A number of EPRI Cycle Chemistry target members have developed innovative procedures and processes for the protection of the steam cycle when the unit is off-line and for starting up the units with properly treated water. In developing lay-up practices, the turbine is often neglected. This paper discusses a number of lay-up methods for the entire steam cycle including the turbine. This paper also discusses methods for the proper deaeration and treatment of the boiler fill water prior to startup and how utilities have used these methods to minimize corrosion.

The requirements for availability and operating economy of nuclear power plants have steadily become more stringent in recent years. In addition to implementing technological advances at new and operating power plants (e.g., in the form of advanced designs, processes and materials), plant operators are also increasingly applying supplementary measures to enhance undisturbed operation with high availability and reliability of nuclear power plants.

To help perform effective and reliable monitoring of the water chemistry of nuclear power plants, a number of guidelines for the chemist and the plant operator have been developed to define the necessary parameters with respect to the selected chemistry treatment. This paper deals with the definition of this parameter set, especially with respect to the most recent VGB Guidelines, and gives an overview of the optimal chemistry monitoring strategy.

The fossil power industry in New Zealand is comprised of a combination of 1970s and 1980s vintage gas- and coal-fired conventional units, three large F Class single-shaft combined cycle stations from different manufacturers commissioned from 1998 to 2007, all with horizontal, triple-pressure heat recovery steam generators (HRSGs), and a number of small aero-derivative gas turbine/HRSG co-generation plants.

Flow-accelerated corrosion (FAC) issues, in varying degrees, have occurred at all sites with a number of different monitoring and resolution strategies employed to ensure plant reliability and safe operation. These strategies have included operating and cycle chemistry changes, improved monitoring, increased non-destructive testing (NDT), and improved specification of later units. This paper provides a summary of the New Zealand fossil power industry experiences with FAC in combined cycle gas turbine plants and future activities planned in relation to FAC.

In efforts to comply with the Clean Air Act many coal-fired fossil plants are installing wet flue gas desulfurization (WFGD) systems, also known as scrubbers, to remove sulfur dioxide (SO₂). Limestone slurry is injected into an absorber to promote the formation of calcium sulfate (CaSO₄) or gypsum. Chloride (chlorine in the fuel) becomes dissolved and increases in the absorber loop, which can lead to a more corrosive environment. Inert matter in the limestone also enters the absorber and must be reduced to meet the gypsum quality specification. To control the buildup of chloride and fines in the flue gas desulfurization (FGD) system a continuous blowdown or purge stream is utilized. Environmental regulations on the discharge of treated FGD wastewater are becoming increasingly more stringent to control impacts on the receiving body of water (stream, lake, river, or ocean). These new limitations often focus on heavy metals such as selenium and nutrients including nitrogen and phosphorus compounds. The FGD chloride purge stream is typically treated by chemical addition and clarification to remove excess calcium and heavy metals with pH adjustment prior to discharge. However this process is not efficient at selenium or nutrient removal. Information on a new approach using biological reactor systems or sequencing batch reactors (SBRs) to achieve reductions in selenium and nitrogen compounds (ammonia, nitrite, and nitrate) is discussed. A brief discussion on the physical/chemical pretreatment is also provided.

The presence of biofilm in water systems can contribute to severe plant problems, such as microbiologically influenced corrosion (MIC) and under-deposit corrosion, reduction in heat transfer efficiency, increased chemical costs, and health and safety risks. While it is standard practice to apply treatment chemicals to a water system to control biofilm formation and growth, it is often unclear how these chemicals are performing or will perform in the future – the limited information available to the operator (usually from bacterial plate counts from the bulk water) reflects a system that has since moved several hours or even days into the future, and does not actually tell the operator anything about the sessile bacteria populations on system surfaces. However, on-line and real time monitoring of the water system condition is available that can provide early warning of unsatisfactory biocide performance as well as allow optimization of the chemical dosing regime. Process problems relating to biofilm formation, such as MIC, heat transfer losses and chemical efficacy, can be known and countered before they develop. This performance-based approach to biocide dosing is not only more environmentally sustainable, but costs less and puts less stress on plant materials.

The electrochemical biofilm activity monitoring system is described, and experiences with the use of this on-line, real time technology for biofilm control in a variety of water systems and plant types are presented.

University 101 courses are typically designed to help incoming first-year undergraduate students to adjust to the university, develop a better understanding of the college environment, and acquire essential academic success skills. Why are we offering a special Boiler and HRSG Tube Failures PPChem 101? The answer is simple, yet very conclusive:

• There is a lack of knowledge on the identification of tube failure mechanisms and for the implementation of adequate counteractions in many power plants, particularly at industrial power and steam generators.
• There is a lack of knowledge to prevent repeat tube failures.

The vast majority of BTF/HTF have been, and continue to be, repeat failures. It is hoped that the information about the failure mechanisms of BTF supplied in this course will help to put plant engineers and chemists on the right track. The major goal of this course is the avoidance of repeat BTF. This seventh lesson is focused on flow-accelerated corrosion of water-touched tubes in conventional boilers and heat recovery steam generators.