CN-121971947-A - CO2 capturing unit and method for directly connecting liquid-air energy storage system

Abstract

The invention discloses a CO2 trapping unit and a method for directly connecting a liquefied air energy storage system (liquid air energy storage system, LAES), and the core is to multiplex the existing air adsorption system and heat storage system of the liquefied air energy storage system to realize efficient trapping. After the air containing 400ppm CO2 enters the liquid-air energy-storage adsorption system, the water and CO2 are adsorbed by molecular sieve and other adsorbents, and after the adsorbents are saturated, the air is resolved by pure air to produce resolved gas with the CO2 concentration reaching 3500-4500ppm (ten times of raw material air). The capturing unit is directly connected with the resolved gas outlet and comprises a gas compression system, a drying system, a prepurification unit and a low-temperature rectification purification system which are sequentially connected, and a gas expansion system and a buffer tank can be additionally arranged. The liquefied air energy storage system comprises a heat storage system which is used for storing heat generated by an air compressor in the energy storage process, and the heat of the heat storage system is used for heating the CO2 capture unit to realize the regeneration of the adsorption system of the CO2 capture unit.

Inventors

• TANG SHILI
• JIANG LI

Assignees

• 优能恒创(杭州)科技有限公司

Dates

Publication Date

20260505

Application Date

20260401

Claims (11)

1. 1. The CO2 capturing unit is characterized by comprising a separation and purification assembly for processing analysis gas of the liquid-air energy storage system, wherein an air inlet end of the separation and purification assembly is directly connected with an analysis gas outlet of the liquid-air energy storage system and is used for receiving analysis gas which is generated by analysis of an adsorbent of the liquid-air energy storage system and has concentration of CO2 higher than that of the atmosphere, and a heat storage system of the liquid-air energy storage system is used as a heat source of a self regeneration stage by the separation and purification assembly.
2. 2. The CO2 capture unit of claim 1, wherein the separation and purification assembly comprises a gas compression system, a drying system, a pre-purification unit and a cryogenic rectification purification system connected in sequence, wherein the gas compression system is used for increasing partial pressure of CO2 in the resolved gas, the drying system is used for removing moisture in the resolved gas, the pre-purification unit is used for removing impurities from the resolved gas and enriching CO2, and the cryogenic rectification purification system is used for purifying the enriched CO2 to a preset purity.
3. 3. The CO2 capture unit of claim 2, further comprising a gas expansion system coupled to the byproduct outlet of the cryogenic rectification purification system for performing expansion work on byproducts produced by the cryogenic rectification purification system to effect energy recovery, the recovered energy being used to supplement energy consumption of the gas compression system.
4. 4. The CO2 capture unit of claim 2, wherein the prepurification unit adopts a membrane separation process or a Pressure Swing Adsorption (PSA) process, and the drying system is filled with a high-efficiency water absorbent which is molecular sieve or activated alumina and is used for removing the water content of the resolved gas to be less than or equal to 10ppm.
5. 5. The CO2 capture unit of claim 1, further comprising a resolved gas buffer tank disposed between the inlet end of the separation and purification assembly and the resolved gas outlet of the liquid-air energy storage system for stabilizing the inlet pressure and flow rate of the resolved gas.
6. 6. The CO2 capturing unit according to claim 2, wherein the gas compression system adopts a multi-stage compression mode to raise the partial pressure of CO2 in the resolved gas to 0.5-1.2MPa, a CO2 product outlet of the cryogenic rectification purification system is connected with a product storage tank, and the purity of CO2 stored in the product storage tank is more than or equal to 99.9%.
7. 7. The CO2 capturing method for directly connecting the liquid-air energy storage system is characterized by comprising the following steps of: s1, receiving analysis gas generated by analysis of an adsorbent in a liquid-air energy storage system, wherein the concentration of CO2 in the analysis gas is higher than the atmospheric concentration; S2, preprocessing the analysis gas, wherein the preprocessing at least comprises pressure flow stabilization processing, compression processing and drying processing; S3, pre-purifying the pre-treated analysis gas, removing impurities and enriching CO2 to obtain CO2 enriched gas; s4, carrying out low-temperature rectification purification on the CO2 enriched gas, and separating to obtain a CO2 product with preset purity and a byproduct taking air as a main component; And S5, in the regeneration process of the CO2 capturing unit, a heat storage system of the liquid-air energy storage system is utilized to heat a regeneration medium, so that a heat source is provided for the regeneration process.
8. 8. The method for capturing CO2 according to claim 7, wherein in the step S2, the pressure flow stabilizing treatment is realized by a resolved gas buffer tank, the compression treatment is to raise the partial pressure of CO2 to 0.5-1.2MPa by a multi-stage compression mode, and the drying treatment is to remove the water content of the resolved gas to be less than or equal to 10ppm.
9. 9. The CO2 capturing method according to claim 7, wherein in the step S3, the pre-purification treatment adopts a membrane separation process or a Pressure Swing Adsorption (PSA) process, the operation temperature is 25-40 ℃ and the operation pressure is 0.4-1.0MPa when the membrane separation process is adopted, the operation pressure is about 0.7MPa when the Pressure Swing Adsorption (PSA) process is adopted, the adsorption time is 100-140S, the pressure equalizing time is 10-20S, the desorption pressure is 0.01-0.03MPa, and the concentration of CO2 enriched gas obtained after the pre-purification is more than or equal to 10%.
10. 10. The method for capturing CO2 according to claim 7, wherein in the step S4, the operation pressure of the cryogenic rectification purification system is 0.1-0.3MPa, the temperature of the top of the rectification column is-190 ℃ to-180 ℃, the temperature of the bottom of the column is-56 ℃ to-50 ℃, and the purity of the separated CO2 product is more than or equal to 99.9%.
11. 11. The method for capturing CO2 according to claim 7, further comprising a step S6 of introducing the by-product produced in the step S4 into a gas expansion system, recovering energy by expansion work, wherein the recovered energy is used for supplementing the energy consumption of the compression treatment in the step S2, and the concentration of CO2 in the analysis gas is 3500-4500ppm, which is about 10 times the concentration of atmospheric CO 2.

Description

CO2 capturing unit and method for directly connecting liquid-air energy storage system Technical Field The invention relates to the field of environmental protection and energy storage, in particular to a CO2 capturing unit and method for directly connecting a liquid-air energy storage system, which are used for efficiently recycling CO2 in analysis gas of the liquid-air energy storage system and realizing low-carbon environmental protection and resource recycling. Background The liquefied air energy storage system purifies raw air (wet air containing impurities) from the main air compressor by two parallel arranged air adsorption systems. The two air adsorption systems are operated in an alternating switching manner, namely, when the first air adsorption system adsorbs impurities in the raw material air until the adsorbent is saturated, the second air adsorption system is in a regeneration stage, once the adsorbent of the first air adsorption system is saturated, the second air adsorption system is switched to adsorb the impurities in the raw material air, and at the moment, the first air adsorption system starts the regeneration stage, and the steps are alternately repeated to generate dry air required by liquid air energy storage rectification. The adsorption stage refers to a process in which water, CO2, acetylene, other hydrocarbons, and the like in the humid air are adsorbed to generate dry air when the raw air from the main air compressor passes through the adsorbent. If impurities are not removed before the water enters the liquid-air energy storage cold box, the cooled and frozen water and CO2 are deposited in the low-temperature heat exchanger, the turbine expander or the rectifying tower, heat exchange channels, pipelines and valves are blocked, acetylene is accumulated in liquid oxygen and is more at risk of explosion, so that the liquid-air energy storage equipment is damaged or broken, and therefore the liquid-air energy storage adsorption system has the function of removing impurities such as water, acetylene and CO2 contained in the air, and long-term safe and reliable operation of the liquid-air energy storage equipment is ensured. The adsorbents commonly used in liquid-air energy storage adsorption systems include molecular sieves and alumina, and when the adsorbent is saturated and cannot continue to adsorb impurities, the maximum adsorption capacity of the adsorbent is reached, and at this time, the adsorbent needs to be regenerated to release water and CO2 on the surface of the adsorbent material, which is also called desorption. The resolved gas is mainly air, but contains CO2 with ten times higher concentration than the raw material air, and has extremely high CO2 recovery value. However, in the prior art, the partial analysis gas is mostly and directly discharged, targeted CO2 trapping and utilization are not carried out, meanwhile, the traditional direct air CO2 trapping technology needs to newly establish an independent adsorption system, has the problems of large equipment investment, high energy consumption, low CO2 separation efficiency and the like, and has no efficient trapping technology and device which are directly connected with the existing liquid-air energy storage system. In order to improve the power generation efficiency of the system, the liquid air energy storage system stores heat generated by the main air compressor in the heat storage system in the energy storage process, and then recovers the heat in the heat storage system in the energy release process so as to improve the energy storage efficiency of the system. The heat storage system generally uses one or more heat storage mediums such as pressurized water, heat conducting oil or molten salt according to different temperature ranges. For a CO2 capture unit that requires a regeneration process, its regeneration energy consumption can greatly increase the CO2 capture cost. The liquid-air energy-storage heat-storage system is used as a regeneration heat source of the CO2 trapping unit, so that the comprehensive efficiency of the system can be improved, and the comprehensive cost of CO2 trapping can be reduced. Disclosure of Invention Aiming at the defects that CO2 trapping equipment investment is large, energy consumption is high, and a liquid-air energy storage system analyzes that high-concentration CO2 in gas is not effectively utilized and system waste heat of the liquid-air energy storage system is rich in the prior art, the invention provides the high-efficiency CO2 trapping unit and the method for directly connecting the existing liquid-air energy storage system, and realizes low-cost and high-efficiency CO2 recovery. In order to achieve the above purpose, the core technical scheme of the invention is a CO2 capturing unit directly connected with a liquid-air energy storage system and a corresponding capturing method, and the method comprises the following steps: The CO2 capturing unit directly connected