Model Ace 2000 -Zirconia Flue Gas Oxygen Analyser

The heart of the systems is the Zirconia Sensor, which when maintained at elevated temperatures gives an output (based on Nernst equation) which is a function of the gas constant, the absolute temperature, Faraday`s constant, the natural logarithm of the ratio of the partial pressure of oxygen on the two sides of the cell.

This means if the temperature is held. Constant and air ( 20.9% oxygen ) is used as reference air, the output becomes the inverse logarithm of the partial pressure of oxygen in the measured gas.

Introduction/Application

Oxygen in flue gas analysis is the simplest and least expensive basis for combusion control and can return as much as 90% potential fuel saving provided a rugged accurate oxygen sensor is employed. The importance of minimising excess air is that for each 1% reduction of oxygen in the stack can give a 2% fuel saving.

The Model ACE 2000 is an " in-situ " on-line oxygen analyser package characterised by its robust construction & designed to measure Oxygen concentration in the flue gas from the combustion processes.

Typical application include industrial power and process boilers, refinery process heaters, oxygen enrichment systems, wind boxes, incinerators and air pre-heater leakage. It can be used for moisture analysis.

Output (mv)

The cell is encomposed by a heat shield assembly which allows the sample gas to diffuse through the ceramic filter and also conserve and maintain the requisite temperature. A v-deflector below the filter prevents particulate matter from the flue gas to directly impinge on the filter and retards clogging on the side.

The hollow of the zirconia cell houses the inner probe assembly which consists of a heater, a thermo-couple, a platinum conductor. The heater and thermocouple form the part of the temperature control circuit which maintains a temperature of 843°C (34.1mv) in the vicinity of the cell. The heated temperature is programmable from 750°C to 843°C. The platinum conductor carries the positive signal from the cell to the terminal strips. The negative of the cell is body ground. In case of the heaterless probe, the process temperature itself activates the Zirconia Cell bits range operating temperature 650°C to 1600°C.

To meet the varying stack diameters probes are available in sizes ranging from 18" , 3` , 6` and 9`. The probes are bolted and mounted within a support shield which gives physical protection to the probe.

The Micro - Processor based Electronics is housed in a rugged IP 65 (weather proof) enclosure. The electronics can be mounted close to the probe or in the Control Room with suitable cabling. The electronics is capable of giving

• 4-20 mA isolated output or
• 0-20 mA isolated output for 0-10% O2 or 0-21% O2

Features

• Sensor used is a solid Zirconia Oxide electroyte with a high speed of response and is ideal for closed loop control. The sensor is ruggedly built and does not experience mechanical and thermal shock like other cells in the market, it is also easily replaceable.
• The sensor is suitable for process temperatures upto 760°C and the sensitivity of the cell increases logaritmically when oxygen decreases. These features make the sensor suitable for any fuel and also useful for measuring low oxygen levels.
• Electrodes are self protected in the presence of sulphur or reducing atmopheres. This provid long life for sensing element even in the presence of sulphur and reducing atmospheres.
• In the absence of a sampling systems, the maintenance downtime is reduced drastically. The rapid, accurate and reliable measurement paves the way for significant fuel savings and enhanced safety.
• Oxygen measurement is on a `wet` basis and takes into account moisture. This gives the actual free oxygen available in the gas.
• The ( Calibration facility not available for the heaterless probe ) probe used is the direct insertion `in-situ` type and also facilitates on-site calibration.
• The output from the analyser is suitable for use with indicators, recorders, controllers and data loggers etc.

Optional Features

1. By-pass version of model ACE 2000 suitable for temperatures upto 1000°C.
2. Special probe shields and materials of construction for harsh, erosive or corrosive atmospheres.
3. Auto-purging facility for filter on request.
4. Enclosure for hazardous area on request.