Page 226 - Materials Chemistry, Second Edition

Vadose Zone Soil Remediation 209

standards set emission limitations for dioxins/furans, heavy metals, par-
ticulates, hydrogen chloride, hydrocarbons and carbon monoxide (CO), and
destruction and removal efficiency (DRE) for organics. Because the primary
purpose of a combustion unit is to destroy the organics in the hazardous
waste, the combustion unit must demonstrate a DRE of 99.99% for each prin-
cipal organic hazardous constituent (POHC) in the hazardous waste stream.
The required DRE for certain dioxin-containing wastes is even greater, at
99.9999% [9]. The DRE (in %) is defined as

M in −
DRE = M out (5.49)
M in

where
M = feed rate of a particular POHC to the combustion unit (lb/h or
in
kg/h)
M = output rate of a particular POHC from the combustion unit (lb/h or
out
kg/h)

The exhaust from the combustion unit is usually continuously monitored
and recorded for various constituents, including CO. The combustion effi-
ciency is calculated as follows, and it is typically required to be >99.90%:

[CO]
Combustion efficiency = 2 × 100% (5.50)
2
[CO] +[CO]
where
[CO ] = CO concentration in the exhaust on a dry basis (in ppmV)
2
2
[CO] = CO concentration in the exhaust on a dry basis (in ppmV)

Example 5.32: Determine the Destruction and Removal Efficiencies
The results of a trial burn (T = 2,000°F and residence time = 30 s) of a com-
bustion unit on a waste stream consisting of three POHCs are shown in the
following grid:

Feed (kg/h) Outlet (kg/h)
Benzene (C 6 H 6 ) 500 0.04
Phenol (C 6 H 5 OH) 300 0.04
PCE (C 2 Cl 4 ) 200 0.01

Is this unit in compliance?