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 of U.S. Provisional Patent Application No. 63 / 036,264, filed on June 8, 2020, the entire disclosure of which is incorporated herein by reference.

Background Art

[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 carbon dioxide, and depositing the carbon dioxide in a reservoir such that it cannot re - enter or enter the atmosphere. Separating carbon dioxide from other flue gases in an industrial process is difficult. Geographic sequestration of carbon dioxide on Earth is also difficult. Thus, improvements in separating carbon dioxide from flue gases and sequestering 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 body of water (e.g., an ocean or a body of fresh water) or 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 the liquid carbon dioxide. Liquid carbon dioxide is inert and can be discharged into the ocean at a depth with sufficient pressure without dissolving in seawater and acidifying the ocean. Liquid carbon dioxide may further be densified relative to seawater. Then, the liquid carbon dioxide sinks to the ocean floor or is injected into ocean floor sediments or rocks and is sequestered in an inert state for a long time.

[0004]

[0004] Embodiments may include a method for separating carbon dioxide from other gases using the depth of the ocean. The method may include the step of flowing a first mixture of gases to the depth of the ocean. The first mixture may include carbon dioxide and other gases. The method may also include the step of 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 through a pipe in the ocean. The carbon dioxide may liquefy as a result of the pressure in the pipe at that depth and the temperature effect of the ocean in the pipe. The liquid carbon dioxide may not mix with seawater in the pipe. Liquid carbon dioxide is not carbon dioxide dissolved in water. The method may further include the step of separating the liquid carbon dioxide from other gases. Furthermore, the method may include the step of 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 a water mass to a first depth within the water mass. The first depth may be at least 10 feet below the surface. The system may also include a second pipe configured to deliver a second gas mixture from the first depth of the water mass to the surface of the water mass. 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 liquefied carbon dioxide separated from the first gas mixture from the separation chamber. Furthermore, the system may include a compressor configured to inject the first gas mixture through the first pipe from the surface of the water mass to a first depth.

[0006]

[0006] Embodiments may include a method for separating carbon dioxide from a gas mixture. The method may include the step of flowing a first mixture of gases through a structure, the first mixture containing carbon dioxide and other gases. The method may also include the step of liquefying the carbon dioxide at a location within the structure so 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 is not carbon dioxide dissolved in water. The method may further include the step of separating the liquid carbon dioxide from the other gases to form the separated liquid carbon dioxide. Furthermore, the method may include the step of sequestering the separated liquid carbon dioxide.

[0007]

[0007] A better understanding of the properties and advantages of embodiments of the present invention can be obtained by referring to the following detailed description and accompanying drawings. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows a method, according to an embodiment of the present invention, that utilizes ocean depth to separate carbon dioxide from flue gas. [Figure 2] This figure shows a system for separating carbon dioxide from flue gas according to an embodiment of the present invention. [Figure 3] This figure shows 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] This figure shows a method for sequestering carbon dioxide from flue gas according to an embodiment of the present invention. [Modes for carrying out the invention]

[0009]

[0012] Carbon dioxide, a greenhouse gas, is a byproduct of industrial processes, including refineries, fossil fuel power plants, chemical plants, and any other processes involving hydrocarbon combustion. The sequestration of carbon dioxide is difficult. Carbon dioxide is produced together with other flue gases and should be separated from them before sequestration. Flue gases may contain carbon dioxide, nitrogen, oxygen, and water vapor. Nitrogen can make up about 40–80% of flue gas. Carbon dioxide can make up about 3–50% of flue gas. Water vapor can be removed from flue gas. Nitrogen oxides (NOx) x ), sulfur oxides (SO x Carbon dioxide, carbon monoxide, and particulate matter can constitute a small proportion of flue gas. Separating carbon dioxide from other flue gases can be an expensive process.

[0010]

[0013] Conventional carbon dioxide sequestration methods can also be difficult. Storing carbon dioxide as a compressed gas or liquid is preferable to storing it as an uncompressed gas because the volume occupied by the compressed gas or liquid is smaller. One method of carbon dioxide sequestration involves injecting it deep into the earth's wells. The pressure within the injection well increases with depth, which is favorable for 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, the temperature can increase by about 1.7°F for every 100 feet of depth. Therefore, sequestration at 6,000 feet below the surface would result in an increase of about 100°F.

[0011]

[0014] The ocean provides an environment where, as depth increases, the temperature does not rise, but rather decreases or remains stable within the range of 33°F to 63°F. Furthermore, the decrease in temperature is accompanied by an increase in pressure, which is not normally expected. Within a pipe in the ocean, pressure can accumulate at the depths within the pipe while utilizing 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 the pipe. As used herein, “ocean” is not limited to geographically named oceans (e.g., Atlantic, Pacific). The ocean includes any part of the saltwater mass that covers nearly 75% of the Earth. Non-ocean environments, including freshwater masses of ambient temperature water or air, can be used to cool the pipe while liquefying carbon dioxide.

[0012]

[0015] Furthermore, the unique physical properties of carbon dioxide make carbon dioxide injection even more beneficial. Figure 3 shows the phase diagram of carbon dioxide. Pressure is shown in MPa on the y-axis and temperature in °C on the x-axis. Pressure can be converted to psi, temperature to Fahrenheit, and vice versa. The phase diagram of carbon dioxide shows that at the pressures and temperatures available at ocean depths, carbon dioxide is liquid. 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 liquid. At these pressures and temperatures, a typical flue gas remains in the gaseous phase.

[0013]

[0016] At ocean depths, including ocean depths within the pipe separated from seawater, temperatures below 88°F and pressures exceeding 1,050 psi can be achieved. As a result of the properties of carbon dioxide and flue gas, the carbon dioxide becomes liquid, while the remainder of the flue gas remains gaseous. Separating liquid from gas is easier than separating gas from other gases. Carbon dioxide can condense and essentially leach out of the gas mixture. Liquid carbon dioxide, due to its high density, can move to the bottom of the container and can be removed from the flue gas. Separating liquid carbon dioxide from other gases can be a continuous process within the pipe. The pressure required to liquefy carbon dioxide can also drive the sequestration of the separated carbon dioxide. For example, liquid carbon dioxide cannot have its pressure reduced (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 it may be geologically sequestrated. The remaining flue gas, which has already been treated to meet environmental standards for emissions into the atmosphere from the process plant, can be released into the atmosphere.

[0015]

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

[0016]

[0019] Liquid carbon dioxide also possesses another property that improves isolation techniques in the ocean. Liquid carbon dioxide can increase its density under higher pressures. The density of liquid carbon dioxide can be higher than that of seawater at the same pressure. By placing liquid carbon dioxide at a depth of approximately 9,000 feet (2,473 m), a pressure of approximately 4,000 psi makes the liquid carbon dioxide denser than seawater. The pressure increase of approximately 1,050 psi and 88°F to 4,000 psi for liquid carbon dioxide can be provided by pumps or other suitable devices. When liquid carbon dioxide is released into the ocean, it may sink to the ocean floor. The carbon dioxide can be sent to deep trenches that provide a large reservoir for isolation, or the carbon dioxide can be pumped into marine sediments or oceanic seabed rocks for permanent isolation. However, if the liquid carbon dioxide is not at sufficiently high pressure and sufficiently low temperature, it may 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 returns to gaseous carbon dioxide, which can then dissolve in seawater or be released into the atmosphere.

[0017]

[0020] The movement of liquid carbon dioxide from a first depth where it liquefies to a second depth where it is denser than seawater can be achieved by pumping rather than by compressor, as is typical for the movement of gaseous carbon dioxide. Pumping liquids is generally easier and cheaper than compressing gases. Furthermore, a column of liquid carbon dioxide adds additional pressure to the liquid carbon dioxide below the column. The pressure from the column also reduces the amount of pressure that needs to be added 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 may be provided by the seawater itself. For example, in some embodiments, seawater can be separated from the gas mixture by a movable partition (e.g., a piston) that transmits 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 the compression of the gas at or near the ocean surface, and not due to the 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 in pipelines (e.g., A. Hart et al., "Cryogenic CO2 capture in natural gas," Energy Procedia1 (2009)). Liquefying only some of the gases in a gas mixture can make it difficult to transport the gases together with the liquids. This problem, which is to be avoided in conventional processes, is instead addressed by separating and sequestering carbon dioxide. In embodiments of the present invention, carbon dioxide is liquefied during gas transport.

[0020]

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

[0021]

[0024] In block 104, the method may include the step of liquefying carbon dioxide as a result of a 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 the pipe. The carbon dioxide is not carbon dioxide dissolved 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] Carbon dioxide can be liquefied as a result of the pressure and temperature at that depth. The pressure can be the result of the compression of the gas within 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 a preferred embodiment, the pressure can 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 can be caused by the seawater itself. The pressure can be caused by a column of seawater above the gas (e.g., acting as a piston). The temperature may be less than 88°F. For example, the temperature may be 85°F - 88°F, 80°F - 85°F, 70°F - 80°F, 60°F - 70°F, 50°F - 60°F, 40°F - 50°F, 32°F - 40°F, or 20°F - 32°F. In some embodiments, the pressure may be 600 - 650 psi. The temperature can be the result of the temperature of the seawater at that depth. Other cooling or refrigeration may not be used except for heat transfer from seawater cooled at a lower depth. In some embodiments, the cooling may be included as part of a compression system. The temperature of the compressed gas mixture is brought to the temperature before compression. Such cooling can use a radiator to lower the temperature from about 125°F after compression.

[0023]

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

[0024]

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

[0025]

[0028] In block 108, the method may include the step of flowing a 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 buoyancy. The method may include the step of discharging the second mixture into the atmosphere. The flue gas in the second mixture may already be at a concentration that is acceptable by environmental regulations including those set by the U.S. Environmental Protection Agency and / or other regulatory agencies. In some embodiments, the second mixture can be flowed upward using a compressor.

[0026]

[0029] The method may include the step of flowing the carbon dioxide separated from the other gases to the ocean surface. The carbon dioxide starts as a liquid and then becomes a gas as it approaches the surface. In some embodiments, the separated carbon dioxide may be flowed to land. The carbon dioxide may be geographically isolated. In some embodiments, the carbon dioxide can be used in industrial processes such as the manufacture of carbonate bricks, cement, fuel, or other products.

[0027]

[0030] The method may include a step of flowing liquid carbon dioxide to a second depth. The second depth may be greater 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. Since the liquid is separated 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 and second depths can be applied via a pump or other suitable device. The pressure may increase monotonically from the first depth to the second depth. Thus, the pressure used to liquefy the carbon dioxide may contribute to the pressure used to sequestrate the liquid carbon dioxide.

[0028]

[0031] At a second depth, the density of liquid carbon dioxide may be higher than that of seawater at or near the same depth. The second depth allows for a higher density of liquid carbon dioxide than that of seawater with respect to the temperature, salinity, and density of seawater at a particular location in the ocean. The method may include a step of bringing liquid carbon dioxide into contact with water in the ocean without dissolving it in water. After contact with seawater, the liquid carbon dioxide may form hydrates, and carbon dioxide may be released from the hydrates and not dissolve in water. The method may include a step of releasing the liquid carbon dioxide into seawater. As a result of the higher density of liquid carbon dioxide than that of seawater, the liquid carbon dioxide can flow to the bottom of the ocean. The carbon dioxide can then be sequestered as 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 may be released directly into sediments, rocks, or other formations that make up the seabed or exist beneath the seabed. Deep-sea sediments can have thicknesses of 1 to 4,000 feet. Liquid carbon dioxide may be released to any depth within the sediment. Liquid carbon dioxide may be pumped into shallow marine sediments where carbon dioxide forms hydrates, or it may be held in place by gravity, density differences with seawater, and / or pore pressure.

[0030]

[0033] Carbon dioxide can be released into seawater at a rate of 100,000 to 100 million metric tons per year or more. Flue gas can be released into the atmosphere at a rate 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 that may be present on or beneath the seabed. The liquid carbon dioxide can 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 can be sequestered in mineral form rather than in liquid or gaseous form.

[0032]

[0035] Figure 2 shows a system 200 for separating carbon dioxide from flue gas. System 200 may resemble an oil platform when viewed at sea level. System 200 can be used in any of the manner described herein. The system may include a first pipe 202 configured to deliver a first gas from the surface 206 of a water mass to a first depth 210 within the water mass. The water mass may be an ocean or a freshwater mass. For example, a freshwater mass 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 suitable material. The first pipe 202 may be vertical at the point where carbon dioxide begins to liquefy.

[0033]

[0036] The pipe may have a rated burst strength for any of the pressures described herein. In some embodiments, the pipe may have a rated burst strength for the pressure difference between the pressure inside the pipe and the pressure outside the pipe. The pipe may have the advantage that it does not need to be constructed to withstand the full force of the water mass to its depth, as the pressure inside the pipe partially counteracts the force from the water mass outside the pipe. In some embodiments, the pipe may have a burst strength rating of at least 1,000 psi, including 1,440 psi. The pipe may have a diameter of 0.5 to 1 inch, 1 to 5 inches, 5 to 8 inches, 8 to 10 inches, 10 to 12 inches, 12 to 15 inches, 15 to 20 inches, 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 a second gas mixture from a first depth 210 in the water mass to the surface 206 of the water mass. The second pipe 214 may be in fluid communication with the first pipe 202. The second pipe 214 may be the same as or different in size and / or material as the first pipe 202.

[0035]

[0038] The system 200 may include a separation chamber 218. The separation chamber 218 may be in fluid communication with the first pipe 202 and the second pipe 214. In some embodiments, the separation chamber 218 may be configured to transfer pressure from a water mass at a first depth 210 to the first gas mixture. For example, in some embodiments, the separation chamber 218 may allow seawater to enter. The first pipe 202 may allow seawater to enter, and the pressure caused by the column of seawater may condense carbon dioxide. The seawater may be pumped into the first pipe 202. In some embodiments, the separation chamber 218 may be the portion of the pipe where 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 within the pipe. For example, the pipe may be coiled vertically. The knockout can discharge fluid from the lower spot of the bend and remove gas from the upper part of the bend. The knockout device may include increasing the diameter of the pipe to reduce the flow velocity, allowing time for the liquid or heavier components to separate from the flow by gravity. The knockout device may include an expansion region. The knockout may have a slightly larger pipe section. The slightly larger pipe section allows for gas expansion and separation of the liquid from the gas flow.

[0037]

[0040] In some embodiments, the separation chamber 218 may include flexible or movable components that allow the pressure of seawater to be transmitted to the first gas mixture within the separation chamber 218. The flexible components may be made of flexible material. The pressure of seawater can press against the flexible components, which then press against the first gas mixture at a pressure of 1,050 psi or more.

[0038]

[0041] The system 200 may include a port (222a or 222b). Port 222a or port 222b may be connected to a separation chamber 218. Port 222a or 222b may be configured to discharge liquefied carbon dioxide separated from the first gas mixture from the separation chamber 218. Port 222a or port 222b may be located at the bottom of the separation chamber 218 to allow for the separation of higher-density liquefied carbon dioxide from the first gas mixture.

[0039]

[0042] System 200 may include a compressor 226. The compressor 226 may be configured to inject a first gas mixture from the surface 206 of the water mass through a first pipe 202 to a first depth 210 in the water mass. 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 pressurize the first gas mixture to the full target pressure because the hydrostatic pressure of the gas column above the first depth 210 contributes to the pressure at the first depth.

[0040]

[0043] The system 200 may further include a pump 234. The pump 234 may be in fluid communication with port 222a. The pump 234 may be configured to deliver liquefied carbon dioxide to a second depth 238 of 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.

[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 liquefied carbon dioxide into seawater at a second depth 238. The third pipe 242 may be positioned so that the liquefied carbon dioxide settles on the seabed 244. Liquefied carbon dioxide is inert in seawater. In some embodiments, the third pipe 242 does not need to transport the liquefied carbon dioxide below the surface of the seabed. In other embodiments, the third pipe 242 can transport the liquefied carbon dioxide to seabed sediment 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 seabed sediment or rock. The steel casing may be cemented in place. The casing and surrounding cement may be perforated to allow the liquid carbon dioxide to enter the sediment or rock.

[0042]

[0045] The system 200 may further include a fourth pipe 246. The fourth pipe 246 may be connected to port 222b. The fourth pipe 246 may be configured to deliver carbon dioxide to the surface 206 of the water mass. A pump may flow liquefied carbon dioxide into the fourth pipe 246. In some embodiments, the liquefied carbon dioxide can return to gas as the pressure decreases. The carbon dioxide gas can then rise up the fourth pipe 246. The fourth pipe 246 may deliver carbon dioxide to land 250. The carbon dioxide delivered to land may be geographically sequestrated or used as a raw material for other processes.

[0043]

[0046] In some embodiments, if a fourth pipe 246 is included, the third pipe 242 may be omitted. In other embodiments, if a third pipe 242 is included, the fourth pipe 246 may be omitted.

[0044]

[0047] System 200 may exclude any heat transfer devices, including chillers or refrigerants or other fluids, which are not air or water in a mass of water. For example, System 200 may not include unnatural recirculating fluids that heat up in contact with pipes and then cool down in another area.

[0045]

[0048] Figure 4 shows a method 400 for separating carbon dioxide from a gas mixture. Method 400 is not limited to using ocean depth to generate the pressure and / or temperature required to liquefy the carbon dioxide. Method 400 may also include a step of using a water mass within a single landmass. For example, the water mass may be a lake or reservoir. Method 400 is also not limited to including a water mass for cooling or pressurizing the gas mixture. Method 400 may include a step of 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 also include using all or aspects of System 200.

[0046]

[0049] In block 402, method 400 may include the step of 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. Parts of the pipes may be vertical. In some embodiments, the structure may include a substructure to increase heat transfer from the inside to the outside of the structure. For example, the substructure may include fins.

[0047]

[0050] In block 404, method 400 may include the step of liquefying carbon dioxide at a location such that it forms liquid carbon dioxide as a result of the ambient temperature outside the structure at the location within the structure and the pressure of the mixture inside the structure at the location. The liquid carbon dioxide does not have to 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 of the temperatures described herein. The atmosphere may be 80°F–88°F, 60°F–80°F, 40°F–60°F, 32°F–40°F, 20°F–32°F, 0°F–20°F, or less than 0°F. The ambient air temperature 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 technique (e.g., a water mass).

[0049]

[0052] In some embodiments, the structure at that location may be in contact with water in a water mass other than the ocean. The water mass may be a freshwater water mass, 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 as described herein. For structures in contact with water, the method is similar to that of 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 that location may be in contact with seawater. For example, the structure at that 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 as described herein.

[0051]

[0054] In some embodiments, the structure at that location may be in contact with a refrigerating fluid. The refrigerating 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 within a separate structure inside the structure. Heat transfer between the cooling fluid and the structure will result in the first gas mixture being cooled to a temperature below 88°F, or any temperature as described herein. In some embodiments, the method excludes the use of a refrigerating 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 specified herein. The pressure and temperature at that location may be any temperature or pressure in the carbon dioxide phase diagram that yields liquid carbon dioxide while keeping the other components of the gas mixture in the gas phase.

[0053]

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

[0054]

[0057] In block 408, method 400 may include a step of sequestrating the separated liquid carbon dioxide. The sequestration of liquid carbon dioxide may be the same as or similar to those described herein, including method 100. In some embodiments, the liquid carbon dioxide may be sequestrated underground where the ground is not beneath a mass of water. The underground sequestration may include onshore wells drilled to less than 2,000 feet. As used herein, onshore can mean a landmass not covered by an ocean or features within such a landmass. The onshore wells may be at depths of at least 2,000–2,300 feet, 2,300–2,500 feet, 2,500–2,700 feet, or 2,700–3,000 feet. The onshore wells 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 fed into the onshore well. The pressure required to flow the liquid carbon dioxide may be partially supplied by the pressure for liquefying the carbon dioxide from the first mixture of gases.

[0055]

[0058] Some embodiments may include a system for separating carbon dioxide from flue gas, the system not including a water mass for cooling the gas mixture. The system may include a first pipe configured to withstand a pressure of at least 1,000 psi for the first gas mixture. The first pipe may be in fluid communication with the flue gas output of an industrial process. The first pipe is configured to maintain the 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. A 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 to increase heat transfer from the inside to the outside 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] Certain details of a particular embodiment can be combined in any suitable manner without departing from the spirit and scope of the embodiments of the present invention. However, other embodiments of the present invention may cover specific embodiments relating to each individual aspect, or specific combinations of these individual aspects.

[0058]

[0061] The above description of exemplary embodiments of the present invention is presented for illustrative and explanatory purposes only. It is not intended to be exhaustive or to limit the invention to the exact forms described, and many modifications and variations are possible in light of the above teachings.

[0059]

[0062] The foregoing description includes many details to provide an understanding of various embodiments of the Art for illustrative purposes. However, it will be apparent to those skilled in the art that certain embodiments may be carried out without some of these details or with additional details.

[0060]

[0063] While several embodiments have been described, those skilled in the art will understand that various modifications, alternative structures, and equivalents can be used without departing from the spirit of the invention. Furthermore, to avoid unnecessarily obscuring the invention, some well-known processes and elements have not been described. Moreover, details of any particular embodiment are not necessarily always 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 indicates otherwise, it is understood that each intermediate value up 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 value or intermediate value within the stated range and any other stated value or intermediate value within that stated range is encompassed. The upper and lower limits of these narrower ranges may be independently included in or excluded from the range, and each range in which any, neither, or both of the limits are included in a smaller range, subject to any specifically excluded limits within the stated range, is also encompassed within the invention. Where a stated range includes one or both limits, the range excluding one or both of those included limits is also included.

[0062]

[0065] As used herein and in the appended claims, the singular forms “a,” “an,” and “the” refer to a plurality of objects unless the context clearly indicates otherwise. Thus, for example, a reference to “method” includes a plurality of such methods, and a reference to “pipe” includes a reference to one or more pipes and their equivalents known to those skilled in the art, etc. Hereinafter, the invention has been described in detail for the purposes of clarification and understanding. However, it will be understood that certain changes and modifications may be made within the scope of the appended claims.

[0063]

[0066] All publications, patents, and patent applications cited herein are incorporated herein by whole or in whole for all purposes. There is no prior art to be found.

Claims

1. 1. A method of using depth to separate carbon dioxide from a gas mixture, comprising: flowing a first mixture of gases from a 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 being a product of burning 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, the liquid carbon dioxide being not carbon dioxide dissolved in water; 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 pump the liquid carbon dioxide from the knockout through the body of water; flowing a second mixture of the other gas upwardly to the surface; The method includes:

2. The method of claim 1 , wherein the other gases include products from combusting the hydrocarbon fuel or 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 a 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 a 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 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: pumping the liquid carbon dioxide to the second depth using the pump to increase the density of the liquid carbon dioxide above a 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. 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; discharging 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 the steps of: flowing a first mixture of gases through the structure, the first mixture including carbon dioxide, molecular nitrogen and other gases; said carbon dioxide and said other gases are products of 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 the 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; Venting the separated liquid carbon dioxide from the separation chamber through a knockout; pumping the separated liquid carbon dioxide through the body of water using a pump; sequestering the separated liquid carbon dioxide; The method includes:

17. the structure includes a substructure for increasing heat transfer from an interior of the structure to an exterior 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 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. 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 gas.

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