A novel biogas-to-green methanol device and method

Abstract

The invention belongs to the technical field of clean energy, and specifically relates to a novel biogas-based green methanol device and method, comprising the following steps: S1: raw gas is input into a raw gas compressor and pressurized to 1.3 MPaG, and then preheated to 330°C through a primary convection section of a converter; S2: entering a hydrogenation reactor for olefin saturation to remove olefins and oxygen, and then entering a zinc oxide desulfurization reactor to remove excess hydrogen sulfide gas; S3: the refined raw gas is mixed with water vapor output from a boiler, and then preheated to 600°C through a secondary convection section of a converter and a primary conversion reaction is performed; S4: the gas after the secondary preheating is transported to a 910°C environment of a radiation section of a converter for a secondary conversion reaction; S5: methanol synthesis is performed in an isothermal methanol synthesis tower; the invention can reduce carbon deposition of a catalyst in the process of preparing methanol from biogas, avoid frequent replacement of the catalyst, improve work efficiency and reduce use costs.

Description

Technical Field

[0001] The invention belongs to the technical field of clean energy, and specifically relates to a novel device and method for producing green methanol from biogas. Background Art

[0002] Biogas is a mixture of various gases, the main components of which include methane, carbon dioxide, nitrogen, hydrogen, oxygen and hydrogen sulfide. Methane (CH4) is the main component of biogas, accounting for 50% to 80%. It is a colorless, odorless gas with a high calorific value and is the main source of biogas for energy use. Carbon dioxide (CO2) accounts for about 20% to 40% of biogas. Carbon dioxide is one of the by-products in the biogas fermentation process and has a certain impact on the calorific value and combustion performance of biogas. Nitrogen (N2) accounts for 0% to 5%, mainly from air residues in the raw materials or microbial metabolism. The hydrogen (H2) content is less than 1%. Hydrogen is produced during the biogas fermentation process, but its content is relatively low. The oxygen (O2) content is less than 0.4%; the hydrogen sulfide (H2S) content is between 0.1% and 3%. Hydrogen sulfide is a harmful gas in the biogas fermentation process. It has a pungent odor and toxicity, and has certain hazards to the environment and human health.

[0003] Traditional methanol production methods mainly rely on fossil fuels such as coal, the combustion of which produces a large amount of carbon dioxide and other greenhouse gases, causing adverse effects on the environment. Biogas-to-methanol, on the other hand, can utilize the carbon element in biomass resources and convert it into methanol through a biochemical process, thereby reducing dependence on fossil fuels and carbon emissions. Chinese patent CN113527052A discloses a biogas-to-methanol process, which, based on an electrically heated converter, divides the synthesis gas separated from the upper part of the crude methanol separator and returns it to the inlet of the synthesis gas compressor and the inlet of the raw material heat exchanger, recovers the effective gas in the synthesis gas, and the methane utilization rate in the biogas can reach more than 95%; the raw gas in the converter inlet is preheated by an electric heater, and the temperature of the raw gas in the converter inlet can be flexibly adjusted; the high-temperature conversion gas at the converter outlet is used to produce medium-pressure steam and superheated medium-pressure steam, and the medium-pressure superheated steam produced by the device is all used for steam distribution to adjust the water-steam ratio at the converter inlet, without consuming external steam, reducing energy consumption and improving energy utilization; the converter of the prior art adopts an electric heating method to provide the heat required for the reaction. Compared with the traditional open-fire heating furnace, it does not need to consume fuel gas and does not need to discharge flue gas, saves the complex combustion control system and flue gas waste heat recovery control system of the traditional converter, and simplifies the process flow.

[0004] In the prior art, although high temperature can accelerate the rate of methane reforming reaction, the higher temperature will also cause carbon deposition inside the equipment after the reaction while accelerating the reaction rate, and thus the equipment needs to be frequently cleaned and the catalyst used for the reaction needs to be replaced, resulting in low efficiency and high production cost. Based on this, a new biogas-to-green methanol device and method is proposed. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a novel biogas-to-green methanol device and method.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A novel method for producing green methanol from biogas, characterized in that it comprises the following steps:

[0008] S1: The raw gas is input into the raw gas compressor and pressurized to 1.3MPaG, and then preheated to 330℃ through the primary convection section of the reformer;

[0009] S2: Enters the hydrogenation reactor for olefin saturation to remove olefins and oxygen, and then enters the zinc oxide desulfurization reactor to remove excess hydrogen sulfide gas;

[0010] S3: The refined raw gas is mixed with the steam output from the boiler, and then preheated to 600°C in the secondary convection section of the reformer for the primary reforming reaction;

[0011] S4: transporting the secondary preheated gas to the 910°C environment of the reforming furnace radiation section for secondary reforming reaction;

[0012] S5: synthesizing methanol in an isothermal methanol synthesis tower.

[0013] Furthermore, a nickel-based catalyst is arranged in the primary convection section of the converter, and a converted nickel-based catalyst is arranged in the secondary convection section of the converter.

[0014] Furthermore, between S4 and S5, S401 is also included: the synthesis gas passes through the reforming gas steam generator and the boiler feed water preheater in sequence, and then the synthesis gas is cooled to 40° C. in the water cooler, and liquid water is separated through the water separation tank.

[0015] Furthermore, it also includes S402: removing part of the carbon dioxide from the synthesis gas output from the water separation tank through an adsorption tower, then pressurizing it to 6MPaG through a synthesis gas compressor, mixing it with the purge gas circulated through a purge gas compressor, and entering a pre-tower heat exchanger to be preheated to 215°C.

[0016] Furthermore, it also includes S403: entering a methanol separation washing tower to circulate the top gas phase purge gas, and the methanol at the bottom of the tower enters a methanol distillation tower for distillation after being buffered by an expansion tank. The distillation tower is composed of a pre-distillation tower, a pressure distillation tower and a normal pressure distillation tower.

[0017] A novel biogas-based green methanol device is applicable to a novel biogas-based green methanol method. The converter comprises a shell, an inner tank, a burner, a convection tube and a radiation tube. The inner tank is arranged in the shell, the burner is arranged in the inner tank, the convection tube is arranged around the outside of the inner tank, the radiation tube is connected to the convection tube and passes through the inner tank and is arranged in the inner tank, a convection hole is arranged at the bottom of the inner tank and is connected to the outside of the inner tank, an exhaust port is arranged on the shell for discharging high-temperature gas generated by combustion of the burner, and a primary catalyst and a secondary catalyst are respectively arranged in the convection tube and the radiation tube.

[0018] Furthermore, the convection tube includes a primary convection tube and a secondary convection tube, the primary convection tube is separately arranged on the side wall of the inner tank, the secondary convection tube is arranged in close contact with the inner tank, the primary catalyst is arranged in the secondary convection tube, the output end of the primary convection tube is connected to the hydrogenation reactor, the input end of the secondary convection tube is connected to the zinc oxide desulfurization reactor, and the output end of the secondary convection tube is connected to the radiation tube.

[0019] Furthermore, the primary catalyst is rotatably arranged in the secondary convection tube, and a plurality of inclined air passages are arranged on the primary catalyst, which extend from the center of the circle to the rim surface. The airflow in the inclined air passage impacts the reverse thrust port to drive the primary catalyst to rotate.

[0020] Furthermore, a plurality of reverse thrust ports are provided in the secondary convection tube at positions corresponding to the plurality of inclined air passages of the primary catalyst, and the plurality of reverse thrust ports are used for reverse thrusting the airflow passing through the inclined air passages.

[0021] Furthermore, a plurality of balls are arranged at a downstream end of the primary catalyst to rotate with the secondary convection tube.

[0022] The beneficial effects of the present invention are:

[0023] In the process of preparing carbon monoxide and hydrogen from methane, the conversion is carried out through two conversion reactions. The order of the two conversion reactions is to increase the reaction temperature in turn. In the conversion reaction with a lower initial temperature, when the concentration of methane in the raw gas is high, only part of the methane in the raw gas is converted into hydrogen, carbon monoxide and carbon dioxide, and part of the unreacted methane is further converted through the subsequent secondary conversion reaction, which can reduce carbon deposition while reducing the reaction rate. Since the temperature of the secondary conversion reaction is higher, the reaction rate is faster, and part of the carbon deposition attached to the catalyst of the primary conversion reaction will also be blown along with the flow of the raw gas and move to the radiation section of the secondary conversion reaction. In this process, the temperature of the radiation section reaches 910°C, reaching the ignition point of carbon, so the blown-off carbon reacts again in the radiation section to generate carbon monoxide or carbon dioxide, which can avoid carbon adsorption on the catalyst of the secondary conversion reaction;

[0024] After the raw gas enters the primary catalyst, a part of it passes through the cavity and reacts with the catalyst in the cavity, and the other part passes through the inclined airway, so that the raw gas entering the inclined airway hits the inner wall of the secondary convection tube and rotates the primary catalyst, causing the catalyst inside to flip. The raw gas passing through reacts with the catalyst on the one hand, and on the other hand, it can blow off part of the carbon deposits adhering to the surface of the catalyst and move toward the secondary catalyst in the radiation tube under the action of the raw gas flow. The convection tube surrounds the outside of the inner tank from bottom to top and is connected to the top of the radiation tube. After entering the radiation tube, the raw gas moves from top to bottom, and the secondary catalyst is arranged in the lower middle part of the radiation tube, so that the upper middle part of the radiation tube is used to burn carbon to turn it into carbon monoxide or carbon dioxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to facilitate understanding by those skilled in the art, the present invention is further described below with reference to the accompanying drawings.

[0026] Figure 1 A flow chart of preparing synthesis gas according to the present invention;

[0027] Figure 2 A flow chart of preparing methanol according to the present invention;

[0028] Figure 3 It is a schematic diagram of the internal structure of the reformer of the present invention;

[0029] Figure 4 It is a schematic diagram of the internal structure of the converter liner of the present invention;

[0030] Figure 5 It is a schematic diagram of the structure of the primary catalyst in the secondary convection tube of the present invention.

[0031] Explanation of the reference numerals: 1. Shell; 2. Inner tank; 3. Primary convection tube; 4. Secondary convection tube; 41. Reverse thrust port; 5. Radiant tube; 6. Primary catalyst; 61. Inclined air duct; 7. Secondary catalyst; 8. Burner; 9. Convection hole; 10. Exhaust port. DETAILED DESCRIPTION

[0032] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0033] like Figure 1-5 As shown, a novel method for producing green methanol from biogas of the present invention comprises the following steps:

[0034] S1: The raw gas is input into the raw gas compressor and pressurized to 1.3MPaG, and then preheated to 330℃ through the primary convection section of the reformer;

[0035] S2: Enters the hydrogenation reactor for olefin saturation to remove olefins and oxygen, and then enters the zinc oxide desulfurization reactor to remove excess hydrogen sulfide gas;

[0036] S3: The refined raw gas is mixed with the steam output from the boiler, and then preheated to 600°C in the secondary convection section of the reformer for the primary reforming reaction;

[0037] S4: transporting the secondary preheated gas to the 910°C environment of the reforming furnace radiation section for secondary reforming reaction;

[0038] S5: synthesizing methanol in an isothermal methanol synthesis tower.

[0039] In the process of preparing methanol, the methane in the biogas must first be converted into carbon monoxide and hydrogen through a conversion reaction for the subsequent synthesis of methanol. However, during the conversion reaction, it is generally converted once at a higher temperature in a converter. Although high temperature can accelerate the rate of methane reforming reaction, higher temperature will also cause carbon deposition inside the equipment after the reaction while accelerating the reaction rate, which requires frequent cleaning of the equipment and replacement of the catalyst for the reaction.

[0040] Therefore, in order to reduce carbon deposits during the reaction, in the process of preparing carbon monoxide and hydrogen from methane, the conversion is carried out through two conversion reactions, and the temperatures required for the two conversion reactions are different. The reaction temperature is increased in sequence according to the order of the two conversion reactions.

[0041] In step S1, preheating can raise the temperature of the raw gas to a suitable reaction temperature range of 330°C, which helps to accelerate the chemical reaction rate and make the raw gas collide and react more frequently on the catalyst surface in subsequent steps, thereby improving the reaction efficiency.

[0042] In step S2, the hydrogenation reactor is a key equipment in the biogas treatment process. It provides a high-temperature, high-pressure and catalyst-filled environment, so that the hydrogenation reaction can be carried out efficiently. In the reactor, the biogas as the raw gas is fully mixed with hydrogen and contacts the catalyst to cause olefin saturation and oxygen removal reactions. In the hydrogenation reactor, the biogas (mainly composed of methane, carbon dioxide, etc., and containing a small amount of olefins and oxygen) and hydrogen react with the carbon-carbon double bond (C=C) in the olefin molecule under the action of the catalyst to generate saturated hydrocarbon compounds, thereby removing olefins in the raw gas.

[0043] At the same time, if the biogas contains oxygen, hydrogen can also react with oxygen to generate water (H2O) and release heat, further removing oxygen. The zinc oxide desulfurization reactor is used to remove excess hydrogen sulfide gas. The hydrogenation reactor and zinc oxide desulfurization reactor can remove substances that do not need to participate in the reaction and improve the purity of the raw gas.

[0044] During the conversion reaction, although water vapor is introduced to mix with the raw gas, part of the methane (CH4) in the raw gas will decompose into carbon (C) and hydrogen (H2) under the action of high temperature and catalyst, and the generated carbon will be adsorbed on the surface of the catalyst, resulting in reduced catalyst activity. In the initial conversion reaction at a lower temperature, the reaction rate is reduced due to the lower temperature, that is, when the secondary preheating is about 600°C, 30% to 40% of the methane in the raw gas can be consumed by reaction;

[0045] When the concentration of methane in the raw gas is high, only part of the methane in the raw gas is converted into hydrogen, carbon monoxide and carbon dioxide, while the remaining 60% to 70% of unreacted methane is further converted through subsequent secondary conversion reactions, which can reduce carbon deposits while reducing the reaction rate.

[0046] At the same time, since the temperature of the secondary conversion reaction is higher, the reaction rate is faster. Some of the carbon deposits attached to the catalyst of the primary conversion reaction will also be blown along with the flow of the raw gas and move toward the radiation section of the secondary conversion reaction. In this process, the temperature of the radiation section reaches 910°C, reaching the ignition point of carbon. Therefore, the blown-off carbon reacts again in the radiation section to generate carbon monoxide or carbon dioxide, which can avoid carbon adsorption on the catalyst of the secondary conversion reaction. At the same time, the catalyst on the primary conversion reaction has a slower reaction rate, so the carbon deposits are also reduced, and the concentration of methane in the raw gas can be reduced. After the methane concentration is reduced, methane can be more fully mixed with water vapor to generate carbon monoxide and hydrogen in the secondary conversion reaction, and the carbon deposits generated by the secondary conversion reaction can be ignored.

[0047] Specifically, since the reaction temperatures of the primary conversion reaction and the secondary conversion reaction are different, and the activity of the catalyst under different temperature conditions is different, in order to achieve the best reaction effect, a nickel-based catalyst is provided in the primary convection section of the converter, and a reformed nickel-based catalyst is provided in the secondary convection section of the converter. The nickel-based catalyst has good catalytic activity and selectivity under the condition of 600°C, and can effectively promote the reforming reaction of methane and carbon dioxide in biogas to generate synthesis gas. In addition, the cost of nickel-based catalysts is relatively low, and it is easy to prepare and regenerate; under high temperature conditions such as 910°C, catalysts with high temperature stability and high activity are usually required. High temperature is conducive to the movement of chemical equilibrium in the direction of generating synthesis gas and improving the reaction conversion rate. Therefore, high temperature resistant nickel-based catalysts are used, such as Ni / SBA-15 catalysts or modified versions thereof. These catalysts can maintain good catalytic performance at high temperatures and promote the conversion reaction of biogas.

[0048] After the two conversion reactions are completed, the temperature of the synthesis gas converted from the raw gas reaches about 910°C. It needs to be cooled before entering the next step. In order to avoid energy waste, in one embodiment, between S4 and S5, S401 is further included: the synthesis gas passes through the conversion gas steam generator and the boiler feed water preheater in sequence, and then the synthesis gas is cooled to 40°C in the water cooler, and the liquid water is separated by passing through the water separation tank;

[0049] After the syngas enters the reforming gas steam generator, it contacts the internal heat exchange tubes or heat exchange surfaces. Since the syngas has a high temperature, it can transfer heat to the water in the heat exchange tubes; similarly, the boiler feed water preheater can absorb the high-temperature waste heat in the syngas and preheat the boiler feed water to a certain temperature before sending it to the boiler. In this way, the boiler will require less fuel to heat the preheated feed water, thereby improving the thermal efficiency of the boiler, and the water vapor generated by the boiler can be used to mix with the raw gas during the reforming reaction;

[0050] When the syngas enters the water separator, the liquid water in the syngas will condense and settle at the bottom of the water separator due to the relatively low temperature in the water separator (relative to the syngas temperature). The dry syngas will continue to flow upward and enter the subsequent process flow through the outlet of the water separator. Therefore, the main purpose of the syngas entering the water separator is to use the temperature difference to condense and separate the liquid water in the syngas, so as to ensure the stable operation of the subsequent process and product quality.

[0051] Furthermore, it also includes S402: removing a portion of carbon dioxide from the synthesis gas output from the water separation tank by external green hydrogen or by an adsorption tower VPSA (pressure swing adsorption), and then pressurizing it to 6MPaG by a synthesis gas compressor, mixing it with the purge gas circulated by the purge gas compressor, and entering the heat exchanger before the tower to be preheated to 215°C;

[0052] The adsorption tower captures carbon dioxide in the gas through specific adsorption materials (such as activated carbon, molecular sieves, alkaline metal oxides, etc.). When the synthesis gas containing carbon dioxide passes through the adsorption tower, the carbon dioxide molecules are captured by the micropores or active sites on the surface of the adsorption material, thereby achieving gas separation and purification.

[0053] Further, the method further includes S403: entering a methanol separation and washing tower, circulating the top gas phase purge gas, and the methanol at the bottom of the tower is buffered by an expansion tank and then enters a methanol distillation tower for distillation, wherein the distillation tower is composed of a pre-distillation tower, a pressure distillation tower and an atmospheric distillation tower;

[0054] The working principle of the methanol separation scrubber is based on the principles of solubility and affinity. In the scrubber, polluted gas flows into the tower through the air inlet, and a certain amount of methanol solution is sprayed from the bottom. When the polluted gas passes through the methanol solution, the methanol in the solution will physically adsorb or chemically react with the pollutants in the gas to separate the pollutants. The scrubber is usually equipped with a tower plate or a packing layer to increase the contact area of ​​the substance and improve the absorption efficiency of the pollutants.

[0055] Specifically, solubility refers to the property of pollutants being soluble in methanol solution, and the purpose of separation can be achieved through the solubility of the substance; while affinity refers to the force of mutual attraction between pollutants and methanol molecules, and pollutants are more inclined to be adsorbed or reacted with methanol molecules and separated.

[0056] As a type of gas compression equipment, the main function of the purge gas compressor is to compress specific gases (such as gases generated during the reaction process that need to be discharged or reused) to increase the gas pressure and facilitate storage, transportation or further processing.

[0057] In order to avoid carbon deposition on the catalyst in the above embodiment, the raw gas needs to be converted twice to form synthesis gas, so the converter used for the conversion reaction needs to be improved accordingly. Therefore, the converter includes a shell 1, an inner shell 2, a burner 8, a convection tube and a radiation tube 5. The inner shell 2 is arranged in the shell 1, the burner 8 is arranged in the inner shell 2, the convection tube is arranged around the outside of the inner shell 2, the radiation tube 5 is connected to the convection tube and passes through the inner shell 2 and is arranged in the inner shell 2, the bottom of the inner shell 2 is provided with a convection hole 9 connected to the outside of the inner shell 2, the shell 1 is provided with an exhaust port 10 for discharging the high-temperature gas generated by the combustion of the burner 8, and the convection tube and the radiation tube 5 are respectively provided with a primary catalyst 6 and a secondary catalyst 7;

[0058] A cavity is formed between the shell 1 and the inner liner 2, and the burner 8 is arranged in the inner liner 2. When the burner 8 is burning, a radiation section is formed inside the inner liner 2, and the radiation tube 5 is mainly heated by the heat radiation formed by the combustion of the burner 8. The high-temperature gas formed by the combustion of the burner 8 flows through the convection holes 9 at the bottom of the inner liner 2 to the cavity between the inner liner 2 and the shell 1. The cavity is the convection section. The temperature in the radiation section is higher, and the temperature in the convection section is lower. Therefore, the temperature in the radiation tube 5 is higher, and the temperature in the convection tube is lower, so that high-temperature and low-temperature conversion reactions can be carried out respectively.

[0059] Specifically, the convection tube includes a primary convection tube 3 and a secondary convection tube 4, the primary convection tube 3 is separately arranged on the side wall of the inner tank 2, the secondary convection tube 4 is arranged in close contact with the inner tank 2, the primary catalyst 6 is arranged in the secondary convection tube 4, the output end of the primary convection tube 3 is connected to the hydrogenation reactor, the input end of the secondary convection tube 4 is connected to the zinc oxide desulfurization reactor, and the output end of the secondary convection tube 4 is connected to the radiation tube 5;

[0060] Since the raw gas needs to be heated twice in the convection tube, heated to 330°C in S1 and to 600°C in S3, in order to form different temperatures in the convection tube, the primary convection tube 3 is not attached to the side wall of the inner tank 2. The temperature of the raw gas in the primary convection tube 3 is only heated by the high-temperature gas output from the radiation section. The secondary convection tube 4 is attached to the side wall of the inner tank 2. In addition to absorbing the heat of the high-temperature gas, it can also be heated through the heat transfer of the inner tank 2, so that the temperature of the secondary convection tube 4 is higher.

[0061] Since the conversion reaction rate of the raw gas is low when passing through the primary catalyst 6 in the secondary convection tube 4, some carbon deposits will be left on the catalyst in the primary catalyst 6. In order to clean up the small amount of carbon deposits, in one embodiment, the primary catalyst 6 is rotatably arranged in the secondary convection tube 4, and a plurality of inclined air passages 61 are arranged on the primary catalyst 6, which penetrate from the center of the circle to the rim surface, and the plurality of inclined air passages 61 are used to drive the primary catalyst 6 to rotate;

[0062] The catalyst is cylindrical, and a cavity is provided inside the catalyst for placing the catalyst, and the inclined airway 61 is connected to the cavity. The outlet of the inclined airway 61 has a mesh cover to block the catalyst. After the raw gas enters the primary catalyst 6, a part of it passes through the cavity and reacts with the catalyst in the cavity, and the other part passes through the inclined airway 61, so that the raw gas entering the inclined airway 61 hits the inner wall of the secondary convection tube 4 and rotates the primary catalyst 6, so that the catalyst inside is turned over, and the raw gas passing through reacts with the catalyst on the one hand, and on the other hand, it can blow off part of the carbon deposits adhered to the surface of the catalyst and move toward the secondary catalyst 7 in the radiation tube 5 under the action of the raw gas flow, and the convection tube surrounds the outer side of the inner tank 2 from bottom to top and is connected to the top of the radiation tube 5. After entering the radiation tube 5, the raw gas moves from top to bottom, and the secondary catalyst 7 is arranged in the lower middle part of the radiation tube 5, so that the upper middle part of the radiation tube 5 is used to burn carbon to make it carbon monoxide or carbon dioxide.

[0063] Furthermore, a plurality of reverse thrust ports 41 are provided at positions corresponding to the plurality of inclined air passages 61 of the primary catalyst 6 in the secondary convection tube 4. The plurality of reverse thrust ports 41 are perpendicular to the flow direction of the gas in the inclined air passages 61, and the plurality of reverse thrust ports 41 are used to reverse the airflow passing through the inclined air passages 61. Since the inclined air passages 61 are provided at positions offset from the center of the primary catalyst 6 and are in an eccentric direction, the gas blown out of the inclined air passages 61 will push the primary catalyst 6 to rotate after hitting the inner wall of the secondary convection tube 4. In order to speed up the rotation speed, the reverse thrust ports 41 are provided in the secondary convection tube 4. After the raw gas in the inclined air passages 61 hits the reverse thrust ports 41, a greater thrust can be provided to rotate the catalyst, thereby increasing the rotation speed of the primary catalyst 6.

[0064] Furthermore, a plurality of balls are arranged at the downstream end of the primary catalyst 6 to rotate with the secondary convection tube 4 . The balls can reduce friction and increase the rotation speed of the primary catalyst 6 .

[0065] Working principle:

[0066] (1) The main reaction principle of biogas to methanol:

[0067] CO+2H2≒CH3OH+102.5kJ / mol

[0068] CO2+3H2≒CH3OH+H2O+59.6 kJ / mol

[0069] (2) The main components of biogas are methane (about 60% by volume) and carbon dioxide (about 40% by volume). The methane in biogas can react with water vapor to produce synthesis gas containing hydrogen, carbon monoxide and carbon dioxide. The reaction principle is as follows:

[0070] CnHm+nH2O = nCO+(n+m / 2)H2 ①

[0071] CO+3H2=CH4+H2O ②

[0072] CO+H2O=CO2+H2 ③

[0073] (3) The produced synthesis gas is added with green hydrogen produced by wind power or photovoltaic power or excess carbon dioxide is removed so that the synthesis gas reaches the following hydrogen-carbon ratio for methanol synthesis:

[0074] f = (H2-CO2) / (CO+ CO2)=2.05~2.15

[0075] The crude methanol obtained is subjected to three-tower methanol distillation to obtain green refined methanol that meets the requirements.

[0076] The specific process scheme of this device is as follows:

[0077] After the biogas is pressurized in this device, it enters the biogas refining, and oxygen and hydrogen sulfide gas in the raw material are removed by biogas refining. The refined raw gas is mixed with the water vapor output by the boiler, preheated to 600℃ in the convection section of the converter for the primary conversion reaction, and then enters the radiation section of the converter for the secondary conversion reaction. Under the action of the catalyst, a balanced mixture of hydrogen, methane, carbon monoxide, carbon dioxide and water is produced. The high-temperature synthesis gas from the converter is recovered through the heat exchanger for the production of steam. The cooled synthesis gas is pressurized and enters the methanol synthesis device, where methanol synthesis is carried out in the isothermal methanol synthesis reactor. After cooling in the cooler, crude methanol and water are obtained, which enter the methanol distillation device, and enter the pre-distillation tower, pressure tower and atmospheric pressure tower for methanol distillation respectively. The refined methanol obtained by distillation enters the refined methanol storage tank for storage, which is convenient for subsequent loading and transportation.

[0078] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A biogas-to-methanol device, characterized in that: The device is suitable for the following method, which comprises the following steps: S1: The raw gas is input into the raw gas compressor and pressurized to 1.3MPaG, and then preheated to 330℃ through the primary convection section of the reformer; S2: Enters the hydrogenation reactor for olefin saturation to remove olefins and oxygen, and then enters the zinc oxide desulfurization reactor to remove excess hydrogen sulfide gas; S3: The refined raw gas is mixed with the steam output from the boiler, and then preheated to 600°C in the secondary convection section of the reformer for the primary reforming reaction; S4: transporting the secondary preheated gas to the 910°C environment of the reforming furnace radiation section for secondary reforming reaction; S5: synthesizing methanol in an isothermal methanol synthesis tower; The reformer comprises a shell, an inner shell, a burner, a convection tube and a radiation tube, wherein the inner shell is arranged in the shell, the burner is arranged in the inner shell, the convection tube is arranged around the outside of the inner shell, the radiation tube is connected to the convection tube and penetrates the inner shell and is arranged in the inner shell, the bottom of the inner shell is provided with a convection hole connected to the outside of the inner shell, the shell is provided with an exhaust port for discharging high-temperature gas generated by the burner, and the convection tube and the radiation tube are respectively provided with a primary catalyst and a secondary catalyst; The convection tube includes a primary convection tube and a secondary convection tube, wherein the primary convection tube is separately arranged on the side wall of the inner tank, the secondary convection tube is arranged in close contact with the inner tank, the primary catalyst is arranged in the secondary convection tube, the output end of the primary convection tube is connected to the hydrogenation reactor, the input end of the secondary convection tube is connected to the zinc oxide desulfurization reactor, and the output end of the secondary convection tube is connected to the radiation tube; The primary catalyst is rotatably arranged in the secondary convection tube, and a plurality of inclined air passages are arranged on the primary catalyst, which penetrate from the center of the circle to the rim surface, and the plurality of inclined air passages are used to drive the primary catalyst to rotate; A plurality of reverse thrust ports are arranged in the secondary convection pipe at positions corresponding to the plurality of inclined air passages of the primary catalyst, the plurality of reverse thrust ports are perpendicular to the flow direction of the gas in the inclined air passages, and the airflow in the inclined air passages impacts the reverse thrust ports to drive the primary catalyst to rotate; A plurality of balls rotatably arranged with the secondary convection tube are arranged at a downstream end of the primary catalyst.

2. A biogas-to-methanol device according to claim 1, characterized in that: A nickel-based catalyst is arranged in the secondary convection section of the reformer, and a Ni / SBA-15 catalyst is arranged in the radiation section of the reformer.

3. A biogas-to-methanol device according to claim 2, characterized in that: Between S4 and S5, S401 is also included: the synthesis gas passes through the reformed gas steam generator and the boiler feed water preheater in sequence, and then the synthesis gas is cooled to 40° C. in the intermediate gas-water cooler, and liquid water is separated by passing through the intermediate gas-water separation tank.

4. A biogas-to-methanol device according to claim 3, characterized in that: It also includes S402: removing part of the carbon dioxide from the synthesis gas output from the intermediate gas separation tank through an adsorption tower, then pressurizing it to 6MPaG through a synthesis gas compressor, mixing it with the purge gas circulated through a purge gas compressor, entering a pre-tower heat exchanger to be preheated to 215°C, entering an isothermal methanol synthesis tower to synthesize methanol and again cooling it to 40°C through a pre-tower heat exchanger and a methanol water cooler.

5. A biogas-to-methanol device according to claim 4, characterized in that: It also includes S403: entering the methanol separation washing tower to circulate the top gas phase purge gas, and the methanol at the bottom of the tower enters the methanol distillation tower for distillation after being buffered by the expansion tank. The distillation tower is composed of a pre-distillation tower, a pressure distillation tower and a normal pressure distillation tower.

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