Hybrid system of capturing carbon dioxide-forward osmosis

Abstract

The present invention relates to a forward osmosis-carbon dioxide capture hybrid system comprising: an absorption unit into which exhaust gas is introduced and which adsorbs carbon dioxide through an absorption solution; a forward osmosis unit that delivers the absorption solution to the absorption unit; a membrane distillation unit into which the absorption solution discharged from the absorption unit is introduced; and a stripping unit into which the absorption solution discharged from the membrane distillation unit is introduced and carbon dioxide is discharged; wherein the absorption solution discharged from the stripping unit is delivered to the forward osmosis unit, and the forward osmosis unit performs a forward osmosis process using the absorption solution as a draw solution for the forward osmosis process.

Description

Technology Field

[0001] The present invention relates to a forward osmosis-carbon dioxide capture hybrid system, and more specifically, to a forward osmosis-carbon dioxide capture hybrid system capable of capturing carbon dioxide from exhaust gas with high efficiency without using a heat exchanger. Background Technology

[0002] Exhaust gases contain large amounts of carbon dioxide, which is a major factor contributing to global warming. Various methods are being used to capture this carbon dioxide, and among them, Carbon Capture and Storage (CCS) technology is gaining attention for its ability to suppress carbon dioxide emissions while maintaining existing power generation facilities. This technology involves capturing and transporting large quantities of carbon dioxide gas generated from power plants, steel plants, and cement plants for permanent storage in the ocean or underground.

[0003] Among CCS technologies, carbon dioxide gas capture includes post-combustion, pre-combustion, and oxycombustion technologies, and among these, post-combustion capture technology using the wet absorption method is considered to be a technology that is immediately commercially applicable.

[0004] Among these, post-combustion capture technology using the wet absorption method utilizes an absorbent, but it has been pointed out that this method requires a large amount of energy for regeneration after use, as well as various problems such as heat loss due to water evaporation and corrosion caused by the use of amine solutions. Therefore, various studies are being conducted to improve this and efficiently capture carbon dioxide gas at a lower cost.

[0005] Prior art: Korean Registered Patent 10-1096180 (December 13, 2011) The problem to be solved

[0006] The objective of the present invention is to provide a forward osmosis-carbon dioxide capture hybrid system capable of maximizing energy and resource efficiency without using a separate heat exchanger.

[0007] In addition, another objective of the present invention is to provide a forward osmosis-carbon dioxide capture hybrid system equipped with both carbon dioxide capture and desalination functions. means of solving the problem

[0008] According to one aspect of the present invention, embodiments of the present invention include a forward osmosis-carbon dioxide capture hybrid system.

[0009] In one embodiment, the system comprises: an absorption unit into which exhaust gas is introduced and which adsorbs carbon dioxide through an absorption solution; a forward osmosis unit that delivers the absorption solution to the absorption unit; a membrane distillation unit into which the absorption solution discharged from the absorption unit is introduced; and a stripping unit into which the absorption solution discharged from the membrane distillation unit is introduced and carbon dioxide is discharged; wherein the absorption solution discharged from the stripping unit is delivered to the forward osmosis unit, and the forward osmosis unit performs a forward osmosis process using the absorption solution as a draw solution for the forward osmosis process.

[0010] In one embodiment, after performing the forward osmosis process in the forward osmosis section, the absorption solution may be cooled to a temperature of 30°C to 45°C.

[0011] In one embodiment, the absorption solution that has adsorbed carbon dioxide in the absorption unit is transferred to the stripping unit through the membrane distillation unit, and the absorption solution from which carbon dioxide has been separated in the stripping unit is transferred to the absorption unit through the forward osmosis unit, and the absorption solution transferred from the absorption unit to the membrane distillation unit contains carbon dioxide at a first carbon dioxide concentration, and the absorption solution transferred from the stripping unit to the forward osmosis unit contains carbon dioxide at a second carbon dioxide concentration, and the first carbon dioxide concentration may be provided to be higher than the second carbon dioxide concentration.

[0012] In one embodiment, the temperature of the absorption solution discharged from the absorption section may be 60°C to 80°C, the temperature of the absorption solution discharged from the removal section may be 50°C to 70°C, and the temperature of the absorption solution discharged from the forward osmosis section may be 30°C to 45°C.

[0013] In one embodiment, the forward osmosis unit may use seawater or fresh water as the supply solution.

[0014] In one embodiment, the membrane distillation unit can produce fresh water and utilize waste heat.

[0015] In one embodiment, the absorption solution flowing into the membrane distillation unit contains a high concentration of carbon dioxide, and the absorption solution delivered to the forward osmosis unit may not contain carbon dioxide.

[0016] In one embodiment, the absorbent in the absorption solution transferred from the absorption section to the membrane distillation section is provided at a first absorbent concentration, and the absorbent in the absorption solution transferred from the membrane distillation section to the stripping section is provided at a second absorbent concentration, and the first absorbent concentration may be provided lower than the second absorbent concentration.

[0017] In one embodiment, the concentration of the first absorbent may be 25 wt% to 30 wt%, and the concentration of the second absorbent may be 50 wt% to 60 wt%.

[0018] In one embodiment, the absorbent may include an amine-based absorbent.

[0019] In one embodiment, the absorbent may include monoethanolamine (MEA).

[0020] In one embodiment, the carbon dioxide removal rate in the exhaust gas may be 90% to 95%.

[0021] In one embodiment, the absorption unit includes a tower shape extending in one direction and provided at a first height, the stripping unit is performed by a membrane contactor process, the forward osmosis unit delivers the absorption solution discharged from the bottom of the stripping unit to the bottom of the absorption unit, the membrane distillation unit delivers the absorption solution discharged from the top of the absorption unit to the top of the stripping unit, and the absorption solution can flow from the bottom to the top of the absorption unit.

[0022] In one embodiment, the exhaust gas and the absorption solution flow parallel within the absorption section, the exhaust gas is introduced from the bottom of the absorption section, and the absorption solution is introduced from the bottom of the absorption section in a first manner, and after the first introduction, is introduced from the bottom of the absorption section in a second manner to absorb carbon dioxide from the exhaust gas.

[0023] In one embodiment, the temperature of the absorbing part is 30°C to 60°C, and the lower part of the absorbing part may be provided at a lower temperature than the upper part. Effects of the invention

[0024] According to the present invention as described above, a forward osmosis-carbon dioxide capture hybrid system capable of efficiently capturing carbon dioxide without using a heat exchanger can be provided.

[0025] In addition, according to the present invention, by integrating carbon dioxide capture and desalination, a forward osmosis-carbon dioxide capture hybrid system can be provided that can be easily utilized on ships and the like at a low installation cost. Brief explanation of the drawing

[0026] Figure 1 is a drawing showing a conventional device for capturing carbon dioxide from exhaust gas. FIG. 2 is a diagram showing a forward osmosis-carbon dioxide capture hybrid system according to one embodiment of the present invention. Figure 3 is a schematic diagram showing the functions of the membrane distillation unit and the forward osmosis unit in the forward osmosis-carbon dioxide capture hybrid system of Figure 2. Specific details for implementing the invention

[0027] Specific details of other embodiments are included in the detailed description and drawings.

[0028] The advantages and features of the present invention and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms. Unless otherwise specified in the following description, all numbers, values, and / or expressions representing components, reaction conditions, and the content of components in the present invention should be understood as being modified by the term "approximately" in all cases, as these numbers are approximations reflecting the various uncertainties of measurement that occur in obtaining these values ​​among essentially different things. Furthermore, where a numerical range is disclosed in this description, such range is continuous and, unless otherwise indicated, includes all values ​​from the minimum value of such range to the maximum value including said maximum value. Furthermore, where such range refers to an integer, unless otherwise indicated, it includes all integers including from the minimum value to said maximum value including said maximum value.

[0029] Additionally, when a range is described for a variable in the present invention, it will be understood that the variable includes all values ​​within the described range, including the described endpoints of the range. For example, the range "5 to 10" will be understood to include not only the values ​​5, 6, 7, 8, 9, and 10, but also any sub-ranges such as 6 to 10, 7 to 10, 6 to 9, 7 to 9, etc., and any values ​​between integers valid for the category of the described range, such as 5.5, 6.5, 7.5, 5.5 to 8.5, and 6.5 to 9. For example, the range “10% to 30%” will be understood to include all integers including values ​​such as 10%, 11%, 12%, 13%, etc. and up to 30%, as well as any sub-range such as 10% to 15%, 12% to 18%, 20% to 30%, etc., and any value between valid integers within the stated range category such as 10.5%, 15.5%, 25.5%, etc.

[0030] FIG. 1 is a diagram showing a conventional device for capturing carbon dioxide from exhaust gas. FIG. 2 is a diagram showing a forward osmosis-carbon dioxide capture hybrid system according to an embodiment of the present invention. FIG. 3 is a diagram schematically showing the functions of the membrane distillation unit and the forward osmosis unit in the forward osmosis-carbon dioxide capture hybrid system of FIG. 2.

[0031] A forward osmosis-carbon dioxide capture hybrid system (100) according to an embodiment of the present invention may include: an absorption unit (110) into which exhaust gas is introduced and which adsorbs carbon dioxide through an absorption solution; a forward osmosis unit (120) that delivers the absorption solution to the absorption unit (110); a membrane distillation unit (130) into which the absorption solution discharged from the absorption unit (110) is introduced; and a stripping unit (140) into which the absorption solution discharged from the membrane distillation unit (130) is introduced and carbon dioxide is discharged. The absorption solution discharged from the stripping unit (140) is delivered to the forward osmosis unit (120), and the forward osmosis unit (120) may perform a forward osmosis process using the absorption solution as a draw solution for the forward osmosis process.

[0032] The above flue gas is generated from a power plant or an offshore plant and flows into the absorption unit (110). The absorption unit absorbs carbon dioxide contained in the flue gas by bringing the absorption solution, in which an absorbent that absorbs carbon dioxide (110) is dissolved, into contact with the flue gas. For example, the absorption unit (110) may be provided in the form of an absorption tower.

[0033] The above-described forward osmosis-carbon dioxide capture hybrid system (100) may further include an exhaust gas pretreatment unit (170). The exhaust gas pretreatment unit pretreats the exhaust gas before introducing it into the absorption unit, and can treat the exhaust gas to increase the carbon dioxide absorption efficiency in the absorption unit (110). Specifically, the exhaust gas pretreatment unit (170) can remove dust or moisture contained in the exhaust gas.

[0034] Post-combustion capture is a technology for removing carbon dioxide from exhaust gases following the combustion of fossil fuels using air. This involves the application of devices to capture carbon dioxide (CO2) from mixed gases containing N2, O2, water vapor, and trace gaseous impurities in conventional fossil fuel power plants. Since carbon dioxide exists at a low partial pressure in the composition of exhaust gases emitted from coal and gas-fired power plants, chemical absorption or adsorption processes are applied to capture the carbon dioxide.

[0035] In conventional post-combustion capture processes, where carbon dioxide emitted from combustion gases is captured in a solvent, the solution containing captured carbon dioxide with a high concentration is cooled via a heat exchanger and then undergoes a degassing process. Subsequently, the solution, with its reduced carbon dioxide content, is cooled again via a trim cooler before proceeding to capture carbon dioxide from the exhaust gases. Specifically, after performing the degassing process, the solution containing the captured carbon dioxide is cooled using a trim cooler and reused.

[0036] Referring to FIG. 1, a conventional carbon dioxide capture device (10) includes an adsorption tower (11), a heat exchanger (12), a stripper (13), and a pretreatment device (18). A cooler (14), a heater (15), and pumps (16, 17) are provided in the middle of the passage through which the liquid containing the captured carbon dioxide is delivered to control the temperature and pressure of the liquid containing the captured carbon dioxide. Specifically, exhaust gas is pretreated in the pretreatment device (18) and then flows into the adsorption tower (11), and a portion of the carbon dioxide in the exhaust gas is captured through the liquid flowing into the adsorption tower (11). The liquid containing the captured carbon dioxide is discharged from the adsorption tower (11) and then transferred to the heat exchanger (12) by the pump (16). After being discharged from the heat exchanger (12), it is heated by the heater (15) and transferred to the stripper (13) to discharge the carbon dioxide. In addition, the liquid from which the carbon dioxide has been discharged is transferred to the heat exchanger (12) through the pump (17) after being discharged from the stripper (13), and then transferred to the cooling door adsorption tower (11) through the cooler (14) after being discharged from the heat exchanger (12).

[0037] In other words, when a conventional carbon dioxide capture device (10) captures carbon dioxide using a liquid, a separate heat exchanger (12) must be used, and additional coolers (14) and heaters (15) must be used to control the temperature of the liquid transferred to the heat exchanger (12), resulting in low energy efficiency. Furthermore, to utilize the heat exchanger (12), the liquid flow in the adsorption tower (11) flows from top to bottom, and the exhaust gas flows in opposite directions from bottom to top of the adsorption tower (11). In the conventional carbon dioxide capture device (10), the heat exchanger (12) has low efficiency and high heat loss, resulting in high energy consumption, and requires a separate cooler (14) and heater (15). Additionally, the heat exchanger (12) must be made of a corrosion-resistant material and a material with a high heat transfer rate, which has the disadvantage of high production costs.

[0038] On the other hand, the forward osmosis-carbon dioxide capture hybrid system (100) according to the embodiment of the present invention can cool the absorption solution using a forward osmosis process and a membrane distillation process without using a heat exchanger required in the process of adsorbing and desorbing carbon dioxide onto an absorbent. In addition, the process can be performed with high energy efficiency without using additional coolers and heaters to assist the heat exchanger. Furthermore, the forward osmosis-carbon dioxide capture hybrid system (100) according to the present embodiment consumes less energy compared to using a heat exchanger, and process costs can be reduced by using seawater as the supply solution. Therefore, the forward osmosis-carbon dioxide capture hybrid system (100) can easily capture carbon dioxide at low cost in coastal areas or on the sea, such as on ships.

[0039] The above forward osmosis-carbon dioxide capture hybrid system (100) can reheat the absorption solution that has been diluted and cooled in the above forward osmosis process using waste heat, and can reconcentrate the absorption agent with high efficiency by the above membrane distillation process.

[0040] The above absorbent may include an amine-based absorbent. Specifically, the above absorbent may include monoethanolamine (MEA).

[0041] The above monoethanolamine is a type of primary alkanolamine that reacts with carbon dioxide in an aqueous solution to form a carbamate (MEA + COO - It forms ). The above carbamate is a very unstable compound that reacts with surrounding water to form carbamate ions (MEACOO - It is converted into ). The adsorption of carbon dioxide by an absorbent according to an embodiment of the present invention can be performed according to the following reaction scheme.

[0042] [Reaction Equation]

[0043] Dissociation of water: 2H2O ↔ H3O + + OH -

[0044] Hydrolysis of bicarbonate: HCO3 - + H2O ↔ CO3 -2 + H3O +

[0045] Deprotonation of Alkanolamines: MEAH + + H2O ↔ MEA + H3O +

[0046] Bicarbonate formation: CO2 + OH - ↔ HCO3 -

[0047] Carbamate ion formation: MEA + CO2 + H2O ↔ MEACOO - + H3O +

[0048] In the above-described forward osmosis-carbon dioxide capture hybrid system (100), the concentration of MEA in the absorption solution in the absorption section (110) is 25 wt% to 30 wt%, and the carbon dioxide removal rate in the exhaust gas may be 90% or higher. Specifically, the carbon dioxide removal rate in the exhaust gas may be 90% to 95%. The flow rate of the absorption solution in the absorption section (110) can be controlled in various ways according to the size of the forward osmosis-carbon dioxide capture hybrid system and can be controlled according to the concentration of MEA in the absorption solution.

[0049] The above carbon dioxide removal rate can be expressed by the following formula.

[0050] (Equation) Carbon dioxide removal rate (%) = (1 - C out / C in ) x 100

[0051] Here, the concentration ratio C out / C in represents the dimensionless concentration in the gas flow discharged after the exhaust gas passes through the absorption section. In the initial stage of operation using the absorption section, C in the gas flow out Since is a value of nearly 0, the carbon dioxide removal rate is approximately 100%. On the other hand, if the absorbent contained in the absorption solution no longer absorbs carbon dioxide after sufficient operation time, C out / C in It becomes approximately 1.

[0052] The carbon dioxide removal rate can be controlled according to the temperature of the absorption solution and the concentration of carbon dioxide contained in the absorption solution. Specifically, the higher the temperature of the absorption solution and the higher the concentration of carbon dioxide contained in the absorption solution, the lower the carbon dioxide removal rate. On the other hand, for the forward osmosis-carbon dioxide capture hybrid system to operate efficiently, it is desirable to maintain a predetermined temperature range. Therefore, in order to effectively improve the operating efficiency of the forward osmosis-carbon dioxide capture hybrid system along with the carbon dioxide removal rate, the temperature of the absorption solution in the absorption unit (110) may be 20°C to 40°C, and the temperature of the absorption solution discharged after absorption in the absorption unit (110) may be 60°C to 80°C.

[0053] In the absorption solution transferred from the absorption unit (110) to the membrane distillation unit (130), the absorbent is provided at a first absorbent concentration, and in the absorption solution transferred from the membrane distillation unit (130) to the stripping unit, the absorbent is provided at a second absorbent concentration, and the first absorbent concentration may be provided lower than the second absorbent concentration.

[0054] The removal rate of carbon dioxide increases as the amount of carbon dioxide loaded into the absorbent increases, and thus increases as the concentration of the absorbent in the absorption solution increases. On the other hand, as the concentration of the absorbent in the absorption solution increases, the viscosity of the absorption solution increases. When the viscosity is high, side reactions occur in the absorption section (110), and it becomes difficult to reuse the absorption solution. Therefore, it is advantageous for process efficiency to control the concentration of the absorbent in the absorption solution to have an appropriate viscosity. It is preferable that the average concentration of the absorbent in the absorption solution flowing into the absorption section (110) is 25 wt% to 30 wt%. In addition, the temperature of the absorption solution in the absorption section (110) may be 20 ℃ to 40 ℃. If the temperature of the absorption solution is less than 20 ℃, the viscosity of the absorption solution decreases significantly, making it difficult to operate the system, and if the temperature exceeds 40 ℃, the carbon dioxide absorption capacity decreases, which is problematic.

[0055] In addition, the carbon dioxide absorption reaction by the absorbent in the absorption section is an exothermic reaction, and the lower the temperature, the greater the amount of carbon dioxide loaded into the absorbent.

[0056] The viscosity of the above absorption solution increases as the temperature decreases. In addition, since the absorption efficiency of the absorbent decreases as the temperature increases, it is desirable to control the temperature of the absorption section (110) to a range of 20°C to 40°C as described above. In addition, the temperature of the absorption section (110) can be different for the upper and lower sections, and the lower section of the absorption section can be provided at a lower temperature than the upper section.

[0057] As the temperature of the absorption section (110) decreases, the flow rate of the absorption solution decreases, and the regeneration energy of the absorbent decreases. Since the maximum amount of carbon dioxide loaded into the absorbent is determined by the temperature of the lower part of the absorption section (110), it may be efficient to maintain the temperature of the lower part lower than that of the upper part of the absorption section (110).

[0058] In the absorption section (110), the exhaust gas and the absorption solution flow parallel to each other and may be introduced from the bottom of the absorption section (110). In the absorption section (110) according to the present embodiment, the exhaust gas and the absorption solution may be introduced from the bottom of the absorption section (110) and discharged to the top of the absorption section (110). In the absorption section (110), the exhaust gas may be introduced into the lower center of the absorption section (110) and diffused into the internal space of the absorption section (110), and the absorption solution may be introduced into the interior of the absorption section (110) along the lower edge of the absorption section (110). In the absorption section (110), the exhaust gas may be provided at a high concentration in the part corresponding to the central axis, and may have a concentration gradient in which the concentration decreases in the direction toward the inner surface of the absorption section (110). The above absorption solution can effectively absorb carbon dioxide by having a high contact area with the exhaust gas within the absorption section (110).

[0059] Alternatively, the absorption solution may be introduced first at the bottom of the absorption section (110) and then introduced secondarily to absorb carbon dioxide from the exhaust gas. By introducing the absorption solution in a first and second manner, the absorption of carbon dioxide from the exhaust gas can be performed more efficiently while maintaining the temperature inside the absorption section (110) at a low temperature. The volume of the absorption solution introduced first may be provided to be equal to the flow rate of the absorption solution introduced secondarily.

[0060] In the absorption solution discharged from the absorption unit (110), a portion of the absorbent reacts with the carbon dioxide to form carbamate ions, and the concentration of the absorbent decreases. The membrane distillation unit (130) can be driven using waste heat generated from a device that discharges exhaust gas, and fresh water can be produced by membrane distillation, and the absorbent in the absorption solution flowing into the membrane distillation unit (130) can be re-concentrated to increase the concentration of the absorbent.

[0061] In the above membrane distillation unit (130), the absorption solution discharged from the above absorption unit (110) passes through a hydrophobic separation membrane. At this time, the liquid non-volatile solvent contained in the absorption solution is repelled from the surface of the hydrophobic separation membrane, and only the vapor phase generated in the pores of the hydrophobic separation membrane passes through the pores. Therefore, only pure water in the solvent passes through the hydrophobic separation membrane and condenses immediately. In the above membrane distillation unit (130), the driving force for membrane distillation is a temperature difference, which is accompanied by a vapor pressure difference to promote phase separation. That is, since the membrane distillation process utilizes operating conditions of a lower temperature than distillation and a lower pressure than reverse osmosis, the membrane distillation process is effectively used for wastewater treatment and desalination of boiler feed liquids by utilizing waste heat generated from combined heat and power plants or all chemical processes. In addition, the above membrane distillation unit (130) enables seawater desalination through the membrane distillation process. The above hydrophobic membrane may be composed of one or more of polytetrafluoroethylene (PTFE), polypropylene (PP), and poly(vinylidene fluoride), PVDF.

[0062] The concentration of the first absorbent may be 25 to 30 wt%, and the concentration of the second absorbent may be 50 to 60 wt%. By maintaining the concentrations of the first absorbent and the second absorbent within the aforementioned ranges, the forward osmosis-carbon dioxide capture hybrid system can be operated with high efficiency for a long period without damage.

[0063] The concentration of the absorbent in the above absorption solution is diluted, and the diluted absorption solution can be re-concentrated in a membrane distillation unit (130) using waste heat that is commonly available in post-combustion processes. In addition, the absorbent concentrated in the membrane distillation unit (130) can be reused for carbon dioxide absorption after degassing carbon dioxide and lowering its temperature through a forward osmosis process.

[0064] The above membrane distillation unit (130) can generate fresh water and utilize waste heat. Since the forward osmosis-carbon dioxide capture hybrid system (100) according to the present embodiment can continuously generate water through the generation of fresh water, it can be used efficiently in ships, etc.

[0065] The absorption solution, in which the concentration of the absorbent is controlled through a membrane distillation process in the above membrane distillation unit (130), can be transferred to the above stripping unit (140). The absorption solution can be introduced into the upper part of the above stripping unit (140) and flow downward, allowing carbon dioxide to be discharged to the upper part of the above stripping unit (140).

[0066] The concentration of the second absorbent may be 50 wt% to 60 wt%, and as the concentration of the second absorbent increases, the efficiency of the stripping unit (140) increases due to the increase in the concentration of carbon dioxide contained in the absorbent. The stripping unit (140) is a membrane contact unit using a hydrophobic separation membrane, through which the second absorbent in liquid phase flows on one side and carbon dioxide (removed gas) in gaseous phase flows on the other side, and only carbon dioxide gas from the second absorbent selectively permeates the hydrophobic separation membrane. The stripping unit (140) is driven by a partial pressure difference and removes carbon dioxide in the liquid phase by phase separation into the gaseous phase.

[0067] The above hydrophobic membrane may be composed of one or more of polytetrafluoroethylene (PTFE), polypropylene (PP), and poly(vinylidene fluoride), PVDF. Specifically, the absorption solution flowing into the stripping section may contain a high concentration of carbon dioxide, and the absorption solution delivered to the forward osmosis section may not contain carbon dioxide.

[0068] The internal pressure of the above removal unit (140) may be 1 atm or less, specifically negative pressure (vacuum). By controlling the internal pressure of the above removal unit (140) to the aforementioned range, carbon dioxide contained in the absorption solution can be effectively separated and discharged to the outside. The carbon dioxide discharged from the above removal unit (140) can be stored through a separate carbon dioxide capture unit.

[0069] The absorption solution discharged from the above removal unit (140) can be transferred to the above forward osmosis unit (120). The above forward osmosis unit (120) performs a forward osmosis process, and the absorption solution is used as an induction solution for the forward osmosis process, and the absorption solution can be cooled after the forward osmosis process is performed. The above forward osmosis unit (120) cools the high-temperature absorption solution, and the cooled absorption solution can be reused in the absorption unit.

[0070] Additionally, the forward osmosis unit (120) may use seawater or fresh water as the supply solution. Since the forward osmosis unit (120) can cool the absorption solution using low energy, it does not require a separate cooler to cool the absorption solution, thereby improving the energy efficiency of the forward osmosis-carbon dioxide capture hybrid system (100).

[0071] The above-described forward osmosis-carbon dioxide capture hybrid system (100) can use seawater as a supply solution when it is near the coast or on the sea, such as on a ship. The absorption solution has a higher osmotic pressure than the seawater, and by using the absorption solution as an induction solution, the supply solution, which has a relatively lower temperature, can pass through the membrane and only clean water is delivered to the absorption solution side, thereby effectively cooling the absorption solution.

[0072] After performing the forward osmosis process in the forward osmosis unit (120), the absorption solution can be cooled to a temperature of 20°C to 40°C. The forward osmosis unit (120) can cool the temperature of the absorption solution introduced at a relatively high temperature by using the low temperature of seawater or fresh water. By cooling the absorption solution, the absorption solution can be introduced into the absorption unit (110) and reused without separate treatment.

[0073] The above forward osmosis section (120) is equipped with a forward osmosis membrane having selective permeability properties and is divided into a first solution section into which seawater flows and a second solution section into which the absorption solution flows, with the forward osmosis membrane in between. When seawater flows into the first solution section and the absorption solution flows into the second solution section, a forward osmosis process can be performed in the forward osmosis membrane. Through the forward osmosis process, fresh water is transferred from the first solution section to the second solution section, and in the second solution section, the absorption solution and the fresh water are mixed, so that the temperature of the absorption solution flowing into the second solution section at a high temperature is lowered and the concentration of the absorbent can be lowered.

[0074] In the forward osmosis-carbon dioxide capture hybrid system (100) according to the present embodiment, carbon dioxide absorbed from the exhaust gas can be processed sequentially through the absorption unit (110), membrane distillation unit (130), stripping unit (140), and forward osmosis unit (120) via the absorption solution, and then transferred to the absorption unit (110) for reuse. Pumps (150, 160) are provided between the absorption unit (110) and the membrane distillation unit (130) and between the stripping unit (140) and the forward osmosis unit (120), respectively, to control the flow rate of the absorption solution.

[0075] The absorption solution in which carbon dioxide has been adsorbed in the absorption unit (110) is transferred to the stripping unit (140) through the membrane distillation unit (130), and the absorption solution in which carbon dioxide has been separated in the stripping unit (140) can be transferred to the absorption unit (110) through the forward osmosis unit (120). The absorption solution transferred from the absorption unit (110) to the membrane distillation unit (130) contains carbon dioxide at a first carbon dioxide concentration, and the absorption solution transferred from the stripping unit (140) to the forward osmosis unit (120) contains carbon dioxide at a second carbon dioxide concentration, and the first carbon dioxide concentration may be provided to be higher than the second carbon dioxide concentration.

[0076] Specifically, the removal rate of the carbon dioxide may be 90% or more, and more specifically, the carbon dioxide may be completely removed.

[0077] Additionally, the temperature of the absorption solution discharged from the absorption section (110) may be 60°C to 80°C, the temperature of the absorption solution discharged from the removal section (140) may be 50°C to 70°C, and the temperature of the absorption solution discharged from the forward osmosis section (120) may be 30°C to 45°C.

[0078] In the forward osmosis-carbon dioxide capture hybrid system (100) according to an embodiment of the present invention, the absorption solution can be continuously circulated in the forward osmosis-carbon dioxide capture hybrid system (100) by controlling the first and second carbon dioxide concentrations and the temperature of the absorption solution within the aforementioned range, thereby enabling efficient removal of the carbon dioxide.

[0079] The forward osmosis-carbon dioxide capture hybrid system (100) according to the present embodiment can reheat the absorption solution, which has been diluted and cooled in the forward osmosis section (120), using waste heat, and re-concentrate it in the membrane distillation section (130) to reuse the absorbent with high efficiency. In addition, carbon dioxide can be captured with high energy efficiency through a membrane-based hybrid process without using a separate heat exchanger such as a cooler.

[0080] Alternatively, the absorption section (110) may include a tower shape that extends in one direction and is provided at a first height, and the stripping section (140) may be performed by a membrane contactor process. The forward osmosis section (120) may transfer the absorption solution discharged from the bottom of the stripping section (140) to the bottom of the absorption section (110), and the membrane distillation section (130) may transfer the absorption solution discharged from the top of the absorption section (110) to the top of the stripping section (140), and the absorption solution may be provided to flow from the bottom to the top of the absorption section (110).

[0081] By providing a membrane distillation unit (130) for the flow of the absorption solution connecting the upper portions of the absorption unit (110) and the removal unit (140), and providing a forward osmosis unit (120) for the flow of the absorption solution connecting the lower portions of the absorption unit (110) and the removal unit (140), the carbon dioxide removal and the temperature and concentration of the absorption solution can be efficiently controlled.

[0083] A person skilled in the art to which the present invention pertains will understand that the present invention may be implemented in other specific forms without altering its technical concept or essential features. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims set forth below rather than by the detailed description above, and all modifications or variations derived from the meaning and scope of the claims and equivalent concepts should be interpreted as being included within the scope of the present invention. Explanation of the symbols

[0084] 100 : Forward Osmosis-Carbon Capture Hybrid System 110 : Absorbent part 120 : Forward osmosis part 130 : Membrane distillation unit 140 : Removal part

Claims

Claim 1 A forward osmosis-carbon dioxide capture hybrid system comprising: an absorption unit into which exhaust gas is introduced and which adsorbs carbon dioxide through an absorption solution; a forward osmosis unit that delivers the absorption solution to the absorption unit; a membrane distillation unit into which the absorption solution discharged from the absorption unit is introduced; and a stripping unit into which the absorption solution discharged from the membrane distillation unit is introduced and carbon dioxide is discharged; wherein the absorption solution discharged from the stripping unit is delivered to the forward osmosis unit, and the forward osmosis unit performs a forward osmosis process using the absorption solution as a draw solution for the forward osmosis process. Claim 2 A forward osmosis-carbon dioxide capture hybrid system according to claim 1, wherein after performing the forward osmosis process in the forward osmosis section, the absorption solution is cooled to a temperature of 30°C to 45°C. Claim 3 A forward osmosis-carbon dioxide capture hybrid system according to claim 1, wherein the absorption solution in which carbon dioxide has been adsorbed in the absorption section is transferred to the stripping section through the membrane distillation section, the absorption solution in which carbon dioxide has been separated in the stripping section is transferred to the absorption section through the forward osmosis section, the absorption solution transferred from the absorption section to the membrane distillation section contains carbon dioxide at a first carbon dioxide concentration, the absorption solution transferred from the stripping section to the forward osmosis section contains carbon dioxide at a second carbon dioxide concentration, and the first carbon dioxide concentration is provided to be higher than the second carbon dioxide concentration. Claim 4 A forward osmosis-carbon dioxide capture hybrid system according to claim 1, wherein the temperature of the absorption solution discharged from the absorption section is 60 ℃ to 80 ℃, the temperature of the absorption solution discharged from the removal section is 50 ℃ to 70 ℃, and the temperature of the absorption solution discharged from the forward osmosis section is 30 ℃ to 45 ℃. Claim 5 A forward osmosis-carbon dioxide capture hybrid system according to claim 1, wherein the forward osmosis unit uses seawater or fresh water as a supply solution. Claim 6 A forward osmosis-carbon dioxide capture hybrid system according to claim 1, wherein the membrane distillation unit generates fresh water and utilizes waste heat. Claim 7 A forward osmosis-carbon dioxide capture hybrid system according to claim 1, wherein the absorption solution flowing into the membrane distillation unit contains a high concentration of carbon dioxide, and the absorption solution delivered to the forward osmosis unit does not contain carbon dioxide. Claim 8 A forward osmosis-carbon dioxide capture hybrid system according to claim 1, wherein the absorbent dissolved in the absorption solution transferred from the absorption section to the membrane distillation section is provided at a first absorbent concentration, the absorbent dissolved in the absorption solution transferred from the membrane distillation section to the stripping section is provided at a second absorbent concentration, and the first absorbent concentration is provided lower than the second absorbent concentration. Claim 9 A forward osmosis-carbon dioxide capture hybrid system according to claim 8, wherein the concentration of the first absorbent is 25 wt% to 30 wt% and the concentration of the second absorbent is 50 wt% to 60 wt%. Claim 10 In claim 8, the absorbent is a forward osmosis-carbon dioxide capture hybrid system comprising an amine-based absorbent. Claim 11 In claim 10, the absorbent is a forward osmosis-carbon dioxide capture hybrid system comprising monoethanolamine (MEA). Claim 12 A forward osmosis-carbon dioxide capture hybrid system according to claim 1, wherein the carbon dioxide removal rate from the exhaust gas is 90% to 95%. Claim 13 A forward osmosis-carbon dioxide capture hybrid system according to claim 1, wherein the absorption unit comprises a tower shape extending in one direction and provided at a first height, the stripping unit is performed by a membrane contactor process, the forward osmosis unit delivers an absorption solution discharged from the bottom of the stripping unit to the bottom of the absorption unit, the membrane distillation unit delivers an absorption solution discharged from the top of the absorption unit to the top of the stripping unit, and the absorption solution flows from the bottom to the top of the absorption unit. Claim 14 A forward osmosis-carbon dioxide capture hybrid system according to claim 13, wherein the exhaust gas and the absorption solution flow parallel within the absorption section, the exhaust gas is introduced from the bottom of the absorption section, and the absorption solution is introduced from the bottom of the absorption section in a primary manner, and then introduced from the bottom of the absorption section in a secondary manner to absorb carbon dioxide from the exhaust gas. Claim 15 A forward osmosis-carbon dioxide capture hybrid system according to claim 1, wherein the temperature of the absorption portion is 30°C to 60°C and the lower portion of the absorption portion is provided at a lower temperature than the upper portion.

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