Environmental Engineering Reference
In-Depth Information
1,800
250
SO
2
1,600
200
1,400
1,200
150
Generation
1,000
800
100
600
NO
x
400
50
200
CO
2
_
-
6:00 pm
12:00 am
6:00 am
12:00 pm
6:00 pm
Source: CEMS, BENTEK Energy
FIGURE 2.23
J.T. Deeley plant generation and emissions on November 8-9, 2008.
the remainder of the day, generation held between 199 and 178 MWh—10
MWh below the pre-event generation level—yet SO
2
emissions exceeded
pre-event levels by an average of 161 lb until 9:00 p.m. when it finally fell
back as generation again declined. NO
X
and CO
2
both rose slightly as coal
generation fell, but, as the generation came back online, emissions quickly
returned to and held at their pre-event levels. The behavior depicted in
Figure 2.23 suggests that the emission rates did not fall proportionately to
generation.
Figure 2.24 shows the impact of the November 8-9 event on emission
rates. Emission rates for SO
2
, CO
2
, and NO
X
rose significantly immedi-
ately after Deeley generation was cycled and decreased as generation
was brought back online. SO
2
rates did not return to their pre-event levels
until late in the day. Interestingly, when generation dropped around 10:00
p.m. on November 9, NO
X
rates again rose. In comparison to November
8, emission rates on November 9 are significantly higher. If generation at
Deeley remained constant instead of variable on November 9, the emission
rates would have been similar to those of November 8. The top left line in
Figure 2.25 depicts the 247 MW of avoided generation due to cycling for
wind on November 9.
To calculate emissions associated with the event, Method C (discussed in the
PSCO section) was employed. The stable day rates evidenced on November
8 before the wind event were used to calculate avoided emissions and then
compared to the actual emissions from November 9. The event resulted in
2,506 lb incremental SO
2
and 717 lb incremental NO
X
and saved 120 tons of
CO
2
. Cycling J.T. Deeley to compensate for wind generation produced more
SO
2
and NO
X
emissions than would have been generated if the plant gener-
ated the same amount of power at a flat level. Due to cycling, J.T. Deeley
