US3238632A - Method and apparatus to dry powdery substances under a vacuum using electrical gas discharges - Google Patents

Method and apparatus to dry powdery substances under a vacuum using electrical gas discharges Download PDF

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Publication number
US3238632A
US3238632A US220454A US22045462A US3238632A US 3238632 A US3238632 A US 3238632A US 220454 A US220454 A US 220454A US 22045462 A US22045462 A US 22045462A US 3238632 A US3238632 A US 3238632A
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United States
Prior art keywords
vacuum
powdery
discharge
gas discharge
powdery substances
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Expired - Lifetime
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US220454A
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English (en)
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Voigtlaender-Tetzner Gerhard
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Leybold Anlagen Holding AG
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Leybold Anlagen Holding AG
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B5/00—Drying solid materials or objects by processes not involving the application of heat
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B5/00—Drying solid materials or objects by processes not involving the application of heat
    • F26B5/04—Drying solid materials or objects by processes not involving the application of heat by evaporation or sublimation of moisture under reduced pressure, e.g. in a vacuum
    • F26B5/048—Drying solid materials or objects by processes not involving the application of heat by evaporation or sublimation of moisture under reduced pressure, e.g. in a vacuum in combination with heat developed by electro-magnetic means, e.g. microwave energy

Definitions

  • the present invention relates generally to a method for vacuum drying or vacuum degassing substances in powder form, and especially substances having a small average grain size, preferably below cm.
  • the cause of this very undesirable effect is the formation of surface forces which increase to extreme extents when the particles approach intimate contact with each other.
  • a similar effect is used in technical fields in slip gauges. In such devices the sections adhere to each other tightly when the surfaces contact one another. The reason for this is that the surfaces are very uniform or smooth and the contacting and adhering is due to molecular adhesion forces.
  • Another object of the present invention is to provide a method of the character described wherein agglomerations of powdery substances under the effect of surface forces are prevented during drying or degassing processes.
  • a body of powdery substance is provided and is subjected to the influence of a vacuum.
  • an electrical gas discharge is created i the body of powdery material.
  • gas discharge has the conventional meaning of a discharge 3,238,632 Patented Mar. 8, 1 966 formed under reduced pressure by the application of a break-down voltage between a pair of electrodes.
  • the discharge paths thereby formed create channels in the powder layers and thus loosen the powder particles.
  • the electrode discharge processes can be caused to occur to the greatest degree in certain preferred portions of the body of powdery material.
  • a uniform effect is desired, i.e., an effect of the electrical discharge upon the entire powdery body is desired and may be uniform throughout.
  • the gas discharge may be caused by a high frequency electric alternating field which may preferably be generated with the aid of a known Tesla transformer or coil. This type of discharge causes only a little heat to be generated in the powdery substance and this heat also contributes to the acceleration of the drying and degassing processes.
  • glow discharges of low luminous flow may be used within the powder layer.
  • the greater mechanical forces provided by the spark discharge are generally more advantageous. Since, in the instant invention, an electrical gas discharge is to be maintained in the body of powdery material, it should be noted that at least during a portion of the drying and degassing process the pressure within the receiving container must not be lowered to the extent that the electrical discharge will be extinguished.
  • FIGURE 1 is a schematic view of an arrangement for degassing fine grain powders.
  • FIGURE 2 is a graphical view illustrating the relative gas withdrawal of fine grain powders according to the present invention and according to prior art processes.
  • FIGURE 1 illustrates a vessel or receiving container 1 in which a body of fine grain powdery material 2 is disposed.
  • This powdery material can be formed of Aerosil powder having a medium grain size of 10- cm.
  • a heating coil 3 is disposed around the outer wall of the container 1 and this coil may be activated or heated by connected it with a current supply.
  • a discharge probe 4 extends into the powdery body of material 2 and is connected at one end to a Tesla transformer 6 by means of a connection line 5.
  • the other pole of the Tesla transformer 6 is grounded by means of connection line 7.
  • the inner wall of the container 1 acts as a counter electrode for the discharge probe 4, and is also grounded by means of a line 8.
  • the receiving container 1 is sealed by closure element 11 and is connected to a vacuum pump 10 by means of an evacuating line or conduit 9.
  • a pressure measuring device 13 of a known construction, for example, an ionization manometer, is connected to the evacuating line 9.
  • a ventilating valve 14 is connected to the evacuating line 9 and both of these connections are provided by means of a cross piece 12 formed of conduit material.
  • a filter 15 is disposed in the evacuating line 9 and in the flow path and upstream of, or before, the cross piece 12 and prevents the fine grained powder from entering the measuring device 13 and the pump 1t). Downstream or behind the cross piece 12 and in the evacuating line 9 is a sealing or blocking valve 16.
  • the Aerosil powder had a medium or average grain size of 10' cm. and an initial moisture content of 1.5%.
  • the graph clearly shows that a desired high value of gas withdrawal of the powder can be obtained with the method according to the present inven tion.
  • a more extensive degassing of the body of powdery material is provided than is possible with evacuation or operation without the benefit of this discharge effect.
  • the vacuum treatment of the body of powdery material when gas discharge is carried out simultaneously therewith, is degassed about ten times as much as is provided without this auxiliary measure. It is essential that such a strong degassing can be accomplished with minimal heating of the powdery body.
  • a method for vacuum treatment of powdery substances having small average grain size of below 10- cm. comprising the steps of depositing a body of powdery material in an evacuable chamber, subjecting the body of powdery material to a vacuum, and, at least during a portion of the time that it is subjected to the vacuum, creating an electrical gas discharge through the interior portions of the body of powdery material so as to cause agitation thereof.
  • Apparatus for vacuum treatment of powdery substances comprising, in combination:
  • gas discharge producing means comprising an electrode disposed within said chamber and a power supply for applying a break-down voltage to said electrode, said gas discharge producing means adapted to produce an agitating gas discharge through the interior portions of a body of powdery substance in said chamber while a vaccum is produced therein.
  • said vacuum tight chamber is a grounded electrically conductive container and provides a discharge path for the gas discharge produced by said gas discharge producing means.
  • said gas discharge producing means includes a Tesla transformer device adapted to produce a spark discharge.
  • the apparatus according to claim 2 including, in addition to said gas discharge producing means, heating means adapted to produce heating of the body of powdery substance.
  • a method for vacuum treating an average powdery substance having a grain size below 10 cm. comprising the steps of depositing the powdery substance in a vacuum chamber so as to at least partially bury an electrode disposed within said vacuum chamber, evacuating said vacuum chamber, and producing a gas discharge at said electrode so as to cause agitation of the powdery substance during said evacuation step.

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  • Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Molecular Biology (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physical Or Chemical Processes And Apparatus (AREA)
  • Drying Of Solid Materials (AREA)
US220454A 1961-08-30 1962-08-30 Method and apparatus to dry powdery substances under a vacuum using electrical gas discharges Expired - Lifetime US3238632A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DEL39906A DE1140875B (de) 1961-08-30 1961-08-30 Verfahren zur Vakuumtrocknung oder -entgasung von pulverfoermigen Stoffen

Publications (1)

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US3238632A true US3238632A (en) 1966-03-08

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DE (1) DE1140875B (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3455031A (en) * 1967-08-29 1969-07-15 Sun Freeze Inc Method for vacuum dehydration and apparatus therefor
EP0707186A1 (de) * 1994-10-11 1996-04-17 JOHNSON & JOHNSON MEDICAL, INC. Plasmaunterstützte Vakuumtrocknung
CN110073158A (zh) * 2016-09-09 2019-07-30 Sp工业股份有限公司 蒸汽可灭菌冷冻干燥系统中的计量器的重复无菌使用

Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB911885A (de) *
US773875A (en) * 1903-06-23 1904-11-01 Automatic Weighing Machine Company Method of compacting finely-divided materials.
US773876A (en) * 1903-06-23 1904-11-01 Automatic Weighing Machine Company Method of compacting finely-divided materials.
US2038251A (en) * 1933-01-03 1936-04-21 Vogt Hans Process for the thermic treatment of small particles
FR898989A (fr) * 1942-07-31 1945-05-14 Patentwervertungs Gmbh Hermes Procédé et appareillage pour le traitement de matières solides dans un champ de haute fréquence
US2442114A (en) * 1944-04-27 1948-05-25 Rca Corp Method of and apparatus for subjecting materials to a radio-frequency field
US2585825A (en) * 1942-06-26 1952-02-12 Nyrop Johan Ernst Method of drying, concentrating by evaporation, or distilling heatsensitive substances
US2605554A (en) * 1947-08-05 1952-08-05 Lyophile Cryochem Corp Process for the desiccation of labile aqueous materials
GB704491A (en) * 1952-01-02 1954-02-24 British Oxygen Co Ltd Improvements in or relating to the reactivation of adsorbent materials
US3011543A (en) * 1957-07-12 1961-12-05 Jr Samuel L Mccormick Spray dryer
US3060297A (en) * 1959-09-22 1962-10-23 Ralph G Sargeant Electrical apparatus for removing water from liquid mixtures

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB586693A (en) * 1944-09-08 1947-03-27 Nat Res Corp Improvements in desiccation methods and apparatus

Patent Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB911885A (de) *
US773875A (en) * 1903-06-23 1904-11-01 Automatic Weighing Machine Company Method of compacting finely-divided materials.
US773876A (en) * 1903-06-23 1904-11-01 Automatic Weighing Machine Company Method of compacting finely-divided materials.
US2038251A (en) * 1933-01-03 1936-04-21 Vogt Hans Process for the thermic treatment of small particles
US2585825A (en) * 1942-06-26 1952-02-12 Nyrop Johan Ernst Method of drying, concentrating by evaporation, or distilling heatsensitive substances
FR898989A (fr) * 1942-07-31 1945-05-14 Patentwervertungs Gmbh Hermes Procédé et appareillage pour le traitement de matières solides dans un champ de haute fréquence
US2442114A (en) * 1944-04-27 1948-05-25 Rca Corp Method of and apparatus for subjecting materials to a radio-frequency field
US2605554A (en) * 1947-08-05 1952-08-05 Lyophile Cryochem Corp Process for the desiccation of labile aqueous materials
GB704491A (en) * 1952-01-02 1954-02-24 British Oxygen Co Ltd Improvements in or relating to the reactivation of adsorbent materials
US3011543A (en) * 1957-07-12 1961-12-05 Jr Samuel L Mccormick Spray dryer
US3060297A (en) * 1959-09-22 1962-10-23 Ralph G Sargeant Electrical apparatus for removing water from liquid mixtures

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3455031A (en) * 1967-08-29 1969-07-15 Sun Freeze Inc Method for vacuum dehydration and apparatus therefor
EP0707186A1 (de) * 1994-10-11 1996-04-17 JOHNSON & JOHNSON MEDICAL, INC. Plasmaunterstützte Vakuumtrocknung
US5656238A (en) * 1994-10-11 1997-08-12 Johnson & Johnson Medical, Inc. Plasma-enhanced vacuum drying
CN1089252C (zh) * 1994-10-11 2002-08-21 庄臣及庄臣医药有限公司 等离子增强真空干燥
CN110073158A (zh) * 2016-09-09 2019-07-30 Sp工业股份有限公司 蒸汽可灭菌冷冻干燥系统中的计量器的重复无菌使用
CN110073158B (zh) * 2016-09-09 2021-04-27 Sp工业股份有限公司 蒸汽可灭菌冷冻干燥系统中的计量器的重复无菌使用

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