Efficient energy-saving rectification separation process of ligustrazine

Abstract

This invention discloses a high-efficiency and energy-saving distillation separation process for privet aldehyde, belonging to the field of fragrance preparation and distillation separation technology. The specific process includes the following steps: Privet aldehyde crude product is pretreated by alkali washing and water washing, and then fed into a partition column for distillation separation; the overhead vapor of the partition column is compressed and heated by an MVR compressor, and then fed into the reboiler of the partition column as a heat source; the side stream of the partition column collects the crude privet aldehyde product, which is then sent to a refining column for final refining to obtain the finished privet aldehyde product; the operating pressure of the refining column is higher than that of the partition column, and the overhead vapor of the refining column serves as a supplementary heat source for the reboiler of the partition column; during the distillation separation process, nitrogen gas is independently introduced into the partition column and the refining column for protection, and the nitrogen pressure in each column is 2-5 mmHg higher than the operating pressure of that column. Through the synergistic effect of MVR heat pump distillation, partition column technology, and differential pressure heat coupling, significant energy savings are achieved in the privet aldehyde distillation separation process.

Description

Technical Field

[0001] This invention belongs to the field of fragrance preparation and distillation separation technology, specifically referring to a high-efficiency and energy-saving distillation separation process for privet aldehyde. Background Technology

[0002] Ligustral (CAS No.: 68039-49-6), chemically named 2,4-dimethyl-3-cyclohexen-1-carboxaldehyde, is an important synthetic fragrance compound with a fresh, green leaf aroma. It is widely used in daily chemical fragrances, food flavorings, and tobacco flavorings. Ligustral typically comprises a mixture of two isomers: 2,4-dimethyl-3-cyclohexenylcarboxaldehyde (isomer I) accounts for approximately 75-80% and is the main aroma contributor; 3,5-dimethyl-3-cyclohexenylcarboxaldehyde (isomer II) accounts for approximately 20-25%. Ligustral has a boiling point of 75-78℃ / 10mmHg (1333.2Pa) and a relative density of 0.928-0.941 (20℃), classifying it as a thermosensitive aldehyde compound.

[0003] Currently, the industrial production of privet aldehyde mainly adopts the Diels-Alder addition reaction route, which involves using 2-methyl-1,3-pentadiene and acrolein as raw materials to undergo a cycloaddition reaction under heating and pressure to obtain crude privet aldehyde. After the reaction, the crude privet aldehyde usually contains unreacted acrolein (light component, boiling point 52.5℃), the target product privet aldehyde, and high-boiling-point polymerization byproducts generated during the reaction (heavy component). It needs to be purified by distillation to obtain the finished privet aldehyde product that meets the quality requirements of fragrances.

[0004] In existing technologies, the distillation separation of crude privet aldehyde mainly employs the following technical solutions: I. Conventional three-tower series distillation process.

[0005] Existing patent CN121064023A discloses a process for preparing privet aldehyde, in which the distillation separation step adopts a three-tower series distillation method, that is, the crude privet aldehyde after the addition reaction is separated and purified by passing it through a light-removal tower, a medium-removal tower and a purification tower in sequence. Although this process can obtain privet aldehyde products with high purity (GC content can reach more than 99%), it has many shortcomings: (1) the three towers operate independently, the equipment investment is large and the land area is large; (2) each tower consumes steam and circulating water separately, and the overall energy consumption index remains high; (3) the process flow is long, the operation is complicated and the production cycle is long.

[0006] II. Alkali washing-water washing-distillation process.

[0007] The prior art CN103232332A discloses a method for preparing privet aldehyde, in which crude privet aldehyde is washed with an alkaline solution and then washed with water until neutral. Then, it is distilled under inert gas protection, and the fraction with a boiling point of 78-83℃ / 10mmHg is collected to obtain the finished privet aldehyde. Although this process uses inert gas protection in the distillation stage, the alkaline washing-water washing process can only remove acidic impurities. The large quantities of light components such as acrolein and heavy components such as polymerization byproducts present in the crude product still need to be removed by distillation. Furthermore, the distillation stage only involves single-tower distillation, resulting in limited separation efficiency, making it difficult to simultaneously achieve both product yield and purity.

[0008] Third, existing energy-saving distillation technologies have not yet been applied in the field of privet aldehyde.

[0009] Divided-wall distillation technology is a thermally coupled distillation technique that combines two distillations into one. By installing longitudinal partitions within a single column shell, it achieves efficient separation of a three-component mixture, saving over 30% on equipment investment and 25%-35% on energy consumption. However, to date, there have been no reports of the application of this advanced energy-saving distillation technology in the field of privet aldehyde distillation separation.

[0010] Furthermore, privet aldehyde, as an α,β-unsaturated aldehyde compound, contains carbon-carbon double bonds and aldehyde groups in its molecular structure. When heated for extended periods at high temperatures, it is highly susceptible to the following side reactions: (1) oxidation reaction, where the aldehyde group is oxidized to a carboxyl group in the presence of oxygen, generating the corresponding carboxylic acid compound; (2) polymerization reaction, where the carbon-carbon double bond undergoes free radical polymerization or thermal polymerization at high temperatures, generating a high-boiling-point polymer; and (3) condensation reaction, where aldehyde groups undergo aldol condensation and other side reactions under thermal action. These side reactions not only lead to a decrease in the yield of privet aldehyde but also cause the product to darken in color and deteriorate in aroma quality, severely impacting its application value in the fragrance industry. In existing technologies, although some processes mention inert gas protection during the distillation stage, this is limited to the product collection stage and does not extend throughout the entire distillation process, resulting in limited protection effectiveness.

[0011] To address the aforementioned technical issues, there is an urgent need to develop a privet aldehyde distillation and separation process that combines high efficiency and energy saving with high-quality product protection. Summary of the Invention

[0012] To address the needs and problems mentioned in the background above, the present invention provides a high-efficiency and energy-saving distillation separation process for privet aldehyde, which at least partially solves the above problems.

[0013] According to the technical solution of the present invention, a high-efficiency and energy-saving distillation separation process for privet aldehyde is provided, comprising the following steps: After pretreatment by alkali washing and water washing, the crude privet aldehyde is sent to the adjacent column for distillation separation. The steam at the top of the adjacent column is compressed and heated by the MVR compressor, and then sent to the reboiler of the adjacent column as a heat source. The crude privet aldehyde product is extracted from the side stream of the adjacent tower and sent to the refining tower for final refining to obtain the finished privet aldehyde product. The operating pressure of the refining column is higher than that of the adjacent column, and the top steam of the refining column serves as a supplementary heat source for the reboiler of the adjacent column. During the distillation separation process, nitrogen gas is independently introduced into the partition column and the refining column for protection, and the nitrogen pressure in each column is 2-5 mmHg higher than the operating pressure of the column.

[0014] Preferably, the partition tower is provided with a longitudinal baffle, which divides the tower into a pre-separation section and a main separation section. The crude privet aldehyde is fed from the pre-separation section, and the crude privet aldehyde is extracted from the side stream of the main separation section. The operating pressure of the partition tower is 10~20 mmHg absolute, the top temperature is 75~85℃, and the bottom temperature is 105~120℃. The compression ratio of the MVR compressor is 2.5~3.5, which compresses and heats the top vapor to 125~145℃.

[0015] Preferably, the MVR compressor adopts a multi-stage compression method, with each stage having a compression ratio of no more than 2.0.

[0016] Preferably, the bottom of the partition tower is also equipped with an auxiliary reboiler, which is heated by external live steam during the process start-up phase or when the MVR compressor is insufficient to ensure stable system operation.

[0017] Preferably, the operating pressure of the refining column is 30~80 mmHg absolute pressure, the top temperature is 95~125℃, and the bottom temperature is 120~135℃; when the top steam of the refining column is used as a supplementary heat source for the reboiler of the adjacent column, the top steam temperature of the refining column is 3~8℃ higher than the bottom temperature of the adjacent column.

[0018] Preferably, the independent nitrogen protection for the partition tower and the refining tower is specifically achieved by connecting the main nitrogen pipe to an independent nitrogen branch for each tower. Each branch is equipped with a precision pressure reducing valve, a back pressure valve, and a pressure sensor. Each branch independently controls the nitrogen pressure, so that the nitrogen pressure in each tower is 2-5 mmHg higher than the operating pressure of the tower.

[0019] Preferably, the crude privet aldehyde is preheated to 60-70°C by a preheater before entering the adjacent tower. The heat source of the preheater comes from the bottom discharge of the refining tower.

[0020] Preferably, the method further includes online monitoring of the ratio of privet aldehyde isomer I (2,4-dimethyl-3-cyclohexenylformaldehyde) and isomer II (3,5-dimethyl-3-cyclohexenylformaldehyde) in the overhead distillate of the purification column, and dynamically adjusting the reflux ratio of the purification column based on the monitoring results, including the following steps: When the content of isomer I is lower than the target value, increase the reflux ratio; When the content of isomer I reaches the target value, maintain or reduce the reflux ratio.

[0021] Preferably, the theoretical number of plates in the partition column is 45 to 55, of which the pre-separation section has 20 to 25 plates and the main separation section has 25 to 30 plates; the theoretical number of plates in the refining column is 15 to 25.

[0022] Preferably, the crude privet aldehyde contains 60-75 wt% privet aldehyde, 5-15 wt% acrolein, and 10-25 wt% high-boiling-point heavy components; the light component fraction of acrolein is collected from the top of the partition column, and the high-boiling-point heavy component fraction is collected from the bottom of the partition column.

[0023] This invention has at least the following beneficial effects: 1. This invention achieves significant energy savings in the privet aldehyde distillation and separation process through the synergistic effect of three energy-saving methods: MVR heat pump distillation, partitioned column technology, and differential pressure thermal coupling.

[0024] 2. This invention achieves precise control of the content of isomer I through online GC monitoring and intelligent reflux ratio control, thus ensuring batch-to-batch stability of product quality.

[0025] 3. This invention, through full-process nitrogen protection, not only inhibits the oxidative deterioration of privet aldehyde but also reduces the concentration of flammable gases in the distillation system, thereby improving process safety. Simultaneously, the MVR heat pump system uses steam and water as the circulation medium, avoiding the use of environmentally harmful or corrosive refrigerants, further reducing safety and environmental risks. Attached Figure Description

[0026] Figure 1 This is a simplified process flow diagram of the present invention. Detailed Implementation

[0027] The technical solutions in the embodiments will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection.

[0028] This invention provides a highly efficient and energy-saving distillation separation process for privet aldehyde, comprising the following steps: (a) Crude product pretreatment: The crude privet aldehyde was pretreated by alkaline washing and water washing.

[0029] Specifically, the crude privet aldehyde contains 60-75 wt% privet aldehyde, 5-15 wt% acrolein, and 10-25 wt% high-boiling-point heavy components. The alkaline washing involves washing the crude privet aldehyde with a 5-15 wt% sodium carbonate or sodium hydroxide solution at a temperature of 20-40°C for 10-30 minutes, with a volume ratio of alkali solution to crude product of 0.5-2:1. After alkaline washing, the product is allowed to stand and separate into layers; the oil layer is then collected. Next, the product is washed 2-3 times with water until neutral, allowed to stand and separate into layers again, and the oil layer is collected.

[0030] Preferably, the alkaline solution is a 10wt% sodium carbonate solution, and the alkaline washing temperature is 25-30℃.

[0031] The pretreated crude privet aldehyde product enters the preheater for preheating. The preheater uses the waste heat from the bottom of the refining tower as a heat source to preheat the crude privet aldehyde product to 60-70℃.

[0032] (II) Pre-separation and main separation of adjacent towers: The preheated crude privet aldehyde product enters the adjacent column for distillation and separation.

[0033] A partition column is a distillation column with longitudinal partitions installed inside the shell of a distillation column. The longitudinal partitions divide the column into a pre-separation section (feed side) and a main separation section (product side). The section above the partitions is the common distillation section at the top of the column, and the section below the partitions is the common stripping section at the bottom of the column.

[0034] The operating pressure of the partition column is 10-20 mmHg (absolute pressure), the top temperature is 75-85℃, and the bottom temperature is 105-120℃. The theoretical number of trays in the pre-separation section is 20-25, with an operating reflux ratio of 0.5-1.5; the theoretical number of trays in the main separation section is 25-30, with an operating reflux ratio of 1.0-2.5. Preferably, the longitudinal baffles in the partition column divide the column diameter into sections with the pre-separation section occupying 35-50% of the column cross-sectional area and the main separation section occupying 50-65% of the column cross-sectional area.

[0035] Crude privet aldehyde is fed from the middle of the pre-separation section. In the pre-separation section, the light components (mainly acrolein) are enriched at the top of the column, the heavy components are enriched at the bottom of the column, and privet aldehyde migrates towards the product side (main separation section). In the main separation section, privet aldehyde undergoes fine separation from the heavy components.

[0036] The light component (acrylaldehyde content ≥98wt%) is collected from the top of the adjacent column and returned to the Diels-Alder addition process for recycling; the crude privet aldehyde product with a purity of 92-95wt% is collected from the side stream (middle of the main separation section) of the adjacent column; and the high-boiling-point heavy component is collected from the bottom of the adjacent column.

[0037] (III) MVR heat pump compression cycle: The steam at the top of the adjacent tower is separated into gas and liquid and then enters the MVR compressor for compression and heating.

[0038] The temperature of the steam at the top of the adjacent column is 75-85℃, and the pressure is 10-20 mmHg (absolute pressure). The MVR compressor uses a screw compressor or a centrifugal compressor with a compression ratio of 2.5-3.5 to compress and heat the steam at the top of the column to 125-145℃. Preferably, the compression ratio is adjusted in real time according to the temperature of the steam at the top of the adjacent column and the required temperature of the bottom column, ensuring that the temperature of the compressed steam is at least 10℃ higher than the temperature of the bottom column of the adjacent column.

[0039] As a further improvement to this invention, the MVR compressor can employ either single-stage compression or multi-stage compression; when multi-stage compression is used, the compression ratio of each stage does not exceed 2.0. Using multi-stage compression can reduce the single-stage compression ratio, improve compressor efficiency, and reduce energy consumption.

[0040] The compressed, high-temperature, high-pressure steam is fed into the reboiler of the adjacent column as a heat source. The temperature of the compressed steam is at least 10°C higher than the temperature of the reboiler of the adjacent column to ensure sufficient heat transfer temperature difference in the reboiler for effective heat exchange. The compressed steam condenses in the reboiler, releasing latent heat to heat the liquid in the column bottom. The condensed liquid is collected as a light component product (acrylonitrile).

[0041] Preferably, the motor power of the MVR compressor is configured based on the top steam flow rate and the required compression ratio. For a processing capacity of 1000 kg / h of crude privet aldehyde, when the compression ratio is 2.5-3.5, it is recommended to configure the motor power to be 100-200 kW (depending on the top steam flow rate, working fluid properties, and compressor efficiency). The specific power needs to be determined by thermodynamic calculations based on the top steam flow rate, temperature, pressure, and working fluid properties.

[0042] (iv) Differential pressure thermal coupling refining: The crude privet aldehyde product (purity 92-95wt%) collected from the side stream of the adjacent tower enters the refining tower for final refining.

[0043] The operating pressure of the refining column is 30-80 mmHg (absolute pressure), which is higher than the operating pressure of the adjacent column; the top temperature of the refining column is 95-125℃, and the bottom temperature is 120-135℃; the theoretical number of plates in the refining column is 15-25, and the operating reflux ratio is 1.5-3.0.

[0044] After condensation, a portion of the vapor at the top of the refining tower is returned to the refining tower, while the remainder is collected as privet aldehyde. The purity of the privet aldehyde product is ≥99.5 wt%.

[0045] Because the operating pressure of the refining column (30-80 mmHg) is higher than that of the adjacent column (10-20 mmHg), the condensation temperature of the vapor at the top of the refining column (100-130℃) is higher than that of the bottom of the adjacent column (105-120℃). The condensation temperature of the vapor at the top of the refining column is 3-8℃ higher than that of the bottom of the adjacent column. Therefore, the vapor at the top of the refining column can serve as a supplementary heat source for the reboiler of the adjacent column. After the vapor at the top of the refining column condenses and releases heat in the reboiler of the adjacent column, the condensate returns to the reflux tank of the refining column.

[0046] Furthermore, the steam at the top of the refining column is first pressurized and heated by a heat pump compressor before being used as a heat source for the reboiler of the adjacent column, with a compression ratio of 1.2-1.8.

[0047] As a further improvement of this embodiment of the invention, the bottom of the adjacent tower is also equipped with an auxiliary reboiler. The auxiliary reboiler is heated by external live steam during the process start-up phase or when the MVR compressor is insufficient to ensure stable system operation.

[0048] (v) Synergistic thermal integration of differential pressure thermal coupling and MVR heat pump: In the above process, the MVR heat pump cycle of the partition tower and the differential pressure thermal coupling between the refining tower and the partition tower constitute a dual thermal integrated network: First-stage heat integration: The steam at the top of the adjacent tower is compressed to 125-145℃ by the MVR compressor and then used as the heat source for its own reboiler, realizing the self-circulation of heat within the tower; The second level of heat integration: the top steam of the refining tower (high pressure tower) serves as a supplementary heat source for the reboiler of the adjacent tower, realizing the cascade utilization of heat between the towers.

[0049] The dual-heat integrated network is connected through pipes and heat exchangers and is equipped with automatic regulating valves to dynamically distribute heat sources according to the heat demand of each tower.

[0050] (vi) Independent nitrogen protection system: Throughout the entire distillation process, from the crude product feed to the product collection, nitrogen gas is continuously introduced for protection.

[0051] The inert gas is nitrogen with a purity of ≥99.9%. Nitrogen is introduced from one or more of the following locations: (a) preheater inlet; (b) divider tower feed inlet; (c) divider tower top; (d) refining tower feed inlet; (e) refining tower top.

[0052] Unlike existing technologies that use a single nitrogen protection system, this invention employs an independent branch nitrogen protection system to address the varying operating pressures of each tower. Specifically, the main nitrogen pipe is connected to independent nitrogen branches for each tower, and each branch is equipped with a precision pressure reducing valve, a back pressure valve, and a pressure sensor. Each branch independently controls the nitrogen pressure, ensuring that the nitrogen pressure in each tower is 2-5 mmHg higher than its operating pressure, and that the system oxygen content is controlled below 50 ppm. This nitrogen protection system maintains a slightly positive pressure state in each tower, meaning the nitrogen pressure in each tower is 2-5 mmHg higher than its operating pressure.

[0053] Specifically, the nitrogen branch pressure of the adjacent tower is controlled at 12-25 mmHg (absolute pressure), and the nitrogen branch pressure of the purification tower is controlled at 32-85 mmHg (absolute pressure). Each branch is independently pressure-regulated and independently controlled to ensure that gas backflow and pressure interference do not occur between negative pressure towers with significant pressure differences.

[0054] As a further improvement of this invention, before entering the preheater, the crude privet aldehyde product passes through a degasser to remove the oxygen dissolved in the crude product under absolute pressure of 50-100 mmHg and temperature of 40-60°C, thereby further reducing the oxygen content of the distillation system.

[0055] (vii) Intelligent reflux ratio control based on product isomer ratio: An online gas chromatography (GC) monitoring system was installed in the purification column to detect in real time the ratio of privet aldehyde isomer I (2,4-dimethyl-3-cyclohexenylformaldehyde) and isomer II (3,5-dimethyl-3-cyclohexenylformaldehyde) in the top distillate of the column.

[0056] The reflux ratio of the purification column is dynamically adjusted based on monitoring results: When the content of isomer I is lower than the target value (≥75wt%), increase the reflux ratio by 0.5-1.0 to improve the separation effect; When the content of isomer I reaches the target value (≥75wt%), maintain or appropriately reduce the reflux ratio to save energy.

[0057] The sampling interval for online GC monitoring is 5-30 minutes, and the adjustment of the reflux ratio is automatically executed by the PLC or DCS control system.

[0058] Preferably, the target content of isomer I is 75-82 wt%.

[0059] As a preferred embodiment of the present invention, the internal components of the partition tower and the refining tower adopt high-efficiency structured packing, which is selected from metal wire mesh corrugated packing or perforated plate corrugated packing, with a specific surface area of ​​250-750 m² / m³. Using structured packing can effectively reduce the tower pressure drop and the tower bottom temperature, which is beneficial for protecting the heat-sensitive privet aldehyde.

[0060] As a preferred technical solution of the present invention, the process also includes a start-up steam system, which is used to provide an initial heat source when the device is started for the first time. After the MVR heat pump system and the differential pressure thermal coupling system are running normally, the start-up steam system automatically switches to standby mode.

[0061] It should be noted that the low-grade steam discharged from the top of a distillation column typically has a high latent heat of condensation. In conventional processes, this heat is carried away by circulating water cooling, resulting in significant energy waste. This invention employs MVR heat pump technology, using a mechanical compressor to compress and heat the top steam (compression ratio 2.5-3.5, temperature rise 40-60℃), making its temperature at least 10℃ higher than the bottom temperature, thus meeting the requirements for use as a heat source for the reboiler. The compressed steam condenses and releases heat in the reboiler, transferring the latent heat to the bottom liquid, achieving the recycling of the waste heat from the top of the column within the column. This process consumes only a small amount of electricity, replacing the consumption of a large amount of live steam. By increasing the compression ratio to 2.5-3.5, the temperature after compression is ensured to reach 125-145℃, meeting the requirement of a heat transfer temperature difference of at least 10℃ between the compressed steam and the bottom temperature (105-120℃).

[0062] For the separation of the three components—light component (acrylonitrile), product (purslane), and heavy component—from crude privet aldehyde, conventional processes require two or three distillation columns operating in series. The partition column, by incorporating longitudinal baffles, integrates the pre-separation section and the main separation section within the same column shell, achieving complete thermal coupling of vapor and liquid flow on both sides of the baffle. The baffle effectively avoids the backmixing effect of intermediate components in traditional multi-column series processes, thus improving separation efficiency.

[0063] The operating pressure of the refining column (30-80 mmHg) is higher than that of the adjacent column (10-20 mmHg), resulting in a higher condensation temperature of the vapor at the top of the refining column (100-130℃) compared to the bottom temperature of the adjacent column (105-120℃). The condensation temperature of the vapor at the top of the refining column is 3-8℃ higher than that of the bottom of the adjacent column. Utilizing this temperature difference, the vapor at the top of the refining column is used as a heat source for the reboiler of the adjacent column, thus transferring the waste heat from the top of the high-pressure column to the bottom of the low-pressure column and avoiding the waste of latent heat from the vapor at the top of the high-pressure column.

[0064] To address the varying operating pressures of each column, an independent nitrogen protection system is employed. Each column is equipped with a separate nitrogen branch, each featuring a precision pressure-reducing valve, back pressure valve, and pressure sensor. Each branch independently controls its nitrogen pressure, ensuring that the nitrogen pressure in each column is 2-5 mmHg higher than its operating pressure. This independent branch design prevents gas backflow and pressure interference between columns with significant pressure differences. The introduction of nitrogen reduces the partial pressure of oxygen in each distillation column, inhibiting the oxidation reaction of privet aldehyde at high temperatures. Simultaneously, nitrogen, acting as a carrier gas, lowers the partial pressure of each component within the column, contributing to lower operating temperatures and reducing heat-sensitive decomposition. Slight positive pressure operation ensures that external air cannot infiltrate the system.

[0065] The aroma quality of privet aldehyde mainly depends on the content of isomer I, and the isomer ratio may fluctuate between different batches of crude product. By monitoring the isomer ratio in real time through online GC and dynamically adjusting the reflux ratio based on the monitoring results, the stability of product quality is ensured, while avoiding the energy waste caused by a fixed high reflux ratio.

[0066] Privet aldehyde is prone to polymerization and oxidation at high temperatures, necessitating that controlling the highest temperature of the entire system be a primary constraint. MVR heat pumps require a relatively small temperature difference between the top and bottom of the column, while differential pressure heat coupling requires the top temperature of the purification column (high-pressure column) to be higher than the bottom temperature of the adjacent column (low-pressure column). Both have high requirements for temperature parameters. This embodiment of the invention enables the two heat recovery systems to work collaboratively by precisely setting the operating pressure (10-20 mmHg for the adjacent column, 30-80 mmHg for the purification column) and the MVR compression ratio (2.5-3.5).

[0067] Example 1 Take 1000 kg of crude privet aldehyde (containing 68.5 wt% privet aldehyde, 11.2 wt% acrolein, and 20.3 wt% high-boiling-point heavy components), wash with 10 wt% sodium carbonate solution (alkali to crude product volume ratio 1:1, temperature 30℃, stirring for 20 min), allow to stand for separation, collect the oil layer, and wash twice with water until neutral. The pretreated crude product is preheated to 65℃ in a preheater (heat source from the bottom of the refining tower) and then enters the adjacent tower.

[0068] The adjacent column is equipped with longitudinal baffles. The pre-separation section occupies 40% of the column's cross-sectional area, and the main separation section occupies 60%. The operating pressure of the adjacent column is 15 mmHg (absolute pressure), the top temperature is 80℃, and the bottom temperature is 115℃. The pre-separation section has a theoretical number of 22 plates and a reflux ratio of 1.0; the main separation section has a theoretical number of 28 plates and a reflux ratio of 1.8. The crude product is fed from the middle of the pre-separation section.

[0069] The top steam of the adjacent column (temperature 80℃, pressure 15mmHg) is compressed in a single stage by an MVR screw compressor at a compression ratio of 3.0, raising its temperature to 135℃. This compressed steam is then sent to the reboiler at the bottom of the adjacent column as a heat source (the compressed steam temperature of 135℃ is 20℃ higher than the bottom temperature of 115℃, meeting the requirement of a heat transfer temperature difference of ≥10℃). Acrolein (content 98.5wt%) is collected from the top of the column and returned to the addition process for recycling; crude privet aldehyde (purity 94.2wt%) is collected from the side stream; and heavy components are collected from the bottom of the column.

[0070] The crude privet aldehyde product from the side stream enters the refining column. The operating pressure of the refining column is 60 mmHg (absolute), the top temperature is 118℃, and the bottom temperature is 128℃. The theoretical number of trays in the refining column is 20, and the reflux ratio is 2.2. The top vapor temperature of the refining column is 118℃, and the bottom temperature of the adjacent column is 115℃. The condensation temperature of the top vapor in the refining column is 3℃ higher than that in the adjacent column, satisfying the thermal coupling condition. The top vapor in the refining column serves as a supplementary heat source for the reboiler of the adjacent column. The privet aldehyde product is collected after condensation at the top of the refining column.

[0071] Each tower is independently protected with nitrogen gas (purity ≥99.9%). The nitrogen pressure in the adjacent tower is 17 mmHg (2 mmHg higher than the tower pressure), and the nitrogen pressure in the refining tower is 65 mmHg (5 mmHg higher than the tower pressure). The system oxygen content is ≤45 ppm. The crude product is degassed by a degasser (absolute pressure 60 mmHg, temperature 50℃) to remove dissolved oxygen before entering the preheater.

[0072] Example 2 Take 1000 kg of crude privet aldehyde, the same as in Example 1, and perform alkaline washing, water washing pretreatment, and preheating according to the method in Example 1.

[0073] The diverter column operates at an absolute pressure of 12 mmHg, with a top temperature of 77°C and a bottom temperature of 112°C. The pre-separation section has a theoretical plate count of 20 and a reflux ratio of 0.8; the main separation section has a theoretical plate count of 25 and a reflux ratio of 1.5. An MVR compressor with a compression ratio of 3.2 compresses the top vapor from 12 mmHg to 38 mmHg, raising the temperature from 77°C to 138°C (26°C higher than the bottom temperature of 112°C). The refining column operates at an absolute pressure of 55 mmHg, with a top temperature of 115°C and a bottom temperature of 126°C. The refining column has a theoretical plate count of 18 and a reflux ratio of 2.0. The top vapor from the refining column is pressurized and heated by a heat pump compressor (compression ratio 1.3) and then used as a supplementary heat source for the reboiler of the diverter column.

[0074] The nitrogen pressure in the adjacent tower is 15 mmHg (3 mmHg higher than the tower pressure), the nitrogen pressure in the purification tower is 60 mmHg (5 mmHg higher than the tower pressure), and the oxygen content in the system is ≤40 ppm.

[0075] Example 3 Take 1000 kg of crude privet aldehyde (privet aldehyde 65.2 wt%, acrolein 14.5 wt%, heavy components 20.3 wt%) and pretreat it according to the method in Example 1.

[0076] The operating pressure of the adjacent column is 18 mmHg (absolute pressure), with a top temperature of 83°C and a bottom temperature of 118°C. The pre-separation section has a theoretical number of 24 plates and a reflux ratio of 1.2; the main separation section has a theoretical number of 30 plates and a reflux ratio of 2.2. The MVR compressor has a compression ratio of 2.8, compressing the top vapor from 18 mmHg to 50 mmHg and raising the temperature from 83°C to 133°C (15°C higher than the bottom temperature of 118°C). The operating pressure of the refining column is 75 mmHg (absolute pressure), with a top temperature of 123°C and a bottom temperature of 133°C. The refining column has a theoretical number of 22 plates and a reflux ratio of 2.5. The top vapor temperature of the refining column is 123°C, 5°C higher than the bottom temperature of the adjacent column (118°C), and is directly used as a supplementary heat source for the reboiler of the adjacent column.

[0077] The nitrogen pressure in the adjacent tower is 22 mmHg (4 mmHg higher than the tower pressure), the nitrogen pressure in the purification tower is 80 mmHg (5 mmHg higher than the tower pressure), and the oxygen content in the system is ≤50 ppm.

[0078] Example 4 Take 1000 kg of crude privet aldehyde (privet aldehyde 71.3 wt%, acrolein 8.7 wt%, heavy components 20.0 wt%) and pretreat it according to the method in Example 1.

[0079] The diverter column operates at an absolute pressure of 10 mmHg, with a top temperature of 75°C and a bottom temperature of 108°C. The pre-separation section has a theoretical plate count of 25 and a reflux ratio of 0.6; the main separation section has a theoretical plate count of 28 and a reflux ratio of 1.2. The MVR compressor uses a two-stage compression process with a compression ratio of 1.6 per stage and a total compression ratio of 2.56, compressing the top vapor from 10 mmHg to 26 mmHg and raising the temperature from 75°C to 130°C (22°C higher than the bottom temperature of 108°C). The refining column operates at an absolute pressure of 40 mmHg, with a top temperature of 105°C and a bottom temperature of 121°C. The refining column has a theoretical plate count of 16 and a reflux ratio of 1.8. The top vapor from the refining column is pressurized and heated by a heat pump compressor (compression ratio 1.5) and then used as a supplementary heat source for the reboiler of the diverter column.

[0080] The nitrogen pressure in the adjacent tower is 14 mmHg (4 mmHg higher than the tower pressure), the nitrogen pressure in the purification tower is 45 mmHg (5 mmHg higher than the tower pressure), and the oxygen content in the system is ≤35 ppm.

[0081] Example 5 Take 1000 kg of crude privet aldehyde (privet aldehyde 66.8 wt%, acrolein 12.3 wt%, heavy components 20.9 wt%) and pretreat it according to the method in Example 1.

[0082] The operating pressure of the adjacent column is 20 mmHg (absolute pressure), with a top temperature of 85°C and a bottom temperature of 120°C. The pre-separation section has a theoretical number of 20 plates and a reflux ratio of 1.0; the main separation section has a theoretical number of 25 plates and a reflux ratio of 2.0. The MVR compressor has a compression ratio of 2.5, compressing the top vapor from 20 mmHg to 50 mmHg and raising the temperature from 85°C to 130°C (10°C higher than the bottom temperature of 120°C, meeting the minimum heat transfer temperature difference requirement). The operating pressure of the refining column is 80 mmHg (absolute pressure), with a top temperature of 125°C and a bottom temperature of 135°C. The refining column has a theoretical number of 24 plates and a reflux ratio of 2.8. The top vapor temperature of the refining column is 125°C, 5°C higher than the bottom temperature of the adjacent column (120°C), and directly serves as a supplementary heat source for the reboiler of the adjacent column.

[0083] The nitrogen pressure in the adjacent tower is 24 mmHg (4 mmHg higher than the tower pressure), the nitrogen pressure in the purification tower is 85 mmHg (5 mmHg higher than the tower pressure), and the oxygen content in the system is ≤48 ppm.

[0084] Example 6 Take 1000 kg of crude privet aldehyde (privet aldehyde 69.7 wt%, acrolein 10.1 wt%, heavy components 20.2 wt%) and pretreat it as in Example 1.

[0085] The operating pressure of the adjacent column is 14 mmHg (absolute pressure), with a top temperature of 78°C and a bottom temperature of 113°C. The pre-separation section has a theoretical number of 23 plates and a reflux ratio of 0.9; the main separation section has a theoretical number of 27 plates and a reflux ratio of 1.6. The MVR compressor has a compression ratio of 3.0, compressing the top vapor from 14 mmHg to 42 mmHg and raising the temperature from 78°C to 135°C (22°C higher than the bottom temperature of 113°C). The operating pressure of the refining column is 58 mmHg (absolute pressure), with a top temperature of 116°C and a bottom temperature of 127°C. The refining column has a theoretical number of 20 plates and a reflux ratio of 2.1. The top vapor from the refining column is pressurized and heated by a heat pump compressor (compression ratio 1.4) and then used as a supplementary heat source for the reboiler of the adjacent column.

[0086] Before entering the preheater, the crude product undergoes a degassing unit (absolute pressure 60 mmHg, temperature 50℃) to remove dissolved oxygen. The nitrogen pressure in the adjacent tower is 18 mmHg (4 mmHg higher than the tower pressure), and the nitrogen pressure in the refining tower is 63 mmHg (5 mmHg higher than the tower pressure). The system oxygen content is ≤30 ppm.

[0087] Example 7 Take 1000 kg of crude privet aldehyde (privet aldehyde 63.5 wt%, acrolein 15.0 wt%, heavy components 21.5 wt%) and pretreat it as in Example 1.

[0088] The operating pressure of the adjacent column is 16 mmHg (absolute pressure), with a top temperature of 81°C and a bottom temperature of 116°C. The pre-separation section has a theoretical number of 22 plates and a reflux ratio of 1.1; the main separation section has a theoretical number of 26 plates and a reflux ratio of 1.9. The MVR compressor has a compression ratio of 2.9, compressing the top vapor from 16 mmHg to 46 mmHg and raising the temperature from 81°C to 134°C (18°C higher than the bottom temperature of 116°C). The operating pressure of the refining column is 65 mmHg (absolute pressure), with a top temperature of 120°C and a bottom temperature of 130°C. The refining column has a theoretical number of 20 plates and a reflux ratio of 2.3. The top vapor temperature of the refining column is 120°C, 4°C higher than the bottom temperature of the adjacent column (116°C), and is directly used as a supplementary heat source for the reboiler of the adjacent column.

[0089] The purification column is equipped with an online GC monitoring system, sampling at 15-minute intervals to monitor the isomer I / II ratio in real time. When the isomer I content is below 78%, the reflux ratio automatically increases by 0.5; when the isomer I content is ≥78%, the current reflux ratio is maintained. The nitrogen pressure in the adjacent column is 20 mmHg (4 mmHg higher than the column pressure), and the nitrogen pressure in the purification column is 70 mmHg (5 mmHg higher than the column pressure). The system oxygen content is ≤42 ppm.

[0090] Example 8 Take 1000 kg of crude privet aldehyde (privet aldehyde 70.8 wt%, acrolein 9.5 wt%, heavy components 19.7 wt%) and pretreat it as in Example 1.

[0091] The operating pressure of the adjacent column is 11 mmHg (absolute pressure), with a top temperature of 76°C and a bottom temperature of 110°C. The pre-separation section has a theoretical number of 24 plates and a reflux ratio of 0.7; the main separation section has a theoretical number of 29 plates and a reflux ratio of 1.4. The MVR compressor has a compression ratio of 3.4, compressing the top vapor from 11 mmHg to 37 mmHg and raising the temperature from 76°C to 142°C (32°C higher than the bottom temperature of 110°C). The operating pressure of the refining column is 45 mmHg (absolute pressure), with a top temperature of 108°C and a bottom temperature of 122°C. The refining column has a theoretical number of 17 plates and a reflux ratio of 1.9. The top vapor from the refining column is pressurized and heated by a heat pump compressor (compression ratio 1.6) and then used as a supplementary heat source for the reboiler of the adjacent column.

[0092] The crude product is first deoxygenated in a degasser (absolute pressure 70 mmHg, temperature 45℃) before entering the preheater. The refining column is equipped with online GC monitoring, with a sampling interval of 10 minutes, and the target content of isomer I is set at 80%. The nitrogen pressure in the adjacent column is 15 mmHg (4 mmHg higher than the column pressure), and the nitrogen pressure in the refining column is 50 mmHg (5 mmHg higher than the column pressure). The system oxygen content is ≤28 ppm.

[0093] Example 9 Take 1000 kg of crude privet aldehyde (privet aldehyde 67.3 wt%, acrolein 11.8 wt%, heavy components 20.9 wt%) and pretreat it as in Example 1.

[0094] The operating pressure of the adjacent column is 17 mmHg (absolute pressure), with a top temperature of 82°C and a bottom temperature of 117°C. The pre-separation section has a theoretical number of 21 plates and a reflux ratio of 1.0; the main separation section has a theoretical number of 27 plates and a reflux ratio of 2.1. The MVR compressor has a compression ratio of 2.7, compressing the top vapor from 17 mmHg to 46 mmHg and raising the temperature from 82°C to 131°C (14°C higher than the bottom temperature of 117°C). The operating pressure of the refining column is 70 mmHg (absolute pressure), with a top temperature of 122°C and a bottom temperature of 132°C. The refining column has a theoretical number of 23 plates and a reflux ratio of 2.6. The top vapor temperature of the refining column is 122°C, 5°C higher than the bottom temperature of the adjacent column (117°C), and is directly used as a supplementary heat source for the reboiler of the adjacent column.

[0095] The purification column is equipped with online GC monitoring with a sampling interval of 20 minutes, and the target content of isomer I is set at 77%. The nitrogen pressure in the adjacent column is 21 mmHg (4 mmHg higher than the column pressure), the nitrogen pressure in the purification column is 75 mmHg (5 mmHg higher than the column pressure), and the oxygen content in the system is ≤45 ppm.

[0096] Example 10 Take 1000 kg of crude privet aldehyde (privet aldehyde 72.1 wt%, acrolein 8.2 wt%, heavy components 19.7 wt%) and pretreat it as in Example 1.

[0097] The operating pressure of the adjacent column is 13 mmHg (absolute pressure), with a top temperature of 77°C and a bottom temperature of 112°C. The pre-separation section has a theoretical number of 23 plates and a reflux ratio of 0.8; the main separation section has a theoretical number of 28 plates and a reflux ratio of 1.7. The MVR compressor uses a two-stage compression, with a compression ratio of 1.7 per stage and a total compression ratio of 2.89, compressing the top vapor from 13 mmHg to 38 mmHg and raising the temperature from 77°C to 138°C (26°C higher than the bottom temperature of 112°C). The operating pressure of the refining column is 58 mmHg (absolute pressure), with a top temperature of 116°C and a bottom temperature of 128°C. The refining column has a theoretical number of 19 plates and a reflux ratio of 2.2. The top vapor of the refining column is pressurized and heated by a heat pump compressor (compression ratio 1.3) and then used as a supplementary heat source for the reboiler of the adjacent column.

[0098] The crude product is first deoxygenated by a degasser (absolute pressure 55 mmHg, temperature 48℃). The refining column is equipped with online GC monitoring, with a sampling interval of 12 minutes, and the target content of isomer I is set at 79%. The nitrogen pressure in the adjacent column is 17 mmHg (4 mmHg higher than the column pressure), and the nitrogen pressure in the refining column is 63 mmHg (5 mmHg higher than the column pressure). The system oxygen content is ≤32 ppm.

[0099] Comparative Example 1 Take 1000 kg of crude privet aldehyde (privet aldehyde 68.5 wt%, acrolein 11.2 wt%, heavy components 20.3 wt%), the same as in Example 1, and perform alkaline washing and water washing pretreatment according to the method in Example 1.

[0100] The pretreated crude product is sequentially fed into a three-column series distillation system consisting of a light component removal column, a medium component removal column, and a refining column. The light component removal column operates at 15 mmHg (absolute pressure), with a top temperature of 80°C and a reflux ratio of 2.0, removing light components such as acrolein. The medium component removal column operates at 15 mmHg (absolute pressure), with a top temperature of 85°C and a reflux ratio of 1.5, performing pre-separation of privet aldehyde from heavy components. The refining column operates at 15 mmHg (absolute pressure), with a top temperature of 88°C and a reflux ratio of 2.5, performing final refining. The vapors from the top of each column are condensed using circulating water, and the reboiler is heated by live steam. Nitrogen gas is only introduced for protection during the product collection stage of the distillation process.

[0101] Comparative Example 2 Take 1000 kg of crude privet aldehyde, the same as in Example 1, and pretreat it according to the method in Example 1.

[0102] The same partitioned column structure as in Example 1 was used (22 pre-separation sections, 28 main separation sections, operating pressure 15 mmHg, top temperature 80°C, bottom temperature 115°C, reflux ratio 1.0 / 1.8). The crude privet aldehyde product collected from the side stream was fed into the refining column (20 theoretical plates, operating pressure 15 mmHg, reflux ratio 2.2) for final refining. However, the top vapor of the partitioned column was not compressed by MVR and was directly condensed by circulating water; the top vapor of the refining column was also condensed by circulating water, without inter-column thermal coupling. The bottoms of both columns were heated by external live steam. Nitrogen gas was used for protection throughout the entire process.

[0103] Comparative Example 3 Take 1000 kg of crude privet aldehyde, the same as in Example 1, and pretreat it according to the method in Example 1.

[0104] The same partitioned tower structure and MVR heat pump system as in Example 1 were used, but the MVR compressor compression ratio was only 2.0, compressing the top steam from 15 mmHg to 30 mmHg and raising the temperature from 80°C to 115°C. The compressed steam temperature of 115°C is the same as the bottom temperature of the partitioned tower (115°C), resulting in a 0°C heat transfer temperature difference, making effective heat exchange impossible. External live steam is required to assist in heating the bottom of the tower. The crude privet aldehyde product from the side stream enters the refining tower (20 theoretical plates, operating pressure 15 mmHg, reflux ratio 2.2) for final refining. No differential pressure thermal coupling is established between the refining tower and the partitioned tower; the top steam of the refining tower is condensed by circulating water. The bottoms of both towers are heated jointly by external live steam and the MVR heat pump system. Nitrogen gas is used for protection throughout the process.

[0105] The above embodiments and comparative examples were tested using the following methods: Product purity and isomer ratio were determined using gas chromatography (GC). Sample preparation: Take about 1 μL of privet aldehyde sample and inject it directly with a microsyringe, or dilute it with an appropriate solvent (such as anhydrous ethanol) before injection.

[0106] Chromatographic separation: Under specified chromatographic conditions, the sample is separated by a capillary column, and each component elutes in sequence according to its retention time.

[0107] Quantitative calculation: The content of privet aldehyde was calculated using the area normalization method. The chromatographic peak area of ​​the main component of privet aldehyde was recorded, and its percentage content in the sample was calculated.

[0108] Overall distillation yield: based on actual operational metering and material balance of the examples and comparative studies.

[0109] Calculation formula: , Where: Y is the overall distillation yield (%); m 成品 The weight of the finished product of privet aldehyde (kg); P 成品 Purity of privet aldehyde in the finished product (%); m 粗品 Mass of crude privet aldehyde (kg); P 粗品 The percentage of privet aldehyde in the crude product is %.

[0110] Total energy consumption data was calculated using energy metering data from the actual operation of each embodiment and comparative example. Energy consumption items included steam consumption, circulating water consumption, and electricity consumption. Total energy consumption was calculated according to the "Requirements for the Configuration and Management of Energy Metering Instruments in Chemical Enterprises" (GB / T 21367) and the "General Rules for Calculating Comprehensive Energy Consumption" (GB / T 2589), by uniformly converting different forms of energy such as steam, circulating water, and electricity into standard coal (or equivalent electricity) before summing and comparing.

[0111] The above-mentioned Examples 1-10 and Comparative Examples 1-3 were tested respectively, and the data obtained are shown in Table 1 below: Table 1

[0112] Note: Total energy consumption is based on Comparative Example 1 (conventional three-tower series distillation) as 100% of the baseline value.

[0113] In summary, the purity of the privet aldehyde products in all embodiments of the present invention is between 99.4% and 99.7%, which is significantly better than the 99.1% of Comparative Example 1. This indicates that the partition column eliminates the backmixing effect of intermediate components and the secondary purification effect of the purification column. Among them, the purity of the products in Examples 3, 6, and 10 reaches 99.7%, which is the highest among all examples. According to the QB / T 4651-2014 standard, the privet aldehyde content (GC) of the product must meet the corresponding indicators, and all embodiments of the present invention far exceed the standard requirements.

[0114] The content of isomer I in each embodiment of the present invention ranged from 76.8% to 80.2%, all higher than the 74.5% in Comparative Example 1. Examples 8 (80.2%) and 10 (79.3%) showed the best performance, demonstrating the precise control of the isomer ratio by the online GC intelligent reflux ratio control system. The lower content of isomer I in the comparative examples (comparative Example 1 was only 74.5%) indicates insufficient selectivity for isomer separation by traditional distillation processes.

[0115] The overall distillation yields of the various embodiments of this invention ranged from 94.4% to 96.5%, all superior to the 93.0% of Comparative Example 1. This indicates that continuous independent nitrogen protection effectively suppressed the thermosensitive oxidation and polymerization side reactions of privet aldehyde. Among them, Example 10 achieved the highest yield (96.5%), which was 3.5 percentage points higher than the conventional process.

[0116] The total energy consumption of the various embodiments of the present invention is 29.8%-34.2% of that of the conventional process, i.e., energy saving of 65.8%-70.2%. Among them, embodiments 8 and 10 have the lowest energy consumption (29.8% and 30.0% respectively), and the best energy saving effect. Comparative Example 2 (only the adjacent tower) saves about 32.0% of energy, and Comparative Example 3 (adjacent tower + MVR, but insufficient compression ratio) saves about 52.0% of energy. The triple energy saving method (MVR heat pump + adjacent tower + differential pressure thermal coupling) of the various embodiments of the present invention has a significant energy saving effect.

[0117] In Comparative Example 3, the MVR compression ratio was only 2.0, and the steam temperature after compression was only 115°C, the same as the bottom temperature of the adjacent tower (115°C). The heat transfer temperature difference was 0°C, making effective heat exchange impossible. In the embodiments of this invention, the compression ratio is between 2.5 and 3.5, and the steam temperature after compression is 10-32°C higher than the bottom temperature, ensuring the effective operation of the MVR heat pump system.

[0118] Each embodiment of the present invention employs independent nitrogen protection, with nitrogen pressure in each tower independently controlled (12-25 mmHg for the adjacent tower, 32-85 mmHg for the purification tower), effectively preventing gas backflow caused by significant pressure differences. The system oxygen content is controlled at 30-50 ppm, effectively suppressing the oxidation side reaction of privet aldehyde, resulting in superior product yield and quality compared to the comparative example.

[0119] The comparison of the various embodiments shows that: the MVR compression ratio between 2.8 and 3.2 yields the best overall performance (Examples 1, 6, 8, and 10); the refining tower operating pressure between 55 and 65 mmHg results in the highest thermal coupling efficiency (Examples 1, 6, and 10); the degasser pretreatment can reduce the system oxygen content to below 30 ppm, further improving product purity and yield (Examples 6, 8, and 10); online GC intelligent control can precisely regulate the isomer I content to the target value (Examples 7-10). The two-stage compression scheme (Examples 4 and 10) reduces the single-stage compression load while maintaining a high compression ratio, thus improving compressor efficiency.

[0120] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-efficiency and energy-saving distillation separation process for privet aldehyde, characterized in that, Includes the following steps: After pretreatment by alkali washing and water washing, the crude privet aldehyde is sent to the adjacent column for distillation separation. The steam at the top of the adjacent column is compressed and heated by the MVR compressor, and then sent to the reboiler of the adjacent column as a heat source. The crude privet aldehyde product is extracted from the side stream of the adjacent tower and sent to the refining tower for final refining to obtain the finished privet aldehyde product. The operating pressure of the refining column is higher than that of the adjacent column, and the top steam of the refining column serves as a supplementary heat source for the reboiler of the adjacent column. During the distillation separation process, nitrogen gas is independently introduced into the partition column and the refining column for protection, and the nitrogen pressure in each column is 2-5 mmHg higher than the operating pressure of the column.

2. The high-efficiency and energy-saving distillation separation process for privet aldehyde according to claim 1, characterized in that, The partition tower is equipped with a longitudinal baffle, which divides the tower into a pre-separation section and a main separation section. The crude privet aldehyde is fed into the pre-separation section, and the crude privet aldehyde is extracted from the side stream of the main separation section. The operating pressure of the partition tower is 10~20 mmHg absolute, the top temperature is 75~85℃, and the bottom temperature is 105~120℃. The compression ratio of the MVR compressor is 2.5~3.5, which compresses and heats the top vapor to 125~145℃.

3. The high-efficiency and energy-saving distillation separation process for privet aldehyde according to claim 1, characterized in that, The MVR compressor uses a multi-stage compression method, with each stage having a compression ratio of no more than 2.

0.

4. The high-efficiency and energy-saving distillation separation process for privet aldehyde according to claim 1, characterized in that, The bottom of the adjacent tower is also equipped with an auxiliary reboiler, which is heated by external live steam during the process start-up phase or when the MVR compressor is insufficient to ensure stable system operation.

5. The high-efficiency and energy-saving distillation separation process for privet aldehyde according to claim 1, characterized in that, The operating pressure of the refining column is 30~80 mmHg absolute pressure, the top temperature is 95~125℃, and the bottom temperature is 120~135℃. When the top steam of the refining column is used as a supplementary heat source for the reboiler of the adjacent column, the top steam temperature of the refining column is 3~8℃ higher than the bottom temperature of the adjacent column.

6. The high-efficiency and energy-saving distillation separation process for privet aldehyde according to claim 1, characterized in that, Nitrogen gas is independently supplied to the partition tower and the refining tower for protection. Specifically, the main nitrogen gas pipe is connected to an independent nitrogen gas branch for each tower. Each branch is equipped with a precision pressure reducing valve, a back pressure valve, and a pressure sensor. Each branch independently controls the nitrogen gas pressure, so that the nitrogen gas pressure in each tower is 2-5 mmHg higher than the operating pressure of the tower.

7. The high-efficiency and energy-saving distillation separation process for privet aldehyde according to claim 1, characterized in that, Before entering the adjacent tower, the crude privet aldehyde is preheated to 60-70°C by a preheater, the heat source of which comes from the bottom discharge of the refining tower.

8. The high-efficiency and energy-saving distillation separation process for privet aldehyde according to claim 1, characterized in that, It also includes online monitoring of the ratio of privet aldehyde isomer I (2,4-dimethyl-3-cyclohexenylformaldehyde) and isomer II (3,5-dimethyl-3-cyclohexenylformaldehyde) in the overhead distillate of the purification column, and dynamically adjusting the reflux ratio of the purification column based on the monitoring results, including the following steps: When the content of isomer I is lower than the target value, increase the reflux ratio; When the content of isomer I reaches the target value, maintain or reduce the reflux ratio.

9. The high-efficiency and energy-saving distillation separation process for privet aldehyde according to claim 2, characterized in that, The theoretical number of plates in the partition column is 45-55, of which the pre-separation section has 20-25 plates and the main separation section has 25-30 plates; the theoretical number of plates in the refining column is 15-25.

10. The high-efficiency and energy-saving distillation separation process for privet aldehyde according to claim 1, characterized in that, The crude privet aldehyde contains 60-75 wt% privet aldehyde, 5-15 wt% acrolein, and 10-25 wt% high-boiling-point heavy components; the light component fraction of acrolein is collected from the top of the partition column, and the high-boiling-point heavy component fraction is collected from the bottom of the partition column.

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