Utility slashes fuel usage using Emerson optimisation strategies

Emerson Process Management has completed a combined cycle optimisation project that generated operational improvements and slashed average fuel usage at a large power-generating unit operated by one of the largest utilities in the US.

To help the utility reduce fuel costs during unit start-up, Emerson combined its expertise in combined cycle plant control and operations with several of its Ovation Advanced Power Applications. The result was a 67% reduction in average 2x1 hot start fuel usage. Additionally, average transition fuel usage — the fuel used to bring another combustion turbine/heat recovery steam generator (HRSG) train online and blend it with the running units — was reduced by 31%.

These fuel reductions and corresponding improvement in start-up time are particularly significant, as this unit averages 50 hot starts and 300 hot transitions a year. Emissions are also expected to decline accordingly.

Based on the success of this project, Emerson will implement its combined cycle optimisation program at several additional units owned by this utility.

“Over the last decade, we’ve seen combined cycle plants shift from baseload to more flexible operation with increased cycling frequency,” said Bob Yeager, president of Emerson Process Management’s Power & Water Solutions. “Our extensive balance-of-plant experience has shown that for power blocks experiencing heavy cycling, it is critical to look at the complete operational cycle from shutdown back through the start-up in order to drive maximum performance.”

Emerson’s combined cycle optimisation program is based on a highly structured process involving close collaboration with the customer. The initial stages of the optimisation project entail collecting historical process data to generate models of the plant’s current operating performance in order to identify opportunities for improvement. Emerson then develops and deploys dynamic performance metrics, which are created in standard Ovation logic, that serve as the basis for tracking and validating improvements throughout the project.

Once the optimised start-up process is validated through analysis and testing, Emerson’s power experts focus on reducing variability through increased task automation and reduced dependency on manual operator intervention. Advanced control strategies that actively control HRSG energy distribution to coordinate combustion turbine firing, steam turbine generator loading, and steam bypass and attemperation result in steam flows and conditions that minimise energy losses within engineering constraints.