Power Engineering_Clyde Bergemann Coal Ash Handling Article

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117
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Regulating
Coal Ash
February 2013 • www.power-eng.com
A South Carolina utility recently converted one of its plants to a dry ash handling system and
installed this continuous dewatering and recirculation system from United Conveyor Corp.
The technology combines the benefits of a recirculation system and the proven technology
of a submerged flight conveyor. Photo courtesy of United Conveyor
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Clyde Bergemann’s patented DRYCON™ technology
is a mechanical conveyor that conveys and cools
bottom ash without the use of water. Photo courtesy
of Clyde Bergemann
Coal Ash Handling & Storage:
Shifting Direction
Utilities investigate options as EPA is expected
to issue final rule on coal ash handling
F
By Russell Ray, Managing Editor
our years after more than
one billion gallons of
coal ash slurry spilled
from a storage pond at
the Kingston Power Plant
in eastern Tennessee, environmental
groups are still waiting for the U.S.
Environmental Protection Agency to
finalize tougher standards for handling and storing coal ash.
Their wait may soon be over.
Industry observers expect the EPA
to issue a rule this year expanding the
oversight of bottom ash management
and disposal at U.S. power plants.
The proposed rules would require
coal-fired power plants to eliminate
wet ash handling and phase out surface impoundments, or ponds, within
five years. Anticipating tougher standards, most power producers have already studied the cost of converting to
dry bottom ash systems and are bracing for the regulatory changes. The cost
of compliance could exceed $20 billion industrywide, according to a 2010
EPA study.
“The overwhelming majority of utilities have done some level of technology investigation and definitely a budget study,” said Kevin McDonough,
director of sales Americas for United
Conveyor Corp. “Almost all of them
have gone that far, so that they understand what technical options are out
there and, of course, the approximate
cost associated with it.”
The potential market for dry bottom
ash conversions is significant. Less
than 1 percent of the nation’s coalfired plants are equipped with dry bottom ash systems, said Ron Grabowski,
vice president of Business Development at Clyde Bergemann. More than
90 percent of bottom ash systems remain wet.
“Most likely you’re going to have to
be a zero discharge plant,” Grabowski
said. “If you’re using water to move
around your bottom ash, you can’t discharge it.”
In 2010, the EPA offered two proposals to regulate the handling and disposal of coal ash. The first option calls
for classifying coal ash as a special
waste regulated by the Resource Conservation and Recovery Act (RCRA)
Subtitle C hazardous waste provisions. Under the second option, coal
ash disposal would be regulated under RCRA’s Subtitle D nonhazardous
waste provisions.
In either case, wet ash handling
would be eliminated and surface impoundments would be phased out
within five years.
“We don’t think they’re going to reclassify bottom ash to be a hazardous
material,” Grabowski said. “I think
they recognize there are beneficial
uses for ash as a byproduct. They simply want to persuade plants to eliminate the discharge of water.”
In December 2008, a 40-acre coal
ash storage pond at Tennessee Valley
Authority’s Kingston plant in Harriman, Tenn., failed. The earthen wall
collapsed, spilling more than 1 billion
gallons of coal ash slurry, damaging 40
homes and contaminating the Emory
and Clinch Rivers. The cleanup costs
for TVA: About $1 billion.
“Since that time, TVA has responded
aggressively to wet-to-dry conversions
and has converted wet system at
both Kingston and Bull Run to dry,”
McDonough.
The incident prompted the EPA to
pursue a new rulemaking, but the
agency delayed issuing a final rule after intense political pressure from utilities, coal-mining companies and coal
ash recyclers who fear classifying coal
ash as a hazardous waste would stigmatize their products.
Meanwhile, Congress has proposed
legislation that would pre-empt EPA’s
proposed rules by granting states the
authority to regulate coal ash disposal through the use of permitting
programs. Critics say the legislation
would keep states in control and stymie the EPA’s effort to promulgate
new rules for the disposal of coal
ash, also known as coal combustion
description of the technologies availresiduals (CCR).
According to a report by the non- able to power producers.
partisan Congressional Research Service, the legislation provides states too Clyde Bergemann
much discretion in adopting a permit
Coal-fired power plants have four
program or applying
basic options to upfederal standards for “We don’t think
grade their existing
disposal of coal ash.
wet bottom ash systhey’re going
“EPA would have
tem. The first two
no authority to com- to reclassify
options not only
pel states to adopt bottom ash to
eliminate the use of
and implement the
an ash pond but also
be a hazardous
program according
eliminate the need
to provisions in the material.”
of a wet impounded
proposed
amend- - Ron Grabowski, Clyde
bottom ash hopper.
ments to RCRA,” the Bergemann
The other two opreport found.
tions keep the wet
Coal-fired power plants have three impounded bottom ash hopper but
options for the disposal of coal ash. eliminate the ash pond.
Dry ash can be disposed in landfills.
What follows is a brief description
According to the EPA, more than 30 of each, listed in the typical order of
percent of coal combustion waste from power plant preference:
power plants is disposed in dry landConvert to a dry bottom ash
fills. Coal ash is, of course, stored in system
ponds, which account for 20 percent of
Clyde Bergemann’s DRYCON techcoal ash disposal. About 40 percent of nology is a mechanical conveyor that
coal ash is recycled and used in a wide conveys and cools bottom ash without
range of industrial applications.
the use of water. With the successful
More than 300 coal-fired plants in wet to dry conversion of two 650-MW
the United States dispose of coal ash in units in Florida, the industry is now
on-site landfills, according to an EPA seeing the benefits of this technology.
report. Nearly 150 plants use off-site Dry bottom ash handling provides the
commercial landfills for coal ash dis- most benefits over all other bottom
posal. Nearly 160 U.S. plants use coal ash technologies. In addition to water
ash ponds for disposal.
elimination, DRYCON™ will increase
The size of coal ash disposal units boiler efficiency, reduce power concan range from modest to very large, sumption and reduce maintenance.
with some ponds covering 1,500 acres
The advantages of using this sysor more.
tem are: Increased boiler efficiency,
Meanwhile, power producers using reduced maintenance, reduced power
ponds to store coal ash have important consumption and complete water
choices to make. They have several op- elimination. The disadvantages: A 20tions and solutions to choose from as to- 30-day boiler outage and a direct
they prepare to comply with stricter path from under the boiler is required.
federal regulation.
Convert to a Submerged ScrapPower producers seek solutions er Conveyor (SSC) semi dry system
from companies like Clyde BergeAn SSC can reduce water usage but
mann and United Conveyor Corp., not eliminate it. In most cases, power
two of the leading suppliers of dry ash plants that can be fitted with a SSC can
handling systems. What follows is a also be fitted with a DRYCON unit.
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The advantages of converting to this system are:
Reduced power consumption, reduced maintenance
and low water consumption. The disadvantages:
It’s not a dry system,
boiler efficiency will not
increase, it needs a direct
path from under the boiler
and a 20- to- 30-day outage is required.
Divert ash slurry to
a Remote Submerged
Scraper Conveyor
Clyde Bergemann’s patent pending ASHCON
technology is also a semi
dry system. Its major advantage is that
is can be installed remotely from the
boiler to intercept bottom ash slurry
and dewater it without the use of an
ash pond. Because of its low height, in
most cases, the existing bottom slurry
pumps can be reused.
The advantages: No outage is required,
reduced power consumption, allows reuse of slurry pumps and the wet bottom
ash hopper is unaffected. The disadvantages: It’s not a dry system, there is no
increase in boiler efficiency and the wet
bottom ash hopper is unaffected.
In addition to water elimination, DRYCON™
will increase boiler efficiency, reduce power
consumption and reduce maintenance.
Photo courtesy of Clyde Bergemann
Divert ash slurry to traditional
Dewatering Bins
Though this is a viable option, it is
typically the least desired. Dewatering
bins are a 40-plus year old technology
and reviewed as a last resort when
pond elimination is being considered.
Many plants with dewatering bins
have reached the end of their expected life cycle. Thirty-year-old dewatering bins can be worn and structurally unsound. In this situation plants
investigate a bottom ash upgrade
rather than replacement.
The advantages: Reduced power
consumption, no outage is required
and the wet bottom ash hopper is unaffected. The disadvantages: It’s not a
dry system, slurry pumps may need
to be modified, there’s no increase in
boiler efficiency and additional slurry
pumps may be needed to pump the
slurry up the tall height of the new
dewatering bins.
Excerpted and posted with permission to Clyde Bergemann Power Group Americas from Power Engineering
February © 2013 PennWell Corporation
Clyde Bergemann Power Group Americas Inc.
4015 Presidential Pkwy
Atlanta, GA 30340
1-888-882-2314 • www.cbpg.com • [email protected]