Process for the separation of two liquid immiscible organic comp

Details Process for the separation of two liquid immiscible organic comp Process for the separation of two liquid immiscible organic comp

1991-10-17

1993-07-06

Spear, Frank

Liquid purification or separation

Processes

Liquid/liquid solvent or colloidal extraction or diffusing...

210690, 210800, 210307, B01D 17022

Patent

active

052250849

DESCRIPTION:

BRIEF SUMMARY
This invention relates to a process for the separation of at least one liquid organic component dispersed in a liquid primarily containing organic constituents by sedimentation of the organic component, the organic component and the residual liquid differing from one another in density.
Both here and in the following, the term "liquid" means the liquid as a whole before separation, the term "organic component" means only the constituent dispersed in droplet form, the term "constituents" means all the constituents of the liquid to be treated and the term "residual liquid" means the liquid after separation of the organic component.
Two organic liquids which are not completely miscible with one another often have to be separated from one another. The two liquids are whirled around and mixed by pumps, pipes and apparatus so intensively that one liquid is finely dispersed in the other. The two liquids may be separated by sedimentation of more or less large drops. Vertical or horizontal separators are used for this purpose. Where static separators, for example decanters, are used, very long residence times of up to 14 days are required. To shorten this time, it has already been proposed to use separators following the static separators, for example for the reaction product obtained after a transesterification reaction (cf. Seifen-Ole-Fette-Wachse, Vol. 114, 1988, page 596, 2nd paragraph and FIG. 3). However, the use of such separators does involve operational problems which occur in cases of variations in throughput, raw material quality and raw materials, for example oils having different chain lengths, different degrees of saturation and different impurities, and in the event of temperature fluctuations. Further disadvantages of such a proposal are high investment, maintenance and energy costs.
In another process for the separation of petroleum-water mixtures or kerosene-water mixtures known from DE-OS 23 03 990 and GB-PS 1,409,045, a coalescence aid is introduced before sedimentation. Coalescence processes such as these are also known from DE 31 11 554 A1 and DE 27 55 837 A1. This coalescence aid may assume different forms, for example it may be in the form of wire nets, filaments or fibers. It is important in this regard that the surface of the coalescence aid should differ in its wettability in respect of the two liquids. This wettability is determined by the interfacial tension of the liquid with respect to the coalescence aid. Where known coalescence aids of this type are used for the separation of one organic liquid from another organic liquid under the described typical working conditions known for the separation of water from organic substance or organic substance from water, it has been found that the coalescence aid, particularly when used to separate immiscible oleochemical substances, has no effect on the coalescence of the dispersed organic component.
The problem addressed by the present invention is to provide a process of the type mentioned at the beginning by which the residence time hitherto required is considerably reduced.
According to the invention, the solution to this problem is characterized in that, before sedimentation, the liquid flows through a fiber bed, in that the organic component and the residual liquid have different interfacial tensions with respect to the material of the fiber bed, in that the liquid has such a temperature and such a concentration of the organic component to be separated off that at least two liquid phases are formed in equilibrium. The rate of flow of the mixture through the fiber bed is determined by the wettability of the fibers and by the interfacial tension of the two liquids. It must be determined by tests.
It has surprisingly been found that, where fiber filters are used as the coalescence aid and where narrow operating ranges are maintained, the dispersed droplets of the organic component coalesce A successful result is crucially determined by the choice of the rate of flow in dependence upon the interfacial tensions with the fiber bed and between the

REFERENCES:
patent: 3894943 (1975-07-01), Hartmann et al.

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