Separation device and separation method of 1, 4-cyclohexanedimethanol

Abstract

The invention discloses a 1, 4-cyclohexanedimethanol separation device and a separation method, the 1, 4-cyclohexanedimethanol separation device comprises: a tower body, a partition plate vertically arranged in the tower body divides the space in the tower body into a pre-fractionation section and a side line section which are arranged side by side; a rectifying section communicated with the pre-fractionation section and the side line section is formed above the partition plate, and the top of the rectifying section is connected with a condenser; a stripping section communicated with the pre-fractionation section and the side line section is formed below the partition plate, and the bottom of the stripping section is connected with a reboiler; a raw material inlet is formed in the middle of the pre-fractionation section; a product extraction opening is formed in the middle of the side line section; and a fluid channel communicated with the pre-fractionation section and the side line section is formed at the bottom of the partition plate. Direct transverse transfer of a heavy component liquid phase is realized through the fluid channel at the bottom of the partition plate, and a secondary heating process of reboiling of a material at the bottom of the tower is avoided, so that the risk of CHDM thermal degradation is reduced, and the problem of serious polymerization loss in a traditional process is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-performance polyester monomer separation and purification, in particular to a 1,4-cyclohexanedimethanol separation device and method. BACKGROUND

[0002] 1,4-cyclohexanedimethanol (CHDM) is a key monomer for high-performance polyesters, widely used in food packaging, medical devices and other fields, with a growing global market. In the mainstream DMT hydrogenation production process, there are significant technical bottlenecks in the separation process: due to the high normal boiling point of CHDM, which is as high as 283℃, it needs to undergo two high-temperature heating in the traditional two-tower rectification process, which causes the dehydration and dehydrogenation of heat-sensitive materials, resulting in serious product polymerization loss. Patents WO2013019441A1 and CN116037001A both use this two-tower separation process, which not only has high energy consumption - requires two sets of reboiling condensing systems, but also causes separation work waste due to axial backmixing of intermediate component CHDM when its proportion exceeds 80%. Although the dividing wall distillation technology has achieved 15-40% energy saving in the separation of aromatic hydrocarbons (such as CN101429089B) and dihydric alcohol rectification (such as CN104447200B), it still faces special challenges when applied to CHDM system: high-boiling by-products are prone to cause wall plate blockage, and fluctuations in feed components affect control stability, while the separation of cis-trans isomers needs to be addressed.

[0003] Existing technologies attempt to optimize the separation process but still fail to break through the fundamental limitations. For example, Chinese patent CN115054940A discloses a "gas-liquid separation and purification device" that improves separation efficiency through specific structural design: including a separation cylinder, the side wall of the separation cylinder is provided with a drainage cavity, the separation cylinder is provided with a top cover, the top cover is provided with a feed pipe, the feed pipe is provided with a plurality of connecting rods, one end of the connecting rods is provided with an inner cylinder, the inner cylinder is provided with a plurality of reflux grooves, the inner cylinder is provided with a baffle one, the separation cylinder is provided with a condensing disc. This device separates by cooling and solidifying dimethyl terephthalate, although it realizes heat recycling, but it still belongs to the two-tower process derivative technology. This improvement does not solve the core defect of CHDM being heated multiple times, and the dividing wall distillation technology has not been successfully applied in the CHDM separation field. Therefore, developing a dividing wall distillation system that adapts to the characteristics of CHDM material, while ensuring product purity, has become a technical problem that the industry urgently needs to break through. SUMMARY

[0004] The first invention of the scheme is to solve the technical defects of the existing double-tower rectification process, that is, the serious polymerization loss of CHDM caused by multiple heating and the high energy consumption of the equipment. By setting a vertical partition plate in the tower body, the space is divided into a pre-fractionation section and a side line section, and a rectification section and a stripping section connected with the two sections are constructed. In combination with the fluid channel at the bottom of the partition plate, the three components are separated synchronously in a single tower. Thus, the secondary heating link of CHDM is eliminated, the degradation risk of heat-sensitive materials is reduced, and the energy consumption is also reduced.

[0005] The second invention of the scheme is to solve the problem of uneven distribution of feed caused by the CHDM proportion exceeding 80% in the divided wall column. By eccentrically setting the partition plate to expand the volume of the side line section, the mass transfer efficiency of high-concentration materials is optimized.

[0006] The third invention of the scheme is to overcome the defect of insufficient control precision of the double reflux path of the divided wall column. The distributor double branch ends are accurately positioned in a specific area of the tray to avoid the back mixing of light components to the side line section.

[0007] The fourth invention of the scheme is to prevent the gas phase entrainment during the side line extraction from causing fluctuations in product purity. By designing a U-shaped downcomer at a high position combined with a balance pipe, the dynamic stability of the gas-liquid two-phase is maintained.

[0008] In order to achieve the above-mentioned purposes, the following technical solutions are adopted in the present application: A separation device for 1,4-cyclohexanedimethanol, comprising: a tower body, a partition plate vertically arranged inside the tower body divides the space in the tower into a pre-fractionation section and a side line section arranged side by side; a rectification section is formed above the partition plate, which connects the pre-fractionation section and the side line section; a condenser is connected to the top of the rectification section; a stripping section is formed below the partition plate, which connects the pre-fractionation section and the side line section; a reboiler is connected to the bottom of the stripping section; a raw material inlet is arranged in the middle of the pre-fractionation section; and a product outlet is arranged in the middle of the side line section.

[0009] The divided wall rectification device constructed by the scheme divides the space in the tower into a pre-fractionation section and a side line section arranged side by side through a vertical partition plate, forming two physically isolated processing chambers. The rectification section connects the top of the two chambers to receive the rising gas phase flow, and the stripping section connects the bottom of the two chambers to process the descending liquid phase material. This structure compresses the three-component separation process into a single tower, eliminates the repeated heating link of intermediate products, and fundamentally reduces the degradation risk of heat-sensitive materials. The optimization of the tower height and the equipment area significantly reduces the capital cost, and the simplification of the reboiling system directly reduces the energy consumption. Further, the fluid channel is a detachable distribution channel plate, which is provided with different density of through holes, so that gas and liquid can pass through; the through holes with different densities are determined according to the state and particle size of the materials in the pre-fractionation section and the side line section, the aperture of the through holes corresponding to the pre-fractionation section is slightly larger, and the aperture of the through holes corresponding to the side line section is smaller, thereby preventing the product in the side line section from flowing back to the stripping section.

[0010] As preferred, the partition wall is arranged eccentrically relative to the central axis of the tower body, so that the cross-sectional area of the side line section is larger than that of the pre-fractionation section; the bottom of the partition wall forms a fluid passage connecting the pre-fractionation section and the side line section. The eccentric arrangement of the partition wall optimizes the spatial distribution for the high-concentration characteristics of the main product. The enlarged volume of the side line section enhances the processing capacity for CHDM, and the reduced volume of the pre-fractionation section improves the separation efficiency of light components. The use of an asymmetric structure matches the actual material distribution requirements of the vapor-liquid load, effectively suppresses the back-mixing of light components to the side line, and ensures the purity of the main product. The fluid passage connects the stripping section with the pre-fractionation section and the side line section, and the heavy components and part of the CHDM in the pre-fractionation section flow downward into the stripping section for rectification. The heavy components are distilled from the bottom, and the CHDM-rich gas passes through the fluid passage into the side line section for further rectification. Through the arrangement of the partition wall, CHDM is enriched in the side line section, avoiding the back-mixing effect in the rectification tower, thereby achieving the effects of energy saving and improving the purity.

[0011] As preferred, the condenser outlet is connected to the inlet of the reflux tank, the outlet of the reflux tank is connected to the inlet of the distributor through a reflux pump, and the outlet of the distributor extends to the top openings of the rectification section and the side line section, respectively. The condensation reflux system realizes double-path precise control through the distributor. The reflux tank buffers the condensation fluctuation of the gas phase, the reflux pump provides stable hydraulic power, and the distributor divides and delivers the condensed liquid to the top of the rectification section and the side line section. This configuration can solve the coordination problem of the double-reflux path unique to the divided wall column, ensure the stability of the two-section independent reflux parameters, and avoid the risk of local dry plate or flooding.

[0012] As preferred, in the branch pipelines of the distributor outlet, the end of the first branch is located above the uppermost tray of the rectification section, and the end of the second branch is located above the uppermost tray of the side line section. The ends of the two branches of the distributor are located in specific areas above the uppermost tray, ensuring that the reflux liquid uniformly covers the tray surface. The differentiated pattern of the central distribution in the rectification section and the circumferential distribution in the side line section adapts to different vapor-liquid load characteristics, maintaining the stability of the entire tower in fluid mechanics.

[0013] As preferred, the outlet of the reboiler is connected to the bottom of the stripping section, and the bottom of the stripping section is connected to the inlet of the reboiler through a circulating pump to form a reboiling circulation loop. The reboiling circulation loop uses a circulating pump to force the liquid phase of the stripping section to flow through the reboiler, preventing high-boiling heavy components from remaining at the bottom of the tower. The circulation inlet is located at the lowest point to ensure that the material fully participates in the vaporization process, and the outlet gas phase directly returns to maintain system pressure balance, thereby effectively suppressing the risk of coking.

[0014] As preferred, the product sampling outlet is connected to the inlet of an external downcomer, and the top of the downcomer is provided with a balance pipe connected to the gas phase space at the top of the side line section at the other end.

[0015] Further, the downcomer is in U-shaped structure, the top of which is higher than the design liquid level of the side line segment. The gas-liquid dynamic isolation system is constructed by combining the downcomer and the balance pipe, the balance pipe is connected to the top of the downcomer and the gas phase space at the top of the tower, the siphon effect in the production process is eliminated through pressure transmission, in addition, the U-shaped structure forms a liquid seal to block the gas phase channel, the high design of the U-shaped downcomer provides sufficient static pressure head to resist pressure fluctuation in vacuum working condition, completely solves the problem of gas entrainment, maintains the stability of the gas-liquid interface, especially adapts to sudden changes in operating conditions, and guarantees the stability of the purity of the product.

[0016] As preferred, a rotatable baffle is arranged in the fluid channel, and the rotatable baffle is connected to an external operating handle through a rotating shaft penetrating the tower wall. The rotatable baffle is arranged in the fluid channel, and the real-time control of the transfer flow of heavy components can be realized through a mechanical adjusting mechanism. The operator manually optimizes the opening degree according to the change of the working condition, avoids the risk of automatic system failure, improves the flexibility of device operation, and enhances the risk resistance.

[0017] The application also discloses a separation method of 1,4-cyclohexanedimethanol by using the separation device, which comprises the following steps: inputting CHDM-containing raw material liquid through a feed inlet of a pre-fractionation section; performing light component production through the top of a rectification section; performing heavy component production through the bottom of a stripping section; and performing CHDM product production through the middle of a side line section. The operation process is carried out around the single-tower space: the CHDM-containing raw material liquid enters from the middle of the pre-fractionation section, and natural stratification is formed in the tower. The heavy component liquid phase is produced from the bottom of the tower; the light component vapor rises to the top of the rectification section and is partially produced; the heavy component concentrated liquid sinks to the bottom of the stripping section and is continuously discharged; and finally, the high-purity CHDM product is obtained at the middle of the side line section. The whole process only undergoes a single heating and cooling cycle, the equipment pipeline is greatly simplified, and the operator only needs to monitor five key control points. In particular, under the vacuum environment, the U-shaped downcomer cooperates with the balance pipe to form double protection, so that the product production is not disturbed by the gas phase.

[0018] As preferred, the distributor is used to perform the shunting action of the reflux liquid to the top of the rectification section and the top of the side line section. The shunting action of the distributor makes the light component separation and the CHDM purification process decoupled, the double-path independent control adapts to the fluctuation of the feed composition, and the system operation stability is maintained.

[0019] Therefore, the application has the following beneficial effects: The CHDM is separated by single-tower integrated structure, the eccentric partition plate design of the divided-wall rectification tower and the synergistic effect of the multi-hole channel plate are combined, the energy consumption is reduced under the premise of ensuring the product purity of 99.5%, and the polymerization risk caused by secondary heating is eliminated.

[0020] The single-tower structure integrates a pre-fractionation section and a side section, eliminates a second rectifying tower and its supporting reboiling condensing system, reduces the number of equipment and pipeline connection points, and significantly saves energy consumption and investment costs.

[0021] The U-shaped downcomer cooperates with the balance pipe to form a gas-liquid isolation mechanism, prevents gas phase from leaking into the product stream during production, maintains the stability of CHDM purity, and responds to pressure fluctuations under vacuum operation.

[0022] The eccentric arrangement of the partition plate and the rotatable baffle adapt to changes in feed components, optimize material distribution and flow control, improve system operation flexibility, and simplify manual adjustment complexity. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 It is a typical two-tower process schematic diagram of the existing CHDM separation process.

[0024] In the figure: 1-light component rectifying tower; 2-light component overhead condenser; 3-light component overhead reflux tank; 4-light component overhead reflux pump; 5-light component bottom circulating pump; 6-light component bottom reboiler; 7-heavy component rectifying tower; 8-heavy component overhead condenser; 9-heavy component overhead reflux tank; 10-heavy component overhead reflux tank; 11-heavy component bottom circulating pump; 12-heavy component bottom reboiler.

[0025] Figure 2 It is a process schematic diagram of the present application.

[0026] In the figure: 1-dividing wall rectifying tower; 2-pre-fractionation section; 3-side section; 4-distillation section; 5-distillation section; 6-overhead condenser; 7-overhead reflux tank; 8-overhead reflux pump; 9-CHDM product delivery pump; 10-partition plate; 11-bottom recirculation pump; 12-bottom reboiler.

[0027] Figure 3 It is a schematic diagram of the installation of the partition plate in the present application.

[0028] In the figure: 1-dividing wall rectifying tower; 2-pre-fractionation section; 3-side section; 10-partition plate.

[0029] Figure 4 It is a schematic diagram of the installation of the fluid passage in the present application.

[0030] In the figure: 10-partition plate; 101-rotatable baffle; 102-fluid passage; 103-via.

[0031] Figure 5 It is a schematic diagram of the structure of the fluid passage in the present application.

[0032] In the figure: 2-pre-fractionation section; 3-side section; 101-rotatable baffle; 102-fluid passage; 1031-large hole; 1032-small hole. Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Examples of the embodiments are shown in the drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout.

[0034] Example 1 This embodiment discloses a separation device for 1,4-cyclohexanediethanol, comprising: a column body, wherein a vertically arranged partition plate inside the column body divides the column space into a pre-fractionation section and a side stream section arranged side by side; a rectification section connecting the pre-fractionation section and the side stream section is formed above the partition plate, and a condenser is connected to the top of the rectification section; a stripping section connecting the pre-fractionation section and the side stream section is formed below the partition plate, and a reboiler is connected to the bottom of the stripping section; a raw material inlet is provided in the middle of the pre-fractionation section; a product outlet is provided in the middle of the side stream section; and a fluid channel connecting the pre-fractionation section and the side stream section is formed at the bottom of the partition plate.

[0035] The wall-mounted distillation unit constructed in this scheme divides the internal space of the column into a parallel pre-fractionation section and a side-stream section using vertical partition plates, forming physically isolated dual processing chambers. The rectification section connects to the top of the dual chambers to receive the rising gaseous stream, while the stripping section connects to the bottom of the dual chambers to process the descending liquid stream. This structure compresses the three-component separation process into a single column, eliminating the repeated heating of intermediate products and fundamentally reducing the risk of degradation of heat-sensitive materials. The optimization of column height and equipment footprint significantly reduces infrastructure costs, and the simplification of the reboiler system directly reduces energy consumption.

[0036] In this embodiment, the partition plate is eccentrically positioned relative to the central axis of the tower, making the cross-sectional area of ​​the side stream section larger than that of the pre-fractionation section. This eccentric placement of the partition plate optimizes spatial allocation to address the high concentration characteristics of the main product. The increased volume of the side stream section enhances the processing capacity for CHDM, while the reduced volume of the pre-fractionation section improves the separation efficiency of light components. The asymmetric structure ensures that the vapor-liquid load matches the actual material distribution requirements, effectively suppressing backmixing of light components to the side stream and guaranteeing the purity of the main product.

[0037] The condenser outlet is connected to the reflux tank inlet; the reflux tank outlet is connected to the distributor inlet via a reflux pump; the distributor outlet extends to the top opening of the rectification section and the top opening of the side stream section, respectively. The condensation reflux system achieves precise dual-path control through the distributor. The reflux tank buffers fluctuations in vapor-phase condensation, the reflux pump provides stable hydraulic power, and the distributor diverts the condensate to the top of the rectification section and the side stream section. This configuration solves the unique challenge of coordinating the two reflux paths in a split-wall column, ensuring stable reflux parameters for both sections and avoiding the risk of localized dry plate or flooding.

[0038] The branch pipelines of the distributor outlet have a first branch end located above the uppermost tray of the rectifying section and a second branch end located above the uppermost tray of the side-cut section. The reboiler outlet is connected to the bottom of the stripping section; the bottom of the stripping section is connected to the inlet of the reboiler through a circulating pump to form a reboiling circulation loop. The product outlet is connected to the inlet of an external downcomer; the downcomer top is provided with a balance pipe, and the other end of the balance pipe is connected to the top gas phase space of the side-cut section. The downcomer has a U-shaped structure, and the top highest point is higher than the design liquid level height of the side-cut section.

[0039] The two branch ends of the distributor are located in a specific area above the uppermost tray to ensure that the reflux liquid uniformly covers the tray surface. The differentiated mode of the central distribution of the rectifying section and the circumferential distribution of the side-cut section adapts to different vapor-liquid load characteristics and maintains the stability of the whole column in fluid mechanics. The reboiling circulation loop uses a circulating pump to force the liquid phase of the stripping section to flow through the reboiler to prevent high-boiling heavy components from being retained at the bottom of the column. The circulating inlet is located at the lowest point to ensure that the material fully participates in the vaporization process, and the outlet gas phase is directly returned to maintain system pressure balance, thereby effectively suppressing the risk of coking. The combination of the downcomer and the balance pipe forms a gas-liquid dynamic isolation system. The balance pipe connects the top of the downcomer and the top gas phase space of the column, eliminates the siphon effect during the product extraction process through pressure transmission, and forms a liquid seal through the U-shaped structure to block the gas phase channel. The high design of the U-shaped downcomer provides sufficient static pressure head to resist pressure fluctuations in vacuum conditions, completely solves the problem of gas entrainment, maintains the stability of the gas-liquid interface, and especially adapts to sudden changes in operating conditions to ensure the stability of product purity.

[0040] In addition, a rotatable baffle is arranged in the fluid passage of the divided wall rectifying column, and the rotating shaft of the baffle penetrates the column wall horizontally and is connected to an external handwheel operating mechanism. The arc edge of the baffle matches the cross section of the passage, and the effective flow area of the passage is changed by rotating the angle, thereby adjusting the gas distribution ratio from the stripping section to the pre-fractionation section and the side-cut section. The operator rotates the handwheel according to the change of the feed composition, and when the heavy component content increases, the opening is increased to increase the gas flow of the pre-fractionation section; when the light component increases, the opening is reduced to strengthen the rectification effect of the side-cut section. By setting this structure, active control of the gas distribution ratio can be realized, avoiding the risk of automatic valve failure, and at the same time, the product purity stability can be ensured by optimizing the gas flow distribution in real time.

[0041] Specifically, as Figure 2 , 3As shown, in this embodiment, the divided wall rectifying column 1 serves as the device main body, and the vertically arranged dividing wall plate 10 inside the device is a rectangular metal dividing wall plate, extending downward from the top of the column to span 16 theoretical plates, dividing the space inside the column into the pre-fractionation section 2 and the side section 3 side by side. According to the patent claim, the eccentric installation of the dividing wall plate makes the cross-sectional area of the side section 3 larger than that of the pre-fractionation section 2, to meet the processing requirements of CHDM high-concentration materials. The column body is provided with a total of 29 theoretical plates: the 6 plates above the dividing wall plate constitute the rectification section 4, the 7 plates below the dividing wall plate constitute the stripping section 5, and the 16 plates in the area of the dividing wall plate are evenly distributed in the pre-fractionation section 2 and the side section 3. The flange at the top of the rectification section 4 is connected to the column top condenser 6, and the outlet of the condenser is connected to the inlet of the vertical column top reflux tank 7 through a stainless steel pipeline. The outlet at the bottom of the reflux tank 7 is connected to the inlet of the column top reflux pump 8, and the outlet of the column top reflux pump is divided into two paths: one path returns to the top of the column as reflux, and the other path is connected to the inlet of the distributor. The distributor divides the liquid into two independent streams, which are sent to the top of the pre-fractionation section 2 and the top of the side section 3, respectively. The flange at the bottom of the stripping section 5 is connected to the inlet of the column bottom reboiler 10, and the outlet of the reboiler is directly connected to the gas phase space at the bottom of the stripping section 5 through a short pipe. The liquid phase outlet at the bottom of the stripping section 5 is connected to the inlet of the reboiler 10 through the column bottom recirculation pump 11, forming a forced circulation loop. The flange at the middle of the side section 3 is connected to the inlet of the CHDM product delivery pump 9, realizing continuous product extraction. The raw material feeding pipe is welded in the middle of the pre-fractionation section 2, corresponding to the 7th theoretical plate.

[0042] When the system is running, the CHDM-containing raw material liquid is input from the middle of the pre-fractionation section 2, and initial separation is achieved under the action of the column plates: the light components vapor rise to the rectification section 4, and the heavy components liquid sink to the upper part of the stripping section 5. The materials in the side section 3 form a CHDM concentration peak area at the 14th theoretical plate from the top of the side section under the synergistic action of the descending liquid phase in the rectification section 4 and the ascending gas phase in the stripping section 5. The light component vapor at the top of the rectification section 4 is liquefied into the reflux tank 7 through the condenser 6, and the reflux pump 8 delivers the condensed liquid to the distributor, which injects the liquid into the top of the pre-fractionation section 2 and the side section 3 according to the actual demand ratio, maintaining independent reflux control of the two sections. The CHDM product extracted from the middle of the side section 3 is guided out of the system by the delivery pump 9. The heavy components at the bottom of the stripping section 5 are forced to flow through the reboiler 10 by the recirculation pump 11, part of which is vaporized and returned to the column, and the non-vaporized residual liquid is continuously extracted. This structure realizes threefold optimization: first, the heavy components are exempted from secondary heating, directly reducing the risk of CHDM thermal degradation; second, the single column integrates dual functional zones, reducing the number of equipment connection points by 70%, significantly reducing the leakage probability; third, the eccentric dividing wall plate 10 optimizes space distribution, expanding the volume of the side section 3 to match the CHDM high-concentration characteristics, which has been verified to improve mass transfer efficiency by more than 10%.

[0043] The dual independent control of the liquid distributor decouples the light component separation from the CHDM purification process, significantly enhancing the ability to cope with fluctuations in feedstock composition. The recirculation pump 11 is designed to force flow in the stripping section 5, preventing the retention of high-boiling substances from coking, and its inlet is located at the lowest point in the tower bottom to ensure that the material is fully involved in the circulation. The tower body sealing structure adopts double mechanical seals to meet the needs of boiling point reduction and ensure system safety. Test data show that this structure shortens the residence time of CHDM in the side line section 3 to 35 minutes, more than 50% less than the traditional process, and the product purity is stably maintained above 99.5%. The overall equipment passes through space reconstruction and path optimization, simplifying the 16 control parameters of the traditional double-tower system to 5 core nodes, namely the feed amount, transfer rate, and three-way output, improving system stability, and the reboiler 10 energy consumption of 42 kW confirms the significant optimization of heat energy utilization efficiency.

[0044] Before starting the device, the system needs to complete the gas tightness test and nitrogen replacement. The operator first starts the tower bottom recirculation pump 11 to establish the liquid phase circulation flow in the stripping section 5, and then slowly increases the heat load of the tower bottom reboiler 10, with a temperature rise rate of not more than 25°C per hour. When the bottom temperature of the stripping section 5 approaches the boiling point of the heavy component, the CHDM-containing raw material liquid is pumped in through the feed inlet at the position of the 7th theoretical plate in the middle of the pre-fractionation section 2, and the initial feed amount is controlled at 30% of the design flow. As the material continues to be input, the heavy component liquid phase naturally settles under the action of gravity. At this time, the light component vapor begins to accumulate at the top of the rectification section 4, and the tower top condenser 6 is started to liquefy the vapor and flow into the tower top reflux tank 7.

[0045] When the liquid level of the reflux tank 7 reaches the operating line, the tower top reflux pump 8 is started to transport the condensed liquid to the liquid distributor. The distributor divides the liquid into two independent streams according to the preset ratio: one is sent to the top of the pre-fractionation section 2 to maintain the separation of the light component, and the other is sent to the top of the side line section 3 to promote the purification of CHDM. When the temperature in the middle of the side line section 3 stabilizes in the CHDM boiling point characteristic interval, the CHDM product delivery pump 9 is started to be taken out, and the initial output is set to 50% of the design value. At the same time, the heat load of the reboiler 10 is adjusted to continuously discharge the heavy component residue at the bottom of the stripping section 5.

[0046] During stable operation, the operator monitors five core parameters: feed flow, fluid channel material transfer state, rectification section top output, side line section 14th theoretical plate temperature, and stripping section heavy component discharge temperature. The vacuum system maintains a tower top pressure of 0.01 bar, and under this condition, the CHDM boiling point is reduced to the process safety range.

[0047] The actual operation data shows that the device needs 8 hours of operation cycle from cold start to output qualified CHDM products. When the feed composition fluctuates ± 15%, the system can recover to steady state within 90 minutes by synchronously adjusting the distributor split ratio and the reboiler 10 load. In daily operation, the CHDM concentration at the 14th theoretical plate of the side line section 3 is continuously stabilized above 99.5%, and the recovery rate is maintained at 98.5%. The temperature monitoring of the heavy component outlet can effectively prevent coking, and the forced flow of the tower bottom recirculation pump 11 shortens the residence time of the heavy component in the high temperature zone.

[0048] When the planned shutdown operation is performed, the feed is first cut off, and after the materials in the tower are completely discharged through the product pump 9 and the heavy component outlet, the nitrogen blowing program is executed. In abnormal condition handling, if the distributor is stuck, it can be switched to manual mode to independently control the two section reflux amounts; when the heat source of the reboiler 10 is unexpectedly interrupted, the basic separation function can still be maintained for 30 minutes relying on the heat storage in the tower. The equipment installation needs to ensure that the distance between the bottom of the fluid passage and the tower bottom is greater than the height of the heavy component liquid layer, and the height difference between the two branches of the distributor is strictly controlled within 5 mm to avoid hydraulic imbalance. The test record of 120 hours of continuous operation shows that the heat load of the reboiler 10 is stably maintained at 42 kW, and there is no equipment blockage caused by material polymerization. The single tower structure reduces the external connection points by 70%, and the equipment maintenance cycle is extended to 1.5 times of the traditional process.

[0049] Example 2 In this embodiment, the dividing wall column is used as the core equipment, and the vertically arranged dividing wall plate 10 in the column is made of stainless steel, which extends from the top of the column to span 16 theoretical plates, and divides the space in the column into a pre-fractionation section and a side line section side by side. According to the right book requirement, the eccentric installation of the dividing wall plate makes the cross-sectional area of the side line section larger than that of the pre-fractionation section, which is suitable for the material characteristics that CHDM accounts for more than 80% in the feed. The column body is provided with a total of 29 sieve trays: 6 sieve trays above the dividing wall plate constitute the rectifying section, and 7 sieve trays below the dividing wall plate constitute the stripping section. The top of the rectifying section is connected with a shell-and-tube type column top condenser through a flange, and the outlet of the condenser is connected with a vertical column top reflux tank through a stainless steel pipeline. The bottom outlet of the reflux tank is connected with a centrifugal column top reflux pump, and the outlet of the centrifugal column top reflux pump is divided into two routes through a three-way valve: one route returns to the top of the column as reflux, and the other route is connected with the inlet of the liquid distributor. The liquid distributor divides the liquid into two independent streams, which are respectively sent to the distributors at the top of the pre-fractionation section and the top of the side line section. The bottom of the stripping section is connected with the reboiler inlet through a flange, and the outlet of the reboiler is directly connected with the gas phase space at the bottom of the stripping section through a short pipe. The liquid phase outlet at the bottom of the stripping section is connected with the reboiler inlet through a high-temperature resistant circulating pump to form a forced circulation loop, and the outlet branch of the circulating pump is connected with the heavy component outlet pipeline. The product sampling pipe is welded at the 14th theoretical plate in the middle of the side line section, and is connected with a gear type CHDM conveying pump. The feed inlet is arranged in the middle of the pre-fractionation section, and the position corresponds to the 7th theoretical plate from the top of the section. In addition, as shown in the figure, the pre-fractionation section is provided with a liquid level controller, and the liquid level controller is connected with the liquid distributor through a control line. Figure 4 、 5As shown in the embodiment, the partition wall plate 10 adopts an adjustable partition wall plate assembly that can be adjusted in the width direction, ensuring complete isolation of the pre-fractionation section 2 and the side line section 3 while being able to be adjusted according to the material quantity on both sides. The adjustable partition wall plate assembly includes a partition wall plate and a rotatable baffle plate 101 arranged at the bottom of the partition wall plate. The through holes 103 arranged on the fluid passage include large holes 1031 and small holes 1032 with different hole diameters arranged on both sides of the partition wall plate. The large holes 1031 match the pre-fractionation section, and the small holes 1032 match the side line section, preventing the product of the side line section from flowing back to the distillation section again.

[0050] The system airtightness detection and nitrogen replacement are performed before the device is started. The operator first starts the tower bottom recirculation pump to establish the distillation section liquid phase flow. The reboiler heat load is increased at a temperature rise rate of 20°C per hour, and when the bottom temperature of the distillation section reaches the initial boiling point interval of the heavy component, the DMT two-stage hydrogenation product is pumped into the pre-fractionation section through the 7th theoretical plate feed port. The feed composition strictly follows the data of the embodiment: a total flow of 381.12 kg / h, of which CHDM is 365.65 kg / h, light components (including MCHC, methanol, etc.) are 15.49 kg / h, and heavy components (including HMCME, HEX, etc.) are 14.98 kg / h. In this embodiment, the initial feed quantity can be set to 110 kg / h. After the material enters the pre-fractionation section, gas-liquid separation is achieved under the action of the tower plate: about 145.7 kg / h of CHDM gas phase rises with the light components to the rectification section, and about 283.4 kg / h of CHDM liquid phase sinks with the heavy components. The heavy component liquid phase sinks to the distillation section through the through channel at the bottom of the partition wall plate, which relies on gravity and does not require mechanical transportation.

[0051] When the top temperature of the rectification section drops to about 95°C, the tower top condenser is started to liquefy the light component vapor, and the condensed liquid flows into the tower top reflux tank. When the liquid level of the reflux tank reaches 50% of the operating liquid level, the tower top reflux pump is started to transport to the distributor at a flow rate of 85 kg / h. The distributor divides the liquid according to the preset ratio: the flow rate transported to the top of the pre-fractionation section accounts for 60%, and the flow rate transported to the top of the side line section accounts for 40%. This shunt ratio is dynamically adjusted according to the feed composition. When the temperature of the 14th theoretical plate of the side line section is stable at 210°C, which corresponds to the boiling point of CHDM at 0.01 bar pressure, the CHDM product delivery pump is started to be extracted, and the initial extraction quantity is set to 180 kg / h, which is gradually increased to 362 kg / h according to the tower plate temperature distribution gradient. At the same time, three core parameters are monitored: the light component extraction flow rate at the top of the rectification section is strictly maintained at 5.5 kg / h, the CHDM purity of the side line section middle extraction sample is confirmed to be not less than 99.5% through testing, and the heavy component extraction quantity at the bottom of the distillation section is stable at 14.6 kg / h. The reboiler heat load is finally adjusted to 42 kW, and the vacuum system maintains the tower top operating pressure at 0.01 bar through the pressure regulating valve.

[0052] The material balance was verified by real-time monitoring: the total amount of feedstock was 381.12 kg per hour, which was equal to 5.5 kg per hour of light component, 362 kg per hour of CHDM and 14.6 kg per hour of heavy component. The calculated CHDM recovery rate was 362 divided by 365.65 multiplied by 100%, i.e. 98.5%. During the operation, the pressure difference of the fluid channel was monitored, and when the pressure difference exceeded 0.5 kPa, the opening of the channel was increased to prevent flooding; the temperature gradient of the side line section was maintained at 8°C per plate from the 10th to 18th plate, and if the gradient was abnormal, the shunt ratio of the distributor to the side line section was adjusted. The gasification rate at the outlet of the reboiler was controlled in the range of 25-30%, which was achieved by adjusting the frequency of the circulating pump.

[0053] When the CHDM concentration in the feedstock was increased to 380 kg per hour, the operator increased the shunt ratio of the distributor to the side line section to 45%, and at the same time, the heat load of the reboiler was increased to 45 kW, and the system recovered to steady state within 2 hours. If the pressure was increased to 0.015 bar due to fluctuations in the vacuum system, the temperature of the 14th plate of the side line section was increased by 3°C, at which time the standby vacuum pump was automatically started, and the CHDM purity fluctuation was controlled within 0.15%. A temperature monitoring point was set in the heavy component outlet pipeline, and when the temperature dropped by 5°C, it was judged that the reboiling efficiency was reduced, triggering the circulating pump speed-up program. The continuous operation record showed that the CHDM purity was stable in the range of 99.5%-99.7%, the CHDM residual amount in the heavy component was less than 0.8%, and the steam consumption per ton of product was 1.8 tons, which was 27.6% lower than that of the traditional process.

[0054] The comparative example of the present application used a two-tower rectification separation process for CHDM separation. The feedstock properties of the comparative example were consistent with Examples 1 and 2, and were shown in Table 1: Table 1 The comparative example used a sequential separation process, as shown in Figure 1As shown, the feed stream enters the 7th tray of the light component rectifying tower 1, the light component is condensed by the overhead condenser 2 and enters the reflux tank 3, the reflux is controlled by the reflux pump 4, and finally the overhead take-off flow rate is 5.5 kg / h; the CHDM and heavy component are transported from the bottom of the tower by the circulating pump 5 and heated by the reboiler 6, and then enter the 6th tray of the heavy component rectifying tower 7. In the heavy component tower, the CHDM product is condensed by the overhead condenser 8 and enters the reflux tank 9, which is controlled by the reflux pump 10, and the heavy component is discharged from the bottom of the tower by the circulating pump 11 and the reboiler 12. The purity and recovery rate of the CHDM product are set to 99.5% and 98.5%, respectively. The light component tower 1 has a total of 16 trays, and the bottom heat load is provided by the reboiler 6, which is 4.68 kW; the heavy component tower 7 has a total of 13 trays, and the bottom heat load is provided by the reboiler 12, which is 53.3 kW; the total number of trays of the two towers is 29, and the total heat load is 57.98 kW. This sequential separation method avoids the high temperature operation of reverse separation and prevents the decomposition of the heat-sensitive material CHDM.

[0055] Comparative analysis: In Examples 1 and 2, the total energy consumption of the divided wall rectifying tower is 42 kW, and in the comparative example, the total energy consumption of the light component tower and the heavy component tower is 57.98 kW, so compared with the comparative example, the energy consumption of the present scheme is saved by about 27.6%.

[0056] In terms of tower equipment cost, the total number of trays used in the examples and the comparative example process is the same, but the divided wall rectifying tower has only one condensation and reboiling system, while the comparative example needs two condensation and reboiling systems; at the same time, the divided wall rectifying tower has only one tower shell, and the required packing is less than that of the traditional two rectifying towers, thereby realizing a certain degree of equipment investment saving.

[0057] The divided wall rectifying tower in Example 1 only occupies one set of conventional rectifying tower equipment area, while the traditional two towers occupy two sets of conventional rectifying tower equipment area. When the factory land area is tight, the example has a great advantage.

Claims

1. A separation device for 1,4-cyclohexanediethanol, characterized in that... include: The tower body, wherein vertically arranged partition plates inside the tower body divide the internal space into a pre-fractionation section and a side-line section; Above the partition plate, a rectification section is formed, connecting the pre-fractionation section and the side stream section, with a condenser connected to the top of the rectification section; below the partition plate, a stripping section is formed, connecting the pre-fractionation section and the side stream section, with a reboiler connected to the bottom of the stripping section; a raw material inlet is provided in the middle of the pre-fractionation section; a product outlet is provided in the middle of the side stream section; and a fluid channel is formed at the bottom of the partition plate, connecting the pre-fractionation section and the side stream section.

2. The separation device according to claim 1, characterized in that: The partition plate is eccentrically positioned relative to the central axis of the tower body, so that the cross-sectional area of ​​the side section is larger than that of the pre-fractionation section.

3. The separation device according to claim 1, characterized in that: The condenser outlet is connected to the reflux tank inlet; the reflux tank outlet is connected to the distributor inlet via a reflux pump; the distributor outlet extends to the top opening of the rectification section and the top opening of the side section, respectively.

4. The separation device according to claim 3, characterized in that: In the branch pipeline of the distributor outlet, the end of the first branch is located above the uppermost tray of the rectification section, and the end of the second branch is located above the uppermost tray of the side stream section.

5. The separation device according to claim 1, characterized in that: The reboiler outlet is connected to the bottom of the stripping section; the bottom of the stripping section is connected to the reboiler inlet via a circulation pump, forming a reboiler circulation loop.

6. The separation device according to claim 1, characterized in that: The product outlet is connected to the inlet of an external downcomer; a balance pipe is installed at the top of the downcomer, and the other end of the balance pipe is connected to the gas phase space at the top of the side section.

7. The separation device according to claim 6, characterized in that: The downcomer has a U-shaped structure, with its highest point being higher than the designed liquid level height of the side section.

8. The separation device according to any one of claims 1-7, characterized in that: A rotatable baffle is installed inside the fluid channel, and the rotatable baffle is connected to an external operating handle via a rotating shaft that passes through the tower wall.

9. A separation method, employing the apparatus of claim 1, characterized in that... include: The CHDM-containing feed liquid is fed through the pre-fractionation section inlet; The transfer of the liquid phase from the pre-fractionation section to the side section is performed through the fluid channel; Light components are extracted via the top of the rectification section; Heavy components are extracted by means of the bottom of the stripping section; CHDM product extraction is performed through the middle of the side segment.

10. The separation method according to claim 9, characterized in that: The distributor performs the function of diverting the reflux liquid to the top of the rectification section and the top of the side section.

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