Method for separating carbon dioxide from flue gas and method for sequestrating liquid carbon dioxide

Abstract

Systems and methods for separating carbon dioxide from flue gas and sequestering the carbon dioxide are described herein. By using the properties of carbon dioxide and the temperature of a water body (e.g., ocean or freshwater body) or the temperature of the ambient atmosphere, gaseous carbon dioxide can be converted to a liquid and separated from other gases. The pressure used to separate carbon dioxide from other gases can also be used to sequester liquid carbon dioxide. Liquid carbon dioxide is inert and can be discharged into the ocean without dissolving in seawater and acidifying it. Liquid carbon dioxide may even be made denser than seawater. The liquid carbon dioxide then sinks to the bottom of the ocean or is injected into marine sediments or sediments and rocks below the seafloor, where it remains inert and sequestered for an extended period of time.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 036,264, filed June 8, 2020, the entire contents of which are incorporated herein by reference. [Background technology]

[0002]

[0002] Carbon dioxide is a known greenhouse gas. Industrial processes that burn hydrocarbons produce carbon dioxide as a by-product. One way to mitigate the impact of carbon dioxide production on climate change is carbon dioxide sequestration. Carbon dioxide sequestration involves removing carbon dioxide from the atmosphere before it is released from an industrial process, or capturing the carbon dioxide, and depositing the carbon dioxide in a reservoir so that it cannot re-enter or enter the atmosphere. Separating carbon dioxide from other flue gases from industrial processes is difficult. Geographical sequestration of carbon dioxide on Earth is also difficult. Therefore, improvements in separating carbon dioxide from flue gases and sequestrating carbon dioxide are desired. These and other needs are addressed. Summary of the Invention

[0003]

[0003] Embodiments of the present invention enable efficient separation and sequestration of carbon dioxide. By using the properties of carbon dioxide and the temperature of a water body (e.g., ocean or freshwater body) or the temperature of the ambient atmosphere, gaseous carbon dioxide can be converted to a liquid and separated from other gases. The pressure used to separate carbon dioxide from other gases can also be used to sequester liquid carbon dioxide. Liquid carbon dioxide is inert and can be discharged into the ocean at depths with sufficient pressure without dissolving in seawater and acidifying the ocean. Liquid carbon dioxide may even be made denser than seawater. The liquid carbon dioxide then sinks to the bottom of the ocean or is injected into sediments or rocks on the ocean floor, where it remains inert and sequestered for long periods of time.

[0004]

[0004] Embodiments may include a method of separating carbon dioxide from other gases using ocean depth. The method may include flowing a first mixture of gases to a depth in the ocean. The first mixture may include carbon dioxide and other gases. The method may also include liquefying the carbon dioxide as a result of the depth and / or temperature of the ocean to form liquid carbon dioxide. The first mixture of gases may flow in a pipe in the ocean. The carbon dioxide may liquefy as a result of pressure in the pipe at the depth and the temperature effect of the ocean on the pipe. The liquid carbon dioxide may not mix with seawater in the pipe. The liquid carbon dioxide is not carbon dioxide dissolved in water. The method may further include separating the liquid carbon dioxide from the other gases. Additionally, the method may include flowing a second mixture of other gases upward to the ocean surface.

[0005]

[0005] Embodiments may include a system for separating carbon dioxide from other gases. The system may include a first pipe configured to deliver a first gas mixture from the surface of the water body to a first depth within the water body. The first depth may be at least 10 feet below the water surface. The system may also include a second pipe configured to deliver a second gas mixture from the first depth of the water body to the surface of the water body. The second pipe may be in fluid communication with the first pipe. The system may also include a separation chamber in fluid communication with the first pipe and the second pipe. The system may include a port connected to the separation chamber. The port may be configured to discharge the liquefied carbon dioxide separated from the first gas mixture from the separation chamber. Further, the system may include a compressor configured to inject the first gas mixture through the first pipe from the surface of the water body to the first depth.

[0006]

[0006] Embodiments may include a method for separating carbon dioxide from a gas mixture. The method may include flowing a first mixture of gases through a structure, the first mixture including carbon dioxide and other gases. The method may also include liquefying the carbon dioxide at a location within the structure to form liquid carbon dioxide as a result of an ambient temperature outside the structure and a pressure of the mixture within the structure at the location. The liquid carbon dioxide is not carbon dioxide dissolved in water. The method may further include separating the liquid carbon dioxide from the other gases to form separated liquid carbon dioxide. Additionally, the method may include sequestering the separated liquid carbon dioxide.

[0007] A better understanding of the nature and advantages of embodiments of the present invention may be obtained with reference to the following detailed description and accompanying drawings. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 illustrates a method of utilizing ocean depth to separate carbon dioxide from flue gas, according to an embodiment of the present invention. [Figure 2] 1 illustrates a system for separating carbon dioxide from flue gas according to an embodiment of the present invention. [Figure 3] This is a diagram showing the phase diagram of carbon dioxide according to DAVoormeij et al., "Geological and Mineral CO2 Sequestration Options: A Technical Review," Geological Fieldwork 2002, Paper 2003-1. [Figure 4] FIG. 1 illustrates a method for sequestrating carbon dioxide from flue gas according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009]

[0012] Carbon dioxide, a greenhouse gas, is a by-product of industrial processes, including refineries, fossil fuel power plants, chemical plants, and any other process involving hydrocarbon combustion. Carbon dioxide sequestration is difficult. Carbon dioxide is produced along with other flue gases and must be separated from other flue gases before sequestration. Flue gas may contain carbon dioxide, nitrogen, oxygen, and water vapor. Nitrogen may make up approximately 40-80% of the flue gas. Carbon dioxide may be approximately 3 to 50% of the flue gas. Water vapor can be removed from the flue gas. Nitrogen oxides (NO x ), sulfur oxides (SO x ), carbon monoxide, and particulate matter may make up a small percentage of the flue gas. Separation of carbon dioxide from other flue gases can be an expensive process.

[0010]

[0013] Traditional carbon dioxide sequestration can also be difficult. Storing carbon dioxide as a compressed gas or liquid is preferable to storing it as an uncompressed gas because compressed gas or liquid occupies a smaller volume. One method of sequestering carbon dioxide involves injecting it deep into a well in the Earth. The pressure in the injection well increases with depth, favoring the liquid phase of carbon dioxide or compressed gas. However, the temperature of the rock surrounding the injection well also increases with depth. For example, temperature can increase by approximately 1.7°F for every 100 feet of depth. Thus, sequestration 6,000 feet below the surface results in an increase of approximately 100°F.

[0011]

[0014] The ocean provides an environment where temperature does not increase with depth, but rather decreases or remains stable in the range of 33°F to 63°F. Furthermore, the decrease in temperature is accompanied by an increase in pressure, which is not typically expected. Within a pipe in the ocean, pressure can build up at depth within the pipe while taking advantage of the natural and ambient cooling available from the ocean water surrounding the pipe. As a result, it is advantageous to inject carbon dioxide into the ocean within a pipe. As used herein, "ocean" is not limited to geographically named oceans (e.g., the Atlantic and Pacific Oceans). The ocean includes any part of the saltwater mass that covers approximately 75% of the Earth. Non-ocean environments, including freshwater bodies of water or air at ambient temperatures, can be used to cool the pipe while liquefying the carbon dioxide.

[0012]

[0015] Furthermore, the unique physical properties of carbon dioxide make its injection even more beneficial. Figure 3 shows a phase diagram for carbon dioxide. Pressure is shown on the y-axis in MPa, and temperature is shown on the x-axis in °C. Pressure can be converted to psi, and temperature can be converted to degrees Fahrenheit, and vice versa. The carbon dioxide phase diagram shows that carbon dioxide is a liquid at pressures and temperatures available at ocean depths. For example, the critical point of carbon dioxide is approximately 1,050 psi and 88°F (7.38 MPa and 31.1°C). At temperatures below 88°F and pressures above 1,050 psi, carbon dioxide is a liquid. At these pressures and temperatures, typical flue gas remains in the gas phase.

[0013]

[0016] At ocean depths, including those in pipes separated from seawater, temperatures below 88°F and pressures above 1,050 psi can be achieved. Due to the properties of carbon dioxide and flue gas, carbon dioxide becomes a liquid, while the remainder of the flue gas remains a gas. Separating a liquid from a gas is simpler than separating a gas from another gas. Carbon dioxide can condense and essentially flow out of the gas mixture. Liquid carbon dioxide, due to its higher density, can migrate to the bottom of the vessel and be removed from the flue gas. Separation of liquid carbon dioxide from other gases can be a continuous process within the pipe. The pressure used to liquefy the carbon dioxide can also drive the sequestration of the separated carbon dioxide. For example, liquid carbon dioxide cannot be reduced in pressure (e.g., to atmospheric pressure) before being sent for sequestration. Additional pressure may be applied to the liquid carbon dioxide to aid in sequestration.

[0014]

[0017] The separated carbon dioxide may be returned to the surface and then used for other purposes or may be geologically sequestered. The remaining flue gas, which has already been treated at the process plant to meet environmental standards for emissions to the atmosphere, may be released to the atmosphere.

[0015]

[0018] Pressures within the pipe can reach 1,050 psi due to a combination of compression at or near surface pressure and the weight of the fluid column. Pressures within the pipe can reach 1,050 psi at depths of 500 to over 3,000 feet. The temperature of seawater at these depths is typically well below 88°F. Going to greater depths (e.g., about 3,000 feet or 914 meters) can result in higher pressures, typically lower temperatures.

[0016]

[0019] Liquid carbon dioxide also has other properties that improve ocean sequestration technology. Its density can increase under higher pressures. Its density can be made higher than that of seawater at the same pressure. By taking liquid carbon dioxide to a depth of approximately 9,000 feet (2,473 m), a pressure of approximately 4,000 psi makes it denser than seawater. The pressure increase of approximately 1,050 psi and 88°F to 4,000 psi can be provided by a pump or other suitable device. Releasing liquid carbon dioxide into the ocean can cause it to sink to the ocean floor. It can be pumped into deep trenches, which provide a large reservoir for sequestration, or it can be pumped into marine sediments or oceanic subsurface rocks for permanent sequestration. However, if the liquid carbon dioxide is not at a sufficiently high pressure and low enough temperature, it can be less dense than the surrounding seawater. As used herein, "seawater" includes any saltwater in the ocean. The liquid carbon dioxide then rises and eventually reverts to gaseous carbon dioxide, which can then be dissolved in seawater or released into the atmosphere.

[0017]

[0020] The movement of liquid carbon dioxide from a first depth where the carbon dioxide liquefies to a second depth where the liquid carbon dioxide is denser than seawater can be accomplished by a pump rather than a compressor, as is typical for the movement of gaseous carbon dioxide. Pumping a liquid is generally easier and cheaper than compressing a gas. Furthermore, the column of liquid carbon dioxide exerts additional pressure on the liquid carbon dioxide below the column. The pressure from the column also reduces the amount of pressure that needs to be applied by the pump to achieve the isolation pressure where the liquid carbon dioxide is denser than seawater.

[0018]

[0021] In some embodiments, the pressure required for the phase change of gaseous carbon dioxide to liquid carbon dioxide can be provided by the seawater itself. For example, in some embodiments, the seawater can be separated from the gas mixture by a movable partition (e.g., a piston) that transfers the pressure of the seawater to the gas without direct contact between the seawater and the gas. In preferred embodiments, the pressure applied to the gas mixture is due to compression of the gas at or near the ocean surface, and not due to pressure from the seawater.

[0019]

[0022] Liquefied gases, such as carbon dioxide, in gas mixtures are often considered a problem to be avoided when transporting gases by pipeline (e.g., A. Hart et al., "Cryogenic CO2 capture in natural gas," Energy Procedia 1 (2009)). Liquefying only some of the gas in a gas mixture can make it difficult to move the gas along with the liquid. This problem, which is avoided in conventional processes, is instead a solution to separating and sequestering the carbon dioxide. In an embodiment of the present invention, the carbon dioxide is liquefied during gas transportation.

[0020]

[0023] FIG. 1 illustrates a method 100 for separating carbon dioxide from other flue gases using ocean depth. Method 100 may be an example of any of the methods described herein and may be used with any of the systems described herein. In block 102, the method includes flowing a first mixture of gases to a first depth within the ocean. The first mixture of gases may flow in a pipe. The flow may be turbulent (e.g., a Reynolds number greater than 2,900) or laminar (e.g., a Reynolds number less than 2,000). The flow rate of the first gas mixture may be 50-100 mmcfd (million cubic feet per day), 100-200 mmcfd, 200-500 mmcfd, 500-1,000 mmcfd, or even higher. The first mixture may include carbon dioxide and other gases. The other gases may include flue gases that do not contain carbon dioxide. The other gases may include products from burning hydrocarbon fuels, molecular nitrogen, or molecular oxygen. The other gases may or may not contain water. Water can be removed before flowing the first mixture of gases to the first depth in the ocean. Carbon dioxide can be 3% or more by mass of the first mixture of gases. For example, carbon dioxide can be 3%-5%, 5%-10%, 10%-20%, or more than 20% of the first mixture of gases. The first depth can be deep enough that the pressure in the pipe and the temperature of the pipe provided by the seawater are sufficient to convert the carbon dioxide from a gas to a liquid. For example, the first depth can have a temperature and pressure that is in the liquid phase of the carbon dioxide phase diagram of Figure 3. The first mixture can be flowed to the first depth by a compressor.

[0021]

[0024] At block 104, the method may include liquefying the carbon dioxide resulting from the first depth in the ocean to form liquid carbon dioxide. The carbon dioxide may be liquefied in a pipe. The first depth in the ocean may be a first depth in a pipe. The carbon dioxide is not dissolved carbon dioxide in seawater. The first depth may be at least 10 feet. For example, the first depth may be 10 to 50 feet, 50 to 500 feet, 500 to 1,000 feet, 1,000 to 1,500 feet, 1,500 to 2,000 feet, 2,000 to 2,500 feet, 2,500 to 3,000 feet, 3,000 to 3,500 feet, 3,500 to 4,000 feet, 4,000 to 4,500 feet, 4,500 to 5,000 feet, or greater than 5,000 feet.

[0022]

[0025] The carbon dioxide may liquefy as a result of pressure and temperature at that depth. The pressure may be the result of compression of the gas in the pipe. The pressure may be at least 500 psi. By way of example, the pressure may be 500-1,000 psi, 1,000-1,300 psi, 1,300-1,400 psi, 1,400-1,500 psi, or greater than 1,500 psi. In preferred embodiments, the pressure may be caused by compression at or near the ocean surface and the weight of the fluid column above the depth. In some embodiments, the pressure may be caused by the seawater itself. The pressure may be caused by a column of seawater above the gas (e.g., as a piston). The temperature may be less than 88°F. For example, the temperature may be 85°F to 88°F, 80°F to 85°F, 70°F to 80°F, 60°F to 70°F, 50°F to 60°F, 40°F to 50°F, 32°F to 40°F, or 20°F to 32°F. In some embodiments, the pressure may be 600 to 650 psi. The temperature may be a result of the temperature of the seawater at that depth. No other cooling or refrigeration may be used, except for heat transfer from the cooling seawater at lower depths. In some embodiments, cooling may be included as part of the compression system to bring the temperature of the compressed gas mixture down to the temperature before compression. Such cooling may use a radiator to reduce the temperature from approximately 125°F after compression.

[0023]

[0026] The carbon dioxide liquefaction may be performed in a vertical or substantially vertical section of the pipe. The section of the liquefaction pipe need not be horizontal (e.g., 0°). The angle of the pipe section may be 10° to 30°, 30° to 45°, 45° to 60°, 60° to 80°, 80° to 85°, or 85° to 90°. In this way, the liquid carbon dioxide can move by gravity in the same direction as the other gases in the gas mixture, and therefore, gas transport is not adversely affected by having liquid in the pipe.

[0024]

[0027] In block 106, the method may include separating the liquid carbon dioxide from the other gases. The separation of the liquid carbon dioxide may be by condensing the carbon dioxide to become a liquid while the other gases remain gaseous. The liquid may move to the bottom of a chamber, and the other gases may move to the top of the chamber. The chamber may be referred to as a separation chamber or a CO2 capture chamber. The separation of the liquid carbon dioxide from the other gases may not involve an absorbent, adsorbent, or membrane. The separation of the liquid carbon dioxide may be the result of the carbon dioxide becoming a liquid due to temperature and pressure and not due to other unit operations or other techniques for liquefying carbon dioxide.

[0025]

[0028] At block 108, the method may include flowing the second mixture of other gases upward to the ocean surface. Flowing the second mixture of other gases upward to the ocean surface may be a result of the other gases being less dense than liquid carbon dioxide and buoyant. The method may also include releasing the second mixture into the atmosphere. The flue gases in the second mixture may already be at a concentration permitted by environmental regulations, including regulations set by the U.S. Environmental Protection Agency and / or other regulatory agencies. In some embodiments, the second mixture may be flowed upward using a compressor.

[0026]

[0029] The method may include flowing the carbon dioxide, which has been separated from other gases, to the ocean surface. The carbon dioxide begins as a liquid and then becomes a gas as the carbon dioxide approaches the surface. In some embodiments, the separated carbon dioxide may be flowed to land. The carbon dioxide may be geographically sequestered. In some embodiments, the carbon dioxide may be used in industrial processes, such as the production of carbonate bricks, cement, fuel, or other products.

[0027]

[0030] The method may include flowing the liquid carbon dioxide to a second depth. The second depth may be deeper than the first depth. The second depth may be at least 7,000 feet. For example, the second depth may be 7,000-8,000 feet, 8,000-9,000 feet, 9,000-10,000 feet, 10,000-11,000 feet, 11,000-12,000 feet, or greater than 12,000 feet. Because the liquid is separate from the gas, a pump can be used to flow the liquid carbon dioxide from the first depth to the second depth. The pressure at the second depth may be at least 3,000 psi, including 3,000-3,500 psi, 3,500-4,000 psi, 4,000-4,500 psi, 4,500-5,000 psi, or greater than 5,000 psi. The pressure difference between the first depth and the second depth can be applied via a pump or other suitable device. The pressure can increase monotonically from the first depth to the second depth. Thus, the pressure used to liquefy the carbon dioxide can contribute to the pressure used to sequester the liquid carbon dioxide.

[0028]

[0031] At the second depth, the density of the liquid carbon dioxide may be greater than the density of seawater at or near the same depth. The second depth may make the liquid carbon dioxide denser than seawater for the temperature, salinity, and density of seawater at a particular location in the ocean. The method may include contacting the liquid carbon dioxide with water in the ocean without dissolving the liquid carbon dioxide in the water. The liquid carbon dioxide may form a hydrate after contacting the seawater, and the carbon dioxide may be released from the hydrate and not dissolve in the water. The method may include releasing the liquid carbon dioxide into the seawater. As a result of the density of the liquid carbon dioxide being greater than the density of seawater, the liquid carbon dioxide may flow to the bottom of the ocean. The carbon dioxide may then be sequestered because it is stable at the bottom of the ocean. The bottom of the ocean may include the bottom of an ocean trench.

[0029]

[0032] In some embodiments, liquid carbon dioxide can be released directly into the sediments, rocks, or other geological formations that make up or lie beneath the seafloor. Deep-sea sediments can be 1 to 4,000 feet thick. Liquid carbon dioxide can be released at any depth within the sediments. Liquid carbon dioxide can be pumped into shallow marine sediments where the carbon dioxide forms hydrates, or it can be held in place by gravity, density differences with seawater, and / or pore pressures.

[0030]

[0033] Carbon dioxide can be emitted into the seawater at rates of 100,000 to 100 million metric tons per year or more. Flue gas can be emitted into the atmosphere at rates of 100,000 to 500 million metric tons per year or more.

[0031]

[0034] In some embodiments, liquid carbon dioxide may be injected into basalt rocks that may be present on or beneath the ocean floor. The liquid carbon dioxide may react with the basalt to form calcium and / or magnesium carbonate minerals. The carbon dioxide may be incorporated into the mineral matrix. As a result, the carbon dioxide may be sequestered in mineral form rather than in liquid or gas form.

[0032]

[0035] FIG. 2 illustrates a system 200 for separating carbon dioxide from flue gas. The system 200 may resemble an oil platform when viewed from the ocean surface. The system 200 may be used in any of the methods described herein. The system may include a first pipe 202 configured to deliver a first gas from a surface 206 of a body of water to a first depth 210 within the body of water. The body of water may be an ocean or a body of freshwater water. For example, the body of freshwater water may be a lake or a reservoir. The first depth 210 may be at least 2,400 feet. For example, the first depth 210 may be 0.5 to 1 foot, 1 to 25 feet, 25 to 50 feet, 50 to 150 feet, 150 to 200 feet, 200 to 500 feet, 500 to 1,000 feet, 1,000 to 1,500 feet, 1,500 to 2,000 feet, 2,000 to 2,500 feet, 2,500 to 3,000 feet, 3,000 to 3,500 feet, 3,500 to 4,000 feet, 4,000 to 4,500 feet, 4,500 to 5,000 feet, or greater than 5,000 feet. The first depth may be deep enough to cool the first pipe to liquefy the carbon dioxide. The first pipe 202 and any other pipes disclosed herein may be stainless steel or any other suitable material. The first pipe 202 may be vertical at a point where the carbon dioxide begins to liquefy.

[0033]

[0036] The pipe can have a burst strength rated for any of the pressures described herein. In some embodiments, the pipe can have a burst strength rated for the pressure difference between the pressure inside the pipe and the pressure outside the pipe. The pipe can have the advantage that it does not need to be constructed to withstand the full force of the depth of the water body, since the pressure inside the pipe partially counteracts the force from the water body outside the pipe. In some embodiments, the pipe can have a burst strength rating of at least 1,000 psi, including 1,440 psi. The pipe can have a diameter of 0.5 to 1 inch, 1 to 5 inch, 5 to 8 inch, 8 to 10 inch, 10 to 12 inch, 12 to 15 inch, 15 to 20 inch, or greater than 20 inches.

[0034]

[0037] The system 200 may include a second pipe 214. The second pipe 214 may be configured to deliver the second gas mixture from a first depth 210 within the body of water to a surface 206 of the body of water. The second pipe 214 may be in fluid communication with the first pipe 202. The second pipe 214 may be the same or a different size and / or material as the first pipe 202.

[0035]

[0038] System 200 may include a separation chamber 218. Separation chamber 218 may be in fluid communication with first pipe 202 and second pipe 214. In some embodiments, separation chamber 218 may be configured to transfer pressure from the body of water at first depth 210 to the first gas mixture. For example, in some embodiments, separation chamber 218 may allow seawater to enter. First pipe 202 allows seawater to enter, and pressure caused by the column of seawater may condense carbon dioxide. Seawater may be pumped into first pipe 202. In some embodiments, separation chamber 218 may be the portion of the pipe where the carbon dioxide condenses.

[0036]

[0039] The separation chamber 218 may include a "knockout" device similar to those used in oil fields. A knockout, viewed horizontally, includes one or more bends in the pipe. For example, the pipe may be wound up or down. The knockout can vent fluid from the low spot of the bend and remove gas from the top of the bend. The knockout device may include an increased diameter of the pipe to reduce flow velocity, allowing time for liquids or heavier components to separate from the flow by gravity. The knockout device may also include an expansion area. The knockout may be a slightly larger section of pipe. The slightly larger section of pipe allows for expansion of the gas and separation of the liquid from the gas flow.

[0037]

[0040] In some embodiments, the separation chamber 218 may include a flexible or movable component that allows the pressure of the seawater to be transferred to the first gas mixture within the separation chamber 218. The flexible component may be a flexible material. The pressure of the seawater can press against the flexible component, which in turn presses against the first gas mixture with a pressure of 1,050 psi or greater.

[0038]

[0041] System 200 may include a port (222a or 222b). Port 222a or port 222b may be connected to separation chamber 218. Port 222a or 222b may be configured to discharge the liquefied carbon dioxide separated from the first gas mixture from separation chamber 218. Port 222a or port 222b may be at the bottom of separation chamber 218 so that the denser liquefied carbon dioxide can be separated from the first gas mixture.

[0039]

[0042] The system 200 may include a compressor 226. The compressor 226 may be configured to inject the first gas mixture from the surface 206 of the water body through the first pipe 202 to a first depth 210 within the water body. The compressor 226 may be configured to provide a pressure of at least 1,050 psi to the first gas in the first pipe 202 at the first depth 210. The compressor 226 may be part of a process plant 230. The process plant 230 may be any plant that produces carbon dioxide and flue gas. The compressor does not need to compress the first gas mixture to the full target pressure because the hydrostatic pressure of the column of gas above the first depth 210 contributes to the pressure at the first depth.

[0040]

[0043] System 200 may further include a pump 234. Pump 234 may be in fluid communication with port 222a. Pump 234 may be configured to flow the liquefied carbon dioxide to a second depth 238 of at least 7,000 feet. For example, the second depth may be between 7,000 and 8,000 feet, between 8,000 and 9,000 feet, between 9,000 and 10,000 feet, between 10,000 and 11,000 feet, between 11,000 and 12,000 feet, or greater than 12,000 feet.

[0041]

[0044] The system 200 may further include a third pipe 242 in fluid communication with the pump 234. The third pipe 242 may be configured to discharge the liquefied carbon dioxide into seawater at a second depth 238. The third pipe 242 may be positioned so that the liquefied carbon dioxide sinks to the seabed 244. The liquefied carbon dioxide is inert in seawater. In some embodiments, the third pipe 242 may not transport the liquefied carbon dioxide below the surface of the seabed. In other embodiments, the third pipe 242 may transport the liquefied carbon dioxide to sediment on the seabed or to sediment or rock below the seabed. The third pipe 242 may include a steel casing that is inserted into a borehole in the sediment or rock on the seabed. The steel casing may be cemented in place. The casing and surrounding cement may be perforated to place the liquid carbon dioxide into the sediment or rock.

[0042]

[0045] System 200 may further include a fourth pipe 246. Fourth pipe 246 may be connected to port 222b. Fourth pipe 246 may be configured to deliver the carbon dioxide to the surface 206 of the water body. A pump may flow the liquefied carbon dioxide through fourth pipe 246. In some embodiments, the liquefied carbon dioxide can revert to a gas with a decrease in pressure. The carbon dioxide gas can then rise up fourth pipe 246. Fourth pipe 246 may deliver the carbon dioxide to land 250. The carbon dioxide delivered to land may be geographically sequestered or used as a feedstock for other processes.

[0043]

[0046] In some embodiments, if the fourth pipe 246 is included, the third pipe 242 may not be included. In other embodiments, if the third pipe 242 is included, the fourth pipe 246 may not be included.

[0044]

[0047] System 200 may exclude any heat transfer device that includes a chiller or refrigerant or other fluid that is not atmospheric or body of water. For example, system 200 may not include a non-naturally recirculating fluid that heats in contact with pipes and then cools in another area.

[0045]

[0048] FIG. 4 illustrates a method 400 for separating carbon dioxide from a gas mixture. Method 400 may not be limited to using ocean depths to generate the pressure and / or temperature to liquefy the carbon dioxide. Method 400 may also include using a body of water within a single land mass. For example, the body of water may be a lake or reservoir. Method 400 may also not include a body of water to cool or pressurize the gas mixture. Method 400 may include air-cooling the gas mixture to a temperature below 88°F and pressurizing it with a compressor to the pressure required to liquefy the carbon dioxide. Method 400 may include using all or aspects of system 200.

[0046]

[0049] At block 402, the method 400 may include flowing a first mixture of gases through a structure. The first mixture may include carbon dioxide and other gases. The structure may include pipes, including any pipes described herein. A portion of the pipes may be vertical. In some embodiments, the structure may include substructures to increase heat transfer from the inside of the structure to the outside of the structure. For example, the substructures may include fins.

[0047]

[0050] At block 404, the method 400 may include liquefying the carbon dioxide at a location within the structure to form liquid carbon dioxide as a result of the ambient temperature outside the structure at the location and the pressure of the mixture within the structure at the location. The liquid carbon dioxide may not be carbon dioxide dissolved in water.

[0048]

[0051] In some embodiments, the structure at that location may be in contact with the atmosphere. The ambient temperature may be less than 88°F or any temperature described herein. The atmosphere may be between 80°F and 88°F, 60°F and 80°F, 40°F and 60°F, 32°F and 40°F, 20°F and 32°F, 0°F and 20°F, or below 0°F. The temperature of the ambient air may depend on the local weather, season, and / or climate. In situations where the ambient temperature of the atmosphere exceeds 88°F, the gas mixture may be diverted to a structure equipped with an alternative cooling technology (e.g., a water mass).

[0049]

[0052] In some embodiments, the structure at the location may be in contact with water in a body of water other than an ocean. The body of water may be a freshwater body, including a lake or reservoir. The ambient temperature of the water in contact with the structure may be less than 88°F, or any temperature described herein. For structures in contact with water, the method is similar to method 100 and may incorporate features of method 100. Similarly, method 100 may incorporate features of method 400.

[0050]

[0053] In some embodiments, the structure at the location may be in contact with seawater. For example, the structure at the location may be in contact with the ocean. The ambient temperature of the water in contact with the structure may be less than 88°F, or any temperature described herein.

[0051]

[0054] In some embodiments, the structure at the location may be in contact with a refrigerated fluid. The refrigerated fluid may include any suitable refrigerant. In some embodiments, the cooling fluid may be air-cooled to a temperature below 88°F. The cooling fluid may flow outside the structure or in a separate structure within the structure. Heat transfer between the cooling fluid and the structure results in the first gas mixture being cooled to a temperature below 88°F, or any temperature described herein. In some embodiments, the method excludes the use of a refrigerated fluid or any non-natural means (e.g., chillers, cryogenic fluids) for cooling the structure below ambient temperature.

[0052]

[0055] The pressure at that location may be greater than 1,000 psi or any pressure described herein. The pressure and temperature at that location may be any temperature or pressure in the carbon dioxide phase diagram that results in liquid carbon dioxide while maintaining the other components of the gas mixture in the gas phase.

[0053]

[0056] At block 406, method 400 may include separating the liquid carbon dioxide from other gases to form separated liquid carbon dioxide. The separation of the liquid carbon dioxide may be the same as or similar to any separation described herein, including block 106 of method 100.

[0054]

[0057] At block 408, method 400 may include sequestering the separated liquid carbon dioxide. The sequestration of the liquid carbon dioxide may be the same or similar to that described herein, including method 100. In some embodiments, the liquid carbon dioxide may be sequestered underground where the ground is not under a body of water. Subterranean sequestration may include an onshore well drilled to a depth of less than 2,000 feet. As used herein, onshore may refer to a land mass or feature within such a land mass that is not covered by ocean. The onshore well may be at a depth of at least 2,000 to 2,300 feet, 2,300 to 2,500 feet, 2,500 to 2,700 feet, or 2,700 to 3,000 feet. The onshore well may have a temperature suitable for maintaining the carbon dioxide as a liquid. The liquid carbon dioxide may be removed from the knockout device and pumped to an onshore well. The pressure required to flow the liquid carbon dioxide may be partially provided by the pressure used to liquefy the carbon dioxide from the first mixture of gases.

[0055]

[0058] Some embodiments may include a system for separating carbon dioxide from flue gas, where the system does not include a body of water for cooling the gas mixture. The system may include a first pipe configured to withstand a pressure of at least 1,000 psi of the first gas mixture. The first pipe may be in fluid communication with a flue gas output of an industrial process. The first pipe is configured to maintain a temperature of the first gas mixture below 88°F. The system may include a separation chamber in fluid communication with the first pipe. A port may be connected to the separation chamber. The port may be configured to discharge the liquefied carbon dioxide separated from the first gas mixture from the separation chamber. The compressor may be configured to pressurize the first gas mixture to at least 1,000 psi.

[0056]

[0059] The first pipe may include a substructure for increasing heat transfer from the interior of the structure to the exterior of the structure. The substructure may be any substructure described herein. The ambient temperature outside the pipe may be less than 88°F or any temperature described herein. In some embodiments, the system may include a chiller or other suitable device for cooling the first pipe with a cooling fluid.

[0057]

[0060] The specific details of particular embodiments may be combined in any suitable manner without departing from the spirit and scope of the embodiments of the invention, however, other embodiments of the invention may be directed to specific embodiments of each individual aspect or to particular combinations of these individual aspects.

[0058]

[0061] The foregoing description of exemplary embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form described, and many modifications and variations are possible in light of the above teaching.

[0059]

[0062] In the foregoing description, for purposes of explanation, numerous details are set forth in order to provide an understanding of various embodiments of the present technology. However, it will be apparent to one skilled in the art that certain embodiments may be practiced without some of these details or with additional details.

[0060]

[0063] While several embodiments have been described, those skilled in the art will recognize that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the invention. Moreover, certain well-known processes and elements have not been described to avoid unnecessarily obscuring the invention. Furthermore, the details of any particular embodiment may not always be present in variations of that embodiment, and may be added to other embodiments.

[0061]

[0064] Where a range of values ​​is provided, unless the context clearly dictates otherwise, it is understood that each intervening value, to one-tenth of the lower limit, between the upper and lower limits of that range is also specifically disclosed. Each smaller range between any stated or intervening value in a stated range and any other stated or intervening value in that stated range is encompassed. The upper and lower limits of these smaller ranges may independently be included or excluded, and each range in which either, neither, or both limits are included in the smaller range, subject to any specifically excluded limit in the stated range, is also encompassed within the invention. Where a stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included.

[0062]

[0065] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, a reference to a "method" includes a plurality of such methods, a reference to a "pipe" includes a reference to one or more pipes and equivalents thereof known to those skilled in the art, and so forth. The present invention has been described in detail herein for purposes of clarity and understanding. However, it will be understood that certain changes and modifications can be practiced within the scope of the appended claims.

[0063]

[0066] All publications, patents, and patent applications cited herein are incorporated by reference in their entirety for all purposes. None is admitted to be prior art.

Claims

1. 1. A depth-based method for separating carbon dioxide from a gas mixture, comprising: flowing a first mixture of gases from the surface of a body of water to a depth within said body of water, said first mixture comprising carbon dioxide and other gases, said first mixture of gases including products of combustion of a hydrocarbon fuel, said carbon dioxide being at least 3% by mass of said first mixture of gases; compressing the first mixture of gases to a pressure of at least 1,000 psi; liquefying the carbon dioxide to form liquid carbon dioxide at the depth within the body of water, wherein the liquid carbon dioxide is not carbon dioxide dissolved in water; and separating the liquid carbon dioxide from the other gases in a separation chamber within the body of water; venting the liquid carbon dioxide from the separation chamber through a knockout; using a pump to flow the liquid carbon dioxide from the knockout through the body of water; flowing the second mixture of the other gases upwardly to the surface; A method comprising:

2. The method of claim 1 , wherein the first mixture comprises molecular nitrogen.

3. 10. The method of claim 1, wherein the pressure of the first mixture is at least 1,050 psi at the depth within the body of water.

4. 4. The method of claim 3, wherein the pressure is the result of (1) compression of the first mixture at the surface and (2) the weight of the first mixture above the depth.

5. 4. The method of claim 3, wherein the temperature of the first mixture at the depth within the body of water is less than 88°F.

6. 10. The method of claim 1, wherein the pressure of the first mixture is at least 1,300 psi at the depth within the body of water.

7. 10. The method of claim 1, further comprising contacting the liquid carbon dioxide with the water within the body of water without dissolving the liquid carbon dioxide in the water.

8. The method of claim 1 further comprising the step of releasing the second mixture into the atmosphere.

9. The method of claim 1 , further comprising flowing carbon dioxide separated from the other gases onto the surface of the body of water.

10. flowing the carbon dioxide separated from the other gases to land; geographically isolating the liquid carbon dioxide; The method of claim 1 further comprising:

11. the water body is an ocean, the depth is a first depth; The method comprises: using the pump to pump the liquid carbon dioxide to the second depth so that the density of the liquid carbon dioxide is greater than the density of seawater at the second depth; releasing the liquid carbon dioxide into the seawater; flowing the liquid carbon dioxide to the bottom of the ocean as a result of the density of the liquid carbon dioxide relative to the density of the seawater, thereby sequestering carbon dioxide; The method of claim 1 further comprising:

12. 12. The method of claim 11, wherein the second depth is at least 7,000 feet.

13. 12. The method of claim 11, further comprising contacting the liquid carbon dioxide with seawater at the second depth to increase the density of the liquid carbon dioxide.

14. the water body is an ocean, the depth is a first depth; The method comprises: flowing the liquid carbon dioxide to a second depth of at least 7,000 feet to increase the density of the liquid carbon dioxide above a density of seawater at the second depth; releasing the liquid carbon dioxide into sediment above the ocean floor or into sediment or rocks below the ocean floor, thereby sequestering the carbon dioxide; The method of claim 1 further comprising:

15. 10. The method of claim 1, wherein the step of separating the liquid carbon dioxide from the other gases does not include using an absorbent, an adsorbent, or a membrane.

16. 1. A method for separating carbon dioxide from a gas mixture, comprising: flowing a first mixture of gases through the structure, the first mixture including carbon dioxide and other gases; the first mixture of gases comprises products from burning a hydrocarbon fuel; the carbon dioxide is at least 3% by mass of the first mixture of gases; the structure being in contact with water within a body of water; compressing the first mixture of gases to a pressure of at least 1,000 psi; liquefying the carbon dioxide at a location within the structure to form liquid carbon dioxide as a result of an ambient temperature outside the structure at the location and a pressure of the first mixture within the structure at the location, wherein the liquid carbon dioxide is not carbon dioxide dissolved in water; separating the liquid carbon dioxide from other gases to form separated liquid carbon dioxide in a separation chamber within the body of water; Discharging the separated liquid carbon dioxide from the separation chamber through a knockout; using a pump to pump the separated liquid carbon dioxide through the body of water; sequestering the separated liquid carbon dioxide; A method comprising:

17. the structure includes a substructure for increasing heat transfer from the inside of the structure to the outside of the structure; 17. The method of claim 16.

18. the water body is a freshwater body, the ambient temperature is less than 88°F; 17. The method of claim 16.

19. At said position, said structure is in contact with seawater; the ambient temperature is less than 88°F; 17. The method of claim 16.

20. At said location, said structure is in contact with a cooling fluid; the cooling fluid has a temperature of less than 88°F; 17. The method of claim 16.

21. 17. The method of claim 16, wherein the pressure is greater than 1,050 psi.

22. producing a first mixture of said gases in a process plant; flowing the first mixture of gases from the process plant through a pipe to the surface of the body of water; The method of claim 1 , wherein flowing the first mixture of gases from the surface to the depth comprises flowing the first mixture of gases through the pipe.

23. 17. The method of claim 16, wherein the structure includes a flexible or movable component for transmitting pressure from the body of water at a first depth to the first mixture of gases.

24. The method of claim 16, wherein the first mixture comprises molecular nitrogen.

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