POWER December 2021 - 33

COAL POWER
Case #1
Parameter
Full load
Current low load/%
of full load
Lowest load,
demonstrated
Demonstrated
reduction
Lowest load,
projected
Superheater
temperature
Reheater
temperature
Economizer gas exit
temperature
O2
CO
NOX
NOX
Units
Cyclone
(MW net)
595
Cyclone
595
Cyclone
172
Cyclone
284
Case #2
Case #3
Case #4
Case #5
Pulverized
coal
700
(MW net) 275/46% 275/46% 100/58% 150/53% 285/41%
(MW net)
(% of max)
(MW net)
Projected reduction (% of max)
(°F)
(°F)
(°F)
(% wet)
(ppm)
(ppm)
(lb/MMBtu)
170
29%
150
25%
968
964
565
9.40
77
246
0.560
170
29%
150
25%
961
889
666
6.38
26
281
0.490
70
40%
55
32%
833
799
600
4.17
1
505
0.760
100
35%
100
35%
872
882
772
3.88
11
497
0.735
146
21%
150
21%
999
976
523
8.21
64
279
0.570
Table 2. This table shows low-load test result data from several coal-fired power plants that
EAPC has assisted. All were safely able to reduce load significantly below their previous lowload
setpoint. Source: EAPC Industrial Services
■ Prove that safe low-load operation optimization
and increased ramp rate is
achievable and repeatable.
■ No changes to system configuration
and no new capital investment.
■ Minimize auxiliary power/station service.
Unit Flexibility and Asset Optimization
is a collaborative effort between
the power producer's engineering, operations,
and controls departments, and
EAPC Industrial Services. The team identifies
and documents their objectives.
Design data, operating data, equipment
manuals, and drawings are collected.
Plant staff is interviewed to review past
unit low-load history and known potential
obstacles that may limit the unit's ability
to achieve a certain low load.
A new test plan is developed, approved,
and testing is scheduled. During
testing, the unit load is reduced following
the schedule in varying increments
depending upon how the unit responds
(Table 2). At a predetermined load, the
unit will be held steady for overnight
observation and data collection. Key performance
indicator (KPI) data points are
collected every one to three hours during
the testing.
This process is repeated each day
with a new low-load target. If the unit
December 2021 | POWER
experiences issues with stability and/or
control at any point, the load reduction is
put on hold until the unit stabilizes, and
the issue is addressed and eliminated via
team discussion and action items.
Low-load operation optimization normally
takes four to five days of testing,
with the unit parked overnight each night.
The unit is tested with different mill or cyclone
configurations to test the impacts
on steam temperatures, turbine metal
temperatures, heat rate, and backend
temperatures that can impact emissions
and/or balance of plant (BOP) operations.
Ramp rate improvement testing follows
the same process over a four- to fiveday
period, with multiple tests at different
ramp rates over the entire load range, as
required by the client. Controls tuning is
frequently required with both low-load operation
optimization and improved ramp
rates, as the units have not been tuned
for these new modes of operation.
Challenges to Successful Unit
Flexibility and Asset Optimization
The most challenging obstacle in
achieving successful Unit Flexibility
and Asset Optimization at any plant can
be achieving buy-in from the entire operations
www.powermag.com
cessfully
operated their units in some
cases for 30-40 years. Their main goal
has long been to operate the plant each
day at full load in a safe and stable manner,
and to minimize any downtime between
scheduled outages.
The power generation industry has
been very successful in this mode of
operation, but now operators are being
tasked with a complete change in operating
philosophy and must understand
the critical importance unit flexibility will
play in keeping units in service. In each
unit tested to date, I've been told by
control room operators (CROs) that the
unit will never operate below 50-55%,
and that the unit will certainly trip if it
is operated below a certain MW load.
In each case, the onsite testing proved
that the units could be operated within
a new load range well below what they
had been previously operated at.
The project manager must possess
the technical knowledge that only comes
with having operated a power plant, and
the individual must be able to troubleshoot,
and address and resolve issues,
that develop as the unit is operated at
lower loads. The project manager must
also be approachable and share all information
with the CROs to build a level
of trust. This provides the CROs with a
comfort level to operate the unit in new
load ranges and at higher ramp rates. No
one knows the unit better than the guys
and gals that have operated it day in and
day out for several years.
Another challenge plants often face
is inadequate operating procedures.
Existing standard operating procedures
(SOPs) may need to be revised or entirely
new SOPs may need to be developed
to provide the plant operations department
with a clear and concise procedure
to limit plant trips and ensure safe operation
in a new mode.
department. The operations
department has been trained and sucPlant
managers must also find ways
to reduce costs and further limit unit
downtime, while still operating units in
a safe and stable manner, providing high
availability and reliability. Fuel costs provide
the largest area of cost reductions.
Producers need to actively pursue revised
coal contracts with their suppliers
and lower transportation costs as well.
Coal-fired plants, coal mines, and the railroads
must work together to bring down
the cost/MWh so coal-fired plants can
remain competitive in today's market.
Other areas for cost reduction include
workforce reduction via increased automation,
reduced outage timeframe, and
optimized plant operation.
33
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POWER December 2021

Table of Contents for the Digital Edition of POWER December 2021

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