A low energy consumption separation system in acetic acid production

Abstract

The utility model provides a kind of low-energy consumption separation system in acetic acid production, including rectification module, heat energy integrated module, steam distribution module, energy conversion module, energy guide pipeline;With rectification module as core, the steam in the top of the light removal tower is handled by heat energy integrated module, and secondary steam is divided into two ways by steam distribution module: first way is transported to rectification module reboiler group by energy guide pipeline;Second way enters energy conversion module, and after being handled by generator set, collection transmission group, liquid of terminal gas-liquid separator is connected back heat energy integrated module by pipeline, forming closed-loop energy circulation system. Through the system of the utility model, energy consumption can be greatly reduced, with good economic benefit and environmental benefit.

Description

Technical Field

[0001] This invention belongs to the field of acetic acid preparation technology, specifically to a low-energy separation system for acetic acid production. Background Technology

[0002] Acetic acid, also known as acetic acid, is a basic organic chemical raw material. Its derivatives are widely used in key sectors of the national economy, such as pharmaceuticals, pesticides, and food. The methanol carbonylation method, which emerged in the 1960s, revolutionized acetic acid production. This technology uses methanol and carbon monoxide as raw materials and achieves a highly efficient carbonylation reaction through a rhodium-based or iridium-based catalyst system. It boasts significant advantages such as high atom economy, mild reaction conditions, and excellent product purity, and has become the mainstream technology in modern acetic acid production.

[0003] However, the complex composition of the acetic acid reaction products (including acetic acid, water, iodomethane, and byproducts) poses a significant challenge to subsequent separation processes. The distillation stage accounts for 70%-80% of the total energy consumption, primarily due to thermodynamic contradictions in the multi-tower system: the azeotropic nature of acetic acid and water necessitates high reflux ratio operation in the dehydration tower, while corrosive components like iodomethane require the use of corrosion-resistant materials such as titanium alloys. However, the low thermal conductivity of these materials further exacerbates energy loss. In traditional processes, the steam at the top of the dehydration tower is often directly condensed and discharged, failing to achieve cross-tower thermal coupling and resulting in significant waste of waste heat. Simultaneously, the carbonylation reaction liquid requires multiple stages of separation, including flash evaporation, light component removal, dehydration, and purification, resulting in a fragmented process and a lack of systematic integration and recycling of the energy network.

[0004] In view of the above, this utility model is hereby proposed. Utility Model Content

[0005] The primary objective of this invention is to provide a low-energy-consumption separation system for acetic acid production. Through the coordinated layout of a distillation module, a thermal energy integration module, a vapor distribution module, and energy-conducting pipelines, it enables the recycling and reuse of energy in the distillation section and provides energy to other sections in acetic acid production, thereby saving costs and achieving neutralized energy utilization.

[0006] In order to achieve the above-mentioned objectives of this utility model, the following technical solution is adopted:

[0007] A low-energy separation system for acetic acid production includes a distillation module, a thermal energy integration module, a vapor separation module, an energy conversion module, and an energy conduction pipeline;

[0008] The starting point of the distillation module, the top steam outlet of the light tower, is connected to the thermal energy integration module. The thermal energy integration module divides the secondary steam generated by the thermal energy integration module into two paths through the connected steam distribution module. The first outlet of the two paths is connected to the reboiler group of the distillation module through the energy conduction pipe. The energy conduction pipe is configured as a double-layer structure with an outer tube and an inner tube coaxial, and the interlayer of the double-layer structure is filled with heat-insulating material. The inner tube is configured as a variable diameter structure. The second outlet of the two paths is connected to the energy conversion module through a first branch. The energy conversion module includes a generator set and a collection and transmission group. The generator set is connected to the collection and transmission group and then to the distillation module. The end of the collection and transmission group is connected to a gas-liquid separator. The liquid outlet of the gas-liquid separator is connected to the energy integration module through a liquid pipe.

[0009] In this invention, the coordinated design of the thermal energy integration module and the steam distribution module achieves multi-stage utilization and closed-loop recovery of energy during the acetic acid distillation process, significantly reducing the overall energy consumption of the system. The steam distribution module divides the secondary steam in a 7:3 ratio, with 70% of the secondary steam being transported first through a double-layered energy-conducting pipeline to the reboiler group (reboiler for the light-light tower, dehydration tower, product tower, and stripping tower) within the distillation module, reducing the amount of external steam required to replenish each reboiler. The energy-conducting pipeline features a double-layer design. Specifically, both the inner and outer pipe walls are 5mm thick, with the inner pipe having an inner diameter of 250mm. The interlayer is filled with 30-50mm thick high-performance thermal insulation material, and the outer pipe has an inner diameter of 290-310mm. At the bend, a tapered pipe is used to change the inner pipe diameter to 190mm. This tapered pipe avoids the turbulent vortices caused by the stepped diameter change, preventing a sharp drop in pressure and a concentrated, powerful impact on the pipe wall. A multi-layer composite process ensures a seamless insulation layer, effectively preventing heat loss. The variable diameter design of the inner pipe and the vacuum insulation layer formed after the diameter change significantly reduce steam transmission heat loss compared to traditional single-pass pipelines and also increase steam delivery speed. The remaining 30% of the secondary steam enters the energy conversion module through another route to convert thermal energy into electrical energy, which is used to meet the power needs of equipment such as the circulating pump and control valves in the distillation module. Next, the liquid components in the secondary steam used for power generation are recovered by the gas-liquid separator in the subsystem. The liquid components are then returned to the thermal energy integration module through pipelines and exchanged with the initial raw material (steam from the top of the light-duty tower) in reverse, reducing the amount of external water supply and saving steam costs.

[0010] Preferably, the distillation module includes a light-light product removal column, a dehydration column, a product column, and a stripping column connected in sequence;

[0011] The top of the finished product tower is provided with a steam outlet, which is connected to the reboiler of the dehydration tower through a reflux pipe to form a closed-loop energy utilization for heat exchange. The reflux pipe is also provided with a pressure control module and a condenser for the finished product tower.

[0012] In the distillation module of this system, the closed-loop design of steam exiting the product column, flowing to the reboiler in the dehydration column, and then returning to the product column further enhances the steam utilization efficiency of this invention. First, the pressure control module pressurizes the steam at the top of the product column. This steam then drives the reboiler liquid in the dehydration column, reducing the amount of external steam supplied to the dehydration column reboiler and achieving efficient recycling of thermal energy within the distillation module.

[0013] Preferably, the generator set includes a buffer tank, a screw expander, and a motor. The buffer tank is connected to the screw expander unit via a steam duct. The output end of the screw expander unit is connected to the motor via a transmission device. The output end of the motor generates electrical energy to supply the distillation module.

[0014] This invention employs a generator set design that links a buffer tank, a screw expander, and a motor. This collaborative mechanism achieves efficient conversion and stable output of secondary steam energy. The buffer tank, acting as a pressure regulating unit for the secondary steam entering the screw expander, can stabilize the pressure of the secondary steam in a short time, ensuring the stability of the steam at the screw expander inlet. The screw expander converts the steam's thermal energy into mechanical energy and transmits it to the motor. The electrical energy output by the motor is then processed by the collection and transmission group to form industrial power, which can be directly supplied to equipment with high power demand, such as circulating pumps and reflux pumps, in the distillation module, achieving partial power self-sufficiency for the system.

[0015] Preferably, an annular distributor is provided at the end of the energy-conducting pipe. The annular distributor has 6-8 spiral guide vanes evenly distributed circumferentially in its annular chamber. The guide angle of each spiral guide vane is 25°-35°, which evenly distributes the secondary steam to the branch channel outlet. An independent pipe is provided between the branch channel outlet and the reboiler.

[0016] Preferably, the independent pipe has a double-layer cylindrical shell structure, with the inner pipe wall coated with a phase change material layer and the outer layer being an insulation shell. The interlayer of the double-layer cylindrical shell is filled with heat insulation material. The phase change material layer is composed of composite phase change material and has a thickness of 1.5-3.5 mm, which is compatible with the reboiler.

[0017] Preferably, the thermal energy integration module includes a steam valve, a compressor, a boiler heat exchanger, and a waste heat boiler connected sequentially along the steam flow direction. The waste heat boiler is connected to the condensate outlet of the reboiler group through a recovery pipe to reduce the external water supply to the waste heat boiler.

[0018] In this invention, the combination design of an annular distributor and a double-layer pipeline connected to the end of the energy-conducting pipe enables precise control of the directional delivery and thermal management of secondary steam. The annular distributor's annular chamber contains 6-8 circumferentially distributed spiral guide vanes (guide angle 25°-35°) that reconstruct the flow field, converting the secondary steam into a uniform flow state for distribution to each reboiler. This eliminates deviations in the flow rates connecting the reboiler and the branches, and eliminates localized overheating fluctuations in the reboiler caused by uneven distribution.

[0019] The independent pipeline's double-layer cylindrical shell structure further enhances heat retention and dynamic temperature regulation capabilities. The phase change material layer on the inner pipe wall is composed of a fatty acid / nano-graphite composite, with a phase change temperature precisely matched to the reboiler inlet requirements (i.e., temperature control of each column within 110-160℃). When steam temperature fluctuations exceed ±5℃, the phase change layer absorbs heat, suppressing temperature fluctuations within ±1.5℃, thus controlling steam fluctuations in the pipeline. Specifically, 1.5mm corresponds to the low-temperature section (110-120℃), with each 0.5mm increase in thickness corresponding to a 10℃ increase in temperature, up to 3.5mm suitable for the high-temperature section (150-160℃). Combined with the aerogel material for the interlayer and the titanium alloy construction of both inner and outer pipes, this significantly reduces the overall heat loss rate of the pipeline. This design avoids localized reboiler overheating leading to acetic acid decomposition, while simultaneously increasing the effective steam utilization rate to 96%. The double-pipe design also significantly reduces heat loss, and the combination of insulation and phase change materials maintains long-lasting insulation performance.

[0020] Preferably, the thermal energy integration module is further provided with a waste heat steam outlet, which is connected to the condensation module of the light-light-removal tower through a first branch pipe. The condensation module includes a first-stage condenser and a second-stage condenser arranged in series. The first-stage condenser and the second-stage condenser are connected to a separator through a third branch pipe and a fourth branch pipe. The top outlet of the separator is connected to the light-light-removal tower, and the bottom outlet is connected to the synthesis section in acetic acid production through a pipe.

[0021] In this invention, a cross-section energy-material collaborative recovery network is constructed through the staged coupling design of the waste heat steam outlet of the thermal energy integration module and the condensation module of the light phase removal tower, realizing the deep utilization of waste heat and the directional circulation of high-purity materials. The third and fourth branch pipes pour the two-stage condensate into a separator for efficient separation. In the separator, the condensate separates into light and heavy phases. 70% of the light phase is returned to the top of the light phase removal tower via a reflux pump, 30% of the light phase is returned to the synthesis section via a dilute acetic acid pump, and the heavy phase liquid is pumped to the synthesis section.

[0022] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0023] This invention utilizes a closed-loop dual-cycle design for heat exchange and power generation to integrate discrete thermal energy in the distillation module into a continuous energy network. Secondary steam is generated by exchanging heat between the top steam of the light-light product removal tower and the waste heat boiler. This secondary steam is supplied to the reboiler group of the distillation module and other sections in acetic acid production. A portion of the secondary steam is also converted into electrical energy through an energy conversion module to power some equipment. Simultaneously, heat exchange occurs between the top steam of the finished product tower and the bottom liquid of the dehydration tower within the distillation module. This not only helps reboil the bottom liquid in the dehydration tower but also aids in cooling the top steam of the finished product tower. This reduces the system's demand for external thermal and electrical energy, achieving comprehensive energy utilization and saving production costs. Furthermore, it reduces carbon dioxide emissions, making this invention both economically and environmentally beneficial. Attached Figure Description

[0024] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0025] Figure 1 This is a schematic diagram of a low-energy separation system for acetic acid production according to the present invention.

[0026] Figure 2-1 This is a schematic diagram of the oblique front side of the energy-conducting pipe;

[0027] Figure 2-2 This is a schematic diagram showing the diameter variation of the inner tube of the energy-conducting pipe.

[0028] Figure 3-1 This is a schematic diagram of the pressure-temperature relationship curve of the light-weight removal tower of this utility model;

[0029] Figure 3-2 This is a schematic diagram of the pressure-temperature relationship curve of the finished tower of this utility model.

[0030] In the attached diagram, the components represented by each number are shown below:

[0031] 1-Light weight removal tower, 101-First stage condenser, 102-Second stage condenser, 2-Dehydration tower, 201-Dehydration tower feed pump, 202-Dehydration tower reboiler, 3-Product tower, 301-Product tower top steam valve, 302-Product tower compressor, 303-Product tower feed pump, 304-Product tower condenser, 4-Stripping tower, 401-Stripping tower condenser, 402-Stripping tower feed pump, 5-Steam valve, 6-Compressor, 7-Boiler heat exchanger 8-Waste heat boiler, 9-Energy conduction pipe, 10-Ring distributor, 11-Independent pipe, 12-Energy conversion module, 13-Gas-liquid separator, 14-First branch pipe, 15-Third branch pipe, 16-Separator, 17-Fourth branch pipe, 18-Recirculation pump, 19-Dilute acetic acid pump, 20-Gas-liquid component pipe, 21-Steam distribution module, 22-Outer pipe, 23-Inner pipe, 24-Insulation material, 25-Another energy conduction pipe, 26-Dense phase pump. Detailed Implementation

[0032] The technical solution of this utility model will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are only some embodiments of this utility model, not all embodiments, and are only used to illustrate this utility model, and should not be regarded as limiting the scope of this utility model. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0033] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0034] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0035] To more clearly illustrate the technical solution of this utility model, the following description is provided in the form of specific embodiments.

[0036] Example 1

[0037] The structure of a low-energy separation system in acetic acid production according to this embodiment is shown in the reference. Figure 1 As shown, its specific workflow is as follows:

[0038] A gaseous material containing acetic acid, iodomethane, water, and other components from the synthesis section is fed into the distillation module. First, it enters the bottom of the light component removal tower 1 through the gas-liquid component pipeline 20 to remove the light components. Then, the bottom liquid of the light component removal tower is sent to the dehydration tower 2 for processing through the dehydration tower feed pump 201 to obtain the dehydration tower bottom liquid. The dehydration tower bottom liquid is sent to the product tower 3 for processing through the product tower feed pump 303 to obtain the product acetic acid and the product tower bottom material. Then, the product tower bottom liquid is sent to the stripping tower 4 through the stripping tower feed pump 402. The stripping tower 4 separates the product tower bottom liquid. The vapor generated at the top of the stripping tower 4 is condensed and separated into the product tower for reuse through the stripping tower condenser 401. The stripping tower bottom liquid generated at the bottom of the tower is sent to the outside through the waste acid pipeline.

[0039] In the distillation module, the steam generated in the product column 3 is discharged from the top steam outlet. The steam in the product column 3 is pressurized (pressurized to 5 Bar and heated to 178.9°C) through the top steam valve 301 and the product column compressor 302 to obtain heated steam. The heated steam is connected to the dehydration column reboiler 201 through the reflux pipe to form a heat exchange cooling and save the external steam requirement of the dehydration column 2. The remaining heat is then cooled and returned to the product column 3 through the dehydration column reboiler 202 and the product column condenser 304.

[0040] The steam separated inside the light-weight product tower 1 is discharged through the steam outlet at the top of the tower. Then, the steam is pressurized by steam valve 5 and compressor 6, where it is pressurized to 5 Bar and heated to 152.4℃ to increase its temperature, resulting in pressurized steam. This pressurized steam is then introduced into boiler heat exchanger 7 for heat exchange with waste heat boiler 8. The secondary steam generated by waste heat boiler 8 is divided into two paths by steam distribution module 21: the first outlet, with 70% flow, is transported via double-layer energy-conducting pipe 9 to the reboiler group in the distillation module; the energy-conducting pipe 9 adopts a coaxial structure of stainless steel outer tube 22 and variable-diameter titanium alloy inner tube 23, with a 45mm thick nano-aerogel insulation material 24 filling the interlayer. Figure 2-1 (2-2) An annular distributor 10, with six 30° spiral guide vanes at the end, evenly distributes secondary steam to independent pipes 11 connected to each reboiler. The steam is then transported to the reboilers of each tower and to other heat-requiring sections in acetic acid production via another energy-conducting pipe 25. The cooled steam then returns to the thermal energy integration module, reducing the external feedwater volume of the waste heat boiler 8. The second outlet has a 30% flow rate passing through the generator set in the energy conversion module 12, generating electricity which is then returned to the distillation module via a collection and transmission group to power the condenser, pumps, etc. The generated steam enters the gas-liquid separator 13, where the liquid water returns to the waste heat boiler 8 to mix and recycle with the external feedwater, reducing the external feedwater volume of the waste heat boiler 8. The independent pipes 11 employ a double-layer cylindrical shell structure made of titanium alloy, with a 3.5mm phase change material layer coated on the inner wall and an aerogel interlayer.

[0041] The steam generated by the light phase removal tower 1 passes through the boiler heat exchanger 7, and the remaining heat enters the condensation module through the first branch pipe 14. This module includes a first-stage condenser 101 and a second-stage condenser 102 connected in series. The first-stage condenser 101 enters the separator 16 through the third branch pipe 15, and the second-stage condenser 102 enters the separator 16 through the fourth branch pipe 17. In the separator 16, the condensed liquid is separated into two phases: light acetic acid (36.2 wt.%, iodomethane 4.8 wt.%, water 57.4 wt.%, other 1.6 wt.%) and heavy phase (acetic acid 2.4 wt.%, iodomethane 94.2 wt.%, other 3.4 wt.%). 70.6% of the light phase is returned to the top of the light phase removal tower 1 via the reflux pump 18, and 29.4% of the light phase is returned to the synthesis section via the dilute acetic acid pump 19. 100% of the heavy phase is transported to the synthesis section via the heavy phase pump 26.

[0042] Example 2

[0043] The specific workflow of a low-energy separation system for acetic acid production in this embodiment is as follows:

[0044] A gaseous material containing acetic acid, iodomethane, water, and other components from the synthesis section is fed into the distillation module. First, it enters the bottom of the light component removal tower 1 through the gas-liquid component pipeline 20 to remove the light components. Then, the bottom liquid of the light component removal tower is sent to the dehydration tower 2 for processing via the dehydration tower feed pump 201 to obtain the dehydration tower bottom liquid. The dehydration tower bottom liquid is then sent to the product tower 3 for processing via the product tower feed pump 303 to obtain the product acetic acid and the product tower bottom material. Next, the product tower bottom liquid is sent to the stripping tower 4 through the stripping tower feed pump 402. The stripping tower 4 separates the product tower bottom liquid. The vapor generated at the top of the stripping tower 4 is condensed and separated into the product tower for reuse via the stripping tower condenser 401. The stripping tower bottom liquid generated at the bottom of the tower is sent to the outside through the waste acid pipeline.

[0045] In the distillation module, the steam generated in the product column 3 is discharged from the top steam outlet. The steam in the product column 3 is pressurized (pressurized to 8 Bar and heated to 201°C) by the top steam valve 301 and the product column compressor 302 to obtain heated steam. The heated steam is connected to the dehydration tower reboiler 201 through the reflux pipe to form a heat exchange cooling and save the dehydration tower 2 from the external steam requirement. The remaining heat is then cooled and returned to the product column 3 through the dehydration tower reboiler 202 and the product column condenser 304.

[0046] The steam separated inside the light-weight product tower 1 is discharged through the steam outlet at the top of the tower. Then, the steam is pressurized by steam valve 5 and compressor 6, where it is pressurized to 3 Bar and heated to 133.5℃ to increase its temperature and obtain pressurized steam. This pressurized steam is then introduced into boiler heat exchanger 7 for heat exchange with waste heat boiler 8. The secondary steam generated by waste heat boiler 8 is divided into two paths by steam distribution module 21: the first outlet, with 65% flow, is transported via double-layer energy-conducting pipe 9 to the reboiler group in the distillation module; the energy-conducting pipe 9 adopts a coaxial structure of stainless steel outer tube 22 and variable-diameter titanium alloy inner tube 23, with a 35mm thick nano-aerogel insulation material 24 filling the interlayer. Figure 2-1(2-2) An annular distributor 10, with eight 25° spiral guide vanes at the end, evenly distributes secondary steam to independent pipes 11 connected to each reboiler. The steam is then transported to the reboilers of each tower and to other heat-requiring sections in acetic acid production via another energy-conducting pipe 25. The cooled steam then returns to the thermal energy integration module, reducing the external feedwater volume of the waste heat boiler 8. The second outlet, with a 35% flow rate, passes through the generator set in the energy conversion module 12 to generate electricity, which is then returned to the distillation module via a collection and transmission group to power the condenser, pumps, etc. The generated steam enters the gas-liquid separator 13, where the liquid water returns to the waste heat boiler 8 to mix and recycle with the external feedwater, reducing the external feedwater volume of the waste heat boiler 8. The independent pipes 11 employ a double-layer cylindrical shell structure made of titanium alloy, with the inner wall coated with a 1.5mm phase change material layer and the interlayer composed of aerogel.

[0047] The steam generated by the light phase removal tower 1 passes through the boiler heat exchanger 7, and the remaining heat enters the condensation module through the first branch pipe 14. This module includes a first-stage condenser 101 and a second-stage condenser 102 connected in series. The first-stage condenser 101 enters the separator 16 through the third branch pipe 15, and the second-stage condenser 102 enters the separator 16 through the fourth branch pipe 17. In the separator 16, the condensed liquid is separated into two phases: light acetic acid (36.2 wt.%, iodomethane 4.8 wt.%, water 57.4 wt.%, other 1.6 wt.%) and heavy phase (acetic acid 2.4 wt.%, iodomethane 94.2 wt.%, other 3.4 wt.%). 70.6% of the light phase is returned to the top of the light phase removal tower 1 via the reflux pump 18, and 29.4% of the light phase is returned to the synthesis section via the dilute acetic acid pump 19. 100% of the heavy phase is transported to the synthesis section via the heavy phase pump 26.

[0048] Example 3

[0049] The specific implementation method is the same as that in Example 1, except that the annular distributor 10 replaces the spiral guide vane with a straight guide vane with a fixed angle of 30 degrees that cannot be adjusted.

[0050] Example 4

[0051] The specific implementation method is the same as that in Example 1, except that the independent pipe 11 in Example 1 is a double-layer cylindrical shell structure made of titanium alloy, with a 0.5mm phase change material layer coated on the inner wall and an aerogel interlayer.

[0052] Example 5

[0053] The specific implementation method is the same as that of Comparative Example 1. The difference is that the independent pipe 11 in Example 1 is a double-layer cylindrical shell structure made of titanium alloy material. The inner pipe wall is not coated with a phase change material layer, and the interlayer is made of aerogel.

[0054] Comparative Example 1

[0055] The specific implementation method is the same as that in Example 1, except that the energy-conducting pipe is replaced by a single-layer stainless steel pipe instead of a double-layer coaxial structure (a coaxial structure of an outer stainless steel pipe and an inner variable diameter titanium alloy pipe, with a 45mm thick nano-aerogel insulation material in the interlayer, and an annular distributor 10 with 6 30° spiral guide vanes at the end).

[0056] Experimental Example 1

[0057] The separation systems of Examples 1-5 and Comparative Example 1 were used to separate gaseous materials from the acetic acid synthesis section to verify the utilization rate of the recovered steam, where the utilization rate = (actual amount of steam used / total amount of steam produced) × 100%. The specific experimental results are shown in Table 1.

[0058] Table 1. Experimental Results

[0059]

[0060] As shown in the table above, the performance of the acetic acid separation system in Comparative Examples 1-5 and Comparative Example 1 in this invention verifies the key role of thermal energy integration and structural optimization in energy saving and emission reduction. Experimental results show that Example 1, employing a four-stage distillation column in series, a double-layer energy-conducting pipeline, and a steam distribution module, achieves a heat recovery rate of 96.2%. Its advantage lies in the synergistic design of steam pressurization and waste heat boiler, maximizing the utilization efficiency of secondary steam. Example 1, using a double-layer energy-conducting pipeline (stainless steel outer pipe + titanium alloy variable diameter inner pipe + 45mm nano-aerogel interlayer), achieves a steam utilization rate of 96.2%, a 27.8% improvement compared to Comparative Example 1 with a single-layer stainless steel pipeline. This demonstrates that the composite structure design of the energy-conducting pipeline in this invention maximizes insulation capabilities. As can be seen from Examples 1 and 3, replacing the spiral guide vane with a fixed straight plate reduces the steam utilization rate, indicating that an adjustable guide structure is crucial for uniform steam distribution. The spiral guide vane ensures uniform steam distribution to the reboiler assembly, reducing the risk of local overheating and resulting in a heat loss rate of less than 5%. In Example 4, the phase change material coating thickness of the independent pipe is reduced, further decreasing the utilization rate to 87.6%, confirming the key role of the phase change layer in temperature maintenance. In Example 5, reducing the phase change coating on the inner wall of the independent pipe leads to a decrease in latent heat absorption efficiency, which is mismatched with the reboiler's required temperature. Comparative Example 1, which uses a single-layer stainless steel pipe, has a utilization rate of only 68.4%, significantly lower than all other examples, highlighting the synergistic effect of the double-layer insulation structure and the phase change material coating. Therefore, the necessity of the multi-stage distillation and steam pressurization of this invention is highlighted, and it is also shown that the combination of the double-layer structure of the energy-conducting pipe and the phase change coating in the independent pipe can reduce most of the heat loss and achieve optimal steam utilization.

[0061] Experiment Example 2

[0062] In a plant specializing in acetic acid production (annual output of 200,000 tons), the low-energy separation system of Example 1 of this utility model was used for industrial-scale verification in acetic acid production. The focus was on investigating heat recovery efficiency, steam savings, and carbon emission performance, and analyzing the relationship between tower pressure and temperature. The plant's original separation section was simply formed by connecting the light-light product removal tower, dehydration tower, and finished product tower sections of the distillation module of this utility model. The results are shown in Tables 2-4 below.

[0063] Table 2. Performance Results

[0064]

[0065] Table 3. Relationship between steam pressure and temperature at the top of the light-weight product removal tower ( Figure 3-1 )

[0066]

[0067] Table 4. Relationship between steam pressure and temperature at the top of the finished product tower ( Figure 3-2 )

[0068]

[0069] As shown in the table above, the low-energy separation system of Embodiment 1 of this utility model was used for verification. The results show that the system achieved a steam utilization rate of 96.2%, which is significantly improved compared to the original process of the plant. This utility model's system demonstrates significant energy-saving and emission-reduction benefits: using the top steam of the light-duty tower to heat the waste heat boiler generates secondary steam for use in any stage of production, saving 24 t / h of heating steam. The top steam of the finished product tower is pressurized by a compressor, significantly enhancing the heat exchange driving force with the bottom liquid of the dehydration tower, achieving a steam saving of 17 t / h. This design overcomes the shortcomings of traditional processes that directly discharge low-temperature steam. Two heat exchanges can save 41 t / h of heating steam. The two technologies working together achieve an annual steam saving of 3.3 × 10⁻⁶ tons compared to the traditional process (annual output of 200,000 tons). 5 One ton of steam currently costs 300 yuan, meaning approximately 100 million yuan can be saved annually. In terms of environmental benefits, the steam saving reduces standard coal consumption by 22,400 tons and lowers CO2 emissions by 82,500 tons per year.

[0070] The pressure-temperature relationship data (Table 3-4) reveals the core mechanism of the system's efficient operation: the steam temperature at the top of both towers increases monotonically with increasing operating pressure (absolute pressure), confirming that the saturated steam pressure increases with increasing temperature. In this experimental example, after the steam at the top of the light acetic acid removal tower is pressurized to 3 Bar (133.5℃), secondary steam is generated in the waste heat boiler. 70% of this secondary steam is precisely distributed to the reboiler group through energy-conducting pipes, and 30% drives the generator set, achieving rational utilization of thermal energy. The condensate after power generation is recycled back to the waste heat boiler, forming a closed-loop cycle, reducing the need for external water replenishment, and facilitating the exchange of heat energy between the towers and the boiler. This invention achieves two benefits: firstly, multi-stage steam utilization reduces coal consumption; secondly, the power generation module replaces part of the external industrial electricity, both contributing to a reduction in carbon dioxide emissions. In other words, this invention's system significantly improves the thermal efficiency of the acetic acid separation section through a progressive energy-saving architecture of "pressurization and temperature increase—precise distribution—multi-stage recovery," saving costs, achieving comprehensive energy utilization, and reducing carbon dioxide emissions, demonstrating good economic and environmental benefits.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model.

Claims

1. A low-energy separation system for acetic acid production, characterized in that, It includes a distillation module, a thermal energy integration module, a steam distribution module, an energy conversion module, and energy conduction pipelines; The starting point of the distillation module, the top steam outlet of the light tower, is connected to the thermal energy integration module. The thermal energy integration module divides the secondary steam generated by the thermal energy integration module into two paths through the connected steam distribution module. The first outlet of the two paths is connected to the reboiler group of the distillation module through the energy conduction pipe. The energy conduction pipe is configured as a double-layer structure with an outer tube and an inner tube coaxial, and the interlayer of the double-layer structure is filled with heat-insulating material. The inner tube is configured as a variable diameter structure. The second outlet of the two paths is connected to the energy conversion module through a first branch. The energy conversion module includes a generator set and a collection and transmission group. The generator set is connected to the collection and transmission group and then to the distillation module. The end of the collection and transmission group is connected to a gas-liquid separator. The liquid outlet of the gas-liquid separator is connected to the energy integration module through a liquid pipe.

2. The low-energy separation system according to claim 1, characterized in that, The distillation module includes a light component removal column, a dehydration column, a product column, and a stripping column connected in sequence. The top of the finished product tower is provided with a steam outlet, which is connected to the reboiler of the dehydration tower through a reflux pipe to form a closed-loop energy utilization for heat exchange. The reflux pipe is also provided with a pressure control module and a condenser for the finished product tower.

3. The low-energy separation system according to claim 2, characterized in that, The generator set includes a buffer tank, a screw expander, and a motor. The buffer tank is connected to the screw expander via a steam duct. The output end of the screw expander is connected to the motor via a transmission device. The output end of the motor generates electrical energy to supply the distillation module.

4. The low-energy separation system according to claim 2, characterized in that, An annular distributor is provided at the end of the energy-conducting pipe. 6-8 spiral guide vanes are evenly distributed circumferentially within the annular chamber of the annular distributor. The guide angle of each spiral guide vane is 25°-35°, which evenly distributes the secondary steam to the branch channel outlet. An independent pipe is provided between the branch channel outlet and the reboiler.

5. The low-energy separation system according to claim 4, characterized in that, The independent pipe has a double-layer cylindrical shell structure. The inner pipe wall is coated with a phase change material layer, and the outer layer is an insulation shell. The interlayer of the double-layer cylindrical shell is filled with heat insulation material. The phase change material layer is composed of composite phase change material and has a thickness of 1.5-3.5mm, which is matched with the reboiler.

6. The low-energy separation system according to claim 4, characterized in that, The thermal energy integration module includes a steam valve, a compressor, a boiler heat exchanger, and a waste heat boiler connected sequentially along the steam flow direction. The waste heat boiler is connected to the condensate outlet of the reboiler group through a recovery pipe to reduce the external water supply to the waste heat boiler.

7. The low-energy separation system according to claim 2, characterized in that, The thermal energy integration module is also provided with a waste heat steam outlet, which is connected to the condensation module of the light-light-removal tower through a first branch pipe. The condensation module includes a first-stage condenser and a second-stage condenser arranged in series. The first-stage condenser and the second-stage condenser are connected to a separator through a third branch pipe and a fourth branch pipe. The top outlet of the separator is connected to the light-light-removal tower, and the bottom outlet is connected to the synthesis section in acetic acid production through a pipe.

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