Apparatus to contact liquids of different density

Details Apparatus to contact liquids of different density Apparatus to contact liquids of different density

1991-03-18

1993-03-16

Dawson, Robert A.

Liquid purification or separation

Serially connected distinct treating with or without storage...

Cascade

196 1452, 210252, 210634, 261155, 422256, 422257, B01D 1104

Patent

active

051941520

DESCRIPTION:

BRIEF SUMMARY
The invention relates to an apparatus used to contact liquids of different density, more specifically, an apparatus such as a to liquid extractor.
Several types of columnar liquid extractors are known to be used with auxiliary energy to ensure radial mixing between the liquids to be contacted. One of these extractors has a vertical cylindrical casing - column - with a central vertical rotatable shaft on which mixing elements, e.g. blades or discs are mounted line by line. The rotation disperses one of the liquids into the counterflowing other liquid (in continuous phase). In some of these columntype extractors, the mixing zones (stages) are separated by sedimentators (e.g. packing layers, perforated bodies, nets of sieve cloth, etc.). The theoretical number of stages of these mixing-column-type extractors is 2-7 per meter, and the specific load is 20-30 m.sup.3 /m.sup.2 h. This group includes the RDC (rotary disc), OLDSHUE-RUSTHON, SCHEIBEL, KUHNI, RZE (mixing cell), BTC-RDC (internal baffle tube) type extractors known in the professional field (Chem.Ing.T.52. FIG. No. 3.9.3.). Extractors with eccentric rotary shafts are also used, where the rotary disc is asymmetrically arranged (e.g. LUWA-ARD extractor). Its theoretical number of stages is 1-3/m, specific loadability 20 m.sup.3 /m.sup.2 h.
Some columnar extractors are also known, where to improve the efficiency of dispersion induced for efficient contact, pulsation is used instead of mixing. These include the liquid pulsating and vibrating extraction columns. In the former one the liquids counterflowing in the column are pulsated with a pulsator (e.g. piston pulsator) connected with the column. The radial mixing of the pulsated liquids, dispersion of one liquid into the other one takes place with dispersing elements arranged in the column. Such dispersing elements may be for example a charge (Interpack charge, Pall ring, porcelain saddle body). Here, the specific loadability is 15-25 m.sup.3 /m.sup.2 h, the theoretical number of stages 4-7/m, and the rate of pulsation 700-1300 mm/min (Chem.Ing.T.50. FIG. No. 5, 15-19). The dispersing elements may be sieve plates (perforated discs) dividing the column's interior vertically into cells. Their free cross section is 20-30%, specific loadability 30-60 m.sup.3 /m.sup.2 h, theoretical number of stages 4-7/m, while the rate of pulsation 700-1500 mm/min (Chem.Ing. T.50. FIG. No. 5, 19.). In the vibrator-type extraction columns the liquids are contacted, dispersed by up and down vibration of the perforated disc or sieve plates--pulled over a common bar--with the aid of external pulsator. The best known vibrator type extraction column is the KARR column, where the free cross section of the discs is 50-60%, specific loadability 80-100 m.sup.3 /m.sup.2 h and the theoretical number of stages 3-6/m (Chem.Ing. T.50. No. 5).
The specific loadability (m.sup.3 /m.sup.2 h) of the pulsated and non pulsated charged extraction columns is approximately the same, but pulsation of the liquids prevents or at least considerably reduces the channelling frequently occurring in the non-pulsated charged column, furthermore it facilitates renewal of the surface in contact with the continuous phase. The dispersion can be intensified with pulsation, and the theoretical number of stages can be doubled. But some drawbacks in the use of the columns with pulsated charge are that they are sensitive to changes of the load and are unable to react flexibly to fluctuations. Another problem is that solids incidentally present in the liquid upset the extraction process so that the charge- and column-surface becomes dirty. Therefore, the described columns with pulsated charge cannot be used for the extraction of liquid containing solids.
As a result of regular pulsation of the columns, new contacting surfaces are formed, and the dispersion can be intensified in the pulsated sieve plate (perforated disc-type) extraction columns. Consequently, the theoretical number of stages per meter compared with the non-pulsated columns is higher, and compared even

REFERENCES:
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patent: 3837812 (1974-09-01), Boontje
patent: 4276244 (1981-06-01), Gyorgy et al.
patent: 4424131 (1984-01-01), Baird
patent: 4541724 (1985-09-01), Cornelissen
patent: 4855113 (1989-08-01), Yen

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