Oxygen analyser aids efficient combustion

Edited by the Engineeringtalk editorial team Jan 19, 2006

Combustion gas analysis is a key factor in optimising fossil fuel burning efficiency and economy as well as meeting emission requirements.

The new O2Mation Model AV550 from Yokogawa is an averaging oxygen analyser designed for use in large fossil fuel burning processes such as power stations, where combustion gas analysis is a key factor in optimising plant efficiency and economy as well as meeting emission requirements.

The AV550 is a robust, reliable and accurate instrument which combines Yokogawa's expertise in zirconia-based combustion oxygen sensing with a number of features designed to minimise plant downtime and provide technical support to users.

These include intuitive colour touch-screen operation, innovative hardware design and powerful diagnostic tools.

These new process diagnostic tools use historical process data to provide operators with new ways to reduce measurement downtime, and include predictive calibration dates, cell asymmetry alarms and detector validation features.

The predictive calibration and detector validation features reduce the number of redundant calibrations, while the sensor asymmetry alarm provides users with a new insight into the problem of fly-ash plugging by monitoring the particular symptoms of pressure-induced drift.

The averaging oxygen analyser uses up to eight zirconia sensors arrayed at different points across the cross-section of a flue to prevent the significant errors that can be caused by stratification.

The unit will output the average oxygen concentration from a user-selected group of zirconia detectors, with detectors that are in alarm status, under calibration, or not in service being automatically removed from the average output.

This feature is especially useful when plant maintenance schedules call for frequent calibrations.

The O2mation AV550 instrument is based on a modular design with redundant CPU configuration for added reliability and the ability to "hot swap" channel cards to minimise downtime.

The unit is easily expandable to accept up to eight zirconia detectors, and a wide variety of contact outputs, alarms, and analogue output configurations are available for easy set-up and integration into the boiler control system.

The full colour touch screen provides intuitive operation, and features multiple display modes which can show average data, single detector or all detector gas concentrations.

Trend graphing provides normal and stacked trend views of oxygen concentrations.

The AV550 includes eight 4-20mA outputs for individual detectors and three 4-20mA outputs for average oxygen concentration outputs.

Calibration can be automatic or manual, which the touch screen being used to select contact input, calibration activation, range change and detector performance validation.

A housing temperature alarm notifies the user of over-temperature conditions on the electronics, while an asymmetry alarm uses historical calibration data to determine possible measurement errors due to process condition changes.

Remote validation permits control-room activation of zero, span or midpoint gas concentrations without running an actual calibration.

A calibration line purge function allows the gas purge of calibration lines of condensation before the detector is heated up to prevent water damage to the zirconia cell.

The EXAxt ZR22 in-situ type zirconia detector used with the new analyser has been developed from Yokogawa's field-proven Z021D zirconia detector technology.

Available in lengths from 150mm to 5m, the ZR22 can be used in process temperatures up to 700C and in pressurised ducts at up to 2.5bar(g) with the pressure compensating option.

The complete analyser incorporates a re-usable heater and thermocouple assembly, the zirconia cell, and removable reference and calibration lines to create a robust, reliable and accurate oxygen measurement product designed for simple, quick and low-cost operation and maintenance.