GC on Polyethylene Reactor, frequent pluggage problem

[atharwasim]

Dear experts,
We have three on-line Gas Chromatograms on Reactor outlet of our Polyethylene Plant. All three GC,s are suffering from frequent blockage of ports of 10 ports Valves inside 90 Deg C OVEN and Flowmeter in Secondary Sample Conditioning system which also resides in a cabinet maintained at 80 Deg. C temperature.
Process consists on Hydrogen, Nitrogen, Ethylene, Ethan, C4s, C5s and traces of C6s.

Any suggestion to startwith.

Regards,
Athar

[Les]

Does water have any part in the problem? Have you tried a filter upstream of the valve? Maybe dirt? Place a 0.2 micron filters in the sample line and inspect the filter after a few days. I see problems with the lab GC analyzing LPG due to these factors. Water enters the valve and causes rotor scoring from the salts that form upon drying. I get about 2 to 3 months of usage. Then I swap them out and send back to VICI for conditioning. If the valve is down stream of a guard column, some pieces of column may be lodging in the ports.
I have 2 filters before my valves, a 15 and 0.2 micron. The 15 catches teflon from attaching peanut bombs and the 0.2 catches dirt. Even with these filters, I can't stop small amounts of water.

[chromatographer1]

Do you have a properly designed sample conditioning system attached upstream of your GC analyzer? This is designed to clean and filter out contaminants so they will not affect your analyzer. You could have a lot of things from your reactor entering the sample stream.

Les' comments are excellent. Try to identify the material blocking the lines and stop it from entering the sample stream.

[atharwasim]

Thank you les and chromatographer,
It is an on-line application and has primary as well as secondary sample conditioning system. In primary I have 10 and 5 micron filters, in secondary I installed .5 micron filter before injection as les advised. After one week flow dropped again (pre-warnning of blockage), .5 micron filter was found clean.
I think it is polymeration occurs on narrow paths on suitble conditions like 90 deg c temp etc. Any advise? HOW to avoid this?

[chromatographer1]

Your sample conditioning system is not doing the job it is intended to perform. You can try using a swirlclean type filter if it does not have one already. Also the flow of sample through the heated areas may not be fast enough and a buildup of polymer may occur.

I would see your vendor of the sample conditioning system and ask them to fix the problem you are experiencing. They may not have been aware (as you may not have been) concerning polymerization issues in your sample stream.

The problem is one that has been resolved before. I hope you seek proper technical assistance to resolve your problem.

A solution from this forum, from someone who does not have the technical details of your reactor and the sample conditioning system would be haphazard at best.

Good luck and best wishes,

Rod