“Monitoring and Controlling Boiler Water/Steam Cycle Chemistry” Hot Topic Hour, February 21, 2013

 

Safe, reliable and efficient operation of steam generating boilers and HRSGs requires the maintenance of physical and chemical conditions throughout the water/steam circuit that minimizes corrosion and deposit formation. This is especially true in the older plants that are prevalent in our electricity production network. Deposition of contaminants, scaling and corrosion are the cause of many forced outages resulting in lost power generation or product output costing billions of dollars per year. Frequent blow-downs required because of excessive contaminants in the water/steam also contribute to lost production. Inadequate cycle chemistry will cause boiler tube and turbine blade/disc failures and flow-accelerated corrosion (FAC) throughout the circuit. Three presentations today addressed the challenges and provide solutions.

 

Joe Zimmerman, Director of Marketing and Power Industry Sales Manager at Chemtrac, Inc., explained that the adverse effects of particulate material in steam cycle waters are frequently seen throughout the power generation process. Steam cycle corrosion products (transient metal oxides) can lead to deposition and equipment failure. This presentation introduced basic technologies used for continuous detection of insoluble particles at very low concentrations. When such monitoring methods are utilized, real-time corrosion product transport measurement can be implemented as a potential parameter for controlling the power plant cycle.

 

 On-line particle monitoring in contrast to turbidity measurement provides continuous tracking of insoluble metal oxides. The clear advantage over grab or composite samplers was illustrated by using a movie as an example. Rather than one frame or a synopsis you see the whole movie with the particle monitoring system. This provides valuable information relative to system performance and allows immediate action when an event occurs.

 

Greg Thomas, Key Account Manager for Nuclear Power at Hach Ultra Analytics, compared the long time standard amperometric technology to the new optical technology for measurement of low level dissolved oxygen (dO2) in steam cycle water. Optical instruments only require maintenance once per year vs. every six months for electrochemical. The optical instrument is not flow dependent. Both instruments can measure accurately to 1 ppm.  For certain nuclear applications where measurements in parts per billion (ppb) is desirable, the electrochemical method is more accurate.

 

David M. Gray, Senior Product Manager at Mettler-Toledo Thornton, Inc., introduced us to intelligent sensor management. Intelligent digital sensors incorporate the measuring circuit and make the digital conversion computation and even include the memory and basis for predictive maintenance. Online analytical measurements of conductivity, pH, dissolved oxygen, sodium and silica incorporate digital sensors which provide improved performance, a wider range and predictive diagnostics. The digital conductivity sensor provides a 33 percent improvement in system accuracy.

 

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Bios, Abstracts and Photos can be seen at: BIOS, ABSTRACTS, PHOTOS - 2-21-13.htm

 

The individual presentations are as follows: