Environmental Engineering Reference
In-Depth Information
(1200 to 1500°F). Auxiliary fuel is added when necessary to maintain
operating temperature. The sludge solids are injected into the heated
sand bed. Moisture immediately evaporates. Organic matter ignites and
reduces to ash. Residues are ground to fine ash by the sand movement.
Fine ash particles flow up and out of the unit with exhaust gases. Ash
particles are removed using common air pollution control processes.
Oxygen analyzers in the exhaust gas stack control the airflow rate.
Note:
These systems retain a high amount of heat in the sand, so they
can be operated as little as 4 hours per day with little or no reheating.
10.7.5.3 Operational Considerations
The operator of an incinerator monitors various performance fac-
tors to ensure optimal operation. These performance factors include
feed sludge volatile solids content, feed sludge moisture content, oper-
ating temperature, sludge feed rate, fuel feed rate, and air feed rate.
Note:
To ensure that the volatile material is ignited, the sludge must be
heated between 1400 and 1700°F.
To be sure that operating parameters are in the correct range, the
operator monitors and adjusts sludge feed rate, airflow, and auxiliary
fuel feed rate. All maintenance conducted on an incinerator should be in
accordance with the manufacturer's recommendations. The operator of
a multiple hearth or fluidized bed incinerator must be able to recognize
operational problems using various indicators or through observation.
Such observations, causal factors, and recommended corrective actions
are provided below:
•
symptom 1.
Multiple hearth incinerator temperature is too high.
Causal factors:
Excessive fuel feed rate; greasy solids; thermocou-
ple burned out
Corrective actions:
Decrease fuel feed rate; reduce sludge feed
rate; increase air feed rate; replace thermocouple.
•
symptom 2.
Multiple hearth furnace temperature is too low.
Causal factors:
Increase in moisture content of the sludge; fuel sys-
tem malfunction; excessive air feed rate; flame out
Corrective actions:
Increase fuel feed rate until dewatering oper-
ation improves; establish proper fuel feed rate; decrease air feed
rate; increase sludge feed rate; relight furnace.
•
symptom 3.
Oxygen content of the multiple hearth furnace stack
gas is too high.
Causal factors:
Sludge feed rate too low; sludge feed system block-
age; air feed rate too high
Corrective actions:
Increase sludge feed rate; clear any feed sys-
tem blockages; decrease air feed rate.
