The Endura AZ20 oxygen probe measures oxygen concentration in flue gas using an in situ 'wet analysis' method. The 'wet analysis' method avoids measurement error (typically20% of reading higher than the actual value) that is introduced by a sampling system using the 'dry analysis' method.
For customers with an existing installed ZFG2 probe with a ZMT or ZDT transmitter, a 55 V heater version of the Endura AZ20probe (the Endura AZ20 / ZFG2 replacement probe) is available.
System equipment comprises a (flue-mounted) Endura AZ20probe controlled by an integral or remote transmitter. During operation, a zirconia cell within the probe is held at a constant temperature of 700°C (1292 °F) by a probe heater and control
thermocouple assembly. If the heater control circuitry or software fails (unsafe), the probe heater power supply is switched off, ensuring the system fails 'safe' and protects the heater from an over-temp failure.
An output generated at the zirconia cell is processed in the transmitter giving a locally displayed O2 reading and a 4 to 20mA retransmission signal over any range between 0 % and 100% O2.
Optional automatic calibration (AutoCal*) enables automatic,semi-automatic or manual calibration to be performed using a probe-mounted gas control manifold mounted within the probehead. Calibration sequencing is software-controlled from thetransmitter.
Optional restrictors (where fitted*) in the probe head control thetest gas and reference air flow without the need for flowmeters.The probe requires only preset test gas and reference airpressures of 1 bar (15 psi) to maintain a constant flow of 2.2 l /min (4.662 scfh). This flow is not affected by changes in themeasured gas pressure of ± 0.35 bar (5 psi).
Introduction
The Endura AZ25 combustion oxygen analyzer is the latest ina long line of high-quality, combustion gas analyzers fromABB. The AZ25 is designed to measure oxygen concentrationin high temperature furnace atmospheres.
The sensor, based on a zirconium oxide cell, is mounted at thetip of the probe that is inserted directly into the furnace. Theresulting direct, in-situ measurement provides an accurate andrapid oxygen reading, for combustion control / optimizationand process quality control purposes.
The in-situ technique provides a true oxygen measurementinside the process. It eliminates 'equilibrium shift' that iscommon to systems in which gas samples are extracted andcooled before measurement.
Reference air (500 to 1000 ml/min [1 to 2 ft3/hr]) is required foraccurate operation and can be supplied from an ABBmains-powered pump unit or a flow regulator unit.
Unique integrated automatic calibration
The Endura AZ25 automatic calibration system eliminates theneed for the expensive ancillary equipment required forautomatic calibration on traditional flue gas oxygen analyzersystems. ABB’s fully integrated, automatic calibration feature
controls the test gas sequence and detects test gasavailability, eliminating incorrect calibrations due to loss of testgas. Integrated automatic calibration secures the oxygenmeasurement, providing complete confidence in the analyzer's
performance.
Long-term operation without technician intervention minimizesoperating costs, total cost-of-ownership and optimizes systemaccuracy. A significant proportion of service visits to ananalyzer result in 'no fault found'. Endura AZ25's high-quality
manufacture, advanced diagnostics and automatic calibrationis targeted at reducing this wasted effort and cost.
Dependable
— measurement of O2 in a wide variety of processes
— virtually instantaneous response
— resistance to sulphurous reducing atmospheres
Versatile
— 600 to 1250 mm (2 to 4 ft) lengths
— choice of protective sheath materials
— integral thermocouple for automatic temperature
compensation
— high temperature operation up to 1400 °C (2552 °F)
Low cost-of-ownership
— in situ measurement
— no sampling system required
— automatic calibration functionality as standard
— optional automatic calibration hardware
Applications
— Furnace atmosphere monitoring:
— Annealing furnace
— Sintering of metals
— Ferrite sintering
— Whiteheart malleablizing
— Combustion measurement and control in:
—Soaking pits
—Process heaters
—Fluidized bed boilers
—High temperature incinerators
— All other combustion processes where the flue gastemperature is in excess of 600 °C (1112 °F)
Aluminous porcelain
Entry level sheath material suitable for applications withtemperatures up to 1250 °C (2282 °F) – limited resistant tocorrosive chemicals and mechanical and thermal stress.
Recrystallized alumina
Suitable for applications with temperatures up to 1400 °C(2552 °F) resistant to corrosive chemicals and more severemechanical and thermal stress are present.
Incoloy 800
Suitable for applications with temperatures up to 850 °C
(1562 °F) when mounted horizontally and up to 1000 °C
(1832 °F) when mounted vertically.
Offering limited resistance to corrosive chemicals and resistantmechanical and thermal stress.
