Mechanism and Benefits of Microwave Pyrolysis
Author: langfeng1 Time: 2017-10-26
Microwave irradiations an electromagnetic irradiation in the range of wavelengths from 0.01m to 1m and the corresponding frequency range of 0.3–300GHz. Most microwave reactors for chemical synthesis and all domestic microwave ovens operate at 2.45GHz frequency, which corresponds to a wavelength of 12.25cm. According to the interaction of microwave irradiation(electric component of microwave field) with materials, there are three ways in which a material may be categorized:
1) Insulator or microwave-transparent material where microwaves pass through without any losses (e.g. quartz, teflon, etc.),
2) Conductor where the microwaves cannot penetrate and are reflected (e.g.metals),
3) Absorber where the microwaves can be absorbed by the material (e.g.water,oils, etc.).
Microwave dielectrics are known as a material which absorbs microwave irradiation, thus microwave heating is called dielectric heating.
Microwave Pyrolysis technology offers a number of advantages over conventional pyrolysis.
The main advantage is that microwave pyrolysis can be occurred for large size particle feedstocks as the heating is agitated by the polar molecules which oscillate under the influence of an oscillating electric and magnetic field. Compared to fast pyrolysis like fluidized bed, pre-dried biomass is not required in microwave pyrolysis. The moisture in biomass needs to be removed for obtaining high heating rate in conventional fast pyrolysis. But in microwave pyrolysis the moisture is a good adsorption material for irradiation that induces the pyrolysis. Microwave pyrolysis also produces clean products like bio-oil and syngas because the process does not have to use biomass powder and does not require agitation and fluidization. The syngas produced by microwave pyrolysis has higher heating value since it is not diluted by the carrying gas.). Compared to the fast pyrolysis, microwave pyrolysis of biomass produced low liquid yield.