Natural gas pyrolysis hydrogen production complete equipment

Abstract

The application discloses natural gas pyrolysis hydrogen production complete equipment, belongs to natural gas hydrogen production equipment technical field. The equipment includes integratedly arranged pipe type cracking reactor, carbon black separation unit, carbon black backflow combustion unit, combustion heat supply unit and heat exchange unit on the same installation base; the pipe type cracking reactor includes multiple groups of parallelly arranged nickel-containing metal cracking pipes, gas inlet distribution structure and outlet collection structure; the carbon black separation unit is communicated with the outlet collection structure and is used for separating carbon black in the cracking gas; the carbon black backflow combustion unit is communicated with the carbon black separation unit and a combustion chamber and is used for enabling part of the cracking gas to carry separated carbon black into the combustion chamber to be combusted for heat supply; the heat exchange unit utilizes cracking gas waste heat to preheat raw material natural gas and utilizes combustion flue gas waste heat to preheat combustion air. The application realizes integration of natural gas pyrolysis, carbon black separation and reuse and waste heat recovery, and is favorable for improving equipment integration and continuous operation stability.

Description

Technical Field

[0001] This invention relates to the field of natural gas hydrogen production equipment technology, specifically to a complete set of equipment for natural gas pyrolysis hydrogen production. Background Technology

[0002] Hydrogen, as a clean energy carrier, has broad application prospects in fuel cells, transportation, and distributed power generation. Existing hydrogen production technologies mainly include natural gas steam reforming, coal gasification, and water electrolysis. Among them, natural gas steam reforming technology is relatively mature, but it usually requires large-scale reaction, heat exchange, conversion, and carbon treatment equipment, and it produces a certain amount of carbon dioxide during the hydrogen production process, which is not conducive to meeting the needs of small-scale, distributed, and low-carbon hydrogen use scenarios. Direct pyrolysis of natural gas is a hydrogen production route that decomposes methane in natural gas under high-temperature conditions to produce hydrogen and solid carbon. Its main reaction can be represented as CH4→C+2H2. Compared with natural gas steam reforming, the main reaction product of direct pyrolysis of natural gas is not mainly carbon dioxide, and the by-product solid carbon has the potential for further resource utilization, thus having certain application value for low-carbon hydrogen production.

[0003] However, direct pyrolysis of natural gas typically requires high temperatures, placing stringent demands on reactor materials, reaction channel structures, and heating methods. Furthermore, carbon black particles generated during pyrolysis are easily carried into subsequent pipelines and equipment along with the pyrolysis gas. If these particles cannot be separated from the pyrolysis gas in a timely manner, it can easily lead to pipeline blockage, decreased heat exchange performance, or unstable operation of subsequent gas processing units. For carbon black particles of different size ranges, a single separation structure often struggles to balance processing flow rate and fine particle capture effectiveness, affecting the continuous operational stability of the unit. In addition, direct pyrolysis of natural gas is an endothermic process, requiring continuous heating to maintain the pyrolysis reaction temperature. If relying primarily on external fuel or electric heating, the system energy consumption will be high. If the waste heat in the high-temperature pyrolysis gas and combustion flue gas is not utilized effectively, energy efficiency will also decrease.

[0004] Therefore, there is an urgent need to provide a complete set of equipment for hydrogen production from natural gas pyrolysis to improve the problems of the dispersed setting of reaction, carbon black treatment and heating units in the existing natural gas pyrolysis hydrogen production equipment, the difficulty of continuous carbon black transportation, and the insufficient utilization of waste heat from cracking gas and combustion flue gas. Summary of the Invention

[0005] The present invention aims to provide a complete set of equipment for hydrogen production by natural gas pyrolysis, in order to solve the problems of the independent operation of the cracking reaction, carbon black separation and combustion heating units in the existing natural gas pyrolysis hydrogen production equipment, the difficulty in continuous separation and transportation of fine carbon black particles, the large space occupied by the equipment, and the difficulty in separately recovering and utilizing the heat in the cracked gas and the combustion flue gas.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution.

[0007] This invention provides a complete set of equipment for hydrogen production from natural gas pyrolysis, including a tubular pyrolysis reactor, a carbon black separation unit, a carbon black reflux combustion unit, a combustion heating unit, and a heat exchange unit. The tubular pyrolysis reactor includes a combustion chamber, multiple sets of parallel pyrolysis pipes made of nickel-containing metal material, an inlet distribution structure, and an outlet collection structure. The carbon black separation unit is connected to the outlet collection structure, and the carbon black reflux combustion unit is connected to both the carbon black separation unit and the combustion chamber. The heat exchange unit forms a first heat exchange path between the pyrolysis gas and the raw material natural gas, and a second heat exchange path between the combustion flue gas and the combustion air.

[0008] The tubular pyrolysis reactor includes a combustion chamber, multiple sets of parallel-connected pyrolysis pipes, an inlet distribution structure, and an outlet collection structure. The multiple sets of pyrolysis pipes are arranged in parallel within the combustion chamber. The inlet distribution structure delivers the preheated feedstock natural gas to each pyrolysis pipe, and the outlet collection structure collects the pyrolysis gas output from each pyrolysis pipe and delivers it to the heat exchange unit. Thus, multiple parallel reaction channels can be formed within the limited space of the combustion chamber, and the heat generated in the combustion chamber can be transferred from the outside of each pyrolysis pipe to the feedstock natural gas inside the pipe.

[0009] The carbon black separation unit includes multiple cyclone separators connected in series to separate carbon black particles in the pyrolysis gas step by step. Along the flow direction of the pyrolysis gas, the structural dimensions of the subsequent cyclone separator are smaller than those of the preceding cyclone separator, so that carbon black particles of different particle sizes can be separated separately. The solid phase outlet of each cyclone separator can be connected to the carbon black collection and conveying bin, and the gas phase outlet of the final cyclone separator is connected to a water washing device. The water washing device further captures the fine carbon black remaining in the pyrolysis gas after cyclone separation, thereby achieving efficient carbon black removal.

[0010] The carbon black reflux combustion unit is connected to the carbon black separation unit and is used to receive the pyrolysis gas after being processed by the carbon black separation unit. Part of the pyrolysis gas is transported as reflux pyrolysis gas to the carbon black collection and conveying bin, so that the reflux pyrolysis gas carries the carbon black into the combustion chamber. The reflux pyrolysis gas serves as both a carbon black conveying medium and participates in combustion and heating together with the carbon black it carries.

[0011] The heat exchange unit includes a first heat exchange structure and a second heat exchange structure. The first heat exchange structure is located between the outlet of the pyrolysis tube and the carbon black separation unit, and is used to exchange heat between the high-temperature pyrolysis gas and the raw material natural gas before entering the pyrolysis tube, and to recover the sensible heat in the high-temperature pyrolysis gas and carbon black. The second heat exchange structure is located between the flue gas outlet of the combustion chamber and the combustion air inlet, and is used to exchange heat between the combustion flue gas and the combustion air. The two heat exchange paths are isolated from each other, so that the pyrolysis gas and the combustion flue gas transfer heat to the raw material natural gas and the combustion air, respectively.

[0012] It should be noted that the sensible heat recovery channel of the pyrolysis gas adopts a straight-through large-diameter structure, and there are no baffles, fine-pore filters or local diameter reduction sections to block the passage of pyrolysis gas and carbon black particles along the flow direction of the pyrolysis gas; the minimum flow cross-sectional area of ​​the pyrolysis gas channel is not less than the minimum flow cross-sectional area of ​​the pyrolysis gas collecting pipe connected to it, so that the carbon black carried by the pyrolysis gas can pass through the pyrolysis gas channel with the airflow and enter the subsequent carbon black separation unit.

[0013] The pyrolysis gas-natural gas preheater is equipped with a backflush port and a carbon discharge port that are connected to the pyrolysis gas channel. When the equipment is shut down, switched, or when the pressure difference in the pyrolysis gas channel is detected to reach the set value, nitrogen or purified pyrolysis gas is introduced through the backflush port to remove the loose carbon black adhering to the heat exchange wall and discharge it through the carbon discharge port or the pyrolysis gas outlet.

[0014] During normal operation, the cracked gas channel and its heat exchange wall are maintained above the dew point temperature of the moisture and condensable components in the cracked products, so that the carbon black particles pass through the heat exchanger in a dry state with the cracked gas, reducing the possibility of carbon black adhering to the deposit layer; therefore, the cracked gas-natural gas preheater can allow carbon black particles to pass through continuously while preheating the raw material natural gas, without undertaking the function of carbon black filtration or interception.

[0015] Furthermore, the equipment also includes a pretreatment unit, which includes a pre-decarbonization unit. The raw material natural gas first enters the pre-decarbonization unit and comes into contact with the absorbent liquid. The decarbonized raw material natural gas enters the first heat exchange path. The rich liquid after absorbing carbon dioxide is transported to the regenerator by a circulating pump. The regenerator is placed at the flue gas outlet and is regenerated by heating with flue gas. The resulting lean liquid is returned to the absorber for recycling.

[0016] By setting up the pre-decarbonization unit, the carbon dioxide content in the feedstock natural gas entering the cracking pipe can be reduced, thereby reducing the possibility of carbon dioxide reacting with methane under high temperature conditions and forming carbon monoxide in the cracked gas.

[0017] Furthermore, the intake distribution structure includes an intake main pipe and multiple intake branch pipes, each of which is connected to a set of pyrolysis pipes; the outlet collection structure includes multiple outlet branch pipes and a pyrolysis gas collection pipe, each of which is connected to a set of pyrolysis pipes, and the pyrolysis gas output from the multiple outlet branch pipes merges in the pyrolysis gas collection pipe.

[0018] Furthermore, the pyrolysis tubes are arranged at intervals along the width of the combustion chamber, forming a combustion gas flow gap between adjacent pyrolysis tubes, allowing high-temperature combustion gas to flow through the outer periphery of each pyrolysis tube. It should be noted that the inner wall of the pyrolysis tube undergoes high-temperature heat treatment, mainly to remove any residues remaining on the inner wall surface during processing, bending, welding, and storage, and to stabilize the inner wall surface of the pyrolysis tube under high-temperature conditions. The inner wall of the pyrolysis tube after high-temperature heat treatment forms a nickel-containing contact surface, and the raw material natural gas directly contacts the nickel-containing contact surface and is thermally pyrolyzed after entering the pyrolysis tube.

[0019] Before the equipment is put into operation for the first time, the pyrolysis tube is placed at a high temperature of 700°C and maintained for a preset time of 10 hours to remove the processing residues and thermally decomposable deposits on the inner wall surface of the pyrolysis tube. After the high temperature heat treatment is completed and cooled, the pyrolysis tube is checked for air tightness and purged with inert gas. Then, the raw material natural gas that has been decarbonized and preheated is introduced and the temperature is gradually increased to enter the natural gas pyrolysis operation state.

[0020] Furthermore, the flow resistance of each intake branch pipe is the same or similar, so that the flow rate of raw natural gas entering each cracking pipe is relatively balanced; the outlet collection structure is set at the end of the cracking pipe away from the intake distribution structure, so as to reduce the possibility of cracked gas backflow and mutual interference between different cracking pipes.

[0021] Furthermore, each stage of the cyclone separator includes a cylinder, a cone, a tangential inlet, an exhaust pipe, and a solid phase outlet. The pyrolysis gas enters the cylinder through the tangential inlet and forms a rotating airflow. The carbon black particles move towards the inner wall of the cylinder under centrifugal force and enter the solid phase outlet along the cylinder and cone. The separated gas enters the next stage cyclone separator through the exhaust pipe.

[0022] Furthermore, along the flow direction of the cracked gas, the dimensions of the cylinder, tangential inlet, and exhaust pipe of the subsequent cyclone separator are all smaller than the corresponding dimensions of the adjacent preceding cyclone separator, so that the preceding cyclone separator preferentially separates relatively large carbon black particles, and the subsequent cyclone separator further separates relatively small carbon black particles.

[0023] In one embodiment, the multi-stage cyclone separator adopts a three-stage series structure; in other embodiments, the number of stages of the cyclone separator is set according to the raw gas flow rate, carbon black concentration and target dust content.

[0024] Furthermore, the washing device includes a washing container, an air inlet pipe, and an air outlet pipe; the lower end of the air inlet pipe extends below the surface of the washing liquid, so that the pyrolysis gas discharged from the final cyclone separator enters the washing liquid in the form of bubbles. The operating parameters of the washing device are set according to the residual carbon black content in the pyrolysis gas after the final cyclone separation and the allowable dust content downstream; the air inlet of the air outlet pipe is located above the surface of the washing liquid, and the treated pyrolysis gas enters the carbon black reflux combustion unit through the air outlet pipe.

[0025] It should be noted that a demister is provided at the gas phase outlet of the water washing device. The demister can be a wire mesh demister, a baffle demister, or a cyclone demister, used to intercept liquid droplets entrained in the pyrolysis gas after water washing. The pyrolysis gas after water washing is discharged through the outlet pipe after being treated by the demister, so that the pyrolysis gas entering the carbon black reflux combustion unit does not contain visible free liquid droplets.

[0026] Furthermore, the washing container is equipped with a liquid replenishment port, a liquid drain port, and a liquid level detection device to replenish or replace the washing liquid and maintain the washing liquid level within a set range.

[0027] Furthermore, the carbon black collection and conveying chamber is equipped with multiple carbon black inlets, conveying gas inlets, and carbon black outlets; the solid phase outlets of each stage of the cyclone separator are respectively connected to the corresponding carbon black inlets, the reflux branch is connected to the conveying gas inlet, and the carbon black outlet is connected to the reflux fuel inlet of the combustion disc via the carbon black conveying pipe.

[0028] When the equipment is running, the dry carbon black separated by each stage of cyclone separator enters the carbon black collection and conveying chamber under the action of gravity; the carbon black reflux combustion unit conveys part of the separated cracked gas to the reflux branch, and the reflux cracked gas enters the carbon black collection and conveying chamber through the conveying gas inlet, and carries the carbon black into the carbon black outlet when it flows through the carbon black accumulation area at the bottom of the chamber, and is then conveyed to the combustion chamber through the carbon black conveying pipe.

[0029] Using pyrolysis gas as the carbon black conveying medium can eliminate the need for a screw conveyor and other mechanical conveying structures with moving seals between the carbon black collection and conveying chamber and the combustion chamber, and reduce the introduction of external conveying gases unrelated to the combustion process; the combustible components in the reflux pyrolysis gas participate in combustion together with the carbon black it carries, so as to provide heat for the natural gas pyrolysis process in the pyrolysis pipe.

[0030] Furthermore, the combustion heating unit includes a combustion plate, multiple combustion nozzles, a start-up gas inlet, a return fuel inlet, and a combustion air inlet; the multiple combustion nozzles are spaced apart on the combustion plate to disperse the fuel and combustion air into the combustion chamber and reduce the possibility of heat concentrating in localized cracking tubes.

[0031] Furthermore, a temperature detection device is provided in the combustion chamber, a reflux regulating valve is provided in the reflux branch, a combustion supplement regulating valve is provided in the start-up gas inlet, and the controller is connected to the temperature detection device, the reflux regulating valve and the combustion supplement regulating valve respectively.

[0032] The controller adjusts the reflux regulating valve and the combustion regulating valve according to the detection results of the temperature detection device. When the detected temperature in the combustion chamber decreases, the controller first increases the opening of the reflux regulating valve to increase the supply of reflux pyrolysis gas and the carbon black it carries. If the combustion chamber temperature does not recover to the set temperature within a preset time, the combustion regulating valve is opened to supplement the heat supply. When the combustion chamber temperature recovers and remains stable, the combustion regulating valve is reduced or closed to restore the equipment to the operating state where the heat supply is mainly provided by the combustion of reflux pyrolysis gas and carbon black.

[0033] Furthermore, the first heat exchange path has mutually isolated cracked gas channels and feed gas channels; high-temperature cracked gas enters the cracked gas channel, and decarbonized feed gas enters the feed gas channel, and the two exchange heat through heat exchange walls; the heat-exchanged cracked gas enters the carbon black separation unit, and the heat-exchanged feed gas enters the intake distribution structure.

[0034] Furthermore, the second heat exchange path has a flue gas passage and a combustion air passage that are isolated from each other; the flue gas discharged from the combustion chamber enters the flue gas passage, the external combustion air enters the combustion air passage, and the preheated combustion air is delivered to the combustion plate.

[0035] The first and second heat exchange paths are independent of each other to reduce the possibility of mixing between the cracked gas and the combustion flue gas, and to ensure that the raw material natural gas and the combustion air obtain preheating temperatures suitable for subsequent cracking and combustion.

[0036] The pyrolysis tube adopts a tube diameter with a suitable flow rate; a smaller inner diameter is beneficial to increase the specific surface area of ​​the reaction channel and improve heat exchange, but an inner diameter that is too small will increase the gas flow resistance and the risk of carbon black blockage; an inner diameter that is too large will reduce the flow rate of the raw material natural gas, which is not conducive to the discharge of carbon black with the gas flow; therefore, the inner diameter of the pyrolysis tube can be selected within the above range in combination with the flow rate of the raw material natural gas to take into account gas flow, heat exchange and carbon black discharge.

[0037] Along the flow direction of the cracked gas, the diameter of the cylinder of the subsequent cyclone separator is smaller than that of the adjacent preceding cyclone separator. The specific diameter depends on the carbon black particle size distribution, and is generally 60% to 80% of the diameter of the cylinder of the adjacent preceding cyclone separator. The preceding cyclone separator is used to preferentially separate carbon black particles with relatively large particle sizes. The subsequent cyclone separator further separates carbon black particles with relatively small particle sizes by reducing the size of the cylinder and the inlet and outlet structures, thereby enhancing the airflow rotation intensity and centrifugal separation effect.

[0038] Before entering the cracking tube, the raw natural gas is preheated to 500-700°C in a preheating section. The cracking tube then undergoes a high-temperature cracking reaction at 700-1300°C. By preheating the raw natural gas, the sensible heat required for the raw natural gas to rise to the reaction temperature in the cracking tube can be reduced, and the heating process can be shortened.

[0039] The amount of refluxed cracked gas is adjusted according to the combustion chamber temperature, carbon black collection amount, and product gas demand. Under normal operating conditions, the amount of refluxed cracked gas accounts for 1% to 20% of the total output gas of the carbon black reflux combustion unit. The specific reflux ratio is determined according to the carbon black characteristics, carbon black collection amount, and combustion chamber temperature. When the internal reflux heating is insufficient to restore the combustion chamber to the set temperature, external natural gas supplementary combustion is started.

[0040] The heat exchange area of ​​the cracked gas-natural gas preheater and the heat exchange area of ​​the flue gas-air preheater are determined according to the gas flow rate; the pipe diameter, heat exchange length and coiling spacing of the heat exchange tubes are set according to the raw material natural gas flow rate, cracked gas outlet temperature, combustion air flow rate and heat exchange load.

[0041] Compared with the prior art, the present invention can achieve the following beneficial effects: 1. This invention distributes raw natural gas to multiple sets of parallel cracking pipes through an intake distribution structure, and collects the cracked gas output from each cracking pipe through an outlet collection structure. This increases the number of reaction channels and heat exchange area per unit installation space, which is beneficial for the miniaturization and integration of equipment.

[0042] 2. The present invention reduces the structural dimensions of the multi-stage cyclone separator step by step along the direction of pyrolysis gas flow, so that each stage of the cyclone separator can separate carbon black particles of different particle size ranges, and further capture residual fine carbon black through the end water washing device.

[0043] 3. This invention utilizes the partially separated pyrolysis gas as a carbon black conveying medium, allowing the refluxed pyrolysis gas to carry the separated carbon black into the combustion chamber, thereby simultaneously achieving carbon black conveying and fuel reuse, and reducing the need for independent mechanical conveying structures.

[0044] 4. This invention utilizes high-temperature pyrolysis gas to preheat the raw material natural gas and uses combustion flue gas to preheat the combustion air, so that the two waste heats are used for the corresponding process steps, which helps to reduce the external heat supply required to maintain the pyrolysis reaction temperature.

[0045] 5. All functional units are integrated on the same base, and the units are connected by pipelines, which facilitates overall transportation, on-site installation and maintenance. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the process flow of the complete set of equipment for hydrogen production from natural gas pyrolysis according to the present invention; Figure 2This is a schematic diagram of the tubular pyrolysis reactor of the present invention; Figure 3 (a) is a schematic diagram of the cyclone separator of the present invention. Figure 3 (b) is a schematic diagram of the connection structure of the multi-stage cyclone separator, water washing device and carbon black collection and conveying bin of the present invention; Figure 4 This is a schematic diagram of the intake distribution structure of the present invention; Figure 5 This is a schematic diagram of the structure of the pyrolysis tube of the present invention; Figure 6 This is a schematic diagram of the combustion nozzle of the present invention.

[0047] In the diagram: 1. First air preheating pipeline; 2. Second air preheating pipeline; 3. Insulation cotton; 4. Natural gas inlet pipe; 5. Cold water pipe; 6. Preheated air outlet; 7. Combustion pan; 8. Start-up gas inlet; 9. Return fuel inlet; 10. Cracking gas outlet; 11. Combustion nozzle; 12. Cracking gas outlet pipe; 13. Combustion chamber; 14. Outlet collection structure; 15. Cracking pipe; 16. Combustion flue gas outlet; 17. First-stage cyclone separator; 18. Second-stage cyclone separator; 19. Third-stage cyclone separator; 20. Carbon black collection and conveying bin; 21. Water washing device. Detailed Implementation

[0048] 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.

[0049] Example 1 This embodiment provides a complete set of equipment for hydrogen production from natural gas pyrolysis, including a pre-decarbonization unit, a heat exchange unit, a tubular pyrolysis reactor, a carbon black separation unit, a carbon black reflux combustion unit, and a combustion heating unit. In this embodiment, each functional unit is integrated on a base, and the base is provided with a connection structure for transportation and installation to form a skid-mounted equipment structure.

[0050] The base is equipped with multiple mounting seats, on which the tubular pyrolysis reactor, carbon black separation unit, carbon black reflux combustion unit, combustion heating unit, and heat exchange unit are respectively fixed. A centralized pipeline interface is provided on the side of the base, which includes a natural gas inlet, a product gas outlet, a combustion air inlet, a flue gas outlet, and a cooling medium interface. A forklift groove is provided at the bottom of the base, or a lifting connection part is provided at the edge of the base, to facilitate the overall transportation of the equipment, on-site transfer, and rapid pipe connection and installation.

[0051] The pre-decarbonization unit is located between the natural gas feed pipeline and the cracked gas-natural gas preheater, and includes an absorber, a regenerator, a circulating pump, and a regeneration heating component.

[0052] The absorber is equipped with an amine absorbent liquid; the raw natural gas enters the absorber through the raw gas inlet and comes into contact with the absorbent liquid, at least part of the carbon dioxide in the raw natural gas is absorbed by the absorbent liquid; the decarbonized raw natural gas is discharged from the purified gas outlet of the absorber and enters the cracked gas-natural gas preheater.

[0053] In one embodiment, the absorbent is an aqueous solution of methyldiethanolamine, wherein the mass concentration of the aqueous solution of methyldiethanolamine is 40%.

[0054] The rich solution after absorbing carbon dioxide is pumped to the regenerator and heated to 100-120°C in the regenerator for regeneration; the lean solution obtained after regeneration is returned to the absorber for recycling.

[0055] Using a pre-decarbonization unit can reduce the carbon dioxide content in the feedstock natural gas entering the cracking pipe 15, thereby reducing the possibility of carbon dioxide reacting with methane at high temperatures to form carbon monoxide.

[0056] like Figure 2 , Figure 4 and Figure 5 As shown, the tubular pyrolysis reactor includes a combustion chamber 13, multiple sets of pyrolysis pipes 15 arranged in parallel within the combustion chamber 13, an air inlet distribution structure, and an outlet collection structure 14.

[0057] Multiple sets of pyrolysis tubes 15 are arranged laterally at intervals along the combustion chamber 13. A flow gap is formed between adjacent pyrolysis tubes 15 to allow high-temperature combustion gas to pass through, so that the high-temperature gas generated by combustion can flow through the outer periphery of each pyrolysis tube 15 and transfer heat to the raw material natural gas in the pyrolysis tube 15.

[0058] The intake distribution structure includes an intake main pipe and multiple intake branch pipes, each of which is connected to the intake end of a set of cracking pipes 15. After the preheated raw material natural gas enters the intake main pipe, it enters the corresponding cracking pipes 15 through the multiple intake branch pipes. The outlet collection structure 14 includes multiple outlet branch pipes and a cracked gas collection pipe. Each outlet branch pipe is connected to the outlet end of the corresponding cracking pipe 15. The cracked gas output from each cracking pipe 15 enters the cracked gas collection pipe through the outlet branch pipe and is transported to the cracked gas outlet 10 located at the outlet end of the cracked gas outlet pipe 12 through the cracked gas outlet pipe 12, and is output to the outside through the cracked gas outlet 10.

[0059] In this embodiment, the pyrolysis tube 15 is made of nickel-containing stainless steel. Before assembly, the pyrolysis tube 15 is subjected to high-temperature heat treatment at 700°C to remove the surface deposits on the inner wall of the tube, so that the inner wall of the tube after treatment can directly contact the raw material natural gas. The coiling diameter, number of coiling turns, spacing between adjacent tubes and length of the inlet branch pipe of the pyrolysis tube 15 are set according to the raw material gas processing volume and the internal space of the combustion chamber 13.

[0060] The heat exchange unit includes a cracked gas-natural gas preheater and a flue gas-air preheater.

[0061] The cracked gas-natural gas preheater forms the first heat exchange path. The first heat exchange path includes a cracked gas channel and a feed gas channel that are heat-isolated from each other. The high-temperature cracked gas output from the outlet collecting structure 14 enters the cracked gas channel, and the feed gas output from the pre-decarbonization unit enters the feed gas channel. The high-temperature cracked gas and the feed gas exchange heat through the heat exchange wall. The cracked gas after heat exchange enters the carbon black separation unit, and the preheated feed gas enters the intake distribution structure.

[0062] The flue gas-air preheater forms the second heat exchange path; the second heat exchange path includes a flue gas passage and a combustion air passage that are heat-isolated from each other. The combustion flue gas discharged from the combustion chamber 13 enters the flue gas passage, and the external combustion air enters the combustion air passage. The combustion flue gas and the combustion air exchange heat through the heat exchange wall, and the preheated combustion air is delivered to the combustion plate 7; the first heat exchange path and the second heat exchange path are independent of each other.

[0063] The pyrolysis gas-natural gas preheater adopts a shell-and-tube heat exchange structure, which has a pyrolysis gas channel and a feed gas channel that are isolated from each other by heat exchange walls. The pyrolysis gas channel is connected between the outlet collection structure 14 and the carbon black separation unit, and the feed gas channel is connected between the pre-decarbonization unit and the inlet distribution structure.

[0064] In this embodiment, the heat exchange area of ​​the pyrolysis gas-natural gas preheater is 0.022 m². 2 When the high-temperature pyrolysis gas flows through the pyrolysis gas channel, it transfers heat to the raw natural gas in the raw material gas channel, preheating the raw natural gas to 500-700℃.

[0065] The flue gas-air preheater adopts a coiled heat exchange structure, with isolated flue gas passages and combustion air passages, and its heat exchange area is 0.1m². 2 The flue gas passage is connected to the combustion flue gas outlet 16 of the combustion chamber 13, and the outlet of the combustion air passage is connected to the combustion air inlet of the combustion plate 7. When the combustion flue gas flows through the flue gas passage, it preheats the combustion air, and the preheated combustion air enters the combustion plate 7. The diameter of the heat exchange tube, the heat exchange length, the winding spacing, and the installation position of the heat exchanger on the base are set according to the heat exchange load and the available space of the base.

[0066] like Figure 2 As shown, the tubular pyrolysis reactor is equipped with a first air preheating pipe 1 and a second air preheating pipe 2 on its outer side to form a preheating path for the combustion air, so that the waste heat of the combustion flue gas can be used to preheat the combustion air; the reactor is surrounded by heat insulation cotton 3 to reduce the heat loss of the reactor to the external environment; the natural gas inlet pipe 4 is used to transport raw material natural gas to the pyrolysis pipe 15; the outermost part of the reactor is equipped with a cold water pipe 5 to form a water-cooled structure and reduce the temperature of the outer wall of the reactor; the preheated combustion air is output from the preheated air outlet 6 and transported to the combustion heating unit.

[0067] like Figure 3 As shown in (b), the carbon black separation unit includes a first-stage cyclone separator 17, a second-stage cyclone separator 18 and a third-stage cyclone separator 19 connected in series, a water washing device 21 connected to the exhaust pipe of the third-stage cyclone separator 19, and a carbon black collection and conveying bin 20 connected to the solid phase outlet of each stage of the cyclone separator.

[0068] Each cyclone separator includes a cylinder, a cone located at the bottom of the cylinder, a tangential air inlet located on the side of the cylinder, an exhaust pipe located at the top of the cylinder, and a solid phase outlet located at the bottom of the cone.

[0069] The pyrolysis gas enters the first-stage cyclone separator 17 through the tangential inlet and forms a rotating airflow inside the cylinder. The carbon black particles with relatively large particle size and inertia move towards the inner wall of the cylinder under centrifugal force and enter the solid phase outlet along the cylinder and cone. The pyrolysis gas after preliminary separation enters the second-stage cyclone separator 18 through the exhaust pipe.

[0070] The second-stage cyclone separator 18 and the third-stage cyclone separator 19 perform subsequent separation of carbon black particles in the pyrolysis gas according to the same principle.

[0071] In this embodiment, the cylinder diameters of the first-stage cyclone separator 17, the second-stage cyclone separator 18, and the third-stage cyclone separator 19 are 12mm, 8mm, and 6mm, respectively.

[0072] By gradually reducing the structural dimensions of the cyclone separator along the direction of pyrolysis gas flow, the first-stage cyclone separator 17 mainly separates relatively large carbon black particles. Subsequent cyclone separators enhance the airflow rotation effect through smaller structural dimensions, thereby improving the separation of finer carbon black particles.

[0073] In this embodiment, as Figure 3As shown in (a), the cyclone separator includes a cylinder, a cone, a tangential air inlet, an exhaust pipe, and a solid phase outlet. Here, D1 represents the cylinder diameter, Hc1 represents the cone height, b1 represents the tangential air inlet width, a1 represents the tangential air inlet height, Hc2 represents the cylinder height, H1 represents the total height of the cyclone separator, δ1 represents the diameter of the ash discharge port at the solid phase outlet, d1 represents the exhaust pipe diameter, e2 represents the exhaust pipe insertion depth, and e1 represents the length of the straight pipe section at the outlet. The above structural dimensions are matched and set according to the cracked gas processing flow rate, carbon black concentration, target separation particle size, and allowable pressure drop.

[0074] The exhaust pipe of the third-stage cyclone separator 19 is connected to the air inlet pipe of the water washing device 21; the lower end of the air inlet pipe extends below the surface of the washing liquid in the water washing device 21, so that the pyrolysis gas after the three-stage cyclone separation passes through the washing liquid in the form of bubbles.

[0075] The residual fine carbon black in the pyrolysis gas is further captured by the washing liquid, and the treated pyrolysis gas is discharged from the outlet pipe located above the surface of the washing liquid.

[0076] The washing device 21 is also equipped with a liquid replenishment port, a liquid drain port and a liquid level detection device, which are used to replenish or replace the washing liquid and maintain the washing liquid level within a predetermined range.

[0077] The carbon black collection and conveying silo 20 is equipped with multiple carbon black inlets, conveying gas inlets, and carbon black outlets.

[0078] The solid phase outlets of the first-stage cyclone separator 17, the second-stage cyclone separator 18, and the third-stage cyclone separator 19 are respectively connected to the corresponding carbon black inlets. The dry carbon black separated by each stage of the cyclone separator enters the carbon black collection and conveying bin 20 under the action of gravity.

[0079] The inlet of the carbon black reflux combustion unit is connected to the gas phase outlet of the water washing device 21, and has a product gas branch and a reflux branch; the product gas branch is used to output the separated cracked gas as product gas, and the reflux branch is connected to the conveying gas inlet of the carbon black collection and conveying bin 20; the carbon black outlet of the carbon black collection and conveying bin 20 is connected to the reflux fuel inlet 9 of the combustion pan 7 through the carbon black conveying pipe.

[0080] The reflux pyrolysis gas enters the carbon black collection and conveying chamber 20 through the conveying gas inlet and flows through the carbon black accumulation area inside the chamber; the reflux pyrolysis gas carries some dry carbon black into the carbon black outlet and is conveyed to the combustion chamber 13 through the carbon black conveying pipe.

[0081] Under normal operating conditions, the amount of refluxed pyrolysis gas accounts for 1% to 20% of the output gas of the carbon black reflux combustion unit; the reflux ratio can be adjusted according to the temperature of the combustion chamber 13 and the amount of carbon black collected.

[0082] Using reflux pyrolysis gas as the carbon black conveying medium can eliminate the need for the spiral conveying mechanism and moving sealing structure between the carbon black collection and conveying chamber 20 and the combustion chamber 13, and reduce the introduction of external conveying gases that do not participate in combustion.

[0083] The combustion heating unit includes a combustion plate 7 located at the bottom of the combustion chamber 13 and multiple combustion nozzles 11 spaced apart on the combustion plate 7; the combustion plate 7 is provided with a start-up gas inlet 8, a return fuel inlet 9 and a combustion air inlet.

[0084] During the start-up phase, external natural gas enters the combustion plate 7 through the start-up gas inlet 8 and mixes with the preheated combustion air. Then, it is injected into the combustion chamber 13 through multiple combustion nozzles 11 to preheat the combustion chamber 13 and the cracking pipe 15.

[0085] During normal operation, the reflux pyrolysis gas and the carbon black it carries enter the combustion pan 7 through the reflux fuel inlet 9, and after mixing with the combustion air, it is injected into the combustion chamber 13 through multiple combustion nozzles 11. The hydrogen, unreacted methane and other combustible components in the reflux pyrolysis gas participate in combustion together with the carbon black it carries, providing heat for the pyrolysis of natural gas in the pyrolysis tube 15.

[0086] Multiple combustion nozzles 11 are distributed at intervals along the combustion plate 7, so that the flame and high-temperature combustion gas are dispersed along the arrangement area of ​​the pyrolysis tube 15, reducing the possibility of combustion heat being concentrated in the local pyrolysis tube 15.

[0087] In this embodiment, pipeline natural gas with a methane volume fraction of approximately 95% is used as the feed gas.

[0088] When the equipment is started, external natural gas enters the combustion plate 7 through the start-up gas inlet 8, mixes with the combustion air, and is then injected into the combustion chamber 13 through the combustion nozzle 11, causing the combustion chamber 13 and the pyrolysis pipe 15 to gradually heat up.

[0089] Once the temperature inside the combustion chamber 13 reaches the predetermined start-up temperature, the raw material natural gas passes sequentially through the pre-decarbonization unit and the cracked gas-natural gas preheater, and then enters multiple sets of cracking pipes 15 through the intake distribution structure.

[0090] The raw material natural gas is preheated by the cracked gas-natural gas preheater and then enters the cracking pipe 15 for direct pyrolysis, forming cracked gas containing hydrogen, unreacted methane and carbon black particles.

[0091] The pyrolysis gas discharged from each pyrolysis pipe 15 is collected by the outlet collection structure 14 and enters the pyrolysis gas channel of the pyrolysis gas-natural gas preheater, and releases some heat to the raw material natural gas; the pyrolysis gas after heat exchange is then cooled according to the temperature resistance requirements of the carbon black separation unit and the water washing device 21.

[0092] The cooled pyrolysis gas sequentially enters the first-stage cyclone separator 17, the second-stage cyclone separator 18, and the third-stage cyclone separator 19, so that the carbon black particles are separated step by step. The pyrolysis gas after the three-stage cyclone separation enters the water washing device 21 and passes through the washing liquid in the form of bubbling.

[0093] The separated pyrolysis gas enters the carbon black reflux combustion unit, part of which is output as product gas, and the other part enters the reflux branch, carrying the dry carbon black in the carbon black collection and conveying bin 20 into the combustion chamber 13.

[0094] The heat generated by the reflux pyrolysis gas and carbon black combustion is used to maintain the pyrolysis of natural gas in the pyrolysis tube 15. The combustion flue gas is discharged after the combustion air is preheated by the flue gas-air preheater. The equipment is continuously operated until the temperature of the combustion chamber 13, the flow rate of the raw material gas, and the composition of the product gas tend to stabilize, and then sampling and testing are performed.

[0095] The gas composition of the raw material natural gas and the product gas was detected by gas chromatography. Samples were taken at the raw material gas inlet of the pyrolysis tube 15 and the gas phase outlet of the water washing device 21, and the methane conversion rate was calculated based on the molar flow rate of methane at the inlet and outlet.

[0096] The total molar flow rate of the inlet feed gas and the total molar flow rate of the outlet dry gas were measured using gas flow meters installed at the feed gas inlet of the pyrolysis tube and the gas phase outlet of the water washing device, respectively. The measured total molar flow rate was multiplied by the methane molar fraction determined by gas chromatography to obtain the inlet methane molar flow rate. and outlet unreacted methane molar flow rate .

[0097] methane conversion rate Calculate according to the following formula.

[0098]

[0099] The natural gas pyrolysis reaction is an endothermic reaction. During equipment operation, the carbon black reflux combustion unit introduces part of the separated cracked gas into the reflux branch. The refluxed cracked gas enters the carbon black collection and conveying bin, and carries the separated dry carbon black into the combustion chamber. The hydrogen, unreacted methane and other combustible components in the refluxed cracked gas are burned together with the carried carbon black to provide heat for the natural gas pyrolysis reaction in the cracking pipe.

[0100] Under normal operating conditions, the amount of reflux pyrolysis gas accounts for 1% to 20% of the total output of the carbon black reflux combustion unit. When the combustion chamber temperature is lower than the set operating range, the controller prioritizes increasing the amount of reflux pyrolysis gas, ensuring that the amount of reflux pyrolysis gas does not exceed 20% of the total output of the carbon black reflux combustion unit. If the combustion chamber temperature still does not recover after increasing the amount of reflux pyrolysis gas, the controller opens the supplementary combustion regulating valve to supplement heat through external natural gas. After the combustion chamber temperature recovers and remains stable, the controller closes the supplementary combustion regulating valve, allowing the equipment to return to an operating state where heating is mainly provided by reflux pyrolysis gas and carbon black combustion.

[0101] The cracked gas-natural gas preheater uses high-temperature cracked gas to preheat the raw material natural gas; the flue gas-air preheater uses combustion flue gas to preheat the combustion air; the above two waste heat utilization paths can reduce the external heat required for heating the raw material natural gas and preheating the combustion air; since the actual heating state is also affected by factors such as the composition of the raw material natural gas, the reflux flow rate of cracked gas, the amount of carbon black generated, the degree of carbon black combustion, the combustion efficiency and the heat dissipation of the equipment, the equipment maintains the operating temperature of the combustion chamber through the staged reflux and supplementary combustion control methods.

[0102] In one embodiment, when the hydrogen application scenario requires a high hydrogen gas integral number, the product gas branch can also be connected to a gas purification unit. The gas purification unit can use pressure swing adsorption, membrane separation, or a combination thereof to further purify the hydrogen-containing product gas discharged from the gas phase outlet of the water washing device 21.

[0103] The dust content of the outlet gas of the water washing device 21 was determined by the filter membrane weighing method, and the hydrogen gas integral in the outlet gas was determined by the dry basis normalized gas chromatography detection results.

[0104] Testing showed that the methane conversion rate in this embodiment was 98%, and the dust content of the gas exiting the water washing device 21 was less than 1 mg / m³. 3 The hydrogen component in the outlet gas is approximately 90%.

[0105] Example 2 Except for the material of the pyrolysis tube 15, the equipment structure and operating conditions of this embodiment are the same as those of Embodiment 1; in this embodiment, the pyrolysis tube 15 is made of high-nickel stainless steel.

[0106] The volume fraction of methane in the feedstock natural gas, the feedstock gas flow rate, the feedstock gas preheating temperature, the combustion chamber operating temperature, and the carbon black separation method were all the same as in Example 1.

[0107] After the equipment is running stably, the gas composition at the inlet of the pyrolysis tube 15 and the gas phase outlet of the water washing device 21 is detected according to the detection method described in Example 1.

[0108] The methane conversion rate was found to be 95%.

[0109] Example 3 This embodiment describes the graded control method for reflux cracked gas heating and external natural gas supplementary combustion, based on the equipment in Embodiment 1.

[0110] A temperature detection device is installed in the combustion chamber 13, a reflux regulating valve is installed on the reflux branch, and a supplementary combustion regulating valve is installed at the start-up gas inlet 8. The controller is electrically connected to the temperature detection device, the reflux regulating valve and the supplementary combustion regulating valve respectively.

[0111] When the equipment is started, the starting natural gas enters the combustion plate 7 through the starting gas inlet 8, and the blower supplies combustion air to the combustion air inlet, keeping the excess air coefficient α at 1.2; after electric spark ignition, the combustion chamber 13 gradually heats up.

[0112] During normal operation, the controller adjusts the reflux pyrolysis gas flow rate according to the detected temperature in the combustion chamber 13; when the detected temperature is lower than the target operating temperature, the reflux pyrolysis gas flow rate is increased, and when the detected temperature is higher than the target operating temperature, the reflux pyrolysis gas flow rate is decreased.

[0113] After the temperature in the combustion chamber 13 stabilizes, the controller closes the supplementary combustion regulating valve and reduces the opening of the reflux regulating valve according to the temperature in the combustion chamber 13, so that the equipment returns to the operating state mainly based on the reflux pyrolysis gas and carbon black combustion for heating.

[0114] Analysis of Experimental Results In Example 1, the cylinder diameters of the three-stage cyclone separators are 12mm, 8mm, and 6mm, respectively. The cylinder diameter ratio of the second-stage cyclone separator to the first-stage cyclone separator is [missing information].

[0115] D2 / D1×100%=8 / 12×100%≈66.7%.

[0116] The ratio of the cylinder diameter of the third-stage cyclone separator to that of the second-stage cyclone separator is [value missing].

[0117] D3 / D2×100%=6 / 8×100%=75%.

[0118] The fact that the diameter ratios of both stages are within the range of 60% to 80% indicates that the three-stage cyclone separator in this embodiment forms a continuous decreasing relationship in structural dimensions. This decreasing relationship allows the first-stage cyclone separator to have a relatively large processing space, which is used to preferentially separate carbon black particles with larger particle sizes and inertia. The second-stage cyclone separator, through its smaller cylinder and inlet / outlet dimensions, increases the airflow rotation effect within a unit space to further separate finer carbon black particles. The cyclone separation effect is also affected by factors such as inlet velocity, cylinder height, cone angle, exhaust pipe insertion depth, and flow distribution at each stage. Therefore, the cylinder diameter ratio should be set in conjunction with other structural and operating parameters.

[0119] In Example 1, after the pyrolysis gas passes through a three-stage cyclone separator and a water washing device 21 in sequence, the dust content of the gas exiting the water washing device 21 is less than 1 mg / m³. 3 The results show that the progressively smaller three-stage cyclone separator can remove most of the dry carbon black in the cracked gas first, and the end water washing device 21 can further capture the fine carbon black remaining after cyclone separation. The combination of multi-stage cyclone separation and water washing device avoids the problem that a single cyclone separator needs to take into account both large flow rate and fine particle separation effect at the same time, and also reduces the possibility of a large amount of carbon black directly entering the water washing device and causing rapid contamination of the washing liquid.

[0120] Since the dust content at the inlet of the first-stage cyclone separator 17 was not measured in this embodiment, the carbon black separation effect was evaluated based on the dust content of the gas exiting the water washing device 21, and the total carbon black separation efficiency was not calculated.

[0121] In Example 1, the hydrogen gas fraction in the outlet gas of the water washing device 21 was approximately 90%. This result indicates that the gaseous products formed after natural gas cracking are mainly composed of hydrogen, but still contain unreacted methane and other gaseous components originally present in the raw natural gas. The approximately 90% detection result in Example 1 represents the hydrogen gas fraction in the outlet gas of the water washing device 21 and does not indicate the hydrogen purity of the product after gas purification.

[0122] Cyclone separators and water washing devices are mainly used to remove carbon black particles, but cannot remove unreacted methane, nitrogen or other gaseous impurities.

[0123] In one embodiment, a gas purification unit is further provided on the product gas branch. The gas purification unit is a pressure swing adsorption unit, a membrane separation unit, or a combination thereof, used to increase the hydrogen gas fraction in the product gas according to the hydrogen usage scenario.

[0124] In Example 1, the raw natural gas is preheated to 500-700°C by the cracked gas-natural gas preheater before entering the cracking tube 15. The temperature of the cracked gas is reduced to about 200°C after heat exchange. This process shows that some of the heat in the high-temperature cracked gas is transferred to the raw natural gas to be cracked, reducing the sensible heat required for the raw natural gas to rise from room temperature to the cracking temperature in the cracking tube 15. At the same time, the combustion flue gas preheats the combustion air by the flue gas-air preheater, so that the residual heat of the combustion flue gas can be used to increase the temperature of the air entering the combustion chamber 13.

[0125] The two heat exchange paths are independent of each other; the waste heat of the cracked gas is used to preheat the raw material natural gas; the waste heat of the combustion flue gas is used to preheat the combustion air; this structure can prevent the cracked gas and the combustion flue gas from mixing and allow the heat of the two high-temperature gases to be used for their respective process steps.

[0126] Without conducting a complete heat balance measurement of the raw material gas inlet temperature, combustion air inlet and outlet temperatures, combustion flue gas flow rate, and external gas consumption, this embodiment is used to illustrate that the dual heat exchange path can achieve waste heat recovery, and does not quantitatively limit the self-heating degree of the system.

[0127] The carbon black reflux combustion unit introduces part of the separated pyrolysis gas into the carbon black collection and conveying chamber 20, so that the reflux pyrolysis gas flows through the carbon black accumulation area and carries the dry carbon black into the combustion chamber 13.

[0128] This path allows the reflux pyrolysis gas to serve two purposes simultaneously: it acts as both a pneumatic conveying medium for carbon black and a combustion fuel for heating, along with the carbon black it carries. Compared to using a screw conveyor to transport carbon black, this structure eliminates the need for a rotating shaft and dynamic sealing structure between the high-temperature combustion chamber 13 and the carbon black collection and conveying bin 20, which helps reduce drive and sealing maintenance issues under high-temperature and dusty conditions. When the reflux pyrolysis gas volume is maintained at 5%–10%, it can balance carbon black transport and product gas output. When the temperature of the combustion chamber 13 decreases, the controller can temporarily increase the reflux flow rate to improve the supply of internal combustible components and carbon black.

[0129] Example 3 adopts a control sequence that prioritizes internal reflux and then external natural gas supplementary combustion. When the temperature of combustion chamber 13 decreases, the controller first increases the supply of reflux pyrolysis gas and carbon black, giving priority to using the combustibles generated inside the equipment to maintain the pyrolysis temperature. Only when the temperature does not recover after the reflux flow is increased will external natural gas supplementary combustion be started. After the temperature recovers and stabilizes, the external natural gas supply will be shut off. This control method avoids immediately starting external supplementary combustion when the temperature of combustion chamber 13 fluctuates slightly, which helps to reduce the frequent start-stop of external gas and unnecessary consumption.

[0130] The above example is a set of control parameters used in this embodiment. The specific control threshold and delay time can be set according to the pyrolysis tube material, combustion chamber heat capacity and raw gas processing volume.

[0131] Based on the structures and test results of Examples 1-3, the following conclusions can be drawn.

[0132] Under the equipment structure and operating conditions described in Examples 1 and 2, the methane conversion rates reached 98% and 95%, respectively, indicating that the tubular pyrolysis reactor can achieve direct pyrolysis of natural gas. The three-stage cyclone separator adopts a progressively smaller cylindrical structure, and with the addition of an end-of-pipe water washing device, the dust content of the outlet gas can be reduced to below 1 mg / m³, indicating that the combination of cascade cyclone separation and water washing can continuously separate carbon black from the pyrolysis gas. The reflux pyrolysis gas can enter the carbon black collection and conveying bin and carry dry carbon black into the combustion chamber, so that the reflux pyrolysis gas can simultaneously serve as a carbon black conveying medium and combustion fuel, reducing the need for independent mechanical conveying mechanisms. The pyrolysis gas-natural gas preheater and the flue gas-air preheater recover the waste heat of the pyrolysis gas and the waste heat of the combustion flue gas, respectively, which can reduce the external heat required for heating the raw material natural gas and preheating the combustion air. By adopting a staged control method of first increasing the reflux pyrolysis gas and then starting the external natural gas for supplementary combustion, the pyrolysis gas and carbon black generated inside the equipment can be used to maintain the pyrolysis reaction temperature first, and external natural gas can be used to supplement the heat when the internal heat supply is insufficient.

[0133] It should be noted that the directional terms such as "front," "rear," "up," "down," "inner," and "outer" used in this embodiment are only used to illustrate the relative positional relationship between the components in conjunction with the accompanying drawings, and do not constitute a limitation on the installation direction of the equipment.

[0134] The number of cyclone separator stages, the number of pyrolysis tubes, the specific form of each heat exchange path, and the arrangement of each pipeline on the base in this invention can be adjusted according to the equipment's processing capacity and the site of use. As long as multiple sets of parallel pyrolysis tubes, a multi-stage cyclone separation structure with progressively smaller structural dimensions, reflux pyrolysis gas carrying carbon black for combustion heating, and two independent waste heat recovery paths are all implementations of the technical concept of this invention.

[0135] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. All equivalent substitutions, simple modifications, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A complete set of equipment for hydrogen production by natural gas pyrolysis, characterized in that, It includes a tubular pyrolysis reactor, a carbon black separation unit, a carbon black reflux combustion unit, a combustion heating unit, and a heat exchange unit; The tubular pyrolysis reactor includes a combustion chamber, multiple sets of parallel pyrolysis tubes made of nickel-containing metal material disposed in the combustion chamber, an air inlet distribution structure connected to the air inlet end of each pyrolysis tube, and an outlet collection structure connected to the air outlet end of each pyrolysis tube. The carbon black separation unit is connected to the outlet collection structure, and the carbon black reflux combustion unit is connected to both the carbon black separation unit and the combustion chamber. The heat exchange units respectively form a first heat exchange path between the cracked gas and the raw material natural gas, and a second heat exchange path between the combustion flue gas and the combustion air.

2. The complete set of equipment for hydrogen production from natural gas pyrolysis according to claim 1, characterized in that, It also includes a pretreatment unit, which includes a pre-decarbonization unit; the pre-decarbonization unit includes an absorber, a regenerator and a circulating pump, the raw gas inlet of the absorber is connected to the raw natural gas pipeline, the purified gas outlet of the absorber is connected to the first heat exchange path, the rich liquid outlet of the absorber is connected to the regenerator via the circulating pump, and the lean liquid outlet of the regenerator is connected to the absorbent inlet of the absorber.

3. The complete set of equipment for hydrogen production from natural gas pyrolysis according to claim 1, characterized in that, The pyrolysis pipes are arranged along the combustion chamber. The air intake distribution structure includes an air intake main pipe connected to the raw material natural gas pipeline and multiple air intake branch pipes respectively connected to the air intake main pipe and each of the pyrolysis pipes. The outlet collection structure includes multiple outlet branch pipes connected to the outlet end of each of the pyrolysis pipes and a pyrolysis gas collection pipe connected to the multiple outlet branch pipes.

4. The complete set of equipment for hydrogen production from natural gas pyrolysis according to claim 3, characterized in that, The pyrolysis tube is made of iron-nickel metal; the inner wall of the pyrolysis tube is heat-treated at high temperature; the preheating temperature of the raw material natural gas entering the pyrolysis tube is 500-700℃, and the reaction temperature inside the pyrolysis tube is 700-1300℃.

5. The complete set of equipment for hydrogen production from natural gas pyrolysis according to claim 1, characterized in that, The carbon black separation unit includes multiple cyclone separators connected in series. Each cyclone separator includes a cylinder, a cone, a tangential air inlet, an exhaust pipe, and a solid phase outlet. Along the flow direction of the pyrolysis gas, the cylinder diameter of the cyclone separator in the next stage is 60% to 80% of the cylinder diameter of the adjacent cyclone separator in the previous stage, and the structural dimensions of the tangential air inlet and exhaust pipe of the cyclone separator in the next stage are smaller than the corresponding structural dimensions of the adjacent cyclone separator in the previous stage.

6. The complete set of equipment for hydrogen production from natural gas pyrolysis according to claim 5, characterized in that, The carbon black separation unit also includes a water washing device, which includes a water washing container, an air inlet pipe, and an air outlet pipe. The air inlet end of the air inlet pipe is connected to the exhaust pipe of the final stage cyclone separator. The air outlet end of the air inlet pipe extends below the surface of the washing liquid in the water washing container, and the air inlet end of the air outlet pipe is located above the surface of the washing liquid, so that the pyrolysis gas after cyclone separation passes through the washing liquid in a bubbling manner.

7. The complete set of equipment for hydrogen production from natural gas pyrolysis according to claim 5, characterized in that, The carbon black separation unit further includes a carbon black collection and conveying chamber, which is equipped with a carbon black inlet, a conveying gas inlet, and a carbon black outlet connected to the solid phase outlet of each stage of the cyclone separator; the carbon black reflux combustion unit includes a reflux branch, which is connected to the conveying gas inlet, and the carbon black outlet is connected to the combustion chamber via a carbon black conveying pipe, so as to convey carbon black through reflux pyrolysis gas; the amount of reflux pyrolysis gas accounts for 1% to 20% of the total output gas of the carbon black reflux combustion unit under normal operating conditions.

8. The complete set of equipment for hydrogen production from natural gas pyrolysis according to claim 7, characterized in that, The combustion heating unit includes a combustion plate disposed at the bottom of the combustion chamber and a plurality of combustion nozzles spaced apart on the combustion plate. The combustion plate is respectively provided with a start-up gas inlet, a return fuel inlet and a combustion air inlet. The return fuel inlet is connected to the carbon black conveying pipe and the combustion air inlet is connected to the second heat exchange path.

9. The complete set of equipment for hydrogen production from natural gas pyrolysis according to claim 8, characterized in that, It also includes a temperature detection device and a controller. The temperature detection device is disposed in the combustion chamber. A reflux regulating valve is disposed on the reflux branch. A combustion supplement regulating valve is disposed at the start-up gas inlet. The controller is connected to the temperature detection device, the reflux regulating valve and the combustion supplement regulating valve respectively. The controller is used to increase the opening of the reflux regulating valve when the detected temperature in the combustion chamber is lower than the set temperature, and to open the combustion supplement regulating valve when the detected temperature has not recovered to the set temperature within a preset time.

10. The complete set of equipment for hydrogen production from natural gas pyrolysis according to claim 8, characterized in that, The heat exchange unit includes a pyrolysis gas-natural gas preheater and a flue gas-air preheater. The pyrolysis gas-natural gas preheater has a pyrolysis gas channel and a feed gas channel that are heat exchanged and isolated from each other. The flue gas-air preheater has a flue gas channel and a combustion air channel that are heat exchanged and isolated from each other. The pyrolysis gas channel is connected between the outlet collecting structure and the carbon black separation unit, and the combustion air channel is connected to the combustion air inlet of the combustion plate.

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