Nitrogen cycle refrigeration CO washing demethanization CO cryogenic separation device and method

Abstract

The invention discloses a CO cryogenic separation device and method for nitrogen cycle refrigeration and CO washing demethanization, and belongs to the technical field of cryogenic separation. The device comprises an adsorption purification system, a CO cryogenic separation cold box system and a nitrogen refrigeration cycle system which are connected in sequence, purified gas from which impurities are removed by the adsorption purification system enters a CO cryogenic separation cold box system for rectification separation; cO-rich liquid separated in the denitrification tower of the CO cryogenic separation cold box system enters the top of the CO washing and demethanizing tower to serve as washing liquid to replace a condenser at the top of the CO washing and demethanizing tower; the nitrogen refrigeration cycle system guarantees cold and heat balance cycle in the rectification separation process of the CO cryogenic separation cold box system and provides cold energy for the first heat exchanger and the second heat exchanger.

Description

Technical Field

[0001] The invention belongs to the technical field of cryogenic separation, and in particular relates to a nitrogen cycle refrigeration CO washing demethanization CO cryogenic separation device and method. Background Art

[0002] Synthetic Gas is a combination of various gases, the main components of which include hydrogen, carbon monoxide, carbon dioxide, water vapor, nitrogen and methane. Synthetic gas is a product produced by coal gas conversion or natural gas conversion, and is also the raw gas in various chemical processes. Before the syngas enters various devices, it needs to be separated and processed. Depending on the situation, the separation methods and technologies used are also different.

[0003] As a major technical means of syngas separation, cryogenic separation has the advantages of large-scale, small footprint, low unit energy consumption, simple operation, and mature and stable system. CO cryogenic separation technology is a process technology that achieves separation under low temperature conditions by utilizing the solubility differences of different component gases in cryogenic media. Its working principle is to cool the mixed gas in a cryogenic medium to near the dew point, at which time some gas components will condense into liquid, thereby achieving separation from other components, and then by heating, the condensed liquid is vaporized and mixed with the uncondensed gas, thereby achieving the purpose of recovery. This technology is usually used to extract CO products from syngas by cryogenic separation and distillation, which can be used to synthesize acetic acid, ethylene glycol, ethanol, polycarbonate and other substances.

[0004] The existing CO scrubbing and demethanizing towers are equipped with condensers at the top, which can condense part of the gas at the top of the tower into liquid, effectively reducing the temperature at the top of the tower, thereby improving the separation efficiency in the tower. However, the process using this setting is more complicated and consumes more energy, so it is urgent to develop a nitrogen cycle refrigeration CO scrubbing and demethanizing CO deep cold separation device with simplified process, energy saving and emission reduction. Summary of the invention

[0005] The object of the present invention is to solve the deficiencies in the prior art and to provide a nitrogen cycle refrigeration CO washing demethanization CO deep cold separation device and method.

[0006] The specific technical solutions adopted by the present invention are as follows:

[0007] In the first aspect, the present invention provides a nitrogen cycle refrigeration CO2 washing demethanization CO2 cryogenic separation device, comprising an adsorption purification system, a CO2 cryogenic separation cold box system and a nitrogen refrigeration cycle system connected in sequence; the purified gas from which impurities are removed by the adsorption purification system enters the CO2 cryogenic separation cold box system for distillation separation; the CO2 cryogenic separation cold box system comprises a main heat exchanger, a secondary heat exchanger, a stripping tower, a denitrification tower, a CO2 washing demethanizer, a condenser and a hydrogen-rich gas flash tank, wherein the CO2-rich liquid separated in the denitrification tower enters the top of the CO2 washing demethanizer as a washing liquid, replacing the condenser at the top of the CO2 washing demethanizer; the nitrogen refrigeration cycle system ensures the cold and heat balance cycle of the distillation separation process of the CO2 cryogenic separation cold box system, and provides cooling capacity for the main heat exchanger and the secondary heat exchanger.

[0008] Preferably, the connection mode in the CO deep cold separation cold box system is as follows:

[0009] The main heat exchanger and the secondary heat exchanger are both provided with a plurality of hot side inlets, cold side outlets, cold side inlets, and hot side outlets;

[0010] The first hot side inlet of the main heat exchanger on the main heat exchanger is connected to the purified gas from the adsorption purification system, and the first cold side outlet of the main heat exchanger is connected to the inlet of the hydrogen-rich gas flash tank after passing through the first hot side inlet of the secondary heat exchanger and the first cold side outlet of the secondary heat exchanger in sequence; the hydrogen-rich gas outlet of the hydrogen-rich gas flash tank passes through the first cold side inlet of the secondary heat exchanger, the first hot side outlet of the secondary heat exchanger, the first cold side inlet of the main heat exchanger, and the first hot side outlet of the main heat exchanger in sequence, and then exits the CO deep cold separation cold box system, and is connected to the external hydrogen-rich gas recovery device;

[0011] The liquid phase outlet at the bottom of the hydrogen-rich flash tank is connected to the feed port of the stripping tower through a pipeline; the flash steam outlet at the top of the stripping tower passes through the second cold side inlet of the secondary heat exchanger, the second hot side outlet of the secondary heat exchanger, the second cold side inlet of the main heat exchanger, the second hot side outlet of the main heat exchanger, and then exits the CO deep cold separation cold box system, and is connected to the external flash steam recovery device; the liquid phase outlet at the bottom of the stripping tower is divided into two branches, one of which is connected to the feed port of the denitrification tower through a pipeline for distillation separation; the other branch is refluxed to the bottom of the stripping tower after reheating through the secondary heat exchanger;

[0012] The nitrogen-rich gas outlet at the top of the denitrification tower is connected to the condenser and is divided into two branches. One branch passes through the third cold side inlet of the secondary heat exchanger, the third hot side outlet of the secondary heat exchanger, the third cold side inlet of the main heat exchanger, and the third hot side outlet of the main heat exchanger in sequence, and then exits the CO deep cold separation cold box system, and is connected to the external nitrogen-rich gas recovery device; the other branch refluxes to the top of the denitrification tower; the liquid phase outlet at the bottom of the denitrification tower is divided into two branches, one branch is connected to the liquid phase inlet at the bottom of the CO washing demethanizer through a pipeline provided with a throttle valve, and the other branch is refluxed to the bottom of the denitrification tower after reheating through the secondary heat exchanger; the liquid phase outlet in the middle of the denitrification tower is connected to the washing liquid inlet in the middle of the CO washing demethanizer through a pipeline provided with a throttle valve;

[0013] The CO gas outlet at the top of the CO washing and demethanizing tower passes through the fourth cold side inlet of the secondary heat exchanger, the fourth hot side outlet of the secondary heat exchanger, the fourth cold side inlet of the main heat exchanger, and the fourth hot side outlet of the main heat exchanger in sequence, and then exits the CO deep cold separation cold box system, and is connected to the external CO product gas recovery device; the methane-rich gas outlet at the bottom of the CO washing and demethanizing tower passes through the fifth cold side inlet of the secondary heat exchanger, the fifth hot side outlet of the secondary heat exchanger, the fifth cold side inlet of the main heat exchanger, and the fifth hot side outlet of the main heat exchanger in sequence, and then exits the CO deep cold separation cold box system, and is connected to the external methane-rich gas recovery device.

[0014] Furthermore, the connection method of the nitrogen refrigeration cycle system and the CO deep cold separation cold box system is as follows:

[0015] The medium-pressure nitrogen pressurized by the nitrogen refrigeration cycle system passes through the second hot side inlet of the main heat exchanger, the second cold side outlet of the main heat exchanger, the second hot side inlet of the secondary heat exchanger, and the second cold side outlet of the secondary heat exchanger in sequence, and is divided into two branches. The first branch is connected to the condenser through a pipeline provided with a throttle valve. After the second branch merges with the first branch, it passes through the sixth cold side inlet of the secondary heat exchanger, the sixth hot side outlet of the secondary heat exchanger, the sixth cold side inlet of the main heat exchanger, and the sixth hot side outlet of the main heat exchanger in sequence, and then returns to the nitrogen refrigeration cycle system to form a nitrogen refrigeration cycle.

[0016] Furthermore, a throttle valve is provided 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.

[0017] Preferably, the adsorption purification system uses molecular sieves to adsorb CO2, CH3OH, and H2O impurities in the upstream synthesis gas to obtain purified gas.

[0018] Preferably, the concentration of CO2 and CH3OH in the purified gas entering the CO cryogenic separation cold box system is less than 1 ppm.

[0019] Preferably, a first-stage compressor is used in the nitrogen refrigeration cycle system.

[0020] In a second aspect, the present invention provides a method for a CO deep cold separation device for washing and demethanization using the nitrogen cycle refrigeration described in the first aspect, characterized in that:

[0021] The purified gas after impurities are removed by the adsorption purification system enters the CO deep cold separation cold box system, and after being cooled twice by the main heat exchanger and the secondary heat exchanger in sequence, enters the hydrogen-rich flash tank for gas-liquid separation; the hydrogen-rich gas at the top of the hydrogen-rich flash tank passes through the secondary heat exchanger and the main heat exchanger in sequence to be reheated to room temperature before leaving the CO deep cold separation cold box system, and the liquid phase at the bottom of the hydrogen-rich flash tank enters the stripping tower for distillation separation after throttling;

[0022] The low-temperature flash steam at the top of the stripping tower passes through the secondary heat exchanger and the main heat exchanger in turn to be reheated to room temperature before leaving the CO deep cold separation cold box system; the liquid phase at the bottom of the stripping tower is throttled and cooled to become a medium-pressure CO-rich liquid and enters the denitrification tower for distillation separation;

[0023] The low-temperature nitrogen-rich gas at the top of the denitrification tower passes through the condenser, the secondary heat exchanger, and the main heat exchanger in turn to be reheated to room-temperature nitrogen-rich gas and leave the CO deep-cold separation cold box system; the liquid in the middle of the denitrification tower is throttled and enters the CO washing demethanizer as a washing liquid, and the liquid in the middle of the denitrification tower is throttled and also enters the CO washing demethanizer for distillation;

[0024] The low-temperature CO gas at the top of the CO scrubbing demethanizer passes through the secondary heat exchanger and the main heat exchanger to be reheated to room temperature before leaving the CO deep cold separation cold box system; the methane-rich gas at the bottom of the CO scrubbing demethanizer passes through the secondary heat exchanger and the main heat exchanger to be reheated to room temperature after throttling and leaves the CO deep cold separation cold box system;

[0025] The medium-pressure nitrogen pressurized by the nitrogen refrigeration cycle compressor system passes through the main heat exchanger and the secondary heat exchanger in turn to cool down and then becomes liquid nitrogen and is divided into two paths. One path becomes low-pressure liquid nitrogen after throttling and enters the condenser to vaporize into low-pressure nitrogen. The other path merges with the low-pressure nitrogen vaporized by the condenser after throttling, passes through the secondary heat exchanger and the main heat exchanger in turn to provide cooling capacity. After the low-pressure nitrogen is reheated, it returns to the nitrogen refrigeration cycle compressor system for pressurization.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The cryogenic separation device provided by the present invention comprises an adsorption purification system, a CO cryogenic separation cold box system and a nitrogen refrigeration cycle system. No condenser is arranged at the top of the CO washing and demethanizing tower in the CO cryogenic separation cold box system, and the liquid phase (low methane, low nitrogen, high CO content) extracted from the denitrification tower is used as the tower top washing liquid of the CO washing and demethanizing tower to replace the condenser on the top of the CO washing and demethanizing tower. This improvement avoids the waste of throttling heat exchange energy at the top of the two towers at the same temperature due to the limitation of heat exchange temperature difference and the difficulty of complicating the compressor when the top temperature of the denitrification tower is higher than the top temperature of the CO washing and demethanizing tower. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The overall process schematic diagram of the cryogenic separation device provided in this embodiment;

[0029] Figure 2 Schematic diagram of the CO deep cold separation cold box system provided in this embodiment;

[0030] Figure 3 A schematic diagram of a nitrogen refrigeration cycle system process provided in this embodiment;

[0031] In the figure: adsorption purification system 1, CO deep cold separation cold box system 2, nitrogen refrigeration cycle system 3, main heat exchanger 4, secondary heat exchanger 5, stripping tower 6, denitrification tower 7, CO washing demethanizer 8, condenser 9, hydrogen-rich gas flash tank 10, first hot side inlet N1-1 of main heat exchanger, second hot side inlet N1-2 of main heat exchanger, first cold side outlet N2-1 of main heat exchanger, second cold side outlet N2-2 of main heat exchanger, first cold side inlet N3-1 of main heat exchanger, second cold side inlet N3-2 of main heat exchanger, third cold side inlet N3-3 of main heat exchanger, fourth cold side inlet N3-4 of main heat exchanger, fifth cold side inlet N3-5 of main heat exchanger, sixth cold side inlet N3-6 of main heat exchanger, first hot side outlet N4-1 of main heat exchanger, second hot side outlet N4-2 of main heat exchanger, second hot side outlet N4-3 of main heat exchanger, The fourth hot side outlet N4-4, the fifth hot side outlet N4-5 of the main heat exchanger, the sixth hot side outlet N4-6 of the main heat exchanger, the first hot side inlet N5-1 of the secondary heat exchanger, the second hot side inlet N5-2 of the secondary heat exchanger, the first cold side outlet N6-1 of the secondary heat exchanger, the second cold side outlet N6-2 of the secondary heat exchanger, the first cold side inlet N7-1 of the secondary heat exchanger, the second cold side inlet N7-2 of the secondary heat exchanger, the third cold side inlet N7-3 of the secondary heat exchanger, the fourth cold side inlet N7-4 of the secondary heat exchanger, the fifth cold side inlet N7-5 of the secondary heat exchanger, the sixth cold side inlet N7-6 of the secondary heat exchanger, the first hot side outlet N8-1 of the secondary heat exchanger, the second hot side outlet N8-2 of the secondary heat exchanger, the third hot side outlet N8-3 of the secondary heat exchanger, the fourth hot side outlet N8-4 of the secondary heat exchanger, the fifth hot side outlet N8-5 of the secondary heat exchanger, and the sixth hot side outlet N8-6 of the secondary heat exchanger. DETAILED DESCRIPTION

[0032] The present invention is further described and illustrated below in conjunction with the accompanying drawings and specific embodiments. The technical features of each embodiment of the present invention can be combined accordingly without conflicting with each other.

[0033] As a preferred embodiment of the present invention, this embodiment provides a nitrogen cycle refrigeration CO washing demethanization CO deep cold separation device. Figure 1 As shown, it includes an adsorption purification system 1, a CO deep cold separation cold box system 2 and a nitrogen refrigeration cycle system 3 which are connected in sequence.

[0034] The adsorption purification system 1 is used to remove impurities in the upstream synthesis gas. In this embodiment, the adsorption purification system 1 can use a molecular sieve to adsorb CO2, CH3OH, and H2O impurities in the upstream synthesis gas to obtain purified gas. The concentration of CO2 and CH3OH in the purified gas entering the CO deep cold separation cold box system 2 is less than 1ppm.

[0035] The CO deep cold separation cold box system 2 is used for distillation separation of the purified gas after impurities are removed by the adsorption purification system 1. The nitrogen refrigeration cycle system 3 ensures the cold and heat balance cycle of the distillation separation process of the CO deep cold separation cold box system 2, and provides cooling capacity for the main heat exchanger 4 and the secondary heat exchanger 5.

[0036] The CO deep cold separation cold box system 2 includes a main heat exchanger 4, a secondary heat exchanger 5, a stripping tower 6, a denitrification tower 7, a CO washing and demethanization tower 8, a condenser 9 and a hydrogen-rich flash tank 10, wherein the CO-rich liquid separated in the denitrification tower 7 enters the top of the CO washing and demethanization tower 8 as a washing liquid, replacing the condenser at the top of the CO washing and demethanization tower 8.

[0037] like Figure 2 As shown, the connection mode in the CO deep cold separation cold box system 2 is as follows:

[0038] In the present invention, a plurality of hot side inlets, cold side outlets, cold side inlets, and hot side outlets are provided on the main heat exchanger 4 and the secondary heat exchanger 5. The first hot side inlet N1-1 of the main heat exchanger on the main heat exchanger 4 is connected to the purified gas from the adsorption purification system 1, and the first cold side outlet N2-1 of the main heat exchanger is connected to the inlet of the hydrogen-rich gas flash tank 10 after passing through the first hot side inlet N5-1 of the secondary heat exchanger and the first cold side outlet N6-1 of the secondary heat exchanger in sequence. The hydrogen-rich gas outlet of the hydrogen-rich gas flash tank 10 passes through the first cold side inlet N7-1 of the secondary heat exchanger, the first hot side outlet N8-1 of the secondary heat exchanger, the first cold side inlet N3-1 of the main heat exchanger, and the first hot side outlet N4-1 of the main heat exchanger in sequence, and then exits the CO deep cold separation cold box system 2, and is connected to the external hydrogen-rich gas recovery device.

[0039] The liquid phase outlet at the bottom of the hydrogen-rich flash tank 10 is connected to the feed port of the stripping tower 6 through a pipeline provided with a throttle valve. The flash steam outlet at the top of the stripping tower 6 passes through the second cold side inlet N7-2 of the secondary heat exchanger, the second hot side outlet N8-2 of the secondary heat exchanger, the second cold side inlet N3-2 of the main heat exchanger, and the second hot side outlet N4-2 of the main heat exchanger, and then exits the CO deep cold separation cold box system 2, and is connected to the external flash steam recovery device. The liquid phase outlet at the bottom of the stripping tower 6 is divided into two branches, one of which is connected to the feed port of the denitrification tower 7 through a pipeline for distillation separation. The other branch is refluxed to the bottom of the stripping tower 6 after reheating through the secondary heat exchanger 5.

[0040] The nitrogen-rich gas outlet at the top of the denitrification tower 7 is connected to the condenser 9 and is divided into two branches. One branch passes through the third cold side inlet N7-3 of the secondary heat exchanger, the third hot side outlet N8-3 of the secondary heat exchanger, the third cold side inlet N3-3 of the main heat exchanger, and the third hot side outlet N4-3 of the main heat exchanger, and then exits the CO deep cold separation cold box system 2, and is connected to the external nitrogen-rich gas recovery device. The other branch refluxes to the top of the denitrification tower 7. The liquid phase outlet at the bottom of the denitrification tower 7 is divided into two branches, one branch is connected to the liquid phase inlet at the bottom of the CO washing demethanizer 8 through a pipeline provided with a throttle valve, and the other branch is refluxed to the bottom of the denitrification tower 7 after reheating through the secondary heat exchanger 5. The liquid phase outlet in the middle of the denitrification tower 7 is connected to the washing liquid inlet in the middle of the CO washing demethanizer 8 through a pipeline provided with a throttle valve.

[0041] The CO gas outlet at the top of the CO washing and demethanizing tower 8 passes through the fourth cold side inlet N7-4 of the secondary heat exchanger, the fourth hot side outlet N8-4 of the secondary heat exchanger, the fourth cold side inlet N3-4 of the main heat exchanger, and the fourth hot side outlet N4-4 of the main heat exchanger, and then exits the CO deep cold separation cold box system 2, and is connected to the external CO product gas recovery device. The methane-rich gas outlet at the bottom of the CO washing and demethanizing tower 8 passes through the fifth cold side inlet N7-5 of the secondary heat exchanger, the fifth hot side outlet N8-5 of the secondary heat exchanger, the fifth cold side inlet N3-5 of the main heat exchanger, and the fifth hot side outlet N4-5 of the main heat exchanger, and then exits the CO deep cold separation cold box system 2, and is connected to the external methane-rich gas recovery device.

[0042] like Figure 3 As shown, the low-temperature and normal-temperature nitrogen is transformed into medium-pressure and normal-temperature nitrogen by the nitrogen refrigeration cycle system 3 and enters the CO deep-cold separation cold box system 2. The connection method between the nitrogen refrigeration cycle system 3 and the CO deep-cold separation cold box system 2 is as follows:

[0043] The medium-pressure nitrogen pressurized by the nitrogen refrigeration cycle system 3 passes through the second hot side inlet N1-2 of the main heat exchanger, the second cold side outlet N2-2 of the main heat exchanger, the second hot side inlet N5-2 of the secondary heat exchanger, and the second cold side outlet N6-2 of the secondary heat exchanger in turn, and then is divided into two branches. The first branch is connected to the condenser 9 through a pipeline provided with a throttle valve. After the second branch merges with the first branch, it passes through the sixth cold side inlet N7-6 of the secondary heat exchanger, the sixth hot side outlet N8-6 of the secondary heat exchanger, the sixth cold side inlet N3-6 of the main heat exchanger, and the sixth hot side outlet N4-6 of the main heat exchanger in turn, and then returns to the nitrogen refrigeration cycle system 3 to form a nitrogen refrigeration cycle. In this embodiment, a primary compressor is used in the nitrogen refrigeration cycle system 3.

[0044] This embodiment also provides a separation process using the nitrogen cycle refrigeration CO scrubbing demethanization CO cryogenic separation device, which is as follows:

[0045] The purified gas after impurities are removed by the adsorption purification system 1 enters the CO deep cold separation cold box system 2, is cooled to -153°C by the main heat exchanger 4, is cooled to -176°C by the secondary heat exchanger 5, and then enters the hydrogen-rich flash tank 10 for gas-liquid separation.

[0046] The hydrogen-rich gas at the top of the hydrogen-rich flash tank 10 passes through the secondary heat exchanger 5 and the main heat exchanger 4 to return to room temperature, then leaves the CO deep cold separation cold box system 2 and is collected by the external hydrogen-rich gas recovery device. The liquid phase at the bottom of the hydrogen-rich flash tank 10 enters the stripping tower 6 for distillation separation after throttling.

[0047] The low-temperature flash steam at about -176°C at the top of the stripping tower 6 passes through the secondary heat exchanger 5 and the main heat exchanger 4 in turn, and then returns to room temperature and leaves the CO deep cold separation cold box system 2, and is collected by the external flash steam recovery device. The CO-rich liquid at -158°C at the bottom of the stripping tower 6 is throttled and cooled, and becomes a medium-pressure CO-rich liquid and enters the denitrification tower 7 for distillation separation.

[0048] The low-temperature nitrogen-rich gas at the top of the denitrification tower 7 passes through the condenser 9, the secondary heat exchanger 5, and the main heat exchanger 4 in turn to be reheated to room-temperature nitrogen-rich gas, leaving the CO deep cold separation cold box system 2, and is collected by the external nitrogen-rich gas recovery device. The liquid in the middle of the denitrification tower 7 has a high CO concentration and a low CH4 concentration, and then enters the CO washing demethanizer 8 as a washing liquid after throttling. The liquid in the middle of the denitrification tower 7 has a high CO concentration and a low CH4 concentration, and then enters the CO washing demethanizer 8 for distillation.

[0049] The low-temperature CO gas at the top of the CO washing and demethanizing tower 8 passes through the secondary heat exchanger 5 and the main heat exchanger 4 to be reheated to room temperature, then leaves the CO deep cold separation cold box system 2 and is collected by the external CO product gas recovery device. The methane-rich gas at the bottom of the CO washing and demethanizing tower 8 passes through the secondary heat exchanger 5 and the main heat exchanger 4 to be reheated to room temperature, then leaves the CO deep cold separation cold box system 2 and is collected by the external methane-rich gas recovery device.

[0050] The medium-pressure nitrogen pressurized by the nitrogen refrigeration cycle compressor system 3 passes through the main heat exchanger 4 and the secondary heat exchanger 5 in turn to be cooled and then becomes liquid nitrogen and is divided into two paths. One path becomes low-pressure liquid nitrogen after throttling and enters the condenser 9 to be vaporized into low-pressure nitrogen. The other path merges with the low-pressure nitrogen vaporized by the condenser 9 after throttling, passes through the secondary heat exchanger 5 and the main heat exchanger 4 in turn to provide cooling capacity, and the low-pressure nitrogen is returned to the nitrogen refrigeration cycle compressor system 3 for pressurization after being reheated.

[0051] The separation method in the present invention is mainly divided into three parts: the first part is a molecular sieve adsorption purification system 1, which removes CO2 and CH3OH in the synthesis gas to below 1ppm through the process principle of room temperature adsorption and high temperature analysis and enters the CO deep cold separation cold box system 2 to prevent the purified gas from solidifying and freezing in the CO deep cold separation cold box system 2. The second part performs dehydrogenation, denitrification and demethanization in the CO deep cold separation cold box system 2 to produce qualified CO product gas, and the liquid in the middle of the denitrification tower 7 is throttled and connected to the CO washing demethanizer 8 to replace the condenser on the top of the CO washing demethanizer 8. The third part is a nitrogen refrigeration cycle compressor system 3, which supplies pressurized circulating nitrogen to the CO deep cold separation cold box system 2 and pressurizes and circulates the low-pressure nitrogen after cooling, throttling and rewarming in the CO deep cold separation cold box system 2.

[0052] The cryogenic separation device eliminates the condenser at the top of the CO2 scrubbing and demethanizing tower, which increases the simplicity of the circulating refrigeration flow. At the same time, it gets rid of the differentiated demand for cold sources due to different distillation tower top temperatures, thus reducing the waste of heat exchange cooling capacity.

[0053] The above-described embodiment is only a preferred solution of the present invention, but it is not intended to limit the present invention. A person skilled in the relevant technical field may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. A nitrogen cycle refrigeration CO scrubbing demethanization CO cryogenic separation device, characterized in that: The invention comprises an adsorption purification system (1), a CO deep cold separation cold box system (2) and a nitrogen refrigeration circulation system (3) which are connected in sequence; the purified gas after impurities are removed by the adsorption purification system (1) enters the CO deep cold separation cold box system (2) for distillation separation; the CO deep cold separation cold box system (2) comprises a main heat exchanger (4), a secondary heat exchanger (5), a stripping tower (6), a denitrification tower (7), a CO washing and demethanization tower (8), a condenser (9) and a hydrogen-rich gas flash tank (10), wherein the CO-rich liquid separated in the denitrification tower (7) enters the top of the CO washing and demethanization tower (8) as a washing liquid, replacing the condenser at the top of the CO washing and demethanization tower (8); the nitrogen refrigeration circulation system (3) ensures the cold and heat balance cycle of the distillation separation process of the CO deep cold separation cold box system (2), and provides cooling capacity for the main heat exchanger (4) and the secondary heat exchanger (5).

2. The nitrogen cycle refrigeration CO scrubbing demethanization CO cryogenic separation device according to claim 1 is characterized in that: The internal connection mode of the CO deep cold separation cold box system (2) is as follows: The main heat exchanger (4) and the secondary heat exchanger (5) are provided with a plurality of hot side inlets, cold side outlets, cold side inlets, and hot side outlets; The first hot side inlet (N1-1) of the main heat exchanger on the main heat exchanger (4) is connected to the purified gas from the adsorption purification system (1), and the first cold side outlet (N2-1) of the main heat exchanger sequentially passes through the first hot side inlet (N5-1) of the secondary heat exchanger and the first cold side outlet (N6-1) of the secondary heat exchanger, and then communicates with the inlet of the hydrogen-rich gas flash tank (10); the hydrogen-rich gas outlet of the hydrogen-rich gas flash tank (10) sequentially passes through the first cold side inlet (N7-1) of the secondary heat exchanger, the first hot side outlet (N8-1) of the secondary heat exchanger, the first cold side inlet (N3-1) of the main heat exchanger, and the first hot side outlet (N4-1) of the main heat exchanger, and then exits the CO deep cold separation cold box system (2), and is connected to the external hydrogen-rich gas recovery device; The liquid phase outlet at the bottom of the hydrogen-rich gas flash tank (10) is connected to the feed port of the stripping tower (6) through a pipeline; the flash steam outlet at the top of the stripping tower (6) passes through the second cold side inlet (N7-2) of the secondary heat exchanger, the second hot side outlet (N8-2) of the secondary heat exchanger, the second cold side inlet (N3-2) of the main heat exchanger, and the second hot side outlet (N4-2) of the main heat exchanger in sequence, and then exits the CO deep cold separation cold box system (2), and is connected to the external flash steam recovery device; the liquid phase outlet at the bottom of the stripping tower (6) is divided into two branches, one of which is connected to the feed port of the denitrification tower (7) through a pipeline for distillation separation; the other branch is reheated through the secondary heat exchanger (5) and then refluxed to the bottom of the stripping tower (6); The nitrogen-rich gas outlet at the top of the denitrification tower (7) is connected to the condenser (9) and then divided into two branches. One branch passes through the third cold side inlet (N7-3) of the secondary heat exchanger, the third hot side outlet (N8-3) of the secondary heat exchanger, the third cold side inlet (N3-3) of the main heat exchanger, and the third hot side outlet (N4-3) of the main heat exchanger in sequence, and then exits the CO deep cold separation cold box system (2), and is connected to the external nitrogen-rich gas recovery device; the other branch flows back to the top of the denitrification tower (7); the liquid phase outlet at the bottom of the denitrification tower (7) is divided into two branches, one branch is connected to the liquid phase inlet at the bottom of the CO washing demethanizer (8) through a pipeline provided with a throttle valve, and the other branch flows back to the bottom of the denitrification tower (7) after reheating through the secondary heat exchanger (5); the liquid phase outlet in the middle of the denitrification tower (7) is connected to the washing liquid inlet in the middle of the CO washing demethanizer (8) through a pipeline provided with a throttle valve; The CO gas outlet at the top of the CO washing and demethanizing tower (8) passes through the fourth cold side inlet (N7-4) of the secondary heat exchanger, the fourth hot side outlet (N8-4) of the secondary heat exchanger, the fourth cold side inlet (N3-4) of the main heat exchanger, and the fourth hot side outlet (N4-4) of the main heat exchanger in sequence, and then exits the CO deep cold separation cold box system (2), and is connected to an external CO product gas recovery device; the methane-rich gas outlet at the bottom of the CO washing and demethanizing tower (8) passes through the fifth cold side inlet (N7-5) of the secondary heat exchanger, the fifth hot side outlet (N8-5) of the secondary heat exchanger, the fifth cold side inlet (N3-5) of the main heat exchanger, and the fifth hot side outlet (N4-5) of the main heat exchanger in sequence, and then exits the CO deep cold separation cold box system (2), and is connected to an external methane-rich gas recovery device.

3. The nitrogen cycle refrigeration CO scrubbing demethanization CO cryogenic separation device according to claim 2 is characterized in that: The connection method of the nitrogen refrigeration cycle system (3) and the CO deep cold separation cold box system (2) is as follows: The medium-pressure nitrogen pressurized by the nitrogen refrigeration cycle system (3) passes through the second hot side inlet (N1-2) of the main heat exchanger, the second cold side outlet (N2-2) of the main heat exchanger, the second hot side inlet (N5-2) of the secondary heat exchanger, and the second cold side outlet (N6-2) of the secondary heat exchanger in sequence, and then is divided into two branches. The first branch is connected to the condenser (9) through a pipeline provided with a throttle valve. After the second branch merges with the first branch, it passes through the sixth cold side inlet (N7-6) of the secondary heat exchanger, the sixth hot side outlet (N8-6) of the secondary heat exchanger, the sixth cold side inlet (N3-6) of the main heat exchanger, and the sixth hot side outlet (N4-6) of the main heat exchanger in sequence, and then returns to the nitrogen refrigeration cycle system (3), thereby forming a nitrogen refrigeration cycle.

4. The nitrogen cycle refrigeration CO scrubbing demethanization CO cryogenic separation device according to claim 2 is characterized in that: A throttle valve is provided on the pipeline between the liquid phase outlet at the bottom of the hydrogen-rich flash tank (10) and the feed inlet of the stripping tower (6).

5. The nitrogen cycle refrigeration CO scrubbing demethanization CO cryogenic separation device according to claim 1 is characterized in that: The adsorption purification system (1) uses a molecular sieve to adsorb CO2, CH3OH, and H2O impurities in the upstream synthesis gas to obtain purified gas.

6. The nitrogen cycle refrigeration CO scrubbing demethanization CO cryogenic separation device according to claim 1, characterized in that: The concentrations of CO2 and CH3OH in the purified gas entering the CO cryogenic separation cold box system (2) are less than 1 ppm.

7. The nitrogen cycle refrigeration CO scrubbing demethanization CO cryogenic separation device according to claim 1, characterized in that: The nitrogen refrigeration cycle system (3) uses a first-stage compressor.

8. A method for utilizing the nitrogen cycle refrigeration CO scrubbing demethanization CO cryogenic separation device according to any one of claims 1 to 7, characterized in that: The details are as follows: The purified gas from which impurities have been removed by the adsorption purification system (1) enters the CO deep cold separation cold box system (2), passes through the main heat exchanger (4) and the secondary heat exchanger (5) for cooling twice, and then enters the hydrogen-rich flash tank (10) for gas-liquid separation; the hydrogen-rich gas at the top of the hydrogen-rich flash tank (10) passes through the secondary heat exchanger (5) and the main heat exchanger (4) for returning to room temperature, and then leaves the CO deep cold separation cold box system (2); the liquid phase at the bottom of the hydrogen-rich flash tank (10) enters the stripping tower (6) for distillation separation after throttling; The low-temperature flash steam at the top of the stripping tower (6) passes through the secondary heat exchanger (5) and the main heat exchanger (4) in sequence to be restored to room temperature and then leaves the CO deep cold separation cold box system (2); the liquid phase at the bottom of the stripping tower (6) is throttled and cooled to become a medium-pressure CO-rich liquid and enters the denitrification tower (7) for distillation separation; The low-temperature nitrogen-rich gas at the top of the denitrification tower (7) passes through the condenser (9), the secondary heat exchanger (5), and the main heat exchanger (4) in sequence to be reheated to become room-temperature nitrogen-rich gas and leave the CO deep-cold separation cold box system (2); the liquid in the middle of the denitrification tower (7) is throttled and enters the CO washing demethanizer (8) as a washing liquid, and the liquid in the middle of the denitrification tower (7) is also throttled and enters the CO washing demethanizer (8) for distillation; The low-temperature CO gas at the top of the CO scrubbing and demethanizing tower (8) passes through the secondary heat exchanger (5) and the main heat exchanger (4) in sequence to be restored to room temperature before leaving the CO deep cold separation cold box system (2); the methane-rich gas at the bottom of the CO scrubbing and demethanizing tower (8) passes through the secondary heat exchanger (5) and the main heat exchanger (4) in sequence to be restored to room temperature before leaving the CO deep cold separation cold box system (2); The medium-pressure nitrogen pressurized by the nitrogen refrigeration cycle compressor system (3) passes through the main heat exchanger (4) and the secondary heat exchanger (5) in turn to be cooled and then becomes liquid nitrogen and is divided into two paths. One path is throttled to become low-pressure liquid nitrogen and enters the condenser (9) to be vaporized into low-pressure nitrogen. The other path is throttled to merge with the low-pressure nitrogen vaporized by the condenser (9) and passes through the secondary heat exchanger (5) and the main heat exchanger (4) in turn to provide cooling capacity. The low-pressure nitrogen is restored to its temperature and then returns to the nitrogen refrigeration cycle compressor system (3) for pressurization.

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