Page 268 - Wastewater Solids Incineration Systems

230 Wastewater Solids Incineration Systems

combustible gases which must be purged by the natural draft. When the power is
restored, the refractory should be purged to ensure no combustible gases remain. The
induced draft fan can then be started and the emergency bypass stack damper closed.
Depending on how long the power outage lasts, the moisture content of the
smoldering cake can be low. One quick turn of the center shaft could release a large
volume of volatile gases from the cake and create a potentially explosive condition.
Therefore, before starting the center shaft after a power outage, the operator should
reduce its revolution per minute output control to zero. The center shaft should be
started slowly and gradually increased to its normal revolutions per minute. Some
agencies have found that starting and stopping of the center shaft helps the bed to
start burning slowly and uniformly. After the cake contained in the incinerator has
burned out, the incinerator can be restarted using the procedures described in section
2.2.3, Startup from Hot Standby.

2.8.2 High Incinerator Temperature
High temperature within the incinerator results when the combustion process is
allowed to go out of equilibrium. To bring the process back into equilibrium, follow
the procedures described in section 2.6, Combustion and Temperature Control. If
these procedures fail to lower the incinerator temperature, wastewater solids feed
cake should be stopped and the combustion process should be controlled to burn
out the cake in the incinerator. During the burnout, the temperature within the
incinerator may become high; therefore, it is important to provide as much cooling
air as possible. After the combustion process stops, feed cake can be restarted as
described previously.
2.8.3 High Offgas Temperature
High offgas temperature can cause damage to the air pollution control system. If high
temperature is a persistent problem, the operator should increase the water flow to
the precooler. If the high offgas temperature is a result of high incinerator operating
temperature, the following remedies are suggested:
• Increase the water flow to the precooler,

• Stop the burners,
• Decrease the feed to the incinerator,
• Go to emergency bypass stack conditions, and
• Follow the procedures in section 2.6, Combustion and Temperature Control.