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Boiler Layup Review and Marketing Launch. Lou Gehm and John Lucidi - May 2009. Background.
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Boiler Layup Review and Marketing Launch Lou Gehm and John Lucidi - May 2009
Background Combined Cycle power plants burn natural gas to drive a combustion turbine. The heat from this process is used to create steam in a HRSG boiler to drive a steam turbine. All combined cycle plants use this two turbine process.
Application The steam boilers in a HRSG are a series of heat exchanger tubes in any of the boiler drum sections of the HRSG. When the HRSG is cycled off during layup periods, these tubes are very susceptible to corrosion. Corrosion and pitting caused by oxidation can significantly reduce the life of the boiler.
View of a HRSG • Cross section showing boiler drums • Tubes that make up HRSG boiler
Generator sizing Process for laying up boilers will vary from plant to plant. • Purity will range from 98% to 99.9% - ASME spec. calls for 99.6% • Maximum nitrogen requirement will come during a dry layup during which the boiler is completely drained and purged w/ N2. Flow will most likely be 500 – 2500 scfh. • Low pressure required – less than 5 psi
Points worth noting • Because they drain and fill the boiler system with water, operators will usually know the volume of the HRSG boiler tubes and tanks. • Corrosion is not immediate – so flow and purity may not be critical and can vary. • Some level of corrosion will occur anyway, the point is to slow it down. • DI water is another N2 application in power generation. It is usually required w/ a HRSG, and typically sparged or blanketed w/ N2.
Terms • Gas side – outside of the boiler tubes • Water side – inside of the tubes • Wet layup – boiler is not drained • Dry layup – boiler is completely drained • Hot layup – boiler is blanketed with steam • Peaking – plant goes through cycles requiring layup. Most combined cycle plants are peaking plants.
Contacts Ask who is responsible for boiler layup procedures… • Plant chemist or someone in the Water Chemistry department • Plant or Project Engineer • Plant Manager • Maintenance Manager
Marketing Launch Package • HRSG Photo • HRSG Mfgs • Boiler Layup User List • Technical Articles – Vogt & CCJ • Salt Valley Case Study • Boiler Quickstudy & MAP • Potential Leads