Method
7E - Determination of Nitrogen Oxides Emissions from Stationary Sources
(Instrumental Analyzer Procedure)
1.
APPLICABILITY AND PRINCIPLE
4. MEASUREMENT SYSTEM
PERFORMANCE SPECIFICATIONS
6. MEASUREMENT SYSTEM
PERFORMANCE TEST PROCEDURES
6.1 Calibration Gas
Concentration Verification.
6.4 NO to NO Conversion
2 Efficiency.
7.1 Selection of
Sampling Site and Sampling Points.
7.3 Zero and
Calibration Drift Test.
This
method is applicable to the determination of nitrogen oxides (NOx)
concentrations in emissions from stationary sources only when specified within
the regulations.
A
sample is continuously extracted from the effluent stream; a portion of the
sample stream is conveyed to an instrumental chemiluminescent analyzer for
determination of NOx concentration. Performance specifications and test
procedures are provided to ensure reliable data.
Same
as in Method 6C, Sections 2.1 and 2.2.
The
total equipment required for the determination of NOx concentration. The
measurement system consists of the following major subsystems:
3.1.1
Sample Interface, Gas Analyzer, and Data Recorder. Same as in Method 6C, Sections 3.1.1, 3.1.2, and 3.1.3.
3.1.2
NO2 to NO Converter. A
device that converts the nitrogen dioxide (NO2) in the sample gas to nitrogen
oxide (NO).
Same
as in Method 6C, Sections 3.2 through 3.8.
The
output response of the measurement system to a component in the sample gas,
other than the gas component being measured.
Same
as in Method 6C, Sections 4.1 through 4.4.
Prepared
by Emission Measurement Branch EMTIC TM-007E
Technical
Support Division, OAQPS, EPA May 7, 1990
ΡΡΡΡΡΡΡΡΡΡΡΡΡΡΡΡΡΡΡΡΡΡΡΡΡΡΡΡΡΡ
Use
any measurement system for NOx that meets the specifications of this method. A
schematic of an acceptable measurement system is shown in Figure 6C-1 of Method 6C. The essential
components of the measurement system are described below:
5.1.1
Sample Probe, Sample Line, Calibration Valve Assembly, Moisture Removal System,
Particulate Filter, Sample Pump, Sample Flow Rate Control, Sample Gas Manifold,
and Data Recorder. Same
as in Method 6C, Sections 5.1.1 through
5.1.9, and 5.1.11.
5.1.2
NO2 to NO Converter. That
portion of the system that converts NO2 in the sample gas to NO. A NO2 to NO
converter is not necessary if the NO2 portion of the exhaust gas is less than 5
percent of the total NOx
concentration.
5.1.3
NOx Analyzer. An
analyzer based on the principles of chemiluminescence to determine continuously
the NOx concentration in the sample gas stream. The analyzer must meet the
applicable performance specifications of Section 4. A means of controlling the
analyzer flow rate and a device for determining proper sample flow rate (e.g.,
precision rotameter, pressure gauge downstream of all flow controls, etc.) must
be provided at the analyzer.
The
calibration gases for the NOx analyzer shall be NO in N2. Use four calibration
gases as specified in Method 6C, Sections
5.3.1 through 5.3.3. Ambient air may be used for the zero gas.
Perform
the following procedures before measurement of emissions (Section 7).
Same
as in Method 6C, Section 6.1, except if
calibration gas analysis is required, use Method 7,
and change all 5 percent performance values to 10 percent (or 10 ppm, whichever
is greater).
Conduct
an interference response test of the analyzer prior to its initial use in the
field. Thereafter, recheck the measurement system if changes are made in the
instrumentation that could alter the interference response (e.g., changes in
the gas detector). Conduct the interference response in accordance with Section 5.4 of Method 20.
Same
as in Method 6C, Sections 6.2 through 6.4.
If
the NO2 concentration within the sample stream is greater than 5 percent of the
NOx concentration, conduct an NO2 to NO conversion efficiency test in
accordance with Section 5.6 of Method 20.
Select
a measurement site and sampling points using the same criteria that are
applicable to tests performed using Method 7.
Position
the sampling probe at the first measurement point, and begin sampling at the
same rate as used during the response time test. Maintain constant rate
sampling (i.e., ±10 percent) during the entire run. The sampling time per run
shall be the same as the total time required to perform a run using Method 7
plus twice the average system response time. For each run, use only those
measurements obtained after twice the response time of the measurement system
has elapsed to determine the average effluent concentration.
Same
as in Method 6C, Section 7.4.
Same
as in Method 6C, Section 8.
Same
as the bibliography of Method 6C.