How the ups and downs of fuel supply impact gas-turbine operation

Owner/operators attending the Fifth Annual Meeting of the Australasian HRSG Users Group (AHUG) held in Sydney, New South Wales, Dec 8-10, 2015, reported experiencing many of the same problems facing gas-turbine users the world over—some exacerbated by the relatively small size of the electric-generation industry in Australia/New Zealand.

In evidence this year was an underlying concern brought on by the “the export value of gas.” Many plants no longer operate as designed. As operations changed, so did the demands on equipment, systems, chemistry, and plant personnel. New risks appeared. But new lessons learned were brought here, and discussed energetically.

AHUG participants don’t hold back. Interaction at this conference is encouraged and vigorous. Each discussion quickly becomes a dynamic blend of tested knowledge and creative ideas, and in the words of David Addison, a member of the steering committee, “The only bad question is the one you don’t ask! If you show up with a question you’ll get it answered, or you will be a lot further down the path of getting an answer.”

The meeting provided specifics on plant operations, maintenance, cycle chemistry, and storage. It featured interaction among presenters, equipment specialists, and users. Final-day workshops focused on HRSG inspection planning, life assessment, and advanced alloys. All 10 articles in this special HRSG CCJ ONsite are based on the presentations and group discussions at AHUG 2015.

This year, the principal takeaway was the taxing trend toward cycling and, eventually, short- or long-term layup. That means new demands on equipment and operators. It also means new demands on cycle chemistry and monitoring, a greater need for clear policies and procedures, and the ability to manage with reduced staffing and training.

Impact of gas prices on operation. In Australia, inexpensive long-term domestic gas contracts sheltered from the world stage, are gone. Colin Gwynne of Aurecon, a consulting and services firm operating globally, focused on this shift and its largely unexpected impact on daily and long-term plant operations.

Since 2013, the Eastern Australian gas market has moved from domestic power generation supply to export LNG. The driving force: International LNG prices to support gas-fired projects outside Australia. Domestic power demand also has decreased.

Thus local gas suppliers are reluctant to sign long-term domestic supply contracts with traditional power customers. And even though LNG plants in the Middle East have reduced production by about 30% since 2013, new LNG facilities are coming on line in Eastern Australia. Most are capitalizing on an abundant Australian coal-seam gas supply.

The result: Established gas-fired plants now face an uncertain future, and need to change their modes of operation. Most base-load units are moving into a progression of cycling, two-shifting, peaking, and ultimately layup and storage. Cycle chemistry must take a lead role in these modified operations and in any short- or long-term layup activities.

As Gwynne would stress, all of this is new for many power generators. Gone are the days of historically low and stable gas prices. Planning for uncertainty is the new mode for these overlooked long-term customers. Government forecasts show increasing LNG exports through 2020, with no domestic gas-fired power generation additions until 2025. More extreme predictions include a long-term (potential) return to coal-fired generation—the traditional Australian power bedrock. Although this seems unlikely, nothing is certain.

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