Page 36 - Air Pollution Control Engineering

01_chap_wang.qxd 05/05/2004 11:45 am Page 16
16 Lawrence K. Wang et al.

Table 3 (Continued)

SO NO CO HC H S
2 x 2
Gas chromatographic (FID, FPD, and TC)
Applied Science Laboratories, Inc. × ×
Beckman Instruments, Inc. × ×
Bendix Corporation × ×
Byron Instruments, Inc. × ×
GOW–MAC Instrument Co. × ×
Hewlett-Packard, Avondale Div. × ×
Perkin-Elmer Corp. × ×
Tracor, Inc. × × × ×
NDIR
Beckman Instruments, Inc × × × ×
Bendix Corp. × × × ×
Calibrated Instruments, Inc. × × ×
Leeds & Northrup Co. × ×
Mine Safety Appliance Co. × × × ×
Scott Research Laboratories, Inc. ×
NDUV
Beckman Instruments, Inc. ×
E.I. du Pont de Nemours & Co., Inc. × ×
Teledyne Analytical Instruments × ×
UV fluorescence
REM Scientific, Inc. ×
Abbreviations: FPD, flame photometric detector; FID, flame ionization detector: TC, thermal con-
ductivity detector; GC, gas chromatograph; NDIR, nondispersive infrared; UV, ultraviolet; NDUV,
nondispersive UV.

must be placed inside to safeguard the systems. This could require the use of relatively
long sampling tubes, which can result in a potential error by absorption, adsorption, or
fallout of the pollutants. In order to minimize these problems, a molecular diffusion sys-
tem should be used to bring samples close to the instruments (11). This requires the
installation of a large vertical duct or probe through which inlet air can be passed in
laminar flow, as shown in Fig. 4.
This system shows a 15-cm inlet duct with a 150-L/min airflow rate. The top of the
duct is covered to keep debris from falling into the system and should be located about
2 m above the surface of the roof to prevent pickup of dust raised from the roof by
localized turbulent eddies. Sample ports using approx 1.5-cm-diameter tubing and taking
flows of about 5 L/min can then be located in the duct close to the sampling instru-
ments. Note that if many small samples are needed, the duct size and flow should be
increased to provide adequate air for truly representative samples. Unused air from the
duct blower is exhausted outside. All sample lines require periodic checking and clean-
ing. Note that the ends of the small lines shown are gas sample probes with the tips
pointing away from the moving airstream to reduce the chance of picking up entrained
particulate matter.
The relevant data include initial and final airflows, instrument readouts, time, dates,
type of analytical system used, solution preparation dates, and dry weights (e.g., filter