TM 5-810-15
CHAPTER 4
AIR QUALITY CONTROL AND MONITORING EQUIPMENT
The data acquisition system (DAS) stores
4-1. General.
monitored information, performs necessary
Refer to TM 5-815-1 for a detailed description of
calculations and generates the required reports.
the major air quality control devices available for
c. Gas monitors. Gas monitors can be classified
boiler plant emissions control. Air pollution control
as either in situ or extractive.
guidelines are discussed in AR 42049.
(1) In situ analyzers are attached directly to
the probe on the stack or breeching. Access for
4-2. Particulate control systems.
routine maintenance is required and personnel
The types of particulate control systems which are
weather protection may also be desirable for out-
commonly used are mechanical cyclone collectors,
door installations depending upon the climate. In
fabric filter baghouses and electrostatic precipita-
situ monitors relay information to the DAS using 4
tors.
to 20 mA signals.
(2) Extractive monitors pull samples from the
4-3. Flue gas desulfurization systems.
flue gas stream using stack or breeching probes.
The dry and wet types of FGD systems are
The flue gas sample is then transported to the
commonly used to remove sulfur oxides from the
cabinet mounted analyzer located on the plant floor
boiler flue gas.
or ground level as required. This cabinet is placed
to provide convenient access for operation and
maintenance. The interior of the cabinet can also
Two types of systems available for NOx emissions
include any necessary heating, air conditioning or
reduction are selective catalytic reduction (SCR)
humidity control. Extractive systems are further
and selective noncatalytic reduction (SNCR). SCR
classified as either wet, dry or dilution. Since raw
systems require periodic replacement of the cata-
samples contain SO2 and moisture, ambient cooling
lyst. SNOR removal efficiency is maintained only
of wet samples will cause condensation of sulfuric
within a narrow temperature range.
acid. For longevity of the equipment wet sample
tubes must be heated to avoid acid corrosion.
4-5. Air monitoring equipment.
Removal of water from the sample using a cooler
provides a dry sample which no longer requires
a. General. Federal regulations require new
heating. These systems are called dry extractive.
sources to obtain and maintain acid rain permits. A
Dilution extractive systems use clean dry air to
permit is good for five years and must be renewed.
dilute the sample gas in the probe from between 50
Emission allowances are required to emit sulfur
to 200 times. This diluted sample eliminates the
dioxide. Pollutants must be monitored to verify
need for heat traced sample lines, pumps, filters or
compliance with the acid rain program. Reported
dryers. Analyzers are readily available to accurately
values include SO2 (lb/hr), NOx (lb/MB), CO2
and reliably measure diluted pollutant
(lb/hr), excess opacity (percent), and heat input
concentrations.
(MB). Measurement options are available to gas/oil
d. Flue gas flow monitors. Monitoring of flue gas
fired units, depending upon the type or category of
flow is sometimes required. In these cases flue gas
gas/oil unit. Exemptions from acid rain permit
flow is used along with the primary measured value
requirements
including
from
to calculate the reported value. Three types of flue
continuous emissions monitoring (CEMS) are
gas flow monitoring systems that have been used
available to certain types and sizes of emitters by
include ultrasonic monitors, thermal monitors and
petition. A thorough investigation of local, state,
differential pressure monitors.
and federal regulations is required for each new
(1) Ultrasonic flow rate monitors.
source.
Ultrasonic flow monitors consist of two ultrasonic
b. CEMS components. CEMS include four major
transducers mounted at different elevations and on
components or subsystems. Gas monitors measure
opposite sides of the stack. This type of monitor
the concentration of pollutants at a particular point
measures the time required for an ultrasonic pulse
in the flue gas stream. Flow monitors measure flue
to travel from the downstream transducer to the
gas flow and fuel flow monitors measure natural
upstream transducer. The speed of sound in the flue
gas and fuel oil flow rate. Opacity monitors indicate
gas stream and the flue gas stream temperature are
the emission of particulate matter from the stack.
4-1
Previous Page
