EP0985893A1 - Hochdruckmikrowellenofen zum Brennen von keramischem Material - Google Patents

Hochdruckmikrowellenofen zum Brennen von keramischem Material Download PDF

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Publication number
EP0985893A1
EP0985893A1 EP99830546A EP99830546A EP0985893A1 EP 0985893 A1 EP0985893 A1 EP 0985893A1 EP 99830546 A EP99830546 A EP 99830546A EP 99830546 A EP99830546 A EP 99830546A EP 0985893 A1 EP0985893 A1 EP 0985893A1
Authority
EP
European Patent Office
Prior art keywords
container
kiln
ceramic material
opening
microwave
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.)
Granted
Application number
EP99830546A
Other languages
English (en)
French (fr)
Other versions
EP0985893B1 (de
Inventor
Gaudenzio Borelli
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.)
Colorobbia Italia SpA
Original Assignee
Gaudenzio Borelli
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 Gaudenzio Borelli filed Critical Gaudenzio Borelli
Publication of EP0985893A1 publication Critical patent/EP0985893A1/de
Application granted granted Critical
Publication of EP0985893B1 publication Critical patent/EP0985893B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B17/00—Furnaces of a kind not covered by any preceding group
    • F27B17/02—Furnaces of a kind not covered by any preceding group specially designed for laboratory use
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/64—Heating using microwaves
    • H05B6/80—Apparatus for specific applications
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B2206/00—Aspects relating to heating by electric, magnetic, or electromagnetic fields covered by group H05B6/00
    • H05B2206/04—Heating using microwaves
    • H05B2206/046—Microwave drying of wood, ink, food, ceramic, sintering of ceramic, clothes, hair

Definitions

  • the present invention relates to a microwave kiln for firing ceramic material under pressure.
  • kilns comprising a chamber for the combustion of a mixture of air/methane (or other) provided with a duct or flue for evacuation of the fumes are used.
  • the combustion chamber acts as a reaction chamber for the ceramic material being fired.
  • an overpressure is generated inside the combustion/reaction chamber by partially throttling the duct for discharging the fumes.
  • the kilns of the type indicated above furthermore require considerable firing times and result in a significant amount of energy being wasted since most of the heat is lost in the flue emissions.
  • Microwave kilns used in laboratories for firing small quantities of ceramic material are also known.
  • the main object of the present invention is that of proposing a microwave kiln for firing under pressure ceramic material in an industrial quantity, which does not possess the drawbacks mentioned above.
  • 1 denotes in its entirety a kiln for firing ceramic material.
  • This kiln 1 comprises a reactor consisting of a container 2 with a substantially cylindrical shape which extends along a substantially horizontal longitudinal axis 3 and which is made of non-magnetic metallic material, preferably stainless steel.
  • the container 2 consists of a tubular element 4 which is closed at the ends and provided with one or two hatches 5 which are connected to the tubular element 4 itself in a pressure-tight manner.
  • An upper-lateral and axially central portion of the container 2 has, formed in it, an opening 24 which has an elongated rectangular shape from the top downwards and is sealingly closed by means of a curved plate 25 made of material which is transparent to microwaves, preferably teflon.
  • This plate has, arranged opposite it, the outlet mouth of a rectangular waveguide 27 which is connected, at the opposite end, to a magnetron 28.
  • the magnetron 28 is supported, in a manner not shown, on suitable guides so as to be able to perform translatory movements in both directions, over an arc of a circle of about 90° with its center on the axis 3, as a result of the action of an actuator device consisting, for example, of a hydrodynamic piston 29 or other device suitable for the movement described.
  • an actuator device consisting, for example, of a hydrodynamic piston 29 or other device suitable for the movement described.
  • the waveguide 27 moves integrally with the magnetron so that the outlet mouth remains constantly in contact with the plate 25.
  • the waveguide 27 is connected, on the two sides which face the directions of translation, to metal sheets 26 of flexible non-magnetic material.
  • Each of said sheets 26 is connected at the opposite end to a rolling-up device 31 which is known per se and fixed to the container 2 at the top (or bottom) end of the window 25.
  • the container 2 is provided internally with a box-shaped body 13 which is made of - preferably 98% pure - low-density alumina (bubble alumina) bricks.
  • the internal cavity 14 of said box-shaped body 13 forms the firing chamber for the ceramic material. Since the bricks are made of material with a low microwave absorption capacity, the firing chamber 14 is thermally insulated inside the container 2.
  • Microwave-absorbing elements 15 are located adjacent to the walls of the cavity 14 (at the bottom and on the sides in the example shown in Fig. 1).
  • Said elements are, basically, made of material with a high dielectric loss factor and have the characteristic feature that they heat up considerably if subjected to the action of microwaves.
  • an axially central bottom portion of the container 2 has, formed in it, a vertical hole 6 coaxially seating in a sealed manner a shaft 7 having a bottom end 8 arranged underneath the container 2 itself and connected coaxially to the output spindle of an electric motor 9.
  • Said shaft 7 also has a top end 10 extending inside the container 2 and having its free end arranged underneath the axis 3 of the container 2 itself.
  • An edge portion of the surface 11 at the bottom runs along an annular stainless-steel element 12 which is welded to given portions of the internal surface of the container 2 and has the function of a screen for the shaft 7.
  • the motor 9 causes rotation of the surface 11 about the axis of the shaft 7 in a single direction or alternately in both directions. Loading and unloading of the kiln are performed, via hatches 5, by means of extraction of the box-shaped body 13 from the container 2.
  • the microwave electromagnetic field strikes, in a uniform manner, through the teflon plate 25, the absorbent elements 15 and the ceramic material located inside the firing chamber 14, usually contained inside a crucible. Owing to these arrangements, the temperature of the material is substantially homogeneous, without the creation of hot points or cold points, and may reach values even greater than 1300°C.
  • the container 2 is provided with two inlet holes 16 (and, where necessary, outlet holes) for gas flows at a pressure greater than atmospheric pressure (for example four bars and more) and is provided with two holes 17 for connection to special valves (not shown) which can be used to keep the pressure inside the container 2 itself under control.
  • the container 2 also has a hole 18 communicating with a safety valve (not shown) and has a hole 19 through which an Ni/Cr thermocouple 20 extends inside the container 2 itself, said thermocouple being provided with a steel sheath and being designed to keep the temperature of the external shell of the container 2 itself under control.
  • a further hole 21 formed in the container 2 allows the introduction, inside the container 2 itself, of a Pt/Rh thermocouple 22 which is provided with a platinum sheath and extends through the lining 13 as far as the inside of the firing chamber 14, so as to measure the internal temperature of the box-shaped body 14 itself, without being subject to the effect of interference arising from the microwave electromagnetic field.
  • Said gas flows have the function of washing and saturating the reaction environment inside the container 2 and their pressure is fixed and equal to values which, during use, have proved to be ideal for achieving the desired results.
  • two portions of the container 2 arranged in the vicinity of the axial ends of the container 2 itself are transversely delimited by respective grilles 23 which are preferably made of stainless-steel sheet metal and which have the function of delimiting the zone of action of the said electromagnetic field.
  • the kiln described is able to avoid the presence of combustion fumes containing gases which are harmful for the environment, as well as dust, thus avoiding high purification costs.
  • the kiln 1 is able to operate in a mode which saves a great deal of energy since substantially all the energy supplied remains confined inside the container 2: in conventional kilns, on the other hand, at least 40% of the energy supplied is lost in the flue emissions.
  • the kiln 1 is able to achieve a significant reduction in the time required for firing the ceramic material, in particular if the latter absorbs microwaves.
  • one or more 2.45 GHz magnetrons with an overall power output of 100-150 kWatt and with a production capacity of 500-800 kg per firing cycle may be used.
EP99830546A 1998-09-08 1999-09-06 Hochdruckmikrowellenofen zum Brennen von keramischem Material Expired - Lifetime EP0985893B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ITFI980200U 1998-09-08
IT1998FI000200A IT1304897B1 (it) 1998-09-08 1998-09-08 Forno a microonde per la cottura di materiale ceramico sotto pressione

Publications (2)

Publication Number Publication Date
EP0985893A1 true EP0985893A1 (de) 2000-03-15
EP0985893B1 EP0985893B1 (de) 2002-08-21

Family

ID=11352660

Family Applications (1)

Application Number Title Priority Date Filing Date
EP99830546A Expired - Lifetime EP0985893B1 (de) 1998-09-08 1999-09-06 Hochdruckmikrowellenofen zum Brennen von keramischem Material

Country Status (6)

Country Link
EP (1) EP0985893B1 (de)
AT (1) ATE222646T1 (de)
DE (1) DE69902570T2 (de)
DK (1) DK0985893T3 (de)
ES (1) ES2181383T3 (de)
IT (1) IT1304897B1 (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006013437A1 (en) * 2004-07-27 2006-02-09 Colorobbia Italia S.P.A. Micro-wave oven for the preparation of ceramic pigments process using such oven

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10260811B2 (en) 2008-03-05 2019-04-16 Ivoclar Vivadent Ag Dental furnace
DE102008012578C5 (de) 2008-03-05 2022-04-07 Ivoclar Vivadent Ag Dentalofen

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4835354A (en) * 1987-03-30 1989-05-30 Cem Corporation Microwave heating apparatus for laboratory analyses
FR2645391A1 (fr) * 1989-04-04 1990-10-05 Marzat Claude Applicateur micro-ondes alimente sous incidence de brewster
EP0457948A1 (de) * 1990-05-23 1991-11-27 ABBPATENT GmbH Mikrowelleneinrichtung
GB2262333A (en) * 1991-12-13 1993-06-16 Univ Staffordshire Entpr Ltd Microwave heating of ceramics
DE19648366C1 (de) * 1996-11-22 1998-04-02 Riedhammer Gmbh Co Kg Anlage zur thermischen Behandlung von Produkten

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4835354A (en) * 1987-03-30 1989-05-30 Cem Corporation Microwave heating apparatus for laboratory analyses
FR2645391A1 (fr) * 1989-04-04 1990-10-05 Marzat Claude Applicateur micro-ondes alimente sous incidence de brewster
EP0457948A1 (de) * 1990-05-23 1991-11-27 ABBPATENT GmbH Mikrowelleneinrichtung
GB2262333A (en) * 1991-12-13 1993-06-16 Univ Staffordshire Entpr Ltd Microwave heating of ceramics
DE19648366C1 (de) * 1996-11-22 1998-04-02 Riedhammer Gmbh Co Kg Anlage zur thermischen Behandlung von Produkten

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006013437A1 (en) * 2004-07-27 2006-02-09 Colorobbia Italia S.P.A. Micro-wave oven for the preparation of ceramic pigments process using such oven

Also Published As

Publication number Publication date
DE69902570D1 (de) 2002-09-26
EP0985893B1 (de) 2002-08-21
ITFI980200A1 (it) 2000-03-08
ITFI980200A0 (it) 1998-09-08
ATE222646T1 (de) 2002-09-15
DE69902570T2 (de) 2003-04-24
IT1304897B1 (it) 2001-04-05
DK0985893T3 (da) 2002-12-02
ES2181383T3 (es) 2003-02-16

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