Control of Volatile Organic Compounds Emissions from Manufacturing

However, the calculations assume perfect mixing of the offgas and
c~mbustion air. Mixing has been identified as the crucial design
parameter from a theoretical viewpoint.
The test results both indicate an achievable control level of
98 percent at or below 870°C (1600°F) and illustrate the importance of
mixing. Union Carbide results on lab-scale incinerators indicated a
minimum of 98.6 percent efficiency at 760°C (1400°F). Since lab-sca1 e
incinerators primarily differ from field units in their excel lent
mixing, these results verify the theoretical ca1 culations and suggest
that a full-size field unit can maintain similar efficiencies if
designed to provide good mixing. The tests cited in Table D-6 are
documented as being conducted on full -scale incinerators control 1 ing
offgas from air oxidation process vents of a variety of types of
plants. To focus on mixing, industrial units were selected where all
variables except mixing were held constant or accounted for in other
ways. It was then assumed any changes in efficiency would be due to
changes in mixing.
The case most directly showing the effect of mixing is that of
Petro-Tex incinerator. The Petro-Tex data show the efficiency changes
due to modifications on the incinerator at two times after startup.
These modifications (see Section 0.2.3.1, 3. Test Results) increased
efficiency from 70 percent to over 99 percent, with no significant
change in temperature.
A comparison of the Rohm and Haas test versus the Union Carbide
lab test, as presented in Table D-8, indirectly shows the effect of
mixing. The UCC lab unit clearly outperforms the R&H unit. The data
from both units are based on the same temperature, residence time, and
inlet stream conditions. The more complete mixing of the lab unit is
judged the cause of the differing efficiencies.
The six tests of in-place incinerators do not, of course, cover
every feedstock. However, the theoretical discussion given above
indicates that any VOC compound should be sufficiently destroyed at
870°C (1600°F). More critical than the type of VOC is the VOC
concentration in the offgas. This is true because the kinetics of
combustion are not first-order at low VOC concentrations. The Petro-Tex