Process for catalytically pyrolyzing methane-containing streams - Patent Application 20070122997
The method uses bubble breakers to manage gas bubbles in catalytic pyrolysis, preventing catalyst loss and maintaining a uniform flow field, thereby improving the efficiency of methane pyrolysis.
Patent Information
- Application Number
- JP2025535126
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-01-23
- Filing Date
- 2023-12-13
- Publication Date
- 2025-12-18
AI Technical Summary
Gas bubbles in catalytic pyrolysis of methane-containing streams grow and entrain catalyst particles, leading to catalyst loss and clogging, and larger bubbles disrupt the flow field and solid carbon product layer in the reactor.
A method involving a gaseous methane-containing stream fed into a reaction zone with molten salt and catalyst particles, using first and second bubble breakers to break larger bubbles, allowing upward movement of molten salt, solid carbon, and gaseous hydrogen while retaining catalyst particles, and employing an inverted funnel for separation.
Prevents catalyst loss and clogging, maintains a uniform flow field, and minimizes disturbance of the solid carbon layer, enhancing the pyrolysis process efficiency.
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Figure 2025541382000001_ABST
Abstract
Description
[Technical Field]
[0001] The present invention relates to a process for catalytically pyrolyzing a methane-containing stream. [Background technology]
[0002] Methods for catalytically cracking methane-containing streams are known in the art.
[0003] Examples of known processes for catalytically pyrolyzing methane-containing streams are disclosed, for example, in WO 22035963(A2) and WO 2022058355(A1) (also published as Canadian Patent Application Publication No. 3194814(A1)).
[0004] A problem with known methods is that gas bubbles (either formed during catalytic pyrolysis or present in the methane-containing stream undergoing catalytic pyrolysis) tend to grow as they move upward (gas bubble coalescence) and entrain catalyst particles in areas where they are not desired, which can lead, for example, to catalyst loss and clogging of downstream filtration media, or the like.
[0005] A further problem with known processes is that larger bubbles (especially if they are greater than 10 mm in diameter) can create a non-uniform flow field and disrupt any solid carbon product layer that is forming in the upper region (separation zone) of the reactor. Summary of the Invention
[0006] It is an object of the present invention to overcome, minimize or at least reduce one or more of the above problems.
[0007] It is a further object of the present invention to provide an alternative method for catalytically pyrolyzing methane-containing streams, particularly in the presence of molten salts.
[0008] One or more of the above or other objects are achieved, according to the present invention, by a method for catalytically pyrolyzing a methane-containing stream, comprising at least (a) providing a gaseous methane-containing stream; (b) feeding the gaseous methane-containing stream provided in step (a) in the form of bubbles into a reaction zone containing molten salt and catalyst particles, the catalyst particles being suspended in the molten salt; (c) subjecting the methane-containing stream to catalytic pyrolysis in a reaction zone, thereby obtaining solid carbon and gaseous hydrogen; (d) allowing the molten salt, solid carbon, and gaseous hydrogen to migrate upward from the reaction zone to the intermediate zone while the catalyst particles are retained within the reaction zone; (e) optionally allowing a first portion of the molten salt to flow from the intermediate zone to the reaction zone or from an upper portion of the reaction zone to a lower portion of the reaction zone via a return loop; (f) allowing the second portion of the solid carbon, gaseous hydrogen, and molten salt to travel further upward from the intermediate zone to the separation zone; (g) removing solid carbon and gaseous hydrogen from the separation zone by gas entrainment using an inverted funnel; When the molten salt, solid carbon, and gaseous hydrogen are moving upward from the reaction zone to the intermediate zone in step (d), gas bubbles are broken by a first bubble breaker having an opening area of more than 90%; This can be achieved by a method in which, as the molten salt, solid carbon, and gaseous hydrogen move upward from the intermediate zone to the separation zone in step (f), the gas bubbles are broken by a second bubble breaker.
[0009] Surprisingly, according to the present invention, by using a first bubble breaker, it is possible in a surprisingly simple manner to arrange for the upward movement of molten salt, solid carbon, and gaseous hydrogen from the reaction zone to the intermediate zone while the catalyst particles are retained in the reaction zone, which avoids, for example, loss of catalyst and clogging of downstream equipment, such as filters and the like, by the catalyst particles.
[0010] A further advantage of the method according to the invention is that, since the larger bubbles (preferably having a size of at least 10 mm in diameter) are broken by the first bubble breaker into smaller bubbles (preferably having a size of at most 6 mm), the flow field in the separation zone is much more uniform, avoiding disturbance of the carbon product layer that is formed in the separation zone.
[0011] A further advantage is that the second bubble breakers provide for the destruction of larger (preferably at least 10 mm in diameter) bubbles as the molten salt, solid carbon, and gaseous hydrogen travel upward from the intermediate zone to the separation zone in step (f). These second bubble breakers can help minimize disturbance of the solid carbon layer and backmixing of the solid carbon with the molten salt in the intermediate zone.
[0012] In this respect, it is acknowledged that bubble breakers are known per se in the art (see, for example, the article by AHGadallah et al. in Chemical Engineering Sciences 131 (2015) 22-40), but such bubble breakers have not been proposed for use in the catalytic pyrolysis of methane-containing streams in the presence of molten salt, let alone as first and second bubble breakers in the specific setting of the method according to the invention.
[0013] In step (a) of the method according to the invention, a gaseous methane-containing stream is provided.
[0014] The gaseous methane-containing stream provided in step (a) is not particularly limited and is typically natural gas or other methane-containing process gas, but preferably contains at least 70% by volume methane, preferably at least 90% by volume methane. Some other light (C2-C5) hydrocarbons and hydrogen may also be present. When hydrogen is present, it is preferably present in an amount of up to 15.0% by volume.
[0015] In step (b) of the process according to the invention, the gaseous methane-containing stream provided in step (a) is fed in the form of gas bubbles into a reaction zone containing molten salt and catalyst particles, the catalyst particles being suspended in the molten salt.
[0016] Typically, the gaseous methane-containing stream is fed to or near the bottom of the reaction zone using a gas distributor such as a sparger or the like to distribute the methane-containing stream evenly across the cross-section of the reaction zone. Typically, the reaction zone is located in the bottom portion of the vessel.
[0017] Preferably, the gaseous methane-containing stream has a methane content of 0.7 kg / m 2 / min~20.0kg / m 2 / min, preferably 1.4 kg / m 2 / min~5.0kg / m 2 / min flux.
[0018] Those skilled in the art will readily understand that the molten salt is not particularly limited and can be selected from a wide variety of molten salts, such as NaCl, KCl, CaCl, MgCl, NaNO, KNO, Ca(NO), Mg(NO), or mixtures of these salts. Preferably, the molten salt is selected from the group consisting of NaCl, KCl, CaCl, NaNO, KNO, and Ca(NO), more preferably NaCl or KCl. It is particularly preferred that the molten salt has a melting point or melting point range of 500 to 800°C.
[0019] Suitably, the molten salt has a density (at least slightly) lower than the density of the catalyst particles. Preferably, the molten salt has a density of 1000 kg / m 3 ~3000kg / m 3 , preferably 1200 kg / m 3 ~2000kg / m 3 It has a density of
[0020] Those skilled in the art will also readily appreciate that the catalyst particles are not particularly limited.
[0021] Preferably, the catalyst particles are selected from SiC, SiO2, Al2O3, activated carbon, ceramic, etc. Mixtures of materials may be used. Other catalysts (and supports) may also be used to provide suitable hydrodynamic properties (density, diameter, porosity, etc.).
[0022] Suitably, in order to be suspended in the molten salt medium, the catalyst particles have a density close to or (at least slightly) higher than the density of the molten salt. Preferably, the catalyst particles have a density of 1000 kg / m 3 ~3800kg / m 3 , preferably 1400 kg / m 3 ~1800kg / m 3 The density is selected based on the molten salt used. Furthermore, the catalyst particles preferably have an average diameter of 0.6 to 6.0 mm, more preferably 0.8 to 4.0 mm.
[0023] As noted above, the catalyst particles are "suspended" in the molten salt. In other words, the catalyst particles have a density selected to allow them to be suspended in the molten salt under pyrolysis conditions (rather than floating upward, as would be the case if the catalyst particles had a density lower than that of the molten salt).
[0024] In step (c) of the process according to the invention, the methane-containing stream is subjected to catalytic pyrolysis in a reaction zone, thereby obtaining solid carbon and gaseous hydrogen.
[0025] As those skilled in the art are familiar with catalytic pyrolysis in the presence of molten salts, this will not be discussed in detail here.
[0026] Typically, catalytic pyrolysis is carried out in a reaction zone at a temperature of from 600°C to 1000°C, preferably from 850°C to 950°C, and a pressure of from 1.0 bara to 10.0 bara.
[0027] Preferably, the height of the reaction zone (with catalyst particles suspended in the molten salt) is from 0.5 m to 3.0 m, more preferably from 1.0 to 2.0 m.
[0028] In step (d) of the method according to the invention, the molten salt, solid carbon and gaseous hydrogen are transported upward from the reaction zone to the intermediate zone while the catalyst particles are retained within the reaction zone.
[0029] The intermediate zone is typically located above the reaction zone and may form part of the same or a separate vessel.
[0030] The upward movement of the molten salt, solid carbon, and gaseous hydrogen (and potentially unreacted methane) is typically caused by one or more of density differences (with the catalyst particles), the circulation flow of the molten salt, and the upward movement of gas bubbles (either formed during catalytic pyrolysis or present in the methane-containing stream undergoing catalytic pyrolysis). A pump may also be used to help drive the upward flow of the molten salt, solid carbon, and gaseous hydrogen. In cases where a pump is used, it is typically located externally. Preferably, the flux of the molten salt circulation is 5.0 kg / m or less. 2 / sec~130.0kg / m 2 / sec, preferably 35.0 kg / m 2 / sec~75.0kg / m 2 / seconds.
[0031] An important aspect of the present invention is that, as the molten salt, solid carbon, and gaseous hydrogen are moving upward from the reaction zone to the intermediate zone in step (d), larger gas bubbles (preferably at least 10 mm in diameter) are broken by the first bubble breaker. This avoids, or at least minimizes, catalyst particles from becoming entrained with such bubbles and moving upward from the reaction zone to the intermediate zone together with the molten salt, solid carbon, and gaseous hydrogen. Preferably, the bubble breaker breaks (larger) gas bubbles having a size of at least 10 mm in diameter into smaller bubbles (preferably at most 6 mm in diameter).
[0032] Bubble breakers are known per se in the art (although not proposed for use in catalytic pyrolysis of methane-containing streams in the presence of molten salts) and will not be further considered in detail here. Suitable bubble breakers may be of the mesh type, honeycomb monolith type, sieve tray or in the form of vertically extending plates, filters, etc. The bubble breaker may have a lattice structure.
[0033] Preferably, the first and second bubble breakers are in the form of vertically extending plates or filters.
[0034] Preferably, the first bubble breaker is completely immersed in the molten salt.
[0035] The first bubble breaker has an open area of >90% to provide only a low pressure drop (thereby allowing free upward flow of molten salt, solid carbon, and gaseous hydrogen).
[0036] Additionally, the second bubble breaker is preferably only partially immersed in the molten salt. Preferably, the second bubble breaker has an open area of 70-90%. This allows for a higher pressure drop, helps to confine the molten salt below the second bubble breaker, and minimizes disturbance of the solid carbon layer that forms during use.
[0037] In step (e) of the method according to the invention, a first portion of the molten salt is caused to flow via a return loop from the intermediate zone to the reaction zone or from the upper part of the reaction zone to the lower part (downward) of the reaction zone. This provides or at least supports a circulation flow of the molten salt as described above. Preferably, there is at least a return loop between the intermediate zone and the reaction zone.
[0038] This return loop can be located inside the vessel (in the case where the reaction zone and intermediate zone are part of the same vessel), but is preferably located outside the vessel.
[0039] In step (f) of the method according to the invention, the solid carbon, gaseous hydrogen (and any unreacted methane), and a second portion of the molten salt are transferred further up the inorganic from the intermediate zone to the separation zone.
[0040] The separation zone is typically located above the intermediate zone and may form part of the same vessel as the reaction zone and intermediate zone.
[0041] In the (upper) separation zone, separation takes place and due to density differences (between the solid carbon and the molten salt), a molten salt-depleted (or even molten salt-free) top layer of solid carbon forms in the separation zone (above the molten salt).
[0042] As noted above, as the molten salt, solid carbon, and gaseous hydrogen travel upward from the intermediate zone to the separation zone in step (f), larger bubbles (preferably at least 10 mm in diameter) are broken by secondary bubble breakers. These secondary bubble breakers can help minimize disturbance of the solid carbon layer and backmixing of the solid carbon with the molten salt in the intermediate zone.
[0043] In step (g) of the method according to the invention, the solid carbon and gaseous hydrogen (and any unreacted methane) are removed from the separation zone. The solid carbon product, after allowing any residual salts in the carbon to be removed, can be used as a raw material for producing color pigments, fibers, foils, cables, activated carbon, or tires. In addition, the solid carbon product can be mixed with other materials to modify the mechanical, thermal, and / or electrical properties of those materials.
[0044] Those skilled in the art will readily appreciate that the solid carbon and gaseous hydrogen can be removed in a variety of ways.
[0045] According to the present invention, in step (g), solid carbon and gaseous hydrogen are removed from the separation zone by gas entrainment using an inverted funnel. Preferably, an auxiliary gas is supplied to the separation zone to provide higher gas velocities and to assist gas entrainment. This auxiliary gas is typically supplied via a separate inlet. Preferably, the auxiliary gas is selected from an inert gas or a recycle gas stream (e.g., coming from a gas / liquid separator), preferably a recycle gas stream.
[0046] Additionally, in step g), solid carbon and part of the gaseous hydrogen can be removed from the separation zone by means of a screw conveyor, which is known per se in the art and therefore will not be considered further in detail here.
[0047] In a further aspect, the present invention provides an apparatus for catalytically pyrolyzing a methane-containing stream, comprising at least: a reaction zone comprising molten salt and catalyst particles, wherein, in use, a methane-containing stream can be fed into the reaction zone in the form of gas bubbles, the catalyst particles can be suspended in the molten salt, and wherein, in use, the methane-containing stream can undergo catalytic pyrolysis within the reaction zone, thereby obtaining solid carbon and gaseous hydrogen; an intermediate zone for receiving molten salt, solid carbon, and gaseous hydrogen that, in use, migrate upwardly from the reaction zone to the intermediate zone while catalyst particles are retained within the reaction zone; - optionally a feedback loop for allowing a first portion of the molten salt to flow from the intermediate zone to the reaction zone or from an upper part of the reaction zone to a lower part of the reaction zone; a separation zone for receiving a second portion of the solid carbon, gaseous hydrogen, and molten salt that has moved further upward from the intermediate zone to the separation zone and for separating the solid carbon and gaseous hydrogen from the molten salt; a first bubble breaker located between the reaction zone and the intermediate zone, capable of breaking up bubbles (preferably larger, i.e., at least 10 mm in diameter) as the molten salt, solid carbon, and gaseous hydrogen move upward from the reaction zone to the intermediate zone, the first bubble breaker having an open area of more than 90%; a second bubble breaker (preferably larger, i.e., at least 10 mm in diameter) located between the intermediate zone and the separation zone, capable of breaking up bubbles as the molten salt, solid carbon, and gaseous hydrogen move upward from the intermediate zone to the separation zone; an aspirator for gas entrainment to remove solid carbon and gaseous hydrogen from the separation zone using an inverted funnel.
[0048] As noted above, the reaction zone, intermediate zone, and separation zone can be part of the same vessel (or can be part of separate vessels). If they are part of the same vessel, the reaction zone is typically the bottom portion, the separation zone is the top portion (although the vessel may include additional portions), and the intermediate zone is located between the reaction zone and the separation zone.
[0049] The first and second bubble breakers can take a variety of shapes and forms, but preferably the bubble breakers are in the form of vertically extending plates or filters.
[0050] The separation zone preferably has an inlet for supplying an auxiliary gas to assist gas entrainment from the separation zone.
[0051] According to another preferred embodiment, the device additionally comprises a screw conveyor for removing solid carbon and gaseous hydrogen from the separation zone. [Brief explanation of the drawings]
[0052] The invention will now be further illustrated by the following non-limiting figures: [Figure 1]1 shows a schematic representation of a first embodiment of an apparatus for catalytically pyrolyzing a methane-containing stream according to the present invention; [Figure 2] 1 shows a schematic representation of a second embodiment of an apparatus for catalytically pyrolyzing a methane-containing stream according to the present invention; [Figure 3] 1 shows a schematic representation of a third embodiment of an apparatus for catalytically pyrolyzing a methane-containing stream according to the present invention; DETAILED DESCRIPTION OF THE INVENTION
[0053] For purposes of this description, the same reference numbers refer to the same or similar components.
[0054] The apparatus shown in FIG. 1, generally referred to by the reference numeral 1, shows a vessel 2 comprising a reaction zone 3, an intermediate zone 4, a separation zone 5, a return loop 6 for molten salt, a first set 7 of bubble breakers between the reaction zone 3 and the intermediate zone 4, a second set 8 of bubble breakers between the intermediate zone 4 and the separation zone 5, and an aspirator 9.
[0055] In the embodiment of FIG. 1, the reaction zone 3, the intermediate zone 4 and the separation zone 5 form part of one and the same vessel 2.
[0056] Reaction zone 3 contains molten salt and catalyst particles suspended therein. Reaction zone 3 has an inlet 31 at its bottom connected to a gas distributor 32 (such as a sparger) for feeding a methane-containing stream 10 into reaction zone 3 in the form of gas bubbles. Typically, the sparger or similar is arranged to distribute the methane-containing stream evenly across the cross-section of reaction zone 3.
[0057] The intermediate zone 4 is located between the reaction zone 3 and the separation zone 5 .
[0058] The return loop 6 allows a first portion of the molten salt to flow from the intermediate zone 4 to the reaction zone 3 .
[0059] A first set of bubble breakers 7 (having an open area of more than 90%) located between the reaction zone 3 and the intermediate zone 4 is capable of breaking down bubbles (preferably larger, i.e., at least 10 mm in diameter) during use as the molten salt, solid carbon, and gaseous hydrogen travel upward from the intermediate zone 3 to the separation zone 4.
[0060] A second set of bubble breakers 8, located between the intermediate zone 4 and the separation zone 5, is capable of breaking down bubbles (preferably larger, i.e., at least 10 mm in diameter) during use as the molten salt, solid carbon, and gaseous hydrogen travel upward from the intermediate zone 4 to the separation zone 5. The second bubble breakers 8 typically have a smaller open area (preferably 70-90%) than the first bubble breakers 7.
[0061] In the embodiment of Figure 1, the first and second bubble breakers 7, 8 are in the form of vertically extending plates.
[0062] 1, separation zone 5 comprises an aspirator 9 (e.g., in the form of an inverted funnel) for removing solid carbon (formed during use as layer 11 above the molten salt) and gaseous hydrogen from separation zone 5 by gas entrainment. To assist gas entrainment, separation zone 5 has an inlet 51 for supplying auxiliary gas 30.
[0063] 1, a gaseous methane-containing stream 10 is fed in the form of bubbles (via inlet 31 and using gas distributor 32) into reaction zone 3. Reaction zone 3 contains molten salt and catalyst particles suspended in the molten salt.
[0064] In reaction zone 3, the methane-containing stream undergoes catalytic pyrolysis (under suitable catalytic pyrolysis conditions), thereby obtaining solid carbon and gaseous hydrogen.
[0065] The molten salt, solid carbon, and gaseous hydrogen are moved upward from reaction zone 3 to intermediate zone 4 while the catalyst particles are retained within reaction zone 3. The upward movement of the molten salt, solid carbon, and gaseous hydrogen from reaction zone 3 to intermediate zone 4 is typically caused by one or more of density differences (with the catalyst particles), circulation flow of molten salt, and upward movement of gas bubbles (either formed during catalytic pyrolysis or present in the methane-containing stream undergoing catalytic pyrolysis). A pump (not shown) may also be used to help drive the upward flow of the molten salt, solid carbon, and gaseous hydrogen. If a pump is used, it is typically located external to vessel 2.
[0066] Preferably, the height of the reaction zone 3 (with catalyst particles suspended in the molten salt) is from 0.5 m to 3.0 m, more preferably from 1.0 to 2.0 m.
[0067] As the molten salt, solid carbon, and gaseous hydrogen move upward from reaction zone 3 to intermediate zone 4, the (preferably larger) gas bubbles (either formed during catalytic pyrolysis or present in the methane-containing stream undergoing catalytic pyrolysis) are broken by first bubble breaker 7. This also prevents catalyst particles from becoming entrained with the gas bubbles and moving into intermediate zone 4.
[0068] A first portion of the molten salt is then flowed back from the intermediate zone 4 to the reaction zone 3 via return loop 6. As shown in the embodiment of Figure 1, supplemental molten salt 40 can be added (via return loop 6 as shown in Figure 1). Also shown in Figure 1 is flow 50 to a molten salt reservoir (not shown).
[0069] Additionally, the solid carbon, gaseous hydrogen, and second portion of the molten salt are further moved upward from the intermediate zone 4 to the separation zone 5. In the embodiment of Figure 1, a second set of bubble breakers 8 is present to further minimize entrainment of catalyst particles in the second portion of the molten salt flow to the separation zone 5. Preferably, the second bubble breakers 8 have an open area of 70-90%. This allows for a higher pressure drop and helps to confine the molten salt below the second bubble breakers 8, minimizing disturbance of the solid carbon layer that forms during use.
[0070] Thereafter, solid carbon (formed during use as layer 11 on top of the molten salt) and gaseous hydrogen are removed from the separation zone 5, leaving behind the molten salt.
[0071] Figure 2 shows an alternative embodiment of the apparatus 1 according to the invention, in which the apparatus 1 comprises, in addition to an aspirator 9 (not shown in Figure 2), a screw conveyor 12 (connected to a hopper 13) for removing solid carbon and gaseous hydrogen from the separation zone 5. Solid carbon is removed from the hopper 13 as a bottoms stream 60, while gaseous hydrogen is removed as an overhead stream 70.
[0072] Further, in the embodiment of FIG. 2, a first portion of the molten salt is caused to flow from an upper portion of the reaction zone 3 to a lower portion of the reaction zone 3 via a return loop 6 .
[0073] Figure 3 shows an alternative embodiment of the apparatus 1 according to the present invention, in which the second bubble breaker 8 is shown only partially immersed in the molten salt, which serves to further confine the molten salt below the second bubble breaker 8 and minimize disturbance of the solid carbon layer that forms during use.
[0074] Consideration As can be seen from Figures 1, 2 and 3, the method according to the invention allows for a surprisingly simple and effective method for catalytically pyrolyzing methane-containing streams.
[0075] An important aspect of the present invention is that larger bubbles (preferably at least 10 mm in diameter) are broken by a first bubble breaker as the molten salt, solid carbon, and gaseous hydrogen move upward from the reaction zone to the intermediate zone. This avoids entrainment of catalyst particles that could interfere with downstream operation. The presence of larger bubbles is further minimized by using a second set of bubble breakers between the intermediate zone and the separation zone. As a result, disturbance of the solid carbon layer and backmixing of the solid carbon with the molten salt in the intermediate zone induced by larger bubbles can be minimized.
[0076] Those skilled in the art will readily appreciate that many modifications may be made without departing from the scope of the present invention. Furthermore, those skilled in the art will readily appreciate that, although the present invention has been illustrated in some instances with reference to specific combinations of features and means, many of these features and means are functionally independent of other features and means provided in the respective embodiments, such that they may be equally or similarly applied independently in other embodiments.
Claims
1. 1. A method for catalytically pyrolyzing a methane-containing stream, comprising at least (a) providing a gaseous methane-containing stream (10); (b) feeding the gaseous methane-containing stream provided in step (a) in the form of gas bubbles into a reaction zone (3) containing molten salt and catalyst particles, the catalyst particles being suspended in the molten salt; (c) subjecting said methane-containing stream to catalytic pyrolysis in said reaction zone (3), thereby obtaining solid carbon and gaseous hydrogen; (d) allowing the molten salt, solid carbon, and gaseous hydrogen to migrate upward from the reaction zone (3) to an intermediate zone (4) while catalyst particles are retained within the reaction zone (3); (e) optionally allowing a first portion of the molten salt to flow from the intermediate zone (4) to the reaction zone (3) or from an upper part of the reaction zone (3) to a lower part of the reaction zone (3) via a return loop (6); (f) allowing the solid carbon, gaseous hydrogen, and a second portion of the molten salt to move further upward from the intermediate zone (4) to a separation zone (5); (g) removing solid carbon and gaseous hydrogen from said separation zone (5) by gas entrainment using an inverted funnel (9), When the molten salt, solid carbon, and gaseous hydrogen are moving upward from the reaction zone (3) to the intermediate zone (4) in step (d), gas bubbles are broken by a first bubble breaker (7) having an open area of more than 90%; The method of claim 1, wherein gas bubbles are broken by a second bubble breaker (8) as the molten salt, solid carbon, and gaseous hydrogen move upward from the intermediate zone (4) to the separation zone (5) in step (f).
2. 2. A method according to claim 1, wherein the first and second bubble breakers (7, 8) are in the form of vertically extending plates or filters.
3. 3. The method according to claim 1 or 2, wherein the first bubble breaker (7) is completely immersed in the molten salt.
4. 4. The method according to any one of claims 1 to 3, wherein the second bubble breaker (8) is only partially immersed in the molten salt.
5. The method according to any one of claims 1 to 4, wherein the second bubble breaker (8) has an open area of 70 to 90%.
6. The method according to any one of claims 1 to 5, wherein an auxiliary gas (30) is fed to the separation zone (5).
7. A method according to any one of claims 1 to 6, wherein in step (g) solid carbon and gaseous hydrogen are removed from the separation zone (5) by a screw conveyor (12).
8. An apparatus (1) for catalytically pyrolyzing a methane-containing stream, comprising at least a reaction zone (3) comprising molten salt and catalyst particles, into which, in use, a methane-containing stream (10) can be fed in the form of bubbles, said catalyst particles being suspended in said molten salt, and in which, in use, said methane-containing stream can undergo catalytic pyrolysis within said reaction zone (3), thereby obtaining solid carbon and gaseous hydrogen; an intermediate zone (4) for receiving molten salt, solid carbon and gaseous hydrogen which, in use, move upward from said reaction zone (3) to said intermediate zone (4) while said catalyst particles are retained within said reaction zone (3); optionally a return loop (6) for allowing a first portion of said molten salt to flow from said intermediate zone (4) to said reaction zone (3) or from an upper part of said reaction zone (3) to a lower part of said reaction zone (3); a separation zone (5) for receiving the solid carbon, gaseous hydrogen and a second portion of the molten salt that have moved further upward from the intermediate zone (4) to the separation zone (5) and for separating the solid carbon and gaseous hydrogen from the molten salt; a first bubble breaker (7) located between the reaction zone (3) and the intermediate zone (4) that is capable of breaking down bubbles as the molten salt, solid carbon and gaseous hydrogen move upward from the reaction zone (3) to the intermediate zone (4), the first bubble breaker (7) having an open area of more than 90%; a second bubble breaker (8) located between the intermediate zone (4) and the separation zone (5) capable of breaking up bubbles as the molten salt, solid carbon and gaseous hydrogen move upward from the intermediate zone (4) to the separation zone (5); an aspirator (9) for removing solid carbon and gaseous hydrogen from said separation zone (5) by gas entrainment using an inverted funnel.
9. 9. Apparatus (1) according to claim 8, wherein the bubble breaker (7, 8) is in the form of a vertically extending plate or filter.
10. 10. Apparatus according to claim 8 or 9, wherein, in use, the first bubble breaker (7) is fully immersed in the molten salt.
11. Apparatus according to any one of claims 8 to 10, wherein, in use, the second bubble breaker (8) is only partially immersed in the molten salt.
12. 12. The apparatus of claim 8, wherein the second bubble breaker has an open area of 70 to 90%.
13. Apparatus (1) according to any one of claims 8 to 12, wherein the separation zone (5) has an inlet (51) for feeding an auxiliary gas (30).
14. Apparatus (1) according to any one of claims 8 to 13, wherein said apparatus (1) comprises a screw conveyor (12) for removing solid carbon and gaseous hydrogen from said separation zone (5).