Alaskan co-gen plant updates boiler using DeltaV™ system
with FOUNDATION™ fieldbus-based control
 The
first steam and electric power generating plant in Alaska
to implement automated control running on FOUNDATION fieldbus
protocol, is up, running, and warming hearts and homes in
Fairbanks.
State-of-the-art technology replaced outmoded electro-mechanical
control devices on the main boiler, Chena No. 5 (200 Kpph),
in order to increase efficiency and reliability at the plant.
Running on Emerson Process Management's DeltaV system with pre-configured
boiler control strategy and Asset Management
Solutions (AMS) software, the installation also includes 110
fieldbus-compliant transmitters and 36 FIELDVUE digital valve
controllers.
The $1 million advanced control system is part of more than
$4 million invested by Aurora Energy, L.L.C., to improve plant
operation and expand heat distribution throughout the City
of Fairbanks. When the city divested all municipal utilities
in 1998, the District Heat and Electrical Co-generation plant
was purchased by the Usibelli Coal Mine, Inc., the plant's
primary coal supplier. Usibelli formed Aurora to operate the
plant and distribute heat energy.
Fairbanks' winter temperatures often drop to -40 degrees
F, with periods as cold as -70 degrees F. So having reliable
heat free of the maintenance headaches of a furnace is an
attractive alternative, making Usibelli's Aurora investment
in a central heat utility a potentially profitable proposition.
But the plant, which dates back to the 1950s, had been neglected
and was in serious disrepair.
Aurora Energy's Control Systems Engineer Robert Mulford headed
up the cutting-edge conversion, against some skepticism. "Some
said it couldn't be done," says Mulford, "Wagers
were even made in my own plant that we couldn't automate and
bring the boiler on line in time to meet our contractual power
obligations to the grid." He continues, "Engineers
at one consulting firm advised our general manager that I
had 'radical ideas that could be leading the company into
dangerous waters.'"
 Aurora
was aided in this effort by the Emerson Industry
Center PC&E (St. Louis, MO), which provided design, project
management, and implementation services. PCE Pacific, Inc.,
an independent Emerson representative based in Seattle,
WA, supplied the automation system hardware, transmitters,
valve controllers, and ongoing support during the installation
and startup phases. Price Ahtna JV of Anchorage, AK, performed
installation.
Mulford had "never a doubt" that the new automation
system should use smart field instrumentation and the fieldbus
protocol. "Providing a digital signal from point of measurement
to point of final control assures a higher degree of accuracy
and is immune to noise problems attributed to analog systems,"
he says, adding, "This information is easily integrated
into non-control data systems, such as spreadsheets, which
can be used for plant optimization."
Gerald England, Aurora Energy's general manager, notes, "The
project came in on-budget and was completed on schedule. The
plant has been operating continuously since mid-August (1999)
with no interruptions due to the new automation system."
Says PC&E vice president Ron Lutes, "Using fieldbus,
we were able to complete the commissioning in record time.
Aurora Energy now has a very clean control system that can
easily be maintained. Remaining non-fieldbus devices can also
be upgraded without added wiring."
Aurora takes special care to address environmental concerns.
More efficient burning of coal in one location in itself reduces
pollution, and the combustion strategy implemented by the
DeltaV system adds a new level of emission reduction. The
DeltaV system with FOUNDATION fieldbus reacts faster to boiler
upsets, minimizing emissions. The company also plans to tie
the DeltaV system to stack opacity monitors to provide accurate
real-time reporting of opacity violations, minimizing delays
resulting from manual computations.
 "I
call the resulting automation solution an 'optimization system,'"
says Mulford, "because it provides the information needed
to maximize boiler output and increase the efficiency of heat
transfer and distribution. We knew that a digital system would
not solve all our problems, but it gives us the means to solve
problems. As we learn to use the data now at our disposal,
we'll do a better job of recognizing the condition of operating
equipment and diagnosing internal problems."
During the coming winter, plant personnel plan to optimize
boiler combustion and auxiliary operation for greater efficiency.
The asset management system will also be fully implemented
to improve ongoing maintenance. Next year, the company may
upgrade three smaller boilers on the old side of the plant
and bring coal and ash conveying systems into the DeltaV automation
system.
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