Device for preparing absolute ethyl alcohol by using synthesis ammonia liquid nitrogen wash tail gas

Abstract

The utility model belongs to a device for preparing absolute ethyl alcohol by using synthesis ammonia liquid nitrogen wash tail gas. Comprising a liquid nitrogen washing device in the ammonia synthesis system, a gas phase outlet of the liquid nitrogen washing device is connected with a fermentation tank through a pretreatment unit, a liquid phase outlet of the fermentation tank is connected with a membrane separation device, a clear liquid outlet of the membrane separation device is connected with a distillation device, and a product outlet of the distillation device is connected with an absolute ethyl alcohol storage tank through a dehydration tower; the method has the advantages of reducing carbon emission and improving the added value of products.

Description

Technical Field

[0001] The utility model belongs to the technical field of utilization of synthetic ammonia liquid nitrogen washing tail gas, in particular to a device for preparing anhydrous ethanol by utilizing synthetic ammonia liquid nitrogen washing tail gas. Background Art

[0002] In ammonia synthesis systems, the synthetic feed gas undergoes purification through a cryogenic liquid nitrogen process. Components such as carbon monoxide, methane, and hydrogen are adsorbed from the feed gas and then recovered and discharged as liquid nitrogen wash tail gas. Due to environmental protection requirements, liquid nitrogen wash tail gas cannot be discharged directly. Therefore, existing technologies generally use two methods to treat liquid nitrogen wash tail gas: 1. Using the liquid nitrogen wash tail gas as fuel gas, which results in unstable combustion and relatively low thermal efficiency; 2. Sending the liquid nitrogen wash tail gas to a flare for combustion, which wastes liquid nitrogen tail gas resources. Furthermore, both of these treatment methods suffer from high carbon emissions and low value. Utility Model Content

[0003] The utility model provides a device for preparing anhydrous ethanol by washing tail gas with synthetic ammonia and liquid nitrogen, which is used to solve the technical problems raised in the above background technology.

[0004] The technical solution of the utility model is:

[0005] A device for preparing anhydrous ethanol by washing tail gas with synthetic ammonia and liquid nitrogen comprises a liquid nitrogen washing device in a synthetic ammonia system, wherein the gas phase outlet of the liquid nitrogen washing device is connected to a fermentation tank via a pretreatment unit, the liquid phase outlet of the fermentation tank is connected to a membrane separation device, the clear liquid outlet of the membrane separation device is connected to a distillation device, and the product outlet of the distillation device is connected to an anhydrous ethanol storage tank via a dehydration tower.

[0006] The beneficial effects of the utility model are as follows: by utilizing the tail gas produced by the liquid nitrogen washing device for pretreatment, the purpose of making the liquid nitrogen washed tail gas meet the needs of the fermentation tank is achieved; the liquid nitrogen washed tail gas is fermented in the presence of nutrients to produce a fermentation liquid containing ethanol; after treatment by a membrane separation device, a distillation device and a dehydration tower, an ethanol product with a content of more than 99.5% can be obtained; the above method can fix the carbon part in the liquid nitrogen washed tail gas into the product, thereby achieving the characteristics of reducing carbon emissions and increasing the added value of the product.

[0007] Preferably, the pretreatment unit comprises a compressor connected to the gas phase outlet of the liquid nitrogen washing device, the outlet of the compressor is connected to the deoxygenation tower, and the outlet of the deoxygenation tower is connected to the inlet of the fermentation tank.

[0008] Preferably, the concentrated liquid outlet of the membrane separation device is connected to a freeze-drying device, and the outlet of the freeze-drying device is connected to a bacterial protein storage tank.

[0009] Preferably, the wastewater outlet of the distillation device is connected to the washing water inlet of the gas washing tower, the gas inlet of the gas washing tower is connected to the tail gas outlet of the fermentation tank, the gas outlet of the gas washing tower is connected to the inlet of the gas-liquid separator, and the gas phase outlet of the gas-liquid separator is connected to the non-condensable gas treatment part.

[0010] Preferably, the liquid phase outlet of the gas scrubber and the liquid phase outlet of the gas-liquid separator are connected to the liquid phase inlet of the fermenter.

[0011] Preferably, the non-condensable gas processing unit includes a flare device with a first control valve and a fuel gas pipeline network with a second control valve, and the flare device and the fuel gas pipeline network are connected in parallel.

[0012] Preferably, a first three-way valve and a third control valve are provided between the gas phase outlet of the liquid nitrogen washing device and the pretreatment unit, and the third end of the first three-way valve is connected to the non-condensable gas processing part through a fourth valve.

[0013] Preferably, a second tee and a fifth valve are sequentially provided between the wastewater outlet of the distillation device and the washing water inlet of the gas washing tower, and the third end of the second tee is connected to the inlet of the coal mill through a sixth valve.

[0014] Preferably, a third tee is provided between the third end of the second tee and the sixth valve, the third end of the third tee is connected to the sewage treatment device through the seventh valve, the biogas outlet of the sewage treatment device is connected to the PSA purification device through the desulfurization device, and the gas outlet of the PSA purification device is connected to the non-condensable gas treatment part.

[0015] Preferably, the inlet of the sewage treatment device is also connected to the waste liquid outlet of the compressor.

[0016] According to the above scheme, a device for preparing anhydrous ethanol by washing tail gas with synthetic ammonia and liquid nitrogen is prepared. The tail gas produced by the liquid nitrogen washing device is pretreated to achieve the purpose of making the liquid nitrogen washing tail gas meet the needs of the fermentation tank. The liquid nitrogen washing tail gas is fermented in the presence of nutrients to produce a fermentation liquid containing ethanol. After treatment in a membrane separation device, a distillation device and a dehydration tower, an ethanol product with a content of more than 99.5% can be obtained. The above pretreatment includes pressurizing the liquid nitrogen washing tail gas by a compressor and deoxygenating it by a deoxygenation tower. The liquid nitrogen washing tail gas described in the utility model can provide a carbon source for the fermentation tank, thereby allowing bacterial fermentation to produce ethanol fermentation liquid. Furthermore, the concentrated liquid (concentrated bacterial liquid) discharged from the membrane separation device can be freeze-dried to prepare bacterial protein, which can be used as feed in the livestock industry. Compared with traditional treatment methods, the above method can achieve high-value utilization of liquid nitrogen washing tail gas and reduce carbon dioxide emissions compared to direct combustion. It has the advantages of reducing carbon emissions and increasing product added value. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural diagram of the present utility model.

[0018] Numbers in the figure: 1. Liquid nitrogen washing device; 2. Fermentation tank; 3. Membrane separation device; 4. Distillation device; 5. Dehydration tower; 6. Anhydrous ethanol storage tank; 7. Compressor; 8. Deoxygenation tower; 9. Freeze drying device; 10. Microbial protein storage tank; 11. Gas washing tower; 12. Gas-liquid separator; 13. First control valve; 14. Flare device; 15. Second control valve; 16. Fuel gas pipeline network; 17. First three-way valve; 18. Third control valve; 19. Fourth valve; 20. Second three-way valve; 21. Fifth valve; 22. Sixth valve; 23. Coal mill; 24. Third three-way valve; 25. Seventh valve; 26. Sewage treatment device; 27. Desulfurization device; 28. PSA purification device; 29. ​​Liquid phase inlet of fermentation tank. DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is described in detail below with reference to the accompanying drawings. The description in this part is only exemplary and explanatory and should not have any limiting effect on the scope of protection of the present invention.

[0020] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0021] It should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the utility model product is typically placed when in use. These terms are intended solely to facilitate and simplify the description of the utility model and are not intended to indicate or imply that the device or component referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the utility model. Furthermore, the terms "first," "second," and "third," etc., are used solely for distinction and description and should not be construed as indicating or implying relative importance.

[0022] Furthermore, terms such as "horizontal," "vertical," and "overhanging" do not necessarily imply that a component must be absolutely horizontal or overhanging, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but rather that it can be slightly tilted.

[0023] It should also be noted that, in the description of this utility model, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections, electrical connections; direct connections, indirect connections through an intermediate medium, and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this utility model based on the specific circumstances.

[0024] like Figure 1 As shown, the utility model is a device for preparing anhydrous ethanol by washing tail gas with synthetic ammonia and liquid nitrogen, comprising a liquid nitrogen washing device 1 in a synthetic ammonia system, wherein the gas phase outlet of the liquid nitrogen washing device 1 is connected to a fermentation tank 2 through a pretreatment unit, the liquid phase outlet of the fermentation tank 2 is connected to a membrane separation device 3, the clear liquid outlet of the membrane separation device 3 is connected to a distillation device 4, and the product outlet of the distillation device 4 is connected to an anhydrous ethanol storage tank 6 through a dehydration tower 5. The utility model utilizes the characteristic that the liquid nitrogen washing tail gas in the liquid nitrogen washing device 1 contains carbon, pre-treats the liquid nitrogen washing tail gas through the pre-treatment unit, and sends it into the fermentation tank 2. The pre-treated liquid nitrogen washing tail gas provides a carbon source for the bacteria in the fermentation tank 2, so that the bacteria ferment to produce ethanol fermentation liquid. On this basis, the separation treatment of the membrane separation device 3, the distillation treatment of the distillation device 4, and the dehydration treatment of the hydrous ethanol by the dehydration tower 5 are carried out, and finally an ethanol product with a content of more than 99.5% is obtained; the above method can fix carbon in the product and can increase the added value of the product, so as to achieve the characteristics of environmental protection, reduction of carbon emissions and improvement of gas-liquid economic benefits; the main purpose of the pre-treatment unit is to pre-treat the liquid nitrogen washing tail gas so that it meets the requirements of entering the fermentation tank 2. According to the requirements, the pretreatment unit is a conventional pretreatment, and its form may include pressure adjustment, oxygen removal or temperature adjustment, etc.; the liquid nitrogen washing device 1 described in the utility model includes a cold box, a hydrogen separator, a gas-liquid separator, a gas cooler, a gas mixer, a nitrogen washing tower, an adsorber, etc., which are conventionally set and can be directly purchased on the market, so its structure is no longer described; the membrane separation device 3 includes a ceramic membrane, a circulation pump, a cleaning pump, etc., which are conventionally set and can be directly purchased on the market, so its structure is no longer described; the distillation device 4 includes a crude distillation tower, a crude distillation tower reboiler, a crude distillation tower condenser, a distillation tower, a distillation tower reboiler, a distillation tower condenser, a reflux pump, a reflux tank, etc., which are conventionally set and can be directly purchased on the market, so its structure is no longer described.

[0025] Furthermore, the pretreatment unit includes a compressor 7 connected to the gas phase outlet of the liquid nitrogen washing device 1, the outlet of the compressor 7 is connected to the deoxygenation tower 8, and the outlet of the deoxygenation tower 8 is connected to the inlet of the fermentation tank 2. The pretreatment unit described in the present invention includes a compressor 7 for adjusting the pressure of the liquid nitrogen washing tail gas, and a deoxygenation tower 8 for removing oxygen from the tail gas to achieve subsequent fermentation.

[0026] Furthermore, the concentrated liquid outlet of the membrane separation device 3 is connected to the freeze-drying device 9, and the outlet of the freeze-drying device 9 is connected to the bacterial protein storage tank 10. The present invention can produce bacterial protein as a by-product on the basis of producing anhydrous ethanol, and the bacterial protein can be used as feed to achieve the characteristic of improving the economic benefits of gas and liquid. The freeze-drying device 9 described in the present invention includes a drying box, a condenser, a refrigeration unit, etc., which is a conventional configuration and can be directly purchased on the market, so its structure is not described in detail.

[0027] Furthermore, the wastewater outlet of the distillation apparatus 4 is connected to the wash water inlet of the gas scrubber 11, the gas inlet of the gas scrubber 11 is connected to the exhaust gas outlet of the fermenter 2, the gas outlet of the gas scrubber 11 is connected to the inlet of the gas-liquid separator 12, and the gas phase outlet of the gas-liquid separator 12 is connected to the non-condensable gas treatment unit. In the present invention, the wastewater in the distillation apparatus 4 can be used as wash water in the gas scrubber 11 and to scrub the exhaust gas produced by the fermenter 2, thereby realizing the characteristic of waste liquid utilization.

[0028] Furthermore, the liquid phase outlet of the gas scrubber 11 and the liquid phase outlet of the gas-liquid separator 12 are connected to the liquid phase inlet 29 of the fermenter. At the same time, by returning the liquid phase of the gas scrubber 11 and the liquid phase of the gas-liquid separator 12 to the fermenter 4, waste liquid can be recycled and reused, while achieving the characteristic of reducing costs.

[0029] Furthermore, the non-condensable gas processing unit includes a flare device 14 with a first control valve 13 and a fuel gas pipeline network 16 with a second control valve 15. The flare device 14 and the fuel gas pipeline network 16 are connected in parallel. This configuration enables centralized recovery and treatment of waste gas from the entire device, thereby reducing equipment investment costs while meeting environmental requirements. The flare device 14 described in the present invention includes an emergency flare burner, an acid flare burner, an ammonia flare burner, etc., which are conventional and can be purchased directly on the market, so its structure is not further described.

[0030] Furthermore, a first three-way valve 17 and a third control valve 18 are provided between the gas phase outlet of the liquid nitrogen scrubbing device 1 and the pretreatment unit. The third end of the first three-way valve 17 is connected to the non-condensable gas treatment unit via a fourth valve 19. When the synthetic ammonia system is in the initial startup or shutdown phase, the exhaust gas composition of the liquid nitrogen scrubber fluctuates significantly, directly affecting the stable operation of subsequent equipment. Based on this, the present invention, through the above-mentioned arrangement, can achieve emergency treatment of fluctuating exhaust gas while ensuring stable operation of the device.

[0031] Furthermore, a second tee 20 and a fifth valve 21 are sequentially provided between the wastewater outlet of the distillation unit 4 and the wash water inlet of the gas scrubber 11. The third end of the second tee 20 is connected to the inlet of the coal mill 23 via a sixth valve 22. The wastewater from the distillation unit 4 can be used not only in the gas scrubber but also in the coal mill 23. Furthermore, the wastewater from the distillation unit 4 is preferably supplied to the gas scrubber, and if the amount is still too high, it is supplied to the coal mill 23.

[0032] Furthermore, a third tee 24 is provided between the third end of the second tee 20 and the sixth valve 22. The third end of the third tee 24 is connected to the sewage treatment device 26 through the seventh valve 25. The biogas outlet of the sewage treatment device 26 is connected to the PSA purification device 28 through the desulfurization device 27. The gas outlet of the PSA purification device 28 is connected to the non-condensable gas treatment part. When the amount of wastewater from the distillation device 4 supplied to the gas washing tower and the coal mill 23 is still too large, the sewage treatment device 26 can be used for sewage treatment, and the biogas in the sewage treatment device 26 can enter the non-condensable gas treatment part for treatment through the desulfurization device 27 and the PSA purification device 28; the sewage treatment device 26 described in the utility model includes a sedimentation tank, a regulating tank, an anaerobic tank, a biochemical tank, etc., which are conventional settings and can be directly purchased on the market, so its structure is no longer described; the desulfurization device 27 includes a wet desulfurization tower, a rich liquid tank, a lean liquid tank, a regeneration tank, a molten sulfur kettle, a dry desulfurization tower, etc., which are conventional settings and can be directly purchased on the market, so its structure is no longer described; the PSA purification device 28 includes a compressor, an adsorption tower, etc., which are conventional settings and can be directly purchased on the market, so its structure is no longer described.

[0033] Furthermore, the inlet of the sewage treatment device 26 is also connected to the waste liquid outlet of the compressor 7. The sewage treatment device 26 described in the utility model can not only treat the wastewater from the distillation device 4, but also treat the waste liquid produced by the compressor 7, thereby achieving the characteristic of improving equipment utilization.

[0034] As we all know, ethanol has the chemical formula CH3COOH. It is a colorless, transparent liquid with an aromatic odor. Its molecular weight is 46.07 and its density is 0.7893 g / cm 3It has a wide range of solubility and is miscible with water in any ratio. It is also miscible in most organic solvents such as ether, chloroform, glycerol, and methanol. Ethanol is used in edible liquor, fuel, and industrial fields, with the consumption in each field accounting for approximately 28% of liquor, 23% of ethyl acetate, 13.53% of acetaldehyde, ethylamine, and ethyl acrylate combined, and 35% of fuel. Currently, the main ethanol production processes are bio-fermentation and chemical methods. The raw materials for bio-fermentation can be corn, cassava, molasses, straw, and CO2-containing gases, while the chemical method is divided into dimethyl ether carbonylation and acetic acid hydrogenation. The production capacity of corn, cassava, and molasses ethanol is limited by arable land and faces competition with local residents, making it difficult to expand. Raw material prices are also high, and costs are high. Cellulosic ethanol from straw has been slow to develop due to technological immaturity and the high price of cellulase. Dimethyl ether carbonylation and acetic acid hydrogenation require high temperatures and pressures, impose strict safety requirements, and restrict product sales to the fuel sector. This utility model utilizes coal chemical tail gas fermentation to produce ethanol and protein byproducts, achieving carbon sequestration and high-value utilization of tail gas. Specifically, this utility model utilizes tail gas from a liquid nitrogen scrubbing unit in a coal chemical system to produce ethanol and protein byproducts. The tail gas is pressurized by a compressor and then passed into a deoxygenation tower to remove oxygen. The tail gas then enters a fermentation tank where bacterial cells ferment in the presence of a nutrient medium to produce an ethanol-containing fermentation broth. The fermentation broth undergoes membrane separation, distillation, and dehydration to produce 99.5% anhydrous ethanol. The concentrated bacterial broth after membrane separation is freeze-dried to produce protein with a moisture content of less than 10%. This approach conserves resources, reduces carbon emissions, and improves the company's economic benefits.

[0035] The working principle of the utility model is as follows: the liquid nitrogen washing tail gas in the liquid nitrogen washing device 1 enters the compressor 7 for pressure increase, and then enters the deoxidation tower 8 to remove oxygen, so that the oxygen content in the liquid nitrogen washing tail gas is reduced to the ppm level, and then enters the fermentation tank 2. The liquid nitrogen washing tail gas provides a carbon source for the bacteria in the fermentation tank 2. The operating temperature of the fermentation tank 2 is 32-38°C and the pressure is 0.4-0.6MPa; the ethanol-containing fermentation liquid obtained after the fermentation reaction in the fermentation tank 2 enters the membrane separation device 3 for membrane separation treatment, and the clear liquid separated by the membrane enters the distillation device 4 for distillation, and the distillation extracts 95% pure water-containing ethanol is obtained; 95% of the water-containing ethanol is dehydrated through the dehydration tower 5 to obtain 99.5% anhydrous ethanol, which is then sent to the anhydrous ethanol storage tank 6 for temporary storage and sale; the concentrated liquid separated by the membrane separation device 3 enters the freeze-drying device 9 for freeze-drying (the drying temperature of the freeze-drying device 9 is -30°C to -50°C, and the pressure is 0.1Pa to 10Pa) to produce bacterial protein; the bacterial protein enters the bacterial protein storage tank 10 for temporary storage and sale; the wastewater in the distillation device 4 is preferentially sent to the gas washing tower 11 to wash the tail gas from the fermentation tank 2, and the washing The gas after washing enters the gas-liquid separator 12 for gas-liquid separation; the washing water after washing in the gas washing tower 11 and the liquid phase after gas-liquid separation in the gas-liquid separator 12 are jointly fed into the fermentation tank 4 for reuse; the waste water in the distillation device 4 can also be sent to the coal mill in the coal grinding section for preparation of water-coal slurry; when the amount of waste water in the distillation device 4 is too large, it can enter the sewage treatment device 26 for treatment and then be discharged, the biogas in the sewage treatment device 26 enters the desulfurization device 27 for desulfurization, and after desulfurization, enters the PSA purification device 28 for treatment; the gas phase and The gas phase from the gas-liquid separator 12 can be processed in the non-condensable gas treatment unit. Furthermore, when the ammonia synthesis system is in its initial startup phase or the fermenter 2 is shut down due to reasons such as strain replacement, the liquid nitrogen wash tail gas from the liquid nitrogen wash unit 1 can also be processed in the non-condensable gas treatment unit. The non-condensable gas treatment unit comprises a flare device 14 and a fuel gas pipeline 16 arranged in parallel. The gas phase can be selectively directed to the flare device 14 or the fuel gas pipeline 16 depending on actual operating conditions. Furthermore, the wastewater discharged from the compressor 2 in the present invention can also be treated by the aforementioned wastewater treatment unit 26. The essence of the present invention is to synthesize ethanol using a biological method. During the synthesis process, the reaction conditions are normal temperature and pressure, and separation and distillation do not involve high temperature and high pressure, making the production process safe and reliable. Furthermore, the present invention can effectively utilize the liquid nitrogen wash tail gas, reducing the company's carbon dioxide emissions compared to traditional technologies while increasing the added value of the product. Furthermore, the by-product protein in the present invention is a high-value product, and the wastewater and exhaust gas generated during the process can be returned to the system for reuse, achieving full resource utilization and environmental protection.

[0036] The standard parts used in this application document can all be purchased from the market and can be customized according to the description in the specification and drawings. The specific connection methods of each part adopt conventional means such as mature bolts, rivets, welding, etc. in the existing technology. The machinery, parts and equipment all adopt conventional models in the existing technology. The control method is automatic control through a controller. The control circuit of the controller can be implemented by simple programming by technicians in this field, which is common knowledge in this field. In addition, the utility model is mainly used to protect mechanical devices, so the utility model no longer explains the control method and circuit connection in detail. The peripheral controller mentioned in the specification can play a control role for the electrical components mentioned in this article, and the peripheral controller is a conventional known device.

[0037] It should be noted that, in this article, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements that are inherent to such process, method, article or apparatus.

[0038] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. The above are only preferred implementation methods of the present invention. It should be pointed out that due to the limitations of textual expression, there are objectively infinite specific structures. For ordinary technicians in this technical field, without departing from the principles of the present invention, they can make several improvements, modifications or changes, and can also combine the above technical features in an appropriate manner; these improvements, changes or combinations, or the direct application of the concept and technical solution of the utility model to other occasions without improvement, should be regarded as the scope of protection of the present utility model.

Claims

1. A device for preparing anhydrous ethanol by washing tail gas with synthetic ammonia and liquid nitrogen, comprising a liquid nitrogen washing device (1) in a synthetic ammonia system, characterized in that: The gas phase outlet of the liquid nitrogen washing device (1) is connected to the fermentation tank (2) through a pretreatment unit, the liquid phase outlet of the fermentation tank (2) is connected to the membrane separation device (3), the clear liquid outlet of the membrane separation device (3) is connected to the distillation device (4), and the product outlet of the distillation device (4) is connected to the anhydrous ethanol storage tank (6) through a dehydration tower (5).

2. The device for preparing anhydrous ethanol by washing tail gas with synthetic ammonia and liquid nitrogen according to claim 1, characterized in that: The pretreatment unit comprises a compressor (7) connected to the gas phase outlet of the liquid nitrogen washing device (1), the outlet of the compressor (7) is connected to a deoxidation tower (8), and the outlet of the deoxidation tower (8) is connected to the inlet of the fermentation tank (2).

3. The device for preparing anhydrous ethanol by washing tail gas with synthetic ammonia and liquid nitrogen according to claim 1, characterized in that: The concentrated liquid outlet of the membrane separation device (3) is connected to the freeze drying device (9), and the outlet of the freeze drying device (9) is connected to the bacterial protein storage tank (10).

4. The device for preparing anhydrous ethanol by washing tail gas with synthetic ammonia and liquid nitrogen according to claim 1, characterized in that: The wastewater outlet of the distillation device (4) is connected to the washing water inlet of the gas washing tower (11), the gas inlet of the gas washing tower (11) is connected to the tail gas outlet of the fermentation tank (2), the gas outlet of the gas washing tower (11) is connected to the inlet of the gas-liquid separator (12), and the gas phase outlet of the gas-liquid separator (12) is connected to the non-condensable gas treatment part.

5. The device for preparing anhydrous ethanol by washing tail gas with synthetic ammonia and liquid nitrogen according to claim 4, characterized in that: The liquid phase outlet of the gas washing tower (11) and the liquid phase outlet of the gas-liquid separator (12) are connected to the liquid phase inlet (29) of the fermentation tank.

6. The device for preparing anhydrous ethanol by washing tail gas with synthetic ammonia and liquid nitrogen according to claim 4, characterized in that: The non-condensable gas processing unit comprises a flare device (14) with a first control valve (13) and a fuel gas pipe network (16) with a second control valve (15). The flare device (14) and the fuel gas pipe network (16) are connected in parallel.

7. The device for preparing anhydrous ethanol by washing tail gas with synthetic ammonia and liquid nitrogen according to claim 6, characterized in that: A first three-way valve (17) and a third control valve (18) are provided between the gas phase outlet of the liquid nitrogen washing device (1) and the pretreatment unit, and the third end of the first three-way valve (17) is connected to the non-condensable gas treatment part through a fourth valve (19).

8. The device for preparing anhydrous ethanol by washing tail gas with synthetic ammonia and liquid nitrogen according to claim 4, characterized in that: A second tee (20) and a fifth valve (21) are sequentially provided between the wastewater outlet of the distillation device (4) and the washing water inlet of the gas washing tower (11), and the third end of the second tee (20) is connected to the inlet of the coal mill (23) through a sixth valve (22).

9. The device for preparing anhydrous ethanol by washing tail gas with synthetic ammonia and liquid nitrogen according to claim 8, characterized in that: A third tee (24) is provided between the third end of the second tee (20) and the sixth valve (22); the third end of the third tee (24) is connected to a sewage treatment device (26) via a seventh valve (25); the biogas outlet of the sewage treatment device (26) is connected to a PSA purification device (28) via a desulfurization device (27); and the gas outlet of the PSA purification device (28) is connected to a non-condensable gas treatment unit.

10. The device for preparing anhydrous ethanol by washing tail gas with synthetic ammonia and liquid nitrogen according to claim 9, characterized in that: The inlet of the sewage treatment device (26) is also connected to the waste liquid outlet of the compressor (7).

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