ASTM D6831-02

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Designation: D 6831 – 02
Standard Test Method for
Sampling and Determining Particulate Matter in Stack Gases
Using an In-Stack, Inertial Microbalance
This standard is issued under the fixed designation D 6831; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 This test method describes the procedures for determin- 2.1 ASTM Standards:
ing the mass concentration of particulate matter in gaseous D 1356 Terminology Relating to Atmospheric Sampling
streamsusinganautomated,in-stacktestmethod.Thismethod, and Analysis
an in-situ, inertial microbalance, is based on inertial mass D 3154 Test MethodAverageVelocity in a Duct (PitotTube
measurement using a hollow tube oscillator. This method is Method)
describes the design of the apparatus, operating procedure, and D 3685/D 3685M Test Methods for Sampling and Determi-
the quality control procedures required to obtain the levels of nation of Particulate Matter in Stack Gases
precision and accuracy stated. D 3796 Practice for Calibration of Type S Pitot Tubes
1.2 This method is suitable for collecting and measuring D 6331 Test Method for Determination of Mass Concentra-
filterable particulate matter concentrations in the ranges 0.2 tion of Particulate Matter from Stationary Sources at Low
3 2
mg/m and above taken in effluent ducts and stacks. Concentrations (Manual Gravimetric Method)
1.3 This test method may be used for calibration of auto-
3. Terminology
mated monitoring systems (AMS). If the emission gas contains
3.1 For definitions of terms used in this test method, refer to
unstable, reactive, or semi-volatile substances, the measure-
ment will depend on the filtration temperature, and this method Terminology D1356.
3.2 Definition of terms specific to this standard:
(and other in-stack methods) may be more applicable than
out-stack methods for the calibration of automated monitoring 3.2.1 particulate matter—for solid particles of any shape,
structure, or density dispersed in the gas phase at flue gas
systems.
temperature and pressure conditions.
1.4 This test method can be employed in sources having gas
temperatureupto200°Candhavinggasvelocitiesfrom3to27 3.2.1.1 Discussion—In accordance with the described test
method, all material that may be collected by filtration under
m/s.
1.5 This test method includes a description of equipment specified conditions and that remains upstream of the filter and
on the filter after drying under specified conditions are consid-
and methods to be used for obtaining and analyzing samples
and a description of the procedure used for calculating the ered to be particulate matter. For the purposes of this test
method,particulatematterisdefinedbygasbornematter(solid
results.
1.6 Stack temperatures limitation for this test method is or liquid) captured on or in the filter after drying and weighing
in accordance with this test method.
approximately 200°C (392°F).
1.7 This test method may be also be limited from use in 3.2.2 in-stack, inertial microbalance—a mechanical oscilla-
tor constructed of a hollow tube of a specific metal alloy and
sampling gas streams that contain fluoride, or other reactive
species having the potential to react with or within the sample fitted with a filter cartridge that is designed to oscillate at a
frequency that is proportional to the mass of the hollow tube
train.
1.8 This standard does not purport to address all of the oscillator plus the mass of its filter cartridge.
3.2.3 mass transducer—the mass transducer is a principle
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- component of an in-stack inertial, microbalance. The mass
transducer provides the mechanical structure to support and
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. contain the hollow tube oscillator and to support the sample
inlet nozzle fixture, source gas temperature thermocouple, and
s-type Pitot tube assembly. Refer to 6.1.1 for a detailed
This test method is under the jurisdiction of ASTM Committee D22 on description of this component.
Sampling and Analysis of Atmospheres and is the direct responsibility of Subcom-
mittee D22.03 on Ambient Atmospheres and Source Emissions.
Current edition approved October 10, 2002. Published December 2002. Annual Book of ASTM Standards,Vol 11.03.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6831–02
3.2.4 articulating elbow—a mechanical component that predicated on the isolation of the oscillator from external
may be integrated into the sample probe just before the end vibration sources. To remove the potential for external vibra-
connector attaching to the mass transducer. This elbow is used tion to interfere with the measurement process, the mass
control the angle of the mass transducer relative to the sample transducer housing must be sufficiently massive so that any
probe during insertion of the probe and mass transducer into energy that it absorbs from external vibrations will result in the
thestackandwhilepositioningthemasstransducerinletnozzle mass transducer case oscillating at a resonant frequency that is
into the gas stream. much lower the hollow tube oscillator. As a result, a massive
3.2.5 filtration temperature—the temperature of the housing will absorb any external vibrations and prevent those
sampled gas immediately downstream of the filter cartridge. vibrations from affecting the resonance of the hollow tube
3.2.5.1 Discussion—The temperature of the filter cartridge oscillator.
is maintained at the desired temperature by controlling the 4.2 The filter media typically used is PTFE coated glass
temperature of the mass temperature case and cap. fiber filter media (TX-40 or equivalent) although other filter
3.2.6 sampling line—the line in the sampling plane along media can be used if desired. The filter media is mounted in a
which the sampling points are located bounded by the inner specially designed filter cartridge housing that is designed to
duct wall. promote a constant face velocity through the entire surface of
3.2.7 sampling plane—the plane normal to the centerline of
the filter. The junction of the oscillating element and the base
the duct at the sampling position. of the filter cartridge is designed to ensure a leak free union.
3.2.8 sampling point—the specific position on a sampling
4.3 The sample gases are dried using a semi-permeable
line at which a sample is extracted.
membrane dryer followed by silica gel before the sample
3.2.9 weighing control procedures—quality control proce-
volume is measured. An integrated computer-controlled feed-
dures used for verifying the calibration constant for the hollow
back system is used to control the sample flow rate based on
tube oscillator.
stack gas temperature, velocity and gas density measurements,
3.2.9.1 Discussion—Unlike test methods such as D 6331 or
or user input data, to automatically maintain isokinetic sam-
D 3685/D 3685M, this method does not rely on weighing
pling conditions.
sample media in a laboratory before and after a test is
4.4 To account for source gas density (molecular weight)
conducted. The method includes an integrated filter drying
inputstosettheisokineticsamplingconditions,theuserhasthe
mechanism to desiccate the sample collection media in-situ
option to use manually input data acquired using an Orsat
immediately prior to and following each test run. No physical
analyzer and moisture determination apparatus or equivalent
handling of sample collection media takes place prior to the
method or data supplied by an on-board carbon dioxide
start of a test run through final filter analysis for the test run.
analyzer, oxygen analyzer and moisture measurement system.
Consequently, control filters typically used to characterize the
4.5 Valid measurements can be achieved only when:
impact of filter/sample handling and transportation are not
4.5.1 The gas stream in the duct at the sampling plane has a
required with this method.
sufficiently steady and identified velocity, a sufficient tempera-
ture and pressure, and a sufficiently homogeneous composi-
4. Summary of Test Method
tion;
4.1 The in-stack, inertial microbalance method involves the
4.5.2 The flow of the gas is parallel to the centerline of the
use of a filter cartridge affixed at one end of a hollow tube
duct across the whole sampling plane;
oscillator that is housed in a mass transducer housing. The
4.5.3 Sampling is carried out without disturbance of the gas
mass transducer is attached to the end of an integrated sample
stream, using a sharp edged nozzle facing into the stream;
probe and inserted through a port into the stack or duct. A
4.5.4 Isokinetic sampling conditions are maintained
sample is withdrawn isokinetically from the gas stream and
throughout the test within 610 %;
directed through the filter cartridge attached to the end of the
4.5.5 Samples are taken at a pre-selected number of stated
hollow tube oscillator. Captured particulate matter is weighed
positions in the sampling plane to obtain a representative
continuously as the sample gases pass through the filter
sample for a non-uniform distribution of particulate matter in
cartridge and hollow tube oscillator. Sample gases then con-
the duct or stack.
tinue through the heated probe and umbilical assemblies and
4.5.6 The sampling train is designed and operated to avoid
into a gas conditioning/control module where the collected gas
condensation and to be leak free;
sample volume is determined. A calibrated, orifice-based flow
4.5.7 Dust deposits upstream of the filter are recovered or
meter is used to measure the sample gas volume. In sources
taken into account, or both; and
where the particulate matter characteristics can result in
4.5.8 The sampling and weighing procedures include desic-
significant quantity of particulate matter to be trapped on the
cation of the filter immediately before and after each test run is
inlet nozzle walls during sampling, the trapped particulate
conducted.
matter can be recovered after sampling has been completed
using a properly sized brush to detach and recover trapped
5. Significance and Use
particulate matter from the inlet walls.
4.1.1 Discussion—The ability of this mass measurement 5.1 The measurement of particulate matter is widely per-
technique to precisely quantify the mass of the filter and formed to characterize emissions from stationary sources in
collected particulate matter by correlating mass change to a terms of total emission rates to the atmosphere for regulatory
measured frequency change of the hollow tube oscillator is purposes.
D6831–02
5.2 This test method is particularly well suited for use in dry air to desiccate the filter before and after sampling. The
performance assessment and optimization of particulate matter components and features of the mass transducer are described
control systems, continuous particulate matter emissions moni-
in 6.1.1.1-6.1.1.4.
toring systems and the measurement of low concentration
6.1.1.1 MainFlowInletNozzle—Themainflowinletnozzle
particulate matter laden gas streams in the range of 0.2 mg/m
is exchangeable to allow sampling over a wide range of source
to 50 mg/m .
gas velocity conditions (3 m/s - 27 m/s). Recommended are
nozzles having inside diameter ranging from 1.5875 mm
6. System Description
(0.0625 in.) to 3.1750 mm (0.125 in.) to allow isokinetic
6.1 Major Components—The in-stack, inertial microbal-
sampling over a range of gas velocity conditions from 3 to 27
ance measurement system is comprised of five major compo-
m/s.Thenozzlesareconstructedofseamless316stainlesssteel
nents that are listed in the following table.
and are designed with a sharp, tapered leading edge. The
Mass Transducer An assembly that houses the sample filter and
outside leading edge tapered angle is <30°, and the inside
(see 6.1.1) inertial microbalance. Also contains the Pitot tube assembly,
diameter is constant. Verification of the inlet’s inside diameter
stack gas temperature thermocouple, sample inlet nozzle
and mass transducer heaters.
can be performed using precision measuring pins or a mi-
Sample Probe and A heated support conduit for mass transducer, sample
crometer.
ProbeExtensions and purge flow lines; electrical supplies for mass
(see 6.1.2) transducer and probe heaters; mass transducer electrical
6.1.1.2 Purge Flow Supply Line—A separate pneumatic
signal cables; and the pivoting elbow used for positioning
supply line is provided through the mass transducer case to a
the mass transducer into the source gas flow.
Sample A heated, flexible tubing bundle that contains the
tubing coil wrapped on the outside of the mass transducer cap
Pneumatic/ pneumatic lines for transporting the sample and purge
andthenintoafittinglocatedjustdownstreamoftheexchange-
Electrical gases from/to the mass transducer; and the electrical
ableinletnozzle.Thispneumaticlinesuppliesdry,scrubbedair
Umbilical Cables supply and signal cabling.
(see 6.1.3)
to the inlet nozzle for use in drying the filter before and after
Control Unit A unit that contains sample and purge supply flow
sample collection.
(see 6.1.4) sensors and controllers; stack gas velocity pressure and
temperature transducers; sample and purge supply
6.1.1.3 Impact, Wake and Static Pitot Tubes—An impact
pressure and temperature transducers, data acquisition
and wake Pitot tube assembly is of a type S design and
and instrument control systems; sample and purge gas
conditioners; heater relays; and optionally, CO ,O and constructedusing316stainlesssteelnozzles.AstaticPitottube
2 2
moisture measurement systems comprising the real-time
is oriented perpendicular to the gas flow direction and inte-
molecular weight measurement system.
grated into the side of the Pitot tube assembly. Initial calibra-
Pump / Power Unit Contains the sample vacuum and purge supply pumps
(see 6.1.5) and the 24 VDC power supply transformer for the 24
tion of the Pitot tube assembly must be performed by attaching
VDC heaters in the probe and mass transducer.
the assembly to a mass transducer and dynamically calibrating
A block diagram of the major components of an in-stack, the system in a wind tunnel. If damage to the Pitot tube
inertial microbalance system is shown in Fig. 1. assembly occurs or if post-test quality assurance is desired,
6.1.1 Mass Transducer—The mass transducer houses the dimensional c
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