Optimiser eliminates overfiring of power units

The Unit Response Optimiser is now available as an embedded advanced control application in the Emerson Process Management Ovation expert control system, following tests in Baltimore PS

The Unit Response Optimiser is now available as an embedded advanced control application in the Emerson Process Management Ovation expert control system.

This model-based control solution can mean greater profitability for peaking or regulating units, where the ability to move faster and more accurately translates into significant dollars and cents.

The Ovation system is a key technology that powers Emerson PlantWeb digital plant architecture.

The Unit Response Optimiser uses advanced unit analysis and modeling techniques to provide optimal load trajectory and control for improved ramping, startup, unit turndown and overall performance, as well as reduce equipment wear/tear.

Based on historical data, the Unit Response Optimiser models process response and unit characteristics, then calculates a variable derivative ramp rate to optimise plant manoeuverability and AGC (automated generation control) capabilities, eliminate overfiring and provide a greater degree of unit control precision.

The Unit Response Optimiser can improve ramp rates 1-2 percent.

By optimising ramping capabilities, generating units are able to maintain heat rate at a lower capacity and avoid heat degradation, even when operating below generating capacity.

Increased ramp rates, achieved through tightly co-ordinated boiler and turbine operations, improve operational flexibility, manoeuverability and, ultimately profitability of generating units.

Beta test results from the Constellation Energy CP Crane Station Unit 2 in Baltimore demonstrate the improvements that are possible with the Unit Response Optimiser.

This 205-MW facility has been operating as a regulating unit to help maintain regional grid frequency.

In this role, the unit frequently ramps from 100 MW to a full load of 205 MW at a rate of 7 MW per minute.

Prior to installation of the Unit Response Optimiser in June 2006, CP Crane Unit 2 experienced overfiring when ramping up to its full load megawatt target.

This overfiring - which ranged from 80-100F over the operating temperature of 1050F main steam and 1000F reheat - was caused by the inherent lag time in the combustion and steam flow that is ultimately required for the unit to meet its target ramp rate and megawatt production.

Over time, temperature excursions can damage a unit: the excess heat causes metal fatigue that, in turn, results in boiler tube leaks and maintenance outages.

Since its installation in June, the Unit Response Optimiser has eliminated over-fueling and the temperature excursions it causes.

The result: reduced fuel consumption, fewer tube leaks and, consequently, less frequent maintenance outages.

"We've experienced dramatic results with the Unit Response Optimiser," said William Soltysiak, senior engineer at the CP Crane station: "By preventing overfiring, we've been able to greatly reduce equipment wear and tear so we can operate the plant more reliably and maintain our regulation status, which not only has important implications for this plant, but for the region's electricity needs, as well".

Incorporating the Unit Response Optimiser into the Ovation system is just the latest illustration of how Ovation continues to evolve and be enhanced to meet the unique challenges of the power generation industry.

"Emerson knows that for peaking units, in particular, time is money by the minute," said Bob Yeager, president of the Power and Water Solutions division of Emerson.

"By utilising the Unit Response Optimiser, our customers units are able to be more responsive, which translates into greater operational reliability, stability and, ultimately, profitability".

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