A jet loop bubbling bed reactor for hydrogen production by methane cracking

Abstract

The present application belongs to hydrogen production reactor technical field, specifically discloses a kind of for methane cracking hydrogen production jet type loop bubbling bed reactor, including reactor cylinder, N group array nozzle group and gas distributor.N group array nozzle group is sequentially arranged from top to bottom along reactor cylinder side wall, wherein a group is located on the top of side wall as top nozzle group, another group is located on the lower end of side wall as bottom nozzle group.Each nozzle of top nozzle group is obliquely downward jet, each nozzle of bottom nozzle group is obliquely upward jet, the jet direction of each nozzle and the tangent direction of its circumference angle is 25°~45°.Top nozzle group and bottom nozzle group build three-dimensional spiral three-dimensional loop flow field in reactor cylinder by high-speed jet, to prolong the residence path of methane bubble and refine bubble particle size.The present application realizes the efficient loop flow contact of molten metal and methane gas under the condition of no internal component, and improves the conversion rate of methane cracking hydrogen production.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen production reactor technology, and specifically relates to a jet-type circulating bubble bed reactor for hydrogen production from methane cracking. Background Technology

[0002] Molten metal methane cracking for hydrogen production has become an important research direction in the field of clean hydrogen production because it can effectively avoid the problem of carbon deposition and deactivation of solid catalysts and has no direct CO2 emissions. In this process, methane enters the liquid molten metal bed in the form of bubbles through a gas distributor, and the cracking reaction mainly occurs at the gas-liquid interface.

[0003] However, due to the significant density difference between methane and molten metal, and the high surface tension of the molten metal, the introduced bubbles rise rapidly under buoyancy. Simultaneously, these tiny bubbles readily coalesce and grow, resulting in extremely short residence time of methane within the bed, a significantly reduced gas-liquid contact area, low mass transfer and reaction efficiency, and a persistently low single-pass methane conversion rate. To address this problem, existing technologies primarily focus on structural improvements to the gas distributor at the bottom of the reactor, such as using multi-layered concentric rings or microporous nozzles to refine the initial bubbles. However, these solutions only improve the initial dispersion state of the bubbles upon entering the bed and cannot change the inherent physical nature of the bubbles' rapid vertical escape due to the high density difference; that is, they fail to effectively extend the actual residence time of the bubbles within the bed. More importantly, these solutions all rely on incorporating numerous precision internal components within the high-temperature (above 1100℃) molten metal. These components are highly susceptible to material strength degradation and deformation failure in highly corrosive environments, making it difficult for the reactor to operate stably over long periods. If we adopt the approach of adding a guide tube to extend the bubble path in traditional circulating reactors, we cannot avoid the same engineering obstacle that internal components cannot operate for extended periods at high temperatures. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a jet-type circulating bubble bed reactor for methane cracking to produce hydrogen. This reactor addresses the technical issues in existing molten metal methane cracking reactors, which suffer from short bubble residence time, small gas-liquid contact area, and low single-pass methane conversion rate due to the large density difference between methane bubbles and molten metal and the high surface tension of the molten metal. It also avoids the engineering defects of easy failure of internal components in high-temperature molten metal environments.

[0005] The technical solution of the present invention is: a jet-type circulating bubble bed reactor for methane cracking to produce hydrogen, comprising a reactor body, N sets of array nozzles and a gas distributor.

[0006] The interior of the reactor shell is used to accommodate a bed of molten metal. N groups of array nozzles are arranged sequentially from top to bottom along the sidewall of the reactor shell, where N ≥ 2. One group of the N array nozzles is located at the upper end of the sidewall of the reactor shell as the top nozzle group, and another group is located at the lower end of the sidewall of the reactor shell as the bottom nozzle group. Each array nozzle group includes multiple M nozzles distributed circumferentially along the reactor shell, where M ≥ 2. The angle α between the spray direction of each nozzle in the top nozzle group and the axial centerline of the reactor shell is 15° ≥ α ≥ 3°. The angle β between the spray direction of each nozzle in the bottom nozzle group and the axial centerline of the reactor shell is 70° ≥ β ≥ 60°. The angle θ between the spray direction of each nozzle and the circumferential tangent direction at the nozzle's location is 45° ≥ θ ≥ 25°. A gas distributor is located at the bottom of the reactor shell for introducing methane gas into the molten metal bed. The nozzles of the top nozzle group and the nozzles of the bottom nozzle group jointly construct a three-dimensional spiral circulation field with both axial circulation and circumferential swirling components in the reactor cylinder through their respective high-speed jets, so as to extend the residence path of methane bubbles in the molten metal bed and refine the bubble particle size.

[0007] Furthermore, at least one middle nozzle group is provided between the top nozzle group and the bottom nozzle group. The nozzles of the middle nozzle group are arranged in the same way as the nozzles of the top nozzle group to improve the coverage of the circulating flow field in the axial direction of the reactor and eliminate local flow field failure areas.

[0008] Furthermore, the included angle θ of all nozzles in each array nozzle group is taken on the same side of the tangent of the circumference, so as to form a unidirectional swirling flow in the reactor cylinder, enhance the stability of the three-dimensional spiral circulation field, increase the residence time of methane bubbles, and improve the single-pass conversion rate.

[0009] Furthermore, in two adjacent groups of array nozzles, the included angle θ of all nozzles in one group is taken on the same side of the tangent of the circumference, while the included angle θ of all nozzles in the other group is taken on the other side of the tangent of the circumference, so as to form a counter-swirling collision in the reactor cylinder, enhance the gas-liquid mixing and mass transfer effect, and increase the possibility of gas-liquid collision and contact.

[0010] Furthermore, the jet volume of each array nozzle group increases by 1.5% to 5% from top to bottom along the height direction of the reactor cylinder to compensate for the attenuation of circulating kinetic energy caused by the increase in static pressure in the lower part of the reactor, thereby achieving a uniform distribution of axial gas holdup, mass transfer and heat transfer in the reactor.

[0011] Furthermore, the total air intake of the N groups of array nozzles is controlled to be 5% to 15% of the total gas volume processed by the reactor, so as to ensure that the jet drives the circulation and enhances the gas-liquid interface renewal without disturbing the main reaction conditions.

[0012] Furthermore, the spacing between adjacent groups of array nozzles decreases gradually from top to bottom along the height direction of the reactor cylinder, with a decrease of more than 0% and not exceeding 5%, to ensure that the downward circulating velocity in each reaction zone is uniform under a fixed spray intensity, and that there is no significant difference in the flow field intensity between the upper and lower sections.

[0013] Furthermore, the number of nozzles M in each array nozzle group satisfies 4≤M≤10, so as to ensure circumferential uniformity while matching the jet shear strength with the reactor diameter.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention sets a top nozzle group and a bottom nozzle group at the upper and lower ends of the side wall of the reactor cylinder, respectively. Each nozzle of the top nozzle group sprays downward at an angle α of 3° to 15°, and each nozzle of the bottom nozzle group sprays upward at an angle β of 60° to 70°. At the same time, the spray direction of each nozzle forms an angle θ of 25° to 45° with the tangent direction of its circumference. Thus, a three-dimensional spiral circulation field with both axial circulation components and circumferential swirling components can be constructed by relying on the momentum transfer and negative pressure entrainment effect of the jet from the cylinder wall without relying on any internal components extending into the bed. The establishment of this circulating flow field, on the one hand, utilizes the longitudinal closed loop formed by the downward-sloping jet from the top and the upward-sloping jet from the bottom, transforming the trajectory of methane bubbles from the short vertical path in a conventional bubbling bed to a long path of repeated spiral ascent and descent, effectively extending the residence time of methane bubbles in the molten metal bed. On the other hand, the turbulent shearing effect generated by the oblique jets from each nozzle in the central region of the cylinder cuts the introduced large bubbles into numerous microbubbles, while the centrifugal force generated by the circumferential swirling flow inhibits bubble coalescence and growth, significantly increasing the gas-liquid contact surface area. Ultimately, under the synergistic effect of extended residence time and increased contact area, the mass transfer efficiency between methane and the molten metal catalyst is comprehensively improved, and the single-pass conversion rate of methane is significantly increased. Furthermore, the construction of the entire flow field requires no components extending into the bed, fundamentally avoiding the engineering challenge of easy failure of internal components in a high-temperature, highly corrosive molten metal environment, ensuring the reliability of the reactor's long-term operation. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 yes Figure 1 Enlarged view of Z1; Figure 3 yes Figure 1Enlarged view of Z2; Figure 4 yes Figure 1 Enlarged view of Z3; Figure 5 This is a schematic diagram showing the orientation of the included angles θ between the top nozzle group, the middle nozzle group, and the bottom nozzle group in Embodiment 1 of the present invention; Figure 6 This is a schematic diagram showing the orientation of the included angles θ between the top nozzle group, the middle nozzle group, and the bottom nozzle group in Embodiment 4 of the present invention.

[0016] Wherein, 1-reactor cylinder; 2-array nozzle group; 3-gas distributor; 20-nozzle. Detailed Implementation

[0017] The following is combined Figures 1 to 6 The specific embodiments of the present invention will be described in detail below. In the description of the present invention, it should be understood that the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0018] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0019] Example 1 like Figure 1 The above describes a jet-type circulating bubble bed reactor for methane cracking to produce hydrogen, comprising a reactor body 1, N array nozzle groups 2, and a gas distributor 3.

[0020] The reactor cylinder 1 has an inner diameter of D, and its interior is used to accommodate a bed of molten metal with a height of H.

[0021] In this embodiment, N=3, meaning that three array nozzle groups 2 are arranged sequentially from top to bottom along the side wall of the reactor cylinder 1, namely the top nozzle group, the middle nozzle group, and the bottom nozzle group, corresponding to the upper, middle, and bottom reaction zones of the molten metal bed, respectively. Each array nozzle group 2 includes four nozzles 20 evenly distributed around the circumference of the reactor cylinder 1, with a nozzle orifice diameter of d.

[0022] like Figure 2 , Figure 3As shown, the angle between the spray direction of each nozzle 20 in the top nozzle group and the middle nozzle group and the axial centerline of the reactor cylinder 1 is α. Figure 5 As shown, the angle between the spray direction of each nozzle 20 and the circumferential tangent direction at the location of the nozzle 20 is θ. Figure 1 As shown, the height difference between the top nozzle group and the middle nozzle group is h1, and the height difference between the middle nozzle group and the bottom nozzle group is h2.

[0023] like Figure 4 As shown, the angle between the spray direction of each nozzle 20 in the bottom nozzle group and the axial centerline of the reactor cylinder 1 is β, as follows: Figure 5 As shown, the angle between the spray direction of each nozzle 20 and the tangential direction of the circle at the location of the nozzle 20 is θ. Figure 1 As shown, the distance from the bottom nozzle group to the bottom of the reactor cylinder 1 is h3.

[0024] The gas distributor 3 is located at the bottom of the reactor body 1, below the bottom nozzle group, and is used to introduce methane gas into the molten metal bed.

[0025] In this embodiment, the values ​​of each parameter are as follows: α=10°, β=60°, θ=45°, D=150mm, H=1000mm, h1=400mm, h2=400mm, h3=50mm, d=1mm.

[0026] The values ​​of α, β, and θ mentioned above all fall within the ranges defined in this invention: α is 15°≥α≥3°, β is 70°≥β≥60°, and θ is 45°≥θ≥25°. In practical applications, the values ​​can be adaptively adjusted within the above ranges according to the reactor size and processing capacity, and the technical effects of this invention can be achieved.

[0027] like Figure 5 As shown, the included angle θ of each nozzle 20 in the top nozzle group and the middle nozzle group is taken on the same side of the tangent of its circumference, i.e., clockwise, to form a unidirectional swirling flow within the reactor shell 1. The top nozzle group, the middle nozzle group, and the bottom nozzle group eject high-speed fluid through oblique jets. The jet from each nozzle 20 simultaneously forms a circumferential swirling velocity component, a radially inward converging velocity component, and an axial velocity component. The empty top and middle sections have a downward velocity component, and the bottom section has an upward velocity component. Here, A represents the top nozzle group, B represents the middle nozzle group, and C represents the bottom nozzle group.

[0028] The top and middle nozzle groups inject high-speed fluid through oblique jets, simultaneously generating circumferential swirling velocities, radially converging velocities, and downward velocities. Tangential swirling reduces dead zones on the cylinder wall and suppresses carbon black deposition; radial turbulent shearing refines methane bubbles, increasing centrifugal force to disperse molten metal from the center to the sides, thus enhancing wall heat transfer. The superposition of different jets from the multi-layered nozzles constructs a three-dimensional spiral circulation field, significantly extending the gas-phase spiral path and increasing the contact residence time between methane and the molten metal catalytic liquid phase.

[0029] The bottom nozzle assembly injects high-speed fluid through a slanted jet, driving the downward spiral mixing fluid near the cylinder wall to move upward spirally towards the center of the reactor cylinder 1. The bottom nozzle assembly, together with the gas distributor 3 at the bottom of the reactor cylinder 1, provides the upward driving force for the longitudinal circulation.

[0030] The three sets of jet nozzles, together with the high-speed injection of gas distributor 3, construct a three-dimensional spiral circulation field. This field reduces the dead zone on the cylinder wall and inhibits carbon black deposition through tangential swirling flow, while radial turbulent shearing refines methane bubbles and extends the gas-phase spiral path. This doubles the contact residence time between methane and molten metal and increases the gas-liquid contact area. Simultaneously, the increased centrifugal force of the swirling flow disperses the molten metal from the center to the sidewalls, enhancing wall heat transfer. The excellent mixing effect of the circulation ensures thorough mixing of methane and molten metal, promoting heat exchange and driving the methane cracking reaction for hydrogen production. This can improve the efficiency of methane cracking for hydrogen production by 5%.

[0031] Example 2 The difference between this embodiment and embodiment 1 is that the jet volume of each array nozzle group 2 increases by 1.5% to 5% from top to bottom along the height direction of the reactor cylinder 1.

[0032] Specifically, the jet flow rate of the top nozzle group is Q1, the jet flow rate of the middle nozzle group is Q2 = Q1 × (1 + 1.5% ~ 5%), and the jet flow rate of the bottom nozzle group is Q3 = Q2 × (1 + 1.5% ~ 5%). By stabilizing the circulation with a small gas flow rate at the top and compensating for the increase in static pressure and the decrease in circulation kinetic energy with an increasing gas flow rate at the bottom, a uniform distribution of axial gas holdup, mass transfer, and heat transfer in the reactor is achieved.

[0033] The total air intake of the three array nozzle groups 2 is controlled to be 5% to 15% of the total gas volume processed by the reactor. The remaining structure and parameters are the same as in Example 1.

[0034] This embodiment further optimizes the uniformity of the flow field along the reactor axis by using gradient gas distribution of jet volume, thereby enhancing gas-liquid interface renewal and wall heat transfer without disturbing the main reaction conditions.

[0035] Example 3 The difference between this embodiment and embodiment 1 is that the spacing between two adjacent array nozzle groups 2 decreases gradually from top to bottom along the height direction of the reactor cylinder 1, with a decrease of more than 0% and not exceeding 5%.

[0036] Specifically, the spacing between the top nozzle group and the middle nozzle group is h1, and the spacing between the middle nozzle group and the bottom nozzle group is h2, where h2 = h1 × (1 - 0% ~ 5%), i.e., h2

[0037] By gradually decreasing the spacing between groups, the downward circulating velocity in each reaction zone is ensured to be uniform under a fixed injection intensity, with no significant difference in flow field intensity between the upper and lower sections. A complete three-dimensional spiral circulation is constructed throughout the entire domain, with no local flow field failure areas. The remaining structure and parameters are the same as in Example 1.

[0038] Example 4 The difference between this embodiment and Embodiment 1 is that: Figure 6 As shown, in two adjacent array nozzle groups 2, the included angle θ of all nozzles 20 in one group is on the same side of the tangent of the circumference, i.e. clockwise; the included angle θ of all nozzles 20 in the other group is on the other side of the tangent of the circumference, i.e. counterclockwise, so as to form a counter-swirling collision in the reactor cylinder 1.

[0039] Specifically, the included angle θ of all nozzles 20 in the top nozzle group is clockwise, the included angle θ of all nozzles 20 in the middle nozzle group is counterclockwise, and the included angle θ of all nozzles 20 in the bottom nozzle group is clockwise. The adjacent two layers of swirling fluid form a counter-current collision field, which enhances the mixing effect, increases the possibility of gas-liquid collision and contact, and thus improves mass transfer efficiency. The remaining structure and parameters are the same as in Example 1.

[0040] Example 5 The difference between this embodiment and Embodiment 1 is that the values ​​of α, β, and θ are different.

[0041] In this embodiment, the values ​​of each parameter are as follows: α=5°, β=65°, θ=30°, D=200mm, H=1200mm, h1=480mm, h2=480mm, h3=60mm, d=1.2mm.

[0042] The values ​​of α, β, and θ mentioned above all fall within the range of α being 3° to 15°, β being 60° to 70°, and θ being 25° to 45° as defined in this invention.

[0043] ​Under the conditions of α=5°, β=65°, and θ=30°, the top and middle nozzle groups spray at a smaller downward angle, while the bottom nozzle group sprays at a larger upward angle. The tangential angle of each nozzle is taken as the median value. This can still construct a stable three-dimensional spiral circulation field, achieving the technical effect of extending the residence path of methane bubbles and refining the bubble particle size. The remaining structure and parameters are the same as in Example 1.

[0044] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and do not limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the protection scope of the present invention.

Claims

1. A jet-type circulating bubble bed reactor for methane cracking to produce hydrogen, characterized in that, include: The reactor shell, the interior of which is used to contain a bed of molten metal; N array nozzle groups are arranged sequentially from top to bottom along the side wall of the reactor cylinder, where N≥2. One group of the N array nozzle groups is located at the upper end of the side wall of the reactor cylinder as the top nozzle group, and another group of the N array nozzle groups is located at the lower end of the side wall of the reactor cylinder as the bottom nozzle group. Each array nozzle group includes multiple M nozzles distributed circumferentially along the reactor cylinder, where M≥2. The angle α between the spray direction of each nozzle in the top nozzle group and the axial centerline of the reactor cylinder is 15°≥α≥3°. The angle β between the spray direction of each nozzle in the bottom nozzle group and the axial centerline of the reactor cylinder is 70°≥β≥60°. The angle θ between the spray direction of each nozzle and the circumferential tangent direction of the nozzle's location is 45°≥θ≥25°. And a gas distributor, located at the bottom of the reactor shell, for introducing methane gas into the molten metal bed; The nozzles of the top nozzle group and the nozzles of the bottom nozzle group together construct a three-dimensional spiral circulation field with both axial circulation and circumferential swirling components within the reactor cylinder through their respective high-speed jets.

2. The jet-type circulating bubble bed reactor for methane cracking to hydrogen production as described in claim 1, characterized in that, At least one middle nozzle group is also provided between the top nozzle group and the bottom nozzle group, and the nozzles of the middle nozzle group are arranged in the same way as the nozzles of the top nozzle group.

3. The jet-type circulating bubble bed reactor for methane cracking to hydrogen production as described in claim 1, characterized in that, The included angle θ of all nozzles in each array nozzle group is taken on the same side of the tangent of the circumference.

4. The jet-type circulating bubble bed reactor for methane cracking to hydrogen production as described in claim 1, characterized in that, In two adjacent groups of array nozzles, the included angle θ of all nozzles in one group is on the same side of the tangent of the circumference, while the included angle θ of all nozzles in the other group is on the other side of the tangent of the circumference.

5. The jet-type circulating bubble bed reactor for methane cracking to hydrogen production as described in claim 1, characterized in that, The jet volume of each array nozzle group increases by 1.5% to 5% from top to bottom along the height direction of the reactor cylinder.

6. The jet-type circulating bubble bed reactor for methane cracking to hydrogen production as described in claim 1, characterized in that, The total air intake of the array nozzle group described in group N is controlled to be 5% to 15% of the total gas volume processed by the reactor.

7. The jet-type circulating bubble bed reactor for methane cracking to hydrogen production as described in claim 1, characterized in that, The spacing between adjacent array nozzle groups decreases gradually from top to bottom along the height of the reactor cylinder, with a decrease of more than 0% and not exceeding 5%.

8. A jet-type circulating bubble bed reactor for methane cracking to hydrogen production as described in claim 1, characterized in that, The number of nozzles M in each array nozzle group satisfies 4 ≤ M ≤ 10.

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