A dividing wall distillation tower and distillation method for separation of complex multi-component systems

Abstract

The invention discloses a dividing wall distillation tower and a distillation method for separating complex multi-component systems, belonging to the field of distillation technology. The distillation tower comprises a tower body, a first dividing wall and a second dividing wall, wherein the upper part of the first dividing wall extends to the top of the tower body and the lower part is not connected to the bottom of the tower body, and the upper part of the second dividing wall is not connected to the top of the tower body and the lower part extends to the bottom of the tower body; the tower body is provided with a light component outlet, a light component reflux port, a feed port, a heavy component reflux port and a heavy component outlet in sequence from top to bottom relative to the tower wall on the opposite side of the first dividing wall and the second dividing wall; the tower body is provided with a sub-light component outlet, a sub-light component reflux port, a sub-heavy component reflux port and a sub-heavy component outlet in sequence from top to bottom relative to the tower wall on the same side of the first dividing wall and the second dividing wall; and a liquid collector is provided in the tower body and above the second dividing wall. The distillation tower can be used to obtain four products or three products with high purity and stable quality from a four-component system or a three-component system containing azeotropes, respectively, and has a good energy-saving effect.

Description

Technical Field

[0001] The invention belongs to the technical field of distillation, and in particular relates to a dividing wall distillation tower and a distillation method for separating complex multi-component systems. Background Art

[0002] The separation process plays a very important role in chemical production. In the chemical separation process, distillation is the most widely used separation method. High energy consumption has always been an inevitable problem in the distillation process. Research on energy saving in the distillation process has become a research hotspot in recent years. Various high-efficiency thermal coupling distillation and new distillation technologies have also been continuously developed. Among them, the dividing wall column (DWC) is the research focus in this field.

[0003] DWC tower is a tower with a vertical wall in the distillation tower, and the vertical wall can also be extended to the top or bottom of the tower. The two parts of the DWC tower separated by the dividing wall can have a common distillation section or stripping section, or a common distillation section and stripping section at the same time. According to the position of the dividing wall, it can be divided into a fully thermally coupled dividing wall tower (DWC-FC, such as Figure 1 (a)), side distillation dividing wall column (DWC-SR, such as Figure 1 (b)) and side stripping dividing wall distillation column (DWC-SS, such as Figure 1 (c)).

[0004] In the traditional process, two distillation towers, two reboilers and two condensers are needed to separate the three components. However, the DWC only needs one tower and can reduce at least one condenser or one reboiler. The DWC tower is a thermodynamically ideal system structure. When separating a three-component mixture, the same number of theoretical plates is used to complete the same separation task. The DWC tower requires less reboil heat and condensation than the traditional two-tower process. For some given materials, the dividing wall distillation tower requires a smaller reflux ratio than the conventional distillation tower, so the operating capacity is increased, the energy saving can reach more than 60%, and the equipment investment may be saved by 30%.

[0005] DWC towers can be widely used in oil refining, petrochemicals, chemicals and gas separation. For example, CN201820597333.0 applies the dividing wall tower technology to the aromatics extraction distillation device, which reduces the energy consumption of the device, improves the economic efficiency of the device and the ability of long-term stable and reliable operation; CN201210347586.X discloses a systematic method for preparing isopentadiene and dicyclopentadiene, which uses two dividing wall distillation towers, has a simple process, improves the yield and purity, saves more than 30% of energy consumption, and increases the economic benefits of the device; CN201910343639.2 discloses a method and device for separating isopropyl alcohol diisopropyl ether aqueous solution, which integrates heterogeneous azeotropic distillation and pressure swing distillation, dividing wall tower and heat pump technology, solves the separation problem of the complex system of multiple azeotropes, and has the advantages of high efficiency and energy saving, high product purity and recovery rate.

[0006] A single DWC tower with a single partition wall can be used to separate a three-component mixture to obtain three products. For a four-component system, a DWC tower plus an ordinary distillation tower is usually required for separation to obtain four products. There are patents that obtain more products by increasing the number of side-line discharge streams, such as CN201910024467.2; there are also patents that obtain more products by increasing the number of partition walls, such as CN200910234363.0 and CN201810900872.1. But no matter which method, except for the discharge from the top and bottom of the tower, other discharges are essentially side-line discharges. When the product purity requirements are high, the purity and quality stability of the product obtained by the side-line discharge are difficult to guarantee. For some three-component systems containing azeotropes, three products can be extracted using a single DWC tower, but the presence of azeotropes makes the separation process complicated and it is difficult to ensure the purity of the product, especially for processes with high product purity requirements, which are difficult to meet using a single DWC tower. Summary of the invention

[0007] In view of this, the object of the present invention is to provide a dividing wall distillation tower and a distillation method for separating complex multi-component systems, especially a four-component system or a three-component system containing an azeotrope. The use of the distillation tower can obtain multiple products with high purity and stable quality, and has a good energy-saving effect.

[0008] The present invention is achieved through the following technical solutions:

[0009] The present invention provides a dividing wall distillation tower for separating a complex multi-component system, comprising a tower body, and a first dividing wall and a second dividing wall arranged in the tower body and along the axial direction thereof, wherein the upper portion of the first dividing wall extends to the top of the tower body, and the lower portion is not connected to the bottom of the tower body; the upper portion of the second dividing wall is not connected to the top of the tower body, and the lower portion extends to the bottom of the tower body; the tower wall on the tower body and on the opposite side of the first dividing wall and the second dividing wall is provided with a light component outlet, a light component reflux port, a feed port, a heavy component reflux port and a heavy component outlet in sequence from top to bottom ; A secondary light component outlet, a secondary light component reflux port, a secondary heavy component reflux port, and a secondary heavy component outlet are sequentially arranged on the tower body and on the tower wall on the same side relative to the first dividing wall and the second dividing wall from top to bottom; a liquid collector between the secondary heavy component reflux port and the secondary light component reflux port is arranged inside the tower body and above the second dividing wall; the tower body is divided into a light component distillation zone, a light component stripping zone, a common stripping zone, an intermediate stripping zone, a common distillation zone, and an intermediate discharge zone by the feed inlet, the first dividing wall, the second dividing wall, and the liquid collector.

[0010] Furthermore, the feed inlet is arranged at the middle and upper part of the tower body between the light component distillation zone and the light component stripping zone, and the light component distillation zone is above the feed inlet, and the light component stripping zone is below the feed inlet; the light component outlet and the light component reflux port are respectively arranged at the top and upper part of the tower body in the upper area of ​​the light component distillation zone; the heavy component reflux port and the heavy component outlet are respectively arranged at the lower part and bottom of the tower body in the lower area of ​​the common stripping zone; the sub-light component outlet and the sub-light component reflux port are respectively arranged at the top and upper part of the tower body in the upper area of ​​the common distillation zone; the sub-heavy component reflux port and the sub-heavy component outlet are respectively arranged at the lower part and bottom of the tower body in the lower area of ​​the intermediate discharge zone.

[0011] Furthermore, the positional relationship between the first partition wall and the second partition wall is set to an intersecting or non-intersecting arrangement structure according to the relative contents of the light component, the sub-light component, the sub-heavy component and the heavy component in the feed.

[0012] Furthermore, a liquid distribution device is provided below the liquid collector and is higher than the second partition wall. The installation form of the liquid distribution device is a built-in or external structure.

[0013] Furthermore, the light component distillation zone, light component stripping zone, common stripping zone, intermediate stripping zone, common distillation zone, and intermediate discharge zone are all provided with a gas-liquid contact medium, and the gas-liquid contact medium is a filler and / or a tower plate, which is arranged in one or more sections, and a liquid redistributor is provided between every two sections.

[0014] Furthermore, a light component condenser is provided on the loop between the light component outlet and the light component reflux port; a sub-light component condenser is provided on the loop between the sub-light component outlet and the sub-light component reflux port; an intermediate reboiler is provided on the loop between the sub-heavy component reflux port and the sub-heavy component outlet; and a bottom reboiler is provided on the loop between the heavy component reflux port and the heavy component outlet.

[0015] Furthermore, the structure in which the lower part of the second partition wall extends to the bottom of the tower body is replaced by a partition plate that covers the lower part of the second partition wall, and the secondary heavy component reflux port and secondary heavy component outlet are arranged in the lower area of ​​the middle discharge zone and in the lower middle part of the tower body above the partition plate.

[0016] Furthermore, the height of the second partition wall is set according to the content of the secondary heavy component in the feed and the purity requirement for the secondary heavy component.

[0017] The present invention also utilizes the distillation method of the dividing wall distillation tower for separation of complex multi-component systems as described above, comprising: first, a four-component mixture containing A, B, C, and D is introduced into the tower body from the feed inlet, wherein A, B, C, and D are arranged in descending order according to relative volatility; then, part of the four-component mixture entering the tower body is vaporized, and the vapor phase rises and enters the light component distillation zone, and after sufficient gas-liquid contact, the vapor of the light component A is obtained at the top of the tower on the feed side of the tower body, and after condensation by the light component condenser, a part of it is refluxed to the tower body, and a part of it is extracted as product A; furthermore, the liquid phase downwardly passes through the light component stripping zone and the common stripping zone in turn, and after sufficient gas-liquid contact, a heavy component D is obtained at the bottom of the tower body, and after being partially vaporized by heating in a tower bottom reboiler, a part of it is returned to the tower body, and a part of it is extracted as product D; then, after being reboiled in the tower bottom reboiler, a part of it is returned to the tower body, and a part of it is extracted as product D. The steam obtained by partial vaporization rises, and after sufficient gas-liquid contact in the common distillation zone, the proportion is adjusted according to the pressure difference at the top of the tower on the feed side and the non-feed side of the tower body, and then enters the light component distillation zone and the intermediate distillation zone. The steam passes through the intermediate distillation zone and continues to rise to enter the common distillation zone for sufficient gas-liquid contact, and the steam of the sub-light component B is obtained at the top of the tower on the non-feed side of the tower body. After condensation by the sub-light component condenser, part of it is refluxed to the tower body, and part of it is extracted as product B; finally, the liquid flowing out from the bottom of the common distillation zone is collected by the liquid collector, and the proportion is distributed by the liquid distribution device, and then enters the intermediate distillation zone and the intermediate discharge zone for sufficient gas-liquid contact, and the sub-heavy component C is obtained below the intermediate discharge zone. After being heated in the intermediate reboiler and partially vaporized, part of it returns to the tower body, and part of it is extracted as product C.

[0018] The present invention also utilizes the distillation method of the dividing wall distillation tower for separation of complex multi-component systems as described above, comprising: first, a three-component mixture containing A, B, and C is introduced into the tower body from the feed inlet, wherein A, B, and C are arranged in descending order according to relative volatility, B and C will form an azeotrope BC, and the relative volatility of BC is lower than that of C; then, part of the three-component mixture entering the tower body is vaporized, and the vapor phase rises and enters the light component distillation zone, after which the vapor of the vapor rises and enters the light component distillation zone and is fully contacted with the gas and liquid, and then the vapor of component A is obtained at the top of the tower on the feed side of the tower body, and after being condensed by the light component condenser, a part of it is refluxed to the tower body, and a part of it is extracted as product A; furthermore, the liquid phase passes downward in turn through the light component stripping zone and the common stripping zone, after which the vapor and liquid are fully contacted, and then the azeotrope BC is obtained at the bottom of the tower body, and after being partially vaporized by heating in the tower bottom reboiler, a part of it is returned to the tower body, and a part of it is extracted as product A. Then, the steam obtained by partial vaporization in the reboiler at the bottom of the tower rises, and after sufficient gas-liquid contact in the common stripping zone, it enters the light component stripping zone and the intermediate stripping zone in proportion. The steam passes through the intermediate stripping zone and continues to rise into the common rectification zone, after sufficient gas-liquid contact, low-purity component C steam is obtained at the top of the tower on the non-feed side of the tower body, and a part of it is refluxed to the tower body after being condensed by the sub-light component condenser, and a part is taken out and circulated back to the feed port for rectification again; finally, the liquid flowing out from the bottom of the common rectification zone is collected by the liquid collector, and then enters the intermediate stripping zone and the intermediate discharging zone in proportion, after sufficient gas-liquid contact, high-purity component C is obtained below the intermediate discharging zone, and a part of it is returned to the tower body after being partially vaporized by heating in the intermediate reboiler, and a part is taken out as product C.

[0019] The advantages of the present invention are:

[0020] 1. Only one tower is needed to separate the four-component system and obtain four products. Compared with the existing technology, the product quality is stable and the purity is high; the number of equipment is reduced, the equipment investment is saved, the equipment floor space is reduced, and the economy of the process is improved.

[0021] 2. The separation effect of the three-component system containing azeotropes is good, and the obtained product has high purity and high recovery rate, which can meet strict quality requirements.

[0022] 3. The dividing wall distillation tower is a fully thermally coupled distillation tower, which effectively utilizes the heat of the steam in the tower, avoids the waste of condensation heat of the steam at the top of the tower when using an ordinary distillation tower, realizes the recycling of heat energy inside the tower, and avoids the back-mixing effect of the intermediate components. It reduces the mixing problem caused by the different composition of the feed and the logistics on the feed plate, improves the thermodynamic efficiency, and thus produces a good energy-saving effect.

[0023] 4. In the space on one side of the dividing wall of the distillation tower, the temperature increases from top to bottom, with the highest temperature at the bottom of the tower. The function of the bottom reboiler is to provide rising steam, and to avoid the bottom reboiler providing the whole tower rising steam through the intermediate reboiler; compared with the bottom reboiler, the intermediate reboiler can be heated by a low-temperature heat source, reducing the use of high-temperature heat sources, thereby reducing energy costs and improving the economy of the process.

[0024] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings, in which:

[0026] Figure 1 It is a schematic diagram of a distillation tower in the prior art;

[0027] Figure 2 This is a structural schematic diagram of Embodiment 1 of the present invention;

[0028] Figure 3 This is a schematic diagram of the structure of the second embodiment of the present invention; a and b represent the partitions at different heights;

[0029] Figure 4 The position relationship diagram of the first partition wall and the second partition wall of the present invention; a, b, c, d represent four forms respectively

[0030] Figure 5 It is a flow chart of the four-component system of the present invention;

[0031] Figure 6 This is a flow chart of a three-component system containing an azeotrope of the present invention;

[0032] Component number description: 1-tower body; 2-first dividing wall; 3-second dividing wall; 4-feed port; 5-light component outlet; 6-light component reflux port; 7-sub-light component outlet; 8-sub-light component reflux port; 9-sub-heavy component reflux port; 10-sub-heavy component outlet; 11-heavy component reflux port; 12-heavy component outlet; 13-liquid collector; 14-liquid distribution device; 15-partition plate; 16-light component condenser; 17-sub-light component condenser; 18-intermediate reboiler; 19-bottom reboiler;

[0033] Light component distillation zone a, light component stripping zone b, common stripping zone c, intermediate stripping zone d, common distillation zone e, intermediate discharge zone f. DETAILED DESCRIPTION

[0034] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0035] Embodiment 1:

[0036] like Figure 2 As shown, in the present embodiment, the dividing wall distillation tower for complex multi-component system separation has two longitudinal dividing walls arranged inside the tower body 1 of the dividing wall distillation tower, i.e., the upper part of the first dividing wall 2 extends to the tower top, and the lower part is not connected to the tower bottom; the upper part of the second dividing wall 3 is not connected to the tower top, and the lower part can extend to the tower bottom; a feed port 4 is arranged in the middle and upper part of the tower wall on the side close to the first dividing wall 2; a light component outlet 5 is arranged at the top of the tower wall on the same side as the feed port 4, and a light component reflux port 6 is arranged at the upper part; a sub-light component outlet 7, a sub-light component reflux port 8, a sub-heavy component reflux port 9, and a sub-heavy component outlet 10 are arranged in sequence from top to bottom on the non-feed side tower wall; a heavy component reflux port 11 is arranged at the lower part of the tower body 1, and a heavy component outlet 12 is arranged at the bottom. The first dividing wall 2, the second dividing wall 3 and the multiple outlets divide the space inside the tower into 6 areas: light component distillation area a, light component stripping area b, common stripping area c, intermediate stripping area d, common distillation area e, and intermediate discharge area f. A liquid collector 13 and a liquid distribution device 14 are provided between the common rectification zone e and the intermediate stripping zone d and the intermediate discharge zone f. The liquid distribution device 14 may be a built-in distribution device installed in the tower, or an external distribution device installed outside the tower. When an external distribution device is used, a liquid outlet and a liquid inlet are also provided in the area between the liquid collector 13 and the intermediate stripping zone d and the intermediate discharge zone f on the non-feed side tower wall.

[0037] The six regions (abcdef) inside the tower body in this embodiment are all provided with gas-liquid contact media, which are one or two of fillers and trays. The gas-liquid contact media in each region can be divided into one or more sections in the longitudinal direction, and a liquid redistributor is provided between every two sections.

[0038] In this embodiment, there are two arrangements of the first partition wall 2 and the second partition wall 3 in the tower. Figure 4 (Top view from above), that is, intersection ( Figure 4 a) or disjoint( Figure 4 c) Structure, the vertical form is preferred in the specific intersection layout ( Figure 4 b), parallel form is preferred in non-intersecting layout ( Figure 4 d). At the same time, the positional relationship between the first partition wall and the second partition wall is adjusted and determined according to the relative contents of the light component, the second light component, the second heavy component and the heavy component in the feed.

[0039] The distillation method of the dividing wall distillation tower is shown in the process Figure 5 ,include:

[0040] A mixture containing A, B, C, and D (A, B, C, and D are arranged from high to low in terms of relative volatility, and may be four different components, or three components plus an azeotrope) enters the tower body 1 of the dividing wall distillation tower from the feed port 4, is partially vaporized first, and the vapor phase rises into the light component distillation zone a. After sufficient gas-liquid contact, the vapor of component A is obtained at the light component outlet 5 at the top of the feed side of the dividing wall distillation tower, and is condensed by the light component condenser 16, and a part of it is refluxed to the light component through the light component reflux port 6. In the dividing wall distillation tower, a part is extracted as product A; the liquid phase passes downward through the light component stripping zone b and the common stripping zone c in turn, and after sufficient gas-liquid contact, component D is obtained at the heavy component outlet 12 at the bottom of the dividing wall distillation tower. A part of it is heated and partially vaporized by the bottom reboiler 19 and then returns to the dividing wall distillation tower through the heavy component reflux port 11, and a part of it is extracted as product D; the steam obtained by partial vaporization in the bottom reboiler 19 rises and undergoes sufficient gas-liquid contact in the common stripping zone c. Then, the steam enters the light component stripping zone b and the intermediate stripping zone d in a certain proportion; the distribution ratio can be adjusted according to the pressure difference between the feed side and the non-feed side of the dividing wall distillation tower; then the steam continues to rise after passing through the intermediate stripping zone d and enters the common distillation zone e, and after sufficient gas-liquid contact, the steam of the secondary light component B is obtained at the secondary light component outlet 7 at the top of the non-feed side of the dividing wall distillation tower, and after condensation by the secondary light component condenser 17, a part of it is refluxed into the dividing wall distillation tower through the secondary light component reflux port 8, and a part of it is extracted as product B; the liquid flowing out from the bottom of the common distillation zone e is collected by the liquid collector 13, and the collected liquid is redistributed into the intermediate stripping zone d and the intermediate discharge zone f according to the proportion by using the liquid distribution device 14; after sufficient gas-liquid contact, component C is obtained at the secondary heavy component outlet 10 below the intermediate discharge zone f, a part of which is heated and partially vaporized by the intermediate reboiler 18 and returned to the dividing wall distillation tower through the secondary heavy component reflux port 9, and a part of it is extracted as product C.

[0041] By adopting the above scheme, the distillation tower only needs to use one tower to complete the separation of a four-component system or a three-component system containing azeotropes and obtain four products or three products respectively. Compared with the prior art, the product quality is stable and the purity is high; the number of equipment is reduced, the equipment investment is saved, the equipment footprint is reduced, and the economy of the process is improved. At the same time, the dividing wall distillation tower is a fully thermally coupled distillation tower, which effectively utilizes the heat of the steam in the tower, avoids the waste of condensation heat of the steam at the top of the tower when using an ordinary distillation tower, realizes the recycling of heat energy inside the tower, and avoids the back-mixing effect of the intermediate components, reduces the mixing problem caused by the different logistics composition between the feed and the feed plate, and improves the thermodynamic efficiency, thereby producing a good energy-saving effect. Furthermore, in the space on one side of the dividing wall in the dividing wall distillation tower, the temperature tends to increase from top to bottom, and the temperature at the bottom of the tower is the highest. The function of the bottom reboiler is to provide rising steam, and to avoid the bottom reboiler providing rising steam for the entire tower through the intermediate reboiler; compared with the bottom reboiler, the heating of the intermediate reboiler can use a low-temperature heat source to reduce the use of high-temperature heat sources, thereby reducing energy costs and improving the economy of the process.

[0042] Embodiment 2:

[0043] like Figure 3 As shown, the difference between this embodiment and the first embodiment is that: the structure where the lower part of the second partition wall 3 extends to the bottom of the tower body 1 is replaced by a partition plate 15 that covers the lower part of the second partition wall 3. If the first partition wall and the second partition wall are arranged in parallel, the partition plate 15 is closed and connected with the lower part of the second partition wall and the tower wall of the tower body away from the first partition wall to form a groove structure. Figure 4 d; if the first partition wall and the second partition wall are arranged vertically, the partition plate 15 is connected to the lower portion of the second partition wall and one side of the first partition wall and the tower wall to form a closed groove structure, see Figure 4 b; and the middle discharge area f is located above the groove, and the secondary heavy component reflux port and the secondary heavy component outlet are arranged in the lower middle part of the tower body between the lower part of the middle discharge area of ​​the groove and the upper part of the partition.

[0044] The height of the second partition wall 3 in this embodiment can be adjusted and determined according to the content of the secondary heavy component in the feed and the purity requirement of the secondary heavy component. When the content of the secondary heavy component is low or the purity requirement of the secondary heavy component is low, the partition wall can be higher than the lower part of the first partition wall. Figure 3 a, or when the content of the secondary heavy component is high or the purity of the secondary heavy component is required to be high, the partition is lower than the lower part of the first partition wall, see Figure 3 b; When the content of the secondary heavy component is high or the purity of the secondary heavy component is required to be high, the second partition wall can be further lengthened, that is, in the extreme case, Figure 2 As shown, there is no partition 15, and the second dividing wall can extend to the bottom of the column at the longest.

[0045] The following two specific implementation objects are used to describe the working process of this distillation tower in detail:

[0046] First, in the chemical synthesis and separation process using methanol as a solvent, the used methanol contains a variety of light component impurities and heavy component impurities. The impurities are removed by distillation and refined to obtain refined methanol for recycling.

[0047] like Figure 5 As shown, crude methanol containing methyl formate, methanol, fusel oil and water enters the dividing wall distillation tower from the feed port, is partially vaporized, and the vapor phase rises to enter the light component distillation zone a. After sufficient gas-liquid contact, methyl formate vapor is obtained at the top of the feed side of the dividing wall distillation tower. After condensation in the light component condenser, part of it flows back to the dividing wall distillation tower, and part of it is produced as methyl formate product; the liquid phase passes downward in turn through the light component stripping zone b and the common stripping zone c, and after sufficient gas-liquid contact, water is obtained at the bottom of the tower body, part of which is heated by the tower bottom reboiler and partially vaporized and then returned to the tower body, and part of it is produced as purified water; then, the vapor obtained by partial vaporization in the tower bottom reboiler rises, and after sufficient gas-liquid contact in the common stripping zone c, it enters the light component stripping zone according to a certain ratio. b and the intermediate stripping zone d; the distribution ratio can be adjusted according to the pressure difference between the feed side and the non-feed side of the dividing wall distillation tower; after passing through the intermediate stripping zone d, the steam continues to rise and enters the common distillation zone e, and after sufficient gas-liquid contact, methanol vapor is obtained at the top of the non-feed side of the dividing wall distillation tower, and after condensation by the secondary light component condenser, a part of it is refluxed to the tower body, and a part of it is produced as a refined methanol product; then, the liquid flowing out from the bottom of the common distillation zone e is collected by a liquid collector, and the collected liquid is redistributed into the intermediate stripping zone d and the intermediate discharge zone f according to the proportion by using a liquid distribution device, and after sufficient gas-liquid contact, fusel oil is obtained below the intermediate discharge zone f, a part of which is returned to the tower body after being heated and partially vaporized by an intermediate reboiler, and a part of it is produced as a fusel oil product.

[0048] Adopting the above process, the raw material crude methanol flow is 35087kg / h, containing 44.68%w of methanol, 42.74%w of water, 10.83%w of methyl formate, and 1.75%w of fusel oil. After distillation treatment, 15425.8kg / h of refined methanol product can be obtained, wherein the methanol content is 99.9%, the water content is 0.11%, reaching the recycling standard, and the methanol recovery rate is 98.3%. The operating temperature of the dividing wall distillation tower is 30-120°C, the operating pressure is 0.1-0.2MPa (absolute pressure), the feed side tower top reflux ratio is 4.5, and the non-feed side tower top reflux ratio is 3.0.

[0049] Second, DMF (N,N-dimethylformamide) is a widely used chemical raw material and an excellent organic solvent. It is widely used in various production industries such as leather making, chemical industry, medicine, pesticides, etc. DMF is recovered from DMF wastewater and refined into DMF products. The raw materials are composed of water, formic acid and DMF. The DMF content of the obtained DMF product is required to be ≥99.5%, the moisture content is ≤500PPM, and the formic acid content is ≤50PPM. The formic acid and DMF in the system will form a high-boiling azeotrope. Using two ordinary distillation towers or a single DWC tower for separation, the moisture and formic acid content in the DMF product are difficult to meet the requirements. Using the technical solution of the present invention, a DMF product with a DMF content of ≥99.5%, a moisture content of ≤400PPM, and a formic acid content of ≤20PPM can be obtained through distillation treatment.

[0050] like Figure 6 As shown, DMF wastewater containing water, formic acid and DMF enters the dividing wall distillation tower from the feed port, partially vaporizes, and the vapor phase rises to enter the light component distillation zone a. After sufficient gas-liquid contact, water vapor is obtained at the top of the feed side of the dividing wall distillation tower. After condensation by the light component condenser, part of it flows back to the dividing wall distillation tower, and part of it is extracted as purified water; the liquid phase passes through the light component stripping zone b and the common stripping zone c downward in turn, and after sufficient gas-liquid contact, an azeotrope of formic acid and DMF is obtained at the bottom of the dividing wall distillation tower. Part of it is heated by the bottom reboiler and partially vaporized and returns to the dividing wall distillation tower, and part of it is extracted; then, the steam obtained by partial vaporization in the reboiler of the dividing wall distillation tower rises, and enters the light component stripping zone b and the intermediate stripping zone d according to a certain ratio after sufficient gas-liquid contact in the common stripping zone c. The distribution ratio can be adjusted according to the top pressure difference between the feed side and the non-feed side of the dividing wall distillation tower. After passing through the intermediate stripping zone d, the steam continues to rise and enters the common distillation zone e. After sufficient contact between gas and liquid, a certain purity of DMF vapor containing a small amount of water is obtained at the top of the non-feed side of the dividing wall distillation tower. After condensation by the secondary light component condenser, part of it flows back to the dividing wall distillation tower, and part of it is produced and circulated back to the dividing wall distillation tower for distillation again; then, the liquid flowing out from the bottom of the common distillation zone e is collected by the liquid collector. The collected liquid is redistributed into the intermediate stripping zone d and the intermediate discharge zone f in proportion using a liquid distribution device. After sufficient contact between gas and liquid, a higher purity DMF is obtained below the intermediate discharge zone f. Part of it is heated and partially vaporized by the intermediate reboiler and then returned to the dividing wall distillation tower, and part of it is produced as a product.

[0051] By adopting the above process, formic acid and DMF form a high-boiling azeotrope, which is extracted from the bottom of the tower after rectification. Since the water and formic acid content of the DMF product are required to be high, a small amount of water is extracted from the top of the tower on the non-feeding side of the dividing wall distillation tower to avoid the formic acid in the system rising to the top of the tower, thereby causing the formic acid content in the DMF product to exceed the standard. The flow rate of the raw material DMF wastewater is 5000kg / h, containing 81.95%w of water, 18.00%w of DMF, and 0.05%w of formic acid. After distillation treatment, 882.37kg / h of DMF product can be obtained, wherein the DMF content is 99.95%, the water content is 390PPM, the formic acid content is 28PPM, and the DMF recovery rate is 98%. The operating temperature of the dividing wall distillation tower is 60-120°C, the operating pressure is 0.05MPa (absolute pressure), the feed side tower top reflux ratio is 1.5, and the non-feed side tower top reflux ratio is 2.2.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A dividing wall distillation tower for separating complex multi-component systems, comprising a tower body (1) and a first dividing wall (2) and a second dividing wall (3) disposed in the tower body and arranged along the axial direction thereof, characterized in that: The upper portion of the first partition wall extends to the top of the tower body, and the lower portion is not connected to the bottom of the tower body; the upper portion of the second partition wall is not connected to the top of the tower body, and the lower portion extends to the bottom of the tower body; the tower body and the tower wall on the opposite side of the first partition wall and the second partition wall are provided with a light component outlet (5), a light component reflux port (6), a feed port (4), a heavy component reflux port (11) and a heavy component outlet (12) in order from top to bottom; the tower body and the tower wall on the same side of the first partition wall and the second partition wall are provided with a sub-light component outlet (12) in order from top to bottom outlet (7), a secondary light component reflux port (8), a secondary heavy component reflux port (9), and a secondary heavy component outlet (10); a liquid collector (13) is provided between the secondary heavy component reflux port and the secondary light component reflux port in the tower body and above the second partition wall; the tower body is divided into a light component distillation zone (a), a light component stripping zone (b), a common stripping zone (c), an intermediate stripping zone (d), a common distillation zone (e), and an intermediate discharge zone (f) by the feed port, the first partition wall, the second partition wall, and the liquid collector; The feed inlet is arranged at the middle and upper part of the tower body between the light component distillation zone and the light component stripping zone, and the light component distillation zone is located above the feed inlet, and the light component stripping zone is located below the feed inlet; the light component outlet and the light component reflux port are respectively arranged at the top and upper part of the tower body in the upper area of ​​the light component distillation zone; the heavy component reflux port and the heavy component outlet are respectively arranged at the lower part and bottom of the tower body in the lower area of ​​the common stripping zone; the sub-light component outlet and the sub-light component reflux port are respectively arranged at the top and upper part of the tower body in the upper area of ​​the common distillation zone; the sub-heavy component reflux port and the sub-heavy component outlet are respectively arranged at the lower part and bottom of the tower body in the lower area of ​​the intermediate discharge zone; A light component condenser (16) is provided on the loop between the light component outlet and the light component reflux port; a sub-light component condenser (17) is provided on the loop between the sub-light component outlet and the sub-light component reflux port; an intermediate reboiler (18) is provided on the loop between the sub-heavy component reflux port and the sub-heavy component outlet; and a bottom reboiler (19) is provided on the loop between the heavy component reflux port and the heavy component outlet.

2. The dividing wall distillation column for separation of complex multi-component systems according to claim 1, characterized in that: The positional relationship between the first partition wall and the second partition wall is set to an intersecting or non-intersecting arrangement structure according to the relative contents of the light component, the sub-light component, the sub-heavy component and the heavy component in the feed.

3. The dividing wall distillation column for separation of complex multi-component systems according to claim 1, characterized in that: A liquid distribution device (14) is also provided below the liquid collector and is higher than the second partition wall. The installation form of the liquid distribution device is a built-in or external structure.

4. The dividing wall distillation column for separation of complex multi-component systems according to claim 1, characterized in that: The light component distillation zone, light component stripping zone, common stripping zone, intermediate stripping zone, common distillation zone, and intermediate discharge zone are all provided with gas-liquid contact medium, and the gas-liquid contact medium is filler and / or tower plate, which is arranged in one or more sections, and a liquid redistributor is provided between every two sections.

5. The dividing wall distillation column for separation of complex multi-component systems according to any one of claims 1 to 4, characterized in that: The structure in which the lower part of the second partition wall extends to the bottom of the tower body is replaced by a partition plate (15) that covers the lower part of the second partition wall, and the secondary heavy component reflux port and the secondary heavy component outlet are arranged in the lower area of ​​the middle discharge zone and in the lower middle part of the tower body above the partition plate.

6. The dividing wall distillation column for separation of complex multi-component systems according to claim 5, characterized in that: The height of the second partition wall is set according to the content of the secondary heavy component in the feed and the purity requirement for the secondary heavy component.

7. A distillation method using the dividing wall distillation column for separation of complex multi-component systems according to claim 6, characterized in that: include: First, a four-component mixture containing A, B, C, and D enters the tower body from the feed inlet, wherein A, B, C, and D are arranged in descending order according to relative volatility; then, a portion of the four-component mixture entering the tower body is vaporized, and the vapor phase rises and enters the light component distillation zone, and after sufficient gas-liquid contact, the vapor of the light component A is obtained at the top of the tower on the feed side of the tower body, and after condensation by the light component condenser, a portion of it is refluxed to the tower body, and a portion of it is extracted as product A; furthermore, the liquid phase passes downward in turn through the light component stripping zone and the common stripping zone, and after sufficient gas-liquid contact, a heavy component D is obtained at the bottom of the tower body, and after being heated and partially vaporized by the tower bottom reboiler, a portion of it is returned to the tower body, and a portion of it is extracted as product D; Then, the steam obtained by partial vaporization in the reboiler at the bottom of the tower rises, and has sufficient gas-liquid contact in the common distillation zone. After the proportion is adjusted according to the pressure difference at the top of the tower on the feed side and the non-feed side of the tower body, it enters the light component distillation zone and the intermediate distillation zone. The steam passes through the intermediate distillation zone and continues to rise into the common distillation zone. After sufficient gas-liquid contact, the steam of the secondary light component B is obtained at the top of the tower on the non-feed side of the tower body. After condensation in the secondary light component condenser, part of it is refluxed to the tower body, and part of it is extracted as product B; finally, the liquid flowing out from the bottom of the common distillation zone is collected by the liquid collector, and the liquid distribution device distributes the proportion, and then enters the intermediate distillation zone and the intermediate discharge zone. After sufficient gas-liquid contact, the secondary heavy component C is obtained below the intermediate discharge zone. After being partially vaporized by heating in the intermediate reboiler, part of it returns to the tower body, and part of it is extracted as product C.

8. A distillation method using a dividing wall distillation column for separation of complex multi-component systems according to any one of claim 6, characterized in that: include: First, a three-component mixture containing A, B, and C is fed into the tower body from the feed port, wherein A, B, and C are arranged in descending order according to relative volatility, and B and C will form an azeotrope BC, and the relative volatility of BC is lower than that of C; then, the three-component mixture entering the tower body is partially vaporized, and the vapor phase rises into the light component distillation zone, and after sufficient gas-liquid contact, the vapor of component A is obtained at the top of the tower on the feed side of the tower body, and after condensation in the light component condenser, a part of it is refluxed to the tower body, and a part of it is extracted as product A; Furthermore, the liquid phase passes downward through the light component stripping zone and the common stripping zone in turn, and after sufficient gas-liquid contact, an azeotrope BC is obtained at the bottom of the tower body, and after being partially vaporized by heating in a reboiler at the bottom of the tower, a part of it returns to the tower body, and a part of it is extracted as an azeotrope product BC; then, the steam obtained by partial vaporization in the reboiler at the bottom of the tower rises, and after sufficient gas-liquid contact in the common stripping zone, it enters the light component stripping zone and the intermediate stripping zone in proportion, and the steam passes through the intermediate stripping zone and continues to rise into the common rectification zone, and after sufficient gas-liquid contact, The vapor of component C with low purity is obtained at the top of the tower on the non-feed side of the tower body, and after being condensed by the sub-light component condenser, a part of it flows back to the tower body, and a part of it is taken out and circulated back to the feed port for distillation again; finally, the liquid flowing out from the bottom of the common distillation zone is collected by the liquid collector, and enters the intermediate distillation zone and the intermediate discharge zone in proportion, and after sufficient gas-liquid contact, high-purity component C is obtained below the intermediate discharge zone, and after being heated in the intermediate reboiler and partially vaporized, a part of it returns to the tower body, and a part of it is taken out as product C.

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