FINAL REPORT. VOLUME IV. FABRIC FILTER SYSTEMS
STUDY
GCA Corporation
Bedford, Massachusetts
December 1970
Distributed ... 'to foster, serve
and promote the nation's
economic development
and technological
advancement.'
NATIONAL TECHNICAL INFORMATION SERVICE
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m
VOLUME'IV
FABRIC EJLTER SYSTEMS STUDY
Prepared by
GCA CORPORATION
GCA TECHNOLOGY DIVISION
Bedford, Massachusetts
Contract No. CPA*22-69»38
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VOLUME IV
FADRK: FILFER SYSTEM'S SSUDY
Prepared by
GGA CORPORATiCW
GC/:- 7LXH OOLOGY HfVISJ
No. CP/V 22 69-38
December )?7C
Proparef.I for
DIViStOK OF PROCFSS CONTROL ENGIt-:i-T:;li--iC
UATiONA! A!!' FOLLUTiCN t'OMT^OL ADAM'.Nllf/iU'/.i'iQ
i;.S. ni?.r>,j . ..rr;f or rir.AlTH. ElXJ-rAilON .-WO -.VT-ir/M
Public Haci'.!i -^(.r\'!cc
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GCA-TR-70-17-G
FINAL REPORT
VOLUME IV
FABRIC FILTER SYSTEMS STUDY
Prepared by
GCA CORPORATION
GCA TECHNOLOGY DIVISION
Bedford, Massachusetts
Contract No. CPA-22-69-38
December 1970
Prepared for
DIVISION OF PROCESS CONTROL ENGINEERING
NATIONAL AIR POLLUTION CONTROL ADMINISTRATION
U.S. DEPARTMENT OF HEALTH, EDUCATION AND WELFARE
Public Health Service
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FOREWORD
This document is submitted to the Department of Health, Education
and Welfare, National Air Pollution Control Administration, in partial
fulfillment of the requirements under Contract CPA 22-69-38. The
principal technical objectives under the contract were: (1) to evaluate
the status of engineering technology currently available to the researcher,
manufacturer and user of fabric filter systems; (2) investigate the
current practices in the application of fabric filtration; (3) investigate
major air pollution control areas which could be amenable to control
by fabric filtration; (4) make a critical review and engineering evaluation
of the major types of fabric filter devices currently available in order
to assess the strength and weakness of each type of device; (5) prepare
a comprehensive report containing the information collected in the task
areas cited above; and (6) develop five-year research and development
programs specifying the research and development efforts required to
fill the stated technical gaps. The results of the contract efforts
are presented in the following four volumes:
Volume I - Handbook of Fabric Filter Technology
Volume II - Appendices to Handbook of Fabric Filter Technology
Volume III - Bibliography, Fabric Filter Systems Study
Volume IV - Final Report, Fabric Filter Systems Study
The following professional staff members of the GCA Technology Division
contributed to the study and preparation of this report: Dr. Charles E.
Billings, Mr. Richard Dennis, Dr. Leonard M. Seale, and Dr. John Wilder.
The results of the contract efforts, partially presented in this document,
covered the period from January 1969 to January 1971.
Mr. Dale Harmon of the Process Control Engineering Division, National
Air Pollution Control Administration, served as the Contract Project
Officer.
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TABLE OF CONTENTS
CHAPTER 1 INTRODUCTION 1-1
1.1 SUMMARY 1-1
1.2 CONCLUSIONS - 1-3
CHAPTER 2 DATA COLLECTION METHODS 2-1
2.1 EQUIPMENT USERS 2-1
2.2 EQUIPMENT MANUFACTURERS 2-6
2.3 LITERATURE SURVEY 2-12
2.3.1 Indexing and Coding System 2-12
2.3.2 Literature Search 2-13
2.4 OTHER DATA SOURCES 2-16
CHAPTER 3 ANALYSIS OF DATA 3-1
3.1 APPLICATIONS OF FILTER SYSTEMS 3-1
3.1.1 Status and Trends in the Filter Industry 3-1
3.1.2 Distribution of Equipment 3-2
3.1.3 Outlook for New Applications 3-7
3.2 PERFORMANCE ANALYSES 3-9
3.3 COST ANALYSES 3-10
3.4 ENGINEERING DESIGN ANALYSIS 3-12
3.4.1 Collector Design 3-12
3.4.2 Fabric Design 3-13
3.4.3 System Design 3-15
3.5 FUNDAMENTAL ANALYSES 3-15
3.6 OUTLOOK FOR NEW DEVELOPMENTS 3-17
3.6.1 Concurrent R&D in the U.S. 3-18
3.6.2 Collector Developments 3-19
3.6.3 Fabric Developments 3-26
3.6.4 System Instruments and Controls 3-27
3.6.5 Extensions of Fabric Filtration to Gas Collection 3-31
CHAPTER 4 IDENTIFICATION OF RESEARCH AND DEVELOPMENT 4-1
REQUIREMENTS
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4.2 DEFINITION AND CONTROL OF PARTICLE PROPERTIES 4-3
4.2.1 Basic Particle Parameters 4-4
4.2.2 Deposit Modification and Control 4-5
4.2.3 Particle Size Control 4-7
4.3 FABRIC INVESTIGATIONS 4-9
4.3.1 Fabric Surfaces Study 4-10
4.3.2 Fabric Performances 4-13
4.3.3 New Fabric Material Investigations 4-17
4.4 SYSTEM DESIGN STUDIES 4-18
4.4.1 Cleaning Mechanisms and Kinetics 4-19
4.4.2 Improved Fabric Filtration Equipment 4-21
4.4.3 Control Equipment and Instrumentation 4-22
4.4.4 Fabric Filter System Modeling 4-24
4.4.5 Continuation of the Fabric Filter System Study 4-26
4.5 APPLICATION STUDIES 4-29
4.5.1 Identification and Evaluation of New Fabric Filter 4-29
Applications
4.5.2 Demonstration of a High Temperature and High Fil- 4-33
tration Velocity System
4.6 INTEGRATED RESEARCH AND DEVELOPMENT PROGRAMS 4-36
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FABRIC FILTER SYSTEM STUDY
ABSTRACT
This report describes a study directed to the definition of two
alternative five-year research and development programs based on dif-
ferent levels of funding for fabric filter systems used in air pollution
control applications. These plans provide specific performance, to
improve economics of usage, and to promote extension of fabric filtration
to control of a greater number of applications present and future.
Specific tasks undertaken include: A survey of engineering technology
available as data or analytical design and operation equations; the
identification and investigation of current practices, limitations, and
problems of fabric filter systems in present usage and in possible future
applications; and a review of the major types of fabric filter equipment
available. Results of the above efforts have been presented in a com-
prehensive analytical handbook, and in an indexed bibliography of fabric
filtration literature.
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CHAPTER 1
INTRODUCTION
1.1 SUMMARY
In early 1968, the Division of Process Control Engineering (DPCE) of
the Air Pollution Control Office (APCO), Environmental Protection Agency
(EPA) , decided to undertake a comprehensive study of particulate air pol-
lution control equipment. Technical and administrative preparations were
made to fund three major programs:
Systems Study of Fabric Filters
Systems Study of Electrostatic Precipitators
Systems Study of Scrubbers
In response to Request-for-Proposal No. PH22-68-Neg.lO, GCA Technology
Division submitted the successful proposal for the Fabric Filter Systems
Study. Following the contract award in late 1968, Dr. Charles E. Billings
was appointed as the GCA Program Director, and Mr. Dale L. Harmon as the
APCO Program Monitor.
The objectives of the program were to:
1. identify and evaluate the status of current
engineering technology
2. define current practices in the application of
fabric filters for air pollution control
3. identify potential areas for new applications
of fabric filters for air pollution control
4. investigate existing fabric filter systems, and
5. define research and development recommendations
to extend future applications and improve perfor-
mance of existing fabric filter systems.
* Formerly National Air Pollution Control Administration (NAPCA) U. S.
Department of Health Education and Welfare (HEW).
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The program included three major data acquisition activities:
1. a survey of current applications from filter users;
2. a survey of design and application experience
obtained from fabric filter manufacturers and com-
ponent suppliers; and
3. a review of fabric filtration literature.
The results of this study are presented in four volumes as described
below:
Volume 1 - " Handbook of Fabric Filter Technology", a
synthesis of current engineering technology
as applied to the present utilization of
fabric filter systems for air pollution
control.
Volume 2 - "Handbook Appendices for Volume 1".
Volume 3 - "Bibliography", an indexed bibliography of
pertinent literature plus a data storage
and retrieval system for the program
bibliography.
Volume 4 - "Final Report", a. description of the develop-
ment of and recommendations for research and
development programs submitted for considera-
tion by APCO.
The Handbook of Fabric Filter Technology, which represents a major
output of this program, is intended to function as a guide in the design,
development, application and operation of fabric filter systems. The
Chapter contents are summarized in the following listing:
Title
Introduction
Fabric Filtration Technology
Types of Fabric Filters
Fabric Selection
Engineering Design of Fabric Filter System
Fabric Filter Performance
Economics
Operation and Maintenance
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The handbook is aimed primarily at those engineering and scientific
personnel who must deal with air pollution control problems for which
fabric filtration affords a satisfactory solution. The handbook coverage
is broad, ranging from the underlying theoretical aspects to the practical
design and economic consideration encountered in selecting and operating
field installations.
The handbook examines several types of individual applications and
points out the range and importance of the major operating parameters.
1.2 CONCLUSIONS
General conclusions arising from this study are presented in the fol-
lowing section:
1. The estimated yearly sales for fabric filter dust collectors
range from $35 to $50 million for approximately 7500 indi-
vidual units. Although there are about 50 manufacturers of
fabric filter collectors in the U.S.A., nearly 80 percent
of dollar sales are attributable to ten manufacturers.
Sales have increased historically at a rate of 7 percent
annually until recently wherein the rate appears to have
nearly doubled.
2. An additional $25 million yearly are represented by the
sales of fabric media for either new equipment or for
replacement in existing units.
3. There are 10 to 10 fabric filter collectors in use in
the U. S. at the present time. These range in size from
10 to 10 aq. ft. of fabric filter area, with a current
average purchased size of approximately 3000 sq. ft.
4. Due to variations in design, equipment costs per unit size
vary by as much as a factor of ben. A typical purchase
cost for the collector alone is $0.80 per CFM filtered or
$2.40 per CFM installed with all necessary accessories.
The cost of owning and using the equipment, including
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replacement fabric, electric power, labor, and other expenses,
is approximately §1. per CFM per year, again with considerable
variation from one installation to another.
5. An industrial plant may use from one to several hundred
fabric filter collectors for a broad variety of applications.
The selection of fabric filter equipment is usually based
upon its high, 99 percent or greater, particulate removal
characteristics. In some circumstances, however, the choice
may be solely one of economics relative to other dust col-
lection systems, e.g., electrical precipitation or wet
scrubbing. Fabric filter collectors can be used for most
dust and fumes, provided that gas temperatures are maintained
above the dew point and that the upper working temperature of
the fabrics is not exceeded.
6. More than 25 percent of all maintenance costs for fabric
filter systems were associated with fabric repair or replace-
ment. Mainly, these costs resulted from dust-fabric inter-
actions such as blinding or fabric wear, accentuated by the
intense cleaning necessary to overcome particle-fabric
adhesion. Other significant maintenance costs appeared to
arise from the selection of under-designed and less expensive
equipment as a means of cost control.
7. Variations in design of fabric collectors, chiefly in the
method of cleaning the fabric, and variations in fabric
material and weave provide considerable latitude in the
selection of a filter system. Presently, the selection
process depends mainly on experience with similar systems
because the theoretical factors relating fabrics, particles,
and gases in filtration and cleaning are not well established.
As a result of the study, a number of areas for research and
development have been identified. The results of these future
studies are expected to improve greatly the overall perfor-
mance (both cost and efficiency) of existing systems and to
suggest new applications for fabric filter equipment.
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CHAPTER 2
DATA COLLECTION METHODS
Most fabric filter designs are basically unchanged from those con-
ceived approximately 120 years ago. Only within the last 20 years have any
new types or novel designs appeared. Over this period, a tremendous amount
of practical design and usage experience has evolved which, unfortunately.
has never been summarized systematically. The literature reports fragments
of this experience, but because fabric filtration is still as much an art
as a science, the best information sources are the people directly involved
with the equipment. Thus, in addition to a literature review, the present
study required a systematic survey of fabric filtration equipment users,
equipment manufacturers, control agencies, consultants, and laboratories
having interests in fabric filtration.
2.1 EQUIPMENT USERS
The initial approach in the user survey was to establish several broad
industrial categories and to estimate the aggregate effluent source strengths
in each of these. Specific processes and operations significant in particu-
late air pollution were surveyed for description of their characteristic
gas and particulate parameters. The process effluents were then combined
as shown in Table 1 for ten industry classes. This first-order analysis
was instrumental in establishing priorities for the survey effort.
Reference to Column (A), Table 1 provides an estimate of the total
amount of particulate released to the atmosphere for the various industrial
categories assuming that no control measures are exercised. These data,
however, do not take into account other key factors that may influence the
emission ratio. If the potential effluent has sufficient value to warrant
recovery, Column (B), it becomes highly illogical to vent it to the atmos-
phere. On the other hand, any properties of the gas stream, Column (C), or
the particulate matter, Column (D), which present cleaning difficulties tend
to increase its pollution potential. The indices 1 or 2 designating either
a favorable or adverse effect, respectively, have been combined with the
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TABLE 1
GROSS POLLUTION AND POTENTIAL CONTROL
(A)
Total0'
Total Annual Particular
Product _6 Emissions
Category Industry Tons /Year xlO Tons /Year x
(B) (C)
Valuable Gas and Partlculate
B Recoverable Capability
, Product Gas P
10 No Yes Easy Difficult Eas
(D) (E)
Handling b'
Relative0'
articulate Polluting
y Difficult Potential
(2) (1) (1) (2) (I) (2) RP
1 Combustion
Coal
Oil
Incineration
2 Food & Feed
3 Pulp & Paper
4 Inorganic Chemical
5 Organic Chemical
6 Petroleum Refining
Combustion
Catalyst
to
' 7 Non-Metallic
Minerals
Cement
Fertilizer
8 Iron & Steel,
Foundries
9 Non-Ferrous Metals
10 Miscellaneous
375
30
200*)
300
40
100
--
700
3500
500
30
200
10
(Includes highly
37
0.06
10
3
6.4
10
--
1.4
3.5
10
1.5
10
1
toxic o
e.g. pyrophoric metals.
X XX
X X
X X
XX X
X XX
X XX
X XX
X X
XX X
X XX
X X
X X
X X
laterlals, e.g. radioactivity or beryllium
Emissions usually controlled for reasons
296
X 0.5
X 80
3
12.8
20
--
X ' 11.2
3.5
40
X 9
X 80
X 4
and reactive materials
of health and safety.)
a) Ho credit for partlculate controls.
b) Indices (1) and (2) indicate favorable or adverse gas cleaning conditions.
c) RP indicates relative pollution potential
RP-AxBxCxD
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yearly particulate emission rate to establish a descriptor of relative
pollution potential, Column (E). Despite this qualitative approach, the
relative magnitude of these descriptions appear to align well with the
observed pollution levels noted for many major industries.
As a second step in structuring the filter usage survey, a list-in-
breadth was made of all processes for which fabric filters have been used
or might conceivably be used, see Appendix 1, "List of Particulate Sources
and Indications of FF Use Potential". This tabulation represents a conden-
sation of nearly 300 dusts compiled from several sources and including some
sources too small to warrant further attention in this study, e.g., powdered
corn cob; pollens.
Table 1 and Appendix 1 form the basis for estimating the potential
market for FF equipment, i.e., the quantity of emissions and the possibili-
ties of using fabric filters. Also available are data on reported sales of
equipment for the years 1966 and 1967, representing in effect the actual
market for FF equipment. After comparing the latter statistics with the
data of Table 1, a sample listing of fabric filter users was structured as
shown in Table 2.
A comprehensive questionnaire was prepared to obtain complete descrip-
tive, operating, and performance data from fabric filter system users.
This questionnaire (Appendix 2) was approved by the Bureau of Budget as an
instrument of the contract. Meanwhile, preliminary visits were made to
several local users of FF equipment to test the questionnaire prior to
developing the final format. The questionnaire consisted of seven pages:
Page 1. User company, address, key FF personnel
Page 2. Process capacity and emission level
Page 3. FF manufacturer, dimensions, fabric type
Page 4. FF pressure data, economics
Page 5. FF cleaning cycle, dust description
Page 6. Equipment needs, suggestions for future research
Page 7. Miscellaneous fabric and gas properties.
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TABLE 2
FABRIC FILTER SURVEY SAMPLE STRUCTURE, VISITS PLANNED
AND ACCOMPLISHED
I.
II.
III.
IV.
User Category
1. Combustion
2. Food & Feed
3. Pulp & Paper
4. t Inorganic
Chemical
5 . Organic
Chemical
6. i Petroleum
Refining
7. Non-Metallic
Minerals
8. Iron & Steel
Foundries
9. Non-Ferrous
Metals
10. Miscellaneous
Subtotal
Filter Manufac-
turers
Fabric Manufac-
turers
Agencies, etc.
Total
No.
Planned
3
2
1
3
5
1
11
14
8
2
50
7
3
--
60
No.
Visited
5
1
1
3
5
0
15
15
5
2
52
9
4
6_
71
No. Questionnaires
Completed
3
1
0
2
5
0
11
13
5
1
41
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The questionnaire was designed to cover all major aspects of the
design and performance of the equipment and, especially, to obtain the
user's opinions as to how the equipment might be improved. Since the
questionnaire asked over 100 questions, individuals using only a small
filter collector often were not prepared to answer a large percentage of
the questions. In these instances, cooperation was obtained by having the
interviewer personally solicit and record the answers to the appropriate
questions after having submitted the questionnaire previously to the sub-
ject. The above interview could be handled adequately in a one to two
hour period.
Arrangements for plant visits involved several telephone calls and
written communications to guarantee access to the plants and, most impor-
tant, to establish which persons were most familiar with the filtration
equipment. Frequently, several individuals representing management, plant
engineering and maintenance categories were contacted in order to obtain
complete coverage.
During many visits, an informal discussion yielded more information
and engendered more thinking than the formal page-by-page completion of
the questionnaire. Inspection of plant facilities sometimes revealed addi-
tional features about a system which had not been discussed previously.
Follow-up telephone calls were frequently made to clarify or amplify infor-
mation gained during a plant visit.
It was frequently noted that even the most important system variables
(e.g., temperature, flow rate, dust loading, pressure drops) were not known
because the system had no appropriate instrumentation. In the smaller
systems, these variables sometimes had 'never been measured. Although a
thermometer and anemometer were usually carried on the tour, suitable
measuring points were usually not/available. Thus, it became apparent
that (a) the data would be limited both in quality and quantity, and (b)
that future surveys should also include a field measurement activity.
Most of the survey was performed in several two and three day trips
to Ohio, Pennsylvania and New York State. In addition to a few Greater
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Boston firms, scattered visits were also made to Maine, California, West
Virginia, Ontario, Kentucky and Michigan.
The number of individual plants or companies visited, classified ac-
cording to process, is shown in Table 3. In that some 10 to 10 fabric
filter operations are estimated to be in use at the present time, the num-
ber of installations visited represents a very small sampling. Despite
this fact, the discussions and responses to questionnaires resulting from
the survey are believed to represent a good cross-section of the information
available from the field. Had the program permitted a more extensive sur-
vey, several additional process categories and plants might have been in-
cluded (Suggested Survey Extensions, Table 3).
The types of fabric and the manufacturers of fabric filter equipment
described in the user survey are listed in Table 4. In view of the small
sampling and the non-random structuring of the survey, the indicated fre-
quencies should not be extrapolated.
2.2 EQUIPMENT MANUFACTURERS
The most recent survey of fabric filter equipment manufacturers, 1960,
served as a starting point for the present survey. A review of industrial
indices and periodicals produced a list of about 200 companies either known
to manufacture or considered to have a possible interest in the manufacture
of FF equipment. In March, 1969, a letter was sent to each, asking for an
expression of interest and willingness to cooperate in this study. About
40 positive replies were received offering various degrees of cooperation.
A second mailing was made to 75 manufacturers from the same group in
which they were requested to correct and up-date a condensed listing and
description (prepared by GCA) of their product line. From this survey and
a subsequent follow-up, a tabulation of some 50 manufacturers was prepared
that embraced more than 100 different collector models and a wide range of
air flows. A condensed version of these data is shown in Appendix 3. The
complete listing appears in the "Handbook Appendices for Volume 1", Volume
2, "Fabric Filter Manufacturers and Equipment Summary". New manufacturers
appear to enter the market at a, rate of about two per year.
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TABLE 3
FABRIC FILTER USER SURVEY
Category
1
Industry
Combustion
^ Suggested**
Result Survey
Extensions
1 Oil-fired Boiler D
2 Coal-fired Boiler D
3 Coal-fired Boiler Q
4 Municipal Incinerator Q
5 Municipal Incinerator Q
Food & Feed
1 Grain/Flour Mill Q
Pulp & Paper
i Kraft Mill D
Inorganic Chemicals
1 Lime Q
2 Indust. Chem. Q
3 Lime, Gypsum D
Organic Chemicals
1 Carbon Black Q
2 Carbon Black Q
3 Plastics/Res ins Q
4 Polyvinyl Alcohol Q
5 Alum Q
Petroleum Refining
None
Non-Metallic Minerals
1 Cement Plant Q
Municipal Incinerator,
NYC
Powdered Mixes
Fertilizer
Pharmaceuticals
Soap & Detergent
Catalytic Cracking
Mining
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TABLE 3 (Continued)
Category
7(Cont.)
2
3
4
5
Industry
Cement Plant
Cement Terminal
Cement Plant
Cement Plant
*
Result
Q
Q
Q
D
Suggested**
Survey
Extensions
Ceramics
Clay Plant
Lime Plant
Asphalt Batching,
6 Cement Plant' D
7 Cement Plant D
8 Lime Plant Q
9 Stone Crushing Q
10 Gypsum Plant Q,Q
11 Abrasives D
12 Abrasives Q
13 Glass Mfgr. Q
14 Glass Mfgr. D
15 Mineral Wool (Q)
Iron and Steel
1 Electric Furnace Q
2 Electric Furnace Q
3 Electric Furnace Q
4 Electric Furnace Q
5 Elec. Furnace Room Q
6 Cupola Furnace Q
7 Cupola Furnace Q
8 Foundry Q
9 Foundry Q
10 Foundry Q
11 EOF Reladling Q
12 Sinter Line Dropoff Q
Chicago
Asbestos, Quebec
Coal Cleaning
Coke Oven
Sintering
Basic Oxygen Furnace
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TABLE 3 (Continued)
Category
8 (Cont.)
13
14
Industry
Motor Room
Miscellaneous
*
Result
Q
D
Suggested**
Survey
Extensions
10
Non-Ferrous Metals
1 Copper Q,Q
2 Lead Q
3 Aluminum D
4 Brass Refining Q
5 NFM Machining Q
Mi s c e11anepus
1 Product Fabrica- Q
tion
Zinc
Zinc Galvanizing
Aluminum
Lead Smelting
Wood Products
Ultrafiltration
Result: Q, Questionnaire completed
D, General discussion, no questionnaire
**
Plants or operations not included in present survey
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TABLE 4
SUMMARY OF FABRIC TYPES AND COLLECTOR MANUFACTURERS
DESCRIBED IN USER SURVEY
*
Fabric
Cotton
n
Dacron
DynelR
Class
NomexR
OrlonR
Polypropylene (felt)
Wool
Frequency
12
5
1
9
1
2
1
2
33
Percent Frequency
36.4
15.1
3.0
27.3
3.0
6.1
3.0
6.1
100.0
Working temperatures - 16 systems > 200°F, 17 systems < 200°F
Collector Manufacturers Frequency
American Air Filter Company, Inc. 4
Carter-Day Company 3
Dustex Division, American Precision Industries, Inc. 1
Flex-Kleen Corporation, Research Cottrell, Inc. 2
Hydromation Engineering Company 1
G.A. Kleissler Company 1
Northern Blower Division, Buell Engineering Co., Inc. 3
Own Design 4
Pangborn Division, The Carborundum Company 5
W.W. Sly Manufacturing Company 3
The Wheelabrator Corporation 6 >
R: Registered trademark
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During July, 1969, a similar letter survey with a reply card was
directed to more than 80 companies engaged in the manufacture of fiber and
fabrics of the types used in fabric filtration. Although an effort was
made to include all known suppliers of filter bags and envelopes, there
are literally hundreds of sources of textile fiber. Thus, the tabulation,
"1969 Suppliers List: Filter Fabrics and Related Materials" Handbook
Appendices Volume 2 forms the basis for a more detailed future survey of
fiber and fabric sources, finishes, weaves and other fabric properties.
Most manufacturers of fabric filter collectors were not in favor of
participating in this survey. In April, 1969, GCA representatives met with
members of the Fabric Collectors Division of the Industrial Gas Cleaning
Institute (IGCI) in an attempt to develop some basis for cooperation. Group
membership in IGCI represents approximately 80 percent of sales in the in-
dustrial gas cleaning market. IGCI spokesmen stated that the highly pro-
prietary aspects of their products would prevent any free exchange of in-
formation. The concept of cooperative efforts in basic research and devel-
opment were considered reasonable, but no approaches were found acceptable
to IGCI. Therefore, IGCI took no official position, recommending that
member companies establish their own policies.
Replies from individual IGCI member firms reflected for the most part
the IGCI stance, although some suggested that companies asked to supply in-
formation might be compensated for the time and effort involved. This
approach was acceptable to GCA, provided that the data fulfilled the needs
of this study. Although no provision for such effort was included in the
present program budget, it appeared that this avenue might be explored in
future programs.
Despite the official position taken by many companies, it is emphasized
that several did furnish a substantial amount of information and nearly all
furnished their product brochures.
Nine equipment manufacturers were visited, representing a wide range
in sales volume, equipment types, and sizes. Four fabric and fiber manu-
facturers were visited as well as two laboratories engaged in fabric
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research. Both samples, which encompass a much larger percentage of the
manufacturing population than the equipment user survey sample ,are believed
to be representative. In retrospect, however, more fabric information
would be desirable in view of the emphasis now placed on fabric performance.
Some manufacturers were reluctant to suggest installations of their
equipment that might be visited, although most were willing to discuss in-
stallations chat had already been visited by GCA. Most manufacturers were
glad to discuss the types of R & D they considered necessary, although the
expressed opinion of many was that there was not much to be done to improve
the equipment now available.
2.3 LITERATURE SURVEY
A substantial quantity of both domestic and foreign information directly
or indirectly relatable to fabric filtration has been published. Some unpub-
lished literature such as experimental results, internal reports, and guide-
lines to operation of fabric filter equipment, are also available. This
survey consisted of locating useful information; obtaining copies of perti-
nent documents; indexing, coding, and storing the information, and preparing
a bibliographic summary which is published as Volume 3 of this program.
2.3.1 Indexing and Coding System
Faced with the need for organizing a large amount of informa-
tion, a system of descriptors was chosen for classifying and relocating
documents on fabric filtration. The descriptors were structured in several
general categories relating to dust source, dust type, gases, fabric, etc.,
as described in Volume 3. While some investment of time was required to
review and code each document, the descriptor method proved to be very
useful and efficient during the subsequent data analysis phase. The number
of descriptors was limited to approximately 100. In retrospect, however,
it now appears that some of the descriptors might be combined or eliminated,
and others added, especially in the area of system design.
The item index selected was simply a consecutive numbering of
documents in order of their review. Thus, more documents can be added at
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any future time without resorting or renumbering. Numbers used ran from
0010 through 0509. Documents were also cross-indexed by author and by
descriptor, using card sorting methods. It was originally planned to cross-
index all information by computer. When, however, the total number of
documents appeared to be only about 500, this approach was dropped.
2.3.2 Literature Search
The literature reviewed in this survey was obtained from many
*
sources. Four libraries were especially useful: APTIC, Bay Area, APCO,
and GCATD;and provided an estimated 60 percent of the 500 items gathered
in this survey. The remaining 40 percent were acquired through various
abstracting services, the bibliographies of papers previously reviewed,
personnel communications, and assorted periodicals. Table 5 lists these
**
sources along with the approximate coverages furnished by each . /
Copies of many documents were ordered from the John Crerar
Library in Chicago, while others were obtained from the Massachusetts
Institute of Technology Library. Once given an accession number, documents
were reviewed at which time up to 25 appropriate descriptors were selected
from the master listing. These descriptors, plus bibliographic information
were punched on IBM cards. These cards filed in numerical sequence consti-
tute the bibliography cited previously.
* APTIC; Air Pollution Technical Information Center, APCO, Raleigh,
North Carolina. Bay Area; San Francisco Bay Area Pollution Control
District; several copies of this data bank exist, including one at
APTIC. APCO; Process Control Engineering Division, Development
Engineering Branch, Equipment Development Section, Technical Library.
GCATD: GCA Technology Division, Bedford, Massachusetts.
** This list is not in the order of search. A different search sequence
would ascribe slightly different relative importance to these sources.
-------
TABLE 5 . LIST OF SOURCES SEARCHED DURING FABRIC FILTER SYSTEM STUDY
-Years Covered-
SOURCES SEARCHED
Main abstracts:
APT 1C
Bay Area
APCA Abstracts
Brit. AP Abstracts
App. Sci. and Tech. Index
MEDLARS
Fuel Abstracts
Chemical Abstracts
Misc. Abstracts
AP Translations
Guide to Res In AP
AP Publlcns - Sel. Bib. 2
The AP Bibliography 1
AP Titles
AP - A Bibliography 5
Subj. Indx to Llt.AiW Cons. 0
Files at GCA 10
Tech. Lit. File, NAPCA 10
Periodicals - Indices searched:
Filtration & Separation 1
Air Engineering I
Rock Products 1
Textile Ke« Jnl 0
Periodicals - sources, but
not searched completely
Secondary Bibliographic* 5
Companies and Consultants
Approx 30 FF Users 1
Approx IS FF Fabric Mfgra. I
Approx 10 FF Consultants 1
Organisation?:
IGCI 0
Filtration Society 0
Textile Res. Institute 0
Am Foundrymen's Soc. 0
Am Petroleum Inst. 0
Mfg. Chemists Soc. 0
Est. 30 other trade
organisations 0
Total
or 500
items
IOOX,
68
67
66
65
64
63
62
60
58
55
50
>re
40
-------
Despite advances in library science through automation, con-
siderable duplication as well as omissions in technical area and time
were encountered during the literature search. Lack of standard termino-
logy relating to the subject matter also complicated the search process
and many libraries were unable to define the limits of their subject area
coverage.
Although the above difficulties created some delays, it is
believed that the end result covered most of the pertinent and recent
literature on fabric filter technology and that at least 90 percent of the
useful U. S. publications were located. While the literature search was
considered to be essentially of optimum size for the present program, it
could be up-dated and made more complete in any of the following ways:
1. Up-date from mid-1969, using the principal sources listed
in Table 5.
2. Back search the periods before and up to the early 1950's.
The early literature was not searched systematically in
this study, because: (a) there were already some biblio-
graphies of air pollution technology extending back into
the 1800's, and (b) fabric filtration technology prior
to the 1950*s was very limited in types of fabric and
methods of cleaning.
3. Intensify search of the areas already reviewed. Some
obscure journals were noted, but not located in the
present search. In addition, manufacturers may have
some experimental data for release, and sales brochures
can be re-examined from several viewpoints.
4. Broaden the search to related areas such as liquid
filtration, textile finishing, instrumentation, aerosol
science, economics of sheet metal manufacturing or
powder physics. About 100 abstracts in these peripheral
areas were obtained at APTIC which have not been further
processed.
-------
5. Search foreign literature and domestic and foreign
patents. Although patent searches had originally been
considered in the present program, it was later decided
that they would be more relevant to future equipment
development programs.
2.4 OTHER DATA SOURCES
Nearly all the data used in this study came from equipment users,
manufacturers and manufacturers' brochures, or from the open literature.
City and county air pollution control groups in a few instances provided
leads to installations of interest in their geographical areas. Similarly,
a few trade organizations assisted in identifying people or plants that
later contributed to the study. Although more than a dozen trade organi-
zations were contacted, none were able to contribute any new data, with
the exception of IGCI. Discussions with academic and industrial consult-
ants yielded qualitative data that aided in shaping the opinions formed
during the study. Personnel involved in past and current laboratory
studies made at APCO and at the Harvard School of Public Health were
especially helpful. A large amount of unpublished material was contributed
to the study by APCO.
-------
CHAPTER 3
ANALYSIS OF DATA
. '.
In this section, the methods of data analysis and the forms of data
presentation selected for this study are discussed. Generally, data
could be grouped in three main classifications:
. Applications and equipment markets
. Performance, engineering and economic
. Design and improvement of equipment
3.1 APPLICATIONS OF FILTER SYSTEMS
3.1.1 Status and Trends in the Filter Industry
A complete national inventory, listing all particulate sources
and those presently controlled by fabric filters, accompanied by tech-
nical and economic data necessary to provide reliable aggregate estimates
of the present market structure for filters, would be most useful. It
would identify potential R&D requirements as well as providing a valuable
document for national air pollution control policy planning. No such
complete documentation exists. A few air pollution control agencies had
source inventories in various stages of preparation, but access to these
data was generally not permitted.
In the absence of any national inventory of particulate sources,
an attempt was made in this survey to develop some reasonable estimate.
The approach involved a soliciting of sales and use data from a sampling
of individual manufacturers, and by surveying specific industrial sources
to determine the distribution of fabric filter equipment among the dif-
ferent industries. The quality and extent of the data thus obtained,
however, was limited to order of magnitude accuracy.
When filter applications in process industries are included,
.. . 4
the estimate of total yearly sales rises to more than 10 collectors.
Based upon the rate of growth in the number of filter manufacturers, (10
and 30, respectively in 1950 and 1960), the gross number of collectors
sold over the 20 year period, 1950 to 1970, is estimated at 2 x 10
-------
collectors. The same information sources suggest a historical growth rate
in the fabric filter industry of about 77o and within the last few years,
an approximate doubling of this rate. Refining of the above statistics
beyond the levels cited here is beyond the scope of the present program.
o
3.1.2 Distribution of Equipment
In contrast to other types of particulate control equipment,
notably, electrostatic precipitators, fabric filters can be operated
2
economically in all sizes including units with as little as 10 ft cloth
area. This fact, plus the broad capabilities of fabric filter equipment,
K £
explains the 10 to 10 units of equipment that are in use. These appli-
cations might be categorized by effluent volume rate, particle size dis-
tribution, gas temperature, gas or particle corrosivity, industry, product
or plant operations. It is unfortunately very difficult to analyze the
distribution of the equipment because of the lack of national inventory
data noted above.
An important portion of this study was the identification of
needs in specific areas of application, together with a measure of the mag-
nitude of each need, in order to justify possible subsequent R&D atten-
tion. The survey data have been collected across ten industrial cate-
gories, and in these same categories, the equipment distribution was ex-
amined using what manufacturers data were available. Distribution of sales
for two recent years is summarized in Table 6.
Most of these major categories embrace several industries,, e.g.
non-ferrous metals includes primary copper, secondary copper, zinc gal-
vanizing, and aluminum. Only in the non-metallic mineral category was
a systematic survey of air pollution control equipment found. (See Appen-
dix 1, Volume 2). The manufacturers' data in general did not specify the
industrial process on which the filtration equipment was used. Thus,
within the allocated program effort the distribution of filtration equip-
ment among industries and industrial processes could not be determined
quantitatively.
However, numerous APCO and other reports summarizing air pol-
lution control activities in various industries enabled a listing of about
-------
TABLE 6
DISTRIBUTION OF IGCI FABRIC FILTER SALES FOR
AIR POLLUTION CONTROL*
Category
Combustion
Food and Feed
Pulp and Paper
Inorganic Chemicals
Organic Chemicals
Petroleum Refining
Non-metallic Minerals
Iron and Steel
Non-Ferrous Metals
Miscellaneous
Percent Sales,
Count Percent
0.4
5.8
1.2
2.5
13.0
0.6
6.4
12.0
2.1
56.2
1966-67 Averages
Dollar Percent
1.6
5.4
0.9
3.6
18.7
1.2
18.4
29.1
5.2
16.2
Reported in greater detail in Tables 1.4 and 1.5, Volume I.
-------
300 processes generating dusts and fumes. A condensation of this list,
showing present and potential applications for fabric filters appears in
Appendix 1. Usually the data source did not give details as to the ex-
tent of use of fabric filter equipment in these areas, nor were the needs
for fabric filtration R&D usually given. Discussions with users, manu-
facturers, and review of the literature contributed to a subjective appre-
ciation of the relative importance of various applications and needs.
f
Table 7 indicates the prder-of-magnitude potential for fabric
filtration equipment in a variety of industrial applications. To the
present time, use of filtration equipment has been non-existent or at least
very limited in these areas. The specific applications were selected from
a larger list (see Appendix 1) either because they appear to have high po-
tential or because they represent a general class of operations that
might be controlled by filtration equipment. Examples of the latter are
sulphuric acid plants and kraft pulp digesters which typify high moisture
content and odor producing operations, respectively. Successful research
and development of fabric filtration equipment for control of these areas
would have far-reaching applications in other industries.
Three parameters are given in Table 7, each of which is basic
to the economics of the indicated applications. These parameters relate
to the probability that such applications might be considered seriously
in the near future by equipment manufacturers or purchasers without gov-
ernment assistance. The parameters also indicate the probable effect of
government or other third party assistance.
The first parameter, the sales volume of equipment that may be
expected over the next ten year period (Column 1), is a measure of the
interest that equipment manufacturers should have in these areas and
their willingness to personally undertake the necessary R&D work. These
figures are based on a) the present numbers and sizes of plants and the
degree of control presently exercised, b) the likelihood of enforcement
of plant control, c) the rate of growth of plant numbers and sizes, and
d) the replacement rate of present control equipment. It is assumed that
-------
TABU 7
ESTIMATED POTENTIAL OF FABRIC FILTER APPLICATIONS IN SELECTED PROCESSES
Application
(I)
Estimated*'
Filter sales
(10 yr.)
$ x 10-6
(2)
b)
Partlcultte
Yield
TPY x 10'6
(3)
Estimated
RU> Heeds
$
w
Incentive
Filter Sales/
Part. Yield
(5)
Indlcesc)
Part. Yield
R&D Dollars
High Yield
1.
Co«l fjred utility.
low sulphur fuel
900
40
105
20
400
Moderate Yield
2.
3.
4..
5.
6.
LOM
7.
8.
9.
10.
11.
Basic oxygen furnace
Kraft pulping.
Kiln
Recovery furnace
S02 acid- plant,
catalytic
Oil fired utility
Municipal Incineration
Yield
Calcium carbide plant
Cupola, Iron foundry
Kraft digester, odor
control
Secondary zinc processing
Coke ovens, pushing pro-
. ceaa .
40
20
10
10
100
50
0.2
30
2
(small)
20
0.7
0.4
0.2
0.4d>
0.2
0.1
0.03
0.02
0.02")
0.01
.007
3 x 105
5
10 5
2 x 105
105
3 x 10*
3 x 104
105
2 x 105
2 x 105
105
105
60
50
50
30
500
500
7
1500
100
..
3000
2
4
I
4
7
3
0.3
0.1
0.1
0.1
0.07
a) Replacement and substitution In existing plants and Installation In new plants
over the next ten years.
b) Additional partlculate emissions controlled at end of tenth year In tons per year.
c) Incentive Indices
Column 4 - ratio of columns 1 and 2
Column 5 ratio of colunu 2 and 3
d) Potential control of gaseous missions (tonnage not Included) by modified fabric
-------
filtration equipment will be developed to the point of being more attrac-
tive than equipment presently used. The indicated sales figures also
reflect present costs of filtration equipment, modified in accordance with
the problems expected for a proposed application.
The second parameter listed in Table 7 is the particulate
yield, that is, the amount of particulate pollutant that would be con-
trolled by these filter applications over and above the present degree of
control. For example, if filtration equipment were to be used on 100
plants, only 50 of which now have control equipment that is 80 percent
effective, then the filtration equipment is credited in Table 7 with a
yield equal to the emission of 60 uncontrolled plants. However, particu-
late material larger than about 10 microns is excluded from the estimates,
since it will probably be controlled more economically by other gas clean-
ing methods. In addition, the larger size fractions usually present much
less of a health hazard. Any gases that may be controlled are not includ-
ed in the yield figures.
The ratio of sales volume and particulate yield is given in
Column 4. The smaller this index number, the more likely the equipment
would be purchased by the indicated industry in the. absence of any addi-
tional incentive (assuming that pollution enforcement regulations apply
equally to all industries). For example, calcium carbide plants would
much more readily purchase the needed equipment than the iron foundries
and coke oven operators. In these latter cases, even if no R&D studies
were required, the equipment might still not be purchased without further
incentive.
The third basic parameter is the estimated cost of R&D programs
to establish the necessary filtration technology. These estimates are of
course especially difficult to make in a preliminary survey. In making
these estimates, the amount of industry experience with fabric filtra-
tion equipment, as well as the unique problems associated with each appli-
cation have been taken into consideration.
The ratio of particulate yield and R&D cost is given in Col-
umn 5 of Table 7. The larger the number, the more attractive is the
-------
expenditure |frottt the APCO point of view, e.g., the coal fired utility
application JLs especially attractive. In this instance, however, it
would appear reasonable that equipment manufacturers undertake responsi-
ild
bility for R&D needs because of the potential market. This would permit
APCO to support other needed control applications not offering\the same
sales incentives. ' ' ;
, /
3.1.3 Outlook for New Applications '>
\
Present usage of fabric filters is already widespread with
'\ Y
respect to both the number of units in service and the diversity in appli-
cations. It is believed, however,-that there are several operations for
which the substitution of fabric filter equipment might now afford engin-
eering and economic advantages. Additionally, collector design improve-
ments, stricter control requirements and changes in process economics may
lead to many future applications that previously had not been considered
feasible. The development of new processing techniques, e.g., the spray
process for making steel and new industries, and catalyst manufacture,
also point to fabric filtration as a prospective control method.
Thus, although it is difficult to predict the future size of
the fabric filter market, there is no doubt that the number and diversity
of applications will increase significantly.
The enactment of air pollution control legislation, which is
probably an important factor in recent increased usage of fabric filters,
will continue to play a large role for the next five years. Since the
most offensive emission sources have already come under scrutiny and are
being put under control, the following sources are likely subjects of
future attention:
. small volume systems
. remote (isolated) locations
. nuisance emissions
. unique operations
-------
Whereas many industrial processes were uncontrolled 15 years
ago, most new plants now have some degree of control. Within another ten
years, practically all older plants still in operation will use air pollu-
tion control systems if their emissions are in any way offensive.
The trend toward automation and continuous operation as op-
posed to batch processing is common to most industries. For continuous
flow of material, a large and increasing number of solids are now being
handled and processed in granular, powdered or palletized form rather
than in bulk form such as ingot or sheet. Since fabric filters are the
most popular means of dust control for dry powders handling operations,
this particular application may be expected to increase, for both pollu-
tion control and process convenience. In the latter case, the recovery
of valuable fines is an economically attractive practice that does not re-
quire legislative enforcement. The development of improved filter equip-
ment for air pollution control purposes, however, will also lead to still
wider process applications.
The largest users of fabric filter equipment are the metal
industries, e.g., iron and steel, aluminum, copper, zinc and lead. These
industries share the common problems associated with high temperatures and
very small particles that make emission control difficult with present
equipment. However, fabrics and hardware materials able to better with-
stand high temperatures are under continuing development. It may be anti-
cipated that improved fabrics and materials will increase filter usage
in these areas. Several other industries who share these same problems
will also profit by these technical advances.
Operating a filter near the dew point presents a problem com-
mon to many applications. Development of a filter system that can be
continuously operated while damp or wet would result in much wider usage.
The above R&D needs and many others are discussed in Section 3.6.
Combustion processes probably provide the largest current
source of uncontrolled particulate emissions. Special fabric filter de-
signs are now undergoing prototype evaluation on coal and oil-fired power
-------
plants and on municipal incinerators. Although electrostatic precipi-
tators and scrubbers have traditionally been used here (and will continue
to be used in some cases) the indications are that new developments in
filtration technology will greatly expand the use of filters in these
areas. One reason is that filters are also amenable to the control of
sulphur dioxide, other gaseous emissions, and possibly odors by using
absorbing additives. Control of emissions from institutional and domestic
incinerators, from residential and industrial heating plants, and from
automobiles and other vehicles suggest a large market for filtration equip*
ment of some kind, if and when such control is demanded and the equipment
is made available.
In terms of numbers, far more small fabric filters are sold
2
than large filters. For every single 100,000 ft installation, between
2
100 and 1000 units of order 100 ft capacity are sold. In addition to
the new emission regulation now being extended to the smaller sources,
public awareness and concern about their inhalation of small particles
are increasing. For the above reasons, the number of small fabric fil-
ters, sold per year during the next few years is expected to increase
sharply.
Industrial applications, however, will predominate in the
fabric filter market. Certain processes, notably fossil fuel combustion
and waste incineration, are judged to offer high potential for particulate
control by fabric filtration. These and other processes have been listed
in Appendix 1.
3.2 PERFORMANCE ANALYSES
The main reason for using a fabric filter system is to prevent the
release of particulate matter to the plant or outside environment, whether
it be for product recovery or anti-pollution purposes. Therefore, the
principal descriptor of performance is the collection efficiency of the
system.
The collection efficiency for filter installations, on a weight
basis, is remarkably high, almost always over 90%, frequently greater
-------
than 99%, and sometimes 99.9% or better. Other aspects of performance
more difficult to evaluate include the reliability of the equipment in
terms of the percent time it operates properly (usually 95% or better),
and the simplicity of operating and maintenance procedures.
The best efficiency data are probably that reported in the literature
(Appendix 6.4, Volume 2), because the authors reporting efficiency have
either made or had access to actual tests and were willing to document
the results. In contrast, most of the surveyed users of filter equipment
did not know how the efficiency, believing it to be so high that tests
had not been considered necessary. There were exceptions, of course,
particularly among users requested to conform to certain emission stand-
ards. Manufacturers seldom warrant the collection efficiency of their
equipment because the efficiency depends largely on the fabric, the dust
particles, and on the maintenance by the equipment user.
In defense of those users and manufacturers who did not state the
collection efficiency of their equipment, it is emphasized that efficiency
is a variable quantity over both the span of each cleaning cycle and over
the service of the fabric. Since in certain installations the collection
efficiency of the equipment appears marginal with respect to present and
future emission requirements, a study of efficiency is considered to be
one R&D requirement (Chapter 4).
As for the reliability of fabric filter equipment, both the litera-
ture and the user survey provided good qualitative data in the form of
problem commentary and suggestions for improvements (Chapter 8, Volume 1).
3.3 COST ANALYSES
In the previous section, collector performance was examined in terms
of system efficiency, dependability, and ease of operation and mainten-
ance. From a very practical standpoint, these attributes must be measured
against the cost to achieve the desired performance. Given a required
efficiency target, or a not-to-be-exceeded daily or hourly emission rate,
it is essential that cost optimization procedures be conducted to mini-
-------
mize the overall cost of fabric filtration. A detailed presentation of
cost data is given in Volume I, Chapter 7, of the Handbook.
Purchase costs for equipment and fabric media were obtained from
manufacturers, users and the literature whereas maintenance labor re-
quirements were derived chiefly from the user survey.
Data analyses were limited to development of tabular arrays and
averaging methods without attempting to infer quantitative relationships
between costs and the many contributing factors. In view of the rela-
tively small sample size, a more detailed analysis was not considered
justifiable at this time. The first step was to attempt to reduce cost
categories to some common bases as shown in the following tabulation:
1. Installed Cost
F.O.B. Fabric Filter
Freight
Fan and Motor
Ducting
Disposal Equipment
Instrumentation
Planning and Design
Foundation and Installation Labor
Start-up
2. Annual Cost
Electric Power
Cloth Purchases
Labor
Plant Overhead
3. Total Cost of Operation
Annual Cost
Amortization of the Installed Cost
Interest on the Unamortized Amount of Installed Cost
-------
Material costs were further adjusted to reflect 1969 price levels,
using the Marshall and Stevens index. Despite these adjustments, how-
ever, ambiguity remained in some statements of cost, for example, liter-
ature reports stating that "The equipment cost $16,000 including the set
of bags" might be construed to mean the cost of the dust collector as
shipped, the collector alone installed, or installed plus one or more
ancillary cost items. Income tax rebate for costs of replacement parts
such as fabric may or may not have been included. Certain overhead items
may be charged against the filter system or may remain hidden to the
engineer-author making the report. Furthermore, it was not always pos-
sible to clarify these points during interviews with equipment users, al-
though the user data are probably more reliable than the literature data
in these respects.
Equipment manufacturers and others have objected to reporting cost
averages on the grounds that they vary so much, that the averages will
confuse the inexperienced. In order to avoid misleading statements, our
cost averages are qualified by a statement that certain costs may vary by
as much as a factor of ten from one installation to another. Additionally,
specific costs for a number of representative installations have been
tabulated in detail in Appendices to Chapter 7, Volume 1, in an effort to
avoid misunderstandings.
3.4 ENGINEERING DESIGN ANALYSES
3.4.1 Collector Design
Over 100 different filter models are sold by the approximately
50 manufacturers of fabric filters. The word model is used herein to
distinguish between collectors having variations in the design parameters
listed below. Most models are available in either several discrete sizes
or in a virtually unlimited range of sizes:
Collector Design Parameters Analyzed
Type of Filter Element
Bag, Tube or Envelope
Flow Directions
Upward or Downward
Inward or Outward
-------
Length, Diameter, and Spacings of Filter Elements
Type of Element Fastenings
Cleaning Method
Automatic Shaking, Vibration, Rapping
Reverse Flow, with or without Flexure
Pulse, Reverse or Forward
Reverse Jet
Sonic
Manual Shaking
Housing
Materials of Construction
Methods of Joining
Inlet and Outlet Valves
Most manufacturers furnished complete sets of their collector
product brochures thus providing an excellent data base for available
equipment.
The information given in Appendix 3 constitutes a useful guide
in system planning or for equipment purchase since it provides data in
the following areas:
Manufacturer's Name, Address
Model Name
Configuration
Envelope of Cylindrical Filter Element !
Upward of Downward Flow ,
Inside or Outside Filtering I
Method of Cleaning the Filter Fabric 1
Sizes Available as Standard Items '
Types of Service Provided by the Equipment ;
i
It is emphasized that no information on cost or performance ',
appears in Appendix 3. As noted previously, the results of the literature
and user surveys did not provide sufficient data to generate detailed cost :
and performance analyses. Yet, the choice of design parameters given in
Appendix 3 has a far reaching effect upon several factors relating to
cost and engineering performance. The best possible qualitative assess-
ment of these design factors has been discussed in Chapter 3, Volume I.
i
3.4.2 Fabric Design j
While the program plan did not permit an exhaustive survey of !
fiber and fabric manufacturers and filter manufacturers and suppliers, a
-------
list of 55 firms was prepared (Appendix 4, Volume 2), that is estimated
to comprise at least three fourths of such U.S. firms.
There are, however, hundreds of firms throughout the world
including the U.S.A. who are engaged in the manufacture of fibers and
fabric that are not used by or sold to fabric filter manufacturers. These
firms represent additional sources of existing and new filtration mater-
ials depending upon advances in technology and changing economic factors.
The filter fabric manufacturing industry appears to be char-
acterized by a relatively small number of principal fabric weavers and
filters. This is probably the result of competitive factors. First, the
filter fabric market occupies a small portion of the total fabric market
for these manufacturers, and second, the capital investment necessary to
produce filter fabrics is large. Also, the manufacture of such fabrics
continues largely as an art in which experience and reputation are impor-
tant. At the present time, the following observations can be made:
(1) The design of a fabric specifically for dry filtration is limited
mostly to applications having sufficient sales volume to make the enter-
prise profitable; (2) The relatively small number of fabrics used in dry
filtration are sold or supplied by numerous firms under a variety of trade
names; (3) Much of the design technology that has been developed is pro-
prietary; and (4) There appears to be a considerable opportunity for R&D
in the development of the filter fabric.
For the reasons stated above and because of limited perform-
ance and cost data, the analyses of fabric design parameters were treated
on a qualitative basis. (Design: Chapter 4, Volume I; Cost: Chapter 7,
Volume I).
Fabric Design Parameters Reviewed
Fiber Material, Diameter, Length
Yarn Twist, Plies, Weight
Weave Pattern, Felt Construction
Treatments - Chemical, Mechanical
Properties - Chemical, Mechanical
-------
3.4.3 System Design
The collector, the fabric, and the necessary fans, ducting
disposal facilities and other auxiliary components constitute the fabric
filtration system.
In order to assemble a filter system, it is necessary to
consider such factors as the properties of the dust, the steadiness of
the process effluent flow, the ventilation needs at various system exhaust
points and the quality and location of release of the filtered effluent.
The following aspects of system design are discussed in the Handbook,
Chapter 5:
Filtration System Design Analyses
Effluent Definition
Collector Selection or Design
Fabric Selection
Fan Location (Suction or Pressure
Operation)
Cost Trade-offs and Minimization
There are many decisions to be made and many specifications
to be prepared in the design of a fabric filter system. Since the fac-
tors entering into the design of a system may not carry equal weighting
in all situations, no simple design formula can be presented. Consequently,
the approach followed in this study was to describe a general design ap-
proach with emphasis on interrelationships problems to expect and/or to
avoid and methods of minimizing costs. The overall system design process
is one area where R&D effort does not appear helpful, because the process
is so much a matter of experience and judgment. Design or selection of
individual components of the system, however, may be facilitated through
R&D, (Chapter 4).
3.5 FUNDAMENTAL ANALYSES
Although the understanding of many aspects of particle and fiber
relationships is fairly well developed, theories for predicting the
mechanics of collecting and removing particles from a fabric have yet to
-------
Although no results of manufacturers' research have been reported, it is
known that their studies also have followed the same path.
3.6 OUTLOOK FOR NEW DEVELOPMENTS
Fabric filtration has a strong future both in well, established and
in new applications. The use of all types of particulate control equip-
ment will parallel the anticipated industrial growth. In addition,
fabric filtration will increase to a greater extent because of its unique
capabilities. These are notably the ability to collect dust particles at
very high efficiencies which will be of value with stricter emission re-
quirements, and the ability to control smaller sources of emission more
economically than other types of control equipment. Furthermore, fabric
filtetion offers considerable potential for the control of gaseous emissions
for which there is little control technology at the present time. Similarly,
filtration appears adaptable to the abatement of nuisance odors and
visible plumes which will be of increasing value as society continues to
emphasize the individual's esthetic senses as well as his health.
Present applications of fabric filters will expand with improve-
ments in filter equipment and technology. With respect to existing fabric
and hardware designs, some modest gains can be expected due to improved
materials, closer process control, and better understanding of the fil-
tration process. With better understanding, radically new filter designs ,
enabling, for example, economical particulate collection at filtration
velocities of 100 fpm or more, may evolve. Hybridization of control
equipment (e.g., electrostatic fabric precipitatdr-filter; spray-cleaned
filter) may also be expected to result in wider application of the fil-
tration principle.
Traditionally, developments in particulate control equipment
have been slow in starting, as evidenced by the fact that today's basic
equipment differs little from that in use 100 years ago. Most filtration
fabrics are very similar to other textiles. One big reason for the lack
of progress is that successful innovation requires field trials, where
the cost of failure to the trial plant is large. Therefore the risk must
be small, and the innovation can be only a small departure from the
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traditional design. Another reason for slow development is the high
cost of experimentation sufficiently extensive to be meaningful. This
cost is large compared to the R&D budget of most equipment manufacturers
which is low partly because of the highly competitive aspects of filter
manu fac tur ing.
While significant new concepts may not be developed by the individual
manufacturer, limited as he is in available capital and personnel, new
developments nevertheless appear possible. New developments may properly
be the function of a joint organization representing the pooled resources
of several or all manufacturers, such as the Industrial Gas Cleaning
Institute. This practice of joint R&D has been successful in a number
of industries in expanding product acceptance. Alternatively, R&D may be
funded by government agencies who are responsible for particulate con-
trol. Such concerted development efforts might greatly benefit the fabric
filtration industry.
3.6.1 Concurrent R&D in the U.S.
Air pollution control equipment manufacturers are estimated to
have spent $5 x 10 on 1969 R&D programs, based on figures reported for
1965 through 1967 by the IGCI. This is of the order of 4% of total air
pollution control equipment sales, of which about 30% is fabric filtration
equipment. Thus approximately $1.5 x 10 was probably devoted by the
manufacturers to fabric filtration R&D. These figures are compared with
*
those of other industries given by the U.S. Department of Commerce.
Est. 1969 Expend. Est. R&D%
for R&D of Sales
Chemicals & Allied Products $1,760 x 10 3.7
Stone, Clay, and Glass Products 200 x 10 1.3
Fabricated Metal products 185 x 106 0.5
Machinery 1850 x 106 2.9
Motor Vehicles and Other ,
Transportation Equipment 1400 x 10 3.0
Prof, and Scientific instruments 500 x 10 3.3
1969 USDC "Abstract of the U.S."
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When the fabric filtration equipment R&D expenditure of $1.5
x 106 is divided by the number of manufacturers in the U.S. (about 50)
or by the 10 manufacturers accounting for about 80% of the total equip-
ment sales, the expenditure on R&D is estimated to be approximately:
$120,000 for thejtypical large :tnanufacturer
$350,000 for;the'largest manufacturer
$ 0 for the smallest manufacturers
According to the IGCI figures, approximately one-third of
the R&D monies were spent in each of three areas:
. improvement of existing equipment
. development of new equipment,
. research in new areas :
To what extent these expenditures should be truly classified as R&D is
arbitrary; certainly R&D in sheet metal fabrication differs considerably
from that in aerosol physics. Possibly the figure of 4% for fabric
filtration manufacturers is misleadingly large. At any rate, since the
nominal cost of a fabric filtration R&D program is of the order of
$100,000, it would seem that few R&D programs of fundamental nature are
funded by equipment manufacturers.
Filter users perform a smaller amount of R&D than manufac-
turers. Their efforts are generally confined to a specific application
and are generally not made public unless the project is supported in part
by public funds.
3.6.2 Collector Developments
Because fabric filtration equipment has been available for
many years and has been applied to many dusts, it has already been the
focus of many design, operational, maintenance, and economic analyses of
varying depths. Thus, without new or more radical changes in design
concepts, it does not appear likely that much improvement or increased
usage of present equipment will ensue. Manufacturers are of the opinion
they have exhausted all major avenues to improved performance and re-
duced costs. The equipment has been subjected to years of competitive
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selling; indeed, the competitive squeeze has pushed some equipment to the
point of being shoddy. Although this same competition has given us the
reverse jet and the pulse cleaned principles, such innovations occur only
rarely, and are the exception rather than the rule.
Minor innovation continues, of course, in the form of changes
in construction materials, fabrics, and instrumentation. These improve-
ments will continue as long as manufacturers are cognizant of the prob-
lems their customers are having with the equipment (Chapter 8, Volume 1).
But without a much greater effort, only minor developments can be ex-
pected.
This pessimistic view is supported by a review of the costs
of fabric filtration. As Chapter 7, Volume 1 shows, the cost of the
filter itself plus related capital costs represents only about 10% of
the total cost of filtration. Thus to cut manufacturing costs by one
tenth, a major effort for any well-established product, would amount to
a reduction in total user cost of about 1%, which is a rather small in-
centive. Consequently, it is unlikely that much effort will be made.
A similar argument can be made for fabric purchase costs. A longer fab-
ric life is apt to mean a more expensive fabric, but may result in fewer
sales per year. The net manufacturer profit level must be maintained in
order for the R&D necessary for extending fabric life to be volunteered.
(These arguments are superficial to a more complete economic analysis
which involves the supply-demand relationship and the manufacturer's over-
head and profit structure.)
Fortunately, with radical changes in design viewpoint on the
horizon better filtration equipment may result from several potential
"breakthroughs". New particle technology, new demands for gaseous and
odor controls, and new requirements for emission and control reliability
have altered the traditional task of filtration equipment. Changes in
the cost of maintenance labor compared to the cost of equipment must now
be recognized. New configurations are now of marked interest, and even
configurations conceived years ago but rejected because of unfavorable
economics or limited technologies may now be practicable.
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3.6.2.1 High Velocity Filtration.- Although particles can
be filtered over a wide velocity range, the power requirement rises with
increasing velocity. In addition, the collection efficiency may not
necessarily be favored by high-velocity filtration. Despite higher power
costs for increased filter velocity, the size, cost and the space occu-
pied by the collector all decrease with higher air/cloth ratio thus of-
fering interesting trade-off potentials. The cost of maintenance may or
may not decrease. The collection efficiency, however, can be influenced
considerably by fiber geometry, size, and surface treatment, and by con-
trol of the electrostatic relationship between fibers and dust particles.
Since efficiency is also dependent on particle size, collection improves
with agglomeration ahead of the filter. Thus, although present-day tech-
nology appears to require filtration velocities of the order of 1 to
10 fpm, velocities of 100 fpm or considerably higher may eventually soon
be practicable.
Adequate efficiency at 100 fpm using a half-inch mat of stain-
less steel fibers has been reported for a Michigan cupola operation.
Open hearth fumes were successfully collected ten years ago using a 2-
inch deep mat of slag wool, at velocities of 150 fpm. These applications
of high velocity filtration demonstrate the technical feasibility of
particle collection at high velocities.
An important requirement for high velocity filtration is the
cleanability of the medium. For effective operation, all of the dust
deposited during the previous loading cycle must be removed with virtually
no damage to the filter. The open hearth deep bed filter could be ade-
quately cleaned, even though a) such beds of high-temperature fibers tend
to be more fragile than fabrics, and b) the deposit tends to require
more cleaning energy at the higher collection velocities. Although the
other pilot applications mentioned are still in progress, there is little
question that suitable cleaning methods, probably based on current prin-
ciples, will be found.
The final and overriding question is the economics of high-
velocity filtration. The slag wool filter was finally deemed uneconomical
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because of the higher-than-expected cost of generating and recycling the
slag wool. The cupola application uses a fixed rather than a re-cycled
bed; on the other hand the cost of the stainless steel fiber mat is
2
high at the present time (about $10 per ft ). Fiber cost per year is
hoped to be comparable to present fibers. Although it is difficult to
predict what the operating filter pressure loss will be, the fact that
the cupola effluent is under considerable pressure will aid in reducing
overall power requirements. In comparison with the conventional filtra-
tion cost average of $l/CFM-year, projected high-filtration estimates
are attractive.
3.6.2.2 Wet Filtration.- Operating a conventional fabric
filter system near, at, or below the dew point of the gas mixture is al-
most always hazardous for several reasons: Liquid adhering to the fibers
blocks the interstices and raises the pressure differential even to the
point of stopping the flow; liquid acts as an adhesive between particles
and fibers, making a mud not removable by the normal cleaning procedures
and which may plug or blind the fabric irreversibly; many condensates
are acidic and attack the dust collector panels, the fan, and the fabric.
Generally, operation below the dew point is one of the greatest hazards.
On the other hand some cement dust fabric filters are reported
to function adequately when damp. These examples of effective particu-
late control with fabric under dew point conditions may point the way to
a reduction of condensation problems in fabric filtration, enabling cooler
and more economical operation without fabric blinding and plugging. There
are many possibilities for research and development in this area including
the opportunity for concurrent wet-process odor control. The field is
not a fresh one by any means, but new synthetics and changing economics
make reassessment worthwhile.
' 3.6.2.3 Cleaning Methods.- It appears that at present all
possible cleaning methods are being used, e.g., vertical and horizontal
shake, radial pulsing, shock, vibration, etc. Nevertheless, careful
-------
analysis of these present methods will reduce them to a small number of
basic cleaning principles, such as tensile strength rupture, shear and
stripping. A rigorous analytical approach may then suggest other useful
cleaning methods.
Various combinations of cleaning methods are now being used,
for example, shake plus reverse flow, and sonic plus pulse. It is quite
probable that new and perhaps more effective combinations will be sug-
gested by the analyses just described. These analyses would involve de-
tailed study of conventional equipment as well as laboratory cleaning
studies.
3.6.2.4 Porous Ducting.- Many schemes have been tried over
the years to concentrate an aerosol prior to particle removal with the
objective of reducing the size required for the final separating equip-
ment. These attempts have included inertial, electrostatic, thermal and
other separating methods. Except for large particles, however, they have
not been very successful, the main reason being that medium efficiency
collection of small particles costs almost as much as high efficiency
separation.
The concept of using a porous duct ahead of a pressurized
filter to bleed off part of the gas going to the filter has been suggested.
As might be anticipated, the problem is how to clean the inside of the
duct. Sufficiently high velocities (15,000 fpm) are unquestionably
capable of lifting and/or dragging large particles away from a tangential
surface. Possibly a special duct lining configuration and/or high gas
turbulence levels, could make the duct more self-cleaning at lower vel-
ocities. More likely, some additional cleaning process would be needed,
such as internal or external gas pulsing, a reverse jet traveling out-
side the duct, or a spinning hydrofoil inside the duct.
The economics of porous duct separation are only moderately
attractive, but would be more attractive if the permeation velocity
through the duct could be increased above that through the fabric,
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taking advantage perhaps of the fact that no collection of particles is
necessary in the ducting and should be minimized. In adopting the use
of porous ducting, one would be replacing a closely packed system of
fabric cylinders with an elongated metal cylinder. The advantage arises
through utilizing a presently existent but unused area in exchange for
expensive fabric and plant floor area. Additional attractiveness could
conceivably come from new filtration technology.
3.6.2.5 Custom Designs.- At present, only large filter col-
lectors are custom designed for specific applications. Smaller collec-
tors are stocked by manufacturers and their distributors, and sometimes
by users of large numbers of these collectors. In keeping with trends
in other industries, custom designing will become available on smaller
units using computer programs, greater standardization of parts and mod-
ules and automated assembly, etc. This will enable optimization in
shapes and sizes, the use of multiple construction materials and more
economical structures. Even new fabrics will be designed by computer.
Manuals for operation and maintenance will be more closely tailored to
specific applications.
3.6.2.6 Hybrid Filtration.- In the Handbook, various dust
collectors using both fabric filtration and at least one other dust con-
trol principle have been mentioned. Such hybridizations of conventional
types of equipment are summarized below:
I. Fabric filter used as primary stage
A. As an open mesh fabric leading agglomerates
to a secondary collector, e.g., a normal
fabric filter, a cyclone, or a settling
chamber.
II. Fabric filter used as secondary stage
A. As a collector of agglomerates from a
pre-conditioning process such as
1. Triboelectric interaction between
aerosol and mat, mesh, or granules,
in either a fixed or a fluidized bed;
2. Electrostatic corona charging; or
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3. Spray scrubbing with the droplets
fully evaporated. Droplets may
also be charged for added collec-
tion efficiency.
B. As a collector of both wet and dry par-
ticulate, either
1. Self-draining if the liquid fraction
is sufficient, or
2. Spray-cleaned, primarily with rela-
tively open fabrics or mats.
III. Single stage fabric filtration, with added con-
trol;
A. Using an electrostatic control of the deposit
structure, during formation;
B. Electrostatic transfer delay of filtration
to a downstream part of the filter tube,
for greater initial fabric permeability.
C. Electrostatic removal of dust deposit from
fabric.
D. Other kinds of fabric or deposit control.
Since some of these prospects have already been explored by
manufacturers, the first step in any development program would be an
extensive review.
3.6.2.7 Miscellaneous.- Innovations to be seen in future
filter collectors may include:
. rotary filter elements, possibly using centrifugal
force for cleaning
. rotary cleaning vanes or foils past stationary
filter elements
. pleated fabric for more rapid installation in
roll lengths than separate filter elements
. water or oil-sealed bag ends, for more rapid
installation than thimble attachment, and to
eliminate flexure near the thimble
. formed-in-place filter elements, using heat or
time-setting adhesives and blown-in fibers.
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3.6.3 Fabric Developments
Glass filter fabric represents an outstanding filter fabric
breakthrough, primarily because of its temperature capability at low
cost. Considering the materials development programs underway in all
fields - ceramics, alloying, metal fibers, adhesives, laminating, mole-
cular structures, etc. - it is virtually certain that new filtration
fibers will continually be appearing. Along with these new fibers will
be developed better fiber surface treatments for improved performance,
for example, more durable lubricants for high temperature applications.
Improvement in fabric performance is the attribute most widely
sought by filter users. Longer lived fabrics are especially wanted,
notably those capable of withstanding flexure. For some applications of
fabrics not tolerant of flexure rigid fibrous mats appear to be more
feasible. Fabrics resistant to corrosion from acidic gases and fluorides
are much needed. Higher temperature fabrics more capable of functioning
in the range between 200 and 1000 F would find immediate applications
partly because all fabric durability problems are accentuated at increased
temperatures.
One obstacle to the development of more useful fabrics is an
understanding of their requirements at the particle-fabric and particle-
fiber interfaces. Fabrics have traditionally been 100% one material such
as cotton, or glass. The use of two or more materials has more recently
been seen in synthetic blends, and combinations of materials are likely
to increase. For flexure-tolerant fabric, for example, in a situation
where the flexure is primarily two-dimensional, steel-fibered yarn might
be used to withstand the flexure, while in the unflexed dimension less
expensive glass yarn might be used to collect the particles.
Fabrics or filter elements that are manually controllable
may be developed. At present filter elements are passive; once installed
the user has very little control over their performance although he has
modest control of their life. Fabric or filter elements might be con-
trolled in efficiency, or in porosity and permeability, by differential
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tension or positional adjustments of warp or fill yarns. Fabrics having
electrostatically controllable properties for use in hybrid equipment
are within sight, as discussed above. Controllable filter elements would
enable optimization of performance, especially a distribution of perform-
ance over the life of the fabric.
Progress is also to be expected in fiber processing and fab-
ric cost reduction, including simpler methods of combining fibers and
other ingredients into finished filtration materials. Granules or sheet
media other than woven or felted textile may become popular.
Part of the cost of present fabric arises from the many steps
leading to their preparation, fiber spinning, fiber treating, weaving,
finishing, fabric treating, sewing and installation. Possibly an over-
view of this long process would shorten it. For example, fibers being
spun might be blow-cast inside a traveling cylinder, to form an endless
filtration tube having predetermined properties. The tube could be sold
as a roll and cut to length. Or, fibers might be blown as filter aid is
blown into the dust collector, against wire mesh, and then bonded in
place for normal cyclic filtration. The techniques for doing this need
not be too complex for the filter user, especially if the blowing and
bonding equipment were to be incorporated with the basic collector. In-
cipient holes might be patched with this capability of adding and bonding
fibers, somewhat analogous to automobile radiator repair.
3.6.4 System Instruments and Controls
At present, small dust collectors are seldom equipped with
instrumentation, and even the largest filter systems see only marginal
use of control devices.
Those instruments commonly used or potentially useful to
describe or control filter system operations are listed below:
Temperature
Pressure
Indicating ^^^ ./" Flow
n ,. \ / Dew Point
Recording V' Acidity
Controlling^/' N^ Electrometric Properties
Particle Properties
Fabric Properties
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There is a well established trend to select equipment that
operates with a minimum amount of attention, because of the increasing
cost of labor. Since the cost of standard instruments and controls is
not increasing as rapidly as labor, and since the capabilities of these
devices are steadily improving, their increased utilization is inevitable.
Demands on filter systems for more reliable dust collection at lower
costs may also be expected to result in greater application of instru-
ments and controls.
3.6.4.1 Particulate Properties.- Changes in the generating
process temperature and materials handling rate may affect the size,
shape, stickiness, electric charge and electrical conductivity of the
suspended particulates. The influences of these properties on the opera-
tion of the filter system requires better understanding. Likewise, the
stability and uniformity of the particulate loading and the degree of
agglomeration approaching the fabric, will take on added importance.
The effect on system operating cost of one or more of these particulate
properties may well justify sensing and perhaps control of that property
by on-line instrumentation.
There is already a need for on-line continuous duty monitor-
ing of the low-level emissions from fabric filters. Certain emissions
are marginally visible, and at present, visibility is frequently the
criterion for evaluating collection performance. Since barely visible
concentrations are of the same magnitude as legislated values, an instru-
mental aid to emission evaluation is needed. Laboratory instruments are
available, but none are capable of continuous, service-free operation in
a harsh industrial environment.
3.6.4.2 Dust Deposit Control.- The addition of large par-
ticles to the dust deposit may lower the deposit permeation resistance,
improve deposit release from the fabric, and improve the handling of the
collected dust. These particles may be a material foreign to the emis-
sion system (an additive such as limestone added to a flyash), or the
normal larger fraction of emitted particulate kept in suspension by
preventing gravitational or inertial separation prior to the filtration
phase.
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Forced agglomeration of the finer fraction of the process
effluent prior to filtering may also serve to provide larger particles.
In addition, agglomeration will hinder penetration of the fabric by
the fines thus reducing blinding, interstitial abrasion, and seepage
problems. Agglomeration might be enhanced by an increase in retention
time between source and filtration zone or by controlled turbulence dur-
ing the pre-filtration period. Electrostatic charging preceeding filtra-
tion will accelerate the agglomeration process and may also create more
rigid agglomerates. Humidity and temperature doubtless affect agglomera-
tion rate as well as agglomerate structure.
Agglomeration can be achieved with most particulate control
equipment when it is deliberately operated at low efficiency. A low
efficiency and inexpensive electrostatic precipitator, open mesh grid
filter , or even a scrubber can increase the agglomerated fraction of the
aerosol. The open mesh filter appears especially promising if cleaned
by natural or timed loosening of the deposit in such a way that its steady
state efficiency is zero. The "conditioned" or agglomerated material
then passes on to the filter. Agglomeration ahead of the filter, which
usually enhances filter performance, also should be economical from the
system viewpoint. In the extreme case, agglomeration would eliminate the
need for the filter, since the particulates could then be removed mech-
anically by lower cost methods.
The addition of a surfactant might affect the electrostatic
properties of the particles, the rate of agglomeration, the strength of
the agglomerates, the structure of the filter deposit, the ease of de-
posit release from the filter, or the ease of handling of the collected
material.
The emission or source process might be modified for improved
control of particle shape, size and surface properties if the "optimum"
particle could be defined and measured. Although not a new idea, little
has been done in this area for want of particle technology, instruments,
control techniques, and above all, the failure to recognize the high
costs of inadequate particle control.
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3.6.4.3 Gaseous Properties.- A dewpoint sensing and alarm
or control system is widely needed to reduce the danger of condensation
damage while allowing operation of the filter system closer to the dew
point. Cooling the gases an additional 25 F without danger of condensa-
tion could easily mean a 570 smaller flow volume and a commensurate power
cost reduction. The greater saving might be in avoiding incipient con-
densation and its costs.
Temperature, pressure and flow sensors are now readily avail-
able. Closer control and hence more economical operation of the filter
system is often possible using automatic control equipment based on these
sensors. This automatic control equipment is for the most part com-
mercially available.
3.6.4.4 Fabric Instruments.- A notable fabric-related oper-
ating problem is determining when the filter element has had sufficient
cleaning. This is customarily solved by manually adjusting the cleaning
process to obtain a satisfactorily low equilibrium residual filter drag.
Although the manual adjustment process may be practical in some cases,
the rather elementary logic involved suggests replacement by automatic
equipment. Automatic adjustment of the cleaning cycle would enable not
merely daily, but hourly or more frequent adjustment if warranted. It
is only necessary to define the trade-off between the cost related to the
cleaning action and the value received from the lower residual pressure.
A simple instrument for checking tension might be useful.
There is, at present, no way of measuring the tension in the filter ele-
ment, partly because the correct tension is unknown. Another expressed
need is for instrumental aid in locating holes in the filter element and
even more important, potential failure points.
3.6.4.5 Filter Control System.- An increasing number of
sensors that respond rapidly to changes in particle, gas or fabric prop-
erties would appear as likely and necessary components in present and
future fabric filter systems. For optimum utilization and economy,
these sensing instruments could be packaged as standardized modules
-------
for insertion in the central control console. A package would consist of
a solid state logic circuit fabricated as a plug-in module and standard-
ized to adapt to a large number of filter systems. A multiplicity of the
devices could be selected from a catalog to provide operational instruc-
tions, data, recorder procedures and alarm or caution signals. Tha units
would display the dependability of solid state equipment with the cost
advantages of off-the-shelf large production volume equipment.
A modular design control system could be either very simple
or highly sophisticated while using the same basic components. It would
enable more accurate operation than periodic manual adjustment by virtue
of continuous optimization of the performance/cost relationships. The
function of the control system would be the same as that achieved by on-
line computer control in larger processes, but in this case, the "com-
puter" would be merely an assembly of analog logic modules. In design-
ing the control system, the engineer would tend to allow for reserve
system capability.
3.6.5 Extensions of Fabric Filtration to Gas Collection
The selective removal of gaseous components or odors from an
effluent has not until the last ten years, received the attention of
particulate control. Consequently, the technology is still under develop-
ment, partly due to technical obstacles which make,gas and odor control
more difficult and more expensive than particle control.
Most air pollution control equipment is designed either for
particulate or for gaseous control, mainly because of significant dif-
ferences in collection parameters. A notable exception is the wet scrub-
ber in which moderate to high efficiencies are attainable with certain
combinations of particulates and absorbable gases. Simultaneous control
of both solids and gases.however, would be less expensive than separate
control systems because of the sharing of ducting, fans, and in the case
of fabric filter equipment, the filter medium itself.
Since many particulate emitting operations are accompanied
by gaseous pollutants and objectionable odors, collectors designed for
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multipurpose use should have widespread application. The equipment would
presumably incorporate special features for the optimized control of each
type of pollutant.
Several experimental studies have shown that the aeroliza-
tion of finely divided absorptive or adsorptive granular materials into
the gas stream entering the fabric filter, will remove certain gaseous
components.
The fact that good control of high specific surface powder and
contact time are attainable with fabric filter systems suggests advantages
over other collector types. Most recently, the removal of up to 98.47,
of S07 by sodium bicarbonate powder on a fabric filter has been demon-
strated at a coal-fired power plant in a joint AFCO - Air Preheater Co.
study. Fly ash and some N02 are removed at the same time.
The optimum equipment design for gaseous and particulate con-
trol will probably not be much different from present filter designs,
except for the system used to introduce and probably recirculate the ad-
sorbent material. The addition of relatively coarse particle aggregates
to a filter cake should reduce power costs by increasing the cake por-
osity. Recirculation of agglomerated filter deposits appears feasible
but there are no reports of this having been practiced. It would appear
that agglomerate recirculation in conjunction with absorptive powder
recirculation would be attractive in several gas and odor control appli-
cations.
Similarly, although use of odor absorbing additives within
fabric filter equipment has not been reported, it appears a likely pros-
pect. Granular charcoal, catalysts, or fritted impregnated material
could be introduced to and removed from the filter, regenerated in special
closely confined equipment, and then recirculated. The regeneration
process might, in certain cases, develop chemical products of commercial
or combustion value.
A retardant to the development of odor control technology
is that very high control efficiencies are necessary, perhaps 99% or
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higher, in order to notice any reduction in odor, due to the broad re-
sponse characteristics of the nasal system. Another retardant to equip-
ment development is that odor is generally only a nuisance, and the
economic reward for its control is less tenable than that for most other
pollutants.
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CHAPTER 4
IDENTIFICATION OF RESEARCH AND DEVELOPMENT REQUIREMENTS
4.1 INTRODUCTION
During the survey of fabric filter installations described earlier
in Chapter 2 of this volume, those persons most familiar with the day-to-
day operation and upkeep of the systems were personally interviewed.
Their experience with operating problems and costs were of particular in-
terest and, therefore, included in the approximately 130 questions asked
during the interviews were the following:
- What are your principal causes of fabric failure?
- Have you tried other fabrics, and why are you using
the present one?
- Do you receive any complaints regarding the quality
of your filtered effluent?
- Do you have problems associated with fabric blinding?
- What, if any, are the major difficulties with your
filter system?
- What aspects of performance or operation could be
improved, based on your experience?
- What suggestions would you make for improvements in
design or manufacture?
- What do you see as the principle requirements for
research or development?
From the answers to these questions, 112 operating problems were
identified and analyzed (see Chapter 8 of Volume I). Also, from the
answers given, nearly 100 different suggestions for possible research and
development investigations were obtained. These suggestions, which are
presented in Appendix 4, together with other comments made in the litera-
ture and by equipment and fabric manufacturers, form the basis for the
research and development programs that follow. The suggestions of more
than 75 users and manufacturers are represented.
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These suggestions have been interpreted to be research and develop-
ment needs, having varying degrees of importance to the industry. The
needs concern the overall filter system as well as specific system com-
ponents and the selection, and the operation and maintenance of the equip-
ment. The following condensed list enumerates the reported research and
development need areas:
Overall System Costs
Collector Design
Equipment Accesory to Collector
Fabrics - Quality and Design
Bag Fabrication
Selection of Fabric
Particles
Dust Concentration Instrumentation
Maintenance Aids
Process Instrumentation
Problems of Special Industries
Gas Cleaning via Fabric Filtration
Mechanical Aspects of Bag Life
Cake Formation and Cleaning of the Cloth
Chemical Resistance, and Wetness of the Cloth
General Fabric Filter Study Extensions
Generally speaking, the R&D programs that follow are justified by
the present costs of fabric filtration, by less than complete filtration
effectiveness, and by effluents that are presently uncontrolled or con-
trolled by other techniques, but which may be suited to control by fil-
tration. Despite the extensive and continuing development of improvements
in fabric filter systems by the equipment manufacturers, however, fabric
filtration is still costly, and in many cases operates at less than accept-
able efficiencies. In addition, fabric filter systems are not employed
in numerous areas in which they could be applied with appropriate appli-
cations engineering efforts or with the employment of some of the develop-
ing technology in the subsystems or material areas.
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We have grouped the research and development requirements into the
following three categories: (1) Studies of the fundamental particle-fiber-
gas mechanics involved in fabric filtration; (2) Studies aimed at improve-
ment of fabric filter equipment and filter fabrics; and (3) Studies attempt-
ing to demonstrate the effectiveness of fabric filtration in specific
applications. In terms of the organizations, laboratories and personnel
performing the studies, they may be quite different, as are. the objectives
of the studies. To a plant engineer faced with a dust control problem, a
fundamental study on filter-fiber-gas mechanics may appear somewhat aca-
demic, while to a research scientist desiring to improve the agglomerate
structure of the same dust, a field demonstration may seem quite limited.
All three types of study can definitely contribute to the present art,
however, and all have been included within our interpretation of the
expression "Research and Development Need".
4.2 DEFINITION AND CONTROL OF PARTICLE PROPERTIES
Both the performance and cost of fabric collectors are determined by
the properties of the particulate matter being filtered. These properties,
which are not completely defined or understood at present, include the
diameter, size distribution, shape, surface characteristics, electrostatics,
chemical reactivity, adhesiveness and hydroscopicity of the particles.
They affect the structure of the deposited cake; its flow resistance; the
power required for filtration; the rates of plugging and blinding; and the
rate of mechanical abrasion of the fabric. In addition, they influence
the particulate penetration through the filter, and thus, affect the col-
lection efficiency of the system.
If it were possible to determine the relationships between the par-
ticle properties and the cost-performance effects, in advance of extended
operation, significant operating improvements would undoubtedly accrue.
Furthermore, some control of the particulate characteristics might be
exercised, whereas at present this is rarely practiced. It may be possible,
for example, to modify the structural features of the dust deposit, through
an understanding of how the deposit is formed. The control of the particle
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size distribution reaching the filter may, in some cases, improve perme-
ability and possibly the cleanability of the fabric as well.
It is recognized that the selection or design of particulate control
equipment is dependent on both the dust-effluent stream parameters and the
engineering parameters of the filtration system in operation or planned
for installation (i.e., the specific design characteristics of the equip-
ment produced by different fabric filter manufacturers). For this reason
research programs dealing with particle properties should concentrate on
developing basic data relating these properties to operating performance
and cost which can then be applied by the different fabric filter manu-
facturers to specific applications problems and system designs.
4.2.1 Basic Particle Parameters
Statement of Problem - A fabric dust collector should be
designed to meet the filtration requirements of the dust being filtered,
but because the pertinent dust properties cannot be completely specified
at the present time, collector design and use is now less than optimum for
most application areas. The properties requiring theoretical and bench-
scale study include: deposition velocity and particle diameter; length-
diameter ratio; specific surfaces, angularity, and smoothness; chemi-
potential or surface energy, and effects of absorbed molecular layers;
initial electrical charge, distribution of charges, and rates and modes
of charge dissipation; hardness. Because no compilation of contributing
properties is available at this point in time, it is difficult to deline-
ate the relative importance of these factors in dust filtration.
Program Description - A literature, theoretical, and laboratory
study should be made of the particle parameters affecting the filter depo-
sition, accumulation, migration, and removal of representative dusts.
The processes of deposition and removal should be analyzed from theore-
tical considerations to determine the pertinent particle parameters and
to estimate the range over which they are significant. Micromeritics
literature should be surveyed to support the selection of these parameters,
and to provide order-of-magnitude estimates of their effects. These effects
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may then be combined as dimensionless parameters, or in other suitable
ways, to form a practicable basis for laboratory study. The laboratory
phase should verify that these parameter groupings can adequately repre-
sent the characteristics of representative dusts in fabric filtration,
and should provide order-of-magnitude indications of the importance of
these groupings. The study should thus provide a firm basis for more
applied investigations involving specific dust-fabric combinations.
Program Priority - High
Program Duration and Estimated Cost - The total cost for this
program area is estimated to be $110,000 allocated as follows across a
two year period:
First Year Effort
Equipment and Material Costs: $ 7,000
Manpower Costs: $43.000
Total: $50,000
Second Year Effort
Equipment and Material Costs: $10,000
Manpower Costs: $50.000
Total: $60,000
4.2.2 Deposit Modification and Control
Statement of the Problem - There is no universally accepted
theory for describing the dust deposit nor any simple means for measuring
its properties. There are indications that during the deposition process
the dust cake changes from a somewhat open to a more dense structure.
The end result may be described as cake collapse in the extreme case. To
a lesser degree, compression may be engendered by viscous drag effects,
by particle impingement, or by aging processes. Since deposit structure
determines in large part the overall performance of the fabric filter
system, it is difficult at present to establish suitable criteria for the
design of dust collectors.
-------
Program Description - The proposed study must combine the
theoretical aspects of particle technology with engineering practicality.
Deposit structure must be related to key particle parameters such as shape,
size, roughness and cohesive forces. Since the number of such parameters
could well exceed any practical manipulation, it appears advisable to in-
troduce, define and measure a small set of intermediate parameters (or
indices) such as:
. stickiness or cohesiveness
. deposit structure modulus
. probability of a particle depositing
at a fixed site or migrating through
the structure.
Fundamental particle parameters would be selected on the basis of their
contributions to the intermediate parameters. In turn, the latter would
be used to define the engineering aspects of the deposit control mechanisms
including costs, and the overall effectiveness of the filter system.
Task 1. Definition of Deposit - The first study task
will be to examine deposit structure in terms of fundamental properties of
the component particles and relevant structure theory. Deposit parameters
may be defined by geometric, Theological or statistical models of the struc-
ture incorporating whatever practical measurements can be made in the lab-
oratory by microscope techniques, charge measurement, or other methods.
The objectives will be to determine which variables should be incorporated
in the intermediate or "working engineering" parameters for use in successor
laboratory programs.
Task 2. Deposit Changes During Filtering - Selected
dust and fabric combinations along with representative variations of flow
and environmental parameters will form the basis for deposit studies.
Possible reasons for dust cake compression and collapse should be sought
and quantified. Suspect causes of compression are viscous drag which may
result in gradual or abrupt collapse, pressure excursions due to shock
waves from damper closing, mechanical vibrations, bag flexure, and depo-
sition impact of particles upon the collection surface.
-------
Alterations in cake properties can be measured in terms
of permeability, ease of removal, and penetration of particles through the
fabric as evidenced by downstream concentrations. Effects of humidity,
electrostatic charge, surge chambers to minimize pressure pulses during
filtration, additives and other factors that appear to improve cake pro-
perties should be investigated during both the Task 1 and 2 programs.
Task 3. Costing of Cake Control - Those mechanisms or
processes which appear to enhance cake properties will be examined criti-
cally in terms of economic and engineering feasibility. The effectiveness
of the cake control process would be assessed in terms of the basic perfor-
mance parameters, i.e., cake permeability, ease of cleaning, and overall
collection efficiency.
Program Priority - High
Program Duration and Estimated Cost - The total cost of the
program across a two year period is estimated to be $100,000.
First Year Effort
Equipment and Material Costs: $ 7,000
Manpower Costs: 38.000
Total: $45,000
Second Year Effort
Equipment and Material Costs: $ 3,000
Manpower Costs: 52.000
Total: $55,000
4.2.3 Particle Size Control
Statement of the Problem - The particle size properties deter-
mine in large part the porosity of the filter dust deposit and, hence, the
specific resistance of the dust cake. The addition of coarse particles
.is expected to reduce the resistance and possibly also facilitate cleaning,
but the fact that the total dust loading to the filter has increased has
a counter effect on filter pressure drop. Other adverse effects might
include increased mechanical abrasion and penetration through the filter.
-------
For these latter reasons the coarser size fraction is sometimes diverted
by relatively inexpensive inertial devices before the dust reaches the
filter. Prior conditioning of the dust by inducing agglomeration has also
been used to alter the particle size reaching the filter. While the sep-
arate effects of particle size alteration may be estimated, the overall
effects on cost and performance are difficult to predict in a general
manner, or even in a specific application. Because so many of the basic
fabric filter system cost and performance factors are related to particle
size, it appears that a separate study of optimum size control is well
justified.
Program Description
Task 1. Review of Experience in Particle Size Control -
The objective of Task 1 is to provide preliminary estimates of the initial
and operating costs of particle control methods. Primary information
sources will be the open literature including patents, and the unpublished
findings of fabric filter users and manufacturers. Additive techniques not
necessarily directed toward filtration application will also be considered
with respect to cost, materials and effect on size properties. Pre-separa-
tion of large particles by inertial collectors; agglomeration induced by
turbulence, increased retention time, or .electrostatic precipitators; use
of fiber lubricants; and the dimensional aspects of additive particles
should also be considered. The results of this study will include esti-
mates of the cost and performance of any auxiliary fabric filter equipment,
and project the overall filter system costs and performance. Furthermore,
the Task 1 efforts will provide a rational basis for the conduct of labo-
ratory and field experiments outlined below.
Task 2. Experimental Program - In selected applica-
tions, engineering studies will be made to verify the feasibility of the
more promising particle control methods. Pilot equipment would be designed
for laboratory tests and/or whenever possible, field trails. Preliminary
studias would be based on the particle treatments investigated during
Task 1 efforts, i.e., use of different additives, agglomeration techniques,
-------
or recycling of agglomerated hopper dust as the particle conditioner.
Subsequently, those techniques which appeared practicable in terms of cost
and system collection efficiency would be evaluated with various fabric
types, filtering velocities, and cleaning techniques. This program should
furnish improved estimates of how particle control techniques can be best
utilized. At the same time, evaluation methods developed during this study
will permit more rapid assessment of particle control methods proposed in
the future.
Program Priority - Medium
Program Duration and Estimated Cost - The total cost for this
18 month program is estimated to be $100,000 allocated approximately as
follows:
First Year Effort
Equipment and Material Costs: $10,000
Manpower Costs: 60.000
Total: $70,000
Next 6 Month Effort
Equipment and Material Costs: $ 3,000
Manpower Costs: 27.OOP
Total: $30,000
4.3 FABRIC INVESTIGATIONS
A recent survey of problems with operating fabric filter equipment
indicated that over half of the problems reported were in some way asso-
ciated with the fabric. Notable among these were problems of various
types of wear abrasion and problems of dust adhesion in which the dust
could not be removed with the usual cleaning method. Since fabric wear
is often accentuated by a need for excessive cleaning, it is evident that
the fabric surface plays a major role in fabric life and cleaning power
requirements. The fabric surface also affects the dust cake permeability,
and hence, the filtration power requirements. Apart from the fabric sur-
face, the geometry and mechanics of the fabric are related to the cleaning
process and fabric performance generally.
-------
While some laboratory work has been completed which relates fabric
properties to operating cost and performance factors, the studies have
been mainly exploratory. In general, quantitative predictions as to the
effects of fabric properties on system performance and operating cost are
not possible at the present time. This is undoubtedly one of the major
reasons that the needs and requirements have not been fully determined.
Even the selection of fabrics for specific installations is handicapped
by a.sparcity of performance data.
Likewise, the availability of fibers suitable for fabric filtration
appears limited at present, even though these fibers determine, to a large
extent, the characteristics of the filter fabric. Synthetic fibers have
recently made inroads on the traditional use of cotton and wool for filtra-
tion. Unfortunately, the total market for synthetic fiber so far outweighs
the market for filtration fiber that little, if any, synthetic fiber is
designed and produced specifically for dust filtration. This applies as
well to glass fiber, although finishing treatments for glass fiber help
significantly to tailor the material to specific applications. Thus, in
addition to studies of cost and performance of the available fabric media
and their surfaces, additional study should determine how improved fibers
can be manufactured for use in filtration systems.
4.3.1 Fabric Surfaces Study
Statement of Problem - Little is known about the electrical,
geometric, adhesive and mechanical properties of the filter fabric surface
despite the fact that the interface between the dust and fabric surface
is, perhaps, the single most important feature of the entire filter system.
In the present context, the filter fabric "surface" is defined as that
region of the fabric which, in successive loading and cleaning cycles, has
a significant influence on deposition and removal characteristics. Des-
pite the fact that there are many manufacturing techniques that might be
used to produce a broad range of surface properties, the filter user does
not possess the technical data required to specify which attributes are
most desirable in his fabric. Further, the common practice in the filtra-
tion industry has been to adapt available filter materials that appear to
-------
meet immediate gas cleaning needs into woven and felted media. In most
cases, the fabrics have not been designed with filtration applications in
mind.
Program Description - The object of this study is to determine
how the surface properties of filter fabrics affect the operational aspects
of the fabric filter system,, Therefore, the laboratory program should con-
centrate on the investigation of a large number of fabric surfaces. Re-
lated factors entering into overall fabric performance such as dust pro-
perties, gas flow rates, temperature, humidity, etc., should be treated
as minor variables in this study. This research should follow R&D Program
4.2.2, Deposit Modification and Control, since many dust cake parameters
defined in the latter study will provide useful background data.
Task Area 1 - Literature Review, Theoretical Approaches.
Experiment Planning - A review of the available literature and, in parti-
cular, the results of Task 1 of the Deposit Modification and Control Study
represents the logical starting point for this program. The main objectives
will be to define and characterize which fabric surface properties should
play key roles in filter performance. This will entail consideration of
weave, nap, smoothness, chemical treatments, mechanical and electrostatic
properties, and other related factors. In assessing fabric properties,
it must be recognized that in field practice one is dealing almost entirely
with "used" media that contain residual dust deposits, have undergone
stress, and may show altered charge or coating characteristics. The output
from the above study will be a listing of selected variables that: (a) will
be investigated in the successor laboratory program; and (b) represent a
first estimate of what constitutes important procurement specifications.
Task Area 2 - Laboratory Evaluation of Fabric Surface
Parameters - A concurrent laboratory program is proposed since the Task 1
screening studies cannot be accomplished based on theoretical considera-
tions alone. By performing a series of experiments intended to confirm or
negate postulated theories, one can decide which surface properties are
most important. Typical experiments would include the following:
-------
. Determination of the effect of a given
property upon permeability and cleaning
characteristics.
. Determination of pressure drop and collec-
tion efficiency for several fabric permuta-
tions after lengthy fabric conditioning
under specified loading conditions.
. Investigation of cake removal uniformity,
on both a macro-scale and filter pore scale,
possibly using scanning electron microscopy
in the later case.
. Investigation of in-depth particle penetration
by microscopic examination and, possibly, by
x-ray scanning.
Generally, the experiments should be designed so that
the fabric filter property can be shown to exert some quantitative effect
on a readily measured operating parameter, i.e., permeability, collection
efficiency, or cleaning power requirements. For this reason, studies of
individual particle-fiber interactions should not be included in this pro-
gram. The end product of the Task Area 2 studies should: (a) suggest
guidelines for fabric surface optimization, and (b) suggest approaches to
the improved operation of filter collectors.
Program Priority - High
Program Duration and Estimated Cost - The total cost for this
program area is estimated to be $450,000 allocated across a 3% year period:
First Year Effort
Equipment and Material Costs: $ 5,000
Manpower Cost: 95.000
Total: $100,000
Second Year Effort
Equipment and Material Costs: $ 15,000
Manpower Costs: 110.000
Total: $125,000
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Third Year Effort
Equipment and Material Costs: $ 10,000
Manpower Costs: 140.OOP
Total: $150,000
Last Six Month Effort
Equipment and Material Costs: $ 5,000
Manpower Costs: 70.000
Total: $ 75,000
4.3.2 Fabric Performance
Statement of Problem - The overall cost and performance of a
fabric filter system are determined principally by the filter media, the
primary element of the system. The cost of the media itself may represent
only 5 to 20 percent of the overall annual cost, but because the fabric
contributes indirectly to the costs of maintenance, fabric-related costs
may sometimes be as much as 50 percent of the annual operating cost. Thus,
the selection of the most suitable fabric available becomes an important
factor. Usually, fabric selection is based on prior experience or, at
best, on time-consuming trails. Experience is not always an adequate cri-
terion, because it does not necessarily follow that high efficiency col-
lection at costs believed to be reasonable is an indication of the optimum
fabric choice. Furthermore, all fabrics now used in filter systems have
limitations that can conceivably be circumvented through better design.
Since only limited data are available at the present time, a comprehensive
study of all factors entering into the cost and performance of fabric filter
media should be undertaken.
Program Description - All programs outlined in this five task
study are strictly applications oriented. Fundamental aspects will be
considered only as necessary to guide the experiment designs. These studies
relate to common field operating problems, e.g., design of filter elements;
fabric life; reasons for failure such as attrition, temperature effects,
overcleaning; cost factors and overall performance. Data sources will in-
clude the results of field inspections, interviews with users, and pilot
and bench scale laboratory tests.
-------
Task 1. Review of Fabric Manufacturing Methods.
Capabilities and Costs - This study is intended to provide a comprehensive
review of fabric technology as applied to the design and manufacture of
woven and felted media for gas filtration. One objective is to acquaint
the fabric filter user and manufacturer with the capabilities and present
limitations in textile production technology so that proposed new designs
or recommended improvements in filter media will be practically oriented.
Another objective is to direct the attention of the textile manufacturer
to the special needs of the filter user and to encourage further research
in this area.
A survey of fiber properties, spinning and weaving
methods, and mechanical or other finishing techniques, including definitive
statements as to how desired fabric properties can be designed or control-
led should be performed. Data pertaining to materials sources, cost, pre-
cision in' regulation of properties, and textile suppliers will also be
furnished. In addition, special problems attendant with the cutting,
sewing, surface treatments, or attachments of hardware to fabric configura-
tions (bags, tubes, or envelopes) will be examined with respect to their
impact on filter system costs.
Task 2. Field Study of Fabric Attrition - This study
will constitute a field survey of 30 to 50 different filter applications
to determine what role fabric attrition plays in the filter system. At
the present time, neither the individual filter user nor the dust collector
manufacturer have investigated this problem in a truly effective manner.
Furthermore, testing methods commonly used for evaluating fabrics for non-
filtration purposes are not directly applicable to the attrition problem.
Rating of fabrics for thermal, corrosive, or moisture resistance proper-
ties, however, have provided useful guidelines for filter users.
It is recognized that several factors may combine to
cause surface abrasion and internal abrasion or chafing, e.g., bag ten-
sion, grittness of dust, and flexure rate. For this reason, a field
examination of these problems permits a much broader coverage of suspect
-------
factors and their inter-relationships than can be attained in the labora-
tory. The results of the analysis of field problems, however, should pro-
vide logical guidelines for laboratory pilot scale investigations. In
addition, the study output should contain realistic suggestions for extend-
ing fabric life in each of the types of field applications investigated.
Task 3. Laboratory Study of Fabric Attrition by
Abrasion - The frequency of occurrence and the economic losses attributed
to fabric failure due to attrition related to dust particles justify a
separate laboratory study of this problem. The direction for this study
should be guided by the results of the Task 2 studies from which one can
decide which operating parameters, fabric types, and dust properties are
most frequently associated with fabric failure. The current literature
describing the effects of gritty materials upon fabrics relates mainly to
carpeting, clothing canvas and other protective or decorating coverings.
There is little information on surface or interfiber effects, particularly
for the much smaller particle sizes encountered in fabric filter systems.
Therefore, the laboratory study will include the eval-
uation of some 20 to 30 typical filter fabrics with at least five dusts.
Dust properties of interest should be size, hardness, sphericity, angu-
larity and possibly chemical reactivity. Rating procedures will entail
loading the fabrics under standard filtration conditions followed by flex-
ural endurance techniques of the types used in the textile industry. Those
materials showing marked indications of damage will be subjected to testing
at higher temperature or other variations typical of environmental para-
meters. Damage would be assessed in terms of increased dust penetration,
fabric rupture point, interstitial fiber breakage, and loss of fiber nap.
The results of this program, aside from amplifying the Task 1 studies are
intended to suggest improvements in fabric design and in cleaning technology.
Task 4. High Temperature Filtration Substrate
Developments - Fabric filter applications are generally limited to gas
temperatures below about 500 F. Fabric developments over the past 25
years have resulted in: (1) improved polymeric materials to achieve chemical
-------
compatibility with participates or carrying gas, and (2) improved tempera-
ture resistance. There is, however, a class of high temperature applica-
tions associated with furnace and reactor technology that requires expen-
sive gas cooling for use of fabric filters. Although developments in
higher temperature fabrics appear promising, more effort and support are
required to establish their technical and economic feasibility. The pro-
posed study should be directed to thorough review of all metallic, ceramic
and polymeric fibrous or needle developments. It would include the selec-
tion and laboratory testing at high temperature of fabric, web, or other
arrangements on simulant gases and dusts representative of specific high-
temperature applications.
Task 5. Coordinate Fabric Performance Information -
The Handbook of Fabric Filter Technology, although based upon the best
information available at the time, contains limited information on fabric
performance. It is expected that the results of Cleaning Mechanisms and
Kinetics Study and the other R&D programs on fabric filter systems enu-
merated in these R&D recommendations will generate considerable new and
valuable information. These findings should be presented in document form,
probably as revisions of the appropriate Handbook Chapters.
Program Priority - High
Program Duration and Estimated Cost - The total estimated cost
for this 4 year program is $570,000 allocated as follows:
First Year Effort
Equipment and Material Costs: $ 15,000
Manpower Cost: 105,000
Total: $120,000
Second Year Effort
Equipment and Material Costs: $ 25,000
Manpower Costs: 145.OOP
Total: $170,000
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Third Year Effort
Equipment and Material Costs: $ 20,000
Manpower Costs: 150.000
Total: $170,000
Fourth Year Effort
Equipment and Material Costs: $ 5,000
Manpower Costs: 105.000
Total: $110,000
4.3.3 New Fabric Material Investigations
Statement of the Problem - Directly or indirectly, filtration
fiber materials are related to a large fraction of the costs of fabric fil-
tration, and these costs could possibly be reduced by the availability of
improved fibers and also fabric filters could possibly be employed in a
wider range of applications.
Program Description - The recommended study of current fibers
should compare the fiber requirements imposed by dust collectors with the
present production capabilities of fiber manufacturers. This will require
two parallel investigations: first, a survey of the fiber characteristics
contributing to dust collection together with a selection of those charac-
teristics notably lacking; and second, a survey of techniques now used by
manufacturers to control fiber characteristics. The study should provide
an economic justification for the production of improved fibers, and should
outline the type and degree of AFCO support required.
As a result of the initial study efforts, one or more areas of
fiber improvement may require laboratory exploration and field tests. A
present manufacturer of somewhat similar fiber would produce a pilot quan-
tity of the new fiber. This would then be made into a filter fabric and
given suitable testing.
Program Priority - Low
Program Duration and Estimated Cost - The total cost of this
program area is estimated to be $250,000 allocated as follows across a
4 year period:
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First Year Effort
Equipment and Material Costs: $ 5,000
Manpower Costs: 95.000
Total: $100,000
Second Year Effort
Equipment and Material Costs: $10,000
Manpower Costs: 65.000
Total: $75,000
Third Year Effort
Equipment and Material Costs: $ 5,000
Manpower Costs: 32.000
Total: $37,000
Fourth Year Effort
Equipment and Material Costs: $ 8,000
Manpower Costs: 30.000
Total: $38,000
4.4 SYSTEM DESIGN STUDIES
Recent pollution control and industrial economics trends are increas-
ing the importance ascribed to fabric filtration equipment. Higher effi-
ciency and more reliable dust collection calls for improved equipment
which must be better designed than that traditionally available. This
equipment will probably be more expensive, but careful design and selec-
tion of the cleaning process and equipment, the materials of the collector,
and the instruments and controls of the collecting system will minimize
the cost. At present, although only about 5 percent of the daily dust
collection cost is due to the purchase cost of the collector alone, the
indirect costs relating to the design and choice of the collector may be
as much as 20 percent of the daily cost. This includes the effect of the
collector design on maintenance requirements, space requirements, fabric
cleaning, etc. Other aspects of the design of the collecting system have
similar indirect although far reaching effects, notably the fabric clean-
ing" sub-system and the control instrument sub-system. These are each of
sufficient importance to justify a separate study, as outlined below.
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Because so many aspects of the design of filtration systems have far
reaching effects and depend on numerous characteristics of the dust and
gas effluent streams, a study is also needed to synthesize systems-related
information as it develops. Finally, it is recommended that certain in-
formation gathering and dissemination activities be continued as an aid
to the other studies outlined in this document.
4.4.1 Cleaning Mechanisms and Kinetics
Statement of Problem - The successful performance of a fabric
filter system depends upon the continuous or intermittent removal of the
accumulated dust deposit. In current practice, filter surfaces are cleaned
mainly by mechanical methods (shaking, flexing, or vibrating) and aero-
dynamic methods (high or low velocity reverse flow air, and pulse jetting).
With respect to fabric filter systems, the cleaning operation is the only
step requiring the application of external energy aside from the gas moving
and dust disposal equipment common to all dust collecting apparatus. The
cleaning operation bears directly or indirectly upon almost all aspects
of filter system cost.
Despite the importance of cleaning, there still remains much
uncertainty as to which mechanisms predominate in separating the dust from
the fabric surface and what form of energy application produces the most
effective cleaning. Therefore, in order to attain maximum collection
efficiency at the lowest possible cost, it is essential that a systematic
study of cleaning mechanisms and related phenomena be performed.
Program Description - The study emphasis should be directed
to defining the relationship between the bonding (adhesion and cohesion)
and removal forces (i.e., acceleration, flexure, shear, aerodynamic drag,
and pressure contribute to particle removal) existing at the dust-layer
fabric interface. The effectiveness of the cleaning process should be
evaluated in terms of the amount of dust removal, the permeability of
the residual deposit, and the collecting efficiency of the cleaned fabric.
For best utilization of the experimental measurements, tests
should be performed on a pilot scale, although bench scale experiments
-------
may at times provide improved direction to the pilot plant effort. This
approach is intended to provide a maximum extrapolation capability to full
scale equipment.
Experimental measurements should include the following:
Effluent Characteristics - gas velocity, dust concen-
trations, dust type, dust size distribution, pressure
drop, deposit profiles.
Cleaning Parameters - frequency, amplitude, duration,
etc.
Collection Efficiency - initial, final and average.
Direct outputs from this study will include:
Indices of cleaning effectiveness related to cleaning
inputs, generalized for dust and fabric properties
and filtration conditions.
Comparison of cleaning energy or forces to adhesion
and cohesion energy or forces.
Analytical relationships generalizing the cleaning
performance.
Program Priority - High
Program Duration and Estimated Cost - The total cost of the
program is estimated to be $430,000 across a two year period of time:
First Year Effort
Equipment and Material Costs: $ 40,000
Manpower Costs: 180.000
Total: $220,000
Second Year Effort
Equipment and Material Costs: $ 20,000
Manpower Costs: 190,000
Total: $210,000
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4.4.2 Improved Fabric Filtration Equipment
Statement of Problem - An estimated 15 to 20 percent of the
costs of dust filtration are directly or indirectly related to the design
of the dust collector. Improved design and selection should lower costs
and eventually lead to wider acceptance of this method of particulate
control.
Program Description
Task 1. Compilation of Data on New Collector Designs -
Information is available from manufacturers of collector equipment and
certain of the larger equipment users, concerning numerous trials involving
novel configurations, cleaning methods, fabric arrangements, fabric types,
construction materials, etc. These records of R&D effort would be invalu-
able in projecting ahead the types of equipment which can be developed.
A procedure for remuneration to these manufacturers would be established.
Patent literature searches of such topics as fabric design, tensioning
methods, cleaning methods, and collector designs will also yield informa-
tion now unused by the industry, but nonetheless valuable.
A systems analysis of the potential for new collector
designs would be performed. This analysis would begin with conceptual
restraints on filtration media and filter-aided collection devices, media
configuration and packing, deposit removal mechanisms, and human factors
(construction and maintenance). The resulting conceptual possibilities
would be combined into engineering designs for possible subsequent labora-
tory exploration.
Task 2. Selection Guidelines for Collector Users - A
concise guide to the selection of fabric dust collectors should be pre-
pared for the inexperienced purchaser. This might well be a condensation
of portions of the Fabric Filter Systems Handbook. The guide should be
made available at minimum cost to any interested firm including equipment
manufacturers and research organizations. It will serve not only in the
selection of equipment, but with little modification, will enable the pre-
liminary design of collectors and of filtration systems as well.
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Program Priority - Low
Program Duration and Estimated Costs - The total cost of this
program is estimated to be $250,000 across a 2% year period of time:
First Year Effort
Equipment and Material Costs: $10,000
Manpower Costs: 80,000
Total: $90,000
Second Year Effort
Equipment and Material Costs: $15,000
Manpower Costs: 75.000
Total: $90,000
Last 6 Month Effort
Equipment and Material Costs: $12,000
Manpower Costs: 58,000
Total: $70,000
4.4.3 Control Equipment and Instrumentation
Statement of the Problem - Field inspection of existing indus-
trial fabric filter systems has indicated that the employment of control
instrumentation is minimal. The descriptions of many problems reported
for filter systems suggests strongly that inadequate control equipment
and instrumentation have led to costly breakdowns. Since it is expected
that the developing technology will require increased sophistication in
system operation, there is a need to determine what types of sensing, in-
dicating and control equipment should be used to achieve optimum filter
system performance.
Under the present strict ambient air quality regulations it
may be necessary to monitor particulate effluents continuously to ascertain
that emission standards are being met. Such monitoring will undoubtedly
require stricter control of all aspects of the gas cleaning process.
Furthermore, the need for increased investment in filtration equipment will
compel the user to protect his investment with adequate control instru-
mentation.
-------
Pressure loss, temperature, and humidity represent three areas
where current measurements are often lacking or inadequate. Excursions
beyond predetermined working ranges for the above variables can lead to bag
rupture through over-pressure, fabric deterioration by heat, or fabric
blinding by moisture condensation. Other variables affecting system per-
formance include gas flow rates, bag tension, degree of bag cleaning achieved,
dust concentration (inlet and outlet), particle size and electrical proper-
ties of dust. Measurement of the above variables may be used to operate flow
dampers, supply reheat air, regulate cleaning cycles and initiate emergency
control procedures. There are currently some instruments on the market which
can be directly applied to filter applications. There is an apparent need,
however, to develop new instruments specifically for fabric filter operation.
Concurrently, the question of the degree to which instruments will benefit
the filter user should be explored, from the points of view of cost and
system performance.
Program Description - The main objective of this study will be
to establish the combinations of control devices and sensing instruments
that will provide optimum filter performance.
Task 1. Instrument Survey - This task will entail a de-
tailed survey of sources, cost, and performance of available instrumenta-
tion; an analysis of equipment needs with anticipated costs for purchase,
installation, maintenance, estimated size of the instrument market; and
the feasibility of and suggested approaches for development of the needed
instruments. The results of this study will be in the form of a market
guide to instrumentation available to fabric filter users, and the documen-
tation to encourage instrument manufacturers or other agencies to provide
new and improved instrumentation.
Task 2. Control Methods Survey - This task area will in-
volve a survey of current methods and devices used to control key filter
system variables such as pressure, temperature, dew point and gas flow
rates. Emphasis would be placed upon the cost benefits and effectiveness
of these devices in terms of their respective advantages and disadvantages.
-------
For example, temperature, a critical factor in many systems must be con-
trolled by radiative cooling, spray cooling or air dilution. However,
precise regulation is required to maintain temperature levels above the
dew point and in all cases problems of cost, space requirement and relia-
bility must be considered. In such areas as described above, control
systems should be examined in terms of necessary improvements or alterna-
tive systems. The output from this study would be presented in essentially
the same form as that from the Task 1 instrument survey.
Program Priority - Low
Program Duration and Estimated Cost - The total cost for this
one year program is estimated to be $100,000 allocated as follows:
Material and Equipment Costs: $ 5,000
Manpower Costs: 95.000
Total: $100,000
4.4.4 Fabric Filter System Modeling
Statement of Problem - Many parameters influence the perfor-
mance and the total annual cost of filter system operation. .They are so
interwoven, however, that it is difficult even with extensive experience
and dealing with only a single parameter, to see the overall picture and
to appreciate the effects of parametric changes. For example, a change in
dust size properties upstream of the filter may affect the deposit perme-
ability, adhesion, plugging and blinding, seepage, residual profile, and
fabric life. Similarly, dust concentration changes, variations in gas
volume, and humidity, will affect system pressure loss and power require-
ments in numerous ways.
There are, at the present time, only fragmentary models des-
cribing the performance of individual system components based upon labora-
tory measurements, field measurements or purely theoretical considerations.
It should be possible to develop models covering a broader scope and having
greater utility based upon data already available or in the process of
generation by on-going programs. A comprehensive and flexible model could
-------
be applied to the immediate needs of optimizing system design; estimating
installation and operating costs associated with different design approaches
in specific application areas; and investigating the predictions made by
different theoretical approaches for describing dust cake structure and
removal. Such a model or series of sub-models would prove useful as a tool
for evaluating proposed R&D programs and as a predictor of fabric filter
system cost and performance.
Program Description - The program effort should be directed at
developing a computer program adapted to as wide a range of digital equip-
ment as possible. It should be readily comprehensible and simple to use.
The model should provide such information as cost, efficiency, and other
performance factors in terms of inlet dust properties and system design
parameters. It should be applicable to practically all types of fabric
filter systems, and accommodate the range of particulate materials (coarse
dust to fine fume) requiring filtration. An important program output would
be a table of "influence coefficients" showing the percentage change in
given output parameters for changes in selected input parameters. The model
should be flexibly structured to facilitate the inclusion of new technology
as it develops.
Program Priority - Medium
Program Duration and Estimated Cost - Since this program is
dependent on the results of the other research program, it is recommended
that it be conducted with a low level effort across a three year period.
It is estimated that the total program cost would be approximately $150,000
allocated, by year, as follows:
First Year Effort
Computer Cost: $ 5,000
Manpower Cost: 30.000
Total: $35,000
Second Year Effort
Computer Cost: $10,000
Manpower Cost: 65.OOP
Total: $75,000
-------
Third Year Effort
Computer Cost: $ 5,000
Manpower Cost: 35,000
Total: $40,000
4.4.5 Continuation of the Fabric Filter System Study
Statement of the Problem - The fabric filter system study iso-
lated several areas of fabric filter technology and industry characteriza-
tion which were too expensive for complete coverage in the initial program
effort. Moreover, the continuing development of information from on-going
(and contemplated) R&D indicates the need for additional and continuing
compilation, integration and directive activities.
Program Description - The requirements of this study area have
been grouped into a series of three program tasks which are considered nec-
essary to maximize the development of fabric filtration systems; (a) com-
pilation of design data on new fabric filtration equipment, (b) extension
of the technology surveys in fabric filtration and updating of Fabric Filter
Handbook, and (c) conduct of a fabric filtration seminar. Each of these
areas are discussed in the following text.
Task 1. Compilation of Design Data - Until the last twenty
years, fabric filtration equipment was basically unchanged from that exis-
tent in the late 1800's. Recently, substantial innovations in fabrics and
cleaning methods have been made. Further innovation has been projected, as
a result of need for closer control, improved materials, deeper understanding
of the related particle mechanics, etc. In particular, the dust collector
itself may undergo further modification as a result of these recent develop-
ments. A survey of the prospects for collector modification should be made.
Information is available from manufacturers of collector equipment and cer-
tain of the larger users of the equipment, concerning the results of mis-
cellaneous trials involving novel configurations, cleaning methods and
fabric arrangements, fabric types, etc. These records of R&D effort, to-
gether with the design guidelines now being used by the manufacturers, would
be invaluable in projecting ahead the types of equipment which may be
-------
X,
developed. A procedure for remuneration to these manufacturers would be
established. Patent literature searches of such topics as fabric design,
tensioning methods, cleaning methods, and novel collector designs will also
yield valuable information.
A systems analysis of the potential for new collector
designs would be performed. This analysis would begin with conceptual
limitations for filtration media, and filter aided collection devices,
media configuration and packing, deposit removal mechanisms, and human
factors (construction and maintenance). The possibilities would be devel-
oped into conceptual engineering designs for possible subsequent laboratory
exploration.
Task 2. Up-dating of the Handbook of Fabric Filter
Technology - There are a number of areas of fabric filtration technology
which should be examined in greater depth, and summarized as revisions of
portions of the Handbook. These are enumerated below:
1. Wider survey of fiber, fabric, and filter
element sewing firms, and of literature
relating to filtration fabrics.
2. Survey of foreign applications and technology
relating to present and future applications;
engineering, fundamental, or economic data;
and experiential problems and needs. There
is believed to be a considerable German,
Russian, Japanese, and Czechoslovakian
literature body, in particular.
3. Projection of future needs of fabrics and
equipment. This is a difficult task, as
little information regarding future indus-
trial processes is available in any detail.
The projections should consider expected
temperatures, economics of alternative gas
cleaning processes, legislative requirements,
and market sizes based on current trends.
4. Literature survey extensions, including up-
dating of the most recent surveys, incor-
poration of basic science references (e.g.,
adhesion bonds, deposition mechanics, etc.)
and review of literature of the 1950's and
earlier. This task would complement similar
effort in other programs).
-------
Task 3. Fabric Filter Seminar - There is a need for
open discussion among and between filter users and manufacturers in such
areas as filtration fundamentals, engineering technology, experience re-
lating to specific applications, and performance test methods. In the
past, users have seldom had the opportunity to discuss together common
interests in fabric filtration. Manufacturers representing about 80 per-
cent of filter sales are united by the Industrial Gas Cleaning Institute;
however, the information disseminated by the IGCI has generally not been
of a type beneficial to the development of new methods or equipment.
Research organizations would also be interested in a discussion of filtra-
tion practices, potential needs, etc.
It is proposed to hold a Seminar extending over a period
of a few days, to which major fabric filter users, interested research
organizations, and equipment manufacturers would be invited. The seminar
would include:
1. Presentation of results of recent studies
in fabric filtration, fabric and equipment
development, and related technology;
2. Panel and group discussions of organized
topics, such as specific applications of
widespread interest, common usage problems,
types of equipment or configuration;
3. Technical laboratory sessions including
participation as well as demonstration;
testing methods, maintenance techniques,
computations.
This Seminar should be held at a laboratory facility.
One objective of the Seminar would be to determine whether there is suffi-
cient interest to form a special laboratory or filtration institute, which
would be available for specialized measurements, test equipment, and con-
sultation to any member manufacturer, purchaser, or user of fabric filtra-
tion equipment.
-------
Program Priority - Medium
Program Duration and Estimated Cost - The total cost for this
program area is estimated to be $150,000 allocated across a five year
period:
First Year Effort 40,000
Second Year Effort 40,000
Third Year Effort 30,000
Fourth Year Effort 20,000
Fifth Year Effort 20,000
4.5 APPLICATION STUDIES
The improvement and widening of the application of fabric filter con-
trol equipment to particulate collection problems depends on both the
skillful utilization of existing equipment designs and the development of
new designs to meet demanding control requirements which have not been
widely handled by filtration equipment in the past. For example, there
are currently industrial process effluents which are uncontrolled, or
controlled by low efficiency systems, which might be controlled to satis-
factory levels using presently available fabric filtration technology.
These application areas require in-depth engineering studies if the opti-
mum design approaches are to be employed and if the filtration system is
to be validly evaluated for the specific application at hand. There are
also, at present, effluents which are difficult or expensive to control
by fabric filtration equipment and which should be investigated by pilot-
scale equipment if we are to satisfactorily determine the applicability
of filtration equipment. Such pilot-scale investigations should use stan-
dardized test methods, instrument systems and measurement parameters.
4.5.1 Identification and Evaluation of New Fabric Filter Applications
Statement of Problem - Several potential applications of fabric
filtration technology have been considered in a cursory fashion in the
Fabric Filter System Study, but few with the detail required to fully
determine the applicability of filtration systems or to justify prototype
fabrication and demonstration programs. A lack of design criteria for
-------
field measurement techniques, including instrumentation geared specifically
to filter systems, and limited experience with pilot plants have contri-
buted to the slow progress in this area. Furthermore, the initial costs
of undertaking survey and/or research and development programs has obscured,
perhaps, the long term benefits to be realized with respect to improved air
quality and expanded markets for fabric filtration equipment.
Program Description - Three distinct program tasks are out-
lined. First, improved and standardized test methods and test equipment
are widely needed. Second, versatile pilot plant equipment is needed which
can be quickly used in evaluating the performance effects of system design
changes< Third, several industrial processes must be studied to determine
whether and how fabric filtration equipment can best be utilized. These
three tasks may run concurrently, although there will be considerable
advantage to sequential programming if the time frame permits.
Task 1. Development of Test Methods and Equipment -
Performance data reported for both laboratory and field investigations of
fabric filters has often been invalidated because of careless or incorrect
sampling procedures. In addition, experimental methods suitable for labo-
ratory testing may not be applicable to the broad range of operating con-
ditions encountered in the field. It is necessary, therefore, to develop
an assemblage of field instruments in the form of a readily transportable
kit which can be used to evaluate the performance of new or existing filter
installations. The intention is to provide standardized equipment so that
meaningful and readily correlatable data can be obtained from several field
installations.
This study should include: (a) review and ranking of
the parameters important in fabric filtration pilot and laboratory studies;
(b) survey of useful methods for measuring these parameters; (c) review
and selection of types of data analysis and reporting parameters commonly
used; (d) design of a versatile instrument kit for performing important
field measurements; and (e) development of data reduction methods compat-
ible with data inputs. Relative to laboratory studies, the precision
-------
required for measurements should be less rigid than the capability for
adaptation to a broad range of field parameters. The output from this
program constitutes a necessary input for the effective evaluation of any
fabric filter system.
Task 2. Development of Pilot Testing Equipment.. -
New filtration concepts and/or significant changes in existing systems
should undergo laboratory bench and pilot scale screening before any field
trails are considered. Final field evaluations under actual operating
conditions, are usually required prior to fabricating prototype systems.
At present, a few filter manufacturers and user industrial organizations
have experience with field pilot plant installations. Generally, the main
problem areas appear to lie in the bulk of the equipment, the need for
special site preparation, its limited application range, and incomplete
instrumentation. The principal objective of this study is to examine the
practicability of developing versatile, well instrumented pilot testing
systems whose basic dimensions would be of the order of inches rather than
feet. Reduced cost and ease of transport, installation, and operation
would encourage increased field evaluation of new filter applications by
both filter manufacturers and users.
This study would incorporate a review of existing pilot
plant systems and test approaches including those types of instrumentation
which provide the best measures of filter performance. Special emphasis
should be placed upon scaling factors so that the results of small scale
tests can be safely extrapolated to prototype experience. The end result
of this study would be a truly portable pilot plant that can be produced
economically so that extensive field applications can be made.
Task 3. Selection. Description and Demonstration of
Fabric Filter Systems in New Applications Areas - Several sources of par-
ticulate air pollutants may be potentially controllable with fabric fil-
tration. Filter methods have not been used for a variety of sources
because: (a) suitable fabric media are not as yet available; (b) users
or filter manufacturers are not aware of the possibilities; (c) the
-------
particulate effluent is not recognized as presenting a problem at present;
or (d) fabric filtration is believed, correctly or otherwise, to be un-
suited to the application. Preliminary studies have demonstrated the need
for more detailed studies in the following areas: low sulfur, coal-fired
and oil-fired utility boilers; municipal incineration; Kraft pulping,
digester and kiln operation; iron and steel production, cupola and basic
oxygen process furnaces; secondary zinc processing; tail gas treatment,
sulfuric acid manufacture; coke production; and calcium carbide, electro-
metallurgical operations.
Analyses should be made of effluent characteristics and
current control efforts in the complete spectrum of likely applications
areas. To accomplish this it will be necessary to undertake visits to
representative plants, discussions with knowledgeable manufacturers, and
preliminary engineering studies. These initial studies would provide enu-
meration of the potential application areas for fabric filters and outline
those areas which hold the most promise as candidates for filtration systems.
Thus, the studies will result in: (a) the determination of the number of
sources,quantity and nature of the effluents, and related economics; (b)
engineering analyses of the appropriate filtration equipment; and (c)
fabrication of demonstration systems and the conduct of demonstration pro-
grams to demonstrate the economic and performance advantages of selected
fabric filter systems. The results of these studies are expected to extend
the use of fabric filtration methods into areas where existing control
methods (or the lack of) has led to excessive particulate emissions.
Program Priority - High
Program Duration and Estimated Cost - It is recommended that
this program area extend across a 4% year period at a total estimated cost
of $2,400,000, allocated approximately as follows:
First Year Effort
Equipment and Material Costs: $ 50,000
Manpower Costs: 150.,000
Total: $200,000
-------
Second Year Effort
Equipment and Material Costs: $150,000
Manpower Costs: 250.000
Total: $400,000
Third Year Effort
Equipment and Material Costs: $200,000
Manpower Costs: 300.000
Total: $500,000
Fourth Year Effort
Equipment and Material Costs: $250,000
Manpower Costs: 450,000
Total: $700,000
i
Fifth Year Effort
Equipment and Material Costs: $250,000
Manpower Costs: 350.000
Total: $600,000
4.5.2 Demonstration of a High Temperature and High Filtration
Velocity System
Statement of the Problem - Approximately one-third of the par-
ticulate emissions from industrial sources come from sources in which the
effluent streams are in the 900 F or higher range. The employment of
fabric filtration systems in these environments typically requires the
utilization of gas stream cooling by radiative/convective means, dilution
cooling or active cooling by water systems. Even in cases where cooling
systems are employed, temperature surges sometimes occur which may exceed
the capacity of the cooling systems, and which may cause damage to the
operating elements of the filtration system. It appears desirable, there-
fore, to investigate more fully the application of filtration systems
specifically designed to operate in high temperature environments.
The grey iron foundry industry is an industrial source that
is experiencing particulate emissions in excess of current and projected
emission standards and which has traditionally utilized wet caps, inertial
separators and wet scrubbers for particulate control. Since current and
-------
contemplated emission standards effectively preclude the use of wet caps
and inertial separators, the present trend is to use wet scrubbers or
fabric filters to meet efficiency requirements. While more fabric filters
are presently in use than wet scrubbers, no distinct economic advantage
appears for either system. The need to reduce typical cupola gas exit
temperatures from about 2000 F to 500 F to keep within the operating range
of existing fabrics is a cost disadvantage relative to wet scrubbing opera-
tions. In addition, the combination of fine fumes and many potentially
corrosive materials (acid gases, fluorides) makes many types of filter
media susceptible to plugging and chemical attack.
Thus, there is a definite need for the development of a fabric
filter system that can: (a) operate in high temperature and highly corro-
sive environments; (b) that offers collection efficiencies equal to or
better than high-energy scrubbers; and (c) can be installed and operated
at costs lower than those of present fabric filter systems or high energy
scrubber systems.
It appears that a reasonable approach to meeting this need is
to apply the recent developments in filter media materials (i.e., tempera-
ture and corrosion resistance and ability to operate in high filtration
velocity environments) to the specific requirements of cupola emission
control. If a system to meet these requirements can be developed, then
the technology should be applicable to a wide range of industrial applica-
tions that have equally or less demanding emission control requirements
and/or operating environments.
In recent years a number of new fiber media have been developed
(i.e., polyimides, FiberfrajT , and metallic fiber media) which offer: (a)
physical properties compatible with high filtration-velocities; (b) signi-
ficant increases in temperature and corrosion resistance; and (c) capa-
bility for fabrication into felted media which are compatible with re-
verse flow or pulse jet cleaning methods. Preliminary laboratory and
field studies have also suggested that a felted metal fiber media used
to filter the effluent gas may provide more effective and economic
-------
particul&te removal than that afforded by existing systems. The potential
advantages would appear to be in: (a) the high filtration velocities,
~ 100 FIM, (b) the in-place cleaning capability by either reverse flow
air or wet sluicing, and (c) the resistance to chemical and thermal attack.
Program Description - The main objectives of this program are
to demonstrate the engineering feasibility and performance characteristics
of a high velocity filter system, first on a laboratory scale to establish
design parameters, media life, and optimum cleaning methods, and then on
a full scale filter system applied to a real foundry cupola installation.
Task 1. Laboratory Pilot Plant Study - A laboratory
pilot plant system will be constructed in which several types of filter
media in various experimental configurations will be evaluated under simu-
lated field operating conditions. Emphasis will be placed upon the fiber
resistance to thermal and temperature effects as well as the ease with
which particulates can be removed by different methods of cleaning. This
study will embrace the complete range of cupola effluent operating condi-
tions such that design parameters deriving from this study will enable the
construction of a field prototype system.
Task 2. Design and Fabricate Full Scale System - A
full scale system will be designed for an operational cupola installation
of the 20-30 ton/hour capacity range. The system will utilize metallic
fiber media, will operate in the 100 FPM filtering velocity range and will
utilize filter cleaning methods which have been demonstrated as being com-
patible with the media and effluent characteristics. The design goal will
be such that the most stringent, current or projected, emission standards
for cupola sources will be met or exceeded.
Task 3. System Performance Evaluation - Following in-
stallation, a complete evaluation of the system will be completed includ-
ing system performance determination, operating cost determination and
system operating and failure analysis. A large number of effluent mass
and size distribution measurements will be made and compared with measure-
ments made under identical operating conditions prior to installation of
the filtration system.
-------
Program Priority - High
Program Duration and Estimated Cost - The total cost for this
2 year program is estimated to be $440,000 allocated approximately as
follows:
First Year Effort
Equipment and Materials Costs: $ 25,000
Manpower Costs: 125,OOP
Total: $150,000
Second Year Effort
Equipment and Materials Costs: $175,000
Manpower Costs: 115.000
Total: $290,000
4.6 INTEGRATED RESEARCH AND DEVELOPMENT PROGRAMS
Two research and development programs were prepared based on the
overall study results and the definition of specific R&D projects as enu-
merated above. Both programs extend five (5) years in duration, with one
based on an assumed total expenditure of five million dollars and the other
on an assumed total expenditure of two million dollars.
Figure 1 presents the program schedule for the five year programs,
with the projected expenditures for each major program arranged in adja-
cent columns. This permits a ready comparison of how the task funding has
been allocated for the five and two million dollar programs, respectively.
The program sequence appears as given in the preceeding text in which the
composition of the studies range from basic laboratory investigations to
field measurement programs. Although it might be argued that any funda-
mental research should precede pilot or development studies, the need to
implement effective emission controls at the earliest possible date re-
quires a more pragmatic approach. For example, our preliminary estimates
of research needs indicate that relatively large sums should be directed
towards applications studies. Hence, it appears that a concurrent pursuit
of an applied program promises not only a more rapid solution of a field
problem, but also provides added guidance and direction to the fundamental
studies, particularly those cited at medium or low priority programs.
-------
Figure 1. Schedule* lur Five-Year niter Research and
Development Program at the Five-Million and
Two-Million Dollar Level.
I
U)
6.2
4.2.1
4.2.2
Talk
49 ^
.£..}
Taak
4.3
4.3.1
Task
41 9
. J . f.
Task
4.3.3
4.4
4 4.1
4.4.2
RM> Program Area
Definition and Control of Particle
Properties
Basic Particle Parameters
Deposit Modification and Control
1. Definition of Deposit
2. Deposit Changes During Filter-
ing
3. Costing of Cake Control
- Hfcl
rartlcle sixe control
I. Review of Experience in
Particle Six* Control
2. Experimental Program
Fabric Investigations
Fabric Surfaces Study
1. Literature Review, Theoretical
Approaches
2. Laboratory Investigation of
Surface Parameters
'
Fabric Ferzomance
1. Review of Manufacturing
Methods, Capabilities and Costs
2. Field Study of Fabric Attri-
tion
3. Laboratory Study of Fabric
Attrition by Abrasion
4. High Temperature Filtration
Substrate
5. Coordinate Fabric Performance
Information
New Fabric Materials Investigation
Systems Design
. . ,
ean ng ec an sos an
ment
rlorlty
High
High
»j_ j
nea .
High
Hi oh
nign
Low
High
Low
A
Numbers In parentheses Indicate subtask funding.
Pro^r-wo Year
1
234
s
Five HI I lion*
Dollar Progra*
Coat (SOOO)
110
100
(«)
(15)
(30)
100
(40)
(60)
450
(100)
(350)
570
.(75)
(100)
(200)
(100)
(95)
75
430
123
two MllUoa*
Boiler Program
Cost ($000)
110
70
(35)
(25)
(10)
30
(30)
--
200
(100)
(100)
200
(75)
(75)
(50)
--
330
SO
-------
7
i
n»»ire 1 (Continued)
Task
4.4.3
.Task
4.4.4
4.4.5
Task
4.5
4.5.1
Task
4.5.2
Task
R&D Program Area
1. Compilation of Data on Hew
Collector Designs
2. Selection Guidelines for
Collector Users
Control Equipment and Instrumenta-
tion
1. Instrument Survey
2. Control Methods Survey
Fabric Filter Systems Modeling
Continuation of Fabric Filter
System Study
I. Compilation of Design Data
2. Updating of Fabric Filter
Handbook
3. Fabric Filter Seminar
Applications Studies
Identification and Evaluation of
New Fabric Filter Applications
1. Development of Test Methods
and Equipment
2. Development of Pilot Testing
Equipment
3. Selection, Description and
Demonstration of Fabric Filter
Systems in New Applications
Areas
Demonstration of High Temperature
and High Velocity Filter System
1. Laboratory Pilot Plant Study
2. Design and Fabricate Full Scale
System
3. System Performance Evaluation
Priority
Low
Med
Med
High
High
Program Year 1 FJ« Million*
6 | Dollar Program
1 2
i
3
4
T
5
Cost ($000)
(75)
(50)
100
(50)
(50)
150
150
-------
The priorities shown in Figure 1 are based upon the best information
available at the time of report preparation. With respect to basic re-
search, a high priority means that some systems or applications studies
should be approached cautiously until the relationships among basic para-
meters are better understood. On the other hand, high priority assign-
ments for strictly applied research programs reflect control needs for
which solutions should be attempted on the premise that the results of
parallel basic studies can be made available at the proper time. It is
realized that the listings (i.e., areas of research, priorities, funding,
performance periods) in Figure 1 should, of course, be reviewed constantly
in accordance with new technological developments and regulatory standards.
In reducing the funding level from a five million to a two million
dollar five year program, it was difficult to decide which research acti-
vities should be restricted since all programs are considered important
to the advancement of filtration technology. Three criteria were used to
formulate the reduced program. First, certain programs should be continued
even at a reduced level since it is necessary to draw upon several areas in
order to affect a practical engineering solution to a specific filtration
problem. Second, tasks within certain research categories should be
pursued in some logical sequence such that execution of the first task
must preceed the second or third. In these cases, it would appear more
reasonable to perform the sub-task at the originally scheduled level of
effort and to decide later whether further pursuit is justified. Third,
those sub-tasks which might be investigated independently and which repre-
sent correlation and review of previous findings rather than new research
have been assigned a lower priority.
-------
APPENDICES
APPENDIX 1 - POTENTIAL APPLICATIONS FOR FABRIC FILTRATION, NEW AREAS
AND/OR EXPANDED USE IN CURRENT APPLICATIONS
APPENDIX 2 - FABRIC FILTER SYSTEM SURVEY - USER REPORT
APPENDIX 3 - U.S. FABRIC FILTER MANUFACTURERS AND PRODUCTS - 1969
PRINCIPLE MANUFACTURERS OF FABRIC FILTER DUST AND FUME
COLLECTORS
APPENDIX 4 - R&D SUGGESTIONS BASED ON INTERPRETATION OF COMMENTS MADE
DURING SURVEYS
-------
APPENDIX 1
POTENTIAL APPLICATIONS FOR FABRIC FILTRATION,
NEW AREAS AND/OR EXPANDED USE IN CURRENT APPLICATIONS
Process
Existing Control
Methods
Comments
1. Combust ion
a. 100 MW Coal and Oil
h. 10 MW Coal and Oil
c. Low Sulfur Fuels
d. Domestic Heating,
Larger plants
e. Incineration,
Municipal
Institutional
Industrial
(Scrap, Sewage)
2. Pulp and Paper
a. Recovery Furnace
b. Kiln
c. Calciner
ESP, FF
ESP, I
As Above
None
S, WS, FF
I, ESP, WS
ESP, WS
ESP, VS, I
I, WS
Promising, Odor problems
Promising
Lower conductivity does not
favor ESP
See la, b
Promising, Cake conditioning
Required
Some FF Applications
Promising, Odor problems
3. Inorganic Chemicals
a. Fertilizers
Super phosphate
Triple phosphate
b. Lime (CaO)
Kiln
Handling
c. Catalysts
4. Petroleum Refining
a. FCC Reform
b. TCC Hydrogen
c. Waste Boilers
d. Process Heaters
5. Non-Metallic Minerals
a. Cement
Kiln (wet and dry)
b. Asphalt Concrete
ESP, I, WS, FF Promising, curing is uncontrolled
E?P, FF
I, WS, ESP, FF
I, ESP
I
None
ESP, I, FF
I, WS, FF
Promising, not widely used
Promising
Promising, FF not tried
See 4 a
See la, b
See la, b
Promising, use limited at present
See 5a
I = Inertial Collector
ESP = Electrostatic Precipitator
WS = Wet Scrubber
VS «= Venturi Scrubber
FF = Fabric Filter
S » Screen
-------
Process
Existing Control
Methods
Comments
c. Glass
Furnaces
Frit Mfr.
d. Gypsum
Kiln, Kettle
e. Crushed Stone and Gravel
f. Coal Screening
g. Abrasives-Furnaces
h. Mining (Underground)
b. Iron, Steel and Related
Operat ions
a. Cake Production
b. Ore Handling and
Concentrating
c. Sintering
d. Steel Furnaces
Open Hearth
Basic Oxygen
Electric
e. Steel
Pouring
Scarfing
f. Founding
Cupola Furnace
Sand Handling
Continuous Casting
g. Electrometallurgical
Processes
7. Non-Ferrous Metals
a. Aluminum Refining
b. Scrap Fluxing
c. Copper Smelting,
Roasting
d. Lead Smelting
e. Zinc
Sintering
Smelting
WS, FF
VS, FF
ESP, FF
I, FF
FF
FF
WS, FF
Promising, need for improved high
temperature fabrics
As above
Promising, FF not widely used
For old uncontrolled plants
Promising, more control needed
Promising, not widely used
Promising, compact equipment required
FF appears feasible, studies required
Promising
I ESP WS FF Promising, FF not widely used
ESP, WS, FF
ESP, WS
I, WS, FF
I, WS
ESP, WS, FF
I, WS, FF
WS, FF
WS, FF
ESP, WS, FF
ESP, I, FF
WS, FF
I, ESP
ESP, I, WS
Promising, more incentive needed
Promising, studies required
Promising, FF use expanding
Promising
Promising, water problem controllable
Promising, not widely used
FF use should be expanded
Promising, enclosure the main problem
Promising, FF use should be expanded
Promising, studies required
Promising, FF use expanding
Promising, studies required
Promising, limited FF application
Promising, studies required
As above
I = Inertial Collector
ESP = Electrostatic Precipitator
WS = Wet Scrubber
VS = Venturi Scrubber
FF » Fabric Filter
-------
Bureau of Budget No. 85-S69016
Approval Expires Feb. 28, 1970
APPENDIX 2
FABRIC FILTER SYSTEM SURVEY - USER REPORT
Section I. GENERAL INFORMATION Date:.
1. Name & location of company;
a. Name:
b. No., Street:
c. City: State: Zip Code;
2. Location of plant if different from abovet
a. Plant/Division:
b. No., Street:
c . City: State: Zip Code ;
3. Person to contact regarding information contained in this report:
a. Name;
b. Department/Division:
c . Telephone; Area Code I
4. Principal products manufactured at this plant:
Standard Industrial Classification, if known:
NAPCA Form HQ 29
4/69
-------
Section II. GENERAL APPLICATION
Please indicate units when numerical replies are provided, for
example: pounds per hour; tons per day.
1. a. Name of process served by filter:
b. Name of operations generating dust or fume passed to filter:
2. a. Process equip, capacity: b. Approx. proc. rate:_
c. Approx. process temperature:
d. Process (Circle): Continuous batch. Batch timing:
3. Gas characteristics entering collector:
a. Total flow rate, cubic feet per minute (standard or ambient) :_
b. Moisture rate or relative humidity:
c. Temperature entering collector;
d. Type of cooling before collector:
4. Oust or fume particles entering collector:
a. Name of material collected: b. Approx. composition:
c. Weight per hour:_^ or grains per cubic foot:
under (Circle) standard ambient conditions.
d. Is the dust hygroscopic? e. Typical particle size:_
5. a. Fraction of time the fabric filter system is in use on process:_
b. What other cleaning methods have been tried?
c. Reasons for using fabric filtration:^
-------
Section III. FABRIC FILTER SYSTEM DESIGN
1. Installation - Date:_
a. Manufacturer:
b. Approx. cost, collector alone:_
Other auxiliary equipment;_
Model No:
_Fans, ductwork:
Total:
2.
Filter elements
a. Number of compartment3 %
compartment: wide by
b. Arrangement, number of elements per
long by high; Total per comp. :
c. Total filter system area;
d. Please indicate filter element dimensions
on appropriate sketch at right:
e. Dust collects on (Circle):
inside outside
Dust enters (Circle):
bottom top
Filter material
a. Fabric (Circle): Cotton, woven Wool felt Nylon (polyamide)
"Nomex" nylon Dacron (polyester) Orion (acrylo nitride) Glass
Orion-Wool Dynel Vinylidene Chloride Polyethylene Teflon
Polyvlnyl acetate Polypropylene Asbestos Other (specify):
Cat. No:
(Sketch
other)
Used :
b. Manufacturer or supplier:
c. Permeability, if known; New :
d. Could you provide a sample of fabric for inspection? (Circle): Yes No
4. Please indicate on sketch at right
the gas inlet and outlet locations,
and approx. overall collector dimen-
sions. Indicate arrangement of com-
partments .
Are construction prints available for
inspection? (Circle) : Yes No
-------
Section IV. FILTER PERFORMANCE (during normal operation)
1. Pressure drop (inches of water):
a. Pressure drop fully loaded, before cleaning cycle:_
b. Pressure drop after dust removal:
c. Static pressure level, ± 107.:
d. Is a record of pressure drop variation available?
2. Air to Cloth Ratios, or total gas volume filtered per unit time:
a. Fully loaded: b. After dust removal: c. Overall ave. :
3. Performance
a. Collection efficiency: b. Approx. no. of system failures per year:
c. Principal causes of bag failure:
4. Operating costs
a. Filter elements: Typical life: Bag or element costs per year:
Salvage value: Restoration or cleaning of used bags,
process: Approx. process cost:
b. Estimated labor costs per year in man-hours:
Element replacement: Labor categories:
General maintenance: Labor categories :_
c. Other costs, e.g., dust disposal:
5. Fan manufacturer; Designj_
Wheel size: Horsepower:
6. Have you. tried other fabrics on the same dust (Circle): Yes No
Which ones? .
What problems did you encounter and why did you change to the
presently used fabric?
-------
Section V. REMOVAL OF DUSf OEKSSlA w»
1. intermittent cleaning (Circle): shake reverse flow fabric flexing
reverse pulse reverse jet Other (Specify):__
a. Initiation of cleaning (Circle): manual timer pressure limit
b. Frequency of cleaning each element;
e: Approx. tine taken to clean: .' d. No. elements cleaned at once:_
Continuous cleaning (Circle): reverse Jet pulsed air vibration
reverse air traversing carriage Other (Specify):_
a. Compartments shut off by (Circle): damper traveling blower carriage
Other (Specify):
b. Frequency of cleaning each compartment:
c. Approx. time taken to clean each compartment;
d. Number of compartments cleaned at once:_
e. Reverse jet or reverse air characteristics: air volume: velocity:
ring slot size or carriage aperture; traverse rate:_
fan motor horsepower: Other (S pec i f y) :,
f. Reverse air volume set by (Circle): blower capacity orifice
Orifice size if known:
3. Intensity of cleaning: motor horsepower; vibration frequency:_
stroke length: air pressure; Other (Spec if y) :
4. a. Estimated deposit properties: density: thickness:
b. Est. uniformity over bag(Circle): more near bottom than top fairly even
more near inlets Other(Specify);
c. Est. uniformity and effectiveness of removal;
5. Disposal of dust(Circie): return to process manual removal to waste
automatic removal to waste
6. Dust appearance:
a. Collected dust - visual (Circle): dusty fluffy fluidized loose
heavy flaked caked sticky oily damp hard
b. Collected dust - microscopic (Circle): agglomerates over 10 microns size
agglomerates around 1 micron too fine to resolve mixture
Other(Specify):
c. Original dust particles (Circle): spherical granular irregular
fibrous elongated uniform size agglomerates mixture
Other (Specify) :
d. Is there a dust sample available for inspection? (Circle): Yes No
-------
Section VI. OTHER GAS TREATMENT
1. Pre-treatment
a. For dust (Circle and describe);
Settling chamber
Cyclone
Pre-filter
Other
b. For gaseous components, etc. (Circle and describe):
Scrubber
Other
2. Cleaned gas or air (Circle): returns to process discharges outdoors
returns to inside plant volume
3. Quality of effluent gases (Circle): within required limits
no complaints complaints
4. Is your dust generally considered to be a seeper (Circle): Yes No
If yes, do you require or specify special fabrics or fabric treatment
to control seeping (Define and describe);
5. Do you have problems associated with fabric blinding (Circle): Yes No
6. Please indicate:
a. Any major difficulties with your filter system:
b. What aspects of performance or operation could be improved, based on
your field experience;
c. Suggestions for improvements in design or manufacture;
d. Research requirements:
-------
Section VII ADDITIONAL DETAILS
1. Fabric design*.
a. Weave (Circle): plain twill sateen Other:
b. Yarn: (Circle): monofilament multifilament spun staple mixture
c. Weight per unit areaj
d. Working thickness I
e. Napped? Yes No
f. Max. usable temperature:
g. Pre-treatment (Describe treatment):
Fibers:
Filters
2. Gas properties:
a. Specific density (standard or ambient) or constituent makeupt
b. Other pollutants, special constituents^
3. Special problems:
4. Comments -(bag tension, retainment; flow diagram):
-------
APPENDIX 3
U.S. FABRIC FILTER MANUFACTURERS AND PRODUCTS - 1969
(From GCA Survey)
Key to Abbreviations
Configuration
E Envelope or panel type equipment
0 Bag or tube type equipment filtering on the outside of the
cylinder
I Bag or tube type equipment filtering on the inside of the
cylinder
U Upward flow of the dirty gases (bottom entry)
D Downward flow of the dirty gases (top entry)
Cleaning Method;
P Reverse and forward pulsing of single or multiple elements
RJ Reverse jet or traveling blow ring equipment
RF Reverse or backflow of clean air with a minimum of fabric
flexure or motion
RFC Reverse or backflow collapse or flexure of the filter element
S Induced oscillation
V Vibration, rapping, shock, or sound waves
M Direct control of the cleaning intensity and duration.
Assembly;
M Modular, Assembled from self-consistent identical units
C Compartmented, Housing divided into two or more chambers for semi-
independent operation
I Intermittent, Collector must be shut down for fabric cleaning
Co Continuous, Collector need not be stopped for cleaning
CoA Contin. Access, Access to the filter elements is possible dur-
ing operation of the same compartment
-------
APPENDIX 3
U.S. FABRIC FILTER MANUFACTURERS AND PRODUCTS - 1969
Manufacturer
and Configuration
Model E 0 I
Aerodyne Machinery
VS
RAS
SJ
HPE
RSI
Aget Mfg. Co.
FH
FT
1-Bag
Air Preheater
Ray Jet
U
U
U
U
U
U
U D
U
American Air Filter
Amerjet
Amerpulse
Amer Therm
Amer Tube
Arrester
Arrestall
Bahnson
D
D
U
U
X
X
X
Cleaning Method
P RJ RF RF S V M
C
X X
X
X
X
X X
X
X
X
X
X
X
X
X X
X
X X
X X
Cloth Area
Sq.Ft.
Min Max
625 and up
625 and up
8 800
1400 and up
2000 and up
700 2800
120 383
(20) (300)
450 3600
310 2390
61 4400
1320 9660
1339 11675
80; 150 and up
30 180
(1000)
Assembly
M C I Co Co
A
XX X
XX X
X
XX X
X
X X
X
X
X
X
X
X
X X
X X
X
Comments
Cylindrical
Cylindrical
Bottom plenu
-------
APPENDIX 3 (Continued)
Manufacturer
and Configuration
Model E 0 I
Buell-Norblo
Automat ic
Intermittent
Portable
Atmos-Filter
Shaker lea s
luffalp Forge
Aeroturn B
Aeroturn S
Carter-Day
Daynamic DF
CS
RJ
RT.RTR
AC
Cincinnati Fan
Dust Master
Cox Assoc.
Dracco/Fuller
Plenum Pulse
Uni-Filter
U
U
U
U
U
D
U
x U
x U
U
D
x
U
U
U
Cleaning Method
P RJ RF RF S V M
C
x x
X
X X
X
X
X
x
X X
X X
X
X
X
X
X
X
X
Cloth Area
Sq.Ft.
Min Max
960 and up
360 and up
36 135
392 and up
* <» «.
90 and up
628 and up
--, ---
58 1530
58 1530
50 660
50 1217
(6)
300 and up
(500) and up
100 600
As s emb ly
M C I Co Co
A
x x
X X
X
X
X X
X X
XX X
X
X
X
X
X
X
XX X
X
Comments
Vertical shake
Ultrafiltration
Cylindrical
Cylindrical
With Cyclone
Cylindrical or
regular
-------
APPENDIX 3 (Continued)
Manufacturer
arid Configuration
Model E 0 I
Mark II
Glass Cloth
Retro Pulse
Atmos -Filter
Ducon Co.
UVB
UFS
Uniflow
FD
Dustex/Am Prec.
Inductaire
RA
Dusty Pus t^ess
4 Models
Environ. Res. Corp
HI, HA
HC
Flex-Kleen
BV,RA,UD
FK,CT
U
U,D
U
U
U
U
D
U
U
U
U
U
U
U
U
I
Cleaning Method
P RJ RF RF S V M
C
X
X
X
X
X
X
X
X X
X
X X
X
X
X
X
Cloth Area
Sq.Ft.
Min Max
720 and up
80 and up
1000 and up
20 200
40 200
880 and up
50 400
800 and up
225 8500
12 6000
784 and up
125 1300
17 and up
15 2000
Assembly
M C I Co Co
A
X X
XX X
XX X
X
X
X X
X
X X
X
X
X XXX
X
X X
X
Comments
Ultra-filtra-
tion
Cylindrical
-------
APPENDIX 3 (Continued)
Manufacturer
and Configuration
Model E 0 I
Fluidizer
Hoffman
Dustuctor
Hoffcovac
Hydromation
Johnson-March
MB
1000
Kice
Dyna-Jet C,S,M.
R
Kindt Collins
Master
Lams on
Exidust
Macleod
SV
Unit
Tube
U
U
U
D?
U
U
U
U
U
U
X
X
U
Cleaning Method
P RJ RF RF S V M
C
X X
X
X
X
X X
X X
X
X
X X
X
X
X
X
Cloth Area
Sq.Ft.
Min Max
30 63
100 1000
250 1250
1750 and up
10 and up
75 891
20
38 727
880 and up
80 1500
880 and up
As s emb ly
M C I Co Co
A
X
X
X
X
X X
X X
X X
X
X
X
X X
X
Comments
Portable
Cylindrical
Single Bag
I
-------
APPENDIX 3 (Continued)
Manufacturer
and Configuration
Model
E 0 I
Mahon
Meyer
Roto-flo
Pangborn
CH-3
CM.CN.CT
CH-2,CD
CO
Poisi-pulse
Totalaire
Perlite Corp.
H
Precipitair
Pulverizing M/C
Mikro-pulsaire
Mikro-cyl.
Mikro-collecto
Mikro -Custom
U
U
X
U
X
U
U
D
D
U
U
D
U
Cleaning Method
P RJ RF RF S V M
C
X
X
X
X
X
X X
X X
X X
X
X
X
X
X
X
X
Cloth Area
Sq.Ft.
Min Max
265 and up
85 930
400 and up
200 and up
180 and up
1000 and up
11 and up
25 and up
42 900
25 and up
3300 and up
Assembly
M C I Co Co
A
X
X
X
X
X X
X X
X X
X X
X X
X X
X
X
X
Comments
Multi-Tube
Filter
Element
Cylind. or
Regular Ultra
filtration
Multiple Re-
verse Fans
-------
APPENDIX 3 (Continued)
Manufacturer
and Configuration
Model E 0 I
Rees Blow Pipe
Standard
AE
ANS
Unit
Research CottreT
Air -shake
Shake-kleen
Uni-kleen
Also Flex-kleen
Ruemelin
Unit
Standard
Smico
Suction Filter
Systems (Semco)
DC.DCV
Setco
7 AR, 7 GAR,
A Bl
Seversky
U
U
U
U
U
U
(see)
U
U
U
X
U
Cleaning Method
P RJ RF RF S V M
C
X
X
X
X X
X
X
X
x
X
X
X
X
X X
Cloth Area
Sq.Ft.
Min Max
1400 22,000
700 22,000
1500 24,000
380 860
3927 and up
1600 and up
295 1860
53 755
1000 9155
8 3112
50
200 and up
Assembly
M C I Co Co
A
X
X X
X X
X
X X
X X
X
X
XXX
X
X
Comments
Horizontal ait
shake
Portable
Cylindrical/
Rectangular
-------
APPENDIX 3 (Continued)
Manufacturer
and
Model
W.W. Sly
Pactecon-PC
Pactecon-PS
Dynaclone
Intermittent
Economy
Smico
Suction Filter
Sprout-Waldron
Multi-Tube
BV, Series
Sterling
R
Sternvent
Cabinet
" Filter Tube
Tailor
Controlled
Cycle
Torit Corp.
Cabinet
Configuration
E 0 I
X
X
X
X
X
U
U
U
X
U
U
x .
Cleaning Method
P RJ RF RF S V M
C
X
X XX
X
X X
X X
X
* X
X
X
X
X X
X X
Cloth Area
Sq.Ft.
. Min Max
88 1065
88 1065
748 and up
242 and up
176 352
74 100
12 453
111 552
32 1200
426 1800
400 and up
30 1200
Assembly
M C I Co Co
A
X
X
X
X
X
X
X
X
X
X
X X
X
Comments
Controlled
Start-up
I
-------
APPENDIX 3 (Continued)
w
I
Manufacturer
and Configuration
Model E 0 I
United McGill
RF.VAV
MRS, High
Temp.
U.O.P
Aeropulse
Western Precip.
Thermo -flex
Pulsejet-C8
Pulsejet-M8
Wheelabrator
Ultra-Jet
Dustube
Dustube
Young Machinery
Uni-Cage
Uni-Horiz.
Shaker
X
U
u
u
u
u
u
u
u
u
H
U
Cleaning Method
P RJ RF RF S V M
C
X X
X X
X
X X
X
X
X
X
X
X
X
X
Cloth Area
Sq.Ft.
Min Max
4200 22K
75 1135
1130 and up
_ __ ___
273 and up
(10K)
39 and up
27 368
94 631
Assembly
M C I Co Co
A
X
X
XX X
XX X
X
X X
X
X X
X
X X
X
X
Comments
Cylindrical
Also Ultra-
filtration
Cylindrical/
Regular
Horizontal Tubes
-------
APPENDIX 3 (Continued)
PRINCIPLE MANUFACTURERS OF FABRIC FILTER DUST AND FUME COLLECTORS
Aerodyne Machinery Corporation
6330 Industrial Drive
Hopkins, Minnesota 55343
Aget Manufacturing Co.
1408 E. Church St.
Adrian, Michigan 49221
Air Preheater Co.
A Subsidiary of Combustion Eng'g.
Wellsville, New York 14895
American Air Filter Co., Inc.
215 Central Avenue
Louisville, Kentucky 40208
Bahnson Company
1001 South Marshall St.
Winston-Salem, N. Carolina 27108
Buell Engineering Co., Inc.
Northern Blower Division
6409 Barberton Avenue
Cleveland, Ohio 44102
Buffalo Forge Company
490 Broadway
Buffalo, New York 14204
Carter-Day Company
655 19th Avenue, N.E.
Minneapolis, Minn. 55418
Cincinnati Fan & Ventilator Co.
6521 Wiche Road
Cincinnati, Ohio 45237
R.F. Cox Associates
Essex, Massachusetts
Dracco Division
Fuller Company
124 Bridge Street
Catasauqua, Penn. 18032
Ducon Company, Inc.
157 East Second St.
Mineola, Long Island, N.Y. 11500
Dustex Division
American Precision Industries
2777 Walden Avenue
Buffalo, New York 14225
Dusty Dustless
2914 E. Genesee Street
P.O. Box 86
Baldwinsville, N.Y. 13027
Environmental Research Corp.
3725 N. Dunlap St.
St. Paul, Minnesota 55112
Flex-Kleen Corporation
Division of Research-Cottrell
407 South Dearborn St.
Chicago, Illinois 60605
Fluidizer, Inc.
Hopkins, Minnesota
Hoffman Air & Filtration Division
Clarkson Industries, Inc.
P.O. Box 214
Eastwood Station
Syracuse, N.Y. 13206
Hydromation Engineering Co.
39201 Amrhein Road
Livonia, Michigan 48150
Johnson-March Corporation
3018 Market St.
Philadelphia, Pa. 19104
Kice Metal Products Co.
2040 South Mead Avenue
Wichita, Kansas 67211
Kindt-Collins Company
12631 Elmwood Avenue
Cleveland, Ohio 44111
-------
Lamson Division
Diebold, Inc.
306 Lamson Street
Syracuse, N.Y- 13201
Macleod Company
125 Hosteller Road
P.O. Box 452
Cincinnati* Ohio 45421
Mahon Industrial Division
R.C. Mahon Co.
P.O. Box 808
Warren, Michigan 48090
Wm. W. Meyer and Sons, Inc.
8262 Elmwood Avenue
Skokie, Illinois 60076
Pangborn Corporation: Now =
Pollution Control Division
The Carborundum Company
P.O. Box 1269
Middlebrook Industrial Park
Knoxville, Tennessee 37901
Perlite Corporation
200 E. Duttonmill Rd.
Chester, Pennsylvania 19014
Precipitair Pollution Control,Inc.
Chimney Rock Road
Bound Brook, New Jersey 08805
Pulverizing Machinery: Now =
Mikropul Division
The Slick Corporation
10 Chatham Road
Summit, New Jersey 07901
Rees Blow Pipe Manufacturing Co.
2929 Fifth Street
Berkeley, California 94710
Research Cottrell, Inc.
P.O. Box 750
Bound Brook, New Jersey 08805
Ruemelin Manufacturing Co.
3860 North Palmer St.
Milwaukee, Wisconsin 53212
Systems Engineering & Manufact. Co,
6330 Washington Avenue
P.O. Box 7634
Houston, Texas 77007
Setco Industries, Inc.
5880 Hillside Avenue
Cincinnati, Ohio 45233
Seversky Electronatom Corp.
30 Rocketfeller Plaza
New York, N.Y. 10020
W.W. Sly Manufacturing Co.
P.O. Box 5939
Cleveland, Ohio 44101
Smico, Inc.
500 N. MacArthur Blvd.
Oklahoma City, Oklahoma
Sprout-Waldron & Co., Inc.
Muncy, Pennsylvania 17756
Sterling Blower Company
771 Windsor Street
Hartford, Connecticut
Sternvent Company, Inc.
12 Van Dyke Street
Brooklyn, New York 11231
Tailor and Company, Inc.
2403 State Street
Bettendorf, Iowa 52722
Torit Corporation
1133 Rankin Street
St. Paul, Minnesota 55116
United McGill Corporation
Dust Collector Division
883 North Cassady Avenue
Columbus, Ohio 43219
UOP Air Correction Division
P.O. Box 1107
Darien, Connecticut 06820
-------
Western Precipitation Division
P.O. Box 2744 Terminal Annex
Los Angeles, California 90054
Wheelabrator Corporation
Air Pollution Control Division
400 South Byrkit Street
Misawaka, Indiana 46544
Young Machinery Company
Painter Street and Schuyler Avenue
Muncy, Pennsylvania 17756
-------
APPENDIX 4
R&D SUGGESTIONS BASED ON INTERPRETATION OF
COMMENTS MADE DURING SURVEYS
A. Overall fabric filter system costs
1. No comments from field. Cost-effectiveness analysis conspicuous
by absence. Lower costs would make more competitive with other
cleaning technology for certain specific applications (e.g., fly
ash, combustion effluents).
B. Baghouse design
1. Construction materials: steel, concrete, aluminum, etc., in var-
ious conditions of corrosivity.
2. The economics of good baghouse construction; why are they so
flimsy?
3. The economics of building your own baghouse.
4. Need of an inexpensive standard design baghouse, portable, with
adequate instruments and test procedures for pilot studies.
5. A better system of dampers for sealing off a compartment; to aid
in service and maintenance of bags; to enable entering the com-
partment during system operation; and to prevent intrusion of
moisture during down periods.
6. Better quality sealant materials and mechanical assembly to reduce
air leakage.
7. Better flow control at bag inlet, to reduce lower and abrasion of
cloth, e.g., by a study of baffles and their effect on turbulence
and velocities at tube entrance; also to promote large-particle
settling; baffles should be designed for a minimum of abrasive
wear.
8. Design of inlet side of baghouse and hopper to minimize places
for dust accumulation (residual material sometimes catches fire).
9. Designs to minimize maintenance time within the compartment,
especially desired when the dust is hot, noxious, etc.
10. Technique for checking and obtaining the proper bag tension
quickly during replacement, assuming the ideal tension has been
determined.
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11. Consideration of various combinations of demisters/ESP/ FF/ rinsed
screens, etc.; for example, a wet electrostatic filter.
C. Equipment accessory to baghouse
1. Means to cool a hot compartment rapidly prior to maintenance
entry. (Oxygen or moisture content in coolant is not always per-
mitted.)
2. Study of optimum fan design for various applications. Fans wear
and sometimes fly apart with great damage.
3. Better understanding of duct design, to avoid caking and plugging
and if possible to minimize abrasion of duct elbows.
D. Fabrics - Quality and Design
1. Higher temperature, less expensive cloths are needed.
2. Temperature range of cloths is now adequate: longer life, espec-
ially more resistance to flexure, is the major need.
3. Establishment of the relation between temperature and life of var-
ious common fabrics as a guide to their selection.
4. Standardization of cloths: standardization of quality to enable
specification of the desired characteristics and to obtain a
guarantee of cloth performance which is unobtainable at present;
need for more science and less art in filter fabric making.
5. Non-blinding cloths.
6. Elastic cloths which will give rather than tear.
7. Finishes: Need to investigate this important area since little
public information is available. The roles of release agents,
metallic finishes and electrostatic treatments.
8. Projection of future fabric material needs.
9. Need to promote fabric research at installations other than the
traditional fabric manufacturers.
10. Need to survey a wider variety of fiber, cloth, and bag makers.
11. Design of exotic fabrics, for permeability and seepage control
and varying process conditions.
12. Broad study of fabric composite materials, e.g., use of steel
fiber in glass cloth, use of alminates, non-wovens versus cloths,
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in other words, a "systems" expansion of the composite field and
a consideration of possible applications of the resulting mater-
ials.
13. Possible use of scrim or mesh ahead of the fabric to agglomerate
fines without plugging, as an aid to pre-loading the fabric or
to add large very permeable agglomerates to the dust layer on the
fabric; means to dislodge the collections from the scrim period-
ically.
E. Bag Fabrication
1. Investigation of all possible materials for use in filter elements.
2. Need of an ultra-high temperature filter element which might be
.non-flexing. Systems analysis needed.
3. Need for understanding, or for establishing, specifications for
cloth and for bags, to help insure uniformity from order to order
and from supplier to supplier. A listing of the important fabri-
cation parameters.
4. Need for a better thread for sewing seams.
5. A breakdown of the costs and profit margins for the finished bag,
the raw cloth, and the yarn and fiber, as a key to development
and cost reduction.
6. Need for larger fabrics from the weavers.
F. Selection of Fabric
1. What are the rules for selection of the best cloth, if the avail-
able experience isn't enough?
2. A vast study of combinations of dusts and cloths might be made,
but the task would never be done. Laboratory work is at best a
guess since many variables are inevitably missed; yet it is neces-
sary for a new dust application; it often misses the mark widely.
Needed is a statement of what the considerations ought to be in
setting up a lab project; what variables and parameters ought to
be included; and how good can the result be expected to be at
best (and at worst)?
3. Brief survey of the economics of salvaging, cleaning and repair-
ing bags; or discarding them, on an as-needed basis; or on a
fixed period maintenance basis.
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G. Particles
1. Study of agglomeration methods.
2. Understanding of electrostatics in particle collection and cake
removal.
3. Means of control of particles that are sticky when hot or are
pasty when cool.
4. Can turbulence aid pre-agglotneration, and under what conditions?
H. Dust concentration instrumentation
1. Need of method of determining FF load when the collected material
returns to process via a closed system.
2. Need for ultra-low concentrations of toxic material, on an auto-
matic, continuous basis.
3. Standard reliable methods of sampling in low concentrations with
turbulence.
4. Reliable monitor for dirty FF effluent.
5. Quick method or instrument for locating difficult-to-see holes in
bags.
6. Improvements in methods of obtaining particle size distributions.
I. Maintenance Aids
1. Method of keying each bag to its appropriate collector and location,
to avoid misinstallati'.n of the wrong bags.
2. Study to develop a nomogram showing the effect of dust loading on FF
costs along with the reasons.
J. Process Instrumentation
1. Study of standard instrumentation available to control the FFS to
fluctuating processes, to avoid temperature surges, condensation,
etc. Include economics and tell what good instrumentation can
accomplish in terms of reduced power, longer bag life, etc.
2. Development of reliable, inexpensive device to warn against incipient
condensation.
3. Non-plugging pressure sensor for draft control in direct extraction
furnace roof.
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4. Device to warn of baghouse and hopper fires, or to control against
fires.
K. Problems of Special Industries
1. FF research needed toward small combustion sources in urban areas,
heat and power plants, and incinerators. Money and incentive are
especially scarce in these areas.
2. Market study of certain collected materials, to increase their
value and the attractiveness of FF as a process rather than APC.
3° Closer looks at these applications, and the possible government
subsidiation of trials, pilot or full scale, to establish the
performance of FF:
Kraft pulp mill recovery furnace, or lime kiln effluent
Open hearth furnace (pilot feasibility is established)
Sinter process, steel mill
Electric furnace for abrasives
Basic oxygen furnace
Coke plants, several possible applications
4. Instruction for better use of hoods on electric steel furnaces.
5. Need for cake release studies on various dusts in the steel
industry.
6. Large study of the non-ferrous metals area, as an old but very
tough FF application because of fires in the collected material and
sticky fumes among many other adverse factors.
L. Gas Treatment via FF
1. Further development of FF to treat odors as well as to collect
particulate.
M. Mechanical Aspects of Bag Life
1. Study of bag wear wanted by many users.
2. Elimination of bag rips.
3. Study of ring specifications and life (both internal and fastening
rings)
4. Optimization of internal support method for bags, for external filtering
or to prevent collapse when cleaning; must allow for quickest possible
replacement of bags over the support apparatus.
5. Control of bag collapse by strategic yarns and weaves.
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6. Reinforced fabric, wires, or stiffer thread or variations in weave
to control collapse or shake oscillations, effects on cleaning and
general operations.
Longitudinal weave variations to control collapses on reverse air/glass;
high temperature applications; pucker bag shape, versus various combi-
nations of fabric, dust, treatment, process, etc.
7. Determination of ideal length/width ratio of bags
8. Method of determining the proper tension a bag should have for best
performance
9. Study of tension, life, and cleanability; the collapse catenary
10. Study the abrasion of fabrics by interstitial deposits of all
types of dusts; develop a standard test device, and obtain
indices of fabric/dust combinations.
11. Study the abrasion of fabrics by surface impact or friction of
moving dust streams or possibly of deposits of caked material.
12. Study the abrasion of fabrics against support rings, tube collars,
housing walls or wall projections, in the presence of dust. Also
bag-to-bag abrasion.
13. Cutting of cloth by stiff fiber quills.
14. Certain bags fail ten times faster than others in the baghouse; why?
15. Higher air/cloth ratios wanted.
16. Study the effects of underloading and of overloading a FF; give
a cost report.
17. Flexure specified as cause of failure in many cases; extensive
study needed of the mechanisms
18. Popping mentioned also as a cause of failure; how does it contribute
to wear, and what are the pros (cake removal) and the cons of popping
following cleaning.
19. Glass fabric needs a special study ; a number of glass bags are
being shaken for cleaning, by responsible manufacturers.
20. Attempt to lay out ground-rules for the proper choice of fabric, and
cleaning mechanism combination. It may be possible to over-clean
bags; how much is right and how can the right amount be obtained
automatically during operation?
21. A general survey or study of cleaning mechanisms should include
sonic energy, organ pipe effects, electrostatic reverse polarity.
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22. Broad study of effects of sonic frequencies and pulsating frequencies
on caking process and removal process. Employment of hard conductors
in the fabric to carry the vibrations.
23. One reason for short bag life on reverse jet units is the mechanism
on the clean side of the cloth sooner or later gets fouled by leaking
dust, and thereafter the mechanism begins to destroy itself. This
kind of mechanism should be redesigned to protect the machinery,
and thereby increase bag life.
24. Consider an air-borne lubricant to replenish one already on the
cloth, or to enhance operations.
N. Cake Formation and Cleaning of the Cloth
1. Non-blinding cloths are wanted.
2. Cake properties as affected by removal, or addition, of larger
particles in the dust stream by baffles, skimmers, settling
chambers, hoppers, cyclones, etc. for various combinations of
dust, cleaning method, and fabric.
3. Seepage of dust is expected as a matter of course
study should be made for that kind of dust to prevent seepage.
4. A study of adhesion theory should be made, bringing in as many
dust-cloth combinations as possible. Lead chloride doesn't
release well although it did when wool felt was used. A
cloth with fine, slippery fibrils is wanted rather than merely
a smooth cloth. In another case a cementitious deposit
gradually builds up which eventually cracks the bag.
5. Pulsation from the fan is a critical factor in cake formation or
in cake removal . Likewise the pressure surges occurring in
one compartment as another compartment is dampered off may be
a factor in cake mechanics.
0. Cbemical Resistance, and Wetness of the Cloth
1. More corrosion resistant fabrics are wanted, as well as
baghouse and mechanical parts that will stand up better to corrosive
conditions. r
2. Need exists for better control of the gas temperature with respect
to condensible constituents dew point
3. A fabric that could become damp and yet continue to function
would be a help. A substantial economic study of the costs of
supercooling the gas, removing the condensed particulate, and
then slightly reheating the gas above the dew point is needed;
in this way it may be possible to in effect filter below the
dew point. Other approaches may be possible.
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4. Control with respect to dew point is needed to prevent accumulation
of mud on the cooler end of the bags and to prevent plugging
of the hopper material.
P. General FF Study Extensions
1. User survey data should be reviewed by the appropriate FF manufac-
turer to be sure he concurs.
2. Also Projected R&D plans should be reviewed by FF and other manufac-
turers, possibly in a joint seminar, to obtain suggestions and avoid
duplicating work that may have been done and might becovne public
through such a review.
3. A periodic literature review should be established, to maintain
the FFS Data Bank if work is to continue along these lines. In
particular, an effort should go to reviewing the foreign literature.
We should determine which FF manufacturers should review the fogeign
literature, and also avoid duplication of effort at APTIC.
4. A list of likely, qualifying R&D bidder for programs like these should
be collected.
5. APC needs should be projected ahead for several years to see what
temperatures, etc. will be in vogue; what may the economies of the
alternative gas cleaning methods be, and will FF be competitive?
What will the FF needs be?
6. A general computer model of the general FFS could be made up now,
which would be useful in exploring several accumulated theories of cake
structure formation, cake removal, etc. This would more likely be
a tool in feeling out suggested R&D projects than a producer of
data, or a publicized predictor of FF performance.
7. A number of suggestions were made during the survey that are not R&D
suggestions; rather they are clues to better selections of existing
technology, or to better maintenance of equipment now being used.
Accordingly, they should be assembled along the lines of the handbook,
or in the handbook, for FF users, etc.
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ACKNOWLEDGEMENT
The courtesy of a great many authors, publishers, and firms active
in the fabric filtration industry has permitted the use of numerous quo-
tations, tables and figures in the four volumes of this document. GCA
Corporation and APCO are grateful for the use of this material, in the
interests of this important technology. In general, references to the
original publications are made at the end of each volume chapter. In
addition, it has been requested that the following credits be given:
Fluidization and Fluid-Particle Systems by F.A. Zenz and D.F.
Othmer. Copyright (c) 1960 by Litton Educational Publishing,
Inc., published by Van Nostrand Reinhold Company.
Particulate Clouds by H.L. Green and W.R. Lane. Copyright (c)
1964 by Litton Educational Publishing, Inc., published by Van
Nostrand Reinhold Company.
Industrial Dust by P. Drinker and T. Hatch. Copyright 1934 by
McGraw-Hill Book Company. Used with permission of McGraw-Hill
Book Company.
Petroleum Products Handbook by V.B. Gouthrie, Editor. Copyright
1960 by McGraw-Hill Book Co. Used with permission of McGraw-
Hill Co.
Marks' Mechanical Engineers Handbook by T. Baumeister, Editor.
Copyright 1958 by McGraw-Hill Book Company, Inc. Used with
permission of McGraw-Hill Book Co.
Chemical Engineers Handbook by J.H. Perry. Copyrights 1963, 1950,
1941, and 1934 by McGraw-Hill, Inc. Used with permission of McGraw-
Hill Book Co.
Textiles-Fiber to Fabric by M.D. Potter and B.P. Corbman, 4th
Edition. Copyright 1967 by McGraw-Hill, Inc. Used with permis-
sion of McGraw-Hill Book Co.
Filter Materials in High Efficiency Air Filtration (Butterworth
1964) is British Crown copyright.
Reference 50, Chapter 2, Volume I from the British Journal of
Applied Physics is with permission of the Institute of Physics
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4. Title and Subtlti*
FABRIC FILTER SYSTEMS STUDY - VOLUME IV
FINAL REPORT
T Autnorts)
9. Performing Organization Nome end Address
GCA Corporation
GCA Technology Division . .
Bedford, Massachusetts ...
12. Sponsoring Agency Name and Addret*
Division of Process Control Engineering
National Air Pollution Control Administration
U. S. Department of Health, Education and Welfare, PHS
Consumer Protection and Environmental Health Service
Washington, D. C. 20201
5. Report Date
December 1970
6". Performing Organization Code
8. Performing Organization Rept. No.
10. Project/Task/Work Unit No.
IT. Comract7ffririflto7
CPA 22-69-38
r!3. Type of Report & Period Covered
Final
14. Sponsoring Agency Code
l5. Supplementary Notes
16. Abstracts
A Final report is presented which describes a study directed to the de-
finition of two alternative five-year research and development programs
based on different levels of funding for fabric filter systems used in air
pollution control applications. These plans provide specific performance,
to improve economics of usage, and to promote extension of fabric filtratioi
to control of a greater number of applications. Specific tasks undertaken
include: A survey of engineering technology available as data or analyti-
cal design and operation equations; the identification and investigation
of current practices, limitations, and problems of fabric filter systems in
present usage and in possible future applications; and a review of the
major types of fabric filter equipment available.
17. Key Words and Document Analysis, (a). Descriptors
Air pollution control equipment
Filters
Filter materials
Fabrics
Per formance
Design criteria
Cost analysis
Particles
Review
17b. Identlflera/Open-Ended Terms
Fabric filters
Air pollution control
17c. COSATI Field/Group ->/»
18. Distribution Statement
Unlimited
19. Security Class (This Report)
UNCLASSIFIED
30.Security Class. (This Page)
UNCLASSIFIED
21. No. of Pages
129
22. Price
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DISCLAIMER
This report was furnished to the Air
Pollution Control Office by
GCA Corporation
GCA Technology Division
Bedford, Massachusetts
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