Microwave separation of organic chemicals from mixed hazardous waste Page: 4 of 7
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energy than that required for MW heating at 1.0 Hz
by a factor of almost three times. However, these
ratios include enhanced energy absorption due to
cavity resonances as well as differences in
dielectric loss factors at various MW frequencies.
Conventional (MW Power Of)
v 10 n 2s 25 3
Relative Time (10 units -1 min.)
Figure 2. Conventional Heating of Ethylene
Temperature (MW Power Ott)
5 10 15 2D 21
Relative Time (10 units -1 min.)
Figure 3. MW Heating of Ethylene Glycol
Sample, 1.0 GHz @10 watts.
1.5 GHz _-
v 10 15 20
Relative Time (10 units=1 min.)
Figure 4. Frequency Dependence of MW Heating
An indication of the frequency dependence
in the selectivity of MW heating is given. For the
materials tested, the signal frequency bandwidth
of the selectivity is quite broad. Differential
heating with MW energy, by selecting the
appropriate band of signal frequencies, may have
many direct applications hazardous waste
processing. A greater efficiency of the MW
process over that of conventional heating was
observed. The properties of the combined target
organic component with the other waste
components and possibly soil medium in which it
is mixed, are affected by all components of the
mixture. Therefore, it seems probable that the
loss-factor and dielectric constant of the mixture
will need to be monitored on a continuous basis.
However, the information gained by monitoring
will also benefit the treatment process with MW
energy by providing for feedback information.
Thus the system may be continually adjusted to
provide optimum impedance matching, resonant
frequency and EM mode selection.3
The temperature of all components of the
mixture increases as energy is coupled into the
medium. Even though the background materials
may also absorb a portion of the applied MW
energy, the selectivity of the target component
may be narrow enough to allow more rapid
heating. This phenomena would allow for higher
efficiencies in the treatment process as compared
to heating the total medium and all its components
equally. The experiment showed that MW fields
will couple more efficiently and stronger to
organic liquids and solids which have higher loss
factors. MW energy may be absorbed at different
rates depending upon the material and signal
frequencies. Varying energy coupling rates and
the enhancement in vapor emission observed at
different frequency bands are attributed to two
causes. Changes in loss-factor of the material
contribute as well as large EM fields created in the
sample holder due to cavity resonant conditions
established at required frequencies. At resonance
the fields internal to the cavity are stronger and
therefore greater energy absorption by the lossy
organic material filling the cavity is possible. This
phenomena created difficulties in analyzing the
data and separating changes in loss-factor from
resonant effects. However, if the cavity
dimensions can be adjusted so that the resonant
frequency(s) correspond to the material energy-
loss selective frequency(s), then the two
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Anderson, A.A. & Albano, R.K. Microwave separation of organic chemicals from mixed hazardous waste, article, January 1, 1992; Idaho Falls, Idaho. (https://digital.library.unt.edu/ark:/67531/metadc1055675/m1/4/: accessed April 25, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.