Aplicaciones Industriales de Microondas

Area de Física Aplicada UTFSM

Mayo 1998

¿Qué son las microondas?

Radiación electromagnética

¿En que se usan las microndas?

Radares Comunicaciones, enlaces via microondas Hornos de microondas domésticos Usos industriales

¿Que modelos físicos explican la absorción de energía? Polar para el agua Otros

Experiencia en el laboratorio de Física Aplicada de la UTFSM Efectos de la radiación de microondas sobre distintos

minerales de cobre Estudio de la radiación de microondas sobre diferentes

tipos de concentrados Diseño y construcción de un prototipo para el tratamiento

de concentrado de Molibdenita (MoS2)

Diseño y construcción de una planta piloto para la producción de Trióxido de Molibdeno (MoO3)

Fin

NATURE OF MICROWAVE HEATING

Materials respond to microwave processing through several mechanismAmong them are :

dielectric heating

dipole rotation,

resistive heating,

electromagnetic heating

Depending on the substance, the response may be one mechanismexclusively, or to a combination of the processing mechanisms.

Dipole rotation works on electrically neutral polar molecules withspatially separated positíve and negative electric charges. The amplitudeof the mitrowaye field increases from zero in one direction, reaches amaximum, decreases to zero and then increases and reaches its maximumin the opposite direction The molecules exposed to the field respond byrotating their respective polar ends in the direction of the increasingamplitude. The resu¡ting molecular friction generates heat instantaneouslyand uniformly throughout the compound.

Resistive heating (also known as I2R heating) pertains to conductors(or semiconductors) with relativdy high resistivities. There are twosubcategories of hígh resistivity materials that can experience I2R heatingwhen exposed to microwave energy.

1) Those materials having free dectrons or dectron hole pairs. Examplesof these materials are carbon, silicon carbide, semiconductor grade siliconand gallium arsenide.

2) Those materials having ionic content in whích the jons bave sufficientfreedom of movement as to generate significant current. Examples ofthese materials are charged atoms or radicais in electrolytic solutions or insolid matrixes.

Electromagnetic heating occurs where materials which possesssignificant magnetic susceptibility properties are exposed to microwaveenergy. The magnetic poles of these materials are made to rotate in amanner analogous to polar molecules in oscillating electrical fields.Examples of these materials are magnetic oxides.

Dielectric heating is a function of dipole rotation and resistive heating.Relaxation effects with the changing voltages associated with themicrowave field, determine the dielecric properties and the dielectric lossfactor.

Application & Equipment

Industrial:

50 W to 60 kw915 MHz, 2450 MHz

Airport runway de-icingChemical vapor depostionChemically faster reactionsCoaI desulfizationD¡amond film depositionDrying:

clay, ceramic, foam rubber, glue, ink, milk, solids, molds, paper board, pharmaceut¡cals,plaster board, polymers, wood blocks and wood panels.

ECR: electron cyclotron resonanceFume retardant foam cushionsIC photoresist stripperIC layering depositionIC resist curingIC wafer annealingLasers (gas excitation)Mineral/ore extractionNuclear waste disposalOil: liquification of crudePasteurize sewer sludgePlasmas: argon, helium, hydragen, oxygenRubber : curing, foaming, recyclingSintering ceram¡csSolvent recovery