Hydrogen production from hydrocarbons by plasma pyrolysis

Abstract

A method for producing hydrogen and carbon powder from the plasma pyrolysis of hydrocarbons is disclosed and includes a DC n on-transferred electric arc plasma torch, a hot-wall reactor, for example lined with refractory or a graphite (slippery material), and a cyclone. The cyclone is adapted to recover heavier carbon particles and allow part of the hydrogen, unconverted hydrocarbon and lighter carbon particles to be recycled to the reactor to improve the overall yield of hydrogen. The prolonged contact with the plasma plume provides a typically complete conversion to hydrogen and carbon powder due to the hot walls of the reactor. The carbon powder leaving the plasma plume solidifies into a graphite- like powder in the reactor. A turbulence inside the reactor is adapted to prevent the buildup of soot on a reactor surface via the recycling of hydrogen, hydrocarbon gas or carbon powder or a mix of thereof to the reactor.

Description

TITLE

[0001] HYDROGEN PRODUCTION FROM HYDROCARBONS BY PLASMA PYROLYSISCROSS REFERENCE TO RELATED APPLICATIONS

[0002] This Application claims priority on U.S. Provisional Application No. 63 / 107,555, now pending, filed on October 30, 2020, which is herein incorporated by reference.FIELD

[0003] The present subject matter relates to a process for producing hydrogen from methane and other light hydrocarbons using thermal plasma without generating greenhouse gases.BACKGROUND

[0004] The combustion of hydrocarbons, namely for heating, in industrial processes and for transportation generates large amounts of greenhouse gases (GHG), namely carbon dioxide. The accumulation of GHG in the atmosphere creates global warming which endangers the planet and the very existence of the human race. Under the Paris Agreement of 2015, 191 countries have committed to limit global warming to a temperature of 1 .5 °C. Some jurisdictions, namely the European Union, have committed to be carbon neutral by 2050.

[0005] The combustion of hydrogen, namely for heating, in industrial processes and for transportation, generates only water vapor as combustion product, instead of carbon dioxide, limiting global warming. For this reason, many industrial processes are looking to replace fossil fuels and reactants such as coal, oil, and natural gas by hydrogen. It is expected that the demand for low-carbon hydrogen will increase from the current world production rate of 0.46 Mt / y (in 2020) to the target of 7.92 Mt / y in 2030 [1],

[0006] Today, 68% of hydrogen is produced by a process called steam- methane reforming (SMR) and 27% via coal gasification [2]. Low-carbon hydrogen accounts only for 5 % of the global production and is mainly produced by water electrolysis [3]. In the SMR process, methane is reacted with water vapor to produce hydrogen and carbon dioxide, a greenhouse gas. The basic chemical reaction used in steam-methane reforming (SMR) is :

[0007] CH4 + 2 H2O = 4 H2+ CO2

[0008] Therefore, for each mole of hydrogen produced, 0.25 mole of carbon dioxide is produced by the chemical reaction. However, because the molecular weight of hydrogen is only 2 g / mol and the molecular weight of CO2is 44 g / mol, each kg of H2produced will generate 5.5 kg of CO2. Moreover, the SMR process is carried out at high temperature (700-1000 °C) and high pressure (3-25 bar) [4], thereby requiring additional natural gas or oil for heating the reactants. The ratio of the combustion heat from the produced hydrogen to the heat required for the process is 68% [5], This indicates additional GHG emissions of 6 kg of CO2per kg of H2. The total GHG cost for the SMR process is therefore 11.5 kg CO2per kg H2.

[0009] There is thus a high interest in technologies that use clean renewable electricity such as that produced by hydraulic, wind, or solar energy sources to produce hydrogen. The only commercially available process to produce clean hydrogen is water electrolysis. In this process, electrical energy is used to convert water to hydrogen and oxygen. However, water electrolysis process suffers from several drawbacks, including high energy use and the use of a high quantity of exotic materials, which is not sustainable [6], The energy cost alone is substantial because the theoretical energy requirement toelectrolyze water is 40 kWh / kg H2. In practice, the energy consumption is at least 48 kWh / kg H2[7] due to inefficiencies and to the non-ideality of all processes.

[0010] Moreover, there would be an advantage of converting methane, a GHG with a high greenhouse warming potential (GWP), 30 times that of CO2, into innocuous hydrogen. This would limit the manipulation of methane and thus the risk of methane leaks and incomplete combustion. Methane in the atmosphere has doubled over the last 100 years reaching an all-high concentration of 1900 ppb in 2020 [8], contributing to global warming.

[0011] There would therefore be an advantage to have a process that converts methane, a GHG with a high GWP, to hydrogen at a reasonable cost, with efficient energy use and that could be easily scaled-up to industrial scale. It would also be useful to be able to sequester the carbon present in the methane such that it does not escape to the atmosphere in the form of CO2.

[0012] For this purpose, methane pyrolysis can be used to convert methane to hydrogen and carbon through the following reaction:

[0013] CH4+ heat = C + 2 H2

[0014] Several such methods have been developed. However, these methods emphasize on the production of high quality carbon black [9, 10 and 11]. Most of these methods are batch and intend to produce carbon black with specific properties that vary from one batch to another. These methods require a reactor temperature much higher than that required for methane pyrolysis to ensure that carbon black properties, such as specific surface area and hydrophobicity, are met. Thus, these methods have a low heat efficiency and consequently a higher greenhouse emission if the heat source is not electricity.

[0015] Some methods do emphasize on the production of hydrogen at low temperature, but these methods imply the use of costly catalysts such asplatinum-coated alumina

[0012] , These methods do not use the energy intensity that plasma provides.

[0016] Some methods use plasma to decompose methane, but these methods are plagued by the deposition of carbon on the surface of the reactor causing stoppage of the process. Furthermore, these methods are plagued by the requirement to use an inert gas (argon or helium) as the plasma-forming gas. The inert gas dilutes the hydrogen product, must be separated, and adds to the operating cost.

[0017] The present review of the background of the present subject matter states that the available methods to produce hydrogen by pyrolysis of hydrocarbons suffer from various drawbacks, the most important of them being the high energy cost.

[0018] It would therefore be desirable to provide a new method for producing hydrogen with an energy-effective and reliable plasma process. It is desirable to have a pyrolysis process that is energy efficient and that sustains continuous operation, notably by avoiding the accumulation of soot in the reactor. The process should also minimize GHG emissions, and the process should allow the use of hydrocarbons in addition to methane as feedstock and avoid the use of expensive plasma forming gases such as argon and helium.SUMMARY

[0019] It would thus be desirable to provide a novel method for producing hydrogen.

[0020] The embodiments described herein provide in one aspect a method for producing hydrogen and carbon powder from the plasma pyrolysis of hydrocarbons, comprising providing a DC non -transferred electric arc plasma torch, a hot-wall reactor, for example lined with refractory or graphite, and a cyclone.

[0021] For instance, turbulence inside the reactor is adapted to prevent the buildup of soot on a reactor surface via the recycling of hydrogen, hydrocarbon gas or carbon powder or a mix of thereof to the reactor.

[0022] For instance, a hot wall of the reactor is made of a substantially slippery material, such as graphite, such as to prevent accumulation of carbon material on the hot wall.

[0023] For instance, a prolonged contact with a plasma plume is adapted to provide a typically complete conversion to hydrogen and carbon powder.

[0024] For instance, a carbon powder leaving a plasma plume solidifies into a graphite-like powder in the reactor.

[0025] For instance, the cyclone is adapted to recover heavier carbon particles and allow part of the hydrogen, unconverted hydrocarbon and lighter carbon particles to be recycled to the reactor to improve the overall yield of hydrogen.

[0026] For instance, hydrogen and fine carbon leaving the cyclone contains enough thermal energy to be efficiently recovered using a waste heat recovery exchanger.

[0027] For instance, the hot-wall reactor comprises two distinct reaction zones, namely a high temperature zone and a lower temperature zone.

[0028] For instance, the hydrocarbon is a pure hydrocarbon, such as methane, or a mix of hydrocarbons and impurities such as natural gas.

[0029] For instance, the hydrocarbon is a subproduct from wood pyrolysis.

[0030] For instance, the method is used in battery application as electrode material, for instance to enhance performance and stability of lithium-ion batteries.

[0031] For instance, the hydrocarbon to be pyrolyzed is injected at the end tip of the plasma torch.

[0032] The embodiments described herein provide in another aspect a method to produce hydrogen and graphite-like powder that is much less energy intensive than other available methods.

[0033] The embodiments described herein provide in another aspect a method to produce hydrogen with a low carbon footprint.

[0034] The embodiments described herein provide in another aspect a method for producing hydrogen by plasma pyrolysis, wherein the hydrocarbon is a pure hydrocarbon, such as methane, or from a mix of hydrocarbons and impurities such as natural gas.

[0035] The embodiments described herein provide in another aspect a method for producing hydrogen by plasma pyrolysis, wherein the hydrocarbon is a subproduct from wood pyrolysis.

[0036] The embodiments described herein provide in another aspect a method to produce carbon-based powders from hydrocarbon by use of plasma pyrolysis for use in battery application as electrode material for instance to enhance performance and stability of lithium-ion batteries.

[0037] The embodiments described herein provide in another aspect an apparatus for producing hydrogen from hydrocarbons, comprising a plasma torch and a pyrolysis reactor, wherein the reactor is adapted to allow a plasma plume to be in close, and typically continuous, contact with the hydrocarbon reagent.

[0038] For instance, the plasma torch is located on top of the pyrolysis reactor.

[0039] For instance, a hydrocarbon is provided to the pyroiysis reactor via the plasma torch.

[0040] For instance, the hydrocarbon is also provided to the pyrolysis reactor via a distribution annulus.

[0041] For instance, the hydrocarbon is also provided to the pyrolysis reactor via at least one recycled stream.

[0042] For instance, the plasma torch includes a DC non-transferred electric arc plasma torch.

[0043] For instance, the pyrolysis reactor includes a cylindrical vertical pyrolysis reactor.

[0044] For instance, hot walls of the pyrolysis reactor are made of a non- slippery material inside a steel shell and are, for instance, water-cooled outside the steel shell.

[0045] For instance, a cyclone is located downstream, typically below, the pyrolysis reactor and is adapted to collect most of the carbon powder and to separate heavier carbon in the cyclone and to recycle part of fine carbon along with reactor off gas to the pyrolysis reactor or within the plasma torch.

[0046] For instance, a waste heat recovery unit (WHR) is provided for cooling down the hydrogen leaving the cyclone.

[0047] For instance, a gas cooler is provided downstream of the waste heat recovery unit and is adapted to further cool down the hydrogen leaving the waste heat recovery unit.

[0048] For instance, a baghouse is located downstream of the gas cooler for collecting remaining carbon powder and ensure a substantially particle-free hydrogen product.

[0049] For instance, at least one polishing filter is provided to remove trace amounts of residual carbon and volatiles, such as acetylene.

[0050] For instance, at least one polishing filter is provided downstream of the baghouse to remove trace amounts of residual carbon and volatiles, such as acetylene.

[0051] For instance, filters and gas cleaning units are provided for instance if contaminants such as H2S are present in the H2product.

[0052] For instance, a compression unit is provided to raise a hydrogen pressure to a pressure suitable for a pressure-swing adsorption unit, located downstream of the compression unit.

[0053] For instance, a compression unit is provided downstream of the baghouse to raise a hydrogen pressure to a pressure suitable for a pressureswing adsorption unit, located downstream of the compression unit.

[0054] For instance, the pressure-swing adsorption unit is adapted to capture unconverted hydrocarbons, the unconverted hydrocarbons being recycled back to the pyrolysis reactor via a stream.

[0055] For instance, the only fluid flowing through the apparatus is the hydrocarbon to be pyrolyzed.

[0056] For instance, wherein the hydrocarbon to be pyrolyzed is injected at an end tip of the plasma torch.

[0057] For instance, an electric energy input is adapted to directly control a hydrogen production rate from the plasma pyrolysis of hydrocarbons.

[0058] The embodiments described herein provide in another aspect an apparatus such as a plasma torch to produce hydrogen by plasma in which the only fluid flowing through the apparatus is the hydrocarbon to be pyrolyzed.

[0059] The embodiments described herein provide in another aspect an apparatus such as a plasma torch in which the hydrocarbon to be pyrolyzed can be injected at the end tip of the apparatus.

[0060] The embodiments described herein provide in another aspect an apparatus such as a plasma torch in which the plasma reaction does not require a carrier gas or a sheath gas.

[0061] The embodiments described herein provide in another aspect an apparatus such as a plasma torch by which the electric energy input directly controls the hydrogen production rate from the plasma pyrolysis of hydrocarbons.BRIEF DESCRIPTION OF THE DRAWINGS

[0062] For a better understanding of the embodiments described herein and to show more clearly how they may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, which show at least one exemplary embodiment, and in which:

[0063] The sole Figure is a schematic illustration of a method for producing hydrogen in accordance with an exemplary embodiment.DESCRIPTION OF VARIOUS EMBODIMENTS

[0064] The present subject matter consists in the following assembly of technologies and techniques.

[0065] A plasma torch 1 is provided, which medium is a hydrocarbon. The purpose of the plasma torch 1 is to use electricity to efficiently decompose hydrocarbon to carbon and hydrogen.

[0066] Also provided is a cylindrical vertical pyrolysis reactor 2 with the plasma torch 1 located on top thereof. Hot walls of the reactor 2 are constitutedof a non-slippery material inside a steel shell and may be water cooled outside the steel shell. The reactor 2 allows the plasma plume 1a to be in close and continuous contact with the hydrocarbon reagent. The hydrocarbon is provided via the plasma torch 1 , a distribution annulus 10 and side entries 11 on the reactor walls that allow to recycle streams 12 and 13 to the reactor 2.

[0067] A cyclone 3 located below the pyrolysis reactor 2 collects most of the carbon powder. The purpose of the cyclone 3 is to separate the heavier carbon in the cyclone and to recycle part of the fine carbon along with reactor off gas (stream 12) at an inlet of the reactor 2 or within the torch 1 .

[0068] The carbon-based powder produced can have several applications, for example as carbon black, used in battery application as electrode material for instance to enhance performance and stability of lithium-ion batteries, as a carbon rich soil amendment.

[0069] A waste heat recovery unit (WHR) 4 is provided for cooling down the hydrogen leaving the cyclone 3. The WHR unit 4 improves the overall energy efficiency of the method and the recovered energy could be reused within the method or elsewhere. For instance, the recovered heat could be used to heat buildings on site with hot water or steam generated in the WHR unit 4 or to generate electricity via a steam turbine within the WHR unit 4.

[0070] A gas cooler 5, downstream of the waste heat recovery unit 4, is adapted to further cool down the hydrogen leaving the waste heat recovery unit 4. The gas cooler 5 is provided to bring the hydrogen to a temperature close to room temperature for operating baghouse 6.

[0071] A baghouse 6, located downstream of the gas cooler 5, collects the remaining carbon powder and ensures a particle-free hydrogen product.

[0072] A series of polishing filters 7 are provided to remove the trace amounts of residual carbon and volatiles, such as acetylene. Other filters andgas cleaning units may be added to the method if contaminants such as H2S are present in the H2product.

[0073] A compression unit 8 is provided to raise the hydrogen pressure to a pressure suitable for a pressure-swing adsorption unit 9, located downstream of the compression unit 8, and suitable for pipeline distribution.

[0074] The pressure-swing adsorption unit 9 is adapted to capture the unconverted hydrocarbons. The unconverted hydrocarbons are recycled back to the pyrolysis reactor 2 via stream 13, whereas hydrogen is recuperated from the adsorption unit 9. This recycling of material improves the conversion efficiency of the method.

[0075] While the above description provides examples of the embodiments, it will be appreciated that some features and / or functions of the described embodiments are susceptible to modification without departing from the spirit and principles of operation of the described embodiments. Accordingly, what has been described above has been intended to be illustrative of the embodiments and non-limiting, and it will be understood by persons skilled in the art that other variants and modifications may be made without departing from the scope of the embodiments as defined in the claims appended hereto.REFERENCES:[1] IEA, “Hydrogen”, IEA, Paris, 2020.[2] Research and Markets, “Hydrogen Generation Market Size, Share & Trends Analysis Report by Application (Coal Gasification, Steam Methane”, Research and Markets, Dublin, 2020.[3] IEA Bioenergy, “Hydrogen from biomass gasification”, International Energy Agency (IEA), Paris, 2018.[4] Office of Energy Efficiency & Renewable Energy, “Hydrogen Production: Natural Gas Reforming”, Department of Energy (DOE), Washington, 2020.[5] J. Jechura, “Hydrogen from Natural Gas via Steam Methane Reforming (SMR)”, Colorado School of Mines, Golden, 2015.[6] K. Scott, “Introduction to Electrolysis, Electrolysers and Hydrogen Production”, Electrochemical Methods for Hydrogen Production, Cambridge, Royal Society of Chemistry, 2019, pp. 1-27.[7] Thyssenkrupp, “Water electrolysis: Power to gas”, 2020. Available on line: https: / / www.thyssenkrupp.com / en / cornpany / innovation / technologies-for-the- energy-transition / water-electrolysis.html.[8] The 2° Institute, “Methane Levels: Current & Historic Atmospheric CH4", 2020. Available on line: https: / / www.methanelevels.org.[9] Alexander F. Hoermman et al., “Plasma Gas Throat Assembly and Method”, United States Patent No. US 10,138,378 B2, November 27, 2018.

[0010] Peter. L. Johnson et al., “Plasma Reactor”, United States Patent No. 9,574,086 B2, February 21 , 2017.

[0011] Serguei Nester et al., “Method for Carbon Black Production Using Preheated Feedstock and Apparatus for Same”, United States Patent No. US 8,871 ,173 B2, October 28, 2014.

[0012] Suguru Noda et al., “Device for Simultaneously Producing Carbon Nanotubes and Hydrogen”, United States Patent No. US 10,633,249 B2, April 28, 2020

Claims

CLAIMS:1 . A method for producing hydrogen and carbon powder from the plasma pyrolysis of hydrocarbons, comprising providing a DC non-transferred electric arc plasma torch, a hot-wall reactor, for example lined with refractory or graphite, and a cyclone.

2. The method as defined in Claim 1 , wherein turbulence inside the reactor is adapted to prevent the buildup of soot on a reactor surface via the recycling of hydrogen, hydrocarbon gas or carbon powder or a mix of thereof to the reactor.

3. The method as defined in Claim 1, wherein a hot wall of the reactor is made of a substantially slippery material, such as graphite, such as to prevent accumulation of carbon material on the hot wall.

4. The method as defined in Claim 1 , wherein a prolonged contact with a plasma plume is adapted to provide a typically complete conversion to hydrogen and carbon powder.

5. The method as defined in Claim 1 , wherein a carbon powder leaving a plasma plume solidifies into a graphite-like powder in the reactor.

6. The method as defined in Claim 1 , wherein the cyclone is adapted to recover heavier carbon particles and allow part of the hydrogen, unconverted hydrocarbon and lighter carbon particles to be recycled to the reactor to improve the overall yield of hydrogen.

7. The method as defined in Claim 1 , wherein hydrogen and fine carbon leaving the cyclone contains enough thermal energy to be efficiently recovered using a waste heat recovery exchanger.

8. The method as defined in Claim 1 , wherein the hot-wall reactor comprises two distinct reaction zones, namely a high temperature zone and a lower temperature zone.

9. The method as defined in Claim 1 , wherein the hydrocarbon is a pure hydrocarbon, such as methane, or a mix of hydrocarbons and impurities such as natural gas.

10. The method as defined in Claim 1 , wherein the hydrocarbon is a subproduct from wood pyrolysis.

11. The method as defined in Claim 1 , for use in battery application as electrode material, for instance to enhance performance and stability of lithium- ion batteries.

12. The method as defined in Claim 1 , wherein the hydrocarbon to be pyrolyzed is injected at the end tip of the plasma torch.

13. A method to produce hydrogen and graphite-like powder that is much less energy intensive than other available methods.

14. A method to produce hydrogen with a low carbon footprint.

15. A method for producing hydrogen by plasma pyrolysis, wherein the hydrocarbon is a pure hydrocarbon, such as methane, or from a mix of hydrocarbons and impurities such as natural gas.

16. A method for producing hydrogen by plasma pyrolysis, wherein the hydrocarbon is a subproduct from wood pyrolysis.

17. A method to produce carbon-based powders from hydrocarbon by use of plasma pyrolysis for use in battery application as electrode material for instance to enhance performance and stability of lithium-ion batteries.

18. An apparatus for producing hydrogen from hydrocarbons, comprising a plasma torch and a pyrolysis reactor, wherein the reactor is adapted to allow a plasma plume to be in close, and typically continuous, contact with the hydrocarbon reagent.

19. The apparatus as defined in Claim 18, wherein the plasma torch is located on top of the pyrolysis reactor.

20. The apparatus as defined in any one of Claims 18 to 19, wherein a hydrocarbon is provided to the pyrolysis reactor via the plasma torch.

21. The apparatus as defined in Claim 20, wherein the hydrocarbon is also provided to the pyrolysis reactor via a distribution annulus.

22. The apparatus as defined in any one of Claims 20 to 21 , wherein the hydrocarbon is also provided to the pyrolysis reactor via at least one recycled stream.

23. The apparatus as defined in any one of Claims 18 to 22, wherein the plasma torch includes a DC non-transferred electric arc plasma torch.

24. The apparatus as defined in any one of Claims 18 to 23, wherein the pyrolysis reactor includes a cylindrical vertical pyrolysis reactor.

25. The apparatus as defined in any one of Claims 18 to 24, wherein hot walls of the pyrolysis reactor are made of a non-slippery material inside a steel shell and are, for instance, water-cooled outside the steel shell.

26. The apparatus as defined in any one of Claims 18 to 25, wherein a cyclone is located downstream, typically below, the pyrolysis reactor and is adapted to collect most of the carbon powder and to separate heavier carbon in the cyclone and to recycle part of fine carbon along with reactor off gas to the pyrolysis reactor or within the plasma torch.

27. The apparatus as defined in Claim 26, wherein a waste heat recovery unit (WHR) is provided for cooling down the hydrogen leaving the cyclone.

28. The apparatus as defined in Claim 27, wherein a gas cooler is provided downstream of the waste heat recovery unit and is adapted to further cool down the hydrogen leaving the waste heat recovery unit.

29. The apparatus as defined in Claim 28, wherein a baghouse is located downstream of the gas cooler for collecting remaining carbon powder and ensure a substantially particle-free hydrogen product.

30. The apparatus as defined in any one of Claims 18 to 29, wherein at least one polishing filter is provided to remove trace amounts of residual carbon and volatiles, such as acetylene.

31. The apparatus as defined in Claim 29, wherein at least one polishing filter is provided downstream of the baghouse to remove trace amounts of residual carbon and volatiles, such as acetylene.

32. The apparatus as defined in any one of Claims 18 to 31 , wherein filters and gas cleaning units are provided for instance if contaminants such as H2S are present in the H2product.

33. The apparatus as defined in any one of Claims 18 to 32, wherein a compression unit is provided to raise a hydrogen pressure to a pressure suitable for a pressure-swing adsorption unit, located downstream of the compression unit.

34. The apparatus as defined in Claim 29, wherein a compression unit is provided downstream of the baghouse to raise a hydrogen pressure to a pressure suitable for a pressure-swing adsorption unit, located downstream of the compression unit.

35. The apparatus as defined in any one of Claims 33 to 34, wherein the pressure-swing adsorption unit is adapted to capture unconverted hydrocarbons, the unconverted hydrocarbons being recycled back to the pyrolysis reactor via a stream.

36. The apparatus as defined in any one of Claims 18 to 35, wherein the only fluid flowing through the apparatus is the hydrocarbon to be pyrolyzed.

37. The apparatus as defined in any one of Claims 18 to 36, wherein the hydrocarbon to be pyrolyzed is injected at an end tip of the plasma torch.

38. The apparatus as defined in any one of Claims 18 to 37, wherein an electric energy input is adapted to directly control a hydrogen production rate from the plasma pyrolysis of hydrocarbons.

39. An apparatus such as a plasma torch to produce hydrogen by plasma in which the only fluid flowing through the apparatus is the hydrocarbon to be pyrolyzed.

40. An apparatus such as a plasma torch in which the hydrocarbon to be pyrolyzed can be injected at the end tip of the apparatus.

41. An apparatus such as a plasma torch in which the plasma reaction does not require a carrier gas or a sheath gas.

42. An apparatus such as a plasma torch by which the electric energy input directly controls the hydrogen production rate from the plasma pyrolysis of hydrocarbons.- 19 -

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