CN111298471A - Dividing wall rectifying tower for separating complex multi-component system and rectifying method - Google Patents
Dividing wall rectifying tower for separating complex multi-component system and rectifying method Download PDFInfo
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- CN111298471A CN111298471A CN202010239122.1A CN202010239122A CN111298471A CN 111298471 A CN111298471 A CN 111298471A CN 202010239122 A CN202010239122 A CN 202010239122A CN 111298471 A CN111298471 A CN 111298471A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/14—Fractional distillation or use of a fractionation or rectification column
- B01D3/141—Fractional distillation or use of a fractionation or rectification column where at least one distillation column contains at least one dividing wall
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/42—Regulation; Control
- B01D3/4205—Reflux ratio control splitter
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/42—Regulation; Control
- B01D3/4211—Regulation; Control of columns
- B01D3/4216—Head stream
Abstract
The invention discloses a dividing wall rectifying tower for separating a complex multi-component system and a rectifying method, belonging to the technical field of rectification, wherein the rectifying tower comprises a tower body, a first dividing wall and a second dividing wall, the upper part of the first dividing wall extends to the top of the tower body, the lower part of the first dividing wall 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 of the second dividing wall extends to the bottom of the tower body; a light component outlet, a light component return opening, a feed inlet, a heavy component return opening and a heavy component outlet are sequentially arranged on the tower body from top to bottom and opposite to the tower wall on the different side of the first partition wall and the second partition wall; a second light component outlet, a second light component return opening, a second heavy component return opening and a second heavy component outlet are sequentially arranged on the tower body from top to bottom and opposite to the tower wall on the same side of the first partition wall and the second partition wall; a liquid collector is arranged in the tower body and above the second partition wall. The rectifying tower can be used for respectively obtaining four products or three products with high purity and stable quality from four-component systems or three-component systems containing azeotrope, and has good energy-saving effect.
Description
Technical Field
The invention belongs to the technical field of rectification, and particularly relates to a dividing wall rectifying tower for separating a complex multi-component system and a rectifying method.
Background
The separation process plays a very important role in chemical production. In the chemical separation process, rectification is the most widely applied separation method. High energy consumption is an inevitable problem in the rectification process all the time, the research on the energy saving aspect of the rectification process becomes a research hotspot in recent years, various high-efficiency thermal coupling rectification and novel rectification technologies are continuously developed, wherein a Dividing Wall rectifying tower (DWC for short) is the research focus in the field.
The DWC tower is provided with a vertical wall in the rectifying tower, the vertical wall can also extend to the top or the bottom of the tower, and two parts of the DWC tower separated by the dividing wall can have a common rectifying section or a common stripping section or a common rectifying section and a common stripping section at the same time. Depending on the position of the partition wall, there are divided into a completely thermally coupled partition wall column (DWC-FC, FIG. 1(a)), a side-rectification partition wall column (DWC-SR, FIG. 1(b)), and a side-stripping partition wall column (DWC-SS, FIG. 1 (c)).
In the traditional process, two rectifying towers, two reboilers and two condensers are needed to realize the separation of three components, and only one tower is needed to finish the separation by using DWC, and at least one condenser or one reboiler can be reduced. The DWC tower is a thermodynamically ideal system structure, and when the three-component mixture is separated, the same separation task is completed by using the same theoretical plate number, and the DWC tower needs less reboiling heat and condensation amount than the traditional two-tower process. For some given materials, the dividing wall rectifying tower needs smaller reflux ratio than the conventional rectifying tower, so that the operation capacity is increased, the energy is saved by over 60 percent at most, and the equipment investment is possibly saved by 30 percent.
The DWC tower can be widely applied to petroleum refining, petrochemical industry, chemical products and gas separation. For example, CN201820597333.0 applies the bulkhead column technology to an aromatic extraction and rectification device, thereby reducing the energy consumption of the device, and improving the economy and the long-term stable and reliable operation capability of the device; CN201210347586.X discloses a systematic method for preparing piperylene and dicyclopentadiene, which uses two dividing wall rectifying towers, has simple process, improves yield and purity, saves energy consumption by more than 30 percent, and increases economic benefit of the device; CN201910343639.2 discloses a method and a device for separating isopropyl alcohol diisopropyl ether aqueous solution, which integrates heterogeneous azeotropic distillation and pressure swing distillation, a partition tower and a heat pump technology, solves the separation problem of a multi-azeotrope complex system, and has the advantages of high efficiency, energy conservation, high product purity and high recovery rate.
A single-seat DWC column with a single dividing wall can be used to separate a three component mixture to yield three products. For a four component system, one DWC column plus one common rectification column is typically required for separation to obtain four products. There are patents that increase the number of side streams to obtain a greater number of products, such as CN 201910024467.2; there are also patents which increase the number of dividing walls to obtain a greater number of products, such as CN200910234363.0, CN 201810900872.1. However, in either case, the other discharges, apart from the top and bottom discharges, are essentially side discharges. When the requirement on the purity of the product is high, the purity and the quality stability of the product obtained by side line discharging are difficult to ensure. For some three-component systems containing the azeotrope, three products can be extracted by using the single-seat DWC tower, but the separation process becomes complicated due to the existence of the azeotrope, the purity of the product is difficult to ensure, and especially for the process with higher requirement on the product purity, the requirement is difficult to meet by using the single-seat DWC tower.
Disclosure of Invention
In view of the above, the present invention aims to provide a dividing wall distillation column and a distillation method for separating a complex multi-component system, especially a four-component system or a three-component system containing an azeotrope, which can be used to obtain a plurality of products with high purity and stable quality and have a good energy saving effect.
The invention is realized by the following technical scheme:
the invention provides a dividing wall rectifying tower for separating a complex multi-component system, which comprises a tower body, a first dividing wall and a second dividing wall, wherein the first dividing wall and the second dividing wall are arranged in the tower body and are arranged along the axial direction of the tower body; the upper part of the second partition wall is not connected with the top of the tower body, and the lower part of the second partition wall extends to the bottom of the tower body; a light component outlet, a light component return opening, a feed inlet, a heavy component return opening and a heavy component outlet are sequentially arranged on the tower body from top to bottom and opposite to the tower wall on the different side of the first partition wall and the second partition wall; a second light component outlet, a second light component return opening, a second heavy component return opening and a second heavy component outlet are sequentially arranged on the tower body from top to bottom and opposite to the tower wall on the same side of the first partition wall and the second partition wall; a liquid collector between the secondary heavy component reflux port and the secondary light component reflux port is arranged in the tower body and above the second partition wall; the tower body is divided into a light component rectifying area, a light component stripping area, a public stripping area, an intermediate stripping area, a public rectifying area and an intermediate discharging area by a feeding hole, a first partition wall, a second partition wall and a liquid collector.
Further, the feed inlet is arranged at the middle upper part of the tower body between the light component rectifying area and the light component stripping area, the light component rectifying area is arranged above the feed inlet, and the light component stripping area is arranged below the feed inlet; the light component outlet and the light component reflux opening are respectively arranged at the top and the upper part of the tower body in the upper area of the light component rectifying area; the heavy component return port and the heavy component outlet are respectively arranged at the lower part and the bottom of the tower body in the lower area of the public stripping area; the secondary light component outlet and the secondary light component return opening are respectively arranged at the top and the upper part of the tower body in the upper area of the public rectification area; the secondary heavy component return port and the secondary heavy component outlet are respectively arranged at the lower part and the bottom of the tower body in the lower area of the middle discharging area.
Further, the first partition wall and the second partition wall are arranged in an intersecting or non-intersecting arrangement according to the relative amounts of the light fraction, the second heavy fraction and the heavy fraction in the feed.
Furthermore, a liquid distribution device which is higher than the second partition wall is arranged below the liquid collector, and the installation form of the liquid distribution device is a built-in or external structure.
Further, the light component rectifying area, the light component stripping area, the common stripping area, the middle stripping area, the common rectifying area and the middle discharging area are all provided with gas-liquid contact media, the gas-liquid contact media are fillers and/or column plates and are arranged into one section or multiple sections, and a liquid redistributor is arranged between every two sections.
Further, a light component condenser is arranged on a loop between the light component outlet and the light component reflux port; a sub-light component condenser is arranged on a loop between the sub-light component outlet and the sub-light component return opening; an intermediate reboiler is arranged on a loop between the secondary heavy component return port and the secondary heavy component outlet; and a tower bottom reboiler is arranged on a loop between the heavy component return port and the heavy component outlet.
Further, the structure that second partition wall lower part extends to the tower body bottom is replaced by the baffle in second partition wall lower part at the bottom of the pocket, just inferior heavy component backward flow mouth, inferior heavy component export are located middle discharge area lower part region and lower part in the tower body of baffle top.
Further, the height of the second separating wall is set according to the content of the secondary heavy component in the feed and the purity requirement of the secondary heavy component.
The invention also relates to a rectification method using a dividing wall rectification column for complex multicomponent system separation according to the above, comprising: firstly, a four-component mixture containing A, B, C, D enters a tower body from a feed inlet, wherein A, B, C, D of the four-component mixture are arranged from high relative volatility to low relative volatility; then, the four-component mixture entering the tower body is partially vaporized, the vapor phase rises and enters a light component rectification area to be fully contacted with gas and liquid, the vapor of the light component A is obtained at the tower top at the feeding side of the tower body, and after the vapor is condensed by a light component condenser, a part of the vapor flows back to the tower body, and a part of the vapor is extracted as a product A; then, the liquid phase passes through the light component stripping area and the public stripping area downwards and is fully contacted with gas and liquid, a heavy component D is obtained at the tower bottom of the tower body, and part of the heavy component D returns to the tower body after being partially vaporized by a reboiler at the tower bottom, and the other part of the heavy component D is extracted as a product D; then, the steam obtained by partial vaporization of a reboiler at the bottom of the tower rises, after full gas-liquid contact is carried out in a common stripping zone, and after proportion adjustment is carried out according to the pressure difference of the tower tops of a feeding side and a non-feeding side of the tower body, the steam enters a light component stripping zone and an intermediate stripping zone, passes through the intermediate stripping zone and continuously rises to enter the common rectifying zone to be fully contacted with the gas-liquid, the steam of a second light component B is obtained at the tower top of the non-feeding side of the tower body, and after the steam is condensed by a second light component condenser, one part of the steam flows back to the tower body, and the other part of the steam is taken as a; and finally, collecting the liquid flowing out from the bottom of the public rectification area by a liquid collector, distributing the liquid by a liquid distribution device according to a proportion, then enabling the liquid to enter the middle stripping area and the middle discharging area to be fully contacted with gas and liquid, obtaining a secondary heavy component C below the middle discharging area, heating the secondary heavy component C by an intermediate reboiler to vaporize, returning part of the secondary heavy component C to the tower body, and extracting part of the secondary heavy component C serving as a product C.
The invention also relates to a rectification method using a dividing wall rectification column for complex multicomponent system separation according to the above, comprising: firstly, a three-component mixture containing A, B, C enters a tower body from a feed inlet, wherein A, B, C of the three-component mixture is arranged from high relative volatility to low relative volatility, B, C forms 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, the vapor phase rises and enters a light component rectification area to be fully contacted with gas and liquid, the vapor of the component A is obtained at the tower top at the feeding side of the tower body, and after the vapor is condensed by a light component condenser, a part of the vapor flows back to the tower body, and a part of the vapor is extracted as a product A; then, the liquid phase passes through the light component stripping area and the public stripping area downwards and is fully contacted with gas and liquid, an azeotrope BC is obtained at the tower bottom of the tower body, and part of the azeotrope BC returns to the tower body after being partially vaporized by a heating part of a reboiler at the tower bottom, and the other part of the azeotrope BC is extracted as an azeotrope product BC; then, the steam obtained by partial vaporization of a reboiler at the bottom of the tower rises, enters a light component stripping area and an intermediate stripping area in proportion after full gas-liquid contact is carried out in the common stripping area, the steam passes through the intermediate stripping area and continuously rises to enter the common rectifying area to be fully contacted with the gas-liquid, the steam of a component C with low purity is obtained at the top of the tower at the non-feeding side of the tower body, part of the steam condensed by a secondary light component condenser flows back to the tower body, and the other part of the steam is extracted and then circulated back to a feeding hole for rectification again; and finally, collecting the liquid flowing out from the bottom of the public rectification area by a liquid collector, feeding the liquid into the intermediate stripping area and the intermediate discharging area in proportion, fully contacting the liquid with the gas, obtaining a high-purity component C below the intermediate discharging area, heating the component C by an intermediate reboiler to vaporize, returning part of the component C to the tower body, and extracting part of the component C as a product C.
The invention has the advantages that:
1. the separation of a four-component system can be completed by only using one tower to obtain four products, and compared with the prior art, the product has stable quality and high purity; the number of equipment is reduced, the equipment investment is saved, the occupied area of the equipment is reduced, and the economical efficiency of the process is improved.
2. The separation effect on a 3-component system containing the azeotrope is good, and the obtained product has high purity and high recovery rate and can meet strict quality requirements.
3. This dividing wall rectifying column is complete thermal coupling rectifying column, has effectively utilized the heat of steam in the tower, and the waste of top of the tower steam condensation heat when having avoided using ordinary rectifying column has realized the inside heat energy cyclic utilization of tower, has avoided the back mixing effect of middle component simultaneously, reduces the feeding and the feeding board on the mixing problem that the commodity circulation composition is different to arouse, has improved thermodynamic efficiency to produce fine energy-conserving effect.
4. In the space on one side of the partition wall in the partition wall rectifying tower, the temperature is in a rising trend from top to bottom, wherein the temperature at the bottom of the tower is the highest. The function of the tower bottom reboiler is to provide ascending steam, and the tower bottom reboiler is used for avoiding providing the whole tower ascending steam; compared with a tower bottom reboiler, the intermediate reboiler can be heated by adopting a low-temperature heat source, and the use of a high-temperature heat source is reduced, so that the energy cost is reduced, and the process economy is improved.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the means of the instrumentalities and combinations particularly pointed out hereinafter.
Drawings
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the accompanying drawings, in which:
FIG. 1 is a schematic diagram of a prior art rectification column;
FIG. 2 is a schematic structural diagram of an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of a second embodiment of the present invention; a. b respectively represents that the partition boards are at different heights;
FIG. 4 is a view showing the positional relationship between the first and second partition walls according to the present invention; a. b, c and d represent four forms respectively
FIG. 5 is a flow chart of a four component system of the present invention;
FIG. 6 is a flow diagram of an azeotrope-containing three component system of the present invention;
element number description: 1-a tower body; 2-a first dividing wall; 3-a second separation wall; 4-a feed inlet; 5-a light component outlet; 6-light component reflux port; 7-light fraction outlet; 8-a light component reflux port; 9-a second heavies reflux port; 10-secondary heavy component outlet; 11-a heavies return port; 12-a heavy ends outlet; 13-a liquid collector; 14-a liquid dispensing device; 15-a separator; 16-a light component condenser; a 17-sub-light fraction condenser; 18-an intermediate reboiler; 19-bottom reboiler;
a light component rectifying area a, a light component stripping area b, a common stripping area c, an intermediate stripping area d, a common rectifying area e and an intermediate discharging area f.
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention in a schematic way, and the features in the following embodiments and examples may be combined with each other without conflict.
The first embodiment is as follows:
as shown in fig. 2, in the dividing wall distillation column for separating a complex multi-component system in this embodiment, two longitudinal dividing walls are provided inside a column body 1 of the dividing wall distillation column, that is, the upper part of a first dividing wall 2 extends to the top of the column, the lower part of the first dividing wall is not connected with the bottom of the column, the upper part of a second dividing wall 3 is not connected with the top of the column, the lower part of the second dividing wall extends to the bottom of the column, the middle upper part of one side of the column wall close to the first dividing wall 2 is provided with a feed port 4, the top of the column wall on the same side as; the tower wall on the non-feeding side is sequentially provided with a secondary light component outlet 7, a secondary light component return opening 8, a secondary heavy component return opening 9 and a secondary heavy component outlet 10 from top to bottom; the lower part of the tower body 1 is provided with a heavy component return opening 11, and the bottom part is provided with a heavy component outlet 12. The first partition wall 2, the second partition wall 3 and the plurality of outlets divide the space in the column into 6 regions: a light component rectifying area a, a light component stripping area b, a common stripping area c, an intermediate stripping area d, a common rectifying area e and an intermediate discharging area f. A liquid collector 13 and a liquid distribution device 14 are arranged between the common rectification zone e and the intermediate stripping zone d and the intermediate discharging zone f. The liquid distributor 14 may be a built-in distributor installed inside the column or an external distributor installed outside the column, and when an external distributor is used, the liquid outlet and the liquid inlet are further provided in the regions of the column wall on the non-feeding side between the liquid collector 13 and the middle stripping region d and the middle discharging region f.
In the embodiment, the 6 regions (abcdef) in the tower body are provided with gas-liquid contact media which are one or two of fillers and tower plates. The gas-liquid contact medium in each region can be longitudinally divided into one section or a plurality of sections, and a liquid redistributor is arranged between each two sections.
The first partition wall 2 and the second partition wall 3 in this embodiment have two arrangements within the column, see fig. 4 (overhead view), i.e. an intersecting (fig. 4a) or non-intersecting (fig. 4c) configuration, in particular the perpendicular one (fig. 4b) being preferred in the intersecting arrangement and the parallel one (fig. 4d) being preferred in the non-intersecting arrangement. Meanwhile, the positional relationship of the first partition wall and the second partition wall is adjusted and determined according to the relative contents of the light component, the second heavy component and the heavy component in the feed.
The rectification method of the dividing wall rectifying tower has the flow as shown in figure 5, and comprises the following steps:
a mixture (A, B, C, D, which is arranged from high relative volatility to low relative volatility and can be four different components or three components plus an azeotrope) containing A, B, C, D enters a tower body 1 of a dividing wall rectifying tower from a feed inlet 4, is partially vaporized first, a vapor phase rises to enter a light component rectifying area a, after full contact of gas and liquid, steam of a component A is obtained at a light component outlet 5 at the top of the tower at the feed side of the dividing wall rectifying tower, and after condensation of a light component condenser 16, a part of the steam flows back to the dividing wall rectifying tower through a light component reflux inlet 6, and a part of the steam is extracted as a product A; the liquid phase downwards passes through the light component stripping region b and the public stripping region c in sequence, after full contact of gas and liquid, a component D is obtained at a heavy component outlet 12 at the bottom of the dividing wall rectifying tower, part of the component D is heated and vaporized by a tower bottom reboiler 19 and then returns to the dividing wall rectifying tower through a heavy component reflux port 11, and part of the component D is taken as a product D; the steam obtained by partial vaporization of the tower bottom reboiler 19 rises, and enters a light component stripping area b and an intermediate stripping area d according to a certain proportion after full gas-liquid contact is carried out in the common stripping area c; the distribution ratio can be adjusted according to the pressure difference between the feeding side of the dividing wall rectifying tower and the tower top of the non-feeding side; then the steam continuously rises to enter a public rectification area e after passing through an intermediate stripping area d, the steam is fully contacted with gas and liquid, and then the steam of a secondary light component B is obtained at a secondary light component outlet 7 at the top of the non-feeding side of the dividing wall rectification tower, and after the steam is condensed by a secondary light component condenser 17, part of the steam flows back into the dividing wall rectification tower through a secondary light component reflux opening 8, and the other part of the steam is taken as a product B to be extracted; collecting the liquid flowing out from the bottom of the common rectification zone e through a liquid collector 13, and redistributing the collected liquid into the middle stripping zone d and the middle discharging zone f according to the proportion by using a liquid distributing device 14; after full contact of gas and liquid, the component C is obtained at a secondary heavy component outlet 10 below the intermediate discharging area f, part of the component C is heated by an intermediate reboiler 18 to be vaporized and then returns to the dividing wall rectifying tower through a secondary heavy component reflux port 9, and part of the component C is taken as a product C to be extracted.
By adopting the scheme, the rectifying tower can finish the separation of a four-component system or a three-component system containing an azeotrope by only using one tower to respectively obtain four products or three products, and compared with the prior art, the product has stable quality and high purity; the number of equipment is reduced, the equipment investment is saved, the occupied area of the equipment is reduced, and the economical efficiency of the process is improved. Meanwhile, the dividing wall rectifying tower is a complete thermal coupling rectifying tower, the heat of steam in the tower is effectively utilized, the waste of the condensation heat of the steam on the top of the tower when the common rectifying tower is used is avoided, the cyclic utilization of the heat energy in the tower is realized, the back mixing effect of the intermediate components is avoided, the mixing problem caused by different material flow compositions on the feeding plate and the feeding plate is reduced, the thermodynamic efficiency is improved, and a good energy-saving effect is generated. Furthermore, in the space at one side of the partition wall in the dividing wall rectifying tower, the temperature is increased from top to bottom, wherein the temperature at the bottom of the tower is the highest. The function of the tower bottom reboiler is to provide ascending steam, and the tower bottom reboiler is used for avoiding providing the whole tower ascending steam; compared with a tower bottom reboiler, the intermediate reboiler can be heated by adopting a low-temperature heat source, and the use of a high-temperature heat source is reduced, so that the energy cost is reduced, and the process economy is improved.
Example two:
as shown in fig. 3, the present embodiment is different from the first embodiment in that: the structure that 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 is arranged at the bottom 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 connected with the lower part of the second partition wall and the tower wall of the tower body far away from the first partition wall in a sealing way to form a groove structure, as shown in fig. 4 d; if the first partition wall and the second partition wall are vertically arranged, the partition 15 is connected with the lower part of the second partition wall and the first partition wall and the tower wall at one side in a closed manner to form a groove structure, as shown in fig. 4 b; the middle discharging area f is positioned above the groove, and the secondary heavy component return opening and the secondary heavy component outlet are arranged at the middle lower part of the tower body between the lower part of the middle discharging area of the groove and the upper part of the clapboard.
The height of the second dividing wall 3 in this embodiment can be adjusted depending on the content of the secondary heavy fraction in the feed and on the purity requirement for the secondary heavy fraction. The partition can be higher than the lower part of the first partition, see fig. 3a, when the secondary heavy component content is low or the requirement on the secondary heavy component purity is low, or lower than the lower part of the first partition, see fig. 3b, when the secondary heavy component content is high or the requirement on the secondary heavy component purity is high; when the secondary heavies content is high or the requirement for secondary heavies purity is high, the second partition wall can be extended further, i.e. in the extreme case, as shown in fig. 2, without partition 15, and can extend as far as the bottom of the column.
The working flow of the rectifying tower is explained in detail by the following two concrete implementation objects:
firstly, in the chemical synthesis and separation process with methanol as a solvent, the used methanol contains a plurality of light component impurities and heavy component impurities, and the impurities are removed by rectification and refining to obtain refined methanol for recycling.
As shown in fig. 5, crude methanol containing methyl formate, methanol, fusel oil and water enters the dividing wall rectifying tower from a feed inlet, part of the crude methanol is vaporized, a vapor phase rises to enter a light component rectifying area a, after full contact of the gas and the liquid, methyl formate vapor is obtained at the top of the feed side tower of the dividing wall rectifying tower, part of the vapor is condensed by a light component condenser and then flows back to the dividing wall rectifying tower, and part of the vapor is extracted as a methyl formate product; the liquid phase downwards passes through the light component stripping area b and the public stripping area c in sequence, after full contact of gas and liquid, water is obtained at the bottom of the tower body, one part of the water is heated by a reboiler at the bottom of the tower and is vaporized and then returns to the tower body, and the other part of the water is taken as purified water; then, steam obtained by partial vaporization of a reboiler at the bottom of the tower rises, and enters a light component stripping area b and an intermediate stripping area d according to a certain proportion after full gas-liquid contact is carried out in a common stripping area c; the distribution ratio can be adjusted according to the pressure difference between the feeding side of the dividing wall rectifying tower and the tower top of the non-feeding side; the steam continuously rises to enter a public rectification area e after passing through an intermediate stripping area d, methanol steam is obtained at the top of the non-feeding side of the dividing wall rectification tower after full contact of gas and liquid, a part of the methanol steam is condensed by a secondary light component condenser and then flows back to the tower body, and a part of the methanol steam is extracted as a refined methanol product; then, collecting the liquid flowing out from the bottom of the public rectification area e through a liquid collector, redistributing the collected liquid into the middle stripping area d and the middle discharging area f according to the proportion by using a liquid distributing device, fully contacting the liquid with the gas and the liquid, obtaining fusel oil below the middle discharging area f, vaporizing a part of the fusel oil by a heating part of an intermediate reboiler, returning the part of the fusel oil into the tower body, and extracting the other part of the fusel oil as a fusel oil product.
By adopting the flow scheme, the flow rate of raw material crude methanol is 35087kg/h, and the raw material crude methanol comprises 44.68% w of methanol, 42.74% w of water, 10.83% w of methyl formate and 1.75% w of fusel oil. After rectification treatment, 15425.8kg/h of refined methanol product can be obtained, wherein the methanol content is 99.9%, the water content is 0.11%, the recycling standard is reached, and the methanol recovery rate is 98.3%. The operation temperature of the dividing wall rectifying tower is 30-120 ℃, the operation pressure is 0.1-0.2 MPa (absolute pressure), the reflux ratio of the tower top at the feeding side is 4.5, and the reflux ratio of the tower top at the non-feeding side is 3.0.
DMF (N, N-dimethylformamide) is a chemical raw material with wide application, is an excellent organic solvent, and is widely applied to various production industries such as leather making, chemical engineering, medicines, pesticides and the like. DMF is recovered from DMF wastewater and refined into a DMF product, the raw materials comprise water, formic acid and DMF, and the DMF product is required to have a DMF content of more than or equal to 99.5 percent, a water content of less than or equal to 500PPM and a formic acid content of less than or equal to 50 PPM. Formic acid and DMF in the system form a high boiling azeotrope. Two common rectifying towers or a single DWC tower are used for separation, and the moisture and the formic acid content in the DMF product are difficult to meet the requirements. By using the technical scheme of the invention, the DMF product with the DMF content of more than or equal to 99.5 percent, the water content of less than or equal to 400PPM and the formic acid content of less than or equal to 20PPM can be obtained through rectification treatment.
As shown in fig. 6, DMF waste water containing water, formic acid and DMF enters into the dividing wall rectifying tower from the feed inlet, is partially vaporized, and the vapor phase rises to enter into the light component rectifying region a, and after full contact of the gas and the liquid, steam of water is obtained at the top of the tower at the feed side of the dividing wall rectifying tower, and after condensation of the light component condenser, a part of the steam flows back to the dividing wall rectifying tower, and a part of the steam is extracted as purified water; the liquid phase downwards passes through the light component stripping area b and the public stripping area c in sequence, after full contact of gas and liquid, an azeotrope of formic acid and DMF is obtained at the bottom of the dividing wall rectifying tower, part of the azeotrope is heated by a reboiler at the bottom of the dividing wall rectifying tower to be vaporized and then returns to the dividing wall rectifying tower, and part of the azeotrope is extracted; then, the steam obtained by partial vaporization of the reboiler of the dividing wall rectifying tower rises, and enters a light component stripping area b and an intermediate stripping area d according to a certain proportion after full gas-liquid contact is carried out in a common stripping area c. The distribution ratio can be adjusted according to the pressure difference between the feeding side of the dividing wall rectifying tower and the tower top of the non-feeding side. The vapor continuously rises to enter a public rectification area e after passing through an intermediate stripping area d, DMF vapor with a certain purity containing a small amount of water is obtained at the top of the non-feeding side tower of the dividing wall rectification tower after being fully contacted with gas and liquid, a part of the DMF vapor is condensed by a secondary light component condenser and then flows back to the dividing wall rectification tower, and a part of the DMF vapor is extracted and then is circulated back to the dividing wall rectification tower for rectification again; then, the liquid flowing out from the bottom of the common rectification zone e is collected by a liquid collector. The collected liquid is redistributed proportionally into the intermediate stripping section d and the intermediate discharge section f using a liquid distribution device. After full contact of gas and liquid, DMF with higher purity is obtained below the intermediate discharging area f, one part of DMF is heated by an intermediate reboiler to be vaporized and then returns to the dividing wall rectifying tower, and the other part of DMF is taken as a product to be extracted.
By adopting the process, formic acid and DMF form an azeotrope with high boiling point, and are extracted from the bottom of the tower after rectification. Because the water and formic acid content of the DMF product are high, the formic acid in the system is prevented from rising to the tower top to cause the formic acid content in the DMF product to exceed the standard by taking a measure of extracting a small amount of water from the tower top at the non-feeding side of the dividing wall rectifying tower. The raw DMF wastewater flow was 5000kg/h, containing 81.95% w of water, 18.00% w of DMF and 0.05% w of formic acid. After rectification 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 operation temperature of the dividing wall rectifying tower is 60-120 ℃, the operation pressure is 0.05MPa (absolute pressure), the reflux ratio of the tower top at the feeding side is 1.5, and the reflux ratio of the tower top at the non-feeding side is 2.2.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and it is apparent that 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 such 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 such modifications and variations.
Claims (10)
1. A dividing wall rectifying column for separating a complex multi-component system comprises a column body (1), and a first dividing wall (2) and a second dividing wall (3) which are arranged in the column body and arranged along the axial direction of the column body, wherein the upper part of the first dividing wall extends to the top of the column body, and the lower part of the first dividing wall is not connected with the bottom of the column body; the upper part of the second partition wall is not connected with the top of the tower body, and the lower part of the second partition wall extends to the bottom of the tower body; a light component outlet (5), a light component return opening (6), a feed inlet (4), a heavy component return opening (11) and a heavy component outlet (12) are sequentially arranged on the tower body from top to bottom relative to the tower wall on the different side of the first partition wall and the second partition wall; a secondary light component outlet (7), a secondary light component return opening (8), a secondary heavy component return opening (9) and a secondary heavy component outlet (10) are sequentially arranged on the tower body from top to bottom relative to the tower wall on the same side of the first partition wall and the second partition wall; a liquid collector (13) between the secondary heavy component return opening and the secondary light component return opening is arranged in the tower body and above the second partition wall; the tower body is divided into a light component rectifying area (a), a light component stripping area (b), a common stripping area (c), a middle stripping area (d), a common rectifying area (e) and a middle discharging area (f) by a feeding hole, a first partition wall, a second partition wall and a liquid collector.
2. The dividing wall type rectifying tower for the separation of the complex multicomponent system as claimed in claim 1, wherein the feed inlet is arranged at the middle upper part of the tower body between the light component rectifying zone and the light component stripping zone, and the light component rectifying zone is arranged above the feed inlet and the light component stripping zone is arranged below the feed inlet; the light component outlet and the light component reflux opening are respectively arranged at the top and the upper part of the tower body in the upper area of the light component rectifying area; the heavy component return port and the heavy component outlet are respectively arranged at the lower part and the bottom of the tower body in the lower area of the public stripping area; the secondary light component outlet and the secondary light component return opening are respectively arranged at the top and the upper part of the tower body in the upper area of the public rectification area; the secondary heavy component return port and the secondary heavy component outlet are respectively arranged at the lower part and the bottom of the tower body in the lower area of the middle discharging area.
3. The divided wall rectification column for the separation of a complex multicomponent system according to claim 1 wherein the first and second dividing walls are positioned in an intersecting or non-intersecting arrangement depending on the relative amounts of light, lighter, heavier and heavier components in the feed.
4. Dividing wall column for the separation of complex multicomponent systems according to claim 1, characterized in that a liquid distribution device (14) is provided below the liquid collector above the second dividing wall, the liquid distribution device being installed in an internal or external configuration.
5. The dividing wall distillation column for separating a complex multicomponent system according to claim 1, wherein the light component rectification zone, the light component stripping zone, the common stripping zone, the intermediate stripping zone, the common rectification zone and the intermediate discharge zone are all provided with gas-liquid contact media, the gas-liquid contact media are fillers and/or trays, and are arranged into one section or multiple sections, and a liquid redistributor is arranged between each two sections.
6. The dividing wall column for the separation of complex multicomponent systems according to claim 1, wherein a light fraction condenser (16) is provided on the loop between the light fraction outlet and the light fraction reflux inlet; a sub-light component condenser (17) is arranged on a loop between the sub-light component outlet and the sub-light component return opening; an intermediate reboiler (18) is arranged on a loop between the secondary heavy component return port and the secondary heavy component outlet; and a tower bottom reboiler (19) is arranged on a loop between the heavy component return port and the heavy component outlet.
7. A divided wall column rectifier for the separation of complex multicomponent systems according to any of claims 1 to 6, wherein the structure of the lower part of the second dividing wall extending to the bottom of the column body is replaced by a partition (15) which is recessed in the lower part of the second dividing wall, and the secondary heavy component return port and the secondary heavy component outlet are provided in the lower region of the intermediate discharge zone and in the lower middle part of the column body above the partition.
8. The dividing wall column for the separation of complex multicomponent systems according to claim 7, wherein the height of the second dividing wall is set according to the content of the secondary heavy component in the feed and the purity requirement for the secondary heavy component.
9. Method for rectification with a dividing wall column for the separation of complex multicomponent systems according to any of claims 1 to 8, characterized in that it comprises:
firstly, a four-component mixture containing A, B, C, D enters a tower body from a feed inlet, wherein A, B, C, D of the four-component mixture are arranged from high relative volatility to low relative volatility; then, the four-component mixture entering the tower body is partially vaporized, the vapor phase rises and enters a light component rectification area to be fully contacted with gas and liquid, the vapor of the light component A is obtained at the tower top at the feeding side of the tower body, and after the vapor is condensed by a light component condenser, a part of the vapor flows back to the tower body, and a part of the vapor is extracted as a product A; then, the liquid phase passes through the light component stripping area and the public stripping area downwards and is fully contacted with gas and liquid, a heavy component D is obtained at the tower bottom of the tower body, and part of the heavy component D returns to the tower body after being partially vaporized by a reboiler at the tower bottom, and the other part of the heavy component D is extracted as a product D; then, the steam obtained by partial vaporization of a reboiler at the bottom of the tower rises, full gas-liquid contact is carried out in a common stripping area, the steam enters a light component stripping area and an intermediate stripping area after being proportionally adjusted according to the pressure difference of the tower top at the feeding side and the non-feeding side of the tower body, the steam passes through the intermediate stripping area and continuously rises to enter the common rectifying area to be fully contacted with the gas and the liquid, the steam of a second light component B is obtained at the tower top at the non-feeding side of the tower body, and after being condensed by a second light component condenser, one part of the steam flows back to the tower body, and the other part of the steam is taken as a product B to; and finally, collecting the liquid flowing out from the bottom of the public rectification area by a liquid collector, distributing the liquid by a liquid distribution device according to a proportion, then enabling the liquid to enter the middle stripping area and the middle discharging area to be fully contacted with gas and liquid, obtaining a secondary heavy component C below the middle discharging area, heating the secondary heavy component C by an intermediate reboiler to vaporize, returning part of the secondary heavy component C to the tower body, and extracting part of the secondary heavy component C serving as a product C.
10. Method for rectification with a dividing wall column for the separation of complex multicomponent systems according to any of claims 1 to 8, characterized in that it comprises:
firstly, a three-component mixture containing A, B, C enters a tower body from a feed inlet, wherein A, B, C of the three-component mixture is arranged from high relative volatility to low relative volatility, B, C forms 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, the vapor phase rises and enters a light component rectification area to be fully contacted with gas and liquid, the vapor of the component A is obtained at the tower top at the feeding side of the tower body, and after the vapor is condensed by a light component condenser, a part of the vapor flows back to the tower body, and a part of the vapor is extracted as a product A; then, the liquid phase passes through the light component stripping area and the public stripping area downwards and is fully contacted with gas and liquid, an azeotrope BC is obtained at the tower bottom of the tower body, and part of the azeotrope BC returns to the tower body after being partially vaporized by a heating part of a reboiler at the tower bottom, and the other part of the azeotrope BC is extracted as an azeotrope product BC; then, the steam obtained by partial vaporization of a reboiler at the bottom of the tower rises, enters a light component stripping area and an intermediate stripping area in proportion after full gas-liquid contact is carried out in the common stripping area, the steam passes through the intermediate stripping area and continuously rises to enter the common rectifying area to be fully contacted with the gas-liquid, the steam of a component C with low purity is obtained at the tower top at the non-feeding side of the tower body, a part of the steam is condensed by a secondary light component condenser and then flows back to the tower body, and a part of the steam is extracted and then circulated back to a feeding hole for rectification again; and finally, collecting the liquid flowing out from the bottom of the public rectification area by a liquid collector, feeding the liquid into the intermediate stripping area and the intermediate discharging area in proportion, fully contacting the liquid with the gas, obtaining a high-purity component C below the intermediate discharging area, heating the component C by an intermediate reboiler to vaporize, returning part of the component C to the tower body, and extracting part of the component C as a product C.
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