EP1296753B1 - Method and device for reducing byproducts in the mixture of educt streams - Google Patents

Abstract

In a process for mixing reactant streams ( 1, 2; 5 ) to produce a product stream ( 10 ) using a mixing configuration ( 15, 16 ) having a number of reactant feed points, an excess component stream of one reactant is divided into two reactant substreams ( 1, 2 ) and fed into the suction region ( 3, 4 ) of a mixing space ( 12 ) at right angles to a deficient component ( 5 ) entering the mixing space ( 12 ).

Description

The invention relates to a method and an apparatus for Reduction of by-product formation when mixing at least two Educt streams for example in the production of organic mono- or Polyisocyanates by mixing mono- or polyamines with phosgene elevated temperatures.

When amine and phosgene are mixed, for example, by two starting materials call it in the implementation of the amine - which in an organic Solvent is present - it can also form instead of isocyanate of intermediate products, such as the undesirable by-product Urea come. These by-products are found as solid deposits the wall of the reaction container again. The by-product formation can especially when there is backflow in the mixing device comes because product-rich fluid comes into contact with educt-rich fluid. A One way to avoid undesired by-product formation is to in the implementation of the amine, the largest possible excess of phosgene adjust. Because of the high toxicity of the phosgene, however, the setting is a phosgene excess in the implementation highly undesirable.

Deposits or possible caking of at higher mixing temperatures Reactants on the mixing room surfaces can be diluted strongly avoid the reactants. The strong dilution of the reactants in turn causes higher processing costs for the product in the next one Process stage and is therefore only an inadequate alternative Mixing two or more components in the liquid phase are also the pressure losses occurring in the mixing device of concern which the Mixing energy to be used by increasing turbulent diffusion processes not negligible influence.

Therefore, mixing devices for mixing educt streams become known who are in mixing facilities with unmoving and those with have moving components divided. Mixing devices with moving Parts are for example from DE-AS-2 153 268 or US-3,947,484 or as Mixing devices with rotor and stator disks from EP-0 291 819 B1, DE-37 17 057 C2 and US-4,915,509 become known. Becomes a highly toxic substance, such as Processed phosgene, make the storage points more mobile Components of such mixers are a potential source of phosgene leakage the environment and therefore a high security risk.

The sources of danger avoid mixing devices without involvement moving components. A static mixer, for example known from EP-0 322 647 B1 ring hole nozzle. When using a The ring-hole nozzle as a static mixing device becomes one of the two educt streams constricted. The other educt stream becomes smaller in the form of a multitude Rays, which are generated by the holes arranged in a ring, in the constricted beam initiated. The main disadvantage when using a Ring nozzle is, however, the fact that solid deposits already in individual Holes can lead to a lower flow. The one about a scheme Set total volume flow flowing through all holes in the ring nozzle remains constant since the remaining holes are now more heavily loaded. The easing the flow, however, promotes further solid deposition, so that it generally comes earlier that a single one from a multitude of holes clogged.

DE-OS 29 50 216 relates to an alternative to a ring hole nozzle, namely a cylindrical mixing chamber into which fan-like spray jets be initiated. Due to the high pre-pressures required for the procedure are necessary, as well as experience-related blockages caused by Growth and build-up of the liquid phases on the walls of the mixing chamber this approach is unsatisfactory.

US 3,507,626 relates to a venturi mixing device. This Mixing device is specially designed for mixing phosgene with amine Production of isocyanates with a first and a second inlet as well an outlet. A first line section includes a venturi section a converging section, a narrow section and a diverging section Section. A second line section is coaxial in the first line section recorded and acts as the first entry. The second line section includes a bevel leading to the converging section corresponds. The second line section opens into a mixing chamber extends around the venturi section of the first line section. The Mixing device ensures mixing and prevents clogging by the Formation of by-products. A back flow of the mixture through the This will open the inside of the cone-shaped tube prevents the area between its outside and the wall is dimensioned as low as possible. An overgrowth between the axially slidably configured conical dome and the outlet opening of the conically configured tube body is avoided, depending on Accumulation of educt at the exit point of the inside of the cone configured tubular body slidable rod-shaped section that with is provided with a thread, can be moved in the axial direction. This allows the outlet openings between the conical element and the outlet opening can be kept approximately constant. With this Configuration of a mixing device, however, are only injection angles of 45 ° with respect to the coaxial gap between the outer surface of the tubular body and the wall of the pipe section possible.

DE AS 17 92 660 B2 relates to a method and an apparatus for Mixing and reacting an amine with phosgene to an isocyanate. With this The amine and phosgene processes are carried out coaxially and mixed with one another, the two streams of amine and phosgene being ring-shaped or conical are formed at an acute angle to each other at a crossing and mixing point cut and immediately before, at and after this intersection when entering an expanded reaction space can be accelerated. There is an injection gap by an axially adjustable inside a tube Cone limited. Depending on the position of the cone, place it at the outlet of the pipe larger or smaller gap widths appear at the entry gap. Depending on the degree of The device can be used to increase the opening configured in the form of a gap the gap width is adjusted depending on their increase become. Taking into account the axial travel of the conical Bodies that adjust in the axial direction can be adjusted in relation to the gap-shaped or annular-gap-shaped outlet openings maximum Achieve injection angles of 45 ° to 60 °.

Solids possibly accumulating on the edges of the mixing chamber can be removed with cleaning mandrels at the discharge point can be installed movably. EP-0 830 894 A1 discloses one Solution. By means of the cleaning mandrel, which is a movable component, an attempt is made to keep an introduction point free of deposits, whereby - if that highly toxic phosgene is one of the starting materials - a high security risk, as above already mentioned, through the formation of a new potential phosgene exit point is created. A deposit can be removed using the solution carry out solids from the mixing chamber using the cleaning dome, however, this is paid for by the formation of a danger zone in the form of the Storage location of the movable cleaning mandrel.

In view of the prior art shown, the object of the invention based on a blending process with unmoving components available too make with which organic mono- or polyisocyanates continuously and free of deposits while avoiding the formation of by-products have it made.

According to the invention, in a process for mixing educt streams, to produce a product stream, a mixed configuration with a number of Eduktzuführstellen used in which an excess component stream in two Educt partial streams is split, the mixing room in the intake area to be mixed to the deficit component.

By dividing the excess component stream into two Mixing room separate feed streams, the mixing time of the Excess current molecules by shortening the cross diffusion paths with the Shortened deficit component; also the cross diffusion of the deficit component stream in the excess component flows are shortened drastically, so that there is a faster mixing process under Avoidance of by-product formation and deposits can be achieved. By the injection of the excess component into the intake area of a the free jet of the sub-shot component entering the front of the mixing chamber, can the deficit component in the mixing room through the Sheath excess component streams, so that in the wall areas of the Mixing room, the excess component is also present in excess and none Deposits on the walls are possible due to by-product formation.

In a further embodiment of the method on which the invention is based Mixing two educt streams, the distribution ratio of the excess component stream, supplied via two separate feed lines to 1: 1 define so that the part-duct flows as an internal or a outer ring jet can be fed. The distribution ratio of the educt partial flows the excess component can also be varied within wide limits, so the mass flow ratios of the inner part of the educt flow can be admitted outer part educt flow between 0.01 and 1 or also between 100 and 1 vary to the mixing process depending on the selected excess or deficit component to influence.

In the mixing process proposed according to the invention, the Partial product streams that can be fed separately into the mixing room from 1 ° to Feed an angle range of 179 °. To be as pronounced as possible Cause cross diffusion between excess and deficit components, the feed of the component reduct is preferably carried out at an angle of 90 ° based on the exiting at the front of the mixing room Deficit component. To increase the throughput, the Methods proposed according to the invention the inner radius of the inside Mixing room wall and the outer radius of the outside of the mixing room bounding wall, adjust so that there is an enlarged inner Passage area for the mixing and the adjoining it Product discharge sets while keeping the passage speed and the annular gap between the surfaces delimiting the mixing area.

In the proposed method according to the invention for mixing two Educt flows can be an acceleration of the resulting mixing by installing swirl-generating elements, for example in the supply line of the Achieve partial flows of the excess components in the mixing room. On A suitable element that would produce a swirl would be, for example, one in the feed line embedded spiral twisted band or the like.

With a mixing device which is also proposed according to the invention for Mixing educt streams, product streams can be generated, the Mixing device is provided with a number of reactant feed points and the reactant entry points and the mixing space are designed as annular gaps and at the front of the mixing room the entry point for one of the Educt flows is. The mixing space itself can be designed as an annular gap has an adjustable gap between its boundary surfaces. The Entry points of the educt streams which flow into the mixing room can preferably also be formed as a radially extending column, the Length of the mixing space is preferably between 7 and 10 gap widths.

Figur 1

eine Y-förmige Mischeinrichtung,

Figur 2

eine T-förmig ausgebildete Mischkonfiguration,

Figur 3

einen Ringspaltmischraum mit radialen Einleitungsöffnungen für Überschußkomponententeilströme und

Figur 4

eine in einer Zuleitung für den Mischraum angeordnetes drallformiges Element.

The invention can be explained in more detail with the aid of the drawing.
It shows:

Figure 1

a Y-shaped mixing device,

Figure 2

a T-shaped mixing configuration,

Figure 3

an annular gap mixing chamber with radial inlet openings for excess component partial flows and

Figure 4

a swirl-shaped element arranged in a feed line for the mixing space.

1 is a Y-shaped one Mixing device shown.

The Y-shaped mixing configuration 16 according to FIG. 1 shows the two Mixing chamber 12 with respective excess component partial flows Leads. Partial product streams enter the feed lines at the entry points 17, 18 a. The leads are at their respective mouth 22 with connected to the mixing room 12. Not in its configuration from FIG. 1 Mixing chamber 12, which appears in more detail, also occurs on the end face of the Mixing chamber 12, the deficit component 5 - for example by a Axial annular gap amine flowing into the mixing chamber 12. To the Mixing space 12 of the Y-shaped mixing configuration 16 closes an extension of the mixing room 12 in a certain length 14. At the extension 14 of the Mixing room 12 follows the conveyor line for the product stream 10, the leaves the Y-shaped mixing configuration at the product discharge 19.

Fig. 2 shows a T-shaped mixing configuration.

With this mixed configuration, the educt partial flows - such as phosgene - at the product entry points 17, 18 in the feed lines to not closer here shown mixing room 12 a. Located on the front of the mixing room 12 there is a feed line designed as an axial annular gap for a deficit component in the example shown for amine, which in dichlorobenzene in liquid phase is dissolved. The two educt partial flows occur in the illustrated 2 at 90 ° based on the axis of the mixing chamber 12 extending below along its extension 14 into the Mixing room and call yourself through the extremely short cross diffusion paths quickly established mixing reaction. The resulting mixture, the product 19 flows in the direction of the downward extending Mixing room length 14 in the direction of the product discharge 19, where the product 10 shown T-shaped mixing configuration 15 leaves.

The two supply lines, which the part-educt flows about phosgene - via the Product entry points 17 and 18 of the feed lines in the direction of the mouths 22 can promote with swirl-generating components, such as be internally extending internals. The swirl generating Components accelerate the mixing reaction of the two educt streams of the excess component with that at the front of the Mixing chamber 12 entering deficit component, for example of the amine.

Fig. 3 shows an annular gap mixing chamber with radial inlet openings for Excess component substreams.

3 is located in the front surface 9 of the Mixing chamber 12 an opening 8 formed as an axial annular gap through which a deficit component 5 enters the mixing chamber 12. The deficit component 5 essentially emerges from the opening 8 as a free jet and generates an outer one when exiting as a free jet from the end face 9 Suction area 3 and an inner suction area 4. With respect to the Line of symmetry 11 of the mixing device is with the inner suction area 4 suction area of the mixing chamber 12 closer to the line of symmetry 11 referred to, while with the outer suction area 3 of the further from Line of symmetry 11 of the suction area of the mixing space 12 is marked. In the embodiment shown in Fig. 3 occur Partial streams 1 and 2 of the phosgene - each excess component - as inner ring beam 1 or as outer ring beam 2 in a preferred 90 ° amount in the mixing chamber 12 on the front side 9. The face 9 the mixing room 12 need not be a flat surface, it can be section by section be conical, concave or convex. The face 9 opposite edges 23 which limit the mixing space length 14 Areas are preferably rounded so that there are no swirls and Form dead zones at the beginning of the mixing room 12. The the mixing room 12 in Axial direction 14 delimiting side surfaces 6 and 7 are ideal as Cylinder walls executed. However, you can also use sections as Tapered or as a concave or convex extension or narrowing. With such a shape, which limit the mixing space length 14 Walls, there is a continuous transition of the outer boundary surface 7 reach the pipe system connected to the mixing device.

When in the mixing room 12 comes together from the Annular gap opening 8 emerging deficit component 5, and that of the inner Ring beam 1 of the excess component and the outer ring beam 2 of Excess component, an extremely rapid cross-diffusion occurs Molecules of the excess component phosgene with those of the deficit component Amine a. The jet emerging from the annular gap 8 as a free jet the deficit component 5 is within the outer suction area 3 and of the inner suction area 4 from the excess component partial flows 1 and 2 sheathed so that on the mixing space 12 bounding walls 6 and 7 Excess component is present, so that there is also in the Vacuum areas 3 and 4 can not form deposits.

With the proposed method according to the invention for mixing Educt streams, for example for the phosgenation of amines or Let precipitation of vitamins be used, the excess component flow is in two partial educt streams 1, 2 split. The partial educt streams, 1, 2 of Excess component with one of these partial educt streams for example, vertically injected deficiency component in one mixed annular mixing space 12. The partial educt streams are preferred 1, 2 of the excess component in the suction areas 3, 4 of the Free jet of sub-component stream 5 emerging from a nozzle mixed. Due to the non-parallel injection of the deficit component 5 as a free jet and the partial educt streams 1, 2 for example in an angle of 90 ° to the injection direction of the deficit component in the Mixing space 12, which is designed in the form of an annular gap, can be efficiently Vortexing an avoidance of a laminar flow state through the Achieve mixing room 12. Due to the non-parallel injection at any angle From 0 ° to 180 °, cross diffusion and cross exchange processes can be carried out in the Partial educt flows 1, 2 with that in the longitudinal direction of the mixing space 12 injected Undershot component stream 5 achieve mixing are most useful.

In the illustrated embodiment, the feed openings are for the inner Ring beam 1, the outer ring beam 2 and for the deficit component the end face 9 each formed as an annular gap. Alternatively, they could go through a series of closely spaced holes. Also the Orientation of the openings in relation to the mixing space 12 - here as 90 ° angled to each other - could use other angles are shown, the inlet openings of the excess components in relation on the free jet of the deficit component 8 could in the angular range of 1 up to 179 ° to each other. With a suitable choice of Entry points, d. H. the mouths 22 of the feed lines into the mixing space 12 1 and 2, it must be ensured that as far as possible no backflow in of the mixing device occur in that backflows in the mixing device product-rich fluid comes back into contact with educt-rich fluid, which increases the risk of by-product formation, such as urea arises. If the inner boundary surface 24 of an inner cylindrical element 6 when increasing the throughput by proposed mixing device as a core increasing its radius designed, the throughput can be increased, the desired enlarged passage area of the mixing device a constant Passage speed allows, as well as a constant to be maintained Gap width allowed. Because the cross diffusion path and because of the same Velocity gradients, the turbulent cross diffusion remains constant at constant passage speeds, about 10 m / s, through the Mixing device according to the present invention with constant mixing times constant specific power input into the mixing device.

Thus, the method proposed according to the invention is broad regardless of the amount enforced, so that with the invention Procedures also adequately meet the requirements of scale-up capability Dimensions has been taken into account. Of the front 9 of the Mixing room 12 from extending length 14 of the mixing room is a minimum of 1/2 Gap widths and a maximum of 200 column widths 13, the length of which corresponds to the Front 9 adjacent mixing room preferably between 3 to 10 Gap widths 13 are to be selected The length of the mixing chamber 14 is as shown in FIG. 1 and 2 show the product discharge 19, through which the product 10 mixing configuration according to the invention leaves to further process steps run through.

A mixing process is shown in the following example: about 420 kg / h, 2,4-toluenediamine (TDA) are dissolved in 2450 kg / h o-sealing benzene (ODB) premixed and together with 8100 kg / h of a 65% phosgene solution initiated in the mixing device shown in Figure 3. In the illustrated For example, the phosgene represents the excess component, while that in the Dichlorobenzene dissolved TDA is the deficit component 5. The Phosgene solution flows can be in a ratio of 1: 1 in the feed lines to the Educt entry points are divided, the entry diameter of the Mixing device and the gap between the mixing room bounding areas are chosen so that there is a medium Entry rate of the excess component phosgene and Deficit component amine of about 10 m / s and a Exit speed of the product stream 19 of about 10 m / s. To Clear phosgenation and distillative processing resulted in a product yield of about 97%.

Fig. 4 shows an arranged in a feed line of the mixing chamber 12 swirl-promoting element.

It is in the process according to the invention for mixing educt streams possible in the feed lines 20 with their mouths 22 in each Mixing chamber 12 open into swirl-generating elements 21. At the exit from the mouth 22 into the mixing chamber 12 during the mixing process when the swirl in the mixing chamber 12 is released, mixing energy released Accelerate the mixing process. As a spin generator Element 21 could be, for example, a tortuous ribbon or one Integrate the spiral into the supply line 20. The use of a spiral Elementes would also have the advantage of having the inner cylinder 6, which of the symmetry lines 11 is closest to the mixing device fix.

LIST OF REFERENCE NUMBERS

1

inner ring jet (excess component)

2

outer ring jet (excess component)

3

outer suction area

4

inner suction area

5

Deficit component

6

inner cylinder

7

outer cylinder

8th

axial annular gap opening

9

Mixing chamber front side

10

product flow

11

line of symmetry

12

mixing room

13

Mixing chamber size

14

Mixing chamber length

15

T configuration

16

Y-configuration

17

educt

18

educt

19

product discharge

20

supply

21

swirl element

22

muzzle

23

edge

24

wall

Claims (10)

1. A process for mixing feed streams comprising one stream of a deficiency component and a stream of an excess component, which comprises the following process steps:

   dividing the stream of the excess component into at least two feed substreams (1, 2),

   injecting the feed substreams (1, 2) in a non-parallel fashion into the deficiency component (5) in an intake region with mixing of the feed substreams of the excess component (1, 2) and the deficiency component (5) in an annular mixing zone (12).
2. A process as claimed in claim 1, wherein at least one feed substream of the excess component (1) is injected from the inside into the annular mixing zone (12) and at least one feed substream of the excess component (2) is injected from the outside into the annular mixing zone (12).
3. A process as claimed in claim 1, wherein the split ratio of the feed substreams (1, 2) is 0.01-100:1.
4. A process as claimed in claim 1, wherein the feed substreams (1, 2) are fed into the annular mixing zone (12) at an angle in the range from 1° to 179° relative to the free jet of the deficiency component (5).
5. A process as claimed in claim 4, wherein the angle is 90°.
6. An apparatus for mixing at least two feed substreams (1, 2) with a further feed stream as deficiency component (5) to produce a product stream (10), where the mixing apparatus is provided with a number of inlets and the feed streams are introduced into a mixing zone (12) which is configured as an annular gap and whose end face (9) has an inlet (8) for the further feed stream and which has at least two further inlets which allow injection of the at least two feed substreams (1, 2) in a direction which is not parallel to the further feed stream.
7. An apparatus as claimed in claim 6, wherein the mixing zone (12) configured as an annular gap is bounded by an outer surface (6) of an inner cylinder and an inner surface (7) of an outer cylinder which is coaxial (11) with the inner cylinder, with the surfaces (6, 7) being cylindrical or also conical, concave or convex in sections.
8. An apparatus as claimed in claim 7, wherein the mixing zone (12) configured as an annular gap has a gap width (13) between the surfaces (6, 7), with the length (14) of the mixing zone (12) being in the range from half a gap width (13) to 200 gap widths (13).
9. A mixing apparatus as claimed in claim 8, wherein the length (14) of the mixing zone (12) is in the range from 3 to 10 gap widths (13).
10. The use of the process as claimed in any of claims 1 to 5 for preparing isocyanates.

Images