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the magazine of power generation

RegulatingCoal ash

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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Coal ash handling & storage: shifting Directionutilities investigate options as ePa is expected to issue final rule on coal ash handlingBY RuSSEll RAY, MAnAging EditoR

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

Environmental Protection Agency to

finalize tougher standards for han-

dling 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 sur-

face impoundments, or ponds, within

five years. Anticipating tougher stan-

dards, most power producers have al-

ready studied the cost of converting to

dry bottom ash systems and are brac-

ing for the regulatory changes. The cost

of compliance could exceed $20 bil-

lion industrywide, according to a 2010

EPA study.

“The overwhelming majority of util-

ities have done some level of technol-

ogy investigation and definitely a bud-

get study,” said Kevin McDonough,

director of sales Americas for United

Conveyor Corp. “Almost all of them

have gone that far, so that they under-

stand 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 coal-

fired plants are equipped with dry bot-

tom ash systems, said Ron Grabowski,

vice president of Business Develop-

ment at Clyde Bergemann. More than

90 percent of bottom ash systems re-

main 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 dis-

charge it.”

In 2010, the EPA offered two propos-

als to regulate the handling and dis-

posal of coal ash. The first option calls

for classifying coal ash as a special

Four 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.

residuals (CCR).

According to a report by the non-

partisan Congressional Research Ser-

vice, the legislation provides states too

much discretion in adopting a permit

program or applying

federal standards for

disposal of coal ash.

“EPA would have

no authority to com-

pel states to adopt

and implement the

program according

to provisions in the

proposed amend-

ments to RCRA,” the

report found.

Coal-fired power plants have three

options for the disposal of coal ash.

Dry ash can be disposed in landfills.

According to the EPA, more than 30

percent of coal combustion waste from

power plants is disposed in dry land-

fills. Coal ash is, of course, stored in

ponds, which account for 20 percent of

coal ash disposal. About 40 percent of

coal ash is recycled and used in a wide

range of industrial applications.

More than 300 coal-fired plants in

the United States dispose of coal ash in

on-site landfills, according to an EPA

report. Nearly 150 plants use off-site

commercial landfills for coal ash dis-

posal. Nearly 160 U.S. plants use coal

ash ponds for disposal.

The size of coal ash disposal units

can range from modest to very large,

with some ponds covering 1,500 acres

or more.

Meanwhile, power producers using

ponds to store coal ash have important

choices to make. They have several op-

tions and solutions to choose from as

they prepare to comply with stricter

federal regulation.

Power producers seek solutions

from companies like Clyde Berge-

mann and United Conveyor Corp.,

two of the leading suppliers of dry ash

handling systems. What follows is a

description of the technologies avail-

able to power producers.

Clyde Bergemann Coal-fired power plants have four

basic options to up-

grade their existing

wet bottom ash sys-

tem. The first two

options not only

eliminate the use of

an ash pond but also

eliminate the need

of a wet impounded

bottom ash hopper.

The other two op-

tions keep the wet

impounded bottom ash hopper but

eliminate the ash pond.

What follows is a brief description

of each, listed in the typical order of

power plant preference:

Convert to a dry bottom ash system

Clyde Bergemann’s DRYCON tech-

nology is a mechanical conveyor that

conveys and cools bottom ash without

the use of water. With the successful

wet to dry conversion of two 650-MW

units in Florida, the industry is now

seeing the benefits of this technology.

Dry bottom ash handling provides the

most benefits over all other bottom

ash technologies. In addition to water

elimination, DRYCON™ will increase

boiler efficiency, reduce power con-

sumption and reduce maintenance.

The advantages of using this sys-

tem are: Increased boiler efficiency,

reduced maintenance, reduced power

consumption and complete water

elimination. The disadvantages: A 20-

to- 30-day boiler outage and a direct

path from under the boiler is required.

Convert to a Submerged Scrap-er Conveyor (SSC) semi dry system

An SSC can reduce water usage but

not eliminate it. In most cases, power

plants that can be fitted with a SSC can

also be fitted with a DRYCON unit.

waste regulated by the Resource Con-

servation and Recovery Act (RCRA)

Subtitle C hazardous waste provi-

sions. Under the second option, coal

ash disposal would be regulated un-

der RCRA’s Subtitle D nonhazardous

waste provisions.

In either case, wet ash handling

would be eliminated and surface im-

poundments would be phased out

within five years.

“We don’t think they’re going to re-

classify bottom ash to be a hazardous

material,” Grabowski said. “I think

they recognize there are beneficial

uses for ash as a byproduct. They sim-

ply want to persuade plants to elimi-

nate the discharge of water.”

In December 2008, a 40-acre coal

ash storage pond at Tennessee Valley

Authority’s Kingston plant in Harri-

man, 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 af-

ter intense political pressure from util-

ities, coal-mining companies and coal

ash recyclers who fear classifying coal

ash as a hazardous waste would stig-

matize their products.

Meanwhile, Congress has proposed

legislation that would pre-empt EPA’s

proposed rules by granting states the

authority to regulate coal ash dis-

posal through the use of permitting

programs. Critics say the legislation

would keep states in control and sty-

mie the EPA’s effort to promulgate

new rules for the disposal of coal

ash, also known as coal combustion

“We don’t think they’re going to reclassify bottom ash to be a hazardous material.”- Ron grabowski, Clyde Bergemann

ABMA

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investigate a bottom ash upgrade

rather than replacement.

The advantages: Reduced power

consumption, no outage is required

and the wet bottom ash hopper is un-

affected. 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.

The advantages of con-

verting to this system are:

Reduced power consump-

tion, reduced maintenance

and low water consump-

tion. 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 out-

age is required.

divert ash slurry to a Remote Submerged Scraper Conveyor

Clyde Bergemann’s pat-

ent 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 re-

use of slurry pumps and the wet bottom

ash hopper is unaffected. The disadvan-

tages: It’s not a dry system, there is no

increase in boiler efficiency and the wet

bottom ash hopper is unaffected.

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 expect-

ed life cycle. Thirty-year-old dewater-

ing bins can be worn and structur-

ally unsound. In this situation plants

in addition to water elimination, drYcon™ will increase boiler efficiency, reduce power consumption and reduce maintenance. Photo courtesy of clyde Bergemann

Excerpted and posted with permission to Clyde Bergemann Power Group Americas from Power EngineeringFebruary © 2013 PennWell Corporation

Clyde Bergemann Power Group Americas Inc.4015 Presidential Pkwy

Atlanta, GA 30340

1-888-882-2314 • www.cbpg.com • info@us.cbpg.com