POWER April 2011 - 28

PLANT DESIGN
2. Going down, carefully. Given the tight space constraints while demolishing Unit 2 and
beginning Unit 4 foundation work, extreme care and planning was needed to proceed with demolition
of the Unit 2 stack. A protective net was installed around it to prevent accidents to personnel
engaged in other construction activities. Courtesy: Tohoku Electric Power Co.
3. With solar energy, the sky's the
limit. In the second phase of the ongoing replacement
project, the Sendai Thermal Power
Station will integrate a large PV solar power
system that is scheduled to be completed in
2012. Courtesy: Tohoku Electric Power Co.
m3 of nitrogen oxides gas per hour (m3N/h)
to 15 m3N/h.
The new plant reduced the amount of
wastewater generated from 2,000 m3/day to
730 m3/day by eliminating the flue gas desulfurizer.
This improvement resulted from the
reduction of sulfur oxide (SOx
) emissions associated
with switching from coal to natural
gas, according to Koeneke.
The gas turbine provides 66% of the combined-cycle
power output generated in the
new plant. The decrease in power generated
in the steam cycle, and the plant's higher efficiency,
caused a considerable reduction in
the condenser cooling requirement. Accordingly,
hot water discharge to the sea-and the
related impact on the ecosystem-has been
reduced. The original plant discharged 12 m3
per second (m3/s) of seawater to the ocean,
10C hotter than the water taken from the
ocean; in contrast, the new plant discharges
only 10 m3/s of seawater with a temperature
increase of 7C.
Solar Power's Ascent in the Land
The construction team maximized the
recycling of waste to reduce environmental
impact. Valuable waste, including ferrous
materials, was sold. The construction
team used approximately 35,000 cubic
meters (m3) of concrete waste as a regenerated
aggregate and reapplied it during
construction as foundation concrete aggregates,
refilled earth, and sand. This intensive
effort resulted in recycling more than
97% of industrial waste; the exception was
those materials containing asbestos, which
were properly disposed of.
The construction team avoided heavy
hauling during commuting hours; however,
the concrete-pouring activities for the
foundation had to be scheduled from early
morning to late evening. During these activities,
company staff were present at nine
28
nearby school zone intersections to secure
the safety of children.
Environmental Advances
" The CO2
emissions were considerably reduced
by replacing the existing plant with
the new high-efficiency combined-cycle
unit, " Koeneke said. " An approximate 40%
CO2
reduction was achieved by replacing
coal with natural gas and an additional
20% was achieved by increasing the thermal
efficiency of the plant. "
Plant management estimates the annual
CO2 reduction to be approximately 900,000
tons, which derives from a decrease from
0.832-0.885kg/kWh to 0.362kg/kWh. In
addition, nitrogen oxide emissions have
been reduced to approximately 1/20th of
the original plant's emissions-from 316
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of the Rising Sun
Tohoku Electric Power Co. is making an effort
to generate electricity from renewable energy
sources such as solar power while evaluating
the impact of renewable energy on power systems
as well as the cost of using renewable
energy. The Law on Special Measures Concerning
New Energy Use by Electric Utilities
(RPS Law) was fully enacted in April 2003
and mandates that Japanese electric utilities
use specific amounts of renewable energy as
part of their energy generation portfolio.
Accordingly, in the next phase of this replacement
project, the Sendai Thermal Power
Station will integrate a 2-MW photovoltaic
(PV) solar system. Another 1,000 tons of CO2
annual reduction is expected in 2012, when
integration of the new PV system at the plant
site is completed (Figure 3). ■
-Angela Neville, JD, is senior
editor of POWER.
POWER | April 2011

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POWER April 2011

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