A method for conditioning natural gas acetylene feed gas, a method and system for producing acetylene

Abstract

The application discloses a natural gas acetylene raw material gas conditioning method, an acetylene preparation method and system, and belongs to the technical field of natural gas chemical industry. The conditioning method comprises the following steps: a first preheating step, in which raw material natural gas containing high carbon hydrocarbons is preheated to a first temperature; a mixing step, in which the preheated raw material natural gas is mixed with a first flexible oxidant; and a reaction step, in which the mixed raw material natural gas and the first flexible oxidant are subjected to catalytic reaction in a conditioning reactor, so that the high carbon hydrocarbons in the raw material natural gas are converted into low carbon hydrocarbons by reacting with the first flexible oxidant, and the conditioning raw material gas is obtained. The application can effectively solve the problems of early ignition of an acetylene cracking furnace caused by the thermal cracking of high carbon hydrocarbons in natural gas and the poor safety, high energy consumption and unadjustable components of by-product tail gas caused by pure oxygen oxidants in the prior art.

Description

Technical Field

[0001] This invention relates to the field of natural gas chemical technology, specifically to a conditioning method for natural gas acetylene feedstock, a method for producing acetylene, and a system thereof. Background Technology

[0002] Acetylene is an important basic organic chemical raw material, widely used in the production of pharmaceuticals, pesticides, dyes, coatings, fragrances, solvents, adhesives, surfactants, and other products, and is known as the "mother of organic synthesis industry." Industrial production methods for acetylene mainly include the calcium carbide method, electric arc method, plasma method, regenerative furnace pyrolysis method, and natural gas partial oxidation pyrolysis method. With increasingly stringent environmental protection requirements, the calcium carbide method is gradually being restricted due to its high energy consumption and high pollution, while the natural gas partial oxidation method for acetylene production is gaining increasing attention due to its clean and efficient characteristics.

[0003] In the partial oxidation of natural gas to acetylene process, the preheated natural gas undergoes a high-temperature partial oxidation reaction with oxygen in a cracking furnace to produce acetylene and byproduct syngas. One of the key challenges of this process is the early ignition problem in the cracking furnace, i.e., abnormal combustion of the feed gas before or immediately upon entering the main reaction zone of the cracking furnace, leading to frequent unit shutdowns and seriously threatening production safety and operational stability. Studies have shown that the main factors causing early ignition include: residual reducing mechanical impurities in the pipeline, shortened induction period due to excessively high preheating temperature or low flow rate of the feed gas, and excessively high oxygen-to-carbon ratio. Among these, mechanical impurities in the pipeline are the most common cause of early ignition, which usually requires the installation of precision filters in the feed gas pipeline before entering the acetylene cracking furnace, and purging and chemical cleaning before start-up to control it. However, early ignition caused by the production of elemental carbon from high-temperature thermal cracking of natural gas after preheating is often overlooked: high-carbon hydrocarbons in natural gas, i.e., C2... + Hydrocarbons undergo thermal decomposition during preheating to produce elemental carbon. The higher the content of high-carbon hydrocarbons, the lower the thermal decomposition initiation temperature, and the higher the risk of early ignition.

[0004] On the other hand, traditional natural gas acetylene processes generally use pure oxygen as an oxidant. Although pure oxygen is beneficial for improving acetylene yield, its strong oxidizing properties bring the following problems: 1. The friction between oxygen and reducing mechanical impurities in the pipeline can easily cause early ignition accidents; 2. The oxygen-carbon ratio control window is narrow, and if it is too high, the reaction temperature is difficult to control or may even cause an explosion; 3. The production of pure oxygen is energy-intensive, which increases the production cost of acetylene; 4. The composition of the acetylene tail gas produced by pure oxygen oxidation is basically fixed, and it cannot be flexibly adjusted according to the downstream utilization needs, resulting in low efficiency of downstream units or the need for additional process adjustments.

[0005] Therefore, existing natural gas acetylene technologies still suffer from problems such as early ignition caused by carbon buildup from the thermal cracking of high-carbon hydrocarbons, poor safety and high energy consumption in pure oxygen systems, and unadjustable byproduct tail gas components. How to remove high-carbon hydrocarbons from natural gas at the source, while simultaneously reducing the hazard of oxidizers and achieving flexible control over tail gas components, is a pressing technical challenge that needs to be addressed in this field. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a conditioning method for natural gas acetylene feedstock, an acetylene production method, and a system, aiming to solve the problems in the prior art where early ignition of the acetylene cracking furnace is caused by carbon buildup from the thermal cracking of high-carbon hydrocarbons in natural gas, and the poor safety, high energy consumption, and unadjustable by-product tail gas composition caused by pure oxygen oxidants.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for conditioning natural gas acetylene feedstock includes the following steps: The first preheating step involves preheating the raw material natural gas containing high-carbon hydrocarbons to a first temperature. The mixing step involves mixing the preheated raw natural gas with the first flexible oxidant. The reaction step involves catalytically reacting the mixed feedstock natural gas with a first flexible oxidant in a conditioning reactor, so that the high-carbon hydrocarbons in the feedstock natural gas react with the first flexible oxidant to convert them into low-carbon hydrocarbons, thus obtaining the conditioning feedstock gas.

[0008] Furthermore, after the reaction step, the method further includes a second preheating step, in which the conditioning raw material gas is preheated to a second temperature; wherein the first temperature is lower than the second temperature.

[0009] Furthermore, the first temperature is 300℃~500℃, and the second temperature is 600℃~670℃.

[0010] Furthermore, the first flexible oxidant is water vapor or carbon dioxide or a mixture of both in any proportion.

[0011] Furthermore, the conditioning reactor is equipped with a catalyst for catalytic reactions.

[0012] A method for producing acetylene from natural gas includes the following steps: The conditioning step involves conditioning the raw natural gas using the aforementioned conditioning method to obtain conditioned raw gas. The pyrolysis step involves reacting the conditioning feed gas with an oxygen-containing gas to obtain pyrolysis gas containing acetylene. The compression and concentration step involves compressing and concentrating the acetylene-containing cracked gas to obtain the acetylene product.

[0013] A method for producing acetylene from natural gas includes the following steps: The conditioning step involves conditioning the raw natural gas using the aforementioned conditioning method to obtain conditioned raw gas. In the pyrolysis step, the conditioning feed gas is first mixed with a second flexible oxidant to obtain a first mixed gas; then the first mixed gas is second mixed with the oxygen-containing gas to obtain a second mixed gas; the second mixed gas is subjected to an oxidation reaction to obtain acetylene-containing pyrolysis gas. The compression and concentration step involves compressing and concentrating the acetylene-containing cracked gas to obtain the acetylene product.

[0014] Furthermore, after the first mixing, the first mixed gas is preheated to 400°C to 500°C; after the second mixing, the second mixed gas is preheated to 600°C to 670°C.

[0015] Furthermore, the second flexible oxidant is water vapor or carbon dioxide or a mixture of both in any proportion.

[0016] A system for producing acetylene from natural gas, used to implement the above-described method for producing acetylene from natural gas, comprising: The feed gas conditioning unit is used to receive natural gas feedstock and output conditioned feed gas; the feed gas conditioning unit includes a preheater, a conditioning reactor and a postheater connected in sequence. The pyrolysis unit has its inlet connected to the outlet of the raw material gas conditioning unit and an oxygen-containing gas source, respectively, for carrying out an oxidation reaction to obtain pyrolysis gas containing acetylene. The compression and concentration unit is connected to the pyrolysis gas outlet of the pyrolysis unit and is used to compress and concentrate the acetylene-containing pyrolysis gas to obtain acetylene product.

[0017] The beneficial effects of this invention are: This invention employs a feed gas conditioning process, combining stepwise heating and catalytic conversion. Natural gas is first preheated to 300°C–500°C, where high-carbon hydrocarbons react with a flexible oxidant under the action of a catalyst to convert into low-carbon hydrocarbons. The gas is then further preheated to 600°C–670°C before being fed into the cracking furnace. This process removes high-carbon hydrocarbons that are prone to thermal cracking and produce elemental carbon at the source, effectively avoiding early ignition problems in the acetylene cracking furnace caused by carbon buildup. This significantly improves the safety and stability of the unit's operation.

[0018] Furthermore, this invention employs a two-step mixing method: first, the conditioned feed gas is mixed with a second flexible oxidant, and then mixed with oxygen-containing gas before entering the cracking furnace. This method effectively reduces the oxygen partial pressure, moderates the intensity of the cracking reaction, and reduces the amount of pure oxygen used, thereby lowering air separation energy consumption and equipment investment. Simultaneously, by adjusting the ratio of water vapor to carbon dioxide in the flexible oxidant, the hydrogen-to-carbon ratio in the byproduct acetylene tail gas can be flexibly controlled, meeting the needs of downstream chemical processes such as methanol and ammonia synthesis, thus improving the overall economic efficiency of the process. This invention is applicable to natural gas rich in high-carbon hydrocarbons, as well as unconventional natural gas such as associated gas from oil fields and shale gas, and has promising prospects for industrial application. Attached Figure Description

[0019] Fig. 1 This is a process flow diagram of a method for producing acetylene from natural gas provided in Embodiment 2 of the present invention; Fig. 2 This is a process flow diagram of a method for producing acetylene from natural gas provided in Embodiment 4 of the present invention. Detailed Implementation

[0020] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and are therefore merely examples and should not be used to limit the scope of protection of the present invention. Those skilled in the art should understand that the present invention can be implemented even without certain specific details. In some other embodiments, methods, means, equipment, and steps well known to those skilled in the art are not described in detail in order to highlight the spirit of the present invention.

[0021] Unless otherwise specified, in this invention, terms such as "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," "x-direction," "y-direction," and "z-direction" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe orientation or positional relationships in this invention are for illustrative purposes only and should not be construed as limiting this invention. For those skilled in the art, the specific meaning of the above terms can be understood in conjunction with the accompanying drawings and according to the specific circumstances.

[0022] Example 1 See attached Figs. 1-2 This embodiment provides a conditioning method for natural gas acetylene feedstock, used to process natural gas feedstock containing high-carbon hydrocarbons. The specific steps are as follows: The first preheating step involves preheating the raw material natural gas containing high-carbon hydrocarbons to a first temperature. The mixing step involves mixing the preheated raw natural gas with the first flexible oxidant. The reaction step involves catalytically reacting the mixed feedstock natural gas with a first flexible oxidant in a conditioning reactor, so that the high-carbon hydrocarbons in the feedstock natural gas react with the first flexible oxidant to convert them into low-carbon hydrocarbons, thus obtaining the conditioning feedstock gas.

[0023] Specifically, in the first preheating step, the raw material natural gas containing high carbon hydrocarbons is introduced into the preheater and preheated to a first temperature. The first temperature is a lower reaction temperature required for conditioning the reactor. Preferably, the first temperature is 300°C to 500°C. This temperature range is a suitable reaction temperature range for the reaction of high carbon hydrocarbons with the first flexible oxidant. Below 300°C, the reaction rate is slow and it is not conducive to large-scale production. Above 500°C, the structure of the conditioning reactor will change and the investment will be high.

[0024] In the mixing step, the preheated feedstock natural gas is mixed with a first flexible oxidant in a pipeline and then fed into a conditioning reactor. The first flexible oxidant can be steam, carbon dioxide, or a mixture of both in any proportion, and can be adjusted according to the composition of the natural gas feedstock and the downstream demand for acetylene tail gas components.

[0025] In the reaction step, the mixed materials are fed into a conditioning reactor. The conditioning reactor contains a catalyst to catalyze the reaction between high-carbon hydrocarbons in the feedstock natural gas and a first flexible oxidant, converting them into low-carbon hydrocarbons to obtain conditioned feedstock gas. The conversion catalyst packed in the conditioning reactor can be one type or a combination of multiple catalysts, adjustable according to the composition of the natural gas feedstock. All catalysts are commercially available in the art.

[0026] In one specific embodiment of this application, the conditioning feed gas at the outlet of the conditioner can undergo a second preheating step, that is, the intermediate conditioning gas is passed into a post-preheater and preheated to a second temperature to obtain heated conditioning feed gas. The first temperature is lower than the second temperature. The second temperature is the temperature required for the acetylene cracking furnace, preferably 600℃~670℃.

[0027] After the above conditioning treatment, the content of high-carbon hydrocarbons in the natural gas feedstock is significantly reduced, while the content of low-carbon hydrocarbons, mainly methane, is correspondingly increased. The resulting conditioned feedstock gas can be used in the subsequent acetylene cracking process. This conditioning method can effectively avoid the problem of early ignition in the cracking furnace caused by the generation of elemental carbon from the thermal cracking of high-carbon hydrocarbons.

[0028] Example 2 See attached Figs. 1-2 Based on Example 1, this example provides a method for producing acetylene from natural gas, comprising the following steps: In the conditioning step, the raw natural gas is conditioned using the conditioning method described in Example 1 above to obtain conditioned raw gas. The pyrolysis step involves reacting the conditioning feed gas with an oxygen-containing gas to produce pyrolysis gas containing acetylene. The compression and concentration step involves compressing and concentrating the acetylene-containing cracked gas to obtain the acetylene product.

[0029] Specifically, the feedstock natural gas is first preheated to 300°C–500°C in a preheater, then mixed with a first flexible oxidant in a pipeline before entering the conditioning reactor. The conditioning reactor contains a catalyst, which converts the high-carbon hydrocarbons in the feedstock natural gas into low-carbon hydrocarbons under the action of the first flexible oxidant. The conditioning feedstock gas exiting the conditioning reactor then enters a postheater, where it is preheated to 600°C–670°C before being sent to the cracking process.

[0030] After two steps of preheating and conditioning, the raw natural gas reacts with oxygen from the air separation unit in the acetylene cracking furnace to produce acetylene and other products. The carbon black generated in the cracking reaction gas is separated and used as a byproduct. The cracked gas is then sent to the cracked gas compression process. The cracked gas is combined with acetylene-rich recycle gas from the enrichment process, and after being pressurized to approximately 1.18 MPaA by a compressor, it is sent to the enrichment process. A cracked gas holder is located upstream of the compressor to maintain a constant pipeline pressure. The pressurized cracked gas is then selectively absorbed and separated by a solvent into product acetylene gas, byproduct tail gas, and acetylene-rich recycle gas. The recycle gas is then returned to the compression process for further acetylene extraction. For example, N-methylpyrrolidone can be used for selective absorption.

[0031] Using natural gas from a high-carbon hydrocarbon-rich natural gas-to-acetylene plant as feedstock, the method for producing acetylene from natural gas according to the present invention is further described. 1000 kmol / h of natural gas is added to 60 kmol / h of a first flexible oxidant, and after conditioning and cracking according to different ratios of the first flexible oxidant, six implementation schemes are obtained. The process conditions and results are shown in Table 1. Scheme 1 is a comparative example of the traditional process without conditioning; Schemes 2 to 6 are conditioning processes under different H2O / CO2 ratios.

[0032] Table 1. Process conditions and results of different implementation schemes

[0033] Table 1 shows that Scheme 2 has the highest acetylene yield and is suitable for maximizing acetylene production, with a high hydrogen-to-carbon ratio in the byproduct acetylene tail gas. Schemes 2 through 6 show a gradual decrease in the H2O ratio and a gradual increase in CO2 in the flexible oxidant, a gradual decrease in the conversion rate of high-carbon hydrocarbons, a slight decrease in the total acetylene production, and a gradual increase in the amount of byproduct acetylene tail gas and its hydrogen-to-carbon ratio. In practical applications, an appropriate ratio can be selected based on the downstream demand for the hydrogen-to-carbon ratio of the tail gas.

[0034] Furthermore, after conditioning treatment (Schemes 2 to 6), the early ignition frequency of acetylene cracking decreased from 3-5 times per day to 1-2 times per week, a significant reduction in early ignition frequency. Safety was greatly improved. The natural gas-to-acetylene method provided by this invention solves the problem of thermal cracking caused by directly heating high-carbon hydrocarbons in natural gas to high temperatures through the setting of feed gas conditioning and step-by-step heating, thus avoiding the problem of early ignition of the acetylene cracking furnace caused by pyrolysis carbon.

[0035] This embodiment uses natural gas as an example. It is understood that it is also applicable to unconventional natural gas such as associated gas from oil fields, shale gas, coalbed methane, and natural gas hydrates.

[0036] Example 3 See attached Figs. 1-2 Based on Example 2, this example provides a system for producing acetylene from natural gas, used to implement the method described in Example 2. Fig. 1 As shown, the system includes: The feed gas conditioning unit consists of a preheater, a conditioning reactor, and a postheater connected sequentially by pipelines. The inlet of the preheater is connected to the natural gas feed pipeline, and the outlet of the preheater is connected to the inlet of the conditioning reactor via a pipeline. This pipeline is equipped with a first flexible oxidant inlet for injecting the first flexible oxidant into the pipeline to mix with the preheated natural gas. The conditioning reactor is filled with a catalyst, and its outlet is connected to the inlet of the postheater. The outlet of the postheater outputs the conditioned feed gas.

[0037] It should be noted that the raw material natural gas of this invention can be preheated together with the first flexible oxidant in the preheater to the required reaction temperature of the conditioning reactor, or they can be preheated separately to the same reaction temperature. This embodiment describes the process by example where only the natural gas is preheated in the preheater, and the first flexible oxidant is directly injected through an inlet on the pipeline. However, depending on actual process requirements, the inlet of the first flexible oxidant can also be located upstream of the preheater, allowing both to be preheated together in the preheater. Regardless of the preheating method used, it falls within the scope of protection of this invention.

[0038] Cracking Unit: Includes an acetylene cracking furnace. The feed inlet of the cracking furnace is connected via pipeline to the outlet of the preheater and the oxygen pipeline from the air separation unit. The outlet of the cracking furnace is connected to a quench tower, a water washing tower, and a carbon black separator.

[0039] The compression and concentration unit comprises a pyrolysis gas holder, a compressor, a concentration tower, a solvent regeneration tower, and a product refining tower, connected in sequence. The inlet of the pyrolysis gas holder is connected to the gas outlet of the carbon black separator; the outlet of the compressor is connected to the inlet of the concentration tower; the concentration tower has a solvent inlet, a product acetylene outlet, a tail gas outlet, and a recirculated gas outlet; the recirculated gas outlet returns to the compressor inlet through a pipeline; and the solvent regeneration tower is connected to the solvent outlet of the concentration tower.

[0040] During system operation, the raw natural gas is first preheated to the lower reaction temperature required by the conditioning reactor via a preheater. In the conditioning reactor, it undergoes a catalytic reaction with a first flexible oxidant, converting high-carbon hydrocarbons into low-carbon hydrocarbons. The gas exiting the conditioning reactor then passes through a postheater, where it is heated to the temperature required by the acetylene cracking furnace before entering. Finally, it undergoes natural gas cracking to produce acetylene with oxygen in the acetylene cracking furnace. This system enables continuous and stable operation of the method described in Example 2.

[0041] The heat source for the preheater and postheater can be steam, fuel gas, or waste heat from the process, and can be adjusted according to the site conditions. Those skilled in the art can, based on the disclosure of this invention, conventionally select the specific structure of each unit, such as reactor type, tower internals, and catalyst type, without departing from the scope of protection of this invention.

[0042] Example 4 See attached Figs. 1-2 Based on Example 1, this example provides another method for producing acetylene from natural gas, in which the cracking step after the conditioning step adopts a "two-step mixing" approach to further reduce the oxygen partial pressure, moderate the reaction intensity, and regulate the tail gas composition.

[0043] It should be noted that the core of this embodiment lies in the two-step mixing method of the cracking step. This method can be used for both conditioned feed gas and unconditioned feed gas. When the feed gas itself has a low content of high-carbon hydrocarbons or the requirements for early ignition risk are not stringent, the conditioning step can be omitted, and the feed gas can be directly mixed with the second flexible oxidant in the first mixing, with subsequent steps remaining unchanged. This embodiment takes conditioning treatment as an example.

[0044] Conditioning step: The raw natural gas is conditioned using the conditioning method described in Example 1 to obtain conditioned raw gas. This example assumes that the second preheating step has not been performed.

[0045] Pyrolysis steps: such as Fig. 2As shown, the above-mentioned conditioning feed gas is first mixed with a second flexible oxidant from outside the interface in a pipeline to obtain a first mixed gas, which is then preheated to 400℃~500℃. Then, the preheated first mixed gas is mixed a second time with oxygen from the air separation unit in a mixer before the acetylene cracking furnace. The oxygen purity is ≥99.5%, resulting in a second mixed gas, which is preheated to 600℃~670℃ and then introduced into the acetylene cracking furnace. The feed gas ratio after mixing is natural gas: oxygen: water vapor: carbon dioxide = 100:54:4:2. The preheated second mixed gas enters the acetylene cracking furnace and reacts at 0.13~1.4MPa and approximately 1350℃ to produce acetylene and other products. The carbon black generated in the cracking reaction gas is separated and used as a byproduct. The cracked gas is sent to the cracked gas compression process.

[0046] Compression and concentration steps: Same as in Example 2, the pyrolysis gas is subjected to carbon black removal, compression, and concentration to obtain acetylene product.

[0047] The second flexible oxidant can be water vapor, carbon dioxide, or a mixture of both in any proportion, and can be adjusted according to the composition of the natural gas feedstock and the downstream demand for acetylene tail gas components.

[0048] This embodiment employs a two-step mixing and cracking process, where the raw material natural gas is first mixed with the second flexible oxidant in a pipeline, and then mixed with oxygen in a mixer before the acetylene cracking furnace. This reduces oxygen consumption and partial pressure, and effectively slows down the cracking reaction intensity where oxygen directly reacts with natural gas in the acetylene cracking furnace to produce acetylene. This results in relatively mild operating conditions and safer operation of the acetylene cracking system. Furthermore, the composition of the by-product acetylene tail gas is controllable, facilitating downstream utilization.

[0049] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention. Technical aspects, shapes, and structures not described in detail in this invention are all well-known technologies.

Claims

1. A method for conditioning natural gas acetylene feedstock, characterized in that, Includes the following steps: The first preheating step involves preheating the raw material natural gas containing high-carbon hydrocarbons to a first temperature. The mixing step involves mixing the preheated raw natural gas with the first flexible oxidant. The reaction step involves catalytically reacting the mixed feedstock natural gas with a first flexible oxidant in a conditioning reactor, so that the high-carbon hydrocarbons in the feedstock natural gas react with the first flexible oxidant to convert them into low-carbon hydrocarbons, thereby obtaining the conditioning feedstock gas.

2. The conditioning method for natural gas acetylene feedstock according to claim 1, characterized in that, Following the reaction step, the process further includes a second preheating step, in which the conditioning raw material gas is preheated to a second temperature; wherein the first temperature is lower than the second temperature.

3. The conditioning method for natural gas acetylene feedstock according to claim 2, characterized in that, The first temperature is 300℃~500℃, and the second temperature is 600℃~670℃.

4. The conditioning method for natural gas acetylene feedstock gas according to claim 1 or 2, characterized in that, The first flexible oxidant is water vapor or carbon dioxide or a mixture of both in any proportion.

5. The conditioning method for natural gas acetylene feedstock according to claim 1, characterized in that, The conditioning reactor is equipped with a catalyst for catalytic reactions.

6. A method for producing acetylene from natural gas, characterized in that, Includes the following steps: The conditioning step involves conditioning the raw natural gas using the conditioning method described in claim 3 to obtain conditioned raw gas. The pyrolysis step involves reacting the conditioning feed gas with an oxygen-containing gas to obtain pyrolysis gas containing acetylene. The compression and concentration step involves compressing and concentrating the acetylene-containing cracked gas to obtain the acetylene product.

7. A method for producing acetylene from natural gas, characterized in that, Includes the following steps: The conditioning step involves conditioning the raw natural gas using the conditioning method described in claim 1 to obtain conditioned raw gas. In the pyrolysis step, the conditioning feed gas is mixed with the second flexible oxidant for the first time to obtain a first mixed gas; then the first mixed gas is mixed with the oxygen-containing gas for the second time to obtain a second mixed gas; the second mixed gas is subjected to an oxidation reaction to obtain acetylene-containing pyrolysis gas; The compression and concentration step involves compressing and concentrating the acetylene-containing cracked gas to obtain the acetylene product.

8. The method for producing acetylene from natural gas according to claim 7, characterized in that, After the first mixing, the first mixed gas is preheated to 400°C to 500°C; after the second mixing, the second mixed gas is preheated to 600°C to 670°C.

9. The method for producing acetylene from natural gas according to claim 7, characterized in that, The second flexible oxidant is water vapor or carbon dioxide or a mixture of both in any proportion.

10. A system for producing acetylene from natural gas, used to implement the method for producing acetylene from natural gas as described in claim 6, characterized in that, include: The feed gas conditioning unit is used to receive natural gas feedstock and output conditioned feed gas; The raw material gas conditioning unit includes a preheater, a conditioning reactor, and a postheater connected in sequence. The pyrolysis unit has its inlet connected to the outlet of the raw material gas conditioning unit and an oxygen-containing gas source, respectively, for carrying out an oxidation reaction to obtain pyrolysis gas containing acetylene. The compression and concentration unit is connected to the pyrolysis gas outlet of the pyrolysis unit and is used to compress and concentrate the acetylene-containing pyrolysis gas to obtain acetylene product.

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