Carbon dioxide capturing apparatus and process with improved energy efficiency

Abstract

The present invention relates to a carbon dioxide capturing apparatus and process, wherein a carbon dioxide recovery separation membrane process is performed by utilizing the cold heat, as it is, from a carbon dioxide liquefaction process through a separation tower, so that the energy consumed can be remarkably reduced and the carbon dioxide recovery rate can be notably improved through a recirculation separation membrane.

Description

Energy-efficient carbon dioxide capture devices and processes

[0001] It relates to a carbon dioxide capture device and process with improved energy efficiency.

[0002] Recently, with environmental issues such as global warming and climate change caused by greenhouse gases emerging, extensive research is being conducted on carbon dioxide capture technologies to reduce carbon dioxide emissions, a key greenhouse gas. Carbon dioxide capture technologies can be broadly categorized into post-combustion, pre-combustion, and oxyfuel combustion. Post-combustion CO2 capture technologies are further categorized into chemical absorption methods using amine- or ammonia-based absorbents, dry absorption methods using solid absorbents instead of conventional absorbent solutions, and membrane separation methods using membranes.

[0003] Among carbon dioxide capture technologies, membrane separation using membranes offers the advantage of being an environmentally friendly process. To increase carbon dioxide concentration and enhance storage and utilization, a separation tower has been introduced to obtain liquefied carbon dioxide. However, conventional technologies require additional energy consumption, as carbon dioxide is recovered from the low-temperature gas obtained during the liquefaction process by heating or cooling the gas before being supplied to the membrane.

[0004] Therefore, the inventors of the present invention have conducted repeated research to solve the above problems and have discovered that by allowing the low-temperature gas obtained in the liquefaction process to pass through the separation membrane in its low-temperature state and introducing a recirculating separation membrane at the same time, the carbon dioxide recovery rate can be increased and the carbon dioxide separation efficiency can be increased without introducing an additional process, thereby reducing energy consumption, thereby completing the present invention.

[0005] [Prior Art Literature]

[0006] [Patent Document]

[0007] (Patent Document 1) Patent Document 1. Korean Patent Publication No. 10-2021-0104469

[0008] The present invention has been made to solve the above-mentioned problems, and the purpose of the present invention is to provide a carbon dioxide capture device and process including a carbon dioxide capture membrane, a recirculating membrane, a separation tower, and a carbon dioxide recovery membrane, and a carbon dioxide recovery process using the carbon dioxide recovery membrane, which can significantly reduce energy consumption and significantly improve separation efficiency by utilizing the cold heat of the carbon dioxide liquefaction process through the separation tower.

[0009] One aspect of the present invention comprises a first capture membrane for receiving a first capture membrane feed gas containing a carbon dioxide-containing gas mixture and separating the first capture membrane permeate gas and the first capture membrane residual gas; a second capture membrane for receiving a second capture membrane feed gas containing the first capture membrane permeate gas and separating the second capture membrane permeate gas and the second capture membrane residual gas; a recirculation membrane for receiving the second capture membrane residual gas and separating the second capture membrane permeate gas into a recirculation membrane permeate gas and a recirculation membrane residual gas, and circulating the recirculation membrane permeate gas to the second capture membrane; a first heat exchanger for cooling the first heat exchanger feed gas containing the second capture membrane permeate gas; a carbon dioxide purification separation tower for receiving the gas cooled by the first heat exchanger, an upper portion for obtaining a carbon dioxide-containing gas, and a lower portion for obtaining a high-purity carbon dioxide liquid; And a carbon dioxide capture device including a first recovery membrane that receives carbon dioxide-containing gas obtained from the upper portion and separates it into a first recovery membrane permeation gas and a first recovery membrane residual gas.

[0010] Another aspect of the present invention comprises the steps of: supplying a first capture membrane feed gas containing a carbon dioxide-containing gas mixture to a first capture membrane and separating the first capture membrane permeate gas and the first capture membrane residual gas; supplying a second capture membrane feed gas containing the first capture membrane permeate gas to a second capture membrane and separating the second capture membrane permeate gas and the second capture membrane residual gas; supplying the second capture membrane residual gas to a recirculation membrane and separating the second capture membrane permeate gas into a recirculation membrane permeate gas and a recirculation membrane residual gas, and circulating the recirculation membrane permeate gas to the second capture membrane; cooling a first heat exchanger feed gas containing the second capture membrane permeate gas with a first heat exchanger; supplying the gas cooled in the first heat exchanger to a separation tower and obtaining a carbon dioxide-containing gas from an upper portion of the separation tower through a separation and purification process, and recovering a high-purity carbon dioxide liquid from a lower portion; And the present invention provides a carbon dioxide capture process including a step of supplying the carbon dioxide-containing gas obtained from the upper portion to a first recovery separation membrane and separating it into a first recovery separation membrane permeation gas and a first recovery separation membrane residual gas.

[0011] The carbon dioxide capture process and device of the present invention reduces the amount of carbon dioxide emitted by recovering the gas obtained from the separation tower through a separation membrane.

[0012] In addition, the present invention can improve the carbon dioxide recovery efficiency without an additional heat exchange system by recovering carbon dioxide in the gas obtained from the upper part of the separation tower by utilizing the low temperature state formed in the separation tower (liquefaction process).

[0013] In addition, the present invention can reduce the amount of carbon dioxide emitted by recycling the gas flow within the carbon dioxide capture process and device, and increase the separation efficiency by improving the carbon dioxide partial pressure.

[0014] Figure 1 illustrates a carbon dioxide capture process diagram according to one embodiment of the present invention.

[0015] FIG. 2 illustrates a carbon dioxide capture process diagram including a third capture membrane according to another embodiment of the present invention.

[0016] Hereinafter, the present invention will be described in more detail with reference to the attached drawings and examples.

[0017] Figure 1 illustrates a carbon dioxide capture process diagram according to one embodiment of the present invention.

[0018] FIG. 2 illustrates a carbon dioxide capture process diagram including a third capture membrane according to another embodiment of the present invention.

[0019] Hereinafter, the carbon dioxide capture device and process of the present invention will be described in more detail with reference to the above-described Figures 1 and 2.

[0020] One aspect of the present invention comprises a first capture membrane for receiving a first capture membrane feed gas containing a carbon dioxide-containing gas mixture and separating the first capture membrane permeate gas and the first capture membrane residual gas; a second capture membrane for receiving a second capture membrane feed gas containing the first capture membrane permeate gas and separating the second capture membrane permeate gas and the second capture membrane residual gas; a recirculation membrane for receiving the second capture membrane residual gas and separating the second capture membrane permeate gas into a recirculation membrane permeate gas and a recirculation membrane residual gas, and circulating the recirculation membrane permeate gas to the second capture membrane; a first heat exchanger for cooling the first heat exchanger feed gas containing the second capture membrane permeate gas; a carbon dioxide purification separation tower for receiving the gas cooled by the first heat exchanger, an upper portion for obtaining a carbon dioxide-containing gas, and a lower portion for obtaining a high-purity carbon dioxide liquid; And a carbon dioxide capture device including a first recovery membrane that receives carbon dioxide-containing gas obtained from the upper portion and separates it into a first recovery membrane permeation gas and a first recovery membrane residual gas.

[0021] The present invention relates to a device and process for capturing carbon dioxide from a carbon dioxide-containing gas mixture. The type of the carbon dioxide-containing gas mixture is not particularly limited, but in a preferred embodiment, it may refer to exhaust gas.

[0022] Flue gas (exhaust gas) refers to gas emitted from power plants, steel mills, chemical plants, etc., and is mainly generated by the combustion reaction of fossil fuels (hydrocarbons) and basically contains carbon dioxide and moisture. When oxygen-containing gas or air is used as an oxidizer, it may further contain nitrogen and unused oxygen. In addition, gas components resulting from impurities in the raw materials of the combustion process, such as hydrogen sulfide, sulfur oxides, nitrogen oxides, hydrochloric acid, and mercury, may also be contained. However, such impurities may be present in trace amounts or may not be substantially contained in some cases.

[0023] The carbon dioxide capture device of the present invention may further include a first rotating device (102) that compresses the first capture membrane supply gas (204) before supplying it to the first capture membrane (104).

[0024] The above first rotary device (102) may be at least one selected from the group consisting of a compressor, a vacuum pump, and a blower, and a compressor is most preferable in that it implements sufficient pressure for separation efficiency.

[0025] The first rotary machine (102) compresses the first rotary machine supply gas (202) containing a carbon dioxide-containing gas mixture (201).

[0026] When the above carbon dioxide-containing gas mixture (201) is exhaust gas, it is generally at a high temperature, so the first rotary machine (102) may further include a pre-heat exchanger (101) that lowers the temperature of the exhaust gas to room temperature, more specifically, 15 to 50°C.

[0027] The first rotary device (102) compresses the first rotary device supply gas (202) having a normal pressure in the range of about 1.0 to 1.3 bar to a pressure of 2 to 5 bar, preferably 2.0 to 3.5 bar, in order to implement a pressure ratio for performing a separation process in the first capture membrane (104) module described later. If the pressure is compressed below the lower limit, it may be difficult to expect an increase in separation efficiency in the capture membrane, and conversely, if it exceeds the upper limit, energy consumption increases rapidly, which is not preferable.

[0028] If the gas flowing in the liquefaction process contains moisture, the water may freeze during the liquefaction process, which may cause damage and malfunction of devices such as measuring instruments. Therefore, the carbon dioxide capture device of the present invention may further include a dryer for removing moisture from the carbon dioxide-containing gas mixture or the membrane-permeated gas, and the dryer may remove moisture so that the moisture content of the gas flow is about 50 ppm or less, about 30 ppm or less, more specifically about 10 ppm or less, and even more specifically, substantially no moisture is contained. At this time, one or more dryers may be present in the carbon dioxide capture device of the present invention, and preferably, the dryer may remove moisture from any one or more of the gas (203) at the rear end of the first rotating device or the gas (219) at the rear end of the second rotating device described below.

[0029] The above first capture separation membrane (104) receives the first capture separation membrane supply gas (204) and separates it into the first capture separation membrane permeation gas (205) and the first capture separation membrane residual gas (206).

[0030] The first capture membrane supply gas (204) includes a carbon dioxide-containing gas mixture (201) or a gas (203) from the rear end of the first rotary device. In addition, the first capture membrane supply gas (204) may further include at least one of a first recovery membrane permeation gas (225) and a second recovery membrane permeation gas (227), and in this case, the recovery rate of carbon dioxide can be increased and the separation efficiency of carbon dioxide can be further improved.

[0031] The above first capture membrane supply gas (204) is supplied to the first capture membrane (104) and separated into a first capture membrane permeation gas (205) rich in carbon dioxide and a first capture membrane residual gas (206) poor in carbon dioxide.

[0032] The gas separation process through the above membrane may be carried out through a dissolution-diffusion mechanism. At this time, the separation efficiency varies depending on the carbon dioxide permeability (GPU) and carbon dioxide selectivity (e.g., CO2 / N2) of the first capture membrane (104).

[0033] The above first capture separation membrane (104) may be made of one or more materials of polysulfone (PSF) and polyimide (PI).

[0034] Any one or more of the separation processes using the first capture membrane (104), the second capture membrane (106) and the third capture membrane (109) described below may be performed at room temperature, and considering the characteristics of the polysulfone (PSF) or polyimide (PI) membrane material, it is preferable if it can be performed at a low temperature.

[0035] By further installing a vacuum pump in the first capture membrane permeation gas (205) discharge unit, the second capture membrane permeation gas (210) discharge unit to be described later, and the third capture membrane permeation gas (215) discharge unit, the pressure ratio before and after the separation membrane can be increased, thereby improving the separation efficiency.

[0036] The above first capture membrane residual gas (206) may be discharged to the outside as a nitrogen-dominant gas with a low carbon dioxide content.

[0037] The second capture membrane (106) receives the second capture membrane supply gas (209) and separates it into a second capture membrane permeation gas (210) that permeates the second capture membrane and a second capture membrane residual gas (211) that does not permeate the second capture membrane.

[0038] The second capture membrane supply gas (209) includes the first capture membrane permeation gas (205) and the recirculation membrane permeation gas (212) described below. In addition, the second capture membrane supply gas (209) may further include at least one of the first recovery membrane permeation gas (225) and the second recovery membrane permeation gas (227).

[0039] The second capture membrane permeation gas (210) may have a higher carbon dioxide concentration than the first capture membrane permeation gas (205), and the second capture membrane residual gas (211) may have a relatively lower carbon dioxide concentration.

[0040] The carbon dioxide capture device of the present invention can increase the separation efficiency through the second capture membrane (106) by additionally installing a vacuum pump (108) in the discharge section of the second capture membrane permeation gas (210) to discharge the second capture membrane permeation gas (210) at atmospheric pressure or a pressure close thereto, thereby increasing the pressure ratio before and after the separation membrane.

[0041] The above second capture membrane (106) may be made of one or more materials of polysulfone (PSF) or polyimide (PI).

[0042] The carbon dioxide capture device of the present invention may further include a third capture separation membrane (109) depending on the carbon dioxide concentration in the exhaust gas. When the carbon dioxide concentration in the exhaust gas is low, it is preferable to additionally introduce the third capture separation membrane (109) to increase the carbon dioxide recovery rate.

[0043] The third capture separation membrane (109) receives the third capture separation membrane supply gas (214) and separates it into a third capture separation membrane permeation gas (215) that permeates the third capture separation membrane (109) and a third capture separation membrane residual gas (216) that does not permeate the third capture separation membrane (109).

[0044] The third capture membrane supply gas (214) includes the second capture membrane permeation gas (210) and may additionally include at least one of the first recovery membrane permeation gas (225) and the second recovery membrane permeation gas (227).

[0045] A vacuum pump (110) can be additionally installed in the discharge section of the third capture membrane permeation gas (215).

[0046] The third capture membrane permeation gas (215) is characterized by an increased carbon dioxide concentration compared to the second capture membrane permeation gas (210).

[0047] The third capture membrane residual gas (216) that cannot pass through the third capture membrane (109) can be discharged to the outside or circulated to the second capture membrane (106), and circulating to the second capture membrane (106) is more preferable because it can increase the carbon dioxide recovery rate.

[0048] The above-mentioned recirculating separation membrane (107) can receive the second capture separation membrane residual gas (211), separate it into a recirculating separation membrane permeation gas (212) and a recirculating separation membrane residual gas (213), and supply the recirculating separation membrane permeation gas (212) to the second capture separation membrane (106).

[0049] The present invention introduces the recirculating separation membrane (107) so that carbon dioxide that would otherwise be lost when the second capture separation membrane residual gas (211) is discharged to the outside is recycled, thereby increasing the overall recovery rate. In addition, the carbon dioxide is recycled to the second capture separation membrane (106) rather than the first rotary device (102), thereby achieving an excellent carbon dioxide recovery rate without increasing the flow rate of the rotary device and thus increasing power consumption.

[0050] The above-mentioned recirculating membrane permeation gas (212) is characterized by an increase in the carbon dioxide concentration among the second capture membrane residual gas (211) that permeates the recirculating membrane (107).

[0051] The first to third capture membranes and recirculation membranes may be the same or different from each other, and may each be independently made of one or more materials selected from polysulfone (PSF) and polyimide (PI).

[0052] The carbon dioxide capture device of the present invention may further include a second rotating device (111) that compresses the first heat exchanger supply gas (221) before supplying it to the first heat exchanger (113) in order to increase the carbon dioxide separation efficiency.

[0053] The second rotary device (111) may be at least one selected from the group consisting of a compressor, a vacuum pump, and a blower, and a compressor is most preferable in that it provides sufficient pressure for separation efficiency.

[0054] The second rotary device (111) compresses the second rotary device supply gas (218) to create the pressure required for the liquefaction process described below. At this time, the pressure of the compressed gas may be 18 to 50 bar, preferably 21 to 31 bar. If the pressure of the compressed gas is below the lower limit, liquefaction may not occur properly, and conversely, if it exceeds the upper limit, energy consumption may increase significantly.

[0055] The second rotary device supply gas (218) is the first heat exchanger supply gas (221), and more specifically, includes the second capture membrane permeation gas (210) or the third capture membrane permeation gas (215). In addition, depending on the number of recovery membrane processes to be described later, one or more of the first recovery membrane permeation gas (225) and the second recovery membrane permeation gas (227) may be further included.

[0056] As shown in the above drawing 2, when the present invention further includes a third capture separation membrane (109), the second rotary machine supply gas (218) may include the third capture separation membrane permeation gas (215) among the second capture separation membrane permeation gas (210).

[0057] The first heat exchanger (113) receives the first heat exchanger supply gas (221) and cools it to a temperature suitable for producing carbon dioxide, specifically, a temperature of -35 to -18°C, in the separation tower (114) described later.

[0058] The first heat exchanger supply gas (221) may include the second capture membrane permeation gas (210), the third capture membrane permeation gas (215), or the second rotary device rear gas (219).

[0059] The above carbon dioxide purification separation tower includes a separation tower (114) that receives the cooled gas from the first heat exchanger, an upper portion where carbon dioxide-containing gas (224) is obtained, and a lower portion where high-purity carbon dioxide liquid (223) is obtained.

[0060] The number of stages or trays of the above separation tower (114) may be formed from 6 to 10, and may be changed in consideration of the carbon dioxide purity and other process conditions.

[0061] The separation tower supply gas (222) cooled by the first heat exchanger (113) is supplied to the separation tower (114), and through a separation and purification process, high-purity carbon dioxide liquid (223) is obtained from the lower part, and carbon dioxide-containing gas (224) is obtained from the upper part.

[0062] The carbon dioxide molar concentration of the high-purity carbon dioxide liquid (223) obtained from the lower portion above may be 99% or more, and may be 99.9% or more depending on the carbon dioxide use.

[0063] Although high-purity carbon dioxide is recovered through the aforementioned separation membrane and separation tower (114), 100% of the carbon dioxide contained in the exhaust gas cannot be recovered. Therefore, the present invention further includes a recovery separation membrane module that recovers the remaining carbon dioxide in the carbon dioxide-containing gas (224) obtained from the upper portion through the separation tower (114), thereby enabling the recovery of high-purity carbon dioxide liquid and significantly reducing the amount of carbon dioxide emitted.

[0064] The first recovery membrane (115) receives the carbon dioxide-containing gas (224) obtained from the upper portion, separates it into a first recovery membrane-permeated gas (225) that passes through the first recovery membrane (115) and a first recovery membrane-remaining gas (226), and circulates the first recovery membrane-permeated gas (225) to the first rotary device (102), the first capture membrane (104), the second capture membrane (106), the third capture membrane (109), or the second rotary device (111). This not only increases the amount of carbon dioxide recovered, but also reduces the temperature of the gas, thereby improving process efficiency. Most preferably, the first recovery membrane-permeated gas (225) may be circulated to the second rotary device (111) in that the CO2 recovery rate can be significantly improved when circulated to the second rotary device (111).

[0065] The carbon dioxide-containing gas (224) obtained from the upper part of the carbon dioxide purification separation tower is supplied to the first recovery separation membrane (115) and separated into a first recovery separation membrane permeation gas (225) having a relatively high carbon dioxide concentration and a first recovery separation membrane residual gas (226) having a relatively low carbon dioxide concentration.

[0066] The present invention is characterized in that, in a process for recovering carbon dioxide from a carbon dioxide-containing gas (224) obtained from the upper portion of a separation tower (114) after a carbon dioxide liquefaction process through a separation tower (114), the gas that has undergone the liquefaction process is supplied to a separation membrane in its low-temperature state to recover carbon dioxide, thereby improving the carbon dioxide selectivity without an additional compression or cooling process to increase the separation efficiency, thereby significantly improving the separation efficiency. In this case, the process using the first recovery separation membrane (115) and / or the second recovery separation membrane (116) described below may be performed at a low temperature without an additional process (for example, compression or cooling) after the liquefaction process, and more specifically, may be performed at -40 to -10°C, preferably -35 to -18°C.

[0067] The above first recovery membrane (115) may be made of one or more materials selected from polysulfone (PSF) and polyimide (PI). Table 1 below shows the selectivity of a membrane made of polysulfone (PSF) or polyimide (PI) depending on the temperature. As shown in Table 1 below, it can be seen that the membrane made of polysulfone (PSF) or polyimide (PI) has a significantly increased carbon dioxide selectivity at low temperatures.

[0068] Classification PSFPI Temperature CO 2 / N2CO 2 / O2O 2 / N2CO 2 / N2CO 2 / O2O 2 / N2-20℃75.910.57.369.99.97.1-10℃57.99.16.455.29.65.80℃43.27. 26.039.48.24.810℃34.56.17.731.97.34.420℃31.05.75.429.97.54.0

[0069] On the other hand, membranes made of other materials, such as polyamide or polyether, other than polysulfone (PSF) or polyimide (PI), had a minimal effect on improving carbon dioxide selectivity at low temperatures, making them unsuitable for low-temperature processes.

[0070] The low-temperature first recovery membrane-permeating gas (225) that has passed through the first recovery membrane (115) among the above carbon dioxide-containing gases is mixed with the gas supplied to any one of the first rotary device (102), the first capture membrane (104), the second capture membrane (106), the third capture membrane (109), or the second rotary device (111) and circulated, thereby not only increasing the amount of recovered carbon dioxide but also reducing the temperature of the gas, thereby improving process efficiency.

[0071] According to one embodiment of the present invention, in order to minimize the energy required for cooling using the first heat exchanger (113), a second heat exchanger may be further included to recover the cold heat of the first recovery membrane residual gas (226) that does not pass through the first recovery membrane (115). At this time, the second heat exchanger may recover the cold heat by exchanging heat with the first recovery membrane residual gas (226) with a gas supplied to any one of the first rotary device (102), the first capture membrane (104), the second capture membrane (106), the third capture membrane (109), the second rotary device (111), or the first heat exchanger (113).

[0072] The carbon dioxide capture device of the present invention may further include a second recovery separation membrane (116).

[0073] The second recovery separation membrane (116) receives the first recovery separation membrane residual gas (226) that does not pass through the first recovery separation membrane (115), separates it into the second recovery separation membrane permeation gas (227) that passes through the second recovery separation membrane (116) and the second recovery separation membrane residual gas (228), and supplies the second recovery separation membrane permeation gas (227) to the first rotary device (102), the first capture separation membrane (104), the second capture separation membrane (106), the third capture separation membrane (109), or the second rotary device (111).

[0074] At this time, the second recovery membrane permeating gas (227) having a relatively high carbon dioxide concentration by passing through the second recovery membrane (116) is circulated to the first rotary device (102), the first capture membrane (104), the second capture membrane (106), the third capture membrane (109), or the second rotary device (111), thereby lowering the temperature of the raw material gas supplied to the first to third capture membranes and increasing the carbon dioxide content, thereby improving the separation efficiency, as well as minimizing the emission of carbon dioxide and significantly improving the recovery rate.

[0075] According to one embodiment of the present invention, the third heat exchanger is further included to recover the cold heat of the second recovery membrane residual gas (228) that does not pass through the second recovery membrane (116), and the third heat exchanger may recover the cold heat by exchanging heat with the second recovery membrane residual gas (228) with a gas supplied to any one of the first rotary device (102), the first capture membrane (104), the second capture membrane (106), the third capture membrane (109), the second rotary device (111), or the first heat exchanger (113).

[0076] Another aspect of the present invention comprises the steps of: supplying a first capture membrane feed gas containing a carbon dioxide-containing gas mixture to a first capture membrane and separating the first capture membrane permeate gas and the first capture membrane residual gas; supplying a second capture membrane feed gas containing the first capture membrane permeate gas to a second capture membrane and separating the second capture membrane permeate gas and the second capture membrane residual gas; supplying the second capture membrane residual gas to a recirculation membrane and separating the second capture membrane permeate gas into a recirculation membrane permeate gas and a recirculation membrane residual gas, and circulating the recirculation membrane permeate gas to the second capture membrane; cooling a first heat exchanger feed gas containing the second capture membrane permeate gas with a first heat exchanger; supplying the gas cooled in the first heat exchanger to a separation tower and obtaining a carbon dioxide-containing gas from an upper portion of the separation tower through a separation and purification process, and recovering a high-purity carbon dioxide liquid from a lower portion; And the present invention provides a carbon dioxide capture process including a step of supplying the carbon dioxide-containing gas obtained from the upper portion to a first recovery separation membrane and separating it into a first recovery separation membrane permeation gas and a first recovery separation membrane residual gas.

[0077] A step of compressing the first capture membrane supply gas with a first rotating device before supplying it to the first capture membrane.

[0078] The carbon dioxide capture process of the present invention may further include a step of compressing the first capture membrane supply gas (204) using a first rotary device (102) to supply it to the first capture membrane (104).

[0079] The first rotary machine (102) compresses the first rotary machine supply gas (202) containing a carbon dioxide-containing gas mixture (201).

[0080] When the above carbon dioxide-containing gas mixture (201) is exhaust gas, the exhaust gas can generally be captured at a high temperature, and the exhaust gas can be cooled by a pre-heat exchanger (101) and then introduced to the first rotating machine (102).

[0081] The first rotary device supply gas (202) is compressed by the first rotary device (102), and is introduced into the first rotary device (102) at a pressure ranging from 1.0 to 1.5 bar, and then compressed to achieve a pressure ratio for performing a separation process in the first capture separation membrane (104) described later.

[0082] The first rotary device (102) may compress the first rotary device supply gas (202) to a pressure of 2 to 5 bar, preferably 2.0 to 3.5 bar.

[0083] The gas (203) at the rear end of the first rotary machine may have moisture removed through a dryer before being supplied to the liquefaction process described later, and preferably, moisture may be removed from at least one of the gas (203) at the rear end of the first rotary machine or the gas (219) at the rear end of the second rotary machine described later.

[0084] A step of supplying a first capture membrane feed gas containing a carbon dioxide-containing gas mixture to a first capture membrane and separating the gas into a first capture membrane permeation gas and a first capture membrane residual gas;

[0085] The first capture membrane supply gas (204) is supplied to the first capture membrane (104), thereby separating and obtaining the first capture membrane permeation gas (205) that is relatively rich in carbon dioxide and the first capture membrane residual gas (206) that is poor in carbon dioxide.

[0086] The first capture membrane supply gas (204) includes a carbon dioxide-containing gas mixture (201) or a gas (203) from the rear end of the first rotary device. In addition, the first capture membrane supply gas (204) may further include at least one of a first recovery membrane permeation gas (225) and a second recovery membrane permeation gas (227), and in this case, the recovery rate of carbon dioxide can be increased and the separation efficiency of carbon dioxide can be further improved.

[0087] The above first capture separation membrane (104) may be made of one or more materials of polysulfone (PSF) or polyimide (PI).

[0088] The separation process using the first capture membrane (104), the second capture membrane (106) or the third capture membrane (109) described below may be performed at room temperature, and considering the characteristics of the polysulfone (PSF) or polyimide (PI) membrane material, it is preferable if it can be performed at a low temperature.

[0089] The separation efficiency can be improved by additionally installing a vacuum pump (105) in the permeation section of the first capture membrane permeation gas.

[0090] The above first capture membrane residual gas (206) may be discharged to the outside as a nitrogen-dominant gas with a low carbon dioxide content.

[0091] A step of supplying a second capture membrane supply gas containing the first capture membrane permeation gas to a second capture membrane to separate the second capture membrane permeation gas and the second capture membrane residual gas.

[0092] The second capture membrane supply gas (209) is supplied to the second capture membrane (106) to separate and obtain the second capture membrane permeation gas (210) that permeates the second capture membrane and the second capture membrane residual gas (211) that does not permeate the second capture membrane.

[0093] The second capture membrane supply gas (209) includes the first capture membrane permeation gas (205) and the recirculation membrane permeation gas (212) described below. In addition, the second capture membrane supply gas (209) may further include at least one of the first recovery membrane permeation gas (225) and the second recovery membrane permeation gas (227).

[0094] The second capture membrane permeation gas (210) is characterized by having a higher carbon dioxide concentration than the first capture membrane permeation gas (205).

[0095] A vacuum pump (108) can be additionally installed in the permeation section of the second capture membrane permeation gas (210) to increase the pressure ratio before and after the separation membrane, thereby improving the separation efficiency.

[0096] The above second capture membrane (106) may be made of one or more materials of polysulfone (PSF) or polyimide (PI).

[0097] The carbon dioxide capture process of the present invention may additionally introduce a separation membrane process using a third capture membrane (109) depending on the carbon dioxide concentration in the exhaust gas. As the carbon dioxide concentration in the exhaust gas decreases, it is preferable to additionally introduce a third capture membrane (109) to increase the carbon dioxide recovery rate. At this time, as illustrated in FIG. 2, a third capture membrane supply gas (214) containing a second capture membrane permeation gas (210) may be supplied to the third capture membrane (109).

[0098] As illustrated in FIG. 2, when the carbon dioxide capture process of the present invention further includes a step of supplying a third capture membrane supply gas (214) containing a second capture membrane permeation gas (210) to a third capture membrane (109), the second capture membrane permeation gas (210) that permeates the second capture membrane (106) is not directly supplied to the second rotating device (111) or the first heat exchanger (113) described later, but is supplied to the third capture membrane (109) to be separated into a third capture membrane permeation gas (215) that discharges the gas that permeates the third capture membrane (109) and a third capture membrane residual gas (216) that does not permeate the third capture membrane (109).

[0099] The third capture membrane supply gas (214) includes the second capture membrane permeation gas (210) and may additionally include at least one of the first recovery membrane permeation gas (225) and the second recovery membrane permeation gas (227).

[0100] The third capture membrane residual gas (216) that cannot pass through the third capture membrane (109) can be discharged to the outside or circulated to the second capture membrane (106), and preferably, can be circulated to the second capture membrane (106).

[0101] The third capture membrane permeation gas (215) is characterized by an increased carbon dioxide concentration compared to the second capture membrane permeation gas (210).

[0102] The above third capture membrane (109) may be made of one or more materials of polysulfone (PSF) or polyimide (PI).

[0103] A step of supplying the second capture membrane residual gas to a recirculation membrane to separate it into a recirculation membrane permeation gas and a recirculation membrane residual gas, and circulating the recirculation membrane permeation gas to the second capture membrane.

[0104] The second capture membrane residual gas (211) is supplied to the recirculation membrane (107) and separated into a recirculation membrane permeation gas (212) that permeates the recirculation membrane and a recirculation membrane residual gas (212) that does not permeate the recirculation membrane, and the recirculation membrane permeation gas (212) is supplied to the second capture membrane (106).

[0105] At this time, if the residual gas (211) of the second capture membrane is discharged, the carbon dioxide that would otherwise be lost is recycled, thereby increasing the overall recovery rate. In addition, the carbon dioxide is recycled to the second capture membrane (106) rather than the first rotary device (102), thereby achieving an excellent carbon dioxide recovery rate without increasing the flow rate of the rotary device and thus without increasing power consumption.

[0106] The above-mentioned recirculating membrane permeation gas (212) is characterized by an increased carbon dioxide concentration compared to the second capture membrane residual gas (211).

[0107] The above-mentioned recycling membrane may be made of one or more materials of polysulfone (PSF) or polyimide (PI).

[0108] A step of compressing the first heat exchanger supply gas with a second rotary device before cooling it with the first heat exchanger.

[0109] The carbon dioxide capture process of the present invention may further include a step of compressing the first heat exchanger supply gas (221) with a second rotary device (111) before cooling it with the first heat exchanger (113) to increase the carbon dioxide separation efficiency.

[0110] The second rotary device (111) compresses the second rotary device supply gas (218) to form the pressure required for the liquefaction process described later. At this time, the pressure of the compressed gas may be 18 to 50 bar, preferably 21 to 31 bar.

[0111] The second rotary device supply gas (218) is the first heat exchanger supply gas (221), and more specifically, includes the second capture membrane permeation gas (210) or the third capture membrane permeation gas (215). In addition, depending on the number of recovery membrane processes to be described later, one or more of the first recovery membrane permeation gas (225) and the second recovery membrane permeation gas (227) may be further included.

[0112] As shown in the above drawing 2, when the present invention further includes a third capture separation membrane (109), the second rotary machine supply gas (218) may include the third capture separation membrane permeation gas (215) among the second capture separation membrane permeation gas (210).

[0113] As described above, before supplying the second rotary machine rear gas (219) compressed by the second rotary machine to the first heat exchanger (113), a step of removing moisture may be further included. Generally, a cooler for removing moisture is included in the rotary machine (particularly, a compressor), and thus moisture can be removed using this, but a moisture removal step is necessary to prevent freezing of trace amounts of moisture during the liquefaction process.

[0114] A step of cooling the first heat exchanger supply gas containing the second capture membrane permeation gas to the first heat exchanger.

[0115] The first heat exchanger supply gas (221) is supplied and cooled by the first heat exchanger (113) to a temperature suitable for separation and purification and liquefaction of carbon dioxide in the separation tower (114) described later. At this time, the refrigerant of the first heat exchanger may be freon, nitrogen, propylene, etc., and the temperature of the cooled gas may be -35 to -18°C.

[0116] The first heat exchanger supply gas (221) may include the second capture membrane permeation gas (210), the third capture membrane permeation gas (215), or the second rotary device rear gas (219).

[0117] A step of supplying the cooled gas from the first heat exchanger to a separation tower, obtaining carbon dioxide-containing gas from the upper part of the separation tower through a separation and purification process, and recovering high-purity carbon dioxide liquid from the lower part.

[0118] The separation tower supply gas (222) cooled by the first heat exchanger (113) is transferred to the separation tower (114), and through a separation and purification process, high-purity carbon dioxide liquid (223) is produced at the bottom.

[0119] The molar concentration of carbon dioxide in the high-purity carbon dioxide liquid (223) recovered from the bottom of the separation tower (114) may be 99% or more, and may be 99.9% or more depending on the carbon dioxide use.

[0120] A step of supplying the carbon dioxide-containing gas obtained from the upper portion to the first recovery separation membrane to separate it into the first recovery separation membrane permeation gas and the first recovery separation membrane residual gas, and supplying the first recovery separation membrane permeation gas to the first rotary device, the first capture separation membrane, the second capture separation membrane, the third capture separation membrane, or the second rotary device.

[0121] The above carbon dioxide-containing gas (224) is supplied to the first recovery separation membrane (115) and separated into a first recovery separation membrane permeation gas (225), which is a gas stream with a high carbon dioxide concentration, and a first recovery separation membrane residual gas (226), which is a gas stream that remains and has a relatively low carbon dioxide concentration.

[0122] At this time, the process using the first recovery separation membrane (115) and the second recovery separation membrane (116) described later may be performed at a low temperature without an additional process (e.g., compression or cooling) after the liquefaction process, and more specifically, may be performed at -40 to -10°C, preferably -35 to -18°C.

[0123] The first recovery separation membrane (115) may be made of polysulfone (PSF) or polyimide (PI). If the first recovery separation membrane (115) is made of a material other than polysulfone (PSF) or polyimide (PI), the effect of improving carbon dioxide selectivity at low temperatures may be minimal, making it unsuitable for application to low-temperature processes.

[0124] The low-temperature first recovery membrane-permeating gas (225) that has passed through the first recovery membrane (115) among the above carbon dioxide-containing gases may be mixed with the gas supplied to any one of the first rotary device (102), the first capture membrane (104), the second capture membrane (106), the third capture membrane (109), or the second rotary device (111) and circulated, depending on the type and number of capture membranes.

[0125] According to one embodiment of the present invention, the method may further include a step of recovering the cold heat of the first recovery membrane residual gas (226). At this time, the cold heat of the first recovery membrane residual gas (226) may be recovered by heat exchange with a gas supplied to any one of the first rotary device (102), the first capture membrane (104), the second capture membrane (106), the third capture membrane (109), the second rotary device (111), or the first heat exchanger (113).

[0126] A step of supplying the first recovery membrane residual gas to the second recovery membrane to obtain the second recovery membrane permeation gas and the second recovery membrane residual gas, and supplying the second recovery membrane permeation gas to the first rotary device, the first capture membrane, the second capture membrane, the third capture membrane, or the second rotary device.

[0127] According to a preferred embodiment of the present invention, after the step of supplying the carbon dioxide-containing gas (224) to the first recovery separation membrane (115), the step of supplying the first recovery separation membrane residual gas (226) that does not pass through the first recovery separation membrane to the second recovery separation membrane (116) may be further included.

[0128] The first recovery membrane residual gas (226) still contains carbon dioxide, so by further including a second recovery membrane process, the amount of carbon dioxide that is not recovered and is discharged can be minimized. In addition, when the carbon dioxide capture process of the present invention further includes a second recovery membrane process, the first recovery membrane permeation gas (225) may be circulated to the second rotating device (111) or the third capture membrane (109).

[0129] The first recovery membrane residual gas (226) is separated into a second recovery membrane permeate gas (227) having a relatively high carbon dioxide concentration and a second recovery membrane residual gas (228) having a relatively low carbon dioxide concentration by passing through the second recovery membrane (116), and the second recovery membrane permeate gas (227) is circulated to the first rotary device (102), the first capture membrane (104), the second capture membrane (106), or the third capture membrane (109). At this time, the carbon dioxide content of the raw material gas is increased, so that not only can the separation efficiency be improved, but also the emission of carbon dioxide can be minimized and the recovery rate can be improved.

[0130] According to one embodiment of the present invention, the method may further include a step of recovering the cold heat of the second recovery membrane residual gas (228). At this time, the step of recovering the cold heat of the second recovery membrane residual gas (228) may be performed by heat exchanging with a gas supplied to any one of the first rotary device (102), the first capture membrane (104), the second capture membrane (106), the third capture membrane (109), the second rotary device (111), and the first heat exchanger (113).

[0131] According to the most preferred embodiment of the present invention,

[0132] A step of compressing the first capture membrane supply gas with a first rotating device before supplying it to the first capture membrane;

[0133] A step of supplying the second capture membrane permeation gas to a third capture membrane to separate it into a third capture membrane permeation gas and a third capture membrane residual gas; and

[0134] A step of compressing the first heat exchanger supply gas with a second rotary device before cooling it with the first heat exchanger; and

[0135] It further includes a step of supplying the first recovery membrane residual gas to the second recovery membrane to separate it into the second recovery membrane permeation gas and the second recovery membrane residual gas, and supplying the second recovery membrane permeation gas to the second capture membrane.

[0136] Among the second capturing membrane-permeating gases, only the third capturing membrane-permeating gases are compressed by the second rotating device.

[0137] The above third capture membrane residual gas is supplied to the second capture membrane,

[0138] The above first recovery membrane permeation gas is supplied to the second rotating device,

[0139] The above first rotary device compresses the supplied gas to a pressure of 2.0 to 3.5 bar,

[0140] The second rotary device compresses the supplied gas to 21 to 31 bar,

[0141] The cooling in the step of cooling with the first heat exchanger is performed to a temperature of -35 to -18°C,

[0142] The step of supplying the above carbon dioxide-containing gas to the first recovery separation membrane is performed while maintaining the temperature of the first recovery separation membrane in the range of -35 to -18°C,

[0143] The step of supplying the residual gas of the first recovery membrane to the second recovery membrane is performed while maintaining the temperature of the second recovery membrane in the range of -35 to -18°C.

[0144] The first capture membrane, the second capture membrane, the third capture membrane, the first recovery membrane, and the second recovery membrane may be the same or different from each other, and may be made of at least one material selected from the group consisting of polysulfone (PSF) and polyimide (PI).

[0145] When the carbon dioxide capture process of the present invention satisfies all of the above most preferable implementation conditions, it was confirmed that the carbon dioxide recovery rate is maintained at the same level as the initial level even when the carbon dioxide capture process is performed for a long period of time, which is particularly excellent.

[0146] Hereinafter, the present invention will be described in more detail through examples, etc., but the scope and content of the present invention cannot be interpreted as being reduced or limited by the examples, etc. below.

[0147] Example 1

[0148] As shown in Fig. 1, the process was designed, and carbon dioxide in the exhaust gas was captured and liquefied for each flow as shown in Table 2 below, and the process results are shown in Table 4 below. At this time, the first capture membrane (104), the second capture membrane (106), the recirculation membrane (107), the third capture membrane (109), the first recovery membrane (115), and the second recovery membrane (116) were made of polysulfone (PSF) material.

[0149] Flow #Temperature (℃)Pressure (bar)Composition (mol%)Flow rate (Nm) 3 / h)CO2N2O2H2O2011201.0115.33.671.110.096,670202371.0116.13.875.05.191,646203372.716.63.977.32.288,969204372.517.04.079.00.0287,016205370.250.37.242.40.0626,985206372. 52.02.595.560,031207370.250.410.239.40.0436,052208371.350.410.239.40.0436,052209371.351.110.438.40.0437,077210370.287.26.95.80.115,960211371.323.913.063.121,116212370 .250.518.830.79,083213371.33.88.787.512,033218371.388.16.85.00.0819,0182193724.288.16.85.00.0819,0182201823.988.16.85.00.0819,0182211823.688.26.85.019,002222-3323.288 .26.85.019,002223-1821.099.90.112,887224-3421.063.620.915.52,750225-511.395.14.80.16,118226-3420.934.135.530.43,059227-421.378.119.02.91,009228-3420.812.543.643.92,050

[0150] Example 2

[0151] As shown in Fig. 2, the process was designed, and carbon dioxide in the exhaust gas was captured and liquefied for each flow as shown in Table 3 below, and the process results are shown in Table 4 below. At this time, the first capture membrane (104), the second capture membrane (106), the recirculation membrane (107), the third capture membrane (109), the first recovery membrane (115), and the second recovery membrane (116) were made of polysulfone (PSF) material.

[0152] Flow #Temperature (℃)Pressure (bar)Composition (mol%)Flow rate (Nm) 3 / h)CO2N2O2H2O2011201.0115.33.671.110.096,670202371.0116.13.875.05.191,646203372.716.63.977.32.288,969204372.517.04.079.00.0287,016205370.245.27.347.40.0531,307206372.51.12.196.855,709207370.2 45.611.542.90.0443,171208371.345.612.941.50.0347,506209371.346.312.840.90.0348,316210370.283.99.267.80.0819,329211371.321.115.363.628,988212370.246.422.531.111,880213371.33.610.386.117,1092143 71.383.99.26.80.0819,329215370.294.94.30.70.114,994216371.346.026.327.74,335217371.394.94.30.70.114,994218371.394.94.30.70.116,1202193724.294.94.30.70.116,1202202623.994.94.30.70.116,120221262 3.695.04.30.716,104222-3023.295.04.30.716,104223-1821.099.90.113,354224-3121.071.124.94.02,750225-401.395.14.80.11,126226-3120.954.538.96.61,624227-451.387.212.40.4796228-3120.822.964.312.8828

[0153] CO2 recovery rate (%) Example 187.0 Example 290.2

[0154] As shown in Table 4, it can be seen that the carbon dioxide capture device and process according to the present invention has a very high carbon dioxide recovery rate by recovering the gas obtained from the separation tower through a separation membrane and recycling the gas flow.

[0155] [Explanation of symbols]

[0156] 101: Preheat Exchanger

[0157] 102: First rotating machine

[0158] 103: Dryer

[0159] 104: First capture membrane

[0160] 105: Vacuum pump

[0161] 106: Second capture membrane

[0162] 107: Recirculating membrane

[0163] 108: Vacuum pump

[0164] 109: Third capture membrane

[0165] 110: Vacuum pump

[0166] 111: Second rotary machine

[0167] 112: Dryer

[0168] 113: First heat exchanger

[0169] 114: Separation tower

[0170] 115: First recovery membrane

[0171] 116: Second recovery membrane

[0172] 201: Gas mixture containing carbon dioxide

[0173] 202: First rotating machine supply gas

[0174] 203: Rear stage of the first rotating machine

[0175] 204: First capture membrane supply gas

[0176] 205: Gas permeating the first capture membrane

[0177] 206: First capture membrane residual gas

[0178] 207: Mixed gas of the first capture membrane permeate gas and the recirculation membrane permeate gas

[0179] 208: Mixed gas of the first capture membrane permeate gas and the recirculation membrane permeate gas

[0180] 209: Second capture membrane supply gas

[0181] 210: Second capture membrane permeation gas

[0182] 211: Second capture membrane residual gas

[0183] 212: Recirculating membrane permeation gas

[0184] 213: Recirculating membrane residual gas

[0185] 214: Third capture membrane supply gas

[0186] 215: Third capture membrane permeation gas

[0187] 216: Third capture membrane residual gas

[0188] 217: Gas permeating the third capture membrane

[0189] 218: Second rotary machine supply gas

[0190] 219: Second rotary machine rear stage fuselage

[0191] 220: Dryer shear gas

[0192] 221: First heat exchanger supply gas

[0193] 222: Separation tower supply gas

[0194] 223: High-purity carbon dioxide liquid

[0195] 224: Carbon dioxide-containing gas

[0196] 225: First recovery membrane permeation gas

[0197] 226: First recovery membrane residual gas

[0198] 227: Second recovery membrane permeation gas

[0199] 228: Second recovery membrane residual gas

Claims

1. A first capture membrane that receives a first capture membrane feed gas containing a carbon dioxide-containing gas mixture and separates it into a first capture membrane permeate gas and a first capture membrane residual gas; A second capture membrane that receives a second capture membrane supply gas containing the first capture membrane permeation gas and separates it into a second capture membrane permeation gas and a second capture membrane residual gas; A recirculating separation membrane that receives the second capturing membrane residual gas, separates it into a recirculating membrane permeate gas and a recirculating membrane residual gas, and circulates the recirculating membrane permeate gas to the second capturing membrane; A first heat exchanger for cooling a first heat exchanger supply gas containing the second capture membrane permeate gas; A carbon dioxide purification separation tower including a separation tower that receives the cooled gas from the first heat exchanger, an upper portion where carbon dioxide-containing gas is obtained, and a lower portion where high-purity carbon dioxide liquid is obtained; and A carbon dioxide capture device including a first recovery membrane that receives carbon dioxide-containing gas obtained from the upper portion and separates it into a first recovery membrane permeate gas and a first recovery membrane residual gas.

2. A carbon dioxide capture device, characterized in that it further includes a first rotating device for compressing the first capture membrane supply gas before supplying it to the first capture membrane.

3. A carbon dioxide capture device, characterized in that it further includes a second rotating device for compressing the first heat exchanger supply gas before cooling it with the first heat exchanger, in the first paragraph.

4. A carbon dioxide capture device according to claim 3, characterized in that the second rotary device compresses the supplied gas to 18 to 50 bar.

5. A carbon dioxide capture device, characterized in that in the first paragraph, further comprises a second recovery membrane that receives the first recovery membrane residual gas, separates it into a second recovery membrane permeation gas and a second recovery membrane residual gas, and supplies the second recovery membrane permeation gas to the first capture membrane or the second capture membrane.

6. In the first paragraph, a third capturing membrane is further included that receives the second capturing membrane permeation gas and separates it into a third capturing membrane permeation gas and a third capturing membrane residual gas; A carbon dioxide capture device characterized in that only the third separation membrane-permeating gas among the second capture membrane-permeating gas is cooled by the first heat exchanger.

7. A carbon dioxide capture device according to claim 1, characterized in that the temperature of the first recovery membrane is -40 to -10°C.

8. In the first paragraph, a second heat exchanger for recovering the cold heat of the first recovery membrane residual gas is further included; A carbon dioxide capture device, characterized in that the second heat exchanger heat-exchanges the residual gas of the first recovery separation membrane with a gas supplied to either the first capture separation membrane or the first heat exchanger.

9. A carbon dioxide capture device according to claim 1, wherein the first capture membrane, the second capture membrane, and the first recovery membrane are the same as or different from each other and are made of at least one material selected from polysulfone (PSF) and polyimide (PI).

10. A step of supplying a first capture membrane feed gas containing a carbon dioxide-containing gas mixture to a first capture membrane and separating the gas into a first capture membrane permeate gas and a first capture membrane residual gas; A step of supplying a second capturing membrane supply gas containing the first capturing membrane permeate gas to a second capturing membrane to separate the gas into a second capturing membrane permeate gas and a second capturing membrane residual gas; A step of supplying the second capture membrane residual gas to a recirculation membrane to separate it into a recirculation membrane permeation gas and a recirculation membrane residual gas, and circulating the recirculation membrane permeation gas to the second capture membrane; A step of cooling the first heat exchanger supply gas containing the second capture membrane permeation gas by the first heat exchanger; A step of supplying the gas cooled in the first heat exchanger to a separation tower, obtaining a carbon dioxide-containing gas from the upper part of the separation tower through a separation and purification process, and recovering a high-purity carbon dioxide liquid from the lower part; and A carbon dioxide capture process, comprising: a step of supplying carbon dioxide-containing gas obtained from the upper portion to a first recovery membrane and separating it into a first recovery membrane permeate gas and a first recovery membrane residual gas.

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