System for capturing carbon dioxide in flue gas of power plant

Abstract

The utility model provides a power plant flue gas carbon dioxide capture system, which is used for capturing carbon dioxide in power plant flue gas and is beneficial to improving the capture rate of carbon dioxide. The system comprises a booster fan, an adsorption and desorption unit and a vacuum pump, the adsorption and desorption unit comprises a gas inlet end and a gas outlet end, the gas inlet end is connected with the booster fan through a pressurized flue gas conveying pipeline, and the vacuum pump is connected with the gas inlet end through a desorbed gas output pipeline; the gas outlet end is connected with a tail gas output pipeline for outputting tail gas; the adsorption and desorption unit is used for adsorbing carbon dioxide in the pressurized flue gas, discharging the tail gas and desorbing the adsorbed carbon dioxide to obtain carbon dioxide desorbed gas; a carbon dioxide desorbed gas outlet of the vacuum pump is connected with a product gas output pipeline, and a product gas return pipeline is connected between the product gas output pipeline and the gas inlet end; and a tail gas backflow pipeline is connected between the tail gas output pipeline and the gas outlet end.

Description

Technical Field

[0001] The utility model relates to a power plant flue gas carbon dioxide capture technology, in particular to a power plant flue gas carbon dioxide capture system. Background Art

[0002] The large-scale combustion and use of fossil fuels has led to a rapid increase in the concentration of CO2 in the air. The current concentration of CO2 in the atmosphere has exceeded 400ppm, exacerbating the greenhouse effect. CO2 emissions from coal-fired power generation account for the largest proportion, about 40% of the total. CO2 capture has the greatest potential to contribute to carbon dioxide emission reductions.

[0003] At present, all large-scale CO2 capture demonstration projects carried out in China adopt the solvent method. The solvent capture technology has its own advantages and is relatively mature, but the technology has problems such as high energy consumption, serious equipment corrosion, amine escape, and certain secondary environmental pollution, and the room for technological progress is getting smaller and smaller. In comparison, the adsorption method and membrane separation method do not rely on chemical reactions and corrosive solvents, and are superior to the solvent method in terms of mechanism, and there is a large room for reducing energy consumption and comprehensive costs.

[0004] As the upstream link of CCUS (carbon dioxide capture, utilization and storage), CO2 capture accounts for more than 70% of the cost of the entire CCUS technology chain. This is the biggest bottleneck currently restricting the large-scale demonstration and application of CCUS technology. Therefore, the development of efficient and low-cost CO2 capture technology is a key link in accelerating the overall progress of CCUS technology.

[0005] Chinese patent ZL201210572964.4 discloses a system and method for capturing carbon dioxide in flue gas, which first performs a gas adsorption step and then a gas desorption step; the system includes a multi-layer pressure swing adsorption device, which contains at least one adsorption bed, each of which contains at least one water vapor adsorption layer and at least one carbon dioxide adsorption layer; the water vapor adsorption layer is below the carbon dioxide adsorption layer, so that the flue gas first passes through the water vapor adsorption layer and then passes through the carbon dioxide adsorption layer, thereby removing water vapor from the flue gas while separating the carbon dioxide from the flue gas. Utility Model Content

[0006] The utility model provides a power plant flue gas carbon dioxide capture system. The system of the utility model is used to capture carbon dioxide in the power plant flue gas, which is beneficial to improving the carbon dioxide capture rate and the purity of the carbon dioxide product gas.

[0007] In order to achieve the above-mentioned purpose, the utility model provides the following technical solutions:

[0008] The utility model provides a power plant flue gas carbon dioxide capture system, the system comprising a booster fan for pressurizing the power plant flue gas to obtain pressurized flue gas, an adsorption and desorption unit and a vacuum pump;

[0009] The adsorption and desorption unit comprises an air inlet and an air outlet, wherein the air inlet is connected to the booster fan via a booster flue gas delivery pipeline, and the vacuum pump is connected to the air inlet via a desorption gas output pipeline for outputting carbon dioxide desorption gas; the air outlet is connected to an exhaust gas output pipeline for outputting exhaust gas; the adsorption and desorption unit is used to adsorb carbon dioxide in the booster flue gas and discharge the exhaust gas, and to desorb the adsorbed carbon dioxide to obtain the carbon dioxide desorption gas;

[0010] The carbon dioxide desorption gas outlet of the vacuum pump is connected to a product gas output pipeline for outputting carbon dioxide product gas, and a product gas reflux pipeline for reflux part of the carbon dioxide product gas to the adsorption and desorption unit is connected between the product gas output pipeline and the gas inlet end;

[0011] A tail gas reflux pipeline for returning part of the tail gas to the adsorption and desorption unit is connected between the tail gas output pipeline and the gas outlet end.

[0012] In some embodiments, the system further comprises a cooler connected to the product gas output pipeline and configured to perform heat exchange between the carbon dioxide product gas and air for feeding into a power plant boiler to obtain preheated air.

[0013] In some embodiments, the carbon dioxide product gas outlet of the cooler is connected to a product gas buffer tank via a pipeline.

[0014] In some embodiments, the adsorption and desorption unit comprises a plurality of pressure swing adsorption towers arranged in parallel, and each of the pressure swing adsorption towers is provided with the air inlet end and the air outlet end;

[0015] Each of the pressure swing adsorption towers is filled with carbon dioxide adsorption material.

[0016] In some embodiments, the carbon dioxide adsorbent material is a hydrophobic carbon dioxide adsorbent material;

[0017] And / or, the pressure swing adsorption tower is a radial tower.

[0018] In some embodiments, the air inlet end of each of the pressure swing adsorption towers is connected to the pressurized flue gas delivery pipeline through a first branch pipe, and the air inlet end of each of the pressure swing adsorption towers is also connected to the desorbed gas output pipeline through a second branch pipe; the air inlet end of each of the pressure swing adsorption towers is also connected to the product gas reflux pipeline through a sixth branch pipe;

[0019] The gas outlet end of each of the pressure swing adsorption towers is connected to the tail gas output pipeline through a third branch pipe, and the gas outlet end of each of the pressure swing adsorption towers is also connected to the tail gas reflux pipeline through a fifth branch pipe; the gas outlet end of each of the pressure swing adsorption towers is also connected to the pressure equalizing pipeline through a fourth branch pipe.

[0020] In some implementations, each of the first branch pipe, the second branch pipe, the third branch pipe, the fourth branch pipe, the fifth branch pipe and the sixth branch pipe is provided with a valve.

[0021] In some embodiments, the vacuum pump and the booster fan are respectively connected to a steam turbine and driven by the steam turbine.

[0022] In some embodiments, the gas source inlet of the steam turbine is connected to a superheated steam pipeline for conveying superheated steam from a steam network of a power plant, and the gas outlet of the steam turbine is connected to a steam inlet of the steam network of the power plant via a pipeline.

[0023] In some embodiments, the system further comprises a raw gas buffer tank, the raw gas inlet of the raw gas buffer tank is connected to the power plant flue gas raw gas delivery pipeline, and is used to perform gas-liquid separation on the power plant flue gas raw gas and obtain liquid condensed water and power plant flue gas separated from the condensed water; the power plant flue gas outlet of the raw gas buffer tank is connected to the power plant flue gas inlet of the booster fan;

[0024] And / or, the tail gas output pipeline is connected to a decarbonized gas buffer tank capable of storing the tail gas.

[0025] The technical solution provided by the utility model has the following beneficial effects:

[0026] The system of the utility model is adopted to capture carbon dioxide in the flue gas of a power plant, and part of the carbon dioxide product gas is refluxed through the product gas reflux pipeline to enter the adsorption and desorption unit for re-adsorption, and part of the tail gas is refluxed through the tail gas reflux pipeline to enter the adsorption and desorption unit for re-adsorption, which is beneficial to improving the carbon dioxide capture rate and improving the purity of the carbon dioxide product gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic diagram of a power plant flue gas carbon dioxide capture system in one embodiment;

[0028] Figure 2 The figure is a schematic diagram of the pipeline arrangement between multiple pressure swing adsorption towers in an adsorption and desorption unit in one embodiment. DETAILED DESCRIPTION

[0029] In order to facilitate the understanding of the present invention, the present invention will be further described below in conjunction with the embodiments. It should be understood that the following embodiments are only for a better understanding of the present invention and do not mean that the present invention is limited to the following embodiments.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the utility model belongs. The term "and / or" as may be used herein includes any and all combinations of one or more of the related listed items.

[0031] The directional terms such as up, down, left, right, front, back, front, back, top, bottom, etc. mentioned or may be mentioned in this specification are defined relative to the structures shown in the drawings. They are relative concepts and may change accordingly according to their different positions and different usage conditions. The words "inside" and "outside" refer to the directions toward or away from the geometric center of a specific component, respectively. In addition, the terms "first", "second", "third", etc. are used for descriptive purposes only and are not to be understood as indicating or implying relative importance.

[0032] See also Figure 1 The utility model provides a power plant flue gas carbon dioxide capture system, which mainly includes a booster fan K-101, an adsorption and desorption unit 100, a vacuum pump P-101, etc.

[0033] The booster fan K-101 is used to boost the flue gas of the power plant to obtain the boosted flue gas. The booster fan K-101 is, for example, a blower.

[0034] The adsorption and desorption unit 100 is used to capture carbon dioxide in the flue gas of the power plant; specifically, the adsorption and desorption unit 100 includes an air inlet end 200 and an air outlet end 300, the air inlet end 200 and the pressurized flue gas outlet of the booster fan K-101 are connected by a pressurized flue gas delivery pipeline 104, the vacuum pump P-101 and the air inlet end 200 are connected by a desorption gas output pipeline 106 for outputting carbon dioxide desorption gas; the air outlet end 300 is connected to an exhaust gas output pipeline 105 for outputting exhaust gas; the adsorption and desorption unit 100 is used to adsorb carbon dioxide in the pressurized flue gas and discharge the exhaust gas, as well as to desorb the adsorbed carbon dioxide to obtain carbon dioxide desorption gas.

[0035] The carbon dioxide desorption gas outlet of the vacuum pump P-101 is connected to the product gas output pipeline 107 for outputting the carbon dioxide product gas, and a product gas reflux pipeline 112 is connected between the product gas output pipeline 107 and the gas inlet end 200, which is used to reflux at least part of the carbon dioxide product gas output by the vacuum pump P-101 to the adsorption desorption unit 100, so that the adsorption process is again performed in the adsorption desorption unit 100. A tail gas reflux pipeline 111 is connected between the tail gas output pipeline 105 and the gas outlet end 300, which is used to reflux part of the tail gas to the adsorption desorption unit 100, so that the tail gas is again subjected to the adsorption process in the adsorption desorption unit 100. The reflux of the carbon dioxide product gas and the tail gas for re-adsorption is beneficial to improving the capture rate of carbon dioxide in the flue gas of the power plant and to improving the purity of the carbon dioxide product gas.

[0036] See also Figure 1 The system of the utility model also includes a cooler E-101, which is connected to the product gas output pipeline 107 and is used to perform heat exchange between the carbon dioxide product gas and the air for feeding into the power plant boiler to obtain preheated air. The carbon dioxide product gas output under the action of the vacuum pump P-101 has a high temperature. By performing heat exchange with the air for feeding into the power plant boiler, it is possible to fully utilize the waste heat resources and realize heat recovery. The preheated air can subsequently enter the power plant air preheater for further heating and then enter the power plant boiler for use. Furthermore, the carbon dioxide product gas outlet of the cooler E-101 is connected to the product gas buffer tank V-104 through the pipeline 108, and the cooled carbon dioxide product gas is stored in the product gas buffer tank V-104.

[0037] See also Figure 1 The adsorption and desorption unit 100 includes a plurality of pressure swing adsorption towers arranged in parallel, such as pressure swing adsorption towers T101A-T101N, and the number of pressure swing adsorption towers is, for example, 4-8, etc. The pressure swing adsorption tower can directly adopt a conventional or known pressure swing adsorption device in the art, such as a vacuum pressure swing adsorption device. Each pressure swing adsorption tower is respectively provided with an air inlet 200 and an air outlet 300, and each pressure swing adsorption tower is respectively filled with a carbon dioxide adsorption material, preferably a hydrophobic carbon dioxide adsorption material, and the carbon dioxide adsorption material can be an adsorption material known in the art that can realize the adsorption function of carbon dioxide in flue gas, such as a modified carbon-based adsorption material known in the art that can realize carbon dioxide adsorption, such as an activated carbon material or a modified activated carbon material, etc., for example, it can be a carbon-based adsorption material modified by air and / or KOH activation, such as a corresponding material disclosed in the literature (for example, directional preparation of coal-based activated carbon: principle, method, and application, Jie Qiang, Zhang Xianglan, Liang Dingcheng, etc., Coal Science and Technology, 2021, 49 (1): 100-127). Preferably, the pressure swing adsorption tower is a radial tower, and the pressure drop of the adsorption tower is reduced.

[0038] The pipelines between the pressure swing adsorption towers in the adsorption and desorption unit are arranged in Figure 1 There is no specific indication in the text. For details, please refer to Figure 2 The adsorption and desorption units in the figure are equipped with 6 pressure swing adsorption towers in parallel. The air inlet end 200 of each pressure swing adsorption tower is connected to the pressurized flue gas delivery pipeline 104 through the first branch pipe 201, and the air inlet end 200 of each pressure swing adsorption tower is also connected to the desorption gas output pipeline 106 through the second branch pipe 202. The air inlet end 200 of each pressure swing adsorption tower is also connected to the product gas reflux pipeline 112 through the sixth branch pipe 206. Specifically, the first branch pipe 201 is connected to the second branch pipe 202, and the first branch pipe 201 is connected to the second branch pipe 202. The branch pipe 201 is also connected to the sixth branch pipe 206; the outlet end 300 of each pressure swing adsorption tower is connected to the tail gas output pipeline 105 through the third branch pipe 203, and the outlet end 300 of each pressure swing adsorption tower is also connected to the tail gas reflux pipeline 111 through the fifth branch pipe 205, and the outlet end 300 of each pressure swing adsorption tower is also connected to the pressure equalization pipeline 113 through the fourth branch pipe 204, the third branch pipe 203 is connected to the fourth branch pipe 204, and the third branch pipe 203 is also connected to the fifth branch pipe 205. Valves are respectively provided on each first branch pipe 201, each second branch pipe 202, each third branch pipe 203, each fourth branch pipe 204, each fifth branch pipe 205 and each sixth branch pipe 206.

[0039] Specifically, Figure 2As shown, there are specifically 6 pressure swing adsorption towers T-101A, T-101B, T-101C, T-101D, T-101E and T-101F, and valves V1A, V1B, V1C, V1D, V1E and V1F are respectively provided on each first branch pipe 201 between the pressurized flue gas conveying pipeline 104 and the air inlet end 200 of each pressure swing adsorption tower, and valves V3A, V3B, V3C, V3D, V3E and V3F are respectively provided on the second branch pipe 202 between the desorbed gas output pipeline 106 and the air inlet end 200 of each pressure swing adsorption tower, and valves V6A, V6B, V6C, V6D, V6E and V6F are respectively provided on the sixth branch pipe 206 between the product gas reflux pipeline 112 and the air inlet end 200 of each pressure swing adsorption tower. Each third branch pipe 203 between the tail gas output pipeline 105 and the gas outlet end 300 of each pressure swing adsorption tower is provided with valves V2A, V2B, V2C, V2D, V2E, and V2F, respectively; each fifth branch pipe 205 between the tail gas reflux pipeline 111 and the gas outlet end 300 of each pressure swing adsorption tower is provided with valves V5A, V5B, V5C, V5D, V5E, and V5F, respectively; each fourth branch pipe 204 between the gas outlet end 300 of each pressure swing adsorption tower and the pressure equalizing pipeline 113 is provided with valves V4A, V4B, V4C, V4D, V4E, and V4F, respectively. It is well known to those skilled in the art that by switching operations of different valves, cyclic switching operation of each pressure swing adsorption tower under different operating conditions can be achieved, and some adsorption towers can be operated synchronously under different operating conditions. In some examples, Figure 2 Each tower in the adsorption and desorption unit shown can, for example, be cyclically operated in the sequence shown in Table 1 below. For example, each pressure swing adsorption tower is fed into the adsorption tower from the air inlet end 200 through the power plant flue gas in turn for adsorption (corresponding to "X" in Table 1), part of the carbon dioxide product gas is refluxed into the adsorption tower through the air inlet end 200 through the product gas reflux line 112 and the adsorption tower is pressurized (corresponding to "PR" in Table 1), the pressure is equalized and reduced between the adsorption towers (corresponding to "ED" in Table 1), the vacuum pump P-101 is turned on for vacuum desorption to desorb carbon dioxide (corresponding to "V" in Table 1), the pressure is equalized and increased between the adsorption towers (corresponding to "ER" in Table 1), part of the exhaust gas is refluxed into the adsorption tower through the exhaust gas reflux line 111 and the outlet end 300 (corresponding to "WR" in Table 1), and the adsorption tower is pressurized by the exhaust gas reflux (corresponding to "WP" in Table 1); and the cycle is operated in this way.

[0040] Table 1

[0041] Step sequence 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 T-101A X X X X X X PR ED ED V V V V ER ER WR WP WP T-101B WR WP WP X X X X X X PR ED ED V V V V ER ER T-101C V ER ER WR WP WP X X X X X X PR ED ED V V V T-101D V V V V ER ER WR WP WP X X X X X X PR ED ED T-101E PR ED ED V V V V ER ER WR WP WP X X X X X X T-101F X X X PR ED ED V V V V ER ER WR WP WP X X X

[0042] Note: In Table 1, X refers to adsorption, PR refers to product gas reflux, ED refers to average pressure drop, V refers to vacuum extraction, ER refers to average pressure increase, WR refers to tail gas reflux, and WP refers to tail gas pressure increase.

[0043] Preferably, the vacuum pump P-101 and the booster fan K-101 are connected to the steam turbines K-102 and P-102 respectively and driven by the steam turbines, wherein the gas source inlet of the steam turbine is connected to the superheated steam pipeline for conveying superheated steam from the steam network of the power plant, and the gas outlet of the steam turbine is connected to the steam inlet of the steam network of the power plant through the pipeline. That is, the gas source required by the steam turbine is provided by the superheated steam in the steam network of the power plant, and the vacuum pump P-101 and the booster fan K-101 are driven by the steam turbine, so as to achieve energy saving and consumption reduction, and the steam that has done work is sent back to the steam network of the power plant for further heating and pressure raising and then recycled, which is highly coupled with the power plant and has high energy efficiency.

[0044] More specifically, if Figure 1 As shown, the system of the utility model also includes a raw gas buffer tank V-101, and the raw gas inlet of the raw gas buffer tank V-101 is connected to the power plant flue gas raw gas transmission pipeline 101. After the power plant flue gas raw gas enters the raw gas buffer tank V-101, gas-liquid separation is performed therein, and the gas phase is the power plant flue gas separated from the condensed water, and the liquid phase is the condensed water. The power plant flue gas outlet of the raw gas buffer tank V-101 and the power plant flue gas inlet of the booster fan K-101 are connected through a pipeline 103, so that the power plant flue gas separated from the condensed water is sent to the booster fan K-101 for pressurization to obtain the boosted flue gas. The condensed water can be sent to the condensate tank V-102 through the pipeline 102, and the liquid condensed water subsequently output by the condensate pump P-102 is sent to the downstream power plant desulfurization tower through the pipeline 109 for reuse.

[0045] More specifically, the tail gas output pipeline 105 is connected to the decarbonized gas buffer tank V-103, and the tail gas output from the tail gas output pipeline 105 that is not refluxed is sent to the decarbonized gas buffer tank for storage.

[0046] In some embodiments, the power plant flue gas carbon dioxide capture system of the utility model is used to treat power plant flue gas, for example, the power plant flue gas with low carbon dioxide concentration at normal pressure can be concentrated to a carbon dioxide concentration of more than 95%, and the carbon dioxide capture rate can reach more than 80%, for example.

[0047] The power plant flue gas carbon dioxide capture system of the utility model is used to capture carbon dioxide in the power plant flue gas, and double reflux of product gas and tail gas is performed during the capture process; in the preferred embodiment, the heat carried by the product gas is also exchanged with air, which is conducive to the rational use of waste heat resources; in the preferred embodiment, superheated steam from the power plant steam network is used as the gas source, and the vacuum pump P-101 and the booster fan K-101 are driven by the steam turbine, so that the energy in the application scenario is integrated and utilized. The power plant flue gas carbon dioxide capture system based on the utility model is used to capture carbon dioxide in the power plant flue gas, and the required process flow is short, the energy consumption of carbon dioxide capture is low, and the investment cost of the device is low, which is suitable for large-scale low-energy power plant flue gas CO2 capture.

[0048] For ease of understanding, the following is an exemplary introduction to the process of capturing carbon dioxide in flue gas from a power plant using the system of the utility model:

[0049] See also Figure 1 The desulfurized power plant flue gas with low CO2 concentration at normal pressure is sent to the raw gas buffer tank V-101 through the power plant flue gas raw gas pipeline 101 for vapor-liquid separation, and the liquid condensed water is sent to the condensate tank V-102 through the pipeline 102, and is pressurized by the condensate pump P-102 and sent to the downstream power plant desulfurization tower for reuse.

[0050] The gas phase containing saturated water (i.e. the power plant flue gas from which condensed water has been separated) is sent to the blower K-101 for pressurization via pipeline 103. The blower K-101 is driven by a steam turbine. The pressurized flue gas enters the pressure swing adsorption towers T-101A~N via the pressurized flue gas conveying pipeline 104 for adsorption-desorption operation. The operation process of each adsorption tower includes: feeding / adsorption, carbon dioxide product gas reflux / pressurization, pressure equalization and pressure reduction, vacuum desorption through the action of vacuum pump P-101, pressure equalization and pressure increase, tail gas reflux / pressure increase, and so on. The cycle operation is as follows; the number of adsorption towers is 4 to 8, and the adsorption tower is a radial tower structure. The adsorption tower is filled with hydrophobic CO2 adsorption material. Part of the tail gas (i.e. decarbonized gas) containing components such as N2, H2O, and a small amount of CO2 flows back into the adsorption tower through the tail gas reflux pipeline 111, and part enters the decarbonized gas buffer tank, and then enters the chimney of the power plant for discharge. The temperature of the pressurized flue gas boosted by the blower will increase by 10 to 20°C, and the flue gas temperature will be 10 to 20°C higher than the dew point. Equipment such as the adsorption tower can be made of carbon steel.

[0051] The CO2 adsorbed by the adsorbent material in the pressure swing adsorption tower is desorbed by vacuum pump P-101 to obtain a carbon dioxide desorbed gas with a high CO2 content (for example, a CO2 content of more than 95%), which is output from the adsorption tower through the desorbed gas output pipeline 106. The vacuum pump P-101 is driven by a steam turbine. The carbon dioxide product gas discharged by the vacuum pump P-101 is output through the product gas output pipeline 107. The temperature of the product gas is relatively high, and it exchanges heat with the air in the cooler E-101 for heat recovery. The heated air enters the power plant air preheater and enters the power plant boiler after further heating. The carbon dioxide product gas after heat recovery and cooling enters the product gas buffer tank V-104 through pipeline 108, and can then enter the downstream refining device for further processing for utilization or sealing. In some examples, the capture rate of CO2 in power plant flue gas in the system of the utility model can reach more than 80%.

[0052] The following is a further introduction to a specific example of using the system of the utility model to capture carbon dioxide in power plant flue gas through an embodiment:

[0053] Example 1

[0054] like Figure 1-2 As shown, 633465Nm 3 / h, 0.3kPaG, 50℃, low-concentration desulfurized power plant flue gas (million-ton CO2 capture scale) with a CO2 content of 14.52% vol, enters the raw gas buffer tank V-101 through the power plant flue gas raw gas transmission pipeline 101 for vapor-liquid separation to remove entrained moisture, and the liquid condensed water enters the condensate tank V-102 through the pipeline 102. The liquid condensed water is pressurized by the condensate pump P-102 and sent to the downstream power plant desulfurization tower for reuse.

[0055] The gas phase containing saturated water (i.e., the flue gas from the power plant with condensed water separated) enters the blower K-101 through pipeline 103 and is pressurized to 13kPaG. The blower is driven by a steam turbine. The steam comes from the steam network of the power plant. It is superheated steam with a steam pressure of 3.8MPaG and a temperature of 420℃. After the turbine works, it is converted into steam with a pressure of 1.0MPaG and a temperature of 284℃. The steam returns to the steam network for heating and pressure-boosting recycling. The temperature of the pressurized flue gas pressurized to 13kPaG by the blower increases by ~15℃, that is, the flue gas temperature will be ~15℃ higher than the dew point. Carbon steel materials can be used for equipment such as adsorption towers.

[0056] The pressurized flue gas enters the pressure swing adsorption towers T-101A~T-101F through the pressurized flue gas delivery pipeline 104 for adsorption-desorption operation. There are 6 adsorption towers, which are filled with hydrophobic CO2 adsorption materials. The operation process of each adsorption tower includes: pressurized flue gas feeding / adsorption, carbon dioxide product gas reflux / pressurization, pressure equalization and pressure reduction, vacuum desorption through the action of vacuum pump P-101, pressure equalization and pressure increase, tail gas reflux / pressure increase (see Table 1 for details), and so on. Part of the tail gas is refluxed through the tail gas reflux pipeline 111 to increase the pressure of the adsorption tower, which is also beneficial to improve the CO2 capture rate; part of the carbon dioxide product gas is refluxed through the product gas reflux pipeline 112 to increase the pressure of the adsorption tower, which is also beneficial to improve the purity of the CO2 product gas. The adsorption tower is a radial tower structure, and the pressure drop of the adsorption tower is <10kPa. The part of the tail gas containing N2, H2O, a small amount of CO2 and other components that is not refluxed enters the decarbonization gas buffer tank through the tail gas output pipeline 105.

[0057] The CO2 adsorbed by the carbon dioxide adsorption material in the pressure swing adsorption tower is sucked by the vacuum pump P-101 (pumped to a vacuum pressure of -81.3 kPaG), and desorption can obtain carbon dioxide desorption gas with a CO2 content of 95.1 vol%, which is output through the desorption gas output pipeline 106. The vacuum pump P-101 is driven by a steam turbine. The steam comes from the steam network of the power plant. It is superheated steam with a steam pressure of 3.8 MPaG and a temperature of 420°C. After the turbine does work, it is converted into steam with a pressure of 1.0 MPaG and a temperature of 284°C. The steam returns to the steam network for heating and pressure-raising circulation. The temperature of the carbon dioxide product gas discharged by the vacuum pump P-101 rises to 222°C, and is output through the product gas output pipeline 107. It exchanges heat with the air in the cooler E-101 for heat recovery. The heated air enters the power plant air preheater and enters the power plant boiler after further heating. For the air of a 600MW power plant boiler, the temperature can be raised by 25 to 30°C. The carbon dioxide product gas cooled to 45°C after heat recovery enters the product gas buffer tank V-104 through pipeline 108. In this embodiment, the CO2 capture rate can reach 80.5%.

[0058] The main logistics data of this embodiment are shown in Table 2. The captured CO2 flow rate is 145.5t / h. The energy conversion value of the capture energy consumption calculation is shown in Table 3. The capture energy consumption calculation is shown in Table 4. The CO2 capture energy consumption is 0.426GJ / tCO2.

[0059] Table 2 Logistics data of Example 1

[0060]

[0061]

[0062] Note: The numbers after the names of each stream in Table 2 are the labels of the corresponding pipelines. For example, power plant flue gas 101 refers to the power plant flue gas stream transported through the power plant flue gas raw gas transmission pipeline 101.

[0063] Table 3 Energy conversion value

[0064]

[0065] The energy conversion values ​​in Table 3 are from GB / T 50441-2016 Petrochemical Design Energy Consumption Calculation Standard.

[0066] Table 4 Capture energy consumption

[0067]

[0068] Note: The steam energy conversion value is calculated based on the steam state enthalpy entering and leaving the steam turbine.

[0069] Example 2

[0070] like Figure 2 As shown, other conditions are the same as in Example 1. The carbon dioxide product gas discharged from the vacuum pump P-101 (i.e., the product gas transported by the product gas output pipeline 107) is not cooled by heat exchange with the air in the cooler E-101, but is cooled to 45°C with cooling water, which increases the consumption of circulating water. The capture energy consumption is calculated as shown in Table 5. The CO2 capture energy consumption is 0.439 GJ / tCO2.

[0071] Table 5 Capture energy consumption

[0072]

[0073]

[0074] Example 3

[0075] Other conditions are the same as in Example 1. The blower K-101 and the vacuum pump P-101 are both electrically driven, and the CO2 capture energy consumption is 1.021 GJ / tCO2.

[0076] Comparative Example 1

[0077] The other conditions are the same as those in Example 1, except that: no reflux of tail gas and carbon dioxide product gas is performed, and desorption obtains carbon dioxide desorption gas with a CO2 content of 88.7 vol%, the CO2 capture rate can reach 74.2%, and the CO2 capture energy consumption is 0.614 GJ / tCO2.

[0078] Comparative Example 2

[0079] According to the literature (DOI: 10.1016 / j.memsci.2021.119137), CO2-containing flue gas (14 vol%) was captured by membrane separation, which was a pressurized two-stage membrane pilot plant. The inlet temperature and pressure of the simulated flue gas were 4.6 bar and 29 ° C, respectively, and the membrane separator was a polyethylene amine spiral membrane reactor. After the simulated flue gas was captured, the CO2 removal rate was 61.3%, the product gas concentration was 78.5%, and the unit energy consumption was about 809 kWh / tCO2, or 7.45 GJ / tCO2.

[0080] It is easy to understand that the above embodiments are only examples for clear explanation, and do not mean that the present invention is limited to them. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made on the basis of the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from them are still within the protection scope of the present invention.

Claims

1. A power plant flue gas carbon dioxide capture system, characterized in that: The system comprises a booster fan, an adsorption and desorption unit and a vacuum pump for boosting the flue gas of the power plant to obtain the boosted flue gas; The adsorption and desorption unit comprises an air inlet and an air outlet, wherein the air inlet is connected to the booster fan via a booster flue gas delivery pipeline, and the vacuum pump is connected to the air inlet via a desorption gas output pipeline for outputting carbon dioxide desorption gas; the air outlet is connected to an exhaust gas output pipeline for outputting exhaust gas; the adsorption and desorption unit is used to adsorb carbon dioxide in the booster flue gas and discharge the exhaust gas, and to desorb the adsorbed carbon dioxide to obtain the carbon dioxide desorption gas; The carbon dioxide desorption gas outlet of the vacuum pump is connected to a product gas output pipeline for outputting carbon dioxide product gas, and a product gas reflux pipeline for reflux part of the carbon dioxide product gas to the adsorption and desorption unit is connected between the product gas output pipeline and the gas inlet end; A tail gas reflux pipeline for returning part of the tail gas to the adsorption and desorption unit is connected between the tail gas output pipeline and the gas outlet end.

2. The power plant flue gas carbon dioxide capture system according to claim 1, characterized in that: The system further comprises a cooler, which is connected to the product gas output pipeline and is used for performing heat exchange between the carbon dioxide product gas and the air for being fed into the power plant boiler to obtain preheated air.

3. The power plant flue gas carbon dioxide capture system according to claim 2, characterized in that: The carbon dioxide product gas outlet of the cooler is connected to the product gas buffer tank through a pipeline.

4. The power plant flue gas carbon dioxide capture system according to claim 1, characterized in that: The adsorption and desorption unit comprises a plurality of pressure swing adsorption towers arranged in parallel, each of the pressure swing adsorption towers is respectively provided with the air inlet end and the air outlet end; Each of the pressure swing adsorption towers is filled with carbon dioxide adsorption material.

5. The power plant flue gas carbon dioxide capture system according to claim 4, characterized in that: The carbon dioxide adsorbent material is a hydrophobic carbon dioxide adsorbent material; And / or, the pressure swing adsorption tower is a radial tower.

6. The power plant flue gas carbon dioxide capture system according to claim 4, characterized in that: The air inlet end of each of the pressure swing adsorption towers is connected to the pressurized flue gas delivery pipeline through a first branch pipe, and the air inlet end of each of the pressure swing adsorption towers is also connected to the desorbed gas output pipeline through a second branch pipe; the air inlet end of each of the pressure swing adsorption towers is also connected to the product gas reflux pipeline through a sixth branch pipe; The gas outlet end of each of the pressure swing adsorption towers is connected to the tail gas output pipeline through a third branch pipe, and the gas outlet end of each of the pressure swing adsorption towers is also connected to the tail gas reflux pipeline through a fifth branch pipe; the gas outlet end of each of the pressure swing adsorption towers is also connected to the pressure equalizing pipeline through a fourth branch pipe.

7. The power plant flue gas carbon dioxide capture system according to claim 6, characterized in that: Each of the first branch pipe, the second branch pipe, the third branch pipe, the fourth branch pipe, the fifth branch pipe and the sixth branch pipe is provided with a valve respectively.

8. The power plant flue gas carbon dioxide capture system according to any one of claims 1 to 7, characterized in that: The vacuum pump and the booster fan are respectively connected to the steam turbine and driven by the steam turbine.

9. The power plant flue gas carbon dioxide capture system according to claim 8, characterized in that: The gas source inlet of the steam turbine is connected to a superheated steam pipeline for conveying superheated steam from a steam network of a power plant, and the gas outlet of the steam turbine is connected to a steam inlet of the steam network of the power plant through a pipeline.

10. The power plant flue gas carbon dioxide capture system according to any one of claims 1 to 7, characterized in that: The system further comprises a raw gas buffer tank, the raw gas inlet of the raw gas buffer tank is connected to the power plant flue gas raw gas delivery pipeline, and is used to perform gas-liquid separation on the power plant flue gas raw gas and obtain liquid condensed water and power plant flue gas separated from the condensed water; the power plant flue gas outlet of the raw gas buffer tank is connected to the power plant flue gas inlet of the booster fan; And / or, the tail gas output pipeline is connected to a decarbonized gas buffer tank capable of storing the tail gas.

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