Carbon capture system for oxygen-enriched combustion based on molecular sieve adsorption separation

Abstract

The application relates to a carbon capture system for oxygen-enriched combustion based on molecular sieve adsorption separation, and relates to the field of efficient combustion and flue gas pollutant purification treatment. The carbon capture system for the existing power plant applying the oxygen-enriched combustion technology solves the problems of high oxygen enrichment energy consumption and complex system. The utility model is characterized in that air is cooled by a cold water heat exchanger, oxygen in the air is enriched by N-stage oxygen molecular sieve groups, the oxygen-enriched air is mixed uniformly in a mixing tank, the mixed air is subjected to oxygen-enriched combustion in a combustion system, flue gas is subjected to desulfurization and denitrification and water separation, and then the flue gas is subjected to pressurization and cooling to separate liquid carbon dioxide, so that the carbon dioxide in the flue gas is captured. The N-stage oxygen molecular sieve groups greatly reduce the oxygen separation energy consumption, and the concentration of the oxygen-enriched gas can be flexibly adjusted without setting a complex system, so that the utility model is suitable for different types of oxygen-enriched combustion power plants. The utility model is mainly used in the power plant applying the oxygen-enriched combustion technology.

Description

Technical Field

[0001] This utility model relates to the field of high-efficiency combustion and flue gas pollutant purification. Background Technology

[0002] Thermal power plants emit large amounts of flue gas during the combustion of fossil fuels, containing greenhouse gases such as carbon dioxide and nitrogen oxides, which have a significant impact on climate change. Since carbon dioxide emissions from thermal power generation account for more than 40% of global carbon emissions, it has become a key area requiring urgent intervention. Carbon capture technology, as one of the most direct and feasible emission reduction methods currently available, is gradually becoming an important pathway for controlling carbon emissions in the thermal power generation industry.

[0003] Oxygen-enriched combustion and post-combustion carbon capture technologies are currently common methods for carbon capture in thermal power plants. Oxygen-enriched combustion technology can increase the oxygen content in the gas, reduce the nitrogen content in the flue gas, increase the carbon dioxide content, significantly reduce carbon capture energy consumption, improve combustion efficiency, and effectively reduce the emission of pollutants such as nitrogen oxides.

[0004] Conventional oxygen-enriched combustion technology first involves air separation to obtain pure oxygen. The recirculated flue gas and pure oxygen then enter the combustion equipment and undergo a chemical reaction with the fuel before combustion. The flue gas after oxygen-enriched combustion has a high carbon dioxide concentration, which helps reduce the energy consumption for carbon capture after combustion. Conventional chemical absorption or physical separation methods can be used for separation.

[0005] Existing conventional oxy-fuel combustion systems have several problems: the air separation process requires compressing air to 5-7 atmospheres, with separation temperatures ranging from -196 to -180 degrees Celsius, resulting in enormous energy consumption. While air separation produces 100% pure oxygen, most combustion processes cannot utilize pure oxygen and require further reduction of the oxygen concentration before combustion. Currently, a common method is to mix recirculated flue gas with pure oxygen to lower the oxygen concentration in the regulating gas before it enters the burner in the oxy-fuel combustion process, thus reducing the combustion temperature. This method increases system complexity and overall operational difficulty, requires precise control of the recirculated flue gas ratio, and further complicates operation as no flue gas is generated during startup.

[0006] Water drying process after burner combustion:

[0007] The commonly used methods for drying flue gas in conventional thermal power plants are surface condensation and direct spraying. Surface condensation cools the flue gas to remove water, but it is energy-intensive. Spraying can cool flue gas on a large scale, but it cannot completely separate the moisture from the flue gas, requiring further gas-liquid separation, which is a complex process.

[0008] Therefore, the carbon capture systems of thermal power plants using oxygen-enriched combustion technology suffer from problems such as high energy consumption for oxygen enrichment and high energy consumption and inability to achieve satisfactory water separation during the water drying stage, making them unsuitable for large-scale capture. These issues urgently need to be addressed. Utility Model Content

[0009] The purpose of this invention is to solve the problems of high energy consumption and system complexity in existing carbon capture systems for thermal power plants using oxy-fuel combustion technology. This invention provides a carbon capture system based on molecular sieve adsorption and separation during oxy-fuel combustion.

[0010] The carbon capture system based on molecular sieve adsorption separation and oxygen-enriched combustion includes a cold water heat exchanger, two compressors, a carbon capture unit and a compressed gas energy storage unit; it also includes an N-stage oxygen molecular sieve group, a mixing tank, desulfurization and denitrification equipment and a water separation and storage system.

[0011] The N-stage oxygen molecular sieve group consists of N oxygen molecular sieve groups connected in series. The inlet of the first oxygen molecular sieve group serves as the inlet of the N-stage oxygen molecular sieve group, and the oxygen-enriched outlet of the Nth oxygen molecular sieve group serves as the oxygen-enriched outlet of the N-stage oxygen molecular sieve group. Each oxygen molecular sieve group is used for oxygen enrichment, and the adsorption saturation concentration of the N oxygen molecular sieve groups is different. N is an integer, and 2 < N ≤ 4.

[0012] The water separation and storage system is used to separate water vapor and dry flue gas from the flue gas introduced into it, and to store the water vapor.

[0013] The inlet of the cold water heat exchanger is used to receive flue gas. The outlet of the cold water heat exchanger is connected to the inlet of the N-stage oxygen molecular sieve group. The oxygen-enriched outlet of the N-stage oxygen molecular sieve group is connected to the inlet of the mixing tank. The outlet of the mixing tank is connected to the inlet of the first compressor. The outlet of the second compressor is connected to the inlet of the combustion system. The outlet of the combustion system is connected to the inlet of the desulfurization and denitrification equipment. The outlet of the desulfurization and denitrification equipment is connected to the inlet of the water separation and storage system. The flue gas outlet of the water separation and storage system is connected to the inlet of the second compressor. The outlet of the second compressor is connected to the flue gas inlet of the carbon capture unit. The carbon capture unit is used to cool the received dry flue gas and then separate liquid carbon dioxide and impurity gases. The separated impurity gases are then passed into the compressed gas energy storage unit for energy storage.

[0014] Preferably, each oxygen molecular sieve group includes a first oxygen molecular sieve and a second oxygen molecular sieve, which operate in a time-sharing manner;

[0015] The inlets of the first and second oxygen molecular sieves are both used as the inlets of the oxygen molecular sieve group, and the oxygen-enriched outlets of the first and second oxygen molecular sieves are both used as the oxygen-enriched outlets of the oxygen molecular sieve group.

[0016] The mixed gas outlet of the first oxygen molecular sieve and the second oxygen molecular sieve is used to output the mixed gas.

[0017] A valve is installed on the pipeline between the outlet of the cold water heat exchanger and the inlet of the N-stage oxygen molecular sieve group.

[0018] A valve is installed on the pipeline between the inlet of the N-level oxygen molecular sieve group, the oxygen-enriched outlet, and the first inlet of the mixing tank.

[0019] Valves are installed on the pipeline between the inlet and outlet of two adjacent oxygen molecular sieve groups.

[0020] Preferably, there is a one-to-one correspondence between the N oxygen molecular sieve groups and the N preset thresholds in the N-level oxygen molecular sieve group;

[0021] When the oxygen concentration at the oxygen-enriched outlet of one oxygen molecular sieve in the i-th oxygen molecular sieve group of the N-level oxygen molecular sieve group is lower than the i-th preset threshold, the oxygen molecular sieve is determined to be saturated. At this time, the oxygen molecular sieve stops working and another oxygen molecular sieve starts working. The j-th preset threshold is less than the j+1-th preset threshold, where i and j are both integers, and i=1,2……N, j=1,2……N-1.

[0022] Preferably, the oxygen molecular sieve in the oxygen molecular sieve group is a lithium-based molecular sieve or a zeolite molecular sieve composed of lithium.

[0023] The operating temperature of the oxygen molecular sieve group includes the adsorption operating temperature and the desorption operating temperature. The adsorption operating temperature range is 20℃ to 50℃, and the desorption operating temperature range is 100℃ to 250℃.

[0024] Preferably, the water separation and storage system includes a first water molecular sieve, a second water molecular sieve, and a water storage tank, and the first water molecular sieve and the second water molecular sieve operate during separation;

[0025] The air inlets of both the first and second water molecular sieves serve as the air inlets of the water separation and storage system; the flue gas outlets of both the first and second water molecular sieves serve as the flue gas outlets of the water separation and storage system.

[0026] A valve is installed on the pipeline between the air inlet of the water separation and storage system and the air outlet of the desulfurization and denitrification equipment.

[0027] A valve is installed on the pipeline between the flue gas outlet of the water separation and storage system and the air inlet of the second compressor;

[0028] The steam outlets of the first and second water molecule sieves are simultaneously connected to the air inlet of the water storage tank, and valves are installed on the pipelines between the steam outlets of the first and second water molecule sieves and the water storage tank.

[0029] Preferably, the first and second water molecular sieves are type 3A water molecular sieves, and the operating temperatures of both the first and second water molecular sieves include adsorption operating temperature and desorption operating temperature, with the adsorption operating temperature range being 20℃ to 40℃ and the desorption operating temperature range being 150℃ to 250℃.

[0030] Preferably, the carbon capture unit includes a heat exchanger, a refrigerant heat exchanger, a carbon dioxide separator, and a liquid carbon dioxide storage tank.

[0031] A carbon dioxide separator is used to separate liquid carbon dioxide and impurity gases from the incoming flue gas.

[0032] The first air inlet of the heat exchanger serves as the flue gas inlet of the carbon capture unit. The flue gas outlet of the heat exchanger is connected to the air inlet of the refrigerant heat exchanger. The air outlet of the refrigerant heat exchanger is connected to the flue gas inlet of the carbon dioxide separator. The liquid outlet of the carbon dioxide separator is connected to the liquid inlet of the carbon dioxide liquid storage tank, which is used to store liquid carbon dioxide.

[0033] The impurity gas outlet of the carbon dioxide separator is connected to the second air inlet of the heat exchanger, and the impurity gas outlet of the heat exchanger is connected to the compressed gas energy storage unit as the impurity gas outlet of the carbon capture unit.

[0034] Preferably, the carbon capture system based on molecular sieve adsorption separation and oxygen-enriched combustion further includes a power generation unit;

[0035] The power generation unit is used to heat the impurity gas output from the compressed gas energy storage unit, and then use the heated impurity gas to generate electricity before discharging it.

[0036] A valve is installed on the pipeline between the outlet of the compressed gas energy storage unit and the inlet of the power generation unit.

[0037] Preferably, the first structure of the power generation unit is as follows:

[0038] The power generation unit includes a hot water heat exchanger and an expander, which together constitute a power-generating unit; the air inlet of the hot water heat exchanger serves as the air inlet of the power generation unit and is connected to the air outlet of the compressed gas energy storage unit, while the air outlet of the hot water heat exchanger is connected to the air inlet of the expander.

[0039] The impurity gas output from the outlet of the hot water heat exchanger is used to do work on the expander;

[0040] The second structure of the power generation unit is:

[0041] The power generation unit includes M hot water heat exchangers and M expanders, and each hot water heat exchanger and its corresponding expander constitute a power unit; wherein, the outlet of the hot water heat exchanger in each power unit is connected to the inlet of the expander, and the inlet of the hot water heat exchanger and the outlet of the expander serve as the inlet and outlet of the power unit, respectively.

[0042] The impurity gas output from the outlet of the hot water heat exchanger in each working unit is used to perform work on the expander connected to it;

[0043] M power units are connected in series, with the air inlet of the power unit at the beginning serving as the air inlet of the power generation unit, and the air outlet of the power unit at the end serving as the air outlet of the power generation unit; M is an integer, and 2≤M≤10.

[0044] The beneficial effects of this utility model are:

[0045] The utility model first cools the air through a water heat exchanger, then enriches the oxygen in the air using an N-stage oxygen molecular sieve group. After oxygen enrichment and separation, the air enters a mixing tank for homogeneous mixing before entering the combustion system for oxygen-enriched combustion. Following this, the flue gas undergoes desulfurization, denitrification, and water separation, and is then pressurized and cooled to separate liquid carbon dioxide with a purity exceeding 99%, thus completing the capture of carbon dioxide from the flue gas. The process involves increasing oxygen concentration through adsorption using an N-stage oxygen molecular sieve group; separating carbon dioxide from the flue gas through physical separation; and releasing energy through the expansion of a stored high-pressure impurity mixture.

[0046] This invention relates to an N-stage oxygen molecular sieve assembly, which consists of N oxygen molecular sieves connected in series. Firstly, it improves the adsorption efficiency of the molecular sieves and monitors the varying saturation concentrations of oxygen-enriched gas at each stage during the overall adsorption process. Secondly, it promptly removes the nitrogen-containing gas mixture separated during adsorption, reducing the overall system's adsorption and desorption energy consumption. This significantly reduces the energy consumption for oxygen separation, and allows for flexible adjustment of the oxygen-enriched gas concentration without requiring a complex system, making it suitable for different types of oxygen-enriched combustion power plants.

[0047] Specifically, each of the N-stage oxygen molecular sieve groups adsorbs and enriches oxygen in the air, separating a mixed gas containing nitrogen and an oxygen-enriched gas. The oxygen concentration of the oxygen-enriched gas is increased from 21% to 25%-90%, and energy consumption is reduced by more than 30% compared with conventional air separation methods.

[0048] After oxygen-enriched gas enters the combustion system and participates in combustion, the system discharges flue gas. Compared with conventional combustion methods, the flue gas flow rate is reduced by 15%–80%, the carbon dioxide concentration is increased by more than 200%, and the partial pressure of carbon dioxide in the flue gas is greatly increased, significantly reducing the pressure and liquefaction temperature required for carbon dioxide capture. The flue gas is then compressed and cooled by a compressor and a refrigerant heat exchanger, thereby achieving carbon dioxide liquefaction and separation. Compared with the energy consumption of other carbon capture methods, the energy consumption per unit of carbon capture is reduced by more than 50%.

[0049] This invention utilizes a water separation and storage system to dry flue gas and recover moisture from it, enabling the recycling of clean water from the flue gas. It also adsorbs, enriches, and separates carbon dioxide from the dried flue gas at low temperatures, while simultaneously compressing and storing the remaining high-pressure gas. This significantly reduces capture energy consumption, achieving the goals of energy conservation, water conservation, and greenhouse gas emission reduction. Compared to surface condensation, the water separation energy consumption of this invention is lower, and compared to spraying, the water removal rate is higher. Furthermore, this invention can improve the purity of liquid carbon dioxide in subsequent carbon capture processes.

[0050] The carbon capture system based on molecular sieve adsorption separation and oxygen-enriched combustion described in this utility model can increase the oxygen concentration in the air, thereby achieving oxygen-enriched combustion, improving combustion efficiency while reducing flue gas volume and increasing carbon dioxide concentration in the flue gas, thus reducing the difficulty of carbon dioxide capture. At the same time, the system also has flue gas drying and compressed gas energy storage functions, realizing comprehensive flue gas treatment.

[0051] Compared with other systems, the carbon capture system based on molecular sieve adsorption separation and oxygen-enriched combustion described in this invention has the following advantages:

[0052] 1. The oxygen concentration of the gas in oxygen-enriched combustion can reach 90%. Compared with conventional combustion, nitrogen oxide emissions are reduced by more than 50%. Compared with conventional cryogenic air separation oxygen-enriched combustion, oxygen separation energy consumption is reduced by more than 30%.

[0053] 2. The carbon dioxide concentration in the flue gas can reach over 60%.

[0054] 3. The carbon dioxide recovery rate is over 90%.

[0055] 4. The capture energy consumption is low and it has energy storage function. When a 100MW unit uses this system to treat flue gas, the net power consumption is about 10MW.

[0056] 5. This system can flexibly adjust the oxygen concentration and is suitable for different types of power plants, such as gas turbine power plants and coal-fired power plants. Attached Figure Description

[0057] Figure 1 This is a schematic diagram of a carbon capture system based on molecular sieve adsorption separation and oxygen-enriched combustion as described in this utility model;

[0058] Figure 2 This is another structural schematic diagram of the carbon capture system based on molecular sieve adsorption separation and oxygen-enriched combustion described in this utility model. Detailed Implementation

[0059] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0060] It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0061] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the present invention.

[0062] Detailed Implementation Method 1, see [link / reference] Figure 1 and Figure 2 This embodiment describes a carbon capture system based on molecular sieve adsorption separation and oxygen-enriched combustion, which includes a cold water heat exchanger 1, two compressors 7, a carbon capture unit 8, and a compressed gas energy storage unit 9; it also includes an N-stage oxygen molecular sieve group 2, a mixing tank 3, a desulfurization and denitrification device 5, and a water separation and storage system 6.

[0063] The N-level oxygen molecular sieve group 2 consists of N oxygen molecular sieve groups connected in series. The inlet of the first oxygen molecular sieve group serves as the inlet of the N-level oxygen molecular sieve group 2, and the oxygen-enriched outlet of the Nth oxygen molecular sieve group serves as the oxygen-enriched outlet of the N-level oxygen molecular sieve group 2. Each oxygen molecular sieve group is used for oxygen enrichment, and the adsorption saturation concentration of the N oxygen molecular sieve groups is different. N is an integer, and 2 < N ≤ 4.

[0064] The water separation and storage system 6 is used to separate water vapor and dry flue gas from the flue gas introduced into it, and to store the water vapor.

[0065] The inlet of the cold water heat exchanger 1 is used to receive flue gas. The outlet of the cold water heat exchanger 1 is connected to the inlet of the N-stage oxygen molecular sieve group 2. The oxygen-enriched outlet of the N-stage oxygen molecular sieve group 2 is connected to the inlet of the mixing tank 3. The outlet of the mixing tank 3 is connected to the inlet of the first compressor 7. The outlet of the second compressor 7 is connected to the inlet of the combustion system 4. The outlet of the combustion system 4 is connected to the inlet of the desulfurization and denitrification equipment 5. The outlet of the desulfurization and denitrification equipment 5 is connected to the inlet of the water separation and storage system 6. The flue gas outlet of the water separation and storage system 6 is connected to the inlet of the second compressor 7. The outlet of the second compressor 7 is connected to the flue gas inlet of the carbon capture unit 8. The carbon capture unit 8 is used to cool the received dry flue gas and then separate liquid carbon dioxide and impurity gases, and the separated impurity gases are passed into the compressed gas energy storage unit 9 for energy storage.

[0066] The utility model first cools the air through a cold water heat exchanger 1, then enriches the oxygen in the air through an N-stage oxygen molecular sieve group 2. After oxygen enrichment and separation, the air enters a mixing tank 3 to mix the gas evenly. The oxygen-enriched gas then enters a combustion system 4 for oxygen-enriched combustion. After desulfurization, denitrification, and water separation, the flue gas is pressurized and cooled to separate liquid carbon dioxide, thus completing the capture of carbon dioxide in the flue gas.

[0067] The N-stage oxygen molecular sieve group 2 consists of N oxygen molecular sieve groups connected in series. Firstly, it improves the adsorption efficiency of the molecular sieves and monitors the different saturation concentrations of oxygen-enriched gas at each stage during the overall adsorption process. Secondly, it promptly removes the mixed gas containing nitrogen separated during adsorption, reducing the overall system's adsorption and desorption energy consumption. This significantly reduces the energy consumption for oxygen separation and allows for flexible adjustment of the oxygen-enriched gas concentration without requiring a complex system, making it suitable for different types of oxygen-enriched combustion power plants.

[0068] The inlet of the cold water heat exchanger 1 of this invention is used to receive air. The outlet of the cold water heat exchanger 1 passes through an N-stage oxygen molecular sieve group 2 to separate a mixed gas containing nitrogen and oxygen-enriched gas. The oxygen-enriched gas enters the combustion system 4 to participate in combustion, thereby achieving oxygen-enriched combustion. After combustion, the flue gas is discharged from the outlet of the combustion system 4 and enters the desulfurization and denitrification equipment 5 to remove impurities. Then it enters the water separation and storage system 6 to separate water vapor and dry flue gas, and stores the water vapor. At the same time, the dry flue gas separated by the water separation and storage system 6 is sent to the second compressor 7 for compression and then sent to the carbon capture unit 8. The carbon capture unit 8 cools the received dry flue gas and separates liquid carbon dioxide and impurity gases. The separated impurity gases are then passed into the compressed gas energy storage unit 9 for energy storage, thereby achieving low-temperature capture of carbon dioxide.

[0069] The carbon capture system based on molecular sieve adsorption separation for oxygen-enriched combustion described in this invention can achieve oxygen-enriched combustion in thermal power plants with low energy consumption, significantly reducing flue gas flow and increasing the carbon dioxide concentration in the flue gas. Furthermore, it uses a pollution-free and low-energy-consumption physical method to separate carbon dioxide. This invention is applicable to different types of thermal power plants operating under oxygen-enriched combustion, significantly reducing the energy consumption for oxygen separation and carbon capture.

[0070] Furthermore, each oxygen molecular sieve group includes a first oxygen molecular sieve 2-1 and a second oxygen molecular sieve 2-2, which operate in a time-sharing manner;

[0071] The inlets of the first oxygen molecular sieve 2-1 and the second oxygen molecular sieve 2-2 are both used as the inlets of the oxygen molecular sieve group, and the oxygen-enriched outlets of the first oxygen molecular sieve 2-1 and the second oxygen molecular sieve 2-2 are both used as the oxygen-enriched outlets of the oxygen molecular sieve group.

[0072] The mixed gas outlet of the first oxygen molecular sieve 2-1 and the second oxygen molecular sieve 2-2 is used to output the mixed gas.

[0073] A valve 11 is installed on the pipeline between the outlet of the cold water heat exchanger 1 and the inlet of the N-stage oxygen molecular sieve group 2;

[0074] A valve 11 is installed on the pipeline between the air inlet and the oxygen-enriched air outlet of the N-level oxygen molecular sieve group 2 and the first air inlet of the mixing tank 3.

[0075] A valve 11 is installed on the pipeline between the inlet and the outlet of the two adjacent oxygen molecular sieve groups.

[0076] In this preferred embodiment, the simultaneous operation of two oxygen molecular sieves in each oxygen molecular sieve group ensures continuous operation of the system, improves the conversion efficiency of molecular sieve adsorption and regeneration processes, and enables the replacement of molecular sieves without shutting down the system.

[0077] Furthermore, there is a one-to-one correspondence between the N oxygen molecular sieve groups and the N preset thresholds in the N-level oxygen molecular sieve group 2; when the oxygen concentration at the oxygen-enriched outlet of one oxygen molecular sieve in the i-th oxygen molecular sieve group of the N-level oxygen molecular sieve group 2 is lower than the i-th preset threshold, it is determined that the oxygen molecular sieve is saturated with adsorption. At this time, the oxygen molecular sieve stops working and another oxygen molecular sieve starts working; and the j-th preset threshold is less than the j+1-th preset threshold, where i and j are both integers, and i=1,2……N, j=1,2……N-1.

[0078] In practical applications, when N is 3, the first to third preset thresholds are 25%, 50%, and 80%, respectively.

[0079] When the oxygen concentration at the oxygen-enriched outlet of the first oxygen molecular sieve 2-1 or the second oxygen molecular sieve 2-2 in the first oxygen molecular sieve group is lower than 25%, the oxygen molecular sieve is determined to be saturated. At this time, the oxygen molecular sieve stops working, and the other oxygen molecular sieve starts working, so that the two oxygen molecular sieves in the first oxygen molecular sieve group work separately.

[0080] When the oxygen concentration at the oxygen-enriched outlet of the first oxygen molecular sieve 2-1 or the second oxygen molecular sieve 2-2 in the second oxygen molecular sieve group is lower than 50%, it is determined that the oxygen molecular sieve is saturated. At this time, the oxygen molecular sieve stops working, and the other oxygen molecular sieve starts working, so that the two oxygen molecular sieves in the second oxygen molecular sieve group work at the same time.

[0081] When the oxygen concentration at the oxygen-enriched outlet of the first oxygen molecular sieve 2-1 or the second oxygen molecular sieve 2-2 in the third oxygen molecular sieve group is lower than 80%, the oxygen molecular sieve is determined to be saturated. At this time, the oxygen molecular sieve stops working, and the other oxygen molecular sieve starts working, so that the two oxygen molecular sieves in the third oxygen molecular sieve group work separately.

[0082] Furthermore, the oxygen molecular sieves in the oxygen molecular sieve group are lithium-based molecular sieves or zeolite molecular sieves composed of lithium.

[0083] The operating temperature of the oxygen molecular sieve group includes the adsorption operating temperature and the desorption operating temperature. The adsorption operating temperature range is 20℃ to 50℃, and the desorption operating temperature range is 100℃ to 250℃.

[0084] Furthermore, the water separation and storage system 6 includes a first water molecular sieve 6-1, a second water molecular sieve 6-2, and a water storage tank 6-3, and the first water molecular sieve 6-1 and the second water molecular sieve 6-2 operate in a time-sharing manner.

[0085] The air inlets of the first water molecular sieve 6-1 and the second water molecular sieve 6-2 are both used as air inlets of the water separation and storage system 6; the flue gas outlets of the first water molecular sieve 6-1 and the second water molecular sieve 6-2 are both used as flue gas outlets of the water separation and storage system 6.

[0086] A valve 11 is installed on the pipeline between the air inlet of the water separation and storage system 6 and the air outlet of the desulfurization and denitrification equipment 5;

[0087] A valve 11 is installed on the pipeline between the flue gas outlet of the water separation and storage system 6 and the air inlet of the second compressor 7;

[0088] The steam outlets of the first water molecular sieve 6-1 and the second water molecular sieve 6-2 are simultaneously connected to the air inlet of the water storage tank 6-3, and a valve 11 is provided on the pipeline between the steam outlets of the first water molecular sieve 6-1 and the second water molecular sieve 6-2 and the water storage tank 6-3.

[0089] This preferred embodiment provides a specific configuration of the water separation and storage system 6. Regarding the water drying problem, the energy consumption of this invention is lower than that of the surface condensation method, and the water removal rate is higher than that of the spraying method. The water separation and storage system 6 provided by this invention can also improve the purity of liquid carbon dioxide in the subsequent carbon capture process, and the flue gas drying efficiency is higher than that of other methods.

[0090] Furthermore, the first water molecular sieve 6-1 and the second water molecular sieve 6-2 are type 3A water molecular sieves. The operating temperatures of both the first water molecular sieve 6-1 and the second water molecular sieve 6-2 include adsorption operating temperature and desorption operating temperature. The adsorption operating temperature range is 20℃ to 40℃, and the desorption operating temperature range is 150℃ to 250℃.

[0091] The adsorption and desorption operating temperatures of the water molecular sieve set in this preferred embodiment enable the molecular sieve to achieve oxygen separation with low energy consumption, and can improve the service life of the molecular sieve and reduce the capture cost.

[0092] Furthermore, a specific structure of the carbon capture unit 8 is given, which includes a heat exchanger 8-1, a refrigerant heat exchanger 8-2, a carbon dioxide separator 8-3, and a carbon dioxide liquid storage tank 8-4.

[0093] The carbon dioxide separator 8-3 is used to separate liquid carbon dioxide and impurity gases from the incoming flue gas;

[0094] The first air inlet of the heat exchanger 8-1 serves as the flue gas inlet of the carbon capture unit 8. The flue gas outlet of the heat exchanger 8-1 is connected to the air inlet of the refrigerant heat exchanger 8-2. The air outlet of the refrigerant heat exchanger 8-2 is connected to the flue gas inlet of the carbon dioxide separator 8-3. The liquid outlet of the carbon dioxide separator 8-3 is connected to the liquid inlet of the carbon dioxide liquid storage tank 8-4. The carbon dioxide liquid storage tank 8-4 is used to store liquid carbon dioxide.

[0095] The impurity gas outlet of the carbon dioxide separator 8-3 is connected to the second air inlet of the heat exchanger 8-1, and the impurity gas outlet of the heat exchanger 8-1 is connected to the compressed gas energy storage unit 9 as the impurity gas outlet of the carbon capture unit 8.

[0096] The carbon capture unit 8 provided in this preferred embodiment recovers the refrigeration energy consumed by the low-temperature impurity gas, thus reducing capture energy consumption. Carbon dioxide is separated in liquid form, resulting in high purity and facilitating transportation and subsequent utilization. In specific applications, the carbon dioxide separator 8-3 operates at a pressure range of 2 MPa to 4 MPa and a temperature range of -25°C to -50°C. Both the heat exchanger 8-1 and the refrigerant heat exchanger 8-2 are used to cool the gas.

[0097] See Figure 1 and Figure 2The carbon capture system based on molecular sieve adsorption separation and oxygen-enriched combustion also includes a power generation unit 10.

[0098] The power generation unit 10 is used to heat the impurity gas output from the compressed gas energy storage unit 9, and then use the heated impurity gas to generate electricity before discharging it.

[0099] A valve 11 is installed on the pipeline between the outlet of the compressed gas energy storage unit 9 and the inlet of the power generation unit 10.

[0100] This invention utilizes compressed gas energy storage technology in the compressed gas energy storage unit 9 to achieve energy recovery and storage. During the energy storage stage, the high-pressure impurity gas output from the heat exchanger 8-1 can be stored in the form of gas.

[0101] The compressed gas energy storage unit 9 recovers and stores impurity gases other than carbon dioxide in the flue gas. However, because these impurity gases also have relatively high pressure, they can also generate electricity through recovery, thus achieving energy recovery, storage, and recycling. Two different structures of the power generation unit 10 are also shown (see [link]). Figure 1 and Figure 2 Specifically:

[0102] See Figure 1 The first structure of the power generation unit 10 is as follows:

[0103] The power generation unit 10 includes a hot water heat exchanger 10-1 and an expander 10-2, which together constitute a power-generating unit. The air inlet of the hot water heat exchanger 10-1 serves as the air inlet of the power generation unit 10 and is connected to the air outlet of the compressed gas energy storage unit 9. The air outlet of the hot water heat exchanger 10-1 is connected to the air inlet of the expander 10-2.

[0104] The impurity gas output from the outlet of the hot water heat exchanger 10-1 is used to do work on the expander 10-2;

[0105] See Figure 2 The second structure of the power generation unit 10 is as follows:

[0106] The power generation unit 10 includes M hot water heat exchangers 10-1 and M expanders 10-2, and each hot water heat exchanger 10-1 and its corresponding expander 10-2 constitute a power-generating unit; wherein, the outlet of the hot water heat exchanger 10-1 in each power-generating unit is connected to the inlet of the expander 10-2, and the inlet of the hot water heat exchanger 10-1 and the outlet of the expander 10-2 serve as the inlet and outlet of the power-generating unit, respectively;

[0107] The impurity gas output from the outlet of the hot water heat exchanger 10-1 in each working unit is used to perform work on the expander 10-2 connected to it.

[0108] M power units are connected in series, with the air inlet of the power unit at the first end serving as the air inlet of the power generation unit 10, and the air outlet of the power unit at the last end serving as the air outlet of the power generation unit 10; M is an integer, and 2≤M≤10.

[0109] This invention enables the high-pressure impurity gas output from the carbon capture unit 8 to be stored as gas in the compressed gas energy storage unit 9 during the energy storage stage; during the energy release stage, the high-pressure impurity gas can be passed into the expander 10-2 for expansion and power generation, thereby realizing energy conversion and improving energy utilization. The hot water heat exchanger 10-1 is used to heat the gas.

[0110] In practical applications, the specific process of carbon dioxide capture using the aforementioned carbon capture system based on molecular sieve adsorption separation and oxygen-enriched combustion is as follows:

[0111] After the air is cooled by the cold water heat exchanger 1, it is sent to the N-stage oxygen molecular sieve group 2 for oxygen enrichment. The output oxygen-enriched gas is sent to the mixing tank 3 for mixing. After the oxygen-enriched gas concentration is adjusted, it enters the combustion system 4 for combustion. The generated flue gas is desulfurized and denitrified by the desulfurization and denitrification equipment 5 and then sent to the water separation and storage system 6 to separate water vapor and dry flue gas. The separated water vapor is stored.

[0112] The dry flue gas separated by the water separation and storage system 6 is compressed by the compressor 7 and then enters the carbon capture unit 8. The carbon capture unit 8 cools the received dry flue gas and then separates liquid carbon dioxide and impurity gases, and stores the separated liquid carbon dioxide.

[0113] The impurity gas separated by the carbon capture unit 8 is sent to the compressed gas energy storage unit 9 for energy storage, thus completing the carbon dioxide capture.

[0114] Verification experiment:

[0115] In practical applications, the technical effects of this utility model are verified through the following verification experiments. Taking the flue gas treatment of a 100MW unit as an example, the carbon capture system based on molecular sieve adsorption separation and oxygen-enriched combustion is explained:

[0116] See details Figure 1 Carbon dioxide capture and storage stage:

[0117] Air enters the cold water heat exchanger 1, setting the outlet temperature to 25°C. After cooling, the air enters the N-stage oxygen molecular sieve group 2, where the adsorption temperature is adjusted to 25°C and the desorption temperature to 150°C, ultimately achieving an oxygen concentration of 60%. The oxygen-enriched gas then enters the combustion system 4 for combustion. The desulfurization and denitrification equipment 5 is activated, removing impurities from the flue gas before it enters the water separation and storage system 6. The water molecular sieve adsorption temperature is adjusted to 25°C and the desorption temperature to 200°C. The second compressor 7 is activated, drying the flue gas. The outlet pressure of compressor 7 is 3.5 MPa. The heat exchanger 8-1 is activated, and the gas enters it, with its outlet temperature adjusted to 20°C. The gas then enters the refrigerant heat exchanger 8-2, where its temperature is adjusted to -40°C. Finally, the flue gas enters the carbon dioxide separator 8-3, where the liquid carbon dioxide separated by the separator enters the carbon dioxide liquid storage tank 8-4 for storage. The high-pressure impurities are sent to the compressed gas energy storage unit 9.

[0118] Energy release phase:

[0119] The impurity mixture gas in the compressed gas energy storage unit 9 is discharged and sent to the hot water heat exchanger 10-1 and the expander 10-2. After being heated by the hot water heat exchanger 10-1, it performs work on the corresponding expander 10-2. The gas pressure discharged from the hot water heat exchanger 10-1 and the expander 10-2 is 0.1 MPa.

[0120] Compared with other systems, the carbon capture system based on molecular sieve adsorption separation and oxygen-enriched combustion described in this invention has the following advantages:

[0121] 1. The oxygen concentration of the gas in oxygen-enriched combustion can reach 90%. Compared with conventional combustion, nitrogen oxide emissions are reduced by more than 50%. Compared with conventional cryogenic air separation oxygen-enriched combustion, oxygen separation energy consumption is reduced by more than 30%.

[0122] 2. The carbon dioxide concentration in the flue gas can reach over 60%.

[0123] 3. The carbon dioxide recovery rate is over 90%.

[0124] 4. The capture energy consumption is low and it has energy storage function. When a 100MW unit uses this system to treat flue gas, the net power consumption is about 10MW.

[0125] 5. This system can flexibly adjust the oxygen concentration and is suitable for different types of power plants, such as gas turbine power plants and coal-fired power plants.

[0126] While specific embodiments of the present invention have been described herein with reference to them, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A carbon capture system based on molecular sieve adsorption separation and oxygen-enriched combustion, comprising a cold water heat exchanger (1), two compressors (7), a carbon capture unit (8), and a compressed gas energy storage unit (9); characterized in that, It also includes an N-level oxygen molecular sieve group (2), a mixing tank (3), a desulfurization and denitrification equipment (5), and a water separation and storage system (6). The N-level oxygen molecular sieve group (2) consists of N oxygen molecular sieve groups connected in series. The inlet of the first oxygen molecular sieve group is used as the inlet of the N-level oxygen molecular sieve group (2), and the oxygen-enriched outlet of the Nth oxygen molecular sieve group is used as the oxygen-enriched outlet of the N-level oxygen molecular sieve group (2). Each oxygen molecular sieve group is used for oxygen enrichment, and the adsorption saturation concentration of the N oxygen molecular sieve groups is different. N is an integer, and 2 < N ≤ 4. The water separation and storage system (6) is used to separate water vapor and dry flue gas from the flue gas introduced into it, and to store the water vapor; The inlet of the cold water heat exchanger (1) is used to receive flue gas. The outlet of the cold water heat exchanger (1) is connected to the inlet of the N-stage oxygen molecular sieve group (2). The oxygen-enriched outlet of the N-stage oxygen molecular sieve group (2) is connected to the inlet of the mixing tank (3). The outlet of the mixing tank (3) is connected to the inlet of the first compressor (7). The outlet of the second compressor (7) is connected to the inlet of the combustion system (4). The outlet of the combustion system (4) is connected to the inlet of the desulfurization and denitrification equipment (5). The outlet of the desulfurization and denitrification equipment (5) is connected to the inlet of the water separation and storage system (6). The flue gas outlet of the water separation and storage system (6) is connected to the inlet of the second compressor (7). The outlet of the second compressor (7) is connected to the flue gas inlet of the carbon capture unit (8). The carbon capture unit (8) is used to cool the received dry flue gas and then separate liquid carbon dioxide and impurity gas, and pass the separated impurity gas into the compressed gas energy storage unit (9) for energy storage.

2. The carbon capture system based on molecular sieve adsorption separation and oxygen-enriched combustion according to claim 1, characterized in that, Each oxygen molecular sieve group includes a first oxygen molecular sieve (2-1) and a second oxygen molecular sieve (2-2), which operate in a time-sharing manner; The inlets of the first oxygen molecular sieve (2-1) and the second oxygen molecular sieve (2-2) are both used as the inlets of the oxygen molecular sieve group, and the oxygen-enriched outlets of the first oxygen molecular sieve (2-1) and the second oxygen molecular sieve (2-2) are both used as the oxygen-enriched outlets of the oxygen molecular sieve group. The mixed gas outlet of the first oxygen molecular sieve (2-1) and the second oxygen molecular sieve (2-2) is used to output the mixed gas; A valve (11) is installed on the pipeline between the outlet of the cold water heat exchanger (1) and the inlet of the N-stage oxygen molecular sieve group (2). A valve (11) is provided on the pipeline between the inlet and the oxygen-enriched outlet of the N-level oxygen molecular sieve group (2) and the first inlet of the mixing tank (3). A valve (11) is installed on the pipeline between the inlet and outlet of two adjacent oxygen molecular sieve groups.

3. The carbon capture system based on molecular sieve adsorption separation and oxygen-enriched combustion according to claim 2, characterized in that, In the N-level oxygen molecular sieve group (2), there is a one-to-one correspondence between the N oxygen molecular sieve groups and the N preset thresholds; When the oxygen concentration at the oxygen-enriched outlet of one oxygen molecular sieve in the N-level oxygen molecular sieve group (2) is lower than the i-th preset threshold, the oxygen molecular sieve is determined to be saturated. At this time, the oxygen molecular sieve stops working and another oxygen molecular sieve starts working. The j-th preset threshold is less than the j+1-th preset threshold. i and j are both integers, and i=1, 2...N, j=1, 2...N-1.

4. The carbon capture system based on molecular sieve adsorption separation and oxygen-enriched combustion according to claim 2, characterized in that, The oxygen molecular sieves in the oxygen molecular sieve group are lithium-based molecular sieves or zeolite molecular sieves. The operating temperature of the oxygen molecular sieve group includes the adsorption operating temperature and the desorption operating temperature. The adsorption operating temperature range is 20℃ to 50℃, and the desorption operating temperature range is 100℃ to 250℃.

5. The carbon capture system based on molecular sieve adsorption separation and oxygen-enriched combustion according to claim 1, characterized in that, The water separation and storage system (6) includes a first water molecular sieve (6-1), a second water molecular sieve (6-2), and a water storage tank (6-3), and the first water molecular sieve (6-1) and the second water molecular sieve (6-2) work in a time-sharing manner; The air inlets of the first water molecular sieve (6-1) and the second water molecular sieve (6-2) are both used as air inlets of the water separation and storage system (6); the flue gas outlets of the first water molecular sieve (6-1) and the second water molecular sieve (6-2) are both used as flue gas outlets of the water separation and storage system (6). A valve (11) is installed on the pipeline between the air inlet of the water separation and storage system (6) and the air outlet of the desulfurization and denitrification equipment (5). A valve (11) is provided on the pipeline between the flue gas outlet of the water separation and storage system (6) and the air inlet of the second compressor (7). The steam outlets of the first water molecular sieve (6-1) and the second water molecular sieve (6-2) are simultaneously connected to the air inlet of the water storage tank (6-3), and a valve (11) is provided on the pipeline between the steam outlets of the first water molecular sieve (6-1) and the second water molecular sieve (6-2) and the water storage tank (6-3).

6. The carbon capture system based on molecular sieve adsorption separation and oxygen-enriched combustion according to claim 5, characterized in that, The first water molecular sieve (6-1) and the second water molecular sieve (6-2) are type 3A water molecular sieves. The operating temperatures of the first water molecular sieve (6-1) and the second water molecular sieve (6-2) include both adsorption operating temperature and desorption operating temperature. The adsorption operating temperature range is 20℃ to 40℃, and the desorption operating temperature range is 150℃ to 250℃.

7. The carbon capture system based on molecular sieve adsorption separation and oxygen-enriched combustion according to claim 1, characterized in that, The carbon capture unit (8) includes a heat exchanger (8-1), a refrigerant heat exchanger (8-2), a carbon dioxide separator (8-3), and a carbon dioxide liquid storage tank (8-4). The carbon dioxide separator (8-3) is used to separate liquid carbon dioxide and impurity gases from the incoming flue gas; The first air inlet of the heat exchanger (8-1) serves as the flue gas inlet of the carbon capture unit (8). The flue gas outlet of the heat exchanger (8-1) is connected to the air inlet of the refrigerant heat exchanger (8-2). The air outlet of the refrigerant heat exchanger (8-2) is connected to the flue gas inlet of the carbon dioxide separator (8-3). The liquid outlet of the carbon dioxide separator (8-3) is connected to the liquid inlet of the carbon dioxide liquid storage tank (8-4). The carbon dioxide liquid storage tank (8-4) is used to store liquid carbon dioxide. The impurity gas outlet of the carbon dioxide separator (8-3) is connected to the second air inlet of the heat exchanger (8-1), and the impurity gas outlet of the heat exchanger (8-1) is connected to the compressed gas energy storage unit (9) as the impurity gas outlet of the carbon capture unit (8).

8. The carbon capture system based on molecular sieve adsorption separation and oxygen-enriched combustion according to claim 1, characterized in that, It also includes a power generation unit (10); The power generation unit (10) is used to heat the impurity gas output from the compressed gas energy storage unit (9), and then use the heated impurity gas to generate electricity and discharge it. A valve (11) is provided on the pipeline between the outlet of the compressed gas energy storage unit (9) and the inlet of the power generation unit (10).

9. The carbon capture system based on molecular sieve adsorption separation and oxygen-enriched combustion according to claim 8, characterized in that, The first structure of the power generation unit (10) is: The power generation unit (10) includes a hot water heat exchanger (10-1) and an expander (10-2), which together constitute a working unit; the air inlet of the hot water heat exchanger (10-1) is connected to the air outlet of the compressed gas energy storage unit (9) as the air inlet of the power generation unit (10), and the air outlet of the hot water heat exchanger (10-1) is connected to the air inlet of the expander (10-2). The impurity gas output from the outlet of the hot water heat exchanger (10-1) is used to perform work on the expander (10-2); The second structure of the power generation unit (10) is: The power generation unit (10) includes M hot water heat exchangers (10-1) and M expanders (10-2), and each hot water heat exchanger (10-1) and its corresponding expander (10-2) constitute a working unit; wherein, the outlet of the hot water heat exchanger (10-1) in each working unit is connected to the inlet of the expander (10-2), and the inlet of the hot water heat exchanger (10-1) and the outlet of the expander (10-2) serve as the inlet and outlet of the working unit, respectively; The impurity gas output from the outlet of the hot water heat exchanger (10-1) in each working unit is used to perform work on the expander (10-2) connected to it; M power units are connected in series, and the air inlet of the power unit at the first end is used as the air inlet of the power generation unit (10), and the air outlet of the power unit at the last end is used as the air outlet of the power generation unit (10); M is an integer, and 2≤M≤10.

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