogen expander (12), the third hot side inlet of the first heat exchanger (1), the third cold side outlet of the first heat exchanger (1), and the expansion end of the nitrogen expander (12) before connecting to the sixth cold side inlet of the first heat exchanger (1).

8. The apparatus for producing high-pressure CO by pressurized dehydrogenation and demethanization using a nitrogen-throttling expansion CO pump according to claim 7, characterized in that, A throttling valve is provided on the pipe connecting the cold side outlet of the demethanizer reboiler (7) to the fifth cold side inlet of the second heat exchanger (2).

9. The apparatus for producing high-pressure CO by pressurized dehydrogenation and demethanization using a nitrogen-throttling expansion CO pump according to claim 7, characterized in that, A throttling valve is provided on the pipe connecting the cold side outlet of the demethanizer reboiler (7) to the demethanizer condenser (8).

10. A method for preparing high-pressure CO using the apparatus for pressurized dehydrogenation and demethanization of a nitrogen-throttling expansion CO pump according to any one of claims 1 to 9, characterized in that, Specifically as follows: The purified gas from upstream enters the first heat exchanger (1) through a pipeline to cool down and then enters the stripping tower reboiler (3) to provide heat for the stripping tower (5); the cooled purified gas enters the hydrogen-rich flash tank (4) for separation after being further cooled by the second heat exchanger (2). The hydrogen-rich gas at the top of the hydrogen-rich flash tank (4) is reheated by passing through the second heat exchanger (2) and the first heat exchanger (1) in sequence, and then the ambient temperature hydrogen-rich gas exits the cold box; the liquid phase at the bottom of the hydrogen-rich flash tank (4) is throttled and then enters the stripping tower (5) for dehydrogenation treatment. The low-temperature flash steam at the top of the stripping tower (5) is reheated by passing through the second heat exchanger (2) and the first heat exchanger (1) in sequence, and then exits the cold box as ambient temperature flash steam; the liquid phase at the bottom of the stripping tower (5) is throttled and then enters the demethanizing tower (6) for demethanizing treatment. The methane-rich gas at the bottom of the demethanizer (6) is reheated by passing through the second heat exchanger (2) and the first heat exchanger (1) in sequence, and then exits the cold box as ambient temperature methane-rich gas; the gas phase at the top of the demethanizer (6) enters the demethanizer condenser (8) and is completely condensed before entering the demethanizer separator (9). A portion of the liquid phase at the bottom of the demethanizer separator (9) is returned to the top of the demethanizer (6), and the other portion is pressurized to the product pressure by the CO liquid pump (10) and then reheated by the second heat exchanger (2) and the first heat exchanger (1) to obtain high-pressure CO product exiting the cold box. The circulating nitrogen from the nitrogen cycle compressor (11) is divided into two branches. One part of the circulating nitrogen is cooled by the first heat exchanger (1) and then enters the demethanizer reboiler (7) to provide heat for the demethanizer (6). The nitrogen flowing out from the cold side outlet of the demethanizer reboiler (7) is throttled and then reheated by the second heat exchanger (2) and the first heat exchanger (1) before flowing back to the first-stage inlet of the nitrogen cycle compressor (11) to provide cooling for the cold box. The other part is throttled and then enters the demethanizer condenser (8) to provide cooling for the vapor phase condensation at the top of the demethanizer (6). After being reheated by the second heat exchanger (2) and the first heat exchanger (1) in sequence, it flows back to the second-stage inlet of the nitrogen cycle compressor (11) to provide cooling for the cold box. Another portion of the circulating nitrogen from the nitrogen cycle compressor (11) is pressurized at the pressurization end of the nitrogen expander (12) and then enters the first heat exchanger (1) for cooling. After that, it enters the expansion end of the nitrogen expander (12) for expansion and cooling. It merges with the circulating nitrogen from the second heat exchanger (2) and then enters the first heat exchanger (1) to provide additional cooling capacity for the cold box.

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