WO1991008177A1

WO1991008177A1 - Processing of ceramic materials with radio-frequencies of the microwave and uhf zones both modulated or non-modulated

Info

Publication number: WO1991008177A1
Application number: PCT/GR1990/000009
Authority: WO
Inventors: Ioannis Gyllis; Thomas Xenos
Original assignee: Ioannis Gyllis; Thomas Xenos
Priority date: 1989-11-28
Filing date: 1990-11-28
Publication date: 1991-06-13
Also published as: GR2000727Y; AU6753490A; EP0456786A1

Abstract

The present innovation consists of the use of modulated or non-modulated radio-frequencies of the microwave and the UHF zone for the processing of ceramic materials. With the term ''processing'' it is implied the defrosting and drying of raw material whenever necessary, the drying of the shaped product and the ''firing'' in order to obtain its final molecular structure. With the term ''ceramic'' it is implied material ''inorganic non-metal''.

Description

PROCESSING OF CERAMIC MATERIALS WITH RADIO - FREQUENCIES OF THE MICROWAVE AND UHF ZONES BOTH MODULATED OR NON-MODULATED

The up to date technology in proccesing raw matterials for the decrease of humidity (drying) for the production of ceramic products was engaging drying drums and hot air or open flame. The present innovation introduces radio frequencies for the defrost and the drying of raw matterials.

The drying of shaped products traditionally incorporated atmospheric air , the sun and later dryers by means of hot air. Heating of the air is now achieved by means of generators of hot air (heat exchangers). The present innovation introduces the use of radio frequencies for the drying of shaped ceramic products, in considerably shorter time.

The firing of ceramic products , a procedure in which the ceramic material obtains by means of exothermic and isothermic chemical reactions its final molecular structure, which is more stable than that of the unfired (higher energy level), was employing, up to date, firing ovens electrical or open flame ones using for the combustion anything that can be burned (e.g. coal, oil, gas, wood products and by-products etc.) in an oxidizing or reducing or other atmosphere (e.g. nitrogen).

The present innovation introduces the use of radio frequencies so as to provide the ceramic material with the energy required to obtain its final molecular structure i .e. the "firing" of the ceramic material.

Ceramics are generally considered to be dielectric materials. When such a material is exposed to electromagnetic radiation of a given frequency (in the present case UHF or microwaves) then a higher or lower temperature is produced. A correct selection of the energy level and the frequency of the electromagnetic wave gives a dramatic increase of the heat in the mass of the dielectric.

The above described innovation intends on the following :

1 . Minimization of the time for drying and "firing" of the ceramic material. 2. In cases that the application of the tradional methods of firing are unsuccessful or impossible (e.g. highly insulating ceramic masses) this method is giving satisfactory solutions.

3. With this method only one chamber could be required for both drying and firing, and possibly vitrifying instead of a dryer and a kiln that is now used.

The hardware required for the application of this method consists of :

1 ._ a number of "chambers" (one or more)

2._ electromagnetic radiation source arrays and their power supplies and modulators (if needed)

3._ Waveguides or Coaxial cables

4._ Antennas (slot arrays or linear dipole or monopole arrays)

5._ Mode stirrers

6._ Convey or transparent to the frequency of t h e electromagnetic wave applied

7._ Ventilation fans

8._ Microprocessors controlling the measuring devices and the safety aspects

9._ Measuring devices and safety controls.

The above mentioned hardware is placed between the shaping machinery and the automatic packaging of the final product.

The shaped product placed on the conveyor enters the chamber where by means of the electromagnetic radiation the water present in the mass is evaporated and is being removed by the drafts created with the electric fans. Then the "firing" process begins by means of high power electromagnetic radiation modulated if necessary . The frequencies employed are closely related to the mineral present in the mass, the thickness of the mass and the geometrical features of the product. The power of the electromagnetic wave to be radiated is closely related to electromagnetic features of the ceramic mass, and is controlled by means of a microprocessor. The necessary power distribution is obtained by means of the antenna system and the number of electromagnetic sources employed and is determined by the time required for the "firing" process. The required frequency spectrum and bandwidth is obtained by means of modulation, while the various modes by mode stirrers. The whole procedure is computer controlled.

An example of an application where the traditional method of firing is unsatisfactory compared to this innovation is the firing of high thermal resistance building clay blocks. The mass of these blocks is designed and manufactured so as to resist the conduction of heat. Consequently firing of such products requires very long firing schedules with subsequent tremendous energy waste. With this innovation, given the ability of radio frequencies of the UHF and microwave zone to penetrate and attenuate solely in the dielectric mass, the "firing" of the mass is achieved without heat losses in the surrounding environment and subsequent delay in the "firing" schedule.

Claims

1 . Method of preparation of raw material (defrosting and humidity regulation) and the combined drying and subsequent "firing" of heavy clay shaped products (clay bricks, roofing tiles, pavers) characterized by the application of the technology of radio frequencies (both modulated and non- modulated) of the UHF and microwave zone.

2. Method according to claim 1 . for the production of ceramic wall and floor tiles, sanitary ware and whitewashes (cutlery and decorative).

3. Method according to claim 1 . for the production of special ceramics and high technology ceramics (silicon nitrates, silicon carbides, high zircon oxides and high alumina oxides).

4. Method according to claim 1 . for the production of cement.