A low-temperature solid adsorption temperature swing pressure swing coupling method

Abstract

This invention provides a temperature- and pressure-swapping coupling method for low-temperature solid adsorption, belonging to the field of gas separation and purification technology. It can at least partially solve the problems of low adsorption capacity, incomplete desorption, and large adsorbent consumption in existing low-temperature solid adsorption processes. The invention includes: pretreating the gas to be treated to obtain a raw gas and introducing it into a pressure-resistant sealed reactor filled with solid adsorbent; during the adsorption stage, cooling to a preset adsorption temperature and pressurizing to a preset adsorption pressure via a heat exchange structure to adsorb the target gas; monitoring the target gas concentration at the purified gas outlet to determine adsorption termination; during the desorption stage, depressurizing to a preset desorption pressure and heating to a preset desorption temperature to desorb and collect the target gas; monitoring the target gas concentration at the desorbed gas outlet to determine desorption completion, and restoring the initial state to complete one adsorption-desorption cycle. This invention achieves coupled operation of temperature- and pressure-swapping processes, which can increase adsorption capacity by 40% to 70% and reduce adsorbent consumption and equipment size.

Description

Technical Field

[0001] This invention belongs to the field of gas separation and purification technology, specifically relating to a temperature- and pressure-switching coupling method for low-temperature solid adsorption. Background Technology

[0002] Low-temperature solid adsorption processes have attracted widespread attention in the field of gas separation and purification due to their advantages such as mild operating conditions, strong adsorbent selectivity, and no secondary pollution, especially in environmental applications such as carbon dioxide capture. However, the adsorption capacity of adsorbents is generally low at low temperatures, and this core technological bottleneck severely restricts the efficiency of industrial-scale application of this process. In large-scale industrial applications, to meet the requirements of gas throughput and separation efficiency, a large amount of adsorbent must be loaded, which not only significantly increases the reactor volume and equipment manufacturing cost, but also raises the costs of adsorbent procurement, replacement, and storage.

[0003] Currently, most industrially used low-temperature solid adsorption reactors employ a single temperature-switching adsorption method for their adsorption-desorption processes. These reactors are designed to passively rely on the intrinsic adsorption capacity of the adsorbent to complete gas adsorption, and cannot actively optimize the adsorption process through coordinated control of process parameters. In actual operation, the single temperature-switching adsorption method suffers from problems such as incomplete desorption, low adsorbent regeneration efficiency, and high energy consumption. To regenerate the adsorbent, external heating is required to raise its temperature and desorb the target gas. This not only consumes a large amount of energy but may also affect the structural stability of the adsorbent and shorten its service life.

[0004] While some pressure swing adsorption (PSA) processes are already applied to gas separation, the equipment design for these processes does not consider the adaptability to temperature-swinging adsorption, making them unsuitable for direct application in low-temperature solid adsorption scenarios. Furthermore, existing low-temperature adsorption reactors lack pressure control mechanisms, preventing the synergistic enhancement of adsorption capacity through pressure. Therefore, addressing the issues of low adsorption capacity and poor desorption efficiency in low-temperature solid adsorption through synergistic innovation in structural design and process technology has become a pressing technical challenge in this field. Summary of the Invention

[0005] The present invention aims to at least solve one of the technical problems existing in the prior art, and to provide a temperature- and pressure-switching coupling method for low-temperature solid adsorption.

[0006] To achieve the above objectives, the present invention provides a temperature- and pressure-swapping coupling method for low-temperature solid adsorption, comprising: The gas to be treated is pretreated to obtain raw gas, and the raw gas is passed into a pressure-resistant sealed reactor filled with solid adsorbent. The wall of the pressure-resistant sealed reactor is provided with a heat exchange structure. Adsorption stage: The temperature inside the pressure-resistant sealed reactor is controlled to a preset adsorption temperature through the heat exchange structure, and the internal pressure of the pressure-resistant sealed reactor is increased to a preset adsorption pressure. Under the synergistic effect of the preset adsorption temperature and the preset adsorption pressure, the solid adsorbent adsorbs the target gas in the raw gas; and the concentration of the target gas at the purified gas outlet is monitored. When the concentration of the target gas reaches a preset adsorption termination threshold, it is determined that the solid adsorbent has reached a saturated adsorption state, and the adsorption stage ends. Desorption stage: The pressure-resistant sealed reactor is depressurized to a preset desorption pressure, and the temperature inside the pressure-resistant sealed reactor is raised to a preset desorption temperature through the heat exchange structure. Under the synergistic effect of the preset desorption pressure and the preset desorption temperature, the target gas adsorbed on the surface of the solid adsorbent is desorbed, and the gas generated by desorption is discharged and collected. In addition, the concentration of the target gas at the desorbed gas outlet is monitored. When the concentration of the target gas drops to a preset desorption termination threshold, desorption is determined to be complete. The pressure-resistant sealed reactor is then restored to atmospheric pressure and cooled to the preset adsorption temperature, completing one adsorption-desorption cycle.

[0007] Furthermore, the preset adsorption pressure ranges from 0.5 to 1 MPa, and the preset desorption pressure ranges from 100 to 500 Pa.

[0008] Furthermore, the preset adsorption temperature ranges from 30 to 100°C, and the preset desorption temperature ranges from 100 to 200°C.

[0009] Furthermore, during the adsorption stage, the quantitative relationship between the equilibrium adsorption capacity of the solid adsorbent for the target gas and the preset adsorption pressure conforms to the Langmuir isotherm adsorption model: ; in, Indicates the equilibrium adsorption capacity. This indicates the monolayer saturated adsorption capacity of the solid adsorbent. This represents the Langmuir adsorption equilibrium constant in relation to temperature and adsorbent properties. This indicates the operating pressure inside the pressure-resistant sealed reactor.

[0010] Furthermore, the wall thickness of the pressure-resistant sealed reactor is determined according to the formula for calculating the wall thickness of an internal pressure cylinder: ; in, This indicates the calculated wall thickness of the cylinder. Indicates calculated pressure. Indicates the inner diameter of the cylinder. This represents the allowable stress of the material at the design temperature. Indicates the weld joint coefficient. This indicates the additional wall thickness.

[0011] Furthermore, the heat exchange structure is a jacketed heat exchange structure covering the outer wall of the pressure-resistant sealed reactor cylinder, and a closed heat exchange cavity is formed between the jacketed heat exchange structure and the cylinder. The heat exchange area of ​​the closed heat exchange cavity is calculated according to the following formula: ; in, This represents the heat transfer area of ​​the jacketed heat exchange structure. This indicates the outer diameter of the cylinder of the pressure-resistant sealed reactor. This indicates the effective height of the cylinder covered by the jacketed heat exchange structure; A guide plate is provided inside the sealed heat exchange cavity. Cooling medium is introduced during the adsorption stage to achieve cooling, and heating medium is introduced during the desorption stage to achieve heating.

[0012] Furthermore, during the desorption stage, depressurizing the pressure-resistant sealed reactor includes: First, the pressure inside the pressure-resistant sealed reactor is reduced to atmospheric pressure via the vent valve; The pressure inside the pressure-resistant sealed reactor is then reduced to the preset desorption pressure using a vacuum system.

[0013] Furthermore, the solid adsorbent is a low-temperature adsorption type solid adsorbent, including one of potassium-based adsorbents, solid amine adsorbents, amine-functionalized molecular sieves, or amine-functionalized metal-organic framework materials.

[0014] Furthermore, a gas distributor is also provided inside the pressure-resistant sealed reactor. The gas distributor is located below the packing layer of the solid adsorbent and is used to ensure that the raw material gas is evenly distributed before passing through the packing layer. The solid adsorbent filling layer has a detachable structure, the particle size of the solid adsorbent ranges from 0.5 to 5 mm, and the single-layer thickness of the filling layer ranges from 500 to 800 mm.

[0015] Furthermore, during the adsorption and desorption stages, the pressurization device, vacuum system, heat exchange system, and valves are controlled in a coordinated manner by the control system. During the adsorption stage, the empty tower flow velocity of the feed gas entering the pressure-resistant sealed reactor is 0.05–0.15 m / s; In the aforementioned adsorption-desorption cycle, the duration of the adsorption phase is 50–70 min, and the duration of the desorption phase is 100–140 min.

[0016] The beneficial effects of this invention are as follows: This invention designs the pressure-resistant sealed reactor to meet the pressure vessel standard, enabling the reactor to simultaneously perform temperature and pressure regulation.

[0017] During the adsorption stage, the pressure inside the reactor is increased to 0.5–1 MPa by pressurization. According to the Langmuir isothermal adsorption model, under the condition that the adsorption equilibrium constant is large at low temperature, the pressure increase can increase the equilibrium adsorption capacity of the adsorbent by 40%–70%, thereby significantly reducing the amount of adsorbent and the reactor volume for the same treatment scale.

[0018] During the desorption stage, by reducing the pressure inside the reactor to a low-pressure environment of 100-500 Pa and simultaneously increasing the temperature, the target gas adsorbed on the surface of the adsorbent is desorbed. Compared with the single temperature-variable desorption method, the desorption is more thorough, the adsorbent regeneration efficiency is higher, and the desorption energy consumption is lower.

[0019] Therefore, this invention achieves coupled operation of temperature and pressure switching processes, solving the problems of low adsorption capacity, poor desorption efficiency, and large adsorbent consumption in existing low-temperature solid adsorption processes. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the process flow of the low-temperature solid adsorption variable temperature and pressure coupling method in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the pressure-resistant sealed reactor in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram illustrating the relationship between adsorption pressure and adsorption capacity in Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the process flow of the temperature-switching-pressure coupling method for low-temperature solid adsorption in Embodiment 2 of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and beneficial effects of this application clearer, the following detailed description, in conjunction with the accompanying drawings and specific embodiments, further illustrates this application. It should be understood that the specific embodiments described in this specification are merely for explaining this application and are not intended to limit it.

[0022] Example 1 This embodiment provides a temperature-swing pressure-swing coupling method for low-temperature solid adsorption, using a potassium-based particulate adsorbent as the solid adsorbent to capture simulated flue gas containing carbon dioxide. See [link to relevant documentation]. Figure 1 and Figure 2 .

[0023] The pressurized cryogenic solid adsorption reactor used in this embodiment is a vertical cylindrical pressure-resistant and sealed pressure vessel made of 304 stainless steel. The overall structure includes a cylinder, upper head, lower head, jacketed heat exchange layer, adsorbent bed, gas distributor, pressure and temperature monitoring ports, and inlet and outlet flanges. The reactor is designed to meet the requirements for cryogenic-pressurized coordinated operation, and its sealing level meets the airtightness level specified in GB / T 150-2011 "Pressure Vessels" standard.

[0024] In this embodiment, the design parameters of the pressure-resistant sealed reactor are as follows: inner diameter of the cylinder is 300 mm, cylinder height is 1200 mm, design pressure is 1.0 MPa, and design temperature range is 0–300 °C, covering all operating conditions of low-temperature adsorption and temperature-induced desorption. The material is 304 stainless steel, with an allowable stress of 137 MPa at the design temperature, a weld joint coefficient of 0.85, double-sided butt welds, and 100% non-destructive testing. The corrosion allowance is 1 mm, and the wall thickness allowance is 0.3 mm.

[0025] The calculation of the cylinder wall thickness is based on the formula for calculating the wall thickness of an internally pressurized cylinder in GB 150.3-2011: ; in, Calculate the wall thickness for the cylinder, in mm; For pressure calculation, a value of 1.0 MPa is used; The inner diameter of the cylinder is taken as 300 mm. The allowable stress of the material at the design temperature is taken as 137 MPa; This is the welding joint coefficient, with a value of 0.85. This is the additional amount of total wall thickness, i.e. mm.

[0026] Substituting the above values ​​into the formula yields the following result: ; To ensure operational safety and structural stability, a wall thickness of 6mm was used, with a pressure rating of 1.5MPa, meeting the pressure requirements of GB 150 standard. The end caps are standard elliptical heads with the same wall thickness as the cylinder.

[0027] The pressure-resistant sealed reactor features a jacketed heat exchange structure on its wall. The jacket is a fully enclosed structure, covering the outer wall of the reactor cylinder, forming a sealed heat exchange chamber. A low-temperature refrigerant can be introduced into the chamber to cool the adsorption stage, or a high-temperature heat transfer medium can be introduced to raise the temperature during the desorption stage. The upper and lower ends of the jacket are respectively equipped with inlets and outlets for the refrigerant or heat transfer medium. Baffles are installed inside the sealed heat exchange chamber to extend the residence time of the heat transfer medium, improve heat exchange uniformity, and prevent localized temperature deviations from affecting adsorption efficiency. The jacket spacing is 50 mm.

[0028] The heat exchange area of ​​a jacketed heat exchanger structure is calculated using the following formula: ; in, The area of ​​the jacketed heat exchanger is in m². The outer diameter of the reactor cylinder is 300mm (inner diameter) plus 6mm (wall thickness) multiplied by 2, which gives 312mm, or 0.312m. The effective height of the jacketed cylinder is 1000mm, or 1m, in this embodiment.

[0029] Substituting the numerical values, we get: .

[0030] The pressure-resistant sealed reactor is equipped with a fixed-bed adsorbent packing layer with a height of 800 mm. A gas distributor is installed at the bottom of the packing layer to ensure uniform distribution of the feed gas as it passes through. The packing layer has a detachable structure for easy replacement and maintenance of the adsorbent.

[0031] In this embodiment, a potassium-based granular adsorbent is selected as the solid adsorbent, with a particle size range of 2-3 mm and a loading amount of approximately 15 kg. Potassium-based adsorbents are low-temperature adsorption type solid adsorbents, suitable for adsorbing carbon dioxide in a temperature range of 30-100℃ and for desorption and regeneration in a temperature range of 100-200℃.

[0032] The temperature-pressure coupling method for low-temperature solid adsorption in this embodiment specifically includes the following steps: Step S101: Pretreatment Stage. The flue gas to be treated first enters the feed gas pretreatment unit. In the feed gas pretreatment unit, the flue gas to be treated passes through a dust collector to remove dust particles, and then passes through a dryer to remove moisture, obtaining clean feed gas. Simultaneously, the temperature and humidity parameters of the feed gas are monitored by a monitoring device to ensure that the feed gas meets the requirements of the subsequent adsorption process. In this embodiment, the flue gas to be treated is simulated flue gas containing approximately 15 vol% carbon dioxide, with nitrogen as the balance gas.

[0033] Step S102: Adsorption preparation stage. The feed gas inlet valve and reactor inlet valve are opened via the control system, while the desorbed gas outlet valve and vent valve are closed. The low-temperature cooling source device in the heat exchange system is activated, and low-temperature refrigerant is introduced into the sealed heat exchange chamber through the jacketed heat exchange structure on the reactor wall to regulate the reactor temperature to the preset adsorption temperature of 40℃ and maintain it stable.

[0034] Step S103: Pressurized Adsorption Stage. The pressurization device is started, and the pretreated feed gas is pressurized and introduced into the pressure-resistant sealed reactor. Simultaneously, the internal pressure of the reactor is monitored in real time by a pressure sensor installed on the reactor, and the operating parameters of the pressurization device are adjusted to stabilize the internal pressure of the reactor at the preset adsorption pressure of 0.8 MPa.

[0035] Under the synergistic effect of a preset adsorption temperature of 40℃ and a preset adsorption pressure of 0.8MPa, carbon dioxide in the feed gas is adsorbed by potassium-based granular adsorbent in the reactor. The empty column velocity of the feed gas entering the reactor is 0.06m / s. The unadsorbed purified gas is discharged through the purified gas outlet valve to the subsequent purified gas treatment system.

[0036] Under these combined low-temperature and high-pressure conditions, according to the Langmuir isotherm adsorption model: ; in, To balance the adsorption capacity, the unit is mmol / g; The value represents the monolayer saturated adsorption capacity of the potassium-based particulate adsorbent, expressed in mmol / g. is the Langmuir adsorption equilibrium constant, which is related to temperature and adsorbent properties; This represents the operating pressure inside the reactor, expressed in MPa.

[0037] From the above formula, we can see that the adsorption capacity With gas phase pressure The increase is non-linear. At low temperatures, the adsorption equilibrium constant... The larger the pressure, the more significant the gain effect on adsorption capacity.

[0038] In this embodiment, under conditions of 40°C and 0.8 MPa, the equilibrium adsorption capacity of the potassium-based particulate adsorbent for carbon dioxide reaches 3.1 mmol / g, which is approximately 55% higher than the adsorption capacity of approximately 2.0 mmol / g under normal pressure. See also... Figure 3 The figure shows the relationship between adsorption pressure and adsorption capacity. With the adsorption temperature constant, when the pressure is increased from 0.1 MPa to 0.8 MPa, the increase in the numerator term in the Langmuir formula is much greater than the increase in the denominator term, and the increase in the equilibrium adsorption capacity of the adsorbent can reach 40% to 60%.

[0039] Step S104: Adsorption Termination Judgment Stage. The concentration of carbon dioxide in the purified gas is monitored in real time by a concentration monitoring device installed at the purified gas outlet. When the carbon dioxide concentration at the purified gas outlet rises to the preset adsorption termination threshold of 5000 ppm, it is determined that the potassium-based granular adsorbent has reached saturation adsorption. The control system automatically shuts off the pressurization device, the raw material gas inlet valve, and the purified gas outlet valve, and the adsorption stage ends. In this embodiment, the duration of the adsorption stage is approximately 60 minutes.

[0040] Step S105: Desorption Preparation Stage. Open the vent valve to initially depressurize the pressure-resistant sealed reactor, reducing the internal pressure from 0.8 MPa to atmospheric pressure. After depressurization, close the vent valve and open the desorption gas outlet valve. Start the vacuum system. In this embodiment, the vacuum system uses a two-stage vacuum configuration consisting of a Roots vacuum pump and a rotary vane vacuum pump to gradually reduce the internal pressure of the reactor to the preset desorption pressure of 300 Pa and maintain it stable.

[0041] Step S106: Heating and Desorption Stage. Turn off the low-temperature cold source device in the heat exchange system, start the high-temperature heat source device, and introduce steam at a temperature of 200°C into the sealed heat exchange chamber through the jacketed heat exchange structure on the reactor wall as a high-temperature heat medium to raise the temperature of the potassium-based particulate adsorbent to the preset desorption temperature of 180°C.

[0042] Under the combined effect of a preset desorption pressure of 300 Pa and a preset desorption temperature of 180 °C, carbon dioxide adsorbed on the surface of the potassium-based particulate adsorbent is desorbed. The low-pressure environment reduces the partial pressure of carbon dioxide on the adsorbent surface, shifting the adsorption equilibrium towards desorption; the increased temperature provides sufficient kinetic energy for the carbon dioxide molecules to overcome the forces acting on the adsorbent surface. The synergistic effect of these two factors makes the desorption process more thorough. The high-concentration carbon dioxide gas produced during desorption is discharged through the desorption gas outlet valve and enters the target gas collection unit, where it is dried, purified, and stored in a storage tank.

[0043] Step S107: Desorption Termination Judgment and Regeneration Stage. The concentration of carbon dioxide in the desorbed gas is monitored in real time by a concentration monitoring device installed at the desorbed gas outlet. When the carbon dioxide concentration at the desorbed gas outlet drops to a preset desorption termination threshold of 1000 ppm, the desorption process is deemed complete. In this embodiment, the duration of the desorption stage is approximately 120 minutes, and the purity of the desorbed carbon dioxide is greater than 95%.

[0044] After desorption is complete, shut off the vacuum system, high-temperature heat source, and desorption gas outlet valve. Open the vent valve to restore the internal pressure of the reactor to atmospheric pressure. Restart the low-temperature cooling source and use the jacketed heat exchange structure to lower the reactor temperature to the preset adsorption temperature of 40°C, completing reactor regeneration and preparing for the next adsorption-desorption cycle.

[0045] This embodiment utilizes a coupled operation of temperature and pressure swing processes. During the adsorption stage, the synergistic effect of low temperature and increased pressure enhances the adsorption capacity of the potassium-based granular adsorbent for carbon dioxide, increasing it by approximately 55% compared to atmospheric pressure conditions. During the desorption stage, the synergistic effect of low pressure and increased temperature achieves complete desorption and adsorbent regeneration. Compared to existing technologies employing a single temperature swing adsorption method, this embodiment reduces the adsorbent loading by more than 30% at the same treatment scale, lowering reactor volume and equipment manufacturing costs. Simultaneously, it achieves more thorough desorption, higher adsorbent recycling efficiency, and lower desorption energy consumption.

[0046] Example 2 This embodiment provides another low-temperature solid adsorption temperature-swing-pressure coupling method, using solid amine particles as the solid adsorbent to capture simulated flue gas containing a low concentration of carbon dioxide. See [link to relevant documentation]. Figure 4 .

[0047] The pressure-resistant sealed reactor used in this embodiment has a structure that is basically the same as that in Embodiment 1, both being vertical cylindrical pressure-resistant sealed pressure vessels. The difference lies in the material used for the reactor in this embodiment: 316L stainless steel is selected to meet the corrosion resistance requirements of the solid amine adsorbent. The reactor's inner diameter is 200mm, its height is 1000mm, its design pressure is 1.0MPa, and its pressure resistance rating is 1.2MPa. The reactor wall is equipped with a jacketed heat exchange structure with a jacket spacing of 50mm. A guide plate is installed inside the sealed heat exchange chamber, and its structure and function are consistent with those in Embodiment 1.

[0048] In this embodiment, the calculation of the reactor cylinder wall thickness is also based on the formula for calculating the wall thickness of an internally pressurized cylinder in GB 150.3-2011: ; in, The value is 1.0 MPa. The allowable stress of 316L stainless steel at the design temperature is 200 mm. The value is 137 MPa. The value is 0.85. The value is taken as 1.3mm. Substituting this into the calculation yields... It is approximately 2.16mm. To ensure operational safety, the actual wall thickness used is also 6mm.

[0049] The heat exchange area of ​​the jacketed heat exchanger structure is: ; in, It is 212mm, or 0.212m. The effective height of the jacketed cylinder is 800mm, or 0.8m.

[0050] The pressure-resistant sealed reactor is equipped with a fixed-bed adsorbent packing layer with a height of 600 mm. A gas distributor is installed at the bottom of the packing layer, and the packing layer has a detachable structure.

[0051] In this embodiment, PEI-supported mesoporous silica material is selected as the solid amine particle adsorbent, with a particle size range of 0.5–1.0 mm and a loading of approximately 8 kg. PEI-supported mesoporous silica material is a composite adsorbent material in which polyethyleneimine is impregnated onto a mesoporous silica support. Its surface contains abundant amine functional groups, exhibiting excellent chemisorption performance for carbon dioxide, and it belongs to the category of solid amine adsorbents. This material is suitable for adsorbing and capturing low concentrations of carbon dioxide under relatively low temperature conditions.

[0052] The temperature-pressure coupling method for low-temperature solid adsorption in this embodiment specifically includes the following steps: Step S201: Pretreatment stage. The flue gas to be treated enters the raw gas pretreatment unit, where dust particles are removed by a dust collector, and moisture is removed by a dryer to obtain clean raw gas. In this embodiment, the flue gas to be treated is simulated flue gas with a carbon dioxide concentration of approximately 5 vol%.

[0053] Step S202: Adsorption preparation stage. Open the feed gas inlet valve and reactor inlet valve via the control system, and close the desorbed gas outlet valve and vent valve. Start the low-temperature cooling source device in the heat exchange system, and introduce low-temperature refrigerant into the sealed heat exchange chamber through the jacketed heat exchange structure on the reactor wall to regulate the reactor temperature to the preset adsorption temperature of 30℃ and maintain it stable.

[0054] Step S203: Pressurized Adsorption Stage. Start the pressurization device to pressurize the pretreated feed gas and introduce it into the pressure-resistant sealed reactor. Monitor the internal pressure of the reactor in real time using a pressure sensor and adjust the operating parameters of the pressurization device to stabilize the internal pressure of the reactor at the preset adsorption pressure of 0.5 MPa.

[0055] Under the combined effect of a preset adsorption temperature of 30℃ and a preset adsorption pressure of 0.5MPa, carbon dioxide in the feed gas is adsorbed by solid amine granular adsorbent in the reactor. The empty column velocity of the feed gas entering the reactor is 0.11m / s. The unadsorbed purified gas is discharged through the purified gas outlet valve.

[0056] According to the Langmuir isothermal adsorption model: ; Under conditions of 30°C and 0.5 MPa, the equilibrium adsorption capacity of the solid amine particulate material for carbon dioxide reached 3.3 mmol / g, representing an increase of approximately 27% compared to the adsorption capacity of approximately 2.6 mmol / g under ambient pressure. This increase is relatively low compared to the 55% increase observed with the potassium-based adsorbent in Example 1, because the solid amine adsorbent primarily utilizes chemisorption, and pressure has a weaker effect on the chemisorption process than physical adsorption. Even so, pressurization can still increase the concentration of gaseous carbon dioxide to some extent, thereby promoting the chemisorption process.

[0057] Step S204: Adsorption Termination Judgment Stage. The concentration of carbon dioxide at the purified gas outlet is monitored in real time using a concentration monitoring device. When the carbon dioxide concentration at the purified gas outlet rises to the preset adsorption termination threshold of 2000 ppm, it is determined that the solid amine particle adsorbent has reached saturation adsorption. The control system automatically shuts off the pressurization device, the raw material gas inlet valve, and the purified gas outlet valve, ending the adsorption stage. In this embodiment, the duration of the adsorption stage is approximately 60 minutes.

[0058] Step S205: Desorption Preparation Stage. Open the vent valve to initially depressurize the pressure-resistant sealed reactor, reducing the internal pressure from 0.5 MPa to atmospheric pressure. After depressurization, close the vent valve and open the desorption gas outlet valve. Start the vacuum system, which also employs a two-stage vacuum configuration consisting of a Roots vacuum pump and a rotary vane vacuum pump, gradually reducing the internal pressure of the reactor to the preset desorption pressure of 200 Pa and maintaining it stable.

[0059] Step S206: Heating and Desorption Stage. The low-temperature cold source device is turned off, and the high-temperature heat source device is turned on. A heat medium at 150°C is introduced into the sealed heat exchange chamber through a jacketed heat exchange structure to raise the temperature of the solid amine particle adsorbent to the preset desorption temperature of 120°C. In this embodiment, the desorption temperature is 120°C, lower than the 180°C of the potassium-based adsorbent in Example 1. This is because the thermal stability of the solid amine adsorbent is relatively low, and the desorption temperature should not be too high, otherwise it may lead to the thermal degradation of polyethyleneimine molecules, shortening the adsorbent's service life.

[0060] Under the combined effect of a preset desorption pressure of 200 Pa and a preset desorption temperature of 120 °C, carbon dioxide chemically adsorbed on the surface of the solid amine particle adsorbent undergoes desorption. The low-pressure environment reduces the partial pressure of carbon dioxide, and the moderate temperature increase provides the driving force for the desorption process; the synergistic effect of these two factors makes the desorption more thorough. The carbon dioxide gas generated during desorption is discharged through the desorbed gas outlet valve into the target gas collection unit.

[0061] Step S207: Desorption Termination Judgment and Regeneration Stage. The desorption process is considered complete when the carbon dioxide concentration at the desorbed gas outlet drops to a preset desorption termination threshold of 500 ppm. In this embodiment, the desorption stage lasts approximately 120 minutes, and the purity of the desorbed carbon dioxide is greater than 95%.

[0062] After desorption is completed, the vacuum system, high-temperature heat source device and desorption gas outlet valve are shut off, the vent valve is opened to restore the internal pressure of the reactor to normal pressure, the low-temperature cold source device is restarted to reduce the internal temperature of the reactor to the preset adsorption temperature of 30°C, the regeneration of the reactor is completed, and it is ready to enter the next adsorption-desorption cycle.

[0063] This embodiment further verifies the adaptability of the temperature-pressure swing coupling method to different types of low-temperature solid adsorbents. Compared to the potassium-based adsorbent in Example 1, the solid amine adsorbent mainly relies on chemisorption, and the increase in adsorption capacity due to pressure is relatively small, but it can still achieve an increase of about 27%. This embodiment demonstrates that the temperature-pressure swing coupling method is not only applicable to adsorbents that mainly rely on physisorption, but also to solid amine adsorbents that mainly rely on chemisorption, showing good versatility.

[0064] Example 3 This embodiment provides another low-temperature solid adsorption temperature-switching-pressure coupling method, using amine-functionalized molecular sieves as solid adsorbents to capture carbon dioxide in industrial flue gas.

[0065] The pressure-resistant sealed reactor used in this embodiment is a vertical cylindrical pressure-resistant sealed pressure vessel made of 304 stainless steel. The reactor has an inner diameter of 800 mm, a height of 2000 mm, a design pressure of 1.0 MPa, and a pressure resistance rating of 1.5 MPa. The reactor wall is equipped with a jacketed heat exchange structure with a jacket spacing of 60 mm. A baffle plate is installed inside the sealed heat exchange chamber, and its structure and function are consistent with those described in Embodiment 1.

[0066] In this embodiment, the calculation of the reactor cylinder wall thickness is also based on the formula for calculating the wall thickness of an internally pressurized cylinder in GB 150.3-2011: ; in, The value is 1.0 MPa. The value is 800mm. The value is 137 MPa. The value is 0.85. The value is taken as 1.3mm. Substituting this into the calculation, we get: ; To ensure operational safety and structural stability, an actual wall thickness of 8mm was used. The end caps are standard elliptical heads with the same wall thickness as the cylinder.

[0067] The heat exchange area of ​​the jacketed heat exchanger structure is: ; in, It is 816mm, or 0.816m. The effective height of the jacketed cylinder is 1600mm, or 1.6m.

[0068] The pressure-resistant sealed reactor is equipped with a fixed-bed adsorbent packing layer with a height of 800 mm. A gas distributor is installed at the bottom of the packing layer, and the packing layer has a detachable structure.

[0069] In this embodiment, amine-functionalized molecular sieves were selected as the solid adsorbent. Amine-functionalized molecular sieves are composite adsorbent materials in which amine functional groups are grafted onto the surface of a molecular sieve support. They combine the physical adsorption capacity of molecular sieves with the chemical adsorption capacity of amine functional groups for carbon dioxide, exhibiting strong adsorption performance for carbon dioxide in a medium-to-low temperature range. In this embodiment, the amine-functionalized molecular sieves used had a particle size range of 2–4 mm and a loading of approximately 80 kg.

[0070] The temperature-pressure coupling method for low-temperature solid adsorption in this embodiment includes the following specific steps: Step S301: Pretreatment stage. The industrial flue gas enters the raw gas pretreatment unit, where dust particles are removed by a dust collector, and moisture is removed by a dryer to obtain clean raw gas. In this embodiment, the industrial flue gas is flue gas from a coal-fired power plant containing approximately 12 vol% carbon dioxide.

[0071] Step S302: Adsorption preparation stage. Open the feed gas inlet valve and reactor inlet valve via the control system, and close the desorbed gas outlet valve and vent valve. Start the low-temperature cooling source device in the heat exchange system, and introduce low-temperature refrigerant into the sealed heat exchange chamber through the jacketed heat exchange structure on the reactor wall to regulate the reactor temperature to the preset adsorption temperature of 50℃ and maintain it stable.

[0072] Step S303: Pressurized Adsorption Stage. Start the pressurization device to pressurize the pretreated feed gas and introduce it into the pressure-resistant sealed reactor. Monitor the internal pressure of the reactor in real time using a pressure sensor to stabilize the internal pressure at the preset adsorption pressure of 1.0 MPa.

[0073] Under the synergistic effect of a preset adsorption temperature of 50℃ and a preset adsorption pressure of 1.0MPa, carbon dioxide in the feed gas is adsorbed by the amine-functionalized molecular sieve inside the reactor. The empty column velocity of the feed gas entering the reactor is 0.08m / s. The unadsorbed purified gas is discharged through the purified gas outlet valve.

[0074] According to the Langmuir isotherm adsorption model, under conditions of 50℃ and 1.0 MPa, the equilibrium adsorption capacity of amine-functionalized molecular sieves for carbon dioxide can reach 4.5 mmol / g, which is an increase of about 61% compared to the adsorption capacity of about 2.8 mmol / g under normal pressure. This increase is significantly higher than the 27% increase of the solid amine adsorbent in Example 2. This is because amine-functionalized molecular sieves have both physical and chemical adsorption capabilities. The increase in physical adsorption capacity due to pressure is superimposed on the basic capacity of chemical adsorption, resulting in a more significant increase in adsorption capacity.

[0075] Step S304: Adsorption Termination Judgment Stage. When the carbon dioxide concentration at the purified gas outlet rises to the preset adsorption termination threshold of 3000 ppm, it is determined that the amine-functionalized molecular sieve has reached saturated adsorption. The control system automatically shuts off the pressurization device, the raw material gas inlet valve, and the purified gas outlet valve, ending the adsorption stage. In this embodiment, the duration of the adsorption stage is approximately 55 minutes.

[0076] Step S305: Desorption Preparation Stage. Open the vent valve to initially depressurize the pressure-resistant sealed reactor, reducing the internal pressure from 1.0 MPa to atmospheric pressure. After depressurization, close the vent valve and open the desorption gas outlet valve. Start the vacuum system, using a two-stage vacuum configuration consisting of a Roots vacuum pump and a rotary vane vacuum pump, gradually reducing the internal pressure of the reactor to the preset desorption pressure of 400 Pa and maintaining it stable.

[0077] Step S306: Heating and Desorption Stage. Turn off the low-temperature cold source device and start the high-temperature heat source device. Through the jacketed heat exchange structure, introduce steam at a temperature of 220°C into the sealed heat exchange chamber as a high-temperature heat medium to raise the temperature of the amine functionalized molecular sieve to the preset desorption temperature of 150°C.

[0078] Under the combined effect of a preset desorption pressure of 400 Pa and a preset desorption temperature of 150 °C, carbon dioxide adsorbed on the surface of the amine-functionalized molecular sieve is desorbed. The desorption temperature in this embodiment is between 180 °C in Example 1 and 120 °C in Example 2, balancing the thermal stability of the molecular sieve support with the protection requirements of the surface amine functional groups. The carbon dioxide gas generated during desorption is discharged through the desorption gas outlet valve into the target gas collection unit.

[0079] Step S307: Desorption Termination Judgment and Regeneration Stage. The desorption process is considered complete when the carbon dioxide concentration at the desorbed gas outlet drops to a preset desorption termination threshold of 800 ppm. In this embodiment, the desorption stage lasts approximately 130 minutes, and the purity of the desorbed carbon dioxide is greater than 96%.

[0080] After desorption is completed, shut down the vacuum system, high-temperature heat source device and desorption gas outlet valve, open the vent valve to restore the internal pressure of the reactor to normal pressure, restart the low-temperature cold source device to reduce the internal temperature of the reactor to the preset adsorption temperature of 50°C, and complete the regeneration of the reactor.

[0081] This embodiment demonstrates the feasibility of the temperature-swing-pressure coupling method in large-diameter reactors on an industrial scale. Using amine-functionalized molecular sieves at a preset adsorption pressure of 1.0 MPa, the adsorption capacity can be increased by up to 61%, further verifying that composite adsorbent materials with both physical and chemical adsorption capabilities have more significant performance advantages in temperature-swing-pressure coupling processes.

[0082] In summary, the embodiments of the present invention have at least the following technical effects: This invention designs the pressure-resistant sealed reactor to meet the pressure vessel standard, enabling the reactor to simultaneously perform temperature and pressure regulation.

[0083] During the adsorption stage, the pressure inside the reactor is increased to 0.5–1 MPa by pressurization. According to the Langmuir isothermal adsorption model, under the condition that the adsorption equilibrium constant is large at low temperature, the pressure increase can increase the equilibrium adsorption capacity of the adsorbent by 40%–70%, thereby significantly reducing the amount of adsorbent and the reactor volume for the same treatment scale.

[0084] During the desorption stage, by reducing the pressure inside the reactor to a low-pressure environment of 100-500 Pa and simultaneously increasing the temperature, the target gas adsorbed on the surface of the adsorbent is desorbed. Compared with the single temperature-variable desorption method, the desorption is more thorough, the adsorbent regeneration efficiency is higher, and the desorption energy consumption is lower.

[0085] Therefore, this invention achieves coupled operation of temperature and pressure switching processes, solving the problems of low adsorption capacity, poor desorption efficiency, and large adsorbent consumption in existing low-temperature solid adsorption processes.

[0086] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A temperature- and pressure-swapping coupling method for low-temperature solid adsorption, characterized in that, include: The gas to be treated is pretreated to obtain raw gas, and the raw gas is passed into a pressure-resistant sealed reactor filled with solid adsorbent. The wall of the pressure-resistant sealed reactor is provided with a heat exchange structure. Adsorption stage: The temperature inside the pressure-resistant sealed reactor is controlled to a preset adsorption temperature through the heat exchange structure, and the internal pressure of the pressure-resistant sealed reactor is increased to a preset adsorption pressure. Under the synergistic effect of the preset adsorption temperature and the preset adsorption pressure, the solid adsorbent adsorbs the target gas in the raw gas; and the concentration of the target gas at the purified gas outlet is monitored. When the concentration of the target gas reaches a preset adsorption termination threshold, it is determined that the solid adsorbent has reached a saturated adsorption state, and the adsorption stage ends. Desorption stage: The pressure-resistant sealed reactor is depressurized to a preset desorption pressure, and the temperature inside the pressure-resistant sealed reactor is raised to a preset desorption temperature through the heat exchange structure. Under the synergistic effect of the preset desorption pressure and the preset desorption temperature, the target gas adsorbed on the surface of the solid adsorbent is desorbed, and the gas generated by the desorption is exported and collected. In addition, the concentration of the target gas at the desorption gas outlet is monitored. When the concentration of the target gas drops to a preset desorption termination threshold, the desorption is determined to be complete, and the pressure-resistant sealed reactor is restored to atmospheric pressure and cooled to the preset adsorption temperature.

2. The temperature- and pressure-switching coupling method for low-temperature solid adsorption according to claim 1, characterized in that, The preset adsorption pressure ranges from 0.5 to 1 MPa, and the preset desorption pressure ranges from 100 to 500 Pa.

3. The temperature- and pressure-swapping coupling method for low-temperature solid adsorption according to claim 1, characterized in that, The preset adsorption temperature ranges from 30 to 100°C, and the preset desorption temperature ranges from 100 to 200°C.

4. The temperature- and pressure-swapping coupling method for low-temperature solid adsorption according to claim 1, characterized in that, During the adsorption stage, the quantitative relationship between the equilibrium adsorption capacity of the solid adsorbent for the target gas and the preset adsorption pressure conforms to the Langmuir isotherm adsorption model: ； in, Indicates the equilibrium adsorption capacity. This indicates the monolayer saturated adsorption capacity of the solid adsorbent. This represents the Langmuir adsorption equilibrium constant in relation to temperature and adsorbent properties. This indicates the operating pressure inside the pressure-resistant sealed reactor.

5. The temperature- and pressure-swapping coupling method for low-temperature solid adsorption according to claim 1, characterized in that, The wall thickness of the pressure-resistant sealed reactor cylinder is determined according to the formula for calculating the wall thickness of an internal pressure cylinder: ； in, This indicates the calculated wall thickness of the cylinder. Indicates calculated pressure. Indicates the inner diameter of the cylinder. This represents the allowable stress of the material at the design temperature. Indicates the weld joint coefficient. This indicates the additional wall thickness.

6. The temperature- and pressure-swapping coupling method for low-temperature solid adsorption according to claim 1, characterized in that, The heat exchange structure is a jacketed heat exchange structure that covers the outer wall of the pressure-resistant sealed reactor cylinder. The jacketed heat exchange structure and the cylinder form a closed heat exchange cavity. The heat exchange area of ​​the closed heat exchange cavity is calculated according to the following formula: ； in, This represents the heat transfer area of ​​the jacketed heat exchange structure. This indicates the outer diameter of the cylinder of the pressure-resistant sealed reactor. This indicates the effective height of the cylinder covered by the jacketed heat exchange structure; A guide plate is provided inside the sealed heat exchange cavity. Cooling medium is introduced during the adsorption stage to achieve cooling, and heating medium is introduced during the desorption stage to achieve heating.

7. The temperature- and pressure-swapping coupling method for low-temperature solid adsorption according to claim 1, characterized in that, During the desorption stage, depressurizing the pressure-resistant sealed reactor includes: First, the pressure inside the pressure-resistant sealed reactor is released to atmospheric pressure via the vent valve; The pressure inside the pressure-resistant sealed reactor is then reduced to the preset desorption pressure using a vacuum system.

8. The temperature- and pressure-swapping coupling method for low-temperature solid adsorption according to claim 1, characterized in that, The solid adsorbent is a low-temperature adsorption type solid adsorbent, including one of potassium-based adsorbents, solid amine adsorbents, amine-functionalized molecular sieves, or amine-functionalized metal-organic framework materials.

9. The temperature- and pressure-swapping coupling method for low-temperature solid adsorption according to claim 1, characterized in that, The pressure-resistant sealed reactor is also equipped with a gas distributor, which is located below the packing layer of the solid adsorbent and is used to ensure that the raw material gas is evenly distributed before passing through the packing layer. The solid adsorbent filling layer has a detachable structure, the particle size of the solid adsorbent ranges from 0.5 to 5 mm, and the single-layer thickness of the filling layer ranges from 500 to 800 mm.

10. The temperature-switching-pressure coupling method for low-temperature solid adsorption according to any one of claims 1 to 9, characterized in that, During the adsorption and desorption stages, the pressurization device, vacuum system, heat exchange system, and valves are controlled in a coordinated manner by the control system. During the adsorption stage, the empty tower flow velocity of the feed gas entering the pressure-resistant sealed reactor is 0.05–0.15 m / s; In the aforementioned adsorption-desorption cycle, the duration of the adsorption phase is 50–70 min, and the duration of the desorption phase is 100–140 min.

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