HOW GAS ANALYSIS MAKES
COMBUSTION SAFER AND
REDUCES FUEL COSTS
Combustion is a high-temperature reaction
between a fuel and an oxidant (usually air)
and plays a vital role in many industrial
processes. It is particularly important in
the power generation and hydrocarbon
engineering sectors. A perfectly balanced air-fuel ratio will
reduce fuel consumption, lower the
polluting emissions of NOx, SOx, carbon
monoxide (CO) and carbon dioxide, prevent
explosions, and extend the life of plant
equipment.
To control combustion and ensure efficient
fuel consumption, the ratio between air and
fuel must be maintained at an optimum
level. Zirconia analysis for O 2 and COe
Zirconia technology has been a reliable
technology for measuring O 2 in combustion
for the past 50 years. Its speed of response,
simplicity of operation and ease of
installation has made it the preferred
solution for combustion efficiency.
The ability to add a combustibles sensor at
modest cost proved a further advantage,
especially for larger furnaces. Additionally,
Zirconia sensors can be quickly and easily
calibrated while still connected to the
process, confirming analyzer performance.
As a more recent innovation, a flow sensor
in the analyzer verifies that sample gas is
flowing to the Zirconia and combustibles
sensors, and that the probe has not been
blocked by dust.
Balancing combustion efficiency
Too much oxygen (O 2 ) results in cooler
burning, which significantly reduces
combustion efficiency. In addition, the
excess of O 2 available combines with
nitrogen and sulfur to create undesirable
emissions of nitrogen and sulfur oxides
(NOx and SOx).
A low-oxygen, fuel-rich environment results
in incomplete combustion of the fuel,
leading to the formation of combustibles
(typically carbon monoxide) in the exhaust
gas. These conditions also create a high risk
of a dangerous explosion.
On larger furnaces it is now common
to use multiple Zirconia units, because
each analyzer measures a single point,
and in bigger processes there are
different combustion zones, with layering
and convection producing variable
concentrations along the length of the
furnace.
Servomex’s SERVOTOUGH Laser 3 Plus
range offers an accurate, fast-response
measurement for oxygen, CO or CO+CH 4 in a
highly compact installation. Safety Integrity
Level 2 certification enables easy incorporation
into safety systems.
Tunable diode lasers
Tunable Diode Laser (TDL) analyzers offer
an average path rather than single-point
measurement, but they are susceptible
to environmental factors that must be
compensated for. TDL can measure both O 2
and CO, though two lasers are required.
TDL O 2 measurements are comparable with
the Zirconia performance; however, the
speciated CO measurement has a much
faster speed of response, which is ideal for
efficiency and safety.
The TDL analyzer can measure methane
(CH 4 ) and CO at the same time, making it
ideal for use in safety systems to detect
flame-out conditions in natural gas fueled
processes.
O 2 +
COe
Convection Tubing
O
CO 2 +
e
+
O 2 Oe
C
CO
O 2
CO
CO
CO
CO
CO
Servomex combustion measurements
in the process heater
O 2
CO
Servomex’s SERVOTOUGH FluegasExact
2700 delivers ultra-accurate and reliable
measurements of O 2 and combustibles.
Extractive sampling makes it ideal for use in
extreme heated, dusty environments.
A combination of Zirconia analyzers,
measuring oxygen for efficiency, and TDL,
monitoring CO for both efficiency and
safety, provides the best of both worlds for
combustion control.
www.servomex.com
Issue 32 PECM
123