The Evolution of Improved Baghouse Filter Media
as Observed in the Environmental Technology Verification Program
Andrew Trenholm
RTI International
Research Triangle Park, NC
John Mycock
ETS Incorporated
Roanoke, VA
John McKenna
ETS Incorporated
Roanoke, VA
Michael Kosusko
US Environmental Protection Agency
Research Triangle Park, NC
Presented At
Air & Waste Management Association
101st Annual Conference
Portland, OR
June 24-27, 2008
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The Evolution of Improved Baghouse Filter Media
as Observed in the Environmental Technology Verification Program
Paper #176
Andrew Trenholm, RTI International, Engineering Technology Unit, 3040 Cornwallis Road. P.O.
Box 12194, Research Triangle Park, NC 27709-2194
John Mycock, ETS Incorporated, 1401 Municipal Road, NW, Roanoke, VA 24012-1309
John McKenna, ETS Incorporated, 1401 Municipal Road, NW, Roanoke, VA 24012-1309
Michael Kosusko, U.S. Environmental Protection Agency, Office of Research and Development,
National Risk Management Research Laboratory, 109 T.W. Alexander Drive (E343-02),
Research Triangle Park, NC 27711
ABSTRACT
The U.S. Environmental Protection Agency (EPA) implemented the Environmental Technology
Verification (ETV) Program in 1995 to generate independent and credible data on the
performance of innovative technologies that have the potential to improve protection of public
health and the environment. The purpose of this program is to help organizations, industries,
business, states, communities, and individuals make better informed decisions when selecting
new environmental technologies. Technology vendor participation is voluntary, and technologies
are not approved. Quality data, responsive to customer need, are the product of verification
testing. ETV success depends on obtaining and communicating information about the
performance of technologies to those who decide on the selection and implementation of
environmental solutions. The results are publicly available on ETV's web site at
www.epa.gov/etv.
In 1998, the Air Pollution Control Technology Verification Center (APCT Center) instituted a
Baghouse Filtration Products (BFP) Program as part of EPA's ETV program. The purpose of the
BFP program was to verify the performance of baghouse filtration media on removing fine
particles (PM2.s), along with a limited number of other parameters, including pressure drop and
cleaning requirements of commercial-ready products. The expectation was that BFP verifications
would accelerate the market entry of verified fabrics and would thereby help improve the
environment as the new federal fine particle code was implemented at the state level. The BFP
program has been one of the more successful ETV programs, and the vast majority of filtration
fabric suppliers to the domestic bag market have participated in the program. In many cases, the
suppliers have continuously submitted newly developed fabrics for verification. A review of the
data from the program initiation to date is provided in this paper. In general, this review indicates
continuous improvement in the performance of the verified fabrics. A discussion of the
implications of this conclusion is also provided.
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INTRODUCTION
The U.S. Environmental Protection Agency (EPA) implemented the Environmental Technology
Verification (ETV) program in 1995 to generate independent and credible data on the
performance of innovative technologies that have the potential to improve protection of public
health and the environment. The purpose of the ETV program is to help organizations, industries,
business, states, communities, and individuals make better informed decisions when selecting
new environmental technologies. Technology vendor participation is voluntary. Technologies are
not approved or certified for use and no guarantees or recommendations are made. Quality data,
responsive to customer need, are ETV's product. The success of the ETV program depends on
obtaining and communicating information about the performance of technologies to those who
decide on the selection and implementation of environmental solutions.
Information about the ETV program is available at www.epa.gov/etv.1 ETV does not conduct
technology development research. Instead, its function is to test, evaluate, and publish
information about the performance of fully commercial-ready innovative technologies. This
occurs through the development of test protocols, Test and Quality Assurance (test/QA) Plan, the
testing of volunteered technology, and the release of verification reports and statements that
document results. Activities of ETV centers are communicated by media-specific stakeholder
groups, which consist of technical experts in the field; buyers and sellers of technologies; state,
federal, and local permit writers; and others with interest in the area. These groups set priorities
and help develop test protocols and operating procedures.
One focus of ETV is the air pollution control area. The Air Pollution Control Technology
Verification Center (APCT Center) serves as the organizational unit in this area. RTI
International (RTI) is the cooperating partner and verification organization for the APCT Center.
Several other organizations support RTI in various aspects of the work.
Because innovative industrial filters control fine particles, and thus meet an important
environmental need, they have been identified by APCT Center stakeholders as a high-priority
technology group. Baghouse filtration products (BFP) were proposed as a verification technical
area of emphasis within the APCT Center and verifications were initiated there in 2000.
Forecasts indicate that there is a large market for new and retrofit fabric filters. New fabrics have
been developed that offer the combination of highly effective particulate removal and low
operational pressure drop. Improving performance of the fabrics can be observed in verification
test data trends.
VERIFICATION APPROACH FOR BAGHOUSE FILTRATION
PRODUCTS
The verification effort for BFP is intended to verify the performance of industrial air filtration
control technologies. After this technology area was selected, a technical panel (TP) was
assembled to develop the verification protocol. The TP included experts in baghouse filtration
and associated test methods. A balance among permitters, developers or vendors, and users is
sought for TP members. With assistance from the APCT Center staff, the TP develops the
generic verification protocol by first determining performance factors. Second, an evaluation is
made of existing test methods and protocols that may be applicable. To the extent possible, the
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protocol includes elements that are universal to similar technologies. The TP considered many
factors, including efficiency, emission rates, by-products, operating costs, reliability, and
operating limitations. Factors specific to the verification protocol for filtration products included
removal performance by particle size and power consumption caused by pressure drop and
cleaning requirements for the media. The parameters to be tested and the reporting format are
specified in formats useful to vendors, users, and regulators. The TP decided that testing of
filtration products was best accomplished in a laboratory setting.
Drafts of the protocol are reviewed by the APCT Center's director and quality assurance (QA)
manager and by EPA's technical and QA staff. Before any testing begins, the protocol is
supplemented by a detailed test and QA plan. The plan addresses all emission and process data to
be gathered, including project description, project organization and responsibilities, QA
objectives, site selection, sampling and monitoring procedures, analytical procedures and
calibration, data reduction and reporting, and quality control (QC) checks, audits, and
calculations. This plan is reviewed and accepted by the APCT Center and EPA. The BFP
protocol2 and test and QA plan3 are published on the ETV web site.
QA is vital in ensuring credible data in ETV, and its implementation is directed and guided by
the Program's Quality Management Plan (QMP),4 which describes how QA is implemented in
the ETV Program. All ETV Centers have their own EPA-approved QMP, which also complies
with ANSI/ASQC E4-1994, Specifications and Guidelines for Quality Systems for
Environmental Data Collection and Environmental Technology Programs5
Upon completion of verification testing, the data from the test are compiled, checked, and
presented in a form that is consistent with the objectives of the test. All data are assessed as part
of the verification process, and a report is prepared by the ETV center that thoroughly documents
the test results. Any necessary deviations from the plan are explained and documented, raw data
are documented, and QC results are presented. The report provides all necessary information to
support the resulting verification statement.
In addition to the detailed test report, a concise verification statement is prepared for each
vendor's technology and is reviewed and approved by EPA staff. To the extent possible, the
format is consistent with the data requirements of permitting agencies. The verification statement
includes a concise summary of the test report with descriptive information about the system
tested, test methods used and their selection, operating parameters and conditions, statistical
analysis, QA and QC audit results, and any limitations on the collection and use of the test data.
Organizations conducting the testing and providing QA oversight are identified.
VERIFICATION APPARATUS AND PROCEDURES
Under subcontract to RTI, ETS, Inc. (ETS) conducts the verification tests for BFP with the test
apparatus that it built based on the German VDI method 3926 (VDI 1994).6 This equipment
allows the user to measure filter performance under defined conditions with regard to the
filtration velocity, particle size distribution, and cleaning requirements. Filtration and cleaning
conditions can be varied to simulate conditions that prevail in actual baghouse operations.
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The test apparatus shown in Figure 1 consists of a brush-type dust feeder that disperses test dust
into a vertical rectangular duct (raw-gas channel). The dust feed rate is continuously measured
and recorded on an electronic scale beneath the dust feed mechanism. The scale has a continuous
readout with a resolution of 10 grams (g). A radioactive Polonium-210 alpha source is used to
electrically neutralize the dust before its entry into the raw-gas channel. An optical photo sensor
monitors the opacity of the dust and air and verifies that the opacity is stable for the duration of
the test. A portion of the gas flow is extracted from the raw-gas channel through the test filter,
which is mounted vertically at the entrance to a horizontal duct (clean-gas channel).
Figure 1: Diagram of Test Apparatus for Baghouse Filtration Products
DUST FEED FROM EXTERNAL HOPPER
DUST CHARGE NEUTRALIZER
RECTANGULAR CHANNEL
4 3/8" X 11 1/2"
PHOTOMETER
FILTER FIXTURE AND TEST FILTER
CYLINDRICAL EXTRACTION TUBE
CLEAN GAS SAMPLE PORT
RAW GAS SAMPLE PORT
CLEANING SYSTEM
MASS FLOW
CONTROLLER
BACK-UP
FILTER
ABSOLUTE FILTER AND
ANDERSENIMPACTOR
Figure 2 shows a filter sample being installed. Two vacuum pumps maintain airflow through the
raw-gas and clean-gas channels. The flow rates, and thus the filtration velocity through the test
filter, are kept constant using mass flow controllers. High-efficiency filters and pumps to prevent
contamination or damage caused by the dust are installed upstream of the flow controllers. The
cleaning system consists of a compressed-air tank set at 0.52 megapascals above ambient
pressure (75 pounds per square inch gauge), a quick-action diaphragm valve, and a blow tube
25.4 millimeter (mm) diameter (0.1 inch) with a nozzle 3 mm diameter (0.01 inch) facing the
downstream side of the test filter.
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Figure 2: Installing a Fabric Sample in the Test
Apparatus for the Baghouse Filtration Products
Each verification test consists of three test runs,
and each test run consists of three sequential
phases or test periods: a conditioning period, a
recovery period, and a performance test period.
The gas-to-cloth ratio (filtration velocity) and
inlet dust concentrations are maintained at 120
±6.0 meter/hour (6.6 ±0.3 feet per minute) and
18.4 ±3.6 grams per dry standard cubic meter
(g/dscm) (8.0 ±1.6 grains per dry standard cubic
foot), respectively, throughout all phases of the
test.
To simulate long-term operation, the test filter is
first subjected to a conditioning period that
consists of 10,000 rapid-pulse cleaning cycles
under continuous dust loading. During this period, the time between cleaning pulses is
maintained at 3 seconds (s). No filter performance parameters are measured during this period.
The conditioning period is immediately followed by a recovery period, which allows the test
filter to recover from rapid pulsing. The recovery period consists of 30 normal filtration cycles
under continuous dust loading. During a normal filtration cycle, the dust cake is allowed to form
on the test filter until a differential pressure of 1,000 pascals (Pa) (4.0 inches of water gauge is
reached). At this point, the test filter is cleaned by a pulse of compressed air from the clean-gas
side. Immediately after pulse cleaning, the pressure fluctuates rapidly inside the test duct. Some
of the released dust immediately redeposits onto the test filter. The pressure then stabilizes and
returns to normal. Thus, the residual pressure drop across the test filter is measured 3 s after the
conclusion of the cleaning pulse. It is monitored and recorded continuously throughout the filter
medium recovery and performance test periods of each test run.
Performance testing occurs for a 6-hour period immediately following the recovery period (a
cumulative total of 10,030 filtration cycles after the test filter has been installed in the test
apparatus). During the performance test period, normal filtration cycles are maintained and, as in
the case of the conditioning and recovery periods, the test filter is subjected to continuous dust
loading. Outlet mass and particulate matter 2.5 urn in aerodynamic diameter or smaller (PM^.s)
dust concentrations are measured using an inertial impactor located downstream of the test filter
at the end of the horizontal (clean-gas) duct. The impactor consists of impaction stages needed to
quantify total PM and PM2.5 concentrations. The weight gain of each stage's substrate is
measured with a high-resolution analytical balance that is capable of measurements to within
10 jig.
VERIFICATIONS COMPLETED
The ETV Program has verified the performance of 20 BFPs designed primarily to reduce PM2.5
emissions and has one additional verification in progress. All of the verified products are
commercial fabrics used in baghouse emission control devices. The reports on all verifications
can be found at http://www.epa.gov/etv/verifications. Due to the evolving nature of these
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products and their markets, the BFPs' verification statements are valid for 3 years from the date
of verification. Table 1 identifies the verified technologies.
Table 1. ETV-verified baghouse filtration products.
Technology Name
BWF America, Inc. Grade 700 MPS
Polyester Felt
W.L. Gore & Associates, Inc. L3560
Southern Filter Media. PE-16/M-SPES
Donaldson Company, Inc. 6277
filtration media
Donaldson Company, Inc. 6282
filtration media
Donaldson Company, Inc. 6255
filtration media
GE Energy. QG061 filtration media
TDC Filter Manufacturing
Donaldson Company, Inc. 6255-3
filtration media
Verification
Date
September 2005
July 2006
February 2007
May 2007
July 2007
September 2007
In progress
In progress
In progress
Description
A micro-pore-size, high-efficiency, scrim-
supported felt fabric
A membrane and fiberglass fabric laminate
A singed micro-denier polyester felt
An 8 ounces per square yard (opsy) polyester
spun-bond with Tetratex polytetrafluoroethylene
(PTFE) membrane
A 10 opsy pleatable polyphenylene sulfide with
Tetratex PTFE membrane
A woven fiberglass with Tetratex PTFE
membrane
A woven glass substrate with an expanded,
microporous membrane
An 8 opsy non-woven, spun-bond polyester
A woven fiberglass with Tetratex PTFE
membrane
Expired Verifications
Air Purator Corporation Huyglas
1405M
Albany International Corporation
Primatex Plus I
BASF Corporation AX/B A- 14/9-SAXP
1405M
BHA Group, Inc. QG061
BHA Group, Inc. QP131
BWF America, Inc. Grade 700 MPS
Polyester
Inspec Fibres 5512BRF
Menardi-Criswell 50-504
Polymer Group, Inc. DURAPEX PET
Standard Filter Corporation Capture
PE16ZU
Tetratec PTFE Technologies. Tetratex
8005
September 2000
September 2000
September 2000
September 2000
September 2001
June 2002
September 2000
September 2000
September 2001
September 2000
September 2000
An expanded PTFE film applied to a glass felt for
use in hot-gas filtration
A polyethylene terephthalate filtration fabric with
a fine fibrous surface layer
A Basofil filter media
A woven-glass-base fabric with an expanded,
microporous PTFE membrane, thermally
laminated to the filtration or dust cake surface
A polyester needlefelt substrate with an
expanded, microporous PTFE membrane,
thermally laminated to the filtration or dust cake
surface
A micro-pore-size, high-efficiency, scrim-
supported felt fabric
A scrim-supported needlefelt fabric
A singed micro-denier polyester felt
A non-scrim-supported 100% polyester, non-
woven fabric
A stratified micro-denier polyester non-woven
product
A polyester scrim-supported needlefelt fabric
with an expanded PTFE membrane
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Technology Name
Tetratec PTFE Technologies Tetratex
6212
W.L. Gore & Associates, Inc. L4347
W.L. Gore & Associates, Inc. L4427
Verification
Date
September 2001
September 2000
September 2001
Description
A polyester needlefelt fabric with an expanded
PTFE membrane
An expanded PTFE membrane and polyester felt
laminate
A membrane and polyester felt laminate
Figure 3 summarizes the performance data for the 20 BFPs, which have completed verification
to date. Because the ETV program does not compare technologies, the performance results
shown in Figure 3 do not identify the vendor associated with each result and are not in the same
order as the list of technologies in Table 1. The verified results for outlet PM2.5 concentrations
ranged from 2xlO"6 to 3.8xlO"4 g/dscm and total particulate concentrations of 2xlO"6 to 4.2xlO"4
g/dscm. The residual pressure drop ranged from 2.5 to 15.0 centimeters water gauge. The
membrane fabrics tested generally yielded lower PM2.5 (first row) and total PM mass (middle
row) concentrations downstream of the filter and lower pressure drop (third row) across it than
did the no^membrane filters.
Figure 3: Results for Verification Tests of 20 Baghouse Filtration Products
nPM 2.5, 0.1 mg/dscm
IH Total mass, 0.1 mg/dscm
• Pressure drop, cm H20
A-J: Membrane Fabrics. K-S: Non^embrane Fabrics
SCIENTIFIC AND TECHNOLOGY ADVANCEMENT OUTCOMES
The APCT Center's BFP Program has resulted in advancements in science and baghouse media
in addition to the increased knowledge on performance of BFP. The development of the ETV
protocol for BFP has promoted standardization and consistency in evaluating the performance of
baghouse media. The ETV protocol has been adopted by the American Society for Testing and
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Materials (ASTM) as ASTM D6830, Characterizing the Pressure Drop and Filtration
Performance of Cleanable Filter Media. The International Organization for Standardization
(ISO), which is a worldwide voluntary standards organization, has also proposed the ETV testing
protocol as its standard, and it is progressing through the ISO adoption and approval process. In
addition, the development of the protocol and publication of verification results has provided and
will continue to provide valuable scientific information to facilities, vendors, and state and local
agencies. For example, the ASTM method has been used for more than 100 tests over the past 3
years. These tests have been used to screen media during early stage development of new media
and as a QC test for commercial lots of fabric.
The BFP Program has also prompted advancement in the performance of baghouse media. A
review of all of the ETV/BFP test results provides the basis for some interesting observations in
the media performance over time. The trends can be observed in Figure 3, where the
performance of fabrics, which incorporate membranes, are separated from those that do not
contain membranes. Within each type of fabric, the results are presented in chronological order,
relative to the date of the testing. As expected, the PM penetration for the membrane fabrics is
lower. The overall trend for both the membrane and the non-membrane fabrics indicates that the
filtration performance of both types of fabric improves the more current the testing.
This trend of improving performance over time can be observed more clearly if the data are
grouped by time period. Table 2 presents the data as average results for three time periods: initial
verifications conducted in 2000, a second round of verifications conducted in 2001, and the most
recent verifications conducted in 2005 through 2007.
Table 2. Baghouse filtration products performance by time periods.
Time
Period
2000
2001
2005-
2007
Number of
Verifications
10
6
7
Percent of Media
with Membranes
50
67
71
PM25,
mg/dscm
0.0911
0.0120
0.0164
Total Mass,
mg/dscm
0.1164
0.0279
0.0173
Average Delta
P, cm w.g.
10.18
7.00
3.82
cm w.g. = centimeters water gauge; mg/dscm = milligrams per dry standard cubic meter
Figures 4 and 5 graphically show the PM penetration data and delta P data, respectively.
Grouping the data in this manner shows the trends more clearly. For instance, both PM2.s and
total PM penetration decrease over time. Total PM continued to decrease over the time period
observed, whereas the performance of the media for PM2.s may be reaching a plateau. The data
in Table 2 also show the increase in use of membrane fabrics, whereas Figure 5 shows the clear
progress in decreasing the residual delta P without sacrificing PM control. Lower residual delta P
results in energy savings, longer bag life, and lower life-cycle costs.
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Figure 4: Particulate Matter Results by Time Period
|PM 2.5, 0.1 mg/dscm
Total Mass, 0.1 mg/dscm
2000
2001
2005-2007
Figure 5: Residual Pressure Drop Results by Time Period
lAve AP, cmw.g.
2000
2001
2005-2007
One conclusion that may be drawn from these data is that the establishment of the ETV/BFP
program has influenced the development of the filtration fabrics towards better filtration
performance. In essence, because the data are public and the test method is both accepted and
transparent, the fabric developers have a published target performance. The developers use this
information to compete with other developers to create the best performing fabric, which has led
to a continuous improvement in the filtration performance and the increased potential for
environmental improvement.
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REGULATORY COMPLIANCE OUTCOMES
EPA has identified 39 areas of the United States with a total population of 90 million that exceed
the National Ambient Air Quality Standards for PM2.s. Although controls on other pollutants,
such as those required under the 2005 Clean Air Interstate Rule, will help some areas meet the
PM2 5 standards, EPA anticipates that many states will require emissions controls on large
stationary sources of PM2.5. ETV-verified BFPs can be used to meet these requirements. In
addition, the verification data can assist facilities and state and local agencies in evaluating the
technologies' effectiveness for meeting these requirements. The availability of ETV data has also
facilitated the permitting process for users. A vendor of a verified fabric was quoted as saying,
"At least one customer... made his work with permitting easier by running our materials through
the ETV testing process.
The ETV program also supports vendors and users in compliance with state and local air
pollution rules. On November 4, 2005, the California South Coast Air Quality Management
District adopted Rule 1156, which encourages the use of ETV-verified baghouse fabrics to
control PM emissions from cement manufacturing facilities. Paragraph (e)(7) of the rule allows
facilities that use ETV-verified products in their baghouses to reduce the frequency of
compliance testing from annually to every 5 years. EPA's Office of Air Quality Planning and
Standards issued a memorandum to "EPA Regional offices and State Directors, which endorses
the use of verified baghouse filter media and encourages its future use in both permits and in new
or revised regulations wherever appropriate."
REFERENCES
1. U.S. Environmental Protection Agency, Environmental Technology Verification Program
Home Page. See http://www.epa.gov/etv (accessed March 2007).
2. Generic Verification Protocol for Baghouse Filtration Products; ETS, Inc., and RTI
International: Roanoke, VA, and Research Triangle Park, NC, October 2001. See
http://www.epa.gov/etv/pubs/05_vp_bfp.pdf (accessed March 2007).
3. Test/QA Plan for the Verification Testing of Baghouse Filtration Products (Revision 2); ETS,
Inc., and RTI International: Roanoke, VA, and Research Triangle Park, NC, February 2006.
See http://www.epa.gov/etv/pubs/600etv06095.pdf (accessed March 2007).
4. Environmental Technology Verification Program, Quality Management Plan; U.S.
Environmental Protection Agency; Office of Research and Development: Cincinnati, OH,
December 2002; EPA/600/R-03/021.
5. Specifications and Guidelines for Quality Systems for Environmental Data Collection and
Environmental Technology Programs; American National Standards Institute/American
Society for Quality Control (ANSI/ASQC): Milwaukee, WI, 1994; ANSI/ASQC E4-1994.
6. Testing of Filter Media for Cleanable Filters under Operational Conditions; Verein
Deutscher Ingenieure (VDI 3926, Part 2), December 1994. Available from Beuth Verlag
GmbH, 10772 Berlin, Germany.
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KEY WORDS
Baghouse, Particulate Emissions, Verification
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