Method for utilizing heat of propyl acetate recovery tower

Abstract

The invention provides a method for utilizing heat of a propyl acetate recovery tower. The method for utilizing the heat of the propyl acetate recovery tower comprises the following steps: L1, feeding propyl acetate crude ester produced by an esterification tower into a rectifying tower, and purifying to obtain a recovery product and propyl acetate; and L2, the recovery product enters a recovery tower from the top of the recovery tower for recovery treatment, and a gas-phase product at the top of the recovery tower is connected with an esterification tower reboiler through a pipeline and is used for heating the esterification tower reboiler. A high-temperature gas-phase product generated at the top of a recovery tower is used as a heat source of a reboiler of an esterification tower, a heat-conducting coating is arranged on the inner wall of the reboiler of the esterification tower, and graphene and graphene modified by 3-(perfluoro-n-hexyl) epoxypropane, amino POSS and KH560 are introduced as components of the heat-conducting coating. The coating not only has good corrosion resistance, but also greatly improves the heat conduction efficiency of the esterification tower reboiler.

Description

Technical Field

[0001] This invention belongs to the field of propyl acetate production technology, and specifically relates to a method for utilizing the heat of a propyl acetate recovery tower. Background Technology

[0002] In the production of propyl acetate, esterification is typically used to produce crude ester, which is then purified and recycled through processes such as distillation and recovery. The propyl acetate recovery tower is one of the key pieces of equipment in this process; its main function is to further separate and recover valuable components from the products recovered in the distillation tower.

[0003] In existing technologies, propyl acetate recovery towers generate gaseous products rich in low-boiling-point components at the top during operation. Currently, the thermal energy treatment methods for these gaseous products are generally crude and inefficient. A common practice is to completely condense these high-temperature gaseous materials directly in the tower top condenser using a cooling medium (such as circulating cooling water), transferring the large amount of sensible and latent heat they carry to the cooling water. This process not only results in a significant waste of high-quality thermal energy and increases the cooling load and energy consumption of the entire production unit, but also requires downstream energy-consuming equipment such as esterification towers to consume large amounts of fresh steam or other external heat sources to heat their reboilers in order to maintain system operation. This "waste on one hand, replenish on the other" energy utilization model severely limits the improvement of production energy efficiency and increases product production costs and carbon emissions.

[0004] Furthermore, the heat transfer efficiency of the reboiler in the esterification tower, a key component of energy exchange, and the esterification tower itself, directly impacts overall energy consumption. Traditional esterification towers and reboilers are typically made of ordinary metal materials, whose surfaces are susceptible to the effects of the process medium. Long-term operation can lead to scaling or corrosion, resulting in a gradual decrease in heat transfer efficiency. While existing technologies involve applying coatings to the inner walls of the equipment, most coatings focus on corrosion protection and often have poor thermal conductivity. This creates additional thermal resistance between the equipment and the process fluid, actually reducing heat transfer intensity and failing to meet the requirements for efficient energy utilization.

[0005] Therefore, existing technologies mainly suffer from the following problems: Inefficient energy utilization and high energy consumption: The high-quality thermal energy contained in the gaseous products at the top of the recovery tower is not effectively utilized but is wasted through condensation. Simultaneously, the reboiler in the esterification tower requires a large amount of external heat source, resulting in a double waste of energy. Low system thermal integration: The process lacks a systematic and coupled utilization scheme for internal heat, failing to directly use the waste heat from high-temperature stations to heat low-temperature stations, leading to low overall thermodynamic efficiency. The efficiency of key heat transfer equipment needs improvement: Traditional esterification towers and reboilers may suffer from scaling and corrosion on their heat transfer surfaces, and there is a lack of surface treatment technologies that combine excellent corrosion resistance and high-efficiency thermal conductivity, hindering further improvements in heat exchange efficiency.

[0006] In conclusion, developing a method that can efficiently recover and utilize the heat at the top of the recovery tower and significantly improve the heat transfer efficiency of key equipment is of great significance for energy conservation and consumption reduction in the propyl acetate production process. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention develops a method for utilizing heat from a propyl acetate recovery tower. The high-temperature gaseous products generated at the top of the recovery tower are used as the heat source for the reboiler of the esterification tower. A thermally conductive coating is then applied to the inner wall of the reboiler. This coating uses epoxy resin and acrylate monomers as the matrix, and incorporates graphene and graphene modified with 3-(perfluorohexyl)propylene oxide, aminoPOSS, and KH560 as components. This coating not only provides excellent corrosion resistance but also significantly improves the thermal conductivity of the reboiler, ensuring that the heat from the reboiler is transferred to the raw materials more quickly and efficiently, thereby further realizing the benefits of waste heat utilization.

[0008] The purpose of this invention is to provide a method for utilizing the heat of a propyl acetate recovery tower, the method comprising the following steps: L1. The crude propyl acetate produced by the esterification tower is purified in a distillation tower to obtain the recovered product and propyl acetate. L2. The recovered product enters the recovery tower from the top of the recovery tower for recovery processing. The gaseous product at the top of the recovery tower is connected to the reboiler of the esterification tower through a pipeline for heating the reboiler of the esterification tower.

[0009] Specifically, by using the high-temperature gaseous products generated at the top of the recovery tower as the heat source for the reboiler of the esterification tower, the system achieves cascaded and cyclical energy utilization, effectively overcoming the drawbacks of existing technologies where thermal energy is wasted and additional energy consumption coexists. This method, through innovative thermal integration design, directly uses the heat that would otherwise be dissipated by cooling water for heating the upstream processes, significantly reducing the energy consumption and operating costs of the entire production unit.

[0010] The inner surface of the reboiler of the esterification tower is provided with a thermally conductive coating. The thermally conductive coating comprises the following components in parts by weight: 75-85 parts epoxy resin 25-35 parts of acrylate monomer 3-5 parts of initiator 3-5 parts emulsifier 1-3 parts of curing agent 3-5 parts of modified graphene 0.1-10 parts of auxiliary agent 40-65 parts water; The modified graphene is obtained by reacting 3-(perfluorohexyl)propane oxide, aminoPOSS, and KH560 modified graphene.

[0011] Furthermore, the epoxy resin is selected from bisphenol A type epoxy resin.

[0012] Furthermore, the acrylate monomer is selected from one or more of methacrylate, dodecafluoroheptyl methacrylate, and glycidyl methacrylate.

[0013] Furthermore, the additive is selected from one or more of the following: diluent, adhesion promoter, preservative, leveling agent, dispersant, film-forming aid, and surfactant.

[0014] Furthermore, the method for preparing the thermally conductive coating includes: S1. Under the protection of an inert gas, graphene and KH560 are mixed and heated to react, yielding KH560 modified graphene. S2. Mix 3-(perfluorohexyl)propane oxide, amino POSS and KH560 modified graphene, and heat to react to obtain modified graphene. S3. Blend the modified graphene with other components to prepare a coating, and cure it to obtain the thermally conductive coating.

[0015] Furthermore, in step S1, the heating temperature is 60-80°C.

[0016] Furthermore, in step S2, the heating temperature is 95-100℃.

[0017] Further, in step S1, the mass ratio of graphene to KH560 is 3-5:0.5-1.

[0018] Further, in step S2, the mass ratio of 3-(perfluorohexyl)propane oxide, aminoPOSS, and KH560 modified graphene is 3-6:2-3:3-6.

[0019] Furthermore, the thickness of the graphene is 2-12 nm.

[0020] Firstly, in terms of heat recycling, the gaseous products (containing propanol, a small amount of propyl acetate, and water vapor, etc.) at the top of the recovery tower carry the waste heat generated during the reaction. This heat is directly connected to the reboiler of the esterification tower through pipelines for heat exchange. The heat that would otherwise be wasted by direct condensation is reused to heat the reboiler of the esterification tower, reducing the esterification tower reboiler's dependence on external steam or electric heating. This achieves heat recycling at the process flow level and reduces the overall energy consumption loss in production.

[0021] The beneficial effects of this invention are as follows: This invention recovers heat by exchanging heat between the gaseous products at the top of the recovery tower and the reboiler of the esterification tower, and by applying a thermally conductive coating to the inner surface of the reboiler, thus achieving energy utilization. First, graphene is modified using KH560 to introduce epoxy groups into it, and then reacted with 3-(perfluorohexyl)propane oxide and aminoPOSS to obtain modified graphene. This effectively improves the compatibility between the modified graphene and other components of the coating, and also acts as a compatibilizer to improve the compatibility between graphene and other components of the coating. The modified graphene efficiently transfers heat in the coating, allowing the waste heat of the gaseous products in the recovery tower to be transferred more quickly and evenly through the reboiler of the esterification tower to heat the raw materials, improving heating efficiency and significantly reducing dependence on external steam. The introduction of the 3-(perfluorohexyl)propane oxide segment can improve the hydrophobicity and chemical corrosion resistance of the coating, resisting the corrosion of the esterification tower reboiler by the raw materials; and together with dodecafluoroheptyl methacrylate, it can regulate the surface energy of the coating, improve the corrosion resistance of the coating, make it difficult for the raw materials to adhere to the coating surface, and further enhance the antifouling performance of the coating. Furthermore, the introduction of amino POSS groups can graft rigid structures onto the graphene surface, which not only inhibits the aggregation of graphene sheets, but also fills the gaps between graphene and epoxy resin and acrylate monomers, effectively preventing graphene from agglomerating in the coating and ensuring its uniform dispersion in the coating. It also improves the density of the coating, further enhances the rigidity and stability of the coating, and improves the overall thermal conductivity. Attached Figure Description

[0022] Figure 1 A schematic diagram of the esterification reaction apparatus in the method for utilizing the heat of the propyl acetate recovery tower is shown.

[0023] In the diagram: 110, esterification column; 111, distillation column; 112, recovery column; 113, esterification column reboiler. Detailed Implementation

[0024] To more clearly illustrate the technical solution of the present invention, the following embodiments are provided, but the present invention is not limited thereto.

[0025] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0026] Acrylate monomers: dodecafluoroheptyl methacrylate, methyl methacrylate.

[0027] Epoxy resin: Bisphenol A epoxy resin, E-51, purchased from Jiangsu Guangxin Photosensitive New Materials Co., Ltd.

[0028] Leveling agent: BYK-333.

[0029] Dispersant: BYK-111.

[0030] Film-forming aid: Propylene glycol methyl ether acetate.

[0031] Initiator: Ammonium persulfate.

[0032] Emulsifier: Emulsifier CO-436.

[0033] Curing agent: triethylenetetramine.

[0034] 3-(perfluorohexyl)propane oxide: CAS: 38565-52-5.

[0035] KH560: γ-glycidoxypropyltrimethoxysilane.

[0036] Graphene: 2-10nm thick, 5μm wide, G0499, purchased from TCI (Shanghai) Chemical Industry Development Co., Ltd.

[0037] AminoPOSS: Octaammonium-modified cage-like silsesquioxane, 342313, purchased from Xi'an Qiyue Biotechnology Co., Ltd.

[0038] In the embodiments, the heat source for the reboiler of the esterification tower includes a steam heat source and a waste heat source from the recovery tower.

[0039] Example 1 A method for utilizing the heat of a propyl acetate recovery tower, such as Figure 1 As shown, the method for utilizing the heat of the propyl acetate recovery tower includes the following steps: L1. The crude propyl acetate produced by esterification column 110 enters distillation column 111 for purification to obtain the recovered product and propyl acetate. L2. The recovered product is fed into the recovery tower 112 from the top for recovery processing. The gaseous product at the top of the recovery tower 112 is connected to the esterification tower reboiler 113 through a pipeline as a waste heat source for the esterification tower reboiler 113. The esterification tower reboiler 113 is also equipped with a steam heat source. After the raw material in the esterification tower reboiler 113 exchanges heat with the heat source, it enters the esterification tower 110 from the top of the esterification tower reboiler 113. The inner surface of the reboiler of the esterification tower is provided with a thermally conductive coating. The thermally conductive coating comprises the following components in parts by weight: 75 parts epoxy resin 15 parts of methyl methacrylate 20 parts of dodecafluoroheptyl methacrylate 3 parts of initiator 3 parts emulsifier 2 parts of curing agent 3 parts modified graphene 2 parts leveling agent 3 parts dispersant 2 parts of film-forming aid; 40 parts distilled water; The method for preparing the thermally conductive coating includes: S1. Under nitrogen protection, graphene and KH560 were mixed in a mixture of ethanol and water with a volume ratio of 5:1 as solvent, heated to 60℃ and reacted for 24h. The mixture was then filtered, washed and dried to obtain KH560 modified graphene. The mass ratio of graphene to KH560 is 4:0.8; S2. Using dimethylformamide as a solvent, 3-(perfluorohexyl)propane oxide, amino POSS and KH560 modified graphene were mixed, heated to 100℃ and reacted for 10 h. The solvent was then removed to obtain modified graphene. The mass ratio of 3-(perfluorohexyl)propylene oxide, aminoPOSS, and KH560 modified graphene is 3:2:3. S3. According to the above mass proportions, the modified graphene is mixed with other components (except curing agent), heated to 90°C, stirred and reacted for 8 hours, then the curing agent is added, stirred evenly and poured into the inner surface of the reboiler of the esterification tower to cure and cast into a film to prepare the coating. After curing, the thermally conductive coating is obtained.

[0040] Example 2 A method for utilizing the heat of a propyl acetate recovery tower, such as Figure 1 As shown, the method for utilizing the heat of the propyl acetate recovery tower includes the following steps: L1. The crude propyl acetate produced by esterification column 110 enters distillation column 111 for purification to obtain the recovered product and propyl acetate. L2. The recovered product is fed into the recovery tower 112 from the top for recovery processing. The gaseous product at the top of the recovery tower 112 is connected to the esterification tower reboiler 113 through a pipeline as a waste heat source for the esterification tower reboiler 113. The esterification tower reboiler 113 is also equipped with a steam heat source. After the raw material in the esterification tower reboiler 113 exchanges heat with the heat source, it enters the esterification tower 110 from the top of the esterification tower reboiler 113. The inner surface of the reboiler of the esterification tower is provided with a thermally conductive coating. The thermally conductive coating comprises the following components in parts by weight: 80 parts of epoxy resin 20 parts of methyl methacrylate 10 parts of dodecafluoroheptyl methacrylate 4 parts of initiator 4 parts emulsifier 2 parts of curing agent 5 parts of modified graphene 2 parts leveling agent 3 parts dispersant 2 parts of film-forming aid; 45 parts distilled water; The method for preparing the thermally conductive coating includes: S1. Under nitrogen protection, graphene and KH560 were mixed in a mixture of ethanol and water with a volume ratio of 5:1 as solvent, heated to 60℃ and reacted for 24h. The mixture was then filtered, washed and dried to obtain KH560 modified graphene. The mass ratio of graphene to KH560 is 4:0.8; S2. Using dimethylformamide as a solvent, 3-(perfluorohexyl)propane oxide, amino POSS and KH560 modified graphene were mixed, heated to 100℃ and reacted for 10 h. The solvent was then removed to obtain modified graphene. The mass ratio of 3-(perfluorohexyl)propylene oxide, aminoPOSS, and KH560 modified graphene is 3:2:3. S3. According to the above mass proportions, the modified graphene is mixed with other components (except curing agent), heated to 90°C, stirred and reacted for 8 hours, then the curing agent is added, stirred evenly and poured into the inner surface of the reboiler of the esterification tower to cure and cast into a film to prepare the coating. After curing, the thermally conductive coating is obtained.

[0041] Example 3 A method for utilizing the heat of a propyl acetate recovery tower, such as Figure 1 As shown, the method for utilizing the heat of the propyl acetate recovery tower includes the following steps: L1. The crude propyl acetate produced by esterification column 110 enters distillation column 111 for purification to obtain the recovered product and propyl acetate. L2. The recovered product is fed into the recovery tower 112 from the top for recovery processing. The gaseous product at the top of the recovery tower 112 is connected to the esterification tower reboiler 113 through a pipeline as a waste heat source for the esterification tower reboiler 113. The esterification tower reboiler 113 is also equipped with a steam heat source. After the raw material in the esterification tower reboiler 113 exchanges heat with the heat source, it enters the esterification tower 110 from the top of the esterification tower reboiler 113. The inner surface of the reboiler of the esterification tower is provided with a thermally conductive coating. The thermally conductive coating comprises the following components in parts by weight: 85 parts epoxy resin 15 parts of methyl methacrylate 15 parts of dodecafluoroheptyl methacrylate 5 parts of initiator 3 parts emulsifier 2 parts of curing agent 5 parts of modified graphene 2 parts leveling agent 3 parts dispersant 2 parts of film-forming aid 50 parts distilled water; The method for preparing the thermally conductive coating includes: S1. Under nitrogen protection, graphene and KH560 were mixed in a mixture of ethanol and water with a volume ratio of 5:1 as solvent, heated to 60℃ and reacted for 24h. The mixture was then filtered, washed and dried to obtain KH560 modified graphene. The mass ratio of graphene to KH560 is 4:0.8; S2. Using dimethylformamide as a solvent, 3-(perfluorohexyl)propane oxide, amino POSS and KH560 modified graphene were mixed, heated to 100℃ and reacted for 10 h. The solvent was then removed to obtain modified graphene. The mass ratio of 3-(perfluorohexyl)propylene oxide, aminoPOSS, and KH560 modified graphene is 3:2:3. S3. According to the above mass proportions, the modified graphene is mixed with other components (except curing agent), heated to 90°C, stirred and reacted for 8 hours, then the curing agent is added, stirred evenly and poured into the inner surface of the reboiler of the esterification tower to cure and cast into a film to prepare the coating. After curing, the thermally conductive coating is obtained.

[0042] Comparative Example 1 The difference between this comparative example and Example 1 is that in step S2, KH560 modified graphene is used to replace an equal mass of 3-(perfluorohexyl)propane oxide, while other components and preparation methods are the same.

[0043] Comparative Example 2 The difference between this comparative example and Example 1 is that in step S2, 3-(perfluorohexyl) propylene oxide is used to replace an equal mass of KH560 modified graphene, while other components and preparation methods are the same.

[0044] Test Example 1 The stain resistance, corrosion resistance, and steam consumption of the coating in the reboiler of the esterification tower in Example 1 and Comparative Examples 1-2 were tested respectively.

[0045] Stain resistance: Tested according to the provisions of Method 5.5.1.3 B (Oven Rapid Method) in Chapter 5 of GB / T 9780-2013.

[0046] Corrosion resistance test: The salt spray resistance of the samples was tested according to the American standard ASTM B117. Metal samples coated with the coatings of Example 1 and Comparative Examples 1-2 were marked with crosses and placed in a Q-FOG SSP salt spray test chamber for testing. The corrosion was checked, and the degree of protection of the coating to the substrate was judged based on the corrosion condition to test the corrosion resistance of the coating.

[0047] Steam consumption: Record the amount of steam consumed per ton of qualified product in the esterification tower.

[0048] The test results are shown in Table 1.

[0049] Table 1 Performance test results of Example 1 and Comparative Examples 1-2 As can be seen from the data comparison in Table 1, the coating of Example 1 exhibits excellent stain resistance and corrosion resistance, while the system using this coating achieves lower steam consumption. The comparative test data strongly demonstrates that the introduction of perfluorinated segments is key to ensuring the anti-fouling and corrosion resistance of the coating surface; while the introduction of modified graphene significantly improves the thermal conductivity of the coating, thereby achieving energy saving and consumption reduction in the system.

[0050] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0051] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for utilizing the heat of a propyl acetate recovery tower, characterized in that, The method for utilizing the heat from the propyl acetate recovery tower includes the following steps: L1. The crude propyl acetate produced by the esterification tower is purified in a distillation tower to obtain the recovered product and propyl acetate. L2. The recovered product enters the recovery tower from the top of the recovery tower for recovery processing. The gaseous product at the top of the recovery tower is connected to the reboiler of the esterification tower through a pipeline for heating the reboiler of the esterification tower. The inner surface of the reboiler of the esterification tower is provided with a thermally conductive coating. The thermally conductive coating comprises the following components in parts by weight: 75-85 parts epoxy resin 25-35 parts of acrylate monomer 3-5 parts of initiator 3-5 parts emulsifier 1-3 parts of curing agent 3-5 parts of modified graphene 0.1-10 parts of auxiliary agent 40-65 parts water; The modified graphene is obtained by reacting 3-(perfluorohexyl)propane oxide, aminoPOSS, and KH560 modified graphene.

2. The method for utilizing the heat of the propyl acetate recovery tower according to claim 1, characterized in that, The epoxy resin is selected from bisphenol A type epoxy resin.

3. The method for utilizing the heat of the propyl acetate recovery tower according to claim 1, characterized in that, The acrylate monomer is selected from one or more of methacrylate, dodecafluoroheptyl methacrylate, and glycidyl methacrylate.

4. The method for utilizing the heat of the propyl acetate recovery tower according to claim 1, characterized in that, The additives are selected from one or more of the following: diluents, adhesion promoters, preservatives, leveling agents, dispersants, film-forming aids, and surfactants.

5. The method for utilizing the heat of the propyl acetate recovery tower according to claim 1, characterized in that, The method for preparing the thermally conductive coating includes: S1. Under the protection of an inert gas, graphene and KH560 are mixed and heated to react, yielding KH560 modified graphene. S2. Mix 3-(perfluorohexyl)propane oxide, amino POSS and KH560 modified graphene, and heat to react to obtain modified graphene. S3. Blend the modified graphene with other components to prepare a coating, and cure it to obtain the thermally conductive coating.

6. The method for utilizing the heat of the propyl acetate recovery tower according to claim 5, characterized in that, In step S1, the heating temperature is 60-80℃.

7. The method for utilizing the heat of the propyl acetate recovery tower according to claim 5, characterized in that, In step S2, the heating temperature is 95-100℃.

8. The method for utilizing the heat of the propyl acetate recovery tower according to claim 5, characterized in that, In step S1, the mass ratio of graphene to KH560 is 3-5:0.5-1.

9. The method for utilizing the heat of the propyl acetate recovery tower according to claim 5, characterized in that, In step S2, the mass ratio of 3-(perfluorohexyl)propane oxide, aminoPOSS, and KH560 modified graphene is 3-6:2-3:3-6.

10. The method for utilizing the heat of the propyl acetate recovery tower according to claim 5, characterized in that, The thickness of the graphene is 2-12 nm.

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