[Federal Register Volume 62, Number 55 (Friday, March 21, 1997)]
[Proposed Rules]
[Pages 13776-13785]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-7215]
[[Page 13775]]
_______________________________________________________________________
Part V
Environmental Protection Agency
_______________________________________________________________________
40 CFR Part 60, et al.
Hazardous Waste Combustors; Continuous Emissions Monitoring Systems;
Notice of Data Available and Request for Comments; Proposed Rule
Federal Register / Vol. 62, No. 55 / Friday, March 21, 1997 /
Proposed Rules
[[Page 13776]]
ENVIRONMENTAL PROTECTION AGENCY
40 CFR Parts 60, 63, 260, 261, 264, 265, 266, 270 and 271
[FRL-5711-5]
Hazardous Waste Combustors; Continuous Emissions Monitoring
Systems; Proposed Rule--Notice of Data Availability and Request for
Comments
AGENCY: Environmental Protection Agency (EPA).
ACTION: Notice of data availability and request for comments.
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SUMMARY: This announcement is a notice of availability and invitation
for comment on the following reports pertaining to the proposed
requirement for continuous emissions monitoring systems for hazardous
waste combustors (61 FR 17358 (April 19, 1996)): Site-specific Quality
Assurance Test Plan: Method 301 Validation of a Proposed Method 101B
for Mercury Speciation, with Appendices, dated September 27, 1996;
Site-specific Quality Assurance Test Plan: Total Mercury CEMS
Demonstration, Volumes 1 and 2, dated October 11, 1996; Site-specific
Quality Assurance Test Plan: Particulate Matter CEMS Demonstration,
Volume 1, dated August 7, 1996; and Status Report IV: Particulate
Matter CEMS Demonstration, Volumes 1, 2, and 3, dated February 12,
1997.
Readers should note that only comments about new information
discussed in this notice will be considered. Issues related to the
April 19, 1996, proposed rule and subsequent notices that are not
directly affected by the documents or data referenced in this Notice of
Data Availability are not open for further comment.
DATES: Written comments on these documents and this Notice must be
submitted by April 21, 1997.
ADDRESSES: Commenters must send an original and two copies of their
comments referencing Docket Number F-97-CS3A-FFFFF to: RCRA Docket
Information Center, Office of Solid Waste (5305G), U.S. Environmental
Protection Agency Headquarters (EPA, HQ), 401 M Street, SW.,
Washington, DC 20460. Comments may also be submitted electronically
through the Internet to: rcra-docket@epamail.epa.gov. Comments in
electronic format should also be identified by the docket number F-97-
CS3A-FFFFF. All electronic comments must be submitted as an ASCII file
avoiding the use of special characters and any form of encryption.
Commenters should not submit electronically any confidential business
information (CBI). An original and two copies of the CBI must be
submitted under separate cover to: RCRA CBI Document Control Officer,
OSW (5305W), 401 M Street, SW., Washington, DC 20460. For other
information regarding submitting comments electronically, viewing the
comments received, and supporting information, please refer to the
proposed rule (61 FR 17358 (April 19, 1996)). The RCRA Information
Center is located at Crystal Gateway One, 1235 Jefferson Davis Highway,
First Floor, Arlington, Virginia and is open for public inspection and
copying of supporting information for RCRA rules from 9:00 a.m. to 4:00
p.m. Monday through Friday, except for Federal holidays. The public
must make an appointment to view docket materials by calling (703) 603-
9230. The public may copy a maximum of 100 pages from any regulatory
document at no cost. Additional copies cost $0.15 per page.
FOR FURTHER INFORMATION CONTACT: For general information, call the RCRA
Hotline at 1-800-424-9346 or TDD 1-800-553-7672 (hearing impaired)
including directions on how to access electronically some of the
documents and data referred to in this notice electronically. Callers
within the Washington Metropolitan Area must dial 703-412-9810 or TDD
703-412-3323 (hearing impaired). The RCRA Hotline is open Monday-
Friday, 9:00 a.m. to 6:00 p.m., Eastern Time.
Documents referred to in this notice are available from two
electronic sources: the CLU-IN and EMTIC bulletin boards. The CLU-IN
bulletin board is accessible by modem at phone number 301-589-8366 or
by Telnet at clu-in.epa.gov. The EMTIC bulletin board is accessible by
modem at phone number 919-541-5742 or over the Internet at http://
ttnwww.rtpnc.epa.gov/. The reader should note that figures, diagrams,
and appendices may not be available in these electronic documents.
For other information on this notice, contact H. Scott Rauenzahn
(5302W), Office of Solid Waste, 401 M Street, SW., Washington, DC
20460, phone (703) 308-8477, e-mail: rauenzahn.scott@epamail.epa.gov.
SUPPLEMENTARY INFORMATION: On April 19, 1996, EPA proposed revised
standards (herein referred to as ``the proposed rule'') for hazardous
waste combustors (HWCs, i.e., incinerators and cement and lightweight
aggregate kilns that burn hazardous waste). See 61 FR 17358.
I. Introduction and Background
In the proposed rule, EPA proposed requiring that continuous
emissions monitoring systems (CEMS) for particulate matter (PM) and
total mercury (Hg) be used for compliance with the proposed PM and
mercury emission standards. To require CEMS for compliance the Agency,
among other things, determines that the CEMS are commercially available
and meet certain performance specifications. To make these
determinations, the Agency routinely tests CEMS available in the
marketplace. EPA published a notice inviting vendors of PM and Hg CEMS
to participate in a CEMS demonstration test program. (See 61 FR 7232,
February 27, 1996). Ten vendors responded to the Agency's invitation.
They donated nine devices for the test program: six PM CEMS and three
Hg CEMS.1
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\1\ One Hg CEMS vendor was unable to participate.
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Today the Agency is providing notice and opportunity to comment on
the following documents resulting from its CEMS demonstration test
program: (1) Site-specific Quality Assurance Test Plan: Method 301
Validation of a Proposed Method 101B for Mercury Speciation, with
Appendices, dated September 27, 1996; (2) Site-specific Quality
Assurance Test Plan: Total Mercury CEMS Demonstration, Volumes 1 and 2,
dated October 11, 1996; (3) Site-specific Quality Assurance Test Plan:
Particulate Matter CEMS Demonstration, Volume 1, dated August 7, 1996;
and (4) Status Report IV: Particulate Matter CEMS Demonstration,
Volumes 1 and 2, dated February 12, 1997. The purpose of this notice of
data availability (NODA) is to obtain comment on the Agency's approach,
as described in these documents, prior to the end of the demonstration
tests. Comments received will, to the extent possible, be incorporated
into the demonstration test programs. EPA plans to follow this NODA
with a second notice after the testing program has completed or is near
completion. That final notice will contain what EPA believes will be
final draft performance specifications for these CEMS.
The reader should note that one of these documents, the PM CEMS
demonstration test status report, is a draft report which is evolving
over time. The report will be added to and modified substantially as
the program progresses. Therefore, conclusions and discussions in this
report do not necessarily represent EPA's final views. They are
included in this NODA so the reader can fully evaluate the Agency's
[[Page 13777]]
approach and comment on this approach prior to the end of the testing
program.
The remainder of this notice describes the demonstration test
programs for PM and Hg CEMS. It serves as an overview for the reader
and brings to the reader's attention certain areas where EPA requires
input.
II. The PM CEMS Demonstration Tests
A. Background
EPA previously tested PM CEMS at two other sites, the Rollins
incinerator in Bridgeport, NJ, and the LaFarge cement kiln in Fredonia,
KS. Both were short-term tests to determine whether further testing is
warranted.
The purpose of the Rollins Bridgeport tests was to qualitatively
determine whether vendor claims that PM CEMS can be used for compliance
with a PM standard was feasible and to gain insights on the scope and
nature of future tests. Three devices were tested at Rollins: a Sick
RM200 light-scattering CEMS; a BHA CPM1000 time dependant optical
transmission CEMS; and an Emissions SA Beta 5M -gage
CEMS.2 Due to the limited nature of this investigation, though,
there were certain deficiencies in these tests which make quantitative
comparisons of this data to other data difficult. For instance a
calibration of the instruments cannot be performed because manual
method data was obtained over only two particulate emission loadings,
the measured range of emissions was less than one-third of the proposed
HWC PM standard, and only eight valid manual method measurements were
made. However, we did determine that optically based PM CEMS, such as
the light-scattering and time dependant optical transmission
instruments, had a step function increase in their output when
entrained water droplets were encountered in the gas stream.
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\2\ The Beta 5M CEMS is participating in this demonstration as
well.
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Additional tests were conducted in May 1995 at the LaFarge cement
kiln in Fredonia, KS. The purpose of these tests was to conduct a full
calibration of the instruments in accordance with the ISO
(International Standards Organization) specification, to better
determine whether these CEMS could be used for compliance with a PM
standard and whether the ISO performance specification could be used as
a basis of a proposed PM CEMS performance specification, and to gain
insights on future testing. Two devices were tested at LaFarge: the
Sick monitor used in the Rollins tests and an ESC P5A.3 Both are
light-scattering devices. Both devices were installed in April 1995 and
were operated continuously on the cement kiln through July 1995. At
these tests, EPA successfully calibrated these devices in May 1995
using nine valid pairs of M5 runs at three PM loadings. Additional PM
measurements were made approximately one and two months after the
initial calibration. EPA gained the following insights during this test
program:
\3\ The ESC P5A CEMS is participating in this demonstration as
well.
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--The ISO specification can be used as a basis for any performance
specification EPA develops and that the instruments could be calibrated
to particulate emissions obtained from manual method data.
--Response of the instruments to changing PM concentrations was
generally better at this cement kiln than at the previous Rollins test.
--Statistics resulting from these calibrations barely passed the ISO
specification. Other countries (such as Germany) suggest that 15
measurements be made instead of 9 to improve calibration statistics.
Therefore, more than 9 measurements may be necessary.
--The current Method 5(M5) had limitations in measuring low-level
particulate emissions due, in large part, to the difficulty of the
extraction, filter recovery, and weighing steps. This limitation likely
lowered the calibration statistics determined from the data obtained
during these tests.
--PM CEMS could be used for compliance with a PM standard, but longer
term demonstration testing is necessary to ascertain the device's long-
term durability.
The calibration results are summarized in Table 1, below.
Table 1.--May 1995 Calibration Results From the LaFarge PM CEMS Tests
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Confidence Tolerance
Correlation interval interval
CEMS coefficient (CI0.95) (TI0.95)
(r) (percent) (percent)
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ISO Performance Specification................................... 0.90 25 35
Sick RM200...................................................... 0.92 17 29
ESC P5A......................................................... 0.90 20 32
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B. Site Selection
For the PM CEMS demonstration tests, EPA selected the DuPont
Experimental Station hazardous waste incinerator in Wilmington, DE. The
DuPont incinerator receives a variety of wastes from many DuPont
facilities in northern Delaware. As such the waste input to the
incinerator is like that of many commercial incinerators.
The DuPont incinerator has a Nichols Monohearth as its primary
combustion chamber. Waste is fed to this combustion chamber using a ram
feeder for solid waste, a cylindrical chute for batched waste material,
and a Trane Thermal liquid/gas waste burner. The primary chamber
exhausts to a secondary chamber (afterburner) where waste is fed using
a Trane Thermal burner. The flue gas then travels through a spray
dryer, then through a cyclone separator, where dissolved and suspended
solids are removed. The cyclone system discharges to a reverse jet gas
cooler/condenser which reduces the gas temperature to the dew point.
The flue gas then travels through a variable throat venturi scrubber
which removes additional particulate and some acid gasses. The venturi
scrubber exhausts into an absorber neutralized with soda ash scrubbing
solution to absorb acid gasses. The absorber also subcools the flue gas
before traveling through a chevron-type mist eliminator. After passing
through the mist eliminator, the gas travels through a set of electro-
dynamic venturis (EDVs) which are used to remove fine particulate along
with metals that condense onto the fine particulate as a result of the
gas subcooling. The gas then travels through a set of centrifugal
droplet separators and an induction fan, is reheated to eliminate any
visible plume, and is finally discharged to the atmosphere through the
stack. A full description of the incinerator as well as
[[Page 13778]]
a diagram of the system is contained in section 2.2 of the PM Test
Plan.
EPA chose to perform the PM CEMS tests at an incinerator because,
under a normal range of operating conditions, incinerators present a
worse case exhaust stream to challenge multiple PM CEMS technologies in
a long-term test program. For the purpose of demonstrating the
capabilities and limitations of PM CEMS, a worse case exhaust stream
would consist of high moisture (i.e., greater than 20%), average PM
levels below the proposed emission limit, and PM with a wide variation
in physical properties (such as composition, particle size
distribution, shape, color). Incinerators fulfill this worst-case need
in three main ways. First, commercial incinerators and some on-site
incinerators, including the DuPont facility, burn a wide variety of
waste as their primary feedstream. The wide variety of the primary
feedstock 4 has a higher potential to produce highly variable
particulate, which is a worst case test for PM CEMS. This is not the
case for cement or light-weight aggregate kilns (CKs or LWAKs,
respectively.) These sources primarily feed particulate rich process
ingredients (limestone and fly ash for CKs and slate, shale, and clay
for LWAKs). As a result, PM in the flue gases from both CKs and LWAKs
are likely to be overwhelmed by the process dust and be more uniform
than those from an incinerator. Second, many incinerators are equipped
with wet air pollution control system (APCS) technologies which are
able to meet the proposed PM emission limit and produce high moisture.
Finally, these APCS technologies produce a narrow PM size distribution
(i.e., primarily less than 1 micron). This narrow size distribution is
typical of emission levels from wet APCS technologies that are expected
to be installed on HWCs to meet the upcoming MACT standards.
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\4\ Feeds which affect PM emissions include metals, other
solids, and chlorinated solvents.
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The DuPont incinerator was chosen because:
--PM emissions were expected to range from 0.005 to 0.075 gr/dscf (that
is, 17 to 250% of the proposed HWC PM standard), depending on how the
facility operated;
--The facility accepts ``small'' batches of many waste streams and has
limited capacity to burn many waste streams simultaneously, thereby
assuring more dramatic changes in particulate concentrations and
physical characteristics in shorter time intervals, relative to a
larger commercial facility;
--The facility has no ESP or fabric filter for PM control;
--The facility was willing to participate in the test program and allow
necessary modifications to be made;
--The facility was willing and able to vary operating conditions as
required to perform the PM CEMS calibrations; and
--Physical access, both for sampling in the stack and for equipment and
personnel on the adjacent platform, was available to locate six PM CEMS
and a test crew.
A detailed description of the site selection is located in section
1.4 of the PM Test Plan.
C. Revised Manual Method for PM
One issue which PM CEMS vendors raised and which was noted during
the LaFarge tests was that the current manual method for PM (Method 5,
herein refered to as M5,) may be inadequate to make the low-level
measurements required for PM CEMS calibrations. EPA determined that
much of this error comes from sample recovery and analysis. Stacks with
high acid gas, water, and/or adhesive concentrations (i.e., cement kiln
clinker) in the flue gas make the filter stick to the filter housing.
As a result, filter recovery is difficult. For this reason, EPA chose
to modify M5 slightly.
The modification employs the use of a light-weight filter assembly.
The front-half and filter assembly are first pre-tared. The filter
assembly then replaces the current M5 filter housing in the heated box.
After measurement, the entire assembly is desiccated and weighed. This
way the M5 extraction step is eliminated without making fundamental
modifications to M5 itself. Given that this change to M5 is minor and
only affects the extraction and analysis steps, EPA does not believe
that a full field validation of the modification was necessary. Instead
the Agency tested those parts of the method which changed to ensure
that those parts of the process are as good as the current M5. EPA has
initially determined that this modification is acceptable. Completion
of this analysis, including a full write-up of the new method, is
expected soon. A full description of this method will be given in the
later CEMS NODA.
EPA expects this modified method for particulate measurements would
be required for use when calibrating PM CEMS.
D. The PM CEMS Demonstration Test
The PM CEMS demonstration tests started in September 1996 and are
expected to continue until May 1997 or later. The test program started
with an initial calibration of the instruments and followed with
response calibration audits (RCAs) and absolute calibration audits
(ACAs) every four weeks. The program also involves continuously
recording the CEMS data for the duration of the program, documenting
daily calibration and zero checks, documenting all performed
maintenance/adjustments, and documenting all periods in which data was
not available.
A second important aspect of the demonstration tests is to evaluate
the proposed performance specification and data quality objectives
themselves. Proposed performance specification 11 (PS 11) was drafted
and proposed with the idea that it would be modified based on what
these tests showed. The final promulgated specifications will be based
on the data obtained through these tests.
E. PM CEMS Technologies Tested
The six PM CEMS being tested represent three separate PM CEMS
technologies: light-scattering, beta gage (-gage), and
impaction energy devices. Each technology is described below. Full
descriptions of each PM CEMS are found in section 2.7 of the PM CEMS
Test Plan and in the proposals submitted by the vendors. Vendor
proposals are found in docket item S0205. All instruments participating
in this program are provided to the government at no charge.
Light scattering devices work by sending a light beam across the
flue gas and measuring the amount of light reflected back to a detector
located at some angle (other than straight-path transmissivity) from
the light source. These devices can be used either in-situ (i.e., in
the stack) or extractively. These devices are not complex, relative to
other instruments, and as such are relatively inexpensive to purchase.
They also have few moving parts and consequently require little
maintenance. These CEMS are, however, sensitive to PM characteristics,
including composition, density, size distribution, and index of
refractory. Three light scattering devices are participating in the
program: Sigrist Photometer AG model KTNR (supplied by Lisle-Metrix),
Durag model DR-300, and Environmental Systems Corporation (ESC) model
P5A. All three CEMS are installed on more than a hundred stacks
worldwide.
-gage instruments continuously sample extracted flue gas
PM on a filter tape. After the PM sample is collected, the tape moves
so that the collected PM is located between a carbon-14 beta
[[Page 13779]]
radiation source and a detector. This measurement is compared to a
measurement done on the blank filter to obtain the mass of the
collected particulate. As such, these CEMS are continuous samplers but
batch analyzers. These devices are quite complex and as a result cost
more than light-scattering devices. Their complexity also means they
require more maintenance and, as a result, experience more down-time
than light-scattering devices. However, these devices are relatively
independent of the PM characteristics and vendors claim a site-specific
PM calibration is generally not required.5 Two -gage
devices are participating in the program: Verewa model F-904-KD
(supplied by Monitor Labs), and Emissions SA model Beta 5M (supplied by
Environnement USA). Both CEMS are installed on more than a hundred
facilities worldwide.
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\5\ All PM CEMS in this testing program will be calibrated
against the manual method. The claim that -gage PM CEMS do
not require a calibration will be tested as part of this test
program.
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The third type of PM CEMS technology is an impaction energy device
supplied by Jonas Consultants, Inc. This monitor operates by detecting
shock waves caused by particles impacting a probe inserted into the
flue gas. The device counts the number of impacts and the energy of
each impact. This information, coupled with the knowledge of flue gas
velocity, allows the calculation of particulate mass and thus
concentration. However, the probe does alter the velocity profile of
the flue gas near the probe which, in principle, affects the
instrument's response. Thus, EPA believes a site-specific calibration
is necessary to ensure good instrument response. This device has been
installed at few locations, mainly for process control use in steam,
and not for compliance with a flue gas PM standard.
F. Demonstration Test Report
EPA seeks comment on the document Particulate Matter CEMS
Demonstration: Status Report IV, provided in the above referenced
docket. This document describes the interim results from the PM CEMS
demonstration tests EPA is conducting. It contains an analysis of data
obtained from the initial calibration through the Relative Calibration
Audit (RCA) in January 1997. Specific aspects of the report are
discussed below. Subsection 1 describes the limitations EPA has
experienced in this test program. Subsection 2 discusses general
testing issues. Subsection 3 describes the PM CEMS performance
characteristics observed during the initial (and subsequent)
calibration and the RCAs. Subsection 4 describes issues associated with
the proposed performance specifications.
Note that many of the issues described in this section may also
apply to other CEMS, such as the Hg CEMS described in the next section.
Consistency between the two programs will be maintained by handling
similar issues in a similar manner in both programs.
Overall, EPA believes the PM CEMS demonstration is making progress.
EPA was able to calibrate all of the installed devices. The subsequent
RCAs have proved those calibrations to be reliable over time. EPA also
believes that the proposed performance specifications will need to be
modified based on the data and experiences coming out of this program.
1. Limitations of the Test Program
a. CEMS downtime. One limitation of the program is that, unlike
facility personnel, EPA is not on-site all the time. As described in
the test plans, EPA travels to the site every two weeks to, among other
things, perform any maintenance the instruments might require. This
causes CEMS downtime occurring during the program to be overstated
relative to what a real facility would experience if it were using one
of these instruments for compliance.
In addition, CEMS purchased by a facility usually come with a
supply of spare parts so the facility can make minor repairs without
incurring substantial downtime. In this program however, EPA was not
supplied with many of the spare parts it would otherwise get if it had
purchased the instruments. Parts required for routine maintenance must
be ordered from the supplier as needed rather than drawing them from
the facility's store of spare parts. It takes more time to order parts
than to draw from the store of spare parts on-site, so the CEMS are
down longer than they would be if the CEMS were purchased by a facility
for compliance.
Finally, there tends to be no US-based, trained service technicians
to conduct major repairs on many of these instrument. Technicians from
the CEMS manufacturer's native country are often flown in to provide
specialized service. Many of the parts must also be ordered from
suppliers in other countries. This means that, if a major repair is
required, service and parts must be obtained from overseas. This takes
more time than it would if service and parts were available in this
country, and further overstates CEMS downtime.
This is important because one thing EPA is trying to gage in this
program is data availability. Data availability is one minus the CEMS
downtime, expressed as a percentage. If downtime is overstated, data
availability will be understated. EPA anticipates remedying this
situation by subtracting out downtime associated with these
limitations. For instance, if a CEMS requires a minor repair and goes
down soon after EPA leaves the facility, the CEMS will be inoperable
for two weeks, until EPA arrives back at the facility. If the repair
takes eight hours to perform, then EPA will count the downtime as 8
hours, not two weeks. The same approach will be used for the Hg CEMS
program as well.
b. Absolute Calibration Audits. In the proposed rule, EPA proposed
requiring facilities to conduct ``Absolute Calibration Audits'' (ACAs)
every quarter. These tests would be conducted with NIST traceable
standards to ensure the analytical parts of the instrument were still
working properly. Unfortunately, only two vendors (Sigrist and Durag)
have supplied us with these standards. EPA will conduct ACAs on the
instruments as the standards arrive.
At this time, NIST does not have traceable standards for these
instruments. However, German TuV versions of these standards (called
``linearity test kits'') exist for most of these CEMS. We believe that
these TV standards are sufficient substitutes for the yet-to-be-
developed NIST standards to conduct the ACAs.
If these test kits are generally not available to facilities, then
EPA solicits comment on whether the ACA approach should be modified.
For instance, it might be adequate to require a device to make daily
internal zero and span drift measurements and corrections. Most devices
are already configured to make both zero and span drift measurements
and corrections.
c. Inability to repeat tests. It is infeasible to repeat a test
conducted under a set of conditions at this facility due to the wide
variety of ``small'' batches of waste the facility processes and the
hysteresis effect of the APCD. Like a commercial facility, this
incinerator accepts a wide variety of wastes, both hazardous and
industrial, from all DuPont facilities in northern Delaware. The
incinerator often incinerates multiple wastes concurrently. Those
wastes arrive at the incinerator in a random fashion. Batches are also
quite small relative to what would be experienced at a commercial
facility, meaning that transients in PM concentrations and
characteristics are
[[Page 13780]]
more pronounced and shorter in duration.
Further complicating this is the fact that this incinerator is a
zero water discharge facility. This means wastewater from the wet
scrubber is recycled to the spray dryer (upstream from the scrubber)
and injected back into the incinerator exhaust gas. This results in a
hysterisis effect; wastes fed to the incinerator at one time accumulate
in the pollution control system and affect the emissions later. Both
situations affect our ability to repeat tests and, consequently, to
show that CEMS have the same response to the same particulate at a
later time.
d. Inability to test with entrained water droplets. One thing that
attracted EPA to this facility was that it is an incinerator with a wet
air pollution control system and a reheat system to vaporize water
droplets that would otherwise be entrained in the stack gas. EPA
anticipated being able to conduct tests with entrained water droplets
in the stack by turning off the reheat system. The Rollins tests showed
that entrained water droplets are mistaken as particulate by light-
scattering PM CEMS. EPA wished to test the light-scattering devices
with entrained water droplets so it could quantify the effects of
entrained water droplets on light-scattering PM CEMS.
Such tests were planned and conducted in November 1996. But no
entrained water droplets formed despite turning the reheat off. EPA and
DuPont have since concluded that we are unable to predict when
entrained water droplets will occur at the incinerator as currently
configured.\6\ Therefore, it is unlikely that EPA will be able to
conduct tests with entrained water droplets as part of this program.
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\6\ Apparently, there is a 35 deg.F temperature increase across
the induction fan that can not be overcome.
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One approach EPA may take is to use the limited data EPA has from
its earlier Rollins Bridgeport tests of PM CEMS and draw whatever
conclusions it can from that data.\7\ However, EPA believes this data
is insufficient to quantify the effects of entrained water droplets.
For this reason, EPA requests data which quantifies the effects of
entrained water droplets on the calibration of light-scattering PM
CEMS.
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\7\ Based on the Rollins data, EPA qualitatively concluded that
while entrained water droplets did induce a step function increase
in the output from in-situ light-scattering PM CEMS, it did not
affect the calibration so much as to cause the calibration to fail
under this condition. The step function increase was caused by the
in-situ light-scattering PM CEMS mistaking entrained water droplets
for particulate.
This leads EPA to believe that a facility which uses an in-situ
light-scattering PM CEMS for compliance and has entrained water
droplets in the stack gas may experience situations where the actual
PM emissions are lower than those reported by the monitor. The risk
for a such a facility which is in compliance with the PM standard is
that it may experience an increased number of false non-compliances
with the PM standard. EPA hopes to quantify the effects of entrained
water droplets on light-scattering PM CEMS so it can quantify the
risks associated with a false non-compliance in this situation.
This possible false non-compliance possibility can be avoided if
the light-scattering PM CEMS is configured such that it extracts
flue gas from the stack, heats it to above the highest possible dew
point temperature, and measures the heated, extracted gas. One
light-scattering PM CEMS in the program is so configured. Others can
be similarly configured to avoid this potential problem. The trade-
off is that extractive light-scattering PM CEMS cost more than in-
situ units.
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2. General Test Issues
a. Handling of Outliers. Two types of outliers were experienced so
far in the program: paired data and statistical outliers. Each is
discussed below.
i. Paired Data Outliers. EPA is conducting its PM measurements in
such a way that a pair of (two) trains concurrently sample the flue gas
at the same time in the same plane of the stack. The average of these
two concurrent trains is the PM emissions measured by the manual method
for a given run. This methodology usually means the results from the
two trains are similar. This conclusion is substantiated by most of the
data obtained during the test program.
However, there were instances when the results from the pair of
concurrent trains differed substantially. This leads EPA to believe
that there was a problem with one or both of the trains which comprise
such a run. As a result, EPA developed a quality criteria requiring
that the pair of trains which comprise a run not differ substantially.
EPA quantitatively defined this substantial difference by looking at
historical M5 data. Data indicate that results from paired trains such
as these agree with a relative standard deviation (RSD) of 10%.
Therefore, nearly all data should agree to within three times this RSD,
or to within 30% of each other. If the results of paired trains
disagree by more than 30%, the whole run would be thrown out.
EPA anticipates that other situations will arise in which it will
need to disregard data which substantially differs from the historical
data in other ways. The Agency would have serious reservations
regarding this practice of defining what is or is not acceptable data
after the fact if this were a compliance determination. However, this
is not a compliance evaluation, and EPA does not believe the same
cautions apply. In addition, EPA is unable to develop these quality
criteria prior to the start of the program because it does not have a
history of PM data from this facility upon which to base such quality
criteria. EPA believes this approach of developing quality criteria as
the program progresses is reasonable given the unique situation here.
ii. Statistical Outliers. Another type of outlier data experienced
during the program is referred to as ``statistical outliers.''
Statistical outliers are data which are more than three (3) standard
deviations away from the linear regression line that represents the
calibration of the instruments. EPA does not have an opinion on how to
handle statistical outliers and requests comment on how to proceed.
In implementing manual calibration tests for other CEMS, EPA
routinely allows outliers of this kind to be disregarded when
developing the calibration curve. The Agency's logic for disregarding
this data is that it is known that the manual method sometimes
dramatically under-reports emissions for unknown reasons.\8\ Using this
outlier data in the calibration of other CEMS is unwise because: (1)
The error cannot be accounted for by known science; and (2) eliminating
the data causes the slope of the calibration curve to be steeper (i.e.,
numerically larger), therefore it is protective of the environment to
exclude this outlier data. In the case of other CEMS, the statistical
difference is reasonable justification for proving that a problem
occurred while obtaining that data point.
---------------------------------------------------------------------------
\8\ It is believed that the cause is a manual method sample is
not obtained due to spacial differences between the sampling
locations of the manual method and CEMS.
---------------------------------------------------------------------------
Upon closer examination here, however, it is not clear whether the
fact that the data appears to be statistically different is ample
justification to disregard the data. Statistical tests usually involve
the testing of a sample population to see if the sample data is from
the same population as data you are comparing it to. It involves
establishing a null hypothesis which states that the sample is part of
the population (H0: s = p or
s2 = p2, that the mean or
variance, respectively, of the sample data is equal to that of the
population). If the statistical test infers that the null hypothesis is
not true, then an alternate hypothesis, stating that the data is from a
different population than the one you are comparing it to, is accepted
(HA: s p or
s2 p2, that the mean or
variance, respectively, of the sample data is different than that of
the population). In our case here, the
[[Page 13781]]
fact that a statistical outlier is more than three standard deviations
away from the linear regression line would likely lead one to reject
the null hypothesis and say that the outlier is from a different
population than what is represented by the linear regression line.
After determining the data are different, one must determine why. This
analysis is important because it will help determine whether the data
should be kept in the original sample or disregarded.
This situation differs from the other CEMS case because PM CEMS
have known sensitivities to changes in what they are measuring, i.e.,
moisture and the particle's characteristics, such as density, shape,
size distribution, refractory (color), etc. Unfortunately, we do not
know the effects of these changes on the outputs of PM CEMS.9 In
other words, EPA is uncertain whether the statistical outliers were
caused by an error in the manual method measurement process (in which
case the data would be thrown out) or if the error was caused by the
CEMS overstating (or understating) the PM emissions due to changing
particulate properties (in which case the data would be kept in the
data set). In addition, most of the statistical outliers experienced in
this program are ones in which the manual method result is higher than
what the PM CEMS report. Therefore, it would likely be more appropriate
to keep the data in the data set in this case.
---------------------------------------------------------------------------
\9\ EPA's Office of Research and Development recently concluded
a study of how changes in particulate properties affect the output
of PM CEMS. The report describing the results of this study is not
expected to be completed until September 1997.
---------------------------------------------------------------------------
EPA is currently pursuing statistical ways of dealing with outliers
and requests comment on how to deal with this situation. One
alternative is to establish a stringent specification for the
correlation coefficient (yet within the bounds of the data obtained in
this program) and allow facilities to throw out, but report, data that
is farthest away from the linear regression line. ``Farthest away''
could be defined on either a relative or absolute standard deviation
basis. The facility would then substitute in better data if needed to
meet the minimum number of samples or other performance specification
requirements.
b. Extrapolating Data. Another issue is that this facility, while
having a PM permit limit of 0.08 gr/dscf, cannot emit that much
particulate. We expect that similar situations exist throughout the
industry. This is a concern because EPA proposed that facilities
calibrate their PM CEMS to up to two (2) times the emission limit. If
it is physically impossible for a facility to emit this much
particulate, it obviously cannot calibrate the instruments that high.
Therefore, the Agency seeks comment on whether the following
approach is acceptable. EPA believes a facility should calibrate the
CEMS up to the point where, based on historical data the facility has,
the facility is producing the most particulate. This point will serve
as the ``high'' calibration range for this facility's PM CEMS. In
addition, the facility would use the available data and extrapolate the
linear regression line beyond the high calibration range for instances
where the emissions are higher than the historical data indicate. As
the historical data grow for this facility, the facility may notice
times when the PM emissions are more than what the previous historical
data indicated. In this event, the facility would re-calibrate the CEMS
under the previously unknown condition(s) which result in higher
emissions than the old historical data indicated.
A unique case exists when the highest possible emission level is
less than the emission standard. In this case the calibration data
point resulting in the highest PM CEMS output would be the point where
the confidence and tolerance interval tests would be conducted.10
---------------------------------------------------------------------------
\10\ The proposed performance specification states that the 95%
confidence interval for the calibration curve must be no more than
20% of the emission limit at the emission limit. This
is a single point test. In the case where a facility cannot
calibrate up to or above the emission limit, the 95% confidence
interval test for the calibration curve would be 20% of
the emission limit at the point resulting in the highest PM CEMS
output. The same approach would be used for the tolerance interval
test as well.
---------------------------------------------------------------------------
c. Correcting for temperature and dry basis. Some of the PM CEMS
need to correct their output for stack temperature and moisture. These
corrections have not been done for the data in this report. While these
corrections will have a minor effect, the data will change slightly
after the corrections are made. EPA is now correcting the data to
account for changes in temperature and moisture. Future reports will
report all data properly corrected for temperature and moisture.
3. PM CEMS Performance Characteristics
One important aspect of the program is to test and verify that the
performance of these devices meet the characteristics described in the
proposed performance specification (PS) 11. It also serves as a test of
the performance specification itself and proposed data quality
objectives for CEMS described in the proposed Appendix to Subpart EEE.
Data from this demonstration test program will be used to revise PS 11
and the data quality objectives as necessary.
Table 2 lists each of the monitors being tested, the proposed
performance requirement for the devices, and the actual performance
observed during the test program.11 The results in Table 2 do not
include data outliers which have been excluded from the analysis, such
as ``paired data outliers.'' The reader should note that the
correlation coefficient, confidence interval, and tolerance interval
tests apply only to the calibration. These values are reported,
however, for subsequent RCAs even though they do not apply in this
situation. Specific discussion on each performance specification is
discussed, below.
---------------------------------------------------------------------------
\11\ Results from the Jonas analyzer, however, is not reported.
The Jonas analyzer reported results in terms of emission rate (g/s)
rather than emission concentration (mg/dscm). Time is needed to
analyze and correct how to correct these values to the proper units.
---------------------------------------------------------------------------
EPA has been able to generate a linear regression line for the
various PM CEMS. Performance of the devices are nearly identical when
one compares the performance of an in-situ device to the other in-situ
device and extractive devices to one another. In-situ units seem to
show better performance than extractive units regardless of technology
of the CEMS.
[[Page 13782]]
Table 2.--Performance Characteristics of the PM CEMS Being Tested
--------------------------------------------------------------------------------------------------------------------------------------------------------
Performance specification Correlation Confidence Tolerance
-------------------------------------------- coefficient interval interval RCA test Calibration drift Zero drift (ZD)
CEMS Date of test (r) (CI0.95) (TI0.95) (TI0.95) (CD)
--------------------------------------------------------------------------------------------------------------------------------------------------------
20 35 75% 2% of the 2% of
>0.90 % at emission % at emission of data calibration standard the emission
limit limit within limit
TI0.95
--------------------------------------------------------------------------------------------------------------------------------------------------------
ESA.................. Cal................. 0.55 26 38 .............. Pass................. Pass.
01/97............... 0.92 21 25 75 Pass................. Pass.
All Data............ 0.46 35 40 .............. ....................
Verewa............... Cal................. 0.69 27 32 .............. No data.............. Pass.
12/96............... 0.86 24 20 100 No data.............. Pass.
01/97............... 0.93 18 25 100 Fail................. Pass.
All data............ 0.76 18 23 .............. ....................
Durag................ Cal................. 0.72 22 36 .............. Pass................. Pass.
11/96............... -0.38 52 77 75 Pass................. Pass.
12/96............... 0.91 45 73 100 Pass................. Pass.
01/97............... 0.93 20 22 100 Pass................. Pass.
All data............ 0.61 20 35 .............. ....................
ESC.................. Cal................. 0.71 22 36 .............. Pass................. Pass.
11/96............... 0.87 24 31 88 Pass................. Pass.
12/96............... 0.92 42 69 100 Fail................. Pass.
01/97............... 0.93 20 23 100 Pass................. Pass.
All data............ 0.68 18 32 .............. ....................
Sigrist.............. Cal................. 0.64 25 40 .............. Pass................. No data.
11/96............... 0.87 24 31 88 Pass................. No data.
12/96............... 0.90 47 77 100 Pass................. No data.
01/97............... 0.92 21 24 100 Pass................. No data.
All data............ 0.64 19 33 ..............
--------------------------------------------------------------------------------------------------------------------------------------------------------
Note to Table 2: The initial calibration for the Durag, ESC, and Sigrist units was performed in September and October 1996. The initial calibration for
the Verewa unit was performed in September and November. The initial calibration for the ESA unit was performed in September and December.
a. Correlation Coefficient (r). Proposed PS 11 states that the
correlation coefficient be at least 0.90 (See Sec. 4.2.1). Tests to
date indicate that EPA may be unable to produce a linear regression
line which correlates as well as the proposed performance specification
indicates.12 EPA believes this is caused by the fact that this
facility is a worst-case facility for this demonstration test program.
EPA believes the correlation coefficient specification may have to be
lower based on the results of this testing.
---------------------------------------------------------------------------
\12\ Time constraints have required the Agency to temporarily
ignore the quadratic regression approach described in the
performance specification. This analysis will be done for the final
report and the curve which best fits the data will be presented.
---------------------------------------------------------------------------
Particulate properties depend largely on the wastes fed and the
accumulated particulate in the APCS. These properties vary considerably
at this facility, just as the types of wastes fed to the unit vary.
This variability in the particulate properties causes a varied response
from the PM CEMS, which in turn causes the correlation coefficient to
be lower than anticipated. This can be avoided by developing a
calibration curve for every possible set of particulate properties.
However as described in the next paragraph, this may not be possible at
this facility.
The calibration tests were done under as wide a variety of
operating conditions as possible. The proposed performance
specifications and data quality objectives would make a facility such
as this incinerator to have one calibration for every given operating
condition, not one that fits all situations as EPA did here. The Agency
now believes the proposed approach may not be possible for this source.
As mentioned, particulate does accumulate in the APCS causing wastes
fed at one time to influence the type of particulate that is emitted
later. In addition, the wastes arrive at the incinerator in a random,
uncontrollable manner and in ``small'' batches. This makes it extremely
difficult for a facility such as this one to determine what
calibrations it needs and which of those calibrations to use at any
given time. It might be best for a facility such as this one to have
one, not many, calibrations to simplify compliance. EPA seeks comment
on whether this approach, having one calibration curve to cover every
circumstance rather than several for each circumstance, is acceptable.
b. Confidence Interval (CI0.95). Proposed PS 11 states that
CI0.95 be within 20% of the emission limit at the
emission limit. (See Sec. 4.2.2). This test is done by taking the data
from the initial (or subsequent) calibration, calculating the 95%
confidence interval for the regression line, and verifying that the
upper confidence limit at the emission standard is less than the
emission standard plus 20% and that the lower confidence limit at the
emission standard is more than the emission limit minus 20%. In other
words, this is a single point test at the emission limit.13 Based
on standards proposed for HWCs, this means the upper confidence limit
must be less than 83 mg/dscm and the lower confidence limit more than
55 mg/dscm calculated at the emission limit.
---------------------------------------------------------------------------
\13\ See above for the discussion of what to do when it is not
possible to calibrate to the emission limit.
---------------------------------------------------------------------------
Confidence intervals calculated for these PM CEMS are higher than,
but close to the proposed specification. This higher value for the
confidence interval is probably the result of EPA's approach of
generating one calibration curve at this worst-case facility.
c. Tolerance Interval (TI0.95). Proposed PS 11 states that
TI0.95 be within 35% of the emission limit at the
emission limit. (See Sec. 4.2.3). This test is done by taking the data
from the initial (or subsequent) calibration, calculating the 95%
tolerance interval for the regression line, and verifying that the
upper tolerance limit at the emission standard
[[Page 13783]]
is less than the emission standard plus 35% and that the lower
confidence limit throughout the calibration range is more than the
emission limit minus 35%. Like the correlation interval test this is
also a single point test.14
---------------------------------------------------------------------------
\14\ Again, see above for the discussion of what to do when it
is not possible to calibrate to the emission limit.
---------------------------------------------------------------------------
The calculated tolerance intervals for the various PM CEMS being
tested are, like the confidence interval, higher than but close to the
proposed specification.
d. Relative Calibration Audit (RCA) Tests. The proposed data
quality objectives state that, to pass an RCA, 75% of the RCA data must
lie within the 95% tolerance interval. (See Sec. 5.2.3.1 of the
proposed appendix to Subpart EEE.) All the CEMS passed all the RCAs.
Therefore, the initial calibration is still valid over time despite the
changing operating conditions at the facility.
e. Calibration and Zero Drift (CD and ZD). Proposed PS 11 states
that CD be within 2% of the calibration standard and that
the ZD be within 2% of the emission limit. (See Secs. 4.3
and 4.4, respectively). This test would be done during the ACA tests,
which the proposed quality assurance requirements stated would be done
on a quarterly basis.
As discussed above, most of these CEMS internally check zero and/or
calibration drift every day. In cases where one or more of the checks
are not internally done, traceable standards are required to perform
the check. Most vendors have not supplied these NIST traceable
standards (or an acceptable substitute) for the ACAs. The ACAs for this
test program will be done every 4 weeks for these missing parameters as
soon as EPA obtains these standards from the vendors.
Where data is available, most CEMS routinely pass the zero and
calibration checks. In instances where the drift test is failed, the
CEMS automatically adjusts the failed parameter to within
specifications. EPA is now quantifying the ``Pass'' and ``Fail''
indicators shown in the table. Future reports will quantify values for
zero and calibration drift rather than express them in the qualitative
terms ``Pass'' and ``Fail''.
f. Response Time--Continuous CEMS. Proposed performance
specification 11 states that continuous-type CEMS respond to a step
increase in such a way that the CEMS achieve 95% of the final stable
reading within 2 minutes of the start of the step increase. (See
Sec. 4.5.1). This requirement is to be certified by the vendors. The
vendors participating in this program have done so. This specification
will not be tested during this program unless EPA believes the response
time is suspect.
g. Response Time--Batch CEMS. Proposed performance specification 11
states that the response (i.e., sampling) time for batch-type CEMS be
no more than one-third of the averaging period. (See Sec. 4.5.2). The
sampling time for these CEMS are on the order of minutes while the
averaging period for the PM standard was proposed to be two hours, so
this requirement has been met.15 But this specification does raise
several issues which deserve consideration here.
---------------------------------------------------------------------------
\15\ One of the -gage devices has two sample collection
tapes to allow for the continuous sampling of flue gas, but the
other does not. The truly continuous unit collects particulate on
one tape as the second tape is being analyzed. The unit with one
tape samples the extracted gas onto that tape and then analyzes it.
This unit is not a continuous sampler since it is not sampling stack
gas while measuring the accumulated particulate on the tape. The
device with one tape could be configured with two tapes to allow for
the continuous sampling of stack gas. It was not configured with two
tapes for this test program because the vendor was unwilling to
incur the cost of supplying such a device for this test program.
---------------------------------------------------------------------------
While the response time requirement is met for the averaging period
associated with the standard, ten minute and one hour averages were
proposed for PM CEMS when used as an operating parameter, i.e., all
times other than during a comprehensive performance test. The sampling
time for these devices is less than one third of the one hour average,
but not less than one third of the short term ten minute average.
Further complicating this is the fact that the sampling period for
these devices, while less than ten minutes, is more than half of ten
minutes. The result is that no averaging could be done to assure
compliance with a ten minute average. This raises the issue of whether
the sampling period for PM CEMS needs to be less than one third of the
ten minute average. EPA believes not, since this requirement is based
on EPA's belief that a facility will want to base compliance on the
average of at least three data points. If a facility is willing to base
compliance on fewer than three data points, it could be allowed to do
so. This is particularly true for a ten minute average which is likely
to be quite high relative to the standard or the one hour average.
Nonetheless, EPA seeks comment on how to address this for the final
rule.
4. Issues Relative to the Draft Performance Specification 11 for PM
CEMS
a. Performance Specifications which Apply for the Calibration
Curve. The proposed data quality objectives were specific that a
tolerance interval test be used during an RCA to determine whether the
calibration curve is still valid. However, the data quality objectives
were silent on what tests apply to determine whether the initial
calibration is valid. For this reason, EPA wishes to clarify this
point.
To test the validity of the calibration curve, one must check to
make sure the calibration curve passes the correlation coefficient (r),
confidence interval, and tolerance interval tests. The correlation
coefficient is a test of the curve's overall fit. If the calculated
correlation coefficient is greater than the one published in the
performance specification, the calibration curve is acceptable. The
confidence interval test is a single point test at the emission
limit.16 This verifies the fit of the calibration at the emission
limit, a critical point when using a CEMS for compliance. The tolerance
interval test is similar to the confidence interval test in that it is
a single point test.
---------------------------------------------------------------------------
\16\ See above for the special case where a facility cannot
calibrate the PM CEMS to the emission limit.
---------------------------------------------------------------------------
The confidence interval and tolerance interval tests, though, may
be redundant. Therefore, we seek comment on whether only one of these
tests should be used. There is merit to keeping both tests, though. The
confidence interval test, for instance, ensures that the calibration
curve is accurate at the standard, a point where a high degree of
accuracy is required. The tolerance interval test is unique in that it
sets the maximum deviation the tolerance interval lines can be from the
linear regression curve at 35% of the emission limit. Therefore,
commenters should focus their comments on whether these tests are
indeed redundant. Would a failure of one test conclusively mean the
other test is also failed? Conversely, would passing one conclusively
mean a facility would pass the other? If so, which of these tests is
more stringent?
b. Number of Tests for the RCA. During the course of this test
program, EPA has learned that it might be wise to standardize the
number of tests required for the RCA.17 Other Appendix B
performance specifications require that 12 tests be performed for
relative accuracy test audits (RATAs). (RATAs are the equivalent to the
RCA here.)
---------------------------------------------------------------------------
\17\ Section 7.3 of the proposed performance specification 11
for PM CEMS states that the number of tests required for a response
calibration is 15. This should not be confused with the number of
tests for a relative calibration audit. Section 7.3 does not apply
to RCAs.
---------------------------------------------------------------------------
EPA believes the following approach would be acceptable for RCAs
and requests comment on it. A facility
[[Page 13784]]
would perform up to 12 manual method measurements. Manual method tests
may be disqualified and fewer than 12 used if they fail method QA/QC or
the facility's internal data quality standard, but in no case may the
number of RCA tests be lower than 9. If fewer than 9 measurements
remain after the quality audit of the data, a new RCA test is required.
To pass an RCA, more than 75% of the qualifying, good data must lie
within the tolerance interval lines.
III. The Hg CEMS Demonstration Tests
A. Site Selection
For the Hg CEMS demonstration tests, EPA selected the Holnam cement
kiln #2 in Holly Hill, SC. This cement kiln co-fired hazardous waste
with other fuels, including fossil fuels such as coal. As such, this
cement kiln is like many other hazardous waste burning cement kilns.
Holnam Holly Hill kiln #2 is 18.5 feet wide and 580 feet long with
a design capacity of 2,100 tons of clinker per day. The main
ingredients in the cement production are limestone, clay, alumina, and
iron. The facility also obtains additional raw materials, such as fly
ash, to supplement raw materials. Raw materials are ground, mixed with
water, and fed to the cold end of the kiln at a solids content of about
65%. The hot (discharge) end of the kiln is fired primarily by coal,
but petroleum coke, waste carbon, shredded tires, hazardous waste, fuel
oil, and natural gas can also be fired. Kiln #2 has a rated capacity of
600 M-Btu/hr. Gases pass through the electrostatic precipitators (ESPs)
specifically designed and built for this facility, through a transfer
duct, and out the exhaust stack.
EPA chose to perform the Hg CEMS tests at a cement kiln for many
reasons. CKs tend to have higher levels of mercury in their flue gas,
relative to an incinerator or an LWAK, because mercury is fed to the
kiln in the raw material used for cement production. Other HWCs can
better avoid mercury in their feed materials, so it is less likely that
mercury would be present in the flue gases of those sources. Therefore,
a useful Hg CEMS demonstration program can be conducted at a CK since
it has mercury in the flue gas. CKs also have higher PM emissions
relative to other sources. The PM is also likely to contain mercury.
This is because the PM is derived in large part from the raw material
that, in turn, can be a significant source of the mercury fed to the
kiln. Particle bound mercury is difficult for Hg CEMS to measure, so
this represents a worst case for these instruments. Finally, CKs tend
to have air pollution control equipment to control PM only. Other
pollutants are uncontrolled and may be present at high concentrations.
Since these pollutants, such as SO2 and NOX, may interfere
with the Hg CEMS's ability to measure mercury, this again is a worst
case situation for Hg CEMS.
The Holnam Holly Hill cement kiln #2 was chosen because:
--Data indicated the mercury concentration in the flue gas is 17
g/dscm without the need to spike mercury;
--The facility was willing to host the demonstration and allow the
necessary facility modifications;
--Physical access was available at the transfer duct and stack; and
--There was room for installing the Hg CEMS analyzers close enough to
the sampling point to meet the monitor's maximum sample line
requirements.
A detailed description of this selection decision is found in
Section 1.3 of the Hg Test Plan.
B. Speciated Hg Manual Method.
One aspect of the program is to determine how well these Hg CEMS
measure all species of mercury.18 Some mercury monitors measure
just elemental mercury. Total mercury monitors, or Hg CEMS like those
participating in this program, measure all mercury regardless of
species. Most Hg CEMS measure total mercury by first converting all
mercury to elemental mercury and measuring the amount of elemental
mercury in the treated flue gas. Converting all mercury to elemental
mercury adds much complexity to the instrument.
---------------------------------------------------------------------------
\18\ For the purposes of this discussion, mercury species are
defined as particle bound, ionic, and elemental mercury.
---------------------------------------------------------------------------
At the start of this program, no method had been validated to
measure mercury by species. Many types of speciated mercury methods are
currently being developed, so EPA chose to validate one of those
methods to use in this program. This speciated mercury method is
tentatively called Method 101B.19 The report, Site-specific
Quality Assurance Test Plan: Method 301 Validation of a Proposed Method
101B for Mercury Speciation, describes the methodology used to validate
the method.
---------------------------------------------------------------------------
\19\ The reader should note that many methods are currently
being developed to speciate mercury emissions. One of those other
methods may be better than the method chosen here. This method was
chosen because EPA knows how to perform this method. Other methods
are not so well documented. Eventually a method other than the one
used here may be adopted as the EPA method for mercury speciation.
---------------------------------------------------------------------------
While EPA is not ready to release the final report on this
validation, some mention of its validation status is warranted here.
The method passed all Method 301 criteria without correction with the
exception of ionic mercury. The Agency has not yet concluded whether
the method passed for ionic mercury. The issue for ionic mercury is
that the HgCl2 spiking used for the validation varied so much that
it caused the calculated relative standard deviation to be much greater
than Method 301's criteria of 0.50. EPA is now studying how to
eliminate the effects of HgCl2 spiking from the data. We will
release the final validation report after this concern has been
addressed.
Finally, EPA has not yet determined whether this validation at this
cement kiln can be transferred to other sources. Mercury species,
primarily ionic forms such as HgCl2, are very difficult to
generate, transport, and measure. EPA plans to use this method at other
sources. Prior to doing so, though, we will perform tests to determine
how well the validation at the cement kiln transfers to these other
sources. After this work is completed, EPA will be able to determine
whether this method should work at other sources. Until this is done,
however, EPA recommends that a facility wishing to measure mercury by
species first conduct a full Method 301 validation of the speciated
mercury method prior to using it.
The reader should note that EPA has no plans to require facilities
to use M101B. It was validated so EPA could answer questions it had
regarding the ability of the Hg CEMS to measure all species of mercury
simultaneously. A facility would continue to use Method 29 20 to
measure stack mercury emissions, including any stack tests required for
Hg CEMS.
---------------------------------------------------------------------------
\20\ Likewise, a facility could also use Method 101A. M101A is a
mercury-only emission measurement method. M101A is identical to M29
except it uses mini-impingers.
---------------------------------------------------------------------------
C. The Test Plan
Testing started in August 1996 and continued through September. In
October we discovered that all the Hg CEMS had suffered equipment
failures. EPA met with the Hg CEMS vendors soon after the problem was
discovered, and vendors responded to EPA's data availability concerns
by increasing the ruggedness of their equipment. Testing resumed in
December 1996. The monitors have responded with less failures since the
modifications were made.
As was the case in the PM CEMS testing program, relative accuracy
test
[[Page 13785]]
audit (RATA) and ACA tests are being performed every four weeks.
Testing is expected to continue through May 1997 or later.
An important aspect of the Hg CEMS demonstration tests is to test
the performance specifications themselves. Revised specifications will
be promulgated based on the data obtained here and comments received in
response to the CEMS NODAs.
Vendor proposals for this test program are found in docket number
S0205.
D. Hg CEMS Demonstration Test
Due to the sudden stop and restarting of the Hg CEMS demonstration
test program, EPA is not prepared to release an interim report for this
test program. EPA does request comment on the approach we are using to
demonstrate these Hg CEMS and how to address the variability of spiking
during the ACA test.
1. Hg CEMS Demonstration Test Approach
The Agency's approach to demonstrating the Hg CEMS can be found in
the document, Site-specific Quality Assurance Test Plan: Total Mercury
CEMS Demonstration.
2. ACA Tests and Spike Variability
As described in the section above concerning the Method 101B
validation, similar problems have been encountered spiking known
concentrations of elemental (Hg0) and ionic (Hg+2) mercury to
the CEMS. NIST traceable permeation tubes are available for Hg0,
but not for Hg+2. As a result, performing ACA tests on the Hg CEMS
with Hg+2 is very difficult. EPA believes it may need to modify
the proposed performance specification to take this into account.
Therefore, EPA now believes it is prudent to have facilities
conduct ACA (i.e., linearity) tests with Hg0 only. Facilities
would then use this ACA to determine whether the calibration of the
monitor is still valid and, if it fails the ACA (or if this ACA is the
first performed), use the ACA results as the basis for a new
calibration. Spiking with Hg+2 would be done only for the purposes
of ensuring the Hg CEMS adequately measured Hg+2. In other words,
the Hg+2 test would resemble the NOX converter efficiency
test prevalent for NOX CEMS. In this case a facility would spike
an amount of Hg+2 within some range (for instance, within 75 to
125% of the emission standard) and ensure that the measured amount of
Hg reported by the analyzer is within an acceptable range (for
instance, within 20%) of the actual Hg+2 spike
determined by the manual method. The actual ranges will be determined
based on data obtained from these tests. EPA requests comment on
whether this approach is appropriate.
Dated: March 12, 1997.
Elizabeth Cotsworth,
Acting Director Office of Solid Waste.
[FR Doc. 97-7215 Filed 3-20-97; 8:45 am]
BILLING CODE 6560-50-P
