Method and device for extractive distillation

FIELD: chemistry.

SUBSTANCE: method of separation of starting mixture (A) consisting of two or more constituents, by extractive distillation with the selective solvent (S) within dividing wall column (TKW), is proposed. The separation is performed in the dividing wall column (TKW) having a dividing wall aligned in a longitudinal direction (TW) and extending to an upper end of the column and dividing an interior of the column into first region (1), second region (2), and lower combined column region (3). The starting mixture is fed into first region (1), first top stream (B) is taken off from first region (1), and second top stream (C) is taken off from second region (2), with each of the streams having a prescribed specification. The selective solvent (S) is introduced in an upper part of first region (1) and/or in an upper part of second region (2), and flow of solvent (S1) into the first region (1) and/or flow of solvent (S2) into second region (2) are set so that each of the prescribed specifications for top streams (B, C) are met.

EFFECT: invented method of dividing mixtures is more efficient in terms of energy and solvent consumption.

6 cl, 7 dwg, 1 tbl

 

The invention relates to a method for source separation of a mixture of two or more components by extractive distillation, it is suitable for this purpose provided with a partition dividing the column, as well as to their application.

Extractive distillation is a well known method of distillation separation of mixtures containing components that are very little different in terms of their relative volatility or they azeotrope boiling.

Extractive distillation is carried out with the addition of a selective solvent, also known as extracting agent, which has a much higher boiling point than the boiling point you want to divide the mixture, and which due to its selective affinity for the individual components to be separation of the mixture increases the difference in their relative volatility. Essential criteria for the choice of a suitable selective solvent is finding such absorber, which allows separation with minimum circulating phase of the absorber, i.e. which are characterized by a high absorption capacity.

It is known that for complex tasks division, as a rule, mixtures with at least three components, and the individual components must be obtained in pure form, are used equipped with a septum RA is a separating column. They have a separator, i.e. generally flat, situated in the longitudinal direction of the column sheet, which prevents lateral mixing of fluid flows and flash steam in separate zones of the column. Provided with a partition dividing the columns are compared to classical distillation columns economically more advantageous, as they solve the problems of separation, for which in the normal case, you have two columns, one handset, and the cost of investment and energy are much lower.

Carrying out extractive distillation provided with a partition dividing the column is known.

Such methods are described, for example, in DE-C 19958464. Thanks to the special design implementation provided with a partition separating columns, namely due to the fact that the area of selection on the upper end of the column is closed, the temperature in this zone of the column can be adjusted by controlling the available pressure. Due to the fact that the pressure in the closed with the upper side of the zone selection may vary in relation to the operating pressure in the column, the pressure drop can be used to control the flow of steam generated in the divided partial areas of the column.

In accordance with this invention yavlyaetsyaprostota more effective in energy consumption and solvent method, as well as being suitable for this purpose, provided with a partition dividing the column.

This problem is solved by the method of separation of the mixture of two or more components by extractive distillation with a selective solvent provided with a partition dividing the column, which is characterized by the fact that

the method is carried out in a separation column located in the longitudinal direction of the column wall, which is communicated to the upper end of the column and which divides the inside of the columns on the first partial area, the second partial zone and the General area of the column

- original mix served in a first partial area of the first partial zone assign head first stream and the second partial zone assign the second head flow to a preset specification (characteristics),

- selective solvent load in the upper part of the first partial area and/or in the upper part of the second partial area, and

the number loaded into the first partial flow of the solvent and/or the number loaded into the second partial flow of the solvent regulate so that you meet predefined specifications (characteristics) of the head threads.

Unexpectedly, it was found that a simple constructive implementation provided pereg what rodkey separation column, namely, due to the fact that the partition is brought to the upper end of the separation column, both separated by a partition partial areas of the inner space of the column independently of each other can be optimal for the corresponding problem extractive distillation thermodynamic conditions. In particular, it is possible to load the optimal amount of solvent separately in each partial area, so that the absorption capacity of the solvent is most used in both partial areas and a General need in the solvent is reduced to a minimum. At the same time the power consumption is significantly reduced compared to the "classic"with a partition dividing the column.

As the initial mixture, as a rule, suitable mixtures of hydrocarbons or other organic components that are due to small differences in volatility, at least two components or due to the formation of azeotropes can be split only by additive selective solvent, which changes the relative volatility.

The initial mixture is loaded into the first partial area is equipped with a dividing wall separation column, often approximately in its middle third. Depending on the particular composition to be separation of the mixture it is possible that the components is, for example, or a mixture of components with the highest volatility can easily separated by distillation from the other components of the original mixture. In this case, no additives selective solvent in the upper zone of the first partial zone to separate the head stream from a single pure component with the highest volatility or group of components with the highest volatility.

However, as a rule, the separation of the pure component or group of components with the highest volatility in the first partial area of the separation column is only possible with the addition of the selective solvent in the upper zone of the first partial area, and together with this countercurrent to be the splitting of the original mixture. In this case, the selective solvent is loaded under suitable thermodynamic conditions, usually at low temperatures and is loaded components of the initial mixture, with whom he has a high affinity, in contrast to what component or components with which it has a lower affinity, i.e. poorly soluble in the selective solvent components remain in the vapor phase and are assigned as the head of the stream.

Loaded components of the original mixture of the solvent with which it has a higher affinity than with the component or components that are separated from the first partial area as the head of the stream flows on the lower end of the partition in the form of a pair of second partial area provided p is regardly separation columns.

In the second partial area is equipped with a dividing wall separation column, depending on the particular composition to be separation of the initial mixture may be possible to implement a simple distillation separation is better soluble in the selective solvent components, however, can also be that their separation is only possible with the addition of a selective solvent in a counter in the upper area of the second partial zone, i.e. extractive distillation.

Allocated from the second partial zone of the parent thread, as well as allocated from the first partial areas of the stream, to enable a single pure component or group of components with a particular boiling range.

Head-streams of the first and of the second partial zones are usually condense in the condenser at the head of the column, partially loaded as the return product back to the column and the rest are assigned.

For the main flow, as a rule, you specify certain requirements as to the purity, i.e. set specifications (characteristics).

Due to the fact that you want to split the mixture into the two partial areas provided with a partition dividing the column constantly differ from each other in terms of quantity and composition, unless the division performed by extractive distillation, CA the DOI partial area will always require a certain optimal amount of selective solvent, in order to achieve the given specifications (characteristics) of the head threads.

According to the proposed method of extractive distillation in a column equipped communicated to the upper end of the wall, perhaps a simple way to load in one or both partial areas independently from each other are optimal for the corresponding problem of dividing the number of selective solvent.

From the bottom of the column according to one variant of the method according to the invention is given solvent, which is still loaded with one or more components, which is better soluble in the selective solvent. The loaded solvent is then freed from dissolved components under suitable thermodynamic conditions in the degassing column and the purified solvent, as a rule, is recycled to the column extractive distillation.

According to one preferred variant of the method, the lower the total area of the column is given vapor stream is partially or completely condensed, fully or partially removed, and the rest again is returned as the return of the product in the column extractive distillation. In part of the column under these samples dissolved components are complete degassing of the solvent.

In addition, depending on the tasks the division, from each zone of the column, in particular, from the first partial area and/or the second partial zone and/or lower the total area of the column can be defined to have one or more side streams.

According to one particularly preferred in respect of energy consumption the method according to the invention from one or more thermodynamically particularly suitable stages of the column extractive distillation is given to the fluid flow, due to the integration of heat with a hot, degassed solvent is partially or completely evaporates and is returned to the column extractive distillation for the same separation step, from which was allotted to the fluid flow. As a consequence, the total energy consumption can be significantly reduced to approximately the interval from 40 to 60%.

The object of the invention is also provided with a dividing wall separation column for carrying out extractive distillation, which has structural features, namely, that the partition is brought to the top of the column and because of this allows the mixing of fluid flows and flash steam only lower the total area of the column. The so-called first and second partial areas are separated from each other by a partition.

Depending on the composition fed to the extractive column distillation initial mixture, and the given specifications (features which specific) subject to division in the column extractive distillation fractions of the length of a partition, as well as its position relative to the axis of the column may be different. So for example, you can have a partition in the middle or outside mid. The location is outside the middle is often preferred, as the load is liquid and vapour in the two partial areas, as a rule, different.

In the preferred form of execution in the first and/or second partial zone of the column extractive distillation, respectively, over the designated selective supply of the solvent provided a plate backwashing picking up a pair of selective solvent, often three to five plates. Although relatively used type in principle there are no limitations, especially suitable plates for small loads of liquid, in particular, valve, bubble cap plates or plates of Tormann.

The use of plates backwashing in relation to the residual amount of solvent can be obtained particularly clean head a fraction.

One of the most important applications of the method and the column extractive distillation according to the invention is the petrochemical industry, in particular the division With4-factions, With5-fractions, separation of mixtures of fragrances, in particular mixtures of benzene, toluene and xylene, or isomers of xylene.

The invention is explained below using an exemplary embodiment and drawings, to the which show:

Figure 1 - schematic illustration of a first form of execution of the column extractive distillation according to the invention,

Figure 2 is another preferred form of the column extractive distillation according to the invention,

Figure 3 is another form of execution of the column extractive distillation according to the invention,

4 is a preferred form of execution plates backwashing,

5 is a form of execution with integrated degassing solvent

6 is a form complete with plates backwashing and integrated degassing of the solvent and

7 - form of the integration of heat.

The same reference numbers in the drawings indicate the same or corresponding features.

Presented in figure 1 column extractive distillation is made as provided with a partition dividing the columns TKW with passing in the longitudinal direction of the column to the upper end of the partition wall TW. Partition TW divides the inner space of the columns of the first partial zone 1, the second partial zone 2, and the lower total zone 3 columns. In the first partial area 1 column load subject to splitting of the original mixture, namely approximately in the middle of this zone. The first stream of selective solvent is loaded as a stream S1 ver is the Nuits area of the first partial zone 1 and the second stream of selective solvent as stream S2 in the upper area of the second partial zone 2. From the first partial zone 1 is allocated to the first head flow In, is condensed in the condenser at the head of the column, partially as a return of product is fed back to the column, and the rest is given. Similarly, from the second partial area 2 is assigned the second head flow, is condensed in the condenser at the head of the column, the part is returned to the second partial area, and the rest is given.

From the bottom of the column is given loaded with a selective solvent stream SL.

Presented in figure 2 form of execution differs from the forms of execution of figure 1 that in the first partial area 1 is loaded only stream of selective solvent stream S1. Distillation separation in the second partial zone 2 occurs without the addition of the selective solvent.

In run 3 is loaded only one stream of selective solvent, however, in contrast to the forms of execution of figure 2 flow S2 is loaded into the upper zone of the second partial zone 2.

The form of execution according to Fig. 4 in addition to that shown in figure 1 the main form contains plates backwashing R, which are located respectively on top of places supplying a flow of solvent S1 and S2 in partial zones 1 and 2.

In shown in Fig. 5 the form of execution of the lower total zone 3 columns is given steam is brassy side stream, condenses partially or completely in the condenser part is given as a stream D, and the rest as the return of the product is fed back to the column. Under lateral diversion of the flow D loaded solvent by supplying heat completely escaped over the evaporator V in the lower part of the column and is discharged as purified solvent, namely as a stream of SR. The purified solvent after cooling in the condenser preferably is recycled to the extractive distillation.

Presented on Fig.6 form of execution differs from that shown in figure 5 forms of execution location plates backwashing R in the partial zone 1 and 2 over supply respectively flow of solvent S1 and S2.

Fig.7 shows particularly preferred in respect of the consumption variant of the method with integration of heat, with hot, purified solvent, as a stream SR, heats the heat exchangers W abstracted from the column extractive distillation liquid.

Example:

Division With4-fraction by extractive distillation

The task of the division was to share With4-faction with the following composition, wt.%:

PROPADIENE0,03
propene0,02
propyne0,06
n-butane5,74
ISO-butane2,44
n-butene13,88
isobutan25,63
TRANS-butene-2of 4.44
CIS-butene-22,95
1,3-butadiene43,81
1,2-butadiene0,14
butane-10,13
vinylacetylene0,73

in the butane fraction from 90 wt.% butane and butenes fraction with 98 wt.% butane, respectively, as head of products, and the flow of the lower part of the column, which, along with the selective solvent contains 99% 1,3-butadiene, as well as better soluble than 1,3-butadiene components.

As the selective solvent used is N-organic as an aqueous solution from 8.3 wt.% water.

Serves the boot stream in 31.250 kg/h4-faction with the above composition provided in the partition column with 65 theoretical separation plates, and in comparative example used is equipped with a dividing wall column with normal, i.e. not reaching the top of the wall and in the example according to the invention is applied up to the upper end of the column wall. The separation stage is considered from the bottom up. In the comparative example, the partition optimirror t is modynamics and is placed between the 37th and 58th separation steps at 4 bar, accordingly, between the 38th and 60th dividing plates 5 bar.

Critical parameters of the method are summarized in the following table.

Compare.Izopet.Compare.Izopet.
The pressure in the head part [bar]4455
The required capacity of the evaporator [kW]29851211742457020576
The required total amount of solvent [kg/h]542860373110474830366275
The ratio of the separation of solvent*1,32**2,71*1,0**2,80
* on the upper end of the partition
** on the flow of solvent S1/S2 of figure 1

The results in the table show that the required capacity of the evaporator at a pressure of 4 bar in the column for the method according to the invention is 30% lower than for the method in the normal column with the wall and when the pressure in the column 5 bar 16% lower.

In addition, the required total amount of solvent for the same task separation when the pressure in the column of 4 bar with the method according to the invention by 31% no is e, than in a classical column and when the pressure in the column 5 bar 23%. Respectively are lower production costs, particularly energy costs, and investment costs due to the small required cross-section of the column.

In addition, classical, equipped with a partition of the column compared with the column according to the invention with brought to the top of the partition have the additional disadvantage that they are less flexible to changes in working pressure: in order to perform a given task rudelania with the above capacity of the evaporator, when the pressure increases only by 1 bar, namely from 4 to 5 bar, required a design change to the classic, equipped with a septum dividing the columns in the sense that it was necessary to move the partition vertically on one separation stage (from 37th to 38th separation step) and one the degree of change along its length, to move the supply of the source gas mixture for five separation steps down (from the 12th stage of the separation zone of perevozki on the 7th step), and lateral drainage to move one step up.

In contrast to provided with a partition separating column according to the invention when changing the operating pressure of such changes is not required.

1. The method of separation ishodnogo mixture (A) of two or more components by extractive distillation with a selective solvent (S) in provided with a partition dividing column (TKW), characterized in that the method is carried out in the separation column (TKW) located in the longitudinal direction of the column wall (TW), which is communicated to the upper end of the column and which divides the inside of the columns on the first partial area (1), the second partial zone (2) and lower the total area of the column (3), the initial mixture (A) served in the first partial area (1)from the first partial area (1) assign the first head flow (In) and from the second partial area (2) assign the second head flow (C) with a predefined specification, selective solvent (S) are loaded into the upper part of the first partial zone (1) and/or in the upper part of the second partial zone (2) and the number loaded into the first partial area (1) flow of solvent (S1) and/or the number loaded into the second partial area (2) flow of the solvent (S2) is adjusted in such a manner that satisfies predefined specifications head flows (In, With).

2. The method according to claim 1, characterized in that only the upper zone of the first partial zone (1) load the stream of selective solvent (S1).

3. The method according to claim 1, characterized in that only the upper area of the second partial zone (2) load the stream of selective solvent (S2).

4. The method according to claim 1, characterized in that from the bottom of the common area, (3) assign columns lateral flow (D) and loaded solvent (SL) from the bottom is th part of column Tegaserod in the evaporator (V) the bottom of the column and assign as a purified stream of solvent (SR) and preferably recycled to the extractive distillation.

5. The method according to one of claims 1 to 4, characterized in that one or more thermodynamically suitable separation steps assign one or more flow or partial flow of the supplied partition separating columns (TKW), through the integration of heat evaporated partly or fully hot degassed by a stream of solvent (SR) and again serves to provided with a partition dividing column (TKW), preferably on the same stage, which was allotted to the fluid flow or partial flow.

6. Application of the method according to one of claims 1 to 5 for separating mixtures of hydrocarbons, in particular With4-factions, With5-fractions or mixtures of aromatic hydrocarbons, preferably mixtures of benzene, toluene, xylene or mixtures of isomeric xylenes.



 

Same patents:

FIELD: petrochemical processes.

SUBSTANCE: invention relates to a method for continuously separating C4-fraction by extractive distillation using selective solvent on extractive distillation column, which method is characterized by a separation barrier disposed in extractive distillation column in longitudinal direction extending to the very top of the column to form first zone, second zone, and underlying common zone. Butanes (C4H10)-containing top stream is withdrawn from the first zone, butenes (C4H8)-containing top stream is withdrawn from the second zone, and C4H6 stream containing C4-fraction hydrocarbons, which are more soluble in selective solvent than butanes and butenes, is withdrawn from underlying common zone of column.

EFFECT: reduced power consumption and expenses.

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4 dwg, 2 tbl, 5 ex

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16 cl, 3 dwg

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EFFECT: increased separation efficiency.

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6 cl, 7 dwg, 1 tbl

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1 tbl

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SUBSTANCE: to separate a biazetropic mixture butylpropionate-propionic acid used is a method of extractive rectification with application as a separating agent of sulpholane (SF), taken in ratio 1:5-6 to an initial mixture in a column of extraction rectification with efficiency 35-50 t.t., with reflux ratio in the column being 1-3. Withdrawal of butylpropionate in distillate and the mixture propionic acid-sulpholane in the column bottom is carried out. After that, the mixture PC-SF is supplied to the column of the separating agent regeneration with efficiency 8 t.t., value of reflux ratio is 0.5-1.0. The separating agent is withdrawn from the column bottom and supplied into the column. Pressure in the columns constitutes 100 mm Hg. The method makes it possible to obtain the target products (BP, PA) of a specified quality - 99.5 mol%.

EFFECT: simplification of technology and reduction of capital expenditure, increased quality of obtained products.

1 dwg, 1 tbl

FIELD: chemistry.

SUBSTANCE: method of inhibiting polymerisation of vinyl aromatic compounds during extractive distillation includes the following steps: a) providing a mixture containing styrene; b) adding one 2-sec-butyl-4,6-dinitrophenol (DNBP) inhibitor to the mixture; and c) performing extractive distillation of the mixture after step b) to of separate styrene; d) forming less than 200 ppmw of a polymer from the styrene.

EFFECT: minimum polymer formation.

5 cl, 1 tbl, 1 ex

FIELD: power engineering.

SUBSTANCE: invention is intended for extraction distillation. Device for extraction distillation of the extract from the flow of raw material comprises the extraction distillation column, raw material flow supply line, solvent supply line, reboiler with internal steam distributor, connected with the extraction distillation column, water steam supply line, connected with the steam distributor, and water steam supply line from the extraction distillation column, connected with the internal steam distributor. The extract is an aromatic hydrocarbon. Reboiler is selected from the group consisting of the kettle boiler, thermosyphon reboiler and reboiler with forced circulation.

EFFECT: improvement of efficiency of extraction distillation.

10 cl, 1 dwg, 1 ex

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