United States
Environmental Protection
Agency
 Industrial Environmental Research
 Laboratory
 Cincinnati OH 45268
Research and Development
 EPA-600/S2-81-126  Sept. 1981
Project Summary
Characterizing  Baghouse
Performance  to  Control
Asbestos Manufacturing
Source  Emissions
David R. Jones
  This study  is part of  a  research
program designed to improve the
effectiveness  of  airborne  asbestos
fiber removal by baghouses.  A typical
fabric filter baghouse control system,
shown in Figure 1, was automated and
modified to facilitate the use of the
EPA Method 5 sampling train, shown
in Figure 2 to monitor the output of the
baghouse  during  the  commercial
fabrication  of asbestos  containing
materials. Single-point near isokinetic
inlet samplers were installed on each
of four inlet ducts. The baghouse mass
loadings, the  outlet fiber concentra-
tions, and operating conditions of the
fabrication process were  monitored.
Each of three operating parameters of
the baghouse was observed at three
levels. The baghouse research param-
eters were shake amplitude, shake
duration and shake interval.
  Two test series were conducted.
The first was a statistically designed
test series, the results of which were
interpreted using multiple linear
regression analysis on the 1 /3 facto-
rial test design. The linear regression
analysis showed shake duration to be
the  most important parameter, fol-
lowed by the shake amplitude and the
shake  period.  The results indicated
that, at optimum shake interval and
shake duration, a 6-fold improvement
in asbestos fiber emission control was
achieved. The  second test series was
 run to determine whether extending
 shake intervals would produce an
 equivalent 6-fold reduction in fiber
 emissions, and if the mass loading or
 waste type  were more significant
 characteristics. Extending the shake
 intervals did  result in low emissions;
 however, no significant effect on
 control  was  achieved by extending
 shake duration. No detectable change
 in pressure drop was noted up to a 12-
 hour shake interval.
  Statistical evaluation of the first test
 series data  indicated interactions
 between the baghouse parameters.
 The fiber emissions were reduced at
 longer shake  intervals.  The  major
 conclusion reached regarding asbestos
 emission control was that fiber
 emissions were minimized by the least
 frequent disturbance of the bags.
  The Project Report was submitted in
 fulfillment of Contract No. 68-03-
 2558 by I IT Research Institute under
 the sponsorship of the U.S. Environ-
 mental Protection Agency. The report
 covers the period from June 27.1977
 to September 30, 1979.
  This Project Summary was devel-
 oped by EPA's Industrial Environ-
 mental Research Laboratory. Cincin-
 nati. Ohio, to announce key findings of
 the  research project that is fully
documented in a separate report of the
 same title (see Project Report ordering
information at back).

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Figure 1.    Baghouse for asbestos removal, showing plenem. ducting and effluent
            sampling station.
Figure 2.    HVSS sample train and effluent monitor.

                                 2
Introduction
  Processes  involving  asbestiform
minerals are known to produce signif-
icant quantities  of  waste  materials
which release airborne asbestos fibers.
Airborne  asbestos fibers have been
associated with asbestosis and other
respiratory diseases.  The  prevalent
control  device used to minimize the
emission of airborne asbestos fibers to
the environment is a fabric filter used in
a form known as a baghouse.
  This report describes a field research
program whose objective was to mini-
mize asbestos fiber  emissions. The
program  demonstrated that, even
though  a  baghouse has an  extremely
high mass efficiency, literally billions of
fibers per  ho(ur are emitted from a well-
controlled source.
  While current asbestos data do not
permit the determination of the  health
effects,  it  is  prudent to maximize the
control of  asbestos emissions using the
most feasible, economical and effective
methods available.
  Asbestos fibers are implicated in the
development of diseases  with  20-40
year latency periods,  and to date no
threshold  exposure value has as yetj
been defined. It is possible  that even'
very small asbestos fiber emissions
could have a long-term impact on the
national health.
  Previous studies had shown that
fabric filters were the most common and
effective method of controlling emissions
from asbestos processes. Variations in
the  operating baghouse  parameters
were believed to  affect the  degree of
control achieved.  In'this study,  a full-
scale commercial  baghouse was oper-
ated at specified conditions, and  its
degree of  control measured  by moni-
toring emission fiber counts.
  The objective of the study was to
identify  the significant operating pa-
rameters, and  to  determine  what
conditions provide maximum  control of
asbestos  fiber emissions. The fiber
count method was  used, since the
variations  on a mass basis are too small
to measure.
  This research  study has origins in
past projects done at IITRI and in EPA's
continued  interest in the improvement
of control technology for asbestos fiber
emissions  from industrial sources. The
initial effort was a two-phase program
performed under EPA Contract No. 68-
03-1353. Phase I results are reported in
EPA-650/2-74-088 and Phase II result^
in EPA-600/2-76-065.              ^

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Statistical Evaluation  of Bag-
house Test Data
  The pri mary objective of the f ractiona I
factorial statistical evaluation was to
define  guidelines for the optimum
operation  of baghouses for control of
asbestos emissions. This was done on a
full scale baghouse in use on an actual
operation generating asbestos emis-
sions.  The  parameters selected for
investigation were:
  • the period of time between shake
    cycles,
  • the duration of the shake cycle, and
  • the shake amplitude.
  During the first series of tests on the
program a data  base was assembled
permitting statistical analysis of the
three baghouse parameters, monitoring
of the  baghouse  condition, baghouse
inlet loading, and data permitting  a
check on the validity of the samples.
  All of the  data were associated with
93 individual samples taken during the
test program.  The specific  data  base
used in the statistical analysis consisted
of fiber concentration in number of
fibers/SCM. The  data  were obtained
using electron microscopy (EM) on each
of the 93 samples obtained. Additionally,
each of the inlet loading values obtained
from all but combination 2 was also
entered into the analysis as a possible
co-variate  variable.
  Prior to the linear regression analysis
of the design, statistics on each of the
combinations were obtained. These
statistics  were  used  to verify the
homogeneity of the fiber counting data
and various transforms. The variance of
the fiber count data varied widely from
combination to combination (P>.001).
The variance of the square root transform
also fluctuated (0.10 > P>0.05), while
the log transform was more stable (0.3>
P>  0.2). On  the basis of Bartlett's test,
the log transform was considered
suitable for  use in obtaining a pooled
estimate of the standard deviation. The
estimated pooled standard deviation
obtained on  the basis of 81 degrees of
freedom was s = 0.49.
  The summary  of major conclusions
based on linear regression analysis of
the primary data base were:
  • Two of  the  selected parameters,
    shake duration and shake amplitude,
    showed the  maximums in  their
    output curves. The existence of  a
    maximum rather than a minimum
    implies either  that there is no
    optimum,  or  that the optimum is
     outside the experimental range of
     the parameters.
  •  The  shake period showed a mini-
     mum at the midpoint of the values
     studied.
  •  A positive correlation  between
     mass loading of the baghouse and
     the output concentration has been
     obtained.
  •  The  lowest  output concentration
     obtained  is equivalent to  the
     baseline concentration. The base-
     line conditions  are outside  the
     range of parameters studied.
  •  All values of concentration mea-
     sured were at approximately 10 x
     10" to 50 x 106 fibers/SCM. This is
     equivalent to  10-50 fibers/cc in
     the  baghouse outlet. Also, since
     about 10 percent of the total fibers
     are  above 5 /urn  in  length,  the
     OSHA concentrations measured in
     the baghouse plenum would be 1 -5
     fibers/cc.
  There  were  two conclusions which
required  additional study. The first was
that  a  previous study  had showed, by
similar statistical analysis, that the type
of waste  was more significant than the
mass loading. The second was that the
baseline  data,  obtained at a 12-hour
shake period and 300-sec shake dura-
tion, showed an  output concentration
equivalent to the lowest obtained in the
experimental design. The shake period
and  shake duration were greater than
those studies,  while the shake ampli-
tude was identical to the longest ampli-
tude used in the design.

  From the data taken, the conclusions
are:
  •  Extending the length of the period
     between shakes is beneficial.
  •  For some applications, the pressure
     drop is not significantly affected by
     extended shake interval.
  •  Automation of the  shake cycle
     leads to better performance of the
     baghouse.
  •  Shake duration at extended inter-
     vals between  .shakes  is  not  a
     significant parameter.
  •  The  duration of the shake cycle
     seems to  be the most  important
     parameter, both  from statistical
     and  observed standpoints.
  •  Interactions between variables are
     important, but cannot be computed
     from the  partial factorial experi-
     ment. The interactions make  for-
     mulation  of  a design  equation
     impractical.
Conclusions
  The single most important variable in
the  level  of asbestos fiber emissions
from a baghouse is the duration of the
shake time for the bags during the
cleaning operation. The next variable in
importance is the amplitude of the
shake, followed by the shake period.
These three variables account for about
40% of the output variability from a
baghouse.
  The interactions between the three
design  parameters of shake  period,
shake amplitude and shake duration are
important in operating a baghouse. The
measured asbestos fiber emission rate
from a baghouse is dependent on the
material  being processed and the
process rate.
  The lowest values of baghouse output
measured were 6 million fibers/m3 and
the highest 32 million. The lowest value
showed fiber concentration of 0.3
fibers/cc >5 fjm (300,000 fibers/m3 >
5/um) on  the  average. However,  one
sample included in this average approx-
imated the OSHA limit of 2 fibers/cc (2
million fibers/m3> 5jum) of air.  Fiber
counts  exceeding  the  current OSHA
limitof 2 fibers/cc of air >5|/m in length
were numerous.
  The lowest  concentrations of fibers
emitted were  achieved when  the
baghouse was operating at conditions
which favored greater cake build-up on
the bags.  The combination  was: short
shake/small shake amplitude and long
shake period. No detrimental effect on
pressure drop was noted at the most
efficient conditions. In fact, no correla-
tion  of performance with pressure drop
was found. The baghouse, even though
it has an extremely high mass efficiency,
does emit literally billions of fibers per
hour under optimum conditions.

Recommendations
  The baghouse exit air fiber levels
must be reduced below 100,000 fibers
> 5//m per cubic meter to be considered
for recycle. In  lieu  of current optimum
conditions as defined by this research,
the baghouse alone cannot produce the
levels of  control required.  Additional
research is necessary to assess what if
any  control  technology is capable of
producing an emission of less than
100,000 fibers >5^m per cubic meter.
  The  use of  statistical design tech-
niques when evaluating or  optimizing
control device performance is  recom-
mended.  Statistical designs for  con-
tinuous data are quite efficient to  use

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    and  provide  cost  effective programs.
    The  data obtained on  a statistically
    designed  program will  provide,  at a
    minimum, guidance for future work and
    trends; at its best, when all assumptions
    are correct, the maximum information is
    extracted from the data.
           David R. Jones is with IIT Research Institute, Chicago, IL 60616.
           Mary K. Stinson is the EPA Project Officer (see below).
           The complete report, entitled "Characterizing Baghouse Performance to Control
             Asbestos Manufacturing Source Emissions,"(Order No. PB81 -231 250; Cost:
             $8.00, subject to change) will be available only from:
                   National Technical Information Service
                   5285 Port Royal Road
                   Springfield, VA22161
                   Telephone: 703-487-4650
           The EPA Project Officer can be contacted at:
                   Industrial Environmental Research Laboratory
                   U.S.  Environmental Protection Agency
                   Cincinnati, OH 45268
                                                                                 US GOVERNMENT PRINTING OFFICE; 1981 — 757-012/7361
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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