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Backpressure On An Ftir Causing Gas Analysis Problems?

ftir gas analysis emissions

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#1 jonol92

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Posted 10 June 2013 - 09:59 AM

Hello,

 

I'm on an internship with a power station and 

I've been tasked with identifying a way to reduce back pressure to an FTIR currently sampling stack gas from a biomass burning power station.  

 

It is believed that back pressure is causing and inaccurately high reading of CO due to increased density of the sample gas in the cell of the FTIR (its designed to be measuring at atmospheric pressure).  Therefore by reducing the back pressure a more accurate reading for CO should be achieved.

 

The outlet from the FTIR is the inlet to a FID, the outlet of which is released to the atmosphere through a 7mm plastic pipe that drops approximately 1.4m from the FID outlet to the point where gasses are released.

Is there an adjustment i could make to the outlet pipe of the FID to reduce the aforementioned effect and increase gas analysis accuracy?  I thought altering the position of the outlet end of this pipe may help but the difference would probably be very marginal wouldn't it?

 

I'd rather avoid the need for additional materials and just alter whats installed already if possible. 

 

Thanks a lot!

 

J



#2 Art Montemayor

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Posted 10 June 2013 - 12:56 PM

J:

 

Please be courteous to the Forum and always identify your acronyms.  You cannot practically expect your readers to know what you mean by your acronym.  I (and probably a lot of others) don't have the slightest idea what you mean by  "FTIR" and "FID".



#3 jonol92

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Posted 11 June 2013 - 03:27 AM

Sorry, I was in a little bit of a hurry!

 

This is on the continuous emissions monitoring system for the power station.  The FTIR is the fourier transform infra-red device for gas composition monitoring (it's a 'gasmet' model) and the FID is the flame ionisation device.

 

Please let me know if you need any more information that may help, im not really certain what is required for someone to help!

 

Thanks, J



#4 thorium90

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Posted 11 June 2013 - 08:06 AM

In my opinion, it is not necessary to make such changes. Because, any calibration done on it will be be subject to the same restrictions, therefore the analysis will still be accurate as long as the calibration was done regularly enough.



#5 jrtailor09

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Posted 11 June 2013 - 09:14 AM

jonol92

 

Please note that flue gas released to athe atmosphere only. There is some pressure in exhaust duct.

 

There is some standard Auxiliaries system provided by the OEM ( original equipment manufacturer) to measure the concentration of the pollutanats.

 

As far as you will daily Monthly calibration as per vendor recommedation then there should not be any problem.

 

Regards,

Jatin



#6 thorium90

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Posted 11 June 2013 - 10:56 AM

jonol92,

 

Are you sure the CO reading is really inaccurate? Have you tried getting a third party to collect a sample bomb for GC analysis? What are the opinions of the vendor on this issue? To be frank, I think the issue is more likely with temperature than with backpressure. Is the CEMS located in a well regulated temperature controlled environment?


Edited by thorium90, 11 June 2013 - 10:57 AM.


#7 jonol92

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Posted 12 June 2013 - 03:27 AM

Thank you for all your responses.  

 

I thought that as long as calibration is regular enough there shouldn't be an issue.  

 

Honestly im not convinced the reading is too inaccurate (i.e. outside the acceptable limits), rather it would be ideal if it was on the lower limit rather than the upper because it affects output of the power station.  

 

I've worked on the air conditioning of the cabinet it is contained in before and in the summer the temperature becomes very difficult to keep down (if the CEMS hut was any worse it'd be like a greenhouse!) so thank you for that point thorium, i'll revisit that issue.

 






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