Applications of Chemical Kinetics in Environmental Systems - Elements of Environmental Engineering: Thermodynamics and Kinetics - page 404

TABLE 6.22
Results from Fugacity Level II Calculations for Air and
Water Concentrations
K aw

K sw C i a C i w

(Pa −1 m −3 mol −1 )(L −1 kg) (mol −1 m 3 ) (mol −1 m 3 ) I INGTP i Chemical I INHTP i

Benzene 557 5 0.11 0.50 1.0 1.0

Toluene 676 20 0.10 0.42 42 12

Figure 6.76 shows the results of the calculations of risks for various categories as a
function of the process variable, the absorption oil flow rate. I GWP decreases consid-
erably and reaches a minimum at about 50 kg mol/h of oil flow rate. The optimum
therefore with respect to global warming is to work around this value. Initially when
there is no oil flow, all of the VOCs are released to the air and gradually converted
to CO 2 elevating the global warming impact. However, as the oil flow rate increases,
more of the VOCs are recovered and recycled reducing the global warming impact.
As the oil flow rate increases above 50 kg mol/h, the process utilities increase the
emission of CO 2 and therefore negate any advantages due to increased recovery of
VOCs. The smog formation potential, I SFP , appears to decrease considerably above
100 kg mol/h of oil flow rate. Hence, the maximum reduction in the smog formation
potential can be realized at the highest oil flow rate achievable. This also coincides

10 4

1000

100

GWP
SFP
ARP
INGTP
INHTP

10

1

0.1

0 100 200 300 400 500 600

Oil flow rate/kg mol ∙ h -1

FIGURE 6.76 Calculated risks for different categories as a function of the absorption
oil flow rate.