DISTRIBUTOR DEVICE, IN PARTICULAR FOR FALLING FILM EVAPORATORS, AND USE THEREOF

Abstract

The present invention relates to a distributor device (10000) for the even distribution of a fluid (10) into 2 or more fluid streams each containing gas (11) and liquid (12), with a falling film evaporator (100000), in which the distributor device according to the invention serves to distribute the 2 or more fluid streams onto the heating pipes of the evaporator, and to the use of the distributor device (10000) according to the invention and in particular the falling film evaporator (100000) according to the invention in the production and/or preparation of chemical products. The distributor device according to the invention is characterized, in particular, by a swirl breaker (600) for the gas phase (11) which arises from separating the fluid (10) into a gas phase (11) and a liquid phase (12) within the distributor device.

Claims

1-15. (canceled)

16. A device suitable for uniform division of a fluid into n fluid streams each containing gas and liquid, where n is a natural number greater than or equal to 2, the device comprising: (a) an upright cap bounded at the bottom by a plate; (b) an entry port arranged in a lateral delimiting wall of the upright cap, the entry port configured to bring about tangential inflow of the fluid entering therein; (c) an internal arranged upright in the interior of the cap, wherein the internal: (i) together with the interior wall of the cap, forms an annular gap for downflowing liquid, (ii) comprises an upper edge that ends above the entry port and below an upper delimitation of the upright cap so that the upper edge of the internal and the upper delimitation of the cap form a passage for downward-flowing gas, (iii) has, at the top thereof, at least one upper opening for the downward-flowing gas flowing therein, (iv) comprises a lower edge that ends above the plate so that the lower edge of the internal and the plate form a passage for the downflowing liquid, and (v) comprises at least one opening at the bottom thereof that is hydrodynamically connected to the at least one upper opening; and (d) n guide devices, wherein the guide devices protrude through the at least one opening at the bottom of the internal into the internal and the guide devices comprise liquid entry openings and gas entry openings; wherein a swirl breaker is arranged in the interior of the internal, the swirl breaker being configured to reduce or eliminate turbulence in the downward-flowing gas stream and to reduce the rotational energy of downward-flowing gas stream.

17. The device of claim 16, wherein the internal has a cross section that widens in a downward direction.

18. The device of claim 16, wherein a swirl breaker having through-openings is arranged in the annular gap below the entry port, the through-openings being configured to allow flow of the downflowing liquid therethrough.

19. The device of claim 18, wherein the swirl breaker is a metal plate in which the through-openings are formed by at least two holes distributed uniformly over the entire area of the plate and/or by at least one slit that runs through the entire area of the plate.

20. The device of claim 16, wherein the at least one upper opening extends over the entire internal cross section of the internal and/or the at least one opening through which the n guide devices protrude into the internal extends over the entire internal cross section of the internal.

21. The device of claim 16, wherein the n guide devices are tube spouts or constituents of tubes.

22. The device of claim 21, wherein the liquid entry openings: (i) are tangential slits arranged so that the flow of the downflowing liquid produced on the inside of the guide devices has the same direction as the flow of the downflowing liquid produced in the annular gap by the arrangement of the entry port, or (ii) are axial slits.

23. The device of claim 16, wherein the swirl breaker is selected from the group consisting of a swirl cross, a packing, a knitted wire mesh, a perforated plate, and a deflection plate.

24. The device of claim 16, wherein the n guide devices protrude to a height in the range from 10 mm to 100 mm into the internal.

25. A falling film evaporator comprising: (a) an outer, enclosing shell, (b) n tubes fastened in an upper tube plate and a lower tube plate, where n is a natural number greater than or equal to 2, configured so that on the inside of which a liquid film can flow down, (c) an upper distributor device configured to distribute liquid and gas into the individual tubes, (d) a feed device configured to feed a heating medium into a tube exterior space formed by the outside of the tubes and the shell, (e) a discharge device configured to discharge cooled heating medium from the tube exterior space, (f) a vapor offtake device configured to offtake vapor, (g) a liquid offtake device configured to offtake residual liquid not vaporized inside the tubes, and (h) a device configured to separate and collect the residual liquid and the vapor, wherein the upper distributor device is the device of claim 16, where the bottom of the device forms the upper tube plate of the falling film evaporator and the n guide devices are joined to the n tubes at the upper end thereof or the n guide devices are constituents of the n tubes.

26. The falling film evaporator of claim 25, further comprising a return device configured to recirculate part of the residual liquid into the distributor device, where the return device: (i) comprises a mixing device configured to mix the recirculated part of the residual liquid with the fluid before entry into the distributor device, or (ii) opens into an entry port that is different from the entry port and is arranged in a lateral delimiting wall of the cap.

27. A process for producing and/or working-up of a chemical product selected from the group consisting of organic nitro compounds, organic primary amines, isocyanates, polyether polyols and polycarbonates, comprising using the device of claim 16.

28. A process for producing and/or working-up of a chemical product selected from the group consisting of organic nitro compounds, organic primary amines, isocyanates, polyether polyols and polycarbonates, comprising using the falling film evaporator of claim 25.

29. The process of claim 28, comprising using the falling film evaporator in the work-up of an isocyanate for vaporization of the isocyanate.

30. The process of claim 29, comprising using the vaporization of the isocyanate to (i) at least partially remove the isocyanate from a residue-containing distillation bottoms stream from isocyanate production, and/or (ii) to separating a monomeric isocyanate fraction, which is vaporized, from a polymeric isocyanate fraction.

31. The process of claim 29, wherein the isocyanate is selected from the group consisting of tolylene diisocyanate, a diisocyanate and/or polyisocyanate of the diphenylmethane serie, hexamethylene diisocyanate, pentamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, naphthalene diisocyanate, and dicyclohexylmethane diisocyanate.

32. The process of claim 30, wherein the isocyanate is selected from the group consisting of tolylene diisocyanate, a diisocyanate and/or polyisocyanate of the diphenylmethane serie, hexamethylene diisocyanate, pentamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, naphthalene diisocyanate, and dicyclohexylmethane diisocyanate.

Description

EXAMPLES

[0095] Experiments were carried out for a liquid distributor on an industrial scale using a water/air mixture as test system. The test apparatus used, by means of which the conditions in a falling film evaporator were simulated, had a diameter of about 900 mm and 45 tubes. In order to examine the influence of spontaneous evaporation on the liquid distribution, 6 m.sup.3/h of pure water (situation without spontaneous evaporation) were introduced in one case and 6 m.sup.3/h of water plus 560 or 1000 m.sup.3/h of air were introduced via the tangential entry port (situation with spontaneous evaporation) in the other case. In all cases, the liquid volume flows per tube were measured and the standard deviation was determined according to the following equation:

[00001]$\mathrm{Standard}.Math..Math.\mathrm{deviation}.Math.\text{:}.Math..Math.\mathrm{Cv}={\left[\frac{.Math.{\left(\frac{x_{i-\stackrel{\_}{x}}}{\stackrel{\_}{x}}\right)}^2}{n-1}\right]}^{1/2}100\left[\%\right]$

[0096] The symbols here have the following meanings: x, is the measured liquid volume flow per tube, is the arithmetic mean of the measured liquid volume flows over all n tubes and n is the number of tubes

[0097] The distributor was, in all experiments, operated with a liquid level of 50 mm on the tube plate and using tube spouts having tangential inflow slits (rectangular slits having a slit width of 5 mm).

Example 1 (Liquid Distribution with and without Spontaneous Evaporation without Swirl Breaker (600); Comparison)

[0098] A swirl breaker (600) was not used. In the outer annular gap (400) a swirl breaker (700) having a continuous slit for the liquid was used (as depicted in FIG. 2b). The measured volume flow per tube in ascending order are shown in FIG. 7. It can clearly be seen that the distribution deviates ever further from the optimum distribution with increasing proportion of gas phase (corresponding to increasing spontaneous evaporation). At 1000 m.sup.3/h, the relative standard deviation is 34%, which is very high for distributors on an industrial scale. At 0 m.sup.3/h of air, the standard deviation is 12% and is in the region of normal standard deviations for industrial liquid distributors.

[0099] The experiments show that the gas phase greatly disrupts the distribution of the liquid over the tubes, even though gas and liquid were separated cleanly directly after entry into the cap and the liquid is predistributed by the swirl breaker (700).

Example 2 (Liquid Distribution with Spontaneous Evaporation Using Swirl Breaker (600) for the Gas Phase (11); According to the Invention)

[0100] The experiments using 560 m.sup.3/h and 1000 m.sup.3/h of air of example 1 were repeated after installation of the swirl breaker (600). A significant improvement in the liquid distribution is found heresee FIG. 8 (the results from example 1 are also shown for better comparison). At 1000 m.sup.3/h, the relative standard deviation can in this way be reduced from the previous 34% to 16%. The distribution achieved here is close to the distribution using 0 m.sup.3/h of air in example 1. The example thus shows that the negative influence of the air on the liquid distribution can be virtually eliminated by the use of the swirl breaker (600). In the example, a simple swirl breaker (600) having 4 blades was used; this can be optimized further (e.g. 8 blades in order to calm the air flow (in general: the gas flow) to a greater extent).

[0101] In example 2 according to the invention, the liquid distribution could thus be improved significantly compared to example 1 without the liquid being calmed completely on the tube plate (900). Instead, significant circulatory flow in the liquid, which avoids the formation of deposits in systems having a tendency to form them, continues to be visible.