Teledyne 9700 - Flue gas analysis system - Manual (Page 51)

A-7
Flue Gas Analysis System Appendix
TELEDYNE BROWN ENGINEERING
Analytical Instruments
Supporting Equipment for Flue Gas Analysis Systems
Two basic types of sample probes for flue gas applications are shown
in Figures A-1 and A-2. The straight, dry type of probe (Figure A-1)
consists of a length of 1" 316 stainless-steel pipe with a mounting flange or
coupling welded to the outboard end for connection to the duct or stack
(length of probe, as required). The second type is similar to the first except
for the addition of a water spray nozzle .attached to the Outside end of the
probe. This type of probe is used in applications containing large amounts
of particulate matter such as coal-fired boilers, cement and lime kilns, and
high sulfur fuel-oil fired boilers.
Experience has shown that the best service from probes can be ob-
tained by eliminating any cooling or spray water in the portion of the probe
inside of the duct or stack, and that the practice of adding spray nozzles
inside the probe only increases their inclination to plug up. It is beneficial,
however. to add spray water on the outside end of the probe. This cools the
gas quickly and keeps acids and particulate concentrations from building
up in the sample line. It is necessary to run the sample line so that it slopes
continually from the probe to the analyzer system inlet to allow the spray
water to keep the line flushed and prevent the accumulation of particulates
or acid. All sample lines should be run in this manner for best results.
When using a spray nozzle on the probe end, it is recommended that a
drop-out pot be installed on the analyzer system inlet to drain off the water
containing the contaminants before it enters the system. This also prevents
water from building up in the sample line during routine calibration or
system shutdown.
Sample lines can be made from a variety of materials including
stainless steel, PVC, steam hose, Teflon tubing and copper pipe. Tubing
I. D. should be from
7 /
16
" to 5 /
8
". When using dry-type probes without water
washed lines, it is beneficial to use heated lines such as “Dekron” to pre-
vent condensation. This is necessary for any sample line which would be
subject to ambient temperatures which are below freezing.