ENRICHED OXYGEN IN
In a traditional combustion process, oxygen (O 2 ) is supplied to
the combustion reaction in the form of atmospheric air. The O 2
contained within the air combines with hydrogen and carbon
from the fuel source, forming water and carbon dioxide in a
process that releases heat.
THE SERVOMEX SOLUTION
SERVOMEX SUPPLIES THE EFFECTIVE GAS ANALYSIS SYSTEM FOR
MONITORING ENRICHED O 2 IN THE COMBUSTION PROCESS.
SERVOTOUGH OxyExact 2200
in a three-analyzer voting system
ENERGY SAVINGS FROM O 2 INJECTION
Air is composed of approximately 21% O 2 , 78% nitrogen (N 2 ),
and 1% other gases. During combustion, the chemically inert
N 2 in the air dilutes the O 2 , carrying away some of the energy
in the hot combustion exhaust gas.
100% O 2
The efficiency of the process is dependent on both the exhaust
gas temperature and the percentage of the O 2 in the
Performance studies conducted by the US Department of
Energy, using O 2 levels at 100%, have shown a fuel consumption
reduction between 10-20%, alongside NOx reductions of 90%.
Theoretical studies have postulated that fuel savings of 42%
over conventional systems may be possible using O 2 at 95%.
This uses three SERVOTOUGH OxyExact
2200 process O 2 analyzers in a voting
system, located between the air/O 2 mixing
system and the furnace.
At levels above 25%, flammability is increased significantly,
which may impact upon plant safety. For this reason, many
processes limit the O 2 enrichment to between 22-25%, which is
still sufficient to achieve significant fuel savings.
Energy Tips - Process Heating. September 2005
In a three-analyzer voting system, the
process depends on the measurement
made by the majority of analyzers. So,
if only one analyzer reports a significant
change in O 2 levels, it is “outvoted” by
the other two, and no action is taken.
However, if two analyzers detect a
change, their reading is held as correct
and action is taken – in this case to adjust
the O 2 mix accordingly to return it to the
BENEFITS OF OXYGEN-ENRICHED COMBUSTION
Increased efficiency: Lower emissions: Improved stability: Increased productivity:
Flue gas heat losses
are reduced Reduced levels of NOx, carbon
monoxide and hydrocarbons Higher O 2 results in more
stable combustion and higher
temperatures, leading to
better heat transfer The heat generated is
increased for the same
amount of fuel
Increasing the O 2 level in the combustion air to a level above
21% reduces this energy loss, potentially increasing the
efficiency of the combustion process. Typically, liquid O 2 is used
to increase the O 2 concentration in the combustion air before it
enters the furnace.
Accurate monitoring is required to ensure that the O 2
concentration remains within the specified limits, to obtain the
optimum balance between safety and efficiency.
Voting systems allow problems with
analyzers to be detected early without
endangering the process. If two analyzers
return the same measurement and the
third varies, it may suggest a problem
that can be investigated and corrected
before the process is affected.
It also provides a greater degree of
safety, since using a single analyzer
would make it more difficult to detect
measurement variations, allowing
incorrect measurements to go unnoticed
The OxyExact 2200 uses an intelligent
three-enclosure system that enables
simplified, versatile sampling of up to
100% O 2 , with no requirement for pre-
sample drying. It is certified for the use of
enriched O 2 in Zone 1 hazardous areas.
High-precision Paramagnetic sensing
technology provides the accurate
performance required for optimum
process control, while the robust design
ensures reliable operation in
depleting Paramagnetic technology as the
OxyExact 2200s, except for safe areas only.
The advanced communications offered by
the MultiExact 4100s provide easy
integration into voting and control systems.
SERVOPRO MultiExact 4100
SERVOTOUGH OxyExact 2200
Servomex has also recently installed
SERVOPRO MultiExact 4100 analyzers
at a site using oxygen-enriched air for
combustion. These provide accurate
O 2 analysis using the same digital non-
Find out more at: servomex.expert/mag-2200