EL-A offers for microwave application equipment testing plants with different power. Beneath two microwave testing chambers with variable power. Other units are suitable. For special purposes EL-A also builts new testing equipment or changes existing units.
Microwave drying processes will be used for many thermal processes and replace or complete in many cases conventional methods of product heating like contact or convective processes.
Fields of application
Microwave technology is suitable for all products with a high dielectric constant or a marked dipole moment, like water. Also dielectrics with more or less free ions or products with a high dielectric loss factor are suitable for microwave processes. Microwaves penetrate into the heart of the product and heat it uniformly from inside through the whole volume. Surface overheating, possible with conventional methods, is prevented. Microwaves do not heat stainless steel, so it is suitable and used for applicator material and for shielding.
Microwaves will be used as a heat source for the following processes:
- Melting, calcining
- ceramic materials
- synthetic / foam materials
- mineral insulation
Method of operation
Microwaves are generated in a high frequency tube, called magnetron. Because of the geometry of the tube, high voltage and magnetic fields the frequency will be generated in close tolerances. Tube wave guides transmit microwaves with horn radiators or slotted antennas to the applicator room, where microwaves are distributed regularly. In the applicator, which is available for continuous and discontinuous processes, the product is treated by microwaves. From the special form of the applicator results a regular field distribution of the microwaves inside the chamber.
In discontinuous processes a door allows the feeding of the chamber, in continuous processes different continuous feeders are available, which transport the product into and through the applicator room. As feeding equipment are belts or vibration conveyors common. Depending on the consistency of the product it will be fed via sluices, oscillating belts, -tubes or pumps. In continuous processes special microwave sluices prevent the escape of microwaves out of the unit. A ventilation system removes offgas and vapors out of the application chamber. Microwaves do not heat up applicator materials, so in many cases it is not nessecary to insulate the apparatus.
Depending on the special application there are used several small air cooled or bigger water cooled magnetrons. For controlling, smaller magnetrons are tacted, bigger are regulated steplessly. Security systems prevent a overheating and destruction of the magnetrons if there is no product in the applicator. Additionally they protect maintenance personnel. Security switches prevent the loss of microwaves and protect staff during the process, in case of prohibited access.