Volume compensation in the production of hydrogen from hydrocarbons.

Abstract

Thermal cracking of the hydrocarbons to produce hydrogen gas and carbon may be accomplished by heating the molten medium to an operating temperature sufficient to thermally crack the hydrocarbons. The operating temperature may be, for example, in the range of 600°C to 1100°C. The hydrocarbons are mixed into the heated molten medium and the mixed fluid moves through a reactor. In the reactor, the hydrocarbons undergo a thermal cracking reaction that produces hydrogen gas and carbon black. The carbon and hydrogen gas are separated from the molten medium. Means may also be provided for controlling the level of the mixed fluid in the reactor.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Application No. 63 / 280902, filed November 18, 2021, and entitled "Volumetric Compensation in the Production of Hydrogen from Hydrocarbons," which is hereby incorporated by reference for all purposes. For U.S. purposes, this application claims the benefit under 35 U.S.C. § 119 of U.S. Application No. 63 / 280902, filed November 18, 2021, and entitled "Volumetric Compensation in the Production of Hydrogen from Hydrocarbons."

[0002] The present invention relates to the production of hydrogen from hydrocarbons by thermal cracking. The present invention may be embodied, for example, in a reactor for producing hydrogen, a method for producing hydrogen, and a system for producing hydrogen. [Background technology]

[0003] Hydrogen is useful as a fuel for use in chemical processing and for other applications. However, only limited amounts of elemental hydrogen are freely available in nature. Currently, over 96% of all hydrogen used in industry is produced from fossil sources. Methane (CH4), in its pure form or as a component of natural gas, is one of the main sources for mass production of hydrogen. Steam methane reforming (SMR) (see Equation 1) is the primary method for hydrogen production (48% of total global production). CH4+2H2O→CO2+4H2ΔH°=165kJ / mol (1)

[0004] The SMR process releases unwanted greenhouse gases and consumes large amounts of water. At stoichiometric conditions, the SMR process gives 0.5 kg H2 per kg CH4. The industrial process releases 9 to 14 kg CO2 per kg H2. The SMR process also requires water to oxidize carbon monoxide to carbon dioxide in the water-gas shift reaction. Water life-cycle assessments have suggested that the SMR process requires 18 to 32 kg water per kg H2.

[0005] There are various alternative technologies that can produce hydrogen in large quantities from hydrocarbons. These technologies vary in cost and life cycle CO2 emissions. Some of these technologies are coal gasification, biomass gasification, and methane thermal cracking.

[0006] SMR, as well as coal and biomass gasification technologies, can be combined with carbon capture and sequestration (CCS) technologies to reduce their CO2 emissions. However, CCS significantly increases the capital costs of infrastructure and requires significant operating expenses. As a result, the cost of hydrogen production increases with CCS. A 2017 study showed that the SMR process with CCS could reduce CO2 emissions by 53% to 90%, but the cost of hydrogen production increases from $0.2 to $0.5 per kg of H2 produced. Other limitations of CCS technology include how to properly sequester the captured CO2, which increases costs and limits the deployment of CCS technology to favorable geographic locations, such as oil and gas fields.

[0007] Thermal cracking of methane holds promise for producing hydrogen at lower cost and with lower CO2 emissions than SMR. The following references discuss thermal cracking of methane by contacting it with a hot molten medium: - B. Parkinson, J.W. Matthews, T.B. McConnaughy, D.C. Upham, E.W. McFarland, Techno-Economic Analysis of Methane Pyrolysis in Molten Metals: Decarbonizing Natural Gas, Chem. Eng. Technol. 40, no. 6 (2017) 1022-1030. doi:10.1002 / ceat.201600414. - R. Dagle, V. Dagle, M. Bearden, J. Holladay, T. Krause, S. Ahmed, R&D Opportunities for Development of Natural Gas Conversion Technologies for Co-Production of Hydrogen and Value-Added Solid Carbon Products, Argonne National Laboratory, U.S., 2017. - D. Paxman, Experimental and Theoretical Investigation of Solar Molten Media Methane Cracking for Hydrogen Production, University of Alberta, 2014. doi:10.1016 / j.egypro.2014.03.215. - U.P.M. Ashik, W.M.A. Wan Daud, H.F. Abbas, Production of greenhouse gas free hydrogen by thermocatalytic decomposition of methane - A review, Renew. Sustain. Energy Rev. 44 (2015) 221-256. doi:10.1016 / j.rser.2014.12.025. - M. Serban, MA Lewis, CL Marshall, RD Doctor, Hydrogen production by direct contact pyrolysis of natural gas, Energy and Fuels. 17, no. 3 (2003) 705-713. doi:10.1021 / ef020271q. - DC Upham, V. Agarwal, A. Khechfe, ZR Snodgrass, MJ Gordon, H. Metiu, EW McFarland, Catalytic molten metals for the direct conversion of methane to hydrogen and separable carbon, Science 358 (2017) 917-921. doi:10.1126 / science.aao5023.

[0008] The experiments and techno-economic analyses reported in these publications demonstrate that thermal cracking of methane by contacting it with a hot molten medium can work, but problems remain. One problem is that the accumulation of carbon black can impede the production of hydrogen by impeding heat transfer and creating blockages.

[0009] There is a demand for improved technologies that can be applied to the large-scale production of hydrogen, particularly for practical hydrogen production technologies that are cost-effective and have low CO2 emissions. Summary of the Invention

[0010] The present invention has many aspects, including but not limited to: - a method for producing hydrogen by thermal cracking; - A system for producing hydrogen by thermal cracking; - a reactor for producing hydrogen by thermal cracking; - A separation system for separating the products of the thermal cracking reaction Includes.

[0011] One embodiment of the present invention provides a system and method for thermally cracking a hydrocarbon by contacting the hydrocarbon with a hot liquid medium, the system including a feature for compensating for changes in the volume of the mixture of the hydrocarbon and the hot liquid medium. The changes in volume may be due, for example, to changes in the rate at which the hydrocarbon is fed. This embodiment can be applied in reactor types including bubble column reactors, plug flow reactors, capillary reactors, and circulation reactors. The following description provides examples of methods for including the volume compensation feature in systems including circulation flow reactors of the type developed by the inventors, as well as systems applying other types of reactors.

[0012] The feature of compensating for changes in the volume of a mixture of a hydrocarbon and a hot liquid medium may be applied, for example, to a method of thermally cracking a hydrocarbon to produce hydrogen gas, the method including heating a molten medium to an operating temperature sufficient to thermally crack the hydrocarbon, mixing the hydrocarbon with the heated molten medium, pumping the mixed molten medium and hydrocarbon through a reactor such that the hydrocarbon is thermally cracked to produce carbon and hydrogen gas, and separating the carbon and hydrogen gas from the molten medium that has passed through the reactor.

[0013] The feature of compensating for changes in the volume of a mixture of a hydrocarbon and a hot liquid medium may be applied, for example, to a method of thermally cracking a hydrocarbon to produce hydrogen gas, the method comprising pumping a molten medium through a reactor, mixing a hydrocarbon with the molten medium at or upstream of the reactor such that the mixed hydrocarbon and molten medium pass through the reactor, maintaining a temperature of the molten medium within at least a portion of the reactor at an operating temperature sufficient to thermally crack the hydrocarbons and the hydrocarbons in the mixed molten medium to produce carbon and hydrogen gas while at least the mixed hydrocarbon and molten medium pass through the reactor, and separating carbon and hydrogen gas from the molten medium that has passed through the reactor. In some embodiments, the molten medium is tin, aluminum, or zinc that is recycled into a process loop with the reactor.

[0014] The feature of compensating for changes in the volume of a mixture of a hydrocarbon and a hot liquid medium may be applied, for example, to thermal cracking systems employing bubble column reactors, capillary reactors, or recirculating reactors.

[0015] Various features that may be included in the methods according to the above aspects are described herein.

[0016] It is emphasized that the invention relates to all combinations of features described herein, even if these are recited in different claims or different types of claims, provided that the invention is recited in different claims or different types of claims. The apparatus features described herein may be applied in a method according to the invention, and the apparatus according to the invention may be configured to perform the method steps of any described method.

[0017] Further aspects and example embodiments are illustrated in the accompanying drawings and / or described in the following description.

[0018] The accompanying drawings illustrate non-limiting exemplary embodiments of the present invention. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a block diagram of an example system for producing hydrogen by thermal cracking. [Diagram 2] FIG. 1 is a schematic diagram of an example reactor having a header that mixes input feed with a molten medium through injection. [Figure 3A] FIG. 2 is a schematic diagram of an example cross section of a conduit bundle. [Figure 3B] FIG. 2 is a schematic diagram of an example cross section of a conduit bundle. [Figure 3C] FIG. 2 is a schematic diagram of an example cross section of a conduit bundle. [Figure 3D] FIG. 2 is a schematic diagram of an example cross section of a conduit bundle. [Figure 4A] FIG. 2 is a schematic diagram of an example heat flow pattern of a reactor heating system. [Figure 4B] FIG. 2 is a schematic diagram of an example heat flow pattern of a reactor heating system. [Figure 4C] FIG. 2 is a schematic diagram of an example heat flow pattern of a reactor heating system. [Figure 5A] 1A-1C are schematic diagrams of example conduit arrangements for accommodating thermal expansion. [Figure 5B] 1A-1C are schematic diagrams of example conduit arrangements for accommodating thermal expansion. [Figure 5C] 1A-1C are schematic diagrams of example conduit arrangements for accommodating thermal expansion. [Figure 6] FIG. 1 is a schematic diagram of an example reactor having a header that mixes input feed with molten media through bubbling. [Figure 6A] FIG. 13 is a perspective view of an example of parallel channels. [Figure 6B] 6B is a cross-section through the example channel of FIG. 6A in a transverse plane perpendicular to the direction of flow of the molten medium. [Figure 7] FIG. 1 is a schematic diagram of an example vertically oriented reactor. [Figure 8] FIG. 2 is a schematic diagram of an example multi-phase separation unit. [Figure 9] 1 is a schematic diagram illustrating a system for producing hydrogen according to an example embodiment of the present invention. [Figure 10]1 is a schematic diagram illustrating a system for producing hydrogen according to an example embodiment of the present invention. [Figure 11] 1 is a schematic diagram illustrating a system for producing hydrogen according to an example embodiment of the present invention. [Figure 12] 1 is a schematic diagram illustrating a system for producing hydrogen according to an example embodiment of the present invention. [Figure 13] 1 is a schematic diagram illustrating a system for producing hydrogen according to an example embodiment of the present invention. [Figure 14] 1 is a schematic diagram illustrating a system for producing hydrogen according to an example embodiment of the present invention. [Figure 15] 1 illustrates an example system for thermally cracking hydrocarbons having a feature for regulating the rate of change in the volume of hot liquid medium in a reactor. FIG. 2 is a schematic cross-sectional view of an input feedstock thermal cracking system. [Figure 16] 1 illustrates an example system for thermally cracking hydrocarbons having a feature for regulating the rate of change in the volume of hot liquid medium in a reactor. FIG. 2 is a schematic cross-sectional view of an input feedstock thermal cracking system. [Figure 16A] 11 is a flowchart illustrating an example of a level control method. [Figure 17] 1 illustrates an example system for thermally cracking hydrocarbons having a feature for regulating the rate of change in the volume of hot liquid medium in a reactor. FIG. 2 is a schematic cross-sectional view of an input feedstock thermal cracking system. [Figure 17A] 11 is a flowchart illustrating an example of a level control method. [Figure 18] 1 illustrates an example system for thermally cracking hydrocarbons having a feature for regulating the rate of change in the volume of hot liquid medium in a reactor. FIG. 2 is a schematic cross-sectional view of an input feedstock thermal cracking system. [Figure 19] 1 illustrates an example system for thermally cracking hydrocarbons having a feature for regulating the rate of change in the volume of hot liquid medium in a reactor. FIG. 2 is a schematic cross-sectional view of an input feedstock thermal cracking system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Throughout the following description, specific details are given to provide a more thorough understanding of the invention. However, the invention may be practiced without these details. In other instances, well-known elements have not been shown or described in detail to avoid unnecessarily obscuring the invention. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense.

[0021] Hydrogen production system example 1 depicts an example of a hydrogen production system 10. System 10 implements a thermal cracking process. System 10 takes in an input feedstock 11 a hydrocarbon feedstock (e.g., methane, natural gas, processed natural gas (e.g., natural gas that has been processed to remove impurities, e.g., water, sulfur, etc.), other hydrocarbons, or mixtures thereof).

[0022] For methane, the thermal cracking process is represented by the equation: CH4→C(s)+2H2ΔH°=74.8kJ / mol(2) Thermal cracking of methane under stoichiometric conditions gives 0.25 kg H2 and 0.75 kg carbon black per kg CH4. No water is required and the by-product is solid carbon. The density of the carbon product is about 200 to 2100 kg / m 3 The carbon produced can be used in a wide variety of applications and industries, such as tire manufacturing, lithium ion battery electrodes, automotive parts, and carbon reinforced composites (Table 1).

[0023] [Table 1]

[0024] Thermal cracking of methane is an endothermic process. Temperatures in the range of about 800° C. to 1600° C. may be required. Temperatures below 800° C. may be sufficient for thermal cracking of methane or other hydrocarbons when a suitable catalyst is provided. In some embodiments, temperatures in the range of about 1200° C. to 1600° C. are applied in the reactor 14. In some embodiments, temperatures in the range of about 800° C. to 1100° C. are applied in the reactor 14.

[0025] System 10 contacts raw material provided as input feed 11 with melting medium 12. Melting medium 12 is maintained at a temperature sufficient to thermally crack the raw material (e.g., according to equation (2)). Input feed 11 is subjected to thermal cracking upon contact with melting medium 12. In some embodiments, melting medium 12 contains a catalyst that catalyzes a thermal cracking reaction that facilitates one or more of: thermal cracking of input feed 11 at a relatively low temperature; faster completion of thermal cracking of input feed 11; and more complete thermal cracking of input feed 11.

[0026] To flow the molten medium 12 through the loop 12A containing the reactor 14, the molten medium 12 is pumped continuously or intermittently by a pump 13. The pump 13 may include, for example, a cantilever pump, a piston pump, an electromagnetic pump, an educator, or another pump suitable for pumping the hot molten medium 12 with a service pump. Typically, the pump 13 may include any mechanism for circulating the molten medium 12 through the loop 12A, such as by applying a mechanical force to the molten medium 12 (e.g., by a paddle, an impeller, a propeller, a piston, a variable volume vessel such as a bellows, etc.) or by other methods, such as by applying a force by a magnetic and / or electromagnetic field that applies a magnetic and / or electromagnetic force to the molten medium 12, or by circulating the molten medium 12 using gravity (e.g., by raising the molten medium 12 to a position somewhat higher in the loop 12A and allowing the molten medium to flow by gravity). Any practical device capable of taking in melt medium 12 at an inlet and outputting melt medium 12 at an outlet, where the pressure at the melt medium outlet is higher than the pressure at the inlet, can be utilized as pump 13.

[0027] The pump 13 may comprise one or more separate pumps which may be located at one location or distributed throughout the loop 12A.

[0028] In some embodiments, pump 13 operates on a single phase (liquid) material. For example, pump 12 may be located in loop 12A where melt medium 12 is substantially free of any gas.

[0029] Heat 15 may be supplied to the molten material 12 to keep it liquid and to provide one or more locations at a desired temperature. For example, heat may be added upstream of the reactor 14, to the molten medium 12 in the reactor 14, by preheating the input feed 11 (e.g., by heat exchanger 15A) and / or in a separate heat exchanger 15B.

[0030] In some embodiments, one or more heaters are provided outside of reactor 14 and additional heaters are provided within reactor 14 to maintain melting medium 12 at a temperature that allows for good flow of melting medium 12 throughout system 10. The additional heat provided to reactor 14 may raise the temperature of melting medium 12 to an operating temperature sufficient for thermal cracking of the hydrocarbons in input feed 11. The heat input to reactor 14 may also provide the heat required for the thermal cracking reaction.

[0031] Pumping the melting media 12 through the process loop 12A helps reduce or eliminate carbon deposits within the reactor 14.

[0032] Circulating the melting media 12 throughout the system 10 can help mix the input feed material 11 with the melting media 12, which may increase the rate of the thermal cracking reaction. High velocity turbulence can help increase the degree of mixing between the input feed material 11 and the melting media 12.

[0033] Preferably, the melt medium 12 is heated to a temperature above 1000° C. at least at which the flow of the melt medium in the reactor 14 is turbulent, at least at a Reynolds number (Re D In general, the Reynolds number of a fluid flowing through a pipe can be expressed as follows:

[0034]

number

[0035] (where ρ is the density of the fluid, D is the characteristic length, u is the average velocity of the fluid, and μ is the viscosity of the fluid). For conduits with circular cross-sections (e.g., pipes), D is equal to the inner diameter of the respective conduit. For conduits with non-circular cross-sections, D is equal to the hydraulic diameter (D h )

[0036]

number

[0037] where A is the cross-sectional area of ​​the conduit and P is the wetted perimeter of the cross section (the sum of the perimeters of the conduit in contact with the fluid). For example, if the conduit has a rectangular cross section with width W and height H, then D can be calculated as follows if W>>H is more closely approximated as D=2H (e.g., as with the parallel plate conduits described herein):

[0038]

number

[0039] is equal to.

[0040] The example values ​​of the Reynolds number provided herein are given for the case where melt medium 12 flows into reactor 14 without the addition of input feed material 11. For purposes of this disclosure and the appended claims, the Reynolds number can be determined by equation (3) with ρ set to the density of melt medium 12, μ set to the viscosity of melt medium 12, and u set to the possible velocity of melt medium 12 without input feed material 11 and the same flow velocity as melt medium 12.

[0041] The addition of input feed 11 creates a heterogeneous mixed fluid (i.e., a mixed fluid comprised of liquid melting medium 12 and bubbles of gaseous input feed 11) that flows into reactor 14. The density of this mixed fluid may be lower than that of melting medium 12 (due to the presence of low density bubbles in input feed 11). Since the Reynolds number is proportional to both density and velocity, the introduction of input feed 11 to create a mixed fluid in reactor 12 does not tend to have a very large effect on the Reynolds number if the flow rate of melting medium 12 is the same.

[0042] In some embodiments, the momentum of the melting medium 12 is between 30,000 and 100,000,000 Re. DThis may be considered a "high velocity turbulence" region. In some embodiments, the flow of molten medium 12 at least in reactor 14 has a flow velocity of 0.1 m / s and a temperature of molten medium 12 of 1000° C., and is in the range of Re D The reactor 14 is characterized by high velocity turbulence, with a Reynolds number of greater than 60,000. High velocity turbulence (e.g., turbulence with a Reynolds number of at least 3000) helps reduce or avoid carbon deposition on surfaces within the reactor 14.

[0043] In a preferred embodiment, the melt medium 12 is continuously circulated throughout the system 10 by the pump 13. The continuous circulation of the melt medium 12 advantageously minimizes thermal shock and vibration. The rate at which the pump 13 pumps the melt medium 12 may vary.

[0044] In some embodiments, pump 13 is controlled to circulate melting medium 12 intermittently. Intermittent circulation can be advantageous when hydrogen demand is low relative to the capacity of system 10 to produce hydrogen. When hydrogen demand is low, the rate at which input feed 11 is provided to system 10 can be reduced. In response, pump 13 can be operated intermittently or at a slow speed to preserve the efficiency and operating costs of system 10. In such circumstances, operating pump 13 at a slow speed is preferred.

[0045] As mentioned above, the density of the mixed fluid may be lower than the density of the melting medium 12. The density of the mixed fluid depends on the relative amounts of melting medium 12 and gaseous input feed 11 in the volume of the mixed fluid, which in turn depends on the rate at which the gaseous input feed 11 is introduced into the reactor 14. If the gaseous input feed 11 is introduced at a higher rate, the density of the mixed fluid will tend to be lower than if the gaseous input feed is introduced at a slower rate.

[0046] In many applications, it is necessary or desirable to start or stop hydrogen production or adjust hydrogen production to meet demand. For example, during periods of low demand, it may be desirable to reduce hydrogen production. Adjusting the output rate of the thermal cracking system can be accomplished by switching the flow of the input feedstock 11 to start or stop, or by adjusting the transfer rate of the input feedstock 11 into the reactor 14. If the flow rate of the input feedstock 11 into the reactor 14 increases, the volume of the mixed fluid in the reactor 14 will tend to increase. Conversely, if the flow rate of the input feedstock 11 into the reactor 14 decreases, the volume of the mixed fluid in the reactor 14 will tend to decrease. Examples of approaches for adjusting the above changes in the volume of the mixed fluid are described below with reference to Figures 15 to 19.

[0047] Examples of melting media In some embodiments, the melt medium 12 is - liquid metal (which may be a single element or a metal alloy), - Molten salt, - A combination of these Contains:

[0048] In some embodiments, the melt medium 12 has one or more or all of the following characteristics: - Melting point is below 800℃, - Boiling point is over 1000℃, - Density of approximately 2000 to 8000 kg / m 3 Within the range of - low viscosity (for example, the dynamic viscosity of the melting medium 12 at the operating temperature is 0.2 to 20 mPa·s or less); - low vapor pressure (for example, the vapor pressure of the melting medium 12 at the operating temperature is less than or equal to 200 Pa); - a high surface tension at the operating temperature of the melting medium 12 (for example a surface tension of at least 300 mN / m); - low tendency to dissolve hydrogen (e.g., the solubility of hydrogen at the operating temperature of the molten material 12 is 50×10 -2 mL STP / gmetal (where mL STP is the volume of dissolved hydrogen at standard temperature and pressure of 0°C and 1 atm), - High heat capacity (e.g. specific heat capacity C p is at least 250 J / kg K), - A high heat transfer coefficient (e.g., a heat transfer coefficient of at least 20 W / (m·K)), and - High thermal diffusivity (where thermal diffusivity is the heat transfer rate divided by the density and specific heat capacity at constant pressure (e.g., thermal diffusivity of at least 1×10 -5 m 2 / s)

[0049] Factors to consider when selecting the composition of melting medium 12 may include cost and stability under the operating conditions of system 10 .

[0050] Selecting a composition for the melting medium 12 that has a low vapor pressure at the operating temperature of the system 10 helps make the system 10 safe.

[0051] Selecting a composition of the melting medium 12 with a high thermal mass (where thermal mass is the density of the material multiplied by the specific heat capacity of the material at a constant pressure) helps minimize temperature gradients in the melting medium 12. For example, a melting medium 12 with a high thermal mass can reduce radial and axial temperature gradients in the conduits of the reactor 14 while still providing enough heat for the thermal cracking reaction to occur. This can also allow conduits with large dimensions (e.g., length, width, height, diameter) to be used inside the reactor 14 without adversely affecting the kinetics of the thermal cracking reaction.

[0052] In some embodiments, the melting medium 12 contains liquid tin. Liquid tin is advantageously chemically stable within the system 10 and - Melting point is 231.9°C, - Boiling point is 2602℃, - Density at 1000℃ is 6460kg / m 3 , - Viscosity at 1000°C is 0.72 mPa·s, - Vapor pressure at 1492℃ is 132 Pa, - surface tension of approximately 500 mN / m when in contact with an alumina (Al2O3) substrate in an inert medium at 1000 °C; - The solubility of hydrogen in liquid tin is 0.39×10 -2 mL STP / g metal , - The heat at 1000℃ is 2017kJ / (m 3 ·K), and - Heat transfer coefficient at 1000°C is 50.4W / (m K) The composition has desirable physical properties, including:

[0053] In some embodiments, molten media 12 contains liquid aluminum. Liquid aluminum is advantageously less expensive and more readily available than other molten metals and molten salts within system 10; - Melting point is 660.3℃, - Boiling point is 2470℃, - Density at 1000℃ is 2289kg / m 3 , - Viscosity at 1000°C is 0.705 mPa·s, - The heat energy at 1000℃ is 2694kJ / (m 3 ·K), and - Heat transfer coefficient at 1000°C is 100.35 W / (m K) The composition has desirable physical properties, including:

[0054] In some embodiments, the melting medium 12 contains a suitable salt. The suitable salt is advantageously: - have some catalytic activity that can accelerate the thermal cracking process, and - Tends to be cheaper than liquid metal. The salts selected for the melting medium 12 may be selected to avoid salts that are unstable under the operating conditions of the system 10 and salts in which hydrogen is unnecessarily soluble.

[0055] In some embodiments, the melting medium 12 contains a mixture of molten salt and liquid metal. For example, the melting medium 12 may contain a molten salt and liquid metal, where the density of the molten salt is less than the density of the liquid metal. Such a mixture may help minimize the amount of liquid metal lost from the carbon black in the separation unit 16 of the system 10. For example, the carbon black may be suspended throughout the layer of molten salt before it is separated from the melting medium 12.

[0056] In some embodiments, residual amounts of salt removed with the carbon black can be washed away (e.g., with water) to remove the carbon black. The resulting brine (after washing the carbon black) can be treated to remove salts and, optionally, recycled. Other methods can also be utilized to reduce contamination of the carbon black with the melting medium 12 or any of its components.

[0057] Melting medium 12 may contain, for example, any one or combination of the following: - Pb - Sn - In -Bi - Ga -Ag -Al - Zn - NiMo / Al2O3 - 17% Cu-Sn - Liquid platinum alloys, e.g.: 17% Pt-Sn 17% Pt-Bi 62% Pt-Bi - Liquid Nickel Alloy: 17% Ni-In 17% Ni-Sn 73% Ni-In 17% Ni-Ga 17%Ni-Pb 17% Ni-Bi 27%Ni-Au 27% Ni-Bi - LiCl - KCl - KBr - NaBr

[0058] In some embodiments, the melting medium 12 further contains solid particles. The solid particles may, for example, include a catalyst for the thermal cracking reaction. For example, the solid particles may include one or both of nickel and platinum. The solid particles may, for example, include a powder mixed in the melting medium 12. When the size of the solid particles is reduced, the contact area between the solid particles and the input feed material 11 tends to increase. Thus, the rate of the thermal cracking reaction can be increased by providing smaller particles containing a catalyst and / or by increasing the amount of solid particles in the melting medium 12. Such particles may be useful for catalyzing the thermal cracking reaction and / or aiding in the removal of carbon black from the internal surfaces of the system 10. In some embodiments, the density of the solid particles is comparable to the density of the melting material 12.

[0059] Example of operating conditions The operating temperature of the system 10 can be selected based on factors such as the presence or absence of a catalyst, the nature of the feedstock, the supply of melting medium 12, and the optimum temperature for thermal cracking of the feedstock. The melting medium 12 may be heated and maintained at or near the desired operating temperature at which the melting medium 12 is liquid. In some embodiments, the operating temperature is at least 600°C or at least 800°C.

[0060] In some embodiments, the temperature of the molten media 12 in the portion of the system 10 where the thermal cracking process occurs is in the range of 500°C to 1200°C, or in the range of 900°C to 1100°C, or at least 800°C.

[0061] In some embodiments, the temperature of molten medium 12 is higher in some portions of loop 12A than in other portions of loop 12A. In some embodiments, molten medium 12 is cooled before entering portions of loop 12A that do not require high temperatures. For example, the temperature of molten medium 12 may be reduced (e.g., by a heat exchanger that removes heat from molten medium 12) after the molten medium exits reactor 14 and before the molten medium enters pump 13.

[0062] In some embodiments, the molten medium 12 is cooled to a temperature within the rated operating temperature range of the pump 13 before the molten medium 12 enters the pump 13. The molten medium 12 may be cooled, for example, with a heat exchanger, such as heat exchanger 15D, installed upstream of the pump 13. Cooling the molten medium 12 may extend the life of the pump 13. Cooling the molten medium 12 may reduce the maintenance required for the pump 13.

[0063] In some embodiments, the temperature of molten medium 12 in pump 13 is at least 50° C. or at least 100° C. lower than the temperature of molten medium 12 exiting reactor 14 .

[0064] In some embodiments, the pressure of the melt medium 12 in the system 10 is greater than atmospheric pressure, at least within the reactor 14 .

[0065] The input feed 11 and the melting medium 12 are input to the reactor 14. The input feed 11 may be dosed upstream of the reactor 14 and / or into the melting medium 12 inside the reactor 14. In some embodiments, the input feed 11 is pressurized to a pressure above atmospheric pressure. In some embodiments, the input feed 11 is pressurized to a pressure above atmospheric pressure, which exceeds the hydrostatic pressure within the reactor 14. In some embodiments, the input feed 11 and the melting medium 12 are mixed together before entering the reactor 14, as shown at 11A. In some embodiments, the input feed 11 is input directly into the reactor 14.

[0066] Generally, the temperature of the input feed 11 is not critical since the heat content of the input feed 11 is much lower than the heat content of the melting medium 12. For example, the input feed 11 may have a temperature in the range of -60°C to 1600°C. The input feed 11 may be provided as a direct feed from, for example, a natural gas processing and treatment plant. Preferably, the temperature of the input feed 11 is in the range of about 25°C to 1100°C.

[0067] In some embodiments, input feed 11 is preheated before entering reactor 14. For example, heat exchanger 15A can transfer heat to input feed 11 from any one or combination of the following: - the melting medium 12 (for example between the multiphase separation unit 16 and the pump 13), - gaseous species 18 (gas species 42) separated by a multiphase separation unit 16; - the reaction mixture 41, - combustion gases obtained by burning other gases 18B and / or a certain amount of hydrogen 18A; - Combustion gases from other sources; - Exhaust gas or other hot exhaust gas from the reactor 14 (e.g., heated fluid 32) and / or other sources of flue gas; - Other heat sources, e.g. solar heat, waste heat from industrial processes, etc.

[0068] Through contact with the melting medium 12, the input feed 11 is at least partially converted to hydrogen 18A and carbon 19. This conversion may proceed, for example, according to Equation 2. Advantageously, the thermal cracking of the input feed 11 to produce hydrogen and carbon may occur primarily within the bulk of the melting medium 12. For example, at least 65%, or 75%, or 85%, or 90% of the thermal cracking may occur within the bulk of the melting medium. Contact of the input feed 11 with the surface of the conduit 24 is not required to facilitate thermal cracking. In some embodiments, only very small amounts of carbon black are produced on the surface of the conduit 24 (e.g., a few percent or less).

[0069] The mixture of melting medium 12, any remaining input feed 11, hydrogen and carbon (hereinafter referred to as reacted mixture 41) is transferred to multi-phase separation unit 16. The reacted mixture 41 is optionally cooled (e.g., by heat exchanger 15C) before entering multi-phase separation unit 16.

[0070] The multi-phase separation unit 16 operates to separate one or more components of the reacted mixture 41. The separation may be based on density. The multi-phase separation unit 16 separates gaseous species such as any remaining input feed 11, hydrogen and other gases from the reacted mixture 41. The multi-phase separation unit 16 further separates the melting medium 12 and carbon 19. At least a portion of the melting medium 12 is recirculated through the loop 12A by the pump 13.

[0071] The separated gases may be transferred to a gas purification unit 17. Prior to the gas purification unit 17, the collected gases are optionally cooled. The gas purification unit 17 separates the hydrogen 18A from the other gases 18B. The other gases 18B may be recycled. For example, the other gases may be recycled to the input feed 11. In some embodiments, the other gases 18B contain combustible gases that are combusted to generate heat 15 for the heating system 10.

[0072] The system 10 may advantageously provide a relatively fast thermal cracking reaction because the flowing melting medium 12 may transfer heat at a high velocity to the incoming input feed 11. The flowing melting medium 12 may help prevent the buildup of carbon black or other solids within the system 10. This may help maintain efficient transfer of heat 15 into the melting medium 12.

[0073] Reactor 14 may, for example, have a number of conduits 24 through which the mixture of melting medium 12 and input feed 11 may pass. Conduits 24 may be heated (e.g., by passing a heated gas or liquid therethrough).

[0074] The pump 13 generates pressure in the molten medium 12 that allows the reactor 14 to be operated vertically, horizontally, or at any arbitrary angle. A vertically oriented reactor 12 may be compact. However, pumping the molten medium 12 against the hydrostatic pressure of a vertical reactor may increase the pumping power required. For example, if the molten medium 12 contains liquid tin, the hydrostatic pressure due to the weight of the liquid tin at the bottom of a 3 m long vertical tube is about 190 kPa. Orienting the reactor 14 horizontally essentially negates the pumping energy required to overcome the hydrostatic pressure of the molten medium 12.

[0075] Reactor Example FIG. 2 is a schematic depiction of an example reactor 14-1 that can be used as reactor 14 in FIG. 1. Reactor 14-1 receives input feed 11. In reactor 14-1, input feed 11 is mixed with melting medium 12 in header 21A. In some embodiments, input feed 11 is mixed with melting medium 12 through injection. Input feed 11 may be injected through a flow divider 22. The flow divider may have, for example, one or both of a nozzle and a perforated tube, or a bubbler (see FIG. 6). In general, input feed 11 is mixed with molten material 12 by a suitable gas-liquid contacting device that may be located as part of reactor 14 or upstream of reactor 14. The mixture of melting medium 12 and input feed 11 is conveyed through a heated conduit 24 of reactor 14-1. Conduit 24 provides a path through which melting medium 12 may flow. Within reactor 14-1, conduit 24 comprises a tube. In other example embodiments, conduit 24 may comprise a parallel conduit.

[0076] The reactor 14-1 has a collector 28 at an end opposite the header 21A. The collector 28 is coupled to receive the molten medium 12 that has passed through the conduit 24. The collector 28 may be coupled to the conduit 24, for example, by one or more interconnects and junctions. The collector 28 collects the reacted mixture 41. The collector 28 outputs the reacted mixture 41 to the multi-phase separation unit 16. The reacted mixture 41 may be cooled prior to the multi-phase separation unit 16. The reacted mixture 41 is optionally cooled by a heat exchanger 15C (see FIG. 1) prior to being transferred to the multi-phase separation unit 16.

[0077] One or more of the interior walls of the conduit 24, the header 21A and collector 28 and / or any surfaces in contact with the molten media 12 may have a coating. The coating may be selected to extend the life of the conduit 24. The coating may be selected to provide corrosion resistance. The coating may include, for example, one or more of alumina, silicon carbide, zirconium oxide, tungsten carbide, graphite, molybdenum, other ceramics, and / or other metals.

[0078] The coating on the inner wall of conduit 24 optionally contains a material that catalyzes the thermal cracking reaction. The catalytic material may, for example, contain one or both of a nickel-based catalyst and a platinum-based catalyst.

[0079] Conduit bundle 25 is connected to header 21A. Conduit bundle 25 may be connected to header 21A by, for example, a weld or a tie pipe. Header 21A distributes molten medium 12 to conduits 24. Preferably, molten medium 12 is distributed equally among conduits 24. To effectively distribute molten medium 12 equally among conduits 24, the pressure drop along each of conduits 24 should remain similar.

[0080] In conduit 24, the input feed 11 is converted to hydrogen and solid carbon by thermal cracking. It is desirable to minimize the residence time of the produced hydrogen in the reactor 14. Minimizing the residence time of the produced hydrogen in the reactor 14 minimizes the situation where the produced hydrogen participates in other chemical reactions within the reactor 14. Thus, minimizing the residence time of the produced hydrogen in the reactor 14 may reduce the production of intermediate products of the thermal cracking process. Depending on the composition of the input feed 11, the intermediate products may include, for example, ethylene and acetylene.

[0081] Conduit 24 is preferably made of a material capable of withstanding contact with molten material 12 at the operating temperatures of system 10 (e.g., temperatures on the order of 1200° C.). Conduit 24 may be made of a material capable of withstanding contact with molten material 12 at temperatures of, for example, about 1400° C. or greater. Conduit 24 may be made of, for example, one or more of stainless steel 310, stainless steel 316, nickel alloy, Inconel, Hastelloy, and tungsten.

[0082] The conduits 24 may be bundled together in conduit bundles 25 (see, e.g., FIGS. 3A, 3B, 3C, and 3D). Each of the conduit bundles 25 has one or more conduits 24. The conduit bundles 25 may have from 1 to 10,000 conduits 24. The conduit bundles 25 are contained within a shell 27.

[0083] The conduits 24 may have a cross-sectional shape having any suitable shape in a direction transverse to the flow of the molten medium 12. For example, but not limited to, the cross-sectional shape of the conduits 24 may be circular, elliptical, annular, rectangular, square, triangular, any other suitable shape, etc. The conduit bundles 25 and shells 27 may also have a cross-sectional area having any suitable shape in a direction transverse to the flow of the molten medium 12. For example, with respect to the conduits 24, the conduit bundles 25 and shells 27 may have a cross-sectional area that is circular, elliptical, annular, rectangular, etc. Different conduits 24 optionally have different cross-sectional shapes. The cross-sectional shape of the conduits 24 may optionally vary along the length of the conduits 24.

[0084] In some embodiments, the conduit 24 comprises any suitable tube or pipe. The conduit 24 may comprise a tube that is circular in cross section. Figure 3A is a cross section of a conduit bundle 25 in which the conduit 24 comprises a tube that is circular in cross section. The conduit 24 may comprise a tube that is rectangular in cross section. Figure 3B is a cross section of a conduit bundle 25 in which the conduit 24 comprises a tube that is rectangular in cross section.

[0085] In some embodiments, the conduits 24 have the form of annular spaces defined between concentric tubes. Figure 3C is a cross-section of an example of a conduit bundle 25 in which the conduits 24 have spaces between the concentric tubes.

[0086] In some embodiments, the conduits 24 are defined between a pair of parallel plates. Such conduits may also be referred to as "parallel channels" or "parallel conduits." FIGS. 6A and 6B illustrate examples of parallel channels 24. The parallel channels may be defined, for example, between a pair of parallel plates 24A. The edges of each of the parallel plates 24A may be in contact with opposing faces of the shell 27. The edges of the parallel channels are optionally provided by a portion of the shell 27.

[0087] The cross-section of the parallel channels 24 in a plane transverse to the flow direction of the molten medium 12 (see, e.g., Figures 6A and 6B) may have a high aspect ratio (e.g., the thickness of the parallel channels, shown at D1 in Figure 6B, may be significantly smaller than the lateral width of the cross-section, shown at D2 in Figure 6B. D1 may also be significantly smaller than the length D3 of the parallel channels in the flow direction of the molten medium 12 (see, e.g., Figure 6A).

[0088] D2 may be, for example, 10, 20, 40 or more times greater than D1, providing a cross-sectional aspect ratio (D2:D1) of 10:1, 20:1, 40:1 or more. D1 may be defined, for example, by the space between adjacent plates 24A. D2 may be defined, for example, by the width of the shell 27 or the distance between the other side members that close the edge of the parallel channel 24. Within the parallel channels, the molten medium 12 may flow primarily as a two-dimensional flow-through between the parallel plates 24.

[0089] 3D is an example of an elevational cross section of a conduit bundle 25 in which the conduits 24 have parallel channels. Heat may be transferred into the melt media 12 in the channels 24 by a hot fluid introduced into the spaces 24B between the parallel channels 24.

[0090] The characteristics of conduit 24 can affect the conversion of input feed 11 to hydrogen and carbon. For example, the dimensions (e.g., one or more of diameter, length, height, width) and materials of conduit 24 affect the rate of heat transfer to input feed 11 and the residence time of input feed 11 within reactor 14. The heat transfer rate and residence time affect the conversion of input feed 11 to hydrogen.

[0091] Maximizing the heat transfer rate and residence time can increase the conversion of methane to hydrogen. For example, to achieve 50% conversion of methane to hydrogen at a methane flow rate of 0.4 kg / hr and a reactor operating temperature of 1050° C., a conduit 24 that is a 3 to 4 meter long stainless steel pipe having a schedule 40 ¾ inch nominal diameter can be used.

[0092] In a preferred embodiment, conduit 24 is made with the largest dimensions (i.e., one or more of length and diameter, width and height) capable of maintaining the temperature of the mixture throughout reactor 14. If conduit 24 has a tube, the diameter of conduit 24 may be, for example, in the range of ¼ inch to 5 inches. If conduit 24 has a tube, the diameter of conduit 24 is preferably in the range of ¾ inch to 2 inches.

[0093] The length of conduit 24 can be selected based on the temperature of reactor 14, the flow rate of input feed 11, the surface contact area between the bubbles of input feed 11 and molten medium 12, and the composition of molten medium 12. For example, if molten medium 12 is liquid tin, aluminum, or zinc and the temperature of reactor 14 is 1000° C., then conduit 24 to reactor 14-1 should be 3.5 to 4 m long, preferably 3.6 m long, to achieve greater than 60% conversion of methane to hydrogen.

[0094] The heated fluid is transported into the shell 27. Heat from the heated fluid is transferred through the walls of the conduit 24 to the molten material 12. The heat provides the energy for the thermal cracking reaction. To reduce heat transfer to the surroundings, the reactor 14 may be insulated with insulation 29. The insulation 29 may comprise, for example, high temperature insulation. The insulation 29 may comprise ceramic fiber insulation.

[0095] In the example reactor 14-1, the heated fluid is provided by a heating system 30, which may be, for example, combustible natural gas, hydrogen, a mixture of hydrogen and natural gas, or other combustible material to produce heated fluid 32. Other options for heating system 30 include electric heaters, plasma heaters, induction heaters, solar heaters, or other heaters capable of heating fluid 32 to a suitably high temperature (e.g., at or above the operating temperature of melting media 12).

[0096] Heated fluid 32 enters shell 27 at one or more ports 31. Inside shell 27, heated fluid 32 is diverted through reactor 14 to contact the exterior of conduit 24.

[0097] Preferably, the heated fluid 32 is diverted through the reactor 14 such that there is a uniform or quasi-uniform temperature distribution throughout the conduits 24, throughout the conduit bundle 25, and minimal temperature gradients along the conduits 24. Baffles 26 may be provided within the shell 27 to control the flow and / or divergence of the heated fluid 32. The baffles 26 may provide mechanical support to the conduits 24. The heated fluid 32 exits the shell 27 of the reactor 14 through one or more output ports 33.

[0098] Immediately after leaving shell 27, heated fluid 32 may be used at specific points within system 10. For example, heated fluid 32 may be used to heat the exterior surfaces of one or more of pump 13, multiphase separation unit 16, other pipes, other valves, and other exterior surfaces of system 10.

[0099] When the conduits 24 are parallel channels, the heated fluid 32 may be diverted to spaces 24B between the parallel channels where the input ports 31 and output ports 33 are appropriately positioned. In some embodiments, each space 24B between the parallel channels 24 may have their own input port 31 and output port 33 each).

[0100] The division and flow of the heated fluid 32 within the shell 27 may be configured to maximize the conversion of the input feed 11 to hydrogen and carbon black. For example, the division and flow of the heated fluid 32 within the shell 27 may be arranged relative to the flow pattern of the melting medium 12 within the conduit 24 of the reactor 14 to maintain an optimal temperature for the thermal cracking reaction within the conduit 24. In some embodiments, the heated fluid 32 travels through the reactor 14 counter to the flow of the melting medium 12 within the channel 24 such that the heated fluid 32 first transfers heat to the melting medium 12 exiting the channel 24 and then transfers heat to the melting medium 12 entering the channel 24.

[0101] Examples of flow patterns of the heated fluid 32 include counter-flow, cross-flow, and parallel flow configurations, and combinations thereof. In a counter-flow configuration, the heated fluid 32 flows primarily in a direction opposite to the flow of the mixture of melting medium 12 and input feed 11 in the conduit 24. In the above embodiment, the input port 31 may be located near the collector 28, and the output port 33 may be located near the header 21A. FIG. 4A depicts an example of a heating system 30A having a counter-flow configuration with a baffle 26 directing the flow inside the shell 27.

[0102] In the cross-flow configuration, the heating fluid 32 flows primarily in a direction transverse to the conduit 24. In the above embodiment, the input port 31 and the output port 33 may be located at corresponding locations on opposite sides of the reactor 14 (e.g., an input port and a corresponding output port such that a line drawn between the input port and the corresponding output port is approximately perpendicular to the length of the reactor). Figure 4B depicts an example of a heating system 30B having a cross-flow configuration.

[0103] In the parallel flow configuration, the heating fluid 32 flows primarily in the same general direction as the mixture of melting media 12 and input feed 11 in the conduit 24. In the above embodiment, the input port 31 may be located near the header 21A and the output port 33 may be located near the collector 28. FIG. 4C depicts an example of a heating system 30C having a parallel flow configuration with baffles 26 directing the flow inside the shell 27.

[0104] Among the counterflow, crossflow and parallel flow configurations, the counterflow configuration tends to advantageously maintain the greatest temperature gradient (and therefore the highest heat transfer rate) between the heated fluid 32 in the conduit 24 and the mixture of the melting medium 12 and input feed 11. Such a temperature gradient maximizes the heat transfer efficiency, which is defined as the ratio of the actual heat transfer rate to the maximum heat transfer rate possible in the reactor 14. A consistent temperature gradient also helps reduce thermal stresses in the materials of the reactor 14.

[0105] In some embodiments, reactor 14-1 includes fins on the interior and / or exterior surfaces of conduit 24. The fins may improve heat transfer between heated fluid 32 and molten media 12, thereby increasing the conversion of input feed 11 to hydrogen and carbon. Fins on the inside of conduit 24 may also help improve mixing of input feed 11 with molten media 12.

[0106] The fins may extend continuously, intermittently, or in a zigzag configuration along the conduit 24. The fins may extend in a spiral manner around or about the exterior surface of the conduit 24. The shape of the fins may be, for example, any one or any combination of rectangular, trapezoidal, triangular, and elliptical.

[0107] The shell 27 is made from a material rated to withstand the temperature of the heated fluid 32 with a reasonable factor of safety. The shell 27 may be made from any suitable metallic or non-metallic material, such as, for example, stainless steel alloys, nickel alloys, cast iron, refractory blocks, ceramics, and carbon graphite blocks. In some embodiments, the shell 27 is made from one or more of stainless steel 310, stainless steel 316, nickel alloys, Inconel, and Hastelloy.

[0108] The reactor 14 may be constructed to avoid problems that may arise due to differential expansion of components of the reactor 14 as the reactor 14 reaches operating temperature. Construction methods to accommodate thermal expansion may include one or more of the following: - Making some or all of the components of the reactor 14 out of materials that have a relatively low coefficient of thermal expansion (e.g., a coefficient of thermal expansion of less than 2% of the length of the material when the temperature changes between room temperature and 1800°C). - Designing the conduit 24 to accommodate thermal expansion, for example by bending the conduit 24. For example, in some embodiments, the conduit 24 is bent 180° into a hairpin (see FIG. 5A). As another example, the conduit 24 may be bent to include a 90° bend to accommodate expansion. Such a bent conduit 24 may expand freely without the need for stressful welds and fixed joints. In some embodiments, the conduit 24 is connected with a U-shaped pipe (see FIG. 5B). In some embodiments, the conduit 24 is bent less than 90° to accommodate thermal expansion of the conduit 24 (see FIG. 5C). - Incorporating one or more expansion joints into the shell 27 (to allow relative movement of the ends of the shell 27). The use of expansion joints is conventional practice in the design of shell and tube heat exchangers when the shell and tubes have different thermal expansion coefficients.

[0109] In embodiments where shell 27 is made from a material that has a thermal expansion coefficient of less than 2% with a temperature change from 25° C. to 1800° C., one or both ends of conduit 24 may be connected to a U-shaped pipe that may be bent to allow for thermal expansion of conduit 24.

[0110] In some embodiments, the input feed 11 is mixed into the molten medium 12 by bubbling the input feed 11 into the molten medium 12 through small holes. In the above embodiments, the input feed 11 may be bubbled through a bubbler that acts as a gas-liquid contactor. The bubbler may include, for example, one or more of a sparger, a rotary degasser, a sintered metal sparger, a porous metal member (e.g., a porous metal disk), and a porous ceramic member (e.g., a porous ceramic disk). The input feed 11 may be bubbled into the molten medium 12 before or within the reactor 14.

[0111] Figure 6 depicts another example reactor 14-2 that can be used for reactor 14 in system 10 of Figure 1. Reactor 14-2 may have the same or similar structure as reactor 14-1 (Figure 2), except that reactor 14-2 has a header 21B equipped with a bubbler 23. Input feed 11 is bubbled within reactor 14-2 by bubbler 23.

[0112] In some embodiments, the bubble generator 23 comprises a rotary degasser, which generates bubbles through continuous rotation. In some embodiments, the bubble generator 23 comprises one or both of a porous ceramic and a sparger. The pore size of the porous ceramic and / or the sparger directly correlates with the size of the bubbles. For example, to obtain bubbles with a diameter of 50 microns or less, the average diameter of the pores may be 50 microns or less. In some embodiments, the bubble generator comprises a porous metal or ceramic material or a sparger with a pore size in the range of about 2 microns to about 50 microns.

[0113] The resulting bubbles in the input feed 11 may vary in size. The bubble diameter may be, for example, within a range of about 1 micron to 5 millimeters. The surface area of ​​the input feed 11 in contact with the melting medium 12 may be advantageously increased by dividing the input feed 11 into many small bubbles.

[0114] It is advantageous for the bubbles in the input feed 11 to be small and for the dimensions of the conduit 24 to be relatively large (e.g., length, width, height, diameter) while maintaining a reasonably uniform temperature distribution throughout the conduit 24 and a low temperature gradient along the conduit 24. Providing the same amount of input feed 11 in the form of smaller bubbles may generally improve the performance of the reactor 14. Making the bubbles smaller relative to the dimensions of the conduit 24 may advantageously keep the molten medium 12 as a continuous fluid within the reactor 14 while the bubbles are dispersed in the molten medium 12 and form a discontinuous phase. In some embodiments, the bubble size is at least 25 times, or at least 250 times, or at least 1000 times, or at least 4000 times, or at least 10 times larger in area than the cross-sectional area of ​​the path through the reactor through which the mixed molten medium and hydrocarbons flow through the reactor. 6 Twice smaller.

[0115] Bubble coalescence tends to reduce the surface area of ​​the input feed 11 in contact with the molten medium 12. It is advantageous to increase the surface area of ​​the input feed 11 in contact with the molten medium 12. Microbubbles, which are bubbles between 1 and 50 microns in diameter, help disperse the bubbles in the molten medium 12 and reduce bubble-to-bubble coalescence. Uniform distribution of bubbles throughout the molten medium 12 correlates with consistent hydrogen production.

[0116] FIG. 7 depicts an example reactor 14-3 that can be used for reactor 14 of system 10 of FIG. 1. Reactor 14-3 may share similar or similar elements as depicted in reactor 14-1 (FIG. 2) and / or reactor 14-2 (FIG. 6). Reactor 14-3 is assembled to be disposed with a vertically extending conduit 24. Conduit 24 may comprise, for example, parallel conduits. Collector 28A is disposed at the top of reactor 14-3 and header 21C is disposed at the bottom. Reactor 14-3 receives molten media 12 and input feed 11. Molten media 12 is received at the top of reactor 14-3 in conduit 91, which transfers molten media 12 to header 21C disposed at the bottom of reactor 14-3. Divider 22 mixes input feed 11 and molten media 12.

[0117] The mixture of melting media 12 and input feed 11 is conveyed through heated conduit 24 within reactor 14-3 to collector 28A. In this example embodiment, collector 28A is part of multi-phase separation unit 16, which separates the received reacted mixture 41 into gaseous species 42 and liquid / solid species 43. In other embodiments, collector 28A and multi-phase separation unit 16 are separate.

[0118] The molten medium 12 enters and exits the reactor 14-3 at approximately the same height. Advantageously, the U-shaped nature of the reactor 14-3 allows the molten medium 12 to be pumped through the reactor 14-3 without having to overcome the hydrostatic pressure difference caused by the outlet of the reactor 14-3 being at a higher height than the inlet of the reactor 14-3. In the above embodiment, the principles of hydrostatic dynamics assist the pump 13 in circulating the molten medium 12 through the reactor 14-3.

[0119] Examples of separation units The multi-phase separation unit 16 receives the reacted mixture 41 and separates the reacted mixture 41 into gaseous species 42 and liquid / solid species 43 based on density. The multi-phase separation unit 16 may be a separate component or may be part of the reactor 14. FIG. 8 illustrates a schematic of an example of the multi-phase separation unit 16. The multi-phase separation unit 16 has a vessel 50 to which the reacted mixture 41 is transferred. The gaseous species 42 float to the head space 50A of the vessel 50 and are collected. The gaseous species 42 may contain the hydrogen produced, the remainder of the input feed 11, and any other gases present in the reacted mixture 41. The liquid / solid species 43 may contain the carbon 19 produced and the melting medium 12.

[0120] The liquid / solid species 43 are further separated by density. The density of carbon 19 is less than the density of the melting media 12 allowing the carbon 19 to float. A skimmer or other collection mechanism 50B (e.g., chain / conveyor belt, decanter centrifuge, mesh filter, auger) may be provided to collect the carbon 19 from the surface of the melting media 12. The carbon 19 may be removed from the melting media 12 continuously or at regular intervals.

[0121] In some embodiments, the molten medium 12 contains a dense material (e.g., a liquid metal) and a less dense material (e.g., a molten salt). In the above embodiments, a layer 50C of the less dense material may be formed on top of the denser material. In the above embodiments, the carbon 19 may float through layer 50C to the top surface.

[0122] The carbon 19 may be stored in a storage tank 45. The storage tank 45 may be isolated from the multi-phase separation unit 16 by an airlock or one-way valve 47. A vacuum pump 46 may be in communication with the storage tank 45. The vacuum pump 46 may prevent excessive amounts of air from entering the multi-phase separation unit 16.

[0123] The multi-phase separation unit 16 may include an insulator / heater 48. The insulator / heater 48 may maintain a temperature within the multi-phase separation unit 16. The insulator / heater 48 optionally heats the multi-phase separation unit 16. In some embodiments, the pump 13 is integrated with the multi-phase separation unit 16.

[0124] The multi-phase separation unit 16 outputs a gaseous species 42. The gas purification unit 17 receives the gaseous species 42 as an input. The gaseous species 42 may contain a certain amount of carbon 19. To remove the remainder of the carbon 19 present in the gaseous species 42, the gas purification unit 17 may comprise one or more of a cyclone, a filter bag, and a gas separation unit. The gaseous species 42 may be cooled prior to the gas purification unit 17. The gaseous species 42 may be cooled, for example, by a heat exchanger. The gas purification unit 17 separates the hydrogen gas 18A from the other gaseous species 42.

[0125] Gas purification unit 17 may include, for example, a pressure swing adsorption gas separator or a membrane gas separator. For example, hydrogen gas may diffuse through a hydrogen-permeable membrane that blocks other gaseous species 42. In another example, hydrogen may be separated from other gases using molecular sieve adsorbent particles that capture hydrogen but do not adsorb other gases whose molecules are larger than the hydrogen molecule. Molecular sieve adsorbent particles may be utilized to separate hydrogen from other gases, for example, by pressure swing adsorption.

[0126] Examples of other system components The system 10 may further include a pretreatment unit to process the input feedstock 11 prior to the reactor 14. The pretreatment unit may remove one or more substances that are undesirable for the thermal cracking process. Examples of substances that are undesirable for the thermal cracking process include sand, water, oxygen, and sulfur.

[0127] The separated hydrogen 18 can be compressed. The remainder of the other gaseous species 18B may be recycled within the system 10. For example, the remainder of the gaseous species 18B can be purged back into the input feed 11, combusted to heat the reactor 14, or used to generate electricity.

[0128] Examples of uses for produced hydrogen Hydrogen 18A can be used in any application where hydrogen is used, including power generation systems such as fuel cells.

[0129] In some embodiments, the gaseous species 42 are used directly to generate electricity, such as to generate less carbon-intensive electricity, or to reduce the carbon intensity of products in the ammonia, steel, and cement industries.

[0130] The system 10 may optionally include one or more compressors. For example, the compressors may be: increasing the pressure of the input feed 11; increasing the pressure of the gaseous species 42, and / or Increasing the pressure of the collected hydrogen 18A may be provided for one or more of:

[0131] Example System 9 is a more detailed schematic diagram of an example embodiment of the system 10. The input feed 11 contains natural gas. The input feed 11 is compressed by a compressor 51A (COMP1). The compressed input feed 11 (S1) is preheated in a heat exchanger 52A (HEX1) by gaseous species 42 (CH4-H2 mixture). The heated input feed 11 (S2) is mixed with a melting medium 12 (S6) in a mixer 53. The mixture of the input feed 11 and the melting medium 12 (S3) enters and passes through the reactor 14.

[0132] The reacted mixture 41 (S4) passes through a multi-phase separation unit 16 (filter), which mechanically separates the carbon 19 from the melting medium 12. The separated melting medium 12 (S5) is recirculated throughout the system 10 by pump 13.

[0133] The gaseous species 42 (CH4-H2 mixture) passes through heat exchanger 52A (HEX1) and the temperature of the gaseous species 42 is further reduced by heat exchanger 52B (HEX2). The cooled gaseous species 42 (S8) is compressed by compressor 51B (COMP2). The compressed gaseous species 42 (S9) passes through gas purification unit 17, which comprises a pressure swing adsorption (PSA) unit. The separated hydrogen (S10) is compressed by compressor 51C (COMP3) to produce hydrogen 18A (H2out) for transport to end users. The remainder of the gaseous species 18B (P2G) is either reinjected into the input feed 11, saved for use as fuel, or combusted for heat or power generation.

[0134] FIG. 10 illustrates an example embodiment of the system 10. This example embodiment is similar to the embodiment of FIG. 9, except for the addition of a heat exchanger 52C (HEX3) located after the multi-phase separation unit 16. The heat exchanger 52C receives and cools the separated molten medium 12 (S5a) from the multi-phase separation unit 16. The heat exchanger 52C outputs the cooled molten medium 12 (S5b) to the pump 13. Providing some cooled molten medium 12 to the pump 13 may extend the life of the pump 13. For example, the heat exchanger 52C may cool the molten medium 12 to a temperature that is within the operating temperature range of the pump 13.

[0135] FIG. 11 depicts another example of an embodiment of the system 10. The input feed 11 contains natural gas. The input feed 11 is compressed by a compressor 61A (COMP1). The compressed input feed 11 (S1) is preheated in a heat exchanger 62C (HEX3) by a separated melting medium 12 (S5a). The heated input feed 11 (S2) is mixed with the melting medium 12 (S6) in a mixer 63. The mixture of the input feed 11 and the melting medium 12 (S3) passes through a reactor 14.

[0136] The reacted mixture 41 (S4) passes through a multi-phase separation unit 16 (filter). The separated melting medium 12 (S5a) passes through a heat exchanger 62C where it is cooled. The cooled melting medium 12 (S5b) is recirculated by a pump 13 throughout the system 10. The gaseous species 42 (CH4-H2 mixture) is cooled by a heat exchanger 62B (HEX2). The cooled gaseous species 42 (S8) is compressed by a compressor 61B (COMP2). The compressed gaseous species 42 (S9) is transferred to a gas purification unit 17. The gas purification unit 17 comprises a pressure swing adsorption (PSA) unit. The separated hydrogen (S10) is compressed by a compressor 61C (COMP3) to produce hydrogen 18A (H2out) for transport to end users. The remainder of the gaseous species 18B (P2G) is either reinjected into the input feed 11, stored for use as fuel, or combusted for heat or power generation.

[0137] FIG. 12 depicts another example embodiment of system 10. This example embodiment combines features of the example embodiments depicted in FIG. 9 and FIG. 11. In particular, the input feed 11 is first heated in heat exchanger 72C (HEX3) by separated melting medium 12 (S5a) (as in FIG. 11) and then heated again in heat exchanger 72A (HEX1) by gaseous species 42 (CH4-H2 mixture) (as in FIG. 9). Other aspects of the embodiment of FIG. 12 are the same or similar to the embodiments depicted in FIG. 9 and FIG. 11.

[0138] FIG. 13 illustrates an example of another embodiment of the system 10. The input feed 11 contains natural gas. The input feed 11 is compressed by a compressor 81A (COMP1). The compressed input feed 11 (S1) is preheated in a heat exchanger 82C (HEX3) by the reacted mixture 41 (S4a). The heated input feed 11 (S2) is mixed with the melting medium 12 (S6) in a mixer 83. The mixture of the input feed 11 and the melting medium 12 (S3) passes through a reactor 14. The reacted mixture 41 (S4a) passes through a heat exchanger 82C (HEX3) where it is cooled. The cooled reacted mixture 41 (S4b) passes through a multiphase separation unit 16. The separated melting medium 12 (S5) is recirculated by a pump 13 throughout the system 10.

[0139] The gaseous species 42 (CH4-H2 mixture) is cooled by heat exchanger 82B (HEX2). The cooled gaseous species 42 (S8) is compressed by compressor 81B (COMP2). The compressed gaseous species 42 (S9) passes through gas purification unit 16, which comprises a pressure swing adsorption (PSA) unit. The separated hydrogen (S10) is compressed by compressor 81C (COMP3) to produce hydrogen 18A (H2 out) for transport to end users. The remainder of the gaseous species 18B (P2G) is either reinjected into the input feed 11, stored for use as fuel, or combusted for heat or power generation. The above embodiment allows for the separation of carbon 19 from the mixture 41 after reaction at low temperature. The above embodiment may also advantageously cool the melting medium 12 flowing into pump 13 to a temperature below the operating temperature of pump 13.

[0140] FIG. 14 depicts another example embodiment of the system 10. The input feed 11 contains natural gas. The input feed 11 is compressed by a compressor 91A (COMP1) before a methane thermal cracking block 93. The methane thermal cracking block 93 may have any embodiment, some embodiment, or combination of the embodiments described herein. The gaseous species 42 (CH4-H2 mixture) is cooled by a heat exchanger 92 (HEX2). The cooled gaseous species 42 (S8) is compressed by a compressor 91B (COMP2). The compressed gaseous species 42 (P2G) is transported to an end user without further hydrogen purification.

[0141] System design considerations Those skilled in the art will appreciate that the techniques described herein may be utilized to produce hydrogen at low cost.

[0142] The design and operating parameters of the system 10 described herein may be selected to achieve a desired hydrogen recovery. In some embodiments, where cost is a priority, it is optimal to convert 60% of the input feed 11 to hydrogen. Cost is defined as the inverse of efficiency. Efficiency is defined as follows: Efficiency = Heating value of hydrogen produced [J / s] / Input power [J / s] (3)

[0143] To achieve 100% conversion of hydrogen in the molecules of the input feedstock 11 to hydrogen gas, the following costs are possible: - increasing the capital costs of the system 10 (e.g. providing larger equipment, e.g. larger reactors, multi-phase separation units and pumps); - Increased production of by-product species such as ethylene or acetylene, and / or - Reduction in total hydrogen production.

[0144] Factors that may improve the efficiency of the systems described herein include the following: (i) Flow Rate (see Table 2). The optimal flow rate of the input feed 11 and melting medium 12 provides sufficient residence time for the input feed 11 to thermally crack into hydrogen and carbon black. The optimal flow rate of the input feed 11 may depend on the design and operating parameters of the system described herein.

[0145] [Table 2-1]

[0146] [Table 2-2]

[0147] [Table 2-3]

[0148] (ii) The temperature of the melting medium 12. Higher temperatures (e.g., 900° C. to 1200° C.) increase the reaction rate and conversion of the input feed 11 (see Table 3). In some cases, the efficiencies gained from increasing temperatures are offset by increased capital costs, power input to the system 10, and maintenance costs due to reduced equipment and durability of the equipment to withstand operation at higher temperatures, all of which can increase significantly when operating temperatures exceed 1100° C.

[0149] [Table 3-1]

[0150] [Table 3-2]

[0151] (iii) Residence time of the input feed 11 in the reactor 14. Optimal residence time of the input feed 11 in the reactor 14 increases the conversion of the input feed 11 and the total amount of hydrogen produced, lowers the cost of producing hydrogen, and prevents carbon black precipitation in the reactor 14. Optimal residence time is design specific. The optimal residence time of the input feed 11 in the reactor 14 may be influenced by one or more of the following: - flow rate of the input feedstock 11; - the flow velocity of the melting medium 12, - the length and diameter of the conduit 24; - the total number of conduits 24 in the conduit bundle 25; - the temperature of the input feedstock 11; - the temperature of the melting medium 12, - the temperature of the heated fluid 32, - the size of the nozzle of the flow divider 22, and - the size of the gas bubbles generated by the bubble generator 23. (iv) Composition of the melting medium 12. The composition of the melting medium 12 may have one or more of a catalytic effect that may improve efficiency, a higher heat transfer rate than the material of the conduit 24, and a higher heat content than the input feed 12. (v) Recycling of melting media 12 within system 10. (vi) Turbulence of the melting medium 12 . (vii) Bubbling of the input feed 11 through a porous ceramic or sparger having a pore size of 50 microns or less. (viii) Bubble size of the input feed 11. The smaller the bubble size, the greater the surface area of ​​contact between the input feed 11 bubbles and the melting medium 12, which may increase efficiency.

[0152] Factors that can reduce efficiency include: (i) Flow velocity. Flow velocities higher or lower than the optimum flow velocity reduce efficiency. (ii) The composition of the melting medium 12. Increasing the solubility of hydrogen in the melting medium 12 and instability of the melting medium 12 within the system 10 can reduce efficiency. (iii) The pressure in the reactor 14. Increasing the pressure in the reactor 14 reduces efficiency. It is preferred that the reactor 14 be operated at about atmospheric pressure. (iv) Pressure changes within the reactor 14. Hydrostatic pressure within the reactor 14 reduces efficiency.

[0153] Scaling up the production of hydrogen can be achieved by one or more of the following: (i) using multiple reactors 14; (ii) Providing a reactor 14 with more conduits 24; (iii) creating a reactor 14 with a longer conduit 24; (iv) increasing the rate of input feed material 11; (v) increasing the temperature of the melting medium 12; and (vi) Increasing the temperature of the heated fluid 32.

[0154] To increase production, it is preferable to use multiple reactors or more conduits. Increasing the input rate of the hydrocarbons may increase the rate of hydrogen production, but may also reduce the conversion of the input feed 11 to hydrogen, thereby decreasing the overall efficiency of the system 10.

[0155] The techniques described herein can be implemented, for example, at or near natural gas facilities (e.g., pipelines, liquefied natural gas facilities), or at or near the point of use of the produced hydrogen. Such flexibility allows for the implementation of the present technology in any geographic location that has access to natural gas or other suitable hydrocarbons as a feedstock.

[0156] This disclosure describes various methods according to the present invention. Such methods may be applied with systems and devices other than the example systems and devices in the context of the systems depicted in the drawings. Many variations are possible.

[0157] In some embodiments, the method according to the invention may control the flow of molten media through the reactor to meet the demand for hydrogen production and / or the supply of available hydrocarbons to be thermally cracked. For example, when the demand for hydrogen and / or the supply of available hydrocarbons for cracking is low, a system of the general type described herein may be placed in a standby mode where the molten media remains molten but flows at a reduced flow rate or intermittently through the process loop. In the standby mode, the temperature of the molten media may be reduced to a temperature lower than the normal operating temperature.

[0158] During hydrogen production, operating parameters such as the amount of heat supplied to the reactor and / or the flow rate of the melting medium and / or the amount of preheat supplied to the input feed may be adjusted to maintain optimal performance while the amount of input feed is varied.

[0159] Example of volume compensation As mentioned above, changes in the rate at which the input feedstock is transported to the thermal cracking reactor may alter the volume of the mixed fluids in the reactor. These volume changes may be adjusted by providing a volume to the system described herein that allows for adjustment of the fluid level changes in said system or components thereof. However, in some cases, it is advantageous to maintain a fixed or nearly fixed fluid level in the thermal cracking system or components thereof.

[0160] The inventors have identified a need for a method of accommodating mixed fluid volume changes within a thermal cracking system. Such volume changes may result from changes in the density of the mixed fluids as a result of changes in the operation of the thermal cracking system, such as turndown. The challenges of finding a solution to this problem include handling very high temperature fluids, minimizing energy consumption, minimizing heat loss, and providing a system that is cost effective to construct and maintain.

[0161] Providing an overflow weir or drain that defines the maximum fluid level can prevent the fluid level in the reactor from rising above a set level in the event of an increase in the inlet feed. The overflow weir can be provided with a lip that is positioned such that the fluid can spill over the lip if the fluid level in the reactor is higher than the lip. If the volume of fluid in the reactor increases (e.g., as a result of a higher hydrocarbon inlet feed), any excess fluid (i.e., hot liquid medium) can escape over the overflow weir or into the drain, thereby maintaining the fluid level in the reactor at the level defined by the overflow weir or drain.

[0162] When the volume of fluid in the reactor decreases (e.g., as a result of inlet feed turndown), it is necessary to add more fluid (i.e., hot liquid medium) to the reactor to maintain the desired fluid level. Providing a practical and energy efficient mechanism for adding fluid to the reactor is a challenge. This challenge arises in part from the energy required to raise the molten medium, which has a high density. As mentioned above, the density of the molten medium suitable for use in the reactors described herein is greater than 5000 kg / m 3 or even higher. At these densities, it may take a lot of energy to pump the molten medium from a low altitude to a significantly higher altitude. This problem also arises in part because pumps capable of reliably pumping very hot molten medium are expensive, especially when the pump is required to generate sufficient pressure to raise the molten medium significantly.

[0163] Figures 15 to 19 show examples of several mechanisms for maintaining a desired fluid level in the reactor. The approaches illustrated in Figures 15 to 19 can be used in the reactors and systems described above as well as other reactors and systems for thermal cracking of hydrocarbons. For simplicity, some features of Figures 15 to 19 are indicated by references similarly used in Figures 1 to 14, and these features may be as described above. For clarity of explanation, the means for heating the molten medium 12 and the illustrated reactor are not drawn in Figures 15 to 19. These embodiments may implement any suitable heating approach, including the heating approaches described in certain places herein. Heat may be provided through the walls of the reactor, by a heater inside the reactor, by circulating hot gas or other sufficiently hot fluid through channels in the reactor, etc.

[0164] 15 is a schematic cross-sectional view of an example of a system 150 including a reactor 152. The reactor 152 is shown as a plug flow reactor. A pump 153 is operable to pump the hot molten medium 12 through a conduit 154 and circulate it through the channel 24 of the reactor 152. The pump 153 may comprise, for example, a cantilever pump or a well pump configured to withstand contact with the molten medium 12. The molten medium 12 may enter the reactor 152 at any suitable location, for example, at the bottom of the reactor 152 (i.e., a header) or at the top of the reactor 152 (i.e., a collector).

[0165] A suitable hydrocarbon inlet feed 11 enters the reactor 152 at a diverter 22 which diverts the inlet feed 11 as bubbles into channels 24 as described above to produce product gas 18 (containing hydrogen) and carbon black 19. The carbon black 19 and product gas 18 rise to the surface of the molten media 12 and are collected in the headspace 155 of the reactor 152.

[0166] Overflow weir 157 prevents the surface of molten media 12 in reactor 152 from exceeding top surface 156. As molten media 12 is pumped into reactor 152, it rises to top surface 156 and flows over overflow weir 157 into holding tank 158. Holding tank 158 may act as a source of make-up molten media 12 if the level of molten media 12 in reactor 152 drops below a desired level and may also act to receive overflow of molten media 12 from reactor 152.

[0167] The size of the holding tank 158 and the total amount of molten media 12 can be selected such that the surface level of the molten media 12 in the holding tank 158 is below the height of the overflow weir 157 for all expected operating conditions of the system 150.

[0168] If the rate at which inlet feed 11 is introduced drops too quickly such that the surface level of molten media 12 drops below peak level 156, the flow of molten media 12 from pump 153 may return the level of molten media 12 to peak level 156. The level of molten media 12 in holding tank 158 may fluctuate due to changes in the rate at which inlet feed 11 is transported to reactor 152.

[0169] The holding tank 158 may be located at an elevation close to the maximum fluid level 156 so that the pump 153 does not have to pump against a large head and does not require large amounts of power to operate. The holding tank 158 may be integral with or attached to the reactor 152, or may be a separate component connected to the reactor 152 by pipes, channels, ducts, etc.

[0170] Carbon black floating in the head space 155 of the reactor 152 is prevented from entering the holding tank 158. In the illustrated embodiment, the melting medium 12 reaches the overflow weir 157 by a U-trap 159 that intercepts the carbon black 19. A mechanism 160, such as a conveyor, suction device, screw conveyor, conveyor belt, or any suitable mechanical skimming device, is provided to remove the carbon black 19 from the head space 155. The carbon collection system 160 can be mounted vertically or horizontally at a fixed position so that the interface between the carbon black 19 and the melting medium 12 can be maintained at a constant level.

[0171] The pressure in the headspace 155 is equilibrated with the pressure in the holding tank 158 so that the level of melting medium 12 in the reactor 152 is equivalent to the level of melting medium 12 at the overflow weir 157. In the illustrated embodiment, pressure equalization is provided by an equalization path 161. A filter 162 may be provided to prevent carbon black 19 from escaping into the holding tank 158 through the equalization path 161.

[0172] An advantage of system 150 is that the surface level of molten media 12 in reactor 150 can be adjusted automatically and independently of the input volumetric flow rate of input feed 11, so long as pump 153 provides a sufficient flow rate of molten media 12 from holding tank 158 to reactor 152. The amount of molten media 12 in holding tank 158 can be varied without disrupting the operation of reactor 152.

[0173] It is not necessary for the pump 153 to operate continuously. If the system 150 is operating under constant conditions (at constant volumetric flow rate of the input feed 11), there is no reason why the surface level of the molten medium in the reactor 152 should be changed. In some embodiments, the system 150 has a controller that turns on the pump 153 only if the surface level of the molten medium 12 is lower than desired. For example, the pump 153 may be turned on for a period of time in response to a signal from a level detector indicating that the surface level of the molten medium 12 in the reactor 152 is low, and / or the pump 153 may be turned on for a period of time in response to a decrease in the volumetric flow rate of the input feed 11.

[0174] When the level of melt media 12 in holding tank 158 reaches a certain value and remains unchanged for a certain period of time, pump 153 may be powered off. Operating pump 153 intermittently as needed can help extend the life of pump 153 components and reduce maintenance costs.

[0175] Figure 16 is a schematic cross-sectional view of an example of a system 150A having a reactor 152A. System 150A is similar to system 150 of Figure 15, except that reactor 152A is a bubble column type of reactor. System 152A operates to maintain the surface of the molten media 12 in reactor 152A at a maximum fluid level 156 in the same manner as described above for system 150.

[0176] Reactors 152 and 152A can be considered to be bubble column reactors when pump 153 is not operating or is connected such that pump 153 does not circulate the mixed fluid along the reactor. Reactors 152 and 152A can be considered to be plug flow type reactors when pump 153 operates to circulate the mixed fluid along the reactor. The main difference in structure between the illustrated reactors 152 and 152A is that reactor 152 includes heat transfer channels while reactor 152A does not. In reactor 152A, heat is transferred from outside the reactor to the mixed fluid inside the reactor, whereas in reactor 152, head can be transferred by heat transfer channels into the mixed fluid inside the reactor in addition to or instead of heat added to the outside of reactor 152.

[0177] 17-19 illustrate an example of a system that utilizes another approach to maintain a desired level of molten media 12 in a thermal cracking reactor. The systems of FIGS. 17-19 may include, but do not require, a circulation pump to control the level of molten media 12 in the reactor. The systems of FIGS. 17-19 include a holding tank that contains molten media 12. The holding tank is configured such that the surface height of the molten media 12 in the arm of the holding tank is adjusted. The surface height of the molten media 12 in the arm of the holding tank may be raised to a level at which the molten media 12 may enter the reactor from the holding tank, thereby raising the surface height of the molten media 12 in the reactor. The surface level of the molten media 12 in the arm may be lowered to allow the molten media 12 to flow out of the reactor into the holding tank.

[0178] 17 is a schematic cross-sectional view of a system 170 having a reactor 172. Reactor 172 is similar to reactor 152. Reactor 172 may comprise, for example, a bubble column reactor with channels 24 as shown, or a bubble column reactor or plug flow reactor without channels. System 170 optionally includes a recirculation loop 173, optionally including a pump 174.

[0179] As in system 150, system 170 has a spill weir 157 that allows any excess molten media 12 in reactor 172 to spill into holding tank 178. In this embodiment, holding tank 178 has two arms 178A and 178B extending upwardly. Headspaces 179A and 179B of arms 178A and 178B, respectively, are separated from one another by molten media 12 at the bottom of holding tank 178.

[0180] System 170 has a pressure control mechanism 180 operable to vary the relative pressure in headspace 179A and headspace 179B. By increasing the pressure in headspace 179B relative to headspace 179A, the surface level of molten media 12 in arm 178A can be increased. By decreasing the pressure in headspace 179B relative to headspace 179A, the surface level of molten media 12 in arm 178A can be decreased. Headspace 179A extends to a height level above the top of overflow weir 157.

[0181] If it is necessary to add more molten media 12 to the reactor 172, the pressure control mechanism 180 may be operated to raise the surface level of the molten media 12 above the top of the overflow weir 157. This allows the molten media 12 to flow back into the reactor 172 from the arm 178A of the holding tank 178 through the U-trap 159. If the reactor 172 becomes full of molten media in this manner, the level of molten media 12 in the arm 178A may be lowered below the top of the overflow weir 157, allowing any excess molten media 12 in the reactor 172 to escape over the overflow weir 157 into the holding tank 158.

[0182] When reactor 172 is in steady operation (e.g., at operating temperature and processing input feed 11 at a constant flow rate), the level of molten media 12 in arm 178A may be maintained below the level of overflow weir 157, and the level of molten media 12 in reactor 172 may be at the level of the top of overflow weir 157. If the surface level of molten media 12 in reactor 172 rises (e.g., if the flow rate of input feed 11 in reactor 172 increases), any excess molten media 12 may flow over the top of overflow weir 157 and into holding tank 178.

[0183] In system 170, the pressure in headspace 179A of first arm 178A is equilibrated with the pressure in headspace 155 of reactor 172 by equilibration path 161. In system 170, pressure control mechanism 180 includes a source of pressurized gas. Pressurized gas may be selectively admitted to headspace 179B by valve 181A. Pressurized gas may be allowed to exit headspace 179B by valve 181B.

[0184] In the illustrated embodiment, to maintain a desired surface level of the molten media 12 within the reactor 172, a level controller 182 operates valves 181A and 181B to raise and lower the level of the molten media 12 in arm 178A as needed.

[0185] In some implementations, the system 170 has a level sensor that outputs a level signal indicative of the level of the molten medium 12 in the reactor 172, and a level controller 182 that operates in response to the level signal (e.g., by temporarily raising the level of the molten medium 12 in the arm 178A above the top of the overflow weir 157 and then lowering the level of the molten medium 12 in the arm 178A below the top of the overflow weir 157) in response to determining that the level signal indicates that the surface level of the molten medium 12 in the reactor 172 is below a threshold level.

[0186] In some embodiments, the level sensor measures the level of the molten media 12 where the surface of the molten media 12 is not covered by the floating carbon black 19. For example, the level may be measured in a portion of the trap 159 outside the reactor 12. This may avoid any interference with the level measurement that may be caused by the presence of floating carbon black 19.

[0187] The level sensor may include, for example, a non-contact level sensor (e.g., a level sensor that uses radar, ultrasonics, or the like to detect the surface level of the melt media 12). Other suitable types of level sensors may also be used.

[0188] In some embodiments, the controller 182 is configured to determine if the level of the mixed fluid in the reactor 172 is below a particular set point, and if so, transfers molten medium 12 into the reactor such that the level of the mixed fluid in the reactor is at the particular set point. This determination may be based on one or more factors, for example, the measured weight of the reactor and its contents, the history of the volumetric flow rates of the input feed 11, detection of an overflow of molten medium from the reactor, the temperature profile along the reactor, the output of one or more level sensors, etc.

[0189] FIG. 17A is a flow chart illustrating an example of a method for controlling the level of molten media 12 in a reactor 172.

[0190] In some embodiments, the level controller 182 is triggered to fill the reactor 172 in response to a signal indicating that the flow rate of the input feedstock 11 has decreased.

[0191] In some embodiments, the level controller 182 operates periodically or sporadically to fill the reactor 172 with molten material 12. When the reactor 172 does not need to be filled with molten material, any excess molten material 12 simply spills over the overflow weir 157 and into the holding tank 178.

[0192] In some embodiments, the level controller 182 is configured to actively control the surface level of the molten material 12 in the arm 178A to be the same as the desired level in the reactor 172. In the above embodiments, the molten material in the arm 178A may be fluidly connected to the fluid in the reactor 172 by a passageway configured to not convey the carbon black 19 into the holding tank 178 such that the surface level of the molten medium 12 in the reactor 172 is equal to the surface level of the molten medium 12 in the arm 178A.

[0193] The pressurized gas may be any gas that will not interfere with the operation of the system 170, for example, by reacting with the melting medium 12. The pressurized gas may be, for example, an inert gas.

[0194] 18 illustrates system 170A, which is similar to system 170, except that system 170A includes pressure control mechanism 180A operable to control pressure in both headspace 179A and headspace 179B. In addition to valves 181A and 181B, pressure control mechanism 180A of system 170A includes valves 181C and 181D operable to introduce pressurized gas into and evacuate headspace 179A, respectively.

[0195] In some embodiments, level controller 182A of pressure controller 180A is configured to control the pressure in headspace 179A to be equal to the pressure in headspace 155 of reactor 172 (as opposed to equalizing the pressure in headspace 155 and headspace 179A across fluid connection 161). Level controller 182A may obtain input from a pressure sensor monitoring the pressure in headspace 155 and headspace 179A and / or a differential pressure sensor monitoring the pressure difference between headspace 155 and headspace 179A.

[0196] Advantageously, system 170A does not provide a direct path by which carbon black can escape from reactor 172 into holding tank 178. Filter 162 is not required in system 170A.

[0197] 19 is a schematic cross-sectional view of an example system 190 similar to system 170, except that system 190 includes a bubble column reactor 192 instead of reactor 172 having flow channel 24. System 190 may operate to maintain a desired level of the surface of molten media 12 within reactor 192 in the manner described above with reference to FIG.

[0198] The systems illustrated in Figures 15 to 19 may have various advantageous features. One advantage is that the level of molten media 12 in the reactor may be maintained at a desired level even if the volumetric flow rate of the input feed 11 is reduced. This may help maintain efficiency. If the level of molten media 12 in the reactor drops significantly, the residence time of the input feed 11 in the reactor may decrease at a decreasing rate depending on the conversion rate of the input feed 11 to hydrogen and carbon. This problem may be avoided by maintaining the surface of molten media 12 in the reactor at a constant or near constant level.

[0199] As another example, thermal stresses can be reduced in the above system. Thermal expansion of the equipment is inevitable at high temperatures. When changing the temperature of the equipment, the parts may all expand or contract together. This is a particular problem during cold start-up and shutdown processes. Thermal stresses from temperature changes are reduced if the parts exposed to high temperatures can be integrated. For example, the reactor, the carbon black and process gas collection areas, and the holding tanks may all be parts of an integrated structure. Thermal stresses can be further reduced by making all the reactor metal parts from the same metal alloy with the same thermal expansion coefficient. By integrating all of the major parts of the system and making the parts from materials with similar thermal expansion coefficients, stresses on the integrated parts and the linkages between them (e.g., pipes, channels, etc.) caused by thermal expansion are reduced or eliminated.

[0200] Another advantage of the system illustrated in Figures 15-19 is that the surface level of the molten media 12 in the reactor can be kept constant, or nearly constant. This makes it easier to collect the carbon 19 floating on the surface of the molten media 12. The collection device 160 may be simpler and easier to operate and maintain such that the collected carbon 19 is always at the same level. Furthermore, the collection device 160 may be designed not to contact the molten media 12 under any expected operating conditions. This may increase the reliability and lifespan of the carbon collection system 160.

[0201] References (list) The entire disclosures of all applications, patents, and publications, cited above and below, are incorporated herein by reference. However, it will be apparent to those skilled in the art that many variations and modifications can be made without departing from the scope of the invention, as defined in the claims. Reference to prior art in this specification is not, and should not be taken as, an admission, or in any manner suggestion that that prior art forms part of the common general knowledge in Canada or any other country.

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[0203] Interpretation of Terms Except where the context clearly requires otherwise, throughout the specification and claims: - "About" applied to numerical values ​​means ±10%. - "comprise", "comprising" and the like are to be construed in their inclusive sense, i.e., "including but not limited to," as opposed to their exclusive or exhaustive sense. - "connected," "coupled," or any variation thereof means any direct or indirect connection or combination between two or more elements, where the combination or connection between said elements may be physical, logical, or a combination thereof. - The words "herein," "above," "below," and similar words, when used to describe this specification, shall refer to this specification as a whole and not to any particular portions of this specification. - "Or", when referring to a list of two or more items, includes all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list. - The singular forms "a", "an" and "the" also include all appropriate plural references.

[0204] Directional words such as "vertical," "transverse," "horizontal," "upward," "downward," "forward," "backward," "inward," "outward," "left," "right," "front," "back," "top," "bottom," "below," "above," "under," and the like, as used in this specification and any appended claims (if any), are dependent upon the particular orientation of the device as described and illustrated. The subject matter described herein may assume various alternative orientations. Thus, these directional terms are not precisely defined and should not be narrowly interpreted.

[0205] For example, while processes or blocks are shown in a certain order, alternative examples may perform routine procedures or employ systems having blocks in a different order, and some processes or blocks may be removed, moved, added, subdivided, combined, and / or modified to provide alternative or subcombinations. Each of these processes or blocks may be performed in a variety of different ways. Also, while processes or blocks may be shown as being performed sequentially, these processes or blocks may instead be performed in parallel or at different times.

[0206] Moreover, while elements may be shown as being performed sequentially, they may instead be performed simultaneously or in different orders. It is therefore intended that the following claims be interpreted to include all such variations that are within their intended scope.

[0207] When a component (e.g., a pump, reactor, assembly, device, etc.) is referred to above, unless otherwise indicated, a reference to that component (including a reference to "means") should be interpreted as including any component that performs the function of the described component (i.e., is functionally equivalent) as an equivalent of that component, including components that are not structurally equivalent to the disclosed structures that perform the function in the illustrated exemplary embodiments of the invention.

[0208] Specific examples of systems, methods, and devices have been described herein for illustrative purposes. These are merely examples. The techniques provided herein may be applied to systems other than the exemplary systems described above. Many changes, modifications, additions, omissions, and permutations are possible within the scope of the practice of the invention. The invention includes variations of the described embodiments that would be apparent to one of ordinary skill in the art, including variations obtained by replacing features, elements, and / or operations with equivalent features, elements, and / or operations, mixing and matching features, elements, and / or operations from other embodiments, combining features, elements, and / or operations from the embodiments described herein with features, elements, and / or operations of other technologies, and / or omitting to combine features, elements, and / or operations from the described embodiments.

[0209] Various features are described herein as being present in "some embodiments." Such features are not required and may not be present in all embodiments. An embodiment of the invention may include zero, any one, or any combination of two or more of such features. All possible combinations of such features are contemplated by this disclosure, even if such features are shown in different drawings and / or described in different chapters or paragraphs. This is limited only to the extent that some of such features are incompatible with other of such features in the sense that it is not possible for a person of ordinary skill in the art to construct a working embodiment combining such incompatible features. Thus, a description that "some embodiments" have feature A and "some embodiments" have feature B should be interpreted as an explicit indication that the inventors also contemplate an embodiment combining feature A and feature B (unless the description states otherwise or feature A and feature B are essentially incompatible).

[0210] Accordingly, it is intended that the following appended claims and the claims introduced below be construed to include all such modifications, permutations, additions, omissions, and subcombinations that can reasonably be inferred. The claims should not be limited by the preferred embodiments set forth in the examples, but rather should be accorded the broadest interpretation consistent with the specification as a whole.

Claims

1. 1. A method for thermally cracking hydrocarbons to produce hydrogen gas, comprising: Providing a melting medium in a reactor; mixing the hydrocarbon with the melting medium such that the combined hydrocarbon and melting medium passes through the reactor; maintaining a temperature of the melting medium within at least a portion of the reactor at an operating temperature sufficient to thermally crack the hydrocarbons in the mixed melting medium and hydrocarbons to produce carbon and hydrogen gas while at least the mixed hydrocarbons and the melting medium pass through the reactor; separating the carbon and hydrogen gas from the melting medium that has passed through the reactor; adding or removing the molten medium from the reactor so as to maintain a surface level of the molten medium within the reactor at a desired level; A method comprising:

2. placing the molten medium in the reactor in fluid communication with an outlet weir having an uppermost portion at the desired level and flowing the molten medium from the reactor over the outlet weir into a holding tank; pumping the melting medium from the holding tank back into the reactor; performing the pumping substantially continuously while the reactor is operating, or suspending the pumping for at least a period of time when the reactor is operating at steady state conditions; flowing the molten medium through a trap before flowing the molten medium over the outflow weir; The method of claim 1, wherein the trap is a U-trap.

3. 3. The method of claim 2, comprising raising the level of the molten medium in the holding tank above the overflow weir so that the molten medium flows from the holding tank over the overflow weir and back into the reactor.

4. the holding tank includes a first arm and a second arm; 3. The method of claim 2, wherein raising the level of the molten medium in the holding tank above the outflow weir comprises creating a pressure differential within a headspace of the first arm and second arm.

5. collecting the carbon and process gas in the headspace of the reactor; floating the carbon on the surface of the molten medium in the headspace of the reactor; 3. The method of claim 1 or 2, comprising maintaining turbulent flow of the mixed molten medium and the hydrocarbon within the reactor.

6. mixing the hydrocarbon into the molten medium includes introducing bubbles of the hydrocarbon into the molten medium; 3. The method of claim 1 or 2, wherein the bubbles have a diameter at least 25 times smaller in area than the cross-sectional area of ​​the path through the reactor through which the combined melt medium and hydrocarbon flow within the reactor.

7. 3. The method of claim 1 or 2, wherein the reactor comprises a plurality of conduits, and the method comprises flowing a portion of the combined melting medium and hydrocarbons through each of the conduits.

8. 3. The method of claim 1 or 2, wherein the melting medium contains a molten metal and / or a salt.

9. 9. The method of claim 8, wherein the melting medium contains a catalyst that catalyzes the thermal cracking of the hydrocarbons.

10. 3. The method of claim 1 or 2, wherein the hydrocarbon comprises methane or natural gas.

11. 3. The method of claim 1 or 2, wherein separating carbon and hydrogen gas from the melting medium passed through the reactor comprises floating the carbon at an interface between the melting medium and another fluid and collecting the floating carbon.

12. 3. The method of claim 1 or 2, comprising raising the hydrogen gas into a header above the molten media and collecting the hydrogen gas from the header.

13. 3. The method of claim 1 or 2, comprising purifying the hydrogen gas.

14. 1. A system for thermally cracking hydrocarbons to produce hydrogen gas, comprising: a reactor containing a melting medium; a heater operable to heat the melting medium to an operating temperature sufficient to thermally crack the hydrocarbons; a gas fluid contactor operable to mix the hydrocarbon with the melting medium; and a level control means for adding or removing said molten medium from said reactor so as to maintain the surface level of said molten medium within said reactor at a desired level; Including, the system.

15. the level control means includes an outlet weir having an uppermost portion at the desired level, and a holding tank connected to receive melting medium from the reactor that has flowed over the outlet weir; a pump positioned to pump the melting medium from the holding tank back into the reactor; a controller configured to control the pump to operate substantially continuously while the reactor is operating or to discontinue operation of the pump for at least a period of time when the reactor is operating at steady state conditions; a trap disposed between the reactor and the outflow weir; The system of claim 14, wherein the trap is a U-trap.

16. 16. The system of claim 15, wherein the level control means includes means for raising the level of the molten medium in the holding tank above the outflow weir so that the molten medium flows from the holding tank back into the reactor.

17. 16. The system of claim 15, wherein the holding tank includes a first arm and a second arm, and the means for increasing the level of the melting medium in the holding tank includes means for creating a pressure differential within a headspace of the first arm and the second arm.

18. the reactor headspace collects carbon; the reactor is connected to a process loop that includes the reactor and a pump connected to circulate the melting medium through the process loop; 16. The system of claim 14 or 15, wherein the pump is controlled to pump the molten medium through the reactor at a rate such that the flow of the mixed molten medium and the hydrocarbons in the reactor is turbulent.

19. the gas fluid contactor comprises a flow divider, the reactor comprises a plurality of paths, the flow divider configured to divide the hydrocarbons among the plurality of paths; 16. The system of claim 14 or 15, wherein the gas fluid contactor comprises a bubble generator.

20. 1. A method for thermally cracking hydrocarbons to produce hydrogen gas, comprising: heating a melting medium to an operating temperature sufficient to thermally crack the hydrocarbon; mixing the hydrocarbon into the heated melting medium; pumping the combined melting medium and hydrocarbons through a reactor in a turbulent flow so as to thermally crack the hydrocarbons to produce carbon and hydrogen gas; separating the carbon and hydrogen gas from the melting medium that has passed through the reactor; and

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