EP0220912A1 - Procédé pour le séchage d'une matière granulaire et un séchoir à lit projeté pour sa mise en application - Google Patents

Procédé pour le séchage d'une matière granulaire et un séchoir à lit projeté pour sa mise en application Download PDF

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Publication number
EP0220912A1
EP0220912A1 EP86308135A EP86308135A EP0220912A1 EP 0220912 A1 EP0220912 A1 EP 0220912A1 EP 86308135 A EP86308135 A EP 86308135A EP 86308135 A EP86308135 A EP 86308135A EP 0220912 A1 EP0220912 A1 EP 0220912A1
Authority
EP
European Patent Office
Prior art keywords
region
densely packed
falling
drying
bed
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.)
Withdrawn
Application number
EP86308135A
Other languages
German (de)
English (en)
Inventor
Peter Leslie Jones
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.)
Electricity Council
Original Assignee
Electricity Council
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 Electricity Council filed Critical Electricity Council
Publication of EP0220912A1 publication Critical patent/EP0220912A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • 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
    • F26B3/32—Drying solid materials or objects by processes involving the application of heat by development of heat within the materials or objects to be dried, e.g. by fermentation or other microbiological action
    • F26B3/34—Drying solid materials or objects by processes involving the application of heat by development of heat within the materials or objects to be dried, e.g. by fermentation or other microbiological action by using electrical effects
    • F26B3/343—Drying solid materials or objects by processes involving the application of heat by development of heat within the materials or objects to be dried, e.g. by fermentation or other microbiological action by using electrical effects in combination with convection
    • 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
    • F26B3/02—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air
    • F26B3/06—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air the gas or vapour flowing through the materials or objects to be dried
    • F26B3/08—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air the gas or vapour flowing through the materials or objects to be dried so as to loosen them, e.g. to form a fluidised bed
    • F26B3/092—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air the gas or vapour flowing through the materials or objects to be dried so as to loosen them, e.g. to form a fluidised bed agitating the fluidised bed, e.g. by vibrating or pulsating
    • F26B3/0926—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air the gas or vapour flowing through the materials or objects to be dried so as to loosen them, e.g. to form a fluidised bed agitating the fluidised bed, e.g. by vibrating or pulsating by pneumatic means, e.g. spouted beds
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B9/00—Machines or apparatus for drying solid materials or objects at rest or with only local agitation; Domestic airing cupboards
    • F26B9/06—Machines or apparatus for drying solid materials or objects at rest or with only local agitation; Domestic airing cupboards in stationary drums or chambers
    • F26B9/08—Machines or apparatus for drying solid materials or objects at rest or with only local agitation; Domestic airing cupboards in stationary drums or chambers including agitating devices, e.g. pneumatic recirculation arrangements

Definitions

  • the present invention relates to a method of drying particulate material and in particular the use of a spouted bed drier in such a method.
  • the flow of drying air is evenly distributed across the bed and is arranged effectively to fluidise the bed so that all particles of material in the bed are exposed to the drying gas flow.
  • spouted bed drier there are many particulate materials which are difficult to fluidise, especially when wet.
  • another method using a so-called spouted bed drier, is used, in which the drying air is directed upwards from a nozzle usually centrally located in the base of the vessel which is shaped as an inverted cone.
  • the gas stream emerging upwards from the nozzle produces a central column or spout where the particles are relatively loosely packed and rise entrained in the upward stream of gas.
  • the particulate material lies relatively densely packed, slowly descending downwards to the bed to re-enter the spout. In this way, all particles in the bed are exposed to the stream of drying air as they are conveyed upwards in the spout.
  • a so-called draft tube comprising an open ended tube located above the nozzle in the base of the vessel and through with the main upwardly flowing gas stream passses, together with the entrained particulate material.
  • the draft tube effectively separates the rising spout region of material from the falling densely packed region and permits the bed of material to be made considerably deeper.
  • radio frequency or microwave energy for drying sheet or web materials
  • radio frequency heat energy comprising only a small proportion (typically 10 to 25%) of the total heat energy in the drying process including the hot air
  • drying speeds can be improved dramatically. It is believed this improvement arises because the R.F. energy is absorbed internally in the thickness of the material being dried and has the effect of forcing moisture outwards to the surface where it can readily be evaporated in the hot air stream.
  • the efficiency of hot air convective drying when applied to a wet surface is maintained for substantially the whole of the drying cycle.
  • a method of drying particulate material comprising forming a bed of the material, and blowing drying gas upwards through the bed to produce a rising spout region of relatively loosely packed particles entrained in the gas and a falling region of relatively densely packed particles descending to the bed, characterised by the step of applying an R F field substantially only to said falling densely packed region to assist in drying of the particulate material.
  • a spouted drier comprising a vessel containing a draft tube assembly separating a rising spout region from a falling relatively densely packed region, characterised by a first electrode between the rising spout region and the falling relatively densely packed region, a second electrode outside the falling relatively densely packed region, and a source of R F energy connected to the first and second electrodes whereby an R F electric field is set up substantially only in the falling relatively densely packed region to assist in the drying process.
  • the draft tube assembly has cylindrical symmetry about an upwardly extending axis, and comprises an inner cylindrical member confining the rising spout region and an outer cylindrical member forming the first electrode and defining the axially inner surface of the falling relatively densely packed region.
  • the inner cylindrical member should be located and have a diameter selected to meet the necessary aerodynamic requirements of the draft tube.
  • the outer cylindrical member should be positioned radially spaced from the inner cylindrical member, so as to maximise the efficiency of generation of the R F Field in the relatively densely packed region.
  • the second electrode may form an outer cylindrical containment wall for the falling relatively densely packed region. Then the second electrode may be connected to earth potential, thereby to act also as an outer screening cage for the R F field.
  • the illustrated drier comprises a cylindrical vessel 10 made from a non-­magnetic metal enclosed at the bottom and vented at the top.
  • a nozzle 9 is located centrally in the base of the vessel 10 to direct drying air upwardly, substantially along the axis of the vessel.
  • a draft tube assembly 11 is mounted axially inside the vessel 10 by means of electrically insulating support struts 12.
  • the draft tube assembly 11 has an inner cylindrical tube 13 which is aligned with the nozzle 9.
  • An outer cylindrical member 14 is mounted coaxial to the inner tube 13, and is connected thereto by frusto-conical surfaces 15 and 16 at respective ends of the assembly.
  • a batch of particulate material to be dried is put into the vessel 10 forming a relatively densely packed bed of the material in the annular space between the outer element 14 of the draft tube assembly 11 and the vessel 10.
  • the bed extends downwards to a base defined by an inverted frusto-conical element 17 which tends to deflect the particulate material towards the axis of the vessel over the nozzle 9.
  • Drying air blown into the vessel 10 through the nozzle 9 disturbs an axial region of the bed at the base and produces a spout of relatively loosely packed particulate material entrained in the air rising upwards from the nozzle 9 and through the inner tube 13 of the draft tube assembly 11.
  • the frusto-conical member 16 at the lower end of the draft tube assembly 11 is an inverted cone, as illustrated in the drawing, tending to concentrate the spout formed by the nozzle 9 into the inner tube 13.
  • the upper frusto-conical member 15 is shaped to deflect particulate material leaving the upper end of the inner tube 13 and tending to fall back again from the spout, outwards to the surface of the relatively densely packed region of the bed.
  • the outer cylindrical member 14 is made of non-magnetic metal and is connected as indicated at 18 to a source of radio frequency energy, whilst the vessel 10 is connected to earth potential.
  • a radio frequency field is set up in the annular region between the outer cylindrical element 14 and the vessel 10.
  • the R F electric field is selected to be at a suitable frequency to cause losses to occur in the moisture in the particulate material in the relatively densely packed region of the bed, thereby providing heat to assist the drying process.
  • the material is exposed to the electric field as it slowly falls in the relatively densely packed region towards the base of the vessel, and during the course of this exposure moisture from within the particles tends to migrate to the surface of the particles under the influence of the R F heating.
  • the particles are presented again to the spout in the inner tube 13 with substantial surface wetness which is efficiently evaporated during the residence of the particles in the spout rising up in the inner tube 13.
  • the vessel 10 being at earth potential, provides not only one of the electrodes of the R F heating system but also a Faraday cage confining the electric field to within the drying vessel.
  • the inner tube 13 of the draft tube assembly 11 may be electrically connected to the outer cylindrical member 14.
  • the radial spacing between the inner tube 13 and the outer cylindrical member 14 of the draft tube assembly 11 is selected to optimise both the aerodynamic requirements of the draft tube and the electrical requirements of the R F heating system.
  • R F energy In order to control the transfer of R F energy to the densely packed region of the bed, an appropriate matching circuit is included in the R F supply.
  • a typical frequency for the R F energy is 27.12 MHz.

Landscapes

  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Microbiology (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Biomedical Technology (AREA)
  • Biotechnology (AREA)
  • Molecular Biology (AREA)
  • Drying Of Solid Materials (AREA)
EP86308135A 1985-10-29 1986-10-20 Procédé pour le séchage d'une matière granulaire et un séchoir à lit projeté pour sa mise en application Withdrawn EP0220912A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB858526606A GB8526606D0 (en) 1985-10-29 1985-10-29 Drying particulate material
GB8526606 1985-10-29

Publications (1)

Publication Number Publication Date
EP0220912A1 true EP0220912A1 (fr) 1987-05-06

Family

ID=10587395

Family Applications (1)

Application Number Title Priority Date Filing Date
EP86308135A Withdrawn EP0220912A1 (fr) 1985-10-29 1986-10-20 Procédé pour le séchage d'une matière granulaire et un séchoir à lit projeté pour sa mise en application

Country Status (2)

Country Link
EP (1) EP0220912A1 (fr)
GB (2) GB8526606D0 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2002053809A1 (fr) 2000-12-28 2002-07-11 George Hradil Appareil de lit fluidise avec giclage pour mettre en contact des objets au moyen d'un fluide
CN102183123A (zh) * 2011-02-23 2011-09-14 大庆油田有限责任公司 一种交替多喷泉式喷动-移动床干燥器
CN103471350A (zh) * 2012-06-05 2013-12-25 肖炳旺 立式热风物料烘烤烘干箱
EP2949688A1 (fr) 2014-05-27 2015-12-02 Borealis AG Procédé de traitement de polymères au moyen d'un mélangeur de type lit fluidisé à courants de recirculation

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB854025A (en) * 1957-11-05 1960-11-16 Shawinigan Chem Ltd Improvements in and relating to the heating of spouted beds
FR1264123A (fr) * 1960-06-10 1961-06-19 Procédé et appareil de séchage ou autre traitement d'un matériau granulaire ou analogue
DE2135619A1 (de) * 1971-07-16 1973-01-25 Buettner Schilde Haas Ag Trockner fuer rieselfaehiges oder/und flugfaehiges gut
US4349967A (en) * 1980-10-06 1982-09-21 General Electric Company Magnetic field coupled spouted bed system

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB854025A (en) * 1957-11-05 1960-11-16 Shawinigan Chem Ltd Improvements in and relating to the heating of spouted beds
FR1264123A (fr) * 1960-06-10 1961-06-19 Procédé et appareil de séchage ou autre traitement d'un matériau granulaire ou analogue
DE2135619A1 (de) * 1971-07-16 1973-01-25 Buettner Schilde Haas Ag Trockner fuer rieselfaehiges oder/und flugfaehiges gut
US4349967A (en) * 1980-10-06 1982-09-21 General Electric Company Magnetic field coupled spouted bed system

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2002053809A1 (fr) 2000-12-28 2002-07-11 George Hradil Appareil de lit fluidise avec giclage pour mettre en contact des objets au moyen d'un fluide
EP1354078A1 (fr) * 2000-12-28 2003-10-22 George Hradil Appareil de lit fluidise avec giclage pour mettre en contact des objets au moyen d'un fluide
EP1354078A4 (fr) * 2000-12-28 2006-09-27 Technic Appareil de lit fluidise avec giclage pour mettre en contact des objets au moyen d'un fluide
CN102183123A (zh) * 2011-02-23 2011-09-14 大庆油田有限责任公司 一种交替多喷泉式喷动-移动床干燥器
CN103471350A (zh) * 2012-06-05 2013-12-25 肖炳旺 立式热风物料烘烤烘干箱
EP2949688A1 (fr) 2014-05-27 2015-12-02 Borealis AG Procédé de traitement de polymères au moyen d'un mélangeur de type lit fluidisé à courants de recirculation

Also Published As

Publication number Publication date
GB2182427A (en) 1987-05-13
GB2182427B (en) 1989-10-11
GB8526606D0 (en) 1985-12-04
GB8625085D0 (en) 1986-11-26

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Inventor name: JONES, PETER LESLIE