Method and system for preparing methanol by combining coke oven gas and fermented biogas

Abstract

The invention relates to the technical field of methanol preparation, in particular to a method and system for preparing methanol through combination of coke oven gas and fermented biogas, and the method comprises the following steps: S1, mixing coke oven gas, fermented biogas and oxygen, carrying out methane and carbon dioxide dry reforming reaction in the presence of a catalyst, and adjusting the hydrogen-carbon ratio to generate first synthesis gas; s2, performing heat exchange operation and decarburization treatment on the first synthesis gas to obtain second synthesis gas; s3, carbon dioxide separated after decarburization treatment is circulated and used for the dry reforming reaction in the step S1; and S4, carrying out methanol synthesis reaction on the second synthesis gas to obtain crude methanol, and rectifying to obtain methanol. The method provided by the invention has remarkable advantages in the aspects of environmental protection, economy, technology and the like, and is an efficient and sustainable low-carbon methanol production process.

Description

Technical Field

[0001] The present invention relates to the technical field of methanol preparation, and particularly to a method and system for jointly producing methanol from coke oven gas and biogas generated by fermentation. Background Art

[0002] Methanol is an important basic organic chemical raw material and a potential clean fuel, and has wide applications in many fields such as chemical industry and energy. Traditional methanol production mainly relies on the conversion of fossil fuels (such as natural gas or coal) into syngas raw materials for preparation. This method not only faces the problem of limited reserves of fossil resources, but also is accompanied by a large amount of carbon dioxide emissions during the production process. Therefore, it is of great practical significance to develop a more environmentally friendly and sustainable methanol production process.

[0003] On the one hand, coke oven gas is a by-product generated during the coking process. Its main components include hydrogen (mole fraction about 55% - 60%) and methane (mole fraction about 23% - 27%), and also contains a small amount of carbon monoxide (5% - 8%) etc. Due to the high hydrogen content, the hydrogen-carbon ratio will be too high when producing methanol from coke oven gas. If the surplus hydrogen cannot be efficiently utilized, the energy utilization efficiency will be reduced; while separating hydrogen is costly due to the complex components of coke oven gas. On the other hand, biogas (biogas generated by fermentation) is a mixed gas produced by the microbial fermentation of organic substances under anaerobic conditions. Its main components are methane and carbon dioxide, and the carbon dioxide content is relatively high. Carbon dioxide in biogas is a potential carbon source, but due to its chemical inertness, its direct utilization efficiency is relatively low.

[0004] Currently, existing production processes either use coke oven gas raw materials alone to produce methanol (such as publication numbers CN116789519A, CN105732323A), or use biogas alone (such as publication numbers CN202221033476.1, CN202411233113.6) to produce methanol, and fail to give full play to the synergistic advantages of the two. At the same time, there is still a lack of effective technical solutions for how to efficiently utilize coke oven gas with industrial-emitted by-product hydrogen and biogas with biogas-fermentation by-product carbon dioxide to prepare syngas with a hydrogen-carbon ratio of 2, which is suitable for the methanol production process.

[0005] Therefore, there is an urgent need to develop a method and system for efficiently and low-carbon producing methanol by combining coke oven gas and biogas. Summary of the Invention

[0006] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a method and system for jointly producing methanol from coke oven gas and biogas generated by fermentation to solve the problems in the prior art.

[0007] To achieve the above and other related objectives, the present invention first provides a method for jointly producing methanol from coke oven gas and biogas, which specifically includes the following steps:

[0008] S1. Mix coke oven gas, biogas, and oxygen, and carry out the methane dry reforming reaction with carbon dioxide in the presence of a catalyst, and adjust the hydrogen-carbon ratio to generate a first synthesis gas;

[0009] S2. Conduct heat exchange operation and decarbonization treatment on the first synthesis gas to obtain a second synthesis gas;

[0010] S3. Recycle the carbon dioxide separated after decarbonization treatment for use in the dry reforming reaction described in step S1;

[0011] S4. Carry out methanol synthesis reaction on the second synthesis gas to obtain crude methanol, and obtain methanol after rectification.

[0012] The present invention also provides a system for jointly producing methanol from coke oven gas and biogas, including a pretreatment unit (1), a dry reforming reactor (2), a heat exchanger (3), a decarbonization unit (4), a methanol synthesis unit (5), and a methanol purification unit (6) connected in sequence; the dry reforming reactor (2) is also provided with an oxygen inlet (200) for introducing oxygen to carry out the methane dry reforming reaction on coke oven gas and biogas to generate a first synthesis gas; the heat exchanger (3) is connected to the outlet of the dry reforming reactor (2); the decarbonization unit (4) is provided with a decarbonization pipeline (400), the decarbonization unit (4) is connected to one end of the decarbonization pipeline (400), and the other end of the decarbonization pipeline (4) is connected and merged with the biogas input pipeline (110) and the coke oven gas input pipeline (120) and is located upstream of the pretreatment unit (1).

[0013] As described above, the method and system for jointly producing methanol from coke oven gas and biogas of the present invention have the following beneficial effects:

[0014] 1) Reduce carbon dioxide emissions: By jointly utilizing the surplus hydrogen in coke oven gas and the carbon dioxide in biogas, the carbon dioxide that might have been directly emitted is converted into methanol, thereby reducing greenhouse gas emissions;

[0015] 2) Recycle carbon dioxide: Part of the carbon dioxide separated by the decarbonization unit returns to the autothermal reformer to participate in the reaction, further reducing carbon dioxide emissions;

[0016] 3) The catalyst is mature and inexpensive: Through the dry reforming technology, carbon dioxide is converted into carbon monoxide, and a traditional and mature catalyst for synthesizing methanol from carbon monoxide hydrogenation is used, without the need for a new type of catalyst for synthesizing methanol from carbon dioxide hydrogenation that has not been industrialized on a large scale;

[0017] 4) Reduce raw material costs: By using two relatively inexpensive and abundant raw materials, coke oven gas and biogas, to replace traditional fossil fuels, the raw material costs for methanol production are reduced;

[0018] 5) Improve energy utilization efficiency: Through the heat recovery unit, the high-temperature waste heat of the syngas is used to preheat the raw material gas or generate steam, enhancing the energy efficiency of the system;

[0019] 6) Reduce fixed investment and variable costs: Compared with using coke oven gas or biogas alone, the combined process has lower fixed investment and variable costs at a methanol production scale of 300,000 tons / year;

[0020] 9) Simplify the process flow: There is no need for complex hydrogen separation or low-concentration carbon dioxide recovery steps, simplifying the process flow and reducing the operation difficulty and costs;

[0021] 7) Simplify the process flow: There is no need to perform complex hydrogen separation or low-concentration carbon dioxide recovery steps, simplifying the process flow and reducing the operation difficulty and costs;

[0022] 8) Utilize renewable resources: Biogas is a renewable resource. By using it in combination with coke oven gas, the proportion of renewable energy in methanol production is increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It shows a schematic diagram of the system for the method of jointly producing methanol from coke oven gas and fermented biogas according to the present invention.

[0024] Reference numerals:

[0025] 1 Pretreatment unit

[0026] 2 Dry reforming reactor

[0027] 3 Heat exchanger

[0028] 4 Decarbonization unit

[0029] 5 Methanol synthesis unit

[0030] 6 Methanol purification unit

[0031] 110 Fermented biogas input pipeline

[0032] 120 Coke oven gas input pipeline

[0033] 200 Oxygen input port

[0034] 300 Steam pipeline

[0035] 400 Decarbonization pipeline DETAILED DESCRIPTION OF THE INVENTION

[0036] The present invention first provides a method for jointly producing methanol from coke oven gas and fermented biogas, which specifically includes the following steps:

[0037] S1. Mix coke oven gas, biogas from fermentation, and oxygen, and conduct the dry reforming reaction of methane and carbon dioxide in the presence of a catalyst. After adjusting the hydrogen-carbon ratio, produce the first synthesis gas.

[0038] S2. Conduct heat exchange operation and decarbonization treatment on the first synthesis gas to obtain the second synthesis gas.

[0039] S3. Recycle the carbon dioxide separated after decarbonization treatment for use in the dry reforming reaction described in step S1.

[0040] S4. Conduct the methanol synthesis reaction on the second synthesis gas to obtain crude methanol, and obtain methanol after rectification.

[0041] In certain embodiments of the present invention, in step S1, the dry reforming reaction of methane and carbon dioxide is carried out in an autothermal reformer.

[0042] In certain embodiments of the present invention, in step S1, the catalyst is a carbon-resistant methane-carbon dioxide reforming catalyst. In a preferred embodiment of the present invention, the catalyst is a nickel-based catalyst.

[0043] Further, the nickel-based catalyst is a supported nickel catalyst, such as a Ni / Al2O3 catalyst.

[0044] In certain embodiments of the present invention, in step S1, the molar ratio of the coke oven gas to the biogas from fermentation is (20 - 100):(20 - 100). The molar ratio of the coke oven gas to the biogas from fermentation can be selected from any of the following ranges: (20 - 30):(20 - 100), (30 - 40):(20 - 100), (40 - 50):(20 - 100), (50 - 60):(20 - 100), (60 - 70):(20 - 100), (70 - 80):(20 - 100), (80 - 90):(20 - 100), (90 - 100):(20 - 100), (20 - 100):(20 - 30), (20 - 100):(30 - 40), (20 - 100):(40 - 50), (20 - 100):(50 - 60), (20 - 100):(60 - 70), (20 - 100):(70 - 80), (20 - 100):(80 - 90), (20 - 100):(90 - 100).

[0045] In the present invention, the specific components of coke oven gas and biogas from fermentation with different sources are different. Adjusting the hydrogen-carbon ratio can improve the utilization rate of coke oven gas and biogas from fermentation.

[0046] In certain embodiments of the present invention, in step S1, the molar ratio of (H2 - CO2) / (CO + CO2) in the first syngas is less than 2.1 and the molar ratio of H2 / CO is greater than 2 and less than 4.

[0047] In certain embodiments of the present invention, in step S1, the molar ratio of the mixture of coke oven gas and biogas formed by fermentation to oxygen is (2 - 10):1. The molar ratio of the mixture to oxygen is selected from any of the following ranges: (2 - 3):1, (3 - 4):1, (4 - 5):1, (5 - 6):1, (6 - 7):1, (7 - 8):1, (8 - 9):1, (9 - 10):1.

[0048] In certain embodiments of the present invention, in step S1, the oxygen is used as an oxidant to accelerate the reaction process and control the temperature of the dry reforming reaction. In the present invention, the amount of oxygen depends on the specific feed gas and its ratio. Too little oxygen may cause the reaction temperature not to reach the required level, and too much oxygen will cause the reaction temperature to be too high. It can be selected according to actual needs.

[0049] In certain embodiments of the present invention, in step S1, pretreatment of the coke oven gas and biogas formed by fermentation is also included.

[0050] Further, the pretreatment is desulfurization treatment, dechlorination treatment, and / or noble metal removal treatment.

[0051] Among them, when the coke oven gas and / or biogas contains sulfur, desulfurization treatment is carried out. The sulfur content in the coke oven gas and / or biogas after desulfurization treatment is lower than 0.5 ppm. For example, the sulfur content in the coke oven gas and / or biogas can be lower than 0.4 ppm, lower than 0.3 ppm, lower than 0.2 ppm, or lower than 0.1 ppm.

[0052] In a preferred embodiment of the present invention, the sulfur content in the coke oven gas and / or biogas after desulfurization treatment is lower than 0.1 ppm.

[0053] The temperature of the desulfurization treatment is 300 - 400 °C. The temperature of the desulfurization treatment is selected from any of the following ranges: 300 - 320 °C, 320 - 340 °C, 340 - 360 °C, 360 - 380 °C, 380 - 400 °C.

[0054] The pressure of the desulfurization treatment is 10 - 60 bar. The pressure of the desulfurization treatment is selected from any of the following ranges: 10 - 20 bar, 20 - 30 bar, 30 - 40 bar, 40 - 50 bar, 50 - 60 bar.

[0055] Among them, when the coke oven gas and / or biogas from fermentation contains chlorine, dechlorination treatment is carried out, and the chlorine content in the coke oven gas and / or biogas after dechlorination treatment is lower than 0.5 ppm. For example, the chlorine content in the coke oven gas and / or biogas can be lower than 0.4 ppm, lower than 0.3 ppm or lower than 0.2 ppm.

[0056] In a preferred embodiment of the present invention, the chlorine content in the coke oven gas and / or biogas after desulfurization treatment is lower than 0.2 ppm.

[0057] Among them, when the coke oven gas and / or biogas from fermentation contains noble metals, removal of noble metals treatment is carried out, and the noble metal content in the coke oven gas and / or biogas after removal of noble metals treatment is lower than 1 ppb. For example, the noble metal content in the coke oven gas and / or biogas can be lower than 0.8 ppb, lower than 0.6 ppb, lower than 0.4 ppb, lower than 0.2 ppb, lower than 0.1 ppb.

[0058] In a preferred embodiment of the present invention, the noble metal content in the coke oven gas and / or biogas after removal of noble metals treatment is lower than 0.6 ppb.

[0059] In certain embodiments of the present invention, in step S1, the temperature of the dry reforming reaction is 700 - 1000 °C. The temperature of the dry reforming reaction is selected from any of the following ranges: 700 - 750 °C, 750 - 800 °C, 800 - 850 °C, 850 - 900 °C, 900 - 950 °C, 950 - 1000 °C.

[0060] In a preferred embodiment of the present invention, in step S1, the temperature of the dry reforming reaction is 850 - 950 °C.

[0061] In certain embodiments of the present invention, in step S1, the pressure of the dry reforming reaction is 1 - 40 Bar. The pressure of the reforming reaction is selected from any of the following ranges: 1 - 5 Bar, 5 - 10 Bar, 10 - 15 Bar, 15 - 20 Bar, 20 - 25 Bar, 25 - 30 Bar, 30 - 35 Bar, 35 - 40 Bar.

[0062] In a preferred embodiment of the present invention, in step S1, the pressure of the dry reforming reaction is 15 - 25 Bar.

[0063] In certain embodiments of the present invention, in step S1, the first syngas includes a mixture of CO and H2 and unreacted CH4. The molar content of methane in the first syngas is ≤1%. In a preferred embodiment of the present invention, the molar content of methane in the first syngas is ≤0.5%. For example, the molar content of methane in the first syngas is 0.5%, 0.4%, 0.3%, 0.2% or 0.1%.

[0064] In certain embodiments of the present invention, in step S2, a heat exchanger is used for the heat exchange operation. The heat exchange medium of the heat exchanger is water. After passing through the heat exchanger, the water is divided into at least one branch stream, which is used for the methanol rectification in step S4. Other branch streams can also be set, for example, for preheating the raw material gas.

[0065] In certain embodiments of the present invention, in step S2, after the first syngas undergoes the heat exchange operation, the temperature at which it enters the decarbonization unit is 30 - 50°C. The temperature at which the first syngas enters the decarbonization unit after the heat exchange operation is selected from any of the following ranges: 30 - 34°C, 34 - 38°C, 38 - 42°C, 42 - 46°C, 46 - 50°C.

[0066] In a preferred embodiment of the present invention, after the first syngas undergoes the heat exchange operation, the temperature at which it enters the decarbonization unit is 38 - 42°C.

[0067] In certain embodiments of the present invention, the decarbonization method is selected from physical absorption or chemical absorption.

[0068] Furthermore, the physical absorption is pressure swing adsorption; the chemical absorption is amine solution scrubbing.

[0069] In certain embodiments of the present invention, in step S2, decarbonization is also included to adjust the hydrogen-carbon ratio so that the molar ratio of (H2 - CO2) / (CO + CO2) is 2 - 2.1.

[0070] In certain embodiments of the present invention, in step S4, the temperature of the methanol synthesis reaction is 200 - 300°C. The temperature of the methanol synthesis reaction is selected from any of the following ranges: 200 - 220°C, 220 - 240°C, 240 - 260°C, 260 - 280°C, 280 - 300°C.

[0071] In a preferred embodiment of the present invention, in step S4, the temperature of the methanol synthesis reaction is 200 - 250°C.

[0072] In certain embodiments of the present invention, in step S4, the pressure of the methanol synthesis reaction is 5 - 15 MPa. The pressure of the methanol synthesis reaction is selected from any of the following ranges: 5 - 7 MPa, 7 - 9 MPa, 9 - 11 MPa, 11 - 13 MPa, 13 - 15 MPa.

[0073] In a preferred embodiment of the present invention, the pressure of the methanol synthesis reaction is 6 - 7 MPa.

[0074] In some embodiments of the present invention, in step S4, the catalyst used in the methanol synthesis reaction is selected from copper-based catalysts, palladium-based catalysts, copper-based composite catalysts, and / or bimetallic catalysts, etc.

[0075] In a preferred embodiment of the present invention, in step S4, the catalyst used in the methanol synthesis reaction is a copper-zinc-aluminum catalyst (Cu / ZnO / Al2O3).

[0076] In the present invention, by controlling the ratio of coke oven gas, biogas from fermentation, and oxygen in step S1 and the design of the carbon cycle in step S3, the content of carbon dioxide can be ensured to be lower than 13%. When carrying out the methanol synthesis reaction, only conventional, mature, and inexpensive catalysts are needed.

[0077] In some embodiments of the present invention, in step S4, it further includes gas-liquid separation of the crude methanol, the gas phase is recycled to continue the methanol synthesis reaction, and the liquid phase is subjected to rectification treatment.

[0078] The present invention also provides a system for jointly producing methanol from coke oven gas and biogas from fermentation, which includes a pretreatment unit 1, a dry reforming reactor 2, a heat exchanger 3, a decarbonization unit 4, a methanol synthesis unit 5, and a methanol purification unit 6 connected in sequence;

[0079] The dry reforming reactor 2 is also provided with an oxygen inlet 200 for introducing oxygen to carry out methane-carbon dioxide dry reforming reaction on the coke oven gas and biogas from fermentation to generate a first synthesis gas;

[0080] The heat exchanger 3 is connected to the outlet of the dry reforming reactor 2; the decarbonization unit 4 is provided with a decarbonization pipeline 400, one end of the decarbonization unit 4 is connected to the decarbonization pipeline 400, and the other end of the decarbonization pipeline is connected to the biogas from fermentation input pipeline 110 and the coke oven gas input pipeline 120 after they converge and is located upstream of the pretreatment unit 1.

[0081] In some embodiments of the present invention, the dry reforming reactor 2 is a self-heating reforming furnace. In the present invention, the hydrogen-carbon ratio is regulated by adjusting the molar ratio of the coke oven gas and biogas from fermentation introduced into the reforming furnace.

[0082] In some embodiments of the present invention, the heat exchange medium of the heat exchanger 3 is water, and the water is divided into at least one branch after passing through the heat exchanger. The first branch is a steam pipeline 300, and the steam pipeline 300 is connected to the methanol purification unit 6 to provide heat source for the methanol purification unit 6.

[0083] In certain embodiments of the present invention, downstream of the decarbonization unit 4, there further includes a first pressurization unit and a first preheating unit, which are used to increase the temperature and pressure of the second syngas.

[0084] In certain embodiments of the present invention, the decarbonization unit 4 is selected from one of an MDEA decarbonization device, a PSA decarbonization device, a gas separation membrane device, or a cryogenic distillation device.

[0085] In certain embodiments of the present invention, the pretreatment unit 1 includes a second preheating unit, a second pressurization unit, and / or a desulfurization device that are connected in sequence.

[0086] The pretreatment unit further includes a dechlorination device and / or a noble metal removal device. In the present invention, the settings of the devices in the pretreatment unit can be flexibly adjusted according to the specific components in the raw material gas.

[0087] The desulfurization device is a molecular sieve desulfurizer.

[0088] The dechlorination device is an activated carbon adsorption tower or a chemical absorption tower.

[0089] The noble metal removal device is selected from an adsorption separation device.

[0090] The following illustrates the embodiments of the present invention through specific specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0091] Before further describing the specific embodiments of the present invention, it should be understood that the protection scope of the present invention is not limited to the specific embodiments described below; it should also be understood that the terms used in the embodiments of the present invention are for describing specific embodiments, rather than for limiting the protection scope of the present invention; in the specification and claims of the present invention, unless otherwise clearly indicated in the text, the singular forms "a", "an", and "the" include the plural forms.

[0092] When the embodiments give a numerical range, it should be understood that unless otherwise specified in the present invention, any value at both ends of each numerical range and any value between the two ends can be selected. Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the art of this technology. In addition to the specific methods, devices, and materials used in the embodiments, according to the knowledge of those skilled in the art of this technology and the description of the present invention, any methods, devices, and materials similar to or equivalent to the methods, devices, and materials described in the embodiments of the present invention can also be used to implement the present invention.

[0093] Example 1

[0094] The system adopted in the example is as shown in the appendix Figure 1 and the method for jointly producing methanol from coke oven gas and biogas fermentation is as follows:

[0095] A mixture of 17,800 kg / hr of coke oven gas and 15,100 kg / hr of biogas fermentation is compressed to a pressure of 10 bar and a temperature of 350 °C, and then undergoes pretreatment. The specific operation is as follows: it is transported to a desulfurization device, a dechlorination device, and a noble metal removal device that are connected in sequence. After being treated by the above devices, a mixed raw material gas with a temperature of 350 °C, a pressure of 10 bar, a sulfur content of less than 0.2 ppm, a chlorine content of less than 0.3 ppm, and a noble metal content of less than 0.4 ppb is obtained. The temperature, pressure, and composition of the gas after pretreatment are shown in Table 1:

[0096] Table 1 Temperature, pressure, and composition of the gas after pretreatment

[0097]

[0098] After pretreatment, the mixed raw material gas is sent to an autothermal reformer, and 17,400 kg / hr of oxygen is introduced. The oxygen is used for combustion to increase the reaction temperature, and further, under the action of a sufficient amount of nickel-based catalyst (Ni / Al2O3 catalyst), a dry reforming reaction of methane and carbon dioxide is carried out to obtain the first synthesis gas. Among them, the reaction temperature of the dry reforming reactor is 923 °C, and the reaction pressure is 25 bar. The generated first synthesis gas is cooled by a heat exchanger and then enters a decarbonization device to further adjust the hydrogen-carbon ratio to ensure that the molar ratio of (H2 - CO2) / (CO + CO2) is 2. After the hydrogen-carbon ratio is adjusted, the second synthesis gas is obtained, and the carbon dioxide dry basis content in the second synthesis gas is less than 13%. The heat exchange medium in the heat exchanger is water, and the steam generated after the water passes through the heat exchanger is transported through a steam pipeline to a methanol distillation column to provide heat for methanol distillation; the carbon dioxide separated by the decarbonization device is transported through a decarbonization pipeline to the upstream of the pretreatment device and merged with the mixed raw material gas to reduce carbon emissions.

[0099] The second synthesis gas with a reasonable hydrogen-carbon ratio is preheated to 230 °C and pressurized to 60 bar, and then input into a methanol synthesizer, and methanol is generated under the action of a sufficient amount of copper-zinc-aluminum catalyst (Cu / ZnO / Al2O3 catalyst). Among them, the methanol synthesis reaction temperature is 250 °C, and the methanol synthesis reaction pressure is 7 MPa. The gas at the outlet of the methanol synthesis reactor is separated by a flash tank. The gas phase is recycled to the methanol synthesis reactor, and the liquid phase of crude methanol is purified by distillation to remove impurities such as water and dimethyl ether, and finally, a methanol product with a purity of ≥99.85% is obtained. The by-products can be further processed or recycled.

[0100] Comparative Example 1

[0101] At atmospheric pressure, 79000 kg / hr of fermented biogas and 19000 kg / hr of superheated steam are mixed and then fed into an autothermal reformer. 15000 kg / hr of oxygen is introduced, which is used for combustion to increase the reaction temperature. Further, under the action of a sufficient amount of nickel-based catalyst (Ni / Al2O3 catalyst), the dry reforming reaction of methane and carbon dioxide is carried out to obtain the first syngas. Among them, the reaction temperature of the dry reforming reactor is 905 °C and the reaction pressure is 25 Bar. The generated first syngas is cooled by a heat exchanger and then enters a decarbonization unit to further adjust the hydrogen-carbon ratio to ensure that the molar ratio of (H2 - CO2) / (CO + CO2) is 2. After the hydrogen-carbon ratio is adjusted, the second syngas is obtained. The heat exchange medium in the heat exchanger is water, and the steam generated after the water passes through the heat exchanger is transported through a steam pipeline to a methanol distillation column to provide heat for methanol distillation; the carbon dioxide separated by the decarbonization unit is transported through a decarbonization pipeline to the upstream of the pretreatment unit and merged with the mixed raw material gas to reduce carbon emissions.

[0102] The second syngas with a reasonable hydrogen-carbon ratio is preheated to 230 °C and pressurized to 60 Bar, and then input into a methanol synthesizer. Under the action of a sufficient amount of copper-zinc-aluminum catalyst (Cu / ZnO / Al2O3 catalyst), methanol is generated. Among them, the reaction temperature of methanol synthesis is 250 °C and the reaction pressure of methanol synthesis is 7 MPa. The gas at the outlet of the methanol synthesis reactor is separated by a flash tank. The gas phase is recycled to the methanol synthesis reactor, and the liquid phase of crude methanol is purified by distillation to remove impurities such as water and dimethyl ether. Finally, a methanol product with a purity ≥ 99.85% is obtained, and the by-products can be further processed or recycled.

[0103] Comparative Example 2

[0104] At atmospheric pressure, 29000 kg / hr of coke oven gas, 23000 kg / hr of CO2 and 7050 kg / hr of superheated steam are mixed and then fed into an autothermal reformer. 19600 kg / hr of oxygen is introduced, which is used for combustion to increase the reaction temperature. Further, under the action of a sufficient amount of nickel-based catalyst (Ni / Al2O3 catalyst), the dry reforming reaction of methane and carbon dioxide is carried out to obtain the first syngas. Among them, the reaction temperature of the dry reforming reactor is 890 °C and the reaction pressure is 25 Bar. The generated first syngas is cooled by a heat exchanger and then enters a decarbonization unit to further adjust the hydrogen-carbon ratio to ensure that the molar ratio of (H2 - CO2) / (CO + CO2) is 2. After the hydrogen-carbon ratio is adjusted, the second syngas is obtained. The heat exchange medium in the heat exchanger is water, and the steam generated after the water passes through the heat exchanger is transported through a steam pipeline to a methanol distillation column to provide heat for methanol distillation; the carbon dioxide separated by the decarbonization unit is transported through a decarbonization pipeline to the upstream of the pretreatment unit and merged with the mixed raw material gas to reduce carbon emissions.

[0105] The second syngas with a reasonable hydrogen-carbon ratio is preheated to 230 °C and pressurized to 60 Bar, and then input into a methanol synthesizer, where methanol is produced under the action of a sufficient amount of copper-zinc-aluminum catalyst (Cu / ZnO / Al2O3 catalyst). Among them, the methanol synthesis reaction temperature is 250 °C, the methanol synthesis reaction pressure is 7 MPa. The gas at the outlet of the methanol synthesis reactor is separated by a flash tank. The gas phase is recycled to the methanol synthesis reactor, and the liquid phase of crude methanol is purified by distillation to remove impurities such as water and dimethyl ether, and finally a methanol product with a purity ≥ 99.85% is obtained. The by-products can be further processed or recycled.

[0106] The above examples and comparative examples are all about the dosages of different raw material gases (such as coke oven gas, biogas from fermentation, CO2, H2O and O2) at a production scale of 300,000 tons / year of methanol.

[0107] The comparison of the raw material utilization rates of three methanol preparation processes is shown in Table 2:

[0108] Table 2 Comparison of the raw material utilization rates of three methanol preparation processes

[0109]

[0110]

[0111] The above examples are to illustrate the implementation schemes disclosed in the present invention and should not be construed as limitations on the present invention. In addition, various modifications listed herein and changes in the methods of the invention are obvious to those skilled in the art without departing from the scope and spirit of the present invention. Although the present invention has been specifically described in connection with various specific preferred embodiments of the present invention, it should be understood that the present invention should not be limited to these specific embodiments. In fact, all obvious modifications to those skilled in the art as described above to obtain the invention should be included within the scope of the present invention.

Claims

1. A method for jointly producing methanol from coke oven gas and biogas from fermentation, characterized in that, The method includes the following steps: S1. Mix coke oven gas, biogas from fermentation, and oxygen, and carry out methane dry reforming with carbon dioxide in the presence of a catalyst. After adjusting the hydrogen-carbon ratio, produce a first synthesis gas. S2. Conduct heat exchange operation and decarbonization treatment on the first synthesis gas to obtain a second synthesis gas. S3. Recycle the carbon dioxide separated after decarbonization treatment for use in the dry reforming reaction described in step S1. S4. Carry out methanol synthesis reaction on the second synthesis gas to obtain crude methanol, and obtain methanol after rectification.

2. The method according to claim 1, characterized in that, In step S1, any one or more of the following features are included: 11) The methane dry reforming with carbon dioxide reaction is carried out in an autothermal reformer. 12) The catalyst is a carbon-resistant methane reforming catalyst with carbon dioxide; preferably, the catalyst is a nickel-based catalyst. 13) The molar ratio of the coke oven gas to the biogas from fermentation is (20 - 100):(20 - 100). 14) In the first synthesis gas, the molar ratio of (H2 - CO2) / (CO + CO2) is less than 2.1 and H2 / CO is greater than 2 and less than 4. 15) The molar ratio of the mixed gas formed by the coke oven gas and the biogas from fermentation to oxygen is (2 - 10):

1. 16) The temperature of the dry reforming reaction is 700 - 1000 °C. 17) The pressure of the dry reforming reaction is 1 - 40 Bar.

3. The method according to claim 1, wherein It also includes pretreating the coke oven gas and the biogas from fermentation; preferably, the pretreatment is desulfurization treatment, dechlorination treatment, and / or noble metal removal treatment.

4. The method according to claim 3, characterized in that, When sulfur is present in the coke oven gas and / or the biogas from fermentation, desulfurization treatment is carried out. The sulfur content in the coke oven gas and / or the biogas from fermentation after desulfurization treatment is lower than 0.5 ppm; preferably, the sulfur content in the coke oven gas and / or the biogas from fermentation after desulfurization treatment is lower than 0.2 ppm. And / or, the temperature of the desulfurization treatment is 300 - 400 °C. And / or, the pressure of the desulfurization treatment is 10 - 60 bar. And / or, when chlorine is present in the coke oven gas and / or the biogas from fermentation, dechlorination treatment is carried out. The chlorine content in the coke oven gas and / or the biogas from fermentation after dechlorination treatment is lower than 0.5 ppm; preferably, the chlorine content in the coke oven gas and / or the biogas from fermentation after dechlorination treatment is lower than 0.2 ppm. And / or, when noble metals are present in the coke oven gas and / or the biogas from fermentation, noble metal removal treatment is carried out. The noble metal content in the coke oven gas and / or the biogas from fermentation after noble metal removal treatment is lower than 1 ppb.

5. The method according to claim 1, characterized in that, In step S2, any one or more of the following features are included: 21) The heat exchange operation uses a heat exchanger, and the heat exchange medium of the heat exchanger is water. After passing through the heat exchanger, the water is divided into at least one branch. 22) When the first synthesis gas undergoes heat exchange operation and enters the decarbonization unit, the temperature is 30 - 50 °C. 23) The decarbonization method is selected from physical absorption or chemical absorption; preferably, the physical absorption is pressure swing adsorption; preferably, the chemical absorption is amine liquid scrubbing. 24) It also includes adjusting the hydrogen-carbon ratio again after decarbonization to make the molar ratio of (H2 - CO2) / (CO + CO2) be 2 - 2.

1.

6. The method according to claim 1, wherein In step S4, any one or more of the following features are included: 41) The temperature of the methanol synthesis reaction is 200 to 300 °C; 42) The pressure of the methanol synthesis reaction is 5 to 15 MPa; 43) The catalyst used in the methanol synthesis reaction is selected from copper-based catalysts, palladium-based catalysts, copper-based composite catalysts, and / or bimetallic catalysts; 44) It also includes gas-liquid separation of the crude methanol, recycling the gas phase to continue the methanol synthesis reaction, and subjecting the liquid phase to rectification treatment.

7. A system applicable to the method for jointly producing methanol from coke oven gas and biogas from fermentation according to any one of claims 1 to 6, characterized in that, It includes a pretreatment unit (1), a dry reforming reactor (2), a heat exchanger (3), a decarbonization unit (4), a methanol synthesis unit (5), and a methanol purification unit (6) connected in sequence; the dry reforming reactor (2) is also provided with an oxygen inlet (200); the heat exchanger (3) is connected to the outlet of the dry reforming reactor (2); the decarbonization unit (4) is provided with a decarbonization pipeline (400), the decarbonization unit (4) is connected to one end of the decarbonization pipeline (400), and the other end of the decarbonization pipeline is connected after converging with the fermentation biogas input pipeline (110) and the coke oven gas input pipeline (120) and is located upstream of the pretreatment unit (1).

8. The system according to claim 7, wherein The dry reforming reactor (2) is an autothermal reforming furnace; And / or, the heat exchange medium of the heat exchanger (3) is water, and the water is divided into at least one branch after passing through the heat exchanger. The first branch is a steam pipeline (300), and the steam pipeline (300) is connected to the methanol purification unit (6); And / or, the decarbonization unit (4) is selected from one of an MDEA decarbonization device, a PSA decarbonization device, a gas separation membrane device, or a low-temperature rectification device And / or, downstream of the decarbonization unit (4) also includes a first pressurization unit and a first preheating unit.

9. The system according to claim 7, wherein The pretreatment unit (1) includes a second preheating unit, a second pressurization unit, and / or a desulfurization device connected in sequence; preferably, the desulfurization device is a molecular sieve desulfurizer.

10. The system according to claim 7, characterized in that, The pretreatment unit (1) also includes a dechlorination device and / or a noble metal removal device; preferably, the dechlorination device is an activated carbon adsorption tower or a chemical absorption tower; preferably, the noble metal removal device is a chemical adsorption separation device.

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