Nanobubbles and gas-liquid mixtures for enhanced carbon dioxide sequestration

Abstract

To provide a process for the mineralization of CO2 in mafic and ultramafic rocks or storage of CO2 in geological formations.SOLUTION: The present invention discloses a novel process for the mineralization of CO2 in mafic and ultramafic rocks or storage of CO2 in geological formations through the generation and use of nano-sized CO2 bubbles injected into a fluid-mixture.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the benefit of priority of U.S. Provisional Patent Application No. 63 / 303,060, filed Jan. 26, 2022, which is hereby incorporated by reference in its entirety.

[0002] The present invention relates to environmental solutions that rely on CO2 storage and enhanced CO2 mineralization in mafic and ultramafic rocks. More specifically, the present invention relates to an enhanced method for CO2 storage and mineralization by forming nanobubbles of CO2 gas in a fluid mixture injected through a borehole into a formation for mineralization and / or storage.

Background Art

[0003] The competition to enhance and increase the removal of CO2 from the environment has led to several innovations in this field, from rapid removal from the atmosphere to removal from underground storage and from industrial applications. Innovations in various means of measuring the proportion and amount of mineralized and stored CO2 are also relevant fields.

[0004] The ocean absorbs CO2 from the atmosphere, absorbing approximately one-third of the CO2 emitted since the Industrial Revolution due to fossil fuel combustion, deforestation, and cement production (Sabine et al. 2004). While this is beneficial in limiting the rise in atmospheric CO2 concentration and thus the resulting global warming, it has direct impacts on ocean chemistry. Ocean acidification manifests as a decrease in seawater pH and carbonate saturation due to the increase in atmospheric CO2 concentration. There are also indirect and potentially harmful biological and ecological impacts from chemical changes currently occurring in the ocean and those predicted for the future (Barker et al. 2012). Enhanced CO2 mineralization is a recognized method for storing and / or mineralizing CO2 underground or above ground. There is a need for innovative processes for CO2 gas-liquid injection for underground storage and / or mineralization that offer much higher mass transfer ratios and buffering capacity compared to conventional techniques, and that can thereby increase the dissolution rate and concentration of CO2 in fluid mixtures.

[0005] This disclosure provides a method for injecting and dissolving nanobubbles of CO2 gas onto a surface (e.g., on the ground) in a storage tank or injection pipe. This method has proven to be more efficient compared to conventional sparging techniques, which often result in micron-level gas bubble sizes. Micron-sized bubbles have proven difficult to handle during surface sparging due to their larger size, and are more likely to coalesce while being injected into the fluid flow. Coalitioning will then result in the formation of increasingly larger bubble sizes. These coalesced, larger bubble sizes will rise more quickly and rapidly to the surface of the injected fluid. Once on the fluid surface, these bubbles will burst due to the buoyancy effect, releasing CO2 back into the atmosphere and resulting in reduced efficiency of CO2 mineralization. This makes it extremely difficult to control when injecting large amounts of CO2-rich fluid to greater depths due to the increasing hydrostatic pressure. However, when using the proposed CO2 gas-liquid injection process for underground CO2 storage and / or mineralization, the effects of coalescence and buoyancy are reduced when CO2 is injected as nanobubbles and dissolved in a pressurized fluid mixture stream.

[0006] This process offers several advantages over existing technologies, including higher mass transfer rates, thermodynamically metastable bubbles that can remain suspended in the fluid for extended periods, higher buffer capacity, higher CO2 mineralization or storage volume, a shallower CO2 injection depth, and less fluid to be injected. [Overview of the project]

[0007] One embodiment of the present disclosure involves drilling vertical and / or horizontal wells in a mafic or ultramafic rock layer and injecting water rich in CO2 nanobubbles that react with the rock to form carbonate rock, thereby permanently trapping the CO2.

[0008] Another embodiment of the present disclosure is a method for reducing the amount of fluid required to achieve CO2 mineralization. By utilizing nanobubbles, higher CO2 concentrations can be achieved in the same volume of fluid, resulting in enhanced efficiency due to increased mass transfer properties. This also means that the injection depth can be made shallower, making CO2 storage / mineralization more feasible.

[0009] The drawings illustrate embodiments of the disclosed subject matter for illustrative purposes of the present invention. However, it should be understood that this application is not limited to the exact arrangements and means shown in the following drawings. [Brief explanation of the drawing]

[0010] [Figure 1] This is a process flow diagram of an embodiment of the disclosed subject matter. [Figure 2] This is a schematic diagram of an embodiment of the disclosed subject matter. [Figure 3] This is a schematic diagram of an embodiment of the disclosed subject matter. [Figure 4] This is a schematic diagram of an embodiment of the disclosed subject matter. [Figure 5] This is a schematic diagram of an embodiment of the disclosed subject matter. [Modes for carrying out the invention]

[0011] The object, features, and advantages of the present invention will become apparent from the following modes for carrying out the invention. However, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from the modes for carrying out the invention, it should be understood that the modes for carrying out the invention and specific examples are given only by illustrative means, while illustrating specific embodiments of the invention.

[0012] In this specification, the use of the terms "a" or "an" in conjunction with the term "including" in the claims and / or specification may mean "one," but it also coincides with the meanings of "one or more," "at least one," and "one or more." The term "about" generally means plus or minus 5% of the stated value. The use of the term "or" in the claims is used to mean "and / or" unless it is explicitly indicated that it refers only to the options or the options are mutually exclusive, but this disclosure supports the definition that refers only to the options and "and / or."

[0013] Referring here to Figure 1, the described embodiment includes a process for dispersing CO2 gas in a fluid for the purpose of forming nanobubbles. Exemplary laboratory and / or outdoor experimental scale processes can utilize a fluid mixture originally stored on a surface and pumped into an injection well at a pressure of about 10 bar, a CO2 injection material flow rate of about 0.46 g / s, an H2O injection flow rate of about 0.15 l / s, and an injection depth of about 110 mbgl. Other conditions such as a pressure of 10 to 40 bar, preferably 15 to 30 bar, a CO2 injection material flow rate of 0.05 to 5 g / s, preferably 0.25 to 2.5 g / s or 0.5 to 1.5 g / s, an H2O injection flow rate of 0.5 to 10 l / s, 1 to 5 l / s or about 2.5 l / s, and an injection depth of 25 to 1000 mbgl, 50 to 500 mbgl or about 100 mbgl may also be used. Pressurized CO2 (approximately 50 bar, preferably 5–1000 bar, 10–500 bar, or 100–25 bar) is regulated through a manifold and a set of material flow controllers before injection into the pressurized fluid mixture flow. The calculated material flow setpoint controls the overall CO2 injection process in relation to the fluid mixture flow rate. For example, to inject 1 metric ton of CO2 per day in a 900 mbgl zone, a fluid mixture flow rate of 18 l / min and a pressure of 40 bar is preferably used. These values ​​(e.g., pressure, CO2 injection material flow rate, H2O injection flow rate, injection depth, material flow rate setpoint, and 18 fluid mixture flow rates) are exemplary and can be scaled up for commercial-scale processes by multiples of 10, 100, 1,000, 10,000 and / or 100,000.

[0014] Referring to Figure 2, several embodiments of the disclosed invention include a water loop system having a storage module (210), a carbon dioxide injection module and injection well (220), a mafic or ultramafic layer schematically illustrated herein as a horizontal layer (P), and an observation well module (230) for monitoring and controlling the carbon dioxide reaction. The process begins by identifying a suitable location where the rock layer is preferably at least 0.1 km thick or at least 0.5 km thick. An injection borehole is drilled in this rock layer. The borehole is preferably at least 0.5 km deep and up to 1.8 km deep, with preferred depths being 0.8–1.2 km deep or about 1 km mbgl. An observation borehole is drilled alongside the injection borehole using a hydraulic connection between the two holes. An engineered well casing (preferably steel or concrete) is fitted into the injection borehole, which is drilled in a target area for mineralization in the formation (see Figure 3 and further text below for further details). In the continuous injection process, water is first pumped from an observation borehole or another source to a buffer storage tank on the surface. The buffer tank is installed to receive water from different sources, such as groundwater resources, seawater, or treated water. Then, ambient temperature water is pumped under pressure through the injection pipeline to the injection borehole wellhead using a set of booster pumps. The layer temperature at a depth of 1 km is approximately 60-80°C. Pumping water into this layer also helps control the temperature of the target zone, resulting in better control of the reaction rate.

[0015] Referring to Figure 4, the embodiment describes a nanobubble generator. The generator comprises a pump (1), an inlet (2), an air pressure gauge (3), an air connection (4), an air flow meter (5), a pump pressure gauge (6), a discharge flow valve (7), and a starter (8). The bubble generator is typically 6 to 45 m 3It operates at a flow rate of / hr and a maximum liquid pressure of 1.5 bar. Typical operating conditions include a temperature of 5–60°C, preferably 30–40°C, and a CO2 pressure of 1–8.5 bar, preferably 3–4 bar.

[0016] Another embodiment of the present disclosure is a programmable logic controller that automates a CO2 injection process by controlling a CO2 mass flow controller, a fluid mixture booster pump, and their respective valves to enhance the CO2 mass transfer ratio into the fluid mixture flow and achieve a maximum buffer capacity per unit volume.

[0017] In one embodiment of this disclosure, the proposed gas-liquid injection process of the present invention dissolves bubbles with an average diameter of 10-900 nm, 25-750 nm, or 50-500 nm, preferably 60-550 nm, into a fluid mixture. The bubbles have neutral buoyancy and can remain suspended in the fluid for a period of 15 days to a maximum of 3 months without rising to the surface. This allows for shallower injection, a higher gas transfer ratio, and an increased CO2 concentration in the fluid. Studies have shown that this is 11 times better than conventional bubble sizes, e.g., bubbles with an average diameter in the micron range, up to 0.35 h. -1 This shows an enhanced mass transfer coefficient.

[0018] In a further preferred embodiment of the present disclosure, CO2 gas-liquid injection relies on a nanobubble membrane generator that produces billions of CO2 bubbles. Referring to Figure 5, the average count at 2 barG is 3.66 × 10⁶ per ml. 8 These are air bubbles, and at 3 barG, the average count is 9.1 × 10⁶ per ml. 8 These are air bubbles, and at 4 barG, the average count is 9.71 × 10⁶ per ml. 8They were bubbles. The nanoparticle analyzer is used to measure the average bubble number and size through Brownian motion estimation. The analyzer incorporates three lasers of different wavelengths and a color camera for visualizing the displacement of bubbles from 10 nm to 15 microns. The displacement is interpreted as Brownian motion or, for larger bubbles, as settling or creaming, and can thus be easily converted to the particle size for each bubble, enabling high-resolution size distribution analysis. The same technique is also used to measure the average bubble number and density for a specific volume of fluid. The analyzer uses a cuvette containing a black insert that houses a magnetic stirring bar to keep larger bubbles suspended and mix the bubbles between videos. Samples are continuously collected from the nanobubble membrane generator and transferred directly to the system cuvette without further preparation for measuring the average bubble size and density.

[0019] Next, the nanobubbles are injected into the fluid mixture at high pressure (above 25 bar). The buoyancy of the generated nanobubbles is not significant, allowing for an extended suspension in the fluid that results in increased mass transfer within the fluid. Nanobubbles are thermodynamically metastable and allow for a high residence time in the fluid for up to several months.

[0020] Mafic and ultramafic rocks contain silicate minerals including olivine, serpentine, pyroxene, and plagioclase. Olivine rocks often contain magnesium, oxygen, and silicon. Olivine is the most abundant mineral in the Earth's mantle down to a depth of 700 km. The composition typically consists of a combination of SiO4 and Mg 2+ as well as small amounts of Ca 2+ Typically, silicon binds with four oxygen molecules to form a pyramid structure so that the charges of the cations and anions are balanced, and Mg 2+ occupies the empty space between the SiO4 structures. These bonds can be easily induced to react with carbonic acid. The reaction of olivine with CO2 can be achieved by the following reaction pathway.

Chemical formula

[0021] The rate of the reaction has also been demonstrated to increase significantly by introducing water. Water helps CO2 to solubilize and form carbonic acid, thus making the mineralization and ion exchange processes much simpler and more efficient. The following is the reaction pathway in the presence of water.

Chemical formula

[0022] Some ferroperic rocks and ultramafic rocks mainly contain the minerals olivine and pyroxene. In the presence of water and CO2, the following reactions occur.

Chemical formula

[0023] Another aspect relates to a method for carbon dioxide sequestration utilizing pyroxene minerals. Pyroxene is one of the groups of inosilicate minerals that are also abundantly found in ferroperic rocks and ultramafic rocks. The general chemical formula for pyroxene is AB(Si)2O6, where A can be one of the ions such as magnesium, aluminum, etc. Most commonly, pyroxene can often be found as Mg2SiO4 and CaMgSi2O6. Naturally, pyroxene reacts with CO2 according to the following equation.

Chemical formula

[0024] However, similar to olivine, water increases the rate of the reaction, and thus, in the presence of water, the following is the reaction pathway for the CO2 - pyroxene reaction.

Chemical formula

[0025] This disclosure relates to a method utilizing the above reaction pathways (in particular, equations 2-9) for converting and / or storing CO2 into mafic and ultramafic rocks, as defined above as a first aspect of the present invention. The proposed method also enhances the reaction rate and results in the complete mineralization of the total injected CO2 volume within 2-12 months from injection. The present invention also discloses various operating conditions, such as temperature, pressure, and flow rate (depending on rock permeability), which affect process efficiency and result in improved sequestration. Some embodiments of the present invention also encompass engineering aspects, such as the use of renewable energy, water looping, and process configuration and design. Examples of embodiments of the present invention are listed in the following sections [Aspect 1] to [Aspect 10]. [Aspect 1] A method for mineralizing and storing carbon dioxide, CO 2 Generating nanobubbles, As a mixture of carbon dioxide and fluid, the CO 2 The method involves injecting nanobubbles into a rock layer containing smafic or ultramafic rock via injection wells, wherein the carbon dioxide and fluid mixture flows through the injection wells or injection well tubes located in the rock layer, and the injection wells and / or injection well tubes have multiple longitudinal perforations in the rock layer at a depth of 0.4 to 4 km. The carbon dioxide and the carbon dioxide in the fluid mixture are reacted with the rock layer to form calcite and magnesite in the rock layer, A method comprising recycling at least a portion of the fluid from the rock layer through an observation well. [Aspect 2] CO 2 The method for mineralizing and storing carbon dioxide according to embodiment 1, wherein nanobubbles are generated by a nanobubble membrane generator. [Aspect 3] The aforementioned film generator, pump, entrance, Air pressure gauge, Air connection part, Air flow meter, Pump pressure gauge, Discharge flow valve, and A method for mineralizing and storing carbon dioxide according to embodiment 2, comprising a starter. [Aspect 4] The aforementioned CO 2 The method for mineralizing and storing carbon dioxide according to embodiment 3, wherein the nanobubbles have an average diameter of approximately 60 to 550 nm. [Aspect 5] The aforementioned CO 2 The method for mineralizing and storing carbon dioxide according to embodiment 4, wherein the nanobubble generator operates at a pressure of at least 25 bar. [Aspect 6] The method for mineralizing and storing carbon dioxide according to embodiment 5, wherein the fluid mixture comprises at least one selected from the group consisting of water, seawater, brackish water, and a preservative tracer. [Aspect 7] The method for mineralizing and storing carbon dioxide according to embodiment 1, wherein the injection and observation wells have the same depth. [Aspect 8] A method for mineralizing and storing carbon dioxide according to Embodiment 1, further comprising selecting the length and density of the longitudinal boreholes such that the length is at least 15 cm, the injection well tube, and optionally the density along the well casing within the injection well, based on the fluid flow velocity in one or more permeable zones. [Aspect 9] The carbon dioxide mineralization and storage method according to embodiment 5, wherein during the injection, a high-pressure zone is created in the injection well for less than a packed-off interval, and a low-pressure zone is created during the recycling through the observation well. [Aspect 10] The carbon dioxide mineralization and storage method according to embodiment 6, wherein the majority of the carbon dioxide and fluid mixture flows from a high-pressure zone to a low-pressure zone, and the majority of the fluid volume of the carbon dioxide and water mixture is recycled back through the observation well.

Claims

1. A method for mineralizing and storing carbon dioxide, CO ２ Generating nanobubbles, As a mixture of carbon dioxide and fluid, the CO ２ The method involves injecting nanobubbles into a rock layer containing mafic or ultramafic rock via an injection well, wherein the carbon dioxide and fluid mixture flows through the injection well or injection well tube located in the rock layer, and the injection well and / or injection well tube has a plurality of longitudinal boreholes in the rock layer at a depth of 0.4 to 4 km. The carbon dioxide and the carbon dioxide in the fluid mixture are reacted with the rock layer to form calcite and magnesite in the rock layer, A method comprising recycling at least a portion of the fluid of the carbon dioxide and fluid mixture from the rock layer through an observation well.

2. The CO ２ The method for mineralizing and storing carbon dioxide according to claim 1, wherein nanobubbles are generated by a nanobubble generator.

3. The aforementioned nanobubble generator, pump, entrance, Air pressure gauge, Air connection part, Air flow meter, Pump pressure gauge, Discharge flow valve, and The method for mineralizing and storing carbon dioxide according to claim 2, comprising a starter.

4. The aforementioned CO ２ The method for mineralizing and storing carbon dioxide according to claim 3, wherein the nanobubbles have an average diameter of 60 to 550 nm.

5. The method for mineralizing and storing carbon dioxide according to claim 4, wherein the nanobubble generator operates at a pressure of at least 25 bar.

6. The method for mineralizing and storing carbon dioxide according to claim 5, wherein the fluid mixture comprises at least one selected from the group consisting of water, seawater, brackish water, and a preservative tracer.

7. The method for mineralizing and storing carbon dioxide according to claim 1, wherein the injection well and the observation well have the same depth.

8. The method for mineralizing and storing carbon dioxide according to claim 1, further comprising selecting the length and density of the longitudinal borehole, such that the length is at least 15 cm, and the density along the injection well tube, based on the fluid flow velocity in one or more permeable zones of the rock layer.

9. The carbon dioxide mineralization and storage method according to claim 5, wherein a high-pressure zone is created in the injection well during the injection and a low-pressure zone is created through the observation well during the recycling.

10. The method for mineralizing and storing carbon dioxide according to claim 6, wherein the carbon dioxide and fluid mixture flows from a high-pressure zone to a low-pressure zone, and the fluid of the carbon dioxide and fluid mixture is recycled through the observation well.

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