Looking for a Moisture analyzer in a "wet" process air steam

[cdcosta]

I have a process that takes Air from the athmoshpere and is compressed to 20 psig. Then steam is injected into the airsteam to "humidify" the stream before it enters the process.

I am looking from a reliable moisture analyzer that can measure the moisture in the stream after the steam injection point.

We are targeting a moisture content of ~1.8 mol% water in air or 18,000 ppm moisture.

I have tried aluminum oxide and ceramic probes, but the conditions are "too wet" as the probe gets saturated and takes a long time to dry out (2hrs) off line.

The probe must also handle high temperatures. The heat of compression on the exit of the compressor is ~ 160°C. During process starts ups, an in-line heater is also used, which brings the air temperature up to 350°C.

I have also tested an oxygen analyzer (ziroconia) which interpolates moisture content. The results were inconsistant.

Any help would be appreciated.

 

[joisy]

We have installed the dew point meter with aluminium wire in process air line (8 bars) but in about a month the reliabilty of the results got down. So, I do not recommend such devices: heard that there are some other types which more based on mechanical principles than chem/electrical

hope that this can slightly help you

 

[cdcosta]

Joisy,
When you say the reliability goes down, do you mean the sensing device gets contaminated or coated and therefore needs to be cleaned and and calibrated?
Could you give me some information on the unit you you have?

Thanks.

 

[joisy]

Yes, and even after the cleanning it had't recovered its measurement capabilities completely: it has begun to hive the results with the large error.

As I know there is some device with glass tube, using it you can check the humidity by physical view of the quantity of collected liquid. Will check its name with my collegue - as he mentioned of that once.

 

[ihg]

Vaisala (

http://vaisala.com)

have a dewpoint transmitter rated for 350deg C operation which may meet your requirement - quoted 90% response at 135C, wet to dry 50 sec, dry to wet 10 sec. (I havent used it, but happen to have the catalog on my desk)