POWER October 2010 - 50

TOP PLANTS
1. Riding herd over water supplies. The Tolk Station is shown with its evaporation pond in the foreground. It is a zero-discharge plant,
which means that no process waters are discharged off-site. The facility collaborates with nearby Plant X to treat its blowdown water. As a result,
the combined plants' water consumption has been reduced by about 180 million gallons per year. Courtesy: Xcel Energy
■ Carbon monoxide (CO) monitoring system:
2003
■ Pile discharger refurbishment: 2003
■ Tramp metal magnet replacement/upgrade:
2003
■ Replacement automatic sampler system:
2002
Water Conservation Measures
" Operating in a semi-arid region, we have
developed a unique solution to reduce water
supplies at two of our facilities, Tolk Station
and nearby Plant X, " Low said. " By creating
a pipeline to send Plant X's blowdown water
for recycling and additional freshwater to
Tolk Station for treatment, we increased water
recovery from Plant X and eliminated the
need for new sludge and disposal ponds and
a wastewater treatment system at the facility.
As a result, the combined plants' water consumption
was reduced by about 180 million
gallons per year " (Figure 1).
Tolk Station is a zero-discharge plant, which
means that no process waters are discharged offsite.
For example, water is cycled through the
cooling tower 20 times to maximize its usage.
Environmental Performance
Air emissions are controlled at Tolk Station
with the help of the low-sulfur PRB coal and
baghouses. The baghouses remove approximately
99% of particulate emissions from
the flue gas. The particulate or ash collected
at the Tolk Station is recycled as by-products
50
for construction, oil well " mud, " and other
uses rather than sending it to a landfill.
" In order to improve the plant's environmental
performance, in 2009 we purchased
the Neuco Neural Net for both units and the
Zolo Boss system for Unit 2, " Low said.
" MIC adjustable fuel orifices were installed
in 2008 to 2009. This equipment has helped
the plant lower NOx
emissions. "
Coal-Handling Practices
The Powder River Basin Coal Users' Group
(PRBCUG) named the Tolk Station as its
2010 Plant of the Year, citing its safe operations,
high reliability, and environmental
stewardship. The PRBCUG is a trade group
that promotes the safe, efficient, and economic
use of Wyoming's PRB coals by generating
companies.
" Our employees and Savage have strived
for excellence over the past few years, and
this national recognition reflects that effort, "
said Low. " Savage played a big role in winning
this award by operating a well-run coalhandling
facility. "
The facility has been proactive in dealing
with the challenges related to handling large
quantities of coal. For example, significant
work was done in-house to reduce spills and
contain dust throughout the facility at several
transfer points, according to Low. Modifications
and upgrades were made to the chute
work, dust-settling chambers, skirting, as
well as " slider-beds " and belt-scrapers. In
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addition, the staff recently revamped the
water suppression system, which included
relocating and reducing the number of spray
nozzles. The result has been a system with
minimal spillage and dust.
The staff deals with a variety of other challenges
related to burning coal. For example, on
occasion a batch of poor-quality PRB coal will
be blended with a higher-quality PRB coal to
meet operational restrictions on ash, sulfur, and/
or sodium. In addition, to deal with boiler slagging
problems, plant personnel conduct slag surveys
during the normal rounds and as needed.
Workplace Safety
Due to the higher volatility of PRB coal, the
Tolk Station has taken a number of measures
to ensure safe work practices. For example,
the plant installed the Conspec CO monitoring
system and bunker baghouse fire suppression
system.
The plant has an Xcel Energy/Savage
emergency response team (ERT), which has
24 members. As a result of the plant's rural
location, ERT members have received extensive
training for fighting fires. In addition, a
few of the ERT members participate in their
local volunteer fire department crews.
" We also have a mill steam inerting system
that uses turbine extraction steam. The system
is used as a last resort only to control a coal
mill fire. There are no interlocks, " Low said. ■
-Angela Neville, JD, is POWER's
senior editor.
POWER | October 2010

http://www.powermag.com

POWER October 2010

Table of Contents for the Digital Edition of POWER October 2010