Low energy consumption, high capture rate carbon dioxide capture method and capture system

Abstract

The present invention provides a carbon dioxide capture method and capture system with low energy consumption and high capture rate, which is conducive to reducing energy consumption and improving capture rate. The method comprises: introducing the cooled adsorbed flue gas into the adsorption tower that has completed the desorption link to perform the cooling operation of the adsorption tower in the adsorption link, and subjecting the cooled adsorbed flue gas to secondary adsorption treatment in the adsorption tower; the adsorption tower after the cooling operation is pressurized, and then the flue gas to be adsorbed that has been pressurized for the first time, cooled by the first heat exchange with the adsorbed flue gas, pressurized for the second time in the residual pressure recovery machine, and cooled by the second heat exchange with the circulating gas is introduced into the adsorption tower for adsorption treatment until adsorption saturation is reached, and the adsorbed flue gas is obtained through adsorption treatment; the adsorption tower in the adsorption link performs the desorption link after adsorption saturation: the adsorption tower is pressurized, and then the heated circulating gas is introduced to heat it, and then vacuumized to obtain carbon dioxide product gas.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon dioxide capture in flue gas, and in particular to a carbon dioxide capture method and a carbon dioxide capture system with low energy consumption and high capture rate. Background Art

[0002] In recent years, climate change has become a focus of public attention. The large-scale greenhouse gas emissions caused by human activities have brought irreversible and significant impacts to the global ecosystem. Among the many emission reduction technologies, carbon dioxide capture and storage (CCS) is considered to be the key technology to solve the carbon emission problem.

[0003] CO2 capture and storage technology (CCS) has the potential to reduce costs and increase flexibility in achieving greenhouse gas emission reductions. The huge flue gas flow and velocity of atmospheric flue gas in large-scale industries such as coal-fired power plants, steel metallurgy, cement building materials and petrochemicals have increased the cost and technical difficulty of operating large-scale CO2 capture systems. Existing separation technologies face many challenges. Whether it is to store CO2 or to utilize it as a resource, how to achieve efficient and low-energy CO2 capture and separation technology is currently the main bottleneck.

[0004] At present, the most important reason restricting the development of carbon dioxide capture and storage technology is the large investment and high operating cost. The adsorption method has certain advantages due to its simple equipment, easy automation, low corrosion, simple process amplification law, etc. It is one of the most promising important alternative technologies for capturing and separating CO2 gas for large-scale application; however, the adsorption method also has problems such as low separation efficiency, slow desorption rate, long cooling process, and high cost of capturing flue gas with low carbon dioxide content.

[0005] Patent document CN88105938.2 discloses a pressure swing adsorption method for extracting carbon dioxide from various carbon dioxide-rich mixed gases. Carbon dioxide is obtained as a product from the desorption stage. In order to produce high-purity carbon dioxide products, part of the product gas is refluxed into the tower for replacement in the process to further increase the carbon dioxide concentration in the tower. In order to increase the extraction rate of carbon dioxide, it is necessary to recycle the exhaust gas after forward decompression and replacement as a raw material. The carbon dioxide extracted from the carbon dioxide-rich mixed gas by pressure swing adsorption can be used as a chemical raw material, and can also be used in metallurgy, welding, drinking and scientific research.

[0006] Patent document CN202210087934.8 discloses a method for reducing carbon dioxide at the tail of a cement kiln by adsorption, comprising: filling a fixed bed reactor, removing impurities from tail gas, high-temperature adsorption emission reduction treatment, and desorption recovery treatment. Summary of the invention

[0007] In view of the shortcomings and deficiencies of the existing adsorption carbon dioxide capture technology, such as high energy consumption, low capture efficiency, and high operating costs, the present invention aims to provide a carbon dioxide capture system and a method for capturing carbon dioxide using the system. Carbon dioxide capture based on the carbon dioxide capture method and capture system of the present invention is beneficial to reducing energy consumption and improving capture rate.

[0008] To achieve the purpose, the present invention provides the following technical solutions:

[0009] The present invention provides a method for capturing carbon dioxide with low energy consumption and high capture rate.

[0010] Performing carbon dioxide adsorption treatment on the flue gas to be adsorbed in a group of adsorption towers, wherein the group of adsorption towers includes a plurality of adsorption towers, and each of the adsorption towers undergoes an adsorption step and a desorption step respectively;

[0011] The adsorption process comprises: introducing the cooled adsorbed flue gas into the adsorption tower that has completed the desorption process to perform a cooling operation of the adsorption tower in the adsorption process, and subjecting the cooled adsorbed flue gas to a secondary adsorption treatment in the adsorption tower; performing a pressurization operation on the adsorption tower after the cooling operation, and then introducing the adsorbed flue gas that has undergone a first pressurization, a first heat exchange with the adsorbed flue gas to be cooled, a second pressurization in the residual pressure recovery machine due to the mechanical energy provided by the expansion of the adsorbed flue gas, and a second heat exchange with the circulating gas to be cooled, into the adsorption tower that has completed the pressurization operation to perform an adsorption treatment until adsorption saturation is reached, and the adsorbed flue gas is obtained through adsorption treatment;

[0012] After the adsorption tower of the adsorption stage is saturated with adsorption, the desorption stage is performed; the desorption stage comprises: depressurizing the saturated adsorption tower, then introducing heated circulating gas to increase the temperature, and then vacuuming to desorb carbon dioxide to obtain carbon dioxide product gas;

[0013] Among them, the cooled adsorbed flue gas used in the adsorption link is the adsorbed flue gas that is cooled after the adsorbed flue gas expands and does work in the residual pressure recovery machine; the heated circulating gas used in the desorption link is the circulating gas that is heated by the second heat exchange.

[0014] In some embodiments, part of the carbon dioxide product gas is used as the circulating gas; preferably, part of the carbon dioxide product gas is sent to the circulating gas storage tank to supply the circulating gas.

[0015] In some embodiments, the flue gas to be adsorbed is dehydrated in a gas-water separator before being introduced into the adsorption tower.

[0016] In some embodiments, the adsorption tower that has reached the adsorption saturation is connected to the adsorption tower that has completed the cooling operation through a pressure equalizing pipeline, so that the adsorption tower that has reached the adsorption saturation is depressurized and the adsorption tower that has completed the cooling operation is pressurized, thereby realizing the pressure increase operation and the pressure reduction operation.

[0017] In some implementations, the pressure in the adsorption tower that has completed the pressure reduction operation is adjusted to normal pressure, and then the operation of introducing the heated circulating gas to increase the temperature is performed.

[0018] The present invention also provides a carbon dioxide capture system with low energy consumption and high capture rate, comprising: a plurality of adsorption towers respectively provided with air inlets and air outlets, a flue gas input pipeline for conveying flue gas to be adsorbed, a flue gas output pipeline for conveying flue gas after adsorption, a circulating gas storage tank for supplying and storing circulating gas, a circulating gas input pipeline, a circulating gas output pipeline and a carbon dioxide product gas extraction pipeline connected to a vacuum pump; wherein,

[0019] The air inlet end of the flue gas input pipeline is connected to the gas source of the flue gas to be adsorbed, and the air outlet end of the flue gas input pipeline is respectively connected to the air inlet of each adsorption tower to form a connecting air path;

[0020] The air inlet end of the flue gas output pipeline is respectively connected with the air outlet of each adsorption tower to form a connecting air path, and the air outlet end of the flue gas output pipeline is respectively connected with the air inlet of each adsorption tower to form a connecting air path;

[0021] The air inlet end of the circulating gas input pipeline is connected to the air outlet hole of the circulating gas storage tank, and the air outlet end of the circulating gas input pipeline is respectively connected to the air inlet of each adsorption tower to form a connecting air path;

[0022] The air inlet end of the circulating gas output pipeline is respectively connected to the air outlet of each adsorption tower to form a connecting air path, and the air outlet end of the circulating gas output pipeline is connected to the air inlet hole of the circulating gas storage tank;

[0023] The gas inlet end of the carbon dioxide product gas production pipeline is respectively connected to the gas outlet of each adsorption tower to form a connecting gas path;

[0024] A switch valve for controlling the on / off of the communicating gas path is provided on each communicating gas path;

[0025] A booster, a first heat exchanger, a residual pressure recovery machine and a second heat exchanger are sequentially arranged on the flue gas input pipeline along the airflow direction; the flue gas output pipeline passes through the first heat exchanger and the residual pressure recovery machine in sequence along the airflow direction and then is respectively connected to each of the air inlets; the booster is used for the first boosting of the flue gas to be adsorbed; the first heat exchanger is used for the first heat exchange between the flue gas to be adsorbed and the adsorbed flue gas to achieve cooling of the flue gas to be adsorbed; the residual pressure recovery machine is used for obtaining the cooled adsorbed flue gas cooled by expansion work and the flue gas to be adsorbed which is compressed by the mechanical energy provided by the expansion work of the adsorbed flue gas to achieve the second boosting; the circulating gas input pipeline passes through the second heat exchanger and then is respectively connected to each of the air inlets; the second heat exchanger is used for the second heat exchange between the circulating gas transported by the circulating gas input pipeline and the flue gas to be adsorbed to achieve cooling of the flue gas to be adsorbed and obtain heated circulating gas.

[0026] In some embodiments, a pressure equalizing pipeline is further included to connect the adsorption towers to each other so as to balance the pressure between two adsorption towers that are connected to each other, and a switch valve for controlling the opening and closing of the connecting gas path is provided on the connecting gas path formed between any two adsorption towers.

[0027] In some embodiments, an exhaust pipeline is further included, wherein the air inlet end of the exhaust pipeline is respectively connected to the air outlet of each of the adsorption towers to form a connecting air path, and a switch valve for controlling the opening and closing of the connecting air path is provided on the connecting air path.

[0028] In some embodiments, the circulating gas output pipeline is connected to the carbon dioxide product gas production pipeline so that the circulating gas output pipeline is indirectly connected to the gas outlet of each adsorption tower, and the connecting point between the circulating gas output pipeline and the carbon dioxide product gas production pipeline is located downstream of the vacuum pump; switch valves are respectively provided on the pipe section of the carbon dioxide product gas production pipeline downstream of the vacuum pump and on the circulating gas output pipeline downstream of the vacuum pump.

[0029] In some embodiments, the air inlet of each of the adsorption towers is connected to an air inlet branch pipe, and the air outlet of each of the adsorption towers is connected to an air outlet branch pipe;

[0030] The gas outlet end of the smoke input pipeline is connected to each of the gas inlet branches, and a switch valve is provided between the gas outlet end of the smoke input pipeline and each of the gas inlet branches;

[0031] The air inlet end of the smoke output pipeline is respectively connected to each of the air outlet branches, and a switch valve is respectively provided between the air inlet end of the smoke output pipeline and each of the air outlet branches; the air outlet end of the smoke output pipeline is respectively connected to each of the air inlet branches, and a switch valve is respectively provided between the air outlet end of the smoke output pipeline and each of the air inlet branches;

[0032] The outlet end of the circulating gas input pipeline is connected to each of the inlet branch pipes, and a switch valve is provided between the outlet end of the circulating gas input pipeline and each of the inlet branch pipes;

[0033] The air inlet end of the carbon dioxide product gas production pipeline is communicated with each of the air outlet branch pipes, and a switch valve is provided between the air inlet end of the carbon dioxide product gas production pipeline and each of the air outlet branch pipes.

[0034] In some embodiments, a pressure equalizing pipeline is further included, one end of which is connected to each of the air inlet branches, and the other end of which is connected to each of the air outlet branches, and a switch valve is provided between the pressure equalizing pipeline and each of the air inlet branches and between the pressure equalizing pipeline and each of the air outlet branches;

[0035] It also includes an exhaust pipeline, the air inlet end of the exhaust pipeline is respectively connected to each of the air outlet branches, and a switch valve is respectively provided between the air inlet end of the exhaust pipeline and each of the air outlet branches.

[0036] In some embodiments, a gas-water separator is further provided on the flue gas input pipeline downstream of the second heat exchanger along the airflow direction of the flue gas input pipeline, for removing moisture from the flue gas to be adsorbed;

[0037] And / or, a circulating fan is also provided on the circulating gas input pipeline.

[0038] The carbon dioxide capture system described above is used in the carbon dioxide capture method described above.

[0039] The technical solution provided by the present invention has the following beneficial effects:

[0040] The carbon dioxide capture system provided by the present invention is used to capture carbon dioxide in flue gas, which has the characteristics of simple process flow and convenient operation, and can achieve efficient capture of carbon dioxide in flue gas, especially low-concentration carbon dioxide flue gas. The carbon dioxide capture system provided by the present invention is used to capture carbon dioxide in flue gas, which can significantly reduce energy consumption and improve capture efficiency.

[0041] (1) The flue gas to be adsorbed is cooled by exchanging heat with the flue gas after adsorption for the first time, and the flue gas to be adsorbed is pressurized for the second time by the mechanical energy output by the flue gas residual pressure recovery after adsorption through the residual pressure recovery machine. Then, the flue gas to be adsorbed is cooled by exchanging heat with the circulating gas for the second time, and the circulating gas is heated to increase its temperature. This can achieve efficient utilization of thermal energy, obtain flue gas to be adsorbed that meets the adsorption temperature requirements, and obtain hot circulating gas that can be used to heat the adsorption tower in the desorption process. The heat required for heating the adsorption tower can be provided without additional heat input.

[0042] (2) Through the clever arrangement of material flow, the flue gas after adsorption and the flue gas to be adsorbed are coordinated with each other in the residual pressure recovery machine. The flue gas after adsorption expands and cools and performs work externally, so that the flue gas to be adsorbed is pressurized, which can greatly reduce the power demand of the booster used for the flue gas to be adsorbed, and the flue gas after adsorption is greatly cooled to obtain the cooled post-adsorption flue gas that can be used for the cooling operation of the adsorption tower, which greatly simplifies the adsorbent cooling process of temperature swing adsorption, can greatly reduce the cooling time, and improve the efficiency of the overall device; and the expanded and cooled post-adsorption flue gas is introduced into the adsorption tower again, which not only realizes the cooling of the adsorption tower, but also realizes the secondary low-temperature adsorption of the flue gas after adsorption, greatly improves the adsorption effect, and utilizes the improvement of the capture rate of carbon dioxide.

[0043] (3) The present invention realizes pressure energy recovery and heat recycling through reasonable arrangement of the flow directions of various material flows in multiple adsorption towers, based on system optimization design, and coordinated with the improvement of process flow, thereby greatly reducing energy consumption. In some implementation methods, energy consumption is reduced by more than 40% compared with traditional adsorption processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1-Figure 2 Schematic diagram of a carbon dioxide capture system in one embodiment.

[0045] Figure 3 Schematic diagram of a traditional carbon dioxide capture system. DETAILED DESCRIPTION

[0046] In order to facilitate the understanding of the present invention, the present invention will be further described below in conjunction with examples. It should be understood that the following examples are only for a better understanding of the present invention and do not mean that the present invention is limited to the following examples.

[0047] 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 invention belongs. The term "and / or" as may be used herein includes any and all combinations of one or more of the associated listed items.

[0048] 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.

[0049] The present invention provides a method for capturing carbon dioxide with low energy consumption and high capture rate, which mainly comprises:

[0050] The flue gas to be adsorbed is subjected to carbon dioxide adsorption treatment in a group of adsorption towers, wherein the group of adsorption towers includes a plurality of adsorption towers, and each adsorption tower undergoes an adsorption step and a desorption step respectively;

[0051] The adsorption process includes: introducing the cooled adsorbed flue gas into the adsorption tower that has completed the desorption process to perform the cooling operation of the adsorption tower in the adsorption process, and subjecting the cooled adsorbed flue gas to secondary adsorption treatment in the adsorption tower; performing a pressurization operation on the adsorption tower after the cooling operation is completed, and then the flue gas to be adsorbed that has undergone the first pressurization, the first heat exchange with the adsorbed flue gas to be cooled, the second pressurization by the mechanical energy provided by the expansion work of the adsorbed flue gas in the residual pressure recovery machine, and the second heat exchange with the circulating gas to be cooled is introduced into the adsorption tower that has completed the pressurization operation for adsorption treatment until adsorption saturation is reached, and the adsorbed flue gas is obtained after the adsorption treatment;

[0052] After the adsorption tower of the adsorption stage is saturated with adsorption, a desorption stage is performed; the desorption stage includes reducing the pressure of the saturated adsorption tower, then introducing the heated circulating gas to increase the temperature, and then vacuuming to desorb carbon dioxide to obtain carbon dioxide product gas;

[0053] Among them, the cooled adsorbed flue gas used in the adsorption stage is the adsorbed flue gas that is cooled after expanding and doing work in the residual pressure recovery machine; the heated circulating gas used in the desorption stage is the circulating gas that is heated by the second heat exchange.

[0054] The carbon dioxide capture method of the present invention is used to adsorb flue gas, and the process flow is simple, and the pressure change and temperature change are coupled, which is conducive to improving the capture rate of carbon dioxide in flue gas. The adsorption link of the present invention is a high-pressure-low-temperature coupled adsorption, and the low-temperature adsorption condition and the pressurized flue gas to be adsorbed are carried out by the supercharger in coordination with the adsorbed flue gas carrying the residual pressure to expand in the residual pressure recovery machine to provide mechanical energy for the second pressurization to obtain the flue gas to be adsorbed suitable for high-pressure adsorption, and the first heat exchange between the adsorbed flue gas and the flue gas to be adsorbed provides part of the cooling capacity, the second heat exchange between the circulating gas and the flue gas to be adsorbed provides another part of the cooling capacity, and the cooling of the adsorbed flue gas obtained by the expansion and cooling of the adsorbed flue gas in the residual pressure recovery machine provides a low-temperature adsorption environment for the cooling treatment of the adsorption tower. The desorption process of the present invention is a pressure reduction-high temperature coupled desorption. After the adsorption saturated adsorption tower is depressurized (equalized pressure drop), the heated circulating gas obtained by the second heat exchange with the flue gas to be adsorbed is introduced to increase the temperature, and then vacuum is evacuated to perform a pressure reduction-temperature increase coupled desorption process to achieve efficient desorption; and the carbon dioxide product gas generated by desorption can be used as a gas source for the circulating gas. Specifically, before the flue gas to be adsorbed is sent to the adsorption tower, the flue gas to be adsorbed and the adsorbed flue gas obtained in the adsorption step (for example, the flue gas after one adsorption) are heat exchanged in the first heat exchanger to cool the flue gas to be adsorbed for the first time; cooling in this way can reasonably utilize the cold in the flue gas after adsorption, so that the flue gas to be adsorbed can be cooled without the need for additional input of refrigerant. The flue gas to be adsorbed that has undergone the first cooling is heat exchanged with the circulating gas from the circulating gas storage tank in the second heat exchanger, so that the flue gas to be adsorbed is cooled for the second time and the circulating gas is heated; in this way, the cold in the circulating gas and the heat in the flue gas to be adsorbed are reasonably utilized, not only can the flue gas suitable for adsorption in the adsorption tower be obtained, but also the circulating gas with a significantly increased temperature is obtained, which is used for heating the adsorption tower in the heating step, which can greatly save energy consumption. The flue gas to be adsorbed that has undergone the first cooling and the flue gas after adsorption are respectively introduced into the residual pressure recovery machine, and the flue gas after adsorption expands in the residual pressure recovery machine to do work externally and achieves the cooling of the flue gas after adsorption, and at the same time, the flue gas to be adsorbed is pressurized in the residual pressure recovery machine; in this way, the residual pressure in the flue gas after adsorption is fully utilized, the flue gas after adsorption expands in the residual pressure recovery machine, and its pressure energy is converted into mechanical energy that can compress the flue gas to be adsorbed, and at the same time, the flue gas after adsorption is cooled and cooled in the process of expanding and doing work externally, and the flue gas after adsorption after cooling is obtained, which can be used for cooling the adsorption tower in the cooling step.Flue gas often contains more nitrogen and other gases that are difficult to adsorb, so there is residual pressure in the flue gas after adsorption, which is a high-pressure exhaust gas. In the prior art, the flue gas after one adsorption is directly discharged, resulting in the residual pressure in the flue gas after adsorption not being reasonably utilized. The present invention reuses the flue gas after adsorption, on the one hand, so that the residual pressure therein is utilized, and on the other hand, the flue gas after adsorption will cool down after the residual pressure recovery machine expands and does work, and it is passed into the adsorption tower again to achieve cooling of the adsorption tower and secondary adsorption of the flue gas after adsorption, thereby improving the carbon dioxide capture rate.

[0055] Specifically, before the first cooling, the flue gas to be adsorbed is pressurized in a booster. Since the flue gas to be adsorbed will have a certain temperature rise after the pressurization, it will be cooled in the subsequent first heat exchanger.

[0056] In a preferred embodiment, part of the carbon dioxide product gas is sent to the circulating gas storage tank for use as circulating gas, that is, part of the carbon dioxide product gas is produced downstream, and part is supplied as circulating gas.

[0057] In some specific embodiments, the flue gas to be adsorbed is dehydrated in a gas-water separator before being sent to the adsorption tower. In some specific embodiments, during the desorption process, the adsorption tower is evacuated by a vacuum pump.

[0058] In some embodiments, when the adsorption tower reaches the adsorption saturation, the following pressure equalization operation is performed before the temperature increase operation: the adsorption tower that has reached adsorption saturation is connected to the adsorption tower that has completed the temperature reduction operation through a pressure equalization pipeline, so that the adsorption tower that has reached adsorption saturation is depressurized and the adsorption tower that has completed the temperature reduction operation is pressurized. In some embodiments, after the pressure equalization operation is completed and before the temperature increase operation is performed, the following operation is also included: the pressure in the adsorption tower that has completed the pressure reduction operation is adjusted to normal pressure, and then the temperature increase operation is performed by introducing the heated circulating gas.

[0059] See also Figure 1 The present invention also provides a carbon dioxide capture system, which can be used to implement the carbon dioxide capture method described above. The capture system mainly includes multiple adsorption towers, a flue gas input pipeline 7, a flue gas output pipeline 8, a circulating gas storage tank 13, a circulating gas input pipeline 10, a circulating gas output pipeline 11, a carbon dioxide product gas extraction pipeline 9 and a vacuum pump 14. In some embodiments, there are more than 3 adsorption towers. Figure 1 Shown is a carbon dioxide capture system comprising adsorption towers 1-6.

[0060] Each adsorption tower is provided with an air inlet and an air outlet, and the adsorption tower is filled with an adsorbent for adsorbing carbon dioxide in the flue gas. The adsorbent can be an adsorbent commonly used in the art for adsorbing carbon dioxide, and there is no particular limitation on this.

[0061] The flue gas input pipeline 7 is used to transport the flue gas to be adsorbed (i.e., new flue gas that needs to be treated with carbon dioxide adsorption). The air inlet end of the flue gas input pipeline 7 is connected to the gas source that supplies the flue gas to be adsorbed, and the air outlet end of the flue gas input pipeline 7 is respectively connected to the air inlet of each adsorption tower to form a connecting air path; the connecting air paths formed between the air outlet end of the flue gas input pipeline 7 and each air inlet are respectively provided with switch valves, so that the opening and closing of each connecting air path can be controlled respectively, that is, the opening and closing operation of the switch valves at different positions can allow the flue gas to be adsorbed transported by the flue gas input pipeline 7 to enter the adsorption tower where the adsorption treatment of the flue gas to be adsorbed is required.

[0062] The flue gas output pipeline 8 is used to transport adsorbed flue gas, which is flue gas that has been adsorbed in the adsorption tower, for example, flue gas that has been adsorbed once in the adsorption tower. The air inlet end of the flue gas output pipeline 8 is connected to the air outlet of each adsorption tower and forms a connecting air path respectively; the connecting air paths formed between the air inlet end of the flue gas output pipeline 8 and each air outlet are respectively provided with switch valves, so that the opening and closing of each connecting air path can be controlled respectively, that is, the air inlet end of the flue gas output pipeline 8 can be connected to the air outlet of the adsorption tower that needs to output the adsorbed flue gas through the opening and closing operation of the switch valves at different positions, so that the adsorbed flue gas can be output. The outlet ends of the flue gas output pipeline 8 are respectively connected to the air inlet of each adsorption tower to form connecting air paths; the connecting air paths formed between the outlet end of the flue gas output pipeline 8 and each air inlet are respectively provided with switch valves, so that the on and off of each connecting air path can be controlled separately, that is, the outlet end of the flue gas output pipeline 8 can be connected to the air inlet of the adsorption tower that needs to introduce the adsorbed flue gas through the opening and closing operation of the switch valves at different positions.

[0063] The circulating gas storage tank 13 is used to supply and store circulating gas. The air inlet end of the circulating gas input pipeline 10 is connected to the air outlet of the circulating gas storage tank 13, and the air outlet end of the circulating gas input pipeline 10 is respectively connected to the air inlet of each adsorption tower to form a connecting air path; the connecting air paths formed between the circulating gas input pipeline 10 and each air inlet are respectively provided with a switch valve, so that the opening and closing of each connecting air path can be controlled respectively, that is, the air outlet end of the circulating gas input pipeline 10 can be connected to the air inlet of the adsorption tower that needs to be fed with circulating gas by opening and closing the switch valves at different positions.

[0064] The air inlet end of the circulating gas output pipeline 11 is connected to the air outlet of each adsorption tower and forms a connecting air path. The connecting air paths formed between the air inlet end of the circulating gas output pipeline 11 and each air outlet are provided with switch valves, so that the opening and closing of each connecting air path can be controlled respectively, that is, the air inlet end of the circulating gas output pipeline 11 can be connected to the air outlet of the adsorption tower that needs to output the circulating gas by opening and closing the switch valves at different positions. The air outlet end of the circulating gas output pipeline 11 is connected to the air inlet hole of the circulating gas storage tank 13, so that the circulating gas output by the circulating gas output pipeline 11 can be returned to the circulating gas storage tank 13.

[0065] The vacuum pump 14 is arranged on the carbon dioxide product gas extraction pipeline 9. The air inlet end of the carbon dioxide product gas extraction pipeline 9 is connected to the air outlet of each adsorption tower and forms a connecting air path. The connecting air paths formed between the air inlet end of the carbon dioxide product gas extraction pipeline 9 and each air outlet are respectively provided with switch valves, so that the opening and closing of each connecting air path can be controlled respectively, that is, the air inlet end of the carbon dioxide product gas extraction pipeline 9 can be connected to the air outlet of the adsorption tower that needs to extract carbon dioxide product gas by opening and closing the switch valves at different positions. On the flue gas input pipeline 7, along the air flow direction of the flue gas to be adsorbed conveyed by the flue gas input pipeline 7, a booster 15, a first heat exchanger 16, a residual pressure recovery machine 17 and a second heat exchanger 23 are arranged in sequence. That is, the flue gas to be adsorbed conveyed by the flue gas input pipeline 7 will first pass through the booster for the first pressurization during the conveying process, then enter the first heat exchanger 16 for the first heat exchange, pass through the residual pressure recovery machine 17 for the second pressurization, and pass through the second heat exchanger 23 for the second heat exchange. The flue gas output pipeline 8 passes through the first heat exchanger 16 and the residual pressure recovery machine 17 in sequence along the airflow direction of the adsorbed flue gas it transports; specifically, the first heat exchanger 16 is used to perform the first heat exchange between the flue gas to be adsorbed transported through the flue gas input pipeline 7 and the adsorbed flue gas transported through the flue gas output pipeline 8, so as to cool the flue gas to be adsorbed; the residual pressure recovery machine 17 is used to pressurize the flue gas to be adsorbed transported through the flue gas input pipeline 7 for the second time and to expand the adsorbed flue gas transported through the flue gas output pipeline 8 to perform work externally and be cooled. Specifically, the flue gas to be adsorbed is compressed in the residual pressure recovery machine under the action of the mechanical energy provided by the expansion work of the adsorbed flue gas and is pressurized for the second time. At the same time, the expansion work of the adsorbed flue gas is cooled to obtain the cooled adsorbed flue gas. After the circulating gas input pipeline 10 passes through the second heat exchanger 23, it is connected to each of the air inlets. The second heat exchanger 23 is used to exchange heat between the circulating gas transported by the circulating gas input pipeline 10 and the flue gas to be adsorbed, so as to achieve the re-cooling of the flue gas to be adsorbed and obtain the heated circulating gas. The first heat exchanger 16 can make use of the coldness of the flue gas after adsorption with a relatively lower temperature, and achieve the cooling of the flue gas to be adsorbed without additional coldness input. Through the second heat exchanger 23, heated circulating gas and cooled flue gas to be adsorbed can be obtained without additional heat input, on the one hand, flue gas suitable for adsorption in the adsorption tower is obtained, and on the other hand, heated circulating gas that can be used for heating the adsorption tower is obtained. Through the residual pressure recovery machine, the residual pressure of the flue gas after adsorption is fully utilized, and the flue gas after adsorption that can be used for cooling the adsorption tower is obtained, and the flue gas to be adsorbed is re-pressurized. Through the carbon dioxide capture system of the present invention, low energy consumption and high capture rate carbon dioxide adsorption capture in flue gas can be achieved.

[0066] In the present invention, each specific device or element involved can directly adopt a conventional device or element with corresponding functions in the art. For example, the residual pressure recovery machine 17 (or residual pressure recovery refrigerator) can adopt the existing residual pressure recovery device in the art that can realize the corresponding function. The flue gas after adsorption is passed into the expansion end of the residual pressure recovery machine to expand and do work externally, converting the pressure energy in the flue gas after adsorption into mechanical energy, and at the same time using the mechanical energy to compress the flue gas to be adsorbed that is passed into the compression end of the residual pressure recovery machine, so that the flue gas to be adsorbed is pressurized; the flue gas after adsorption enters the residual pressure recovery machine 17 and is greatly cooled during the expansion process to obtain cooled flue gas after adsorption; the residual pressure recovery device has been reported in many prior arts, such as but not limited to the residual pressure recovery devices reported in patent documents CN202610241U, CN202272884U, etc. By using the residual pressure recovery machine, the power demand of the supercharger required for supercharging the flue gas to be adsorbed can be greatly reduced.

[0067] Furthermore, the carbon dioxide capture system of the present invention also includes a pressure equalizing pipeline 19, which is used to connect the various adsorption towers to each other so that pressure balance can be achieved between two adsorption towers that are connected to each other, and a switching valve for controlling the opening and closing of the connecting gas path is provided on the connecting gas path formed between any two adsorption towers; when it is necessary to perform pressure equalization operation on certain adsorption towers, the opening and closing operations of the switching valves at different positions can be used to connect the adsorption towers that need to be pressure equalized to achieve pressure equalization.

[0068] Furthermore, the carbon dioxide capture system of the present invention also includes an emptying pipeline 12, the air inlet end of the emptying pipeline 12 is respectively connected with the air outlet of each adsorption tower to form a connecting air path, and the connecting air paths formed between the air inlet end of the emptying pipeline 12 and each air outlet are respectively provided with switch valves for controlling the opening and closing of the connecting air paths; thus, when it is necessary to empty or relieve the pressure on a certain adsorption tower, the air outlet of the target adsorption tower is connected to the emptying pipeline 12 by opening the switch valves at different positions.

[0069] In some embodiments, the air inlet of the circulating gas output pipeline 11 is indirectly connected to the air outlet of each adsorption tower. Figure 1, the air inlet end of the circulating gas output pipeline 11 is connected to the carbon dioxide product gas extraction pipeline 9, thereby indirectly connected to the gas outlet of each adsorption tower, the connecting point between the circulating gas output pipeline 11 and the carbon dioxide product gas extraction pipeline 9 is located downstream of the vacuum pump 14, and a switch valve 20 is provided on the pipe section of the carbon dioxide product gas extraction pipeline 9 downstream of the vacuum pump 14, and a switch valve 21 is provided on the circulating gas output pipeline 11 downstream of the vacuum pump 14. In this embodiment, the switch valve on the connecting gas path formed between the air inlet end of the carbon dioxide product gas extraction pipeline 9 and the gas outlet of each adsorption tower can be shared with the switch valve on the connecting gas path formed between the air outlet end of the circulating gas output pipeline 11 and the gas outlet of each adsorption tower, for example, the two share the switch valves 9a-9f, and do not need to be set separately. In some specific embodiments, when the vacuum pump 14 is turned on, the switch valve 20 on the pipe section of the carbon dioxide product gas extraction pipeline 9 downstream of the vacuum pump 14 is opened.

[0070] In some embodiments, see Figure 1 , the air inlet of each adsorption tower is connected to an air inlet branch pipe, such as air inlet branch pipes 1a-6a, and the air outlet of each adsorption tower is connected to an air outlet branch pipe, such as air outlet branch pipes 1b-6b. The air outlet end of the flue gas input pipeline 7 is connected to each air inlet branch pipe 1a-6a, so that a connecting air path is formed between the air outlet end of the flue gas input pipeline 7 and each air inlet, and a switch valve, such as a switch valve 7a-7f, is provided between the air outlet end of the flue gas input pipeline 7 and each air inlet branch pipe 1a-6a, so as to realize the on-off control of the connecting air paths at different positions;

[0071] The air inlet end of the smoke output pipeline 8 is respectively connected to each of the air outlet branches 1b-6b, so that a connecting air path is formed between the air inlet end of the smoke output pipeline 8 and each of the air outlets, and a switch valve, such as a switch valve 8g-8l, is respectively provided between the air inlet end of the smoke output pipeline 8 and each of the air outlet branches 1b-6b, so that the on-off control of the connecting air path at different positions can be achieved. The air outlet end of the smoke output pipeline 8 is respectively connected to each of the air inlet branches 1a-6a, so that a connecting air path is formed between the air outlet end of the smoke output pipeline 8 and each of the air inlets, and a switch valve, such as a switch valve 8a-8f, is respectively provided between the air outlet end of the smoke output pipeline 8 and each of the air inlet branches 1a-6a, so that the on-off control of the connecting air path at different positions can be achieved.

[0072] The outlet end of the circulating gas input pipeline 10 is connected to each of the air inlet branches 1a-6a, so that a connecting air path is formed between the outlet end of the circulating gas input pipeline 10 and each of the air inlets. A switch valve, such as the switch valve 10a-10f, is respectively provided between the outlet end of the circulating gas input pipeline 10 and each of the air inlet branches 1a-6a, so that the on-off control of the connecting air paths at different positions can be realized.

[0073] The air inlet end of the carbon dioxide product gas production line 9 is connected to each outlet branch pipe 1b-6b, so that a connecting air path is formed between the air inlet end of the carbon dioxide product gas production line 9 and each outlet port, and a switch valve, such as a switch valve 9a-9f, is provided between the air inlet end of the carbon dioxide product gas production line 9 and each outlet branch pipe 1b-6b, so that the on-off control of the connecting air path at different positions can be realized. Specifically, as mentioned above, when the air inlet end of the circulating gas output line 11 is connected to the carbon dioxide product gas production line 9, and thus indirectly connected to the outlet port of each adsorption tower, the air inlet end of the carbon dioxide product gas production line 9 is connected to each outlet branch pipe, which will also make the air inlet end of the circulating gas output line 11 connected to each outlet branch pipe.

[0074] One end of the pressure equalizing pipeline 19 is connected to each air inlet branch 1a-6a, and the other end is connected to each air outlet branch 1b-6b, and switch valves 19g-19l are respectively provided between the pressure equalizing pipeline 19 and each air inlet branch, and switch valves 19a-19f are respectively provided between the pressure equalizing pipeline 19 and each air outlet branch; thereby, the connection and pressure equalization between the target adsorption towers can be achieved through the opening and closing operations of the switch valves at different positions.

[0075] The air inlet end of the emptying pipeline 12 is connected to each of the air outlet branches 1b-6b, and a switch valve, such as a switch valve 12a-12f, is provided between the air inlet end of the emptying pipeline 12 and each of the air outlet branches 1b-6b, so that the emptying or pressure relief operation of the target adsorption tower can be achieved through opening and closing operations at different positions.

[0076] In some preferred embodiments, participating Figure 1 Along the airflow direction of the flue gas to be adsorbed transported by the flue gas input pipeline 7, after the second heat exchanger 23 (i.e., downstream of the second heat exchanger 23), a gas-water separator 18 is also provided on the flue gas input pipeline 7 for removing moisture from the flue gas to be adsorbed.

[0077] In some preferred embodiments, participating Figure 1 A circulating air fan 22 is also provided on the circulating gas input pipeline 10 .

[0078] The carbon dioxide capture system provided by the present invention can, in a specific application process, enable each adsorption tower to cyclically operate in different working states and cyclically operate in the adsorption link and the desorption link by opening and closing the switch valves on the connecting gas paths formed between different pipelines and different adsorption towers. This will be further explained below.

[0079] The carbon dioxide capture system provided by the present invention uses the ingenious arrangement of each pipeline, and makes the material flows transported by different pipelines ingeniously interconnect through the booster 15, the first heat exchanger 16, the second heat exchanger 23 and the residual pressure recovery machine 17 to utilize heat and pressure energy. Specifically, the first heat exchanger 16 allows the flue gas to be adsorbed transported by the flue gas input pipeline 7 to exchange heat with the adsorbed flue gas transported by the flue gas output pipeline 8, and the second heat exchanger 23 allows the flue gas to be adsorbed transported by the flue gas input pipeline 7 to continue to exchange heat with the circulating flue gas after adsorption. The circulating gas transported by the gas input pipeline 10 is heat exchanged to obtain flue gas to be adsorbed that meets the adsorption temperature requirement, and a greatly heated circulating gas is obtained, which is passed into the adsorption tower for heating and desorption; and the residual pressure carried by the adsorbed flue gas output by the flue gas output pipeline 8 can be recycled through the residual pressure recovery machine 17 to obtain pressurized flue gas to be adsorbed and cooled adsorbed flue gas, and the cooled adsorbed flue gas is passed into the adsorption tower to cool the adsorbent and realize secondary adsorption of the adsorbed flue gas. Carbon dioxide capture based on the above-mentioned carbon dioxide capture system can greatly reduce the energy consumption required for carbon dioxide capture and help improve the carbon dioxide capture efficiency.

[0080] In some preferred embodiments, the present invention implements the carbon dioxide capture method mentioned above in the present invention based on the above carbon dioxide capture system, and the method specifically comprises: through the opening and closing operation of the switch valves on the different connecting gas paths formed in each carbon dioxide capture system, each adsorption tower is cyclically operated in the adsorption stage and the desorption stage respectively: the adsorption stage comprises:

[0081] The switch valve on the connecting air path between the gas outlet end of the flue gas output pipeline 8 and the gas inlet of the adsorption tower is opened, and the cooled and adsorbed flue gas is introduced into the adsorption tower through the flue gas output pipeline 8, so as to cool the adsorption tower in the adsorption link, and at the same time, the cooled and adsorbed flue gas is subjected to secondary adsorption treatment in the adsorption tower. In the working section, the switch valve on the connecting air path formed between the gas inlet end of the exhaust pipeline 12 and the gas outlet of the adsorption tower in the cooling operation can be opened, so that the adsorbed flue gas entering the adsorption tower in the cooling operation is discharged from the gas outlet of the adsorption tower and then discharged from the exhaust pipeline 12.

[0082] After the temperature reduction operation is completed, the adsorption tower performs a pressure increase operation (eg, pressure equalization).

[0083] Then, the switch valve on the communicating air path between the air outlet end of the flue gas input pipeline 7 and the air inlet of the adsorption tower is opened. The switch valve on the communicating air path between the air inlet end of the flue gas output pipeline 8 and the air outlet of the adsorption tower is also in an open state.

[0084] The flue gas to be adsorbed transported by the flue gas input pipeline 7 first flows through the booster 15 for the first boosting, then flows through the first heat exchanger 16, and performs the first heat exchange with the adsorbed flue gas in the first heat exchanger 16, so that the flue gas to be adsorbed is cooled; then flows through the residual pressure recovery machine 17 for the second boosting, then flows through the second heat exchanger 23, and performs the second heat exchange with the circulating gas transported by the circulating gas input pipeline 10 in the second heat exchanger 23, so as to be cooled. The flue gas to be adsorbed that has undergone the first boosting, cooling, second boosting, and cooling is sent to the adsorption tower that has completed the above-mentioned boosting operation through the output end of the flue gas input pipeline 7 and the air inlet of the adsorption tower; the flue gas to be adsorbed is adsorbed in the adsorption tower until it reaches adsorption saturation, and the adsorbed flue gas is obtained through the adsorption treatment.

[0085] The adsorbed flue gas is output through the gas outlet of the adsorption tower and enters the flue gas output pipeline 8, and is output from the flue gas output pipeline 8 and flows through the first heat exchanger 16, undergoing the first heat exchange with the flue gas to be adsorbed transported by the flue gas input pipeline 7, and then flows through the residual pressure recovery machine 17, in which it expands to do work externally and obtains the cooled adsorbed flue gas; the cooled adsorbed flue gas is used to pass into the adsorption tower in the cooling operation of the adsorption link to implement the cooling operation.

[0086] After the adsorption tower in the adsorption stage reaches adsorption saturation, the switch valve on the connecting air path between the outlet end of the flue gas input pipeline 7 and the air inlet of the adsorption tower with adsorption saturation is closed, that is, the flue gas to be adsorbed is no longer introduced; and the desorption stage is carried out.

[0087] The desorption process includes:

[0088] The saturated adsorption tower is subjected to a depressurization operation;

[0089] Then, the switch valve on the connecting air path between the outlet end of the circulating gas input pipeline 10 and the air inlet of the adsorption tower with saturation of adsorption is opened, and the air inlet end of the circulating gas output pipeline 11 is kept connected with the air outlet of the adsorption tower with saturation of adsorption, and the adsorption tower with saturation of adsorption enters the heating operation; the circulating gas from the circulating gas storage tank 13 outputted through the circulating gas input pipeline 10 flows through the second heat exchanger 23 and is heat-exchanged with the flue gas to be adsorbed delivered by the flue gas input pipeline 7 to obtain heated circulating gas, and the heated circulating gas continues to be delivered through the circulating gas input pipeline 10 and enters the adsorption tower from the air inlet of the adsorption tower, so that the adsorbent in the adsorption tower is heated; the circulating gas entering the adsorption tower is outputted from the air outlet of the adsorption tower and returned to the circulating gas storage tank 13 via the circulating gas output pipeline 11. In this section, when the circulating gas output pipeline 11 is connected with the carbon dioxide product gas production pipeline 9 so that the circulating gas output pipeline 11 is indirectly connected with the gas outlets of each adsorption tower, by opening the switch valve on the connecting gas path between the gas inlet end of the carbon dioxide product gas production pipeline 9 and the gas outlet of the adsorption saturated adsorption tower, the gas inlet end of the circulating gas output pipeline 11 and the gas outlet of the adsorption saturated adsorption tower can also be maintained connected. In this case, it is necessary to close the switch valve on the pipe section of the carbon dioxide product gas production pipeline 9 located downstream of the vacuum pump 14, and open the switch valve on the circulating gas output pipeline 11 located downstream of the vacuum pump 14.

[0090] When the adsorption tower completes the heating operation, the switch valve on the connecting air path between the outlet end of the circulating gas input pipeline 10 and the air inlet of the adsorption tower that has been heated is closed, that is, no more circulating gas is introduced; the switch valve on the connecting air path between the air inlet end of the carbon dioxide product gas extraction pipeline 9 and the air outlet of the adsorption tower that has been heated is opened, and the vacuum pump 14 is turned on; after the vacuum pump 14 is evacuated, the adsorption tower that has been heated up allows the carbon dioxide adsorbed by the adsorbent to be efficiently desorbed under the conditions of high temperature and vacuum low pressure coupling; the desorbed carbon dioxide is extracted through the carbon dioxide product gas extraction pipeline 9, for example but not limited to entering the downstream carbon dioxide product gas storage tank. During the vacuuming process, it is preferred to keep the air inlet end of the circulating gas output pipeline 11 connected to the air outlet of the adsorption tower in the desorption working state, so that part of the desorbed carbon dioxide enters the circulating gas storage tank 13.

[0091] When the adsorption tower is in the stage of completing desorption, the vacuum pump 14 is turned off to stop vacuuming, and the switch valve on the connecting gas path between the air inlet end of the carbon dioxide product gas extraction pipeline 9 and the air outlet of the adsorption tower that has completed desorption is closed, and at the same time, the air inlet end of the circulating gas output pipeline 11 and the air outlet of the adsorption tower that has completed desorption are no longer connected in this section. At this time, the adsorption tower can enter the adsorption stage again and repeat the above operation; no further description is given for this.

[0092] In the specific application process, different adsorption towers may be in different working states at different times. For example, in a certain working condition, adsorption tower 6 is in the section of the adsorption link where the flue gas to be adsorbed is introduced for adsorption, adsorption tower 2 is in the cooling operation section of the adsorption link, adsorption tower 3 is in the vacuum section of the desorption link, adsorption tower 1 is in the pressure boosting operation section of the adsorption link, adsorption tower 5 is in the pressure reducing operation section of the desorption link, and adsorption tower 4 is in the heating section of the desorption link.

[0093] In some embodiments, the adsorption tower that has reached adsorption saturation is interconnected with the adsorption tower that has completed the cooling operation through the pressure equalizing pipeline 19, so that the adsorption tower that has reached adsorption saturation is depressurized (i.e., depressurization operation), and the adsorption tower that has completed the cooling operation is pressurized (i.e., boosting operation). Specifically, the pressure equalization is performed by opening and closing the switch valve on the connecting air path formed between the pressure equalizing pipeline 19 and the air inlet and air outlet of different adsorption towers, so that the adsorption tower that has reached adsorption saturation and the adsorption tower that has completed the cooling operation are interconnected.

[0094] Furthermore, in some embodiments, the pressure in the adsorption tower that has completed the depressurization operation is adjusted to normal pressure, and then the temperature-raising operation is performed by introducing the heated circulating gas; specifically, the adsorption tower that has completed the depressurization operation is connected to the evacuation pipeline 12 so that the pressure in the adsorption tower reaches normal pressure. Specifically, the pressure relief operation is performed by opening the switch valve on the connecting gas path formed between the gas inlet end of the evacuation pipeline 12 and the gas outlet of the adsorption tower that needs to enter the temperature raising step.

[0095] In some embodiments, along the airflow direction of the flue gas input pipeline 7, after the second heat exchanger 23, a gas-water separator 18 is further provided on the flue gas input pipeline 7 for removing moisture from the flue gas to be adsorbed; the flue gas to be adsorbed transported by the flue gas input pipeline 7 passes through the second heat exchanger 23 for heat exchange, then enters the gas-water separator 18 to remove moisture therein, and then enters the adsorption tower in the adsorption working state.

[0096] In some implementations, a circulating fan 22 is further provided on the circulating gas input pipeline 10; specifically, for example, the circulating gas transported by the circulating gas input pipeline 10 is pressurized by the circulating fan and then enters the second heat exchanger 23 for heat exchange.

[0097] Preferably, in the present invention, the circulating gas in the circulating gas storage tank 13 is carbon dioxide.

[0098] In the present invention, the flue gas to be adsorbed can be any flue gas containing carbon dioxide, for example, flue gas from a power plant, flue gas from a cement plant, flue gas from a steel plant, flue gas from a metallurgical plant, and the like.

[0099] In some embodiments, the flue gas to be adsorbed is pressurized by a booster and after being pressurized by a residual pressure recovery machine 17, the pressure reaches 0.1-2MPa(A). The residual pressure of the flue gas after adsorption is used to drive the compressor in the residual pressure recovery machine 17 to pressurize the flue gas to be adsorbed. Compared with the prior art that directly uses a booster to pressurize to the same pressure level, the present invention can use the residual pressure in the flue gas after adsorption to achieve the pressurization of the flue gas to be adsorbed, and compared with relying solely on the booster to pressurize, it can greatly reduce energy consumption. In some embodiments, the present invention recovers energy consumption of the flue gas after adsorption in the residual pressure recovery machine 17, which is not less than 40% of the traditional boosting energy consumption.

[0100] In some embodiments, after the flue gas to be adsorbed passes through the first heat exchanger 16 and the second heat exchanger 23 for heat exchange, the temperature is reduced to no higher than 40° C., for example, no higher than 30° C. In some embodiments, according to the temperature requirement of the flue gas to be adsorbed, other heat exchangers (for example, a heat exchanger using cooling water as a refrigerant) may be further added to obtain the target temperature, but this does not mean that the present invention must set up additional other heat exchangers.

[0101] In some embodiments, the adsorption tower in the adsorption step performs adsorption treatment of flue gas at an adsorption pressure of 0.1-2 MPa(A). In some embodiments, the adsorption tower in the desorption step performs desorption treatment at a pressure of 0-0.1 MPa(A) and a temperature of 40-150°C.

[0102] In some embodiments, the adsorbed flue gas enters the residual pressure recovery machine 17 to expand and do work, and the adsorbed flue gas with a temperature reduced to below -10°C can be obtained, for example, the adsorbed flue gas can be around -10°C, -20°C, -40°C, or -100°C.

[0103] In some embodiments, the carbon dioxide capture system of the present invention can be centrally controlled through a control system. For example, the carbon dioxide capture system of the present invention can automatically implement corresponding operations of the carbon dioxide capture method through the control of the control system, such as controlling the opening and closing operations of each switch valve.

[0104] The present invention provides the above-mentioned carbon dioxide capture method, which has the following significant advantages: through the flow arrangement of the material flow streams between the adsorption towers under different working conditions, the flue gas to be adsorbed is heat exchanged with the flue gas after adsorption, and the circulating gas is heat exchanged with the flue gas to be adsorbed for a second time, so as to obtain the flue gas to be adsorbed that meets the temperature required for adsorption, and at the same time obtain the heated circulating gas; the residual pressure carried by the flue gas after adsorption is recovered in the residual pressure recovery machine, so that the flue gas to be adsorbed is pressurized, and the adsorbed flue gas after expansion and cooling is obtained; the heated circulating gas is sent to the adsorption tower that needs to be heated and is about to enter the desorption section, so as to realize the heating of the adsorbent in the adsorption tower and facilitate the subsequent rapid and efficient desorption of high-temperature vacuum coupling; the expanded and cooled adsorbed flue gas is sent to the adsorption tower that completes the desorption link to quickly cool it down and realize the secondary adsorption of flue gas, thereby improving the carbon dioxide capture efficiency. The energy of the carbon dioxide capture method provided by the present invention is optimized, which greatly reduces the energy consumption required for carbon dioxide capture, and can significantly improve the carbon dioxide capture rate and the efficiency of the overall process operation. By utilizing the capture system and capture method of the present invention to treat flue gas, the energy consumption for carbon dioxide capture is greatly reduced, which is more than 40% lower than that of the traditional adsorption process; the CO2 capture rate is greatly improved compared with the traditional process, with the capture rate increased by more than 5%; the cooled post-adsorption flue gas is fully utilized to cool the adsorption tower, which simplifies the adsorbent cooling process of temperature-variable adsorption, can greatly reduce the cooling time, and improve the efficiency of the overall device; the carbon dioxide gas is used as the circulating gas to heat the adsorbent, which can effectively ensure the purity of the finished CO2 gas, and at the same time, through multiple circulations of the circulating gas during operation, the dynamic stability of the circulating gas concentration and the dynamic stability of the finished CO2 gas concentration can be achieved.

[0105] Anything not specifically described herein can be understood or known by those skilled in the art based on conventional technical means or common knowledge, and will not be elaborated on herein.

[0106] The present invention is further illustrated by means of specific embodiments below.

[0107] The carbon dioxide capture system involved in the following Example 1 is shown in Figure 1-2 As shown, the specific description of the carbon dioxide capture system can be referred to the above description, and will not be repeated here. Where the method operations involved in the following embodiments are not described in detail, refer to the above description.

[0108] Example 1

[0109] Flue gas from the desulfurization tower of the power plant (flue gas to be adsorbed), flue gas flow rate 12000Nm 3 / h, the flue gas temperature is 40°C; during operation, the flue gas is transported through the flue gas input pipeline 7, and flows through the booster 15, the first heat exchanger 16, the residual pressure recovery machine 17, the second heat exchanger 23 and the gas-water separator 18 in sequence; the flue gas to be adsorbed is pressurized to 200 kPa (the temperature rises to about 120°C) in the first stage of the booster 15, cooled (cooled to about 60°C) by the first heat exchanger 16, and then enters the residual pressure recovery machine 17 for the second stage of pressurization to reach 300 kPa (the temperature rises to about 140°C), then enters the second heat exchanger 23 for heat exchange (cooled to about 40°C), and then enters the gas-water separator 18 for dehumidification, and the resulting flue gas has a pressure of 295 kPa and a temperature of 40°C.

[0110] In a certain working condition, the adsorption tower 1 completes the desorption process, turns off the vacuum pump 14, and closes the switch valves 20, 21, and 9a. The switch valves 8a and 12a are opened, and the adsorption tower 1 performs a cooling operation. The cooled adsorbed flue gas (temperature -10°C) transported by the flue gas output pipeline 8 enters the adsorption tower 1 to cool the adsorbent in the adsorption tower 1, and at the same time, the adsorbed flue gas undergoes secondary adsorption in the adsorption tower 1; the adsorbed flue gas entering the adsorption tower 1 is discharged from the gas outlet of the adsorption tower 1 into the exhaust pipeline 12. In a certain working condition, the cooled adsorbed flue gas entering the adsorption tower 1 is the cooled adsorbed flue gas obtained after the adsorbed flue gas discharged from the gas outlet of the adsorption tower 5 passes through the first heat exchanger 16 and the residual pressure recovery machine 17.

[0111] When the adsorbent in the adsorption tower 1 is cooled to 40° C., the cooling operation of the adsorption tower 1 is completed and the switch valves 8a and 12a are closed.

[0112] Then, the adsorption tower 1 is pressurized. Under certain working conditions, the adsorption tower 5 reaches adsorption saturation. The adsorption saturated adsorption tower 5 is connected with the adsorption tower 1 that has completed the cooling operation (open the switch valves 19a, 19g, 19e, and 19k), so that the adsorption tower 1 can be pressurized and the adsorption tower 5 can be depressurized. After the pressure boosting operation is completed, the switch valves 19a, 19g, 19e, and 19k are then closed.

[0113] Afterwards, the switch valve 7a between the outlet end of the flue gas input pipeline 7 and the inlet branch pipe 1a connected to the air inlet of the adsorption tower 1 is opened, and the switch valve 8g between the inlet end of the flue gas output pipeline 8 and the outlet branch pipe 1b connected to the air outlet of the adsorption tower 1 is opened; the flue gas to be adsorbed with a pressure of 295 kPa and a temperature of 40°C enters the adsorption tower 1 through the flue gas input pipeline 7 for adsorption treatment, and the carbon dioxide therein is adsorbed by the adsorbent to obtain adsorbed flue gas; the adsorbed flue gas is output from the air outlet of the adsorption tower 1 and enters the flue gas output pipeline 8. The adsorbed flue gas is transported through the flue gas output pipeline 8 and flows through the first heat exchanger 16 to exchange heat with the flue gas to be adsorbed transported by the flue gas input pipeline 7, and then flows through the residual pressure recovery machine 17, in which the adsorbed flue gas expands to do work and cools, to obtain the cooled adsorbed flue gas (temperature is -10°C). In a certain working condition, the adsorption tower 3 is in cooling operation, and the cooled adsorption flue gas obtained from the adsorption tower 1 in the above-mentioned residual pressure recovery machine 17 is sent to the adsorption tower 3 to quickly cool the adsorbent in the adsorption tower 3.

[0114] When the adsorbent in the adsorption tower 1 reaches adsorption saturation, close the switch valve 7a and the switch valve 8g, and stop passing the flue gas to be adsorbed into the adsorption tower 1. The adsorption tower 1 enters the desorption stage. In a certain working condition, the cooling of the adsorption tower 3 is completed; by opening the switch valves 19a, 19g, 19c, and 19i, the adsorption tower 1 and the adsorption tower 3 are connected through the pressure equalizing pipeline 19, the adsorption tower 1 can be depressurized (i.e., the pressure reduction operation), and the adsorption tower 3 can be pressurized (i.e., the pressure boosting operation), and the pressure of the adsorption tower 1 is reduced from 295kPa to 160KPa. Then close the switch valves 19a, 19g, 19c, and 19i, open the switch valve 12a, so that the air outlet of the adsorption tower 1 is connected to the exhaust pipeline, and the pressure of the adsorption tower 1 drops to normal pressure. Close the switch valve 12a.

[0115] Then open the switch valves 9a and 10a. If the switch valve 21 is in the closed state at this time, open the switch valve 21 at the same time, and the adsorption tower 1 enters the heating operation; the circulating gas in the circulating gas storage tank 13 is transported by the circulating gas input pipeline 10, and after being pressurized by the circulating fan 22, it enters the second heat exchanger 23 to exchange heat with the flue gas to be adsorbed transported by the flue gas input pipeline 7 to obtain the heated circulating gas, and the heated circulating gas (temperature is 120°C) enters the adsorption tower 1 to heat the adsorbent in the adsorption tower 1; the circulating gas is discharged from the outlet of the adsorption tower 1 and enters the circulating gas output pipeline 11, and returns to the circulating gas storage tank 13.

[0116] When the adsorbent in the adsorption tower 1 is heated to 80°C, the heating operation of the adsorption tower 1 is completed, the switch valve 10a is closed, and the circulating gas is stopped. The vacuum pump 14 and the switch valve 20 are turned on to evacuate the adsorption tower 1, and the carbon dioxide adsorbed by the adsorbent is desorbed. The concentration of carbon dioxide in the desorbed gas is 95.5%, part of which is extracted through the carbon dioxide product gas extraction pipeline 9 and sent to the downstream finished CO2 unit, and part of which is sent to the circulating gas storage tank 13 through the circulating gas output pipeline 11.

[0117] Referring to the above process, the adsorption tower 1 cyclically operates in the adsorption stage and the desorption stage; the description of the working process of the other adsorption towers can refer to the above description of the adsorption tower 1, which will not be repeated one by one.

[0118] The carbon dioxide in the flue gas was captured according to Example 1, and the test results are shown in Table 1 below.

[0119] Comparative Example 1:

[0120] The carbon dioxide capture system used in this comparative example is shown in Figure 2 The carbon dioxide capture system is a conventional carbon dioxide capture system in the art. All the operations not specifically described below are carried out in accordance with conventional operations in the art, which are well known to those skilled in the art based on their conventional technical knowledge, and will not be described in detail.

[0121] Flue gas from the desulfurization tower of the power plant, flue gas flow rate 12000Nm 3 / h, the flue gas temperature is 40°C, pressurized to 300 kPa by compressor 505, cooled by heat exchanger 506, dehumidified by gas-water separator 507, and the obtained flue gas to be adsorbed (pressure is 295 kPa, temperature is 40°C) enters the adsorption tower 101 of the primary adsorption unit 100 for adsorption treatment to obtain adsorbed flue gas. The adsorbed flue gas in the adsorption tower 101 is discharged through the exhaust pipeline 504.

[0122] When the carbon dioxide in the adsorbent of the adsorption tower 101 reaches adsorption saturation, stop passing the flue gas to be adsorbed into the adsorption tower 101, connect the adsorption tower 101 and the adsorption tower 102 to each other through the pressure equalization pipeline 502, perform pressure equalization operation, reduce the pressure of the adsorption tower 101 from 295kPa to 160KPa (the corresponding adsorption tower 102 is pressurized), and then connect the exhaust pipeline 504 to the adsorption tower 101 to make the pressure in the adsorption tower 101 reach normal pressure, that is, reverse operation; turn on the vacuum pump 300 to decompress and desorb the adsorption tower 101, and the concentration of carbon dioxide in the desorbed gas is 43.2%.

[0123] The gas desorbed from the adsorption tower 101 (ie, desorbed gas) is output through the pipeline 503, pressurized to 250 KPa by the compressor 400, and enters the adsorption tower 203 of the secondary adsorption unit 200 for secondary adsorption, and CO2 in the desorbed gas is adsorbed.

[0124] Each adsorption tower in the primary adsorption unit 100 and the secondary adsorption unit 200 undergoes: adsorption, pressure reduction (average pressure reduction), inversion, desorption, and pressure increase (average pressure increase). The concentration of the dioxide tower (product gas) in the gas desorbed from the adsorption tower of the secondary adsorption unit is 96.2%. The working state of each adsorption tower is switched by opening and closing the switch valves on different pipelines connected to each adsorption tower.

[0125] Carbon dioxide in flue gas was captured according to Comparative Example 1, and the test results are shown in Table 1 below.

[0126] Table 1

[0127]

[0128] Note: In Table 1, the carbon dioxide capture rate refers to the mass percentage of captured carbon dioxide in the flue gas to be adsorbed.

[0129] In summary, it can be seen that the carbon dioxide capture system of the present invention is used to treat flue gas according to the carbon dioxide capture method of the present invention. Compared with the traditional carbon dioxide capture system, it does not require a multi-stage adsorption unit, and the system structure and process flow are simpler, and can greatly reduce energy consumption and improve the carbon dioxide capture rate, while taking into account a higher product gas concentration.

[0130] 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 thereto. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from this are still within the protection scope of the present invention.

Claims

1. A method for capturing carbon dioxide with low energy consumption and high capture rate, characterized in that: Performing carbon dioxide adsorption treatment on the flue gas to be adsorbed in a group of adsorption towers, wherein the group of adsorption towers includes a plurality of adsorption towers, and each of the adsorption towers undergoes an adsorption step and a desorption step respectively; The adsorption process comprises: introducing the cooled adsorbed flue gas into the adsorption tower that has completed the desorption process to perform a cooling operation of the adsorption tower in the adsorption process, and subjecting the cooled adsorbed flue gas to a secondary adsorption treatment in the adsorption tower; performing a pressurization operation on the adsorption tower after the cooling operation, and then introducing the adsorbed flue gas that has undergone a first pressurization, a first heat exchange with the adsorbed flue gas to be cooled, a second pressurization in the residual pressure recovery machine due to the mechanical energy provided by the expansion of the adsorbed flue gas, and a second heat exchange with the circulating gas to be cooled, into the adsorption tower that has completed the pressurization operation to perform an adsorption treatment until adsorption saturation is reached, and the adsorbed flue gas is obtained through adsorption treatment; After the adsorption tower of the adsorption stage is saturated with adsorption, the desorption stage is performed; the desorption stage comprises: depressurizing the saturated adsorption tower, then introducing heated circulating gas to increase the temperature, and then vacuuming to desorb carbon dioxide to obtain carbon dioxide product gas; Among them, the cooled adsorbed flue gas used in the adsorption link is the adsorbed flue gas that is cooled after the adsorbed flue gas expands and does work in the residual pressure recovery machine; the heated circulating gas used in the desorption link is the circulating gas that is heated by the second heat exchange.

2. The method for capturing carbon dioxide according to claim 1, characterized in that: Part of the carbon dioxide product gas is used as the circulating gas.

3. The method for capturing carbon dioxide according to claim 2, characterized in that: Part of the carbon dioxide product gas is sent to a circulating gas storage tank to supply the circulating gas.

4. The method for capturing carbon dioxide according to claim 1, characterized in that: The flue gas to be adsorbed is dehydrated in a gas-water separator before being introduced into the adsorption tower.

5. The method according to any one of claims 1 to 4, characterized in that: The adsorption tower that has reached the adsorption saturation is connected to the adsorption tower that has completed the cooling operation through a pressure equalizing pipeline, so that the adsorption tower that has reached the adsorption saturation can be depressurized and the adsorption tower that has completed the cooling operation can be pressurized, thereby realizing the pressure increasing operation and the pressure reducing operation.

6. The method according to any one of claims 1 to 4, characterized in that: The pressure in the adsorption tower after the pressure reduction operation is adjusted to normal pressure, and then the operation of introducing the heated circulating gas to increase the temperature is performed.

7. A low energy consumption, high capture rate carbon dioxide capture system, characterized in that: include: A plurality of adsorption towers each having an air inlet and an air outlet, a flue gas input pipeline (7) for conveying flue gas to be adsorbed, a flue gas output pipeline (8) for conveying flue gas after adsorption, a circulating gas storage tank (13) for supplying and storing circulating gas, a circulating gas input pipeline (10), a circulating gas output pipeline (11), and a carbon dioxide product gas extraction pipeline (9) connected to a vacuum pump (14); wherein: The air inlet end of the flue gas input pipeline (7) is connected to the gas source of the flue gas to be adsorbed, and the air outlet end of the flue gas input pipeline (7) is respectively connected to the air inlet of each adsorption tower to form a connecting air path; The air inlet end of the flue gas output pipeline (8) is respectively connected to the air outlet of each adsorption tower to form a connecting air path, and the air outlet end of the flue gas output pipeline (8) is respectively connected to the air inlet of each adsorption tower to form a connecting air path; The air inlet end of the circulating gas input pipeline (10) is connected to the air outlet hole of the circulating gas storage tank (13), and the air outlet end of the circulating gas input pipeline (10) is respectively connected to the air inlet of each adsorption tower to form a connecting air path; The air inlet end of the circulating gas output pipeline (11) is respectively connected to the air outlet of each adsorption tower to form a connecting air path, and the air outlet end of the circulating gas output pipeline (11) is connected to the air inlet hole of the circulating gas storage tank (13); The gas inlet end of the carbon dioxide product gas extraction pipeline (9) is respectively connected to the gas outlet of each adsorption tower to form a connecting gas path; A switch valve for controlling the on / off of the communicating gas path is provided on each communicating gas path; The flue gas input pipeline (7) is provided with a booster (15), a first heat exchanger (16), a residual pressure recovery machine (17) and a second heat exchanger (23) in sequence along the airflow direction; the flue gas output pipeline (8) passes through the first heat exchanger (16) and the residual pressure recovery machine (17) in sequence along the airflow direction and then is connected to each of the air inlets respectively; the booster (15) is used for the first boosting of the flue gas to be adsorbed; the first heat exchanger (16) is used for the first heat exchange between the flue gas to be adsorbed and the adsorbed flue gas to achieve the first heat exchange between the flue gas to be adsorbed and the adsorbed flue gas; The flue gas is cooled, the residual pressure recovery machine (17) is used to obtain the cooled adsorbed flue gas cooled by expansion work and the flue gas to be adsorbed which is compressed by the mechanical energy provided by the expansion work of the adsorbed flue gas to achieve a second pressurization; the circulating gas input pipeline (10) is connected to each of the air inlets after passing through the second heat exchanger (23), and the second heat exchanger (23) is used to make the circulating gas transported by the circulating gas input pipeline (10) and the flue gas to be adsorbed perform a second heat exchange to achieve cooling of the flue gas to be adsorbed and obtain heated circulating gas.

8. The carbon dioxide capture system according to claim 7, characterized in that It also includes a pressure equalizing pipeline (19) for interconnecting the adsorption towers to balance the pressure between two interconnected adsorption towers, and a switch valve for controlling the opening and closing of the connecting gas path is provided on the connecting gas path formed between any two adsorption towers.

9. The carbon dioxide capture system according to claim 7, characterized in that It also comprises an exhaust pipeline (12), the air inlet end of the exhaust pipeline (12) is respectively connected to the air outlet of each of the adsorption towers to form a connecting air path, and a switch valve for controlling the opening and closing of the connecting air path is provided on the connecting air path.

10. The carbon dioxide capture system according to any one of claims 7 to 9, characterized in that: The circulating gas output pipeline (11) is connected to the carbon dioxide product gas production pipeline (9) so that the circulating gas output pipeline (11) is indirectly connected to the gas outlet of each adsorption tower. The connecting point between the circulating gas output pipeline (11) and the carbon dioxide product gas production pipeline (9) is located downstream of the vacuum pump (14). Switch valves are respectively provided on the pipe section of the carbon dioxide product gas production pipeline (9) located downstream of the vacuum pump (14) and on the circulating gas output pipeline (11) located downstream of the vacuum pump (14).

11. The carbon dioxide capture system according to claim 10, characterized in that The air inlet of each of the adsorption towers is connected to an air inlet branch pipe, and the air outlet of each of the adsorption towers is connected to an air outlet branch pipe; The gas outlet end of the smoke input pipeline (7) is respectively connected to each of the gas inlet branch pipes, and a switch valve is respectively provided between the gas outlet end of the smoke input pipeline (7) and each of the gas inlet branch pipes; The air inlet end of the smoke output pipeline (8) is respectively connected to each of the air outlet branch pipes, and a switch valve is respectively provided between the air inlet end of the smoke output pipeline (8) and each of the air outlet branch pipes; the air outlet end of the smoke output pipeline (8) is respectively connected to each of the air inlet branch pipes, and a switch valve is respectively provided between the air outlet end of the smoke output pipeline (8) and each of the air inlet branch pipes; The outlet end of the circulating gas input pipeline (10) is respectively connected to each of the inlet branch pipes, and a switch valve is respectively provided between the outlet end of the circulating gas input pipeline (10) and each of the inlet branch pipes; The air inlet end of the carbon dioxide product gas production pipeline (9) is respectively connected to each of the air outlet branch pipes, and a switch valve is respectively provided between the air inlet end of the carbon dioxide product gas production pipeline (9) and each of the air outlet branch pipes.

12. The carbon dioxide capture system according to claim 11, characterized in that It also includes a pressure equalizing pipeline (19), one end of which is connected to each of the air inlet branches, and the other end of which is connected to each of the air outlet branches, and a switch valve is provided between the pressure equalizing pipeline (19) and each of the air inlet branches and between the pressure equalizing pipeline (19) and each of the air outlet branches; It also comprises an exhaust pipeline (12), the air inlet end of the exhaust pipeline (12) being respectively connected to each of the air outlet branches, and a switch valve is respectively provided between the air inlet end of the exhaust pipeline (12) and each of the air outlet branches.

13. The carbon dioxide capture system according to any one of claims 7 to 9, characterized in that: Along the airflow direction of the flue gas input pipeline (7), downstream of the second heat exchanger (23), a gas-water separator (18) is also provided on the flue gas input pipeline (7) for removing moisture from the flue gas to be adsorbed; And / or, a circulating air fan (22) is also provided on the circulating gas input pipeline (10).

14. The carbon dioxide capture system according to any one of claims 7 to 13 is used to implement the carbon dioxide capture method according to any one of claims 1 to 6.

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