Industry publication, December 2001

NYC 9/11 Public Portal Document

1 E C n •: CuA-Sl-Jj] ! the manufacturers of HRSGs to respond in kind to ensure an overall improvement in the integrated CC plant and handle tougher temperature and pressure con­ ditions. Triple-pressure reheat steam sys­ Building tems, for example, now are offered by all m^or HRSG manufacturers. POWER Plants Triple-pressure steam systems yield

mil IN lower stack temperatures than older, dual-pressure systems because they re­ cover more thermal energy from GT ex­ haust That’s good for cycle efficiency, LATIN which developers and financiers like, but ui&inn America? it limits the fuel choice to natural gas, say many HRSG users. Users have found that in the presence of even low levels of sul­ fur—such as when firing No. 2 fuel oil— stack temperatures must be kept above 330°F to avoid acid-gas corrosion. 'I i r-

SANTOS CMI IS A RELIABLE AND EXPERIENCED CONTRACTOR j Merchant OFFERING CLIENTS IN THE POWER j SECTOR THE FOLLOWING SERVICES: 1 n I‘ Z developers j. r need to pay par- / Detail Engineering ft ticular attention / Procurement { Uo HRSG oj^- / Construction: I / Civil Works ^Wlng’. Issues.'y i Mechanical Installation Electrical instalation Another design issue is installation of a I damper in the HRSG exhaust stack. Many INSTRUMENTATION & CONTROL. ; developers choose to omit the device to reduce cost But users have found this can shorten HRSG tube life. HRSGs without stack dampers depressurize within a few

a hours after shutdown, meaning almost every restart is from cold conditions. On the typical P22 steam header, cold-start fetigue damage may be 30 to 40 times that caused by a hot start because of the “con­ densate quench” phenomenon. Merchant developers need to pay par­ !! ticular attention to tube life, stack corro­ sion, and other HRSG operating issues because of the need for cycling capabil­ ity in today’s competitive market. The HRSG’s increased physical size, elevated gas temperature, and tougher steam conditions—when coupled to advanced GTs—have also substantially increased thermal stresses and fatigue damage, par­ • I ticularly in the superheater section. HRSG design often fails to take these increased Contact us stresses into account, engineers say. Im­ prudent operating procedures, some tak­ tvww.santoscmi.com •. info-^uio.santoscmi.com en directly from suppliers’ manuals, fur­ Corporoie Headquariers in Ecuador ther aggravate the situation, according to (5932) 2503 - 632 / 2557 - 754 bofler experts. □ By Robert Swaneka'mp

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