System for preparing acrylic acid by utilizing carbon dioxide through electro-biological coupling

Abstract

A system for preparing acrylic acid by utilizing carbon dioxide through electro-biological coupling is characterized by comprising an electro-catalysis methanol production unit, a biological fermentation 3-hydracrylic acid production unit, a 3-hydracrylic acid purification unit and an acrylic acid production unit which are connected in sequence, the electro-catalysis methanol production unit is used for carrying out electro-catalysis on hydrogen produced by water through solar electrolysis and carbon dioxide directly captured by air under the action of a ZnO-ZrO2 catalyst to obtain methanol; the unit for producing the 3-hydracrylic acid through biological fermentation takes the methanol obtained by the electrocatalysis unit as a substrate to carry out biological fermentation, and a fermentation product is subjected to gas-liquid separation to obtain fermentation liquor containing the 3-hydracrylic acid; the 3-hydracrylic acid purification unit is used for carrying out solid-liquid separation on the obtained fermentation liquor of the 3-hydracrylic acid and extracting to obtain the 3-hydracrylic acid; the acrylic acid production unit is used for carrying out dehydration reaction on the purified 3-hydracrylic acid to obtain acrylic acid; carbon dioxide is fixed through an electrocatalysis and biological fermentation coupling technology, and the problem that existing fossil-based raw materials are high in dependency degree is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of electrocatalysis and bio-fermentation conversion, and in particular relates to a system for preparing acrylic acid by utilizing carbon dioxide through electro-biological coupling. Background Art

[0002] The global annual demand for acrylic acid is about 6.2 million tons, and the annual growth rate is expected to be about 3.7% from 2020 to 2025. High-purity acrylic acid is mainly used to produce polymers with strong water absorption performance, anionic polyelectrolytes and detergent additives, and can be used in disposable diapers, feminine hygiene products, water treatment and other fields. Acrylic acid is also used to produce acrylates, mainly used to produce polymers, used as coatings (decoration, masonry and industrial coatings), adhesives and binders (for paper, leather and textiles). Although acrylic acid can currently be manufactured using propylene (derived from crude oil) as raw material, the market price fluctuates with the fluctuation of propylene prices, and it is highly dependent on fossil-based raw materials. The realization of low-cost, green, low-carbon and sustainable acrylic acid production faces huge challenges. Therefore, it is of great practical significance to explore practical and efficient acrylic acid manufacturing processes.

[0003] Existing acrylic acid relies on the oxidation production of propylene from fossil-based raw materials. For example, Chinese patent application CN109876543A discloses an improved oxidation catalyst for acrylic acid production and its application method. The patent application proposes a cobalt-manganese-molybdenum composite catalyst, which can improve the oxidation selectivity of propylene under lower temperature and pressure conditions by optimizing the composition ratio and preparation process of the catalyst, thereby increasing the yield of acrylic acid. Although the patent application has improved the yield of acrylic acid to a certain extent by improving the catalyst, its raw materials are still based on traditional fossils, and the stability, recycling and reaction conditions of the catalyst are still complicated. These problems have limited the wide application and economic benefits of this method to a certain extent.

[0004] Carbon dioxide is the main source of greenhouse gases, and its emissions have a significant impact on climate change. By converting it into useful high-value-added products, it can not only reduce the carbon dioxide content in the atmosphere and effectively alleviate the problem of global warming, but also serve as a cheap and renewable resource to replace traditional fossil fuel raw materials and improve the sustainable utilization efficiency of resources. Therefore, how to utilize carbon dioxide as a resource is a necessary path to achieve coordinated development of the economy and the environment, and how to develop a system for preparing acrylic acid using carbon dioxide coupling is particularly important. Summary of the invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a system for preparing acrylic acid by utilizing carbon dioxide through electro-biocoupling. Based on the coupling of carbon dioxide electrocatalysis and methanol biofermentation, a new coupled system for preparing acrylic acid is developed to solve the problem of high dependence on fossil-based raw materials in the existing acrylic acid preparation method.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A system for preparing acrylic acid by using carbon dioxide through electro-biological coupling, comprising an electrocatalytic methanol production unit, a biological fermentation 3-hydroxypropionic acid production unit, a 3-hydroxypropionic acid purification unit and an acrylic acid production unit connected in sequence;

[0008] The electrocatalytic methanol production unit is used to electrocatalyze hydrogen produced by solar electrolysis of water and carbon dioxide captured directly from air under the action of a ZnO-ZrO2 catalyst to produce methanol;

[0009] The biological fermentation unit for producing 3-hydroxypropionic acid is used to carry out biological fermentation using the methanol obtained by the electrocatalytic unit as a substrate, and to separate the fermentation product into gas and liquid to obtain a fermentation liquid containing 3-hydroxypropionic acid;

[0010] The 3-hydroxypropionic acid purification unit is used to perform solid-liquid separation on the obtained 3-hydroxypropionic acid fermentation broth to obtain 3-hydroxypropionic acid after extraction;

[0011] The acrylic acid production unit is used to obtain acrylic acid by dehydrating the purified 3-hydroxypropionic acid.

[0012] The electrocatalytic methanol production unit specifically includes a first compressor 1, a first mixer 4, a second compressor 5, a first heat exchanger 6 and a methanol synthesis reactor 7, the gas phase inlet and outlet of which are connected in sequence; the liquid phase outlet of the methanol synthesis reactor 7 is connected to the liquid phase inlet of the second pump 8 of the biological fermentation 3-hydroxypropionic acid production unit; the gas phase inlet of the first mixer 4 is connected to the outlet of the electrolytic reaction tank 3, and the liquid phase inlet of the electrolytic reaction tank 3 is connected to the liquid phase outlet of the first pump 2.

[0013] The biological fermentation unit for producing 3-hydroxypropionic acid specifically includes a second pump 8, a second heat exchanger 9, a fermentation tank 10 and a first flash tank 13, which connect the liquid phase inlet and outlet in sequence. The liquid phase end of the fermentation tank 10 is connected to the liquid phase port of the first storage tank 11 through a third pump 12. Pichia yeast is inoculated in the fermentation tank 10. The first storage tank 11 is used to provide the fermentation tank 10 with buffer and nutrients required for the biological reaction. The liquid phase port of the first flash tank 13 is connected to the inlet of the second storage tank 14 of the 3-hydroxypropionic acid purification unit.

[0014] The 3-hydroxypropionic acid purification unit specifically includes a second storage tank 14, a fourth pump 15, a dissolved air flotation reactor 16, an extractive distillation tower 20, a separator 21, a first vacuum distillation tower 22, a fifth pump 23 and a fourth heat exchanger 24, the gas phase port of the dissolved air flotation reactor 16 is connected to a gas storage device 19, a third heat exchanger 18 and a third compressor 17 in sequence, and the liquid phase port of the fourth heat exchanger 24 is connected to the liquid phase port of the dehydration reactor 25 of the acrylic acid production unit.

[0015] The acrylic acid production unit includes a dehydration reactor 25, a second vacuum distillation tower 26 and a third vacuum distillation tower 27, to which a liquid phase inlet and outlet are sequentially connected.

[0016] The present invention also includes a cogeneration unit, which is respectively connected to the biological fermentation 3-hydroxypropionic acid production unit, the 3-hydroxypropionic acid purification unit and the acrylic acid production unit, and is used to convert waste into electrical energy, thermal energy and nitrogen-containing sludge.

[0017] The cogeneration unit includes a second mixer 28, an anaerobic fermentation tank 29, a second flash tank 30, a third mixer 31, a combustion chamber 32, a gas turbine 34, and a fifth heat exchanger 35, which sequentially connect the liquid inlet and outlet. The gas phase end of the combustion chamber 32 is connected to the gas phase port of the fourth compressor 33; the liquid phase port of the second flash tank 30 is connected to the liquid phase end of the centrifuge 36, and the liquid phase port of the second mixer 28 of the cogeneration unit is respectively connected to the solid phase port of the dissolved air flotation reactor 16 of the 3-hydroxypropionic acid purification unit, the liquid phase port of the separator 21 of the 3-hydroxypropionic acid purification unit and the top of the third vacuum distillation tower 27 of the acrylic acid production unit.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The connection between water electrolysis and methanol synthesis in the electrocatalytic methanol production unit designed by the present invention realizes the electrocatalysis of hydrogen produced by solar electrolysis of water and carbon dioxide captured directly from air under the action of ZnO-ZrO2 catalyst to produce methanol;

[0020] (2) The present invention couples the electrocatalytic methanol production unit with the biological fermentation unit for producing 3-hydroxypropionic acid, the 3-hydroxypropionic acid purification unit, and the acrylic acid production unit, so as to realize the use of carbon dioxide as raw material, methanol as intermediate, biological fermentation and product purification to obtain 3-hydroxypropionic acid, and then 3-hydroxypropionic acid as raw material to obtain acrylic acid through dehydration, thereby resource-utilizing carbon dioxide for biological transformation to obtain acrylic acid. In this system, since the coupling design of the electrocatalytic methanol production unit and the biological fermentation unit for producing 3-hydroxypropionic acid can realize the preparation of acrylic acid using carbon dioxide as raw material, such a design can achieve the beneficial effect of reducing greenhouse gas emissions while resource-utilizing carbon sources, thereby realizing the successful preparation of high-value-added acrylic acid from carbon resources, and can replace the existing method for preparing acrylic acid from fossil-based raw materials; secondly, the method for preparing acrylic acid by coupling electrocatalysis and biological fermentation combines the existing technologies, and realizes the successful preparation of acrylic acid by connecting technologies in different fields in series. Therefore, the system can solve the problem of high dependence on fossil-based raw materials in the existing method for preparing acrylic acid.

[0021] (3) The present invention can also be expanded to include a cogeneration unit, which can ferment the wastewater generated by the whole process with the solid biomass byproduct generated by the oil extraction unit to produce biogas, burn the biogas and unreacted waste gas and use them to generate electricity, and the generated electricity and heat energy can be used to supply electricity and heat for the system of the present invention, thereby achieving efficient energy recovery and utilization. The wastewater generated by the whole process and the solid biomass byproduct generated by the oil extraction unit are fermented to produce nitrogen-containing sludge, which is dehydrated and sold as a nitrogen fertilizer byproduct, thereby improving the economic efficiency of the process.

[0022] In summary, the present invention couples the electrocatalytic methanol production unit, the biological fermentation 3-hydroxypropionic acid production unit, the 3-hydroxypropionic acid purification unit and the acrylic acid production unit; and develops a coupled system for preparing acrylic acid to solve the problem of high dependence on fossil-based raw materials in the existing acrylic acid preparation method. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention discloses a process flow of a system and method for preparing acrylic acid by utilizing carbon dioxide through an electrocatalytic and biological fermentation coupling system.

[0024] Figure 2 The present invention utilizes carbon dioxide to couple the electrocatalysis and biological fermentation system structure diagram.

[0025] In the figure: 1-first compressor; 2-first pump; 3-electrolysis reaction tank; 4-first mixer; 5-second compressor; 6-first heat exchanger; 7-methanol synthesis reactor; 8-second pump; 9-second heat exchanger; 10-fermentation tank; 11-first storage tank; 12-third pump; 13-first flash tank; 14-second storage tank; 15-fourth pump; 16-dissolved air flotation reactor; 17-third compressor; 18-third heat exchanger; 19- Gas storage tank; 20-extraction distillation tower; 21-separator; 22-first vacuum distillation tower; 23-fifth pump; 24-fourth heat exchanger; 25-dehydration reactor; 26-second vacuum distillation tower; 27-third vacuum distillation tower; 28-second mixer; 29-anaerobic fermentation tank; 30-second flash tank; 31-third mixer; 32-combustion chamber; 33-fourth compressor; 34-gas turbine; 35-fifth heat exchanger; 36-centrifuge. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0027] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0028] See also Figure 1 , a system for preparing acrylic acid by using carbon dioxide through electro-biological coupling, comprising an electrocatalytic methanol production unit, a biological fermentation 3-hydroxypropionic acid production unit, a 3-hydroxypropionic acid purification unit and an acrylic acid production unit connected in sequence;

[0029] The electrocatalytic methanol production unit is used to electrocatalyze hydrogen produced by solar electrolysis of water and carbon dioxide captured directly from air under the action of a ZnO-ZrO2 catalyst to produce methanol;

[0030] The biological fermentation unit for producing 3-hydroxypropionic acid is used to carry out biological fermentation using the methanol obtained by the electrocatalytic unit as a substrate, and to separate the fermentation product into gas and liquid to obtain a fermentation liquid containing 3-hydroxypropionic acid;

[0031] The 3-hydroxypropionic acid purification unit is used to perform solid-liquid separation on the obtained 3-hydroxypropionic acid fermentation broth to obtain 3-hydroxypropionic acid after extraction;

[0032] The acrylic acid production unit is used to obtain acrylic acid by dehydrating the purified 3-hydroxypropionic acid.

[0033] See also Figure 2 The electrocatalytic methanol production unit comprises a first compressor 1, a first mixer 4, a second compressor 5, a first heat exchanger 6 and a methanol synthesis reactor 7, the gas phase inlet and outlet of which are connected in sequence; the liquid phase outlet of the methanol synthesis reactor 7 is connected to the liquid phase inlet of the second pump 8 of the biological fermentation 3-hydroxypropionic acid production unit; the gas phase inlet of the first mixer 4 is connected to the outlet of the electrolytic reaction tank 3, and the liquid phase inlet of the electrolytic reaction tank 3 is connected to the liquid phase outlet of the first pump 2; the first pump 2 receives water and pressurizes it, the electrolytic reaction tank 3 is used to electrolyze water into hydrogen and oxygen under the action of solar energy, and the first compressor 1 is used to receive carbon dioxide and pressurize it The discharge port of the first compressor 1 and the discharge port of the electrolytic reaction tank 3 are both connected to the feed port of the first mixer 4; the first mixer 4 is used to completely mix the carbon dioxide, hydrogen and oxygen, the mixed gas outlet of the first mixer 4 is connected to the inlet of the second compressor 5, and the second compressor 5 is used to compress the mixed gas of carbon dioxide, hydrogen and oxygen; the outlet of the second compressor 5 is connected to the first heat exchanger 6, and enters the methanol synthesis reactor 7 after heat exchange, and the methanol synthesis reactor 7 is used to react carbon dioxide and hydrogen to produce methanol, and the produced methanol enters the biological fermentation unit for producing 3-hydroxypropionic acid as the raw material of the next unit.

[0034] See also Figure 2The biological fermentation unit for producing 3-hydroxypropionic acid comprises a second pump 8, a second heat exchanger 9, a fermentation tank 10, a first storage tank 11, a third pump 12, and a first flash tank 13. The outlet of the methanol synthesis reactor 7 is connected to the inlet of the second pump 8, which is used to pressurize the methanol of the electrocatalytic methanol production unit and transport it to the second heat exchanger 9. After heat exchange in the second heat exchanger 9, the methanol enters the fermentation tank 10 for biological fermentation; the first storage tank 11 is used to receive buffer and nutrients for biological reaction; the buffer includes but is not limited to pH buffer, and the nutrients include but are not limited to nitrogen source and trace elements; the outlet of the first storage tank 11 is connected to the inlet of the third pump 12, and the outlet of the third pump 12 is connected to the inlet of the fermentation tank 10. The third pump 12 is used to pump the buffer and nutrients. The fermentation tank 10 is pressurized and sent to the fermentation tank 10; the fermentation tank 10 is inoculated with Pichia yeast, and the fermentation tank 10 is used to allow methanol, oxygen, buffer and nutrients to undergo biological fermentation under the action of Pichia yeast to obtain a fermentation liquid, wherein the fermentation liquid is methanol and oxygen converted into 3-hydroxypropionic acid and biomass; the outlet of the fermentation tank 10 is connected to the inlet of the first flash tank 13, and the first flash tank 13 is used to separate the remaining gas and fermentation liquid after the biological fermentation; the first flash tank 13 body is provided with a fermentation liquid outlet and a waste gas outlet, and the waste gas outlet of the first flash tank 13 is connected to the inlet of the third mixer 31 for mixing waste.

[0035] See also Figure 2 The 3-hydroxypropionic acid purification unit specifically includes a second storage tank 14, a fourth pump 15, a dissolved air flotation reactor 16, an extractive distillation tower 20, a separator 21, a first vacuum distillation tower 22, a fifth pump 23 and a fourth heat exchanger 24, the gas phase port of the dissolved air flotation reactor 16 is connected to the gas storage device 19, the third heat exchanger 18 and the third compressor 17 in sequence, and the liquid phase port of the fourth heat exchanger 24 is connected to the liquid phase port of the dehydration reactor 25 of the acrylic acid production unit.

[0036] The second storage tank 14 is used to receive the fermentation liquid from the biological fermentation unit for producing 3-hydroxypropionic acid, the fourth pump 15 is used to pressurize the fermentation liquid, and the dissolved air flotation reactor 16 is used to perform solid-liquid separation between the fermentation liquid and the biomass; the dissolved air flotation reactor 16 is provided with a fermentation liquid outlet and a waste residue outlet, and the waste residue outlet of the dissolved air flotation reactor 16 is connected to the inlet of the second mixer 28 for mixing waste. The third compressor 17 is used to receive and compress air, and the outlet of the third compressor 17 is connected to the air storage 19, which is used to store compressed air, and the outlet of the air storage 19 is connected to the inlet of the dissolved air flotation reactor 16 for dissolving air. The outlet of the dissolved air flotation reactor 16 is connected to the inlet of the extractive distillation tower 20, which is used to add an extractant to extract 3-hydroxypropionic acid from the fermentation liquid to obtain a mixed solution; the outlet of the extractive distillation tower 20 is connected to the inlet of the separator 21, which is used for waste liquid and a mixed liquid containing 3-hydroxypropionic acid; the separator 21 body is provided with a mixed liquid outlet containing 3-hydroxypropionic acid and a waste liquid outlet, and the waste liquid outlet of the separator 21 is connected to the inlet of the second mixer 28 for mixing The mixed liquid outlet containing 3-hydroxypropionic acid of the separator 21 is connected to the first vacuum distillation tower 22. The first vacuum distillation tower 22 is used to separate the extractant and the 3-hydroxypropionic acid obtained by extraction. After the extractant flows out from the top of the first vacuum distillation tower 22, it enters the extractive distillation tower 21 for reuse. The 3-hydroxypropionic acid at the bottom outlet of the vacuum distillation tower 22 is connected to the fifth pump 23. The 3-hydroxypropionic acid after pressurization is connected to the fourth heat exchanger 24 through the outlet of the fifth pump 23 for heat exchange.

[0037] See also Figure 2 The acrylic acid production unit includes a dehydration reactor 25, a second vacuum distillation tower 26 and a third vacuum distillation tower 27, the outlet of the fourth heat exchanger 24 is connected to the inlet of the dehydration reactor 25, and the dehydration reactor 25 is used to dehydrate the high-purity 3-hydroxypropionic acid obtained by the 3-hydroxypropionic acid purification unit to produce acrylic acid; the outlet of the dehydration reactor 25 is connected to the second vacuum distillation tower 26, and the second vacuum distillation tower 26 is used to separate the incompletely dehydrated 3-hydroxypropionic acid and acrylic acid, 3-hydroxypropionic acid flows out from the bottom of the second vacuum distillation tower 26 and refluxes to the dehydration reactor 25, and acrylic acid flows from the top of the second vacuum distillation tower 26 to the third vacuum distillation tower 27; the third vacuum distillation tower 27 separates acrylic acid and waste liquid, and high-purity acrylic acid flows out from the bottom of the tower as a product, and the top effluent of the third vacuum distillation tower 27 is connected to the second mixer 28.

[0038] See also Figure 2 The present invention also includes a cogeneration unit, which is respectively connected to the biological fermentation 3-hydroxypropionic acid production unit, the 3-hydroxypropionic acid purification unit and the acrylic acid production unit, and is used to convert waste into electrical energy, thermal energy and nitrogen-containing sludge.

[0039] The cogeneration unit includes a second mixer 28, an anaerobic fermentation tank 29, a second flash tank 30, a third mixer 31, a combustion chamber 32, a gas turbine 34, and a fifth heat exchanger 35, which sequentially connect the liquid inlet and outlet. The gas phase end of the combustion chamber 32 is connected to the gas phase port of the fourth compressor 33; the liquid phase port of the second flash tank 30 is connected to the liquid phase end of the centrifuge 36, and the liquid phase port of the second mixer 28 of the cogeneration unit is respectively connected to the solid phase port of the dissolved air flotation reactor 16 of the 3-hydroxypropionic acid purification unit, the liquid phase port of the separator 21 of the 3-hydroxypropionic acid purification unit and the top of the third vacuum distillation tower 27 of the acrylic acid production unit. The waste gas, waste liquid and waste residue generated in the whole process enter the anaerobic fermentation tank 29 through the second mixer 28, and the waste gas and nitrogen-containing sludge are generated by fermentation in the anaerobic fermentation tank 29. The outlet of the anaerobic fermentation tank 29 is connected to the liquid inlet of the second flash tank 30. The second flash tank 30 body is provided with a waste gas outlet and a nitrogen-containing sludge outlet. The waste gas outlet is connected to the inlet of the third mixer 31, and the outlet of the third mixer 31 is connected to the inlet of the combustion chamber 32, and is mixed with the compressed air from the fourth compressor 33 for combustion. The outlet of the combustion chamber 32 is connected to the inlet of the gas turbine 34, and the outlet of the gas turbine 34 is connected to the inlet of the fifth heat exchanger 35, and the process tail gas is output through the fifth heat exchanger 35. The outlet of the nitrogen-containing sludge of the second flash tank 30 is connected to the inlet of the centrifuge 36, and after centrifugation in the centrifuge 36, the process byproduct nitrogen fertilizer is output.

[0040] In the entire system, the arrangement of the first compressor 1, the first pump 2, the second compressor 5, the second pump 8, the third pump 12, the fourth pump 15, the third compressor 17, the fifth pump 23, and the fourth compressor 33 can provide power for the system operation by pressurizing the gas or liquid.

[0041] The working principle of the present invention specifically includes:

[0042] (1) Electrocatalytic methanol production unit: The first pump 2 receives water and pressurizes it to 3 bar. The pressurized water is electrolyzed by solar energy in the electrolysis reaction tank 3 to produce hydrogen and oxygen. The electrolysis efficiency is about 90%. The first compressor 1 is used to receive carbon dioxide and pressurize it to 3 bar. The ratio of carbon dioxide and hydrogen introduced into the production system is maintained at 1:3. Carbon dioxide, hydrogen and oxygen are completely mixed in the first mixer 4, and then the mixed gas is pressurized to 10 bar in the second compressor 5, and then the temperature is controlled at 315°C by the first heat exchanger 6. Methanol synthesis is then carried out in the methanol synthesis reactor 7 under the pressure conditions of 10 bar and 315°C, and the methanol conversion efficiency is about 10%.

[0043] (2) Bio-fermentation unit for producing 3-hydroxypropionic acid: Sodium hydroxide solution is used as a buffer to adjust the pH value in the fermentation tank so that the fermentation conditions are maintained at a weakly acidic pH value of about 6.0 to 6.5. Ammonia is used as a nutrient for the bio-fermentation. After the sodium hydroxide solution and ammonia are mixed in the first storage tank 11, they are pressurized to 3 bar by the third pump 12 and then enter the fermentation tank 10. Methanol and oxygen from the electrocatalytic methanol production unit enter the fermentation tank 10. Methanol, oxygen, sodium hydroxide solution and ammonia are fermented at 30°C and 1 bar with the participation of Pichia pastoris to convert methanol into 3-hydroxypropionic acid and biomass to obtain fermentation liquid. The fermentation liquid and the remaining waste gas in the fermentation tank 10 are separated in the first flash tank 13, and the separated fermentation liquid is received by the second storage tank 14. The remaining waste gas is connected to the inlet of the third mixer 31.

[0044] (3) 3-Hydroxypropionic acid purification unit: The fermentation liquid from the first flash tank 13 enters the second storage tank 14, is pressurized to 3 bar by the fourth pump 15, and then enters the dissolved air flotation reactor 16. After the air is pressurized to 3 bar by the third compressor 17, it enters the dissolved air flotation reactor 16 through the air storage tank 19. At the same time, 100 mg / L flocculant is added to the dissolved air flotation reactor 16 to assist in removing the waste residue. In the dissolved air flotation reactor 16, air is introduced into the fermentation liquid to generate tiny bubbles, thereby separating the fermentation liquid from the waste residue. Under the action of the flocculant, the removal efficiency of the waste residue in the fermentation liquid can reach more than 95%. 3-Hexanol is added as an extractant, and the 3-hydroxypropionic acid in the fermentation liquid is extracted by the extractive distillation tower 20 to obtain a mixed solution with an extraction efficiency of about 90%. It is then distilled in the first vacuum distillation tower 22, and high-purity 3-hydroxypropionic acid flows out of the bottom outlet of the first vacuum distillation tower 22. The high-purity 3-hydroxypropionic acid is pressurized to 3 bar by the fifth pump 23 and heated to 230° C. by the fourth heat exchanger 24 .

[0045] The waste liquid separated by the separator 21 enters the second mixer 28 for subsequent treatment.

[0046] During the distillation process, 1-hexanol flows out from the top of the first vacuum distillation tower 22 and enters the extractive distillation tower 21 for reuse.

[0047] (4) Acrylic acid production unit: High-purity 3-hydroxypropionic acid is dehydrated in a dehydration reactor 25 at 230°C and 1 bar to produce crude acrylic acid with a conversion rate of about 80%. The second vacuum distillation tower 26 separates the incompletely dehydrated 3-hydroxypropionic acid and acrylic acid. The 3-hydroxypropionic acid flows out of the bottom of the second vacuum distillation tower 26 and flows back to the dehydration reactor 25 for reuse. The crude acrylic acid is separated in the third vacuum distillation tower 27, and the purity of the product acrylic acid can reach 99.7wt%.

[0048] (5) Cogeneration unit: The waste gas, waste liquid and waste residue generated in the whole process enter the anaerobic fermentation tank 29 through the second mixer 28, and produce waste gas and nitrogen-containing sludge through anaerobic fermentation at 35°C and 1 bar. Afterwards, the waste gas and nitrogen-containing sludge are separated in the second flash tank 30.

[0049] The waste gas separated in the second flash tank 30 is mixed with the waste gas separated in the first flash tank 13 in the third mixer 31 and then enters the combustion chamber 32. At the same time, the air from the fourth compressor 33 is compressed to 3 bar and then enters the combustion chamber 32. Waste gases such as methane and hydrogen burn with oxygen in the combustion chamber 32 at 1600°C. The combustion process generates a large amount of high-temperature waste heat, which is used to generate electricity through the gas turbine 34. At the same time, high-temperature waste heat is obtained and used to heat the electrocatalytic methanol production unit, the biological fermentation 3-hydroxypropionic acid production unit, the 3-hydroxypropionic acid purification unit, and the acrylic acid production unit through heat exchange equipment. The high-temperature gas generated by the gas turbine 34 for power generation is cooled by the fifth heat exchanger 35 to obtain cooling gas, which is discharged as process tail gas.

[0050] The nitrogen-containing sludge separated in the second flash tank 30 is centrifuged in the centrifuge 36 to become a process by-product nitrogen fertilizer with a moisture content of about 52%, which is used in agricultural production.

[0051] The present invention constructs a process simulation for preparing acrylic acid from carbon dioxide via an electrocatalytic and biofermentation coupling system, determines corresponding key operating parameters by analyzing energy flow and material flow, and connecting and coupling each component unit, and provides a technical path for directly preparing acrylic acid from carbon dioxide via electrocatalytic and biofermentation coupling technology. This process can not only reduce dependence on fossil-based products in the process of social development, but also realize the preparation of high value-added products from greenhouse gases.

[0052] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A system for preparing acrylic acid by using carbon dioxide through electro-biocoupling, characterized in that: It includes an electrocatalytic methanol production unit, a biological fermentation 3-hydroxypropionic acid production unit, a 3-hydroxypropionic acid purification unit and an acrylic acid production unit connected in sequence; The electrocatalytic methanol production unit is used to electrocatalyze hydrogen produced by solar electrolysis of water and carbon dioxide captured directly from air under the action of a ZnO-ZrO2 catalyst to produce methanol; The biological fermentation unit for producing 3-hydroxypropionic acid is used to carry out biological fermentation using the methanol obtained by the electrocatalytic unit as a substrate, and to separate the fermentation product into gas and liquid to obtain a fermentation liquid containing 3-hydroxypropionic acid; The 3-hydroxypropionic acid purification unit is used to perform solid-liquid separation on the obtained 3-hydroxypropionic acid fermentation broth to obtain 3-hydroxypropionic acid after extraction; The acrylic acid production unit is used to obtain acrylic acid by dehydrating the purified 3-hydroxypropionic acid.

2. The system for preparing acrylic acid by using carbon dioxide through electro-biocoupling according to claim 1, characterized in that: The electrocatalytic methanol production unit specifically comprises a first compressor (1), a first mixer (4), a second compressor (5), a first heat exchanger (6) and a methanol synthesis reactor (7) whose gas phase inlet and outlet are connected in sequence; the liquid phase outlet of the methanol synthesis reactor (7) is connected to the liquid phase inlet of the second pump (8) of the biological fermentation 3-hydroxypropionic acid production unit; the gas phase inlet of the first mixer (4) is connected to the outlet of the electrolytic reaction tank (3), and the liquid phase inlet of the electrolytic reaction tank (3) is connected to the liquid phase outlet of the first pump (2).

3. The system for preparing acrylic acid by using carbon dioxide through electro-biocoupling according to claim 1, characterized in that: The biological fermentation unit for producing 3-hydroxypropionic acid specifically comprises a second pump (8), a second heat exchanger (9), a fermentation tank (10) and a first flash tank (13) which sequentially connect the liquid phase inlet and outlet; the liquid phase end of the fermentation tank (10) is connected to the liquid phase port of the first storage tank (11) via a third pump (12); the fermentation tank (10) is inoculated with Pichia pastoris; the first storage tank (11) is used to provide the fermentation tank (10) with a buffer and nutrients required for the biological reaction; and the liquid phase port of the first flash tank (13) is connected to the inlet of the second storage tank (14) of the 3-hydroxypropionic acid purification unit.

4. The system for preparing acrylic acid by using carbon dioxide through electro-biocoupling according to claim 1, characterized in that: The 3-hydroxypropionic acid purification unit specifically comprises a second storage tank (14), a fourth pump (15), a dissolved air flotation reactor (16), an extractive distillation tower (20), a separator (21), a first vacuum distillation tower (22), a fifth pump (23) and a fourth heat exchanger (24) whose liquid phase inlet and outlet are connected in sequence, the gas phase port of the dissolved air flotation reactor (16) is connected in sequence to a gas storage device (19), a third heat exchanger (18) and a third compressor (17), and the liquid phase port of the fourth heat exchanger (24) is connected to the liquid phase port of a dehydration reactor (25) of an acrylic acid production unit.

5. The system for preparing acrylic acid by using carbon dioxide through electro-biocoupling according to claim 1, characterized in that: The acrylic acid production unit comprises a dehydration reactor (25), a second vacuum distillation tower (26) and a third vacuum distillation tower (27) to which a liquid phase inlet and outlet are sequentially connected.

6. The system for preparing acrylic acid by using carbon dioxide through electro-biocoupling according to claim 1, characterized in that: It also includes a cogeneration unit, which is respectively connected to the biological fermentation 3-hydroxypropionic acid production unit, the 3-hydroxypropionic acid purification unit and the acrylic acid production unit. The cogeneration unit is used to convert waste into electricity, heat energy and nitrogen-containing sludge.

7. The system for preparing acrylic acid by using carbon dioxide through electro-biocoupling according to claim 6, characterized in that: The cogeneration unit comprises a second mixer (28), an anaerobic fermentation tank (29), a second flash tank (30), a third mixer (31), a combustion chamber (32), a gas turbine (34), and a fifth heat exchanger (35), the gas phase end of the combustion chamber (32) being connected to the gas phase port of a fourth compressor (33); the liquid phase port of the second flash tank (30) being connected to the liquid phase end of a centrifuge (36); and the liquid phase port of the second mixer (28) of the cogeneration unit being respectively connected to the solid phase port of a dissolved air flotation reactor (16) of a 3-hydroxypropionic acid purification unit, the liquid phase port of a separator (21) of the 3-hydroxypropionic acid purification unit, and the top of a third vacuum distillation tower (27) of an acrylic acid production unit.

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