US3834877A - Method for starting and stopping a multistage liquid-liquid extraction system - Google Patents

Method for starting and stopping a multistage liquid-liquid extraction system Download PDF

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Publication number
US3834877A
US3834877A US00313244A US31324472A US3834877A US 3834877 A US3834877 A US 3834877A US 00313244 A US00313244 A US 00313244A US 31324472 A US31324472 A US 31324472A US 3834877 A US3834877 A US 3834877A
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US
United States
Prior art keywords
mixing
zone
space
auxiliary space
auxiliary
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Expired - Lifetime
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US00313244A
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English (en)
Inventor
H Ahonen
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Kemira Oyj
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Kemira Oyj
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Publication date
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D11/00—Solvent extraction
    • B01D11/04—Solvent extraction of solutions which are liquid
    • B01D11/0446—Juxtaposition of mixers-settlers
    • B01D11/0457—Juxtaposition of mixers-settlers comprising rotating mechanisms, e.g. mixers, mixing pumps

Definitions

  • the invention relates to a method and device for stopping and starting an extraction apparatus and specifically to a method for stopping and starting an extraction apparatus of the type introduced in the U.S.A., patent application Ser. No. 178,729.
  • the object of the present invention is to provide a method for stopping and starting an extraction apparatus which contains several preferably vertically stepped extraction stages in series, each consisting of a mixing zone, a settling zone, and an auxiliary space into which heavy phase is fed from the lower part of the settling zone and from which it is further fed into the mixing zone.
  • Lightweight phase again, is conducted into the mixing zone from the settling zone of the preceding stage in order to mix it with the heavy phase and to pump the formed vdispersion into the settling zone of the same stage.
  • the object is also to provide an extraction apparatus for counter-current extraction, an apparatus which can be stopped and restarted without danger of forming any false dispersion after the restarting.
  • the stopping and starting of the apparatus can also be achieved with considerably greater freedom than in the multiphase mixer-settler apparatuses, to which the starting device here described has not been applied.
  • the extraction apparatus is stopped by (a) closing the connection between the mixing space and its auxiliary space and mixing is discontinued, so that the dispersion cannot ⁇ flow back into the auxiliary space; after the heavy and the lightweight phases have separated from each other in the mixing zone, the heavy phase in the lower part of the mixing zone is allowed to ilow by its own weight into the auxiliary space by opening the connection between the mixing space and its auxiliary space, the level in which is kept considerably lower than the liquid level in the mixing zone during the operation, then the connection between the auxiliary space and the mixing zone is reclosed; and (b) the extraction is started by tirst starting the mixing in the mixing zone while the connection between the mixing zone and the auxiliary space is carefully opened, and finally the feeding of heavy phase from the settling zone into the auxiliary space is started after the surface level of the heavy phase in the auxiliary space has lowered sufiiciently.
  • each step or stage consists of three separate or partitioned chambers, namely, mixing chamber S, settling chamber L, and auxiliary space 11.
  • the different stages have been indicated with subindices n-l, n, n-l-l, etc.
  • the lower part of settling chamber L has been connected to auxiliary space 11 with overflow pipe 10, which has been fitted into auxiliary space 11 and which can be regulated in the vertical direction so that the overflow stops completely when the end of the pipe is at its highest position.
  • the regulating margin required by the pipe downwards from this highest position is determined by the spacing of the stages and the desired level of the interface between the heavy and the lightweight phases in the settler.
  • auxiliary space 11 has ybeen connected to the lower part of mixing chamber S with overflow pipe 5 provided with valve 6.
  • Mixing chamber S also contains a vertical shaft rotated by motor M.
  • At the lower part of the shaft there is heavy phase pump turbine 2 in pump box 8 and in the middle of the shaft, mixer 1 which moves the dispersion along head pressure pipe 7 in front of the mixer and dispersion pipe 3 into settling chamber L.
  • Number 9 refers to the lightweight phase return pipe tted betweensettling chamber L and mixing chamber S, and 4 indicates lightweight phase overow pipe from settling chamber L into the upper part of mixing chamber S of the following phase.
  • the lightweight phase has been indicated with ruling slanted to the left and the heavy phase with ruling slanted to the right.
  • Lightweight phase iiows from settling chamber Ln 1 along overflow pipe 4 into mixing chamber Sn of the following phase and from there further under the inliuence of mixer 1 through head pressure pipe 7 and dispersion pipe 3 into settling chamber Ln, where the lightweight phase separates again into a separate phase, etc.
  • the heavy phase iiows counter-currently in relation to the lightweight phase.
  • the heavy phase separated at the bottom of settling chamber Ln+1 is fed into auxiliary space 11 through overiiow pipe 10, which has been connected to the lower part of settling chamber LMI, lturns on the vertical plane, and is thus regulatable in the vertical direction.
  • auxiliary space 11 Heavy phase is pumped into mixing space S so that the surface level in auxiliary space 11 is considerably lower than in mixing chamber Sn into which heavy phase ows through pipe 5.
  • the pumping effect is created with pump turbine 2 fitted in the pump box at the bottom of mixing chamber Sn, and mixing of the heavy phase with the lightweight phase is achieved with mixer 1, whereafter the dispersion is fed into settling chamber Ln, where the heavy phase again separates into its own phase, etc.
  • each stage has been provided with auxiliary space 11, the volume of which and the height at which it is placed must be such that it can receive all heavy phase settling in the settler after the stopping when valve 6 is opened.
  • auxiliary space 11 which the heavy phase of the preceding phase enters along overow pipe 10, it is possible to regulate the height of this overow pipe.
  • the heavy phase is fed into the lower part of mixing space S separate from the lightweight phase, which enters mixing space S from above or in the middle. Because of its greater density the heavy phase ows into mixing space S even without any pumping, but in this modification pump turbine 2 is used at the bottom of the mixing space; under normal operating conditions the pump turbine keeps the level in auxiliary space 11 considerably lower than the level in mixing space S.
  • the dispersion can be fed directly into settling space L along pipe 7, 3. It is also possible to create the ow without auxiliary devices, owing to a rise in the center of gravity in mixing space S.
  • head pressure pipe 7 or the like is used near the mixing turbine. Keeping the level in settler L higher than the level in mixing tank S makes it possible to return lightweight phase back into mixing tank S of the same phase and to change the phase proportions in mixing chamber S independently of the entering flows of the entire extraction apparatus.
  • the advantage thus gained is that the desired dispersion can be kept in mixing chamber S, usually with the heavy phase in drops and dominant and stable.
  • Head pressure pipe 7 or a corresponding device makes also possible an inner circulation of the heavy phase; the circulation may be needed to create more advantageous settling properties.
  • valve 6 in pipe 5 between mixing tank S and auxiliary space 11 is closed simultaneously and, if necessary, the overflow pipe in auxiliary space 11 is raised so that there is no further flow into auxiliary space 11 from the preceding settler, and after a while the dispersion has separated into two phases in the mixing tank, at which time valve 6 can be opened into auxiliary space 11 and the heavy phase can be drained entirely from mixing space S.
  • valve 6 When the extraction apparatus is restarted, valve 6 is first kept closed and then opened slowly, which eliminates the formation of a false dispersion,
  • the stages are hydraulically independent of each other.
  • the capacity of the apparatus is independent of the densities of the liquids and the variations of the densities.
  • a process for the countercurrent extraction between a heavier liquid and a lighter liquid comprising a plurality of horizontally displaced extraction stages, each stage comprising a mixing zone, a settling zone and an auxiliary zone, said auxiliary zone being disposed between each settling zone and the mixing zone of the preceding extraction stage, and in which the lighter liquid is conveyed from the settling zone to the mixing zone of each subsequent extraction stage, which process requires occasional stopping and restarting, which comprises the steps of z (a) introducing the heavier liquid from the lower part of the settling zone of one extraction stage into the auxiliary zone of the same stage and introducing said heavier liquid from said auxiliary zone into the mixing zone of the preceding stage,
  • said auxiliary zone being of such volumn that it is capable of receiving all the heavy liquid which has 5 settled in the mixing zone of the next preceding stage after step (e) and (k) said auxiliaryzone being so located with respect to the mixing zone that said heavier liquid in said step (f) ows to the auxiliary zone due to the difference in hydrostatic pressure.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Extraction Or Liquid Replacement (AREA)
US00313244A 1971-12-10 1972-12-08 Method for starting and stopping a multistage liquid-liquid extraction system Expired - Lifetime US3834877A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FI713526A FI47155C (fi) 1971-12-10 1971-12-10 Tapa ja laite neste-nesteuuttolaitteen käynnistämiseksi ja pysäyttämis eksi.

Publications (1)

Publication Number Publication Date
US3834877A true US3834877A (en) 1974-09-10

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ID=8508534

Family Applications (1)

Application Number Title Priority Date Filing Date
US00313244A Expired - Lifetime US3834877A (en) 1971-12-10 1972-12-08 Method for starting and stopping a multistage liquid-liquid extraction system

Country Status (8)

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US (1) US3834877A (enExample)
CA (1) CA973333A (enExample)
DE (1) DE2231634A1 (enExample)
FI (1) FI47155C (enExample)
FR (1) FR2162582B1 (enExample)
GB (1) GB1395605A (enExample)
SE (1) SE371103B (enExample)
ZM (1) ZM18672A1 (enExample)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113101698A (zh) * 2021-04-20 2021-07-13 安徽省圣丹生物化工有限公司 一种除草剂生产用连续萃取系统

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NO154655C (no) 1978-10-12 1986-11-26 Sjeldne Jordarter Forskning Anordning ved mixer-settlere.
CN102676812B (zh) * 2012-06-04 2013-07-24 江西稀有金属钨业控股集团有限公司 一种湿法萃取有机夹带余酸回收装置及其回收方法

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113101698A (zh) * 2021-04-20 2021-07-13 安徽省圣丹生物化工有限公司 一种除草剂生产用连续萃取系统

Also Published As

Publication number Publication date
SE371103B (enExample) 1974-11-11
CA973333A (en) 1975-08-26
DE2231634A1 (de) 1973-06-14
GB1395605A (en) 1975-05-29
FI47155B (enExample) 1973-07-02
FI47155C (fi) 1973-10-10
ZM18672A1 (en) 1973-09-21
FR2162582B1 (enExample) 1980-03-21
FR2162582A1 (enExample) 1973-07-20

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