CN-122006403-A - Double-fixed bed CO for phase-change capsule circulation thermal management2Trapping system and process

CN122006403ACN 122006403 ACN122006403 ACN 122006403ACN-122006403-A

Abstract

The invention discloses a phase-change capsule circulation heat management double-fixed bed CO 2 trapping system which comprises a to-be-trapped gas tank, a first fixed bed, a second fixed bed, a capsule heat exchange bin, a low-temperature heat pump, a first fan, a second fan, a carbon dioxide compressor and a carbon dioxide storage tank, wherein the closed loop reinforcement of adsorption heat release, heat storage and regeneration heat release is realized by the cooperation of the double-fixed bed alternate adsorption and desorption operation and the circulation heat exchange of a phase-change capsule, the transportation and stable supply of heat in time and space are realized, the external energy supply requirement of the system is obviously reduced while the adsorption efficiency is ensured, and the system stability and the amplification feasibility are improved.

Inventors

ZHAO CHUANWEN
SUN ZEHUA
WU JINGWEN
Hu Baichuan
HAO YUXIN
YAO YIQIAN
QI QINGFANG

Assignees

南京师范大学

Dates

Publication Date: 20260512
Application Date: 20260306

Claims (10)

1. A double-fixed bed CO 2 capturing system for phase-change capsule circulation thermal management is characterized by comprising a to-be-captured flue gas tank, a first fixed bed, a second fixed bed, a capsule heat exchange bin, a low-temperature heat pump, a first fan, a second fan, a carbon dioxide compressor and a carbon dioxide storage tank, wherein: the outlet of the flue gas tank to be trapped is connected with a flue gas main pipeline through a throttle valve of the flue gas tank to be trapped in sequence, and the flue gas main pipeline is respectively communicated with inlets at the lower parts of the first fixed bed and the second fixed bed through a first fixed bed flue gas throttle valve and a second fixed bed flue gas throttle valve, so that the flue gas to be trapped is adsorbed through the fixed beds from bottom to top; The upper parts of the first fixed bed and the second fixed bed are respectively connected with a first heat exchanger and a second heat exchanger, and the opening and the closing of the first fixed bed throttle valve and the second fixed bed throttle valve are controlled; the lower parts of the first fixed bed and the second fixed bed are respectively provided with an independent carbon dioxide gas channel and a capsule solid channel, wherein the first fixed bed lower carbon dioxide throttle valve and the second fixed bed lower carbon dioxide throttle valve are connected with a carbon dioxide storage tank in parallel through a carbon dioxide storage tank throttle valve and used for blowing and regenerating carbon dioxide gas to the corresponding fixed bed in a desorption stage; the capsule heat exchange bin is respectively communicated with the capsule channels of the two fixed beds through a left valve of the capsule heat exchange bin and a right valve of the capsule heat exchange bin and is used for recovering heat from the high-temperature capsules of the desorption bed; The capsule heat exchange bin is connected with the low-temperature heat pump, and heat is transferred to the low-temperature heat pump after heat exchange, the low-temperature heat pump forms a closed heat cycle with the system through a low-temperature heat pump right valve and a low-temperature heat pump left valve, a broken line represents an energy transfer loop, and the recovered heat is conveyed to a fixed bed in a desorption state after being lifted to a higher temperature to supply heat for desorption regeneration; The first fan and the second fan are respectively communicated with the upper ends of the two fixed beds through a first fan throttle valve and a second fan throttle valve, are respectively connected with a left valve of the capsule heat exchange bin and a right valve of the capsule heat exchange bin, can blow phase-change capsules in the fixed bed to the capsule heat exchange bin after adsorption is finished, and can convey the capsules after heat exchange to another fixed bed in the next circulation stage.
2. A carbon dioxide capturing process using the system according to claim 1, comprising the steps of (1) constructing a double fixed bed adsorption system by providing at least two fixed bed reactors, a first fixed bed and a second fixed bed, respectively, in which a honeycomb structured packing coated with a potassium-based adsorbent is packed; the system is internally provided with a flowable phase-change capsule and a heat pump unit for heat recovery and upgrading, wherein (2) isothermal adsorption and in-situ heat storage are carried out, namely flue gas containing CO 2 is introduced into a first fixed bed in an adsorption state, meanwhile, the phase-change capsule in a cooling state is introduced into a honeycomb channel or a gap of the fixed bed, a potassium-based adsorbent captures CO 2 and releases reaction heat, the phase-change capsule absorbs the reaction heat through solid-liquid phase change in situ, the bed temperature is controlled in a preset adsorption temperature range, (3) the capsule separation and heat extraction are carried out, namely, when the first fixed bed adsorbs saturation or the phase-change capsule finishes phase change, the phase-change capsule carrying latent heat is separated and discharged from the first fixed bed and is conveyed to an external capsule heat exchange bin, 4) the heat release and the capsule regeneration are carried out, namely, in the capsule heat exchange bin, the phase-change capsule is released to the evaporation side of the heat pump system and is restored to a solid cooling state, and then the adsorption step is returned to be recycled, and (5) the heat pump temperature and the adsorbent regeneration are carried out, namely, the heat pump unit utilizes consumed electric energy to lift the low-grade heat recovered from the phase-change capsule to the regeneration temperature and convey the low-grade heat to a second fixed bed in a desorption state, and the potassium-based adsorbent is driven to decompose and release the latent heat carrier 2 , so that the CO is regenerated.
3. The phase-change capsule circulation thermal management double-fixed bed CO 2 capturing process according to claim 2, wherein the honeycomb structured packing in the step (1) is a silicon dioxide honeycomb monomer, the inner wall of a pore canal of the honeycomb structured packing is attached with a K 2 CO 3 /Al 2 O 3 composite adsorbent by a coating method, and the mass ratio of K 2 CO 3 to Al 2 O 3 in the composite adsorbent is (3-5): 3.
4. The phase-change capsule circulation heat-managed double-fixed bed CO 2 capturing process according to claim 3, wherein the coating method comprises the steps of mixing K 2 CO 3 with aluminum sol to prepare slurry, coating the slurry into honeycomb carrier pore channels, drying and calcining to form, wherein the coating times are 2.
5. The process for capturing CO 2 by using a double fixed bed for cyclic thermal management of a phase change capsule according to claim 2, wherein the phase change capsule in the step (1) is a microcapsule with a core-shell structure, the core material is paraffin, the phase change temperature is set to be 50-70 ℃, the phase change temperature is matched with the optimal adsorption activity temperature of a potassium-based adsorbent, and the shell material is silicon dioxide or PMMA.
6. The phase-change capsule cycle thermal management double-fixed bed CO2 capturing process according to claim 2, wherein in the step (2), the preset adsorption temperature is 60+/-2 ℃, and the adsorption reaction exotherm is absorbed by adding the phase-change capsule, so that the approximate isothermal adsorption is realized.
7. The phase change capsule circulation thermal management double-fixed bed CO2 capturing process according to claim 2, wherein the capsule separation mode in the step (3) is realized by utilizing the flowability difference of the phase change capsules and fixed bed honeycomb fillers, and comprises one or more of gravity sedimentation separation and pneumatic blowing separation, wherein the honeycomb structured fillers are fixed, and the phase change capsules flow in honeycomb pore channels or flow in filler gaps as mobile phases.
8. The phase-change capsule circulation thermal management double-fixed bed CO 2 capturing process according to claim 2, wherein in the step (5), the heat pump unit is a compression heat pump or an absorption heat pump, and the heat pump unit is used for raising the heat from a low temperature of 60+/-2 ℃ to a high temperature of 100-150 ℃.
9. The phase-change capsule cycle thermal management double fixed bed CO 2 capture process of claim 2, wherein high concentration CO 2 produced by desorption is collected and used as an industrial feed gas for methanol synthesis or as a shielding gas for external supply.
10. The dual fixed bed CO 2 capture system for cyclic thermal management of phase change capsules according to claim 1, wherein the system further comprises a thermal management control unit, which monitors the bed temperature distribution and the capsule outlet temperature in real time, and adjusts the heat pump compressor power and the capsule circulating pump rotational speed by frequency conversion to maintain the thermal balance of the system.

Description

Double-fixed bed CO 2 trapping system and technology for phase-change capsule circulation thermal management Technical Field The invention belongs to the technical fields of gas separation, energy chemical industry and energy conservation and environmental protection, relates to a high-efficiency low-energy-consumption trapping technology for low-concentration carbon dioxide in coal-fired flue gas and industrial tail gas, and in particular relates to a double-fixed-bed CO2 trapping system and technology for phase-change capsule circulation thermal management. Background Under the drive of global climate change and a 'two carbon' target, carbon dioxide trapping, utilization and sequestration (CCUS) become an important technical path for industrial emission reduction. In the existing CO 2 capturing process, although the application of wet amine absorption is wide, the problems of high regeneration energy consumption, high equipment corrosion and operation and maintenance cost and the like are generally existed, and in contrast, the solid adsorption method is considered to be one of potential routes for replacing wet amine absorption due to the characteristics of low theoretical energy consumption, no corrosion, flexible operation and the like. However, the existing potassium-based solid adsorbent still faces two key bottlenecks in engineering application, namely bed temperature rise and capacity reduction caused by adsorption heat release, CO 2 adsorption process is accompanied by obvious heat release, the adsorption capacity is reduced by the bed temperature rise, effective trapping capacity and penetration time are influenced, and the problems of high flow resistance and high pressure drop generated by a traditional fixed bed reactor when large-volume flue gas is treated are solved, so that a large amount of fan/compressor power is consumed, and obvious mass transfer limitation and parasitic energy consumption are formed. In order to solve the problems, researches have been proposed to introduce a Phase Change Material (PCM) into an adsorption system for heat management, namely, the PCM can absorb a large amount of latent heat at a nearly constant temperature near a phase change point, so that temperature peaks are restrained, a bed layer is kept in an optimal adsorption temperature interval, and the effective capacity is maximized, but from the engineering realization point of view, the idea of the traditional PCM coupling adsorption still has a further optimization space, namely, on one hand, adsorption heat release has a characteristic of low grade heat and is directly used for desorption regeneration, and on the other hand, the heat in the adsorption and desorption processes is not matched with the space in time, so that the heat is difficult to be stably recovered and used for regeneration. Therefore, a process flow capable of realizing continuous heat recovery, temperature level elevation and stable heat supply regeneration in a fixed bed adsorption/desorption system is needed to improve the overall energy efficiency and economy. Disclosure of Invention In order to solve the problems, the invention discloses a double-fixed bed CO2 trapping system and a process for cyclic thermal management of phase-change capsules, which realize closed-loop reinforcement of adsorption heat release, heat storage and regeneration heat release by the aid of the cyclic heat exchange of the phase-change capsules through the alternate adsorption and desorption operation of the double-fixed beds, and realize 'carrying' and stable supply of heat in time and space, so that the stability and the amplification feasibility of the system are improved. In order to achieve the above purpose, the technical scheme of the invention is as follows: the double-fixed bed CO2 trapping system for the phase-change capsule circulation heat management comprises a to-be-trapped gas tank, a first fixed bed, a second fixed bed, a capsule heat exchange bin, a low-temperature heat pump, a first fan, a second fan, a carbon dioxide compressor and a carbon dioxide storage tank, wherein: the outlet of the flue gas tank to be trapped is connected with a flue gas main pipeline through a throttle valve of the flue gas tank to be trapped in sequence, and the flue gas main pipeline is respectively communicated with inlets at the lower parts of the first fixed bed and the second fixed bed through a first fixed bed flue gas throttle valve and a second fixed bed flue gas throttle valve, so that the flue gas to be trapped is adsorbed through the fixed beds from bottom to top; The upper parts of the first fixed bed and the second fixed bed are respectively connected with the first heat exchanger and the second heat exchanger, and the opening and the closing are controlled through a throttle valve on the first fixed bed and a throttle valve on the second fixed bed. The gas subjected to heat exchange enters a carbon dioxide compressor through a throttle valve of th