POWER October 2012 - 57

COAL COMBUSTION
10. Steady data. Trends of main steam temperatures and CFB bed pressure drop have greatly
improved since Aurora was introduced. The data shown is for Unit 2 and covers the period from
Jan. 1, 2006, through Jan. 21, 2009. Aurora was introduced in June 2008. Source: JEA
MW
400
380
360
340
320
300
280
260
240
220
Steam temp (F)
Bed DP (in. H20)
1000
800
600
400
200
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11. Stable fuel and lime consumption. With the addition of Aurora, fuel and lime
consumption is much more stable, which is indicative of steady, long-term boiler efficiency. The
data shown is for Unit 2 and covers the period from Jan. 1, 2006, through Jan. 21, 2009. Aurora
was introduced in June 2008. Source: JEA
MW
400
380
360
340
320
300
280
260
240
220
Fuel flow (tons/hr)
Limestone flow (tons/hr)
250
200
150
100
50
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sions output, yet NGS now spends $1
million less for ammonia to achieve NOx
compliance and has not experienced any
emissions excursions since using Aurora.
The additive has had minimal impact on
ash being used for landfilling or beneficial
reuse. The only significant effect identified
was if the bed ash were to be used in
the production of such products as bricks
or construction substrate, the resulting
product would have a lower compressive
strength. Finally, permitting authorities
have deemed Aurora an " inert " substance
and thus exempted the product from air
emission permitting requirements.
By improving fluidization within the
CFB boiler, and thus combustion, JEA has
achieved the goal of long-term reliability
and maximum operating efficiency. Further
October 2012 | POWER
refinements by optimization analyses and
fine-tuning of the boilers resulted in an unprecedented
forced outage rate of less than
1% in 2010, 2011, and the first half of 2012.
Cost savings related to combustion improvement
and process optimization is estimated
conservatively at $22 million per
year, in addition to the $1 million saved
through reduced ammonia usage. As a very
welcome side benefit, NGS now produce
an extra 1.5% of power, with the same
amount of fuel consumed prior to the addition
of Aurora. ■
-John Kang (kangjj@jea.org) is
manager of reliability engineering,
Dan Porter is plant engineer, and Ron
Beverly is CFB specialist for JEA. Bill
Leach (bleach@k-tclay.com) is director
of research for Imerys.
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57
MW
MW
12/14/05
3/24/06
7/2/06
10/10/06
1/18/07
4/28/07
8/6/07
11/14/07
2/22/08
6/1/08
9/9/08
12/18/08
3/28/09
12/14/05
3/24/06
7/2/06
10/10/06
1/18/07
4/28/07
8/6/07
11/14/07
2/22/08
6/1/08
9/9/08
12/18/08
3/28/09
Fuel and limestone flow (tons/hr)
Steam temp, F and CFB bed pressure drop (in. H20)

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POWER October 2012

Table of Contents for the Digital Edition of POWER October 2012