Low-water-carbon-ratio methane conversion method and system

Abstract

The invention provides a low-water-carbon-ratio methane conversion method which comprises the following steps: 1) pretreating first raw material gas, mixing the pretreated first raw material gas with third raw material gas, carrying out first methane conversion reaction, supplementing first oxygen-enriched gas in the reaction process, and reacting to obtain a first-stage reaction product; 2) pretreating a second raw material gas, mixing the pretreated second raw material gas with the first-stage reaction product obtained in the step 1), carrying out a second methane conversion reaction, supplementing a second oxygen-enriched gas in the reaction process, and carrying out a reaction to obtain a second-stage reaction product; the invention further provides a system suitable for the low-water-carbon-ratio methane conversion method, external heat supply is not needed in the methane conversion reaction, energy consumption is reduced, the water-carbon ratio is low, and synthesis gas with the hydrogen-carbon ratio of 0.6-4.0 can be prepared.

Description

Technical Field

[0001] The invention relates to the field of synthesis gas preparation methods, and in particular to a method and system for low water-to-carbon ratio methane conversion. Background Art

[0002] Methane is a potent greenhouse gas, with a greenhouse effect about 23 times that of carbon dioxide. It is commonly found in coal gas layers, biogas, etc. At the same time, methane is the main component of natural gas. As a clean energy source, it has a high calorific value, stable combustion, and the carbon dioxide and water vapor produced after combustion have little impact on the environment. The consumption of methane can promote the optimization of energy structure and the utilization of clean energy. Synthesis gas is an important chemical raw material, with CO and H2 as its main components. It can be used to synthesize ammonia, methanol, ethanol, etc., and plays an important role in the chemical, energy, power and metallurgical industries. The main components of synthesis gas are carbon and hydrogen. Various resources rich in C and H can be used as raw materials for synthesis gas production. Methane can be converted into synthesis gas through methane steam reforming, methane partial oxidation, methane carbon dioxide dry reforming technology (DRM) or their mixed reforming.

[0003] The first stage of methane conversion furnace is a typical shell-and-tube reactor. The tubular reactor has become an important equipment in chemical production with its high heat transfer efficiency, simple operation, good safety and high volumetric efficiency. It is particularly suitable for reactions with large thermal effects and high conversion rates, and can achieve segmented temperature control to meet the needs of large-scale and continuous production. However, when the reaction rate is low, the required long pipeline may bring economic and operational challenges; in particular, the operating conditions of nearly 1,000 degrees Celsius under high pressure in the methane conversion process have stringent requirements on the reactor's high temperature resistance, high pressure resistance, and efficient heat transfer, and the expensive reaction tubes on the market still cannot meet the requirements. In addition, the tubular reactor has high requirements for materials, and stability and uniformity must be maintained to ensure a smooth reaction. At the same time, the tubular reactor filled with catalysts is also relatively complicated in terms of maintenance and catalyst replacement. In order to prevent carbon deposition in the furnace tubes of the first stage of methane conversion furnace, a higher water-carbon ratio is required. The water-carbon ratio in industry is generally higher than 3, or even higher than 3.5.

[0004] The natural reforming furnace has demonstrated remarkable efficiency in industrial production due to its unique design advantages. The natural reforming furnace uses castables for thermal insulation, and the furnace wall bears pressure without having to withstand high temperatures, so the natural reforming furnace has low material requirements. From a process perspective, it cleverly uses the heat generated by the charge itself to maintain the normal operation of the furnace. Except for necessary preheating, it requires almost no external heat source, thereby achieving efficient use of reaction heat. In addition, the structure of the natural reforming furnace is usually simple and compact, with a small size, which not only reduces the cost of engineering investment, but also facilitates installation and maintenance. These comprehensive advantages make the natural reforming furnace very popular in the methane reforming process and have been widely used and promoted.

[0005] Among the existing methane conversion technologies, the common ones include:

[0006] In the first process, the first stage furnace and the second stage furnace are connected in series, that is, the shell-and-tube reactor is connected in series with the natural reforming furnace. The water-carbon ratio of the first stage furnace in the series process determines the water-carbon ratio of the process. Therefore, the water-carbon ratio of the entire process is high, the energy consumption is high, and the heat utilization rate is low. At the same time, about 30% to 40% of the total natural gas is used as fuel for combustion and heating in the first stage furnace, which wastes precious raw materials and emits low-concentration carbon dioxide. The second process is improved on the basis of the first process, that is, the heat of the high-temperature product from the autothermal reforming furnace is used to provide the raw gas of the tubular reactor for heating and pre-conversion, which can further improve the utilization efficiency of heat. However, the tubular reactor that withstands high temperature and high pressure has strict material requirements and high cost, and the catalyst in the tube is easily heated unevenly, resulting in carbon deposition and deactivation, and the operation stability is poor. The third process cancels the tubular reactor and directly passes the pretreated raw gas directly into the autothermal reforming furnace for reaction, which can appropriately reduce the water-carbon ratio of the system. It is generally used for the conversion of raw gas with low methane content such as coke oven gas and industrial venting gas, but this process still has problems such as small methane processing capacity.

[0007] Therefore, there is an urgent need for a methane conversion process method that has no tubular reactor, low water-to-carbon ratio, low energy consumption, is safe and stable, and can be mass-produced. Summary of the invention

[0008] In view of the shortcomings of the prior art mentioned above, the object of the present invention is to provide a method and system for low water-to-carbon ratio methane conversion, which is used to solve the problems of high water-to-carbon ratio, high energy consumption, poor operating stability and small process throughput of the shell-and-tube reactor process in the existing methane conversion technology.

[0009] To achieve the above object and other related objects, the present invention provides a method for converting methane with a low water-to-carbon ratio, comprising the following steps:

[0010] 1) Pre-treating the first raw gas and mixing it with the third raw gas to perform a first methane conversion reaction, adding the first oxygen-rich gas during the reaction, and obtaining a primary reaction product;

[0011] 2) Pre-treating the second raw gas and mixing it with the primary reaction product obtained in step 1) to perform a second methane conversion reaction, adding a second oxygen-rich gas during the reaction to obtain a secondary reaction product;

[0012] The first raw gas and the second raw gas are independently selected from any one or more of natural gas, biogas, coalbed methane, coke oven gas, oilfield gas, refinery gas, methanol synthesis purge gas, and Fischer-Tropsch synthesis purge gas;

[0013] The third raw gas is selected from any one or more of water vapor, carbon dioxide, and carbon dioxide-rich gas.

[0014] The present invention also provides a system suitable for the low water-to-carbon ratio methane conversion method as described above, the system comprising a primary reactor and a secondary reactor connected in series in sequence;

[0015] It also includes a first pretreatment device and a second pretreatment device, wherein the feed port of the first pretreatment device is connected to the feed pipeline of the first raw gas, and the discharge port of the first pretreatment device is connected to the feed port of the primary reactor; the feed port of the second pretreatment device is connected to the feed pipeline of the second raw gas, and the discharge port of the second pretreatment device is connected to the feed port of the secondary reactor;

[0016] The feed port of the primary reactor is also connected to the third raw gas feed pipeline and the first oxygen-rich gas feed pipeline, and the discharge port of the primary reactor is connected to the feed port of the secondary reactor;

[0017] The feed port of the secondary reactor is also connected to the second oxygen-rich gas feed pipeline, and the discharge port of the secondary reactor is connected to the product collection pipeline.

[0018] As described above, the method and system for low water-to-carbon ratio methane conversion of the present invention have the following beneficial effects:

[0019] The method for low water-to-carbon ratio methane conversion of the present invention is as follows: pre-treating a first raw gas containing methane and a second raw gas, respectively performing methane conversion reactions, and then performing a second methane conversion reaction on a reaction product of the first raw gas after the first methane conversion reaction and the second raw gas. By arranging the reactions in series, the processing amount of methane is increased. Furthermore, in the present invention, the molar ratio of water vapor to carbon in alkanes in the mixed gas obtained by mixing the first raw gas and the third raw gas is (0-2.0):1, the water-to-carbon ratio is low, steam is saved, and energy consumption is reduced. The method of the present invention can obtain a synthesis gas with a hydrogen-to-carbon ratio of 0.6-4.0.

[0020] The system of the present invention, which is suitable for a low water-to-carbon ratio methane conversion method, has no open flame device, reduces floor space, and has low investment; has relatively loose requirements on catalysts, and the system can operate for a long period of time; and does not require external heating, thereby reducing low-concentration carbon emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Shown is a system schematic diagram of the method for low water-to-carbon ratio methane conversion of the present invention.

[0022] Description of Figure Numbers

[0023] P1: first pretreatment device; P2: second pretreatment device; E1: primary reactor; E2: secondary reactor; 10: first raw gas; 20: second raw gas; 30: third raw gas; 11: first oxygen-rich gas; 12: second oxygen-rich gas. DETAILED DESCRIPTION

[0024] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0025] Please refer to the attached drawings. It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and the drawings only show the components related to the present invention rather than the number, shape and size of the components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0026] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] The first aspect of the present invention provides a method for low water-to-carbon ratio methane conversion, comprising the following steps:

[0028] 1) Pre-treating the first raw gas 10 and mixing it with the third raw gas 30 to perform a first methane conversion reaction, adding the first oxygen-rich gas 11 during the reaction, and obtaining a primary reaction product;

[0029] 2) Pre-treating the second raw gas 20 and mixing it with the primary reaction product obtained in step 1) to perform a second methane conversion reaction, adding the second oxygen-rich gas 12 during the reaction to obtain a secondary reaction product;

[0030] The first raw gas 10 and the second raw gas 20 are independently selected from any one or more of natural gas, biogas, coalbed methane, coke oven gas, oilfield gas, refinery gas, methanol synthesis purge gas, and Fischer-Tropsch synthesis purge gas;

[0031] The third raw gas 30 is selected from any one or more of water vapor, carbon dioxide, and carbon dioxide-rich gas.

[0032] In the low water-to-carbon ratio methane conversion method of the present invention, the first oxygen-rich gas 11 and the second oxygen-rich gas 12 are each independently selected from high-purity oxygen, air, nitrogen-enriched air or oxygen-enriched air.

[0033] Wherein, the molar flow ratio of the first raw material gas 10 in step 1) to the second raw material gas 20 in step 2) is (50-200):(50-200). For example, (50-60):(50-200), (60-70):(50-200), (70-80):(50-200), (80-90):(50-200), (90-100):(50-200), (100-110):(50-200), (110-120):(50-200), (120-130):( 50~200)、(130~140):(50~200)、(140~150):(50~200)、(150~160):(50~200)、(160~170):(50~200)、(170~180):(50~200)、(180~190):(50~200)、(190~200):(50~200 )、(50~200):(50~60)、(50~200):(60~70)、(50~200):(70~80)、(50~200):(80~90)、(50~200):(90~100)、(50~200):(100~110)、(50~200):(110~120)、(50~200):(120 ~130), (50~200):(130~140), (50~200):(140~150), (50~200):(150~160), (50~200):(160~170), (50~200):(170~180), (50~200):(180~190) or (50~200):(190~200).

[0034] The molar flow ratio of the first oxygen-enriched gas 11 in step 1) to the second oxygen-enriched gas 12 in step 2) is (50-200):(50-200). For example, (50-60):(50-200), (60-70):(50-200), (70-80):(50-200), (80-90):(50-200), (90-100):(50-200), (100-110):(50-200), (110-120):(50-200), (120-130):( 50~200)、(130~140):(50~200)、(140~150):(50~200)、(150~160):(50~200)、(160~170):(50~200)、(170~180):(50~200)、(180~190):(50~200)、(190~200):(50~200 )、(50~200):(50~60)、(50~200):(60~70)、(50~200):(70~80)、(50~200):(80~90)、(50~200):(90~100)、(50~200):(100~110)、(50~200):(110~120)、(50~200):(120 ~130), (50~200):(130~140), (50~200):(140~150), (50~200):(150~160), (50~200):(160~170), (50~200):(170~180), (50~200):(180~190) or (50~200):(190~200).

[0035] In step 2), water vapor and / or carbon dioxide are also added to the second raw gas 20, and the molar ratio of the water vapor, carbon dioxide and carbon in the alkane in the second raw gas is (0-0.5):(0-0.5):1. For example, (0-0.2):(0-0.5):1, (0.2-0.4):(0-0.5):1, (0.4-0.5):(0-0.5):1, (0-0.5):(0-0.2):1, (0-0.5):(0.2-0.4):1 or (0-0.5):(0.4-0.5):1. Here, carbon dioxide or water vapor refers to all CO2 and H2O entering the secondary reactor E2.

[0036] In the low water-to-carbon ratio methane conversion method of the present invention, the molar ratio of water vapor to carbon in alkanes in the mixed gas obtained by mixing the first raw gas 10 and the third raw gas 30 in step 1) is (0-2.0):1. For example, it is (0-0.5):1, (0.5-1.0):1, (1.0-1.5):1 or (1.5-2.0):1.

[0037] In the low water-carbon ratio methane conversion method of the present invention, the molar ratio of carbon dioxide to carbon in alkanes in the mixed gas obtained by mixing the first raw gas 10 and the third raw gas 30 in step 1) is (0-2.0): 1. For example, it is (0-0.5): 1, (0.5-1.0): 1, (1.0-1.5): 1 or (1.5-2.0): 1. In the present invention, the "carbon in alkanes" refers to the carbon in all alkanes in the first raw gas, because the raw materials generally contain a small amount of ethane, propane, etc.

[0038] In the low water-to-carbon ratio methane conversion method of the present invention, the pretreatments in step 1) and step 2) are desulfurization treatment and / or dechlorination treatment and / or compression treatment.

[0039] Wherein, the first raw gas 10 is subjected to desulfurization treatment when containing sulfur, and the sulfur content in the raw gas after desulfurization treatment is less than 0.5 ppm. For example, it is less than 0.5 ppm, less than 0.4 ppm, less than 0.3 ppm, less than 0.2 ppm or less than 0.1 ppm. In a preferred embodiment of the present invention, the sulfur content in the raw gas after desulfurization treatment is less than 0.1 ppm.

[0040] When the second raw gas 20 contains sulfur, desulfurization treatment is performed, and the sulfur content in the raw gas after desulfurization treatment is less than 0.5 ppm. For example, it is less than 0.5 ppm, less than 0.4 ppm, less than 0.3 ppm, less than 0.2 ppm or less than 0.1 ppm. In a preferred embodiment of the present invention, the sulfur content in the raw gas after desulfurization treatment is less than 0.1 ppm.

[0041] When the first raw gas 10 contains chlorine, dechlorination treatment is performed, and the chlorine content in the raw gas after dechlorination treatment is less than 0.5ppm. For example, it is less than 0.5ppm, less than 0.4ppm, less than 0.3ppm, less than 0.2ppm or less than 0.1ppm. In a preferred embodiment of the present invention, the chlorine content in the raw gas after dechlorination treatment is less than 0.1ppm.

[0042] When the second raw gas 20 contains chlorine, dechlorination treatment is performed, and the chlorine content in the raw gas after dechlorination treatment is less than 0.5ppm. For example, it is less than 0.5ppm, less than 0.4ppm, less than 0.3ppm, less than 0.2ppm or less than 0.1ppm. In a preferred embodiment of the present invention, the chlorine content in the raw gas after dechlorination treatment is less than 0.1ppm.

[0043] In the low water-to-carbon ratio methane conversion method of the present invention, the first methane conversion reaction and the second methane conversion reaction are both carried out in an autothermal reforming furnace.

[0044] The first methane conversion reaction and the second methane conversion reaction are both carried out under catalyst conditions. The catalyst is a nickel-based catalyst. In a preferred embodiment of the present invention, the nickel-based catalyst is a Ni / Al2O3 catalyst. The content of Ni in the catalyst is 12 to 16 wt%. More preferably, the content of Ni is 14.5 wt%.

[0045] In the low water-to-carbon ratio methane conversion method of the present invention, the temperature of the first raw gas 10 and the second raw gas 20 after pretreatment is 25-500°C, 25-50°C, 50-100°C, 100-150°C, 150-200°C, 200-250°C, 250-300°C, 300-350°C, 350-400°C, 400-450°C or 450-500°C, and the pressure is 5-60bar, 5-10bar, 10-15bar, 15-20bar, 20-25bar, 25-30bar, 30-35bar, 35-40bar, 40-45bar, 45-50bar, 50-55bar or 55-60bar.

[0046] In the low water-to-carbon ratio methane conversion method of the present invention, in step 1), the pressure of the first methane conversion reaction is 5 to 60 bar. For example, 5 to 10 bar, 10 to 15 bar, 15 to 20 bar, 20 to 25 bar, 25 to 30 bar, 30 to 35 bar, 35 to 40 bar, 40 to 45 bar, 45 to 50 bar, 50 to 55 bar or 55 to 60 bar. In a preferred embodiment of the present invention, the pressure of the first methane conversion reaction is 20 to 40 bar.

[0047] In the low water-to-carbon ratio methane conversion method of the present invention, in step 1), the discharge temperature of the primary reaction product is 800-1200° C. For example, 800-850° C., 850-900° C., 900-950° C., 950-1000° C., 1000-1050° C., 1050-1100° C., 1100-1150° C. or 1150-1200° C. In a preferred embodiment of the present invention, the discharge temperature of the primary reaction product is 900-1000° C.

[0048] In the low water-to-carbon ratio methane conversion method of the present invention, in step 2), the pressure of the second methane conversion reaction is 5 to 60 bar. For example, 5 to 10 bar, 10 to 15 bar, 15 to 20 bar, 20 to 25 bar, 25 to 30 bar, 30 to 35 bar, 35 to 40 bar, 40 to 45 bar, 45 to 50 bar, 50 to 55 bar or 55 to 60 bar. In a preferred embodiment of the present invention, the pressure of the first methane conversion reaction is 20 to 40 bar.

[0049] In the low water-to-carbon ratio methane conversion method of the present invention, in step 2), the discharge temperature of the secondary reaction product is 800-1200° C. For example, 800-850° C., 850-900° C., 900-950° C., 950-1000° C., 1000-1050° C., 1050-1100° C., 1100-1150° C. or 1150-1200° C. In a preferred embodiment of the present invention, the discharge temperature of the secondary reaction product is 900-1000° C.

[0050] In the low water-to-carbon ratio methane conversion method of the present invention, in step 2), the molar ratio of hydrogen to carbon monoxide in the secondary reaction product is 0.6 to 4.0. For example, it is 0.6 to 1.0, 1.0 to 1.5, 1.5 to 2.0, 2.0 to 2.5, 2.5 to 3.0, 3.0 to 3.5 or 3.5 to 4.0. In a preferred embodiment of the present invention, the molar ratio of hydrogen to carbon monoxide in the secondary reaction product is 1.0 to 2.0.

[0051] The second aspect of the present invention provides a system suitable for the low water-to-carbon ratio methane conversion method as described above, the system comprising a primary reactor E1 and a secondary reactor E2 connected in series in sequence;

[0052] It also includes a first pretreatment device P1 and a second pretreatment device P2, wherein the feed port of the first pretreatment device P1 is connected to the feed pipeline of the first raw gas 10, and the discharge port of the first pretreatment device P1 is connected to the feed port of the primary reactor E1; the feed port of the second pretreatment device P2 is connected to the feed pipeline of the second raw gas 20, and the discharge port of the second pretreatment device P2 is connected to the feed port of the secondary reactor E2;

[0053] The feed port of the primary reactor E1 is also connected to the third raw gas 30 feed pipeline and the first oxygen-rich gas 11 feed pipeline, and the discharge port of the primary reactor E1 is connected to the feed port of the secondary reactor E2;

[0054] The feed port of the secondary reactor E2 is also connected to the feed pipeline of the second oxygen-rich gas 12, and the discharge port of the secondary reactor E2 is connected to the product collection pipeline.

[0055] In the system of the present invention, the primary reactor E1 and the secondary reactor E2 are both autothermal reforming furnaces, that is, natural reforming reactors.

[0056] Example 1

[0057] The system used in this embodiment is as shown in the attached Figure 1 As shown, the method of low water-to-carbon ratio methane conversion adopted is as follows:

[0058] After the natural gas at normal pressure is compressed to 30 bar and the temperature is raised to 300°C, it is transported to the desulfurization device, where inorganic sulfur and organic sulfur in the natural gas are removed until the total sulfur content is below 0.2 ppm, and the raw gas with a temperature of 300°C and a pressure of 30 bar is obtained. The raw gas is divided into two streams, one for the first raw gas and the other for the second raw gas.

[0059] 100,000 Nm 3 / h first raw gas and 150,000 Nm 3 / h superheated steam (third raw gas, i.e., superheated water vapor) is mixed and introduced into the primary autothermal reforming reactor, and 50,000 Nm 3 / h oxygen (first oxygen-rich gas) for combustion, the reactor is loaded with nickel-based catalyst, and the reaction product obtained by the first methane reforming reaction is mixed with 50,000 Nm 3 / hThe second raw gas is mixed and introduced into the secondary autothermal reforming reactor, and 42,000 Nm 3 / h oxygen (second oxygen-rich gas) is used to assist combustion; after heat recovery and decarbonization of the obtained product, a synthesis gas with a hydrogen-to-carbon ratio of 2.6 can be obtained, and the reaction can proceed stably.

[0060] Example 2

[0061] The system used in this embodiment is as shown in the attached Figure 1 As shown, the method of low water-to-carbon ratio methane conversion adopted is as follows:

[0062] After the natural gas at normal pressure passes through the compressor, its pressure is increased to 30 bar and its temperature rises to 300°C. It is then transported to the desulfurization device. After passing through the desulfurization device, the inorganic sulfur and organic sulfur in the natural gas are removed until the total sulfur content drops below 0.2ppm. The natural gas is then divided into two streams, one for the first raw gas and the other for standby.

[0063] 100,000 Nm 3 / h first raw gas and 60,000 Nm 3 / h superheated steam, 100,000 Nm 3 / h CO2 (superheated steam and CO2 are used as the third raw gas) is mixed and introduced into the primary autothermal reforming reactor, and 65,000 Nm 3 / h oxygen (first oxygen-rich gas) for combustion, the reactor is loaded with nickel-based catalyst, and the reaction product obtained by the first methane reforming reaction is mixed with 50,000 Nm 3 / h backup natural gas, 50,000 Nm 3 / h CO2 (backup natural gas and CO2 as the second feed gas) is mixed and introduced into the secondary autothermal reforming reactor, and 40,000 Nm 3 / h oxygen (second oxygen-rich gas) is used to assist combustion, and the product obtained can be heat recovered and decarbonized to obtain a synthesis gas with a hydrogen-to-carbon ratio of 1, and the reaction can proceed stably.

[0064] Example 3

[0065] The system used in this embodiment is as shown in the attached Figure 1 As shown, the method of low water-to-carbon ratio methane conversion adopted is as follows:

[0066] After the pressure of coke oven gas at normal pressure is increased to 30 bar and the raw gas temperature is 280°C by the compressor, it is transported to the desulfurization device, and the total sulfur content in the coke oven gas is reduced to below 0.2ppm after passing through the desulfurization device, thereby obtaining the first raw gas. Another natural gas raw material is increased to 30 bar and the temperature is raised to 300°C by the compressor, and then transported to the desulfurization device, and the inorganic sulfur and organic sulfur in the natural gas are removed to reduce the total sulfur content to below 0.2ppm after passing through the desulfurization device, thereby obtaining the second raw gas.

[0067] 100,000 Nm 3 / h coke oven gas raw material (first raw gas) and 44,000 Nm 3 / h superheated steam (third raw gas) is mixed and introduced into the primary autothermal reforming reactor, and 17,000 Nm 3 / h oxygen (first oxygen-rich gas) for combustion, the reactor is loaded with nickel-based catalyst, and the reaction product obtained by methane reforming reaction is mixed with 30,000 Nm 3 / h natural gas raw material (second raw gas) is mixed and introduced into the secondary autothermal reforming reactor, and 22,000 Nm 3 / h oxygen (the second oxygen-rich gas) is used to assist combustion, and the product obtained can be heat recovered and decarbonized to obtain a synthesis gas with a hydrogen-to-carbon ratio of 2.9, and the reaction can proceed stably.

[0068] Example 4

[0069] The system used in this embodiment is as shown in the attached Figure 1 As shown, the method of low water-to-carbon ratio methane conversion adopted is as follows:

[0070] The coke oven gas at normal pressure is increased to 30 bar by the compressor and the raw gas temperature is 280°C, and then it is transported to the desulfurization device. After passing through the desulfurization device, the total sulfur content in the coke oven gas is reduced to below 0.2 ppm, which is the first raw gas. There is also a supply of pretreated natural gas with a temperature of 300°C and a pressure of 30 bar for standby.

[0071] 100,000 Nm 3 / h coke oven gas raw material (first raw gas) and 16,000 Nm 3 / h superheated steam, 29,000 Nm 3 / h CO2 (superheated steam and CO2 are used as the third raw gas) is mixed and introduced into the primary autothermal reforming reactor, and 22,000 Nm 3 / h oxygen (first oxygen-rich gas) to assist combustion. The reactor is loaded with nickel-based catalysts, and the reaction products obtained by methane reforming reaction are mixed with 50,000 Nm 3 / h pre-treated natural gas, 50,000 Nm 3 / h CO2 (pre-treated natural gas and CO2 as the second raw gas) are mixed and introduced into the secondary autothermal reforming reactor, and 20,000 Nm 3 / h oxygen (second oxygen-rich gas) is used to assist combustion, and the product obtained can be heat recovered and decarbonized to obtain a synthesis gas with a hydrogen-to-carbon ratio of 1.3, and the reaction can proceed stably.

[0072] Example 5

[0073] The system used in this embodiment is as shown in the attached Figure 1 As shown, the method of low water-to-carbon ratio methane conversion adopted is as follows:

[0074] After the biogas under normal pressure is compressed to 30 bar and the raw gas temperature is 280℃, it is transported to the desulfurization device, and the total sulfur content in the biogas is reduced to below 0.2ppm. The raw gas composition of biogas after desulfurization is: 40% CO2, 59.5% CH4, 0.5% N2.

[0075] 100,000 Nm 3 / h biogas raw gas (first raw gas) and 50,000 Nm 3 / h superheated steam (third raw gas) is mixed and introduced into the primary autothermal reforming reactor, and 40,000 Nm 3 / h oxygen (first oxygen-rich gas) for combustion support, the reactor is loaded with nickel-based catalyst, and the reaction product obtained by methane reforming reaction is mixed with 100,000 Nm 3 / h biogas raw gas (second raw gas) is mixed and then introduced into the secondary autothermal reforming reactor, and 39,000 Nm 3 / h oxygen (the second oxygen-rich gas) is used to assist combustion, and the product obtained can be heat recovered and decarbonized to obtain a synthesis gas with a hydrogen-to-carbon ratio of 1.2, and the reaction can proceed stably.

[0076] The feed and reaction conditions of various raw materials in the low water-to-carbon ratio methane conversion process of Examples 1 to 5 are shown in Table 1:

[0077] Table 1

[0078]

[0079]

[0080] In Table 1, the composition of coke oven gas (COG) is: 58% H2, 6% CO, 2% CO2, 0% O2, 29% CH4, 1% H2O, 4% N2; the composition of biogas is 40% CO2, 59.5% CH4, 0.5% N2; the density of the catalyst is 1t / m 3 ; The Ni content in the catalyst is 14.5wt%.

[0081] Comparative Example 1

[0082] Using the same inlet gas composition as in Example 1, if a single autothermal reforming furnace is selected, the process flow is as follows: The natural gas is subjected to the same pretreatment to obtain the raw gas. 150,000 Nm 3 / h raw gas and 150,000 Nm 3 / h superheated steam is mixed and introduced into the primary autothermal reforming reactor, and 92,000 Nm 3 / h oxygen combustion. The reactor is loaded with nickel-based catalyst (340m 3 ) to carry out methane reforming reaction, the conditions are the same as those in Example 1. When this intake gas composition is used, the catalyst will be deactivated by carbon deposition. In order to ensure the normal operation of the process, additional superheated steam is required.

[0083] Comparative Example 2

[0084] Using the same inlet gas composition as in Example 2, if a single autothermal reforming furnace is selected, the process flow is as follows: The natural gas is subjected to the same pretreatment to obtain the raw gas. 150,000 Nm 3 / h raw gas and 60,000 Nm 3 / h superheated steam, 150,000 Nm 3 / h CO2 is mixed and introduced into the primary autothermal reforming reactor, and 105,000 Nm 3 / h oxygen combustion. The reactor is loaded with nickel-based catalyst (310m 3 ) to carry out methane reforming reaction, the conditions are the same as those in Example 2. When this intake gas composition is used, the catalyst will be deactivated by carbon deposition. In order to ensure the normal operation of the process, additional superheated steam is required.

[0085] Comparative Example 3

[0086] Using the same inlet gas composition as in Example 3, if a single autothermal reforming furnace is selected, the process flow is as follows: natural gas and coke oven gas are subjected to the same pretreatment to obtain raw gas. 100,000 Nm 3 / h coke oven gas raw material, 30,000 Nm 3 / h natural gas raw material and 44,000 Nm 3 / h superheated steam is mixed and introduced into the primary autothermal reforming reactor, and 39,000 Nm 3 / h oxygen combustion. The reactor is loaded with nickel-based catalyst (128m 3 ) to carry out methane reforming reaction, the conditions are the same as those in Example 3. When this intake gas composition is used, the catalyst will be deactivated by carbon deposition. In order to ensure the normal operation of the process, additional superheated steam is required.

[0087] Comparative Example 4

[0088] Using the same inlet gas composition as in Example 4, if a single autothermal reforming furnace is selected, the process flow is as follows: natural gas and coke oven gas are subjected to the same pretreatment to obtain raw gas. 100,000 Nm 3 / h coke oven gas raw material, 50,000 Nm 3 / h natural gas raw material and 16,000 Nm 3 / h superheated steam, 79,000 Nm 3 / h CO2 is mixed and introduced into the primary autothermal reforming reactor, and 44,000 Nm 3 / h oxygen combustion. The reactor is loaded with nickel-based catalyst (118m 3 ) for methane reforming reaction, the conditions are the same as those in Example 4. When this intake gas composition is used, the catalyst will be deactivated by carbon deposition. To ensure the normal operation of the process, additional superheated steam and water vapor are required.

[0089] Comparative Example 5

[0090] Using the same inlet gas composition as in Example 5, if a single autothermal reforming furnace is selected, the process flow is as follows: The biogas is subjected to the same pretreatment to obtain the raw gas. 200,000 Nm 3 / h biogas raw material and 50,000 Nm 3 / h superheated steam is mixed and introduced into the primary autothermal reforming reactor, and 79,000 Nm 3 / h oxygen combustion. The reactor is loaded with nickel-based catalyst (174m 3 ), and methane reforming reaction is carried out under the same conditions as in Example 5. When this intake gas composition is used, the catalyst will be deactivated by carbon deposition. In order to ensure the normal operation of the process, additional superheated steam and water vapor are required.

[0091] In summary, the method for low water-carbon ratio methane conversion of the present invention conducts methane conversion reaction in batches in a series of reactors to obtain a synthesis gas product with a hydrogen-carbon ratio of 0.6 to 4.0, and no external heating is required during the reaction process. The water-carbon ratio is low, which can save steam and reduce energy consumption; the external combustion is cancelled, and carbon dioxide can be fully utilized, reducing carbon and being environmentally friendly; there is no open flame device in the system, which can reduce the land occupation and reduce costs; and the requirements for catalysts are relatively loose, and the system can operate for a long time. At the same time, the processing capacity of methane can be increased by setting multiple autothermal reforming furnaces in series / parallel. Therefore, the present invention effectively overcomes the various shortcomings in the prior art and has a high industrial utilization value.

[0092] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for converting methane at a low water-to-carbon ratio, characterized in that: The following steps are involved: 1) Pre-treating the first raw gas (10) and mixing it with the third raw gas (30) to carry out a first methane conversion reaction, adding the first oxygen-rich gas (11) during the reaction, and obtaining a primary reaction product; 2) Pre-treating the second raw gas (20) and mixing it with the primary reaction product obtained in step 1) to carry out a second methane conversion reaction, adding a second oxygen-rich gas (12) during the reaction to obtain a secondary reaction product; The first raw gas (10) and the second raw gas (20) are independently selected from any one or more of natural gas, biogas, coal-bed gas, coke oven gas, oil field gas, refinery gas, methanol synthesis purge gas, and Fischer-Tropsch synthesis purge gas; The third raw gas (30) is selected from any one or more of water vapor, carbon dioxide, and carbon dioxide-rich gas.

2. The method for low water-to-carbon ratio methane conversion according to claim 1, characterized in that: Also includes one or more of the following characteristics: A) the first oxygen-enriched gas (11) and the second oxygen-enriched gas (12) are each independently selected from high-purity oxygen, air, nitrogen-enriched air or oxygen-enriched air; B) the molar flow ratio of the first raw material gas (10) in step 1) to the second raw material gas (20) in step 2) is (50-200):(50-200); C) The molar flow ratio of the first oxygen-rich gas (11) in step 1) to the second oxygen-rich gas (12) in step 2) is (50-200): (50～200)； D) In ​​step 2), water vapor and / or carbon dioxide are also added to the second raw gas (20).

3. The method for low water-to-carbon ratio methane conversion according to claim 1, characterized in that: In step 1), the molar ratio of water vapor to carbon in alkanes in the mixed gas obtained by mixing the first raw gas (10) and the third raw gas (30) is (0-2.0):

1.

4. The method for low water-to-carbon ratio methane conversion according to claim 1, characterized in that: In step 1), the molar ratio of carbon dioxide to carbon in alkanes in the mixed gas obtained by mixing the first raw gas (10) and the third raw gas (30) is (0-2.0):

1.

5. The method for low water-to-carbon ratio methane conversion according to claim 1, characterized in that: The pretreatments in step 1) and step 2) are desulfurization treatment and / or dechlorination treatment and / or compression treatment.

6. The method for low water-to-carbon ratio methane conversion according to claim 5, characterized in that: When the first raw gas (10) contains sulfur, desulfurization treatment is performed, and the sulfur content in the raw gas after the desulfurization treatment is less than 0.5 ppm; And / or, when the second raw gas (20) contains sulfur, desulfurization treatment is performed, and the sulfur content in the raw gas after the desulfurization treatment is lower than 0.5 ppm.

7. The method for low water-to-carbon ratio methane conversion according to claim 5, characterized in that: When the first raw gas (10) contains chlorine, dechlorination treatment is performed, and the chlorine content in the raw gas after the dechlorination treatment is less than 0.5 ppm; And / or, when the second raw gas (20) contains chlorine, dechlorination treatment is performed, and the chlorine content in the raw gas after the dechlorination treatment is less than 0.5 ppm.

8. The method for low water-to-carbon ratio methane conversion according to claim 1, characterized in that: The first methane conversion reaction and the second methane conversion reaction are both carried out in an autothermal reforming furnace; And / or, the first methane conversion reaction and the second methane conversion reaction are both carried out under catalyst conditions; and / or, the temperature of the first raw gas (10) and the second raw gas (20) after pretreatment is 25 to 500° C. and the pressure is 5 to 60 bar; And / or, in step 1), the pressure of the first methane conversion reaction is 5 to 60 bar; And / or, in step 1), the discharge temperature of the primary reaction product is 800-1200° C.; And / or, in step 2), the pressure of the second methane conversion reaction is 5 to 60 bar; And / or, in step 2), the discharge temperature of the secondary reaction product is 800-1200° C.; And / or, in step 2), the molar ratio of hydrogen to carbon monoxide in the secondary reaction product is 0.6 to 4.

0.

9. A system applicable to the low water-to-carbon ratio methane conversion method according to any one of claims 1 to 8, characterized in that: The system comprises a primary reactor (E1) and a secondary reactor (E2) which are sequentially connected in series; It also includes a first pretreatment device (P1) and a second pretreatment device (P2), wherein the feed port of the first pretreatment device (P1) is connected to the feed pipeline of the first raw material gas (10), and the discharge port of the first pretreatment device (P1) is connected to the feed port of the primary reactor (E1); the feed port of the second pretreatment device (P2) is connected to the feed pipeline of the second raw material gas (20), and the discharge port of the second pretreatment device (P2) is connected to the feed port of the secondary reactor (E2); The feed port of the primary reactor (E1) is also connected to the third raw material gas (30) feed pipeline and the first oxygen-rich gas (11) feed pipeline, and the discharge port of the primary reactor (E1) is connected to the feed port of the secondary reactor (E2); The feed port of the secondary reactor (E2) is also connected to the feed pipeline of the second oxygen-rich gas (12), and the discharge port of the secondary reactor (E2) is connected to the product collection pipeline.

10. The system according to claim 8, characterized in that The primary reactor (E1) and the secondary reactor (E2) are both autothermal reformers.

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