Page 410 - Air Pollution Control Engineering

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Catalytic Oxidation 383
Table 6
Typical Pressure Drops for Catalytic Incinerators
Equipment type Heat recovery HR(%) Pressure drop P (in. H O)
2
Catalytic incinerator
(fixed-bed) 0 6
Heat exchanger 35 4
Heat exchanger 50 8
Heat exchanger 70 15
Note: The pressure drop is calculated as the sum of the incinerator and heat-exchanger pressure drops.

Table 7
Comparison of Calculated Values and Values Supplied by the Permit Applicant for
Catalytic Incinerator
Calculated value Reported
(example case) a value
Continuous monitoring of temperature rise
and pressure drop across catalyst bed Yes —
Supplementary fuel flow rate, Q 179 scfm —
f
Dilution airflow rate, Q 0 —
d
Combined gas stream flow rate, Q 20,000 scfm —
com
Catalyst bed volume, V 40 ft 3 —
bed
a Based on emission steam 2.

4.3. System Pressure Drop

The total pressure drop for a catalytic oxidizer depends on the type of equipment
employed in the system as well as other design considerations. The total pressure drop
required across a catalytic incineration system determines the waste gas fan size and
horsepower requirements, which, in turn, determine the fan capital cost and electricity
consumption.
An accurate estimate of system pressure drop would require complex calculations.
A preliminary estimate can be made using the approximate values listed in Table 6.
The system pressure drop is the sum of the pressure drops across the oxidizer and the
heat exchanger.
The pressure drop can then be used to estimate the power requirement for the waste
gas fan using the empirical relationship
∆ P
−
Power = 1.17 × 10 V (10)
4
ε
where Power is the fan power requirement (kWh), V is the waste gas flow rate (scfm),
∆P is the system pressure drop (inches of water column), and ε is the combined motor
fan efficiency (dimensionless) (approx 60%).