EXPERT FOCUS
OXYGEN ANALYSIS IN ETHYLENE
OXIDE PRODUCTION FLARE STACK EMISSIONS
Ethylene oxide (C 2 H 4 O) is a versatile
chemical building block used in the
manufacture of many products including
glycol-based antifreeze, synthetic
clothing fibers, foam rubber, detergents,
paint, various modern plastics, and as
an important sterilizing agent. Reliable
oxygen (O 2 ) monitoring is essential for
safety and efficiency in the C 2 H 4 O
production process. A flare stack is one of the most important
safety mechanisms in industrial plants,
burning off flammable gases released by
pressure relief valves, thereby avoiding
unplanned pressure build-ups and
disposing of excess gases.
VOTING SYSTEM LOCATION
OXYGEN
REACTOR 1
REACTOR 2
REACTOR 3
The desired C 2 H 4 O intermediate is
produced by feeding the two primary
feedstock materials, in minor amounts,
to a reactor maintained between 145 and
365psig (260psig is typical) and 200-300 o C
(392-572 o F). A suitable catalyst, usually
silver oxide, is also used.
ETHYLENE
POTASSIUM
CARBONATE
REACTOR 4
CARBON
DIOXIDE
REMOVAL
POTASSIUM
BICARBONATE
Most C 2 H 4 O is commercially produced
by the direct oxidation of ethylene (C 2 H 4 ),
using a mix of air and pure O 2 .
The exothermic nature of the process
means that safety is of paramount
concern. Ethylene is a very reactive gas,
and readily burns to form carbon dioxide
(CO 2 ) and water vapor (H 2 O). If not
carefully handled, it does this explosively.
GAS
COMPRESSOR
MIX NOZZLE
The analyzer’s Paramagnetic sensor
responds specifically to changes in
gaseous O 2 levels, while the only sample
preparation components required are a
filter and a pressure reducing station.
The non-depleting Paramagnetic cell
should never need replacement, and
requires only occasional calibration
checks, especially when used in safety
shutdown duties. It provides proven,
A flare stack is an elevated vertical stack
or chimney, and steam-assisted flaring of
the associated gas occurs at the top of
this structure to control the combustion
efficiency (CE).
Combustion of the vent gas is a much
more environmentally responsible
process than simply releasing the gas into
the air. For example, if methane is burnt,
the products are carbon dioxide (CO 2 )
and water, which are much less harmful
than releasing methane itself.
Flares are active all the time, with a
continuous release of gas being burned
off at the flare stack. When this mix of
steam and hydrocarbons is correct, the
flame is clean and no harmful emissions
escape into the atmosphere.
SERVOMEX ANALYZER SOLUTIONS FOR THE FLARE STACK PROCESS
ETHYLENE
OXIDE ABSORBER
SERVOTOUGH OxyExact 2200
Using air as the oxidant means that
the inherently high proportion of
nitrogen acts as a major diluent, keeping
components outside of the explosive
limit. It is essential to keep O 2 levels
below 8% to avoid formation of an
explosive mixture. However, it must be
above 5%, otherwise the C 2 H 4 O yield
becomes uneconomic.
FAT WATER
EO
RECOVERY
When the process uses pure O 2 , the
desirable operating range is very different
and much narrower, typically 0.8% O 2
with a variation of ±0.1% O 2 .
Integrated Systems (SIS) required for safe
operation and production.
The OxyExact 2200 can be used to
measure the quality of the O 2 feedstock.
More critically, however, it is employed in
a voting system – either one out of two or
two out of three – to measure O 2 on the
inlet and each outlet of the reactors. The
OxyExact 2200 is SIL 2 hardware compliant
to make integration into such safety
systems simple. Ethylene oxide reactors are monitored
on a frequent basis, to detect gases
other than O 2 in order to assess
conversion efficiency and unwanted
waste compound build-up. Signals from
these analyzers can be continuously fed
to the OxyExact 2200s to modify the
O 2 analyzer output as required. This
produces an online O 2 reading to better
than ±0.02% accuracy.
These safety critical measurements are
a fundamental element of the Safety
SERVOTOUGH
SpectraScan 2400 SERVOMEX
H2scan SERVOTOUGH
Oxy 1900
A Tunable Filter Infrared absorption
on-line gas analysis platform ideal for
continuous flow-through monitoring of
light hydrocarbons. Non-depleting thin film technology
providing a robust and reliable direct
measurement of hydrogen. Award-winning, safety-enhanced
digital O 2 analyzer designed to deliver
accurate Paramagnetic measurements in
challenging applications.
SERVOTOUGH
OxyExact 2200 SERVOTOUGH
Laser 3 Plus Process
In either case, the reactions are optimized
by keeping the O 2 level as high as possible
to obtain the best yield, while remaining
within safe limits.
long-term stability, reliability, and a fast
speed of response.
Want expert support customized to your process?
Contact us now: servomex.expert/contact-us
P10
They are also used for the planned
combustion of gases over short periods
during plant start-ups or shut-downs,
both full and partial, and are employed
by petrochemical facilities, natural gas
processing facilities, chemical plants
and refineries.
LEAN WATER
A PARAMAGNETIC O 2 ANALYSIS SOLUTION
The SERVOTOUGH OxyExact 2200
gas analyzer is ideal for monitoring
these processes.
SERVOMEX’S BENCHMARK-LEVEL ANALYSIS OF HYDROCARBON COMPONENTS AND
OXYGEN MIXTURES ACROSS THE FLARE STACK PROCESS
See our analyzers
across the process
OVERLEAF
Hazardous area process O 2 analyzer
using high-precision Paramagnetic
sensing technology for ultimate
monitoring performance.
Highly-compact Tunable Diode Laser
gas monitor for fast and accurate O 2
measurements in in-situ cross-stack
applications.
P11