Environmental Engineering Reference
In-Depth Information
associated mass transfer. In “traditional” commercial processes, air containing 2%-3% ozone by
weight is injected through a diffuser and bubbles upward through a contactor at or near atmospheric
pressure. Mass transfer of ozone from the gas phase to the liquid (and diffusion/mixing within the
liquid) is a very slow and inefi cient process. As a result, destruction requires contact or residence
times as long as 20 min. HiPOx incorporates high-pressure, high-precision distribution of ozone
and reagents and high-efi ciency mixing in order to maximize mass transfer, manage localized
reagent and ozone concentrations, and reduce the mass-transfer limitation on the overall oxidation
rate by orders of magnitude. Figure 7.10 illustrates how higher ozone concentrations (8%-10% by
weight in air), higher operating pressure (25-30 pounds per square inch gauge [psig] versus ambient
pressure), and efi cient, in-line mixing are combined to maximize mass transfer and reaction efi -
ciency. The dosed l uid l ows immediately through a static mixer followed by a reaction zone spe-
cii cally designed for the required residence time. A critical design feature of the distributed-injection
approach is the low, local concentrations of ozone and hydrogen peroxide.
While the AOT system was being designed and fabricated, the existing treatment system piping
was modii ed to accommodate the system upgrade. The piping is coni gured with valves to allow
bypass of the existing air-stripper systems or bypass of the HiPOx system, or operation of both
systems in series, as a safety precaution. Some of the existing piping and pipe racks were utilized in
the i nal installation coni guration.
The AOT system was delivered to AFP 44 in June 2008 on a l atbed truck trailer. The AOT unit,
which is installed in a steel CONEX box, was placed on an existing, unused concrete slab with a
crane (Figure 8.13). The unit is connected to the power supplies utilizing existing transformers.
FIGURE 8.13
Advanced oxidation unit delivery and placement.
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