AADCO 737 Series, Operating Instructions Manual

Page: 23 / 72

19
10.0 METHANE REACTORS.
10.1
The methane reactors are canisters, Figures 5, 7, and 7a (20), containing a
low temperature catalyst, a heating system, and a temperature controller. The
system temperature is factory set at the optimum temperature for the
destruction of methane (about 290

C ± 10

C). A cooling coil Figures 5, 7, and
7a (27) is placed between the methane reactor and the exit fitting labeled
PURE AIR so that the temperature of the effluent hydrocarbon free air does not
exceed 40

C.
10.2
This reactor, when installed in any 737-series pure air generator, is electrically
controlled by the POWER switch, Figure 4 (2), located on the face of the
generator unit. The equilibration time, from initial power, is about sixty minutes.
IT IS ADVISED THAT NO INSTRUMENTATION BE CONNECTED TO THE
PURE AIR GENERATOR DURING THIS INTERVAL SINCE COPIOUS
AMOUNTS OF WATER ARE DRIVEN FROM THE CATALYST DURING THIS
PERIOD, See Figure 14.
10.3
During this initial “burn-in” a low flow of air should be permitted to pass through
the methane reactor to sweep the accumulated water from the reactor and
effluent tubing prior to connection to the using the equipment. A rotameter
reading of about 1/4 scale, set with the OUTPUT FLOW ADJUST, Figure 4
(13), and about 20-psig output pressure, set with the OUTPUT PRESSURE
REGULATOR, Figure 4 (5), should be adequate.
10.4
The methane reactor will accommodate hydrocarbons, methane, and carbon
monoxide concentrations in air to 500-ppm. Most ambient levels are below 5-
ppm. The life span of the catalyst is almost indefinite though rapidly poisoned
by halogenated and sulfur compounds. It is for this reason that the methane
reactor is always located after the purification reactor. The efficiency of the
methane reactor for methane is expressed by the nomograph on Figure 16.
10.5
The methane reactor is recommended for the generation of air which is to be
hydrocarbon and carbon monoxide free. It is widely used in determining
ambient methane levels, reactive versus non-reactive hydrocarbons, as source
air for CO, CH
4
, and THC analyzers, preparation of air blends, combustion air
for TOC an
alyzers, etc. A pure air generator with a “C” purification reactor is
usually employed in conjunction with the methane reactor for these
applications. See Section 9.9.
10.6
To remove the low level CO
2
formed during the catalytic reaction, AADCO
Instruments offers an in-line, see through , CO
2
-indicating scrubber (part no.
737-120). This device is offered for those users who may be concerned with