POWER February 2011 - 30

INSTRUMENTATION & CONTROL
Increasing Generation Ramp Rate
at Morgantown Generating
Station's Coal-Fired Units
At Morgantown Generating Station, plant personnel used innovative methods
to combine model predictive control with distributed control system-based
process control algorithms to improve waterwall temperature control and
main steam temperature control and to enhance unit ramp rate capability.
The previous heat rate and NOx optimization performance gains were retained.
Focusing beyond basic loops of feedwater, air, and O2, the project
considered issues such as PID controller override configuration and limitations.
The techniques used to overcome these challenges improved unit
ramp rate capability beyond any previous unit performance.
By Donald Andrasik and John McNulty, GenOn Energy; John Gay, Power Max Consulting Inc.; and Don Labbe, Invensys Operations
Management
T
he typical coal-fired power plant has
been updated with digital controls and
other performance and environmental
improvements by the time it reaches middle
age. Units 1 and 2 of GenOn Energy's Morgantown
Generating Station-which is situated
on the Potomac River near Newburg, in
Charles County, Md.-represent that class of
plants with a twist. Over the years, a widening
of the coal specifications and modifications
to coal mill equipment adversely affected
waterwall outlet steam temperature
control and thereby unit ramp rate. With a
recent emphasis on economic dispatch of the
two units, those ramp rates had to increase in
order to remain competitive.
Morgantown's two units are are splitfurnace
630-MW coal-fired once-through
units constructed in the 1970s. The plants
were retrofitted in the mid-1990s with lowNOx
burners.
A modern distributed control
system (DCS) also was installed at that time,
enabling significant control and ramp rate
improvement. Furthermore, a dynamic NOx
/
heat rate optimization system (based on model
predictive control and neural nets) combined
with an intelligent sootblower optimization
system were integrated with the DCS in 2006
to meet near-term NOx
objectives.
Plant Profile
Each unit consists of a single tandem-compound
turbine generator and a single pulverized
coal-fired once-through controlled
circulation supercritical boiler utilizing a
single reheat-regenerative cycle. The steam
30
The 54th Annual ISA Power Industry Division
(POWID) Conference and 20th Annual
Joint International Society of Automation
(ISA) POWID/EPRI Controls and Instrumentation
Conference will take place
at the Embassy Suites Hotel in Concord,
North Carolina, June 5-10, 2011. This
year's conference theme is " Power Generation
Automation Today: Beyond the Original
Intention. "
ISA POWID is an organization of those
interested in the development and application
of instrumentation and controls in
www.powermag.com
the power generation industry. This event
will provide power generation industry
leaders with information on the latest
innovations in instrumentation, automation,
security, and business systems technologies
in the largest single event of its
type. ISA POWID joined with EPRI in 1991
to sponsor what is commonly known as
the POWID/EPRI Controls and Instrumentation
Conference.
More information on the conference
is available at www.isa.org/~powid/
powid_2011_%20main.htm.
POWER | February 2011
generators are, in essence, twins; the turbine
generators are of like capability but were designed
and built by two manufacturers.
Unit 1 (Westinghouse) has a nameplate
rating of 572.5 MW; the Unit 2 (General
Electric) rating is 575.2 MW. Both units
have throttle steam conditions of 3,500 psig,
1,000F, reheat steam temperature of 1,000F,
and seven stages of feedwater heating.
Both 625-MW steam generating units were
designed and manufactured by Combustion Engineering
Inc. and are designed to deliver maximum
continuous steam at a rate of 4,250,000
pounds of steam per hour with steam pressure
of 3,810 psig, and steam temperature of 1,005F
at the superheater outlet. The units were placed
into service in 1970 and 1971.
Mark It On Your Calendar
The State of the Control System
The units were retrofitted with the original
equipment manufacturer's Low NOx
Concentric
Firing System II in 1994. This retrofit necessitated
replacement of the original electric
analog control system with a modern DCS.
The DCS allowed for continuous unit improvements
through the implementation of increasingly
advanced control strategies. Automatic
control in the low-NOx
mode was extended to
equipment-limited maximum generation capacity.
Robust urgent and emergency plant and
component protection required runback rates of
50% per minute and rundown rates of 70 MW
per minute at maximum load in order to maintain
operating pressures, temperatures, and excess
oxygen (O2
) levels within safe ranges.

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POWER February 2011

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