Carbon fiber manufacturing system and method

Abstract

To provide a method for producing carbon fibers at a reduced cost, and a system for producing carbon fibers.SOLUTION: There is provided a method comprising: contacting a carbon fiber seed to a carbon-metal melt; and drawing the carbon fiber seed to form carbon fibers. There is also provided a system and apparatus that comprises: a carbon fiber reactor for producing the carbon fibers, in which the reactor comprises: a container for contacting with a carbon-metal melt; and a plurality of nozzles through which a plurality of menisci are formed from the carbon-metal melt for contact with a carbon seed to produce the carbon fibers.SELECTED DRAWING: Figure 1

Description

Background Art

[0001] The present disclosure relates to the production of carbon fibers.

[0002] The United States and the broader international community still lack scalable and low-cost carbon fiber production technologies.

[0003] The raw material used to make carbon fibers is called a precursor. Approximately 90% of carbon fibers are currently produced from polyacrylonitrile (PAN) fiber precursors, and the remaining 10% are made from rayon precursors or petroleum pitch fiber precursors. Carbon fibers are sold as fiber tows wound on bobbins, and a typical carbon fiber tow is composed of 1,000 to 50,000 fibers, each with a diameter of 5 to 15 μm and each with a length of 1 to 10 km. Commercial carbon fiber production using PAN fiber precursors (the "PAN-based method") involves relatively expensive unit operations including spinning, stabilization, carbonization, and graphitization. The manufacturing cost is typically approximately $22 per kg, and the PAN precursor accounts for approximately 50% of that cost. Therefore, alternative approaches to carbon fiber production using lower-cost precursors have the potential to replace current PAN-based carbon fiber production. In fact, optimized high-strength, commercial-grade carbon fibers are generally sold retail at $30 to $100 per kg, depending on the specific optimization. Therefore, the commercial market for PAN-based carbon fibers is currently limited to high-performance applications (e.g., aerospace applications).

Summary of the Invention

Problems to be Solved by the Invention

[0004] To reduce the cost of carbon fibers, alternatives that are not as expensive as PAN precursors are being pursued, such as precursors based on cellulose (e.g., viscose, rayon, lyocell, tire cord cotton, Fortisan, Cupro, Bocell), lignin, polyethylene, polyvinylidene chloride-polyvinyl chloride copolymer, polybutadiene, polystyrene, and poly(p-phenylene benzobisoxazole). However, carbon fibers produced from these precursors may lack the desired mechanical properties or uniformity, may involve further processing, or may require additional energy input that hinders their use.

[0005] As an alternative to the production of polymer-based carbon fibers, vapor-grown carbon fibers by thermal decomposition of benzene are being studied, in which carbon fibers grow on a substrate periodically seeded with nanometer-sized catalysts. Although this method can grow fibers 1 - 10 cm in length, issues such as dimensional non-uniformity, low yield, and discontinuous operation can arise, and any possible overcoming of these issues may require further processing.

[0006] This disclosure relates to the production of carbon fibers.

[0007] Some aspects of this disclosure provide a method comprising contacting a carbon fiber seed with a meniscus of a carbon-metal melt and withdrawing the carbon fiber seed from the meniscus at a draw rate to form a carbon fiber.

[0008] Some aspects of this disclosure provide a system comprising a carbon fiber reactor for manufacturing carbon fibers and a heater for heating a carbon-metal melt, wherein the reactor includes a container for contacting the carbon-metal melt and a plurality of nozzles through which a plurality of menisci are formed by the carbon-metal melt for contact with carbon seeds to manufacture carbon fibers.

[0009] Some aspects of the present disclosure are systems comprising a carbon fiber reactor for manufacturing carbon fibers, the reactor comprising a container for contacting a carbon-metal melt, and a plurality of nozzles through which a plurality of menisci are formed by the carbon-metal melt for contact with carbon seeds to produce carbon fibers. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The following figures are included to illustrate certain aspects of the present disclosure and should not be considered exclusive. The disclosed subject matter is capable of considerable modification, alteration, combination, and equivalents in form and function, as will occur to one of ordinary skill in the art having the benefit of this disclosure.

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Mode for Carrying Out the Invention

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In case of conflict, the present document, including definitions, will control. Preferred methods and materials are described below, but similar or equivalent methods and materials can be used in the practice or testing of the present disclosure. The materials, methods, and articles disclosed herein are for illustrative purposes only and not intended to be limiting.

[0022] The singular forms "a", "an", and "the" include plural references unless the context clearly dictates otherwise.

[0023] As used in this specification and the appended claims, the term "comprising" can include embodiments of "consisting of" and "consisting essentially of". As used herein, the terms "comprise(s) / include(s)", "having / has", "can", "contain", and variations thereof are intended to be open-ended transitional phrases that require the presence of the recited element or step and permit the presence of other elements or steps. However, such descriptions should also be construed as describing compositions, mixtures, or processes as "consisting of" and "consisting essentially of" the recited elements or steps, thereby allowing only the presence of the recited elements or steps, together with any impurities that may result therefrom, and excluding other elements or steps.

[0024] Unless otherwise indicated, numerical values in the specification are to be understood as including numerical values which are the same when reduced to the same number of significant figures and numerical values which differ from the recited value by less than the experimental error of conventional measurement techniques of the type used to measure a particular value.

[0025] All ranges disclosed herein include the recited endpoints and can be combined independently (e.g., the range of "2 to 10" includes the endpoints 2 and 10 and all intermediate values). The endpoints and any values disclosed herein are not limited to the exact ranges or values, and to the extent that they include approximate values of these ranges and / or values, they are sufficiently imprecise.

[0026] As used herein, the term of approximation can be applied to modify any quantitative representation that can vary without causing a change in the associated basic function. Thus, values modified by one or more terms such as "about" and "substantially" may not be limited to the exact values specified in some cases. The modifier "about" should also be regarded as disclosing a range defined by the absolute values of two endpoints. For example, the expression "about 2 to about 4" also discloses the range of "2 to 4". The term "about" may mean ±10% of the indicated number. For example, "about 10%" may indicate a range of 9% to 11%, and "about 1%" may mean 0.9 to 1.1.

[0027] Regarding the description of numerical ranges herein, each intervening number between them having the same degree of accuracy is explicitly contemplated. For example, regarding the range from 6 to 9 (6~9), the numbers 7 and 8 are contemplated in addition to 6 and 9, and regarding the range from 6.0 to 7.0 (6.0~7.0), the numbers 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, and 7.0 are explicitly contemplated.

[0028] As used herein, the term "liquidus" and its grammatical variants mean the temperature above which the material is completely liquid, and the liquidus is the maximum temperature at which crystals can coexist in a melt melted at thermodynamic equilibrium.

[0029] As used herein, the term "condense / condensing" and its grammatical variants mean a phase change from a gas to a liquid, and do not include the proportion of the substance undergoing the phase change. For example, a catalytic gas can condense into a catalytic vapor that contains the catalyst in the liquid phase (e.g., as droplets) and optionally further contains the catalyst in the gas phase.

[0030] As used herein, the term "catalytic vapor" and its grammatical variants mean liquid catalyst droplets suspended in a gas that may or may not contain a catalyst in the gas phase. When describing a reaction with a catalytic vapor, the reaction can occur by the gas-phase catalyst and / or the liquid-phase catalyst.

[0031] As used herein, the term "carbon-metal melt" and its grammatical variants mean a carbon-metal (C-M) liquid solution or a molten metal containing dissolved carbon, where the molten metal (M) is composed of one or more metals (e.g., M = Co, Fe, La, Mn, Ni, Pd, Pt, Rh, Ru, Si, etc.). The carbon-metal melt can contain elemental carbon derived from a plurality of carbon sources (e.g., hydrocarbon pyrolysis, biochar, recycled plastics, petcoke, etc.) combined in various ratios with one or more metal (M) elements including any one or more of the alkali metals, alkaline earth metals, transition metals, post-transition metals, lanthanide metals, and actinide metals listed above. Various further examples of carbon sources and metals are described later herein. In one or more specific aspects of the present disclosure, the composition of the carbon-metal melt has a high carbon solubility (about 5 mol / mol to about 50% mol / mol, including any value and subset therebetween, such as x m > 5% mol / mol) at a low temperature (e.g., about 1,000 °C to about 2,000 °C, including any value and subset therebetween, such as T C < 2,000 °C) and does not preferentially form stable metal-carbide compounds (e.g., CaC2, HfC, LaC2, Mg2C, Mo2C, NbC, Nb2C, TaC, Ta2C, TiC, VC, V2C, WC, W2C, or ZrC) on solid carbon (graphite) upon cooling.

[0032] As shown in FIG. 1 depicting the Ni-C binary phase diagram, when carbon fibers are manufactured according to various aspects of the present disclosure, the carbon-metal melt saturates when passing through the liquidus line.

[0033] As used herein, the term "carbon fiber seed", and its grammatical variants, refers to a carbon filament composed of hexagonal microcrystals of carbon (space group P63 / mmc), also known as graphite, having a diameter of at least about 5 μm width, a length of at least about 1 mm, and a 3 bulk density of less than about 2.2 g / cm. In one or more aspects of the present disclosure, for example, the width of the carbon fiber seed may range from about 5 μm to about 50 μm, the length of the carbon fiber seed may range from about 1 mm to about 1 m, and the bulk density of the carbon fiber seed may range from about 1.7 g / cm 3 to about 2.2 g / cm 3 and may include any value and subset therebetween. In some cases, the bulk density of the carbon fiber seed is less than about 2.0 g / cm 3 or less than about 1.8 g / cm 3 . The hexagonal microcrystals of the carbon fiber seed are aligned along their c-axes perpendicular to the carbon-filament axis and have a length of at least about 5 nm, a width of at least about 2 nm, and a lattice plane spacing (d 002 or c / 2) greater than about 0.33 nm. In one or more aspects of the present disclosure, for example, the length of the hexagonal microcrystals may range from about 5 nm to about 20 nm, the width of the hexagonal microcrystals may range from about 2 nm to about 5 nm, and the lattice plane spacing of the hexagonal microcrystals may range from about 0.33 nm to about 0.35 nm, each including any value and subset therebetween. In one or more aspects of the present disclosure, the carbon fiber seed can be obtained from commercially graded carbon fibers (e.g., spools containing bundles of such carbon filaments).

[0034] As used herein, the term "carbon source" and its grammatical variants mean a substance from which the carbon raw material is derived. As used herein, the term "carbon precursor raw material" and its grammatical variants mean a solid-phase ("solid") carbon precursor, mainly in the form of carbon powder, pellets (e.g., compressed blocks), or aggregates (e.g., agglomeration of pellets), for direct use in the production of high-value carbon fibers. The term "carbon precursor raw material" is used herein with the same meaning as the terms "carbon precursor" and "carbon raw material".

[0035] As used herein, the term "capillary die-based fiber shaper technology" and its grammatical variants mean a technique for forming carbon fibers that utilizes capillary channels that enable a carbon-metal melt to rise (either up or down) through the opening of a die by the action of capillary force. Examples of such capillary die-based fiber shaper technology for use in the present disclosure include, but are not limited to, the micro-pull-down (μ-PD) method and the edge-defined film fed growth (EFG) method. The μ-PD method produces carbon fibers when pulled down from a meniscus suspended from a capillary die containing a carbon raw material, and conversely, the EFG method produces carbon fibers when pulled up from a meniscus supported by a capillary die immersed in a carbon solution. Although various aspects of the present disclosure are generally described with reference to the μ-PD method, it should be understood that various aspects of the present disclosure are equally applicable to the EGF method without limitation.

[0036] The methods and apparatuses of the present disclosure use low-value (or low-cost) carbon precursor raw materials derived from low-value (or low-cost) carbon sources for use in the production of high-value carbon fibers, and the production thereof involves a two-step procedure.

[0037] The first step involves producing a solid carbon raw material (derived from a carbon source) that has at least about 95% mol / mol of elemental carbon, less than about 5% mol / mol of heteroatoms, and less than about 5% mol / mol of metallic impurities. The heteroatoms are not considered to be particularly limited and depend at least on the selected carbon source. Examples include, but are not limited to, S, N, O, Cl, F, etc., and any combination thereof. The metallic impurities are not considered to be particularly limited and depend at least on the selected carbon source. Examples include, but are not limited to, Al, Ca, Fe, Mg, Na, K, Si, Ti, V, etc., and any combination thereof. In one or more aspects of the present disclosure, for example, the carbon raw material has an elemental carbon composition in the range of about 95% mol / mol to about 99.999% mol / mol, a heteroatom composition in the range of about 5% mol / mol to about 1 part per million by volume (ppmv) mol / mol, and a metallic impurity composition in the range of about 5% mol / mol to about 1 ppmv mol / mol, each including any value and subset therebetween.

[0038] The atomic structure of carbon raw materials can vary from completely amorphous to pure graphite. The carbon raw materials can be derived from a number of carbon sources (e.g., biomass, plastics, fossil fuels, petroleum coke, etc., including those described later in this specification), and can be derived through various chemical processes (e.g., biomass treatment, oil refining by-products (petroleum coke), hydrocarbon pyrolysis (e.g., natural gas, acetylene, benzene, etc.) and any combination thereof). In one or more embodiments, the carbon raw materials can be derived from the pyrolysis of natural gas (methane pyrolysis). In one or more embodiments of the methane pyrolysis process according to the present disclosure, a hot gaseous metal (e.g., Zn) is fed into the reactor simultaneously with cold methane, where the gaseous metal is cooled, which includes the formation of nano-sized droplets that catalyze the methane pyrolysis reaction as a result, and the heat of vaporization provides the pyrolysis reaction (endothermic). One or more embodiments of the methane pyrolysis process for inducing the carbon raw materials of the present disclosure are made with reference to the use of hot gaseous Zn, while, without limitation, any other metal (e.g., cesium, selenium, rubidium, potassium, cadmium, sodium, polonium, tellurium, magnesium, ytterbium, lithium, strontium, thallium, calcium, etc., and any combination thereof) can be used in the pyrolysis reaction for the production of the carbon raw materials described herein without departing from the scope of the present disclosure.

[0039] The second step involves utilizing a carbon-metal melt in the presence of carbon fiber seeds that are continuously pulled using capillary die-based crystal shaper technology (the "carbon fiber manufacturing process", or the "carbon fiber growth process", and grammatical variants thereof). The carbon fiber manufacturing process utilizes the capillary die-based crystal shaper technology described above in this specification, including, without limitation, the μ-PD process or the EFG process. The present disclosure can be achieved by using these techniques as a means to facilitate carbon deposition and carbon fiber growth, about 10 2 ~ about 10 4Utilize a large temperature gradient of K / mm. The carbon fiber manufacturing process is differentiated from previous capillary die-based crystal fiber growth techniques in that the fiber composition (pure carbon) does not represent a carbon-metal melt (also referred to as the "mother solution composition"). In one or more aspects of the carbon fiber manufacturing process of the present disclosure, control of carbon fiber growth can be achieved by using a die capillary through which molten carbon diffuses.

[0040] The present disclosure aims to reduce the cost of carbon fiber production to below approximately $22 per kg, which is the current standard cost. In some cases, the cost can be reduced to less than approximately $15 per kg, or less than approximately $10 per kg, or less than approximately $7 per kg, excluding graphitization and stabilization post-treatment. In these cost reductions, carbon fibers produced in accordance with various aspects of the present disclosure can penetrate large market areas such as the automotive, marine, and construction sectors, among several fields that have not been widely used conventionally due to cost concerns. For example, in the automotive market segment, a reduction in the cost of carbon fiber can enable a carbon fiber-reinforced polymer composite body to economically replace a steel body, thereby reducing the weight of the vehicle and increasing fuel efficiency by up to approximately 28%. As a result, transportation energy consumption in the United States can be reduced by up to 7.9 quads per year, and CO2 emissions can potentially be reduced by approximately 1.4 Gt (about 8% of the total energy and emissions in the United States).

[0041] In various aspects, to achieve the desired reduction in carbon fiber production costs described herein, lower-value (or lower-cost) carbon raw materials are used rather than the more expensive PAN raw materials that are used to produce most of today's carbon fibers. The source of carbon raw materials for use in the various aspects of the present disclosure is not considered to be particularly limited. Examples of suitable carbon raw materials include solid carbon derived from hydrocarbon gases (e.g., methane, ethane, propane, butane, acetylene, etc.), hydrocarbon liquids (e.g., hexane, benzene, etc.), hydrocarbon solids (e.g., paraffin wax, naphthalene, etc.), and any combination thereof, but are not limited thereto. Other carbon raw materials can be derived from industrial or natural environmental processes such as natural gas, flare natural gas, biogas, pyrolysis gas, petcoke, coal, soot, recycled pure carbon fiber waste, recycled carbon fiber composite waste, plastics, recycled plastics, biomass, organic waste, petroleum, oils (e.g., synthetic oil and / or natural oil), biochar, other fossil fuels, etc., and any combination thereof. Thus, one or more components of natural gas, flare natural gas, biogas, pyrolysis gas, petcoke, coal, soot, recycled pure carbon fiber waste, recycled carbon fiber composite waste, plastics, recycled plastics, biomass, organic waste, petroleum, oils (e.g., synthetic oil and / or natural oil), biochar, other fossil fuels, etc., and any combination thereof should be understood to include any one, two or more, or all of the hydrocarbon components (e.g., the gases, liquids, solids described herein). Advantageously, these lower-value carbon raw materials can not only contribute to the reduction of the cost of carbon fibers, but also contribute to realizing environmental and economic benefits that were not previously utilized.

[0042] For example, the inherent compositional variability, intermittency, and relatively high cost of transportation of flare natural gas present significant challenges for market use. As a result, approximately 1% of annual gas production is burned or vented to the atmosphere, resulting in concerns related to environmental impact and an estimated annual domestic loss of approximately $1 billion. As a result of these concerns, recent approaches to recovering flare gas for various uses have been explored. These uses include on-site power generation, modular liquefied natural gas recovery, and small modular natural gas liquefaction. However, such uses remain insufficiently cost-effective at the scale required to address the flaring rate in individual petrochemical facilities. Other low-value carbon sources have traditionally suffered from similar problems and may now be made available in accordance with various aspects of the present disclosure. Carbon fiber manufacturing process

[0043] The carbon fiber manufacturing process of the present disclosure is different from conventional commercial carbon fiber production processes. Specifically, the carbon fiber manufacturing process of the present disclosure can form a carbon-metal melt solution using solid carbon as a raw material obtained from a methane pyrolysis process, whereby the molten elemental carbon becomes a molten metal-carbon meniscus, and this is cooled to be below the liquidus temperature of the melt in the presence of carbon fiber seeds. At this time, as the equilibrium carbon solubility of the carbon-metal melt decreases, carbon is promoted to crystallize on the carbon fiber seeds located at the bottom of the meniscus. When carbon fibers grow, as described herein, using capillary die-based fiber shaper technology (e.g., μ-PD method, EFG method, or any other capillary die-based fiber shaper technology fiber growth method), carbon fibers are continuously pulled out from the meniscus, thereby forming carbon fibers, and by using a shaper nozzle (also called a die in the art), accurate dimensional control becomes possible. The use of these crystal fiber growth technologies has not been conventionally used in carbon fiber production on a commercial scale. Also, as described herein, the use of these crystal fiber growth technologies contributes to a reduction in the cost of carbon fibers, particularly in combination with other cost-saving measures described herein. That is, although the crystal fiber growth process of the present disclosure is mainly described with reference to a carbon-metal melt formed by inputting solid carbon obtained from a methane pyrolysis process, without departing from the scope of the present disclosure, other carbon sources can similarly be used in the μ-PD carbon fiber manufacturing process.

[0044] The carbon fiber growth described in this specification is based on continuously transporting carbon through a microchannel nozzle fabricated at the bottom of a crucible into a carbon-metal melt (produced, for example, from solid carbon obtained from the methane pyrolysis process described later in this specification in the presence of a metal). Advantageously, the disclosed process does not require the starting carbon to be of the same or substantially the same phase or atomic structure as the produced carbon fiber. Thus, it becomes possible to use low-value carbon as a carbon source raw material for producing carbon fibers. Further, the high temperature gradient near the solid-liquid interface results in high growth stability and uniform distribution of carbon in the produced fibers. The high temperature gradient also reduces or eliminates continuous supercooling, whereby a relatively fast carbon fiber growth rate can be used.

[0045] Figure 2 shows a non-limiting example of a μ-PD carbon fiber growth apparatus 200. It should be understood that the EFG method can use a similar apparatus, in which case the carbon fiber is pulled upward instead of downward. Thus, the following description with reference to Figure 2 is not limited to the pulling direction from the meniscus for forming the carbon fiber.

[0046] As shown, the apparatus 200 includes a crucible 202. The material of the crucible 202 is a material having a melting point higher than the growth temperature of the desired crystalline fiber and can be mechanically strong enough to operate at the growth temperature during the production of the crystalline fiber. A carbon-metal melt 204 for forming carbon fibers is heated inside the crucible 202. The bottom portion of the crucible includes a microchannel nozzle 206, which has a length x. At the nozzle 206 and above the nozzle 206, the carbon-metal melt 204 in the crucible 202 is heated to a temperature above the liquidus. Below the nozzle 206, a meniscus 208 is formed by the carbon-metal melt. The temperature below the nozzle 206 and the temperature at the meniscus 208 are below the liquidus. The carbon fiber seed 210 is oriented below the nozzle 206 so as to contact the meniscus 208. The carbon fibers grow at the meniscus 208 and away from the seed 210 by continuously pulling downward (in the direction of the illustrated arrow) the crystallized carbon from the carbon-metal melt 204. The pulling rate must be set to maintain the contact between the seed 210 and the meniscus 208.

[0047] The size (diameter) and shape of the nozzle 206 determine the size and shape of the resulting carbon fibers and can be varied by skillful manipulation. The length x of the nozzle 206 may be from 1 μm to 1,000 μm, such as from 1 μm to 500 μm, or from 5 μm to 250 μm, or from 5 μm to 10 μm. Typically, the nozzle 206 has a spherical or hemispherical shape and has a diameter of from 1 μm to 100 μm, such as from 1 μm to 50 μm, or from 5 μm to 25 μm, or from 5 μm to 10 μm. Thus, the carbon fibers produced according to the μ-PD method of the present disclosure can have a diameter of from 1 μm to 100 μm, such as from 1 μm to 50 μm, or from 5 μm to 25 μm, or from 5 μm to 10 μm. It should be understood that nozzles of other shapes can be used according to the desired shape of the resulting carbon fibers, such as square, rectangular, or other polygonal shapes (for example, for producing carbon fiber sheets), without departing from the scope of the present disclosure.

[0048] For a specific carbon-metal melt, the maximum drawing speed (the drawing speed as shown in Figure 2, or the pulling speed when using, for example, the EFG method) can be estimated according to the length x of the nozzle 206 and the liquidus temperature. The maximum drawing speed (dx / dt) is determined by the carbon diffusion coefficient D in a specific carbon-metal melt composition through the length x of the shaper's nozzle 206 from the melt to the meniscus 208. The diffusion distance through the nozzle 206 is [Number] as follows. Thus, for example, at x = 10 μm, carbon fibers with a diameter of approximately 10 μm can be pulled down (or pulled up when using EFG) from the Ni-C alloy raw material at a speed of 1,000 mm / min and must be operated at 2,150 °C based on the carbon diffusion coefficient in nickel.

[0049] For example, depending on various factors, especially factors such as the composition of the carbon-metal melt and the diffusibility of carbon, the drawing speed using the capillary die-based fiber shaper technology of the present disclosure can be from about 10 mm / min to about 10,000 mm / min, such as 10 mm / min to 1,000 mm / min, or 100 to 5,000 mm / min, or about 1,000 to 10,000 mm / min, and the desired carbon fibers obtained can have a length of about 0.5 km to about 50 km, or 1 km to 30 km, or 1 to 10 km.

[0050] Figure 3 shows a non-limiting example of the carbon fiber reactor 300 of the present disclosure. It should be understood that the EFG method can use a similar device, in which case the carbon fiber is pulled upward instead of downward. Therefore, referring to Figure 3 and described later is not limited to the drawing direction from the meniscus for forming the carbon fiber.

[0051] The carbon fiber reactor 300 of the present disclosure is sized for the commercial production of high-value carbon fibers, such as from low-value carbon raw materials received from the methane pyrolysis process described herein. The reactor 300 includes a common crucible 302 for forming a container 303 for heating a carbon-metal melt 304. As shown, the container 303 can receive a large volume of solid carbon raw material into a common container 303, where the solid carbon raw material is heated to a temperature above the liquidus to form a carbon-metal melt 304. The volume capacity of the reactor 300 can depend on a number of factors including, but not limited to, the amount of solid carbon raw material received from a particular mine site, the available space for installation of the apparatus, etc. The carbon fiber reactor 300 can have a volume capacity of the container 303 of about 1 mL or more, such as 1 mL to 1,000 mL, or about 10 mL to about 800 mL, or about 500 mL to about 1,000 mL. However, it should be noted that larger volume capacity containers 303 are contemplated without departing from the scope of the present disclosure, depending on the amount of carbon fiber to be produced.

[0052] A plurality of nozzles 306, each having a length of x, extend from the container 303. For simplicity, four nozzles 306 are shown, but it should be understood that the number of nozzles 306 for commercial-scale carbon fiber production according to the present disclosure is significantly greater while having a similar configuration. In fact, the carbon fiber manufacturing process can be designed to produce from about 1 kg / day to about 10,000 kg / day (e.g., 100 kg / day to 10,000 kg / day, or 7,000 kg / day to 10,000 kg / day, or about 8,000 kg / day), and thus, depending on the diameter, length, and desired draw rate of the nozzles, up to millions of nozzles may be required.

[0053] As described above, the plurality of nozzles 306 can be up to several million or more. The plurality of nozzles can be 100,000 to 50 million, or 1 million to 40 million, or 5 million to 40 million. In some embodiments, the nozzles 306 are in the form of an array having the nozzles in an X-by-Y array (or grid) pattern, where X is an integer in the range of 20 to 5,000 nozzles (or 40 to 4,000 nozzles, or 40 to 2,000 nozzles), and Y is an integer in the range of 2,000 to 2,000,000 nozzles (or 2,000 to 1,500,000 nozzles, or 2,000 to 1,000,000 nozzles). The reactor 300 is preferably designed to supply various compositions of solid carbon raw materials for forming carbon-metal melts and carbon fibers obtained therefrom at once. Further, depending on a number of factors such as production capacity, input concentration of the carbon raw material, etc., a part of the nozzles may be blocked without departing from the scope of the present disclosure, or alternatively, it may be made inoperable during a specific carbon fiber manufacturing process.

[0054] For example, based on the carbon fiber drawing speed from a Ni-C alloy raw material at 2,150°C and 1,000 mm / min described above, carbon fibers with a diameter of 10 μm are desirable (i.e., the nozzles have a diameter of 10 μm), and a methane pyrolysis process that produces Ni-C solid raw materials at 1.6 t / day requires 8 million nozzles such as in a 2,000×4,000 array.

[0055] As similarly described above with reference to FIG. 3, in the plurality of nozzles 306 and on top of the plurality of nozzles 306, within the vessel 303 of the crucible 302, the carbon-metal melt 304 is heated to a temperature above the liquidus. Below each of the plurality of nozzles 306, a meniscus 308 is formed by the carbon-metal melt. The temperature below the plurality of nozzles 306 and at the meniscus 308 is below the liquidus. The carbon fiber seeds 310 are oriented below the plurality of nozzles 306 such that each meniscus 308 contacts them. The carbon fibers grow at the meniscus 308 and away from the seeds 310 by continuously pulling downward (in the direction of the illustrated arrow) the crystallized carbon from the carbon-metal melt 304. The pulling rate must be set to maintain contact between the seeds 310 and the meniscus 308.

[0056] FIG. 4 shows a non-limiting example of a carbon fiber manufacturing system 400 of the present disclosure.

[0057] The system includes a carbon fiber reactor 402. The carbon fiber reactor 402 may be substantially similar to the carbon fiber reactor 300 described in FIG. 3, comprising a vessel 303 and a plurality of shaped nozzles 306. The reactor 402 receives a solid carbon raw material 404, such as that derived from a low-value carbon source, such as flare natural gas from an oil and gas well site. In such an example, the solid carbon 404 may be transported from an oil and gas production site to a centralized facility equipped with the carbon fiber manufacturing system 400. The centralized facility may be located at the well site itself or provided at a local location without departing from the scope of the present disclosure. Further, before introducing the solid carbon 404 into the reactor 402, the solid carbon 404 can be stored in a storage container for later use. In this way, all or only a portion of the solid carbon 404 can be used in any single carbon fiber manufacturing process.

[0058] Solid carbon 404 is heated in reactor 402 in the presence of a metal (or the solid carbon 404 itself may already have metal impurities), and one or more heaters 406 above the liquidus form a carbon-metal melt to form a carbon melt. The heater may be, for example, an electric heater, an induction heater, a boiler, a heat exchanger, etc., and any combination thereof, provided that, alone or in combination, they can heat the solid carbon 404 in reactor 402 above the relevant liquidus (e.g., 1,000 °C to 3,000 °C, or 1,500 °C to 2,500 °C). The heat source of heater 406 may comprise a tubular heating element, a cartridge heater, a strip heater, a cast-in heater, etc., and any combination thereof.

[0059] The molten metal-carbon meniscus is formed in each of the (available) nozzles of reactor 402, and the melt in the meniscus is cooled below the liquidus temperature of the melt in the presence of carbon fiber seeds provided in each nozzle. The carbon fibers are continuously pulled at a desired draw rate using the μ-PD method described herein. Each carbon fiber is collected by a fiber winder 408. The fiber winder 408 may be operated by a motor 410 or other system (e.g., a conductive drive type electric control circuit) and may consist of a plurality of spools that rotate when carbon fibers are collected on the spools. The rotational speed of the plurality of spools will depend on the specific draw rate of the carbon fiber manufacturing process, and each of the plurality of spools may receive carbon fibers from a plurality of nozzles. For example, each spool may contain from about 1,000 to about 50,000 fibers, the fibers having a diameter of about 5 to about 15 μm and a length of about 1 to about 50 km. Each spool is capable of storage or immediate transport to the market (indicated by the arrow).

[0060] In some embodiments, the carbon fibers may be further processed after production. For example, the carbon fibers may be optionally graphitized to improve the mechanical properties of the carbon fibers. Graphitization may be carried out, for example, at about 1,500 °C to about 3,000 °C.

[0061] The carbon fibers produced according to the methods described herein, using low-value carbon raw materials derived from methane pyrolysis and formed using a crystal fiber forming method such as the μ-PD method or the EFG method, are suitable for use as an alternative to currently available carbon fibers. Advantageously, as described herein, they exhibit equivalent mechanical properties (ASTM D4018-99) while significantly reducing costs. Methane Pyrolysis Process - Carbon Source for Carbon-Metal Melts

[0062] As described above, in one or more embodiments, the solid carbon for use as a raw material in the carbon fiber manufacturing process of the present disclosure can be derived from any source. In certain embodiments, the source is derived from a methane pyrolysis process that utilizes a low-value carbon source and produces hydrogen and solid carbon, as described later herein.

[0063] The methane pyrolysis process of the present disclosure is optimized for solid carbon production, with hydrogen being produced as a by-product, which can be used to provide heat for the process. In one or more embodiments, the pyrolysis process uses a low-boiling metal (e.g., zinc, or any other suitable metal) in the gas phase to catalyze methane pyrolysis upon condensation into nano-sized droplets, whereby the evaporation enthalpy of the metal provides the heat of reaction for methane pyrolysis.

[0064] Figure 5 shows a part of the methane pyrolysis process described in this specification. First, the catalyst gas [catalyst (g)] condenses into catalyst droplets of the catalyst liquid [catalyst (l)]. The condensation of the catalyst gas into the catalyst liquid is exothermic, involving a negative change in enthalpy. As shown, the catalyst liquid then catalyzes the decomposition of the hydrocarbon gas [hydrocarbon (g)], forming solid carbon [C(s)] and hydrogen [H2(g)]. However, this figure does not prevent the gas-phase catalyst from also catalyzing the decomposition reaction.

[0065] The heat of reaction in the hydrocarbon decomposition process is positive and thus endothermic. The superheated catalyst gas at partial pressure (P C ) can be mixed with the much lower temperature hydrocarbon gas (P H ), with the total reactor pressure being P 合計 = P M + P H and the catalyst filling rate being f = P M / P 合計 . Without being limited by theory, it is believed that the catalyst, hydrocarbon, and reactor conditions (e.g., pressure and temperature) can be selected such that the exothermic process of condensing the catalyst gas into the catalyst liquid provides sufficient heat for the pyrolysis reaction.

[0066] As a particular preferred example, the methane pyrolysis process uses condensed gaseous zinc (e.g., T bUsing homogeneous nucleation (at 900 °C and a partial pressure of 1 bar), nanosized droplets can be formed at a high filling rate, achieving a high catalytic surface density for catalyzing methane pyrolysis. These droplets with a large surface area result in methane pyrolysis with a high reactor space-time yield, a high gas space velocity per hour, and a high single-pass methane conversion rate (e.g., about 80% or more, or about 90% or more). These characteristics enable a desirable dense, modular methane pyrolysis configuration and transportability. Furthermore, while the enthalpy of condensation for zinc is an energy of about -115 kg / mol, the heat of reaction for the zinc-catalyzed pyrolysis of methane is only about 75 kg / mol of energy. Therefore, the condensation part of this method can provide the pyrolysis enthalpy, which simplifies the reactor heat management and has the potential to reduce production costs because even if there is additional energy input, it is only required to a minimal extent. Zinc-based methane pyrolysis can also easily separate solid carbon because a trace amount of zinc catalyst can easily evaporate from the solid carbon. When the hydrocarbon source is natural gas, it reacts conveniently to produce a solid that can be easily separated, providing an inherent getter system for removing contaminants (e.g., H2S, CO2, etc.) from solid carbon.

[0067] FIG. 6 shows a non-limiting example of the methane pyrolysis process 600 of the present disclosure.

[0068] The catalyst source 602 is evaporated (604) to produce a catalyst gas 606. Optionally, an inert carrier gas for the decomposition reaction (e.g., argon, nitrogen, etc., and any combination thereof) can be included in the evaporation.

[0069] The catalyst suitable for use in the method described in this specification preferably has a boiling point of over about 700 °C to less than about 1,200 °C (or about 800 °C to about 1,100 °C, or about 900 °C to about 1,000 °C). Examples of the catalyst include, but are not limited to, metals, molten salts, ionic liquids, etc. Examples of metal catalysts include, but are not limited to, zinc, cesium, selenium, rubidium, potassium, cadmium, sodium, polonium, tellurium, magnesium, ytterbium, lithium, strontium, thallium, calcium, etc., and any combination thereof. Preferred metal catalysts include, but are not limited to, zinc, sodium, magnesium, and any combination thereof. Suitable salt catalysts may be salts containing (a) an alkali metal cation, an alkaline earth metal cation, a transition metal cation, or other metal cation, and (b) anions such as nitrate ion, citrate ion, halide ion, cyanide ion, and hydride ion. Specific examples of salt catalysts include, but are not limited to, sodium chloride, sodium bromide, sodium iodide, sodium sulfate, lithium chloride, lithium bromide, lithium iodide, lithium sulfate, potassium chloride, potassium bromide, potassium iodide, potassium fluoride, magnesium chloride, magnesium bromide, calcium iodide, zinc chloride, zinc bromide, etc., and any combination thereof.

[0070] The temperature of the catalyst gas 606 is higher than the boiling point of the catalyst. The temperature of the catalyst gas 606 is preferably about 5 °C to about 500 °C (or about 5 °C to about 50 °C, or about 50 °C to about 100 °C, or about 100 °C to about 250 °C, or about 200 °C to about 500 °C) higher than the boiling point of the catalyst.

[0071] Next, the catalyst gas 606 is condensed (608) to form a catalyst vapor 610 containing catalyst droplets. The condensation is achieved by lowering the temperature of the catalyst gas 606, which can be achieved in various ways. For example, the reactor can be designed to have the catalyst gas 606 pass through a portion of the reactor that is sufficiently cooler than the catalyst gas 606 to produce the catalyst vapor 610. In another example, the catalyst gas 606 can be contacted (e.g., mixed) (614) with a hydrocarbon gas 612 having a temperature low enough to promote the condensation 608 of the catalyst gas 606. In this example, the hydrocarbon gas 612 may be at a temperature about 5 °C to about 500 °C (or about 5 °C to about 50 °C, or about 50 °C to about 100 °C, or about 100 °C to about 250 °C, or about 200 °C to about 500 °C) lower than the boiling point of the catalyst.

[0072] The pressure of the catalyst gas 606 can affect the size and density of the catalyst droplets, and a higher pressure can result in more dense catalyst droplets. The pressure of the catalyst gas 606 may be about 0.1 bar to about 200 bar (or about 0.1 bar to about 25 bar, or about 0.5 bar to about 100 bar, or about 10 bar to about 200 bar).

[0073] The catalyst vapor 610 may contain catalyst droplets having a diameter of about 5 nm to about 1,000 nm (or about 5 nm to about 150 nm, or about 10 nm to about 250 nm, or about 250 nm to about 1,000 nm). Further, the catalyst vapor 610 may contain catalyst droplets such that about 60 vol% or less (or about 0.1 vol% to about 60 vol%, or about 0.1 vol% to about 5 vol%, or about 0.1 vol% to about 10 vol%, or about 5 vol% to about 30 vol%, or 25 vol% to about 50 vol%) of the catalyst vapor 610 is the catalyst droplets (or catalyst liquid). Thus, the catalyst surface density of the catalyst vapor 610 per reactor volume is at most about 10,000 m 2 / m 3 (or about 1,000 m 2 / m 3 ~ about 100,000 m 2 / m 3 or about 5,000 m 2 / cm3 ~about 20,000 m 2 / m 3 、or about 15,000 m 2 / cm 3 ~about 30,000 m 2 / cm 3 ) may be sufficient.

[0074] By having a large catalyst surface area, a higher gas hourly space velocity per hour becomes possible, which can improve the commercial viability of the methods described herein and enable a portable design that is small and modular for use in carbon fiber production according to the present disclosure. The methods described herein are from about 1,000 h -1 ~about 100,000 h -1 (or about 1,000 h -1 ~about 10,000 h -1 、or about 1,000 h -1 ~about 5,000 h -1 、or about 5,000 h -1 ~about 25,000 h -1 、or about 25,000 h -1 ~about 100,000 h -1 ) and can be carried out at a gas hourly space velocity per hour. A higher catalyst surface density contributes, at least in part, to the required higher gas hourly space velocity per hour.

[0075] Catalyst vapor 610 and hydrocarbon gas 612 react such that the catalyst (gas phase and / or liquid phase) catalyzes the decomposition reaction 616 of hydrocarbon gas 612. FIG. 6 shows hydrocarbon gas 612 and the catalyst (gas phase and / or liquid phase) in contact during the formation of catalyst vapor 610. However, hydrocarbon gas 612 can be introduced into the process at any point before reaction 616, including during evaporation, during condensation, after condensation, and any combination thereof. For example, hydrocarbon gas 612 can be introduced into the process at multiple locations.

[0076] The hydrocarbon gas 612 may include C1 - C20 alkanes (linear, branched, and / or cyclic), C1 - C20 alkenes (linear, branched, and / or cyclic), C1 - C20 alkynes (linear, branched, and / or cyclic), C6 - C20 arenes, and any combination thereof. For example, the hydrocarbon gas may include methane, ethane, and / or propane. For use in the present disclosure, the hydrocarbon gas 612, as described above herein, is derived from low - value carbon sources and any combination (e.g., natural gas (e.g., flare natural gas), biogas, pyrolysis gas, petcoke, coal, soot, recycled carbon fiber waste, recycled plastic, biomass, organic waste, other fossil fuels, etc., and solid carbon derived from any combination thereof).

[0077] Generally, since the catalyzed decomposition reaction 616 occurs with little or no reactive oxygen - containing compounds present, the production of carbon dioxide is minimized. For example, the gas phase to which the catalyst (gas - phase and / or liquid - phase) is exposed preferably has a cumulative amount of oxygen - containing compounds that are reactive and produce carbon dioxide of less than about 1 vol% (or 0 vol% - about 1 vol%, or about 0.01 vol% - about 0.1 vol%) during the decomposition reaction. Such oxygen - containing compounds include, but are not limited to, oxygen (O2), carbon monoxide, water, etc., and any combination thereof.

[0078] The catalyst vapor 618 containing hydrogen, catalyst droplets, optionally a catalyst gas, and carbon is further condensed to separate (620) a gas component 622 (e.g., hydrogen gas, optionally unreacted hydrocarbon gas, and optionally a catalyst gas) from a solid / liquid mixture 624 containing carbon and a catalyst liquid.

[0079] The hydrogen in the gas component 622 can be further separated from other components, for example, by a condenser and / or other separator.

[0080] Next, the solid carbon 628 can be separated (626) from the mixture 624 by known methods including mechanical separation (e.g., filtration, gravity separation, powder separation, etc.) and / or thermal separation (e.g., by evaporation of the catalyst). For example, an induction heating method is performed to more efficiently evaporate the catalyst from the solid carbon using a high vapor pressure catalyst such as zinc. Further, such a method applies heat to the catalyst, thereby reducing the additional heat required for downstream evaporation when the catalyst returns to the catalyst source 602 by reuse.

[0081] Next, the catalyst liquid 630 can be recycled (632) and returned to the catalyst source 602. As an alternative to separation 626 prior to the recycling 632 procedure, the mixture 624 can be reused (634) and returned to the catalyst source 602, and carbon 638 can be separated (636) from the catalyst source 602.

[0082] The catalyst is preferably selected such that (a) the carbon and the catalyst do not react or form an alloy, and (b) the carbon does not dissolve in the catalyst liquid, whereby the carbon can naturally exist as a solid phase separable from the catalyst in liquid form (e.g., slag, carbon fiber, graphene, diamond, glassy carbon, high purity graphite, carbon nanotube, carbon black, coke, activated carbon, etc., and as any combination thereof). Separating the carbons 628, 638 from the mixture 624 or the catalyst source 602 can be achieved by filtration, gravity separation, mechanical removal of suspended solid carbon, powder separation, etc., and any combination thereof.

[0083] FIG. 7 shows a system 700 of a non-limiting example of the present disclosure.

[0084] As used herein, when describing components of a system coupled by a flow, "coupling" means a fluid and / or solid that can move or be transported from one component to another, or between components. When crossing a coupling, the fluid and / or solid can move through hardware such as lines, pipes, pumps, conveyors, augers, extruders, connectors, heat exchangers, valves, mass flow controllers, cooling towers, compressors, boilers, reactors, etc., to ensure proper operation and safety means within the system. When using a single flow to describe a coupling, the flow can be physically implemented as multiple lines, pipes, etc., and can include additional hardware along the flow without limitation. Further, as will be apparent to those skilled in the art, the system 700 shown in this non-limiting example can include additional components such as compressors, membranes, valves, flow meters, heat exchangers, traps, etc., for the proper and safe operation of the methods described herein.

[0085] System 700 includes a catalyst source evaporator 702 coupled to a reactor 706 via a flow 704. The catalyst source evaporator 702 evaporates a catalyst source within the catalyst source evaporator 702 to produce a catalyst gas and conveys this to the reactor 706 via the flow 704. Optionally, an inert carrier gas (e.g., argon, nitrogen, etc., and any combination thereof) that is inert to the decomposition reaction can be included in the flow 704.

[0086] System 700 also includes a hydrocarbon source 708 connected to reactor 706 via flow 710. As shown, flow 710 passes through cooling column 712, thereby heating the hydrocarbons in flow 710. Hydrocarbon source 708 may be obtained from a flare gas stack, pipeline, tank, truck tank, distillation column, etc., and any combination thereof. When hydrocarbons from hydrocarbon source 708 are introduced into reactor 706, the hydrocarbons must be hydrocarbon gas. In particular, the methane pyrolysis process of the present disclosure is robust to various types of hydrocarbon gas raw materials, including wet gas, dry gas, sour gas, and acid gas raw materials.

[0087] As shown, the hydrocarbon gas is introduced into reactor 706 downstream of the catalyst gas. However, in an alternative embodiment, the hydrocarbon gas can be introduced upstream of the catalyst gas or in parallel with the catalyst gas.

[0088] Continuing to refer to FIG. 7, within reactor 706, the catalyst gas becomes catalyst vapor and reacts with the hydrocarbon gas. The hydrocarbon gas must be introduced into the reactor in a manner that mitigates the formation of turbulence or vortices and promotes the condensation of catalyst droplets in the catalyst vapor.

[0089] The hydrocarbon gas reacts with a catalyst (in the gas and / or liquid phase) to produce hydrogen and solid carbon. Thus, the effluent stream 714 from the reactor 706 contains hydrogen, the catalyst (in the gas and / or liquid phase), and carbon solids, and may further contain unreacted hydrocarbon gas, and / or by-products, and / or a carrier gas. Stream 714 fluidly couples the reactor to a cooling column 712. Within the cooling column, the catalyst condenses into a liquid, separating the catalyst from the other gas-phase components of stream 714 (e.g., hydrogen, unreacted hydrocarbon gas, by-products, and / or carrier gas). However, some of the catalyst may remain in gaseous form. The catalyst liquid and solid carbon pool settle to the bottom of the cooling column 712, while the gas-phase components remain above the settling section within the cooling column 712. The gas-phase components exit the column 712 via stream 716. Stream 716 connects the cooling column 712 to a separator 718. The separator 718 separates hydrogen from the other gas components, producing a hydrogen stream 722 and a stream 720 that contains unreacted hydrocarbons, reaction by-products (if present), carrier gas (if present), and / or catalyst gas (if present). In the separator 718, the catalyst gas, if present, may condense into a catalyst liquid, thereby generating other streams (not shown) that can be recycled back to the catalyst source evaporator 702 or, if a catalyst liquid is present, to other streams or components. The separator 718 may operate by condensation, filtration, and / or other suitable principles.

[0090] As shown, stream 720 connects the separator 718 to the reactor 706 for further reaction of the components of stream 720. However, recycling is not required in the systems and methods described herein.

[0091] The hydrogen-containing stream 722 can be at a high temperature and can be beneficially used as a heat source for use in the methane pyrolysis process, such as by recirculation (dashed line) to the cooling tower 712 or the catalytic source evaporator 702. In another case, the hydrogen-containing stream 722 can be compressed, stored, and / or transported as desired, or can be used as a source for heating the methane pyrolysis process. The stream 722 may contain 80 vol% or more (or 80 vol% to 100 vol%, or 90 vol% to 100 vol%, or 95 vol% to 99.5 vol%) of hydrogen.

[0092] The catalytic liquid and solid carbon pooled at the bottom of the cooling column 712 are separated. The method and / or system for separating the catalytic liquid and solid carbon vary depending on, among other factors, the catalyst, the solubility of the catalyst and / or alloy formation with carbon, and the relative density of the catalytic liquid and solid carbon. In the system 700 shown in FIG. 7, the solid carbon is insoluble in the catalytic liquid and the solid carbon has a lower density than the catalytic liquid. Accordingly, the solid carbon floats in the pooled catalytic liquid. Accordingly, the upper part of the pooled material can be extracted from the column 712 by the stream 726. The stream 726 fluidly connects the cooling column 712 to the separator 728. The separator 728 can operate by evaporation, filtration, and / or other suitable principles for separating the catalyst from the solid carbon to produce a stream 730 containing solid carbon and a stream 732 containing the catalyst.

[0093] As shown, the stream 732 connects the separator 728 to the catalytic source evaporator 702. However, reuse is not required in the systems and methods described herein. The stream 732 may contain 80 vol% or more (or 80 vol% to 100 vol%, or 90 vol% to 100 vol%, or 95 vol% to 99.5 vol%) of the catalytic liquid.

[0094] The bottom of the pooled material is a catalyst liquid that has little or no solid carbon, and thus can be recycled back to the catalyst source evaporator 702 via flow 724. Flow 724 connects the cooling column 712 to the catalyst source evaporator 702. Again, recycling is not required but is preferred in the systems and methods described herein. Flow 724 may contain 80 vol% or more (or 80 vol% - 100 vol%, or 90 vol% - 100 vol%, or 95 vol% - 99.5 vol%) of the catalyst liquid.

[0095] The stream 730 containing solid carbon is used to process high-value carbon fibers using the carbon fiber manufacturing process described herein. Stream 730 may contain 80 vol% or more (or 80 vol% - 100 vol%, or 90 vol% - 100 vol%, or 95 vol% - 99.5 vol%) of solid carbon.

[0096] The methane pyrolysis process described herein (e.g., system 700 of FIG. 7) is preferably used on-site at oil and gas well sites to minimize transportation and equipment costs. In some cases, the methane pyrolysis process may be small-sized, modular, and outdoor movable. For example, when referring to a hydrocarbon source of natural gas (e.g., flare gas), the methane pyrolysis process may have a maximum display capacity of about 100 Mcfd, such as in the range of about 10 Mcfd to about 100 Mcfd, or about 30 Mcfd to about 100 Mfcd, or about 50 Mfcd to about 100 Mfcd.

[0097] However, it should be understood that without departing from the scope of this disclosure, the methane pyrolysis (and carbon fiber manufacturing process) may be used at a location remote from any site. Integrated Methane Pyrolysis Process and Carbon Fiber Manufacturing Process

[0098] In some cases, the methane pyrolysis process and the carbon fiber manufacturing process can be integrated into a single reactor. The integrated reactor separates the pyrolysis process from the carbon fiber manufacturing process.

[0099] FIG. 8 shows a non-limiting example of an integrated carbon fiber system 800 of the present disclosure.

[0100] System 800 includes a methane pyrolysis section 802 that includes a molten methane pyrolysis catalyst as described above. The molten catalyst can be heated by an internal or external (e.g., jacketed) heat source. The inlet receives low-value carbon 804 (e.g., flare natural gas) such as those described above. Methane pyrolysis occurs in pyrolysis section 802, which may be in the form of a bubble column reactor. Carbon dissolves to form a molten ternary alloy, and a nucleation zone is provided on surface 806. A carbon fiber seed is provided in nucleation zone 806, where carbon fibers nucleate and are continuously pulled upward (vertically, upward arrow) in a manner similar to the form of the μ-PD method described above and collected on one or more bobbins (spools) 808. Hydrogen by-product 810 exits system 800 and may, in some cases, be recycled back to the reactor to produce heat.

[0101] The continuous draw carbon fiber manufacturing method described with reference to integrated system 800 is equally applicable to the μ-PD method described herein, where pyrolysis section 802 is oriented such that carbon fibers nucleate and the growth of the carbon fibers is achieved by being pulled downward as described above. Exemplary Embodiments

[0102] Clause 1. A method comprising contacting a carbon fiber seed with a carbon-metal melt and pulling out the carbon fiber seed at a draw rate to form a carbon fiber.

[0103] Clause 2. When the pulling speed is the pulling-down speed from the meniscus of the carbon-metal melt, the temperature of the carbon-metal melt above the meniscus is above the liquidus line, the temperature below the meniscus is below the liquidus line, and when the pulling speed is the pulling-up speed from the meniscus of the carbon-metal melt, the temperature of the carbon-metal melt below the meniscus is above the liquidus line, and the temperature above the meniscus is below the liquidus line. The method according to claim 1.

[0104] Clause 3. The method according to clause 1 or 2, wherein the pulling speed is from about 1 mm / min to about 10,000 mm / min.

[0105] Clause 4. The method according to clause 3, wherein the pulling speed is 1,000 mm / min.

[0106] Clause 5. The method according to any one of clauses 1 to 4, wherein the carbon fiber has a diameter in the range of about 1 μm to about 100 μm.

[0107] Clause 6. The method according to any one of clauses 1 to 5, wherein the carbon fiber has a length of about 0.5 km to about 50 km.

[0108] Clause 7. The method according to any one of clauses 1 to 6, wherein the carbon-metal melt contains a carbon source selected from the group consisting of hydrocarbon gas, hydrocarbon liquid, hydrocarbon solid, natural gas, flare natural gas, biogas, pyrolysis gas, petcoke, coal, soot, recycled pure carbon fiber waste, recycled carbon fiber composite waste, plastic, recycled plastic, biomass, organic waste, petroleum, oil, biochar, fossil fuel, etc., and any combination thereof.

[0109] Clause 8. The method according to clause 7, wherein the carbon source is derived from the pyrolysis reaction of a reaction gas selected from the group consisting of hydrocarbon gas, natural gas, flare natural gas, biogas, pyrolysis gas, and any combination thereof.

[0110] Clause 9. The method according to Clause 8, comprising: evaporating a catalyst source to generate a catalyst gas; condensing the catalyst gas to generate a catalyst vapor containing catalyst droplets suspended in the gas phase; and contacting the catalyst vapor with the reaction gas to catalyze the decomposition reaction of the gas into hydrogen gas and the carbon source.

[0111] Clause 10. The method according to Clause 8 or Clause 9, wherein the catalyst gas before condensation is at a temperature about 5 °C to about 500 °C higher than the boiling point of the catalyst.

[0112] Clause 11. The method according to any one of Clauses 8 to 10, wherein condensing the catalyst gas includes exposing the catalyst gas to the reaction gas, and the reaction gas is at a temperature below the boiling point of the catalyst.

[0113] Clause 12. The method according to any one of Clauses 8 to 11, wherein the catalyst is a metal catalyst selected from the group consisting of zinc, cesium, selenium, rubidium, potassium, cadmium, sodium, polonium, tellurium, magnesium, ytterbium, lithium, strontium, thallium, calcium, and any combination thereof.

[0114] Clause 13. The method according to Clause 12, wherein the metal catalyst is zinc.

[0115] Clause 14. A system comprising a carbon fiber reactor for manufacturing carbon fibers and a heater for heating a carbon-metal melt, wherein the reactor includes a container for contacting the carbon-metal melt and a plurality of nozzles through which a plurality of menisci are formed by the carbon-metal melt for contact with carbon seeds to manufacture the carbon fibers.

[0116] Clause 15. The system according to Clause 14, further comprising the carbon source connected to the carbon fiber reactor such that the container of the carbon fiber reactor receives the carbon source, and the carbon-metal melt includes at least a portion of the carbon source.

[0117] Clause 16. The system according to Clause 14 or Clause 15, wherein the container has a volume capacity of about 1 mL to about 1,000 mL.

[0118] Clause 17. The system according to any one of Clauses 14 to 16, wherein the plurality of nozzles includes about 100,000 to about 50 million individual nozzles.

[0119] Clause 18. The system according to any one of Clauses 14 to 17, wherein the plurality of nozzles have a diameter of about 1 μm to about 100 μm.

[0120] Clause 19. The system according to any one of Clauses 14 to 18, wherein the plurality of nozzles have a length of about 1 μm to about 1,000 μm.

[0121] Clause 20. The system according to any one of Clauses 14 to 19, further comprising a fiber winder for receiving carbon fibers produced from the carbon fiber reactor.

[0122] Clause 21. An apparatus comprising a carbon fiber reactor for producing carbon fibers, wherein the reactor includes a container for contacting a carbon-metal melt, and a plurality of nozzles through which a plurality of menisci are formed by the carbon-metal melt for contact with carbon seeds to produce the carbon fibers.

[0123] To facilitate a better understanding of the embodiments of the present invention, the following examples of preferred or representative embodiments are provided. The following examples should not be read to limit or define the scope of the present invention.

Examples

[0124] In this example, a carbon fiber manufacturing process using μ-PD was evaluated.

[0125] A thermogravimetric analyzer was used as a microreactor for methane pyrolysis. The setup included a metal catalyst (10 - 100 mg) in an alumina pan exposed to methane (5 vol%) for up to 5 hours. The reaction rate and Arrhenius parameters of methane pyrolysis were benchmarked against solid Ni, which were in agreement with the reported data (A = 5.1 mmol / cm2s, and E a = 87 kJ / mol). Methane pyrolysis at 800 °C on unseeded molten Ni 0.07 Ga 0.93 resulted in the formation of filamentous solid carbon with lengths up to 320 μm and varying orientation and straightness, as shown in Fig. 9. Elemental analysis of the carbon fibers showed a residual metal content of 2.1 mol%.

[0126] Directional solidification simulations were used to evaluate the production of carbon fibers and establish a quantitative model for the microstructure formation process of crystal fiber growth. A phase - field model for the directional solidification of a single - component supercooled melt was used to simulate the fiber drawing process, where the change between liquid (ξ = 0) and solid (ξ = 1) was enabled by the phase - order parameter (ξ) of the material. The free energy of the system, described by the free - energy function (F), was assumed to include a composition - dependent component and a curvature - dependent component. The phase - formation process was governed by the diffusion - dependent Allen - Cahn equation and the phase flux measured by the chemical potential gradient. The simulation domain (51×51 nodes) was a supercooled liquid C with a single crystal of radius R0 seeded, where P ΔT / ΔH fusIt was set as the initial value as (ξ = 2). The solid phase (ξ = 1) was crystallized and then removed from the interface at a constant dimensionless velocity (U). The simulation results are shown in FIGS. 10A to 10D, and these results are reported after 500 repetitions. The microstructure dependencies of the initial seed size (R0) and the pulling velocity (U) are represented by the contour diagrams of the order parameter. In FIG. 10A, dendritic growth into the carbon melt is expected using a small carbon seed size (R0 = 1) and a pulling velocity (U = 4). FIG. 10B models the seed size (R0 = 1) and the pulling velocity (U = 14). FIG. 10C models the seed size (R0 = 6) and the pulling velocity (U = 14). FIG. 10D models the seed size (R0 = 1) and the pulling velocity (U = 40). The model shows that high aspect ratio carbon fibers under optimal conditions can be pulled from the molten metal.

[0127] Accordingly, the present invention is well adapted to attain the above-described objects and advantages, as well as those inherent therein. The specific embodiments disclosed above are merely exemplary, and the present invention can be modified and implemented in different but equivalent ways that will be apparent to those skilled in the art having the benefit of the teachings herein. Further, it is not intended to be limited to the details of the structures or designs shown herein other than as described in the following claims. Accordingly, the specific exemplary embodiments disclosed above may be varied, combined, or modified, and it is clear that all such variations are contemplated within the scope and spirit of the present invention. The invention disclosed herein by way of example may be practiced in the absence of any element not specifically disclosed herein and / or in the absence of any element disclosed herein. Compositions and methods are described with the terms "comprising," "containing," or "including" various components or steps, but the compositions and methods may also "consist essentially of" or "consist of" the various components and steps. All numbers and ranges disclosed above may vary somewhat. Whenever a numerical range having a lower limit and an upper limit is disclosed, any number and any included range within that range are specifically disclosed. In particular, all ranges of values (in the form of "from about a to about b," or equivalently "approximately a to b," or equivalently "from approximately a - b") disclosed herein are to be understood to set forth all numbers and ranges subsumed within the broader range of values. Also, the terms in the claims have their plain ordinary meaning unless explicitly and clearly defined by the patent owner. Additionally, when used in the claims, the indefinite articles "a" or "an" are defined herein to mean one or more of the elements they introduce.

Claims

**Claim 1** Contacting a carbon fiber seed with a carbon-metal melt, and withdrawing the carbon fiber seed from the carbon-metal melt at a drawing rate to form carbon fibers, wherein the carbon fibers have a diameter in the range of about 1 μm to about 100 μm. **Claim 2** The method according to claim 1, wherein when the drawing rate is the rate of pulling down from the meniscus of the carbon-metal melt, the temperature of the carbon-metal melt above the meniscus is above the liquidus, and the temperature below the meniscus is below the liquidus; when the drawing rate is the rate of pulling up from the meniscus of the carbon-metal melt, the temperature of the carbon-metal melt below the meniscus is above the liquidus, and the temperature above the meniscus is below the liquidus. **Claim 3** The method according to claim 2, wherein the drawing rate is from about 10 mm / min to about 10,000 mm / min. **Claim 4** The method according to claim 3, wherein the drawing rate is 1,000 mm / min. **Claim 5** The method according to claim 1, wherein the carbon fibers have a length in the range of about 0.5 km to about 50 km. **Claim 6** The method according to claim 1, wherein the carbon-metal melt comprises a carbon source selected from the group consisting of hydrocarbon gas, hydrocarbon liquid, hydrocarbon solid, natural gas, flare natural gas, biogas, pyrolysis gas, petcoke, coal, soot, recycled pure carbon fiber waste, recycled carbon fiber composite waste, plastic, recycled plastic, biomass, organic waste, petroleum, oil, biochar, fossil fuel, and any combination thereof. **Claim 7** The method according to claim 6, wherein the carbon source is derived from a pyrolysis reaction of a reaction gas selected from the group consisting of hydrocarbon gas, natural gas, flare natural gas, biogas, pyrolysis gas, and any combination thereof. **Claim 8** The method according to claim 7, wherein the pyrolysis reaction comprises evaporating a catalyst source to generate a catalyst gas, condensing the catalyst gas to generate a catalyst vapor containing catalyst droplets suspended in the gas phase, and contacting the catalyst vapor with the reaction gas to catalyze the decomposition reaction of the gas into hydrogen gas and the carbon source. **Claim 9** The method according to claim 8, wherein the catalyst gas before condensation is at a temperature about 5 °C to about 500 °C higher than the boiling point of the catalyst source. **Claim 10** The method according to claim 8, wherein condensing the catalytic gas includes exposing the catalytic gas to the reaction gas, and the reaction gas is at a temperature below the boiling point of the catalytic source. **Claim 11** The method according to claim 8, wherein the catalytic source is a metal catalyst selected from the group consisting of zinc, cesium, selenium, rubidium, potassium, cadmium, sodium, polonium, tellurium, magnesium, ytterbium, lithium, strontium, thallium, calcium, and any combination thereof. **Claim 12** The method according to claim 11, wherein the metal catalyst is zinc.

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