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DKL Engineering, Inc.
Handbook of Sulphuric Acid Manufacturing
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Sulphuric Acid
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Process Engineering Data Sheets - PEDS
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Preface
Contents
Instrumentation - NOx
June
4, 2006
Introduction Principle of Operation Installation Instruments |
Associated Links |
NOx in the form of NO2
and NO is of primary importance in the area of combustion and the proper
operation of a fuel fired boiler, furnace, etc. In sulphuric acid plant
application NOx is a concern in both metallurgical and regeneration acid plants.
NOx can be produced in the upstream metallurgical process or in the regeneration
furnace. Measurement of NOx is important to determine how much is entering
the contact section and how much is leaving in the stack. Emission of NOx
in the stack can lead to a poor stack appearance and may exceed local emission
limits.
Ultraviolet Light Absorption - This technique is based on the differential
absorption of UV-visible light by the sample stream at two different
wavelengths. Radiation from a selected light source passes through the
sample and into the photometer, where a semi-transparent mirror splits it into
two beams. The measuring beam passes through an optical filter which
excludes all wavelengths except one absorbed strongly by the sample constituent
under analysis. The reference beam is filtered to a wavelength which the
sample absorbs weakly or not at all. Each beam then falls on a photodiode
which converts the light signal to an electrical current proportional to the
light intensity of the beam.
A logarithmic amplifier, in turn, provides a voltage proportional to the
negative logarithm of the photodiode currents. The differential of the
amplifier outputs provides a single output linearly proportional to the
concentration of the measured constituent in the sample, in accordance with
Beer's law. The split-beam technique is inherently accurate and
interference-free because the wavelengths are examined simultaneously.
Adverse sample conditions, such as particle matter turbidity and fluctuations in
light intensity, produce an equal effect on the intensity of the energy at both
wavelengths and, therefore, cancel out.
Process gas is drawn into the analyzer where the nitrogen dioxide (NO2)
in the sample is analyzed directly by the difference in light absorption by NO2
at two different wavelengths (436 nm measuring wavelength and a 578 nm reference
wavelength). Since nitric oxide (NO) is essentially transparent in the
visible light and ultraviolet, it first must be quantitatively converted to NO2.
The process gas sample can be reacted oxygen at 5 atmosphere pressure in the
sample cell. The reaction is both rapid and reproducible.
Manufacturer | Type | Range | Model No. | Remarks |
AMETEK | Ultraviolet Light Absorption | NOx: 0-100 ppm
wet O2: 2-25% wet |
4610 | Meets all
known EPA requirements Sample Flow: 10 SCF/h Instr. Air: 2 SCFM field unit 2 SCFM probe Electrical: 2 kVa Oxygen: 60 psig, welding grade Sample taken to analyzer |
SICK | Light Absorption | GM 30 |