In the last eleven months, nine papers have been published in this journal dealing either exclusively or largely with the behavior of organics in the fossil plant cycle. Surprisingly, the major focus of these papers is not on natural organics, extractables, or leachables from ion exchange resins; organic plant cycle treatment chemicals are the main theme. As you might expect, these papers are not able to address all aspects of this very complex topic. The fact that such papers are written, read, and discussed substantiates the need for more information relating to this subject. For this reason, PowerPlant Chemistry has decided to contact major suppliers of organic plant cycle treatment chemicals and ask them the questions that we have received from our readers. This time, our interviewee is Luis Carvalho representing GE Water & Process Technologies.

Water (resource) issues will continue to have an increased impact on plant design and operation. Closed-loop, evaporative coolers can help deliver required cooling water temperatures and maintain plant performance while utilizing water streams currently considered to be unusable with conventional towers and heat exchangers. This paper introduces these versatile systems, explaining how they can provide solutions to water use, water quality, and outlet temperature, as well as contribute to a reduction in plant emissions (carbon footprint).

Base loaded drum-type boilers on all volatile treatment with good makeup purity and a tight condenser normally maintain boiler water cation conductivities below 0.5 µS · cm^–1. Trace contamination can cause this cation conductivity to rise to 1 µS · cm^–1 or higher. Conservative facilities use 1 µS · cm^–1 as the maximum cation conductivity limit for all operating pressures. We prefer this approach. However, some facilities (particularly units which cycle) have sufficient baseline contamination that it is difficult to maintain cation conductivities below 1 µS · cm–1 in the boiler water. The higher levels of cation conductivity usually provide an indication of the mineral acid anions present in the boiler water. The amounts of these anions often exceed the equivalent amount of sodium present in the boiler water. While the boiler water sample pH may be satisfactory (alkaline) when measured at room temperature, the high volatility and low dissociation constant of ammonia at operating temperatures can be insufficient to neutralize trace levels of mineral acids in the solution concentrating at tube surfaces during operation. If the concentration mechanism is sufficient, underdeposit acid corrosion and hydrogen damage can result. To avoid this corrosion, small amounts of sodium hydroxide can be easily estimated (one basically needs the boiler water sodium analyzer to read 54 µg · kg^–1 (54 ppb) per µS · cm^–1 of boiler water cation conductivity) and fed to ensure that the mineral acid anions at tube surfaces are neutralized. The amounts of caustic needed are noticeably lower than those used for boilers on caustic treatment. While not implemented, the basic concept was first developed and recommended to one of our clients in 2004. This paper provides background on the "sodium balancing" treatment approach and limitations and recommendations regarding its application.

Press Release of the International Association for the Properties of Water and Steam 2009 Meeting and information about IAPWS releases, guidelines, and other documents

Long-term protection of electric power generating station boilers depends upon the quality of their feedwater chemistry with respect to the transport and deposition of corrosion products to the boilers from various corrosion sources in the plant's condensate and feedwater cycle. It is in the utility's best interests to expand their programs to include ways to reduce the transport of corrosion products, especially those that occur during plant start-ups. Condensate filtration is a strategy employed by some utilities with demonstrable results in minimizing corrosion product transport and achieving a return on their investment.

This paper provides a comparative review of available condensate filtration technologies as well as performance data from fossil plants with the new large diameter high flow filtration systems. Additionally, the paper identifies critical parameters to consider before installation as well as the necessity for agreement between utilities and suppliers on common filtration terminology definitions, to insure an "apple-to-apple" basis when comparing a system or technology from more than one supplier.

Iron is transported around steam/water circuits as dissolved ions and particulate oxides. It is necessary, in operational plant, to minimise the source terms and to do whatever practicable to limit the formation of deposits. The sources of soluble iron species are influenced by local changes in chemical conditions, particularly pH and redox potential. The mechanisms by which mobile particulate oxides are generated are discussed. These are also influenced by changing pH and redox conditions.

The accumulation of deposits is governed by flow effects, concentration processes in boiling zones and changes in solubility with temperature, as well as by electrochemical and local chemical factors. Realistic targets for the limitation of the transport of iron in steam/water circuits are considered. Although it is concluded that some iron transport in steam/water circuits is inevitable, it remains practicable to set realistic targets, and to demonstrate that they can be achieved.

The approach used in the paper for condensation of flowing steam is based on binary nucleation of the chemical impurity NaCl and water. Physical and mathematical models are briefly described and applied on the steam flow with condensation in a convergent-divergent nozzle and in a turbine cascade. The binary nucleation numerical model is tested by the calculation of the flow with condensation in the nozzle with a low expansion rate in the divergent nozzle part of about P= 1 000 s^–1. Calculation results of pressure distribution are compared with experiments. The binary nucleation numerical model is used for the calculation of the steam flow with condensation through the 2D-nozzle blade cascade of the first wet stage of the low pressure part of a condensing steam turbine. The calculated flow in the cascade is subsonic.