US3764007A - Separation process for solid particles of differing shape - Google Patents

Separation process for solid particles of differing shape Download PDF

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Publication number
US3764007A
US3764007A US00150531A US3764007DA US3764007A US 3764007 A US3764007 A US 3764007A US 00150531 A US00150531 A US 00150531A US 3764007D A US3764007D A US 3764007DA US 3764007 A US3764007 A US 3764007A
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United States
Prior art keywords
suspension
discs
process according
particles
separation
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Expired - Lifetime
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US00150531A
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English (en)
Inventor
E Schmid
R Egli
B Bruttel
R Nascher
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Lonza AG
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Lonza AG
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D21/00—Separation of suspended solid particles from liquids by sedimentation
    • B01D21/24—Feed or discharge mechanisms for settling tanks
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D21/00—Separation of suspended solid particles from liquids by sedimentation
    • B01D21/26—Separation of sediment aided by centrifugal force or centripetal force
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D21/00—Separation of suspended solid particles from liquids by sedimentation
    • B01D21/26—Separation of sediment aided by centrifugal force or centripetal force
    • B01D21/262—Separation of sediment aided by centrifugal force or centripetal force by using a centrifuge

Definitions

  • the present invention is concerned with a process for the separation of solid particles, of different shape but of similar weight, wherein the particles to be separated are suspended in a liquid.
  • the suspension In the suspension there is produced, with the exclusion of turbulence, a flow velocity profile by imparting to a 2 20 mm. thick layer of the suspension, a rotary movement by the use of two discs, at least one of which is rotating, which discs bound the layer of suspension above and below, there being a difference of rotational speed between the two discs.
  • Those particles which, due to their form, are not carried by the suspending liquid throughout the flow thereof, separate out from the suspension.
  • the separated particles are withdrawn from the suspension at a separation zone.
  • the present invention is also concerned with a device for carrying out the process, the device comprising a separation vessel, consisting of a flat cylindrical part with a central flowout opening in the bottom, constituting a lower rigid disc, thecentral flowout opening leading into a settling vessel, at least one inlet situated between the central flowout opening and the periphery, at least one outflow, for the withdrawal of the suspension, on the periphery of the vessel constructed tangentially as an overflow, for the removal of those particles not separated as a result of their different shape, and a vertically freely moving, rotating disc, the diameter of which is slightly smaller than the inner diameter of the separation vessel and which, on the upper surface, is attached to a drive mechanism for rotating the disc.
  • a separation vessel consisting of a flat cylindrical part with a central flowout opening in the bottom, constituting a lower rigid disc, thecentral flowout opening leading into a settling vessel, at least one inlet situated between the central flowout opening and the periphery, at least one outflow, for the withdrawal of
  • the problem forming the basis of the present invention is to bring about a separation of particles of different shape but the same weight by means of a simple and effective process and with the use of a simple device.
  • a process for the separation of solid particles of different shape but of similar weight wherein the particles to be separated are suspended in a liquid.
  • the suspension In the suspension there is produced, with the exclusion of turbulence, a flow velocity profile or distribution by imparting to a 2 20 mm. thick layer of the suspension, a rotary movement by the use of two discs, at least one of which is rotating, which discs bound the layer of suspension above and below, there being a difference of rotational speed between said two discs.
  • Those particles which, due to their form, are not carried in suspension by the suspending liquid throughout the flow profile thereof, separate out from the suspension.
  • the separated particles separate out from the suspension.
  • the separated particles are withdrawn from the suspension a separation area.
  • the rotational speed difference of the discs can be produced by allowing the two discs to rotate at different speeds. It is also possible to rotate the'discs in opposite directions. Preferably, for reasons of simplicity of structure of the apparatus, one of the discs, in general the one which contains an inlet and an outlet, will be stationary, only the second disc being allowed to rotate.
  • the relative rotational speed of the rotating discs depends upon a. their diameter, b. the nature, composition, difference in shape and size, as well as the specific weight, of the particles to be separated and c. the viscosity of the suspension liquid.
  • the process is generally carried out in such a manner that, when using water as a suspension liquid, the product of diameter and frequency difference of the discs gives a constant of between 300 and 350 cm./min., especially of 320 330 cm./min.
  • the thickness of the layer of liquid between the discs and thus also the distance between the discs should be constant over the whole surface and, in the case of water, is expediently 4 6 mm. and especially about 5 mm.
  • the solids content in the case of the separation of whiskers, shouldpreferably be between 5 100 mg. solids, more preferably 20 50 mg. solids, per litre of suspension liquid.
  • the efficiency can be considerably increased so-that the product of diameter and frequency of the disc gives a constant of between 300 and 1,000 cm./min., especially of 500 to 900 cm./min.
  • the solids content per litre can be increased to 50 100 mg. and preferably to 200 500 mg.
  • suspension liquid depending upon the nature of the particles to be separated, there can be used all known liquids, for example, water, acetone, alcohols or hydrocarbons, water and/or acetone preferably being used.
  • the process is carried out continuously by feeding in the crude suspension through an inlet on the bottom of the separation vessel between the periphery and the centre thereof, for example, at a point half way along the radius of the disc.
  • the total flowthrough amount is linearly dependent upon the disc surface area and, in the case of water, is, as has been found by experience, 200 600 litres, pref erably 400 500 litres, of crude suspension per hour .the outlet opening should be at least 10 20 percent,
  • outlet opening opens into a settling vessel.
  • the separated particles are withdrawn from the settling vessel. This can take place through an outlet in the settling vessel.
  • the particles remaining in the suspension are withdrawn in the form of a suspension, expediently on the uid is also moved.
  • the liquid exhibits a large velocity profile of flow, not only in the dimension between the discs but also, in particular, in the direction between the edge and the centre point of the discs.
  • the phenomenon of separation is believed to be due to several factors. Since the speed of rotation of the discs and the speed of flow of the suspension are relatively low, centrifugal forces do not substantially act on the particles. However, due to the difference in shape of the particles, certain of the particles will be carried up by and flow with the liquid as it moves through flow velocity profile. For instance, the rodlet particles of whiskers have a relatively large surface area and therefore move with the suspending liquid.
  • nodule particles of the whiskers have a much smaller relative surface area and ar not carried by the suspending liquid. Rather, these nodule particles endeavor to cover the shortest possible path, which is increasingly the case in the direction of the centre point of the discs, in the region of which they can be withdrawn.
  • the suspension intended for the particle separation in expediently taken from a storage vessel.
  • the process according to the present invention can be carried out batchwise or continuously, a continuous method of working being preferred. Several separation steps can also be connected in parallel.
  • the process according to the present invention is especially for the separation of the rodlets of whiskers from, for example, the spheroidal small nodules consist of the same material as the whiskers.
  • the agglomerates are spheroidal small nodules consisting of intimately felted, extremely fine hairs made of the same materials as the rodlets.
  • the process of the present invention is, however, not limited to the separation of rodlets from nodules of whiskers. On the contrary, it can be used in all cases where, in a liquid, there are present light and homogeneously suspendable particles, the shapes of which differ sufficiently in order to undergo the described separation effect.
  • a separation vessel which comprises a flat, cylindrical part provided with a central outlet opening in the bottom thereof.
  • This outlet opening in the bottom opens into a settling vessel.
  • the inlet opening or openings are provided between the central outlet opening and a peripheral overflow, for example, at a point above half way along the radius of the disc.
  • they can also be arranged either near tothe centre or near to the disc edge. They can be of round or flattened oval shape, in which case the longer axis must lie tangentially. If, for example, in the case of a comparatively large separation unit, several inlet openings are provided, then these should be equidistant from the centre point of the disc.
  • the withdrawal of the still remaining suspension, including the particles which are not separated takes place through at least one outlet tangentially arranged on the periphery of the vessel, this outlet being constructed as an overflow.
  • the rotating disc is constructed, for example, as a vertically freely moving floating body, driven by means of a motor via a ball-and-socket joint.
  • the rotating disc should extend uniformly up to the region of the edge of the separation vessel.
  • the suspension intended for the particle separation is passed from the storage vessel into the separation vessel by means of a pump, the speed of which can be precisely regulated to insure that the flow is without turbulence.
  • the central flow off which passes through the settling vessel, can also be controlled by a slowly running pump. It is also possible to control the flow-off pipe by means of a magnetic valve provided with a time relay, an impedance coil thereby being placed before the magnetic valve. The crosssection of the pipe should thereby be completely open or completely closed.
  • the central flowoff pipe opens into an air-tight, closed vessel.
  • the liquid When filling this vessel, the liquid must force out the air present therein.
  • the amount of escaping air can be regulated by a stopcock so that, in end effect, the amount of suspension flowing out through the central flow-off opening can also be regulated.
  • the suspension containing the purified rodlets of the whiskers, which leaves the separation device via a peripheral overflow, is expediently passed to a filter for recovery of the rodlets.
  • a substantially concentrated suspension by means of a pump, into a homogeniser, where it is suitably diluted before passing into the separation vessel.
  • the homogeniser thereby serves, in particular, substantially to separate the still substantially agglomerated whiskers and to separate the nodules as efficiently as possible. It is thus possible to sup ply the separation device with a very homogeneous suspension.
  • FIG. 1 is a flow diagram of a plant using one separation unit
  • FIG. 2 is a vertical cross-section of a separation vessel
  • FIG. 3 is a horizontal cross-section of the separation vessel
  • FIG. 4 is a diagrammatic cross-section through a homogeniser
  • FIG. 5 is a section along the line V-V of FIG. 4.
  • the device comprises a storage vessel (1), which contains the material to be separated suspended in a liquid.
  • the suspension is usually stirred.
  • a pump (2) the speed of which can be precisely regulated
  • the suspension is fed through an inlet (4) into a separation device, a homogeniser (15) preferably being inserted between the storage vessel (1) and the separation device.
  • a homogeniser preferably being inserted between the storage vessel (1) and the separation device. It is also possible to store the suspension in concentrated form in the storage vessel (1) and, before separation, to dilute it to the desired extent, the agglomerate present also being substantially broken up due to the action of the homogeniser (15).
  • the homogeniser (15) is supplied with dilution liquid through a pipe (3), proved with a stopcock and a flowmeter.
  • the separation device comprises a rotatable disc (11 which is provided with a central hole (5) and which floats on the liquid.
  • the disc (11) is rotated by means of a shaft connected via a ball-and-socket joint (12) to amotor.
  • the disc is of such a size that it extends almost to the edge (13) of the separation vessel.
  • the separated particles pass through the central opening (5) into a settling vessel (6) and then through a pipe system (7), into which is incorporated a pump (16) for regulation of the flowoff, to a filter (8).
  • the suspension containing the whiskers leaves the separation device through a tangential outlet (10) constructed as an overflow (14), which can lead, for example, to a filter or centrifuging device.
  • FIGS. 2 and 3 further details are illustrated, the same reference numerals being used as in FIG. 1.
  • the inlet (4) for the crude suspension is provided on the bottom, which constitutes thelower disc, between the periphery and the centre, for example, at a point half way along the radius of the disc.
  • FIGS. 4 and 5 of the accompanying drawings show schematically the construction of the homogeniser (15).
  • This comprises an inlet (17) for water and inlet (18) for the concentrated suspension.
  • the rotor (19) is provided with a bearing (20) which is cooled directly by inflowing water.
  • the rotor has a diameter of 75 mm. and an edge length of 50 mm. and rotates at a speed of glycol in a storage vessel.
  • the suspension was passed at a rate 1,500 r.p.m.
  • the dilute and thoroughly dispersed whisker suspension leaves the homogeniser through an outlet (22).
  • the efficiency of the homogeniser can be improved by the provision of baffle plates (21).
  • EXAMPLE 1 EXAMPLE 2 2 g. of crude whiskers were dispersed in 500 ml. glycol with the use of a modified, high-speed kitchen mixer. This dispersion was then made up to 1 litre with of 3.6 litres per hour into an operating homogeniser filledwith fresh water. Through another inlet, 30 litres per hour of fresh water were supplied to the homogeniser. After passing through the homogeniser, the very homogeneous dispersion obtained was passed directly into a disc separation device of 30 cm. diameter. The distance between the discs was 5 mm. and the speed of rotation was 30 rpm. After an experimental period of about 17 minutes, the concentration in the separation unit reached 200 250 mg./litre. 1.2 g. of nodule-free material was removed from the periphery of the separation vessel and 0.8 g. of nodules leave the separation unit through its central opening.
  • said suspending liquid comprises water and/or acetone.
  • a separation vessel having a cylindrical peripheral wall and a disc-shaped bottom, said bottom having a central flowout opening therein, said bottom further having at least one suspension inlet situated between said central opening and said peripheral wall, said peripheral wall having at least one suspension outlet in the form of a tangential overflow;
  • Device comprising a storage vessel for said suspension to be fed to said separation vessel.
  • Device further comprising an open storage vessel which, for the continuous operation of said device, is adapted to be filled at intervals, and which has a pump attached to an outlet thereof.
  • Device further comprising a dilution and homogenizing device provided with an inlet, a stopcock and a flowmeter for dilution liquid, said dilution and homogenizing device being connected to the inlet of said separation vessel.
  • a pump connected to said settling vessel.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Separation Of Solids By Using Liquids Or Pneumatic Power (AREA)
  • Treatment Of Liquids With Adsorbents In General (AREA)
US00150531A 1970-07-15 1971-06-07 Separation process for solid particles of differing shape Expired - Lifetime US3764007A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CH1074270A CH513675A (de) 1970-07-15 1970-07-15 Trennverfahren für feste Teilchen unterschiedlicher Gestalt

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US3764007A true US3764007A (en) 1973-10-09

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US (1) US3764007A (enExample)
BE (1) BE770079A (enExample)
CH (1) CH513675A (enExample)
DE (1) DE2134908A1 (enExample)
FR (1) FR2098417B1 (enExample)
GB (1) GB1353395A (enExample)
NL (1) NL7109746A (enExample)
SU (1) SU402182A3 (enExample)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4249700A (en) * 1979-07-02 1981-02-10 Exxon Research & Engineering Co. Recovery of silicon carbide whiskers from coked, converted rice hulls by liquid-liquid separation
US4256571A (en) * 1979-10-09 1981-03-17 Silag, Inc. Recovery of silicon carbide whiskers from coked, converted rice hulls by selective flocculation-liquid extraction
WO1992016279A1 (en) * 1991-03-25 1992-10-01 Gösta Walin Havsteknik Ab A method of separating particles from a base liquid, and a device for performing the method

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2513936C2 (ru) * 2010-12-29 2014-04-20 Государственное образовательное учреждение высшего профессионального образования Нижегородский государственный технический университет им. Р.Е. Алексеева (НГТУ) Установка для классификации зерен абразивного материала
AT522689B1 (de) * 2020-06-15 2021-01-15 Andritz Delkor Pty Ltd Vorrichtung und verfahren zur trennung einer suspension

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4249700A (en) * 1979-07-02 1981-02-10 Exxon Research & Engineering Co. Recovery of silicon carbide whiskers from coked, converted rice hulls by liquid-liquid separation
US4256571A (en) * 1979-10-09 1981-03-17 Silag, Inc. Recovery of silicon carbide whiskers from coked, converted rice hulls by selective flocculation-liquid extraction
WO1992016279A1 (en) * 1991-03-25 1992-10-01 Gösta Walin Havsteknik Ab A method of separating particles from a base liquid, and a device for performing the method
US5501803A (en) * 1991-03-25 1996-03-26 Gosta Wahlin Havsteknik Ab Method and apparatus for separating particles from a base liquid

Also Published As

Publication number Publication date
CH513675A (de) 1971-10-15
SU402182A3 (enExample) 1973-10-12
FR2098417B1 (enExample) 1976-03-19
NL7109746A (enExample) 1972-01-18
GB1353395A (en) 1974-05-15
DE2134908A1 (de) 1972-01-20
BE770079A (fr) 1972-01-17
FR2098417A1 (enExample) 1972-03-10

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