Page 44 - Wastewater Solids Incineration Systems

Safety 13

• Purging of the combustion area before startup.
• Adequate instrumentation, including temperature, pressure, and feed monitors.
• Adequate equipment sizing and control provisions to ensure proper combus-
tion conditions.
• Flue gas ductwork and equipment designed to prevent leakage of exhaust gas
into the building.

Special design considerations for a fluid bed incinerator include the following:
• The combustion of the dewatered cake takes place in the reactor vessel, generally
under positive pressure. The reactor vessel should be designed according to the
applicable structural and welding standards for the pressures to be encountered.
• The reactor uses lances for auxiliary fuel when the incinerator is at operating
temperature. A preheat burner is used for the initial warm up of the inciner-
ator. Operating practices, equipment, and interlocks must be selected to pre-
vent accumulation of natural gas, fuel oil, or other fuels in the reactor, particu-
larly in a cooled reactor. These provisions include use of block and bleed
valves on the fuel supply lines and removable oil lances to prevent leakage to
the incinerator bed when the incinerator is not operating.
• The reactor refractory should be installed in a manner that prevents develop-
ment of pockets between the shell and refractory, which could allow com-
bustible gases to accumulate and cause minor explosions that cause damage.
Pockets would also permit condensate to collect on the interior of the reactor
shell which could lead to corrosion.

Special design considerations for a multiple-hearth incinerator include the fol-
lowing:
• An emergency bypass damper and ductwork should be provided for venting
of combustion gases in the event of power failure.
• Purging of the incinerator before starting burners.

4.0 OPERATING SAFETY PROVISIONS

Experienced operators with proper training and well-defined operating procedures
have an important role in the safe operation of an incineration system. Well-trained
and experienced operators recognize unusual and unsafe conditions and act to
reduce the risk of injury to personnel, fires, and explosions.