Page 311 - Wastewater Solids Incineration Systems

272 Wastewater Solids Incineration Systems

A suitable container or conveying system is required to remove and store sand.
In addition, makeup sand needs to be added to the bed regularly. Operators also
need to check for sand in the wind box. This sand also needs to be removed at least
annually.

2.4 External Shell Maintenance
The operator should regularly check the external shell visually for hot spots or corro-
sion. If hot spots are observed, the incinerator should be shut down as soon as pos-
sible and cooled. An internal inspection should be carried out to determine the cause.
Hot spots typically are caused by cracks in the refractory (typically around nozzles in
the bed area). Bed material and gases that are under pressure migrate to the shell and
overheat it. If hot spots are found in the refractory they should be repaired.

2.5 Shutdown Maintenance
An annual inspection should be carried out on fluid bed incinerators. This requires
shutting down and cooling the incinerator. The incinerator should be cooled at a rate
not exceeding 37°C (100°F) per hour. This can be done by using the fluidizing air
blower. Extreme care is needed to prevent the refractory from being overstressed
during cool down.
When the incinerator is cooled to room temperature all inspection doors should
be opened and inspection can begin (refer to Table 11.1). All fuel guns should be dis-
connected from the fuel source and removed. The fuel supply to the preheat burners
must be isolated.

2.6 Refractory Repair
Refractory repairs in the fluid bed incinerator consist of patching spalled surfaces
with plastic or castable refractory and filling cracks with refractory mortar. Occasion-
ally bricks need to be replaced. The majority of refractory work occurs within the bed
area where the fluidizing sand may cause some erosion. Most plants do not have staff
qualified to repair refractory or have an inventory of refractory. A contractor must be
hired to perform the work. Contractor qualifications, brick shapes, and refractory
materials are discussed in the MHF section of this chapter.

2.7 Recordkeeping

The following information should be recorded when an incinerator is first assembled:
• Manufacturer and construction drawings.