Page 203 - Wastewater Solids Incineration Systems

170 Wastewater Solids Incineration Systems

a bag failure will be noticed by an increase in the particulate emissions or flue gas
opacity. Periodic maintenance includes inspections inside the units and replacement
of the bags. Immediately after installation of a new set of bag filters, a bag leakage
check using a fluorescent dye and dark light should be conducted to ensure there is
no leakage of particulates.

3.0 CURRENT AIR POLLUTION CONTROL SYSTEMS

State departments of environmental protection and local APC boards have required
more stringent control of regulated pollutants, including particulate matter, acid
gases, and metals such as mercury. More elaborate APC systems have been devel-
oped and installed on newer incinerators in the United States. A noteworthy exam-
ples of such an installation is found in Ypsilanti, Michigan. The Ypsilanti plant has
one fluid bed incinerator rated at 69 metric tonne/d (76 dry ton/d).
A simplified process flow diagram of the Ypsilanti, Michigan, plant is shown in
Figure 7.16. The plant uses a fluid bed incinerator equipped with a primary heat
exchanger to recover sufficient heat to achieve autogenous combustion. At the Ypsi-
lanti plant, flue gas exiting the primary heat exchanger proceeds through a secondary
heat exchanger, a Venturi scrubber, a tray scrubber, and a wet ESP. The cooled and
saturated flue gas then proceeds through a gas conditioner which heats the gas
stream and lowers its relative humidity. The heat source to the gas conditioner is hot
air supplied by the secondary heat exchanger. The heated flue gas is then conveyed
to an activated carbon adsorber which removes the mercury.
Pollutant emissions from the plant are well below all regulatory requirements.
Typical emissions achieved at the plant are shown in Table 7.3. Note that the APC
system achieves 99% and greater removal of mercury.

4.0 EMISSIONS MONITORING
Continuous emissions monitoring systems are now required as a result of the U.S.
EPA Part 503 regulations. These regulations require continuous monitoring of stack
gas concentration of total hydrocarbons (THCs) using a flame-ionization detector.
Because concentrations must be reported on a dry basis corrected to 7% oxygen, the
flue gas moisture content and percent oxygen must also be determined. As an alter-
nate to total hydrocarbons, the U.S. EPA will accept continuous monitoring of carbon
monoxide. In general, a carbon monoxide analyzer is easier to operate and maintain