Low temperature pressure swing adsorption carbon dioxide capture process suitable for cold environments

Abstract

The present application relates to the technical field of carbon capture, and discloses a low-temperature pressure swing adsorption carbon dioxide capture process suitable for cold environments, which utilizes an environmental cold source to pretreat raw material gas to -20°C to 10°C, and captures the raw material gas under a pressure of 0.2-1.0 MPa through an adsorption tower composed of a buffer layer, a carbon dioxide selective adsorption layer and a support layer. Subsequently, light components are recovered through a concurrent pressure reduction, and carbon dioxide is desorbed under an absolute pressure of 10-30 kPa by using a vacuum suction unit, and finally, regeneration is completed through purging with a purified gas and stepwise pressure increase. The present application replaces traditional heat swing with pressure swing, eliminates the dependence on external high-temperature heat sources, and significantly reduces the energy consumption of capture in extremely cold environments. The system adopts a modularized skid-mounted design, cooperates with a self-limiting temperature electric heat tracing and a temperature difference compensation mechanism, and ensures the operation stability and engineering adaptability of the device in extremely cold and heat source limited scenarios.

Description

Technical Field

[0001] This invention relates to the field of carbon capture technology, specifically a low-temperature pressure swing adsorption carbon dioxide capture process suitable for cold environments. Background Technology

[0002] Carbon dioxide capture, at its core, involves the efficient separation and recovery of carbon dioxide gas from industrial emission sources. In the industrial field, pressure swing adsorption technology utilizes the differences in the adsorption capacity of solid adsorbents for gas components under different pressures, achieving the separation and purification of mixed gases through periodic pressure changes.

[0003] In practical applications of existing technologies, carbon dioxide capture often employs liquid chemical absorption or thermal swing adsorption. Liquid chemical absorption captures carbon dioxide through a chemical reaction between an organic amine solution and the carbon dioxide, followed by regeneration of the rich solution using high-temperature steam. Thermal swing adsorption involves passing industrial exhaust gas into an adsorption bed filled with a solid adsorbent. After adsorption is completed at room temperature or high temperature, an external heat source is introduced to heat the bed to between 80°C and 120°C. The decrease in adsorption capacity due to the increased temperature promotes carbon dioxide desorption. Subsequently, a cooling medium is used to lower the bed temperature back to the adsorption initiation temperature, completing one operating cycle.

[0004] However, existing carbon dioxide capture technologies suffer from severe energy consumption bottlenecks in cold environments and scenarios where heat sources are limited. Because their desorption process is highly dependent on external high-temperature heat sources for heating and regeneration, the system needs to consume a large amount of energy to offset the temperature difference in the environment and maintain the regeneration temperature under extremely cold conditions. This heat-driven regeneration method results in extremely high overall energy consumption per unit mass of carbon dioxide captured, which is difficult to meet the requirements of a low-carbon economy. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a low-temperature pressure swing adsorption carbon dioxide capture process suitable for cold environments, thus solving the problems mentioned in the background section.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] The first aspect of this invention provides a low-temperature pressure swing adsorption carbon dioxide capture process suitable for cold environments. Its core lies in utilizing the natural cold source provided by the cold environment to drive the adsorption and desorption of carbon dioxide through pressure swing, thereby eliminating the dependence of traditional thermal swing adsorption processes on external high-temperature heat sources. The process includes the following steps: S100: Raw material gas pretreatment. The raw material gas enters the pretreatment module, where it is cooled by atmospheric heat exchange through a low-temperature heat exchanger, adjusting its temperature to the range of -20°C to 10°C. During this process, impurities are removed and the raw material gas undergoes deep dehydration.

[0008] S200: Low-temperature, high-pressure adsorption. The regulated feed gas is introduced into the adsorption tower under adsorption conditions at a pressure of 0.2-1.0 MPa. Carbon dioxide molecules enter the selective adsorption layer under low-temperature, high-pressure conditions, utilizing the selective adsorption characteristics of the adsorbent to capture carbon dioxide, while non-adsorbed components are discharged as purified gas. During adsorption, the mass transfer zone movement velocity... Satisfy the following formula:

[0009] In the formula, This indicates the apparent empty gas velocity of the feed gas within the adsorption tower; This indicates the packing density of the carbon dioxide selective adsorption layer; This indicates the equilibrium adsorption capacity of the adsorbent under the current pressure; This indicates the initial mass concentration of carbon dioxide in the feed gas.

[0010] S300: Stepped depressurization recovery. After adsorption saturation, the feed gas input is stopped, and the adsorption tower undergoes co-current depressurization. The light component gas released during the depressurization process is guided to other adsorption towers in the repressurization stage, realizing the recovery of pressure energy and material.

[0011] S400: Countercurrent vacuum desorption. A countercurrent vacuum is applied to the adsorption tower via a vacuum pumping unit, reducing the absolute pressure inside the tower to 10-30 kPa. In this low-temperature environment, the partial pressure of carbon dioxide is significantly reduced, causing carbon dioxide molecules to desorb from the adsorbent pores and form carbon dioxide product gas.

[0012] S500: Bed regeneration and adsorption initialization. Purified gas is introduced to purge the carbon dioxide selective adsorption layer, removing residual carbon dioxide. Subsequently, the internal pressure of the adsorption tower is restored to the preset adsorption pressure through staged pressurization.

[0013] This process utilizes the principle that the physical adsorption capacity of carbon dioxide is enhanced under low-temperature conditions, and its equilibrium adsorption capacity... Follow the formula below:

[0014] In the formula, This indicates the maximum monolayer adsorption capacity of the solid adsorbent at the current temperature; Represents the affinity constant; This indicates the partial pressure of carbon dioxide in the feed gas. Maintaining a high affinity constant at low temperatures is achieved through this method. This allows for a higher capture rate at lower operating pressures, thereby reducing system energy consumption and preventing structural degradation of the adsorbent due to frequent hot and cold cycles.

[0015] A second aspect of this invention provides a low-temperature pressure swing adsorption carbon dioxide capture system suitable for cold environments. The system includes a pretreatment module, a multi-tower parallel adsorption module, a vacuum suction unit, and an automated control system. The pretreatment module is equipped with a filter assembly, a deep dehydration assembly, and a low-temperature heat exchanger utilizing atmospheric cold. The multi-tower parallel adsorption module comprises several adsorption towers arranged in parallel. The interior of each adsorption tower is filled from top to bottom with a buffer layer, a carbon dioxide selective adsorption layer, and a support layer, with a height ratio set to 1:6:1 to 1:8:1. Pressure and temperature sensors are integrated inside each adsorption tower. The vacuum suction unit is connected to the bottom outlet of the adsorption tower. The automated control system is electrically connected to the sensors and each actuator.

[0016] This system ensures the cycle time of multiple towers by controlling the phase difference of the adsorption towers through an automated control system. Continuity:

[0017] In the formula, Indicates the adsorption time; Indicates the duration of downstream pressure reduction; Indicates the duration of vacuum desorption; Indicates the duration of low-pressure purging; This indicates the duration of repressurization.

[0018] To address significant fluctuations in ambient temperature, the system uses an automated control system to adjust the opening of the bypass valve on the cryogenic heat exchanger in real time. The inlet temperature of the mixed gas... Satisfy the following formula:

[0019] In the formula, This indicates the mass flow rate of the raw gas flowing through the main path of the low-temperature heat exchanger; This indicates the temperature of the gas after the main path has been cooled. This indicates the mass flow rate of the raw gas flowing through the bypass valve branch; This indicates the initial temperature of the feed gas in the bypass branch. This regulation mechanism ensures a constant inlet gas temperature. Furthermore, the system utilizes PTFE insulation pads and insulation layers to control heat loss, and uses electric heat tracing to compensate for and maintain the valve assembly at [temperature missing]. Operational reliability under environmental conditions, output heat power of electric heating tape satisfy:

[0020] In the formula, The overall heat transfer coefficient; For effective heat exchange area; The preset minimum operating temperature; The ambient temperature; This refers to the thermal efficiency of the insulation layer.

[0021] This invention achieves carbon dioxide capture in cold and heat-limited scenarios through the synergy of the above-mentioned process steps and system structure, reduces the overall power consumption of the system, and improves the engineering adaptability of the device under extreme climatic conditions.

[0022] This invention provides a low-temperature pressure swing adsorption carbon dioxide capture process suitable for cold environments. It offers the following advantages: 1. This invention utilizes a pressure-oscillating adsorption mechanism under low-temperature conditions, leveraging the enhanced physical adsorption affinity of carbon dioxide at low temperatures to achieve highly efficient carbon dioxide separation without relying on an external high-temperature heat source. Since the equilibrium adsorption capacity is positively correlated with the affinity constant and the partial pressure of carbon dioxide, the system significantly increases the maximum adsorption capacity of the monolayer by maintaining a low inlet temperature, allowing the device to achieve the predetermined capture rate at a relatively low operating pressure. This desorption mechanism avoids the energy input required for high-temperature regeneration in traditional processes, significantly reducing the overall energy consumption per unit mass of carbon dioxide captured and solving the problem of high carbon capture costs caused by limited energy supply in cold regions.

[0023] 2. This invention achieves continuity in the capture process and long-term stability of the system operation through multi-tower parallel pressure cycle scheduling logic and frequency conversion control. The automated control system dynamically adjusts the phase difference of each adsorption tower based on the mathematical correlation between the mass transfer zone movement speed, adsorption time, and cycle period, ensuring that the pressure fluctuation in the main inlet pipe remains at a low level. The co-current depressurization step recovers light component gases from the dead space, reducing the load on the vacuum desorption stage. By eliminating frequent alternating hot and cold cycles, the thermal stress damage to the adsorbent is alleviated, the structural deterioration rate is reduced, and the adsorbent's service life is extended, reducing maintenance costs and system downtime risks associated with replacing core materials in extremely cold and remote areas.

[0024] 3. This invention enhances the engineering adaptability of the device under extreme climatic conditions through the synergistic design of a modular skid-mounted structure and a multi-stage temperature control compensation mechanism. Utilizing natural atmospheric cold sources in conjunction with a low-temperature heat exchanger, and combined with a bypass valve's hybrid regulation logic, constant control of the inlet air temperature is achieved despite environmental fluctuations. To address the risk of equipment failure in extremely cold environments, the system calculates the heat loss of the insulation layer and configures a self-regulating electric heating tape, ensuring the reliability of critical actuators such as valve groups. The emergency circulation mode maintains bed activity by adjusting the purging rate and utilizing adsorption heat, guaranteeing the device's basic operational capability in ultra-low temperature environments and meeting the requirements of rapid deployment and high environmental resistance for carbon capture equipment in remote oil and gas fields and distributed point sources. Attached Figure Description

[0025] Figure 1This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the PSA adsorption tower structure of the present invention; Figure 3 This is a schematic diagram of the low-temperature PSA adsorption-desorption cycle steps of the present invention. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Please see the appendix Figure 1 - Appendix Figure 3 This invention provides a low-temperature pressure swing adsorption carbon dioxide capture process suitable for cold environments, comprising the following steps: S100: Raw material gas pretreatment.

[0028] The feed gas first enters the pretreatment unit, where impurities are removed through physical filtration and chemical drying. It then enters the cryogenic heat exchanger. The cryogenic heat exchanger utilizes atmospheric cold energy from the cold environment as the main cold source, regulating the temperature of the feed gas within a preset low-temperature range through heat exchange. Simultaneously, it ensures that the gas state entering subsequent stages conforms to the adsorbent's low-temperature operating window and prevents residual moisture from freezing at extremely low temperatures.

[0029] S200: Low-temperature high-pressure adsorption.

[0030] The pretreated and cooled feed gas enters a specific adsorption tower in the PSA adsorption tower group under adsorption conditions at a preset pressure. Utilizing the selective adsorption characteristics of carbon dioxide molecules on the surface and within the pores of the solid adsorbent, carbon dioxide is retained inside the bed, while the unadsorbed light component gases are discharged as purified gas from the top of the adsorption tower.

[0031] S300: Stepped pressure reduction recovery.

[0032] After the single-tower adsorption reaches its saturation critical point, the feed gas input is stopped, and the system enters the co-current depressurization stage. Non-target light component gases within the dead space of the adsorption tower are released through a controlled pressure reduction. The released gas is then guided through pipelines to other adsorption towers in the repressurization stage within the system, achieving pressure balance and material recycling within the system.

[0033] S400: Countercurrent vacuum desorption.

[0034] The adsorption tower is evacuated countercurrently by a vacuum pumping unit, disrupting the adsorption equilibrium. Without adding an external heat source, a significant negative pressure difference is used as the desorption driving force, causing the carbon dioxide molecules adsorbed within the adsorbent pores to desorb. The high-concentration carbon dioxide gas released during desorption is the product gas, which is sent to subsequent processing stages through the product gas outlet.

[0035] S500: Bed regeneration and adsorption initialization.

[0036] After desorption is complete, the repressurization stage begins. By introducing some purified gas or through a step-by-step pressurization operation, the internal pressure of the adsorption tower is restored to the adsorption initiation pressure, making the adsorption tower ready to enter the S200 step again.

[0037] In the above architecture, the pretreatment unit and the cryogenic heat exchanger work together in a cascaded manner. The cryogenic heat exchanger utilizes an external ambient cold source, and adjusts the cooling supply through a variable frequency fan or cooling medium circulation to precisely control the feed gas inlet temperature. to Within the range.

[0038] An adsorption tower group consists of three or more adsorption towers connected in parallel. Each adsorption tower contains, from top to bottom, a buffer layer, a carbon dioxide selective adsorption layer, and a support layer. The carbon dioxide selective adsorption layer embeds pressure and temperature sensors to collect bed state parameters in real time. The buffer layer stabilizes the airflow distribution, and the support layer supports the adsorbent and filters fine dust. An automated control system controls the switching of inlet and outlet valves for each tower based on sensor feedback data or preset time periods, ensuring continuous operation of the collection process over time.

[0039] The vacuum suction unit achieves deep desorption through a multi-stage vacuum pump assembly, reducing the absolute pressure inside the adsorption tower to [value missing]. At low temperatures, the adsorbent's affinity for carbon dioxide increases, allowing for lower desorption pressures that ensure its regeneration rate. The carbon dioxide collected at the product gas outlet is then compressed and purified to industrial-grade form for storage.

[0040] The feed gas pretreatment module addresses issues such as moisture freezing, impurity deposition, and fluctuations in adsorption heat balance in cold environments by adjusting the quality of the raw gas source. The module consists of a filtration assembly, a deep dehydration assembly, and a low-temperature heat exchanger connected sequentially via process piping.

[0041] The specific implementation process of feed gas pretreatment and low-temperature control is as follows: S101: Removal of impurities from raw material gas.

[0042] The raw gas enters the filtration assembly in the pretreatment module. The filtration assembly uses a precision filter element to trap solid particles and dust in the raw gas. The specific structure of the filtration assembly can be selected by those skilled in the art based on the dust concentration of the raw gas source; this is common knowledge in the field and will not be elaborated further here.

[0043] S102: Deep dehydration of raw gas.

[0044] The filtered feed gas enters the deep dehydration unit. The deep dehydration unit uses molecular sieve adsorbents to lower the dew point of the feed gas to [value missing]. In cold environments, deep dehydration ensures that the feed gas does not produce liquid water or ice crystals during subsequent cooling, thereby protecting the carbon dioxide selective adsorption layer from moisture interference and preventing blockage of pipeline valves.

[0045] S103: Cold energy exchange and intake air temperature control.

[0046] The dried feed gas enters a low-temperature heat exchanger. The low-temperature heat exchanger utilizes the natural atmospheric cold source in the cold environment as the main cold source, and lowers the feed gas temperature to [temperature value missing] through heat exchange regulation. The preset range. Raw material gas inlet temperature T in The adjustment satisfies the following heat balance formula:

[0047] In the formula, This indicates the heat flow rate exchanged by the low-temperature heat exchanger; This indicates the specific heat capacity at constant pressure of the raw gas; Indicates the mass flow rate of the raw gas; This indicates the initial temperature of the raw gas before it enters the low-temperature heat exchanger. This indicates the final inlet temperature of the raw gas after it has been regulated by the low-temperature heat exchanger and enters the adsorption tower group.

[0048] S104: Temperature fluctuation compensation.

[0049] The automated control system monitors the temperature sensor at the outlet of the cryogenic heat exchanger in real time. When changes in ambient temperature cause... When the temperature deviates from the preset range, the automated control system adjusts the opening of the bypass valve of the cryogenic heat exchanger to mix part of the uncooled feed gas with the cooled feed gas, thereby achieving temperature difference compensation. The final inlet temperature of the mixed gas... Follow the calculation relationship as follows:

[0050] In the formula, This indicates the mass flow rate of the raw gas flowing through the main path of the low-temperature heat exchanger; This indicates the temperature of the gas after the main path has been cooled. This indicates the mass flow rate of the raw gas flowing through the bypass valve branch; This indicates the initial temperature of the feed gas in the bypass branch.

[0051] The feed gas pretreatment module uses a staged cooling logic to ensure that the feed gas reaches the low-temperature steady state required for pressure swing adsorption before entering the multi-tower parallel adsorption module. The low-temperature heat exchanger adopts a finned tube structure and is equipped with an external insulation layer to reduce heat loss. The deep dehydration component has two sets of parallel units. When one dehydration unit reaches saturation, the automatic control system switches to the other set to perform the dehydration task. The saturated dehydration unit is regenerated using the purified gas discharged from the system.

[0052] The internal structure and material ratio of the adsorption tower serve as the structural basis for achieving low-temperature pressure swing adsorption. It receives the low-temperature feed gas delivered by the feed gas pretreatment module and provides reaction space for the adsorption and desorption cycles in the process flow. Each adsorption tower in the adsorption tower group adopts a vertical pressure vessel structure, and its interior is divided into multiple filling zones from top to bottom according to the feed gas flow direction.

[0053] The implementation details of the internal structure of the adsorption tower and the material proportioning are explained below: S201: Layered packing of the adsorption tower.

[0054] The adsorption tower is sequentially filled with a buffer layer, a selective carbon dioxide adsorption layer, and a support layer from the feed gas inlet to the purified gas outlet. The buffer layer, located at the top of the tower near the feed gas inlet, is mainly composed of large-particle inert alumina spheres and is used to evenly distribute the incoming gas flow and intercept trace impurities remaining in the feed gas. The selective carbon dioxide adsorption layer, located in the middle of the tower, is the functional area for capturing carbon dioxide and is filled with a solid adsorbent that selectively adsorbs carbon dioxide. The support layer, located at the bottom of the tower, consists of multi-stage crushed stone and stainless steel wire mesh, used to support the weight of the selective carbon dioxide adsorption layer and prevent the solid adsorbent particles from being lost with the gas flow.

[0055] S202: Material proportioning and filling height control.

[0056] To balance adsorption efficiency and pressure drop within the column at low temperatures, the filling height ratio of the buffer layer, the selective carbon dioxide adsorption layer, and the support layer is set to 1:6:1 to 1:8:1. The packing density of the solid adsorbent in the selective carbon dioxide adsorption layer is... Satisfy the following formula:

[0057] In the formula, This represents the total mass of solid adsorbent added to the carbon dioxide selective adsorption layer; This indicates the design volume of the carbon dioxide selective adsorption layer; This indicates the bed porosity. By controlling the packing density, it is ensured that the residence time of the feed gas within the bed meets the requirements of carbon dioxide adsorption kinetics.

[0058] S203: Arrangement of bed monitoring elements.

[0059] Pressure and temperature sensors are distributed within the carbon dioxide selective adsorption layer. The pressure sensors are located on the inlet and outlet sides of the layer to monitor pressure values ​​during adsorption, depressurization, and vacuuming processes. Temperature sensors are arranged longitudinally at equal intervals along the central axis of the layer to capture temperature gradient changes generated during adsorption.

[0060] S204: Adsorption capacity verification.

[0061] Equilibrium adsorption capacity of solid adsorbents at low temperatures Follow the formula below:

[0062] In the formula, This indicates the maximum monolayer adsorption capacity of the solid adsorbent at the current temperature; Represents the affinity constant; This indicates the partial pressure of carbon dioxide in the feed gas. Within the operating temperature range, the affinity constant can be increased by reducing the intake air temperature. This enables the improvement of carbon dioxide capture rate under lower operating pressure.

[0063] The shell material of the adsorption tower is made of special steel for cryogenic pressure vessels to meet the brittle protection requirements in cold environments. The strength calculation and manufacturing process of the adsorption tower shell can be designed by those skilled in the art according to relevant standards; such details are well-known in the field and will not be elaborated upon here.

[0064] The particle size of the solid adsorbent in the carbon dioxide selective adsorption layer is controlled between 3mm and 5mm. A stainless steel grid is installed between the buffer layer, support layer, and carbon dioxide selective adsorption layer to physically isolate different packing materials. The automated control system determines the internal pressure difference of the adsorption tower based on signals obtained from pressure sensors and adjusts the heat exchange intensity of the cryogenic heat exchanger according to the values ​​from temperature sensors.

[0065] Through the above-mentioned internal structural design and material ratio, the adsorption tower utilizes the physical property that enhances carbon dioxide adsorption capacity under low temperature conditions, and achieves carbon dioxide separation in conjunction with subsequent pressure shifting steps.

[0066] The PSA six-stage cycle process, based on the structural conditions set by the internal structure of the adsorption tower and the material ratio, uses an automated control system to control the adsorption towers in the multi-tower parallel adsorption module to operate alternately according to a preset time sequence, achieving continuous carbon dioxide capture. The cycle process... It fluctuates within a temperature range, with pressure changes being the primary driving force.

[0067] The specific implementation steps of the PSA six-stage cycle process are as follows: S301: Low-temperature high-pressure adsorption stage.

[0068] The feed gas, after being pretreated and adjusted to a preset temperature and pressure, enters the adsorption tower under adsorption conditions. The adsorption pressure is maintained at... Within this pressure range and low temperature environment, carbon dioxide molecules in the raw material are retained by the carbon dioxide selective adsorption layer. The purified gas discharged from the adsorption tower outlet enters the purified gas collection manifold. The mass transfer zone movement velocity v during the adsorption process... z Satisfy the following formula:

[0069] In the formula, This indicates the apparent empty gas velocity of the feed gas within the adsorption tower; This indicates the packing density of the carbon dioxide selective adsorption layer; This indicates the equilibrium adsorption capacity of the adsorbent under the current pressure; This indicates the initial mass concentration of carbon dioxide in the feed gas. The automated control system switches the adsorption tower to the next stage when the monitored carbon dioxide concentration at the adsorption tower outlet reaches the breakthrough threshold.

[0070] S302: Downflow pressure reduction stage.

[0071] After the adsorption tower completes its adsorption task, the automated control system closes the feed gas inlet valve. The pressure inside the adsorption tower decreases from the adsorption pressure in the co-current direction. The gas released during this co-current pressure reduction is mainly the light component gas retained in the pores of the adsorbent and the bed space. The light component gas released during this co-current pressure reduction is guided to other adsorption towers in the system that are in the initial stage of pressurization through connecting pipelines.

[0072] S303: Countercurrent vacuum desorption stage.

[0073] The adsorption tower enters desorption mode, and the vacuum pump unit starts. The vacuum pump performs countercurrent suction on the bed through the outlet at the bottom of the adsorption tower, reducing the absolute pressure inside the adsorption tower to [value missing]. As the pressure decreases, carbon dioxide molecules adsorbed in the carbon dioxide selective adsorption layer desorb, forming a high-concentration carbon dioxide product gas, which is then transported to the product compression and storage unit.

[0074] S304: Low-pressure purging and regeneration stage. At the end of vacuum desorption, purified gas supplied by the purified gas collection manifold is introduced to back purge the adsorption tower. The purging gas passes through the carbon dioxide selective adsorption layer, pushing the carbon dioxide gas remaining in the gaps between the adsorbent particles toward the product gas outlet.

[0075] S305: Stepped repressurization stage.

[0076] After purging, the adsorption tower begins to restore pressure. The adsorption tower first receives light component gas from other adsorption towers in the co-current depressurization phase for initial pressurization, then introduces purified gas or feed gas to raise the internal pressure of the adsorption tower to the preset adsorption pressure. The pressurization rate is adjusted via a frequency converter valve to prevent sudden pressure changes in the bed layer that could cause adsorbent particle wear.

[0077] S306: Multi-tower continuous operation switching.

[0078] The multi-tower parallel adsorption module controls the phase difference of each adsorption tower through actuators, ensuring that at any given time, there are adsorption towers in the low-temperature, high-pressure adsorption stage and another adsorption tower in the countercurrent vacuum desorption stage. The cycle time between each adsorption tower is [not specified]. Satisfy the following formula:

[0079] In the formula, Indicates the adsorption time; Indicates the duration of downstream pressure reduction; Indicates the duration of vacuum desorption; Indicates the duration of low-pressure purging; This indicates the duration of repressurization.

[0080] During the cycle, the power consumption of the vacuum suction unit is related to the initial pressure and target vacuum level inside the adsorption tower. The frequency conversion adjustment algorithm for the vacuum pump unit and the opening and closing timing of the solenoid valves can be conventionally set by those skilled in the art according to the actual processing scale; these are well-known technologies in the field and will not be elaborated upon here.

[0081] Pressure and temperature sensors inside the adsorption tower feed data back to the automated control system in real time. When the temperature sensor detects that the temperature of the carbon dioxide selective adsorption layer has dropped to a threshold due to desorption endothermic heat, the automated control system adjusts the purge gas flow rate in step S304 or adjusts the pressurization time in step S305 to maintain the bed temperature using the heat from the incoming gas. above.

[0082] Through the aforementioned six-stage pressure oscillation cycle, the system releases carbon dioxide from the adsorbent by utilizing changes in the pressure gradient without using an external high-temperature heat source.

[0083] The system optimization and emergency response mechanism for cold environments ensures the stable operation of the cryogenic pressure swing adsorption carbon dioxide capture device in low-temperature and heat-constrained environments. Through structural enhancement and control logic adjustments, this mechanism addresses engineering challenges related to equipment cryogenic brittleness, fluid phase change, and distributed deployment.

[0084] The specific implementation details of system optimization and emergency response in cold environments are as follows: S501: Structural brittleness protection and heat loss control.

[0085] The adsorption tower assembly and its supporting pipelines are covered with an insulation layer. A polytetrafluoroethylene (PTFE) heat insulation pad is installed between the support structure and the base of the adsorption tower to cut off the heat conduction path from the metal components to the ground and prevent stress damage to the foundation structure due to cold contraction.

[0086] S502: Cryogenic fluid antifreeze and heat tracing compensation.

[0087] Self-regulating heating cables are installed at the valve assemblies of the raw gas pretreatment module and the vacuum suction unit. When the ambient temperature is lower than... At this time, the automated control system activates the electric heating tape to prevent valve seal failure. The output heat power of the electric heating tape... Follow the calculation formula below:

[0088] In the formula, This represents the overall heat transfer coefficient of the piping system; This indicates the effective heat transfer area of ​​the heated surface. Indicates the preset minimum operating temperature; Indicates the current ambient temperature; This indicates the thermal efficiency of the insulation layer. The automated control system adjusts the current to ensure that the output heat power is used only to compensate for heat loss from the environment, without increasing the operating temperature of the carbon dioxide selective adsorption layer.

[0089] S503: Modular deployment and expansion.

[0090] The multi-tower parallel adsorption module adopts a skid-mounted modular design. Each skid-mounted unit integrates a preset number of adsorption towers, valve assemblies, and a local controller. The capture capacity is linearly expanded by connecting multiple skid-mounted units in parallel, based on the amount of carbon dioxide emissions. Standardized interfaces are used to connect the modules.

[0091] S504: Emergency response under extreme low temperatures.

[0092] When the ambient temperature drops to the lower limit of the adsorbent's operating temperature, or when the heat exchange system fails, causing abnormal inlet gas temperature, the automatic control system activates the emergency cycle mode. In emergency cycle mode, the automatic control system reduces the amount of purified gas purging in step S304, utilizing the adsorption heat generated during the adsorption stage to maintain the activity within the carbon dioxide selective adsorption layer. Simultaneously, the vacuum pumping unit switches to intermittent operation to reduce mechanical wear of the vacuum pump in a low-temperature lubrication environment.

[0093] Regarding the specific materials used for thermal insulation and the circuit protection design of the electric heating cable, those skilled in the art can configure them according to relevant engineering specifications. The relevant content is well-known in the field and will not be elaborated here.

[0094] The automated control system obtains the operating status by monitoring temperature and pressure sensors at various points. If the pressure difference between the vacuum pump outlet pressure and the vacuum level inside the adsorption tower exceeds a preset threshold, the automated control system determines that the pipeline is frosted and blocked, and controls the valve group to switch to the backup pipeline.

[0095] Through the aforementioned system optimization and emergency response mechanisms, the cryogenic pressure swing adsorption carbon dioxide capture device can adapt to... The system utilizes a combination of modular design and electric heat tracing compensation to achieve continuous operation in distributed application scenarios in cold regions, mitigating environmental temperature differences.

[0096] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A low-temperature pressure swing adsorption carbon dioxide capture process suitable for cold environments, characterized in that, Includes the following steps: S100: Raw material gas pretreatment: The raw material gas is cooled to -20°C to 10°C by using an ambient cold source through a low-temperature heat exchanger in the pretreatment module; S200: Low temperature and high pressure adsorption: The pretreated raw gas enters the adsorption tower in the multi-tower parallel adsorption module at a pressure of 0.2-1.0MPa. The carbon dioxide is retained by the carbon dioxide selective adsorption layer, and the purified gas is discharged from the top of the adsorption tower. S300: Stepped depressurization recovery: When the feed gas input is stopped, the adsorption tower performs co-current depressurization to release the light component gas, and guides the light component gas to other adsorption towers that are in the repressurization stage; S400: Countercurrent vacuum desorption: The adsorption tower is evacuated in a countercurrent manner through the vacuum suction unit, reducing the absolute pressure inside the adsorption tower to 10-30 kPa, so that carbon dioxide molecules are desorbed to form carbon dioxide product gas. S500: Bed regeneration and adsorption initialization: The carbon dioxide selective adsorption layer is purged with purified gas, and the internal pressure of the adsorption tower is restored to the preset adsorption pressure through a staged pressurization operation.

2. The low-temperature pressure swing adsorption carbon dioxide capture process suitable for cold environments according to claim 1, characterized in that, In S100, the raw gas passes through a filter assembly to remove impurities, then through a deep dehydration assembly to lower the dew point of the raw gas to below -50°C, and finally enters the low-temperature heat exchanger for cold energy exchange.

3. The low-temperature pressure swing adsorption carbon dioxide capture process suitable for cold environments according to claim 2, characterized in that, In S100, the automated control system monitors the temperature sensor at the outlet of the low-temperature heat exchanger in real time. When the ambient temperature fluctuates and causes the feed gas inlet temperature to deviate from the range of -20°C to 10°C, the automated control system adjusts the opening of the bypass valve of the low-temperature heat exchanger to mix part of the uncooled feed gas with the cooled feed gas to achieve temperature difference compensation.

4. The low-temperature pressure swing adsorption carbon dioxide capture process suitable for cold environments according to claim 1, characterized in that, In S200, the adsorption tower is sequentially filled with a buffer layer, a carbon dioxide selective adsorption layer, and a support layer from the raw gas inlet to the purified gas outlet; the filling height ratio of the buffer layer, the carbon dioxide selective adsorption layer, and the support layer is 1:6:1 to 1:8:

1.

5. The low-temperature pressure swing adsorption carbon dioxide capture process suitable for cold environments according to claim 4, characterized in that, In S200, temperature sensors are arranged longitudinally at equal intervals inside the carbon dioxide selective adsorption layer, and pressure sensors are arranged on the inlet and outlet sides. The automatic control system determines the pressure difference inside the adsorption tower based on the signal obtained by the pressure sensor, and adjusts the heat exchange intensity of the low-temperature heat exchanger based on the value of the temperature sensor.

6. The low-temperature pressure swing adsorption carbon dioxide capture process suitable for cold environments according to claim 1, characterized in that, In the S400, the vacuum suction unit uses a multi-stage vacuum pump group to suction the adsorption tower, and the carbon dioxide product gas is compressed and purified before entering the carbon dioxide product gas storage tank for storage.

7. The low-temperature pressure swing adsorption carbon dioxide capture process suitable for cold environments according to claim 1, characterized in that, In S500, the adsorption tower first receives light component gas transmitted from other adsorption towers in the co-current depressurization stage for initial pressurization, and then introduces purified gas to raise the internal pressure of the adsorption tower to the preset adsorption pressure. The pressurization rate is adjusted by a frequency conversion control valve.

8. The low-temperature pressure swing adsorption carbon dioxide capture process suitable for cold environments according to claim 1, characterized in that, The multi-tower parallel adsorption module controls the phase difference of each adsorption tower through an actuator, ensuring that at any given time, there is an adsorption tower in the low-temperature and high-pressure adsorption stage and another adsorption tower in the countercurrent vacuum desorption stage.

9. The low-temperature pressure swing adsorption carbon dioxide capture process suitable for cold environments according to claim 1, characterized in that, When the ambient temperature is lower than the lower limit of the adsorbent's operating temperature, the automatic control system starts the emergency cycle mode. By reducing the amount of purified gas purging in the S500, the adsorption heat generated during the adsorption stage is used to maintain the activity inside the carbon dioxide selective adsorption layer, and the vacuum pumping unit is controlled to switch to intermittent operation.

10. A low-temperature pressure oscillation adsorption carbon dioxide capture system suitable for cold environments, used to implement the process described in any one of claims 1 to 9, characterized in that, include: The pretreatment module is equipped with a filtration assembly, a deep dehydration assembly, and a low-temperature heat exchanger; The multi-tower parallel adsorption module consists of multiple adsorption towers arranged in parallel. The adsorption towers are equipped with a carbon dioxide selective adsorption layer, a pressure sensor and a temperature sensor. The vacuum suction unit is connected to the bottom outlet of the adsorption tower via pipeline; An automated control system is electrically connected to the temperature sensor, pressure sensor, and actuators on the pipeline.

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