Handbook of Solvents - George Wypych - ChemTech - Ventech!

22.4 Application of solar photocatalytic oxidation 1567
Figure 22.4.8. The effect of sunlight fluctuations on the
photothermal destruction of methyl ethyl ketone in the parabolic
trough, photothermal reactor. MEK conversion, insolation level, and
reactor temperature are plotted as a function of continuous outdoor
illumination time.
isobutyl ketone, toluene, n-butyl
acetate, xylenes, and ethyl benzene.
When the reactor reached an
operating temperature of 170 o C,
complete VOC destruction was
achieved for the entire run except
for a period of peak VOC emissions
beginning at 9:30 and ending
at 9:45. Thus, during this four hour
period, the PCO process destroyed
virtually all of the VOCs in the slip
stream from the paint booth exhaust.
The total time averaged
conversion is estimated to be
greater than 95%. These data were
used to design the solar-driven,
photothermal reactor system.
Based on the lamp tests, the
5-SCFM thermal photoreactor system was tested with methyl ethyl ketone (MEK), a paint
solvent surrogate. Figure 22.4.8 shows the results of on-sun testing with this system. The
Y-axis plots three factors: temperature in o C x100 MEK, conversion as a fraction with 1
equaling 100% conversion, and solar insolation as mW/cm 2 . The X-axis plots illumination
time in minutes. This test was performed on a hazy day with numerous clouds to evaluate
the system under challenging conditions. Though conversion and reactor temperature parallel
the insolation, they do so in a less than 1:1 ratio. This is likely due to the square root dependence
of reaction rate on light intensity and to the heat transfer (insulative)
characteristics of the ceramic support. 100% conversion was achieved when insolation levels
were above 3.5 mW/cm 2 and
reactor temperatures above 175 o C.
The photothermal reactor
was tested in July, 1997 for three
weeks on paint booth emissions
using natural sunlight. A representative
data set for July 22, 1997 is
shown in Figure 22.4.9 in which
the total VOC concentration for
the inlet and the outlet of the parabolic
trough, photothermal reactor
is plotted against illumination
time. The solvent stream, which
varied with time, generally contained
about 140 ppmv of toluene,
Figure 22.4.9. VOC concentration from paint solvents as a function
of illumination time during photocatalytic treatment with a concentrating,
parabolic trough, solar photoreactor.
methyl ethyl ketone, methyl
isobutyl ketone, xylenes, butyl acetate
and ethyl benzene. The oper-