System and method for producing low-density carbon fiber from coal

Abstract

To provide a system and method for manufacturing affordable carbon fiber insulation as an alternative to glass fiber insulation to improve energy efficiency in a building environment.SOLUTION: An embodiment disclosed herein relate to a system and a method for processing coal. A direct air capture system includes a voltage source and a coal-derived electroactive polymer electrically connected to the voltage source, in which applying voltage to the coal-derived electroactive polymer causes carbon dioxide to bind to the coal-derived electroactive polymer. The method for capturing carbon dioxide includes introducing the electroactive polymer into a gas stream containing carbon dioxide, applying voltage to the electroactive polymer to bind the carbon dioxide to the electroactive polymer, and reversing the polarity of the voltage applied to the electroactive polymer to release the carbon dioxide.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This application is based on and claims priority to U.S. Provisional Patent Application No. 63 / 031,725, entitled "SYSTEMS AND METHODS FOR MANUFACTURING LOW-DENSITY CARBON FIBER FROM COAL," filed May 29, 2020, the disclosure of which is incorporated by reference in its entirety.

[0002] FIELD OF THE INVENTION The embodiments described herein relate generally to carbon products and methods for processing carbon-based materials. More particularly, the embodiments relate to low-density carbon fibers and systems and methods for producing low-density carbon fibers from coal. [Background technology]

[0003] Fiber materials are used in many different applications across a wide range of industries, including commercial aviation, recreation, industry, and transportation. Carbon fiber is used in a variety of composite materials due to its excellent properties, including high strength, high modulus, and high electrical conductivity. Summary of the Invention [Problem to be solved by the invention]

[0004] Carbon fibers produced using previously known methods, such as conventional carbon fibers (e.g., polyacrylonitrile (PAN)-based carbon fibers, pitch-based carbon fibers, or cellulose-based carbon fibers) that can be produced by carbonizing organic fibers through heat treatment, exhibit low electrical conductivity and are expensive to develop. As a result, carbon fiber manufacturers and users continue to seek new and improved methods for producing carbon fibers. Many of the systems and methods described herein can utilize low-cost, high-yield coal-based pitch precursors, which are advantageous over conventional high-cost, low-yield PAN- or cellulose-based insulating fibers. The systems and methods described herein can also provide low-cost pitch-based carbon fibers that significantly reduce costs compared to current carbon fibers, allowing them to be used in a wide range of useful applications. For example, the systems and methods can produce affordable carbon fiber insulation as an alternative to glass fiber insulation to improve energy efficiency in the built environment. [Means for solving the problem]

[0005] Embodiments disclosed herein relate to methods for producing low-density carbon fibers from coal. Embodiments herein also relate to direct air capture systems including coal-derived electroactive polymers and methods for capturing carbon dioxide (CO2) from gas streams. The methods disclosed herein may include continuous processes. As an example, the methods disclosed herein may include a direct air capture system including a coal-derived electroactive polymer for capturing CO2 from a gas stream.

[0006] In some embodiments, a method for processing coal can include subjecting raw coal to a liquefaction process to form a pitch resin, subjecting the pitch resin to a variable crystallinity spinning process to form raw fibers, subjecting the raw fibers to an oxygen stabilization process, and subjecting the stabilized fibers to a carbonization process to form low thermal conductivity carbon fibers. In some embodiments, the method for processing coal can further include adding a blending additive to the pitch resin before or during the variable crystallinity spinning process. The blending additive can include one or more of an isotropic pitch, a variable degree of anisotropy pitch, and a thermoplastic blending additive. In some embodiments, the thermoplastic blending additive includes at least one of a phenolic resin and a lignin. In some embodiments, the variable crystallinity spinning process includes a meltblown solvated-spinning system.

[0007] In some embodiments, the method of treating coal can include foaming the raw fibers to create voids in the carbon fibers. In embodiments, the method of treating coal can include adding an oxygen-containing additive to the pitch resin before or during the variable crystallinity spinning process. The oxygen-containing additive can include an oxygen-containing polymeric material. In some embodiments, the method of treating coal can include adding one or more compounds containing heteroatoms to the pitch resin before or during the variable crystallinity spinning process. The one or more compounds containing heteroatoms include oxygen or nitrogen. In some embodiments, the method of treating coal can also include treating low thermal conductivity carbon fibers to produce carbon fiber insulation. In some embodiments, the low thermal conductivity carbon fibers can have a thermal conductivity that depends on the temperature and resonance time of the oxygen stabilization treatment. In some embodiments, subjecting the raw fibers to an oxygen stabilization treatment can include introducing a gas or steam during the oxygen stabilization treatment to determine the heat transfer coefficient of the low thermal conductivity carbon fibers.

[0008] In one embodiment, a direct air capture system is disclosed. The direct air capture system can include a voltage source and a coal-derived electroactive polymer electrically connected to the voltage source. The direct air capture system can be configured to bind carbon dioxide to the coal-derived electroactive polymer when a voltage is applied to the coal-derived electroactive polymer. In some embodiments, the coal-derived electroactive polymer includes low thermal conductivity carbon fibers. The coal-derived electroactive polymer can include at least one of graphene, graphene oxide, graphene nanotubes, and graphene dots. In some embodiments, the direct air capture system can include graphene nanotubes configured to provide additional voids to promote greater thermal insulation properties. In some embodiments, the coal-derived electroactive polymer is obtained from coal by a predetermined process. The predetermined process can include subjecting raw coal to a liquefaction process to form anthracene, oxidizing the anthracene to form anthraquinone, chlorinating the anthraquinone to form dichloroanthraquinone, and polymerizing the dichloroanthraquinone to produce the coal-derived electroactive polymer. In some embodiments, the anthraquinone can be chlorinated with hydrochloric acid.

[0009] In some embodiments, a method for capturing carbon dioxide is disclosed. The method for capturing carbon dioxide can include introducing an electroactive polymer into a gas stream, applying a voltage to the electroactive polymer to bind carbon dioxide to the electroactive polymer, and reversing the polarity of the voltage applied to the electroactive polymer to release the carbon dioxide. The gas stream can include a quantity of carbon dioxide. In some embodiments, the electroactive polymer can include at least one of carbon nanotubes, graphene, graphene oxide, graphene dots, and combinations thereof. The electroactive polymer can be configured to increase the electrical conductivity of the electroactive polymer. In some embodiments, the method for capturing carbon dioxide can further include collecting the carbon dioxide and converting the carbon dioxide into at least one of a synthesis gas, a hydrocarbon material, and a densified liquid.

[0010] Features from any of the disclosed embodiments may be used in combination with each other without limitation. Additionally, other features and advantages of the present disclosure will become apparent to those skilled in the art through a review of the following detailed description and accompanying drawings. [Brief explanation of the drawings]

[0011] The accompanying drawings illustrate several embodiments of the present disclosure, with like reference numerals indicating the same or similar elements or features in different views or embodiments shown in the drawings.

[0012] [Figure 1] 1 is a flowchart of a method of forming a low-density carbon fiber, according to one embodiment.

[0013] [Figure 2] 1 is a flowchart of a method for capturing carbon dioxide, according to one embodiment.

[0014] [Figure 3] 3 is a schematic diagram of a direct air capture system capable of implementing the method illustrated in FIG. 2, according to one embodiment.

[0015] [Figure 4] 1 is a flowchart of a method for obtaining electroactive polymers from coal, according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] This specification presents examples of embodiments of the present invention, and is not intended to limit the scope, application, or configuration of the present invention as defined by the appended claims. Accordingly, changes may be made in the function and arrangement of the disclosed elements, and steps or components may be omitted, substituted, or added as appropriate in various embodiments, without departing from the spirit and scope of the present disclosure. For example, described methods may be performed in an order different from that described, and various steps may be added, omitted, or combined. Additionally, features described with respect to some embodiments may be combined with other embodiments.

[0017] Systems and methods for processing coal-derived pitch, as well as products formed or produced thereby, are provided. The systems and methods described herein facilitate the production of low-cost, low-thermal-conductivity carbon fiber products. For example, many carbon fiber products produced in accordance with the present disclosure have lower densities than conventional carbon fiber products produced from similar materials. Low-density carbon fiber products retain heat and reduce heat transfer, imparting properties that reduce thermal conductivity to the carbon fiber products compared to conventional carbon fibers. The low-thermal-conductivity carbon fiber products produced in accordance with many of the systems and methods described herein are unexpected to those skilled in the art. Many embodiments of the systems and methods described herein enhance the conversion of coal-based pitch intermediate products into useful products, such as high-carbon-content pitch fiber products with low thermal conductivity. These products may be suitable as thermal insulation and / or low-density carbon fibers. In particular, the present technology utilizes a specially designed system and one or more blend additives to tailor at least one carbon fiber physical property, such as the density (specific gravity) and / or thermal conductivity of the carbonized fiber.

[0018] FIG. 1 is a flowchart of a method 100 for producing low thermal conductivity carbon fiber insulation, according to an embodiment. For example, the method 100 includes step 102, in which raw coal is subjected to a liquefaction process effective to form pitch resin. Coal liquefaction is a process in which coal is converted into a liquid. Several processes are used to accomplish this step, with the two most common being the indirect route and the direct route. In some embodiments, the indirect route consists of two steps: first, coal is gasified with steam and oxygen to produce synthesis gas (syngas), which is then washed to remove dust, tar, and acid gases. The next step is to convert this synthesis gas into various hydrocarbons using a Fischer-Tropsch process, which involves reacting the synthesis gas with a catalyst. For example, the hydrocarbons may include pitch resin. In the direct route, coal is crushed and reacted with a catalyst, followed by the addition of hydrogen at high temperature and pressure in the presence of a solvent to produce hydrocarbons, such as pitch resin.

[0019] In embodiments, the pitch resin is then subjected to a variable crystallinity spinning process effective to form raw fibers in step 104. In many embodiments, the present systems and methods include at least one of two processes for disrupting the densified crystalline graphite structure associated with the carbon fibers. The two processes for disrupting the densified crystalline graphite structure can include physically altering the spinning conditions in the variable crystallinity spinning process and chemically altering the pitch composition with one or more blend additives. Spinning conditions can be physically altered in the low crystallinity spinning process to better promote disruption of liquid crystal formation. In some embodiments, spinning conditions can be physically altered by one or more of the following: turbulent spinneret design, low draw ratios for green spun fibers, meltblown solvation spinning systems versus pure resin melt spinning, use of flow inverters or frit flow redistributors in the spinneret capillary channels, creation of voids (such as nano-sized bubbles) in the spun fibers by foaming, and / or use of specialized spinnerets for hollow fiber formation with one or more cross-sectional holes, or a combination thereof.

[0020] In some embodiments, the variable crystallinity spinning process can include a meltblown solvating spinning system.

[0021] Method 100 can also include step 106, which involves subjecting the raw fibers to an oxygen stabilization step. In some embodiments, the raw fibers can undergo a stabilization step in which air (oxygen), and possibly additional gases or steam, are introduced to convert the linear atomic bonding of the fibers to a more thermally stable form. The raw carbon fibers must be stabilized prior to the calcination step of the overall process in step 108, described below. This stabilization prevents the molecules within the carbon fibers from relaxing and becoming misaligned during the calcination step. Stabilization maintains molecular integrity and allows the fibers to remain in their solid form through final processing steps.

[0022] In some embodiments, stabilization of the fibers can be performed at temperatures between 200 and 300°C and include a resonance time of 30 to 120 minutes. During this resonance time, the fibers can be exposed to an air atmosphere containing approximately 21% oxygen. Additional gases or vapors can be added to the stabilization atmosphere to alter the reactions occurring within the pitch of the fibers. During step 106, which includes stabilization, the fibers can be maintained under tension to prevent relaxation and misalignment of the pitch molecules. Pitch-based carbon fibers typically undergo ester and anhydride compound formation within the pitch during step 106. Pitch-based fibers can also undergo loss of aromatic content during step 106.

[0023] Method 100 may also include step 108. In step 108, the stabilized fibers are subjected to a carbonization step effective to form low thermal conductivity carbon fibers. In some embodiments, carbonization is a process in which the stabilized fibers are heated and volatile products (liquids and gases) are driven off, leaving behind solid low thermal conductivity carbon fibers.

[0024] In some embodiments, one or more blend additives can be added to the pitch resin before or during the variable crystallinity spinning process, as shown in step 110. The pitch composition can also be chemically modified with one or more blend additives to make it more conducive to disrupting liquid crystal formation. The inclusion of one or more blend additives can result in carbon fibers having lower densities than conventionally formed carbon fibers. The resulting carbon fibers can include properties more similar to or superior to those of rayon carbon fibers, such as lower thermal conductivity. In some embodiments, the pitch composition can be varied by utilizing isotropic pitch and / or anisotropic pitch with a degree of anisotropy between 0% and 80% as a blend additive (or neat) in place of the highly discotic liquid crystal-containing mesophase pitch. In some embodiments, the blend additive can include one or more pitches with varying degrees of anisotropy. The pitch can be made anisotropic through the use of one or more heat treatments.

[0025] In some embodiments, as shown in step 112, the pitch composition can be varied by utilizing an oxygen-containing additive, such as an oxygen-containing polymeric material. The oxygen-containing additive can be added to the pitch resin before or during the variable crystallinity spinning process. In some embodiments, as shown in step 114, the pitch composition can be varied by utilizing one or more compounds containing heteroatoms such as oxygen or nitrogen. The one or more compounds containing heteroatoms can be added to the pitch resin before or during the variable crystallinity spinning process. In some embodiments, the pitch composition can be varied by utilizing one or more thermoplastic blending additives (e.g., phenolic resin, lignin, etc.) that may contain heteroatoms such as oxygen or nitrogen. Mixing materials containing heteroatoms (such as oxygen) into the pitch during fiber spinning can reduce the fiber density. Examples of one or more thermoplastic blending additives containing heteroatoms such as nitrogen or oxygen include, but are not limited to, polyphenol-formaldehyde resin, lignin, polyethylene oxide, polyvinyl alcohol, poly DL lactide, polymethyl methacrylate, or combinations thereof. In some embodiments, one or more of the heteroatom-containing additives can be derived from coal. Below are some examples of blend additives that can be added to the pitch resin to affect the crystallinity of the fiber. TIFF2025160928000002.tif66168Polyphenol-formaldehyde resin TIFF2025160928000003.tif64168Lignin TIFF2025160928000004.tif17168Polyethylene oxide (PEO) TIFF2025160928000005.tif14168Polyvinyl alcohol TIFF2025160928000006.tif22168Poly DL-lactide (PLA)

[0026] The physical and chemical processes described above to disrupt the dense, crystalline graphite structure associated with carbon fibers can modify pitch-based carbon fibers to approach the microstructural characteristics and resulting density and insulating properties associated with cellulose-based (rayon) carbon fibers. Tables 1 and 2 below provide a comparison of the properties of PAN-, pitch-, and rayon-based carbon fibers. TIFF2025160928000007.tif55169 TIFF2025160928000008.tif51168

[0027] In some embodiments, method 100 can also include step 116. In step 116, the low thermal conductivity carbon fibers can be processed to produce carbon fiber insulation. The carbon fiber insulation can include several forms, such as panels, boards, rolls, foams, felt, etc. In some embodiments, method 100 can also include step 118. Step 118 can include foaming the raw fibers, which is effective to create voids within the carbon fibers. In some embodiments, foaming can make the carbon fibers less dense and improve their insulating properties.

[0028] Low density carbon fibers formed according to one or more of the methods and systems described herein can be utilized in direct air capture (DAC) systems, such as thermoelectric DACs or DACs using coal-derived electroactive polymers (EAPs).

[0029] 2 is a flowchart of a method 200 for capturing carbon dioxide (CO) according to one embodiment of the present invention. In some embodiments, the method 200 can include step 202 of placing an electroactive polymer in a gas stream. The gas stream can include carbon dioxide. In some embodiments, the gas stream can include a feed gas stream or an exhaust gas stream. The method 200 can further include step 204 of applying a voltage to the electroactive polymer such that the carbon dioxide binds to the electroactive polymer.

[0030] In some embodiments, the coal-derived EAP can retain ketone functionality, which promotes carbon dioxide binding to the EAP when a voltage is applied thereto. In step 206 of method 200, once the EAP binding sites are saturated with bound or adsorbed carbon dioxide, the polarity of the voltage can be reversed, resulting in the bound carbon dioxide being debound, i.e., released in large quantities, from the EAP. Because polarity can be reversed in a battery-like system comprised of an EAP, separate materials are not required for the anode and cathode within the system. These properties allow the use of a feed gas with a relatively low concentration of carbon dioxide (e.g., 415 ppm in air), and the amount of carbon dioxide bound can be increased by passing the feed gas over the EAP multiple times. In some embodiments, carbon nanotubes, graphene, graphene oxide, graphene dots, or combinations thereof, and / or other coal-derived conductive carbon materials can also be added to the system to enhance the conductivity of elements containing the EAP. Method 200 can further include step 208, in which the carbon dioxide is collected and converted into at least one of a synthesis gas, a hydrocarbon material, and a densified liquid.

[0031] FIG. 3 is a schematic diagram of a direct air capture system capable of implementing the method illustrated in FIG. 2 , according to one embodiment. Accordingly, a DAC system 300 having low-density carbon fibers is also disclosed herein, which may include an EAP 302 according to any of the systems and methods described above. In some embodiments, a DAC system 300 using coal-derived EAP 302 may not include low-density carbon fibers, but may additionally or alternatively include other coal-derived materials, such as coal-derived graphene or graphene oxide. The DAC system 300 includes a voltage source 304. In one example, the voltage source 304 may include a generator, a battery, or a cell. In some embodiments, the voltage source 304 may include a DC voltage source or an AC voltage source. The voltage source 304 may include a voltage-controlled voltage source or a current-controlled voltage source. The DAC system 300 is configured to bind carbon dioxide from a gas stream 306. When a voltage is applied to the coal-derived EAP 302, the carbon dioxide binds to the coal-derived EAP 302. When the binding sites of the EAP become saturated with bound or adsorbed carbon dioxide, the carbon dioxide is released. The polarity of the voltage can be reversed to release the bound carbon dioxide from the EAP 302 and / or DAC system 300. As noted above, the polarity can be reversed in a battery, so that system 300 does not require separate materials for the anode and cathode. DAC system 300 is configured to produce gas stream 308 having a lower concentration of CO than gas stream 306. In some embodiments, gas stream 308 does not contain CO.

[0032] In one embodiment, the coal-derived EAP 302 includes low thermal conductivity carbon fibers. In some embodiments, the coal-derived EAP can include at least one of graphene, graphene oxide, graphene nanotubes, carbon nanotubes, and graphene dots. The DAC system 300 can include graphene nanotubes configured to provide additional voids to promote greater thermal insulation properties.

[0033] Thermoelectric DAC systems or DAC systems using coal-derived EAPs can be used in a variety of situations. For example, thermoelectric DAC systems or DAC systems using coal-derived EAPs can be used to combat the harmful effects of carbon dioxide during the construction of new buildings or structures. Panel-like structures including thermoelectric DAC systems or DAC systems using coal-derived EAPs can be added to buildings to capture carbon dioxide during and after the construction of the building. The building can be configured to capture carbon dioxide in the thermoelectric DAC system or DAC system using coal-derived EAPs. The carbon dioxide captured in the thermoelectric DAC system or DAC system using coal-derived EAPs incorporated into a building can be utilized in a number of materials, such as hydrocarbon materials or reverse water gas shift, which converts carbon dioxide into synthesis gas and densified liquids.

[0034] FIG. 4 is a flowchart of a method 400 for producing electroactive polymers (EAPs) from coal, according to one embodiment. Coal-derived EAPs may be formed from anthracene. In some embodiments, method 400 may include step 402, in which coal may undergo liquefaction effective to produce anthracene and / or other polycyclic aromatic hydrocarbons (PAHs). Method 400 may further include step 404, in which the coal-derived anthracene is then effectively oxidized to form anthraquinone or a similar product. The anthraquinone may then be chlorinated in step 406, for example, with hydrochloric acid, effective to form dichloroanthraquinone. The dichloroanthraquinone is then polymerized in step 408 to form the EAP.

[0035] In some embodiments, coal-derived EAP can be derived from a solvation meltblown process. Figure 5 is an illustration of a solvation meltblown process 500 according to one embodiment of the present invention. The solvation meltblown process produces a carbon fiber web of small-diameter fibers that increase the surface area of ​​the active material and sequester carbon dioxide molecules. The solvated carbon material is fiberized by feeding it through a die head 502 and a die 504 with a closely flowing high-velocity primary air stream. As the fibers enter the forming chamber, they are cut (e.g., by an air knife) and exposed to a cooling or secondary air stream that solidifies the carbon material. The carbon fibers and carbon fiber fragments are then accumulated on a collection roller 506, forming a continuous web 508 of material.

[0036] As used herein, the terms "about" or "substantially" refer to a tolerance of ±10% or ±5% of the term modified by "about" or "substantially." Furthermore, the terms "less than," "less than," "greater than," and "more than" include the endpoints modified by those terms.

[0037] Although various aspects and embodiments of the present invention have been disclosed herein, other aspects and embodiments are also contemplated. For purposes of description, specific terms have been used above to provide a thorough understanding of the embodiments. However, it will be apparent to those skilled in the art that the described embodiments need not be limited to these specific terms. That is, the descriptions of specific embodiments set forth herein are presented for purposes of illustration and description. They are not intended to limit the embodiments to the precise forms disclosed. It will be apparent to those skilled in the art that numerous modifications and variations are possible in light of the above teachings.

[0038] Features of any disclosed embodiment can be used in combination with each other without limitation. In addition, other features and advantages of the present disclosure will become apparent to those skilled in the art through a review of the detailed description and accompanying drawings. Various inventions have been described herein with reference to certain specific embodiments and examples. However, those skilled in the art will recognize that many variations are possible without departing from the scope and spirit of the invention disclosed herein, in that the invention as set forth in the following claims is intended to cover all variations and modifications of the disclosed invention without departing from the spirit of the invention. As used in this specification and the claims, the terms "including" and "having" shall have the same meaning as the inclusive term "comprising."

[0039] Terms of degree (e.g., "about," "substantially," "generally," etc.) indicate structurally or functionally insignificant variations. As an example, when a term indicating a quantity includes a term of degree, the term of degree is interpreted to mean ±10%, ±5%, or +2% of the term indicating the quantity. As an example, when a term of degree is used to modify a shape, the term of degree indicates that the shape modified by the term of degree has the appearance of the disclosed shape. For example, the term of degree can be used to indicate that a shape has rounded corners instead of sharp corners, curved edges instead of straight edges, one or more protrusions extending therefrom, is rectangular, is the same as the disclosed shape, etc.

Claims

1. 1. A direct air capture system comprising: a voltage source; and a coal-derived electroactive polymer in electrical communication with the voltage source, the coal-derived electroactive polymer configured to bind carbon dioxide when a voltage is applied to the coal-derived electroactive polymer.

2. The direct air capture system of claim 1 , wherein the coal-derived electroactive polymer comprises low thermal conductivity carbon fibers.

3. 10. The direct air capture system of claim 1, wherein the coal-derived electroactive polymer comprises at least one of graphene, graphene oxide, graphene nanotubes, and graphene dots.

4. 10. The direct air capture system of claim 1, further comprising graphene nanotubes adapted to provide additional voids that promote greater thermal insulation properties.

5. The coal-derived electroactive polymer is subjecting the feed coal to a liquefaction process to form anthracene; oxidizing the anthracene to form anthraquinone; chlorinating the anthraquinone to form dichloroanthraquinone; polymerizing the dichloroanthraquinone to form a coal-derived electroactive polymer; 10. The direct air capture system of claim 1 obtained from coal by a process comprising:

6. 10. The direct air capture system of claim 1, wherein the anthraquinone is chlorinated with hydrochloric acid.

7. placing the electroactive polymer in a gas stream comprising carbon dioxide; applying a voltage to the electroactive polymer to bind the carbon dioxide to the electroactive polymer; reversing the polarity of the voltage applied to the electroactive polymer to release the carbon dioxide; 1. A method for capturing carbon dioxide, comprising:

8. 10. The method of claim 7, wherein the electroactive polymer can comprise at least one of carbon nanotubes, graphene, graphene oxide, graphene dots, and combinations thereof configured to enhance the electrical conductivity of the electroactive polymer.

9. 8. The method of claim 7, further comprising collecting the carbon dioxide and converting the carbon dioxide into at least one of a synthesis gas, a hydrocarbon material, and a densified liquid.

Images