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Nitrogen Flowmeter


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#1 kinetic123

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Posted 23 April 2014 - 04:14 PM

Hi

 

One of our customer wants to install a corriolis mass flowmeter for nitrogen to be used for reactor blanketing. From the process instruction sheets, it can be seen that the flow rate is normally between 3 to 15 m3/hr depending on product to be manufactured in the product.

 

The flowmeter supplier needs flow rate data in kg/hr but customer has data in m3/hr and customer do not know if this flow rate is Nm3/hr [normal], Sm3/hr [standard] or Am3/hr [actual]. 

 

How to get flow rate in kg/hr?

 

Thanks

 



#2 latexman

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Posted 23 April 2014 - 04:33 PM

Are you a ChE by degree?  If not, what?  Thank you.



#3 kinetic123

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Posted 23 April 2014 - 04:51 PM

latexman,

 

Yes, I am. Sorry, why you are asking this?

Is my question not logical?

Thanks



#4 latexman

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Posted 23 April 2014 - 07:07 PM

I have been a ChE for 35 years.  I've specified hundreds of flow meters.  Your question is logical, but, like your customer, it lacks the detail needed to progress to an answer.  I wanted to know if you were a ChE with degree, a ChE student, or something else so I could chose the right vocabulary.

 

A picture is worth a thousand words.  Can you upload the P&ID?  Or, the PFD?  Or, a well labelled sketch?

 

If not, what kind of meter is used now?  What is the actual T and P, or ranges of T's and P's, at the point where the flow is measured?

 

This is not really important to answer the question, but why is the RX blanketed with nitrogen?  Flammability?  N2 is consumed in the rxn?  Color issues if not inerted?  Moisture issues?  What?  Is this the only N2 user in the plant?  The reason I ask is we just monitor the liquid level in our liquid N2 tank.  We have no flow meters on our blanket systems.  We use conservation vents and maintain a slight pressure of N2 in tanks and RXs.  If the usage gets high, folks start listening for leaks, sssssssssss, and fix them.  And, why an expensive meter like a coriolis meter?  There must be a less expensive choice!  A rotameter comes to mind.  You can probably get a rotameter for 1/10th the cost of a coriolis meter.  The installation of a rotameter is much less complex and expensive than a coriolis meter.  Just wondering.



#5 kinetic123

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Posted 24 April 2014 - 02:37 AM

Latexman,

 

Thanks for your reply. I know your concern now on using the right vocabulary. Thanks. Please see the attached simplified sketch.

At the moment, customer is using rotameter but it’s very old now and customer was not happy with the accuracy and also change of piping configuration.

Reactor needs N2 blanket due to the presence of flammable solvent and also to prevent oxidation of product.

Reactor is vented to the atmosphere indirectly i.e. through the catch pot and the arrangement is like - reactor-condenser-catch pot.

Not sure, if conservation vent valve [pressure vac vent valve] could be used for the arrangement we have.

N2 is supplied to flowmeter at 1.5barg and at ambient temperature.

Any further help/comment?

Thanks in advance.

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#6 Mahesh@A&M

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Posted 24 April 2014 - 12:33 PM

Kinetic,

 

Is this a reactor or storage tank?

 

If this is a reactor, do you vent continuously or after the reaction? What is the reaction T and P ? 

 

For nitrogen blanketing purposes, maintain poistive pressure in the reactor.



#7 kinetic123

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Posted 24 April 2014 - 03:18 PM

Mahesh@A&M

 

This is the simplified version of the sketch and the reactor would be vented only during reaction stage.

 

The maximum operating temp during reaction is 200degC and of course, as the reactor is blanketed by nitrogen which signifies the maximum pressure during reaction stage is 1.5barg.

 

Any further help please on how to get N2 in kg/hr?



#8 latexman

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Posted 24 April 2014 - 07:15 PM

Using the T and P at flow conditions and an appropriate equation of state, calculate the density of the nitrogen.

 

Multiply the density x the volumetric flow rate to get a mass flow rate, after taking care of any unit conversions.



#9 breizh

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Posted 24 April 2014 - 07:56 PM

Hi ,

 

You may find useful this spread sheet , in addition to Latexman's comments (above).

 

Hope this helps

 

Breizh



#10 kinetic123

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Posted 28 April 2014 - 10:02 AM

Thanks latexman and Breizh






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