Principles of microwave technology
    Microwave technology originated in the 1930s , initially applied to the field of communications . Microwave technology used in the communication can be traced back beyond the 1970s , mainly used in food processing, wood drying , plastics, rubber processing , ceramics and pre- cured , while it is in the field of environmental protection , especially in the waste treatment applications are rarely discussed. Until the last ten years, many studies showed that: compared with the conventional microwave treatment of the waste has more advantages, such as significantly reduced pollutant content, rapid heating up to high temperatures , selective heating , the process is fast , easy to control, , and its waste treatment application has a very promising future.
    Microwave is a frequency range between radio waves and infrared waves, electromagnetic waves , the frequency of 300 MHz ~ 300 GHz, which 2. 45 GHz is the most common household microwave frequencies. Microwave heating of materials , there are three mechanisms : a first mechanism , polar molecules under the effect of the applied microwave electromagnetic field , along with the original chaotic rapid changes in the molecular orientation , molecular or atomic electron clouds shift occurs resulting dipole movement , showing positive and negative polarity , because changes in the electromagnetic field speeds up to 2.45 billion times , such high-speed wheel pendulum motion, so that heat generated by the friction between molecules ; second mechanism , the magnetic material in the microwave field, the magnetic group branch changes this change of hysteresis generating heat ; third mechanism , a conductive material under the action of the microwave field to produce a current flow of current generates heat . Microwave radiation-induced temperature rise rate at which the substance and microwave frequencies and their respective wavelengths , the material ( medium ) the electric field of the scale, properties of the material to be heated ( dielectric constant , dielectric loss energy dissipation capacity or media ) factors such as the . Microwave surface of the material is not from the material begins to heat , but from all directions evenly penetrate the material even after heating , but only a medium microwave and limited penetration depth .
    Now the microwave heating applications in many areas of research, which has the microwave energy saving and processing time , etc. into full play . With conventional heating techniques
, Microwave heating has the following advantages :
   ( 1 ) fast and efficient ;
   ( 2 ) energy saving ;
   ( 3 ) the heat source is not in direct contact with the heating material ;
   ( 4 ) capable of selective heating ;
   ( 5 ) easy to control ;
   ( 6 ) devices are small and no waste generation .