WO1987005991A1 - Procede de sechage continu sous vide grossier d'un liquide et appareil de sechage utilise dans ledit procede - Google Patents

Procede de sechage continu sous vide grossier d'un liquide et appareil de sechage utilise dans ledit procede Download PDF

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Publication number
WO1987005991A1
WO1987005991A1 PCT/DK1987/000032 DK8700032W WO8705991A1 WO 1987005991 A1 WO1987005991 A1 WO 1987005991A1 DK 8700032 W DK8700032 W DK 8700032W WO 8705991 A1 WO8705991 A1 WO 8705991A1
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WO
WIPO (PCT)
Prior art keywords
conveying means
liquid
container
microwaves
drying
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/DK1987/000032
Other languages
English (en)
Inventor
Niels Peter Agdal
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of WO1987005991A1 publication Critical patent/WO1987005991A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
    • B01D3/10—Vacuum distillation
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23B—PRESERVATION OF FOODS, FOODSTUFFS OR NON-ALCOHOLIC BEVERAGES; CHEMICAL RIPENING OF FRUIT OR VEGETABLES
    • A23B2/00—Preservation of foods or foodstuffs, in general
    • A23B2/90—Preservation of foods or foodstuffs, in general by drying or kilning; Subsequent reconstitution
    • A23B2/97—Preservation of foods or foodstuffs, in general by drying or kilning; Subsequent reconstitution using irradiation or electric treatment, e.g. ultrasonic waves
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23B—PRESERVATION OF FOODS, FOODSTUFFS OR NON-ALCOHOLIC BEVERAGES; CHEMICAL RIPENING OF FRUIT OR VEGETABLES
    • A23B5/00—Preservation of eggs or egg products
    • A23B5/02—Drying; Subsequent reconstitution
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D1/00—Evaporating
    • B01D1/0011—Heating features
    • B01D1/0017—Use of electrical or wave energy
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D1/00—Evaporating
    • B01D1/22—Evaporating by bringing a thin layer of the liquid into contact with a heated surface
    • B01D1/24—Evaporating by bringing a thin layer of the liquid into contact with a heated surface to obtain dry solids
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B3/00—Drying solid materials or objects by processes involving the application of heat
    • F26B3/18—Drying solid materials or objects by processes involving the application of heat by conduction, i.e. the heat is conveyed from the heat source, e.g. gas flame, to the materials or objects to be dried by direct contact
    • F26B3/20—Drying solid materials or objects by processes involving the application of heat by conduction, i.e. the heat is conveyed from the heat source, e.g. gas flame, to the materials or objects to be dried by direct contact the heat source being a heated surface, e.g. a moving belt or conveyor
    • F26B3/205—Drying solid materials or objects by processes involving the application of heat by conduction, i.e. the heat is conveyed from the heat source, e.g. gas flame, to the materials or objects to be dried by direct contact the heat source being a heated surface, e.g. a moving belt or conveyor the materials to be dried covering or being mixed with heated inert particles which may be recycled
    • 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

  • This invention relates to a process for continuous, delicate vacuum drying a liquid having a content of dissolved and/or suspended solids, according to which the liquid is distributed on the surface of substantially spherical conveying means and are dried thereon to a powder that is separated from the conveying means.
  • the process relates to a drying apparatus to be used in the carrying out of said process.
  • the heating surface or the drying gas has a substantially higher temperature than the average temperature desired to be obtained for the material to be dried.
  • microwaves are used as the source of heat which, as known, allow for obtaining an increase of temperature of a material in which they are absorbed, the heat energy being generated within the material, so that no contact is required with any surface or any gaz having a higher temperature than that desired in the material during drying.
  • microwaves energy has been used as a source of heat for the vacuum drying of concentrated fruit juice, the highly viscous, concentrated material on a conveyor belt being passed through the zone of microwaves, thereby effecting a strong bubble formation and drying to produce a powder.
  • GB patent No. 593,806 discloses a process, according to which particularly penicilium-containing substrate is subjected to drying bathwise in vacuum by microwaves heating, the liquid to be dehydrated being placed in a bowl-shaped container subjected to rotation, presumably with a view to enlarge the liquid surface.
  • This process cannot be continuously carried out as a continuous process, and it is time-consuming due to the fact that the diffusion of volatile components through already dried material must take place during the drying process, in particular during the final steps of the process.
  • US patent No. 3,859,734 discloses a method related to the latter of the above mentioned methods, but according to which the drying of the liquid distributed onto the conveying means is effected under subatmospheric pressure.
  • the energy required for the evaporation is supplied by heating the conveying means outside the drying zone. This obviously implies that the conveying means will have a temperature substantially exceeding the temperature to be obtained for the liquid to be evaporated at the moment they get into contact with the liquid to be dried and, consequently, the heating of the liquid will not be so gentle as desired.
  • the accepted German patent speicfication No. 20 58 774 relates to a method of processing solids or liquids in a high-frequency field, e.g. with a view to the drying of the materials concerned.
  • the material to be dehydrated is mixed with auxiliary means of dielectric material with a view to obtain an improved exploitation of the high-frequency energy.
  • the auxiliary means are heated by the microwaves and the heat generated within the auxiliary means is conventionally transmitted to the liquid by conduction and convection, thereby entailing the disadvantageous results caused thereby with respect to the risk of heat damage to sensitive products.
  • the method is only illustrated in connection with the dehydration of materials of a comparatively good thermostability.
  • microwaves is used in its widest sense, including microwaves having frequencies in the range from some hundreds to some thousands MHz.
  • Materials exposed to radiation by such waves receive a heating that may occur evenly all over the volume of the material and which, apart from the field intensity in the radiation zone and the frequency of the rays, depends on the dielectric properties of the material.
  • conveying means made from a material which is only slightly heated when passing the field of microwaves, it is obtained that the liquid to be dried at no moment and not even locally attains a temperature exceeding the intended one to provide a suitable rate of evaporation at the subatmospheric pressure used in each individual case.
  • the temperature increase obtained in a material as a result of microwave absorption may be somewhat uneven in areas having sharp edges.
  • This problem is solved by the process according to the present invention by making use of spherical conveying means so that any portion of the fluid film on the conveying means attains the same temperature.
  • the liquid is distributed onto the surface of the conveying means while accommodated in the top portion of a vacuum container filled with conveying means or immediately before being fed into it, and the conveying means are then made to pass through a field of microwaves maintained in the container by discharging the conveying means from the bottom of the container, then feeding them back into the top portion of said container.
  • the balls rub against each other and against the walls of the container, therereby entailing the advantageous effect that the pulverized deposits provided on the surface of the conveying means will be substantially dissociated from the conveying means upon reaching the bottom of the container, and the pulverized material obtained by drying may therefore be separated from the conveying means solely by passing the discharged mixture of conveying means and powder across a perforated plate or screen through whose apertures the pulverized material passes.
  • the pulverized material may subsequently be discharged for instance through a sluice sealed by vacuum.
  • the drying process according to the invention is particularly gentle, it is particularly suitable for drying liquids sensitive to heat, e.g. aqueous liquids containing easily denaturable proteins, such as blood, serum, sheet water and eggs or liquids containing flavouring components that are volatile or sensitive to heat, such as coffee or tea.
  • aqueous liquids containing easily denaturable proteins such as blood, serum, sheet water and eggs
  • liquids containing flavouring components that are volatile or sensitive to heat, such as coffee or tea.
  • the process is for instance applicable with respect to liquids concentrated beforehand by evaporation in a known manner.
  • the invention further relates to a drying apparatus for use in carrying out the process, said drying apparatus being of the type comprising a cylindrical vertical container substantially filled with spherical conveying means onto which the liquid to be dried is distributed, said container being provided at its top portion either with members for separately feeding conveying means and liquid or members for feeding conveying means sprayed beforehand with the liquid to be dried, and being provided at its bottom portion with members for discharging conveying means and dried material, and members for feeding back discharged conveying means into the top portion of the container, said container being sealed by vacuum and provided with members to be connected with a vacuum source, said drying apparatus being characterized in that a) at least one section of the cylindrical walls of the container is made from a material that is highly microwaves penetrable, b) microwaves producing members encircling at least part of said section, and c) the conveying means are made from a material absorbing or reflecting microwaves only to a slight degree.
  • Said section of the vertical cylindrical walls that must be well microwaves penetrable is expediently prepared from a plastic material while the remainder of the container may appropriately be made from stainless steel. Alternatively, the entire container may be made from plastic material.
  • the microwaves producing members provided around at least part of the section made from plastic material in such a manner that a homogeneous field of microwaves is yielded in a zone of the container and the members concerned are appropriately shielded by means of a Faraday-cage.
  • Microwaves producing members are well known and applied to a large extent for the heating of articles of food. Examples of such members are magnetrons.
  • Another type of microwaves producing apparatus is designated klystron.
  • the drying apparatus according to the invention is illustrated in detail by means of the drawing that very schematically shows an embodiment of the apparatus.
  • the container 1 is over a condenser 4 connected with a vacuum source (not shown) through a conduit 5.
  • the container 1 is approximately filled with spherical conveying means 6, preferably produced from a plastic material, such as polycarbonate or teflon.
  • a liquid distributor 7 that may for instance be constituted by a pressure nozzle , is arranged in the space above the conveying means in the container, the solution or suspension to be dried being distributed through said liquid distributor onto the surface of the conveying means.
  • the container 1 is provided with a conical bottom through which the conveying means are continuously discharged. This causes the conveying means moistened with suspension or solution to move downwards through the container under considerable mutual friction.
  • the wet conveying means pass the section 2 in which a microwave field prevails, the temperature rises in the liquid layer coating the conveying means to a value corresponding to or near to the boiling point of the liquid at the vacuum sustained in the container 1.
  • the conveying means possess such dielectric properties that they only slightly the microwaves, the temperature of the surface of the conveying means will not exceed the temperature occurring in the liquid layer that covers them.
  • the material which was initially solved or suspended in the liquid forms - after the conveying means have passed the zone facing section 2 - a powder layer on the conveying means which, dependent on the nature of the material to be dried, adheres more or less to the surface of the conveying means.
  • the conveying means discharged from the bottom portion of the container are fed back into the top portion of the container, as schematically illustrated.
  • Any system known per se, e.g. a system of worms (not shown) may be used for discharging and feeding back the conveying means into the top portion of the container.
  • the worm discharging the conveying means and the powder obtained by the drying step may be provided at its lower part with, a perfo rated plate or for instance a vibrating sieve and therebeneath a vacuum proof powder sluice 8, known per se, from which the powder is fed into a collecting container 9.
  • separate members may be provided externally of the container for wetting the conveying means with liquid to be dried before feeding the conveying means into the container 1.
  • Such alternative members may for instance include a container in which the liquid is sprayed onto the conveying means while keeping them moving by mechanical stirring or tumbling.
  • the proportion between the quantity of liquid supplied to the container and the quantity of conveying means recycled therein and thus also the thickness of the liquid layer on the surface of the conveying means depends, inter alia, on the viscosity and the sensitivity to heat of the liquid, and it is therefore adjusted in each individual case.
  • the quantity of liquid can be adjusted to the quantity of circulating spheres so as to obtain a determined thickness of the liquid layer on the conveying means in the range of 0.2 mm.
  • the apparatus according to the invention in contradiction to prior devices effecting a similar cycling of conveying means - is adapted to effect drying under subatmospheric pressure, it does not need - in contradiction to said prior devices based on air-drying - to be connected with carbon filters or the like to prevent unpleasant smell even when drying products with an evil smell.
  • the apparatus may as well be able to entail advantages when used as an evaporating apparatus in association with distilling processes, i.e. processes in which the desired product is constituted by the liquid phase or fractions thereof.

Landscapes

  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Polymers & Plastics (AREA)
  • Food Science & Technology (AREA)
  • Zoology (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Health & Medical Sciences (AREA)
  • Molecular Biology (AREA)
  • Microbiology (AREA)
  • Drying Of Solid Materials (AREA)

Abstract

Des liquides, susceptibles de subir des dommages dus à la chaleur et contenant des particules solides dissoutes et/ou suspendues, sont séchés sous vide tout en étant répartis sur la surface d'éléments transporteurs sphériques (6), l'énergie nécessaire à l'évaporation étant produite par un champ de micro-ondes. Les éléments transporteurs sont produits à partir d'un matériau n'étant chauffé qu'à un faible degré par les micro-ondes. Un appareil de séchage, servant à réaliser ledit procédé, comprend un conteneur étanche au vide (1), à travers lequel circulent les éléments transporteurs (6), qui traversent ainsi une zone qui est entourée par un matériau perméable aux micro-ondes et autour de laquelle sont disposés les organes producteurs des micro-ondes. Des organes (7) sont disposés dans la partie supérieure du conteneur, afin de permettre l'alimentation en éléments transporteurs et en liquide à sécher, et des éléments (8) sont disposés dans la partie inférieure du conteneur, afin de permettre l'évacuation des éléments transporteurs et du matériau en poudre obtenu par l'opération de séchage.
PCT/DK1987/000032 1986-04-02 1987-04-01 Procede de sechage continu sous vide grossier d'un liquide et appareil de sechage utilise dans ledit procede Ceased WO1987005991A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DK148386A DK148386A (da) 1986-04-02 1986-04-02 Fremgangsmaade til kontinuerlig, skaansom vakuumtoerring af en vaeske samttoerreapparat til udoevelse af fremgangsmaaden
DK1483/86 1986-04-02

Publications (1)

Publication Number Publication Date
WO1987005991A1 true WO1987005991A1 (fr) 1987-10-08

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/DK1987/000032 Ceased WO1987005991A1 (fr) 1986-04-02 1987-04-01 Procede de sechage continu sous vide grossier d'un liquide et appareil de sechage utilise dans ledit procede

Country Status (2)

Country Link
DK (1) DK148386A (fr)
WO (1) WO1987005991A1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0420499A3 (en) * 1989-09-28 1991-07-03 Kabushiki Kaisha Hikoma Seisakusho Raw sewage drying apparatus
EP0864535A3 (fr) * 1997-03-12 1999-07-14 Nukem Nuklear GmbH Méthode et dispositif d'évaporation d'une solution saline
CN112425649A (zh) * 2019-08-26 2021-03-02 内蒙古伊利实业集团股份有限公司 液态介质的微波杀菌设备及杀菌方法

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE707925C (de) * 1938-07-10 1941-07-08 Siemens Schuckertwerke Akt Ges Verfahren zum Zerkleinern, insbesondere Zerpulvern, von Kohle und anderem Gut
GB593806A (en) * 1944-01-31 1947-10-27 Rca Corp Improvements in the dehydration of fluid materials by high frequency electric fields
US3653424A (en) * 1968-10-31 1972-04-04 Eric Harald Carlsson Method and apparatus for concentrating solutions or suspensions or for recovering the dry substance thereof
US3859734A (en) * 1973-01-18 1975-01-14 Sintab Swedinventor Ab Methods and plants for drying material in liquid solid, suspended or granulated form, e.g. blood-plasma, digested sludge, forage, fish, cereals, etc.
DE2058774B2 (de) * 1970-11-30 1978-03-09 Basf Ag, 6700 Ludwigshafen Verfahren und Vorrichtung zur Wärmebehandlung von rieselfähig-festen, teigigen oder flüssigen Stoffen

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE707925C (de) * 1938-07-10 1941-07-08 Siemens Schuckertwerke Akt Ges Verfahren zum Zerkleinern, insbesondere Zerpulvern, von Kohle und anderem Gut
GB593806A (en) * 1944-01-31 1947-10-27 Rca Corp Improvements in the dehydration of fluid materials by high frequency electric fields
US3653424A (en) * 1968-10-31 1972-04-04 Eric Harald Carlsson Method and apparatus for concentrating solutions or suspensions or for recovering the dry substance thereof
DE2058774B2 (de) * 1970-11-30 1978-03-09 Basf Ag, 6700 Ludwigshafen Verfahren und Vorrichtung zur Wärmebehandlung von rieselfähig-festen, teigigen oder flüssigen Stoffen
US3859734A (en) * 1973-01-18 1975-01-14 Sintab Swedinventor Ab Methods and plants for drying material in liquid solid, suspended or granulated form, e.g. blood-plasma, digested sludge, forage, fish, cereals, etc.

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0420499A3 (en) * 1989-09-28 1991-07-03 Kabushiki Kaisha Hikoma Seisakusho Raw sewage drying apparatus
AU627056B2 (en) * 1989-09-28 1992-08-13 Nikken Corporation Raw sewage drying apparatus
EP0864535A3 (fr) * 1997-03-12 1999-07-14 Nukem Nuklear GmbH Méthode et dispositif d'évaporation d'une solution saline
CN112425649A (zh) * 2019-08-26 2021-03-02 内蒙古伊利实业集团股份有限公司 液态介质的微波杀菌设备及杀菌方法
CN112425649B (zh) * 2019-08-26 2023-01-20 内蒙古伊利实业集团股份有限公司 液态介质的微波杀菌设备及杀菌方法

Also Published As

Publication number Publication date
DK148386D0 (da) 1986-04-02
DK148386A (da) 1987-10-03

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