Method and device for preparing hydrogen and carbon black by efficient and rapid thermal cracking of natural gas

Abstract

The application discloses a method and device for preparing hydrogen and carbon black through efficient and rapid thermal cracking of natural gas, and belongs to the technical field of clean energy and carbon material preparation. The method adopts a small-diameter multi-turn tubular reaction channel made of a high-temperature-resistant nickel-containing alloy, carries out high-temperature hydrogen reduction heat treatment on the inner wall of the tube, causes the skin oxide layer and adhering matters to fall off, and forms a catalytically active layer; the purified and preheated methane-containing raw material gas is introduced into the tubular reaction channel, non-oxidation thermal cracking occurs in the high-temperature and second-level residence time without participation of an oxidant and without loading of an independent particulate catalyst, hydrogen-containing gas and carbon black are generated, the high-speed airflow in the small-diameter flow channel is used to carry the carbon black out, and wall surface carbon black deposition or blockage is prevented, so that the cracking reaction efficiency is reduced; the device comprises a raw material preheater, a tubular cracking reactor, a product cooling unit, a gas-solid separation unit and a heat supply system; the application can improve the short-residence-time cracking conversion rate of methane and weaken carbon black deposition.

Description

Technical Field

[0001] This invention relates to the field of clean energy and carbon material preparation technology, specifically to a method and apparatus for the efficient and rapid thermal cracking of natural gas to prepare hydrogen and carbon black. Background Technology

[0002] Hydrogen is an important raw material and energy carrier in fields such as fuel cells, chemical synthesis, metallurgical reduction, and energy storage. Existing natural gas-to-hydrogen processes mainly include steam reforming, partial oxidation, and autothermal reforming. These processes typically require multiple steps such as steam supply, reforming, conversion, decarbonization, and purification, resulting in long processes and carbon-containing gas emissions.

[0003] Direct thermal cracking of methane produces hydrogen and solid carbon via the reaction pathway CH4→C+2H2, without requiring all the carbon in methane to be converted into carbon dioxide, and yields usable carbon black. However, due to the stable molecular structure of methane, conventional non-catalytic thermal cracking typically requires high temperatures and long residence times, leading to increased reactor volume and heating load.

[0004] To improve methane cracking rates, some technologies load nickel-based, iron-based, or carbon-based granular catalysts into the reactor. However, granular catalysts are easily deactivated by the generated solid carbon and require loading, separation, regeneration, or replacement, leading to system complexity. Furthermore, granular catalysts and carbon black can collectively increase reactor pressure drop. On the other hand, ordinary metal tubes or inert reactor tubes primarily serve for transport, pressure bearing, and heat transfer, failing to fully utilize the reactor wall surface to promote methane cracking.

[0005] How to provide a method for the efficient and rapid thermal cracking of natural gas to produce hydrogen and carbon black to solve these problems has become an urgent issue for those skilled in the art. Summary of the Invention

[0006] This invention aims to provide a method and apparatus for the efficient and rapid thermal cracking of natural gas to produce hydrogen and carbon black. The high-temperature resistant nickel-containing alloy pipe simultaneously functions as both a cracking reaction channel and a catalytic carrier on its wall. A catalytically active layer is formed on the inner wall of the pipe through high-temperature hydrogen reduction heat treatment. By matching the diameter of the tubular reaction channel with the feed flow rate, the methane-containing feed gas entering the tubular reaction channel is maintained at an inlet linear velocity sufficient to promote the movement of cracked carbon black towards the outlet, thereby improving methane cracking efficiency and reducing the risk of pressure drop and blockage caused by continuous carbon black deposition.

[0007] Furthermore, the tubular reaction channel adopts a multi-turn tubular structure to increase the effective heat transfer path and inner wall contact area within the limited heating space.

[0008] Furthermore, by coordinating the raw material flow rate, the effective length of the reaction channel, and the reaction temperature, the methane-containing raw material gas is kept in the high-temperature reaction zone for a residence time on the order of seconds.

[0009] To solve the above-mentioned technical problems, the present invention provides the following technical solution: This invention provides a method for the efficient and rapid thermal cracking of natural gas to prepare hydrogen and carbon black, comprising the following steps: S1. A tubular pyrolysis reactor is provided, wherein the tubular pyrolysis reactor is provided with a multi-turn tubular reaction channel made of high-temperature resistant nickel alloy, and the inner diameter of the tubular reaction channel is not greater than 30mm. S2. The inner wall of the tubular reaction channel is subjected to high-temperature hydrogen reduction heat treatment to remove the surface oxide layer and adhering substances of the inner wall of the tubular reaction channel, expose the nickel-containing active components on the surface of the inner wall of the tube and form a catalytic active layer, increase the reactive sites on the surface of the inner wall of the tube, and enhance the early reaction of the methane-containing feed gas. S3. The methane-containing feed gas, preheated to 400-600°C, is introduced into the tubular reaction channel. Under conditions where no oxidant is involved and no independent particulate catalyst is loaded, non-oxidative thermal cracking is carried out at a high temperature of 600-1200°C. The inlet linear velocity of the methane-containing feed gas entering the tubular reaction channel is not less than 10 m / s, so that the generated carbon black is discharged from the tubular reaction channel with the cracked gas. In this invention, the inlet linear velocity refers to the linear velocity of the methane-containing feed gas when it enters the tubular reaction channel. By matching the feed flow rate with the diameter of the tubular reaction channel, the inlet linear velocity of the methane-containing feed gas is made not less than 10 m / s, which can improve the flow carrying capacity of the gas in the tubular reaction channel, so that the carbon black generated by pyrolysis moves with the pyrolysis gas to the outlet, and reduce the continuous deposition of carbon black on the inner wall of the pipe. S4. Cool and separate the discharged pyrolysis products into gas and solid components to obtain hydrogen-containing gas and carbon black. The tubular reaction channel simultaneously constitutes a thermal decomposition reaction channel and a wall-mounted catalyst support.

[0010] Preferably, in step S1, the tubular reaction channel is a multi-turn tubular structure formed by bending high-temperature nickel-containing alloy tubing, and includes a first tube layer and a second tube layer arranged adjacent to each other along the tube thickness direction. The first tube layer and the second tube layer each include multiple straight tube sections arranged parallel to each other and bent tube sections located at the ends of the straight tube sections. The bent tube sections in the same tube layer are respectively connected to adjacent straight tube sections, so that the fluid flows in opposite directions between adjacent straight tube sections.

[0011] More preferably, the bends in the first and second pipe layers are staggered along the pipe thickness direction and at least partially overlap in the orthographic projection direction, so that the bends in the first and second pipe layers form a stacked arrangement at the upper and lower ends of the tubular reaction channel.

[0012] The high-temperature resistant nickel-containing alloy is a nickel-containing heat-resistant austenitic stainless steel, an iron-nickel-based heat-resistant alloy, or a nickel-based heat-resistant alloy. After the inner wall of the tubular reaction channel is subjected to high-temperature hydrogen reduction heat treatment, the nickel-containing components on the inner wall surface are exposed, and a catalytic active layer containing dispersed nickel-containing active sites is formed. The catalytic active layer has a micro-uneven structure.

[0013] It should be noted that the dispersed nickel-containing active sites referred to in this invention refer to the presence of nickel elements or nickel phases in a dispersed state on the inner wall surface of the tube after activation treatment, which are used to promote the adsorption and activation of methane in the initial stage of cracking, and do not require that the mass content of nickel elements be the highest in the entire detection area.

[0014] Preferably, in step S2, the hydrogen-containing reducing atmosphere is composed of hydrogen and nitrogen, and the volume fraction of hydrogen is 10% to 50%; the tubular reaction channel is heated to 400-600°C at a heating rate of 5 to 20°C / min and held at that temperature for 1 to 6 hours.

[0015] The present invention also provides an apparatus for the efficient and rapid thermal cracking of natural gas to produce hydrogen and carbon black using the above method, comprising a raw material pretreatment unit, a raw material preheater, a tubular cracking reactor, a product cooling unit, a gas-solid separation unit, and a heating system; wherein the raw material pretreatment unit, the raw material preheater, the tubular cracking reactor, the product cooling unit, and the gas-solid separation unit are connected in sequence. The tubular pyrolysis reactor includes a heating chamber and a tubular reaction channel disposed within the heating chamber. The tubular reaction channel is made of a high-temperature resistant nickel-containing alloy tube, and the inner wall of the tubular reaction channel has a catalytically active layer formed by high-temperature hydrogen reduction heat treatment. The raw material preheater is connected to the inlet of the tubular reaction channel and is used to preheat the methane-containing raw material gas before sending it into the tubular reaction channel. The gas-solid separation unit is connected to the outlet of the tubular reaction channel and is used to perform gas-solid separation of hydrogen-containing gas and carbon black pyrolysis products. It is equipped with a hydrogen-containing gas outlet and a carbon black outlet. The heating system is used to maintain the pyrolysis temperature in the heating chamber by means of combustion heating of raw gas or electric heating.

[0016] Preferably, the tubular reaction channel includes a first tubular layer and a second tubular layer arranged adjacent to each other along its thickness direction. Each of the first tubular layer and the second tubular layer includes a plurality of straight pipe sections arranged in parallel to each other and a bent pipe section located at the end of the straight pipe section. The gas-solid separation unit includes a cyclone separator, and the raw material preheater includes a heat exchanger. The heat exchanger is provided with a raw material gas channel and a pyrolysis product heat exchange channel. The raw material gas channel is connected to the inlet of the tubular reaction channel, and the pyrolysis product heat exchange channel is connected to the pyrolysis product outlet of the tubular pyrolysis reactor. When the heating system adopts a raw material gas combustion heating method, the heat exchanger is also provided with a combustion flue gas heat exchange channel, which is connected to the combustion flue gas outlet of the heating system.

[0017] This invention uses a high-temperature resistant nickel-containing alloy to make a small-diameter multi-turn tubular reaction channel; the high-temperature resistant nickel-containing alloy can be nickel-containing heat-resistant austenitic stainless steel, iron-nickel-based heat-resistant alloy or nickel-based heat-resistant alloy, with an inner diameter of no more than 30 mm; the tubular reaction channel adopts a continuously curved multi-turn structure to obtain a longer heating path and a larger inner wall area per unit reactor volume within a limited heating space.

[0018] The raw material preheater is connected to the inlet of the tubular reaction channel and is used to preheat the methane-containing raw material gas before sending it into the tubular reaction channel. The gas-solid separation unit is connected to the outlet of the tubular reaction channel and is used to perform gas-solid separation of hydrogen-containing gas and carbon black pyrolysis products. It is equipped with a hydrogen-containing gas outlet and a carbon black outlet. The heating system is used to maintain the pyrolysis temperature in the heating chamber by means of combustion heating of raw gas or electric heating.

[0019] Preferably, the tubular reaction channel includes a first tubular layer and a second tubular layer arranged adjacent to each other along its thickness direction. Each of the first tubular layer and the second tubular layer includes a plurality of straight pipe sections arranged in parallel to each other and a bent pipe section located at the end of the straight pipe section. The bends in the first and second pipe layers are staggered along the pipe thickness direction and at least partially overlap in the orthographic projection direction, so that the bends in the two pipe layers form a stacked arrangement at the upper and lower ends of the tubular reaction channel. The gas-solid separation unit includes a cyclone separator, and the raw material preheater includes a heat exchanger. The heat exchanger is provided with a raw material gas channel and a pyrolysis product heat exchange channel. The raw material gas channel is connected to the inlet of the tubular reaction channel, and the pyrolysis product heat exchange channel is connected to the pyrolysis product outlet of the tubular pyrolysis reactor. When the heating system adopts a raw material gas combustion heating method, the heat exchanger is also provided with a combustion flue gas heat exchange channel, which is connected to the combustion flue gas outlet of the heating system.

[0020] This invention uses a high-temperature resistant nickel-containing alloy to make a small-diameter multi-turn tubular reaction channel; the high-temperature resistant nickel-containing alloy can be nickel-containing heat-resistant austenitic stainless steel, iron-nickel-based heat-resistant alloy or nickel-based heat-resistant alloy; the tubular reaction channel adopts a continuously curved multi-turn structure to obtain a longer heating path and a larger inner wall area per unit reactor volume within a limited heating space.

[0021] Before the cracking reaction is initiated, a hydrogen-containing reducing atmosphere is introduced into the tubular reaction channel, and the tube is heated for high-temperature activation. This treatment causes the surface oxide layer and adhering substances on the inner wall of the tube to fall off, exposing nickel-containing active sites and forming a micro-surface with uneven texture. The activated inner wall of the tube promotes methane cracking, transforming the tube from a simple high-temperature transport component into a wall-mounted catalytic reaction channel.

[0022] The methane-containing feed gas is purified and preheated before entering the tubular reaction channel. Purification is used to reduce the impact of sulfur-containing components, moisture and solid impurities on the wall activity, and preheating is used to shorten the temperature rise process of the feed gas in the cracking reactor. The methane-containing feed gas is subjected to high-temperature thermal cracking without the participation of oxidant and without the loading of independent particulate catalyst.

[0023] In one embodiment, the sulfur content in the methane-containing feed gas entering the tubular reaction channel is no higher than 1000 ppm and the moisture content is less than 500 ppm, so as to reduce the influence of sulfur-containing components and moisture on the surface condition of the inner wall of the activated tube and the cracking reaction process.

[0024] The small-diameter structure increases the contact between the gas and the activated inner wall, while the multi-turn structure extends the effective heating path, and the activated inner wall increases the pyrolysis reaction rate in a short time. At the same time, by matching the raw material flow rate with the pipe diameter, the pyrolysis gas carries the generated carbon black to the outlet, reducing the formation of a continuous coating layer of carbon black on the activated inner wall.

[0025] After the pyrolysis products are discharged from the pipe outlet, they undergo heat exchange and cooling, and then one or more of cyclone separation, inertial separation, and filtration separation to obtain hydrogen-containing gas and carbon black. The hydrogen-containing gas can be further purified by adsorption, membrane separation, or directly enter the subsequent utilization unit.

[0026] Compared with the prior art, the present invention can achieve the following beneficial effects: 1. The tube structure material also serves as the wall catalyst support. Through hydrogen-containing reducing high-temperature activation, a micro-rough active layer with exposed active sites is formed on the inner wall of the high-temperature alloy tube, eliminating the need to fill the reactor with independent particulate catalysts.

[0027] 2. The activated inner wall, small-diameter multi-turn flow channel, and second-level residence time work synergistically. The small diameter increases the wall contact area per unit gas volume, the multi-turn flow channel extends the heating path, and the activated inner wall improves the degree of pyrolysis in a short time.

[0028] 3. The generated carbon black is carried out by the gas flow inside the pipe, which reduces the continuous deposition of carbon black on the inner wall and the covering of active sites, resulting in a smaller increase in reactor pressure drop during continuous operation.

[0029] 4. The activated nickel alloy tubes showed a significantly higher methane conversion rate compared to unactivated tubes of the same material and inert tubes, indicating that the technical effect did not solely originate from the high temperature or the nickel-containing material itself.

[0030] 5. The waste heat from pyrolysis products or heating flue gas can be used for raw material preheating, while obtaining hydrogen-containing gas and carbon black, thereby improving the comprehensive utilization of raw materials and heat. Attached Figure Description

[0031] Figure 1 This is a schematic diagram showing the overall distribution, top tube distribution, and connection arrangement of the multi-turn tube reaction channel of the present invention; Figure 2 This is a connection diagram of the experimental system of the present invention; Figure 3 Scanning electron micrograph and elemental distribution of the inner wall of a nickel alloy tube after activation treatment; Figure 4 The images show the surface morphology of the nickel alloy tube before and after activation treatment, as well as the surface height distribution in the corresponding areas. Figure 5 The curve shows the change in methane conversion rate with residence time at high temperature. Figure 6 Scanning electron micrographs of carbon black obtained from pyrolysis at different magnifications; Figure 7 The nitrogen adsorption-desorption curves are for carbon black obtained from pyrolysis. Detailed Implementation

[0032] The present application will now be described in further detail with reference to the accompanying drawings. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0033] Example 1 High-temperature resistant austenitic stainless steel pipe is selected, with the main components being: Ni 38.0–46.0%, Cr 19.5–23.5%, Mo 2.5–3.5%, Cu 1.5–3.0%, Ti 0.6–1.2%, with the balance being Fe and C ≤0.05%. The pipe wall thickness is 2mm, the inner diameter is 20mm, and the total length is 10 meters. The pipe is bent into a multi-turn tubular structure that extends back and forth, as shown in the figure. Figure 1 As shown.

[0034] like Figure 1 As shown, the tubular reaction channel includes multiple straight pipe sections arranged in parallel to each other and bent pipe sections located at the ends of the straight pipe sections; the bent pipe sections in the same pipe layer connect adjacent straight pipe sections, allowing the gas to flow continuously in different directions between adjacent straight pipe sections; the bent pipe sections in the first pipe layer and the bent pipe sections in the second pipe layer are staggered along the pipe thickness direction and at least partially overlap in the orthographic projection direction, so that the bent pipe sections of the two pipe layers form a stacked arrangement at the upper and lower ends of the tubular reaction channel; this structure can increase the length of the heating channel and the contact area of ​​the inner wall of the pipe within a limited heating space, and is conducive to forming a compact multi-turn heating path.

[0035] A hydrogen-containing reducing atmosphere with 50% hydrogen gas and the remainder nitrogen gas was introduced into the tube for high-temperature reduction treatment. The temperature was increased to 500℃ at a rate of 10℃ / min and held at 500℃ for 4 hours. After the holding period, the tube was cooled under a protective atmosphere.

[0036] like Figure 3 As shown, (a) is a scanning electron microscope image of the inner wall of the nickel alloy tube after activation treatment, used to observe the microstructure of the inner wall of the tube after activation treatment; (b) is a general map of elemental distribution of the inner wall after activation treatment; and (c) to (f) are the surface distribution maps of C, Fe, Ni and O elements in the corresponding regions, respectively.

[0037] Depend on Figure 3 As shown in (a), after high-temperature hydrogen reduction heat treatment, a continuously distributed micro-uneven structure forms on the inner wall surface of the tube; from Figure 3 As shown in (b) to (f), the main elements can be detected in a dispersed state on the inner wall surface after activation treatment. Among them, Ni element maintains a certain distribution in the inner wall region, indicating that high-temperature hydrogen reduction heat treatment can change the original coverage state of the inner wall, expose the nickel-containing active components, and provide reactive sites for subsequent methane cracking.

[0038] like Figure 4 As shown, (a) is the surface morphology of the nickel alloy tube before activation treatment, (b) is the surface morphology of the nickel alloy tube after activation treatment, (c) is the surface height distribution map of the corresponding area before activation treatment, and (d) is the surface height distribution map of the corresponding area after activation treatment.

[0039] Depend on Figure 4 (a) and Figure 4 As can be seen in (b), the surface morphology of the inner wall of the tube changes after high-temperature hydrogen reduction heat treatment; from Figure 4 (c) and Figure 4 As shown in (d), the height of the inner wall surface of the tube increases after activation treatment, forming a microstructure with concave and convex features. The test results show that after high-temperature hydrogen reduction heat treatment, the inner wall of the tube forms a micro-surface structure with different concave and convex features, and its surface roughness is about 40 μm.

[0040] Example 2 use Figure 2 The experimental system shown is used to conduct rapid thermal cracking experiments on natural gas. The experimental system includes a feed gas supply section, a preheating section, a tubular cracking reactor, a product cooling section, and a gas-solid separation section. The methane-containing feed gas is preheated in a heat exchanger after flow control, and then enters the tubular reaction channel set in the heating furnace. The cracking products are discharged from the pipe outlet, cooled by a cooling device, and enter the gas-solid separation unit to separate carbon black and hydrogen-containing gas. This experimental system is used to verify the continuous implementation of feed preheating, tubular cracking, product cooling, and gas-solid separation steps.

[0041] Bottled methane with a volume fraction of 99.9% was used as the methane-containing feed gas. The feed gas was preheated to 500°C by a heat exchanger before entering the tubular reaction channel obtained in Example 1. Electric heating was used to maintain the high temperature of the reaction zone outside the tube. The temperature of the heating zone where the tubular reaction channel was located was controlled at 900°C (using a thermometer inside a muffle furnace). The flow rate of the methane-containing feed gas was adjusted by a mass flow meter to vary the inlet linear velocity of the methane-containing feed gas entering the reaction coil within the range of 1–18 m / s. Simultaneously, a carbon black collection device was installed at the outlet of the pyrolysis pipeline to measure the amount of carbon black discharged with the pyrolysis gas under various inlet linear velocity conditions and to evaluate the effect of the inlet linear velocity on carbon black deposition inside the tube. The degree of influence of gas velocity on carbon black deposition was expressed as the carbon black deposition rate (w). c The evaluation is performed using the following formula: ; In the formula, Indicates the carbon black deposition rate; The amount of carbon black collected in the bag per unit time, in grams; This represents the theoretical carbon black yield per unit time, expressed in grams (g).

[0042] The carbon black deposition results at different inlet linear velocities are shown in Table 1. The experimental results show that as the inlet linear velocity of the methane-containing feed gas increases, the carbon black deposition rate gradually decreases. When the inlet linear velocity increases from 8 m / s to 10 m / s, the carbon black deposition rate decreases from 7.6% to 1.9%. When the inlet linear velocity further increases to 12 m / s, the carbon black deposition rate decreases to 0.8%. When the inlet linear velocity is 15–18 m / s, the carbon black deposition rate remains at approximately 0.7%.

[0043] It can be seen that when the inlet linear velocity of the methane-containing feed gas is not less than 10 m / s, the ability of the gas in the pipe to carry out the carbon black generated by cracking is significantly improved, which can significantly reduce the continuous deposition of carbon black in the tubular reaction channel.

[0044] After being discharged from the pipe outlet, the pyrolysis products are first cooled and then subjected to gas-solid separation. Gas composition is analyzed by gas chromatography, and carbon black is characterized by weighing and morphology. In representative experiments, the methane conversion rate can reach 99%, and the hydrogen integral in the hydrogen-containing gas is greater than 99%. The obtained carbon black has a particle size mainly of 0.5–3 μm, and its morphology is as follows: Figure 6 As shown, after 3 hours of continuous operation, the pressure drop in the reactor increased by less than 10%, and no obvious blockage was found.

[0045] Figure 5 Representative results under the reaction conditions are presented; with the increase of residence time, the overall methane conversion rate increases, reaching a maximum of 99.49%. The obtained carbon black particle size is mainly distributed in the range of 0.3–2 μm, and the specific surface area is 2.41 m². 2 / g.

[0046] Comparative Example 1 Using an 8mm inner diameter corundum tube as an inert reaction channel, methane thermal cracking was carried out under the same conditions. Test results showed that the methane conversion rate was 62%, and the hydrogen yield was approximately 1.24 Nm³. 3 / Nm 3 Methane; the results indicate that, under short residence time conditions, homogeneous thermal pyrolysis in an inert reaction tube alone is insufficient to achieve the conversion level of an activated nickel alloy tube.

[0047] Comparative Example 2 In another set of parallel material comparison experiments, inert corundum tubes with the same inner diameter and effective length, nickel alloy tubes without high-temperature hydrogen reduction heat treatment, and nickel alloy tubes of the same material with high-temperature hydrogen reduction heat treatment were used as reaction channels. Methane high-temperature cracking reaction was carried out under the same conditions of 1000℃. The results are shown in Table 2. The methane conversion rates of inert corundum tubes with an inner diameter of 20 mm, unactivated metal tubes, and activated metal tubes were 38%, 64%, and 94%, respectively. The conversion rate of the metal tubes was 26 percentage points higher than that of the inert corundum tubes, indicating that the inner wall material of the iron-nickel metal has a substantial contribution to the cracking promotion effect. The conversion rate of the activated metal tubes was 30 percentage points higher than that of the unactivated tubes of the same material, indicating that the catalytic active layer formed by the high-temperature hydrogen reduction heat treatment has a further promoting effect on methane cracking.

[0048] Test and Results Analysis In this experiment, the methane conversion rate was calculated as follows: Ethylene and ethane contents were less than 1%, so they were ignored. The calculation formula is as follows: ; In the formula, This indicates the single-pass conversion rate of methane; This indicates the volume fraction of hydrogen in the pyrolysis product gas. This indicates the volume fraction of methane in the pyrolysis product gas.

[0049] like Figure 6 As shown, (a) is a low-magnification scanning electron microscope image of the carbon black obtained from pyrolysis, used to observe the overall aggregation state of the carbon black; (b) is a carbon black particle distribution morphology image at a higher magnification; (c) is a magnified microscopic morphology image of carbon black particles in a local area; Figure 6 As can be seen from (a) to (c), the carbon black obtained by pyrolysis mainly exhibits a particulate aggregate morphology, with individual particles being spherical or nearly spherical in shape, and the particle size mainly distributed in the micrometer range. This result indicates that the present invention can produce carbon black products with particulate morphology as a byproduct while obtaining hydrogen-containing gas. Figure 7 The nitrogen adsorption-desorption curves shown indicate that the obtained carbon black has certain adsorption capacity and pore structure characteristics, and has the potential to be further utilized as a carbon black material.

[0050] Table 2 shows the comparison results of inert corundum tubes, unactivated nickel alloy tubes, and activated nickel alloy tubes under the same conditions. The methane conversion rates of inert corundum tubes, unactivated nickel alloy tubes, and activated nickel alloy tubes are 38%, 64%, and 94%, respectively, indicating that both the nickel alloy tubes and the catalytic active layer formed by high-temperature hydrogen reduction heat treatment can promote methane cracking.

[0051] Under similar short residence time conditions, iron-nickel metal materials generally exhibit higher methane conversion rates than inert corundum tubes, with differences in forming stability and high-temperature surface conditions among different materials. This result indicates that using a high-temperature resistant alloy as a tubular reaction channel and forming a catalytic active layer through high-temperature hydrogen reduction heat treatment can improve the methane short residence time cracking effect.

[0052] Table 1. Comparison of carbon black deposition rate under different inlet linear velocities

[0053] Table 1 is used to evaluate the effect of the inlet linear velocity of the methane-containing feed gas on the carbon black deposition rate. Under the same reaction conditions, the carbon black deposition rate decreases significantly with the increase of the inlet linear velocity. In particular, when the inlet linear velocity increases from 8 m / s to 10 m / s, the carbon black deposition rate decreases from 7.6% to 1.9%, indicating that controlling the inlet linear velocity to be no less than 10 m / s can significantly improve the gas's carrying capacity for cracked carbon black and reduce the continuous deposition of carbon black on the inner wall of the catalytic active material.

[0054] Table 2. Results of intra-group comparisons of different reaction pathways

[0055] Table 2 is used to evaluate the effects of reaction channel material and high-temperature hydrogen reduction activation treatment on methane cracking. Under the same reaction conditions, the methane conversion rate of the unactivated nickel alloy tube was 26 percentage points higher than that of the inert corundum tube, indicating that the nickel alloy tube has a promoting effect on methane cracking. The nickel alloy tube of the same material that underwent high-temperature hydrogen reduction activation treatment further increased the conversion rate by 30 percentage points compared with the unactivated nickel alloy tube, indicating that the catalytic active layer formed by the high-temperature hydrogen reduction heat treatment can further improve the degree of methane cracking.

[0056] Industrial Implementation During industrial scale-up, multiple tubular reaction channels can be connected in parallel within the same heating chamber. The inlets of each tube are connected through a distribution manifold, and the outlets of each tube are connected to the product cooling unit through a collection manifold. Each branch can be equipped with a flow regulating component to keep the flow rate and residence time in different tubes within a predetermined range.

[0057] The heating system can employ electric heating, feed gas combustion heating, or other indirect heating methods; the sensible heat of the pyrolysis products or the sensible heat of the combustion flue gas can be used for feed gas preheating via a heat exchanger. Gas-solid separation can be achieved using a combination of multi-stage cyclone separation and high-temperature resistant filtration, with carbon black collected under sealed conditions to minimize dust escape.

[0058] The technical concept of this invention lies in utilizing a high-temperature resistant nickel-containing alloy tube to simultaneously constitute a thermal decomposition reaction channel and a wall-mounted catalytic support. A catalytically active layer is formed on the inner wall of the tube through high-temperature hydrogen reduction heat treatment. Furthermore, by matching the diameter of the tubular reaction channel with the feed flow rate, the decomposition gas maintains a flow state capable of carrying the generated carbon black towards the outlet. Based on this, the use of multi-turn flow channels and short residence time further improves the heating efficiency and rapid decomposition effect within the limited heating space. The material grade, number of tube layers, heating method, and downstream purification method can be adjusted according to the processing scale.

[0059] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for the efficient and rapid thermal cracking of natural gas to prepare hydrogen and carbon black, characterized in that, Includes the following steps: S1. Provide a tubular pyrolysis reactor, wherein the tubular pyrolysis reactor is provided with a tubular reaction channel made of high-temperature resistant nickel alloy tube, and the inner diameter of the tubular reaction channel is not greater than 30mm. S2. A hydrogen-containing reducing atmosphere is introduced into the tubular reaction channel, and the inner wall of the tubular reaction channel is subjected to high-temperature hydrogen reduction heat treatment to reduce the surface oxide layer of the inner wall of the tube and remove the adhering substances, thereby exposing the nickel-containing active components on the surface of the inner wall of the tube and forming a catalytic active layer. S3. The preheated methane-containing feed gas is introduced into the tubular reaction channel. Under the condition that no oxidant is involved and no independent particulate catalyst is loaded, a thermal cracking reaction is carried out at 600-1200℃. The inlet linear velocity of the methane-containing feed gas when it enters the tubular reaction channel is not less than 10m / s, so that the generated carbon black is discharged from the tubular reaction channel with the cracked gas. S4. Cool and separate the discharged pyrolysis products into gas and solid components to obtain hydrogen-containing gas and carbon black. The tubular reaction channel simultaneously constitutes a thermal decomposition reaction channel and a wall-mounted catalyst support.

2. The method for preparing hydrogen and carbon black by efficient and rapid thermal cracking of natural gas according to claim 1, characterized in that, In step S1, the high-temperature resistant nickel-containing alloy is a nickel-containing heat-resistant austenitic stainless steel, an iron-nickel-based heat-resistant alloy, or a nickel-based heat-resistant alloy.

3. The method for preparing hydrogen and carbon black by efficient and rapid thermal cracking of natural gas according to claim 1, characterized in that, In step S1, the tubular reaction channel is a multi-turn tubular structure.

4. The method for preparing hydrogen and carbon black by efficient and rapid thermal cracking of natural gas according to claim 1, characterized in that, After the inner wall of the tubular reaction channel is subjected to high-temperature hydrogen reduction heat treatment, the nickel-containing components on the inner wall surface are exposed, and a catalytic active layer containing dispersed nickel-containing active sites is formed. The catalytic active layer has a micro-uneven structure.

5. The method for preparing hydrogen and carbon black by efficient and rapid thermal cracking of natural gas according to claim 1, characterized in that, In step S2, the hydrogen-containing reducing atmosphere is composed of hydrogen and nitrogen; the tubular reaction channel is heated to 400-600°C and kept at that temperature for 1-6 hours.

6. The method for preparing hydrogen and carbon black by efficient and rapid thermal cracking of natural gas according to claim 1, characterized in that, In step S3, the sulfur content in the methane-containing feed gas entering the tubular reaction channel is no higher than 1000 ppm, and the moisture content is less than 500 ppm.

7. The method for preparing hydrogen and carbon black by efficient and rapid thermal cracking of natural gas according to claim 1, characterized in that, In step S3, the methane-containing feed gas is preheated using a heat exchanger. The heat exchanger receives the high-temperature pyrolysis products discharged from the tubular pyrolysis reactor or the combustion flue gas discharged from the heating system to preheat the methane-containing feed gas before it enters the tubular reaction channel.

8. The method for preparing hydrogen and carbon black by efficient and rapid thermal cracking of natural gas according to claim 1, characterized in that, In step S3, a high-temperature pyrolysis reaction is carried out in the tubular reaction channel, and the resulting pyrolyzed carbon black is spherical or near-spherical particles.

9. An apparatus for producing hydrogen and carbon black from natural gas through efficient and rapid thermal cracking according to any one of claims 1 to 8, characterized in that, It includes a raw material pretreatment unit, a raw material preheater, a tubular pyrolysis reactor, a product cooling unit, a gas-solid separation unit, and a heating system; the raw material pretreatment unit, the raw material preheater, the tubular pyrolysis reactor, the product cooling unit, and the gas-solid separation unit are connected in sequence. The tubular pyrolysis reactor includes a heating chamber and a tubular reaction channel disposed within the heating chamber. The inner wall of the tubular reaction channel has a catalytically active layer formed by high-temperature hydrogen reduction heat treatment. The raw material preheater is connected to the inlet of the tubular reaction channel and is used to preheat the methane-containing raw material gas before sending it into the tubular reaction channel. The gas-solid separation unit is connected to the outlet of the tubular reaction channel and is used to perform gas-solid separation of hydrogen-containing gas and carbon black pyrolysis products. It is equipped with a hydrogen-containing gas outlet and a carbon black outlet. The heating system is used to maintain the pyrolysis temperature in the heating chamber by means of combustion heating of raw gas or electric heating.

10. The apparatus for efficient and rapid thermal cracking of natural gas to produce hydrogen and carbon black according to claim 9, characterized in that, The tubular reaction channel includes a first tubular layer and a second tubular layer arranged adjacent to each other along the stacking direction. Each of the first tubular layer and the second tubular layer includes multiple straight pipe segments that are parallel to each other and bent pipe segments that connect adjacent straight pipe segments. The bent pipe segments in the first tubular layer and the bent pipe segments in the second tubular layer are staggered along the stacking direction and at least partially overlap in the orthographic projection direction. The gas-solid separation unit includes a cyclone separator, and the raw material preheater includes a heat exchanger. The heat exchanger is provided with a raw material gas channel and a pyrolysis product heat exchange channel. The raw material gas channel is connected to the inlet of the tubular reaction channel, and the pyrolysis product heat exchange channel is connected to the pyrolysis product outlet of the tubular pyrolysis reactor. When the heating system adopts a raw material gas combustion heating method, the heat exchanger is also provided with a combustion flue gas heat exchange channel, which is connected to the combustion flue gas outlet of the heating system.

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