Process and system for the production of methanol from biogas

Abstract

The present application relates to the chemical industry field, disclose a method and system for preparing methanol from biogas. The method comprises the following steps: biogas is subjected to primary pressure boosting, desulfurization and secondary pressure boosting to obtain desulfurized and pressure-boosted biogas; at least part of the desulfurized and pressure-boosted biogas is subjected to catalytic reforming reaction; the obtained conversion gas is subjected to heat exchange and cooling to obtain cooled conversion gas and steam; the steam is used as raw material and combined with one of the desulfurized and pressure-boosted biogas to perform catalytic reforming reaction; the cooled conversion gas is subjected to decarburization, pressure boosting and methanol synthesis reaction to obtain methanol and purge gas. The method and system can realize high utilization of carbon resources in biogas, and can recycle heat, carbon dioxide, hydrogen and biogas waste generated in the process of preparing methanol from biogas. In addition, the multi-stage pressure boosting method can avoid the problems of high energy consumption and high equipment requirement caused by sequential single pressure boosting, thereby reducing the overall investment cost, and the whole process is green and pollution-free.

Description

Technical Field

[0001] This invention relates to the field of methanol synthesis technology, and more specifically to a method and system for preparing methanol from biogas. Background Technology

[0002] Methanol is an important industrial chemical raw material and intermediate, widely used in organic synthesis, pharmaceuticals, pesticides, coatings, and dyes. At the same time, methanol is also a clean fuel, used in the production of methanol fuel and methanol gasoline.

[0003] The main technical routes for producing methanol are: (1) Methanol from natural gas: using natural gas as raw material, methanol is produced through catalytic conversion; this technical route has the advantages of abundant raw materials, mature process and good product quality, but the cost is high, and the extraction and use of natural gas are also restricted by environmental protection and energy security; (2) Methanol from coal: using coal as raw material, methanol is produced through gasification, purification and synthesis processes; although this technical route has a lower cost, there are problems such as environmental pollution and energy consumption; (3) Methanol from biomass: using biomass (such as wood, agricultural waste, etc.) as raw material, methanol is produced through gasification, fermentation and other processes, and the produced methanol is called green methanol; this technical route has the advantages of environmental protection and renewability, but there are certain challenges in terms of raw material sources and production costs.

[0004] With the increasing severity of global climate change and environmental problems, reducing carbon emissions and achieving carbon neutrality has become a global consensus. However, under existing technologies, the production of green methanol faces challenges such as large investment, high costs, long process flow, numerous equipment, high hydrogen consumption, high energy consumption, and insufficient carbon emissions. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of high investment, high cost, long process flow, many equipment, high hydrogen consumption, high energy consumption and insufficient carbon emissions in the existing technology for preparing green methanol. It provides a method and system for preparing methanol from biogas. This method and system can achieve high utilization of carbon resources in biogas, reuse the heat, carbon dioxide, hydrogen and biogas waste generated in the process of preparing methanol from biogas, and avoid the problems of high energy consumption and high equipment requirements of sequential single pressurization by adopting a multi-stage pressurization method, thereby reducing the overall investment cost. The whole process is green and pollution-free.

[0006] To achieve the above objectives, the present invention provides a first method for preparing methanol from biogas, the method comprising the following steps:

[0007] A1: Pressurize the biogas to obtain pressurized biogas, then desulfurize it to obtain desulfurized biogas, pressurize the desulfurized biogas to obtain desulfurized pressurized biogas, and subject at least a portion of the desulfurized pressurized biogas to a catalytic reforming reaction to obtain converted gas;

[0008] A2: The reformed gas is heat-exchanged with water to obtain cooled reformed gas and steam, and at least a portion of the steam is used as a raw material to participate in the catalytic reforming reaction;

[0009] A3: The cooled conversion gas is decarbonized to obtain decarbonized conversion gas, which is then pressurized to obtain decarbonized pressurized conversion gas, and then methanol synthesis reaction is carried out to obtain methanol and purge gas;

[0010] The H / C modulus ratio of the decarbonization conversion gas is 1.9-2.2.

[0011] A second aspect of the present invention provides a second method for preparing methanol from biogas, the method comprising the following steps:

[0012] B1: Pressurize the biogas to obtain pressurized biogas, then desulfurize it to obtain desulfurized biogas, pressurize the desulfurized biogas to obtain desulfurized pressurized biogas, and subject at least a portion of the desulfurized pressurized biogas to a catalytic reforming reaction to obtain converted gas;

[0013] B2: The reformed gas is heat-exchanged with water to obtain cooled reformed gas and steam, and at least a portion of the steam is used as a raw material to participate in the catalytic reforming reaction;

[0014] B3: The cooled conversion gas is heated by decarbonization treatment, then heat exchanged with water, and then decarbonized to obtain decarbonized conversion gas. Then it is pressurized to obtain decarbonized pressurized conversion gas, and then methanol synthesis reaction is carried out to obtain methanol and purge gas.

[0015] The H / C modulus ratio of the decarbonization conversion gas is 1.9-2.2.

[0016] A third aspect of the present invention provides a third method for preparing methanol from biogas, the method comprising the following steps:

[0017] C1: Pressurize the biogas to obtain pressurized biogas, then desulfurize it to obtain desulfurized biogas, pressurize the desulfurized biogas to obtain desulfurized pressurized biogas, and subject at least a portion of the desulfurized pressurized biogas to a catalytic reforming reaction to obtain converted gas;

[0018] C2: The reformed gas is heat-exchanged with water to obtain cooled reformed gas and steam, and at least a portion of the steam is used as a raw material to participate in the catalytic reforming reaction;

[0019] C3: The cooled conversion gas is used to heat the methanol synthesis reaction, then it exchanges heat with water, and then undergoes decarbonization treatment to obtain decarbonized conversion gas. Then it is pressurized to obtain decarbonized pressurized conversion gas, and then the methanol synthesis reaction is carried out to obtain methanol and purge gas.

[0020] The H / C modulus ratio of the decarbonization conversion gas is 1.9-2.2.

[0021] The fourth aspect of this invention provides a fourth method for preparing methanol from biogas, the method comprising the following steps:

[0022] D1: Pressurize the biogas to obtain pressurized biogas, then desulfurize it to obtain desulfurized biogas, pressurize the desulfurized biogas to obtain desulfurized pressurized biogas, and subject at least a portion of the desulfurized pressurized biogas to a catalytic reforming reaction to obtain converted gas;

[0023] D2: The reformed gas is heated by water to obtain cooled reformed gas and steam, and at least a portion of the steam is used as a raw material to participate in the catalytic reforming reaction;

[0024] D3: The cooled conversion gas is used to heat the methanol synthesis reaction, then to heat the decarbonization process, then to exchange heat with water, then to carry out the decarbonization process to obtain decarbonized conversion gas, then to pressurize it to obtain decarbonized pressurized conversion gas, then to carry out the methanol synthesis reaction to obtain methanol and purge gas.

[0025] The H / C modulus ratio of the decarbonization conversion gas is 1.9-2.2.

[0026] Preferably, the purge gas is subjected to hydrogen separation to obtain hydrogen and hydrogen-lean purge gas;

[0027] The hydrogen-poor off-gas serves as fuel to provide heat for the catalytic reforming reaction.

[0028] Preferably, the hydrogen is used as a raw material for the methanol synthesis reaction and / or as a raw material for the catalytic reforming reaction.

[0029] Preferably, at least a portion of the desulfurized and pressurized biogas is used as fuel to provide heat for the catalytic reforming reaction.

[0030] Preferably, the conditions for the catalytic reforming reaction include: a temperature of 750-960°C and a pressure of 0.05-5 MPaG.

[0031] Preferably, the conditions for the methanol synthesis reaction include: a temperature of 220-320℃ and a pressure of 0.8-15 MPaG.

[0032] Preferably, the biogas contains 0-3.5% sulfur by volume, 0-45% carbon dioxide by volume, and 50-65% methane by volume.

[0033] Preferably, the temperature of the biogas is 20-65℃ and the pressure of the biogas is 0.001-0.15MPaG.

[0034] Preferably, the pressure of the pressurized biogas is 0.02-10 MPaG.

[0035] Preferably, the sulfur content in the desulfurized and pressurized biogas is 0-20 ppmv.

[0036] Preferably, the temperature of the cooling conversion gas is 40-420℃.

[0037] Preferably, the pressure of the decarbonization and pressurization conversion gas is 4-15 MPaG.

[0038] The fifth aspect of the present invention provides a system for implementing a first method for producing methanol from biogas, the system comprising: a primary pressurization unit, a desulfurization unit, a secondary pressurization unit, a catalytic reforming unit, a heat recovery unit, a decarbonization unit, a pressurization unit, a methanol synthesis unit, and a decarbonization control unit;

[0039] The biogas to be treated enters the primary pressurization unit and is pressurized to obtain pressurized biogas. Then it enters the desulfurization unit for desulfurization treatment to obtain desulfurized biogas. Next, it enters the secondary pressurization unit for pressurization to obtain desulfurized pressurized biogas. At least a portion of the desulfurized pressurized biogas enters the catalytic reforming unit for catalytic reforming reaction to obtain converted gas.

[0040] The converted gas enters the heat recovery unit and exchanges heat with water to obtain cooled converted gas and steam. At least part of the steam enters the catalytic reforming unit to participate in the catalytic reforming reaction.

[0041] The cooled conversion gas enters the decarbonization unit for decarbonization treatment to obtain decarbonized conversion gas, and then enters the pressurization unit for pressurization to obtain decarbonized pressurized conversion gas, which then enters the methanol synthesis unit for methanol synthesis reaction to obtain methanol and purge gas.

[0042] The decarbonization control unit is connected to the decarbonization unit and is used to control the H / C modulus ratio of the decarbonization conversion gas to be 1.9-2.2.

[0043] The sixth aspect of the present invention provides a system for implementing a second method for producing methanol from biogas, the system comprising: a primary pressurization unit, a desulfurization unit, a secondary pressurization unit, a catalytic reforming unit, a heat recovery unit, a decarbonization unit, a pressurization unit, a methanol synthesis unit, and a decarbonization control unit;

[0044] The biogas to be treated enters the primary pressurization unit and is pressurized to obtain pressurized biogas. Then it enters the desulfurization unit for desulfurization treatment to obtain desulfurized biogas. Next, it enters the secondary pressurization unit for pressurization to obtain desulfurized pressurized biogas. At least a portion of the desulfurized pressurized biogas enters the catalytic reforming unit for catalytic reforming reaction to obtain converted gas.

[0045] The converted gas enters the heat recovery unit and exchanges heat with water to obtain cooled converted gas and steam. At least part of the steam enters the catalytic reforming unit to participate in the catalytic reforming reaction.

[0046] The cooled conversion gas enters the decarbonization unit to provide heat for the decarbonization process, then returns to the heat recovery unit to exchange heat with water, and then re-enters the decarbonization unit for the decarbonization process to obtain decarbonized conversion gas. It then enters the pressurization unit to obtain decarbonized pressurized conversion gas, and then enters the methanol synthesis unit to carry out the methanol synthesis reaction to obtain methanol and purge gas.

[0047] The decarbonization control unit is connected to the decarbonization unit and is used to control the H / C modulus ratio of the decarbonization conversion gas to be 1.9-2.2.

[0048] The seventh aspect of the present invention provides a system for implementing a third method for producing methanol from biogas, the system comprising: a primary pressurization unit, a desulfurization unit, a secondary pressurization unit, a catalytic reforming unit, a heat recovery unit, a decarbonization unit, a pressurization unit, a methanol synthesis unit, and a decarbonization control unit;

[0049] The biogas to be treated enters the primary pressurization unit and is pressurized to obtain pressurized biogas. Then it enters the desulfurization unit for desulfurization treatment to obtain desulfurized biogas. Next, it enters the secondary pressurization unit for pressurization to obtain desulfurized pressurized biogas. At least a portion of the desulfurized pressurized biogas enters the catalytic reforming unit for catalytic reforming reaction to obtain converted gas.

[0050] The converted gas enters the heat recovery unit and exchanges heat with water to obtain cooled converted gas and steam. At least part of the steam enters the catalytic reforming unit to participate in the catalytic reforming reaction.

[0051] The cooled conversion gas enters the methanol synthesis unit to heat the methanol synthesis reaction, then returns to the heat recovery unit to exchange heat with water, then enters the decarbonization unit for decarbonization treatment to obtain decarbonized conversion gas, then enters the pressurization unit for pressurization to obtain decarbonized pressurized conversion gas, and then enters the methanol synthesis unit for the methanol synthesis reaction to obtain methanol and purge gas.

[0052] The decarbonization control unit is connected to the decarbonization unit and is used to control the H / C modulus ratio of the decarbonization conversion gas to be 1.9-2.2.

[0053] The eighth aspect of the present invention provides a system for implementing a fourth method for producing methanol from biogas, the system comprising: a primary pressurization unit, a desulfurization unit, a secondary pressurization unit, a catalytic reforming unit, a heat recovery unit, a decarbonization unit, a pressurization unit, a methanol synthesis unit, and a decarbonization control unit;

[0054] The biogas to be treated enters the primary pressurization unit and is pressurized to obtain pressurized biogas. Then it enters the desulfurization unit for desulfurization treatment to obtain desulfurized biogas. Next, it enters the secondary pressurization unit for pressurization to obtain desulfurized pressurized biogas. At least a portion of the desulfurized pressurized biogas enters the catalytic reforming unit for catalytic reforming reaction to obtain converted gas.

[0055] The converted gas enters the heat recovery unit and exchanges heat with water to obtain cooled converted gas and steam. At least part of the steam enters the catalytic reforming unit to participate in the catalytic reforming reaction.

[0056] The cooled conversion gas enters the methanol synthesis unit to heat the methanol synthesis reaction, then enters the decarbonization unit to heat the decarbonization process, then returns to the heat recovery unit to exchange heat with water, then enters the decarbonization unit to undergo the decarbonization process to obtain decarbonized conversion gas, then enters the pressurization unit to pressurize the gas to obtain decarbonized pressurized conversion gas, then enters the methanol synthesis unit to carry out the methanol synthesis reaction to obtain methanol and purge gas;

[0057] The decarbonization control unit is connected to the decarbonization unit and is used to control the H / C modulus ratio of the decarbonization conversion gas to be 1.9-2.2.

[0058] Preferably, the system further includes a hydrogen separation unit; the purge gas enters the hydrogen separation unit for hydrogen separation to obtain hydrogen and hydrogen-lean purge gas;

[0059] The hydrogen-lean off-gas is used as fuel to enter the catalytic reforming unit and provide heat for the catalytic reforming reaction.

[0060] Preferably, the hydrogen gas enters the booster unit as a raw material for the methanol synthesis reaction; and / or

[0061] The hydrogen gas enters the catalytic reforming unit to participate in the catalytic reforming reaction.

[0062] Preferably, at least a portion of the desulfurized and pressurized biogas is used as fuel to enter the catalytic reforming unit to provide heat for the catalytic reforming reaction.

[0063] Compared with existing technologies, the method and system described in this invention can achieve high utilization of carbon resources in biogas, reuse the heat, carbon dioxide, hydrogen and biogas waste generated in the process of biogas to methanol, and avoid the problems of high energy consumption and high equipment requirements of sequential single pressurization by adopting a multi-stage pressurization method, thereby reducing the overall investment cost. The whole process is green and pollution-free. Attached Figure Description

[0064] Figure 1 This is a schematic diagram of the system for preparing methanol from biogas in Example 1 of the present invention;

[0065] Figure 2 This is a schematic diagram of the system for preparing methanol from biogas in Example 2 of the present invention;

[0066] Figure 3 This is a schematic diagram of the system for preparing methanol from biogas in Example 3 of the present invention;

[0067] Figure 4 This is a schematic diagram of the system for preparing methanol from biogas in Example 4 of the present invention;

[0068] Figure 5 This is a schematic diagram of the system for preparing methanol from biogas in Example 5 of the present invention;

[0069] Figure 6 This is a schematic diagram of the system for preparing methanol from biogas in Example 6 of the present invention;

[0070] Figure 7 This is a schematic diagram of the system for preparing methanol from biogas in Example 7 of the present invention;

[0071] Figure 8 This is a schematic diagram of the system for preparing methanol from biogas in Example 8 of the present invention;

[0072] Figure 9 This is a schematic diagram of the system for preparing methanol from biogas in Example 9 of the present invention;

[0073] Figure 10 This is a schematic diagram of the system for preparing methanol from biogas in Example 10 of the present invention;

[0074] Figure 11 This is a schematic diagram of the system for preparing methanol from biogas in Comparative Example 1 of the present invention.

[0075] Explanation of reference numerals in the attached figures

[0076] 1. Primary booster unit; 2. Desulfurization unit

[0077] 3 Secondary boost unit 4 Catalytic reforming unit

[0078] 5. Heat recovery unit; 6. Decarbonization unit

[0079] 7. Boost unit; 8. Methanol synthesis unit

[0080] 9 Hydrogen separation unit 10 Decarbonization control unit Detailed Implementation

[0081] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0082] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0083] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating relative importance or implying the number of technical features indicated. Therefore, unless otherwise stated, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; "multiple" means two or more. The term "comprising" and any variations thereof mean non-exclusive inclusion, where one or more other features, integers, steps, operations, units, components, and / or combinations thereof may be present or added.

[0084] Furthermore, terms such as "upper," "lower," "inner," and "outer" indicating orientation or positional relationships are based on the orientation or relative positional relationships shown in the accompanying drawings. They are merely simplified descriptions for the convenience of describing this application and do not indicate that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0085] Furthermore, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0086] This invention provides a first method for preparing methanol from biogas, the method comprising the following steps:

[0087] A1: Pressurize the biogas to obtain pressurized biogas, then desulfurize it to obtain desulfurized biogas, pressurize the desulfurized biogas to obtain desulfurized pressurized biogas, and subject at least a portion of the desulfurized pressurized biogas to a catalytic reforming reaction to obtain converted gas;

[0088] A2: The reformed gas is heat-exchanged with water to obtain cooled reformed gas and steam, and at least a portion of the steam is used as a raw material to participate in the catalytic reforming reaction;

[0089] A3: The cooled conversion gas is decarbonized to obtain decarbonized conversion gas, which is then pressurized to obtain decarbonized pressurized conversion gas, and then methanol synthesis reaction is carried out to obtain methanol and purge gas;

[0090] The H / C modulus ratio of the decarbonization conversion gas is 1.9-2.2.

[0091] In the first method for preparing methanol from biogas described above, when all the desulfurized and pressurized biogas undergoes catalytic reforming, the biogas is sequentially pressurized, desulfurized, and then pressurized again to obtain desulfurized and pressurized biogas that meets the pressure required for the catalytic reforming reaction. Then, the biogas undergoes catalytic reforming to obtain converted gas, the main components of which are carbon monoxide, hydrogen, and small amounts of methane and carbon dioxide. This avoids the problems of high single-pressurization pressure ratio, high energy consumption, and high equipment requirements caused by a single pressurization of the biogas for catalytic reforming.

[0092] Next, the converted gas exchanges heat with water, causing the temperature of the converted gas to decrease and become cooled converted gas, while the temperature of the heat exchange medium water increases and it is converted into steam. The steam then participates in the catalytic reforming reaction as a raw material, thereby realizing the further utilization of heat and raw materials and reducing the overall energy consumption.

[0093] The cooled conversion gas is then decarbonized to obtain decarbonized conversion gas. The H / C modulus ratio of the decarbonized conversion gas is controlled to be 1.9-2.2, thereby improving the raw material utilization rate of the subsequent methanol synthesis reaction. Then, the gas is pressurized to obtain decarbonized pressurized conversion gas, which meets the pressure required for the methanol synthesis reaction. Then, it enters the methanol synthesis unit 8 to carry out the methanol synthesis reaction, and obtains methanol and purge gas.

[0094] In the first method for preparing methanol from biogas described above, when a portion of the desulfurized and pressurized biogas undergoes catalytic reforming, the remaining portion of the desulfurized and pressurized biogas is used as fuel to provide heat for the catalytic reforming reaction. Based on this, the utilization rate of biogas can be further improved, and the utilization of biogas calorific value can be increased. This avoids the problems of low biogas calorific value, excessive sulfur content in flue gas, and equipment corrosion that exist when biogas is directly used as fuel.

[0095] In all the methods described in this invention, in a preferred embodiment, the desulfurized and pressurized biogas used as fuel accounts for 1-50% of the total volume of the desulfurized and pressurized biogas.

[0096] In all the methods described in this invention, in a preferred embodiment, in order to further improve the utilization rate of biogas and improve the utilization of carbon resources in biogas, the H / C modulus ratio of the decarbonized conversion gas is 2-2.15.

[0097] In this invention, the “H / C modulus ratio” refers to the ratio of the number of moles of (H2-CO2) to the number of moles of (CO+CO2).

[0098] In all the methods described in this invention, in a preferred embodiment, in order to improve the utilization rate of the biogas, the off-gas is further utilized by separating hydrogen from the off-gas to obtain hydrogen and hydrogen-lean off-gas; the hydrogen-lean off-gas is used as fuel to provide heat for the catalytic reforming reaction, thereby reusing the hydrogen-lean off-gas, improving the utilization rate of biogas, and reducing the release of pollutants.

[0099] In all the methods described in this invention, in a preferred embodiment, in order to improve the utilization rate of hydrogen, the hydrogen is used as a raw material for the methanol synthesis reaction to adjust the H / C modulus ratio of the decarbonization conversion gas, thereby improving the utilization rate of the raw materials for the methanol synthesis reaction.

[0100] In another preferred embodiment of all the methods described in this invention, in order to improve the utilization rate of hydrogen, the hydrogen is used as a raw material in the catalytic reforming reaction.

[0101] In another preferred embodiment of all the methods described in this invention, in order to further improve the utilization rate of hydrogen, the hydrogen is divided into two streams. One stream is used as a raw material for the subsequent methanol synthesis reaction to adjust the H / C modulus ratio of the decarbonization conversion gas, thereby improving the utilization rate of the raw material for the methanol synthesis reaction. The other stream is used as a raw material for the catalytic reforming reaction, thereby extending the operation cycle of the catalytic reforming reaction by about 5%.

[0102] In this invention, all "heat exchange" refers to non-contact heat exchange.

[0103] In all the methods described in this invention, the desulfurization method is selected from at least one of wet oxidation desulfurization, low-temperature methanol washing desulfurization, wet amine desulfurization, and adsorption desulfurization.

[0104] In all the methods described in this invention, the catalytic reforming reaction is selected from at least one of methane steam reforming, methane autothermal reforming, and methane carbon dioxide steam dual reforming.

[0105] In all the methods described in this invention, in a preferred embodiment, in order to improve energy utilization, the steam participating in the catalytic reforming reaction as a raw material accounts for 5.5-100% of the total steam volume.

[0106] In all the methods described in this invention, in a preferred embodiment, in order to improve the feedstock utilization rate of the catalytic reforming reaction, the conditions of the catalytic reforming reaction include: a temperature of 750-960°C and a pressure of 0.05-5 MPaG; preferably, the pressure is 0.75-3.5 MPaG.

[0107] In all the methods described in this invention, in a preferred embodiment, in order to improve the raw material utilization rate of the methanol synthesis reaction, the conditions for the methanol synthesis reaction include: a temperature of 220-320°C and a pressure of 0.8-15 MPaG.

[0108] In all the methods described in this invention, in a preferred embodiment, the volume content of sulfur-containing gas in the biogas is 0-3.5%, the volume content of carbon dioxide in the biogas is 0-45%, and the volume content of methane in the biogas is 50-65%.

[0109] In all the methods described in this invention, in a preferred embodiment, the temperature of the biogas is 20-65°C and the pressure of the biogas is 0.001-0.15 MPaG.

[0110] In all the methods described in this invention, in a preferred embodiment, the pressure of the pressurized biogas is 0.02-10 MPaG.

[0111] In all the methods described in this invention, in a preferred embodiment, the sulfur content in the desulfurized and pressurized biogas is 0-20 ppmv.

[0112] In all the methods described in this invention, in a preferred embodiment, the temperature of the cooling conversion gas is 40-420°C.

[0113] In all the methods described in this invention, in a preferred embodiment, the pressure of the decarbonization booster gas is 4-15 MPaG.

[0114] The first method for producing methanol from biogas described above is implemented in the following system, which includes: a primary pressurization unit 1, a desulfurization unit 2, a secondary pressurization unit 3, a catalytic reforming unit 4, a heat recovery unit 5, a decarbonization unit 6, a pressurization unit 7, a methanol synthesis unit 8, and a decarbonization control unit 10.

[0115] The biogas to be treated enters the primary pressurization unit 1 and is pressurized to obtain pressurized biogas. Then it enters the desulfurization unit 2 for desulfurization treatment to obtain desulfurized biogas. Next, it enters the secondary pressurization unit 3 and is pressurized to obtain desulfurized pressurized biogas. At least a portion of the desulfurized pressurized biogas enters the catalytic reforming unit 4 for catalytic reforming reaction to obtain converted gas.

[0116] The converted gas enters the heat recovery unit 5 to exchange heat with water, and obtains cooled converted gas and steam. At least part of the steam enters the catalytic reforming unit 4 to participate in the catalytic reforming reaction.

[0117] The cooled conversion gas enters the decarbonization unit 6 for decarbonization treatment to obtain decarbonized conversion gas, and then enters the pressurization unit 7 for pressurization to obtain decarbonized pressurized conversion gas, and then enters the methanol synthesis unit 8 for methanol synthesis reaction to obtain methanol and purge gas.

[0118] The decarbonization control unit 10 is connected to the decarbonization unit 6 and is used to control the H / C modulus ratio of the decarbonization conversion gas to be 1.9-2.2.

[0119] In all the systems described in this invention, the primary boosting unit 1, the secondary boosting unit 3, and the boosting unit 7 all include a compressor, which is selected from at least one of a reciprocating compressor, a centrifugal compressor, and an axial compressor; preferably a reciprocating compressor.

[0120] In the system described in this invention, the heat recovery unit 5 includes at least one of a steam generator, a raw material preheater, a demineralized water deaerator, an air cooler, and a water cooler.

[0121] In the system for implementing the first method of biogas to methanol described in this invention, when all the desulfurized and pressurized biogas enters the catalytic reforming unit 4 for catalytic reforming reaction, the secondary pressurization unit 3 is connected to the catalytic reforming unit 4 through a pipeline. In this embodiment, the biogas to be treated sequentially passes through the primary pressurization unit 1, the desulfurization unit 2, and the secondary pressurization unit 3 for primary pressurization, desulfurization, and secondary pressurization to obtain desulfurized and pressurized biogas, which meets the pressure required for the catalytic reforming reaction. Then, it enters the catalytic reforming unit 4 for catalytic reforming reaction to obtain converted gas. The main components of the converted gas are carbon monoxide, hydrogen, and small amounts of methane and carbon dioxide. Based on this, the problems of high single pressurization pressure ratio, high energy consumption, and high equipment requirements caused by the biogas to be treated undergoing catalytic reforming reaction through a single pressurization can be avoided.

[0122] The converted gas then enters the heat recovery unit 5 to exchange heat with water, thereby lowering the temperature of the converted gas to obtain cooled converted gas, while the temperature of the heat exchange medium water rises and is converted into steam; at least a portion of the steam enters the catalytic reforming unit 4 to participate in the catalytic reforming reaction, thereby realizing further utilization of heat and raw materials and reducing overall energy consumption.

[0123] The cooled conversion gas then enters the decarbonization unit 6 for decarbonization treatment to obtain decarbonized conversion gas. At the same time, the decarbonization control unit 10 connected to the decarbonization unit 6 controls the H / C modulus ratio of the decarbonized conversion gas to be 1.9-2.2, thereby improving the raw material utilization rate of the subsequent methanol synthesis reaction. Then, it enters the pressurization unit 7 for pressurization to obtain decarbonized pressurized conversion gas that meets the pressure required for the methanol synthesis reaction. Next, it enters the methanol synthesis unit 8 for methanol synthesis reaction to obtain methanol and purge gas.

[0124] In the method system for producing methanol from biogas according to the present invention, when the desulfurized and pressurized biogas enters the catalytic reforming unit 4 for catalytic reforming reaction, the secondary pressurization unit 3 is connected to the catalytic reforming unit 4 through two pipelines. In this embodiment, the biogas to be treated sequentially passes through the primary pressurization unit 1, the desulfurization unit 2, and the secondary pressurization unit 3 for primary pressurization, desulfurization, and secondary pressurization to obtain desulfurized and pressurized biogas, which meets the pressure required for the catalytic reforming reaction. Then, the desulfurized and pressurized biogas is divided into two streams, one of which enters the... Catalytic reforming unit 4 performs a catalytic reforming reaction to obtain converted gas. The main components of the converted gas are carbon monoxide, hydrogen, and small amounts of methane and carbon dioxide. Another stream enters the catalytic reforming unit 4 as fuel to provide heat for the catalytic reforming reaction. Based on this, the problems of high single-pressurization pressure ratio, high energy consumption, and high equipment requirements caused by catalytic reforming of biogas to be treated through a single pressurization can be avoided. At the same time, it can also improve the utilization rate of biogas and avoid the problems of low calorific value of biogas, excessive sulfur content in flue gas, and equipment corrosion caused by directly using biogas as fuel.

[0125] The converted gas then enters the heat recovery unit 5 to exchange heat with water, thereby lowering the temperature of the converted gas to obtain cooled converted gas, while the temperature of the heat exchange medium water rises and is converted into steam; at least a portion of the steam enters the catalytic reforming unit 4 to participate in the catalytic reforming reaction, thereby realizing the utilization of the heat of the converted gas and the further utilization of the steam, reducing the overall energy consumption.

[0126] The cooled conversion gas then enters the decarbonization unit 6 for decarbonization treatment to obtain decarbonized conversion gas. At the same time, the decarbonization control unit 10 connected to the decarbonization unit 6 controls the H / C modulus ratio of the decarbonized conversion gas to be 1.9-2.2, thereby improving the raw material utilization rate of the subsequent methanol synthesis reaction. Then, it enters the pressurization unit 7 for pressurization to obtain decarbonized pressurized conversion gas that meets the pressure required for the methanol synthesis reaction. Next, it enters the methanol synthesis unit 8 for methanol synthesis reaction to obtain methanol and purge gas.

[0127] In a preferred embodiment, the system further includes a hydrogen separation unit 9; the purge gas enters the hydrogen separation unit 9 for hydrogen separation to obtain hydrogen and hydrogen-lean purge gas; the hydrogen-lean purge gas is used as fuel to enter the catalytic reforming unit 4 to provide heat for the catalytic reforming reaction, thereby further improving the utilization rate of biogas, and avoiding the problems of low biogas calorific value, excessive sulfur content in flue gas, and equipment corrosion that exist when directly using biogas as fuel; specifically, the hydrogen separation unit 9 is connected to the methanol synthesis unit 8, and the hydrogen separation unit 9 is connected to the catalytic reforming unit 4.

[0128] In a preferred embodiment, the hydrogen enters the booster unit 7 as a raw material for the subsequent methanol synthesis reaction, adjusting the H / C modulus ratio of the decarbonization conversion gas, thereby improving the utilization rate of the raw materials for the methanol synthesis reaction; specifically, the hydrogen separation unit 9 is connected to the booster unit 7.

[0129] In another preferred embodiment, the hydrogen enters the catalytic reforming unit 4 to participate in the catalytic reforming reaction, thereby improving the utilization rate of hydrogen; specifically, the hydrogen separation unit 9 is connected to the catalytic reforming unit 4.

[0130] In another, more preferred embodiment, in order to improve the utilization rate of hydrogen, the hydrogen is divided into two streams. One stream enters the booster unit 7 as a raw material for the subsequent methanol synthesis reaction, adjusting the H / C modulus ratio of the decarbonization conversion gas, thereby improving the utilization rate of the raw material for the methanol synthesis reaction. The other stream enters the catalytic reforming unit 4 to participate in the catalytic reforming reaction. Specifically, the hydrogen separation unit 9 is connected to the booster unit 7 and the catalytic reforming unit 4, respectively.

[0131] The present invention also provides a second method for preparing methanol from biogas, the method comprising the following steps:

[0132] B1: Pressurize the biogas to obtain pressurized biogas, then desulfurize it to obtain desulfurized biogas, pressurize the desulfurized biogas to obtain desulfurized pressurized biogas, and subject at least a portion of the desulfurized pressurized biogas to a catalytic reforming reaction to obtain converted gas;

[0133] B2: The reformed gas is heat-exchanged with water to obtain cooled reformed gas and steam, and at least a portion of the steam is used as a raw material to participate in the catalytic reforming reaction;

[0134] B3: The cooled conversion gas is heated by decarbonization treatment, then heat exchanged with water, and then decarbonized to obtain decarbonized conversion gas. Then it is pressurized to obtain decarbonized pressurized conversion gas, and then methanol synthesis reaction is carried out to obtain methanol and purge gas.

[0135] The H / C modulus ratio of the decarbonization conversion gas is 1.9-2.2.

[0136] In the second method for preparing methanol from biogas described above, when all the desulfurized and pressurized biogas undergoes catalytic reforming, the biogas is sequentially pressurized, desulfurized, and then pressurized again to obtain desulfurized and pressurized biogas that meets the pressure required for the catalytic reforming reaction. Then, the biogas undergoes catalytic reforming to obtain converted gas, the main components of which are carbon monoxide, hydrogen, and small amounts of methane and carbon dioxide. This avoids the problems of high single-pressurization pressure ratio, high energy consumption, and high equipment requirements caused by a single pressurization of the biogas for catalytic reforming.

[0137] Next, the converted gas exchanges heat with water, causing the temperature of the converted gas to decrease and become cooled converted gas, while the temperature of the heat exchange medium water increases and it is converted into steam. The steam then participates in the catalytic reforming reaction as a raw material, thereby realizing the further utilization of heat and raw materials and reducing the overall energy consumption.

[0138] The cooled conversion gas is then used to heat the decarbonization process, followed by heat exchange with water, and then decarbonization is performed to obtain decarbonized conversion gas. The H / C modulus ratio of the decarbonized conversion gas is controlled to be 1.9-2.2. Based on this, the heat of the cooled conversion gas can be further utilized to reduce the energy consumption required for decarbonization and improve the raw material utilization rate of the subsequent methanol synthesis reaction. Then, the gas is pressurized to obtain decarbonized pressurized conversion gas, which meets the pressure required for the methanol synthesis reaction. Then, it enters the methanol synthesis unit 8 to carry out the methanol synthesis reaction, and methanol and purge gas are obtained.

[0139] In the second method for preparing methanol from biogas described above, when a portion of the desulfurized and pressurized biogas undergoes catalytic reforming, the remaining portion of the desulfurized and pressurized biogas is used as fuel to provide heat for the catalytic reforming reaction. Based on this, the utilization rate of biogas can be further improved, and the utilization of biogas calorific value can be increased. This avoids the problems of low biogas calorific value, excessive sulfur content in flue gas, and equipment corrosion that exist when biogas is directly used as fuel.

[0140] The second method for producing methanol from biogas described above is implemented in the following system, which includes: a primary pressurization unit 1, a desulfurization unit 2, a secondary pressurization unit 3, a catalytic reforming unit 4, a heat recovery unit 5, a decarbonization unit 6, a pressurization unit 7, a methanol synthesis unit 8, and a decarbonization control unit 10.

[0141] The biogas to be treated enters the primary pressurization unit 1 and is pressurized to obtain pressurized biogas. Then it enters the desulfurization unit 2 for desulfurization treatment to obtain desulfurized biogas. Next, it enters the secondary pressurization unit 3 and is pressurized to obtain desulfurized pressurized biogas. At least a portion of the desulfurized pressurized biogas enters the catalytic reforming unit 4 for catalytic reforming reaction to obtain converted gas.

[0142] The converted gas enters the heat recovery unit 5 to exchange heat with water, and obtains cooled converted gas and steam. At least part of the steam enters the catalytic reforming unit 4 to participate in the catalytic reforming reaction.

[0143] The cooled conversion gas enters the decarbonization unit 6 to provide heat for the decarbonization process, then returns to the heat recovery unit 5 to exchange heat with water, and then re-enters the decarbonization unit 6 to perform the decarbonization process, obtaining decarbonized conversion gas. It then enters the pressurization unit 7 to pressurize, obtaining decarbonized pressurized conversion gas, and then enters the methanol synthesis unit 8 to perform the methanol synthesis reaction, obtaining methanol and purge gas.

[0144] The decarbonization control unit 10 is connected to the decarbonization unit 6 and is used to control the H / C modulus ratio of the decarbonization conversion gas to be 1.9-2.2.

[0145] In the system for implementing the second method of biogas to methanol described in this invention, when all the desulfurized and pressurized biogas enters the catalytic reforming unit 4 for catalytic reforming reaction, the secondary pressurization unit 3 is connected to the catalytic reforming unit 4 through a pipeline. In this embodiment, the biogas to be treated sequentially passes through the primary pressurization unit 1, the desulfurization unit 2, and the secondary pressurization unit 3 for primary pressurization, desulfurization, and secondary pressurization to obtain desulfurized and pressurized biogas, which meets the pressure required for the catalytic reforming reaction. Then, it enters the catalytic reforming unit 4 for catalytic reforming reaction to obtain converted gas. The main components of the converted gas are carbon monoxide, hydrogen, and small amounts of methane and carbon dioxide. Based on this, the problems of high single pressurization pressure ratio, high energy consumption, and high equipment requirements caused by the biogas to be treated undergoing catalytic reforming reaction through a single pressurization can be avoided.

[0146] The converted gas then enters the heat recovery unit 5 to exchange heat with water, thereby lowering the temperature of the converted gas to obtain cooled converted gas, while the temperature of the heat exchange medium water rises and is converted into steam; at least a portion of the steam enters the catalytic reforming unit 4 to participate in the catalytic reforming reaction, thereby realizing further utilization of heat and raw materials and reducing overall energy consumption.

[0147] The cooled conversion gas then enters the decarbonization unit 6 to provide heat for the decarbonization process. It then returns to the heat recovery unit 5 to exchange heat with water, and then enters the decarbonization unit 6 again for decarbonization to obtain decarbonized conversion gas. This allows for further utilization of the heat from the cooled conversion gas. Simultaneously, the decarbonization control unit 10, connected to the decarbonization unit 6, controls the H / C modulus ratio of the decarbonized conversion gas to 1.9-2.2, thereby improving the raw material utilization rate for the subsequent methanol synthesis reaction. The gas then enters the pressurization unit 7 for pressurization, obtaining decarbonized pressurized conversion gas to meet the pressure required for the methanol synthesis reaction. Finally, it enters the methanol synthesis unit 8 for the methanol synthesis reaction, yielding methanol and purge gas.

[0148] In the system for implementing the second method of biogas to methanol according to the present invention, when the desulfurized and pressurized biogas enters the catalytic reforming unit 4 for catalytic reforming reaction, the secondary pressurization unit 3 is connected to the catalytic reforming unit 4 through two pipelines. In this embodiment, the biogas to be treated sequentially passes through the primary pressurization unit 1, the desulfurization unit 2, and the secondary pressurization unit 3 for primary pressurization, desulfurization treatment, and secondary pressurization to obtain desulfurized and pressurized biogas, which meets the pressure required for the catalytic reforming reaction. Then, the desulfurized and pressurized biogas is divided into two streams, one of which enters the... Catalytic reforming unit 4 performs a catalytic reforming reaction to obtain converted gas. The main components of the converted gas are carbon monoxide, hydrogen, and small amounts of methane and carbon dioxide. Another stream enters the catalytic reforming unit 4 as fuel to provide heat for the catalytic reforming reaction. Based on this, the problems of high single-pressurization pressure ratio, high energy consumption, and high equipment requirements caused by catalytic reforming of biogas to be treated through a single pressurization can be avoided. At the same time, it can also improve the utilization rate of biogas and avoid the problems of low calorific value of biogas, excessive sulfur content in flue gas, and equipment corrosion caused by directly using biogas as fuel.

[0149] The converted gas then enters the heat recovery unit 5 to exchange heat with water, thereby lowering the temperature of the converted gas to obtain cooled converted gas, while the temperature of the heat exchange medium water rises and is converted into steam; at least a portion of the steam enters the catalytic reforming unit 4 to participate in the catalytic reforming reaction, thereby realizing the utilization of the heat of the converted gas and the further utilization of the steam, reducing the overall energy consumption.

[0150] The cooled conversion gas then enters the decarbonization unit 6 to provide heat for the decarbonization process. It then returns to the heat recovery unit 5 to exchange heat with water, and then enters the decarbonization unit 6 again for decarbonization to obtain decarbonized conversion gas. This allows for further utilization of the heat from the cooled conversion gas. Simultaneously, the decarbonization control unit 10, connected to the decarbonization unit 6, controls the H / C modulus ratio of the decarbonized conversion gas to 1.9-2.2, thereby improving the raw material utilization rate for the subsequent methanol synthesis reaction. The gas then enters the pressurization unit 7 for pressurization, obtaining decarbonized pressurized conversion gas to meet the pressure required for the methanol synthesis reaction. Finally, it enters the methanol synthesis unit 8 for the methanol synthesis reaction, yielding methanol and purge gas.

[0151] In a preferred embodiment, the system further includes a hydrogen separation unit 9; the purge gas enters the hydrogen separation unit 9 for hydrogen separation to obtain hydrogen and hydrogen-lean purge gas; the hydrogen-lean purge gas is used as fuel to enter the catalytic reforming unit 4 to provide heat for the catalytic reforming reaction, thereby further improving the utilization rate of biogas, and avoiding the problems of low biogas calorific value, excessive sulfur content in flue gas, and equipment corrosion that exist when directly using biogas as fuel; specifically, the hydrogen separation unit 9 is connected to the methanol synthesis unit 8, and the hydrogen separation unit 9 is connected to the catalytic reforming unit 4.

[0152] In a preferred embodiment, the hydrogen enters the booster unit 7 as a raw material for the subsequent methanol synthesis reaction, adjusting the H / C modulus ratio of the decarbonization conversion gas, thereby improving the utilization rate of the raw materials for the methanol synthesis reaction; specifically, the hydrogen separation unit 9 is connected to the booster unit 7.

[0153] In another preferred embodiment, the hydrogen enters the catalytic reforming unit 4 to participate in the catalytic reforming reaction, thereby improving the utilization rate of hydrogen; specifically, the hydrogen separation unit 9 is connected to the catalytic reforming unit 4.

[0154] In another, more preferred embodiment, the hydrogen is divided into two streams: one stream enters the booster unit 7 as a raw material for the subsequent methanol synthesis reaction, and the other stream enters the catalytic reforming unit 4 to participate in the catalytic reforming reaction; specifically, the hydrogen separation unit 9 is connected to the booster unit 7 and the catalytic reforming unit 4 respectively.

[0155] A third aspect of the present invention provides a third method for preparing methanol from biogas, the method comprising the following steps:

[0156] C1: Pressurize the biogas to obtain pressurized biogas, then desulfurize it to obtain desulfurized biogas, pressurize the desulfurized biogas to obtain desulfurized pressurized biogas, and subject at least a portion of the desulfurized pressurized biogas to a catalytic reforming reaction to obtain converted gas;

[0157] C2: The reformed gas is heat-exchanged with water to obtain cooled reformed gas and steam, and at least a portion of the steam is used as a raw material to participate in the catalytic reforming reaction;

[0158] C3: The cooled conversion gas is used to heat the methanol synthesis reaction, then it exchanges heat with water, and then undergoes decarbonization treatment to obtain decarbonized conversion gas. Then it is pressurized to obtain decarbonized pressurized conversion gas, and then the methanol synthesis reaction is carried out to obtain methanol and purge gas.

[0159] The H / C modulus ratio of the decarbonization conversion gas is 1.9-2.2.

[0160] In the third method for preparing methanol from biogas described above, when all the desulfurized and pressurized biogas undergoes catalytic reforming, the biogas is sequentially pressurized, desulfurized, and then pressurized again to obtain desulfurized and pressurized biogas that meets the pressure required for the catalytic reforming reaction. Then, the biogas undergoes catalytic reforming to obtain converted gas, the main components of which are carbon monoxide, hydrogen, and small amounts of methane and carbon dioxide. This avoids the problems of high single-pressurization pressure ratio, high energy consumption, and high equipment requirements caused by a single pressurization of the biogas for catalytic reforming.

[0161] Next, the converted gas exchanges heat with water, causing the temperature of the converted gas to decrease and become cooled converted gas, while the temperature of the heat exchange medium water increases and it is converted into steam. The steam then participates in the catalytic reforming reaction as a raw material, thereby realizing the further utilization of heat and raw materials and reducing the overall energy consumption.

[0162] The cooled conversion gas heats the methanol synthesis reaction, then exchanges heat with water, and then undergoes decarbonization treatment to obtain decarbonized conversion gas. The H / C modulus ratio of the decarbonized conversion gas is controlled at 1.9-2.2. Based on this, the heat of the cooled conversion gas can be further utilized to reduce the energy consumption required for the methanol synthesis reaction, while improving the raw material utilization rate of the subsequent methanol synthesis reaction. Then, the gas is pressurized to obtain decarbonized pressurized conversion gas, which meets the pressure required for the methanol synthesis reaction. Then, it enters the methanol synthesis unit 8 to carry out the methanol synthesis reaction, and obtains methanol and purge gas.

[0163] In the third method for preparing methanol from biogas described above, when a portion of the desulfurized and pressurized biogas undergoes catalytic reforming, the remaining portion of the desulfurized and pressurized biogas is used as fuel to provide heat for the catalytic reforming reaction. Based on this, the utilization rate of biogas can be further improved, and the utilization of biogas calorific value can be increased. This avoids the problems of low biogas calorific value, excessive sulfur content in flue gas, and equipment corrosion that exist when biogas is directly used as fuel.

[0164] The third method for producing methanol from biogas described above is implemented in the following system, which includes: a primary pressurization unit 1, a desulfurization unit 2, a secondary pressurization unit 3, a catalytic reforming unit 4, a heat recovery unit 5, a decarbonization unit 6, a pressurization unit 7, a methanol synthesis unit 8, and a decarbonization control unit 10. The biogas to be treated enters the primary pressurization unit 1 and is pressurized to obtain pressurized biogas. Then, it enters the desulfurization unit 2 for desulfurization treatment to obtain desulfurized biogas. Next, it enters the secondary pressurization unit 3 for pressurization to obtain desulfurized pressurized biogas. At least a portion of the desulfurized pressurized biogas enters the catalytic reforming unit 4 for catalytic reforming reaction to obtain converted gas.

[0165] The converted gas enters the heat recovery unit 5 to exchange heat with water, and obtains cooled converted gas and steam. At least part of the steam enters the catalytic reforming unit 4 to participate in the catalytic reforming reaction.

[0166] The cooled conversion gas enters the methanol synthesis unit 8 to heat the methanol synthesis reaction, then returns to the heat recovery unit 5 to exchange heat with water, and then enters the decarbonization unit 6 for decarbonization treatment to obtain decarbonized conversion gas, then enters the pressurization unit 7 for pressurization to obtain decarbonized pressurized conversion gas, and then enters the methanol synthesis unit 8 to carry out the methanol synthesis reaction to obtain methanol and purge gas.

[0167] The decarbonization control unit 10 is connected to the decarbonization unit 6 and is used to control the H / C modulus ratio of the decarbonization conversion gas to be 1.9-2.2.

[0168] In the system for implementing the third method of biogas to methanol described in this invention, when all the desulfurized and pressurized biogas enters the catalytic reforming unit 4 for catalytic reforming reaction, the secondary pressurization unit 3 is connected to the catalytic reforming unit 4 through a pipeline. In this embodiment, the biogas to be treated sequentially passes through the primary pressurization unit 1, the desulfurization unit 2, and the secondary pressurization unit 3 for primary pressurization, desulfurization, and secondary pressurization to obtain desulfurized and pressurized biogas, which meets the pressure required for the catalytic reforming reaction. Then, it enters the catalytic reforming unit 4 for catalytic reforming reaction to obtain converted gas. The main components of the converted gas are carbon monoxide, hydrogen, and small amounts of methane and carbon dioxide. Based on this, the problems of high single pressurization pressure ratio, high energy consumption, and high equipment requirements caused by the biogas to be treated undergoing catalytic reforming reaction through a single pressurization can be avoided.

[0169] The converted gas then enters the heat recovery unit 5 to exchange heat with water, thereby lowering the temperature of the converted gas to obtain cooled converted gas, while the temperature of the heat exchange medium water rises and is converted into steam; at least a portion of the steam enters the catalytic reforming unit 4 to participate in the catalytic reforming reaction, thereby realizing further utilization of heat and raw materials and reducing overall energy consumption.

[0170] The cooled conversion gas then enters the methanol synthesis unit 8 to provide heat for the methanol synthesis reaction. It then returns to the heat recovery unit 5 to exchange heat with water, and then enters the decarbonization unit 6 for decarbonization treatment, obtaining decarbonized conversion gas. This further utilizes the heat from the cooled conversion gas. Simultaneously, the decarbonization control unit 10, connected to the decarbonization unit 6, controls the H / C modulus ratio of the decarbonized conversion gas to 1.9-2.2, thereby improving the raw material utilization rate of the subsequent methanol synthesis reaction. It then enters the pressurization unit 7 for pressurization, obtaining decarbonized pressurized conversion gas to meet the pressure required for the methanol synthesis reaction. Finally, it enters the methanol synthesis unit 8 for the methanol synthesis reaction, yielding methanol and purge gas.

[0171] In the system for implementing the third method of biogas to methanol according to the present invention, when the desulfurized and pressurized biogas enters the catalytic reforming unit 4 for catalytic reforming reaction, the secondary pressurization unit 3 is connected to the catalytic reforming unit 4 through two pipelines. In this embodiment, the biogas to be treated sequentially passes through the primary pressurization unit 1, the desulfurization unit 2, and the secondary pressurization unit 3 for primary pressurization, desulfurization, and secondary pressurization to obtain desulfurized and pressurized biogas, which meets the pressure required for the catalytic reforming reaction. Then, the desulfurized and pressurized biogas is divided into two streams, one of which enters the... Catalytic reforming unit 4 performs a catalytic reforming reaction to obtain converted gas. The main components of the converted gas are carbon monoxide, hydrogen, and small amounts of methane and carbon dioxide. Another stream enters the catalytic reforming unit 4 as fuel to provide heat for the catalytic reforming reaction. Based on this, the problems of high single-pressurization pressure ratio, high energy consumption, and high equipment requirements caused by catalytic reforming of biogas to be treated through a single pressurization can be avoided. At the same time, it can also improve the utilization rate of biogas and avoid the problems of low calorific value of biogas, excessive sulfur content in flue gas, and equipment corrosion caused by directly using biogas as fuel.

[0172] The converted gas then enters the heat recovery unit 5 to exchange heat with water, thereby lowering the temperature of the converted gas to obtain cooled converted gas, while the temperature of the heat exchange medium water rises and is converted into steam; at least a portion of the steam enters the catalytic reforming unit 4 to participate in the catalytic reforming reaction, thereby realizing the utilization of the heat of the converted gas and the further utilization of the steam, reducing the overall energy consumption.

[0173] The cooled conversion gas then enters the methanol synthesis unit 8 to provide heat for the methanol synthesis reaction. It then returns to the heat recovery unit 5 to exchange heat with water, and then enters the decarbonization unit 6 for decarbonization treatment, obtaining decarbonized conversion gas. This further utilizes the heat from the cooled conversion gas. Simultaneously, the decarbonization control unit 10, connected to the decarbonization unit 6, controls the H / C modulus ratio of the decarbonized conversion gas to 1.9-2.2, thereby improving the raw material utilization rate of the subsequent methanol synthesis reaction. It then enters the pressurization unit 7 for pressurization, obtaining decarbonized pressurized conversion gas to meet the pressure required for the methanol synthesis reaction. Finally, it enters the methanol synthesis unit 8 for the methanol synthesis reaction, yielding methanol and purge gas.

[0174] In a preferred embodiment, the system further includes a hydrogen separation unit 9; the purge gas enters the hydrogen separation unit 9 for hydrogen separation to obtain hydrogen and hydrogen-lean purge gas; the hydrogen-lean purge gas is used as fuel to enter the catalytic reforming unit 4 to provide heat for the catalytic reforming reaction, thereby further improving the utilization rate of biogas, and avoiding the problems of low biogas calorific value, excessive sulfur content in flue gas, and equipment corrosion that exist when directly using biogas as fuel; specifically, the hydrogen separation unit 9 is connected to the methanol synthesis unit 8, and the hydrogen separation unit 9 is connected to the catalytic reforming unit 4.

[0175] In a preferred embodiment, the hydrogen enters the booster unit 7 as a raw material for the subsequent methanol synthesis reaction, adjusting the H / C modulus ratio of the decarbonization conversion gas, thereby improving the utilization rate of the raw materials for the methanol synthesis reaction; specifically, the hydrogen separation unit 9 is connected to the booster unit 7.

[0176] In another preferred embodiment, the hydrogen enters the catalytic reforming unit 4 to participate in the catalytic reforming reaction, thereby improving the utilization rate of hydrogen; specifically, the hydrogen separation unit 9 is connected to the catalytic reforming unit 4.

[0177] In another, more preferred embodiment, the hydrogen is divided into two streams. One stream enters the booster unit 7 as a raw material for the subsequent methanol synthesis reaction, adjusting the H / C modulus ratio of the decarbonization conversion gas to improve the utilization rate of the raw material for the methanol synthesis reaction. The other stream enters the catalytic reforming unit 4 to participate in the catalytic reforming reaction. Specifically, the hydrogen separation unit 9 is connected to the booster unit 7 and the catalytic reforming unit 4, respectively.

[0178] The fourth aspect of this invention provides a fourth method for preparing methanol from biogas, the method comprising the following steps:

[0179] D1: Pressurize the biogas to obtain pressurized biogas, then desulfurize it to obtain desulfurized biogas, pressurize the desulfurized biogas to obtain desulfurized pressurized biogas, and subject at least a portion of the desulfurized pressurized biogas to a catalytic reforming reaction to obtain converted gas;

[0180] D2: The reformed gas is heated by water to obtain cooled reformed gas and steam, and at least a portion of the steam is used as a raw material to participate in the catalytic reforming reaction;

[0181] D3: The cooled conversion gas is used to heat the methanol synthesis reaction, then to heat the decarbonization process, then to exchange heat with water, then to carry out the decarbonization process to obtain decarbonized conversion gas, then to pressurize it to obtain decarbonized pressurized conversion gas, then to carry out the methanol synthesis reaction to obtain methanol and purge gas.

[0182] The H / C modulus ratio of the decarbonization conversion gas is 1.9-2.2.

[0183] In the fourth method for preparing methanol from biogas described above, when all the desulfurized and pressurized biogas undergoes catalytic reforming, the biogas is sequentially pressurized, desulfurized, and then pressurized again to obtain desulfurized and pressurized biogas that meets the pressure required for the catalytic reforming reaction. Then, the biogas undergoes catalytic reforming to obtain converted gas, the main components of which are carbon monoxide, hydrogen, and small amounts of methane and carbon dioxide. This avoids the problems of high single-pressurization pressure ratio, high energy consumption, and high equipment requirements caused by a single pressurization of the biogas for catalytic reforming.

[0184] Next, the converted gas exchanges heat with water, causing the temperature of the converted gas to decrease and become cooled converted gas, while the temperature of the heat exchange medium water increases and it is converted into steam. The steam then participates in the catalytic reforming reaction as a raw material, thereby realizing the further utilization of heat and raw materials and reducing the overall energy consumption.

[0185] The cooled conversion gas is used to heat the methanol synthesis reaction, then to heat the decarbonization process, and then exchange heat with water. Following this, decarbonization is performed again to obtain decarbonized conversion gas. The H / C modulus ratio of the decarbonized conversion gas is controlled to be 1.9-2.2. Based on this, the heat of the cooled conversion gas can be further utilized to reduce the energy consumption required for the methanol synthesis reaction and improve the raw material utilization rate of subsequent methanol synthesis reactions. The gas is then pressurized to obtain decarbonized pressurized conversion gas, which meets the pressure required for the methanol synthesis reaction. This gas then enters the methanol synthesis unit 8 for the methanol synthesis reaction, yielding methanol and purge gas.

[0186] In the fourth method for preparing methanol from biogas described above, when a portion of the desulfurized and pressurized biogas undergoes catalytic reforming, the remaining portion of the desulfurized and pressurized biogas is used as fuel to provide heat for the catalytic reforming reaction. Based on this, the utilization rate of biogas can be further improved, and the utilization of biogas calorific value can be increased. This avoids the problems of low biogas calorific value, excessive sulfur content in flue gas, and equipment corrosion that exist when biogas is directly used as fuel.

[0187] The above-mentioned fourth method for producing methanol from biogas is implemented in the following system, which includes: a primary pressurization unit 1, a desulfurization unit 2, a secondary pressurization unit 3, a catalytic reforming unit 4, a heat recovery unit 5, a decarbonization unit 6, a pressurization unit 7, a methanol synthesis unit 8, and a decarbonization control unit 10.

[0188] The biogas to be treated enters the primary pressurization unit 1 and is pressurized to obtain pressurized biogas. Then it enters the desulfurization unit 2 for desulfurization treatment to obtain desulfurized biogas. Next, it enters the secondary pressurization unit 3 and is pressurized to obtain desulfurized pressurized biogas. At least a portion of the desulfurized pressurized biogas enters the catalytic reforming unit 4 for catalytic reforming reaction to obtain converted gas.

[0189] The converted gas enters the heat recovery unit 5 to exchange heat with water, and obtains cooled converted gas and steam. At least part of the steam enters the catalytic reforming unit 4 to participate in the catalytic reforming reaction.

[0190] The cooled conversion gas enters the methanol synthesis unit 8 to heat the methanol synthesis reaction, then enters the decarbonization unit 6 to heat the decarbonization process, then returns to the heat recovery unit 5 to exchange heat with water, then enters the decarbonization unit 6 to perform the decarbonization process, obtaining decarbonized conversion gas, then enters the pressurization unit 7 to pressurize, obtaining decarbonized pressurized conversion gas, then enters the methanol synthesis unit 8 to perform the methanol synthesis reaction, obtaining methanol and purge gas;

[0191] The decarbonization control unit 10 is connected to the decarbonization unit 6 and is used to control the H / C modulus ratio of the decarbonization conversion gas to be 1.9-2.2.

[0192] In the system of the fourth method for preparing methanol from biogas described in this invention, when all the desulfurized and pressurized biogas enters the catalytic reforming unit 4 for catalytic reforming, the secondary pressurization unit 3 is connected to the catalytic reforming unit 4 via a pipeline. In this embodiment, the biogas to be treated sequentially passes through the primary pressurization unit 1, the desulfurization unit 2, and the secondary pressurization unit 3 for primary pressurization, desulfurization, and secondary pressurization to obtain desulfurized and pressurized biogas, which meets the pressure required for the catalytic reforming reaction. Then, it enters the catalytic reforming unit 4 for catalytic reforming to obtain converted gas. The main components of the converted gas are carbon monoxide, hydrogen, and small amounts of methane and carbon dioxide. Based on this, the problems of high single-pressurization pressure ratio, high energy consumption, and high equipment requirements caused by the biogas to be treated undergoing catalytic reforming through a single pressurization can be avoided.

[0193] The converted gas then enters the heat recovery unit 5 to exchange heat with water, thereby lowering the temperature of the converted gas to obtain cooled converted gas, while the temperature of the heat exchange medium water rises and is converted into steam; at least a portion of the steam enters the catalytic reforming unit 4 to participate in the catalytic reforming reaction, thereby realizing further utilization of heat and raw materials and reducing overall energy consumption.

[0194] The cooled conversion gas enters the methanol synthesis unit 8 to heat the methanol synthesis reaction, then enters the decarbonization unit 6 to heat the decarbonization process, and then returns to the heat recovery unit 5 to exchange heat with water. It then enters the decarbonization unit 6 again for decarbonization, yielding decarbonized conversion gas, thus further utilizing the heat from the cooled conversion gas. Simultaneously, the decarbonization control unit 10, connected to the decarbonization unit 6, controls the H / C modulus ratio of the decarbonized conversion gas to 1.9-2.2, thereby improving the raw material utilization rate of the subsequent methanol synthesis reaction. It then enters the pressurization unit 7 for pressurization, obtaining decarbonized pressurized conversion gas to meet the pressure required for the methanol synthesis reaction. Finally, it enters the methanol synthesis unit 8 for the methanol synthesis reaction, yielding methanol and purge gas.

[0195] In the system for implementing the fourth method of biogas to methanol according to the present invention, when the desulfurized and pressurized biogas enters the catalytic reforming unit 4 for catalytic reforming reaction, the secondary pressurization unit 3 is connected to the catalytic reforming unit 4 through two pipelines. In this embodiment, the biogas to be treated sequentially passes through the primary pressurization unit 1, the desulfurization unit 2, and the secondary pressurization unit 3 for primary pressurization, desulfurization treatment, and secondary pressurization to obtain desulfurized and pressurized biogas, which meets the pressure required for the catalytic reforming reaction. Then, the desulfurized and pressurized biogas is divided into two streams, one of which enters the... Catalytic reforming unit 4 performs a catalytic reforming reaction to obtain converted gas. The main components of the converted gas are carbon monoxide, hydrogen, and small amounts of methane and carbon dioxide. Another stream enters the catalytic reforming unit 4 as fuel to provide heat for the catalytic reforming reaction. Based on this, the problems of high single-pressurization pressure ratio, high energy consumption, and high equipment requirements caused by catalytic reforming of biogas to be treated through a single pressurization can be avoided. At the same time, it can also improve the utilization rate of biogas and avoid the problems of low calorific value of biogas, excessive sulfur content in flue gas, and equipment corrosion caused by directly using biogas as fuel.

[0196] The converted gas then enters the heat recovery unit 5 to exchange heat with water, thereby lowering the temperature of the converted gas to obtain cooled converted gas, while the temperature of the heat exchange medium water rises and is converted into steam; at least a portion of the steam enters the catalytic reforming unit 4 to participate in the catalytic reforming reaction, thereby realizing the utilization of the heat of the converted gas and the further utilization of the steam, reducing the overall energy consumption.

[0197] The cooled conversion gas enters the methanol synthesis unit 8 to heat the methanol synthesis reaction, then enters the decarbonization unit 6 to heat the decarbonization process, and then returns to the heat recovery unit 5 to exchange heat with water. It then enters the decarbonization unit 6 again for decarbonization, yielding decarbonized conversion gas, thus further utilizing the heat from the cooled conversion gas. Simultaneously, the decarbonization control unit 10, connected to the decarbonization unit 6, controls the H / C modulus ratio of the decarbonized conversion gas to 1.9-2.2, thereby improving the raw material utilization rate of the subsequent methanol synthesis reaction. It then enters the pressurization unit 7 for pressurization, obtaining decarbonized pressurized conversion gas to meet the pressure required for the methanol synthesis reaction. Finally, it enters the methanol synthesis unit 8 for the methanol synthesis reaction, yielding methanol and purge gas.

[0198] In a preferred embodiment, the system further includes a hydrogen separation unit 9; the purge gas enters the hydrogen separation unit 9 for hydrogen separation to obtain hydrogen and hydrogen-lean purge gas; the hydrogen-lean purge gas is used as fuel to enter the catalytic reforming unit 4 to provide heat for the catalytic reforming reaction, thereby further improving the utilization rate of biogas, and avoiding the problems of low biogas calorific value, excessive sulfur content in flue gas, and equipment corrosion that exist when directly using biogas as fuel; specifically, the hydrogen separation unit 9 is connected to the methanol synthesis unit 8, and the hydrogen separation unit 9 is connected to the catalytic reforming unit 4.

[0199] In a preferred embodiment, the hydrogen enters the booster unit 7 as a raw material for the subsequent methanol synthesis reaction, adjusting the H / C modulus ratio of the decarbonization conversion gas, thereby improving the utilization rate of the raw materials for the methanol synthesis reaction; specifically, the hydrogen separation unit 9 is connected to the booster unit 7.

[0200] In another preferred embodiment, the hydrogen enters the catalytic reforming unit 4 to participate in the catalytic reforming reaction, thereby improving the utilization rate of hydrogen; specifically, the hydrogen separation unit 9 is connected to the catalytic reforming unit 4.

[0201] In another, more preferred embodiment, the hydrogen is divided into two streams. One stream enters the booster unit 7 as a raw material for the subsequent methanol synthesis reaction, adjusting the H / C modulus ratio of the decarbonization conversion gas to improve the utilization rate of the raw material for the methanol synthesis reaction. The other stream enters the catalytic reforming unit 4 to participate in the catalytic reforming reaction. Specifically, the hydrogen separation unit 9 is connected to the booster unit 7 and the catalytic reforming unit 4, respectively.

[0202] The following examples further illustrate the method and system for producing methanol from biogas according to the present invention. These examples are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following examples.

[0203] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available.

[0204] The composition of the biogas to be treated in the following examples and comparative examples is shown in Table 1;

[0205] Table 1

[0206] composition Content (volume %) <![CDATA[N2]]> 5 <![CDATA[CO2]]> 38 <![CDATA[CH4]]> 55.45 <![CDATA[H2S]]> 0.5 <![CDATA[H2O]]> 0.05 CO 0.4 <![CDATA[O2]]> 0.5 <![CDATA[H2]]> 0.1 total 100.00

[0207] Example 1

[0208] See also Figure 1 In this embodiment Figure 1 The system shown is implemented and includes: a primary pressurization unit 1, a desulfurization unit 2, a secondary pressurization unit 3, a catalytic reforming unit 4, a heat recovery unit 5, a decarbonization unit 6, a pressurization unit 7, a methanol synthesis unit 8, a hydrogen separation unit 9, and a decarbonization control unit 10.

[0209] The biogas to be treated (flow rate of 120,000 Nm³) 3 The biogas produced at a pressure of 0.015 MPa and a temperature of 30°C is pressurized sequentially through a primary pressurization unit 1 to obtain pressurized biogas (pressure 0.5 MPaG). This biogas then enters the desulfurization unit 2 and the secondary pressurization unit 3 for desulfurization and secondary pressurization, resulting in desulfurized pressurized biogas (pressure 1.1 MPaG, sulfur content less than 10 ppm). This desulfurized pressurized biogas is divided into two streams. One stream enters the catalytic reforming unit 4 and undergoes a carbon dioxide-methane-water vapor dry-wet dual catalytic reforming reaction at 870°C and a pressure of 1.1 MPaG to obtain converted gas. The other stream (accounting for 35% of the total volume of the desulfurized pressurized biogas) serves as fuel in the catalytic reforming unit 4, providing heat for the catalytic reforming reaction.

[0210] The converted gas enters the heat recovery unit 5 (sequentially connected to a steam generator, raw material preheater, demineralized water deaerator, air cooler, and water cooler) to exchange heat with water, thereby lowering the temperature of the converted gas to obtain cooled converted gas (temperature 40°C), while the temperature of the heat exchange medium water rises and it is converted into steam (pressure 3.5 MPaG); a portion of the steam (accounting for 45% of the total steam volume) enters the catalytic reforming unit 4 to participate in the catalytic reforming reaction;

[0211] The cooled conversion gas enters the decarbonization unit 6 and undergoes decarbonization treatment at a temperature of 55°C and a pressure of 0.6 MPaG to obtain decarbonized conversion gas (carbon dioxide volume content of 3%, H / C modulus ratio of 2.12). Then, it enters the pressurization unit 7 for pressurization at an operating pressure of 8 MPaG to obtain decarbonized pressurized conversion gas. Next, it enters the methanol synthesis unit 8 and undergoes methanol synthesis reaction at a temperature of 295°C and a pressure of 8 MPaG to obtain methanol and purge gas.

[0212] The purge gas enters the hydrogen separation unit 9 for hydrogen separation to obtain hydrogen (recovery rate 75%) and hydrogen-lean purge gas; the hydrogen-lean purge gas is used as fuel to enter the catalytic reforming unit 4 to provide heat for the catalytic reforming reaction, and the hydrogen (purity 99%) is recycled.

[0213] Example 2

[0214] See also Figure 2 In this embodiment Figure 2 The system shown is implemented and includes: a primary pressurization unit 1, a desulfurization unit 2, a secondary pressurization unit 3, a catalytic reforming unit 4, a heat recovery unit 5, a decarbonization unit 6, a pressurization unit 7, a methanol synthesis unit 8, a hydrogen separation unit 9, and a decarbonization control unit 10.

[0215] The biogas to be treated (flow rate of 120,000 Nm³) 3 The biogas produced at a pressure of 0.015 MPa and a temperature of 30°C is pressurized sequentially through a primary pressurization unit 1 to obtain pressurized biogas (pressure 0.5 MPaG). This biogas then enters the desulfurization unit 2 and the secondary pressurization unit 3 for desulfurization and secondary pressurization, resulting in desulfurized pressurized biogas (pressure 1.1 MPaG, sulfur content less than 10 ppm). This desulfurized pressurized biogas is divided into two streams. One stream enters the catalytic reforming unit 4 and undergoes a carbon dioxide-methane-water vapor dry-wet dual catalytic reforming reaction at 870°C and a pressure of 1.1 MPaG to obtain converted gas. The other stream (accounting for 35% of the total volume of the desulfurized pressurized biogas) serves as fuel in the catalytic reforming unit 4, providing heat for the catalytic reforming reaction.

[0216] The converted gas enters the heat recovery unit 5 (sequentially connected to a steam generator, raw material preheater, demineralized water deaerator, air cooler, and water cooler) to exchange heat with water, thereby lowering the temperature of the converted gas to obtain cooled converted gas (temperature 40°C), while the temperature of the heat exchange medium water rises and it is converted into steam (pressure 3.5 MPaG); a portion of the steam (accounting for 45% of the total steam volume) enters the catalytic reforming unit 4 to participate in the catalytic reforming reaction;

[0217] The cooled conversion gas enters the decarbonization unit 6 and undergoes decarbonization treatment at a temperature of 55°C and a pressure of 0.6 MPaG to obtain decarbonized conversion gas (carbon dioxide volume content of 3%, H / C modulus ratio of 2.12). Then, it enters the pressurization unit 7 for pressurization at an operating pressure of 7.9 MPaG to obtain decarbonized pressurized conversion gas. Next, it enters the methanol synthesis unit 8 and undergoes methanol synthesis reaction at a temperature of 295°C and a pressure of 7.9 MPaG to obtain methanol and purge gas.

[0218] The purge gas enters the hydrogen separation unit 9 for hydrogen separation, yielding hydrogen (recovery rate 75%) and lean hydrogen purge gas; the lean hydrogen purge gas is used as fuel in the catalytic reforming unit 4 to provide heat for the catalytic reforming reaction; the hydrogen (flow rate 310 Nm³) 3 The fuel ( / h) enters the booster unit 7 as a raw material for the subsequent methanol synthesis reaction.

[0219] Example 3

[0220] See also Figure 3 In this embodiment Figure 3 The system shown is implemented and includes: a primary pressurization unit 1, a desulfurization unit 2, a secondary pressurization unit 3, a catalytic reforming unit 4, a heat recovery unit 5, a decarbonization unit 6, a pressurization unit 7, a methanol synthesis unit 8, a hydrogen separation unit 9, and a decarbonization control unit 10.

[0221] The biogas to be treated (flow rate of 120,000 Nm³) 3 The biogas produced at a pressure of 0.015 MPa and a temperature of 30°C is pressurized sequentially through a primary pressurization unit 1 to obtain pressurized biogas (pressure 0.5 MPaG). This biogas then enters the desulfurization unit 2 and the secondary pressurization unit 3 for desulfurization and secondary pressurization, resulting in desulfurized pressurized biogas (pressure 1.1 MPaG, sulfur content less than 10 ppm). This desulfurized pressurized biogas is divided into two streams. One stream enters the catalytic reforming unit 4 and undergoes a carbon dioxide-methane-water vapor dry-wet dual catalytic reforming reaction at 870°C and a pressure of 1.1 MPaG to obtain converted gas. The other stream (accounting for 35% of the total volume of the desulfurized pressurized biogas) serves as fuel in the catalytic reforming unit 4, providing heat for the catalytic reforming reaction.

[0222] The converted gas enters the heat recovery unit 5 (sequentially connected to a steam generator, raw material preheater, demineralized water deaerator, air cooler, and water cooler) to exchange heat with water, thereby lowering the temperature of the converted gas to obtain cooled converted gas (temperature 40°C), while the temperature of the heat exchange medium water rises and it is converted into steam (pressure 3.5 MPaG); a portion of the steam (accounting for 45% of the total steam volume) enters the catalytic reforming unit 4 to participate in the catalytic reforming reaction;

[0223] The cooled conversion gas enters the decarbonization unit 6 and undergoes decarbonization treatment at a temperature of 55°C and a pressure of 0.6 MPaG to obtain decarbonized conversion gas (carbon dioxide volume content of 3%, H / C modulus ratio of 2.12). Then, it enters the pressurization unit 7 for pressurization at an operating pressure of 7.9 MPaG to obtain decarbonized pressurized conversion gas. Next, it enters the methanol synthesis unit 8 and undergoes methanol synthesis reaction at a temperature of 295°C and a pressure of 7.9 MPaG to obtain methanol and purge gas.

[0224] The purge gas enters the hydrogen separation unit 9 for hydrogen separation to obtain hydrogen (recovery rate 75%) and hydrogen-lean purge gas; the hydrogen-lean purge gas is used as fuel to enter the catalytic reforming unit 4 to provide heat for the catalytic reforming reaction;

[0225] The hydrogen gas was divided into two streams, one of which was (210 Nm³). 3 The gas enters the booster unit 7 as a feedstock for the subsequent methanol synthesis reaction, while another gas (100 Nm³ / h) enters the booster unit 7. 3 The substance enters the catalytic reforming unit 4 ( / h) to participate in the catalytic reforming reaction.

[0226] Example 4

[0227] See also Figure 4 In this embodiment Figure 4 The system shown is implemented and includes: a primary pressurization unit 1, a desulfurization unit 2, a secondary pressurization unit 3, a catalytic reforming unit 4, a heat recovery unit 5, a decarbonization unit 6, a pressurization unit 7, a methanol synthesis unit 8, a hydrogen separation unit 9, and a decarbonization control unit 10.

[0228] The biogas to be treated (flow rate of 120,000 Nm³) 3 The biogas produced at a pressure of 0.015 MPa and a temperature of 30°C is pressurized sequentially through a primary pressurization unit 1 to obtain pressurized biogas (pressure 0.5 MPaG). This biogas then enters the desulfurization unit 2 and the secondary pressurization unit 3 for desulfurization and secondary pressurization, resulting in desulfurized pressurized biogas (pressure 1.1 MPaG, sulfur content less than 10 ppm). This desulfurized pressurized biogas is divided into two streams. One stream enters the catalytic reforming unit 4 and undergoes a carbon dioxide-methane-water vapor dry-wet dual catalytic reforming reaction at 870°C and a pressure of 1.1 MPaG to obtain converted gas. The other stream (accounting for 35% of the total volume of the desulfurized pressurized biogas) serves as fuel in the catalytic reforming unit 4, providing heat for the catalytic reforming reaction.

[0229] The converted gas enters the heat recovery unit 5 (sequentially connected to a steam generator, raw material preheater, demineralized water deaerator, air cooler, and water cooler) to exchange heat with water, thereby lowering the temperature of the converted gas to obtain cooled converted gas (temperature 250°C), while the temperature of the heat exchange medium water increases and it is converted into steam (pressure 3.5 MPaG); a portion of the steam (accounting for 45% of the total steam volume) enters the catalytic reforming unit 4 to participate in the catalytic reforming reaction;

[0230] The cooled conversion gas enters the decarbonization unit 6 to provide heat for the decarbonization process, and the temperature is reduced to 210°C. Then it returns to the heat recovery unit 5 to exchange heat with water, and the temperature is reduced to 55°C. Then it enters the decarbonization unit 6 for decarbonization to obtain decarbonized conversion gas (carbon dioxide volume content is 3%, H / C modulus ratio is 2.12). Then it enters the pressurization unit 7 for pressurization, and the operating pressure is 7.9 MPaG to obtain decarbonized pressurized conversion gas. Then it enters the methanol synthesis unit 8 to carry out the methanol synthesis reaction at a temperature of 295°C and a pressure of 7.9 MPaG to obtain methanol and purge gas.

[0231] The purge gas enters the hydrogen separation unit 9 for hydrogen separation to obtain hydrogen (recovery rate 75%) and hydrogen-lean purge gas; the hydrogen-lean purge gas is used as fuel to enter the catalytic reforming unit 4 to provide heat for the catalytic reforming reaction;

[0232] The hydrogen gas was divided into two streams, one of which was (210 Nm³). 3 The gas enters the booster unit 7 as a feedstock for the subsequent methanol synthesis reaction, while another gas (100 Nm³ / h) enters the booster unit 7. 3 The substance enters the catalytic reforming unit 4 ( / h) to participate in the catalytic reforming reaction.

[0233] Example 5

[0234] See also Figure 5 In this embodiment Figure 5 The system shown is implemented and includes: a primary pressurization unit 1, a desulfurization unit 2, a secondary pressurization unit 3, a catalytic reforming unit 4, a heat recovery unit 5, a decarbonization unit 6, a pressurization unit 7, a methanol synthesis unit 8, a hydrogen separation unit 9, and a decarbonization control unit 10.

[0235] The biogas to be treated (flow rate of 120,000 Nm³) 3The biogas produced at a pressure of 0.015 MPa and a temperature of 30°C is pressurized sequentially through a primary pressurization unit 1 to obtain pressurized biogas (pressure 0.5 MPaG). This biogas then enters the desulfurization unit 2 and the secondary pressurization unit 3 for desulfurization and secondary pressurization, resulting in desulfurized pressurized biogas (pressure 1.1 MPaG, sulfur content less than 10 ppm). This desulfurized pressurized biogas is divided into two streams. One stream enters the catalytic reforming unit 4 and undergoes a carbon dioxide-methane-water vapor dry-wet dual catalytic reforming reaction at 870°C and a pressure of 1.1 MPaG to obtain converted gas. The other stream (accounting for 35% of the total volume of the desulfurized pressurized biogas) serves as fuel in the catalytic reforming unit 4, providing heat for the catalytic reforming reaction.

[0236] The converted gas enters the heat recovery unit 5 (sequentially connected to a steam generator, raw material preheater, demineralized water deaerator, air cooler, and water cooler) to exchange heat with water, thereby lowering the temperature of the converted gas to obtain cooled converted gas (temperature 250°C), while the temperature of the heat exchange medium water increases and it is converted into steam (pressure 3.5 MPaG); a portion of the steam (accounting for 45% of the total steam volume) enters the catalytic reforming unit 4 to participate in the catalytic reforming reaction;

[0237] The cooled conversion gas enters the methanol synthesis unit 8 to provide heat for the methanol synthesis reaction. The temperature is reduced to 180°C, and then it returns to the heat recovery unit 5 to exchange heat with water, where the temperature is reduced to 55°C. Then it enters the decarbonization unit 6 for decarbonization treatment to obtain decarbonized conversion gas (carbon dioxide volume content of 3%, H / C modulus ratio of 2.12). Then it enters the pressurization unit 7 for pressurization at an operating pressure of 7.9 MPaG to obtain decarbonized pressurized conversion gas. Then it enters the methanol synthesis unit 8 to carry out the methanol synthesis reaction at a temperature of 295°C and a pressure of 7.9 MPaG to obtain methanol and purge gas.

[0238] The purge gas enters the hydrogen separation unit 9 for hydrogen separation to obtain hydrogen (recovery rate 75%) and hydrogen-lean purge gas; the hydrogen-lean purge gas is used as fuel to enter the catalytic reforming unit 4 to provide heat for the catalytic reforming reaction;

[0239] The hydrogen gas was divided into two streams, one of which was (210 Nm³). 3 The gas enters the booster unit 7 as a feedstock for the subsequent methanol synthesis reaction, while another gas (100 Nm³ / h) enters the booster unit 7. 3 The substance enters the catalytic reforming unit 4 ( / h) to participate in the catalytic reforming reaction.

[0240] Example 6

[0241] See also Figure 6 In this embodiment Figure 6The system shown is implemented and includes: a primary pressurization unit 1, a desulfurization unit 2, a secondary pressurization unit 3, a catalytic reforming unit 4, a heat recovery unit 5, a decarbonization unit 6, a pressurization unit 7, a methanol synthesis unit 8, a hydrogen separation unit 9, and a decarbonization control unit 10.

[0242] The biogas to be treated (flow rate of 120,000 Nm³) 3 The biogas produced at a pressure of 0.015 MPa and a temperature of 30°C is pressurized sequentially through a primary pressurization unit 1 to obtain pressurized biogas (pressure 0.5 MPaG). This biogas then enters the desulfurization unit 2 and the secondary pressurization unit 3 for desulfurization and secondary pressurization, resulting in desulfurized pressurized biogas (pressure 1.1 MPaG, sulfur content less than 10 ppm). This desulfurized pressurized biogas is divided into two streams. One stream enters the catalytic reforming unit 4 and undergoes a carbon dioxide-methane-water vapor dry-wet dual catalytic reforming reaction at 870°C and a pressure of 1.1 MPaG to obtain converted gas. The other stream (accounting for 35% of the total volume of the desulfurized pressurized biogas) serves as fuel in the catalytic reforming unit 4, providing heat for the catalytic reforming reaction.

[0243] The converted gas enters the heat recovery unit 5 (sequentially connected to a steam generator, raw material preheater, demineralized water deaerator, air cooler, and water cooler) to exchange heat with water, thereby lowering the temperature of the converted gas to obtain cooled converted gas (temperature 320°C), while the temperature of the heat exchange medium water increases and it is converted into steam (pressure 3.5 MPaG); a portion of the steam (accounting for 45% of the total steam volume) enters the catalytic reforming unit 4 to participate in the catalytic reforming reaction;

[0244] The cooled conversion gas enters the methanol synthesis unit 8 to heat the methanol synthesis reaction, reducing the temperature to 250°C. It then enters the decarbonization unit 6 to heat the decarbonization process, reducing the temperature to 200°C. Next, it returns to the heat recovery unit 5 and exchanges heat with water, reducing the temperature to 55°C. It then enters the decarbonization unit 6 again for decarbonization, yielding decarbonized conversion gas (3% carbon dioxide volume content, H / C modulus ratio 2.12). This gas then enters the pressurization unit 7 for pressurization, operating at 7.9 MPaG, yielding decarbonized pressurized conversion gas. Finally, it enters the methanol synthesis unit 8 at 295°C and 7.9 MPaG for methanol synthesis, yielding methanol and purge gas.

[0245] The purge gas enters the hydrogen separation unit 9 for hydrogen separation to obtain hydrogen (recovery rate 75%) and hydrogen-lean purge gas; the hydrogen-lean purge gas is used as fuel to enter the catalytic reforming unit 4 to provide heat for the catalytic reforming reaction;

[0246] The hydrogen gas was divided into two streams, one of which was (210 Nm³).3 The gas enters the booster unit 7 as a feedstock for the subsequent methanol synthesis reaction, while another gas (100 Nm³ / h) enters the booster unit 7. 3 The substance enters the catalytic reforming unit 4 ( / h) to participate in the catalytic reforming reaction.

[0247] Example 7

[0248] See also Figure 7 In this embodiment Figure 7 The system shown is implemented and includes: a primary pressurization unit 1, a desulfurization unit 2, a secondary pressurization unit 3, a catalytic reforming unit 4, a heat recovery unit 5, a decarbonization unit 6, a pressurization unit 7, a methanol synthesis unit 8, a hydrogen separation unit 9, and a decarbonization control unit 10.

[0249] The biogas to be treated (flow rate of 120,000 Nm³) 3 The biogas (at a pressure of 0.015 MPa and a temperature of 30°C) is sequentially pressurized through a primary pressurization unit 1 to obtain pressurized biogas (at a pressure of 0.5 MPaG). It then enters the desulfurization unit 2 and the secondary pressurization unit 3 for desulfurization and secondary pressurization to obtain desulfurized pressurized biogas (at a pressure of 1.1 MPaG, with a sulfur content of less than 10 ppm). All of the desulfurized pressurized biogas enters the catalytic reforming unit 4, where it undergoes a carbon dioxide-methane-water vapor dry-wet dual catalytic reforming reaction at a temperature of 870°C and a pressure of 1.1 MPaG to obtain converted gas.

[0250] The converted gas enters the heat recovery unit 5 (sequentially connected to a steam generator, raw material preheater, demineralized water deaerator, air cooler, and water cooler) to exchange heat with water, thereby lowering the temperature of the converted gas to obtain cooled converted gas (temperature 40°C), while the temperature of the heat exchange medium water rises and it is converted into steam (pressure 3.5 MPaG); a portion of the steam (accounting for 60% of the total steam volume) enters the catalytic reforming unit 4 to participate in the catalytic reforming reaction;

[0251] The cooled conversion gas enters the decarbonization unit 6 and undergoes decarbonization treatment at a temperature of 55°C and a pressure of 0.6 MPaG to obtain decarbonized conversion gas (carbon dioxide volume content of 3%, H / C modulus ratio of 2.12). Then, it enters the pressurization unit 7 for pressurization at an operating pressure of 7.9 MPaG to obtain decarbonized pressurized conversion gas. Next, it enters the methanol synthesis unit 8 and undergoes methanol synthesis reaction at a temperature of 295°C and a pressure of 7.9 MPaG to obtain methanol and purge gas.

[0252] The purge gas enters the hydrogen separation unit 9 for hydrogen separation to obtain hydrogen (recovery rate 75%) and hydrogen-lean purge gas; the hydrogen-lean purge gas is used as fuel to enter the catalytic reforming unit 4 to provide heat for the catalytic reforming reaction;

[0253] The hydrogen gas is divided into two streams, one of which is 1500 Nm³. 3 The gas enters the booster unit 7 as a feedstock for the subsequent methanol synthesis reaction, while another gas (1200 Nm³ / h) enters the booster unit 7. 3 The substance enters the catalytic reforming unit 4 ( / h) to participate in the catalytic reforming reaction.

[0254] Example 8

[0255] See also Figure 8 In this embodiment Figure 8 The system shown is implemented and includes: a primary pressurization unit 1, a desulfurization unit 2, a secondary pressurization unit 3, a catalytic reforming unit 4, a heat recovery unit 5, a decarbonization unit 6, a pressurization unit 7, a methanol synthesis unit 8, a hydrogen separation unit 9, and a decarbonization control unit 10.

[0256] The biogas to be treated (flow rate of 120,000 Nm³) 3 The biogas (at a pressure of 0.015 MPa and a temperature of 30°C) is sequentially pressurized through a primary pressurization unit 1 to obtain pressurized biogas (at a pressure of 0.5 MPaG). It then enters the desulfurization unit 2 and the secondary pressurization unit 3 for desulfurization and secondary pressurization to obtain desulfurized pressurized biogas (at a pressure of 1.1 MPaG, with a sulfur content of less than 10 ppm). All of the desulfurized pressurized biogas enters the catalytic reforming unit 4, where it undergoes a carbon dioxide-methane-water vapor dry-wet dual catalytic reforming reaction at a temperature of 870°C and a pressure of 1.1 MPaG to obtain converted gas.

[0257] The converted gas enters the heat recovery unit 5 (sequentially connected to a steam generator, raw material preheater, demineralized water deaerator, air cooler, and water cooler) to exchange heat with water, thereby lowering the temperature of the converted gas to obtain cooled converted gas (temperature 250°C), while the temperature of the heat exchange medium water increases and it is converted into steam (pressure 3.5 MPaG); a portion of the steam (accounting for 60% of the total steam volume) enters the catalytic reforming unit 4 to participate in the catalytic reforming reaction;

[0258] The cooled conversion gas enters the decarbonization unit 6 to provide heat for the decarbonization process, and the temperature is reduced to 210°C. Then it returns to the heat recovery unit 5 to exchange heat with water, and the temperature is reduced to 55°C. Then it enters the decarbonization unit 6 for decarbonization to obtain decarbonized conversion gas (carbon dioxide volume content is 3%, H / C modulus ratio is 2.12). Then it enters the pressurization unit 7 for pressurization, and the operating pressure is 7.9 MPaG to obtain decarbonized pressurized conversion gas. Then it enters the methanol synthesis unit 8 to carry out the methanol synthesis reaction at a temperature of 295°C and a pressure of 7.9 MPaG to obtain methanol and purge gas.

[0259] The purge gas enters the hydrogen separation unit 9 for hydrogen separation to obtain hydrogen (recovery rate 75%) and hydrogen-lean purge gas; the hydrogen-lean purge gas is used as fuel to enter the catalytic reforming unit 4 to provide heat for the catalytic reforming reaction;

[0260] The hydrogen gas is divided into two streams, one of which is 1500 Nm³. 3 The gas enters the booster unit 7 as a feedstock for the subsequent methanol synthesis reaction, while another gas (1200 Nm³ / h) enters the booster unit 7. 3 The substance enters the catalytic reforming unit 4 ( / h) to participate in the catalytic reforming reaction.

[0261] Example 9

[0262] See also Figure 9 In this embodiment Figure 9 The system shown is implemented and includes: a primary pressurization unit 1, a desulfurization unit 2, a secondary pressurization unit 3, a catalytic reforming unit 4, a heat recovery unit 5, a decarbonization unit 6, a pressurization unit 7, a methanol synthesis unit 8, a hydrogen separation unit 9, and a decarbonization control unit 10.

[0263] The biogas to be treated (flow rate of 120,000 Nm³) 3 The biogas (at a pressure of 0.015 MPa and a temperature of 30°C) is sequentially pressurized through a primary pressurization unit 1 to obtain pressurized biogas (at a pressure of 0.5 MPaG). It then enters the desulfurization unit 2 and the secondary pressurization unit 3 for desulfurization and secondary pressurization to obtain desulfurized pressurized biogas (at a pressure of 1.1 MPaG, with a sulfur content of less than 10 ppm). All of the desulfurized pressurized biogas enters the catalytic reforming unit 4, where it undergoes a carbon dioxide-methane-water vapor dry-wet dual catalytic reforming reaction at a temperature of 870°C and a pressure of 1.1 MPaG to obtain converted gas.

[0264] The converted gas enters the heat recovery unit 5 (sequentially connected to a steam generator, raw material preheater, demineralized water deaerator, air cooler, and water cooler) to exchange heat with water, thereby lowering the temperature of the converted gas to obtain cooled converted gas (temperature 250°C), while the temperature of the heat exchange medium water increases and it is converted into steam (pressure 3.5 MPaG); a portion of the steam (accounting for 60% of the total steam volume) enters the catalytic reforming unit 4 to participate in the catalytic reforming reaction;

[0265] The cooled conversion gas enters the methanol synthesis unit 8 to provide heat for the methanol synthesis reaction. The temperature is reduced to 180°C, and then it returns to the heat recovery unit 5 to exchange heat with water, where the temperature is reduced to 55°C. Then it enters the decarbonization unit 6 for decarbonization treatment to obtain decarbonized conversion gas (carbon dioxide volume content of 3%, H / C modulus ratio of 2.12). Then it enters the pressurization unit 7 for pressurization at an operating pressure of 7.9 MPaG to obtain decarbonized pressurized conversion gas. Then it enters the methanol synthesis unit 8 to carry out the methanol synthesis reaction at a temperature of 295°C and a pressure of 7.9 MPaG to obtain methanol and purge gas.

[0266] The purge gas enters the hydrogen separation unit 9 for hydrogen separation to obtain hydrogen (recovery rate 75%) and hydrogen-lean purge gas; the hydrogen-lean purge gas is used as fuel to enter the catalytic reforming unit 4 to provide heat for the catalytic reforming reaction;

[0267] The hydrogen gas is divided into two streams, one of which is 1500 Nm³. 3 The gas enters the booster unit 7 as a feedstock for the subsequent methanol synthesis reaction, while another gas (1200 Nm³ / h) enters the booster unit 7. 3 The substance enters the catalytic reforming unit 4 ( / h) to participate in the catalytic reforming reaction.

[0268] Example 10

[0269] See also Figure 10 In this embodiment Figure 10 The system shown is implemented and includes: a primary pressurization unit 1, a desulfurization unit 2, a secondary pressurization unit 3, a catalytic reforming unit 4, a heat recovery unit 5, a decarbonization unit 6, a pressurization unit 7, a methanol synthesis unit 8, a hydrogen separation unit 9, and a decarbonization control unit 10.

[0270] The biogas to be treated (flow rate of 120,000 Nm³) 3 The biogas (at a pressure of 0.015 MPa and a temperature of 30°C) is sequentially pressurized through a primary pressurization unit 1 to obtain pressurized biogas (at a pressure of 0.5 MPaG). It then enters the desulfurization unit 2 and the secondary pressurization unit 3 for desulfurization and secondary pressurization to obtain desulfurized pressurized biogas (at a pressure of 1.1 MPaG, with a sulfur content of less than 10 ppm). All of the desulfurized pressurized biogas enters the catalytic reforming unit 4, where it undergoes a carbon dioxide-methane-water vapor dry-wet dual catalytic reforming reaction at a temperature of 870°C and a pressure of 1.1 MPaG to obtain converted gas.

[0271] The converted gas enters the heat recovery unit 5 (sequentially connected to a steam generator, raw material preheater, demineralized water deaerator, air cooler, and water cooler) to exchange heat with water, thereby lowering the temperature of the converted gas to obtain cooled converted gas (temperature 320°C), while the temperature of the heat exchange medium water increases and it is converted into steam (pressure 3.5 MPaG); a portion of the steam (accounting for 60% of the total steam volume) enters the catalytic reforming unit 4 to participate in the catalytic reforming reaction;

[0272] The cooled conversion gas enters the methanol synthesis unit 8 to heat the methanol synthesis reaction, reducing the temperature to 250°C. It then enters the decarbonization unit 6 to heat the decarbonization process, reducing the temperature to 200°C. Next, it returns to the heat recovery unit 5 and exchanges heat with water, reducing the temperature to 55°C. It then enters the decarbonization unit 6 again for decarbonization, yielding decarbonized conversion gas (3% carbon dioxide volume content, H / C modulus ratio 2.12). This gas then enters the pressurization unit 7 for pressurization, operating at 7.9 MPaG, yielding decarbonized pressurized conversion gas. Finally, it enters the methanol synthesis unit 8 at 295°C and 7.9 MPaG for methanol synthesis, yielding methanol and purge gas.

[0273] The purge gas enters the hydrogen separation unit 9 for hydrogen separation to obtain hydrogen (recovery rate 75%) and hydrogen-lean purge gas; the hydrogen-lean purge gas is used as fuel to enter the catalytic reforming unit 4 to provide heat for the catalytic reforming reaction;

[0274] The hydrogen gas is divided into two streams, one of which is 1500 Nm³. 3 The gas enters the booster unit 7 as a feedstock for the subsequent methanol synthesis reaction, while another gas (1200 Nm³ / h) enters the booster unit 7. 3 The substance enters the catalytic reforming unit 4 ( / h) to participate in the catalytic reforming reaction.

[0275] Comparative Example 1

[0276] See also Figure 11 This comparative example is in Figure 11 The system shown is implemented and includes: a primary pressurization unit 1, a desulfurization unit 2, a catalytic reforming unit 4, a heat recovery unit 5, a decarbonization unit 6, a pressurization unit 7, and a methanol synthesis unit 8.

[0277] The biogas to be treated (flow rate of 120,000 Nm³) 3The biogas produced at a pressure of 0.015 MPa and a temperature of 30°C is pressurized in a primary pressurization unit 1 to obtain pressurized biogas (pressure 2.8 MPaG). This pressurized biogas then enters the desulfurization unit 2 for desulfurization treatment, yielding desulfurized pressurized biogas (pressure 2.5 MPaG, sulfur content 30 ppm). This desulfurized pressurized biogas then enters the catalytic reforming unit 4, where it undergoes a carbon dioxide-methane-water vapor dry-wet dual catalytic reforming reaction at a temperature of 870°C and a pressure of 2.5 MPaG to obtain converted gas.

[0278] The converted gas enters the heat recovery unit 5 (sequentially connected to a steam generator, raw material preheater, demineralized water deaerator, air cooler, and water cooler) to exchange heat with water, thereby lowering the temperature of the converted gas to obtain cooled converted gas (temperature 40°C), while the temperature of the heat exchange medium water rises and it is converted into steam (pressure 3.5 MPaG); a portion of the steam (accounting for 60% of the total steam volume) enters the catalytic reforming unit 4 to participate in the catalytic reforming reaction;

[0279] The cooled conversion gas enters the decarbonization unit 6 and undergoes decarbonization treatment at a temperature of 55°C and a pressure of 2.1 MPaG to obtain decarbonized conversion gas (carbon dioxide volume content of 3%, H / C modulus ratio of 2.01). Then, it enters the pressurization unit 7 for pressurization at an operating pressure of 8 MPaG to obtain decarbonized pressurized conversion gas. Next, it enters the methanol synthesis unit 8 and undergoes methanol synthesis reaction at a temperature of 295°C and a pressure of 8 MPaG to obtain methanol and purge gas.

[0280] Test case

[0281] The energy consumption for methanol processing, biogas carbon resource utilization rate, production cost and operating cost in the examples and comparative examples were calculated, and the results are shown in Table 2. The operating cost of Example 1 was taken as 100%, and the operating costs of other examples and comparative examples were compared with the cost of Example 1.

[0282] Table 2

[0283]

[0284] As can be seen from the results in Table 1, the method for preparing methanol from biogas described in this invention has a simple process, does not require external fuel supply, and has made significant progress in terms of methanol processing energy consumption, biogas carbon resource utilization rate, production cost, and operating cost. This invention has low processing energy consumption, high biogas carbon resource utilization rate, and reduced production and operating costs. At the same time, the entire preparation process is green and environmentally friendly, and can utilize various waste gases.

[0285] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing methanol from biogas, characterized in that, The method includes the following steps: A1: Pressurize the biogas to obtain pressurized biogas, then desulfurize it to obtain desulfurized biogas, pressurize the desulfurized biogas to obtain desulfurized pressurized biogas, and subject at least a portion of the desulfurized pressurized biogas to a catalytic reforming reaction to obtain converted gas; A2: The reformed gas is heat-exchanged with water to obtain cooled reformed gas and steam, and at least a portion of the steam is used as a raw material to participate in the catalytic reforming reaction; A3: The cooled conversion gas is decarbonized to obtain decarbonized conversion gas, which is then pressurized to obtain decarbonized pressurized conversion gas, and then methanol synthesis reaction is carried out to obtain methanol and purge gas; The H / C modulus ratio of the decarbonization conversion gas is 1.9-2.

2.

2. A method for preparing methanol from biogas, characterized in that, The method includes the following steps: B1: Pressurize the biogas to obtain pressurized biogas, then desulfurize it to obtain desulfurized biogas, pressurize the desulfurized biogas to obtain desulfurized pressurized biogas, and subject at least a portion of the desulfurized pressurized biogas to a catalytic reforming reaction to obtain converted gas; B2: The reformed gas is heat-exchanged with water to obtain cooled reformed gas and steam, and at least a portion of the steam is used as a raw material to participate in the catalytic reforming reaction; B3: The cooled conversion gas is heated by decarbonization treatment, then heat exchanged with water, and then decarbonized to obtain decarbonized conversion gas. Then it is pressurized to obtain decarbonized pressurized conversion gas, and then methanol synthesis reaction is carried out to obtain methanol and purge gas. The H / C modulus ratio of the decarbonization conversion gas is 1.9-2.

2.

3. A method for preparing methanol from biogas, characterized in that, The method includes the following steps: C1: Pressurize the biogas to obtain pressurized biogas, then desulfurize it to obtain desulfurized biogas, pressurize the desulfurized biogas to obtain desulfurized pressurized biogas, and subject at least a portion of the desulfurized pressurized biogas to a catalytic reforming reaction to obtain converted gas; C2: The reformed gas is heat-exchanged with water to obtain cooled reformed gas and steam, and at least a portion of the steam is used as a raw material to participate in the catalytic reforming reaction; C3: The cooled conversion gas is used to heat the methanol synthesis reaction, then it exchanges heat with water, and then undergoes decarbonization treatment to obtain decarbonized conversion gas. Then it is pressurized to obtain decarbonized pressurized conversion gas, and then the methanol synthesis reaction is carried out to obtain methanol and purge gas. The H / C modulus ratio of the decarbonization conversion gas is 1.9-2.

2.

4. A method for preparing methanol from biogas, characterized in that, The method includes the following steps: D1: Pressurize the biogas to obtain pressurized biogas, then desulfurize it to obtain desulfurized biogas, pressurize the desulfurized biogas to obtain desulfurized pressurized biogas, and subject at least a portion of the desulfurized pressurized biogas to a catalytic reforming reaction to obtain converted gas; D2: The reformed gas is heated by water to obtain cooled reformed gas and steam, and at least a portion of the steam is used as a raw material to participate in the catalytic reforming reaction; D3: The cooled conversion gas is used to heat the methanol synthesis reaction, then to heat the decarbonization process, then to exchange heat with water, then to carry out the decarbonization process to obtain decarbonized conversion gas, then to pressurize it to obtain decarbonized pressurized conversion gas, then to carry out the methanol synthesis reaction to obtain methanol and purge gas. The H / C modulus ratio of the decarbonization conversion gas is 1.9-2.

2.

5. The method according to any one of claims 1-4, characterized in that, The purge gas is subjected to hydrogen separation to obtain hydrogen and hydrogen-lean purge gas. The hydrogen-lean off-gas serves as fuel to provide heat for the catalytic reforming reaction; and / or The hydrogen is used as a raw material for the methanol synthesis reaction and / or as a raw material for the catalytic reforming reaction; and / or At least a portion of the desulfurized and pressurized biogas is used as fuel to provide heat for the catalytic reforming reaction.

6. The method according to any one of claims 1-5, characterized in that, The conditions for the catalytic reforming reaction include: a temperature of 750-960℃ and a pressure of 0.05-5 MPaG; and / or The conditions for the methanol synthesis reaction include: a temperature of 220-320℃ and a pressure of 0.8-15 MPaG.

7. The method according to any one of claims 1-6, characterized in that, The biogas contains 0-3.5% sulfur by volume, 0-45% carbon dioxide by volume, and 50-65% methane by volume; and / or The biogas has a temperature of 20-65℃ and a pressure of 0.001-0.15 MPaG; and / or The pressure of the pressurized biogas is 0.02-10 MPaG; and / or The sulfur content in the desulfurized and pressurized biogas is 0-20 ppmv; and / or The temperature of the cooling conversion gas is 40-420℃; and / or The pressure of the decarbonization booster gas is 4-15 MPaG.

8. A system for producing methanol from biogas, the system being used to implement the method of claim 1, characterized in that, The system includes: a primary pressurization unit (1), a desulfurization unit (2), a secondary pressurization unit (3), a catalytic reforming unit (4), a heat recovery unit (5), a decarbonization unit (6), a pressurization unit (7), a methanol synthesis unit (8), and a decarbonization control unit (10); The biogas to be treated enters the primary pressurization unit (1) and is pressurized to obtain pressurized biogas. Then it enters the desulfurization unit (2) for desulfurization treatment to obtain desulfurized biogas. Then it enters the secondary pressurization unit (3) for pressurization to obtain desulfurized pressurized biogas. At least part of the desulfurized pressurized biogas enters the catalytic reforming unit (4) for catalytic reforming reaction to obtain converted gas. The converted gas enters the heat recovery unit (5) to exchange heat with water, and obtains cooled converted gas and steam. At least part of the steam enters the catalytic reforming unit (4) to participate in the catalytic reforming reaction. The cooled conversion gas enters the decarbonization unit (6) for decarbonization treatment to obtain decarbonized conversion gas, and then enters the pressurization unit (7) for pressurization to obtain decarbonized pressurized conversion gas, and then enters the methanol synthesis unit (8) for methanol synthesis reaction to obtain methanol and purge gas; The decarbonization control unit (10) is connected to the decarbonization unit (6) and is used to control the H / C modulus ratio of the decarbonization conversion gas to be 1.9-2.

2.

9. A system for producing methanol from biogas, the system being used to implement the method of claim 2, characterized in that, The system includes: a primary pressurization unit (1), a desulfurization unit (2), a secondary pressurization unit (3), a catalytic reforming unit (4), a heat recovery unit (5), a decarbonization unit (6), a pressurization unit (7), a methanol synthesis unit (8), and a decarbonization control unit (10); The biogas to be treated enters the primary pressurization unit (1) and is pressurized to obtain pressurized biogas. Then it enters the desulfurization unit (2) for desulfurization treatment to obtain desulfurized biogas. Then it enters the secondary pressurization unit (3) for pressurization to obtain desulfurized pressurized biogas. At least part of the desulfurized pressurized biogas enters the catalytic reforming unit (4) for catalytic reforming reaction to obtain converted gas. The converted gas enters the heat recovery unit (5) to exchange heat with water, and obtains cooled converted gas and steam. At least part of the steam enters the catalytic reforming unit (4) to participate in the catalytic reforming reaction. The cooled conversion gas enters the decarbonization unit (6) to provide heat for the decarbonization process, then returns to the heat recovery unit (5) to exchange heat with water, and then re-enters the decarbonization unit (6) to perform the decarbonization process, obtaining decarbonized conversion gas, which then enters the pressurization unit (7) to pressurize, obtaining decarbonized pressurized conversion gas, and then enters the methanol synthesis unit (8) to perform the methanol synthesis reaction, obtaining methanol and purge gas; The decarbonization control unit (10) is connected to the decarbonization unit (6) and is used to control the H / C modulus ratio of the decarbonization conversion gas to be 1.9-2.

2.

10. A system for producing methanol from biogas, the system being used to implement the method of claim 3, characterized in that, The system includes: a primary pressurization unit (1), a desulfurization unit (2), a secondary pressurization unit (3), a catalytic reforming unit (4), a heat recovery unit (5), a decarbonization unit (6), a pressurization unit (7), a methanol synthesis unit (8), and a decarbonization control unit (10); The biogas to be treated enters the primary pressurization unit (1) and is pressurized to obtain pressurized biogas. Then it enters the desulfurization unit (2) for desulfurization treatment to obtain desulfurized biogas. Then it enters the secondary pressurization unit (3) for pressurization to obtain desulfurized pressurized biogas. At least part of the desulfurized pressurized biogas enters the catalytic reforming unit (4) for catalytic reforming reaction to obtain converted gas. The converted gas enters the heat recovery unit (5) to exchange heat with water, and obtains cooled converted gas and steam. At least part of the steam enters the catalytic reforming unit (4) to participate in the catalytic reforming reaction. The cooled conversion gas enters the methanol synthesis unit (8) to heat the methanol synthesis reaction, then returns to the heat recovery unit (5) to exchange heat with water, and then enters the decarbonization unit (6) for decarbonization treatment to obtain decarbonized conversion gas, then enters the pressurization unit (7) for pressurization to obtain decarbonized pressurized conversion gas, and then enters the methanol synthesis unit (8) for the methanol synthesis reaction to obtain methanol and purge gas; The decarbonization control unit (10) is connected to the decarbonization unit (6) and is used to control the H / C modulus ratio of the decarbonization conversion gas to be 1.9-2.

2.

11. A system for producing methanol from biogas, the system being used to implement the method of claim 4, characterized in that, The system includes: a primary pressurization unit (1), a desulfurization unit (2), a secondary pressurization unit (3), a catalytic reforming unit (4), a heat recovery unit (5), a decarbonization unit (6), a pressurization unit (7), a methanol synthesis unit (8), and a decarbonization control unit (10); The biogas to be treated enters the primary pressurization unit (1) and is pressurized to obtain pressurized biogas. Then it enters the desulfurization unit (2) for desulfurization treatment to obtain desulfurized biogas. Then it enters the secondary pressurization unit (3) for pressurization to obtain desulfurized pressurized biogas. At least part of the desulfurized pressurized biogas enters the catalytic reforming unit (4) for catalytic reforming reaction to obtain converted gas. The converted gas enters the heat recovery unit (5) to exchange heat with water, and obtains cooled converted gas and steam. At least part of the steam enters the catalytic reforming unit (4) to participate in the catalytic reforming reaction. The cooled conversion gas enters the methanol synthesis unit (8) to heat the methanol synthesis reaction, then enters the decarbonization unit (6) to heat the decarbonization process, then returns to the heat recovery unit (5) and exchanges heat with water, then enters the decarbonization unit (6) to perform the decarbonization process, obtaining decarbonized conversion gas, then enters the pressurization unit (7) to pressurize, obtaining decarbonized pressurized conversion gas, then enters the methanol synthesis unit (8) to perform the methanol synthesis reaction, obtaining methanol and purge gas; The decarbonization control unit (10) is connected to the decarbonization unit (6) and is used to control the H / C modulus ratio of the decarbonization conversion gas to be 1.9-2.

2.

12. The system according to any one of claims 8-11, characterized in that, The system also includes a hydrogen separation unit (9); The purge gas enters the hydrogen separation unit (9) for hydrogen separation to obtain hydrogen and hydrogen-lean purge gas; The lean hydrogen offgas is used as fuel to enter the catalytic reforming unit (4) to provide heat for the catalytic reforming reaction; and / or The hydrogen gas enters the booster unit (7) as a raw material for the methanol synthesis reaction; and / or The hydrogen gas enters the catalytic reforming unit (4) to participate in the catalytic reforming reaction; and / or At least a portion of the desulfurized and pressurized biogas is used as fuel to enter the catalytic reforming unit (4) to provide heat for the catalytic reforming reaction.

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