Page 258 - Wastewater Solids Incineration Systems

220 Wastewater Solids Incineration Systems

startup process may take approximately 24 hours to raise the incinerator temperature
from ambient temperatures to operating conditions.
Feeding of wastewater solids to the incinerator can begin after the air pollution
control system is started and the emergency bypass stack (also known as the emer-
gency relief stack) is closed. See section 2.3, Steady State Process Control, for addi-
tional details.

2.2.2 Hot Standby
Hot standby occurs when the incinerator temperature is decreased from the oper-
ating temperature by decreasing the burner controllers to low fire and reducing the
number of online burners to one. The incinerator internal temperature would then
decrease and stabilize between approximately 316 and 427°C (600 and 800°F) until
the feeding process recommences.
Hot standby maintains sufficient heat within the refractory to allow for a more
rapid startup than a cold startup and prevent the refractory from absorbing mois-
ture. As indicated in section 2.2.1, Cold Startup, it takes approximately 24 hours to
bring incinerator temperatures up to operating conditions from ambient tempera-
tures. Therefore, a hot standby condition is preferred when there are temporarily
no solids to burn, when minor maintenance needs to be performed on the inciner-
ator or the incinerator subsystems, or when the incinerator is getting ready to be
placed into service.

2.2.3 Startup from Hot Standby
Under hot standby conditions, the incinerator and its ancillary equipment are ready
to be placed into service. To be put into service, the temperature must be raised to
593°C (1100°F) or higher to facilitate proper combustion, the air pollution control
system must be started, and the emergency bypass stack must be closed before initi-
ating cake feed to the incinerator.
To raise the temperature from hot standby to operating temperature, the operator
should increase an upper hearth burner controller to raise the incinerator temperature
by no more than 10°C (50°F) per hour. When the temperature in any location within
the incinerator reaches 538°C (1000°F), the rate of temperature increase may be raised
to 38°C (100°F) per hour until the interior temperature reaches 593°C (1100°F) or
higher. As noted in the cold startup procedures, this temperature should be main-
tained for three to four hours before feed cake is introduced to the incinerator.