March 2015 | POWER www.powermag.com 1
ON THE COVERNational Oilwell Varco, in partnership with Oasys,
offers forward osmosis systems for use in the oil and gas industry
for treating exploration and production wastewaters. Forward
osmosis, especially as a companion to reverse osmosis, is beginning
to see use in the power industry as well. Courtesy: Oasys Water
COVER STORY: WATER & WASTEWATER22 Water and Wastewater
Treatment Technology Update
Youve heard of reverse osmosis (RO), but now its being joined by
a new treat-ment known as forward osmosis (FO). In addition to RO,
FO, and membrane bioreac-tors, advances in membranes and
zero-liquid discharge offer new options to power plants.
28 Feedwater Chemistry Meets Stainless Steel, Copper, and
IronWhether you operate an older plant with a mix of piping metals
or a newer one with the latest alloys, this article covers the
chemistry options that operators have to minimize corrosion in a
critical area of the plant.
34 Mining for Lithium in Geothermal Brine: Promising but
PriceyBrine, the wastewater stream from geothermal power
production, is highly corro-sive and hard on piping systems.
Recently, a U.S. company developed a method that both recovers
valuable minerals from that brine and makes the remaining fluid
much less problematic for reinjection. Trouble is, an inability to
fund the enterprise may spell the companys demise.
SPECIAL REPORT: AUXILIARY SYSTEM EFFICIENCY & RELIABILITY36
Save Power with Natural Cooling for Building Ventilation
Coal-fired power plants release a large amount of heat during
the combustion pro-cess. Switching from forced to natural
ventilation in the boiler building can yield potential energy
savings.
38 SCR Reheat Burners Keep NOx in Spec at Low LoadsOptimal NOx
removal by a selective catalytic reduction (SCR) system requires
the inlet gas temperature to remain within a prescribed range. How
does a baseload unit meet NOx permit limits when its cycled and SCR
inlet gas temperatures dip?
FEATURES
COMBINED CYCLE GAS TURBINES
42 Protecting Steam Cycle Components During Low-Load Operation
of Combined Cycle Gas Turbine Plants Know the tradeoffs when
operating combined cycle plants at low loads. The solution to one
problem may trigger another problem or cause actual damage to your
plant.
46 Are Flexible Generation Plants Performing as
Expected?Designed from the start for cycling and fast starts, the
new flex generation com-bined cycle plants promised to avoid the
trauma inflicted upon earlier gas plants by more aggressive
operational modes. One of the earliest plants to adopt the
technol-ogy reports positive results.
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Established 1882 Vol. 159 No. 3 March 2015
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