Agitating – Having specified feed means
Reexamination Certificate
1999-03-26
2001-01-23
Soohoo, Tony G. (Department: 1723)
Agitating
Having specified feed means
C366S348000
Reexamination Certificate
active
06176608
ABSTRACT:
The present invention relates to a method for conducting the solutions of liquid—liquid extraction, which in the mixing unit are mixed into a dispersion, from the mixing unit further to the separation part. The invention also relates to an apparatus for realizing the method. The method how the dispersion is conducted into the separation part essentially affects the flow field of the whole separation part and its controllability. The object of the method and apparatus according to the invention is to enhance an intensified separation of the solutions by employing arrangements that align the dispersion flow in the sideways direction, attenuate and smooth it and make the horizontal and vertical feeding directions equally important as well as lower the counterpressure directed to the dispersion feed from the side of the separation part.
The present invention also enables the construction of very large extraction plants, up to total flows of 5,000-6,000 m
3
/h, whereas the maximum total flows processed with conventional technology are 3,000 m
3
/h. As for the feeding arrangements in the separation part, it has been difficult to move over to larger flows, because along with larger total flow volumes, also the bottom of the mixing unit must always be constructed lower, and thus further from the separation part bottom level. This is due to the fact that the mixers are designed according to a given solution delay time, and the separation parts respectively according to a given separation capacity in relation to the surface area. In the case of large total flows, this means that the bottoms of the mixing units are 2-5 m lower than the bottom of the separation part.
According to the present invention, it is now possible to make use of the above described difference between the mixing and separation unit, by improving in the mixing unit the orientation of the dispersion formed of two separate solutions, when the dispersion is fed into the separation part, in order to separate into two different phases. The arrangement of the invention is compatible with the method and apparatus introduced in the FI patent application 93 5393. Thus the feeding arrangements described in said application and in the present application do not require that the mixing unit is divided into several serially connected spaces in order to keep their bottom levels near to each other or on the same level as the bottom level of the separation parts. In most cases in conventional extraction systems the dispersion is conducted into the separation part as surface flow, horizontally via the side of the mixing unit, so that it proceeds as a strong flow in the lengthwise direction of the separation part and enters the separation part. A strong surface flow occurring in the middle of the separation part hampers an even distribution of the dispersion over the whole transversal area of flow.
According to the FI patent application 93 5393, the removal of the mixing unit dispersion takes place along the height of the whole settler, in which case there is achieved the advantage that by directing the flow to be vertical, the dispersion can be conducted into the separation part as attenuated by gravitation. In the apparatus described in said FI application, the last mixer is arranged on the lengthwise axis of the settler, and the uptake shaft in between the mixer and the settler is a direct channel, so that it is located tangentially with respect to the mixing direction of the mixer, equals in size to the whole settler and has a width about half of the mixer diameter.
Particularly in extraction plants treating large solution flows, the length of the pipelines set demands on the placing of mixers. In order to keep the transfer distances of settled solutions as short as possible, it is advantageous that in each extraction step, the first device of the mixing unit, i.e. the pumping unit, is located in the corner of the mixing unit. On the other hand, the object is to achieve a compact mixing unit, where the transfer distances of the dispersion flowing from one device of the mixing unit to another should remain as short as possible and thus the phases would not have time to separate in the transfer pipework. It is naturally advantageous that the dispersion can, immediately when it flows out of the mixer, be turned, by means of an uptake shaft, to be parallel to the lengthwise axis of the separation part, but the placing of the last mixer on the center line of the separation part is not always possible due to the reasons described above; in that case the dispersion flow must be aligned and oriented towards the center line of the settler, although the location of the last mixer should deviate from the center line.
The present invention relates to a method and apparatus for conducting the dispersion from the mixing unit into the separation unit in conditions where a dispersion flow that is discharged from the mixing unit asymmetrically with respect to the lengthwise axis of the separation unit is turned and aligned to be symmetrical prior to feeding it into the separation unit. In order to turn the dispersion flow, the last mixer in the mixing unit is provided with flow-turning members. From the last mixer, the dispersion is first conducted along with a horizontal dispersion channel arranged on the same level as the bottom level of the mixer, to a dispersion uptake shaft connected to said channel and rising essentially vertically upwards. The uptake shaft is located on the lengthwise axis of the separation part, so that the dispersion channel leading from the mixer to the uptake shaft forms an angle with the lengthwise axis of the separation part, the size of said angle being 0-60°. According to the invention, the dispersion flow direction is thus turned to be symmetrical with the lengthwise axis of the separation part by means of flow baffles provided in the last mixer and by means of a flow-turning dispersion channel. Next, the dispersion is conducted to the front end of the separation part, from the uptake shaft opening along the whole width of the separation part, which uptake shaft also is advantageously expanding towards the separation part and has a bottom part that rises towards the separation part. According to another preferred embodiment, the uptake shaft is located underneath the front end of the separation part, and the dispersion is conducted to the bottom part of the separation part. The essential novel features of the invention are apparent from the appended patent claims.
REFERENCES:
patent: 1083102 (1913-12-01), Jackson
patent: 1843157 (1932-02-01), Howe
patent: 2342559 (1944-02-01), Sebald et al.
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patent: 2671647 (1954-03-01), Wolpert
patent: 3565404 (1971-02-01), Reid et al.
patent: 4534655 (1985-08-01), King et al.
patent: 4786187 (1988-11-01), Nyman et al.
patent: 5662871 (1997-09-01), Nyman et al.
Hultholm Stig-Erik
Kuusisto Raimo
Lilja Launo
Lyyra Juhani
Nyman Bror
Morgan & Finnegan, L.D.P.
Outokumpu Technology Oy
Soohoo Tony G.
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