Contents Issue 5 (2001)

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Neville F. Rieger and R. Barry Dooley

The Influence of Electrostatic Charge in the Phase Transition Zone of a Steam Turbine

This paper describes the latest understanding of electrostatic effects in condensing steam. The physics of condensation and of the corona have been investigated at the molecular level. The role of electrostatic charge has been considered. Recent test results concerning electrostatic charging in steam turbines have been reviewed in preparation for the next scheduled EPRI test at AEP’s Conesville Station in 2001.

PowerPlant Chemistry 2001, 3 (5)

Nicolas C. Woodhouse

Factors Affecting Leachate Production at Lethabo Power Station Ash Dump

Lethabo Power Station is capable of generating 3700 MW, burning low-grade coal, with a high ash content. The ash is disposed off by controlled staking of the moist ash on a designated ash dump. In the early 1980’s, several possible options were considered. Moist stacking on level spoils and overburden was selected.
The climatic balance for the area was evaluated and it was assigned a “B-“ classification.
Investigations done in the past were studied to see if practice supported the belief that there is a very low risk of leachate production from the ash dump.

PowerPlant Chemistry 2001, 3 (5)

Sharon P. Mellor and Felix W.R. Matthee

Operating Experience Gained During the Copper Oxide Plugging Incident in Koeberg Unit 1 Generator Stator

In June 1999 Koeberg’s Unit 1 started to experience adverse operating conditions that were later ascribed to blockages in the hollow conductors of the generator stator. These blockages were attributed to copper oxide plugs, which developed progressively during the following year and culminated in reduced power operation. Many attempts were made to address the plugging by implementing various off-line and on-line cleaning processes. Subsequent to a successful on-line cleaning operation, the unit was returned to full power and the chemistry regime for the stator cooling water system was changed to allow for operation at an elevated pH.
This paper discusses Koeberg’s experience with copper oxide blockages, describes the initial indications of the problem and the impact on the operating parameters. The remainder of the paper focuses on the actions taken to address the deteriorating situation and the different cleaning methods implemented to remove the copper oxide deposits. The paper concludes with the current status of the Unit 1 generator stator and the lessons learned during the resolution of this problem.

PowerPlant Chemistry 2001, 3 (5)

Traksel and Donald A. Vinnicombe

Recent Advances in Ultraviolet Light (UV) Technologies in Water Treatment

UV light is part of the electromagnetic spectrum, situated between X-rays and visible light, with a wavelength between 100 and 400 nm. The UV spectrum is spilt into a number of bands, namely, UV-A, UV-B, UV-C, and vacuum UV. Each band is used in specific applications, with UV-C and parts of UV-B being used for disinfection purposes (between 200 and 315 nm). Vacuum UV is associated with the oxidation of organic carbon.
UV disinfection technology has been around for a long time (since the end of the 19th century), but major advances have been made only in the last few decades. These advances includes lamp manufacture technology with respect to output, wavelength spread and operating life, configuration design and monitoring.
Total organic carbon reduction in water has usually been associated with the vacuum UV band. The use of specialized medium pressure lamps, as well as the combination of medium pressure and low pressure lamps has shown a number of advantages.

PowerPlant Chemistry 2001, 3 (5)

Karol Daucik

Accumulation of Ionic Impurities in Water/Steam Cycle

Contamination of water/steam cycle in fossil fired power plants with ionic impurities is the main subject of this paper. It goes through the sources of contamination and their elimination. The primary means of contaminant removal, e.g., blow down and condensate polishing, are only briefly mentioned. A number of other possibilities to remove contaminants are discussed. Particularly contaminants accumulating in various places by deposition are on the agenda. The operational adjustments resulting in release of deposits are described.

PowerPlant Chemistry 2001, 3 (5)

Frances M. Cutler

Causes and Cures for Chloride Leakage out of Condensate Polishers

This paper extensively deals with all aspects of chloride leakage out of condensate polishers. In the past, the determination of chloride at concentrations below 50 µg kg-1 (ppb) was difficult and not often performed outside of an analytical laboratory. At power generating plants, chloride in condensate, feedwater, and steam was usually monitored indirectly by measuring conductivity after the sample had been passed through a cation column. However, since conductivity is a non-specific measurement and carbon dioxide was commonly present in the condensate/steam cycle of units without condensate polishers, it was difficult to accurately measure low concentrations of chloride. The consequences of an unacceptable chloride level, such as boiler tube failure resulting from acid chloride attack or chloride stress corrosion of turbine blades, was often the first alert to its unwanted presence.
Fortunately for today’s high pressure steam generators and nuclear generating stations, the development of new analytical tools such as degassed cation conductivity and the ion chromatograph opened the way for accurate determination of µg kg-1 (ppb) or sub µg kg-1 (ppt or sub ppb) levels of chloride. Fully armed with the ability to monitor chloride at very low levels, we now only need to know where to look.
The author discusses a wide variety of sources and causes of condensate polisher chloride leakage. One source focused on is organic chloride - organic chlorides present in raw water and passing through the makeup water treatment installations as well as on residual organic chloride from resin manufacture.
The results of studies performed at Southern California Edison to evaluate the release of sodium, chloride, and sulfate from polishers and to determine polisher limitations are presented. The effect of different regeneration procedures on the chloride level in polisher effluent is discussed as well as the kinetics and equilibrium chloride leakage out of condensate polishers. The impact of carbonate/bicarbonate on chloride and sodium leakage is explained and additional sources of chloride and other contaminants are identified.

PowerPlant Chemistry 2001, 3 (5)