Waste heat recovery circulating system for directly capturing carbon dioxide from air

Abstract

The invention relates to the technical field of gas separation and waste heat recovery, and particularly discloses a waste heat recovery circulating system for directly capturing carbon dioxide from air, which comprises: a, an adsorption / desorption tower filled with an amino-functionalized mesoporous material as a CO2 adsorbent for adsorbing and desorbing CO2 in air; the compressor is connected to the adsorption / desorption tower and used for pressurizing water vapor carrying CO2 in the desorption stage so as to increase the condensation temperature; the amido-functionalized mesoporous material is filled in the adsorption / desorption tower as a CO2 adsorbent, so that efficient CO2 trapping capacity is realized, the amido-functionalized mesoporous material selectively adsorbs CO2 and H2O, and the residual purified gas is discharged, so that the selective adsorption capacity not only improves the trapping efficiency of CO2, but also improves the adsorption efficiency of CO2. In addition, due to high stability and reproducibility of the amino-functionalized mesoporous material, the system can stably operate for a long time, and the maintenance cost is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas separation and waste heat recovery, and in particular relates to a waste heat recovery circulation system for direct air capture of carbon dioxide. Background Art

[0002] As global climate change becomes increasingly severe, reducing atmospheric carbon dioxide (CO 2 ) concentration has become a focus of widespread international attention. Against this background, direct air capture of CO 2 As an effective means of carbon emission reduction, the technology has been widely studied and developed in recent years. This technology directly captures CO from the atmosphere through specific adsorption materials. 2 , making it possible to achieve large-scale carbon capture and storage (CCS).

[0003] Conventional direct air capture technologies mainly rely on chemical adsorption or physical adsorption materials to capture CO 2 However, these technologies face many challenges in practical applications. 2 Selectivity and adsorption capacity directly determine the capture efficiency and economy. Although traditional adsorption materials, such as activated carbon and molecular sieves, have certain CO2 adsorption capacity, their selectivity is poor and their regeneration energy consumption is high, which limits their wide application and leads to poor performance of the device. Therefore, staff need to improve them. Summary of the invention

[0004] The object of the present invention is to provide a waste heat recovery circulation system for direct air capture of carbon dioxide to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A waste heat recovery cycle system for direct air capture of carbon dioxide, comprising:

[0007] a. Adsorption / desorption tower, which is filled with amine-functionalized mesoporous materials as CO 2 Adsorbents for adsorption and desorption of CO from air 2 ;

[0008] b. Compressor, connected to the adsorption / desorption tower, used to carry CO in the desorption stage 2 The water vapor is pressurized to increase the condensation temperature;

[0009] c. Separation box, connected to the outlet of the compressor, is used to receive the pressurized water vapor and perform gas-liquid separation to recover pure CO 2 ;

[0010] d. A heat pump type steam generator, connected to the separation tank, for recovering the heat energy carried by the cooling water during the separation process and using the heat energy to produce the water vapor required during the desorption process;

[0011] e. A heat exchanger, arranged in the adsorption stage and the desorption stage, for adjusting the temperatures of the air and the steam, and for condensing the water vapor after desorption;

[0012] f. A control system, for controlling the operations of the compressor, the heat pump type steam generator, the heat exchanger and the adsorption / desorption tower to achieve continuous CO 2 capture and waste heat recovery.

[0013] Preferably, the adsorption / desorption tower further includes a switching valve for switching the flow paths of the air and the steam between the adsorption stage and the desorption stage.

[0014] Preferably, in the adsorption stage, air is blown into the heat exchanger by a blower and is adsorbed by the adsorbent for CO 2 under the temperature range of -45 to 45 degrees Celsius and the CO 2 concentration condition of 400 ppm, and the remaining purified gas is discharged from the adsorption / desorption tower.

[0015] Preferably, in the desorption stage, high-temperature steam is introduced into the adsorption / desorption tower to maintain the temperature of the adsorbent at 80 to 120 degrees Celsius, thereby desorbing the adsorbed CO 2 and being carried away from the adsorption / desorption tower by the water vapor.

[0016] Preferably, the compressor pressurizes the water vapor carrying CO 2 to at least 1.5 atm to increase the condensation temperature, so as to maximize the recovery of the latent heat of phase change during the condensation process.

[0017] Preferably, the heat pump type steam generator uses the heat energy carried by the cooling water in the separation tank to produce the water vapor required during the desorption process, realizing the recycling of water.

[0018] Preferably, it further includes an air pretreatment module for removing particulate matters, dust and other impurities in the air before the air enters the adsorption / desorption tower.

[0019] Preferably, it further includes a data interface for connecting to external devices or networks to achieve remote monitoring and data transmission.

[0020] Preferably, the heat pump type steam generator has a steam heat recovery rate of at least 50% to 70%.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] (1) By filling the amino-functionalized mesoporous material as CO2 Inside the adsorption / desorption tower, the adsorbent achieves high-efficient CO 2 trapping ability. Due to its specific chemical structure and pore characteristics, this material can effectively adsorb CO in the air 2 . During the adsorption stage, air is blown into the heat exchanger by a fan and adjusted to appropriate temperature, CO 2 concentration, and relative humidity conditions, and then enters the adsorption / desorption tower. The amino-functionalized mesoporous material selectively adsorbs CO 2 , while the remaining purified gas is discharged. This selective adsorption ability not only improves the CO 2 trapping efficiency but also ensures the emission quality of the purified air. In addition, the high stability and regenerability of the amino-functionalized mesoporous material enable the system to operate stably for a long time, reducing the maintenance cost.

[0023] (2) By pressurizing the water vapor carrying CO 2 with a compressor, the condensation temperature is increased. During the desorption stage, high-temperature steam is introduced into the adsorption / desorption tower to desorb the adsorbed CO 2 , and it is carried away by the water vapor. The water vapor carrying CO 2 then enters the compressor for pressurization. The pressurized water vapor can release more latent heat of phase change during the condensation process, thereby improving the condensation efficiency. Increasing the condensation temperature not only helps to maximize the recovery of latent heat of phase change but also makes the condensation process more efficient and stable. In addition, the pressurized water vapor is easier to achieve gas-liquid separation in the subsequent separation process, thereby increasing the recovery rate of pure CO 2 .

[0024] (3) By using a heat pump type steam generator to recover the heat energy carried by the cooling water during the separation process, the recycling of heat energy is realized. In the separation tank, the pressurized water vapor undergoes gas-liquid separation to recover pure CO 2 . During this process, the cooling water will carry away a large amount of heat energy. The heat pump type steam generator uses the heat energy in these cooling waters to produce the water vapor required during the desorption process. The recycling of heat energy not only significantly reduces the energy consumption of the system but also improves the energy utilization efficiency of the entire system. Compared with the traditional steam purge without heat recovery cycle, the energy consumption of this system is significantly reduced. In addition, the high heat recovery rate of the heat pump type steam generator further enhances the economy and environmental protection of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic diagram of the thermal cycle steam adsorption and desorption of the present invention;

[0026] Figure 2 is a schematic diagram of the inside of the separation tank of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0028] Embodiment 1:

[0029] Please refer to Figures 1 to 2 As shown, a waste heat recovery cycle system for direct air capture of carbon dioxide includes:

[0030] a. An adsorption / desorption tower filled with an amino-functionalized mesoporous material as a CO 2 adsorbent for adsorbing and desorbing CO in the air 2 ;

[0031] Let the adsorption capacity of CO 2 be Q and the adsorption efficiency be η, then there is:

[0032]

[0033] where k 1 is the adsorption coefficient, is the concentration of CO in the air 2 t is the adsorption time, A is the surface area of the adsorbent, and Q max is the maximum adsorption capacity.

[0034] b. A compressor connected to the adsorption / desorption tower for pressurizing the water vapor carrying CO 2 during the desorption stage to increase the condensation temperature;

[0035] Let the outlet pressure of the compressor be P, then there is:

[0036]

[0037] where P 0 is the inlet pressure of the compressor, V is the work volume of the compressor, C 0 is the specific heat capacity at constant volume of the gas, and T is the gas temperature.

[0038] c. A separation box connected to the outlet of the compressor for receiving the pressurized water vapor and performing gas-liquid separation to recover pure CO 2 ;

[0039] Let the separation efficiency be ε, then there is:

[0040]

[0041] where C resThe residual CO2 concentration after separation, C in The CO2 concentration before separation.

[0042] d. A heat pump type steam generator, connected to the separation tank, for recovering the heat energy carried by the cooling water during the separation process and using the heat energy to produce the water vapor required during the desorption process;

[0043] Assuming the heat pump efficiency is COP, then there is:

[0044]

[0045] Among them, Q out Is the heat energy output by the heat pump, and W is the electric energy consumed by the heat pump.

[0046] e. A heat exchanger, arranged in the desorption stage, for condensing the water vapor after desorption;

[0047] Assuming the heat exchanger efficiency is η_h, then there is:

[0048]

[0049] Among them, T out Is the heat exchanger outlet temperature, T in Is the heat exchanger inlet temperature, T hot Is the hot fluid temperature, T cold Is the cold fluid temperature.

[0050] f. A control system, used to control the operations of the compressor, heat pump type steam generator, heat exchanger and adsorption / desorption tower to achieve continuous CO 2 Capture and waste heat recovery.

[0051] The formula Q in a represents the adsorption amount of CO 2 , which is proportional to the adsorption coefficient k 1 , the CO concentration in the air 2 C CO2 , the adsorption time t and the adsorbent surface area A. The adsorption efficiency η is the ratio of the actual adsorption amount to the maximum adsorption amount.

[0052] The compressor outlet pressure P in the formula of b is derived through the ideal gas state equation, considering the influence of the compressor work volume V, the gas constant volume specific heat capacity C V And the gas temperature T.

[0053] The separation efficiency ε in the formula of c is the ratio of the difference between the residual CO concentration after separation and the CO concentration before separation to the CO concentration before separation. 2 Concentration and the CO concentration before separation 2 Concentration difference and the CO concentration before separation 2 Concentration ratio.

[0054] The coefficient of performance (COP) of the formula heat pump in d is the ratio of the thermal energy output by the heat pump to the electrical energy consumed, reflecting the energy conversion efficiency of the heat pump.

[0055] The heat exchanger efficiency η_h in e is the ratio of the difference between the outlet temperature and the inlet temperature of the heat exchanger to the difference between the temperature of the hot fluid and the temperature of the cold fluid, measuring the heat transfer efficiency of the heat exchanger.

[0056] The adsorption / desorption tower further includes a switching valve for switching the flow path of air and steam between the adsorption and desorption stages.

[0057] In the adsorption stage, air is blown into the adsorption / desorption tower by a fan and adsorbed by the adsorbent for CO at a temperature range of -45 to 45 degrees Celsius and a CO concentration condition of 400 ppm. 2 The remaining purified gas is discharged from the adsorption / desorption tower. 2

[0058] In the desorption stage, high-temperature steam is introduced into the adsorption / desorption tower to maintain the adsorbent temperature at 80 to 120 degrees Celsius, thereby desorbing the adsorbed CO. 2 It is carried away from the adsorption / desorption tower by water vapor.

[0059] The compressor pressurizes the water vapor carrying CO to at least 1.5 atm to increase the condensation temperature, thereby maximizing the recovery of the latent heat of phase change during the condensation process. 2

[0060] The heat pump type steam generator utilizes the thermal energy carried by the cooling water in the separation tank to produce the water vapor required during the desorption process, realizing the recycling of water.

[0061] It further includes an air pretreatment module for removing particulate matter, dust, and other impurities from the air before it enters the adsorption / desorption tower.

[0062] It further includes a data interface for connecting to external devices or networks to achieve remote monitoring and data transmission.

[0063] The heat pump type steam generator has a steam heat recovery rate of at least 50% to 70%.

[0064] Basic adsorption efficiency:

[0065]

[0066] Compressor work efficiency:

[0067]

[0068] Comprehensive efficiency of heat pump and heat exchanger:

[0069]

[0070] Integrating the above formulas gives:

[0071]

[0072] E total (Total efficiency) is a measure of the overall performance of the system, which is a comprehensive manifestation of adsorption efficiency, compressor work, heat pump efficiency, and heat exchanger efficiency.

[0073] k 1 (Adsorption coefficient) is a constant that affects the adsorption rate.

[0074] (CO2 concentration in air) is the CO2 concentration in the input air.

[0075] A (adsorbent surface area) is the effective surface area of the adsorbent.

[0076] λ (attenuation coefficient) is the coefficient by which the adsorption rate decays over time.

[0077] t ads (Adsorption time) is the duration of the adsorption stage.

[0078] N comp (Number of compressors) is the number of compressors in the system.

[0079] P n (Compressor outlet pressure) is the outlet pressure of the nth compressor.

[0080] V n (Compressor work volume) is the work volume of the nth compressor.

[0081] C V,n (Specific heat capacity at constant volume of gas) is the specific heat capacity at constant volume of the gas in the nth compressor.

[0082] T n (Gas temperature) is the temperature of the gas in the nth compressor.

[0083] η comp,n (Compressor efficiency) is the efficiency of the nth compressor.

[0084] μ (compressor efficiency decay factor) is the decay coefficient of the compressor efficiency with the increase in the number.

[0085] ε sep (Separation efficiency) is the separation efficiency of CO2 in the separation tank.

[0086] Q HP (Heat output of heat pump) is the heat energy output by the heat pump.

[0087] COPHP (Heat pump efficiency) is the energy conversion efficiency of the heat pump.

[0088] ηh (heat exchanger efficiency) is the heat transfer efficiency of the heat exchanger.

[0089] ΔT ex (Heat exchanger temperature difference) is the temperature difference between the hot and cold fluids of the heat exchanger.

[0090] T hot (Hot fluid temperature) is the temperature of the hot fluid of the heat exchanger.

[0091] ν (relative humidity influence coefficient) is the influence coefficient of relative humidity on the system performance.

[0092] RH (relative humidity) is the relative humidity of the input air.

[0093] E total The value range of E is [0, +∞), and the larger the value, the better the overall performance of the system.

[0094] The system mainly includes an adsorption / desorption tower, a compressor, a switching valve, an air pretreatment module, a high-temperature steam source, a separation box, and a heat pump type steam generator. The adsorption / desorption tower is filled with an amino-functionalized mesoporous material as the CO 2 adsorbent.

[0095] During operation, the air first passes through the air pretreatment module to remove impurities such as particulate matter and dust, and then is blown into the gas channel of the heat exchanger in the adsorption / desorption tower by a fan. Under the temperature range of -45 to 45 degrees Celsius and the CO 2 concentration condition of 400 ppm, the CO 2 in the air is adsorbed by the adsorbent, and the remaining purified gas is discharged from the adsorption tower. When the adsorbent reaches saturation, the switching valve switches to the desorption stage, and the high-temperature steam source injects high-temperature steam into the adsorption tower to maintain the adsorbent temperature at 80 to 120 degrees Celsius, desorbing the adsorbed CO 2 , and being carried away from the adsorption tower by water vapor.

[0096] The water vapor carrying CO 2 is pressurized to at least 1.5 atm by the compressor to increase the condensation temperature, and then cools down and condenses through heat exchange. The condensed water vapor enters the separation box for gas-liquid separation to recover pure CO 2 . During the separation process, the heat energy carried by the cooling water is recovered by the heat pump type steam generator for producing the water vapor required in the desorption process, realizing the recycling of water.

[0097] Subsequently, high-purity CO 2 can be continuously enriched, and at the same time, the waste heat and phase change latent heat in the regenerated steam are recovered to reduce the cycle energy consumption.

[0098] Air pretreatment module:

[0099] Function: Remove particulate matter, dust, and other impurities from the air.

[0100] Input: Raw air.

[0101] Output: Purified air.

[0102] Adsorption / desorption tower:

[0103] Function: In the adsorption stage, adsorb CO 2 and H 2 O; in the desorption stage, desorb the adsorbed CO 2 .

[0104] Input: Purified air (adsorption stage); high-temperature steam (desorption stage).

[0105] Output: Remaining purified gas (adsorption stage); water vapor carrying CO 2 .

[0106] Compressor:

[0107] Function: Pressurize the water vapor carrying CO 2 to increase the condensation temperature.

[0108] Input: Water vapor carrying CO 2 .

[0109] Output: Pressurized water vapor.

[0110] Separator box:

[0111] Function: Receive the pressurized water vapor and perform gas-liquid separation to recover pure CO 2 .

[0112] Input: Pressurized water vapor.

[0113] Output: Pure CO 2 ; cooling water (carrying heat energy).

[0114] Heat pump steam generator:

[0115] Function: Recover the heat energy carried by the cooling water during the separation process and use the heat energy to produce the water vapor required in the desorption process.

[0116] Input: Cooling water (carrying heat energy).

[0117] Output: Water vapor required in the desorption process.

[0118] Heat exchanger:

[0119] Function: Set in the adsorption stage and desorption stage, used to adjust the temperature of air and steam, and condense water vapor after desorption.

[0120] Input: Air (adsorption stage); water vapor (desorption stage).

[0121] Output: Adjusted air (adsorption stage); condensed water vapor (desorption stage).

[0122] Control system:

[0123] Used to control the operation of the compressor, heat pump type steam generator, heat exchanger and adsorption / desorption tower to achieve continuous CO 2 Capture and waste heat recovery.

[0124] Example 2:

[0125] Please refer to Figures 1 to 2 As shown, during operation, air is blown into the adsorption tower through a fan at a flow rate of 200 ml / min and adsorbed under the conditions of a temperature range of -45 to 45 degrees Celsius and a CO2 concentration of 400 ppm. When the adsorbent reaches saturation, the switching valve switches to the desorption stage, and high-temperature steam at 120 degrees Celsius is introduced into the adsorption tower from a high-temperature steam source at a flow rate of 100 ml / min for 0.3 hours to desorb the adsorbed CO 2 .

[0126] The water vapor carrying CO 2 is pressurized to 1.5 atm by a compressor and then enters the heat exchanger to cool and condense. The condensed water vapor enters the separation tank for gas-liquid separation to recover pure CO 2 . The cooling water generated during the separation process is recovered by the heat pump type steam generator and used to produce the water vapor required during the desorption process.

[0127] Calculated according to the following formula:

[0128]

[0129] t ads，2 is the duration of the adsorption stage in Example 2.

[0130] V comp,2 is the working volume of the compressor in Example 2.

[0131] C V,comp,2 is the specific heat capacity at constant volume of the gas in the compressor in Example 2.

[0132] T comp,2 is the temperature of the gas in the compressor in Example 2.

[0133] η comp,2 is the efficiency of the compressor in Example 2.

[0134] ε sep，2 is the separation efficiency of the separation tank in Example 2.

[0135] Q HP，2 is the thermal energy output by the heat pump in Example 2.

[0136] COP HP，2 is the energy conversion efficiency of the heat pump in Example 2.

[0137] η h,2 is the heat transfer efficiency of the heat exchanger in Example 2.

[0138] ΔT ex，2 is the temperature difference between the hot and cold fluids of the heat exchanger in Example 2.

[0139] T hot，2 is the temperature of the hot fluid of the heat exchanger in Example 2.

[0140] E spec2 The value range of E is [0, +∞), and the larger the value, the better the overall performance of the system.

[0141] After calculation, the steam heat recovery rate reaches about 60%, and the energy consumption is significantly reduced compared with the traditional steam purging without heat recovery cycle.

[0142] Example 3:

[0143] Please refer to Figures 1 to 2 As shown, in the adsorption stage, the system uses a more efficient amino-functionalized mesoporous material as the adsorbent and optimizes the internal structure of the adsorption tower to improve the adsorption efficiency and mass transfer rate. At the same time, the air pretreatment module uses a more refined filtration technology to remove fine particles and impurities in the air and avoid contaminating the adsorbent.

[0144] In the desorption stage, the system uses a steam source at a higher temperature and optimizes the steam flow rate and desorption time to ensure that the CO 2 in the adsorbent is completely desorbed. In addition, the system also introduces advanced compressor technology and heat exchanger design to increase the condensation temperature and the efficiency of recovering the latent heat of phase change.

[0145] Calculated according to the following formula:

[0146]

[0147] is the adsorption coefficient of the more efficient adsorbent in Example 3.

[0148] A t is the effective surface area of the more efficient adsorbent in Example 3.

[0149] fads (t) is a complex function describing the variation of adsorption efficiency with time.

[0150] t ads，3 is the duration of the adsorption stage in Example 3.

[0151] N comp,3 is the number of compressors in Example 3.

[0152] P n,3 is the outlet pressure of the nth compressor in Example 3.

[0153] V n,3 is the working volume of the nth compressor in Example 3.

[0154] C V,n,3 is the nth compressor in Example 3.

[0155] After optimization and improvement, both the CO 2 capture efficiency and the steam heat recovery rate are significantly improved. The experimental results show that under the same conditions, the CO 2 capture efficiency is increased by about 10% compared with Example 2, and the steam heat recovery rate reaches about 70%.

[0156] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A waste heat recovery circulation system for direct air capture of carbon dioxide, characterized in that: include: a. Adsorption / desorption tower, which is filled with amine-functionalized mesoporous materials as CO2 adsorbents to adsorb and desorb CO2 from the air; b. A compressor, connected to the adsorption / desorption tower, used to pressurize the water vapor carrying CO2 during the desorption stage to increase the condensation temperature; c. A separation box, connected to the outlet of the compressor, is used to receive the pressurized water vapor and perform gas-liquid separation to recover pure CO2; d. a heat pump type steam generator connected to the separation tank for recovering the heat energy carried by the cooling water during the separation process and for using the heat energy to produce the water vapor required in the desorption process; e. Heat exchangers, which are arranged in the adsorption and desorption stages to adjust the temperature of air and steam and to condense water vapor after desorption; f. Control system, used to control the operation of compressor, heat pump type steam generator, heat exchanger and adsorption / desorption tower to achieve continuous CO2 capture and waste heat recovery.

2. The waste heat recovery circulation system for direct air capture of carbon dioxide according to claim 1, characterized in that: The adsorption / desorption tower further includes a switching valve for switching the flow paths of air and steam between the adsorption and desorption stages.

3. The waste heat recovery circulation system for direct air capture of carbon dioxide according to claim 1, characterized in that: During the adsorption stage, air is blown into the heat exchanger through a fan, and CO2 is adsorbed by the adsorbent at a temperature range of -45 to 45 degrees Celsius and a CO2 concentration of 400 ppm. The remaining purified gas is discharged from the adsorption / desorption tower.

4. The waste heat recovery circulation system for direct air capture of carbon dioxide according to claim 1, characterized in that: In the desorption stage, high-temperature steam is introduced into the adsorption / desorption tower to maintain the adsorbent temperature at 80 to 120 degrees Celsius, thereby desorbing the adsorbed CO2 and carrying it out of the adsorption / desorption tower by water vapor.

5. The waste heat recovery circulation system for direct air capture of carbon dioxide according to claim 1, characterized in that: The compressor pressurizes the water vapor carrying CO2 to at least 1.5atm to increase the condensation temperature, thereby maximizing the recovery of latent heat of phase change during the condensation process.

6. The waste heat recovery circulation system for direct air capture of carbon dioxide according to claim 1, characterized in that: The heat pump steam generator utilizes the heat energy carried by the cooling water in the separation box to produce the water vapor required in the desorption process, thereby realizing the recycling of water.

7. The waste heat recovery circulation system for direct air capture of carbon dioxide according to claim 1, characterized in that: It also includes an air pre-treatment module for removing particulate matter, dust and other impurities from the air before the air enters the adsorption / desorption tower.

8. The waste heat recovery circulation system for direct air capture of carbon dioxide according to claim 1, characterized in that: It also includes a data interface for connecting with an external device and a network to achieve remote monitoring and data transmission.

9. The waste heat recovery circulation system for direct air capture of carbon dioxide according to claim 1, characterized in that: The heat pump type steam generator has a steam heat recovery rate of at least 50% to 70%.

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