Method for producing dimethyl ether from biogas by prying type self-heating

Abstract

The present application provides a kind of pry installation type self-heating type methane preparation dimethyl ether method.The method includes the pretreatment of methane and air, and part of methane is used to carry out reforming reaction to obtain synthesis gas, and another part of methane is used to heat combustion furnace, then the synthesis gas is cooled, separated and dehydrated, and then input into dimethyl ether synthesizer to synthesize dimethyl ether, then the crude product of dimethyl ether is separated and purified, and part of the separated gas is used for circulation, and another part of the gas is used for combustion heating.The present application uses part of methane for heating, so that the method has weak dependence on supporting common infrastructure;By using gradient arrangement of flue pipe heat exchanger, heat can be fully utilized;By recycling the unreacted synthesis gas in the dimethyl ether synthesis stage into the dimethyl ether synthesis tower, the raw material utilization rate is improved;Through multi-stage heat exchange, efficient use of heat is realized, and efficient, green and continuous production of green dimethyl ether is further realized.

Description

Technical Field

[0001] This invention relates to a method for producing dimethyl ether from skid-mounted self-heating biogas, belonging to the field of comprehensive energy recovery and utilization. Background Technology

[0002] Biogas is a combustible mixture of gases produced by the fermentation (anaerobic fermentation) of various organic materials (livestock manure, landfill waste, industrial organic wastewater, sewage sludge, etc.) by microorganisms. The main components of biogas are CH4 and CO2. Methane is the second most human-related greenhouse gas after carbon dioxide, with a global warming potential 28 times that of carbon dioxide, and contributes approximately one-third to the global greenhouse effect.

[0003] Traditional biogas utilization primarily involves using it for power generation or as fuel. Landfill gas is a type of biogas. As of the end of 2020, my country had 1,871 sanitary landfills, but only 270 biogas power generation projects were connected to the grid during the same period. Most landfill biogas resources are not effectively utilized. Generally, after collection, methane is converted to carbon dioxide through flaring to reduce methane emissions and further mitigate the greenhouse effect. However, while converting methane to CO2 reduces methane emissions, CO2 is still released into the atmosphere, failing to curb the greenhouse effect. Furthermore, the gas production of most biogas projects is affected by seasonality, with significant periods of abandonment or underutilization. In summary, current technologies result in insufficient utilization and energy waste of biogas energy. Since methane and carbon dioxide in biogas are both greenhouse gases, flexible carbon storage and energy utilization synergistic technologies are urgently needed.

[0004] In view of this, it is indeed necessary to propose a skid-mounted self-heating biogas production method for dimethyl ether to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a skid-mounted self-heating biogas method for producing dimethyl ether, in order to solve the problems of insufficient utilization of biogas energy and energy waste in the process of biogas application in the prior art.

[0006] To achieve the above objectives, the present invention provides a method for preparing dimethyl ether from skid-mounted self-heating biogas, comprising:

[0007] S1. After desulfurization and ammonia removal treatment, the biogas is stored in the first storage tank. Part of the biogas in the first storage tank is fed into the combustion furnace to increase the temperature of the combustion furnace.

[0008] S2. The combustion furnace is equipped with a first heat exchanger and a reforming reactor. The biogas in the first storage tank is input into the first heat exchanger for preheating, and then input into the reforming reactor for reforming reaction to obtain syngas.

[0009] S3. The synthesis gas is sequentially cooled, separated into gas and liquid, dehydrated, and pressurized before being fed into the second storage tank.

[0010] S4. The synthesis gas in the second storage tank is preheated and then fed into the dimethyl ether synthesis tower. Under the action of the catalyst, crude dimethyl ether product is prepared. The crude dimethyl ether product is condensed and fed into the absorption tower to separate the water-soluble and water-insoluble gases in the crude dimethyl ether product. The separated gas is depressurized and fed into S3 to mix with the synthesis gas.

[0011] S5. The separated liquid is fed into the degassing tower and heated to initially separate the impurity gas dissolved in the liquid from the dimethyl ether. After the impurity gas is depressurized, it is fed into the decarbonization tower together with the other part of the gas separated in the absorption tower. The residual gas output from the decarbonization tower is preheated and then fed into the combustion furnace in S1 for combustion.

[0012] S6. Desorb the CO2 adsorbed in the decarbonization tower and input the CO2 into the first heat exchanger in S2 to mix with biogas and then input into the reforming reactor.

[0013] S7. The liquid in the degassing tower is fed into the distillation tower to purify and store the dimethyl ether in the liquid.

[0014] As a further improvement of the present invention, S1 includes: biogas is compressed to 0.15 MPa by a first compressor and then fed into a first desulfurization tower to remove sulfur-containing compounds in the biogas to below 10 ppm, then fed into a second desulfurization tower to remove sulfur-containing compounds in the biogas to below 1 ppm, then fed into an ammonia removal tower to remove ammonia in the biogas to below 1 ppm and then fed into a first storage tank for storage; a third heat exchanger is provided in the combustion furnace, and air is pressurized to 0.15 MPa by a blower and then fed into the third heat exchanger for preheating, and then fed into the combustion furnace to mix with the biogas and burn.

[0015] As a further improvement of the present invention, S2 includes: the reforming reactor includes a first, second and third reforming reactor arranged sequentially from top to bottom, the first heat exchanger is located on the side of the first reforming reactor away from the second reforming reactor, the biogas is preheated in the first heat exchanger and then passes through the first, second and third reforming reactors in sequence for reforming reaction to obtain syngas, and the temperature of the syngas at the outlet of the third reforming reactor is 800-850°C.

[0016] As a further improvement of the present invention, S3 includes: a portion of the biogas gas in the first storage tank is fed into the combustion furnace after passing through the second heat exchanger; the synthesis gas gas exchanges heat with the biogas used for combustion through the second heat exchanger; then it is fed into the first cooler to reduce the temperature of the synthesis gas to room temperature and then into the first separator; the separated gas is fed into the drying tower for dehydration; then it is fed into the second compressor to be pressurized to 3MPa and stored in the second storage tank.

[0017] As a further improvement of the present invention, S4 includes: the synthesis gas flow in the second storage tank is fed into the dimethyl ether synthesis tower after passing through the fourth heat exchanger, the synthesis gas undergoes a synthesis reaction at 200-300°C to generate crude dimethyl ether product, the crude dimethyl ether product flows through the fourth heat exchanger for heat exchange and is then fed into the second cooler to cool down to 25°C, and then fed into the absorption tower for gas-liquid separation.

[0018] As a further improvement of the present invention, the hydrogen-to-carbon ratio of the synthesis gas in the dimethyl ether synthesis tower is 0.8-1.2, and the absorbent in the absorption tower is water or a dimethyl ether solution.

[0019] As a further improvement of the present invention, S5 includes: a first reboiler is provided at the bottom of the degassing tower to heat the degassing tower; a first condenser is provided at the top of the degassing tower to condense the dimethyl ether gas in the degassing tower; and the residual gas output from the decarbonization tower is preheated in a fifth heat exchanger in the combustion furnace before being fed into the combustion furnace for combustion.

[0020] As a further improvement of the present invention, S7 includes: a second reboiler is provided at the bottom of the distillation column to heat the distillation column; a second condenser and a collector connected to a third storage tank are provided at the top of the distillation column; the dimethyl ether gas is liquefied at the second condenser and transferred to the third storage tank for storage through the collector; the liquid at the bottom of the column flows into a fourth storage tank for storage and can flow out of the fourth storage tank and be input into the absorption tower to absorb the crude dimethyl ether product.

[0021] As a further improvement of the present invention, the method includes a water tank for storing condensate. After the condensate flows out of the water tank, it cools the syngas, crude dimethyl ether product, degassing tower and distillation tower respectively. Then it flows into an air cooler to cool the condensate and is circulated back to the water tank.

[0022] As a further improvement of the present invention, the method includes an oil tank for storing heat transfer oil, a sixth heat exchanger at the top of the combustion furnace, through which the heat transfer oil flows to heat the heat transfer oil, the synthesis gas flows through a seventh heat exchanger and exchanges heat with the heat transfer oil in the seventh heat exchanger, the heat transfer oil flows through the dimethyl ether synthesis tower, degassing tower and distillation tower to heat the heat transfer oil, and the heat transfer oil flows through an eighth heat exchanger and exchanges heat with the condensate to cool the heat transfer oil.

[0023] The beneficial effects of this invention are as follows: The skid-mounted, self-sufficient biogas method for producing dimethyl ether uses a portion of the biogas for heating to provide the heat required during operation, thus reducing reliance on shared infrastructure. The preheating of the feed gas at the combustion furnace inlet utilizes a flue gas heat exchanger, arranged according to the temperature gradient, to fully utilize the heat. By recycling a portion of the unreacted synthesis gas from the dimethyl ether synthesis stage back into the dimethyl ether synthesis tower, the feed gas utilization rate is improved. Furthermore, the gas from the top of the absorption tower and degassing tower flows into the decarbonization tower to remove CO2, thus... The fuel components are mixed with biogas and fed into the combustion furnace for use as fuel. CO2 is desorbed and then mixed with biogas to adjust the hydrogen-to-carbon ratio of the feedstock in the reforming reaction, thus achieving efficient utilization of the feedstock. The heat utilization efficiency is improved through multi-stage heat exchange. The reactors used in both the reforming reaction and the dimethyl ether synthesis reaction are microchannel reactors, which can more efficiently control the reactor temperature and flexibly adjust the production scale. This method has low dependence on supporting utility equipment and high energy utilization through the cascade utilization of heat, enabling efficient, green, and continuous production of green dimethyl ether. Attached Figure Description

[0024] Figure 1 This is a flowchart of the method for preparing dimethyl ether from skid-mounted self-heating biogas in this invention.

[0025] Figure 2 This is a process flow diagram of a skid-mounted self-heating biogas production process for dimethyl ether according to a preferred embodiment of the present invention.

[0026] Explanation of reference numerals in the attached drawings: First compressor 11, First desulfurization tower 12, Second desulfurization tower 13, Ammonia removal tower 14, First storage tank 15, Fan 16, Second heat exchanger 17, Combustion furnace 21, First heat exchanger 22, Third heat exchanger 23, First reforming reactor 24, Second reforming reactor 25, Third reforming reactor 26, First cooler 31, First separator 32, Drying tower 33, Second compressor 34, Second storage tank 35, Fourth heat exchanger 41, Dimethyl ether synthesis tower 4 2, Second cooler 43, Absorber 51, First pressure reducing valve 52, Second pressure reducing valve 53, Degassing tower 54, First reboiler 55, First condenser 56, Third pressure reducing valve 57, Decarbonization tower 58, Fifth heat exchanger 59, Distillation tower 61, Second reboiler 62, Second condenser 63, Third storage tank 64, Collector 65, Fourth storage tank 66, Oil tank 71, Sixth heat exchanger 72, Seventh heat exchanger 73, Eighth heat exchanger 74, Water tank 81, Air cooler 82, Pump 9. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] Please see Figure 1 and Figure 2 As shown, this invention discloses a skid-mounted, self-heating biogas method for producing dimethyl ether (DME), suitable for remote locations and areas with low redundancy in supporting public utilities. This method efficiently utilizes biogas and reduces the environmental impact of methane and carbon dioxide. Furthermore, it provides a flexible, self-heating skid-mounted process and equipment for the complete or partial production of DME, offering independent energy systems for biogas projects, landfills, and other methane-rich gas collection scenarios.

[0029] The green dimethyl ether produced by this method and apparatus can be used as a chemical raw material or as a propellant, refrigerant, solvent, foaming agent, etc., for the development of green products; it can be used as a green liquid energy source to provide power for vehicles and ships, and fuel for boilers and stoves; it can be used as a hydrogen storage energy source to provide an easy-to-transport, easy-to-store, easy-to-produce and easy-to-use hydrogen source for hydrogen energy utilization sites; it can also be used as a carbon storage energy source, which can be sealed for years and used when needed to mitigate carbon emissions.

[0030] It should be noted that the device for preparing dimethyl ether from biogas using this technical solution is a skid-mounted type, that is, a mobile container type, which makes the device easy to transport and utilize biogas in remote locations, thus improving the practicality of this method. In addition, the self-heating method means that this method does not rely on external energy or material supplementation. All the energy required in the production process is provided by biogas, that is, a portion of the biogas is used for combustion heating to provide the heat required for the reaction.

[0031] In a first embodiment of the present invention, the method for preparing dimethyl ether from skid-mounted self-heating biogas includes:

[0032] S1. After desulfurization and ammonia removal, the biogas is stored in the first storage tank 15. Part of the biogas in the first storage tank 15 is fed into the combustion furnace 21 to increase the temperature of the combustion furnace 21.

[0033] Biogas is compressed to 0.15 MPa by the first compressor 11 and then fed into the first desulfurization tower 12 to remove sulfur compounds from the biogas to below 10 ppm. It is then fed into the second desulfurization tower 13 to remove sulfur compounds from the biogas to below 1 ppm, and then fed into the ammonia removal tower 14 to remove ammonia from the biogas to below 1 ppm before being fed into the first storage tank 15 for storage. The combustion furnace 21 is equipped with a third heat exchanger 23. Air is pressurized to 0.15 MPa by the blower 16 and then fed into the third heat exchanger 23 for preheating. It is then fed into the combustion furnace 21 to mix with the biogas and burn.

[0034] Specifically, biogas from the biogas storage tank with a flow rate of 0.2650 kmol / h and a process biogas / fuel biogas ratio of 2.346 is pressurized to 0.15 MPa by the first compressor 11 and then sent to the first desulfurization tower 12. It undergoes coarse desulfurization treatment with an iron-based desulfurizing agent, removing H2S from the biogas to below 10 ppm. The coarsely desulfurized biogas is then sent to the second desulfurization tower 13 (ZnO), where H2S is removed to below 1 ppm. It then enters the ammonia removal tower 14, where an adsorbent is used to remove ammonia from the biogas to below 1 ppm. The purified biogas is stored in the first storage tank 15. Air is drawn in by the blower 16 and pressurized to 0.15 MPa before entering the third heat exchanger 23 for preheating. After preheating, it enters the combustion furnace 21 along with the combustion biogas for combustion to provide heat. The biogas composition is: CH4: 0.027 kmol / Nm³. 3 Biogas, CO2: 0.018 kmol / Nm 3 Biogas, specifically process biogas, is the biogas that flows from the first storage tank 15 into the reforming reactor to undergo a reforming reaction. Combustion biogas is the biogas that flows out of the first storage tank 15 and is fed into the combustion furnace 21 for combustion to heat the combustion furnace 21.

[0035] S2. The combustion furnace 21 is equipped with a first heat exchanger 22 and a reforming reactor. The biogas in the first storage tank 15 is fed into the first heat exchanger 22 for preheating, and then fed into the reforming reactor for reforming reaction to obtain syngas.

[0036] The reforming reactor includes a first reforming reactor 24, a second reforming reactor 25, and a third reforming reactor 26 arranged sequentially from top to bottom. A first heat exchanger 22 is located on the side of the first reforming reactor 24 away from the second reforming reactor 25. After being preheated in the first heat exchanger 22, the biogas passes through the first reforming reactor 24, the second reforming reactor 25, and the third reforming reactor 26 in sequence for reforming to obtain syngas. The temperature of the syngas at the outlet of the third reforming reactor 26 is 850°C.

[0037] Reforming reactions include:

[0038] CH4 + CO2 → 2CO + 2H2;

[0039] CH4→C (s) +2H2;

[0040] CO2 + H2 → CO + H2O;

[0041] 2CO→C (s) +CO2.

[0042] Specifically, the first reforming reactor 24, the second reforming reactor 25, and the third reforming reactor 26 are all equipped with Ni / CeO2-Al2O3 catalysts to catalyze the reforming reaction of biogas. The process biogas flows sequentially from top to bottom through the first heat exchanger 22, the first reforming reactor 24, the second reforming reactor 25, and the third reforming reactor 26, undergoing reforming reactions to obtain syngas. The syngas temperature at the outlet of the third reforming reactor 26 is 800-850℃, wherein the CH4 conversion rate in this reforming reaction is 92.34%, and the CO2 conversion rate is 94.88%. Preferably, the syngas temperature at the outlet of the third reforming reactor 26 is 850℃.

[0043] In this process, the high-temperature syngas exchanges heat with the biogas in the second heat exchanger 17, which lowers the temperature of the syngas to 600℃ and raises the temperature of the biogas, thereby improving the thermal efficiency of the biogas combustion in the combustion furnace 21. After passing through the second heat exchanger 17, the syngas flows into the seventh heat exchanger 73 to exchange heat with the heat transfer oil. This lowers the temperature of the syngas to 300℃ and heats the heat transfer oil, allowing the heat in the combustion furnace 21 to be stored through the heat transfer oil.

[0044] S3. The synthesis gas is sequentially cooled, separated into gas and liquid, dehydrated, and pressurized before being fed into the second storage tank 35.

[0045] Synthesis gas, after exiting the seventh heat exchanger 73, enters the first cooler 31 to lower its temperature to room temperature, and then enters the first separator 32. The separated gas enters the drying tower 33 for dehydration, and then enters the second compressor 34 to be pressurized to 3 MPa before being stored in the second storage tank 35. The liquid separated in the first separator 32 can be discharged as wastewater or recycled as condensate within this method; no restriction is imposed here.

[0046] S4. The synthesis gas in the second storage tank 35 is preheated and then fed into the dimethyl ether synthesis tower 42. Under the action of the catalyst, crude dimethyl ether product is prepared. The crude dimethyl ether product is condensed and fed into the absorption tower 51 to separate the water-soluble and water-insoluble gases in the crude dimethyl ether product. The separated gas is depressurized and fed into S3 to mix with the synthesis gas.

[0047] The syngas gas from the second storage tank 35 is fed into the dimethyl ether synthesis tower 42 after passing through the fourth heat exchanger 41. The syngas undergoes a synthesis reaction at 250°C to produce crude dimethyl ether. The crude dimethyl ether product then passes through the fourth heat exchanger 41 for heat exchange and is subsequently cooled to 25°C in the second cooler 43. It is then fed into the absorption tower 51 for gas-liquid separation. The hydrogen-to-carbon ratio of the syngas in the dimethyl ether synthesis tower 42 is 0.86, and the absorbent in the absorption tower 51 is water or a dimethyl ether solution.

[0048] Specifically, the syngas in the second storage tank 35 exchanges heat with the crude dimethyl ether product at the fourth heat exchanger 41 to raise the temperature of the syngas to 150°C while simultaneously lowering the temperature of the crude dimethyl ether product. The syngas then enters the dimethyl ether synthesis tower 42, where excess heat is absorbed by heat transfer oil to maintain the temperature at 200-300°C for the dimethyl ether synthesis reaction. Further, the heat transfer oil stabilizes the equipment temperature at 250°C to ensure the normal progress of the dimethyl ether synthesis reaction. The dimethyl ether synthesis reaction is as follows:

[0049] CO + 2H₂ → CH₃OH;

[0050] 2CH3OH→CH3OCH3+H2O;

[0051] CO + H₂O → CO₂ + H₂.

[0052] The dimethyl ether synthesis tower 42 uses a CuZn / Al2O3 catalyst. In this reaction, the single-pass CO conversion rate reaches 78.96%, the dimethyl ether selectivity is 98.99%, the dimethyl ether recovery rate in the absorption tower 51 is 99%, and the absorbent is a water / dimethyl ether solution taken from the bottom of the distillation tower 61.

[0053] S5. The separated liquid is fed into the degassing tower 54 and heated to initially separate the impurity gas dissolved in the liquid from the dimethyl ether. After the impurity gas is depressurized, it is fed into the decarbonization tower 58 together with the other part of the gas separated in the absorption tower 51. The residual gas output from the decarbonization tower 58 is preheated and then fed into the combustion furnace 21 in S1 for combustion.

[0054] The degassing tower 54 is equipped with a first reboiler 55 at its bottom to heat the tower, and a first condenser 56 at its top to condense the dimethyl ether gas inside. Impurity gases exit from the top of the degassing tower 54 and, after being depressurized by a third pressure-reducing valve 57, are fed into the decarbonization tower 58. Liquid dimethyl ether flows out from the bottom of the degassing tower 54 and into the distillation tower 61, where 99% of the dimethyl ether is separated at the bottom of the degassing tower 54 and enters the distillation tower 61 for concentration.

[0055] Specifically, in step S4, a portion of the water-insoluble gas separated in the absorption tower 51 is mixed with the syngas output from the drying tower 33 after passing through the first pressure reducing valve 52. The mixed gas is then fed into the second compressor 34 for compression, and subsequently fed into the second storage tank 35 for circulation. Another portion of the water-insoluble gas separated in the absorption tower 51 is also fed into the decarbonization tower 58 after passing through the second pressure reducing valve 53 to mix with impurity gases and remove CO2.

[0056] The residual gas output from the decarbonization tower 58 is preheated in the fifth heat exchanger 59 inside the combustion furnace 21 before being fed into the combustion furnace 21 for combustion. This maintains the gas pressure balance within the device and ensures gas flow, allowing some substances in the biogas that cannot participate in the reaction to be burned and output, thus improving the service life of this method.

[0057] S6. Desorb the CO2 adsorbed in the decarbonization tower 58 and input the CO2 into the first heat exchanger 22 in S2 to mix with biogas and then input into the reforming reactor.

[0058] Specifically, carbon dioxide is adsorbed in the decarbonization tower 58, and then removed. The removed carbon dioxide is then fed into the first heat exchanger 22. By adding carbon dioxide, the hydrogen-to-carbon ratio of the process biogas fed into the combustion furnace 21 is adjusted to be in the range of 0.8-1.2, preferably 0.86.

[0059] S7. The liquid in the degassing tower 54 is fed into the distillation tower 61 to purify and store the dimethyl ether in the liquid.

[0060] A second reboiler 62 is provided at the bottom of the distillation column 61 to heat the distillation column 61, so that the liquid placed at the bottom of the distillation column 61 can be heated and dimethyl ether can be vaporized from the liquid. Part of the liquid at the bottom of the column flows into the fourth storage tank 66 for storage under the drive of pump 9, and part of it flows to the biogas digester under the drive of pump 9, while the other part flows to the absorption tower 51 to dissolve the gaseous dimethyl ether in the absorption tower 51, realizing circulation and reducing the environmental pollution and energy consumption of this method.

[0061] The distillation column 61 is equipped with a second condenser 63 and a collector 65 connected to a third storage tank 64 at the top of the column. Dimethyl ether gas is liquefied at the second condenser 63 and transferred to the third storage tank 64 through the collector 65 for storage. The liquid at the bottom of the column flows into the fourth storage tank 66 for storage and can flow out of the fourth storage tank 66 and enter the absorption column 51 to absorb the crude dimethyl ether product.

[0062] Specifically, in distillation column 61, dimethyl ether with a concentration higher than 99.5% is condensed and collected at the top of the column and stored in the third storage tank 64. During the distillation process, the loss of dimethyl ether is less than 0.1%.

[0063] This method includes a water tank 81 for storing condensate. The condensate is used to cool the equipment requiring cooling in this method. After flowing out of the water tank 81, the condensate, driven by the pump 9, cools the syngas, crude dimethyl ether product, degassing tower 54, and distillation tower 61 respectively. Then, it flows into the air cooler 82 to further cool the condensate before circulating it back to the water tank 81. This setup achieves water circulation, preventing wastewater from flowing out and causing environmental pollution.

[0064] This method includes an oil tank 71 for storing heat transfer oil, which facilitates heat transfer between the various devices in the method. A sixth heat exchanger 72 is provided at the top of the combustion furnace 21. The heat transfer oil flows through the sixth heat exchanger 72 to heat it. The synthesis gas flows through the seventh heat exchanger 73 and exchanges heat with the heat transfer oil in the seventh heat exchanger 73. The heat transfer oil flows through the dimethyl ether synthesis tower 42, the degassing tower 54, and the distillation tower 61 to heat it. The heat transfer oil flows through the eighth heat exchanger 74 and exchanges heat with the condensate to cool it.

[0065] In other words, two pumps 9 are installed at the oil tank 71. One pump 9 drives the heat transfer oil to the sixth heat exchanger 72 and the seventh heat exchanger 73 to heat the heat transfer oil. The other pump 9 drives the heat transfer oil from the oil tank 71 to the dimethyl ether synthesis tower 42 to maintain the temperature of the dimethyl ether synthesis tower 42. Then, the heat transfer oil is mixed with the heat transfer oil that has passed through the sixth heat exchanger 72 and the seventh heat exchanger 73. The mixed heat transfer oil is then fed into the first reboiler 55 and the second reboiler 62 to heat the degassing tower 54 and the distillation tower 61, respectively. After that, it is fed into the eighth heat exchanger 74 to exchange heat with the condensate and then fed into the oil tank 71 for circulation.

[0066] In this embodiment, the total carbon utilization rate is 46.80%, and the energy consumption is 5116.75 kJ / mol biogas.

[0067] In this embodiment, the first reforming reactor 24, the second reforming reactor 25, the third reforming reactor 26, and the dimethyl ether synthesis tower 42 are all microchannel reactors to increase the specific surface area of ​​the reactors, which can reach 10,000-50,000 m². 2 / m 3 It has high heat exchange efficiency. The combustion furnace 21 includes a reactor zone and a flue zone. The first reforming reactor 24, the second reforming reactor 25 and the third reforming reactor 26 are located in the reactor zone. The sixth heat exchanger 72, the fifth heat exchanger 59, the third heat exchanger 23 and the first heat exchanger 22 are all housed in the flue zone and arranged from top to bottom in the flue zone. There are gas nozzles on both sides of the reactor zone to radiate heat to the reactor and ensure uniform heating.

[0068] The temperature in the reactor zone is controlled within a safe range of 600-800℃. The reactor zone is divided into a first, second, and third heating zone from top to bottom. The temperature in the first heating zone is controlled at 600-650℃, the temperature in the second heating zone is controlled at 700-750℃, and the temperature in the third heating zone is controlled at 800-850℃. The temperature of the heat transfer oil in oil tank 71 is 180℃.

[0069] In this embodiment, heating is achieved through biogas combustion and combustion furnace 21. Of course, in other embodiments, combustion furnace 21 can be set to electric heating, that is, solar energy, wind energy, tidal energy, biomass energy, exhaust wind heat energy, etc. can be used to generate electricity and heat combustion furnace 21 through electricity. At the same time, combustion furnace 21 can also be set to multi-energy coordinated heating, that is, biogas combustion and electric heating are coordinated to avoid energy waste. There are no restrictions here.

[0070] Example 2

[0071] The structure and working principle of this embodiment are the same as those of Embodiment 1. The main difference is that green dimethyl ether is prepared under the operating parameters of a process biogas / gas combustion rate of 3.895 and a hydrogen-to-carbon ratio of 0.95 in the dimethyl ether synthesis process. During the dimethyl ether synthesis process, the syngas circulation rate is 0, the CO2 circulation rate is 90%, and the single-pass CO conversion rate is 83.52%. The final yield is 0.50199 kg / Nm³. 3 Dimethyl ether from biogas.

[0072] Example 3

[0073] The structure and working principle of this embodiment are the same as those of Embodiment 1. The main difference is that green dimethyl ether is prepared under the operating parameters of a process biogas / gas combustion rate of 11.399 and a hydrogen-to-carbon ratio of 0.98 in the dimethyl ether synthesis process. During the dimethyl ether synthesis process, the syngas circulation rate is 0, the CO2 circulation rate is 50%, and the single-pass CO conversion rate is 83.55%. The final yield is 0.49793 kg / Nm³. 3 Dimethyl ether from biogas.

[0074] Example 4

[0075] The structure and working principle of this embodiment are the same as those of Embodiment 1. The main difference lies in the operating parameters: green dimethyl ether is prepared under the following conditions: process biogas / gas combustion biogas ratio is 929,000, and the hydrogen-to-carbon ratio in the dimethyl ether synthesis process is 0.81. During the dimethyl ether synthesis process, the syngas recycle rate is 50%, the CO2 recycle rate is 0, and the single-pass CO conversion rate is 51.41%. The final yield is 0.46426 kg / Nm³. 3 Dimethyl ether from biogas.

[0076] In summary, the skid-mounted self-sufficient biogas method for producing dimethyl ether of the present invention utilizes microchannel reactors, resulting in a large specific surface area and high heat exchange efficiency. This allows for efficient temperature control of the reactors and improves energy utilization efficiency. Furthermore, by using a portion of the biogas for heating to provide the heat required during operation, the method is less dependent on shared infrastructure. The unreacted syngas from the dimethyl ether synthesis stage is partially recycled back into the dimethyl ether synthesis tower 42, improving raw material utilization. Gas from the tops of the absorption tower 51 and degassing tower 54 flows into the decarbonization tower 58 to remove CO2, and the combustible components are mixed with biogas before entering the combustion furnace 21 as fuel. The CO2, after desorption, is mixed with the biogas to adjust the hydrogen-to-carbon ratio of the raw materials in the reforming reaction, achieving efficient utilization of the raw materials. This method eliminates the need for process water, resulting in low energy consumption in the reforming reaction, and the separation process after dimethyl ether synthesis is simple and efficient.

[0077] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for producing dimethyl ether from skid-mounted self-heating biogas, characterized in that, include: S1. After desulfurization and ammonia removal treatment, the biogas is stored in the first storage tank. Part of the biogas in the first storage tank is fed into the combustion furnace to increase the temperature of the combustion furnace. S2. The combustion furnace is equipped with a first heat exchanger and a reforming reactor. The biogas in the first storage tank is input into the first heat exchanger for preheating, and then input into the reforming reactor for reforming reaction to obtain syngas. S3. The synthesis gas is sequentially cooled, separated into gas and liquid, dehydrated, and pressurized before being fed into the second storage tank. S4. The synthesis gas in the second storage tank is preheated and then fed into the dimethyl ether synthesis tower. Under the action of the catalyst, crude dimethyl ether product is prepared. The crude dimethyl ether product is condensed and fed into the absorption tower to separate the water-soluble and water-insoluble gases in the crude dimethyl ether product. The separated gas is depressurized and fed into S3 to mix with the synthesis gas. S5. The separated liquid is fed into the degassing tower and heated to initially separate the impurity gas dissolved in the liquid from the dimethyl ether. After the impurity gas is depressurized, it is fed into the decarbonization tower together with the other part of the gas separated in the absorption tower. The residual gas output from the decarbonization tower is preheated and then fed into the combustion furnace in S1 for combustion. S6. Desorb the CO2 adsorbed in the decarbonization tower and input the CO2 into the first heat exchanger in S2 to mix with biogas and then input into the reforming reactor. S7. The liquid in the degassing tower is fed into the distillation tower to purify and store the dimethyl ether in the liquid; The reforming reactor includes a first, second, and third reforming reactor arranged sequentially from top to bottom. The first heat exchanger is located on the side of the first reforming reactor away from the second reforming reactor. The biogas is preheated in the first heat exchanger and then passes through the first, second, and third reforming reactors in sequence for reforming. The first, second, and third reforming reactors, as well as the dimethyl ether synthesis tower, are all microchannel reactors. The combustion furnace includes a reactor zone and a flue zone. The first, second, and third reforming reactors are located in the reactor zone. The reactor zone has a first, second, and third heating zone from top to bottom. Gas nozzles are located on both sides of the reactor zone to radiate heat to the first, second, and third reforming reactors. The flue area contains a sixth heat exchanger, a fifth heat exchanger, a third heat exchanger, and a first heat exchanger arranged from top to bottom. The sixth heat exchanger is used to heat the heat transfer oil. The fifth heat exchanger is used to preheat the residual gas output from the decarbonization tower before it is fed into the combustion furnace for combustion. The third heat exchanger is used to preheat the air pressurized by the blower before it is fed into the combustion furnace to mix with the biogas and burn.

2. The method for producing dimethyl ether from skid-mounted self-heating biogas according to claim 1, characterized in that, S1 includes: Biogas is compressed to 0.15 MPa by the first compressor and then fed into the first desulfurization tower to remove sulfur compounds to below 10 ppm. It is then fed into the second desulfurization tower to remove sulfur compounds to below 1 ppm, and then into the ammonia removal tower to remove ammonia to below 1 ppm before being fed into the first storage tank for storage. The combustion furnace is equipped with a third heat exchanger. Air is pressurized to 0.15 MPa by a blower and then fed into the third heat exchanger for preheating before being fed into the combustion furnace to mix with the biogas and burn.

3. The method for preparing dimethyl ether from skid-mounted self-heating biogas according to claim 1, characterized in that, S2 includes: The temperature of the syngas at the outlet of the third reforming reactor is 800-850℃.

4. The method for producing dimethyl ether from skid-mounted self-heating biogas according to claim 1, characterized in that, S3 includes: a portion of the biogas gas in the first storage tank is fed into the combustion furnace after passing through the second heat exchanger; the synthesis gas gas exchanges heat with the biogas used for combustion through the second heat exchanger; then it is fed into the first cooler to reduce the temperature of the synthesis gas to room temperature and then into the first separator; the separated gas is fed into the drying tower for dehydration; then it is fed into the second compressor to be pressurized to 3MPa and stored in the second storage tank.

5. The method for producing dimethyl ether from skid-mounted self-heating biogas according to claim 1, characterized in that, S4 includes: The synthesis gas from the second storage tank is fed into the dimethyl ether synthesis tower after passing through the fourth heat exchanger. The synthesis gas undergoes a synthesis reaction at 200-300°C to generate crude dimethyl ether. The crude dimethyl ether flows through the fourth heat exchanger for heat exchange and is then fed into the second cooler to cool down to 25°C. Subsequently, it is fed into the absorption tower for gas-liquid separation.

6. The method for preparing dimethyl ether from skid-mounted self-heating biogas according to claim 5, characterized in that: The hydrogen-to-carbon ratio of the synthesis gas in the dimethyl ether synthesis tower is 0.8-1.2, and the absorbent in the absorption tower is water or a dimethyl ether solution.

7. The method for preparing dimethyl ether from skid-mounted self-heating biogas according to claim 1, characterized in that, S5 includes: The degassing tower is equipped with a first reboiler at the bottom to heat the degassing tower, and a first condenser at the top of the degassing tower to condense the dimethyl ether gas in the degassing tower; the residual gas output from the decarbonization tower is preheated in the fifth heat exchanger in the combustion furnace and then fed into the combustion furnace for combustion.

8. The method for preparing dimethyl ether from skid-mounted self-heating biogas according to claim 1, characterized in that, S7 includes: The distillation column is equipped with a second reboiler at the bottom to heat the column. The top of the distillation column is equipped with a second condenser and a collector connected to a third storage tank. The dimethyl ether gas is liquefied at the second condenser and transferred to the third storage tank for storage through the collector. The liquid at the bottom of the column flows into a fourth storage tank for storage and can flow out of the fourth storage tank and be fed into the absorption tower to absorb the crude dimethyl ether product.

9. The method for producing dimethyl ether from skid-mounted self-heating biogas according to claim 1, characterized in that: This method includes a water tank for storing condensate. After the condensate flows out of the water tank, it cools the syngas, crude dimethyl ether product, degassing tower and distillation tower respectively. Then it flows into an air cooler to cool the condensate and is circulated back to the water tank.

10. The method for preparing dimethyl ether from skid-mounted self-heating biogas according to claim 9, characterized in that: This method includes a tank for storing heat transfer oil. A sixth heat exchanger is provided at the top of the combustion furnace. The heat transfer oil flows through the sixth heat exchanger to heat the heat transfer oil. The synthesis gas flows through a seventh heat exchanger and exchanges heat with the heat transfer oil in the seventh heat exchanger. The heat transfer oil flows through the dimethyl ether synthesis tower, degassing tower, and distillation tower to heat the dimethyl ether synthesis tower, degassing tower, and distillation tower. The heat transfer oil flows through an eighth heat exchanger and exchanges heat with the condensate to cool the heat transfer oil.

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