Responsibility for keeping power plants running falls directly on the shoulders of plant personnel, so they need to understand what can go wrong, receive information on the current condition of the equipment, and fix things when equipment fails or performs poorly.
Many reports, tests, conferences and case studies have been published on maintaining and upgrading boilers, steam turbine-generators, heat exchangers, environmental control equipment and other major equipment items in fossil steam plants. Many of these ways of using better technology have been demonstrated in operating plants around the world. As innovations continue to emerge, it is valuable to review and assess the advances for plant operators. This also supports the steadily growing requirements for plant staff to be trained in the best methods to detect and avoid equipment failures and anomalies to minimize operating and maintenance costs.
The Electric Power Research Institute (EPRI) report, Productivity Improvement Handbook for Fossil Steam Plants, now in its third edition (EPRI document #1022520),
As part of EPRI’s Productivity Improvement Expert Reviews (PIER), each of the more than 300 case studies collected in these reports since 1998 has been critically assessed by technical experts with skills in the specific upgrades, who have discussed the improvements with power plant staff and judged their potential for future use in the fossil industry.
The objectives of the EPRI reports are:
- To identify the key factors that permit fossil steam plants to operate productively
- To review recent improvements in fossil steam plants that have been tested and validated in operating power stations
- To extract from published conferences and reports the salient features of each improvement, including the problem that was to be solved and any issues that arose during the upgrade
- To determine the perceived benefits of the upgrade through discussions with the power plant staff involved
- To make an objective, technical assessment of the improvement and suggest how others might be able to use the information that has been learned
The reports assemble these case studies on subjects spanning the power plant from the boiler to the steam turbine, and including plant auxiliaries and environmental control equipment. The information in the handbook is organized so that a reader can quickly grasp the current state of the art practices in maintaining fossil steam units, obtain guidance on specific plant problems and move ahead with solutions. In addition, the most recent report looks at emerging technologies that promise major new breakthroughs for fossil plant operations. Improvements in reliability, performance, plant flexibility, emissions control and equipment life are described.
The case studies and future advances are presented in chapters on boilers and auxiliaries, steam turbines and auxiliaries, and environmental controls. In keeping with the state of the generating business climate today, much of the interest is on CO2 and mercury controls. Other key case studies discuss improvements in boiler tube failure avoidance and cycle chemistry, turbine and generator upgrades, and improved boiler combustion.
These case studies are of particular interest to plant engineers and plant operators in identifying the successes of recent years and providing a look forward to the new advances almost ready for broad application. All of the companies and plants cited in the reports have taken positive steps to advance the operational performance of their plants and should take much credit for the results.
The following are excerpts from some examples of these case studies.
Boilers and auxiliaries
Case study: Allegheny Energy evaluates co-firing and compares emissions and performance at Willow Island and Albright
Overview: Co-firing is the firing of two dissimilar fuels at the same time in the same boiler. From July 1, 2000, through March 31, 2004, Allegheny Energy Supply Co., LLC (Allegheny) conducted an extensive demonstration of woody biomass co-firing at its Willow Island and Albright Generating Stations. This demonstration, co-funded by the United States Department of Energy (USDOE) and Allegheny, and supported by EPRI’s Biomass Interest Group (BIG), evaluated impacts of sawdust co-firing in both cyclone boilers and tangentially-fired (T-fired) pulverized coal boilers. Co-firing in the cyclone boiler — Willow Island Generating Station Unit #2 — evaluated impacts of sawdust alone and sawdust blended with tire-derived fuel (TDF). The biomass was blended with coal on its way to the combustion system. Co-firing in the pulverized coal boiler — Albright Generating Station — evaluated the impact of co-firing on emissions of oxides of nitrogen (NOX) when the sawdust was injected separately into the furnace.
Key takeaways: In both the Willow Island and Albright demonstrations, co-firing created reductions in emissions of SO2, fossil CO2 and mercury. Co-firing did not impact CO or opacity emissions. At Albright Generating Station, co-firing caused a significant reduction in NOX emissions. Some of that reduction came from the sawdust directly; much of that reduction came from the ability to increase the use of the SOFA system without increasing unburned carbon in the flyash.