Separation method and system of 1, 4-butanediol

Abstract

The invention relates to the technical field of chemical engineering, and discloses a separation method and system of 1, 4-butanediol, and the separation method comprises the following steps: concentrating and dehydrating a feed containing 1, 4-butanediol in a rectifying tower; and introducing a concentrated solution at the bottom of the rectifying tower into a dividing wall tower for refining, carrying out heat exchange on a gas-phase component evaporated from the top of the dividing wall tower and a heat exchanger at the bottom of the rectifying tower, and extracting 1, 4-butanediol from the discharge side of the dividing wall tower. According to the present invention, with the partition rectification structure in the dividing wall column, the light component and the heavy component are effectively shunted in the column, the high-purity 1, 4-butanediol can be directly extracted from the middle side line, and the accumulation of the near-boiling impurities in the side line region is reduced; the tower top steam of the dividing wall tower is used for heating the rectifying tower kettle, efficient coupling and recycling of heat between towers are achieved, the heat transfer efficiency is improved, the externally supplied steam consumption is remarkably reduced, and therefore the overall energy consumption in the separation process is reduced.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, specifically to a method and system for separating 1,4-butanediol. Background Technology

[0002] 1,4-Butanediol is an important basic organic chemical raw material, widely used in the preparation of thermoplastic polyurethane (TPU), polytetrahydrofuran (PTMEG), spandex, and biodegradable plastics such as polybutylene terephthalate (PBAT) and polybutylene adipate (PBS). With increasingly stringent environmental requirements, replacing traditional non-biodegradable plastics with biodegradable plastics has become an industry trend. However, biodegradable materials are relatively expensive, and the high energy consumption in the 1,4-butanediol production process is a significant factor restricting cost reduction and limiting large-scale application. Even in the currently relatively low-cost acetylene-aldehyde process, the energy consumption in the 1,4-butanediol refining stage remains high, urgently requiring new processes and procedures to achieve both energy and cost reductions.

[0003] In existing technologies, various improved schemes have been proposed for the purification of 1,4-butanediol. For example, some technologies introduce compound extractants to increase the relative volatility between 1,4-butanediol and near-boiling byproducts such as 2-(4-hydroxybutoxy)tetrahydrofuran, thereby obtaining 1,4-butanediol products with extremely high purity, reducing 1,4-butanediol loss, and achieving high separation efficiency. However, such processes require specialized extraction towers, extractant recovery and regeneration units, resulting in complex system processes, large equipment investments, and the energy consumption of extractant recycling itself, indicating room for improvement in overall energy efficiency.

[0004] Other technical solutions disclose multi-effect distillation processes that connect multiple units in series for 1,4-butanediol dehydration, desalting, residue removal, and product purification. These systems incorporate internal heat optimization, improving the recovery rate and purity of 1,4-butanediol through measures such as n-butanol recovery and residual 1,4-butanediol re-recovery. However, such systems typically involve multiple distillation columns, resulting in complex structures and high equipment investment and operating costs. In particular, dehydration and concentration columns often employ parallel arrangements of pressurized and vacuum dehydration columns, while retaining separate overhead condensers and reboilers for both atmospheric and vacuum concentration columns. This makes it difficult to efficiently match the heat generated at the top of the atmospheric column with the heat required by the vacuum column, leading to insufficient utilization of the heat gradient.

[0005] In the acetylacetonate process, the resulting 1,4-butanediol mixture contains only about half 1,4-butanediol, with the remainder mainly consisting of water and low-boiling substances such as n-butanol, hydroxybutyraldehyde, pentanediol, and methylbutanediol, as well as high-boiling substances such as 2-(4-hydroxybutoxy)tetrahydrofuran, sodium formate, and tar. Current production processes often employ conventional distillation for purification, typically involving multiple distillation columns, including a concentration column, a salt column, a high-boiling column, and a low-boiling column. First, water and butanol are separated in the concentration column, followed by the sequential removal of tar, high-boiling substances, and low-boiling substances. Because 1,4-butanediol accounts for only half of the raw material, the amount of evaporation required for distillation is relatively large. At the same time, 1,4-butanediol has a high boiling point and its boiling point is close to that of key impurities such as 2-(4-hydroxybutoxy)tetrahydrofuran and methyl-butanediol, making separation difficult. A high reflux ratio must be used to meet the purity requirements of the product, which requires a large amount of steam. The energy consumption of the distillation unit often accounts for more than half of the energy consumption of the entire production process, keeping the production cost of 1,4-butanediol products high. Summary of the Invention

[0006] This invention provides a method and system for separating 1,4-butanediol, which solves the problems of complex purification processes, numerous distillation towers, and the need for sequential separation of light and heavy components in multiple distillation towers in the prior art, resulting in insufficient utilization of heat in the cascade, leading to high steam consumption, high energy consumption, and high equipment investment.

[0007] In a first aspect, the present invention provides a method for separating 1,4-butanediol, comprising the following steps: The feed containing 1,4-butanediol is concentrated and dehydrated in a distillation column; The concentrate from the bottom of the distillation column is introduced into a separate column for purification. The vapor phase from the top of the separate column is exchanged with the heat exchanger at the bottom of the distillation column, and 1,4-butanediol is collected from the outlet side of the separate column.

[0008] The feed containing 1,4-butanediol includes 1,4-butanediol, water, n-butanol, hydroxybutyraldehyde, pentanediol, methylbutanediol, 2-(4-hydroxybutoxy)tetrahydrofuran, sodium formate, and tar, etc.

[0009] In one optional embodiment, the operating pressure P1 at the top of the distillation column, the pressure drop ΔP of the distillation column, and the operating pressure P2 at the top of the diverter column satisfy the following: .

[0010] In one optional embodiment, a portion of the material on the discharge side of the partition tower is introduced into a condensing device for condensation and then circulated back to the discharge side; Preferably, the material below the discharge port on the discharge side of the adjacent tower is introduced into the condensing device for condensation and then circulated back to the discharge port below.

[0011] In one alternative embodiment, the heat load Q5 of the condenser, the heat load Q1 of the bottom heat exchanger of the distillation column, the reflux ratio R of the top of the partition column, the discharge rate D of the top of the partition column, and the vaporization enthalpy ΔH of the top of the partition column satisfy Q5≤1.2×(R+1)×D×ΔH-Q1.

[0012] In one optional embodiment, the distillation column has a top pressure of 10–250 kPa and / or a top temperature of 45–120 °C, and / or a reflux ratio of 0.15–1, and / or a bottom temperature of 70–145 °C.

[0013] In one optional embodiment, the top pressure of the partition column is 5-15 kPa, and / or the top temperature is 146-170 °C, and / or the top reflux ratio is 10-50, and / or the bottom temperature is 175-190 °C, and / or the theoretical plate number is 30-100.

[0014] In a second aspect, the present invention provides a 1,4-butanediol separation system, comprising: Distillation column, with the reboiler connected to a heat exchanger; The feed side of the partition column is connected to the bottom outlet of the distillation column, and the top outlet of the partition column is connected to the bottom heat exchanger of the distillation column for heat exchange.

[0015] In one alternative embodiment, the discharge side of the partition tower is connected to a circulation pipeline, and a condensation device is connected to the circulation pipeline; the condensation device includes an intercooler.

[0016] In one optional embodiment, the discharge side of the partition tower is provided with a discharge port for extracting 1,4-butanediol, and the circulation pipeline is connected below the discharge port.

[0017] In one optional embodiment, the partitions in the partition tower are arranged along its axial direction, with the upper end of the partition located at 5% to 30% of the top tray of the partition tower and the lower end located at 70% to 95% of the top tray of the partition tower.

[0018] The technical solution of this invention has the following advantages: The 1,4-butanediol separation method of this invention combines a first distillation column and a partition column to form a coupled system of multi-effect distillation and partition distillation, enabling continuous connection between dehydration concentration and product purification in different columns, achieving deep coupling of heat, materials, and separation processes. The first distillation column achieves efficient removal of water and n-butanol from the feed, providing a stable high-concentration butanediol stream for subsequent purification. After the concentrate from the bottom of the column enters the partition column, the light and heavy components are initially separated in the partitioned sections. The light components rise to the top of the column, while the heavy components are enriched at the bottom. The middle side stream is used to collect high-purity butanediol product at the optimal position, thereby significantly improving the separation effect between the target component and near-boiling impurities.

[0019] Meanwhile, this invention achieves reverse-stage heat recovery between columns by directly introducing the overhead steam from the diverter column into the reboiler of the first distillation column and reboiling it in the first heat exchanger. This allows the high-temperature overhead steam to condense and return to the diverter column after heating, enabling simultaneous condensation of light components and energy utilization. This self-circulating heat structure significantly reduces the first distillation column's dependence on external steam supply, reduces the reboiler load, and improves thermal efficiency, allowing the entire distillation system to achieve the same separation requirements with lower energy consumption. Furthermore, an intercooler is arranged below the sidestream exit point of the diverter column. Local condensation and reflux increase the liquid-to-gas ratio in the sidestream region, further enhancing the separation process. This makes it easier to efficiently separate near-boiling impurities such as 1,4-butanediol and 2-(4-hydroxybutoxy)tetrahydrofuran, improving the purity of the sidestream product and stabilizing unit operation.

[0020] The coupling device for separating 1,4-butanediol of the present invention integrates the heat coupling method of the partitioned column structure and multi-effect distillation into the same system, enabling continuous circulation of materials between dehydration, high-efficiency purification, light and heavy component separation, and inter-column heat recovery. The internal structure of the partitioned column allows the separation task that originally required multiple columns to be completed in a single column, significantly reducing the configuration of auxiliary equipment such as condensers and reboilers, and lowering the investment and floor space required for the equipment. At the same time, the heat recovery path between the column bottom and the column top ensures maximum utilization of thermal energy, improving system energy efficiency and thermal stability. Through the above structural design, the present invention significantly improves the product purity and impurity control of 1,4-butanediol, reduces steam energy consumption, and significantly improves the overall process operation economy and separation efficiency. Attached Figure Description

[0021] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the system assembly structure for separating 1,4-butanediol according to the present invention.

[0023] Explanation of reference numerals in the attached figures: 1. First distillation column; 2. Second distillation column; 3. First heat exchanger; 4. Second heat exchanger; 5. Third heat exchanger; 6. Fourth heat exchanger; 7. Intercooler. Detailed Implementation

[0024] The following embodiments are provided to better understand the present invention, but the following embodiments do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the scope of protection of the present invention.

[0025] The detection methods involved in the embodiments and comparative examples of this invention are as follows: the purity of 1,4-butanediol was analyzed and determined using the method in GB / T24768-2009 Industrial 1,4-butanediol; the content of 2-(4-hydroxybutoxy)tetrahydrofuran was detected by gas chromatography.

[0026] like Figure 1 As shown, this embodiment provides a system for separating 1,4-butanediol, including a first distillation column 1 and a second distillation column 2. The first distillation column 1 is a butanediol dehydration and concentration column, which introduces feed from the outside containing 1,4-butanediol, water, n-butanol, hydroxybutyraldehyde, pentanediol, methyl-butanediol, 2-(4-hydroxybutoxy)tetrahydrofuran, sodium formate, and tar, and dehydrates and concentrates it. The light components containing water and n-butanol are removed from the top of the column, and the concentrated liquid mainly containing 1,4-butanediol and a small amount of heavy components such as hydroxybutyraldehyde and tar is collected from the bottom of the column.

[0027] The second distillation column 2 is internally equipped with vertical baffles, dividing it into four parts: the feed side, the discharge side, the upper space, and the lower space. The butanediol concentrate flowing out of the bottom of the first distillation column enters the feed side of the second distillation column. Light components containing water, hydroxybutyraldehyde, pentanediol, and methyl-butanediol are collected from the top of the second distillation column. Refined 1,4-butanediol product is collected from the side stream of the discharge side of the second distillation column. Heavy components containing 2-(4-hydroxybutoxy)tetrahydrofuran, sodium formate, and tar are collected from the bottom of the second distillation column.

[0028] The first distillation column is equipped with a first heat exchanger 3 at the bottom and a second heat exchanger 4 at the top. The second distillation column 2 is equipped with a third heat exchanger 5 at the top and a fourth heat exchanger 6 at the bottom. The gas at the top of the second distillation column is sent to the first heat exchanger 3 at the bottom of the first distillation column to exchange heat with the liquid in the bottom of the first distillation column. After being partially condensed, it enters the third heat exchanger 5 and is completely condensed into liquid. Part of the liquid is collected as a light component, and the other part is refluxed as the liquid at the top of the second distillation column 2.

[0029] The inlet of the first heat exchanger 3 is connected to the top gas outlet of the second distillation column 2. It is used to heat the liquid in the bottom of the first distillation column 1 by using the gas distilled from the top of the second distillation column as the heating medium, and to condense the light components from the second distillation column 2, and output the cooled and condensed light components from its heat medium outlet.

[0030] The light component condensate from the outlet of the heat medium in the first heat exchanger 3 enters the third heat exchanger 5 for further condensation. Part of it is used as liquid reflux in the second distillation column 2, and part of it is extracted as light components.

[0031] In the above method for separating 1,4-butanediol, in order to achieve sufficient separation of 1,4-butanediol from key impurities, an intercooler 7 is installed below the 1,4-butanediol product side stream of the second distillation column. The return port of the intercooler is located one tray below the 1,4-butanediol side stream plate. The outlet and return port of the intercooler are both located on the same side of the 1,4-butanediol side stream of the second distillation column partition.

[0032] In the above method for separating 1,4-butanediol, the local separation effect of the partition column can be enhanced without increasing the separation energy consumption. Therefore, the heat load Q5 (kJ / h) of the intercooler, the heat load Q1 (kJ / h) of the first heat exchanger, the reflux ratio R at the top of the second distillation column, the distillate rate D (kg / h) at the top of the second distillation column, and the vaporization enthalpy ΔH (kJ / kg) of the material at the top of the second distillation column should satisfy Q5≤1.2×(R+1)×D×ΔH-Q1.

[0033] The internal components of the first and second distillation columns can be plate columns, packed columns, composite columns of plate and packed columns, or other types of internal components.

[0034] Example 1 Combination Figure 1 The system shown is for separating 1,4-butanediol. This embodiment provides a method for separating 1,4-butanediol, as detailed below: (1) The feed is sent to the first distillation column 1 for concentration and dehydration. Light components including water and n-butanol are removed from the top of the column, and a concentrated liquid containing hydroxybutyraldehyde, tar and 1,4-butanediol is obtained from the bottom of the column. The feed is a mixture of 1,4-butanediol obtained during the synthesis of 1,4-butanediol via the acetylacetyl method, with a feed flow rate of 26,500 kg / h. It contains 1,4-butanediol, water, n-butanol, hydroxybutyraldehyde, tar, methanol, hydrogen, 2-methyl-1,4-butanediol, 2-(4-hydroxybutoxy)tetrahydrofuran, pentanediol, and sodium formate. By mass fraction, the feed contains 54 wt% 1,4-butanediol, 43.5 wt% water, 0.95 wt% n-butanol, 0.5 wt% 2-(4-hydroxybutoxy)tetrahydrofuran, 0.05 wt% sodium formate, 0.05 wt% hydroxybutyraldehyde, and the remainder is tar, etc. The operating conditions of the first distillation column 1 are as follows: the pressure at the top of the column is absolute 110 kPa, the temperature at the top of the column is 98 ℃, the reflux ratio is 0.15, the temperature at the bottom of the column is 116 ℃, the theoretical number of plates is 22, the total pressure drop is 15 kPa, and the heat load of the first heat exchanger is Q1 = 8169 kW.

[0035] (2) The concentrate obtained in step (1) is sent to the second distillation column for secondary concentration. The second distillation column is a partitioned distillation column with a total of 50 theoretical plates and 35 theoretical plates in the partitioned section. The partitions in the partitioned section are placed along the axis, and the feed inlet is located at the 20th plate from the top on one side of the partitioned section. The internal space of the second distillation column is divided into four sub-spaces: A, B, C, and D by a partition. The space B located at the top of the partition and the space C located at the bottom of the partition are connected on the left and right sides. The concentrate from the first distillation column 1 enters the space A on the left side of the partition for preliminary separation. The light components gather in the upper space B, and the heavy components gather in the lower space C, thus achieving the preliminary separation of light and heavy components.

[0036] (3) Remove light components including water, hydroxybutyraldehyde, pentanediol and 2-methyl-1,4-butanediol from the top of the second distillation column; collect 1,4-butanediol product from the 15th plate from the top of the right side space D side line of the column, in which the purity of 1,4-butanediol can reach more than 99.8% and the content of 2-(4-hydroxybutoxy)tetrahydrofuran is less than 0.07%; discharge heavy components including 2-(4-hydroxybutoxy)tetrahydrofuran, sodium formate and tar from the bottom of the column; The operating conditions of the second distillation column are as follows: the pressure at the top of the column is absolute 5 kPa, the temperature at the top of the column is 146 ℃, the reflux ratio is 30, and the temperature at the bottom of the column is 175 ℃.

[0037] (4) The first heat exchanger 3 at the bottom of the first distillation column uses the light component removed in step (3) as the heat medium to heat and reboil the liquid at the bottom of the first distillation column, while simultaneously cooling and condensing the light component removed in step (3) to obtain the light component condensate; after condensation, part of the light component removed at the top of the column is used as reflux liquid, and the other part is used as wastewater and directly enters the wastewater treatment system.

[0038] (5) A liquid stream is collected from the 18th plate from top to bottom in the space on the right side of the second distillation column and enters the intercooler 7. After cooling, it returns to the 16th plate. The distillate flow rate at the top of the second distillation column is D=1400kg / h, the reflux ratio is R=30, and the latent heat of vaporization of the top component is ΔH=763.5kJ / kg. Therefore, the heat load Q5 of the intercooler should meet the following: Q5≤1.2×(R+1)×D×ΔH-Q1=1.2×(30+1)×1400×763.5-8169×3600=10354680kJ / h=2875kW; In this embodiment, the heat load of the intercooler 7 is controlled at 2800kW. In this embodiment, the first distillation column 1 and the second distillation column 2 constitute a double-effect distillation. The top temperature of the second distillation column 2 is 146°C, which completely replaces steam as the heat source of the first heat exchanger 3 of the first distillation column 1. It exchanges heat with the bottom liquid of the first distillation column at 116°C to provide gas phase for the first distillation column. At the same time, part of the gas at the top of the second distillation column 2 is condensed into liquid and then enters the third heat exchanger 5 to be completely condensed into liquid. Part of it is used as reflux to provide liquid for the second distillation column, and the other part is collected as light components.

[0039] Example 2 The only difference between this embodiment and embodiment 1 is that step (5) is omitted and the intermediate cooler 7 is not installed.

[0040] In this embodiment, light components including water, hydroxybutyraldehyde, pentanediol, and 2-methyl-1,4-butanediol are removed from the top of the second distillation column; 1,4-butanediol product is collected from the 15th plate from the top down in the right side space D of the column, wherein the purity of 1,4-butanediol can reach more than 99.8%, and the content of 2-(4-hydroxybutoxy)tetrahydrofuran is 0.09%.

[0041] The results of this embodiment show that although the purity of the obtained 1,4-butanediol product can reach over 99.8%, the content of 2-(4-hydroxybutoxy)tetrahydrofuran is 0.09%, which is higher than the product index of Example 1. This indicates that without the intercooler 7, the liquid-to-gas ratio in the side stream region of the adjacent column is insufficient, leading to a decrease in the separation efficiency of 2-(4-hydroxybutoxy)tetrahydrofuran near the side stream. By adding the intercooler 7 and introducing local condensation reflux below the side stream, the mass transfer process in this region can be effectively enhanced, thereby significantly reducing the content of key impurities in the side stream product.

[0042] Example 3 The only difference between this embodiment and Embodiment 1 is the pressure at the top of the first distillation column. In this embodiment, the pressure of the first distillation column is 400 kPa. The operating pressures P1 and P2 of the first and second distillation columns no longer satisfy the pressure relationship proposed in this invention. The bottom temperature of the first distillation column is 160°C, which is higher than the vapor temperature of the second distillation column top temperature of 155°C. The reboiler of the first distillation column bottom needs to be heated by additional steam, and at the same time, the condenser at the top of the first distillation column needs to use cooling water entirely. The first and second distillation columns cannot form a double-effect distillation system, and the steam energy consumption increases by 8169 kW compared to Example 1.

[0043] Example 4 The only difference between this embodiment and Embodiment 1 is that the heat load Q5 of the intercooler is different. In this embodiment, the heat load Q5 of the intercooler is 4000kW, Q5>1.2×(R+1)×D×ΔH-Q1. The final result of the heat balance shows that the heat at the top of the second distillation column cannot meet the needs of the reboiler of the first distillation column. It is necessary to add one reboiler in parallel or in series in the first distillation column, which will consume an additional 1100kW of steam heat.

[0044] Example 5 Combination Figure 1 The system shown is for separating 1,4-butanediol. This embodiment provides a method for separating 1,4-butanediol, as detailed below: (1) The feed is sent to the first distillation column 1 for concentration and dehydration. Light components including water and n-butanol are removed from the top of the column, and a concentrated liquid containing hydroxybutyraldehyde, tar and 1,4-butanediol is obtained from the bottom of the column. The feed is a mixture of 1,4-butanediol obtained during the synthesis of 1,4-butanediol via the acetylacetyl method, with a feed flow rate of 26,500 kg / h. It contains 1,4-butanediol, water, n-butanol, hydroxybutyraldehyde, tar, methanol, hydrogen, 2-methyl-1,4-butanediol, 2-(4-hydroxybutoxy)tetrahydrofuran, pentanediol, and sodium formate. By mass fraction, the feed contains 54 wt% 1,4-butanediol, 43.5 wt% water, 0.95 wt% n-butanol, 0.5 wt% 2-(4-hydroxybutoxy)tetrahydrofuran, 0.05% sodium formate, 0.05% hydroxybutyraldehyde, and the remainder is tar, etc. The operating conditions of the first distillation column 1 are as follows: the pressure at the top of the column is absolute 10 kPa, the temperature at the top of the column is 45℃, the reflux ratio is 0.5, the temperature at the bottom of the column is 70℃, the theoretical number of plates is 10, the total pressure drop is 7 kPa, and the heat load of the first heat exchanger is Q1, which is 7850 kW.

[0045] (2) The concentrate obtained in step (1) is sent to the second distillation column for secondary concentration. The second distillation column is a partitioned distillation column with a total of 30 theoretical plates and 20 theoretical plates in the partitioned section. The partitions in the partitioned section are placed along the axis, and the feed inlet is located at the 15th plate from the top on one side of the partitioned section. The internal space of the second distillation column is divided into four sub-spaces: A, B, C, and D by a partition. The space B located at the top of the partition and the space C located at the bottom of the partition are connected on the left and right sides. The concentrate from the first distillation column 1 enters the space A on the left side of the partition for preliminary separation. The light components gather in the upper space B, and the heavy components gather in the lower space C, thus achieving the preliminary separation of light and heavy components.

[0046] (3) Remove light components including water, hydroxybutyraldehyde, pentanediol and 2-methyl-1,4-butanediol from the top of the second distillation column; collect 1,4-butanediol product from the 12th plate from the top of the right side space D side line of the column, in which the purity of 1,4-butanediol can reach more than 99.6% and the content of 2-(4-hydroxybutoxy)tetrahydrofuran is less than 0.09%; discharge heavy components including 2-(4-hydroxybutoxy)tetrahydrofuran, sodium formate and tar from the bottom of the column; The operating conditions of the second distillation column are as follows: the pressure at the top of the column is absolute 10 kPa, the temperature at the top of the column is 160 ℃, the reflux ratio is 10, and the temperature at the bottom of the column is 180 ℃.

[0047] (4) The first heat exchanger 3 at the bottom of the first distillation column uses the light component removed in step (3) as the heat medium to heat and reboil the liquid at the bottom of the first distillation column, while simultaneously cooling and condensing the light component removed in step (3) to obtain the light component condensate; after condensation, part of the light component removed at the top of the column is used as reflux liquid, and the other part is used as wastewater and directly enters the wastewater treatment system.

[0048] (5) A liquid stream is collected from the 16th plate from top to bottom in the space on the right side of the second distillation column and enters the intercooler 7. After cooling, it returns to the 13th plate. The distillate flow rate at the top of the second distillation column is D=1400kg / h, the reflux ratio is R=50, and the latent heat of vaporization of the top component is ΔH=763.5kJ / kg. Therefore, the heat load Q5 of the intercooler should meet the following requirements: Q5≤1.2×(R+1)×D×ΔH-Q1=1.2×(50+1)×1400×763.5-7850×3600=37156680kJ / h=10321kW; In this implementation, the heat load of the intercooler 7 is controlled to be 10000kW. In this embodiment, the first distillation column 1 and the second distillation column 2 constitute a double-effect distillation. The top temperature of the second distillation column 2 is 160°C, which completely replaces steam as the heat source of the first heat exchanger 3 of the first distillation column 1. It exchanges heat with the bottom liquid of the first distillation column at 70°C to provide gas phase for the first distillation column. At the same time, part of the gas at the top of the second distillation column 2 is condensed into liquid and then enters the third heat exchanger 5 to be completely condensed into liquid. Part of it is used as reflux to provide liquid for the second distillation column, and the other part is collected as light components.

[0049] Example 6 Combination Figure 1 The system shown is for separating 1,4-butanediol. This embodiment provides a method for separating 1,4-butanediol, as detailed below: (1) The feed is sent to the first distillation column 1 for concentration and dehydration. Light components including water and n-butanol are removed from the top of the column, and a concentrated liquid containing hydroxybutyraldehyde, tar and 1,4-butanediol is obtained from the bottom of the column. The feed is a mixture of 1,4-butanediol obtained during the synthesis of 1,4-butanediol via the acetylacetyl method, with a feed flow rate of 26,500 kg / h. It contains 1,4-butanediol, water, n-butanol, hydroxybutyraldehyde, tar, methanol, hydrogen, 2-methyl-1,4-butanediol, 2-(4-hydroxybutoxy)tetrahydrofuran, pentanediol, and sodium formate. By mass fraction, the feed contains 54 wt% 1,4-butanediol, 43.5 wt% water, 0.95 wt% n-butanol, 0.5 wt% 2-(4-hydroxybutoxy)tetrahydrofuran, 0.05% sodium formate, 0.05% hydroxybutyraldehyde, and the remainder is tar, etc. The operating conditions of the first distillation column 1 are as follows: the top pressure is absolute 250 kPa, the top temperature is 120℃, the reflux ratio is 1, the bottom temperature is 145℃, the theoretical number of plates is 30, the total pressure drop is 20 kPa, and the heat load of the first heat exchanger is Q1, which is 8500 kW.

[0050] (2) The concentrate obtained in step (1) is sent to the second distillation column for secondary concentration. The second distillation column is a partitioned distillation column with a total of 30 theoretical plates and 25 theoretical plates in the partitioned section. The partitions in the partitioned section are placed along the axis, and the feed inlet is located at the 15th plate from the top on one side of the partitioned section. The internal space of the second distillation column is divided into four sub-spaces: A, B, C, and D by a partition. The space B located at the top of the partition and the space C located at the bottom of the partition are connected on the left and right sides. The concentrate from the first distillation column 1 enters the space A on the left side of the partition for preliminary separation. The light components gather in the upper space B, and the heavy components gather in the lower space C, thus achieving the preliminary separation of light and heavy components.

[0051] (3) Remove light components including water, hydroxybutyraldehyde, pentanediol and 2-methyl-1,4-butanediol from the top of the second distillation column; collect 1,4-butanediol product from the 12th plate from the top of the right side space D side line of the column, in which the purity of 1,4-butanediol can reach more than 99.6% and the content of 2-(4-hydroxybutoxy)tetrahydrofuran is less than 0.09%; discharge heavy components including 2-(4-hydroxybutoxy)tetrahydrofuran, sodium formate and tar from the bottom of the column; The operating conditions of the second distillation column are as follows: the pressure at the top of the column is absolute 15 kPa, the temperature at the top of the column is 170 ℃, the reflux ratio is 50, and the temperature at the bottom of the column is 190 ℃.

[0052] (4) The first heat exchanger 3 at the bottom of the first distillation column uses the light component removed in step (3) as the heat medium to heat and reboil the liquid at the bottom of the first distillation column, while simultaneously cooling and condensing the light component removed in step (3) to obtain the light component condensate; after condensation, part of the light component removed at the top of the column is used as reflux liquid, and the other part is used as wastewater and directly enters the wastewater treatment system.

[0053] (5) A liquid stream is collected from the 16th plate from top to bottom in the space on the right side of the second distillation column and enters the intercooler 7. After cooling, it returns to the 13th plate. The distillate flow rate at the top of the second distillation column is D=1400kg / h, the reflux ratio is R=50, and the latent heat of vaporization of the top component is ΔH=763.5kJ / kg. Therefore, the heat load Q5 of the intercooler should meet the following requirements: Q5≤1.2×(R+1)×D×ΔH-Q1=1.2×(50+1)×1400×763.5-8500×3600=34816680kJ / h=9671kW; In this implementation, the heat load of the intercooler 7 is controlled to be 9500kW. In this embodiment, the first distillation column 1 and the second distillation column 2 constitute a double-effect distillation. The top temperature of the second distillation column 2 is 170°C, which completely replaces the steam as the heat source of the first heat exchanger 3 of the first distillation column 1. It exchanges heat with the bottom liquid of the first distillation column at 145°C to provide the gas phase for the first distillation column. At the same time, part of the gas at the top of the second distillation column 2 is condensed into liquid and then enters the third heat exchanger 5 to be completely condensed into liquid. Part of it is used as reflux to provide liquid for the second distillation column, and the other part is collected as light components.

[0054] Comparative Example 1 The feed flow rate, feed composition, and separation requirements of this comparative example are exactly the same as those of Example 1, but the process settings are different, as follows: This comparative example uses a conventional butanediol refining process. The entire separation system consists of a concentration tower, a salt tower, a high-boiling tower, and a low-boiling tower, comprising a total of four distillation columns. First, water and light components such as n-butanol are removed in the concentration tower (C1) to obtain a concentrate containing tar, hydroxybutyraldehyde, and butanediol. Subsequently, it passes through the salt tower (C2) to remove tar and salt impurities, then through the high-boiling tower (C3) to remove high-boiling impurities such as 2-(4-hydroxybutoxy)tetrahydrofuran and sodium formate, and finally through the low-boiling tower (C4) to remove low-boiling substances such as pentanediol and methyl-butanediol, thus achieving the purification of the butanediol product.

[0055] Under the same feed flow rate and separation requirements, a detailed comparison of the energy consumption of Comparative Example 1 and Example 1 is shown in Table 1 below; Table 1: Energy consumption comparison results between Comparative Example 1 and Example 1

[0056] Comparing Example 1 and Comparative Example 1, it can be seen that the total steam energy consumption of Comparative Example 1 is 24903 kW, while Example 1 significantly reduces the overall steam consumption to only 11884 kW by recovering the vapor phase heat from the top of the second distillation column for heating the bottom of the first distillation column and utilizing the partitioned column structure to achieve the separation function of the two columns within a single column. Compared with the conventional process, the reduced steam energy consumption fully demonstrates that the partitioned column coupled multi-effect distillation process proposed in this invention can significantly improve thermal energy utilization efficiency and greatly reduce operating costs. Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for separating 1,4-butanediol, characterized in that: Includes the following steps: The feed containing 1,4-butanediol is concentrated and dehydrated in a distillation column; The concentrate from the bottom of the distillation column is introduced into a separate column for purification. The vapor phase from the top of the separate column is exchanged with the heat exchanger at the bottom of the distillation column, and 1,4-butanediol is collected from the outlet side of the separate column.

2. The method for separating 1,4-butanediol according to claim 1, characterized in that: The operating pressure P1 at the top of the distillation column, the pressure drop ΔP of the distillation column, and the operating pressure P2 at the top of the diverter column satisfy the following conditions: 。 3. A method for separating 1,4-butanediol according to claim 1 or 2, characterized in that: The material on the discharge side of the partition tower is introduced into the condensing device for condensation and then circulated back to the discharge side; Preferably, the material below the discharge port on the discharge side of the adjacent tower is introduced into the condensing device for condensation and then circulated back to the discharge port below.

4. A method for separating 1,4-butanediol according to any one of claims 1-3, characterized in that: The heat load Q5 of the condenser, the heat load Q1 of the heat exchanger at the bottom of the distillation column, the reflux ratio R at the top of the diverter column, the discharge rate D at the top of the diverter column, and the vaporization enthalpy ΔH at the top of the diverter column satisfy Q5≤1.2×(R+1)×D×ΔH-Q1.

5. A method for separating 1,4-butanediol according to any one of claims 1-3, characterized in that: The distillation column has a top pressure of 10–250 kPa and / or a top temperature of 45–120 °C, and / or a reflux ratio of 0.15–1, and / or a bottom temperature of 70–145 °C.

6. A method for separating 1,4-butanediol according to any one of claims 1-3, characterized in that: The pressure at the top of the partition column is 5–15 kPa, and / or the temperature at the top of the column is 146–170 °C, and / or the reflux ratio at the top of the column is 10–50, and / or the temperature at the bottom of the column is 175–190 °C, and / or the number of theoretical plates is 30–100.

7. A separation system for 1,4-butanediol, characterized in that: include: Distillation column, with the reboiler connected to a heat exchanger; The feed side of the partition column is connected to the bottom outlet of the distillation column, and the top outlet of the partition column is connected to the bottom heat exchanger of the distillation column for heat exchange.

8. The 1,4-butanediol separation system according to claim 7, characterized in that: The discharge side of the partition tower is connected to a circulation pipeline, and a condensation device is connected to the circulation pipeline.

9. The 1,4-butanediol separation system according to claim 8, characterized in that: The discharge side of the partition tower is provided with a discharge port for extracting 1,4-butanediol, and the circulation pipeline is connected below the discharge port.

10. A 1,4-butanediol separation system according to any one of claims 7-9, characterized in that: The partitions in the partition tower are arranged along its axial direction. The upper end of the partition is located at 5% to 30% of the top of the partition tower, and the lower end of the partition is located at 70% to 95% of the top of the partition tower.

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