DE2527984A1 - METHOD AND DEVICE FOR MULTI-STAGE LIQUID-LIQUID COUNTER-CURRENT EXTRACTION - Google Patents

Description

Method and device for multistage liquid-liquid countercurrent extraction

The invention relates to a method and a device for multi-stage Plüssig-Liquid-G-egenstrom-extraction.

With multi-stage extractors, which are based on the mixer-separator principle work, agitators such as propeller, turbine, blade stirrers etc. are used as mixing devices. Elements or centrifugal pumps and other retentive Kisch and conveying elements used (DT-PS 1.080.552; DT-AS 1,209,994; U.S. Patent 2,594,675; U.S. Patent 3-325,255). In these extractors, the separators are individual Some steps are arranged one above the other in the shape of a tower and housed within a common jacket. As mixers are inside the jacket in special chambers arranged agitators and next to the separators arranged pumps with single drive and also multi-chamber pumps with one common drive for several pump elements.

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With iixtractors with horizontally next to or behind one another arranged stages are the agitator elements of the mixer both within the same housing as the separating chamber as well as in separate boilers, which are connected to the separators by pipelines.

The use of rotating or other mechanically operated mixing devices for chopping and intensive Mixing of the two liquid phases has a major disadvantage, which is that it is not possible to to disperse and mix liquid phases only to the extent that as is required for the exchange of substances.

Dispersions are always produced, which are much finer than are mated, often it even comes to undesirable ones Emulsions.

These fine dispersions and emulsions require significantly more time than they do to separate into the clear liquid phases relatively coarse dispersions, which are necessary for the implementation of mass transfer processes, so that large-volume Separation chambers are required.

Mixers that also have to fulfill a conveying function are particularly critical. It's not practical here possible to limit the pump output to the required mixing output. Also have the listed Hish organs have a very poor efficiency.

Another disadvantage is that with these extractors, the mixer and pump output in each stage must always be adapted to the quantities that flow through the individual stages. One often carries one for this purpose the phases in the cycle for which additional energy is required.

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So-called static mixers have recently become known, v / which no longer have any mechanically "moving parts" and make it possible to produce dispersions with a predeterminable 2-droplet size and a narrow size distribution.

Such known static mixers consist of a number of mixing elements arranged one behind the other in a tubular housing. The number of mixing elements used in each case is determined on the basis of the desired degree of dispersion and mixing. The phases to be mixed or dispersed are introduced into separate inlet openings at one end of the tubular housing: the dispersion produced exits axially from the mixer housing at the opposite end (GAY 1971, October; Sulzer company publication Agc 10 6/62 Dr. Tauscher). These static mixers are used, among other things, for 1-stage direct current washing processes.

The invention is based on the object of avoiding the disadvantages of the mechanical mixer and multi-stage countercurrent extraction and washing processes using static mixers without the interposition of pumps or other mechanical conveying devices.

According to the invention, this object is achieved by mixing the substance-exchanging phases in a static mixer dispersed and mixed only until the mass transfer is ended between the two phases that you then the dispersion in a separator in the separates pure phases and each of the separated phases is fed in counterflow to the mixer of the next stage, the continuation of the liquid phases by buoyancy and gravitational forces.

Pur the implementation of such a multi-stage countercurrent extract ions process is an extractor based on the mixer-separator principle particularly suitable, in which the Piiasenscheider towers on top of each other

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are arranged and which is characterized by that as a mixer static mixer

I 'I

be used.

Sacb. a further embodiment of the invention Extractors assigns one to the static mixer in each Step on the side in the middle of the separator and connect it on the inlet side via a line or a channel with the outlet for clear heavy phase of the separator of the level above and via a second line or channel with the outlet for clear light phase of the separator level below.

The top and bottom stages differ from the other stages according to the invention in that at least in the uppermost stage instead of connecting the mixer to the outlet for the heavy phase of the above lying separator an inlet connection for the introduction of the extractor to be supplied from the outside heavy phase and at least in the lowest stage instead of connecting the mixer to the outlet for the light phase of the separator below, an inlet connection for the introduction of the extractor light phase to be supplied from the outside is provided.

The mixer can be flanged to the outside of the separator at the side be, but it is preferably arranged within the separation chamber or via a nozzle or a Manhole flanged to the side of the separator so that it protrudes as far as possible into the separator.

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For variable adjustment of the separating mirror level In the separation chamber, the lines for the light and heavy phase from the separator to the mixer can be used an adjustable throttle member can be arranged.

Ξ-ine advantageous further embodiment of the. according to the invention Sxtraktors consists in the fact that you have an outlet connection at least on the Abseh.eideka.mmer of the top step for the removal of clear, light phase and that there is an outlet connection at least at the lowest level for the removal of clear heavy phase.

The weight or buoyancy of the liquid column is used to overcome the pressure loss in the static mixer of the heavy or the light phase, from which, according to the well-known Hegel, the distance (H) of the static Liischsrs can set by the neighboring separators (see Fig. 2):

Here ^ p, r is the pressure drop of the static mixer T is the density of the heavy phase Cr is the density of the light phase.

It is structurally particularly favorable to arrange the static mixer halfway up the separator so that the height of the Separator must be at least equal to 2 χ Η.

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The advantages of the tower extractor according to the invention with static mixers compared to conventional mixer-separator types "consist in particular that

there are no 'mechanically moving parts' tt & d therefore

no signs of wear and tear and no shaft seals are required.

The structural design is significantly simplified and the Dispersion can be precisely determined.

The energy consumption is very low and there is no need to recycle the substance-exchanging phases.

The design of the extractor according to the invention makes it possible also to reduce the separator volume significantly, whereby Material cost savings as well as product and solvent or detergent savings through the reduced Result in filling volume.

Compared to sieve bottom, packed or pulsating Extractors are particularly advantageous that no backmixing occurs and therefore an approx is achieved.

There are no problems with scaling up.

Since there are no mechanically moving parts, the extractor is free from vibrations. The extractor according to the invention also enables the use of any separation aids such as plate packs, chip or fiber fillings, electrostatic precipitators etc. for quick separation of the dispersion.

The invention is illustrated in the drawings and is described in more detail below:

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£ 3 show

Figure 1 using the example of a 4-stage extractor Arrangement of static mixers,

FIG. 2 shows a section of the third stage of the extractor according to the invention with external ones Connecting lines,

Figure 3 shows another embodiment of the invention

Spacious extractor with internal mixers and internal connection channels,

FIG. 4 shows an embodiment of the point at which the liquid phases are introduced into the mixer,

FIG. 5 shows a further embodiment of the introduction point of the liquid phases in the mixer.

Figure 6 a 16-stage extractor for the extraction of Aromatics from a hydrocarbon cut

Zs mean: 1, 1 ^f , 1 ", 1 '" mixer, 2, 2', 2 », 2" »separator,

3 supply line for light phase, 3 '"discharge for light phase,

4 deduction for heavy phase, 4 ¹ "supply line for heavy phase,

5 Dispersion exit, 6 'line light phase from stage 1 to lischer 1', 6 "line light phase from stage 2 to chisel 1", 6 ¹ ' ¹ line light phase from stage 3 to lüischer 1'", 7 Line for heavy phase from level 2 to Uiseher 1, 7 'line heavy phase from level 3 to I.Iischer 1' and 7 "line heavy phase from level 4 to LIi3eher 1", S throttle valve, 9 and 10 separate inlet openings, ^ » 12 perforated diaphragm, 13 antechamber, 14 central tube

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11 ilantely and 15 ring canal, 101 initiation a.es to be extracted Hydrocarbon cut, 102 discharge point for Solvent, 103 discharge solvent containing aromatic compounds, 104 line for aromatic-free raffinate, 105 inlet solvent-free Extract return, 106 removal of the solvent- and ■ aronate-free raffinate, 107 feed for washing water and 103 Removal of solvent-based washing water.

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The mode of operation of the extractor according to the invention is based on

the figure 1 explained in more detail, which represents a 4-stage Sxtraktor.

Each "e \ stages" consists of a static mixer 1, 1 ^f , 1 ", 1 '" and a separator 2, 2', 2 "and 2"'. Mixers and separators on adjacent stages are connected to one another by pipes.

It should contain an N-Methy! Pyrrolidon (HIP) Hydrocarbon fraction to be washed with water remove the NMP to a residual content of 50 ppm.

The contaminated hydrocarbon reaction is specific

Weight of 820 kg / m ³ .

The specific lighter hydrocarbon fraction is in the The lowest stage is fed to the static mixer via line 3. The specifically heavier water is in the top Stage fed via line 4 '"to the static mixer 1'",

The washed light hydrocarbon fraction is withdrawn from the Y / ash tower in the top stage at 3 '";

specifically yß
the heavy wash water laden with NMP leaves the wash tower in the lowest stage via 4.

The light phase lays in countercurrent to the heavy phase the following way back through the extractor shown:

Entry through line 3 into mixer 1, which at the same time heavy phase from the separator 2 'via the line 7, due to the gravity, flows in. The mixer is like that designed that in the present Pail the wash water, which forms the heavy phase, is only dispersed to the extent that as it is necessary for the mass transfer. The in Mixer formed and placed in the separator. 2 introduced dispersion therefore separates very quickly into a

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heavy5, aqueous phase, which is at the bottom of the Separator, and the lighter hydrocarbon ph -.- '. Se, which is below the bottom of the above Separation chamber accumulates. From here the light phase flows through the line 6 'by means of buoyancy. to the LIischer 1 'of the 2nd stage, which also Heavy phase from the separator 2 ″ of the 3 · stage, due to the gravity, flows in.

Ir. Liischer 1 ^! Both phases are mixed and dispersed to bring about the exchange of substances. The dispersion then flows into the separator 2 ', where the two phases separate again. As a result of the buoyancy force, the light phase continues to flow via line 6 "then to mixer 1" of the 3rd stage, before it meets the heavy phase from separator 2 '"of the A stage, which by gravity acts via line 7" dem Kischer flows in. As before, the dispersion required for the mass transfer takes place in the mixer and then the phase separation takes place in the separator 2 ". The light phase flows through the buoyancy force from here to the mixer 1 '" of the 4th and last stage, where it is connected to the via line 4'"The fresh Y / ash water supplied is mixed to carry out the mass transfer. The washed light hydrocarbon phase subsequently separated from the dispersion in the separator 2 '" is removed via line 3'"in the upper part of the separator.

Ris; ur 2 shows in an enlarged representation a detail of the 3rd stage of the multi-stage washing and extraction turret according to the invention with pipes 6 ″ and 7 ″ arranged outside the jacket 11 and mixer 1 ″ arranged inside the separator 2 ″. To influence the separating mirror level in the separator, 2 ^e throttle fitting 8 is provided in lines 6 ″ and 7 ″. The mixer 1 ″ contains, for example, 5 common mixing elements. The two

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Liquids to be dispersed are at one end of the static mixer introduced into the mixer via separate inlet ports 9 and 10; the dispersion produced exits at 5 at the other end of the mixer.

FIG. 3 shows a section from a structurally modified extractor with mixer 1 ″ and lines 6 ″ and 7 ″ arranged within the separation chambers Throttle fittings 8 in the lines 6 ″ and 7 ″ can be replaced by a single throttle point, such as, for example, by the perforated diaphragm 12 shown in FIG. 3 in the line 7 ″ for the heavy phase. In such a case with constant operating conditions, the hydraulic conditions are also constant, so that a change, which is possible with adjustable throttle valves, is not necessary. The required throttling effect can be calculated unambiguously according to the known laws of hydrodynamics and the throttle orifice can also be dimensioned according to the known rules.

The introduction of the liquid phases into the mixer must take place in such a way that the heavy phase does not get into the line of the light phase can get and vice versa, so that light phase cannot get into the line of the heavy phase, this ensures that both phases flow together only through the mixer.

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Figures 4 a and 4 "b show the structural configuration of the Ξ-inleitungsstelle of the liquid phases in the mixer. This dip the inlet tube 6 ^T and 7 'as in the arranged before the Liischer antechamber 13 a that the Γ-Iündung the light phase is higher than the mouth of the difficult phase or the mouth of the heavy phase is lower than the mouth of the light phase.

In another embodiment of the point at which the liquid phases are introduced into the mixer according to Pigur 5 , the light phase is introduced through a tube 14 arranged centrally in the axial direction in the antechamber 13 of the mixer. The 3chv. ^{The first} phase is introduced into the antechamber through an annular channel 15 that concentrically surrounds the central tube 14, the mouth of the annular channel 15 in front of the mouth of the central tube 14 by at least the length of the outer diameter of the P.ingkan-ls 15 in the direction of flow.

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FIG. 6 shows the use of a 16-stage extractor for extracting aromatics from an aromatics-containing hydrocarbon cut by means of a solvent and washing out the solvent containing the (essentially) aromatics-free raffinate by means of water. The levels are counted from bottom to top. 12 stages are provided for aromatic extraction; 4 further stages are intended for washing out the solvent with water.

The hydrocarbon cut 101 to be extracted is introduced as a light phase into the mixer of the 3rd stage _t together with the light hydrocarbon phase separated in the separator of the 2nd stage. A common solvent 102 (for example an N-methylpyrrolidone-glycol mixture) is introduced into the mixer of the 12th stage as the heavy phase. The aromatic-containing solvent 103 is drawn off as a heavy phase via a level control from the lowest stage of the extractor.

A largely solvent-free extract return 105 is fed as a light phase into the mixer of the lowest (= first) stage initiated.

The largely aromatic-free raffinate 104, which has absorbed solvent in the course of the extraction process, and as light phase in the separator of the 12th stage is fed directly into the mixer of the 13th stage, which is the lowest Level of 4 washing levels.

The required wash water 107 is introduced as a heavy phase into the mixer of the uppermost (= sixteenth) stage. From the The raffinate 106, which is largely free of solvents and aromatics, is drawn off as a light phase in the top-level separator.

The solvent-containing wash water 103 is controlled by a level controller removed as the heavy phase from the separator of the 13th stage.

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Claims (7)

- 13- Claims A method of multistage Plüssig-Liquid-Cregenstrom-2ztraktion, characterized in that the substance-exchanging phases are dispersed and mixed in a static mixer until the substance exchange between the two phases has ended; that the dispersion is then converted into the pure in a separator Phases are separated and each of the separated phases is fed in countercurrent to the 2-mixer of the respective next stage, the conductors of the liquid phases being carried out by buoyancy and gravitational forces. 2) .ijxtraktor according to the mixer-separator principle for carrying out the method according to claim 1 with phase separators arranged one above the other in a tower-like manner, characterized in that static mixers are used as the mixer. 3) Extractor according to claim 2, characterized in that the static mixer in each stage is arranged laterally in the middle of the separator and on the 5inla3seite via a line or a channel with the outlet for clear heavy phase of the separator of the level above and a the second line or duct connects to the clear light phase outlet of the separator of the stage below. 4-) Zxtraktor according to claims 1 and 2, characterized in that at least in the uppermost stage an inlet port for the introduction of the heavy phase to be fed to the extractor from the outside and at least in the lowest stage an inlet pipe for the introduction of the extractor from light phase to be supplied externally is provided. -H- ^.: GiNAL INSPECTED 609882/0507 5) extract or s according to one or more of the preceding claims 1 to 3> characterized in that the mixer is arranged within the separator. 6) Extractor according to one or more of the preceding claims 1 to 5, characterized in that an adjustable throttle element is arranged in each case on the lines for light and heavy phase from the separator to the mixer. 7) Sxtraktor according to one or more of the preceding claims 1 to 6, characterized in that at least one outlet port for the removal of clear light phase at the separation chamber of the uppermost stage and that one outlet port for the removal of clearer at least at the lowest stage difficult phase. 609882/0507