Handbook of Solvents - George Wypych - ChemTech - Ventech!

22.4 Application of solar photocatalytic oxidation 1563
Figure 22.4.2. Schematic of the 10 SCFM parabolic trough, solar photoreactor system used at Fort Carson U. S.
Army Installation.
Table 22.4.2. Breakdown of solvent emissions from painting operations at Fort
Carson in 1994. VOC refers to volatile organic compounds, HAP to hazardous air
pollutants, MEK to methyl ethyl ketone, and MIBK to methyl isobutyl ketone
Paint Type
Total
usage, l/yr
VOC,
lbs/yr
HAP,
lbs/yr
MEK,
lbs/yr
Toluene,
lbs/yr
MIBK,
lbs/yr
Xylene,
lbs/yr
Solvent base 19,656 110,074 5405 3931 491 0 983
Thinner 983 7235 722 552 0 174 0
A small field test system, consisting of a photoreactor packed with Degussa
TiO 2-coated glass beads, was used to assess treatability of the slipstream and provide design
data for the pilot scale system. The small reactor operated with a flow rate of 20 liters/minute
provided by a pump connected to the paint booth exhaust vent line and variable reactor
temperature (ambient to 200 o C). Inlet and outlet VOC concentrations were simultaneously
measured by two gas chromatographs directly connected to both lines. This arrangement
provided real time monitoring of the inlet and outlet VOC concentrations during painting
operations.
The resultant treatability data was used to size a 5-SCFM pilot-scale system (Figure
22.4.2) also built by Industrial Solar Technologies. This system consists of a parabolic
trough reflector to focus incident sunlight onto a receiver tube containing the catalyst. The
trough has a 91 cm aperture width and is 243 cm long. The reflective surface is covered with
SA-85 (3M Company), a polymer film that reflects greater than 90% of the incident radiation
onto the catalyst tube, providing both heat and light for reaction. The catalyst-containing
receiver tube is a 3.81 cm I.D. borosilicate tube packed with 1.9 cm ceramic berl saddles
coated with 2.0 wt% platinum on TiO 2. A higher weight loading of platinum was used in the
field test because of the variable VOC composition of the paint booth stream. Operating
temperatures of 200 o C were obtained, depending on cloud cover, during most of the day.
Note that a thermally heated, lamp-illuminated system will provide similar performance as
the solar-based system described here. The reflective trough rotates around the fixed receiver
tubes by means of a gear motor. A control and photodiode arrangement activate the
gear motor, permitting the trough to track the sun throughout the day. Paint booth emissions
were sampled directly from the exhaust stream via 10.1 cm aluminum ducting. On-line
analysis of the inlet and outlet concentrations was provided by sample lines connected to the
MTI gas samplers. Reactor temperature and inlet flows were measured continuously.