H2S/SO2 On-Line Analyzer

[ponderer]

We have a big sulfur plant with capacity of 500ton sulfur/day.

We have a long term struggle with the on-line H2S/SO2 analyzer.

Is there any expert can teach us how to maintain this instrument?

 

[hacksaw]

Sounds like a Claus furnace? Where (in the process) are you measuring the H2S? and where are you measuring the SO2.

 

[ponderer]

Downstream of the last sulfur condenser.

 

[hacksaw]

a big concern is the sulfur carry over. Is that the reason for the high maintainance?

I believe that you shoud be controlling the furnace on temperature with the gas analysis as far down stream as you can get.

 

[ponderer]

Yes, we encounter plugging of the sampling line very often.

Thanks for your guidance.

 

[hacksaw]

the usual tricks are use of a sampling point where sulfur vapor is simple not possible, near the tail end of the plant.

we focused on locating the sample point and use of insitu UV meas. as oposed to extractive types at least for the SO2.

The H2S meas. usually requires an extractive sample. Sample systems are commercially available. They can be built but not with the resources that is commonly available in a plant.

If you are getting incomplete combustion of the H2S then you need to focus on the temperature controls. There are several established methods for acturate and traceable measurments of you reaction zone temperatures. Believe that solving the control issues will reduce your analyzer maintenance considerably.

Good Luck,

 

[TJCB]

Ensure your sample line is heat/steam traced to prevent pluggage over time.

Do you have feed forward as well as feed backward control on your sulphur plant (feed forward is based on your acid gas / sour gas flows and assumed composition , feed backward is based on your 2:1 H2S to SO2 tail gas analyser and should control your trim air valve)? The comination of these controls helps steady your tail gas control.

 

[BillHaddad]

Dear Ponderer,
Your problem is not unique. I know of several possible causes and corresponding solutions to your problem some of which have already been mentioned by our peers. However, a more detailed discussion of your situation would be needed to determine the actual cause and a corresponding permanent solution.

Two quick and easy things you can try are reducing the sample flow rate through your sample line and increasing the frequency of sample line back-flushing. Unfortunately, often this is not enough and then one must look to see if the problem is related to a 'fix-able' process problem or if one needs to look to new hardware for a permanent solution.

I would be happy to introduce you to several technical experts(not salesmen)in SRU operation and TGAs who can help you determine the root cause of your problem. If you are interested, please e-mail your contact info to me at William.Haddad@AMETEK.com. If you can also include additional info on your process (std 3-stage claus?, oxygen enriched?, TGTU?, burning SWS?, etc.) it will help me to determine which colleague will best be able to assist you with your troubleshooting.

In the spirit of honest disclosure, I do work for AMETEK Process Instruments (

http://www.ametekpi.com)

who has been a manufacturer of tail gas analyzers for many years.