MEMORANDUM

TO:		PM NAAQS Docket (OAR-2001-0017)

From:		EPA, Clean Air Markets Division

Subject:	Cost Estimates for Modification Options to Improve Existing ESP
Performance

Date:		August 21, 2006

This memorandum contains (see next page) a write-up that describes the
assumptions, methodologies, and results of the estimates for developing
the performance improvements and costs associated with the selected
electrostatic precipitator (ESP) modification options.  The estimates
were developed as part of the EPA’s RIA analyses.

PERFORMANCE AND COST IMPACTS OF 

SELECTED ESP MODIFICATION OPTIONS

This write-up covers the assumptions, methodologies, and results of the
estimates for developing the performance improvements and costs
associated with the selected electrostatic precipitator (ESP)
modification options.  The cost estimates developed were of the
order-of-magnitude type and were based on information available from
published sources.

Several modification options are available to enhance the particulate
removal performance of existing ESP installations.  These options
include upgrade of existing ESP auxiliaries, such as automatic voltage
controllers and rappers, and repair of damaged areas, such as bent
collecting plates and broken discharge electrodes.  However, only
relatively small performance gains are expected from application of such
options, as it is believed that many ESP installations are properly
designed and well maintained.  The modification options that can provide
significant performance improvements for the existing ESP include:

Increase in the existing collection plate area

Installation of a flue gas conditioning system

Installation of a downstream supplemental baghouse

Installation of bags in the last one or two ESP fields

Installation of an agglomerator

Of the above options, only the first and the fifth can be applied to
most ESPs, without any concerns with the operating parameters, such as
type of coal fired, flue gas temperature, etc.  Therefore, these are the
two options that were considered for the present estimates.  These apply
to both cold-side and hot-side ESPs.

An increase in the existing ESP collection plate area can be achieved by
several different methods, such as 1) addition of collecting area in
series with the existing ESP, 2) addition of collecting area in parallel
with the existing ESP, and 3) increase in the height of the existing
collection plates.  Any of these three methods can be used by an
existing installation, depending on the present design and space
availability.

The overall collection plate area of an ESP is divided in several fields
(perpendicular to the gas flow) that can be operated independent of each
other.  In general, an ESP has three or more fields.  For the present
estimates, the following two alternatives for increasing ESP collection
plate area were considered:

Addition of collection plate area equivalent to one field

Addition of collection plate area equivalent to two fields

An agglomerator is a charging/mixing device installed at the inlet to
the existing ESP.  In the bipolar charging section, the flue gas flow is
split into a number of streams, each of which is either positively or
negatively charged.  In the mixing section, the small positively charged
particles combine electrostatically with the large negatively charged
particles to form large particles which are easier to collect in an ESP.
 Detail information on this technology can be found at the website of
the technology supplier.

The performance and cost impacts of the above ESP modification options
are discussed in the following sections.

Performance Improvements

The performance benefit of additional collection plate area was
estimated for two different coal types: bituminous and sub-bituminous. 
It should be noted that an ESP installed for a bituminous-coal
application has a lower specific collection area (SCA) than that
installed for sub-bituminous coal.  [Here SCA is defined as the ESP’s
collecting plate area in square feet (ft2) per 1,000 actual cubic feet
per minute (acfm) of flue gas.]  This is because the ash particles from
sub-bituminous coals have a significantly higher ash resistivity that
makes it harder for ESPs to collect this type of ash.  This difference
was considered when evaluating the ESPs for the two coal types.  The
case for bituminous coal conservatively assumed an ESP with three
fields, with each field consisting of 50 SCA.  With the increased SCA
equivalent to one and two fields, the estimated increase in performance
is shown below:,

ESP Modification Type	SCA,

Ft2/1,000 acfm	Particulate Collection Efficiency, %	Reduction in
Particulate Mass Loading, %

Original ESP	150	97.7	NA

One field addition	200	98.7	43.4

Two fields addition	250	99.25	67.4



In the second case for sub-bituminous coal, the original ESP was assumed
to contain 300 SCA, with each field consisting of 100 SCA.  The
estimated increases in the ESP performance with the two alternatives for
additional plate area are shown below:2

ESP Modification Type	SCA,

ft3/1,000 acfm	Particulate Collection Efficiency, %	Reduction in
Particulate Mass Loading, %

Original ESP	300	99.0	NA

One field addition	400	99.51	51.0

Two fields addition	500	99.82	82.0



The above estimates were repeated, using different original SCAs for the
ESPs.  The reduction in particulate mass loading was little changed with
these different original SCAs.  The above comparisons showed performance
improvement to be higher for the bituminous coal than for the
sub-bituminous coal.  Therefore, for conservatism, the lower levels of
improvement for the bituminous coal were selected as average values to
be used for use in further EPA’s analyses and evaluations.

The reported data with the addition of an agglomerator at existing ESP
installations show reduction in particulate mass loading of
approximately between 30 and 60 percent.  At one plant, the reported
test data show an average emission reduction of approximately 38
percent.  Since, this reduction is at the low end of the reported range
of performance improvement for the agglomerator, it was selected for
further EPA’s analyses and evaluations.

Cost Estimates

Cost estimates were developed to obtain capital costs, fixed O&M costs,
and variable O&M costs.  Algorithms were developed to allow
determination of these costs for varying plant sizes (in MW).  These
costs were developed for the following ESP modification options:

Addition of collection plate area equivalent to one ESP field

Addition of collection plate area equivalent to two ESP fields

Addition of an agglomerator

Addition of collection plate area equivalent to two ESP fields and an
agglomerator

The following sources and assumptions were used for developing these
cost estimates:

Capital costs were based on values and factors provided in published
literature for the same type of ESP modifications as used for these
estimates.,,,

Annual fixed O&M costs were assumed to be 1.5 percent of the capital
costs.

Variable O&M costs were assumed to consist of increased power
consumption due to larger ESP area, agglomerator, and increased pressure
drop for the induced draft (ID) fans.  Increase in solid waste (ash
collected in the ESP) due to improved ESP performance was assumed to be
negligible.  The increased ID fan pressure drop occurs in the additional
ducting, new ESP sections, and agglomerator.  The pressure drop
increases were estimated to be 0.4 in. wt. for the addition of one ESP
field, 0.7 in. wt. for the addition of two ESP fields, 1.0 in. wt. for
the addition of the agglomerator, and 2.0 in. wt. for the addition of
both two ESP fields and agglomerator (taking into account more
complicated ducting).  The cost of electricity is assumed to be 40
mills/kWh.

It was assumed that the existing ID fans would be able to handle the
relatively small increase in pressure drop due to the addition of one
ESP field, two ESP fields, or the agglomerator.  However, addition of
both the two field ESP and the agglomerator would require a replacement
of the existing ID fan(s).  The cost of new ID fans were developed using
an EPA cost model, CUECost. 

All costs estimates developed were based on the year 2005 dollars.

The overall results of the cost estimates are provided below:

Agglomerator Costs

Capital Cost in $/kW = 8.0 x (250/MW)0.3			(MW is unit size in MW)

Variable O&M cost in mills/kWh  = 	0.021			(same for all unit sizes) 

Fixed O&M Cost increase is negligible			

Costs for Adding an Equivalent Surface Area of One Field

Capital Cost in $/kW = 13.75 x (250/MW)0.3		(MW is unit size in MW)

Variable O&M cost in mills/kWh  = 	0.009			(same for all unit sizes) 

Fixed O&M Cost in $/kW-yr	=  0.24 x  (250/MW)0.3	(MW is unit size in MW)

Costs for Adding an Equivalent Surface Area of Two Fields

Capital Cost in $/kW = 17.5 x (250/MW)0.3			(MW is unit size in MW)

Variable O&M cost in mills/kWh  = 	0.013			(same for all unit sizes) 

Fixed O&M Cost in $/kW-yr	=  0.31 x  (250/MW)0.3	(MW is unit size in MW)

Costs for Adding an Equivalent Surface Area of Two Fields, Agglomerator,
and ID Fans

Capital Cost in $/kW = 37.2 x (250/MW)0.3			(MW is unit size in MW)

Variable O&M cost in mills/kWh  = 	0.042			(same for all unit sizes) 

Fixed O&M Cost in $/kW-yr	=  0.53 x  (250/MW)0.3	(MW is unit size in MW)

   HYPERLINK "http://www.indigotechnologies.com.au/agg_overview.php" 
http://www.indigotechnologies.com.au/agg_overview.php , accessed on
August 17, 2006

 “A Manual on the Use of Flue Gas Conditioning for ESP Performance
Enhancement,” EPRI CS-4145, August 1985

   HYPERLINK
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http://hamon-researchcottrell.com/Center_Fundamentals_03.asp , accessed
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   HYPERLINK "http://www.indigotechnologies.com.au/" 
http://www.indigotechnologies.com.au/ , accessed on August 17, 2006.

 R. Crynack, et al., “Reducing Fine Particulate Emissions from US
Coals Using the Indigo Bipolar Agglomerator,”   HYPERLINK
"http://www.indigotechnologies.com.au/" 
http://www.indigotechnologies.com.au/ , accessed on August 17, 2006.

 M. Sankey, “  HYPERLINK
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placements%20and%20Rebuilds%20%20Where%20does%20the%20money.pdf" 
Precipitator Replacements & Rebuilds - Where does the money go? ,”  
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 R. Mastropietro, “  HYPERLINK
"http://hamon-researchcottrell.com/HRCTechnicalLibrary/Electrostatic%20P
recipitator%20Rebuild%20Strategies%20for%20Improved%20P.pdf" 
Electrostatic Precipitator Rebuild Strategies for Improved Particulate
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 M. Sankey, et al., “  HYPERLINK
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Electrostatic Precipitator Upgrade Strategies - Get the Most From What
you Have ’”   HYPERLINK
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 R. Truce, et al., "Indigo Bi-Polar Agglomerators Reduce PM2.5 Emissions
and Opacity on Three Coal Fired Boilers in the U.S.," 22nd International
Pittsburgh Coal Conference, Sept. 12-15, 2005.

 S. Khan, et al., “Updating Performance and Cost of NOx Control
Technologies in the Integrated Planning Model,” Mega Symposium, August
31 to September 3, 2004, Washington, DC.

 CUECost’s software and documentation,   HYPERLINK
"http://www.epa.gov/ttn/catc/products.html#cccinfo" 
http://www.epa.gov/ttn/catc/products.html#cccinfo , accessed on August
21, 2006.

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