In-line Oxygen Monitoring

[heieup]

We are looking to install in-line oxygen monitoring in order to monitor the overall performance of our plant.

Does anyone have any experience of such systems and any advice as to what to look for when surveying the market.

The monitor will be situated in a waste gas main and will be subject to the following conditions

gas flow 143 m3/s
gas temperature = 160°C;
static pressure = 120 mbar;

 

[EngineerBSME]

Oxygen probe location and number, length, and spacing of probes per duct is usually the most controversial subject to be faced throughout the duration of the installation. Whatever the decision must be continuously defended on a scientific basis.

Selection of oxygen sensor supplier is the second most controversial subject. Some probe materials will disappear in certain environments. Other probes can not be readily disassembled once exposed to high temperatures. ie the fastener screws corrode in place.

Consider submitting a gas analysis to the probe supplier prior to selecting the sensor.

Probe averages and duct averages and system total averages are to be considered in the oxygen analyzer system. Individual probe LED readouts, duct averages, and total averages are recommended.

Signal outputs as inputs to the associated control systems will become invaluable.

Probes fail. Time delays vary. A mechanical or programmable switch to eliminate a "probe of questionable value" is imperative in resolving operational parameters as mentioned in paragraph 1 above. Decide and select whether the probe should fail high or fail low. Regardless of the decision, remember the probe will select it's own mode of failure sometimes ie below norm or above norm due to buildup or corrosion.

Select a reliable vendor that makes site visits upon your request. What does the oxygen probe name, Westinghouse Hagan Rosemount, for example, imply?

Consider purchasing or leasing a portable probe prior to the installation to take some representative data.

Consider paying an unabiased consultant to visit the facility, review the application, and make recommendations. It is a good investment that will make you look good. Without a consultant to share responsibility and explain options during subsequent operation and maintenance, you can waste a lot of time and money with misapplications, poor location choices, poor vendor selection, poor electronic selections. Some sales personnel are equally adequate consultants. Free lunches or eat your lunch. Your choice.

 

[dsthokal]

I have been using zironium oxide online O2 monitoring probe for last 2 years which is working perfectly. Forbes Marshall or Rosemount are supplying such sensors nowdays which can easily work in temps upto 300 deg C.

These sensors give 4-20 mA output which can be used for controlling the combustion air through VFD attached to CA fan motor or giving input to burner modulation system via suitable controller.